Underground Construction - June 2022 - 37

REHABTECHNOLOGY
North Carolina Utility Battles
I&I with Impressive Results
The Town of Wingate, N.C. Public
Works Director Eugene Jones noticed
two pump stations were running on average
of four hours every day. However,
during rain events, the pump stations
would run up to 35 hours straight. After
further inspection, Jones found that infiltration
and inflow (I&I) was the cause of
the long run times.
Wingate is a suburb 25 miles east of
Charlotte, N.C., with a population of
about 3,500. Wingate is most known for
Wingate University with more than 3,600
students. The town has a total area of 1.89
square miles - all of it land. Wingate provides
retail wastewater service to its citizens
and the university and has approximately
23.6 miles of mostly vitrified clay
pipe (VCP) and polyvinyl chloride pipe
(PVC) pipelines, and 537 manholes that
are maintained by the Wingate Public
Works Department.
While reviewing the Town's equipment,
it was noticed that two pump stations
near Dianne Street were running an
average of four hours every day - without
a rain event. However, during rain events,
the pump stations would run up to 35
hours straight causing strain on the pump
equipment, as well as elevated power bills
due to excessive run times.
Public Work's Director Eugene Jones
inspected the manholes that fed to the
two problematic pump stations. His inspection
found that infiltration and inflow
(I&I) into the manholes was the culprit
causing the long run times of the pumps.
Jones contacted Tonia Barton of ProCoat
Inc. who specializes in the rehabilitation
UCONonline.com | JUNE 2022 37
of sewer manholes and wastewater water
treatment plants in North Carolina.
Solution
After further inspection of 61 manholes
on the Dianne Street line - approximately
half of which were experiencing infiltration
- it was concluded that injection
grouts would be the ideal solution to eliminate
the infiltration flowing through defects.
Barton used a combination of injection
grouts and used different techniques
depending on the manhole's material.
The two grouts used were Avanti's AV202
Multigrout and AV-275 Soilgrout.
AV-202 Multigrout is a water-activated
polyurethane designed for sealing
high-volume water leaks
in cracks or
joints in concrete structures and is often
used in conjunction with AV-219
Fibrotite (Oakum). When Oakum is saturated
with grout and then worked into
leaking cracks or joints, it is activated by
the water leak and acts as a gasket, swelling
to shut down the leak.
AV-275 Soilgrout is a hydrophobic
polyurethane that uses a catalyst (AV276)
for its reaction and is designed to react
quickly with moisture to bind together
and waterproof loose granular soils.
AV-275 and AV-276 are mixed together
prior to injection. AV-275 expands up to
30 times, filling voids around the outside
of manholes or other concrete structures.
" Out of the 28 manholes grouted,
half were grouted using the curtain
grouting technique, and the other half
were point repaired, " Barton explained.
" Approximately 40 percent of the manholes
were brick and mortar which
generally required the curtain grouting
approach so multiple leaks could be
stopped at once. Curtain grouting essen
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