Congress passed the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) in 1980. The word Superfund comes from a provision in the original CERCLA that raised funds for cleanups by taxing certain petroleum and chemical companies. CERCLA gives EPA the authority to investigate and address threats posed by abandoned hazardous waste sites. It also gives EPA the authority to identify parties responsible for the contamination and compel them to pay costs associated with cleanups and risk reduction.
As part of the Superfund process, investigators collect samples of soil and groundwater at, and usually in the vicinity of, sites under evaluation, looking for hazardous chemicals. Of particular interest are chemicals that have or may reach receptors (for example people drinking water from contaminated wells, or children playing in yards). Information about site-related chemicals and receptors goes into a complex formula, called the hazard ranking system (HRS), that generates a score for each site.
Sites with scores of 28.5 or higher may go on the National Priority List (NPL). However, there are many Superfund sites that are not on the NPL. Some proceed under the Superfund Alternative Approach. Others proceed under state supervision, or achieve cleanup through an emergency action that results in immediate removal of contamination. The ultimate goal of all of the processes is to implement a remedy that adequately addresses risks associated with the chemical release at a site. EPA deletes sites that have adequately addressed risk from the NPL, a process called delisting.