In 1983, the State of Montana filed a natural resource damage lawsuit against the Atlantic Richfield Co. (ARCO) to recover damages for:
- injuries to the water, soils, fish and wildlife in the basin
- the public’s lost use and enjoyment of these injured resources
Since 1990, the Natural Resource Damage Program within the Montana Department of Justice has been responsible for performing the necessary natural resource damage assessments and pursuing the lawsuit against ARCO. The state has settled its lawsuit through a series of settlement agreements completed in 1999, 2005 and 2008. In addition to the lawsuit against ARCO, in 2008 the state completed settlements for the Mike Horse Dam site and in 2009, for the East Helena site.