County Environmental Services ran a leachate treatment plant at the site. On the day of the incident, an operator let a treatment tank overflow, spilling leachate into a bunded area. The bund did not have impermeable walls and the leachate leaked into a tributary of the Connon stream killing more than 100 trout.
The company did not report the incident to the Environment Agency, despite being required to by its waste management licence.
Samples taken from the stream showed it to have ammonia levels more than fifty times above the permitted levels.
Appearing before East Cornwall magistrates on 16 May, the company pleaded guilty to one charge of causing polluting matter to enter controlled waters, contrary to section 85(1) of the Water Resources Act 1991, and to two of breaking conditions of its waste management licence contrary to section 33(6) of the Environmental Protection Act 1990.
It was fined £15,000 in total and made to pay £2,264 in costs.
This was not the first incident to occur at the site. Last August, County Environmental had to pay more than £58,000 for odour offences at the site (ENDS Report 380, pp 47 ). And in 2004, the company was fined more than £13,000 for polluting a river with silt (ENDS Report 354, pp 66 ).