Green Parking Lot Field Test in Sainte-Julie: a Decentralized Approach to Stormwater Management

Savaria Experts-Conseils Inc., in partnership with the City of Sainte-Julie, will conduct a field test to assess materials and designs for optimizing stormwater infiltration in a parking lot and a downtown driveway. At the moment, according to municipal regulations, parking lots must be paved with impermeable materials, but this situation puts severe pressure on the storm sewer system and receiving environments. With this project, the two partners hope to show the benefits of permeable paving and amend municipal regulations to authorize this approach. The test, which includes creation of rain gardens, is divided into three parts. The first phase will be an in-depth study of substrate layout design to increase infiltration to 100% and reduce the amount of substrate to replace during site development. In the second phase, Savaria Experts-Conseils will compare the efficiency of various native plants, according to height and root density. Plants will also be chosen for their drought tolerance to reduce watering when there is no rain. The third phase will determine the durability of two porous materials—a grass-planted parking lot and a driveway paved with porous concrete—and determine whether suitable infiltration occurs throughout the test period. Sainte-Julie will be involved in monitoring pavement operation with a view to large-scale replication in the municipality. Beforehand, Savaria Experts-Conseils consulted projects in Quebec City and the RCM of Brome-Missisquoi for guidance as to what components to study, specifically the type of substrate used. By demonstrating the possibility of capturing 100% of the 90th percentile rainfall on the site, this project shows many potential benefits: reduction of heat islands, reduction of parking lot maintenance and replacement costs, increased resistance during seasonal fluctuations and winter maintenance, improved management of excess runoff, and reduction of the volume of water flowing into the storm sewer system. The partners have developed a communication and awareness plan to promote the green parking lots so that the concept will be used throughout the area and replicated by citizens and merchants. The partners will also make a list of native plants that foster infiltration in southern Quebec rain gardens with clay soil. (Project description from original funding application)