3 days ago
Trent: Cracking the mystery of Montreal's self-destructing roads
Let's try to crack that great Montreal mystery: Why do we build self-destructing roads?
When it comes to durability, all roads lead to Rome. While our roads barely last 50 years, some ancient paved Roman roads still survive. A metre thick, they were built on compacted soil in four layers: crushed rock, mortared crushed rock, concrete, and stone pavers.
Two millennia later, in 1816, roads of compacted gravel called macadam were developed by John McAdam — not, however, the John Macadam whose name graces the rather more digestible macadamia nut. Macadam was far inferior to its Roman equivalent, without even a concrete layer because 'modern' concrete was first used for paving in 1865. By 1904, macadam had tar added to it as a binder and dubbed 'tarmac.' We call it asphalt.
Roadbuilding techniques have essentially remained unchanged ever since, but stresses on roads have multiplied — think of the pounding of 50,000-kilogram loaded trucks compared to wagon-wheeled carts.
For many Quebec roads, crushed and compacted gravel topped with asphalt is still common. The City of Montreal usually specifies 20 centimetres of concrete under the asphalt. Some highways and airport runways use up to 50 cm of concrete with no asphalt — giving a boost to strength and possibly longevity.
Water is the great destroyer of building materials: it corrodes metals, rots wood and weakens concrete. The Romans understood the danger of water acting on their handiwork: They built watertight roads with a cambered surface for water run-off. In our climate, when water penetrates the rigid sponge that is concrete, it expands as it freezes, tearing apart the concrete after repeated freeze-thaw cycles.
Then there's potable water. For 'home delivery' of water, Romans used pipes made of lead — plumbum, whence the word 'plumber.' Don't mock the Romans for poisoning themselves: One-third of U.S. cities still have lead in their water service lines, as does Montreal. One more reason why our roadways need to get deconstructed.
Along with water pipes, Montreal buries utilities such as gas, power and telecom trunk lines underneath concrete roads and sidewalks, requiring jackhammers or diamond-bladed saws to get at them whenever inaccessible via manholes. Any such cuts in the road surface by Énergir, Hydro-Québec and Bell Canada can ruin a road's watertightness, shortening its life.
But how do other northern cities manage to have decent roads and we don't?
Chronic underinvestment aside, the underlying cause is probably the sort of contractor building our roads. Even if we delude ourselves that the widespread corruption uncovered by the 2011-2015 Charbonneau commission of inquiry into the Montreal construction industry is now behind us, today's crumbling road infrastructure is a poisoned legacy, a product of 50 years of bid-rigging, dodgy engineering firms and complicit bureaucrats or politicians. When contractors cheat on price, they cheat on quality.
We have to attract a new class of skilled road contractors and shift the obligation to perform onto them. One way is to have the contractor design, build and then maintain the road in good condition at their cost for (say) 30 years. Contractors would have an inescapable incentive to build well and durably. (If ever they go under, their performance bond kicks in.)
While the design-build-maintain method falls under the general category of Public Private Partnerships (PPP), using it for street construction offers minimal snares. While not everyone would declare the PPP that created the MUHC Glen complex was an unalloyed success, using PPP for building streets is a far cry from building and maintaining a hospital. The cause and effect of pavement failures are relatively evident.
Repeated contracts for self-destructing roads constitute a gift that keeps on giving. It's time to end this generosity.
