Cast Iron Trunk Watermains in the City of Toronto

Transmission watermains in the city of Toronto use predominantly the following two material types: cast iron with cement mortar lining (“CML”) and CML steel with concrete encasement. The focus of this paper is to discuss the history, current condition, the city’s cast iron watermain rehabilitation plan, and a few recent highlight projects related to cast iron trunk watermain replacement. Record drawings show that cast iron pipes in Toronto’s transmission water system were used from 1900s to early 1950s. After 1950s, cement mortar lined steel pipes with concrete encasement were the predominant standard for new trunkmains. Currently, there are about 100 km of cast iron trunk watermain ranging from 600mm to 900mm in diameter still in service today. Most of them in the older parts of Toronto such as downtown core and west end of downtown Toronto. Currently, the city has planned $153 million (Canadian Dollars—“CAD”) over the next 10 years to replace and rehabilitate cast iron trunkmains to restore the useful life of our trunkmain linear infrastructure.