Under The Pond

By Jeff Griffin, Senior Editor | March 2013, Vol. 68 No. 3

In a part of the country where rocky soils make underground construction difficult, Maine contractor Enterprise Trenchless Technologies, Inc. (ETTI) has built a solid reputation for successfully completing challenging horizontal directional drilling installations, many beneath bodies of water.

A recent project installed a 500-foot-long segment of 12-inch water main under Brandy Pond in the picturesque tourist town of Naples, nestled in western foothills of Maine. The job was a part of the Naples Causeway Restoration Project which included removal of an old draw bridge and constructing a new aesthetically-pleasing arched bridge. The water line was an important element of the restoration project because it connected the town’s fire suppression system, which previously was supplied by water from separate sources on each side of the causeway.

The project owner was the Town of Naples. Wyman & Simpson, Richmond, ME, was the prime contractor. Because the design of the new bridge could not accommodate suspending the water pipe from the bridge, it was necessary to take the pipe under the floor of the pond. Wyman & Simpson turned to ETTI to make the crossing by horizontal directional drilling.

“Directional drilling was the only feasible option to get the water line across the water,” said Scott Kelly, ETTI president.

Water crossing challenges
Water crossings always involve complications and the Naples job was no exception. Using a wireline system to track the bore path while beneath bodies of water adds cost to the job. Employing conventional walk-over trackers usually requires crew members to move along the bore path in a boat.

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ETTI used a Ditch Witch JT8020 drill unit with 80,000 pounds of pullback to make the installation, setting up on the east side of the causeway in the parking lot of a marina which had ample space for the drill unit, fluid system and support equipment. The drill rig was positioned for the surface launch about 200 feet from the water’s edge.

Starting the pilot bore was delayed a day by rough waters -- too choppy for the ETTI crew of two to take out their small boat to operate the handheld tracking receiver as it followed the path of the bore head. Depth readings also would be taken at various points.

Kelly said boat traffic also could cause potential complications.