DETAILED SYSTEM UNDERSTANDING SUPPORTS PROJECT REFINEMENT DURING CSO LTCP IMPLEMENTATION PHASE

In March 2000, the Springfield Water and Sewer Commission (SWSC) completed a draft combined sewer overflow (CSO) Long Term Control Plan and Environmental Impact Report (March 2000 LTCP). The March 2000 LTCP established a range of projects organized into multiple phases to be implemented in accordance with an Administrative Order (AO) schedule negotiated with the Massachusetts Department of Environmental Protection (DEP) and the United States Environmental Protection Agency Region I (EPA). As the March 2000 LTCP moved into the implementation phase, the SWSC followed an approach of updating the level of system understanding in the vicinity of the projects, creating the opportunity to cost-effectively refine or modify the projects to achieve a similar or greater level of CSO control. The SWSC's Clinton Street screening and disinfection facility project is presented as an example of this approach.As a result of this reassessment, a project was identified that is recommended to be implemented in lieu of the Clinton Street screening and disinfection facility. The project consists of separation of the combined sewers to outfalls 007 (Rowland Street) and 049 (Springfield Street). Following the sewer separation work, CSO discharges at outfall 049 will be permanently eliminated, and CSO discharges at outfall 007 will be eliminated in storms up to and including the 2-year, 24-hour storm. In the near term, outfall 007 will remain open for relief in storms greater than the 2-year, 24-hour storm. It may be feasible to fully eliminate the CSO discharges at outfall 007 as part of a subsequent phase of work. The elimination of the CSO at outfall 049 and significant reduction of CSO at outfall 007 will provide a greater net reduction in annual bacteria load to the Connecticut River compared to the Clinton Street screening and disinfection facility, and will provide the SWSC with greater flexibility in implementing additional CSO controls along the Connecticut River while maintaining consistency with the March 2000 LTCP.