Upper Valais completes mercury-contaminated soil clean-up

The canton of Valais has completed the clean-up of mercury-contaminated soil in residential and agricultural areas of the Upper Valais, SRF reported on Tuesday. Individual plots will be remediated later as part of planned construction projects.

The work removed 3,531 kilograms of mercury from the soil. Lonza remediated more than 100,000 square metres in residential areas by excavating contaminated material and replacing it with clean soil. Around 66,000 square metres of agricultural land were also treated.

The contamination came to light in 2010 during construction work on the A9 motorway. Until the 1970s, the then chemical company Lonza had discharged more than 30 tonnes of mercury through an open wastewater channel. Some of the mercury settled in the channel, and farmers spread the resulting sludge on fields as fertiliser, contaminating neighbouring plots as well.

Authorities then examined the soil between Visp and Niedergesteln and identified the affected plots, including gardens and playgrounds. Lonza, the canton and the affected municipalities developed a clean-up strategy. Pilot projects began in 2016, followed by systematic remediation in 2017 in residential areas where the soil contained more than two milligrams of mercury per kilogram.

The canton government said the main objectives had been achieved, describing the completion as an important milestone. Environmental organisation WWF and the Association of Doctors for the Environment welcomed the result as a major success for the environment and the health of the Upper Valais population.

However, further work remains, including the clean-up of the Lonza landfill at Gamsenried and the Grossgrundkanal, a canal in Raron that carried Lonza’s wastewater and has not yet been remediated.

Josef Kämpfen, who owns a house in Raron, said he was informed in 2014 that the soil around his property was contaminated. Workers removed up to two metres of soil in some places because the mercury had penetrated deeply. Kämpfen said he had initially feared the contamination would reduce the value of his house, but now considers the matter closed: “I don’t think about the mercury anymore.”