Pacific Foundation | Geotechnical Excellence

(360) 200-6608

Get in touch


Building the future

Washington Park Reservoir

The Project

Construction of a seismically reinforced underground reservoir in Washington Park to provide water supply for over 360,000 people.

The Solution

The project scope included the construction of a 16,500 SF temporary soldier pile wall, a 28,500 SF permanent soldier pile wall, 166 drilled shafts, dewatering, cathodic protection, instrumentation, and toe-block anchors.

The Result

This new, seismically reinforced below-ground reservoir that will supply water to Portland’s west side, serving over 360,000 people and ensuring reliable access to clean drinking water.

Scope of Work

The project includes building a new, seismically reinforced below ground reservoir. This very large drilling project included the design and construction of a:

    1. 16,500 SF temporary soldier pile wall with 230 tiebacks.
    2. 28,500 SF permanent soldier pile wall with 860 permanent DCP tieback anchors and pile lengths up to 92 feet.
    3. A total of 166 42” and 60” diameter drilled shafts with up to 35 feet of embedment into R3 and R4 basalt.
    4. Dewatering, cathodic protection, instrumentation and toe-block anchors.
    5. Drilled shafts utilizing a Bauer BG40, sectional casing, and tremie systems.
    6. Soldier piles drilled in both CFA and conventional modes.


Washington Park Reservoir-area


The new reservoir will preserve the historic drinking water function provided by the original reservoirs at the site and be engineered to withstand ongoing landslide encroachment and potentially catastrophic effects of a major earthquake. A reflecting pool/water feature will be constructed on top in the same general footprint as the historical Reservoir 3. Reservoir 4 will be disconnected from the public drinking water system and a lowland wildlife habitat area, bioswale, and reflecting pool will be constructed in the basin.

When complete and online, the new underground reservoir will supply water to Portland’s west side and serve more than 360,000 people, including all downtown businesses and residents, 20 Portland public schools, three hospital complexes, more than 60 parks, and the Oregon Zoo.

Washington Park Reservior

Project Timeline



  • July 1, 2016: Begin construction
  • December 31, 2019: Complete construction on new Reservoir 3
  • December 31, 2020: Disconnect Reservoir 4 from the public water system
  • 2023-2024: Complete project completed

Upcoming Work and Project Impacts

The project will span eight years. The first two years (2016-2018) will trigger the most significant impacts to traffic, transportation, and parking in the park. Washington Park users are encouraged to travel to and move safely around the park and its attractions by using the bus and light rail, walking, biking and skating, and taking the free park shuttle. Visit and for transit options.

    Let's get Connected

    Have a Question?

    Want to learn more about our expertise or to discuss an upcoming project? Click on the button below to contact us via phone, email or contact form.