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Building the Dempster Highway: an engineering challenge

When Yukon Highway No. 5 was built, it penetrated some of the most challenging and enigmatic wilderness in Canada.

When Yukon Highway No. 5 was built, it penetrated some of the most challenging and enigmatic wilderness in Canada. It was the homeland of the Vuntut Gwitchin, the Tr’ondek Hwech’in, and the Nacho Nyak Dun, known only to the families that hunted, trapped and travelled over the land.

The European history for the region consisted of a few noteworthy events. These included the arrival of the Hudson’s Bay Company, the tragedy of the Mounted Police patrol which perished in 1911 and Corporal W.J.D. Dempster, who found their sad remains, and the hunt for the mad trapper of Rat River, which ended on the frozen Eagle River in February of 1932.

Oil exploration commenced on the Eagle Plain around 1954, but the Liberal government of the day refused to consider building a road to this region. The Conservative government of John Diefenbaker was elected in 1957 on an election platform including the “Roads to Resources” program, which was intended to reach and exploit Canada’s vast northern resources.

Under the direction of Alvin Hamilton, the minister of Northern Affairs and National Resources, the Dempster Highway became the centrepiece of this program. With the oil industry proposing to invest $150 million to $250 million in oil exploration, Hamilton stated that $5 million to $8 million would complete the road construction in four or five years. The discovery of oil on the Eagle Plain was announced August 17, 1959.

At first, it was known as the “Flat Creek Road,” the “Flat Creek to Chapman Lake Road,” or the “Flat Creek to Aklavik Road.” Its ultimate destination became the yet-to-be-built community of Inuvik, a former oil well drill site known as Aklavik E-3.

Initial proposals considered three possible routes for the highway, one starting near Elsa and Keno City, the other two originating near Dawson City. Engineers settled upon a route near Dawson that followed the path of Cat trains - Caterpillar tractors pulling strings of sleds - that were hauling equipment and supplies to the drilling rigs on the Eagle Plain.

This route crossed the Klondike River near Flat Creek, proceeded up the north Klondike River valley and followed the Blackstone River as far as Chapman Lake, a distance of 125 kilometres. Survey work progressed through 1958, and construction of the first 48 kilometres began in 1959.

Boyde White, who worked on the construction during the first two years, said the road initially followed the Cat train trails, which ran close to the Klondike River, but after numerous washouts, the road was relocated to higher ground. The first section of the road was built to a lower standard and later required extensive upgrading.

Replacement of Alvin Hamilton by a less enthusiastic Walter Dinsdale as minister, as well as the poor production results of the wells drilled, led to construction being put on hold in 1962. The road was maintained seasonally for the next few years. The only event of note occurred in August 1964, when then minister Arthur Laing, in response to petitions by the Vancouver Yukoners Association and the Yukon Order of Pioneers, directed that the road be henceforth known as the Dempster Highway.

Interest in the highway was rekindled with the announcement of an oil discovery at Prudhoe Bay, Alaska, and the prospect of a pipeline over the Dempster route. From 1970, construction contracts were awarded annually. In 1971, the Department of National Defence built a bridge over the Ogilvie River for $504,000. A second, more challenging bridge spanning the Eagle River was built between July 1976 and July 1977.

Meanwhile, road construction proceeded from both ends until they met between the Eagle River and the Richardson Mountains. The final cost of the 735 kilometre-long highway: an estimated $132 million. An interim ferry was placed on the Peel River in 1979, and on Discovery Day that year, dignitaries including Northern Affairs Minister Jake Epp and member of Parliament Erik Nielsen attended an official ribbon-cutting ceremony near the Klondike River bridge, at the southern end of the highway.

Sadly, John Diefenbaker, the man who conceived of the “Roads to Resources” program in the first place, died two days before the ceremony.

The construction of the highway posed many challenges. It was the most northerly major highway project of its time. It ran through virtually uncharted wilderness and the engineers building the road had little precedent to work with - the only previous construction over similar permafrost terrain was the Alaska Highway. The route was remote, making logistics challenging and construction costly.

The seasonal extremes of weather (that regularly plummeted below the limits of the mercury thermometer in the winter) and daylight (weeks of total darkness in December and January) had to be dealt with. In December 1979, a highway crew became trapped in the Richardson Mountains during a spectacular blizzard and nearly perished before being rescued.

The route had to be selected where rock and gravel were easily reached. Heavy rainfall would cause washouts, which had to be repaired before further work could be done. Sections were moved or grades improved to avoid disastrous repetitions.

Permafrost was a unique challenge during construction of the Dempster Highway. The moisture-laden subsoil, which is rock-hard when frozen, turns to mush when disturbed. Experiments were run to test various methods of insulation to prevent dangerous heat transfers and melting. These were costly and therefore impractical.

Experience determined that a gravel road bed at least 1.4 metres thick, laid on top of the ground without disturbing the subsurface, was sufficient to stabilize the road. Being frozen, the ground is also impermeable. Engineers had to address the resulting problems of water accumulation and drainage.

The Eagle River Bridge was a case study in design for remote permafrost conditions. It was a joint exercise involving engineers from the Department of Public Works, who designed it, the Department of Indian and Northern Affairs, who paid for the materials, and the Canadian army, who built it as part of a 1976-77 training program.

The steel superstructure of the bridge was assembled where it was fabricated in Hamilton, Ontario, to familiarize the engineers with its assembly, and to ensure that every part was accounted for and fit properly. Any problems in these areas would lead to lengthy delays once it was delivered to the site.

Work had to be scheduled around weather conditions. The piles supporting the bridge had to be driven into frozen ground, and then insulated to ensure that the permafrost would not be disrupted.

Because of the sub-zero temperatures at the time that the concrete was poured, the steel components and the surrounding air temperature were kept above freezing to allow the concrete to cure properly. Special polyethylene tents were built over the concrete pile caps and monitored around the clock to ensure that the temperature never dropped during the several days required for curing of the concrete.

Not much thought is given to the challenges that were overcome to construct the Dempster Highway. Every year thousands of travellers drive one of the most spectacular highways in the world without giving a second thought to the road - unless, of course, they have a flat tire.

This article was provided by the Association of Professional Engineers of Yukon.