London Tideway Tunnels Modernising London’s Sewerage System

Rob Furniss AECOM Water Global Director of Community Infrastructure The Background to London’s Sewers 1848 – Cholera deaths peak In London 1858 - The Great Stink – Parliament suspended

London Cholera Deaths 16000

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0 1831 1833 1848

3 “Lost” rivers of London

Stoke River Roding Hampstead Newington

Islington Bow Barking Creek Black Notting Hill Ditch Erith

Waterloo Chelsea Woolwich

Battersea

Eltham Roehampton Forest Hill Streatham

BevBev erley erley BrookBrook

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4 London’s Sewers - Evolution and Complexity

Original sewers and local collectors River Wall

Plan River Thames Bazalgette’s Storm relief Interceptor sewers and Sewers pumping station Ground level High Tide

Low Tide

Section 5 Intercepting sewers

H Central London n ig er hL rth e Intercepting Sewers No ve Stoke l at the present day Newington W L Hampstead . 2 ic l No k a Abbey Mills Leve n dle e Pumping Mid B r Station a Crossness Islington n c N D I o Bow L h r Pumping Station s the o o rn . 1 l Ou No 2 w g e tfall s l . e S o e v o L w e e L N B r e dle Low Level f r Mid h v c a n e n ra l ly B orther No. 1 c il N n el h ad LowL ev Notting Hill cc Pi ing W ump m e rn P Waterloo Ber o s ste n n O te We tion nc d er utfall No. 1 r Sta Bra h s S h o. 2 n N e out tfall N l o. y rn Ou ve 1 outhe Le S am o. 2 Woolwich lh h ow . 2 l N u c L v el No e F an n Le v r er Deptford e B th w uth h Level No. L Sou Lo o ern ig ern S H Pumping h outh 1 g S on Station i si H en n t h r x e Eltham High LevelE c h n Sou t Roehampton a Forest h r m

c B Hill a a n fr h f a E s r w i Streatham B Le

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6 1859 – 1865 Construction of Bazalgette’s new interceptor sewers

Northern Outfall Sewer Sewer tunnels

7 The Victorian legacy

8 After 150 years …….an Upgrade is Required Urban Wastewater Treatment Directive

10 London’s sewerage system today – mostly combined

Beckton STW Crossness STW

Percentage Connected

Separate system

Partially separate system

Combined system

11 Distribution of impermeability in the Thames Tideway catchment

12 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 57 existing Combined Sewer Overflows

14 Existing Combined Sewer Overflows

15 Discharging CSO

16 London Tideway Tunnels - CSOs proportion of discharge

17 Thames Tunnel CSOs proportion of discharge

18 Increasing recreational use of River Thames

19 Headline news

20 The Solution The London Tideway Tunnels Solutions?

Action before sewer : NO Source Control & Sustainable Urban Drainage Systems (SUDS) Within sewer network : NO Localised storage & separation.

In-river: More ‘Bubbler’ & NO ‘Skimmer’ vessels.

Intercept overflows: YES central storage & transfer.

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 Pump out to Beckton STW Houses of Tower of Parliament London Thames Barrier Crossness STW

Western Hammersmith PS Earl PS PS Heathwall PS Greenwich PS

Proposed Lee Tunnel Proposed Thames Tunnel Combined Sewer Overflow (CSO) Pumping station Combined Sewer Overflow (CSO) Gravity STW Sewage treatment works PS Pumping station

23 CSO Interception

Ground level High Tide

Low Tide

Section

Interception chamber and drop shaft

Main tunnel

Connection tunnel 24 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 2011.

• Construction not expected to start until 2012/13 for completion by 2020.

25 Lee Tunnel - general geology

10 PUMPINGBECKTON SHAFT OVERFLOW BECKTON SHAFT 10

0 THAMES RIVER 0

-10 -10

-20 -20

-30 -30

-40 -40

-50 -50

-60 -60 ELEVATION (mOD) (mOD) ELEVATIONELEVATION -70 -70

-80 -80 THE -90 ‘THE GREENWICH -90 PLAISTOW FAULT ZONE -100 GRABEN’ -100 1+491 1+936 2+591 3+126 3+409 3+905 4+831 5+468 6+061 6+904 0+000 0+587 1+090 CHAINAGE

KEY TO MADE GROUND / ALLUVIUM RIVER TERRACE GRAVEL LONDON CLAY FORMATION HARWICH FORMATION GEOLOGY

LAMBETH GROUP THANET SAND FORMATION WHITE CHALK SUBGROUP

POSITION OF MID LAMBETH GROUP HIATUS BOREHOLE AND DESIGNATION

GEOLOGICAL FAULT (PHASE 1 , PHASE 2 ) 26

Thames Tunnel – ground conditions

Thanet Sands and Lambeth London Clay Chalk Beds

29 29 Tideway Tunnels – 8.8m OD tunnel boring machine (TBM) Technical challenges

• Tunnel-to-tunnel connections beneath river

• Lining durability - 150 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 Earth Pressure Balance Machine drives

30 Ground investigations

31 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 Assessment of fluvial impact of works

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

34 The search for shaft sites

35

35 Consultation

36 Page 36 Timeline

Commission Consultation Public Planning Thames Report began consultation on application Tunnel to preferred sites Thames Government Tunnel Mid 2010 Dec 2006 Autumn 2008 2011 2020

Minister’s Planning Site Lee Finalise list Thames Commission decision application identification Tunnel of sites Tunnel Lee Lee contract contract Tunnel Tunnel award awards & & Beckton Spring- Summer Beckton Mar 2007 STW Autumn 2009 2012 2010 STW

May 2008 Early 2010 2014

37 Thank You

Questions?