The leak caused a national furore last autumn (ENDS Daily 21 October 1997). It has led to temporary bans in several countries on sales of the Rhône Poulenc sealant used in the tunnel and a swathe of technical, judicial and criminal investigations, all of which are still continuing.
Initial concern over the toxic effects of acrylamide has abated. In January the Swedish Environmental Protection Agency (EPA) reported that acrylamide levels had rapidly declined in drinking water wells around the tunnel site in the Halland's ridge close to Helsingborg. Toxic effects "are not long-term in nature, nor will they spread over a larger area," the EPA said.
Interviewed by ENDS Daily today, Gunnar Gozikowski, chief government inspector for drinking water went further. "It was never a catastrophe," he said. "The risk was very small, even in the beginning, but we have a policy that drinking water should not be contaminated, even at low levels."
Three wells in the area remain contaminated with acrylamide, according to officials, and substantial quantities of acrylamide are still in groundwater around the tunnel shaft in which 1,400 tonnes of Rhoca Gil sealant were applied, some 10% of which failed to set properly.
A massive clean-up operation has been launched to remove acrylamide from groundwater around the tunnel, led by Sweden's National Rail Administration. During February, 1,600 boreholes were drilled from the affected tunnel into surrounding rock, from which 1,300 cubic metres of water a day are being extracted for ozone treatment to destroy the acrylamide.
The operation is going well, a rail administration official told ENDS Daily today, and received approval last week from an independent expert committee. "A lot of acrylamide broke down [naturally] before we started cleaning up," said Christina Held. "With the amount of acrylamide left in the mountain we expect to complete the clean-up by the summer."
Meanwhile, concern is now focusing on physical effects on the area's water table, which has been drastically lowered by leakage into the unsealed tunnel, a phenomenon made worse by the clean-up operation. Previously close to the ground surface, the water table above the tunnel has fallen 100m, according to an EPA official, with effects spreading 1.5km each side of the tunnel.
Much of the Halland's ridge above the tunnel is classified as a local or national nature reserve, the official said, commenting that the drop in water levels could have serious ecological effects, as well as depriving farmers of groundwater supplies.
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