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by Jim
Schill
Recently, west coast pipe rehabilitation
contractor ARB, Inc, Lake Forest, CA, was able to do something
few contractors in North America have, replace a 6-inch 10
gauge steel water main with 8-inch HDPE through pipe bursting.
The project, completed for the South Tahoe Public Utility
District (STPUD), South Lake Tahoe, CA, was accomplished with
the help of trenchless equipment manufacturer and Associate
NUCA member TT Technologies, Aurora, IL.
The existing 330-ft steel water
main was being replaced as part of a water tank rehabilitation
project. Because the line ran through a section of national
forest, open cutting was not an option. Pipe bursting was
the method of choice for this particular project. However,
traditional pneumatic pipe bursting has been largely unsuccessful
in bursting ductile and steel pipe. ARB Rehabilitation Manager
Dave Arthurs turned to the hydraulically powered Grundoburst
from TT Technologies.
Bursting Steel
The recently introduced Grundoburst
1000G (the largest of three models) is a hydraulically operated
static bursting system. According to TT Technologies Pipe
Bursting Specialist Collins Orton, several of the system’s
features make bursting steel, as well as ductile iron, possible.
He said, "During the static bursting process, a special
bladed roller cutting head is pulled through the existing
line by the bursting unit. As the bladed rollers are pulled
through, they split the host pipe. An expander attached
to the rollers forces the fragmented pipe into the surrounding
soil while simultaneously pulling in the new pipe."
The specially designed bladed
rollers are essential to the bursting process. The blades
actually split the host pipe instead of ripping or tearing
it. This makes the process very clean and prevents potential
damage to the product pipe.
According to Orton, this is a
significant advancement in trenchless pipe replacement.
He said, "I see this technology having a great impact
on the gas and water industries. There are miles of steel
and ductile iron lines in California and throughout North
America that are undersized and/or deteriorating and need
to be replaced. Some are even required by legislation to
be replaced. Being able to replace and upsize these lines
without digging them up, is a benefit to everyone."
The Job
For the STPUD project the ARB
crew dug a 5-ft x 15-ft launch at the beginning of the run
and another 5-ft x 20-ft exit pit 330 feet away. The bursting
unit was positioned in the exit pit and connected to a hydraulic
power pack. The crew then began inserting the Quicklock
bursting rods through the host pipe and into the launch
pit. The patented rods are linked together, not threaded.
This speeds installation and breakdown, and prevents twisting
in the line during operation. A flexible guide rod attached
to the front of the first rod was used to help ensure the
smooth installation of Quicklock rods.
Once at the launch pit, the ARB
crew removed the guide rod and attached the bladed cutting
wheels, bursting head, expander and new HDPE. The entire
configuration was then pulled back through the host pipe
by the hydraulic bursting unit. The 8-inch HDPE was installed
without incident.
After the HDPE was in place,
the ARB crew removed the bursting equipment. The new main
was then chlorinated, tested and put into service.
Arthurs said, "Our crew
was very impressed by how easy the machine was to operate.
They were even more impressed that we were able to split
steel pipe. Overall, we were very pleased with the results
of the project. This was our first attempt bursting steel
pipe. I anticipate a good deal more of this work in the
future."
Utility Contractor,
March 2001, Pages 31,34
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