Willamette Water Supply Project on track for 2026 completion

Special Reports

When completed, the new system will provide drinking water to thousands of people in Washington County.

WILSONVILLE, Ore. (KOIN) — In Wilsonville, the fall rains aren’t slowing down the work on the Willamette Water Supply Project. 

Construction crews are driving equipment through mud, digging trenches and laying massive pipes. 

“About 25% of the 30 miles of pipeline has been constructed, and some of our big facility work is about to begin,” explained Marlys Mock, communications supervisor with the Tualatin Valley Water District and spokesperson for the project. She said crews are in the thick of construction right now. 

The Willamette Water Supply Project is a massive pipe system that will supply drinking water to three communities: the Tualatin Valley Water District, Beaverton and Hillsboro. All three areas expect significant population growth in the next 50 to 100 years and intend to use the water supply project as a way to meet the needs of future Washington County residents. 

Construction crews work to install pipe for the Willamette Water Supply Project in Wilsonville on Sept. 27, 2021. (KOIN)

The three communities started exploring options for a new drinking water system about 10 years ago, Mock said. The City of Hillsboro was particularly concerned about finding a back-up water supply. Hillsboro Water’s current source water is from the Upper Tualatin River and its tributaries. In the summer, the river level drops too low for reliable use, so Hillsboro customers depend upon water stored in the Barney and Hagg Lake reservoirs to meet demand. If the Scoggins Dam on Hagg Lake failed during a Cascadia Subduction Zone earthquake, the city’s supply could be extremely limited. 

Before construction began about eight years ago, Mock said engineers and experts surveyed the region to determine what the best water source would be. 

“They looked at a bunch of different alternatives and determined that the Willamette River in Wilsonville was going to be the easiest to build the least cost,” Mock said. 

Although it was the most affordable option, the Willamette Water Supply Project is still expected to cost $1.3 billion. The partnered communities have received several federal loans through the Water Infrastructure Finance and Innovation Act to help fund the project. 

In 2018, they received $617 million in loans from the Environmental Protection Agency and in 2019 they received $640 million from the EPA. The communities also increased rates for customers to help shoulder the cost of the project. 

Since its inception, water system designers have focused on ways to make the 30 miles of pipeline as seismically resilient as possible. Geologists fear the Pacific Northwest could experience a magnitude 9.0 Cascadia Subduction Zone earthquake at any time. The zone is a fault that stretches about 700 miles from Northern California to British Columbia. If the faultline shifts, the Portland metro area is likely to experience major tremors. 

So, with this in mind, the pipelines and storage tanks involved in the project are reinforced to decrease the likelihood of them cracking or breaking during an earthquake. Construction workers installed FLEX-TEND joints at places where pipes meet to allow them more flexibility when the ground is in motion. 

The black pipe connecting to the light yellow pipe is called a FLEX-TEND joint. It’s meant to bend and move during an earthquake rather than break. Crews are installing it in the Willamette Water Supply Project. (KOIN)

Crews are also reinforcing the riverbank along the Willamette River and have created a system that will block large pieces of debris from entering the water intake facility in the event of an earthquake. 

The project is designed to minimize its impact on the environment. Crews have been laying pipe under roadways as much as possible to avoid disturbing soil in other places. 

Mock said before construction began, researchers determined the project wouldn’t have a negative impact on the water levels of the Willamette River. She said even though the water will be pumped to far-away parts of Washington County, most of it will make its way back to the Willamette River because Washington County returns its filtered wastewater to the Tualatin River, which then flows into the Willamette. 

Mock said this is a once-in-a-lifetime legacy project and she feels confident it will supply a lot of people with high-quality drinking water. She said the water in the Willamette River has become cleaner over the years and the raw water will be treated at a new state-of-the-art facility in Sherwood.

Marlys Mock, communications supervisor with the Tualatin Valley Water District, stands next to Steve Clapper, program inspector for the Willamette Water Supply Project, at the Wilsonville construction site on Sept. 27, 2021. (KOIN)

“For me, it’ll be over 10 years in my career working on such a big project with such a big impact for a lot of the largest businesses and for thousands of people in Washington County. It’s pretty satisfying,” she said. 

Mock said they’re about to start work on the water treatment plant in Sherwood and a water reservoir tank on Cooper Mountain in Beaverton.

Project officials still expect most of the construction will be completed in 2025. July 1, 2026 is the date they expect the new system will come online. 

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