A major fish kill on a tributary of the River Shannon happened just days after maintenance work at a licensed landfill site operated by Limerick County Council, according to an environmental report, writes Karl Hanlon.
The interim report, which was commissioned by the local authority following the fish kill in May, said the timing of the incident "inevitably focused attention" on work carried out by the local authority on surface-water settlement tanks.
An investigation was launched into the cause of the fish kill after up to 1,000 adult brown trout were found dead on a stretch of the White River between Gortadroma and Ballyhahill in Co Limerick.
Up to 5,000 salmon smolt which were recently placed in the river were also feared dead following the suspected pollution incident in May.
Local people have expressed anger that years of hard work to develop the potential of the White River as a destination for anglers may have been in vain.
Investigations carried out into the cause of the fish kill have concentrated on a stretch of river near Gortadroma dump, a licensed landfill site operated by Limerick County Council since 1990.
An interim report carried out by Enviros Consulting Ltd on behalf of the local authority has found the fish kill happened immediately after annual maintenance works carried out by council staff at the landfill site.
The works involved the discharge of water from the upper part of surface settlement tanks to the White River, and the removal of silt and water from the lower part of the tank to the tip head.
According to the interim report, river water samples analysed after the fish kill did not give any indication of the probable cause of the incident.
However, the report added that analysis of remaining water in the tank revealed high levels of ammonia which were probably high enough to cause the fish kill.
Previous high levels of ammonia in the water site have been traced back to the emission of leachate from old cells at the landfill, according to the report.
"There have been ongoing problems involving old cells at the landfill which are liable to release small amounts of effluent or leachate, and we are continually working to contain this," said a spokesman for Limerick County Council.
The report added that future maintenance works on the surface water settlement tank at the landfill would be carried out "in accordance with best practice procedures with due regard to weather conditions and flow conditions in the White River". It added that the council has agreed to assist with restocking the affected portion of the river following the fish kill.
Locals in west Limerick have voiced strong concerns about Gortadroma dump since it was first opened by Limerick County Council in 1990.
Shannon Regional Fisheries Board is also investigating the recent fish kill, and a spokesman said yesterday its report would be completed within weeks.