Underground Construction - July 2017 - 30

Pipe Slitting

Use of the pipe slitting technique eliminated the
need for a 2-foot-wide trench across the airport's
paved surface to replace a deteriorating water
supply line. Routine and even emergency airfield
activities continued without any interruption from
the noninvasive technique.

tooling, giving him a similarly noninvasive, trenchless alterative for
non-frangible pipe materials like
HDPE or copper. These pipe materials deform rather than fracture,
making them poor candidates for
basic pipe bursting. Pipe slitting
tools feature blades that sever
pipes laterally, as well as expanders that press the old pipe away
from the pipe path to make room
for new pipe drawn in place by the
tooling assembly as it progresses.
Johnson believed the pipe slitting technique would be ideal for
the thin-walled HDPE of Frasca's
water line. However, he needed
more than twice the length of his
PB30 cable to slit from the hangar's tee to the FBO.
He contacted HammerHead
Trenchless representative Nate
Hrabosky to get a longer cable,
but Hrabosky counseled against
using a PB30 unit for a run of that
length. It would certainly have
more than enough power, but the
compact PB30 has no cable handling system.
"Can you imagine the weight of
350 feet of ¾-inch cable? It would
be difficult to move, let alone manhandle during the pull, with all
that cable having nowhere to go.
For longer pipe slitting and pipe
bursting runs, a winch-like device

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is a much better option," explained
Hrabosky.
The HammerHead HydroGuide HG12 comes with its own
2,080 feet of 5/8-inch cable and a
pulling capability rated to 12 tons.
Hrabosky also brought Johnson
a lower slitting unit and two pipe
slitting heads with replaceable
hardened-steel blades from HammerHead Trenchless' Same Path
pipe slitting system.

Pipe slitting
Hrabosky stayed onsite to help
Johnson, who used a mini-excavator to dig up and remove the
300 feet of water line that ran
between the hangars. Where the
tee had been, Johnson widened his
4-foot-deep, 2-foot-wide trench
to accommodate the self-deploying downrigger of the winch. This
5-foot long, 4-foot-wide pit provided sufficient room for backing
to support the pull against the
trench's soil wall.
Once the downrigger was deployed and set against the backing,
Johnson threaded the winch's cable through a slitting head pointed
toward the FBO. According to Hrabosky, slick plastic pipe can have
a tendency to slide in the ground
toward the downrigger during a

pull. Placing a second slitter backward on the cable in the working
pit slits pipe before it gets to the
downrigger.
Then Johnson paid out the cable completely through the water
line to attach it to the Same Path
assembly in the FBO's basement.
The new 1¼-inch HDPE pipe was
attached behind the slitting assembly. The FBO basement gave Johnson plenty of room to work with
the stiff coil of new HDPE as it
was drawn through the hole in the
foundation wall, following the pipe
slitter assembly it was attached to.
Johnson took the precaution of
taping a copper tracer wire to the
new HDPE, which would be pulled
in with it. Should something go
wrong, Johnson would be able to
locate the wire. Plastic pipe itself
cannot be located.
The pipe slitting process itself
was quick and simple. "The pull is
always the easy part," said Johnson. "We finished the run in about
35 minutes."

911
Johnson knew that trenchless
alternatives to open-cut pipe replacement added greatly to the service he could offer his customers.
It would save them demolition and

restoration costs. It would allow
pipe replacement without marring
surface attractions. However, he
probably was not thinking of it as
potentially lifesaving until this job.
"An ambulance drove past us
where we were working to meet a
medevac plane that had landed,"
Johnson explained. "I could see a
little girl on the stretcher as they
rushed her from the plane to the
ambulance. She probably couldn't
have been more than four years
old. Had we cut a 4-foot-deep
trench across that tarmac, I don't
know ... I suppose they would have
still made it work out somehow
... maybe found a way to drive
around. But they didn't have to.
Nothing we were doing was in
their way."
Mid-State's use of trenchless
techniques to replace sewer pipe
and water lines did save Frasca Field the cost of cutting up its
tarmac. Its greater value, however, was that it permitted routine
airport operations to carry on
unabated, including emergency
services.
FOR MORE INFORMATION:
Mid-State Sewer Services
(217) 344-5424
HammerHead
(800) 331-6653, hammerheadmole.com
Underground Construction July 2017

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Underground Construction - July 2017

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