London Tideway Tunnels Modernising London s Sewerage System Rob Furniss

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1 London Tideway Tunnels Modernising London s Sewerage System Rob Furniss AECOM Water Global Director of Community Infrastructure

2 The Background to London s Sewers

3 1848 Cholera deaths peak In London The Great Stink Parliament suspended London Cholera Deaths

4 B ev ev erley B rook Lost rivers of London Hampstead Stoke Newington River Roding Notting Hill Islington Bow Black Ditch Barking Creek Erith Chelsea Waterloo Woolwich Battersea Roehampton Streatham Forest Hill Eltham

5 London s Sewers - Evolution and Complexity Original sewers and local collectors River Wall Bazalgette s Interceptor Sewers Plan Storm relief sewers and pumping station River Thames Ground level High Tide Low Tide Section 5

6 Intercepting sewers Notting Hill Hampstead Stoke Newington Waterloo Bow Central London Intercepting Sewers at the present day HighLevel Northern Abbey Mills Pumping Station Wick Middle Level No. 2 Lane Branch Islington Northern Outfall Isle of Dogs Branch Low Level Middle Level No. 1 LowLevel No. 2 Crossness Pumping Station Sewer Low LevelNo. 1 Northern PiccadillyBranch Southern Ber Western Pumping Station Outfall No. 1 Southern Outfall No. 2 nch mondsey Bra Weste estern Roehampton Streatham Forest Hill Deptford Pumping Station Eltham Woolwich thern High LevelNo. 2 No. 1 Southern Low Level Branch Fulham Level No. 1 SouthernHigh SouthernLow Level No. 2 High LevelExtension Sou Lewisham Branch EffraBranch /127 6

7 Construction of Bazalgette s new interceptor sewers Northern Outfall Sewer Sewer tunnels 7

8 The Victorian legacy 8

9 After 150 years.an Upgrade is Required

10 Urban Wastewater Treatment Directive 10

11 London s sewerage system today mostly combined Beckton STW Crossness STW Percentage Connected Separate system Partially separate system Combined system 11

12 Distribution of impermeability in the Thames Tideway catchment 12

13 Combined Sewer Overflows (CSOs) Sir Joseph Bazalgette s sewerage system constructed with 57 CSO points along the tidal River Thames. CSOs prevent flooding to buildings and streets by diverting excess sewage into the river when full to capacity after rainfall. On average, in excess of 32 million tonnes of untreated sewage is estimated to be discharged annually. Discharges occur more than once a week on average. Many sewers run 80% full on dry weather flow As little as 2mm of rainfall can trigger a discharge. 13

14 57 existing Combined Sewer Overflows 14

15 Existing Combined Sewer Overflows 15

16 Discharging CSO 16

17 London Tideway Tunnels - CSOs proportion of discharge 17

18 Thames Tunnel CSOs proportion of discharge 18

19 Increasing recreational use of River Thames 19

20 Headline news 20

21 The Solution The London Tideway Tunnels

22 Solutions? Action before sewer: Source Control & Sustainable Urban Drainage Systems (SUDS) Within sewer network: Localised storage & separation. In-river: More Bubbler & Skimmer vessels. NO NO NO Intercept overflows: central storage & transfer. YES 22

The Thames and Lee tunnels Option 1c This figure is indicative only and subject to site selection process and further design work Abbey Mills PS Houses of Parliament Tower of London Pump out to

23 The Thames and Lee tunnels Option 1c This figure is indicative only and subject to site selection process and further design work Abbey Mills PS Houses of Parliament Tower of London Pump out to Beckton STW Thames Barrier Crossness STW Hammersmith PS Western PS Heathwall PS Earl PS Greenwich PS STW PS Proposed Lee Tunnel Proposed Thames Tunnel Combined Sewer Overflow (CSO) Pumping station Combined Sewer Overflow (CSO) Gravity Sewage treatment works Pumping station 23

24 CSO Interception Ground level High Tide Low Tide Section Interception chamber and drop shaft Main tunnel Connection tunnel 24

25 London Tideway Tunnels Lee Tunnel 6.9km tunnel from Abbey Mills Pumping Station to Beckton STW. 400m project. Largest single contract ever awarded by Thames Water. Will intercept 16 million cubic metres of storm sewage that currently makes its way into the River Thames. Thames Tunnel 32.2km (20 mile) tunnel from west London to Beckton Sewage Treatment Works. Starting point still to be determined, major shaft sites and combined sewer overflow connection points required. Planning application to be submitted Construction not expected to start until 2012/13 for completion by

Lee Tunnel - general geology 10 0 BECKTON PUMPING SHAFT BECKTON OVERFLOW SHAFT RIVER THAMES 10 0-10 -10-20 -20 ELEVAT TION (mod) -30-40 -50-60 -70-30 -40-50 -60-70 -80-90 -100 THE PLAISTOW GRABEN THE

26 Lee Tunnel - general geology 10 0 BECKTON PUMPING SHAFT BECKTON OVERFLOW SHAFT RIVER THAMES ELEVAT TION (mod) THE PLAISTOW GRABEN THE GREENWICH FAULT ZONE CHAINAGE KEY TO GEOLOGY MADE GROUND / ALLUVIUM RIVER TERRACE GRAVEL LONDON CLAY FORMATION HARWICH FORMATION LAMBETH GROUP THANET SAND FORMATION WHITE CHALK SUBGROUP POSITION OF MID LAMBETH GROUP HIATUS BOREHOLE AND DESIGNATION GEOLOGICAL FAULT (PHASE 1, PHASE 2) 26

29 Thames Tunnel ground conditions London Clay Thanet Sands and Lambeth Beds Chalk 29 29

30 Tideway Tunnels 8.8m OD tunnel boring machine (TBM) Technical challenges Tunnel-to-tunnel connections beneath river Lining durability yr design life Transient pressure waves Aquifer protection Proximity to other tunnels Settlement impact on third parties Construction logistics: 80m water pressure through chalk/very long drives Earth Pressure Balance Machine 30

31 Ground investigations 31

32 CSO interception Challenges 34 CSOs Up to 60m 3 /s Up to 30m dia shafts Up to 75m deep De-aeration Air release CSO interception in river or busy London Streets 32

33 Assessment of fluvial impact of works 33

34 Operation and maintenance - purpose made inspection vehicle in Milwaukee sewer tunnel 34

35 The search for shaft sites 35 35

36 Consultation Page 36 36

37 Timeline Report to Government Consultation began Public consultation on preferred sites Planning application Thames Tunnel Commission Thames Tunnel Dec 2006 Autumn 2008 Mid Minister s decision Mar 2007 Planning application Lee Tunnel & Beckton STW Site identification Spring- Autumn 2009 Lee Tunnel contract award Finalise list of sites Summer 2010 Thames Tunnel contract awards 2012 Commission Lee Tunnel & Beckton STW May 2008 Early

38 Thank You Questions?

CROSSRAIL INFORMATION PAPER D8 TUNNEL CONSTRUCTON METHODOLOGY

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