1. Inflow and Infiltration

Inflow and infiltration are terms used to describe the ways that groundwater and stormwater enter the sanitary sewer system. Rain and stormwater enter the system in two ways:

• Inflow occurs when rain gutter downspouts, weeping tiles, and sump pumps discharge directly into sewers via direct connections.
• Infiltration occurs when groundwater enters the sewer system through broken or cracked sewer pipes and manholes.

The City’s sanitary sewer system was designed to transport wastewater alone, meaning that the addition of stormwater to the system creates a surcharge of sewage. During heavy rainfall, the addition of rainwater to the system results in more sewage than can be treated and processed at the treatment plant in a short period of time. This surcharge of water can be damaging to wastewater treatment infrastructure and can cause sewer backups in residential homes. To protect the treatment plant and private properties, wastewater may be diverted around the secondary treatment. This diversion around one process is called a “bypass.” As climate change progresses over the coming years, it is anticipated that Greater Sudbury will experience a higher frequency of heavy rainfall events, adding stress to our water infrastructure and treatment systems.

If you want to be notified every time there is a bypass event, signup on the Bypass Alerts page.