You are here:
Review of Sewer Design Criteria and RDII Prediction Methods
Citation:
LAI, DENNIS. Review of Sewer Design Criteria and RDII Prediction Methods. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/010, 2008.
Impact/Purpose:
to inform the public
Description:
Rainfall-derived Infiltration and Inflow (RDII) into sanitary sewer systems has long been recognized as a source of operating problems in sewerage systems. RDII is the main cause of sanitary sewer overflows (SSOs) to basements, streets, or nearby streams and can also cause serious operating problems at wastewater treatment facilities. SSOs usually contain high levels of pathogenic microorganisms, suspended solids, toxic pollutants, floatables, nutrients, oxygen-demanding organic components, and oil and grease. There are serious concerns of potential health and environmental risks associated with these discharges. The Nation’s sanitary sewer infrastructure is aging, with some sewers dating back over 100 years. Nationwide, there are more than 19,500 municipal sanitary sewer collection systems serving an estimated 150 million people and about 40,000 SSO events per year. To assist municipalities in developing plans to mitigate SSO problems, the U.S. Environmental Protection Agency (EPA) in 2002 signed a cooperative research and development agreement (CRADA) with Camp Dresser & McKee Inc. (CDM) to develop a public-domain Sanitary Sewer Overflow Analysis and Planning (SSOAP) Toolbox. It contains a suite of computer software tools to facilitate the analysis of RDII and performance of sanitary sewer systems. In addition, the CRADA includes a recently published technical guide (EPA/600/R-07/111) and a SSOAP user’s manual being prepared to guide the application of the Toolbox. A beta version of SSOAP is planned to be released to the public in 2008. This report primarily provides a literature review of the RDII quantification methods (Chapter 4) to support the development of the SSOAP Toolbox under the CRADA. The literature review is centered on the 1999 WERF report in which eight methods are thoroughly assessed using real data from three sewerage agencies. While there is no single RDII method that is universally applicable, the RTK method was chosen to be implemented in the Toolbox as it is probably the most widely accepted one. The method has long been an option in the EPA Storm Water Management Model (SWMM) and is extensively used. Other RDII methods can be included in future expansion of the Toolbox. Since RDII is closely associated with the structural conditions of sewers and the hydrologic/hydraulic criteria used to design them, Chapters 1 to 3 are included to provide background information. Chapter 1 summarizes the nation’s wastewater infrastructure conditions and problems, origins of and problems caused by infiltration and inflow, and EPA regulatory approaches to address the aging systems and SSOs. Chapter 2 presents the components of wastewater flows that form the basis for sanitary sewer design. Historical and current sewer design practices and flow design standards of selected states and local sewerage agencies are described in Chapter 3.
URLs/Downloads:
Review of Sewer Design Criteria and RDII Prediction Methods (PDF, NA pp, KB, about PDF)URL.PDF (PDF, NA pp, 22 KB, about PDF)