Mudslide closes Highway 530 near Oso through Monday morning

UPDATE 2:30 p.m.: Highway 530 will stay closed east of Oso at least until Monday morning due to safety concerns about a slow-moving mudslide on a hillside above the roadway, state officials said.

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UPDATE 10:30 a.m.: Highway 530 remained closed at Oso Loop Road, about one and a half miles east of Oso, as a precaution.

The slide occurred on a Department of Natural Resources road that runs through private property, said Kris Olsen, a spokeswoman with the state Department of Transportation. The slide is above the south side of the highway, about 1.5 miles west from where the 2014 disaster.

State geologists observed cracks in the road when they visited early Friday afternoon, Olsen said. Several hours later, they returned and saw that the land had shifted about 2 feet.

“It is actively moving up there,” Olsen said.

People voluntarily left 10 homes. Occupants of another home decided to stay put.

More than a dozen experts from the state and Snohomish County were at the slide site on Saturday morning to evaluate safety risks.

No updates were expected before noon.

Officials at the Oso fire station included Snohomish County Executive Dave Somers and Councilman Nate Nehring.

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UPDATE: Highway 530 remained closed near Oso on Saturday morning as engineers assess risks from a mudslide discovered a day earlier.

Washington state Department of Transportation had no estimate for when the roadway would reopen, spokeswoman Nicole Daniels said shortly after 8 a.m. State geotechnical engineers were on the scene.

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OSO — Highway 530 was closed near Oso on Friday night as a precaution because of a mudslide. No property damage or injuries were reported. Voluntary evacuations of about 10 properties were ongoing as of 10 p.m., mostly along Whitman Road.

At least one home was threatened, officials said.

The unstable hillside is on private land above the highway. The ground was moving, but slowly, according to the Snohomish County Sheriff’s Office.

“This is all a precaution,” sheriff’s spokeswoman Shari Ireton said.

The location is southwest of the 2014 disaster site, near Skaglund Hill, according to the state Department of Transportation. It also is south of the highway. A state geologist was there earlier Friday after reports of cracks along a back-country road.

Area affected by voluntary evacuation off of SR530. No injuries, no property damage. Evacuation and road closure a precaution. pic.twitter.com/Q6SoU39s9H

— Snohomish Sheriff (@SnoCoSheriff) April 8, 2017

The road closure started around 8 p.m. at Milepost 36, which is between the Oso fire station and the 2014 disaster site. The closure was expected to last until daylight Saturday, when crews can get a better view.

Heavy rain has saturated the ground in parts of Western Washington, and there have been repeated warnings of potential slides in the region. Those generally are different than the deep-seated geological shift in 2014 that took 43 lives and blocked the North Fork Stillaguamish River.

The slide that prompted the highway closure Friday appeared to be in the same area as large cracks that have developed along a U.S. Forest Service road near Oso, prompting a closer look by county officials for potential mudslide risks.

A county employee on Friday documented what appeared to be an ongoing mudslide on the south side of Highway 530, near Milepost 35. That area is west of Skaglund Hill, where the state has performed millions of dollars in work to reinforce steep slopes.

A county engineer said the tension cracks deserve further examination by specialists, though Lidar surface-mapping data did not show an obvious history of landslides in the area. Local, state and federal officials were alerted to the situation. The rain and the area’s soil characteristics add to the concern.