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EF/ ICR Logo National Treated Water Levels of Total Trihalomethanes for OCTOBER - DECEMBER 1997



REMINDER: Data Purpose: The ICR data were collected as part of a national research project to support development of national drinking water standards. They should NOT be used to determine local water systems compliance with drinking water standards, nor should they be used to make personal judgements about individual health risks.

Units: Sample measurements are taken in micrograms per Liter (ug/L) and are regulated in milligrams per Liter (mg/L). A microgram per Liter is equivalent to one contaminant part per billion (ppb). A ppb can be thought of as one grain of salt in a swimming pool. Data for Total Trihalomethanes, haloacetic acids 5, and bromate are presented in ppb. 1 mg/L = 1000 ug/L, or 0.080 mg/L = 80 ug/L = 80 ppb, which happens to be the TTHM standard in the Stage 1 DBP Rule.

Calculation in Regulations is Different: Comparisons with compliance calculations based on the existing Total Trihalomethanes standard in CFR Part 141.30 may not be warranted since the standard is based on an annual average of public water system quarterly averages and not on treatment plant results as shown here. Also the results here are based on different types of samples.

Results of Zero: A result of zero may indicate that a sample was analyzed, but that the result was less than the lowest value that the analytical method can reliably report.



National Treated Ground Water Levels of Total Trihalomethanes


Table of National Ground Water Total Trihalomethanes Levels

Levels of Total Trihalomethanes (ppb) Water Type Number of Plants
0 - 10 Ground Water 50
10 - 20 Ground Water 7
20 - 30 Ground Water 13
30 - 40 Ground Water 8
40 - 50 Ground Water 2
50 - 60 Ground Water 4
60 - 70 Ground Water 3
70 - 80 Ground Water 2
80 - 90 Ground Water 2
110 - 120 Ground Water 1


National Treated Surface Water Levels of Total Trihalomethanes


Table of National Surface Water Total Trihalomethanes Levels

Levels of Total Trihalomethanes (ppb) Water Type Number of Plants
0 - 10 Surface Water 15
10 - 20 Surface Water 29
20 - 30 Surface Water 42
30 - 40 Surface Water 59
40 - 50 Surface Water 42
50 - 60 Surface Water 26
60 - 70 Surface Water 19
70 - 80 Surface Water 12
80 - 90 Surface Water 4
90 - 100 Surface Water 7
100 - 110 Surface Water 5


Results for mixed water (ground water and surface water) and purchased water can be found under water system summary reports.


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