Contamination released at a gasoline station contaminated groundwater within a public wellhead protection zone. ERA conducted subsurface investigations and groundwater modeling to establish the extent of contamination and the future impact on residential and public drinking wells located downgradient of the station. Our risk assessment and evaluation concluded that the plume had stabilized due to natural biodegradation, and that Monitored Natural Attenuation was the best remedial action. Subsequent monitoring confirms these conclusions.