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. Due to the large elevation drop between Hetch Hetchy and the city, several hydroelectric power stations were constructed along the long Hetch Hetchy aqueduct.TC History. Wonders Construction of the Moccasin Powerhouse began in 1921 and was completed on August 14, 1925. The Moccasin Dam was completed in 1930 as a regulating afterbay for the Moccasin Powerhouse.
