New Transmission Watermain Specifications—City of Toronto

This paper discusses pipe material specification used by the city of Toronto to construct large diameter (generally diameter 750 to 2,250 mm) transmission mains. Lower diameter distribution mains are generally constructed using PVC and ductile iron. Prior to 2013, Toronto only used to permit welded steel concrete encased pipe for large diameter transmission mains. However, after 2013, Toronto permitted other pipe materials for transmission mains. Pipe materials such as prestressed concrete pressure pipe, HDPE, PVC, ductile iron, stainless steel have been used for large diameter transmission mains in various municipalities in Ontario. Each pipe material has individual pros and cons, which can be mitigated depending on the circumstances. While opening up the pipe material, it was felt that a specification for the transmission main pipe material was essential to ensure 80–100 year service life of the transmission main irrespective of the pipe material. This paper will present the process used to develop the new Toronto Large-Diameter Watermain Standard Specifications, the risk-assessment method used to determine localized allowable materials and joints, restrictions, and Toronto’s special requirements. The paper will summarize Toronto technical standard TS7.80, a public resource available to all.