Written by Rachel Laplante, M.Sc | September, 2022
In the first article, we saw that overflows are wastewater discharges into waterways that occur mainly during heavy rainfall and snowmelt. We also discussed their effects on the environment and human health. In this article, we will instead focus on the legislation in place in Quebec to monitor overflows, as well as on the actions that can be taken to mitigate their impacts, taking into account the effects of climate change.
Municipal Legislation in Quebec
In 2014, the Regulation respecting municipal wastewater treatment works (ROMAEU, Q-2, r.34.1) came into force in Quebec. It aims to reduce pollution from overflows in order to better protect sources of drinking water, along with aquatic life, bathing areas, and ecosystems. To achieve this, ROMAEU oversees the collection of both quality data on overflows throughout Quebec, as well as the quantity of overflows that is permitted per structure. All municipalities must monitor overflows in their territory. Municipalities must, therefore, either have an electronic recorder or note the movement of a particular marker each week so as to determine the frequency, duration, and time of overflows for all structures with an average annual flow exceeding 10 m3/day and which are under the 54th parallel. Two of the important ROMAEU standards are that overflows in dry weather (without rain) are not permitted, and that the number and quantity of overflows is limited for each structure annually. In order to collect this information, municipalities must fill out a monthly form for each structure, in which they count the number of overflows, the context (rain, melting snow, emergency, etc.), the duration, and an estimate of the volume, where possible. Municipalities must also complete an annual report summarizing overflows, including instances of non-compliance and remedial measures. This regulation is a step in the right direction when it comes to having a portrait of the significance of overflows in our waterways. Subsequently, concrete actions are also needed to reduce the impact of these overflows.
Finally, overflow data from these various municipalities is compiled by the MELCC in a database called the Monitoring municipal water treatment works system (SOMAEU), which is available online.
Mitigation of the Impact of Overflows
In order to mitigate the impact of overflows, several actions can be taken by municipalities and citizens. These actions mainly consist of reducing the amount of water entering our sewers, as well as the time it takes for this water to reach our sewers.
As a citizen, it is possible to install a rainwater collector, divert runoff from their foundations, build a rain garden or build infiltration wells that allow water to be distanced from their foundation drain which is connected to the sewer network. In general, the goal here is to reduce the amount of impermeable surfaces, such as concrete, to allow for better runoff. Greening is, therefore, also an action to consider.
On a larger scale, building a separate sewer system is ideal. As we saw in the last article, a sewer system is made up of one conduit that transports domestic wastewater to treatment plants and another conduit that discharges rainwater into the environment. Although sanitary sewers are advantageous to avoid many overflows, rainwater and runoff can still be contaminated. Therefore, it is also necessary to remove pollutants present in the air and on the ground. This can be done by sweeping the street to remove rubbish and de-icing salt, for example.
The conservation of wetlands is also important, since they can help increase water infiltration, reduce runoff speed, and increase the capture of pollutants. Finally, increasing green areas in municipalities can greatly improve infiltration and groundwater recharge. The number and volume of overflows are amplified by soil sealing and the reduction of vegetation. These practices produce an increase in the volume of runoff water that goes into the sewers, as well as the probability of observing overflows in rainy weather. This is why the regreening of the urban environment can be part of the solution to overflows in tomorrow’s cities.
In order to mitigate the impact of climate change on overflows, the most significant action that can be taken is to increase the volumes of the pipes used to transport water. However, this action alone is not sufficient and must be combined with others. Regreening, establishing retention basins and correcting problems in the current network (e.g. presence of roots) are also necessary to reduce the impact of overflows.
In Quebec, the ROMAEU was set up to monitor municipal wastewater treatment works. This data on overflows (grouped in the SOMAEU) is necessary in order to locate the watercourses most impacted by overflows. By better knowing the places most impacted by overflows it could be possible to identify the places most conducive to recreational activities since, as we know, overflows can have an impact on human health. In addition, this could make it possible to better target priority locations for making changes that would minimize the impact of overflows. These changes can be made at both the individual and municipal level. Within the context of climate change, the actions with the greatest impact are the modification of the sewer network and the regreening of urban areas. In short, overflows are a reality of our society, and certain actions must be taken to reduce their impact on the environment as much as possible.
AGIR MASKINONGÉ. (2013). LE RUISSELLEMENT DES EAUX – COMMENT AGIR CHEZ VOUS POUR GARDER VOTRE LAC EN SANTÉ. HTTPS://WWW.AGIRMASKINONGE.COM/_FILES/UGD/9BD761_B9D014646F2045D9B77CF2DBEB05198B.PDF
CITY OF VANCOUVER. (2019).RAIN CITY STRATEGY: A GREEN RAINWATER INFRASTRUCTURE AND RAINWATER MANAGEMENT INITIATIVE.HTTPS://VANCOUVER.CA/FILES/COV/RAIN-CITY-STRATEGY.PDF
GARDE-RIVIÈRE DES OUTAOUAIS. (2018). RÉDUIRE LES SURVERSES D’ÉGOUTS UNITAIRES : UN GUIDE POUR L’ACTION COMMUNAUTAIRE. HTTPS://OTTAWARIVERKEEPER.CA/WP-CONTENT/UPLOADS/2018/10/GUIDE-DES-SURVERSES-D%C3%A9GOUTS-UNITAIRES.PDF
MADOUX-HUMERY, A. S. (2015). CARACTÉRISATION DES DÉBORDEMENTS D’ÉGOUTS UNITAIRES ET ÉVALUATION DE LEURS IMPACTS SUR LA QUALITÉ DE L’EAU AU NIVEAU DES PRISES D’EAU POTABLE [DOCTORAL DISSERTATION, ÉCOLE POLYTECHNIQUE DE MONTRÉAL].HTTPS://PUBLICATIONS.POLYMTL.CA/2044/1/2015_ANNESOPHIEMADOUXHUMERY.PDF
MAILHOT, A., BOLDUC, S., DUCHESNE, S., & VILLENEUVE, J. P. (2008). ADAPTATION AUX CHANGEMENTS CLIMATIQUES (CC) EN MATIÈRE DE DRAINAGE URBAIN AU QUÉBEC: REVUE DE LITTÉRATURE ET ANALYSE CRITIQUE DES MESURES DE CONTRÔLE À LA SOURCE: VERSION FINALE.
MAILHOT, A., BOLDUC, S., TALBOT, G., & KHEDHAOUIRA, D. (2014). GESTION DES EAUX PLUVIALES ET CHANGEMENTS CLIMATIQUES. UNIVERSITÉ DU QUÉBEC, INSTITUT NATIONAL DE LA RECHERCHE SCIENTIFIQUE, CENTRE EAU TERRE ENVIRONNEMENT.
MINISTÈRE DE L’ENVIRONNEMENT ET DE LA LUTTE CONTRE LES CHANGEMENTS CLIMATIQUES. (2022). DÉBORDEMENTS ET DÉRIVATIONS D’EAUX USÉES. HTTPS://WWW.ENVIRONNEMENT.GOUV.QC.CA/EAU/EAUX-USEES/OUVRAGES-MUNICIPAUX/DEBORDEMENTS.HTM
MINISTÈRE DE L’ENVIRONNEMENT ET DE LA LUTTE CONTRE LES CHANGEMENTS CLIMATIQUES. (2021). ENCADREMENT DES DÉBORDEMENTS ET DES DÉRIVATIONS D’EAUX USÉES PAR LE MINISTÈRE. HTTPS://WWW.ENVIRONNEMENT.GOUV.QC.CA/EAU/EAUX-USEES/OUVRAGES-MUNICIPAUX/DEBORDEMENTS/ENCADREMENT.PDF
RÈGLEMENT SUR LES OUVRAGES MUNICIPAUX D’ASSAINISSEMENT DES EAUX USÉES. RLQ, C. Q-2, R. 34-1. HTTPS://WWW.LEGISQUEBEC.GOUV.QC.CA/FR/DOCUMENT/RC/Q-2,%20R.%2034.1