Oil & Grit Separators (OGS), Spill Containment Chambers (SCC) and Pumping Stations (PS)

A series of storm sewer networks will collect and convey rainfall runoff from the majority of The Parkway corridor. Refer to the Phase 2 Highway and Roadway Drainage Design Report (PIE/Dillon Consulting; 2012) for design details of The Parkway storm sewer system.

There are two storm sewer networks associated with the Marentette Mangin Drain. The first one will collect rainfall runoff from Highway 3 EBL (SR-1) and a portion of the T-2 tunnel top. Flows will discharge by gravity to Pond 5. The second storm sewer network will discharge to OGS-1 for pre-treatment prior to discharging to SCC-1. The SCC will in turn discharge to PS-1 which is designed with 100 percent peak flow redundancy for the 100-year return period event peak flow with a minimum of four pumps. Details of the pumping station will be provided under separate cover.

Stormwater Management Facilities

Pond 5 is the only stormwater management associated with the Marentette Mangin Drain and will receive flows from PS-1. Pond 5 has been designed to provide water quality and quantity treatment in accordance with the Ontario Ministry of the Environment (MOE) Stormwater Management Planning and Design Manual (2003) to meet Ministry and project specific design criteria

8 Design Analysis

8.1 Design Criteria

Project specific design standards and criteria are defined in the Executed Project Agreement (Schedule 15-2, Part 2 – Design and Construction Requirements, Article 7 Drainage and Erosion Control Design Criteria). Article 7 lists drainage design requirements for The Parkway and provides a list of reference documents applicable to The Parkway drainage design and stormwater management plan.

The design standards and criteria from Article 7 provide design guidance with respect to drainage elements such as storm sewers, roadside ditches, pumping stations, stormwater management facilities and watercourses. In general, the design criteria provided the drainage design requirements for the conveyance of stormwater, quantity control, quality control and flood protection. They can be summarized as follows:

Stormwater Conveyance – The roadway drainage system for Highway 401 and roadways below grade will be constructed to convey the 100-year design event. The drainage system will be designed to prevent flooding of the travelled Highway 401 lanes. For sections of Highway 3 that are at-grade, the minor system will be designed to convey the 10-year design storm flow and the major system will be design to convey the 100-year design storm flow.

Stormwater Quantity Control – Post development peak flows will be controlled to pre-development levels for a range of design events up to and including the 100-year event.