Lake Oswego Wastewater Treatment Plant Replacement, Oregon

Lake Oswego’s wastewater treatment plant replacement has a builder and a price after years of false starts. The City Council on Oct. 13, 2026, approved a contract with Jacobs to design, build, operate and maintain a new plant in the Foothills District, next to the aging Tryon Creek Wastewater Treatment Plant. Design and construction will cost $372 million, with operations running about $6.5 million a year.

Tryon Creek sits where its namesake creek meets the Willamette River. It dates to the mid-1960s, was expanded in 1976 and modified in 2003, and it’s owned and run by the city of Portland, which uses it to treat flows from parts of southwest Portland and nearby Multnomah and Clackamas county areas as well as Lake Oswego. Portland had shelved a long list of upgrades while Lake Oswego studied building something new.

Project Scope

The new plant will be smaller than the one it replaces, and it’s being designed to keep running after a major earthquake, as new state codes require. It’s also supposed to treat all wet-season flows, something the current plant can’t do, and cut dry-season pollutant discharges to the Willamette by about half. The city has written stiff odor penalties into the contract and put Jacobs on the hook for complaints, a sensible move for a plant in a neighborhood the city wants to redevelop.

Demolition of existing buildings on the new site is expected in early 2027. Construction should take about five years. Portland will pay 30% of the costs under an intergovernmental agreement that splits the bill by flow, and the land transfers once the plant is commissioned.

The city hasn’t published a design capacity or named a treatment process.

Why It Matters

The deal got here the hard way. Lake Oswego’s earlier partner, EPCOR, came back with a final offer of $674 million before the two sides failed to agree on terms and the city dissolved the agreement in 2024. When the city went back to the market that fall, Jacobs was the only firm that showed interest. The new number is far lower, but with one bidder the city had no competing price to test it against.

Ratepayers carry the rest. Sewer rates rise 28% starting July 2027, roughly $25 to $30 a month for an average customer, followed by annual inflation adjustments of about 3.9%. A federal WIFIA loan, reported at $123 million, and municipal bonds fill out the financing. Single-source design-build-operate deals can work, but the operating years are where this contract will be judged.

Project Team & Details