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Portland’s first chief water engineer, Isaac Smith, identified a pair of ravines flowing down the West Hills and determined in the early 1890s that the location would serve as a suitable spot for a reservoir for West Portland.

The Portland Water Bureau is now in the midst of a $190 million project to shore up Smith’s site. As it turned out, the Washington Park site has a large landslide that pushes against the reservoir. Plus the structure was determined to be at risk of failure in a massive earthquake. Also, the reservoir’s open-air design was deemed unwise.

Construction to address those issues began in 2016. A two-year pause is scheduled in 2020-21 to allow the reservoir to settle. Then a reflecting pool for visitors will be built atop the reservoir, along with other features. Completion is scheduled for 2024.

The reservoir walls will be surrounded with blocks of a product called Geofoam, which looks like Styrofoam and is used to cushion the reservoir from the crush of land gradually pressing down the hill. Instruments will be placed with the Geofoam to monitor its compression. Eventually, the foam will have to be replaced.

鈥淲e can’t stop the slide,鈥� said Stan VandeBergh, a West Yost Associates principal engineer who has stayed with the project since retiring from the Water Bureau. 鈥淲e just have to manage it crushing against the reservoir, and that’s how we’re proposing to do it.鈥�

Hoffman Construction is serving as general contractor. Participation of women- and minority-owned businesses is at 32 percent 鈥� above the city’s goal of 22 percent, said Cary Bubenik, operations manager for Hoffman Construction.

Sub-bids for about $15 million of work on the reflecting pools and other amenities will be available in 2021 or 2022, Bubenik said.

Approximately 50 workers are on site each day. Much of the work now involves driving shafts up to 100 feet underground. The network of 176 shafts 鈥� reinforced with no. 18 rebar weighing 13.6 pounds per foot 鈥� will support the reservoir’s weight. Pacific Foundation crews are installing the shafts at a rate of about two a day, Bubenik said.

A 鈥渢oe block鈥� concrete wall that’s 15 feet high, 15 feet deep and 900 feet long will help to hold back the landslide.

It’s all meant to shore up the reservoir site. The Washington Park reservoirs dated to 1894. Millions of gallons of water sitting in seismically vulnerable reservoirs uphill from downtown Portland came to be seen as an unacceptable risk.

鈥淭he driver of this project is seismic,鈥� VandeBergh said.

The reservoir will be served by pipes made to twist instead of break during an earthquake. They’re being installed inside protective concrete so they won’t be pressed in by fill dirt.

The project repurposes two 1890s gatehouses that were made from poured concrete, then chiseled to look like masonry. The structures will house the systems used to filter the reflecting pools. The gatehouses received new floors and reinforced walls.

The new reservoir will actually have less storage capacity than the old ones 鈥� 12.4 million gallons, down from about 17 million. That’s because of the decision to retire the lower reservoir and concentrate storage in the upper vessel.

Construction managers have had to use creative staging for the project, which is hemmed in by roads. Traffic on Southwest Sherwood Boulevard is readily visible from the site. In the beginning of the project, Uber drivers were coming through the construction site on Southwest Murray Street, Bubenik said. A gate fixed that issue.

Hoffman Construction and the Water Bureau have engaged in extensive outreach to neighborhood groups and Washington Park institutions including the Oregon Zoo, Bubenik said.