An investigation was performed to assess the potential for faulting at one of the world’s largest proposed water filtration plants designed by Brown and Caldwell-Camp Dresser and McKee for the Los Angeles Department of Water and Power. Filtration capacity is 900 ft3/sec from the Los Angeles Aqueduct water supply. The site is located near Sylmar, California, an area subjected to ground rupture that accompanied the February 9, 1971, M6.4 San Fernando earthquake.