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What Homeowners need to Know
Inflow,
Infiltration and Overflows
Unlike water pipes, always full
because of the pressure used to deliver water into homes, sewer pipes are
rarely full when wastewater is flowing from homes to the sewage treatment
plant. When water pipes break, crack or are broken, they leak water out;
sewer systems, on the other hand, allow groundwater and storm water to leak
in.
When groundwater or storm water
leaks into the sewer system, it takes up extra space that could be carrying
wastewater. If the pipes become overloaded, raw sewage may overflow at
points throughout the sewer system before it reaches the treatment plant.
Inflow and infiltration
are terms used to describe how storm water and groundwater get into the
sewer system.
Inflow
Inflow is storm water that is directly piped into a separate sanitary sewer
system to control runoff. These connections, which may include storm drains
in streets, parking lots and driveways and roof gutters, exist in a
combined sewer system because it is designed to carry both wastewater and
storm water. Storm water should never be connected into a sanitary
system designed to carry only wastewater.
Some examples of the way inflow
affect the sewer system:
In some cases, homeowners or
contractors have illegally attached roof drainpipes and basement sump
pumps to the sanitary sewer.
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Example of inflow: A downspout connected directly to the sanitary
sewer system.
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Infiltration
Infiltration is excess water that gets into the sewer system through open
joints, cracks, and breaks in the pipes. These deficiencies may allow
constant infiltration of groundwater. The average sewer pipe is designed to
last about 20-50 years, depending on the material. In many cases in this
region, collection system pipes and household laterals have gone much
longer without inspection or repair and are likely to be cracked or broken.
Some examples of the way
infiltration affect the sewer system:
Cracked or collapsed sewer pipes,
caused by deterioration over time, or poor design, installation or
maintenance, allow groundwater into the collection system.
Sewer lines are installed beneath
a creek or stream because creeks are usually at the lowest point in the
area, and it is more expensive to install pipes under a street. These sewer
lines are therefore highly susceptible to infiltration when they crack or
break. In some cases, broken lines have been known to drain entire streams
into the local sewer system.
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Example of infiltration: A deteriorated house lateral that allowed
water to seep into the sewer collection system.
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Inflow and infiltration play a
significant role in the sewage overflow problem.
Of course, wet weather magnifies
the problem: Inflow and infiltration can add as much as 3,000 gallons of
storm water per person per day to the sewers, instead of the average daily
100 gallons per person of water use that is typical during dry weather. That's
an overload of 30 times more flow per day during rain or snow melt, which
then causes sewage to overflow into creeks, streams and rivers at hundreds
of locations throughout Sellersburg before reaching the sewage treatment
facility.
Overflows
When an overflow occurs in a separate sanitary sewer system,
it is called a sanitary sewer overflow (SSO). This may occur at
an overflow
structure, into a street from a manhole cover or into the
basement of homes. Overflow structures, which were legal at the time of
construction, and unintentional SSO’s both, are
illegal in separate sanitary sewer systems under the Clean
Water Act.
While every community is likely
to experience at least a few overflows in their sewer system, the older
communities located in the Downtown experience the most overflows due to
their low location in the system. The sewer collection systems in these
areas not only carry their own sewage (and in many cases storm water), but
they also receive the wastewater flow from their neighboring areas
upstream. The complex network of integrated sewer collection system pipes
throughout the Sellersburg service area makes it critical for all areas to
collaborate on and share the responsibility for developing and implementing
long-term solutions to the overflow problem.
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