eCFR Reference Browser

---

title: "40 CFR §141.623"

source: "https://www.ecfr.gov/current/title-40/section-141.623"

title_number: "40"

volume_number: "25"

chapter_number: "Unknown"

subchapter_code: "D"

subchapter_subject: "WATER PROGRAMS (CONTINUED)"

part_code: "141"

part_subject: "NATIONAL PRIMARY DRINKING WATER REGULATIONS"

subpart_code: "V"

subpart_subject: "Stage 2 Disinfection Byproducts Requirements"

section_number: "141.623"

section_subject: "Reduced monitoring."

cfr_reference: "40 CFR 141.623"

title_name: "Title 40"

title_subject: "Protection of Environment"

parts_covered: "Parts 136 to 149"

revised_date: "Revised as of July 1, 2019"

publication_date: "As of July 1, 2019"

contains_description: "Containing a codification of documents of general applicability and future effect"

publication_info: "Published by the Office of the Federal Register National Archives and Records Administration as a Special Edition of the Federal Register"

---

(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).

(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.

§141.623 - Reduced monitoring.