The Town of Newmarket and Civica Infrastructure Inc. worked together on an Inflow and Infiltration (I/I) reduction project in southern Newmarket on behalf of Bazil Developments Inc. The purpose of this project was to identify sources of I/I entering the sanitary sewers and develop remediation plans to reduce these extraneous flows. The project involves a flow monitoring program consisting of over 10 flow meters placed in strategic locations and 3 rain gauges, which were used identify areas within the study area that have high I/I. Sanitary sewer evaluation surveys (SSES) such as fog & dye testing, CCTV and maintenance hole inspections were used to locate defects within the sanitary system (1,067 sanitary manholes and 65.3 km of sanitary pipes). Nearly 100 sources of infiltration within sanitary pipes were identified (i.e. drippers, runners and gushers), I/I flows were quantified for each defect, and remediation was executed through tendering works to contractors or through internal remediation expertise to complete cost-effective fixes. Additional defects identified include sanitary maintenance holes susceptible to surface flooding during large rain events, with photo and video evidence to support surface flows entering the sanitary system. Dual-drainage modelling was also utilized to identify areas within the study catchment that were susceptible to surface ponding. These modelling results were overlayed with the sanitary network using GIS mapping to identify maintenance holes susceptible to flooding so they could be sealed with an appropriate water-tight cover.