Underground Infrastructure - July 2023 - 38

Rehab Technology
These factors are typically reviewed
and evaluated through the planning and
design phases to ensure that the proper
rehabilitation technique is chosen for the
intended application. This was the case
for this project where, given the design
criteria and site layout, cured-in-place
pipe (CIPP) was the most cost-effective,
best-fit solution to fully restore this failing
segment.
CIPP is engineered and manufactured
to project specifications and is
designed as an independent solution to
meet the pipe rehabilitation goals. This
pipe-within-a-pipe method can rehabilitate
almost any pipeline between 6- and
96-inch diameter and is a fully structural
AWWA Class IV solution, meaning there
is no reliance on the existing host pipe for
the new service life.
related to the focus of the intended inspection.
In addition, sometimes the location
where the leak surfaces is not where the
leak actually occurs. When a pipeline has
a leak, depending on the topography, soil
conditions and other adjacent infrastructure
features, it can begin to show itself in
another location that is not as intuitive.
For a sanitary sewer overflow (SSO)
situation, as was the case here, the first
priority is to mitigate the leak and provide
a temporary repair to stop further
leaking. With this repair in place, a team
of engineers and operators can then begin
the design and implementation of a longterm
solution.
sion was constructed in 1989. The most
recent addition was an 18-inch force main
pipeline constructed in 2009 to interconnect
into the 24-inch pipeline just before
the upsize to the 27-inch diameter section.
In August of 2018, a leak was discovered
by Plano in a storm drain located
under the 16-inch force main. The issue
was a fascinating discovery due to the
rare circumstances - one pipe's leak was
being captured by another pipe.
This is an important lesson when inspecting
portions of infrastructure: you
never know what you will find that is not
38 JULY 2023 | UndergroundInfrastructure.com
Once the leak location was determined
and accessed, crews set up a stilling
well and pumped the leaking fluid to a
nearby manhole. The use of pump trucks
and sump pumps facilitated the transfer
of this fluid to the manhole to evacuate
the leaking sewer effluent.
When addressing an isolated failure
location, all focus and resources go to
mitigating the issue. There is one main
goal: stop the leak. However, when looking
at a larger, long-term solution, there
are several factors that need to be considered,
such as maintenance of traffic flows,
community disruption, temporary flow
bypass and excavation access points.
CIPP can be installed up to several
hundred feet at one time and does not
hinder the flow capacities of the pipelines.
With only two small excavation pits
on either end of the pressure CIPP installation,
and the ability to bypass or reroute
the flow, the rest of the facility operations
above the pipeline will not be disrupted
during the rehabilitation process.
Solution
For this 16-inch emergency force main
repair, Insituform's pressure-rated CIPP,
InsituMain, was installed to fully restore
the failing segment of the pipeline.
InsituMain can be manufactured and
installed in a wide range of diameters
and operating pressures with physical
properties exceeding ASTM F1216 and
AWWA M28.
NTMWD required a 150-psi pressure-rated
lining system. At this pressure
rating, the close fitting InsituMain liner
had a thickness of just 8.5 mm. With an
overall diameter loss of less than 0.67
inches and a Hazen-Williams friction
coefficient of at least 140, flow capacities
were not jeopardized for this project.
With a lining system that met the
technical requirements by NTMWD,
the team needed to put the solution into
action by accelerating the contracting
process. The contract between NTMWD
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Underground Infrastructure - July 2023

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