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Thames Tunnel
Preliminary environmentalinformation report
Volume 3: Alternatives
Regulations 2 and 10 of the Infrastructure Planning(Environmental Impact Assessment) Regulations 2009
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Phase two consultation documentation
Project informationpapers
• Build
• Changes
• Consultation
• Design
• Environment
• Funding
• Managingconstruction
• Odour
• Options
• Overow
• Regulatoryframework
• Routeandtunnelalignment
• Routetoconsent
• Settlement
• Siteselection
• Timing• Transport
Technical documents
• Airmanagementplan
• Bookofplans
• CodeofconstructionpracticePartA:Generalrequirements
• Consultationstrategyandstatementofcommunityconsultation
• Designdevelopmentreport
• Draftwastestrategy
• Interimengagementreport
• NeedsReport• Phasetwoschemedevelopmentreport
• Preliminary environmental information report
• Reportonphaseoneconsultation
• Backgroundtechnicalpaper
• Siteselectionmethodologypaper
Site information papers• AbbeyMillsPumpingStation
• ActonStormTanks
• AlbertEmbankmentForeshore
• BarnElms
• BecktonSewageTreatmentWorks
• BekesbourneStreet
• BlackfriarsBridgeForeshore
• CarnwarthRoadRiverside
• ChambersWharf
• ChelseaEmbankmentForeshore
• CremorneWharfDepot
• DeptfordChrurchStreet
• DormayStreet• EarlPumpingStation
• FalconbrookPumpingStation
• GreenwichPumpingStation
• HammersmithPumpingStation
• HeathwallPumpingStation
• JewsRow
• KingEdwardMemorialParkForehore
• KingGeorge’sPark
• KirtlingStreet
• Otherworks
• PutneyBridgeForeshore
• ShadThamesPumpingStation
• VictoriaEmbankment
Foreshore
General
• Yourguidetophasetwoconsultation
• WhydoesLondonneedtheThamesTunnel?
• Feedbackform
• Equalitiesform
• Customeroverviewleaet
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Page i Preliminary environmental informationreport
Thames Tunnel
Preliminary environmental information report
List of contents
Non technical summary
Part A: Preliminary project information
Volume 1 Introduction
Volume 2 Proposed development
Volume 3
Volume 4
Alternatives (this document)
Scoping Opinions and technical engagement
Volume 5 Assessment methodology
Volume 6 Project-wide assessment
Part B: Preliminary site information
Volume 7 Acton Storm Tanks CSO interception and main tunnel reception site
Volume 8 Hammersmith Pumping Station CSO interception site
Volume 9 Barn Elms CSO interception site
Volume 10 Putney Bridge Foreshore CSO interception site
Volume 11 Dormay Street CSO interception and connection tunnel sequential drive
siteVolume 12 King George’s Park CSO interception and connection tunnel reception
site
Volume 13 Carnwath Road Riverside main tunnel drive and reception, andconnection tunnel reception site
Volume 14 Falconbrook Pumping Station CSO interception site
Volume 15 Cremorne Wharf Depot CSO interception site
Volume 16 Chelsea Embankment Foreshore CSO interception site
Volume 17 Kirtling Street main tunnel double drive site
Volume 18 Heathwall Pumping Station CSO interception site
Volume 19 Albert Embankment Foreshore CSO interception site
Volume 20 Victoria Embankment Foreshore CSO interception site
Volume 21 Blackfriars Bridge Foreshore CSO interception site
Volume 22 Chambers Wharf main tunnel drive and reception and connection tunnelreception site
Volume 23 King Edward Memorial Park CSO interception site
Volume 24 Earl Pumping Station CSO interception site
Volume 25 Deptford Church Street CSO interception site
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Page ii Preliminary environmental informationreport
Volume 26 Greenwich Pumping Station CSO interception and connection tunneldrive site
Volume 27 Abbey Mills Pumping Station main tunnel reception site
Volume 28 Beckton Sewage Treatment Works site
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Page iii Preliminary environmental informationreport
Thames Tunnel
Preliminary environmental information report
Volume 3: AlternativesList of contents
Page number
1 Introduction ...................................................................................................... 1 1.2 Statutory requirements ............................................................................ 1 1.3 Content and structure .............................................................................. 2
2 Strategic alternatives ....................................................................................... 3 2.1 Non-tunnel alternatives ............................................................................ 3 2.2 Storage tunnel options ............................................................................. 5 2.3 Ministerial approval .................................................................................. 9 2.4 Validation of Option 1c ............................................................................ 9
3 Tunnel routes ................................................................................................. 14 3.1 Introduction ............................................................................................ 14 3.2 Thames Tunnel alignments ................................................................... 14 3.3 Reasons for selection of the Abbey Mills route ...................................... 18
4 Main tunnel construction sites and drive strategy ...................................... 24 4.1 Introduction ............................................................................................ 24 4.2 Site selection ......................................................................................... 24 4.3 Drive strategy ........................................................................................ 25
5 CSO sites ........................................................................................................ 39 5.1 Introduction ............................................................................................ 39 5.2 Acton Storm Relief ................................................................................. 39 5.3 Hammersmith Pumping Station ............................................................. 39 5.4 West Putney Storm Relief...................................................................... 40 5.5 Putney Bridge Storm Relief ................................................................... 40 5.6 Frogmore Storm Relief – Bell Lane Creek ............................................. 41 5.7 Frogmore Storm Relief – Buckhold Road .............................................. 41 5.8 Jews Row: Wandle Valley Storm Relief and Falconbrook Storm Relief 41 5.9 Falconbrook Pumping Station ................................................................ 42 5.10 Lots Road Pumping Station ................................................................... 42 5.11 Ranelagh ............................................................................................... 42
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Page iv Preliminary environmental informationreport
5.12 Heathwall Pumping Station and South West Storm Relief .................... 42 5.13 Clapham Storm Relief and Brixton Storm Relief .................................... 43 5.14 Regent Street ........................................................................................ 43 5.15 Fleet Main .............................................................................................. 44 5.16 Shad Thames Pumping Station ............................................................. 44 5.17 North East Storm Relief ......................................................................... 44 5.18 Holloway Storm Relief ........................................................................... 45 5.19 Earl Pumping Station ............................................................................. 45 5.20 Deptford Storm Relief ............................................................................ 45 5.21 Greenwich Pumping Station .................................................................. 46
Glossary .................................................................................................................. 47 References .............................................................................................................. 62
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Page v Preliminary environmental informationreport
List of figures
Page number
Vol 3 Figure 3.2.1 Alternative alignments of Thames Tunnel .................................. 15Vol 3 Figure 4.3.1 Main tunnel shaft zones .............................................................. 26
Vol 3 Figure 4.3.2 Main tunnel shaft zones for Comparison 1 ................................. 28
Vol 3 Figure 4.3.3 Main tunnel shaft zones for Comparison 2 ................................. 30
Vol 3 Figure 4.3.4 Main tunnel sites Comparison 3, Option A1 ............................... 33
Vol 3 Figure 4.3.5 Main tunnel sites Comparison 3, Option A2 ............................... 33
Vol 3 Figure 4.3.6 Main tunnel sites Comparison 3, Option B ................................. 35
Vol 3 Figure 4.3.7 Main tunnel sites Comparison 3, Option C ................................. 36
List of tables
Page number
Vol 3 Table 2.2.1 Summary assessment of options December 2006 ........................ 8
Vol 3 Table 2.4.1 Advantages and disadvantages of options .................................. 10
Vol 3 Table 2.4.2 Summary of main options and estimated costs ........................... 12
Vol 3 Table 3.2.1 Key aspects of the three tunnel alignment alternatives ............... 17
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Page vi Preliminary environmental informationreport
List of abbreviations
AADT Annual Average Daily Traffic
ACE Arts Culture and Entertainment
AM MorningAOD Above Ordnance Datum
APZ Archaeological Priority Zone
AQEG Air Quality Expert Group
AQMA Air Quality Management Area
AQO Air Quality Objective
ARS Artificial Recharge Scheme
ASR Aquifer Storage and Recovery
ASSI Area of Special Scientific Interest
ATC Automated Traffic Counter
ATD Above Tunnel Datum (defined at ~100m AOD)
AURN Automatic Urban and Rural Network
BAP Biodiversity Action Plan
BGS British Geological Survey
BMWP Biological Monitoring Working Party
BOD Biochemical Oxygen DemandBPIP Building Profile Input Programme
BPM Best Practicable Means
BS British Standard
CABE Commission for Architecture and the Built Environment
CAMS Catchment Abstraction Management Strategy
CCI Community Conservation Index
CCSS Community Consultation Strategy
CCTV Closed Circuit Television
CDA Critical Drainage Area
CEMP Construction Environment Management Programmes
CIRIA Construction Industry Research and Information Association
CLR Contaminated Land Report
CoCP Code of Construction Practice
CoPA Control of Pollution Act
CROW Countryside and Rights of WayCSO Combined Sewer Overflow
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Page vii Preliminary environmental informationreport
dB Decibel
dB LAeq,T a equivalent continuous A-weighted sound pressure level havingthe same energy as a fluctuating sound over a specified timeperiod T
DCMS Department for Culture, Media and SportDCO Development Consent Order
DCLG Department for Communities and Local Government
DCMS Department for Culture media and Sport
Defra Department of the Environment, Food and Rural Affairs
DfT Department for Transport
DMP Development Management Plan
DMPD Development Management Policies Document
DMRB Design Manual for Roads and Bridges
DO Dissolved Oxygen
DPD Development Plan Document
DTM Digital Terrain Mapping
EA Environment Agency
EC European Commission
EcIA Ecological Impact Assessment
eVDV Estimated Vibration Dose ValueEEA European Economic Area
EFRA Environment Food and Rural Affairs Committee
EH English Heritage
EHO Environmental Health Officer
EIA Environmental Impact Assessment
EMEP European Monitoring and Evaluation Programme
EN English Nature
EPA Environment Protection Agency
EPB Earth Pressure Balance
EPBM Earth Pressure Balance Machine
EqIA Equality Impact Assessment
EQS Environmental Quality Standard
ES Environmental Statement
EU European Union
FAQ Frequently Asked QuestionsFIDOR Frequency, Intensity, Duration, Offensiveness, Receptor
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FRA Flood Risk Assessment
GARDIT General Aquifer Research Development and Investigation Team
GI Ground Investigation
GiGL Greenspace Information for Greater London
GIS Geographical Information System
GLA Greater London Authority
GLHER Greater London Historic Environment Record
GQA General Quality Assessment (EA water quality classification)
GSHP Ground Source Heat Pump
GWB Groundwater Body: distinct volume of groundwater within anaquifer or aquifers
GWMU Ground Water Management UnitH2S Hydrogen sulphide
ha hectares
HA Highways Authority
HDV Heavy Duty Vehicle
HEA Historic Environmental Assessment
HER Historic Environment Record
HGV Heavy Goods Vehicle
HIA Health Impact Assessment
HIAB Hydrauliska Industri AB Company
HPA Health Protection Agency
HQ Headquarter
HRA Habitats Regulations Assessment
HTC Hammersmith Town Centre
HWR Hazardous Waste Regulations (2005)
IEEM Institute of Ecology and Environmental Management
IEMA Institute of Environmental Management and Assessment
IMD Index of Multiple Deprivation
IPC Infrastructure Planning Commission
Iron Age 600 BC – AD 43
JNCC Joint Nature Conservation Committee
kg kilograms
km kilometre
kVA kilo watt amperes
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kW kilowatt
l/d litres per day
l/s litres per second
LA Local Authority
LAARC London Archaeological Archive and Research Centre
LAQM Local Air Quality Management
LAQN London Air Quality Network
LB London Borough
LBAP Local Biodiversity Action Plan
LDF Local Development Framework
LGV Light Goods Vehicle
LHA Local Highway AuthorityLMB Lambeth Mottled Beds
LNR Local Nature Reserve
loWR List of Wastes Regulations 2005
LSB Lower Shelly Beds
LtB Laminated Beds
LTI London Tideway Improvements
LTT London Tideway Tunnels
LUL London Underground Limited
LVMF London View Management Framework
m metre
m AOD metres above Ordinance Datum (see AOD)
m ATD metres above temporary datum, (see ATD)
m/s metres per second
MAGIC Multi-Agency Geographic Information for the Countryside
Mbgl Metres below ground levelMEICA Mechanical Electrical Instrumentation Controls Automation
Ml/d Megalitres per day (million litres per day)
MoD Ministry of Defence
MOL Metropolitan Open Land
MOLA Museum of London Archaeology
NE Natural England
NESR North East Storm Relief
NCR National Cycle Route
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Page x Preliminary environmental informationreport
NGR National Grid Reference
NMR National Monuments Record
NNR National Nature Reserve
NO2 Nitrogen dioxide
NOx Oxides of nitrogen
NPPF National Planning Policy Framework
NPS National Policy Statement
NRMM Non Road Mobile Machinery
NSIP Nationally Significant Infrastructure Project
NSRA National Small-bore Rifle Association
NTS Non Technical Summary
OCU Odour Control UnitOfwat The Water Services Regulations Authority
OS Ordnance Survey
OUE European Odour Unit
PAH Polycyclic aromatic hydrocarbons
PCB Polychlorinated Biphenyl
PEI Preliminary Environmental Information
PEIR Preliminary Environmental Information Report
PEL Probable Effect Levels
PICP Pollution Incident Control Plan
PIP Project Information Paper
PLA Port of London Authority
PM Afternoon
PM10 Particles on the order of ~10 micrometers or less
PPC Pollution Prevention and Control
PPE Personal Protective EquipmentPPG Pollution Prevention Guidance
PPS Planning Policy Statement
PPV Peak Particle Velocity
PRoW Public Rights of Way
PS Pumping Station
pSPA Potential Special Protected Area
PWS Public Water Supply
RAMS Risk Assessment Method Statement
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Page xi Preliminary environmental informationreport
RAMSAR The Convention on Wetlands of International Importance
RB Royal Borough
RBKC Royal Borough of Kensington and Chelsea
RBMP River Basin Management Plans
RDB Red Data Book
RHS Royal Horticultural Society
RPG Regional Planning Guidance
RSPB Royal Society for the Protection of Birds
RDB Red data book
RTC Real Time Control
RTD River Terrace Deposits
SA Sustainability AppraisalSAC Special Area of Conservation
SAM Scheduled Ancient Monument. More commonly referred to as‘Scheduled Monument’
SCI Statement of Community Involvement
SCL Sprayed Concrete Lining
SFRA Strategic Flood Risk Assessment
SI Statutory Instrument
SINC Site of Importance for Nature Conservation
SMI Site of Metropolitan Importance
SNCI Site Nature Conservation Importance
SO2 Sulphur dioxide
SoCC Statement of Community Consultation
SPA Special Protection Area
SPD Supplementary Planning Document
S-P-R Source-pathway-receptor
SPZ Source Protection Zone
SR Storm Relief
SRN Strategic Road Network
SSR Site Suitability Report
SSSI Site of Special Scientific Interest
STW Sewage Treatment Works
SUDS Sustainable (Urban) Drainage Systems
SWMP waste - Site Waste Management Plan
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Page xii Preliminary environmental informationreport
SWMP water – Surface Water Management Plan
t tonne
TA Transport Assessment
TAS Thames Archaeological Survey
TBC To be confirmed
TBM Tunnel Boring Machine
TDP Thames Discovery Programme
TEBP Thames Estuary Benthic Programme
TEL Threshold Effect Levels
TfL Transport for London
TFRM Tideway Fish Risk Model
TH Tower HamletsTLRN Transport for London Road Network
Tpa tonnes per annum
TPO Tree Preservation Order
TT Thames Tunnel
TTQI Thames Tideway Quality Improvements
TTSS Thames Tideway Strategic Study 2005
TWU Thames Water Utilities
UDP Unitary Development Plan
UK United Kingdom
UKHO United Kingdom Hydrographic Office
UMB Upper Mottled Beds
UPN Upnor Formation
UWWTD Urban Waste Water Treatment Directive
UWWTR Urban Waste Water Treatment Regulations
UXO Unexploded OrdnanceVDV Vibration Dose Value
VNEB OA Vauxhall Nine Elms Battersea Opportunity Area
WCA Wildlife and Countryside Act
WEEE Waste Electrical and Electronic Equipment Directive
WFD Water Framework Directive
WIA Water Industry Act 1991
WRAP Waste Resources Action Programme
WSI Written Scheme of Investigation
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WWT Wildfowl and Wetlands Trust
ZTV Zone of Theoretical Visibility
ZVI Zone of Visual Influence
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Volume 3: Alternatives Section 1: Introduction
Page 1 Preliminary environmental informationreport
1 Introduction
1.1.1 This volume describes the main alternatives considered to the proposeddevelopment and presents an outline of the how strategic alternatives(tunnel and non-tunnel), alternative tunnel routes, alternative sites and
alternative functions at sites have been considered. Details are presentedon how environmental and other factors associated with the alternatives,and the consultation that has been undertaken on alternatives, hasinfluenced the site and design selections.
1.2 Statutory requirements
Infrastructure Planning EIA Regulations (2009)
1.2.1 Under the Infrastructure Planning (Environmental Impact Assessment)Regulations 2009, the Environmental Statement (ES) and prior to that thePreliminary Environmental Information Report (PEIR) must contain “an
outline of the main alternatives studied by the applicant and an indicationof the main reasons for the applicant’s choice, taking into account theenvironmental effects” (see regulation 2(1) and paragraph 18 of Part 1 ofSchedule 4).
1.2.2 In response to this requirement, this Volume of the PEIR provides anoutline of:
a. the strategic (ie tunnel and non tunnel) alternatives which have beenconsidered to address the problem of the Combined Sewer Overflow(CSO) discharges into the Thames Tideway and the main reasons forchoosing a full length storage and transfer tunnel solution; and
b. the alternatives which have been considered in order to identify thetunnel route, drive strategies and the location of preferred work sites,along with the main reasons for the choices made.
Draft National Planning Statement on Waste Water
1.2.3 The draft National Policy Statement on Waste Water (NPS) was publishedin April 2011. The draft NPS sets out the proposed policy framework toinform planning decisions on applications for large wastewaterinfrastructure projects.
1.2.4 The draft NPS considers alternative methods of meeting demand which
could obviate the need to invest in nationally significant wastewaterprojects. Key methods include reducing domestic and industrialwastewater production, for example by improving water efficiency; greateruse of sustainable drainage systems (SUDs); building sewers separatefrom surface water drains; and decentralising wastewater treatmentinfrastructure.
1.2.5 The draft NPS concludes that these measures will mitigate the need fornew infrastructure to some extent but that "the need for new wastewaterinfrastructure projects will remain in some circumstances." The documentnotes that such need will increase in response to climate change,
population growth or more stringent environmental standards.
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Volume 3: Alternatives Section 1: Introduction
Page 2 Preliminary environmental informationreport
1.2.6 The draft NPS states that the Thames Tunnel has since 2007 been the"preferred infrastructure solution" to address the problem of pollutioncaused by untreated sewage and rainwater discharges from London'scombined sewer overflows into the River Thames.
1.3 Content and structure1.3.1 This volume describes the alternatives to the proposed development, and
presents how strategic alternatives (tunnel and non-tunnel), alternativetunnel routes, alternative sites and alternative functions at sites have beenconsidered.
1.3.2 This volume does not consider detailed site-specific environmental designevolution; these are provided, where relevant, in the appropriate sitespecific assessment Volumes (7-28).
1.3.3 This volume outlines the alternatives considered in respect of:
a. alternatives to tunnel storage (of CSO discharges);b. alternative tunnel routes;
c. alternative drive strategies and main construction sites;
d. alternative CSO interception sites
1.3.4 This volume describes the main alternatives and main reasons forselecting the Thames Tunnel project as defined by the preferred schemeat phase two consultation sufficient for the requirements of theRegulations. The volume does not, however, seek to provide a fullchronological summary of the various studies and work undertaken. For a
full understanding of the background to the project development thefollowing references are relevant:
a. TTSS Steering Group Report February 20051
b. TTSS Solutions Group Working Report Volumes I and II, February2005
2
c. Thames Tideway Tunnel and Treatment, Solutions Working GroupReport (December 2006)
3
d. Thames Tideway Tunnel and Treatment Summary Report TacklingLondon’s Sewer Overflows, Executive Summary (2007)
4
e. Regulatory Impact Assessment – sewage collection and treatment forLondon (Defra, March 2007)
5
f. Lee Tunnel Environmental Statement (Alternatives chapter)
6
g. Needs Report and appendices (available as part of the phase twoconsultation materials).
1.3.5 Section 2 of this volume considers the strategic alternatives to a storageand transfer solution to the CSO discharges. Section 3 then considers thevarious tunnel route alternatives which have been considered. Section 4considers the alternative drive strategies and alternative main constructionsites which have been considered. Finally Section 5 considers thealternatives to each of the CSO sites which are included within thePreferred Scheme.
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Volume 3: Alternatives Section 2: Strategic alternatives
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2 Strategic alternatives
2.1 Non-tunnel alternatives
2.1.1 There are a number of possible alternative strategies for dealing with theCSO issue. As identified in the Thames Tideway Strategic Study(Steering Group Report February 2005, Section 0.5 and others), these canbe broadly divided into four main strategies based upon the location of thesolution. These are:
a. addressing the problem at the CSOs themselves (by capture and / orstorage and / or treatment)
b. addressing the problem at source before the sewerage system byexclusion or control of rainwater run-off into the sewerage system, eg,source control, detention ponds and other similar Sustainable UrbanDrainage Systems (SUDS) techniques
c. addressing the problem within the sewerage system itself byattenuation within the system or by the provision of new on- or off-linetanks and separation of the sewerage system
d. addressing the problem in the river using remedial measures eg, byincreasing dissolved oxygen with river craft and treatment withhydrogen peroxide.
2.1.2 The first strategy, addressing the problem at the CSOs has been identifiedas providing the only [feasible] solution to the CSO problem. It is the onlystrategy which (i) is capable of providing a complete solution and (ii) doesnot require an extensive retro-fit or replacement of existing systems, which
would be impractical to implement. It is therefore identified as thepreferred strategy.
2.1.3 The second strategy, addressing the problem at source, has beendiscounted because of a lack of available space in London, the disruptionthat would be caused for any meaningful retro-fit of SUDS and thedisproportionate cost even to provide a partial solution.
2.1.4 The third strategy, addressing the problem within the sewage system, hasbeen discounted as it requires very extensive landtake to support severalstorage tanks (and tunnels) which would be of much greater volume thanone large tunnel. Furthermore attenuation may lead to unacceptable
sewer flooding, on- or off-line storage does not meet the quality objectivescost effectively and separation is not considered technically oreconomically feasible.
2.1.5 The fourth strategy, addressing water quality in the river, has beendiscounted as these can only be short term reactive measures: once theCSO discharges are in the river the polluting effects and associatedenvironmental damage can only be partially ameliorated and the sewagederived litter problems cannot be adequately addressed. In short it fails toprovide a true solution as the pollution has already occurred.
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Volume 3: Alternatives Section 2: Strategic alternatives
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Options for dealing with the CSO discharges at the CSOs
2.1.6 As determined above, the strategy of dealing with the CSO problem at theCSOs was identified by Thames Water as the preferred wider strategy.Within this wider strategy, there are a number of sub-options and theseare reviewed below.
Storage and transfer tunnel
2.1.7 This option intercepts CSO flows along the Thames Tideway, stores themwithin a tunnel with transfer and pump out at a controlled rate for treatmentat a suitable location. This was identified as the only solution whichcombines capture of the unacceptable discharges with primary andsecondary treatment thus meeting water quality objectives and capacityrequirements in an appropriate way.
Transfer tunnel
2.1.8 This option would intercept CSO flows in a similar manner, capture themwithin a tunnel and would then carry them downstream to a high capacitypumping station and screening plant for untreated discharge to the lowerreaches of the Thames Tideway. This option was discounted as it doesnot provide primary or secondary treatment and so only moves theproblem further down the Thames Tideway. This option would also have ahigh capacity pumping requirement with high peaks of energyconsumption.
Multiple screened outlets
2.1.9 This option would use multiple, purpose built pumping and screening
stations connected via collection and distribution tunnels to intercept flowsfrom the CSOs with subsequent discharge to the Thames Tideway. Thisoption was discounted as it does not provide primary or secondarytreatment and would have a major impact at screening plant and pumpingstation locations with high land take requirements.
Multiple screened outlets with storage
2.1.10 This option is a hybrid of a storage tunnel and storage shafts (see below).It would incorporate a second tunnel to store the first flush of storm waterthat would be stored and pumped out for treatment at a sewage works. Itwas however discounted as it only provides primary / secondary treatment
for a proportion of the discharges. As for Multiple Screened Outletsabove, major impacts would occur at screening plant and pumping stationlocations with high land take requirements.
Storage shafts
2.1.11 This option would require large storage shafts constructed in the foreshorenext to the CSOs and incorporate a static screen whereby two thirds ofstorm water is screened and returned to the Thames Tideway and theremainder is pumped back into the sewerage system for treatment. Thisoption was discounted and it provides only primary / secondary treatmentfor a proportion of the discharges and would generate severe impacts to
large areas of foreshore at storage shaft locations. The option is alsodisproportionately expensive compared to other options.
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Screening at individual CSOs
2.1.12 This option would involve the installation of screening plant immediatelyadjacent to or upstream of the CSO discharge locations but wasdiscounted as it does not provide primary or secondary treatment andwould generate major impacts at screening plant locations.
Displacement
2.1.13 This option is based on a conduit normally left full and discharging to alarge wetlands area over an extended period. The option was discountedas no suitable site is available and there would be substantial potential forsepticity of sewage arising from the extended period of retention.
Identified solution
2.1.14 All of the above alternatives to the storage tunnel approach havesignificant or insurmountable engineering challenges and have beendiscounted as too expensive and / or disruptive to implement. As stated
above, the storage tunnel solution was identified by Thames Water as theonly solution to the CSO problem since it combines capture of theunacceptable discharges with primary and secondary treatment sufficientto achieve the quality objectives.
2.2 Storage tunnel options
2.2.1 In July 2006, the then Minister of State for Climate Change and theEnvironment wrote to Thames Water, requesting, inter alia, thedevelopment, assessment and costing of two principal storage tunneloptions for tackling the CSOs. These were:
a. a 32km tunnel to intercept all unsatisfactory CSOs (including AbbeyMills) along the length of the tidal Thames from Hammersmith toBeckton STW; and
b. two tunnels comprising a West tunnel (from Hammersmith toHeathwall with pump out to the existing sewer network) and aseparate East tunnel (connecting Abbey Mills to Beckton, eitherdirectly or via Charlton).
2.2.2 The second group of options, based on a two tunnel solution were derivedfrom an alternative solution (to a single tunnel from Hammersmith toBeckton), presented in a report prepared by Jacobs Babtie (Jacobs
Babtie February 2006) at the request of Ofwat. This alternative involvedtwo short tunnels (west and east tunnels), a new treatment facility nearHeathwall Pumping Station in central London, screening plant andenhanced primary treatment plant at Abbey Mills.
2.2.3 Thames Water brought together key stakeholders in a number of workinggroups to develop options, one of which was the Planning andEnvironment Working Group including the GLA, LTGDC, the Associationof Local Government, LBN and the EA. The purpose was to develop theplanning and environmental aspects of these options and assist in theirassessment. The two main tunnel options (and variants) were
subsequently defined using the following nomenclature:
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a. Option 1a – Full length storage tunnel, 7.2m diameter with Abbey Millslink joining at Greenwich;
b. Option 1b – Full length storage tunnel, 6m diameter, otherwise as 1a;
c. Option 1c – Full length storage tunnel, 7.2m diameter, tunnels with
direct Abbey Mills link;d. Option 2a – West tunnel, 7.6m diameter and East tunnel, 13m
diameter;
e. Option 2b – West tunnel, 7.6m diameter and East tunnel, 10mdiameter with supplementary additional treatment capacity; and
f. Option 2c – West tunnel, 7.6m diameter and East tunnel (viaCharlton), 10m diameter.
2.2.4 The results of the tunnel optioneering study were presented in a report toDefra in December 20067
Vol 3 Table2.2.1
. For each option, this report included technical
reviews, consideration of planning and environmental constraints (andbenefits), potential for early part delivery in respect of the Abbey Mills CSO(the Lee Tunnel) and a Cost Benefit Analysis. The options are reviewed inthe paragraphs that follow and this is then summarised in
.
Option 1a - Full tunnel, 7.2m diameter, Abbey Mills link via Charlton
2.2.5 This option would meet long term water quality objectives and dissolvedoxygen objectives and would have lower odour risks since better flushingwould be possible. The construction risks would be higher because ofuncertain geology in the Lower Lee Valley area. Risks would be lower for
a 7.2m tunnel compared to a larger tunnel (eg, 10m) tunnel. It would notsupport a standalone project for the Abbey Mills CSO since a non ThamesWater site would need to be acquired and in addition it would require thepart completion of the Thames Tunnel.
Option 1b - Full tunnel, 6m diameter, Abbey Mills link via Charlton
2.2.6 This option would meet long term water quality objectives, although itwould result in some more untreated releases of sewage than for a largerdiameter tunnel. Dissolved oxygen objectives would be met with thisoption and there would be lower odour risks since better flushing would bepossible. As for Option 1a described above, the construction risks would
be higher because of uncertain geology in the Lower Lee Valley area.Risks would be lower for a 6m tunnel compared to a larger tunnel such asconsidered under Option 1a. It would not support a standalone project forthe Abbey Mills CSO since a non Thames Water site would need to beacquired and it would also require the part completion of the ThamesTunnel.
Option 1c - Full tunnel, 7.2m diameter, direct Abbey Mills link
2.2.7 This option would meet both long term water quality objectives anddissolved oxygen objectives. Odour risks would be reduced due to betterflushing being possible. This option would also avoid the uncertain
geology in the Lower Lee Valley area and due to its smaller diameterconstruction risks would be lower. In addition, this option supported a
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standalone project for the Abbey Mills CSO as all surface sites would beowned by Thames Water and no additional land acquisition would benecessary. This stand alone project which captures the Abbey Mills CSObecame the Lee Tunnel and is currently under construction.
Option 2a - West tunnel, 7.6m diameter and East tunnel, 13m
diameter, direct Abbey Mills link
2.2.8 This option avoids the uncertain geology in the Lower Lee Valley areawhich lowers construction risks and there would be no additional landacquisition necessary as all surface sites required would be owned byThames Water, thereby supporting a standalone project for the AbbeyMills CSO. However, this option would not meet long term water qualityobjectives because 25% (by volume) of CSOs would not be captured.Dissolved oxygen objectives would only be met initially but not in the longterm by 2020. This option would also have higher odour risks as flushingwould be more difficult and due to its larger diameter tunnels construction
risks would be higher.
Option 2b - West tunnel, 7.6m diameter and East tunnel, 10mdiameter with supplementary additional treatment capacity, directAbbey Mills link
2.2.9 As Option 2a described above, this option avoids the uncertain geology inthe Lower Lee Valley area lowering construction risks. There would be noadditional land acquisition necessary for this option as all surface sitesrequired would be owned by Thames Water, thereby supporting astandalone project for the Abbey Mills CSO. However, this option wouldnot meet long term water quality objectives because 25% (by volume) of
CSOs would not be captured and dissolved oxygen objectives would onlybe met initially but not by 2020. This option would also have higher odourrisks as flushing would be more difficult. Although lower than for Option2a, construction risks would be higher for this option due to its largerdiameter tunnels.
Option 2c - West tunnel, 7.6m diameter and East tunnel, 10mdiameter, Abbey Mills link via Charlton
2.2.10 This option, as options 2a and 2b described above, avoids the uncertaingeology in the Lower Lee Valley area, thereby lowering construction risks.Long term water quality objectives would not be met by this option
because 25% (by volume) of CSOs would not be captured and dissolvedoxygen objectives would only be met initially but not by 2020. This optionwould also have higher odour risks as flushing would be more difficult andconstruction risks would be higher due to its larger diameter tunnels. Inaddition, there would be land acquisition issues with this option as not allland required would be owned by Thames Water. Therefore this optionwould not support a standalone project for the Abbey Mills CSO.
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Vol 3 Table 2.2.1 Summary assessment of options December 2006
Option Long-termWQobjectives?
DOObjectives?
OdourRisk?
ConstructionRisk?
supportsstand-aloneproject forAbbey Mills
CSO?
1a yes yes lower -betterflushing
higher - lowerLee Valleygeology
lower - smalltunneldiameter
no - landacquisitionissues
& requires partcompletion ofThames Tunnel
1b yes - butmoreuntreated
releases
yes lower -betterflushing
higher - lowerLee Valleygeology
lower - smalltunneldiameter
no - landacquisitionissues
& requires partcompletion ofThames Tunnel
1c yes yes lower -betterflushing
lower - avoidslower LeeValley
lower - smalltunneldiameter
yes - all surfacesites owned byTW
2a no - 25%(byvolume) ofCSOs notcaptured
(yes) - initiallybut not by2020
higher -difficult toflush
lower - avoidslower LeeValley
higher - largertunneldiameter
yes - all surfacesites owned byTW
2b no - 25%(byvolume) ofCSOs notcaptured
(yes) - initiallybut not by2020
higher -difficult toflush
lower - avoidslower LeeValley
higher - largertunneldiameter
yes - all surfacesites owned byTW
2c no - 25%(byvolume) ofCSOs notcaptured
(yes) - initiallybut not by2020
higher -difficult toflush
higher - lowerLee Valleygeology
higher - largertunneldiameter
no - acquisitionissues
Conclusion
2.2.11 As summarised in the table above and in the preceeding paragraphs, theDecember 2006 study by Thames Water concluded that Option 1c(highlighted), although marginally the most expensive, would deliver themaximum benefits and be the best value, with construction risks that areconsidered manageable, and enabled an early phased solution (through
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the direct Abbey Mills – Beckton link). Each variant of the two tunnelsolution (and so the Jacobs Babtie alternative) was rejected on the basisof the above reasons and notably the failure to meet long-term waterquality objectives.
2.2.12 Option 1c was based on two schemes comprising a 7.2m diameterStorage Tunnel linking CSOs from Hammersmith to Beckton (the 'ThamesTunnel') and a 7.2m diameter Storage Tunnel linking Abbey Mills -Beckton (the ‘Lee Tunnel’). The Lee Tunnel is currently (2011) underconstruction.
2.3 Ministerial approval
2.3.1 The March 2007, Defra published a Regulatory Impact Assessment (RIA)in connection with collection and treatment of sewage in London. TheRIA, concluded in paragraph 11.7, by saying:
“Having considered the recent report by TW, and a range of issues
including legal obligations, compliance risks, timetables, cost benefitanalysis, affordability and feasibility, it is recommended that a phased,single tunnel approach, which addresses all the unsatisfactoryoverflows, is the minimum required to meet our obligations. It istherefore proposed that TW are asked to proceed urgently with thedevelopment and implementation of a scheme which reduces andlimits pollution from storm water overflows (starting with Abbey Millspumping station) of the Beckton and Crossness sewer system in themost cost effective way. Such an approach, which may be based onoption 1c, offers the quickest prospect of making a significant impacton the volume of the discharges, and it would convey a sense ofurgency and commitment to take measures to comply as soon aspossible.”
2.3.2 In his letter of 17 April 2007, the then Minister, Ian Pearson, endorsed theOption 1 type approach in order to make progress toward compliance withthe Urban Waste Water Treatment Directive (UWWTD) (and associatedduties under the Water Industry Act and the Urban Waste WaterTreatment (England and Wales) Regulations 1994) as quickly as possibleand requested that Thames Water makes provision for the design,construction and maintenance of a scheme for the collecting systemsconnected to Beckton and Crossness sewage treatment works.
2.3.3 Thames Water actioned the Minister’s request to make provision for thedesign, construction and maintenance of a scheme involving a full lengthstorage tunnel. It has planned the strategy for implementation and aappointed a London Tideway Tunnels Delivery Team (LTTDT) to deliverthe Lee Tunnel and the provision for the Thames Tunnel – the LondonTideway Tunnels. The Lee Tunnel is currently (2011) under constructionwith target completion in 2015.
2.4 Validation of Option 1c
2.4.1 With the LTTDT in place working on the design for the Thames Tunnel,
Thames Water undertook a parallel series of studies during the first sixmonths of 2009 to reassess a number of strategic alternatives to ensure
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that the most cost-effective solution was being progressed to address therequirements of the UWWTD. Two main groups of alternatives wereconsidered in three studies:
a. Separation of Foul and Storm Water collection networks and
b. Retrofitting Source control and SUDS2.4.2 Other approaches such as hybrid solutions / partial separation, real time
control, screening and dispersed storage were also re-examined to see ifthese approaches (which could be at least partial alternatives) couldcontribute to the cost effectiveness of the project. The following tables(Tables 5.9 and 5.10 from the Needs Report) summarize the results of thestudies in relation to separation and SUDs and compare these twoalternatives against the Thames Tunnel.
Vol 3 Table 2.4.1 Advantages and disadvantages of options
Option Advantages DisadvantagesFull-length storage tunnel(Abbey Mills route)
Complies with UWWTDand environmentalobjectives
Cheapest option
Least disruption tobusinesses and residents
Is capable of beingdelivered by target date of2020
Use of river for materialstransportation wherepracticable and economic
Least amount of landneeded
Adaptable and flexible
More spills (4) andgreater volumedischarged in typical yearthan other tunnel options
High operating costs
High carbon footprint
Full-length storage tunnel(Rotherhithe route)
Complies with UWWTDand environmentalobjectives
Is capable of being
delivered by target date of2020
High operating costs
High carbon footprint
Full-length storage tunnel(River Thames route)
Complies with UWWTDand environmentalobjectives
Least spills (2) of tunneloptions
Is capable of beingdelivered by target date of2020
High operating costs
High carbon footprint
Separation using newstorm water sewers or
Sewer flooding reliefcan be incorporated
Cannot comply withUWWTD or
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Option Advantages Disadvantages
new foul sewers (withstorm water in existingcombined network)
environmental objectives
Very disruptive tobusiness, residents and
transportationNot possible tocomplete by 2020, withover 35 yearimplementation period
Very expensive
High whole lifeoperating costs, affectedby need for estimated 48or more new pumpingstations
High carbon footprint
Sustainable drainagesystems (SUDS)
Desirable andmandatory for new builddevelopments, but difficultto retrofit
Enhances theenvironment
Can manage surfacewater flooding
Low whole life operatingcosts
Low carbon footprint
Cannot comply withUWWTD orenvironmental objectives
Very disruptive tobusiness, residents andtransportation
Not possible tocomplete by 2020, withover 30 year
implementation periodVery expensive
Complex logisticalprocesses for planningpermission
Legal and regulatoryobstacles toimplementation
2.4.1 Combining the advantages and disadvantages with the cost estimatesproduced for each alternative approach is set out in the table below.
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Vol 3 Table 2.4.2 Summary of main options and estimated costs
OptionResponse toneed
Estimatedcosts1
(£ millions)Comments
Full-lengthstorage tunnel(Abbey Millsroute)
Complies withUWWTD andenvironmentalobjectives
3,588(accuracyrange +/-10% to +/-
25%)
Most cost effective scheme.Spills at CSOs limited to 4events in a typical year.
Least disruption to residents,businesses andtransportation.
Is capable of being deliveredby target date of 2020.
Full-lengthstorage tunnel(Rotherhitheroute)
Complies withUWWTD andenvironmentalobjectives
4,310(accuracyrange +/-10% to +/-
25%)
Spills at CSOs limited to 2events in a typical year.
Is capable of being deliveredby target date of 2020.
Full-lengthstorage tunnel(River Thamesroute)
Complies withUWWTD andenvironmentalobjectives
4,336(accuracyrange +/-10% to +/-
25%)
Spills at CSOs limited to 2events in a typical year.
Is capable of being deliveredby target date of 2020.
Separation
using newstorm watersewers or newfoul sewers(with stormwater inexistingcombinednetwork)
New sewerage
designed for 1 in30 storms.
Will alleviatesewer flooding.
Would eventuallycomply withUWWT andenvironmentalobjectives
14,000
(variance+50% to -30%)
Cost significantly greater
than tunnel option.Significant disruption toresidents, businesses andtransportation.
Prolonged timescale forcompletion; eg, 30 years at£400m spend per annum, sonot capable of complyingwith UWWTD andenvironmental objectives by2020.
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OptionResponse toneed
Estimatedcosts1
(£ millions)Comments
Sustainable
drainagesystems(SUDS)
In certain
catchments a37% reduction inimpermeablearea potentiallycontributing toCSO dischargescould beachieved.
13,000
(variance+50% to -30%)
High cost and time to
implement.Reduction in impermeablearea still results in more thanten* CSO spills in a typicalyear.
Not able to achievecompliance withrequirements of UWWTD.
Not applicable to inner citycatchments and manypractical limitations toimplementation.
1 Cost base date of December 2008.* Maximum spill frequency allowed by other EU Member States regarding their
interpretation of the requirements of the UWWTD.
2.4.2 On the basis of the above comparisons, both SUDS and Separation wereagain discounted as viable alternatives (as they had previously beenwithin the TTSS). The tunnel route options are discussed in detail inSection 3.
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3 Tunnel routes
3.1 Introduction
3.1.1 During 2009-2010, a range of routes were considered for the route of themain storage and transfer tunnel (the Thames Tunnel). Three routes wereput forward at the phase one consultation stage.
3.1.2 In broad terms the route must start in west London and follow the route ofthe River Thames eastwards, intercepting those CSOs identified forinterception and ensuring flows can be transferred to Beckton STW fortreatment. The precise route is influenced by the locations of the shaftsrequired to construct the tunnel and intercept the CSOs.
3.2 Thames Tunnel alignments
3.2.1 Three tunnel routes were compared against each other using a range ofcriteria from the five disciplines of engineering, planning, environment,
community and property, using professional judgement to balance theissues and compare the effects of the tunnel routes, and their associatedconstruction sites. In so doing, consideration of the overall impact of eachof the tunnel routes drew upon the site selection work outlined in Section 4of this volume.
3.2.2 The three alternative alignments for the Thames Tunnel considered indetail and consulted on are shown on Vol 3 Figure 3.2.1.
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V o l u m e 3 : A l t e r n a t i v e s
S e c t i o n 3 : T u n n e l r o u t e s
P a g e
1 5
P r e l i m
i n a r y e n v i r o n m e n t a l i n f o r m a t i o n r e p o r t
V o l 3 F i g u r e 3 . 2 . 1
A l t e r n a
t i v e a l i g n m e n t s o f T h a m e s T u n n e l
A b b e y M i l l s r o u t e
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River Thames route
3.2.3 The River Thames route, which largely follows the river from west Londondownstream crossing the Greenwich Peninsula, underground, and on toBeckton STW. The tunnel system would intercept CSO discharges from
the Acton Storm Relief Sewer at the upstream end by connection tunnel tothe main tunnel at Hammersmith Pumping Station.
3.2.4 This route option follows the River Thames from west London to theGreenwich Peninsula, where it takes a shortcut below land. It thencontinues beneath the River Thames all the way to Beckton SewageTreatment Works (STW) in the east. This is the longest tunnel option.
3.2.5 It would capture the most untreated sewage from the CSOs along theriver, but would also be the most expensive. This is the route that wasidentified in the December 2006 report to Government (note that “theAbbey Mills route” (see further below) was not available at that time
because a shallower Lee Tunnel alignment was then proposed whichwould have precluded connection with the deeper Thames Tunnel.
Rotherhithe route
3.2.6 The Rotherhithe route, which cuts across both the Greenwich and theRotherhithe Peninsulas. The tunnel system would intercept CSOdischarges from the Acton Storm Relief Sewer at the upstream end byconnection tunnel to the main tunnel at Hammersmith, and would connectto the overflow shaft at Beckton STW at the downstream end, exactly asfor the tidal River Thames route.
3.2.7 This route option follows the River Thames from west London as far as theRotherhithe Peninsula, where it then passes below the land, beforecontinuing along the River Thames, under the Greenwich Peninsula andthen on to Beckton STW.
3.2.8 This option would not capture as much of the overflowing sewage as theRiver Thames route as it is slightly shorter but it still improves the waterquality of the River Thames.
Abbey Mills route
3.2.9 The Abbey Mills route differs from the other routes by connecting theThames Tunnel to the head of the Lee Tunnel at Abbey Mills. Theopportunity to connect the Thames Tunnel to the head of the Lee Tunnelarose as that tunnel was slightly deeper than originally proposed becauseof a need to avoid difficult geological features along the route.
3.2.10 The upstream tunnel system would be the same as the River Thames orRotherhithe tunnel alignments from the interception of Acton Storm ReliefSewer as far as Rotherhithe, but would then veer northeast to Abbey Mills.CSOs to be intercepted downstream of Rotherhithe would connect back tothe main tunnel by connection tunnels except for Charlton Storm ReliefCSO which would be addressed by local modifications and an alternativemeans of control.
3.2.11 This option is up to 9km shorter than the two other alignments andtherefore would need fewer construction sites and hence would involve
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less construction work and fewer construction related environmentalimpacts. It would use less carbon and would be considerably cheaper.
3.2.12 It would capture slightly less sewage, however, the overall river waterquality would still be significantly improved and meet the project objectivesset by the Environment Agency.
Summary
3.2.13 Key aspects of the three tunnel alignment options which were presented inthe Phase One consultation are summarised in the table below. Additionaldetails on all three routes are also presented in Section 2 (Vol 3 Table2.4.1 and Vol 3 Table 2.4.2).
Vol 3 Table 3.2.1 Key aspects of the three tunnel alignmentalternatives
Category River Thames
route
Rotherhithe
route
Abbey Mills
routeMain tunnel length (km)(7.2km diameter)
31.3 29.6 22.3
Number of main shafts(diameters)
10(20m to 25m)
8(20m to 25m)
5(20m to 25m)
Connection tunnellengths (km) (diameters)
8.6*(2.2 to 4.5m)
8.6*(2.2m to 4.5m)
8.8*(2.2m to 4.5m)
Total storage volume(million m3 (includes Lee
Tunnel)
1,855 1,781 1,505
Number of CSOs directlyconnected
22 22 21
Number of CSOsotherwise connected orlocally addressed
12 12 13
Maximum number of spillevents in a typical yearper CSO (from theCategory 1 and 2 CSOsin the Beckton andCrossness catchments)
2 2 4
* These lengths all exclude some of the smaller connection tunnel lengths that wereincluded within the summation of connection tunnel lengths.
3.2.14 All three Thames Tunnel alignment options meet all four of the EA waterquality standards.
a. All options deliver low residual CSO spills during the typical year. Forthe accepted typical year, the number of CSO spills at controlledlocations is no more than four at the largest CSO locations and
generally less than three at most locations.
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b. The three options (with STW capacity improvements, the Lee Tunneland 2021 conditions) capture between 97% and 98% of the estimatedCSO discharge volumes in a typical year rainfall.
c. None of the options demonstrate any benefit over the others regardingwater quality, significant CSO event or volume captured.
3.3 Reasons for selection of the Abbey Mills route
3.3.1 The majority of the main tunnel alignment is common for the RiverThames, Rotherhithe and Abbey Mills routes; the project from Acton toKing’s Stairs Gardens being identical for all three routes. Tunnelalignments vary west of King’s Stairs Gardens, but some of the preferredsites (at CSO interception locations) are common. Therefore, of the 24sites required for the River Thames and Rotherhithe routes and the 22sites required for the Abbey Mills route, 20 are common to all three routes.
3.3.2 An assessment was made in 2010 by the engineering, planning,
environment, community and property disciplines, who considered theoverall construction project, nature of the affected sites and theirsurroundings, and other strategic and cumulative issues. The results ofthe assessments are summarized below
Engineering
3.3.3 The Abbey Mills route is 9km and 6.7km less than the River Thames andRotherhithe routes respectively and the cost of the project isapproximately £700m less. Despite having a reduced internal volume, thehydraulic performance of the Abbey Mills route is still considered
compliant with the requirements of the UWWTD.3.3.4 From an overall health and safety hazard perspective, the reduction in
scope for the Abbey Mills route reduces the likelihood of constructionrelated risks. In addition, the River Thames and Rotherhithe routes drivethrough water-bearing chalk with much higher ground water pressureswhich would increase wear on the TBM and the risks to personnel carryingout TBM maintenance. Other greater tunnelling risks associated with theRiver Thames and Rotherhithe routes include driving through a muchgreater length of flint bearing chalk, a greater number of fault zones andthe construction of more deep shafts and CSO connections. However, theAbbey Mills route follows an alignment at the top of the chalk, close to the
underside of the Thanet Sands along the Limehouse Cut, which couldmake TBM face interventions hazardous and complex.
3.3.5 The substantial reduction in construction scope associated with a shortertunnel length and fewer main construction sites, coupled with tunnellingthrough less hazardous ground results in the Abbey Mills route being asafer construction choice. The reduced scope was also considered toreduce overall procurement risk by placing less stress on the procurementchain. Finally, these reasons, together with lower costs for a solutionconsidered acceptable in relation to the requirements of the UWWTD wereall engineering reasons to conclude that the Abbey Mills route is preferred.
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Planning
3.3.6 The strategic comparison of the three alternative tunnel route optionsfocussed on a number of recurring cumulative planning considerations.These comprise the nature of the affected land (greenfield, previouslydeveloped and foreshore), the impact upon safeguarded wharves and theRiver Thames, and the prospects for enacting current planningpermissions and emerging proposals.
3.3.7 These considerations affect all three routes, but the Abbey Mills routeincorporates comparatively fewer greenfield and previously developedsites than either the River Thames or Rotherhithe routes. As a result, theoverall number of sites which would affect public open space,employment, regeneration and safeguarded wharf designations, is fewer,as well as the number of sites that would require mitigation againstpotential policy conflicts.
3.3.8 The level of impacts upon sites with extant permission or forthcomingproposals is also reduced in respect of the Abbey Mills route.
3.3.9 It is noted that the Abbey Mills route does increase the relative number offoreshore sites however, although it reduces the effects upon the use ofKing Edward Memorial Park.
3.3.10 The loss and replacement of public open space, particularly within areasof deficiency, and the potential for conflict with regeneration proposals, arein any case significant issues that require further investigation and ongoingmonitoring.
3.3.11 The potential for a reduced cumulative impact upon these planning
considerations is the main reason for the planning discipline to selectAbbey Mills as the preferred main tunnel route.
Environment
3.3.12 As noted above, the Abbey Mills Route is 9km and 6.7km less than theRiver Thames and Rotherhithe routes respectively. This means that theAbbey Mills Route would generate less excavated material, require lessmaterial for its construction and need less energy in its construction. TheAbbey Mills main tunnel route will therefore have a lower ‘carbon footprint’than the two other routes.
3.3.13 The Abbey Mills main tunnel route would be dependent on fewer shaftsites than either the River Thames route or Rotherhithe route, and shouldtherefore generate the least site related cumulative environmental effects.
3.3.14 A preliminary assessment of cumulative effects of the shaft sites acrossthe three routes suggested that was the case. The shaft sites required forthe Abbey Mills Route would require fewer jetty structures to be built in theriver and so minimize foreshore ecology impacts. The shaft sites requiredfor the Abbey Mills Route are also likely to impact fewer built heritagereceptors. The lower number of shaft sites required for the Abbey Millsroute would lead to less disturbance of contaminated ground and result in
adverse air quality impacts at fewer sites than the other two routes.
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3.3.15 The Abbey Mills Route was therefore identified as the preferred maintunnel route from an environmental perspective.
Community
3.3.16 From a community impacts perspective, all three of the route options have
the potential to impact on a number of sensitive receptors.
3.3.17 Although it is not possible to estimate the exact numbers of people orhouseholds affected at this stage, cumulatively the Abbey Mills routewould impact on fewer residential neighbourhoods due to the shortertunnel length and the route alignment.
3.3.18 None of the route options appear likely to result in significant impacts onproperties providing health or educational services. All three routes havethe potential to impact on the church and chapel located adjacent to theKing Stairs Garden’s site, while the River Thames and Rotherhithe routescould also impact on community worship events taking place in a
warehouse opposite the proposed Charlton site.
3.3.19 Community cohesion and the health and wellbeing of local people may beimpacted by the use of a number of sites required to construct all threeroutes. A maximum of seven of the common, River Thames andRotherhithe sites affect open space or parkland. No route option reducesthis number. The cumulative impact is likely to be relatively small sincethe open space sites are not geographically close and serve communitiesat different sides of the river.
3.3.20 Of particular importance was the amount of public open space likely to betemporarily lost at Barn Elms and King’s Stairs Gardens. For the River
Thames and Rotherhithe routes, there would also be a temporary loss ofpublic space at King Edward Memorial Park. Pepys Park (adjacent theConvoys Wharf site on the River Thames and Rotherhithe routes) andFrank Banfield Park (opposite Hammersmith Pumping Station site) arealso likely to face some disruption due to their vicinity to significantconstruction works.
3.3.21 All three route options require the use of sites which may impact on thelocal economy through the displacement of active businesses. Onbalance, the Abbey Mills route appears preferable as this route does notrequire the Charlton site, and therefore involves the relocation of fewer
businesses overall.3.3.22 Overall, from a community impacts perspective, there are advantages and
disadvantages to all three route alignments. King’s Stairs Gardens is aparticularly critical site as its use is vital to all three route options and theconstruction works proposed are likely to have a number of significantimpacts on the local community. No route avoids significant likelycommunity impacts, but the cumulative socio-economic impacts are likelyto be slightly fewer with the Abbey Mills route. The Abbey Mills maintunnel route would be dependent on fewer shaft sites than either the RiverThames route or Rotherhithe route, and should therefore generate less
site related cumulative community impact.
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Property
3.3.23 All three route options would give rise to property issues, and the preferredsites fall within the following categories: development sites, local authorityowned parks, occupied industrial estates, Thames Water property andforeshore sites.
3.3.24 In terms of main shaft sites, the River Thames route and Rotherhithe routewould require three development sites, two local authority owned parks,part of an industrial estate and an existing Thames Water operational site.
3.3.25 For the Abbey Mills route considerations are the same as for the RiverThames route, except that the number of main sites was reduced to five,with one development site and the industrial estate at Charlton beingremoved from consideration. Beckton STW is also replaced by AbbeyMills PS.
3.3.26 In cumulative terms the property issues associated with the Abbey Mills
route were therefore less, although a number of issues remain to beaddressed for all three routes, particularly in terms of potentially highacquisition costs of development sites, establishing the ability to securethe rights required to public parks, and the need to provide compensationfor relocated businesses.
3.3.27 The Abbey Mills Route was therefore identified as the preferred maintunnel route from a property perspective.
The preferred scheme
3.3.28 In conclusion, the recommendation to the Government, in 2010, for the UK
to be able to meet the requirements of the Urban Waste Water TreatmentDirective (beyond the construction of the Lee Tunnel and the sewagetreatment works upgrades underway at Mogden, Crossness and BecktonSTWs) was a preferred scheme for the Thames Tunnel based on:
a. the Abbey Mills Route
b. a main tunnel, 23km long with an internal diameter of 7.2m
c. the direct interception of 21 CSOs
d. the indirect interception of a further 12, and a local solution for theremaining CSO
e. the selection of five out of 52 shaft sites from the Final Short List,including three where main shaft sites are combined with CSOinterception sites
f. the selection of seventeen out of 71 CSO sites from the Final ShortList.
Site related issues
3.3.29 The overall number of sites associated with the Abbey Mills route whichwould affect employment, regeneration, property, sites with currentplanning applications or extant permission and safeguarded wharf
designations would be fewer, as well as the number of sites that wouldrequire mitigation against potential policy conflicts.
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3.3.30 In particular, the omission of several sites from the Abbey Mills routereduces the compensation costs and also reduces the impact of theproject on the community.
3.3.31 The shaft sites required for the Abbey Mills route also impact the fewestsites with medium-high archaeological potential and the fewest sites withvalued townscape character and/or River Thames frontage than the othertwo routes. The lower number of shaft sites required for the Abbey Millsroute would lead to the least disturbance of contaminated ground andlower cumulative noise impacts than the other two routes.
3.3.32 The Abbey Mills route would require fewest in-river jetty structures to bebuilt, although all three route options impact the foreshore in some way at14 sites (interception chambers, temporary access, shafts or temporary jetties). The Abbey Mills route has a greater number of foreshore shaftsites, which is likely to increase the permanent mitigation requirements forthis route in relation to environmental and ecological issues.
3.3.33 The loss and potential replacement of public open space is an issuecommon to all routes, particularly within areas of deficiency. The potentialfor conflict with regeneration proposals require further investigation andongoing monitoring, but the Abbey Mills route requires fewer large-scaleshaft sites that are earmarked for regeneration.
Overall construction scope and scheme purpose
3.3.34 The Abbey Mills main tunnel route is 9km and 6.7km shorter than theRiver Thames and Rotherhithe routes respectively, and the project isestimated to cost approximately 18% (£750m) less to build and cost £126k
less to run per year than the River Thames route. Despite having areduced internal volume, the hydraulic performance of the Abbey Millsroute is still considered compliant with the requirements of the UWWTD.
3.3.35 The Abbey Mills route has a substantially shorter main tunnel, with fewestmain construction sites, and would generate least excavated materials,require least energy to build, least energy to run, and would therefore havethe lowest carbon footprint.
3.3.36 From an overall health and safety perspective, the reduction in scope forthe Abbey Mills route reduces the likelihood of construction related risks.The River Thames and Rotherhithe routes drive through a greater length
of faulted flint-bearing Chalk with much higher ground water pressures,which would increase wear on the TBM and the hazards to personnelcarrying out TBM maintenance. These issues also increase overallprogramme risk for the longer tunnel options.
3.3.37 However, the Abbey Mills route follows an alignment at the top of theChalk, close to the underside of the Thanet Sands along the LimehouseCut, which could make TBM face interventions more hazardous andcomplex. The Abbey Mills route also passes underneath more privatelandowners and bridges along the Limehouse Cut, which increases thenumber of third-party stakeholders. However, the depth to the top of the
tunnel along this length is greater than 50m and it would therefore have avery limited potential for impact on surface structures.
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Conclusion
3.3.38 All three tunnel routes have merits and demerits, but it has beenconcluded that the Abbey Mills route has several considerable advantagesand was selected as the preferred route for Phase 1 Consultation. Thesubstantial reduction in construction scope associated with the shortesttunnel length and fewest main construction sites, coupled with tunnellingthrough less difficult ground, results in the Abbey Mills route being thesafest and least cost construction choice. In cumulative terms, it has been judged to have the least environmental impact, slightly fewer communityimpacts, fewest property issues and lower planning risks.
3.3.39 The Phase 1 work (including the consultation) supported the conclusionthat the Abbey Mills route was the most appropriate route. Based on thisthe Abbey Mills route was therefore retained as the preferred route forphase two consultation and is the basis of the project described in Volume2 of the PEIR and assessed in the technical volumes.
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4 Main tunnel construction sites and drive strategy
4.1 Introduction
4.1.1 The site selection process (see below) searched for the following types of
sites that would be needed to construct and operate the project:a. CSO sites (with and without a connection tunnel)
b. main tunnel drive sites
c. main tunnel reception sites
d. main tunnel intermediate sites
4.1.2 The main tunnel would be constructed using tunnel boring machines(TBMs). A series of main tunnel sites would be required to allow theTBMs to start from shafts known as drive shafts, and to be taken out atshafts known as reception shafts. Further details of these site types (with
example layouts) are presented in Volume 2 of the PEIR. It should benoted that further work concluded there was no requirement for specificintermediate sites (possible sites for online interception of the TBM).
4.1.3 A range of sites along the preferred tunnel route were considered. Thissection focuses on those sites which are needed to construct the maintunnel and the major connection tunnels (b – c above) as well as therelated drive strategy.
4.1.4 CSO sites must be located close to the existing CSOs, which vary in sizeand location. Each CSO site must accommodate the permanentstructures required for the operation of the system (the interception of the
CSOs) and, on a temporary basis, the construction equipment required tocreate the CSO interception. The consideration of alternative CSO sites isoutlined in Section 5. In some cases it is possible to establish a maintunnel construction site at a CSO site and reduce the overall number ofdeep shafts required by the project.
4.2 Site selection
4.2.1 The site selection methodology was finalised in May 2009, and drawsupon best practice and reflects the principles and requirements of relevantplanning policy and sustainability principles. A multi-disciplinary approach
was used, drawing upon the technical knowledge and expertise ofengineering, planning, environmental, property and community specialists.
4.2.2 In summary the site selection methodology comprises three main stages,which are set out below. At each stage planning, environmental,engineering, community and property considerations were taken intoaccount.
Stage 1
4.2.3 This stage involved the identification of all sites that are potentially suitableto fulfil the engineering functions required. This stage utilised a filteringprocess, carried out in three main parts:
a. 1A – The creation of a long list of potential sites
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b. 1B – The creation of a short list of potential sites
c. 1C – The creation of a preferred list of sites.
Stage 2
4.2.4 This stage was the phase one public consultation on the preferred schemeconsisting of:
a. a series of preferred CSO sites and shaft sites
b. a preferred route; alongside
c. other previously considered sites and routes.
4.2.5 The Statement of Community Consultation (SoCC) and the CommunityConsultation Strategy (CCS) also provide further supporting information onhow consultation is carried out.
4.2.6 This stage was undertaken between 13 September 2010 and 11 January
2011 and provided an opportunity to hear the views of communities livingin the vicinity of any preferred or shortlisted sites, statutory consultees andany other interested parties across all three main tunnel routes (seeSection 3).
Stage 3
4.2.7 This stage comprises the final selection of sites, and includes revisions tothe Preferred List of Sites following consultation if necessary, along withthe production of a Final Site Selection Report (SSR).
4.2.8 During the site selection process if any of the shaft or CSO sites areeliminated for any reason then a targeted repeat of Stages 1-3 areundertaken as appropriate in order to fill in any site gaps.
4.2.9 A targeted repeat would be caused by, for example: there being significantchanges of circumstances in relation to existing sites or combinations ofsites; new or replacement sites being required or found; or the engineeringdesign developing in unexpected ways.
4.3 Drive strategy
4.3.1 To manage the total number of combinations of tunnel drive and receptionsite options, which together make up a ‘drive option’, the availableshortlisted sites were grouped together in zones. The zones were based
on the geographical locations of the sites along the line of the RiverThames as shown below. The zones were numbered and named forconvenient referencing as shown in the figure. All the shortlisted shaftsites fall within one of the zones.
4.3.2 Nine zones were identified along the length of the preferred Abbey Millsroute. A series of potential drive options were identified using the mostsuitable site (as identified through implementation of the site selectionmethodology) within each zone. All drive options required a main tunnelsite in zone S0 (Acton), zone S5 (Battersea) and zone S11 (Abbey Mills)because. No suitable main tunnel sites were available within zone S1
(Hammersmith) or zone S4 (Lots Road). Note that Zones 8, 9 and 10 notrelevant to the Abbey Mills tunnel route and are not shown on the diagram.
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4.3.3 The phase one preferred scheme (Abbey Mills route) and the twoalternative routes (River Thames and Rotherhithe) at phase one each hadproposed drive strategies associated with them. Since the Abbey Millsroute has been selected, the drive strategies for the other two routes arenot viable alternatives in relation to the Abbey Mills route and are not
covered by this assessment.
4.3.4 The phase two preferred scheme for Abbey Mills differs in important waysfrom the phase one preferred scheme including the sites and the drivestrategy. The following review does not revisit the full drive strategy forthe phase one preferred scheme since it is not a viable alternative to thephase two scheme. Further details can be found in the phase two schemedevelopment report (available as part of phase two consultation).
4.3.5 The figure below presents the main tunnel shaft zones used in consideringalternatives for the drive strategy.
Vol 3 Figure 4.3.1 Main tunnel shaft zones
S0 – Acton
S1 – Hammersmith
S2 – Barn Elms
S3 – Wandsworth Bridge
S4 – Lots Road
S5 – Battersea
S6 – Shad
S7 – Limehouse
S11 – Abbey Mills
4.3.6 This meant that a series of comparisons could be made, based aroundusing a main tunnel site either in zone S2 (Battersea) or zone S3(Wandsworth) and a main tunnel site either in zone S6 (Shad) or zone S7(Limehouse) (in each case there was no requirement for a site in bothzones as they are too close together) and deciding whether each of therequired main tunnel sites should be a drive site or reception site.
4.3.7 In order to assess the suitability of the identified main tunnel drive options,having regard to the comparative advantages and disadvantages of themost appropriate site identified for each zone, a series of comparisonswere used to make choices between drive options. Further details andmore extensive background to the various drive options is provided in the
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Phase Two Scheme Development Report (available as part of phase twoconsultation).
4.3.8 With each comparison made, it was possible to eliminate a number ofdrive options until the list was finally reduced to one: the preferred tunnel
drive option. The comparisons that had to be made to arrive at a preferredoption included:
a. Comparison 1: Comparing the use of Chambers Wharf (Zone S6,Shad) with the use of King Edward Memorial Park (Zone S7,Limehouse) for a main tunnel site.
b. Comparison 2: Comparing the use of Barn Elms (Zone S2, BarnElms) with the use of Carnwath Road Riverside (Zone S3,Wandsworth) for a main tunnel drive site.
c. Comparison 3: Comparing the use of Abbey Mills Pumping Station(Zone S11, Abbey Mills) as main tunnel drive site or main tunnel
reception site (and associated implications for a connection tunnel atChambers Wharf, Zone S6, Shad).
4.3.9 Each of these comparisons – and the conclusions reached at the preferredscheme workshops by engineering, planning, environment, communityand property disciplines – are discussed in turn below. It should be notedthat, in many instances, the advantages and disadvantages of optionswere finely balanced, and that a collective view was taken by disciplinerepresentatives in order to identify the preferred options.
Comparison 1: Comparing the use of Chambers Wharf with the useof King Edward Memorial Park for a main tunnel site (drive or
reception)
4.3.10 This choice compares options that include a main tunnel site in Zone S6with those that rely on a main tunnel site in Zone S7. There are no optionsthat require a main tunnel site in both zones. By making this sitecomparison, the nine drive options that include a main tunnel site in ZoneS6 were compared with the nine drive options that include a main tunnelsite in Zone S7. Note that prior to this comparison, Chambers Wharf hasalready been identified as a preferred site in Zone S6, Shad.
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Vol 3 Figure 4.3.2 Main tunnel shaft zones for Comparison 1
S6 – Shad
S7 – Limehouse
S11 – Abbey Mills
Main tunnel site
Main tunnel alignment
KEY:
4.3.11 Considerations in favour of using Chambers Wharf (Zone S6) and nothaving a main tunnel site at King Edward Memorial Park (Zone S7)included the following:
a. Engineering: It is important to select the least risk and mostpredictable tunnel boring machine for the expected geologicalconditions. The increased length of the tunnel drive between Zone S5(Battersea) and King Edward Memorial Park would increase the risksassociated with tunnelling due to the longer tunnel drive and thechange in ground conditions just east of Tower Bridge. A tunnel drivebetween Zone S5 and Chambers Wharf would be shorter and presentless risk.
b. Planning: Chambers Wharf is a brownfield site and subject to fewerpolicy restrictions than King Edward Memorial Park, which is adesignated public open space in an area with an identified deficiencyof open space. The park is also within a conservation area.
c. Environment: Chambers Wharf is a brownfield site, already identifiedfor development and, on balance, its use is preferable to King EdwardMemorial Park as the overall environmental impacts are likely to beless. Mitigation measures would, however, be required for ChambersWharf.
d. Community: The temporary loss of a large part of King EdwardMemorial Park and the impact that this would have on park usersmeant a preference for the brownfield site Chambers Wharf, althoughit is acknowledged that both sites are within proximity of residentialproperties.
e. Property: The use of King Edward Memorial Park would introduceacquisition risks due to the possible need for a special parliamentary
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procedure. There is no acquisition risk for Chambers Wharf as it isowned by Thames Water (having been acquired by Thames Water toensure the opportunity to consider this site can be taken).
4.3.12 Conversely, considerations in favour of using King Edward Memorial Park
(Zone S7) and not having a main tunnel site at Chambers Wharf (ZoneS6) included:
a. Engineering: King Edward Memorial Park is large enough to containthe full temporary construction area required without the extensiononto the foreshore that would be needed at Chambers Wharf. A maintunnel site at King Edward Memorial Park could be combined with thesite required for interception of the CSO at this location, and wouldavoid the need for an additional site.
b. Planning: No specific advantages of using King Edward MemorialPark were identified, as compared to Chambers Wharf.
c. Environment: Using King Edward Memorial Park reduces the needfor extending the temporary construction area onto the foreshore atChambers Wharf.
d. Community: No specific advantages of using King Edward MemorialPark were identified, as compared to Chambers Wharf.
e. Property: Acquisition costs are likely to be lower than the value of theChambers Wharf site (although Chambers Wharf is owned by ThamesWater, if it is not needed as a Thames Tunnel worksite, it could besold for a sum that is likely to be not less than its acquisition cost,thereby avoiding a significant loss to the project). Discretionary
purchase costs are likely at both locations.
4.3.13 Based on the above considerations, on balance, the preference is to useChambers Wharf as a main tunnel drive site, eliminating options that useKing Edward Memorial Park for this purpose. As a result of thiscomparison, the options that used a main tunnel drive site in Zone S7(King Edward Memorial Park) were eliminated.
Comparison 2: Comparing the use of Barn Elms with the use ofCarnwath Road Riverside for a main tunnel drive site
4.3.14 This choice compares options that include a main tunnel drive site in Zone
S2 with those that rely on a main tunnel drive site in Zone S3. There areno options that require a main tunnel drive site in both zones. This sitecomparison allows a comparison of the remaining drive options, six ofwhich include a main tunnel site in Zone S2 and three of which include amain tunnel site in Zone S3.
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Vol 3 Figure 4.3.3 Main tunnel shaft zones for Comparison 2
S0 – Acton
S1 – Hammersmith
S2 – Barn Elms
S3 – Wandsworth Bridge
S4 – Lots Road
S5 – Battersea
Main tunnel alignment
KEY:
Main tunnel site
4.3.15 Considerations in favour of using Carnwath Road Riverside (Zone S3) andnot having a main tunnel drive site at Barn Elms (Zone S2) included thefollowing:
a. Engineering: Carnwath Road Riverside includes a safeguardedwharf and has much better river access for transportation ofconstruction materials, using significantly larger barges than can reachBarn Elms. The need for new jetty and wharf facilities would be
reduced compared to Barn Elms. Health and safety issues associatedwith using the river and, in particular, the dangers of interfacing withpleasure boat users are reduced at Carnwath Road Riverside, as areinterfaces with people using the Thames Path.
b. Planning: Carnwath Road Riverside is a brownfield site which ispartly vacant, while Barn Elms is a greenfield site. Use of CarnwathRoad Riverside is supported in policy terms by its brownfield andsafeguarded wharf status, although the area of Carnwath RoadRiverside and beyond is currently proposed for regeneration within thedraft South Fulham Riverside Supplementary Planning Document .
Barn Elms is subject to policy constraints, including Metropolitan OpenLand, public open space, proximity to a Site of Special ScientificInterest and Sites of Nature Conservation Importance. The ThamesPath at Carnwath Road Riverside is already diverted around part ofthe proposed site, and further diversion is considered more acceptablethan at Barn Elms on the basis that it is less well used and, at BarnElms, a diversion island around the worksite would be too long and notconsidered as feasible.
c. Environment: In overall terms, the use of a brownfield site will havefewer environmental impacts than use of a greenfield site at Barn
Elms. In particular, use of Barn Elms may impact on nearby ecologicalsites, including the London Wetland Centre Site of Special Scientific
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Interest and River Thames and Beverley Brook Sites of NatureConservation Importance. However, mitigation measures would stillbe required at Carnwath Road Riverside.
d. Community: Use of Carnwath Road Riverside avoids potential
impact on users of Barn Elms sports fields and the loss of two to threesports pitches, and possible relocation of the scout hut and boathouse.It also reduces the potential impact on recreational river users, asthere are fewer using the Thames in the vicinity of Carnwath RoadRiverside than the popular waters around Barn Elms. There are alsolikely to be less users of the Thames Path in this area.
e. Property: Acquisition of Carnwath Road Riverside would not requireuse of a special parliamentary procedure, whereas use of open spaceat Barn Elms, which is owned and operated by a local authority, maybe subject to this procedure. Discretionary purchase costs are to beexpected at either site.
4.3.16 Conversely, considerations in favour of using Barn Elms (Zone S2) andnot having a main tunnel drive site at Carnwath Road Riverside (Zone S3)included the following:
a. Engineering: Barn Elms is a large open area with potential forconstruction operations to take sufficient space. No major buildingdemolition would be required and the site could be combined with theWest Putney CSO interception site, thereby avoiding the need toacquire an extra site.
b. Planning: Carnwath Road Riverside would require relocation of
existing retail/warehouse businesses. Consolidation of land uses atBarn Elms from combining the main tunnel and CSO site would bepossible.
c. Environment: No specific advantages of using Barn Elms wereidentified, as compared to Carnwath Road Riverside.
d. Community: There are potentially less residential properties in thenearby area and thus less impact on community in the immediatevicinity (however, impact of construction works may be more difficult tomitigate on this more tranquil site).
e. Property: Lower acquisition costs are expected at Barn Elms
compared to Carnwath Road Riverside.
4.3.17 Based on the above considerations, on balance, the preference is to useCarnwath Road Riverside as a main tunnel drive site, eliminating optionsthat use Barn Elms for this purpose. As a result of this comparison, the sixoptions that use a main tunnel site in Zone S2 (Barn Elms) wereeliminated.
Comparison 3: Comparing the use of Abbey Mills Pumping Stationand Chambers Wharf as main tunnel drive site or main tunnelreception site
4.3.18 The final comparisons between the three remaining drive options involvedmaking choices between the use of Abbey Mills Pumping Station or
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Chambers Wharf as a main tunnel drive site or reception site (withassociated implications for the connection tunnel to Greenwich PumpingStation). The three options included:
a. Option A: Abbey Mills would be used as a drive site to drive the tunnel
to Chambers Wharf. Chambers Wharf would be used a reception siteto receive the tunnel boring machine from Abbey Mills and to receivethe tunnel boring machine from the drive site in Zone S5. ChambersWharf would also be used to either drive or receive the connectiontunnel to/from Greenwich Pumping Station.
b. Option B: Abbey Mills would be used as a drive site to drive the tunnelto Chambers Wharf. Chambers Wharf would be used to receive thetunnel boring machine from Abbey Mills. Chambers Wharf would alsobe used as a drive site to drive the main tunnel to Zone S5 and toreceive the connection tunnel from Greenwich Pumping Station. It isnot possible to drive the connection tunnel from Chambers Wharf
since the site is not big enough to support concurrent drive operationsand because there is insufficient time to build one tunnel and then theother.
c. Option C: Abbey Mills Pumping Station would be used as a receptionsite to receive the tunnel boring machine from Chambers Wharf.Chambers Wharf would be used as a drive site to drive the tunnel toAbbey Mills. Chambers Wharf would also be used to receive thetunnel boring machine from Zone S5 and to receive the connectiontunnel from Greenwich Pumping Station. It is not be possible to drivethe connection tunnel from Chambers Wharf since the site is not big
enough to support concurrent drive operations and because there isinsufficient time to build one tunnel and then the other.
4.3.19 The three options are illustrated and discussed below.
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Option A (A1 and A2)
Vol 3 Figure 4.3.4 Main tunnel sites Comparison 3, Option A1
Main tunnel drive site
Connection tunnel drive site
Reception site
Main tunnel alignment
Connection tunnel alignment
KEY:
S6 – Shad
S7 – Limehouse
S11 – Abbey Mills
Greenwich
Pumping Station
A1
Vol 3 Figure 4.3.5 Main tunnel sites Comparison 3, Option A2
Main tunnel drive site
Connection tunnel drive site
Reception site
Main tunnel alignment
Connection tunnel alignment
KEY:
S6 – Shad
S7 – Limehouse
S11 – Abbey Mills
Greenwich
Pumping Station
A2
4.3.20 Considerations in favour of Option A included the following:
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a. Engineering: Driving from Abbey Mills avoids the need for temporaryriver reclamation and demolition of the existing jetty at ChambersWharf (it would be possible to drive the connection tunnel toGreenwich on a smaller site without demolishing the jetty).
b. Planning: There would be less impact on residential amenity atChambers Wharf and this option would avoid temporary additionalencroachment into the river (a strategic policy area) at ChambersWharf. However, there would potential be a significant increase in theamount of material required to be transported from Abbey Mills byroad (assuming transport by barge is limited), with a consequentincrease in impact on residential amenity.
c. Environment: Abbey Mills Pumping Station is, on balance, slightlypreferred as a drive site to Chambers Wharf if material could betransported by barge. However, if this is not possible, it becomesmore preferable to drive from Chambers Wharf, where the river could
be used to remove excavated materials, thus resulting in less roadvehicles having to travel past sensitive residential receptors nearAbbey Mills.
d. Community: This option has greater impact on residents at AbbeyMills. It also reduces the impact on those at Chambers Wharf as,although the site could still be used to drive the smaller connectiontunnel, it would not be required for one of the main tunnel drives.
e. Property: Use of Abbey Mills as a drive site would reduce significantpotential for discretionary purchase costs at Chambers Wharf (likely tobe significantly higher than Abbey Mills drive site discretionary
purchase costs). This option avoids partial construction in theforeshore and associated acquisition risks.
4.3.21 Drive options for the Greenwich connection tunnel are evaluated in thefollowing section.
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Option B
Vol 3 Figure 4.3.6 Main tunnel sites Comparison 3, Option B
S6 – Shad
S7 – Limehouse
S11 – Abbey Mills
Greenwich
Pumping Station
Main tunnel drive site
Connection tunnel drive site
Main tunnel alignment
Connection tunnel alignment
KEY:
4.3.22 Considerations in favour of Option B included the following:
a. Engineering: This option would result in reduced construction risksassociated with the concentrated tunnelling operations required at thedouble drive site in Zone S5. It avoids the need for temporaryreclamation of the river at Chambers Wharf. However, ChambersWharf could not be used as both a main tunnel drive site and for aconnection tunnel drive to Greenwich Pumping Station.
b. Planning: No specific advantages were identified, given that anincreased level of activity at Chambers Wharf is likely to have greaterimpact on residential amenity and would require additionalencroachment into the river, which is a strategic policy area.
c. Environment: No specific advantages were identified, althoughAbbey Mills Pumping Station is, on balance, slightly preferred as adrive site to Chambers Wharf if material could be transported bybarge.
d. Community: No specific advantages are associated with this option.
e. Property: No specific advantages are associated with this option.
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Option C
Vol 3 Figure 4.3.7 Main tunnel sites Comparison 3, Option C
Main tunnel drive site
Connection tunnel drive site
Reception site
Main tunnel alignment
Connection tunnel alignment
KEY:
S6 – Shad
Greenwich
Pumping Station
S7 – Limehouse
S11 – Abbey Mills
4.3.23 Considerations in favour of Option C included the following:
a. Engineering: There would be significantly better river access forremoval of excavated materials at Chambers Wharf than Abbey Mills.Further technical work and discussions with the Lee Tunnel projectteam and Olympic Delivery Authority on their experience for theOlympic Park has shown that transporting material to and from theAbbey Mills site by the River Lee is highly undesirable when materialneeds to be transported daily over a two- to three-year period. Thislevel of barge movements would be required if Abbey Mills PumpingStation was used as a main tunnel drive site, given the volume ofexcavated material that would be produced.
b. Planning: This option offers a potential reduction in the amount ofmaterial required to be transported from Abbey Mills by road(assuming transport by barge is not viable), with a consequentreduction in impact on amenity.
c. Environment: This option would avoid the need for works in theChannelsea River or potential impact on the road network at AbbeyMills in the event that barges could not be used from Abbey Mills, andrelated environmental impacts.
d. Community: The use of larger barges from Chambers Wharf (whichwould not be possible at Abbey Mills) would reduce impacts on localcommunities from traffic movements associated with a drive site.
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e. Property: The potential for discretionary purchase costs at AbbeyMills will be minimised if it is used as a reception site.
4.3.24 Based on the above considerations, on balance, it was concluded that‘Option C’, ie, driving the main tunnel from Chambers Wharf to Abbey Mills
(and using Chambers Wharf to receive tunnel boring machines from ZoneS5), should be selected. One of the main factors that influenced thisdecision was that further technical work and discussions with the LeeTunnel project team and Olympic Delivery Authority on their experiencewith the Olympic Park has shown that transporting substantial materialvolumes to and from the site by the River Lee is not desirable. Therefore,the use of Chambers Wharf as a main tunnel drive site, with the ability totransport material by barge, was considered more acceptable than the useof Abbey Mills as a drive site with possible reliance on road transport toremove material.
Conclusion
4.3.25 Based on the above comparisons and conclusions reached by alldisciplines at the preferred scheme workshops, the preferred drive optionfor connecting the main tunnel sites was identified as follows:
a. Main drive from Carnworth Road Riverside to Acton Storm Tanks.
b. Main drive from Kirtling Street to Carnworth Road Riverside
c. Main drive from Kirtling Street to Chamber Wharf
d. Main drive from Chambers Wharf to Abbey Mills
e. Long connection tunnel drive from Greenwich PS to Chambers Wharf
4.3.26 Whilst the above comparisons describe the main steps taken to identifythe preferred drive strategy, it is also necessary to consider the main drivesites and the alternatives to them. The main alternatives are representedby the other short-listed sites in each area.
4.3.27 Carnworth Road Riverside was chosen as a main drive site in the westbecause the site is brownfield, the presence of wharfs and width ofThames would allow use of barges to remove material during constructionand the site has good access to major road network. Other short-listedsites considered in this area were Barn Elms, Feathers Wharf and FulhamDepot.
4.3.28 Kirtling Street was chosen as a main double drive site in the central part ofthe route because the site is brownfield in a mainly industrial area, hasdirect river access with potential to allow use of barges to remove materialduring construction and has good access from Nine Elms Lane (A3025).In addition it would cause less disruption to residents than some othershort-listed sites and would not affect early stages of Battersea PowerStation Redevelopment. Other short-listed sites considered wereBattersea Park, Battersea Power Station, Part of Battersea Power Station,Heathwall Pumping Station and Midddle Wharf, Post Office site on NineElms Lane, a site on Post Office Way, Depots on Ponton Road, an Open
Space off Grosvenor Road and the Foreshore at Riverside House nearVauxhall Bridge
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4.3.29 Chambers Wharf was chosen as a main drive site in the eastern part ofthe route because the site is brownfield, has direct river access withpotential allow use of barges to remove material during construction andthere would be no need to divert Thames Path. King Stairs Gardens wasthe only other short-listed site in this area.
4.3.30 The above drive strategy is that presented at phase two consultation andassessed within the PEIR (as defined in Volume 2).
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5 CSO sites
5.1 Introduction
5.1.1 This section provides an overview of the interception requirements at each
CSO and the identification of the preferred CSO site. At each CSO wherean interception is required, a series of alternatives have been consideredin order to identify the preferred site.
5.1.2 Much of the text is drawn from the Phase two scheme development report(available as part of the phase two consultation materials) and focuses onthe identified site and other short-listed sites in the vicinity. Other siteswhich did not progress beyond the long list in each location are notreviewed since they do not generally represent viable alternatives. Wherereference is made to a preferred site at Phase 1, this refers to the site asdefined within the EIA Scoping Report (March 2011).
5.1.3 In summary, each site will be required for construction purposes forapproximately one to four years, and will be between 1,500m2 and7,500m2 in size.
5.1.4 Each site was considered on its own merits and the fact that a site isidentified as a preferred site does not necessarily mean that it is free fromconstraints, rather that it is considered the most suitable, or leastconstrained, site in a required location compared to the alternativesconsidered.
5.2 Acton Storm Relief
5.2.1 Three sites were shortlisted for interception of this CSO, although one(Chiswick Maternity Hospital) was later discounted as development on sitemeant it was no longer available.
5.2.2 At phase one Acton Storm Tanks was the preferred site for CSOinterception and it remains the preferred site at phase two. In summary,this site was selected as it is an existing Thames Water site and wouldhave fewer impacts on residential amenity than the other potential site(Welstead Way car park).
5.2.3 At phase two it is also proposed that the main tunnel is extended to ActonStorm Tanks. This site will therefore intercept the Acton storm relief CSO
and be a main tunnel reception site. The site was chosen as a maintunnel reception site at phase two because the Hammersmith PS site wasunavailable as a main tunnel site (because of ongoing development) and a6m main tunnel is required between Carnwath Road Riverside and Acton.
5.2.4 The position of the main shaft has been moved to the northern part of thesite to minimise any potential impact on residents of Warple Way.
5.2.5 Full details of this site (including the requirement to use this site as a maintunnel site as well as for CSO interception) are provided in Volume 7.
5.3 Hammersmith Pumping Station
5.3.1 At phase one Hammersmith Pumping Station was a preferred main tunnelreception site, and was also the preferred site for CSO interception. At
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phase two this is no longer a main tunnel reception site Schemedevelopment work and the submission of a new planning application forthe land adjacent to the pumping station since phase one (and indicationsthat this development will commence shortly) have eliminated thepossibility of this site being used as a main tunnel reception site (the site is
to be developed and is no longer available for this use). It is however stillnecessary to intercept the CSO in this location. Several alternativelocations were assessed as short-listed sites for this interception includingFrank Banfield Park and the foreshore adjacent to Chancellor’s Wharf.
5.3.2 A smaller site adjacent to the pumping station is however the preferredsite for CSO interception for phase two as this can be utilised inconjunction with the development of the surrounding site. The site canalso be located in close proximity to the existing pumping station. Thedrop shaft is located further away from existing residential dwellings thanthe other shortlisted sites, which means that construction effects can be
more effectively managed. The site is also brownfield land and has goodaccess.
5.3.3 Full details of this site are provided in Volume 8.
5.4 West Putney Storm Relief
5.4.1 At phase one, Barn Elms, was a preferred main tunnel reception site, andwas also the preferred site for CSO interception.
5.4.2 As a result of scheme development work, Carnwath Road Riverside isnow preferred to Barn Elms for use as a main tunnel drive site. This siteremains, however, the preferred site for CSO interception for phase two.
This is because it avoided the need to relocate an existing business andcommunity facilities, avoided the ecological impact of working in theforeshore and had less impact on the local community than othershortlisted sites.
5.4.3 The four sites shortlisted for interception of the West Putney Storm ReliefCSO were the preferred site, the adjacent foreshore, the boat repair yardoff Putney Embankment and Leader’s Gardens. At phase one the southeast corner of Barn Elms Sports Fields was the preferred site for CSOinterception (and was sited alongside the main tunnel site at Barn Elms).In summary this site was chosen for CSO interception as it would allowcombination of works with main shaft site, safe, efficient working, had goodaccess and would require fewer enabling works than other options.
5.4.4 Full details of this site are provided in Volume 9.
5.5 Putney Bridge Storm Relief
5.5.1 The existing sewerage system is configured so that two large branches join together beneath the main road junction at the southern end of PutneyBridge, just upstream of the CSO discharge point. Both branches of thesewerage network need to be intercepted. Consequently the only viablelocation to intercept all flows for the Putney Bridge SR would bedownstream of the discharge point in the foreshore. Therefore, allshortlisted sites are located in the foreshore.
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5.5.2 Four CSO sites were shortlisted for interception of this CSO, all four ofwhich were located in the foreshore, two to the west and two to the east ofPutney Bridge.
5.5.3 At phase one the preferred site was identified to the west of PutneyBridge. This site was identified as it was considered that, when comparedto alternatives, use of this site would minimise adverse construction effectsupon the multiple sensitive receptors located on the eastern side of thebridge.
5.5.4 At phase two the preferred site remains the same although the sitelocation has however moved slightly to the west to minimise impactsfurther.
5.5.5 Full details of f this site are provided in Volume 10.
5.6 Frogmore Storm Relief – Bell Lane Creek
5.6.1 Two sites were originally shortlisted for interception of this CSO, namely asmall business site on Bell Lane Creek and the nearby London Borough ofWandsworth Maintenance Depot. At phase one the former was selectedas the preferred site for CSO interception as it was anticipated that fewerpeople would be affected than if the depot site was selected. .
5.6.2 Following phase one, new information was received on availability of analternative site, known as Dormay Street, to the north of the preferred site,which had not previously been considered. This alternative site – a vacantsite – is the phase two preferred site as it would avoid the loss of anexisting business and has fewer other constraints than the alternatives,including the small business site on Bell Lane Creek.
5.6.3 Full details of this site are provided in Volume 11.
5.7 Frogmore Storm Relief – Buckhold Road
5.7.1 Two sites were shortlisted for interception of this CSO namely KingGeorge’s Park and the car park off Broomhill Road. At phase one KingGeorge’s Park was the preferred site and it remains the preferred site atphase two. In summary this site is preferred as it would allow efficientworking and would result in fewer impacts on residential amenity than thealternative car park site.
5.7.2 Full details of this site are provided in Volume 12.5.8 Jews Row: Wandle Valley Storm Relief and Falconbrook
Storm Relief
5.8.1 At phase one the concrete batching plant, west of Wansworth Bridge wasidentified as the preferred site with two other alternative short-listed sitesconsidered, namely the foreshore at the end of Jews Row and an area ofOpen Space off Old York Road, Swandon Way.
5.8.2 However, further scheme development work undertaken since phase oneconsultation has concluded that it is no longer necessary to identify a site
for interception of these two CSOs. This is because modifications thathave been recently made within the sewer system sufficiently reduce the
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number of spills to the river without the need to carry out any further works(see Volume 2, Other Works for further details)
5.9 Falconbrook Pumping Station
5.9.1 Four sites were originally shortlisted for interception of this CSO. At phase
one the preferred site was Bridges Court Car Park.
5.9.2 Scheme development work took into account consultation feedbackreceived at phase one consultation and further engineering design workthat had been undertaken. As a consequence a new site at FalconbrookPumping Station has been identified as the preferred site for phase twoconsultation. In summary this site is considered most suitable as it is aThames Water owned site and has less impact upon residential amenitythan alternative sites namely Bridges Court Car Park, the Foreshore nearLondon Heliport and two different sites within York Gardens
5.9.3 Full details of this site are provided in Volume 14.
5.10 Lots Road Pumping Station
5.10.1 Only one site was originally shortlisted for interception of this CSO. Atphase one the Cremorne Wharf Foreshore, was the preferred site.
5.10.2 Scheme development work took into account new information on theavailability of the Cremorne Wharf Depot site, phase one consultationfeedback and further engineering design work that had been undertaken.As a consequence a new site at the adjacent Cremorne Wharf Depot hasbeen identified as the preferred site for phase two consultation. Insummary this site is considered more suitable than the foreshore site as it
is on brownfield land, will not result in disruption to the foreshore habitatsand has less impact upon residential amenity compared to thealternatives.
5.10.3 Full details of this site are provided in Volume 15.
5.11 Ranelagh
5.11.1 Only one site was originally shortlisted for interception of this CSO and theLow Level Sewer No 1.
5.11.2 At phase one the preferred site was therefore Chelsea EmbankmentForeshore (west of Chelsea Bridge. At phase two the preferred site
remains Chelsea Embankment foreshore although the site’s location withinthe foreshore has been moved slightly to a new site Chelsea EmbankmentForeshore (opposite Bull Ring Gate). Although the decision was finelybalanced this site has been chosen because it is considered to give rise tofewer effects overall notably reduced impacts on Ranelagh Gardens.
5.11.3 Full details of this site are provided in Volume 16.
5.12 Heathwall Pumping Station and South West Storm Relief
5.12.1 At phase one Heathwall Pumping Station and land at the adjacentTideway Walk Industrial site were identified as a preferred main tunnel
drive site in this location, and it was also the preferred site for CSOinterception. The alternatives considered were Battersea Park, Battersea
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Power Station, the four different areas of industrial land, three of whichwere to the west of Kirtling Street and one south of Nine Elms Lane.
5.12.2 At phase two Tideway Walk/Heathwall Pumping Station is no longerproposed as a main tunnel drive site, but it is still necessary to interceptthe CSO in this location. The Thames Tideway Walk site is currently beingdeveloped for housing and will therefore not be available as a drive site.
5.12.3 Three sites were originally shortlisted for the CSO interception alone, onefor Heathwall Pumping Station outfall and two for the South West StormRelief. The sites adjoined, or were part of the earlier Tideway Walk site.
5.12.4 Following scheme development work a main tunnel site has beenidentified for phase two at a site at Kirtling Street, which is located to thewest of the Thames Tideway Walk site. Therefore the main tunnel siteand Heathwall Pumping Station CSO site can no longer be combined.
5.12.5 Scheme development work reconsidered the most appropriate site for
CSO interception and for phase two the CSO interception site will be atHeathwall Pumping Station rather than the adjacent foreshore because itis owned by Thames Water and avoids the foreshore impacts.
5.12.6 Full details of the site are provided in Volume 18.
5.13 Clapham Storm Relief and Brixton Storm Relief
5.13.1 In total four sites were shortlisted for consideration for this interception,including the preferred site, two other foreshore sites (one south ofVauxhall Bridge and one adjacent to St George’s Wharf) and an areas ofOpen Space at Claylands Road. At phase one the preferred site for
interception of both CSOs was a site on the Albert EmbankmentForeshore. This remains the phase two preferred site. In summary thissite is preferred as, compared to the alternatives, it would have leastimpact on residential amenity, allows access and minimises impact on theflow of the river.
5.13.2 Full details of the site are provided in Volume 19.
5.14 Regent Street
5.14.1 A site is needed to intercept the Regent Street CSO and connect to thenorthern Low Level Sewer No.1.
5.14.2 Two sites were shortlisted for this CSO, namely the preferred site and analternative short-listed site in Victoria Embankment Gardens. At phaseone Victoria Embankment Foreshore was the preferred site and it remainsthe preferred site at phase two. In summary this site is preferred as it isconsidered less likely to give rise to conflict with planning policy,particularly that relating to heritage and open space designationscompared to the alternative. It also reduces the risk of working alongsidethe District and Circle line underground tunnels.
5.14.3 Full details of the site are provided in Volume 20.
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5.15 Fleet Main
5.15.1 A site is needed to intercept the Fleet Main CSO and northern Low LevelSewer No.1
5.15.2 Only one site was shortlisted for the Fleet CSO and northern Low Level
Sewer No.1. This site at Blackfriars Bridge Foreshore, was the phase onepreferred site and remains the preferred site at phase two. Whilst the sitewill require careful mitigation it is the only potentially suitable site in thishighly constrained location.
5.15.3 Full details of the site are provided in Volume 21.
5.16 Shad Thames Pumping Station
5.16.1 At phase one a site at Druid Street was identified as the preferred site forinterception of this CSO. However, scheme development workundertaken since phase one consultation has identified that, by carrying
out modifications and upgrades within the Shad Thames Pumping Station,an interception to the storm relief sewer is not needed. As aconsequence, there is no requirement for a site at Druid Street.
5.16.2 The works at Shad Thames Pumping Station include modifications to thepumps and internal pipework, demolition of the existing superintendent’sbuilding behind the existing pumping station, construction of a new, slightlylarger annex to replace the superintendent’s building and house newelectrical equipment, and some modifications to the existing sewersoutside the pumping station. There is no CSO drop shaft construction atthe site and no connection to the tunnel. Further details are provided inVolume 2.
5.17 North East Storm Relief
5.17.1 Two sites were originally shortlisted for interception of this CSO, namelyand area within King Edward Memorial Park the park itself and an area onthe foreshore. At phase one the preferred site was the foreshore and amodified version of this site (which includes a small area of the park)remains the preferred site at phase two. In summary, it is considered that,compared to the alternative, this site will have least impact upon the localcommunity and local businesses with concurrent work at two sites in closeproximity putting more construction traffic onto the local roads.
Consideration was also given to tunnel alignment under buildings anddisruption to businesses in reaching this conclusion.
5.17.2 In addition to the above “single site” approach to interception, as a resultof consultation, several alternatives were explored which involved ashallow interception in the Park itself linked to a deeper shaft at anothersite via a short connection tunnel. The deeper shaft at the other site wouldthen link to the main tunnel. Three alternative sites were reviewed for thisoff-site deep shaft, namely Heckford Street Industrial Area, Shadwell Basinand LImehouse Basin. The Heckford Street alternative proved technicallybetter than the other two. In a direct comparison, the foreshore site wasretained as the preferred site since it gives the opportunity for the use ofbarges, only requires one construction site (rather than two), requires less
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infrastructure and reduces the extent of tunnelling under buildingsrequired by the project.
5.17.3 Full details of the site are provided in Volume 23.
5.18 Holloway Storm Relief
5.18.1 At phase one Butcher Row was identified as the preferred site forinterception of this CSO with two alternative short-listed sites considered,namely the foreshore off Narrow Street (near the junction with SpertStreet) and St James’s Gardens, off Butcher Row and Tubbel Approach.However, scheme development work undertaken since phase oneconsultation has identified that, by carrying out modifications to theexisting sewer, there is no need to intercept the storm relief sewer andconnect it to the tunnel. As a consequence there is no requirement for asite at Butcher Row, but instead there are works that need to be carriedout on the existing sewer in Bekesbourne Street.
5.18.2 The works in Bekesbourne Street include construction of a chamberaround the existing sewer, and installation of a new penstock and flapvalve. There is no connection of these works to the tunnel. Further detailsare provided in Volume 2.
5.19 Earl Pumping Station
5.19.1 Six sites were shortlisted for interception of this CSO being. the preferredsite, the foreshore adjacent to the boatyard and Helsinki Square, the CarPark at Helsinki Square, the Boat Yard at Calypso Way, the Car Park atthe corner of Grove Street and Plough Way. At phase one the preferred
site was Earl Pumping Station itself and adjoining industrial premises(between Yeoman Street and Croft Street). This remains the preferredsite for phase two. In summary these sites were selected primarily tomake use of a Thames Water site and allow all new CSO assets to bewithin an extended Thames Water operational site.
5.19.2 Full details of the site are provided in Volume 24.
5.20 Deptford Storm Relief
5.20.1 Three sites were originally shortlisted for this CSO being namely thePhase 1 preferred site at Borthwick Wharf Foreshore, the AHOY Centre atthe junction of Borthwick Street and an area of open space at DeptfordGreen.
5.20.2 Since phase one scheme development work has been undertaken toaddress matters raised at phase one consultation and engineeringconcerns regarding CSO interception and construction access. As aconsequence of this work at phase two the preferred site is a triangulararea of land at Deptford Church Street. In summary, this site is preferredas it is more accessible than Borthwick Wharf Foreshore, it is not so closeto dense residential development and it does not encroach in to the RiverThames.
5.20.3 Full details of the site are provided in Volume 25.
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5.21 Greenwich Pumping Station
5.21.1 Two sites were shortlisted for interception of this CSO namely the Phase 1preferred site at Greenwich Pumping Station and the foreshore near theGreenwich Foot Tunnel. Greenwich Pumping Station remains ourpreferred site at phase two, however an amended version of the site interms of size and layout has been identified. This site incorporates landat Phoenix Wharf to the north in order to allow the site to be used for aCSO connection tunnel drive site as well as a CSO interception. Insummary it was judged the most suitable site as it allows use of anexisting Thames Water site, with consequent operational efficiencies and acontrolled environment.
5.21.2 Full details of the site are provided in Volume 26.
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Glossary
Term Description
A-weighted sound A-weighted decibels, abbreviated dBA, or dBa, or dB(a), arean expression of the relative loudness of sounds in air asperceived by the human ear.
Above OrdinanceDatum
Ground elevation is measured relative to the mean sea levelat Newlyn in Cornwall, referred to as Ordnance Datum (OD),such that heights are reported in metres above or below OD.
abstraction Removal of water from a source of supply (surface orgroundwater).
Air QualityManagement Area
Areas where the local authority determines the national airquality objectives are not likely to be achieved by therelevant deadlines.
air quality sensitivereceptors
People, property or designated sites for nature conservationthat may be at risk from exposure to air pollutants that couldpotentially arise as a result of the proposeddevelopment/project.
alluvium Sediment laid down by a river. Can range from sands andgravels deposited by fast flowing water and clays that settleout of suspension during overbank flooding. Other depositsfound on a valley floor are usually included in the termalluvium (eg, peat).
Annual MeanConcentration The average (mean) of the hourly pollutant concentrationsmeasured or predicted for a one year period.
anthropogenic Originating as a result of human activities.
aquiclude A hydrogeological unit which, that allows groundwatermovement at negligible rates, even though porous andcapable of storing water. Groundwater movement insufficientto allow appreciable supply to a borehole or spring.Aquicludes tend to act as an impermeable barrier.
aquifer A permeable geological stratum or formation that is capableof both storing and transmitting water in significant amounts.
Archaeological PriorityArea/Zone
Areas of archaeological priority, significance, potential orother title, often designated by the local authority.
backgroundconcentration
The contribution to the total measured or predictedconcentration of a pollutant that does not originate directlyfrom local sources of emissions.
Basal Sands The Upnor Beds (the lower unit of the Lambeth Group) andthe Thanet Sands.
base case The base case for the assessment is a future case, withoutthe project, in a particular assessment year.
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Term Description
baseflow The component of river flow derived from groundwatersources rather than surface run-off.
baseline The existing conditions against which the likely significant
effects due to a proposed development are assessed.
benthic invertebrates Invertebrates which are found within or on the river bed.
Bentonite An absorbent aluminium phyllosilicate, in general, impureclay consisting mostly of montmorillonite. Mixed with water,it forms a slurry commonly used as drilling fluid and groundsupport in tunnelling.
borehole A hole drilled into the ground for geological investigation orfor the exploitation of geological deposits or groundwater. Anabstraction borehole is a well sunk into an aquifer from which
water will be pumped.brickearth Wind-blown dust deposited under extremely cold, dry post -
glacial conditions suitable for making bricks.
British Standard Produced by the BSI Group in order to set up standards ofquality for goods and services.
Bronze Age 2,000–600 BC.
Building recording Recording of historic buildings (by a competentarchaeological organisation) is undertaken ‘to documentbuildings, or parts of buildings, which may be lost as a result
of demolition, alteration or neglect’, amongst other reasons.Four levels of recording are defined by Royal Commission onthe Historical Monuments of England (RCHME) and EnglishHeritage. Level 1 (basic visual record); Level 2 (descriptiverecord), Level 3 (analytical record), and Level 4(comprehensive analytical record).
bunding Also called a bund wall, bunding is a separated area within astructure designed to prevent inundation or breaches ofvarious types.
campshed An area of stone, concrete or timber laid on the river / sea
bed, that is exposed at low tide, allowing vessels to restsafely and securely in place.
catchment The area from which surface water and/or groundwater willcollect and contribute to the flow of a specific river,abstraction or other specific discharge boundary. Can beprefixed by ‘surface water’ or ‘groundwater’ to indicate thespecific nature of the catchment.
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Term Description
CatchmentAbstractionManagement Strategy
(CAMS)
The Environment Agency’s strategy for water resourcesmanagement in England and Wales through licensing waterabstraction. CAMS is used to inform the public on water
resources and licensing practice; provide a consistentapproach to local water resources management; and help tobalance the needs of water-users and the environment.
catenary A curve formed by a perfectly flexible, uniformly dense, andinextensible cable suspended from its endpoints.
Cetaceans Whales, dolphins and porpoises.
Chalk A soft white limestone (calcium carbonate) formed from theskeletal remains of sea creatures.
Community
Conservation Index.(CCI)
Method for evaluating invertebrate communities based on
species rarity, diversity and abundance.
cofferdam A temporary or permanent enclosure built across a body ofwater to allow the enclosed area to be pumped out creating adry work environment.
combined sewer A sewer conveying waste water of domestic or industrialorigin and rain water.
combined seweroverflow (CSO)
A structure, or series of structures, designed to allow spillageof excess waste water from a combined sewer under highrainfall conditions. Flows may discharge by gravity or bypumping.
conceptual model A simplified representation or qualified description of thebehaviour of the hydrogeological system. A quantitativeconceptual model includes preliminary calculations and flowand mass balances.
Conservation area Conservation areas defined by Local Planning Authoritiesaccording to the provisions of the Planning (Listed Buildingsand Conservation Areas) Act 1990.
construction site The area of site that would be used during the construction
phase.
Core Strategy The statutory plan which sets out a borough’s planningpolicies in relation to the management of development andland use. Supersedes the Unitary Development Plan inBoroughs where it has been adopted.
crawler crane A mobile crane, usually with caterpillar tracks.
CSO connectionculvert
The flow from the existing CSO is diverted to the location ofthe drop shaft. The drop shaft location requires suitableaccess for construction and maintenance.
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Term Description
CSO connectiontunnel
The flow from the drop shaft is transferred to the ThamesTunnel through a connection tunnel. These vary in diameterfrom 2.2m to 5.0m Long connection tunnels can be up to
4,615m in length.CSO drop shaft The shaft connects the flow down to the Thames Tunnel.
The shaft sizes depend on the amount of flow to beintercepted and the de-aeration requirements and the depthdepends on the location of the Thames Tunnel. The sizeranges from 6m to 25m and depth from 25 to 75m.
CSO interception site Site where the flows from an existing CSO would beredirected to the main Thames Tunnel.
curtilage An area of land or structures around a dwelling or otherstructure.
cut Excavated material to be re-used within the development as‘fill’ or removed off-site.
dB LAeq,T the equivalent continuous A-weighted sound pressure levelhaving the same energy as a fluctuating sound over aspecified time period T.
de-aeration chamber An area within the shaft and/or associated pipe work, whereair is removed from liquids.
decibel (dB) Logarithmic ratio used to relate sound pressure level to astandard reference level.
determinands Influencing or determining elements or factors.
Development Plan In London these refer to the borough Unitary DevelopmentPlans.
dewatering wells A system used to locally lower groundwater levels aroundthe worksite to provide stable working conditions whenexcavating.
diaphragm wall A diaphragm wall is a reinforced concrete retaining wall thatis constructed in-situ. A deep trench is excavated andsupported with bentonite slurry, and then reinforcing steel isinserted into the trench. Concrete is poured into the trenchand only after this does excavation in front of the retainedearth commence.
discharge The release of substances (eg, water, sewage, etc.) intosurface waters, ground or sewer.
drawdown A lowering of the water level in a borehole or aquifer, usuallyin response to abstraction.
Drinking WaterStandards
Legal standards set in Europe in the Drinking Water Directive1998 together with UK national standards to maintain
wholesomeness of potable water.
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Term Description
early medieval AD 410 – 1066. Also referred to as the Saxon period.
effect The result of an impact on a particular resource or receptor.
effluent The treated wastewater discharged from the SewageTreatment Works.
Environmental ImpactAssessment (EIA)
An assessment of the likely significant effects that aproposed project may have on the environment, consideringnatural, social and economic aspects, prepared inaccordance with the 2009 Infrastructure Planning EIARegulations.
Environmental QualityStandards (EQS)
The concentration of chemical pollutants assessed to havedetrimental effects on water quality in terms of the health ofaquatic plants and animals. EQS are established in the WFD
(Annex V) through the testing of the toxicity of the substanceon aquatic biology.
EnvironmentalStatement (ES)
A document to be prepared following an EIA which providesa systematic and objective account of the EIA’s findings,prepared in accordance with the 2009 Infrastructure PlanningEIA Regulations.
Evaluation(archaeological)
A limited programme of non–intrusive and/or intrusivefieldwork which determines the presence or absence ofarchaeological features, structures, deposits, artefacts orecofacts within a specified area.
Excavation(archaeological)
A programme of controlled, intrusive fieldwork with definedresearch objectives which examines, records and interpretsarchaeological remains, retrieves artefacts, ecofacts andother remains within a specified area. The records madeand objects gathered are studied and the results published indetail appropriate to the project design.
fault A structural planar fracture or discontinuity within lithologicalstrata due to strain or compression, in which significantdisplacement is observable.
FIDOR Factors that will determine the severity of an odour asdefined by the Environment Agency; Frequency, Intensity,Duration, Offensiveness, Receptor.
fill Material required to raise existing ground levels. This canutilise ‘cut’ material generated within the site, or necessitatethe importation of material.
findspot The location at which an item was found.
foul sewer A sewer conveying waste water of domestic and/or industrialorigin, but little or no rain water.
fracture A breakage in a rock mass. Present at any scale, but isgenerally used for large scale discontinuities.
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Term Description
GARDIT General Aquifer Research Development and InvestigationTeam (Thames Water, the Environment Agency and LondonUnderground with the support of organisations such as the
Corporation of London, Envirologic, the Association of BritishInsurers (ABI) and BT).
global warming The gradual increase in the temperature of the earth'satmosphere, believed to be due to the greenhouse effect,caused by increased levels of carbon dioxide,chlorofluorocarbons, and other pollutants.
Green Flag Benchmark national quality standard for parks and greenspaces in the United Kingdom.
groundwater Water contained in underground strata, predominantly inaquifers.
groundwater flooding Inundation of land or basements as groundwater levels riseand the groundwater discharges to the surface orunderground structures.
groundwater rebound The rise in groundwater level that occurs after cessation ofabstraction.
GWB Groundwater Body: distinct volume of groundwater within anaquifer or aquifers.
Harwich Formation A dark brown slightly glauconitic clay with localised finesand.
haul roads Temporary roads provided within the contractors site area toallow the transportation of material around the site.
heritage asset A building, monument, site, place, area or landscapepositively identified as having a degree of significancemeriting consideration in planning decisions. Heritageassets are the valued components of the Historicenvironment. They include designated heritage assets andassets identified by the local planning authority (includinglocal listing).
Historic environmentRecord (HER)
Archaeological and built heritage database held andmaintained by the County authority. Previously known as theSites and Monuments Record.
Homezone Designated residential area with streets designed to operateprimarily as a space for social use.
Holywell NodularChalk
Generally hard nodular chalks with thin flaser marls. In parts,there are significant proportions of shell debris. Inter-beddedcoloured marl and chalk succession characteristic of thePlenus Marls Member are found at its base. Above this, the
Melbourn Rock Member is distinguishable by its lack of shellmaterial.
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hydraulic conductivity A constant of proportionality in Darcy’s law that allows thecalculation of the rate of groundwater flow from the hydraulicgradient. For a unit hydraulic gradient, the higher the
hydraulic conductivity the higher the rate of groundwaterflow.
hydraulic gradient In an aquifer this is the rate of change of groundwater levelper unit distance in a given direction. Groundwater flows inthe direction of the decline in hydraulic gradient.
hydrograph A graph showing a plot of water flow or level with time,applicable to both surface water and groundwater.
impact A physical or measurable change to the environmentattributable to the project.
interception chamber This structure is required to be built around the existingoverflow either on land or at the discharge point in theforeshore. The chamber has a weir and valves to divert theflow in to the Thames Tunnel system. It is likely to be areinforced concrete cut and cover box structure. In someother cases the structure is required to be built adjacent toan inlet or sump of a pump station from which the flow isdiverted
Iron Age 600 BC – AD 43.
jacked caission A caisson is a retaining, water-tight structure open to the air.
A jack is used to push the caisson into the ground, with theinternal area then excavated.
LAeq(T) Equivalent continuous sound level is a notional steady soundlevel which would cause the same A-weighted sound energyto be received as that due to the actual and possiblyfluctuating sound over a period of time (T). It can also beused to relate periods of exposure and noise level. Thus, forexample, a halving or doubling of the period of exposure isequivalent in sound energy to a decrease or increase of3dB(A) in the sound level for the original period.
LAmax The maximum sound level measured on the A- weightedscale occurring during an event.
Lambeth Group Complex sequence of highly variable inter-bedded sedimentswhich include clay, sands, pebble beds and Shelly beds.
Laminated Beds Fine to coarse sand or clay with occasional black organicmatter.
later medieval AD 1066 – 1500.
Lee Tunnel The Lee Tunnel comprises a 7.2m diameter storage andtransfer tunnel from Abbey Mills Pumping Station to Beckton
STW and the interception of the Abbey Mills CSO.
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Lewes Nodular Chalk Hard to very hard nodular chalks and hardgrounds with inter-bedded soft to medium hard chalks and marls. Moreabundant softer chalks towards the top.
licence Formal permit allowing the holder to engage in an activity (inthe context of this report, usually abstraction), subject toconditions specified in the licence itself and the legislationunder which it was issued.
listed building A structure of architectural and/or historical interest. Theseare included on the Secretary of State's list, which affordsstatutory protection. These are subdivided in to Grades I, II*and II (in descending importance).
lithology The general characteristics of a rock or sedimentaryformation.
Local Air QualityManagement (LAQM)
Local areas where the local authority determines the nationalair quality objectives are not likely to be achieved by therelevant deadlines.
Local DevelopmentFramework (LDF)
Collection of planning documents prepared by the LocalPlanning Authority outlining the management of developmentand land use in a Borough.
locally listed building A structure of local architectural and/or historical interest.These are structures that are not included in the Secretary ofState’s Listing but are considered by the local authority to
have architectural and/or historical merit.Local Plan An area specific plan to interpret and apply the strategy set
out in the Structure Plan, to provide a detailed basis for thecontrol of development, to provide a basis for co-ordinatingnew development and to bring planning issues before thepublic.
London Clay Fine sandy silty clay to silty clay.
London Tideway
Improvements (LTI)
The LTI comprise five separate improvement projects atThames Water’s five Tideway sewage treatment works
(STWs): Mogden, Beckton, Crossness, Riverside and LongReach.
London Tideway
Tunnels (LTT)
The LTT comprises two separate projects: the Lee Tunneland the Thames Tunnel.
Lower aquifer Consisting of the Upnor Beds (the lowest unit of the LambethGroup), the Thanet Sands and the Chalk.
made ground Artificial deposit. An archaeologist would differentiatebetween modern made ground, containing identifiablymodern inclusion such as concrete (but not brick or tile), and
undated made ground, which may potentially containdeposits of archaeological interest.
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main tunnel driveshaft site
Site that would be used to insert and then drive the TBM.
main tunnel reception
shaft site
Site that would be used to remove the TBM from the Thames
Tunnel at the end of the drive.
Mesolithic 12,000 – 4,000 BC.
mitigation measures Actions proposed to prevent or reduce adverse effectsarising from the whole or specific elements of thedevelopment.
Neolithic 4,000 – 2,000 BC.
New Pit Chalk Non-nodular chalk, massively bedded, with fairly regularlydeveloped marl seams and sporadic flints.
nitrogen dioxide (andoxides NO2 and NO) A product of combustion processes. Nitrogen dioxide isassociated with adverse effects on human health.
Non-TechnicalSummary (NTS)
A report which briefly describes the main points discussed inthe Environmental Statement in a clear manner without theuse of technical jargon and phraseology. This report is arequirement of the 2009 Infrastructure Planning EIARegulations.
Ofwat The Water Services Regulations Authority, a governmentbody set up in 1989 to regulate the activities of the watercompanies in England and Wales.
olfactometry Odour panel sampling carried out in laboratory conditions.
Palaeo-environmental Related to past environments, ie, during the prehistoric andlater periods. Such remains can be of archaeologicalinterest, and often consist of organic remains such as pollenand plant macro fossils which can be used to reconstruct thepast environment.
Palaeolithic 700,000–12,000 BC.
palstave A Middle Bronze Age axe.
particulate matter(PM)
Solid particles or liquid droplets suspended or carried in theair and includes the same matter after it has deposited ontoa surface. For the purposes of this assessment the termincludes all size fractions of suspended matter, such as dust,PM10 and PM2.5.
passive filter chamber A structure containing carbon which absorbs odour from airflowing out of the Tunnel, without the assistance ofmechanical pumping.
PEIR Preliminary Environmental Information Report is a documentsetting out initial environmental information. In accordance
with the Planning Act 2008, it is a requirement that this is thesubject of pre-application consultation.
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pelagic invertebrates Invertebrates which are found in the water column.
perched water Is groundwater in an aquifer present above the regionalwater table, as a result of a (semi-)impermeable layer of rock
or sediment above the main water table/aquifer, below theground surface.
permeability The capacity of soil or porous rock to transmit water.
pH A measure of the acidity or basicity of an aqueous solution.
piezometer A borehole designed specifically to allow the measurementof groundwater level.
piezometric surface The level or head to which groundwater would rise in apiezometer if it is free to seek equilibrium with theatmosphere.
Pollution IncidentControl Plan
Written procedures put in place for dealing with spillages andpollution.
porous Containing void spaces. Most sedimentary rocks are porousto some extent, and the term is commonly applied in arelative sense, generally restricted to rocks which havesignificant effective porosity.
preferred route Refers to Option 3 – Abbey Mills route, which runs fromAction Storm Tanks in west London to Limehouse then turnsnortheast to Abbey Mills Pumping Station, where it connects
with the Lee Tunnel. preferred scheme Refers to the preferred route and construction sites.
preferred site Sites assessed as most suitable following review of suitabilityof each shortlisted site by taking in to accountengineering,planning, environment, property and communityconsiderations.
preservation by record Preservation by recording and advancement ofunderstanding of asset significance’. This is a standardarchaeological mitigation strategy where heritage assetsremains are fully excavated and recorded archaeologicallyand the results published. For remains of lessersignificance, preservation by record might comprise anarchaeological watching brief.
preservation in situ Archaeological mitigation strategy where nationally important(whether designated or not) heritage assets are conserved in situ for future generations, typically through modifications todesign proposals to avoid damage or destruction of suchremains.
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Principal Aquifer A geological stratum that exhibits high inter-granular and/orfracture permeability. This strata has the ability to supportwater supply and/or river base flow on a strategic scale.
Principal Aquifers equate in most cases to aquiferspreviously referred to as Major Aquifers.
Public Water Supply Term used to describe the supply of water provided by awater company.
Putty Chalk Putty chalk (clay characteristics) near the surface of the unitabove firm to soft non-nodular chalk with flint (Upper Chalkundivided) above hard nodular chalk with flints (LewesChalk).
RAMSAR An international treaty for the conservation and sustainable
utilisation of wetlands.RBMP River Basin Management Plans – these are the relevant
plans that outline the state of water resources within a RiverBasin District relevant to the objectives of the WFD.
RDB3 The rarest and most threatened species are often listed inthe Red Data Book of Insects1
reach
, within which there are threecategories. Taxa in danger of extinction are referred to asRDB 1 species; those considered to be vulnerable and likelyto move into the endangered category are listed under RDB2, whilst rare species occur on RDB 3.
Section of river between two points.
River TerraceDeposits
Extensive alluvial sand and gravel deposits laid down in abraided river system in river terraces since the Anglianglaciations.
real time control(RTC)
Where live data is used to manipulate control equipment inorder to best manage the flow of storm water and sewagewithin the capacity of the system.
receptors People (both individually and communally) and the socio-economic systems they support.
recharge Water that percolates downwards from the surface toreplenish the water table.
Red route The red route is a network of roads designated by Transportfor London that carry heavy volumes of traffic and areessential for the movement of traffic and public transport.These comprise mainly of major routes into and aroundLondon. Transport for London are responsible for enforcingthe red routes which include clearways, parking and loadingbays, bus lanes, yellow box junctions and banned turns.
1Bratton, (1991) Red Data Book for Insects
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risk assessment Assessment of the risks associated with an activity or objectand possible accidents involving a source or practice. Thisincludes assessment of consequence.
Roman AD 43 – 410.
SAM Scheduled Ancient Monument. More commonly referred toas ‘Scheduled Monument’.
saline intrusion Entry of brackish or salt water into an aquifer, from the sea orestuary. This may be natural or induced by excessive oruncontrolled groundwater abstraction.
saturated zone The zone in which the voids in a rock or soil are filled withwater at a pressure greater than atmospheric pressure.
Scheduled Monument An ancient monument or archaeological deposits designated
by the Secretary of State as a ‘Scheduled AncientMonument’ and protected under the Ancient Monuments Act.
Scoping Opinion The formal view of the determining authority on the range oftopics and issues to be considered by the EnvironmentalImpact Assessment, as referred to in the 2009 InfrastructurePlanning EIA Regulations.
Scoping Report The document prepared by the applicant setting out theproposed approach to the Environmental ImpactAssessment, including the range of topics and issues to beaddressed, as referred to in the 2009 Infrastructure PlanningEIA Regulations.
Screening Opinion The formal view of the determining authority on the need foran Environmental Impact Assessment to be undertaken, asreferred to in the 2009 Infrastructure Planning EIARegulations.
Seaford Chalk The upper unit of the White Chalk, comprising of as firm tosoft non-nodular Chalk with flint beds. Thin marl seams arefound towards its base and and absent higher up. A hardground marks the top of the Seaford Chalk.
secant piles Alternate piles in-filled with concrete to form a water-tightretaining wall.
Secondary Aquifers Either permeable strata capable of supporting local suppliesor low permeability strata with localised features such asfissures. The term Secondary Aquifer replaces thepreviously used name of Minor Aquifer. There are twoclasses of Secondary Aquifer. “Secondary A” are capable ofsupporting water supplies at a local rather than strategicscale and “Secondary B” are lower permeability layers whichmay store and yield limited amounts of groundwater due to
localised features such as fissures, thin permeable horizonsand weathering.
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short listed sites Sites idenitfied following an assessment of long list sites inaccordance with the Site Selection Methodology.
SINC (Grade B) Site of Nature Conservation Importance (Grade II of Borough
importance).
SINC (Grade L) Site of Nature Conservation Importance (Grade I of Localimportance).
SINC (Grade M) Site of Nature Conservation Importance (Grade III ofMetropolitan importance).
Site For the purposes of the PEIR assessment, the “site” isdeemed as the entire area located within the Limit of Land tobe Acquired or Used. It should not be inferred that this entire‘site’ area will be physically separated (ie, hoarded or fenced)
for the construction duration.Site of SpecialScientific Interest(SSSI)
An area given a statutory designation by English Nature orthe Countryside Council for Wales because of its natureconservation value.
site strip Materials such as hard standing and vegetation includingincidental topsoil (including potential contaminated soil).
Sites and MonumentsRecord
A record of sites of archaeological interest.
sprayed concrete
lining
An efficient method for constructing the tunnel lining with a
layer of sprayed concrete. This is instead of using pre-castconcrete segments.
strata Layers of rock, including unconsolidated materials such assands and gravels.
stratigraphy The study of stratified rocks, their nature, their occurrence,their relationship to each other and their classification.
sulphur dioxide (SO2) A colourless gas with a choking smell, the main product ofthe combustion of sulphur contained in fuels.
superficial deposits Overarching term for recent generally unconsolidated or
loosely consolidated deposits of sand, gravel, silt, clay, etcon top of bedrock. Synonymous with ‘drift’ – generallysupersedes the term.
surface water This is a general term used to describe all water featuressuch as rivers, streams, springs, ponds and lakes.
surface water runoff Water that travels across the ground rather than seeping into the soil.
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Thames Tunnel The Thames Tunnel comprises a full-length storage andtransfer tunnel from Acton Storm Tanks to Beckton SewageTreatment Works in East London and the interception of
specific CSOs along the Thames Tideway with a diameterbetween 6.5m and 7.2m.
Thanet Sands Coarsening upward sequence of well sorted fine grainedsand which has a higher clay / silt content towards the lowerpart of the sequence, and evidence of intense bioturbationremoving bedding structures.
The project The Thames Tunnel project.
tidal excursion Length of river channel swept by water from a dischargepoint in one tidal cycle. In the case of the River Thames thisis considered to 13km up and downstream of the discharge
point.
Tideway Fish RiskModel
Tool developed on behalf of Thames Water to assess theeffects of lapses in water quality caused by CSO dischargeson Tideway fish populations.
TransportAssessment (TA)
The formal assessment of traffic and transportation issuesrelating to the proposed development. The findings areusually presented in a report which accompanies theplanning application.
truncate Partially or wholly remove. In archaeological terms remains
may have been truncated by previous construction activity.typical year A typical year relates to an actual year, eg, the
corresponding meteorological dataset for that year used inthe modelling which was 1979-80. The correspondingmeteorological dataset is used as it would give a betterindication of conditions rather than using a recent year ofdata where the meteorological data may not be consistentwith a rainfall event leading to the tunnel emissions.
underground pressurerelease chamber
An enclosed space below the ground surface where air isreleased to atmosphere, should the pressure within the
Tunnel exceed a set value.
Unitary DevelopmentPlan (UDP)
The statutory plan which sets out a unitary authority’splanning policies.
unproductive strata These are rocks which are generally unable to provideusable water supplies and are unlikely to have surface waterand wetland ecosystems dependent upon them.
Upnor Formation Variably bioturbated fine- to medium-grained sand withglauconite, rounded flint pebbles and minor clay, withdistinctive pebble beds and base and top.
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Upper aquifer Comprising the water bearing strata above the London Clay,namely the River Terrace Deposits and the Alluvium.
Upper Mottled Beds A bluish grey mottled with greenish brown clay.
Upper Shelly Beds Contains shell fragments within a flinty gravel or a sandy clay
Urban Waste WaterTreatment Directive
The Urban Waste Water Treatment Directive (1991) has theoverall aim of protecting the environment from the adverseeffects of urban waste water discharges.
valve chamber An underground structure on the sewer system containingvalves which are used to isolate the flow between differentparts of the sewer system. For example, flap valves preventthe flow from the river travelling back up the sewer or into thetunnel.
ventilation column A stack through which air is released.
Water FrameworkDirective (WFD)
An EC Directive seeking to improve water quality in riversand groundwater in an integrated way (2000).
watching brief(archaeological)
An archaeological watching brief is a formal programme ofobservation and investigation conducted during anyoperation carried out for non–archaeological reasons.
water table Level below which the ground is saturated with water. Thewater table elevation may vary with recharge andgroundwater abstraction.
Waste Electrical andElectronic EquipmentDirective (WEEE)
The WEEE Directive aims to reduce the amount of electricaland electronic equipment going to landfill and to encourageeveryone to reuse, recycle and recover it.
White Chalk subgroup Chalk with flints, with discrete marl seams, nodular chalk,sponge-rich and flint seams throughout. Flint typology andmarl seam incidence is important for correlation. Comprisesof Seaford Chalk, Lewes Nodular Chalk, New Pit Chalk andHolywell Nodular Chalk.
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References
1 Thames Tideway Strategic Study Report, February, 2005, Thames Water2 Thames Tideway Strategic Study Report Solutions Group Working Report Volumes
I and II, February 20053 Thames Tideway Tunnel and Treatment, Solutions Working Group Report(Thames Water December 2006)4 Thames Tideway Tunnel and Treatment Summary Report Tackling London’s SewerOverflows, Executive Summary, Thames Water (2007)5 Regulatory Impact Assessment – sewage collection and treatment for London(Defra, March 2007) http://archive.defra.gov.uk/corporate/consult/waste-water/101116-wastewaterpolicy-condoc-annex2.pdf 6 Scott Wilson, May 2008, Lee Tunnel and Beckton STW Extension Environmental
Statement7 Thames Tideway Tunnel and Treatment, Solutions Working Group Report(Thames Water December 2006)
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Phase two consultation (Autumn 2011)