BASEMENT FLOODING AREA 9 INFLOW AND INFILTRATION REDUCTION PILOT PROJECT - PROJECT DESCRIPTION

Civica was retained by the City of Toronto (the City) to complete an Inflow and Infiltration (I&I) reduction study for Basement Flooding Study Area 9. The study area has experienced systemic basement flooding problems during extreme rainfall events since its initial construction (1950s). This I&I study was undertaken to satisfy the recommendations of Municipal Class Environmental Assessment (EA), Schedule B titled “Basement Flooding Study Area 9” (2012) and to quantify the effort required to reduce I&I to an acceptable level. The preferred mitigation strategy involved the disconnection of 80% of the foundation drains connected to the sanitary system plus the disconnection of 12 downspouts, sealing of 60 sanitary manholes, 1 basement walkout drain and 1 sanitary cleanout. The resulting flow and hydraulic conditions meet the City’s criteria for basement flooding protection (greater than 1.8 m of freeboard of adjacent basements), at the lowest cost. The solution had an estimated cost of $6,652,150. The resulting peak flow post-mitigation for the May 12, 2000 event is 172 L/s, reducing the peak I&I rate from 4.3 L/s/ha to 3.8 L/s/ha in the study area. An implementation strategy was also proposed, including description of work required and timelines to complete the work