Page 73

BACKNEXT

The Teton Dam Disaster, June 5, 1976
One Idaho reclamation project failed, spectacularly and tragically. The Teton Dam, built on the Teton River 3 miles upstream from Newdale, was designed to provide irrigation water to farms in the Upper Valley of the Snake River, north and east of Rexburg.

The possibilities of a dam on the Teton River were discussed as early at 1904. The Teton Dam was authorized in 1964, and the construction contract was awarded in December, 1971. The dam was finished in November, 1975. Filling began on October 3, 1975, and continued until the dam failed on June 5, 1976. At that time, the reservoir was 302 feet deep, with its surface at 5302 feet elevation, 3.3 feet below the spillway. Leaks below the dam were first noticed on June 3, 1976, but were not considered cause for alarm. However, starting at 7: 00 a.m. on June 5th, dam personnel noted leaks both in the abutment rock at the north bank of the river at the base of the dam and about 100 feet from the top of the dam. These leaks worsened and by mid-morning warnings were sent out that the dam might fail. Failure occurred at 11:50 am. Fourteen persons died in the flood. Property damage was estimated at $400 million to $1 billion.

The Independent Panel to Review Cause of Teton Dam Failure reported on December 31, 1976, that the dam failed because of a combination of geological factors and design decisions. Additional allegations of improper construction procedures were also expressed.

(above) About 10:45 a.m. June 5, 1976. Flow of muddy water is increasing from dam. Two D-8 Caterpillar Dozers were sent in (from top) to fill hole at elevation 5,200 ft. All photos are from U.S. Bureau of Reclamation. (above center) About 11:20 a.m. Dozers are lost in hole. (above right) Dam crest breaching. 11:55 a.m. June 5, 1976. (bottom center) Early afternoon, June 5, 1976. (bottom right) Late afternoon June 5, 1976.