Peninsula Watershed’s Oldest Dam Still Going Strong

It was San Francisco’s first water source outside City limits.

Pilarcitos Dam—situated deep in the Peninsula Watershed’s remote Pilarcitos Canyon—turned 153 this year. It survived the earthquakes of 1906 and 1989 with no damage, it’s still in service today, and planning is under way to extend its operating life for years to come.

Pilarcitos Dam showing Reservoir and Camp, Copy of Pix. #2 in 1904 Spring Valley Album, pg. 14, * The photo was taken winter 1866-67*

Today, the 1866 earth-fill dam holds Pilarcitos Creek raw water for delivery primarily to the Coastside County Water District in Half Moon Bay, with some water also diverted as supplemental supply to Lower Crystal Springs Reservoir. Water releases from the dam also improve downstream fish habitat, and the secluded woodsy canyon is a safe haven for nesting Marbled murrelets.

Peninsula Watershed, Pilarcitos Reservoir and Dam
Peninsula Watershed, Pilarcitos Reservoir and Dam