The Last Word On Nothing

This week I received an email from an R&D engineer at Canada’s National Research Council. Hossein Babaei and his team in the Ocean, Coastal and River Engineering division have been doing computational modelling of the ways in which the ice in an ice road deforms under the tyres of slow-moving versus speeding trucks. They then compare that modelled behaviour with what they can see from satellite imagery. He says that radar from 400 km away in orbit can sense those waves under the ice, even though on the ground, it is only perceptible through the ice’s groaning and crackling noises.

Hossein had come across the post below from more than a decade ago–I visited the ice road construction project in 2007–and he wanted to follow up on a claim I had made that the truck that follows a speeding vehicle has more risk of going through the ice than the speeder himself. He wanted to investigate it further, but sadly I don’t still have my notes. If you enjoyed the post, too, and want to know more about how things really work, I highly recommend Hossein’s paper on the subject.

In the wake of the smash hit History Channel series Ice Road Truckers, now in its fifth season, my town has become an unlikely celebrity. The reality of the ice road is quite different from the documentary series’ portrayal, and I thought I might break down the mechanics of the thing, having spent quite a bit of time on it.

A private road jointly run by mining giants Rio Tinto, De Beers and BHP Billiton, the Tibbitt-to-Contwoyto winter road is the longest of its kind, at 568 kilometres (353 miles) up into the Canadian tundra. Eighty-seven percent of the ride is on lake ice, and there are 64 portages between lakes. It’s open for only two months every year, but serves as the main conduit for bringing fuel and supplies up to four diamond mines. A land link offers transport at a fraction of the cost of air freight.

It all starts in July, when helicopters survey the route from the air, checking for changes in terrain and currents, and mapping the area in detail. One year’s winter-road route is never quite the same as the last.

In November and December the helicopters are launched again, flying the route using ground-penetrating radar to measure ice thickness. The builders then send out a light tracked vehicle, which gingerly creeps onto the ice to validate thicknesses.

If it’s touch-and-go, they’ll follow up with amphibious Hagglund vehicles that don’t mind getting wet if the ice fails. There’s an escape hatch in the top and a pair of protruding arms designed to stop any falls through the ice. Their first task is to plow the road of snow, allowing the cold to penetrate into the ice. Plowing is only the beginning. This is no pick-up hockey rink: By the height of the season the road has to be more than a metre thick. So December and January sees the 160 construction employees – mostly farmers whose agricultural downtime coincides with the winter-road season – bringing out water trucks to flood the road.

It doesn’t take long for a surface layer of water to freeze, smoothing the road and building up its thickness. By late January the ice should be 70 centimetres (2 feet, 4 inches) at its thinnest, from put—in to take-out. Then, the road is declared open for light truckloads.

Making that call has become a science. If a load is too heavy or a vehicle drives too fast, it causes ice-deflection and water-motion, creating waves under the ice that can break through and crack the road. The feeling of driving on a solid substance belies the reality – ice floats on the water and bends easily under the weight of a truck. Though trucks aren’t allowed to travel the road alone, they must maintain 500 metres distance from each other in order not to compromise the integrity of the ice and cause a blowout. In some places, the speed limit is as low as 10 km/h (6mph).

It won’t be the speeder who suffers. It’s the guy driving behind him who could fall through. The depression made by a loaded truck starts the wave moving under the ice. As long as the truck doesn’t catch up to the wave it created, the stress on the ice should be acceptable.

Tailgating poses another danger. Two trucks’ waves can meet and amplify. And there are countless other dangers: Severe storms cause whiteouts that can send a driver off course onto unsafe ice. Trucks could hit a pressure ridge and cause a cracking domino-effect along the lake. Early in the season there can be overflow around the shore as water seeps out the edges of a lake and washes back over the surface. Even the overland sections of the road (called “portages,” per boating tradition) are fraught with peril. A breakdown of any kind could threaten the driver with exposure to extreme cold.

While safety comes first, the bottom line remains the imperative, so unless a blizzard is brewing or the ice is shoddy, the mines keep trucks moving at 20-minute intervals, 24 hours per day, all season long. They have to make the most of the hauling window – they never know when it might end. It’s a big build-up for a small span of time, and there’s always a game to expand the season for an extra day or two, to plow a little earlier, flood a little more. They’ve even talked about holding a winter-road snowmobile rally to pack down the route.

The North’s weather is in constant flux, and in 2006 the diamond mines received a swift kick in the wallet: the ice road had its worst year ever. An early spring followed a warm winter and forced the ice road closed on just its 50^th day of operation, while one-quarter of the mine-bound freight was still stuck in Yellowknife. When the mining companies got the hefty bill for airlifting the remainder they took it as a call to do their homework on climate change.

According to an engineering firm hired by the ice-road operators, the season will dwindle from its current 65-to-70 day window to a 54-day average by 2020; meanwhile, each year will be more of a gamble as weather becomes more variable and extreme temperatures more common.

So they considered alternatives. They looked at airships, hoverbarges and tundra railways, but none seemed practical or available on short notice. They decided on a seasonal overland road that covers about half the route.

Meanwhile, the History Channel is hooked on my town. They’ve set up shop filming the second season of Ice Pilots NWT, about local bush pilots Buffalo Airways, who still fly in a fleet of World War Two-era craft. I’m still waiting for my casting call.