Basin Mining Area

Superfund National Priorities List inclusion (status and HRS score shown above) is the EPA's formal designation that a contaminated site qualifies for long-term federal cleanup authority under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). A federal-facility classification means the site is owned or operated by a federal agency, which routes cleanup responsibility differently than a privately owned site.

"Construction Complete" (status shown above) is an EPA milestone marking that the physical remedy work is finished, not that the site has exited EPA oversight; long-term monitoring can continue afterward. Deletion from the NPL is a separate, later step the EPA takes only once it determines every planned response action is finished.

NPL listing is a cleanup-authority designation in the EPA record, not a quantitative health-risk score. HRS scores of 28.50 or above qualify a site for the NPL under the EPA screening model (toxicity, pathways, waste quantity, and affected population factors). For current site conditions and official community notices, see the EPA Regional Superfund profile and the Montana environmental agency.