Rainfall-derived infiltration and inflow (RDII) is the increased portion of water flow in a sanitary sewer system that occurs during and after a rainfall as a source of operating problems in sanitary sewer systems. RDII is the main cause of sanitary sewer overflows (SSO) to
- basements,
- streets, or
- nearby receiving waters.
The extent of infiltration also correlates with the condition of aging sewers. Excessive RDII can also cause serious operating problems at wastewater treatment facilities. There is a need to develop methodologies and computer tools to assist communities in developing an optimal capital improvement program, while providing flexibility for future improvements.
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