The detailed SWM plan includes five pumping stations and seven SWM ponds to service all new sections of Highway 401 and the majority of Highway 3. Runoff from the remaining sections of Highway 3 and other tableland areas, which cannot outlet to a pumping station or SWM pond, will be managed utilizing a combination of oil & grit separators and vegetated swales. Landscaping and environmental design elements are also integrated into the detailed SWM plan to provide passive water quality treatment. These measures serve as at-source controls by reducing runoff potential, promoting infiltration and evapotranspiration, and serve as a landscape buffer at the property line and along roadsides.

With respect to the detailed SWM plan for the Marentette Mangin Drain, runoff from The Parkway will be captured and conveyed by two systems of storm sewers; one that outlets to Pumping Station 1 (PS-1) and one that outlets to Pond 5. PS-1 will pump runoff to Pond 5 which will provide water quality and quantity treatment prior to discharging to the Drain. Refer to the Phase 2 Highway and Roadway Drainage Design Report (PIE/Dillon Consulting, 2012) for design details of The Parkway storm sewer system.

9.2   Water Quality Control

As noted in Section 9.1, water quality treatment will be achieved by means of vegetated swales and stormwater management Pond 5. The Marentette Mangin Drain SWM plan utilizes a multi component approach to achieve the water quality control criterion outlined in Section 8.1. Water quality treatment in the table land areas will be provided by managing runoff through a landscaping planting strategy. Further water quality enhancement will be achieved via swales along the recreational trail. Pond 5 has been designed as a wet pond in accordance with the MOE Stormwater Management Planning and Design Manual (2003) to provide enhanced water quality treatment for The Parkway runoff.

9.3     Water Quantity Control

As previously discussed in Section 8.2.3 and illustrated in Table 8.5, the 6-, 12- and 24-hour durations of the 2- through 100-year return period events were simulated using the MTO 1997 IDF curves to identify the most stringent storage requirements. The 24-hour 100-year event was found to require the highest peak flow rate control and runoff volume storage requirements, and was therefore used as the basis for the design of Pond 5.

Table 8.5 (provided again on the following page) summarizes the existing and future peak flow rates at the at the Lambton Street storm sewer inlet for the 24-hour duration of the 2- through 100-year return period events using the MTO District 1 IDF curves. The table illustrates that future peak flow rates have been controlled to rates similar to, but less than existing. The existing and future conditions modeling parameters and output are provided in Appendix D.