 The old earthen dam became a causeway between Upper and Lower Crystal Springs Reservoirs when the latter was formed by Herman Schussler's 150 foot tall concrete Crystal Springs Dam, which dammed up San Mateo Creek to form the lower (northern) reservoir in 1888.The causeway is now crossed by Highway 92.Laguna Creek flows north through the Filoli estate and has tributaries that descend from the western slope of Edgewood County Park and the eastern slope of the Santa Cruz Mountains.