To ensure that the City of Toronto’s goal to increase urban forest cover to 40% can move forward sustainably, minimizing conflicts between green and grey infrastructure and identifying solutions to existing conflicts has become a priority. The Toronto Green Standard means that more trees are being planted, and there is increasing potential for conflicts to arise. As cities like Toronto contend with the planting of trees in dense urban centres with a high concentration of underground and overhead utilities and infrastructure, solutions are needed to address tree utility conflicts proactively and effectively. When trees are planted in close proximity to water and wastewater infrastructure, potential conflicts include increased repair time and maintenance costs during emergency or planned infrastructure repairs, and tree root intrusion into sewers which can cause sewer back-ups and property damage.

This project and the resulting comparative analysis provide information which the city can use to develop and assess options by synthesizing and summarizing standards, guidance and best practices for tree planting near water/wastewater infrastructure across North America. The project also provides recommendations and preferred approaches for Toronto Water to consider when addressing conflicts between grey and green infrastructure.