Bridge plan moves forward as Denali Park Road landslide speeds up

People stand at the edge of a steep drop in a gravel road through a mountain pass
Officials inspect a 40-foot drop on the Denali Park Road at mile 45 where a worsening landslide has prompted a plan to span it with bridge. (National Park Service photo)

A slumping section of the Denali National Park road dropped an unprecedented amount over the winter, underscoring the need for a planned bridge over the unstable stretch of road near Polychrome Pass, according to park officials.

“It was really sobering to arrive on scene and see that 40-foot cliff on that eastern side of the slump this year,” said Denali National Park acting superintendent Brooke Merrell.    

The Pretty Rocks landslide is the result of movement — accelerated by climate change — of what’s known as a rock glacier underlying the road. The landslide prompted park officials to close the 92-mile Denali Park Road at roughly its halfway point last year, and the closure is expected to remain in place through summer 2023.

Earlier this month, Merrell said, crews clearing snow from the road found significant new slumping at the site.

“Its just over twice as far as it slumped the year before, which is consistent,” she said. “We’ve been watching it since about 2016, and each winter it sloughs about twice as far as the year before.”

Park crews have filled the slump with gravel for years to keep the road drivable. But last August, acceleration of the slide forced the closure of the road and serious consideration of a permanent fix. 

The Park Service conducted an environmental review of a proposal to span the slide area with a 400-foot bridge anchored on solid ground on either side. That plan was approved last month.

There’s $25 million in the federal infrastructure law to pay for the first part of the estimated two-year project, which also includes some other Polychrome area road work.

“Our partners at Federal Highways are getting ready to issue a request for proposals for contractors to submit their design build proposals for this bridge,” Merrell said.     

Merrell said the timing should allow initial work to get underway this summer. Additional funds will be needed to build the bridge, but how much depends on the selected contractor’s design. 

Until the bridge is completed, Merrell said park visitor buses will only travel to the East Fork River, at mile 43.

“We’ve been working on making a safe spot for both transit and tour buses to turn around at the site,” she said. 

Merrell said the only visitor access beyond mile 43 will be by plan.

“You can fly to Kantishna,” she said. “Several of our inholder lodges are operating as fly-in operations this year.”

Merrell said the Park Service will not be operating its Wonder Lake campground near the end of the Park Road, but visitors can still apply for backcountry permits. She notes that Denali visitation is forecast to rebound to pre-pandemic levels this summer.

“Indicators are that we’ll likely be as busy as we were in 2019, which was a record-setting year for us,” she said.        

Denali had more than 6 million visitors in 2019.

Dan Bross is a reporter at KUAC in Fairbanks.

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