Sewage from the majority of York Region's communities is collected through local and regional sewer systems. This collection system is extensive and varies in age and condition.
Sewer System Statistics
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Length of public wastewater mains - 3300 km
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Estimated length of private mains including service laterals and mains on private property - 1600 km
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Manholes – 43 700
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Average Age – Approx. 40 years
As these systems age, there is a higher chance that inflow and infiltration (I&I) will enter the sewers. Inflow and Infiltration (I&I) is a technical term for rainwater and/or groundwater that enters the sewage system and adds clean water flow to the regular sanitary sewage flows.
In some cases, older construction practices allowed for direct connections of the household storm water drainage system to the sanitary system. For example, some residential areas constructed in the 1960s and 1970s allowed rain water downspouts from houses to connect to the sanitary system.
Inflow: Inflow is water from rainfall, snowfall or snow melt that enters the sewage system from yard, roof and footing drains, from cross-connections with storm drains, downspouts, and through holes in manhole covers. Peak inflow usually occurs during heavy storm events, which can result in sewer backups or system overflows.
Infiltration: Infiltration is groundwater that enters sewer pipes and manholes through holes, breaks, joint failures, connection failures and other openings. Infiltration quantities often exhibit seasonal variation in response to groundwater levels. Storm events can trigger a rise in groundwater levels and increase infiltration flows. The highest infiltration flows are seen after large storm events or after long periods of precipitation.
Image Source: King County, WA Department of Natural Resources and Parks, Wastewater
Treatment Division. (2008)
York Region and the municipalities are working together to identify the sources of inflow and infiltration and repair and/or disconnect reduce flows.
What are we doing about inflow and infiltration reduction?
Why should we reduce I&I?
How do we find the sources of inflow and infiltration?
I & I Reduction – Mitigating Measures
Frequently Asked Questions
Related Links
The Town of Aurora was successful in receiving The Building Canada Fund – Ontario grant to help improve wastewater infrastructure and to support their I&I reduction strategy.
Visit the
Building Canada Fund website for more information.
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