Stonington Borough WPCF - Secondary Wastewater Treatment in Stonington, Connecticut

Stonington Borough Water Pollution Control Facility (WPCF) is a municipal wastewater treatment plant located at 1 Front Street in Stonington, Connecticut, United States. The plant serves a population of approximately 1,900 residents and operates as part of the town's wastewater infrastructure in the Southeastern Connecticut Planning Region. The facility provides secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal plants discharging to surface waters. With a design capacity of 2,498.36 m³/day and an average daily discharge volume of 794.94 m³/day, the plant operates well below its capacity, indicating room for future growth or seasonal variations. As a coastal plant within 10 km of the Atlantic Ocean, it must comply with stringent National Pollutant Discharge Elimination System (NPDES) permits issued by the Connecticut Department of Energy and Environmental Protection. The treated effluent is discharged into local waters that drain into Fishers Island Sound and ultimately the Atlantic Ocean. This coastal discharge requires careful management to protect marine habitats, including shellfish beds and eelgrass meadows that are ecologically sensitive to nutrient loading. The plant's secondary treatment helps reduce organic pollutants and suspended solids, supporting water quality in the downstream environment.

The plant discharges into waters flowing to Fishers Island Sound, a coastal embayment connected to Block Island Sound and the Atlantic Ocean. This area supports diverse marine life, including commercially important fish and shellfish species. Nutrient inputs from wastewater can contribute to algal blooms and hypoxia in coastal waters, making effective treatment critical for maintaining ecological balance.