Water Treatment Plant

Demolition of the sedimentation basins at the WTP
Newly installed auger cast piles for the new admin building
New finished water pumps connected to the clearwell
Preparing new filter slabs to be poured
The new ballasted flocculation is a major step in the treatment process
The new gravity thickener thickens river sediments removed during treatment

Latest Construction News

Latest Construction News

Facility Overview

(click image to open PDF, 326 kb)

Video Updates

About the Project

Construction is underway to upgrade the Lake Oswego - Tigard Water Treatment Plant (WTP) located in West Linn.

Lake Oswego’s original water treatment plant was constructed in this location in 1968. The facility has treated Clackamas River water to high drinking water standards for several generations. Although the facility has been updated over the years, it is too old and undersized to meet the current and future demand in Lake Oswego and Tigard.

The new treatment plant will produce high-quality drinking water using ozone technology to assure a reliable and consistent supply of water for thousands of customers in Lake Oswego and Tigard. The treatment plant design incorporates energy efficiency, renewable energy components, and sustainable operational practices. The new plant will be better able to withstand large seismic events, and a tie in with the City of West Linn’s system will allow the new treatment plant to serve as a back-up water source for West Linn.

To learn more about the seismic improvements to the water system, read The Lake Oswego Tigard Water Partnership Prepares for the Big Quake.

To learn more about ozone treatment, read State of the Art Water Treatment.


Schedule is subject to change


August 2013 – Spring 2017


Construction began in August 2013 on the new seismically resilient treatment plant. Final completion is expected in spring 2017.

The Lake Oswego Tigard Water Partnership is committed to working with neighbors to help reduce construction impacts and keep neighbors informed.Monthly neighborhood construction meetings are held once a month on the 3rd Tuesday at 6 p.m. at the Robinwood Station. Come visit with staff and the contractor to learn about construction, discuss concerns and ask questions.  Visit the current meetings page for information about the next meeting. 

Construction Tours at the Plant: Join us for a free public tour to view construction activity at the WTP site. In addition to learning about the construction phases of the project, you can watch the activity take place. Tours are held every second month, on the fourth Thursday starting at 10:00 a.m. for 30 minutes. Advanced registration is required and space is limited. As the tour is located within an active construction zone, visitors will be required to wear sturdy, closed in shoes. Hard hats and vests will be provided by project staff.

Planning History

The Lake Oswego Tigard Water Partnership began discussions with the Robinwood Neighborhood Association in early 2010. 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 big role in design concepts with the addition of numerous plant layout changes and amenities requested by neighbors.

More information?