Risky Business

Adding GNSS to the process gives Canadian firm confidence in horizontal directional drilling operation.

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In utility installation, when the most direct route from Point A to Point B is not do-able because of an impediment–a structure, a road, a stream, etc.–contractors in that field most often turn to horizontal directional drilling (HDD). This technique uses specialized technology to slant the pipe slightly downward under the problematic area and back up again once past it. For each drill shot, however, careful pre-planning and mapping is needed to ensure accuracy along the pipe’s subterranean route. In a recent major project in Winnipeg, Manitoba, specialty contractor Outdoor Solutions, found that using GNSS to pre-survey the route for each of their drill shots afforded a higher level of confidence in the success of those efforts. As a result, installation of more than 3 km of water main–under all of the areas described above–is proceeding on pace and, more importantly, on target.

New Kind of Port
The project in which Outdoor Solutions is involved is one of the most ambitious of its kind in Canada today. Named CentrePort Canada, it is essentially creation of a 20,000-acre inland port and Foreign Trade Zone. The combination of its central Canada location, its proximity to a direct corridor south through the U.S. to the Gulf of Mexico, and its excellent access via road, rail and air, is fueling it as an industrial development destination.

"This has been a vision of Manitoba’s for some time now and it is great to be a part of helping make it all happen," said Darren Minaker, owner of Outdoor Solutions. "Already nearly 500 companies have established a presence here and the project with which we are involved will only help take that number much higher."

That project is the installation of 23 km of 18-inch diam. force main water pipe linking a soon-to-be-completed $43 million water treatment plant to the west with a millionplus gallon reservoir in the northwestern part of the development area.

"This will certainly provide a muchneeded service, opening up the potential for new businesses to CentrePort," said Minaker. "However, getting that pipeline from the treatment plant to the reservoir means first getting it past a number of obstacles. And that’s where we come in."

Plan Twice, Drill Once
On one particularly vexing section of the pipe’s path, the water main encounters two sections of highway, a creek bed and two rail crossings, each of which had to be dealt with through the use of a Ditch Witch JT-60 directional drill. While fully-confident in the unit’s capabilities, Minaker said he was aware of similar operations that had gone bad due to lack of pre-planning.

"I know of some river shots that failed because there was not enough advance work done and I never want that to be the case on any of our projects," he said. "So I started considering the best possible approach and felt that the use of GPS– which we were very familiar with from our previous site prep operation–could fit nicely with HDD work."

While the directional drilling machine has intricate controls, including an electronic guidance system to direct the drill head, Minaker felt it was imperative to accurately pre-plan each drill shot, removing any doubt as to accuracy of location. Using a HiPer Ga base station and FC-250 field controller, both from Topcon Positioning Systems, he set to marrying the two technologies–GNSS and HDD–together.

Knowing Your Place
Minaker said that what he does in advance of every drill shot is not all that dissimilar to his work in general construction survey situations. It all begins with materials prepared by the project engineers.

"The engineers for this job provided us with a cross section indicating how deep they needed the pipe, calling out key points such as areas under creeks, highways, rail lines and any other existing pipes," said Minaker. "While they want to make sure that we are exactly that deep under key points, the only way I can feel comfortable about that number is if I know the surface elevation. So, using GPS, we do a topo of the surface and then use that data to create a cross section of the existing ground with the depths at those key points. I have the drill shot broken down into 9 m intervals and can tell the HDD locator and the drill operator exactly how deep we need to be at each of those specific intervals."

The CentrePort Canada project is complicated further by the fact that each of those obstacles has its own criteria, both for how deep pipe must be buried beneath it and for the material in which that pipe must be encased.

"We need to be four meters under any railway and 3 m below the bottom of an existing creek," said Minaker. "However, the stream is adjacent to an elevated highway so once we get past that creek and under that highway, we are seven meters under the roadbed."

A Cut Above
As mentioned, Outdoor Solutions’ portion of the job represents only 3 km of the total project distance. The primary 20 km is being handled by the general contractor, Manitoba-based E.F. Moon Construction, Ltd. Based on their own experience and on success Minaker has had in his past site prep work, they took some steps to help make the excavation facet of the job faster and more accurate as well.

"E.F. Moon is tackling all the open cuts on this project, that is, all of the areas in which HDD is not needed," he said. "To help with that part of the operation, they had local specialists Lawson Consulting & Surveying generate the 3D files needed to use GNSS-based machine control. As a result, using a Cat 336E excavator equipped with Topcon X63, Moon was able to know their exact centerline and depth of cut throughout the length of the project."

The CentrePort pipeline project began in October 2014 and is expected to be wrapped up by September 2015, in advance of a Spring 2016 opening of both the water treatment plant and reservoir.

"When you factor in the length of winters up here, eleven months is really not a lot of time to put down 23 km of pipe," said Minaker. "So the technologies we’ve used–both in positioning and drilling–have really helped keep things on track. However, for me the real benefit the Topcon system has provided out here has been the degree to which it reduces my risk; there are no surprises. For me, GPS is a huge planning advantage. When used with an HDD machine, it allows me to know exactly where I’m going to be before I get there–every time. You just can’t put a price on that."

Larry Trojak of Minnesota-based Trojak Communications, is a freelance marketing content specialist. He writes extensively for the geopositioning, utility, aggregate processing, recycling, construction, and demolition markets.

A 4.797Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE