In the Long-Term 2 Rule, the bin scenario represents source water concentrations used to assess what?

• A. Maximum contamination risk
• B. Average concentration for theoretical potential contamination
• C. Median contamination potential
• D. Minimum contamination potential

Answer: (B)

In LT2, the binning approach groups source water concentrations into ranges and uses a representative value from each range to model potential contamination. The bin scenario specifically uses the average concentration within that bin as the basis for evaluating treatment needs under LT2. This lets regulators consider a typical, not extreme, level within that range to assess how much treatment is needed for potential contamination. So the bin scenario represents the average concentration for theoretical potential contamination. It isn’t about the maximum or minimum value, and it isn’t selecting a median for a decision; it’s about using the bin’s average to model a plausible contamination scenario.