AWWA JTMGT64452

With increasing federal regulations on storm water management, utilities now have to manage both the quantity and quality of storm water runoff that occurs from developed and undisturbed land. This challenge is particularly acute for utilities that have a legacy combined sewer system, which conveys both storm water and sanitary sewage to the treatment facilities. On normal flow conditions, the combined sanitary sewer system functions well in conveying the combined flows to the treatment facilities. However, in times of heavy rainfall, due to the excessive storm water runoff, the system carries flows that are in excess of treatment capacity. When such situations occur, the combined sewer system triggers a Combined Sewer Overflow (CSO), wherein a portion of the untreated flows are directly diverted to surface water streams, bypassing treatment. The CSOs significantly impair downstream surface water quality, endangering aquatic life while also posing a health hazard. To mitigate CSOs, Municipalities that have legacy combined sewer systems typically develop and implement CSO mitigation plans. Successful implementation of CSO mitigation tasks requires significant financial investments. Therefore, municipalities with combined sewer systems have a greater need to not only aggressively manage storm water runoff but also to develop a financing mechanism to meet the investment and operational needs of CSO mitigation. This paper describes a three-phased framework that municipalities with a legacy combined sewer system can utilize to develop a storm water user fee program. The framework facilitates the determination of storm water revenue requirements, and the development of an equitable and defensible storm water user fee. The framework and the illustrative values presented are based on the storm water user fee that was developed recently for the City of Wilmington, Delaware. The framework described here is applicable not only to municipalities that have a legacy of combined sewer infrastructure, but also to any utility that maintains a combined water/sewer enterprise fund, without delineating a distinct chart of accounts for storm water operations. Includes figures.