Last season, Enbridge Gas Distribution performed ongoing mainte-nance on hundreds of gas pipes beneath Toronto’s streets with vir-tually no disruption to traffic or local business.

How did its crews accomplish this?

Instead of breaking the pavement with jackhammers and backhoesto gain access to underground pipelines, crews used an innovativeand extremely cost-effective new family of technologies and tools –“keyhole” coring and pavement reinstatement. The process allowscrews to do repair or maintenance work on underground pipes orother buried equipment from the road surface – safely, efficiently,and without the need for more costly and disruptive excavationmethods. Enbridge Gas Distribution developed Keyhole technologyas a pilot program more than a decade ago. The company has test-ed it on hundreds of excavations, through a wide range of severeclimatic conditions – without a single failure.

“A heavy-duty truck-mounted rig cuts an 18" (0.5 metre) diametercore out of the pavement,” explains Bill Elliott, Enbridge GasDistribution’s Toronto-based Field Manager of Maintenance. “Thiscoring unit is purpose-built to cut through any paved surface –including reinforced concrete – in less than 15 minutes.”

The crew then removes and sets aside the core, “vacuum exca-vates” the underground pipes and equipment, and repairs leaks ordo other maintenance from the surface, using special long-handledtools. “Once the repair has been completed,” says the GasTechnology Institute’s Keyhole technology Project CoordinatorDennis Jarnecke, “the hole is back-filled, and the core bonded backinto place with a special compound. The roadway or sidewalk isthen as good as new.”

Actually, it’s better than new. Tests conducted by reputable inde-pendent research organizations (including the National ResearchCouncil, the US Army Corps of Engineers, Golder Associates andthe University of Illinois at Urbana-Champaign confirm that thestrength of the bond compound is five times greater than the man-dated load-bearing standard set by the city of Toronto. Within 30minutes, it can support the combined weight of six transit buses.This process can add years to the life of the roadway, compared totraditional methods.

“It’s amazing,” Elliott said. “After only half an hour, we can re-openthe site to pedestrian and vehicle traffic. We can promptly move onto the next site instead of having to monitor a temporary pavingrepair until it is complete. And the process literally pays for itself from

the savings in paving costs – a huge benefit to utility companieslooking for ways to reduce maintenance and repair costs to helpkeep their rates down.”

Keyhole technology is also environmentally-friendly. There’s no needfor temporary patching, repaving of the roadway or disposal ofdebris created during excavation. Instead, crews can reuse portionsof roadway materials that once became construction waste.

“In addition, the process is win-win for us and for the municipality,”says Kathy O’Neill, an Inspector for the Keyhole program atEnbridge. “Not only is the precise circular cut 80% smaller than aconventional rectangular road-cut, it is almost invisible after therepair, which makes it aesthetically pleasing to the municipality thatowns the road. The high-strength, waterproof bond and circularshape of the cores also mean no more corner stress cracks in theroad and no groundwater leaks that penetrate the subsurface andcan cause potholes.”

The company used this technology to complete more than 300cores and reinstatements in Toronto during 2003, and plans to do1,500 more in 2004. A growing number of other jurisdictions haveaccepted the coring process as a permanent pavement reinstate-ment method.

“It’s the most exciting and productive maintenance innovation thatI’ve come across in my more than 25 years with the company,” con-cludes Scott McClelland, Enbridge Gas Distribution’s OperationsManager for the Toronto region. “Based on our experience so far,Keyhole coring is rapidly becoming a welcome addition to the toolswe use in our construction and maintenance operations.”

For more information on the Keyhole program atEnbridge Gas Distribution, please contact:

Gord ReynoldsManagerKeyhole TechnologyEnbridge Gas Distribution

Telephone: 416-461-0408Fax: 416-461-5944Mobile: 416-732-2200e-mail: gord.reynolds@enbridge.comwww.enbridge.com/keyhole

Toronto crews have “concrete” solution for repairing underground pipes

05-0702JULY 04