Asda Stores Ltd was convicted on Tuesday at Belfast Magistrates Court of causing pollution to the Six Mile Water River at Ballyclare.
Asda pleaded guilty and was fined a total of £7,500 plus £15 Offender Levy.
Detailing the incident, a Department of Agriculture, Environment and Rural Affairs (DAERA) statement read: “On February 11, 2019 a water quality inspector (WQI) acting on behalf of the Northern Ireland Environment Agency (NIEA) and duty emergency pollution officer (DEPO) responded to a number of reports of oil present in the Six Mile Water at Ballyclare.
“The inspectors began to investigate the report of pollution associated with a spill of red diesel fuel on the Asda Ballyclare site. Together with representatives from the Northern Ireland Fire and Rescue Service, the NIEA officials inspected the delivery yard where the spill of red diesel had occurred.
“The NIEA officials observed two integrally bunded tanks adjacent to a large generator, fuel oil/red diesel was observed on the ground surrounding the tanks.”
The department added: “A site drainage channel was located to the rear of the tanks. The overflow from the bunded area at one of the tanks was the source of the problem.
“The NIEA officials and NIFRS proceeded to a culvert discharge to the Six Mile Water adjacent to the Sixmile Leisure Centre car park where they observed red diesel actively discharging to the river.
“NIEA officials deployed oil absorbent booms preventing further discharges of oil to the river. The oil interceptor within the Asda site was emptied by a clean-up company, who also carried out a cleanup and remediation of the affected area adjacent to the impacted culvert.
“In accordance with procedures a statutory sample of the red diesel was collected and analysed.”
In a statement, a spokesperson for Asda said: “We work hard to help protect the local environments in which we operate and take our responsibilities very seriously. This was an isolated incident that was caused by an accidental spillage and we would like to reassure local residents that immediate action was taken to fix the issue.
“The spillage was contained to a very small area and the river was not contaminated. We are sorry for any upset or inconvenience this has caused and also thank our colleagues for their prompt action to help resolve the issue.”