City of Vancouver identifies need to accelerate sewer separation work

Flooding at the intersection of Broadway and Cambie Street in Vancouver on October 12, 2017. (Alex Couillard/submitted)

Vancouver City Council has approved a new strategy that outlines the urgency to accelerate reinvestments into the sewer system.

The City of Vancouver has been falling behind its 2011-enacted goal of separating 1% of its sewers annually due to the significant cost escalation of replacing the infrastructure.

Currently, 56% of Vancouver’s mainline sewers are separated, and about 60% of its property plumbing connections are separated.

The practice of separating sewers splits sanitary sewage waters (from buildings) and rainwater (from the streets) into different pipes. This not only reduces the release of polluted sewage waters into Vancouver’s waterways but also replaces aging pipes and increases capacity to accommodate densification, population and employment growth, and the expected future increase in frequency in high rainfall events from climate change.

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Without accelerating separation work, sewer overflows from urban rainwater runoff could increase in frequency. This is particularly an issue for East False Creek (between Cambie Bridge and Science World), which is at the bottom of the hill — where rainwater and sewage flows get mixed up.

“During periods of high rain, stormwater runoff raises the levels of flow in the combined sewage system above the capacity of the pipes designed to carry flow to the treatment plant. This excess flow during storm events (a mixture of untreated sewage and stormwater) is then released directly into False Creek,” reads a 2006 report from the BC Ministry of Environment.

Estimated frequency of combined sewer overflow events in Vancouver in 2020. (City of Vancouver)

According to City of Vancouver staff, sewer backups are generally caused by factors such as blocked, clogged, and damaged pipes, as well as undersized pipes with inadequate capacity and heavy rainfall events that overwhelm sewers. But the leading cause of sewer backups in Vancouver is tree root intrusion into pipes — a tradeoff for a city with an ambitious tree-planting initiative — as well as oil, fat, and grease buildup. The average lifespan of a sewage pipe is 100 years.

The City’s newly approved Healthy Waters Plan contemplates the theoretical scenario of achieving 100% sewer separation by 2050. This would require an average renewal and separation rate of 1.6% per year — well above the 1% annual target that is not currently achieved. Annual spending to support a 1.6% annual separation target would have to increase from $36 million per year to $99 million per year, using the previous 2019-2022 capital plan budget for sewer renewals as the baseline.

Last year, the previous City Council approved a 70% increase in the municipal government’s sewer and drainage systems totalling $656 million in the 2023-2026 capital plan budget — up from $380 million in the previous capital plan.

Vancouver sewage and rainwater management costs, historical and forecast. (City of Vancouver)

Last month, City staff told City Council the limitations of existing sewer capacity in low-density, single-family neighbourhoods present a major challenge for allowing significantly more densification in such areas. For this reason, City staff have only proposed gentle densification of multiplexes (up to six units per single-family lot) in single-family areas to avoid the need to perform expensive sewer upgrades, which carries a cost of between $4,000 and $10,000 for every one-metre segment of underground pipe.

In 2018, the municipal government enacted the separate Utilities Development Cost Levy (UDCL) on top of the regular DCL to cover the cost of major utility upgrades in areas experiencing significant densification, especially within the Cambie Corridor. The UDCL is intended to have “growth pay for growth.”

Increased sewage water collected into the pipes also necessitates increased sewage treatment capacity, which is driving Metro Vancouver Regional District’s plan to build a new replacement Iona Wastewater Treatment Plant, located just northwest of Vancouver International Airport.

But its $10 billion construction cost is drawing the ire of Vancouver’s newly elected civic politicians, including Mayor Ken Sim. The new Iona plant will almost exclusively serve residents and businesses within the City of Vancouver, which means ratepayers within this jurisdiction will be largely responsible for its cost. If the project proceeds as planned, it is anticipated ratepayers could see an annual rate hike of $500 to support the new plant’s construction and operating costs.

Vancouver’s population is currently hovering at about 660,000 residents, and it is forecast to grow to 920,000 by 2050. Hundreds of thousands of jobs will also be added to the city over the coming decades.

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