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The first Washington Park reservoirs, built in 1894, featured state-of-the-art engineering.

Their replacement, now being built by general contractor Hoffman Construction in Portland’s West Hills, will as well 鈥� but at a 21st century level.

Originally, two large concrete vessels were constructed to hold the city’s drinking water. The Portland Water Bureau, for many reasons, years ago began an effort to replace one and decommission the other. Ground was broken in 2016.

One of the major reasons why the project is so challenging is because it’s taking place on an ancient landslide that is still moving 鈥� approximately a quarter of an inch each year.

鈥淭he different elements had to be done in a specific order to not trigger that landslide,鈥� said Thomas Gilman, a project engineer with the Water Bureau. 鈥淗offman and its subcontractors did an excellent job working around tight constraints of the site to move forward, with 50-foot limits on excavation before they can place things back, all the coordination between trades, and how complicated it was and how well all that coordination went with the site restrictions and constraints we had.鈥�

Construction of a 12.4 million-gallon, enclosed, concrete box is now essentially done. It’s engineered to withstand a magnitude 9.0 earthquake and continue providing water following such an event. The concrete box had to be anchored to bedrock with dozens of reinforced pilings up to 5 feet thick, some extending more than 100 feet into the soil.

Cary Bubenik, operations manager for Hoffman Construction, said the new Washington Park reservoir resembles the 25 million-gallon one his firm completed at Kelly Butte in 2016 鈥� but not exactly.

鈥淚t’s a different structural design,鈥� Bubenik said, noting that upon completion of the new reservoir at least two years will be required for soil at the site to settle completely.

鈥淭he tank on reservoir 3, it doesn’t settle; it’s the fill that’s anticipated to move,鈥� he said. 鈥淭he main things were how to go about early on for identifying concrete cracks and leaks, identifying the leaks and the commissioning procedure. That’s what we’ll bring forward from Kelly (Butte). The rest of the project, they’re pretty different designs and fills. This one is much more complicated.鈥�

Another difference between the two projects will be eventual construction of reflecting pools atop both the new underground reservoir and the decommissioned reservoir, which was filled with excavated material from the latest project. The pools will be modeled after the original reservoirs, which were open air. They closed for security reasons in the wake of 9/11.

The final result will be a huge positive for the surrounding neighborhood, said Kathy Goeddel, a member of the Arlington Heights Neighborhood Association board. It worked closely with the Water Bureau and Hoffman Construction to ensure the project’s impact to the area would be minimal.

鈥淭hey came to us before the project started,鈥� she said. 鈥淭hey told us what they were planning to do and the time frame 鈥� when they would be closing things off and how many thousands of truckloads of concrete there would be. And they asked for feedback.鈥�

That made a big difference for local residents, Goeddel said.

鈥淚t’s just been really good communication,鈥� she said. 鈥淚t is a disruptive project, but it’s going to be gorgeous in a couple of years; it will be better than what we had before.鈥�

Neighborhood input, she added, helped transform what would have been a standard industrial project into a public attraction.

鈥淲hen we started it was going to be a covered, ugly pock on the park,鈥� she said. 鈥淏ut they came up with a plan, (and) coordinated with neighbors and others to keep it beautiful and historic. Now it will be open to the public with beautiful reflective pools and gardens, and you’ll be able to walk around it, which we haven’t been able to do for a very long time.鈥�