Excess water that flows into sewer pipes from stormwater and groundwater is called inflow and infiltration, or I&I. Stormwater rapidly flows into sewers (inflow) via roof drain downspouts, foundation drains, storm drain cross-connections, and through holes in manhole covers. Groundwater (infiltration) seeps into sewer pipes through holes, cracks, joint failures, and imperfect connections. Most I&I is caused by aging infrastructure that needs maintenance or replacement.

ECUA has committed considerable resources to the elimination and reduction of sewer inflow and infiltration (I&I) in the last three fiscal years. This is an issue that affects, and is of great concern to wastewater utilities throughout North America. ECUA has laid out a 15-year plan to address the situation. Protecting public health and the environment – and reducing wastewater treatment and transmission costs are direct benefits of a regional I&I control program.