A toxic waste dump discovered in Limerick during excavations for the main drainage scheme has been linked to an environmental accident at the old city gasworks more than four decades ago.
The Environmental Protection Agency has been informed of the 100-tonne dump, which contains heavy metals and benzenes and which was discovered in a disused sewer under the city's Dock Road.
A clean-up operation will involve cutting into the Victorian culvert from the road and removing the sludge with machinery.
The discovery was made by engineers working on the €200 million main drainage scheme, which is expected to be completed by next year.
Analysis of the material, which was traced back to a tank which ruptured at the old city gasworks, revealed that it contains cadmium, chromium, arsenic, zinc, selenium and copper, along with sulphate, chloride and benzenes, a carcinogenic material.
Efforts have been made to get the exact date of the incident through the archives of the Limerick Leader newspaper.
Mr Séamus Ryan, project manager for Limerick Main Drainage, said the concentrations were enough to classify the material as toxic, but were similar to the residues found in road tar.
"It is a residual product in the manufacture of gas," he said.
At the time, gas was manufactured from oil and bitumen. The gasworks closed in 1987 and the site was taken over by Bord Gáis.
Mr Ryan said the waste was being removed on safety grounds and to avoid a hold-up in the construction of the Dock Road interceptor sewer, which will have a diameter of 2.8 metres.
The sludge is being removed for storage in metal barrels before being sent to a licensed German contractor for incineration.
The city manager, Mr Brendan Keating, said the city council was concerned. It would co-operate fully with the EPA in any investigation.
"We are particularly pleased that we have discovered it and are in a position to rectify the problem in the best and most appropriate environmental manner," he said.
The chief executive of the Shannon Regional Fisheries Board, Mr Eamon Cusack, said he was concerned about whether the sludge had been entering the river.
"We will be following up investigations on it. It is too late if the stuff has been entering the estuary, but we want to find out more about the exact cocktail that is there and how serious it is."