Ellensburg-Moxee Foundations

River Crossing Structure Replacements

The Ellensburg-Moxee River Crossing project was a critical infrastructure upgrade designed to improve the safety and efficiency of a 115 kV transmission line crossing the Yakima River in Central Washington. Observed and modeled flooding of the river necessitated the removal of three existing wood transmission structures and replacing them with two taller three-pole foundations on either side of the river. Owner, Bonneville Power Administration (BPA), commissioned the project to ensure the safety and reliability of the line, taking long-term flooding and erosion concerns into account.

Team Members

Bonneville Power Administration

Crux Subsurface

Crux’s Role

Crux was contracted to install drilled pier foundations to support the two river-crossing structures. Geotechnical conditions featured river-rock soils, gravels, and cobbles with clayey sand. These soils were very dense and wet with silt and required the installation of CMPs to eliminate caving potential. Piers were successfully installed to diameters of 11 feet and depths of 21.25 feet, and Crux completed concrete and CSL testing to assist in final approval.

Challenges included working under existing overhead lines, requiring coordination with Qualified Electrical Workers during crane-supported rebar activities. Constraining the project timeline this work had to be completed within a tight, two-week outage window. Additional challenges included working in the very hot (100-degree Fahrenheit), dusty, and dry environment, which required crews to maximize work during the cooler morning hours and constantly be aware of potential fire hazards.

None of these challenges however affected execution or the timeline of the project. The successful completion of the Ellensburg-Moxee project was significant to BPA in eliminating future constructability challenges controlled by the wet geotechnical conditions.

All foundation work was successfully completed within the confined outage window, and BPA was complimentary of Crux’s constant communication and exemplary safety standards throughout the length of the project.