Barnard Construction Co., Inc.

Owner:

Brookfield Smoky Mountain Hydropower, LLC

Scope Of Work

When dam officials observed cloudy-water seepage at the downstream toe of Chilhowee Dam, Brookfield Smoky Mountain Hydropower (Brookfield) took action and lowered the reservoir so that dam safety personnel could inspect and perform a thorough geotechnical investigation of the dam. Discovering that seepage through the earthen embankment had contaminated a portion of the dam’s clay core, Brookfield, along with their Engineer of Record WSP, solicited Barnard’s help to brainstorm potential repair options, ultimately leading to finalizing a design for repairs. With the goal of ensuring public safety and the continued use of the Chilhowee Dam and Hydroelectric Facility, Brookfield contracted with Barnard to address the seepage issues and rehabilitate the dam's north embankment.
 
Located in the foothills of the Great Smoky Mountains, the Chilhowee Dam was constructed in 1955 to generate hydroelectric power for a nearby aluminum plant. The dam has two rockfill embankments and an 85-foot-high by 1,500-foot-long clay core. To eliminate seepage through the clay core, we first excavated approximately 40 feet of upstream embankment material to remove soft clay in a confined area near the dam’s non-overflow section. We utilized a graduated/careful approach to perform this work and excavated a ramp and working platform to within 2 feet of the reservoir surface elevation. Our subcontractor Drill Tech then constructed a secant pile wall and secant pile box that allowed our team to excavate inside the secant pile box to a depth of 30 to 35 feet below the reservoir surface elevation. Upon reaching the required excavation depth, we began fill operations with cement bentonite inside the secant pile box. Using this unique construction approach allowed our team to maintain visual observation and confirmation of the repair. Once backfill of the secant pile box was complete, the upstream embankment was reconstructed using graduated/careful backfill methods, ensuring no cross-contamination of the five-zoned embankment. The completion of this project marked Barnard’s successful implementation of the design focused on addressing issues with the original foundation preparation, thereby eliminating seepage through the dam’s clay core.