Coosa Water Authority would like its roughly 2,000 customers to know that they have not actually been exposed to dangerous levels of fluoride in their drinking water.
This month, Coosa Water mailed a “Fluoride MCL Violation” notice to customers along with its 2024 Water Quality Report. The notice follows a template set by the state that is required to run in the event of a violation.
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As detailed in the notice, the Running Annual Average reported for each of the three quarters between October 2024 and June 2025 showed fluoride levels of about 16 mg/L, which is four times the maximum contamination level, or MCL, of 4 mg/L.
For reference, the target fluoride concentration is around 0.7 mg/L.
If the fluoride concentration were indeed 16 mg/L for nine months, people who consumed the water would need to look out for potentially dire health effects, as provided in the notice.
However, Coosa Water Manager Cole Sullivan explained that the violation stemmed from a single abnormal test sample collected in August 2024.
Coosa Water does two kinds of fluoride testing: monthly with the Georgia Department of Public Health and quarterly with the Environmental Protection Division of the Georgia Department of Natural Resources.
The monthly test is called a split-sample test, because a water sample is taken and split in two, with one half of the sample tested in-house and the other mailed to a Public Health lab for independent comparison testing.
Water samples for monthly testing are collected from random places within the distribution system, making them representative of the water that is coming out of taps in homes and businesses.
All the monthly tests during the violation period came back within an acceptable range of the target fluoride concentration, as usual. These results have been uploaded for the public at https://coosawater.com/.
Quarterly testing for the EPD, however, consists of a single sample being collected and sent to the state every three months. This sample is required to be taken from one of the four large wells Coosa Water uses to treat and distribute drinking water.
Sampling inside the wellhouses is much more difficult than pulling from a fire hydrant or turning on a faucet somewhere in the system; the wells are large, but the sampling locations are close to the injection sites where fluoride is added for treatment.
On Aug. 5, 2024, a Coosa Water employee took and sent the quarterly testing sample from one of these wells. Sullivan said it was not until October that he learned the sample tested remarkably high for fluoride, at 62 mg/L – nearly 16 times the maximum contamination level.
Confused, Sullivan contacted the state to ask about the “crazy result,” which came nowhere near matching the normal level of fluoride measured in the monthly testing that occurred the same day.
The result could have happened from a mistake at the state testing lab, but EPD told Sullivan it was likely due to incorrect sampling, that is, taking a sample too close to an injection site that contains a much higher concentration of fluoride than a sample of water that has been properly mixed inside the well.
“They said we could have re-sampled, but we didn’t know anything about it until October, so by that time, it was too late for us to re-do that one sample to try to prove that it wasn’t that way,” Sullivan said.
Unfortunately, the “damage” was done; for the sake of transparency and because the re-testing window had passed for that monitoring period, EPD decided to let the abnormal sample stand, which resulted in a violation being issued, Sullivan said.
And since the Running Annual Average is determined using the four most recent quarters, it will take a full year for the abnormal result to be removed from the RAA calculation, making it seem like the fluoride concentration is high enough to warrant a violation for four straight quarters.
For further illustration, the quarterly testing sample taken in October 2024 read 1.2 mg/L, in January 2025 read 1.3 mg/L, and in April 2025 read 0.39 mg/L – all within acceptable range of the target fluoride concentration and well below the 62 mg/L from August 2024.
The four-quarter running average for the above test results comes to 16.2 mg/L, or four times higher than the maximum contamination level – which is how the violation is being calculated and assessed.
Sullivan fully anticipates the RAA will be back in compliance once the abnormal quarterly test result rolls off the annual average later this year.
To Sullivan’s knowledge, this is the only time an issue like this has ever come up; still, Coosa Water is working to establish better sampling procedures inside the wellhouses to prevent a similar problem moving forward.
