WYDOT defends Teton Pass detour as politicos, engineers question plans

Plan hasn’t been released for Teton Pass temporary fix, fueling speculation and questions from the public

By Billy Arnold, Jackson Hole News&Guide via Wyoming News Exchange
Posted 6/19/24

JACKSON — Bob Hammond has heard the criticism: The Wyoming Department of Transportation is moving too fast as it rebuilds the part of Teton Pass that collapsed last week. But WYDOT’s …

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WYDOT defends Teton Pass detour as politicos, engineers question plans

Plan hasn’t been released for Teton Pass temporary fix, fueling speculation and questions from the public


JACKSON — Bob Hammond has heard the criticism: The Wyoming Department of Transportation is moving too fast as it rebuilds the part of Teton Pass that collapsed last week. But WYDOT’s Jackson-based engineer sees speed as a necessity.

As Hammond and a team of WYDOT geologists and contractors from Evans Construction and HK Contractors move earth around the “Big Fill,” which collapsed in a landslide, he’s thinking of the Teton Valley, Idaho-based nurses at St. John’s Health who can’t get to Jackson or are spending hours more commuting. He’s thinking of their patients and the other regular workers who commute the pass on a daily basis.

Hammond wants to get Teton Pass rebuilt quickly to ease those workers’ hour-and-45-minute commutes.

“At the same time, I would never build a road that isn’t safe — that I wouldn’t drive with my kids,” he said.

But in Jackson and across the country, politicians and geotechnical engineers, the folks responsible for manipulating dirt for human benefit, are raising questions about WYDOT’s plans for the temporary bypass. They’re asking whether safety is being compromised for speed.

Other geotechnical engineers and landslide experts say building a temporary road section quickly isn’t abnormal.

Still, with concerns about stability in the area, those engineers want more information about WYDOT’s plans. They’re hesitant to opine on the department’s work without seeing more. WYDOT had not publicly released a formal plan for the bypass by press time Tuesday. In the absence of information, people are speculating.

“People do need to know,” said George Machan, an engineer and expert in landslides who has worked with WYDOT for years, and consulted for the Town of Jackson as officials responded to the Budge Slide in 2014.

That year, the first thing Machan did when he arrived in Jackson was talk at a public meeting.

“Some people may be averse to talking in public or try to avoid it like the plague,” Machan said. “But I can see it would benefit the DOT if they would share what they know with the public.”

Hammond, meanwhile, said a public meeting is a good idea. The problem is time. WYDOT is focused on the rebuild, and organizing a meeting would be onerous.

He also implored the public to trust the engineers on the ground. While onlookers are asking many valid questions, they’re not seeing all the information that he and other WYDOT geologists are, Hammond said.

Engineers are also attempting to mitigate many of the concerns that people are raising, he added.

“There’s a lot of people who don’t know what we’re building up here and a lot of people who really want to know,” he said. “But it’s one of those things where you can’t explain it to everybody all the time.”

Valid questions

Without more information, Jackson Town Councilor Jessica Sell Chambers is questioning whether WYDOT has done its homework, relying on conversations with geotechnical engineers who don’t want to be named — and one engineer from Kansas who has attracted a significant YouTube following by commenting on the rebuild.

Why, they ask, did WYDOT reopen the road after shooting cracks appeared on Thursday, June 6? Why is the department building a temporary bypass next to the fill that collapsed without first completing an analysis of the underlying soils? And how can officials be certain that the new route won’t fail in the same way?

“They have not demonstrated that they have taken the necessary look at the situation,” Chambers told the News&Guide. “And they’re putting it right next to the piece that failed.”

Chambers has raised concerns in a letter to the editor that printed in the Casper-Star Tribune and on the website for Idaho News 8. She submitted the same letter to the News&Guide, which chose not to print it. This newspaper does not print opinion pieces submitted by people who are running for local office. Chambers is running for mayor.

Geotechnical engineers who spoke with the News&Guide on the condition of anonymity echoed the concerns that Chambers and Casey Jones, the Kansas-based engineer, have been raising about why WYDOT is moving forward with a rebuild before completing the stability analysis. Others echoed concerns that Machan raised: Placing too much fill material underneath the bypass could either stress the walls of the curve that failed, or put too much pressure on the underlying soil that caused the collapse nearby.

“At what point of adding more material do you get to the point where you’ve tipped the stability and made another problem?” Machan asked. Without a plan released, it’s hard to know, he said.

In a 45-minute interview Monday, Hammond and WYDOT Geologist James Dahill answered a handful of questions. Then, in an hour-and-a-half interview at the pass jobsite Tuesday, Hammond answered more.

But there are still outstanding questions like why, exactly, the department believes the ground under the temporary bypass won’t pose a problem, even though it has some of the same characteristics as the soil that failed.

The department has also not yet formally calculated a factor of safety for the temporary bypass. That’s a number that expresses how much stronger a system is than it needs to be for an intended load. And, while Dahill said WYDOT would release a diagram outlining plans for the bypass, that wasn’t available by press time Tuesday.

Cracks in the asphalt

To have a landslide you need four things, Hammond said: a “driving force” at the top of a hill, which pushes material downhill, a lack of “resisting force” at the bottom of the hill to prop that earth up, a “nasty” layer that creates instability, and water, which creates a slick plane for earth to move across.

In this case, Dahill and Hammond said the weak layer was in the “native soil” underneath the 70 feet of fill — the “Big Fill” — that WYDOT engineers placed on the mountainside to make the grade of Teton Pass suitable for driving in the 1960s. There also wasn’t much “resisting force,” Hammond said. The grade of the “Big Fill” was too steep. Typically, when building an embankment for a road, engineers will make sure it rises 1 foot for every 2 feet of base area. The “Big Fill” was far steeper than that.

“It was not even close,” Hammond said.

Over decades, as snow melted, it caused problems. The “driving force” — the pavement on the road and the fill material underneath — pushed down on the subsurface and caused cracking. WYDOT geologists knew there was a slow-moving landslide in the area. But it was exactly that, Hammond said: slow moving.

Last fall, road crews paved over that spot to make it smoother for motorists and plow drivers. When they did, they also installed an inclinometer in the “Big Fill,” a device that helps detect soil movement. In mid-May the department read the device and saw that the slope had moved “very little,” Hammond said.

“That’s what it had been doing for 20-plus years,” Hammond said. “It really wasn’t that big of a deal.”

It became a big deal when a motorcyclist hit an 8-inch crack on Thursday, June 6. Later that day, WYDOT patched the crack to allow commuters to get home. Hammond had a worker watch the crack throughout the evening, but they eventually went home. Another worker was going to come out at first light to continue the watch, but a mudslide let loose elsewhere in the early hours of the morning, closing the pass.

Chambers and Jones, the engineer, say the mudslide saved WYDOT from tragedy. Drivers could have died.

But Hammond said that even by 10 and 11 a.m. on Friday, June 7, the road near the cracks was still safe enough to drive on. WYDOT engineers passed through the area to reach the mudslide. It wasn’t until later in the day the cracks began expanding.

At that point, if the road weren’t already closed, Hammond said WYDOT would have closed the road.

Questioning the rebuild

When roads collapse in a landslide, it’s very common for a department of transportation to build a temporary road, said Ben Leshchinsky, a geotechnical engineer at Oregon State University who specializes in landslides.

Some temporary bypasses can take months to build, but the length of the project depends on the severity and size of the slide.

The key to building a bypass is to do so safely, which often involves removing material from the area where the ground’s unstable and installing temporary drainage to prevent future slides.

WYDOT is not installing drainage in the area, Hammond said, because the new fix is at a high point.

Water will naturally drain off to the south, he said.

The department is also stacking 30 to 40 feet of fill on the inside of the old curve to build the new curve. Hammond said the department is addressing Machan’s concerns about overfilling the interior by removing material from the “Big Fill,” and redistributing it under the bypass. That, he said, should remove the “driving force” that caused the road to collapse, and create more “resisting force” to bolster stability.

“He’s taking away driving forces,” said Dahill, the WYDOT geologist, “and moving and putting them over here, where they’re outside of the area of disturbance.”

WYDOT determined that the bypass is on stable terrain by looking at geologic maps, physical observations on the ground, and drilling in the subsurface. The department’s geologists have determined both that the soil under the bypass is similar to the soil under the “Big Fill” and that failure isn’t a risk under the temporary road.

Hammond said he’s relying on geologists’ expertise, and moving forward.

But onlookers question whether the department can make that determination without completing its analysis. A full geotechnical analysis can take weeks, or months, engineers said.

“I’m not saying that this is going to fail, or what they’re doing isn’t viable,” said Jones, the Kansas engineer. “I’m just saying there’s no way they could have addressed the underlying questions.

“Is this a matter of risk taking? Or do they have more information they haven’t provided to the public?”

Hammond said the analysis is ongoing, and will inform the full rebuild of the road. In the meantime, he said results are coming in that confirm that the ground underneath the bypass is stable.

Leshchinsky and other engineers said it’s possible to move forward with a bypass before a geotechnical analysis is complete. But, if WYDOT does, it needs to monitor the bypass for movement and water issues.

“Ideally we would have information about what’s going on in the ground,” Leshchinsky said. “When we lack that information, the big key is monitoring.”

WYDOT plans to do that.

“We will install instrumentation to monitor that ground from the time it’s constructed, and we will monitor it going forward until a permanent solution is designed and put in place,” Dahill said.

Teton Pass, WYDOT