Zimovia Highway landslide repairs will exceed $1.2 million

The cost of clearing landslide debris, digging up the roadbed to install three large culverts to carry runoff from the mountainside, building up a new base and shoulders, and then paving the rebuilt section of Zimovia Highway with concrete will exceed $1.2 million.

It could be another couple weeks before the work is finished and the highway restored to two-lane traffic, said a state official.

Fortunately, the Alaska Department of Transportation had enough sections of 36-inch-diameter culvert on hand in Wrangell for the job, avoiding the need to ship the large pieces into town, Chris Goins, the department's regional director for Southeast, said on Dec. 13.

In addition, the U.S. Forest Service had some unused 72-inch corrugated metal culvert sections available in Wrangell, which the agency contributed to the effort, Goins said.

The culvert sections will be banded together to stretch at least 60 feet in length to carry runoff water from the mountainside safely under the roadbed and into Zimovia Strait, he said.

In all, two 36-inch culverts and the 72-inch passageway will replace a single 24-inch culvert under the highway in the area of the Nov. 20 landslide at 11-Mile, Goins said. The slide crushed the 24-inch culvert.

The additional capacity is needed to handle all the water coming down from the mountainside that was stripped of trees and much of its ground cover. "The slide (area) now is more like a parking lot," Goins said, with water flowing freely downhill instead of being absorbed by the ground cover.

"It's very muddy," he said of the runoff, which carries with it a lot of material as it further erodes the hillside. The 36-inch culverts will need to be cleaned to keep the passageway clear, but the larger pipe under the highway, with its stronger flows and steeper angle toward Zimovia Strait, "is self-cleaning," Goins said.

After installation of the large culvert is completed, expected by early this week, work will begin preparing the new roadbed for concrete.

Though the highway is asphalt, there is no asphalt plant in town for the repair job. Besides, asphalt paving requires warmer temperatures than concrete, the DOT official explained. Concrete can cure at temperatures above 32 degrees, he said.

As of Monday, the weather forecast through Dec. 27 showed temperatures ranging between 32 and 42 degrees.

The cold-weather-cure concrete was barged into town for the job. The new pavement will be at least four inches thick, Goins said.

After digging out and preparing the roadbed, workers will build the wooden forms and pour the concrete for half the width of the highway, giving it three days to cure, Goins said, then switch to paving the other lane.

Wrangell-based Brett Woodbury's BW Enterprises has been doing the clearing, excavating, hauling and rebuilding work. "They're one of the best contractors we've ever seen," the state official said. The company also will take on the paving work.

Until the road is repaved, the state and borough are limiting traffic through the area to one lane at specified periods each day.

Goins estimated the entire job - from clearing to paving - will cost more than $1.2 million.

That estimate does not include the borough's costs of clearing the slide area outside of the highway right of way.

The state disaster relief fund will cover individual assistance grants to property owners who incurred expenses directly related to the landslide, in addition to the borough's expenses for Search and Rescue, cleanup, police and utility crews.

If the total cost exceeds a federal threshold, the state can request a federal disaster declaration, which could bring in money from the U.S. Treasury to relieve the state from paying 100% of the costs.

In addition to state and borough personnel in town, the Department of Transportation flew in a geotechnical engineer, landslide specialist, drone operator and other experts to help with the Wrangell operation, Goins said.

The department also brought in its own Starlink satellite hookup to provide internet and cell service for workers, DOT spokesman Sam Dapcevich said. The Starlink hookup allowed Goins and other state officials to watch live feeds from the drone and on-the-ground crews.

The department has installed a docking station near 11-Mile so that a remotely operated drone can take video to monitor the area. "We plan to have that one for months, if not years," Goins said.

The deadly landslide covered a width of about 450 feet as it spilled across the highway, taking out at least 200 feet of asphalt on the upland side of the road, Goins said. The trees and debris flow "heavily hammered the road."

In addition to digging up and removing the muddy slurry that covered the road and shoulders, workers had to dig down to reach a stable base before filling in with rock to prepare a new surface for paving.

The contractor also dug out a sediment basin on the upland side of the road to retain runoff water and mud so that the flow does not wash out the highway, Goins explained.