Village of Itasca, IL:
Proactive I/I Reduction Saves Village
Millions of Dollars
Background
Wastewater collection systems are an essential part of municipal infrastructure.
Deterioration of these collection systems is quickly becoming a problem for
communities across the country because it leads to infiltration and inflow (I/I).
Infiltration is groundwater that leaks into the system through sewer joints,
cracked pipes, and defects in manhole walls. Inflow is stormwater that enters
directly into the sanitary sewer system. Common sources of inflow are roof
downspouts and storm water drainage structures that are directly connected
to the sanitary sewer system, as well as leaking manhole covers that are
subject to inundation during rainstorms.
I/I can significantly increase both average and peak flows to a community’s
wastewater treatment plant, which increases operating and capital costs and also
leads to problems with excess flow during wet weather. The Village of Itasca’s
sewer system has experienced I/I in the past, but a comprehensive and consistent
maintenance program has drastically decreased the amount of I/I.
Solution
Itasca combats I/I by replacing manhole covers; repairing manholes;
disconnecting area drains, downspouts, and open cleanouts from the sanitary
sewer system; and making repairs to building lateral and mainline sewers.
The Village also uses a sanitary sewer televising and rehabilitation program to
reduce I/I. The goal of this program was to televise all of the Village’s sanitary
sewers within an eight-year period, identify defects, and make the necessary
repairs. To date, the Village has completed inspection of approximately 75 percent
of the sewer system. After the entire system has been televised, the program
will begin again so that each sewer segment will be inspected at an interval of
no more than eight years.
Over the last few years, the Village has also completely replaced its Central Trunk
Sewer, which begins near I-290 and runs through downtown Itasca to the
wastewater treatment plant. This project eliminated several defects that had
previously contributed a significant amount of I/I.
Results
Itasca’s aggressive I/I reduction program has been an obvious success. In
1995-1996, the average daily flow to Itasca’s wastewater treatment plant was
2.45 mgd. The current two-year average daily flow is 1.99 mgd (calculated using
flow data from 2004 and 2006 because 2005 was an exceptionally dry year).
Therefore, the I/I reduction program has reduced the average daily flow by
almost 0.5 mgd or 20 percent.
This reduction in Itasca’s wastewater flows has not only saved thousands of
dollars in annual operating costs, but it will also save Itasca millions of dollars as
it undertakes a plan to design and construct a new wastewater treatment plant.
“While I/I reduction can be a multi-year effort, the rewards and savings down the line can be substantial. Our new Wastewater Treatment Plant will cost millions less due to our ongoing I/I reduction efforts. Implementing an annual televising and rehabilitation program has ensured that our collection system remains in good condition now and for the foreseeable future.”
Ross Hitchcock
General Services Superintendent
Village of Itasca
