Crystal Springs Dam is a

gravity dam A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation to oppose the horizontal pressure of water pushing against it. ...

constructed across the San Mateo Creek which is in

San Mateo County San Mateo County ( ), officially the County of San Mateo, is a county located in the U.S. state of California. As of the 2020 census, the population was 764,442. Redwood City is the county seat, and the third most populated city following Daly ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It impounds water to form the Lower Crystal Springs Reservoir which sits atop the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonics, tectonic boundary between the Pacific Plate and the North American Plate, and its motion is Fault (geology)#Strike-slip fau ...

in a rift valley created by the fault. The dam itself is located about 300 yards (273 meters) east of the fault. It was among the first concrete gravity dams built in the western United States. Skyline Boulevard runs over the dam, which also forms the trailhead of the popular

Sawyer Camp Trail Sawyer Camp Trail is a popular trail located in the San Andreas Fault rift valley in San Mateo County, California near Hillsborough and the San Mateo Highlands. Officially, it is a segment of the longer Crystal Springs Regional Trail. Approximat ...

History

The structure was completed in 1888. At the time of its completion, it was the largest concrete structure in the world. The designer was

Hermann Schussler Hermann Schüssler or Schussler (August 4, 1842 – April 27, 1919) was a German civil engineer and designer of dams, famous for designing the Crystal Springs Dam and Comstock water system. Early years Hermann Schussler was born in what is t ...

, Chief Engineer of the Spring Valley Water Company. The dam was constructed by separately pouring large blocks of the structure in place, and allowing them to set before pouring the adjoining blocks. An important design feature is that neither the horizontal nor the vertical joints line up. This helps the structure act as a single monolithic construction despite being made of thousands of individual blocks. Schussler ensured that each block of the dam was poured with concrete made to the exact proportions of his mix specifications. In 1976, the dam was designated as a California Historic Civil Engineering Landmark by the

American Society of Civil Engineers American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

Quake proof

The dam has survived both the

1906 San Francisco earthquake At 05:12 Pacific Standard Time on Wednesday, April 18, 1906, the coast of Northern California was struck by a major earthquake with an estimated moment magnitude of 7.9 and a maximum Mercalli intensity of XI (''Extreme''). High-intensity sha ...

and the

1989 Loma Prieta earthquake The 1989 Loma Prieta earthquake occurred on California's Central Coast on October 17 at local time. The shock was centered in The Forest of Nisene Marks State Park in Santa Cruz County, approximately northeast of Santa Cruz on a section of t ...

– despite its location about 300 yards east of the

. It was subject to severe shaking in both earthquakes.

Repairs

The

San Francisco Public Utilities Commission The San Francisco Public Utilities Commission (SFPUC) is a public agency of the City and County of San Francisco that provides water, wastewater, and electric power services to the city and an additional 1.9 million customers within three San Franc ...

began the process of renovating the dam in 2003. A major step in the renovation process, doubling the width of the main spillway and raising the dam to increase the water storage capacity, was completed in 2012. The renovations, which are intended to improve the reliability of the system in the event of an earthquake, were completed in 2016. Skyline Boulevard on top of the dam was closed for construction in October 2010. Construction completed in late 2018 and the roadway was reopened in January 2019. The bridge closed again to vehicular traffic on February 10, 2020, for the Lower Crystal Springs Dam Pond and Parapet Project with an expected completion and re-opening date of April 3, 2020. File:Crystal Springs Dam Leeside.jpg, Crystal Springs Dam from downstream File:Crystal Springs Reservoir.jpg, Lower Crystal Springs Reservoir File:Crystal Springs Reservoir aerial view, February 2018.JPG, Aerial view of the Crystal Springs Reservoir from the southeast File:Crystal Springs Dam from under highway 35.jpg, View from under the

California State Route 35 State Route 35 (SR 35), generally known as Skyline Boulevard for most of its length, is a mostly two-lane state highway in the U.S. state of California. It runs along the ridge of the Santa Cruz Mountains from the high point of State Route 17 ...

roadway that was added atop the dam

References

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External links

San Francisco Public Utilities Commission

SFPUC Project Description

San Mateo County History Museum
Buildings and structures in San Mateo County, California Dams in California Hetch Hetchy Project Dams completed in 1888

History

Quake proof

Repairs

See also

References

Further reading

External links