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Engineering Design StatementDoc Ref: 7.18 APFP Regulations 2009: Regulation 5(2)(q)
Box 56 Folder B January 2013
Engi
neer
ing
Des
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Stat
emen
t
Thames Tideway Tunnel Thames Water Utilities Limited
Application for Development ConsentApplication Reference Number: WWO10001
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Thames Tideway Tunnel
Engineering Design Statement
List of contents
Page number
1 Executive summary ......................................................................................... 1
2 Background ...................................................................................................... 3
2.1 Purpose of this report .............................................................................. 3
2.2 Need for the project ................................................................................. 3
2.3 Solution.................................................................................................... 4
2.4 Design life ................................................................................................ 6
2.5 Proposed development ............................................................................ 7
3 Engineering considerations .......................................................................... 19
3.1 Introduction ............................................................................................ 19
3.2 CSO control ........................................................................................... 19
3.3 Storage and transfer of flows ................................................................. 26
3.4 Hydraulics .............................................................................................. 27
3.5 Air management .................................................................................... 35
3.6 Operation and maintenance .................................................................. 38
3.7 Ground conditions ................................................................................. 39
3.8 Sizing of structures and other components............................................ 44
3.9 Flood defences and surface water drainage .......................................... 54
3.10 Health and safety considerations ........................................................... 55
3.11 Technical standards .............................................................................. 55
4 Programme assumptions .............................................................................. 61
4.1 General assumptions ............................................................................. 61
4.2 Working hours ....................................................................................... 63
4.3 Rationale for 24-hour continuous tunnelling .......................................... 63
4.4 Assumed advance rates ........................................................................ 64
5 Flexibility for design and construction assumptions ................................. 67
5.1 Construction information ........................................................................ 67
5.2 Tunnel alignment and external dimensions ........................................... 67
5.3 Structure location and external dimensions ........................................... 68
5.4 Permanent foreshore structures ............................................................ 69
5.5 Final appearance, finishes and landscaping .......................................... 69
Engineering design statement i
6 Tunnels ........................................................................................................... 71
6.1 Principles guiding tunnel alignment ....................................................... 71
6.2 Main tunnel ............................................................................................ 76
6.3 Connection tunnels ................................................................................ 80
7 Acton Storm Tanks ........................................................................................ 85
7.1 Introduction ............................................................................................ 85
7.2 Structures .............................................................................................. 85
7.3 Limits and zones .................................................................................... 87
7.4 Access ................................................................................................... 89
8 Hammersmith Pumping Station .................................................................... 91
8.1 Introduction ............................................................................................ 91
8.2 Structures .............................................................................................. 91
8.3 Limits and zones .................................................................................... 93
8.4 Access ................................................................................................... 95
9 Barn Elms ....................................................................................................... 97
9.1 Introduction ............................................................................................ 97
9.2 Structures .............................................................................................. 97
9.3 Limits and zones .................................................................................... 99
9.4 Access ................................................................................................. 101
10 Putney Embankment Foreshore ................................................................. 103
10.1 Introduction .......................................................................................... 103
10.2 Structures ............................................................................................ 103
10.3 Limits and zones .................................................................................. 106
10.4 Access ................................................................................................. 108
11 Dormay Street ............................................................................................... 111
11.1 Introduction .......................................................................................... 111
11.2 Structures ............................................................................................ 111
11.3 Limits and zones .................................................................................. 113
11.4 Access ................................................................................................. 114
12 King George’s Park ...................................................................................... 117
12.1 Introduction .......................................................................................... 117
12.2 Structures ............................................................................................ 117
12.3 Limits and zones .................................................................................. 119
12.4 Access ................................................................................................. 120
13 Carnwath Road Riverside ............................................................................ 123
13.1 Introduction .......................................................................................... 123
13.2 Structures ............................................................................................ 123
Engineering design statement ii
13.3 Limits and zones .................................................................................. 125
13.4 Access ................................................................................................. 126
14 Falconbrook Pumping Station .................................................................... 129
14.1 Introduction .......................................................................................... 129
14.2 Structures ............................................................................................ 129
14.3 Limits and zones .................................................................................. 131
14.4 Access ................................................................................................. 133
15 Cremorne Wharf Depot ................................................................................ 135
15.1 Introduction .......................................................................................... 135
15.2 Structures ............................................................................................ 135
15.3 Limits and zones .................................................................................. 137
15.4 Access ................................................................................................. 139
16 Chelsea Embankment Foreshore ............................................................... 141
16.1 Introduction .......................................................................................... 141
16.2 Structures ............................................................................................ 141
16.3 Limits and zones .................................................................................. 144
16.4 Access ................................................................................................. 145
17 Kirtling Street ............................................................................................... 147
17.1 Introduction .......................................................................................... 147
17.2 Structures ............................................................................................ 147
17.3 Limits and zones .................................................................................. 148
17.4 Access ................................................................................................. 150
18 Heathwall Pumping Station ......................................................................... 151
18.1 Introduction .......................................................................................... 151
18.2 Structures ............................................................................................ 151
18.3 Limits and zones .................................................................................. 154
18.4 Access ................................................................................................. 155
19 Albert Embankment Foreshore ................................................................... 157
19.1 Introduction .......................................................................................... 157
19.2 Structures ............................................................................................ 157
19.3 Limits and zones .................................................................................. 160
19.4 Access ................................................................................................. 161
20 Victoria Embankment Foreshore ................................................................ 163
20.1 Introduction .......................................................................................... 163
20.2 Structures ............................................................................................ 163
20.3 Limits and zones .................................................................................. 165
20.4 Access ................................................................................................. 167
Engineering design statement iii
21 Blackfriars Bridge Foreshore ...................................................................... 169
21.1 Introduction .......................................................................................... 169
21.2 Structures ............................................................................................ 169
21.3 Limits and zones .................................................................................. 172
21.4 Access ................................................................................................. 174
22 Shad Thames Pumping Station .................................................................. 175
22.1 Introduction .......................................................................................... 175
22.2 Structures ............................................................................................ 175
22.3 Limits and zones .................................................................................. 177
22.4 Access ................................................................................................. 178
23 Chambers Wharf .......................................................................................... 179
23.1 Introduction .......................................................................................... 179
23.2 Structures ............................................................................................ 179
23.3 Limits and zones .................................................................................. 181
23.4 Access ................................................................................................. 182
24 King Edward Memorial Park Foreshore ..................................................... 183
24.1 Introduction .......................................................................................... 183
24.2 Structures ............................................................................................ 184
24.3 Limits and zones .................................................................................. 186
24.4 Access ................................................................................................. 188
25 Earl Pumping Station ................................................................................... 189
25.1 Introduction .......................................................................................... 189
25.2 Structures ............................................................................................ 189
25.3 Limits and zones .................................................................................. 191
25.4 Access ................................................................................................. 193
26 Deptford Church Street ............................................................................... 195
26.1 Introduction .......................................................................................... 195
26.2 Structures ............................................................................................ 195
26.3 Limits and zones .................................................................................. 197
26.4 Access ................................................................................................. 199
27 Greenwich Pumping Station ....................................................................... 201
27.1 Introduction .......................................................................................... 201
27.2 Structures ............................................................................................ 201
27.3 Limits and zones .................................................................................. 203
27.4 Access ................................................................................................. 205
28 Abbey Mills Pumping Station ...................................................................... 207
28.1 Introduction .......................................................................................... 207
Engineering design statement iv
28.2 Structures ............................................................................................ 207
28.3 Limits and zones .................................................................................. 208
28.4 Access ................................................................................................. 209
29 Beckton Sewage Treatment Works ............................................................ 211
29.1 Introduction .......................................................................................... 211
29.2 Structures ............................................................................................ 211
29.3 Limits and zones .................................................................................. 213
29.4 Access ................................................................................................. 214
30 Bekesbourne Street ..................................................................................... 215
30.1 Introduction .......................................................................................... 215
30.2 Structures ............................................................................................ 215
30.3 Limits and zones .................................................................................. 216
30.4 Access ................................................................................................. 217
Abbreviations ........................................................................................................ 219
Glossary ................................................................................................................ 221
Appendix A: Time distance diagrams ................................................................ 233
List of figures
Page number
Figure 2.1 Proposed sites and tunnels ..................................................................... 11
Figure 3.1 CSOs to be controlled by the project ....................................................... 19
Figure 3.2 Isometric view of a typical CSO interception arrangement ...................... 24
Figure 3.3 Permanent scour protection at toe of river walls ...................................... 50
Figure 3.4 Tunnel section showing limits of deviation ............................................... 52
Figure 6.1 Cutterhead and front of the Slurry TBM used to construct the Lee Tunnel ................................................................................................................. 73
Figure 6.2 Shield and first back-up trailer of the Slurry TBM used to construct the Lee Tunnel ...................................................................................................... 74
Figure 6.3 Horizontal alignment from Acton Storm Tanks to Carnwath Road Riverside ................................................................................................................. 76
Figure 6.4 Horizontal alignment from Carnwath Road Riverside to Kirtling Street .... 77
Figure 6.5 Horizontal alignment from Kirtling Street to Chambers Wharf ................. 78
Figure 6.6 Horizontal alignment from Chambers Wharf to Abbey Mills Pumping Station ..................................................................................................... 79
Engineering design statement v
List of tables
Page number
Table 2.1 Summary of sites ...................................................................................... 12
Table 2.2 Summary of tunnels .................................................................................. 15
Table 3.1 Methods of CSO flow control .................................................................... 20
Table 3.2 Typical year CSO performance and design flow rates .............................. 29
Table 3.3 Air management flow rates and ventilation column sizes ......................... 36
Table 3.4 Geology of the London Basin ................................................................... 40
Table 3.5 Chalk aquifer groundwater levels in 2008 east of Tower Bridge ............... 44
Table 3.6 Horizontal limits of deviation ..................................................................... 52
Table 4.1 Assumed shaft construction rates ............................................................. 64
Table 4.2 Assumed main tunnel drive rates.............................................................. 65
Table 4.3 Assumed long connection tunnel drive rates ............................................ 65
Table 4.4 Assumed tunnel secondary lining rates .................................................... 65
Table 6.1 Connection tunnels ................................................................................... 80
Engineering design statement vi
1 Executive summary
1 Executive summary 1.1.1 The purpose of this report is to describe the engineering components of
the Thames Tideway Tunnel project and set out the factors that influenced the size, arrangement and level of detail of the components. This report should be read in conjunction with the drawings in the Book of Plans, which accompanies the application.
1.1.2 The first part of the report describes the engineering considerations that were taken into account during the design development process and the second part sets out the results of the application of these considerations to each tunnel and site.
1.1.3 The first part sets out: a. London’s sewerage overflow problem, the proposed solution and its
design life b. the following engineering considerations:
i CSO control ii storage and transfer of CSO discharges iii hydraulics iv air management v operation and maintenance vi ground conditions vii structure sizing viii technical standards
c. programme assumptions d. flexibility of design and construction assumptions
1.1.4 The second part comprises: a. a section in relation to tunnels that includes:
i the guiding principles for tunnel alignments ii a description of each section of the main tunnel iii a description of each connection tunnel
b. a section in relation to each site that includes: i structure, sizing and layout ii limits and zones iii access requirements
Engineering design statement 1
1 Executive summary
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Engineering design statement 2
2 Background
2 Background
2.1 Purpose of this report 2.1.1 The purpose of this report is to describe the engineering components of
the Thames Tideway Tunnel project (the ‘project’) and set out the factors that influenced the size, arrangement and level of detail of the components. This report should be read in conjunction with the drawings in the Book of Plans, which accompanies the application.
2.1.2 This report addresses both the proposed above-ground and below-ground structures. Further information on factors that influenced the architectural and landscape design of the above-ground structures is provided in the Design and Access Statement, which accompanies the application.
2.1.3 The dimensions, levels, areas and volumes provided in this report are approximate.
2.2 Need for the project 2.2.1 London’s sewer system was designed in the 1800s to handle wastewater
and rainwater (combined sewage) through a combined collecting system. Combined sewer overflows (CSOs) were incorporated into the sewer system as relief structures to prevent flooding caused by sewer overloading, especially during periods of heavy rainfall. Currently, discharges into the tidal Thames occur more than 50 times in a typical year at the most frequently overflowing CSOs in the Beckton and Crossness catchments, to the north and south of the river respectively. An estimated 39 million m3 of combined sewage enters the river in a typical year from these catchments.
2.2.2 The Environment Agency assessed the CSO discharges from the Beckton and Crossness catchments. It considered the volume and frequency of the different discharges and assessed their impact on river water quality and ecology. The CSOs were then categorised and a total of 36 CSOs were identified as ‘unsatisfactory’ and requiring attention. 34 of the unsatisfactory CSOs discharge into the tidal Thames and two into the River Lee.
2.2.3 The project, when connected to the Lee Tunnel, would comprise a full-length tunnel to store and transfer discharges from CSOs from west to east London to Beckton Sewage Treatment Works (STW) for treatment. The primary objective of the project is to control discharges from CSOs in order to meet the requirements of the European Union Urban Waste Water Treatment Directive (91/271/EEC) (UWWTD) and the related United Kingdom (UK) Urban Waste Water Treatment Regulations.
2.2.4 The UWWTD concerns the collection, treatment and discharge of urban wastewater and the treatment and discharge of wastewater from certain industrial sectors. The objective of the Directive is to protect the environment from the “adverse effects of the above-mentioned waste
Engineering design statement 3
2 Background
water discharges”. The Urban Waste Water Treatment Regulations 1994 (SI1994/2841) transpose this Directive into English law.
2.2.5 Other European Union and UK legislation also forms part of the legal framework within which the project is to be designed and delivered. The Water Framework Directive, and the regulations which transpose it within the UK, set out various ‘environmental objectives’ relating to surface water quality to be achieved by 2015, 2021 and 2027. In order to achieve these objectives in the UK, the Environment Agency is responsible for producing river basin management plans. The River Basin Management Plan for the River Thames, published in December 2009, states that the London Tideway Tunnels (ie the Thames Tideway Tunnel and the Lee Tunnel); “represent the primary measures to address point source pollution from the sewer system and are fundamental to the achievement of good status in this [Estuaries and Coastal Waters] catchment”.
2.2.6 More detail on the need for the project is provided in the Needs Report, (supporting document) and updated in the Planning Statement, which accompanies the application.
2.2.7 The National Policy Statement for Waste Water (the ‘NPS’) (designated on 26 March 2012) sets out government policy for the provision of major wastewater infrastructure of national significance. The NPS confirms the need for the “Thames Tunnel”1 project, which is considered crucial in order to meet the Government’s obligations under the UWWTD. It also confirms that the project is the preferred solution to meet this identified need.
2.3 Solution 2.3.1 The Thames Tideway Strategic Study (supporting document) was set up
in 2001 and reported in February and November 2005. Specific environmental objectives in relation to combined sewage discharges were developed by the Thames Tideway Strategic Study needed to be addressed by the project in order to reduce: a. the adverse environmental impacts on river ecosystems and fish
species in particular b. unacceptable aesthetic issues c. the elevated health risks for recreational users of the tidal Thames.
2.3.2 The Thames Tideway Strategic Study established that these environmental objectives can only be met at least cost by completing both quality improvements to the treatment works discharges and by constructing a storage2 tunnel to transfer flows from unsatisfactory CSOs for treatment.
2.3.3 Ian Pearson, the then Minister of State for Climate Change and the Environment, in a letter to the Chief Executive Officer of Thames Water dated 17 April 2007, stated that his view was that: “a full-length storage
1 The name of the project changed from Thames Tunnel to Thames Tideway Tunnel in July 2012 2 It should be noted that wastewater is only stored in the tunnel for a temporary period until it can be pumped out at Beckton STW
Engineering design statement 4
2 Background
tunnel with additional secondary treatment at Beckton sewage treatment works – is needed. This is both to provide London with a river fit for the 21st century, and for the UK to comply with the requirements of the UWWTD concerning provision of collecting systems and, in particular, limitation of pollution from storm water overflows.”
2.3.4 Mr Pearson subsequently requested that Thames Water “make provision for the design, construction, and maintenance of a scheme for the collecting systems connected to Beckton and Crossness sewage treatment works which involves a full-length storage tunnel with additional secondary treatment at Beckton sewage treatment works”.
2.3.5 This solution is reviewed in the Needs Report in the context of modelling, alternative solutions, and solutions used elsewhere in Europe.
2.3.6 Thames Water maintains a numerical hydraulic model that represents the sewer system for the Beckton and Crossness catchments. This model continued to be developed since 2006. As part of the model development work, a programme of flow monitoring of the system was implemented, including monitoring at CSO locations. In parallel with the hydraulic model, a water quality model of the Thames Estuary from Teddington weir to Southend was developed to enable the Environment Agency to understand the impacts of discharges from sewage treatment works and CSOs on water quality. The catchment model was used to test the impacts of variations on a tunnel solution and various options, such as retrofitting green infrastructure and separating sewers. Climate change projections were also taken into account. The models demonstrated that the ‘do nothing’ option is unacceptable. The modelling also confirmed that the construction of the full-length storage tunnel is necessary to achieve the required reduction in the frequency and volume of CSO discharges.
2.3.7 Alternative technologies were explored such as source control (methods of managing and reducing rainwater (storm water) run-off at site level), sewer separation (separating storm water and foul water networks), partial separation, dispersed storage units (capturing storm water and controlling the outflow), CSO screening and Sustainable Drainage Systems (SuDS) (techniques employing ponds, swales, green roofs, detention ponds and permeable surfaces). None of these options were considered to be suitable, cost-effective solutions that could achieve compliance with the UWWTD, nor assist in meeting the Water Framework Directive objective to attain good ecological potential in the tidal Thames, within the same time frame as the full-length storage tunnel solution.
2.3.8 A review of solutions used elsewhere in Europe established that most major cities in the European Union have had or are having to address the issue of CSO discharges from their sewer networks. A review of the approaches to UWWTD compliance in relation to CSOs by certain major and many smaller cities across the European Union demonstrated that the most common approach to resolving CSO issues was to create extra capacity by constructing detention tanks and/or trunk or interceptor sewers. Cities such as Helsinki, Naples, Stockholm and Vienna already use tunnels to resolve their CSO issues. Paris, like London, is in the process of developing a tunnelled storage and conveyance system.
Engineering design statement 5
2 Background 2.3.9 The full-length storage and transfer tunnel solution achieves compliance
with the UWWTD and also provides benefits in terms of improved river water quality, aesthetics, health of recreational users and the sustainability of the aquatic environment in the tidal Thames. It is the most cost-effective solution, which would be the least disruptive to residents, businesses and transportation compared to alternatives. It also has the shortest implementation time.
2.4 Design life 2.4.1 The design life for the project is 120 years. Therefore the project would
need to be resilient to change. Changes that will affect flows in the system will occur in both the population and the climate. The project’s resilience to change is addressed in the Resilience to Change report, which accompanies the application.
2.4.2 The Resilience to Change report demonstrates that population growth will reduce the spare capacity in London’s sewers. It also demonstrates that climate change will impact on rainfall over the catchments and increase the tidal Thames’s sensitivity to residual CSO discharges as a result of predicted changes in river parameters such as temperature and fresh water flow.
2.4.3 In the project’s base condition, sewage treatment works upgrades and the Lee Tunnel (in operation without the Thames Tideway Tunnel), the total volume of CSO discharges in a typical year would be 17.6 million m3 and some unsatisfactory CSOs would discharge into the river over 50 times. When the Thames Tideway Tunnel project is in operation, the total discharge volume would reduce to 2.4 million m3 and the maximum number of residual discharge events from the controlled CSOs would reduce to four in a typical year. When the median climate change scenario is applied, along with the projected population growth in the catchments, the total discharge volume in the 2080s would increase to 3.5 million m3 and the maximum number of CSO events from controlled CSOs would increase to five in a typical year.
2.4.4 Changes in temperature will affect the future quality of river water in the tidal Thames; summer river water temperatures are predicted to increase by 2.5 to 3.0oC in the 2080s. This change will take place within the context of a much-reduced frequency of CSO discharges due to the operation of the project infrastructure. However, because of the increased temperature and reduced freshwater flow, when residual CSO discharges do occur, there is an increased risk of failure of the current dissolved oxygen standards. Such failures of the standards may require future system adaptations.
2.4.5 Modifications to the project would not handle the chronic nature of diminished river water quality due to climate change in the future. More appropriate adaptations that could be implemented in the future are set out in the Resilience to Change report. These adaptations include further improvements to the sewage treatment works and the catchment-wide implementation of SuDS. Although this is not a feasible response to deal
Engineering design statement 6
2 Background
with CSO discharges now or in the future, it could, however, augment the CSO control achieved by the project and mitigate climate change.
2.4.6 The Resilience to Change report concluded that the project would continue to provide its essential contribution to achieving the necessary CSO control and improvement in river water quality in the tidal Thames for its entire design life. Prudent adaptations to the sewer system could be implemented in the future to maintain the significantly improved river water quality conditions created by the project, but climate change and population projections do not require changes to the current design.
2.4.7 The project, or components of the project, may last for more than 120 years; however, this duration is the objective for the project’s functional life, assuming that adequate regular inspection and maintenance is carried out. Adequate maintenance includes inspection, preventative maintenance and normal repair and replacement of ancillary parts in accordance with industry standards, facility operations and maintenance manuals. The design life of the major civil engineering components is 120 years.
2.4.8 It is not practical for mechanical, electrical, instrumentation, control and automation (MEICA) plant to be designed to last for 120 years. Therefore the design life for these elements is defined as follows: a. 60 years for interception mechanical gates b. 20 years for other mechanical and electrical plant c. ten years for analytical and process instruments d. seven years for control and instrumentation systems.
2.4.9 The Environment Agency established the Thames Estuary 2100 project with the aim of developing a long-term flood risk management plan for London and the Thames Estuary. The plan suggests that the height of the tidal Thames flood defences could be raised in the future. This was taken into account as the ability to raise river walls or flood defences at a later date was incorporated into the designs for the relevant sites.
2.5 Proposed development 2.5.1 The project would comprise the following elements:
a. a main tunnel from Acton Storm Tanks to Abbey Mills Pumping Station, which would require five main tunnel sites (one of which would also intercept one CSO)
b. two long connection tunnels (the Frogmore connection tunnel and the Greenwich connect tunnel) and nine short connection tunnels
c. control of 18 CSOs by diverting intercepted flows into the main tunnel, which would require 16 CSO sites
d. control of two CSOs by locally modifying the sewerage system, which would require two system modification sites
e. works to drain down the tunnel system at Beckton Sewage Treatment Works.
Engineering design statement 7
2 Background 2.5.2 The Thames Tideway Tunnel’s main tunnel would connect to the Lee
Tunnel at Abbey Mills Pumping Station. The Lee Tunnel receives flow from the Abbey Mills Pumping Station CSO and connects Abbey Mills Pumping Station to Beckton Sewage Treatment Works. All flows entering the both tunnels would be transferred to Beckton Sewage Treatment Works via the Lee Tunnel.
Sites 2.5.3 The five main tunnel sites would accommodate shaft and tunnel
construction activities, which would vary depending on the types of activity, as follows: a. Main tunnel drive sites would be used to assemble and then drive the
tunnel boring machine (TBM). They would therefore deal with the material excavated from, and primary lining of, the main tunnel. They would also provide access for secondary lining.
b. Main tunnel reception sites would be used to remove the TBM from the tunnel at the end of a drive. They would also provide access for secondary lining.
2.5.4 The 16 CSO sites would be required to construct the CSO interception structures.
2.5.5 The two system modification sites would be required to construct the alterations to the existing sewerage system to control CSO flows by means other than interception.
2.5.6 Works associated with the project would be required at Beckton Sewage Treatment Works to: a. extend the pumping capacity by installing two new pumps in the
Tideway Pumping Station and pipeline works to transfer flows from the Tideway Pumping Station to the inlet works
b. install additional mechanical and electrical equipment at the inlet works
c. construct two shafts and a siphon tunnel to transfer tunnel overflows to the Lee Tunnel overflow shaft.
2.5.7 The main tunnel sites and CSO sites were selected in accordance with the Site selection methodology paper (refer to Volume 2 of the Final Report on Site Selection Process, which accompanies the application). The sites are illustrated in Figure 2.1 and summarised in Table 2.1. For information on how these sites were selected, refer to the Final Report on Site Selection Process.
2.5.8 The Site selection background technical paper (refer to Volume 2 of the Final Report on Site Selection Process) was prepared to support the Site selection methodology paper. It defines the site sizes for each of the site types including the CSO, main tunnel drive and main tunnel reception sites. The site sizes set out in this paper assume that the available land is reasonably flat, a regular, essentially rectangular shape, and has direct access from roads and (where appropriate) the River Thames. In practice most of the selected sites do not meet these criteria and therefore the
Engineering design statement 8
2 Background
actual areas required would depend on many factors including shape, topography and connectivity.
2.5.9 The site layouts provided in the Book of Plans were developed by following these general steps: a. identify sites in accordance with the Site selection methodology paper b. collate records and data on existing site features, topography, CSOs
and other utilities c. size structures to satisfy hydraulic, pneumatic, structural and other
design criteria d. identify design options for CSO interception, shaft location and tunnel
alignment e. consider the land areas required for temporary works, as defined in
the Site selection background technical paper, and the most appropriate means of safe access to the roads and the River Thames (where appropriate)
f. identify and minimise or mitigate project and health and safety risks g. determine the preferred design option and optimise to minimise
temporary and permanent land requirements h. define the site parameters and limits of land to be acquired or used
(LLAU). 2.5.10 The areas inside the LLAU at each site vary in order to accommodate the
specific use and arrangement of each site within their land constraints. Further information in relation to each site is provided in Sections 7 to 30 below. Where a site is identified in Table 2.1 as a foreshore site, eg, Putney Embankment Foreshore, the drop shaft and other essential structures would be located on the riverward side of the existing river walls.
Tunnels 2.5.11 The main tunnel would be constructed from five sites and require four
TBMs (including Earth Pressure Balance (EPB) TBMs and Slurry TBMs). 2.5.12 The 16 CSO sites would connect flows from 18 CSOs to the main tunnel in
three ways: a. via long connection tunnels that would connect to the main tunnel via
a shaft (two long connection tunnels would control five CSOs) b. via short connection tunnels that would connect directly to the main
tunnel (nine short connection tunnels would control 11 CSOs) c. via drop shafts connected directly to the main tunnel, which would
require no connection tunnel (two CSOs). 2.5.13 The long connection tunnels would be long enough to be driven by TBMs. 2.5.14 The construction method for the short connection tunnels would depend
on the ground conditions and the selected contractor’s preference. It is anticipated that the methods would include sprayed concrete linings, pipe
Engineering design statement 9
2 Background
jacking and TBMs. The short connection tunnels would be driven from CSO drop shafts. The connections to the main tunnel would be undertaken after the main tunnel has been constructed at that point.
2.5.15 A siphon tunnel would be required as part of the works at Beckton sewage treatment works, which would be long enough to be driven by TBMs.
2.5.16 The tunnels are illustrated in Figure 2.1 and summarised in Table 2.2.
Engineering design statement 10
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eptio
n an
d sh
ort c
onne
ctio
n tu
nnel
driv
e si
te
6 28
,000
Lond
on B
orou
gh o
f W
ands
wor
th
CS
O s
ite
Dor
may
Stre
et
CS
O in
terc
eptio
n an
d lo
ng c
onne
ctio
n tu
nnel
driv
e si
te to
Kin
g G
eorg
e’s
Par
k an
d to
Car
nwat
h R
oad
Riv
ersi
de
12
10,0
00
Lond
on B
orou
gh o
f W
ands
wor
th
CS
O s
ite
Kin
g G
eorg
e’s
Par
k C
SO
inte
rcep
tion
and
conn
ectio
n tu
nnel
rece
ptio
n si
te
9 4,
100
Lond
on B
orou
gh o
f H
amm
ersm
ith a
nd
Fulh
am
mai
n tu
nnel
si
te
Car
nwat
h R
oad
Riv
ersi
de
Mai
n tu
nnel
sin
gle
driv
e si
te to
Act
on
Sto
rm T
anks
, sin
gle
rece
ptio
n si
te fr
om
Kirt
ling
Stre
et, a
nd lo
ng c
onne
ctio
n tu
nnel
rece
ptio
n si
te fr
om D
orm
ay
Stre
et
25
36,1
00
Eng
inee
ring
desi
gn s
tate
men
t 12
2 B
ackg
roun
d
Loca
l aut
horit
y Si
te ty
pe
Site
nam
e Si
te u
ses
Inte
rnal
sha
ft di
amet
er (m
) A
rea
insi
de
the
LLA
U
(m2 )
Lond
on B
orou
gh o
f W
ands
wor
th
CS
O s
ite
Falc
onbr
ook
Pum
ping
S
tatio
n
CS
O in
terc
eptio
n an
d sh
ort c
onne
ctio
n tu
nnel
driv
e si
te
9 5,
300
Roy
al B
orou
gh o
f K
ensi
ngto
n an
d C
hels
ea
CS
O s
ite
Cre
mor
ne
Wha
rf D
epot
C
SO
inte
rcep
tion
and
shor
t con
nect
ion
tunn
el d
rive
site
8
6,30
0
Roy
al B
orou
gh o
f K
ensi
ngto
n an
d C
hels
ea
CS
O s
ite
Che
lsea
E
mba
nkm
ent
Fore
shor
e
CS
O in
terc
eptio
n an
d sh
ort c
onne
ctio
n tu
nnel
driv
e si
te
12
24,8
00
Lond
on B
orou
gh o
f W
ands
wor
th
mai
n tu
nnel
si
te
Kirt
ling
Stre
et
Mai
n tu
nnel
dou
ble
driv
e si
te to
C
arnw
ath
Roa
d R
iver
side
and
to
Cha
mbe
rs W
harf
30
52,2
00
Lond
on B
orou
gh o
f W
ands
wor
th
CS
O s
ite
Hea
thw
all
Pum
ping
S
tatio
n
CS
O in
terc
eptio
n an
d sh
ort c
onne
ctio
n tu
nnel
driv
e si
te
16
12,7
00
Lond
on B
orou
gh o
f La
mbe
th
CS
O s
ite
Alb
ert
Em
bank
men
t Fo
resh
ore
CS
O in
terc
eptio
n an
d sh
ort c
onne
ctio
n tu
nnel
driv
e si
te
16
31,0
00
City
of W
estm
inst
er
CS
O s
ite
Vic
toria
E
mba
nkm
ent
Fore
shor
e
CS
O in
terc
eptio
n an
d sh
ort c
onne
ctio
n tu
nnel
driv
e si
te
13
15,5
00
Eng
inee
ring
desi
gn s
tate
men
t 13
2 B
ackg
roun
d
Loca
l aut
horit
y Si
te ty
pe
Site
nam
e Si
te u
ses
Inte
rnal
sha
ft di
amet
er (m
) A
rea
insi
de
the
LLA
U
(m2 )
City
of L
ondo
n C
SO
site
B
lack
friar
s B
ridge
Fo
resh
ore
CS
O in
terc
eptio
n si
te –
dro
p sh
aft o
n lin
e of
the
mai
n tu
nnel
24
38
,800
Lond
on B
orou
gh o
f S
outh
war
k sy
stem
m
odifi
catio
n si
te
Sha
d Th
ames
P
umpi
ng
Sta
tion
Sys
tem
mod
ifica
tion
site
to c
ontro
l the
C
SO
N
/A
2,30
0
Lond
on B
orou
gh o
f S
outh
war
k m
ain
tunn
el
site
C
ham
bers
W
harf
Mai
n tu
nnel
sin
gle
driv
e si
te to
Abb
ey
Mills
Pum
ping
Sta
tion,
sin
gle
rece
ptio
n si
te fr
om K
irtlin
g S
treet
, and
long
co
nnec
tion
tunn
el re
cept
ion
site
from
G
reen
wic
h P
umpi
ng S
tatio
n
25
28,2
00
Lond
on B
orou
gh o
f To
wer
Ham
lets
C
SO
site
K
ing
Edw
ard
Mem
oria
l Par
k Fo
resh
ore
CS
O in
terc
eptio
n si
te –
dro
p sh
aft o
n lin
e of
the
mai
n tu
nnel
20
20
,100
Lond
on B
orou
gh o
f Le
wis
ham
C
SO
site
E
arl P
umpi
ng
Sta
tion
CS
O in
terc
eptio
n si
te –
dro
p sh
aft o
n lin
e of
long
con
nect
ion
tunn
el
17
6,00
0
Lond
on B
orou
gh o
f Le
wis
ham
C
SO
site
D
eptfo
rd
Chu
rch
Stre
et
CS
O in
terc
eptio
n si
te –
dro
p sh
aft o
n lin
e of
long
con
nect
ion
tunn
el
17
12,5
00
Roy
al B
orou
gh o
f G
reen
wic
h C
SO
site
G
reen
wic
h P
umpi
ng
Sta
tion
CS
O in
terc
eptio
n an
d lo
ng c
onne
ctio
n tu
nnel
driv
e si
te to
Cha
mbe
rs W
harf
17
24,4
00
Eng
inee
ring
desi
gn s
tate
men
t 14
2 B
ackg
roun
d
Loca
l aut
horit
y Si
te ty
pe
Site
nam
e Si
te u
ses
Inte
rnal
sha
ft di
amet
er (m
) A
rea
insi
de
the
LLA
U
(m2 )
Lond
on B
orou
gh o
f N
ewha
m
mai
n tu
nnel
si
te
Abb
ey M
ills
Pum
ping
S
tatio
n
Mai
n tu
nnel
sin
gle
rece
ptio
n si
te. A
sh
ort l
engt
h of
spr
ayed
con
cret
e lin
ed
mai
n tu
nnel
wou
ld b
e co
nstru
cted
at
this
site
from
the
Tham
es T
idew
ay
Tunn
el s
haft
to th
e Le
e Tu
nnel
sha
ft
20
37,3
00
Lond
on B
orou
gh o
f N
ewha
m
n/a
Bec
kton
S
ewag
e Tr
eatm
ent
Wor
ks
Tran
sfer
flow
s fo
r tre
atm
ent.
Tunn
el
driv
e an
d re
cept
ion
shaf
ts.
9 (in
let s
haft)
7
(out
let s
haft)
15
9,10
0
Lond
on B
orou
gh o
f To
wer
Ham
lets
sy
stem
m
odifi
catio
n si
te
Bek
esbo
urne
S
treet
S
yste
m m
odifi
catio
n si
te to
con
trol t
he
CS
O
N/A
1,
200
Tabl
e 2.
2 Su
mm
ary
of tu
nnel
s
Tunn
el
From
To
Le
ngth
(m
) In
tern
al
diam
eter
(m
)
Ass
umed
co
nstr
uctio
n m
etho
d M
ain
grou
nd
type
Mai
n tu
nnel
C
arnw
ath
Roa
d R
iver
side
A
cton
Sto
rm T
anks
6,
950
6.5
EP
B T
BM
Lo
ndon
Cla
y
Mai
n tu
nnel
K
irtlin
g S
treet
C
arnw
ath
Roa
d R
iver
side
5,
000
7.2
EP
B T
BM
Lo
ndon
Cla
y,
Lam
beth
Gro
up
Eng
inee
ring
desi
gn s
tate
men
t 15
2 B
ackg
roun
d
Tunn
el
From
To
Le
ngth
(m
) In
tern
al
diam
eter
(m
)
Ass
umed
co
nstr
uctio
n m
etho
d M
ain
grou
nd
type
Mai
n tu
nnel
K
irtlin
g S
treet
C
ham
bers
Wha
rf 7,
670
7.2
EP
B T
BM
Lo
ndon
Cla
y,
Lam
beth
Gro
up,
Than
et S
ands
, C
halk
Mai
n tu
nnel
C
ham
bers
Wha
rf A
bbey
Mills
Pum
ping
S
tatio
n 5,
520
7.2
Slu
rry T
BM
C
halk
Mai
n tu
nnel
A
bbey
Mills
Pum
ping
S
tatio
n m
ain
tunn
el s
haft
Lee
Tunn
el S
haft
F 60
7.
2 S
CL
Cha
lk
Leng
th o
f mai
n tu
nnel
25
,200
Frog
mor
e co
nnec
tion
tunn
el
Dor
may
Stre
et
Kin
g G
eorg
e’s
Par
k 51
0 2.
6 to
3.0
E
PB
TB
M o
r op
en s
hiel
d Lo
ndon
Cla
y
Frog
mor
e co
nnec
tion
tunn
el
Dor
may
Stre
et
Car
nwat
h R
oad
Riv
ersi
de
610
2.6
to 3
.0
EP
B T
BM
or
open
shi
eld
Lond
on C
lay
Leng
th o
f Fro
gmor
e co
nnec
tion
tunn
el
1,12
0
Gre
enw
ich
conn
ectio
n tu
nnel
G
reen
wic
h P
umpi
ng
Sta
tion
Cha
mbe
rs W
harf
4,61
0 5.
0 S
lurry
TB
M
Cha
lk
Leng
th o
f Fro
gmor
e an
d G
reen
wic
h co
nnec
tion
tunn
els
5,73
0
Ham
mer
smith
sh
ort c
onne
ctio
n tu
nnel
Ham
mer
smith
Pum
ping
S
tatio
n M
ain
tunn
el
300
4.0
SC
L or
TB
M
Lond
on C
lay
Eng
inee
ring
desi
gn s
tate
men
t 16
2 B
ackg
roun
d
Tunn
el
From
To
Le
ngth
(m
) In
tern
al
diam
eter
(m
)
Ass
umed
co
nstr
uctio
n m
etho
d M
ain
grou
nd
type
Wes
t Put
ney
shor
t con
nect
ion
tunn
el
Bar
n E
lms
Mai
n tu
nnel
22
0 2.
2 S
CL
or T
BM
Lo
ndon
Cla
y
Put
ney
Brid
ge
shor
t con
nect
ion
tunn
el
Put
ney
Em
bank
men
t Fo
resh
ore
Mai
n tu
nnel
50
2.
2 S
CL
Lond
on C
lay
Falc
onbr
ook
shor
t con
nect
ion
tunn
el
Falc
onbr
ook
Pum
ping
S
tatio
n M
ain
tunn
el
260
3.2
SC
L or
TB
M
Lond
on C
lay
Lots
Roa
d sh
ort
conn
ectio
n tu
nnel
C
rem
orne
Wha
rf D
epot
M
ain
tunn
el
190
3.0
SC
L or
TB
M
Lond
on C
lay
Ran
elag
h co
nnec
tion
tunn
el
Che
lsea
Em
bank
men
t Fo
resh
ore
Mai
n tu
nnel
70
4.
0 S
CL
Lond
on C
lay
Hea
thw
all
conn
ectio
n tu
nnel
H
eath
wal
l Pum
ping
S
tatio
n M
ain
tunn
el
60
4.0
SC
L La
mbe
th G
roup
Cla
pham
/Brix
ton
conn
ectio
n tu
nnel
A
lber
t Em
bank
men
t Fo
resh
ore
Mai
n tu
nnel
20
3.
0 S
CL
Lam
beth
Gro
up
Reg
ent S
treet
co
nnec
tion
tunn
el
Vic
toria
Em
bank
men
t Fo
resh
ore
Mai
n tu
nnel
30
3.
0 S
CL
Lam
beth
Gro
up
Leng
th o
f sho
rt c
onne
ctio
n tu
nnel
s 1,
200
Bec
kton
sip
hon
tunn
el
Inle
t sha
ft O
utle
t sha
ft 73
0 2.
8 E
PB
TB
M
Lam
beth
Gro
up
Eng
inee
ring
desi
gn s
tate
men
t 17
2 B
ackg
roun
d
This
pag
e is
inte
ntio
nally
left
blan
k
Eng
inee
ring
desi
gn s
tate
men
t 18
3 Engineering considerations
3 Engineering considerations
3.1 Introduction 3.1.1 This section sets out the engineering design considerations associated
with the following: a. CSO control b. storage and transfer of CSO discharges c. hydraulics d. air management e. operation and maintenance f. ground conditions g. structure sizing h. technical standards.
3.2 CSO control
Method of flow control 3.2.1 The Environment Agency evaluated 57 CSOs and identified 36 of them as
unsatisfactory; 34 of the unsatisfactory CSOs would be controlled by the project, one by the Lee Tunnel, and one by a separate project at Wick Lane. Figure 3.1illustrates the 34 CSOs to be controlled by the project.
Figure 3.1 CSOs to be controlled by the project
3.2.2 During and following storm events, sewage and rainwater run-off mix
within the combined sewers. When the capacity of the sewerage system is exceeded, the flows discharge into the tidal Thames via CSOs to avoid flow backing up into houses and businesses. The project’s interception works would comprise structures to divert flows into the tunnel system (ie, the main tunnel and the network of connection tunnels that link it to the
Engineering design statement 19
3 Engineering considerations
CSO interception structures) where they would be stored and transferred to Beckton STW for treatment. The CSO outfalls would be retained to enable discharges to the tidal Thames when the tunnel system reaches capacity.
3.2.3 Design development work determined that not all of the 34 CSOs would require individual CSO interception works to be adequately controlled. It would be possible to use existing sewers and pumping station operation modifications to control the overflows of some CSOs. This has the advantage of reducing the number of worksites required. The 34 CSOs would be controlled by the following methods, which are summarised in Table 3.1: a. Method A: 15 CSOs would be controlled by diverting their flows into
the main tunnel. Each of these CSOs requires a worksite. b. Method B: Three other CSOs would also be controlled by diverting
their flows into the main tunnel adjacent to a local connection to the existing northern Low Level Sewer No.1 to divert some of its flow into the main tunnel.
c. Method C: Ten other CSOs would be controlled due to the extra capacity in the northern Low Level Sewer No.1 created by Method B so no extra worksites would be required for these CSOs.
d. Method D: Five other CSOs would be controlled by means of modifications to the operation of the existing sewerage system, including adjustments to existing pumping stations and local in-sewer modifications, in order to store and transfer flows to the sewage treatment works via the existing sewer system. Only two CSOs would require worksites.
e. Method E: Local in-sewer modification works already carried out (not as part of the project) control the flows of one CSO.
Table 3.1 Methods of CSO flow control
CSO Method of flow control Site Acton Storm Relief Method A: interception Main tunnel site: Acton
Storm Tanks
Stamford Brook Storm Relief
Method D: control measures at other CSOs would indirectly control this CSO
No site required
North West Storm Relief Method D: control measures at Hammersmith Pumping Station would indirectly control this CSO
No site required
Hammersmith Pumping Station
Method A: interception and pumping station operation changes
CSO site: Hammersmith Pumping Station
West Putney Storm Relief
Method A: interception CSO site: Barn Elms
Engineering design statement 20
3 Engineering considerations
CSO Method of flow control Site Putney Bridge Method A: interception CSO site: Putney
Embankment Foreshore
Frogmore Storm Relief – Bell Lane Creek Frogmore Storm Relief – Buckhold Road
Method A: interception CSO site: Dormay Street
CSO site: King George’s Park
Jews Row – Wandle Valley Storm Relief Jews Row – Falconbrook Storm Relief
Method E: CSO is controlled by modifications already in place
No site required
Falconbrook Pumping Station
Method A: interception and pumping station operation changes
CSO site: Falconbrook Pumping Station
Lots Road Pumping Station
Method A: interception CSO site: Cremorne Wharf Depot
Church Street Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Queen Street Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Smith Street – Main Line Smith Street – Storm Relief
Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Ranelagh Method B: interception and connection to the northern Low Level Sewer No.1
CSO site: Chelsea Embankment Foreshore
Western Pumping Station
Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs and possible pumping station operation changes
No site required
Heathwall Pumping Station
Method A: interception CSO site: Heathwall Pumping Station
South West Storm Relief Method A: interception
Engineering design statement 21
3 Engineering considerations
CSO Method of flow control Site Kings Scholars Pond Method C: controlled
indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Clapham Storm Relief Method A: interception CSO site: Albert Embankment Foreshore Brixton Storm Relief Method A: interception
Grosvenor Ditch Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Regent Street Method B: interception via connection to the northern Low Level Sewer No.1
CSO site: Victoria Embankment Foreshore
Northumberland Street Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Savoy Street Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Norfolk Street Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Essex Street Method C: controlled indirectly by connection relief works on the northern Low Level Sewer No.1 at other CSOs
No site required
Fleet Main Method B: interception and connection to the northern Low Level Sewer No.1
CSO site: Blackfriars Bridge Foreshore
Shad Thames Pumping Station
Method D: pumping station modifications
System modification site: Shad Thames Pumping Station
Engineering design statement 22
3 Engineering considerations
CSO Method of flow control Site North East Storm Relief Method A: interception CSO site: King Edward
Memorial Park Foreshore
Holloway Storm Relief Method D: local is-sewer modifications
System modification site: Bekesbourne Street
Earl Pumping Station Method A: interception CSO site: Earl Pumping Station
Deptford Storm Relief Method A: interception CSO site: Deptford Church Street
Greenwich Pumping Station
Method A: interception and pumping station operation changes
CSO site: Greenwich Pumping Station
Charlton Storm Relief Method D: control measures at Greenwich Pumping Station and improvements at Crossness STW would indirectly control this CSO
No site required
Engineering design statement 23
3 Engineering considerations
Components 3.2.4 The objectives for intercepting flows at the relevant CSOs include:
a. redirect and control flows from the combined sewer b. transfer flows from the combined sewer into the main tunnel c. retain the existing river outfall, or construct new outfalls for when the
tunnel system is full, to direct residual flows into the tidal Thames. CSO sites
3.2.5 The typical components of CSO interception works are illustrated in Figure 3.2. Figure 3.2 Isometric view of a typical CSO interception arrangement
a. Interception chamber: this chamber would intercept flows en route to
the outfall and transfer them to the main tunnel. When the tunnel system is full, the chamber would revert to existing conditions and allow flows to discharge into the river.
b. Valve chambers: flow control equipment and penstocks would be incorporated into the interception chamber where practicable, but may need to be housed in separate valve chambers.
c. Ventilation structures: when the tunnel system fills with flows, the air in the system would be displaced, and when the flow drains the air would need to return. The design also incorporates a means of refreshing the air within the system when it is empty. The air management system would involve a combination of air extraction structures, air intake structures, and air treatment equipment.
Engineering design statement 24
3 Engineering considerations
d. Electrical and control kiosk: the electrical or hydraulic components of the flow control equipment and air treatment plant would be housed in an electrical and control kiosk.
e. Connection culvert: the connection culvert would transfer flows from the interception chamber/valve chamber into a drop shaft. The culvert can comprise several sections, depending on the location of the valves and penstocks.
f. CSO drop shaft: the drop shaft would transfer flows vertically from the connection culvert to the connection tunnel/main tunnel via a vortex drop structure inside the drop shaft. The vortex drop structure would dissipate the energy created by the large drop height and de-aerate the flows at the bottom of the drop shaft.
g. Connection tunnel: the connection tunnel (if required) would transfer flows from the CSO drop shaft to the main tunnel via one of three basic arrangements: i Type A: a connection tunnel between a drop shaft and a shaft on
the main tunnel ii Type B: a connection tunnel between a drop shaft and the main
tunnel iii Type C: a connection tunnel between a drop shaft and another
drop shaft h. Connection tunnel are not required when the shaft located is on the
main tunnel (a main tunnel shaft or a CSO drop shaft). 3.2.6 At three CSO sites, additional works would be undertaken to connect to
the northern Low Level Sewer No.1 and divert some of its flow during rainfall events into the drop shaft and the main tunnel. This would avoid the need for worksites at ten other CSOs, whose flows would be handled by the capacity created in the northern Low Level Sewer No.1. These ten CSOs are located along the northern bank of the River Thames (Chelsea Embankment and Victoria Embankment). Intercepting them would entail significant additional works on or near the embankment and in the foreshore, of a similar scale to the works proposed at Victoria Embankment Foreshore. Therefore the connection to the northern Low Level Sewer No. 1 at three sites (where works were required anyway) would significantly reduce the project’s impact on the road network and the river environment. Main tunnel sites
3.2.7 For the five sites required to construct the main tunnel, typical components of would include: a. Main tunnel shaft: where flows enter the tunnel system at main tunnel
shafts these shafts would act as drop shafts; at other main tunnel shafts flows would pass through the bottom of the shaft.
b. Ventilation structures: the air management system would involve a combination of air extraction structures, air intake structures, and air treatment equipment.
Engineering design statement 25
3 Engineering considerations
c. Electrical and control kiosk: the electrical or hydraulic components of the air treatment plant would be housed in an electrical and control kiosk. Where CSO flows enter the tunnel system at main tunnel shafts, the electrical or hydraulic components of the flow control equipment would also be housed in an electrical and control kiosk.
System modification sites+ 3.2.8 Only two of the five CSOs that would be controlled by modifications to the
existing sewerage system rather than interception would require worksites: Shad Thames Pumping Station (Shad Thames Pumping Station CSO) and Bekesbourne Street (Holloway Storm Relief CSO).
3.3 Storage and transfer of flows 3.3.1 The flows would mainly pass into the tunnel system by gravity. However,
some interception works would be located downstream of existing pumping stations and therefore pumping of some flow would still be required.
3.3.2 Intercepting, storing and transferring flows in the tunnel system would be controlled and directed by mechanical equipment, such as hydraulic gates, valves or penstocks.
3.3.3 Flows would be stored in the tunnel system until they can be pumped to Beckton STW for treatment. The flows would move along the tunnel system by gravity, through the Lee Tunnel to the Tideway Pumping Station in Beckton STW. This pumping station, built as part of the Lee Tunnel project, would transfer the flows for treatment when capacity is available. It is large enough to ensure that the tunnel system can be emptied within 48 hours, to avoid flows becoming septic.
3.3.4 The size of the tunnel has a direct relationship with residual CSO discharges and compliance with the UWWTD. The Thames Tideway Strategic Study established that an internal diameter of 7.2m for the tunnel would provide a storage volume of approximately 1.6 million m3. This volume is sufficient capacity for flows resulting from localised or catchment wide rainfall events.
3.3.5 This volume would meet the UWWTD requirements in terms of the number and volume of residual discharges that would occur when the tunnel system reaches capacity. It would also meet the water quality objectives set out in the Thames Tideway Strategic Study and the hydraulic requirements developed by means of pneumatic and transient modelling.
3.3.6 The Lee Tunnel and its associated shafts would contribute approximately 350,000m3 of storage volume.
3.3.7 The combined storage volume of the shafts and tunnels of the Lee Tunnel and the Thames Tideway Tunnel would be 1.6 million m3 at 100m Above Tunnel Datum (ATD – see glossary for explanation of tunnel datum). The tunnel system would be operated to maintain controlled water levels to 100m ATD or lower.
Engineering design statement 26
3 Engineering considerations 3.3.8 The approximate internal diameter of the main tunnel would be 7.2m along
most of its length, which can be reduced to an approximate internal diameter of 6.5m for the western section between Acton Storm tanks and Carnwath Road Riverside and still achieve the 1.6 million m3 capacity requirement. The storage volume of the Thames Tideway Tunnel alone would be approximately 1.25 million m3.
3.3.9 The project would also incorporate some real time control. Hydraulic penstocks, built as part of the interception works, would be remotely operated to reduce inflow rates when significant widespread storms occur. They could also be used to reserve storage capacity within the tunnel system to capture more flow from CSOs located in more sensitive stretches of the tidal Thames. This work continues to be developed with the Environment Agency.
3.3.10 The Tideway Pumping Station would, at times, transfer some flows from the main tunnel to the new Tideway CSO on the tidal Thames (built as part of the Lee Tunnel project) via the Beckton siphon tunnel. This bypass pumping would achieve the overall level of control targeted for the CSOs and control discharges from the Abbey Mills Pumping Station CSO.
3.3.11 Additional treatment capacity is being created at Beckton sewage treatment works as part of a separate project to extend and upgrade the treatment works. This would ensure sufficient capacity to treat the stored flows from both the Lee Tunnel and the Thames Tideway Tunnel.
3.4 Hydraulics
CSO volume, spills and flow rates 3.4.1 The UWWTD does not specify numerical values of residual CSO
discharges to the river that would constitute compliance, either in terms of volume, number or duration of discharges. The project’s CSO control targets were therefore developed based on discussions with the Environment Agency. The design team established that actively keeping the 34 unsatisfactory CSOs to a maximum of four residual discharges each in a typical year would meet the Environment Agency’s objective to “limit pollution from unsatisfactory CSOs”. This objectively particularly seeks to limit ecological damage by complying with dissolved oxygen standards established for the tidal Thames by the Thames Tideway Strategic Study.
3.4.2 The Environment Agency stated in a letter dated 4 July 2012: “To reiterate our conclusions and continuing support for the Thames Tunnel, the proposed system operating strategy will control CSOs to a level that is compliant with the objectives of the Thames Tideway Strategic Study and in so doing limits [sic] pollution from CSOs and thereby meets [sic] the requirements of that part of the UWWTD”.
3.4.3 The design of the project was based on the following assumptions: a. Capacity will be expanded to 27m3/s at Beckton STW and to 12.9m3/s
at Crossness STW as part of separate projects within the London Tideway Improvements Programme.
Engineering design statement 27
3 Engineering considerations
b. The new Tideway CSO will be created at Beckton STW by the Lee Tunnel project.
c. The 7.2m internal diameter Lee Tunnel from Abbey Mills Pumping Station to Beckton STW and the Tideway CSO will be implemented by the Lee Tunnel project.
d. Pumping capacity of the Tideway Pumping Station on completion of the Thames Tideway Tunnel project will be 12.2m3/s.
3.4.4 The catchment model for the Beckton STW and Crossness STW catchments was used to assess compliance with the UWWTD and develop the interception requirements and tunnel operating strategy. The sewer catchment modelling software used on the project, InfoWorksCS, is a proprietary package that is the industry standard throughout the UK and is widely used internationally. It enables a combination of foul water from domestic, commercial/industrial use, rainfall run-off flows and infiltration to be dynamically routed through catchment systems. It also predicts rates of discharge, flow levels, and volumes throughout the system.
3.4.5 The most typical 12 month period of rainfall observed between 1970 and 2011 was October 1979 to September 1980. This ‘typical year’ was used to evaluate the sewerage system’s performance.
3.4.6 Typical year CSO performance and design flow rates are presented in Table 3.2 including: a. the total volume and number of CSO discharge events during the
typical year for the existing system b. the total volume and number of CSO discharge events during the
typical year for the 2020s condition with STW improvements and the Lee tunnel in place (the base condition for evaluating the performance of the project)
c. the total volume and number of CSO discharge events during the typical year once the project is operational
d. the peak flows that the CSO interception structures are designed to handle (design flow rate).
Engineering design statement 28
3 E
ngin
eerin
g co
nsid
erat
ions
Tabl
e 3.
2 Ty
pica
l yea
r CSO
per
form
ance
and
des
ign
flow
rate
s
Ex
istin
g sy
stem
B
ase
cond
ition
Pr
ojec
t ope
ratio
nal
CSO
re
f C
SO n
ame
Site
nam
e To
tal
volu
me
(m3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Des
ign
flow
rate
(m
3 /s)
CS
01X
Act
on S
torm
Rel
ief
Act
on S
torm
Tan
ks
312,
000
29
178,
000
17
0 0
10
CS
02X
Sta
mfo
rd B
rook
Sto
rm
Rel
ief
No
site
requ
ired
500
2 30
0 2
400a
2 n/
a
CS
03X
Nor
th W
est S
torm
R
elie
f N
o si
te re
quire
d 2,
800
1 3,
900
1 60
0 1
n/a
CS
04X
Ham
mer
smith
P
umpi
ng S
tatio
n H
amm
ersm
ith
Pum
ping
Sta
tion
2,21
0,00
0 51
2,
350,
000
54
104,
000
1-3b
42
CS
05X
Wes
t Put
ney
Sto
rm
Rel
ief
Bar
n E
lms
35,0
00
30
37,0
00
31
1,50
0 1
2
CS
06X
Put
ney
Brid
ge
Put
ney
Em
bank
men
t Fo
resh
ore
68,0
00
33
71,0
00
33
1,60
0 1
5
CS
07A
Frog
mor
e S
torm
R
elie
f – B
ell L
ane
Cre
ek
Dor
may
Stre
et
18,0
00
32
19,0
00
32
500
1 3
CS
07B
Frog
mor
e S
torm
R
elie
f – B
uckh
old
Roa
d K
ing
Geo
rge’
s P
ark
86,0
00
21
89,0
00
21
1,50
0 1
9
CS
08A
Jew
s R
ow –
Wan
dle
Val
ley
Sto
rm R
elie
f N
o si
te re
quire
d 30
0 1
3,00
0 2
0 0
n/a
Eng
inee
ring
desi
gn s
tate
men
t
29
3 E
ngin
eerin
g co
nsid
erat
ions
Exis
ting
syst
em
Bas
e co
nditi
on
Proj
ect o
pera
tiona
l
CSO
re
f C
SO n
ame
Site
nam
e To
tal
volu
me
(m3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Des
ign
flow
rate
(m
3 /s)
CS
08B
Jew
s R
ow –
Falc
onbr
ook
Sto
rm
Rel
ief
No
site
requ
ired
7,40
0 2
7,50
0 2
7,60
0 2
n/a
CS
09X
Falc
onbr
ook
Pum
ping
S
tatio
n Fa
lcon
broo
k Pu
mpi
ng
Sta
tion
709,
000
42
780,
000
42
45,0
00
4 22
CS
10X
Lots
Roa
d P
umpi
ng
Sta
tion
Cre
mor
ne W
harf
Dep
ot
1,14
0,00
0 38
1,
260,
000
42
92,0
00
4 18
CS
11X
Chu
rch
Stre
et
No
site
requ
ired
0 0
0 0
0 0
n/a
CS
12X
Que
en S
treet
N
o si
te re
quire
d 0
0 0
0 0
0 n/
a
CS
13A
Sm
ith S
treet
– M
ain
Line
N
o si
te re
quire
d 1,
400
4 1,
500
4 1,
500
4 n/
a
CS
13B
Sm
ith S
treet
– S
torm
R
elie
f N
o si
te re
quire
d 0
0 0
0 0
0 n/
a
CS
14X
Ran
elag
h C
hels
ea E
mba
nkm
ent
Fore
shor
e 28
3,00
0 26
30
6,00
0 29
19
,000
2
20
Nor
ther
n Lo
w L
evel
S
ewer
No.
1 co
nnec
tion
near
R
anel
agh
CS
O
Che
lsea
Em
bank
men
t Fo
resh
ore
n/a
n/a
n/a
n/a
n/a
n/a
17
Eng
inee
ring
desi
gn s
tate
men
t
30
3 E
ngin
eerin
g co
nsid
erat
ions
Exis
ting
syst
em
Bas
e co
nditi
on
Proj
ect o
pera
tiona
l
CSO
re
f C
SO n
ame
Site
nam
e To
tal
volu
me
(m3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Des
ign
flow
rate
(m
3 /s)
CS
15X
Wes
tern
Pum
ping
S
tatio
n N
o si
te re
quire
d 2,
050,
000
37
2,32
0,00
0 41
24
6,00
0 4
n/a
CS
16X
Hea
thw
all P
umpi
ng
Sta
tion
Hea
thw
all P
umpi
ng
Sta
tion
655,
000
34
748,
000
39
63,0
00
4 12
CS
17X
Sou
th W
est S
torm
R
elie
f 22
8,00
0 13
23
9,00
0 13
3,
900
1 31
CS
18X
Kin
g S
chol
ars
Pond
N
o si
te re
quire
d 1,
400
3 1,
800
3 50
0 2
n/a
CS
19X
Cla
pham
Sto
rm R
elie
f A
lber
t Em
bank
men
t Fo
resh
ore
13,0
00
6 14
,000
6
7,90
0 1
10
CS
20X
Brix
ton
Sto
rm R
elie
f 26
5,00
0 29
27
9,00
0 31
5,
700
1 12
CS
21X
Gro
sven
or D
itch
No
site
requ
ired
2,60
0 3
3,00
0 4
600
2 n/
a
CS
22X
Reg
ent S
treet
V
icto
ria E
mba
nkm
ent
Fore
shor
e 22
,000
5
26,0
00
10
0 0
18
CS
23X
Nor
thum
berla
nd
Stre
et
No
site
requ
ired
72,0
00
13
88,0
00
14
300
1 n/
a
CS
24X
Sav
oy S
treet
N
o si
te re
quire
d 8,
500
20
8,60
0 20
80
0 4
n/a
CS
25X
Nor
folk
Stre
et
No
site
requ
ired
0 0
0 0
0 0
n/a
CS
26X
Ess
ex S
treet
N
o si
te re
quire
d 2,
100
3 2,
300
3 0
0 n/
a
CS
27X
Flee
t Mai
n B
lack
friar
s B
ridge
Fo
resh
ore
521,
000
21
571,
000
23
37,0
00
4 46
Eng
inee
ring
desi
gn s
tate
men
t
31
3 E
ngin
eerin
g co
nsid
erat
ions
Exis
ting
syst
em
Bas
e co
nditi
on
Proj
ect o
pera
tiona
l
CSO
re
f C
SO n
ame
Site
nam
e To
tal
volu
me
(m3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Tota
l vo
lum
e (m
3 )
No.
of
sp
ills
Des
ign
flow
rate
(m
3 /s)
Nor
ther
n Lo
w L
evel
S
ewer
No.
1 co
nnec
tion
near
Fle
et
Mai
n C
SO
Che
lsea
Em
bank
men
t Fo
resh
ore
n/a
n/a
n/a
n/a
n/a
n/a
15
CS
28X
Sha
d Th
ames
P
umpi
ng S
tatio
n S
had
Tham
es
Pum
ping
Sta
tion
92,0
00
15
100,
000
15
72,0
00
4 n/
a
CS
29X
Nor
th E
ast S
torm
R
elie
f
Kin
g E
dwar
d M
emor
ial P
ark
Fore
shor
e 78
2,00
0 31
84
8,00
0 32
85
,000
4
30
CS
30X
Hol
low
ay S
torm
Rel
ief
Bek
esbo
urne
Stre
et
7,90
0 9
8,50
0 10
7,
000
2 n/
a
CS
31X
Ear
l Pum
ping
Sta
tion
Ear
l Pum
ping
Sta
tion
539,
000
26
594,
000
30
51,0
00
4 24
CS
32X
Dep
tford
Sto
rm R
elie
f D
eptfo
rd C
hurc
h S
treet
1,
470,
000
36
1,98
0,00
0 39
16
3,00
0 4
29
CS
33X
Gre
enw
ich
Pum
ping
S
tatio
n G
reen
wic
h P
umpi
ng
Sta
tion
8,32
0,00
0 51
3,
940,
000
28
573,
000
4 36
CS
34X
Cha
rlton
Sto
rm R
elie
f N
o si
te re
quire
d 60
0 2
900
2 90
0 2
n/a
a Sm
all d
iffer
ence
s in
vol
ume
resu
lt fro
m ro
undi
ng o
f sm
all c
hang
es.
b Ope
ratio
n of
the
Ham
mer
smith
Pum
ping
Sta
tion
(and
oth
er s
ensi
tive
CS
O lo
catio
ns) w
ill be
det
erm
ined
with
futu
re o
pera
tiona
l ex
perie
nce
and
inpu
t fro
m th
e E
nviro
nmen
t Age
ncy.
Eng
inee
ring
desi
gn s
tate
men
t
32
3 Engineering considerations
Flow control 3.4.7 The project forms a part of the wider London Tideway Improvements
Programme, which includes the Lee Tunnel and improvements at Mogden, Crossness, Longreach, Riverside and Beckton sewage treatment works. Each component of the system would be mutually dependent and operated as a whole system.
3.4.8 The flows into the Lee Tunnel and Thames Tideway Tunnel system during large rainfall events would be controlled to limit the potential for adverse hydraulic and pneumatic conditions. Flows would be controlled by shutting hydraulic penstocks when preset peak flow targets or water levels within the system are reached. The Tideway Pumping Station would also pump bypass flow to the Tideway CSO when there is insufficient capacity at Beckton STW and pre-set water levels are reached.
3.4.9 Penstocks would be locked shut when personnel access the tunnel system to ensure safe working within the downstream system.
3.4.10 In order to protect the tunnel system from inflow from high water levels in the tidal Thames, new one-way flap valves would provide backflow protection. Additional protection would be provided by existing tide gates and control penstocks could also be closed, if necessary.
Flow drop 3.4.11 The distance between the top and bottom of the drop shafts is significant;
if the intercepted flows are allowed to fall uncontrolled, they would gain considerable energy that would eventually destroy the structure. Vortex drop structures have a proven record of limiting the destructive energy of falling water over large vertical distances and require minimal plan area and smaller shafts.
3.4.12 Vortex drop structures would be used in drop shafts throughout the project. They consist of a vortex generator at the end of the connection culvert at the top of the drop shaft, a vortex drop tube within the drop shaft, and de-aeration structures at the base of the drop shaft to release entrained air.
3.4.13 The vortex generator is a vertically steep culvert with a horizontally narrow throat, which accelerates the intercepted flows towards the inside of the curved vortex drop tube. The flows then travel in a circular motion along the inside surface of the vortex drop tube to the bottom. This process entrains a significant volume of air into the flow which, if allowed into the tunnel, could accumulate, pressurise and release in an uncontrolled way when it reaches upstream or downstream shafts. Therefore a key element of the design is to pass the flows through the de-aeration structures at the bottom of the shaft to remove entrained air and re-circulate it back up the drop shaft.
3.4.14 The vortex drop structure is suitable for a wide range of inflows at each site. The de-aeration chamber would either be located vertically within the drop shaft or in a horizontal section of the connection tunnel depending on the local ground conditions.
Engineering design statement 33
3 Engineering considerations 3.4.15 Due to the intermittent nature of flow interception, it is not economically
feasible to install energy recovery devices in the drop shafts.
Pneumatic and transient responses 3.4.16 Subjecting large sewers to rapidly varying flow conditions can lead to the
risk of: a. damaging transient pressure waves developing within the tunnels
when huge bodies of water change momentum b. pockets of air being trapped within the tunnel when stretches of the
tunnel fill prematurely or differentially c. explosive release of compressed air and water mixtures (geysering).
3.4.17 These effects were an important factor in sizing and locating tunnels and shafts to minimise the risk of damaging pressure waves or geysering. Pneumatic and transient computer modelling was undertaken to design the most suitable configuration and operating strategy for the tunnels.
Hydraulic considerations affecting design 3.4.18 Minimum gradients for the main tunnel and connection tunnels were set in
order to promote self-cleansing. The gradients were derived from CIRIA 141 Criteria 1: flows in the tunnel should have the capacity to transport a minimum concentration of fine-grained or low density particles in suspension, with a sediment bed of up to two percent of the tunnel’s diameter.
3.4.19 The average velocities would be limited in straight and curved connection culverts. Flows from connection tunnels into the main tunnel would have a set maximum velocity to avoid excessive backwater effects in the main tunnel. The angle of connection tunnel entries into the main tunnel would be a minimum of 700 pointing downstream, as model tested.
3.4.20 The maximum velocity for discharges through orifices, valves or other flow constriction devices would be restricted in order to limit erosion damage. The average velocity at flap gates, penstocks and other obstructions in the approach channels to vortex drops would also be restricted to maintain stable conditions in the vortex approach channels.
3.4.21 Velocities in vortex drop tubes would be in excess of 10m/s. Suitable materials and construction methods shall be identified to endure high velocities and abrasion; this has been satisfactorily achieved on other projects. The minimum horizontal and vertical angles of the vortex generator shall be determined by physical and computational model testing.
3.4.22 All hydraulic components of the system, including interception chambers, connection culverts, vortex generators, vortex drop tubes and connection tunnels would be designed for the maximum design flow.
3.4.23 The minimum level of the shaft cover slabs would be 104m ATD to ensure that water does not flow out of low-lying shafts when the tunnel is operating at the highest water level.
Engineering design statement 34
3 Engineering considerations
3.5 Air management 3.5.1 For much of the time the tunnel system would be empty. When it is empty
and while it is filling, the air management system would keep the air in the tunnels fresh.
3.5.2 The air management system would include: a. two active mechanical ventilation plants at the western end of the main
tunnel (at Acton Storm Tanks and Carnwath Road Riverside) b. an active mechanical ventilation plant at the end of the Greenwich
connection tunnel (at Greenwich Pumping Station) c. passive ventilation installations at all other tunnel shaft sites.
3.5.3 The air management system would be integrated with the Lee Tunnel active mechanical ventilation plant at Abbey Mills Pumping Station and Beckton Sewage Treatment Works.
3.5.4 The objective is to maintain a negative pressure relative to atmospheric pressure within the tunnel system when it is empty and when filling at a low rate. This would minimise air releases at other sites (those with passive ventilation systems), maintain fresh air in the system and ensure that all released air would be treated at mechanically ventilated sites. When flows are diverted into the tunnel system, the displaced air would be treated at the mechanically ventilated sites until the rate of air displacement is higher than the total ventilation capacity available. This would only occur during large storms – estimated to be for a short duration approximately four times a year. The excess air would bypass the mechanical plant and be released via a high ventilation column.
3.5.5 Passive ventilation installations would only operate when the shaft that the installation serves is drowned by the rising wastewater in the tunnel. At these sites 100% of the air released during the typical year is treated by the passive filter. The treated air (downstream of the filter) exits through a ventilation column or structure. A high pressure release structure is located upstream of the carbon filter and will only operate very infrequently during very large storms when the capacity of the filter is exceeded.
3.5.6 The following ventilation structures would be required at two sites with mechanical ventilation plant (Acton Storm tanks and Carnwath Road Riverside): a. above-ground ventilation structure housing fans within acoustic
enclosures b. below-ground air treatment chambers and ducts c. ventilation column(s) approximately 15m high d. pressure relief and air inlet structures.
3.5.7 At Greenwich Pumping Station, the mechanical ventilation plant would be mainly housed within the existing disused East Beam Engine House. The plant would include air ducts, fans within acoustic enclosures, air
Engineering design statement 35
3 Engineering considerations
treatment units and air release structures. The CSO drop shaft at this site would also incorporate a pressure relief and air inlet structure.
3.5.8 At Abbey Mills Pumping Station there would be a ventilation structure, a ventilation column and a connection to the Lee Tunnel project’s mechanical ventilation plant.
3.5.9 The following ventilation structures would be required at the sites with passive ventilation installations: a. a below-ground air treatment chamber and air ducts b. above-ground ventilation structure(s) or column(s) incorporating a
pressure relief structure (the columns would typically be approximately 4m to 8m high)
c. a ventilation column to serve the CSO interception/valve chamber (approximately 6m high).
3.5.10 The inflow and movement of flows within the tunnel system determines how much entrained air enters the system and how much air is displaced from the system. Air release rates can be calculated for each main tunnel shaft or CSO drop shaft. The typical year rainfall and design storms were used to determine the average and peak air releases from each shaft.
3.5.11 The Air Management Plan, which accompanies the application, describes how the tunnel system as a whole would be operated. This includes a range of operating conditions for the main tunnel including ‘empty’, ‘filling’, ‘partially full’, ‘storing’ and ‘emptying’.
3.5.12 The design air flow rate at each site (determined by pneumatic modelling) influences the size and number of above-ground ventilation structures and columns required. At most sites, weighted dampers in below-ground chambers would regulate air releases. At passive ventilation plants the above-ground ventilation columns would be standardised into three types of column (where feasible). The columns would feature an architectural design. The standard sizes of the three types of column would be as follows: a. Type A: cross-sectional area of 0.35m2 b. Type B: cross-sectional area of 0.6m2 c. Type C: cross-sectional area of 1m2.
3.5.13 The air treatment capacity for each site is set out in Table 3.3 along with the proposed size of the ventilation structure or column.
Table 3.3 Air management flow rates and ventilation column sizes
Site name Treatment capacity
(m3/s)
Type of ventilation structure
Ventilation structure size (m2)
Ventilation column size (m2)
Acton Storm Tanks 20 active plant relief 8.5 inlet 1.0
outlet*2 No 1.1 outlet*1 No 2.0
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3 Engineering considerations
Site name Treatment capacity
(m3/s)
Type of ventilation structure
Ventilation structure size (m2)
Ventilation column size (m2)
Hammersmith Pumping Station
0.5 combined with venturi structure
outlet*0.36 relief 0.3
n/a
Barn Elms 0.5 combined with kiosk
outlet*0.36 relief 0.1
n/a
Putney Embankment Foreshore
0.5 1 No Type A n/a outlet*0.35
Dormay Street 0.5 combined with kiosk
outlet*0.3 relief 0.5
n/a
King George’s Park 0.5 1 No Type A n/a outlet*0.35
Carnwath Road Riverside
20 active plant relief 10.7 inlet 0.6
outlet*2 No 1.1 outlet*1 No 6.2
Falconbrook Pumping Station
0.5 combined with air treatment chamber
outlet*0.38 relief 0.2
n/a
Cremorne Wharf Depot
0.5 2 No Type B n/a outlet*1.2
Chelsea Embankment Foreshore
0.5 2 No Type B n/a outlet*1.2
Kirtling Street 2 combined with kiosk
outlet*4 n/a
Heathwall Pumping Station
0.1 breather unit 0.2 n/a
Heathwall Pumping Station
1 1 No Type C n/a outlet*1.2
Albert Embankment Foreshore
1 2 No Type B n/a outlet*1.2
Victoria Embankment Foreshore
0.5 2 No Type B n/a outlet*1.2
Blackfriars Bridge Foreshore
2 5 No Type C
n/a outlet*5
Chambers Wharf 3 3 No Type C n/a outlet*3
King Edward Memorial Park Foreshore
2 2 No Type C n/a outlet*2
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3 Engineering considerations
Site name Treatment capacity
(m3/s)
Type of ventilation structure
Ventilation structure size (m2)
Ventilation column size (m2)
Earl Pumping Station 1 combined with shaft superstructure
outlet*1.44 relief 2.2
n/a
Deptford Church Street
3 4 No Type C n/a outlet*4
Greenwich Pumping Station
4 active plant outlet*2 No 0.2 relief 2.3
n/a
* these vents also allow air into the system
3.6 Operation and maintenance 3.6.1 The interception and storage aspects of the tunnel system would be
operated using automated systems. The systems would include equipment to collect data on water levels and flows and send it electronically for remote analysis and equipment to control plant, including valves and penstocks, from a remote location. These systems are widely known as supervisory control and data acquisition systems (SCADA). Local manual control at each site would also be possible in the event that SCADA control fails or needs to be overridden. The system would predominantly be controlled by measuring flow rates and levels and in the tunnel and a central control centre would have an overview of the system.
3.6.2 Thames Water operational personnel would periodically require access to the tunnel system for inspection and maintenance purposes. This would likely include: a. main tunnel, connection tunnel, main tunnel shaft and CSO drop shaft
inspections once every ten years (the first inspection would take place within two to three years of commencing operations)
b. equipment inspections or maintenance once every three to six months, eg ventilation equipment and penstocks, which would be located in chambers rather than deep shafts
c. Unplanned visits for maintenance or repairs, eg in the event of a blockage or an equipment failure.
3.6.3 For health and safety reasons, access into the shafts would be via man-riders lowered from cranes due to the depth of the shafts. Man-riders are cages specifically designed to move people by crane.
3.6.4 All main tunnel sites and CSO sites would require the following: a. space adjacent to the shaft to accommodate mobile cranes to move
people and materials in and out of the shaft for inspections and maintenance
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3 Engineering considerations
b. manhole covers accessible by mobile cranes to enable periodic inspections
c. adequate access from the highway network to enable cranes and other vehicles to enter the site.
Access 3.6.5 The site-specific access arrangements are set out in Sections 7 to 0. The
typical access arrangements are summarised below. 3.6.6 Site visits would be required approximately every three to six months to
inspect equipment in structures such as air treatment chambers, ventilation columns, vortex drops, interception chambers, valve chambers and electrical and control kiosks. This would likely involve a visit by personnel in vans during normal working hours. The ground-level access covers in the areas of hardstanding at each site would be opened to inspect and carry out any minor maintenance of below-ground equipment. Access to interception and valve chambers would be via fixed ladders within the chambers.
3.6.7 Approximately once every three years, the filter media in the air treatment chambers would need to be replaced. This would be carried out via the access covers.
3.6.8 It is anticipated that once every ten years, a major internal inspection of the main tunnel and underground structures would be required. It is likely that this would involve an expert team of inspection personnel, a small support crew with support vehicles, and two mobile cranes to lower the inspection team and equipment into the main tunnel shaft. This process would take several weeks. Temporary fencing would be erected around the working area.
3.6.9 In the event of a major blockage, a mobile crane or jetting lorry would be brought to the site to clear the blockage via the appropriate access cover.
3.7 Ground conditions 3.7.1 The design took due account of the ground conditions including the
geology and hydrogeology along the route alignment.
Geology 3.7.2 The geology along the route was established using the British Geological
Survey ‘Lithoframe50’ model, supplemented by project-specific site investigations including a seismic refraction survey, ground and over-water boreholes, field and laboratory testing, and installation of piezometers to establish water levels.
3.7.3 The basic geological descriptions within the London Basin geological sequence are set out in Table 3.4.
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3 Engineering considerations
Table 3.4 Geology of the London Basin
Era Group Formation Brief description of formation
Approximate range of
thickness (m)
Recent Alluvium Soft clays, silts, sands and gravels – may contain peat 0 to 5
Floodplain Terrace
Medium to dense sand, flint and chert gravel, occasional cobbles and boulders 0 to 10 Kempton
Park Terrace
Tertiary Thames London Clay
Very stiff, fissured, silty, occasionally slightly sandy clay
>100
Harwich
Swanscombe member: Sandy clay to clayey sand (< 2m) with some fine to medium black rounded gravel Blackheath member: Dense to very dense flint gravel (with occasional cobbles) in silty or clayey, glauconitic, fine to medium sand matrix Oldhaven member: Very dense clayey sand with gravel and shells – often cemented as limestone
0 to 10
Lambeth Group
Woolwich
Stiff, dark grey to black clay with locally abundant shell debris and strong limestone beds (100 to 200mm thick)
10 to 20
Reading
Very stiff to hard, multi-coloured (light blue-grey mottled red, orange, brown and purple), locally sandy clay
Upnor Gravel, glauconitic and organic sand, silt and clay 5 to 7
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3 Engineering considerations
Era Group Formation Brief description of formation
Approximate range of
thickness (m)
Thanet Sand Formation (including Bullhead Bed at base <~0.5m)
Very dense silty to very silty sand. The lowest ~0.5m sometimes consists of fine, medium and coarse, angular flint gravel
10 to 15
Cretaceous Chalk Seaford*
Homogeneous chalk with nodular flint horizons (>100mm thick)
circa 40
Lewes* Heterogeneous nodular chalk with nodular flint horizons and marl seams
circa 50
*Limited to those formations of the ‘White Chalk’ subgroup expected within the project (Upper and Middle Chalk are now known collectively as ‘White Chalk’).
3.7.4 The distribution of strata along the route is largely controlled by the London Basin Syncline, which today plunges gently westwards. Beneath a cover of made ground and recent deposits, the succession of tertiary deposits is gradually exposed west to east along the River Thames until Chalk occurs at an outcrop around Greenwich.
3.7.5 The anticipated geology at the main tunnel invert is as follows: a. London Clay Formation runs from the western end of the tunnel to just
west of Albert Bridge (Harwich at the base approximately between Cremorne Wharf and Albert Bridge).
b. Lambeth Group starts to enter the tunnel invert just east of Albert Bridge, forming the lower third of the face by Chelsea Bridge, and the full-face by Tideway Walk. The tunnel continues in full-face Lambeth Group to just east of London Bridge.
c. Thanet Sand Formation occurs within the invert and the lower third of the face between Blackfriars Bridge and London Bridge, becoming full-face from just east of London Bridge to just west of Tower Bridge.
d. White Chalk subgroup occurs downstream from just east of Tower Bridge.
3.7.6 Faulting at London Bridge is expected to repeat the sequence, and mixed-face conditions in the Lambeth Group and Thanet Sand Formation are expected from Chelsea Bridge through to Tower Bridge, with only a short section wholly in the Thanet Sand Formation close to Tower Bridge.
3.7.7 Various structural geological models provide different interpretations of the structural setting across the London Basin; however, they all generally indicate regular faulted block groundmass in Chalk and northwest by southeast trending faults that cut the basic east-west main synclinal form.
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3 Engineering considerations 3.7.8 The dominant structural geological features are:
a. The Hammersmith Reach Fault Zone, a series of north-northwest to south-southeast trending faults beneath and adjacent to the eastern side of Hammersmith Bridge. A 5m displacement is noted to the east.
b. The Putney Bridge Fault, a series of southeast to northwest trending faults on the syncline with the axis to the west of Putney Bridge, with vertical displacement on top of Lambeth Group strata on the eastern hanging wall of approximately 2m.
c. The Chelsea Embankment (Albert Bridge) Fault Zone, a series of north to south and south-southwest to north-northeast trending faults between Battersea and Chelsea bridges, which would intersect the tunnel alignment at nearly perpendicular. Up to 5m vertical displacement of strata is noted over this zone, resulting in uplift of the top of Lambeth Group deposits on the eastern side of Albert Bridge.
d. The Lambeth Anticline, a north-northwest to south-southeast trending faulted anticline between Vauxhall and Lambeth Bridges that would intersect the tunnel alignment at an oblique angle with a difference in strata level of approximately 5m.
e. The London Bridge Fault Graben, a southeast to northwest trending graben-type feature arranged between Cannon Street and Tower Bridge, with known vertical displacement in excess of 10m.
f. The Greenwich Fault Zone, a southwest to northeast trending feature, which was investigated in detail in 2008 as part of the Lee Tunnel project ground investigation. Up to 20m down-throw is anticipated to the northwest in a series of stepped faults. The fault runs generally parallel to the main syncline, southwest to northeast from Greenwich to Beckton, crossing the River Thames downstream of the Thames Barrier. It is in close proximity to Greenwich Pumping Station.
3.7.9 Other structural features include the North Greenwich Syncline (now more generally known as the Plaistow Graben), Millwall Anticline and Beckton Anticline, all of which trend northeast to southwest, contrary to the main basin axis.
3.7.10 There are risks of scour hollows located on previous drainage channels formed by the River Thames, which are often found at the confluence of the existing tributaries, eg at the River Fleet, River Lee and River Wandle. The features usually contain a variety of granular deposits and/or disturbed natural materials and are localised and steep-sided.
3.7.11 The scour hollow in the vicinity of the Blackwall Tunnel is the only scour hollow known to penetrate into Chalk. Elsewhere, the hollows only affect the tertiary deposits and, more particularly, London Clay. Basal depths are normally 5m to 20m below ground level, with the exception of 33m at Battersea Power Station and Hungerford Bridge.
3.7.12 Of the known scour hollows, only the hollow at Hungerford Bridge is close to the main tunnel. This feature attains a base level of 72mATD in London Clay near the south bank, equivalent to only 10m above the tunnel crown.
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3 Engineering considerations
Such features may, however, have greater implications for the shallower connection tunnels in other locations.
3.7.13 The presence of flints within the Chalk may cause severe wear to the TBM, which would require frequent and hazardous interventions to inspect and maintain the TBM cutterhead. Therefore, an important part of the project’s ground investigations was to investigate the structure and permeability of the Chalk and the characteristics of flint-related features.
3.7.14 A number of flint bands are present within the Chalk. Within the Seaford Chalk, two well-defined flint bands used as marker horizons (not necessarily the thickest seams) are the Bedwells Columnar and Seven Sisters. The Bedwells typically comprise a discontinuous layer of very large, irregular flints, up to approximately 500mm high by 300mm in diameter. Previous projects have determined that they have a compressive strength of up to 900MPa. Seven Sisters is a continuous band, with flints between 100mm and 150mm thick.
3.7.15 It is therefore important to select the appropriate TBM; a Slurry TBM is preferred for the section of the route in Chalk. A slurry TBM was used successfully on the Channel Tunnel Rail Link River Thames crossing next to the QE2 Bridge. Most recently, the same type of TBM was procured by the Lee Tunnel project contractor. The advantages of this type of TBM include the ability to deal with water-bearing fissures in Chalk and to convey flint pieces in a fluid slurry, rather than a potentially damaging abrasive paste from an EPB TBM. Selecting a Slurry TBM for Chalk would reduce the need for hazardous interventions; however, Slurry TBMs are not appropriate for clay of the type expected along other sections of the tunnel alignment.
Hydrogeology 3.7.16 The major aquifer of the London Basin lies in Chalk. It is wholly unconfined
to the east but confined to the west below the tertiary strata and the London Clay Formation in particular. The Chalk aquifer is generally in hydraulic continuity with the overlying Thanet Sand Formation and sometimes the base of the Lambeth Group, particularly the gravel part of the Lower Mottled Beds and the Upnor Formation. The Environment Agency refers to this combined aquifer as the Chalk-Basal Sands aquifer.
3.7.17 Local aquicludes can exist in the overlying Lambeth Group, in particular the Woolwich Formation Laminated Beds, which lead to perched groundwater tables. Historical records of other engineering schemes state that these ‘perched’ features may retain hydrostatic pressures of up to 40m, which could result in high inflows at tunnel level and particularly into shafts during construction.
3.7.18 The Harwich Formation (Blackheath Member) is also known to contain high groundwater levels in places, which may cause problems during tunnel construction.
3.7.19 A minor regional aquifer lies within the floodplain and river terrace deposits. Due to its connection to the River Thames, it is generally tidal,
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3 Engineering considerations
with an average level of 100mATD +/- 2.5m (equivalent to 0mAOD+/- 2.5m).
3.7.20 Regional monitoring of the Chalk aquifer is reported by the Environment Agency; specific monitoring data is available over the years 2000 to 2008. Data indicates a depressed groundwater table in central London at 60mATD with groundwater levels close to Blackfriars Bridge at 62mATD. However, the latest ground investigations indicate that groundwater levels in the Chalk from Rotherhithe to Charlton are 10m higher than the reported Environment Agency levels.
3.7.21 Groundwater pressure in the Chalk would have an important bearing on tunnelling, especially the construction of junctions between the main tunnel and the connection tunnels. Table 3.5 sets out the 2008 levels and imposed pressure at tunnel invert in the Chalk aquifer east of Tower Bridge, using data obtained from the Environment Agency.
Table 3.5 Chalk aquifer groundwater levels in 2008 east of Tower Bridge
Tunnel section Tower Bridge Shadwell Abbey Mills
Approx tunnel invert 50 mATD 45 mATD 40 mATD
Approx GWT level 2008 72 mATD 78 mATD 92 mATD
Approx GWT pressure 2.5 bar 3.5 bar 4.0 bar
3.7.22 Short-term effects of pumping can still have a demonstrable impact on
regional equipotentials. For example, levels decreased significantly as a result of abstractions in supply wells at Battersea/Brixton that commenced in 2002. The groundwater level was drawn down by approximately 18m local to the wells, 10m in central London near the River Fleet, and 6m in the vicinity of Tower Bridge and Battersea Power Station.
3.7.23 The Environment Agency reports that the groundwater that feeds the Chalk aquifer from the southeast interacts with the River Thames from Greenwich to Woolwich as it flows northwest to Stratford, then west to central London. In the Greenwich to Woolwich area, there is evidence of saline intrusion into the aquifer.
3.8 Sizing of structures and other components
General 3.8.1 The structures and components of the project identified in Section 2.5
were sized to satisfy the functional requirements described in Sections 3.4 to 3.8. They are illustrated in the drawings provided in the Book of Plans. As a general rule, tunnels and other structures were kept as small as possible to minimise impacts and cost while meeting the functional requirements and health and safety objectives. Foreshore sites in particular would be designed to minimise river encroachment.
Engineering design statement 44
3 Engineering considerations 3.8.2 Design is an on-going process that starts with concept identification and
finishes with detailed specifications for every single component. The designs submitted to support the application were completed to the stage where a defendable definition of the components and the space required to construct, operate and maintain them is established. Further design development would continue post approval when selecting contractors and throughout the construction period; therefore some flexibility is required. A detailed explanation of the allowed flexibility is provided in Section 4.
3.8.3 The technical standards referred to when designing and sizing the structures are set out in Section 3.9.
3.8.4 The structures in the drawings were sized taking account of the assumed construction information and ground conditions at each location. Construction information provided in the Book of Plans and Environmental Statement, which accompanies the application, is illustrative of the nature, type, timing, extent and layout of the temporary works and methods that would be required. It is also representative of practical methods that may be used to construct the works; it therefore formed a suitable basis for design and assessment purposes.
3.8.5 The ground conditions vary depending upon location as generally described in Section 3.7.
Provision for ship impact protection of structures 3.8.6 Several of the proposed development sites are located in the river or on
the embankment of the River Thames. At these locations, the shafts and other structures are potentially vulnerable to impact and damage from aberrant river ships and vessels including ferries, tugs and barges. It is therefore appropriate to minimise the risk of impact by making navigational safety the highest priority for design, whilst also considering which ships could impact the structures and what the likely consequences would be.
3.8.7 Designing the shape and size of the foreshore structures was primarily driven by engineering considerations including health and safety; however, it was also important to consider townscape and heritage issues. For example, the structure at Victoria Embankment Foreshore was designed to be rectangular to be in keeping with existing structures in this sensitive historic setting. The evolution of the architectural and landscape design for this and all other sites is provided in the Design and Access Statement.
3.8.8 Whilst recognising that the detailed design of the works will be completed later, all of the foreshore structures illustrated on the drawings were designed to minimise encroachment into the foreshore as far as possible while complying with engineering, navigation and aesthetic requirements.
3.8.9 Eurocode standard: BS EN 1991-1-7 requires designers to consider accidental actions but neither Thames Water nor any other UK agencies have design standards that directly apply to ship impacts on fixed wastewater structures in the River Thames. There is, however, an American guide for the design of bridge piers that provides a method for combining probabilities. This method was used to generate realistic impact loads from specific types of ships that use different reaches of the
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3 Engineering considerations
tidal Thames. The types of ships and associated speeds were agreed with the Port of London Authority.
3.8.10 Initial design work determined that ships could strike the new foreshore structures with considerable force and cause significant damage, including potential breaching of the shafts and chambers, which would let the river flow into the tunnel or the existing sewer network. A minor breach that only resulted in limited inflow or that could be quickly repaired would be acceptable.
3.8.11 The consequences of a significant breach could include: a. operational failure of the tunnel system forcing it to be taken out of
service pending major repairs – repairs of this magnitude would likely take several months to plan and complete and during that period CSOs would discharge directly to the river
b. flooding of low-lying land and habitable property basements from the existing sewer network
c. flooding at remote low-lying land in the vicinity of main tunnel and CSO drop shafts from the tunnel and shafts due to the connectivity created by the system itself (eg a breach at Blackfriars Bridge Foreshore could theoretically flood from the drop shaft at Earl Pumping Station).
3.8.12 Since it is possible for ships to hit the new structures and because the consequences of breach could be serious, further work was completed to calculate potential forces from ship impacts. This work adopted a probabilistic approach based on ships that use different stretches of the River Thames and considered bathymetry and possible vessel approach directions.
3.8.13 In-river dolphin piled structures would need to be substantial and placed a significant distance from the shafts to adequately resist vessel impacts. This would lead to higher navigation risks. Dolphins were therefore discounted.
3.8.14 Designing the shafts and chambers to resist ship impact forces can only commence once the preliminary general arrangements have been developed taking account of hydraulic, aesthetic, fluvial, geology, construction methods, operation and maintenance, and other functional requirements. Since these general arrangements take time to design, it was necessary to make preliminary assumptions for ship impact protection in sizing the foreshore structures. The design team therefore sought to create foreshore structures with a ‘reasonable’ resistance capacity against ship impacts. This preliminary work demonstrated that a 4m thick buffer zone would prevent any significant breaches. Furthermore, depending on the location and subject to detailed design at a later stage, a thinner buffer zone might be feasible. A 4m wide vessel impact buffer zone has been assumed for planning and assessment purposes unless stated otherwise.
3.8.15 More detailed design calculations were completed for two typical types of shaft (a diaphragm wall drop shaft at Blackfriars Bridge Foreshore and a segmental drop shaft at Victoria Embankment Foreshore) in order to confirm that the 4m allowance is adequate for planning and assessment
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3 Engineering considerations
purposes. The calculations established that at Blackfriars Bridge Foreshore the buffer zone adjacent to the diaphragm wall drop shaft can be reduced to approximately 3m. The large diaphragm wall expected at this location can be strengthened and would contribute significantly to the ship impact protection system.
3.8.16 In addition to drop shafts, foreshore CSO sites incorporate flap valves and penstocks to control the flows entering the tunnel system and to prevent high water levels flowing back into the existing sewer network. Any significant breach of the structures upstream of the flap valves would not flood the shaft and tunnel system but would potentially cause the existing sewer network to flood. Therefore ship impact protection for these locations is less important and would be considered further for the detailed design.
3.8.17 The Site works parameter plans in the Book of Plans indicate a solid orange line that defines the maximum extent of the top of river/parapet wall. These lines are based on the 4m buffer zone around the shafts (except at Blackfriars Bridge Foreshore) and would not be exceeded. The plans are complimented by Design Principles, which accompany the application. The design principles enshrine a vision for the project that would be achieved by reducing the scale of structures in or over the River Thames as far as possible. Smaller structures would be designed and constructed (where feasible) if they meet all the functional requirements including vessel impact protection and comply with the design principles.
3.8.18 Creating 'notches' within the buffer zones around shafts to form intertidal habitat areas would be considered on a site-by-site basis. However, it is unlikely that they would be feasible in areas where they would cause a navigational hazard, or where heritage considerations dominate aesthetic design considerations, or where the highest ship impact forces would most likely occur. Notches in other parts of the foreshore structures would also need to take account of other requirements such as overall aesthetics and suitability in areas of public realm, and the need for safe local vessel mooring and manoeuvring. If any notches are incorporated in the detailed designs, they would be marked to signal their presence to river users.
Tunnel and shaft linings 3.8.19 The shafts and tunnels would be lined to ensure structural stability and to
limit the potential for groundwater to enter the system, or conversely, for wastewater to enter the ground. The linings would be designed to last for the life of the tunnel with appropriate maintenance.
3.8.20 In most cases, the shaft and tunnel linings would be designed and constructed in two parts. The primary lining would be constructed as the shaft or tunnel is excavated; the secondary lining would be constructed at a later date. The primary lining would support the ground and exclude groundwater in the short term and, in some cases, may be adequate without secondary lining. The secondary lining would enhance the primary lining to ensure long-term durability and performance.
Engineering design statement 47
3 Engineering considerations 3.8.21 The assumed design for the approximately 7.2m internal diameter main
tunnel comprises a 0.35m thick precast reinforced concrete primary lining, and a 0.3m thick cast in-situ reinforced secondary lining.
Tunnel protection zone and safeguarding 3.8.22 A tunnel protection zone is established to protect and safeguard tunnels
from future development once they have been constructed. For this project the tunnel protection zone allowance around the tunnel is 6m (measured from the internal diameter of the tunnel) as illustrated in Figure 3.4. The 6m allowance from the internal diameter provides a nominal 5m zone from the assumed main tunnel outside diameter when allowing for the thickness of the tunnel lining. The 6m allowance provides a larger zone for tunnels that would have thinner tunnel lining systems.
3.8.23 Any development inside this zone could disrupt uniform confinement of the tunnel and potentially render it unable to withstand the internal water pressure as it fills during a storm event. The development-free zone also reduces the risk of blow-out from the tunnel and limits the need for special measures during any adjacent pile foundation construction, basement excavation or tunnelling.
3.8.24 Thames Water should be consulted in relation to any development within the tunnel protection zone. This would trigger detailed consultation and assessment on a case-by-case basis.
Safeguarding for shafts and other structures 3.8.25 Thames Water should also be consulted on any future development within
10m of the outside structural surface of main tunnel shafts, drop shafts and other structures. This would trigger detailed consultation and assessment on a case-by-case basis. Development would only be constrained to the extent necessary to protect the shafts and structures.
Scour and accretion 3.8.26 The bed of the River Thames is characterised by a veneer of mobile
sediments (predominantly gravels) overlying a stiff clay that is more resistant to erosion. The surface level of mobile sediments is variable and responds to tides and fluvial events. The permanent foreshore structures and the temporary construction works could locally accelerate river flows, which in turn may erode (or scour) the river bed.
3.8.27 Scour is an important consideration because it could remove valuable habitats or disperse sediment which, when re-deposited, might affect navigation or smother habitats (accretion).If structures are not protected from scour at the toe, they may eventually be undermined and fail.
3.8.28 Two types of scour were considered in developing the design and control procedures: a. local or ‘abutment’ scour immediately adjacent to a structure, caused
by accelerated flows around the structure b. general ‘contraction’ scour as the narrowed channel responds to the
presence of the new structures.
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3 Engineering considerations
Scour and accretion: Temporary works 3.8.29 Design work was undertaken to estimate the scour and accretion that
would be caused by the proposed works. However, given the conservative nature of the modelling predictions and the degree of uncertainty associated with them, rather than providing temporary scour protection during construction, any potential scour development during construction would be monitored and protection measures provided only when an appropriate trigger level is reached. This approach is likely to reduce the amount of scour protection used and consequently reduce the level of encroachment. This approach is regarded as the most appropriate during construction, particularly given the views of statutory stakeholders, who wish to ensure that the impacts on the existing river bed are minimised and that existing substrates, channel depths and habitats are retained where possible.
3.8.30 Temporary construction structures in the river would include cofferdams, platforms and barge-handling facilities, including jetties and campsheds. The final layout and design of these structures would be determined by the appointed contractors, who would also carry out the scour monitoring and mitigation. Contractors would be able to collect river bed samples and improve the reliability of the assumptions used to predict scour.
3.8.31 Where accretion caused by the project adversely affects the authorised navigation channel or other areas of the river, it would be dredged.
3.8.32 This approach is explained in detail in the project Scour and Accretion Monitoring and Mitigation Plan for Temporary Works in the Foreshore (refer to the Environmental Statement, Vol 3 Appendix L). The monitoring and mitigation plan would be agreed with key stakeholders and subject to a requirement of the Development Consent Order, if approved.
3.8.33 Any protection measures required to stabilise scour that develops during the temporary works would be removed following construction, unless otherwise agreed with the Port of London Authority and the Environment Agency.
Scour: Permanent works 3.8.34 Scour protection for permanent structures would not be provided in the
same way as temporary structures because it is not necessary or practical to monitor scour over the life of the structures (at least 120 years). It is also important to note that observations on scour and the effectiveness of any mitigation used during temporary construction phase is likely to inform the final extent and type of the scour protection for the permanent operational structures.
3.8.35 Notwithstanding the preceding paragraph, the predicted extent of scour at each site was calculated and preliminary protection/avoidance measures developed. The extent of protection calculated in this way is shown in Figure 3.3 and on the plans in the Book of plans. These measures would also protect the river beds from scour caused by vessels manoeuvring adjacent to the structures. Since scour protection would be provided, it is assumed that no sediment would be released as a result of the project and
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3 Engineering considerations
therefore accretion in the authorised navigation channel should not be an issue during the operational phase of the project. Figure 3.3 Permanent scour protection at toe of river walls
3.8.36 The widths of scour protection would be measured from the outside face
of the base of the river wall, and may include the river wall toe at some sites. Where sites have a non-vertical wall, this will be further out into the river than the ‘orange parameter line’ which defines the top of the wall. The outside face of the river wall at river bed level will be slightly closer (than the base of the wall) to the orange parameter line, but since the river bed level at most sites has natural variation; the base of wall is used. The allowance from the outer edge of the illustrated extent of scour protection (and the outer edge of the CSO apron where applicable) to the ‘green parameter line’ is generally 3m. This is based on engineering judgement and provides a safety factor for detailed scour design.
3.8.37 A number of different materials could be used to mitigate scour, which are discussed in detail in the CIRIA Manual on scour at bridges and other hydraulic structures; Report C551 (2002). The final design of the scour protection would depend on a number of factors including cost, availability of materials, and site and environmental considerations. In practice, the protection would extend from the toe of the new structure and be resistant to erosion in the area of accelerated flows. The material would be placed to avoid any significant loss of depth and should be flexible to respond to scour at its edge, which might result from natural changes in the bed.
Ora
nge
line
Gre
en li
ne
Scour protection
width
300mm natural river
bed
River bed
Engineering design statement 50
3 Engineering considerations 3.8.38 The appointed contractors would be responsible for the final design of any
scour protection measures, in the bed area shown within parameters defined in the Book of Plans.
3.8.39 Scour protection has also been shown on the plans where CSOs discharge into the tidal Thames. This is to prevent scour occurring as a result of residual CSO discharges. These outfall scour protection aprons are similar to and replace existing aprons at the CSOs. Aprons at abandoned CSOs would be removed as shown on the plans.
3.8.40 The river bed would be monitored to check that the permanent scour protection is effective (using the approaches defined in the strategy for Scour and Accretion Monitoring and Mitigation Plan for Temporary Works in the Foreshore) and continued for three years after its installation. Monitoring would only be extended beyond three years if there is clear evidence of on-going scour or accretion as a direct result of the project. If monitoring during this period identifies scour or accretion caused by the project then it would be rectified.
Scour: Third party infrastructure 3.8.41 The presence of temporary or permanent structures in the river may cause
scour that affects existing third party infrastructure including river walls, bridge piers and shallow tunnels. This potential impact would be assessed and protection provided as necessary. The aim is to have an asset protection agreement with the asset owners.
3.8.42 Any scour protection measures required to protect existing third party infrastructure would remain in place following construction, unless otherwise agreed with the relevant statutory authorities and the third party.
Limits and zones 3.8.43 The following limits and zones apply to the plans and drawings in the
application: a. order limits b. limits of deviation (associated with tunnels) c. limits of land to be acquired or used (associated with sites) d. limits of permanent works (land to be acquired permanently) e. land to be acquired permanently (subsoil only) f. limits of permanent access (permanent rights of access required) g. zone within which the shaft would be located h. zone within which permanent above-ground structures would be
located i. zone within which all permanent structures would be located j. zone within which required landscaping would be located.
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3 Engineering considerations
Order limits 3.8.44 The order limits are defined on the Works plan and section drawings in
Section 1 of the Book of Plans. They represent the limits within which the project works would be carried out. They encompass the tunnel limits of deviation and site LLAU.
Limits of deviation 3.8.45 Limits of deviation for the tunnels include allowances for a protection zone
(see Section 3.8.22) and an ‘alignment adjustment’ (see Section 5.2). These are illustrated in Figure 3.4.
Figure 3.4 Tunnel section showing limits of deviation
3.8.46 The vertical tunnel limit is 3 metres for all tunnels. The horizontal tunnel
limits of deviation are given in Table 3.6. Table 3.6 Horizontal limits of deviation
Tunnel Limits of deviation (m from tunnel centreline)
Main tunnel (7.2m internal diameter) 14.60
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3 Engineering considerations
Tunnel Limits of deviation (m from tunnel centreline)
Main tunnel (6.5m internal diameter) 14.25
Connection tunnel (5.0m internal diameter) 13.50
Connection tunnel (2.6m internal diameter) 20.00
Short connection tunnels Irregular as shown on plans
3.8.47 The proportion of the project that only require permanent acquisition of
subsoil are defined on the Land acquisition plans in Section 2 of the Book of Plans by the pale grey shaded ‘land to be acquired permanently (subsoil only)’ areas.
Limits of land to be acquired or used 3.8.48 The LLAU apply to sites that have been sized in accordance with the steps
identified 2.5.9 and are defined on the Works plan and section drawings in Section 1 of the Book of Plans. They include: a. areas that would be used temporarily for construction b. areas that would be used for utility and highway works c. areas that would be required for the permanent works d. areas that would be required for access to the permanent works.
3.8.49 The areas that would be used to construct the permanent works are defined on the Land acquisition plans in Section 2 of the Book of Plans by the grey-shaded ‘limits of permanent works (land to be acquired permanently)’ areas.
3.8.50 The areas that would be required for access to the permanent works are defined on the Land acquisition plans in Section 2 of the Book of Plans by the black-shaded ‘limits of permanent access (permanent rights of access required)’ areas.
3.8.51 The areas that would be used temporarily for construction are the un-shaded areas inside the LLAU.
Parameters 3.8.52 Approximate locations of the main tunnel shafts and CSO drop shafts are
illustrated on the drawings in the Book of Plans. As flexibility is required at this stage in the project (refer to para. 5.3.1), a set of blue ‘zone within which the shaft would be located’ parameter lines are indicated on the Site works parameter plan drawings in the site-specific sections of the Book of Plans. The reasons why flexibility for shaft locations are required is explained in Paragraph 5.3.1.
3.8.53 Approximate locations of above-ground structures such as electrical and control kiosks, ventilation structures and ventilation columns are illustrated on the drawings in the Book of Plans. As flexibility is required at this stage in the project, a set of purple ‘zone within which permanent above ground structures would be located’ parameter lines are indicated on the Site
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3 Engineering considerations
works parameter plan drawings. The reasons why flexibility for above-ground structure locations are required is explained in Paragraph 5.3.3.
3.8.54 Approximate locations of all site structures (above and below ground) are illustrated on the drawings in the Book of Plans. As flexibility is required at this stage in the project, a set of green ‘zone within which all permanent site structures would be located’ parameter lines are indicated on the Site works parameter plan drawings. The reasons why flexibility for near surface below-ground structure locations are required is explained in Paragraph 5.3.2.
3.8.55 At some sites, landscaping works would simply comprise reinstatement. However, at others landscaping would involve new planting or surface treatments. Where landscaping proposals would change specific areas of the sites, the areas are defined by the orange ‘zone within which required landscaping would be located’ parameter areas on the Site works parameter plan drawings.
3.8.56 The ‘limits of permanent works (land to be acquired permanently)’ encompass the above four zones.
Ordnance Survey mapping and topographical survey 3.8.57 The limits and parameter zones are defined on the plans using the
Ordnance Survey base mapping, which is also used for land registration purposes. Topographical surveys of each of the sites were commissioned; the proposed layout of the permanent works is defined on the plans using the information from these surveys. There are discrepancies between these two sets of information, which is noted on the Permanent works layout, Proposed landscape plans and Proposed site features plans.
3.9 Flood defences and surface water drainage
Flood defence levels 3.9.1 The design of all the foreshore and riverside sites maintains the existing
flood defence levels and makes provision to meet future requirements (refer to Section 2.4.9 and the site-specific chapters of the Design and Access Statement).
3.9.2 In order to ensure that the tunnel and connected structures and sewers cannot be inadvertently flooded, all access covers would be at or higher than strategic flood defence levels, eg at Victoria Embankment Foreshore, or located behind flood defence walls, eg at Chelsea Embankment Foreshore. For this reason, flood defence walls cannot be set back behind the shafts.
3.9.3 The consequence of a breach or failure of flood defences near the site could result in loss of power, automatic control and system monitoring functions. Any local air management equipment present at the sites could also fail due to loss of power, control and, potentially, by flooding of filter media. Loss of these local functions would not compromise the long term operation of the tunnel as flow into the tunnel could be controlled, if
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required, by manual operation of actuated penstocks while electro mechanical systems are serviced or replaced. It is envisaged that most of the affected plant could be serviced or replaced and returned to automatic operation within a few weeks of the flood subsiding.
3.9.4 Flooding of the tunnel itself caused by a local breach of flood defences would not create conditions dissimilar to those under which the tunnel is designed to operate and would not compromise the long term operation of the tunnel. It is envisaged that following a flood event the tunnel would be emptied at Beckton STW by pumping to either the sewage treatment works or directly to river, depending on the sewage content and the salinity of the captured floodwaters.
Surface water drainage 3.9.5 The Design Principles document defines standards to be followed for the
design of surface water drainage on all sites. These include compliance with the Floods and Water Management Act 2010 and the Mayor’s Essential Standard.
3.10 Health and safety considerations 3.10.1 The project delivery team sought to comply with all industry codes and
project standards with the aim of achieving world-class health and safety objectives, by means of risk assessment and management practices. A plan and various policies are in place to ensure compliance with the Construction (Design & Management) Regulations 2007.
3.11 Technical standards 3.11.1 The design of the project is based on the relevant European EN standards
with National Appendices and appropriate UK technical standards for the design, construction, installation and maintenance of both the infrastructure and the electrical and mechanical plant.
3.11.2 The design team sought to create feasible design and construction approaches to identify the order limits for the project including the LLAU. These limits were used to assess impacts, identify and mitigate risks, and prepare a robust cost estimate and programme. The application drawings are underpinned by preliminary design engineering drawings, design reports, analysis, project standards and various other documents.
3.11.3 The approaches were based on international and UK best practice. Lessons learned from schemes in the UK and overseas were also applied to this project.
3.11.4 The design life of the structures is 120 years; the objective was for minimal maintenance and ten-yearly inspections of the deep components. All components that require more regular inspection would be located on or within 14m of the surface to simplify access and minimise health and safety risks.
3.11.5 The detailed design and construction would be undertaken by suitably experienced and qualified contractors. The contractors would be given
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3 Engineering considerations
performance specifications to ensure that the system meets the above requirements and Thames Water3 would monitor implementation to ensure compliance.
3.11.6 The design of the above-ground elements of the project would also be governed by the design principles that underpin the architectural and landscape designs set out in the Book of Plans and the Design and Access Statement. The design principles were developed in consultation with local authorities and strategic stakeholders and would govern the final detailed design of the above-ground structures and spaces associated with the project.
Thames Water Standards 3.11.7 Thames Water has developed a series of standard practice documents,
which provide guidance and design criteria for the development of any new infrastructure. The standard practice documents relevant to the project include: a. Tunnels and Tunnelling. Standard Practice Document B07 Issue 2.0 b. Sewerage. Standard Practice Document B04 Issue 2.0
3.11.8 In general and where relevant, the principles detailed in the standard practice documents were followed in developing the project design criteria to ensure that the infrastructure would be compatible with existing sewerage infrastructure and its operation and maintenance regime. However, some of the guidance in the standard practice documents has been superseded by the criteria set out in this document to obtain the most economic design solution for this project, which is significantly larger than other projects normally undertaken by Thames Water. The full design criteria contained in this document therefore supersedes the design criteria contained in the standard practice documents B04 and B07.
Specifications 3.11.9 Particular Specifications prepared for the project would be based on the
following documents: a. Specification for Tunnelling 3rd Edition, British Tunnelling Society,
London, Thomas Telford (2010) b. New Civil Engineering Specification for the Water Industry (CESWI)
seventh edition, WRcplc (2011) c. ICE Specification for piling and embedded retaining walls, second
edition, ICE, Thomas Telford Publishing (2007) d. Water Industry Mechanical and Electrical Specification (WIMES),
Pump Centre.
3 Thames Water Utilities Ltd (TWUL). The Draft Development Consent Order (DCO) contains an ability for TWUL to transfer powers to an Infrastructure Provider (as defined in article 2(1) of the DCO) and/or, with the consent of the Secretary of State, another body.
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3 Engineering considerations
British Standards and Eurocodes 3.11.10 The design shall accord with the current British Standards (BS). A list of
current British Standards relevant to the design can be found in the following documents: a. BS EN 1991-1-7 Eurocode 1 – Actions on Structures – Part 1-7:
General Actions – Accidental Loads b. NA to BS EN 1991-1-7 National Annex to Eurocode 1 – Actions on
Structures – Part 1-7: General Actions – Accidental Actions c. BS EN 1992-1-1 Eurocode 2 – Design of Concrete Structures –Part 1-
1: General Rules and Rules for Buildings d. NA to BS EN 1992-1-1 National Annex to Eurocode 2 – Design of
Concrete Structures – Part 1-1: General Rules and Rules for Buildings.
3.11.11 Structural references: a. Designers' Guide to Eurocode 1: Actions on Structures: Actions on
buildings (except wind), EN 1991-1-1, 1991-1-3 and 1991-1-5 to 1-7 b. Manual for the design of concrete building structures to Eurocode 2,
The Institution of Structural Engineers (September 2006) c. AASHTO Guide Specifications and Commentary for Vessel Collision
Design of Highway Bridges, 2nd Edition, with 2010 Interim Revisions.
Other key reference documents 3.11.12 Some key reference documents used to develop the design criteria are
listed below: a. Tunnelling references and standards
i Code of practice for safety in tunnelling in the construction industry, BS6164 (2011)
ii The Joint Code of Practice (JCoP) for Risk Management of Tunnel Works in the UK, joint publication by the Association of British Insurers and the British Tunnelling Society (2003)
iii Tunnel Lining Design Guide, British Tunnelling Society and Institution of Civil Engineers (2004)
iv Guide to best practice for the installation of pipe jacks and microtunnels, Pipe Jacking Association (1995)
v Safety of New Austrian Tunnelling Method (NATM) Tunnels, Health & Safety Executive Books, HMSO, Norwich (1996)
vi The collapse of NATM tunnels at Heathrow Airport, Health & Safety Executive Books, HMSO, Norwich (2000)
vii Sprayed Concrete Linings (NATM) for tunnels in soft ground, Institution of Civil Engineers design and practice guides, Thomas Telford, London (1996)
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viii Guidelines for the Design of Shield Tunnel Lining: Working Group No. 2; ITA: Tunnelling and Underground Space Technology, Vol 15, No. 3 (2000)
ix Guidelines for the Design of Tunnels: ITA, Tunnelling and Underground Space Technology, Vol 3, No. 3 (1988)
x STUVA (Studiengesellschaft fur UnterirdischeVerkerhsanlagene.V.) recommendations for allowable water seepage into tunnels
xi On Structural Design Models for Tunnels in Soft Ground, Underground Space, Vol 9, Duddeck D and Erdmann J (1985)p. 246 to 259
xii The circular tunnel in elastic ground, Geotechniqué 25, No 1, Muir Wood, A.M.(1975) p. 115 to 127
xiii Discussion on ‘Muir Wood, A.M., The circular tunnel in elastic ground. Geotechniqué 25, No 1, Curtis, D.J. (1975), p. 115 to 127’, Geotechniqué, Vol 26 (1976) p. 231
b. Materials references and standards i Technical Report No 63 Guidance for the Design of Steel-Fibre-
Reinforced Concrete, Concrete Society Working Group (2007) ii Specification and Guidelines for Self Compacting Concrete,
EFNARC (Feb 2002) iii National Structural Steel Specification for Building Construction,
fifth edition, the British Constructional Steelwork Association Ltd (2007)
iv BRE Special Digest 1- Concrete in Aggressive ground, third edition (2005)
c. MEICA references and standards i The Confined Space Regulations 1997, HMSO ii Dangerous Substances and Explosive Atmosphere Regulations
(DSEAR), HMSO (2002) iii Electricity at Work Regulations 1989, HMSO iv Provision and Use of Work Equipment Regulations 1998, HMSO v Control of Substances Hazardous to Health Regulations 2002,
HMSO vi The Pressure Equipment Regulations 1999, HMSO vii The Lifting Operations and Lifting Equipment Regulations 2008,
HMSO viii DIN SI5/62 Carbon Bed Adsorbers – Fire and Explosion Safety
Issues, HSE (2007) ix Risk Assessment Data Directory - Land transport accident
statistics, Report No. 434 – 9, International Association of Oil & Gas Producers, (2010)
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3 Engineering considerations
x Sewers for Adoption, sixth edition,(WRc plc) (2006) xi Design Manual: Odor and Corrosion Control in Sanitary Sewerage
Systems and Treatment Plants, EPA625185018, (October 1985) xii BS EN 62040 Uninterruptible Power Supplies xiii BS 7671 Requirements for Electrical Installations (2008) xiv BS 7775:2005 Penstocks for use in water and other liquid flow
applications —Specification xv BS EN 61439 Low-voltage switchgear and control gear
assemblies xvi BS EN 60079 Explosive atmospheres xvii BS 4142 Method for rating industrial noise affecting mixed
residential and industrial areas xviii BS EN 60529 Degree of protection provided by enclosures xix BS 4211 Specification for permanently fixed ladders xx BS 5925 Code of practice for ventilation principles and design for
natural ventilation xxi BS EN 13779: Ventilation for non-residential buildings -
Performance requirements for ventilation and room-conditioning systems
xxii BS EN ISO 14122 Safety of machinery xxiii EH40/2005 Workplace exposure limits, HSE (2005) xxiv Building regulations Volume B2 Fire Safety for Buildings other
than Dwellings d. Ventilation
i BS6164 Code of practice for safety in tunnelling in the construction industry (ventilation section)
ii H1 - Environmental Risks Assessment, Environment Agency iii H4 – Odour, Environment Agency iv Olfactometry Determination of Odour Intensity, VDI 3882 Part 1,
Verein Deutsche Ingenieur (1992) v WWN01 Thames Water Asset Standard – sewage pipelines vi WWP0.6 Thames Water Asset Standard – odour control process vii WWO 10.3 Thames Water Asset Standard – odour control by dry
scrubbing.
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4 Programme assumptions
4 Programme assumptions
4.1 General assumptions 4.1.1 The programme for delivery of the project is influenced by the Department
for the Environment, Food and Rural Affairs’ Regulatory impact assessment – sewage collection and treatment for London, which concluded that Thames Water should be asked to proceed urgently with a tunnel-based solution to resolve the excessive CSO discharges in London. It is also influenced by the NPS, which establishes the need for the project and states that appropriate strategic alternatives have been considered and that the project is the only option to address the problem of unacceptable CSO discharges within a reasonable time at a reasonable cost, subject to the requirements of the Planning Act 2008.
4.1.2 Determining the reasonable period time in which to construct the project included consideration of the above references, construction industry practices, the need to work safely and efficiently, and potential environmental impacts. Working too quickly or too slowly would also adversely affect cost.
4.1.3 For planning purposes and as a basis for determining environmental impacts, the overall shaft and tunnel construction programme is based upon completing the main works within a period of about six years. This period would include setting up sites, construction of shafts, tunnelling, secondary lining, construction of other structures, MEICA work and site restoration. Work undertaken to identify all feasible tunnel drive options is documented in the Engineering options report – Abbey Mills route (Spring 2012). Evaluating the tunnel drive options has been completed in accordance with the site selection process and is documented in the Final Report on Site Selection Process.
4.1.4 The main factors that affect the duration of the construction programme include the following: a. Depth and ground conditions at tunnel drive shafts: the time required
to construct a shaft to launch a TBM is critical to the programme. Deep shafts in more difficult ground conditions (eg chalk) that require ground dewatering and diaphragm wall methods would take longer than shallower shafts in more favourable conditions (eg London clay).
b. Length of tunnel drive: the duration of a drive is generally proportional to its length. The average tunnel drive rates would reduce for very short drives for which a greater proportion of the time is used establishing the back-up equipment for the TBM. The geological conditions also affect the rate of tunnelling that can be assumed in each area.
c. TBMs should be matched to the geology in order to optimise tunnelling production rates and to ensure that drive lengths are reasonable. Very long drives increase the risk of mechanical breakdowns and
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interventions to repair the cutterhead, whereas very short drives are inefficient.
4.1.5 In order to complete the project within this timeframe, there would be simultaneous construction activity within the tunnel and at several sites at any given time.
4.1.6 Figure A.1 to Figure A.4 are ‘time-distance diagrams’ (alternatively called time-chainage diagrams) which illustrate how construction work could progress over time. Each figure represents an assumed programme scenario based on the assumptions described. On the diagrams the horizontal axis represents the distance along the tunnel alignment. The vertical axis represents the passage of time. Construction at a single site or shaft is illustrated as a series of vertical lines because location does not change with time. The length of the vertical line illustrates the duration of the task. So for instance at Kirtling Street, vertical lines are shown for the durations of site set-up, shaft construction, construction of other structures, MEICA work and site restoration. Construction of the tunnels and secondary lining, which are carried out between one site and another, are illustrated as inclined lines because the location (or distance along the tunnel) of these activities changes with time. In this way, the progress line for the TBM driven from Kirtling Street to Carnwath Road Riverside is illustrated as an inclined line which starts from Kirtling Street and progresses diagonally downward to the point representing Carnwath Road Riverside.
4.1.7 Figure A.1 to Figure A.4 are assumed and simplified programmes. In practice construction of such a complex project would require consideration and programming of thousands of individual activities. Furthermore, the lines representing tunnelling progress were drawn assuming that work progresses at average advance rates; however, in practice the day-to-day and week-to-week rates would vary depending on a number of complex factors. For example, it is not unusual for work to start slowly as the construction teams become familiar with the plant and adopted methods (often called the ‘learning curve’) and the simplified programmes do not show these variations. In addition there are periods when the TBM require maintenance and these are not shown.
4.1.8 Advance works including procurement, detailed design, planning and utility work would (where appropriate) be carried out before the main six year period. System-wide testing and commissioning would follow the completion of the main works. Some sites would be used for shorter periods of time as there would be less work to carry out (eg the duration of works at Abbey Mills Pumping Station is assumed to be four years). Flexibility is also required at all sites (refer to Section 5).
4.1.9 For assessment of impacts, it was assumed that construction at each site would occur over a number of ‘site years’. If, for example, work at a site starts in May, the first site year would be from May in the first year to April the following year. Site years for each site are shown in Figure A.1 to Figure A.4 and are referenced in the Environmental Statement.
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4.2 Working hours 4.2.1 The programme is underpinned by assumptions regarding working hours,
taking account of the fact that the project involves constructing major underground structures and tunnels at worksites through the centre of London. The assumed working hours at each site are defined in the Code of Construction Practice, which accompanies the application.
4.3 Rationale for 24-hour continuous tunnelling 4.3.1 Successful tunnelling and underground works in London and around the
world are normally constructed on a continuous 24 hour 7 day a week basis for reasons including: a. It is more practical and efficient and leaves the tunnel safe and stable. b. Safety: particularly in poor ground conditions, stopping work increases
the risk of ground relaxation and potential collapse along with uncontrolled water ingress in certain circumstances.
c. Frequent stopping and starting puts additional strain on the construction plant and increases the risks of breakdowns, which lead to delays and greater health and safety risks.
d. It limits settlement effects at the surface as stopping work allows the ground to relax and increases the time before the tunnel lining is installed.
e. It reduces programme duration and construction impacts. f. It reduces cost because capital investment in site establishment and
tunnelling operations is considerable and continuous working maximises sites’ efficiency and reduces standing time.
4.3.2 Types of continuous activities mainly include underground activities and works such as: a. construction of tunnels using shields and TBMs, and erection of linings
immediately behind the TBM or shield. b. construction of secondary linings using insitu reinforced concrete lining
techniques. 4.3.3 During 24-hour working, the environmental impacts are concentrated
around the shaft and excavated material handling areas. Where appropriate, mitigation measures including noise barriers and enclosures would be provided. These measures are defined in the Code of Construction Practice.
4.3.4 Deliveries to and removal of materials from drive sites would be limited to normal working hours unless otherwise agreed with the local authority or under exceptional circumstances for special or abnormal deliveries.
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4.4 Assumed advance rates
Shafts 4.4.1 Table 4.1 provides the typical progress rates in the construction
programme for main tunnel shafts and CSO drop shafts. The rates were determined by construction experts and compared with rates on similar projects in London.
Table 4.1 Assumed shaft construction rates Activity Average rate
(m/week) Excavation for caisson or SCL >20m diameter shaft 4
Excavation for caisson or SCL 20m diameter shaft 5
Excavation for caisson or SCL <20m diameter shaft 6
Secondary lining to shafts 6
Shaft internal platforms including vortex structures 6
Diaphragm wall panels 1 No. 3.6m wide panel/week
Diaphragm wall – internal shaft excavation rate 4
Tunnels 4.4.2 The drive rates are based on 24-hour working and were determined by
tunnelling experts in consultation with contractors and TBM manufacturers. The rates were also compared with rates achieved on similar tunnels such as the Channel Tunnel Rail Link in London, which used similar-sized machines.
4.4.3 The rates allow for ground conditions and the type of TBM. A reduced rate has been assumed for the last section of the tunnel drive from Kirtling Street to Chambers Wharf as EPB TBMs do not work efficiently in Chalk.
4.4.4 The rates are long-term averages and peak weekly outputs would likely be considerably more. The rates also allow for routine TBM face interventions and maintenance work.
4.4.5 Tunnelling cannot start until the drive shaft has been built. An allowance was made for an incremental launch to build the TBM and establish its back-up equipment. A further allowance was made at the start of each tunnel to allow the operators and construction crew to learn to use the plant efficiently.
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4 Programme assumptions 4.4.6 The main tunnel drive rates in the assumed construction programme are
set out in Table 4.2. Table 4.2 Assumed main tunnel drive rates
Ground conditions TBM type Average rate (m/week)
London Clay EPBM 100
Woolwich and Reading/Thanet Sands EPBM 90
Chalk EPBM 50
Chalk Slurry TBM 80
4.4.7 Connection tunnel drive rates in the assumed construction programme are set out in Table 4.3
Table 4.3 Assumed long connection tunnel drive rates Connection tunnel Ground
conditions TBM type Average rate
(m/week) Frogmore connection tunnel London Clay EPBM 60
Greenwich connection tunnel Chalk Slurry TBM 80
Tunnel secondary lining 4.4.8 Construction of the tunnel secondary lining can only be started when the
tunnel drive is complete. The progress rates provided in Figure A.1 to Figure A.4 were assumed. Construction of the secondary lining would only be carried out from suitable shaft sites; it may start from one shaft and end at another or it may start mid-tunnel and progress towards two shafts.
Table 4.4 Assumed tunnel secondary lining rates Tunnel Average rate (m/week) Main tunnel 140
Long connection tunnel 100
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5 Flexibility for design and construction assumptions
5 Flexibility for design and construction assumptions
5.1 Construction information 5.1.1 Construction information provided in the Book of Plans and Environmental
Statement is illustrative of the nature, type, timing, extent and layout of the temporary works and is representative of practical methods that may be used. On that basis, this information was used as a suitable basis for assessment of environmental impacts.
5.1.2 Flexibility within the LLAU is required to enable contractors to: a. use alternative methodologies, plant and equipment, based on their
experience and expertise, in order to construct the works as efficiently and as safely as possible
b. develop temporary works designs and methodologies based on more detailed site and geological information available at the time of construction
c. arrange sites to take account of actual surroundings and land use at the time of construction in order to minimise disruption and nuisance to third parties
d. implement alternative procurement and contract packaging arrangements, which may, for example, change the construction phasing and assumptions in relation to the duration of the works.
5.2 Tunnel alignment and external dimensions
Main tunnel and long connection tunnels 5.2.1 A defined vertical and horizontal ‘alignment adjustment’ allowance within
the tunnel limits of deviation is defined in the Book of Plans, which relates to: a. tunnel construction tolerances because it is not physically possible to
construct a tunnel without small deviations from the theoretical alignment
b. small adjustments to the design alignment to increase clearances and minimise impacts on existing above-or below-ground third party infrastructure
c. small adjustments to the design alignment to suit the methodology, eg the length of straight-line ‘shunts‘ out of shafts (the initial section of tunnel built from the shaft) and transitions between straight and curved sections of the alignment
d. detailed design of primary and secondary tunnel linings to suit contractors’ methodologies and TBM designs –the detailed design of linings would be the contractors’ responsibility and requires flexibility in the external diameter
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5 Flexibility for design and construction assumptions
e. tunnel interaction with shafts including permitted amendments to: i shaft locations within the parameters defined in the Book of Plans ii shaft to tunnel offsets, for example, to optimise internal access
and hydraulic arrangements iii tunnel alignment within the limits of deviation.
5.2.2 The horizontal ‘alignment adjustment’ allowance would not be included when finalising the extent of land to be acquired after the tunnels have been built.
Short connection tunnels 5.2.3 In addition to issues identified for main and long connection tunnels, a
larger horizontal ‘alignment adjustment’ is required to avoid poor ground and to minimise construction and safety risks. There can be high degrees of local variability in geological strata. Constructing the short connection tunnels and the junctions with the main tunnel would be challenging and safety critical, and would be heavily influenced by the geology and groundwater pressure. Because the tunnels are predominantly located under the river, wider alignment adjustments would have negligible impacts on third parties.
5.3 Structure location and external dimensions
Shafts 5.3.1 The zones in which the main tunnel shafts and CSO drop shafts would be
located are defined on the Site works parameter plans for each site in the Book of Plans. Varying degrees of flexibility for the zones were determined on a site-by-site basis that depend on and allow for: a. detailed design of final hydraulic, structural and access arrangements
and construction methods –adjustments to the final shaft locations and external dimensions may be required
b. the final architectural and landscaping site layout and appearance; the Proposed site features plans and Proposed landscape plans are either indicative or illustrative and the degree of flexibility varies depending on existing site constraints, engineering requirements, ventilation, operational access, and the degree of agreement with stakeholders
c. the need to minimise impacts on the river at foreshore sites d. final tunnel alignments e. methods of shaft construction f. detailed design of primary and secondary shaft linings to suit the
contractors’ methodologies.
‘Near surface’ below-ground chambers and culverts 5.3.2 The zones in which near surface below-ground chambers and culverts are
located are defined on the Site works parameter plans in the Book of
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5 Flexibility for design and construction assumptions
Plans. Varying degrees of flexibility for the zones were determined on a site-by-site basis that depend on and allow for: a. final site layout and appearance b. detailed design of the final hydraulic, ventilation, structural and below-
ground access c. methods of shaft construction d. shaft locations e. final sizing of mechanical plant, eg final flap valve and penstock
arrangements may require adjustments in the final sizing and location of structures
f. detailed structural design.
Above-ground ventilation structures and electrical and control kiosks
5.3.3 The zones in which above-ground ventilation structures and electrical and control kiosks are located are defined on the Site works parameter plans in the Book of Plans. Flexibility within defined limits to allow for: a. final architectural and landscaping site layout and appearance b. adjustments to shaft and ‘near surface’ below ground chambers and
culverts c. final ventilation design and plant selection, which would be supplied by
specialist ventilation and odour treatment process contractors and designs may vary across suppliers
d. detailed structural design.
5.4 Permanent foreshore structures 5.4.1 The maximum extent of the foreshore structures is defined on the Site
works parameter plans in the Book of Plans. There is flexibility to reduce their footprints if the shafts and other structures can be safely accommodated and provided that final designs meet fluvial, ship impact protection, architectural, landscape and structural design requirements.
5.5 Final appearance, finishes and landscaping 5.5.1 The layout of most sites in the application plans and drawings are
indicative or illustrative and the degree of flexibility varies from site to site. The final designs and layouts would be agreed with the appropriate local planning authority at a later date and would comply with the Design Principles document. The appearance of ‘foreshore heritage sites’ must be in-keeping with their settings. There is generally greater flexibility on the final appearance of less sensitive sites, sites where the degree of agreement with stakeholders on the desired final architectural and landscaping arrangements is less established, and where the future use of a site and the surrounding developments is less certain.
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6.1 Principles guiding tunnel alignment
Safety 6.1.1 Under the Construction (Design and Management) Regulations 2007
(CDM), designers’ obligations are, insofar as reasonably practicable, to avoid foreseeable risks to the health and safety of any person carrying out construction work. The designer must eliminate hazards that may give rise to risks and reduce risks from any remaining hazards.
6.1.2 Tunnelling is one of the higher risk operations in the construction industry, therefore health and safety is a prime focus of the design, alongside system performance. The design process, including selecting the alignment, was shaped by assessment of risk, which is a formal requirement of the CDM regulations. The specific risks that influenced the tunnel alignment included: a. the need to avoid deep foundations where known or foreseeable b. the potential for scour holes or other poor ground in London Clay (the
flexibility of the limits of deviation was increased) c. the potential for very difficult ground conditions in the Lambeth Group
(connection tunnels were shortened as far as possible to enable ground treatment from the surface or in-tunnel ground freezing etc).
d. the difficulty of tunnelling in Chalk (short connection tunnels for deep main tunnel shafts in chalk were eliminated, except for the connection to the Lee Tunnel).
Shaft locations 6.1.3 Tunnel shaft locations were derived after an extensive exercise looking at
the CSO locations, suitability of available sites (which are of limited size and number in the urban environment), and tunnel drive strategies in accordance with the Site selection methodology paper. The final shaft locations are identified in the Final Report on Site Selection Process.
Hydraulic controls 6.1.4 It is fundamental to meet hydraulic requirements in order to convey flows
in the tunnel (see Section 3.4). In practice, the horizontal alignment is controlled by factors other than hydraulics, such as minimum excavated radius. However, hydraulics is the critical factor for the vertical alignment; de-aeration also influenced the length and diameter of connection tunnels close to some shafts.
6.1.5 The depth of the main tunnel at its downstream end is dictated by the invert level at Shaft F at Abbey Mills (the Lee Tunnel Shaft), which is 40.184m ATD. Upstream, the tunnel depth is dictated by hydraulic constraints –predominantly gradient constraints– and existing buried infrastructure.
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6 Tunnels 6.1.6 Hydraulics dictates the acceptable range of gradients for the tunnel. The
tunnel needs to be self-cleansing therefore velocities during event cycles must exceed 1 m/s, which requires a gradient of at least 1 in 850. The target gradient for the main tunnel is 1 in 800.
6.1.7 A single gradient for the whole tunnel length would be preferred to ensure well-conformed hydraulic behaviour. Changes in gradient are only permitted at online shaft locations. Tunnel gradients would be constant between online shafts and along connection tunnels. A constant gradient would be maintained between Acton Storm Tanks and Carnwath Road Riverside and between Carnwath Road Riverside and Abbey Mills Pumping Station.
6.1.8 The following interrelated issues influenced the selection of the gradient: a. localised hydraulic requirements of the design b. depth of shafts c. acceptable clearances to third party infrastructure d. ground conditions, especially in relation to the construction of shafts
and tunnel junctions.
Tunnel connections 6.1.9 There are a variety of means of connecting CSO drop shafts to the main
tunnel. At some locations, the drop shaft is remote from the main tunnel and the connection tunnel connects to it directly in a concrete-lined underground chamber. In these locations, the main tunnel alignment needs to be straight for at least 5m either side of the connection centreline. This straight section allows special straight lining sections to be built into the tunnel to facilitate construction of the junction sometime after the main tunnel has been excavated. One exception to this rule was made for the Hammersmith short connection tunnel, which joins the main tunnel on a 600m radius curve to negotiate an alignment below a proposed residential development.
6.1.10 An angle of 70° is required between the main tunnel and the connection tunnel to direct the flow from the connection tunnel downstream in the main tunnel; angles greater than 70° are not favoured from a hydraulic design perspective. Angles less than 70° are not favoured from a structural design perspective because they would need larger openings in the main tunnel lining and are more difficult to construct safely.
6.1.11 Vertically, connection tunnels join the main tunnel axis-to-axis to simplify construction.
6.1.12 Where connection tunnels join at main tunnel shafts, the connection level is dictated by the gradient of the connection tunnel and constraints along its alignment.
Minimum radii 6.1.13 The main tunnel would have an excavated diameter of approximately 8.1m
for the drive between Acton Storm Tanks and Carnwath Road Riverside and approximately 8.8m until Abbey Mills Pumping Station. A closed-face
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TBM would be used to construct the main tunnel: an EPB machine would be used in London Clay and Lambeth Group and a slurry machine in Chalk. Figure 6.1 and Figure 6.2 illustrate the Slurry TBM used to construct the Lee Tunnel. Similar machines would be used on this project.
6.1.14 TBMs of this type have a long cylindrical shield immediately behind the cutterhead that dictates the minimum curve radius that can be excavated. The shield has to be long enough to accommodate the drive train, main bearing, slurry system or screw, shove rams, segment erector, and tail seal etc. Back-up trailors are pulled behind the shield. With this scale of tunnel, the preferred minimum horizontal radius is 600m. The TBM would likely be articulated in order to negotiate this radius. This minimum radius allows for the fact that slightly tighter radii may be required to carry out alignment corrections during the drive to stay within the limits of deviation. Figure 6.1 Cutterhead and front of the Slurry TBM used to construct
the Lee Tunnel
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Figure 6.2 Shield and first back-up trailer of the Slurry TBM used to construct the Lee Tunnel
6.1.15 Radii as low as 400m are possible (with special provisions); however, this
increases cost, risk, time and the potential to damage tunnel lining segments of the TBM. These special provisions may include: a. It is possible to include TBM articulation joints along the main shield. b. A tail skin articulation joint is always fitted to allow alignment
adjustment with the tunnel lining segments. c. Back-up trailers may need to be shortened to negotiate the tighter
curve. d. Rail and pipe lengths may need to be shortened during the curve. e. The alignment/survey laser may need to be moved up more
frequently. f. The secondary lining shutter may need to be shortened to suit the
tighter radius, and the construction programme may be increased as a result.
6.1.16 Therefore, 600m has been taken as the minimum radius for the main tunnel alignment.
6.1.17 The connection tunnels would be smaller in diameter (less than 5.5m) and excavated using a variety of methods depending on depth, geology, length, diameter, and third party constraints. The preferred minimum
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horizontal radius for these smaller tunnels would be 400m. Open-face machines and sprayed concrete lining methods enable tighter radii. However, closed-face TBM construction is preferred for the long main tunnel drives for programme, cost and constructability reasons. SPRAYED CONCRETE LINING has limitations relating to drive length, geology, depth, and water ingress etc.
Alignment through online shafts 6.1.18 When a TBM passes through an online shaft, the rings and shove frame
do not have the lateral restraint normally offered by the surrounding ground. In order to minimise lateral loads, a 15m straight section of tunnel was introduced either side of online shafts. This section would also satisfy a hydraulic aim to minimise turbulence within the shafts.
6.1.19 In some locations it would be necessary for the tunnel to change direction within a shaft. In such cases, the contractor would need to make special arrangements to accommodate the thrust of the machine as it leaves the shaft. For hydraulic reasons the minimum preferred angle of incidence between the in-coming and out-going tunnels is 135°. However, exceptions would be possible subject to appropriate hydraulic assessment. Two special arrangements assessed as acceptable would also accommodate third party infrastructure constraints: a. at Kirtling Street the angle of incidence would be 125° b. at Abbey Mills Pumping Station the angle of incidence would be 123°.
Existing infrastructure 6.1.20 Ground movement leading to settlement is an inevitable consequence of
tunnelling and construction of underground infrastructure. It can be controlled by appropriate methods and controls. In order to minimise settlement, the tunnel alignment is constrained by the presence of existing infrastructure such as tunnels, bridges, buildings, foundations, utilities, and river walls. In order to minimise the ground movement risks to third party infrastructure, the tunnel would pass below the River Thames and other watercourses(where possible) in order to maximise separation from infrastructure. Where it would pass under land, it would follow roads or other open linear features as far as practical.
6.1.21 The alignment would pass close to the mid-point of bridge spans, where possible, in order to ensure the maximum clearance to bridge foundations to minimise the risk of settlement to the bridge piers. First spans of bridges where services pass from the bridge deck and abutments to the ground are more susceptible to differential movement. First spans would be avoided as far as possible
6.1.22 Where the tunnel alignment passes beneath built-up areas, it would avoid larger structures that would likely have piled foundations which will rely on ground reaction closer to the tunnelling depths.
6.1.23 The minimum clearance between the extrados of the tunnel and existing infrastructure is 3m. The actual clearance would generally be significantly
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greater, depending on geometric constraints and the need to limit the impact of ground movement.
6.1.24 An additional consideration when selecting the alignment was, as far as possible, to facilitate access from the surface (over water or unobstructed land) to enable emergency interventions to the TBM face during construction.
6.1.25 Ground movement and settlement caused by tunnelling and other construction has been assessed and the approach to monitoring and mitigation to be implemented as part of the asset protection process is described in the Settlement information paper.
6.2 Main tunnel
Vertical alignment 6.2.1 Due to the existing London Ring Main tunnel and other existing
underground infrastructure located at a similar level to the Thames Tideway tunnel, the vertical alignment was split into two sections: a. Acton Storm Tanks shaft to Carnwath Road Riverside shaft b. Carnwath Road Riverside shaft to Lee Tunnel Shaft F at Abbey Mills
Pumping Station. 6.2.2 Each section has a different constant gradient, separated by a vertical
step in the main tunnel shaft at Carnwath Road Riverside.
Horizontal alignment From Acton Storm Tanks to Carnwath Road Riverside Figure 6.3 Horizontal alignment from Acton Storm Tanks to Carnwath
Road Riverside
6.2.3 From the Acton Storm Tanks shaft, the main tunnel would run south
through a developed urban area. The alignment would pass under gardens or along roads where possible to avoid buildings as far as
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possible. It would also run under and along the existing Acton Storm Water Outfall Sewer tunnel from Acton Storm Tanks to Netheravon Road.
6.2.4 The tunnel alignment would cross the above-ground District and Piccadilly line railway near Stamford Brook Station, cross Chiswick High Road, and continue down Netheravon Road.
6.2.5 As the tunnel passes beneath the River Thames, it would cross above the Thames Water Ring Main and then under the western playing fields of St Paul’s School before turning eastwards parallel to Lillian Road. It would continue eastward to the south side of St Paul’s School’s eastern playing fields, to the south of the Hammersmith Bridge underneath residential properties in Riverview Gardens, and then back under the River Thames.
6.2.6 The Hammersmith connection tunnel would join the main tunnel approximately 250m to the east of the Hammersmith Bridge abutment, opposite the park in front of St Edmund’s Square. From here to Carnwath Road Riverside it would run entirely under the River Thames, with two connection tunnels to the Barn Elms drop shaft and the Putney Embankment Foreshore drop shaft. It would pass above the Thames Water Lee Valley Tunnel and beneath the Richmond to Fulham high pressure gas pipeline, with 8m of vertical separation.
6.2.7 The approximate internal diameter of the main tunnel changes from 6.5m to 7.2m at Carnwath Road Riverside. The Frogmore connection tunnel from the King George’s Park and Dormay Street CSO drop shafts would connect to the Carnwath Road Riverside main tunnel shaft. Carnwath Road Riverside to Kirtling Street
Figure 6.4 Horizontal alignment from Carnwath Road Riverside to Kirtling Street
6.2.8 From Carnwath Road Riverside the main tunnel would generally follow the
river to Kirtling Street. The alignment would run east, crossing under the proposed alignment of the Wimbledon to Kensal Green National Grid cable tunnel, approximately 110m east of the Carnwath Road Riverside main tunnel shaft.
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6 Tunnels 6.2.9 East of Carnwath Road Riverside, the main tunnel would pass under an
industrial estate including a PC World store then towards the southern side of the river to connect with the Falconbrook connection tunnel. It would pass through the northern span of the Wandsworth Bridge.
6.2.10 After crossing beneath Wandsworth Bridge, the main tunnel would turn towards the southern bank to shorten the length of the Falconbrook connection tunnel.
6.2.11 Towards the Lots Road connection tunnel to the north, it would pass below the second span (from the west) of the Battersea Rail Bridge before crossing back to the northern bank of the river to connect to the Lots Road connection tunnel.
6.2.12 From the Lots Road connection tunnel, the main tunnel would follow the Chelsea Reach of the River Thames, passing under Battersea Bridge and Albert Bridge.
6.2.13 From the junction with the Ranelagh connection tunnel, it would cross the mid span of Chelsea Bridge and the second span (from the south) of Grosvenor Bridge.
6.2.14 From Grosvenor Bridge, the main tunnel would turn toward Kirtling Street on the south side of the River Thames. The main tunnel would pass beneath the jetty in front of the Cringle Dock refuse transfer station before reaching the Kirtling Street main tunnel shaft. Kirtling Street to Chambers Wharf
Figure 6.5 Horizontal alignment from Kirtling Street to Chambers Wharf
6.2.15 The main tunnel would head southeast, staying to the north of a residential
development currently under construction in order to minimise the impact on known current and future developments that have received planning permission. The tunnel would then head east, passing under the jetty adjacent to the Tideway Industrial Estate as close to the south bank of the river as possible in order to minimise the length of the Heathwall/SWSR connection tunnel.
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6 Tunnels 6.2.16 The main tunnel would continue to the south of the river centreline and
pass below the first span (from the south) of Vauxhall Bridge, in order to minimise the length of the Clapham/Brixton connection tunnel and stay clear of existing buildings.
6.2.17 The main tunnel would then head north and cross the central span of Lambeth Bridge and beneath the Jubilee Line tunnels. As it approaches the Victoria Embankment Foreshore site, it would move to the western side of the river centreline, passing under the third span (from the west) of Westminster Bridge as close to the western side of the river as possible to reduce the length of the Regent Street connection tunnel.
6.2.18 After the Regent Street connection tunnel, the main tunnel would pass below the second span (from the west) of Hungerford Bridge and the BT St Martins General Post Office Tunnel. It would then continue on the northern side of the river centreline to pass under the second span (from the north) of Waterloo Bridge. Approaching the online Blackfriars Bridge Foreshore CSO drop shaft, it would move to the northern side of the river with a straight section to take the tunnel alignment through the drop shaft.
6.2.19 The main tunnel would then pass below the middle of the second spans (from the north) of Blackfriars road and rail bridges. From the east of the Blackfriars bridges, the tunnel would follow the middle of the river as far as possible, passing below the middle spans of Millennium Bridge, Southwark Bridge, Cannon Street Bridge, London Bridge and Tower Bridge.
6.2.20 After crossing Tower Bridge mid span, the alignment would move across to the southern side of the river in front of St Saviour’s Dock. This section of the route has been moved away from the authorised navigation channel of the river and to align with the shaft at Chambers Wharf. Chambers Wharf to Abbey Mills Pumping Station Figure 6.6 Horizontal alignment from Chambers Wharf to Abbey Mills
Pumping Station
6.2.21 The main tunnel alignment would cross from the south bank of the river at
the Chambers Wharf main shaft, to the north bank at King Edward Memorial Park Foreshore.
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6 Tunnels 6.2.22 From the King Edward Memorial Park Foreshore CSO drop shaft (on-line),
the main tunnel would continue eastwards towards the entrance to the Limehouse Basin. The alignment would turn northward to pass under the Old Sun Wharf as it cuts across towards the east side of the basin.
6.2.23 North of the basin, the main tunnel would thread between the tower block buildings of Basin Approach, to avoid passing directly beneath these structures. The main tunnel alignment also avoids the high-rise buildings of Park Height Court on Wharf Lane and The Mission on Commercial Road. It would then follow the Limehouse Cut towards Abbey Mills Pumping Station.
6.2.24 Following the Limehouse Cut as far as the Blackwall Tunnel Northern Approach Road, the main tunnel would pass under the low rise buildings at Barratt Industrial Park as it turns to a more northerly direction across the River Lee. Keeping to the west of the gas holders, the main tunnel would cross under the surface rail tracks of the District Line and across the Channelsea River, passing into the Abbey Mills Pumping Station land where the main tunnel shaft is located.
6.3 Connection tunnels 6.3.1 The connection tunnels are listed in Table 6.1 along with their associated
CSOs and sites. Table 6.1 Connection tunnels
Tunnel name CSO name Site name Hammersmith connection tunnel
Hammersmith Pumping Station
Hammersmith Pumping Station
West Putney connection tunnel
West Putney Storm Relief Barn Elms
Putney Bridge connection tunnel
Putney Bridge Putney Embankment Foreshore
Frogmore connection tunnel
Frogmore storm Relief – Bell Lane Creek Frogmore storm Relief – Buckhold Road
Dormay Street King George’s Park
Falconbrook connection tunnel
Falconbrook Pumping Station
Falconbrook Pumping Station
Lots Road connection tunnel
Lots Road Pumping Station
Cremorne Wharf Depot
Ranelagh connection tunnel
Ranelagh Chelsea Embankment Foreshore
Heathwall/SWSR connection tunnel
Heathwall Pumping Station South West Storm Relief
Heathwall Pumping Station
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Tunnel name CSO name Site name Clapham/Brixton connection tunnel
Clapham Storm Relief Brixton Storm Relief
Albert Embankment Foreshore
Regent Street connection tunnel
Regent Street Victoria Embankment Foreshore
Greenwich connection tunnel
Greenwich Pumping Station Deptford Storm Relief Earl Pumping Station
Greenwich Pumping Station Deptford Church Street Earl Pumping Station
Hammersmith connection tunnel 6.3.2 The Hammersmith connection tunnel would join the Hammersmith
Pumping Station drop shaft to the main tunnel under the river. The connection tunnel would pass through a new development that is proposed on the east bank of the river.
West Putney connection tunnel 6.3.3 The West Putney connection tunnel would join the Barn Elms drop shaft,
on the south side of the Beverly Brook gas main, to the main tunnel.
Putney Bridge connection tunnel 6.3.4 The Putney Bridge connection tunnel would join the Putney Embankment
Foreshore drop shaft with the main tunnel under the river.
Frogmore connection tunnel 6.3.5 The Frogmore connection tunnel would be approximately 1,100m long and
connect the drop shaft at King George’s Park to the main tunnel at Carnwath Road Riverside main tunnel shaft via the online drop shaft at the Dormay Street site. This tunnel would pass through a built-up area with existing tunnels. Consequently, the route is relatively convoluted.
6.3.6 At King George’s Park the connection tunnel would head north from the drop shaft under Buckhold Road, 3.0m above and parallel to the proposed National Grid Tunnel. A 100m radius curve has been introduced to avoid the proposed and recent multi-storey development properties on the west side of Buckhold road and also the existing shopping centre and car park on the east side of Buckhold Road.
6.3.7 From the north of Wandsworth High Street, the connection tunnel would generally follow Church Row and Wandsworth Plain to avoid passing directly beneath All Saint’s Church and the other buildings along these roads. It then passes beneath the buildings between Frogmore and Dormay Streets before reaching the drop shaft at Dormay Street. The tunnel would also avoid passing beneath buildings with deep piled foundations along Frogmore.
6.3.8 The connection tunnel alignment continues through the drop shaft and then follows the line of Bell Lane Creek into the River Thames and under
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the viaduct. The connection tunnel would join the main tunnel at Carnwath Road Riverside main tunnel shaft after crossing the Thames.
Falconbrook connection tunnel 6.3.9 The Falconbrook connection tunnel links the Falconbrook Pumping Station
drop shaft to the main tunnel at a chamber mid-river. The connection tunnel would pass between proposed developments at Bridges Wharf and Prices Court. The alignment might need local adjustment within the limit of deviation once the final details of the two developments are known. The connection tunnel would cross under the existing UKPN Wimbledon Pimlico cable tunnel beneath York Road.
Lots Road connection tunnel 6.3.10 The Lots Road connection tunnel would join the Cremorne Wharf Depot
drop shaft and the main tunnel under the river.
Ranelagh connection tunnel 6.3.11 The Ranelagh connection tunnel would join the Chelsea Embankment
Foreshore drop shaft and the main tunnel under the river. With approval already obtained from the promoter of Crossrail 2, the drop shaft would be situated within the safeguarded zone for the proposed Crossrail Chelsea to Hackney Line. As the connection tunnel would be constructed on the geological boundary with the Lambeth Group, the main tunnel is aligned to make this connection tunnel as short as possible within the constraints of third party infrastructure, while meeting the hydraulic requirements for de-aeration, in order to minimise health and safety risks associated with constructing the connection tunnel. Refer also to para. 6.1.2.
Heathwall/SWSR connection tunnel 6.3.12 The Heathwall/SWSR connection tunnel would join the Heathwall
Pumping Station drop shaft to the main tunnel. As the connection tunnel would be constructed within the Lambeth Group, the main tunnel would be aligned to make this connection tunnel as short as possible within the constraints of third party infrastructure in order to minimise health and safety risks associated with constructing the connection tunnel. Refer also to para. 6.1.2.
Clapham/Brixton connection tunnel 6.3.13 The Clapham/Brixton connection tunnel would join the Albert Embankment
Foreshore drop shaft to the main tunnel under the river. As the connection tunnel would be constructed within the Lambeth Group, the main tunnel would be aligned to make this connection tunnel as short as possible within the constraints of third party infrastructure in order to minimise health and safety risks associated with constructing the connection tunnel. Refer also to para. 6.1.2.
Regent Street connection tunnel 6.3.14 The Regent Street connection tunnel would join the Victoria Embankment
Foreshore drop shaft to the main tunnel under the river. As the connection
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tunnel would be constructed within the Lambeth Group, the main tunnel would be aligned to make this connection tunnel as short as possible within the constraints of third party infrastructure in order to minimise health and safety risks associated with constructing the connection tunnel. Refer also to para. 6.1.2.
Greenwich connection tunnel 6.3.15 The Greenwich connection tunnel would be approximately 4,600m long
and link the drop shafts at the Greenwich Pumping Station, Deptford Church Street and Earl Pumping Station sites and connect them to the main tunnel shaft in Chambers Wharf. This connection tunnel would be constructed entirely in Chalk. It would pass through a dense urban area, which would make it impossible to avoid existing buildings and infrastructure completely.
6.3.16 The vertical alignment for this connection tunnel would be constrained by the operational Jubilee Line tunnels, the proposed UK Power Networks New Cross to Wellclose Square Cable Tunnel and their New Cross to Hurst Green Tunnel, which both pass above the connection tunnel. To minimise the impact, the connection tunnel alignment has been lowered to increase clearance to the Jubilee Line to approximately 10m.
6.3.17 From Chambers Wharf, the connection would tunnel head in a southerly direction under residential properties in Bevington Street, Riverside Primary School and properties in Spenlow House. The connection tunnel would then pass underneath Jamaica Road at almost 90°, before passing beneath low rise residential property and heading in an approximately south east direction towards Southwark Park. Prior to entering the park, the connection tunnel would navigate between the foundations of two six-storey buildings, namely Lockwood Square and Marden Square.
6.3.18 The connection tunnel would then pass under the centre portion of the park, traversing to the south eastern end towards Surrey Quays Station on the London Overground Network. The connection tunnel would pass next to a new piled building bounding the London Overground Station before passing further south next to the high-rise building of Dunlin House, and under the high rise building of Jura House and Husborne House before meeting the drop shaft at Earl Pumping Station.
6.3.19 The connection tunnel would exit at the drop shaft at Earl Pumping Station towards Yeoman Street industrial works and saw mill. The connection tunnel would then align between high-rise buildings at Pendennis House, Argosy House and Eddystone Tower.
6.3.20 The connection tunnel would then pass beneath the industrial units of Crown Wharf scrap yard, New Baltic Wharf, Park Wharf, and Bridge Wharf before aligning below Evelyn Street.
6.3.21 The connection tunnel would follow the alignment of Evelyn Road until Langford House, where the alignment turns south towards the drop shaft at Deptford Church Street and passes under the low rise Akwaaba Centre and several low-rise buildings on Deptford High Street. Prior to entering
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the drop shaft, the tunnel alignment curves round St Paul’s Church, generally along the alignment of Crossfield Street.
6.3.22 The connection tunnel would leave the drop shaft at Deptford Church Street before passing under the rail viaduct for the main line trains to London Bridge, passing close to the lifting bridge on Deptford Creek, under the precast Docklands Light Railway (DLR) viaduct to the final drop shaft at Greenwich Pumping Station.
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7 Acton Storm Tanks
7 Acton Storm Tanks
7.1 Introduction 7.1.1 The proposed development site is located in the London Borough of
Ealing and is in close proximity to the boundaries of the London Borough of Hammersmith and Fulham and the London Borough of Hounslow.
7.1.2 The majority of the site comprises a Thames Water operational facility, including six open storm tanks, an existing pumping station and associated infrastructure.
7.1.3 The site is bounded to the north by Canham Road and also by a private dwelling and land owned by London Borough Ealing which consist of a number of residential dwellings and scrub land.
7.1.4 The east and southeast of the site are bounded by Warple Way and residential properties.
7.1.5 To the west and southwest the site is bounded by third party land used as a private car park.
7.1.6 The site would be used as a main tunnel reception site to perform the following functions: a. receive the main tunnel from Carnwath Road Riverside b. Intercept flows from the Acton Storm Relief CSO c. provide air management and ventilation facilities d. provide access for operation and maintenance (including vehicle
access to the main tunnel) e. provide emergency egress from the tunnel and main tunnel shaft
during maintenance operations. 7.1.7 Drawings of the site are provided in Section 5 of the Book of Plans.
7.2 Structures 7.2.1 The principal structures would comprise:
a. a main tunnel shaft b. an above-ground interception chamber c. an above-ground overflow weir chamber d. a valve chamber e. a ventilation column f. a number of above-ground ventilation structures g. a number of below-ground noise control chambers h. two below-ground air treatment chambers.
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Size 7.2.2 The main tunnel shaft would have an approximate internal diameter of
15m and be approximately 31m deep from top of cover slab to invert of the tunnel. The shaft shall be located within an area currently occupied by the two northern most storm tanks. These two tanks would be decommissioned and filled to existing ground level as part of the proposals. The shaft access covers would be finished at existing ground level.
7.2.3 The internal diameter of the main tunnel shaft is dictated by the size of the main tunnel, and partly by the plan area required in the shaft base for de-aeration of the flows descending from the connection culvert through the vortex drop. The size of the shaft also needs to reflect safe operational access requirements.
7.2.4 The external diameter of the main tunnel shaft is dictated by the construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The shaft would be predominantly excavated in London Clay ground conditions. The depth of the shaft is determined by the depth of the main tunnel.
7.2.5 The size of the interception chamber is dictated partly by the size and location of existing infrastructure and partly by the design flow rate to be intercepted (10 m3/s, see Table 3.2). Hydraulic modelling was undertaken to estimate the chamber size. The size of the chamber also needs to reflect safe operational access requirements.
7.2.6 The sizes of the below-ground ventilation structures and air treatment chambers are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
7.2.7 The ventilation column would be approximately 5m x 4.5m by 15m high. The cross-sectional area of the ventilation column is dictated by the peak air flow rate. The height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR).
7.2.8 The size of the above-ground ventilation structures containing the fans are dictated by the air flow rate and the equipment they will contain.
7.2.9 The size of the above-ground weir overflow chamber is dictated by hydraulic requirements and the existing site boundary. The height of the new overflow chamber would match the height of the existing above ground chamber it will connect to.
7.2.10 The electrical and control equipment would be located within the existing pumping station building.
Layout 7.2.11 The location of the main tunnel shaft is dictated by the requirements to
consolidate new and existing infrastructure in the northern area of the site. The exact location of the shaft is dictated by the position of the two northern storm tanks and the existing infrastructure.
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7 Acton Storm Tanks 7.2.12 The location of the interception chamber is dictated by the existing
infrastructure located within the site. 7.2.13 There must be sufficient space between the main tunnel shaft and the
interception chamber to accommodate the valve chamber and the minimum length of connection culvert required to provide a stable approach flow to the vortex generator located within the top of the shaft.
7.2.14 The air treatment chamber and acoustic attenuation chambers would be situated underground to minimise the number of above-ground structures. They must be surrounded by hardstanding to facilitate inspection and maintenance.
7.2.15 The layout of below ground infrastructure has been developed to try and locate as much equipment as practical within the footprint of the existing two northern storm tanks.
7.2.16 The ventilation column would be located in the north west of the site. Its location has been developed to fit in with the surrounding context by balancing the distance between adjacent properties, operational maintenance requirements and consolidate the proposed new infrastructure.
7.2.17 The location of the overflow chamber is dictated by the existing above ground chamber it would connect to. The layout of the chamber is also influenced by the existing site boundary.
7.2.18 The alignment of the new pipework along the western boundary of the site is dictated by the available clearance between the existing storm tanks and the site perimeter.
7.2.19 The layout of the structures and associated hardstanding area has been developed to concentrate the permanent works in the northern area of the site.
7.2.20 The electrical and control kiosk would be located within the existing pumping station building to minimise visual impact.
7.2.21 Refer to the Design and Access Statement Section 4 for more information on architectural considerations.
7.3 Limits and zones
Temporary works 7.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. The Thames Water Acton Storm Tanks site for construction of the
permanent works. b. An area of vegetation located south of residential properties on
Canham Road. The LLAU does not include the rear gardens of residential properties on Canham Road.
c. An area along Canham Road would facilitate modifications to existing kerb lines at the junction with Warple Way and Stanley Gardens. It
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would also enable the construction of a new vehicle access in to the site. The area would also allow for the potential strengthening of the carriageway if required. It is not proposed to close Canham Road to either pedestrians or vehicles.
d. A proportion of the third party land currently used for vehicle car parking. This would be required to provide suitable working area to construct new pipework within the Acton Storm Tanks site. The alignment of the LLAU would require a greater area at the northern and southern ends of the car park to facilitate the construction of two hydraulic chambers. It is proposed to construct the pipework and chambers within the perimeter of the Thames Water site if possible and not beneath the third party land.
7.3.2 The LLAU covers an area of approximately 23,200m2 and the assumed hoarded area would be approximately 20,200m2(based on the illustrative Construction phases – phase one drawing).
7.3.3 The Site selection background technical paper Section 4.6(see the Final Report on Site Selection Process Volume 2) stated that the area of main tunnel reception sites where shafts are constructed in London Clay/Lambeth Group/Thanet Sand Formation would be approximately 5,000m2.
7.3.4 The assumed hoarded area of the Acton Storm Tanks site contains an area for the permanent works, construction offices and welfare buildings, material handling and storage, concrete batching plant, a storage area, site power, parking, site roads and Thames Water operational areas. It is greater than the expected site size range because the hoarding follows the perimeter of a Thames Water operational site which contains the four remaining storm tanks and other operational areas, (10,500m2) which would only be available to the contractor for short term use when necessary. The remaining part of the contractor’s site also contains operational areas and is of an irregular shape. The LLAU extends beyond the Thames Water compound in several locations to facilitate temporary or permanent works. It extends onto the highway (Warple Way, Stanley Gardens and Canham Road) to the north and east of the site to accommodate highway access and strengthening works, and onto a private car park to the west of the site to provide a construction working area and to enable the possible construction of a chamber.
Permanent works 7.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) allows the main tunnel shaft to be relocated a short distance within the storm tanks to provide some flexibility as the design is developed.
7.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by the northern and western boundary of the site. The zone extends to include the existing pumping station in the north east of the site. The zone includes a suitable corridor along the south west of the site to allow for the
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construction of pipework and a hydraulic chamber within the perimeter of the Acton Storm Tanks site.
7.3.7 The zone within which the permanent above-ground structures for the ventilation column and above-ground ventilation structures/hydraulic chambers would be located (denoted by purple lines on the Site works parameter plan) allows these structures to be located in the north of the site. The configuration of the zone allows for many of the air management structures to either be located closer to Canham Road or in the area of vegetation behind the rear gardens of properties along Canham Road. The new overflow weir chamber and interception chamber would be located adjacent to the existing Stamford Brook Weir chamber.
7.3.8 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) allows for flexibility to provide visual mitigation landscaping along the eastern perimeter of the site adjacent to Warple Way. A secondary zone allows for suitable landscaping to the north of the site adjacent to No. 5 Canham Road in order to manage surface water drainage on the site in line with the Mayor of London’s Essential Standard.
7.4 Access 7.4.1 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure. 7.4.2 Primary access to the hardstanding areas would be from within the
Thames Water operational compound utilising the existing site access at the junction of Canham Road and Warple Way. Infrequent access would be required via the provision of a new secondary access off Canham Road. This new access gate would be used for either long or abnormal vehicles associated with the major maintenance operation.
7.4.3 Access covers would be finished at the new ground level of the permanent hardstanding area. All access covers would be accessible from surface and would not be buried.
7.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paragraphs. 3.6.6 to 3.6.9 respectively.
7.4.5 Vehicles would be used with the ten-yearly inspections of the main tunnel. These vehicles would enter the tunnel via a large access opening in the main tunnel shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
.
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8 Hammersmith Pumping Station
8 Hammersmith Pumping Station
8.1 Introduction 8.1.1 The proposed development site is located in the London Borough of
Hammersmith and Fulham. It comprises a main site including Hammersmith Pumping Station, part of a vacant former industrial site, under construction as the Fulham Reach development, and the Hammersmith Pumping Station highway works site.
8.1.2 The main site is bounded to the northwest by Chancellor’s Road, to the northeast by Distillery Road, and to the southeast and southwest by the Fulham Reach development (currently under construction). The small highway works site is located at the junction of Distillery Road and Chancellor’s Road. The surrounding area is a mix of residential properties and modern office developments. The River Thames is located immediately to the west of the Fulham Reach development. Distillery Road separates the site from Frank Banfield Park to the northeast, which includes a children’s play area.
8.1.3 The site would be used as a CSO site to perform the following functions: a. intercept gravity flows from the Hammersmith Pumping Station CSO b. accommodate a vortex drop and horizontal de-aeration chamber c. provide the Hammersmith connection tunnel d. provide air management and ventilation facilities e. provide access for operation and maintenance f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 8.1.4 Drawings of the site are provided in Section 6 of the Book of Plans.
8.2 Structures 8.2.1 The principal structures would comprise:
a. an interception chamber incorporating a dry weather flow pumping station and valve chamber
b. a connection culvert c. a drop shaft d. ventilation structures including:
i a below-ground air treatment chamber ii an above-ground ventilation structure for the drop shaft iii an above-ground ventilation structure and associated ventilation
column(s) for the existing pumping station inlet channel. This is a replacement structure for the existing screen house which would be demolished.
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iv ventilation columns for the interception chamber e. a local penstock control panel f. an electrical and control equipment. This would be housed inside the
existing pumping station building.
Size 8.2.2 Design flow rate is 42 m3/s (see Table 3.2). 8.2.3 The interception chamber, valve chamber and dry weather flow pumping
station are integrated as one structure. The size of this structure is dictated by: the size of flows to be intercepted, the depth and existing construction of Hammersmith Pumping Station, the design flow rate of the dry weather flow pumping station and safe access requirements for operations and maintenance.
8.2.4 The drop shaft size would have an approximate internal diameter of 11m and be approximately 33m deep from the top of the cover slab to invert of the connection tunnel.
8.2.5 The internal diameter of the shaft is dictated partly by the size of the connection tunnel and partly by the need to provide safe maintenance access.
8.2.6 The external diameter of the drop shaft is dictated by construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The drop shaft would be predominantly excavated in London Clay ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel and the associated connection tunnel at that point.
8.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
8.2.8 An above-ground ventilation structure would allow for venting of the drop shaft. The structures plan footprint is partly dictated by the peak air flow rate which is used to size the equipment contained within it and partly by architectural considerations as its length and height are sized to match the adjacent venturi building. The proposed height complies with the minimum height to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR).
8.2.9 The six ventilation columns serving the interception chamber would each have an approximate internal diameter of 0.3m and would be 8.5m minimum to 9.0m maximum high. The number and diameter of the ventilation columns is dictated by the peak air flow rate. The minimum height is determined by the height of the adjacent Hammersmith Pumping Station building and the maximum by the aesthetic proportions of the columns.
8.2.10 The plan size of the inlet channel ventilation structure and column(s) is dictated by the peak air flow rate to be vented but would not exceed the footprint size of the existing screen house. The minimum height of the ventilation column(s) is determined by the results of odour dispersion
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modelling and the maximum height would not exceed that of the existing screen house.
8.2.11 The size of the penstock control panel that would be located adjacent the existing pumping station building is dictated by the size of the electrical control equipment within it. It would be approximately 1.5m high.
Layout 8.2.12 The location of the interception chamber is dictated by the location and
layout of Hammersmith Pumping Station. Flows need to be intercepted upstream of the pumps. The interception chamber would be located to avoid construction beneath the superstructure of the existing pumping station and also to suit the structural configuration of the existing inlet channel.
8.2.13 The drop shaft would be located within the Fulham Reach mixed-use development site as it is near to the interception chamber and the currently undeveloped site allows for adequate construction area. The location has been agreed with the site developer to fit with the proposed development footprint.
8.2.14 The connection culvert location is dictated by the location of the interception chamber and drop shaft as its purpose is to transfer flow between the two structures.
8.2.15 The air treatment chamber would be located underground within the existing Hammersmith Pumping Station site boundary for ease of maintenance access.
8.2.16 The above-ground ventilation structure for the drop shaft is located within the Hammersmith Pumping Station site for ease of maintenance access. It is positioned adjacent to the existing venturi building to avoid obstructing vehicle access within the site and for aesthetic reasons.
8.2.17 The inlet channel ventilation structure and column(s) would be located above the inlet channel.
8.2.18 The ventilation columns for the interception chamber and penstock control panel would be located adjacent to the pumping station superstructure to avoid obstructing vehicle access within the site and for aesthetic reasons.
8.3 Limits and zones
Temporary works 8.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within two separate LLAU boundaries. a. The primary area includes:
i The entire Hammersmith Pumping Station site and the northwest part of the Fulham Reach development site for construction of the permanent works.
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ii An area on Chancellors Road would be required to enable construction of a new pipeline and on Distillery Road for construction of temporary and permanent site accesses.
b. The secondary area would be located at the junction of Chancellor’s Road and Distillery Road and is required to enable temporary kerb realignment.
8.3.2 The primary LLAU covers an area of approximately 6,100m2 and the assumed hoarded area would be approximately 3,800m2. The secondary LLAU covers an area of approximately 60m2 (based on the illustrative Construction phases – phase one drawing).
8.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
8.3.4 The assumed hoarded area of the Hammersmith Pumping Station site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching plant, a storage area, site power, site roads and Thames Water operational areas. It is in the upper end of the expected site size range as it would be a connection tunnel drive site. The primary LLAU includes the assumed hoarded area, the remaining part of the Thames Water Pumping Station site and a section of Chancellor's Road for the construction of a new pipe, and a section of Distillery Road for the construction site access works. The secondary LLAU allows for minor highway works.
Permanent works 8.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone is constrained by the proposed building footprint of the Fulham Reach development.
8.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is dictated by a number of considerations: a. It allows for a permanent access to be constructed between the shaft
and Distillery Road. The alignment is positioned to suit the Fulham Reach development footprint.
b. It allows for flexibility in locating the interception chamber, the connection culvert and ducting between the shaft and the pumping station site as the design is developed.
c. It allows for flexibility in the alignment of a pipeline to be constructed to an existing manhole in Chancellor’s Road.
d. It allows for flexibility in positioning of the underground structures within Hammersmith Pumping Station as the design is developed.
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8 Hammersmith Pumping Station 8.3.7 The zone in which the drop shaft ventilation structure would be located
(denoted by a purple line on the Site works parameter plan) allows the structure to be relocated to a position adjacent to the south west wall of the pumping station.
8.3.8 The zone within which the interception chamber vent columns and penstock control panel would be located (denoted by a purple line on the Site works parameter plan) allows these structures to be moved parallel to the south east wall of the pumping station.
8.3.9 The zone within which the ventilation structure and column(s) serving the inlet channel would be located (denoted by a purple line on the on the Site works parameter plan) is governed by the underlying footprint of the inlet channel. It allows flexibility for these structures to be relocated to a new position above the channel.
8.4 Access 8.4.1 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure. 8.4.2 Access to the drop shaft would be via a new permanent access road,
located within the Fulham Reach development, from Distillery Road. 8.4.3 Access to the structures within Hammersmith Pumping Station would be
via the two existing entrances off Chancellor’s Road. 8.4.4 Access covers would be finished at ground level. 8.4.5 Site visits would be required on an approximate weekly basis for the dry
weather flow pumping station. 8.4.6 The three to six monthly, three yearly and ten yearly site visits and major
blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively. 8.4.7 During maintenance activities vehicles would park either at the
Hammersmith Pumping Station site or on the area of permanent hardstanding within the Fulham Reach development.
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9 Barn Elms
9 Barn Elms
9.1 Introduction 9.1.1 The proposed site is situated within the London Borough of Richmond
upon Thames. 9.1.2 It will be situated within the southern area of the Barn Elms Schools
Sports Centre. The site situated with the Thames Path and River Thames to the east, and the Beverley Brook Watercourse to the south and west. The Beverley Brook Footpath is situated between the perimeter fence of the playing fields and the watercourse.
9.1.3 The Barn Elms Schools Sports Centre is a playing fields facility serving numerous local schools. The area is predominately grassed playing fields with multiple marked sports pitches. Two changing room facilities, a number of track and field facilities and associated car park hard standing are located towards the north of the sports centre playing fields.
9.1.4 A Boat House, Sailing Club and Canoe Club facilities are situated along the eastern side of the schools playing field area. The vehicle and pedestrian access for this facility utilises the existing tree lined access road which runs through the centre of the playing fields.
9.1.5 The London Wetland Centre, a Site of Special Scientific Interest (SSSI) is located to the north of the Barn Elms Schools Sports Centre.
9.1.6 The Barn Elms Playing Field recreational facilities are located to the west of the site. Facilities include marked sports pitches, an athletics track, a fishing lake and a number of tennis courts. It should be noted that the Barn Elms Playing Fields are an independent facility to the Barn Elms Schools Sports Centre.
9.1.7 The busy Thames Path is situated to the east of the site and the Beverley Brook footpath is located to the south and west of the site.
9.1.8 The site would be used as a CSO site to perform the following functions: a. intercept flows from the West Putney Storm Relief CSO b. accommodate a vortex drop and de-aeration chamber c. provide the West Putney connection tunnel d. provide air management and ventilation facilities e. provide access for operation and maintenance f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 9.1.9 Drawings of the site are provided in Section 7 of the Book of Plans.
9.2 Structures 9.2.1 The principal structures would comprise:
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a. an interception chamber incorporating a flow diversion structure and a valve chamber
b. a connection culvert c. a valve chamber d. a drop shaft e. ventilation structures including a below-ground air treatment chamber
and an above-ground ventilation column f. an electrical and control kiosk integrated with the ventilation column.
Size 9.2.2 The size of the interception chamber is dictated partly by the size and
depth of the West Putney Storm Relief sewer and partly by the design flow rate to be intercepted (2 m3/s, see Table 3.2). Hydraulic modelling was undertaken to estimate the chamber size. The size of the chamber also needs to reflect safe operational access requirements.
9.2.3 The sizes of the valve chamber and connection culvert are dictated by the design flow rate and the depth of the structures by the depth of the West Putney Storm Relief sewer.
9.2.4 The drop shaft would have an approximate internal diameter of 6m and be approximately 34m deep from top of cover slab to invert of the connection tunnel.
9.2.5 The internal diameter of the drop shaft is dictated partly by the size of the connection tunnel (approximately 2.2m internal diameter), and partly by the plan area required in the shaft base for de-aeration of the flows descending through the vortex drop. The size of the shaft also needs to reflect safe operational access requirements.
9.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The drop shaft would be predominantly excavated in London Clay ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel and associated connection tunnel at this point.
9.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
9.2.8 The ventilation column serving the drop shaft would have an approximate internal diameter of 0.6m and be approximately 4m minimum to 6m maximum high. The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high. The two ventilation columns would be incorporated into a combined structure. The size of the combined ventilation column structure is dictated by the louvres located in the base of the column and safe operational access requirements.
9.2.9 The number and diameter of the ventilation columns are dictated by the peak air flow rate. The minimum height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply
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with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
9.2.10 The electrical and control kiosk would be approximately 5m by 2.5m by 3m high.
9.2.11 The size of the electrical and control kiosk is dictated by the size of the equipment that it would house.
9.2.12 The electrical and control kiosk and the ventilation columns would be contained within one combined above ground structure. This would be enclosed within a habitat surround to minimise its visual appearance and promote ecology and biodiversity in the area.
Layout 9.2.13 The location of the interception chamber is dictated by the location of the
existing West Putney Storm Relief Sewer, which is laid beneath the south eastern corner of the Barn Elms Schools Sports Centre.
9.2.14 There must be sufficient space between the drop shaft and the interception chamber to accommodate the valve chamber and the minimum length of connection culvert required to provide a stable approach flow to the vortex generator located within the top of the drop shaft.
9.2.15 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures.
9.2.16 The integrated electrical and control kiosk and ventilation column would be located on the periphery of the site in order to minimise any visual impact and avoid conflict with the playing field.
9.2.17 The permanent infrastructure would be surrounded by an area of permanent hardstanding to facilitate operational maintenance. The finished level of this hardstanding needs to be approximately 700mm above the low lying surrounding playing fields for hydraulic reasons.
9.2.18 The layout of the structures and associated hardstanding area was developed to avoid significant encroachment into the playing fields area and the permanent loss of any sports pitches.
9.2.19 Refer to the Design and Access Statement Section 6 for more information on architectural considerations.
9.3 Limits and zones
Temporary works 9.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas with one LLAU boundary including: a. The south eastern corner of the playing fields would be for
construction of the permanent works. b. The adjacent Beverley Brook footpath would enable the erection of
site hoarding. It is not proposed to close this footpath.
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c. A strip connecting the area listed above, with the Queen Elizabeth Walk public highway. The LLAU would be bounded by the sports field perimeter fence to east and the pitches to the west. The LLAU would be bounded to the north by the Queen Elizabeth Walk footpath to the north. The LLAU includes an area for the demolition of an existing changing room facility and an area for the provision of a replacement facility.
9.3.2 The LLAU covers an area of approximately 31,200m2 and the assumed hoarded area would be approximately 7,900m2 (2,300m2 excluding the fenced access road)(based on the illustrative Construction phases – phase one drawing).
9.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
9.3.4 The assumed hoarded area of the Barn Elms site contains an area for the permanent works, construction offices and welfare buildings, material handling and storage, concrete batching plant, a storage area, site power, steel reinforcement preparation area and site roads. It is in the upper end of the expected site size range as it would be a connection tunnel drive site. In addition to the hoarded construction site, this site requires a long hoarded access road to provide access to the highway. The LLAU includes both assumed hoarded areas, a width of land sufficient to construct the access road and an area within which the track and field facilities and changing rooms may be relocated.
Permanent works 9.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) allows the drop shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone would prevent the shaft getting too close to the tree lined Beverley Brook footpath or encroaching too far into the playing fields.
9.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by the Beverley Brook footpath to the south and east, and the sports centre playing pitches to the west and north. The zone extends between the permanent hard standing in the south, to the Queen Elizabeth Walk public highway to the north. This allows for the construction of the permanent operational access route.
9.3.7 The zone within which the permanent above-ground structures for the combined electrical and control kiosk and the ventilation column would be located (denoted by purple lines on the Site works parameter plan) allows these structures to be relocated a small distance in the corner of the playing fields.
9.3.8 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) allows for
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suitable landscaping to the north and west of the permanent hardstanding area. The zone extends between the permanent hardstanding in the south, to the Queen Elizabeth Walk public highway to the north. This allows for the construction of the reinforced grass permanent access route from the public highway in order for this to be integrated with the existing landscaping. Landscaping is also required in order to mitigate the impact of the new areas of permanent hardstanding and structures and to integrate the proposed raised ground level with the existing landscape.
9.4 Access 9.4.1 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure. 9.4.2 Access to the hardstanding area would require the construction of a
permanent access road to connect to the public highway at Queen Elizabeth Walk.
9.4.3 Access covers requiring regular access would be finished at the new ground level of the permanent hardstanding area. All access covers would be accessible from surface and would not be buried.
9.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
9.4.5 The ten yearly inspection would involve temporarily placing ground protective matting on areas of grass adjacent to the access route and permanent hardstanding. This would facilitate suitable standing area for the support equipment and vehicles.
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10 Putney Embankment Foreshore
10 Putney Embankment Foreshore
10.1 Introduction 10.1.1 The proposed CSO site is situated within the London Borough of
Wandsworth. 10.1.2 It will be situated upon the foreshore of the River Thames, upstream of
Putney Bridge. The site is bounded by the bridge to the southeast and Putney Pier to the northwest. The Embankment carriageway is located to the southwest. A public slipway/drawdock and part of Putney Bridge is located within the site area.
10.1.3 A secondary site will be required for the provision of a temporary slipway whilst the existing slipway is unavailable during the construction stage.
10.1.4 The site for the temporary boat public slipway/drawdock will be approximately 300m west of Putney Bridge.
10.1.5 A high number of recreational river users, comprising both motorised vessels and rowing and sailing boats use the adjacent section of the River Thames. A high proportion of these vessels are associated with the numerous rowing club facilities located approx 300m west of the site. The University Boat Race starting stone is located within the site.
10.1.6 Putney Pier is located to the northwest of the site. The pier has a high frequency of vessel movements and serves both scheduled and chartered services. The pier has two permanent residential vessels moored against it one of which lies within the site.
10.1.7 The site would be used as a CSO site to perform the following functions: a. Intercept flow from the Putney Bridge CSO b. accommodate a vortex drop and de-aeration chamber c. provide the Putney Bridge connection tunnel d. provide air management and ventilation facilities e. provide access for operation and maintenance f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 10.1.8 Drawings of the site are provided in Section 8 of the Book of Plans.
10.2 Structures 10.2.1 The principal structures would comprise:
a. an interception chamber b. a connection culvert c. two valve chambers d. a drop shaft
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e. a new CSO outfall f. ventilation structures including a below-ground air treatment chamber,
a below ground louvre chamber and above-ground ventilation columns g. two electrical and control kiosks h. a foreshore structure accommodating the majority of these structures.
Size 10.2.2 The size of the interception chamber is dictated partly by the size and
location of the Putney Bridge CSO and partly by the design flow rate to be intercepted (5 m3/s, see Table 3.2). Hydraulic modelling was undertaken to estimate the chamber size. The size of the chamber also needs to reflect safe operational access requirements.
10.2.3 The sizes of the connection culvert and valve chambers are dictated by the design flow rate and safe operational access requirements. The depth of the structures is dictated by the requirement to provide suitable clearance between the top of the culvert and the river foreshore.
10.2.4 The drop shaft would have an approximate internal diameter of 6m and be approximately 36m deep from top of cover slab to invert.
10.2.5 The internal diameter of the drop shaft is dictated partly by the size of the connection tunnel (approximately 2.2m internal diameter), and partly by the plan area required in the shaft the vortex drop and safe operational access requirements.
10.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The drop shaft would be predominantly excavated in London Clay ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel and associated connection tunnel at this point.
10.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
10.2.8 The ventilation column serving the drop shaft would have an approximate internal diameter of 0.6m and be between approximately 4m minimum to 8m maximum high. The project’s ‘signature’ ventilation column design would be used.
10.2.9 The total cross-sectional area of the signature ventilation column is dictated by the peak air flow rate. The minimum height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
10.2.10 The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
10.2.11 The height of the smaller diameter ventilation columns is consistent with Thames Water standards (see para. 3.11.7).
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10 Putney Embankment Foreshore 10.2.12 The size of the below-ground ventilation louvre chamber is dictated by the
size of the louvres and the safe operational access requirements. 10.2.13 Two electrical and control kiosks would be required to minimise the above-
ground structures on the permanent foreshore structure. 10.2.14 The Waterman’s Green electrical and control kiosk would be
approximately 5m by 2m by 3m high. 10.2.15 The electrical and control kiosk located upon the foreshore structure would
be approximately 2m by 2m by 2.5m high. 10.2.16 The sizes of the electrical and control kiosks are dictated by the size of the
equipment that they would house. 10.2.17 The size of the foreshore structure is dictated by the size of the drop shaft,
hydraulic chambers, ventilation and air treatment chambers, and the ship impact protection zone. The size also needs to reflect safe operational access requirements.
Layout 10.2.18 The location of the interception chamber is dictated by the location of the
existing Putney Bridge CSO, which discharges beneath the southern shore arch of Putney Bridge.
10.2.19 The location of the permanent foreshore structure has sought to maximise the separation to the listed Putney Bridge. It has also ensured the historic public draw dock/slipway is retained along its existing alignment.
10.2.20 The air treatment chamber and associated louvre chamber would be situated underground in order to minimise the number of above-ground structures.
10.2.21 The ventilation columns and the electrical and control kiosk would be located on the periphery of the foreshore structure in order to minimise any visual impact and allow suitable area for safe operational access requirements.
10.2.22 The permanent infrastructure would be surrounded by an area of permanent hardstanding to facilitate operational maintenance. The finish level of this hardstanding needs to be equal to, or above the local flood protection level. This is above the existing level of the majority of the Embankment carriageway. The level difference between the new foreshore structure and existing carriageway would connected by a series of tapered steps.
10.2.23 There must be sufficient space in the permanent foreshore structure to accommodate the valve chambers, air treatment chamber, louvre chamber, ventilation column and electrical and control kiosk. The size of the foreshore structure must allow the minimum length of connection culvert required to provide a stable approach flow to the vortex generator located at the top of the drop shaft. The structure must also allow suitable area for safe operational access requirements.
10.2.24 The layout of the structures and associated hardstanding area was developed to avoid significant encroachment into the river.
Engineering design statement 105
10 Putney Embankment Foreshore 10.2.25 Refer to the Design and Access Statement Section 7 for more information
on architectural considerations.
10.3 Limits and zones
Temporary works 10.3.1 The limits of land to be acquired or used (LLAU) for the required working
area to construct the works encompasses a number of areas within two separate LLAU boundaries. a. The primary area includes:
i The foreshore adjacent and beneath Putney Bridge for construction of the permanent works.
ii An area westwards to include Putney Pier. This would enable the possible installation of scour protection measures around the pier supports and the possible temporary relocation of an existing residential houseboat.
iii An area eastwards to a point approximately 40m downstream of Putney Bridge. This would enable the construction of the temporary cofferdam beneath the bridge and the possible installation of scour protection in the vicinity of the cofferdam and bridge piers.
iv Sections of the eastbound carriageway of Lower Richmond Road and the adjacent footpath. This would enable the construction of ducting between the electrical and control kiosk located upon Waterman’s Green and the permanent foreshore structure.
v The vault structures beneath the carriageway of Putney Bridge Approach and sections of the external grounds of St Marys church. This would enable access into the vaults for minor modifications to the existing infrastructure and the installation of ventilation ducting. It is not proposed to close the carriageway of either Putney Bridge or Putney Bridge Approach.
vi Part of the Embankment junction for utility diversions and kerb alterations.
vii Sections of the footway on the eastern side of Putney Bridge. This would allow for the construction of the ventilation column serving the interception chamber.
b. The secondary area is for the construction of the temporary slipway and includes: i The foreshore adjacent to Chas Newens Marine. The LLAU
includes sections of the eastbound Embankment carriageway and the adjacent footway. This would enable the formation of the associated construction site and unloading of deliveries. It is not proposed to close the carriageway of the Embankment.
ii The existing mooring located outside has Newens Marine. These moorings would need to be suspended or relocated during the
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10 Putney Embankment Foreshore
construction and removal of the temporary slipway. This is to provide sufficient working area. The moorings would be reinstated during the operational stage of the temporary slipway.
10.3.2 The primary LLAU covers an area of approximately 16,300m2 and the assumed cofferdam area would be approximately 4,400m2(based on the illustrative Construction phases – phase one drawing). The secondary LLAU covers an area of 11,700m2 for the construction of the temporary slipway.
10.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
10.3.4 The assumed cofferdam area of the Putney Embankment Foreshore site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching plant, a storage area, site power, steel reinforcement preparation area and site access roads. It is in the upper end of the expected site size range as it would be a connection tunnel drive site. The primary LLAU includes the assumed cofferdam area and part of the river needed to facilitate construction of the temporary cofferdam and permanent foreshore structure. It also includes an area for construction of a campshed and an area to allow for the relocation of a houseboat and potential temporary scour protection to the river bed. The campshed facility would occupy an area of approximately 400m2 in the river foreshore and would be used for transport of materials by river. The primary LLAU also includes public highway (Embankment, Lower Richmond Road, Putney High Street and Putney Bridge) for highway works and part of the below ground internal structure of Putney Bridge to allow for the installation of new ventilation pipework and a ventilation column. The secondary LLAU allows for construction of a temporary slipway and includes part of Embankment highway as a worksite and the River Thames as a worksite and for river access. The LLAU also encompasses a number of moorings that may need to be suspended.
Permanent works 10.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone would prevent the drop shaft intruding too far into the river or fouling the existing river wall.
10.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by the River Thames to the north and reflects the requirements of the interception chamber, the connection culvert, the permanent foreshore structure, scour protection and outfall apron. The southern extent of the zone is bounded by the Lower Richmond Road and Putney Bridge Approach carriageways where the alignment of the zone reflects the
Engineering design statement 107
10 Putney Embankment Foreshore
requirements for the Waterman’s Green kiosk, associated ducting and modifications to existing infrastructure within the vaults beneath Putney Bridge Approach.
10.3.7 The zone within which the permanent above-ground structures would be located (denoted by the purple lines on the Site works parameter plan) has four distinct areas. a. The zone, in which the main ventilation column and electrical control
kiosk located upon the permanent foreshore structure, is situated to the west of the new structure. This allows flexibility for the location of these structures.
b. The zone in which the electrical and control kiosk situated on Waterman’s Green allows for flexibility in an approximate east/west direction.
c. The zone in which the interception chamber would be located is beneath the southern shore arch of Putney Bridge. This zone allows flexibility for the location and size of the chamber to be modified if required.
d. The zone in which the ventilation column serving the interception chamber is situated on the south eastern side of Putney Bridge allows flexibility in a north/south direction.
10.3.8 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) is confined to the new foreshore structure and is in order to allow landscaping of the new area of public realm.
10.4 Access 10.4.1 The permanent foreshore structure would provide a hardstanding area for
access purposes. The area would provide access to the drop shaft, valve chambers, air treatment chamber and louvre chamber access covers. It would also provide access to the main ventilation column and the electrical and control kiosk.
10.4.2 Access to the interception chamber would be via the valve chamber and connection culvert. Direct access into the interception chamber is not practical and would not be provided.
10.4.3 All access covers would be finished at ground level. 10.4.4 The three to six monthly, three yearly and ten yearly site visits and major
blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively. 10.4.5 Maintenance vehicles would occasionally park on the permanent
foreshore structure. 10.4.6 The ten yearly inspection would require suspension of a number of
adjacent parking bays to provide suitable parking. 10.4.7 Access to the electrical and control kiosk on Waterman’s Green would be
via the Green and be pedestrian only. Direct vehicle access to the kiosk would not be possible. The delivery of any heavy tools or equipment would
Engineering design statement 108
10 Putney Embankment Foreshore
be via a lorry and crane parked within the eastbound carriageway of Lower Richmond Road or from the public slipway. This would require appropriate approvals and traffic management.
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10 Putney Embankment Foreshore
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Engineering design statement 110
11 Dormay Street
11 Dormay Street
11.1 Introduction 11.1.1 The proposed development site is located in the London Borough of
Wandsworth. The site comprises part of the Frogmore Industrial Complex and Causeway Island, and the junction of The Causeway, Armoury Way and Dormay Street.
11.1.2 The site is bounded by railway lines and a vehicle storage area to the north, and The Causeway to the east, beyond which is the River Wandle. The south of the site backs onto clusters of industrial buildings along Dormay Street including Wentworth House (a Grade II listed building). A public house, the Armoury, and a row of cottages and terraced properties are located further south at the junction of Dormay Street and Armoury Way. A London Borough of Wandsworth maintenance depot is situated to the west. Bell Lane Creek runs through the centre of the site. The wider area comprises mixed commercial, industrial and residential uses. The Frogmore Complex forms part of a wider industrial area.
11.1.3 The site would be used as a CSO site to perform the following functions: a. drive the Frogmore connection tunnel in two directions: to Carnwath
Road riverside to the north and King George’s Park in the south b. intercept flows from the Frogmore Storm Relief - Buckhold Road CSO c. accommodate a vortex drop and de-aeration chamber d. provide air management and ventilation facilities e. provide access for operation and maintenance f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 11.1.4 Drawings of the site are provided in Section 10 of the Book of Plans.
11.2 Structures 11.2.1 The principal structures would comprise:
a. an interception chamber b. a connection culvert c. a valve chamber d. a drop shaft e. a below ground air treatment chamber f. an above ground ventilation structure and ventilation column g. an electrical and control kiosk integrated with the ventilation structure
and ventilation column.
Engineering design statement 111
11 Dormay Street
Size 11.2.2 The size of the interception chamber is dictated partly by the size, depth
and flow within the Frogmore Storm Relief - Buckhold Road CSO (3 m3/s, see Table 3.2), and partly by safe operational access requirements. Hydraulic modelling was undertaken as part of developing the chamber size.
11.2.3 The size of the valve chamber is dictated by the design flow rate, depth of the Frogmore Storm Relief - Buckhold Road CSO and requirements for safe operational access requirements.
11.2.4 The drop shaft would have an approximate internal diameter of 12m and be approximately 24m deep from top of the cover slap to invert of the connection tunnel.
11.2.5 The internal diameter of the drop shaft is governed partly by the plan area required in the base of the shaft for de-aeration of the flows descending through the vortex drop and partly by the size of the connection tunnel.
11.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The drop shaft would be predominantly excavated in London Clay ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel and associated connection tunnel at this point.
11.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
11.2.8 The ventilation structure serving the drop shaft is integrated with the electrical and control kiosk. The ventilation structure has a minimum height of 4m and a maximum of 6m. The electrical and control kiosk has a minimum height of 3m and maximum of 6m.
11.2.9 The plan size of the integrated structure is dictated by the size of the equipment within it. The minimum height for the ventilation structure is determined by the equipment it will contain and to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The minimum height for the electrical and control kiosk is to accommodate the equipment within it and access considerations. The maximum height of the entire structure is influenced by aesthetics.
11.2.10 The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
11.2.11 The height of the smaller diameter ventilation column is consistent with Thames Water standards (see para. 3.11.7).
11.2.12 The diameter of the ventilation column serving the drop shaft is dictated by the peak air flow rate and its height by the results of odour dispersion modelling.
Engineering design statement 112
11 Dormay Street
Layout 11.2.13 The location of the interception chamber is dictated by the location of the
existing sewer which lies within the London Borough of Wandsworth depot.
11.2.14 The drop shaft would be located at the northern end of Dormay Street. It is located to suit the Local Borough of Wandsworth’s intended future use of the site which is parking of municipal vehicles.
11.2.15 The valve chamber would be located adjacent to the drop shaft with sufficient clearance to provide stable approach flow to the vortex generator located within the drop shaft and to allow differential movement between structures.
11.2.16 The air treatment chamber would be located underground in order to maximise the area that could be utilised by the depot operations.
11.2.17 The integrated electrical and control kiosk and ventilation structure would be located adjacent to the drop shaft and valve chamber for functional reasons. It would be set back from the river wall by 4m to allow for potential provision of a riverside walk at a future date by others.
11.2.18 The ventilation column serving the interception chamber would be located adjacent to the river wall to avoid obstructing depot operations.
11.3 Limits and zones
Temporary works 11.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. Land to the south of Bell Lane Creek within the London Borough of
Wandsworth depot and the northern end of Dormay Street for construction of the permanent works.
b. Causeway Island, to the north of Bell Lane Creek, which would be used as a construction compound.
c. The Causeway, a private road, which would be used for access to the Causeway Island construction site for light vehicles.
d. Bell Lane Creek to allow for temporary connection between the two worksites either side of the creek.
e. The Armoury Way/Dormay Street intersection to allow for reconfiguration of the junction.
11.3.2 The LLAU covers an area of approximately 10,000m2 and the assumed hoarded area would be approximately 3,900m2 (based on the illustrative Construction phases – phase one drawing).
11.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
Engineering design statement 113
11 Dormay Street 11.3.4 The assumed hoarded area of the Dormay Street site contains an area for
the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching plant, storage areas for segments and general use, site power, parking and site roads. It is in the upper end of the expected site size range as it would be a connection tunnel drive site, and consists of two irregularly shaped areas connected by a temporary bridge which is also within the assumed hoarded area. The LLAU includes both the assumed hoarded areas, part of Dormay Street which requires stopping up and for highway access work, and part of Bell Lane Creek which runs between the two sites to allow for river wall strengthening works in the river and also the construction of a temporary bridge and crane over-sailing. It also includes The Causeway which is a private road and the junction of Dormay Street and Armoury Way to allow for possible junction modifications and traffic management measures.
Permanent works 11.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone is constrained by the alignment of the river wall to the north.
11.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by the river wall to the north and the local borough depot to all other sides. It allows for the location of the structures within it to be adjusted as part of design development.
11.3.7 The zone within which the integrated electrical and control kiosk and ventilation structure would be located (denoted by the purple line on the Site works parameter plan) allows flexibility for this structure to be located either side of the shaft. The zone is constrained to the north by the 4m set back to allow for a possible future riverside walkway.
11.3.8 The zone within which the ventilation column serving the interception chamber would be located (denoted by the purple line on the Site works parameter plan) allows flexibility for the column to be located to best suit the depot layout.
11.3.9 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) allows for an intertidal terrace to provide aquatic habitat. This is in order to mitigate the loss of intertidal habitat at other sites.
11.4 Access 11.4.1 Post construction the northern end of Dormay Street would be
permanently stopped up and incorporated into the London Borough of Wandsworth Depot. A new access gate will be provided to the depot site approximately in line with the northern property boundary of the Panorama Antennas site.
Engineering design statement 114
11 Dormay Street 11.4.2 Access to the permanent works will be from Dormay Street via the new
depot entrance. 11.4.3 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure. 11.4.4 The interception chamber would be located within an existing area of
hardstanding. 11.4.5 All access covers would be finished at ground level. 11.4.6 The three to six monthly, three yearly and ten yearly site visits and major
blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively. 11.4.7 Vehicles would park on the area of permanent hardstanding during
operations and maintenance visits. 11.4.8 The ten yearly inspection would require coordination with the local
borough to ensure alternative parking arrangements are made for their vehicle fleet during this period.
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11 Dormay Street
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Engineering design statement 116
12 King George’s Park
12 King George’s Park
12.1 Introduction 12.1.1 The proposed development site is located in the London Borough of
Wandsworth. The site is located at the northern tip of King George’s Park and comprises open space (grass), footpaths and established trees.
12.1.2 The site is bounded by Buckhold Road to the west, Neville Gill Close to the east and the remainder of the park to the south.
12.1.3 The general vicinity is mixed, comprising residential and commercial/retail uses. Wandsworth Town Centre is 100m to the north, with Southside Shopping Centre to the east and The Business Village is under construction to the west. King George’s Park extends to the south and there is a residential terrace which fronts onto Buckhold Road. King George’s Park includes a children’s nursery, recreational facilities, a small pond and open spaces.
12.1.4 The site would be used as a CSO site with the drop shaft constructed at the head of the Frogmore connection tunnel. This site would not be used to drive the Frogmore connection tunnel. It would perform the following functions:
a. Intercept flows from the Frogmore Storm Relief - Buckhold Road CSO b. accommodate a vortex drop and de-aeration chamber c. provide air management and ventilation facilities d. provide access for inspection and maintenance e. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 12.1.5 Drawings of the site are provided in Section 11 of the Book of Plans.
12.2 Structures 12.2.1 The principal structures would comprise:
a. an interception chamber incorporating a flow diversion structure and valve chamber
b. a connection culvert c. a drop shaft d. ventilation structures including: a below-ground air treatment chamber
and above-ground ventilation columns and ventilation structure housing louvres.
e. an electrical and control kiosk.
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12 King George’s Park
Size 12.2.2 The size of the interception chamber is dictated partly by the size, depth
and flow within the Frogmore Storm Relief - Buckhold Road CSO (9 m3/s, see Table 3.1), and partly by access requirements. Hydraulic modelling was undertaken as part of developing the chamber size.
12.2.3 The size of the valve chamber is dictated by the design flow rate, depth of the Frogmore Storm Relief - Buckhold Road CSO and requirements for safe operational access.
12.2.4 The drop shaft would have an approximate internal diameter of 9m and be approximately 21m deep from top of the cover slap to invert of the tunnel.
12.2.5 The internal diameter of the drop shaft is governed by the plan area required in the base of the shaft for de-aeration of the flows descending through the vortex drop.
12.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The drop shaft would be predominantly excavated in London Clay ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel and associated connection tunnel at this point.
12.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
12.2.8 The ventilation column serving the drop shaft would have an approximate internal diameter of 0.7m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
12.2.9 The total cross-sectional area of the signature ventilation column is dictated by the peak air flow rate. The minimum height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
12.2.10 The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
12.2.11 The height of the smaller diameter ventilation column is consistent with Thames Water standards (see para. 3.11.7).
12.2.12 The size of the above-ground ventilation structure is dictated by the size of the louvres and the safe operational requirements.
12.2.13 The electrical and control kiosk, including the ventilation structure which is integrated as one unit, would be approximately 8.5m x 3m x 3m high. The size is dictated by the size of the equipment housed inside.
Layout 12.2.14 The location of the interception chamber is dictated by the location of the
existing sewer which lies within the northern tip of King George’s Park.
Engineering design statement 118
12 King George’s Park 12.2.15 The drop shaft would be located in close proximity to the interception
chamber to minimise the footprint of the permanent works within the park. It is also located to avoid the proposed National Grid Wimbledon to Kensal Green cable tunnel being constructed by others beneath the site. The shaft’s location would also avoid the root protection zone of a black poplar tree on the south eastern site boundary and a mature red oak tree on the northern tip.
12.2.16 The valve chamber and connection culvert would be located between the interception chamber and drop shaft. A minimum length of connection culvert is required to provide stable approach flow to the vortex generator located within the drop shaft.
12.2.17 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures It would be located beneath hardstanding to facilitate inspection and replacement of filter media.
12.2.18 The electrical and control kiosk, ventilation structure and interception chamber ventilation column would be located on the periphery of the site in order to minimise any impact on public use of the open space and to offer ease of operational access.
12.2.19 The ventilation column serving the drop shaft would be located within the area of hardstanding as an architectural feature.
12.2.20 Refer to the Design and Access Statement Section 9 for more information on architectural considerations.
12.3 Limits and zones
Temporary works 12.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within two separate LLAU boundaries. a. The primary area includes:
i The northern part of King George’s Park for construction of the permanent works
ii the southern footpath of Buckhold Road to allow landscaping works
iii areas of the northbound carriageway of Neville Gill Close to enable construction of a site access
b. The secondary area is for kerb realignment and pedestrian refuge relocation at the junction of Buckhold Road and Neville Gill Close.
12.3.2 The LLAU covers an area of approximately 4,100m2 and the assumed hoarded area would be approximately 1,800m2 (based on the illustrative Construction phases – phase one drawing).
12.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth
Engineering design statement 119
12 King George’s Park
Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
12.3.4 The assumed hoarded area of the King George’s Park site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching plant, a storage area, site power and site roads. It is in the upper end of the expected site size as it would be a connection tunnel reception site. The LLAU includes the assumed hoarded area, an area in the park for the diversion of an internal park footpath, and an area of road for highway works. This includes kerb and traffic island modification works at the junction of Buckhold Road and Neville Gill Close. It also includes areas in the park that would only be used for shorter periods of time for landscaping purposes.
Permanent works 12.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone is constrained by the alignment of the existing storm relief sewer and root protection area of a high value tree which borders the site to the south east.
12.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded to the east by Neville Gill Close and the park to all other sides. It allows for the location of the interception chamber to be adjusted along the line of the Frogmore Storm Relief and for the other structures to be adjusted to align with the interception chamber.
12.3.7 The zone within which the electrical and control kiosk, ventilation structure and the interception chamber ventilation column would be located (denoted by one of the purple lines on the Site works parameter plan) allows flexibility for these structures to move in a north south direction along the Neville Gill Close boundary.
12.3.8 The zone within which the ventilation column serving the drop shaft would be located (denoted by the other purple line on the Site works parameter plan) allows flexibility for the column to be located to suit the landscaping design.
12.3.9 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) allows for landscaping around the area of the permanent works. This is required in order to mitigate the impact of the new areas of permanent hardstanding and structures and to integrate these with the existing park. Landscaping is also required in order to maintain the existing flood conveyance route across the site.
12.4 Access 12.4.1 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure.
Engineering design statement 120
12 King George’s Park 12.4.2 A new permanent access would be created off Neville Gill Close. 12.4.3 Access covers would be finished at ground level. 12.4.4 The three to six monthly, three yearly and ten yearly site visits and major
blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively. 12.4.5 Vehicles would park on the area of permanent hardstanding. 12.4.6 The ten yearly inspection would require suspension of parking restrictions
on Neville Gill Close to provide suitable parking.
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12 King George’s Park
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Engineering design statement 122
13 Carnwath Road Riverside
13 Carnwath Road Riverside
13.1 Introduction 13.1.1 The proposed development site is located within the London Borough of
Hammersmith and Fulham. It comprises the foreshore of the River Thames, Hurlingham Wharf, Whiffin Wharf, and a small area of roadway.
13.1.2 The site is bounded to the north by Carnwath Road, the Piper Building and the Piper Centre. Further residential properties occupy the wider area to the northeast. To the east is Carnwath Road Industrial Estate, which contains two-storey industrial, warehouse and retail units. To the south of Carnwath Road and on the eastern side of the site is a residential block that overlooks the site and the River Thames. To the west of the site are blocks of residential accommodation. Facing this residential use and on the opposite side of Carnwath Road are purpose-built industrial units. Within the wider area further to the west is The Hurlingham Club, a private members’ club, situated in Hurlingham Park. Hurlingham Business Park to the northwest consists of industrial and commercial buildings. Philpot Square, a four-storey residential block and two superstores are located on the eastern side of Peterborough Road. A small highway works site is located at the junction of Wandsworth Bridge Road and Carnwath Road.
13.1.3 The site would be used as a main tunnel drive and reception site to perform the following functions:
a. drive the main tunnel to Acton Storm Tanks b. receive the main tunnel from Kirtling Street c. receive the Frogmore connection tunnel from Dormay Street d. accommodate a vortex drop de-aeration chamber e. provide air management and ventilation facilities f. provide access for operations and maintenance (including vehicle
access to the main tunnel) g. provide emergency egress from the tunnel and main tunnel shaft
during maintenance operations. 13.1.4 Drawings of the site are provided in Section 9 of the Book of Plans.
13.2 Structures 13.2.1 The principal structures would comprise:
a. a main tunnel shaft b. below-ground air treatment and acoustic attenuation chambers c. a ventilation building d. a ventilation column.
Engineering design statement 123
13 Carnwath Road Riverside
Size 13.2.2 The main tunnel shaft would have an approximate internal diameter of
25m and be approximately 42m deep from finished ground level to invert of the main tunnel.
13.2.3 The internal diameter of the shaft is dictated by construction requirements as the shaft will act as a main tunnel drive and reception site and therefore must have sufficient room to accommodate the TBM and associated support equipment.
13.2.4 The external diameter of the main tunnel shaft is dictated by the construction method, which is anticipated to be sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The shaft would be predominantly excavated in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group. The depth of the shaft is determined by the depth of the main tunnel.
13.2.5 The size of the below-ground air treatment chambers is dictated by the peak air flow to be treated, which is determined by pneumatic modelling.
13.2.6 The size of the acoustic attenuation chamber is dictated by the required amount of noise attenuation, which is determined by the proximity of noise receptors.
13.2.7 The ventilation building has approximate dimensions of 20m long x 8m wide x 5.5m high.
13.2.8 The size and height of the ventilation building is dictated by the size of the equipment within it and requirements for safe operational and maintenance access.
13.2.9 The ventilation column would be approximately 15m high. The cross-sectional area of the column is dictated by the peak air flow rate. The height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR).
Layout 13.2.10 The location of the main tunnel shaft was based on the following
considerations: a. It would avoid a proposed National Grid power tunnel which would
pass beneath eastern part of the site currently occupied by the Carnwath Road Industrial Estate.
b. It would not affect the long term operation of the safeguarded Hurlingham Wharf.
c. It would locate all access covers and above-ground structures within Whiffin Wharf which does not have safeguarded status.
d. The shaft would be located as far east as practical on Whiffin Wharf with the only encroachment onto Hurlingham Wharf being underground. This maximises the distance to adjacent residential dwellings at the west end of the site and the future potential development on the remainder of Whiffin Wharf.
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13 Carnwath Road Riverside
e. The shaft would be as close to the river as practical to balance the need to maximise distance to The Piper Building residents while allowing a buffer to the shaft to protect it from ship impact. It would also enable the main tunnel to avoid passing beneath Wandsworth Bridge abutment and pass centrally through the first arch.
13.2.11 The ventilation building would be orientated perpendicular to the river to reduce visual impact for The Piper Building residents and maximise the distance to residents on the western end of the site
13.2.12 The ventilation column would be located adjacent to the river wall to maximise distance from adjacent receptors and minimise visual impact.
13.2.13 Refer to the Design and Access Statement Section 10 for more information on architectural considerations.
13.3 Limits and zones
Temporary works 13.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within two separate LLAU boundaries. a. The primary area includes:
i Whiffin Wharf, Hurlingham Wharf and Carnwath Road Industrial Estate for construction of the permanent works
ii an area of river foreshore fronting the above areas and Carnwath Road for barging facilities located within the river.
b. The secondary area is to facilitate kerb realignment works which would be located at the Carnwath Road/Wandsworth Bridge Road junction. The area includes an access strip through the PC World car park.
13.3.2 The primary LLAU covers an area of approximately 34,900m2 and the assumed hoarded area would be approximately 15,800m2 (based on the illustrative Construction phases – phase one drawing). The secondary LLAU would cover approximately 1,200m2 for highway works.
13.3.3 The Site selection background technical paper Section 4.4 (see the Final Report on Site Selection Process Volume 2) stated that the area of main tunnel drive sites where shafts are constructed in London Clay/Lambeth Group/Thanet Sand Formation could range from approximately 15,000m2 to 18,000m2.
13.3.4 The assumed hoarded area of the Carnwath Road Riverside site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage including tunnel lining segments, concrete batching plant, a storage area, site power, and site roads. It is in the lower end of the expected site size range for a main tunnel drive site indicating the site is constrained in size so there would be additional constraints on the construction layout, methods and programme. The primary LLAU area includes the assumed hoarded area and an area for construction of a jetty/campshed. These facilities would occupy an area of approximately 3200m2 in the river foreshore and would
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13 Carnwath Road Riverside
be used for transport of materials by river. The primary LLAU also extends onto the Thames Path to allow for the erection of hoardings and for its route to be modified during the construction period. It also extends onto the footway of Carnwath Road to allow for the construction of temporary site accesses. The secondary LLAU area at the junction of Carnwath Road and Wandsworth Bridge Road is needed for highway works to allow access for heavy goods vehicles.
Permanent works 13.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed.
13.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by Carnwath Road to the north, the river to the south and the boundary with Hurlingham Wharf to the east (including the small intrusion for the main tunnel shaft into Hurlingham wharf). The western zone boundary runs approximately parallel to the site boundary but is offset to the east to avoid sterilising the western part of Whiffin Wharf for future development.
13.3.7 The zone within which the ventilation building would be located (denoted by a purple line on the Site works parameter plan) allows for location of the building structure to be adjusted as the design develops.
13.3.8 The zone within which the ventilation column would be located (denoted by a purple line on the Site works parameter plan) allows for location of the column to be adjusted as the design develops.
13.3.9 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) allows for suitable landscaping of the hardstanding area which is retained for operations and maintenance activities and which is also proposed as an area of public realm.
13.4 Access 13.4.1 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure. 13.4.2 A new permanent access off Carnwath Road would be provided. 13.4.3 Access covers requiring regular access would be finished at ground level.
Access covers requiring infrequent access (typically once every ten years) would be buried.
13.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
13.4.5 Vehicles would park on the area of permanent hardstanding during maintenance and operations activities.
13.4.6 The ten yearly inspection would involve temporarily removing elements of the landscaping to expose and open any buried access covers.
Engineering design statement 126
13 Carnwath Road Riverside 13.4.7 Vehicles would be used with the ten-yearly inspections of the main tunnel.
These vehicles would enter the tunnel via a large access opening in the main tunnel shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
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13 Carnwath Road Riverside
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Engineering design statement 128
14 Falconbrook Pumping Station
14 Falconbrook Pumping Station
14.1 Introduction 14.1.1 The proposed site is situated within the London Borough of Wandsworth.
The site is situated to the east of York Road. The site is broadly rectangular and is currently accessed via narrow residential roads (Newcomen Road and Lavender Road) and York Gardens to the east.
14.1.2 Immediately adjoining the site to the north is the York Gardens Adventure Playground. To the south is the York Garden Library and Community Centre with the York Gardens extending beyond and also to the east and north.
14.1.3 The nearest residential properties are located approximately 46m to the east of the site and are eight storeys high (Pennethorne House). York Road (A3205) bounds the site to the west.
14.1.4 The site is predominantly hardstanding and houses an operational pumping station and associated sewerage and utilities infrastructure. The pumping station buildings and enclosed compound account for approximately half of the site area considered. The majority of the remaining land outside the compound remains in Thames Water ownership, but is publicly accessible. An above/ below ground structure (Venturi Chamber) is situated outside the compound wall within the public area.
14.1.5 The pumping station compound and venturi chamber are accessed regularly by Thames Water operational staff.
14.1.6 An area of the site is currently occupied by a disused public convenience, beneath which is situated the substructure of a former pumping station.
14.1.7 The site would be used as a CSO to perform the following functions: a. intercept gravity flows from the Falconbrook Pumping Station CSO b. accommodate a vortex drop shaft and de-aeration chamber c. provide the Falconbrook connection tunnel d. provide air management and ventilation facilities e. provide access for operation and maintenance f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 14.1.8 Drawings of the site are provided in Section 12 of the Book of Plans.
14.2 Structures 14.2.1 The principal structures would comprise:
a. an integrated interception chamber, valve chamber and dry weather flow pumping station
b. a connection culvert
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14 Falconbrook Pumping Station
c. a drop shaft d. a valve chamber serving the dry weather flow pumping station e. ventilation structures including an above-ground air treatment chamber
and above-ground ventilation columns f. an electrical and control kiosk located within the existing pumping
station building.
Size 14.2.2 The size of the interception chamber is dictated partly by the size and
depth of the incoming pipework to the interception chamber and partly by the design flow rate to be intercepted (22 m3/s, see Table 3.2). The size and layout of the chamber reflects the above and below ground site constraints. Hydraulic modelling was undertaken to estimate the chamber size. The size of the chamber also needs to reflect safe operational access requirements.
14.2.3 The size and depth of the connection culvert are dictated by the design flow rate and the requirements for it to pass beneath existing pipework.
14.2.4 The drop shaft would have an approximate internal diameter of 9m and be approximately 40m deep from top of cover slab to invert of the connection tunnel.
14.2.5 The internal diameter of the drop shaft is dictated partly by the size of the connection tunnel (approximately 3.9m internal diameter for its initial length), and partly by hydraulic requirements. The size of the shaft also needs to reflect safe operational access requirements and existing sewer infrastructure located on the site.
14.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a sprayed concrete lining for the primary lining and cast in-situ concrete for the secondary lining. The drop shaft would be predominantly excavated in clay ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel and associated connection tunnel at this point.
14.2.7 The size of the above-ground air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
14.2.8 The ventilation column serving the drop shaft would have an approximate internal diameter of 0.7m and be approximately 4m minimum to 8m maximum high. It would be integrated into the above-ground air treatment chamber.
14.2.9 The number and diameter of the ventilation columns are dictated by the peak air flow rate. The minimum height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
Engineering design statement 130
14 Falconbrook Pumping Station 14.2.10 The demolition of the existing above-ground screening chamber building
would necessitate an additional ventilation column. The ventilation column serving the screening chamber would have an approximate internal diameter of 0.7m and be approximately 4m minimum to 8m maximum high.
14.2.11 The electrical and control equipment would be located within the existing pumping station building.
Layout 14.2.12 The location of the interception chamber is dictated by the configuration of
the existing incoming pipework which is laid beneath the external compound of the pumping station. The location of the chamber also heavily influenced by the requirements to keep the chamber within the compound of the pumping station.
14.2.13 The valve chamber would be combined with the interception chamber due to above and below-ground site constraints.
14.2.14 The location of the drop shaft is dictated by a number of existing large diameter pipes serving the pumping station and the substructure of a historic pumping station located within the site. The location is also dictated by the hydraulic requirements. The layout would need to incorporate a minimum length of connection culvert to provide a stable approach flow to the vortex generator located at the top of the drop shaft.
14.2.15 The finish level of the drop shaft would be approximately 1m above the existing ground level for hydraulic reasons.
14.2.16 The air treatment chamber would be situated in an above ground structure located within external compound of the pumping station.
14.2.17 The ventilation column serving the drop shaft and the electrical and control kiosk would be integrated into one above-ground structure. This would be located within the external compound of the pumping station.
14.2.18 The ventilation column serving the screening chamber would be located within the external compound of the pumping station.
14.2.19 The electrical and control kiosk would be located within the existing pumping station building.
14.2.20 The permanent infrastructure would be surrounded by an area of permanent hardstanding to facilitate operational maintenance.
14.2.21 The layout of the structures and associated hardstanding area was developed to provide an improved area of public realm.
14.2.22 Refer to the Design and Access Statement Section 11 for more information on architectural considerations.
14.3 Limits and zones
Temporary works 14.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within two separate LLAU boundaries.
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14 Falconbrook Pumping Station
a. The primary area includes: i The compound area of Falconbrook Pumping Station, its external
compound and an area of publically accessible land which surrounds the pumping station for construction of the permanent works.
ii The LLAU includes the former disused public conveniences and the compound surrounding the venturi structure located to the west of the pumping station.
iii The LLAU includes the access road which is located to the south of the pumping station, which serves both the pumping station and the adjacent York Gardens Library and Community Centre. This is required for the formation of the construction site.
iv The LLAU incorporates the footway serving the library/community centre and the vehicle turning area outside the facility. This would be required to provide improvements to pavement surfacing as part of the works. Pedestrian and vehicle access to the library/community centre would be maintained. The LLAU includes a small area of York Gardens to maintain vehicle access to the library/community centre during the construction period.
v The LLAU includes a section of the southbound carriageway of York Road and the adjacent footway. It is not proposed to close the carriageway to traffic, or to close the footway to pedestrians. This area is required for the formation of the two new temporary vehicle access points required for the construction phase.
vi The LLAU includes the access road to the east of the site which provides access to the pumping station, York Gardens Adventure Playground and York Gardens Library and Community Centre off Lavender Road. It is not required to close this access road. This area is required to enable maintenance vehicles to access the new infrastructure once it has been completed. It is not proposed to use this access road, located on the east of the pumping station, for construction vehicles.
b. The secondary area would be for the temporary relocation of a bus stop.
14.3.2 The primary LLAU covers an area of approximately 4,500m2 and the assumed hoarded area would be approximately 2,000m2 (based on the illustrative Construction phases – phase one drawing). The secondary LLAU covers an area of approximately 800m2 for highway works.
14.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
14.3.4 The assumed hoarded area of the Falconbrook Pumping Station site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching
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14 Falconbrook Pumping Station
plant, a storage area, site power, site roads and an existing electricity sub-station building It is in the lower end of the expected site size range for a connection tunnel drive site indicating the site is constrained in size so there would be additional constraints on the construction layout, methods and programme. The primary LLAU includes the assumed hoarded area, the remaining part of the Thames Water Pumping Station site, part of York Gardens for a worksite and permanent access from Lavender Road and an area of road for highway works. The highway works are in York Road and include for the construction of two temporary site accesses and for the potential construction of a ventilation pipe and chamber in the footway. The secondary LLAU also allows for highway works in York Road and York Gardens to create a temporary replacement bus stop.
Permanent works 14.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone was derived to position the shaft between the existing below ground infrastructure located within the site and provide suitable above ground hardstanding during operational maintenance activities.
14.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by the York Road to the west and the existing pumping station building / sub-station to the east. The zone extends slightly into the eastern footway of York Road to allow for the below- ground horizontal de-aeration recirculation vent. The zone extends from the access road serving the library/community centre to the south and the existing venturi structure to the north.
14.3.7 The zone within which the permanent above-ground structures for the combined electrical and control kiosk and the ventilation columns would be located (denoted by purple lines on the Site works parameter plan) allows for these structures to be located within the external compound of the existing pumping station.
14.3.8 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) allows for suitable landscaping to surround the permanent hardstanding area. The zone extends to the external boundary of the York Gardens Adventure Playground to the north and the external boundary of the library/community centre to the south in order to mitigate the impact of the proposed works and to integrate the proposed raised ground level with the existing public realm. The zone extends to the rear of the York Road footway to the west and to the electrical substation building to the east in order to integrate the new landscaping with the existing adjacent footways.
14.4 Access 14.4.1 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure.
Engineering design statement 133
14 Falconbrook Pumping Station 14.4.2 Access to the hardstanding area would be from an easterly direction and
utilise the existing access road which serves the pumping station, York Gardens Adventure Playground and York Gardens Library and Community Centre from the Lavender Road public highway.
14.4.3 The hydraulic requirements require the access covers serving the drop shaft to be located approximately 1m above the existing low lying ground level. The majority of access covers located within the external compound area of the pumping station would be finished at existing ground level, with the exception of those serving the valve chamber. These would be finished approximately 1.5m above the existing ground level. All access covers would be accessible from surface and would not be buried.
14.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
14.4.5 The existing pumping station compound and venturi chamber would still be accessed regularly by Thames Water operational staff.
14.4.6 The area within the limits of permanent access would not require any permanent works to be constructed within it, but would be required to provide Thames Water with the rights to use the land for access to the permanent works for operational and maintenance activities. The area within the limits of permanent access incorporates the short length of access road between the limits of permanent works and the Lavender Road public highway.
Engineering design statement 134
15 Cremorne Wharf Depot
15 Cremorne Wharf Depot
15.1 Introduction 15.1.1 The proposed development site is located in the Royal Borough (RB) of
Kensington and Chelsea. It comprises the existing council depot including a pier, an existing campshed on the River Thames Foreshore and the Grade II listed Thames Water Lots Road Pumping Station. The Lots Road Pumping Station combined sewer overflow (CSO) discharges into the River Thames under the pier. The site extent is defined by the limits of land to be acquired or used (LLAU) and covers an area of approximately 0.6 hectares. The depot site is designated as a safeguarded wharf by the Mayor of London.
15.1.2 The site is bounded to the northeast by Chelsea Wharf. To the east and south of the site is bounded by the River Thames and Chelsea Creek which forms the boundary of the London Borough of Hammersmith and Fulham. The site is bounded to the west by a strip of cleared land that is part of the Lots Road Power Station site currently undergoing redevelopment. To the northwest are residential properties along Lots Road
15.1.3 The site would be used as a CSO site to perform the following functions: a. Intercept pumped flow from the Lots Road Pumping Station CSO b. accommodate a vortex drop and de-aeration chamber c. provide the Lots Road connection tunnel d. provide air management and ventilation equipment e. provide access for operation and maintenance f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 15.1.4 Drawings of the site are provided in Section 13 of the Book of Plans.
15.2 Structures 15.2.1 The principal structures would comprise:
a. an interception chamber b. a valve chamber c. a connection culvert d. a drop shaft e. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns f. electrical and control equipment located within the existing pumping
station building with a local control pillar located outside the building.
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15 Cremorne Wharf Depot
Size 15.2.2 The size of the interception chamber is dictated by the size and depth of
the Counters Creek Sewer, the angle of flow from Lots Road Pumping Station (which enters Counters Creek Sewer approximately 5m upstream of the chamber), and the design flow rate to be intercepted (18 m3/s, see Table 3.2). Hydraulic modelling was undertaken to determine the chamber size.
15.2.3 The size of the connection culvert is dictated by the design flow rate and the depth of Counters Creek Sewer.
15.2.4 The drop shaft would have an approximate internal diameter of 8m and be approximately 42m deep from top of cover slab to invert of the connection tunnel.
15.2.5 The internal diameter of the drop shaft is dictated by the requirements for de-aeration of the flow and requirements for access. The shaft access covers would be finished at existing ground level.
15.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be sheet piled cut-off to the river terrace gravels and SCL with a secondary concrete internal lining. The drop shaft would be predominantly excavated in London Clay ground conditions. The depth of the drop shaft is determined by the depth of the Lots Road connection tunnel, which in turn is determined by the depth of the main tunnel at this point.
15.2.7 The two ventilation columns serving the drop shaft would have an approximate internal diameter of 0.9m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
15.2.8 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing two columns of smaller diameter is considered preferable to providing a single column with a larger diameter, refer to the Design and Access Statement Section 12 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
15.2.9 An existing ventilation column on the corner of the pumping station building would be used to ventilate the interception chamber. This vent would be replaced or modified to make it more sensitive to the listed façade of the building.
15.2.10 The sizes of the below-ground ventilation structure and air treatment chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
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15 Cremorne Wharf Depot
Layout 15.2.11 The location of the interception chamber is dictated by the location of the
existing sewer that is to be intercepted. 15.2.12 The position of the drop shaft would allow for the reinstatement of the
existing depot building. However the zone in which the shaft would be located allows a wide degree of flexibility in the shaft location in order to accommodate potential changes to the proposed future use of the site as the design develops, as described in the section below.
15.2.13 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures, however it would be located outside of the footprint of the reinstated depot building and beneath an area of hardstanding to facilitate inspection and replacement of filter media.
15.2.14 The ventilation columns would be located on the periphery of the site in order to minimise any impact on the use of the site once the works are complete.
15.2.15 Electrical and control equipment would be located within the existing listed pumping station building. Interventions to the building have been designed to be as unobtrusive as possible, with cable ducts entering the building below-ground, using existing (redundant) penetrations in the basement wall.
15.2.16 Refer to the Design and Access Statement Section 12 for more information on architectural considerations, including consideration of the listed pumping station.
15.3 Limits and zones
Temporary works 15.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. The council depot for construction of the permanent works. b. Lots Road Pumping Station to allow electrical and control equipment
to be installed within the existing building. c. The jetty so that the existing outfall may be accessed. d. Part of the River Thames to provide for barge loading of materials
using the existing campshed. e. Part of the highway for kerb realignment works.
15.3.2 The LLAU covers an area of approximately 6,300m2 and the assumed hoarded area would be approximately 3,700m2 (based on the illustrative Construction phases – phase one drawing).
15.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth
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15 Cremorne Wharf Depot
Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
15.3.4 The assumed hoarded area of the Cremorne Wharf Depot site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching plant, a storage area, site power, and site access roads. It is in the upper end of the expected site size range as it would be a short connection tunnel drive site and includes access roads to and from Lots Road. The LLAU includes the assumed hoarded area, the Thames Water Lots Road Pumping Station, which would be used to house electrical and control equipment, the existing jetty and an area for renovation of a campshed. This facility would occupy an area of 400m2 in the river foreshore and would be used for transport of materials by river.
Permanent works 15.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is large enough to allow flexibility for potential changes to the proposed future use of the site (by others) as the design develops. These include the potential for wharf configurations different from the existing configuration, future residential development (RB Kensington and Chelsea have submitted a planning application for mixed use residential development of the site), or the need to upgrade the pumping station. All these potential scenarios put different constraints on the location of the drop shaft, and as it is not known at the time of application which scenario may eventuate, flexibility is required in order to be able to accommodate this uncertainty.
15.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) consists of the majority of the land-based area of the site (i.e. Lots Road Pumping Station and Cremorne Wharf). The size of this parameter results from the flexibility required of the drop shaft location, i.e. given that the drop shaft could be located in a range of positions, the other structures that connect to the shaft could also be located in a range of positions. It includes the pumping station building because the electrical and control equipment would be installed within the pumping station building.
15.3.7 The zone within which the ventilation columns serving the drop shaft would be located (denoted by the purple line on the Site works parameter plan) is coincident with the green line. This also reflects the flexibility required of the drop shaft location, given that the ventilation columns would be connected to the drop shaft.
15.3.8 The design of the reinstated depot facilities would respect the historic setting of the listed pumping station, in particular the footprint of the depot building would be set back from south west corner of listed pumping station and the building would not be physically attached to the pumping station. Further the depot building shall not exceed height and roofline of the pumping station building in accordance with the approved plans.
Engineering design statement 138
15 Cremorne Wharf Depot 15.3.9 The layout of the permanent works and depot reinstatement shall not
prejudice the future opening of the Thames Path across the property by others.
15.4 Access 15.4.1 The works would be accessed via two existing Thames Water and Royal
Borough of Kensington and Chelsea depot access points from Lots Road. 15.4.2 The area around the permanent works would be finished with
hardstanding to allow crane access to the structures and to allow the site to revert back to the local authority on completion of the tunnel works, as a depot and safeguarded wharf.
15.4.3 The footprint of the reinstated depot facilities would be constrained to the east and west of the site where crane access would be required to the shaft, interception chamber, and tidal flap valve chamber. Therefore no above ground buildings/structures that could compromise crane operations would be located in these areas.
15.4.4 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) may be buried.
15.4.5 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
15.4.6 The ten yearly inspection may involve temporarily removing elements of the landscaping to expose and open any buried access covers.
15.4.7 The area within the limits of permanent access would not require any permanent works to be constructed within it, but would be required to provide Thames Water with the rights to use the land for access to the permanent works for operational and maintenance activities. The area within the limits of permanent access incorporates the short length of access road between the limits of permanent works and the Lots Road public highway.
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15 Cremorne Wharf Depot
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16 Chelsea Embankment Foreshore
16 Chelsea Embankment Foreshore
16.1 Introduction 16.1.1 The proposed development site is located in the Royal Borough (RB) of
Kensington and Chelsea. It comprises an area of the River Thames foreshore, a section of river wall, pavement and carriageway of the Chelsea Embankment (A3212), and a small part of Ranelagh Gardens. The Ranelagh combined sewer overflow (CSO) discharges into the River Thames along this section of the Chelsea Embankment. The site extent is defined by the limits of land to be acquired or used (LLAU) and covers an area of approximately 2.5 hectares (ha).
16.1.2 The site is bounded to the north by the Royal Hospital and its South Grounds and Ranelagh Gardens (the latter two both Grade II registered historic park and gardens). The tidal Thames bounds the site to the east, south and west. Further to the east is the Grade II listed Chelsea Bridge (A3216) and Chelsea Embankment Gardens, and to the west is a section of the river wall which is Grade II listed.
16.1.3 The site would be used as a CSO site to perform the following functions: a. intercept flow from the Ranelagh CSO b. in conjunction with connections to the northern Low Level Sewer No.1
at the Victoria Embankment Foreshore and Blackfriars Bridge Foreshore sites, control the flow from ten other CSOs along the embankment that would have otherwise required direct interception by making a connection to the northern Low Level Sewer No.1
c. accommodate two vortex drops (one for the interception of the Ranelagh CSO and one for the connection to the Low Level Sewer No. 1) and a de-aeration chamber
d. provide the Ranelagh connection tunnel e. provide air management and ventilation facilities f. provide access for operation and maintenance g. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 16.1.4 Drawings of the site are provided in Section 14 of the Book of Plans.
16.2 Structures 16.2.1 The principal structures would comprise:
a. an interception chamber, valve chamber and connection culvert to divert the flow from the existing CSO into the CSO drop shaft
b. an overflow weir chamber, valve chamber and connection culvert to divert the flow from the existing Low Level Sewer No. 1 into the CSO drop shaft
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16 Chelsea Embankment Foreshore
c. a drop shaft d. a new CSO outfall e. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns f. two electrical and control kiosks g. a foreshore structure accommodating the majority of these structures.
Size 16.2.2 The size of the Ranelagh CSO interception chamber is dictated by the size
and depth of the existing sewer and the design flow rate that is to be intercepted (20 m3/s, see Table 3.2). Hydraulic modelling was undertaken to determine the chamber size.
16.2.3 The size of the northern Low Level Sewer overflow weir chamber is dictated by the size and depth of the northern Low Level Sewer No. 1 and the design flow rate that is to be controlled (17 m3/s, see Table 3.2).Hydraulic modelling was undertaken to determine the chamber size.
16.2.4 The size of the connection culverts is dictated by the design flow rate to be controlled by the overflow weir and the depth of the overflow weir chamber.
16.2.5 The drop shaft would have an approximate internal diameter of 12m and be approximately 45m deep from top of cover slab to invert of the connection tunnel.
16.2.6 The internal diameter of the drop shaft is dictated by the need to have two vortex drop tubes and the requirements for access. The shaft access covers would be finished at ground level.
16.2.7 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be segmental caisson with bottom underpinning. The drop shaft would be predominately excavated in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group. The depth of the drop shaft is determined by the depth of the Ranelagh connection tunnel, which in turn is determined by the depth of the main tunnel at this point.
16.2.8 The two ventilation columns serving the drop shaft would have an approximate internal diameter of 0.9m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
16.2.9 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing two columns of smaller diameter is considered preferable to providing a single column with a larger diameter, refer to the Design and access statement Section 13 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive
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16 Chelsea Embankment Foreshore
Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
16.2.10 The ventilation column serving the Ranelagh CSO interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
16.2.11 The ventilation column serving the Low Level Sewer overflow weir chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
16.2.12 The height of the smaller diameter ventilation columns is consistent with Thames Water standards (see para. 3.11.7).
16.2.13 The sizes of the below-ground ventilation structure and air treatment chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
16.2.14 The size of the electrical and control kiosks is determined by the equipment they would house, although the inclusion of two smaller kiosks rather than one large kiosk is driven by aesthetics.
16.2.15 The size of the foreshore structure is dictated by the size of the drop shaft, hydraulic chambers, ventilation and air treatment chambers, and the ship impact protection zone. The size also needs to reflect safe operational access requirements.
Layout 16.2.16 The location of the Ranelagh interception chamber is dictated by the
location of the existing sewer that is to be intercepted. 16.2.17 The location of the overflow weir chamber is dictated by the location of the
northern Low Level Sewer No. 1 sewer that is to be controlled and the alignment of Chelsea Embankment carriageway (i.e. the chamber is located where the northern Low Level Sewer No. 1 is closest to the kerb and would therefore cause the least disruption to traffic during construction).
16.2.18 The position of the drop shaft would minimise the length of the connection tunnel to the main tunnel (see also para. 6.3.11).
16.2.19 The location of the shaft also allows the foreshore structure to be aligned with the historic axis of the Royal Hospital Chelsea (refer to the Design and Access Statement Section 13 for more information).
16.2.20 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures. It has been accommodated within the overall footprint of the foreshore structure and would be beneath an area of hardstanding to facilitate inspection and replacement of filter media.
16.2.21 The ventilation columns serving the drop shaft and the Ranelagh interception chamber would be located on the periphery of the foreshore structure in order to allow views along the axis from the Royal Hospital through the Royal Hospital Garden entrance gates to the foreshore.
Engineering design statement 143
16 Chelsea Embankment Foreshore 16.2.22 The ventilation columns serving the northern Low Level Sewer No. 1
overflow weir chamber would be located near the chamber, clear of nearby trees, and clear of the gate which would be used for the utility company to access the diverted services.
16.2.23 Electrical and control equipment kiosks would be located on the periphery of the foreshore structure in order to allow views along the axis created by Monument Walk from the Royal Hospital through the Royal Hospital Garden entrance gates to the foreshore.
16.3 Limits and zones
Temporary works 16.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. Part of the River Thames for construction of the permanent works. b. Part of the footway and carriageway as the overflow weir chamber and
connection culvert must be located on the line on the line of the northern Low Level Sewer No. 1, which is located under the carriageway of Chelsea Embankment.
c. A small area of Ranelagh Gardens to include the edge of the overflow weir chamber, which would just extend into the gardens and to allow for the services diversions which are necessary to build the overflow weir chamber.
d. The ‘Bull Ring’ and the surrounding carriageway to allow for paving treatment and other landscaping to tie the foreshore structure into the existing space.
16.3.2 The LLAU covers an area of approximately 24,800m2, the assumed primary hoarded land area would be approximately 200m2, the assumed secondary hoarded land area would be approximately 450m2 and the assumed cofferdam areas would be approximately 5,200m2 (based on the illustrative Construction phases – phase one drawing).
16.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
16.3.4 The assumed primary hoarded and cofferdam area of the Chelsea Embankment Foreshore site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, concrete batching plant, storage areas for segments and general use, site power, and site access roads. It is just greater than the upper end of the expected site size range because it would be a short connection tunnel drive site. The secondary assumed hoarded area is required for construction of an overflow weir chamber on the northern Low Level Sewer No.1, a short distance from the primary site (CSO interception chamber). The LLAU includes the assumed primary hoarded
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16 Chelsea Embankment Foreshore
and cofferdam area, the secondary assumed hoarded area, an area to facilitate construction of the connection culvert between the primary and secondary site areas, part of the river needed to facilitate construction of the temporary cofferdam and scour protection, a campshed and the permanent foreshore structure. The campshed would occupy an area of approximately 400m2 in the river foreshore and would be used for transport of materials by river. In addition the LLAU includes the ‘Bull Ring’ and surrounding area to allow paving works.
Permanent works 16.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is positioned on the foreshore structure. The zone provides a small degree of flexibility for the drop shaft to move a short distance as the design is developed.
16.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) mainly consists of the foreshore for the foreshore structure, scour protection and outfall apron. The area also includes overflow weir chamber and connection culvert.
16.3.7 The two zones within which the electrical and control kiosks and the ventilation columns serving the drop shaft, interception chamber, and the valve chamber would be located (denoted by the purple lines on the Site works parameter plan) are on the periphery of the foreshore structure and have a small degree of flexibility whilst allowing views along the axis from the Royal Hospital through the Royal Hospital Garden entrance gates to the foreshore.
16.3.8 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) includes the foreshore structure to provide landscaping to the new area of public realm, the area of paving in front of the Bull Ring Gates in order to visually connect the new structure to the historic axis of the Royal Hospital Monument Walk, and an area in Ranelagh Gardens in order to reinstate the green screening around the gardens which would be removed as part of the utility diversion works.
16.4 Access 16.4.1 The works in the foreshore would be accessed from Chelsea Embankment
via a new mountable kerb and strengthened footway across the Thames Path. The overflow weir chamber would generally be accessed from covers in the northern footway of Chelsea Embankment, with some equipment requiring infrequent access to be accessed from covers in the carriageway.
16.4.2 An area of permanent hardstanding would be provided for access purposes. This area would surround the permanent infrastructure.
16.4.3 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) would be buried.
Engineering design statement 145
16 Chelsea Embankment Foreshore 16.4.4 The three to six monthly, three yearly and ten yearly site visits and major
blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively. 16.4.5 The ten yearly inspection would involve temporarily removing elements of
the landscaping to expose and open any buried access covers.
Engineering design statement 146
17 Kirtling Street
17 Kirtling Street
17.1 Introduction 17.1.1 The proposed development site is located in the London Borough of
Wandsworth, and is also close to the London Borough of Lambeth and the City of Westminster. It comprises a former petrol station, a warehouse and a depot (which are all part of the consented Battersea Power Station redevelopment site), an active concrete batching works on a designated safeguarded wharf, additional warehouses and commercial units. It also extends out into the River Thames foreshore.
17.1.2 The site is bounded to the north by the River Thames, to the east by the Tideway Walk (Riverlight) development (under construction) and the Thames Tideway Tunnel project’s Heathwall Pumping Station site beyond, to the south by Nine Elms Lane and New Covent Garden Market beyond, and to the west by a Waste Transfer Station and Thames Water’s Ring Main Pumping Station and the disused Battersea Power Station beyond.
17.1.3 The site would be used as a main tunnel double drive site to perform the following functions: a. drive the main tunnel in two directions concurrently: to Chambers
Wharf in the east and to Carnwath Road Riverside in the west b. provide air management and ventilation facilities c. provide access for operation and maintenance (including vehicle
access to the main tunnel) d. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 17.1.4 No CSO would be intercepted at this site. 17.1.5 Drawings of the site are provided in Section 15 of the Book of Plans.
17.2 Structures 17.2.1 The principal structures would comprise:
a. a main tunnel shaft b. ventilation structures including a below-ground air treatment chamber
and above ground ventilation column combined with an electrical and control kiosk.
Size 17.2.2 The main tunnel shaft would have an approximate internal diameter of
30m and be approximately 48m deep from top of cover slab to invert of the tunnel. The shaft access covers would be finished at existing ground level.
Engineering design statement 147
17 Kirtling Street 17.2.3 The internal diameter of the main tunnel shaft is dictated partly by the size
of the main tunnel, but primarily by the need to operate two TBMs simultaneously.
17.2.4 The external diameter of the shaft is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The shaft would be excavated predominantly in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group. The depth of the shaft is determined by the depth of the main tunnel at this point.
17.2.5 The sizes of the below-ground ventilation structure and air treatment chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
17.2.6 The combined ventilation column and electrical and control kiosk would be approximately 5m by 3m by 4m minimum to 6m maximum high.
17.2.7 The size of the combined ventilation column and electrical and control kiosk is dictated by the peak air flow rate and by the size of the electrical and control equipment it would house. The minimum height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
Layout 17.2.8 The main tunnel shaft would be positioned to minimise the need to tunnel
beneath adjacent land and structures. The position is also constrained by the extent to which the tunnel would have to change direction within the main tunnel shaft for hydraulic reasons.
17.2.9 The ventilation structure and air treatment chamber would be situated underground in order to minimise the number of above-ground structures. They would be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
17.2.10 The combined ventilation column and the electrical and control kiosk would be located on the periphery of the site to minimise any impact on the future use of Kirtling Wharf. The structure would be sited either to the west of the main tunnel shaft, near the boundary of the waste transfer station (Cringle Dock), or to the east, near the boundary of the former Victoria and Albert Museum warehouse.
17.2.11 Refer to the Design and Access Statement Section 14 for more information on architectural considerations.
17.3 Limits and zones
Temporary works 17.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including:
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17 Kirtling Street
a. The Brooks Court office complex, the Cable and Wireless depots, the Securicor depot (between Cringle Street and Kirtling Street), the former Victoria and Albert Museum warehouse at 88 Kirtling Street and Kirtling Wharf (also known as Cringle Wharf)for construction of the permanent works.
b. Kirtling Wharf is an operational concrete batching plant. The northern part of the wharf would be the location for the main shaft. The existing concrete batching plant would remain operational during the construction period and would be relocated to the southern part of wharf.
c. Part of the River Thames for a temporary jetty. The jetty would be used to transport excavated material from the main tunnel shaft and tunnel and aggregates for secondary lining of the main tunnel.
17.3.2 The LLAU covers an area of approximately 52,200m2 and the assumed hoarded area would be approximately 22,800m2 (based on the illustrative Construction phases – phase one drawing).
17.3.3 The Site selection background technical paper Section 4.4 (see the Final Report on Site Selection Process Volume 2) stated that the area of main tunnel double drive sites could range from approximately 20,000m2 to 40,000m2.
17.3.4 The assumed hoarded area of the Kirtling Street site contains an area for the permanent works, construction offices and welfare buildings, material handling and storage including tunnel lining segments, a storage area, site power, steel reinforcement preparation area, concrete batching plant and site roads. It is in the lower end of the expected site size range for a double drive site and consists of two irregularly shaped areas indicating the site is constrained in size so there would be additional constraints on the construction layout, methods and programme. The LLAU area includes both of the assumed hoarded areas, the relocated Cemex concrete batching works, and an area for construction of a jetty/campshed. This facility would occupy an area of approximately 4500m2 in the river foreshore and would be used for transport of materials by river.
Permanent works 17.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) allows some flexibility for the position of the main tunnel shaft to be moved a short distance as the design is developed.
17.3.6 The zone within which all permanent site structures would be located (denoted by the green line on the Site works parameter plan) allows a small degree of flexibility on the location of the structures as the design develops, but minimises impact on the future operation of Kirtling Wharf.
17.3.7 The two zones within which permanent above-ground structures may be located (denoted by the two purple lines on the Site works parameter plan) lie at the western and eastern edges of the site in order to minimise the impact on users of Kirtling Wharf. The zones are alternative locations for the combined ventilation column and the electrical and control kiosk. Both
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17 Kirtling Street
zones would allow flexibility for movement of the structure in a north-south direction, while keeping it out of the way of the operational wharf.
17.4 Access 17.4.1 The works would be accessed via an existing entrance to the concrete
batching works off Kirtling Street. 17.4.2 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure and would allow the site to continue to operate as a wharf.
17.4.3 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) may be buried.
17.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
17.4.5 The ten yearly inspection may involve temporarily removing elements of the landscaping to expose and open any buried access covers.
17.4.6 Vehicles would be used with the ten-yearly inspections of the main tunnel. These vehicles would enter the tunnel via a large access opening in the main tunnel shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
Engineering design statement 150
18 Heathwall Pumping Station
18 Heathwall Pumping Station
18.1 Introduction 18.1.1 The proposed development site is located in the London Borough of
Wandsworth and is also close to the London Borough of Lambeth. It comprises Thames Water’s Heathwall Pumping Station, and incorporates Middle Wharf which is a designated Safeguarded Wharf.
18.1.2 The site is bounded to the north by the River Thames, to the east by open space and Elm Quay residential block beyond, to the south by Nine Elms Lane, and to the west by the Tideway Industrial Estate (now a re-development site called ‘Riverlight’) and the Kirtling Street site.
18.1.3 The site would be used as a CSO site to perform the following functions: a. intercept the pumped flow from Heathwall PS CSO b. intercept gravity flow from South West Storm Relief CSO. c. accommodate two vortex drops (one for the interception of the
Heathwall PS CSO and one for the South West Storm Relief CSO) and a de-aeration chamber
d. provide the Heathwall/SWSR connection tunnel e. provide air management and ventilation facilities f. provide access for operation and maintenance g. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 18.1.4 Drawings of the site are provided in Section 16 of the Book of Plans.
18.2 Structures 18.2.1 The principal structures would comprise:
a. an interception chamber, valve chamber and connection culvert to divert the flow from the existing Heathwall Pumping Station CSO into the drop shaft
b. modifications to the existing South West Storm Relief CSO chamber and construction of an interception chamber and valve chamber to divert the flow from the South West Storm Relief CSO into the drop shaft, including raising of the cover slab of the existing chamber above ground level
c. a drop shaft d. a new CSO outfall for the Heathwall Pumping Station CSO e. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns
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18 Heathwall Pumping Station
f. electrical and control equipment located within the existing pumping station and two local control pillars outside the existing pumping station
g. a foreshore structure accommodating the Heathwall Pumping station CSO interception structures.
Size 18.2.2 The size of the interception chamber to intercept the flow from Heathwall
Pumping Station is dictated by the size and depth of the outlet and the design flow to be intercepted (12m3/s, see Table 3.2), and the fact that the flow has be to dropped underneath the existing South West Storm Relief outfall culverts. The Heathwall Pumping Station interception chamber includes the Heathwall Pumping Station drop shaft, which drops the intercepted flow a short distance to below the existing South West Storm Relief outfall culverts.
18.2.3 The size and depth of the connection culvert between the Heathwall interception structures and the South West Storm Relief CSO drop shaft is dictated by the design flow rate and the depth of the South West Storm Relief outfall culverts under which it must pass.
18.2.4 The size of the interception chamber to intercept the flow from the South West Storm Relief CSO is dictated by the size and depth of the existing chamber on the sewer and the design flow to be intercepted (31m3/s, see Table 3.2).
18.2.5 The size and depth of the connection culvert between the South West Storm Relief interception structures and the South West Storm Relief CSO drop shaft is dictated by the design flow rate and the depth of the existing chamber.
18.2.6 The South West Storm Relief CSO drop shaft would have an approximate internal diameter of 16m and be approximately 46m deep from top of cover slab to invert of the tunnel.
18.2.7 The internal diameter of the drop shaft is dictated by the requirements for de-aeration of the flow and requirements for access.
18.2.8 The external diameter of the drop shaft is dictated by the construction method which is anticipated to be segmental caisson and bottom underpinned. The drop shaft would be predominately excavated in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group. The depth of the drop shaft is determined by the depth of the Heathwall/SWSR connection tunnel, which in turn is determined by the depth of the main tunnel at this point.
18.2.9 The ventilation column serving the South West Storm Relief CSO drop shaft would have an approximate internal diameter of 1.2m and be approximately 4m minimum to 8m maximum high. This ventilation column would be of the project’s ‘signature’ design.
18.2.10 The ventilation column serving the South West Storm Relief interception chamber would have an approximate internal diameter of 0.6m and be
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18 Heathwall Pumping Station
approximately 4m minimum to 8m maximum high. This ventilation column would also be of the project’s ‘signature’ design.
18.2.11 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
18.2.12 The ventilation column serving the Heathwall Pumping Station drop shaft would have an approximate internal diameter of 0.225m and be a maximum height of 6m.
18.2.13 The height of the smaller diameter ventilation column is consistent with Thames Water standards (see para. 3.11.7).
18.2.14 The sizes of the below-ground ventilation structure and air treatment chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
18.2.15 The size of the foreshore structure is dictated by the size of the Heathwall interception structures, and the ship impact protection zone. The size also needs to reflect safe operational access requirements.
Layout 18.2.16 The location of the Heathwall interception chamber is dictated by the
location of the Heathwall Pumping Station outlet. 18.2.17 The location of the South West Storm Relief interception chamber is
dictated by the location of the existing chamber to which a connection would be made.
18.2.18 The position of the drop shaft under Middle Wharf would allow for intercepting two CSOs within one site and makes use of land that is already owned. The extent of below-ground structures and sewers on the Heathwall Pumping Station site prevents the drop shaft being located within the pumping station site boundary.
18.2.19 The ventilation structure and air treatment chamber would be situated underground in order to minimise the number of above-ground structures. They would be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
18.2.20 The ventilation column serving the drop shaft would be located adjacent to the drop shaft, but within the pumping station compound to minimise any effects on the future use of Middle Wharf.
18.2.21 The ventilation column serving the South West Storm Relief interception chamber would be located on top of the interception chamber, within the pumping station compound.
18.2.22 The ventilation column serving the Heathwall Pumping Station interception chamber would be located close to the interception chamber, but within the pumping station compound to keep the new area of public realm free of clutter.
Engineering design statement 153
18 Heathwall Pumping Station 18.2.23 Electrical and control equipment would be located within the existing
pumping station building with a local control pillar near the Heathwall Pumping Station interception structure and another local control pillar near the South West Storm Relief interception structure.
18.2.24 Refer to the Design and Access Statement Section 15 for more information on architectural considerations.
18.3 Limits and zones
Temporary works 18.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. Middle Wharf for construction of the permanent works (this is where
the South West Storm Relief CSO drop shaft would be located). b. The Heathwall Pumping Station to allow electrical and control
equipment to be installed within the existing building and to allow ventilation columns to be located within the existing compound.
c. Part of the River Thames to allow for the construction of the interception structure to intercept the Heathwall Pumping Station CSO, the relocation of the Battersea Barge, and to provide for barge loading of excavated materials.
18.3.2 The LLAU covers an area of approximately 12,700m2, the assumed hoarded land area would be approximately 2,100m2 and the assumed cofferdam area would be approximately 1,200m2 (based on the illustrative Construction phases – phase one drawing).
18.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
18.3.4 The assumed hoarded and cofferdam area of the Heathwall Pumping Station site contains areas for the permanent works, material handling and storage, concrete batching plant, a storage area, site power and site roads. It is in the middle of the expected site size range but because it is a short connection tunnel drive site this indicates the site is constrained in size so there would be additional constraints on the construction layout, methods and programme. The LLAU includes the assumed hoarded and cofferdam area and the Heathwall Pumping Station which would be used to house the electrical and control equipment. It also includes part of the river needed to facilitate construction of the temporary cofferdam and scour protection, a campshed and the permanent foreshore structure. The campshed would occupy an area of approximately 400m2 in the river foreshore and would be used for transport of materials by river.
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18 Heathwall Pumping Station
Permanent works 18.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) positioned on Middle Wharf and provides a small degree of flexibility for the drop shaft to move a short distance as the design is developed.
18.3.6 The zone within which all permanent site structures would be located (denoted by the green line on the Site works parameter plan) consists of the majority of the land-based area of the site (i.e. Heathwall Pumping Station, Middle Wharf, and the proposed foreshore structure including scour protection) but excludes an area that Thames Water operations uses to access Heathwall Pumping Station.
18.3.7 The two zones within which all permanent above-ground structures would be located (denoted by the purple line on the Site works parameter plan) provide flexibility to locate the structures within the existing Thames Water compound.
18.3.8 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) includes the foreshore structure and Thames Path in order to provide landscaping to the new area of public realm, and the footway of Nine Elms Lane in order to landscape the footway in accordance with Transport for London’s Nine Elms Lane Public Realm Design.
18.4 Access 18.4.1 The works would be accessed via four existing entrances off Nine Elms
Lane (two to the pumping station and two to Middle Wharf). 18.4.2 The area around the CSO drop shaft would be finished with hardstanding
to allow crane access to the structure and to allow the site to operate as a wharf.
18.4.3 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) would be buried.
18.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
18.4.5 The ten yearly inspection would involve temporarily removing turf and other landscaping to expose and open any buried access covers.
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18 Heathwall Pumping Station
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Engineering design statement 156
19 Albert Embankment Foreshore
19 Albert Embankment Foreshore
19.1 Introduction 19.1.1 The proposed development site is located within the London Borough of
Lambeth. It comprises the foreshore of the River Thames parallel to Albert Embankment (A3036) between St George Wharf and Tintagel House and includes Lack’s Dock and the Thames Path. The Grade II* listed Vauxhall Bridge crosses the site at its southern end.
19.1.2 The site is bounded by the River Thames to the north, south and west. Residential properties are located at Peninsula Heights to the northeast of the site and St George Wharf to the south, beyond Vauxhall Bridge. The Vauxhall Cross building and two high rise office buildings (Camelford House and Tintagel House) are located along the eastern boundary.
19.1.3 The site would be used as a CSO site to perform the following functions: a. intercept flow from Clapham Storm Relief CSO b. intercept flow from the Brixton Storm Relief CSO c. accommodate a vortex drop and de-aeration chamber d. provide air management and ventilation facilities e. provide the Clapham/Brixton connection tunnel f. provide access for operation and maintenance g. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 19.1.4 Drawings of the site are provided in Section 17 of the Book of Plans.
19.2 Structures 19.2.1 The principal structures would comprise:
a. interception chambers b. valve chambers c. connection culverts d. a drop shaft e. a new CSO outfall serving both the Clapham Storm Relief CSO and
Brixton Storm Relief CSO (to be known as the Effra CSO) f. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns g. two electrical and control kiosks and one local control pillar h. two foreshore structures accommodating the majority of these
structures.
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19 Albert Embankment Foreshore
Size 19.2.2 The size of the interception chamber is dictated by the size and depth of
the existing CSOs and the design flow to be intercepted (10 m3/s from Clapham Storm Relief and 12 m3/s from Brixton Storm Relief, see Table 3.2
19.2.3 The drop shaft would have an approximate internal diameter of 16m and be approximately 48m deep from top of cover slab to invert of connection tunnel.
19.2.4 The internal diameter of the drop shaft is dictated by the requirements for de-aeration of the flow and requirements for access.
19.2.5 The external diameter of the drop shaft is dictated by the construction method which is anticipated to be diaphragm wall with dewatering to limit settlement to the adjacent building. The drop shaft would be predominately excavated in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group. The depth of the drop shaft is determined by the depth of the Clapham/Brixton connection tunnel, which in turn is determined by the depth of the main tunnel at this point.
19.2.6 The two ventilation columns serving the drop shaft would have an approximate internal diameter of 0.9m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
19.2.7 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing two columns of smaller diameter is considered preferable to providing a single column with a larger diameter, refer to the Design and access statement Section 16 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
19.2.8 The ventilation column serving the Clapham Storm Relief CSO would have an internal diameter of approximately 0.3m and be a maximum 6m high.
19.2.9 The two ventilation columns serving the interception chamber would also have an internal diameter of approximately 0.3m and be a maximum 6m high.
19.2.10 The height of the smaller diameter ventilation columns is consistent with Thames Water standards (see para. 3.11.7).
19.2.11 The sizes of the below-ground ventilation structure and air treatment chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
19.2.12 The size of the electrical and control kiosks is determined by the equipment they would house. Two kiosks are required because one controls equipment located within the interception structure located near
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19 Albert Embankment Foreshore
the south abutment of Vauxhall Bridge and the other controls equipment within the drop shaft structure to the north of Lack’s Dock.
19.2.13 The size of the foreshore structure located near the south abutment of Vauxhall Bridge is dictated by the position of Clapham SR and Brixton SR CSOs, and the bridge abutment.
19.2.14 The size of the foreshore structure located to the north of Lack’s Dock is dictated by the size of the drop shaft, ventilation and air treatment chambers, and the ship impact protection zone. The size also needs to reflect safe operational access requirements. It allows for a widened access to the north of Lack’s Dock to provide access for cranes and maintenance vehicles onto the drop shaft, and the radius of the corner maximises visibility for vessels entering the water from Lack’s Dock.
Layout 19.2.15 The location of the interception chamber in the foreshore is dictated by the
positions of the existing Clapham Storm Relief and Brixton Storm Relief CSOs.
19.2.16 The position of the drop shaft is influenced by the location of the existing river wall, the lines of the existing river walls of Albert Embankment to the north and Vauxhall Cross to the south, and the proximity of Lack’s Dock and the need to minimise effects on lines of sight into the river for users of Lack’s Dock.
19.2.17 The ventilation structure and air treatment chamber would be situated underground in order to minimise the number of above-ground structures. They would be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
19.2.18 The two ventilation columns serving the drop shaft would be located towards the edge of the foreshore structure so that they are close to the drop shaft that they would be ventilating.
19.2.19 The ventilation column serving the Clapham Storm Relief would be located adjacent to the existing sewer, and on the edge of the riverside walkway so as not to obstruct pedestrian movement along the Thames Path.
19.2.20 The ventilation columns serving the interception structure would be located on either side of the entrance to the foreshore structure so as to provide a symmetrical layout around the new opening in the river wall parapet.
19.2.21 One electrical and control kiosk would be located underneath Vauxhall Bridge to minimise clutter within the public realm while keeping close enough to the equipment that it is controlling within the interception structure, with a small local control pillar located on the foreshore structure to allow a line of sight between an operator and the below-ground equipment that is being controlled.
19.2.22 The second electrical and control kiosk would be located next to the drop shaft so that it is close enough to the equipment that it is controlling within the shaft structure. The kiosk would be located towards the back of the structure, within a line of trees, to minimise clutter to the public realm.
Engineering design statement 159
19 Albert Embankment Foreshore 19.2.23 Refer to the Design and access statement Section 16 for more information
on architectural considerations.
19.3 Limits and zones
Temporary works 19.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. Part of the River Thames for construction of the permanent works and
barge loading (option A and B). b. Part of the Thames Path to allow access and working area for
construction (option A and B). c. Part of the pavement and roadway to allow access off of the highway
(option A and B). d. Lack’s Dock to allow access (option A) to the working area for
construction. e. Part of the above ground car park at Tintagel House to allow access to
the working area for construction (option B). f. Part of the above ground car park and the access road to the
underground car park at Camelford House to allow access to the working area for construction (Option B).
19.3.2 The LLAU covers an area of approximately 31,000m2, the assumed hoarded land area would be approximately 1,300m2 and the assumed cofferdam areas would be approximately 7,900m2(based on the illustrative Construction phases – phase one drawing).
19.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
19.3.4 The assumed hoarded and cofferdam area of the Albert Embankment Foreshore site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, a storage area, site power, steel reinforcement preparation area, shotcrete production area and site roads to the Albert Embankment. It is greater than the expected site size range because it would be a short connection tunnel drive site, the drop shaft would be constructed using diaphragm walling and the interception chamber and drop shaft would be located in two separate cofferdams. The LLAU area includes the assumed hoarded and cofferdam areas and part of the river needed to facilitate construction of the two temporary cofferdams and scour protection, a campshed and two permanent foreshore structures. The campshed would occupy an area of approximately 1300m2 in the river foreshore and would be used for transport of materials by river. In addition the LLAU includes two construction access options. The access between Camelford House and
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19 Albert Embankment Foreshore
Tintagel House which requires an area of 650m2 would not be required if Lack’s Dock is used.
Permanent works 19.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is positioned on the foreshore structure. The zone provides a small degree of flexibility for the drop shaft to move a short distance as the design is developed.
19.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) consists of the majority of the river-based area of the site for the foreshore structures, scour protection, outfall apron and connection. The zone allows a small degree of flexibility on the location of the structures as the design develops.
19.3.7 The five zones within which permanent above-ground structures may be located (denoted by the purple lines on the Site works parameter plan) have been delineated both to maximise available working areas for Thames Water operations while respecting the setting of the existing structures, in particular the listed Vauxhall Bridge, and avoiding obstructing the Thames Path and new public realm.
19.3.8 The zones within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) include the two new foreshore structures in order to allow landscaping of the new areas of public realm and a section of Lack’s Dock in order to integrate the landscaping with the existing public realm.
19.4 Access 19.4.1 The works would be accessed via Lack’s Dock, from Albert Embankment. 19.4.2 An area of permanent hardstanding would be provided for access
purposes. This area would surround the permanent infrastructure. 19.4.3 Access covers requiring regular access would be finished at ground level.
Access covers requiring infrequent access (typically once every ten years) would be buried.
19.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
19.4.5 The ten yearly inspection would involve temporarily removing paving slabs and other landscaping to expose and open any buried access covers.
19.4.6 The area within the limits of permanent access would not require any permanent works to be constructed within it, but would be required to provide Thames Water with the rights to use the land for access to the permanent works for operational and maintenance activities. The area within the limits of permanent access incorporates the following areas: a. Lack’s Dock and the access road to it from Albert Embankment, to
allow operational access to both the drop shaft and the interception chamber sites.
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19 Albert Embankment Foreshore
b. The Thames Path in front of Vauxhall Cross, to allow operational access to the interception chamber site.
Engineering design statement 162
20 Victoria Embankment Foreshore
20 Victoria Embankment Foreshore
20.1 Introduction 20.1.1 The proposed development site is located within the City of Westminster.
The site would comprise a section of the River Thames foreshore, and a section of pavement and roadway of the Victoria Embankment (A3211). The site extent is defined by the limits of land to be acquired or used (LLAU) and covers an area of approximately 1.8 hectares.
20.1.2 The site is bounded to the north, east and south by the River Thames and to the west by the Victoria Embankment (A3211). To the north of the site, is the restaurant ship, Hispaniola, and beyond that the Hungerford Bridge and the Golden Jubilee footbridges and the Embankment Pier. The pub/restaurant boat, the Tattershall Castle, is within the LLAU. The London Eye is located to the southeast of the site on the opposite river bank. Three moorings lie to the south of the site as well as the Whitehall Stairs which project into the river. The Royal Air Force memorial is situated on top of Whitehall Stairs. The closest buildings to the site are those along Whitehall Court to the west of Whitehall Gardens, which include some residential properties and a hotel.
20.1.3 The site would be used as a CSO site to perform the following functions: a. control the flow from the Regent Street CSO by connecting to the
northern Low Level Sewer No. 1 b. in conjunction with connections to the northern Low Level Sewer No.1
at the Chelsea Embankment Foreshore and Blackfriars Bridge Foreshore sites, control the flow from ten other CSOs along the embankment that would have otherwise required direct interception
c. accommodate a vortex drop and de-aeration chamber d. provide the Regent Street connection tunnel e. provide air management and ventilation facilities f. provide a replacement mooring g. provide access for operation and maintenance h. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 20.1.4 Drawings of the site are provided in Section 18 of the Book of Plans.
20.2 Structures 20.2.1 The principal structures would comprise:
a. an overflow weir chamber, valve chamber and connection culvert to divert the flow from the existing northern Low Level Sewer No.1 into the drop shaft
b. a drop shaft
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20 Victoria Embankment Foreshore
c. a new CSO outfall (the existing CSO outfall would remain – to be known as Regent Street B CSO and Regent Street A CSO respectively)
d. ventilation structures including below-ground air treatment chamber and above-ground ventilation columns
e. electrical and control kiosks f. a foreshore structure enclosing the majority of these structures.
Size 20.2.2 The size of the overflow weir chamber is dictated by the size and depth of
the northern Low Level Sewer No.1 and the design flow to be controlled (18m3/s, see Table 3.2).
20.2.3 The size of the connection culvert is dictated by the design flow rate and the depth of the northern Low Level Sewer No.1.
20.2.4 The drop shaft would have an approximate internal diameter of 13m and would be approximately 51m deep from top of cover slab to invert of the connection tunnel.
20.2.5 The internal diameter of the drop shaft is dictated by the requirements for de-aeration of the flow and requirements for access. The shaft access covers would be finished at existing ground level to tie into the landscape design.
20.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be segmental caisson with bottom underpinning. The drop shaft would be predominately excavated in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group. The depth of the drop shaft is determined by the depth of the Regent Street connection tunnel, which in turn is determined by the depth of the main tunnel at this point.
20.2.7 The two ventilation columns serving the drop shaft would have an approximate internal diameter of 0.9m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
20.2.8 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing two columns of smaller diameter is considered preferable to providing a single column with a larger diameter, refer to the Design and Access Statement Section 17 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
20.2.9 The ventilation column serving the overflow weir chamber would have an approximate internal diameter of 0.3m and be approximately 6m high.
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20 Victoria Embankment Foreshore 20.2.10 The height of the smaller diameter ventilation column is consistent with
Thames Water standards (see para. 3.11.7). 20.2.11 The sizes of the below-ground ventilation structures and air treatment
chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
20.2.12 The size of the electrical and control kiosk is determined by the equipment it would house.
20.2.13 The size of the foreshore structure is dictated by the size of the drop shaft, hydraulic chambers, ventilation and air treatment chambers, and the ship impact protection zone. The size also needs to reflect safe operational access requirements.
Layout 20.2.14 The location of the overflow weir chamber is determined by the location
and hydraulic characteristics of the existing sewer and the hydraulic interaction between the sewer and nearby overflows.
20.2.15 The position of the drop shaft would minimise the encroachment of the foreshore structure into the river.
20.2.16 The ventilation structure and air treatment chamber would be situated underground in order to minimise the number of above-ground structures. However they would be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
20.2.17 The ventilation columns serving the drop shaft would be located adjacent to the shaft to minimise the size of below-ground ventilation structures.
20.2.18 The ventilation column serving the overflow weir chamber would be located along the eastern edge of the footway near the overflow weir chamber. It would be located in the line of proposed replacement tree planting so as not to obstruct pedestrian movement along the Thames Path.
20.2.19 The electrical and control kiosk would be located at the back of the foreshore structure, adjacent to the existing Thames Path, and in combination with other amenity buildings (suggested for use as a commercial kiosk/café) would act to delineate the structure from the Thames Path.
20.2.20 Refer to the Design and Access Statement Section 17 for more information on architectural considerations.
20.3 Limits and zones
Temporary works 20.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. Part of the River Thames for construction of the permanent works and
barge loading.
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20 Victoria Embankment Foreshore
b. Part of the Victoria Embankment to allow access to the site and utility diversion work in the carriageway.
c. Part of the River Thames to allow for construction of temporary and replacement moorings.
20.3.2 The LLAU covers an area of approximately 15,500m2, the assumed hoarded land area would be approximately 500m2 and the assumed cofferdam area would be approximately 3,800m2(based on the illustrative Construction phases – phase one drawing).
20.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
20.3.4 The assumed hoarded and cofferdam area of the Victoria Embankment Foreshore site contains an area for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, storage areas for caisson segments and general use, site power, and site roads. It is in the upper end of the expected site size range as it would be a short connection tunnel drive site. The LLAU area includes the assumed hoarded and cofferdam areas and part of the river needed to facilitate construction of the temporary cofferdam and scour protection, a campshed, permanent foreshore structure and relocated moorings. The campshed would occupy an area of approximately 1300m2 in the river foreshore and would be used for transport of materials by river. In addition the LLAU includes part of the road to allow for utility diversions to take place and access to the site.
Permanent works 20.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is positioned on the foreshore structure. The zone provides a small degree of flexibility for the shaft to move a short distance as the design is developed.
20.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) consists of Victoria Embankment footway and the foreshore for the foreshore structure, scour protection and outfall apron. The zone allows a small degree of flexibility for the location of structures to move a short distance as the design develops.
20.3.7 The two zones within which the ventilation columns serving the interception chamber and drop shaft would be located (denoted by purple lines on the Site works parameter plan) are located in the footway and foreshore structure respectively. The zones are clear of trees and allow flexibility for the location of structures to move a short distance as the design develops.
20.3.8 The zone within which the electrical and control kiosks would be located (also denoted by a purple line on the Site works parameter plan) is located partly on the Victoria Embankment footway and partly on the foreshore
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20 Victoria Embankment Foreshore
structure. The zone is clear of trees and allows flexibility for the location of structures to move a short distance along the footway as the design develops.
20.3.9 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) includes the foreshore structure to provide landscaping to the new area of public realm.
20.4 Access 20.4.1 The works in the foreshore would be accessed from Victoria Embankment
via a new mountable kerb and strengthened footway across the Thames Path.
20.4.2 An area of permanent hardstanding would be provided for access purposes. This area would surround the permanent infrastructure.
20.4.3 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) would be buried.
20.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
20.4.5 The ten yearly inspection would involve temporarily removing paving slabs and other landscaping to expose and open any buried access covers.
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Engineering design statement 168
21 Blackfriars Bridge Foreshore
21 Blackfriars Bridge Foreshore
21.1 Introduction 21.1.1 The proposed development site is located within the City of London, close
to the boundary of the City of Westminster. It comprises the River Thames to the west and east of Blackfriars Bridge (A201), sections of the Victoria Embankment slip road up to Blackfriars Bridge and areas of the pavement along Victoria Embankment and Paul’s Walk. The site is defined by the limits of land to be acquired or used (LLAU) and covers an area of approximately 3.15 hectares for the main site (west of the bridge) and 0.8 hectares for the secondary site (east of the bridge).
21.1.2 The site is bounded to the north by the A3211 (Victoria Embankment/ Blackfriars Underpass / Upper Thames Street), beyond which are multi-storey office buildings. It is bounded to the east, south and west by the River Thames. To the west of Blackfriars Bridge is the Blackfriars Millennium Pier, the vessel President and Chrysanthemum Pier.
21.1.3 The site would be used as a CSO site to perform the following functions: a. intercept flow from the Fleet Main CSO b. in conjunction with connections to the northern Low Level Sewer No.1
at the Chelsea Embankment Foreshore and Victoria Embankment Foreshore sites, control the flow from ten other CSOs along the embankment that would have otherwise required direct interception by making a connection to the northern Low Level Sewer No.1
c. accommodate two vortex drops (one for the interception of the Fleet Main CSO and one for the connection to the Low Level Sewer No. 1) and a de-aeration chamber
d. provide air management and ventilation facilities e. provide a replacement pier f. provide access for operation and maintenance (including vehicular
access to the main tunnel) g. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 21.1.4 Drawings of the site are provided in Section 19 of the Book of Plans.
21.2 Structures 21.2.1 The principal structures would comprise:
a. an interception chamber, valve chamber and connection culvert to divert the flow from the existing CSO into the drop shaft
b. an overflow weir chamber, valve chamber and connection culvert to divert the flow from the existing Low Level Sewer No.1 into the CSO drop shaft
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21 Blackfriars Bridge Foreshore
c. a drop shaft on the line of the main tunnel d. a new CSO outfall e. ventilation structures including below-ground air treatment chamber
and above-ground ventilation columns f. two electrical and control kiosks g. a foreshore structure accommodating the majority of these structures.
Size 21.2.2 The sizes of the Fleet interception chamber and the northern Low Level
Sewer No.1 overflow weir chamber are determined by the depth of the existing CSO and sewer and the design flow rates that are to be intercepted (46 m3/s and 15 m3/s respectively, see Table 3.2). Hydraulic modelling was undertaken to determine the size of the interception works.
21.2.3 The size and depth of the connection culverts is dictated by the design flow rates and the depths of the interception chamber and overflow weir chamber.
21.2.4 The drop shaft would have an approximate internal diameter of 24m and be approximately 53m deep from top of cover slab to invert of the connection tunnel.
21.2.5 The internal diameter of the drop shaft is dictated by the need to have two vortex drop tubes, the requirements for de-aeration of the flow accounting for the fact that the main tunnel runs through the bottom of the shaft and the requirements for access.
21.2.6 The external diameter of the drop shaft is dictated by the construction method which is anticipated to be a primary diaphragm wall with a secondary concrete lining. The drop shaft would be predominately excavated in London Clay ground conditions, but the base of the shaft would extend into the Lambeth Group and Thanet Sands. The depth of the shaft is determined by the depth of the main tunnel at this point.
21.2.7 The five ventilation columns serving the drop shaft would have an approximate internal diameter of 1.2m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
21.2.8 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing five columns is considered preferable to providing more smaller diameter columns - refer to the Design and Access Statement Section 18 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
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21 Blackfriars Bridge Foreshore 21.2.9 The ventilation column serving the Fleet interception chamber would have
an approximate internal diameter of 0.7m and be approximately 4m minimum to 8m maximum high.
21.2.10 The ventilation column serving the overflow weir chamber would have an approximate internal diameter of 0.3m and be approximately 6m high.
21.2.11 The height of the smaller diameter ventilation columns is consistent with Thames Water standards (see para. 3.11.7).
21.2.12 The sizes of the below-ground ventilation structures and air treatment chamber are dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
21.2.13 The size of the electrical and control kiosks is determined by the equipment they would house. Two kiosks are required because one controls equipment located within the interception structures located towards the east of the foreshore structure and the other controls equipment within the shaft towards the west of the foreshore structure.
21.2.14 The size of the foreshore structure is dictated by the size of the drop shaft, hydraulic chambers, ventilation and air treatment chambers, and the ship impact protection zone. The size also needs to reflect safe operational access requirements.
Layout 21.2.15 The location of the interception chamber is dictated by the location of the
existing sewer, which discharges underneath Blackfriars Bridge. 21.2.16 The location of the overflow weir chamber on the northern Low Level
Sewer No.1 would minimise the extent of utilities to be diverted and minimises impact on the road network.
21.2.17 The position of the drop shaft balances the need to minimise the encroachment of the foreshore structure into the river (for navigational safety and ecological reasons), would provide sufficient separation from the Waterloo and City Line tunnels and enable the tunnel to pass mid-span underneath Blackfriars road and rail bridges.
21.2.18 The ventilation structure and air treatment chamber would be situated underground in order to minimise the number of above-ground structures. However, they would be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
21.2.19 The ventilation columns serving the drop shaft would be located adjacent to the shaft to minimise the size of below-ground ventilation structures and to be clear of the entrance to the public space.
21.2.20 The ventilation column serving the interception chambers would be located near the chambers and clear of nearby trees.
21.2.21 One electrical and control kiosk would be located underneath the ‘undercroft’ area formed by the Blackfriars Bridge westbound off-ramp. This would allow the kiosk to be close enough to the equipment that it is controlling in the interception structures while keeping the public realm free of clutter.
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21 Blackfriars Bridge Foreshore 21.2.22 The second electrical and control kiosk would be located adjacent to the
drop shaft, marking the break in the existing river wall parapet while keeping close enough to the equipment that it is controlling within the drop shaft.
21.2.23 Refer to the Design and Access Statement Section 18 for more information on architectural considerations.
21.3 Limits and zones
Temporary works 21.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within two separate LLAU boundaries. 21.3.2 The primary area includes:
a. The main work site to the west of, and underneath, Blackfriars Road bridge, including: i Part of the River Thames for construction of the permanent works
and barge loading. ii The Chrysanthemum Pier and the President moorings to allow the
President to be temporary relocated during construction. iii The Blackfriars Millennium Pier as the pier needs to be relocated
to allow the construction of the permanent works. iv The old Blackfriars Pump House on Blackfriars Millennium Pier,
which would need to be demolished to allow construction of the permanent works.
v The Blackfriars Bridge westbound off-ramp, as the low level sewer, to which a connection would be made, lies beneath the ramp.
vi Part of the Victoria Embankment to allow access to the site. vii a specialist sports facility underneath the Blackfriars Bridge
westbound off-ramp b. The secondary area is Blackfriars Pier site for relocation of the
Blackfriars Millennium Pier and includes: i Part of the River Thames to construct the relocated pier ii Part of Paul’s Walk to construct the access to the relocated pier.
21.3.3 The primary LLAU covers an area of approximately 30,500m2, the assumed hoarded land area would be approximately 1,700m2 and the assumed cofferdam area would be approximately 10,200m2 (based on the illustrative Construction phases – phase one drawing).The secondary LLAU covers an area of approximately 8,300m2 for the relocation Blackfriars Millennium Pier.
21.3.4 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in London Clay/Lambeth
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21 Blackfriars Bridge Foreshore
Group/Thanet Sand Formation, the site size may need to range from approximately 1,500m2 to 5,000m2.
21.3.5 The assumed hoarded and cofferdam area of the Blackfriars Bridge Foreshore site contains areas for the permanent works, construction offices and welfare buildings, material handling and storage, site power, steel reinforcement preparation area and site roads. It is greater than the expected site size range because it would have a large diameter shaft constructed by diaphragm walling. The scale of the permanent works reflects the scale of the flows that would be controlled and the fact that a connection needs to be made to both the northern Low Level Sewer No1 and the Fleet Main CSO. The LLAU area includes the assumed hoarded and cofferdam areas and part of the river needed to facilitate construction of the temporary cofferdam and scour protection, permanent foreshore structure and replacement moorings. In addition the LLAU includes part of the road to allow access to the site and construction of the connection to the Low Level sewer.
Permanent works 21.3.6 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is positioned on the foreshore structure. The zone provides a small degree of flexibility for the drop shaft to move a short distance as the design is developed.
21.3.7 The zone within which all the permanent site structures would be located (denoted by the western green line on the Site works parameter plan) mainly consists of the foreshore for the foreshore structure, scour protection and outfall apron. The area also includes where the President could be located, and part of Blackfriars Bridge. The zone allows a small degree of flexibility on the location of the structures as the design develops.
21.3.8 The zone within which the Blackfriars Millennium Pier would be relocated (denoted by the eastern green line on the Site works parameter plan) constrains the location of the pontoon relative to the authorised navigation channel, but allows some flexibility for the pontoon to move east or north as the design develops.
21.3.9 The three zones within which permanent above-ground structures may be located (denoted by the purple lines on the Site works parameter plan) have been delineated both to maximise public space while respecting the setting of the existing structures.
21.3.10 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) includes the foreshore structure to provide landscaping to the new area of public realm and a section to the east of Blackfriars Rail Bridge in order to mitigate the works to relocate Blackfriars Millennium Pier.
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21 Blackfriars Bridge Foreshore
21.4 Access 21.4.1 The works in the foreshore would be accessed from Victoria Embankment
via a new mountable kerb and strengthened footway across the Thames Path.
21.4.2 An area of permanent hardstanding would be provided for access purposes. This area would surround the permanent infrastructure.
21.4.3 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) would be buried.
21.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
21.4.5 The ten yearly inspection would involve temporarily removing paving slabs and other landscaping to expose and open any buried access covers.
21.4.6 Vehicles would be used with the ten-yearly inspections of the main tunnel. These vehicles would enter the tunnel via a large access opening in the on-line drop shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
Engineering design statement 174
22 Shad Thames Pumping Station
22 Shad Thames Pumping Station
22.1 Introduction 22.1.1 Shad Thames Pumping Station is located in the London Borough of
Southwark and consists of a early 20th century Thames Water operational pumping station, fronting onto Maguire Street. To the rear of the pumping station building is a narrow yard which contains a number of ancillary buildings, including transformers, HV switchgear and a three-storey facilities building. The later formerly accommodated the site superintendent and is located in the northwest corner of the pumping station site.
22.1.2 The proposed site also includes the intersection of Maguire Street with Gainsford Street.
22.1.3 The Shad Thames Pumping Station CSO is located on the foreshore of the River Thames approximately 50m north of the pumping station.
22.1.4 The current vehicular access to the pumping station is via double doors on the Maguire Street frontage of the pumping station building. Pedestrian access is via a gated passage along the northern boundary of the site off Maguire Street The site is bounded to the north by residential Grade II listed Wheat Wharf, to the east by Maguire Street, the Clove Building and Design Museum and to the south by the residential blocks of Tamarind Court and Coriander Court, which are located on opposite sides of Maguire street. The site is bounded to the west by a courtyard car park associated with residential block Vanilla and Sesame Court which is accessed from Gainsford Street. Below this courtyard in the basement is a privately run car park not directly associated with the residential properties, which is accessed from Curlew Street.
22.1.5 The site would be used to modify the existing sewerage network and perform the following functions: a. mobilisation of storage capacity within the Southwark and Bermondsey
Storm Relief Sewer to retain storm water flows and reduce the number of discharges to river
b. return of flow stored in the Southwark and Bermondsey Storm Relief Sewer to the high level sewerage system for transfer to treatment.
22.1.6 Drawings of the site are provided in Section 20 of the Book of Plans.
22.2 Structures 22.2.1 The principal structures would comprise:
a. electrical switchgear and facilities building b. drain-down pumping station within existing pumping station building c. connection chamber and chamber housing sensor
Engineering design statement 175
22 Shad Thames Pumping Station
d. pipework.
Size 22.2.2 The drain-down pumping station wet well would have an internal diameter
of approximately 3.6m and be approximately 15m deep from existing ground level to the invert of the wet well. The lower section of the wet well would be constructed through the existing pumping station basement slab, which is approximately 7m below existing ground level. The upper section of the wet well would be proud of the basement slab.
22.2.3 The internal diameter of the drain-down pumping station wet well is dictated by the size of the pumps and pipework to be accommodated within the structure.
22.2.4 The external diameter of the drain-down pumping station is dictated by the construction method, which for the lower section is anticipated to be either sinking or underpinning precast concrete segmental shaft linings. The pumping station would be predominantly excavated in London Clay ground conditions, although River Terrace Deposits may be encountered immediately below the basement slab. The upper section of the structure, proud of the basement slab, would be surrounded with concrete to achieve water retaining requirements. Below the basement floor slab, excavation would be predominately in London Clay with some sands, gravels. The depth of the wet well is determined by the depth of the existing storm pump sumps.
22.2.5 The electrical switchgear and facilities building is approximately 9.5m high. The size of the electrical switchgear and facilities building is dictated by the size of electrical switchgear and facilities that need to be accommodated within the building.
22.2.6 The ventilation column serving the drain-down pumping station would have an approximate internal diameter of approximately 0.225m and be approximately 9.5m high.
22.2.7 The number and diameter of the ventilation column is dictated by the peak air flow rate.
22.2.8 The size of the connection chamber, the chamber housing the sensor and the diameter of new pipework has been dictated by hydraulic and/or operational requirements.
Layout 22.2.9 The location of the drain-down pumping station is dictated by the layout of
the existing pumping station building and other below-ground structures. The location of the drain-down pumping station within the existing pumping station building would allow the majority of future maintenance can be carried out within an operational Thames Water site.
22.2.10 The electrical switchgear and facilities building would be located at the location of the former facilities building, which would be demolished, in order to keep the building within the existing pumping station site boundary.
Engineering design statement 176
22 Shad Thames Pumping Station 22.2.11 The ventilation column would be located to maximise its distance from
receptors including adjacent residential properties. 22.2.12 The locations of the connection chamber and the chamber housing the
sensor are dictated by the locations of the existing sewers to which they connect and hydraulic requirements.
22.2.13 Pipework in the highway is located to minimise interfaces with existing utilities and associated structures. Pipework in Shad Thames Pumping Station would be located to facilitate connection to pumps and structures as required.
22.2.14 Refer to the Design and Access Statement Section 19 for more information on architectural considerations.
22.3 Limits and zones
Temporary works 22.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. The existing pumping station site for construction of the permanent
works. b. Maguire Street and part of Gainsford Street for construction of the
pipework and chambers in the highway. c. A section of Shad Thames Pumping Station at the junction with
Maguire Street in order to allow highway modifications at its junction with Maguire Street.
d. Part of the Vanilla and Sesame Court car park to the rear of the pumping station site in order to demolish and reinstate the boundary wall.
22.3.2 The LLAU covers approximately 2,300m2 and the assumed hoarded area would be approximately 1,100m2 (based on the illustrative Construction phases – phase one drawing).
22.3.3 The Shad Thames Pumping Station site is a system modification site. As system modifications are not typical, but vary in each case no site size guide was appropriate and therefore none are provided in the Site selection background technical paper.
Permanent works 22.3.4 The zone within which all the permanent site structures would be located
(denoted by the green line on the Site works parameter plan) includes sections of the carriageway and footway along Maguire Street in order to allow the position of the connection chamber, pipework and cabling to be adjusted. The zone also includes a section of Gainsford Street in order to allow the position of the chamber housing the sensor to be adjusted.
22.3.5 The zone within which the permanent above-ground structures for the electrical switchgear and facilities building and ventilation column (denoted
Engineering design statement 177
22 Shad Thames Pumping Station
by one of the purple lines on the Site works parameter plan) allows these structures to be relocated in a north-south direction.
22.4 Access 22.4.1 Access to the electrical switchgear and facilities building would be via the
existing pumping station building, using existing accesses, or via the existing gated pedestrian access from Maguire Street.
22.4.2 Access to the drain-down pumping station would be via a new vehicle access to the existing pumping station building on Maguire Street.
22.4.3 Access to the connection chamber and chamber housing sensor would be via the existing road network. Access covers for these structures would be finished at ground level.
22.4.4 Site visits would be required approximately every one to three months to carry out inspections and maintenance of the drain down pumping station. This frequency is the same as existing. It is likely that this would involve a visit by staff in a small van.
22.4.5 Should a blockage occur, a mobile crane or van would be brought to site to clear the blockage. Should access to the below-ground chambers in Maguire Street and Gainsford Street be required then traffic management, possibly including a temporary road closure, may be required.
Engineering design statement 178
23 Chambers Wharf
23 Chambers Wharf
23.1 Introduction 23.1.1 The proposed development site is located in the London Borough of
Southwark. The site comprises an area cleared for redevelopment that has planning permission for a future residential development; part of the site is also located in the foreshore of the tidal Thames.
23.1.2 The site is bounded to the east by Loftie Street and to the south by Chambers Street, beyond which is a development site where residential properties are proposed.
23.1.3 The nearest residential buildings to the west of the site are Luna House and Axis Court apartment blocks, and the nearest residential buildings to the east of the site are the Fountain Green Square houses.
23.1.4 St. Michael’s Roman Catholic Secondary School is to the south west and Riverside Primary School is to the southeast.
23.1.5 The site would be used as a main tunnel site to perform the following functions: a. drive the main tunnel to Abbey Mills Pumping Station. b. receive the main tunnel from Kirtling Street. c. receive the Greenwich connection tunnel from Greenwich Pumping
Station. d. provide air management and ventilation facilities e. provide access for operation and maintenance(including vehicle
access to the main tunnel) f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 23.1.6 Drawings of the site are provided in Section 21 of the Book of Plans.
23.2 Structures 23.2.1 The principal structures would comprise:
a. a main tunnel shaft b. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns c. an electrical and control kiosk.
Size 23.2.2 The main tunnel shaft would have an approximate internal diameter of
25m and be approximately 58m deep from ground level to invert of the tunnel.
Engineering design statement 179
23 Chambers Wharf 23.2.3 The internal diameter of the main tunnel shaft is primarily dictated by the
working area required to drive the main tunnel TBM to Abbey Mills Pumping Station, receive the Greenwich connection tunnel TBM from Greenwich Pumping Station and receive the main tunnel TBM from Kirtling Street.
23.2.4 The external diameter of the main tunnel shaft is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The main tunnel shaft would be predominantly excavated in the Lambeth Group, Thanet Sands and chalk ground conditions, although the top of the shaft would pass through shallow layers of the River Terrace Deposits and London Clay. The depth of the main tunnel shaft is determined by the depth of the main tunnel at this point.
23.2.5 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
23.2.6 The three ventilation columns serving the main tunnel shaft would have an approximate internal diameter of 1.2m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
23.2.7 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing three columns is considered preferable to providing more smaller diameter columns, refer to the Design and Access Statement Section 20 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
23.2.8 The electrical and control kiosk would be approximately 4m by 2.5m by 2.5m high.
23.2.9 The size of the electrical and control kiosk is dictated by the size of the equipment that it would house and the proposed brown roof on the structure.
Layout 23.2.10 The location of the main tunnel shaft is dictated partly by the hydraulics of
the intersecting tunnels and partly to align the main tunnel away from the footprint of high rise buildings.
23.2.11 The location of the main tunnel shaft has been further refined within the northeast corner of the site to avoid encroaching into the foreshore and to minimise the impact on the future residential development.
23.2.12 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures and is located in an area of hardstanding to facilitate inspection and replacement of the filter media. The location of the chamber has also been selected to fit within the future residential development layout.
Engineering design statement 180
23 Chambers Wharf 23.2.13 The ventilation columns and the electrical and control kiosk would be
located on the periphery of the site in order to minimise any impact on public use of the future residential development open space.
23.2.14 Refer to the Design and Access Statement Section 20 for more information on architectural considerations.
23.3 Limits and zones
Temporary works 23.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within two separate LLAU boundaries. a. The primary area includes:
i An area for construction of the permanent works bounded by Chambers Street, Loftie Street, the land boundary with Luna House and Axis Court and a line extending approximately 60m into the River Thames as measured from the edge of the existing decking.
ii A section of public realm space in Fountain Green Square and a section of public realm space to the north of Luna House, in order to allow construction of the new river wall.
iii Three areas to allow for diversion of existing utilities in the carriageways and footways of Chambers Street, Loftie Street and East Lane.
b. The secondary area in Bevington Street in order to allow the construction of temporary pedestrian crossing.
23.3.2 The primary LLAU covers an area of approximately 28,000m2, the assumed hoarded area would be approximately 10,900m2 and the assumed cofferdam area would be approximately 8,600m2 (based on the illustrative Construction phases – phase one drawing). The secondary LLAU covers an area of approximately 200m2 for highway works.
23.3.3 The Site selection background technical paper Section 4.4 (see the Final Report on Site Selection Process Volume 2) stated that the area of main tunnel drive sites for shafts and tunnel that would constructed in Chalk would be approximately 20,000m2.
23.3.4 The assumed hoarded and cofferdam area of the Chambers Wharf site contains areas for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, a concrete batching plant, storage areas for tunnel lining segments and general use, site power, steel reinforcement preparation area and site roads. It is just under the expected site size range for a single drive site indicating the site is constrained in size so there would be additional constraints on the construction layout, methods and programme. The primary LLAU area includes the assumed hoarded and cofferdam areas, part of the river needed to facilitate construction of the temporary cofferdam and an area for mooring barges which are to be used for transport of materials by river. In addition, this LLAU includes roads adjacent to the site to allow for utility
Engineering design statement 181
23 Chambers Wharf
diversions. The secondary LLAU area includes for highway works associated with provision of a pedestrian crossing.
Permanent works 23.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the main tunnel shaft to allow the main tunnel shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone was delineated to prevent the main tunnel shaft intruding into the foreshore and for the shaft to be located in a position compatible with the proposed residential development.
23.3.6 The zone within which all permanent site structures would be located (denoted by the green line on the Site works parameter plan) extends a short distance into the foreshore in order to allow for the new river wall construction. The zone also includes a section of the decking to the west of the site where a connection to the existing flood defences would be made. The zone extends around the main tunnel shaft to allow for an area of hardstanding to operate and maintain the main tunnel shaft, ventilation structures and electrical and control kiosk. The size of the zone allows the arrangement of the working area and access road to be adjusted.
23.3.7 The zone within which the permanent above-ground structures for the electrical and control kiosk would be located (denoted by one of the purple lines on the Site works parameter plan) allows this structure to be relocated in a north-south direction.
23.3.8 The zone within which the permanent above-ground structures for the ventilation columns serving the main tunnel shaft would be located (denoted by the second purple line on the Site works parameter plan) allows these structures to be relocated to provide some flexibility as the design is developed.
23.4 Access 23.4.1 A new access to the site would be provided from Loftie Street and a new
access road and areas of hardstanding would be provided within the site for maintenance vehicles to access the main tunnel shaft and ventilation structure access covers and the electrical and control kiosk.
23.4.2 Access covers would be finished at ground level. 23.4.3 The three to six monthly, three yearly and ten yearly site visits and major
blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively. 23.4.4 Vehicles would be used with the ten-yearly inspections of the main tunnel.
These vehicles would enter the tunnel via a large access opening in the main tunnel shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
Engineering design statement 182
24 King Edward Memorial Park Foreshore
24 King Edward Memorial Park Foreshore
24.1 Introduction 24.1.1 The proposed development site lies in the Shadwell ward of the London
Borough of Tower Hamlets on the north bank of the River Thames. The site lies in the foreshore of the River Thames and within the southern portion of the King Edward Memorial Park.
24.1.2 The site comprises hard-surfaced areas currently forming part of the Thames Path, a small area of green space and part of the multi-purpose sports pitches to the west. Access to the site would be gained via Glamis Road.
24.1.3 The park is bounded by The Highway to the north, Glamis Road to the west, Shadwell Basin Outdoor Activity Centre and the River Thames to the south, and the residential Free Trade Wharf building to the east.
24.1.4 The North East Storm Relief CSO runs beneath the King Edward Memorial Park in a south-easterly direction and currently discharges into the tidal Thames through the river wall in this location. The CSO point consists of three large openings in the river wall. The Rotherhithe Tunnel passes beneath the King Edward Memorial Park in a north-easterly direction and emerges in Limehouse. The presence of the tunnel is marked by a ventilation building in the southern portion of the park, close to the River Thames wall.
24.1.5 The King Edward Memorial Park itself is a well-maintained recreational area, comprising large grassed areas with pedestrian paths, mature trees, a multipurpose sports pitch, a bowling green, a children’s play area, a bandstand and large paved seating areas facing onto the River Thames and near the memorial, alongside The Highway. The eastern part of the park, closest to Free Trade Wharf building, is locally designated as a wildlife area and is planted as a wildflower meadow.
24.1.6 During park opening hours, the Thames Path runs from Glamis Road in the west, through a narrow alleyway, into the park and past the Rotherhithe Tunnel ventilation building, along the river frontage, and exits the park in front of Free Trade Wharf building in the east. There is an alternative Thames Path available which runs up Glamis Road and along The Highway.
24.1.7 The site would be used as a CSO site to perform the following functions: a. Intercept flow from the North East Storm Relief CSO b. accommodate a vortex drop and de-aeration chamber c. provide air management and ventilation facilities d. provide access for operation and maintenance e. provide emergency egress from the tunnel and drop shaft during
maintenance operations 24.1.8 Drawings of the site are provided in Section 25 of the Book of Plans.
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24 King Edward Memorial Park Foreshore
24.2 Structures 24.2.1 The principal structures would comprise:
a. an interception chamber b. a valve chamber c. a connection culvert d. a drop shaft on the line of the main tunnel e. a storm overflow chamber f. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns g. an electrical and control kiosk h. a foreshore structure accommodating the majority of these structures.
Size 24.2.2 The size of the interception chamber is dictated partly by the size and
depth of the North East Storm Relief CSO and partly by the design flow rate to be intercepted (30 m3/s, see Table 3.2). Hydraulic modelling was undertaken to estimate the chamber size.
24.2.3 The sizes of the valve chamber and connection culvert are dictated by the design flow rate and the depth of the structures by the depth of the North East Storm Relief CSO and by the geometry of the vortex generator.
24.2.4 The drop shaft would have an approximate internal diameter of 20m and be approximately 60m deep from ground level to invert of the tunnel.
24.2.5 The internal diameter of the drop shaft is dictated partly by the size of the main tunnel (approximately 7.2m internal diameter), which would pass through it, and partly by the plan area required in the drop shaft base for de-aeration of the flows descending from the connection culvert through the vortex drop.
24.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The drop shaft would be predominantly excavated in the Lambeth Group, Thanet Sands and Chalk ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel at this point.
24.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
24.2.8 The two ventilation columns serving the drop shaft would have an approximate internal diameter of 1.2m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
24.2.9 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing
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24 King Edward Memorial Park Foreshore
two columns is considered preferable to providing more smaller diameter columns, refer to the Design and Access Statement Section 21 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
24.2.10 The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
24.2.11 The height of the small diameter ventilation column is consistent with Thames Water standards (see para. 3.11.7).
24.2.12 Changes in air pressure cause by rising / falling water level in the valve chamber and outfall chamber would be relieved by ventilation at ground level.
24.2.13 The electrical and control kiosk would be approximately 6.5m by 3m by 3m high.
24.2.14 The size of the electrical and control kiosk is dictated by the size of the equipment that it would house and architectural finishes to the kiosk.
24.2.15 The size of the foreshore structure is dictated by the size of the drop shaft, hydraulic chambers, ventilation and air treatment chambers, and the ship impact protection zone. The size also needs to reflect safe operational access requirements.
Layout 24.2.16 The location of the interception chamber is dictated by the location of the
existing North East Storm Relief Sewer, which discharges through the river wall at the eastern side of the site.
24.2.17 The drop shaft would be located within the foreshore as far away from the Rotherhithe Tunnel as possible. The drop shaft would also be located between the Cole Stairs CSO to the west of the drop shaft and the Bell Wharf CSO to the east of the drop shaft.
24.2.18 There must be sufficient space between the drop shaft and the interception chamber to accommodate the valve chamber and the minimum length of connection culvert required to provide a stable approach flow to the vortex generator located at the top of the drop shaft.
24.2.19 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures, however it must be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
24.2.20 The electrical and control kiosk would be located on the periphery of the site in order to minimise any impact on public use of the open space. The ventilation columns would be located in the foreshore area of the site for architectural reasons and close to the drop shaft and interception chamber in order to minimise the number of below-ground chambers and ventilation ducts required.
Engineering design statement 185
24 King Edward Memorial Park Foreshore 24.2.21 Refer to the Design and Access Statement Section 21 for more
information on architectural considerations.
24.3 Limits and zones
Temporary works 24.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. An area bounded by Free Trade Wharf, the Rotherhithe Tunnel
ventilation structure, a line extending approximately 66m into the River Thames and a line extending approximately 22m into King Edward Memorial Park both as measured from the line of the existing river wall for construction of the permanent works.
b. An area at the western side of King Edward Memorial Park in order to allow an access for construction vehicles from Glamis Road to the park.
c. An area at the western side of King Edward Memorial Park to allow reconfiguration of the existing sports pitch and relocation of the existing children’s playground (these areas are only within the LLAU for the provision of these facilities and are not for use by the contractor).
d. An area along the southern side of King Edward Memorial Park in order to allow an access road for construction vehicles from Glamis Road to the primary construction area.
e. Part of the carriageway and footways of Glamis Road and the junction of Glamis Road with The Highway in order to allow sufficient area for the diversion of existing utilities and utility connections.
24.3.2 The LLAU covers an area of approximately 20,100m2, the assumed hoarded land area would be approximately 3,700m2 and the assumed cofferdam area would be approximately 4,300m2 (based on the illustrative Construction phases – phase one drawing).
24.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed in Chalk, the site size may need to range from approximately 1,500m2 to 7,500m2.
24.3.4 The assumed hoarded and cofferdam area of the King Edward Memorial Park Foreshore site contains areas for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, a storage area, site power, steel reinforcement preparation area and site roads. It is greater than the upper end of the expected site size range because it would have a large diameter shaft constructed in chalk by diaphragm walling and includes an access road as the site in not adjacent to a highway. The LLAU area includes the assumed hoarded and cofferdam area and part of the river needed to facilitate construction of the temporary cofferdam, campshed and permanent foreshore structure. The campshed would occupy an area of approximately 1100m2 in the river
Engineering design statement 186
24 King Edward Memorial Park Foreshore
foreshore and would be used for transport of materials by river. In addition the area within the LLAU allows for the temporary diversion of the Thames Path, relocation of the children’s playground, reconfiguration of the multipurpose sports pitch and highway and utilities works in Glamis Road/The Highway.
Permanent works 24.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the drop shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone was delineated to prevent the drop shaft intruding into the existing river wall or the permanent river wall.
24.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) would include the permanent access road and would allow for the adjustment of the access road alignment in a north-south direction. The western side of the zone extends into the carriageway of Glamis Road where a permanent access from Glamis Road would be required. The zone would also include the foreshore structure, scour protection and outfall apron. The zone would also include a section of the land in the park, to allow for the relocation of below-ground structures if necessary. The eastern side of the zone includes an area around the electrical and control kiosk to allow for hardstanding and vehicle access to the electrical and control kiosk.
24.3.7 The zone within which the permanent above-ground structures for the electrical and control kiosk would be located (denoted by one of the purple lines on the Site works parameter plan) allows the location of this structure to be adjusted if necessary.
24.3.8 The zone within which the permanent above-ground structures for the ventilation columns serving the drop shaft would be located (denoted by the second purple line on the Site works parameter plan) allows these structures to be relocated within the western area of the site.
24.3.9 The zone within which the above-ground structures for the ventilation column serving the interception chamber would be located (denoted by the third purple line on the Site works parameter plan) allows this structure to be relocated within the eastern area of the site.
24.3.10 The zone within which the above-ground structures for the local control pillar would be located (denoted by the forth purple line on the Site works parameter plan) allows this structure to be relocated in an east-west direction.
24.3.11 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) includes the new foreshore structure in order to allow landscaping of the new area of public realm and an area of the park to the north of the foreshore in order to integrate the landscaping with the existing park. The zone also extends to the entrance on Glamis Road in order to allow for the construction of the permanent access route and reconfigured Thames Path, which need to be integrated with the existing park. The zone also includes an area for
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24 King Edward Memorial Park Foreshore
relocation of the children’s playground and reconfiguration of the multi-purpose sports pitch prior to the commencement of construction.
24.4 Access 24.4.1 A new access to the site would be provided from Glamis Road and a new
access road and areas of hardstanding would be provided within the site for maintenance vehicles to access the main tunnel shaft and ventilation structure access covers and the electrical and control kiosk.
24.4.2 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) would be buried.
24.4.3 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
24.4.4 The ten yearly inspection would involve temporarily removing turf and other landscaping to expose and open any buried access covers.
24.4.5 Vehicles would be used with the ten-yearly inspections of the main tunnel. These vehicles would enter the tunnel via a large access opening in the on-line drop shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
Engineering design statement 188
25 Earl Pumping Station
25 Earl Pumping Station
25.1 Introduction 25.1.1 The proposed development site is located in the London Borough of
Lewisham and is also next to the London Borough of Southwark to the north and west. It comprises the operational Thames Water Earl Pumping Station and adjacent industrial land.
25.1.2 The site is bounded to the north by Chilton Grove, to the east by Yeoman Street and to the west by Croft Street. Occupied commercial/industrial units and a row of two-storey terraced houses with gardens lie adjacent to the southern site boundary and the first dwelling in the terrace sits adjacent to the site boundary. Immediately west of the site on Croft Street is a five-storey block of flats and a large industrial unit. The surrounding area is predominantly industrial to the south and east, and there is housing to the west and north.
25.1.3 The site would be used as a CSO site to perform the following functions: a. Intercept gravity flow from the Earl Pumping Station CSO b. accommodate a vortex drop and de-aeration chamber c. provide air management and ventilation facilities d. provide access for operation and maintenance e. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 25.1.4 Drawings of the site are provided in Section 22 of the Book of Plans.
25.2 Structures 25.2.1 The principal structures would comprise:
a. an interception chamber b. a valve chamber c. a connection culvert d. an online drop shaft e. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns f. a pump sump and associated pipework to drain the existing storm
pumping station wet well after storms g. electrical and control equipment within the existing pumping station
buildings.
Size 25.2.2 The plan size of the interception chamber is limited by the space between
the existing storm and dry weather pumping stations, and its depth by the
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25 Earl Pumping Station
depth of the sewer linking them. The size of the chamber is also influenced by the design flow rate to be intercepted (24 m3/s, see Table 3.2). Hydraulic modelling was undertaken to verify the chamber size.
25.2.3 The sizes of the valve chamber and connection culvert are dictated by the design flow rate and the depth of the structures by the depth of the interception chamber.
25.2.4 The drop shaft would have an approximate internal diameter of 17m and be approximately 51m deep from ground level to invert of the tunnel. As the ground level at the site is low, the cover slab of the drop shaft is approximately 3m above ground level to meet hydraulic requirements.
25.2.5 The internal diameter of the drop shaft is dictated partly by the size of the Greenwich connection tunnel (approximately 5m internal diameter), which would pass through it, and partly by the plan area required in the shaft base for de-aeration of the flows descending from the connection culvert through the vortex drop.
25.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The drop shaft would be excavated in River Terrace Deposits, the Lambeth Group, Thanet Sands and, predominantly, in Chalk ground conditions. The depth of the drop shaft is determined by the depth of the Greenwich connection tunnel at this point.
25.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
25.2.8 The ventilation column serving the drop shaft would be approximately 4.8m minimum to 8m maximum high.
25.2.9 The number and diameter of the ventilation columns are dictated by the peak air flow rate. The minimum height of the ventilation column is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
25.2.10 Air movement in the shaft is also managed by another ventilation structure. At this Thames Water site this structure has been located on top of the shaft to simplify the arrangement. The plan areas and heights of this structure above ground level are approximately: a. 4m by 4m by 5m high minimum and 6m by 8m by 7m high maximum
25.2.11 The minimum and maximum dimensions of the ventilation structure allows for design development and flexibility in air damper arrangement.
25.2.12 The two ventilation columns serving the interception and valve chambers would each have an approximate internal diameter of 0.225m and be approximately 6m high.
25.2.13 The height of the smaller diameter ventilation column is consistent with Thames Water standards (see para. 3.11.7).
25.2.14 The electrical and control panel would be installed in the existing storm pumping station building.
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Layout 25.2.15 The location of the interception chamber is dictated by the need to
intercept flows between the existing dry weather and storm pumping stations.
25.2.16 The drop shaft would be located to the south of the existing pumping station site because there is not sufficient space for it within the existing pumping station site boundary. The shaft would be located as far as possible away from the existing houses to the south on the eastern side of Croft Street.
25.2.17 The valve chamber and connection culvert positions are dictated by the locations of the interception chamber and drop shaft. The valve chamber would be located to provide the minimum length of connection culvert required to provide a stable approach flow to the vortex generator located at the top of the drop shaft.
25.2.18 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures, and due to lack of space would be located over the connection culvert. The air extract from the drop shaft would need to be above ground to prevent risk of flooding from the drop shaft via the air ducts, and has been incorporated into the northern end of the shaft superstructure to achieve a compact and aesthetically pleasing architectural solution.
25.2.19 The ventilation column serving the drop shaft would be attached to the valve chamber to enable a compact arrangement suitable for the limited size of the existing site and to minimise the additional land required. The ventilation columns for the interception chamber would be located against the existing storm pumping station for similar reasons. The electrical and control panels would be located inside the existing storm pumping station.
25.2.20 Refer to the Design and Access Statement Section 22 for more information on architectural considerations.
25.3 Limits and zones
Temporary works 25.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. The existing pumping station site plus as an area to the south currently
occupied by industrial premises for construction of the permanent works.
b. Part of Croft Street to allow diversion of the Earl Sewer around the drop shaft position, because the drop shaft is tight against the back of the Croft Street footway. Also, minor highway works are required in Croft Street, including temporary removal of traffic calming measures.
c. Part of Chilton Grove to allow safe construction of the pump sump for suction culvert draw down, and temporary removal of traffic calming measures.
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25 Earl Pumping Station
d. Part of Yeoman Street to provide space for traffic marshalling. This would be required because there is insufficient space with the site off-highway for holding vehicles.
25.3.2 The LLAU covers an area of approximately 6,000m2 and the assumed hoarded area would be approximately 3,500m2 (based on the illustrative Construction phases – phase one drawing).
25.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed Chalk, the site size may need to range from approximately 1,500m2 to 7,500m2.
25.3.4 The assumed hoarded area of the Earl Pumping Station site contains areas for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, a storage area, site power, steel reinforcement preparation area and site roads. It is in the lower end of the expected site size range, partly within the existing Thames Water operational pumping station site and is constrained in size so there would be additional constraints on the construction layout, methods and programme. The LLAU includes the assumed hoarded and areas and parts of the roads around the site to allow for highway and utilities works.
Permanent works 25.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone was delineated to prevent the drop shaft intruding into Croft Street.
25.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by existing buildings and structures within the existing pumping station site, and encompasses most of the western half of the construction site south of the existing pumping station site. This latter area provides space for the diversion of an existing sewer around the drop shaft, leaves space for a future access road between the site structures and the residential properties to the south, and releases the eastern part of the construction site south of the existing pumping station site for redevelopment.
25.3.7 There are three zones within which the permanent above-ground structures would be located (denoted by one of the purple lines on the Site works parameter plan). The zone for the shaft superstructure and ventilation structure allows for any variation in the shaft location and slight changes to the overall superstructure size or shape, and is constrained on the west side by Croft Street. The zone for the interception and valve chamber is constrained on the west side by the existing dry weather pumping station and on the east by the need to maintain vehicular access between the interception and valve chambers and the existing storm pumping station. The zone for the interception chamber ventilation columns allows for variation in their position whilst avoiding obstruction into or passed the existing storm pumping station.
Engineering design statement 192
25 Earl Pumping Station 25.3.8 The zone within which required landscaping would be located (denoted by
the orange hatched area on the Site works parameter plan) includes the roof of the above ground shaft superstructure, in order to mitigate the impact of the structure and the area immediately around the shaft that will be required for access.
25.4 Access 25.4.1 The two existing entrances into Earl Pumping Station, from Chilton Grove
and Yeoman Street, would be retained and supplemented by a new access from Croft Street south of the drop shaft.
25.4.2 The primary fence line would be that of the existing pumping station site, with the drop shaft superstructure extending outside it to the south. A new gateway would be provided in the southern fence, just east of the drop shaft, for access to the drop shaft from the pumping station.
25.4.3 Prior to redevelopment of the south-eastern part of the construction site, a temporary fence would be provided to separate the retained south-western part of the site from the development site. Temporary gates would be provided between the shaft superstructure and the southern temporary fence to restrict access from Croft Street to the area ‘behind’ the drop shaft. The area south and east of the drop shaft superstructure could be open to public access after redevelopment of the south-eastern part of the site, depending on the design of the redevelopment.
25.4.4 The stairs to the drop shaft superstructure roof would be accessed from within the pumping station fence for security and ease of access for maintenance personnel.
25.4.5 Since the drop shaft, valve chamber and part of the interception chamber roofs would be above-ground level and thus inaccessible to vehicles, lightweight access covers are proposed for these areas. All other access covers would be at ground level.
25.4.6 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
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26 Deptford Church Street
26 Deptford Church Street
26.1 Introduction 26.1.1 The proposed development site is located in the London Borough of
Lewisham, and is close to the London Borough of Greenwich to the north and east. The site comprises an area of public open space with a number of mature trees and highway.
26.1.2 The site is triangular in shape, bounded to the north by Coffey Street and the Grade I Listed St Paul’s Church, to the east by Deptford Church Street (A2209) – beyond which is the Sue Godfrey Nature Reserve – and to the southwest by Crossfield Street and St Joseph’s Roman Catholic Primary School.
26.1.3 The nearest residential buildings are the five-storey Congers House and Farrer House, which lie approximately 50m to the east. The nearest residential buildings to the west of the site are the three-storey properties that front Deptford High Street.
26.1.4 The site would be used as a CSO site with the drop shaft constructed on the line of the Greenwich connection tunnel. This site would not be used to drive a tunnel. It would perform the following functions: a. control the flow of the Deptford Storm Relief CSO by intercepting flows
in the Deptford Storm Overflow sewer b. accommodate a vortex drop and de-aeration chamber c. provide air management and ventilation facilities d. provide access for operation and maintenance e. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 26.1.5 Drawings of the site are provided in Section 23 of the Book of Plans.
26.2 Structures 26.2.1 The principal structures would comprise:
a. an interception chamber incorporating a flow diversion structure and a valve chamber
b. a connection culvert c. an online drop shaft d. ventilation structures including a below-ground air treatment chamber
and above-ground ventilation columns e. an electrical and control kiosk.
Size 26.2.2 The size of the interception chamber is dictated partly by the size and
depth of the Deptford Storm Overflow sewer and partly by the design flow
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rate to be intercepted (29 m3/s, see Table 3.2). Hydraulic modelling was undertaken to estimate the chamber size.
26.2.3 The sizes of the valve chamber and connection culvert are dictated by the design flow rate and the depth of the structures by the depth of the Deptford Storm Overflow sewer.
26.2.4 The drop shaft would have an approximate internal diameter of 17m and be approximately 48m deep from ground level to invert of the tunnel.
26.2.5 The internal diameter of the drop shaft is dictated partly by the size of the Greenwich connection tunnel (approximately 5m internal diameter), which would pass through it, and partly by the plan area required in the shaft base for de-aeration of the flows descending from the connection culvert through the vortex drop.
26.2.6 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The drop shaft would be predominantly excavated in Thanet Sands and chalk ground conditions although the top of the shaft would pass through shallow layers of the River Terrace Deposits and the Lambeth Group. The depth of the drop shaft is determined by the depth of the Greenwich connection tunnel at this point.
26.2.7 The size of the air treatment chamber is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling.
26.2.8 The four ventilation columns serving the drop shaft would have an approximate internal diameter of 1.2m and be approximately 4m minimum to 8m maximum high. These ventilation columns would be of the project’s ‘signature’ design.
26.2.9 The total cross-sectional area of the signature ventilation columns is dictated by the peak air flow rate. The number and diameter of the ventilation columns are dictated by aesthetic considerations (i.e. providing four columns is considered preferable to providing more smaller diameter columns, refer to the Design and Access Statement Section 18 for more details). The minimum height of the ventilation columns is designed to meet EA guidance criteria for odour dispersion and to comply with the Dangerous Substances and Explosive Atmospheres Directive (DSEAR). The maximum height is influenced by the aesthetic proportions of the columns.
26.2.10 The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high.
26.2.11 The height of the smaller diameter ventilation column is consistent with Thames Water standards (see para. 3.11.7).
26.2.12 The electrical and control kiosk would be approximately 5.9m by 2.3m by 6m high minimum and 8m by 5m by 3m high maximum.
26.2.13 The minimum size of the electrical and control kiosk is dictated by: the size of the equipment that it would house. The maximum would match the width of buffer tree planting designed to form a solid screen between Deptford Church Street and the green area; a size to accommodate an
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information board and to provide support for a beam and trellis screen structure.
Layout 26.2.14 The location of the interception chamber is dictated by the location of the
existing sewer, which lies under the western carriageway of Deptford Church Street.
26.2.15 The drop shaft would be located as far as possible from the nearby Grade I Listed St Paul’s Church and St Joseph’s Roman Catholic Primary School while ensuring adequate access around the drop shaft during construction.
26.2.16 There must be sufficient space between the drop shaft and the interception chamber to accommodate the valve chamber and the minimum length of connection culvert required to provide a stable approach flow to the vortex generator located at the top of the drop shaft.
26.2.17 The air treatment chamber would be situated underground in order to minimise the number of above-ground structures, however it must be located beneath an area of hardstanding to facilitate inspection and replacement of filter media.
26.2.18 The ventilation columns and the electrical and control kiosk would be located on the periphery of the site in order to minimise any impact on public use of the open space.
26.2.19 Refer to the Design and Access Statement Section 23 for more information on architectural considerations.
26.3 Limits and zones
Temporary works 26.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within five separate LLAU boundaries. a. The primary area includes:
i An area bounded by Deptford Church Street, Crossfield Street and Coffey Street for construction of the permanent works.
ii Part of the western carriageway of Deptford Church Street because the existing sewer to be intercepted lies under this road. The eastern carriageway would be made two-way during the construction of the interception chamber, and an existing pedestrian crossing would be temporarily relocated during the works.
iii The eastern part of Crossfield Street would be modified for use as one-way traffic and the western part would be re-opened for one-way traffic.
iv Part of Coffey Street because it would be modified for use as one-way traffic.
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26 Deptford Church Street
v An area westwards to provide a fire assembly point for St Joseph’s Roman Catholic Primary School close to the school grounds.
vi Part of the open space northwest of the junction of Coffey Street and Deptford High Street to provide a secondary fire assembly point for St Joseph’s Roman Catholic Primary School.
b. Four secondary areas in Deptford Church Street would allow bus-stops to be temporarily relocated.
26.3.2 The primary LLAU covers an area of approximately 11,800m2 and the assumed hoarded area would be approximately 4,200m2 (based on the illustrative Construction phases – phase one drawing). The four secondary LLAUs cover a total area of approximately 700m2 for highway works.
26.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2) stated that for CSO sites, where drop shafts need to be constructed Chalk, the site size may need to range from approximately 1,500m2 to 7,500m2.
26.3.4 The assumed hoarded area of the Deptford Church Street site contains areas for the permanent works, construction offices and welfare buildings, material handling and storage, a storage area, site power, steel reinforcement preparation area and site roads. It is in the middle of the expected site size range but is space constrained because it has a shaft constructed by diaphragm walling. This indicates the site is constrained in size so there would be additional constraints on the construction layout, methods and programme. The primary LLAU includes the assumed hoarded area and roads around the site to allow for highway works that include the temporary relocation of a pedestrian crossing, provision of temporary school evacuation areas and traffic management in Deptford Church Street involving temporary closure of two traffic lanes. There are four smaller LLAU areas for the provision of temporary replacement bus stops.
Permanent works 26.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed. The zone was delineated to prevent the drop shaft intruding into Crossfield Street or the connection tunnel getting too close to the Grade I Listed St Paul’s Church.
26.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by Crossfield Street to the south and by Coffey Street to the north. On both sides, the zone includes sections of the footway (pavement) where works would be required. The eastern side of the zone extends to the central reservation of Deptford Church Street, as the interception chamber would be located in the western carriageway. The zone would allow the location of the interception chamber to be adjusted along the Deptford
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26 Deptford Church Street
Storm Relief Sewer if necessary. The western side of the zone is a short distance west of the proposed location of the ventilation structure.
26.3.7 The zone within which the permanent above-ground structures for the electrical and control kiosk and the ventilation column serving the interception chamber would be located (denoted by one of the purple lines on the Site works parameter plan) allows these structures to be relocated in a north-south direction.
26.3.8 The zone within which the permanent above-ground structures for the ventilation columns serving the drop shaft would be located (denoted by the second purple line on the Site works parameter plan) allows these structures to be relocated along the southern side of the site.
26.3.9 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) is the Crossfield amenity space which is to be re-landscaped for amenity use following completion of the works in order to mitigate the impact of the new structures and areas of hardstanding.
26.4 Access 26.4.1 Two permanent hardstanding areas would be provided for access
purposes. The first would extend from Crossfield Street to Coffey Street west of the drop shaft, and would provide access to the drop shaft and ventilation structure access covers. The second would be in the north eastern corner of the site, accessed via Coffey Street, and would provide access to the interception chamber and valve chamber access covers and to the electrical and control kiosk.
26.4.2 Access covers requiring regular access would be finished at ground level. Access covers requiring infrequent access (typically once every ten years) would be buried.
26.4.3 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
26.4.4 The ten yearly inspection would involve temporarily removing turf and other landscaping to expose and open any buried access covers.
26.4.5 There would be one access cover in the western (north-bound) carriageway of Deptford Church Street. This cover would be accessed once every ten years for major maintenance of the flap valves, and would require a temporary lane closure in Deptford Church Street.
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27 Greenwich Pumping Station
27 Greenwich Pumping Station
27.1 Introduction 27.1.1 Greenwich Pumping Station site comprises the existing Thames Water
operational site and Phoenix Wharf. The site is located in the Royal Borough of Greenwich and is immediately to the west of the London Borough of Lewisham administrative boundary along Deptford Creek.
27.1.2 The character of the site is industrial and consists of four Grade II listed heritage assets, including three buildings associated with the original pumping station and the railway viaduct that crosses the centre of the site.
27.1.3 Norman Road and the former Greenwich Industrial Estate, currently under construction for a mixed use development including residential, hotels and community uses, are located east of the site. A recently completed multi storey residential development forms the southern boundary on Greenwich High Road and a hotel development forms the site’s southwest boundary. Greenwich High Road contains a mix of residential apartment blocks, terrace housing and retail terraces.
27.1.4 Deptford Creek is located to the west of the site and is characterised predominantly by industrial and commercial development, including two and three-storey warehouses ranging from small units to large-scale sheds.
27.1.5 The site would be used as a CSO site to perform the following functions: a. drive the Greenwich connection tunnel to Chambers Wharf (via
Deptford Church Street and Earl Pumping Station) b. intercept gravity flow from the Greenwich Pumping Station CSO c. accommodate a vortex drop and de-aeration chamber d. provide air management and ventilation facilities e. provide access for operation and maintenance (including vehicle
access to the connection tunnel) f. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 27.1.6 Drawings of the site are provided in Section 24 of the Book of Plans.
27.2 Structures 27.2.1 The principal structures would comprise:
a. an interception chamber incorporating a valve chamber b. a connection culvert c. a drop shaft d. a ventilation structure on the roof of the drop shaft
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27 Greenwich Pumping Station
e. renovation of the Grade II Listed East Beam Engine House and installation of ventilation equipment in it.
Size 27.2.2 The size of the interception chamber is dictated largely by the need to
provide sufficient overflow weir length to cater for the design flows (36m3/s, see Table 3.2) and constraints imposed by the available space between existing chambers, sewers and the Grade II Listed East Beam Engine House and Boiler House.
27.2.3 The sizes of the valve chamber and connection culvert are dictated by the design flow rate and the depth of the intercepted sewers.
27.2.4 Hydraulic modelling was undertaken to confirm the adequacy of the chamber sizes.
27.2.5 The drop shaft would have an approximate internal diameter of 17m and be approximately 46m deep from ground level to invert of the tunnel.
27.2.6 The internal diameter of the drop shaft is dictated partly by the size of the Greenwich connection tunnel (approximately 5m internal diameter), which is driven from it, and partly by the plan area required in the shaft base for de-aeration of the flows descending from the connection culvert through the vortex drop.
27.2.7 The external diameter of the drop shaft is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The drop shaft would be predominantly excavated in River Terrace Deposits, the Lambeth Group, Thanet Sands and Chalk ground conditions. The depth of the drop shaft is determined by the depth of the Greenwich connection tunnel at this point.
27.2.8 The capacity of the air treatment equipment is dictated by the peak air flow rate to be treated, which is determined by pneumatic modelling. The number and size of the individual filter units and fans is dictated by the need for all the equipment to pass through the doorway into the Grade II Listed East Beam Engine House, which houses the ventilation equipment.
27.2.9 Air movement in the shaft is also managed by another ventilation structure. At this Thames Water site this structure has been located on top of the shaft to simplify the arrangement. The plan area and heights of this structure above ground level are approximately: a. 4m by 3m and between 3m high minimum and 5m high maximum
27.2.10 The minimum and maximum dimensions of the ventilation structure allow for design development and flexibility in air damper arrangement.
Layout 27.2.11 The location of the drop shaft is dictated by the need for it to be kept
outside the 5m exclusion zone from the edge of the DLR viaduct, be sufficiently far from the East Beam Engine House to avoid unacceptable settlement to this Grade II Listed building, and if possible avoid the East Greenwich Sewer. In practice, there is no shaft location which gives adequate clearance from all three. Since the clearance from the DLR and
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27 Greenwich Pumping Station
avoidance of undue damage to the East Beam Engine House both have statutory force, the shaft has had to be moved over the East Greenwich Sewer and towards the East Greenwich Relief Sewer. This relief sewer is a 1970s tunnel of 1.9m finished internal diameter, and so is considered to be reasonably resistant/ resilient to damage. The shaft location also needs to permit an alignment for the Greenwich long connection tunnel that avoids the DLR viaduct column piled foundations.
27.2.12 In its proposed location, the drop shaft would clash with the brick egg-shaped East Greenwich Sewer, and so this sewer would need to be diverted into the East Greenwich Relief Sewer just west of the shaft. At the proposed diversion location, which is within the Thames Water site, the two sewers are only about 5m apart.
27.2.13 The location of the interception chamber is dictated by the need to intercept the five incoming trunk sewers (Low Level No 1 Main Line, Low Level No 1 Bermondsey Branch, Low Level No 2, East Greenwich Sewer and East Greenwich Relief Sewer) and at a location where the flows can be conveyed to the drop shaft. To meet the latter constraint, the interception chamber needs to be on the north-east side of the conjunction of the sewers, otherwise the connection culvert would have to pass under some of the incoming trunk sewers. Since these sewers are 150 years old, brick and large diameter, such a crossing is undesirable for health and safety and operational risk reasons.
27.2.14 The valve chamber would be integral with the interception chamber to minimise the overall chamber footprint and so fit between the existing sewers and chambers.
27.2.15 Because of the constrained space available for the interception/valve chamber, it would be necessary to demolish the existing auxiliary pump chamber, which has been disused since the beam engines were removed.
27.2.16 To avoid the need for a separate ventilation building, the ventilation equipment would be located in the disused East Beam Engine House. This building is Grade II Listed, and bringing it back into active use is welcomed by conservation interests. Discharge of treated air would be through two existing openings in the building wall at height, and so no new ventilation columns are required. In addition, a ventilation structure would be required on the roof of the drop shaft to house pressure relief dampers.
27.2.17 The electrical and control panels would be located inside the East Beam Engine House, and thus there would be no need for a separate kiosk or building.
27.2.18 Refer to the Design and Access Statement Section 24 for more information on architectural considerations.
27.3 Limits and zones
Temporary works 27.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including:
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27 Greenwich Pumping Station
a. The majority of the existing Thames Water site for construction of the permanent works.
b. Phoenix Wharf to the north, and the intervening land under the DLR and main line railway viaducts which would be used as a construction compound.
c. Part of Norman Road to allow construction of new and modified site entrances off that road.
27.3.2 The LLAU covers an area of approximately 21,400m2 and the assumed hoarded area would be approximately 18,000m2(based on the illustrative Construction phases – phase one drawing).
27.3.3 The Site selection background technical paper Section 3.3 (see the Final Report on Site Selection Process Volume 2 ) stated that for CSO sites, where drop shafts need to be constructed Chalk, the site size may need to range from approximately 1,500m2 to 7,500m2, but that the largest CSO site areas would be those where the drop shaft is large, deep, used as a drive shaft, is constructed using diaphragm wall techniques, and where the connection tunnel is large and is in Chalk so a slurry TBM is required in which case the site area would need to be approximately 12,000m2.
27.3.4 The assumed hoarded areas of the Greenwich Pumping Station site contain part of the existing Thames Water Greenwich Pumping Station and Phoenix Wharf. The site contains areas for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, segment and general storage areas, site power, steel reinforcement preparation area and site roads. It is greater than the expected site size range because part of the site is within a Thames Water operational pumping station site which has an elevated DLR line running across it so construction activities/facilities would be split up with internal site access roads between discrete areas. Phoenix Wharf is separated from the Pumping Station site by a railway viaduct. The LLAU includes the assumed hoarded area, the Thames Water power generator site, the railway viaduct, part of Norman Road which is needed for highway works, and a temporary diversion of a right of way.
Permanent works 27.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the drop shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed.
27.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) is bounded by the existing Thames Water property boundary on the west and north sides, the existing pumping station on the south (but including this building at there will be power and telemetry cables within the building), and on the east side a line within the existing Thames Water boundary which avoids existing trees.
27.3.7 The zone within which the permanent above-ground structures for the drop shaft (denoted by one of the purple lines on the Site works parameter
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27 Greenwich Pumping Station
plan), which has a roof level approximately 1m above ground level, is centred on the drop shaft but reduced on the north side to avoid intruding into the 5m exclusion zone for the DLR viaduct.
27.3.8 The zone within which the permanent above-ground structures for the interception and valve chambers would be located allows these structures to be relocated slightly in any direction.
27.3.9 The zone within which required landscaping would be located (denoted by the orange hatched area on the Site works parameter plan) includes the roof of the shaft in order to mitigate the impact of the structure. The zone also includes land adjacent to the shaft and the northern part of the Thames Water site, in order to allow essential tree planting and to mitigate the impact of the works.
27.4 Access 27.4.1 Hardstanding would be constructed around the drop shaft and
interception/valve chambers, connecting to and partial replacing existing access roads. Access from the highway would be via existing gates. The gate immediately east of the drop shaft would be widened at the start of construction and would be retained permanently in its widened state.
27.4.2 Since the roofs of the drop shaft and the interception/valve chambers would be raised approximately 1m above ground level, access covers into them would be finished flush with the top of the drop shaft/chamber.
27.4.3 Access into the East Beam Engine House would be through the existing doors, which are on the building’s north-west side. An existing but bricked-up personnel doorway near the northern end of the East Beam Engine House, which leads into the office part of the building (the old boiler house), would be re-opened and fitted with a fire-escape door.
27.4.4 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively
.
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28 Abbey Mills Pumping Station
28 Abbey Mills Pumping Station
28.1 Introduction 28.1.1 The proposed development site is located in the London Borough of
Newham. It comprises an area of Thames Water operational land at Abbey Mills Pumping Station. The site lies inland adjacent to the tidal and navigable River Lee.
28.1.2 The site is bounded to the north by operational pumping station infrastructure and buildings and to the east by the Channelsea River, beyond which is an area of disused land and the Channelsea Business Centre on Canning Road. To the southeast of the site is the Channelsea River and Abbey Creek. To the west, the site is bounded by the Prescott Channel and allotments. The surrounding land is predominantly industrial with residential areas to the north of the site. Land to the west of the site, known as Three Mills Islands, comprises a landscaped grassed area and warehouses including Three Mills studio.
28.1.3 The site would be used as a main tunnel reception site to perform the following functions: a. receive the main tunnel from Chambers Wharf b. connect the main tunnel to the Lee Tunnel c. provide air management and ventilation facilities d. provide access for operation and maintenance (including vehicle
access to the main tunnel) e. provide emergency egress from the tunnel and drop shaft during
maintenance operations. 28.1.4 Drawings of the site are provided in Section 27 of the Book of Plans.
28.2 Structures 28.2.1 The principal structures would comprise:
a. a main tunnel shaft b. a short section of 7.2m internal diameter main tunnel between the
shaft and the Lee Tunnel Shaft F (existing by then) c. ventilation structures and column on the shaft roof connected to the
(existing by then) Lee Tunnel air treatment plant d. an electrical and control kiosk
Size 28.2.2 The main tunnel shaft would have an approximate internal diameter of
20m and be approximately 66m deep from ground level to invert of the tunnel.
Engineering design statement 207
28 Abbey Mills Pumping Station 28.2.3 The internal diameter of the shaft is dictated by the size of TBM to be
received. 28.2.4 The external diameter of the drop shaft is dictated by the construction
method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The drop shaft would be predominantly excavated in the Lambeth Group, Thanet Sands and Chalk ground conditions. The depth of the drop shaft is determined by the depth of the main tunnel.
28.2.5 The ventilation column serving the shaft would have an approximate internal diameter of 1m and be approximately 9m high. The diameter of the ventilation column is dictated by the peak air flow rate. The minimum height of the ventilation column is determined by the results of odour dispersion modelling and the maximum height is influenced by the aesthetics proportions of the columns.
28.2.6 Air movement in the shaft is also managed by three other ventilation structures. At this Thames Water site these structures have been located on top of the shaft to simplify the arrangement. The plan areas and heights of these structures are approximately: a. 2m by 2m by 2m high minimum and 4m by 4m by 4m high maximum b. 2m by 3m by 2.5m high minimum and 4m by 5m by 4.5m high
maximum c. 4m by 3m by 2m high minimum and 7m by 6m by 5m high maximum
28.2.7 The minimum and maximum dimensions of the ventilation structures allow for design development and flexibility in air damper arrangement.
28.2.8 The electrical and control kiosk would be approximately 4m by 2m by 3m high. The size of the electrical and control kiosk is dictated by the size of the equipment that it would house.
Layout 28.2.9 The location of the main tunnel shaft is as close as possible to the (by then
existing) Lee Tunnel shaft F whilst minimising risk of settlement or other damage to that shaft.
28.2.10 The ventilation structures and column would be located on the shaft roof to minimise the space requirement.
28.2.11 The electrical and control kiosk would be located nearby on the periphery of the hard standing around the shaft.
28.2.12 Refer to the Design and Access Statement Section 25 for more information on architectural considerations.
28.3 Limits and zones
Temporary works 28.3.1 The LLAU for the required working area to construct the works is within
the existing Thames Water Abbey Mills Pumping Station site, except for an extension across the Prescott Channel at the south-west of the site to
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28 Abbey Mills Pumping Station
allow construction of a temporary footbridge for diversion of a footpath should barging be used.
28.3.2 The LLAU covers an area of approximately 37,300m2 and the assumed hoarded area would be approximately 22,600m2 (based on the illustrative Construction phases – phase one drawing).
28.3.3 The Site selection background technical paper Section 4.6 (see the Final Report on Site Selection Process Volume 2) stated that the area of main tunnel reception sites where shafts are constructed in Chalk would be approximately 7,500m2.
28.3.4 The assumed hoarded area of the Abbey Mills Pumping Station site contains areas for the permanent works, construction offices, welfare and workshop buildings, material handling and storage, a storage area, site power, parking, steel reinforcement preparation area and site roads. It is much higher than the expected site size range because of the long narrow shape of the site, the long access road needed to connect the permanent works with the highway and because there is ample space available within this existing Thames Water land. The LLAU includes the assumed hoarded area, the Lee Tunnel shaft, ventilation structure and kiosk which have an interface with the proposed works, and an area of the Prescott Channel which allows the contractor the option of transporting materials by barge.
Permanent works 28.3.5 The zone within which the shaft would be located (denoted by the blue line
on the Site works parameter plan) is centred over the main tunnel shaft to allow the shaft to be relocated a short distance to provide some flexibility as the design is developed.
28.3.6 The zone within which all the permanent site structures would be located (denoted by the green line on the Site works parameter plan) would allow the location of the structures to be adjusted if necessary due to design development.
28.3.7 The zone within which the permanent above-ground structures for the electrical and control kiosk and ventilation structures would be located (denoted by the purple line on the Site works parameter plan) would allow the location of the structures to be adjusted if necessary due to design development.
28.4 Access 28.4.1 A permanent hardstanding area would be provided around the main tunnel
shaft for access purposes. This would be accessed via access roads within the Thames Water site either existing or constructed for the Lee Tunnel. Access from the public highway would be via an existing entrance off Gay Road.
28.4.2 The three to six monthly, three yearly and ten yearly site visits and major blockage site visits are described is paras. 3.6.6 to 3.6.9 respectively.
Engineering design statement 209
28 Abbey Mills Pumping Station 28.4.3 Vehicles would be used with the ten-yearly inspections of the main tunnel.
These vehicles would enter the tunnel via a large access opening in the main tunnel shaft cover slab. A four-person cradle would enter via a separate access opening in the same cover slab. A further access opening would be provided for CCTV surveys and secondary man access if required.
Engineering design statement 210
29 Beckton Sewage Treatment Works
29 Beckton Sewage Treatment Works
29.1 Introduction 29.1.1 Beckton STW, located in the London Borough of Newham, is the largest
STW in the UK, with substantial areas of plant machinery, tanks and buildings. It is one of the dominant historical land use features of the area.
29.1.2 The proposed site is located in the western and southern part of the operational Beckton STW. The site is surrounded by operational infrastructure associated with the STW and land under development for the STW extension and the Lee Tunnel.
29.1.3 Jenkins Lane waste transfer station, a cinema and retail complex and the A13 (Alfred’s Way) trunk road lie to the north of the STW. The sewage treatment work’s eastern boundary is the tidal confluence of the River Roding (Barking Creek) and the River Thames. East of Barking Creek is a large timber yard and other warehouses. A mixture of business parks and retail parks, vacant land and the River Thames lie to the south of the STW. To the west of the STW is the A1020 (Royal Docks Road) and a mixture of business parks and retail parks beyond. There are residential properties in the vicinity of the site.
29.1.4 The Beckton STW upgrade and Lee Tunnel projects are currently under construction at the STW. To ensure the proposed Thames Tideway Tunnel works co-ordinate with these emerging projects, and any final design amendments associated with them, there are with illustrative design for the proposals at this site.
29.1.5 The site would perform the following functions: a. Provide additional capacity to pump-out the tunnel system when the
Thames Tideway Tunnel system is commissioned. b. Provide a siphon tunnel to facilitate bypass pumping when the tunnel
system becomes full to avoid need to discharge to river at Abbey Mills Pumping Station.
29.1.6 Drawings of the site are provided in Section 28 of the Book of Plans.
29.2 Structures 29.2.1 The principal structures would comprise:
a. a flow transfer pipeline and associated chambers to deliver additional flows from the existing Tideway Pumping Station to the sewage treatment works (STW) inlet works, to supplement an existing one constructed for the Lee Tunnel.
b. A siphon tunnel and inlet and outlet shafts to permit discharge from the Tideway Pumping Station to bypass the STW treatment units and discharge directly to the Tidal Thames (via the Tideway CSO being constructed by the Lee Tunnel project), and connecting pipes and culverts and an electrical and control kiosk.
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29 Beckton Sewage Treatment Works
c. Installation of two additional main pumps in the Tideway Pumping Station, together with associated pipework, and associated electrical equipment in the existing Power System Complex building.
d. Installation of duplicate grit removal gantries at the STW inlet works.
Size 29.2.2 The flow transfer pipeline would be sized for a flow of 7.65m3/s, being half
the maximum discharge from the Tideway Pumping Station. The flow transfer pipeline currently under construction for the Lee Tunnel will take the other half of the flow. The pipeline would be approximately 2.1 to 2.5m internal diameter depending on its detail design.
29.2.3 The siphon tunnel and associated works would be sized to take a flow of 15.25m3/s, being the maximum discharge from the Tideway Pumping Station. The tunnel would be approximately 2.8m internal diameter.
29.2.4 The siphon tunnel inlet shaft is sized for launch of the TBM and would be approximately 9m internal diameter. The siphon tunnel outlet shaft is sized for reception of the TBM and would be approximately 7m internal diameter. The depth of the siphon tunnel (approximately 30m deep to invert) is dictated by the minimum depth required for the tunnel to be in consistent ground over its length and to limit settlement of existing structures above the tunnel to an acceptable level. The tunnel passes though several slip planes of the Greenwich Fault.
29.2.5 The external diameter of the siphon tunnel shafts is dictated by the construction method, which is anticipated to be a primary diaphragm wall with a secondary concrete internal lining. The shafts would be predominantly excavated in made ground Lambeth Group and Thanet Sands, with an additional clay layer at the inlet shaft. The depth of the shafts is determined by the depth of the siphon tunnel.
29.2.6 The connection culvert from the siphon outlet shaft to the (existing by then) Overflow Shaft would be 3.6m wide by 3m high internally, dictated by the design flow rate and the size of the valve chamber. The valve chamber is sized to house the flap valves and penstocks required for the design flow rate.
29.2.7 The chambers/shafts for the flow transfer pipeline and for the siphon tunnel would be connected to adjacent existing chambers and shafts by air bridges and utilise the existing air treatment plant provided for the existing chambers and shafts. The air bridges would be sized for the peak air flow rate, which is during priming of the pipeline/tunnel.
29.2.8 The discharge chamber for the flow transfer pipeline would be approximately 15m x 4m in plan, extending about 2m above ground level and 5m below ground level.
29.2.9 The three duplicate grit removal gantries at the STW inlet works would be each approximately 10m x 4m x 5m high, and similar in design to the existing gantries.
29.2.10 The 17m by 7m by 8m high electrical and control kiosk for the siphon tunnel inlet shaft is sized to accommodate the mechanical, electrical and
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29 Beckton Sewage Treatment Works
control equipment and access facilities associated with the siphon inlet tunnel.
Layout 29.2.11 In order to avoid existing major gas mains and other services, the flow
transfer pipeline would either be buried/ tunnelled (up to 10m deep) or elevated above-ground level, or a combination of the two. The route of the pipeline would be selected to avoid structures both existing and currently under construction.
29.2.12 The flow transfer pipeline discharge chamber would be located on the north side of the Northern Outfall Sewer just upstream (west) of the STW inlet works, and discharge into the five barrels of the Northern Outfall Sewer via buried pipelines. The chamber would need to be close to the Northern Outfall Sewer whilst providing clearance for the chamber’s foundation piles from the Northern Outfall Sewer. The chamber would also need to be close to the Inlet Works.
29.2.13 One end of the siphon tunnel route would need to be close to the (by then existing) flow transfer collection chamber from which it receives flow, and the other end near the existing overflow shaft to which it discharges. The tunnel route would avoid existing and proposed structures with piled and/or deep foundations.
29.2.14 The electrical and control equipment for the two additional Tideway Pumping Station pumps would be housed within the existing Power Supply Complex building and its adjacent compound.
29.2.15 The electrical and control kiosk for the siphon inlet shaft would be located adjacent to the shaft.
29.3 Limits and zones
Temporary works 29.3.1 The LLAU for the required working area to construct the works is entirely
within the Thames Water STW site. It covers both the areas where construction would occur and access roads between the work sites and the public highway.
29.3.2 The LLAU covers approximately 159,100m2 and the assumed hoarded area would be approximately 39,500m2 (based on the illustrative Construction phases – phase one drawing)
29.3.3 Works at and near the STW inlet works and Northern Outfall Sewer would be carried out from the north side of them, to avoid need for work outside existing Thames Water land.
Permanent works 29.3.4 The zone within which the siphon tunnel shafts would be located (denoted
by the blue lines on the Site works parameter plan) is centred over the shafts to allow flexibility to adjust their position as the design is developed, and to accommodate any amendments to works currently under construction by the Lee Tunnel project.
Engineering design statement 213
29 Beckton Sewage Treatment Works 29.3.5 The zone within which all the permanent site structures would be located
(denoted by the green line on the Site works parameter plan) is in two parts. The first is for the flow transfer pipeline and associated chambers, and is sized to accommodate variation of the pipeline route due to design development. The second zone is that for the siphon outlet shaft and its associated valve chamber and connection culvert.
29.3.6 The zone within which the permanent above-ground structures would be located (denoted by the purple lines on the Site works parameter plan) is also in two parts. The first is for the flow transfer pipeline, associated chambers and the electrical and control kiosk for the siphon inlet shaft and is sized to accommodate an above-ground pipeline and variation of the pipeline route due to design development. The second zone is that for the siphon outlet shaft and its associated valve chamber.
29.4 Access 29.4.1 Permanent hardstanding areas would be provided around shafts and
chambers to facilitate maintenance. These would connect to existing hardstanding or access roads within Beckton STW. Access from the public highway would be via the STW entrance off Jenkins Lane.
29.4.2 Inspections of below-ground equipment would be required approximately every three to six months, and would be carried out as part of the maintenance activity for the sewage treatment plant and generally by personnel based at Beckton STW.
29.4.3 Should a major blockage occur, a crane or jetting lorry would be brought to the site to clear the blockage.
29.4.4 It is anticipated that once every ten years, a major internal inspection of the siphon tunnel and shafts would be required. It is likely that this would involve an expert team of inspection staff, a small support crew with support vehicles, and two mobile cranes to lower the inspection team into the shafts. This process would take several days.
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30 Bekesbourne Street
30 Bekesbourne Street
30.1 Introduction 30.1.1 The proposed development site is located in the London Borough of
Tower Hamlets. The site comprises areas of carriageway, footway, parking spaces and a small area of private land and includes a number of trees.
30.1.2 The site is broadly linear and includes a section of the roadway, parking spaces and footway of Bekesbourne Street. A section of the roadway and footway of Ratcliffe Lane at its junction with Bekesbourne Street is also required and a section of private land adjacent to Limehouse DLR station.
30.1.3 The nearest residential buildings are the six storey John Scurr House which adjoins the east boundary of the site on Bekesbourne Street and other two and four storey residential buildings which adjoin the west boundary of the site on Bekesbourne Street.
30.1.4 The site would be used as a system modification site to perform the following functions: a. control the flow of the Holloway Storm Relief CSO by diverting flows in
the Holloway Storm Relief Sewer to the northern Low Level Sewer No.1.
b. provide a penstock and flap valve chamber c. provide ventilation facilities d. provide access for operation and maintenance.
30.1.5 Drawings of the site are provided in Section 26 of the Book of Plans.
30.2 Structures 30.2.1 The principal structures would comprise:
a. a chamber incorporating a penstock and a flap valve. b. an above ground ventilation column. c. an electrical and control kiosk.
Size 30.2.2 The size of the penstock and flap valve chamber is dictated partly by the
size and depth of the Holloway Storm Relief Sewer and partly by the size of the equipment to be installed within the chamber.
30.2.3 The penstock and flap valve chamber would have approximate internal dimensions of 5.0m by 4.6m and be approximately 8m deep from ground level to invert of the chamber.
30.2.4 The external dimensions of the penstock and flap valve chamber are dictated by the construction method, which is anticipated to be either
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30 Bekesbourne Street
secant piling or sheet piling with in-situ reinforced concrete internal walls. The penstock and flap valve chamber would predominantly be excavated in gravels / sands and clay ground conditions. The depth of the penstock and flap valve is determined by the depth of the Holloway Storm Relief Sewer at this point.
30.2.5 The ventilation column serving the interception chamber would have an approximate internal diameter of 0.225m and be approximately 6m high. The number and diameter of the ventilation columns are dictated by the peak air flow rate. The height of the ventilation column is consistent with Thames Water standards (see para. 3.11.7).
30.2.6 The electrical and control kiosk would be approximately 5m by 2m by 2.5m high.
30.2.7 The size of the electrical and control kiosk is dictated by the size of the equipment that it would house and architectural finishes to the kiosk.
Layout 30.2.8 The location of the penstock and flap valve chamber is dictated by the
location of the existing Holloway Storm Relief Sewer, which lies under the carriageway of Bekesbourne Street.
30.2.9 The penstock and flap valve chamber would be located as far as possible from the nearby residential properties while ensuring adequate public vehicle access outside the hoarded working area during construction.
30.2.10 The electrical and control kiosk would need to be located as close as possible to the penstock and flap valve chamber in order to satisfy operational requirements.
30.2.11 The ventilation column would be located in order to maximise its distance from residential properties.
30.2.12 Refer to the Design and Access Statement Section 27 for more information on architectural considerations.
30.3 Limits and zones
Temporary works 30.3.1 The LLAU for the required working area to construct the works
encompasses a number of areas within one LLAU boundary including: a. The carriageway, parking spaces and footway of Bekesbourne Street
south of the junction of Bekesbourne Street and Ratcliffe Lane for construction of the penstock and flap valve chamber, electrical and control kiosk and for utility diversions.
b. An area of the carriageway and footway of Ratcliffe Lane at the junction with Bekesbourne Street construction of the ventilation duct and utility diversions.
c. An area of the carriageway and footway of Bekesbourne Street north of Ratcliffe Lane to allow modifications to a manhole cover.
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30 Bekesbourne Street
d. An area of private land north of Ratcliffe Lane and adjacent to Limehouse DLR station for construction of the ventilation column and utility diversions.
30.3.2 The LLAU along Bekesbourne Street is sufficiently wide to maintain a single lane for vehicle access around the area of the construction works. The LLAU has also been sized to allow sufficient area for the diversion of existing utilities.
30.3.3 The LLAU covers approximately 1,200m2 and the assumed hoarded area would be approximately 300m2 (based on the illustrative Construction phases – phase one drawing).
30.3.4 The Bekesbourne Street site is a system modification site. As system modifications are not typical, but vary in each case no site size guide was appropriate and therefore none are provided in the Site selection background technical paper.
Permanent works 30.3.5 The zone within which all the permanent site structures would be located
(denoted by the green line on the Site works parameter plan) includes a section of the carriageway along Bekesbourne Street in order to allow the position of the ventilation duct to be adjusted. The zone also includes several parking spaces along Bekesbourne Street in order to allow the location of the electrical and control kiosk to be adjusted. The south side of the zone extends into the carriageway and parking spaces along Bekesbourne Street in order to allow space for the diversion of existing utilities. The north side of the zone extends into the carriageway and footway of Ratcliffe Lane in order to allow the position of the ventilation duct and ventilation column to be adjusted.
30.3.6 The zone within which the permanent above ground structures for the electrical and control kiosk (denoted by one of the purple lines on the Site works parameter plan) allows this structure to be relocated in a north-south direction.
30.3.7 The zone within which the permanent above ground structures for the ventilation column serving the penstock and flapvalve chamber (denoted by the second purple line on the Site works parameter plan) allows the position of the column to be adjusted in an east-west direction.
30.4 Access 30.4.1 Access to the penstock and flap valve chamber, electrical and control
kiosk and ventilation column would be via the existing road network. 30.4.2 Access covers would be finished at ground level. 30.4.3 Site visits would be required approximately every three to six months to
carry out inspections of the penstock and flap valve chamber, ventilation column and electrical and control kiosk. It is likely that this would involve a visit by staff in a small van. Staff would open access covers to inspect and carry out minor maintenance of below-ground equipment.
Engineering design statement 217
30 Bekesbourne Street 30.4.4 Should cleaning be required, a jetting lorry would be brought to the site to
undertake work via the appropriate ground-level access cover. It is anticipated that once every ten years large access covers in Bekesbourne Street would be accessed for major maintenance of the flap valve and penstock and this would require a temporary road closure of Bekesbourne Street.
Engineering design statement 218
Abbreviations
Abbreviations AASHTO American Association of State Highway and Transportation Officials AOD Above Ordnance Datum (Newlyn) ATD Above Tunnel Datum (where Tunnel Datum is 100m below Ordnance
Datum Newlyn: 100m ATD equals 0m AOD) BS British Standard BRE British Research Establishment BTS British Tunnelling Society C Centigrade CDM Construction (Design and Management) Regulations 2007 CESWI Civil Engineering Specification for the Water Industry CIRIA Construction industry research and information association CSO Combined sewer overflow DIN DeutschesInstitutfürNormung DLR Docklands Light Railway EFNARC European Federation of Specialist Construction Chemicals and Concrete EPB Earth pressure balance EU European Union GWT Groundwater table HMSO Her Majesty's Stationery Office HSE Health and Safety Executive ICE Institution of Civil Engineers ITA International Tunnelling and Underground Space Technology JCoP Joint Code of Practice LLAU Limits of land to be acquired or used m Metre m2 Square metre m3 Cubic metre m3/s Cubic metre per second MEICA Mechanical, electrical, instrumentation, control and automation MPa Mega Pascal NATM New Austrian Tunnelling Method NPS National Policy Statement SCL Sprayed concrete lining STW Sewage Treatment works TBM Tunnel boring machine UK United Kingdom UWWTD Urban Waste Water Treatment Directive WIMES Water Industry Mechanical and Electrical Specification
Engineering design statement 219
Abbreviations
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Engineering design statement 220
Glossary
Glossary
Term Description Above Ordnance Datum
Ground elevation is measured relative to the mean sea level at Newlyn in Cornwall, referred to as Ordnance Datum (OD), and heights are reported in metres above or below OD.
Above Tunnel Datum Above Tunnel Datum where Tunnel Datum is 100m below Ordnance Datum Newlyn: 100m ATD equals 0m AOD
acoustic enclosures An enclosed structure installed around plant or machinery to reduce or attenuate noise.
aesthetic Aesthetic effects are associated with human sensory or emotional values and judgements. They often relate to environmental effects on human receptors through the senses of sight, smell, taste, and sound.
aggregate Coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are a component of composite materials such as concrete and asphalt concrete. The aggregate serves as reinforcement to add strength to the overall composite material.
air management structures
Collective term for ventilation equipment to be provided by the Thames Tideway Tunnel project.
anticline A fold that is convex up and has its oldest beds at its core.
aquiclude An impermeable body of rock or stratum of sediment that acts as a barrier to the flow of groundwater.
aquifer A permeable geological stratum or formation that is capable of both storing and transmitting water in significant amounts. A permeable strata, either through intergranular and/or fracture permeability, that is capable of supporting water supply and/or river base flow. There are two types of aquifers, principal and secondary, depending on whether they are regionally or locally important.
asset An existing or proposed/planned physical object, whose stability, form or function is responsive to ground movements to such an extent that these responses need to be fully understood and investigated prior to commencing construction works.
bentonite An absorbent aluminium phyllosilicate, in general, impure clay consisting mostly of montmorillonite. Mixed with water, it forms slurry, commonly used as a drilling fluid and for ground
Engineering design statement 221
Glossary
Term Description support in tunnelling.
borehole A hole drilled into the ground for geological investigation or for the exploitation of geological deposits or groundwater. An abstraction borehole is a well sunk into an aquifer from which water is pumped.
British Standard Produced by the BSI Group in order to set up standards of quality for goods and services.
brown roof A roof that supports a wide variety of plant and animal species and reduces storm water run-off.
cable duct Pipework (generally below-ground) in which a cable is housed.
chainage distance measured along a tunnel
caisson A watertight chamber that is open at the bottom and contains air under pressure used to carry out construction work under water.
campshed An area of stone, concrete or timber lain on the river/sea bed that is exposed at low tide to allow vessels to rest safely and securely in place.
catchment The area from which surface water and/or groundwater collects and contributes to the flow of a river, abstraction or other specific discharge boundary. Can be prefixed by ‘surface water’ or ‘groundwater’ to indicate the specific nature of the catchment.
Chalk In the project area, chalk is firm, white, fine-grained limestone with conspicuous semi-continuous nodular and tabular flint seams.
cofferdam A temporary wall that is constructed around the outside of a working area within a river that is then pumped dry. The inside of the cofferdam can be filled to create a safe working area.
collecting system A system of conduits that collects and conducts urban wastewater.
combined sewer A sewer that conveys both rainwater and wastewater of domestic or industrial origin.
combined sewer overflow (CSO)
A structure, or series of structures, that allows sewers that carry both rainwater and wastewater to overflow into a river when at capacity during periods of heavy rainfall. The flows are discharged in order to prevent the sewers backing up and flooding streets or houses. Flows may discharge by gravity or by pumping.
Engineering design statement 222
Glossary
Term Description confluence A gathering, flowing, or meeting together at a juncture or
point.
connection culvert A covered channel structure to connect the interception chamber to the drop shaft.
connection tunnel A tunnel that connects a drop shaft to the main tunnel.
construction site The area of a site used during the construction phase.
CSO site A site that contains the CSO interception chambers, connection culverts and the drop shaft from which the connection tunnel is built. Each site needs to be able to provide enough space for all construction-related activities, which would vary depending on the diameter of the shaft and method of tunnel construction.
culvert A covered structure that conveys a flow under a road, railroad or other obstruction. Culverts are mainly used to divert stream or rainfall run-off to prevent erosion or flooding on highways.
cutterhead The rotating head on a TBM that cuts and excavates the ground
de-aeration chamber An area within the shaft and/or associated pipe work where air is removed from liquids.
development Development is defined under the 1990 Town and Country Planning Act (as amended) as “the carrying out of building, engineering, mining or other operation in, on, over or under land, or the making of any material change in the use of any building or other land”. Most forms of development require planning permission.
dewatering The removal of water from solid material or soil by wet classification, centrifugation, filtration, or similar solid-liquid separation processes, such as removal of residual liquid from a filter cake by a filter press as part of various industrial processes. Construction dewatering is a term used to describe removal or draining groundwater or surface water from a riverbed, construction site, caisson or mine shaft, by pumping or evaporation.
diaphragm wall A diaphragm wall is a reinforced concrete retaining wall constructed in-situ. A deep trench is excavated and supported with bentonite slurry, and then reinforcing Material (normally steel) is inserted into the trench. Concrete is poured into the trench and only after this can excavation in front of the retained earth commence.
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Glossary
Term Description dissolved oxygen level
Indicator of water quality – a higher level is preferable.
drive site A main tunnel site that contains the shaft from which the tunnel boring machine is ‘driven’ forward, ie, starts from. Excavated material is removed from and segments are fed into the tunnel via the shaft at the drive site.
drop shaft A circular, vertical concrete structure to drop flows from a CSO to a main tunnel. Drop shafts also provide access to construct the connection tunnels.
earth pressure balance
A mechanised tunnelling method in which spoil is admitted into the tunnel boring machine via a screw conveyor (cochlea) arrangement, which allows pressure at the face of the tunnel boring machine to remain balanced without the use of slurry.
effect The result of an impact on a particular resource or receptor.
electrical and control kiosk
A structure that houses electrical and control equipment (not necessarily a building).
encroachment With regards to the Thames Tideway Tunnel project, this refers to the extent that proposed structures extend into the river or foreshore.
Environmental Impact Assessment (EIA)
An assessment of the likely significant effects that a proposed project may have on the environment that considers natural, social and economic aspects, which is prepared in accordance with the Infrastructure Planning EIA Regulations 2009.
excavated material The earth/soil/ground material removed when shafts, tunnels and other structures are excavated. Excavated material can be either topsoil, subsoil or other material, such as rock, etc.
fault A structural planar fracture or discontinuity within lithological strata due to strain or compression in which significant displacement is observable.
fault zone A region (metres to kilometres wide) that is bounded by major faults within which subordinate faults may be arranged variably or systematically. Single fault zones are marked by fault gouge, breccias, or mylonites.
flint A form of chert (silica, SiO2) found in chalk deposits, flint is a chemical sedimentary rock that forms from the remains of silica-bodied organisms.
flood plain Generally low-lying areas adjacent to a watercourse or the tidal lengths of a river or sea where water flows in times of flood or would flow but for the presence of flood defences.
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Glossary
Term Description flood risk assessment
An assessment of the likelihood of flooding in a particular area in order to carefully consider development needs and mitigation measures.
fluvial The processes associated with rivers and streams and the deposits and landforms they create.
foreshore Ground uncovered by a river when the tide is low.
foul sewer A sewer that conveys wastewater of domestic or industrial origin, but little or no rainwater.
geyser intermittent discharge of water ejected turbulently and accompanied by a vapour phase
global warming The gradual increase in the temperature of the earth's atmosphere, believed to be due to the greenhouse effect, caused by increased levels of carbon dioxide, chlorofluorocarbons, and other pollutants.
graben A depressed block of land bordered by parallel faults; the result of a block of land being downthrown, producing a valley with a distinct scarp on each side. Grabens often occur side-by-side with horsts. Horst and graben structures are indicative of tensional forces and crustal stretching.
ground investigations Information gathering and collation regarding existing geotechnical ground information to enable the design process (eg, boreholes, groundwater monitoring, trial holes, etc).
ground treatment A range of measures to improve the properties of the naturally occurring ground or to counter the potential pore water pressure changes arising from underground working/excavations in order to facilitate tunnel or shaft construction and/or reduce ground movement caused by works.
groundwater All water below the surface of the ground in the saturation zone and in direct contact with the ground or subsoil. Water contained in underground strata, predominantly in aquifers.
Harwich Formation Dark brown, lightly glauconitic clay with localised fine sand.
hydraulic gradient The rate of change of groundwater level per unit distance in a given direction in an aquifer. Groundwater flows in the direction of the decline in hydraulic gradient.
hydrogeology The area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquifers).
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Glossary
Term Description hydrology The study of the movement, distribution, and quality of water
throughout the Earth, including the hydrologic cycle, water resources and environmental watershed sustainability.
impact A physical or measurable change to the environment that is attributable to the Thames Tideway Tunnel project.
infiltration The process whereby water seeps into a pipe via imperfections such as cracks, etc.
InfoWorksCS Urban drainage network modelling software.
interception chamber A structure constructed around an existing combined sewer that diverts stormwater from the sewer into a new system of structures to transfer storm water flow to a sewage treatment works.
interceptor sewer A sewer that captures spillages from existing sewers and transports them to be properly treated.
intervention Maintenance work to maintain a TBM that requires workers to leave the security of the machine and enter the ground ahead of the cutterhead
Lambeth Group A complex sequence of highly variable inter-bedded sediments that includes clay, sands, pebble beds and Shelly beds.
launch shaft or drive shaft
The main shaft from which a tunnel boring machine is ‘launched’ ie, starts from. Excavated material is removed from and segments are fed into the tunnel at the launch/drive shafts.
layout The way buildings, routes and open spaces are placed or laid out in relation to each other on the ground.
Lee Tunnel The Lee Tunnel project, currently under construction (2012), will intercept the Abbey Mills Pumping Station CSO, store and then transfer flows to Beckton Sewage Treatment Works.
limits of deviation (LODs)
Land boundary limits within which permanent structures must remain.
limits of land to be acquired or used (LLAU)
Land outside the limits of deviation that is available for construction but not to accommodate permanent structures.
lining A structural member that is used in tunnels or shafts (vertical or inclined) to withstand ground and hydrostatic loads, both internal and external (eg, PCC, insitu, SGI).
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Glossary
Term Description listed buildings A structure of architectural and/or historical interest included
on the Secretary of State’s list, which affords statutory protection. Such buildings are subdivided in to Grades I, II* and II (in descending importance).
main tunnel The continuous large diameter tunnel from Acton Storm Tanks to Abbey Mills.
main tunnel drive site A site used to insert and drive a tunnel boring machine.
main tunnel reception site
A site used to remove the tunnel boring machine from the main tunnel at the end of the drive.
main tunnel site A site from which the main tunnel would be built. Each site needs to provide enough space for all construction-related activities, which would vary depending on the type of tunnel boring machine used and whether the site is a drive site, double drive site or reception site.
mitigation measures Proposed actions to prevent or reduce adverse effects arising from the whole or specific elements of a development.
modelling Simulation of a proposed design (eg, hydraulic modelling of a drainage network, physical modelling of drop shafts or odour modelling, etc).
monitoring Monitoring, recording and collection of existing situation data prior to construction (eg, CSO spill frequency, vehicle or pedestrian traffic movements or building settlement monitoring before or during construction).
olfactometry Odour panel sampling carried out in laboratory conditions.
open space
All space of public value, including landscaped public areas, playing fields, parks and play areas as well as areas of water such as rivers, canals, lakes and reservoirs that offer opportunities for sport and recreation or provide visual amenity.
operational phase Once construction work is complete and the tunnel system is in use.
overflow weir chamber
Used to manage and divert overflows from an existing sewer into the new system of connection culverts, CSO drop shafts and tunnel.
parapet A wall-like barrier at the edge of a roof, terrace, balcony or other structure.
air treatment chamber
A structure containing carbon that absorbs odour from air flowing out of a tunnel, without the assistance of mechanical pumping.
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Glossary
Term Description permeability A measure of the ability of a material (such as rocks) to
transmit fluids.
piezometer A small-diameter observation well used to measure the hydraulic head of groundwater in aquifers
precast concrete segmental lining
Tunnel or shaft lining composed of precast, usually reinforced, concrete elements (segments) designed to form a specific shape, normally circular.
Public Right of Way Route to which the public has right of access.
pumping station A vertical circular structure with pumps at the bottom used to lift stormwater flows up to a sewage treatment works.
reception site A main tunnel site that would contain the shaft from which a tunnel boring machine would be ‘received’ ie, ends up. The tunnel boring machine would be removed from the tunnel via the shaft at the reception site.
risk assessment Assessment of the risks associated with an activity or object and possible accidents involving a source or practice. This includes assessment of consequence.
Run-off Run-off is the movement of land water to oceans chiefly in the form of rivers, lakes, and streams. Run-off consists of precipitation that does not evaporate, transpire or penetrate the surface to become groundwater. Excess run-off can lead to flooding, which occurs when there is too much precipitation.
safeguarded wharf A wharf that is protected by the Mayor of London and the Port of London Authority, to ensure that it is retained as a working wharf and protected from redevelopment into other uses.
scale The height, width and length of proposed buildings in relation to their surroundings.
scour Movement of riverbed materials due to the force of the water.
secant piles Alternate piles in-filled with concrete to form a water-tight retaining wall. A sub-surface barrier installed around construction sites in order to control inflows of shallow groundwater typically composed of intersecting concrete or overlapping shafts of concrete.
secondary lining A second, internal lining of the tunnel to provide additional strength.
segments Multiple precast concrete segments made in factories that are joined together to build a tunnel. Shafts are also sometimes constructed from segments.
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Glossary
Term Description sewage derived litter Rubbish that originates from sewage, such as toilet paper.
sewage or wastewater
Water-borne wastes from domestic uses of water derived from households, trade and industry.
sewerage A system of pipes to collect and transport domestic and industrial wastewater.
shaft Duct, pipe or vertical tunnel.
sheet or secant pile wall
A sub-surface barrier installed around construction sites in order to control inflows of shallow groundwater typically composed of intersecting concrete or overlapping shafts of concrete.
slipway A sloping surface leading down to a body of water from which boats may be launched.
slurry Normally a mixture of bentonite and water to form a dense liquid capable of supporting open excavations, such as bored piles and diaphragm walls. Also used in slurry tunnel boring machines to support the face and transport excavated material through a pumped system.
source control Methods of managing and reducing stormwater run-off at site level.
sprayed concrete lining
A structural element formed by the application of a mixture of cementitious material, aggregate, water, fibre or other types of reinforcement and admixtures, projected into place from a nozzle at high velocity to produce a dense, homogenous mass that is applied directly to the ground surface in one or more layers.
statutory Required by law.
storage and transfer tunnel
A sewer that captures spillages from existing sewers and transports them to be properly treated.
stormwater Rainwater that funnels into sewers and mixes with sewage and is either treated at sewage works or overflows into rivers.
surface water A general term used to describe all water features such as rivers, streams, springs, ponds and lakes.
surface water run-off Water that travels across the ground and hard surfaces rather than seeping into the soil eg, from paved roads and buildings.
sustainable drainage system (SuDS)
A drainage system that controls the quantity and speed of rainwater run-off from a development as defined in the Environment Agency and London Plan hierarchy.
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Glossary
Term Description temporary works Works required to facilitate construction, including any works
left in place after completion.
Thames Path A designated footpath that follows the route of the tidal Thames.
Thanet Sand Coarsening upward sequence of well-sorted fine grained sand that has a higher clay/silt content towards the lower part of the sequence, and evidence that intense bioturbation has removed bedding structures.
Tideway The tidal area of the Thames (ie, from Teddington to the Thames Estuary).
topography The study and description of Earth's surface shape and features or those of planets, moons, and asteroids, especially as depicted in maps.
trunk sewer A sewer that receives a number of tributary sewers and serves a large area.
tunnel alignments The horizontal and vertical routes of proposed tunnels, including connection tunnels and shaft sites.
tunnel boring machine (TBM)
A machine that has a circular cross-section used to excavate tunnels through a variety of geological conditions.
tunnel datum A datum based on Ordnance Datum used to design tunnels that pass below sea level. By using a lower datum as the base point, negative numbers can be avoided in calculations, which eliminates a possible source of mistakes.
typical year A typical year relates to an actual year, eg, the corresponding meteorological dataset for 1979-80, which was the year used in the modelling. The corresponding meteorological dataset provides a better indication of conditions than a recent year of data in which the meteorological data may not be consistent with a rainfall event leading to the tunnel emissions.
Upnor Formation Variably bioturbated fine to medium-grained sand with glauconite, rounded flint pebbles and minor clay, with distinctive pebble beds, base and top.
urban wastewater Domestic wastewater or the mixture of domestic wastewater with industrial wastewater and/or rainwater run-off.
Urban Wastewater Treatment Directive 1991 (UWWTD)
The overall aim of the UWWTD is to protect the environment from the adverse effects of urban wastewater discharges.
utilities Assets belonging to utility companies, including Thames Water, that range from aged, rigid cast-iron pipework to flexible cables and ductwork. Liaison with utility companies to acquire third-party asset
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Glossary
Term Description information, facilitate required diversion applications and procure new supplies.
valve chamber An underground structure on the sewer system that contains valves used to isolate the flow between different parts of the sewerage system. For example, flap valves prevent flow from the river travelling back up the sewer or into tunnels.
venturi reduction in fluid pressure that results when a fluid flows through a constricted section of pipe.
ventilation building A building that contains fans and filters to remove and treat air from the tunnel.
ventilation column A vertical pipe through which air is released.
ventilation duct Pipework (generally below ground) through which air moves.
ventilation structure An above-ground or below-ground structure that is part of the tunnel ventilation system.
wastewater or sewage
Waterborne wastes from domestic uses of water, derived from households, trade and industry.
Water Framework Directive (WFD)
A European Commission (EC) Directive that seeks to improve water quality in rivers and groundwater in an integrated way (2000).
water table The level below which the ground is saturated with water. The water table elevation may vary with recharge and groundwater abstraction.
weir A dam in a watercourse or sewer that alters and manages the flow.
works All construction work associated with the construction of the Thames Tideway Tunnel project.
worksite Site on which construction works are carried out.
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Glossary
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Appendix A: Time distance diagrams
Appendix A: Time distance diagrams A.1.1 The following time distance diagrams are appended:
a. Figure A.1 Assumed summary programme for the main tunnel including drive and reception shafts
b. Figure A.2 Assumed summary programme for the CSO drop shafts along the main tunnel
c. Figure A.3 Assumed summary programme for the Frogmore connection tunnel and Beckton Sewage Treatment Works
d. Figure A.4 Assumed summary programme for the Greenwich connection tunnel
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Appendix A: Time distance diagrams
Figure A.1 Assumed summary programme for the main tunnel including drive and reception shafts
Engineering design statement 234
Appendix A: Time distance diagrams
Figure A.2 Assumed summary programme for the CSO drop shafts along the main tunnel
Engineering design statement 235
Appendix A: Time distance diagrams
Figure A.3 Assumed summary programme for the Frogmore connection tunnel and Beckton Sewage Treatment Works
Engineering design statement 236
Appendix A Time distance diagrams
Figure A.4 Assumed summary programme for the Greenwich connection tunnel
Engineering design statement 237
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Copyright notice Copyright © Thames Water Utilities Limited January 2013. All rights reserved. Any plans, drawings, designs and materials (materials) submitted by Thames Water Utilities Limited (Thames Water) as part of this application for Development Consent to the Planning Inspectorate are protected by copyright. You may only use this material (including making copies of it) in order to (a) inspect those plans, drawings, designs and materials at a more convenient time or place; or (b) to facilitate the exercise of a right to participate in the pre-examination or examination stages of the application which is available under the Planning Act 2008 and related regulations. Use for any other purpose is prohibited and further copies must not be made without the prior written consent of Thames Water. Thames Water Utilities LimitedClearwater Court, Vastern Road, Reading RG1 8DB The Thames Water logo and Thames Tideway Tunnel logo are © Thames Water Utilities Limited. All rights reserved. DCO-DT-000-ZZZZZ-071800
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