Hazardous Ranking System (HRS, US)
The HRS is a score attached to a site following an EPA preliminary assessment of the public health and environmental threat posed by a proposed NPL site. The HRS score reflects different dimensions of health and environmental risk potential. These include an assessment of: (1) the likelihood that a site is already releasing or has the potential to release toxins into the environment; (2) the characteristics of the kinds of hazardous waste on site, including their potential to interact and produce more serious threats; and (3) whether there are human populations or sensitive environmental areas or assets that may be affected by releases from the site.
In making these assessments, EPA examines the ways in which hazards at a site may migrate from that site, and the possible environmental mediums involved. This includes assessment of ground/drinking water migration, surface/drinking water migration, soil exposure likelihoods for nearby residents and sensitive ecosystem areas, and the potential for toxins on the site to migrate in the air.
When a proposed NPL site receives a score of 28.5 or higher on the HRS, the site is placed on the NPL.