The state's standard is that no greater than 5 percent of samples should be undetectable for two months in a row, Apperson said.
Pippel said that there was no reason to notify residents of the situation, from either a regulatory or operational standpoint.
Drops in chlorine levels are "not uncommon," Pippel said, adding that low chlorine levels over an extended period of time would be more of a concern.
Chlorination is important in the water treatment plant, where it is used to get rid of contaminants, but once treated water leaves the plant, chlorine serves more of a "maintenance" purpose, she said.
The drop in chlorine levels in August occurred because high summer temperatures expedite chlorine depletion, and the water temperatures in the tank at the time were near 80 degrees, Snader wrote in his report.
Turnover of water in the tank had been low because settings on a new pump-regulating system were not utilizing the tank enough, Snader wrote. Those settings were adjusted so water in the tank is replaced with freshly treated water more often and chlorine levels were increased, he wrote.
The drop in chlorine was not connected to a separate issue reported to MDE on Sept. 8, when someone identifying themself as a plant employee called the police and alleged that a degreaser was pumped into the Sharpsburg water supply, Apperson said.
That report was untrue, Pippel said. The misunderstanding stemmed from the fact that the county's supplier had provided liquid chlorine in containers that were previously used for a cleaner called Citrisol, she said.
The containers did, in fact, contain liquid chlorine, and had been labeled as such, but the supplier had not blacked out the previous chemical name, Pippel said.
The county contacted the supplier and was told the containers had been cleaned and sanitized prior to reusing for liquid chlorine, Apperson said.
Citrisol is a natural, organic food-grade cleaner, he said.
"All of the questionable containers were removed by Aug. 17 and now the plant is only accepting shipments in containers used only for the specific chemical that they are using," according to an MDE report on the incident.
MDE staff contacted county officials by phone and followed up with a site visit, Apperson said. There were no violations associated with the matter, but MDE's Water Supply Program told the county they should have notified the state as soon as they discovered the potential problem, Apperson said.
Pippel said county staff routinely test chemicals upon receipt to verify the contents and ensure they meet strength requirements.