August 13, 2015
Property Owner for Sampling Station at:
RE: Special Notice of Drinking Water Monitoring Results
Enclosed are the results of recent water system monitoring conducted in August 2015. As indicated on the data summary sheets, no water quality violations have been observed .
However, you are receiving this special notice because one of the test results exceeded the notification threshold for a single sample. The enclosed summary sheet indicates that one test result recently exceeded the threshold for trihalomethanes (THMs). However, the average of several test results indicates that water quality at your location meets drinking water quality standards.
For many water standards, multiple water samples are necessary to accurately characterize the quality of the water in a large distribution system over time. A violation of some water quality standards occurs when the average of several samples exceeds the allowable limit (annual average). This kind of standard is developed when the objective is to understand if a long-term or chronic risk exists.
Water Treatment and Water Quality Standards
Drinking water is treated with chlorine to kill harmful bacteria so the water is safe to use for drinking, cooking, bathing, and swimming. Chlorine is a strong chemical that kills bacteria but also reacts with other compounds present in water to form chemicals referred to as “disinfection by-products.” This group of disinfection by-products includes a family of chemicals called Trihalomethanes (THMs, also referred to as Total THMs or TTHMs). THM formation increases as water temperature rises and as water age increases, so the highest THM levels are generally found during the hottest summer months in the parts of the water distribution system that are the farthest distance from the treatment plants where the water has been in the pipes for the longest amount of time.
THM’s are regulated by the North Carolina Department of Environment and Natural Resources (DENR) through rules prescribed by the U.S. Environmental Protection Agency (EPA) under the federal Safe
Drinking Water Act. According to public health officials, the regulations were established because laboratory animal testing indicates high consumption of THMs over an extended period of time
(equivalent to 20 – 30 years in humans) seems to be associated with a higher risk of some types of liver and kidney cancers in those animals. However, continued research has shown inconsistent results. The
International Agency on Cancer Research and the World Health Organization have concluded there is not enough evidence to prove that THMs pose a health risk to humans. Nonetheless, EPA has made
THM regulations more stringent several times, most recently in 2012/2013.
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Next Steps
No action on your part is needed at this time. Mecklenburg County Health Department officials and
N.C. DENR officials agree the water distributed to Charlotte Water customers complies with federal
Safe Drinking Water Act and NC DENR requirements and is safe to use for drinking, cooking, bathing, and swimming.
THMs do not affect taste, color or odor of drinking water.
Charlotte Water will:
1.
Minimize formation of THMs in the drinking water system through on-going optimized operation including strategically flushing water through fire hydrants and automated flushing valves;
2.
Optimize existing treatment processes within the plants to minimize potential for THM formation as much as possible;
3.
Continue frequent sampling and analysis of drinking water to confirm quality;
4.
Communicate with customers about water quality test results;
5.
Share information and strategies with other water users who draw water from the Catawba lakes; and
6.
Expedite evaluation and implementation of changes to the drinking water treatment process which could reduce THM formation and further protect the quality of the drinking water.
If you have any questions, please do not hesitate to contact me at bgullet@charlottenc.gov
or 704-336-
4962. You may also contact Mecklenburg County Medical Director, Stephen Keener at Stephen.Keener@MecklenburgCountyNC.gov
or 704-314-9022.
Sincerely,
Barry Gullet, P.E.
Director, Charlotte Water
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