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Groundwater Environment Management - Dewatering and Monitoring StrategyDoc Ref: APP128

Folder 200 12 February 2014DCO-DT-APP-ZZ100-280000

Thames Tideway Tunnel Thames Water Utilities Limited

Application for Development ConsentApplication Reference Number: WWO10001

Groundwater environmental management dewatering and monitoring strategy

100-XX-XXX-00000-000000 | AG | Feburary 2014

Groundwater environmental management – dewatering and monitoring strategy


Page i

Thames Tideway Tunnel

Groundwater environmental management – dewatering and monitoring strategy

List of contents

Page number

Executive summary ................................................................................................. iii

EX 1 Groundwater environmental management – dewatering and monitoring strategy .................................................................................................... iii

2 Part A: Introduction and baseline ................................................................... 1

2.1 Introduction .............................................................................................. 1

2.2 Objectives ................................................................................................ 2

2.3 Scope of groundwater monitoring ............................................................ 2

2.4 Structure of document ............................................................................. 4

2.5 Project context ......................................................................................... 6

2.6 Baseline ................................................................................................... 9

2.7 Pollutant linkages .................................................................................. 14

3 Part B: Dewatering strategy .......................................................................... 19

3.1 Thames Tideway Tunnel project‟s approach to dewatering ................... 19

3.2 Dewatering requirements and ongoing testing ...................................... 22

3.3 Mitigation ............................................................................................... 25

3.4 Dewatering plan ..................................................................................... 25

4 Part C: Groundwater management and monitoring .................................... 28

4.1 Groundwater management and monitoring strategy .............................. 28

4.2 Assessment of risk along the tunnel route and proposed remedial works37

4.3 Initial assessment and compliance criteria for groundwater .................. 38

4.4 Monitoring deliverables .......................................................................... 40

4.5 Contingency action plan ........................................................................ 41

4.6 Reporting and sign-off ........................................................................... 42

5 Part D: Groundwater monitoring - plans ...................................................... 44

5.1 Overarching Thames Tideway Tunnel project Groundwater monitoring management plan .................................................................................. 44

5.2 Proposed scope of Contractor Groundwater monitoring plan ................ 46

5.3 Monitoring schedule .............................................................................. 48

5.4 Contingency planning ............................................................................ 50


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5.5 Reporting ............................................................................................... 53

Appendices ............................................................................................................. 57

Appendix A : Upper Aquifer monitoring locations ............................................. 59

Appendix B : Thanet Sand Formation.................................................................. 61

Appendix C : Chalk monitoring locations ........................................................... 63

Appendix D : Water quality long list .................................................................... 65

6 References ...................................................................................................... 71

Executive summary


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Executive summary

EX 1 Groundwater environmental management – dewatering and monitoring strategy

EX 1.1 The Groundwater environmental management – dewatering and

monitoring strategy is an updated version of the Groundwater environmental monitoring strategy issued as part of the Environmental Statement (ES) (Doc. ref: 6.02.03, Vol 3, Appendices (F to M), Appendix K) in February 2013.

EX 1.2 The report is divided into four sections:

a. Part A – provides the Thames Tideway Tunnel project (the „proejct‟) context and a background baseline summary

b. Part B – explains the draft dewatering strategy, summarises the project approach to dewatering, the embedded design measures and the dewatering plan

c. Part C – identifies the objectives of the groundwater monitoring strategy, the network and monitoring methodologies

d. Part D – explains the groundwater monitoring plans, the overarching management protocols for construction phase (and operational phase) monitoring and an outline content for Contractor monitoring plans.

EX 1.3 The new sections of this strategy, Parts B and D have been added in response to the Relevant Representation from the Environment Agency (May 2013).

EX 1.4 Compliance with this document is secured by project-wide Requirement PW14, which relates to groundwater and dewatering monitoring and management.

EX 1.5 Part B of this document summarises the dewatering assessment presented in the ES (Volume 3 to 27 Section 13). For each shaft site, the proposed construction methods and amounts of dewatering are presented (these were the same values used to assess the impact of dewatering within the ES). The construction methods have been chosen to keep duration of pumping and the rates to a minimum. The dewatering requirements are the best available estimates. These values are subject to change in the light of new information obtained from pumping tests, additional ground investigation and further design by the Contractors. The main works Contractors will be responsible for preparing individual site-specific dewatering plans. The Employer will review and approve the site-specific dewatering plans prior to submission to the Environment Agency for approval.

EX 1.6 Part D is made up of the overarching groundwater management (GWM) plan. This plan will apply during construction (and operational phase) and will be used by the Employer to assess Contractor performance and identify/assess differences across the project. The Contractor GWM plans

http://infrastructure.planningportal.gov.uk/wp-content/ipc/uploads/projects/WW010001/2.%20Post-Submission/Application%20Documents/Environmental%20Statement/6.2.03_Environmental_Statement_Volume_3_Appendices_F_to_M.pdf

Executive summary


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will include details of the monitoring network, methodologies, contingency planning and reporting. Three different types of reports may be used; incident notification reports (following breaches of trigger levels or pollution incidents), quarterly factual reports and annual interpretative reports. Reports will be submitted to the Environment Agency in accordance with a time-frame agreed pursuant to Section 4.6 below.

EX 1.7 The inclusion of new section in Part C – Section 4.2 is designed to address concerns over the potential risk of mobilisation and migration of pre-existing contaminants affecting the lower aquifer as a result of construction. The main works Contractors will be responsible for obtaining the approval of their construction plans by the Environment Agency before tunnelling begins.

EX 1.8 Any changes to this strategy will be submitted to the Environment Agency for approval prior to implementation.

2 - Part A: Introduction and baseline


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2 Part A: Introduction and baseline

2.1 Introduction

2.1.1 The project will install a tunnel to transfer sewage from the most polluting combined sewer overflows (CSO) under central London to Beckton Sewage Treatment Works, via the Lee Tunnel (which will run between Abbey Mills and Beckton). The tunnel will extend from Ealing in the west, to Newham in the east and Greenwich in the southeast. It is proposed to construct 24 shafts both to facilitate the construction of the tunnel and to connect the tunnel to the CSOs.

2.1.2 The Groundwater environmental management – dewatering and monitoring (GEM DM) strategy represents an updated version of the Groundwater environmental monitoring strategy, which was appended to the ES. An update has been undertaken in response to the Relevant Representation from the Environment Agency (EA) (May 2013) which requested that a dewatering strategy be secured as part of the Draft DCOi.

2.1.3 The groundwater monitoring strategy and the dewatering strategy are secured via project-wide Requirement PW14ii of Schedule 3 of the DCO. PW14 relates to groundwater and dewatering monitoring and management and states that:

2.1.4 “Groundwater and dewatering monitoring and management shall be carried out in accordance with the Groundwater Environmental Management - Dewatering and Monitoring Strategy. Any alterations to the strategy should be submitted to, and agreed, by the Environment Agency.”

2.1.5 Part B of this document contains the dewatering strategy and outline plan.

2.1.6 Parts C and D of this document contains the groundwater monitoring strategy and plan.

2.1.7 The results of the monitoring required by this strategy will be reported annually as an interpretive groundwater environmental monitoring report and via quaterly factual reports which will be issued to the Environment Agency for approval. Details of the reporting protacol is included in Section 4.5.

2.1.8 The following terminology is used in this document, consistent with that used in the Code of Construction Practice (CoCP):

a. The Employer in the party in whom the DCO powers are vested, or transferred under the terms of the DCO, and implements the project, including where appropriate the Employer‟s project management organisation.

i The Draft Thames Water Utilities Limited (Thames Tideway Tunnel) Development Consent Order.



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b. The Contractor is the party engaged by the Employer to exercise the powers described in the DCO.

2.2 Objectives

2.2.1 The objective of this document is to set out a strategy to manage and monitor the effects of the proposal on groundwater quality and quantity in the upper and lower aquifer throughout construction (including dewatering) and operation of the Thames Tideway Tunnel. This includes measures to monitor the following:

a. mobilisation and migration (with the prevailing groundwater flow) of constituents (for example approved grout mixes) used in tunnel/shaft construction, both during construction and in the long term

b. increased turbidity in groundwater due to the physical action of tunnelling construction within the Chalk, and subsequent migration with the prevailing groundwater flow

c. effects of seepage from the tunnel on groundwater quality

d. mobilisation of contaminant already present in groundwater by the creation of alternative pathways, or significantly altering existing pathways

e. changes in water quality and levels as a result of dewatering and the effectiveness of mitigation measures to counter these effects.

2.2.2 This strategy sets out the approach that will be taken to the installation and monitoring of existing and additional monitoring holes for baseline, construction, post-construction and long-term monitoring. It provides the process for determining Alert and Trigger levels and identifies generic mitigation measures and a contingency action plan in the event of significant exceedances during and post construction.

2.2.3 The strategy has been developed in consultation with the Environment Agency and reviewed at regular intervals. Revisions to the Groundwater environmental management dewatering and monitoring strategy shall be the responsibility of the Employer and must be approved by the Environment Agency; the Environment Agency and Contractor(s) may request amendments to the strategy if required.

2.3 Scope of groundwater monitoring

2.3.1 Monitoring of construction and operational effects are embedded in the environmental design of the project through the application of this groundwater environmental management – dewatering and monitoring strategy. The monitoring includes both groundwater levels and groundwater quality. The monitoring regime described in the report will be developed during the life of the project to ensure that the Employer and the Contractors can identify and respond to changes in groundwater levels or groundwater quality as a result of any changes in the project design and/or the site conceptual model.



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Baseline groundwater monitoring

2.3.2 Ongoing baseline groundwater monitoring will continue prior to construction.

2.3.3 The pre-construction baseline will inform the setting of alert and trigger levels, for both quality and levels, for the construction monitoring phase. These alert and trigger levels will be proposed by the Employer and approved by the Environment Agency. Any changes to the Alert and Trigger Levels proposed by the Contractors must be approved by the Employer and the Environment Agency before use.

Construction monitoring

2.3.4 Construction groundwater monitoring will be undertaken as described in Part D by the Contractor(s) during all phases of construction of the Thames Tideway Tunnel project. The results shall be reported to the Employer and the Environment Agency. The overall construction programme would be from 2016 until 2022.

2.3.5 Given that changes to groundwater generally take place slowly, it will be necessary to continue groundwater monitoring for a minimum of two years after the end of any construction ground disturbance unless otherwise approved by the Environment Agency. In certain situations, the construction monitoring may run into the period when operational monitoring is being carried out (see paras. 2.3.7 to 2.3.9).

2.3.6 The pre-construction monitoring dataset will be used to establish a baseline against which the operational phase monitoring will be compared. It is recognised that changes may occur not as a result of the project but during the period of its construction. In such circumstances, the pre-construction baseline will be compared to the operational monitoring and modified if deemed appropriate. Any modifications to the baseline shall be provided to the Environment Agency for approval two months before adoption.

Operational monitoring

2.3.7 It is recognised that operational monitoring will be required throughout the commissioning and operational life of the project. The Employer will be responsible for ensuring that the operational monitoring is undertaken. The operational monitoring results shall be reported quarterly via factual reports and annually in the form of an interpretative report to the Environment Agency by the Employer.

2.3.8 Operational groundwater monitoring will be the same as that undertaken during construction and will continue for a minimum of two years after operation commences (the first year of operation is anticipated to be 2023).

2.3.9 Monitoring requirements will be reviewed with the Environment Agency after a two-year period.



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2.4 Structure of document

2.4.1 Part A of this document contains the project context, the proposed construction methods, the geology to be encountered and the source-pathway-receptor model.

2.4.2 Part B presents the dewatering strategy which forms part of the overall groundwater environmental management – dewatering and monitoring strategy. The dewatering plan is the method by which the dewatering strategy will be delivered for the project. The dewatering plan is presented in outline in Part B. Individual site dewatering plans will be submitted by the Contractors to the Environment Agency for approval in advance of dewatering works being undertaken. The Contractors will be responsible for obtaining all necessary licences and permits for abstraction and discharge for dewatering.

2.4.3 Part C presents the groundwater management and monitoring strategy, including details of the monitoring network, the measurement procedures and the suites of determinants to be analysed. The Employer will be responsible for the groundwater monitoring strategy.

2.4.4 Part D presents the overarching project groundwater monitoring management plan that will apply during pre-construction, construction and operation. The Employer will be responsible for implementing the overarching groundwater monitoring plan. Also presented is the proposed scope of the Contractor groundwater monitoring plans that will be implemented by the Contractors during construction of the project. The Contractor Groundwater Monitoring Plans for each Contractor geographical region sit within the overarching plan described in Part D. The Employer will be responsible for delivering the groundwater monitoring during the pre-construction and operational phases of the project.

2.4.5 Figure 2.1 below shows the relationships between the Groundwater Monitoring Strategy and the Dewatering Strategy.



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Figure 2.1: Monitoring Hierarchy Schematic

Part C and Part D

Employer's Groundwater

Monitoring Strategy

Employer's Overarching

Groundwater Monitoring Plan

Contractor's Groundwater

Monitoring Plan (West)


Monitoring Plan (Central)


Monitoring Plan (East)

Part B

Employer's Dewatering Strategy

Employer's Dewatering Plan

Contractor's site Dewatering Plans

(West)


(Central)


(East)



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2.5 Project context

Project layout

2.5.1 The proposed tunnel alignment and locations of the shafts are shown in Appendix Figure A.1, 0 and Figure C.1.

Tunnel construction

2.5.2 The elements of construction for the proposed development, relevant to the consideration of groundwater includes:

a. A main tunnel approximately 25km in length and extending from Acton Storm Tanks to Abbeys Mills Pumping Station.

b. Two long connection tunnels:

i Greenwich connection tunnel (4.6km) from Greenwich Pumping Station to Chambers Wharf

ii Frogmore connection tunnel (1.1km) between the main tunnel at Carnwath Road Riverside and south to King George‟s Park.

c. Nine short connection tunnels totalling approximately 1.2km which will be constructed in the London Clay and the Lambeth Group.

Shaft construction

2.5.3 The Thames Tideway Tunnel requires the construction of 24 shafts, and associated shallow infrastructure, at 23 sites (two shafts are required at Beckton Sewage Treatment Works).

2.5.4 The depth of the shafts depends on their location with shaft depth becoming deeper from west to east. Where a shaft would interact with the lower aquifer, dewatering or alternative groundwater control would be required to enable construction. The construction methods likely to be employed at each shaft site are described in Table 1. Note that the Contractors may use alternative construction methods; Table 1 presents current assumptions of likely methods based on typical construction practices on similar schemes and taking into account the local ground conditions at each shaft site.



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Table 1: Shaft method of construction

Area Shaft site Sprayed

concrete lining (SCL)

Piled walliii Segmental

shaft Diaphragm

wallsiv Depressurisationv of Lambeth Group

We

st

Acton Storm Tanks

Hammersmith Pumping Station

Barn Elms

Putney Bridge Foreshore

Dormay Street

King George‟s Park

Carnwath Road Riverside

Falconbrook Pumping Station

Cremorne Wharf Depot

Central Chelsea Embankment Foreshore

*

Kirtling Street **

Heathwall Pumping Station

iii Sheet or secant pile wall – a sub-surface structure installed to support excavation and which amongst other things helps to control inflows of shallow groundwater typically

formed of intersecting concrete or overlapping shafts of concrete. iv Diaphragm wall – a sub-surface barrier installed around construction works to support the required excavation and which amongst other things helps to control inflows of

groundwater typically formed of reinforced concrete. This barrier would extend down by up 8m below the base of the shaft invert, for structural reasons and to increase the length of the flow path and hence reduce the amount of groundwater inflows v Depressurisation – a term used to describe dewatering or lowering of hydraulic pressures in a confined aquifer.



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Area Shaft site Sprayed

concrete lining (SCL)

Piled walliii Segmental

shaft Diaphragm

wallsiv Depressurisationv of Lambeth Group

Albert Embankment Foreshore

Victoria Embankment Foreshore

Blackfriars Bridge Foreshore

Ea

st

Chambers Wharf

King Edward Memorial Park Foreshore

Earl Pumping Station

Deptford Church Street

Greenwich Pumping Station

Abbey Mills Pumping Station

Beckton Sewage Treatment Works

* Sprayed concrete lining is expected to be required for the construction of the connection tunnel at Chelsea Embankment Foreshore. ** Sprayed concrete lining is expected to be required for the construction of the chambers at the Kirtling Street site.



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Shaft dewatering

2.5.5 No dewatering of the upper aquifer is expected to be required for construction due to planned piling, segmental shaft or diaphragm walls which would seal out the River Terrace Deposits.

2.5.6 Groundwater levels would however have to be lowered in the vicinity of the central and eastern area shafts by dewatering of the lower aquifer to allow construction of the main tunnel shafts and CSO drop shafts. These areas are where either construction activities extend down into the lower aquifer or where the construction activities come close enough to the lower aquifer for them to be affected by the groundwater under high pressure, potentially causing heave effects (uplift).

2.5.7 No dewatering is anticipated to be required for the construction of the main tunnel or the Greenwich connection tunnel even though these will be within the lower aquifer in the eastern area.

2.5.8 Short connection tunnels in the central section will require dewatering or depressurisation. The dewatering proposed at the shaft sites associated with these connection tunnels (at Cremorne Wharf Depot, Chelsea Embankment Foreshore, Heathwall Pumping Station, Albert Embankment Foreshore and Victoria Embankment Foreshore) is expected to be sufficient for the construction of the connection tunnels.

2.5.9 Further details on the rates and duration of pumping are given in Section 3.2.

2.6 Baseline

Geology

Regional geology

2.6.1 The regional geology of the London Basin is summarised in Table 2 below.

Table 2: Regional geology (solid strata) of the London Basin

Era Group Formation Approx

thickness (m)

Palaeogene Thames Bagshot Formation 10-25

Claygate Member

London Clay

30-90

Harwich Formation 0-10

Lambeth Woolwich and Reading Beds 10-20

Upnor Formation 5-7

Thanet Sands 0-30



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Era Group Formation Approx

thickness (m)

Cretaceous Chalk 180-245

(Source: BGS Memoir Geology of London 2004)

2.6.2 Not all formations are represented throughout the London Basin and superficial deposits comprising Alluvium, Terrace Gravels, Brickearth and Peat are often present, and these may be overlain or replaced by Made Ground.

2.6.3 The following sections describe the anticipated tunnel geology and the geology at each shaft site. The bedrock and superficial deposits are shown in Appendix Figure A.1, Figure B.1 and Figure C.1.

Tunnel alignment geology

2.6.4 The route of the main tunnel will pass from west to east through a sequence of sedimentary strata from the London Clay Formation for approximately 9,150m then through the Lambeth Group (7,550m), Thanet Sands Formation (2150m) and finally into the Chalk Group (6,300m). This sequence is shown in Table 3.

Table 3: Geology of main tunnel and connection tunnel sections

Geology Tunnel

chainage m (start)

Tunnel chainage m

(end)

Approx. m ATD (start)

Approx. m ATD (end)

Main Tunnel – Acton Storm Tanks to Abbey Mills

London Clay 0 9150 75 61

Lambeth Group 9150 16700 61 51

Thanet Sands 16700 18850 51 51

Chalk 18850 25150 51 49

Greenwich Connection Tunnel – Chambers Wharf to Greenwich Pumping Station

Chalk 0 4600 49 59

Frogmore Connection Tunnel – King George’s Park to Carnwath Road Riverside

London Clay 0 1120 83 55

( m ATD – metres above tunnel datum) (Conversion from m ATD to m AOD can be done by subtracting 100 mAOD)

Shaft geology

2.6.5 Of the 23 shafts, eight shafts will extend down into the London Clay Formation, seven into the Lambeth Group/Upnor Formation and eight into the Thanet Sands/Seaford Chalk. The geology and hydrogeology at these sites are summarised in Table 4 below.



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Table 4: Geology at base of drop shaft sites

Site name Approx.

shaft depth (m)

Geology

Acton Storm Tanks 30.8 London Clay Formation

Hammersmith Pumping Station 32.6 London Clay Formation

Barn Elms 33.8 London Clay Formation

Putney Embankment Foreshore 36.2 London Clay Formation

Dormay Street 23.6 London Clay Formation

King George's Park 20.4 London Clay Formation

Carnwath Road Riverside 42.3 Lambeth Group

Falconbrook Pumping Station 40.1 London Clay Formation

Cremorne Wharf Depot 42.1 London Clay Formation

Chelsea Embankment Foreshore

45.5 Lambeth Group

Kirtling Street 47.6 Upnor Formation

Heathwall Pumping Station 46.3 Lambeth Group

Albert Embankment Foreshore 47.1 Upnor Formation


49.5 Lambeth Group

Blackfriars Bridge Foreshore 53.3 Thanet Sands Formation

Chambers Wharf 57.3 Chalk

King Edward Memorial Park Foreshore

60.3 Chalk

Earl Pumping Station 50.4 Chalk

Deptford Church Street 47.8 Chalk

Greenwich Pumping Station 45.9 Chalk

Abbey Mills Pumping Station 66.8 Chalk

Beckton Sewage Treatment Works - Drive Shaft

32.0 Upnor Formation

Beckton Sewage Treatment Works - Reception Shaft

30.0 Thanet Sands Formation

Hydrogeology

2.6.6 The hydrogeological baseline for the project is summarised below and described in more detail in the ES.

2.6.7 The Chalk is the main aquifer of the London Basin and is confined over much of the area by the Tertiary formations (the Lambeth Group and Thanet Sands) and superficial deposits (Alluvium and River Terrace



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Deposits). The Chalk is classified by the Environment Agency as a Principal Aquifer. The Upnor Formation, Thanet Sands and Chalk are referred to as the lower aquifer.

2.6.8 The most permeable superficial deposits, the River Terrace Deposits, are referred to as the upper aquifer and are classified by the Environment Agency as a Secondary A Aquifer. The Alluvium, overlying the River Terrace Deposits, may act as confining layer for the upper aquifer at certain locations. At other locations, the Alluvium may be in hydraulic continuity with the upper aquifer.

2.6.9 The upper and lower aquifers are generally hydraulically separated by the London Clay Formation. The London Clay Formation is considered to act as an aquiclude between the upper and lower aquifers. Any groundwater present in a majority of the London Clay Formation is likely to consist of localised seepages and/or minor flows. The London Clay Formation is absent or less than 1m thick at the King Edward Memorial Park, Earl Pumping Station, Deptford Church Street and Greenwich Pumping Station shaft sites and therefore in these locations, depending on local conditions, the upper and lower aquifers may be in hydraulic continuity.

2.6.10 The Harwich Formation is present across much of the assessment area and is considered to form a minor aquifer unit where it is isolated from the lower aquifer by the Lambeth Group.

2.6.11 Within the Lambeth Group, several confined groundwater bodies are expected to be encountered. Groundwater is expected to be present through the Upper Shelly Beds and Upper Mottled Beds (potentially small inflows) and under high pressure within the Laminated Beds (formerly part of the Woolwich Formation).

2.6.12 The Thanet Sands and the Upnor Beds (lower unit of the Lambeth Group) are known as the „Basal Sands‟ and are in hydraulic continuity with the Chalk aquifer beneath London. The Basal Sands is classified by the Environment Agency as a Secondary Aquifer.

2.6.13 The regional direction of groundwater flow within the London Basin is towards an area of low piezometric levels within central London. However, the groundwater gradient may be affected locally by abstractions, particularly during peak demand periods associated with major licences.

2.6.14 There are limited monitoring boreholes within the upper aquifer and at most shaft sites it has not been possible to accurately determine the direction of groundwater flow at these depths; however, it is likely to be local and towards the River Thames due to surrounding topography.

2.6.15 The Chalk groundwater level is shown in Appendix Figure C.1 (Environment Agency, 2011). The lower aquifer is likely to be confined and the tunnel is likely to be below the water table of the lower aquifer as it passes from the Lambeth Group into the Thanet Sands.

Licensed abstractions

2.6.16 There is one Environment Agency licensed abstraction (28/39/39/0225) from the upper aquifer located within 1km of the proposed shaft sites and



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the tunnel route. This licensed abstraction abstracts from the River Terrace Deposits.

2.6.17 There are 40 Environment Agency licensed abstractions from the lower aquifer either located within 1km (where abstractions are identified to be of particular importance and are beyond a kilometre from the tunnel they have been considered) of the proposed shaft sites or the tunnel route. The licensed abstraction sources listed in Table 5 all abstract from the lower aquifer. In addition, there is one source in the upper aquifer, located in the central area which is used for industrial, commercial and public service purposes. The abstractions from the lower aquifer are summarised in table below.

Table 5: Environment Agency licensed abstractions from the lower aquifer

Area Licence purpose No. of licences

Central

Drinking water supply 11

GSHP (heat pump or cooling)

12

Industrial, commercial & public service (process water or irrigation)

4

Eastern

Drinking water supply 5

GSHP (cooling) 3

Industrial, commercial & public service (amenity top-up water or horticultural)

4

2.6.18 There are three unlicensed abstractions from the Chalk aquifer located

within 1km of the shaft sites and tunnel route, based on information provided by the London boroughs. One of these unlicensed sources is used for drinking water supply and the purpose of the remaining two is unknown.

Source protection zones

2.6.19 The Environment Agency defines Source Protection Zones (SPZ) around all public water supply abstractions sources and large licensed private abstractions used for human consumption in order to safeguard groundwater resources from potentially polluting activities. SPZs are split into three zones: an SPZ 1 defined as a modelled 50-day travel time to a source; an SPZ 2 defined as a modelled 400-day travel time to a source; and an SPZ 3 represents the modelled total catchment zone of a source.

2.6.20 The proposed Kirtling Street and Heathwall Pumping Station shaft sites are located within SPZ 1 associated with the Thames Water Battersea public water abstraction.



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2.6.21 The proposed Deptford Church Street shaft is located within SPZ 3 of the Thames Water Deptford public water abstraction. Greenwich Pumping Station shaft is located within SPZ 1 of the Deptford abstraction.

2.6.22 The tunnel crosses SPZ 1 and 2 associated with the Battersea abstraction, and passes in close proximity to the SPZ 1 associated with the Mantilla Ltd Dolphin Square private water supply.

2.6.23 The tunnel passes through SPZ 1 and 2 associated with the Thames Water Deptford abstraction between the Earl and Greenwich Pumping Station sites.

2.7 Pollutant linkages

Sources of contamination

2.7.1 Existing sources of contamination will be identified from the ground investigation and monitoring works undertaken as part of the project. Land quality assessment will be undertaken and reported in line with the contaminated land DCO Requirements.

2.7.2 Baseline groundwater quality data have been compared to UK drinking water standards and relevant Environmental Quality Standards (EQS).

2.7.3 Potential new sources of contamination have been identified based on typical construction practices on similar schemes and taking into account the planned operational activities.

Made ground

2.7.4 The proposed development will involve the removal of the Made Ground from within the footprint of the shaft as part of the development of the shafts. It is considered that other potential sources of contamination from shaft sites would be removed, subject to the findings of the Quantitative Risk Assessments (QRAs) and/or Detailed Quantitative Risk Assessments (DQRAs) to be undertaken for each site.

2.7.5 The Quantitative Risk Assessments (QRAs) will be undertaken by the relevant Contractors for each shaft site prior to construction works commencing at that site. Once the Contractor(s) have been appointed, a schedule of when each QRA will be undertaken will be produced. This schedule will also consider priority sites, as advised by the local planning authorities and/or the Environment Agency, to ensure that sufficient time is available for additional investigation and/or monitoring to take place.

Upper aquifer

2.7.6 Widespread existing groundwater contamination has been identified within the River Terrace Deposits (upper aquifer). Table 6 summarises pollutants detected to date.



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Table 6: Elevated concentrations of determinands within upper aquifer

Locations (nearest shaft) Borehole Response zone strata

Detected determinands*

Acton Storm Tanks SA4302 ALV

1,1,1–Trichloroethane, Benzene, Diuron, Trichloroethene, Xylene, Nickel


PR1088U RTD

Carbendazim, Carbetamide, Chlortoluron, Cypermethrin, Diuron, Mercury, Xylene,

Heathwall Pumping Station PR1085 ALV Benzene, Benzo[a]Pyrene, Cadmium, Mercury, Aluminium, Lead

King Edward Memorial Park

SR1033A RTD

Benzene, Cadmium, Cypermethrin, Mercury, Xylene, Aluminium, Arsenic, Chromium, Lead, Nickel, Zinc

Bell Lane Creek (Dormay Street)

SR1108 RTD Benzene, Bromate, Chloroform, Clopyralid, Mercury, Xylene

Jews Row (Carnwath Road Riverside)

SR1102A RTD

Benzene, Benzo[a]Pyrene, Cypermethrin, Mercury, Trietazine, Xylene, Arsenic, Nickel

Bridge Court Car Park (Falconbrook Pumping

Station) SA1099A RTD

Benzene, Dalapon, Mercury, Trichloroethene,

Earl Pumping Station SA6455,

SA6450 and SR4118

RTD

Anthracene, Benzene, Fluoranthene, Naphthalene, Phenol, Polycyclic Aromatic Hydrocarbons (PAH) and Xylene

*Non-hazardous substances are listed where they have breach their respective standard either EQS or DWS (whichever is lowest value).



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Lower aquifer

2.7.7 Several „hotspots‟ of groundwater contamination have been identified within the Thanet Sands and the Chalk (lower aquifer), around the central and eastern shaft sites. This contamination is spatially variable and indicative of poor groundwater quality near the shaft sites and the tunnel route. Table 7 summarises pollutants detected to date.

2.7.8 Approximately ten shaft sites (out of a total of 13 central and eastern sites) are known to be or expected to be contaminated within the lower aquifer.

2.7.9 In addition, elevated baseline levels of salinity are present within the upper and lower aquifers along the eastern part of the main tunnel route and around the eastern shaft sites. The occurrence of brackish conditions is to be expected given the close proximity of the tunnel route to the tidal Thames.

Table 7: Elevated concentrations of determinands within lower aquifer

Locations Borehole Response zone strata



SR1089 TSF

Benzo[a]Pyrene, Carbendazim, Chlortoluron, Diuron, Mercury, Aluminium, Arsenic


SR1061A TSF

Benzene, Benzo[a]Pyrene, Carbendazim, Cypermethrin, Diuron, Mercury, PAHs, Toluene, Xylene, Aluminium, Lead, Molybdenum, Titanium, Zinc


SR1033H Chalk Benzo[a]Pyrene, Mercury, Xylene,

Earl Pumping Station SR1048 Chalk

Benzene, Benzo[a]Pyrene, Cypermethrin, Mecoprop, Mercury, PAHs, Toluene, Xylene, Aluminium, Barium, Tin, Titanium


SR1024 Chalk

Atrazine, Benzo[a]Pyrene, Cadmium, Cypermethrin, Dichlorprop, Diuron, Mercury, Xylene, Aluminium, Barium, Tin, Titanium

Kings Stairs Garden (near Chambers Wharf)

SR1055 Chalk

Benzene, Cadmium, Mercury, PAHs, Toluene, Xylene, Arsenic, Barium, Lead, Nickel, Titanium



Page 17

Locations Borehole Response zone strata


Abbey Mills to King Stairs Route

SR3007 Chalk

1,2–Dichloroethane, Benzene, Benzo[a]Pyrene, Mercury, PAHs, Toluene, Xylene, Aluminium, Lead, Titanium

Earl Pumping Station SA6451 & SA6455

TSF Anthracene, Benzene, heavy metals, Naphthalene, Phenol, PAHs and Xylene

*Non hazardous substances listed where they have breach their respective standards, either EQS or DWS (whichever is lowest value) .

Construction materials

2.7.10 There is the potential for construction materials to come into contact with groundwater. As set out in the CoCP Part A Section 8, approval will be sought from the Environment Agency regarding all materials prior to use. As part of the approval process, QRAsvi will be undertaken to determine whether the materials pose a risk to groundwater quality. QRAs will be secured via the site specific contaminated land DCO requirements. The materials that may be used and have the potential to act as sources of pollution include:

a. Bentonite Support Fluid for Diaphragm Wall

b. Diaphragm Wall and Base Slab Concrete

c. Shaft/ Tunnel Grout and Tail Skin Sealant.

Tunnel seepage

2.7.11 Seepage of CSO discharges during operation of the tunnel has the potential to act as a source of pollution.

Pathways

2.7.12 There is the potential for a pathway to the lower aquifer at the following shaft sites:

a. Blackfriars Bridge Shaft which penetrates the Thanet Sands

b. Chambers Wharf, King Edward Memorial Park, Earl Pumping Station, Deptford Church Street, Greenwich Pumping Station, and Abbey Mills Pumping Station shafts, all within the Chalk

c. Kirtling Street and Albert Embankment Foreshore, whose base slabs are within the Upnor Formation.

2.7.13 No other potential pathways to the lower aquifer have been identified.

Receptors

2.7.14 The main receptors are the upper aquifer (River Terrace Deposits), lower aquifer, and the various groundwater abstractions (see Section 2.6).

vi These QRAs will be undertaken by the relevant Contractors for each shaft site prior to construction works

commencing at that site.



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Monitoring of linkages

2.7.15 The identified potential linkages discussed above are based on current information. The potential linkages will be further assessed through investigation and monitoring.

2.7.16 As part of the groundwater monitoring required by PW14 of Schedule 3 of the DCO, groundwater quality monitoring will be introduced at each shaft site and between certain shaft sites prior to construction (see Appendix Figure A.1, Figure B.1 and Figure C.1). Depending on the shaft/tunnel construction depths, monitoring of the upper aquifer and (where relevant) the lower aquifer water quality will be required. Para. 4.1.3 discusses and elaborates on the need for groundwater quality monitoring locations across the project area.

3 - Part B: Dewatering strategy


Page 19

3 Part B: Dewatering strategy

3.1 Thames Tideway Tunnel project’s approach to dewatering

Overall approach

3.1.1 The project‟s approach to dewateringvii is to keep the duration of pumping and the rates to a minimum. This will be achieved by minimising dewatering outside of the works. Groundwater will be controlled as follows:

a. Within the Chalk and Thanet Sands: internal dewatering with cut-off from the wider aquifer with diaphragm walls and ground treatment (eg, fissure grouting or ground freezing) will be used to minimise the volume of dewatering required.

b. Within the Lambeth Group: local depressurisation using drains or vacuum ejectors in the sand lenses. Given nature of the Upnor Formation (lower part of the Lambeth Group) freezing of sand horizons may be required.

3.1.2 By applying these control measures(which are secured via the DCO Requirement PW14 in Schedule 3), this will ensure that the following objectives are met:

a. The project is compliant with Environmental Permitting Regulations (EPR) - Schedule 22 (England and Wales) 2010 with respect to dewateringviii.

b. Adequate protection of surface water and groundwater resources, in line with principles as set out under the Water Resources Act 2003 (required for abstraction licence applications).

c. Construction effects arising directly or indirectly from dewatering systems and from discharges to the water environment are mitigated.

3.1.3 The Employer is aware of proposed changes to Environment Agency licensing policy which will mean that licences with damaging effects on the environment will not be issued by the Environment Agency. A number of previously exempt activities, including dewatering, are likely to require authorisation from the Environment Agency (licences or permits) from 2014 onwards. The Contractors shall be responsible for obtaining all necessary licences and permits from the Environment Agency prior to dewatering commencing. The Contractors shall be responsible for ensuring compliance with the conditions of all licences and permits granted by the Environment Agency.

vii

Dewatering – the control of groundwater levels, usually by abstraction, to enable construction to continue below the water table-. viii

Schedule 22 – groundwater activities of EPR 2010 (see page 164).



Page 20

3.1.4 The project‟s approach aims to minimise any movements of poor quality groundwater as a result of dewatering activities.

3.1.5 Any water pumped from the ground via dewatering systems would be discharged to the river (in the majority of cases) or to a Thames Water sewer (in a limited number of situations). Settlement and/or treatment will be applied where necessary. A permit to discharge dewatering water will be obtained in all cases from the Environment Agency (see Section 3.3for further details).

Embedded design measures

3.1.6 Dewatering will be required during the construction of some of the shafts, for a number of the short connection tunnels and associated entry / exit of the Tunnel Boring Machine (TBM).

3.1.7 The Thames Tideway Tunnel project will reduce the amount of dewatering by constructing barriers to cut-off (seal out) any flows from the River Terrace Deposits (upper aquifer). The form of barrier which will be used in this situation is either a sheet pile or secant pile walls, which will be driven down into the relatively impermeable London Clay Formation.

3.1.8 In the lower aquifer, the Thames Tideway Tunnel project will use diaphragm wall techniques (as described in para 3.1.1) to increase the length of flowpaths and hence reduce the inflows from the Lambeth Group, Thanet Sand Formation and the Chalk. Dewatering wells drilled inside the diaphragm wall (referred to as internal dewatering) are shown schematically in Figure 3.1Internal dewatering from within a diaphragm wallInternal dewatering from within a diaphragm wall. The barrier to flow created by the diaphragm wall (d-wall) means that drawdowns of tens of metres inside the d-wall can be achieved with only drawdowns of only a few centimetres on the outside of the d-wall. D-wall techniques will be extensively used in eastern and central areas of Thames Tideway Tunnel project. In certain locations, ground treatment will be used to further reduce any drawdown effects caused by dewatering.



Page 21

Figure 3.1 Internal dewatering from within a diaphragm wall

In a few locations, notably in the central area, it may be necessary to depressurise the Lambeth Group in order to make cross-connections between shafts and tunnels. Depressurisation may be achieved by ejector wells drilled outside the periphery of jacked caissons or around the deeper parts of shaft sinking where underpinning techniques are being used.

3.1.9 The tunnelling techniques proposed to be used on the project will not involve dewatering. The main types of TBMs to be used are Earth Pressure Balancing Machine (EPBM) and Slurry Machines (British Standard, 2011). These types of TBMs can work against high pressures and in general do not require dewatering for tunnel construction. Depressurisation may be required for the construction of a number of the short connection tunnels to the main tunnel.

Code of Construction Practice

3.1.10 All dewatering works will be undertaken in accordance with the Code of Construction Practice (CoCP), as well as this GEM DM strategy. Relevant measures included within the CoCP (Part A) Section 8 to ensure effects on groundwater are minimised are as follows:

a. A precautionary approach, involving targeted risk-based audits and checks of water quality monitoring, will be applied to licensed abstractions thought to be at risk.

b. Monitoring arrangements for dewatering permits and any permits required on change of licensing regulations will be developed in liaison with the Environment Agency (para. 2.6.15).

c. At the end of construction where temporary support for excavations does not form part of the operational structure it will be removed, piped through or cut down to avoid the build-up of groundwater on the upstream side of underground structures.

Diaphragm wall

Dewatering wells inside diaphragm wall

Ground treatment

Not to scale For illustrative purposes only

Tunnel



Page 22

Stakeholder engagement

3.1.11 As part of the project there have been regular Technical Working Group (TWG) meetings with Environment Agency, at which experts from both groundwater resources and groundwater quality sections of the Environment Agency have attended. These meetings have enabled the latest design thinking for the Thames Tideway Tunnel and the proposed methods of construction to be developed.

3.2 Dewatering requirements and ongoing testing

Anticipated construction methods for shafts and dewatering requirements

3.2.1 The ES (Volume 3 to 27, Section 13) includes detail of indicative construction methods. A summary of the method of dewatering at all of the sites and an estimate of the amount of dewatering (used to assess the impact of dewatering within the ES) is given in Table 8.

Table 8: Summary of anticipated dewatering methods and amounts of dewatering

Area* Site Dewatering method Average rate of

dewatering (m3/d)

Ce

ntr

al

Chelsea Embankment

Depressurisation of Lambeth Group

Less than 200

Kirtling Street *** Dewatering wells in Chalk of the lower aquifer (external)

440



Less than 200


Dewatering wells in Upnor Formation of lower aquifer (external)

Less than 200



Less than 200

Blackfriars Bridge Foreshore***

Dewatering wells in Chalk of lower aquifer (external)

1,100

Ea

ste

rn

Chambers Wharf Dewatering wells in Chalk of lower aquifer (internal**)

Less than 200


Dewatering wells in Chalk of lower aquifer (internal)

Less than 200



Less than 200



Less than 200

Greenwich Dewatering wells in Chalk of Less than 200



Page 23

Area* Site Dewatering method Average rate of

dewatering (m3/d)

Pumping Station lower aquifer (internal)

Abbey Mills Pumping Station


Less than 200

Beckton Sewage Treatment works


Less than 200

* Construction dewatering at the western sites are all anticipated to be less 20m3/d. ** Internal dewatering – pumps located inside a diaphragm wall on the Lee Tunnel

project have recorded rates of between 1 and 5 l/s (or 86 - 432m3/d) at the Beckton

Overflow Shaft. *** It is anticipated that the these volumes will be lower following the application of the

measures outlined in Section 3.1.

3.2.2 The dewatering requirements are the best available estimates at the time of DCO submission. These values are subject to change in the light of new information obtained from pumping tests, additional ground investigation and further design by the main works Contractors.

3.2.3 There will be no dewatering of the upper aquifer at any of the shafts or during the construction of the short connection tunnels.

3.2.4 Figure 3.2 provides the draft dewatering phasing across all sites for the duration of the project. This programme will be subject to amendments over the course of the design and construction phase.



Page 24

Figure 3.2: Draft dewatering phasing during project

Grey – Western area, Orange – Central area, Light green – Eastern area, Turquoise blue – Construction period



Page 25

3.3 Mitigation

3.3.1 The project has embedded environmental measures into the dewatering design in order to reduce the environmental impacts of the proposal. The Groundwater environmental management – dewatering and monitoring strategy has been developed as a means of identifying and addressing impacts which occur as a result of the development. Part C and D of this strategy outline how groundwater levels and quality will be monitored and how specific mitigation measures will be applied should adverse impacts be identified.

3.4 Dewatering plan

3.4.1 The dewatering plan is the method by which the dewatering strategy will be delivered and is secured via DCO Requirement PW14. The objectives are to ensure:

a. The project is compliant with Environmental Permitting Regulations (EPR) (England and Wales) (2010) with respect to construction dewatering.

b. Adequate protection of surface water and groundwater resources, in line with principles as set out under the Water Resources Act 2003 (for abstraction licence applications) and the Water Framework Directive.

c. That any construction effects arising directly or indirectly from dewatering systems and discharges to the water environment are mitigated.

3.4.2 The structure and contents of the plan are described below.

Part I

3.4.3 Part I of the dewatering plan will be a project-wide overview of dewatering, prepared by the Employer and submitted to the Environment Agency for approval. This section will be common to each of the site specific method statements prepared by each of the three main works Contractors. The main elements of Part I will be as follows:

a. Provide an overview of expected dewatering across the whole of the project.

b. Put Part II in context of the wider project.

c. Summarise all the licenses and permits to abstract and discharge from dewatering systems issued by the Environment Agency.

3.4.4 The monitoring arrangements for abstractions and discharges will be developed by the Contractors in liaison with Environment Agency and presented on a site by site basis in Part II of the dewatering plan.

Part II

3.4.5 Part II of the dewatering plan will be prepared by the Contractors on a site-by-site basis. Part II of the dewatering plan comprises a series of



Page 26

site-specific dewatering plans. The site-specific dewatering plans will be informed by two components:

a. Method Statement

b. Monitoring Plan.

3.4.6 Each site-specific dewatering plan will be prepared by the Contractor and submitted to the Environment Agency for approval no later than six weeks in advance of works commencing at the site. Dewatering may not commence otherwise than in accordance with the approved site-specific dewatering plan. The site-specific dewatering plans shall include all necessary licences and permits (from the Environment Agency).

3.4.7 Prior authorisation will be obtained from the local sewerage provider for discharge to sewer.

3.4.8 Depending on the quality of groundwater (based primarily on concentrations of hazardous substances), an outline of pre-treatment measures would be provided to the Environment Agency and/or sewerage provider for approval.

3.4.9 Site Method statements shall include the following:

a. main discharge points for the site and down-hydraulic gradient of discharge points

b. details of well installation

c. details of monitoring network (surface and groundwater)

d. details of equipment used

e. proposed construction sequence

f. licences and permits from the Environment Agency

g. prior authorisation from local sewerage provider

h. outline of any pre-treatment required prior to discharge approved by the Environment Agency.

3.4.10 The Site Monitoring Plan shall include the following (site monitoring plans are detailed in Part D):

a. ground and surface water monitoring methodology for both quality and quantity

b. ground and surface water monitoring schedule for both quality and quantity

c. Alert and Trigger Levels

d. protocols for responding to exceedances of Alert and Trigger Levels

e. reporting alert and trigger level exceedances in „incident‟ reports.

Management structure

3.4.11 The Employer will be responsible for setting assessment and compliance criteria in consultation with the Environment Agency. The setting of compliance criteria will be undertaken once the main works Contractors



Page 27

have been appointed; the compliance criteria are is likely to be set in late 2014 or early 2015.

3.4.12 The Employer will hand over responsibility for dewatering monitoring during construction to the Contractors.

Overarching management protocols

3.4.13 The Employer will review and approve the site-specific dewatering plans prior to submission to the Environment Agency for approval.

3.4.14 The Employer will review the monitoring reports, as required under the various permits and provide comments to Contractors within four weeks of receipt of all the reports.

4 – Part C: Groundwater management and monitoring


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4 Part C: Groundwater management and monitoring

4.1 Groundwater management and monitoring strategy

Objectives and rationale

4.1.1 Based on the source-pathway-receptor linkages identified above, monitoring of groundwater in the lower aquifer is proposed to enable the following:

a. Collection of groundwater level data pre-construction, and during construction and operation to provide a baseline and to assess whether the tunnel and shafts have significantly impacted groundwater flow during construction and operation.

b. Collection of groundwater quality samples pre-construction to establish baseline groundwater quality and identify trends and determine trigger levels, where possible.

c. Assessment of risk of mobilisation and migration of pre-existing contaminants affecting the lower aquifer (ie. if source-pathway-receptor linkages exist) as a result of construction.

d. Tunnel and shaft groundwater remediation works (to be agreed with Environment Agency).

1.1.2 For the construction and operational phases:

a. Collection of groundwater quality samples during both phases , to establish whether:

i mobilisation and migration of constituents in grout/ lubricant mixes has taken place

ii increases in turbidity in groundwater due to the physical action of tunnelling construction within the chalk can be detected

iii significant changes in water quality as a result of dewatering and tunnel seepages have occurred

iv mobilisation and migration of contaminants has taken place.

4.1.2 Before reviewing the monitoring deliverables in each of the three phases, a summary of the monitoring network and methodologies to be used is given.

Proposed monitoring holes

4.1.3 A total of 44 groundwater monitoring locations have been selected along the tunnel alignment to satisfy the above objectives. The locations of the boreholes have been chosen based on the tunnel/ shaft geology, anticipated groundwater flow directions during abstraction, proximity to groundwater abstractions, and groundwater quality. They also take into account existing third part monitoring locations, for example Environment



Page 29

Agency and Thames Water Monitoring boreholes. Out of the 44 monitoring boreholes, 11 are found in western area, 17 in the central area and 18 in the eastern area.

4.1.4 The borehole locations are shown for superficial deposits in Appendix Figure A.1, the Thanet Sands in Appendix Figure B.1, and the Chalk in Appendix Figure C.1. The purpose and justification of each borehole is summarised in Error! Reference source not found..

4.1.5 The network of monitoring holes will be reviewed following further site investigation currently being undertaken for the Thames Tideway Tunnel project. For example, if a sufficient thickness of clay in the Lambeth Group is present below the base of the shafts at Kirtling Street, Heathwall Pumping Station, Albert Embankment Foreshore and Victoria Embankment Foreshore and the risks of the construction of the shaft polluting the lower aquifer is shown to be negligible then monitoring of the lower aquifer at these locations may not be necessary.

4.1.6 Groundwater level recorder/logger will continue to be installed in selected boreholes within the Thanet Sands and/or Chalk where it is proposed to dewater and where the borehole is positioned to monitor the impacts of construction on a licensed abstraction.


Groundwater environmental management dewatering and monitoring strategy Page 30

Table 9: Purpose and justification of monitoring boreholes

Locations Borehole

Status

(as of 22/01/2014)

Purpose* Response Zone Relative Depth Justification

Main Tunnel

Acton Storm Tanks SA4302 Existing GWQL ALV Shallow Shaft – water quality/levels

Hammersmith Pumping Station

6150 Proposed GWQL RTD Shallow Replacement borehole to be drilled Spring 2014. Shaft – water quality/levels

Barn Elms SA1115 Existing GWQL RTD Shallow Shaft – water quality/levels

Putney Embankment Foreshore

SA6910 Existing GWQL RTD Shallow Shaft – water quality/levels

Carnwath Road Riverside SA6308 (tbc) Existing GWQL RTD Shallow

Eight shallow boreholes now available on site, one to be selected. Shaft – water quality/levels

Bridge Court Car Park (Falconbrook Pumping Station)

SA6332 Existing GWQL RTD Shallow Off-site and on-site boreholes to monitored to confirm representative quality. On site boreholes to be used for shaft – water quality/levels

Cremorne Wharf Depot SA6362 Existing GWQL MG/RTD Shallow

Existing borehole now dry, switch proposed borehole SR6302. Shaft – water quality/levels


SR1091 Existing GWQL RTD Shallow Shaft – water quality/levels

SR1089 Existing GWQL/ logger TSF Deep Shaft – water quality/levels/Depressurisation LG

Kirtling Street

SR6907 Existing GWQL/ logger* CHALK Deep Shaft – water quality/ levels/DWS 28/39/42/0072/Depressurisation LG by under draining Chalk

B/h 2 Existing GWQL RTD Shallow Shaft – water quality/levels


PR1085 Existing GWQL ALV Shallow Shaft – water quality/levels

SR6908 Existing GWQL/ logger* CHALK Deep Shaft – water quality/levels/DWS 28/39/39/0141


SR6090 Proposed GWQL RTD Shallow Shaft – water quality/levels

SR6091 Proposed GWQL CHALK Deep Shaft – water quality/levels/Depressurisation LG by under draining Chalk

SR6906 Proposed GWQL/ logger* CHALK Deep Shaft – water quality/levels/DWS 28/39/39/0139


SA1066D Existing GWQL RTD Shallow Shaft – water quality/levels

4053 Proposed GWQL/ logger TSF Deep Shaft – water quality/levels/Depressurisation of LG


6391 Proposed GWQL RTD Shallow Shaft – water quality/levels

SR6390 Proposed GWQL/ logger CHALK Deep Shaft – water quality/levels/Depressurisation LG by under draining Chalk

SR6905 Existing GWQL/ logger CHALK Deep Borehole sampled in the interim until proposed borehole are drilled

City Hall (between Blackfriars Bridge and

City Hall Existing GWQL/logger* CHALK Deep Agreement with City Hall to sample their boreholes. Shaft – water quality/levels/DWS 28/39/42/0062



Locations Borehole

Status

(as of 22/01/2014)

Purpose* Response Zone Relative Depth Justification

Chambers Wharf)

Chambers Wharf

SR6574 Proposed GWQL/ logger CHALK Deep Shaft – water quality/levels/Dewatering of Chalk (internal)

SA6576 Proposed GWQL RTD Deep Shaft – water quality/levels/Dewatering of Chalk (internal)

Kings Stairs Garden (near Chamber Wharf)

SR1055 Existing GWQL* CHALK Deep Shaft – water quality/levels/DWS 28/39/42/0048


SR1033H Existing GWQL CHALK Deep Shaft – water quality/levels/Dewatering of Chalk (internal)

SR1033A Existing GWQL RTD Shallow Shaft – water quality/levels

Abbey Mills to King Edward Memorial Park

SR3007 Existing GWQL CHALK Deep Tunnel – water quality/levels

Abbey Mills PS

PW1 Existing Lee

Tunnel GWQL* CHALK Deep

Shaft – water quality/levels/DWS 29/38/09/0149/Dewatering of Chalk (internal)

BH13D-1 (tbc)

Existing Lee Tunnel

GWQL* RTD Shallow Shaft – water quality/levels/DWS 29/38/09/0149/Dewatering of Chalk (internal)

SP1-CH Existing Lee

Tunnel GWQL/ log*ger CHALK Deep

Shaft – water quality/levels/DWS 29/38/09/0149/Dewatering of Chalk (internal)

SR4082 Existing CHALK Deep Interim until access available to Lee Tunnel boreholes

Greenwich Connection Tunnel

Surrey Quays Shopping Centre (BH3) (near Earl Pumping Station)

SR4021 Proposed GWQL/ logger* CHALK Deep Shaft – water quality/levels/DWS 28/39/42/0048


4093


SR4118

SR6457 Existing GWQL CHALK Deep Shaft – water quality/levels/Dewatering of Chalk (internal)

SA6453A Existing GWQL TSF Deep Shaft – water quality/levels






SR1024 Existing GWQL* CHALK Deep Shaft – water quality/ level/ DWS 28/39/43/0019/ Dewatering of Chalk (internal)

PR1023 Existing GWQL ALV Shallow Shaft – water quality/levels

4087 Existing GWQL/logger* CHALK Deep

Shaft – water quality/levels/ DWS 28/39/43/0019/ Dewatering of Chalk (internal)

Frogmore Connection Tunnel

Dormay Street PR1107 Existing GWQL RTD Shallow Shaft – water quality/levels

King George‟s Park SA1110 Existing GWL MG Shallow Shaft – water levels insufficient recharge for water quality sampling)



Note: MG-Made Ground, RTD-River Terrace Deposits, ALV-Alluvium and TSF-Thanet Sand Formation, GWQL – Groundwater quality and level monitoring from boreholes

*Trigger monitoring boreholes to ensure protection of particular abstraction sources



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4.1.7 Borehole construction has been and will continue to be in accordance with: BS ISO 5667-22: 2009 “Water Quality – Sampling – Part 22: Guidance on the design and installation of groundwater monitoring points”

4.1.8 The boreholes intended to measure water levels in, and enable sample collection from the lower aquifer (Thanet Sands overlying the Chalk aquifer) are referred to here as deep boreholes.

4.1.9 The boreholes intended to measure water levels and groundwater quality of the upper aquifer (River Terrace Deposits or Alluvium) in the vicinity of the shafts are referred to here as shallow boreholes.

4.1.10 The deep borehole well screens will be installed within either the Chalk or Thanet Sands using a minimum screen length of 10m. A bentonite seal will be used through the overlying stratums to ensure that no contamination pathway is created between the lower and the upper aquifers. For the same reason, standard practice aquifer protection methods will be employed during drilling (see CoCP (Part A)).

4.1.11 All construction details will be provided once installation has been completed.

4.1.12 Measurements shall be made in SI units and level data shall be in metres above ordnance datum.

Sample collection methodology

General

4.1.13 Groundwater will be sampled in accordance with BS ISO 5667-11: 2009 “Water Quality – Sampling – Part 11: Guidance on sampling of groundwaters”.

Data loggers

4.1.14 Data loggers will be installed within trigger monitoring boreholes (see Table 9) to record measurements of water level, pH, temperature, electrical conductivity, and turbidity at 1 hour intervals.

Groundwater

4.1.15 Groundwater samples will not be collected from monitoring holes until the standing water/stagnant water has been purged/removed, to ensure that the groundwater sample collected is representative of groundwater within a given formation. Prior to purging the well, a dip meter will be used to establish the groundwater level.

4.1.16 Some groundwater chemistry parameters are unstable and are liable to change during sample collection, handling, transport and storage. Representative readings of the following parameters will be taken in the field, before the samples are placed in suitable containers:

a. pH value

b. Electrical Conductivity (μS/cm)

c. Redox Potential

d. Dissolved Oxygen (percentage)



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e. Temperature (oC).

Monitoring frequency

Baseline

4.1.17 Baseline monitoring has commenced using the current monitoring network.

4.1.18 Sampling the monitoring holes will continue on a quarterly basis before construction starts (or until sufficient data has been gathered) and to analyse for the parameters identified in Table 10. Any new boreholes will be sampled and a comprehensive suite of analysis completed using the long list (see Appendix D). If any new determinants are picked up by the use of the long list, the results will be used to update the project list.

4.1.19 Data loggers are being and will continue to be used to monitor water level, pH, temperature, electrical conductivity, turbidity (if the shaft/ tunnel is within the Chalk) at 1 hour intervals to provide a pre-construction baseline.

Construction

4.1.20 Data loggers will continue to be used to monitor water level, pH, temperature, electrical conductivity, and turbidity (if the shaft/ tunnel is within the Chalk) at 1 hour intervals.

4.1.21 Monthly borehole monitoring of groundwater quality will be undertaken using the parameters identified in Table 10.

4.1.22 If dewatering is required at a shaft site then weekly monitoring of discharge water (in-line tap) will be undertaken using the parameters identified in Table 10.

Operation

4.1.23 Data loggers will continue to be used to monitor water level, pH, temperature, electrical conductivity, and turbidity (where the shaft/ tunnel is within the Chalk) at 1 hour intervals for a period of up to two years.

4.1.24 Quarterly monitoring of groundwater quality will be undertaken using the parameters identified in Table 10 for a minimum period of two years or as agreed with the Environment Agency. The monitoring results shall be reported to the Environment Agency within two months for each round of monitoring.

Long term

4.1.25 The requirements for long-term monitoring will be agreed with the Environment Agency following completion of construction (or a minimum of two years after operation commences). The necessary scope of operational groundwater quality monitoring will be initially quarterly. This frequency will be reviewed by the Employer after two years and any changes submitted to the Environment Agency for approval. It is anticipated that the long-term monitoring will be progressively scaled back in the future; any change to the long term monitoring regime would be submitted to the Environment Agency for approval in advance of any change.



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Determinands for analysis

4.1.26 The list of determinands for analyses has been developed in consultation with the Environment Agency. It is proposed that this list of determinands continues to be used to define baseline groundwater quality for the Thames Tideway Tunnel project. Baseline monitoring will be an iterative process, the first round of monitoring at any borehole will use an extended list, the “long list” (see Appendix D), to define baseline conditions. This long list consists of around 300 substances and Gas Chromatography Mass Spectrometry scans to identify additional parameters.

4.1.27 All subsequent rounds of monitoring will use the Thames Tideway Tunnel specific substance list (the project list), consisting of approximately 80 substances (including field parameters, major and minor ions, metals, herbicides, pesticides, Poly-Aromatic Hydrocarbons (PAH), phenols, solvents, urons and pyrethroids). The provisional project list is summarised in Table 10 but will be confirmed based on the monitoring results.

4.1.28 Those additional substances detected from the long list sampling will be added to the project list for on-going monitoring. Once the construction materials have been identified (ie grouts, tail skins sealant) and groundwater contaminants investigated and identified, the project list will be further updated. The project list is not definitive and will routinely be reviewed and updated.

Table 10: Determinands for analysis – project list

Determinands Limit of

detection Units

Calcium <7.4 mg/l

Magnesium <0.1 mg/l

Sodium <2.5 mg/l

Potassium <0.75 mg/l

Alkalinity (Carbonate) <4

mg/l as CaCO3

Alkalinity (Bicarbonate) <10 mg/l

Chloride <0.05 mg/l

Sulphate <1.7

mg/l as SO4

1,1,1-Trichloroethane <1.3 μg/l

1,1,2-Trichloroethane <2.2 μg/l

1,2-dichloroethane <1 μg/l

Ammonia <0.05 mg/l as N

Atrazine <0.003 μg/l

Bentazone <0.008 μg/l



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detection Units

Benzene <0.007 μg/l

Bromate <0.5 μg/l

Carbon tetrachloride <0.07 μg/l

Chlorfenvinphos <0.009 μg/l

Chloroform <0.6 μg/l

Cypermethrin <0.005 μg/l

Diazinon <0.009 μg/l

Dichloromethane <3 μg/l

Diuron <0.005 μg/l

Isoproturon <0.003 μg/l

Mecoprop <0.01 μg/l

Nitrate <0.043 mg/l as N

Pentachlorophenol <0.02 μg/l

Permethrin-cis+trans <0.01 μg/l

Phenol <0.5 μg/l

Propetamphos <0.005 μg/l

Simazine <0.004 μg/l

Tetrachloroethene (PCE) <0.09 μg/l

Trichloroethene (TCE) <0.07 μg/l

Xylene-p+m <0.09 μg/l

Aluminium <0.012 mg/l

Arsenic <1 μg/l

Benzo(a)pyrene <0.001 μg/l

Boron <10 μg/l

Cadmium <1.5 μg/l

Carbendazim <0.003 μg/l

Carbetamide <0.006 μg/l

Chlortoluron <0.004 μg/l

Chromium <0.7 μg/l

Clopyralid <0.019 μg/l

Copper <5.5 μg/l

Cyanazine <0.007 μg/l

Dalapon <0.05 μg/l

Dichlorprop <0.011 μg/l



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detection Units

Fluoride <0.06 mg/l

Glyphosate <0.014 μg/l

Lead <5 μg/l

MCPA <0.009 μg/l

Mercury <0.002 μg/l

Metazachlor <0.008 μg/l

Nickel <4 μg/l

Propazine <0.004 μg/l

Terbutryn <0.003 μg/l

Trietazine <0.006 μg/l

Trifluralin <0.01 μg/l

Zinc <5 μg/l

Others

Barium <2 μg/l

Iron <0.018 mg/l

Manganese <0.012 mg/l

Molybdenum <5 μg/l

Strontium <0.29 mg/l

Tin <5 μg/l

Titanium <16 μg/l

Cypermethrin <0.1 μg/l

Total PAH <0.1 μg/l

Ethylbenzene <1 μg/l

o-Xylene <1 μg/l

Toluene <0.06 μg/l

Total Petroleum Hydrocarbons (TPH) <10 μg/l

pH <1 pH units

4.2 Assessment of risk along the tunnel route and proposed remedial works

4.2.1 No tunnelling works from a drive site shall be undertaken until the following has been submitted, as part of the Groundwater Monitoring Plans, and approved by the Environment Agency.

a. A preliminary risk assessment of potential contamination plumes along the tunnel route, including results from the monitoring scheme and



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identification of previous uses at ground level with potential for contaminants to reach the lower aquifer within the vicinity of the tunnel and the potential contaminants associated with those uses. In particular, the assessment should focus on the areas where a conceptual model of the tunnel alignment links the source with pathways and receptors.

b. If the outcome of the preliminary risk assessment identifies a potential impact on receptors, the proposed groundwater monitoring plans will be amended to reflect the findings and potential additional monitoring required.

c. Remedial groundwater works as mitigation shall be proposed where a detailed quantitative risk assessment identifies an unacceptable risk to receptors. The proposal shall include an options appraisal and full details of the remedial works required and how they are to be undertaken.

d. Proposals for additional and/or more frequent monitoring (including long term monitoring) are to be based on the risk identified.

4.2.2 The Groundwater Monitoring Plans shall be implemented as approved unless otherwise agreed with the Environment Agency.

Tunnel unexpected contamination

4.2.3 If in undertaking the tunnelling works, contamination not previously identified is found to be present, a revised Groundwater Monitoring Plan shall be submitted to and approved in writing by the Environment Agency. The remedial groundwater works shall be implemented as approved unless otherwise agreed with the Environment Agency.

4.3 Initial assessment and compliance criteria for groundwater

4.3.1 The baseline groundwater level and water quality data will be used to derive initial assessment and compliance criteria against which project impacts can be assessed. These initial criteria will be derived by the Employer project team in consultation with the Environment Agency (Part D).

4.3.2 A two-tier system of screening criteria shall be adopted.

a. Assessment criteria (Alert Levels) will be used to provide early warning of potential issues.

b. Compliance criteria (Trigger Levels) will be used to identify potentially significant risks to receptors.

4.3.3 Alert levels will be used on a day-to-day basis internally by the Contractor. Alert levels aim to draw the attention of the Contractor‟s site management team to the development of adverse trends in monitoring. This should be treated primarily as an early warning system to enable appropriate investigative or corrective measures to be implemented so that the risk of



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breaching a compliance limit can be reduced and before impacts can cause harm to the environment or human health.

4.3.4 Comparison of measured water quality with Trigger levels will be used to demonstrate compliance with agreed water quality standards to stakeholders. Trigger Levels are standards agreed with the Environment Agency through the approval of the dewatering plan. Breaches of the Trigger Levels should be prevented.

4.3.5 Alert and Trigger levels will not be derived for every water quality monitoring determinand. Instead, key indicator parameters shall be identified using a risk-based approach that reflects the baseline water quality dataset. The indicator parameters will be agreed with the Environment Agency through the approval of the dewatering plan. The choice of indicator parameters shall be reviewed by the Contractor at least annually for adequacy; any proposed changes must be approved by the Employer and the Environment Agency prior to implementation.

4.3.6 Alert and Trigger levels shall be derived on a borehole-specific basis. The levels shall be based on the baseline dataset and shall take into account existing variability and trends. Statistical methods shall be used where possible to derive appropriate Alert and Trigger levels. The Alert and Trigger levels shall be reviewed at least annually by the Contractor for adequacy; any proposed changes must be approved by the Employer and the Environment Agency prior to implementation.

4.3.7 The Alert and Trigger levels, and associated procedures will determine whether contingency plans need to be activated. The assessment process involves evaluation of the significance of a departure from baseline conditions.

4.3.8 During construction, the groundwater level and quality data will be screened on a weekly basis using data loggersix. The loggers will measure physical and chemical parameters as listed in Table 11.

Table 11: Data logger physical and chemical parameter monitoring

Test Unit Alert Level Type

Trigger Level Type

Basis

pH pH units

range range Range based on baseline monitoring

EC (20°C) mS /cm

>value >value Value based on baseline monitoring

Turbidity Ntu >value >value Value based on baseline monitoring

ix Unless otherwise agreed with the Environment Agency on a site-specific basis.



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Temperature °C >Step-change

>Step-change

Step-change (e.g. ±20%) based on baseline monitoring

Water level M >value >value Value based on baseline monitoring and impact assessment

4.4 Monitoring deliverables

4.4.1 The groundwater monitoring deliverables (at the following project stages: pre-construction, during construction and during operational phases) are shown below. The monitoring frequency will be as outlined above.

Baseline groundwater monitoring

4.4.2 Baseline monitoring by the Employer has already commenced and is reported in the ES groundwater baseline monitoring report.

Pre-existing contamination risk assessments

4.4.3 A preliminary risk assessment of potential contamination plumes along the tunnel route, for sites identified as having a potential to connection to the lower aquifer.

Pre-construction baseline groundwater monitoring

4.4.4 Baseline groundwater quality monitoring will be the responsibility of the Employer. The baseline groundwater quality monitoring will involve:

a. continuous groundwater level, electrical conductivity, temperature, pH and turbidity using downhole loggers at identified trigger sites;

b. quarterly monitoring of a range of organic and inorganic determinands; and

c. identification of baseline conditions, including trends, Alert and Trigger Levels of key determinands.

4.4.5 A one-off pre-construction groundwater baseline monitoring report for the whole Thames Tideway Tunnel project will be provided by the Employer, no later than three months prior to appointment of the Contractors, to the Environment Agency for approval. The baseline conditions, trigger levels and alert levels will be set out, against which construction monitoring can be compared.

Construction monitoring

4.4.6 Construction groundwater quality monitoring will be undertaken by the Contractor(s), which will involve:

a. continuous groundwater level, electrical conductivity, temperature, pH and turbidity using downhole loggers at trigger sites

b. monthly monitoring of a range of organic and inorganic determinands



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c. weekly monitoring of pumped water during dewatering activities of a range of organic and inorganic determinands

d. comparison of construction monitoring with baseline trends and identified trigger levels

e. consistency checks on measurements with blank samples and/or inter-laboratory comparisons.

4.4.7 Construction monitoring reports will be produced by the Contractor and the Employer for the Environment Agency to the schedule defined in the approved monitoring plan (discussed further in Part D). A final Construction Groundwater Environmental Monitoring Report will also be produced by the Employer.

Operational monitoring

4.4.8 Operational groundwater quality monitoring will be undertaken by the Employer and will involve:

a. continuous groundwater level, electrical conductivity, temperature, pH and turbidity using downhole loggers at trigger sites

b. quarterly monitoring of a range of organic and inorganic determinands for a minimum of two years

c. comparison of operational monitoring with baseline trends and identified trigger levels

d. consistency checks on measurements with blank samples and/or inter-laboratory comparisons.

4.4.9 Long-term groundwater quality monitoring will be undertaken by the Employer, which will involve the annual operational monitoring of a range of organic and inorganic determinands.

4.4.10 The frequency and detail of monitoring will be amended to suit conditions. Any changes to the monitoring regime will be subject to the approval of the Environment Agency.

4.5 Contingency action plan

4.5.1 If, during construction or operation, trigger levels are exceeded the contingency action plan (CAP) will be followed. This will include the following actions:

a. Notification of the exceedances to the Environment Agency, as soon as possible

b. Determining the cause of any exceedances

c. Evaluation of location, likely scale, duration and effect

d. Identification of appropriate mitigation or remediation measures.

4.5.2 Potential solutions are to be identified by the Contractor in advance and an emergency preparedness plan drawn up.



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4.5.3 In all cases, the need for remediation should be balanced against the risk posed to groundwater receptors and the benefits gained by remediation. Remedial actions and their objectives shall be agreed in with the Environment Agency.

4.5.4 Any exceedances of alert levels will be reported to Environment Agency using the agreed reporting process. Only in cases where trigger levels are subsequently exceeded will the Environment Agency be contacted specifically.

4.6 Reporting and sign-off

4.6.1 The responsibility for reporting will be in-line with the deliverables for pre-construction, during construction and operation phases set out above.

Baseline groundwater reporting

4.6.2 An Environmental Statement baseline groundwater monitoring report containing all the groundwater levels and groundwater quality information used in the preparation of the ES has been prepared.

4.6.3 Following the completion of the pre-construction baseline monitoring and prior to the start of construction, a second baseline monitoring report and „contingency action plan‟ will be prepared three months before the start of construction and submitted to the Environment Agency. This „pre-construction‟ baseline report will include all historic and current groundwater level and quality data, including the most recent Thames Tideway Tunnel and Environment Agency information, along with interpretation of data provided. Trends in key water quality parameters will be assessed and appropriate alert and trigger levels defined at this stage.

Construction reporting

4.6.4 During construction groundwater quality monitoring reports will be prepared by the Contractors in accordance with the schedule defined in the approved monitoring plan. The purpose of the monitoring reports is to document compliance with the requirements of the monitoring plan. These monitoring reports shall be submitted to the Environment Agency for comment.

4.6.5 At the end of construction period (or a minimum of two years after construction ground disturbance, whichever is the laterx), a „pre-start of operation baseline monitoring report‟ will be prepared by the Employer and submitted to the Environment Agency for approval. This document will form the basis for modifying any of the construction-phase baseline against which the operational monitoring will be compared. It is recognised that construction and operational monitoring are two different actions with different monitoring, although there may be some common overlaps.

x This is assumed to be during 2024.



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Operational reporting

4.6.6 For the operational monitoring phase, annual reports will be submitted to the Environment Agency for information.

5 – Part D: Groundwater monitoring - plans


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5 Part D: Groundwater monitoring - plans

5.1 Overarching Thames Tideway Tunnel project Groundwater monitoring management plan

Overview

5.1.1 The overarching Groundwater monitoring management plan aims to aid implementation of the Groundwater management and monitoring strategy (Part C).

5.1.2 Management of the groundwater monitoring will be incorporated into the wider Environmental management plan.

Management structure

5.1.3 Responsibility for undertaking the groundwater monitoring during construction is devolved to the Contractors.

5.1.4 The Employer will be responsible for:

a. Baseline groundwater monitoring during the pre-construction period.

b. Setting initial assessment and compliance criteria in consultation with the Environment Agency.

c. Managing co-ordination of the monitoring programmes between the Contractors during construction.

d. Groundwater monitoring during operational phase.

Objectives

5.1.5 The objectives of the groundwater monitoring management plan are:

a. Continue groundwater level and quality monitoring using a risk-based groundwater monitoring network to characterise the underlying and surrounding groundwater systems in the pre-construction period for future comparison against any project-related impacts.

b. Prepare a pre-construction baseline monitoring report prior to the start of the construction phase, including development of appropriate initial compliance and assessment criteria taking into account existing variability and trends in the baseline data.

c. Enable routine monitoring of groundwater levels and quality during construction is undertaken by Contractors to discern breaches of Alert and Trigger levels.

d. Review combined monitoring results across the project area as a whole during construction to assess local and regional impacts.

e. Prepare a „pre-start of operation baseline monitoring report‟ in 2024 or in an agreed time-frame with the Environment Agency.

f. Carry out routine monitoring of groundwater levels and quality during operation phase to discern breaches of Alert and Trigger levels.



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Overarching management protocols for construction monitoring

5.1.6 Overarching management of the monitoring programme by the Employer is required to ensure consistency between the three project areas, East, Central and West, which are monitored by the three Contractors (and as defined in Table 1).

5.1.7 The Employer will review and approve the Contractor Groundwater monitoring plans prior to submission to the Environment Agency for approval. This review process shall include:

a. Assessment of consistency in approach by the three Contractors with respect to:

i monitoring methodology

ii choice of contamination indicator species

iii designated alert and trigger levels

iv contingency plans

v reporting templates.

b. Identification and resolution of any significant discrepancies between neighbouring Contractors‟ Groundwater monitoring plans.

5.1.8 The Employer will be consulted in the event that the approved contingency plans need to be activated.

5.1.9 The Employer shall review the Quarterly and Annual monitoring reports and provide comments to Contractors within four weeks of receipt of all three reports. The scope of this review shall include:

a. Assessment of Contractor compliance with agreed monitoring plan.

b. Assessment of Contractor performance against groundwater-related KPIs.

c. Identification and assessment of any significant discrepancies between neighbouring Contractors findings or conclusions.

d. Identification and assessment of any spatial or temporal patterns affecting the project as a whole.

e. Identification and assessment of any consistency issues between Contractors that might result from proposed amendments to monitoring plans.

f. Identification and assessment of groundwater-related issues that might affect the Operational phase of the project.

5.1.10 The findings of this overarching monitoring review process shall be presented by the Employer to the Environment Agency in an Annual monitoring management review report.

5.1.11 Where incidents of trigger value exceedances take place, then these will be reported by the Contractor to the Environment Agency as soon as possible after the event.



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5.1.12 The Employer shall be responsible for mediating disputes between Contractors over groundwater issues along the boundaries between areas.

5.2 Proposed scope of Contractor Groundwater monitoring plan

Overview

5.2.1 The Contractor shall be responsible for groundwater monitoring during the Construction phase (and for at least twelve months following completion of construction to enable preparation of „pre-start of operation baseline monitoring report‟).

5.2.2 The Contractor shall prepare a detailed Contractor Groundwater monitoring plan. The Contractor Groundwater monitoring plan must be approved by the Employer and the Environment Agency prior to construction works commencing on site. It should be consistent with the existing GWM strategy and overarching GWM plan.

5.2.3 The Contractor Groundwater monitoring plan shall include the following elements:

a. management structure, including roles and responsibilities within Contractor team

b. monitoring network already in existence

c. monitoring measurements and methodology

d. monitoring schedules

e. data management procedures

f. data review procedures, including comparison with assessment and compliance criteria

g. contingency actions, and

h. reporting procedures.

5.2.4 The Contractor Groundwater monitoring plan shall include details of the

QA/QC protocols that will be implemented to provide confidence in the groundwater monitoring results.

5.2.5 The Contractor Groundwater monitoring plan shall be submitted no later than three months before construction to the Employer for comment. The Employer‟s comments should be addressed prior to submission of the Plan to the Environment Agency for approval, in line with the Requirements of PW14 of Schedule 3 of the Development Consent Order (DCO).

5.2.6 The Contractor Groundwater monitoring plan shall be a live document and subject to regular review by the Employer for adequacy (at least annually). The Contractor shall not deviate from the approved Contractor



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Groundwater monitoring plan without written permission from the Employer and the Environment Agency.

Monitoring network

5.2.7 The Contractor Groundwater monitoring plans shall present details regarding the groundwater monitoring network (most probably the existing network) that will be used during the Construction phase.

5.2.8 As a minimum, groundwater monitoring shall be undertaken in the monitoring boreholes summarised in Table 9. Additional monitoring locations may be utilised by the Contractor as required.

5.2.9 The Contractor shall be responsible for maintaining the groundwater monitoring network during the Construction phase.

5.2.10 The Contractor Groundwater monitoring plan shall include a protocol and schedule for regular monitoring point inspection and maintenance. This shall include procedures for the repair and replacement of monitoring points as required.

5.2.11 Each new or repaired monitoring point should be designed, constructed, supervised and certified in accordance with normal engineering CQA procedures. Detailed borehole logs for each monitoring point should be provided.

5.2.12 An up-to-date register of all permitted monitoring points should be incorporated within the Contractor Groundwater monitoring plan and annual review report.

Monitoring methodology

5.2.13 The Contractor shall be responsible for undertaking groundwater monitoring as summarised in Table 9.

5.2.14 The Contractor Groundwater monitoring plan shall present details regarding the groundwater monitoring methodology that will be implemented during the Construction phase for approval by the Employer and the Environment Agency.

5.2.15 The Contractor Groundwater monitoring plan shall specify a process for managing any required changes in monitoring methods, procedures or protocols over the life of the project taking into account the need for reliable comparison of future monitoring results against the baseline dataset.

5.2.16 Each measurement specification should include:

a. the measurement method

b. detailed protocols for sampling and/or measurement and record keeping

c. QA/QC protocols.

Sampling and field analysis

5.2.17 The Contractor Groundwater monitoring plan shall specify field protocols with respect to:



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a. monitoring network condition inspections

b. in situ groundwater measurement protocols:

i manual measurements

ii data loggers.

c. water sampling method(s) and protocols, including purging (where appropriate)

d. field analysis protocols

e. sample handling protocols:

i sample containers and preservation

ii sample labelling

iii sample storage and transportation.

f. QA/QC protocols.

5.2.18 The sample collected or measurement made should not be affected by contamination from surface run-off, contact with the sampling equipment or extraneous matter that may have entered the monitoring structure. Nor should it be affected by the products of reaction with materials used in the construction of the monitoring point, sampling equipment or containers.

5.2.19 The Contractor Groundwater monitoring plan shall reference appropriate protocols for managing any waste waters generated during sampling procedures (e.g. purging).

5.2.20 The Contractor Groundwater monitoring plan shall reference appropriate protocols for managing HSE hazards and risks during field activities.

Laboratory analysis

5.2.21 The Contractor Groundwater monitoring plan shall specify laboratory analysis protocols with respect to:

a. laboratory selection, including accreditation requirements

b. analytical suite (as per the project list at the time)

c. analytical methods

d. detection limits

e. QA/QC protocols.

5.2.22 The analytical methods adopted should not be affected by cross-contamination, poor recovery, interference or instrument errors.

5.3 Monitoring schedule

5.3.1 The Contractor Groundwater monitoring plan shall present a detailed schedule for groundwater monitoring.

5.3.2 As a minimum, groundwater monitoring shall be undertaken at the frequency defined in sections 4.1.19 to 4.1.22. Additional monitoring



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rounds may be undertaken by the Contractor (on behalf of the Thames Tideway Tunnel) as required.

Data management and review

5.3.3 The Contractor shall be responsible for managing the groundwater monitoring data collected.

5.3.4 The Contractor Groundwater monitoring plan shall specify protocols for data management, including:

a. data collection

b. data collation

c. data validation

d. data storage.

5.3.5 As a minimum, monitoring data shall be validated within five working days of receipt.

5.3.6 The Contractor shall be responsible for keeping original monitoring records and submitting these to the Employer on completion of construction (for the Contractor‟s respective area).

5.3.7 Water level and quality data shall be stored in Excel-compatible formats.

5.3.8 Initial Alert and Trigger Levels shall be provided to the Contractor by the Employer at the start of the construction period.

5.3.9 The Contractor shall be responsible for reviewing the groundwater monitoring data collected and for interpreting the results.

5.3.10 The data review process shall be undertaken in a timely manner. The Contractor Groundwater monitoring plan shall specify the required timescales for data reviews and turnaround time at analytical laboratories.

5.3.11 The Contractor‟s review of the validated data should include:

a. comparison of actual against specified monitoring

b. evaluation of significance of QA/QC data

c. application of assessment and compliance tests

d. a review of the conceptual site model (i.e. current understanding of the hydrology and hydrogeology of the site)

e. a review of the significance of risks and impacts.

5.3.12 The Contractor shall be responsible for ongoing review of the Alert and Trigger Levels for adequacy during the construction period.

5.3.13 When risks are re-evaluated or monitoring data reveal unexpected variation or trends, it may be necessary to review and occasionally change assessment or compliance criteria. However, any proposed changes to the Alert and Trigger Levels used in the Contractor Groundwater monitoring plan need to be justified technically and may be implemented only after consultation and agreement between the Contractor, the Employer and the Environment Agency.



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5.4 Contingency planning

5.4.1 The Contractor Groundwater monitoring plan shall outline a phased contingency response process that shall be implemented by which the risks to the project and nearby receptors can be assessed and managed in the event of any breach of approved Alert or Trigger Levels.

5.4.2 Where risks are unacceptable, corrective or remediation measures should be initiated and a strategy to monitor their effectiveness should be determined within 1 week of the Trigger Level exceedance being confirmed by the laboratory and in consultation with the Environment Agency.

5.4.3 In all cases, the need for remediation should be balanced against the risk posed to groundwater receptors and the benefits gained by remediation. In complex cases, specialist advice should be taken and remedial actions and their objectives agreed in consultations between the Contractor and the Environment Agency.

5.4.4 Recommended contingency strategies are outlined below; the Contractor Groundwater monitoring plan may include alternative or additional contingency plans as appropriate. The Contractor Groundwater monitoring plan shall specify the required timescales and parties responsible for implementing each action.

Assessment criteria (Alert Levels)

5.4.5 Assessment criteria are intended to draw the attention of site management to the development of adverse trends in monitoring data or the breach of a specified Alert Level. The assessment process involves evaluation of the significance of a departure from baseline conditions. The assessment criteria should be treated primarily as an early warning system to enable appropriate investigative or corrective measures to be implemented, particularly where there is the potential for a compliance limit to be breached.

5.4.6 The Contractor Groundwater monitoring plan shall specify the assessment criteria being applied, including the Alert Levels and the protocols for identifying adverse trends.

5.4.7 If an Alert Level is breached on a single occasion:

a. notify Site Management Team

b. repeat sampling round if no routine sampling is planned within 14 days

c. report in next quarterly factual monitoring report.

5.4.8 If an Alert Level is breached on three consecutive monitoring rounds or if annual review process identifies significant adverse trends in four monitoring rounds, further assessment will be required:

a. Characterise observed issues (desk-based data review), including:

i parameter(s) involved

ii magnitude of exceedance(s)



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iii frequency of exceedance(s)

iv spatial pattern

v temporal trends.

b. Review relevant site activities.

c. Review potential cause(s) for observed results (both within and from outside Contractor‟s area).

d. Review monitoring plan for adequacy.

e. Undertake additional investigation or monitoring (if required) to better characterise issue.

f. Identify likely cause(s) for observed results.

5.4.9 If the observed issue is considered to relate to the project:

a. consult with regulator(s)/stakeholders (as appropriate)

b. review significance of potential risks to receptors

c. implement mitigation measures (as appropriate) to try and halt or reverse adverse trends and/or manage risks for receptors

d. carry out ongoing monitoring at an increased frequency and review to confirm effectiveness of measures implemented.

5.4.10 The assessment findings and actions shall be reported in the next monitoring report.

Compliance Criteria (Trigger Levels)

5.4.11 If a Trigger Level is breached on a single occasion:

a. notify Site Management Team in writing

b. undertake Assessment of Significance (desk-based data review):

i parameter(s) involved

ii magnitude of exceedance(s)

iii frequency of exceedance(s)

iv spatial pattern

v temporal trends

vi risks to nearby receptors

c. repeat sampling round if no routine sampling is planned within 7 days

d. prepare notification report and inform key stakeholders.

5.4.12 If a Trigger Level breach:

a. occurs on three consecutive monitoring rounds, or

b. is part of a significant adverse trend, or

c. is considered to indicate an immediate and significant risk to nearby receptors.

5.4.13 The Contractor shall undertake the following additional actions:



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a. Prepare notification report and inform key stakeholders (eg, Environment Agency, the Employer), as soon as possible.

b. Notify other relevant stakeholders within one week as appropriate, eg, other abstractors.

c. Review relevant activities occurring on site.

d. Review potential cause(s) for observed results.

e. Review existing monitoring plan for adequacy.

f. Undertake additional targeted monitoring or investigation (if required) to better characterise issue.

g. Identify likely cause(s) for observed results.

5.4.14 If the observed issue is considered to relate to the project:

a. Review significance of risks to nearby receptors.

b. Develop strategy within 1 week of the Trigger Level exceedance being confirmed by the laboratory, to mitigate and/or remediate issue(s) in consultation with key stakeholders.

c. Implement mitigation and/or remedial measures (as appropriate) to reduce risk of future breaches affecting project or nearby receptors.

d. Ongoing monitoring and review to confirm effectiveness of measures implemented.


Emergency measures

5.4.16 Additional groundwater monitoring may be required in the event of a pollution incidentxi,xii accidentally occurring at or near the site. The scope of any such additional monitoring shall be proposed by the Contractor for the approval of the Employer and the Environment Agency. The scope should be targeted to reflect the nature of pollution incident and potential risks. This cannot be readily defined in advance of any incident occurring. Instead, the Contractor Groundwater monitoring plan must include a phased process by which the necessary scope of additional monitoring is to be proposed by the Contractor for approval by the Employer and the Environment Agency following a pollution incident.

5.4.17 In the event of a pollution incident, the Contractor shall undertake the following additional actions:

a. Comply with agreed pollution incident response plans.

b. Notify key stakeholders (eg, Environment Agency and the Employer) as soon as possible.

xi The Construction Environmental Management Plan for each site will include pollution incident response plans.

xii A pollution incident would be defined as any incident which results in pollution which has the potential to impact

groundwater resources.



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c. Review significance of risks to nearby groundwater receptors.

d. Notify other relevant stakeholders within 1 week as appropriate, eg, other nearby abstractors.

e. Review existing groundwater monitoring plan for adequacy.

f. Design additional targeted monitoring or investigation (if required) to better characterise issue; consult with the Environment Agency and other stakeholders as appropriate.

g. Undertake additional targeted monitoring or investigation (if required) and review results.

h. Develop strategy to mitigate and/or remediate issue(s) in consultation with key stakeholders.

i. Implement mitigation and/or remedial measures (as appropriate) to reduce risk of future breaches affecting project or nearby receptors.

j. Ongoing monitoring and review to confirm effectiveness of measures implemented.


5.5 Reporting

5.5.1 The Contractor shall be responsible for reporting the groundwater monitoring results during construction. The monitoring reporting shall include:

a. notification reports (if required)

b. quarterly factual reports

c. annual interpretative reports.

5.5.2 The monitoring reports shall be:

a. submitted on time

b. quality assured

c. collated and presented in a consistent format.

5.5.3 The templates for the monitoring reports shall be approved in advance by the Employer in consultation with the Environment Agency. The reporting templates may not be altered without approval from the Employer.

5.5.4 The reports shall be submitted electronically in PDF format. The factual data shall be submitted in an Excel-compatible format.

Notification report

5.5.5 Notification reports shall be used to disseminate information regarding breaches of Trigger Levels or pollution incidents. These reports should provide clear, concise information and carry a recommendation for action (or advise of action taken). Notification reports should be issued within a time frame approved by the Employer and the Environment Agency.



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5.5.6 Notification reports should include:

a. date and time of issue of report

b. name, position and contact information for person issuing report

c. date and time of monitoring surveys or observations that confirm the breach of a compliance limit, or an actual pollution incident

d. pollution incident recorded or compliance limit breached

e. details of any emergency contingency actions implemented

f. an indication of the urgency of response needed by the Employer and/or the Environment Agency.

5.5.7 In instances where assessment criteria or compliance limits are breached regularly and action is being implemented by the site operator (eg, where remedial measures are underway or where the source of contamination to groundwater is being investigated), alternative ongoing reporting procedures may be agreed between the site operator and the Environment Agency to avoid unnecessary duplication of notification reports.

Quarterly factual report

5.5.8 Factual monitoring reports shall be prepared by each Contractor quarterly.

Table 12: Factual monitoring report requirements

Suggested chapter heading

Recommended content

Summary of monitoring completed

Self-audit of compliance with monitoring plan requirements.

Summary of key results Groundwater level data in graphical form

Key groundwater quality data to be displayed in graphical form

Breaches of Alert Levels in tabular form

Breaches of Trigger Levels in tabular form

Recommendations made and outcomes

Urgent actions

Mitigation and/or remedial measures (if required) to manage groundwater-related risks to project or nearby receptors

Appendices Factual datasets (electronic).

5.5.9 The quarterly factual reports shall be submitted to Thames Water within

four weeks of the end of each quarter. The quarterly reports shall be made available to the Environment Agency (or via project data portal) by the Employer.

Annual interpretative report

5.5.10 Interpretative monitoring reports shall be prepared by each Contractor annually.



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Table 13: Annual interpretative monitoring report requirements

Suggested chapter heading

Recommended content

Summary of monitoring completed

Self-audit of compliance with monitoring plan requirements

Updated register of monitoring network

Summary of key results Groundwater level data in graphical form

Spatial contour plots of groundwater levels in upper and lower aquifers

Key groundwater quality data to be displayed in graphical form

Spatial plots of groundwater salinity (EC) in upper and lower aquifer at an appropriate scale

Groundwater quality data in graphical form for agreed indicator species

Breaches of Alert Levels in tabular form

Breaches of Trigger Levels in tabular form

Summary of QA/QC checks e.g. ionic balance calculations

Interpretation of results Review of key groundwater issues and patterns (in context of existing conceptual model and baseline dataset)

Update or refinement of conceptual model (if appropriate)

Likely causes of significant groundwater issues

Influence of site activities on groundwater

Influence of off-site/third party activities on local and regional groundwater

Assessment of risks to nearby receptors

Adequacy of monitoring Gap analysis

Review for adequacy taking into account project activities and past monitoring results.

Recommendations Proposed modifications to monitoring plan (if required)

Changes to monitoring network

Changes to monitoring frequency

Changes to sampling methodology

Changes to analytical suite

Proposed revisions to Alert and Trigger Levels (if appropriate)

Mitigation and/or remedial measures (if required) to manage groundwater-related risks to project or nearby receptors

Other proposed modifications to site activities to better manage risks to/from groundwater (if appropriate)



Page 56

5.5.11 The annual reports shall be submitted by the Contractors in draft to the Employer within four weeks of monitoring year end. The approved draft final annual reports shall be submitted by the Contractors to the Environment Agency within two months of monitoring year end. Following receipt of corrections and comments from the Environment Agency, the final report will be produced within one month of receipt of these comments.

Appendices


Page 57

Appendices

List of figures

Page number

Figure A.1 GWMS – Upper Aquifer monitoring locations (existing and proposed) ... 59

Figure B.1 GWMS – Thanet Sand Formation monitoring locations (existing and proposed) ......................................................................................................... 61

Figure C.1 GWMS – Chalk monitoring locations (existing and proposed) ................ 63

Appendices


Page 58

This page is intentionally blank

Appendices


Page 59

Appendix A: Upper Aquifer monitoring locations

Figure A.1 GWMS – Upper Aquifer monitoring locations (existing and proposed)

Appendices


Page 60

This page is left intentionally blank

!.

!.

!.

!.

!.!.

!.!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

!.

HAMMERSMITH& FULHAM

KENSINGTON& CHELSEA

CITY OFWESTMINSTER

CITY OFLONDON

TOWERHAMLETS

NEWHAM

GREENWICH

LEWISHAM

SOUTHWARK

LAMBETH

WANDSWORTH

HOUNSLOW

RICHMONDUPON

THAMES

EALING

CAMDEN ISLINGTON HACKNEY

BRENT

20

10

-40

-20

0-1

0

PR1023

PR1085

PR1107

SA1066D

SA1098

SA1099A

SA1110

SA1115

SA4303

SR1033A

SR1092

SA4031

SR6576

6090

6391

SA6450

SA6361

SA6910 SA6308

BH13D-1

AMP

CRR

BEL

AEF

CHW

CEF

AST

GPS

KEM

PEF

VEF

HEA

DCS

DST

HAM

BBF

KSTBH2

FOR INFORMATION

1,000 0 1,000500 m

Location

Project Wide

Document Information

Environmental Statement Groundwater Monitoring Baseline Report

Recommended & active upper aquifergroundwater quality monitoring locations

Figure 1

August 2013

Scale 1 : 57,721 at A3

±Keyplan:

Key


London Clay Formation

Lambeth Group

Chalk

Thanet Sands Formation

Local Authority Boundary

!. Existing Upper Aquifer Boreholes

!. Proposed Upper Aquifer Boreholes

EA Chalk PiezometricLevel (mAOD) - Jan 11

Superficial Geology

Head

River Terrace Deposits(Undifferentiated)

Sand and Gravel of Uncertain Ageand Origin

Interglacial Lacustrine Deposits

Alluvium

Kempton Park Gravel Member

Langley Silt Member

Taplow Gravel Formation

Lynch Hill Gravel Member

Hackney Gravel Member

Boyn Hill Gravel Member

Black Park Gravel Member

Mapping reproduced by permission of OrdnanceSurvey on behalf of HMSO. © Crown Copyright andDatabase right 2012. All rights reserved. OrdnanceSurvey licence number 100019345

© Thames Water Utilities Ltd 2008

Site Abbreviations

Sites

AMP - Abbey Mills Pumping Station

AST - Acton Storm Tanks

AEF - Albert Embankment Foreshore

BEL - Barn Elms

BST - Beckton Sewage Treatment Works

BBF - Blackfriars Bridge Foreshore

CRR - Carnwath Road Riverside

CHW - Chambers Wharf

CEF - Chelsea Embankment Foreshore

CWD - Cremorne Wharf Depot

DCS - Deptford Church Street

DST - Dormay Street

EPS - Earl Pumping Station

FPS - Falconbrook Pumping Station

GPS - Greenwich Pumping Station

HPS - Hammersmith Pumping Station

HEA - Heathwall Pumping Station

KEM - King Edward Memorial Park Foreshore

KGP - King George’s Park

KST - Kirtling Street

PEF - Putney Embankment Foreshore

VEF - Victoria Embankment Foreshore

Appendices


Page 61

Appendix B: Thanet Sand Formation

Figure B.1 GWMS – Thanet Sand Formation monitoring locations (existing and proposed)

Appendices


Page 62


!.

!.

!.

HAMMERSMITH& FULHAM

KENSINGTON& CHELSEA

CITY OFWESTMINSTER

CITY OFLONDON

TOWERHAMLETS

NEWHAM

GREENWICH

LEWISHAM

SOUTHWARK

LAMBETH

WANDSWORTH

HOUNSLOW

RICHMONDUPON

THAMES

EALING


BRENT

20

10

-40

-20

0-1

0

SR1089

SA6453A

4053

CWD

KGP

AMP

CRR

BEL

AEF

CHW

CEF

AST

GPS

KEM

PEF

VEF

HEA

DCS

DST

HAM

EPS

FPS

BBF

KST

FOR INFORMATION

1,000 0 1,000500 m

Location

Project Wide



Recommended & active TSF groundwaterquality monitoring locations

Figure 2

August 2013

Scale 1 : 57,721 at A3

±Keyplan:

Key



Lambeth Group

Chalk



!. Existing TSF Boreholes

!. Proposed TSF Boreholes


Source Protection Zones

Zone I (Inner Protection Zone)

Zone II (Outer Protection Zone)

Zone III (Total Catchment)

Solid Geology

Claygate Member


Harwich Group

Lambeth Group

Thanet Sand

Chalk Formation



Site Abbreviations

Sites




BEL - Barn Elms








DST - Dormay Street











Appendices


Page 63

Appendix C: Chalk monitoring locations

Figure C.1 GWMS – Chalk monitoring locations (existing and proposed)

Appendices


Page 64


!H!H

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!.

!.

!.!.

!.

!.

!.

!.

!.

!.

!.

HAMMERSMITH& FULHAM

KENSINGTON& CHELSEA

CITY OFWESTMINSTER CITY OF

LONDON

TOWERHAMLETS

NEWHAM

GREENWICH

LEWISHAM

SOUTHWARK

LAMBETH

WANDSWORTH

HOUNSLOW

RICHMONDUPON

THAMES

EALING


BRENT

20

10

-40

-20

0-1

0

SR1024

SR1033H

SR1055

SR3007

SR4117

SR6902

PW1

SP1-CH

6091

6909

SR6574

6906

6908

6390

4021

4087

SR4082

SR6457

SR6905

SR6907

CWD

KGP

AMP

CRR

BEL

AEF

CHW

CEF

AST

GPS

KEM

PEF

VEF

DCS

DST

HAM

EPS

FPS

BBF

KST

FOR INFORMATION

1,000 0 1,000500 m

Location

Project Wide



Recommended & active Chalk groundwater quality monitoring locations

Figure 3

August 2013

Scale 1 : 57,721 at A3

±Keyplan:

Key



Lambeth Group

Chalk



!. Existing Lower Aquifer Boreholes

!. Proposed Lower Aquifer Boreholes


Source Protection Zones

Zone I (Inner Protection Zone)

Zone II (Outer Protection Zone)

Zone III (Total Catchment)

Solid Geology

Claygate Member


Harwich Group

Lambeth Group

Thanet Sand

Chalk Formation



Site Abbreviations

Sites




BEL - Barn Elms








DST - Dormay Street











Appendices


Page 65

Appendix D: Water quality long list

Appendices


Page 66


Name Units Method EA suiteCALCIUM : MAGNESIUM RATIO UNITLESS Calculated YESCONDUCTIVITY @25C uS/cm Field YESHARDNESS TOTAL - as CACO3 mg/l Calculated YESIONIC BALANCE (ANIONS/CATIONS) % Calculated YESNITRATE - as N mg/l Calculated YESOXYGEN DISSOLVED (INSTRUMENTAL - IN SITU) - AS O mg/l Calculated YESOXYGEN DISSOLVED (INSTRUMENTAL) - AS % SATN % Field YESPAHS, TOTAL ug/l Calculated YESPH IN SITU MEASUREMENT PHUNITS Field YESSODIUM : CHLORIDE RATIO UNITLESS Calculated YESTEMPERATURE WATER CEL Field YESARSENIC - AS AS ug/l Low YESSELENIUM - AS SE ug/l Low YESFAECAL COLIFORMS PRESUMPTIVE NO/100ml Low YESSTREPTOCOCCI FAECAL PRE-MF NO/100ml Low YESCYANIDE - AS CN mg/l Low YESALKALINITY PH 4.5 - as CACO3 mg/l Low YESAMMONIA - AS N mg/l Low YESCARBON DIOXIDE FREE - AS CO2 mg/l Low YES

CARBON ORGANIC DISSOLVED - AS C mg/l Low YESCHLORIDE ION - AS CL mg/l Low YESFLUORIDE - AS F mg/l Low YESNITRITE - as N mg/l Low YESNITROGEN TOTAL OXIDISED - AS N mg/l Low YESORTHOPHOSPHATE - as P mg/l Low YESPH - AS PH UNITS PHUNITS Low YESSILICATE REACTIVE DISSOLVED - AS SIO2 mg/l Low YESBROMATE mg/l Low YESBROMIDE ION - AS BR mg/l Low YESIODIDE ION - AS I mg/l Low YES

(2,4,5-TRICHLOROPHENOXY)ETHANOIC ACID ug/l Low YES(2,4-DICHLOROPHENOXY)ETHANOIC ACID ug/l Low YES2,3,6-TBA {2,3,6-TRICHLOROBENZOIC ACID}{CAS RN 5 ug/l Low YES2,4-DB ug/l Low YESBENAZOLIN ug/l Low YESBENTAZONE ug/l Low YESBROMOXYNIL ug/l Low YESCLOPYRALID ug/l Low YESDICAMBA {3,6-DICHLORO(O-METHOXYBENZOIC ACID)} ug/l Low YESDICHLORPROP ug/l Low YESFENOPROP ug/l Low YESFLUROXYPYR ug/l Low YESIOXYNIL ug/l Low YESMCPA { } ug/l Low YESMCPB ug/l Low YESMECOPROP { } ug/l Low YESPICHLORAM ug/l Low YESTRICLOPYR ug/l Low YESMERCURY - AS HG ug/l Low YESALUMINIUM - AS AL ug/l Low YESANTIMONY - AS SB ug/l Low YESBARIUM - AS BA ug/l Low YESBERYLLIUM - AS BE ug/l Low YESBORON - AS B ug/l Low YESCADMIUM - AS CD ug/l Low YESCALCIUM - AS CA mg/l Low YESCHROMIUM - AS CR ug/l Low YESCOBALT - AS CO ug/l Low YESCOPPER - AS CU ug/l Low YESIRON - AS FE ug/l Low YESLEAD - AS PB ug/l Low YESLITHIUM - AS LI ug/l Low YESMAGNESIUM - AS MG mg/l Low YESMANGANESE - AS MN ug/l Low YESMOLYBDENUM - AS MO ug/l Low YESNICKEL - AS NI ug/l Low YESPOTASSIUM - AS K mg/l Low YESSILVER - AS AG ug/l Low YESSODIUM - AS NA mg/l Low YESSTRONTIUM - AS SR ug/l Low YESSULPHATE - AS SO4 mg/l Low YESTHALLIUM - TOTAL AS TL ug/l Low YESTIN - AS SN ug/l Low YESTITANIUM ug/l YESURANIUM - AS U ug/l Low YESVANADIUM - AS V ug/l Low YESZINC - AS ZN ug/l Low YESALUMINIUM DISSOLVED - AS AL ug/l Low YESBARIUM DISSOLVED - AS BA ug/l Low YESBORON DISSOLVED- AS B ug/l Low YESCADMIUM DISSOLVED ug/l Low YESCALCIUM DISSOLVED - AS CA mg/l Low YESCHROMIUM (DISSOLVED) ug/l Low YESCOPPER (DISSOLVED) ug/l Low YESIRON DISSOLVED - AS FE ug/l Low YESLEAD (DISSOLVED) ug/l Low YESLITHIUM DISSOLVED - AS LI ug/l Low YESMAGNESIUM DISSOLVED - AS MG mg/l Low YESMANGANESE DISSOLVED - AS MN ug/l Low YESNICKEL (DISSOLVED) ug/l Low YESPOTASSIUM DISSOLVED - AS K mg/l Low YESSODIUM DISSOLVED - AS Na mg/l Low YESSTRONTIUM DISSOLVED - AS SR ug/l Low YESZINC (DISSOLVED) ug/l Low YESACENAPTHENE ug/l Low YESACENAPTHYLENE ug/l Low YESANTHRACENE ug/l Low YESBENZ[A]-ANTHRACENE ug/l Low YESBENZO-[A]-PYRENE ug/l Low YESBENZO-[B]-FLUORANTHENE ug/l Low YESBENZO-[GHI]-PERYLENE ug/l Low YESBENZO-[K]-FLUORANTHENE ug/l Low YESCHRYSENE ug/l Low YES

Name Units Method EA suiteDIBENZ-[A,H]-ANTHRACENE ug/l Low YESFLUORANTHENE ug/l Low YESFLUORENE ug/l Low YESINDENO-[1,2,3-CD]-PYRENE ug/l Low YESNAPHTHALENE ug/l Low YESPHENANTHRENE ug/l Low YESPYRENE ug/l Low YES1,2,3-TRICHLOROBENZENE ug/l Low YES1,2,4-TRICHLOROBENZENE ug/l Low YES1,3,5-TRICHLOROBENZENE ug/l Low YES

2,3,5,6-TETRACHLOROAMINOBENZENE {2,...ANILINE} ug/l Low YES2,3,5,6-TETRACHLOROTHIOANISOLE ug/l Low YESALDRIN ug/l Low YESCHLORDANE CIS/Z/ALPHA ug/l Low YESCHLORDANE TRANS ug/l Low YESCHLOROPROPHAM ug/l Low YESCHLOROTHALONIL ug/l Low YESCIS-HEPTACHLOR EPOXIDE ug/l Low YESDDE (OP) ug/l Low YESDDE (PP) ug/l Low YESDDT (OP) ug/l Low YESDDT (PP) ug/l Low YESDICHLOBENIL ug/l Low YESDIELDRIN ug/l Low YESENDOSULPHAN ALPHA ug/l Low YESENDOSULPHAN BETA ug/l Low YESENDRIN ug/l Low YESHCH ALPHA ug/l Low YESHCH BETA ug/l Low YESHCH DELTA ug/l Low YESHCH GAMMA ug/l Low YESHEPTACHLOR ug/l Low YESHEXACHLORO 1,3 BUTADIENE ug/l Low YESHEXACHLOROBENZENE ug/l Low YESISODRIN ug/l Low YESMETHOXYCHLOR ug/l Low YESPCB CONGENER 028 ug/l Low YESPCB CONGENER 052 ug/l Low YESPCB CONGENER 101 ug/l Low YESPCB CONGENER 105 ug/l Low YESPCB CONGENER 118 ug/l Low YESPCB CONGENER 138 ug/l Low YESPCB CONGENER 153 ug/l Low YESPCB CONGENER 156 ug/l Low YESPCB CONGENER 180 ug/l Low YESPENDIMETHALIN ug/l Low YESPROPACHLOR ug/l Low YESTDE (OP) ug/l Low YESTDE (PP) ug/l Low YESTECNAZENE ug/l Low YESTRANS-HEPTACHLOR EPOXIDE ug/l Low YESTRIFLURALIN ug/l Low YESATRAZINE { } ug/l Low YESATRAZINE DESETHYL {DE-ETHYL ATRAZINE} ug/l Low YESATRAZINE DESISOPROPYL ug/l Low YESAZINPHOS-ETHYL ug/l Low YESAZINPHOS-METHYL ug/l Low YESBENDIOCARB ug/l Low YESBUPIRIMATE ug/l Low YESCARBOPHENOTHION ug/l Low YESCHLORFENVINPHOS ug/l Low YESCHLORPYRIFOS ug/l Low YESCHLORPYRIPHOS-METHYL ug/l Low YESCOUMAPHOS ug/l Low YESCYANAZINE ug/l Low YESDESMETRYNE ug/l Low YESDIAZINON ug/l Low YESDICHLORVOS ug/l Low YESDIMETHOATE ug/l Low YESETHION ug/l Low YESETHOFUMESATE ug/l Low YESFENCHLORPHOS {RONNEL.} ug/l Low YESFENITROTHION ug/l Low YESFENPROPIMORPH ug/l Low YESFENTHION ug/l Low YESFONOFOS ug/l Low YESIODOFENPHOS ug/l Low YESIPRODIONE ug/l Low YESIRGAROL 1051 ug/l Low YESMALATHION ug/l Low YESMETALAXYL ug/l Low YESMETAZACHLOR ug/l Low YESMEVINPHOS ug/l Low YESNAPROPAMIDE ug/l Low YESPARATHION {PARATHION ETHYL} ug/l Low YESPARATHION-METHYL { } ug/l Low YESPHORATE ug/l Low YESPIRIMICARB ug/l Low YESPIRIMIPHOS METHYL {METHYL PIRIMIPHOS} ug/l Low YESPIRIMIPHOS-ETHYL ug/l Low YESPROCHLORAZ ug/l Low YESPROMETHRYN ug/l Low YESPROPAZINE ug/l Low YESPROPETAMPHOS ug/l Low YESPROPYZAMIDE ug/l Low YESSIMAZINE ug/l Low YESTERBUTRYN ug/l Low YESTRIAZOPHOS ug/l Low YESTRIETAZINE ug/l Low YES2,3-DIMETHYLPHENOL {2,3-XYLENOL} ug/l Low YES2,4,5-TRICHLOROPHENOL ug/l Low YES2,4,6-TRICHLOROPHENOL ug/l Low YES2,4-DICHLOROPHENOL ug/l Low YES2,4-DIMETHYLPHENOL {2,4-XYLENOL} ug/l Low YES2,5-DICHLOROPHENOL ug/l Low YES2,5-DIMETHYLPHENOL {2,5-XYLENOL} ug/l Low YES2,6 DIMETHYLPHENOL {2,6 XYLENOL} ug/l Low YES2,6-DICHLOROPHENOL ug/l Low YES

Name Units Method EA suite2-CHLOROPHENOL ug/l Low YES2-METHYLPHENOL {O-CRESOL} ug/l Low YES3,4 DIMETHYLPHENOL {3,4 XYLENOL} ug/l Low YES3,5-DIMETHYLPHENOL {3,5-XYLENOL} ug/l Low YES3-CHLOROPHENOL ug/l Low YES3-METHYLPHENOL {M-CRESOL} ug/l Low YES4-CHLORO-3-METHYLPHENOL {P-CHLORO-M-CRESOL} ug/l Low YES4-CHLOROPHENOL ug/l Low YES4-METHYLPHENOL {P-CRESOL} ug/l Low YESPENTACHLOROPHENOL ug/l Low YESPHENOL ug/l Low YESGCMS : Low Level Semi-Volatile Screen : Gwtrs Text LowBIFENTHRIN ug/l Low YESCYFLUTHRIN ug/l Low YESCYPERMETHRIN ug/l Low YESCYPERMETHRIN ID ug/l Text YESDELTAMETHRIN ug/l Low YESFLUMETHRIN ug/l Low YESLAMBDA CYHALOTHRIN ug/l Low YESPERMETHRIN, CIS ug/l Low YESPERMETHRIN, TRANS ug/l Low YESCHLORMEQUAT ug/l Low YES1,1,1-TRICHLOROETHANE ug/l Low YES1,1,2-TRICHLOROETHANE ug/l Low YES1,1-DICHLOROETHANE ug/l Low YES1,1-DICHLOROETHENE ug/l Low YES1,2 -DICHLOROETHENE (CIS) ug/l Low YES1,2 -DICHLOROETHENE (TRANS) ug/l Low YES1,2-DICHLOROETHANE {ETHYLENE DICHLORIDE} ug/l Low YES1,2-DIMETHYLBENZENE {O-XYLENE} ug/l Low YESBENZENE ug/l Low YESBROMODICHLOROMETHANE ug/l Low YESCHLORODIBROMOMETHANE ug/l Low YESETHENYLBENZENE {VINYLBENZENE} {STYRENE} ug/l Low YESETHYLBENZENE ug/l Low YESGCMS : Volatile Screen for Gwtrs text LowTETRACHLOROETHENE (PER/TETRACHLOROETHYLENE) ug/l Low YESTETRACHLOROMETHANE {CARBON TETRACHLORIDE} ug/l Low YESTOLUENE (METHYLBENZENE) ug/l Low YESTRIBROMOMETHANE {BROMOFORM} ug/l Low YESTRICHLOROETHENE (TRICHLOROETHYLENE) ug/l Low YES

TRICHLOROMETHANE {CHLOROFORM} ug/l Low YESXYLENE (META & PARA){1,3+1,4-dimethylbenzene} ug/l Low YESMETHANE - AS CH4 mg/l Low YES1,1,1,2 -TETRACHLOROETHANE ug/l Low YES1,1,2,2-TETRACHLOROETHANE {ACETOSAN}{BONAFORM}{C ug/l Low YES

ETHYL TERTIARY BUTYL ETHER (ETBE) ug/l Low YESMTBE {METHYL TERT-BUTYL ETHER} ug/l Low YESTERTIARY AMYL METHYL ETHER (TAME) ug/l Low YESSULPHIDE - AS S mg/l Low YESALDICARB ug/l Low YESALDICARB SULPHONE ug/l Low YESALDICARB SULPHOXIDE ug/l Low YESASULAM ug/l Low YESCARBARYL ug/l Low YESCARBENDAZIM ug/l Low YESCARBETAMIDE ug/l Low YESCARBOFURAN ug/l Low YESCHLORIDAZON ug/l Low YESCHLOROTOLURON ug/l Low YESCHLOROXURON ug/l Low YESDIFLUROBENZURON ug/l Low YESDIURON ug/l Low YESETHIOFENCARB ug/l Low YESFENURON ug/l Low YESISOPROTURON (DIIP1,3DITHIOLAN-2-YLIDENEMALONATE) ug/l Low YESLINURON ug/l Low YESMETHABENZTHIAZURON ug/l Low YESMETHIOCARB ug/l Low YESMETHOMYL ug/l Low YESMETOXURON ug/l Low YESMETSULFURON - METHYL ug/l Low YESMONOLINURON ug/l Low YESMONURON ug/l Low YESNEBURON ug/l Low YESOXAMYL ug/l Low YESPROPOXUR ug/l Low YESFLUTRIAFOL ug/l Low YESBICARBONATE - AS HCO3 mg/l Calculated YESMulti residual (GCMS) scan, determinands tested listed below text low YES1200: Trihalomethn, ug/l NO5955: SI-G2, UNITLESS NO5957: SI-G4, UNITLESS NO6906: TETRACHLOROE, ug/l NO6940: PhenolsSWAD, ug/l NO8383: Xylene Tot, ug/l NO9695: HcarbonsFilt, ug/l NO9823: Permthrn c+t, ug/l NO6946: Cyanide elib, ug/l NO9880: Nitrate -NO3, mg/l NO1,1-Dichloropropene NO1,2-Dichloropropane NO1,3-Dichloropropane TRANS NO2 4 5-T NOAmmonium mg/l NOBromomethane NOChloroethane NOClofenvinfos NO

Name Units Method EA suiteCOD NOChloromethane NODalapon NODDT TOTAL NODelta.-Lindane NODichlorobenzoic Acid NODichlorodifluoromethane NODichloromethane NOEndosulfan A NOEndosulfan B NOGasoline Range Organics/Extractable Petroleum Hydrocarbons Organics (as a screening for light (C4-C10) and heavy (C10-C40) hydrocarbons) NOGlyphosate NOPhosphamidon NOPhosphate NOTrichlorofluoromethane NOTurbidity NOVinylChloride NO

References


Page 71

6 References

British Standard 6164, 2011. Code of practice for health and safety in tunnelling in the construction industry

Environment Agency, 2013. Thames Tideway Tunnel Planning Inspectorate Reference: WW01001. Section 56 response dated 24th May 2013. TT_RReps_240513.

Environment Agency, 2011. Management of the London Basin Chalk Aquifer. Status Report 2011.

Environment Agency, 2006. The London Catchment Abstraction Management Strategy (CAMS). Final Strategy Document (2006). Available at: http://publications.environment-agency.gov.uk/PDF/GETH0406BKRM-E-E.pdf. Accessed April 2012.

ES, 2013 Volume 3: Project-wide effects assessment, Section 3: Water resources – groundwater, Thames Tunnel Tideway, Environmental Statement.

Mott MacDonald, July 2010. Lee Tunnel, Groundwater Monitoring Strategy, Version 2.3.

WJ Groundwater, 2012. Lee Tunnel Abbey Mills Shaft F Pump Out Test Factual Report. 432/1770 (March 2012)

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