The U.S. Department of Interior’s Bureau of Reclamation has awarded a $19.7 million contract to NW Construction Inc. for dam safety modifications to Boca Dam.
Boca Dam, on the Little Truckee River in California, will be modified to better resist seismic forces during an earthquake.
Based on extensive engineering analysis, Reclamation found that Boca Dam and Dike is at risk from structural failure during an earthquake due to the presence of sand and gravel within the dam’s foundation. During an earthquake, the dam has the potential to slump or crack, leading to overtopping or a breach.
The Safety of Dams Act requires Reclamation to reduce the risk of Boca Dam structural failure within acceptable levels.
Modifications will involve removing a sand and gravel lens on the downstream side of the dam and constructing a downstream stability berm to buttress the dam. The spillway will also be seismically retrofitted and the dam crest will be 25 feet wider with a reinforced concrete road surface.
Boca Dam and Reservoir are components of the Truckee Storage Project, which was completed in 1937 and is operated and maintained by the Washoe County Water Conservation District.
Reclamation says construction may begin as early as April 2019 and continue until October 2020. The reservoir will be operated 28 feet lower during construction, from June 2019 to November 2019, to allow access to a borrow area within the reservoir that will provide the earthen material for the stability berm.