infiltration inflowExcessive Infiltration/Inflow (I/I) reduces both capacity and life expectancy of sewer systems and wastewater treatment facilities. 

I/I is a growing concern within older sewer collection system infrastructures and can significantly decrease the available capacity of wastewater treatment facilities over time.  I/I, which can enter the collection system through defective pipes, pipe joints, connections, manholes, sump pumps, roof leaders, cellar/foundation drains, manhole covers, deteriorated manhole structures, and/or cross-connections with storm drain systems can be identified by several different methods including closed circuit television inspections (CCTV), smoke testing, flow isolation, manhole inspections, dyed water flooding, and building inspections.

Excessive I/I within a sanitary sewer system takes up capacity that could otherwise be used for wastewater, resulting in the need to build additional capacity in wastewater treatment plants and pipes — the cost of which becomes the burden of municipalities and ratepayers. Reducing I/I in the system not only decreases present and future wastewater treatment costs, but also lowers the risk of sanitary sewer overflows and protects the environment. Therefore, in 2014 MassDEP made changes to Operation and Maintenance Regulations, 314 CMR 12.04(2), which requires municipalities to develop and implement an ongoing I/I program to do the following:

  • Identify and eliminate excessive I/I sources
  • Focus on inflow sources
  • Phased evaluation of sewer system consistent with MassDEP Guidance
  • I/I mitigation for new connections for some systems

The new regulations require that municipalities submit an I/I analysis to MassDEP in accordance with 314 CMR 12.04(2) by December 2017. The analysis must address excessive I/I based on MassDEP’s Guidelines for Performing I/I Analyses and Sewer Systems Evaluation Survey, as well as assess the risk for sanitary sewer overflows for the 5-year 24-hour storm. Of note: Guidelines for Performing I/I Analyses and Sewer Systems Evaluation Survey, originally published in 1993, is in the process of being updated. The update is expected to be finalized in the summer of 2016.

Municipalities that have completed the assessment and the Sewer System Evaluation Survey prior to the 2014 changes and are in the process of implementing the recommended actions identified in the Sewer System Evaluation Survey may submit those plans, along with an update of completed items and a schedule for items still to be completed, on or before December 31, 2017.

Tata & Howard has extensive experience with I/I investigations. For more info, please click here.