July 30, 2010

FEATURE | Site services

ROBERT B SOMERVILLE

Directional drilling helps keep community relations on a good footing because it is less disruptive.

Directional drilling less disruptive for locals

PETER KENTER

correspondent

While Canada offers plenty of open spaces as potential wind farm sites, there’s a catch.

To make them viable they have to be located near existing transmission lines.

The Talbot Wind Energy Project being constructed along Lake Erie in the Municipality of Chatham-Kent near Ridgetown fits the bill.

To assure local residents the construction and operation of the wind farm would have as little effect as possible on both the environment and the site, developer Res Canada chose directional drilling to lay as much of the electrical infrastructure as possible.

That’s one of the lessons learned in previous wind farm projects where local opposition was galvanized against invasive construction methods.

“In some wind farms, they put the electrical infrastructure overhead on poles along the road,” says Abe Dyck, manager, Contracts and Business Development, with the Robert B. Somerville Co. Limited. “Where they couldn’t get agreement with the local utility to use existing hydro poles, they had to erect a second set of poles.”

The company has been working since May to install 70-kilometres of cable consisting of three primary, one fibre and one ground cable in a polyethylene conduit about eight inches in diameter.

Dyck says a considerable portion of the infrastructure is being installed using simple open cut technology where soil beds for conduit are merely compacted and backfilled.

“The directional drilling is used in front of people’s properties, or in front of businesses where the owner doesn’t want to see things disrupted,” says Dyck. “The municipality also had century-old trees along the roadways they didn’t want to see harmed.”

Installation is further constricted by existing infrastructure, including utility poles and a patchwork of public and private property access requirements. Archaeological studies also identified areas of historic interest that were to be left undisturbed.

Directional drilling lengths have ranged from as little as 20 metres to as many as 500 metres, using multiple horizontal directional drilling rigs including units manufactured by American Auger and Vermeer directional drills.

Crews dig a pilot hole, pushing a bore head connected to a hollow pipe into the ground. As each joint of drill pipe enters the ground, a new one is added. A jet of high-pressure drilling fluid, most commonly a mixture of bentonite clay and water, provides the majority of the drilling action, though the units can also take advantage of a rotating drill bit. The fluid performs double duty, also cooling and lubricating the pipe.

During the drilling process, crew members use a locating machine to determine the exact position of the drill head, which reports back on its angle of access, depth, rotation, direction and temperature. That data is fed back to the unit, which self-adjusts to drill according to plan. When the drill head emerges on the other side, the bit is removed and replaced by a reamer which is pulled back while rotating the drill pipe.

Once the diameter had been achieved, the conduit pipe is attached to the reamer and pulled back through the hole, while drilling fluid is pumped in to fill any voids between pipe and soil.

“On jobs in urban centres such as Toronto, the Robert B. Somerville Co. typically relies on directional drilling as its primary approach. “For a rural area, this turned out to be a large directional drilling project, with more crossings than we anticipated,” says Dyck.

Occasionally, the drilling machines dig up a surprise, such as the day at Ripley Wind Farm near Kincardine when crews found artillery shells buried beneath the ground.

“The site was near Camp Borden where they used these areas for practice rounds,” says Dyck. “We brought in an artillery expert who proved they weren’t live ammunition.”

Work on the underground collection system at Talbot should be completed in October.

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