MORE than 100 fish were killed when chlorine from a water treatment plant leaked into a brook.

Blackburn magistrates heard that North West Water were responsible for the treatment works at Revidge from which extremely high levels of the chemical escaped as a result of a "foreseeable and preventable" incident.

North West Water pleaded guilty to causing polluting matter to enter controlled waters at Sholey Brook at Wilpshire and was fined £12,000 and ordered to pay £2,188 costs to the Environment Agency which brought the prosecution.

Sue Tysoe, prosecuting, said brown trout and bullheads had died as a result of the pollution in May.

Environment agency investigators traced the course of the chlorine to a drain which fed into the brook close to Knowsley Road. When they went to the water treatment plant at Ramsgreave they found a pink liquid, smelling strongly of bleach or chlorine, which was spilled in an area surrounded by a stone wall. The investigators discovered that the liquid was added to drinking water to purify it and that over the weekend it had leaked from a faulty valve and into the walled area. From there it had gone down a drain which connected with the surface water drain nearby and eventually ran into the brook. Miss Tysoe said the incident was foreseeable and preventable.

She said. "The walled area should have formed a water tight barrier and the fact that the value failed is something that could have been considered a possibility. The operatives on site clearly had inadequate instructions and knowledge of the drain and did not know there was a direct link to the surface water drainage system."

Angela Muston, for North West Water, said the company took its environmental responsibilities seriously and had reacted swiftly to resolve the problem at Ramsgreave. She said the equipment had been fitted at Ramsgreave by contractors and the eventual spillage had been the result of one value seal failing, an alarm not been connected and a second seal being missing.

"As a result the chemicals leaked into a containment area which the staff believed to be a bund," said Miss Muston. "The employees believed that the drain was a self-contained sump and that the spillage had been contained."

She said that since the incident the correct seals have been fitted to the equipment, all alarms are working and the drain has been removed.

"North West Water accepts that it made mistakes that lead to this accident but, because of the modifications made at Ramsgreave, the company is confident this incident will not be repeated," she added.