Define the Hazard Ranking system (HRS)

- A procedure for ranking uncontrolled hazardous waste sites in terms of the potential threat based upon the containment of the route of release, hazardous substances, characteristics and amount of the substances, and similarly targets.

- Represents the relative hazards posed by a site and potential for human and environmental exposure.

- The Hazard Ranking system score is based on the probability of contamination from four pathways - groundwater, surface water, soil and air.