Right now Edmonton is the pothole capital of Canada, hands down. There is no competition. Our average of 450,000 repairs per year dwarfs even those of larger cities like Toronto (140,000 to 280,000), Montreal (35,000 to 50,000) and Calgary (30,000 to 40,000). Clearly, there’s something about Edmonton and asphalt that do not get along. To find out what, exactly, that X factor is, I turn to Hugh Donovan, a construction-services engineer for the city and manager of its Engineering Services Quality Assurance Laboratory. (He’s also, in Dunford’s words, “our asphalt nerd.”)
Like Dunford, Donovan is realistic about the impact his work can have on the city’s roads. “I’m not sure I can actually design and build a road in Edmonton that will never, ever have a pothole,” he says. “It doesn’t matter how good a mix I make. There are extenuating circumstances I have no control over.”
One of those circumstances is temperature. The oils used in Edmonton’s asphalt cements have a temperature range of close to 90 degrees Celsius: from 58C to -28C. “Below that,” Donovan says, “the road will crack.” But we all know that Edmonton can sit for long periods of time in temperatures -28C and colder. So why use this type of oil at all?
Because the alternative would be far worse. The other available oil product has a range of 52C to -34C, which, Donovan says, would likely cover the bottom end, since asphalt takes up to a week to fully absorb the colder air temperatures. But in the height of summertime, Edmonton’s black, heat-absorbing roads routinely get past that 52C upper threshold. In the absence of an oil that can handle our city at both its hottest and its coldest, Donovan has had to make a choice. “I can’t have an asphalt that flows off the roads in the middle of summer,” he says. “So we accept the cracking.”
This compromise doesn’t sit well with Kim Krushell, the three-term city councillor for Ward 2. (She is not seeking re-election this month.) Krushell says that what’s needed for Edmonton’s roads is not an unlimited budget, but a larger change in how we approach road materials in general. “I don’t disagree that we need to fix potholes,” she says. “But I don’t think the way to solve it is to just pour money into it. I think the way to solve it is to look at new technologies.”