The stability evaluation and the design for the upgrade are based on the maximum credible earthquake (MCE) on the Hayward Fault, which has a moment magnitude of 7.25. As a comparison, the 1989 Loma Prieta earthquake had a moment magnitude of 6.9. Monitoring data before and after the Loma Prieta earthquake had an estimated moment magnitude of 8.0. No evidence of instability or apparent damage was reported after the 1906 San Francisco earthquake. The Hayward Fault earthquake in 1868 had an estimated moment magnitude of 6.8, and it occurred before the construction of Chabot Dam. It is important to note that the recent earthquakes have been on different faults, and represent lower levels of seismic risk. T this time, EBMUD is completing the seismic upgrade of Chabot dam based on the MCE on the Hayward Fault which represents the most severe earthquake forces among the Bay Area faults at the dam site.