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I&I Problems & Removal
I&I Problems
During significant rain events, storm and ground water can find its way into the sanitary sewer system through inflow and infiltration (I&I). When this excess water enters the sanitary sewer system, it can create the following problems:
  • I&I increases the flow in the sanitary sewer system beyond the designed capacity of the pipes. When this happens, the excess wastewater can lead to basement backups and/or sanitary sewer manhole overflows.
  • Storm and ground water that enters the sanitary sewer system is transported to the Water Reclamation Facility and unnecessarily treated. This leads to higher treatment costs for the utility and its customers.
  • If I&I is not addressed, the sanitary sewer pipes may have to be up sized to handle these peak flows to reduce backups and overflows. These projects are expensive and do not completely solve the problem.

Why Remove Sources of I&I?
Depending on the type of I&I connection(s), just a couple of properties with sources of I&I can overload a sanitary sewer line during a rain event. When the line becomes overloaded, the wastewater looks for the lowest point to release the pressure building up in the pipe. This can be a basement drain or a sewer manhole.

Although a property owner may have I&I connections on their property and never have a problem, they could be contributing to a sewer backup in the basement of a neighbor or the overflow of wastewater from a sewer manhole. Removing sources of I&I can help to reduce the occurrences of backups and overflows. Any reduction in the amount of stormwater entering the sanitary sewer system is a public benefit to all Knoxville residents. The benefits include:
  • Decreased occurrences of basement backups
  • Compliance with Iowa Department of Natural Resources regulations
  • Reduced claims and claim related costs associated with backups
  • Better protection of the environment from the impact of overflows
  • Reduced treatment costs
  • Increased capacity of the sanitary sewer system
  • Reduced need for expensive projects to handle excess flow