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Slow landslide eyed in Washington near 2014 disaster site

Associated Press logo Associated Press 4/11/2017
This April 8, 2017 photo provided by the Washington State Department of Natural Resources shows state geologist Dave Norman, right, and geotechnical engineer Gabe Taylor inspecting the head scarp of a landslide slide on State Route 530 near the town of Oso in northwestern Oregon.The discovery of the slow-moving landslide near the site of a 2014 Washington state mudslide that killed 43 people has prompted transportation officials to close until Thursday, April 13, as a precaution. © Washington State Department of Natural Resources via AP This April 8, 2017 photo provided by the Washington State Department of Natural Resources shows state geologist Dave Norman, right, and geotechnical engineer Gabe Taylor inspecting the head scarp of a landslide slide on State Route 530 near the town of Oso in northwestern Oregon.The discovery of the slow-moving landslide near the site of a 2014 Washington state mudslide that killed 43 people has prompted transportation officials to close until Thursday, April 13, as a precaution.

OSO, Wash. — A slow-moving landslide near the site of a Washington state mudslide that wiped out a neighborhood and killed 43 people in 2014 has prompted officials to close a state highway as a precaution and recommend evacuations for a handful of residents, officials said.

The area of the slide near the tiny community of Oso about an hour's drive north of Seattle was being tracked by geologists Monday for ground movement. Residents of about a dozen homes were recommended by authorities to evacuate.

Landslides are common in rainy Washington state and there have been an unusually high number of them recently following months of wet weather, said Joe Smillie, a spokesman with the Department of Natural Resources.

Heavy recent rains probably contributed to the ground movement, authorities said. It happened in an area with a history of slides going back hundreds if not thousands of year, he said.

The location is about 1.5 miles (2.4 kilometers) away from the site of the March 22, 2014 mudslide that was the deadliest in U.S. history.

About 270 million cubic feet (7.6 million cubic meters) of earth slid down across the Stillaguamish River, spreading out for more than half a mile (one kilometer).

A portion of State Route 530 was buried under as much as 20 feet (6.1 meters) of muck and was closed for over two months. It's the same highway that authorities have shut down through Thursday.

The slope where the current slide is located moved about 4 feet (1.2 meters) last week between Tuesday and Saturday but has not moved since then, said Smillie said.

"If the entire 24-acre (10-hectare) slide were to give way, it could completely cover Highway 530," the agency said in a statement Sunday. "There's still a heightened risk that this slide could still move."

No injuries or damage to private property have been reported, but road damage included cracks of 6 inches (15 centimeters) last Tuesday that grew to 2 feet (60 centimeters) by the weekend.

Authorities do not know whether the logging near it played a role in causing the ground movement.

The 2014 slide happened after several weeks of heavy rains, destroying a neighborhood of nearly 50 single-family homes.

A team of scientists said intense rainfall likely played a major role, but no clear cause was determined. Others factors included groundwater seeping into the slide's mass plus changes in slope and soil weakened by previous landslides.

Oso is in northwestern Washington. Smillie said there have been about 100 landslides in northeastern Washington over the last month as heavy mountain snowpack melted.

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Information from: KOMO-TV, http://www.komotv.com/

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