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SOMBA K'E/YELLOWKNIFE
GNWT road builders are hoping a test construction project 40 km west of Yellowknife will answer an age old question once and for all: how does one build a road over permafrost that lasts?

Rick Menard holds a piece of cellular concrete ­ a material that Department of Transportation officials hope will provide structural support to problem areas of the highway and insulate permafrost, slowing melting ­ at a construction site around kilometre 300 on Highway 3 on Sept. 6." - Laura Busch/NNSL photo

Work crews are currently working on four test sections of road around kilometre 300 on Highway 3 using four different methods of construction.

"The hope is that we will come up with a system that absolutely protects the permafrost as much as possible," said Kevin McLeod, director of highways and marine services for the Department of Transportation.

The area of Highway 3 that poses the most problems is the stretch between Yellowknife and Behchoko, said Rick Menard, senior project officer with the department's design and construction section.

This section of highway is a notoriously bumpy ride. Last week, Yellowknifer Robin Imbeault rolled his Jeep halfway between Behchoko and Yellowknife due to a bumpy stretch of road.

"It's happened my whole life," said Blair Weatherby, president of the NWT Trucking Association who has been involved in the Yellowknife trucking business for most of his life. "The problems are constant, they're never going to fix it but hopefully they make it better."

Weatherby said that, aside from the bumps and holes in the highway, he deals with premature wear and tear on his vehicles because of the state of the highway.

"It's great," he said about the current construction project. "They need to do that ­ they need to figure out a possible way to make it better."

This section of road often heaves and sinks as permafrost under the road melts and covering permafrost with a highway only hastens the melting process, said Menard.

"The key thing is not to allow heat into the permafrost," he said.

Within this problem section of road, the most difficult areas to engineer and maintain are the areas where the road transitions from bedrock to softer material, said Jan Sterling, an engineers representative for BGC Engineering, the firm working on the project. Also, areas where water must drain below the road pose a particular set of problems, she said.

When Yellowknifer visited the work site, the crew was working on a section that involved using cellular concrete ­ a special mix of concrete that somewhat resembles the inner layer of an Aero bar ­ as a means to insulate the permafrost and prevent the melt that occurs under the highway.

"This will provide some structural support as well as thermal benefits ­ it will provide some insulation," said Sterling.

Beside the 40-metre section of cellular concrete, crews are installing geo-grid ­ a synthetic mesh material that will provide the road with structural support but no thermal benefits. Equipment is being installed under each of the test areas to monitor underground temperatures during the one-year testing period.

Besides this two methods, the project will test two new drainage techniques. Typical round culverts tend to trap water, which can thaw the ground below faster than it would otherwise and cause other problems, said Sterling.

One of these tests involves corse rock installed under the highway with a small arch culvert to drain water and the other involves a large arch culvert, she said.

An arch culvert is similar to the top half of a standard culvert with the bottom portion open to the ground below, said Menard. This should stop water from sitting in the area and allow it to drain naturally, further preserving the permafrost.

Construction on the four test sections began in early August and are scheduled to be completed by late October. They will then be monitored for one year to determine which methods work best in certain situations.

"We're trying to develop tools for specific problems," said Menard. "...(However), everything is a matter of budget, and we have a lot of roads."

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