What is I&I? Infiltration and Inflow is clean storm and/or groundwater that enters the sanitary sewer system through holes, breaks, joint failures, connection failures, illegal connections (sump pumps, down spouts/gutters, and footing drains), and from cross-connections with storm sewers. Most inflow comes from stormwater and most infiltration comes from groundwater. High groundwater levels and storm events can contribute to excessive sewer flows.
I&I affects the size of flow conveyed through the system and pumping stations and the cost to treat the flows. Ultimately, this affects the taxes businesses and residents pay to operate and maintain the sewers. Private property I&I can contribute substantially to the problem. An 8-inch diameter sewer can adequately convey flow from roughly 200 homes. However, only 8 sump pumps operating at full capacity can overload the same 8-inch diameter sewer.
The Erie County Division of Sewerage Management (DSM) maintains a proactive approach to sanitary sewer maintenance which includes sewerline flushing, root treatment, manhole inspection and GPS. To minimize and eliminate extraneous stormwater from entering the sanitary sewer system a Division wide program is currently being utilized. Some of the investigative techniques are used to identify sources of I&I include the following:
- Flow Monitoring: Determines the amount of I&I entering a sanitary sewer system. Sensors are placed into the flow and the data is analyzed to determine if more investigation is required in the study area.
- Smoke Testing: Identifies connected downspouts and other inflow sources, such as cross connections with the storm sewer system and deficiencies in and around manholes and sewers. The testing involves placing a blower over a manhole to push a non-toxic, odorless “smoke” into the sewerline and laterals.
- Televising and Dye Testing: a non-toxic dye is added to a possible I&I source like storm drains and ditches. The sewerline is then televised, using a camera to look for cracks, root intrusions, and dye colored infiltration. The video from the camera also serves as a condition assessment for the sewers to determine locations for repairs and rehabilitation projects.
- House Inspections: Includes interior and exterior plumbing inspections to help property owners eliminate illegal or improper stormwater connections like sump pumps, roof drains and more.
- Lateral Rehabilitation: Also available to agreeing homeowners, is a Lateral Replacement Program to replace older private deficient laterals (typically clay tile) that is dependent on development in the specific ECSD. Click the link for more information.
Once I&I sources are identified, several repair and rehabilitation methods are used, including replacement, spot repair, and manhole repair. Trenchless Technologies are also being used, including PipePatch and Cured-In-Place Pipe (CIPP) Lining to help the DSM rehabilitate the sewer infrastructure.
For more information on the DSM's I&I program, call (716) 858-8437 or (716) 858-6586 .