In general, the tunnel needs to follow the route of the River Thames so that it can be connected to the combined sewer overflows (CSOs) that are located along the riverbanks.
Following the route of the river also means that we can make use of the River Thames itself to transport materials and minimise the number of existing buildings and structures that the tunnel will pass beneath.
This route option follows the same route as Options 1 and 2 from west London as far as Limehouse but then it turns northeast, running more than 50 metres beneath the London boroughs of Tower Hamlets and Newham to Abbey Mills Pumping Station near Stratford, where it connects with the Lee Tunnel. (The Lee Tunnel is to run from Abbey Mills Pumping Station to Beckton STW and will be completed in 2014.)
This option is up to 9 kilometres shorter than Options 1 and 2 and therefore considerably cheaper.
Our studies show that even though it would capture slightly less sewage, the overall river water quality would still be much improved and meet the project objectives set by the Environment Agency.
Option 1 - River Thames route
This route option follows the River Thames from west London to the Greenwich Peninsula, where it takes a shortcut below land. It then continues beneath the River Thames all the way to Beckton Sewage Treatment Works (STW) in the east.
This is the longest tunnel option. It would capture the most untreated sewage from the CSOs along the river, but would also be the most expensive.
This is the route that was recommended in the December 2006 report to Government.
Option 2 - Rotherhithe route
This route option follows the River Thames from west London as far as the Rotherhithe Peninsula, where it then passes below the land, before continuing along the River Thames, under the Greenwich Peninsula and then on to Beckton STW.
This route has the advantage of reducing the length of the main tunnel and would therefore make it slightly cheaper.
This option does not capture as much of the overflowing sewage as Option 1 as it is slightly shorter but it still improves the water quality of the River Thames.