TETON DAM COLLAPSE

Teton Dam Collapse

Teton Dam Collapse

Introduction

The failure of the Teton Dam during initial filling of the reservoir on June 5, 1976 killed fourteen people and caused hundreds of millions of dollars in property damage downstream. A thorough investigation identified the causes of the failure and suggested improvements for the design and construction of earthen dams.

Dams impound water in vast reservoirs to provide flood control, hydroelectric power, recreation, and other benefits. The earliest use of dams was probably irrigation. Dams have been very useful to the development of civilization. However, the potential energy of the water reservoir can cause considerable damage if the dam fails.

The danger is more than theoretical. Throughout history, dams have failed and lives have been lost. Levy and Salvadori (1992) point out that a dam failure in Grenoble, France, was recorded as early as 1219. For dams built in the United States before 1959, on the average one in fifty failed.

Levy and Salvadori (1992) describe the failures of the South Fork Dam and the Malplasset Dam in detail. The failure of the South Fork Dam on May 31, 1889, released a wall of water 12 meters (40 feet) high traveling at 32 kph (20 mph) that killed nearly 3,000 in Johnstown, Pennsylvania, and other towns. This disaster is known as the Johnstown Flood. More recently, the Malplasset concrete arch dam in France failed on December 2, 1959, when the abutment shifted due to a weak seam in the rock. Almost 400 lost their lives (Levy and Salvadori, 1992).

Some of the factors influencing dam safety and performance can be reviewed through the case of the Teton Dam, a large earthen dam in eastern Idaho that failed on June 5, 1976.  

Design and Construction

The Teton Dam was situated on the Teton River, three miles northeast of Newdale, Idaho. It was designed to provide recreation, flood control, power generation, and irrigation for over 40,000 hectares (100,000 acres) of farmland. The Office of Design and Construction, U.S. Bureau of Reclamation (USBR), at the Denver Federal Center, designed the dam and the construction contract was awarded to the team of Morrison-Knudsen-Kiewit in December of 1971.

The preparations for this dam project had been underway for many years. The first active site investigation in the area occurred in 1932 (Teton Dam Failure @ 2002). Between 1946 and 1961, eight alternate sites within about 16 km (10 miles) of the selected site were investigated. Between 1961 and 1970, approximately 100 borings were taken at the site (Independent Panel, 1976).

The design of the foundation consisted of four basic elements: 1) 21 meter (70 foot) deep, steep-sided key trenches on the abutments above the elevation of 1,550 meters (5,100 feet); 2) a cutoff trench to rock below the elevation of 1,550 meters (5,100 feet); 3) a continuous grout curtain along the entire foundation; and 4) the excavation of rock under the abutments (Independent Panel, 1976). These elements for the foundation were important because the types of rock located in this area, basalt and rhyolite, are not ...