American Falls Dam, a 94ft-high composite concrete and earth gravity-type dam on the Snake River in Power County, near the town of American Falls, Idaho, will undergo maintenance and rehabilitation in 2020 and 2021, the US Bureau of Reclamation (USBR) has announced.

The dam was originally completed in 1928 and was reconstructed and replaced under authority of Safety of Dams Act in 1978.

With a storage capacity of 1,700,000 acre-feet, American Falls Reservoir is the largest reservoir of the Minidoka Project. The dam and reservoir comprise a multipurpose facility from which principle benefits include irrigation, power generation (through a power plant owned and operated by Idaho Power Company), flood control, fish and wildlife resources, and recreation. About 889,282 acres of land downstream of American Falls on the Snake River Plain area are irrigated annually with water stored in American Falls Reservoir.

The planned construction activities will address the need for replacement and repair of deteriorating concrete on the spillway, spillway gate operator decks, downstream dam face, adits, and stilling basin structures, which have experienced degradation over 40 years in service. Construction activities will consist of the hydro demolition, cutting, removal, and replacement of existing damaged concrete and reinforcing on these components, and replacement or modification of an existing drain grate in the stilling basin. Construction will take place from June to November 2020 and mid-July to November 2021.

In preparation for this project, USBR completed an Environmental Assessment (EA) to examine the potential effects of the proposed actions. Based on the results of the EA, USBR issued a Finding of No Significant Impact (FONSI).