For over 100 years the Portland Water Bureau has successfully supplied growing Portland communities with safe water. The Bureau supplies water to both eastern and western communities by utilizing six pipelines that cross the Willamette River either by being suspended under a bridge or by crossing under the river itself.
The Willamette River Crossing (WRX) project was developed in anticipation of the Cascadia Subduction Zone (CSZ) earthquake. Though the last CSZ earthquake was over 300 years ago, seismologists predict a thirty to thirty-five percent change of a CSZ earthquake in the next fifty years. The WRX project will improve water infrastructure by protecting and adding redundancy to pipes located in the liquefaction zone.
The Portland Water Bureau has estimated that water pipeline failure due to the CSZ earthquake would affect the industrial and commercial districts on both the east and west sides of the Willamette River. This accounts for roughly 32,000 customers, twenty percent of their customers, three major hotel complexes, a third of Portland employment, and $8.2 billion annual economic activity.
Given the urgency and risk of the matter, the Portland Water Bureau prioritized the WRX project and opted for a design-build approach. Other seismic improvement projects have also been prioritized, including Kelly Butte, Powell Butte, and Washington Park reservoirs. The Portland Water Bureau is confident that these projects allow Portland’s water infrastructure to withstand the impact of the CSZ, allowing the city to recover and resume water delivery quickly.
WRX will include the installation of a new pipeline located deeper underneath the Willamette river to avoid the liquefaction zone. Considering the design-build approach for the project, James W. Fowler Co. (JWF) is involved in both the design and construction phases. Approaching the project as a design-build allows for both the Portland Water Bureau and JWF. to work hand in hand to create the highest level of efficiency and collaboration. This increased communication and decrease of touch points throughout the project helps to minimize adverse impacts, ensuring timely construction completion while proving the best overall value.
The pipeline, located just north of the Marquam Bridge, is estimated to be 3 to 4.5 LF and will use welded steel pipes. Pipes will be placed underneath the Willamette River using Horizontal Directional Drilling (HDD), microtunneling, and open-cut trenching methods. The drill rig will be stationed and operated on the west side of the river while the pipe lay-down and pull-back will be located on the east side.
The design-build approach allows JWF to collaborate with Stantec Consultants, the engineer of record, to design the pipeline. The pipeline will include seismically resilient pipeline appurtenances including isolation valves and vaults. This project also includes the design and installation of cathodic protection systems, connection to existing water main headers on both sides of the crossing, and restoration of areas disturbed by the construction.
JWF loves a challenge, this project will challenge all teams involved to work through hurdles and creatively develop solutions. Given crossing a major river is no easy task, the team will be challenged with identifying geotechnical specifications and mitigating environmental costs. A significant part of defining geotechnical specifications is drilling holes and identifying soil conditions. Having done their homework the JWF team feels prepared to tackle any challenge that comes their way. The JWF crew has researched old records, secured old building permits and pile drives, and has also incorporated both sonic borehole and mud rotary to the strategy. The JWF team identified contaminated and hazardous material in the ground during geotechnical surveying processes. To limit the cost for the owner, JWF has extended environmental investigation to precisely identify the limit of the hazardous and contaminated soil.
JWF is proud to partner with the Portland Water Bureau to provide peace of mind to communities on the east and west side of the Willamette River.
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