Underground Construction - September 2019 - 35

Directional Drilling

Making the Grade: Tracking On-Grade Bores
Two 300-foot bores, 17 feet deep, through
44,000 psi of basalt - all at a 0.75 percent
grade. It's just another day's work for
Logan Kallwick and his crews.
"That job was a tough one," said Kallwick,
field supervisor for Downing Diversified in
Kalama, Wash. "But those are the kind of
jobs we're known for. We have a reputation
in the Portland (Ore.) area for going after
grade bores and doing them right."
Combined with maximum productivity
from a fleet of directional drills and the
skillful expertise that comes from decades
of experience, the company's reliance on
accurate walkover locating and seamless
data transmission to a display on the drill
has enabled the company to trim time off
difficult grade bores.
The St. Helen's job, for example, went
quicker than one might think. Chipping
away at the volcanic rock was so difficult,
the pit itself took the general contractor
more than two weeks to dig. Even so, the
entire job was completed in just 21 days.
Using a Ditch Witch JT40 directional
drilling rig, Kallwick's team installed 600 feet
of 14-inch HDPE pipe in the tough basalt
terrain of St. Helen's, Ore. The crew maintained less than two feet of fall in each of the
two 300-foot bores. That kind of precision
drilling doesn't just happen - it's earned.
"You have to be thorough," Kallwick said.
"It's not a typical bore where you're just
shooting from point A to point B. You'll
usually see guys go six, eight, 10 feet at a
time between checks and locates. But when
we were piloting that bore, I was checking
every two to three inches to make sure we
were sitting on grade and making corrections every bit of the way."

Time investment
Of course, that kind of intensity takes
time. That's why grade bores typically take
longer than usual. The key, Kallwick says,
is to make sure that extra time is spent
moving forward, not idle.
For example, the company utilizes
walkover tracking rather than relying on
both a front and a back locate, which could
translate into two or three time-consuming
locates per check. In walkover mode, the
Subsite Electronics TK RECON system used

provides immediate locates directly over
the head, instantly feeding that information to a Subsite display on the drill. Rather
than waiting for a locator to take readings
30 feet in front of the head or 20 feet
behind it to get direction and depth data,
the drill operator gets accurate information
quickly, right at the drill seat.
"We're doing these bores where we've
got to have three quarters of an inch precision with just 0.75 percent deviation, and
we're 17-feet deep in some of the hardest
material you can find," said Kallwick.
"We're still able to track the head quickly
and accurately and complete these jobs
successfully. I have immediate information
at my fingertips so I can sit on the drill and
interpret depths and percentages constantly as we're moving. I can continue to progress forward instead of waiting around for
that information to relay and then having
to take my time to move forward. Without
it, you could take three or four times longer
to do something like this."
Kallwick also pointed out a time-saving
benefit when it comes to vibration.
"We started shooting one of these grade
bores - a 1.2 percent - using a different
locating system. But with all the vibration,
our pitches were jumping from a plus seven
percent down to a minus four percent. We
would have to stop to get a reading in the
middle. But the TK RECON system seems
to buffer the percentages and give us a
consistent reading as we move along. It'll
go up and down a little bit, but that's what
the head is actually doing so we'll make
adjustments. It saves a ton of time."
From storm systems and gravity sewer
lines to a 1,100-foot shot with a six-inch

pipe for jet fuel at the Portland International
Airport, Downing Diversified has tackled
all kinds of tough grade bores.

Reputation
"If you have that, then it comes down to
using the right equipment and making sure
it is calibrated and operating properly. For
locating, that means using something accurate and reliable enough for direct walkover
locates in deep, difficult conditions. It's vital
that your locator is walking and standing
right over that head, so you know exactly
where it is at that time."
As municipalities, general contractors and
others continue to recognize the benefits
of directional drilling for grade projects,
more of these opportunities are becoming
available. When bidding and planning for
these jobs, it's important to know that
boring on grade at tight tolerances and
for long distances is not only possible
with walkover locating, it's preferred.
This enables contractors to be more
productive and successful which, ultimately,
is good for the industry as a whole.
The Downing Diversified team has more
than 30 years' experience in the HDD
industry. Jimmy Downing began gaining
his extensive knowledge and love of drilling
in 1989 when his father purchased the first
model drill manufactured by Ditch Witch
(one of the first mini rigs to come to the
Pacific Northwest). In 2012, he founded his
own company, Downing Diversified. *
FOR MORE INFORMATION
Downing Diversified, (360) 673-4433,
downingdiversified.com
Subsite Electronics, (800) 846-2713, subsite.com
Ditch Witch, (800) 654-6481, ditchwitch.com
UConOnline.com | SEPTEMBER 2019

http://www.downingdiversified.com http://www.subsite.com http://www.ditchwitch.com http://www.UConOnline.com

Underground Construction - September 2019

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