3/29/2021
Crews safely remove last of rockslide on SH-55 and will resume previous construction schedule
SMITHS FERRY – Over the weekend, Idaho Transportation Department contractors successfully removed an undercut outcropping of rock that remained from a rockslide near Smiths Ferry on March 15, completing a critical safety intervention to allow a return to normal work.
B-roll video of the blast and preparation is available for download and use by clicking here.
The outcropping presented a considerable safety hazard to the public using Idaho State Highway 55 below. ITD brought in a nationally-recognized team of geotechnical engineers to assess the situation and develop a blasting plan to remove the remaining material. The blast occurred Sunday at 4 p.m. after the road was closed for the day.
“It was a picture-perfect blast,” said ITD Project Manager Alex Deduck. “We needed to remove roughly 1500 tons of material sitting 30-50 feet above the roadway. The narrow landing area made this incredibly difficult, but the team did a great job.”
The blast required several days of preparation. A survey crew scaled across the rock face to determine drilling locations. Then, a blasting plan was drawn up. On Saturday, an excavator and drilling machine were flown above the rock face to drill holes and set charges.
“The use of a helicopter was cheaper and faster for us,” said Deduck. “The terrain here is steep and covered in trees. It would have taken several days to pioneer a path to the slide location.”
The blast area is now under a 48-hour observation period to watch for additional movement. Following that, the blasted material will be removed. The road will remain closed except from 8 a.m. to 3 p.m. every day, when a single lane of alternating traffic will be allowed. ITD encourages motorists to us U.S. 95 as an alternate route.
ITD will provide another update this Wednesday evening.
The landslide occurred within the work zone of an ITD project to improve safety and mobility of ID-55 between Smiths Ferry and the Rainbow Bridge. For more information about that project, visit the project web page at ITDprojects.org/ID55smithsferry.