Boise & Garden City

Fears of a landslide in Boise Foothills grow

Terra Nativa's Damaged Streets

Cracks in Alto Via Court have worsened the last few weeks, to the point Ada County Highway District says it can't keep up.
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Cracks in Alto Via Court have worsened the last few weeks, to the point Ada County Highway District says it can't keep up.

The ground is breaking beneath the Foothills dream homes, and the people who live in them want answers.

What’s causing the road, Alto Via Court, to crack? What damaged at least one home so badly that it’s uninhabitable? Are other homes on the street at risk? Could the pace of the movement, which experts estimate is one to two inches per week, accelerate a “catastrophic slide,” as the Ada County Highway District cautioned when it closed the street Thursday to all but local traffic?

Above all: What will fix the problem?

At least three teams of experts — working for the highway district, city of Boise and developers Richard Pavelek and Tim Day — are trying to get to the bottom of these questions. So far, their studies have yet to yield a conclusion on what’s causing the damage, much less a solution for it.

Meanwhile, “out of an abundance of caution,” the city emailed people living on Alto Via, suggesting they “consider the option of finding other accommodations “ until more information is available. The police will keep a close eye on the homes.

“Our hearts go out to these folks,” city spokesman Mike Journee said. “These are people’s homes.”

LOOSE GROUND

The anxiety started in mid-March, when Boise first fielded reports that shifting ground had damaged a home built in 2013 in the latest phase of the Terra Nativa development, located in the Boise Foothills off Table Rock Road.

The street, sidewalks and curbs have sustained damage, too.

Pavelek and Day, who have finished six houses on the street and plan to build another seven, commissioned a geotechnical report studying the characteristics of the ground underneath Terra Nativa. The city hired a team of engineers to work with them and review the report.

Preliminary analysis of the report led to concerns that the ground shift wasn’t isolated to the street and one house. Since then, the damage has worsened.

The street is badly damaged now, so much so that the highway district concluded crews can’t keep up with all the new cracks and breaches.

Several people who live on Alto Via said they didn’t want to talk Friday. Efforts to contact Pavelek and Day were unsuccessful.

Buck Harris, who lives on Table Rock Road on a contour of the same hillside, said he’s not worried about his house. It was built in the late 1990s, he said, and the dirt there is hard. If there were problems, they would be evident by now.

He said his wife is a little worried.

COUNTERMEASURES

Chances of sudden, intense rain this weekend were a factor in the highway district’s decision to close Alto Via, spokesman Craig Quintana said.

The district sought the help of outside engineers who, along with its own experts, concluded that a major dose of moisture could further destabilize the hillside and contribute to a dangerous landslide, Quintana said. The district’s experts were the first to warn of a fast, major slide.

The highway district installed meters to monitor ground moisture just below Table Rock Road up the hill from Alto Via, Quintana said. Additionally, the district has a large pump in place to extract water from the storm drain system at Alto Via in case shifting ground compromises the pipe that’s there now, further destabilizing the ground. The drain pipe is cracked, Quintana said, but it’s been repaired and is water-tight and working.

Next week, the district plans to bring in a landslide expert to help gauge risk.

FOOTHILLS BUILDING REQUIREMENTS

Before construction, Boise policy requires a licensed engineer to conduct surveys of geological characteristics for the ground beneath every Foothills development, Journee said.

The city requires the same geotechnical surveys for each lot in a development, he said. The city then hires third-party engineers to review the survey reports for accuracy and potential problems.

Every Foothills development also requires a grading plan, the extent of which depends on the results of the surveys, Journee said. The same step is required for each lot.

After the Alto Via shift came up, Journee said, the city pulled its geological documentation for the construction of Terra Nativa and found no red flags.

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