SCIENCETECH · HISTORICAL MARKER
Pactola Dam & Reservoir
Johnson Siding, South Dakota
· Flood Control, Irrigation & Recreation
Science & Tech
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Construction of Pactola Dam began in 1952 and was completed in 1956, with nearly 200 men working at times on the project. Unskilled workers earned $1.25 an hour and skilled workers $2.75 an hour. The work placed 2,163,251 cubic yards of impervious earthfill and 2,156,742 cubic yards of rockfill, for a total of 4,319,993 cubic yards of embankment fill. Although there were no accidental deaths during the four years of construction, numerous injuries resulted from the steep terrain and outcroppings of hard rock known as amphibolite. In 1972, a severe thunderstorm dropped up to 17 inches of rain on the east slopes of the Black Hills; Rapid City was flooded, but the drainage above Pactola Dam received much less rain. Concerns about a possible future storm led to modifications to ensure the dam's continued safety and reliability, including the largest modification completed by Reclamation in 1987, which raised the dam 15 feet and added a new, larger spillway to accommodate extreme floods. Additional modifications have allowed frequent cleanup and maintenance in the outlet works while continuing to provide year-round instream flows below the dam for the blue ribbon fishery and other wildlife. Today, Pactola Dam and Reservoir provide recreation opportunities through facilities and public access managed cooperatively by Reclamation, the U.S. Forest Service, and the South Dakota Department of Game Fish and Parks.
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Johnson Siding, South Dakota
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