Understanding the geology, hydrology, and geochemistry of a contaminated formation is critical to groundwater modeling, wellfield design, and remediation design. Information collected about site geology may include geologic cross-sections, lateral continuity of saturated zones, and hydraulic communication between adjacent formations. Important hydrologic information includes hydrologic properties of formations, water levels in wells, groundwater velocity, dispersivity values, regional groundwater use inventory, and contaminant migration pathways. Geochemical characterization includes determination of adsorption characteristics and biodegradation. Once all characteristics of a site have been evaluated, remediation specialists can develop an action plan.