Thames Water has been setting out its proposals this month to build a new £280 million flood relief sewer for Counters Creek in London as part of its phase one consultation on the plans.

The water company has been holding a series of local exhibitions about the scheme during January – the final one is due to take place on Tuesday 27^th January at the Holland Park Ecology Centre.

Heavy rainfall in July 2007 caused widespread basement sewer flooding in Hammersmith & Fulham and Kensington & Chelsea. A number of properties also flooded during storms in 2004 and 2005, with some residents reporting sewer flooding up to six times in recent years. To date customers in over 1,700 basement properties in the area have been assessed to flood due to the overloaded sewer system.

Thames Water plans to connect the existing sewers running through the Counters Creek catchment into the proposed storm relief sewer at the following five locations, known as interception sites:

• Kensington Olympia - The proposed drive site and an interception site for the storm relief sewer.
• 5* Car Wash Shepherds Bush - A proposed interception and reception site.
• Upper Addison Gardens - A proposed interception and reception site.
• Mund Street - A proposed interception site.
• Cremorne Wharf - The proposed reception, interception, pumping station and combined sewer outfall site.

The selection of the proposed route and sites for the construction of the new storm relief sewer was a multistage process, with some stages happening in parallel - as the engineering team refined a proposed route this fed into the sites selected for further study.

Initially, Thames Water used a computer model to identify how the sewer system works in the Counters Creek catchment. From this, the team identified where flows in existing sewers need to be intercepted by the proposed storm relief sewer. The work confirmed that it would not be possible to capture all the flows entering the proposed sewer in the most extreme storms.

As a result Thames Water needs to retain the ability to pump sewage into the River Thames (or potentially the Thames Tideway Tunnel when operational), as a last resort to prevent flooding at properties. The water company therefore needs to connect the proposed sewer to a pumping station and a sewer outfall point.

The proposed storm relief sewer will collect excess storm water from the five interception sites and store the flows until the storm has passed. Once flows in the sewer network return to normal, the storm water will be pumped back into the sewer network and onwards to Beckton Sewage Treatment Works in east London.

The interception sites also define where Thames Water will need construction sites to build the storm relief sewer.

Running from Shepherds Bush down to the River Thames, the proposed storm relief sewer will be approximately five kilometres long, four metres in diameter and at its deepest point the sewer will be almost 40 metres underground. The sewer will in effect act as a giant reservoir which will absorb surplus water until there is enough capacity to drain the rain water into the rest of the network.

Subject to achieving planning permission later this year, the construction phase of the project is planned to start in late 2016 and finish in early 2020.

Phase one of the consultation closes on 8^th February 2015. Click here to access the consultation online.