Washington Park Reservoir Replacement

About This Project

Carlson provided the special inspection and materials testing for the Washington Park Reservoir Replacement

In order to comply with federal and state mandates and ensure a healthy, resilient, and secure water system, this eight-year capital improvement project to update the Washington Park reservoir site in the West Hills of Portland is underway.

Currently, Washington Park’s open Reservoirs 3 (upper) and 4 (lower) occupy the site along with two gate houses, a weir building, three pump houses, a generator house, and associated underground piping. The reservoirs are part of an ingenious gravity‚Äźfed drinking water system constructed more than 120 years ago in 1893 and 1894, respectively.

The Washington Park Reservoir Improvements Project entails building a new, seismically reinforced below ground reservoir. The reservoir will not only maintain the historic drinking water function provided by the original reservoirs, but will be engineered to withstand ongoing landslide encroachment and potentially catastrophic effects of a major earthquake and will feature a reflecting pool 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 habitat area/bioswale and a reflecting pool will be constructed in the basin.

When complete and online, the new underground reservoir will supply water to Portland’s west side, including all downtown businesses and residents, the Oregon Zoo, more than 60 parks, six hospitals, and 20 Portland public schools.

Project team members include the Portland Water Bureau (owner), Cornforth Engineering (geotechnical engineer of record), Hoffman Construction Company (general contractor), and Coffman Excavation (earthwork contractor). Carlson has been retained by Hoffman and Coffman Excavation to provide quality control testing services during the anticipated 8-year long project.

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Project Services

  • Full-time density testing
  • Daily sampling of soil-cement blended materials
  • Daily preparation of specimens for compressive strength testing
  • Modified Proctor testing
  • Comprehensive strength testing
  • Erosion control monitoring