Dirty work kept out of sight
Firm uses robot to fix sewers without digging
In the back of a five-tonne truck, Matt Bradbury’s fingers fly across the computer keyboard and his eyes rarely stray from images on a small video screen.
Bradbury seems to be directing some sort of surgery: A camera wends its way along a narrow tube, revealing protrusions that are obliterated by a whirling cutting device. A rush of liquid occasionally obscures the scene.
In fact, he’s performing a task few of us care to think about: inspecting, cleaning and measuring a sewer pipe that carries wastes from a house — in this case, in downtown Hamilton — to the mainline under the street.
It’s part of an award-winning, Ontario-designed system that inspects and repairs these residential lines, known as laterals, without digging even a shovel-full of earth. Homeowners can continue to flush toilets and use sinks while the work is underway. In fact, unless they look out and see the trucks, they won’t be aware it’s happening.
While another local company performs similar work on a much smaller scale, “nobody anywhere does it like this,” says Kim Lewis, CEO of the LiquiForce Group of Companies — an 80-employee business based in Kingsville, Ont., near the western end of Lake Erie — which invented the system.
Everything about this kind of work “is moving very quickly,” says Mike Willmets, executive director of the North American Society for Trenchless Technology, which last year gave LiquiForce its product-innovation award.
Most of the hundreds of thousands of laterals serving Ontario homes are sections of clay pipe strung together. As they age, they crack, are invaded by tree roots or become clogged with sewage gunk.
All repairs used to require excavating a trench to access damaged pipe. For the past decade or so, new technology has let laterals be renewed with much less disruption.
One version involves digging a shaft down to each end of the pipe, inserting a cable, then pulling through a “burster” that smashes the old pipe out of the way and drags a plastic replacement into place.
When pipes haven’t collapsed, a resin-impregnated tube can be projected into the pipe, where it hardens in place; in effect, creating a new structure inside the old one. That can be done from a basement access point or, more commonly, a single shaft dug outside.
LiquiForce’s innovation, 10 years in development and covered by dozens of patents, eliminates digging. Instead, a computer-controlled “tool” is dropped into the main line through a manhole and, manipulated by operators like Bradbury in a truck above, travels to the small opening of each lateral to do its work.
It completes rehabilitations in two visits.
During the first visit, the robotic device inspects the pipe, then cuts out roots and other intrusions with spinning chains or a warthog — a water jet exerting 2,300 pounds of pressure per square inch at up to 40,000 revolutions per minute. Finally, with spring-loaded calipers, it precisely measures the interior diameter and length. The measurements are sent to the LiquiForce plant in Kingsville, so a custom-fitting liner can be built. A few days after the initial visit, a second crew returns to the site, adds resin to the liner, folds it like an inside-out sock, packs it in a launcher and, again using computer controls, guides everything to the lateral. There, the launcher shoots the liner up the pipe. The liner inverts into place in seconds; then air pressure is applied for 90 minutes while it hardens tight against the pipe’s inner wall. This new pipe within a pipe should be good for 100 years, Lewis says. All four regions in the 905 have tested or used the system. It’s being tried elsewhere in Canada and interest is developing in the United States. It works best in preventive programs, like Hamilton’s, which not only reduce the chance of sewer backups but also eliminate leaks. When groundwater seeps into laterals, Lewis notes, it adds to the burden on the sewage treatment system. When sewage leaks out, it can contaminate surrounding soil and groundwater. Most cities, including Toronto, only respond to emergencies. In 2006, Hamilton took responsibility for its 225,000 laterals and began conducting preliminary surveys of their condition. With that information, it lists priority areas and hires contractors to do further inspections and repairs. For the past two years, it has contracted LiquiForce for this work. “We can look at projections into the future; what will be needed and when,” says John Murray, the city’s manager of asset management. “We’ve become a bit of a national leader.” Each year, the city averages about 1,200 inspections and 500 relining jobs, Murray says. “We have a long way to go.” City-funded repairs go only to the property line. Some municipalities let homeowners pay to extend the work to the house. But that’s not allowed in Hamilton, mainly because the legal department doesn’t want the city associated with private arrangements. In any case, few people choose the extended work where it is offered. Peel Region also has a preventive program and, through open bidding, hires LiquiForce for some repairs, says water and waste water manager Simon Hopton. No-dig repairs often cost less than other methods, depending mainly on the lateral’s length, but major savings come from not disturbing what’s above the line. “The social cost could outweigh the lining cost,” says Mark Bajor, a project manager with Halton Region. “When you start looking at digging driveways and flower beds, that’s sometimes not factored in.” Toronto offers sewer relining only when a homeowner requests it, and contracts the work through public tenders, says Mario Crognale, director of district operations at Toronto Water.