(a) Your IDSE report must include your recommendations and justification for where and during what month(s) TTHM and HAA5 monitoring for subpart V of this part should be conducted. You must base your recommendations on the criteria in paragraphs (b) through (e) of this section.
(b) You must select the number of monitoring locations specified in the table in this paragraph (b). You will use these recommended locations as subpart V routine compliance monitoring locations, unless State requires different or additional locations. You should distribute locations throughout the distribution system to the extent possible.
| 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: | ||||||
| <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 | |
| ≥5,000,000 | per quarter | 20 | 8 | 7 | 5 | |
| Ground water: | ||||||
| <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 | |
| ≥500,000 | per quarter | 8 | 3 | 3 | 2 | |
1All systems must monitor during month of highest DBP concentrations.
2Systems 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.
(c) You must recommend subpart V compliance monitoring locations based on standard monitoring results, system specific study results, and subpart L compliance monitoring results. You must follow the protocol in paragraphs (c)(1) through (c)(8) of this section. If required to monitor at more than eight locations, you must repeat the protocol as necessary. If you do not have existing subpart L compliance monitoring results or if you do not have enough existing subpart L compliance monitoring results, you must repeat the protocol, skipping the provisions of paragraphs (c)(3) and (c)(7) of this section as necessary, until you have identified the required total number of monitoring locations.
(1) Location with the highest TTHM LRAA not previously selected as a subpart V monitoring location.
(2) Location with the highest HAA5 LRAA not previously selected as a subpart V monitoring location.
(3) Existing subpart L average residence time compliance monitoring location (maximum residence time compliance monitoring location for ground water systems) with the highest HAA5 LRAA not previously selected as a subpart V monitoring location.
(4) Location with the highest TTHM LRAA not previously selected as a subpart V monitoring location.
(5) Location with the highest TTHM LRAA not previously selected as a subpart V monitoring location.
(6) Location with the highest HAA5 LRAA not previously selected as a subpart V monitoring location.
(7) Existing subpart L average residence time compliance monitoring location (maximum residence time compliance monitoring location for ground water systems) with the highest TTHM LRAA not previously selected as a subpart V monitoring location.
(8) Location with the highest HAA5 LRAA not previously selected as a subpart V monitoring location.
(d) You may recommend locations other than those specified in paragraph (c) of this section if you include a rationale for selecting other locations. If the State approves the alternate locations, you must monitor at these locations to determine compliance under subpart V of this part.
(e) Your recommended schedule must include subpart V monitoring during the peak historical month for TTHM and HAA5 concentration, unless the State approves another month. Once you have identified the peak historical month, and if you are required to conduct routine monitoring at least quarterly, you must schedule subpart V compliance monitoring at a regular frequency of every 90 days or fewer.
[71 FR 483, Jan. 4, 2006, as amended at 74 FR 30958, June 29, 2009]
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