Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) passed by Congress in 1980, the U.S. Environmental Protection Agency (EPA) was authorized to take remedial actions to clean up certain sites that are contaminated by hazardous substances. To cover the costs of cleanup, EPA was authorized to make the owners and operators of contaminated sites and the generators and transporters of the hazardous substances pay. The law also created a fund known as "Superfund" to help cover cleanup costs at sites placed on the National Priorities List (NPL) of seriously contaminated sites.

CERCLA allows EPA to undertake both short- and long-term removals of hazardous substances. If a hazardous waste release poses an immediate threat to public health or the environment, EPA can step in promptly. If a release is serious, but not immediately life-threatening, EPA can undertake long-term remedial response actions. Long-term actions can only be conducted at sites listed on the NPL.

To determine if a site qualifies for cleanup under the Superfund program, EPA scores the site using the Hazard Ranking System (HRS). The HRS takes into account the volume and toxicity of the contamination and the number of people that may be affected by it, then generates a score from 0 to 100. Sites that score above 28.5 qualify for listing on the NPL. The following sites in Idaho are currently listed on the NPL:

More information on Idaho 's Superfund sites can be found on EPA's National Priorities List Sites in Idaho Web page.