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 14000 12000 10000 8000 6000 4000 2000 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 Brook Brook 8383 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 rn i the g Nor h L Hampstead e Central London Stoke ve Newington l Middle Level No. 2 Intercepting Sewers W i ck L at the present day Islington a n Abbey Mills e B Pumping o. 1 r vel N a Station Middle Le n Bow c Notting Hill h L c D n h I o ra s W llyB o N i L w o 2 l o d w . g ca Level o e rth e c N i s L s P No er Crossness e o rth n e te rn B O f Pumping Station v u r mping r Se t u e f n Western P Lo lNo. 1 a w al e l wL ev n er l Station c Waterloo h am N Be m lh r o u h l o n F nc ve . Bra n ra Le 1 c d B ow h s rn L v e Sout he Le el No. 2 y rn w Sout he Outf Southern Lo u all No So th Southern Outfall No. 2 . 1 ern RoehamptonHig sion High Level No. h L xten Deptford lNo. 2 evelE 1 e v Woolwich Pumping e L h c Station h n ig a H r n Forest er aB Souh StreathamEffr Hill t m h Eltham a c h n 3288-03/127 s a ew i r L B 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?.