1. Keyhole technology: a solid
solution for our road surfaces
Natural gas utilities must regularly maintain
the underground pipes and equipment in
municipalities across the country. “That’s
why many gas distribution companies are
focused on developing evermore efficient
methods for accessing those pipes, imple-
menting better tools for the maintenance
and inspection of newer gas mains and lat-
eral service lines, and improving their prac-
tices for locating pipes, repairing patches
and core sampling,” points out Gord
Reynolds, Enbridge Gas Distribution’s
Manager, Keyhole Technology.
The most promising tool in their toolkit is a
cost-efficient family of technologies and
techniques that allow companies to work
on underground pipes from above. It’s
called Keyhole technology, and it has been
in development for more than a decade at
Enbridge Gas Distribution.
Gas utilities traditionally use conventional Crews deploy specialized Keyhole coring equipment.
pavement breaking methods such as jack-
hammers or concrete-breakers to obtain access to pipes that need Crews remove the solid core and use vacuum excavation tools to suck
maintenance or repair. If necessary, they shore up the hole and put out the dirt and debris until they can see the main pipe – in some cases
a person into the excavation to do the work. Once they’ve com- up to four to five feet (1.2 to 1.5 metres) down. Then they repair the
pleted the job, they fill the open excavation with clean granular pipe from the surface with specialized long-handled tools.
backfill and top it off with a ‘cold patch’ of tar or asphalt. A piercing tool used by Enbridge’s crew may be only one to seven
Eventually, a paving contractor arrives and patches the area with inches (2.5 to 17.8 cm) in diameter, but it is designed to stay on
concrete, leaving a rectangular 2' x 4' (0.8 metres x 1.2 metres) course from the surface, through difficult soils or obstructions. “It’s
scar on the road. The process can take anywhere from several basically a piston within a casing, equipped with a spring-loaded
days to months. chisel head,” explains Dan Ferguson, President of Footage Tools, a
Keyhole technology, in contrast, deploys a single specialized truck construction tool manufacturing company. “Compressed air drives
to the site. It’s equipped with special Keyhole coring equipment – the chisel head forward from the main casing at a rate of approxi-
a powerful core saw, made of carbide or diamond bits – that mately nine times per second. This creates a pilot bore that can be
carves out a round core up to 24" (0.61 metres) deep and 18" (0.5 up to 150' (45.7 metres) long for the tool to follow, ensuring a high
metres) in diameter. This saw can cut through just about any pave- degree of accuracy. The body of the tool maintains a solid position
ment, sidewalk or road, from asphalt to reinforced concrete. “Jack- and direction in the ground. The head moves independently like a
hammering 18" (0.5 metres) of reinforced concrete would normally small jackhammer and its stepped cone head design can pene-
take 45 minutes to an hour,” says Enbridge Gas Distribution’s Field trate any pipe.”
Manager Bill Elliott. “We can core it out in about 15 to 20 minutes. When they’ve completed their repairs or maintenance work, the
And that’s not even considering the difference in ergonomics crew reinserts the core into the original hole. Frequently, they are
between operating a jackhammer and operating a drill switch. It able to re-use the materials previously removed. Finally, they per-
saves on the body.” manently re-bond the core into the pavement with a special adhe-
sive material proprietary to Enbridge Gas Distribution.
JULY 04 Continued on next page

2. The whole process – from coring to repairing to pavement rein- • making Horizontal Directional Drilling (HDD) suitable for smaller
statement – takes two to three hours. hole applications. HDD is a “family” of construction methods
“Once you put the core back in, it is virtually indistinguishable from used to install new pipes or conduits without the need for major
the existing surface,” says Elliott. “Its circular shape resists surface excavations. Normally an environmentally benign fluid-filled
cracking. Motorists enjoy a smoother ride when their vehicle tires “pilot bore” keeps the earth stable until the pipe can be
aren’t traveling over the perpendicular edge of a square hole.” installed. These units will work within the confined or limited
access, enabling crews to do work behind 30-inch (76 cm)
“At the same time, residents, businesses and drivers benefit
backyard gates;
through less disruption and noise, quicker repair times, fewer
and shorter gas service interruptions and reduced traffic • pressure-testing fittings after installation to make sure that pipes
inconvenience.” have been properly installed; and
Just as significantly, there’s no need for a crew to come back • as a result of work with GTI & Keyspan (Brooklyn Union), insert-
months or years later to repair the road. In fact, the process leaves ing a live camera into low-pressure mains to pinpoint joints and
the road strong enough to carry the weight of six city buses within service Ts in cast-iron mains.
half an hour. According to an independent 10-year longitudinal One day these applications will not be restricted to the natural gas
study prepared by Golder Associates – a highly respected interna- industry. “Once Keyhole technology becomes more wide-spread,
tional engineering firm that provides science and engineering con- the telecommunications and cable industry will use this technology
sulting services – repaired cores reach the standard required by for test holes, service drops and shallow splice pits,” says
municipalities within 30 to 45 minutes, and continue to strengthen Enbridge’s Gord Reynolds.
to a safety factor in excess of 15 times the required standard with- “It will become an invaluable tool for any enterprise that requires
in five hours. There were no failures, despite a wide range of cli- daylighting of utilities, test holes, locates for directional drilling,
mate extremes, and despite the fact that many reinstatements inspection holes for pipeline integrity and subsurface utility engi-
were on major arterial routes, where average daily traffic was neering. Its potential is huge.”
greater than 20,000 vehicles.
For more information on the Keyhole program at
“The equipment, procedures and materials developed and used by
Enbridge Gas Distribution over the last 10 years will ensure satis- Enbridge Gas Distribution, please contact:
factory long-term performance of pavement reinstatement,” said
Gord Reynolds
the Golder report.
Manager
The natural gas industry, not surprisingly, has been taking notice. Keyhole Technology
Enbridge Gas Distribution will be using Keyhole technology: Enbridge Gas Distribution
• to cut unused mains into sections and fill them with sealants to
Telephone: 416-461-0408
make them unusable;
Fax: 416-461-5944
• to more easily and quickly locate above-ground posts that mark
Mobile: 416-732-2200
the position of critical underground infrastructure; and
e-mail: gord.reynolds@enbridge.com
• to prepare the pipe and micro-weld anodes and test stations
www.enbridge.com/keyhole
to the metal of the pipe. Sacrificial anodes help slow down
corrosion on Enbridge’s infrastructure. An electric current flows
away from a cathode on the pipe toward the anode, drawing
corrosion with it.
Looking toward the future, the biggest potential application for
Keyhole technology could be in installation of new services through
the keyhole, such as:
• scraping pipes clean and protect them from oxidization over
time;
• 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;
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