An Approach For Protecting Unconfined Drinking Water Aquifers Against Effluent Contamination

Regions of the Mid-Atlantic outside of public water & sewer service areas typically rely upon on-site drinking water wells and wastewater discharge systems to meet sanitary needs. Unconfined aquifers that supply groundwater and receive wastewater discharges require a measure of protection against effluent-borne contamination, accordingly. Herein we explore soil and hydrogeologic evaluations supportive of large effluent discharges to drinking water aquifers (i.e. greater than 5,000 gallons per day). We will review wastewater disposal systems discharging to unconfined aquifers of the fractured crystalline rocks of the Piedmont and sandy deposits of the Atlantic Coastal Plain Physiographic Province. We will present an overview of site and subsurface characterization procedures, predictive analyses and regulatory approval processes. Case histories will include an effluent spray irrigation facility in woodlands of the Coastal Plain and a deep trench septic disposal system in the Piedmont. We will present and discuss representative soil profile descriptions, soil infiltration rates, monitoring well logs, wet season water levels, horizontal hydraulic conductivity and predictive groundwater impact analyses.