Development of improved risk assessment tools for prioritizing hazardous and radioactive-mixed waste disposal sites

It is the intent of all environmental regulations to minimize the risks to man and his environment that arise from a regulated activity. Because lower levels of risk are generally accompanied by higher environmental control costs, optimum management is achieved by balancing risks and costs. Currently, the US Environmental Protection Agency employs the Hazard Ranking System (HRS) to evaluate the environmental risks associated with inactive hazardous waste sites for the purpose of establishing the National Priorities List. Recently, investigators modified the HRS to more realistically evaluate the risks posed by radioactive waste constituents. Although results from applying the modified HRS will be useful for comparing the priority of DOE sites to non-DOE sites, the methodology is still overly subjective. To provide DOE with a better management tool for prioritizing funding allocations for further site investigations and possible remediations, Pacific Northwest Laboratory is developing a more objective, scientifically based, risk assessment methodology called the Remedial Action Priority System (RAPS). This methodology will be developed using empirically, analytically, and semianalytically based mathematical algorithms to predict the potential for contaminant migration from a site to receptors of concern using pathways analyses. Four major pathways for contaminant migration will be considered in the RAPS methodology: groundwater, overland, surface water, and atmospheric. Using the predictions of contaminant transport, simplified exposure assessments will be performed for receptors of interest. The risks associated with the sites will then be calculated relative to other sites for each pathway and for all pathways together. The RAPS methodology will require minimum user knowledge of risk assessment and the least possible amount of input data, and is being designed to operate on a personal computer. 17 references, 3 figures, 1 table