The 4th of July Waters that Didn’t

The 4^th of July should have been an anniversary for the ages—commemorating the flow of the first outside drinking waters into San Francisco.

At least that was the intention in 1862, when construction of a brand new dam on the Peninsula Watershed--the Pilarcitos--was rushed to time the arrival of the first Peninsula waters with the nighttime fireworks. While the fireworks went off on schedule, the water didn't start coming in until early the next morning on July 5. 

Previously the young, fast-growing city had relied on sources within its own boundaries, such as Lobos and Islais creeks, Mountain Lake and various wells. It was the Spring Valley Water Company (one of several private utility companies serving the people of San Francisco) that first looked to the neighboring Peninsula as an abundant source of additional drinking water.  

That first dam was soon replaced by another four years later. The second one survived the earthquakes of 1906 and 1989, and is still in service today.

It holds Pilarcitos Creek raw water primarily for delivery to the Coastside County Water District in Half Moon Bay. We also release reservoir water to improve fish habitat downstream. Some also still goes to the SFPUC's Crystal Springs Reservoir and the Hetch Hetchy Regional Water System for supplemental supply.