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For decades, observers have seen the city of Portland tackle projects to address aging, dilapidated infrastructure.聽 One of the most important ones now taking place will be much less conspicuous.

The Willamette River Crossing Project is an estimated $88 million effort to build a seismically resilient water pipeline underneath the Willamette River and connect two large header pipes 鈥� one on each side. Those header pipes provide connections for six water pipelines across the river and act like a manifold for the city’s water supply system.

鈥淲ater from Bull Run (Watershed) comes from the east side, and we have six ways for that water to get underneath the Willamette,鈥� said Tim Collins, a project manager and supervising engineer with the Portland Water Bureau. 鈥淲here we’re standing today (Jan. 20), we can see four of them.鈥�

The new pipeline will align roughly with Mill Street on the east side of the river. It will feature 39-inch-diameter steel pipe running roughly 150 feet beneath the riverbed. The engineers intend to use horizontal directional drilling to embed the pipe in the Troutdale Formation 鈥� an ancient layer of large rocks. When the pipeline is set around three years from now, it will run roughly one mile in length from downtown on the west side to somewhere in the vicinity of Southeast Seventh Avenue and Mill Street on the east side.

Getting there, however, has been a challenge for the project team. This past summer, exploratory work with a hydraulically powered percussion probing machine found that soils in the route originally planned for the pipeline could not support horizontal directional drilling. This led to delays so that engineers could develop a better map of soils.

鈥淲hat we had before was a lot of information on the shore,鈥� Collins said. 鈥淏ut we didn’t have good information on the river.鈥�

Instead of the anticipated bedrock, drilling crews encountered saturated sediments completely unsuitable for the purpose, Collins said.

鈥淵ou have a whole lot of loose gravel and crappy stuff, and you can drill through it, but the gravels collapse on the back side of the drill steel,鈥� he said. 鈥淵ou can get through it, but you can’t get back. We started over there and that happened to us.鈥�

Right now, a crew from Holt Services of Vancouver, Washington, is taking soil samples from a variety of depths beneath the river. This work will guide engineers as they reconfigure the work needed to bore through the earth and place the new pipeline. All of this work is taking place under the watch of contractor James W. Fowler Co. of Dallas.

鈥淲e stepped back and said, 鈥極K, this isn’t going to work,’鈥� Collins said. 鈥淲e need to figure out how to get through that formation, and that’s why we’re here today. We’re going to do it differently than the first time around so that we can observe and understand what that old formation looks like so we can decide whether we go above it or below it.鈥�

Crews are currently sampling up to 200 feet beneath the riverbed, down into the Troutdale Formation. Two different methods are being used. In the first, a pointed drilling head is driven into the sediments in order to measure depth and soil compaction. In the second, called sonic drilling, lengths of drill steel essentially vibrate into the sediments, where an open-ended bit collects samples into plastic bags.

鈥淭hat’s useful because what that does is show you exactly what the formation is,鈥� Collins said. 鈥淲e’re doing the type that tells us how strong it is, and we’re doing the sampling that tells us what the material is.鈥�

The pipeline is being placed in solid rock to help it withstand seismic events. The flexibility of steel pipe as well as its placement will do that. By contrast, the other five pipelines either sit in shallow trenches on the bottom of the river, or are attached to a bridge (the Ross Island Bridge, for instance). Neither of those placements is ideal from a seismic safety standpoint.

The new pipeline will help ensure that West Portland facilities, including critical health care ones, continue to receive water in an emergency from the new, seismically enhanced reservoir at Washington Park.

鈥淭he two projects are not that useful without each other,鈥� said Katy Asher, a senior communications specialist with the Water Bureau. 鈥淵ou have storage and transmission. But if you can’t get it there, who cares if you’re storing it there or vice versa. It doesn’t matter if you have a good receptacle if you can’t get it there.鈥�