About the Project

The Tryon Creek Wastewater Treatment Plant is aging and in need of major upgrades to continue to reliably meet Oregon Department of Environmental Quality water quality requirements. Lake Oswego, with Portland’s support, is exploring building a new wastewater treatment facility to replace the old plant under a Private-Public Partnership.


The Tryon Creek Wastewater Treatment Plant (TCWTP) was built in 1964 and is owned and operated by the Portland Bureau of Environmental Service (BES). It is strategically located at the confluence of Tryon Creek and the Willamette River in Lake Oswego. TCWTP treats sewage collected from parts of southwest Portland, unincorporated areas of Multnomah and Clackamas counties, and the City of Lake Oswego. Treated wastewater is discharged to the Willamette River via an outfall system.

Currently, wastewater treatment operations and maintenance costs are split between Portland and Lake Oswego. On average, Lake Oswego contributes approximately 70 percent of the flow volume.

Purpose of the Project 

The existing Tryon Creek Wastewater Treatment Plant is aging and parts of the plant are at the end of their useful life cycle.

The facility needs significant investments to continue to reliably meet current and potentially more stringent Oregon Department of Environmental Quality (ODEQ) permit requirements and protect it against climate change.

Before investing in aging technologies and processes, the City of Lake Oswego, with Portland’s support, is exploring whether a new, resilient, and state-of-the-art wastewater treatment facility can be built to replace the aging TCWTP at a cost similar to or less than the costs of upgrading, modifying, and operating the existing facility.

Project Benefits 

A new, state-of-the-art wastewater treatment facility will produce cleaner water and ensure more environmentally sustainable services at a similar cost to upgrading the existing aging facility.

Some additional benefits include:

  • Smaller footprint that enables riverfront property to be restored for future use
  • Odor control
  • More visually appealing design for the neighborhood
  • Energy efficient
  • Greater climate resiliency
  • State-of-the-art AquaNereda® water treatment technology
  • Higher quality treated water returned to the Willamette River

Next Steps

The project is in the early stages of design under a Public-Private Partnership.

A robust public involvement process will seek community feedback and stakeholder input to help shape the design of the facility. Visit our ‘Get Involved‘ page for upcoming opportunities. You can also register for e-news updates below!

For more information on the project, visit our Frequently Asked Questions page.

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You can also email info@lakeoswegowastewaterfacility.org