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Reporting & Recordkeeping


You must report the following information for each monitoring location to Drinking Water Services within 10 days of the end of any quarter in which monitoring is required:
  • Date and result of each sample taken during the last quarter.
  • Whether the MCL was violated at any monitoring location.
  • Any operational evaluation levels that were exceeded during the quarter and, if so, the location and date, and the calculated TTHM and HAA5 levels.
You must keep a copy of your Stage 2 monitoring plan and all monitoring results for 10 years.

In addition, you must continue to report the information required under Stage 1. These requirements include:
  • TOC monitoring (required if you are a surface water system that uses conventional treatment, optional if you want to qualify for reduced TTHM and HAA5 monitoring).
  • Disinfectant residual (chlorine, chloramine, or chlorine dioxide) monitoring (required for all systems).
  • Chlorite monitoring (required if you use chlorine dioxide).
  • Bromate monitoring (required if you use ozone).

Calculating LRAA and OEL

The following spreadsheet calculates the locational running annual average (LRAA) and operational evaluation level (OEL) for each sampling location. Note: During the transition period from Stage 1 to Stage 2, the Stage 1 data would not be included in the 3 preceding quarters.

Consumer Confidence Reports (CCRs)

If you are a community water system, you must include the following information in your annual Consumer Confidence Report (CCR):
  • Highest overall LRAA for both TTHM and HAA5.
  • LRAA for all locations where the MCL is exceeded.
  • Range of individual sample results for all monitoring locations.