TTHM LRAA Data

Total Trihalomethanes (TTHMs) are regulated by the Safe Drinking Water Act through the Stage 2 Disinfectant Byproduct Rule. The City of Bloomington Utilities collects monthly samples at 8 testing locations throughout the distribution system and follows a quarterly compliance schedule. Compliance is calculated on a Locational Running Annual Average (LRAA). The Maximum Contaminant Level for TTHMs is 80 µg/l. Micrograms per liter (µg/l) is equal to parts per billion (ppb). One part per billion is roughly equal to a teaspoon of water in an Olympic-size swimming pool.