Last month, the drinking water in Bellevue tested positive twice for coliform bacteria, indicating possible exposure to human or animal feces.
The Public Works Department took care of the problem by flushing water mains and temporarily increasing chlorine levels at the city's water source, a natural spring in Muldoon Canyon, east of the city.
Department of Environmental Quality engineer David Anderson said the city's water tested positive on May 12, sparking an investigation as to the cause.
"This was cause for concern, but not for alarm," he said. "The test was negative for E. coli, which would have been cause for alarm."
Coliform bacteria naturally occur in the environment, but can come from feces. Most types are harmless to humans, but E. coli is one type that causes disease.
He said that by May 13, the city's water had tested negative for coliform, quickly enough not to have to warn residents under Idaho law. Bellevue's drinking water is tested monthly for impurities that include bacteria.
"As long as the city continues to check chlorine levels on a frequent basis and continues to send in bacteria tests, everything should be fine."
Public Works Director George Tanner said the bacteria might have collected long ago in water lines. He said some valves along water mains that were replaced last summer in the southeast corner of the city had not been opened.
"There could have been sediment in there," he said. "That is our best guess."
Tanner said the city's wells were not in operation at the time of the positive bacteria test.
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