The term “infiltration and inflow” (also called I & I) refers to the various ways groundwater and stormwater make its way into a sanitary sewer system. You see, in an ideal world, a sanitary sewer system contains wastewater only. However, we don’t live in an ideal world and excess water from sources other than toilets, sinks, and showers finds its way into sewers, unfortunately. This excess water is called ‘clearwater’ even though it’s mainly dirty groundwater and stormwater.
Clearwater is a problem because…
When clearwater gets into a sewer system it causes an increase in the amount of wastewater in the sewer system. This is because clearwater – once it’s in the sewer system – is seen as wastewater and treated as wastewater.
This is bad because wastewater costs money to transport and treat. When there’s an increased amount of wastewater the cost associated with transporting and treating it is passed along to rate payers. This could result in higher sewer bills - which is why we're working now to identify the sources of I&I in our service areas and address the root causes to ensure we maintain a closed system that isn't adding unnecessary treatment costs for cleanwater that finds its way into our system.
I&I
