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US Hwy 95, Bonners Ferry Landslide

Bonners Ferry, Idaho
Improvements to a tortuous, three-mile stretch of US Highway 95 near Bonners Ferry, Idaho included crossing an ancient landslide with a keytrench embankment; however, a massive and rapid earthflow occurred during construction. The 500-foot-wide slide involved an estimated 400,000 cy of material, undermined the highway, and 1,200 feet down slope it buried and scoured a county road and Union Pacific Railroad tracks.

Landslide Technology was retained by Idaho Transportation Department for emergency response to evaluate slide causation and assist with recommendations to remediate the slide area. Subsurface conditions consist of layered clayey silt, silt and sand with natural water contents close to the Liquid Limit. The cause of the flow slide was determined to be a combination of factors including pre-existing marginal stability, high groundwater pressures with local artesian conditions, and liquefaction during keytrench excavation.
​
To proceed with highway construction, remedial measures included a rock shear key across the earthflow. Since the slide debris was sensitive to liquefaction, the remainder of the keytrench was not constructed and the embankment foundation was improved by capping the slide debris with a pervious sand layer and installing wick drains to dissipate excess water pressure. An added benefit of the wick drains included improvement of the liquefaction resistance of the slide debris in the event of an earthquake.
Highway 95, Bonners Ferry, Idaho Landslide
Highway 95, Bonners Ferry, Idaho Landslide

Services Provided:

  • Emergency response assessments
  • Geologic reconnaissance of landslide areas
  • Evaluation of remedial alternatives
  • Buttresses and shear keys
  • Dewatering systems

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  • Home
  • Specialty Services
    • Geotech. Asset Mgmt. >
      • Montana Rock Slope Asset Mgmt. Program (RAMP)
      • Alaska Geotech Asset Mgmt
      • Ohio Landslide Inventory
    • Rope Access
    • 3D Modeling
    • Dam Safety & Slope Stability
    • Const. Sequence Modeling
    • Geotechnical Instrumentation
    • Construction Engineering
    • Expert Witness
  • Landslides
    • Hydropower >
      • Bull Run Flume
      • Swift Powerhouse
      • Frog Lake Dam Slide
    • Transportation >
      • Hwy 101 Johnson Creek
      • Looking Glass Hill Slides
      • SR 87 Arizona Slide
      • Togwotee Pass Road
      • Scoby Hill Landslide
      • Wrangell Airport
      • Snowbasin Access Road
      • Beartooth Debris Flows
      • Three Capes Scenic Loop Landslide
      • Richardson Hwy Slide
      • Bonners Ferry Landslide
      • Light Rail Station
      • Skagway Submarine Slide
    • Natural Resources >
      • West Africa Gas Pipeline
      • Greens Creek Mine Road
    • Private Clients >
      • Wasco County Landfill Landslide
  • Rock Slopes
    • Hydropower >
      • Biscuit Rock Rockslide
      • Skagit River Rockfall
      • JC Boyle Canal Rockfall
      • Prospect Dam Rockfall
      • Iron Gate Dam Rockfall
      • Cougar Dam Rockfall
    • Transportation >
      • I-15 (D3) Rock Slope Mitigation
      • Ketchikan Third Avenue
      • US Hwy 2 Libby Rockfall
      • Banks - Lowman Hwy
      • SR 191 Rock Cut Design
      • Going-to-the-Sun Road
      • SR 12 Rockfall Mitigation
      • Lakeside Rockfall
      • US 2 Badrock Canyon
      • South Tongass Highway
      • Weeksville Rock Bolting
      • US 26 Cove Palisades
  • Key Staff
    • Mike Meyer
    • Gerry Heslin
    • George Machan
    • Charlie Hammond
    • Brent Black
    • Darren Beckstrand
    • Chris Carpenter
    • Ben George
    • Wade Osborne
    • Tom Westover
    • Aine Mines
    • Adam Koslofsky
    • Logan Allender
    • Andy Kost
    • Collin McCormick
    • Anna Casady
    • Noah Kimmes
    • David LaPorte
    • Justin McCarley
    • Aleyna Donaldson
    • Michael Bunn
    • Andy Vessely
    • Larry Pierson
    • Derek Cornforth (Founder)
  • Resources
  • Contact Us