Underground Construction - May 2019 - 23

"We usually work year-round, no matter what the weather is like,"
he explained. "Over the years, we've gotten good at staying warm and
ensuring our machinery is ready to go no matter what the temperature is."

Two-month-long project
For the Garden City sewer expansion project, Glenn's crew was pulled
in to perform four, 42-inch auger bores at depths of 12 to 13 feet in
sandy soils. Bore distances were 75, 272, 280 and 383 feet long, and
the bores exited into manholes at a 0.06-percent drop, so everything
had to be on target.
"Over the years, we've done around 10 bores in the Garden City
area, so we knew what to expect on this one," Glenn explained. "Soil
conditions are sandy, which makes it a major challenge to stay ongrade. Sandy soils can have air voids, water pockets and areas with
sandstone. We also have to battle with the sand packing in around
the casing because of the vibration in the hole."
This project was slated to take a total of 10 weeks, but thanks
to a new tool in the Horizontal Boring & Tunneling fleet, the crew
wrapped everything up two weeks early.
The crew used the McLaughlin ON-TARGET auger boring steering
system to keep the casings on-grade with minimal side deviation.
The 42-inch steering head is welded onto the front of the first casing
being installed. Crew members are then able to check and maintain
the line throughout the bore, with twin-line projection LED lights
enclosed in the steering head, and control the movement of the
steering head-as well as hydraulic, water and electrical lines-from
a self-contained control station.
Horizontal Boring & Tunneling used the system with its existing
auger boring machine. "We're familiar with McLaughlin auger boring
equipment, but that's not what we had on this job-we were using
another manufacturer's machine," explained Glenn. "What's nice
about this system is that it will work with any auger boring machine-it doesn't matter who made it, which makes it a pretty darn
cost-effective option to add to a job."
The ON-TARGET steering system is an upgrade to how crew
members would typically handle these bores. Glenn said they would
have normally used a conventional head with left and right pads and
would have pulled the auger out every 40 feet to measure where they
were. Then, they would adjust direction as needed, reset the auger
and do another 40 to 60 feet. At 100 feet, they would also shoot the
line grade.
"The conventional way is a much more time-consuming process,"
he added. "The ON-TARGET system saves a ton of time-on this job
a full two weeks."

Attention to the details
The six-person crew, along with a pair of John Deere excavators,
prepared for the bores by digging entrance pits. They set 32-foot
trench boxes with a 15-foot spread at a depth of 12 to 13 feet for the
75- and 272-foot bores. They dug a 64-foot long pit between the 280and 383-foot bores, since those backed up to each other. Compacted
rock was used for a base in all the entrance pits.
The shorter bores were under a road that leads to the dairy plant
and the driveway of a trucking company that hauls milk out of the
facility. The 280-foot bore was under a state highway, and the longest
shot was under a road to a sandpit.
"Interrupting everyday operations at the plant or the trucking

company was not an option, which is why the project called us in,"
said Glenn. "While I'm sure people knew there was an underground
crew working in the area, no one had to change normal routines to
accommodate us."
After preparing each entrance pit, the auger boring machine was
lowered into the ground where the first piece of casing with the steering head was added. The crews worked the shorter bores in 20-foot
increments. On the longer bores, they would install 40-foot joints,
which certainly sped up production rates.
"By the time we got to the longer bores, we had complete confidence in the steering system," said Glenn. "So, we welded up two
casings at a time. On the first day of the last bore, we did 100 feet,
120 feet on the second day and 160 feet on the third day. The bore
went quickly."
More important than production rates, was accuracy and quality.
"This was our first time using the steering system, so I was a bit
nervous on the first bore," Glenn said. "We hit all of our marks right
on target." *
FOR MORE INFORMATION:
Horizontal Boring & Tunneling Co., (402) 266-5347, hbttrenchless.com
HammerHead, (800) 331-6653, hammerheadmole.com
John Deere, (309) 748-0114, johndeere.com
UConOnline.com | MAY 2019

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Underground Construction - May 2019

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