Crystal Springs Dam

Probably the world’s first large mass concrete dam constructed.  Designer and builder, Hermann Schussler, pioneered the use of on-site concrete mixing and the use of a series of interlocking concrete blocks that significantly increased Its strength and seismic resistance.

The construction of Crystal Springs Dam, originally known as Lower Crystal Springs Dam, began in 1887 with some site work in 1886.  The dam’s construction was completed in 1889 with the height of the dam raised in 1890 to 145 ft above the foundation.  The reservoir impounded by Crystal Springs Dam has a maximum volume of 66,850 ac-ft (21.8 billion gal). The dam’s crest length is 601 ft, and its concrete volume is 157,000 cy.   The dam is now owned and operated by San Francisco Public Utilities Commission.  The dam is a curved-gravity concrete dam and was the first large mass concrete dam constructed in the United States, probably the first in the world. The dam was shaken by the 1906 San Francisco Earthquake and again by the 1989 Loma Prieta Earthquake due to its proximity to the San Andreas fault trace, which is located about 1,100 ft west of the dam. The dam does not appear to have experienced any damage from either earthquake.

The dam was designed and constructed under the leadership of Chief Engineer Hermann Schussler (M. ASCE).  Schussler was born in Germany in 1842 and received his engineering education in Switzerland and Germany, then moving to San Francisco in 1864.  He was hired by the Spring Valley Water Company from which he retired in 1919.

Crystal Springs Dam was constructed utilizing several first uses of Schussler’s innovative practices; they transformed how the materials used to make concrete would be prepared and how large mass concrete dams would be constructed in the future. These concrete innovations included the careful crushing of local rock and the washing of aggregate to remove impurities on site, the use of steam-powered equipment to crush the aggregate and to then mix it with washed sand and water on site, using the equipment designed by Schussler.  The concrete dam design and construction innovations associated with Mr. Schussler included the use of a series of interlocking concrete blocks that significantly increased the dam’s strength and seismic resistance.  Also, the surface of the raw new concrete was roughened to remove latencies and to ensure proper block-to-block adhesion; the concrete surface was covered with burlap and wetted periodically to prevent exothermic heat buildup, which could lead to cracking; and the joints between individual concrete blocks were staggered.

Schussler originally wanted to construct the dam as a stone masonry structure but was unable to find a local source of competent stone, forcing him to shift his design concept to the use of mass concrete.  In 1886, there was no Portland cement industry in the United States capable of supplying the quantities required, and Schussler had to obtain the cement from Portland, England.  The cement was shipped 16,000 nautical miles in watertight barrels by sailing ship from Portland, England, to San Francisco, California via Cape Horn.  The barrels of cement were then shipped to the dam site by rail to San Mateo and then by horse-drawn freight wagons.

References:
Historic American Engineering Record (HAER); “Lower Crystal Springs Dam”, September 2010, 21 pages plus photographs.
Journal of Electricity Power and Gas, San Francisco, CA, December 11, 1909; “The Water Supply of San Francisco”.
Meacham, Laura G. “Hermann Schussler: The Invisible Architect of Western Water Conveyance Systems”, Master of Arts Thesis, University of Nevada, Reno, May 2022.
O’Neill, Gary M. “Hermann Schussler: A Biography, Senior thesis, Pomona College, Pomona, CA April 1974.
O’Neill, Gary M. “Hermann Schussler and the Spring Valley Water System; La Peninsula, The Journal of the San Mateo County Historical Association, Vol. XXVI, No. 2, August 1990.
San Francisco Public Utilities Commission; Undated monograph (late 1970s?): “No. 2-1 Lower Crystal Springs Dam, Owner: City of San Francisco Public Utilities Commission” 9 pages.
San Francisco Section, ASCE, October 1977; “Historic Civil Engineering Landmarks of San Francisco and Northern California, pp 20 – 24.
Schussler, Hermann, Chief Engineer, Spring Valley Watter Company; “The Water Supply of San Francisco, California, Before, During and After the Earthquake of April 18, 1906, and the Subsequent Conflagration”, July 23, 1906.
Spring Valley Water Company, San Francisco, CA, October 31, 1912; “The Future Water Supply of San Francisco, a report to the Honorable the Secretary of the Interior and the Advisory Board of Engineers of the United States Army”.
Memoir of Hermann Frederick August Schusler, ASCE Transactions, 1919-1920, pages 2329-30.