Remediation Contaminated site hazard in Bottmingen BL is averted 33 years after the accident

The remediation work on the Wuhrmatt site in Bottmingen BL has been completed after two years. The solvents in the subsoil have been reduced to such an extent that there is no longer any danger to the environment. This was announced on Thursday by the Basel Cantonal Department of Building and Environmental Protection (BUD). Two accidents in 1991 had contaminated the soil.

For safety reasons, the groundwater and soil air will continue to be monitored regularly over the next two years.

For the remediation of the contaminated solvents, the groundwater was lowered in stages from May 2022. The pollutants were removed from the ground using a soil vapor extraction system. Filter systems then cleaned the pumped-out groundwater and soil air, preventing excessive odor and noise pollution, according to the press release.

Hundreds of liters of solvent leaked during two accidents

The remediation facilities were able to reduce the concentration of pollutants in the groundwater and soil air to below the legal limits after around 15 months of operation.

The authorities discovered the solvent contamination on the site back in 1997. They were caused by two accidents six years earlier. In each case, several hundred liters of solvent leaked from a degreasing bath and partially seeped away. As a result, the groundwater and subsoil were permanently contaminated.

Reasons for the long period of time until remediation

The reason for the long period of time between the accidents and the remediation is that there were no established procedures for dealing with solvent damage throughout Switzerland at the time, as the BUD wrote in response to an inquiry from the Keystone-SDA news agency. These were first developed a few years later. In addition, the canton also had to reach an agreement with the affected parties in accordance with the cooperation principle of the Contaminated Sites Ordinance, which was very time-consuming, writes BUD.

The costs for the remediation amounted to around one million francs, which was 400,000 francs below the original estimate. The owner bears 30 percent of the costs, the canton and federal government 70 percent,

SDA