Source water type | Population size category | Monitoring periods and frequency of sampling | Distribution system monitoring locations1 | ||||
Total per monitoring period | Near entry points | Average residence time | High TTHM locations | High HAA5 locations | |||
Subpart H | |||||||
[LESS THAN]500 consecutive systems | one (during peak historical month)2 | 2 | 1 | 1 | |||
[LESS THAN]500 non-consecutive systems | 2 | 1 | 1 | ||||
500-3,300 consecutive systems | four (every 90 days) | 2 | 1 | 1 | |||
500-3,300 non-consecutive systems | 2 | 1 | 1 | ||||
3,301-9,999 | 4 | 1 | 2 | 1 | |||
10,000-49,999 | six (every 60 days) | 8 | 1 | 2 | 3 | 2 | |
50,000-249,999 | 16 | 3 | 4 | 5 | 4 | ||
250,000-999,999 | 24 | 4 | 6 | 8 | 6 | ||
1,000,000-4,999,999 | 32 | 6 | 8 | 10 | 8 | ||
[GREATER THAN EQUAL TO]5,000,000 | 40 | 8 | 10 | 12 | 10 | ||
Ground Water | |||||||
[LESS THAN]500 consecutive systems | one (during peak historical month)2 | 2 | 1 | 1 | |||
[LESS THAN]500 non-consecutive systems | 2 | 1 | 1 | ||||
500-9,999 | four (every 90 days) | 2 | 1 | 1 | |||
10,000-99,999 | 6 | 1 | 1 | 2 | 2 | ||
100,000-499,999 | 8 | 1 | 1 | 3 | 3 | ||
[GREATER THAN EQUAL TO]500,000 | 12 | 2 | 2 | 4 | 4 |
1 A dual sample set (i.e., a TTHM and an HAA5 sample) must be taken at each monitoring location during each monitoring period.
2 The peak historical month is the month with the highest TTHM or HAA5 levels or the warmest water temperature.
40 C.F.R. §141.601