Source water type | Population size category | Monitoring frequency1 | Distribution system monitoring location | |||
Total per monitoring period2 | Highest TTHM locations | Highest HAA5 locations | Existing subpart L compliance locations | |||
Subpart H: | ||||||
[LESS THAN]500 | per year | 2 | 1 | 1 | ||
500-3,300 | per quarter | 2 | 1 | 1 | ||
3,301-9,999 | per quarter | 2 | 1 | 1 | ||
10,000-49,999 | per quarter | 4 | 2 | 1 | 1 | |
50,000-249,999 | per quarter | 8 | 3 | 3 | 2 | |
250,000-999,999 | per quarter | 12 | 5 | 4 | 3 | |
1,000,000-4,999,999 | per quarter | 16 | 6 | 6 | 4 | |
[GREATER THAN EQUAL TO]5,000,000 | per quarter | 20 | 8 | 7 | 5 | |
Ground water: | ||||||
[LESS THAN]500 | per year | 2 | 1 | 1 | ||
500-9,999 | per year | 2 | 1 | 1 | ||
10,000-99,999 | per quarter | 4 | 2 | 1 | 1 | |
100,000-499,999 | per quarter | 6 | 3 | 2 | 1 | |
[GREATER THAN EQUAL TO]500,000 | per quarter | 8 | 3 | 3 | 2 |
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. §141.605