RAINFALL AND COLLECTION SYSTEM PLANNING

EPA has three programs designed to address urban wet weather discharges. These are the combined sewer overflow (CSO) program, the storm water program, and the emerging sanitary sewer overflow (SSO) program. The majority of discharges from collection systems that fall under the regulations that guide these programs are rainfall-induced. Developing an understanding of the cause and effect relationship between rainfall and discharges from collection systems is important for the design, operation and maintenance of collections systems. It is also important for regulatory purposes, as each program has different control requirements, and the implementation of program-specific requirements can vary from state-to state.This paper describes the importance of obtaining good rainfall data and developing a good understanding of rainfall characteristics. The paper focuses on the collection and analysis of rainfall data, followed by a discussion of rainfall-related program requirements that affect collection systems.