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HDD solves sensitive gas pipeline crossings.

Horizontal directional drilling (HDD) is often the solution selected for pipeline projects that face environmental issues. This was the case when FPL Energy LLC needed to bring natural gas to a site where a 1,790 MW state-of-the-art power plant was being built in Forney, TX, 20 miles east of Dallas.

Duke/Fluor Daniel (D/FD) of Charlotte, NC, was selected by FPL Energy to provide engineering, procurement, construction and commissioning services for the Forney power project. FPL Energy, a subsidiary of FPL Group Inc., will own and operate the facility. When completed in summer 2003, the plant will be one of the largest independent power plants in Texas.

D/FD President and CEO Jeff Faulk said the Forney project is the largest power plant, in terms of generation capacity, that his company has engineered and constructed. During peak construction, the project is expected to employ up to 950 people.

Two gas pipeline companies--TXU Lone Star and Kinder Morgan--were charged with building pipelines to bring gas to the new plant.

TXU completed a two-mile 24-inch diameter pipeline from its existing gas transmission system in eastern Dallas County to the Forney Plant.

Kinder Morgan's portion of the project involved the construction of 82-miles of 30-inch diameter pipeline from Lamar County to Kaufman County, which adjoins Dallas County to the east.

Under the direction of prime contractor Sheehan Pipe Line Construction Company, Tulsa, OK, the longer Kinder Morgan pipeline project posed several challenges. The route of the pipeline intersects environmentally sensitive aqueduct locations at two different points: It crosses the aqueduct that is a fresh water source for the city of Greenville and a second location in nearby Dallas County.

Pipeline installations at both aqueduct crossings involved HDD, as did a crossing of an interstate highway and the North Texas Municipal Water District (NTMWD) pipeline.

Prior to any of the actual pipeline construction, Kinder Morgan provided everyone involved in open-cut construction and HDD on the project with environmental and safety training.

Construction crews were also refreshed on corrosion control devices, handing potential spills and--for the HDD operators--what to do in the event of a frac out. Since two of the planned drills were under aqueducts, Kinder Morgan was especially wary of a frac out at these locations.

To reinforce this concern, the HDD contractors on the project were required to have someone on site monitoring drilling activity at all times. In the unlikely event that a frac out occurred, monitoring would allow drilling to be immediately halted and the frac out quickly contained and brought under control.

HDD Crossings

Trans American Underground LTD President Keith L. Whitaker whose company completed four crossings on the project, pointed out that in order to cope with subsoil conditions Trans America relied on an American Augers DD-330 drilling rig and an American Augers MP 500 Mud System to complete the four crossings.

"The four HDD crossings included a 1,095-foot drill under the Greenville Aqueduct, a 1,069-foot drill under the NTMWD pipe-line, a 1,013-foot crossing under I-30 in Royce City, just east of Dallas, and a 940-foot drill under 72-inch and 84-inch O.D. pipelines that are part of the aqueduct system in Dallas County," Whitaker explained.

The line pipe selected for the crossings was 30-inch O.D. 450 heavy wall steel pipe. Each drill section weighed between 120,000 pounds and 170,000 pounds.

Whitaker said the crossing at the Greenville aqueduct, the NTMWD pipeline and I-30 were all completed within a 25 day period. Crews set up to complete the fourth and final 940-foot crossing under the Dallas aqueduct on August 24, and completed it four days later on August 29.

He also noted that an important part of the project was planning and teamwork. In the early stages, a major focus was to ensure environmental protection measures were in place to handle any possible emergency. As work on the environmental installations progressed, Sheehan's crews carried out all pipe handling on the job.

Whitaker said Kinder Morgan had provided sufficient right-of-way at each respective drill site to allow his crews to set up their drilling equipment and for Sheehan's crews to string the pipe and place it on rollers.

The Trans American Underground executive explained that the 1,095-foot Greenville aqueduct crossing proved to be the most challenging. Crews were drilling under one of only two sources of fresh water being fed into the city's treatment plant. "Any disruption to the treatment plant was totally unacceptable," he said.

Whitaker said the 10-inch pilot bore at this location was drilled with the American Augers DD-330. The bore reached a total depth of 42 feet.

Hard grey shale, about 25 feet below the aqueduct, precluded the use of a fluid jet steering head during the drilling of the pilot bore," he explained. "Instead, a mud motor was selected for its rugged cutting capabilities."

Upon completing the pilot bore, the bore was enlarged with a 24-inch reamer, 34-inch reamer and then a 44-inch reamer to accommodate the 30-inch O.D. pipe.

"A 40-inch football (barrel reamer) was used to swab the holes and clean out any excess materials," he said. "In preparation for final line pull-in, the drill stem was attached to the 40-inch barrel reamer. Behind that, a 150-ton swivel with a pull eye was connected and welded directly to the pull head on the pipe string to be pulled into the bore."

Pipe pull-in on all four crossings averaged two to three hours each. "This was primarily due to the quality of the hole that can be drilled and reamed in grey shale. That kind of a formation makes a very good slick bore to pull any product back through with minimal resistance," Whitaker concluded.
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Author:Tubb, Rita
Publication:Underground Construction
Date:Nov 1, 2002
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