Measured CSO Contribution to River Quality Deterioration and Methodologic Approach for Negative Influence Evaluation

It has been observed that, with conventionally designed interceptors, combined sewer overflows (CSOS) occur almost every time a rain event generates runoff. For example, in the City of Quebec (Quebec, Canada), the maximum rainfall that does not generate runoff is equal to 2.0mm (1). Although, the reality of such overflows is acknowledged and it is possible to control them through better management (real-time control, offline-system storage), the necessity of such interventions has not yet been demonstrated.