The view from the backyard of the new homes was postcard-worthy — jutting out on a manmade ledge on a steep slope, overlooking a picturesque canyon and a popular trail winding through the trees below.
But it wasn’t long before there were serious problems.
Within eight months of the homes’ completion, a field inspection showed that the driveway slabs were separating and the soil was cracking in the backyards. A few months later, cracks had developed in the cement walkway to the front steps, according to thousands of pages of records I received from Draper City through a public records request.
And in just over a year, one end of the lots had settled by nine inches, putting stress on the structures. The builder thought the hill could be stabilized and the home saved, resulting in a flurry of discussions about how to do that. An engineer said in October 2022 that within two weeks the home might be unsafe to occupy — but later backed away from that assessment.
Later that month, though, the city had seen enough: the homes were deemed unsafe and the owners were told they needed to vacate the premises.
Of course, we know how it ended, thanks to the jaw-dropping video that showed the moment the hillside beneath the homes gave way and two slid into a ravine.
The question that had been on my mind was, given more than a year of back-and-forth between the homebuilder and Draper City, and extensive geotechnical and engineering reviews, how did this happen?
It appears, based on the documents, that construction crews who built the ledge the homes were perched upon were either sloppy or cut corners, failing to comply with the requirements designed to ensure the stability of the slope.
(Francisco Kjolseth | The Salt Lake Tribune) Robert Gehrke.
According to a memo from November, five months before the homes collapsed, the geotechnical firm that had studied the project had concluded that crews had failed to remove vegetation before building up the hillside and failed to fully compact the fill soil beneath the spot the homes would stand.
Boreholes turned up loose soils and vegetation that shouldn’t have been there. “The fill in this ravine was clearly not reworked as structural fill at depth since the respective homes on these lots have settled nearly 9 inches in the corners located above the ravine,” Intermountain GeoEnvironmental Services, Inc., the consulting firm for the developer, wrote in a Dec. 8, 2022, memo.
IGES recommended in their geotechnical hazards report that a drain be installed to keep the soils from becoming saturated, but, according to the memo, “IGES is not aware of a drain being constructed at this location.”
By that time, some 30 to 40 feet below the home’s foundations, the ground was sinking and slipping as the loose soils settled, exacerbated by the water that had seeped in.
In a November meeting, one of the consultants hired by the city noted that the retaining walls below the two lots “showed signs of bulging,” and warned the instability could get worse.
Alan Taylor, of Taylor Geotechnical, wrote in a memo to Draper City building official Keith Collier that, if the homes were moving during the relatively dry autumn months, that movement “could increase noticeably in April [2023] after the spring thaw and seepage pressures in the soil mass are present.”
Taylor was right. On the night of April 21, amid heavy runoff and a driving rainstorm, the hillside gave way and two homes crumpled into the ravine.
The developer of the subdivision, EDGE Homes, declined to say if it believed the loose fill dirt caused the failure. In the immediate aftermath of the slide, company officials attributed the incident to the failure of a retaining wall.
“We do not express any opinions about the IGES report as the investigation is ongoing,” the company said in a recent statement.
EDGE said it was finalizing a remediation plan that will “allow us to stabilize the area and conduct additional investigations to gain a better understanding of the factors that contributed to the collapse of the homes and the failure of the retaining walls.”
The collapsed homes have been repurchased from the owners, the company said, and EDGE is paying the expenses of the neighbors who were displaced.
The entire Hidden Canyon project went through a rigorous review process, due to the fact that it was built in an area that is well-known to be prone to landslides. Draper’s Geologic Hazards Ordinance required EDGE to hire a geotechnical consultant (IGES in this case) and submit the reports for review by consultants hired by the city.
The documents released by Draper show that over the course of more than a year, the city pressed the developers over and over for more data and additional answers to questions — requiring additional soil studies and validation for the plans they put forward.
“It’s a long and sometimes painful process,” Draper City administrator David Dobbins told me. “Our goal is to have them substantiate their plans with data.”
The exchanges between the city and the technical firm generated thousands of pages and yielded a series of recommendations from the firm, including the removal of vegetation before the hillside is graded and the compaction of the fill used in the project.
Those recommendations were incorporated as conditions for the city’s approval of the project.
We don’t know the reason — whether it was to save money or time, or just sloppiness — but those requirements weren’t followed. Now it’s easy to see the consequences, from an empty space overlooking a canyon where those houses once stood.
