I&I

“I&I” is a short acronym for a huge problem most sewer communities face, Infiltration and Inflow.  Inflow occurs when rainwater is misdirected into the sanitary sewer system instead of storm sewers.  Examples are: roof leaders, yard and area drains, manhole covers, and cross connections from storm drains. The remedy for inflow is to remove improper connections to the sanitary sewer system.  Infiltration occurs when ground water seeps into the sanitary sewer system through cracks or leaks in sewer pipes. The cracks or leaks may be caused by age related deterioration, loose joints, damage or root infiltration. The remedy for infiltration is repairing or replacing the leaking infrastructure.  Ignored I&I results in excessive flows in the sewers and into the wastewater treatment plant.  This becomes a very costly problem for all of us.  I&I can also be classified as RII (rain induced I&I) and as storm induced I&I which could include melting snow, flooding streams as well as rain.

I&I affects the quantity of wastewater that needs to be treated, the capacity of your community’s sewer pipes, wastewater treatment plant and ultimately, the rate businesses and residents pay to operate and maintain them.  The worst impact of I&I is the possibility that the excess sewage flows out of the sewer pipe and into our environment.    I&I takes up valuable capacity in the WWTP and may limit future sewer connections.  I&I adversely affects the nutrient loadings for the plant discharge.  If this is ignored,  I&I could cost this community  millions of dollars.

The municipality is responsible for maintaining the sewers on streets and public right of ways.  Your community has an on-going program to reduce the quantity of I&I in the sanitary sewer system.  A pothole in the street is easy for all of us to see and know that repairs are needed. Since the sewers are underground, special equipment and techniques are used to locate problems.  Specialized robotic video cameras are lowered into manholes and travel down the sewer pipes.  Flow meters, smoke testing, conductivity sampling are also used in our program to locate problems in sewers.  Several sections of the sewers have been replaced.  After problems are located, repair and rehabilitation contracts are bid and awarded.  Continued investigations and repairs of sewers will persist for many years.

Homeowners are responsible for maintaining their building sewers on their private property.  You, as a homeowner, can reduce I&I from your property.

  • Check that rain gutters and outside drains are not connected to the sewer system.  Disconnect any drains that are found to be connected.
  • Avoid planting trees and shrubs over building sewers. The roots can damage the structure of the sewer pipe and cause leaks.
  • Make sure that the caps are on your cleanouts. Lawn mowers tend to break the plastic caps.  Replacement lids are available at your local hardware store.
  • Ensure that basement drains are not connected to the sanitary sewer and install a sump pump to the stormwater drainage system instead.
  • Replace any known broken, leaky or problem sections of sewer pipe that are located on your property.

Recent regulations imposed by PADEP (Chesapeake Bay Strategy) have changed impacts of I&I.  Some limits get more stringent as the flows to the plant increase.  This means higher costs for construction, operation, and maintenance to meet these stricter limits.   For example, at the current design flow of 8 MGD, our limits for Total Nitrogen will be 6 mg/L.  To increase our plant capacity by only 20%, the limits for Nitrogen would decrease to 4.8 mg/L and the costs to the Township could more than double!  This is just one example how reducing I&I is a cost-effective solution.  It does, however, need everyone to do their share by repairing and maintaining their building sewers on their property.

Use the link below to see flow rate to the plant.  Normal flow rate is about 4 mgd.

http://doverwwtp.dyndns-office.com:8080/frmflowstatus.aspx