Hetch Hetchy Dam and Reservoir Expansion – Yosemite National Park CA

Description

The Public Works Administration (PWA) funded a major increase in the height of the O’Shaughnessy Dam, which creates Hetch Hetchy Reservoir.  The dam had been completed by the city of San Francisco in 1923, after years of controversy over flooding the magnificent Hetch Hetchy Valley, the smaller twin of Yosemite Valley.  This was the height of the dam-building era in America.

When San Francisco sought to expand the reservoir’s capacity, the PWA provide funding for the project, which was completed in 1937-38. The dam was raised by 86 feet and the width of the dam enlarged at the same time.  

“In 1923, the Public Utilities Commission of the city and county of San Francisco expended $8,300,000 on the construction of the O’Shaughnessy Dam, which was a gravity-type arched dam, rising to a height of 226 feet above the bed of the stream. Between 1923 and 1936, due to increased population and water consumption in San Francisco and its environs, a reservoir of greater magnitude became necessary and this project was undertaken with the aid of the P.W.A. It consisted of increasing the height of the dam from its original 226 feet to a height of 312 feet, an increase of 86 feet, and in doing this the volume of concrete was practically doubled. … The enlargement of this dam was completed in 1938 at a construction cost of $3,623,634 and a project cost of $4,279,049.” (Short and Brown, p. 521)