CHEMICAL CONTAMINANT REACTIONS AND ASSESSMENT OF SOIL CLEANUP LEVELS FOR PROTECTION OF GROUNDWATER

About 70 percent of hazardous waste sites listed in the National Prior ity List (NPL) have some ground-water contamination that may require r emediation. Such remediation is inadequate if the unsaturated soils ab ove will continue to act as a source of groundwater contamination. Con sequently, for most of these sites, it becomes necessary to determine what the cleanup levels for contaminants in soils should be so that su bsequent contribution of contaminants from these soils to groundwater would not exceed groundwater protection levels. Representation of the dynamics of interactions between contaminants and soils is very comple x, requiring among others, a thorough understanding of the chemical pr ocesses that influence the behavior of the contaminant once it enters the subsurface. Because of such complexities, environmental profession als frequently utilize methods with very simple assumptions that tend to err on the conservative side. While the public may feel protected, the needless spending of dollars could be avoided if attempts are made to incorporate, where possible, such complexities in the modeling eff orts so that the system is represented as accurately as possible.