Disinfection Byproduct Rule

Effective January 1, 2004, the Arizona Department of Environmental Quality has enacted the Disinfectant Byproducts Rule R18-4-214-02. The rule is designed to enforce those water systems that chose to chlorinate to perform monthly chlorine samples in the distribution system, and to annually test for TTHM (Total Trihalomethanes) and HAA5 (Haloacetic Acids 5).

The city has been chlorinating its source water at the well sites for years. The city chlorinates at the lowest possible levels between .02 and .04 parts per million. The City’s Public Works Department chlorinates to maintain chlorine residual (kill) in the distribution system, to protect the system from Coliform and E. Coli Bacteria.

The HAA5 and TTHM testing is a chemical byproduct of chlorination and in high amounts may be cancerous according to the United States Environmental Protection Agency. The City of Show Low has been proactive with this rule and we have already tested for these precursors last year.

Test Results
The results of the 4 tests are as follows:
  • 3 of the tests showed only a trace for TTHM’s and  the other sample were <5.
  • The MCL (Maximum Contaminate Level) for TTHM is 60 MCL. The Water Department will be testing for these chemicals again this summer in the warmest month of the year.
Additional Information
For questions regarding the testing process and/or testing results, please contact Courtney Carpenter, Water Supervisor at 928-532-4108.