On the clear and chilly days of late January, a barge was spotted just offshore from the South Waterfront. A tugboat taxi transported crew to this barge that extracted underground core samples and brought them to the surface. Knowing what lies beneath the Willamette River is a key component of the Willamette River Crossing project’s exploratory phase. We plan to install a pipe deep under the Willamette River will make sure that we can get water to the west side of Portland following a serious earthquake.
This complex project is many years in the making. It’s challenging to run an earthquake-resilient pipe through the heart of the city. We are burying it deep underground, far deeper than any of the current crossings, none of which are expected to survive a major earthquake. The current pipes that carry water from the east to the west side are more than 50 years old, and installed when we knew much less about our region’s vulnerabilities to earthquakes.
Now that we know about the potential for big earthquakes, we know that this project is key to our region’s ability to recover economically after an earthquake. Investment in this project makes sure that we can fight fires and bring water to crucial facilities, like hospitals.
The Willamette River Crossing Project finished its geotechnical probe in August 2020, and the team has been using the results to plan the next phase of the project.
Here's some key findings:
Working underground is challenging
Especially in an urban environment. Knowing this from the beginning allowed us to make a smaller investment in exploring the proposed path for the pipe using a geoprobe to drill a smaller hole before going “full bore.” This has provided us with a chance to refine the design to adapt to new information as we proceed.
More exploration ahead
The geotechnical probe showed that more geotechnical exploration is needed to choose the best tunneling technology and route to cross the Willamette River. We will likely have to make changes to depth or drilling technologies to move the project forward.
Changing depth: If we go deeper, we can get below a layer of loose gravels that were a challenge during the geoprobe. To go deeper, we must collect more information about the soil at that depth.
Changing technology: Another option is to use a different drilling technology that can move through the cobbles without going deeper. So while we are sampling deeper soils, we are also measuring information that will show us whether the new technology would work.
Our contractor will build on the information collected from the geotechnical probe and borings we are currently doing to design and construct the pipeline.
More exploration means more time.
Our team is evaluating alternative construction sequences, different routes the pipe could take, and alternative tunneling technology. We expect this next phase of exploration to last about six months. We’ll update the project website at portland.gov/water/wrx with new information as it becomes available.