A model-based assessment of infiltration and inflow in the scope of controlling separate sanitary overflows at pumpi ng stations

Infiltration & Inflow (I&I) are a major cause for s eparate sanitary sewers overflows (SSOs). A proper planning of actions for controlling SSOs n eeds a precise quantification of these events, as well as an identification of the respect ive contributions of infiltration into sewer and inappropriate connection of runoff water to san itary sewers. For these purposes a specific model is being developed and validated on a dozen c atchments of Nantes Metropole urban community. This paper details the issues of SSOs co ntrol and the method which is proposed to deal with them. Results are presented about the screening of observed overflows according to their causes, and about the efficiency of the mo del for simulating peak flows and overflow risks. The overall capacity of the model to extrapo late infiltration and inflow discharge from meteorological data is fairly good, but its ability to reproduce peak flows leading to pumping capacity saturation is less satisfying.