Investigators found 336 illegal spills in the seven years to March 2020 at the firm’s Bodmin sewage works. Sewage reached the River Camel, a protected conservation area known for Atlantic salmon, otters and bullhead fish.
Untreated sewage was released 231 times between 2016 and 2021 at Harlyn beach in Cornwall, which is popular with families and tourists.
South West Water pleaded guilty to six illegal spills at nearby Holywell sewage pumping station.
Sewage flowed into Hooe Lake in Plymouth for 88 hours over a bank holiday weekend from 28 August to 1 September 2020 after a failure at the pumping station there.
Clarissa Newell, the Environment Agency’s environment manager for Devon and Cornwall, said: “Getting to this point and securing these guilty pleas was only possible thanks to years of thorough investigation and hard work by Environment Agency officers.”
The Environment Agency continued to do everything in its power to ensure “polluters must pay”, she said.
South West Water said the charges related to “historic matters between 2015 and 2021” and it had invested significantly since then, preventing more than 8,300 spills and cutting storm overflow use by 17% in the past year, with spill duration down by 25%.
It said upgrades had been made at the sites involved and it had worked to remove surface water and illegal connections from the network.
A spokesperson apologised “for what happened in the past” and said the firm remained focused on delivering cleaner rivers and seas.
South West Water was fined £2.15m in 2023 for similar pollution offences.
