Amending the Foundation Drainage Policy and Storm Sewer Quality Limit for Manganese

Developments cannot proceed without adequate servicing infrastructure. Accordingly, the Foundation Drainage Policy prohibits groundwater discharges to the City's sewer systems to preserve the capacity required to support Toronto's continued growth and intensification. The policy amendments proposed in this report strike a balance between introducing greater flexibility to facilitate new housing development and maintaining the Foundation Drainage Policy's core objective of protecting sewer system capacity. Following stakeholder consultations, hydraulic capacity analyses of the sewer system and background research, effective October 1, 2026, Foundation Drainage Policy amendments will allow a limited quantity of foundation drainage containing groundwater to be discharged into the City's storm sewers, under the following conditions: - Foundation drainage flows meet the quality limits for storm sewer discharge in the Sewers By-law; - The storm sewer to which the foundation drain connects will discharge directly to a watercourse or Lake Ontario without interacting with the combined sewer system (i.e., there is no interaction with any flow control structures); - The maximum dry-weather discharge rate from foundation drainage is 3 Litres per second per hectare for sites > 0.7 hectare, and 2 Litres per second for sites ≤ 0.7 hectare; and - The total discharge rate under wet-weather conditions to the storm sewer from the site (i.e., both foundation drainage and stormwater) complies with all stormwater management targets per the City's Wet Weather Flow Management Guidelines. Staff also recommend an increase to the manganese quality limit for discharges to the storm sewer system from 0.05 milligrams per litre to 2.0 milligrams per litre, which will exclude higher concentrations associated with non-natural manganese sources (e.g., brownfield properties). Toronto Water staff consider the health and environmental risks associated with this recommendation to be low because anticipated groundwater discharge volumes will be limited, and because manganese levels in most groundwater samples naturally cluster around low concentrations. This report was developed in consultation with Development Review, who agree with the findings and recommendations.

Council's decision and to make such clarification, minor modifications, technical or stylistic refinements as may be identified by the City Solicitor.