AWWA DPOC56510

The upcoming Stage 2 Disinfectants and Disinfection Byproducts Rule (DBPR) will require Community Water Systems (CWSs) to conduct an Initial Distribution System Evaluation (IDSE). The IDSE is intended to select new compliance monitoring sites within the water distribution system that more accurately reflect sites representing high TTHM and HAA5 levels than those sites currently used for compliance. They will be based either on system specific monitoring or other system specific data that provides equivalent or better information on site selection. Systems will recommend new or revised monitoring sites to their State/Primacy Agency based on their IDSE study. As utilities prepare for the Stage 2 DBPR, all options for conducting the IDSE should be considered. Utilities may conduct a Standard Monitoring Program as outlined in the IDSE guidance. This process involves sampling at several new distribution system monitoring locations in addition to current compliance monitoring locations every two months over the course of one year. In lieu of conducting a Standard Monitoring Program to identify distribution system locations with high DBP levels, the Rule also allows for System Specific Studies. In these studies, systems may perform an IDSE study based on other system specific monitoring or system specific data that will provide comparable or superior selection of new monitoring sites that target high DBP levels.