Como Dam was completed in 1910 by local irrigators and rehabilitated on its crest and upstream face by the Bureau of Reclamation in 1954. This semi hydraulic earthfill dam at the end of a natural lake is 70 feet high with a crest length of 2,550 feet and contains 1,114,000 cubic yards of earth and rock. In 1976, the district built concrete protection walls on each side of the spillway section up to elevation 4,249.0 feet, the same elevation as the crest of the dam. Under the Safety of Dams Program, designs for the walls were furnished to the district to correct low points in the dam fill adjacent to the spillway.
Between 1992 and 1994, major modifications to Como Dam were performed to mitigate concerns associated with seepage and piping, liquidfication during a large seismic event, and overtopping during large floods. During these modifications, the spillway crest was raised to elevation 4246.0 feet increasing the active reservoir capacity from 35,100 acre-feet to 38,500 acre feet. The State of Montana paid for this work and obtained 3,000 acre-feet of capacity for storing water to use in enhancing minimum streamflows in the Bitterroot River.