The Teton Dam
The US Bureau of Reclamation, part of the Department of the Interior, is responsible for water resource management as it applies to the diversion of water for its delivery to consumers. Dams are one of the tools which they use in that role, which besides creating reservoirs for the routing of water for drinking and irrigation also creates hydro-electric power. In 1972, after years of debate, lawsuits, protests by environmentalists, and controversy over its necessity, the Bureau of Reclamation began construction of a dam on the Teton River in Idaho, despite geologists’ claims that the area was both seismically active and composed of material largely unsuitable for the purpose.
The area around the dam and beneath it contained numerous fissures and cracks which the builders decided could be sealed with grout. More fissures were discovered as the dam was under construction, which raised the cost of the project and delayed work on the actual dam. Some of what were called fissures in public discussions of the project were actually void spaces the size of caves. Some were determined to be of no consequence as far as the function of the dam was concerned, and left alone. The effect was as if one was building a sand castle while using a grill for a base, with perforated sides.
As the earthen dam was erected, hollow spaces undetected from the surface were created inside the dam itself, as some of the earth settled into cracks and fissures without collapsing the surface soil. These hollow spaces ran through the interior of the earthen dam like tunnels, with no evidence of their existence visible to an observer at the surface. In November of 1975 the dam construction phase was completed and the filling of the reservoir was scheduled to begin. Filling the reservoir was to be at a rate of about one foot per day. In the spring of 1976, as a result of the heavy snows of the preceding winter the rate of filling was increased to about double the original rate.
In May 1976 the rate was doubled again, and in early June leaks were apparent. Neither the dam’s spillway nor its main outlet were ready for service, they were at the time blocked in preparation for painting that month. The emergency outlet was serviceable, but insufficient to relieve enough pressure on the dam if it began to fail. The reservoir was near full capacity. On June 5, a Saturday, dark spots appeared on the face of the dam, indicating the presence of water. The spots grew both larger and darker. As water seeped through it carried more and more of the earthen structure with it. Just before noon the dam collapsed as the water from the reservoir poured through.
Downstream thousands of homes and businesses were destroyed by the onrush of water. The Hibbard and Rexburg area lost over 80% of the structures and buildings in their communities. The lower watershed of the Teton River had most of its topsoil stripped away. Rebuilding took years. Lawsuits and claims against the Bureau of Reclamation began almost immediately, eventually totaling $320 million by 1987. The official investigation did not assign blame for the catastrophic failure of the dam, announcing that it was a combination of geological factors and engineering and construction decisions. As of the early twenty-first century there are no plans in place to rebuild the dam.