More than 1,200 fish have been recorded as dead following a 'serious' pollution incident on a tributary of the River Ouse.
The Environment Agency said the fish - including sea trout, brown trout and coarse fish - died after around 20,000 litres of slurry entered Plumpton Mill Stream last week (Tuesday, November 29).
The Agency says its pollution officers were informed of the incident at around 8:15am the following day (Wednesday, November 30) and were able to reduce the impact of the pollution by holding the water flow at local weirs and oxygenating the watercourse by using aerating pumps.
Operations continued through to the weekend with the Environment Agency increasing the flow of water to move the remaining pollution downstream.
James Farrell, area duty manager at the Environment Agency, said: "As a result of early reports from the local community, we were able to respond quickly to reduce the impacts to fish and wildlife and stop the situation escalating into a much worse incident.
"Clearly we are very disappointed that so many fish have died, but we will work with local partners to help the environment recover. Members of the public are reminded to report any pollution incidents via our hotline: 0800 80 70 60."
Last week principal of Plumpton College Jeremy Kerswell said the leak was the result what appeared to be a mechanical failure on one of the college's agricultural slurry containers.
Later this week, a spokesman for the college said: "On the evening of November 29, the college was alerted to an emergency with one of its slurry storage systems, which inadvertently led to waste water and slurry running off the college fields and into one of the water courses.
"The college is naturally devastated by the continued impact this will have on the local environment. Action was immediately taken to ensure this was effectively contained on site, meaning there has been no further contamination into the stream since Wednesday morning and the watercourse is now running clear.
"The college has been working proactively with the Environment Agency (EA) over the last six months to improve the impact of its farming activity on the local environment. It has worked closely with the EA over the weekend to implement an action plan with its contractors to pump the majority of slurry out of the river Bevern before it reached the Ouse.
"The EA have recognised that this has had a significant impact on helping to reduce ammonia levels in the water. The college management team are currently conducting an internal investigation into this matter and will be working with their new farm manager to commission a full review of the farming practices and system at Wales Farm. This recent episode in no way reflects the teaching and learning practice across The college’s land-based provision.
"They will continue to work with the EA and their ecological consultants to monitor the streams on site and are planning to meet with representatives from the EA, the Ouse and Adur River Trust and other local groups in the coming week to discuss further ways in which they can proactively support the restoration of those areas affected."
The Environment Agency has previously worked closely with the Ouse and Adur Rivers Trust to improve the river environment in these important trout streams, including investment in eel passage and fish refuges.
A spokesman for the Trust said: "The lasting damage to all natural life from this incident will be immense and will take years to redress.
"The Plumpton College authorities admit responsibility and have said they are sorry. However, it should be borne in mind that this is not the first occasion on which they have polluted this stream. Since 2011 we have recorded eight previous pollution events from the college.
"We were told last year that they had refurbished their slurry management infrastructure and reviewed operational procedures so that these episodic pollutions would now cease. This is manifestly not the case.
"The fact that an educational institution involved in training farming students and also running a fisheries management course can show such a flagrant disregard for the environment beggars belief."
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