What is Infiltration & Inflow?
Infiltration & Inflow (I & I) refers to water from storm events and elevated groundwater tables entering the sanitary and combined sewer systems. Infiltration occurs as a result of elevated groundwater levels, not an individual rain event. This clean water can enter the system through cracked or broken sewer lines, open joints, or leaky manhole covers. Inflow is directly attributable to a rain event. Direct inflow occurs during the rain event, when clean water from roof leaders (downspouts), foundation and yard drains, and catchbasins discharge into the sewer system. Delayed inflow refers to water that continues to enter the system days after a storm event has ended. Delayed inflow is usually the result of basement sump pumps. The Town of South Hadley has developed an I & I Control Plan as required by the Wastewater Treatment Plants NPDES Permit, and must implement the components of this plan over the course of the five years covered by the NPDES Permit.
