Figure: 30 TAC §290.115(c)(3)
| Source Water Type | Population Size Category | Monitoring Frequency 1 | Distribution System Monitoring Location Total per Monitoring Period |
|---|---|---|---|
| Surface or GUI | less than 500 | Annual | Monitoring may not be reduced. |
| 500 to 3,300 | Annual | 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter.2 | |
| 3,301 to 9,999 | Annual | 2 dual sample sets: one at the location and during the quarter with the highest TTHM single measurement, one at the location and during the quarter with the highest HAA5 single measurement. | |
| 10,000 to 49,999 | quarterly | 2 dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs | |
| 50,000 to 249,999 | quarterly | 4 dual sample sets at the locations with the two highest TTHM and two highest HAA5 LRAAs | |
| 250,000 to 999,999 | quarterly | 6 dual sample sets at the locations with the three highest TTHM and three highest HAA5 LRAAs | |
| 1,000,000 to 4,999,999 | quarterly | 8 dual sample sets at the locations with the four highest TTHM and four highest HAA5 LRAAs | |
| 5,000,000 or more | quarterly | 10 dual sample sets at the locations with the five highest TTHM and five highest HAA5 LRAAs | |
| Ground-water | less than 500 | every third year (triennial) | 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter. 2 |
| 500 to 9,999 | Annual | 1 dual sample set per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter.2 | |
| 10,000 to 99,999 | Annual | 2 dual sample sets: one at the location and during the quarter with the highest TTHM single measurement, one at the location and during the quarter with the highest HAA5 single measurement | |
| 100,000 to 499,999 | quarterly | 2 dual sample sets at the locations with the highest TTHM and highest HAA5 LRAAs | |
| 500,000 or more | quarterly | 4 dual sample sets at the locations with the two highest TTHM and two highest HAA5 LRAAs |
1Systems on quarterly monitoring must take dual sample sets every 90 days.
2Systems on annual monitoring and surface water systems serving 500 to 3,300 people will use a single site if the highest TTHM and HAA5 concentrations occur at the same time and place. Any such system may be required to take individual TTHM and HAA5 samples (instead of a dual sample set) at sites identified as the highest TTHM and HAA5 sites, respectively. If separate sites for individual TTHM and HAA5 samples are used, then the TTHM sample must be collected during the quarter with highest historical TTHM levels and the HAA5 sample must be collected during the quarter with the highest historical HAA5 level.