The Downstream Defender® surface water treatment separator saved a precious part of London’s remaining medieval common from the threat of pollution from nearby highways.
The wetland habitat at Shortwood Pond, London, UK, is a chalk spring-fed pond with no outlet and a Site of Special Scientific Interest. It is home to endangered species such as the Brown Galingale plant and the Little Whirlpool Ramshorn snail.
Road drainage works in the 1970s directed stormwater runoff into the pond. In recent years increasing traffic had been causing a decline in water quality, with an increase in sediment smelling strongly of hydrocarbons. There was also no protection from a major spillage event.
A Downstream Defender® advanced hydrodynamic separator was installed to remove and retain sediments and sediment associated hydrocarbons. The captured pollutants are retained in the unit and are not washed out by high storm flows as they would be in conventional gully pots. The liquid hydrocarbons and floatable pollutants are also retained.
The project was completed within a tight budget and kept to a small footprint. Apart from chamber emptying, maintenance is minimal.
“… we have found the Downstream Defender® is ideally suited to protecting the pond, because it separates out and retains the sediments. We were able to oversize the Downstream Defender® to cope with 50 l/s (790 GPM) and help protect the site against future large storm events.”
David Funchal, Project Engineer, Mouchel