Achieving Infiltration/Inflow Removal Goals with a Comprehensive Approach

Over the past 10 years, the Town of Saugus, Massachusetts (The Town) has experienced several large rain events that have caused significant sanitary sewer overflows (SSOs). Extraneous water entering the sanitary collection system has exceeded the design capacity of the sewer system, forcing the Town to pump excess wastewater directly into the Saugus River in order to protect the Town's main pumping station and its residents. An administrative consent order was issued to the Town by the Massachusetts Department of Environmental Protection (MassDEP) that required an immediate evaluation of the sewer system to assess alternatives and produce a recommended program to control the sanitary sewer overflows.A SSO facilities plan evaluated several options to control SSOs. Ultimately, the study recommended comprehensive rehabilitation of nine critical sub-systems over a 10-year period at a cost of $32 million to achieve a 10-year level of control. The plan included complete comprehensive rehabilitation of the public sewer system in these sub-systems, including lining all mainline sewers, service lateral connections from the main to the first joint, and all manholes, as well as a town-wide private inflow removal in an effort to achieve a 40%-50% reduction of during a 10-year storm event.A pilot program was initiated to allow the project team to evaluate the effectiveness of the public and private comprehensive plan and to determine if removal goals could be met before proceeding with the entire program. Service connections on private property were intentionally not addressed in the pilot program sub-system in an effort to reduce costs and to properly evaluate the contribution of infiltration/inflow (I/I) from private service laterals.This paper will detail the effectiveness of the first three years of the comprehensive rehabilitation program, and discuss rehabilitation techniques, costs, private inflow removal, product warranty inspections, and results from pre- and post-construction metering linear regression analysis to determine percentages of I/I removed.