Idaho Transportation Department officials are closely watching a cliff face that has been shifting and spilling rocks and boulders onto a stretch of U.S. Highway 95, 6 miles south of Riggins.
Jessica Williams, a spokeswoman for the department, said Tuesday there appeared to be little movement of the rock in the previous 24 hours at the site near milepost 188. Before that, however, survey points at the top of the rock cliff continued to separate, indicating the slide, that originally happened July 3, had not yet stabilized.
“We had survey points up on the slope that we were monitoring,” Williams said. “They were blocks of rock we were monitoring to determine any movement that we needed to be concerned about.”
Last week, rock scalers and engineers noticed significant changes in the rock, prompting the department to pull workers away from the bottom of the cliff where they were trying to remove rockfall and build a temporary bypass around the slide.
While some of the first rock that fell July 3 was large, some of the boulders that crashed down late last week were as much as 40 feet in diameter, Williams said.
“We pulled people off the temporary road at the bottom of the slide, and that was a valid call. Because overnight those boulders came down, and when they crashed down it invalidated our survey points,” she said. “We had to start over and had to get new survey points, because the slope has changed.”
Rock scalers continue to work at the top of the cliff, knocking down loose rock and setting new survey points to see if the slope is still moving and whether it is safe to bring crews back in to remove the rock. Various methods, including controlled blasting, will be required to break the boulders into pieces and remove them with heavy equipment.
The report for Tuesday, Williams said, was encouraging.
“It was reported that, so far today, the survey points movement has remained quiet since yesterday,” she said. “Every day it changes a little bit. The limitation is time. We need time to ensure that there’s no movement and to ensure that it’s safe and stable to bring crews in. But we don’t know if it’s safe, because we haven’t monitored the area long enough.”
Traffic, meanwhile, has been diverted onto the Old Pollock Road that parallels the highway on the other side of the Little Salmon River. Williams said beginning today, one-lane traffic will be allowed to pass on the road from 5 a.m. to 8 p.m.
“We just want to make sure we do our part to maintain the integrity of the route so we can keep it as a viable option while we continue to work on removing the rock” from the highway, she said.
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