Facts
In the 1990s, the Department of Construction, Transport and Environment of the Canton of Aargau initiated the investigation of the former landfills F., G. and [H.] in Untersiggenthal. On February 17, 2000, it assessed the site [H.] located on plot No. 1965 as requiring remediation. Subsequently, various investigation and monitoring measures were carried out.
On April 10, 2007, the then owner of plot No. 1965, B.B., requested the issuance of a cost-sharing order. By order of October 12, 2009, the Department imposed 25% of the costs on B.B. as the polluter in possession and 75% on A. Immobilien AG (formerly: [L.]) as the polluter in conduct.
Both B.B. and A. Immobilien AG filed appeals against this order. After the death of B.B. in August 2011, his heirs joined the proceedings. On April 13, 2016, the Department decided again on the cost allocation and ordered that the necessary costs of a total of CHF 4,884,697.50 be imposed 23.695% on the community of heirs, 1.305% on I. AG and 75% on A. Immobilien AG.
The community of heirs, I. AG and A. Immobilien AG filed appeals against this order with the Administrative Court. The court upheld the appeal of I. AG and amended the cost allocation, so that the necessary costs were imposed 76.305% on A. Immobilien AG and 23.695% on the community of heirs.
Considerations
According to Article 32d of the Federal Act on Environmental Protection (USG), the polluter bears the costs for necessary measures for the investigation, monitoring and remediation of contaminated sites. If there are multiple polluters involved, they bear the costs in proportion to their shares in the causation.
The Administrative Court qualified A. Immobilien AG (formerly: [L.]) as the polluter in conduct, as it, as the operator of the [H.] landfill, had not properly disposed of chemical waste, thereby leading to the endangerment of the groundwater and the need for…