The evaluation of waste disposal sites is becoming more comprehensive in response to increasing regulatory requirements and the extent to which geologic studies specified by regulatory guidelines varies. The intent of disposal requirements for new and for existing facilities is to understand the fate of contaminants at the specific site. This necessitates definition of the groundwater system and an assessment of the ability of the subsurface materials to minimize the impact of the contaminants on the environment.
Projects in various geologic provinces have demonstrated that waste disposal evaluations must be site-specific because of local variations which exist. Relevant hydrogeologic conditions and important site-specific variations are described for the Coastal Plain, the Piedmont, and the Valley and Ridge physiographic provinces of the eastern United States. Multi-phased evaluations are logical considering these variations.
The geologic emphasis changes with successive phases of evaluation and whether the evaluation involves a new or an existing site. In siting new facilities, the initial phases often involve definition of the most suitable geologic characteristics of the province for comparison of several alternate sites. The initial phase of evaluation for existing facilities requires combining knowledge of areal geology with facility operational information to properly plan the site investigation. During subsequent phases, geologic studies typically include a detailed assessment of localized hydrogeologic units as well as determination of the availability and suitability of soils and rock for construction materials.