Friday Harbor STP - Wastewater Treatment in Friday Harbor, Washington

Friday Harbor STP is a municipal wastewater treatment facility located in Friday Harbor, Washington, on San Juan Island. It serves a population of approximately 2,680 residents in this coastal community. The plant is part of the region's infrastructure managed by local authorities. The plant has a designed capacity of 1.00 million gallons per day. As a US facility, it operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Washington State Department of Ecology. Treatment processes for plants of this scale typically include secondary treatment to meet state and federal standards. The treated effluent is discharged into the marine waters of the Salish Sea, a critical ecosystem supporting salmon, orcas, and diverse marine life. The plant's location on San Juan Island places it within a sensitive coastal environment where nutrient management is important for water quality.

The plant discharges into the Salish Sea, a complex estuarine system connecting to the Pacific Ocean via the Strait of Juan de Fuca. This marine environment supports critical habitats for endangered Southern Resident killer whales, Chinook salmon, and forage fish. Nutrient and pathogen control are essential to protect shellfish beds and recreational waters in the San Juan Islands.