Frost heaves and roadways: expensive fixes versus dealing with the bumps

Published: Nov. 4, 2019 at 5:15 PM AKST
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A little more than two hours north of Anchorage on the Glenn Highway, you'll find spectacular views. But it's a one-mile stretch of road around mile post 116 that a viewer asked us to look into.

On either side of the corridor in question, fluorescent orange road signs signal "rough road."

"Sometimes it'll be a hump. Sometimes it'll be a dip, and that can happen at different times throughout and the Spring, and well, all year round," Shannon McCarthy, spokesperson for the Alaska Department of Transportation's central region, explained to KTUU.

We drove the section of road in question. A series of rolling dips and bumps seem okay to manage if you're traveling slowly enough, but a few caught us by surprise, with bigger jolts and bounces than we'd prepared for.

We weren't the only drivers encountering a rollercoaster ride. Semis. Big trucks. Small trucks. SUVs. Cars. Every one of them experiencing a bounce.

McCarthy told KTUU water intrusion causes frost heaves.

"It's seeping into the sub base and of course then freezing and thawing and so that will cause what we call a differential settlement," she said.

Our viewer who wrote in was concerned about traffic safety and preventing crashes. They wondered why a better fix couldn't be achieved.

"This is actually a very stretch safe stretch of highway," McCarthy said.

Transportation records from 2013-2017 show just four crashes in the area. One involved serious injuries and was the result of a high-speed crash, she said. Another was a low-speed crash caused during winter conditions. The remaining two occurred when vehicles struck animals.

"Taking a look at it they actually analyzed it for highway safety improvement highway funds. It did not qualify whatsoever," she said.

Again, back to our viewer's question - why not just permanently fix it and be done with it?

"It is correct that a permanent fix would be to dig it out. Those can be very expensive and we would like to have that be part of a larger project. Any one particular dig out would be about $300,000 to $400,000," McCarthy said.

For now, the plan is to keep using superficial asphalt patches, accompanied by roadside warning signs when the road - and the ride - get bumpy.

"Paying attention to those signs is really critical for driving," McCarthy said.

One tricky aspect of navigating the corridor is that the signs don't tell you how much to drop your speed.

McCarthy said, advisory speeds are posted when DOT determines a section of highway is in need of such notices.

McCarthy's advice? Slow down.

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