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Tempe exceeds limit on TTHMs in drinking water

This is not an emergency; Tempe's water is safe

Post Date:06/12/2017 12:34 PM

Stage 2 Disinfection By-Products Rule TTHM MCL Violation 


Total Trihalomethanes (TTHM) MCL Violation at the City of Tempe

Our water system recently violated a drinking water standard. Although this incident was not an emergency, as our customers, you have a right to know what happened and what we are doing to correct this situation.

Este informe contiene información importante acerca de su agua potable. Haga que alguien lo traduzca para usted, o hable con alguien que lo entienda.

We routinely monitor for the presence of drinking water contaminants. We monitor for one group of contaminants, Total Trihalomethanes (TTHM), at eight monitoring stations spread across the city.  Testing results from August 2016 to May 2017 show that site A-10 located in west Tempe on the southeast corner of Baseline Road and 48th Street recently exceeded the standard, or maximum contaminant level (MCL), for TTHM as an annual average during this period. The standard for TTHM is 80 parts per billion (ppb). It is determined by averaging all the samples collected at each sampling location for the past 12 months. The level of TTHMs averaged at site A-10 for August 2016 to May 2017 was 85ppb.

What does this mean?

This is not an emergency. If it had been an emergency, you would have been notified within 24 hours.

TTHMs are four volatile organic chemicals which form when disinfectants react with natural organic matter in the water.  People who drink water containing TTHMs in excess of the MCL over many years may experience problems with their liver, kidneys, or central nervous system, and may have an increased risk of getting cancer.

What should I do?

  • There is nothing you need to do, and you can safely continue normal use of Tempe’s drinking water. You do not need to boil your water or take other corrective actions. If your water ever became unsafe to drink, you would be notified within 24 hours.
  • If you have a severely compromised immune system, have an infant, are pregnant, or are elderly, you may be at increased risk and should seek advice from your health care providers about drinking this water during the interim time period while the city is resolving the issue.

What is being done?

The City of Tempe has implemented several immediate responses to ensure that TTHMs return to target levels.  Measures include:

·       Using wells to blend TTHM-free water in the entire system

·       System flushing at strategic locations within our water system

·       Chemical adjustments at water treatment plants

Tempe will be conducting daily water sampling to evaluate the effectiveness of these and other strategies. Water Utilities staff is working 24 hours a day, 7 days a week to resolve the issue as quickly as possible.

For more information, please contact the City of Tempe Environmental Services Section at (480) 350-2678.

*Please share this information with all the other people who drink this water, especially those who may not have received this notice directly (for example, people in apartments, nursing homes, schools, and businesses). You can do this by posting this notice in a public place or distributing copies by hand or mail.*

This notice is being sent to you by the City of Tempe. State Water System ID#: 07-100.

Date distributed:  June 12, 2017.


Media contacts: Shannon Reed 480-639-9045; Nikki Ripley 480-313-8850

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