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Area 451 Restricted Dredge Deposit Zone 2 Site Characterisation Report Report

December 2013

Environmental Resources Management Limited

Incorporated in the United Kingdom with registration number 1014622

Registered Office: 2nd Floor, Exchequer Court, 33 St Mary Axe, London, EC3A 8AA

Boskalis Westminster Limited

Area 451 Restricted Dredge Deposit Zone 2 Site Characterisation Report Report

December 2013

For and on behalf of Environmental Resources Management Approved by: Kevin Murphy _____________ Signed: ________________________________ Position: Partner ________________________ Date: 10 December 2013 __________________

This report has been prepared by Environmental Resources Management the trading name of Environmental Resources Management Limited, with all reasonable skill, care and diligence within the terms of the Contract with the client, incorporating our General Terms and Conditions of Business and taking account of the resources devoted to it by agreement with the client. We disclaim any responsibility to the client and others in respect of any matters outside the scope of the above. This report is confidential to the client and we accept no responsibility of whatsoever nature to third parties to whom this report, or any part thereof, is made known. Any such party relies on the report at their own risk.

Jennie.Cripps

Kevin Murphy

CONTENTS

1 NEED FOR THE NEW SITE 1

1.1 INTRODUCTION 1

1.2 SHORT AND LONG TERM DISPOSAL NEEDS 3

1.3 SUITABILITY AND CAPACITY OF EXISTING DISPOSAL SITES 4

1.4 POTENTIAL ALTERNATIVE DISPOSAL SITES 4

1.5 DETERMINATION OF THE ACCEPTABILITY OF THE MATERIAL FOR SEA DISPOSAL 5

1.6 STRUCTURE OF THIS REPORT 5

2 DEPOSIT SITE CONSIDERATIONS 6

2.1 SITE DESCRIPTION 6

2.2 DEPOSIT SITE CHARACTERISTICS 9

2.3 BENTHIC CONSIDERATIONS 21

2.4 FISHERY CONSIDERATIONS 23

2.5 MARINE MAMMALS 25

2.6 PROTECTED AREAS AND SPECIES 26

2.7 INFRASTRUCTURE AND OTHER OPERATIONS 32

2.8 ARCHAEOLOGY AND CULTURAL HERITAGE 32

3 MATERIAL CHARACTERISTICS 35

3.1 MATERIAL TYPES 35

3.2 MATERIAL QUANTITIES 37

3.3 CHARACTERISTICS OF MATERIAL DURING DEPOSITION 39

3.4 CHARACTERISTICS OF MATERIAL IN-SITU 42

4 ASSESSMENT OF POTENTIAL EFFECTS 43

4.1 EFFECTS OF DEPOSITION ON WATER COLUMN 43

4.2 EFFECTS OF DEPOSITION ON SEABED CONDITIONS 43

4.3 EFFECTS ON IDENTIFIED RECEPTORS 44

5 REASON FOR SITE SELECTION 47

6 MONITORING PROPOSALS 48

REFERENCES 49

ANNEX A FIGURE A.1 RDDZ 2 RESOURCE GEOLOGY AND THICKNESS

(SUPPLIED BY BWL)

ENVIRONMENTAL RESOURCES MANAGEMENT BOSKALIS WESTMINSTER LTD

1

1 NEED FOR THE NEW SITE

1.1 INTRODUCTION

Background 1.1.1

Boskalis Westminster Limited (BWL) has identified a solution to a long

standing problem associated with large dredge projects that produce

aggregates of sufficient quality and quantity for re-use in projects such as

beach replenishment.

In many cases those considering dredge operations that will give rise to

quantities of sands and gravels that could be used beneficially have sought

such schemes but technical and operational issues have precluded them being

viable options. In most cases the beneficial schemes require volumes of

aggregate delivered in small amounts over periods of time that do not tie in

with the relatively fast turn around and high rate of generation that

characterises capital and maintenance dredge schemes. Furthermore the

ability to stock pile the required material ashore is difficult as there is usually

a lack of space within a distance of the beneficial use site to make the required

transportation of the material to site viable.

BWL has identified a viable opportunity to provide a site offshore that can

hold sands and gravels arising from capital and maintenance dredge schemes

so that it can be re-used in beneficial schemes at a later date in a manner that

fits with the beneficial schemes timings and requirements. This approach

supports the various aims of waste legislation in avoiding disposal where

possible.

The Waste Framework Directive (EC, 2008) details the waste hierarchy which

is shown in Figure 1.1.


2

Figure 1.1 Waste Hierarchy

The Marine Management Organisation (MMO) Marine licensing guidance 3

(MMO, 2011) states that the processing and final destination of the dredged

material determines its status within the waste hierarchy. The MMO note also

requires applicants to consider viable and practical alternative means of

disposal for dredged material. As the material to be deposited within the

Area 451 site will be re-dredged for beneficial re-use schemes at a later date at

a time to suit the project, the material will fall under the re-use category of the

waste hierarchy. This is far more preferable than the main option for this

material which is disposal to a licensed offshore disposal ground.

The benefits of depositing this type of material at the Area 451 site will mean

less of the capacity at the nearby disposal ground, the Nab Disposal Ground,

will be consumed by the non-dispersible dredged arisings, ensuring future

disposal needs can be met for longer. Furthermore, re-use of the sand and

gravels in this way will reduce pressures on primary aggregate resources and

establishment of the deposition site within an actively dredged extraction area

will ensure that disturbance to the seabed environment within the region is

focused on areas of existing disturbance.

It is accepted by BWL that the proposed deposit site requires classification and

therefore characterisation. The most logical process is to characterise the site

in line with the MMO Disposal Site characterisation process, but noting that

the site is not a disposal site but rather relocation of material to a holding site

prior to its movement to the site of beneficial re-use. This is an accepted

approach as detailed by the MMO’s guidance note and Apitz (2010)

classification of sediment management approaches.


3

Deposit or Disposal 1.1.2

Due to time constraints BWL requires the site to be licensed as soon as

possible. Realising the unique nature of the request BWL is happy for the site

to be characterised in line with current MMO requirements but wishes to

ensure that the matter of classification can be re-visited at a later date.

The proposed deposit site sits within Area 451, a recently re licenced

aggregate extraction area. The material dredged from a licensed aggregate

extraction area is not classed as a waste and can be taken ashore and moved

without having to comply with The London Convention 1972 or the OSPAR

Convention 1992. These pieces of legislation cover the control of waste and

dumping activity. Under the OSPAR Convention dumping is classified as:

(f) "Dumping" means (i) any deliberate disposal in the maritime area of wastes or other matter

(1) from vessels or aircraft; (2) from offshore installations;

(ii) any deliberate disposal in the maritime area of (1) vessels or aircraft; (2) offshore installations and offshore pipelines.

(g) “Dumping” does not include

(i) ….. (ii) placement of matter for a purpose other than the mere disposal thereof, provided that, if the placement is for a purpose other than that for which the matter was originally designed or constructed, it is in accordance with the relevant provisions of the Convention; and …

For this reason the following document talks about deposition rather than

disposal.

1.2 SHORT AND LONG TERM DISPOSAL NEEDS

BWL is regularly involved in capital and maintenance dredge projects that

will produce sands and gravels of sufficient quality and quantity to warrant

re-use rather than loss to a disposal ground.

BWL has very recently been awarded the contract to carry out the

Southampton Approaches and Channel Dredge (SACD) for ABP

Southampton. This dredge programme will give rise to 4.5-5.0 million m3 of

material of which it is estimated >500,000 m3 will be good quality sands and

gravels. It is these sands and gravels that will be deposited at the Area 451

deposit site if permitted.

In the longer term there may be further capital and maintenance projects in

the region that give rise to sands and gravels in sufficient quantity and quality

to warrant set aside for beneficial reuse at a later date rather than loss to a


4

disposal ground. In these situations and where permitted the material will be

deposited within the Area 451 site, within the capacity of the site.

BWL are therefore seeking to characterise the Area 451 deposit site for

deposition and temporary storage of material from both the SACD and future

projects as appropriate.

1.3 SUITABILITY AND CAPACITY OF EXISTING DISPOSAL SITES

There are several marine disposal sites in the South Coast Region and the Nab

Tower site (W1060) is the main site for the region. The Nab Tower is 11.94

km2 in extent and is a dispersal site. The site has been used for the disposal of

capital and maintenance dredge material, silt washings from land-processed

marine aggregates, re-deposited contaminated aggregates, sewage sludge and

liquid industrial wastes. The disposal of liquid industrial wastes ceased at

Nab Tower in 1985 and the disposal of sewage sludge ceased in 1998.

Between 1984 and 1998, an average of approximately 264,000 wet tonnes of

sewage sludge was disposed of annually. The majority of material disposed at

Nab Tower is now maintenance and capital dredge material from the nearby

ports. Between 1998 and 2008 4.65 million tonnes of capital and maintenance

dredge material, silt washings, and re-deposited contaminated aggregates

were deposited at the Nab Tower site (annual average of 423,617 tonnes)

(EMU, 2012).

Whilst the Nab Tower disposal site could accommodate the volume of

materials being considered here it is a dispersive site and the heavier material

fractions are unlikely to disperse from the site resulting in reduction in the

capacity of the site. By depositing the heavier material fractions at an

alternative site, capacity of the Nab Tower site will be maintained whilst also

resulting in additional benefits.

1.4 POTENTIAL ALTERNATIVE DISPOSAL SITES

As outlined in the Environmental Statement (ES) for the SACD (ABPmer,

2012) alternative uses for the dredged material could not be readily found.

Where a potential need had been identified, operational constraints meant it

could not be satisfied. The only viable option identified was disposal to the

Nab Disposal Ground, which will continue to take the finer fractions from the

SACD.

There are no other viable alternatives to the options already considered for the

SACD.


5

1.5 DETERMINATION OF THE ACCEPTABILITY OF THE MATERIAL FOR SEA DISPOSAL

The material to be deposited within the Area 451 deposit site will be sands

and gravels of marine origin. These resources by their nature have minimal

fines associated with them and therefore there is a reduced possibility of

contamination levels that would preclude deposit at sea. The material

characteristics are discussed further in Section 3.

1.6 STRUCTURE OF THIS REPORT

The information within this report is provided to address the information

requirements outlined in the MMO Marine licensing guidance 3 (MMO, 2011)

and the more detailed Cefas guidance (Birchenough and Vivian) to enable

designation of a new deposition site and its characterisation. The remainder of

this characterisation report contains the following sections:

Section 2 – Deposit Site Considerations

Section 3 – Material Characteristics

Section 4 – Assessment of Potential Effects

Section 5 – Reason for Site Selection

Section 6 – Proposed Monitoring


6

2 DEPOSIT SITE CONSIDERATIONS

2.1 SITE DESCRIPTION

Area 451 is located 12 km off the east coast of the Isle of Wight, east and

adjacent to the Nab Disposal Site. Westminster Gravels Ltd (WGL), a sister

company of BWL, currently holds a 15 year aggregate dredging licence, due to

expire March 31st 2028, for Area 451. The proposed deposit area is known

as the Restricted Dredge Deposit Zone 2 (RDDZ 2) section of aggregate Area

451 and occupies an area of 0.6 km2 at the centre of Area 451 in water depths

of 25 m to 40 m below Chart Datum. Co-ordinates for RDDZ 2 are presented

in Table 2.1 and the location of the deposit site is presented in Figure 2.1.

Table 2.1 Proposed Deposit Site, RDDZ 2 Coordinates (WGS84)

Node Longitude (DDM) Latitude (DDM)

A 0° 57.6840 W 50° 34.6463 N

B 0° 57.4384 W 50° 34.7881 N

C 0° 57.4765 W 50° 34.5364 N

D 0° 56.8666 W 50° 34.6804 N

E 0° 56.6961 W 50° 34.7044 N

F 0° 56.6427 W 50° 34.7628 N

G 0° 56.4394 W 50° 34.7592 N

H 0° 56.3388 W 50° 34.7898 N

I 0° 56.3388 W 50° 34.9154 N

J 0° 56.7713 W 50° 34.9237 N

K 0° 57.2148 W 50° 34.8593 N

The current licence at Area 451 was determined on 7th February 2013 and

permits the removal of 18.75 million tonnes of sediment over a 15 year period,

with a maximum annual tonnage of 2.5 million tonnes and no rollover. The

average extraction tonnage is expected to be approximately 1.25 million

tonnes.

Area 451 has been dredged for the past 10 years for sand and gravel resource

being worked in zones in line with industry best practice, RDDZ 2 being one

such zone. To date and since December 2006, approximately 2,313,000 m3 of

aggregate has been removed from the RDDZ 2 mainly for beach

replenishment schemes but also smaller volumes for use in the aggregate

industry. This extraction has lowered the seabed in RDDZ 2. This lowering is

clearly visible in Figure 2.2 which presents the difference between the 2006

pre-dredge bathymetry and the 2012 bathymetry. All aggregate extraction

dredging has been undertaken using a trailer suction hopper dredgers, and

monthly Electronic Monitoring System (EMS) data were recorded.

RYDE

NEWPORT

CLIENT: SIZE: TITLE:

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Boskalis Westminster Limited A4 Figure 2.1Location of Proposed Deposit Site RDDZ02

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ERMEaton HouseWallbrook CourtNorth Hinksey LaneOxford OX2 0QSTelephone: 01865 384800Facsimile: 01865 2049820 6

Kilometres

Restricted Dredge Deposit Zone 02 (RDDZ02)Aggegrate Licence Area 451Nab Tower Disposal Ground

Figure 2_1 - Location of the Proposed Deposit SiteRDDZ 2.mxd

1:200,000


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Boskalis Westminster Limited A3 Figure 2.2RDDZ 2 2006 - 2012 Bathymetric Difference Plot

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ERMEaton HouseWallbrook CourtNorth Hinksey LaneOxford OX2 0QSTelephone: 01865 384800Facsimile: 01865 204982

Figure 2_2 - RDDZ 2 2006 - 2012 Bathymetric Difference Plot.mxd

Depth Reduction 2006 - 2012Approximate change in level (metres)

-0.1-1.0-2.0-4.0

-6.0-8.0-10.0-12.0-14.5

Depth Increase

NOTE: Due to the scale of original figure (A1) an approximate legend was drafted for legibility


9

Under the current aggregate extraction Marine Licence, WGL is required to

undertake both baseline and future monitoring surveys. The baseline surveys

were carried out for Area 451 in 2012, providing geophysical, multibeam

bathymetry and drop down video (DDV) data at selected sites.

The subsequent Conservation Review (FugroEmu, 2013) which examined the

side scan sonar and targeted DDV footage, highlighted the presence of blue

mussel beds within an area of Area 451. WGL has placed an exclusion zone

around the beds, as agreed by the MMO, and no extraction activity is

permitted within these zones. The relevance of the deposit activity to these

blue mussel beds is discussed further in Section 4.

2.2 DEPOSIT SITE CHARACTERISTICS

Existing Sediment Characteristics 2.2.1

The sediment characteristics of the proposed deposit site within Area 451 are

well understood having been assessed for aggregate extraction purposes

through a number of recent surveys. These survey data have been used to

generate the figures presented in this section. In addition recent and historic

data have been assessed for the:

South Coast Region Marine Aggregates Regional Environmental

Assessment (MAREA) (EMU, 2012) and supporting studies;

Area 451 Environmental Statement (2012);

South Coast Regional Environmental Characterisation (REC) (James et

al 2010); and

Coastal Impact Study (CIS) for Area 451 (HR Wallingford 2011).

Using the best available data (side scan sonar, bathymetry and vibrocore data)

BWL has produced a detailed site characterisation plan for RDDZ 2. This

figure details the geology and sediment characteristics of the area as well as

showing cross sections of the site to assist understanding of the current

bathymetry of the site. Due to the size of this figure, Figure A.1 is provided at

Annex A.

Figure 2.3 shows the locations of the vibrocores available within RDDZ 2. The

data gained from these vibrocores have been used to generate the Particle Size

Distribution (PSD) curve for RDDZ 2 shown in Figure 2.3. Figure 2.4 presents

the PSD of the surface sediments at the time of the survey ie prior to

subsequent aggregate extraction activity.

From the vibrocore data collected it can be seen that the material within

RDDZ 2, at surface and depth is predominantly sand and gravel Figure 2.5

shows examples of some of the vibrocores and associated data collected from

RDDZ 2.

VC9 (2007)

VC6 (2007)

VC5 (2007)

VC2 (2003)

VC12 (2007)

HPC8 (2006)HPC7 (2006)HPC5 (2006)

HPC4 (2006)HPC3 (2006)

HPC2 (2006)

HPC1 (2006)VC23 (2001)

VC22 (2001)

VC21 (2001)

VC20 (2001)

VC19 (2001)HPC12 (2006)HPC11 (2006)

HPC10 (2006)


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Boskalis Westminster Limited A4 Figure 2.3Location of Vibrocores in RDDZ 2


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Vibrocore LocationsRestricted Dredge Deposit Zone 02 (RDDZ02)Aggregate Licence Area 451

Figure 2_3 - Location of Vibrocores in RDDZ 2.mxd

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Figure 2.4 Pre Aggregate Extraction PSD Curve for RDDZ 2

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Vc 19

Vc 20

Vc 21

Vc 22

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HPC 03

HPC 04

HPC 05

HPC 07

HPC 08

HPC 10

HPC 11

HPC 12

Vc 5/07

Vc 6/07

Vc 9/07

Vc 12/07

Figure 2.5a Vibrocore Photos and Logs of Some Vibrocores taken in RDDZ 2

Figure 2.5b Vibrocore Photos and Logs of Some Vibrocores taken in RDDZ 2

Figure 2.5c Vibrocore Photos of Some Vibrocores taken in RDDZ 2

Figure 2.5d Vibrocore Photos of Some Vibrocores taken in RDDZ 2

Figure 2.5e Vibrocore Photos of Some Vibrocores taken in RDDZ 2

Figure 2.5f Vibrocore Photos of Some Vibrocores taken in RDDZ 2


18

The proposed deposit site has been an active dredged zone for 10 years and as

a result of a number of significant beach replenishment schemes a shallow but

well defined depression in the seafloor where resource has been removed.

There is a very slow rate of sediment infilling in this area, suggesting low

levels of mobile sediments in the area (ERM, 2012, p74).

As reported in the Area 451 ES (ERM, 2012) the coarse sediments found in

exposed offshore locations such as Area 451 are not generally associated with

contaminants, which if pollutants are present, are more likely to be associated

with areas of high proportions of silts and clays. The sands and gravels

within the proposed deposit site are considered by the South Coast MAREA to

have low sediment contaminant concentrations.

Water Quality 2.2.2

General Considerations

The South Coast MAREA describes water quality in the region as generally

good, which reflects the open water, dispersive and well flushed current

regime in the area and its distance from sources of contaminants, such as

major urban areas. CEFAS holds limited monitoring data for winter

suspended concentrations to the north of the proposed deposit site and

described the area as having a mean suspended sediment concentration (SSC)

of 25 mg l-1 (range 4 to 45 mg l-1) (Cefas, 2001).

Plumes

Sediment plumes in the vicinity of RDDZ 2 are currently generated by

aggregate extraction at Area 451 and disposal activity at the Nab Disposal

Ground. As reported in the SACD ES (ABPmer 2012), the Nab Deposit

Ground, adjacent to the RDDZ 2 area, is a highly dispersive site that has been

used for many years as a licensed disposal site. The Nab Disposal Ground

receives an average of about 447,000 m3 of sediment per year from

maintenance dredging in Southampton Water and the Test, Itchen and

Hamble Estuaries. A similar order of magnitude of sediment is deposited in

the Nab Disposal Ground from other areas such as Portsmouth, Chichester

and Langstone Harbours, the Nab Channel and the Medina. To date, no

environmental impacts of significance have been identified (ABPmer, 2012,

Cpt 10).

Bathymetry 2.2.3

Seabed levels across the proposed deposit site range from 25 m below CD to

the north and east of the site, to 40 m below CD at the southwest tip of the site.

The centre of the site lies approximately 35 m below CD and forms a

significant depression in a northeast – southwest orientation within the site, as

shown in Figure 2.2.

As shown in Figure A.1 (Annex A) the proposed deposit site lies on younger

gravel terrace facies, bordered to the south, north and west by basal facies and


19

clay/sand/gravel facies to the east. The clay/sand/gravel facies are

relatively featureless, with small areas of irregular hummocky seabed

southwest of the site, whilst there are a number of minor sand ribbons and

sand waves within the basal facies to the west and north of the site.

Bathymetric surveys have been regularly carried out and are required to be

undertaken every two years within Area 451. Figure 2.6 shows the current

bathymetry of RDDZ 2 and the depression within the deposit site has an

estimated volume capacity of 2.2 to 2.3 million m3 to return it to its pre dredge

level.

The mega ripples within the depression in the proposed deposit area shown

in Figure 2.6 and Figure A.1 are formed through the action of wave and current

driven sediment transport, which is explained in greater detail in the Area 451

CIS (HR Wallingford, 2011). The mega ripples are formed in alignment with

the depression, in a northeast – southwest orientation and run the length of

the depression. The sand ribbons and sand waves in proximity to the site are

also aligned in the same orientation. A detailed description of the bathymetry

within RDDZ 2 is available in the CIS, Plume Dispersion and Model

Validation Reports (HR Wallingford, 2011) which is Annex B of the Area 451

ES (ERM, 2012).

Physical Oceanography 2.2.4

As detailed in the South Coast MAREA (Emu 2012) the predominant angle of

wave approach in the central part of the English Channel is from the west and

southwest. Whilst the area to the east of the Isle of Wight is fairly sheltered

from these waves, wave refraction around the island results in swell waves

from these directions propagating across the proposed deposit site and on into

the eastern Solent. Winds from the south, southeast and east also produce

occasionally severe storm wave conditions at the proposed deposit site,

although the shorter fetch lengths across the Channel to the French coast limit

the wave heights and periods from these sectors.

Tidal currents at the proposed deposit site are often strong, especially during

spring tides and in areas where the seabed contours cause constriction of

flows. The nearest Admiralty tidal diamond is located approximately

0.5 nautical miles to the east of the proposed deposit site, where the tidal flows

are reported to be predominantly northeasterly or southwesterly with peak

flows of about 1.1 ms-1 on spring tides and about 0.56 ms-1 on neap tides.

These current speeds will regularly mobilise sand on the seabed but are much

less likely to mobilise gravel or coarser sediment particles. The flow and wave

conditions of the region are discussed in greater detail within the South Coast

MAREA (Emu 2012) and supporting technical reports presented in Appendix

A to the MAREA (HR Wallingford 2010) and Appendix 6A (HR Wallingford

2012).


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Boskalis Westminster Limited A3 Figure 2.6Current (2012) Bathymetry of RDDZ 2

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Figure 2_6 - Current 2012 Bathymetry of RDDZ 2.mxd


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2.3 BENTHIC CONSIDERATIONS

Data from ten macrobenthic surveys carried out between 1995 and 2010 in the

east of Isle of Wight area were analysed and presented in Section 6.3 of the

2012 Area 451 ES (ERM, 2012). These datasets comprised a total of 562

benthic grab samples. 17 biotopes were identified, all of which fall under UK

BAP priority habitat classification. Area 451 did not appear distinct from the

surrounding region, although there was much variation between samples.

As shown in Figure 2.7; nine biotopes were identified within the 4 km physical

effect footprint(1) of Area 451. These biotopes are listed in Table 2.2.

Table 2.2 Habitats and Biotopes Mapped within 4 km of Area 451

Biotope Assignment Description

CR.MCR.SfR.Pid Piddock with a sparse associated fauna in

sublittoral very soft chalk or clay

SS.SCS.CCS.PomB Pomatoceros triqueter with barnacles and

bryozoan crusts on unstable circalittoral

cobbles and pebbles

SS.SMx.IMx.CreAsAn Crepidula fornicate with ascidians and

anemones on infralittoral coarse mixed

sediment

SS.SSa.IFiSa.NcirBat Nephtys cirrosa and Bathyporeia spp. in

infralittoral sand

SS.SCS.ICS.Glap Glycera lapidum in impoverished infralittoral

mobile gravel and sand

SS.SCS.CCS.MedLumVen Mediomastus fragilis, Lumbrineris spp. and

venerid bivalves in circalittoral mixed gravelly

sand

SS.SBR.PoR.SspiMx Sabelleria spinulosa on stable circalittoral mixed

sediment

SS.SBR.Smus.MytSS Mytilus edulis beds on sublittoral sediment

SS.SSa.IFiSa.ScupHyd Sertularia cupressina and Hydrallmania falcate on

tide-swept sublittoral sand with cobbles or

pebbles

The most abundant recorded biotope within the proposed deposit area is

Pomatoceros triqueter with barnacles and bryozoan crusts on unstable

circalittoral cobbles and pebbles.

(1) 4km is identified in the Area 451 ES (ERM, 2012) as the maximum distance from the licence area over which physical

effects resulting from aggregate extraction activity at Area 451 will be felt. RDDZ 2 sits within Area 451 and therefore

within this physical effect footprint.


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Boskalis Westminster Limited A4 Figure 2.7Biotopes in relation to the RDDZ 2

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Restricted Dredge Deposit Zone 02 (RDDZ02)Restricted Dredge Zone 024km BufferAggregate Licence Area 451

Figure 2_7 - Biotopes in relation to the RDDZ 2.mxd

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BiotopesCR.MCRSS.SBR.PoR.SspiMxSS.SBR.SMus.MytSSSS.SCS.CCS.MedLumVenSS.SCS.CCS.PomBSS.SCS.ICS.GlapSS.SCS.ICS.SSh

SS.SMx.IMx.CreAsAnSS.SSa.CMuSa.AalbNucSS.SSa.IFiSa.IMoSaSS.SSa.IFiSa.NcirBatSS.SSa.IFiSa.ScupHydSS.Sa.IFiSa.TbAmPo


23

2.4 FISHERY CONSIDERATIONS

Commercial Fisheries 2.4.1

As reported in the Area 451 ES (ERM, 2012), a number of UK and international

fishing fleets operate in the vicinity of Area 451 and depositing dredged

material at the proposed site may cause some disruption to these fishing

activities. Noting that RDDZ 2 lies within an active aggregate extraction area

and activity in this area is notified regularly to fishermen, disruption will be

far less than in an area where no activity currently occurs.

The Solent is an important fishing ground and the East Solent from

Southampton Water to beyond the Nab Tower Disposal Site is an active

inshore finfishing area and a dredging and potting ground for several species

of shellfish, crabs and lobsters.

The reporting unit of fisheries data in the UK is the ICES (International

Council for the Exploration of the Sea) rectangle, approximately 30 x 30

nautical miles. RDDZ 2 lies in ICES rectangle 30E9. As presented in Figure

2.8 4,156 tonnes of finfish and shellfish were landed in 2012 from ICES

rectangle 30E9, with molluscs making up 2,648 tonnes of this catch. Of the

total tonnage of molluscs landed, 2,383 tonnes were whelks. 489 tonnes of

crustaceans were landed in 2012 – a higher tonnage than in previous years

with the brown crab Cancer pagurus making up a significant proportion of

catch. It is though that this species of crab has a ‘hen crab run’ coinciding

with RDDZ 2, but this has not been confirmed (Plumb 1996). Only 22 tonnes

of pelagic fish were landed in 2012, the second lowest tonnage recorded since

2004.

Figure 2.8 Total Finfish and Shellfish landings, ICES 30E9, 2012


24

As described in the SACD ES (ABPmer 2012) the Solent fishing industry

makes an important contribution to the area’s economy, landing catches

estimated at around £7.9 million in 2006. More recently there has been an

increase in charter and casual angling vessels, which is now a year round

industry and of considerable importance to the local economy (Walmsley &

Pawson, 2007).

The Area 451 ES (ERM 2012) stated that there are little or no trawler, shellfish

dredger, seiner and netter fishing activities within the Area 451 application

area, and therefore the RDDZ 2 area. Detailed data on the ICES landing

statistics for 30E9 can be found in the Area 451 ES (ERM 2012).

Recreational Fisheries 2.4.2

The south coast region has a well-established and popular recreational fishery

due to its good accessibility and numerous sheltered areas. It attracts

recreational shore and boat anglers all year round, the majority of which are

line anglers.

The main fish species of recreational interest are bass (Dicentrarchus labrax),

rays (Raja clavata and Raja undulata), mackerel (Scomber scombrus), tope

(Galeorhinus galeus), smoothound (Mustelus canis), spurdog (Squalus acanthias),

conger eel (Conger conger), and black seabream (Spondyliosoma cantharus).

Large cod (Gadus morhua) can also be caught in autumn and winter whilst

plaice can be caught in spring. Fish landings are not monitored for

recreational fishing and therefore do not appear in official statistics, however,

there is a high intensity of charter vessels and hobby angling in the region

indicating the importance of recreational fishing in this area.

There are no wrecks within the RDDZ 2 area, and anglers tend to fish more

over wreck sites and towards the Overfalls, southeast of RDDZ 2, where fish

are in higher abundance. As a result, levels of recreational fishing in RDDZ 2

are relatively low, with preferred sites nearby.

Spawning and Nursery Grounds 2.4.3

The key spawning areas which overlap with or have been identified in close

proximity to the RDDZ 2 area are those of cod, plaice, sandeel and sole, see

Section 6.4 of the Area 451 ES (ERM, 2012). The species with a nursery area

that interacts with the RDDZ 2 area are plaice, sole, thornback ray, tope,

undulate ray and edible crab. The key fish and shellfish spawning and

nursery areas in the area are presented in Figures 6.10 and 6.11 of the Area 451

ES (ERM 2012). Furthermore, the maps produced in the South Coast MAREA

(Emu 2012) are sourced from Ellis et al (2010), to distinguish between areas of

low intensity spawning and high intensity spawning, from Coull et al (1998)

and from consultation with local fishermen.

Brown crab spawn in November/December and incubate their eggs until the

following April to June. During the incubation period the hen brown crab


25

carrying the egg mass on their underside remain largely sedentary and buried

in the sediment. During this period of relative immobility the hen crabs and

eggs would be more susceptible to loss and damage from direct smothering.

Juveniles are also vulnerable to loss from sediment deposit activities within

nursery grounds. RDDZ 2 overlaps with potential brown crab spawning and

nursery areas on the South Coast (Figure 6.12, pg 6-32, ERM 2012) noting that

the extent of these areas is not well defined. Impacts from the dredging

activities assessed in the Area 451 ES on crabs and from suspended sediments

are considered to be of a small magnitude given the area dredged at any one

time and the duration and extent of sediment plumes.

2.5 MARINE MAMMALS

The waters of southern England around the Isle of Wight support a low

abundance and diversity of marine mammals (cetaceans (1) and pinnipeds (2))

compared to other coastal areas of the UK. The marine environment around

the Isle of Wight supports relatively few cetaceans. Species diversity and

abundances are listed as low, with only four out of 26 UK cetacean species

recorded in these waters (Seawatch Foundation 2011). The predominantly

shallow coastal habitat favours inshore water species such as bottlenose

dolphin (Tursiops truncates) and harbour porpoise (Phocoena phocoena). In

deeper offshore waters more than 10 km from shore, long finned pilot whales

(Globicephala melas) are seasonal visitors between November and January.

Short-beaked common dolphin (Delphinus delphis) is another deeper water

species occasionally recorded in the region between August and December

(James et al 2010; Jones et al 2004; Emu 2012).

There are no significant haul out or breeding sites for either common seal or

grey seal around the Isle of Wight, although there is a known harbour seal

haul out site at Poole Harbour. Both species are also occasionally recorded in

the area, with regular sightings at Chichester Harbour (James et al 2010; Jones

et al 2004). The species regularly or occasionally recorded around the Isle of

Wight are listed in Table 2.3.

No marine mammal species have been recorded with any regularity within

the RDDZ 2 area and densities within the region are low, however it is

possible that small numbers of both cetaceans and seals pass through or

forage within the RDDZ 2.

(1) Whales, dolphins and porpoises belong to the taxonomic order of Cetacea and are referred to as cetaceans. (2) Seals belong to the taxonomic family Pinnipedia and are referred to as pinnipeds.


26

Table 2.3 Marine Mammals Recorded around the Isle of Wight

Common

Name

Scientific Name Distribution

Harbour

porpoise

Phocoena phocoena Occur in small numbers in nearshore waters all around the

coast of the UK. Most abundant in April and between August

to October.

Bottlenose

dolphin

Tursiops truncatus Recorded annually in small numbers during the summer in

the Solent and around St. Catherine’s Point. Favour

prominent headlands and enclosed bays and have been

sighted off Bembridge. Semi-resident group recorded off

Durlston Head in Dorset.

Common

dolphin

Delphinus delphis Recorded more commonly offshore, the common dolphin

prefers deeper waters than the more coastal bottlenose

dolphin. Recorded more frequently to the west of the Isle of

Wight around Poole Bay between August and December.

Long-finned

pilot whale

Globicephala melas Found more commonly in the Western Channel, the long

finned pilot whale is also more of a deep water species.

However it migrates to the east towards the Isle of Wight

around November.

Common

seal

Phoca vitula Common seal favour sheltered inshore areas, using islands

and sandbanks as haul-out sites. They are more localised

than grey seal, staying in the same general area to feed and

rest and do not form as large breeding colonies.

Grey seal Haliocherous

grypus

Prefer more remote shorelines to common seal, and are more

prevalent in northwest waters of the UK, but can travel large

distances in search of food.

Source: James et al (2010); Jones et al (2004); SCDA (2012)

2.6 PROTECTED AREAS AND SPECIES

Designated Sites 2.6.1

The deposition site is not located within or overlapping with any designated

site. Those designated sites within 20km of the deposition site which have a

marine or coastal element to their designations are listed in Table 2.4 and

shown in Figure 2.9.

Table 2.4 Designated Sites in the Vicinity of the RDDZ 2

Site Statutory

Designation

Approximate

Distance from

RDDZ 2 (km)

Remarks Reason for Designation

South Wight Maritime SAC, Natura

2000 site

8.5

Large marine SAC extending approximately

8.5 km from the south coast of the Isle of

Wight.

Designated for the Annex 1 habitats reefs, sea

caves and vegetated sea cliffs.

Solent and Isle of Wight

Lagoons

SAC 15.6 One site on the eastern coast of the Isle of

Wight

Encompasses a series of lagoons, including

percolation, isolated and sluiced lagoons, with

associated specialised plant and animal

communities.

Solent Maritime SAC, Natura

2000 site

19.4 Covers areas of the northern coast of the Isle

of Wight and the south shores of the

mainland, and contains Chichester and

Langstone Harbours.

Designated for the Annex 1 habitats estuaries,

Spartina swards and Atlantic salt meadows.

Solent and

Southampton Water

SPA, Ramsar

Site, Natura

2000 site

13.6 Covers extensive areas of the north coast of

the Isle of Wight and the south coast of the

mainland.

Designated for a number of Annex 1 species

including breeding populations of four tern

species, and large wintering populations of teal,

dark- bellied Brent geese and black tailed godwit.

Whitecliff Bay &

Bembridge Ledges

SSSI 13.8 Extensive areas of intertidal sand, rock,

shingle and cliffs at eastern most point of the

Isle of Wight.

The site includes a series of actively eroding cliffs which yield important fossils from the Eocene-Oligocene boundary.

Bembridge Downs SSSI 13.9 To the south of Bembridge Ledges on the

eastern side of the Isle of Wight.

The site is designated for its vertical sea cliffs and associated flora and fauna, and its cliff top grassland as well as its geological interest.

Brading Marshes to St

Helen’s Ledges

SSSI 15.2 Immediately to the north of Bembridge

Ledges on the east coast of the Isle of Wight.

Brading Marshes comprises an extensive area of neutral and acid grassland, saline and freshwater lagoons and pools, botanically rich ditches, reedbeds, and areas of ancient woodland peripheral to the former harbour.

Ryde Sands & Wootton

Creek

SSSI 18.1 On the north eastern shore of the Isle of Wight The site is designated, inter alia for its important

examples of intertidal habitats, fauna and flora

and its beds of eel grass

Bracklesham Bay SSSI 18.9 A long stretch of coast with associated pasture

to the west of Selsey Bill.

Designated for its shingle ridge and un-improved

pasture and associated flora.

Site Statutory

Designation

Approximate

Distance from

RDDZ 2 (km)

Remarks Reason for Designation

Bembridge rMCZ (22) 9.1 Coastal area around the eastern edge of the

Isle of Wight

Identified as a rMCZ for its rocky reef habitats,

sea grass beds and fish fauna

Offshore Overfalls rMCZ (17) 0.5 Area of sand and gravel banks to the south

east of the Isle of Wight

Identified as a rMCZ for its unique relict glacial

sand and gravel deposits which support a rich

fish fauna.

Utopia

(including North

Utopia Ref. Area 13)

rMCZ (28) 7.9 Small site to the south west of Selsey Bill Identified as a rMCZ for its benthic fauna

including sponges and anemones

Selsey Bill and the

Hounds

rMCZ (25.2) 16.7 Coastal area around Selsey Bill Identified as a rMCZ for peat and clay exposures,

rocky habitats and rich fauna.

Source: SCDA (2012), JNCC website (2011), Natural England website (2011).

Offshore Overfalls

Bembridge

KingmereNorris to Ryde

Yarmouth to Cowes Selsey Bill and the Hounds

The Needles

Utopia

Fareham Creek

Pagham Harbour


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Boskalis Westminster Limited A4 Figure 2.9Designated Sites in the Vicinity of the RDDZ 2

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Restricted Dredge Deposit Zone 02 (RDDZ02)Maritime Conservation Zone (rMCZ)Special Protection Areas (SPA)Special Areas of Conservation (SAC)Ramsar

Figure 2_9 - Designated Sites in the Vicinity of theRDDZ 2.mxd

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New Forest SPA and Ramsar

Solent MaritimeSAC

Solent and Southampton WaterSPA and Ramsar

Portsmouth HarbourSPA and Ramsar

Solent MaritimeSACChichester and Langstone HarbourSPA and Ramsar

Pagham HarbourSPA and Ramsar

South Wight MaritimeSAC


30

Protected Species 2.6.2

Blue Mussels (Mytilus Sp.)

Blue mussel beds can be supporting or sub features of habitats listed in Annex

I of the Habitats Directives. In addition, blue mussels on sediment (intertidal

and subtidal) are a priority habitat within the UK Biodiversity Action Plan

(now the UK Post 2010 Biodiversity Framework) (Fugro Emu, 2013).

The Area 451 Conservation Review (Fugro Emu, 2013) highlighted the

presence of dense aggregations of mussels within and adjacent to Area 451,

the nature of which match Annex I (EC Habitats Directive 92/43/EEC) criteria

for reef. Following the Conservation Review and in consultation with the

MMO and its advisors WGL placed an Exclusion Zone (EZ) around the beds

in which no aggregate extraction will occur. The extent of the EZ included a

buffer of 100 metres to ensure the stability of the beds is not undermined as a

result of substrate slipping into dredged areas. The EZ in place is shown on

Figure 2.10.

The good quality sidescan sonar data reviewed for the Conservation Review

showed that the boundaries between the mussel features and the ambient

seabed are distinct allowing for accurate mapping. As shown in Figure 2.10,

RDDZ 2 does not overlap with the blue mussel beds and at its closet point

RDDZ 2 is over 1km away from the beds.

The Conservation Review (Fugro Emu 2013) found that the mussels were

found in association with ’mounds’ of relatively consolidated mud. Whilst

the exact origin (geogenic or biogenic) of the silty sediment could not be

ascertained with certainty, as the area around the mounds are

characteristically sand and gravel, it is suggested that due to their association

with patches of mussels, the mounds seem indicative of mussel mud, i.e.

biogenic. Due to the cohesive nature of the mussel mud, the deposits may

last for several years after mussels have disappeared (Holt et al (1998). This

substrate was found to differ from the surrounding seabed, and is considered

to consolidate the sediment. These mud formations, in association with blue

mussels were also found to be slightly raised above the seabed. The sidescan

sonar data has shown that the boundaries between the mussel features and

the ambient seabed are distinct allowing for accurate mapping.

The Review goes on to note that the Nab Tower Disposal Ground is in close

proximity to Area 451 and may provide some of the fine sediments that

contribute to these features.


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Boskalis Westminster Limited A4 Figure 2.10Area 451 Blue Mussel Bedsand the RDDZ 2.


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Restricted Dredge Deposit Zone 02 (RDDZ 2)Blue Mussel Bed Exclusion ZoneBlue Mussel Bed Exclusion Zone 100m BufferAggregate Licence Area 451

Figure 2_10 - Area 451 Blue Mussel Beds and theRDDZ 2..mxd

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32

Other Protected Species

The Conservation Review for Area 451 (Fugro Emu, 2013) identified

brittlestars Ophiothrix fragilis associated with the blue mussels, but not in

sufficient enough numbers to constitute a brittlestar bed. As there is no

brittlestar bed present and an EZ is in place around the blue mussel bed with

which the brittlestar are associated, brittlestar are not considered to be a

constraint to or be adversely impacted by deposition at RDDZ 2 and are

therefore not considered further.

No other protected species are present within RDDZ 2.

2.7 INFRASTRUCTURE AND OTHER OPERATIONS

The South Coast region supports a variety of marine infrastructure including

commercial ports, military ports, navigation and shipping routes, oil and gas

exploration and development, aggregate extraction, cables and pipelines and

disposal sites.

Figure 2.11 shows the infrastructure and other operations within the region

around Area 451 RDDZ 2. As shown on Figure 2.11 there is no significant

infrastructure or development overlapping or near to the deposit site. The

exception is the Area 451 Aggregate Extraction area and the Nab Disposal

Ground which lies immediately to the west of the deposit site.

The deposit site sits within an active aggregate extraction area, Area 451, managed by BWL the same company proposing to undertake the deposit of sand and gravel within RDDZ 2. Details and history of Area 451 are outlined in Section 2.1. The details and history of the Nab Disposal Ground are outlined in Section 1.3.

2.8 ARCHAEOLOGY AND CULTURAL HERITAGE

A number of recent reports prepared for Area 451 (Emu 2011 and Wessex

Archaeology 2013) have been reviewed to establish the archaeological status

of any archaeological sites likely to be impacted by deposition activities at the

deposit site.

Figure 2.12 shows that there are no sites of archaeological or cultural heritage

importance within RDDZ 2 and therefore likely to be impacted by the

deposition site activity.

PORTSMOUTHGOSPORT

FAREHAM

BOGNOR REGIS

RYDE

HAVANTCHICHESTER

NEWPORT

LITTLEHAMPTON


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Boskalis Westminster Limited A4 Figure 2.11Infrastructure and Other Developments in Proximity to RDDZ 2


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Figure 2_11 - Infrastructure and OtherDevelopments in Proximity to RDDZ 2 A02.mxd

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Restricted Dredge Deposit Zone 02 (RDDZ 2)Nab Tower Disposal GroundAggregate Licence Area 451Pilotage Station

MarinaRYA ClubRYA Training Centre

Heavy Recreational UseMedium Recreational UseLow Recreational UseRacing AreaGeneral Sailing AreaSubmarine CableFishing facilityHarbour facilityOil barrierPipeline

DiffuserFishing facilityHarbour facilityInstallation, TemplateInstallation, UndefinedMarine farm/cultureMast

Offshore platform

Pile

Pipeline, Joint

Pipeline, Manifold

Storage tank

Offshore turbineWellhead

DiffuserFishing facilityHarbour facilityLog pondMarine farm/cultureOffshore platformTurbine, WindWellhead

Nab Anchorages


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Boskalis Westminster Limited A4 Figure 2.12RDDZ 2 and and Sites of Archaeological ImportanceIncluding UKHO Wreck Sites


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UKHO Live WreckRestricted Dredge Deposit Zone 02 (RDDZ02)Aggegrate Licence Area 451

Figure 2_12 - RDDZ 2 and and Sites ofArchaeological Importance Including UKHO Wreck

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35

3 MATERIAL CHARACTERISTICS

3.1 MATERIAL TYPES

The material to be deposited with the RDDZ 2 site will consist predominantly

of sands and gravels of marine origin, arising from consented dredging

programmes, and will be deemed acceptable for disposal to sea ie there will be

no contamination that exceeds the Cefas action levels.

As presented in Figure 2.4 the current sediment composition at the site is sand

and gravels. Figure 3.1 shows the pre-aggregate extraction surface PSD curve

for the RDDZ 2 overlain with the marine sand and fluvial sand and gravel

PSD envelopes for the SACD. The detailed SACD PSD data are presented

within Appendix B of the SACD ES (Figures B.8 and B.9, APBmer, 2012). As

can be seen from these data, sediment characteristics of the sand and gravel

material to be dredged and deposited are very similar to the pre dredge

sediment characteristics at the deposit site.

Figure 3.1 RDDZ 2 PSD Curve Overlain with the SACD Sand and Gravel Sediment Fraction Envelope

Source: BWL, 2013.


37

3.2 MATERIAL QUANTITIES

The volumes of sand and gravel to be deposited in RDDZ 2 will not exceed the

capacity of the existing depression, which has a volume of approximately 2.3

million m3.

BWL is proposing to deposit the material utilising a grid approach and

wherever possible segregating material types for subsequent re-use ie the

sands will be deposited and stored in a different zone to the fluvial gravels.

The proposed grid system shown in Figure 3.2 identifies a number of zones

which run parallel to the tidal currents. The zone dimensions are 500m x 100m

and are further sub-divided into 100m x 100m cells. Using the pre-dredge

bathymetry and the recent baseline multibeam bathymetry the volume of each

100m x 100m cell has been calculated by BWL and is presented on Figure 3.2.

The quantity of any dredge load will be calculated by ullage and the

destination i.e. the zone and cells to be filled, will be allocated prior to

deposition. The vessel will deposit the material within its hold by bottom

dumping the cargo. This process involves the vessel opening the hopper doors

beneath the hopper or hold, upon which the material sits. As the doors open

the material is released and under its own weight descends through the water

column to the seabed. Any deposition will be carried out whilst underway in

order to provide as smooth a seabed as possible.

With the careful management of deposition within pre-defined zones and cells

the subsequent re-dredge and re-use can be carefully targeted and provide a

fully auditable process.

The rate of deposition cannot be quantified as this is dependent on a number

of as yet unknown variables such as the number and size of dredgers, the

programme of works, weather, sea and current conditions.


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Boskalis Westminster Limited A3 Figure 3.2BWL RDDZ 2 Zoning Grid and Zone Volumes

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Eaton HouseWallbrook CourtNorth Hinksey LaneOxford OX2 0QSTelephone: 01865 384800Facsimile: 01865 204982

Figure 3_2 - BWL RDDZ 2 Zoning Grid and Zone Volumes.mxd


39

3.3 CHARACTERISTICS OF MATERIAL DURING DEPOSITION

The behaviour of material when it is deposited is dependent upon a number

of factors, including vessel type and deposition method, material type and

local tidal currents. Sediment plumes will occur during the deposition of

material onto the seabed in RDDZ 2, however, the sediment proposed for

deposition within RDDZ 2 comprises mainly sands and gravels rather than

fines, and as such any plumes created should be relatively localised and short-

term. Sands and gravels once released into the water column will descend to

the seabed quicker than finer material, reducing the time the majority of the

material will be influenced by tidal currents and therefore transported from

the site of deposition.

Figure 3.3 shows the maximum predicted extent of the plume generated from

aggregate extraction in the region (Figure 5.11 from the Area 451 ES (ERM

2012)) based on plume data from the SC MAREA (Emu 2012)). Plumes up to

50 mgl-1 occur relatively consistently up to approximately 1000 m from the

east/northeast and west/southwest of licence boundaries. Plumes are

generally reduced to the north and south of the licences. Given the

consistency in distance for plume dispersion in Figure 3.3 it can be assumed

that disposal of a material, similar to that found in aggregate extraction

plumes, in RDDZ 2 area would produce a similar size plume, or indeed a

smaller plume if the material is a heavier fraction.

The SACD ES provided detailed modelling outputs that showed the extent of

plumes generated as a result of deposition of sand at the Nab Disposal

Ground, located adjacent to the RDDZ 2 area (Figure 3.4). Plumes of up to

50 mgl-1 from this sand deposition are predicted to occur up to 400 m from the

deposition site on the peak flood tide (1).

Based on the above assumption that plume generation is relatively consistent

across the region it can also be assumed that deposition of sand in RDDZ 2

will produce a similar plume to that shown in Figure 3.4. However, given that

the material to be deposited at RDDZ 2 will consist of more gravel it is likely

that the plume shown in Figure 3.4 will represent a worst case plume as it

contains a higher proportion of fines than will be deposited at RDDZ 2.

(1) The MAREA considers plumes on the peak flood and ebb tides, hence the comparison given here.

RYDE

NEWPORT


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Boskalis Westminster Limited A4 Figure 3.3Maximum Extent of Suspended Sediment Plume Footprints and Concentrations


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Restricted Dredge Deposit Zone 02 (RDDZ02)Aggegrate Licence Area 451

Suspended Sediment Plume FootprintPeak Concentration (mg/l)

20 - 4950 - 99100 - 139140 - 200201 - 320

Figure 3_3 - Maximum Extent of SuspendedSediment Plume Footprints and Concentrations.mxd

1:160,000

Area 122/3

Area 340

Area 351

Area 451


41

Figure 3.4 ABPmer Figure Showing the Initial Plume Following Disposal of Sand

Source: ABPmer, 2012. Appendix C.


42

ABPmer have prepared an addenda to the SACD ES (ABPmer 2013), to update

the ES with the revised disposal operations ie the use of RDDZ 2 to take

certain sand and gravel fractions of the SACD dredge arisings. In this

document ABPmer confirm that the plumes modelled for the SACD disposal

operations at the Nab Disposal Ground (Appendix C, ABPmer 2012) are

applicable to the RDDZ 2 site, stating that:

‘…the worst case scenario (for changes in SSC) for the proposed deposit at RDDZ 2

is represented by the modelled distribution shown in Figure C90 (Appendix C

ABPmer 2012) although the ‘centroid’ of movement will be displaced approximately

0.6km to the east. This model scenario assumes that all of the sediment deposited is

available for redistribution by re-erosion from the seabed given sufficient

hydrodynamic conditions. In actual fact, gravels are unable to be re-suspended, and

these will ‘armour’ the bed and lock a proportion of the finer sediments comprising the

deposits, preventing their onward movement. The levels of SSC are, therefore, likely to

be slightly overstated in the modelling whilst the overall extent of the change (i.e. the

shape of the plume) is well represented.’ (ABPmer 2013).

3.4 CHARACTERISTICS OF MATERIAL IN-SITU

Once in situ the sand and gravel material will behave similarly to the sand

and gravel material that existed at the site before aggregate extraction

commenced. There is a very slow rate of sediment infilling in this area,

suggesting low levels of mobile sediments in the area (p74 ERM, 2012).

Movement of the material once in situ will therefore be minimal. The

depression in which the material is to be deposited (depicted in the cross

section shown on Figure A.1) will further assist containment of the material.

The gridded deposition approach to be adopted by BWL will ensure that

shoaling of material is minimised. It is worth noting that creation of

pronounced mounds of material during deposition will make re-dredge of the

material at a later time for beneficial re-use schemes difficult and is therefore

something BWL will manage to avoid as far as possible. It is proposed that

static dumping is avoided and dumping occurs whilst the vessel is underway.


43

4 ASSESSMENT OF POTENTIAL EFFECTS

4.1 EFFECTS OF DEPOSITION ON WATER COLUMN

As discussed in Section 2.2.2, water quality in RDDZ 2 is generally good and

reflects the open water, dispersive and well flushed current regime in the area

and its distance from sources of contaminants such as major urban areas.

The sediment discharged will contain sand and gravel and will have a greater

density and velocity on entering the water surface than finer sediments. The

greater momentum and negative buoyancy of the discharged material mean

that the deposited sands and gravels will descend rapidly to the bed. Pebbles

and gravel will fall almost immediately to the bed and will not, in normal

conditions, be transported out of the deposit area.

Discharging the sediment to the water column will generate suspended

sediments which could result in a local increase in turbidity and reduced

water clarity and have potential secondary impacts on biological receptors.

As discussed in Section 3.3 plume will dissipate relatively quickly after

deposition ceases but will continue to occur intermittently during deposition

activities for the medium term (ie the lifetime of the deposition operations).

The potential impacts on water quality as a result of dredge plumes and

elevated suspended sediment are considered to be of small magnitude and

unlikely to breach any water quality standards or classifications.

4.2 EFFECTS OF DEPOSITION ON SEABED CONDITIONS

Bathymetry 4.2.1

The primary impacts of the proposed operations upon the bathymetry of

RDDZ 2 will be the reduction in depth as a result of the deposition of up to 2.3

million m3 of sands and gravels. Beyond RDDZ 2 there will be no changes in

bathymetry as a result of deposition activity in RDDZ 2.

Due to the change in bathymetry there is the potential for changes to currents

and tidal flows. However, the impacts on geology, geomorphology and

sediments are predicted to be small as they will occur over a limited spatial

area, mainly within RDDZ 2, and will predominantly reflect the conditions

that existed prior to dredging in Area 451.

Physical Oceanography 4.2.2

The deposition of sand and gravel proposed in RDDZ 2 has the potential to

change the topography of the seabed, which in turn could lead to changes in

the wave state. The Coastal Impact Study conducted in 2012 for the Area 451

ES reported that changes to the wave state and depth are constrained, and in


44

waters greater than 15 m depth changes to the seabed as a result of the

proposed deposition activities would not be expected to affect the wave state.

As a result, impacts on waves are predicted to be spatially limited and small

scale as the RDDZ 2 area lies in water depth of 25 m to 40 m below CD.

Depositing of sediment will take place using a grid technique (as presented in

Figure 3.2) to ensure managed deposition across the site. This will also aid in

monitoring the decrease in water depth across RDDZ 2, and depositing

operations will be capped at the pre-dredged level.

4.3 EFFECTS ON IDENTIFIED RECEPTORS

Benthic Environment 4.3.1

The recent Area 451 ES (ERM, 2012) considered the impacts to the benthic

environment in detail. Due to RDDZ 2 lying within Area 451 the following

assessment draws upon the Area 451 ES findings.

Benthic characteristics for the RDDZ 2 area are presented in Section 2.3. Area

451, within which the RDDZ 2 site lies, is an active dredging area, and has

been for 10 years. The invertebrate communities present in RDDZ 2 are

therefore relatively tolerant to changes in suspended sediments. Given the

low sensitivity and low exposure to a change in suspended sediment

concentrations likely during sediment deposition, and despite their indirect

importance to nature conservation features, the impact to invertebrate

communities is considered to be not significant.

Furthermore, as outlined in Section 3.1 all material deposited within RDDZ 2

will be a similar sediment type to that which exists at the site, so sediment

characteristics post deposition will remain relatively unchanged and as such,

benthic community structures will not be impacted.

Commercial Fisheries 4.3.2

The impacts to fisheries of deposition at RDDZ 2 have been described in

Section 2.4. Further detail can also be found in the Area 451 ES (ERM, 2012)

and the SACD ES (ABPmer, 2012). The South Coast MAREA (Emu, 2012)

highlighted that the only fish or shellfish species that has the potential to be

impacted by sediment depositing activities within the east of Isle of Wight

sub-region is the brown crab. All other potential effects of sediment

deposition on fish and shellfish species were assessed as not significant.

The effects of smothering and contamination of feeding grounds from sediment deposition was deemed insignificant by the SACD ES, whilst the loss of shellfish prey was considered insignificant to minor adverse, depending on the nature conservation importance of the fish species. Therefore it is concluded that there will be no adverse impacts upon commercial fisheries as a result of deposition activity at RDDZ 2.


45

Recreational Fisheries 4.3.3

Although recreational fisheries in the south coast region have increased in

popularity, there is a low recorded level within RDDZ 2, primarily due to the

lack of wrecks and more suitable grounds nearby. In addition, as RDDZ 2 lies

within the active dredge zone of Area 451 there will be no additional loss of

potential fishing grounds. Therefore it is concluded that there will be no

adverse impacts upon recreational fisheries as a result of deposition activity at

RDDZ 2.

Spawning and Nursery Grounds 4.3.4

Although there are insufficient data to define its extent, a brown crab

spawning area and ‘hen crab run’ is thought to coincide with the proposed

deposit site (Plumb 1996). The potential for smothering of suitable habitats

for critical phases of life history for the brown crab is considered by the South

Coast MAREA to be of minor significance. Noting that the scale of the

activities considered within the South Coast MAREA are much greater than

those proposed for RDDZ 2 and that the Area 451 ES considered the

magnitude of activity in Area 451 to be small given the area dredged at any

one time and the duration and extent of sediment plumes, it is therefore

concluded that the deposition activity within RDDZ 2, being of smaller

magnitude that the activity in Area 451, will not have an adverse impact upon

brown crab spawning and nursery grounds.

As previously discussed, the sediment to be deposited will be similar to those

that currently exist in RDDZ 2 so there will be no significant change in

sediment type at RDDZ 2. This will maintain the current conditions for the

spawning and nursery grounds within and around the deposition area. It is

therefore concluded that there will be no adverse impacts upon spawning and

nursery grounds as a result of deposition activity at RDDZ 2.

Marine Mammals 4.3.5

As discussed in Section 2.5, marine mammal distribution was reported to be

low within and around Area 451 and found that it was unlikely for there to be

any significant impacts on marine mammals as a result of dredging activities

to the east of the Isle of Wight, or within the whole of the South Coast MAREA

study area. The Area 451 ES (ERM, 2012) concluded that the impacts to

marine mammals as a result of aggregate extraction at Area 451 are Not

Significant. As the deposition activity within RDDZ 2 lies within Area 451 and

will result in impacts similar to or less than those assessed for the Area 451 ES,

marine mammals are not considered likely to be adversely impacted by

deposition at RDDZ 2.

Protected Areas and Species – Blue Mussel Beds 4.3.6

RDDZ 2 does not overlap with the identified blue mussel beds in Area 451, as

shown on Figure 2.10.


46

It is noted in the conservation review (Emu, 2013) that the mussel beds lie

within the plume extent of the Nab Disposal Ground, suggesting that the blue

mussel beds are tolerant of the levels of SSC resulting from disposal activity at

the Nab Disposal Ground. As there is no overlap of RDDZ 2 with the blue

mussel beds and that the plume resulting from the deposition activity of sand

and gravel will not be greater than that already experienced by the beds from

the Nab Disposal Ground, which takes significant amounts of fine material for

disposal (therefore producing greater plumes), it is concluded that any

impacts from the deposition activity at RDDZ 2 will be within that already

occurring and will therefore not result in any adverse impacts to the blue

mussel beds.

Infrastructure and Other Operations 4.3.7

Aggregate Extraction Area 451

The deposit site sits within an active aggregate extraction area, Area 451,

managed by the same company proposing to undertake the deposit of sand

and gravel within RDDZ 2. BWL is therefore able to manage its operations,

both aggregate extraction and deposition, within Area 451 to avoid

operational overlaps and to ensure that the conditions placed on vessel

operation with Area 451 by the Marine Licence L/2012/00277/1 are complied

with.

Additionally the benefits of siting the deposition site within an existing area of

activity, as discussed in Section 1, will be that disturbance associated with the

activity occurs within an area already impacted. For these reasons it is

concluded there are no adverse effects resulting from the deposition activity

with RDDZ 2 upon aggregate extraction at Area 451.

Nab Disposal Ground

Area 451 has existed alongside the Nab Disposal Ground for the past ten years

without incident or issue. The deposit activity at RDDZ 2 will not overlap

with activity at the Nab Disposal Ground.

Additionally the deposit site is being proposed to help maintain capacity at

the Nab Disposal Ground as outlined in Section 1. Through maintaining

capacity at the Nab Disposal Ground there will be secondary benefits to other

operations in the region which dispose of capital and maintenance dredgings

to the site. If the sites capacity were to be reached then another disposal site

would need to be found. For these aforementioned reasons it is concluded

there are no adverse effects resulting from the deposition activity with RDDZ

2 upon the Nab Disposal Ground and there is a positive benefit in terms of

preserving >500,000 m3 of capacity at the site.


47

5 REASON FOR SITE SELECTION

As outlined in the previous sections there are significant benefits to

establishing a site that has the capacity to accommodate large volumes of sand

and gravel generated from capital and maintenance dredge schemes,

particularly when dredge regimes and possible beneficial re-use cannot be

aligned to make use of the material as it arises. BWL has identified RDDZ 2 as

a site with sufficient capacity and characteristics to provide such a holding

facility.

The classification of a deposition site at RDDZ 2 will result in significant

benefits, ensuring that sand and gravel that could be utilised for re-use is not

‘lost’ through disposal to the Nab Disposal Ground, as well as assisting to

maintain capacity at the Nab Disposal Ground, a dispersive site, by depositing

the much less dispersive sand and non-dispersive gravel elements at RDDZ 2

instead. Importantly the proposed RDDZ 2 site will assist BWL, those

requiring capital and maintenance dredge schemes and the Regulator to

consider re-use of materials that would otherwise be disposed of, enabling all

to support the Waste Framework Directive (EC, 2008) waste hierarchy and

aims of other waste legislation in avoiding disposal where possible.

As outlined in Section 4 there are no adverse impacts likely to occur as a result

of deposition activity in RDDZ 2. RDDZ 2 sits within an active aggregate

extraction area and there will be no discernible difference between the impacts

that may occur as a result of the deposition activity and those already

occurring from the extraction activity at Area 451.

For these reasons RDDZ 2 is put forward by BWL as a viable site to hold

material once dredged, to enable it to be considered for viable beneficial re-use

that will arise in the future.


48

6 MONITORING PROPOSALS

It is recognised by BWL that some monitoring will be required to demonstrate

that the deposit operations and associated environmental effects occur as

anticipated. BWL therefore propose that the following monitoring will be

undertaken if the RDDZ 2 is characterised as a deposit site for sand and gravel

material.

Pre-deposition bathymetric survey. A recent high quality baseline

multibeam bathymetric survey and side scan sonar survey has been

carried out as part of the Area 451 baseline survey Marine Licence

requirements.

Post-deposition bathymetry survey. A post deposition multibeam

bathymetry survey of the zones and cells (Figure 3.2) used for deposition

plus a 500m buffer will be undertaken once deposition for a campaign has

ceased. This will provide confirmation that deposition has not exceeded

the available capacity of RDDZ 2 and will provide the basis for any dredge

re-use strategy.

Deposition within Area 451 RDDZ 2 will be managed as defined in Section

3.2. Cargo ullage reports will be kept during deposition activity.

A report of the post deposition multibeam survey and cargo ullage reports

will be made available to the regulator and its advisors.

As RDDZ 2 sits within Area 451 where possible the monitoring requirements

will be accommodated within the monitoring regime of Area 451.


49

REFERENCES

ABPmer, 2013. Variation to Southampton Approach Channel Dredge Marine

Licence: Supplementary Information. Report R.2198

ABPmer, 2012. Environmental Statement for Port of Southampton:

Southampton Approach Channel Dredge - Updated by Further Information.

ABP Marine Environmental Research, Research Report R.2015.

Apitz, S. E., 2010. "Waste or resource? Classifying and scoring dredged

material management strategies in terms of the waste hierarchy." Journal

of Soils and Sediments 10: 1657 - 1668.

Birchenough, A. C., and Vivian, C. M. G., no date given. Case Studies to

Demonstrate the Selection of Dredged Material Disposal Sites at Sea. Cefas

Ref ME1401 CDEV Thematic R&D Project.

CEFAS, 2001. The Impact of Disposal of Marine Dredged Material on the

South Wight Maritime and Solent Maritime Candidate Special Areas of

Conservation (cSACs). A review of existing consents for the sea disposal of

dredged material, as required under the Conservation (Natural Habitats &c)

Regulations, 1994. Pp 16.

Coull K.A., Johnstone R., and Rogers S.I., 1998. Fisheries Sensitivity Maps in British Waters. Published and distributed by UKOOA Ltd. Ellis, J.R., Milligan, S.P., Readdy, L., Taylor, N. and Brown, M.J. 2012. Spawning and nursery grounds of selected fish species in UK waters. Sci. Ser. tech. Rep., Cefas, Lowestoft, 147: 56 pp.

EMU Limited, 2012. South Coast Marine Aggregate Regional Environmental

Assessment, Volumes 1 and 2. Report for the South Coast Dredging

Association. Report Ref: J/1/06/1870.

ERM, 2012. Area 451 – East Isle of Wight Marine Licence Application: Final

Environmental Statement. Ref 0128267.

Fugro Emu Ltd, 2013. Area 451 Conservation Review. Report Number:

13/J/03/2195/1450.

Holt, T.J., Rees, E.I., Hawkins, S.J., and Seed, R. 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 Pages

HR Wallingford, 2012. South Coast Dredging Association MAREA: Flow and

wave model validation. Report EX 6664.

HR Wallingford, 2011. Area 451, St Catherine’s Coastal Impact Study. Report

EX 6458.


50

HR Wallingford, 2010. South Coast Dredging Association MAREA: Summary

report. Report EX 6212

James, J W C, Pearce, B, Coggan, R A, Arnott, S H L, Clark, R, Plim, J F, Pinnion, J, Barrio Frójan, C, Gardiner, J P, Morando, A, Baggaley, P A, Scott, G, Bigourdan, N. 2010. The South Coast Regional Environmental Characterisation. British Geological Survey Open Report OR/09/51. 249 pp.

Jones, L.A., Irving, R., Cosgrove, A.R.P., Coyle, M.D., Gilliland, P.M., Murray, A.R. (2004). Eastern Channel Marine natural Area Profile: A contribution to regional planning and management of the seas around England. Peterborough: English Nature.

MMO Marine licensing guidance 3 Dredging, disposal and aggregate

dredging (MMO, 2011)

Plumb, T.W. (1996). Fisheries intensity study revised area 395- South East of

nab tower, Solent

Walmsley, S.A., and Pawson, M.G., 2007. The coastal fisheries of England and

Wales, Part V: a review of their status 2005-6. Science Series Technical Report,

Cefas Lowestoft, 140: 83pp.

Waste Framework Directive (EC, 2008) Council Directive 2008/98/EC

Wessex Archaeology, 2013. Area 451 Marine Aggregates Extraction

Archaeological Assessment of 2012 Geophysical Data, Archaeological Baseline

Report. Ref: 87920.02.

Annex A

Figure A.1. RDDZ 2 Resource

Geology And Thickness (Supplied

By BWL)

© ERM This print is confidential and is supplied on the understanding that it will be used only as a record to identify or inspect parts, concepts or designs and that it is not disclosed to other persons or to be used for construction purposes without permission.


DATE: 25/11/2013

DRAWN: AZ

CHECKED: EB

APPROVED: KM

PROJECT: 0128267


KEY:

Boskalis Westminster Limited A1 Figure A.1RDDZ 2 Resource Geology and Thickness (Supplied by BWL)

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ERMEaton HouseWallbrook CourtNorth Hinksey LaneOxford, OX2 0QSTelephone: 01865 384800Facsimile: 01865 204982

Figure A1 - RDDZ 2 Resource Geology andThickness.mxd

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