Natural gas utilities must regularly maintainthe underground pipes and equipment inmunicipalities across the country. “That’swhy many gas distribution companies arefocused on developing evermore efficientmethods for accessing those pipes, imple-menting better tools for the maintenanceand inspection of newer gas mains and lat-eral service lines, and improving their prac-tices for locating pipes, repairing patchesand core sampling,” points out GordReynolds, Enbridge Gas Distribution’sManager, Keyhole Technology.

The most promising tool in their toolkit is acost-efficient family of technologies andtechniques that allow companies to workon underground pipes from above. It’scalled Keyhole technology, and it has beenin development for more than a decade atEnbridge Gas Distribution.

Gas utilities traditionally use conventionalpavement breaking methods such as jack-hammers or concrete-breakers to obtain access to pipes that needmaintenance or repair. If necessary, they shore up the hole and puta person into the excavation to do the work. Once they’ve com-pleted the job, they fill the open excavation with clean granularbackfill and top it off with a ‘cold patch’ of tar or asphalt. Eventually, a paving contractor arrives and patches the area withconcrete, leaving a rectangular 2' x 4' (0.8 metres x 1.2 metres)scar on the road. The process can take anywhere from severaldays to months.

Keyhole technology, in contrast, deploys a single specialized truckto the site. It’s equipped with special Keyhole coring equipment –a powerful core saw, made of carbide or diamond bits – thatcarves out a round core up to 24" (0.61 metres) deep and 18" (0.5metres) in diameter. This saw can cut through just about any pave-ment, sidewalk or road, from asphalt to reinforced concrete. “Jack-hammering 18" (0.5 metres) of reinforced concrete would normallytake 45 minutes to an hour,” says Enbridge Gas Distribution’s FieldManager Bill Elliott. “We can core it out in about 15 to 20 minutes.And that’s not even considering the difference in ergonomicsbetween operating a jackhammer and operating a drill switch. Itsaves on the body.”

Crews remove the solid core and use vacuum excavation tools to suckout the dirt and debris until they can see the main pipe – in some casesup to four to five feet (1.2 to 1.5 metres) down. Then they repair thepipe from the surface with specialized long-handled tools.

A piercing tool used by Enbridge’s crew may be only one to seveninches (2.5 to 17.8 cm) in diameter, but it is designed to stay oncourse from the surface, through difficult soils or obstructions. “It’sbasically a piston within a casing, equipped with a spring-loadedchisel head,” explains Dan Ferguson, President of Footage Tools, aconstruction tool manufacturing company. “Compressed air drivesthe chisel head forward from the main casing at a rate of approxi-mately nine times per second. This creates a pilot bore that can beup to 150' (45.7 metres) long for the tool to follow, ensuring a highdegree of accuracy. The body of the tool maintains a solid positionand direction in the ground. The head moves independently like asmall jackhammer and its stepped cone head design can pene-trate any pipe.”

When they’ve completed their repairs or maintenance work, thecrew reinserts the core into the original hole. Frequently, they areable to re-use the materials previously removed. Finally, they per-manently re-bond the core into the pavement with a special adhe-sive material proprietary to Enbridge Gas Distribution.

Keyhole technology: a solid solution for our road surfaces

Crews deploy specialized Keyhole coring equipment.

Continued on next pageJULY 04

The whole process – from coring to repairing to pavement rein-statement – takes two to three hours.

“Once you put the core back in, it is virtually indistinguishable fromthe existing surface,” says Elliott. “Its circular shape resists surfacecracking. Motorists enjoy a smoother ride when their vehicle tiresaren’t traveling over the perpendicular edge of a square hole.”

“At the same time, residents, businesses and drivers benefitthrough less disruption and noise, quicker repair times, fewer and shorter gas service interruptions and reduced traffic inconvenience.”

Just as significantly, there’s no need for a crew to come backmonths or years later to repair the road. In fact, the process leavesthe road strong enough to carry the weight of six city buses withinhalf an hour. According to an independent 10-year longitudinalstudy prepared by Golder Associates – a highly respected interna-tional engineering firm that provides science and engineering con-sulting services – repaired cores reach the standard required bymunicipalities within 30 to 45 minutes, and continue to strengthento a safety factor in excess of 15 times the required standard with-in five hours. There were no failures, despite a wide range of cli-mate extremes, and despite the fact that many reinstatementswere on major arterial routes, where average daily traffic wasgreater than 20,000 vehicles.

“The equipment, procedures and materials developed and used byEnbridge Gas Distribution over the last 10 years will ensure satis-factory long-term performance of pavement reinstatement,” saidthe Golder report.

The natural gas industry, not surprisingly, has been taking notice.

Enbridge Gas Distribution will be using Keyhole technology:

• to cut unused mains into sections and fill them with sealants tomake them unusable;

• to more easily and quickly locate above-ground posts that markthe position of critical underground infrastructure; and

• to prepare the pipe and micro-weld anodes and test stations to the metal of the pipe. Sacrificial anodes help slow down corrosion on Enbridge’s infrastructure. An electric current flowsaway from a cathode on the pipe toward the anode, drawing corrosion with it.

Looking toward the future, the biggest potential application forKeyhole technology could be in installation of new services throughthe keyhole, such as:

• scraping pipes clean and protect them from oxidization overtime;

• hooking into ‘tracer wires’, which are attached to plastic pipe,along with a conductive source, so the company can more easily and quickly locate the pipe when necessary;

• making Horizontal Directional Drilling (HDD) suitable for smallerhole applications. HDD is a “family” of construction methodsused to install new pipes or conduits without the need for majorexcavations. Normally an environmentally benign fluid-filled “pilot bore” keeps the earth stable until the pipe can be installed. These units will work within the confined or limitedaccess, enabling crews to do work behind 30-inch (76 cm)backyard gates;

• pressure-testing fittings after installation to make sure that pipeshave been properly installed; and

• as a result of work with GTI & Keyspan (Brooklyn Union), insert-ing a live camera into low-pressure mains to pinpoint joints andservice Ts in cast-iron mains.

One day these applications will not be restricted to the natural gasindustry. “Once Keyhole technology becomes more wide-spread,the telecommunications and cable industry will use this technologyfor test holes, service drops and shallow splice pits,” saysEnbridge’s Gord Reynolds.

“It will become an invaluable tool for any enterprise that requiresdaylighting of utilities, test holes, locates for directional drilling,inspection holes for pipeline integrity and subsurface utility engi-neering. Its potential is huge.”

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

06-0167