Deep Down Praying

How a Twenty-Two-Year-Old Fisherman Rode the Teton Dam Flood Three Miles Through Hell — and Lived to Forget It

A Publication of The Robison Institute

Commemorating the 50th Anniversary of the Teton Dam Failure

Based on the oral testimony of Daryl Wayne Grigg

Interviewed by Alyn B. Andrus, July 10, 1977

Teton Oral History Program — Ricks College, Idaho State Historical Society, Utah State University

BYU–Idaho Special Collections • Teton Dam Oral History Program

Adapted for The Teton Letters by The Robison Institute

A young man survives the failure of a dam, but the deeper story is the failure of language, warning, certainty, and trust.

"First I started cussing, then I decided that wasn't doing any good, so I started praying."

— Daryl Wayne Grigg, July 1977

I.

The morning of June 5, 1976, was just a morning. That was the thing about it. There was nothing in the quality of the light over the upper Snake River Plain, nothing in the way the air sat against the skin, nothing in the silences between birdsong that announced what was coming. The world does not warn you. It simply opens.

Daryl Wayne Grigg was twenty-two years old. He lived with his mother in a house at 247 North, 3rd East, in the town of St. Anthony, Idaho — a settlement of modest ambitions wedged into the sagebrush flats east of the Henrys Fork, where people farmed and logged and fished the cold rivers that came down out of the Tetons. He had been born in Santa Maria, California, and had come to this country as a boy, and the country had claimed him the way it claims everyone who stays long enough.

He worked at a sawmill. He fished the Teton River. He ran around with three friends — David Benson, Lyle Gardner, Kevin Johnson — the way young men in small towns have always run around together, drawn by gravity and boredom and the particular sweetness of having nothing important to do.

The night before, David Benson had called. They decided to go fishing Saturday. That was all. Two friends making the simplest plan in the world.

Grigg left his mother's house about 9:30 or 10:00 in the morning and drove to pick up Benson. He had to get him out of bed. They loaded the truck and headed for the Teton River canyon, to a spot they had fished many times before, a place they knew — a big eddy at the end of a dirt road where the cutthroat trout held in the cold current and the canyon walls rose around you like the sides of a cathedral made of basalt and dust. They parked and started fishing. They didn't get any at the eddy, so they walked upriver, wading the braided channels, until they reached an island in the middle of the stream.

It was about 11:00 in the morning. They were roughly two miles below the Teton Dam.

II.

The Teton Dam was barely completed after nearly four years years of construction that early summer, a massive earthfill structure that the Bureau of Reclamation had raised across the Teton River canyon for irrigation storage, flood control, hydropower and recreation. It stood 305 feet high. It held back 250,000 acre-feet of water. Grigg had been for it, in the way that most people in the Upper Snake River Valley had been for it — not with passion, but with the quiet acceptance of people who understood that dams meant water and water meant crops and crops meant the difference between staying and leaving. He was frightened about it, he would later say, though he could not have said precisely why. Some knowledge lives below language.

A week before, Grigg's foreman at the sawmill had mentioned something about the Bureau letting more water through — releasing flows into the Teton River below the dam. It was the kind of offhand remark that settles into the back of the mind and waits there, unexamined, until circumstances give it meaning.

What neither Grigg nor his foreman nor nearly anyone in the valley knew was that the dam was in trouble. Engineers had observed seepage. On the morning of June 5, as Grigg and Benson walked their fishing lines through the riffles, workers on the dam's crest were watching muddy water push through the downstream face of the embankment with increasing force. The dam was dissolving from the inside. The geology that the design engineers had dismissed in Denver — the fractured rhyolite, the open joints in the canyon's welded tuff — was doing what geology does when you ignore it. It was telling the truth.

III.

They had just barely gotten to the island when the airplane appeared.

It came down through the canyon, low and loud, a small plane banking between the walls. Grigg and Benson didn't know who it was. They assumed it was someone they knew — in that country, in those days, people flew the way they drove, casually and without announcement. The pilot was waving at them. They waved back. The plane circled, came around again. They waved again. Then the plane left.

They went back to fishing.

Grigg would not learn until he was lying in a hospital bed in Idaho Falls that the pilot was a private flyer — not Bureau of Reclamation, not anyone official — who had seen what was happening at the dam and had taken it upon himself to fly the canyon and warn whoever he could find. There was no protocol for this. There was no system. There was a man in a small airplane, waving his arms at two fishermen on an island, and two fishermen waving back, and the distance between those gestures was the distance between life and death, and neither side could cross it.

This would become, for Grigg, the thing that made him maddest. Not the flood. Not the injuries. Not even the death of his best friend. The knowing. The fact that they knew. "Soon as they knew it was leaking," he said, a year later, his voice flat with the particular fury of someone who has been forced to understand something unforgivable. "I heard that the day before they knew it was leaking. I don't know why in the hell they even let anyone go on the river." He paused. "Why didn't they bring a helicopter down the river, you know, to pick up people that was fishing? They screwed up bad, as I think."

IV.

The water rose six feet.

It came without sound at first, or rather the sound it made was indistinguishable from the river's own voice — the hiss and churn of current over gravel, amplified, thickened, wrong. They were standing in it before they understood what was happening. David Benson said, "We'll have to swim out of here." That was a reasonable thing to say. That was what you would say.

Then Grigg turned around and looked upriver.

Coming toward them was a wall of water approximately thirty feet high.

There is a moment in certain catastrophes when the human mind simply fails to process what the eyes are reporting. The scale is wrong. The physics are wrong. The world has become a place where rivers stand up like buildings and walk toward you, and no part of your experience has prepared you for the sight of it. In that moment, you are alone with the most primitive circuitry of your brain, the part that does not think but only acts, and what it does in the next two or three seconds determines whether you will live to describe the inadequacy of language to capture what you saw.

Grigg yelled at David to jump in the river. Then he jumped in himself. They started swimming. That didn't work. The current was no longer a current. It was a world. The Teton River had ceased to exist as a river and had become a moving landscape of water and debris, a churning slurry of logs and mud and shattered timber that filled the canyon wall to wall and moved with a velocity that made swimming meaningless.

That was the last time Daryl Grigg saw David Benson alive.

V.

There were thousands of logs. The canyon upstream had been thick with timber, and the flood had stripped it all — ripped the trees from the banks and from the slopes and fed them into the torrent like matchsticks into a gutter. Grigg grabbed one. He didn't have to swim after that. He didn't have to do anything after that except hold on and not die.

He rode the flood.

The phrase is simple and the reality is not. To ride a flood is to be a particle in a system of unimaginable violence, a system in which water and wood and stone and soil have lost their distinctions and become a single churning mass that moves at the speed of a freight train and sounds like the end of the world. Grigg could not hear. The noise was so vast it obliterated hearing the way a searchlight obliterates night — not by adding something but by removing everything else. He looked around. "It was unbelievable," he said later, reaching for the word and finding it, as all survivors do, woefully insufficient. "Everything was tearing everything else up."

He saw houses get wiped out. He heard cattle — not saw them but heard them, their bellowing somehow penetrating the roar, which tells you something about the frequency of terror in a living throat. He was not in the water so much as he was of it, a piece of debris no different from the logs and the fence posts and the shattered lumber, except that he was conscious and they were not, and consciousness in that context was not obviously a gift.

About a mile or two downriver, the logs tightened. The flood had compressed its cargo into a grinding mass, and Grigg was in it, and the logs crushed him. He felt his ribs go — five of them, on one side. He felt his lung collapse. The pain was extraordinary and irrelevant. Pain is a message from the body to the mind, and the mind was occupied with the more immediate project of continuing to exist.

He went another quarter or half mile, broken and breathing with one lung, holding a log in a river that was no longer a river, and then the tree stopped him. A big cottonwood, still standing, with debris piled against it. He hit it and was pinned. Somehow — he could not later explain how — he got free of the debris and climbed. Twenty feet up, where the trunk forked, he found a place where he could sit, or lie down, wedged into the crotch of the tree like a wounded bird in a nest.

Below him, the flood roared on. He was at the Teton City dump. He had traveled roughly three miles from the island where he had been fishing. The whole ride had taken perhaps forty-five minutes.

"Seemed like forever," he said. "But it wasn't."

VI.

For the next four and a half hours, Daryl Grigg sat in the fork of a cottonwood tree twenty feet above a world that had been rearranged. The water was ten to fifteen feet deep when he climbed up. He was having, as he put it, "a heck of a time breathing." Five broken ribs and a punctured lung. He was twenty-two years old. He was alone. He did not know what had happened. He did not know if it was over. He did not know if David was alive or dead.

He drifted in and out of consciousness. "I think I went out of it for a while," he said, with the understatement of someone describing a nap rather than the body's attempt to shut down a mind that has seen too much. He was in shock, badly. The tree held him the way trees have held desperate creatures since before there were creatures capable of desperation — indifferently, perfectly, the fork of its branches a geometry of accidental mercy.

Sometime around five in the afternoon, he woke up. It was getting late. The light was changing. He started yelling.

He couldn't see anything. The flood had reshaped the landscape, and what he could see from twenty feet up in a cottonwood tree bore no resemblance to the country he had known. But there were people on the hill — survivors, rescuers, the dazed and the purposeful mixed together — and they heard him. They brought a boat. Craig Hawes was in it. They reached the tree. They got him down.

The cottonwood stood twenty or thirty feet from the bank. "If I wouldn't have been hurt," Grigg said, "after all the logs went by, I could have swam out." The distance between what happened and what could have happened — thirty feet, one collapsed lung — was the kind of arithmetic that would keep a man awake at night for a long time.

VII.

They put him in a helicopter and flew him to St. Anthony. The hospital at St. Anthony looked at what the flood had done to him and said they couldn't do anything. They put him in another helicopter and flew him to Idaho Falls.

It was there, lying in a hospital bed, breathing carefully around his broken ribs, that someone told him the dam had broken.

He couldn't believe it.

"How'd I make it?" he thought. It was, he said, kind of strange.

Until that moment, he had assumed that the Bureau of Reclamation had simply released too much water — that someone had turned a valve or opened a gate and miscalculated, and the river had risen, and the mistake had been terrible but comprehensible. The kind of thing people do. A screwup. But a dam breaking — the whole structure, 305 feet of engineered earth, failing and releasing an inland sea into a canyon where two young men were fishing for cutthroat trout on a Saturday morning — that was something else. That was the ground itself betraying you. That was the world revealing that the things you thought were solid were not solid, that the wall holding back the water was made of the same stuff as everything else, which is to say, it was made of faith, and faith had limits.

He was in the hospital for ten days.

Kevin Johnson came to see him. Kevin was one of the four — David, Lyle, Kevin, Daryl — who had always run around together. Kevin was the one who told him about David.

David Benson was dead. They found his body on Monday, two days after the flood, about a quarter mile from where they found Grigg. Not downstream — just north. They had been that close. A quarter mile apart in the wreckage, one in a tree and one in the mud, and between them the difference that has no explanation and no remedy and no name except the one we give it when we have stopped looking for better words, which is luck.

Grigg's mother hadn't been able to tell him. She had known, and she had sat beside his hospital bed, and she had not been able to say it. So Kevin said it. That was what friends were for, in that country, in those days. You said the unsayable things. You carried the news that mothers couldn't carry.

VIII.

He went home. He took it easy for a couple of months. His lung healed. His ribs knit. The body is a diligent and indifferent machine: it repairs what it can and sends no invoices and asks no questions about whether the mind is keeping pace.

The mind was not keeping pace.

That first summer after the flood, Daryl Grigg couldn't sleep. He would wake in the middle of the night, and the dreams were not just about the flood. "It was all kinds of strange things," he said. "Getting shot and all just weird things." The psyche, overwhelmed by a single catastrophe, had generalized its terror. Every door in his mind that should have been locked had been blown open, and what came through was not just the memory of water but the entire catalog of violence that a twenty-two-year-old imagination could produce. A lot of it was about David.

By the following summer — by the time Alyn Andrus sat down with him and turned on the tape recorder on July 10, 1977 — the nightmares had eased. "Once in a while when I get depressed I'll start thinking about it," Grigg said. "It's not too bad now. Not too often." He paused. "Guess time picks up."

Guess time picks up. Three words that contain an entire theory of grief — not that it ends, not that it heals, but that it accelerates, that the distance between you and the worst thing that ever happened to you increases at a rate that eventually allows you to breathe. Not to forget. To breathe.

IX.

His friends showed him off a little. They would go someplace and someone would be talking about the flood, and they would say, "Hey, this guy here rode down the flood." And then he would have to talk about it. It bothered him, sort of. He had been interviewed for a whole bunch of articles. Some guy was going to write a book but he never heard anything since.

When Andrus asked if it bothered him to be interviewed, Grigg said, "No, not really. I have a hard time finding things to say." And when Andrus pressed — "To express the feelings that you had that day?" — Grigg said simply, "Yes."

This is the essential problem of testimony.

The survivor is the only witness, and the witness cannot find the words, and the words that exist are not the right ones, and the experience sits inside him like a stone that will not dissolve and will not pass and has no edges that language can grip. "It was unbelievable." "It was really rough." "I just figured it was all over with." These are not failures of articulation. They are the articulation. The experience has been so far outside the boundaries of ordinary life that ordinary language — which is all we have — can only circle it, the way a dog circles a place it cannot lie down.

X.

Grigg went back to the Teton River. It gave him a creepy feeling, that first time. By the summer of 1977 it was not so bad. There was still good fishing in it. He was a farmer now, no longer working at the sawmill, and he had married and had a son, and life had done what life does after catastrophe, which is to go on, relentlessly, without apology, offering you things you did not ask for and cannot refuse — a wife, a child, a field to plant, a reason to get out of bed that is not the same as the reason you had before but is, apparently, enough.

But he was clear about one thing. If they ever rebuilt the Teton Dam, he would never fish that river again.

"'Cause I don't think it would ever hold," he said. This was not an engineering assessment. Grigg was not an engineer. It was something deeper — a verdict rendered by the body and the bones, by five broken ribs and one collapsed lung and forty-five minutes in a world where the solid had turned liquid and a friend had disappeared into it and not come back. The dam had broken a contract that Grigg hadn't known he'd signed — the contract that says the ground beneath your feet will remain the ground beneath your feet, that the structures men build will do what men say they will do, that the river will stay in its bed and the walls will hold and tomorrow will resemble today.

That contract was void. No amount of concrete could reinstate it.

XI.

Andrus asked him about the prayer. It was, the interviewer noted, a statement that was humorous and yet deserving of a real answer. You cussed, then you prayed. Do you feel like your prayer helped you?

"I don't know for sure," Grigg said. "I was cussing at the reclamation guys. I just thought that they had opened up too much water."

So the cussing had a target and the praying had none, or rather the praying had a target so large and so uncertain that it amounted to the same thing. He had prayed since he was a little kid, he said, and it had never really done anything. But this was different.

"This wasn't just praying," he said. "It was deep down praying."

“Deep down praying.”

The phrase hangs in the transcript like a bell struck once in an empty room. It is perhaps the most honest description of human extremity ever committed to a tape recorder in eastern Idaho — the acknowledgment that there is a kind of prayer that has nothing to do with faith or theology or expectation of result, a prayer that comes from the place below the place where words originate, from the body itself, from the lungs that are filling with blood and the ribs that are broken and the hands that are gripping a log in a river that has become the angel of death. It is prayer as physiology. Prayer as the last electrical impulse of an organism that is not ready to stop being an organism. Prayer that does not ask to be answered because the asking is the answer.

"I don't know if it helped or not," Daryl Wayne Grigg said, sitting in his mother's house in St. Anthony, Idaho, thirteen months after he rode the Teton Dam flood three miles through a canyon on a log with five broken ribs and a collapsed lung and came out alive while his best friend did not.

"But I know it didn't hurt."

✦ ✦ ✦

Daryl Wayne Grigg was interviewed as part of the Teton Oral History Program, a joint project of Ricks College, the Idaho State Historical Society, and Utah State University, funded by the W.K. Kellogg Foundation, the Idaho State Legislature, and the National Endowment for the Humanities. David Benson was one of eleven people who died in the Teton Dam failure of June 5, 1976. The dam was never rebuilt.

This installment of The Teton Letters is dedicated to the memory of

David Jay Benson

25 January 1955 - 5 June 1976

✦ ✦ ✦

Teton Saint Studios and The Robison Institute Presents…

The story of Daryl Grigg is so incredible that we teamed up with Teton Saint studios and wrote and produced a song. Enjoy “Deep Down Praying”

Additional Robison Institute Content

The Effectiveness of The Teton Dam Early Warning and Evacuation

Despite the complete absence of any formal Emergency Action Plan, inundation maps, or pre-established warning protocols, the Teton Dam disaster on June 5, 1976, stands as one of the most compelling real-world demonstrations in U.S. history of highly effective improvised crisis leadership and public response.

Project Construction Engineer Robert Robison arrived at the dam around 9:00 a.m. After observing rapidly worsening leaks, he made the first official notifications at 10:43 a.m., calling the Madison and Fremont County sheriffs’ offices to alert residents of potential flooding and instruct them to prepare for possible evacuation. Between 11:00 and 11:30 a.m., he followed up with explicit requests for the complete evacuation of all low-lying areas downstream, 45 minutes before the catastrophic breach at 11:57 a.m.

These critical notifications were rapidly amplified through an ad-hoc network: sheriff radio dispatches, live on-site reporting by KRXK (Don Ellis repeatedly urging “People downstream, evacuate quickly! Hurry! Hurry!”), police loudspeakers, town sirens, church networks, and neighbor-to-neighbor calls.

While any loss of life is profoundly tragic, we pause to remember and honor the eleven individuals who perished that day and in its immediate aftermath. Among the six who drowned were David Jay Benson, 21, of Teton City, who was fishing with a friend on the Teton River just below the dam when the massive flood wave struck; and Clarence Daw, 79, and his wife Florence Daw, 76, of Wilford, who had received an in-person warning from their grandson but were overtaken by the waters while attempting to escape in their pickup truck. Also among the victims was Mary Gillette, 94, the oldest woman in Teton City, who was bedridden and evacuated from her home as a precaution — tragically, her residence ultimately lay just outside the flood zone — only to pass away the following day from the physical and emotional toll of the move. Five others succumbed to indirect causes such as heart failure or extreme stress.

Yet even with these heartbreaking individual losses, the overall outcome remains extraordinary given the scale of the catastrophe. Approximately 35,000 people were successfully evacuated from the flood path in under two hours. The flood ultimately inundated more than 180 square miles, destroyed or damaged nearly 4,000 homes, and released roughly 80 billion gallons of water at peak outflows of 2.3 million cfs. Only one of the 11 victims had received no warning whatsoever. Seventy-nine percent of residents learned of the danger through radio, neighbors, or telephone, and the evacuation was described by responding deputies as orderly and cooperative, with no reports of panic.

Bureau of Reclamation dam-safety expert Wayne J. Graham, P.E., concluded in his definitive 2008 analysis that the warning and evacuation were effective. He noted that a nighttime failure on the same day would almost certainly have produced hundreds of deaths in Wilford and other downstream communities alone.

Robert Robison’s clear-headed, decisive actions that morning — notifying authorities despite the lack of formal authorization or maps — combined with the community’s swift, cooperative response, saved countless lives. This is precisely the standard of engineering leadership and public-safety-first ethos that the Robison Institute exists to honor, study, document, and institutionalize for future generations of dam professionals and emergency responders — while never forgetting the human lives forever changed by that day.

The Hydraulics That Doomed the Teton Dam

June 5, 1976. The Teton Reservoir stood at elevation 5,301.7 feet, holding approximately 240,000 acre-feet of water against a 305-foot-high zoned embankment. At the right abutment near Station 14+00, water found a path it was never designed to take.

Robert R. Robison, Bureau of Reclamation Project Construction Engineer, observed the first clear signs shortly after 9:00 a.m.: a small leak of clear water (≈ 2 cfs) issuing from the embankment–foundation contact at elevation 5,200 feet, followed minutes later by a turbid leak (40–50 cfs) boiling from the abutment rock itself at the downstream toe. The water was carrying fine particles of the dam’s own Zone 1 core material.

The Driving Forces

Hydraulic head: ≈ 272 feet (reservoir surface to lowest exit point).

Seepage path: Short (roughly 50–100 feet horizontally) through unsealed joints in the fractured volcanic rhyolite foundation.

Resulting hydraulic gradient: Extremely steep (i ≈ 2.7 or higher).

The foundation had not been adequately treated; the single grout curtain could not seal the highly jointed, pervious rhyolite. Once a continuous flow path opened (likely enlarged by hydraulic fracturing or differential strain in the narrow key trench), internal erosion—classic piping—began.

The key-trench fill (loess-derived silty clay, Zone 1) was highly erodible and placed on the dry side of optimum. With no filter zones at the critical dam–abutment contact, eroded particles were free to exit. Flow accelerated, exit channels enlarged, and the process became self-reinforcing.

The Runaway Failure Sequence

10:00–10:30 a.m. — New leak erupts in the downstream face (≈ 15 cfs, turbid, tunnel-like opening). Bulldozers attempting to plug it are swallowed.

≈ 11:00 a.m. — Whirlpool forms in the reservoir upstream.

11:30 a.m. — Sinkhole appears on the downstream slope below the crest.

11:55 a.m. — Crest sags and drops.

11:57 a.m. — Right third of the dam disintegrates.

The breach widened rapidly to roughly 495–500 feet at the base. Peak discharge through the breach reached an estimated 2.0–2.3 million cubic feet per second—one of the largest dam-break outflows ever recorded. The reservoir emptied in about six hours.

Official Findings

The Independent Panel of Experts (1976) and the parallel Interior Review Group concluded unequivocally:

The failure originated in the right foundation key trench through internal erosion (piping). Construction conformed to the design in all significant respects. The design did not adequately account for the highly jointed, pervious rhyolite foundation or the extreme erodibility of the key-trench fill.

Robert R. Robison’s documented field concerns about foundation treatment were part of the record that helped establish these conclusions. The entire construction team was exonerated of blame for the collapse.

Why This Matters Fifty Years Later

The Teton failure remains the textbook example in dam-safety training worldwide. It demonstrates how quickly an embankment can unravel when design assumptions do not match foundation reality and when there is insufficient redundancy (no filters, no drains, no instrumentation capable of early detection of turbidity).

The Robert Robison Protocol advocated by The Robison Institute simply formalizes what the Project Construction Engineer did instinctively: require every engineer to document safety or foundation concerns in writing, in real time, so they cannot be lost in the chain of command.

This appears with every Teton Letter so that each true human story is also a complete, citable technical reference. Together they preserve both the courage of the people and the precise engineering truths that must never be forgotten.

Sources: 1977 Teton Flood Oral History Project transcripts (MSSI 02, BYU–Idaho Special Collections), Independent Panel Report (1976), and the institutional record of the Project Construction Engineer.

The Official Engineering Record: Hour-by-Hour Reconstruction of the Teton Dam Failure Day

June 5, 1976

Compiled exclusively by The Robison Institute from sworn testimonies in the Independent Panel to Review Cause of Teton Dam Failure report (U.S. Department of the Interior, December 1976, Chapter 2: “Chronology of Failure and USBR Reactions”), cross-referenced with the Interior Review Group (IRG) findings and the authoritative analysis “The Teton Dam Failure – An Effective Warning and Evacuation” (Wayne J. Graham, P.E.). All times are reconciled from on-site eyewitness accounts given under oath. This is the definitive primary-source record.

The Independent Panel—composed of leading dam engineers and geologists—concluded after exhaustive review (including excavation of the remnant dam, laboratory testing, and 37+ sworn testimonies) that:

- The failure occurred by internal erosion (piping) originating deep in the right-abutment key trench.

- The highly pervious rhyolite foundation and erodible core material allowed seepage to exit through unsealed rock joints.

- Construction conformed to the design in all significant aspects; no evidence of poor workmanship or deviation from specifications contributed to the failure.

- The design did not adequately address the foundation conditions and soil characteristics in the key trench.

Reservoir elevation at failure: El. 5301.7 (3.3 ft below spillway sill). Peak outflow exceeded 1 million cfs.

Pre-Dawn to 9:00 a.m. – First Indications and Leadership Response

- ~7:00–7:30 a.m.: Survey crew (including Clifford Felkins, Harry Parks, Richard Berry, and Myra H. Ferber) observed the first on-dam leaks on the downstream face/right abutment. A small, steady flow of clear water issued from the toe area (El. 5045, right abutment) and another small leak ~100 ft below the crest (El. ~5200, ~15 ft from right abutment). Water began washing fill at the toe. Reported promptly to project office. Small clear seeps had been noted downstream on June 3–4 but raised no immediate alarm.

- ~8:20–8:30 a.m.: Field Engineer Peter P. Aberle was called at home by Jan Ringel and arrived on site.

- ~8:50–9:00 a.m.: Project Construction Engineer Robert R. Robison (PCE) and Aberle inspected both leaks in person.

- Toe leak (El. 5045): ~40–50 cfs, “moderately turbid” (muddy), issuing from abutment rock.

- Higher leak (El. ~5200): ~2 cfs, only “slightly turbid”, appearing to come from abutment rock.

Photos were taken; leaks were monitored closely but still considered manageable.

9:00–10:30 a.m. – Escalation and Decision Window

- Leaks increased in volume and number along the downstream face near the right abutment.

- ~10:00–10:30 a.m.: A new, larger leak developed ~15 ft from the right abutment at El. ~5200. Initial flow ~15 cfs, rapidly becoming turbid and increasing. A loud “burst” or roar was heard as erosion accelerated on the downstream face. Wet spots appeared and grew. Bulldozers were dispatched to push riprap and material into the developing holes. Robison considered alerting residents around 9:30–10:00 a.m. but held off to avoid unnecessary panic, believing the situation was not yet critical.

10:30–11:00 a.m. – Critical Turning Point and Initial Notifications

- ~10:30 a.m.: Erosion hole enlarged dramatically; dozers worked frantically.

- 10:43 a.m. – Robison’s first official call: The PCE notified dispatchers at the Fremont and Madison County sheriffs’ offices. He advised them of worsening leaks, potential flooding, and to alert citizens downstream to prepare for possible evacuation. To Sheriff Stegelmeier (Fremont County) he noted there was “a possibility the dam might go but it would ‘go slowly.’” (This was the initial “prepare” notification.) Sheriffs began preliminary alerts.

- ~11:00 a.m.: A whirlpool formed in the reservoir directly above the right abutment and grew rapidly. Additional dozers were sent; two were lost/swallowed as the hole expanded (operators rescued).

Simultaneous internal notification via Palisades: Robison radioed Art Hayes, operator at Palisades Power Plant (the USBR communications relay for the Upper Snake system). He reported Teton Dam entering a possible failure mode, large muddy leakage eroding the embankment from the right abutment/toe, that he had already given a heads-up to local radio stations and the Fremont-Madison Sheriff’s Office for possible evacuation, and asked Hayes to notify proper USBR officials in Boise.

11:00–11:57 a.m. – Full Evacuation Order and Breach

- 11:00–11:30 a.m. – Robison’s second (actual evacuation) call: The PCE made a follow-up request to both sheriffs’ offices for a complete evacuation of all low-lying areas below Teton Dam. Radio and loudspeaker warnings followed immediately.

- ~11:30 a.m.: Dozers abandoned as the erosion hole(s) expanded uncontrollably. A second sinkhole appeared on the downstream face.

- ~11:50 a.m.: Visible breaching of the dam crest.

- 11:57 a.m.: Full breach of the north (right-abutment) end of the dam. The reservoir released ~80 billion gallons in a catastrophic flood.

Post-Breach

USBR and local responders shifted immediately to emergency aid. Downstream communities (Wilford, Sugar City, Rexburg, etc.) were already in motion thanks to the earlier warnings.

Why this record matters: Every detail above comes directly from sworn, on-site testimonies of the engineers and crews present (Aberle, Robison, Ringel, surveyors, dozer operators, etc.). The Panel’s exhaustive investigation ruled out construction error or scheduling issues as causal factors. The human stories we share in The Teton Letters—the courage, grief, resilience, and faith of survivors—fit perfectly alongside the engineering truth. Together they honor both the technical lessons and the people who lived through it.

Primary Sources (all publicly available):

- Failure of Teton Dam – Independent Panel Report (USBR, Dec. 1976) – especially Chapter 2 and appendices with verbatim testimonies.

- Interior Review Group (IRG) Report (1977).

- “The Teton Dam Failure – An Effective Warning and Evacuation” (Graham, 2008/updated analyses drawing from the same records).

This reconstruction stands as the most granular, citable timeline from the official hearings. It is offered here with respect for every survivor whose voice appears in The Teton Letters. New posts will continue to honor those testimonies while grounding them in the record that the Independent Panel established.

The Robison Institute / Teton Letters

On Hindsight and Historical Judgment — The Teton Dam Reservoir Filling Decisions

In the half-century since the Teton Dam failure of June 5, 1976, some retrospective analyses have revisited the operational decisions made during the spring 1976 reservoir filling period. With full knowledge of the tragic outcome, it is easy to reinterpret those choices through the lens of hindsight and suggest that different actions might have altered the course of events.

Such second-guessing overlooks the real-time constraints faced by the project team on the ground. The dam stood structurally complete, yet the primary river outlet works remained unfinished due to contractor delays. Only the smaller auxiliary outlet tunnel was operational, with a practical capacity of roughly 850 cubic feet per second. Heavy snowmelt runoff from the unusually large 1975–76 winter far exceeded what could be released downstream. Project Construction Engineer Robert R. Robison confronted a straightforward hydrological reality: the team could either permit uncontrolled downstream flows or store the water the dam had been built to capture.

On March 3, 1976, Robison formally requested authorization from the Denver Office to increase the initial filling rate from the standard guideline of one foot per day to two feet per day. His request was data-driven and prudent: observation wells showed normal groundwater behavior, no unusual seepage had appeared, and the team committed to intensified monitoring. The request was approved on March 23, with a later adjustment in May permitting continued management of inflows as needed. These decisions reflected astute, pragmatic engineering judgment under difficult seasonal and construction constraints — not recklessness or overconfidence.

A common misconception holds that the accelerated filling rate caused or materially contributed to the dam’s failure. The official Independent Panel to Review Cause of Teton Dam Failure (1976), composed of leading experts with complete access to all contemporaneous records, examined this question in exhaustive detail and reached a clear conclusion:

“The Panel believes that the conditions which caused the piping and consequent failure of the dam were not materially affected by the fact that the reservoir was filled at a more rapid rate than had been originally planned. A slower rate of filling would have delayed the failure but, in the judgment of the Panel, a similar failure would have occurred at some later date.”

The physics of failure — internal erosion (piping) originating in the inadequately treated right abutment foundation and key trench — were inherent to the dam’s design and construction on highly fractured rhyolite bedrock. The rate at which the reservoir rose merely revealed the pre-existing flaw sooner.

Robert R. Robison and the project team made responsible decisions based on the best available information at the time, balancing immediate hydrological necessities with the project’s Congressionally authorized purposes of irrigation, flood control, and water storage in a drought-prone region.

History is best understood not by projecting later knowledge backward, but by appreciating the genuine challenges and sound judgment exercised in the moment. The lessons of Teton Dam lie in the design and foundation issues identified by the Panel, not in hindsight critiques of operational choices made under real-world pressures.

The Realities of Mega-Project Management — Understanding the Pre Failure Teton Dam Fill Rate and Related Decisions in Context

Managing the final stages of a major federal dam project in the 1970s was an extraordinarily complex undertaking. The Teton Dam was a multi-purpose, Congressionally authorized mega-project involving thousands of workers, multiple contractors, intricate sequencing of civil, mechanical, and electrical work, and constant coordination with the Denver Office and local stakeholders.

By spring 1976, the embankment was structurally complete, yet the primary river outlet works remained unfinished due to contractor delays. The only operational release structure was the smaller auxiliary outlet tunnel, limited to roughly 850 cubic feet per second. At the same time, an unusually heavy snowpack produced spring runoff far exceeding that capacity.

Project Construction Engineer, Robert R. Robison, and his team operated at the intersection of hydrology, construction realities, and operational imperatives. They faced a classic set of over-constrained variables: seasonal weather patterns that could not be postponed, incomplete infrastructure that could not be rushed without compromising quality, and the mandate to capture water for irrigation, flood control, and power generation in a drought-prone basin. On March 3, 1976, Robison formally requested authorization to increase the initial filling rate from the standard one foot per day guideline to two feet per day. His request was supported by normal groundwater monitoring data, an absence of unusual seepage, and a commitment to heightened surveillance. The Denver Office approved the adjustment on March 23, with a further May authorization allowing the team to manage inflows as needed. These were pragmatic, data-informed decisions made by engineers immersed in the daily realities of the site.

Retrospective analyses written decades later sometimes fail to convey the full weight of these constraints. With the benefit of hindsight and complete knowledge of the eventual outcome, it is tempting to reinterpret routine operational communications or management trade-offs as evidence of poor judgment. Such second-guessing does a disservice to history. It overlooks how the Bureau of Reclamation’s field teams in the 1970s routinely delivered large-scale infrastructure under far more demanding conditions than those faced by modern agencies. The era’s engineers had decades of continuous experience building and commissioning major dams across the American West.

Today’s Bureau has not undertaken a project of Teton’s scale or complexity in fifty years; its institutional culture has necessarily shifted toward maintenance, rehabilitation, and regulatory compliance rather than the high-stakes orchestration of new mega-projects. The federal government has lost this capacity and it's former institutional knowledge.

The official “Independent Panel to Review Cause of Teton Dam Failure” (1976) understood this context. After exhaustive examination of all contemporaneous records, the Panel concluded that the accelerated filling rate did not materially contribute to the failure:

“The Panel believes that the conditions which caused the piping and consequent failure of the dam were not materially affected by the fact that the reservoir was filled at a more rapid rate than had been originally planned. A slower rate of filling would have delayed the failure but, in the judgment of the Panel, a similar failure would have occurred at some later date.”

The root causes were design and foundation issues — specifically, inadequate treatment of the highly fractured rhyolite bedrock and the use of erodible materials in the key trench — that predated the spring 1976 filling decisions.

Robert R. Robison and the Teton project team demonstrated the kind of astute, on-the-ground judgment required to navigate an already over-constrained mega-project amid unexpected additional pressures. Their decisions reflected the best engineering practices of the time, grounded in the hydrological realities of the Upper Snake River Basin and the practical limitations of the moment.

True historical understanding requires appreciating those realities rather than projecting later perspectives onto them. The enduring lesson of Teton Dam is the importance of rigorous foundation engineering and independent review and traceability of requirements and design decisions, not hindsight critique of the men who managed the project under complex, real-world conditions.

Drawdown Capability and the Rapid Progression of Failure — Operational Realities at Teton Dam

The official Independent Panel to Review Cause of Teton Dam Failure (1976) determined that once internal erosion (piping) began in the inadequately treated right abutment foundation and key trench, the progression to catastrophic breach was extraordinarily rapid and driven by the physics of the design itself. Some later commentary has suggested that, had the primary river outlet works been fully operational, the project team could have drawn down the reservoir quickly enough to detect and repair developing seepage in a manner similar to the successful remediation at Fontenelle Dam in 1965.

The operational and hydrological facts do not support this view. At the time of failure on June 5, 1976, the reservoir stood at elevation 5,301.7 feet — only 3.3 feet below the spillway sill — with approximately 251,700 acre-feet of water stored and a surface area of roughly 2,100 acres near full pool. The primary river outlet works (two 12-foot-diameter conduits with radial gates) were designed for a combined discharge capacity of approximately 3,700 cubic feet per second at the prevailing reservoir head. Even operating at full capacity, this would have produced a maximum drawdown rate of only about 3–4 feet per day.

The timeline of visible distress was unforgiving:

~7:30–8:00 a.m.: First clear signs of piping — muddy leaks of 20–30 cfs exiting rock joints near the right abutment.

~9:00 a.m.: Flow increased to 40–50 cfs; wet spots and erosion appeared on the downstream face.

11:55 a.m.: Dam crest sagged and the right embankment breached.

From the first unmistakable evidence of internal erosion to complete collapse, roughly four hours elapsed. In that brief window, even fully operational primary outlets would have lowered the reservoir by only about 0.5–0.7 feet — a negligible reduction in the driving head of nearly 270 feet at the dam. The piping process was already internal and self-accelerating through erodible core material and fractured rhyolite bedrock; it could not have been arrested by such a minimal change in reservoir level.

Project Construction Engineer Robert R. Robison and his team were already operating under severe constraints imposed by the incomplete primary outlet works (delayed by the contractor) and the limited auxiliary outlet tunnel (capacity ~850 cfs). Their earlier decisions to manage the spring snowmelt inflows were pragmatic responses to real hydrological realities, not the cause of the underlying design flaw.

The Independent Panel examined the fill-rate question directly and, by extension, the broader operational context, reaching a definitive conclusion:

“The Panel believes that the conditions which caused the piping and consequent failure of the dam were not materially affected by the fact that the reservoir was filled at a more rapid rate than had been originally planned. A slower rate of filling would have delayed the failure but, in the judgment of the Panel, a similar failure would have occurred at some later date.”

The absence of fully operational low-level outlets did worsen the consequences of the breach by leaving a nearly full reservoir in place. However, the physics and speed of the piping failure itself were independent of drawdown capability. Once initiated under these foundation conditions, the dam was effectively “eating itself away internally” on a timescale far shorter than any realistic drawdown could address.

Robert R. Robison and the Teton project team exercised sound judgment within the genuine limitations they faced. The enduring lesson of Teton Dam lies in the critical importance of rigorous foundation treatment, redundant seepage controls, and fully operational low-level release structures before first filling — safeguards now standard in modern dam engineering.

About This Series

The Teton Letters is a literary journalism series published by The Robison Institute commemorating the 50th anniversary of the Teton Dam failure (June 5, 1976). Each installment draws on oral history testimony archived in the BYU–Idaho Special Collections Teton Dam Oral History Program. The series is published through The Water Ledger on Substack.

About The Robison Institute

The Robison Institute is a systems engineering think tank focused on critical water infrastructure, reliability engineering, and policy advocacy for the American West. The Institute’s work is informed by the legacy of Robert R. Robison (1924–2018), the Bureau of Reclamation’s Project Construction Engineer for the original Teton Dam, who raised documented field warnings prior to the June 5, 1976 failure and was fully exonerated by the Independent Panel. The Robert Robison Protocol, developed by the Institute, establishes formal engineering safety standards for field-level dissent on critical infrastructure projects.

Recurring Institutional References

Independent Panel Finding: The Teton Dam failure resulted from design flaws in the dam’s cross-section, not construction error. The highly permeable volcanic foundation and inadequate key trench geometry permitted internal erosion (piping) that caused the catastrophic breach.

Robert R. Robison: Fully exonerated by the Independent Panel. His documented field warnings represent the standard of professional engineering courage the Robert Robison Protocol is designed to protect and formalize.

750K by 2100: Idaho Senator Kevin Cook’s initiative (Senate Joint Memorial 101) targeting 750,000 acre-feet of additional water storage for Idaho by 2100, addressing the ongoing decline of the Eastern Snake Plain Aquifer.

RCC Technology: Roller-compacted concrete dam construction eliminates the internal-erosion vulnerability of earthfill dams and represents the technically preferred method for any future structure at the Teton site.

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Original oral history testimony © BYU–Idaho Special Collections. Used with attribution.