On April 30, there was a landslide about half the length of a football field and 15 feet deep on the slope above the Marriott Mountainside hotel at Park City Mountain.
No one was injured, but the ground floor of the hotel had minor damage, including a displaced storm drain.
The new Kings Crown development sits on the hill above the landslide. The developer of that project, Rory Murphy, said there was no damage.
Utah Geological Survey Geologist Ben Erickson said the main cause of the slide was the record snowpack melting. He added it is a complicated landslide and will take a thorough investigation to see what factors contributed to it.
The clay material that has filled up holes of bedrock in the mountainside is what made this incident so unique to other landslides.
“The water penetrates into those fractures and interacts with the clay, causes it to become slippery, and it then causes all of the fractures to mobilize and to follow gravity and slide down the slope,” Erickson said.
He said normally most landslides they see are a big clay mass, and bedrock failures like the one in Park City are uncommon.
“Bedrock is usually really competent and can withstand a lot. But because it’s been fractured and has had so much material get in between those fractures, that’s where we can get to the state where it was able to fail, and collapse, and slide down.”
Erickson said the fractures in the bedrock took millions of years to form.
The geological survey also recently looked at a slide that was about two tennis courts wide on a hill behind a townhome on Cove Canyon Dr. in the Snyderville Basin.
No injuries were reported, but the deck of the home was damaged, and the slide remains active.
“It’s been slowly moving forward and dropping down," Erickson said. "That’s what we kind of anticipate — is slow moving, but where we can see inches to feet in a day where this can happen.”
He said they anticipate seeing more landslides across the state as the Spring melt continues, adding that rain will make the ground more active.
“Water is always a key driver with landslides. There’s other things that can impact it, but in most cases an increase of water will cause a lot of ground failures, just because of the way it interacts with the ground.”
Erickson said water seeping out of the ground is an early sign that a landslide could occur. He encouraged people to report anything suspicious to local authorities, or contact the Utah Geological Survey.
