Boca Dam Safety of Dams Project
Boca Dam, Truckee Storage Project, California
Reclamation has completed the Corrective Action Study and has identified the preferred alternative to carry forward into the final design phase of the project to address the risk of earthquake damage at Boca Dam. The dam is located in Nevada County, California, about 5 miles northeast of the City of Truckee, on the confluence with the Truckee River.
Boca Dam is located in a seismically active area. Exploration and analyses indicate that foundation materials beneath the dam may be susceptible to loss of strength during a major earthquake. The loss of strength, known as liquefaction, could result in substantial consequences, although the possibility of dam failure is remote. Analyses also indicate the dam’s concrete spillway may have seismic deficiencies.
Boca Dam was completed in 1939 and has a structural height of 116 feet and a crest length of 1,630 feet. The dam provides flood protection for Reno and Sparks, Nevada. The dam impounds Boca Reservoir, which has a storage capacity of 41,141 acre-feet at water surface elevation 5605. The reservoir is used to regulate the Truckee River and provide water for irrigation, recreation, fish and wildlife benefits, and drought supplies for municipal and industrial users in the Reno metropolitan area. The dam is owned by Reclamation and operated and maintained by the Washoe County Water Conservation District.
Status: The preferred alternative includes excavation of a shear key at the downstream toe of the dam and dike to remove a portion of the potentially liquefiable foundation soils. In addition, a stability berm will be constructed to aid in stabilizing the dam and dike during an earthquake. Also, the spillway crest structure will be retrofitted to withstand earthquake damage. The modifications to the existing structures are not expected until 2016 or later.