Underground Infrastructure - October 2023 - 38

REHABTECHNOLOGY
Innovative Solution for Managing
I&I Challenges in Sanitary Districts
Tim Nichols
A major challenge sanitary districts everywhere face is recurring
and growing inflow and infiltration (I&I), from substantial
amounts of groundwater and stormwater entering the
sewer during periods of heavy rain. This issue is of paramount
importance, as heavy rainfall can cause the intrusion of large
volumes of groundwater and stormwater into the sewer system,
overwhelming pump stations and treatment plants, and
even causing costly sewer overflows.
The Truckee Sanitary District (TSD), Calif., is the public
agency responsible for collecting and conveying wastewater
in the greater Truckee area outside Lake Tahoe, Calif. Serving
a population of approximately 25,000 people in a 39-squaremile
service area, The TSD collection system contains about
200 miles of sewer mains, 16,000 laterals and 43 lift stations.
Although the TSD sanitary sewer system is designed to
convey a large amount of wastewater, it still saw significant
and problematic spikes in flows during rain events - despite
best efforts and use of all available technology.
" The spikes in flows happened almost concurrently with
rain events, " said Blake Tresan, TSD general manager and
chief engineer. " It would rain, and data from our real-time flow
meters would almost immediately indicate a spike in flows. As
soon as the rainstorm ended, the flows would quickly go back
to normal levels. "
According to Tresan, the water was not infiltrating through
the system's pipes for the simple reason that they were buried
six feet underground. If that were the main route, he notes, " It
would take much longer for that rainwater to get there. "
Also, if the I&I flow would have been coming through the
buried portion of the pipe and manhole network, the flow increase
would have been delayed until groundwater levels had
increased. In addition, I&I would have continued after the
rain event until groundwater levels subsided.
The conclusion was that the I&I flow appeared to be
coming through parts of the collection system exposed to
surface run-off.
" The only place where the sewer system meets the ground
surface is at the top of manholes and lateral cleanouts, " said
Tresan, " so we decided to zero in on the manholes as a likely
source of I&I. "
Manhole lubricant, sealant
In 2021, Oatey Co. and TSD joined forces to create Hercules
Shutout, a manhole lubricant and sealant.
After experimenting with various products, the TSD team
knew it was on to something when it applied a pipe-joint lubricant
to the manhole frame - and it actually worked.
From there, TSD considered developing its own product,
but ultimately decided to partner with Oatey to repurpose
its solution for sewer-related applications. By submitting the
I&I solution on Oatey's Idea Portal, TSD was able to work
38 OCTOBER 2023 | UndergroundInfrastructure.com
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Underground Infrastructure - October 2023

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