Boise & Garden City

Shifting Foothills ground near Table Rock getting worse

Ground instability recently caused a home in the Boise Foothills’ Terra Nativa housing development to shift, inflicting damage on the home. The city of Boise, Terra Nativa’s developers and teams of experts are working to determine the cause of the instability and how to fix it.
Ground instability recently caused a home in the Boise Foothills’ Terra Nativa housing development to shift, inflicting damage on the home. The city of Boise, Terra Nativa’s developers and teams of experts are working to determine the cause of the instability and how to fix it. kgreen@idahostatesman.com

A report may point to stability problems for neighbors of an upscale home off Table Rock Road that has already sustained damage and been deemed too unsafe to live in because the earth under it moved unexpectedly.

Boise spokesman Mike Journee stressed Wednesday afternoon the danger to other houses is potential, not certain. The walls of one other house in the area — on the other side of the same street and about 300 feet to the south — are showing some superficial cracking, but there is no apparent damage to the foundation or structural elements, Boise assistant city engineer Rob Bousfield said Thursday. Experts are working on the theory that the cracking walls are related to the same earth movement that’s affecting the first house.

“Most houses, if you saw that, you wouldn't really think too much about it. But, given the situation, it's something that we'll monitor,” Bousfield said. “It's just, more or less, I'm going to say, a warning sign of something to watch.”

Journee said the city’s concern for other houses is based on preliminary analysis of a geotechnical report commissioned by developers Richard Pavelek and Tim Day, who have built six homes in the latest phase of the Terra Nativa subdivision in the Foothills north of the Table Rock recreation area and plan to build at least seven more. Boise Public Works officials and a team of engineers the city hired to consult on the Foothills ground stability want to spend more time reviewing the report before drawing final conclusions.

Pavelek said he was optimistic his team of experts would find what caused the home he built in 2013 to shift, then fix the problem.

“We’re probably getting close to knowing how to stop it,” he said. “We’re zeroing in on some causes and zeroing in on some answers.”

The woman who owns the house that was damaged asked the Statesman not to disclose its location or her name out of concerns for her security. She would not comment on the extent of damage to the house or whether it could be fixed.

Bousfield said the damage has gotten worse in recent days. He said the foundation is cracked, the floor is buckling and some walls have cracks big enough to see through. The city initially deemed the house unsafe to live in, but have allowed people to enter it. Now, with the condition of the house deteriorating, Boise officials are considering restricting anyone from entering the house. That decision is up to Jason Blais, Boise’s chief building official, Bousfield said.

“When you get into the structural (defects), you start to get worried,” Bousfield said. “Not that it's imminently going to collapse or anything like that, but that's where you start to worry, where there's uncertainty about it. So that's when you pull people out.”

The unsafe designation will stay in place until the damage is repaired and an engineer is comfortable the home is stable, Bousfield said.

No such restrictions are in place for the second damaged house.

“I think it's a long way from that,” Bousfield said. “We'll continue to monitor the situation.”

Pavelek said the road where the home shifted has been in place for a decade and never had a problem. This winter, he said, something happened that damaged the woman’s house. He said he didn’t know what caused the earth movement.

The city first received reports in mid-March that a Foothills home, as well as the street in front of it, had shifted and been damaged, Journee said. Since then, city staff has worked as a go-between for the neighbors, developer and utility companies. The Public Works Department began working with Pavelek and his team of geotechnical experts, partly out of concern for sewer and other utility infrastructure in the area. Boise hired engineering firm CH2M Hill to provide technical expertise, Journee said.

Shortly after the earth movement came to light, local water company Suez began to worry that instability in the ground would cause a water main line in the area to break, draining a water-storage tank, which could in turn cause greater instability, Journee said. The company recently shut down the water main and installed a temporary, above-ground line to get water to nearby houses.

Journee said the city retrieved the development’s original documents analyzing the ground under Terra Nativa and found no red flags. Those documents include the developers’ original geotechnical analysis and an independent review of the analysis that the city requires.

Look down from this high-end housing development into the Treasure Valley.

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