EPA Offers Initial Distribution System Evaluation Guidance Manual, Tool

EPA announced on Feb. 8 that it posted on its Web site a manual that explains the Stage 2 Disinfectant Byproduct Rule: Initial Distribution System Evaluation (IDSE) requirements to utilities and provides guidance to states and EPA (since EPA will be performing activities in some states prior to those states receiving primacy) on reviewing completed IDSE plans and reports.

The manual covers the four options for fulfilling the IDSE requirement: Very Small System Waiver, 40/30 Certification, Standard Monitoring and System Specific Studies. Flow charts, tear-out requirements sheets, templates and examples are provided to help utilities understand requirements and options for complying. This technical manual provides detail on how utilities can use different types of data to help select monitoring sites for the evaluation.

Soon to be posted on the guidance Web page is the IDSE Tool, a web-based electronic wizard designed to help water systems through the entire IDSE process. Systems first use the wizard to determine which IDSE option is best for them. The IDSE Tool then creates custom forms for the selected option and guides the system step-by-step through the forms that can then be submitted electronically. The IDSE tool also is available on CD-ROM.

An IDSE is required as part of Stage 2 Disinfectants and Disinfection Byproducts Rule (DBPR). IDSEs are one-time studies conducted by water systems to identify distribution system locations with high concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs). Water systems will use results from the IDSE, in conjunction with their Stage 1 DBPR compliance monitoring data, to select compliance monitoring locations for the Stage 2 DBPR.

Additional information on Initial Distribution System Evaluation (IDSE) and IDSE Tool can be accessed at http://www.epa.gov/safewater/disinfection/stage2/compliance_idse.html.

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