If trenchless technology in North America is in its adolescence, then it can be said that auger boring is the grandfather of all trenchless methods. While trenchless methods such as cured-in-place pipe, horizontal directional drilling and microtunneling didn’t come about until the 1970s and later, auger boring had long been an established method for installing pipe with minimal surface disruption.
The roots of auger boring can be traced to coal mines of West Virginia where the technology was used to excavate coal seams beginning in the 1930s (Martin and Grolewski, 2011). For the most part, the basic technology has remained the same with evolutionary improvements in safety, power and capabilities.
The North American Society for Trenchless Technology defines auger boring as “a technique for forming a bore from a drive pit to a reception pit, by means of a rotating cutting head” in which “spoil is removed back to the drive shaft by helically wound auger flights rotating in a steel casing.” Auger boring is typically used for short bores in diameters ranging up to 72 in. and beyond in a range of soil conditions.
One of the historic limitations to auger boring has been in the ability to steer. The traditional method allows for grade accuracy but limited capabilities to steer left and right. Steering the machine involved pulling the augers out and sending workers to the face to make adjustments. In the last decade, however, new methods for installing pipes on line and on grade have had an impact on the auger boring market. Specifically, the development of pilot tube or guided boring methods, which provide precise bores in displaceable soils, can be used in conjunction with auger boring to expand its capabilities.
The pilot tube or guided boring method uses theodolites or lasers in conjunction with a slant-face bit to provide tightly controlled line and grade accuracy in displaceable soil conditions. Once this initial bore is completed, conventional auger boring techniques can be used that follows the alignment of the pilot, allowing for greater accuracy.
“There has been development of the pilot tube guided boring equipment and that technology has really aided the auger boring business,” said Dan Liotti, president of Midwest Mole, a leading trenchless contractor based in Indianapolis. “Once your pilot bore is completed, you connect your leading piece of casing to pilot and that guides your bore. Now we’re able to do very long shots — 300, 400 ft — on really tight line and grade control, which really wasn’t possible before.
“It used to be that auger boring was more of an art because you’re in the pit, 200 ft away from your leading edge, and you had to rely on the feel of the machine and the thrust and push pressures. Now there is a lot more science to the technology.”
While the pilot tube or guided boring technology works well in displaceable soils, other technologies have been developed for use harder ground, including rock up to 25,000 psi, allowing auger boring technology to be used in conditions that were previously left for other methods. These technologies incorporate a cutting head instead of a slant-face bit to complete the pilot bore.
One technology using a cutterhead with rolling disc cutters expands the capabilities of auger boring further, said Arvid Veidmark, executive vice president for Specialized Services Co. (SSC), based in Phoenix. “The new technology enables us to contend with mixed soil and rock conditions that in the past we would have done by hand tunneling. It allows us to contend cobbles and small boulders intermixed wit sand, clay and caliche. It hasn’t changed the foundational process of auger boring; it has just given us the ability to apply it more broadly.”
In addition to steering capabilities, manufacturers are providing machines with more thrust and horsepower, which enable longer drives and larger diameters, said Jimmy Lee, field service technician for American Augers. “It used to be that a 200-ft bore was scary,” he said. “Now we are seeing 600-ft drives with 54-in. pipe. We did a bore of 500-ft with 84-in. pipe. We are reaching out there farther and farther.”
As with any trenchless project, proper planning is the key to success in auger boring. “Proper set up is 85 percent of the job,” Lee said. “I see a lot of problems that arise because the pit is not properly set up. Another factor is taking your time when completing the bore. It is always better in the long run to get it done right the first time.”
Soil investigations are also recommended for auger boring projects, particularly conventional auger boring, which is not conducive for crossing mixed face conditions.
Auger boring has always filled a niche within the trenchless marketplace and recent developments ensure that it will be there for some time to come. “Auger boring is a very solid, cost-effective method of installation, and the advent and incorporation of new technologies allow you to do so much more with the machines than in years past.”
Jim Rush is editor of Trenchless Technology.
AUGER BORING RIG MANUFACTURERS
58256 266th St.
Brownsdale, MN 55918 USA
135 US Route 42
West Salem, OH 44287 USA
315 Pekin Ave SE
East Canton, OH 44730 USA
1687 Cleveland Ave.
PO Box 789
Ashland, OH 44805 USA
Horizontal Equipment Mfg. Inc.
PO Box 5886
Pinehurst, NC 28374 USA
Icon Equipment Distributors Inc./Bohrtec
300 Ryders Ln.
East Brunswick, NJ 08816 USA
McLaughlin Group Inc.
2006 Perimeter Rd.
Greenville, SC 29605 USA
Michael Byrne Mfg.
1855 Earth Boring Rd.
Mansfield, OH 44903 USA
The Robbins Company
29100 Hall St
Solon, OH 44139 USA
1210 Vermeer Road East
Pella, IA 50219 USA
Horizontal Boring Helps Update Pioneer Village
Located just north of Phoenix off of the Interstate 17 sits Pioneer Village, a historic park that educates locals and visitors about Arizona’s history in the territorial days from 1863 to 1912. Opened in 1969 by the Arizona Pioneer Association, it has been a popular destination for field trips, serving over 1 million children. In 2010 the private association was no longer able to keep the park open and the City of Phoenix purchased it and began to make improvements to the facilities. One needed upgrade was to the utilities, including an expanded water source to the village.
Specialized Services Co. (SSC) was selected as the horizontal boring subcontractor by Quest Civil Ventures, the general contractor on the project. A 36-in. steel casing would have to cross from the east side of I-17 to the village on the west side to carry a 16-in. water line. I-17 carries three lanes of traffic in each direction at this location creating the need for a 400-ft bore to span the distance, one of the longest bores performed by SSC to date. To add to the challenge, the final foot of the bore on the west side of the freeway would be crossing under a main fiber optic line that serviced the nearby federal prison and a large portion of northern Arizona.
Co-owner of SSC and head of field operations, Abe Veidmark, was up for the challenge. The combination of the length, solid rock soil conditions and extremely critical line and grade made this a job that demanded his leadership and expertise. SSC was equipped to do this job having added a 36-in. Robbins SBU (Small Boring Unit) head to its equipment fleet in 2009. Prior to the use of SBUs, this job would have had to be performed using hand tunnel to contend with the rock conditions. This would have created a footage production rate of 4 ft per day, whereas the SBU was able to generate 20 ft per day.
The bore was started with the SBU and a 36/600 American Augers bore machine. After 200 ft was installed, the weight of the auger was too much for this bore machine and it was replaced with a 48/54 Barbco bore machine which offered greater horsepower to keep the auger spinning. The bore was completed on almost perfect line and grade, finishing only 2 in. to the right and 3 in. low, easily clearing the fiber-optic line and in exact location needed for the open-cut crews to tie onto. Upon conclusion of the bore, the 16-in. waterline was pushed through the steel casing by SSC on stainless steel casing spacers, connecting the historic village to its new water supply.
Article supplied by Specialized Services Co., Phoenix.