[1] The embankment structure gave way on June 10, 1964, after heavy rains caused flooding on Birch Creek.
The dam collapsed and sent a 30-foot (9.1 m) wall of water down the creek bed.
The nearby dam at Lower Two Medicine Lake also failed, and at least 28 people were killed.
[3] The reservoir is also contained by a secondary earthen dike (National Inventory of Dams ID MT00580) with a height of 53 feet (16 m) and a length of 457 feet (139 m), also completed in 1967.
[4] The reservoir, Swift Reservoir, has a maximum storage capacity of 34,000 acre-feet (42,000,000 m3), normal storage of 30,000 acre-feet (37,000,000 m3),[3] and a normal elevation of 4,890 feet (1,490 m).