100 YEAR STORM SSO CONTROL PROGRAM

Many municipalities are investing significant resources to the development and implementation of Sanitary Sewer Overflow (SSO) elimination programs. Successful programs employ a variety of evaluation, planning, design, and implementation tools, including collection system flow monitoring and hydraulic models developed and calibrated using actual flow data. These models are often used to comply with regulatory requirements associated with wet-weather Combined Sewer Overflow (CSO) and SSO control programs. Models are vital to the analysis of existing and proposed system performance under a variety of possible hydrologic and hydraulic scenarios.While modeling efforts are critical to system assessment and planning, models must be supported and complemented by thorough review of existing records, input from system operators and managers, and, most important, field verification of existing system conditions. This paper focuses on the importance of well planned hydraulic modeling efforts, which incorporate flow monitoring and field investigation. The ultimate results is an SSO control program that implements the best SSO control alternatives in terms of life-cycle costs and likely environmental impacts. The 100 Year-24 Hour Storm (4.7 inches in 24 hours) was used as the criteria by the Michigan Department of Environmental Quality (MDEQ) to measure the future performance of the SSO elimination measures. The appropriate quantity and quality of hard data gained by initial identification and condition assessment yields the model inputs necessary for reliable long-term system planning.