Volunteer surveys expose widespread sewage leaks contaminating London’s rivers and streams

The Outpost Safari volunteer programme, run by the Zoological Society of London, surveyed 22.4 km of the River Brent and identified 44 polluting outfalls among 123 inspected sites, prompting emergency alerts to Thames Water for 15 high-priority cases. Similar inspections on the River Wandle found nine active leaks, including two severe ones, while the Ravensbourne and Pinn recorded 18 and 17 polluting outfalls respectively, with several severe incidents reported.

Misconnected household plumbing, often resulting from renovations, is the primary cause, affecting individual homes, blocks of flats and entire estates. Thames Water, supported by the Environment Agency, is deploying containment booms and aims to investigate reports within two hours, notifying owners to fix faults within a voluntary 12-week period. City Hall recently hired a full-time enforcement officer to focus on west London, where the Brent river suffers the worst water quality, described as “pretty disgusting” by project officer Ella Carbery-Tarrant.