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The City of Portland, Oregon

Portland Water Bureau

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Washington Park Reservoir Improvement Project

  • Project Updates Stay in the know about project progress! Sign up to receive emailed updates.

  • Upper Reservoir - Pump House View The new reservoir is engineered to withstand ongoing landslide encroachment and seismic events.

  • Serving Portland Since 1895 When completed, the new reservoir will provide service for at least another 100 years.

  • Lower Reservoir 4 - Downtown View A lowland wildlife habitat area, bio-swale, and reflecting pool will be constructed.

  • Supplying Water to Portland's West Side Serving more than 360,000 people, 20 schools, three hospital complexes, 60 parks, and major attractions.

  • Upper Reservoir 3 - Grand Staircase View The new reservoir, in the footprint of the historic Reservoir 3 (upper), features a reflecting pool at ground level.

  • Washington Park Reservoir Improvement Project A new 12.4-million gallon, seismically reinforced underground reservoir.

  • Lower Reservoir 4 - Powerhouse View Existing Reservoir 4 (lower) will be disconnected from the public drinking water system.

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Updated: September 11, 2019

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What's Happening Now 

About 60% of the reservoir foundation has been put into place now, and 20% of the wall sections have been constructed. Crews will continue to prep and pour foundation slabs and wall sections through the end of the year. By the end of year, the first of the support columns will be poured. Columns will support the roof of the new reservoir when it’s in place.To see the August 2019 updates with information and photos of work performed over the past month, click HERE.

Concrete Pour Dates

Dates are approximate and may change due to weather, material availability, or other factors. Work can begin as early as 3:30 a.m. on these dates.

September 24 - Foundation Slab

September 12, 23 & 27 - Wall Sections

Noise Permit, December 2018 - November 2019 (more information HERE)

Due to the size and volume of concrete needed, deliveries will begin in the early morning, in some cases as early as 2:30 am and will continue through the day, with new concrete trucks arriving approximately every 3 - 5 minutes. Concrete deliveries should be completed before 6 pm but on site work will continue beyond that time to complete the finishing work.


Managing the placement and curing of concrete at the Washington Park Reservoir Improvement Project is a delicate act, particularly during the warmer months. As concrete is “batched at the plant” and as it is placed and cures, its temperature heats up. During warm weather, it can heat to temperatures that cause thermal stresses and potential concrete damage. To reach the needed strength for the finished concrete, the heat levels need to be controlled to maintain the tolerances called for in the reservoir design.

To ensure the concrete does not overheat during the warmer months, the contractor will cool the concrete with liquid nitrogen. In the Reservoir 4 area, a liquid nitrogen tank and four bays are being temporarily installed. As concrete trucks enter the project site they will pull into one of the bays where the load will be injected and mixed with liquid nitrogen. Then the truck will move to the construction zone up in Reservoir 3 and the concrete will be pumped into the waiting forms. To see a video of this process, click HERE

Things to know about liquid nitrogen:

  • Possible presence of fog: The boiling point of liquid nitrogen is -321 degrees Fahrenheit. When it hits air, it boils and chills the surrounding air, causing the humidity in the air to condense into fog. When this process is in operation neighbors may notice a fog in the area of Reservoir 4.
  • Liquid nitrogen is cold enough to cause severe frostbite upon contact with living tissue.  Workers will be wearing proper safety gear when injecting the nitrogen into the concrete trucks to help prevent contact or inhalation of the extremely cold vapor.
  • A common use of liquid nitrogen is in the freezing and transport of food products.
  • For more information on liquid nitrogen, click HERE.

To see a map of the construction site, click HERE.

To see the May 2019 updates with information and photos of work performed over the past month, click HERE.

See how the elements of the new reservoir fit together within the footprint of the historic reservoir HERE.

Did You Know?

We’re working to insure our water is safe and abundant for generations to come. Learn about the benefits to filtration HERE.

Project Overview

Including the project description, map and schedule

Community Outreach History

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Traffic Impacts

Beginning April 2, 2018