The massive rockslide on Highway 55 near Smith’s Ferry that resulted in a two-week closure was caused in part by construction.
In a news release, the Idaho Department of Transportation says that the slide occurred in a work zone where crews were cutting into the hillside to create extra room for the highway and improve safety. Water from melting snow seeped into a cut, destabilized the hillside, and ultimately caused the slide. ITD says this was a localized event and the greater hillside remains stable.
ITD initially said there was “no indication the work there directly triggered the slide.”
To prevent future rockslides, the department has hired geotechnical experts to enhance the reinforcement of the hillside as cuts are created.
“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 rockfall 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.”
Currently, Highway 55 is open to a single lane of alternating traffic near Smith’s Ferry. There is an additional closure Monday through Thursday from 10 a.m. to 2 p.m. as crews remove debris and continue blasting.