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by Jim
Schill
When
the benefits of trenchless pipe bursting are discussed,
key phrases like no-dig, minimal disruption, cost savings,
increased capacity and environmentally friendly are
often heard. The images they conjure are immediate:
a beautifully landscaped yard left unharmed, a roadway
that remains open to traffic, boulevard trees untouched.
Chalkboards, desks, computers and lockers don’t
immediately come to mind. They did recently for Tim
Evans, however.
Evans,
wastewater division manager for Enviro-Flow Companies,
Zanesville, OH, was recently approached by school officials
at the Guernsey-Noble Vocational School in Senecaville,
OH, about problems with a sanitary sewer main. The
main traveled directly underneath the school and had
been plagued by reoccurring blockage. Evans said, "An
open cut project was not the best option. With the
amount of potential disruption inside the school from
an open cut application, we suggested a trenchless
replacement option, pneumatic pipe bursting."
For
the bursting project, Evans chose the Grundocrack pneumatic
pipe bursting system from TT Technologies. TT Technologies’ pipe
bursting specialist Mark Maxwell was contacted for technical
support.
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The
150-ft sewer main ran beneath the school, traveling
under the school’s kitchen and several computer
classrooms. Trenchless pipe bursting was chosen to
minimize disruption and costs.
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Experienced
Contractor
Enviro-Flow
Companies was founded in 1976. The company provides industrial
and municipal water and wastewater services throughout
the state of Ohio. Over the past 25 years, the company’s
services have grown to include, among others, pipe line
televising and inspection, I & I studies, sewer cleaning,
electronic pipe location, manhole rehabilitation and, most
recently, pipe bursting.
Evans
said, "Enviro-Flow
Companies has two divisions. First, Enviro-Flow Service
Co. serves all of Ohio. This division takes care of commercial,
industrial and municipal customers. Second is a plumbing
and drain service. That division takes care of residential
and commercial customers for Licking, Muskingum, Guernsey,
Perry, Morgan and Noble counties." Enviro-Flow would
tackle the troubled sewer main at Guernsey-Noble Vocational
School.
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Enviro-Flow
Companies selected a 5.75-inch diameter pneumatic
Grundocrack PCF 145 from TT Technologies for bursting
the cast iron main. Note the long guide head on the
front of the tool. Equipped with cutting blades, the
guide head is one component that makes bursting cast
iron possible.
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Tuberculated
Line
The combination 4- and 6-inch diameter cast iron sewer main
was installed when the school was built in 1969. Over the
past several months the line experienced numerous backups
and forced school officials to take action.
Evans
said, "The
line kept plugging up. We’d go up there and jet it;
clean it out. Finally it got to the point where I said,
‘Listen, this is silly. Let’s televise it and
see what the problem is and see if we can’t get this
fixed.’ After looking at the line, we recommended
that it be replaced."
The
150-foot section of main ran below the school’s
kitchen area and crossed under several computer classrooms.
Approximately 60 feet of the main was 4-inch diameter
cast iron, and the remaining 90 feet was 6-inch cast
iron. Seven lateral connections also needed to be excavated
and replaced. One of the most challenging aspects of
the job, however, was overcoming the host pipe material,
cast iron.
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The
pneumatic pipe bursting tool enters the launch pit.
Approximately 60 feet of the run was upsized from
4-inch cast iron to 6-inch HDPE. The remaining 90
feet was replaced size for size, 6-inch cast iron
to 6-inch HDPE.
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Tool Configuration
Cast
iron pipe tends to break several feet in front of a standard
pipe bursting tool. This causes the potential for two major
problems. First, the shards of cast iron pipe are sharp
and can actually cut winch lines. Second, pipe fragments
can build up making the host pipe impassable. This can cause
the pneumatic pipe bursting tool to change direction and
veer off course.
Essential
to the success of the job was the use of a guide head
or "schnozz." The
guide head is attached to the front of the pipe bursting
tool and adds needed tool length. Because the guide head
is smaller in diameter than the host pipe, it guides
the tool and allows it to get into the pipe and break
it at its weakest point, the inside.
Besides adding
tool length, the guide head helps protect the winch line.
In many configurations, the winch line is connected to the
front of the guide head instead of the front of the tool.
This keeps the line ahead of the actual bursting and out
of the way of shards of pipe.
Maxwell
said, "Cutting
blades can be used in conjunction with a guide head.
The blades are welded directly to the guide head. The
blades focus the percussive action of the tool and greatly
enhance overall bursting power, allowing the tool to
successfully burst difficult host pipes, like cast iron
as well as many point repairs like PVC."
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The
exit pit was located outside of the building. The
new HDPE section was connected to the remaining cast
iron section with a mechanical joint. The cast iron
main traveled an additional 90 feet where it tied
into a manhole.
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Site Prep
Work
began on the project in mid July. The Enviro-Flow crew used
a TT Technologies 5.75-in. diameter Grundocrack PCF 145
pneumatic pipe bursting system, equipped with an 7-in. rear
expander and a specially-designed guide head with cutting
blades for cast iron pipe. A 10-ton Grundowinch was used
to guide the bursting tool through the host pipe.
According
to Maxwell, the Grundowinch also played a key role.
Maxwell said, "The Grundowinch provides constant
tension at variable speeds. It is able to compensate
for changes in bursting speed and is able to prevent
slack from developing in the line. This ensures a smooth
bursting operation."
The
Enviro-Flow crew dug a 4-ft. by 12-ft. launch pit inside
the school with a mini excavator. Evans said, "The excavator is
extremely compact, just 36 inches wide. In this situation
it allowed us to get into areas that normally we’d
need to dig by hand. It definitely saved us time."
The launch pit
was located beside the kitchen. The gravity-fed line was
approximately 50 inches deep at the start of the bursting
run and 72 inches deep at the end. The crew fused 150 feet
of 6-inch High Density Polyethylene (HDPE) pipe and staged
it through the kitchen area to the outside of the building.
The exit pit was dug at the end of the run, outside, 150
feet away. The 10-ton Grundowinch was placed at the exit
and bursting was ready to begin.
Bursting
in Action
Bursting operations went extremely well. The entire 150-foot
run was completed in just 30 minutes. Evans said, "One
of the school’s officials wanted to come down and watch
the pipe bursting in action. We told him we’d be ready
to go around 2:00. Well he was running a little behind
schedule and called when he was ready to come down. We
had to tell him that the pipe was already in the ground!"
After the burst
was complete, the Enviro-Flow crew tied in the seven lateral
lines using service saddles and specially designed tee connections
for HDPE pipe. Each lateral connection took approximately
one hour to complete. The new HDPE section of main was connected
to the remaining section of cast iron pipe with a mechanical
joint adapter. The remaining section of main traveled an
additional 90 feet before tying into a manhole.
Bursting
Benefits
School officials were extremely pleased with the results
of the pipe bursting project. Evans said, "Pipe bursting
the project probably saved us two to three weeks over an
open cut. Plus it would have been a lot more expensive for
the school if they had to go in there and replace carpet,
replace a bunch of tile, and disconnect and move all the
computers. We were able to save the school a tremendous
amount money and time through pipe bursting." Note:
Advantica, formerly British Gas, owns the method patent
on pipe bursting.
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A
bird’s eye view of the bursting operations.
The school was able to avoid costly restoration through
the use of trenchless pipe bursting.
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