by Jim Johnson
In March 1996, Pennsylvania American
Water Co. (PA-American) had nine crews armed with piercing tools
installing water mains beneath roadways in a primarily rural
area. The objective was to connect approximately 450 new services.
Soil components were expected to be mostly clay, occasionally
mixed with rock.
However, it was not expected that
a crew would encounter a solid wall of limestone when performing
a short bore.
 Demo
Requested
Although PA-American already
owned several piercing tools, the company needed to add
to its fleet to accomplish these water-line installations
in a timely manner. This was the opportunity that 247 Equipment
Co. sales manager Mike Schultz had been waiting for. 247
Equipment is an equipment sales and rental operation based
in Eighty Four, PA.
Schultz received an initial request
from Bill Daschbach, operations manager of PA-American's
office in Bethel Park, PA, for a demonstration of a Grundomat piercing tool with its patented reciprocating head. The
Grundomat is manufactured by TT Technologies, Inc., Aurora,
IL.
Schultz arranged the particulars
with Dave Benz, purchasing agent in the Bethel Park office.
Based on the background information provided, Schultz supplied
a 3-in. piercing tool from the company's rental fleet. The tool
came with 50 ft hose and in-line lubricator.
On
Site
While PA-American crews had prepared
the entry area, they discovered that the sand and clay soil
was peppered with an unusually high concentration of rock. What
they didn't know was this was only a forecast of what was waiting
ahead.
Once the piercing tool was launched
for the 25-ft bore, crews moved to the other side of the road
to prepare the exit area. There, they quickly discovered the
shelf of limestone. A jackhammer was used to create an exit
area for the tool.
Even with this seemingly impenetrable
obstacle ahead, the piercing tool was left to continue the bore
as a test of its tenacity. At around 23 ft, the tool slowed
dramatically, yet it continued to make progress. PA-American's
crew chief Tony Cappetta estimated at that point there was 12
to 18 in. of limestone between the tool and blue sky.
Crew members and onlookers were amazed
when the piercing tool's chisel tip first chipped through the
stone in the exit pit. "Just two and a half hours from the time
we started the tool until it poked its head out the other side,"
Schultz said. Normally, this type of short bore can be completed
in 20 to 30 minutes.
The amount of rock restricted the
area of the exit pit, not allowing enough room to remove the
tool. Crews backed out the tool, slid a 3/4-in. copper pipe
into the bore and tapped the pipe.
Reciprocating
Heads
Grundomat pneumatic piercing tools
have a reciprocating stepped-cone head for power and accuracy.
The tiers of the stepped-cone head act as a stabilizer through
an assortment of mixed soils. The reciprocating chisel tip functions
like a pneumatic hammer, breaking up obstacles in the path of
the tool.
To aid in a successful bore, TT Technologies'
in-line lubricators provide a pre-established amount of bio-degradable
pneumatic tool lubricant to properly mix with the compressed
air as it enters the piercing tool. Pneumatic piercing tools
perform better and require less maintenance when the piston/cylinder
combination is well lubricated during use.
Reactions
and Response
When the eight other PA-American
crews heard about the successful bore, they stopped by the site
to see it for themselves. "Everybody was amazed," Schultz said.
One PA-American employee kept the
piercing tool in his car for the next two weeks because he "didn't
want anyone else to use it." PA-American crews traditionally
perform bores through difficult soils with auger boring machines.
The uncommon soil conditions in the area of the isolated bore
allowed the piercing tool to demonstrate its full potential.
As in most trenchless boring operations,
tools are selected based on apparent soil conditions.
"In no way could we envision what
was going to happen," Schultz said. "But it couldn't have gone
any better."
Jim Johnson is a writer for Lime
Valley Advertising, Inc., Mankato, MN.
Trenchless Technology,
July 1996, Page 37
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