In 1914 Congress approved the Raker Act, allowing San Francisco to construct a dam and reservoir in the Hetch Hetchy Valley of Yosemite National Park for the purpose of public water supply.
The Moccasin Creek Fish Hatchery was constructed downstream of the dam in 1954,[5] and raises trout for stocking in high elevation streams in the Tuolumne River watershed, and for the nearby, much larger Lake Don Pedro.
[8] The dam started to leak and evacuations were issued for a small number of houses and a campground downstream before water levels subsided.
[11] The main Moccasin Powerhouse is situated at the eastern (upstream) end of the reservoir, and consists of two units with a total capacity of 100 megawatts.
[12] Moccasin is the furthest downstream of San Francisco's three hydroelectric plants (the others are Kirkwood, near Hetch Hetchy Reservoir and Holm near Cherry Lake).