Cooper Mountain Reservoir #2 Project Completion

In the summer of 2023, the City of Beaverton completed two major water infrastructure projects, increasing the reliability for the growing community demand. GRI played a role in helping bring one of the water infrastructure projects to life, Cooper Mountain Reservoir #2. GRI completed a geotechnical investigation that included geologic information review and site reconnaissance, subsurface explorations, seismic refraction survey, laboratory testing, and seismic and engineering analysis.  The information obtained from the investigation was used to evaluate geologic hazards, slope stability, and subsurface conditions and develop seismic and engineering conclusions and recommendations for design and construction of the project. Additionally, GRI provided was onsite periodically to evaluate temporary excavation and foundation subgrade for the reservoir and related project elements and site grading.

The now operational 5.5-million-gallon water reservoir (and other facility improvements) doubled the water storage capacity serving the entire City of Beaverton, as the Cooper Mountain Reservoirs are at the highest point of the city’s water supply. The new concrete water reservoir has a diameter of 180 feet and a height of about 30 feet and included an approximately 1,400-foot-long transmission waterline upgrade from the reservoir eastward in SW Kemmer Road to connect into additional newly installed sections of waterline. The new reservoir is a key capital improvement that enhances the resiliency of the area by being constructed in accordance with modern seismic standards to withstand a large seismic event including the Cascadia Subduction Zone earthquake.

The completed reservoir is partially buried behind a berm adjacent to the roadway and the area surrounding the reservoir is planted with trees and shrubs to provide an aesthetically pleasing appearance. In the future, it will also serve the South Cooper Mountain development and the continuous development in the Urban Reserve Area.

Congratulations to the City of Beaverton and the project team on the expansion of water storage in the area!