Laser-Guided System Helps Complete Three Intricate Bores
Plains Midstream Canada selected Specialized Services Company (SSC) to install sleeves at three locations to accommodate a new line being added to the underground infrastructure used to load and unload LPG from tankers and railcars at the Bumstead facility, an underground LPG storage cavern located along the Interstate 10 corridor between Phoenix and Los Angeles.
Project owner Plains Midstream, headquartered in Houston, is involved in crude oil transportation, gathering, marketing, terminaling and storage as well as marketing and storage of liquefied petroleum gas (LPG).
Situated some 2,000 feet below ground at the juncture of a major rail line and tanker truck transit point, the 133-million-gallon facility is composed of three underground salt-dome storage caverns, a 24-car rail rack and three truck racks on the surface with the capability to unload six trucks simultaneously. To expedite the loading and unloading of tankers and railcars more quickly, Plains Midstream installed an additional 6-inch diameter high-pressure gas line.
The project awarded to SSC involved installing six separate 12-inch diameter steel casing sleeves with a 3/8-inch wall thickness at three separate locations. Abe Veidmark, vice president of the auger division for SSC explained the challenges faced by the trenchless installation contractor, and the decision to use an innovative new approach for completing these intricate bores.
“It wasn’t so much the ground conditions or pitch, but rather the pinpoint accuracy of the line grade we needed to achieve for us to succeed,” he said. “When installing smaller material with standard auger boring, it is nearly impossible to steer with the accuracy required for all of these bores. In all likelihood there would have been a good deal of drifting (with auger boring), something inherent with this method for shorter distances. All of these bores were less than 200 feet.”
After reviewing the specifications and intricacies they would face at each of the three sites, Abe, along with brother Arvid, executive vice president and senior estimator for SSC, recommended an innovative, alternative approach. Months prior, Arvid attended a demonstration where a Vermeer laser-guided boring system is featured that had the capability to complete smaller-diameter bores with pinpoint accuracy and strict on-grade precision. Although designed primarily for sewer and water projects, the two felt the AXIS™ guided boring system was the answer they were looking for.
AXIS is a pit-launched trenchless installation method designed to achieve precise, on-grade accuracy while eliminating some of the difficult steps associated with other installation techniques. The system was designed to install 8-18-inch pipe at lengths up to 350 feet, although larger diameter and longer length bores have been completed. AXIS is also capable of maintaining the strict tolerance and accuracy required for the types of installations facing SSC as specified in the Plains Midstream job. The system requires an entry pit where the core of the system is placed, composed of the rack, drill casings, drill head and pipe laser. Located outside the launch pit is the vacuum power unit, vacuum tank and the rack power unit.