The 1976 Collapse of the Teton Dam, Idaho: Investigating the Geologic Evidence

Visit what remains of Teton Dam, site of the Idaho's greatest disaster in modern times. On June 5, 1976, this recently constructed earthen dam catastrophically failed as the reservoir behind it neared full capacity. Join geology professor Shawn Willsey as he examines the geology behind this tragedy.

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Shawn Willsey
College of Southern Idaho
315 Falls Avenue
Twin Falls, ID 83303

[oldskool]

I was a couple months shy of 16 when the dam broke. I'll never forget living through that disaster as long as I live. My grandparents lived in Rexburg. I also had two Aunt & Uncles and their kids (my cousins) living in Rexburg. I was spending the summer with my grandparents. If the Dam would have broke in the middle of the night there would have been a major loss of human life. We had about 20 minutes to take what we could and get out of town. I drove my Uncles pickup with his horse trailer attached and their horse loaded up. The water was coming into the north side of Rexburg when we were all driving out. We got to higher ground just outside of town on farmland southeast of Rexburg. By then the entire town was underwater. All of my relatives homes and possessions were flooded and ruined. Whatever they brought with them was all they had left. I learned about loss, heartache, and death. How easily ones life can change dramatically so quickly. I saw drowned cattle bloated from the sun. The stench of death. I saw families in complete shock dealing with having no worldly possessions to go home to. Just a bunch of debris and nasty stinky sticky mud everywhere. The rest of my summer was spent helping my relatives clean up their properties. Talk about a major life experience as a 15 yr old. I have a heavy heart everytime I see some of the natural disasters (flood, tornadoes, fires, etc.) that occur quite often it seems. Again I can't imagine what would have occurred if this disaster happened at 1 or 2 in the morning. I'm 63 now but can still remember that panic like it was yesterday.

[brettdavis]

This took my home and the homes of many of my family. If it had happened in the middle of the night my family would have been wiped from existence. I can give you a detailed guided tour of many things to see beyond what is just at the dam site so you can get a better feel for it. There are places you can still see the damage that was never fixed.

[craighoover]

I remember this event well and worked for a road painting company at the time and we worked in locations in east Idaho affected by the flooding. It was an eye popping experience for me. I had heard that the substrate was known to be questionable. Thanks for bringing this material out for all of us to actually see and virtually touch.

[nimajnebsurrab]

I was 6 years old when the dam broke. I grew up west of here in Mud Lake. The Teton Dam breaking is one of my earliest memories. My dad took us by the dam during construction after a trip to my grandparent's home in Teton Valley. Thanks for the video!

[JustMe-vvvy]

I grew up in Rigby. What I remember is how opposed the old timers like my grandfather (who had been a miner, a carpenter, & built irrigation gates, stores, homes etc.) were to a dam in that location. He was in his 80's & swore that the area around the purposed dam was too unstable for it to be built there. He had passed by the time I was stationed in Hawaii and received the call from my family that they had had a close call, but were safe. Guess they were right. It never hurts to listen to the old timers who have lived on the land all of their lives. I am enjoying your series, as I remember climbing the Menan butte to observe the same geology with our science teacher in the early 1970's. Thanks.

[dylanhalifaux]

I am from this area. It's very cool seeing videos for the whole world done on all this amazing geography I get to see every day.

[GGsInterests]

My brother and I went through the area a day before the dam broke. Our father in Pennsylvania thought we had died in the disaster. We missed the whole thing, never knew about it until we saw the news in the next hotel we stayed in, but didn't call home because we'd never heard any news about Idaho before at home in PA, and we planned to be back home the next day. Thanks for posting this.

[drmichaelshea]

It’s good to have you back, Prof. Willsey. I was a busy medical student when the Teton damn failed, but I do remember it. Thanks for the presentation. The failure due to the permeability of the rock makes me think of the unrecognized or ignored cracks that are developing in our culture, and I wonder what the consequences will be by the time my granddaughter is an adult. It’s a scary thought.

[slikrhodez]

This was one of my favorite places to explore when I was a student at Ricks College in the mid-80's. Thanks for sharing!

[careyallen]

I've lived in Idaho for almost 20 years now. And have learned a lot about the states since we've been here. But I didn't know this. Thanks, Shawn, this is great information. I love learning new things about Idaho.

[Sylvan_dB]

Drilling holes and grouting is a pretty standard process to control water migration thru the natural rock surrounding the engineered dam. This is called a grout curtain, and one was installed for the Oroville dam in California during the spillway reconstruction. Like all engineering, the problems come when interfacing the engineered components to the real world.

In the Teton dam case test holes were drilled, data collected, and in the final design the engineers specified the number of holes, an estimated amount of grout and a target injection pressure to ensure the porosity in the rock was sealed. Grouting is done by injecting grout (concrete) into the hole until that target pressure is reached. If a hole does not accept the expected amount of grout, or the pressure doesn't rise as grout is injected, the engineering on that real world interface is not correct. Usually there is a range of expected values and additional decisions or steps to be taken as construction reveals new knowledge about the real world. A critical decision failure during Teton dam construction was when this design specified PSI was not reached, and far more grout was pumped into the bore holes than estimated and still the holes kept accepting grout. Finally the contractor (perhaps in limited consultation) decided it was enough holes and enough grout and called it done. This was the time when the original design should have been questioned. If the engineer specified a design, but that design did not match the actual conditions found in the real world, the design was flawed and in this case the flaw was fatal.

The failure to control water migration thru the surrounding rock allowed water to travel thru the rock to the interior of the dam which caused the Teton dam to fail.

[IceStationZebra]

I was in high school back in the UK then, when this happened. But I don't recall seeing any reports on the catastrophe in any of the UK newspapers. A fascinating and devastating story though. Thanks for sharing this Shawn.

[melissasueh.]

I have been to the overlook a couple of times with my husband and children. The first time was in winter and the remains of the dam were covered with snow. It was hauntingly beautiful. Anyone who is in the area, whether visiting or living here, ought to go visit the place. The fishing in the river is also worth the hike or the drive down there.

[ccaudi]

The Teton Dam failure found me working as a young, wet-behind-the-ears analyst for the Congressional Research Service and its senior specialist, Dr Warren Viessman. Dr Viessman was present at all the post failure panels, hearings and discussions Congress held during the aftermath of the tragedy. He later authored a publication for the Senate's Energy and Natural Resources subcommittee and Sen. Frank Church. It was quite an energetic introduction for me to the Federal side of water resources and public works in the West. Thanks Shawn for the video and an up-close view of the reasons for the failure.

[blipco]

I read about this dam and many others in the book "Cadillac Desert". There was a dam building craze in America (both cash dams and flood control) and when running out of suitable areas to place dams, they started building them on previously rejected sites. If I recall, the engineers at the Teton had grout injected but they never reached a point where they were 100% sure it was sealed. They basically said "this is good enough". But it wasn’t. Thank you Shawn Willsey for this very detailed look at the geology of this site. I’m stunned they built the dam here. I wouldn’t have. It’s not hindsight, it’s common sense.

[michelepromastertravel]

I always enjoy your lectures. I learn so much, and you present it in an interesting way. thanks.

[jameshovey]

I remember learning about this, and going to the same site when i was in elementary school (early 90's). I drive near this area weekly for work, but unfortunately dont get to stop. Thanks for making this video! This brings back a lot of memories!

[jeffcooper]

Great video. I lived in Idaho Falls when the dam broke, and it was a big deal and really scary to see the Snake River roaring through town.

[Anne_]

I was in my 20s when this happened, living in Eastern Washington. I remembered the news coverage through that day. I was so horrified hearing the reports and pictures on the news. I've always been concerned about dirt dams. Of course I've always been used to big cement dams on the Columbia. Thanks for showing me this site. Clearly seeing the rocks there it was not a good place to build. You are correct, it was a different time and era then. So often I find myself saying to young people that it was a completely different world then.

[tthappyrock]

I lived in Eastern Oregon at the time of the collapse. I'm surprised that I don't remember hearing about it! The underlying geology of huge structures such as this is extremely important! There was a dam in California decades earlier which experienced such a tragic failure. We know so much more these days, thankfully!