Appearing before Eastbourne magistrates on 16 June, the company pleaded guilty to causing sewage to enter Mill Ditch and Shine Water Lakes, contrary to section 85(1) of the Water Resources Act 1991. It was ordered to pay £897 costs on top of the £9,000 fine.
During a storm last October, a valve closed the sewer entering the pumping station, diverting water into a storm tank. The valve was supposed to open again when the flow rate dropped, but due to a mechanical failure, it failed to do so and sewage was diverted into the tank and into the river via an overflow.
The pumping station was visited by Southern Water personnel after the incident began, but they failed to notice the problem. It only came to light three days later when a member of the public saw dead fish along Mill Ditch and called the Environment Agency.
Tests later revealed the water to have ammonia levels of 40-50mg/l and a BOD level of 241mg/l, only slightly below the level for raw sewage. Over 70 fish died.
Southern has now been fined £57,000 this year for five offences.