When Transit Expansions Requires You to Really Understand Your Water System

This paper outlines water distribution system research, planning, modeling, testing, and operations required by the city of Toronto to help facilitate transit expansion. The city of Toronto is experiencing public transit expansion not seen in a generation. This expansion is happening in a dense urban environment with water infrastructure that developed and evolved for over a hundred years. As transit is designed and constructed, water infrastructure often needs to be relocated or isolated while work occurs around it. These relocations and isolations mean shutting down watermains. No matter how big or small, shutting down a watermain has an impact on the system. Sometimes the magnitude of impact can be hard to predict. Most watermain networks have built-in redundancy. During ongoing transit construction, the sheer number of shutdowns required can stretch the limits of that redundancy. In some cases, critical pipes pose a significant challenge just to turn them off, let alone for much duration. In the case of large diameter transmission watermains, isolating them can take months of planning, and in some cases, new supplies need to be constructed before the pipe can be deactivated. To ensure uninterrupted supply to residents and businesses, an intimate understanding of the system is needed. To assist the transit authority requires a close working relationship and early planning.