What are the results of the TTHM samplings in my local drinking water?

The PUD met the TTHM standards set forth by the GA Environmental Protection Division at all sampling sites except for the monitoring location on the southeast end of Barnett Shoals.  The site is one of eight sampling locations throughout Athens-Clarke County.  

The Georgia Rules for Safe Drinking Water and Title 40 CFR141.64(b) set the locational running annual average (LRAA) maximum contaminant level (MCL) at 0.080 mg/L.  The LRAA of four-quarters is used to determine if a water system violates the MCL. When a new quarterly sample is taken, the oldest results are removed from the LRAA.  Similar to how a poor grade has lasting effects on a GPA, the high 3Q2021 result, combined with the removal of the low 1Q2021 in the calculations, resulted in a violation for 1Q2022 despite the individual quarterly sample falling below the MCL. 

PUD sampling results for 2Q2022 find the LRAA below the MCL and return the utility to compliance.  The elevated 3Q2021 will drop from future calculations.  With this increased test result rolling off the LRAA and the actions the PUD has taken to address elevated TTHMs, we anticipate the TTHM LRAA to remain below the MCL, as was the case for the past thirteen years since the EPA's Stage 2 Disinfectants and Disinfection Byproducts monitoring requirements began.  The table below displays the quarterly results from this location.

Barnett Shoals Road Quarterly Sampling Results

Third Quarter 2021 ResultsFourth Quarter 2021 ResultsFirst Quarter 2022 ResultsSecond Quarter 2022 Results
Quarter*mg/LQuarter mg/LQuartermg/LQuartermg/L
4Q20200.0834Q2020no longer in the calculation4Q2020no longer in the calculation4Q2020no longer in the calculation
1Q20210.0401Q20210.0401Q2021no longer in the calculation1Q2021no longer in the calculation
2Q20210.0772Q20210.0772Q20210.0772Q2021no longer in the calculation
* Quarters are referred to as "Q."  The number before Q indicates which quarter the results reference, and the last numbers identify the year.  For example, 1Q2021 references the first quarter of 2021. 
** "N/A" is provided for samples not yet gathered.
*** LRAA refers to the Locational Running Annual Average, with a maximum contaminant level (MCL) of 0.080 mg/L.


Show All Answers

1. What are Total Trihalomethanes (TTHM)?
2. What are the standards for TTHM in my drinking water?
3. What are the results of the TTHM samplings in my local drinking water?
4. What can cause elevated levels of TTHM?
5. What are the possible health risks of TTHM in my water?
6. What actions is the Public Utilities Department taking to reduce the TTHM in our water?
7. Why do we add disinfectant to our water?
8. Where can I get additional information?