4.1.4 Coyote Dam

Coyote Dam experienced almost no damage during the 1984 Morgan Hill Earthquake. Its construction finished in 1936. This dam is an earthfill embankment dam with foundation of dam consisted of bedrock. At time, one of few dams constructed on known fault.

Morgan Hill earthquake (Tepel, 1985)

The Morgan Hill Earthquake occurred on April 24, 1984. The earthquake occurred on the Calaveras Fault with a magnitude of 6.2. Coyote dam is located 15 miles from the epicenter and the dam is near the southern portion of the subsurface rupture zone.

The dam preformed well, given very large accelerations. No repairs needed. The SCVWD emergency response program dispatched senior inspectors immediately after the earthquake to observe the status of the dam at that time.

Cross-section of Coyote Dam

Sources:

Sherard, James L., Sc.D., Richard J. Woodward, M.S., Stanley F. Gizienski, M.S., and William A. Clevenger, B.S., Earth and Earth-Rock Dams, Engineering Problems of Design and Construction, John Wiley and Sons, Inc., 1963.

Tepel, Robert E., M. EERI, “The Morgan Hill Earthquake of April 24, 1984 – Effects on Facilities of the Santa Clara Vallet Water District,” Earthquake Spectra, Vol. 1, No. 3, May 1985, pp. 633-656.

Brina Mortensen, Coyote Dam Performance during the Morgan Hill Earthquake in 1984, Case History Report, 2.15, 2008

California Geologic Survey, Probabilistic Seismic Hazards Assessment,

http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamap.asp