Understanding and Assessing Impacts
The sanitary waste system takes wastewater discharged from toilets, sinks and other household plumbing through municipal sewer pipes to a treatment facility. Independent (i.e. separated) waste and stormwater sewer systems have been municipal best practice for new developments for the past six decades. However, before current practices were adopted, the homes were serviced with a combined sewer system to carry both sanitary waste and stormwater. These combined systems are proving to be outdated, as they are designed to discharge untreated sewage into local waterbodies during intense precipitation events—compromising stormwater runoff quantity and quality, and threatening fish habitats. Homes connected to combined sewers are also prone to damage from the backup of sanitary wastewater. In Metro Vancouver, the largest impact of climate change is expected to be increased frequency and severity of intense rainfall events. This made it crucial for the region to assess vulnerabilities and devise a plan that improved stormwater management by replacing outdated combined sewer infrastructure. Member municipalities of Metro Vancouver combined efforts with provincial and federal environmental agencies to form the Stormwater Interagency Liaison Group in 2002. The organization conducted research related to stormwater management and analyzed long-term rainfall records and climate scenarios to gain a better understanding of risk levels which would inform adaptation actions and their timelines. It was to map out which municipalities had the highest percentage of combined sewers in the region. Combined sewers are less common in Greater Vancouver than in many other large, older cities in North America, which made the task of replacing these systems more feasible.