Thames Water Utilities Limited has been fined £4m for discharging half a million litres of sewage into Seacourt Stream and Hinksey Stream in Oxford over two days in July 2016.
The discharge flowed for at least 3.5km along the streams, through a pub garden and past community allotments, causing the deaths of up to 3,000 fish.
The court heard that the company had failed to carry out essential maintenance in a sewer it knew was vulnerable to blockages. There was no system in place to identify blockages or pollution; the company instead relied on public observations.
The incident was reported to the Environment Agency by canoeists who found themselves paddling among dead fish in sewage. Senior officer Robert Davis said: “Sewage pollution was bank to bank and there was a foul stench [...] Among the dead fish, fisheries officers observed hundreds more on the surface, suffering and gasping for oxygen”.
The court also heard that, during a major sewer renewal project in 2012, Thames Water had opted for a solution that saved millions of pounds and, critically, relied on six-monthly sewer cleaning to prevent blockages. However, it had no documented programme for sewer maintenance, despite knowing of the maintenance requirement and the risk of blockage and pollution if this was not carried out.
The investigation found that the company had failed to adequately maintain this section of sewer for at least 16 years. The Agency had issued two formal warnings in February and March 2012 after earlier pollution from the same point due to a blockage.
The judge said: “This fine sends out a clear warning to the boards of all water companies – invest heavily in maintaining your sewers and don’t drop the ball when it comes to carrying out that maintenance. Incidents like this are preventable and are completely unacceptable, particularly at a time when the need to protect the water environment for wildlife and people has never been greater and when public consciousness on environmental matters is so high.”
This brings the total fines levied against Thames Water since 2017 to £32.4m, for 11 cases of water pollution in Oxfordshire, Buckinghamshire and Berkshire.