The London Tideway Tunnels Creating a cleaner, healthier River Thames Sian Thomas, Thames Tunnel Project Manager 14 October 2008

2 Improving the Tidal River Thames Latest contribution to river water quality improvements –Building on the legacy of Sir Joseph Bazalgette’s intercepting sewers –Many years of investment in Sewage Treatment Works (STWs) in the Thames catchment area Main drivers –River quality (fish, health & litter) –UK compliance with legislation –Reputation of London as a world class city Two separate tunnels – the Thames Tunnel and Lee Tunnel – reducing discharges from CSOs Investment to improve the STWs discharging into the tidal River Thames

3 River Roding Barking Creek Beverley Brook River Lee 8383 Counters Creek Forest Hill Stoke Newington Hampstead Roehampton Streatham Eltham Woolwich Bow Islington Waterloo Graveney Stamford Brook Black Ditch Earl Peck Effra Falcon Brook Wandle Beverly Brook Ravensbourne Deptford Creek Oldbourne Westbourne Tyburn Hackney Brook Walbrook Hounds Ditch Fleet Battersea Chelsea Quaggy Neckinger KidBrook Kings Scholar’s Pond Erith Notting Hill Kilburn The Old Rivers of London

4 Intercepting Sewers by the Metropolitan Board of Works

5 Storm Relief Sewers & Pumping Stations 1910 to 1960

6 London’s Sewerage System

7 Combined Sewer Overflows (CSOs) Bazalgette’s sewerage system designed with 57 Combined Sewer Overflow (CSO) points along the tidal River Thames – public health driver CSOs prevent flooding to buildings and streets by spilling excess sewage into the river during heavy or prolonged rainfall 32 million tonnes (average) of diluted storm sewage discharged annually Up to 60 discharges a year on average – more than once a week.

8 21 st Century Challenges Increasing urbanisation – paving over of gardens; loss of land available to soak up rainfall Climate change leading to more frequent, more intense storm events. August 2004: average monthly rainfall within a couple of hours (west London). Population growth – more than a million additional people in London by 2029

9 CSO Impacts Reduced levels of oxygen affect aquatic wildlife e.g. Aug 2004 event - 10,000 fish and 100,000 fish fry killed Visible littering of the river shoreline from sewage- derived litter Potential health risks to river users

10 Milestone Dates February 2000 Thames Tideway Strategic Study (TTSS) set up to investigate and propose solutions to CSO discharges February 2005 TTSS concluded need for both improvements to the existing STWs and building a tunnel to intercept 36 of the most polluting Tideway CSOs August 2005 Ofwat commissioned independent review by Jacobs Babtie July 2006 Government instructed Thames Water to evaluate two options for a tunnel under the tidal Thames

11 Milestone Dates December 2006 Submitted our report to Government on the assessment of the two options detailing costs and benefits March 2007 Minister Ian Pearson announced Government’s decision to support the development and implementation of the full-length tunnel solution March 2008 Appointed CH2M HILL as Programme Management capability to assist with delivery of the Tideway Tunnel

12 Thames Tideway An Integrated Solution London Tideway Tunnels and improvements to London’s five main STWs Beckton, Crossness, Mogden, Longreach and Riverside improvements – funding agreed with Ofwat as part of Price Review process. Beckton STW improvements needed to increase flow to treatment and treat storm sewage pumped out from the London Tideway Tunnels.

13 London Tideway Tunnels Proposed Concept Lee Tunnel (Abbey Mills to Beckton STW) 6.9km long, >7m diameter, up to 75m deep If approved approx 5 years to construct Beckton STW Extensions If approved approx 5 years to construct Thames Tunnel (West London to Beckton STW) 32.2km long, >7m diameter, up to 75m deep If approved approx 8 years to construct

14 Thames Tunnel Overview 32.2km tunnel from west London to Beckton STW in east London Several major shaft sites along the tunnel route 34 CSOs will connect into the tunnel If approved, tunnel construction could start in 2012, lasting approximately 8 years

15 Thames Tunnel Tunnelling and CSO Connection Sites Sites required for three main purposes: -Main construction shafts (X 3 – 5 approx) -Intermediate construction shafts (X 3 – 4 approx) -CSO connections (X 34) Initial briefings held with 13 London Boroughs (Autumn 2008) Site selection methodology under development for consultation Securing sites is key to ongoing design development Key constraints and challenges - Tunnelling at depth in varying ground conditions - CSO connections, surface works and connection to main tunnel - Stakeholder engagement is vital

16 Blackfriars Bridge CSO Engineering Challenges

17 Lee Tunnel OJEU Notice Dec 2007 Planning Application Lee Tunnel and Beckton STW May 2008 Lee Tunnel Contract Award Mar 2009 Commission Lee Tunnel and Beckton STW June 2014 Minister’s Decision Mar 2007 Thames Tideway Tunnel Timeline Lee Tunnel, Beckton STW and Thames Tunnel Thames Report to Government Dec 2006 Planning Application Thames Tunnel 2011 Thames Tunnel Contract Awards 2012 Commission Thames Tunnel June 2020 Start Site Investigation Thames Tunnel 2008