Missouri Rock, Ozark Mountains Big Challenge To Gas Line Installation

September 2011, Vol. 66 No. 9

Challenging underground projects attract interest -- contractors who complete difficult jobs like to talk about them and manufacturers of equipment used are quick to tout the capabilities of their products.

Summit Utilities Management Services LLC, Littleton, CO, recently completed a 49-mile-long natural gas transmission line through Missouri’s rugged Ozark Mountains that certainly qualifies as a major challenge worth talking about. In fact, Bret Brown, Summit’s business development and construction manager, called the project the most difficult he’s ever worked on.

The route for the 8-inch steel pipeline was from Aurora to Branson, MO, a popular family vacation center that is home to Silver Dollar City, more than 50 live performance centers, a dozen championship golf courses and a host of other attractions.

Summit was the project manager and the project owner was Southern Missouri Gas.

“This project had the hardest rock we’ve ever encountered, from 16,000 to 22,000 psi,” said Brown. “In addition to the hard rock, work was made more difficult by the terrain’s ups and downs, steep side slopes and drop offs. I’ve had pipe projects in rock in the Rocky Mountains at elevations from 9,500 to 12,000 feet. This one was much more difficult than the Rockies.”

The majority of the pipe was installed by open-cut construction, using six 440-horsepower chain trenchers. Trench width was 24-inches with depths averaging six feet.

Horizontal directional drilling also played an important role on the project. Brown said HDD was used throughout the project, primarily for road crossings and going under streams and rivers.

“There were 40 bores on the route ranging from 80 to more than 500 feet with the average length 150 feet,” said Brown. “The longest was 1,200 feet under a river.”

Rock conditions made HDD segments challenging. The rigs used by Summit included a Ditch Witch JT100 and JT4020, both All Terrain (AT) models for drilling in rock.

The JT100 is the largest Ditch Witch drill unit powered by a 268-horsepower diesel engine. It produces 100,000 pounds of pullback, 12,000 foot pounds of torque and a maximum spindle speed of 270 rpm.

The JT4020 produces 40,000 pounds of pullback, 5,000 foot pounds spindle torque and spindle speeds to 250 rpm.

The dual-pipe All Terrain drilling system is designed to drill through hard rock without the use of a mud motor.

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