(a) You may reduce monitoring to the level specified in the table in this paragraph (a) any time the LRAA is <=0.040 mg/L for TTHM and <=0.030 mg/L for HAA5 at all monitoring locations. You may only use data collected under the provisions of this subpart or subpart L of this part to qualify for reduced monitoring. In addition, the source water annual average TOC level, before any treatment, must be <=4.0 mg/L at each treatment plant treating surface water or ground water under the direct influence of surface water, based on monitoring conducted under either Sec. 141.132(b)(1)(iii) or Sec. 141.132(d). ----------------------------------------------------------------------------------------------------------------
Distribution system
Source water type Population Monitoring frequency \1\ monitoring location per
size category monitoring period----------------------------------------------------------------------------------------------------------------Subpart H:
<500 .......................... monitoring may not be
reduced.
500-3,300 per year.................. 1 TTHM and 1 HAA5 sample:
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;
1 dual sample set per
year if the highest TTHM
and HAA5 measurements
occurred at the same
location and quarter.
3,301-9,999 per year.................. 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.
10,000-49,999 per quarter............... 2 dual sample sets at the
locations with the
highest TTHM and highest
HAA5 LRAAs.
50,000-249,999 per quarter............... 4 dual sample sets--at the
locations with the two
highest TTHM and two
highest HAA5 LRAAs.
250,000-999,99 per quarter............... 6 dual sample sets--at the
9 locations with the three
highest TTHM and three
highest HAA5 LRAAs.
1,000,000-4,99 per quarter............... 8 dual sample sets--at the
9,999 locations with the four
highest TTHM and four
highest HAA5 LRAAs.
=5, per quarter............... 10 dual sample sets--at
000,000 the locations with the
five highest TTHM and
five highest HAA5 LRAAs.Ground Water:
<500 every third year.......... 1 TTHM and 1 HAA5 sample:
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;
1 dual sample set per
year if the highest TTHM
and HAA5 measurements
occurred at the same
location and quarter.
500-9,999 per year.................. 1 TTHM and 1 HAA5 sample:
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;
1 dual sample set per
year if the highest TTHM
and HAA5 measurements
occurred at the same
location and quarter.
10,000-99,999 per year.................. 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.
100,000-499,99 per quarter............... 2 dual sample sets; at the
9 locations with the
highest TTHM and highest
HAA5 LRAAs.
=50 per quarter............... 4 dual sample sets at the
0,000 locations with the two
highest TTHM and two
highest HAA5 LRAAs.----------------------------------------------------------------------------------------------------------------\1\ Systems on quarterly monitoring must take dual sample sets every 90 days.
(b) You may remain on reduced monitoring as long as the TTHM LRAA <=0.040 mg/L and the HAA5 LRAA <=0.030 mg/L at each monitoring location (for systems with quarterly reduced monitoring) or each TTHM sample <=0.060 mg/L and each HAA5 sample <=0.045 mg/L (for systems with annual or less frequent monitoring). In addition, the source water annual average TOC level, before any treatment, must be <=4.0 mg/L at each treatment plant treating surface water or ground water under the direct influence of surface water, based on monitoring conducted under either Sec. 141.132(b)(1)(iii) or Sec. 141.132(d).
(c) If the LRAA based on quarterly monitoring at any monitoring location exceeds either 0.040 mg/L for TTHM or 0.030 mg/L for HAA5 or if the annual (or less frequent) sample at any location exceeds either 0.060 mg/L for TTHM or 0.045 mg/L for HAA5, or if the source water annual average TOC level, before any treatment, 4.0 mg/L at any treatment plant treating surface water or ground water under the direct influence of surface water, you must resume routine monitoring under Sec. 141.621 or begin increased monitoring if Sec. 141.625 applies.
(d) The State may return your system to routine monitoring at the State's discretion.