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 London1858 - The Great Stink – Parliament suspended

12000

14000

16000

London Cholera Deaths

0

2000

4000

6000

8000

10000

1831 1833 1848

3

“Lost” rivers of London

River Roding

Barking Creek

Stoke NewingtonHampstead

BowIslington

Waterloo

Black

DitchErith

Notting Hill

Bev erley B rookBev erley B rookBev erley B rookBev erley B rook

8383

Forest Hill

Roehampton

Streatham

Eltham

WoolwichWaterloo

Battersea

Chelsea

4

Plan

London’s Sewers - Evolution and Complexity

Original sewers and local collectors River

Wall

RiverThames

Section

High Tide

Low Tide

Storm relief sewers and pumping station

Bazalgette’s Interceptor Sewers

Thames

Ground level

5

Intercepting sewers

Central LondonIntercepting Sewersat the present day

Hampstead

StokeNewington

Notting Hill

Bow

Waterloo

Abbey MillsPumping Station

Middle Level No. 1

PiccadillyBranch

High Level

Western

BermondseyBranch

Wick

Do

gs B

ran

ch

Lo

w L

evel

Northern

Northern Outfall

Sou

Isle

of

thern Outfall No. 1

NorthernLowLevelNo. 1

Lan

eB

ranch

LowLevel No. 2

Middle Level No. 2

Southern Outfall No. 2

Islington

Western Pumping

Station

CrossnessPumping Station

Sewer

3288-03/127

Roehampton

Streatham

ForestHill

Eltham

Woolwich

DeptfordPumpingStation

Western

Fulham

Branch

High LevelExtension

Southern

Low Level

SouthernHigh Level No. 1

Effra B

ran

ch

mondsey

Branch Southern Outfall No. 1

SouthernLow L

evel No. 2

Lewish

am

Bra

nch

Sou

Hig

h L

evel

No. 2

ther

n

Southern Outfall No. 2No. 1

Western Pumping

Station

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

Separate system

Partially separate system

Combined system

Percentage Connected

Crossness STW

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 SolutionThe London Tideway Tunnels

Solutions?

Action before sewer: Source Control &

Sustainable Urban

Drainage Systems

(SUDS)

NO

Within sewer network:

Localised storage &

separation.

NO

In-river: More ‘Bubbler’ &

‘Skimmer’ vessels. NO

Intercept overflows:

central storage &

transfer.

YES

22

Pump out toBeckton STW

Crossness

Abbey

Mills PS

Houses of

Parliament

Tower ofLondon

Thames Barrier

The Thames and Lee tunnels Option 1c

This figure is indicative only and subject to site selection process and further design work

Earl PS

Greenwich PS

Proposed Lee Tunnel

Proposed Thames Tunnel

Combined Sewer Overflow (CSO) Pumping station

Combined Sewer Overflow (CSO) Gravity

Sewage treatment works

Pumping station

CrossnessSTW

WesternPS

Heathwall PS

HammersmithPS

STW

PS

23

CSO Interception

Section

High Tide

Low Tide

Ground level

Main tunnel

Interception chamber and drop shaft

Connection tunnel

24

London Tideway Tunnels

Thames Tunnel

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.

• 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.

Thames Tunnel

25

10

0

-20

-30

-40

-50

-10

10

0

-20

-30

-40

-50

-10

ELE

VA

TIO

N (

mO

D)

RIV

ER

TH

AM

ES

BE

CK

TO

N O

VE

RF

LO

W S

HA

FT

BE

CK

TO

N P

UM

PIN

G S

HA

FT

Lee Tunnel - general geology

-100

-60

-70

-80

-90

-100

-60

-70

-80

-90

ELE

VA

TIO

N (

mO

D)

MADE GROUND / ALLUVIUM RIVER TERRACE GRAVEL LONDON CLAY FORMATION HARWICH FORMATION

LAMBETH GROUP THANET SAND FORMATION WHITE CHALK SUBGROUP

KEY TO GEOLOGY

THE GREENWICH FAULT ZONE

‘THE PLAISTOW GRABEN’

1+

090

6+

061

6+

904

3+

905

2+

591

1+

491

1+

936

3+

126

3+

409

4+

831

5+

468

0+

587

0+

000

CHAINAGE

GEOLOGICAL FAULT

POSITION OF MID LAMBETH GROUP HIATUS BOREHOLE AND DESIGNATION

(PHASE 1, PHASE 2) 26

Thames Tunnel – ground conditions

29

London ClayThanet Sands and Lambeth

BedsChalk

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

30

Earth Pressure Balance Machine

• Aquifer protection

• Proximity to other tunnels

• Settlement impact on third parties

• Construction logistics: 80m water

pressure through chalk/very long

drives

Ground investigations

31

Challenges

• 34 CSOs

• Up to 60m3/s

• Up to 30m dia

shafts

• Up to 75m deep

CSO interception

• 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

Page 3636

Timeline

Reportto

Government

Dec 2006

Planningapplication

ThamesTunnel

2011

CommissionThamesTunnel

2020

Consultation began

Autumn 2008

Public consultation on preferred sites

Mid 2010

Minister’sdecision

Mar 2007

ThamesTunnel

contract awards

2012

Site identification

Spring-Autumn 2009

Finalise list of sites

Summer 2010

Planning application

Lee Tunnel

& Beckton STW

May 2008

LeeTunnel

contractaward

Early 2010

CommissionLee

Tunnel&

Beckton STW

2014

37

Thank You

Questions?