Frozen landslide threatens to devour Dalton Highway

khopkins@adn.comDecember 1, 2012 

A mysterious blob of frozen soil, rocks and trees is creeping toward the Dalton Highway, threatening to block the haul road that serves as a lifeline for Alaska's oil and gas industry. It could happen as soon as end of the decade.

University of Alaska Fairbanks researchers who have been studying the slow-moving landslide just south of the Brooks Range since 2008 say it is crawling closer to the highway every day. The scientists suspect climate change may have caused the 300-foot-wide finger of debris -- once thought to be motionless -- to gain speed as it slides toward the road.

"It's this giant moving mass and it's going to destroy anything in its way," said Rob Harper, a spokesman for the Alaska University Transportation Center.

The wave of frozen mud, snow and plants slowly spilled from the mountains within the past 5,000 years, researchers said. It is now within about 150 feet of the highway. Moving at a average rate of more than a centimeter a day, it could swamp the Dalton within five to 10 years, said Institute of Northern Engineering hydrologist Ronald Daanen.

"The sooner we come up with a viable solution, the better it is. There isn't a lot of time left," said Daanen, who will present information about the hazard at a worldwide meeting on geophysical sciences next week in San Francisco.

Transportation planners across the country are grappling with extreme weather such as floods, storms and unusual snowfall due to changing weather patterns. In the Alaska Arctic, the frozen debris encroaching on the Dalton Highway presents a new kind of puzzle.

As permafrost shrinks and summers grow longer in the southcentral Brooks Range, researchers wonder: How do you stop an accelerating, landslide-like ocean of mud and splintered trees from destroying one of the state economy's most important roadways?

The blob in question is at Mile 219 of the Dalton Highway, about 40 miles north of Coldfoot as the highway enters the Brooks Range. It is massive. More than 60 feet tall and as long as 10 football fields.

When it reaches the road, it will dump 22,000 tons of soil and rocks on the highway every year, the researchers wrote in a study proposal made earlier this year to the Department of Transportation.

That's akin to piling about 440 dump trucks full of frozen, earthy slop on the only road that connects North Slope oil and gas fields to the rest of Alaska. Another 700 feet beyond the roadway, also in the path of the debris field, is the buried trans-Alaska oil pipeline.

MYSTERY CLUMP

A now-retired U.S. Geological Survey geologist, Thomas Hamilton, mapped the debris fields in the late 1970s or early '80s, according to the university researchers. Hamilton called the mounds "flow slides" at the time, but did not study them in depth.

In 2006, Daanen was working at the university's Geophysical Institute Permafrost Lab when he made a trip with his wife up the Dalton Highway. He noticed what geologists call "drunken trees" in the southern Brooks Range.

The spruce trees, jutting at odd angles, were a clue that the ground might be moving as permafrost thawed below. Daanen drove slower. He saw the lopsided trees were collected together in clumps.

"It struck me that these are all on some sort of a land form that I hadn't seen before," he said.

Visiting scientists have assumed the formations were rock glaciers, collections of rock debris frozen in ice that can form as glaciers recede or under other conditions.

Daanen and geological engineer Margaret Darrow, who is leading the university research, writes that they appear to be something else entirely.

With the help of Hamilton, the researchers gave the blobs a name: "Frozen debris lobes." They described the little-understood phenomenon in an article published earlier this year in the journal of Natural Hazards and Earth System Sciences.

"Our results indicate that frozen debris-lobes have responded to climate change by becoming increasingly active during the last decades, resulting in rapid downslope movements," the researchers wrote.

The debris lobe menacing the Dalton absorbs trees and vegetation as it marches forward, Darrow said. Standing along the highway, a five- or six-hour drive from Fairbanks, the heap assumes a monster-movie quality. All that's missing is the ominous music.

"You stand there, you look up at this huge hill and it's looming over you. And you know it's coming," she said.

What makes the formation unique from traditional landslides is that parts of it are frozen and parts of it are thawed as it moves downhill, Darrow said.

Based on historical aerial photos, the formation appears to have seeped from a hollow in the mountain slopes toward the highway. Set in motion by gravity, it's been moving for at least 10 years but wasn't close enough to the road to draw any great concern from the Transportation Department, said Billy Connor, a former DOT research manager and head of the university's Alaska University Transportation Center.

"It's like a big mud flow that's slowly moving down the hill toward the roadway. And it appears at this point in time it's the result of permafrost thawing up on the hillside," Connor said.

EXPENSIVE SOLUTIONS

Over the summer, the Transportation Department drilled holes in the "frozen debris lobe" closest to the highway to perform preliminary research. Daanen, Darrow and other university researchers plan to report their latest findings to the state by the end of the year.

After that, the department will begin considering options for saving the highway from the creeping debris, said Jeff Currey, a materials engineer for the Department's northern region.

Whatever the answer, it won't be cheap.

"Any solutions will probably cost millions of dollars and certainly some of them would cost tens of millions," Currey said.

Building a bridge over the lobe might work, though it would have to be almost 100 feet high and is among the most expensive options. It also wouldn't stop the debris from creeping onward toward the trans-Alaska oil pipeline buried west of the highway.

Currey estimates that the debris could take another 20 years or more to reach the pipeline after it arrives at the road, making the highway the more immediate concern.

Engineers could try freezing the debris back in place by super cooling the ground or building a barrier to hold it back. Simply hauling the mud, rocks and trees away might not work.

Digging away the face of the lobe might cause it to move even more quickly toward the highway -- a problem common to efforts to combat landslides, Darrow said.

"If you take out the toe, you remove the part that's holding it back and it just makes it go even faster," she said.

The scientists said they are just beginning to learn how the debris lobe was formed and why it's moving, questions they must answer before planners decide how to stop the blob from overtaking the highway.

"We are just scratching the surface. ... We're looking at data. But in terms of really understanding what is going on? No. We are not there yet," Daanen said.

At stake is a roadway that transportation planners sometimes jokingly call "the road to the bank."

The Dalton was built in 1974 as construction began on the oil pipeline. It remains partially unpaved today, a 414-mile lifeline that begins north of Fairbanks at the Elliott Highway, climbs through the Brooks Range and ends at Deadhorse near Prudhoe Bay.

Most Alaskans will never drive the highway. Daily traffic on the road averaged just 200 vehicles in 2011, and two-thirds of those were heavy trucks, according to the Transportation Department. But the road is a vital supply link to industry, funneling truckloads of pipe for drilling wells, fuel and even small buildings to the North Slope oil fields that fund state government.

The debris field at Mile 219 of the highway is the closest to the road, but Daanen has identified more than 150 such formations across the southern Brooks Range. A few of those also may threaten the highway in the future, researchers said.

"In the short run, the first thing we want to do is understand what the mechanism of movement is and try to come up with some idea for dealing with it," said Currey, the DOT materials engineer.

"We realized we better figure out what's going on here and get with it," he said.


Read The Village, the ADN's blog about rural Alaska, at adn.com/thevillage. Twitter updates: twitter.com/adn_kylehopkins. Call Kyle Hopkins at 257-4334.

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