O'Shaughnessy Dam in Hetch Hetchy Valley
Many engineers may not be fully aware of the history of the Hetch Hetchy project. The following facts are taken from a July, 1931, paper by M. M. O’Shaughnessy, the then San Francisco City Engineer, and to a large degree, the “father” of the Hetch Hetchy project. The project was not finished but was nearing completion in 1931.
The Hetch Hetchy valley is on the Tuolumne River, in the northern part of Yosemite National Park. The watershed is 420,000 acres in extent, and the original capacity was designed to furnish 400 million gallons of water per day to San Francisco. Supplemental water supplies became a necessity for San Francisco by the early 1900s and studies were undertaken to locate suitable, available sources. The City Engineer, after evaluation of alternatives, selected the Tuolumne as being best.
The city filed for water rights under California law but federal approval was also required because of the National Park location. Early federal requests were denied, but in 1908 the Secretary of the Interior gave limited approval and based on that San Francisco voters approved bond issues totaling $45.6 million. However, a later Secretary proposed rescinding the federal permit, so the city sought Congressional approval. After lengthy controversy, the Raker Act was finally signed by President Wilson and the city commenced construction in 1914. The Act included a number of special conditions and requirements with which the city had to comply. There were later bond issues to complete the overall project.
As built, the O’Shaughnessy dam was a total of 344 feet high with a crest elevation of 3,726 feet. It contained nearly 400,000 cubic yards of concrete, and cost about $7 million.
The portion of the original project not yet completed in 1931 involved transmission of the water from the Sierra to the Peninsula, with tunnels, and pipelines crossing the San Joaquin Valley and the Bay. The project also included electrical generation and transmission facilities.
Mr. O’Shaughnessy concludes his paper with “The design and construction have been characterized by care and conservatism. The work is being prosecuted efficiently and economically, largely by day labor, under the control of the City Engineer and his staff of able assistant engineers”.
If the dam is to be removed, one of the important questions is the unique quality of the water behind the present dam. O’Shaughnessy notes that it had only 15 ppm of total solids and a hardness of 2.6, which he calls “absolutely pure”. (Can replacement storage match this quality?)
More agencies than San Francisco have a major stake in the question of demolishing the dam and developing new storage. San Francisco has customers in both San Mateo and Alameda Counties, including the City of Hayward, which can be affected not only by the quantity and quality of future supplies, but may also be called upon to contribute to the cost. Public and political consensus will be difficult to achieve.
The Hetch Hetchy proposal illustrates a trend which involves and challenges engineers. There is a widening disconnect in California, and this country, between an ever-growing population and the preservation and expansion of facilities which provide the vital resources to support that population. Water is a critical such resource, along with food and energy.
In California certain groups have been successful in efforts to divert water supplies to protect or restore fish populations by removal of other dams, such as on the Klamath River, and restoration of the San Joaquin River, and they are challenging pumping in the Delta. Opposition has generally blocked new dams for water supply and flood control. Beyond that, some groups demand more renewable energy, while at the same time objecting to wind power systems and proposed locations for solar power installations. Certainly we can make better use of what we have, but if the population is to continue to grow, society must choose between what some see as degradation of the environment and others see as essential for maintaining the economy and the standard of living.
What will history say about how we have dealt with these issues?
The Hetch Hetchy valley is on the Tuolumne River, in the northern part of Yosemite National Park. The watershed is 420,000 acres in extent, and the original capacity was designed to furnish 400 million gallons of water per day to San Francisco. Supplemental water supplies became a necessity for San Francisco by the early 1900s and studies were undertaken to locate suitable, available sources. The City Engineer, after evaluation of alternatives, selected the Tuolumne as being best.
The city filed for water rights under California law but federal approval was also required because of the National Park location. Early federal requests were denied, but in 1908 the Secretary of the Interior gave limited approval and based on that San Francisco voters approved bond issues totaling $45.6 million. However, a later Secretary proposed rescinding the federal permit, so the city sought Congressional approval. After lengthy controversy, the Raker Act was finally signed by President Wilson and the city commenced construction in 1914. The Act included a number of special conditions and requirements with which the city had to comply. There were later bond issues to complete the overall project.
As built, the O’Shaughnessy dam was a total of 344 feet high with a crest elevation of 3,726 feet. It contained nearly 400,000 cubic yards of concrete, and cost about $7 million.
The portion of the original project not yet completed in 1931 involved transmission of the water from the Sierra to the Peninsula, with tunnels, and pipelines crossing the San Joaquin Valley and the Bay. The project also included electrical generation and transmission facilities.
Mr. O’Shaughnessy concludes his paper with “The design and construction have been characterized by care and conservatism. The work is being prosecuted efficiently and economically, largely by day labor, under the control of the City Engineer and his staff of able assistant engineers”.
If the dam is to be removed, one of the important questions is the unique quality of the water behind the present dam. O’Shaughnessy notes that it had only 15 ppm of total solids and a hardness of 2.6, which he calls “absolutely pure”. (Can replacement storage match this quality?)
More agencies than San Francisco have a major stake in the question of demolishing the dam and developing new storage. San Francisco has customers in both San Mateo and Alameda Counties, including the City of Hayward, which can be affected not only by the quantity and quality of future supplies, but may also be called upon to contribute to the cost. Public and political consensus will be difficult to achieve.
The Hetch Hetchy proposal illustrates a trend which involves and challenges engineers. There is a widening disconnect in California, and this country, between an ever-growing population and the preservation and expansion of facilities which provide the vital resources to support that population. Water is a critical such resource, along with food and energy.
In California certain groups have been successful in efforts to divert water supplies to protect or restore fish populations by removal of other dams, such as on the Klamath River, and restoration of the San Joaquin River, and they are challenging pumping in the Delta. Opposition has generally blocked new dams for water supply and flood control. Beyond that, some groups demand more renewable energy, while at the same time objecting to wind power systems and proposed locations for solar power installations. Certainly we can make better use of what we have, but if the population is to continue to grow, society must choose between what some see as degradation of the environment and others see as essential for maintaining the economy and the standard of living.
What will history say about how we have dealt with these issues?
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