Inspecting Hoover Dam Following an Earthquake

Written by: Doug Hendrix

Nathaniel Gee, Chief Engineer with the LCR's Engineering Services Office, inspects one of the spillways at Hoover Dam. Photograph provided by Alex Stephens, Photographer, Bureau of Reclamation.The recent earthquakes that rattled Southern California and parts of Nevada didn’t damage Hoover Dam. Following the 6.4 and 7.1 magnitude earthquakes that first struck near Ridgecrest, California, on July 4th and 5th respectively, Reclamation staff immediately inspected the dam and found no evidence of any damage.

“Hoover Dam reacted satisfactorily to all of the recent large earthquakes,” said Nathaniel Gee, Chief of the Engineering Services Office with Reclamation’s Lower Colorado Region. “If our on-site and remote monitoring devices confirm seismic activity at or near the dam, inspectors will physically walk the dam looking for settlement, cracking, sloughing or movement of the dam. Inspectors also look for movement at the toe and abutments of the dams and for any changes in water clarity or quantity of water flow at the outlet works, as well as look for any signs of distress in the control towers and the spillways.”

To ensure that all of Reclamation’s 360 high and significant hazard storage dams and dikes that form part the western United States’ critical water infrastructure remain safe and secure following an earthquake significant enough to trigger an inspection, engineers immediately inspect facilities within the active seismic zone to determine if the ground shaking or vibrations from an earthquake caused any structural distortions or damage to the dam, its foundation, and appurtenant power generation and water delivery structures.

Instrumentation throughout the dam is also checked and the readings from those devices are noted, Gee added. The gates and other control equipment are also checked to ensure operational capabilities are in order.

Close to the epicenter of the recent earthquakes, relatively minor damage was reported. There were some isolated reports of building fires in Ridgecrest near the epicenter. The main quake on July 5 cut power to at least 3,000 residents in Ridgecrest – with seismic effects felt across much of Southern California, parts of Arizona and Nevada, and as far north as the San Francisco Bay Area. An estimated 20 million people experienced the foreshock, and approximately 30 million people experienced the main shock.

Published on July 26, 2019