Seattle - A swath of state Route 410 east of Chinook Pass near Naches will probably remain closed all winter, says a spokeswoman for the Washington State Department of Transportation.
A massive landslide buried a quarter-mile section of the roadway Sunday morning, shoving broken chunks of pavement into the Naches River and changing its course.
Engineers and environmental scientists are examining the landslide, said Meagan McFadden with the DOT. The hillside that slumped is continuing to move, she said.
It’s not clear yet whether it will be possible to remove the mountain of debris, or whether the road will have to be rerouted, McFadden added. “It’s going to take us some time to get in there and do the work.”
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Residents are able to leave the area via the Bethel Ridge logging road, McFadden said. It takes about two hours to navigate the rough, one-way road.
Electrical power to the area was shut off shortly after the slide as a precautionary measure.
There was some speculation that operations at a gravel mine might have triggered the slide, but that doesn’t appear to be the case, McFadden said. The pit and several pieces of heavy equipment were completely buried by the slide.
What caused the slide isn’t known. There’s been no discernible rainfall in the area.
The flood danger from the Naches River appears to have subsided, McFadden said.
When the river was blocked by the debris, it rose 30 feet before finding a new route. The river is now flowing over a part of the Nile River Road, which runs along the river’s southern bank. About 25 homes were damaged by the floodwaters, and five were hit by the landslide.
The slide destroyed at least two homes. About 80 people were evacuated. A total of about 1,500 people live in the affected area.
While geologists assess the hill’s stability, hundreds of people in the Nile area likely will remain without power for a few days. Pacific Power officials said they don’t want to restore power until the ground stops shifting.
Authorities advised evacuation for all homes within a four-mile radius of the Nile, including a boarding school for troubled youths, although a handful of residents chose to stay.
Transportation officials began monitoring the area about 2 p.m. Saturday, when early indications of the slide became evident.