Contaminated Sediment in Wandsworth – When Testing Pays Off

Removal of the Wandle half-tide weir

 

A recent article in Dredging and Port Construction reported that silt build-up over 25 years at the Wandle tidal weir in Wandsworth was not only affecting the habitat for fish and wildlife but also a peaceful, open area for the public.

 

With backing from the Environment Agency, Marine Management Organisation, Port of London Authority and Wandsworth Borough Council, Thames Water has removed the tidal weir, sludge and silt.

 

This is part of its improvement work to offset the impact of construction of the Tideway tunnel.  The tunnel is a major new sewer that will help tackle the problem of overflow from the capital’s Victorian sewers and will protect the River Thames.

 

The weir site had been classed as fully contaminated but new testing using amphibious craft by Land &Water (a specialist dredging and remediation organisation and a TEP member) revealed that 85% of the material was non-hazardous. This totally changed the way the project was handled.

 

The clean dredged material was transported by barge to Land &Water’s site at Rainham Marshes in Essex, formerly a military firing range and now a protected Site of Special Scientific Interest.

 

The hazardous material was segregated and sent to a hazardous waste treatment centre in Cambridgeshire, thus minimising the environmental impact of transport for disposal. The reclassification also considerably reduced the financial impact.

 

Source: Slinn, Tony. 2017, Contaminated sediment- when testing pays off.  Dredging and Port Construction.