There are few studies examining the impacts of groundwater quality on residential property values. Using a unique dataset of groundwater well tests, we link residential transactions to home-specific contamination levels and undertake a hedonic analysis of homes in Lake County, Florida; where groundwater pollution concerns stem primarily from agricultural runoff. We find that testing and contamination yield a 2% to 6% depreciation, an effect that diminishes after the situation is resolved. Focusing specifically on nitrogen-based contamination, we find prices decline mainly at concentrations above the regulatory health standard, suggesting up to a 15% deprecation at levels twice the standard.