40 CFR 141.623 - Reduced monitoring.

§ 141.623 Reduced monitoring.

(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 § 141.132(b)(1)(iii) or § 141.132(d).

Source water type Population size category Monitoring
frequency 1
Distribution system monitoring location per 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.
250,000-999,999 per quarter 6 dual sample sets - at the locations with the three highest TTHM and three highest HAA5 LRAAs.
1,000,000-4,999,999 per quarter 8 dual sample sets - at the locations with the four highest TTHM and four highest HAA5 LRAAs.
≥5,000,000 per quarter 10 dual sample sets - at 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.
100,000-499,999 per quarter 2 dual sample sets; at the locations with the highest TTHM and highest HAA5 LRAAs.
≥500,000 per quarter 4 dual sample sets at the 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 § 141.132(b)(1)(iii) or § 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 § 141.621 or begin increased monitoring if § 141.625 applies.

(d) The State may return your system to routine monitoring at the State's discretion.

This is a list of United States Code sections, Statutes at Large, Public Laws, and Presidential Documents, which provide rulemaking authority for this CFR Part.

This list is taken from the Parallel Table of Authorities and Rules provided by GPO [Government Printing Office].

It is not guaranteed to be accurate or up-to-date, though we do refresh the database weekly. More limitations on accuracy are described at the GPO site.


United States Code

Title 40 published on 10-May-2017 04:28

The following are ALL rules, proposed rules, and notices (chronologically) published in the Federal Register relating to 40 CFR Part 141 after this date.

  • 2017-04-11; vol. 82 # 68 - Tuesday, April 11, 2017
    1. 82 FR 17406 - Use of Lead Free Pipes, Fittings, Fixtures, Solder and Flux for Drinking Water; Extension of Comment Period
      GPO FDSys XML | Text
      ENVIRONMENTAL PROTECTION AGENCY
      Proposed rule; extension of comment period.
      Comments must be received on or before May 17, 2017.
      40 CFR Parts 141 and 143