Landslide south of Anchorage creates ‘unusual’ highway blockage

Rocks, mud and trees slid onto the Seward Highway near Mile 105 on Monday. (Photo courtesy Alaska Department of Transportation and Public Facilities)

A landslide early Monday on the Seward Highway blocked traffic between Anchorage and points south for more than five hours.

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Rocks, mud and trees slid down a mountainside and across both lanes of the highway near Mile 105, which is between Anchorage and Girdwood about a mile from Indian. The debris hit a car, took out a guardrail and reached the nearby railroad tracks, according to the Department of Transportation and Public Facilities.

Department spokesperson Shannon McCarthy visited the site of the slide and later spoke driver of the car that was struck, who said she was uninjured.

“We saw some broken plastic parts,” McCarthy said. “She said that the back window had been smashed out.”

Alaska State Troopers first notified DOT of debris on the roadway a little before 6 a.m. McCarthy said scattered rocks are common on that stretch of highway, so the lone heavy equipment operator sent to deal with the debris was not expecting to find such a large pile.

“It’s at the base of a mountain, and there’s cliffs, and so oftentimes there are rockfalls,” McCarthy said. “It’s very active. It’ll fall right into the roadway.”

McCarthy said the equipment operator quickly realized he was dealing with something much larger than a few rocks and shut down the highway. The pile was about four feet deep and 75 feet wide, McCarthy said.

DOT geologist Craig Boeckman climbed up the slope at first light to see if it was safe to send in crews. Once he gave them the thumbs up, the equipment operators had the highway cleared and reopened a little after 11 a.m.

“This landslide feature was definitely unusual,”¬†Boeckman said.

Boeckman said he’s only seen one other true landslide on the Seward Highway in the last 15 years. That was about 100 miles to the south and more the result of a small avalanche, he said.

As for Monday’s landslide, Boeckman said his guess is that water from two small drainages running down the slope froze and created a fragile dam.

“Perhaps that kind of blocked it off and then we got this warm-up and a lot of rain, kind of built up behind possibly a frozen area. That eventually thawed and it all just came down,” Boeckman said.

McCarthy, the DOT spokesperson, said motorists should keep an eye out for rocks or other debris on the highway, which will be difficult to see in the dark. And she said the DOT is still evaluating the nearby terrain for any further landslide problems.