Water Treatment Plant

Facility Overview

(click image to open PDF, 326 kb)

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Lake Oswego's original water treatment plant was constructed in 1968, in unincorporated Clackamas County. The area was incorporated into the City of West Linn at a later date. The facility has treated Clackamas River water to drinking water standards for almost 50 years.

The plant had an initial treatment capacity of 10 million gallons per day (MGD) and was expanded to 16 MGD in the 1980s. Although the facility has been updated over the years, it was too old and undersized to meet the current and future demand in Lake Oswego and Tigard.

As part of the project, the plant capacity was expanded to 38 MGD and began supplying water to both Lake Oswego and Tigard customers in the summer of 2016. The new treatment plant produces high-quality drinking water using high rate, conventional sedimentation and filtration plus ozone technology, to assure a reliable and consistent supply of water for more than 90,000 thousand customers in Lake Oswego and Tigard.

The facility is staffed with nine full-time operators, keeping the plant running smoothly every day of the year. All operators hold water treatment certifications from the Oregon Health Authority and continue to upgrade skills and learn the newest treatment techniques through continuing education opportunities.

The treatment plant was designed to incorporate energy efficiency, renewable energy components, and sustainable operational practices. The plant is better able to withstand large seismic events, and a tie in with the City of West Linn’s system allows the plant to serve as a back-up water source for West Linn in an emergency.

Planning History and Public Amenities

The Partnership engaged plant neighbors and the Robinwood Neighborhood Association in the early stages of the project. After two years, and more than 20 meetings, neighbors and the Partnership developed a Good Neighbor Plan (pdf, 308 kb). It contains the Partnership’s commitments for design, construction, and operations of the new facility.

Neighborhood input played a significant role in overall design of the treatment plant, with the addition of numerous plant layout changes and amenities requested by neighbors. The new site features a two-acre park-like setting, a new pedestrian pathway connecting Mapleton Drive and Kenthorpe Way, sidewalks along the plant frontages and a rain-garden open to the public. More than 300 trees and 25,000 native plants and shrubs were planted at the facility.


Construction on the new seismically resilient plant began in summer 2013 and was completed in summer 2017. On August 31, 2017, a ribbon-cutting of the new pedestrian pathway connecting Mapleton Drive and Kenthorpe Way was held with more than 175 neighbors, to commemorate the pathway and celebrate the end of plant construction.

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