Stormwater and sewage don’t mix, and keeping them separate is key to protecting our homes, our waterways, and our community’s future. In Welland, 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 neighbourhood growth, and cost more to treat water that doesn’t truly need full-scale sewage treatment. This project is here to highlight how the City is tackling I&I and how residents can play an important role in keeping our system strong and resilient.

How the sewer system works
Welland’s sewer systems are designed to keep stormwater and sewage separate. Stormwater flows to outfalls along the Welland River or Canal, while the sanitary system carries wastewater to the Welland Wastewater Treatment Plant. 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 or unsealed maintenance holes 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 treatment plant beyond capacity, raising 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.

City studies in flood-prone areas identified more than 2,300 inflow sources, with most on private property. Many are downspouts and foundation drains tied into sanitary sewers. In the coming weeks, the City will contact affected homeowners to request their voluntary cooperation in disconnecting these connections.

Here's a video that explains foundation drain disconnection:

Programs and support
The City offers a grant program that provides up to $7,500 to help homeowners make improvements that reduce basement flooding. Visit the City's Sewage Water Alleviation Program (SWAP) page for details.

We’ll also host an Open House where residents can learn more about inflow and infiltration, available SWAP funding, and practical steps to disconnect downspouts, foundation drains, or other inflow sources.

How the City is taking action
City crews are repairing damaged sanitary lateral cleanouts, disconnecting catch basins from the sanitary system, and inspecting maintenance holes for leaks.

Each year, we also run a sewer lining program that reinforces pipes with structural liners to seal cracks and prevent infiltration. Where lining isn’t enough, we excavate and repair problem areas.

By working together, we can strengthen Welland’s flood resilience and protect critical infrastructure.