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Water Treatment Plant

The Zenith Water Treatment Plant is shown in Sioux City. Samples collected from one of the city's eight testing sites in August exceeded the standardized measurement for trihalomethanes.

SIOUX CITY -- Sioux City's water plant superintendent said he doesn't foresee the public facing any immediate health risks from a recent drinking water standard violation involving trihalomethanes.

"Being this is the first violation we've ever had or exceeded a maximum contaminant level, we don't believe there are any health risks associated with this violation at all," Brad Puetz said. "We don't take it lightly. We're working very hard to get back to where we need to be."

Samples collected from one of the city's eight testing sites on Aug. 14 exceeded the standardized measurement for trihalomethanes, disinfection byproducts. The consumption of water containing trihalomethanes in excess of the Environmental Protection Agency's maximum contaminant level (MCL) over many years has been linked with liver, kidney and central nervous system problems, as well as increased risk of bladder, colon and rectal cancers. The EPA projects that the standard will prevent nearly 280 bladder cancer cases annually.

According to the EPA, trihalomethanes are a group of four chemicals that are formed along with other disinfection byproducts when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic and inorganic matter in water. The trihalomethanes are chloroform, bromodichloromethane, dibromochloromethane and bromoform.

August testing results revealed that the total trihalomethanes (TTHM) level in the 6500 block of Whispering Creek Drive was 0.130 milligrams per liter (mg/L). The average TTHM level at that site over the last year was 0.083 mg/L, which exceeds the EPA's MCL of 0.080 mg/L.

Julie Sievers, a senior environmental specialist with the Iowa Department of Natural Resources, said the DNR believes that the public has a right to know when the standard is exceeded, therefore the department requires public notification when a system has a violation. Sievers said the DNR encourages members of the public who have concerns about the violation to talk to their physicians about their individual health circumstances.

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Sievers said such a violation is a common one for a surface water or influenced ground water system. She said the level of organic matter and chlorine in the water, as well as water temperature and water age are associated with the formation of trihalomethanes.

"During August, three out of the four of those were at the level that accelerates or increases the formation," said Sievers, who noted that Sioux City's water system's chlorine levels were normal.

Puetz said he believes higher Missouri River levels and warmer water contributed to the violation.

"When the water is warmer, chlorine reacts and creates disinfection byproducts much quicker than it does with cool water," he said.

Sievers said the city has taken steps to get back into compliance with the standard, including using more of its deep well water, which is colder and lower in organic matter. She said the city has collected additional samples and that those test results should be available in the coming weeks. She said the next required samples won't be taken until November.

"It takes three violations in a 12-month period and then we would require remediation. I don't anticipate that the city will get there, because they've taken immediate action," said Sievers, who said remediation typically involves a capital cost or improvement. "If they still show elevated levels, I'm sure they would look at other things they could do, but I expect (the levels) will be much lower."

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