On 17 September 2007, a chemical was accidentally flushed into the Wandle from Thames Water's Beddington sewage works. The chemical was being used to clean, but instead of being put back through the treatment works, it was accidentally put into the river. This resulted in over 2,000 fish of various species being killed. The company failed to tell the Environment Agency of the incident, as the site manager thought it wasn't important. 