Source water type | Population size category | Monitoring Frequency1 | Distribution system monitoring location total per monitoring period2 |
Subpart H: | |||
[LESS THAN]500 | per year | 2 | |
500-3,300 | per quarter | 2 | |
3,301-9,999 | per quarter | 2 | |
10,000-49,999 | per quarter | 4 | |
50,000-249,999 | per quarter | 8 | |
250,000-999,999 | per quarter | 12 | |
1,000,000-4,999,999 | per quarter | 16 | |
[GREATER THAN EQUAL TO]5,000,000 | per quarter | 20 | |
Ground Water: | |||
[LESS THAN]500 | per year | 2 | |
500-9,999 | per year | 2 | |
10,000-99,999 | per quarter | 4 | |
100,000-499,999 | per quarter | 6 | |
[GREATER THAN EQUAL TO]500,000 | per quarter | 8 |
1 All systems must monitor during month of highest DBP concentrations.
2 Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, except for subpart H systems serving 500-3,300. Ground water systems serving 500-9,999 on annual monitoring must take dual sample sets at each monitoring location. All other systems on annual monitoring and subpart H systems serving 500-3,300 are required to take individual TTHM and HAA5 samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. For systems serving fewer than 500 people, only one location with a dual sample set per monitoring period is needed if the highest TTHM and HAA5 concentrations occur at the same location and month.
40 C.F.R. §141.621