FAQ: Design

How big will the pipe be? How many miles will it be?

The pipe will range from between 48”-66” in diameter. The full length of the pipeline is planned to be more than 30 miles long, traveling from Wilsonville to Hillsboro and Beaverton.

What is the schedule for a preferred alignment?

A preferred pipeline route was selected early in 2015 using feedback from the public and other stakeholders, along with a robust set of pipeline route selection criteria and input from local jurisdictions. As more is learned during design, the preferred route will be refined and new routes considered.

Route selection criteria include community acceptance, resiliency from earthquakes and other natural disasters, constructability, ratepayer costs, and others.

How will the new water supply add to reliability for the region?

One of the primary objectives of the Willamette Water Supply Program is to increase resiliency and reliability in the region’s water supply. The Willamette River will be an additional source of high quality water for the Tualatin Valley Water District, the City of Hillsboro and the City of Beaverton,  providing reliability following a disaster or other service interruptions. The facilities are being designed to be operational after a major earthquake.

How do you maintain or repair the pipeline in a tunnel under Wilsonville Road?

The pipeline will be designed such that maintenance or repairs will be infrequent. If repairs are needed, the pipeline under Wilsonville Road will have access hatches that allow it to be repaired from inside the pipe. Maintenance workers will be able to access the pipe through these access shafts located at each end of the tunnel. To help prevent breaks, the pipeline will be installed inside a metal casing that will cross under the roadway to protect the pipe during a large earthquake.

Will you install fire hydrants along the pipeline route?

Under current State law urban services cannot be provided to rural areas and currently fire hydrants are not planned to be installed on the transmission main. However, providing resiliency in the system will help the stability of the region overall.

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