Planning Public and Private I/I Reduction Program that Ensures Performance and Maximizes Participation for The Region of York

This paper presents a comprehensive public and private Inflow and Infiltration (I&I) reduction pilot program implemented by the Regional Municipality of York. The program aimed to maximize private property participation. The Region employed a Model at the Source hydrologic and hydraulics (H&H) modeling approach to identify and quantify the sources of I&I. A 37- hectare residential area in northeast Newmarket, Ontario was used as a pilot study area. The modeling approach identified the sources of I&I, including mains trenches, lateral houseconnection trenches, house foundations, and maintenance hole lids. The H&H model was calibrated to the Region’s downstream permanent flow meter data and updated to represent the system’s condition after the application of several proposed I&I reduction technologies. The Region’s 25-year four-hour design storm was used to predict I&I reductions. A 33% reduction in peak flow and a 34% reduction in I&I volumes were predicted during the first 24 hours of the storm event when replacing or lining the house laterals from sewer mains to house connections. Continuous simulation for one year demonstrated a total volume reduction of 23%. The modeling approach also revealed that redirecting half of the splashing roof leaders away from house foundations could achieve an additional peak I&I reduction of 21.3% and a volume reduction of 12%. Alternatively, assuming foundation drains exist and can be connected to sump pumps, the modeling approach indicated that installing sump pumps in 25% of the houses could lead to a peak flow reduction of 24% and a volume reduction of 11%. Minimal impact on I&I reduction is indicated from plugging the pick holes of the maintenance manhole lids. Overall, this paper highlights the success of the comprehensive I&I reduction program in the Region, showcasing the effectiveness of various remediation measures on the private side and identifying further improvements to reducing I&I effectively. The private side I&I reduction pilot program is used by the Region to scale up to other locations by adapting a similar modeling approach and applying lessons learned from implemented I&I reduction activities