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Future Capacity Limitations of Existing Outfall

The Duffin Creek WPCP has an outfall that extends 1.1 kilometres into Lake Ontario with a diameter of 3 meters (10 ft) which was constructed in 1978. During the most recent (Stage 3) Expansion Environmental Assessment (EA), a modelling exercise was completed as part of the Receiving Water Impact Assessment Study. The study indicated that when flows reach 560 MLD, the Ministry of the Environment (MOE) requirement with respect to the initial dilution in the near field region will no longer be met.

As a condition of the Certificate of Approval (CofA) for the plant operations, the Ministry of the Environment has directed the Regional Municipalities of York and Durham to address the limitations to the existing outfall at the Duffin Creek WPCP.  To provide a margin of safety, the Ministry has directed that the additional outfall capacity be provided by the time the average flow from the facility reaches 520 MLD.  It is expected that average flows from the facility will reach 520 MLD at the earliest by 2019.  It is proposed to have a solution in place by that time.