STEP back in time with me to a year which saw the further promotion of air travel by flying on the bigger than ever Boeing 747 aircraft. IBM was telling the world that computers would make our lives easier. The next US president was about to be elected, and the nation was 200 years old. The school year had just ended with parents planning for the upcoming summer vacation period.

Now step back with me not only in time, but to the eastern border of Idaho, US. It is June 1976. The Bureau of Reclamation (USBR) was about to commission another one of its many dams within the US. In fact, this was just one of over 300 dams that USBR had built up to this time. When construction began in 1972, Teton dam was to be a multi-purpose dam with benefits for irrigation, flood control, power and recreation. The dam was located in Idaho on the Teton river, approximately 64km west of Grand Teton National Park, Wyoming. It was constructed of earth and rock, which was to create a lake 27.4km in length with a total reservoir capacity of close to 370Mm3.

Teton dam had a total height of over 93m above its foundation. The main low level outlet works and 20kW power plant and pumping plant were located at the left downstream toe of the dam embankment. The total capacity of the outlet works was approximately 96m3/sec. The right portion of the dam contained a spillway with a total capacity of approximately 509m3/sec plus a low-level auxiliary outlet works used to bypass river flows during final construction of the dam’s embankment.

The snowpack in Eastern Idaho was above normal in spring of 1976, but a warm, wet spring had produced abnormal early spring flood flows within the Upper Snake river basin. USBR was placing the final touches on the construction of Teton dam as the reservoir began to fill with flood waters from the westerly flange of the Teton mountain range. It was expected that it would take approximately two years to fill the reservoir with normal runoff conditions.

The early flood flows of 1976 in Upper Teton river were contained within the dam’s reservoir. In May 1976, flood flows caused the reservoir to fill at the rate of 0.6-0.9m per day. It had earlier been determined that a rate of 0.3m per day would be established for first fill criteria of the reservoir. However, the painting of the main outlet works by the Boise-based Morrison-Knudsen Company and Peter Keiwit Sons of Omaha, had delayed larger operational releases. This required releases to be made from the auxiliary outlet tunnel, which had a limited capacity to pass only 1/4 of the total flood flows being experienced at the time. As a result, the reservoir was allowed to store the excessive flood flows. USBR was confident that the dam’s integrity was in no way threatened at the time.

River operations

For the past six months, I had been preparing to take over as USBR’s chief of Minidoka river operations within the Upper Snake river system, from Terry Gulley who was retiring. The Upper Snake river system consists of a series of dams owned by USBR, starting with Jackson Lake dam within the Teton National Park of Wyoming, Palisades dam and power plant on the Idaho/Wyoming stateline, American Falls dam, Minidoka dam and power plant, plus Island Park and Grassy lake on the north fork of the Snake river. Gulley and I had toured the Teton dam and power plant earlier in the spring of 1976 in preparation of taking over operations from the Denver Construction Group. The dam was authorised by Congress in 1964 for the purpose of controlling periodic flooding within the Lower Teton river valley area. The Teton dam would have held an active storage of 333M m3 of water. In contrast, Palisades dam can hold 1.7B m3 and American Falls 2B m3. Shortly after it was authorised, the dam became controversial and dragged on until the 9th US Circuit Court of Appeals ruled against those attempting to block completion of the dam in 1974.

The Teton dam project had its design and construction problems, mainly associated with the basalt foundation and wind blown type (silty) soils, with which the dam was constructed. The keyway trench, dug laterally across the 91m canyon, was 27m deep into the canyon floor with a bottom width of 6m. In the bottom of the trench were three parallel rows of grout curtains set approximately 3m apart. The keyway trench and curtains extended up the canyon walls into the basalt, and cement was force-pumped into canyon cracks. The amount of cement grout was much greater than expected by USBR design engineers.

It was within this framework that I came to work on Saturday morning, 5 June 1976, to provide for flood operations of the Upper Snake river reservoirs. A fellow USBR friend, visiting me from Riverton, Wyoming, accompanied me to the office. The water operational phone calls to the various dams and contracted river gauge readers were rather routine. I had been made aware earlier in the morning of a small amount of leakage below the dam, but it was being monitored by the construction personnel. I had completed the operational calls and was preparing to leave the office when the phone rang unexpectedly.

Dam failure

The call was from Art Hayes, Palisades power plant operator, whom I had spoken with earlier in the morning on operational changes. Hayes indicated that he had Robby Robison, Teton dam field construction engineer, on the radio. I was informed that Robison was providing notice to USBR that Teton dam was entering into a possible failure mode and that the proper USBR officials should be notified. Palisades dam and Teton were the only facilities which had radio communications at the time, due to the fact that Palisades dam was to provide for supervisory control of the Teton power plant operations.

I immediately asked Hayes what Robison meant by ‘possible failure of Teton dam’. Hayes then asked Robison for further clarification. I could hear Robison on the radio in the background explaining that there was a large leakage of water from the right abutment and toe area of the dam. The leakage was muddy and had started out earlier in the morning at 0.06m3 and was now at large flow eroding a portion of the dam’s embankment. As a precaution, he had alerted a couple of the local radio stations as to possible problems at the dam. He also indicated that earlier he had given a heads-up to the Fremont-Madison Sheriff’s Office to the possible evacuation of the area below the dam.

I indicated to Hayes that I had heard Robison’s radio response, and requested that he ask about opening the low-level outlet gates to start emergency releases from the reservoir. I had read about the 1965 emergency evacuation of water from the Fontenelle dam, located on Green river of Wyoming. The emergency releases had caused flooding of the downstream community of Green River, Wyoming, but had saved the USBR dam. At this time in history, standard operating procedures (SOP) or emergency preparedness plans (EPP) were non-existent.

Robison again requested that I notify the proper USBR officials on the situation at Teton dam. He said he did not have personnel nor time to do anything with the low-level outworks and that he was mobilising the contractor’s equipment in an attempt to stabilise erosion occurring at the toe of the dam. His staff were notifying residents immediately below the Teton canyon of the impending failure. I told Hayes to inform Robison that I would immediately notify USBR officials of the situation.

As the minutes slipped away, I made my first call to Carlos Randolph, the Minidoka project superintendent, who lived less than ten minutes from the office. I breathed a sigh of relief when he answered the phone. I quickly informed him of the problem at Teton. Randolph never doubted what I was saying or questioned my report, but quickly instructed me to call Don Tracy power chief of the Minidoka project.

I immediately called Tracy, and his wife answered the phone. She explained that Tracy was at the Burley Airport preparing to fly his small private plane to Reno, Nevada. I quickly told her of the situation. Her response was one of dismay, after which she said, ‘I will get hold of Don’.

Upon hanging up the telephone I received a call from Pete Husky, relief operator at the Palisades power plant, indicating that the Teton Construction Office had radioed and reported that the dam had been completely breached. Robby Robison had requested the Fremont-Madison County Sheriff to call for a complete evacuation of all low-lying areas below Teton dam.

At this time, Carlos Randolph arrived at the office. I apprised Randolph of the situation and he ordered me to call Max VanDenBerg, Pacific Northwest river operations coordinator, and brief him on the situation. Randolph immediately called Rod Vissia, Pacific Northwest regional director, in Boise, Idaho. Randolph was able to reach him at his home and briefed him on the situation at Teton dam.

Meanwhile, I called VanDenBerg at his home to inform him of the dam failure. I told him about the telephone and radio conversations that I had with Palisades dam operators and with Robison. He indicated that he would call his supervisor John Walker, chief of Pacific Northwest Regional Operations.

Upon hanging up the phone, I received another call from the Palisades dam operator that a radio message had been received from one of the construction staff members, reporting that a 23m wall of water was proceeding down the Teton River Canyon and would soon break out onto the Teton Plains some 8km below the dam.

Operational releases

Don Tracy arrived at the office. Randolph, Tracy and I immediately started discussions on operational releases from Palisades dam, located on the main stem of the Snake river. It was decided to keep the power plant at full capacity of 430MW, but to curtail all flood operational releases being made and store the excessive flood flows in Palisades and Jackson lake reservoirs. We knew that the electrical power service would be interrupted in the area below Teton dam and wanted to keep as much local service power available in Southeastern Idaho as possible.

Tracy phoned local Bonneville Power officials notifying them of the Teton dam failure and preparing them to schedule load shedding and rescheduling as necessary. This included local power needs of Fall River Electric Company, in the immediate area below Teton dam, and with Idaho Power and Utah Power Companies, who both provided the general service needs within Southeastern Idaho.

I contacted Jackson lake dam facility manager, Keith Ebersole, who was located at the dam in Jackson, Wyoming. I apprised him of the situation and requested that he reduce releases from that facility and store excessive flood flows in Jackson lake reservoir. We discussed the present spring flood runoff situation briefly. Ebersole indicated that the peak of the runoff from the West Yellowstone area had already occurred and felt that his facility was in a position to store additional flood flows for a few days, depending on future weather conditions.

By this time, approximately 30 minutes had passed since receiving notice that the dam had failed. Discussion within our office centered on how to further curtail or minimise the effects of the flood flows expected to continue down the Upper Snake river basin. Office staff heard of the Teton dam failure and started to arrive. One person had a portable radio tuned to a radio station in the Idaho Falls area, approximately 80km from Teton dam. We heard reports from local reporters in aircraft over the dam area observing a wall of water moving at a rate of 16-24km per hour, having a breadth of nearly 12.9km in width.

I called Captain Wadsworth, Bonneville County civil defence coordinator, to make him aware of the impending flood waters bearing down on Idaho Falls, Idaho. He indicated that he was in the process of getting his command centre up to operational status and would stay in communication with our office.

We then further examined necessary actions needed to be taken by our office. Irrigation diversions were being taken from the Snake river below Palisades dam, which amounted to approximately 50% of the power plant releases of 254.7m3. Since the flows had been reduced from Palisades dam, the flows within the irrigation canals would be reduced due to a decrease in hydraulic head at the various diversion dams below the dam. Randolph requested that I call the Upper Snake water master to ensure that irrigation canals withdraw all the water possible in order to reduce flows in the lower portions of the Snake river where Teton flood waters would enter at the confluence of the north fork of Snake river in the Menan Butte area.

I called Art Larson, District 01 water master, who was in charge of all Upper Snake river irrigation diversions, to provide for continued maximum irrigation diversions within the Upper Snake Valley. This would minimise the flows within the main stem of the river to more fully accommodate the Teton flood waters. I stated that approximately 113.2m3 had been reduced from Palisades dam, with total flow at approximately 254.7m3 through the power plant. I requested that the irrigation districts assist in further opening irrigation diversion dam gates in order to sustain their present flows, due to a decrease in hydraulic head at the diversion dams caused by the reduce flows out of Palisades dam.

Randolph discussed the operations of the Lower Snake river reservoir system with the office staff. He wanted a definite procedure established for curtailment of the flood waters and management of the dam releases and reservoir storage.

Since American Falls dam and reservoir had a safety of dams (SOD) restriction of 616M m3 placed on the facility several years earlier, there was space available to store the Teton flood water. The SOD concern with the American Falls dam was associated with aggregate deterioration of the concrete within the structure. However, group consensus was that the excess flood waters could be captured and released in a safe manner downstream.

I developed a couple of operational options for American Falls dam and Minidoka dam located immediately downstream of American Falls. The options included storing all the water in American Falls reservoir or releasing large flood type flows from American Falls dam storing some into surcharge space within Lake Walcott behind Minidoka dam. Randolph elected to store only part of the excess flood waters in American Falls reservoir releasing flood flows to Lake Walcott, but not to be in excess of earlier flood releases from American Falls dam. This called for immediate increase of flows back up to the original flood flow experiences during May 1976. Randolph indicated the need to reassure the public below American Falls reservoir that the Teton flood water would be contained with no increase in flows other than those experienced the month earlier. He then ordered me to start releases from American Falls and Minidoka dams.

I contacted Alan Templeton, facility manager of American Falls dam, explaining the situation and the need to start increasing releases from the dam. I also called the Minidoka dam power plant, requesting similar increases. We continued our coordination efforts during that evening. At midnight, the US Geological Survey reported the flood waters had not yet entered the main stem of the Snake river near area of Menan Butte. This was primarily due to heavy riparian forest and brush within the North Fork of Snake river which slowed the advancement of the flood waters.

The next morning, Sunday 6 June, I reported to the office to relieve other staff members who had spent the night monitoring the situation. The flood waters were reported to have reached the small community of Roberts at 5am on 6 June. The waters next hit the City of Idaho Falls hard at 11am, causing concern for three main bridges over the Snake river. City crews cut a canal around the abutment of the debris-clogged Broadway bridge, saving it as the flood crest passed at approximately 12pm. The smaller community of Firth, some 25.7km below Idaho Falls, was next in line to be hit by the flood.

National disaster

On 6 June 1976, President Ford declared four flood-torn counties a national disaster area. Those included Madison, Fremont, Bonneville and Bingham counties, with Jefferson county being later added to that list.

Blackfoot, Idaho, some 105km from Teton dam, became the next victim of its flood waters. The city had flood dikes and was attempting to strengthen them in hopes of saving the lower areas of the community. However, by 5am on Monday 7 June, the strain of the flood waters broke the dikes and flooded 150 homes and a number of businesses. Below Blackfoot, the flood waters spread out onto agricultural lands and inundated some rural farm homes before entering American Falls reservoir, which ultimately stemmed the flood. The amount of Teton flood waters that entered American Falls reservoir was approximately half of that released from its reservoir.

The scope of the devastation became apparent over the following week. There was the destruction of homes; irrigation facilities, bridges, entire sections of highway and railways were washed away; thousands of acres of cropland were buried by silt or eroded; thousands of livestock were drowned; and a death-like pall shrouded the landscape as the water slowly receded back into the Snake river.

Within weeks, Congress passed the Teton Disaster Relief Bill providing US$1.5B for the flood recovery programme. USBR established the Rexburg Disaster Field Office with the assistance of the Small Business Administration. The processing of the claims took approximately four years with the total claim costs being approximately US$400M. The construction costs of Teton dam were earmarked at US$55M.

In 1977, President Carter pushed for additional funding to have the US Army Corps of Engineers (USACE) accomplish an inspection of the nation’s high hazard dams under the National Dam Inspection Act of 1972. In parallel time, President Carter’s 1979 executive order merged many of the separate disaster-related responsibilities into a new Federal Emergency Management Agency (FEMA). During the time USACE was providing the dam inspection programme, a study of the nation’s dam programs was initiated. These studies provided for federal guidelines on dam safety and were published on 25 June 1979, placed under the coordination of FEMA.