7 Environmental Baseline and Assessment of Impacts – North ...74f85f59f39b887b696f-ab656259048fb93837ecc0ecbcf0c557.r23.cf… · overlying alluvial clay deposits. The solid geology,

Crossrail Line 1 Mott MacDonald Assessment of Water Impacts Technical Report Cross London Rail Links Limited

203357/31/Final/Feb 05 Chapter 7 - North East Section rev103.doc

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7 Environmental Baseline and Assessment of Impacts – North East Route Section

7.1 Overview of Route Section

The North East Route Section covers the route from Stratford Station to Shenfield in the east. The figure below shows the route alignment.

Figure 7.1: North East Route Section Alignment

The main works are summarized below. Sections 7.2 to 7.4 outline sources of data, baseline conditions and impacts at a route section level. Sections 7.5 onwards discuss baseline conditions and impacts relevant to each individual route window.

(i) Permanent Works

Crossrail services within the North East Route Section would run on the existing electric suburban tracks of the GEML. Little new rail alignment would be created, although new track would be required to provide a freight loop between Goodmayes and Chadwell Heath in order to replace an existing loop at Manor Park, which would be removed. Also, the reconstruction of Shenfield station would be undertaken as well as new junction works at Ilford.

Crossrail would require new or extended platforms at several stations in order to accommodate its 200 m long trains. At Romford and Ilford, new station buildings and other facilities would be provided as well.

Crossrail’s other major facility on this line is a new depot and stabling sidings to the west of Romford station and south of the GEML. This is linked to the eastbound and westbound Crossrail running lines by an dive-under (rail underpass) enabling Crossrail trains to access



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the depot without hindering services on the main lines. Stabling sidings would also be provided on re-modelled existing sites at Gidea Park and Shenfield. New sidings would be constructed at Aldersbrook (near Ilford) to facilitate fit-out of the Crossrail tunnels, and at Pitsea for disposal of excavated material.

(ii) Construction Works

Major works to tracks would be carried out for the proposed tunnel logistics site at Aldersbrook between Manor Park and Ilford; the restoration of a redundant freight loop between Goodmayes and Chadwell Heath; and for the construction of a diveunder to the new depot at Romford.

Platform extensions, which would be undertaken at several stations, would involve:

• break out and removal of existing surfaces and ramps;

• excavation of foundations to about 1 m depth;

• construction of platforms either using crosswalls and pre-cast concrete planks, using a proprietary system or traditional construction;

• fitting of reinforced concrete screed, pre-cast concrete copings, tactile strips and the levelling of the surface;

• adjustment of track alignments, if required; and

• modifications to OHLE and signalling as necessary.

The scale of the works along the route varies. Relatively minor works, such as station platform extensions, would take place in some route windows with more substantial works, such as the development of Romford depot, taking place in others. The table below summarises the main works (including major enabling works) that would take place in the north east section. Those route windows containing the more substantial works are highlighted with shading.

Table 7.1: Main Elements of the Project in the North East Route Section (route windows with major works are highlighted)

Route Window Main Project Works NE1 Stratford Station (Biggers Road to Carnarvon Road)

Platform alterations

NE2 Forest Gate Station (Carnarvon Road to Balmoral Road)

Platform extensions

NE3 Manor Park Station (Balmoral Road to Gloucester Road)

Platform extensions Shortening of freight loop



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Route Window Main Project Works NE4 Ilford Station (Gloucester Road to Hainault Street)

Extension of platforms and removal of the bay platform Construction of a new ticket hall New sidings for construction/fitout of the central area tunnels (Aldersbrook sidings)

NE5 Seven Kings Station (Hainault Street to St Albans Road)

Platform extensions

NE6 Goodmayes Station (St Albans Road to Wadeville Avenue)

Platform extensions Introduction of new freight loop (Chadwell Heath Loop)

NE7 Chadwell Heath Station (Wadeville Avenue to Whalebone Lane South)

Platform extensions Track works Introduction of new freight loop (Chadwell Heath Loop)

NE8 Romford Depot (west) (Whalebone Lane South to Sheringham Avenue)

Romford Depot Underpass and associated track works Widening of Jutsums Lane bridge

NE9 Romford Station & Depot (east) (Sheringham Avenue to Carlisle Road)

Extension of platforms Reconstruction of the ticket hall and extension of the ticket hall Construction of a new depot New stabling sidings

NE10 Gidea Park Station (Carlisle Road to Upper Brentwood Road)

Platform extensions

NE11 Gidea Park Stabling Sidings (Upper Brentwood Road to Briars Walk)

New stabling sidings

NE12 Harold Wood Station (Briars Walk (western end) to Harold Court Road)

Platform extensions

NE13 LB Havering / Brentwood DC Boundary (Harold Court Road to M25)

None

NE14 Brook Street (M25 to Kavanaghs Road)

None

NE15 Brentwood Station (Kavanaghs Road to Seven Arches Road)

Platform extensions



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Route Window Main Project Works NE16 Thrift Wood (Seven Arches Road to Woodway)

None

NE17 Shenfield Station (Woodway to Brentwood Long Ridings school)

New stabling sidings. A new platform face

R1 Pitsea

New rail sidings

7.2 Sources of Information

Data on the baseline conditions has been obtained from various sources, including the Environment Agency, Thames Water Utilities Ltd, English Nature and various London Boroughs and District Councils. The table below contains information about the data obtained and used in the assessment.

Table 7.2: Sources of Data – North East Route Section

Subject Data Source Date received Groundwater Groundwater quality records Environment Agency November 2002 Groundwater Groundwater abstraction licenses Environment Agency

Thames Region November 2002

Groundwater Section 32 consents Environment Agency Thames Region

October 2003

Groundwater Abstractions in determination Thames Water October 2003 Groundwater Abstractions determined in March

2004 Thames Water August 2004

Groundwater Protected Groundwater Rights Personal contact with London Boroughs and District Councils

November 2002

Groundwater Source Protection Zones Environment Agency Thames Region

November 2002

Groundwater Source Protection Zones Environment Agency Southern Region

December 2002

Groundwater Groundwater quality records Environment Agency Thames

November 2002

Groundwater Chalk Water Levels January 2003 Environment Agency July 2003 Surface Water Indicative flood plains Environment Agency November 2002 Surface Water Surface Water Discharges Environment Agency

Thames Region May 2003

Surface Water Surface Water Abstraction Licenses Environment Agency Thames Region

December 2002

Surface Water Main rivers Environment Agency Thames Region

February 2003

Surface Water Other watercourses 1:5,000 (Crossrail) and 1:25,000 (OS) maps

n/a



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Subject Data Source Date received Surface Water GQA and RQO Environment Agency

Thames Region May 2003

Surface Water GQA and RQO Environment Agency Website

June 2003

Surface Water Flood Zone Maps (Zone 3), June 2004

Environment Agency December 2004

Surface Water Flood Levels Environment Agency Thames

October 2003

Other SSSI, SPA, SAC, NNR, Ramsar English Nature November 2002

7.3 Baseline Information – North East Route Section

7.3.1 Introduction

The route window descriptions of baseline conditions include a summary of the baseline data, relevant for the window. Baseline data are assessed according to the scope and methodology described in Chapters 2 to 4, even though the environmental receptor in question may be outside the route window. This is noted wherever it applies.

Maps have been produced showing the following baseline data: groundwater abstractions, 2003 Chalk water levels, area affected by saline intrusion, groundwater protection zones, surface water abstractions and discharges, main rivers and floodplains.

7.3.2 Geology and Hydrogeology

(i) Stratigraphy

The geological formations within the North East Route Section are described in the following sections. The geological description is based on geological maps and information from geological records along the alignment. A summary of the general stratigraphy is presented in the table below. An indication of the geology in relation to the vertical alignment of Crossrail Line 1 is shown in Appendix C and is discussed in (vii) below.

Table 7.3: Stratigraphy

Period Group Formation Description HydrogeologicalProperties

Made Ground Recent Alluvium

Quaternary Drift Langley, Ilford, Crayford and Dartford Silts

Brickearths.

Permeable shallow aquifer in direct continuity with River Thames and other surface



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Period Group Formation Description HydrogeologicalProperties

River Terrace Deposits / FloodplainGravels (including Boyn Hill Gravel andTaplow Gravel)

Gravel. Clayey and sandy in part.

Boulder Clay Heterogeneous till.

Glacial Sands and Gravels,

waters. Silt layers and clayey horizons in the Boulder Clay act as weak aquitards.

Bagshot Beds Sand Claygate Beds Sand and Loam London Clay Formation

Stiff grey brown heterogeneous clay with closely spaced fissures.

Very low permeability aquitard separating upper and lower aquifers.

Thames Group

Harwich Formation Dense to very dense black rounded and sub-rounded, medium to coarse flint gravel, occasional cobbles, dark brown silty or clayey fine to medium sand matrix.

Weak aquifer

Stiff red, blue, grey and brown laminated silty clay with fine to medium sand in the top part.

Aquitard Reading Formation

Stiff/hard buff blue, grey, black, sometimes mottled purple blocky slightly sandy silty clay, with occasional calcareous concentrations and limestone.

Aquitard

Shelly occasionally laminated silty clay or clayey silt with a little fine sand and impersistent hard limestone beds.

Aquitard

Dark grey shelly silty clay including oysters, sometimes in layers forming hard beds, with occasional laminated grey clay and silt.

Aquitard

Lambeth Group

Woolwich Formation

Mottled blue grey and brown laminated silty clay/clayey silt/fine to medium sand, with occasional wood fragments.

Aquitard

Palaeogene(Tertiary)

Thanet Sands Greenish and brownish grey, silty, fine-grained sand. Bioturbation.

Minor aquifer

Cretaceous Chalk Poorly cemented and porous, typically massively bedded and well jointed, fissured white limestone.

Major aquifer



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(ii) Drift Geology

The surface geology along the proposed Crossrail route comprises unconsolidated deposits commonly grouped as ‘Drift’, and comprising artificial ‘Made Ground’, Alluvium, assorted sands and gravels and Boulder Clay. The highly permeable sands and gravels dominate the hydrogeological properties of the Drift, and, as such, this geological unit is considered to form an upper, shallow aquifer. This shallow aquifer is typically in hydraulic continuity with local watercourses. The shallow aquifer receives both urban and natural recharge, and infiltration from streams. The gravels typically have a thickness of less than 10 m, with a variable permeability, possibly ranging from 10 m/d to more than 500 m/d. CIRIA (1993) quotes Foster (1971) as giving values in the range 50 to 150 m/d with a specific yield of 10 to 20%. Occasionally, the sands and gravels may be confined by a thin, (i.e. less than 3 m) cover of overlying alluvial clay deposits. The solid geology, London Clay, outcrops or is very shallow to the east of Goodmayes.

(iii) Thames Group

Underneath the Drift deposits are the Bagshot and Claygate Beds. However, they are only present in areas around Brentwood and comprise relative thin layers of sand and loam. The main solid geology is the London Clay which is found as a relatively thick, folded layer along most of the route section. It gradually thickens to the east from being very thin around Maryland Station. The London Clay is a stiff clay containing sandy lenses and nodular concretions. Due to the complex folding of the strata, the exact position of the upper and lower boundaries of the clay is not well defined unless verified by site investigation. The London Clay has a very low permeability (the vertical permeability is typically less than 5×10-6 m/d) and therefore acts as a very low permeability aquitard, overlying the Lambeth Group and separating the shallow aquifer in the Drift from the deep aquifer of the Thanet Sands and Chalk. Although some groundwater exists in sandy lenses within the London Clay, it is considered to be effectively isolated from the shallow and deep aquifers.

The Harwich formation lies beneath the London Clay and is generally less than 2 m thick, however it is often absent. It is part of the same group as the London Clay, but is considered to be a separate unit. Typically, the Harwich Formation comprises flint gravel with occasional cobbles, in a dark brown, fine to medium sand matrix. Although groundwater usually exists in the Harwich Formation, it is considered to be effectively isolated from the shallow and deep aquifers.

(iv) Lambeth Group

The Lambeth Group, formerly termed the Woolwich and Reading Beds, collectively form a folded layer beneath the London Clay which has a moderate to low permeability. As such they may be classified as an aquitard which forms a hydrogeological extension of the overlying London Clay aquitard. Sand lenses, where present, may contain groundwater under pressure. These layers may be recharged at the sub-crop in the bed of the River Thames but are otherwise separate from the shallow and deep aquifers.



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(v) Thanet Sands

The Thanet Sands comprise a thin, folded layer of fine grained sands and silty sands, with a distinctive basal bed of green coated flints, which are well-developed in places. The Thanet Sands form the arenaceous part of the deep aquifer. This aquifer is generally separated from the shallow aquifer by the intervening aquitard formed by the Woolwich and Reading Formations and the London Clay. Where the aquitard is absent, as in the vicinity of the River Thames, the shallow and deep aquifers are in hydraulic continuity with each other and also with the river.

(vi) Chalk

The Upper Chalk underlies the Thanet Sands and forms the carbonate, bedrock part of the deep aquifer. The Chalk is known to have a low matrix permeability and, often, limited fissuring in the area along the North East Route Section.

(vii) Geological Structure

The North East Route Section runs over an area of low relief on the northern flank of the London Basin syncline. The Lambeth Group and older rocks are present everywhere but there are a few areas in the west of the route section where the London Clay is absent as a result of surface erosion. BGS sheet 257 shows clearly the areas in the west where rivers and streams have cut down through the Floodplain and Taplow Gravels producing narrow ribbons of exposed London Clay or Alluvium. Further to the north east where the Boulder Clay generally outcrops, it too has been eroded locally to expose the underlying Glacial Sands and Gravels, Bagshot Beds, Claygate Beds or London Clay.

BGS sheet 257 does not show any faults in the vicinity of the route alignment. However, Flavin (1982) presents an east-west cross section to the south of the route alignment which shows a narrow fault bounded block east of the River Roding and another from east of the River Beam to west of the River Ingrebourne. Within these blocks, the strata have been displaced to higher levels and the London Clay is thinner or absent. Flavin also presents a plan which suggests that not all the faults extend as far north as the alignment. According to work produced by The University of Reading there are a number of orthogonal dip and strike faults with intermediate anticlines and synclines. The presence of these other structural faults is thought not to affect the strata significantly. The route alignment east of the River Roding runs near to the “A2” anticline where the base of the London Clay has been identified at around 97 mATD.

An indicative geological long section for the route from Stratford to Royal Oak Portal (route window NE1) to Harold Wood (route window NE12) is given on Figure C9 in Appendix C. This long sections is based on layers used in the LBGM and does not contain any details of inferred faulting or local folding. The geological long section has not been extended from Harold Wood to Shenfield since the London Clay is present everywhere.



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(viii) Groundwater Levels

Groundwater levels in the shallow aquifer tend to be perched above the underlying clay strata and thus have significant local variations superimposed on a regional gradient sloping down towards the Thames. In general, there is not much information available on the shallow groundwater levels except from a few geotechnical investigations.

To date, there has been no monitoring of groundwater levels by Crossrail along the North East Route Section. The 2003 Environment Agency Chalk groundwater levels are shown on the drawings. A small mound in the groundwater levels is located north of the Bow Triangle and immediately east of the River Lea. There are various different interpretations as to the cause of this mound; however, at this point there is a window in the London Clay where the underlying Lambeth Group is exposed at the surface. The increase in groundwater levels may be due to an increased recharge in this area, or due to the structure and the positioning of certain low permeability barriers on the edge of the window in the London Clay, or due to a combination of both. These possibilities were incorporated in the LBGM. Dewatering for construction of the Channel Tunnel Rail Link (CTRL) may have lowered the groundwater levels locally around Stratford and some other abstractions, known as the ELRED scheme, have been licensed to Thames Water and these also assisted with CTRL construction.

Since the mid 1960s reduction in groundwater usage has led to a gradual rise in groundwater levels in and around Central London and south-west Essex and recovery of groundwater levels within the cones of depression. At present, Chalk groundwater levels along the North East Route Section are thought to be stable other than where affected by the CTRL and ELRED schemes but the monitoring network is very sparse. It is unusual for groundwater levels in this area to have been modified by long term abstraction since very few wells or adits have been constructed for water supply.

(ix) Groundwater Quality

The shallow aquifer receives recharge from urban run-off, rainfall, stream infiltration and direct rainfall recharge in green areas. The groundwater is very rarely of a quality suitable for potable supply and is therefore seldom abstracted.

There is not much information available on the properties of the Chalk aquifer. In areas where London Clay is present in reasonable thicknesses the deep Chalk aquifer is thought to be potable since the London Clay protects it from surface pollution. The groundwater in the area around Stratford is likely to have been affected by the saline intrusion from the Thames. A zone of the expected extent of saline intrusion has been estimated based on the limited historic records and groundwater monitoring results and is shown on the Drawings. Appendix C contains two figures showing the extent of saline intrusion based on the 150 mg/l and 177 mg/l isochlors across London as reported in 1972 and 1995 respectively.

(x) Groundwater Vulnerability

The majority of the area along the North East Route Section is classified as ‘Minor Aquifer (variably permeable)’ with a soil class of HU. The HU rating is given because soil information for urban areas is less reliable and based on fewer observations than in rural areas, so the worst case is assumed (A.NE.1). As such land is classified as having high leaching potential



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(HU) until proved otherwise (Groundwater Vulnerability of West London, Sheet 39, 1:100 000 map). Additionally, there are areas at Ilford and between Romford and Brentwood classified as ‘Non-Aquifer (negligibly permeable)’.

(xi) Groundwater Abstractions

All groundwater abstractions located within a 500 m corridor either side of the route alignment, within a 1000 m radius of each station, or those which may have a source protection zone that extends into this buffer zone, have been identified. These groundwater abstractions consist of licensed wells, protected groundwater rights and abstractions in determination and Section 32 consents other than in the Environment Agency’s Anglian Region. Appendix C lists details and locations of all the groundwater abstractions obtained.

There are only few abstractions along the North East Route Section. The permeability of the Chalk is very low in this region making it difficult to abstract reasonable quantities of water. The groundwater abstractions on the route are all located in the area between River Lea and the River Rom with the exception of a very small abstraction to the east of Brentwood Station. Extensive adits were required at the Dagenham and Seven Kings sources confirming the low permeability east of the River Rom (these sources are outside the route windows). There are a few abstractions from the river gravels, and they all abstract for non-potable use. The other licensees abstract from the Chalk aquifer and mainly for non-potable use.

The Environment Agency establishes source protection zones (SPZs) for bigger abstractions. However, none of these are a concern for the assessment of the North East Route Section. In order to assess a potential risk on the abstractions, calculations have, therefore, been undertaken by Mott MacDonald to produce approximate time of travel zones (TTZ), corresponding to a travel time of 50 and 400 days. This is explained in more detail in Appendix D.

The inner SPZ is defined as the 50 day travel time area; (with a minimum 50 m radius), and the outer as the 400 day travel time area or 25% of the total catchment, whichever is biggest. It must be noted that the TTZs calculated by Mott MacDonald are approximations used to determine whether the catchment area to the well would extend into the alignment area and, therefore, potentially could be affected by the works providing the intervening aquitards were bypassed somehow.

7.3.3 Surface Water

(i) Main Rivers

The methodology considers impacts on all rivers within 500 m of the route alignment and within 1000 m of stations. The route alignment crosses a few main rivers; the Roding, Rom and Ingrebourne, as shown on the drawings. They all eventually flow into the Thames estuary. There are also several minor watercourses present and they would be described under the relevant route windows.



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(ii) Floodplains and Flood Levels

The Environment Agency has developed Flood Zone Mapping, showing the possible extent of a 1:100 year flood (Zone 3) for main rivers and the Thames Estuary. The North East route alignment would cross the flood zones associated with the rivers Roding, Rom, Beam and Ingrebourne. The tidal zone associated with the Thames extends into route window NE 1 west of Stratford Station and along the River Roding near Ilford Station and Aldersbrook Sidings in route window NE4. The extents of the flood zones are shown on the Drawings.

Flood levels to the upstream and downstream of the route alignment have been obtained for the main rivers in the area for which data has been available, see the table below. Further details are given in the flood risk assessments presented in Appendix H. In order to take climate change into account, most developments have been asked to use levels from model runs using 100 year flows plus a 20% increase according to the Office of Deputy Prime Minister’s document, PPG25.

PPG25 also refers to ‘functional floodplain’ and this is an important distinction from ‘floodplain’ since where effective flood defences exist the functional floodplain may be much smaller than the topographic floodplain. An area protected by a flood defence and shown by the Environment Agency as being in a Defended Flood Zone is assumed (A.NE.2) to be classed as not being on the functional floodplain and therefore new development would be exempt from a need to consider compensatory storage. The Environment Agency has confirmed that the London area is regarded as fully protected from tidal floods by the estuary flood defences as shown on the Flood Zone mapping.

Table 7.4: Modelled Flood Levels

River

Model node point

(NGR)

Flood level

(mATD)

Comment

Easting Northing 100 year1

River Roding (including Alders Brook)

Model data not available

Mayes Brook Culverted River Rom 551256 188370 111.561 River Beam model

553498 189744 128.509 Ravensbourne 553541 189688 128.331

River Beam model

555368 190999 126.415 Ingrebourne 555402 190926 125.831

River Ingrebourne model

Note 1 – See Appendix H

(iii) Surface Water Quality

Water quality information for the major rivers along the North East Section has been provided by the Environment Agency. The River Quality Objective (RQO) represents the target water quality for each river. RQOs are mainly used to set conditions in the licences granted to industry and commerce for surface water discharges. The General Quality Assessment (GQA) is the Environment Agency’s national method for classifying water quality in rivers and canals. The water quality is assessed using four separate categories: chemistry, biology, nutrients, and aesthetics.



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GQA and RQO have been reported, where data is available, for all river reaches crossing or downstream of the Crossrail route alignment. The data are from 2003 and are presented in Appendix C.

(iv) Surface Water Abstractions

The methodology for the assessment of licensed surface water abstractions considers primarily, sites within the route corridor and secondarily, intakes further downstream of the corridor. It is expected that the Environment Agency’s objection to a temporary or permanent discharge or, possibly, a temporary abstraction would be governed by their RQO for the surface water body since this encompasses potential derogation of abstraction licenses.

There are a few surface water abstractions relevant for the North East Route Section. They are located in the Ingrebourne and Beam river systems downstream of the route alignment.

(v) Surface Water Discharges

The Environment Agency has provided details of consented surface water discharges along the route alignment. There are several discharges along the North East Route Section and the majority are Thames Water Utility sewer outlets. Appendix C shows details of the consented surface water discharges and their locations are marked on the drawings.

7.3.4 Designated Nature Conservation Sites

Digital data sets of all designated national and international nature conservation sites (SSSI, SPA, SAC, NNR and Ramsar) have been obtained from English Nature. Sites within 2 km of the route and those downstream of river crossings have been noted and the citations reviewed to establish which sites have water features that may be susceptible to impacts imposed by the works. Two sites have been identified relevant for the North East Route Section: the Ingrebourne Marshes and Thorndon Park to the south of Brentwood. Further consideration of ecological designations and aquatic ecology issues is given within the Ecology Technical Report.

7.4 Impacts and Mitigation – North East Route Section

7.4.1 Potential Impacts on Groundwater and Generic Mitigation

This section presents an overview of the route section wide impacts in the North East Route Section and the reasons why certain potential impacts are considered as not applicable or insignificant after generic mitigation. A summary of the route section wide impacts and generic mitigation register is given in Appendix F. In general, the route section wide impacts are taken, by default, to be applicable in all route windows and are, therefore, not discussed in the text for each.

Exceptions to the default position can occur where either the work is different from the general case or there are environmental receptors that have special features. The locations



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of the exceptions are listed in the text below and further details are discussed in the later sections on the relevant route windows.

The route wide impacts on groundwater and generic mitigation (see Chapter 4) are not examined below. In particular, many construction activities leading to potential pollution of surface and groundwater as temporary impacts would be dealt with through the provisions for generic mitigation described in Appendix B and are therefore not discussed in detail herein.

(i) Groundwater Levels and Flows

There would be no construction work in the deep aquifer in the North East Route Section.

Temporary: The construction of Crossrail is assessed as having no significant temporary effects on groundwater levels and flows in the shallow aquifer in the North East Route Section. An exception may occur at the diveunder for Romford Depot as described in route window NE8.

Permanent: No significant, permanent effects on groundwater levels and flows in the shallow aquifer are expected in the North East Route Section since there are no long cut off structures. An exception would occur at the diveunder for Romford Depot as described in route window NE8.

(ii) Groundwater Quality

Temporary: Temporary impacts on water quality in the shallow aquifer could occur as a result of site operations and these are considered elsewhere under route wide impacts (see Chapter 4). In the built up areas of the route section, the shallow aquifer is generally non-potable and not utilised and so any water quality impacts would be minor. A more general set of exceptions may occur where contaminated land or groundwater exists and the groundwater flow regime in the shallow aquifer is modified by the works. These potential impacts would be investigated and any necessary mitigation measures proposed during the detailed design and construction phases as part of the procedures for dealing with contaminated land.

Water quality in the deep aquifer of the North East Route Section would not be impacted by site operations since the aquifer is everywhere protected by low permeability overlying strata of the upper Lambeth Group and, generally, the London Clay.

Permanent: Minor permanent impacts on water quality are foreseen in the shallow aquifers wherever track drainage is modified. Track drainage would be to Network Rail standards and is discussed in more detail in Chapter 4. However, the shallow aquifer is usually non-potable and not utilised (although an exception occurs in route window NE14) and any water quality impacts are assessed as being insignificant.

There is a small, generic, residual risk of piling for new foundations providing a hydraulic pathway through the London Clay or upper Lambeth Group and allowing cross contamination to occur. However, piling would not normally extend more than 10 m and so would not result in an impact where there is a sufficient thickness of low permeability strata. Sites with less



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than 10 m of suitable strata and with contaminated shallow groundwater would be identified as the geotechnical studies for foundations progress and alternative foundation designs or suitable piling methods adopted or specific mitigation measures incorporated as required.

(iii) Mitigation and Compensation at Existing Wells

The following strategy would minimise and manage the residual risks to existing groundwater abstractions. This strategy is reduced in scope to that applied in some other route sections since no impacts on the deep aquifer are considered likely in the North East Route Section. The strategy is referred to in the relevant route windows where abstraction sources or Time of Travel Zones occur.

A design check as part of the EIA and consultation process would focus on the spatial relationship between the railway and the abstraction well. Construction levels would be compared with data on lengths of borehole already sealed off by grouting and casing, data on zones of inflow that supply the abstraction boreholes and adits, as well as data from stratigraphy and deeper site investigation (SI) drilling. The actual risk of derogation of quality at the borehole would be refined after examination of both the horizontal and vertical separation of the source and receptor of the potential pollutants.

Consultation with well owners has commenced in order to obtain the site specific data on the well owner’s arrangements for routine water quality monitoring at abstraction sources.

7.4.2 Potential Impacts on Surface Water and Generic Mitigation

The route wide impacts on surface water and generic mitigation described in Chapter 4 are not re-examined in this section. As described for groundwater in Section 7.4.1 above, potential temporary pollution of surface water from construction activities would be dealt with through the provisions for generic mitigation described in Appendix B.

(i) Floodplains and Cross-Drainage Structures

Temporary and Permanent: In general, no remodelling of cross-drainage structures or construction on unprotected floodplains is planned that may reduce the floodplain storage by taking up storage space below the design 1:100 year plus 20% increase in peak discharge flood level required by PPG25 (issued by ODPM).

An exception would occur at Romford Depot diveunder where a pipe culvert would be moved (route window NE8). An extension to the bridge / culvert over the River Ravensbourne would also be required under the Gidea Park Stabling Sidings (route window NE11). The platform extension and proposed road bridge replacement over the River Rom near Romford Station (route window NE9) would be at a high level and would use existing abutments and there would be no change in hydraulic performance. The possible road bridge replacement over the River Roding at Aldersbrook (route window NE 4) would be designed not to cause any change in hydraulic performance.

Any new drainage measures on the longer stretches of new or modified railway alignment at Romford Maintenance Depot, Chadwell Heath Loop and Aldersbrook Sidings would reduce



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any surface runoff to greenfield rates unless outfalling to a combined sewer. Sewered watercourses are known to exist near or under some stations, the River Rom runs close to Romford and it is likely that there are existing piped drains disposing into this. It is possible that the western end of the route usually relies on the free draining properties of the gravelly Drift rather than piped track drains at the stations. However, this is less likely beyond Gidea Park where the railway runs, sometimes in cutting, over London Clay. Further discussions with Network Rail, Thames Water and the Environment Agency would take place during detailed design to determine if any consents or permits need to be obtained or revised.

(ii) Surface Water Quality

Temporary: The proposed works are assessed as having no generic temporary impacts on surface water quality since, through the provisions for generic mitigation described in Appendix B, construction site practices would be organised to avoid pollution as discussed in Chapter 4 for route wide generic mitigation and in Section 7.4.1 above for groundwater.

Specific precautions would be required at Romford Station due to the proximity of the River Rom and possibly at other stations where streams have been sewered. These are discussed in the relevant route windows.

Permanent: In general the works would generate no permanent impacts because there are no discharge consents being sought or modified. There may be some minor changes in runoff planned where track drainage is upgraded. There would also be some betterment where existing track and platform drainage arrangements are upgraded with the possible inclusion of silt or oil interceptors.

7.5 Route Window NE1 – Stratford Station

7.5.1 Scheme Description

(i) Overview

The main works in this route window would involve ensuring that platform five is suitable for use by Crossrail trains. The works would involve the widening of platform five, which forms part of island platform three/four/five. Some refurbishment works in addition to the fitting of new platform furniture would also be undertaken on the platforms.

The current platform four (used by the DLR services) would be filled in to provide more space on platform five, the westbound Crossrail platform. DLR is constructing a new platform arrangement for its services and has planning permission for these works (received September 2004). The new DLR platform arrangements would be in place by 2006.

The works at Stratford station would be carried out within the existing railway corridor at the eastern end of the station from sections of the existing platform three/four/five. In addition, there would be a site adjacent to the current station track that would be used for storage.

The figure below shows the main features within the route window.



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Figure 7.2: Route Window NE1 – Stratford Station

(ii) Duration of Works

Overall, the construction works would take approximately four months to complete.

7.5.2 Additional Description Assumed for Water Resources Assessment

The drainage from the widened platform would match the existing drainage system, and it is assumed (A.NE.3) that the drainage design would be appropriate to avoid any pollution of the deep groundwater aquifer after taking into account the geology.

7.5.3 Baseline Data

The superficial deposits of the route window comprise floodplain Gravels and Alluvium with unknown thickness. The London Clay is thought to be absent or possibly thin with the superficial deposits underlain directly by the Lambeth Group. The top of the Chalk is expected to be at approximately 75 m ATD.

The 2003 Environment Agency data indicate that the deep aquifer groundwater levels in route window NE1 were between 85 to 90 mATD. Groundwater quality in the deep aquifer is likely to be reasonable, with increasing salinity towards the southern corner of the route window. There is one Thames Water licence granted in March 2004 within the route window (Id 99) and the alignment passes over the 50 day TTZ although Stratford Station lies within the 400 day TTZ associated with this abstraction. There are another three 400 day TTZs (Id 30, 51 and 100) extending into the route window.

Waterworks River crosses the route alignment in the western end of the route window and Channelsea River crosses Stratford Station in a culvert. The Flood Zone 3 extends onto the western side of the route window reaching Stratford Station. The defended flood level is



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currently 105.23 mATD, assuming (A.NE.4) the Thames Barrier is closed. There are no surface water abstractions, but there is a surface water discharge licensed to Costain Skanska Bachy JV (CANM.0517) for general construction work, which discharges into a balancing pond outfalling into the River Lea.

Baseline data relevant for route window NE1 are summarised in the table below.

Table 7.5: Summary of Baseline - Route Window NE1

Item Subject Details Id Drawing 1E0421-

1a Geology – Superficial deposits

Floodplain Gravels and Alluvium

1b Solid geology Lambeth Group above Chalk (from approx. 75 mATD)

2 Chalk groundwater levels Approx. 90 mATD (2003) E1E00-E00-F-00301

3 Groundwater quality Shallow: Non-potable Deep: Possibly marginally affected by saline intrusion

E1E00-E00-F-00301

4 Groundwater abstractions and protected rights

1 abstraction 99 E1E00-E00-F-00301

5 Groundwater protection zones

1 nr 50 day TTZ 4 nr 400 day TTZ

99 30*, 51*, 99,100*

E1E00-E00-F-00301

6a Main Rivers Waterworks River E1E00-E00-F-00201

6b Other watercourses Channelsea River E1E00-E00-F-00201

7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge 1 to balancing pond CANM.0517 E1E00-E00-

F-00201 10 Floodplains Flood Zone 3 The Thames E1E00-E00-

F-00201 * Well not within the route window

7.5.4 Impact Assessment

Chapter 4 and Section 7.4 describe route wide and route section wide impacts and generic mitigation measures respectively. In addition, route window specific impacts and mitigation measures have been identified and are described below. A summary is given in Appendix F.

(i) Groundwater

Temporary: Stratford station lies on the 400 day TTZ for a groundwater abstraction (Id 99). The site is underlain by superficial deposits and these are likely to be directly above the Lambeth Group.



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Good site practice would be implemented to avoid significant pollution of groundwater, particularly within the 400 day TTZ. Consultation with the well owners is currently taking place and appropriate monitoring, mitigation and compensation measures would be agreed as required. A specific risk is present as contamination may be mobilised from ground breaking works in land currently assessed as being polluted. However, this risk is assessed to be insignificant since there are no deep ground works to be constructed and the deep aquifer is protected by the Lambeth Group. Attenuation and dilution in the deep aquifer would reduce the risk further. If necessary, the scope of the contaminated land and geotechnical site investigations would include consideration of deeper boreholes to confirm the presence of low permeable strata of significant thicknesses to provide a sufficient barrier to migration of polluted water. Contaminated land remedial work would include suitable mitigation measures to protect groundwater and this is covered in the associated contaminated land technical report. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: None.

(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the Channelsea River which may be connected via existing drainage pipes or storm water sewers. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: None.

(iii) Residual Impacts

There would be no significant residual impacts from temporary or permanent works.

7.6 Route Window NE2 – Forest Gate Station


(i) Overview

The main works in this route window comprise platform extensions. The GEML platforms (island platforms two and three and platform one) would be extended westwards by 19 m to 205 m to accommodate 10-car Crossrail trains. Platform works would be carried out in conjunction with track realignments and signal work.

Works would be carried out from within the existing fenced boundary of the railway and include a small area to the south of the station for storage. This worksite would be accessed from Earlham Grove. The works would be serviced by an additional site on former railway land at the eastern end of Manor Park station.



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Figure 7.3: Route Window NE2 – Forest Gate Station


Overall, the construction works would take approximately 10 months to complete.


The total additional platform area would be around 270 m2 (0.027 ha). A pre-cast concrete or traditional platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m.

The drainage from the extended platforms would match the existing drainage system, and it is assumed (A.NE.3) that the drainage design would be appropriate to avoid any pollution of the deep groundwater aquifer.

7.6.3 Baseline Data

The superficial deposits of the route window comprise Floodplain Gravels and Taplow Gravels with unknown thicknesses. The London Clay is thought to be thin or possibly absent with the superficial deposits underlain directly by the Lambeth Group. The top of the Chalk is expected to be at approximately 80 mATD.

The water level in the Chalk aquifer was around 90 mATD in 2003. Groundwater quality in the deep aquifer is likely to be reasonable. There are two licensed groundwater abstractions within the route window. One abstraction is licensed to the London Borough of Newham (Id 30) for the purpose of makeup water and abstracts from the Chalk aquifer. Thames Water Utilities Ltd owns the other licence which was granted in March 2004 (Id 100). The station is



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within the 50 day TTZ of one abstraction (Id 100). There are two other 50 day TTZs (Id 30 and 101) and four 400 day TTZs (Id 30, 99, 100 and 101) extending into the route window.

There are no rivers, surface water abstractions or surface water discharges within route window NE2.





Taplow Gravels and Floodplain Gravels

1b Solid geology London Clay, Lambeth Group and Chalk (from approximately 80 mATD)

2 Chalk groundwater levels Approx. 90 mATD (2003)

E1E00-E00-F-00301

3 Groundwater quality Shallow: Likely to be non-potable Deep: Likely to be potable


2 abstraction licenses

30, 100 E1E00-E00-F-00301


3 nr 50 day TTZs 4 nr 400 day TTZs

30, 100, 101 30, 99, 100, 101

E1E00-E00-F-00301

6a Main rivers None 6b Other watercourses None 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10 Floodplains and flood levels None



(i) Groundwater

Temporary: Forest Gate Station lies on the 50 day TTZ for a groundwater abstraction (Id 100). The site is underlain by Terrace Gravels and the Chalk aquifer may be only protected by the Lambeth Group if the London Clay is absent.

Good site practice would be implemented to avoid significant pollution of groundwater, particularly within the 50 day TTZ. Consultation with potentially affected well owners is taking



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place and appropriate monitoring, mitigation and compensation would be agreed as required. A specific risk is present as contamination may be mobilised from ground breaking works in land currently assessed as being polluted. However, this risk is assessed to be insignificant since there are no deep ground works to be constructed and the deep aquifer is protected by the Lambeth Group. Attenuation and dilution in the deep aquifer would reduce the risk further. If necessary, the scope of the contaminated land and geotechnical site investigations would include consideration of deeper boreholes to confirm the presence of low permeable strata of significant thicknesses to provide a sufficient barrier to migration of polluted water. Contaminated land remedial work would include suitable mitigation measures to protect groundwater and this is covered in the associated contaminated land technical report. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no residual impacts.

Permanent: None.

(ii) Surface Water

Temporary: None.

Permanent: None.



7.7 Route Window NE3 – Manor Park Station


(i) Overview

The main works in this route window, which is located in LB Newham, comprise platform extensions. The GEML platforms (platforms one, two and three) would be extended westwards and eastwards by 22 m to 205 m to accommodate 10-car Crossrail trains. Platform one would be widened and the track that passes to the south of platform one (the ‘Up Independent Goods Loop’) would be removed from Forest Gate to east of Manor Park station. A replacement goods loop would be provided between Goodmayes and Chadwell Heath.

Platform works would be undertaken in conjunction with track realignments and signal works. The existing footbridge/walkway between platforms one and two/three would be modified with stairs to platform one.




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Figure 7.4: Route Window NE3 – Manor Park Station


Subject to possession planning requirements and excluding final commissioning, the construction works would take approximately one year to complete.


A pre-cast concrete or traditional platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m.

The drainage from the extended platforms would match the existing drainage system.

The existing footbridge/walkway would be modified. A pile depth of 10 m is assumed (A.NE.5) for assessment purposes.

The section of existing up goods loop track from Forest Gate junction to a point to the east of Manor Park platforms would be removed. The trackbed would be cleared and drainage cut back to suit the new platform layout. There would be excavations to allow for a 200 mm ballast depth.

7.7.3 Baseline Data

The geology of the route window comprises London Clay covered by Floodplain and Taplow Gravels, with the exception of the eastern part where the River Roding and associated floodplain cross the alignment. Here a borehole record shows that Alluvium is present and is expected to directly overlie the Lambeth Group. Thicknesses of the London Clay and gravel



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drift deposits are unknown. The top of the Chalk is expected to be at approximately 80 mATD.

In 2003 the Chalk groundwater level was around 90 mATD. There are two Thames Water abstraction licences granted in March 2004 (Id 100 and 101). There are two 50 day TTZs (Id 101 and 102) and four 400 day TTZs (Id 100, 101, 102 and 103) extending into the route window. Manor Park Station is located on the 400 day TTZ for one abstraction (Id 101).

The Alders Brook passes in the north eastern part of the route window. Flood Zone 3 extends into the east of the route window associated with the River Roding. There are no surface water discharges or abstractions within the route window.

A surface water sewer crosses from north to south under the station and it is likely to receive any piped surface water runoff from platforms and canopies or any piped track drains.





Terrace Gravels and Alluvium

1b Solid geology London Clay, Lambeth Group and Chalk (from apprx. 80 mATD)

2 Chalk groundwater levels Apprx. 90 mATD (2003) E1E00-E00-F-00301



2 abstraction licences 100, 101 E1E00-E00-F-00301


2 nr 50 day TTZs 4 nr 400 day TTZs

101, 102* 100, 101,102*, 103*

E1E00-E00-F-00301

6a Main rivers Alders Brook E1E00-E00-F-00201

6b Other watercourses None 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10 Floodplains Flood Zone 3 The Thames River Roding

E1E00-E00-F-00201

* Well not within the route window



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(i) Groundwater

Temporary: Manor Park station lies on the 400 day TTZ for a groundwater abstraction (Id101). The site is underlain by Terrace Gravels and London Clay of unknown thickness above the Lambeth Group and the Chalk.

Good site practice would be implemented to avoid significant pollution of groundwater, particularly within the 400 day TTZ. Consultation with potentially affected well owners is taking place, and appropriate monitoring, mitigation and compensation measures would be agreed as required. A specific risk is present as contamination may be mobilised from ground breaking works, especially any piled foundations for the modified footbridge, in land currently assessed as being polluted. However, this risk is assessed to be insignificant since any piles would be designed and constructed to avoid creating a potential pathway. Furthermore, there are no other deep ground works to be constructed and the deep aquifer is protected by the Lambeth Group. Attenuation and dilution in the deep aquifer would reduce the risk further. If necessary, the scope of the contaminated land and geotechnical site investigations would include consideration of deeper boreholes to confirm the presence of low permeable strata of significant thicknesses to provide a sufficient barrier to migration of polluted water. Contaminated land remedial work would include suitable mitigation measures to protect groundwater and this is covered in the associated contaminated land technical report. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: None

(ii) Surface Water

Temporary: None.

Permanent: None





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7.8 Route Window NE4 – Ilford Station


(i) Overview

The works include the provision of a new station building accessible from Cranbrook Road, York Place and Ilford Hill, and temporary tunnel fit out sidings on derelict land at the Aldersbrook sidings site to the west of the North Circular Road. The works to Ilford station would be undertaken within a railway cutting.


Figure 7.5: Route Window NE4 – Ilford Station

(ii) Ilford Station

The proposed station building would be located west of the existing building and would consist of a public concourse area in the existing station entrance to Cranbrook Road, a walkway along the north boundary extending over platform five, a main ticket hall and concourse area over the five tracks to access a new entrance from York Place, and the ramp area leading up from Ilford Hill. To accommodate longer Crossrail trains at Ilford station, platforms two, three and four would be extended westwards by 19 m to 205 m and platform four/five to 5 m in width. The proposed extension of platform four/five and the increase in platform width to accommodate the stair/escalator would require the realignment of track five. This would result in the shift northwards of track five and the widening of platform five. The existing ticket hall would be demolished.



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Works at Ilford station would be carried out from areas within the existing fenced boundary of the railway.

(iii) Aldersbrook Sidings

Crossrail would rebuild the disused Aldersbrook sidings to the west of Ilford station. These would be used during the construction phase as a tunnelling logistics site. The railway training school building would be demolished, a new road access would be provided. When rebuilt, the site would consist of six sidings, a widened embankment and a hard standing area.

Works at the Aldersbrook sidings logistic site would be carried out from within the existing fenced boundary of the railway and also on the adjacent disused training school site to the south of the GEML adjacent to the existing track towards London. It may be necessary to undertake strengthening works to the bridge over the Alders Brook.

(iv) Duration of Works

Subject to possession planning requirements and excluding final commissioning, the construction works at Ilford station would take around two years to complete and at Aldersbrook depot would take about one year and two months and would continue as a construction depot throughout the tunnelling works.


It is assumed (A.NE.6) that surface water runoff from the sidings area would be directed to the Alders Brook. It is also assumed (A.NE.6) that this drainage could be retained with appropriate modifications to carry any surface water that was not liable to contamination.

The existing Ilford Station has five platforms located in a cutting, all of which serve the GEML. A pre-cast concrete or traditional platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m. Drainage from the extended platforms would match the existing drainage system.

7.8.3 Baseline Data

The geology of the route window comprises London Clay overlain by Taplow Gravels, Brickearth, Floodplain Gravels and Alluvium. In Andrews et al (1995) it is suggested that a fault line runs along the River Roding where the route alignment crosses the river. London Clay is not present in a borehole adjacent to the River Roding which is likely to have been caused by erosion of the London Clay in a fault bounded block. The London Clay is expected to be thicker to the east of this fault. Brickearth deposits occur in the east of the area and are expected to overlie Taplow Gravels, where they are present.

The Chalk groundwater level was 80 to 90 m ATD in 2003. There are no licensed groundwater abstractions within the route window.



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The River Roding splits into two slightly north of the route window NE4 and the two branches flow through the route window and cross the route alignment; the smaller (Alders Brook) to the west of Ilford Golf Course and the main branch to the east of the A406, before meeting again at the southern boundary. The water quality of the River Roding at this location has a chemical GQA of D (fair) and a RQO of Grade 3. Flood Zone 3 crosses the route window. This is associated with the River Roding and the tidal River Thames. There are two surface water discharges, one licensed to Lattice Property Holdings (CTLR.0063) for public gas supply and one licensed to Thames Water (TEMP.1814) for a pumping station. Both discharge into the River Roding. There are no surface water abstractions within the route window.





Alluvium, Floodplain Gravels, Brickearth and Taplow Gravels

1b Solid geology London Clay over Lambeth Group (London Clay is absent around the River Roding)

2 Chalk groundwater levels Approx. 90 mATD (2003) E1E00-E00-F-00301



None


None

6a Main rivers River Roding Alders Brook

E1E00-E00-F-00201

6b Other watercourses None 7 River quality GQA: Fair (D)

RQO: Grade 3 River Roding

8 Surface water abstraction None 9 Surface water discharge 2 CTLR.0063

TEMP.1814 E1E00-E00-F-00201

10a Floodplains Flood Zone 3 Roding Thames

E1E00-E00-F-00201

10b Flood levels None available





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(i) Groundwater

Temporary: Good site practice would be implemented to avoid significant pollution of shallow groundwater, particularly since it could potentially migrate into the Alders Brook or River Roding. A specific risk is present as contamination may be mobilised from ground breaking works in land currently assessed as being polluted where associated with past rail construction work or with historical activities on the site, particularly the disused sidings. Contaminated land remedial work would include suitable mitigation measures to protect groundwater and this is covered in the associated contaminated land technical report. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: None.

(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of or runoff to surface waters, specifically the Alders Brook and River Roding which may be connected via existing drainage pipes or storm water sewers. Good site practice would also be important for the possible road bridge replacement over the Alders Brook. The worksite at Aldersbrook Sidings would be within the river buffer zone for Alders Brook, and, therefore, approval from the Environment Agency would be required as specified in the provisions for generic mitigation described in Appendix B. Surface runoff would be a special concern if the works at the sidings led to relatively large areas of exposed trackbed or earthworks compared to other sites. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: The Alders Brook could be contaminated from the increased operations of trains on the sidings. Use of the site by diesel powered construction trains and as a logistics site for tunnel fit out would increase the risk of further contamination compared to operation of electric trains. The track bed and drainage would be constructed so that no surface water would run off directly into the river, leading to no significant residual impacts.

It is predicted that, providing the strengthening works to the bridge over the Alders Brook do not change the span, headroom or soffit levels, there would be no residual flood risk. Following a condition survey of the bridge to find out what works are required, further consultation should be undertaken with the Environment Agency. The area designated for extension of the sidings would be significantly above the flood levels and there is no risk that any of the proposed works would impact on the floodplain of Alders Brook. Further explanation is provided in Appendix H.


There would be no significant residual impacts from permanent or temporary works.



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7.9 Route Window NE5 – Seven Kings Station


(i) Overview

Within this route window, two GEML platforms (island platforms two, three and platform four) would be extended westwards by 18 m to 205 m to accommodate 10-car Crossrail trains. Platform works would be carried out in conjunction with track realignments, OHLE and signal works.

The works at this station would be carried out from the existing fenced boundary of the railway on platforms four and two/three. The worksite would be located to the north west of the existing station within the grounds of Canon Palmer Catholic School.


Figure 7.6: Route Window NE5 – Seven Kings Station


Overall, the construction works would take approximately five months to complete.


The existing Seven Kings Station has four platforms located in a cutting, all of which serve the GEML. The total additional platform area would be around 180 m2 (0.018 ha). A pre-cast concrete platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m.



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The platform extensions would require cutting back of the cutting slope and extension of the existing retaining wall over a 15 m length. The drainage from the extended platforms would match the existing drainage system.

7.9.3 Baseline Data

The geology of the route window consists of London Clay overlain by Taplow Gravels and Brickearth.

In 2003 the Chalk groundwater level was 80 to 90 mATD. There are no licensed groundwater abstractions within the route window.

The Seven Kings River, a tributary of River Roding, crosses the route alignment to the east of Seven Kings Station apparently being piped at this location. However, the Flood Zone 3 associated with Seven Kings River crosses the route window. There are no surface water discharges or abstractions within the route window.





Brickearth and Taplow Gravels

1b Solid geology London Clay 2 Chalk groundwater levels 80 to 90 mATD (2003) E1E00-E00-

F-00301 3 Groundwater quality Shallow: Likely to be non-

potable Deep: Likely to be potable


None


None

6a Main rivers None 6b Other watercourses Seven Kings River (piped) 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10a Floodplains Flood Zone 3 Seven Kings River

E1E00-E00-F-00201

10b Flood levels None available



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(i) Groundwater

None.

(ii) Surface Water

Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the Seven Kings River which may be connected via existing drainage pipes or storm water sewers. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.



7.10 Route Window NE6 – Goodmayes Station


(i) Overview

The main works in this route window comprise platform extensions at Goodmayes station and the construction of the Chadwell Heath freight loop.




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Figure 7.7: Route Window NE6 – Goodmayes Station

(ii) Goodmayes Station

The platform extensions comprise the eastward extension of two GEML platforms (platforms two, three and four) by 16 m to 205 m to accommodate 10-car Crossrail trains. The construction works at Goodmayes station would take approximately five months to complete. The construction of the Chadwell Heath freight loop would partially overlap these works and would occur over a four month period. The construction works for the loop spans both this route window and Route Window NE7.

Works at the Goodmayes station worksite would be carried out from within the existing fenced boundary of the railway on platforms four and two/three. The worksite servicing activities on the site would be located on redundant railway land to the north east of the existing station next to platform one.

(iii) Freight Loop

The currently disused Goodmayes to Chadwell Heath freight loop would be reinstated to replace the goods loop at Manor Park. This work would include the removal of the existing redundant loop track. The trackbed would need to be lowered at the bridge at both Goodmayes and Chadwell Heath stations. Associated signalling works would take place, in addition to the installation of the crossover at the western end of the station. OHLE and signalling would then be installed. A new drainage system and a walkway would be installed adjacent to the tracks.

This track work would be carried out from within the existing fenced boundary of the railway to the south of the existing track. The main worksite would be located at the eastern end of the station with another to the south of the existing tracks at Goodmayes station.



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The existing Goodmayes Station has four platforms located in a cutting, all of which serve the GEML. The total additional platform area would be around 160 m2 (0.016 ha). A pre-cast concrete platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m. The drainage from the extended platforms would match the existing drainage system.

There would be minimal excavations for works to the goods loop, except to allow for a 200 mm ballast depth and the removal of tree roots. There appears to be no existing drainage on the GEML at this location and a small drainage pipe would be required alongside the new track. It is expected that this would be connected to the existing drainage.

7.10.3 Baseline Data

The geology of the route window consists of London Clay overlain by Taplow Gravels and Brickearth. Information from one borehole and geological maps indicates that the superficial deposits are approximately 8 m thick and the London Clay around 20 m thick.

In 2003 the groundwater level was 80 to 90 mATD. There are no licensed groundwater abstractions within the route window.

The Seven Kings River, a tributary of River Roding, crosses the route alignment to the east of Seven Kings Station. It is assumed (A.NE.7) that the river is piped at this point. Mayes Brook crosses the route alignment between Goodmayes and Chadwell Heath Stations. It also appears to be piped or may have been turned into a sewer. Flood Zone 3 associated with Seven Kings River crosses the route window.

There are no surface water abstractions or discharges within the route window.






1b Solid geology London Clay 2 Chalk groundwater levels 80 to 90 mATD (2003) E1E00-E00-




None


None

6a Main rivers None



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6b Other watercourses Seven Kings River (piped) Mayes Brook (piped)

E1E00-E00-F-00202

7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10a Floodplains Flood Zone 3 Seven Kings River

E1E00-E00-F-00202

10b Flood levels Not available



(i) Groundwater

None.

(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the Seven Kings River and Mayes Brook which may be connected via existing drainage pipes or storm water sewers. However, work would be within the existing track and would not lead to large areas of exposed earthworks. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: It is assumed (A.NE.8) that there would not be any change in surface runoff from the goods loop. There appears to be no existing drainage on the GEML at this location and a small drainage pipe would be required alongside the new track. It is expected that this would be connected to the existing drainage.





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7.11 Route Window NE7 – Chadwell Heath Station


(i) Overview

The main works comprise platform extensions to Chadwell Heath station and the construction of the Chadwell Heath freight loop.


Figure 7.8: Route Window NE7 – Chadwell Heath Station

(ii) Chadwell Heath Station

The GEML platforms two, three and four would be extended westwards by 16 m to 205 m to accommodate 10-car Crossrail trains. New platform furniture and lighting would be provided and minor station refurbishment works would be carried out.

Works at the station would be carried out from within the existing fenced boundary of the railway on platforms two/three and four. The worksite servicing activities on the site would be located within an existing car park off Valance Avenue.

(iii) Freight Loop

The currently disused single line to the south of the main lines would be reinstated to replace the goods loop at Manor Park. These works would include the removal of the existing redundant track. Once track beds are prepared and the new track is laid, OHLE and



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signalling would be installed. A new drainage system and a walkway would also be installed adjacent to the tracks.

The freight loop track work would be carried out from within the existing fenced boundary of the railway to the south of the existing track. The main worksite would be located at the eastern end of the station; a second would be located south of the existing tracks at Goodmayes station.


The existing Chadwell Heath Station has four platforms located in a cutting, all of which serve the GEML. The total additional platform area would be around 160 m2 (0.016 ha). A pre-cast concrete platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m. The drainage from the extended platforms would match the existing drainage system. The trackbed would need to be lowered at the bridge at both Goodmayes and Chadwell Heath stations.


The geology of the route window comprises London Clay discontinuously overlain by Taplow Gravels and Brickearth. The superficial deposits appear to have been locally eroded away in the area where Mayes Brook crosses the route alignment. The London Clay is likely to be about 20 m thick.

The Chalk groundwater level was around 90 mATD in 2003. There are two groundwater abstractions within the route window. One is licensed to Dairy Crest Ltd (Id 25) and abstracts from the deep Chalk aquifer for process water. The other is a protected groundwater right (Id 62) also owned by Dairy Crest. The associated 50 day and 400 day TTZs are all within the route window.

Mayes Brook crosses the route window in the north western corner. There are no surface water discharges or abstractions within the route window.






1b Solid geology London Clay 2 Chalk groundwater levels Apprx. 90 mATD (2003) E1E00-E00-

F-00302



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1 abstraction licence 1 protected right

25 62

E1E00-E00-F-00302



25, 62 25, 62

E1E00-E00-F-00302

6a Main rivers None 6b Other watercourses Mayes Brook E1E00-E00-

F-00202 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10 Floodplains None



(i) Groundwater

None.

(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the Mayes Brook which may be connected via existing drainage pipes or storm water sewers. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: A new drainage system would also be installed adjacent to the tracks at the Freight Loop. It is expected that this would be connected to the existing drainage. There would be no significant residual impact.





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7.12 Route Window NE8 – Romford Depot (West)


(i) Overview

The main works in this route window comprise the construction of a rail underpass in order to reduce conflicting movements between trains on the GEML and those moving to and from a new Romford depot. This would also require works to Jutsums Lane bridge.


Figure 7.9: Route Window NE8 – Romford Depot (West)

(ii) Romford Depot Underpass

At the west end of the site and to the east of the bridge over Whalebone Lane South, a new junction, including the tracks on the northern side of the alignment currently used by Metro services, would be created. The alignment of the GEML would be extended to the north to accommodate two tracks that would be used to access the depot site from the west. The works, involving provision of a widened embankment and a new retaining wall from Whalebone Lane South to the Jutsums Lane bridge, would require acquisition of the southern edge of the West Ham United FC training ground and part of Westland’s Playing Field. The two new tracks would continue to the eastern border of the West Ham United FC training ground where they would descend through a new rail underpass beneath the GEML before accessing the depot on the south side of the line.

The main construction works would comprise the following:



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• Construction of cuttings and embankments supported by retaining walls on the north and south sides of the Crossrail alignment from the area currently occupied by the gymnasium at the West Ham FC training grounds up to the position of the box. The embankment would be widened from east to west as piled, reinforced or un-reinforced slopes dependent on their height.

• Construction of a grade separated junction and underpass to allow Crossrail trains to pass between the north and south of the existing GEML railway track. The twin Crossrail tracks would run from a junction with the electric lines to the east of Whalebone Lane Bridge under the GEML and into the depot.

• Construction of a new bridge over Jutsums Lane to the south of the existing bridge on which Crossrail track would be constructed to enter and exit the depot and associated facilities.

The areas to be used for the construction of Romford depot (west) and Romford depot (east) form one continuous works corridor spanning both route window NE8 and NE9. Works to construct Romford depot (west) would be carried out from within the railway boundary and from two areas of land to the north and south of the existing tracks. To the north of the existing track part of the Westland’s Playing Fields would be used to construct the approach ramp and underpass and a section of adjacent open land would be used as a construction compound. To the south of the existing track, an area of open land to the rear of 208 Crow Lane would be used as a second construction area. In addition, there would be a worksite used specifically for the Romford gas pipeline diversions.

(iii) Jutsums Lane Bridge Works

Having passed through the new underpass, the two tracks would climb a new ramp to cross an extended bridge over Jutsums Lane. A new retaining wall and embankment would be constructed on the southern boundary of this new alignment. A new departures and arrivals road would also be constructed between Jutsums Lane and a point immediately east of the underbridge to allow access between the depot and the fast lines.


Subject to possession planning requirements and excluding final commissioning, the works to the underpass, along with the Jutsums Lane Bridge track works and facilities up to Romford Stadium, would take about four years and eight months. The construction of the depot itself, east of Romford Stadium, is detailed in route window NE9.


The Crossrail lines would be on the northern side of the GEML. Therefore, the approach to the site requires a grade separation of the approach lines from the GEML to link to Romford Depot which is on the southern side. Two additional tracks on the north side of the alignment would be constructed with a 1 in 43 gradient on a 400 m radius curve. The alignment within this route window is on an embankment estimated to be between 1 m and 3 m above the surrounding ground level. The existing embankment would need to be widened locally to



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accommodate the two additional tracks. The additional track would require drainage which would be designed in accordance with the appropriate Network Rail Design Standards. The surface water drainage proposals would utilise existing sewer systems, with consideration for SUDS solutions where appropriate. The presence of gravelly soils indicates that SUDS techniques could be considered.

The two additional tracks would pass under the GEML in a new diveunder structure. The approach ramps and the diveunder structure would have a length of approximately 700 m with 550 m in retained cut. This diveunder structure would comprise a 40 m by 17.5 m reinforced concrete box, through which the twin track Crossrail lines would pass. The box would be constructed off-line within a temporary works cofferdam or, possibly, a cutting, in Westlands Playing Fields. It would then be pushed into its final position. The clear height between the GEML track and the base of the box is estimated at just over 8 m; therefore, the excavation depth is likely to be up to 6 m deep (approx. 110 mATD).

A cantilever secant pile wall construction is understood as being appropriate for construction. A cement bentonite slurry wall cut off (to complete the box) would be required parallel to the embankment to form the box slide portal which could be easily demolished during the slide. Depending on the grading and permeability of the embankment fill and ground below the embankment, jet grouting could be used to provide groundwater cut-off in the temporary condition within the embankment. It is predicted that some groundwater control in the form of pumped wells would also be required to lower the watertable in the shallow aquifer in addition to the secant walls and cement bentonite slurry.

There are two drainage channels within the route window that would require diversion. Both run through Westland’s Playing Fields in open channels perpendicular to the railway. The western channel runs down to the railway, then runs along the toe of the embankment to join the eastern channel. The western channel would be diverted to run along the toe of the extended embankment. The eastern drainage channel runs down to the railway, then is culverted beneath the railway line at the approximate position of the proposed grade separation box structure. Next to the eastern drainage channel is a subsurface, 900 mm diameter trunk water main owned by Essex and Suffolk Water. Both the channel and the water main would have to be permanently diverted. It is assumed (A.NE.9) that eastern drainage channel would be diverted through a pipe culvert beneath the proposed Crossrail lines and the existing GEML since the alternative option with an inverted siphon would require higher maintenance. However, the final design has not yet been confirmed.

Pumping from the shallow aquifer would be required during construction. It is proposed to provide a pumping station, with a reservoir if required, on the south side of the GEML embankment. This would enable any water entering the structure to be pumped away into the existing pipe which runs between Nr 208 and Nr 218 Crow Lane. This is based on the assumption (A.NE.10) that Thames Water would accept the water into their surface water drainage system.

To the east of the diveunder the line returns to the level of the main line on a 1 in 43 gradient to allow it to pass over a new bridge to be constructed spanning Justums Lane. The bridge is likely to require construction to a depth of up to approximately 1.5 m, and piling to greater depths may be required depending on the ground conditions and chosen design.



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The geology of the route window consists of London Clay discontinuously overlain by Taplow Gravels and Brickearth. The London Clay is expected to be moderately shallow. However, information from boreholes around the proposed work site shows that the superficial deposits comprise Made Ground (0.3 m to 2 m thick) and River Terrace Deposits (4 m to 7 m thick). The London Clay is generally 4 m to 9 m below ground level (expected to be approximately 115 mATD at the base of the embankment). Shallow groundwater levels were recorded between 1.2 mBGL and 5.1 mBGL. The Chalk groundwater levels were about 90 mATD in 2003.

There is one protected groundwater right owned by Dairy Crest Ltd (Id 62). It is assumed (A.NE.11) that abstraction is taking place from the Chalk. There are two 50 day and two 400 TTZs (Id 25 and 62) extending into the south-western corner of the route window.

As described above, the two drainage channels join and pass in a small pipe culvert beneath the railway line at the approximate position of the proposed grade separation box structure. It is assumed (A.NE.12) that the pipeline continues down to the minor road parallel to the railway and joins into the sewer system. The eastern stream is thought to become a sewer to the south (which could be associated with the former Wantz Stream). The water quality in the existing channels is unknown and it is unlikely that any records exist. The channels are likely to be hydraulically connected to groundwater in the shallow aquifer.

There are two surface water discharges. Both are licensed to Thames Water (TEMP.2049 and TEMP.0794) for pumping stations and both discharge into Wantz Stream. The route window does not lie on a floodplain, however, although not indicated in associated documentation, localised flooding may occur adjacent to the drainage ditches in Westlands Playing Fields.






1b Solid geology London Clay 2 Chalk groundwater levels 90 mATD E1E00-E00-




1 abstraction licence 62 E1E00-E00-F-00302



25*, 62 25*, 62

E1E00-E00-F-00302

6a Main rivers None 6b Other watercourses Two minor drainage E1E00-E00-



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channels F-00202 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge 2 TEMP.2049

TEMP.0794 E1E00-E00-F-00202

10 Floodplains None * Not located within the route window



(i) Groundwater

Temporary: It is predicted that some pumping from the shallow aquifer would be required during construction of the diveunder. The amounts pumped during construction of the approach ramps would vary depending on the depth and type of retaining wall and floor slab. Where foundations are deep enough, the walls would act as a lateral cut off and where the foundations are shallow, groundwater would continue to flow under the structure. At intermediate locations dewatering and grouting may be required. The underpass structure itself would be constructed off line from GEML in an area isolated from the shallow aquifer by a cut off wall. The impact of dewatering is assessed to be significant due to the amount of drawdown required. However, the volumes of water to be pumped are predicted to be modest, there are no abstractions that would be affected and it is probable that the water can be returned to the surface water culverts or ditches (which would have a similar water quality since they are hydraulically connected) providing the turbidity is treated to a suitable level Good practice covering dewatering and effluent disposal would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: The diveunder and approaches would provide a barrier to flows in the surface aquifer over a length of a maximum length of approximately 550 m. A rise and fall in the groundwater levels of around 2 m in the shallow aquifer would be expected on opposite sides of, and 20 m away from, the structure. However, the flows are likely to be low and would redistribute elsewhere. Changes to groundwater levels would be mitigated by the existing cut off ditch running along the north side of the railway which would be realigned leading to no significant residual impacts.

A slight reduction in natural infiltration would be expected from the change to land surfaces in areas underlain by the new base slab. The amount of water infiltrating into the shallow gravels would be maintained where possible through the use of an appropriate technique for discharging surface water with measures to control run off intensity, which would ensure that no significant adverse impacts would occur.



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(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the two surface ditches north of the railway and their outfall. This would be a special concern during the works to the diveunder and approach ramps where there would be relatively large areas of exposed earthworks compared to other sites. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

There would be a temporary impact caused by diverting the surface drains and the water pipeline potentially leading to local flooding upstream of the GEML. Storage, pump sizes and diversion pipe diameters would be selected carefully and the provisions for generic mitigation described in Appendix B would be applied as appropriate to mitigate the impacts. Consultation with Thames Water and the Local Authority would be undertaken and an acceptable solution developed during the detailed design. There would be no residual impact.

Permanent: Extending the embankment and additional track drainage would possibly lead to an increase in surface water runoff. The drainage would be designed to control runoff intensity. The use of SUDS techniques would be considered at the detailed design phase to achieve this. However, if additional water is discharged to sewer this would lead to a reduction in sewer capacity. Consultation with Thames Water has been initiated.


There would be no significant residual impacts from temporary or permanent works. There would be a minor, temporary, non significant residual impact on groundwater levels in the shallow aquifer caused by dewatering for construction of the diveunder. There would also be a minor, permanent, non significant residual impact on groundwater levels in the shallow aquifer caused by the diveunder acting as a barrier to groundwater flow.

There would be minor, temporary and permanent, non significant residual impact on surface water flows caused by increased runoff.

7.13 Route Window NE9 – Romford Station and Depot (East)


(i) Overview

The main works in this route window would consist of a new depot and stabling sidings located on the old goods yard site to the west of Romford station and on the south side of the GEML. In addition, the works would include a rebuild and extension to Romford station.




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Figure 7.10: Route Window NE9 – Romford Station and Depot (East)

(ii) Romford Depot (East)

The new maintenance depot building would be constructed between Sandgate Close and Nursery Walk and to the north of the Gas Works site. It would consist of eight covered tracks in a building 260 m in length, 68 m wide and up to 12 m high. The total floor space of the depot is 22 000 m2.

To the north east of the building on an area of land to the north of Old Church Hospital and bounded to the east by Waterloo Road, an additional 10 tracks would be constructed to stable trains. To accommodate the stabling sidings, the pedestrian underpass that carries Nursery Walk beneath the site would be extended.

The works would involve:

• Installation of two temporary sidings for excavated materials handling and removal and importation of fill material.

• Removal of existing track, ground treatment or removal or capping to deal with contaminants.

• Earth works and construction of retaining walls to raise the area upon which the new sidings would be built. The reinforced retaining walls would be constructed on piled foundations around the perimeter of where the sidings would be constructed.

• Construction of a secondary access point to the east of the depot site that would be constructed to provide access from the depot, across the GEML lines to the electric lines.

• Ten stabling sidings would then be constructed. The sidings would be arranged in pairs and walkways would be constructed between them.



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• Construction of a wheel lathe facility, train washing facilities and a paint shed and associated sidings connecting to the depot access track and to the GEML.

• Construction works to Nursery Walk underpass. The walkway would be extended between Nursery Walk and Stockland Road constructed using pre-cast concrete arches on reinforced concrete abutments founded on piles.

• Installation of the depot control room and OHLE facilities.

• Construction of the maintenance sidings and the associated depot building.

• Construction of a wheel lathe facility, train washing facilities and a paint shed and associated sidings connecting to the depot access track and to the GEML.

The areas to be used for the construction of Romford depot (west) and Romford depot (east) form one continuous works corridor spanning both route window NE8 and NE9. Works taking place to construct Romford depot (east) would be carried out from land within the railway boundary, from land to the south of the existing tracks that is currently occupied by a part of the Royal Mail sorting office parking area, derelict land and a part of the local gas works yard. The eastern part of the main site for the Romford depot (east) works would be located within railway land at the western end of Atlanta Boulevard.

(iii) Romford Station

To accommodate longer Crossrail trains, platform five would be extended westwards by 18 m to 205 m, to accommodate an overall train length of 200 m. The island platforms three/four would be extended by 21.5 m. The existing ticket hall is too small to satisfy the requirements of a principal station. A new ticket hall and associated staff accommodation would be developed on the site as an extension to the original ticket hall. The River Rom passes beneath the western end of the station.

A platform extensions works area would be located in an existing car park on the southeastern corner of Exchange Street and would be used for platform extensions and bridge construction works over the River Rom.


Subject to possession planning requirements and excluding final commissioning, the construction of Romford depot (east) would take about five years and six months.

Subject to possession planning requirements and excluding final commissioning, the construction at Romford station would take about two years.


Romford Maintenance Depot: The building is positioned on an area which is lower than the rest of the site. The existing railway is on an embankment typically 3 m to 4 m above the level of the land immediately to the north. To avoid a steep gradient on the tracks approaching the building, the depot floor would be approximately 3 m to 4 m above the



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existing ground level. Depending on the building loads and ground conditions, shallow foundations could be used for the building structure. In order to provide groundwater cut off and prevent migration of contamination, use of a slurry wall cut off would be considered around the perimeter of the site.

New surface and foul water drainage would be installed at the depot site. Surface water drainage proposals would utilise existing sewer systems, with consideration for SUDS solutions where appropriate. Foul runoff generated by the site would be conveyed to existing and/or new sections of sewer. In some locations, such as the carriage washing facility, recycling of wash water would be undertaken. It is assumed (A.NE.13) that the floor of the maintenance building would contain an impermeable membrane to prevent infiltration of contaminated water into the underlying surface aquifer. Trains would be washed prior to entering the maintenance building.

Proposed utilities works would require a sewer to be diverted (AW/051, see Appendix G) to the west at Waterloo Road. Track works would also require the diversion of two high pressure gas pipes (AW/046 and 047, see Appendix G), which commence to the west of Romford diveunder and lead to Romford Gasworks. Towards the existing depot, the proposed maintenance depot intersects with a Gasworks pressure reduction station; this station would need moving to the current location of the northernmost gas holder, which would in turn be demolished. Construction of the diversion would be in open cut with pipejacking under the railway itself at a depth of 1-2 m. Gas storage facilities would need replacing.

Romford Station: The northern platform extension would be built over an existing culvert of the River Rom, between the end of the brick viaduct supporting the station and the embankment and retaining wall. The void to be spanned is approximately 8 m long by 4 m wide. Excavations would be required for the footing on the viaduct and within the railway embankment. At present, it is assumed (A.NE.14) that these would be relatively small excavations, with an estimated volume of approximately 15 m3 and it is assumed (A.NE.15) that the platform extension would be supported by a single span with concrete pad foundations. The depth of excavation required for the emergency escape bridge would be decided once the condition of the existing soil behind the wall was established, but for the purpose of this assessment 300 mm piles to a depth of 10 m are assumed (A.NE.16).

All excavations would be less than 0.5 m below the lowest level of the track foundation; the lowest level of the foundations being at the top of the existing retaining wall. The retaining wall on the north side of the station may need to be increased in height to support the platform extension. Waterproofing and surfacing would be applied to the new platform extensions and drainage would be installed at the back of the platform.

At the northern end of the station, works for new steelwork frames would require new footings, probably using mini piling techniques. At the southern end there are a number of brickwork arches which are partially backfilled with earth and contained by a retaining wall. Significant temporary works would be required to stabilise the existing wall above the arches. Two new MIP lifts are proposed and these would be supported by a steelwork frame and founded upon an in situ concrete pit.



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The geology of route window NE9 comprises mainly London Clay overlain by Taplow Gravels. However, the Taplow Gravels are absent in a narrow area around the River Rom where London Clay is exposed and partly overlain by Recent Alluvium (river deposits).

Results from a recent geotechnical desk study shows that the geology of the west and northern end of the route window comprises Made Ground, overlying Taplow Gravels and London Clay. The thickness of the Taplow Gravels is reasonably consistent (approximately 5 m), with the London Clay being 6 m below ground level.

The geology of the eastern part of the site along Waterloo Road generally comprises between 0.3 m and 2.0 m of Made Ground and topsoil, overlying 4 m to 7 m of River Terrace Deposits. London Clay is typically 4 to 9 m below ground level. The River Terrace Deposits tend to thicken (approximately 7 m thick) north of the railway embankment, and gradually decrease to 4 m thick at Oldchurch Road. Localised pockets of Alluvium 0.3 m to 0.9 m thick are found on top of the River Terrace Deposits.

At Romford Gas Works, the following geological sequence was recorded:

Table 7.13: Geological Sequence at Romford Gas Works

Thickness (m) Geological Sequence Minimum Maximum

Made Ground 0.3 0.6 Alluvium 0 0.9 River Terrace Deposits

3.6 3.9

London Clay 12.3 16.8 Thanet Sands1) 29.5 34 Upper Chalk >100 >100

1) Likely to be the combined thickness of the Lambeth Group and Thanet Sands

In 2003, Chalk groundwater levels in this area were around 90 mATD, with the groundwater flowing into a piezometric depression in the west. At Romford Gas Works, shallow groundwater was recorded at between 1.2 mBGL to 1.8 mBGL. A single protected groundwater right is located at a hospital on Waterloo Road (Id 61). The current purpose and aquifer type are unknown; however, the well was formerly used for a brewery in Waterloo Road. It is assumed (A.NE.17) that abstraction is taking place from the Chalk. The TTZ to this well is within the route window but does not cross the alignment.

The River Rom (and its associated floodplain) crosses the route alignment within this route window. It passes just west of the station in a culvert. In this reach, the River Rom has a chemical GQA of E (poor) and a RQO of Grade 4. There is also a minor tributary which is assumed (A.NE.18) to run in a pipe or sewer to the north of the alignment. The flood levels have been calculated as part of the River Beam model (Environment Agency 2003) and the 100-year flood level around Romford Station has been calculated as 111.56 mATD.

There are two surface water discharges licensed to Romford United Reformed Church (CEMR.0160) and to M Ronchetti (CANM.0500). They both discharge into the River Rom



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system. There is one surface water abstraction in the River Rom system. The abstraction is located 2 km downstream of the station and is licensed to Ford Motor Company for process water (licence no 08/37/55/0091).





Alluvium and Taplow Gravels

1b Solid geology London Clay 2 Chalk groundwater levels 90 mATD (2003) E1E00-E00-




1 protected abstraction right 61 E1E00-E00-F-00302


1 nr 50 day TTZ 1nr 400 day TTZ

61 E1E00-E00-F-00302

6a Main rivers River Rom E1E00-E00-F-00202

6b Other watercourses Minor tributary of River Rom 7 River quality GQA: Poor (E)

RQO: Grade 4 River Rom

8 Surface water abstraction 1 in River Rom 08/37/55/0091* E1E00-E00-F-00202

9 Surface water discharge 2 CEMR.0160 CANM.0500

E1E00-E00-F-00202

10a Floodplains Station - Flood Zone 3 Depot – none

River Rom E1E00-E00-F-00202

10b Flood levels Modelled to 111.56 mATD River Rom * Not located within the route window



(i) Groundwater

Temporary: Locally contaminated land or groundwater is likely to be associated with the old stabling site and in particular the gas works site. Works could lead to mobilisation of contaminants that could contaminate the shallow groundwater and potentially migrate from the shallow groundwater into the River Rom. However, it is proposed to carry out further



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investigations and consider alternative design solutions including possible installation of a slurry cut off wall to prevent migration of contaminants. Contaminated land remedial work would include suitable mitigation measures to protect groundwater and this is covered in the associated contaminated land technical report. This would lead to a non-significant impact. No groundwater abstractions would be affected as the single abstraction (Id 61) is assumed (A.NE.17) to abstract from the Chalk.

Permanent: None.

(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the River Rom. This would be a special concern during the works for the platform extension and road bridge over the existing lined channel and because the works at the depot would lead to relatively large areas of exposed trackbed or earthworks compared to other sites and the depot area may be drained by pipes or ditches to the river. The worksite at Romford Station would be within the buffer zone of the River Rom, and, therefore, approval from the Environment Agency would be required as specified in the provisions for generic mitigation described in Appendix B. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

The station is located on the floodplain to the River Rom. However, the topographic data shows the track at approximately 122 mATD, which is significantly above the modelled 111.56 mATD level of the 100 year+20% flood event. Therefore, there is no risk that any of the proposed temporary works would impact on the floodplain of the River Rom.

Permanent: The construction of a depot building would lead to a significant increase in surface water run-off and foul water discharged to sewer, which would lead to a reduction in available sewer capacity. The additional runoff would be attenuated to acceptable flow rates and any soakaways would be sited taking into account the measures used to mitigate the ground contamination. Consultation with Thames Water has been initiated.

The potential impacts on surface water runoff from the proposed station modifications are assessed as being not significant. The detailed design would incorporate measures to control runoff intensity taking into account the performance of any existing track drainage and would determine if this is piped to an outfall or to sewer. Consultation with Thames Water has been initiated.

As described in Appendix H, the platform extension and the proposed new bridge can be achieved without any effect on the hydraulic performance of the River Rom. This is because the soffit of the new deck would be placed well above 100 year+20% flood water level and no changes made to the wetted channel.


Contaminated land remedial work at the proposed Depot and provision of drainage would avoid further degradation of shallow groundwater quality and the water quality in the River Rom. However, there would be a risk of a minor, temporary, non significant residual impact.



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7.14 Route Window NE10 – Gidea Park Station


(i) Overview

The main works in this route window comprise platform extensions. The eastern end of two GEML island platforms (platform 3 and platform 4) would be extended eastwards by 22 m to 205 m to accommodate 10-car Crossrail trains. New platform furniture and lighting would be provided and minor station refurbishment works would be carried out. Works at this station would be carried out from within the existing fenced boundary of the railway on platforms three and four. It is proposed that the worksite would occupy the whole of the station car park.


Figure 7.11: Route Window NE10 – Gidea Park Station


Construction at Gidea Park station would take place over approximately three months.


The existing Gidea Park Station has four platforms located in a cutting, all of which serve the GEML. The total additional platform area would be around 110 m2 (0.011 ha). A pre-cast concrete or traditional platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of



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approximately 1 m. The drainage from the extended platforms would match the existing drainage system.


The geology of the route window consists of London Clay, in areas overlain by recent Boyn Hill Gravels.

The Chalk groundwater level was around 90 mATD in 2003. There are no licensed groundwater abstractions within the route window.

River Ravensbourne, a tributary of River Rom, runs in the south-eastern part of the route window and the River Rom in the north western part. They do not cross the route alignment within this route window.

There are three surface water discharges within the route window. The first is licensed to Thames Water (TEMP.1454) for a pumping station and discharges into the River Rom. The second is licensed to Mclean Homes North London Ltd (CEUR.0052) and discharges into the River Ravensbourne. The purpose of the discharge is undefined. The third surface water discharge is licensed to London & Quadrant Housing Trust (CENR.0108) for multiple domestic property and also discharges into the River Ravensbourne. There are no surface water abstractions within the route window.





None

1b Solid geology Boyn Hill Gravels and London Clay

2 Chalk groundwater levels 90 mATD (2003) E1E00-E00-F-00302



None


None

6a Main rivers River Ravensbourne River Rom

E1E00-E00-F-00202

6b Other watercourses None 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge 3 TEMP.1454

CEUR.0052 E1E00-E00-F-00202



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CENR.0108 10 Floodplains Flood Zone 3 River Rom

River Ravensbourne



(i) Groundwater

None.

(ii) Surface Water

None.



7.15 Route Window NE11 – Gidea Park Stabling Sidings


(i) Overview

The proposed Crossrail works at Gidea Park involve the extension of existing sidings and provision of new sidings in order to provide stabling for Crossrail trains.




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Figure 7.12: Route Window NE11 – Gidea Park Stabling Sidings

(ii) Gidea Park Stabling Sidings

Crossrail’s stabling sidings at Gidea Park would include the rebuilding of the existing sidings which lie in a shallow cutting to the east of Upper Brentwood Road. The existing sidings would be extended northwards with three new tracks provided. In total, seven sidings would be provided for Crossrail trains, each 240 m in length. All works would be undertaken in existing railway land and a new retaining wall constructed on the northern boundary.

After site set up and construction of the access road main works would be carried out as follows:

• Extension of the existing culvert where the sidings cross over Ravensbourne Brook constructed using reinforced concrete slabs on piled foundations.

• Installation of piles between Cambridge Avenue and the River Ravensbourne and extension of the existing retaining wall to accommodate the length of the new sidings followed by removal of a strip of ground in front of the extended retaining wall to track level.

• Removal of the existing OHLE and excavation and preparation of the trackbeds adjacent to the new retaining wall followed by installation of four new single ended sidings to the north of the existing double ended sidings.

• Signalling and OHLE would be installed in stages to suit the track realignments and the new sidings during the track works.

The Gidea Park stabling sidings would be constructed to the north of the electric lines immediately to the east of Gidea Park station. Works would be carried out from within the existing railway boundary.



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(iii) Duration of Works

Subject to possession planning requirements and excluding final commissioning, the construction works at Gidea Park stabling sidings would take approximately one year and eight months to complete.


Earthworks would be required for the construction of the four sidings to the north of the site. The existing sidings would be removed, an existing retaining wall would be extended and new sidings, turnouts and connections installed, along with new drainage. Piling operations would be to a depth greater than 0.5 m below the lowest track foundation.

Bridge works would be required over the River Ravensbourne. At present, the river approaches the tracks in a concrete channel and it is assumed (A.NE.19) at this stage that the watercourse passes underneath the tracks in a concrete box culvert structure. The existing 54 m long culvert under the railway would be extended to allow four additional tracks to cross. The new extension structure would be independent of the existing channel lining and walls since the condition of the existing culvert is unknown.

Drainage of the existing sidings has not been studied in detail. However there is a pipe discharging into the Ravensbourne Brook and it is likely that all rainwater collected on railway land is discharged to this watercourse. 250 mm diameter track drainage would be provided at a depth of between 1 m and 1.5 m below rail level, this would be connected into the existing drainage. The drainage to the new sidings would probably be directed to the Ravensbourne Brook assuming (A.NE.20) that no unacceptable risk of contamination is determined.


The geology of the route window consists of London Clay; in areas overlain by recent Boyn Hill Gravels.

The Chalk groundwater level was around 90 mATD in 2003. There are no licensed groundwater abstractions within the route window.

The sidings cross the River Ravensbourne on a culvert or bridge. The Flood Zone 3 crosses the route window and the flood levels in the Ravensbourne have been calculated as part of the Beam model (Environment Agency 2003). The 100-year flood levels were calculated to be 128.33 and 128.51 mATD downstream and upstream respectively where the alignment crosses. Alternative results from a model in 2004 gave levels of 129.24 and 130.09 mATD.

There are two surface water discharges, one licensed to Mclean Homes North London Ltd (CEUR.0052) and one licensed to Thames Water (TEMP.2025) for a pumping station which discharges into the Ravensbourne. There is one surface water abstraction in the River Rom system. It is located 10 km downstream of the alignment and is licensed to Ford Motor Company for process water (licence no 08/37/55/0091).




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Table 7.16: Summary of Baseline – Route Window NE11



None or thin layer of Made Ground


2 Chalk groundwater levels 90 mATD (2003) E1E00-E00-F-00302



None


None

6a Main rivers E1E00-E00-F-00202

6b Other watercourses River Ravensbourne E1E00-E00-F-00202

7 River quality Not applicable 8 Surface water abstraction 1 08/37/55/0091* E1E00-E00-

F-00202 9 Surface water discharge 2 CEUR.0052

TEMP.2025 E1E00-E00-F-00202

10a Floodplains Flood Zone 3 Ravensbourne 10b Flood levels Modelled from 128.33 to

130.09 mATD Ravensbourne

* Not located within the route window



(i) Groundwater

Temporary: Contamination has been assessed as being locally present at the old stabling site and a specific risk exists because contaminants could migrate into the River Ravensbourne. The provisions for generic mitigation described in Appendix B sets out measures to remediate this contamination and there would be no residual impacts.

Permanent: None.



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(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the River Ravensbourne which may be connected via existing drainage pipes or storm water sewers. This would be a special concern during the works to the culvert and if the works at the sidings led to relatively large areas of exposed trackbed and earthworks compared to other sites. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and, therefore, there would be no significant residual impacts.

There is limited potential that the works to the river crossing would lead to a temporary loss of flood storage capacity while a new deck over the existing channel is installed. However, the application of measures described in Appendix B would ensure that no significant impacts occur.

Permanent: The River Ravensbourne could be contaminated from the increased operations of the trains on the sidings on the culvert extension. The track bed would be constructed so that no surface water would run off directly into the river leading to no significant residual impacts.

The detailed design would take into account the performance of any existing track drainage in the sidings area and determine if this is piped to an outfall or to sewer. However, the existing drainage system at the siding area would be upgraded, which is likely to lead to minor increase in runoff. Design of any soakaways would take into account the likelihood of historic contamination. Further discussions with the Environment Agency and Network Rail would take place as part of the detailed design to determine if there are any consents or permits need to be revised.

As described in the Flood Risk Assessment (see Appendix H), it is possible that there would be a small increase in headloss due to 16 m length of new culvert proposed during the 100 year+20% flood event. This can be mitigated by appropriate detailed design including improvements to the entry and exit conditions to the culvert. Consultation with the Environment Agency would be undertaken during the detailed design.

Appendix H also describes how the Ravensbourne 100 year flood levels, from the Agency’s Washlands 2004 catchment modelling, are partly above the elevation of current land on which the proposed sidings would be constructed to the east of the river. There may be minor filling of the floodplain around the existing culvert walls and also some displacement of flood storage. This is subject to model verification and detailed design, so it is registered as a concern, but it is expected that the residual risk would not be significant.

Work would take place within the buffer zone and as required by the provisions for generic mitigation described in Appendix B, consultation with the Environment Agency would be undertaken.


The scale of the works to the bridge over the River Ravensbourne makes it likely that there would be a temporary impact on the surface water flow. In the permanent condition, there



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would be some minor filling around the existing culvert. These are assessed as non significant impacts.

7.16 Route Window NE12 – Harold Wood Station


(i) Overview

The main works in this route window comprise platform extensions. Two GEML platforms (platform three and platform four) would be extended eastwards by 38 m to 205 m to accommodate 10-car Crossrail trains. In addition, new platform furniture and lighting would be fitted and minor station refurbishment works would be carried out. Construction works would be carried out from within the existing fenced boundary of the railway on platforms two/three and four.


Figure 7.13: Route Window NE12 – Harold Wood Station


The works would take approximately four months to complete


The total additional platform area would be around 460 m2 (0.046 ha). A pre-cast concrete or traditional platform system would be used, supported on load bearing beams and founded on



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individual mini piles or mass concrete strips with excavation depths of approximately 1 m. The drainage from the extended platforms would match the existing drainage system.


The geology of the route window consists of London Clay overlain by recent Boyn Hill Gravels localised around Harold Wood Station. A narrow band of Alluvium is present in an area in the vicinity of the River Ingrebourne.

The Chalk groundwater level was between 90 and 100 mATD in 2003. There are no licensed groundwater abstractions within the route window.

The River Ingrebourne crosses the route alignment 600 m east of Harold Wood Station. Paine’s Brook (or Carter’s Brook) joins the River Ingrebourne just north of the route alignment. The chemical GQA of the River Ingrebourne in this reach is classed as fair (Grade D), with a RQO of Grade 3. Flood Zone 3 associated with both rivers is present within the route window. The flood levels in the Ingrebourne have been estimated as part of the Ingrebourne model (Environment Agency, 2003). The 100-year flood levels around the location where the alignment crosses have been calculated to between 125.83 and 126.42 mATD.

There are three surface water discharges, two at the same location are licensed to Thomas Bates & Son Ltd (CEER.0009 and CEXR.0165) and one is licensed to Thames Water (TEMP.2414) for sewerage disposal works. Both discharge into the River Ingrebourne. There are two surface water abstractions in the River Rom system. The abstractions are located 3.5 and 7 km downstream of the route alignment and are licensed to Upminster Golf Club (licence no. 08/37/55/0045) and AC Tuner & Son (licence no. 08/37/55/0080), both for spray irrigation purposes.





Alluvium in places


2 Chalk groundwater levels 90 to 100 mATD E1E00-E00-F-00302



None


None



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6a Main rivers River Ingrebourne Paines Brook/Carter’s Brook

E1E00-E00-F-00202

6b Other watercourses None 7 River quality GQA: Fair (D)

RQO: Grade 3 Ingrebourne

8 Surface water abstractions 2 08/37/55/0045* 08/37/55/0080*

E1E00-E00-F-00202

9 Surface water discharges 3 CEER.0009 CEXR.0165 TEMP.2414

E1E00-E00-F-00202

10a Floodplains Flood Zone 3 River Ingrebourne Paines Brook

E1E00-E00-F-00202

10b Flood levels Modelled to 125.83 to 126.42 mATD

River Ingrebourne

* Not within the route window



(i) Groundwater

None.

(ii) Surface Water

None.



7.17 Route Window NE13 – LB Havering/Brentwood DC Boundary


No Crossrail works would take place in this route window.




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Figure 7.14: Route Window NE13 – LB Havering/Brentwood DC Boundary


The geology of the route window comprises London Clay, covered in places by Glacial Gravels and Boulder Clay. Alluvium overlies the London Clay along the River Ingrebourne parallel to the route alignment.

The Chalk groundwater level was between 90 and 100 mATD in 2003. There are no licensed groundwater abstractions located within the route window.

The River Ingrebourne and associated Floodplain Zone 3 flows parallel to the north of route alignment in the eastern part of route window NE13. The water quality of the river within the route window varies between a chemical GQA score of good (B) and a Grade 2 RQO in the upstream reach, to a GQA of Fair (D) and a Grade 3 RQO in the down stream reach. A minor tributary of the River Ingrebourne crosses the route alignment under the M25.

There are six surface water discharges. Three of the discharges are licensed to Thames Water for sewerage disposal works (TEMP.2414, CSSC.0328, and CELR.0048) and a further two are licensed to Thames Water for pumping stations (TEMP.1558 and TEMP.0549). All five discharge into the River Ingrebourne. The sixth surface water discharge is licensed to Total Fina Elf UK Ltd (CANM.0025) for retail filling stations and discharges to land via a soakaway.

There are two surface water abstractions in the Ingrebourne river system. The abstractions are located 3.5 and 7 km downstream and are licensed to Upminster Golf Club (licence no. 08/37/55/0045) and AC Tuner & Son (licence no. 08/37/55/0080), both for spray irrigation purposes.




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Boulder Clay and Glacial Gravels

1b Solid geology London Clay 2 Chalk groundwater levels 90 to 100 mATD E1E00-E00-




None


None

6a Main rivers River Ingrebourne E1E00-E00-F-00202

6b Other watercourses Minor tributary of the Ingrebourne

E1E00-E00-F-00202

7 River quality GQA: Fair (D) to good (B) RQO: Grade 2 to 3

Ingrebourne

8 Surface water abstraction 2 08/37/55/0045* 08/37/55/0080*

E1E00-E00-F-00202

9 Surface water discharge 6 TEMP.2414, CSSC.0328 CELR.0048 TEMP.1558 TEMP.0549 CANM.0025

E1E00-E00-F-00202

10 Floodplains Flood Zone 3 Ingrebourne E1E00-E00-F-00202

* Not within the route window


No physical works are currently identified in route window NE13.

(i) Groundwater

None.

(ii) Surface Water

None.



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7.18 Route Window NE14 – Brook Street




Figure 7.15: Route Window NE14 – Brook Street


The geology of the route window comprises London Clay. Bagshot Beds and the Claygate Beds (sand and loam) overlie the London Clay in the south-west part of the route window.

The Chalk groundwater level was around 100 mATD in 2003. A single groundwater abstraction is located in the route window, which is licensed to Bloomfield (Id 42). This source abstracts from the river gravels for the purpose of general farming and domestic use. The associated TTZs are within the route window but are not crossing the alignment. The water levels and water quality in the shallow aquifer in this area are unknown.

The Ingrebourne and a minor tributary cross the route alignment. The chemical GQA of the Ingrebourne is good (Grade B), with a RQO of Grade 2. The Flood Zone 3 associated with the River Ingrebourne crosses the route alignment within the route window.



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There are three surface water discharges located within route window NE14. Two are licensed to Thames Water (TEMP.0549 and TEMP.1698) for sewerage network and one to Total Fina Elf UK Ltd (CANM.0025). They all discharge into the River Ingrebourne system. There is one surface water abstraction on the tributary of the River Ingrebourne upstream of the route alignment. The source is licensed to Bloomfield for the purpose of spray irrigation. There are two additional surface water abstractions in the Ingrebourne river system. The abstractions are located some 5 and 9 km downstream of the river crossing and are licensed to Upminster Golf Club (licence no. 08/37/55/0045) and AC Tuner & Son (licence no. 08/37/55/0080), both for spray irrigation purposes.



Item Subject Details Id Drawing 1E0421


None or thin layer of Made Ground

1b Solid geology Bagshot Beds, Claygate Beds and London Clay

2 Chalk groundwater levels 100 mATD E1E00-E00-F-00303



1 abstraction license 42



42 42

6a Main rivers River Ingrebourne

E1E00-E00-F-00203

6b Other watercourses Minor tributary of the River Ingrebourne

7 River quality GQA: Good (B) RQO: Grade 2

River Ingrebourne

E1E00-E00-F-00203

8 Surface water abstraction 3 08/37/55/0068 08/37/55/0045* 08/37/55/0080*

E1E00-E00-F-00203

9 Surface water discharge 4 TEMP.0549 CANM.0025 TEMP.1698

E1E00-E00-F-00203

10 Floodplains Flood Zone 3 * Not within the route window





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(i) Groundwater

None.

(ii) Surface Water

None.



7.19 Route Window NE15 – Brentwood Station


(i) Overview

The main works in this route window comprise platform extensions. Two GEML platforms (platforms three and four) would be extended eastwards by 21 m to 205 m to accommodate 10-car Crossrail trains.

The platform works would comprise widening to the north side of platform four and of island platform two/three to accommodate 10-car Crossrail trains. In addition, new platform furniture and lighting would be fitted and minor station refurbishment works would be carried out.

Construction works would be carried out from within the existing fenced boundary of the railway on platforms two/three and four. The worksite servicing activities on the site would be located in part of the existing station car park to the north east of platform four.




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Figure 7.16: Route Window NE15 – Brentwood Station


The works would take approximately four months to complete.


The existing Brentwood Station has four platforms, all of which serve the GEML. The total additional platform area would be around 200 m2 (0.02 ha). A pre-cast concrete or traditional platform system would be used, supported on load bearing beams and founded on individual mini piles or mass concrete strips with excavation depths of approximately 1 m. The drainage from the extended platforms would match the existing drainage system.


The geology of the route window comprises London Clay, Bagshot Beds and Claygate Beds (sand and loam) localised overlain by Boulder Clay. The thicknesses of these deposits are unknown.

The Chalk groundwater level was 100 to 110 mATD in 2003. There are no licensed groundwater abstractions, surface water abstractions or river crossings within the route window.

There is one surface water discharge relevant for the route window. It is licensed to Thames Water (TEMP.1110) for the sewerage network and discharges into the River Ingrebourne. There is a SSSI (Thorndon Park) located 300 m to the south of the route alignment.




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Boulder Clay in places


2 Chalk groundwater levels 100 to 110 mATD (2003) E1E00-E00-F-00303



None


None

6a Main rivers None 6b Other watercourses None 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge 1 TEMP.1110

E1E00-E00-F-00203

10 Floodplains None



(i) Groundwater

None.

(ii) Surface Water

None.





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7.20 Route Window NE16 – Thrift Wood




Figure 7.17: Route Window NE16 – Thrift Wood


The geology of the route window comprises London Clay, Bagshot Beds and Claygate Beds (sand and loam) localised overlain by Boulder Clay and Glacial Gravels. The thicknesses of these deposits are unknown.

There are no licensed groundwater abstractions, surface water abstractions or river crossings within the route window.





Glacial Gravels and Boulder Clay in places


2 Chalk groundwater levels 100 to 110 mATD (2003) E1E00-E00-



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None


None

6a Main rivers None 6b Other watercourses None 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10 Floodplains None



(i) Groundwater

None.

(ii) Surface Water

None.



7.21 Route Window NE17 – Shenfield Station


(i) Overview

Works in this route window include the provision of additional stabling, a new platform and alterations to the Southend and Colchester rail lines.




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Figure 7.18: Route Window NE17 – Shenfield Station

(ii) Stabling Sidings

To accommodate the longer Crossrail trains, the two existing middle sidings at the east end of the station would be extended eastwards by 30 m and increased in number from two to three. New retaining walls and earthworks would be constructed to accommodate the revised layout. The Southend loop (forms the connection between platform five on the electric lines and the Southend Victoria route) and Colchester loop (rejoins the GEML at the eastern end of the Shenfield station layout, immediately beyond the middle sidings) would be modified to accommodate the changes to the sidings.

The worksite area set up within the Shenfield station car park for the station works would also be used for the construction of Shenfield stabling sidings and the associated track realignment. Works to construct the Shenfield stabling sidings would be carried out to the east of the existing Shenfield station between the Southend loop line and the Chelmsford loop line.

(iii) Shenfield Station

A new track would be installed on the north side of platform five to accommodate terminating Crossrail trains. A new platform 210 m long would be constructed on the north side of platform five. To improve operations, Crossrail would install a number of new crossovers at the west end of the station. The southern most section of the three stabling sidings would be amended to facilitate through running of trains.

Main construction works at Shenfield station would be carried out in phases in conjunction with track laying. Works would commence with construction of the new bay platform six to the north of platform five, involving the installation of a piled retaining wall at the bottom of the existing embankment and installation of foundations to the existing platform five riser



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wall. To construct the platform, a section of a ditch running along the existing embankment would need to be diverted and culverted.

Track would be laid and OHLE and signalling modifications would need to be completed to reflect the addition of platform six. A buffer stop would be installed to bay platform six as Crossrail trains would terminate at Shenfield station. New platform furniture and lighting would be fitted and minor station refurbishment works would be carried out.

A storage area for the Shenfield station and platform refurbishment works would be set up to the north west of the existing station within the existing station adjacent to island platform one/two.


Subject to possession planning requirements and excluding final commissioning, the construction works at Shenfield station would take about one year, while the construction works at Shenfield stabling sidings would take about one year and six months.


Ground levels would need to be raised and re-profiled and excavations would be required for the construction of new reinforced earth retaining walls. The optimum design would be a fabric reinforced earth retaining wall, as other designs would be more disruptive. There would also be a piled reinforced concrete retaining end wall to support the tracks at the end of the stabling site. This would require work at a lower level than 0.5 m below the lowest track foundation, but the work would include filling in the existing lower ground between the two existing railway lines. The construction boundary for the works would be within the existing area of the tracks. Piling may be required to a depth of approximately 10 m to ensure that the existing retaining structures remain stable.

New drainage would be provided in the sidings area. The existing drainage would be modified to suit the new layout, although the detailed design for this cannot be confirmed until a full drainage survey has been carried out.

Anglian Water has surface water outfalls from two sewers into the open ditch to the west of Shenfield Station. This ditch enters a culvert beneath the station. The Anglian Water records indicate that the discharge headwalls are part of their asset, but the ditch and culvert are not. To the north of the site, Anglian Water has an existing under-track crossing. This service is very deep beneath the existing railway embankment and is unlikely to require further works as a result of Crossrail.


The geology of the route window comprises London Clay, Bagshot Beds and the Claygate Beds (sand and loam), overlain in places by recent Boulder Clay and Glacial Gravels.



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A small ditch crosses just west of Shenfield station and runs within 100 m of the south east boundary of the sidings and loops. There are no licensed groundwater abstractions, protected rights or surface water abstractions within the route window.





Glacial Gravels and Boulder Clay in places


2 Chalk groundwater levels 100 to 110 mATD (2003) E1E00-E00-F-00303



None


None

6a Main rivers None 6b Other watercourses Ditch, name unknown E1E00-E00-

F-00203 7 River quality Not applicable 8 Surface water abstraction None 9 Surface water discharge None

10 Floodplains None



(i) Groundwater

Temporary: None.

Permanent: The new sidings would be designed to ensure that risks to groundwater features from contamination by railway operations and activities would be controlled. Furthermore, the Crossrail trains would be electrically powered rather than diesel and the potential for pollution is low. These mitigation measures would ensure that no significant adverse impacts occur.



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(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically the ditch to the south of the sidings area which may be connected via existing drainage pipes or storm water sewers. This would be a special concern during the works to the ditch and culvert and also at the sidings since this would lead to relatively large areas of exposed earthworks compared to other sites. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: The detailed design would take into account the performance of any existing track drainage in the sidings area and determine if this is piped to an outfall or to sewer. However, the existing drainage system at the sidings area would be upgraded, which is likely to lead to minor increase in runoff or soakaway in land assessed as being contaminated. Further discussions with the Environment Agency and Network Rail would take place to determine if any consents or permits need to be revised. There would therefore be no significant residual impacts.



7.22 Summary of Significant Impacts and Assessment - Stratford to Shenfield

There would be no residual significant impacts from temporary or permanent works in the North East Route Section. It should be noted that part of the land proposed for the construction of the Gidea Park sidings (NE11) is currently below the elevation of the predicted 1 in 100 year flood level and there may be minor filling around the culvert on the floodplain due to the works. This is subject to model verification and detailed design. It is expected that the residual risk would not be significant.

7.23 Route Window R1 – Pitsea Sidings


The main works within this route window would involve the development of a rail siding for unloading excavated material from rail to road for final delivery to the landfill site at Pitsea. The permanent works would comprise the introduction of railway tracks, trains, lighting columns, unloading equipment, a new access road and a new building at the entrance to the site for use during the transfer of excavated material to the disposal site. On completion of their use for Crossrail, all temporary buildings, sidings and equipment would be removed.

The site is bounded to the north by a belt of open land. The elevated A13 highway passes between 15 and 130 m to the north of the site on the far side of this open land.




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Figure 7.19: Route Window R1 – Pitsea Sidings


The geology comprises London Clay overlain by Boulder Clay.

Groundwater abstractions have not been obtained for the area, but the groundwater resources are assumed (A.NE.21) to be of minor interest due to the proximity of the Thames and the likelihood of brackish water. There are no groundwater source protection zones.

The Pitsea Marshes are located to the south of the railway line. There are several minor watercourses and ditches in the area and the tidal Flood Zone 3 extends to the southern edge of the railway alignment. There are two surface water discharges licensed to Anglian Water for sewage effluent disposal into Pitsea Creek.

Baseline data relevant for route window R1 are summarised in the table below.

Table 7.23: Summary of Baseline - Route Window R1



Boulder Clay

1b Solid geology London Clay 2 Chalk groundwater levels No information 3 Groundwater quality No information 4 Groundwater abstractions

and protected rights No information

5 Groundwater protection zones/Time of travel zones

None



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6a Main rivers None 6b Other watercourses Pitsea Creek and several

ditches.

7 River quality Not applicable

8 Surface water abstraction None 9 Surface water discharge 2 to Pitsea Creek CNTW.0890

CNTW.1280

10 Floodplains and flood levels Flood Zone 3 The Thames



(i) Groundwater

Temporary: None.

Permanent: None.

(ii) Surface Water

Temporary: Good site practice would be implemented to avoid significant pollution of, or runoff to, surface waters, specifically watercourses in the Pitsea Marshes which may be connected via existing drainage pipes or storm water sewers. This would be a special concern if the works at the sidings led to relatively large areas of exposed earthworks compared to other sites. Good practice would be enforced via the provisions for generic mitigation described in Appendix B and therefore there would be no significant residual impacts.

Permanent: Track drainage would be required along the sidings area. No information is available about the existing drainage along the railway line, but due to the high watertable and clay soils it is expected that the tracks are drained to sewer or ditches. The sidings would be installed in an area currently covered by grass and scrubs and the sidings are, therefore, likely to lead to an increased runoff.

The spoil is likely to be unloaded onto trucks to be transported to the landfill site. The detailed design would ensure that no spoil or runoff is lost to the ground and potentially lead to polluted surface run-off to the marshes.

There would be no impacts on the floodplain assuming (A.NE.22) that the sidings are built north of the existing railway.



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There would be no significant residual impacts from temporary or permanent works. There would be a minor, temporary, non significant residual impact on the water quality in Pitsea Marshes caused by contaminated site runoff.

Documents

7 Environmental Baseline and Assessment of Impacts – North ...74f85f59f39b887b696f-ab656259048fb93837ecc0ecbcf0c557.r23.cf… · overlying alluvial clay deposits. The solid geology,