Comparative Risk Assessment: Tools for Remedial Action Planning

ABSTRACT The US Environmental Protection Agency (USEPA) has chosen over 500 hazardous waste disposal sites for the National Priorities List (NPL) under the Comprehensive Environmental Response, Compensation and Liability Act. The priority sites were chosen utilizing the Hazard Response System (HRS) model that was designed to numerically score the relative health and environmental risks at uncontrolled hazardous waste sites. Although the HRS model assigns three scores to a hazardous waste facility (migration, fire and explosion, and direct contact), only the migration hazard mode score was used as a criterion for selection of sites for the NPL. The migration hazard mode score is a composite of separate scores for the potential migration of contaminants by routes involving groundwater, surface water, and air. This paper discusses the details of the HRS, and by way of example some of the methodological limitations and inconsistencies in the model that limit its usefulness. For example, the HRS does not consi...