Water Quality Information

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Sioux City Water Supply Has Levels of Total Trihalomethanes (TTHM) Above Drinking Water Standards

December 5, 2019

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

We routinely monitor for the presence of drinking water contaminants. Testing results we received on December 3, 2019 show that our system exceeds the standard, or maximum contaminant level (MCL), for Total Trihalomethanes (TTHM). The standard for Total Trihalomethanes (TTHM) is 0.080 MG/L. The average level of Total Trihalomethanes (TTHM) at 6500 Whispering Creek over the last year was 0.084 MG/L.

What should I do?

You do not need to use an alternative (e.g., bottled) water supply. However, if you have specific health concerns, consult your doctor.

What does this mean?

This is not an immediate risk. If it had been, you would have been notified immediately.  However, some people who drink water containing trihalomethanes in excess of the MCL over many years may experience problems with their liver, kidneys, or central nervous systems, and may have an increased risk of getting cancer.

What happened? What is being done?             

In August 2019 Total Trihalomethane samples were collected and analyzed.  Those test results put the yearly average for Total Trihalomethanes over the MCL at 6500 Whispering Creek.  At that time all Sioux City residents received public notice regarding this MCL exceedance. 

The fourth quarter sample results, collected in November of 2019, were well below the MCL (0.055 MG/L) but not low enough to drop the yearly average below the MCL of 0.080 MG/L, therefore, you are receiving a second notification. 

For more information, please contact Brad Puetz at 712-279-6156 or

This notice is being sent by SIOUX CITY WATER SUPPLY PWSID#: 9778054  



Drinking Water Consumer Confidence Report

The City of Sioux City's annual Consumer Confidence Water Quality Report (CCR) is a report card to our customers of how well the water treatment and supply system is providing for them. The information in the report shows that we produce the best water for our customers by providing the safest water possible. View the last 3 years of CCR reports below. To request a copy by mail, contact the Water Treatment Plant at 712-279-6156.

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