SLP personnel directed the investigation of a fish kill incident on a large multi-use site in SE England. Operational landuses on the 5 sq. km site included two power stations, an Liquefied Natural Gas (LNG) storage facility, a deep-water port and an aggregates storage and distribution depot. Former landuses on the site included a large Oil Refinery and various Ministry of Defence activities.

The lowland site was characterised by numerous drainage ditches, draining under gravity and via mechanical pumping, into large surface water holding lagoons, which in turn discharged under licence into the adjacent river estuary. A fish kill incident was reported in one of the surface water holding lagoons and the landowner (National Grid) commissioned an investigation into the cause of the incident. SLP personnel directed the design and implementation of a post-event monitoring regime with the ultimate objective of ensuring that measures could be put in place to stop such an incident happening again.

A comprehensive survey of the sites drainage system identified the sampling locations that would best deliver the objective and a comprehensive field monitoring and sampling exercise was undertaken in accordance with a multiple lines of evidence approach. Field monitoring was undertaken for selected key indicators such as pH, dissolved oxygen and redox potential and sediment and water samples were collected for chemical analysis for a wide range of organic and inorganic determinands.

The Environmental Agency were involved from the outset of the project and they approved the sampling plan prior to the field works commencing. The investigation revealed that the fish kill was the result of a contaminant release from one facility as a result of a faulty interceptor, and the fish had died as a result of oxygen depletion in the receiving water course. The operator responsible for the failure was identified and they paid for the necessary remedial works to the drainage system and the restock of the lagoon.