API Publ 4643

This report reviews available resources and methods for obtaining data on diffuse natural groundwater recharge for site-specific assessments (e.g., Tier 2 and Tier 3 Risk Based Corrective Action analyses). Diffuse groundwater recharge is important because it affects the rate at which residual chemicals could be leached from the soil and migrate to groundwater. Accurate recharge estimates are essential for quantifying the risk to groundwater presented by residual chemicals in the vadose zone.