Lake Oswego Wastewater Treatment Facility Online Open House
Is Now Closed

This online open house and survey was held November 9 - December 11, 2022.  Thank everyone who took the survey and the nearly 500 visitors who viewed the online open house.

8 Things to Know

  • 1 The existing Tryon Creek Wastewater Treatment Plant is aging and nearing the end of its useful life
    The existing plant serving all of Lake Oswego and parts of Portland was built in 1964. It is located within Lake Oswego and owned and operated by Portland. The plant needs costly upgrades to continue to reliably meet water quality requirements and reduce risks posed by a changing climate.
  • 2 Lake Oswego, with Portland’s support, is proposing to build a new wastewater treatment facility to replace the old plant
    Both cities have a choice – whether to build a new facility on a different site or invest in aging technologies and processes by upgrading the old plant. The proposed new facility will deliver significant added benefits at a similar cost to upgrading and operating the existing plant.
  • 3 The planned new state-of-the art facility will be more environmentally friendly and sustainable
    It will have a smaller physical, environmental and carbon footprint and use innovative treatment technology that is 40-50% more energy efficient than other options evaluated. Solar panels, electric vehicle charging stations, and reuse of water on site will also be utilized.
  • 4 Designed to complement the Foothills neighborhood
    The facility design, architecture and landscaping will fit into the surrounding neighborhood. Treatment processes will be enclosed to minimize odors, noise, and enhance neighborhood livability.
  • 5 Modern tools and processes will be used for potentially stricter regulatory and permitting needs
    The facility will be built from the ground up to support potentially more stringent regulatory and permitting requirements.
  • 6 More resilient to flooding, earthquakes and climate change
    Design, structure, and a new location will reduce risks from natural disasters and a changing climate.
  • 7 Lake Oswego gains more control
    Portland will transfer ownership of the existing facility to Lake Oswego, giving the City more control over vital services.
  • 8 Prime riverfront property can be reclaimed
    The facility will be relocated at a smaller site. This opens up prime riverfront property for other public benefit. Any future development in the area would be a separate project and subject to additional public input.
lake-oswego-wwtp--LO Willamette Bridge

Neighborhood-Friendly Design Concept

The design concept for the new facility will improve the neighborhood appeal
compared to the existing Tryon Creek plant.

The proposed site for the new facility is at the far northwest corner of the Foothills District. Architecture and landscaping will harmonize with the neighborhood. Treatment processes will be housed in buildings to control noise and odor.

60 Percent Design Renderings

Check out 60% design concepts for the proposed new wastewater treatment facility.
Click and drag dividers to reveal current conditions and proposed facility improvements.

Please note: these are concepts and subject to change once the plans are finalized and the project has initiated the Development Review process. The images shown are in the area of the accompanying photo but may not be from the exact location.

The current, aging Tryon Creek Wastewater Treatment Plant.

The proposed seismically resilient wastewater treatment facility, with solar panels for energy efficiency and sustainability.

Foothills Road heading north.

Modern administration building fits into the Foothills neighborhood.

View of the approximate area for the proposed facility along Foothills Road, looking north.

Neighborhood-friendly administration building viewed from Foothills Road, looking north.

Existing facilities at the current plant take up considerable space in the neighborhood.

The new facility will have a smaller, fully enclosed footprint.

Existing plant needs significant upgrades.

Treatment processes will be enclosed in buildings in the new facility to reduce noise and odor.

Proposed location currently lacks sidewalks, landscaping, and other amenities for the neighborhood.

The proposed design incorporates sidewalks and landscaping that fit into the Foothills neighborhood and adjacent Foothills Park.

Existing treatment plant and adjacent buildings in the Foothills Area – facing west.

New proposed facility facing west.

How the AquaNereda Wastewater Treatment Process Works

The new facility will take advantage of innovative AquaNereda treatment technology. AquaNereda is a highly efficient, biological wastewater treatment technology proven throughout the world. Lake Oswego and Portland will be the first cities of our size in Oregon to use the technology.


    Requires less acreage enabling riverfront property to be restored for other potential uses
    Offers energy savings of 40%-50% compared to Membrane Bioreactor technology
    Provides high water quality using less chemicals and energy
    Needs less maintenance and operations support

Treatment Process Step-by-Step

Click on the highlighted treatment process steps below to learn more.

1. Wastewater


Wastewater collected from the cities of Lake Oswego and Portland.

1. IPS


Influent Pump Station receives the raw wastewater and pumps it up to the Headworks.

2. Influent Screen


Influent Screen remove debris from wastewater.

2. Grit


Sand-like grit is removed to protect downstream equipment.

3. Blowers


Blowers provide oxygen as part of the process to breakdown the wastewater.

3. Peak Storm


Peak Stormwater Flows can be sent directly to the filters.

3. Granular


Aerobic Granular Sludge basins biologically treat wastewater following a sequential reactor-style operation.

3a. Level


Water Level Correction Basin is used to lower the water level a few inches after the Fill/Draw stage.

4. Addtl Solids


Filters remove additional solids and reduce turbidity for a better effluent.

4. UV


Ultraviolet Disinfection destroys bacteria and viruses.

4. ReUse Pump


Reuse Pump Station directs treated water to be used onsite to promote conservation.

5. River Discharge


Clean water is discharged to the Willamette River.

6. Basins


Basins collect diluted waste activated sludge.

6. Sludge


Sludge is pumped through Rotary Drum Thickeners to thicken.

6. Sludge Hold


The Thickened Sludge Holding Tanks hold sludge until it can be pumped to a truck.

6. Sludge Haul


Thickened Sludge is hauled to the Columbia Wastewater Treatment Plant.

Project Delivery and Financing

To assess the viability of the project and determine its cost, Lake Oswego and Portland have been partnering with EPCOR under a preliminary services agreement (PSA). In the future, Lake Oswego may formalize a long-term public-private partnership (P3) agreement with EPCOR, under which EPCOR would design, build, finance, operate and maintain the new wastewater treatment facility while Lake Oswego will own it.

Anticipated Benefits of This Approach Include:

  • Payments tied to performance
    Lake Oswego and Portland do not pay until the facility is operational and payments would be spread out over the life of the asset, subject to the new plant performing at prescribed standards.
  • Financial predictability
    The project is expected to be financed within planned rate increases.
  • Greater control
    Lake Oswego owns the facility.

The project has been accepted by the EPA for a Water Infrastructure Finance and Innovation Act (WIFIA) loan. WIFIA loans couple lower interest rates with flexible, long-term repayment schedules. This is a win-win for the ratepayers of Lake Oswego and Portland. Learn more about WIFIA loans at the project website FAQ.

Frequently Asked Questions

Special Thanks and Appreciation to the Teams at:

At the City of Lake Oswego, we value diversity, equity, and inclusion as essential parts of internal and external policy-making and the delivery of City services. We are committed to making our information accessible to everyone. For accommodations, please contact our ADA Coordinator at 503-635-0282 or email [email protected].