[loripo]

Thames Water are overseeing a huge project to build two new super sewers beneath the Lee and Thames rivers, provided that planning permission etc is granted. Their website says that
The Lee Tunnel, which is the first of two huge tunnels planned over the next ten years - it
will cut in half the 32 million tonnes of storm sewage that currently
overflows into London’s rivers each year. The Government announced its decision to support the London Tideway Tunnels in March 2007.
The proposed Thames Tunnel - the bigger and more complex of the two tunnels - will run 20 miles from west London to east London, helping to prevent discharges from 34 Victorian overflow points along the River Thames. A planning application is expected to be submitted in 2011 and it is hoped the tunnel will be completed in 2020. Extensive investigation works are currently under way to identify the most suitable route for the tunnel and the ground conditions engineers will encounter during tunneling.


A series of boreholes to test the rock layers beneath the Thames have already been made from Barnes to Barking.
Possibly the material removed during this project might also be used to build up the island...