The City of Portland constructed the Tryon Creek Wastewater Treatment Plant (TCWTP) in 1965 within Lake Oswego city limits next to the Willamette River. The city expanded the plant in 1976 and modified the plant in 2003. The plant treats sewage collected from parts of southwest Portland, unincorporated areas of Multnomah and Clackamas counties, and the City of Lake Oswego.

Tryon Creek is an activated sludge, secondary treatment plant. It’s about one-tenth the size of Portland’s Columbia Boulevard Wastewater Treatment Plant.

The City of Portland Bureau of Environmental Services owns and operates the TCWTP, although the plant treats wastewater from sewer customers of both the City of Portland and the City of Lake Oswego under an inter-city contract.

Environmental Services updated the treatment plant's facilities plan in 2014.