Teton Dam

From Wikipedia, the free encyclopedia

This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)

Reservoir information
Teton Dam
The reservoir behind the Teton Dam was emptied within hours of the initial breach
Official name	Teton Dam
Impounds	Snake River
Creates	Teton Reservoir
Locale	Eastern Idaho
Maintained by	United States Bureau of Reclamation
Length	3,100 feet (940 m)
Height	305 feet (93 m)
Width (at base)	1,700 feet (520 m)
Construction began	1975
Opening date	1976
Construction Cost	$3,825,849
Capacity	234,259 acre feet (288,954,000 m³)

The Teton Dam was a federally built earthen dam on the Teton River in southeastern Idaho in the United States which existed for less than one year before suffering a catastrophic failure on June 5, 1976. The collapse of the dam resulted in the deaths of 11 people^[1] and 13,000 head of cattle. The dam cost about USD $100 million to build, and the federal government paid over $300 million in claims related to the dam failure. Total damage estimates have ranged up to $2 billion.^[2] The dam was never rebuilt.

1 Construction
2 Geology
3 The collapse and immediate aftermath
4 Rebuilding and claims
5 Cause of the collapse
6 Notes
7 See also
8 External links

[edit] Construction

The dam was built by the United States Bureau of Reclamation, which ultimately received most of the blame for the collapse.

After the Bureau of Reclamation planning and bidding stages, but before construction of the dam could begin, an allied group of environmental organizations filed a complaint to prevent construction of the dam in Idaho District Court beginning on September 27, 1971. The plaintiffs amended the complaint, Trout Unlimited v. Morton, several times, citing violations of law including the National Environmental Policy Act of 1969 (NEPA). The Idaho District Court dismissed the second amended complaint in September 1972. The trial of Trout Unlimited v. Morton occurred in June and July 1973. On January 24, 1974, the Court found Reclamation's final impact statement complied with the NEPA, and denied the plaintiffs' injunction. [1]

The Teton Dam was located in the Teton Canyon approximately 44 miles (71 km) northeast of the city of Idaho Falls. The Bureau of Reclamation awarded the contract for Teton Dam, including the Power and Pumping Plant, to Morrison-Knudsen Company of Boise, Idaho, and the contractor received the notice to proceed on December 14, 1971. Clearing of the job site started in February 1972. Completed in 1975, it was a 305 foot (93 m) high earthfill dam intended to support irrigation, electricity, flood prevention, and recreation. The site of the dam is accessible to the public.

[edit] Geology

The ruins of the Teton Dam.

The dam site is located in the eastern Snake River Plain, which is a broad tectonic depression on top of rhyolitic ash-flow tuff. The tuff, a late-Cenozoic volcanic rock dating to about 1.9 million years, sits on top of sedimentary rock. The area is very permeable, highly fissured and unstable. Test boreholes, drilled by Bureau engineers and geologists, showed that one side of the canyon was highly fissured, a condition unlikely to be remediated by the Bureau's favoured method of "grouting" (injecting concrete into the substrates under high pressure). No seepage was noted on the dam itself before the date of the collapse. However, on June 3, 1976 workers found two small springs had opened up downstream.

[edit] The collapse and immediate aftermath

At the time of the collapse, spring runoff had almost filled the new reservoir to capacity, with a maximum depth of 240 feet (73 m). Water began seeping from the dam on the Thursday before the collapse, an event not unexpected for an earthen dam.

At 7:30 a.m. on Saturday, June 5, a muddy leak appeared, suggesting sediment was in the water, but engineers didn't believe there was a problem. By 9:30 a.m. the downstream face of the dam had a wet spot on it and embankment material began to wash out. Crews with bulldozers were sent to plug the leak, but were unsuccessful. Local media appeared at the site, and at 11:15 officials told the county sheriff's office to evacuate downstream residents. Work crews were forced to flee on foot as the widening gap swallowed their equipment. The operators of two bulldozers caught in the eroding embankment were pulled to safety with ropes. At 11:55 a.m. Mountain Daylight Time (UTC-6:00), the top of the dam collapsed; two minutes later the remainder disintegrated. By 8:00 p.m. that evening, the reservoir had completely emptied.

The communities immediately downstream, Rexburg, Wilford, Sugar City, Salem, and Hibbard, suffered horribly. Thousands of homes and businesses were destroyed. One estimate placed damage to Rexburg, population 10,000, at 80 percent of existing structures. The small community of Sugar City was literally wiped from the river bank. To the southwest, communities such as Roberts on a lower section of the Snake River received significant damage. The city of Idaho Falls, even further down on the flood plain, had time to prepare. At the old and unstable American Falls Dam downstream, engineers released a significant volume of water before the flood arrived. That dam held, and the flood was over, but tens of thousands of acres of land near the river were stripped of topsoil.^[2] Cleaning up took the rest of the summer.

[edit] Rebuilding and claims

After the dam's collapse, cleanup and rebuilding of damaged property continued for several years. Within a week after the disaster, President Gerald Ford requested a $200 million appropriation for initial payments for damages, without assigning responsibility for Teton Dam’s failure.^{[citation needed]} The dam was never rebuilt.^[1]

The Bureau of Reclamation set up claims offices in Rexburg, Idaho Falls, and Blackfoot. Disaster victims filed over 4,800 claims by January 4, 1977, totalling $194 million. The Federal government paid 3,813 of those claims, $93.5 million, by that date.

Originally scheduled to end in July 1978, the Claims Program continued into the 1980s. At the end of the Claims Program in January 1987, the Federal government had paid 7,563 claims for a total amount of $322 million.

[edit] Cause of the collapse

A wide-ranging controversy erupted from the dam's collapse. According to the Bureau of Reclamation,

Today, Bureau of Reclamation engineers assess all Reclamation dams under strict criteria established by the Safety of Dams program. Each structure is periodically reviewed for resistance to seismic stability, internal faults and physical deterioration.^[3]

However, it is arguable that the tragedy was preventable. There were four key reasons, known prior to construction, why the Teton Dam should not have been built in the first place:

1. it failed cost-benefit analysis, delivering irrigation water at prices far out of reach of local farmers;

2. supposed flood control benefits were illusory, in light of subsequent events tragically so;

3. a significant number of local interests did not want it built and challenged the legality of it in court;

4. it was sited in an area of known instability.

The fact that the Bureau, and state officials, nevertheless insisted that the dam be built remains a blot on the reputations of all concerned.