Challenges and Opportunities for Innovation in the Public Works ...

Trenchless Pipe Replacement
PIM: The Technology can be expected to be up to 44%, depending on
surface conditions which are site-specific.
There used to be only one way to replace a buried
pipeline: dig it up, tear it out, and install a PIM's Benefits
new one. This process can be very expensive, with
much of the cost tied up in restoring surfaces dam- The Fort Belvoir FEAP project successfully demaged
during digging. onstrated several of the pipe mole's benefits, which
include:
Today an alternative to this trenching process is
the pipeline insertion method (PIM). Nicknamed * Limits disruption to the landscape and adjathe
"pipe mole," this technology breaks up an exist- cent structures
ing pipe while it is still in the ground and replaces
it with HDPE pipe of equal or larger diameter. * Avoids interruption to traffic and other local
PIM requires very limited digging at every other activities
manhole, for lateral connections, and where the
mole exits. . Easily corrects hydraulic overloading by inserting
larger diameter pipe
The pipe mole looks like a missile with four fins.
It carries a pneumatic hammer in its nose which e Reaches areas hard to access even by digliterally
bursts its way through an old pipe while ging--easements, rough terrain and sites
dragging the new pipe behind it. The mole is air- with limited work surface
driven. A hydraulic jack "pushing machine" behind
it feeds the new pipe. A cable is attached to the e Improves safety to workers and local resifront
of the mole and to a winch that guides it dents.
through the pipe. In addition to the pneumatic
pipe mole, a hydraulic model is now available. Gaining Acceptance
Fort Belvoir FEAP Demonstration First developed in Great Britain, PIM is becoming
widely accepted in the U.S. for replacing and
At Fort Belvoir, VA, a 240-foot section of sewer upsizing all types of buried pipes (water, sewer,
pipe was replaced using PIM technology. An 8- gas). PIM is patented and marketed in the U.S. by
inch main sewer line replaced an existing 6-inch PIM Corp., Piscataway, NJ. USACERL technical
main that traveled between two manholes and report N-89/07 (April 1989) describes the Fort
under two parking lots, one well traveled street, a Belvoir demonstration in detail. A technical manuretaining
wall, and a fence. None of these struc- script on the technology is also available from
tures was disturbed. USACERL.
The demonstration included tests to determine
the mole's effect on adjacent utilities. Results for
stress on adjacent pipes, vibrational damage, and Points of Contact
pipe deflection were all in acceptable ranges.
Richard Scholze, U.S. Army Construction
Saves Excavation, Replacement Costs Engineering Research Laboratory, PO Box
4005, Champaign, IL 61824-4005, COMM
With trench pipe replacement, site restoration 217-373-6743. Malcolm McLeod, U.S.
accounts for up to 80 percent of the total project Army Engineering and Housing Support
cost. Thus, PIM brings the highest savings to job Center (USAEHSC), Fort Belvoir, VA
sites where surface restoration will ccst the most. 22060-5516, COMM 703-355-2003.
For example, 1989 replacement costs for a hard-toreach
easement averaged $100 per linear foot using
PIM, depending on the length of pipe replaced and
other considerations for upgrading a 6-inch to an 8inch
sewer line. The savings over trench-type work
Issued by USAEHSC, Fort Beloi, VA lAW AR 25-30. Additional copies are available from Ow FEAP Infomatob
Center, PO Box 4005, Champaign, IL 61824-4005, phone 217-352-6511, ext 386.
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