Comprehensive Sanitary Sewer Rehabilitation: Addressing Private Property I/I

The Downers Grove Sanitary District (DGSD) wastewater treatment center (WWTC) receives peak flows during wet weather events that approach ten times the average daily flow. Peak flows resulting from inflow and infiltration (I/I) into the sanitary sewers increase the cost of treatment and result in sanitary sewer overflows (SSOs) and basement backups in the collection system. Due to the limited success of past rehabilitation efforts, the District decided to initiate a comprehensive rehabilitation program in one flow basin that included rehabilitating the sewer mains, manholes and private service laterals. The District also revised its I/I policy to include rehabilitation on private property at the District's expense. Flow monitoring in the sewers indicates that the sewer rehabilitation work has decreased the peak flow in the basin by approximately 42 percent and eliminated SSOs. Despite the rehabilitation work, remaining I/I sources highlight the importance of adequate storm drainage to reducing I/I.