BY JONAS BEALS

Sometime in the next few days, all Stafford County residents will receive a notice in the mail from the county Utilities Department.

Before residents get concerned about what that notice says, Utilities Director Harry Critzer wants everyone to know that Stafford's municipal water is, and has always been, perfectly safe to drink.

"There's no health effect to this at all," he said. "It's just the result of a mathematical calculation."

That calculation found that the Abel Lake water treatment plant has not been removing organic carbon at a rate that meets state and federal guidelines.

Every quarter, the Virginia Department of Health conducts tests on both treated water and the water stored in the reservoir. One of the things it looks for is how effectively the treatment process is removing organic carbon. The carbon comes from decaying organic matter in the reservoir, mostly plant material such as leaves.

Regulators measure the level of total organic carbon to determine the effectiveness of the treatment.

In order to comply with regulations, the 12-month average ratio needs to be 1 or higher when it is measured each quarter.

From July 2010 to June 2011, that ratio was 0.99 for the Abel Lake water system, which primarily serves southern Stafford.

Hugh Eggborn is the engineering field director for the Virginia Department of Health's office of drinking water. He said that although treatment plants don't often exceed the total organic carbon limit, it does happen occasionally. He said that there's little or no difference between the limit and Stafford's ratio, "but we have to deal with actual numbers in the drinking-water field."

Because of that, Stafford officials are required to send a notice to every address in the county. Eggborn said the county has 30 days to inform the public.

"The regulation exists and we have to comply with it," Critzer said.

County spokeswoman Cathy Riddle said that there is no need to boil water or turn to an alternative water source.

"When people get this notice, we don't want them to panic," she said.

On its own, organic carbon is not harmful.