In 1952, the City of Fribourg abandoned the Pérolles trench as a landfill for household refuse in favour of the La Pila site. This site was used until the former Châtillon landfill became operational in February 1973. The current owner of the site is the State (canton) of Fribourg. The area of the landfill has been covered since 1975, is partially forested and covers an area of about two hectares. Since 2004, the La Pila site has been thoroughly investigated in application of the federal ordinance on the remediation of polluted sites. The results show that the old La Pila landfill contains mainly municipal waste (household waste, bulky items), construction site waste and commercial and industrial waste. The latter is in the form of capacitor waste, which is very heavily contaminated with PCBs. The waste also entered the Sarine, which led to fish being contaminated with PCBs. The high concentrations of PCBs detected led to a ban on fishing in the Sarine between the Rossens and Schiffenen dams on 29 August 2007.
At its meeting of 2 October 2007, the State Council adopted a decision to organise the project for the remediation of the former La Pila landfill. Between 2012 and 2014, CSD prepared and implemented the preparatory measures for the partial remediation, which were aimed at removing the highly contaminated material in the Sarine bed and preventing the discharge of pollutants into the Sarine. Further investigations in the Sarine carried out by CSD in 2016 showed the success of the measures implemented: in 2017, fishing was allowed again, though with restrictions.
On the basis of these investigations, CSD worked out 4 remediation variants that would have a sufficient impact on emissions from the former landfill and thus on the quality of the Sarine (water, sediments, fauna). In 2021, the State Council determined partial remediation (decontamination through excavation) as the optimal remediation variant. This measure allows the removal of around 85% of the PCB mass or 65% of the volume of the landfill. In 2022, CSD prepared the preliminary project for the remediation.