TROUTDALE, Ore. - A rockslide blocked the Historic Columbia River Highway east of the Stark Street Bridge in Troutdale on Thursday afternoon.
Several boulders fell onto the road just before noon through the safety fencing that was in place.
The Oregon Department of Transportation said the highway will remain closed on Friday while crews and geologists evaluate the slide and begin to clean it up.
On Friday, rock scalers will inspect the wall above the rockslide to make sure no loose rocks remain that could fall and injure crews working to clear the road below. The rock scalers will rappel 100 feet down the rock wall and remove any potentially dangerous debris, ODOT said.
Once they secure the area, crews will begin to haul the rocks away and check for road damage.
"There has been a little bit more debris coming down, which is an indication that this is not a stable situation right here," ODOT spokesman Don Hamilton said Thursday.
A geology class from Portland Community College happened to be in the area at the time. The instructor, Holly Oakes-Miller, said slides of this kind are not all that unusual.
"The Cascades and the Coast Range both have a pretty high failure rate, and it's due to the fact the slopes are steep and the rocks have been chemically weathered from the top because of lots of rain," she said. "And they have been hydrothermally altered beneath, which basically turns them into weaker rocks than they were. And that made them susceptible to failures as well."
There are no reports of injuries.
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