A rock slide with boulders as big as refrigerators closed Washington state’s principal commercial east-west highway, and traffic backed up for miles along alternate routes, officials said.
Unlike a slide in September, the one that happened before dawn Sunday on Interstate 90 caused no injuries. The mountainside remained unstable, with additional rock expected to come tumbling down onto the road, transportation officials said.
Temperatures were near freezing and the area southeast of Seattle had about seven inches of snowfall the previous night.
A transportation department spokesman, Michael P. Westbay, said as much rock and other debris could come down as the hundreds of tons that hit the road’s westbound lanes in the Cascade Range on Sept. 11, crushing a Volvo and killing three 28-year-old women on their way home from a concert.
“This area is on the list of at least 2,500 potential rock fall areas that the state has been monitoring,” Westbay said. It was scheduled to be reinforced using a method called rock bolting next spring.
Drivers were advised to avoid the area if possible as workers struggled to clear debris near Snoqualmie Pass. About 28,000 motorists cross the pass on an average weekday.