Effect of freeze - thaw cycles on bioretention performance for water quality improvement

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Urbanization leads to increased impermeabilization of surfaces due to roads, parking lots, and buildings. With less opportunities for infiltration, rainwater generates large volumes of runoff that contribute to increased risks of flooding and degradation of water quality. In this context, Low Impact Development has developed and involves the use of stormwater control systems such as bioretention cells, also called rain gardens. Bioretention are depression in the soil that includes an engineered soil media with an enhanced ability to infiltrate water and retain contaminants. The design of these systems is dictated by general recommendations from local conservation authorities that have not been extensively tested in cold climate. The proposed project will evaluate the effects of repeated freezing and thawing cycles on the water quality that exfiltrate from lab-scale bioretention cells. Column experiments designed to realistically represent freeze - thaw cycles will be filled with undisturbed soil cores from an existing bioretention from Ontario. The project will enable to better understand the impact of cold climate on the efficiency of bioretention, and help improve the design of these system for a better protection of aquatic resources.