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Teton Pass reopening planned Friday with ‘slow down point’ following highway collapse

Workers are paving a detour past the section of the vital Highway 22 between Idaho and Wyoming that a landslide undercut and demolished.

Workers pave a portion of the detour around a destroyed section of Highway 22 over Teton Pass on June 25, 2024 while others operate a drill on the alignment of the permanent reconstruction. (Angus M. Thuermer Jr./WyoFile)

by Angus M. Thuermer Jr., WyoFile

TETON PASS—Highway construction workers Tuesday were paving a detour around a missing section of Highway 22 in hopes the temporary fix will open the vital inter-state link to commuters Friday.

The road is expected to open to all traffic, including semi-trucks weighing up to 60,000 lbs., but will be signed with a 20 mph speed limit through the detour.

“It’ll be a slow-down point,” said Keith Fulton, assistant chief engineer for the Wyoming Department of Transportation who described the detour at the construction site. “A little bit of slow-down is better than a big detour.”

A landslide undermined the route over 8,431-foot high Teton Pass the night of June 7, befuddling thousands of Jackson Hole workers who live in nearby Victor, Idaho, where housing is more affordable. For two and a half weeks, they have had to make an 86-mile commute around the Snake River Range and through the town of Alpine instead of their usual 24-mile trip over the pass.

“We have the utmost confidence in this detour.”

WYDOT GEOLOGIST JAMES DAHILL

The change amounts to about four or five hours of driving a day, commuters say, an unsustainable burden on top of a normal eight-hour workday.

That’s going to end, “hopefully by the end of the week,” said Darin Westby, WYDOT director. He made his comments on the edge of freshly laid asphalt as it was being steamrolled amid the industrial cacophony of road construction machinery.

Concrete barriers will line both edges of the detour, which shortcuts the inside of the now-gone original sweeping curve. The new section has an 11.5% grade, steeper than the old road’s 10%.

“We have the utmost confidence in this detour,” said James Dahill, chief engineering geologist with the transportation department.

The Big Refill

It was “a perfect storm” that led to the failure, Dahill said. Rain fell on snow this spring as the temperature suddenly jumped 25 degrees resulting in unusual runoff.

All that water helped undermine “The Big Fill” portion of the highway that was built up five decades ago to span a significant swale in the route’s alignment. The Big Fill, however, was constructed atop “a little pocket of clay” Dahill said.

A saturated embankment and saturated soils contributed to the failure, Dahill said. “It was wet,” he said of the failure point.

Reporters, photographers and elected officials receive a briefing at the Highway 22 detour site on Teton Pass. (Angus M. Thuermer Jr./WyoFile)

Engineer Fulton said clay layers are “usually the slippery spot.” But he didn’t find fault with the original construction, completed more than 50 years ago.

“It gets used a lot,” Fulton said of the highway. “We keep up on maintenance.”

Landslide dangers are part of the nature of the mountain-pass highway beast, Fulton said.

Wyoming will likely qualify for federal funding for 90% of the expected $30 million cost of a permanent reconstruction, officials said. Plans are to rebuild the road in its original location, albeit with lighter embankment material.

The Big Fill, “that was heavy embankment material,” geologist Dahill said.

Although design and engineering is incomplete, the reconstruction will resolve the clay issue one way or another, he said, possibly with steel shafts or some other ground-penetrating columns. Drill holes have revealed no water problems at this point, he said, and underground sensors will reveal both gradual ground motion and any water flow.

Crews, including from emergency contractor Evans Construction, worked 24/7 for weeks, “through Father’s Day and everything else,” said Bob Hammond, WYDOT’s resident engineer in Jackson. “We wanted to get this done in two weeks; it’s taken three.”

A drone captured this photograph of the Big Fill Slide on June 8, the morning it was discovered. (WYDOT)

Although the road will be signed with a 20 mph limit, savvy commuters who aren’t in heavy traffic will likely be able to negotiate the detour a little faster, Hammond said.

Director Westby said he hopes the permanent replacement will be completed “before the real big winter sets in.” He touted cooperation across agencies, states, counties and municipalities and the capabilities of his department, too.

“We have the biggest engineering firm in the State of Wyoming,” he said.


This article was originally published by WyoFile and is republished here with permission. WyoFile is an independent nonprofit news organization focused on Wyoming people, places and policy.

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