Idaho Power’s Brownlee Dam is a hydroelectric earth fill embankment dam on the Snake River, along the Idaho-Oregon border.  The dam impounds the river in the 58-mile long Brownlee Reservoir, and is part of the Hells Canyon Project, which also includes Hells Canyon Dam and Oxbow Dam.

Crux was contracted to complete geotechnical drilling and testing on the spillway of the dam to examine the spillway to rock interface.  Equipment and materials were mobilized onto the spillway utilizing crane support, and 13 geotechnical borings were drilled vertically to either 10 or 40 feet utilizing a track mounted geotechnical drill.  In addition, two borings were drilled for proof testing purposes.  All-thread bar was installed and grouted to the full 40 feet in the first boring and to 30 feet in the second.  This allowed for the two proof tests to effectively test strengths at different depths.

Project challenges included working on the steep, slippery spillway, which was covered by algae and made traction for both crews and equipment difficult.  Crews experimented with various types of traction cleats and ultimately found one which provided adequate traction for the working conditions.  In addition, the drill was retrofit with rubber tracks as opposed to the standard steel for increased mobility.