The Idaho Legislature has appropriated $400,000 to study building a new version of the Teton Dam, the 305-foot earth-fill structure that failed spectacularly in 1976, killing 11 people and 18,000 animals, flooding most of Rexburg, and nearly taking out Idaho Falls.
Teton Dam was the last big dam built anywhere in the West. Virtually all the more economically attractive dam sites had long since been taken. The Bureau of Reclamation (BuRec) could have built Teton farther upstream, closer to the Teton River tributaries' sources in Grand Teton National Park, but even by BuRec standards, the economics of upstream dams looked dubious.
So BuRec chose a site near the edge of a bench above the Snake River plain, closer to the junction of the Teton and Henry's Fork, which then flows into the mainstem Snake. The giant earth-fill dam contained some 10 million cubic feet of dirt and rock, and spanned some 3200 feet between volcanic rock buttresses on either side. The reservoir behind it took years to fill. At the beginning of June 1976, it was almost full, with a quarter million acre-feet of water. Some of the water started seeping through channels in the rock below the northwest end of the dam. A couple of days before the collapse, people saw springs appearing in the rock.
Then, on the morning of June 5, wet spots appeared on the downstream face of the dam. They developed into sinkholes. A couple of bulldozers went out onto the dam and started pushing rocks into the holes. A whirlpool appeared ominously in the reservoir near the dam. The drivers barely got out in time, and the bulldozers themselves disappeared into the growing sinkhole. Everyone cleared out. The dam crest collapsed into a hole. At 11:57 a.m., only a few hours after the wet spots appeared, the whole dam gave way.
A wall of water roared down the riverbed, spread out onto the plain, destroyed houses and outbuildings, and poured into the town of Rexburg. Damage ran to a billion dollars. People worried that the Snake River, swollen with reservoir water, would flood the city of Idaho Falls, and there were some anxious moments when high water reached Idaho's second-largest city, but the Snake didn't quite top the embankments there.
The little farming community of Wilford, closest to the dam, got hit first. One hundred thirty-three of Wilford's 150 houses were destroyed. Six people drowned. After local radio broadcast word that the dam had failed, Alice Birch's two sons talked her into abandoning the Wilford home in which she had lived for 50 years. They and her grandson headed for higher ground. "As they drove toward St. Anthony," Wilda Birch of Idaho Falls wrote in That Day in June, an account of the dam failure published the following year by the Ricks College Press, "they could see the water coming like a huge cloud of dust. They estimated it was 20 feet high." Afterward, "(s)ome men who were on the Teton Hill south of the river reported to the family that when the water hit Alice's house, it lifted it up and over the light wires, and then the house exploded."
In Rigby, between Rexburg and Idaho Falls, Robyn Layton "watched at the window" of a second-floor apartment, from which "the first sign of the flood seemed like brown fingers sliding along the road. Then the rush came and all of a sudden it was there. A swirling brown mass carrying cars, huge logs, sheds, trailers and animals came crashing down Main Street breaking glass in store windows and spilling goods into the water."
Last month, writing in the Idaho Statesman, Rocky Barker noted the irony that "the dam, built for flood control, ended up causing more than a billion dollars in flood damages." (The dam was built for irrigation, electric power, and recreation, too, but flood control was indeed one of its stated purposes.)
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