§141.81. Applicability of corrosion control treatment steps to small, medium, and large water systems. — Inbound Citations

(3) For systems that fail to take one or more actions prescribed by §§ 141.80 through 141.93, the report must include the applicable language of appendix A to this subpart for lead, copper, or both.

(3) Community water systems and non-transient non-community water systems must comply with the requirements of this subpart no later than November 1, 2027, except where otherwise specified in §§ 141.81, 141.84, 141.85, 141.86, and 141.90, or where an exemption in accordance with 40 CFR part 142, subpart C or F, has been issued by the Administrator.

This section provides the requirements for systems and States designating optimal corrosion control treatment (OCCT) for a system that is optimizing or re-optimizing OCCT. All systems must complete the corrosion control treatment requirements in this section as applicable under § 141.81.

(i) If the system exceeds the lead and/or copper action level, the system must implement or re-optimize OCCT in accordance with the deadlines specified in § 141.81, and any other applicable requirements of this subpart.

(c) By the applicable dates under § 141.81, systems shall report the following information:

(1) For water systems demonstrating that they have already optimized OCCT without optimized water quality parameters set by the State, information required in § 141.81(b)(1) through (3).

(2) For systems required to optimize corrosion control, their recommendation regarding optimal corrosion control treatment under § 141.82(a).

(3) For systems required to evaluate the effectiveness of corrosion control treatments under § 141.82(c), the information required by that paragraph.

(4) For systems required to install OCCT or re-optimized OCCT designated by the State under § 141.82(d), a letter certifying that the system has completed installing that treatment.

(5) For systems not required to complete the corrosion control treatment steps under § 141.81(f), a letter certifying that the system has completed the mandatory service line replacement program or that the system has met the minimum annual replacement rate calculated under § 141.81(f)(1)(ii).

Any system subject to the requirements of this subpart shall retain on its premises original records of all sampling data and analyses, reports, surveys, letters, evaluations, schedules, State determinations, and any other information required by §§ 141.81 through 141.88, 141.90, 141.92, and 141.93. Each water system shall retain the records required by this section for no fewer than 12 years.

(f) The State may require a public water system to use bottled water, point-of-use devices, point-of-entry devices or other means as a condition of granting a variance or an exemption from the requirements of §§ 141.61 (a) and (c) and 141.62, to avoid an unreasonable risk to health. The State may require a public water system to use bottled water and point-of-use devices or other means, but not point-of-entry devices, as a condition for granting an exemption from corrosion control treatment requirements for lead and copper in §§ 141.81 and 141.82 to avoid an unreasonable risk to health. The State may require a public water system to use point-of-entry devices as a condition for granting an exemption from the source water and lead service line replacement requirements for lead and copper under § 141.83 or § 141.84 to avoid an unreasonable risk to health.

(ii) The State may require a large water system that does not have to re-optimize under paragraphs (a)(1)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a large water system that does not have to re-optimize under paragraphs (a)(1)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a large water system that does not have to re-optimize under paragraphs (a)(1)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a medium water system that does not have to re-optimize under paragraphs (a)(2)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a medium water system that does not have to re-optimize under paragraphs (a)(2)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a medium water system that does not have to re-optimize under paragraphs (a)(2)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

Small community water systems serving 3,300 or fewer persons and all non-transient non-community water systems that exceed the lead action level, but do not exceed the copper action level, may elect to use this provision in lieu of the corrosion control treatment requirements otherwise applicable to small systems and non-transient non-community water systems in § 141.81(a)(3), if approved by the State. This compliance flexibility is not available to water systems where the State has obtained primacy for this subpart and the State does not adopt regulations to provide compliance flexibility consistent with this section.

(ii) The State may require a small water system that does not have to re-optimize under paragraphs (a)(3)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a small water system that does not have to re-optimize under paragraphs (a)(3)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(ii) The State may require a small water system that does not have to re-optimize under paragraphs (a)(3)(i)(A) through (C) of this section to re-optimize under § 141.82(h).

(i) Section 141.81(b)—for any water system deemed to be optimized under § 141.81(b) of this chapter, any conditions imposed by the State on specific water systems to ensure the continued operation and maintenance of corrosion control treatment in place;

(1) For water systems demonstrating that they have already optimized OCCT without optimized water quality parameters set by the State, information required in § 141.81(b)(1) through (3).

(F) For each water system that has implemented optimal corrosion control pursuant to § 141.82 of this chapter, completed applicable source water treatment requirements pursuant to § 141.83 of this chapter, and/or completed mandatory service line replacement requirements pursuant to § 141.84(d) of this chapter, and the date of the State's determination that these requirements have been met. The date reported must be the latest of the following events:

(1) The date the State received the results of corrosion control evaluations under § 141.82(d) or (e) of this chapter or optimal corrosion control treatment recommendation by the system;

(2) For systems for which the State has designated optimal corrosion control treatment or re-optimized optimal corrosion control treatment under § 141.82(d) of this chapter, the date of the determination and the date the system completed installation of treatment as certified under § 141.90(c)(4) of this chapter;

(3) The date the State designates optimal water quality parameters under § 141.82(f) of this chapter or deems the system to have optimized corrosion control pursuant to § 141.81(b)(1) or (3) of this chapter;

(4) For systems which the State has required to install source water treatment under § 141.83(b)(2) of this chapter, the date of the determination, the date the State designates maximum permissible source water levels under § 141.83(b)(4) of this chapter or determines pursuant to § 141.83(b)(2) that source water treatment is not required; or

(5) For systems required to conduct mandatory service line replacement, the date the system completes mandatory service line replacement pursuant to § 141.84(d) of this chapter.

(6) For systems not required to complete the corrosion control treatment steps under § 141.81(f) of this chapter, the date the system is required to complete mandatory service line replacement pursuant to § 141.84(d) of this chapter.

(1) For water systems demonstrating that they have already optimized OCCT without optimized water quality parameters set by the State, information required in § 141.81(b)(1) through (3).

(i) All water systems with lead or galvanized requiring replacement service lines in their inventories as of November 1, 2027, including those deemed optimized under § 141.81(b)(3), must conduct standard monitoring in the first six-month tap monitoring period following November 1, 2027, unless the system has, before or by that date, met all the following criteria:

(A) The system conducts compliance monitoring of sites that meet the correct priority tiering targeting sites served by lead and galvanized requiring replacement service lines in accordance with paragraph (a)(4) of this section;

(B) The system collects samples in accordance with all sample collection requirements in paragraphs (b)(1) and (3) of this section; and

(C) The system collects either first-liter samples or first-liter-and-fifth-liter- paired samples in accordance with paragraph (b)(1) of this section.

All large water systems and all medium water systems with corrosion control treatment (unless deemed optimized under § 141.81(b)(3)), and all small and medium water systems that exceed the lead action level or copper action level must sample and monitor water quality parameters in addition to lead and copper in accordance with the requirements of this section. Any system may be required to monitor water quality parameters as determined by the State, including as provided in this section.

(1) For water systems demonstrating that they have already optimized OCCT without optimized water quality parameters set by the State, information required in § 141.81(b)(1) through (3).

(F) For each water system that has implemented optimal corrosion control pursuant to § 141.82 of this chapter, completed applicable source water treatment requirements pursuant to § 141.83 of this chapter, and/or completed mandatory service line replacement requirements pursuant to § 141.84(d) of this chapter, and the date of the State's determination that these requirements have been met. The date reported must be the latest of the following events:

(1) The date the State received the results of corrosion control evaluations under § 141.82(d) or (e) of this chapter or optimal corrosion control treatment recommendation by the system;

(2) For systems for which the State has designated optimal corrosion control treatment or re-optimized optimal corrosion control treatment under § 141.82(d) of this chapter, the date of the determination and the date the system completed installation of treatment as certified under § 141.90(c)(4) of this chapter;

(3) The date the State designates optimal water quality parameters under § 141.82(f) of this chapter or deems the system to have optimized corrosion control pursuant to § 141.81(b)(1) or (3) of this chapter;

(4) For systems which the State has required to install source water treatment under § 141.83(b)(2) of this chapter, the date of the determination, the date the State designates maximum permissible source water levels under § 141.83(b)(4) of this chapter or determines pursuant to § 141.83(b)(2) that source water treatment is not required; or

(5) For systems required to conduct mandatory service line replacement, the date the system completes mandatory service line replacement pursuant to § 141.84(d) of this chapter.

(6) For systems not required to complete the corrosion control treatment steps under § 141.81(f) of this chapter, the date the system is required to complete mandatory service line replacement pursuant to § 141.84(d) of this chapter.

(ii) Sections 141.81(b)(4) and (h) and 141.86(c)(2)(iii)(G) and (g)(4)(iii)—determinations of additional monitoring requirements and/or other actions required to maintain optimal corrosion control by systems that change treatment or add a new source of water;

(ii) Sections 141.81(b)(4) and (h) and 141.86(c)(2)(iii)(G) and (g)(4)(iii)—determinations of additional monitoring requirements and/or other actions required to maintain optimal corrosion control by systems that change treatment or add a new source of water;

(2) Systems with corrosion control treatment required to conduct corrosion control studies under § 141.81(d) must evaluate the effectiveness of the following treatments, and if appropriate, combinations of the following treatments, to identify re-optimized OCCT for the system:

(i) Alkalinity and/or pH adjustment or re-adjustment;

(ii) The addition of an orthophosphate- or a silicate-based corrosion inhibitor at a concentration sufficient to maintain an effective corrosion inhibitor residual concentration in all test samples if no such inhibitor is currently utilized;

(iii) The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 1 mg/L (as PO4) in all test samples unless the current inhibitor process already meets this residual; and

(iv) The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 3 mg/L (as PO4) in all test samples unless the current inhibitor process already meets this residual.

(1) For water systems with corrosion control, collect water quality parameters in accordance with § 141.87 and, if the system has not re-optimized OCCT in accordance with § 141.81(d), evaluate compliance options in paragraphs (c)(1) and (2) of this section and corrosion control treatment under § 141.81(d)(1). Water systems with corrosion control treatment in place must continue to operate and maintain optimal corrosion control treatment until the State determines, in writing, that it is no longer necessary, and meet any requirements that the State determines to be appropriate before implementing a State approved alternative compliance option described in this section.

(1) For water systems with corrosion control, collect water quality parameters in accordance with § 141.87 and, if the system has not re-optimized OCCT in accordance with § 141.81(d), evaluate compliance options in paragraphs (c)(1) and (2) of this section and corrosion control treatment under § 141.81(d)(1). Water systems with corrosion control treatment in place must continue to operate and maintain optimal corrosion control treatment until the State determines, in writing, that it is no longer necessary, and meet any requirements that the State determines to be appropriate before implementing a State approved alternative compliance option described in this section.

(2) Any system with corrosion control treatment that exceeds the lead action level that is required to recommend a treatment option to the State in accordance with § 141.81(d)(1)(iii) must recommend designating one or more of the corrosion control treatments listed in paragraph (c)(2) of this section as the optimal corrosion control treatment for that system.

(b) The system must make a compliance option recommendation to the State within six months of the end of the tap sampling period in which the lead action level exceedance occurred. Within six months of the recommendation by the water system, the State must approve or disapprove the recommendation. If the State disapproves the recommendation, the State may designate the other compliance alternative as an option for the system. If the State does not designate the other compliance alternative as an option for the system, the system must comply with the otherwise applicable corrosion control treatment requirements under § 141.81(d) for systems with corrosion control or § 141.81(e) for systems without corrosion control treatment. Water systems must follow the schedules in § 141.81(d) or (e), beginning with step 3 in § 141.81(d)(3) or (e)(3) unless the State specifies optimal corrosion control treatment pursuant to either § 141.81(d)(2) or (e)(2), as applicable. If the system fails to implement the approved alternative compliance option, or the State revokes approval for the alternative compliance option, then the system must follow the requirements for small and non-transient non-community water systems as described under § 141.81(a)(3).

(b) The system must make a compliance option recommendation to the State within six months of the end of the tap sampling period in which the lead action level exceedance occurred. Within six months of the recommendation by the water system, the State must approve or disapprove the recommendation. If the State disapproves the recommendation, the State may designate the other compliance alternative as an option for the system. If the State does not designate the other compliance alternative as an option for the system, the system must comply with the otherwise applicable corrosion control treatment requirements under § 141.81(d) for systems with corrosion control or § 141.81(e) for systems without corrosion control treatment. Water systems must follow the schedules in § 141.81(d) or (e), beginning with step 3 in § 141.81(d)(3) or (e)(3) unless the State specifies optimal corrosion control treatment pursuant to either § 141.81(d)(2) or (e)(2), as applicable. If the system fails to implement the approved alternative compliance option, or the State revokes approval for the alternative compliance option, then the system must follow the requirements for small and non-transient non-community water systems as described under § 141.81(a)(3).

(i) A system that modifies or installs OCCT pursuant to § 141.81(d)(5) or (e)(5) and is required to conduct follow-up monitoring for lead or copper pursuant to § 141.81(d)(6) or (e)(6) must monitor for applicable distribution system and entry point water quality parameters as specified in paragraphs (a)(1) and (2) of this section every six months until the State designates new water quality parameter values for OCCT pursuant to § 141.82(f). Water systems must collect these samples at a regular frequency throughout the six-month monitoring period to reflect seasonal variability.

(i) A system that modifies or installs OCCT pursuant to § 141.81(d)(5) or (e)(5) and is required to conduct follow-up monitoring for lead or copper pursuant to § 141.81(d)(6) or (e)(6) must monitor for applicable distribution system and entry point water quality parameters as specified in paragraphs (a)(1) and (2) of this section every six months until the State designates new water quality parameter values for OCCT pursuant to § 141.82(f). Water systems must collect these samples at a regular frequency throughout the six-month monitoring period to reflect seasonal variability.

(1) Systems without corrosion control treatment required to conduct corrosion control studies under § 141.81(e) must evaluate the effectiveness of each of the following treatments, and if appropriate, combinations of the following treatments, to identify OCCT for the system:

(i) Alkalinity and pH adjustment;

(ii) The addition of an orthophosphate- or a silicate-based corrosion inhibitor at a concentration sufficient to maintain an effective corrosion inhibitor residual concentration in all test samples;

(iii) The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 1 mg/L (as PO4) in all test samples; and

(iv) The addition of an orthophosphate-based corrosion inhibitor at a concentration sufficient to maintain an orthophosphate residual concentration of 3 mg/L (as PO4) in all test samples.

(2) For systems without corrosion control, collect water quality parameters in accordance with § 141.87 and, if the system has not installed OCCT in accordance with § 141.81(e), evaluate compliance options in paragraphs (c)(1) and (2) of this section and corrosion control treatment under § 141.81(e)(1).

(2) For systems without corrosion control, collect water quality parameters in accordance with § 141.87 and, if the system has not installed OCCT in accordance with § 141.81(e), evaluate compliance options in paragraphs (c)(1) and (2) of this section and corrosion control treatment under § 141.81(e)(1).

(1) Any system without corrosion control treatment that is required to recommend a treatment option in accordance with § 141.81(e)(1)(iii) must, based on the results of lead and copper tap sampling and water quality parameter monitoring, recommend designating one or more of the corrosion control treatments listed in paragraph (c)(1) of this section to the State as the optimal corrosion control treatment for that system. The State may require the system to conduct additional water quality parameter monitoring to assist the State in reviewing the system's recommendation.

(b) The system must make a compliance option recommendation to the State within six months of the end of the tap sampling period in which the lead action level exceedance occurred. Within six months of the recommendation by the water system, the State must approve or disapprove the recommendation. If the State disapproves the recommendation, the State may designate the other compliance alternative as an option for the system. If the State does not designate the other compliance alternative as an option for the system, the system must comply with the otherwise applicable corrosion control treatment requirements under § 141.81(d) for systems with corrosion control or § 141.81(e) for systems without corrosion control treatment. Water systems must follow the schedules in § 141.81(d) or (e), beginning with step 3 in § 141.81(d)(3) or (e)(3) unless the State specifies optimal corrosion control treatment pursuant to either § 141.81(d)(2) or (e)(2), as applicable. If the system fails to implement the approved alternative compliance option, or the State revokes approval for the alternative compliance option, then the system must follow the requirements for small and non-transient non-community water systems as described under § 141.81(a)(3).

(b) The system must make a compliance option recommendation to the State within six months of the end of the tap sampling period in which the lead action level exceedance occurred. Within six months of the recommendation by the water system, the State must approve or disapprove the recommendation. If the State disapproves the recommendation, the State may designate the other compliance alternative as an option for the system. If the State does not designate the other compliance alternative as an option for the system, the system must comply with the otherwise applicable corrosion control treatment requirements under § 141.81(d) for systems with corrosion control or § 141.81(e) for systems without corrosion control treatment. Water systems must follow the schedules in § 141.81(d) or (e), beginning with step 3 in § 141.81(d)(3) or (e)(3) unless the State specifies optimal corrosion control treatment pursuant to either § 141.81(d)(2) or (e)(2), as applicable. If the system fails to implement the approved alternative compliance option, or the State revokes approval for the alternative compliance option, then the system must follow the requirements for small and non-transient non-community water systems as described under § 141.81(a)(3).

(i) A system that modifies or installs OCCT pursuant to § 141.81(d)(5) or (e)(5) and is required to conduct follow-up monitoring for lead or copper pursuant to § 141.81(d)(6) or (e)(6) must monitor for applicable distribution system and entry point water quality parameters as specified in paragraphs (a)(1) and (2) of this section every six months until the State designates new water quality parameter values for OCCT pursuant to § 141.82(f). Water systems must collect these samples at a regular frequency throughout the six-month monitoring period to reflect seasonal variability.

(2) Any system that starts step 5 in accordance with paragraph (e)(5) of this section must complete all remaining steps (i.e., steps 6 through 8) in paragraphs (e)(6) through (8) of this section and is not permitted to stop the steps.

(i) A system that modifies or installs OCCT pursuant to § 141.81(d)(5) or (e)(5) and is required to conduct follow-up monitoring for lead or copper pursuant to § 141.81(d)(6) or (e)(6) must monitor for applicable distribution system and entry point water quality parameters as specified in paragraphs (a)(1) and (2) of this section every six months until the State designates new water quality parameter values for OCCT pursuant to § 141.82(f). Water systems must collect these samples at a regular frequency throughout the six-month monitoring period to reflect seasonal variability.

(2) Any system that starts step 5 in accordance with paragraph (e)(5) of this section must complete all remaining steps (i.e., steps 6 through 8) in paragraphs (e)(6) through (8) of this section and is not permitted to stop the steps.

(2) Any system that starts step 5 in accordance with paragraph (e)(5) of this section must complete all remaining steps (i.e., steps 6 through 8) in paragraphs (e)(6) through (8) of this section and is not permitted to stop the steps.

(5) For systems not required to complete the corrosion control treatment steps under § 141.81(f), a letter certifying that the system has completed the mandatory service line replacement program or that the system has met the minimum annual replacement rate calculated under § 141.81(f)(1)(ii).

(F) For each water system that has implemented optimal corrosion control pursuant to § 141.82 of this chapter, completed applicable source water treatment requirements pursuant to § 141.83 of this chapter, and/or completed mandatory service line replacement requirements pursuant to § 141.84(d) of this chapter, and the date of the State's determination that these requirements have been met. The date reported must be the latest of the following events:

(1) The date the State received the results of corrosion control evaluations under § 141.82(d) or (e) of this chapter or optimal corrosion control treatment recommendation by the system;

(2) For systems for which the State has designated optimal corrosion control treatment or re-optimized optimal corrosion control treatment under § 141.82(d) of this chapter, the date of the determination and the date the system completed installation of treatment as certified under § 141.90(c)(4) of this chapter;

(3) The date the State designates optimal water quality parameters under § 141.82(f) of this chapter or deems the system to have optimized corrosion control pursuant to § 141.81(b)(1) or (3) of this chapter;

(4) For systems which the State has required to install source water treatment under § 141.83(b)(2) of this chapter, the date of the determination, the date the State designates maximum permissible source water levels under § 141.83(b)(4) of this chapter or determines pursuant to § 141.83(b)(2) that source water treatment is not required; or

(5) For systems required to conduct mandatory service line replacement, the date the system completes mandatory service line replacement pursuant to § 141.84(d) of this chapter.

(6) For systems not required to complete the corrosion control treatment steps under § 141.81(f) of this chapter, the date the system is required to complete mandatory service line replacement pursuant to § 141.84(d) of this chapter.

(5) For systems not required to complete the corrosion control treatment steps under § 141.81(f), a letter certifying that the system has completed the mandatory service line replacement program or that the system has met the minimum annual replacement rate calculated under § 141.81(f)(1)(ii).

(ii) Sections 141.81(b)(4) and (h) and 141.86(c)(2)(iii)(G) and (g)(4)(iii)—determinations of additional monitoring requirements and/or other actions required to maintain optimal corrosion control by systems that change treatment or add a new source of water;

(11) Section 141.88 and 141.81(h)—reviewing any change in source water or treatment and making related determinations, including approval; establishment of additional requirements to ensure the system will operate and maintain optimal corrosion control treatment; and an evaluation of how this change may impact compliance with other National Primary Drinking Water Regulations in part 141 of this chapter.