Carson City is mailing notices to all 16,000 of its drinking water customers after tests indicated two out of 30 local wells have levels of uranium higher than federal standards allow.
City officials say the situation isn't an emergency and that using bottled water won't be necessary.
Both wells have been shut down and will remain that way until the problem is resolved.
The standard set by the U.S. Environmental Protection Agency for uranium is 30 parts per billion. The average level during the past year from these wells was 34 and 51, said Andrew Burnham, the city's development services director.
These amounts were obtained by averaging the amounts registered during quarterly tests during 2005 on the wells, he said.
Water in the well with the lower amount of uranium may be mixed with other water to bring the level down to the required measure, said Tom Hoffert, the city's public works operations manager.
The well containing water that reaches the higher level of uranium may require other forms of treatment, such as drilling replacement drinking water wells, Hoffert and Burnham said.
Because the city's water system mixes water from a variety of wells before it reaches users - usually three different wells - shutting off the two wells doesn't mean that overall delivery will be hindered, Hoffert said. Wells are routinely shut down for maintenance.
"Most drinking water sources have low levels of radioactive contaminants," according to the EPA. "Certain rock types have naturally occurring trace amounts of 'mildly radioactive' elements."
And in Carson City, granite is prevalent, Hoffert said.
The EPA has found uranium, which naturally occurs in some water sources, can "cause toxic effects to the kidneys," and some people who drink water containing uranium in excess of the amount "over many years may have an increased risk of getting cancer."
"If you have specific health concerns, contact your doctor," Burnham said.
The mailed notices should begin arriving by the middle of the week, Hoffert said.
According to Burnham, the Safari Mobile Home Park in North Carson, which has its own separate water system, was found to have too much uranium in its system. Other communities where higher-than-allowed concentrations of uranium have been found include Hawthorne, Elko, Austin, Zephyr Cove and Washoe Valley.
What is uranium?
Uranium is a chemical element with the symbol U and atomic number 92 in the periodic table. A heavy, silvery-white, toxic, metallic and naturally radioactive element, uranium belongs to the actinide series and its isotope 235U is used as the fuel for nuclear reactors and nuclear weapons. Uranium is commonly found in very small amounts in rocks, soil, water, plants and animals (including humans).
- Source: Wikipedia
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