Collection System Modeling for Planning/Design of Sanitary Sewer Overflow (SSO) Control

The nation's sanitary sewer infrastructure is aging with some sewers dating back over 100 years. There are more than 19,500 municipal sanitary sewer collection systems nationwide serving an estimated 149 million people and comprising about 500,000 sewer miles. Potential health and environmental risks associated with poor performance of many of these systems highlight the need to increase federal regulatory oversight of the management, operation, and maintenance of these systems. As a result, EPA is in the final stage of preparing and issuing a SSO Rule that will add control of SSO to the NPDES permit requirements. This paper provides a preview of the Rule and describes the advantages of employing a collection system modeling approach for capacity assurance of various components of a collection system and development of SSO mitigation plan. A case study at Henrico County, VA is provided to illustrate the application of a collection system modeling approach to plan for sanitary sewer system improvements.