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Going hole hog

Montreal's pothole patching crews use specialized equipment


March 7, 2014
by Kara Kuryllowicz

Canadians in colder climes have long had issues with potholes, but as global warming alters weather patterns, the peculiar mix of deep freezes and balmy thaws has exacerbated the problem.

Asphalt, a mix of gooey bitumen, oil byproducts, gravel and curatives, repels snow and rainwater but once it loses its structural integrity, snow and rain seep in through the cracks. As the water beneath the surface contracts and expands through the freeze-thaw cycles, it pushes out dirt and gravel to eventually create a divot and then a pothole.

Last year, between December 7 and 17 alone, Montreal crews filled about 5,000 potholes. But in early January further weather weirdness had car owners calling 311 to report growing craters, leading city workers to a second round of repairs. The city typically fills between 35,000 and 50,000 potholes annually both manually and with the help of two contractors and their equipment:  Environnement Routier NRJ Inc and Jean-Paul Trahan.

“We fill potholes year-round, but the volume increases during the winter and the spring when we have the worst potholes, which when they’re at least two feet in diameter and six inches deep, can damage a vehicle’s suspension, tires or wheels,” says Champagne. “We call on the contractors and their specialized equipment when we have to repair 5,000 to 10,000 potholes in one or two weeks.”

Which is best, a manual or machined repair in terms of durability and efficiency?
“It’s difficult to track because there are so many and we don’t tend to revisit the intact repairs but one of our assessments did show us the machined repairs usually last at least until spring and up to half last at least two years,” says Champagne, noting that the weather conditions during the repair and the integrity of the surrounding pavement affect the results.

Machined repairs are more efficient because a single operator handles the repair from start to finish and simply drives the entire unit from pothole to pothole. A manual repair can require a crew of five or six people, who have to exit the truck to load and unload materials and equipment for each hole. However, it does provide more flexibility in complex situations.

NRJ currently owns and operates five of Schwarze Industries’ Roadpatcher machines, which automatically repair potholes and other road defects. The machine blows compressed air into the hole to remove as much dust, debris and water as possible. To create a binding surface to which the asphalt fill will properly adhere, an asphalt emulsion is sprayed into the hole. The Roadpatcher accurately controls the aggregate through a positive-flow conveyor system while the asphalt is applied with a spray ring. The unit’s boom has a tube stabilizer that allows the operator to precisely control and place the patching material.

“A few years ago, we hired a lab to calibrate the machines for us and develop an asphalt recipe that suited our weather conditions,” says Steve Bastien, assistant general manager at Environnement Routier  NRJ Inc. “You need to tailor the machine and the asphalt mix to the environment.”

The Roadpatcher units, which cost about $200,000 apiece, have a lifespan of 10 to 15 years if diligently and rigorously maintained, which is crucial since they toil primarily through Montreal’s cold winters. The focus is on daily fluid and pressure checks, lubrication and of course, a walk-around to ensure everything is as it should be. Operators even verify the accuracy of the thermometers to ensure the emulsion is at the manufacturer-specified temperature.

“Because our Roadpatchers are at work in the extreme cold, we customized them to perform and last through Montreal winters by installing a heating element around the spray nozzle and insulating the pipes that carry the asphalt emulsion to the front of the Roadpatcher to keep the mixture hot enough,” says Bastien.

Each machine requires a single operator to direct the machine to the potholes. On a frigid winter day with a biting wind, the operators certainly appreciate the Roadpatcher’s cab which lets them monitor all functions from within.

“It’s more comfortable but most importantly, it’s safer, because they’re protected from the traffic,” says Champagne.

The more experienced Roadpatcher operators train the employees who are new to the Roadpatcher. In addition to learning how to operate the Roadpatcher, they’re also taught how to clean, maintain and troubleshoot it.

“We know that what we’re doing is effective because we use our GPS systems to take us back to the potholes we’ve repaired and year after year they’re still in place,” says Bastien.       B2B