Highway slides challenge DOT
For years, the Alaska Department of Transportation has struggled with what to do about the expensive and unsafe slide areas at 19 Mile and 23 Mile Haines Highway, designated the number one and number nine slope stability hazards in the entire state, respectively.
When rain or snowmelt saturates the unstable Chilkat Mountain slopes at 19 Mile and 23 Mile, debris comes rushing down the mountainside, occasionally overflowing onto the highway. The debris blocking the highway can be five to 20 feet deep.
According to DOT communication officer Jeremy Woodrow, each major slide involves the displacement of 20,000 to 50,000 cubic yards of debris and costs the department $200,000 to $250,000 to clean up.
Not only are the slides expensive, but they pose a significant hazard to motorists. Between 2004 and 2012, the highway has been closed about 10 times, including a multiple-day closure during 2005’s Thanksgiving season.
This September, Haines resident Macky Cassidy was caught in a mudslide at 19 Mile which began pushing her vehicle toward the Chilkat River. A friend arrived in time to tow her Subaru out of the knee-deep muck.
As part of the Haines Highway Improvements project, DOT is looking at several options for mitigating the slide areas, including installing four to six large box culverts big enough to drive a truck through and elevating the road 15 to 18 feet.
Currently, 19 Mile has two culverts about eight feet in diameter. DOT’s local maintenance operations manager Matt Boron says the culverts are “way undersized” and “plug up immediately” when debris flows down the mountain toward the river.
“There are no mechanical means to clean them out. We literally have to clean them out with wheel barrows and water pressure. It’s not a good scene,” Boron said.
The oversized culverts would allow a large piece of equipment to drive through and quickly clear the debris away.
Where that debris will go is also in question, though.
More than 600,000 cubic yards of cleared material is sitting in a DOT right-of-way south of the slide path. “We’re just making a pile to keep the highway open,” Boron said. “We have absolutely nowhere else to put it.”
“It’s our hope that when the improvements go through, they are going to need fill and hopefully they can use that dirt to realign the highway,” he said.
Greg Patz, DOT’s chief of maintenance and operations for the entire state, said that is likely not an option. Most of the material is frost-susceptible, making it an unlikely candidate for road work, he said.
“We’re limited in that there aren’t any good places to haul it. It isn’t usable material and hauling it would be expensive, even if it were (usable),” Patz said.
One of the options DOT is looking at is allowing the material to keep flowing downhill, through the culverts, and then pushing it into the Chilkat River. Patz said, to his knowledge, this has been disallowed for at least the past 15 years he has been on the job.
“The concern is that the quality of material potentially could impact some of the habitat in the river, particularly for spawning salmon,” he said.
DOT is in communications with the U.S. Fish and Wildlife Service, the Department of Natural Resources, Fish and Game, Native landholders and the U.S. Army Corps of Engineers to see if certain amounts of debris could possibly be put in the river at specific times of the year.
The goal of the mitigation isn’t to reduce costs; savings will likely exist, but won’t be very significant, Woodrow said.
“The main idea is not lowering the cost, it’s that it wouldn’t be as big of a danger to traffic,” Woodrow said.
Boron agreed, but said some money might be saved because workers won’t have to spend entire days clearing out the small, clogged culverts. “The whole point is that cars won’t get trapped in (the slide) and the highway won’t ever be closed,” he said.
Boron acknowledges that even with DOT pouring thousands of dollars into designing and constructing creative ways of getting around both the 19 Mile and 23 Mile slides, the problem will never really be solved.
“No matter what we do, it will have to be maintained. Mother Nature is never going to stop throwing stuff down that mountain,” he said.