Credit: Kieran Smith
It is common to see large culverts that discharge rainwater into rivers and lakes as they are installed to keep streets, sidewalks, and basements free from flooding. The dirty truth about these sewer outflows is that in many older cities, what is coming from these pipes may not just be rainwater. Combined Sewer Overflows (CSOs) occur in cities that were built with a combined sewer system through which rainwater and sewage are mixed before treatment. When increased water flow occurs in these systems, such as during a rainfall event or even from water used by the fire department to fight a fire, treatment plants cannot handle the demand. Consequently, the excess wastewater flows directly into adjacent waterways. In 2017, an estimated 164 million cubic meters (or 65,600 Olympic sized swimming pools) of untreated sewage from CSOs was discharged directly into waterways across Canada. This is a serious problem that requires innovative and forward-thinking municipal politicians, along with financial support from provincial and federal governments, to build resilient green infrastructure to better treat and manage wastewater.
CSO Replacement Now
While cities are taking important steps to reduce CSOs by separating sewers, municipal politicians are missing out on the opportunity of a lifetime to fundamentally shape the way that cities manage wastewater by neglecting green innovation. By primarily building separated sewers, which drain rainwater directly into bodies of water, municipal politicians have tried to solve the problem of combined sewer overflows by creating another. The problem with separated sewers is that rainwater carried from the street often contains pollutants such as heavy metals which can be damaging to aquatic habitats. Paradoxically, separated sewers can, in some instances, be just as polluting as combined sewers.
The Solution
The clear solution is a system that employs grey and green infrastructure. Grey infrastructure is a term that relates to the use of concrete, steel, or other inorganic materials as the primary construction material. In wastewater management, grey infrastructure can include pipes, stormwater retention tanks, and even roads. Green rainwater management is a process whereby infrastructure is built using natural elements that mimic natural processes of absorbing and reusing water. Infrastructure such as bioswales, rain gardens, green roofs, permeable pavement, and stormwater tree trenches can all be part of a green rainwater system.
There have been some trailblazing municipalities that have recognized the importance of green infrastructure as a tool to manage CSOs. The City of Portland, Oregon began implementing green infrastructure in 1991 when it was suffering from nearly 23 billion litres of CSO discharge per year. Despite only spending 10% of the project budget on green infrastructure, 35% of stormwater is now managed in that city by green infrastructure. When New York City decided address its combined sewer problem, it determined that building a system combining green and grey infrastructure would cost $1.5 billion less to taxpayers than a grey infrastructure system alone. Though the short-term cost of maintaining green infrastructure was deemed to be higher, in the long term, the green system had a lower overall maintenance cost.
In Canada, the City of Vancouver has taken the important step of creating the Rain City Strategy. This strategy provides a roadmap for reducing CSOs and managing wastewater by employing green and grey infrastructure to meet the goal of treating 90% of the city’s rainwater by 2050. The strategy not only looks at the environmental benefits of the plan but also the social and economic benefits of green infrastructure. The strategy further highlights that beyond its primary purpose, green infrastructure sequesters carbon, reduces the urban heat island effect, and helps mitigate flooding. It also demonstrates that there are many mental and physical health benefits for individuals who interact with, and live around, natural environments.
The Financial Issues Facing Municipalities in Canada
Municipal infrastructure is crumbling across the country. One third of municipal infrastructure in Canada is considered to be in fair, poor, or failing condition and this has implications on quality of life and life safety. Municipal governments often do not have the statutory authority to take on debt for their operating budgets and must handle a disproportionate financial burden for infrastructure. They are also limited in their revenue streams and must rely primarily on user fees and property taxes, and are not allowed to implement a sales tax. As sub-national governments, municipalities in Canada are often called “creatures of the province” and are treated as such instead of a level of government that is respected and treated as a responsible institution. Literature on municipal financing brings forward many of the same issues recently as it did in the 1960s, and it does not seem like the challenges will be resolved anytime soon. Dealing with the CSO problem is not cheap, for example the estimated cost of Winnipeg’s combined sewer replacement program is $2.3 billion, while at the same time that city needs to upgrade its main sewage treatment plant at a price tag of $1.8 billion.
The Challenge for Municipal Leaders Going Forward
The challenge that lies ahead for municipal leaders in Canada who wish to implement a plan like the Rain City Strategy lies first in convincing their city council colleagues and residents that building green infrastructure has merit, and second in convincing senior levels of government that it is worth the expense. Given the potential of constructing green infrastructure as a recovery tool from the economic shock of the COVID-19 pandemic, all levels of government should consider green rainwater management infrastructure as a key pillar in their infrastructure investment and economic recovery plans, despite little public appetite. While Combined Sewer Overflows are a problem that cannot be solved quickly in Canada, senior levels of government need to step up to the plate and help municipalities build infrastructure that is environmentally friendly, improves the lives of residents, and provides resiliency to the challenges of an ever-changing climate. It is time for elected leaders to lead on this important issue.
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