O'Shaughnessy Dam
A curved gravity dam on the Tuolumne River in the Hetch Hetchy Valley of Yosemite National Park.
Plan Around O'Shaughnessy Dam
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O'Shaughnessy Dam Details
Once rivaling the Yosemite Valley in beauty, the Hetch Hetchy Valley is now under water, flooded when the O'Shaughnessy Dam was built in 1923 after years of controversy. Nearly a century later, the battle to dismantle the dam and restore the Valley remains ongoing. Named for the original chief engineer of the Hetch Hetchy Project, Michael M. O'Shaughnessy, the dam impounds up to 360,000 acre feet of water and supplies both water and power to the City of San Francisco, San Mateo County, Alameda County, and the San Joaquin Valley. Water is diverted into the Canyon Tunnel and carried via the Hetch Hetchy Aqueduct to the Bay Area. Originally 227 feet high, the dam was raised to 312 feet in 1938. The reservoir stretches more than eight miles behind the dam into the Hetch Hetchy Valley. The Sierra Club and founder John Muir led the early fight against the dam, which was originally proposed in 1903. Muir famously declared, "Dam Hetch Hetchy! As well dam for water-tanks the people's cathedrals and churches, for no holier temple has ever been consecrated by the heart of man." The Raker Act of 1913, which allowed for the flooding of the valley, specified that no profit could be taken from the water and power derived from the dam, but critics contend that the City of San Francisco has violated that law through contracts with private utility companies.
Difficulty
Low
Distance
N/A
Estimated time
Region
Hetch Hetchy
Nearby Parks Around O'Shaughnessy Dam
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Nearby Points of Interest Around O'Shaughnessy Dam
Use nearby POIs to quickly expand your options beyond O'Shaughnessy Dam while the map context is still fresh.
0.2 mi away
Hetch Hetchy View
Provides a viewpoint of the Valley's waterfalls.
0.3 mi away
Hetch Hetchy (H4)
This glacial valley once rivaled Yosemite in beauty, but was flooded when the O'Shaughnessy Dam was built.
0.3 mi away
Hetch Hetchy View (H5)
Provides a viewpoint of the Valley's waterfalls.
1.9 mi away
Wapama Falls
The larger of two waterfalls located on the northern wall of Hetch Hetchy Valley.
2.6 mi away
Hetch Hetchy Railroad (HHRR)
A 68-mile standard gauge railroad constructed by the City of San Francisco to support construction of the O'Shaughnessy Dam.
