Medical Lake STP | Wastewater Treatment Plant in Medical Lake, Washington

Medical Lake STP is a municipal wastewater treatment facility located in Medical Lake, Washington, serving a population of about 6,860. The plant is situated in Spokane County, an inland area in the eastern part of the state. As a small-to-medium agglomeration, the plant is subject to U.S. EPA National Pollutant Discharge Elimination System (NPDES) permitting requirements under the Clean Water Act. For communities of this size, secondary treatment is typically mandated to meet effluent quality standards before discharge. The plant's treated effluent is discharged into local waterways that drain into the Spokane River system, eventually reaching the Columbia River and the Pacific Ocean. The facility plays a key role in protecting water quality in the region's aquatic ecosystems.

The plant discharges into the Spokane River watershed, which flows into the Columbia River and ultimately the Pacific Ocean. The region supports diverse aquatic life, including salmonid species that rely on clean water for spawning and migration. Protecting water quality in this basin is critical for maintaining ecological health and recreational uses.