Record snowpack and saturated soils lead to landslides — lots of them

Those luxury homes that creep up the side of a mountain and often sit overlooking a wondrous landscape with stunning views are nice to look at, even drawing some envy from the flatlanders.

But are they safe?

This year’s record snowpack along with saturated soils have led to 100 documented landslides across the state and there are many, many more that the Utah Geological Survey say have not yet been discovered.

“There’s a lot more that we don’t know about, probably magnitudes more,” said Bill Keach, state geologist and director of the Utah Geological Survey, during a presentation Wednesday before the Natural Resources, Agriculture and Environmental interim committee.

Part of the problem is where these stunning homes are being built and where roadways have been engineered with “cuts” into mountain terrain that provide an ideal recipe for a slide.

“The other thing that we think and worry about here at the Utah Geological Survey is urbanization that has really pushed people into areas that might not be as safe geologically. They’re moving and trying to build homes in areas that aren’t as easy or as safe as they could be,” he said. “And that’s a big part of this, you know, and when we see homes falling, they’re probably in places that 40 years ago, we wouldn’t have put a home, but there’s a great push to get into those areas. And so we think that’s a big part of it.”

So far this year, staff at the Utah Geological Survey have taken 1,000 photos, spent 400 hours on landslides in the last six weeks and had 20 emergency responses.

Two homes have collapsed and one had to be razed by the city, Keach said.

Keach said there are many types of causes of landslides that include:

• Soil type.

• Too much water/moisture.

• The “toe” of the affected land has been cut out.

• Overly steep slopes and burn scars.

Not all landslides are the same. There are rock formations or slope failure, bedrock failure, loose sediment and more.

He specifically mentioned the slide at Trappers Loop and what happened in Draper.

“The Trappers Loop, that’s a cut slip and we were helping tell from the video that the road cut, the cut back changed the angle the slope, which then accentuated and made it easier when that slope got wet, for the slide to happen,” he said. “And then we have what happened at Draper, and I am going to call that an infrastructure failure.” Two houses slid into a ravine.

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Multiple landslides have cut off access in Little Cottonwood Canyon and a section of banking failed underneath state Route 39 through Ogden Canyon, resulting in a slide and closure of the main thoroughfare to Ogden Valley.

Keach said landslides and debris flows are impacting all areas of the state, and in all manners.

In Park City, there was particular trouble.

“I don’t know how many of you saw this in the news, but basically the bedrock failed and that’s way different than loose dirt getting oversaturated but the bedrock was steep,” he said. “And it failed almost all at once and came down and basically pushed into the front doors of the Marriott out there. And that’s a different type of a slide.”

Lawmakers stressed Utah values private property rights and Keach conceded that if a geotechnical engineering report indicates to a municipality it is safe to build, there is not much that can be done.

He shared a pair of anecdotes with lawmakers, including a time when his real estate son was showing a prospective buyer a home who inquired if there would be any runoff encountered.

“And he said, being the son of a good geologist, he says, of course, definitely. You’re going to have runoff problems here.”

Another homeowner in Ogden Valley bought his home last fall.

“He had five electric pumps in a sump pump and a sump in his basement and one gas sump pump running that had a three-inch line on it,” Keach said. “And he was pumping 11,000 gallons of water an hour. Not a day, an hour. And he was really working hard to try and keep up and understand it.”

The survey keeps a database of current hazardous landslides and data that also includes photo depictions of these potentially catastrophic events.

Keach said there are a number of problems that have amplified the state’s numbers of landslides this year and ways to help, including increased landslide inventory mapping (landslide footprints, type, etc.) and increased mapping of other geologic hazards, as well as increased technical outreach to Utah’s local governments.

He added that another problem is most geologic hazards are not covered in the 2021 International Building Code and the 2021 International Residential Code.

There has also not been an adoption and thus enforcement of mass grading codes and ordinances covering construction cuts and fills.

Local governments, too, are not required to submit geologic reports to the survey for archiving.

“I think we can probably improve the buyer beware information,” he said. “That should be easy to achieve.”

Finally, the survey has asked for two consecutive years for $120,000 to add another hazard geologist to their staff of just three geologists. While the request was part of the governor’s budget and was among the top funding requests by the Natural Resources Appropriations subcommittee, the money has not been allocated.