In 1980, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act, giving the US Environmental Protection Agency the authority to clean up the most contaminated sites in the country. EPA was authorized to go after the owners and operators of contaminated sites, and the generators and transporters of the hazardous substances at those sites, and compel them to pay for the cleanup of their sites. For those sites where the responsible parties couldn't afford to cover all the cleanup costs, Congress also provided a funding source: the billion dollar "Superfund" that gives the program its name. This source of funding has changed over the years, and has relied on Congressional appropriations since 1995, when Superfund taxes levied on petroleum and hazardous substances expired.
To determine if a site qualifies for cleanup under the Superfund program, EPA scores the site using the Hazard Ranking System. The HRS takes into account the volume and toxicity of the contamination, and the number of people that may be affected by it, and generates a score from zero to 100. Sites that score above 28.5 qualify for listing on the NPL. Under CERCLA, the Superfund can only be used to clean up sites on the NPL, unless the cleanup is an emergency response. The following sites in Oregon are listed on the NPL as of March 2015.