Disinfectants-Chlorine Residual

How good has the water quality been in 2014?

Note: Reported RAA for quarters 1-3 are based on results from previous quarters not reported on the disinfectants table. St. John monitoring sites were also included.


MRDL 4 as C12
MRDLG 4 as C12
Violation No
Likely Source Water additive used to control microbes
Average levels of Disinfectant-Chlorine Residuals remained between 0.6 and 0.8; therefore, the water quality for the STT/STJ district was good for 2014.

How does the water quality compare each year?

Compare the levels of disinfectant between each year by placing your cursor over any plot for each corresponding month.
Although water quality has improved slighty over the past few years, 2013 has clearly shown the greatest improvement in quality before declining again in 2014.

Has water quality improved over time?

Disinfectants improve the quality of water.
Yes, the data illustrates an improvement in the quality of water but not by much. The level of quality is currently at average and a goal should be set for further improvement.

Stage 2 Disinfectants and Disinfection By-Products Rule (DDBP)

What were the levels of byproducts contaminating the water (by location) in 2014?

Trihalomethanes and Haloacetic Acids are byproducts of disinfecting water with chlorine. Some people who drink water containing Trihalomethanes in excess of the highest allowed (MCL) over many years may experience problems with their liver, kidneys, or central nervous system, and may have an increased risk of getting cancer.


Range 3.2 - 32.2
MCL 80
Violation No
Likely Source Byproduct of drinking water disinfection
Although levels of Trihalomethanes were much higher than Haloacetics in 2014, levels of both byproducts were generally low overall. Byproduct levels increased notably in Quarter 3 but receded to normal levels in Quarter 4.

Trihalomethane amounts by area

Haleoacetic amount by area

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