Pilot Project for Stormwater Management in Downtown Lac-Mégantic

The City of Lac-Mégantic is undertaking a pilot project to evaluate the control of runoff water volumes from a new parking lot on a recovered downtown site. This project will analyze and orient the development of other municipal parking lots to be rebuilt after the rail accident of 2013. The municipality wants to recreate the drainage conditions existing before the original development of the site in order to reduce the hydrological impacts of the parking lot associated with land urbanization. Because of the height of the water table, the parking lot (49 spaces) will be built to make water flow to the lowered concrete borders incorporating rain gardens and grassed swales. The use of reinforced grass* (for the spaces reserved for the disabled and bicycle racks), as well as the planting of 26 trees, will reduce runoff volumes and counter heat islands. Lac-Mégantic will track the performance of the implemented measures by collecting data over two years of follow-up (until 2018) in order to accurately characterize the behaviour of surface water and the volume of water in the swales for each season. The slopes will also be evaluated to see if they adequately direct the water to the lowered concrete borders. In addition, monitoring will take into account maintenance and snow removal operations on the site and the use of charging stations for electric vehicles. Photos and a summary report will be prepared for each visit. After two years of use, Lac-Mégantic will analyze the results in order to conclude whether corrections should be made and what measures should be incorporated in the design of the city's other parking lots. The project is supervised by a monitoring committee composed of the project manager, members of the municipal technical team (infrastructure and environment), as well as members of the team of consultants in engineering, landscape architecture and urban planning. The project techniques and approaches are consistent with the practices outlined in Québec's storm water management guide. The project is supported by municipal policies, such as the Green Guide (2012-2014), which educates citizens to good environmental practices and the Reconstruction Master Plan, entitled "Reinventing the City", which presents a vision adopted by citizens to rebuild the city centre. Numerous public consultations conducted by the reconstruction office have served to take into account the opinions of the population. The rain gardens to which runoff will be directed have a total capacity to contain a volume of 106 m³, more than all of the expected runoff in a rain of 90th percentile. Retaining the water completely on the site of the parking lot will avoid the flow of sediment, suspended solids and pollutants towards the river. The project proposes innovative technologies (reinforced grass, charging stations for electric vehicles) that will arouse the curiosity of citizens and raise awareness about greener practices. In addition, there is a clear intention to use the results of the pilot project to adjust bylaws to apply across the municipality, in both public and private sectors. * Based on best management practices for stormwater in Québec, reinforced grass employs slabs that form a paving system to slow the water flow and promote evapotranspiration. (Project description from original funding application)