London Tideway Improvements. Richard Aylard

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1 London Tideway Improvements Richard Aylard

2 The lost rivers of London

3 The Great Stink, 1858

4 Bazalgette s interceptor sewers

5 Victorian sewer network Outstanding feat of engineering that has stood the test of time and still serves our capital today. System struggling to cope with the demands of a 21st century city, which has trebled in size and continues to grow. Every year we lose an area of natural drainage equivalent to the size of two Hyde Parks. Upgrade of basic infrastructure essential for long-term health, well being and prosperity of London.

6 Combined Sewer Overflows (CSOs)

7 Combined sewer overflow in action

8 Tidal Thames dissolved oxygen The decline Dissolved Oxygen % Saturation Km from London Bridge

9 Tidal Thames dissolved oxygen

10 Cumulative fish species recorded in Tidal Thames (Fulham Tilbury) Cumulative Species Number

11 June 2011 pollution 30mm of rainfall on June resulted in around 450,000 tonnes of sewage discharging into the river from Mogden sewage works and west London CSOs.

12 Aquatic ecology study Fish and invertebrate surveys are done at sites where works are proposed on the foreshore, as well as control samples Assessment of the benefits and impacts of the Tunnel Field sampling programme Baseline surveys Juvenile fish surveys Novel modelling techniques informing assessment of impacts on fish

13 Key facts and findings 125 species of fish known to occur in the Tideway Low dissolved oxygen events can cause 90% mortality of sensitive species (e.g. smelt, dace, salmon) Juvenile fish surveys added to current understanding of dissolved oxygen related fish mortalities

14 Why tidal flows are important

15 Thames Tideway Strategic Study

16 Solutions? Action before sewer: Source Control and Sustainable Urban Drainage Systems (SUDS) Within sewer network: Localised storage and separation In-river: More Bubbler and Skimmer vessels Intercept overflows: Central storage and transfer

17 London Tideway Improvements Two problems: Three solutions: Overloaded sewage works: Frequently discharging storm sewage into the river after heavy rainfall Overloaded sewer network: Frequently discharging storm sewage into the river via Combined Sewer Overflows (CSOs).

18 Tackling the biggest CSO first The four-mile Lee Tunnel will tackle discharges from the largest overflow at Abbey Mills in Stratford, which accounts for 40 per cent of the total discharge. That's why we're dealing with this, the worst one, first. It will intercept 16 million tonnes of untreated sewage currently discharged into the River Lee annually. Construction is under way and due for completion in The 635m project is the largest in the UK water industry since privatisation in 1989.

19 Upgrading London s major sewage works We re investing 675m to upgrade London s five major sewage works - Mogden (pictured), Beckton, Crossness, Riverside and Long Reach. We are increasing the amount of sewage each site can treat, and improving the standards to which it is treated. This will significantly reduce storm discharges into the River Thames, improve river water quality and improve dissolved oxygen levels in the River Thames, resulting in significant ecological benefits. Construction is well under way. All upgrades are due for completion by 2014.

20 The Thames Tunnel Final and most complex of the three schemes Up to 20 miles long, tackling the 34 most polluting combined sewer overflows along the River Thames. A second phase of public consultation on the preferred tunnel route will start next month for 14 weeks.

21 London Tideway Improvements map

22 Timeline 2000 Thames Tideway Strategic Study commenced 2006 Report to Government 2007 Minister s decision on Thames Tunnel and Lee Tunnel 2009 Ofwat approve funding for Sewage Works Upgrades 2012 Thames Tunnel application for planning consent 2012 Long Reach and Riverside Sewage Works upgrades complete 2013 Mogden Sewage Works upgrade complete 2014 Lee Tunnel complete 2014 Beckton and Crossness Sewage Works upgrades complete 2020 (tbc) Thames Tunnel due for completion

23 Reasons to act now Doing nothing will mean: Continued overflows, causing environmental damage. Continued health risk to river users. Continued adverse impact on attractiveness of river frontage. Risk of heavy fines being imposed on the UK. Without the London Tideway Improvements, the annual CSO discharges would reach 70 million tonnes in a typical year by If the Thames Tunnel is built it will still be functioning in the 22nd century.