Inflow & Infiltration Memo


Inflow and Infiltration (I/I) is the introduction of water into a municipal sewer system as the result of direct inflow from external sources such as a drain pipe or sump pump, or infiltration of groundwater due to leaks in the infrastructure.

This spring, television inspections of several sewer lines and service connections will be conducted to locate potential sources of I/I as recommended on the latest I/I report prepared for the Town. Sources will be scheduled for rehabilitation once located.

The Department of Environmental Protection has mandated a town-wide sewer system metering program, and Inflow & Infiltration Analysis, beginning in early spring 2018. This will help to identify any areas where I/I is coming into the sewer line.

The town’s sewerage flow is measured at metering stations at the town’s borders with Lowell, Dracut and Chelmsford. The Sewer Department receives invoices from these communities that reflect the number of gallons per day passing through the metering stations. Any I/I that is added to the sewer system is included in the gallons recorded at the metering stations.

There are several reasons why it is important to prevent any I/I from entering the sewer system. To reduce gallons (and thereby costs) of how much is traveling through the metering stations, to increase the life cycle of the expensive pumps that move sewerage through the system, and to free up capacity in the system to allow for future connections to sewer.

If you have any questions, please feel free to contact our office at (978) 743-5354.

Tyngsborough Sewer Commission