Stormwater and sewage don’t mix; and keeping them separate is key to protecting our homes, our waterways, and our community’s future. In South Huron, most of our sewers are already separated, but stormwater can still find its way into the sanitary system through inflow and infiltration (I&I). When this happens, it can overwhelm pipes, increase the risk of basement flooding, reduce capacity for future development, and cost more to treat water that doesn’t require full-scale sewage treatment. This project will highlight how the Municipality is tackling I&I and how residents can play an important role in keeping our system strong and resilient.
How the sewer system works
South Huron’s sewer systems are designed to keep stormwater and sewage separate. Stormwater flows to outfalls directly to the Ausable River or to Municipal Drains that eventually outlet to the Ausable River. The sanitary sewer system that services Exeter, Crediton, Centralia, and Huron Park carries wastewater to the Exeter Wastewater Treatment Facility. Although most combined sewers have already been separated, stormwater can still enter the sanitary system through inflow and infiltration.
What is inflow and infiltration?
Inflow and infiltration (I&I) is stormwater that enters sewers dedicated for sanitary flows.
- Inflow happens when drainage features like downspouts, foundation drains, driveway drains, or catch basins are connected to sanitary sewers.
- Infiltration occurs when cracks in sewer pipes, leaky pipe joints, or unsealed manholes allow groundwater to seep in.
Why inflow and infiltration matters.
When stormwater gets into sanitary sewers, it creates costly and disruptive problems:
- The sanitary system is built for steady household flows from showers, toilets, laundry, and dishwashers. Extra rainwater can quickly overwhelm pipes and cause sewer backups.
- Sanitary flows need full treatment before release, but rainwater does not. Treating clean water wastes money and resources.
- Heavy rain can push the sewage pumping stations beyond capacity, increasing the risk of raw sewage overflows into local waterways.
- I&I reduces system capacity that could otherwise support new homes and businesses - limiting growth for our community and economy.
What residents can do.
A single downspout can collect a surprising amount of water - up to 360 litres per minute during heavy rain. With multiple downspouts and foundation drains, one property can add significant inflow to the sanitary system.
You can help by disconnecting these sources and redirecting them to soak into lawns or soil instead. This keeps stormwater out of sanitary pipes and helps recharge groundwater naturally.
Previous Municipal studies in flood-prone areas identified multiple inflow sources, with most being on private property. Many are downspouts and foundation drains tied into sanitary sewers. As part of this initiative to reduce I&I, the Municipality will contact affected property owners to request their voluntary cooperation in disconnecting these connections.
Programs and support
The Municipality has a grant program (ie. Sewer Incentive Program) to assist homeowners make improvements that reduce basement flooding.
An Open House will be held where residents can learn more about inflow and infiltration, available funding, and practical steps to disconnect downspouts, foundation drains, or other inflow sources.
How the Municipality is taking action.
As part of the annual urban street reconstruction program, the Municipality replaces aging sanitary sewer infrastructure to reduce I&I. A multi-year CCTV inspection program was recently completed to assist in identifying I&I in the sanitary sewer system.
The Municipality has an active sanitary sewer maintenance program consisting of sewer flushing, calcite removal, repairing damaged sanitary laterals, and inspecting manholes for leaks to identify and reduce I&I.
By working together, we can strengthen South Huron’s flood resilience and protect critical infrastructure.
