The trenchless process of pipe bursting
has been gaining wide acceptance with municipalities and contractors
throughout North America over the past decade.
 Best known for rehabilitating
municipal water and sewer lines, the rising popularity of pipe
bursting is largely attributable to innovative contractors who
have promoted the trenchless technology as a cost-efficient
method. Another important selling point is the inherent
positive social factors of little to no surface disruption.
As in Europe (where pipe bursting
was developed), North America's infrastructure is showing signs
of age. Water and sewer lines often need rehabilitation
as they get older. However, because of urban build-up,
the traditional method of trenching to replace failed lines
is no longer desirable, if not impossible to do. Therefore,
contractors are frequently turning to trenchless technology
such as pipe bursting as an alternative.
The pneumatic pipe bursting method's
primary application has been to replace clay sanitary sewer
lines from 10 centimeters to nearly one metre in diameter.
The method has also been used successfully for the replacement
of water, storm sewer, gas, telephone and power casings, conduit,
and duct.
Over 90 percent of bursting projects
worldwide have been performed with pneumatic pipe bursting tools
and equipment. This translates into nearly 10,000 kilometres
of successful bursts and replacements.
The bursting process starts with
determining the length of &failed& pipe and exposing it
at two ends (usually at manholes) to serve as entry and exit
points. Then, the bursting tool with expander is positioned
at the entry point. Attached to the head of the tool is
a steel cable emanating from a winch located at the exit point.
The winch is important because it provides constant tension,
helping to guide the tool. The pneumatic tool is then
launched directly into the failed pipe.
The combined effect of the percussive
action of the pneumatic tool and constant tension from the winch
enables the tool to effectively pound through the old pipe.
The expander pushes the host pipe fragments and surrounding
soil out of the way for the safe installation of the new pipe.
The new PE pipe, attached to the back of the tool, follows it
into the bore. Because the expander is selected with the
outer diameter of the new pipe in mind, a tight fit is guaranteed.
Televising of 300 metres of a 50
year old sanitary sewer line within a forest reserve near Chicago,
Illinois showed a high level of infiltration. As a result,
governmental agencies involved decided the line needed to be
replaced.
 &We
had a sensitive area, very mature trees,& stated Teofilo
Noriega, Village of Niles director of public services, referring
to the forest reserve. Traditional methods of trench
and replace were deemed unusable due to a forest service
mandate that no trees could be destroyed in this easement.
Noriega explained how city officials worked as a team to
address to concerns of every government agency involved
in order to arrive at an acceptable solution.
Initially, the trenchless method
of pipe lining was considered. However, it was dismissed
when officials became aware of the extent of tree root intrusion
and sagging found within the pipe.
After learning about the pipe
bursting process and subsequently discussing the merits
of this trenchless process with contractors, municipal officials
allowed bursting to be included into the bid specifications.
&We're not afraid to look at new technology,& offered Noriega.
Scott Jochim, Village of Niles superintendent
of engineering, reviewed video tapes, trade magazine articles
and documented case studies about pneumatic pipe bursting.
Interested by what he saw, Jochim then contacted those municipalities
who have had experience with the trenchless technology to get
their candid reactions to it. &All responses were affirmative,
so we felt comfortable giving it a shot,& said Jochim.
When the Niles rehabilitation job
opened for bid, LoVerde Construction of Wheeling, Illinois researched
the pipe bursting process for bidding purposes. LoVerde
Construction President George LoVerde met with pipe bursting
specialist Rich Prosser of TT Technologies, Inc. TT Technologies
is a licensed manufacturer of pipe bursting equipment in Aurora,
Illinois.
Prosser went through the Village
of Niles specifications and worked with the LoVerde Construction
staff to establish a plan of action. Runs were determined
and tool requirements were discussed.
George LoVerde then compiled an estimate.
Four government entities would be reviewing the bursting specifications.
They included the Cook County Forest Reserve, Metropolitan Water
Reclamation District of Chicago, Village of Niles Public Services,
as well as the State of Illinois.
Based on LoVerde's commitment to
leave the trees in tact, along with an acceptable cost estimate,
LoVerde Construction was awarded the bid. &Our team considered
possible solutions, and the solution was pipe bursting,& said
Noriega.
The contractor utilized a complete
bursting system from TT Technologies, which included a pneumatic
pipe bursting tool, expander, 89 kN hydrostatic winch and bentonite
(lubricant) pump.
Approximately 366 metres of failing
sewer pipe was burst and replaced in three runs. The first
bursting run (76 metres) incorporated the upsizing of 380 millimetre
clay pipe to 405 millimetre PE (SDR 17). The soil was
incredibly dry, due to hundreds of trees that lined and grew
above the sewer line.
Crews used a Grundocrack Gigant (254
millimetre diameter) with a front expander to perform the run.
Even though a Grundomudd pump was providing bentonite lubrication
to the tool and pipe, the burst proceeded more slowly than anticipated
at a rate of about one foot per minute. This was also
the case for the second burst (84 metres).
After considering the slow rate of
the first two runs, the contractor decided to use a Grundocrack
Koloss bursting tool (with rear expander) for the considerably
longer third and final run. The Koloss offered a 40 percent
larger diameter (356 millimetres), and nearly twice the power
compared to the Gigant.
With the final leg of the burst stretching
out 163 metres, there was some concern that drag would become
a factor about midway through the burst due to the combination
of upsizing and fill-in.
The contractor would have preferred
dividing the run into two. But, that would have meant
the destruction of some mature trees for additional entry and
exit pits. With that in mind, crews prepared for one long
burst.
 Crews
pumped bentonite at the maximum capacity for the final run,
and it helped. Moving at a rate of 500 millimetres
per minute, the 163 metres of host pipe was burst and replaced
in less than six hours.
The additional lubrication combined
with a more powerful bursting tool added up to a successful
installation. &With pipe bursting, you pull in one
continuous pipe. That means the opportunity for infiltration
is nonexistent,& said Noriega.
He also stated how pleased the
Village of Niles staff was with the speed of installation.
This offered positive social benefits because residents
did not have to be out of sewer service.
Most important, according to Noriega,
was, &We saved trees, we saved money.&
Contractors from Monterey to Montreal
have shared their pipe bursting success stories and secrets
with each other in order to further the development of this
trenchless technology. As a result, these innovative contractors
have brought pipe bursting to new heights. In fact, pipe
bursting contractors in North America hold the records for largest
diameter bursts and longest single run bursts.
Not only does this bursting technology
limit surface disruption that can result in negative social
and environmental impacts, but it also saves millions of dollars
for municipalities and helps maintain quality infrastructure
for end-users.
TT Technologies
Trenchless Today (Canadian Environment
Protection), September 1997, Vol. 2, No. 2, Pages 19-21
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