The canton of Valais announced progress on Monday in the cleanup of polluted sites. Its next major project will be the former Gamsenried landfill, one of the most complex polluted sites in the country. The first step will be to build a waterproof wall on the site by 2027.
Between 1918 and 1978, the Lonza company deposited waste from chemical production in the Gamsenried landfill (VS), located between Visp and Brig-Glis. Registered in the cantonal register of polluted sites, the largest landfill in Switzerland was classified in 2011 as a contaminated site requiring remediation. Five years ago, benzidine – a product with very high toxicity – was notably detected.
>> Read also: Benzidine levels exceeding limits in Gamsenried landfill (VS)
Protect the water table
Urgent measures were therefore taken, the canton recalled on Monday during a press conference. Ultimately, the sanitation of the premises will involve the construction of a new waterproof wall. This should make it possible to “secure the site”, so that pollutants “no longer flow into the rest of the water table downstream of the landfill”, explains the head of the environment department, Christine Genolet-Leubin in on 12:30 p.m. on RTS.
It will further reduce – by almost 100% – the flow of polluted groundwater outside the landfill. The “L”-shaped wall will be built between the highway and the railway tracks over a length of 1.3 kilometers, supporting the existing hydraulic barrier. It will be 80 centimeters wide and 30 to 32 meters deep.
Complex works
If authorizations are obtained, work will begin next year and last between 18 and 24 months. Provisions of 290 million francs have been made by Lonza, which will cover the cost of production. The old landfill, the entire site of which is the equivalent of forty football fields, should be completely cleaned up within one or two generations, the partners estimate. These speak of “complicated” work to be carried out.
Added to the size of the site and the complexity of the pollutants found is the geographical location. The area is crossed or bordered by the cantonal road, the motorway, the railway lines, a thermal waste recovery and treatment plant and even pylons.
Other sanitation
At a press conference, the canton and Lonza also took stock of the remediation of soil contaminated by mercury between Visp and Niedergesteln. The priority, namely the sanitation of inhabited areas, is “95% complete”, they said. There remain the plots which will be treated as part of future construction projects.
A third of the sanitation of the agricultural area has been completed. As for the third priority, namely the sanitation of the Grossgrundkanal, detailed studies are underway. Lonza discharged its mercury-laden industrial water there between 1930 and the mid-1970s. The pollutant accumulated in the canal’s sludge and sediment.
Radio subject: Emilien Verdon
Web adaptation: edel with ats
