BOISE, Idaho — The Idaho Transportation Department has released more information about a massive rockslide that occurred in a construction zone on Idaho Highway 55 near Smiths Ferry last month.
After assessing the area, ITD has determined it was a localized event, and after additional mitigation, the greater hillside remains stable.
The slide occurred on March 15 within a work zone where crews are cutting into the hillside along the highway to create extra room traffic and enhance the overall safety of the road. Crews are working to reduce the severity of curves, construct wider shoulders, and add guardrail and pullouts along the highway.
Officials say that water from melting snow seeped into the hillside and destabilized it where crews created a cut last fall. To prevent future slides, ITD is reinforcing the hillside as the cuts are made. Geotechnical experts have been hired to assist with this effort.
"Safety is the top priority of the Idaho Transportation Department. We are thankful no one was hurt during the rockslide activity on State Highway 55 last month," said District 3 Administrator Caleb Lakey. "Hillsides and slopes become more unstable when doing work of this nature. We expect rock fall as a part of these projects. We had precautions in place to protect the traveling public in case of any slide activity and are doubling down on those precautions."
Idaho 55 is open to a single lane of alternating one-way traffic. Travelers should plan for a 15-minute delay near the construction zone.
From now until late May, there will be daily closures Monday through Thursday from 10 a.m. – 2 p.m. to allow blasting and debris removal activity.
"I appreciate the public's patience as we responded to this rockslide," said Lakey. "We did not take the reduction of service on this critical corridor lightly. It's a good reminder to drive attentive and be on the lookout for rocks on the roadway during the springtime."
The Smiths Ferry Project is anticipated to continue through fall 2022.