AN environmental firm has been fined £12,000 for allowing silt and oil to be pumped into a Wycombe brook, killing a protected species.

Williams (Southern) Ltd, of Plymouth, let contaminated water get into Abbotsbrook, a tributary of the River Thames, in Bourne End.

This killed bullhead fish, a European protected species, and freshwater shrimp, a court was told.

Environment agency officer Cag Ketenci said: "It is quite ironic that this company caused harm to the environment while actually carrying out work to reduce the risk of this sort of thing happening."

The firm told the agency it had misread site plans which would have shown the tanks, for Shell Cressex service station Bourne End, would lead to the brook.

Residents reported what looked like diesel in the brook in 2006, prompting site visits by the agency on July 14 and 17.

It told the company to stop work - but officers were back on July 20 to investigate another report of pollution.

Officers noticed a strong smell of petrol' the agency said in a statement and the pollution had spead about a third of a mile downstream.

The firm was fined £12,000 and £2,836.16 costs at Wycombe Magistrates Court yesterday.

It admitted one charge of pollution contrary to the Water Resources Act 1991.

Cag Ketenci said: "Despite the best of intentions, by not assessing the risks of causing such problems properly, the company allowed diesel and silt to enter the Abbotsbrook, affecting fish such as bullheads and fresh water shrimp."

An Environment Agency statement said "Officers attending the site found a pipe leading from an exposed pit of contaminated groundwater, which had previously held petrol tanks.

"Water from this pit was being pumped into an oil interceptor connected to the surface water drain and then into the culverted stream beneath the site.

"The pit was being cleared so that modern tanks, which would improve the environmental safety of the site, could be fitted."

It said: "John Whittikar, the director of the company, later admitted in interview that the company thought the interceptor discharged to the foul sewer whilst the site plans showed the interceptor was linked to the culvert, which his staff had missed, despite the previous advice given by the Environment Agency."