ANCHORAGE — The only road leading to Alaska’s North Slope oil fields is again at risk of severe flooding during the spring thaw, with conditions similar to those that intermittently closed portions of the remote highway for more than two months last year.
State transportation crews are digging trenches near a vulnerable northern stretch of the 414-mile Dalton Highway to protect it from overflow from the Sagavanirktok River, generally referred to as the Sag River. Crews also constructed a 5-foot-tall berm over a 3-mile stretch on the east side of the highway earlier this year, Department of Transportation spokeswoman Meadow Bailey said Wednesday.
A stretch of the highway saw unprecedented flooding last year, prompting the intermittent closures. In response to the flooding, Gov. Bill Walker twice issued disaster declarations.
Dubbed the Haul Road, the mostly gravel Dalton is an often desolate stretch that begins near Fairbanks and leads to Deadhorse, the oil industry town serving Prudhoe Bay. It has been featured on the cable show “Ice Road Truckers.”
The amount and configuration of the ice surrounding the highway are similar to last year’s conditions, and so is the current snowpack, Bailey said. Officials also are watching out for a third factor, spring temperatures, which last year were unusually high in the area, hastening the rate of melting.
Temperatures in the area are expected to be above normal in April and May, according to National Weather Service hydrologist Ed Plumb. But that doesn’t necessarily mean a repeat of last year, he said.
“What really matters is how quickly it warms up,” he said.
It’s not uncommon to deal with some overflow from the river, but not at the magnitude seen last year, according to officials. This year, crews are trying to stay on top of the situation.
“We didn’t understand what was happening last year,” Bailey said. “This year, we understand.”
Last summer, crews raised several miles of roadway as much as 8 feet, launching a three-year Dalton Highway reconstruction project that is projected to cost $114 million.
Transportation officials also are working with University of Alaska Fairbanks researchers determine what’s behind the phenomenon. Among them is UAF Civil engineering professor Horacio Toniolo, who said two main factors were involved in last year’s flooding — a significant ice accumulation and a very fast rate of melting.
Researchers are now trying to determine all the various water sources that could be involved in the flooding at a level not seen before at any other time in the highway’s 40 year history, Toniolo said.
“The river was there before and the roadway was there before, and there was no problem,” he said. “So something happened.”