In the Stage 2 Disinfectants and Disinfection Byproducts Rule, new sampling sites are based on what evaluation?

• A. Worst case sites throughout the distribution system
• B. Furthest points in the distribution system
• C. Lifetime distribution system evaluation
• D. Running annual average evaluations

Answer: (C)

In Stage 2 of the Disinfectants and Disinfection Byproducts Rule, where you sample is determined by analyzing how the distribution system could accumulate disinfectant byproducts over time. Operators perform a lifetime distribution system evaluation to identify zones where DBP formation potential is highest given factors like water age, temperature, disinfectant residuals, and historical data. By pinpointing these areas, the sampling plan targets sites that best represent the maximum DBP levels the system could produce, ensuring monitoring data accurately reflects potential exposure.

Other approaches don’t align with the established method: simply picking the farthest points or assuming worst-case locations isn’t the formal evaluation used, and running annual averages is about data analysis rather than site selection. The lifetime distribution system evaluation is the recognized basis for choosing new sampling sites.