MANAGEMENT AND ENGINEERING STRATEGIES TO CONTROL WET WEATHER CONVEYANCE PROBLEMS UNDER PROPOSED U.S. EPA SSO RULE

This paper presents conveyance wet weather control strategies to management and engineering staff who represent a National Pollution Discharge Elimination System (NPDES) permittee. Management Strategies Utility management decisions have a significant influence on the direction and eventual cost of wet weather controls. This paper will preview the effects and consequences of management decisions and offer strategies in the following areas under a proposed U.S. Environmental Protection Agency (EPA) Sanitary Sewer Overflow (SSO) Rule:Capacity, Management, and Operational and Maintenance (CMOM) Program: The extent to which the program is implemented and available for public participation will be extremely important to regulators who later are requested to approve subsequent activities. The subsequent activities primarily include the permittee's request for a remote treatment facility for peak flow treatment upstream of the treatment plant's headworks and for participation in a watershed program. Also, it will be important when seeking an affirmative defense for SSOs resulting from severe natural conditions or conditions caused by other factors as defined by the Prohibition of Discharges provisions of the Rule.Watershed Approach: The permittee has an option of pursuing resolution of wet weather conveyance problems through a watershed approach under certain circumstances. This option has the opportunity to greatly reduce the cost of capital programs and improve area water quality.Integrating Multiple Program Tools such as Data Handling and Visualization Technologies: Management shapes the extent of subsequent engineering evaluations for specific control options and processes. For instance, management's support or non-support of data-handling systems, control options such as infiltration/inflow reduction, storage, wet weather treatment facilities, cost-effective analysis, and public involvement activities has a consequence for overall program costs and acceptance.Engineering Strategies Engineering strategies to control wet weather conveyance problems must balance the permittee's assets and protect the health of the general public. For instance, hydraulic modeling is a significant activity to evaluate existing and future conveyance scenarios. Software and modeling requirements will differ depending on whether the engineer is steered toward the long-term or the watershed approach. The long-term approach will not depend on software with water quality modules. For the watershed approach, these features are important. Other factors such as evaluating continuous time spans—including both dry and wet weather rain periods; selecting a characteristic rain year from historical records; and defining the boundary conditions of an overflow event from the modeling data—are reviewed.