Replacement of Combined Sewers

In 2002, several environmental goals for Metro Vancouver were set under the Liquid Waste Management Plan to combat an expected increase in frequency and severity of intense rainfall events due to climate change. It was considered crucial for the Metro Vancouver area to improve stormwater management by replacing all combined sewer systems with separated sewer systems. Combined sewer systems are designed to discharge untreated sanitary waste into local receiving waterbodies during intense precipitation events, which are ever-increasing due to climate change. Metro Vancouver sought to eliminate the discharge of such pollutants, which threatened fish and their habitat by negatively impacting water quantity and quality. Metro Vancouver and its member municipalities formed the Stormwater Interagency Liaison Group in 2002 to facilitate the coordination of common research related to stormwater management. Sewer studies were initiated that analyzed long-term rainfall records and climate change scenarios. Metro Vancouver launched multi-year sewer separation programs that involved replacing all combined sewers by 2075. While the area has made significant infrastructure improvements, a major challenge that emerged involved addressing sewer laterals on private property. Private sewer laterals seldom receive any maintenance or inspection after their initial construction and most property owners were unaware of the condition of their sewer connections. Metro Vancouver municipalities are considering implementing by-laws that would use the time-of-sale of a home or a property transfer as a triggering circumstance for requiring the rehabilitation of private sewer laterals.

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 These combined systems are proving to be outdated, as they are designed to discharge untreated sewage into local waterbodies during intense precipitation events—compromising stormwater runoff quantity and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.

Identifying Actions

Coordination with member municipalities and provincial and federal environmental agencies was fundamental in the process of researching effective stormwater management practices. In 2002, Metro Vancouver initiated long-term climate change scenario analyses that would inform the scope and timeline of adaptation plans relating to sewer infrastructure upgrades. A comprehensive provincial Liquid Waste Management Plan (formed in 2002) set several environmental goals that would guide Metro Vancouver’s adaptation actions. One of the goals of the plan was to eliminate wet weather combined sewer overflows. To reach that goal, Metro Vancouver committed to the replacement of combined sewers with separated sewer systems. The region’s low proportion of combined sewers relative to other large, older cities in North America made it more feasible to devise multi-year sewer separation programs for several member municipalities in Metro Vancouver. The programs included regular reporting to the public in neighbourhoods where the work is completed, and a schedule for future work to be completed. The region plans to replace most combined sewers by 2050, with the last replaced by 2075. The main purpose of the sewer separation program was the elimination of wet weather combined sewer overflows into the ocean and Fraser River. The infrastructure upgrades were deemed essential in protecting the community’s water quality and preserving local fish habitats.

Implementation

The three municipalities in the Metro Vancouver area with the highest percentage of combined sewers were Vancouver, Burnaby, and New Westminster. These communities were prioritized during the implementation of the infrastructure upgrade plan. As mentioned previously, the timeline for the implementation involved replacing most combined sewers by 2050, with all combined sewers replaced by 2075. As combined sewers are being replaced, municipalities are keeping communities in the loop by reporting to the public when work is completed in their neighbourhood. A detailed schedule of future work has contributed to the efficient and organized implementation of multi-year sewer separation programs. Implementation of infrastructure upgrades in the private portion of the sewer system has lagged behind the work being done in the public sewer systems. Metro Vancouver commissioned research to explore whether it would be feasible to implement a regulatory private sewer lateral certificate program in Metro Vancouver. This research, in conjunction with the outcomes of current sewer separation programs, will help inform future adaptation actions relating to the rehabilitation of outdated private sewer laterals that increase the risk of sewer overflows into the ocean and the Fraser River. The replacement of combined sewers in Metro Vancouver is a long-term initiative that is still in the early stages of the implementation phase. The region has already introduced several separate sewers, and will continue to replace combined systems until 2075 following timelines outlined in a detailed scheduled for future work.

Outcomes and Monitoring Progress

Several combined sewer systems in Metro Vancouver have been replaced with separated systems, reducing the risk of wet weather combined sewer overflows into local waterbodies. The municipalities in the region will continue to make these infrastructure improvements as outlined in the plan until combined sewer overflows are eliminated entirely. A major challenge that has emerged involves addressing sewer laterals on private property. To reduce the risk of sewer backup, considerable work on private properties would need to be done. Lateral sewers in poor condition allow excessive groundwater to flow into the sanitary sewer, resulting in excessive infiltration. The private portion of a sewer system is more difficult for municipalities to tackle because of complex jurisdiction issues. Metro Vancouver conducted intensive research studies which reported that using the time-of-sale of a home or a property transfer as a triggering circumstance for requiring the rehabilitation of private sewer laterals could be a feasible option for long-term management of inflow and infiltration from private properties. It would be the role of municipalities to enforce these recommendations thorough by-laws or various programs. In Metro Vancouver, several jurisdictions, including the City of Surrey and Vancouver, have implemented sewer lateral replacement programs to minimize the long-term impact of inflow and excessive infiltration. Thus, an important lesson learned was that separating combined sewer systems was not enough in achieving the community’s goal of eliminating harmful overflows into waterbodies; it was also necessary to introduce initiatives that incentivize private sewer lateral maintenance and rehabilitation.

Next Steps

Member municipalities of Metro Vancouver will continue to follow multi-year sewer separation programs that outline the replacement of combined sewer systems up until 2075. If the work follows the schedule, most combined sewers will be replaced by 2050 and all will be eliminated by 2075. The research commissioned by Metro Vancouver has informed several recommendations for how to incentivize private property owners to maintain sewer laterals. With commitment from external key professionals in the building, plumbing, real estate, and property transfer industries, municipalities can rely on time-of-sale of a home as a trigger for requiring the rehabilitation of private sewer laterals. The research report also suggests that “success is most likely to result from a staged timeline for implementation, to build understanding of the issues, acceptance of responsibilities, and move towards a general acceptance of the need for regular private sewer lateral maintenance over the long term.” It would be the role of Metro Vancouver municipalities to enforce these recommendations through programs and by-laws as an important next step in the process of improving the region’s sewage system.

Resources

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