The Gravity Of Foothills Developments

slide sign
You don’t have to be Isaac Newton to predict that water runs downhill with the force of gravity, often taking loose soil along with it.

In recent history the Idaho Transportation Department learned the gravity/water/soil lesson on Horseshoe Bend Hill, forcing the relocation of Hwy 55 to its present location.

Same issue caused massive rockslides and road closures below Warm Springs Mesa near the golf course as saturated earth caused rockslides on Warm Springs Ave. when it was also Hwy 21. GROWTHOPHOBES will tell you foot hills development is a slippery slope at best.

Old Hwy 55 after years of washouts and landslides.

Old Hwy 55 after years of washouts and landslides.

Seems there isn’t much in the way of “institutional memory” when it comes to Boise foothills road and home construction. The “Boise Front” is essentially the same piece of land as HSB Hill and Warm Springs Mesa, yet Boise City officials seemed surprised that high-end real estate along Table Rock Road is now slip-sliding a way.

For perspective, think of the foot hills as a giant sponge and all the roads and rooftops as strips of plastic wrap. The sealed parts of the sponge repel the water, but soon there is more water than the sponge can absorb and it either pools or runs off like a flash flood.
It may be nice to look down on your neighbors, but those big roofs, paved driveways and roads all tend to concentrate water and saturate the subsoils. The local precip is about 13 inches annually, but all those green lawns and trees at luxury homes need much more water to survive. We know instances of hillside irrigation flooding downhill neighbor’s basements. The laws of gravity are enforced by Mother Nature.

New home construction in Boise, Idaho.

New home construction in Boise, Idaho.

A Boise City spokesman recently told the STATESMAN that policy “requires a licensed engineer to conduct surveys of geological characteristics for the ground beneath every Foothills development. The city requires the same geotechnical surveys for each lot in a development. 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. The same step is required for each lot.”

A home previously worth hundreds of thousands of dollars and a roadway are now unusable, “baffling the experts.” Could it be the geologists have rocks in their heads and the hydrologists have water on the brain?

Comments & Discussion

Comments are closed for this post.

  1. Greedy City Leadership
    May 8, 2016, 10:30 pm

    The city leaders are greedy for new tax money. Like a junky looking from drug money.

    I bet there’s some over paid person on the payroll or contract that should have prevented this engineering error. Or maybe the city leaders didn’t listen?

  2. “Whoah God only knows, God makes his plan
    The information’s unavailable to the mortal man
    We’re workin’ our jobs, collect our pay
    Believe we’re gliding down the highway, when in fact we’re slip sliding away”
    … Simon and Garfunkel

    Guardian, if you haven’t see it with your camera it is worth a trip from your Bench nest. It’s not just “one home worth hundreds of thousands”– several homes(million dollars+) are in or partly in the affected area…

    The current online streetview of Strata Via is from 2007– the time of all the dirt moving to make the flat area for those houses- it looks up onto the newly formed (2007) Alto Via road. Anyone who has made sandcastles can look at the slope of that new dirt and can understand what is going to happen eventually.
    Im no geologist but Figure 4 on this page looks an awful lot like Alta Via Crt:

    Makes me think of another song, by the Talking Heads – “Burning Down the House”.

  3. To quote Journee from a couple weeks ago (your mayor’s paid spokesperson): “We honestly don’t know what’s going on,” said Journee. “It could likely be a mother nature kind of a situation. We’re still trying to figure that out.” Top-flight analysis from the pols.

  4. No worries. When rich folks make bad decisions they get “bailed out”, unlike poor people’s bad decisions where they go bankrupt and end up in prison.

  5. Rod in SE Boise
    May 9, 2016, 10:40 am

    Guardian, the problem is not the Geologists having rocks in their heads or Hydrologists with water on the brain. The problem is nobody listens to them when they tell it like it is.

    New Orleans – it is below sea level. why are people allowed to live there?

    Cape Hatteras, NC – hurricanes

    Florida – sea level rise will put much of it under water

  6. Sandra Brown
    May 9, 2016, 12:05 pm

    In a cosmic long shot, torrential rains along with a massive earthquake could send the foothills mansions all sliding into the North End, then Anderson Ranch dam would collapse taking Lucky Peak dam (both are fragile earthen dams) out too, flushing the mansion debris and all the “smart growth” and “vibrant downtown” out to sea.

  7. Foothills in Boise are too unstable to build on..
    Northend has a major risk of floods…
    Development on the west end of the valley is eating up farm land…..
    Traffic down town is unbearable….
    If the dams break all is lost for every one…

    You should move to Idaho City where you will be welcomed and safe….. but our mayor resigned… prosecutor lost her job over a DUI in Boise… Sheriff just quit…. and folks are trying to get the county clerk recalled….. and the postal clerk was stealing mail…

    But you are all welcome!

    EDITOR NOTE–Sounds to me that our politicos are smarter than yours. Ours don’t get caught. Most of the time.

  8. Yossarian_22
    May 11, 2016, 11:05 am

    You only have to look at California development to see how these grand plans can crumble and fall. The hydrologist and geologist are the last people to be listened to. Unfortunately, the taxpayer enters the picture, once again. Do impact fees offset these disasters? I doubt it.

  9. “It could likely be a mother nature kind of a situation”. Boise spokesmouth

    Ya think???

    This comment should get one of your dope awards. Gravity is a b*tch.

  10. TS Samualson
    May 12, 2016, 7:03 pm

    On a KTVB story I just read…
    “We had no indication at the time that there was a landslide risk in the area, obviously if we had known that if any of those reports had come back indicating that, then it would’ve been a different story,” said Journee.
    Crazy… From what the geologists say, most, if not all, of the foothills is a landslide risk.

  11. No one is reporting on the rocky drainage swale on Table Rock Road directly above Alto Via. The question is when did ACHD put those rocks in the ditch presumably in order to slow down storm water which was deepening the ditch. Was it before or after the geo-soils tests for the development below?

    I’m not a geo-soils tech, but that rocky swale is slowing down water which is then obviously percolating into the hill. It may be a factor, or not. I saw someone shooting video of it though, but not the news media.

    TS Samuelson: Who? Which geologist said the foothills are a landslide risk? Once every 10,000 years is not much of a risk. There is greater risk of a Boise River flood filling the valley from bench to foothills. Should all new development in that vast area be banned?

    My sources in Boulder Heights tell me they jumped through all the hoops and geo-soils engineers signed off. Do you understand that engineers simply do not sign off on stuff unless they can back it up? If there’s a failure then they get sued. For big money. It’s not unlike medical malpractice.

    Yossarian with the obligatory Californian snark. I can tell you’ve never built so much as a doghouse in CA. I’m willing to bet most if not all developments in LA, Orange and SD counties are required to have geo-soils inspection reports. Ditto that for the Bay Area counties too.

  12. TS Samualson
    May 13, 2016, 3:36 pm

    Boisecynic – KTVB, May 5th
    …Geologist Coyote Short says it’s clear this land will eventually give way.
    Short says geologists can look at this land and easily see that it’s different from the stable sandstone of Table Rock, and instead is made up if unconsolidated material prone to a landslide if enough rain falls.
    “If the ground is already wet beyond saturation it’s waiting to let go, just a little more would unlock the door,” said Short…
    …But Short says the answers as to why the pavement and ground is moving is obvious and so is the outcome.
    “They shouldn’t be building on it they know better. Come on it’s obvious anybody who can read the landscape can see the whole thing is in motion,” he said…

  13. TS:

    Ha, you’re quoting KTVB. Their only interest is selling ads to advertisers. And no, no it is not all that obvious. I think you have 20/20 hindsight goggles on. If it was so obvious, show me where you wrote about this as a disaster in the making. Or where anyone wrote about it.

    Why has KTVB not done the research on the rocks in the ditch on Table Rock Road? When were those placed? Why does curb, gutter, sidewalk and storm drain end just a few hundred yards before the slide problem area? Hey, I’m not defending the developer or those people who built on steep cut and fill banks, but… All I want to know is what did ACHD know and when did they know it about Table Rock Road above?

    Actually, we can go even further. Table Rock and Table Rock Road need to be finished off into an urban park and parkway. For Pete’s sake, people are still 4-wheeling and ripping to shreds the hillside up there. And the city is all worried about 1 little airstrip? When are they going to crack down on the off roaders?

    In fact, I bet some of the fast moving water which was mitigated by the rocks in the ditch, I bet that was caused by run off from the illegal off roading.

  14. Greedy City Leadership
    May 14, 2016, 7:11 pm

    Builders and developers in Idaho have never been held to account. They lay the golden eggs.

    200 square miles of cheap trashy 15 year homes have popped up around here since 1990. Mostly the same builders/developers changing up the front companies every few years. This too shall be swept under the rug. And the local media will assist.

    FORWARD! to the next irresponsible projects of public indebtedness and tax revenue increases!

Get the Guardian by email

Enter your email address: