South West Water has been ordered to pay £65,000 in fines and costs for illegally discharging aluminium chloride into the East Looe River, Cornwall.

The case was brought by the Environment Agency.

On August 22, 2010 an Agency officer visited Lodge Hill Sewage Treatment Works near Liskeard and was told, by a member of staff, there had been a chemical spill at the site the previous day.

The day after the spill the Agency received reports of a fish kill in the East Looe River.

More than 300 sea trout, trout and salmon were found that day over a four mile stretch downstream of the sewage treatment works.

However in view of evidence of a possibly lethal, and completely unrelated sag in dissolved oxygen levels in the water the preceding night, following extensive analysis, tests and research, it wasn’t possible to prove conclusively the cause of the fish deaths.

Known as ‘Claral’, the chemical is used to improve the quality of the final effluent before it leaves the works. The yellow liquid is corrosive and hazardous and must therefore be stored in a bunded tank to minimise the risk of it escaping into the environment. Claral is toxic to fish at particular concentrations.

At Lodge Hill, the chemical is pumped from a tank and into the sewage treatment process via a small pipe. The storage tank is surrounded by a concrete bund with a sealed drainage system that feeds back into the works.

A court heard how at lunch time on August 21, a South West Water operative went to check the level of aluminium chloride and noticed a pipe had broken. He turned off the valve and called for an engineer to fix the broken section of pipe.

Some months later, after examining the chemical storage area more closely, South West Water discovered it was possible for any of the chemical which had spilled outside of the bund to drain to a buried manhole via two perforated power cable conduits. This meant any spill could find its way into the East Looe River. The water company notified the Environment Agency of its discovery.

It is not known how much aluminium chloride reached the river. South West Water should have kept records of its use of Claral and the amount stored at the treatment works, but it didn’t and failed to follow its own storage procedures, the court was told.

‘The toxic nature of aluminium chloride places a special responsibility upon water companies and other users of this chemical to ensure this chemical is handled and stored with great care. Every effort should be made to minimise the risk of it escaping into the environment,’ said Rob Hocking for the Environment Agency.

South West Water of Peninsula House, Exeter, was today fined £15,000 and ordered to pay £50,000 costs after pleading guilty to an offence under the Environmental Permitting Regulations 2010.