Montana Department of Transportation

Public Involvement

S-472 Blue Slide Road Repair
Sanders County

Construction Update

Crews are cleaning out debris in the Cougar Creek culvert and the stream above the culvert this week (November 26 - 30).

  • One lane of alternating traffic controlled by flaggers. Expect 15 minute delays.
  • Speed limit is reduced; slow down and use caution.
  • Depending on weather, crews anticipate completing the work Monday through Wednesday.

Next Steps

MDT is finalizing design and construction plans to replace the culvert at Cougar Creek that washed out in the spring 2018. Construction to replace the culvert is anticipated to begin in spring 2019.

Construction includes:

  • Installing a larger culvert.
  • Removing uphill rocks that are falling hazards.
  • Improving roadside drainages.
  • Replacing rail barriers.
  • Repaving the roadway.

What to expect during construction:

  • Construction is anticipated to take 4–6 weeks to complete.
  • Short-term road closures will be necessary to install the new culvert and remove uphill rocks.
  • One lane will remain open during construction.
  • Traffic will be controlled by a stop light or flaggers.
  • Motorists will travel on gravel at reduced speeds.

Project Overview

Blue Slide Road Project image

The Montana Department of Transportation is reconstructing a section of Blue Slide Road nine miles west of Thompson Falls that was severely damaged in April 2018.

Heavy spring snowmelt combined with heavy rain caused Cougar Creek to overflow and wash out the gravel beneath the pavement on Blue Slide Road.

Reconstruction of the roadway is occurring in two phases.

PHASE 1 | Short-term fix to stabilize and open the roadway to traffic.
May — June 2018

  • Work will be conducted during the day between 7 a.m. and 7 p.m.
  • Traffic will be controlled with stop lights and/or flaggers.
  • Some full closures and detours may be necessary.
  • MDT will notify the community in advance of closures and detours.
  • Once open, motorists will drive on gravel surface and speed limit will be reduced.

PHASE 2 | Long-term fix to prevent future damage.
July — Fall 2018

  • Complete full evaluation and identify issues that caused the damage.
  • Conduct environmental evaluation and hydraulic analysis.
  • Finish rock fall mitigation evaluation.
  • Host public open house to share Phase 2 construction plans.
  • Construction complete in Fall 2018.

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