Tight Urban Directional Drilling

CenterPoint Energy Inc., Houston, TX, is a domestic energy delivery company that includes electric transmission and distribution, natural gas distribution, competitive natural gas sales and services, interstate pipelines and field services operations. It serves more than five million metered electric and natural gas customers in six states: Texas, Arkansas, Louisiana, Minnesota, Mississippi and Oklahoma.

The company’s electric transmission and distribution business, CenterPoint Energy Houston Electric LLC, serves two million metered customers with an infrastructure that includes18,995 miles of underground distribution lines, 27,241 miles of overhead distribution cable and 229 substations.

CenterPoint has continuing programs to maintain and upgrade its transmission and distribution infrastructure.

A current project in downtown Houston is to install 12,788 feet of underground duct bank to contain three 8-inch and three 4-inch PVC conduits from the Garrott Street substation to the Midtown substation and ending at the Polk Street substation. Boyer, Inc., Houston, is the general contractor.

Ninety percent of the route is through urban areas, so only 2,200 feet is projected to be open-cut construction, said Shawn Adams, Boyer general foreman. Horizontal directional drilling (HDD) and wood box tunnels will be used for the remainder of the construction.

Restrictive HDD
Two difficult HDD shots in very restrictive areas were completed by subcontractor Laney Directional Drilling Co., Humble, TX.

“Laney drilled two shots — one for 1,830 feet, the other for 1,300 feet — in two of the
narrowest streets in the most cramped areas on the project,” said Adams. “For these street crossings, we switched from PVC to HDPE and pulled the bundle of three 8-inch conduits, four four-inch conduits, and added a fourth ‘extra’ 4-inch conduit in the 8-inch bundle to space conduits within the package.”

To handle the weight of the bundles, a powerful drill rig was required.

A 300,000-pound-pullback drill rig manufactured by Laney was used for both street crossings, said David Poage, Laney surveyor. The HDD unit is powered by a 500-horsepower engine. It develops 47,000 foot pounds of torque. The machine has a footprint of eight by 48 feet, a tight fit on both locations.

“We had very little room for set up on both entry and exit sides of both bores,” said Poage. “Because of restrictions on the amount of time the drill unit could be in the roadway, we had to move the drill rig from the entry to exit side to pull in the bundles on both installations.”

Drilling conditions were good, Poage said, in soil consisting mostly of clay with some sand. After completion, each pilot bore was enlarged with 22- and 36-reamer passes and then swabbed.

Eight- and four-inch HDPE pipe was fused and bundled for pullback.

“Because of space limitations to layout the assembled bundles,” we had to get creative,” said Boyer’s Adams. On the first 1,830-foot run, we pulled around two 90-degree turns, three 90-degree turns on the second.” Pullbacks required one day.

Pipe handling
On this project, Laney used for the first time a LeValley Industries Deckhand pipe handling system for drill stem during both drilling and pullback operations. Deckhand components mount to the hydraulic and electrical systems of various-size excavators in using quick-connect couplers.

Deckhand components include upper and lower heads with mounting beam and interchangeable grab arms. Deckhand is operated using excavator controls. A display panel allows the operator to monitor and adjust all functions. The three interchangeable grab arms securely lift, lower, tilt and rotate pipe a full 360 degrees, giving operators the versatility to handle pipe in multiple working angles. A display panel allows operators to monitor and adjust all functions, pressures and flows from inside the cab.

Poage said on the CenterPoint project, Deckhand was mounted on a Caterpillar 325 excavator and reduced the time and labor for adding and removing drill stem.
“The Deckhand will provide safety and cost benefits for any HDD project,” said Poage.

Boyer Inc. specializes in rehabilitation and replacement of utility infrastructure and has the capabilities to self-perform more than 95 percent of the projects in which it is involved. In addition, Boyer performs many types of civil construction, inland marine construction, instrumentation and control systems, equipment sales and rental, and landscape and irrigation construction.

Laney Directional Drilling celebrated its 20th anniversary in 2009 and today offers HDD capabilities of installing pipe in diameters of four to 60 inches to distances of more than 7,000 feet. Laney uses drill rigs of its own design and construction and today operates 12 HDD units ranging in size from 300,000 to 1.7 million pounds of pullback.

Laney Directional Drilling, (281) 540-6615, www.laneydrilling.com
Pipe Line Machinery, (713) 939-0007, www.pipelinemachinery.com
Boyer Inc., (713) 466-5395, www.boyerinc.com

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