Thousands of litres of oil have spilled into the environment and polluted a rare chalk stream in London, officials have said.
The Environment Agency said an estimated 4,000 litres of oil had spilled into surface water drains and affected the River Wandle, a once-heavily industrialised chalk stream that has been revived and is now home to wildlife such as brown trout to kingfishers.
A spokesperson for the agency said: “On receiving reports of an oil spill on the River Wandle, officers were immediately deployed to limit damage to the local environment and working with the London Fire Brigade we have put in place measures to stop the leak.”
It is expected that the spill, thought to have come from a storage tank at a nearby bus depot, will affect the Wandle from Beddington to Wandsworth over the coming days.
The Environment Agency spokesperson added: “We are currently gathering evidence and assessing the environmental impact for our investigation, with the pollution source suspected to be a bus depot storage tank in Thornton Heath, Croydon.”
Brown trout have been reintroduced to the river (Alamy/PA)
The Wandle, which flows for nine miles from its source to the Thames, became heavily industrialised from the 17th to 19th centuries, suffering from severe pollution.
For many years the waterway was considered “ecologically dead”, according to the South East Rivers Trust, but there has been a considerable effort to clean up the river and it is now a popular walking trail.
It is home to brown trout, a key chalk stream species, which was re-introduced to the river, while the Wandle and surrounding habitats support wildlife including kingfishers, damselflies and bats.
Chalk streams are a globally rare habitat, most of which are in England, and face a range of threats including climate change, over abstraction of water and pollution from sources including farming, urban run-off and sewage.