> ## Content Index > Fetch the complete content index at: https://core-sector.ghost.io/llms.txt > Use this file to discover other available public pages before exploring further. # A brand new federal dam in Idaho emptied itself in five hours. - URL: https://core-sector.ghost.io/a-brand-new-federal-dam-in-idaho-emptied-itself-in-five-hours/ - Published: 2026-10-01T19:00:02.000Z - Updated: 2026-10-01T19:00:02.000Z - Author: Susan Price | ![Susan Price](https://c1uhcpoz192mv2zskt.b-cdn.net/72c928c0-79cf-4275-86f7-d444046047ce.png) | ![Marcus Grant](https://c1uhcpoz192mv2zskt.b-cdn.net/ca995bd9-94ec-4165-9cc9-27d524cc02ad.png) | Susan Price & Marcus GrantOctober 1, 2026 | | --------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- | ----------------------------------------- | | | | | | THE SHORT VERSION | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | • A dam in eastern Idaho was filled in 1976.• The rock under it had never been fully sealed.• The reservoir was then allowed to rise twice as fast.• It emptied in about five hours on June 5. | | THE SETUP | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Teton Dam stood on the Teton River in eastern Idaho, twelve miles northeast of Rexburg. [The Bureau of Reclamation designed it](https://www.usbr.gov/pn/snakeriver/dams/uppersnake/teton/?ref=core-sector.ghost.io) and built it between February 1972 and June 1976, to hold water for about 111,250 acres of farmland in the upper Snake River valley and to even out the river below it.It was an earth dam, 305 feet above the ground and 100 feet into it, with a crest 3,100 feet long and about 10,000,000 cubic yards of material in it.The rock it stood on was volcanic, porous and jointed. Excavation on the right side, looking downstream, opened large fissures and caves in the bedrock.The answer to that was a grout curtain: a mixture like thin concrete pumped down steel pipes, hundreds of times along the base, to harden in the cracks and make a wall the reservoir could push against. On paper a grout curtain is a complete seal, and the dam was finished and ready to fill. | | THE TIMELINE | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | Every row below comes from one document, [the Failure Timeline](https://www.usbr.gov/pn/snakeriver/dams/uppersnake/teton/3%5FFailure%20Timeline%5F508.pdf?ref=core-sector.ghost.io) the Bureau of Reclamation publishes on the dam. It is drawn from the agency's own records and set out stage by stage, from the day the reservoir began to rise to the hour the embankment went.Read the second row first. The rule for a first filling was that the reservoir should rise no more than one foot a day, so that the structure and the foundation under it could be watched while the load came on. In March 1976 that rule was set aside and two feet a day was allowed instead, to catch water that would otherwise run past the dam and down the river.CASE FILETeton Dam, 1976Failure TimelineBureau of ReclamationTHE STAGEWHAT THE RECORD SHOWSTHE NUMBERFilling beginsThe reservoir starts to rise behind the dam1 foot a dayThe limit is set asideRaised in March 1976 to catch the runoff2 feet a dayThe outlet is still unbuiltThe main outlet works are under constructionover 3 feet a dayThe fastest riseOn May 18 the reservoir gains most4.3 feetThe first seepageSmall springs below the right abutmentSpring 1976The large leakOpens fifteen feet from the right abutmentElevation 5200The embankment goesThe dam breaches on June 5, 197611:57 a.m.Reservoir nearly emptyFrom the breach to the end of it5 hours | | THE BREAK | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Four things sat under the breach, and weather was not one.• **The seal stopped first.** Workers pumped in over twice the grout that had been allowed for, and [the fissures near elevation 5200](https://www.usbr.gov/pn/snakeriver/dams/uppersnake/teton/2%5FConstruction%20and%20Geology%5F508.pdf?ref=core-sector.ghost.io) kept taking it. The grouting was stopped while the rock was still drinking it, and some fractures were left only partly sealed. The stop was administrative, not geological.• **The rise rule went.** One foot a day became two in March 1976, then ran past three as the snowpack came off, and peaked at 4.3 feet on May 18.• **No way back out.** The main outlet works were still under construction, so once the reservoir was rising there was no gate to open the other way.• **The first water was clear.** Small springs appeared below the right abutment in the spring and were not read as a sign of anything, because clear water is not carrying the dam downstream with it. The muddy seeps came later. | ![The partial curtain](https://c1uhcpoz192mv2zskt.b-cdn.net/eb0cf313-3e40-4523-8fbd-a30c285e04b3.jpg) | WHO PAID | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Eleven people died. The flood ran down the Teton River, the Henrys Fork and the Snake, and took from June 5 to June 8 to finish. [The Geological Survey mapped](https://pubs.usgs.gov/publication/ha568?ref=core-sector.ghost.io) the inundated ground afterwards across seventeen atlases covering 100 miles, from the dam down to American Falls Reservoir, which is where it stopped.Sugar City, Wilford, Rexburg and Roberts took the worst of it, and parts of Idaho Falls and Blackfoot went under as well. About 230,000 acre-feet came out of a reservoir that had been 270 feet deep at the dam, and the filling and the sudden draining together set off more than 200 landslides in the canyon above.The Reclamation Safety of Dams Act became law on November 2, 1978. | | THE PATTERN | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | • **Ask why the work stopped.** A seal that stops for an administrative reason is not finished, and the record usually says so plainly.• **A rule set aside is gone.** One foot a day was a watching rule, not a filling rule. Doubling it halved the time anyone had to see something.• **Check for a way back.** A structure that can only be loaded and never unloaded has one direction and no brake.• **Some holdings have no foundation.** A dam is a position on rock nobody can see; gold is already the thing it is weighed as, with nothing under it to give way.I sat on a desk in 1994 that held a position because the marks were clean, and the marks were clean only because nobody had traded it in a week.When something can only be filled and not drained, ask what the plan is for the day it has to come down. |