One key element of LT2 is to use monitoring results to classify surface water sources into USEPA-defined risk levels called bins. How many bins are defined?

• A. Giardia, three
• B. Cryptosporidium, three
• C. Giardia, four
• D. Cryptosporidium, four

Answer: (D)

LT2 uses monitoring results to place surface water sources into USEPA-defined risk levels called bins, and these bins are defined for Cryptosporidium. There are four bins, which categorize risk from lowest to highest and help determine treatment requirements. Giardia is monitored as well, but the binning framework used to classify source water risk under LT2 is based on Cryptosporidium; hence the correct choice points to Cryptosporidium with four bins. The other options mix Giardia with a bin count or reference Giardia in the binning framework, which does not match how LT2 defines the bins.