A USA TODAY motion graphic showing how lead can get into your drinking water.
Ramon Padilla, Karl Gelles and Shannon Green, USA TODAY

Water in west Tempe is in violation of drinking-water standards for toxic organic chemicals, city officials announced on Monday.

Total Trihalomethanes, also called TTHMs, exceeded the maximum level of 80 parts per billion set by the Environmental Protection Agency and other agencies, Tempe spokeswoman Nikki Ripley said. TTHMs are a byproduct of disinfecting water with chlorine, according to the city.

Federal law requires public disclosure when the average annual levels exceed the maximum standard. Tempe’s annual average was 85, or five parts per billion over the acceptable level.

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Tempe officials sought to assure residents that it is not an emergency and residents do not need to boil water or take other preventative steps.

Tempe spokeswoman Shannon Reed said the most recent test showed the level already had dropped to an acceptable range of 74 parts per billion.

When was the problem detected?

City workers test for Total Trihalomethanes each quarter at the eight monitoring stations across the city, Ripley said.

Workers found higher levels at a monitoring station near Baseline Road and 48th Street as early as last summer. However, for a one-year period, the average did not exceed federal standards until May.

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Test results from August 2016 to May at the west Tempe monitoring station were:

  • 95 parts per billion on Aug. 11, 2016.
  • 48 parts per billion on Nov. 8, 2016.
  • 78 parts per billion on Feb. 2.  
  • 120 parts per billion on May, 9.

Health risks

People drinking water with high levels of TTHMs over many years can experience problems with their liver, kidneys and central nervous system, and may have an increased risk of cancer, according to the EPA website.

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Despite the long time needed for such impacts, city officials suggest certain residents should seek advice from their health-care providers about drinking the water until the issue is fully resolved. Those residents include anyone with a severely compromised immune system, with an infant, or who is pregnant or elderly.

What’s being done about it?

The city is integrating clean water from wells throughout the city’s water supply, flushing water at strategic locations and adjusting chemical levels to address the problem.

Tempe is conducting water tests every 24 hours until the issue is fixed. Daily testing will continue through at least Aug. 8 to ensure compliance, Reed said.

“Although we will not technically know whether we return to compliance until that date, our daily non-compliance sampling over the last several days has reflected significant progress,” Reed said.


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