DESIGN CONSTRUCTION OF THE WEST DON LANDS STORM WATER CONVEYANCE SYSTEM

摘要

Waterfront Toronto is undertaking a large scale, urban renewal project of the West Don Lands in Toronto, Ontario. As a part of this development, a large flood protection landform was constructed to protect the site from flooding by the Don River, requiring storm water on the site to be redirected to the west. A new storm water outfall was needed to convey this redirected flow out to Lake Ontario. To meet the City of Toronto's 2006 Wet Weather Flow Management Guidelines, storm water needs to be treated before it can be discharged into the environment. The Storm Water Conveyance System (SWCS) project is the first phase of the overall storm water management for the West Don Lands and includes the entire underground infrastructure to manage storm water flow and to allow for a storm water treatment facility that will be built in the second phase of the project. The major components of the SWCS project are two large-scale underground oil grit separators, a vortex drop shaft, deep rock tunnels, an overland flow inlet, a large diameter storage shaft, an overflow structure, and an outfall connection to Lake Ontario. One of the more unique components of the SWCS project was the overflow structure, a large tower in the center of the main shaft that always contains water at lake level and allows storm water to overflow the storage system in large storms and bypass treatment. This structure was built using precast concrete components that were post-tensioned to secure all the segments together. This approach required significant planning and design to ensure that the pre-cast segments were watertight upon completion. This paper discusses the design and construction of the hydraulic structures and components that make up the entire Storm Water Conveyance System for the West Don Lands redevelopment.