Tri-City Water Resource Recovery Facility Outfall Project

Latest Updates to Clack-A-Mole and the Tri-City Water Resource Recovery Facility Outfall Project

What is an Outfall?

Every day, Clackamas Water Environment Services (WES) cleans more than 10 million gallons of wastewater at its Tri-City Water Resource Recovery Facility in Oregon City. The treated water, called "effluent," is then sent back to the Willamette River. An outfall is the discharge point where the treated water flows into the river.

Cross-section of outfall project

An outfall is designed to maximize mixing and dilution of effluent. The mixing must meet state water quality standards for boating, swimming, fishing, and aquatic resources.

Project Overview

Background

Map of project areaThe current outfall from the Tri-City facility was constructed in 1984 and is nearing capacity during peak wet weather events. In May 2019, the Clackamas County Board of County Commissioners approved an additional Outfall Project, which would be large enough to provide service for decades to come.

The existing outfall is structurally sound and will remain in place for use if needed. The new outfall will use gravity to convey the water from the treatment facility, so it will not require energy to pump water.

Location

The new outfall will run from the Tri-City facility parallel to I-205 and under the OR 99E off ramp. It will continue under Jon Storm Park and discharge into the Willamette River just north of the I-205 Abernethy Bridge. The Oregon City Charter calls for a vote of the people regarding the easements and for the construction of permanent structures unrelated to park use. In November of 2020, Oregon City voters authorized WES to place the wastewater pipeline underground in Jon Storm Park.

Project Planning

The outfall pipeline will tunnel beneath Jon Storm Park. Construction crews will adhere to the Oregon Department of Fish and Wildlife's Willamette River in-water work requirements. The in-water work guidelines were created to minimize potential impacts to fish, Pacific lamprey, wildlife and habitat resources. In addition, WES' consultants are performing an archaeological investigation and working in compliance with the National Historic Preservation Act. WES is also working with the Confederated Tribes of Grand Ronde Tribal Historic Preservation Office.

Construction will use a design-build process, where the design engineers and builders work together under a single contract from the beginning of the project. This method ensures the project stays on schedule and on budget. 

Funding

The project, which has a construction cost of $58,444,000 will be funded as part of WES' Capital Improvement Plan.

Videos

On February 21, a groundbreaking event was held for construction of the new outfall.

On January 23, 2024, the project team held a meeting to update community on the project and answer questions.

Learn more about the project.

Frequently Asked Questions

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The outfall diffuser will contribute to fish recovery in the Willamette River. Its location will be about 1,600 feet upstream of the existing outfall in a deep, stable aquatic bed feature that will better mix and dilute treated wastewater as it enters the Willamette River. It will maintain the existing cold-water fish refuge area at the mouth of the Clackamas River, and minimize future maintenance needs. This will also ensure the water meets state water quality standards, including water chemistry characteristics that fish need.

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Once complete, the outfall will operate without any obstructions to current river uses. Trenchless technologies will be used to minimize impacts to nearby properties and parks. 

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Construction is anticipated in 2024–2025 with operation starting in 2025.

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The outfall will be completely buried and not visible. The outfall will be beneath the river and only smaller pipes will penetrate the river’s bottom. They will be in a deep segment of the river and will not interfere with boating, recreation or aquatic life.

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The diffuser section of the pipeline will be buried under the riverbed, extend beyond the middle of the river and will be located at a particularly deep spot for better mixing that will enhance water quality. The actual diffuser ports will extend up above the diffuser bed. The diffuser is an improved river discharge mechanism that will be built at the end of the outfall.

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Construction crews will strictly adhere to the Oregon Department of Fish and Wildlife’s Willamette River in-water work requirements. The in-water work guidelines were created to minimize potential impacts to fish, Pacific lamprey, wildlife and habitat resources.

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The model-predicted dilutions for the preferred 150-foot long outfall diffuser have been developed using current and future wastewater flows and maximum summer temperatures. The modeled results demonstrate this outfall will be well below the Oregon water quality temperature standards. The design of the diffuser will ensure that the outfall discharge stays well below any temperatures that could affect biological resources.

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WES is actively designing the project to avoid known archaeological resources in the vicinity of the project and will complete a due diligence effort to identify any previously unidentified cultural resources that may be affected by the project. 

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There will be no impacts on the fishery after construction is completed and the outfall is brought online. The outfall location will provide better mixing, which will help improve overall water quality in the river.

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The improved diffuser will ensure that treated wastewater doesn’t disrupt the natural environment and keep the river clean for swimming, boating, fishing, and aquatic life.

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Construction should not impact Abernethy Creek. The tunnel will not be going through bedrock, as bedrock is deeper than our anticipated tunnel corridor. The location of the new outfall diffuser in the Willamette River and the most inshore diffuser port location is approximately 400 feet distance from the mouth of Abernethy Creek. This substantial offshore location will allow a wide inshore region for fish migrating into Abernethy Creek. The project will specifically design the river diffuser ports and velocities to remain below the National Marine Fisheries Service’s “guidance” of less than 8 fps for outfall ports to avoid fish attraction.

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Providing additional outfall capacity and reducing the amount of Infiltration & Inflow of extra water in the collection system will reduce the risk of potential sewer overflows.

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Construction will use a design-build process, where the design engineers and builders work together under a single contract from the beginning of the project. This method ensures the project stays on schedule and on budget.

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Resources

Archaeological Information

Clackamas Water Environment Services consultants are performing an archeological investigation and working in compliance with the National Historic Preservation Act (NHPA). WES is also working with the Confederated Tribes of Grand Ronde Tribal Historic Preservation Office. The project will be done with a federal nexus through the U.S. Army Corps of Engineers, and compliance with the NHPA.

The slide below outlines the general strategy WES will follow to ensure that, through consultation and iterative project design, potential impacts to significant cultural resources will be accounted for and addressed prior to construction.

WES Archaeology Project Steps slide 

Routing Study

Archived Materials

Ballot Measure

News and Media

Meeting Materials

Virtual Open House

WES hosted two virtual open house presentations, on August 26, 2020 and September 21, 2020. View the presentation.

Phone:503-742-4567
Fax:503-742-4565

150 Beavercreek Road #430, Oregon City, OR 97045

Office Hours:

Monday - Thursday
7:30 a.m. – 5 p.m. 
Closed on the lunch hour 12 p.m. – 1 p.m.

Email:
Customer service
wescustomerservice@clackamas.us

Development services and permits
wes-permitservices@clackamas.us

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