AWWA ACE61749

The Initial Distribution System Evaluation (IDSE) requirements of the Stage 2 Disinfection Byproducts Rule (DBPR) are applicable to all systems that add a primary or residual disinfectant other than ultraviolet (UV) radiation to their water. Per the proposed Stage 2 DBPR, the municipality's IDSE report will be due 2 years after promulgation of the rule for systems serving over 10,000 people and smaller systems that are purchasing or selling water to combined systems that include a member serving over 10,000 people (so small systems do their reports concurrent with the systems they are buying from). Systems serving less than 10,000 that do not buy or sell from a combined distribution system with a large member get 4 years to do the IDSE. The Proposed Stage 2 DBPR provides four alternatives for IDSE compliance. The first alternative is to complete the Standard Monitoring Program (SMP). The SMP entails 1 year of distribution system monitoring. The second alternative is to conduct a System-Specific Study (SSS). The SSS is to evaluate DBP concentrations throughout the distribution system using data sources such as historical DBP and disinfectant residual data, water distribution system modeling, and tracer studies. The third alternative is to use a 40/30 Certification. If ALL TTHM compliance samples are less than or equal to 40 µg/L and ALL HAA5 compliance samples are less than or equal to 30 µg/L during the monitoring period specified in the final rule, then the utility may just certify they have met this 40/30 requirement as their IDSE report. The proposed rule said to use the two previous years, e.g. 2002 and 2003, for large systems. Since this rule was delayed, these dates could change, so utilities should check the final rule for these dates. The fourth alternative involves the very small system waiver. Any system serving less than 500 persons can apply to their state for a waiver. Examples of each of the first three approaches above are discussed in this paper and involve the Town of Cary, North Carolina, the Greater Cincinnati Water Works, and the Charleston Commissioners of Public Works. The fourth option is straight-forward and only applicable to very small systems. Includes tables, figures.