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Portland’s water supply system has met the demands of a growing city for more than 125 years. Six pipelines cross the Willamette River to deliver water to Portland’s west side from the east. Some are buried in soils susceptible to liquefaction, others are suspended under bridges. The greatest seismic hazard to existing river crossings is a Cascadia Subduction Zone (CSZ) earthquake. It’s been 317 years since the last CSZ earthquake, and there is a 30–35 percent chance its fault will rupture in the next 50 years.
The Willamette River Crossing Project provides added protection to the backbone of our water supply system.
The risks and consequences of a CSZ earthquake are real and immediate, which is why the Portland Water Bureau has prioritized this project. Along with other system improvement—new reservoirs at Kelly Butte, Powell Butte, and Washington Park—the Willamette River Crossing Project, or WRX, will improve the backbone of Portland’s water system, greatly increasing the entire city’s ability to bounce back and provide water after any seismic event.
The Portland Water Bureau is using a “design-build” method for the Willamette River Crossing Project. This means the project team is collaborating with a contractor to design the project. This allows for feedback loops throughout design that will offer early and ongoing opportunities to mitigate negative construction impacts, which will ultimately improve construction timelines, and provide the best value for our customers.
In 2012, the Portland Water Bureau conducted a thorough study of all potential locations for a new, seismically resilient water main. The study considered such factors as:
The extensive study concluded that the project would best be located in the area demonstrated by the Project Boundary graphic (right). The project location is geologically favorable for a new water main that will add to the resiliency of the entire water system.
This new water main will be placed under the river using the Horizontal Directional Drilling (HDD) method. Given the space requirements of this method, the drill rig will be stationed and operate on the west side of the river, and the pipe lay down and pull back phases will be located on the eastside.
The Portland Water Bureau is working with McMillen Jacobs Associates to explore several alignment options within the study area. The final alignment will be determined using a “best value” selection process and will be selected in early 2018.
The west side connection point will likely be a parking lot located off SW Naito Parkway west of SW Montgomery Street.
The east side connection point will be in the public right of-way somewhere between SE Water Ave and 12th Street and SE Clay and SE Division streets, as shown in the Project Boundary graphic.
The project is in the planning phase, with design and construction anticipated to begin in 2018. WRX will use horizontal directional drilling technology (HDD) which means the project can be constructed without in-water work, and no impacts to shipping, recreation, fish habitat, or other environmental factors. The water main will be approximately 4,500 feet long and 80 feet below the bottom of the Willamette River.
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