Crews are building a detour around a heavily-traveled commuter route between Jackson, Wyo. and eastern Idaho that had showed signs of failure on June 6, and did so despite proactive efforts. Evans Construction of Jackson, Wyo. quickly mobilized the next day to repair a crack and a drop in the road near mile marker 12.8 of SH-22 on Teton Pass. Under an emergency contract for WYDOT, Evans worked through the evening to remove asphalt from the roadway to minimize the weight on the unstable ground.

 “When we realized it was getting dark and we couldn’t proceed, we called it quits for the evening,” says Craig Clarke, construction manager and vice president of Evans Construction. At that time, Clarke says the road was dropping about six inches per hour. The crews moved the construction vehicles a safe distance away and went home. In the early hours of Saturday morning, the roadway failed, “leaving a large cavern with a head scarp of about 50 straight vertical feet,” Clarke says.

No crew members were injured, and no equipment was damaged.

Bob Hammond, resident engineer for WYDOT, says they were aware of the slide potential along the highway and had been regularly monitoring the road, especially as spring runoff increases the erosion.

Evans Construction is staying on to help construct a two-lane detour. WYDOT says geologists and engineers are confident they can build a safe, temporary detour around the slide area using local fill material and paving two temporary lanes. They are hoping to have this temporary detour open to the public, likely with some strict weight and width restrictions, in a couple weeks, Hammond says. A long-term fix will take several months. 

The slide took place on a hairpin curve. The detour will be on the inside of the corner, downslope from the existing fill. "It seems to be more stable area – doesn’t appear to be moving," Clarke says.

Governor Mark Gordon issued an executive order declaring an emergency in response to both the landslide at milepost 12.8 and an unrelated mudslide discovered June 7 at milepost 15. The declaration will help the state access additional resources from the Federal Highway Administration to begin the substantial repairs required.

Constructed in 1969, the nearly 17-mile stretch of highway is regularly monitored for slides, says WYDOT spokesperson Stephanie Harsha. “We have a couple known slide paths in the area so our geology team gets out there regularly to inspect those areas … especially with warming temperatures that cause snowmelt,” she says.

WYDOT will be flying the area with a survey plane and doing some geological drilling in preparation for the reconstruction.  

Crews also continue to manage the mudslide and are cleaning up water, mud and debris as it comes down the mountain. WYDOT says its geologists and engineers are working on a plan to provide more drainage to the affected area by installing a box culvert. They are planning to do this work simultaneously with the temporary detour work at milepost 12.8. While the work is dependent on availability of crews and materials, WYDOT reports a plan to have this work completed when the temporary detour at 12.8 is ready for limited traffic. 

“I’m really impressed with how quickly Evans responded and has collaborated with us on the design,” Hammond says. “They understand how import this route is for the essential workers who travel it every day.” 

Yellowstone National Park and Grand Teton National Park remain open for visitors. WYDOT spokesperson Doug McGee says traffic along Teton Pass is, on average, about 12,257 vehicles per day at this time of year, heading into peak season for the parks. “That number is expected to climb to 15,146 vehicles per day in June and top out in July with more than 16,400 vehicles per day,” he adds.