Circular Economy of Soil: Best Practices in Excess Soil Management in Ontario

This paper proposes a circular economy framework for reuse of excess soil in pit and quarry rehabilitation in Ontario. More than 25 million cubic meters of excess soil is generated by the construction industry in Ontario. The rehabilitation of dormant or active pits and quarries can be a viable option for the reuse of this soil. This paper reviews the best practices for rehabilitation of pits and quarries using excess soil in several jurisdictions in the US and Canada. Next it proposes a safe rehabilitation approach for pits and quarries using excess soil. This approach was designed after studying different possible pathways for migration of contaminants in a pit and/or quarry setting (e.g., soil to groundwater pathway and inhalation of indoor air containing soil vapor). The approach is based on a “layer-cake” method, which may allow for placement of soil meeting one or more generic volume-independent soil quality standards under certain conditions. Each layer will be chosen based on the existing standards of the Ontario Ministry of Environment Conservation and Parks. This framework prescribes Table 1 standards (i.e., background condition standards) as a default reference standard and advocates for its use in settings described by the regulations (e.g., sites located in an environmentally sensitive area). The paper introduces a flowchart that can be used by qualified persons to decide about the layer of the soil to be used for backfilling. A case study in Ontario was assessed, and using the developed approach, an initial rehabilitation plan was developed for it.