The site selection methodology document sets out a process for selecting a “long list” of potential sites for the construction of nearly 40km of deep tunnels that will act as storage and intercept 36 of London’s 57 combined sewer overflows (CSOs).
These sewers deposit 32M.m2 of storm sewage discharge annually into the River Thames.
Deep shafts will be needed for access near each of the CSOs, which run broadly along the alignment of the river Thames. These connect with the deep tunnels.
The methodology will be used to choose and consult on the location of all the CSO tunnels as well as between three and five main shafts that will need to be excavated for the main tunnel boring machines (TBMs). The TBMs will dig 7.2m diameter tunnels under London.
The coming months will see a long list of possible locations for the tunnel which will run from West London to the sewage treatment works in Beckton, East London. Thames Water will then choose a shortlist, said head of the London Tideway Tunnels delivery team Phil Stride.
This list will then go out for further consultation before a “preferred list” of sites is selected and, from that, a “final list”.
“It is a long robust process,” Stride said. “And one that is naturally very iterative, as consultation will lead to changes in design which will, in turn, create new options and so forth.”
The 12 to 18 months of discussions and consultation will not affect the overall timing of the scheme, Stride said, which is due to begin in 2011 and complete in 2020.
Some 26 bodies involved in city administration, including 13 boroughs and 13 other bodies such as the London Mayor’s office, the Olympic Delivery Authority, Network Rail and the Government Office for London are being consulted.