The US Bureau of Reclamation has awarded a $10,708,466 contract to T1 Construction LLC, based in North Bend, Oregon, to repair the Angostura Dam spillway.

The project involves upgrading the access road to the stilling basin and addressing damage caused by freeze-thaw cycles by replacing deteriorated concrete on the dam’s surface.

Construction is expected to take 955 days, mainly due to restrictions on spillway releases. Preparation work will begin this winter and continue into early spring.

Angostura Reservoir, located on the Cheyenne River in Fall River County, South Dakota, was created in 1949 following the construction of Angostura Dam. The reservoir spans over 4,400 water surface acres and features 42 miles of shoreline at the southeastern edge of the Black Hills near the Nebraska border.

The project serves as an important habitat for migrating waterbirds and various passerine species and is a key ecological and recreational resource in the region.

The Angostura Dam is a composite structure combining a concrete gravity section and an earth embankment. The concrete portion includes a gated spillway positioned in the river channel, flanked by two non-overflow sections—one extending to the left abutment and the other adjoining the earth embankment on the right abutment. The dam has a total crest length of 2030ft, with the concrete section measuring 970ft and the earth embankment spanning 1060ft. Its structural height is 193ft, and its hydraulic height rises 136ft above the riverbed.