A FRAMEWORK FOR RISK ASSESSMENT OF DISPOSAL OF CONTAMINATED MATERIALSTREATED BY SOLIDIFICATION STABILIZATION/

Quantitative risk assessment is a tool used at hazardous waste sites t o evaluate the need for treatment and to determine which control strat egies should be implemented. A general approach to conducting quantita tive risk assessments at contaminated sites is reviewed and a framewor k for applying it to evaluating risk associated with groundwater conta mination by disposal of materials treated by solidification and stabil ization is presented. This approach is based on a material balance aro und the disposal zone and the groundwater flowing past it. Two limitin g cases are identified that can control the concentration of contamina nt leaving the leaching zone. The first case occurs when the leachate flow past the solid is low and the contaminant concentration in the le achate can approach that in equilibrium with the pore water in the sol id. The second case occurs when the flow past the solid is sufficientl y large that the concentration of contaminant in the flow is low enoug h that the rate of leaching is not affected. For this case, the flux f rom the solid can be predicted by simple leach models. Examples of app lying this framework to materials treated by solidification/stabilizat ion are presented.