Innovative Level of Service Approach to SSO Planning Moves Towards Implementation

The Town of Tonawanda, NY has a significant number of wet weather sanitary sewer overflows (SSOs) throughout its wastewater collection system - 94 SSOs in all. Excess wet weather flow results in overloading the Town's sanitary sewer system, resulting in SSO discharges. Although the Town has a separate sanitary sewer system, it behaves as a combined or a “hybrid sanitary/combined” system. Based on previous efforts, I/I reduction alone did not provide reliable SSO reduction and elimination. The Town developed a comprehensive approach for evaluating their system that balances regulatory compliance with long-term fiscal sustainability of the Town. The program borrows from the USEPA CSO Control Policy and addresses a number of complex topics, which previously were considered applicable only to CSO abatement. These topics include water quality impact considerations, establishing a cost-effective level of service for sanitary sewer systems, knee-of-curve evaluations of abatement alternatives and affordability considerations.