The cliffs of the Wind River Canyon in Central Wyoming soar into the sky on the east side of U.S. Highway 20 and drop off into the Wind River below on the west.
Literally.
Spring is the busiest time for big chunks of the mountain to break off, causing rockslides and mudslides across the highway .
U.S. 20 is known as one of the most scenic highways in Wyoming and celebrated its 100th anniversary last year as a route to Yellowstone National Park.
It is also fraught with rock falls and mudslides, and drivers are reminded to be aware of not only the beauty surrounding them, but of the falling boulders that could come down at any time.
Driver working for Ryan Bros. Trucking in Thermopolis know the dangers well.
Adam Estenson, the director of risk management for the trucking company, said that he monitors his drivers’ speed through the canyon to minimize the risk to themselves and others.
“We had a truck that was hauling propane and hit a rock with his tire,” Estenson told Cowboy State Daily. “Thank God, he had cell service where he was in the canyon.”
The truck driver had to pull over on the shoulder and the company’s rapid response team were deployed to help. They directed traffic and helped clean up the debris from the rock fall that had demobilized their driver.
As regular drivers through the Wind River Canyon, the truckers are always alert for these potential hazards that may impede them and other drivers.
“A lot of times our drivers will come through the canyon and call our dispatch and say, hey, there's rocks on the road,” Estenson said. “We then notify WYDOT and they hurry out there to take care of it.”
In 2016, a large boulder was dislodged and damaged Highway 20 in the Wind River Canyon, located in central Wyoming. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor) 
Ryan Brothers Trucking located in Thermopolis sends their trucks through the Wind River Canyon regularly. They have a heightened awareness of the dangers and monitor their drivers speeds closely as they navigate the winding roads. Small rocks along Highway 20 have caught drivers by surprise and resulted in tire blowouts. (Courtesy Ryan Brothers Trucking, Thermopolis) 
Rocks are hauled off from rockslides in the Wind River Canyon and later used as fill for other projects. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor) 
In 2015, heavy rainfall over Memorial Day weekend caused mudslides and rockslides which closed the Wind River Canyon for days. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor)
The Dangerous Rains
The rains that bring spring flowers to the canyon and cover the grassy cliffs with bright yellow mule ears, also bring the potential of these rock falls.
“All the big rocks in the canyon, especially on Windy Point, are sitting in rework,” commercial geologist Ed Cole said. “It's already an eroded mountain in the canyon and the rocks are just sitting in that loose soil.”
He explained that as the ground becomes saturated, the sand mixed with smaller rocks erodes much faster than the bedrock. The more durable sandstone and dolomite on top of this sand are then knocked loose and these are the troublemakers in the canyon that the Wyoming Department of Transportation (WYDOT) maintenance crews are on the alert for.
“We have been awfully lucky this year,” WYDOT area supervisor, Clint Huckfeldt said. “The canyon has behaved itself very well, considering the amount of rain that we've gotten.”
Huckfeldt said that anytime that we get rain, WYDOT want motorists to be always aware of the rocks on any of the slopes because you never know when something's going to cut loose.
Although they have been fortunate this year so far with no major rock or mud slides, there is still time for a heavy downpour this season that would potentially result in one of these slides.
“Especially wind driven rain tends to let rocks loose,” Huckfeldt said. “It is definitely a good time to pay attention anytime that there's moisture. Even when we come out of a rain cycle into a drying cycle, it can let rocks loose.”
Another danger that spring brings is the freeze thaw cycle. The black rock at the tunnels of the canyon, a type of altered marble, is especially prone to this type of rockfall.
“The granite formations up there are really tough,” Cole said. “But when any water gets into those cracks and freezes, it breaks them up and they eventually do come out and come loose.”
Be Alert For Dangers
The drivers for Ryan Bros Trucking are trained to be aware of these dangers.
“You got a lot of factors in the canyon,” Estenson said. “It’s an ever-evolving geological structure. It's a windy road and you got a cliff on one side and a river on the other.”
When the trucking company are planning their routes, they will build in extra time when their guys are going through the canyon. Estenson will also give any drivers who are too much in a hurry a coaching session on safety because, as he said, they are never in that big of a hurry to risk lives.
WYDOT has been focused on remediation efforts in the canyon, especially after the 2015 mud and rockslides closed the Wind River Canyon for several days.
“We have been proactively looking at these rockslide areas and I think it's helped us over the last ten years,” WYDOT Public Relations, Cody Beers, said. “We don't have nearly as many major rock events as we've had in the past.”
WYDOT has employed mountain climbers and other companies that have gone into the Wind River Canyon to roll rocks off the cliffside in a controlled environment rather than wait for a rain event to take them out.
While they still get smaller rocks on the road, WYDOT maintenance crews are constantly patrolling the canyon all year long. They also encourage the public to be proactive and call in any rock falls they may see to Highway Patrol.
“Definitely make that call as soon as you have cell phone service coming out of the canyon,” Huckfeldt said. “Troopers will roll on any of the rock calls.”
Huckfeldt recommends being accurate about the size of the rock fall when you call in a report. At times, they have sent out their large equipment when a pickup would have done just as well.
“That's the toughest thing that we come up against is sometimes the reporting isn’t quite accurate,” Huckfeldt said. We'll get a report of a car-sized boulder and we get out there and it's the size of a basketball.”
In those cases, the crews could have gotten to the hazard quicker in a pickup and just manhandled it off the road.
In 2023, a mudslide kept Wyoming Department of Transportation maintenance crews busy as they cleared Highway 20 through the Wind River Canyon in central Wyoming. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor) 
Heavy snowfall is often a concern for rockslides in the Wind River Canyon, Wyoming. This dolomite boulder was loosened after a wet snowfall eroded the dirt from around it. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor) 
A mudslide closed the Highway 20 through the Wind River Canyon in 2015. This historic flood has prompted the Wyoming Department of Transportation to begin looking at alternative routes in case of future catastrophic events. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor) 
Mudslides in the Wind River Canyon have been known to dislodge large boulders which Wyoming Department of Transportation maintenance crews must then clear away. In recent years, technology has improved so that what used to take hours to remove can be done much faster with a hydraulic breaker that fits their backhoe. (Courtesy Clint Huckfeldt, WYDOT Area Supervisor)
Keeping The Canyon Safe
“We're really one big rockslide away from an extended closure of that canyon that could take weeks and probably months for us to clear the rock out and reopen the road,” Beers said.
WYDOT became even more conscious of such a possibility when the canyon was closed for five days in 2015 due to the mudslides that washed out sections of U.S. 20.
“The 8 feet of mud and rock that was across the road will forever stand out in my mind as probably the most significant incident,” Huckfeldt said. “There's also been some huge rocks that we've had on Big Windy that have taken some serious effort to get rid of.”
Huckfeldt said his priority is finding that safety balance for the traveling public through this vital transportation corridor. It is also an on-going concern for Ryan Bros. Trucking who depend on the canyon route for their livelihood.
“Our biggest thing is when the canyon shuts down, we have to deal with the logistics of that,” Estenson said. “We notify customers that we're running behind and so any closure of the canyon affects our business.”
Alternative Route
While the past decade has seen a lot of work in the Wind River Canyon, WYDOT is aware that a closure could still happen. As a result, they have hired a consultant to look at any possible redundant route which could be used in the event of an emergency.
“I always want to keep Wind River Canyon as a route into the Bighorn Basin because it is so incredibly beautiful,” Huckfeldt said. “There's so much history with it being one of the most expensive highways built one hundred years ago and it being an important route to Yellowstone.”
However, for commerce coming in and out of the Bighorn Basin, WYDOT recognizes an alternate route would help make their highway system more resilient.
“We would be able to better serve the people of Wyoming and make sure that they can get where they want to go when they want to go there,” Huckfeldt said.
The beauty of the canyon is not lost, even on those who regularly make a commute through the windy roads.
“It's a magical place to drive through,” Beers said.
Estenson agreed.
“I just can't emphasize enough how beautiful it is and how fortunate we are to be able to drive through it every day,” he said. “It can be dangerous, but it's beautiful. I don't ever say I have to drive through the canyon, I say I get to drive through the canyon.”
Jackie Dorothy can be reached at jackie@cowboystatedaily.com.
