title: Evaluating rain gardens as a method to reduce the impact of sewer overflows in sources of drinking water.
abstract: The implications of climate change and changing precipitation patterns need to be investigated to evaluate mitigation measures for source water protection. Potential solutions need first to be evaluated under present climate conditions to determine their utility as climate change adaptation strategies. An urban drainage network receiving both stormwater and wastewater was studied to evaluate potential solutions to reduce the impact of combined sewer overflows (CSOs) in a drinking water source. A detailed hydraulic model was applied to the drainage basin to model the implementation of best management practices at a drainage basin scale. The model was calibrated and validated with field data of CSO flows for seven events from a survey conducted in 2009 and 2010. Rain gardens were evaluated for their reduction of volumes of water entering the drainage network and of CSOs. Scenarios with different levels of implementation were considered and evaluated. Of the total impervious area within the basin directly connected to the sewer system, a maximum of 21% could be alternately directed towards rain gardens. The runoff reductions for the entire catchment ranged from 12.7% to 19.4% depending on the event considered. The maximum discharged volume reduction ranged from 13% to 62% and the maximum peak flow rate reduction ranged from 7% to 56%. Of concern is that in-sewer sediment resuspension is an important process to consider with regard to the efficacy of best management practices aimed at reducing extreme loads and concentrations. Rain gardens were less effective for large events, which are of greater importance for drinking water sources. These practices could increase peak instantaneous loads as a result of greater in-sewer resuspension during large events. Multiple interventions would be required to achieve the objectives of reducing the number, total volumes and peak contaminant loads of overflows upstream of drinking water intakes.
authors.affiliation: Canada Research Chair in Source Water Protection, École Polytechnique Montréal, P.O. Box. 6079, Succ. Centre-ville, Montréal, Québec H3C 3A7, Canada; Civil, Geological and Mining Engineering, École Polytechnique Montréal, C.P.6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada. Electronic address: laurene.autixier@polymtl.ca.
authors.forename: Laurène
authors.initials: L
authors.lastname: Autixier
authors.affiliation: INRS Centre Eau Terre Environnement, 490, rue de la Couronne Québec, Québec G1K 9A9, Canada. Electronic address: alain.mailhot@ete.inrs.ca.
authors.forename: Alain
authors.initials: A
authors.lastname: Mailhot
authors.affiliation: INRS Centre Eau Terre Environnement, 490, rue de la Couronne Québec, Québec G1K 9A9, Canada.
authors.forename: Samuel
authors.initials: S
authors.lastname: Bolduc
authors.affiliation: Canada Research Chair in Source Water Protection, École Polytechnique Montréal, P.O. Box. 6079, Succ. Centre-ville, Montréal, Québec H3C 3A7, Canada; Civil, Geological and Mining Engineering, École Polytechnique Montréal, C.P.6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada; NSERC Industrial Chair on Drinking Water, École Polytechnique Montréal, P.O. Box. 6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada. Electronic address: anne-sophie.madoux-humery@polymtl.ca.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Madoux-Humery
authors.affiliation: City of Laval, Engineering Services, P.O. Box 422 Station Saint-Martin, Laval, Québec H7V 3Z4, Canada. Electronic address: m.galarneau@ville.laval.qc.ca.
authors.forename: Martine
authors.initials: M
authors.lastname: Galarneau
authors.affiliation: Civil, Geological and Mining Engineering, École Polytechnique Montréal, C.P.6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada; NSERC Industrial Chair on Drinking Water, École Polytechnique Montréal, P.O. Box. 6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada. Electronic address: michele.prevost@polymtl.ca.
authors.forename: Michèle
authors.initials: M
authors.lastname: Prévost
authors.affiliation: Canada Research Chair in Source Water Protection, École Polytechnique Montréal, P.O. Box. 6079, Succ. Centre-ville, Montréal, Québec H3C 3A7, Canada; Civil, Geological and Mining Engineering, École Polytechnique Montréal, C.P.6079, Station Centre-ville, Montréal, Québec H3C 3A7, Canada. Electronic address: sarah.dorner@polymtl.ca.
authors.forename: Sarah
authors.initials: S
authors.lastname: Dorner
mesh_terms: D057231:Climate Change; D003247:Conservation of Natural Resources; D060766:Drinking Water / Q000737:chemistry*; D004784:Environmental Monitoring; D051639:Gardening / Q000379:methods; D011891:Rain; D062065:Wastewater / Q000032:analysis* / Q000706:statistics & numerical data
chemical_list: D060766:Drinking Water; D062065:Wastewater
keywords: Best management practices; Combined sewer overflows; Rain gardens; Source water protection; Stormwater