# 91 FR 39952: Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems

> Federal · Regulations · In force

URL: https://www.frixlaw.com/law-library/statutes/FR_PRORULE_2026-13263

## Section

- **Citation:** 91 FR 39952
- **Heading:** Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems
- **Jurisdiction:** Federal
- **Kind:** Regulations
- **Status:** In force
- **Text as of:** August 14, 2026
- **Source:** Compiled text
- **Location:** Federal Register / Vol. 91 / 91 FR 39952

## Text

or before August 31, 2026. Comments on the information collection provisions of the proposed rule under the Paperwork Reduction Act (PRA) must be received by the Office of Management and Budget's Office of Information and Regulatory Affairs (OMB-OIRA) on or before July 31, 2026. Please refer to the PRA section under “Statutory and Executive Order Reviews” in this preamble for specific instructions. Public meeting: the EPA will hold two identical virtual, public meetings on August 11, 2026 and August 12, 2026 at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials. Please refer to the SUPPLEMENTARY INFORMATION section for additional information on the public meetings.

ADDRESSES:
You may send comments, identified by Docket ID No. EPA-HQ-OW-2023-0469, by any of the following methods:
• Federal eRulemaking Portal: https://www.regulations.gov/ (our preferred method). Follow the online instructions for submitting comments.
• Email: ow-docket@epa.gov
• Include Docket ID No. EPA-HQ-OW-2023-0469 in the subject line of the message.
• Mail: U.S. Environmental Protection Agency, EPA Docket Center, OW Docket, Mail Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.
• Hand Delivery or Courier: EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. The Docket Center's hours of operations are 8:30 a.m. to 4:30 p.m., Monday through Friday (except Federal Holidays).
Instructions: All submissions received must include the Docket ID No. for this rulemaking. Comments received may be posted without change to https://www.regulations.gov, including personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the “Public Participation” heading of the SUPPLEMENTARY INFORMATION section of this document.
The virtual public meeting will be held at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials
/www.regulations.gov, including personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the “Public Participation” heading of the SUPPLEMENTARY INFORMATION section of this document.
The virtual public meeting will be held at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials. The meeting will convene at 12:00 p.m. (local time) and will conclude at 4:00 p.m. (local time). Refer to the SUPPLEMENTARY INFORMATION section of this document for additional information.
FOR FURTHER INFORMATION CONTACT:
Brenda Bowden, Standards and Risk Management Division (SRMD), Office of Ground Water and Drinking Water (OGWDW) (MS 140), Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268; telephone number: 513-569-7961; email address: bowden.brenda@epa.gov; or Rachel Kaiser, SRMD, OGWDW (MS 140), Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268; telephone number: 513-569-7835; email address: kaiser.rachel@epa.gov.

SUPPLEMENTARY INFORMATION:
I. Executive Summary A. Purpose of the Regulatory Action 1. What action is the EPA taking? 2. Does this action apply to me? 3. What is the EPA's authority for taking this action? B. Summary of the Regulatory Action II. Public Participation A. Written Comments B. Participation in Virtual Public Meeting III. General Background Information A. How are the Contaminant Candidate List (CCL), the UCMR program, the Regulatory Determination process, and the NCOD interrelated? B. What public engagement opportunities have been held in preparation for UCMR 6? C. What notable changes are being proposed for UCMR 6? D. How did the EPA identify the contaminants being proposed for UCMR 6? 1. 1,2,3-trichloropropane (1,2,3-TCP) 2. Chlorpyrifos and Chlorpyrifos Oxon E. What other contaminants did the EPA consider for UCMR 6? 1. Microplastics 2. Pharmaceuticals F
COD interrelated? B. What public engagement opportunities have been held in preparation for UCMR 6? C. What notable changes are being proposed for UCMR 6? D. How did the EPA identify the contaminants being proposed for UCMR 6? 1. 1,2,3-trichloropropane (1,2,3-TCP) 2. Chlorpyrifos and Chlorpyrifos Oxon E. What other contaminants did the EPA consider for UCMR 6? 1. Microplastics 2. Pharmaceuticals F. What is the proposed UCMR 6 applicability date? G. What is the proposed UCMR 6 pre-monitoring reporting date? H. What is the proposed UCMR 6 timeline of activities? I. What is the proposed UCMR 6 monitoring design? 1. Sampling, Frequency, and Timing 2. Sampling Locations J. What are the reporting requirements for UCMR 6? K. What are the Consumer Confidence Reporting and Public Notice (PN) Reporting requirements for PWSs that are subject to UCMR? L. How do laboratories become approved to conduct the UCMR 6 analyses? 1. What are UCMR MRLs and how were they determined? 2. Request To Participate 3. Registration 4. Application Package 5. The EPA's Review of Application Package 6. Proficiency Testing 7. Written EPA Approval M. UCMR 6 Laboratory Capacity N. What is the state's role in the UCMR? O. Costs and Benefits 1. What is the estimated cost of this proposed action? 2. What are the costs of alternative approaches to implementing the proposed UCMR 6? 3. What are the benefits of this proposed action? IV. Supporting Information A. Economic Analysis B. How did the EPA consider children's environmental health? C. What documents are being incorporated by reference? 1. Methods From the U.S. Environmental Protection Agency V. Statutory and Executive Orders Reviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review B. Executive Order 14192: Unleashing Prosperity Through Deregulation C. Paperwork Reduction Act (PRA) D. Regulatory Flexibility Act (RFA) E. Unfunded Mandates Reform Act (UMRA) F. Executive Order 13132: Federalism G
otection Agency V. Statutory and Executive Orders Reviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review B. Executive Order 14192: Unleashing Prosperity Through Deregulation C. Paperwork Reduction Act (PRA) D. Regulatory Flexibility Act (RFA) E. Unfunded Mandates Reform Act (UMRA) F. Executive Order 13132: Federalism G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use J. National Technology Transfer and Advancement Act (NTTAA) VI. References Abbreviations and Acronyms
µg/L Microgram per Liter 1,2,3-TCP 1,2,3-Trichloropropane ANCSA Alaska Native Claims Settlement Act ASDWA Association of State Drinking Water Administrators ASTM ASTM International AWIA America's Water Infrastructure Act of 2018 CBI Confidential Business Information CCL Contaminant Candidate List CCR Consumer Confidence Report CFR Code of Federal Regulations CWS Community Water System DDVP Dichlorvos DEET N,N-Diethyl-m-toluamide DWSRF Drinking Water State Revolving Fund EPA Environmental Protection Agency EPTDS Entry Point to the Distribution System FDA Food and Drug Administration FR Federal Register GC/MS Gas Chromatography/Mass Spectrometry GWRMP Ground Water Representative Monitoring Plan ICR Information Collection Request IDC Initial Demonstration of Capability LC/MS/MS Liquid Chromatography/Tandem Mass Spectrometry LCMRL Lowest Concentration Minimum Reporting Level MGK N-octyl bicycloheptene dicarboximide MRL Minimum Reporting Level NAICS North American Industry Classification System NCOD National Contaminant Occurrence Database NPDWR National Primary Drinking Water Regulation NTNCWS Non-transient Non-community Water System NTTAA National Technology Transfer and Advancement Act OGWDW Office of Ground Water and Drinki
est Concentration Minimum Reporting Level MGK N-octyl bicycloheptene dicarboximide MRL Minimum Reporting Level NAICS North American Industry Classification System NCOD National Contaminant Occurrence Database NPDWR National Primary Drinking Water Regulation NTNCWS Non-transient Non-community Water System NTTAA National Technology Transfer and Advancement Act OGWDW Office of Ground Water and Drinking Water OIRA Office of Information and Regulatory Affairs OMB Office of Management and Budget PBI Proprietary Business Information PFAS Per- and Polyfluoroalkyl Substances PFMOAA Perfluoro-2-methoxyacetic acid PFOA Perfluorooctanoic acid PFOS Perfluorooctane sulfonate PN Public Notice PRA Paperwork Reduction Act PT Proficiency Testing PWS Public Water System RFA Regulatory Flexibility Act SBA Small Business Administration SBREFA Small Business Regulatory Enforcement Fairness Act SDWA Safe Drinking Water Act SDWARS Safe Drinking Water Accession and Review System SDWIS/Fed Safe Drinking Water Information System Federal Reporting Services SPE Solid Phase Extraction SRMD Standards and Risk Management Division TFA Trifluoroacetic Acid TFMS Trifluoromethanesulfonic Acid TFSI Bistriflimide UCMR Unregulated Contaminant Monitoring Rule UMRA Unfunded Mandates Reform Act of 1995 USDA United States Department of Agriculture USEPA United States Environmental Protection Agency USGS United States Geological Survey VCSB Voluntary Consensus Standard Body I. Executive Summary
A. Purpose of the Regulatory Action
1. What action is the EPA taking?
The U.S. Environmental Protection Agency (EPA or agency) is proposing the sixth Unregulated Contaminant Monitoring Rule (UCMR 6). Under the Safe Drinking Water Act (SDWA), the UCMR program gathers data about unregulated contaminant occurrence in drinking water. The proposed UCMR 6 would require certain public water systems (PWSs) to collect national occurrence data for 30 unregulated contaminants that are not currently subject to national primary drinking water regulations (NPDWRs)
te CWSs and NTNCWSs required to monitor 924110 Industry Private operators of CWSs and NTNCWSs required to monitor 221310 Municipalities Municipal operators of CWSs and NTNCWSs required to monitor 924110 1 NAICS = North American Industry Classification System. This table is not intended to be exhaustive but rather provides a guide for readers regarding entities likely to be regulated by this action. This table includes the types of entities that the EPA is now aware could potentially be regulated by this action. Other types of entities not included could also be regulated. To determine whether your entity is regulated by this action, you should carefully examine the definition of PWS found in sections 141.2 and 141.3, and the applicability criteria found in section 141.40(a)(1) and (2) of Title 40 in the Code of Federal Regulations (CFR). If you have questions regarding the applicability of this action to a particular entity, consult the person listed in the FOR FURTHER INFORMATION CONTACT section.
3. What is the EPA's authority for taking this action?
As part of its authority under SDWA, the EPA implements section 1445(a)(2), Monitoring Program for Unregulated Contaminants. This section, as amended in 1996, requires that once every five years, beginning in August 1999, the EPA issue a list of unregulated contaminants to be monitored by PWSs. SDWA requires that the EPA enter the monitoring data into the agency's publicly available National Contaminant Occurrence Database (NCOD) for drinking water at https://www.epa.gov/sdwa/national-contaminant-occurrence-database-ncod.
The EPA must vary the frequency and schedule for monitoring based on the number of persons served, the source of supply, and the contaminants likely to be found. The EPA is using its SDWA section 1445(a)(2) authority as the basis for requiring covered systems to monitor for the unregulated contaminants proposed under this rulemaking.
SDWA, as amended by the AWIA (Pub. L
ill generally not consider comments or comment contents located outside of the primary submission ( i.e., on the web, cloud, or other file sharing system). Please visit https://www.epa.gov/dockets/commenting-epa-dockets for additional submission methods; the full EPA public comment policy; information about CBI, PBI, or multimedia submissions; and general guidance on making effective comments.
B. Participation in Virtual Public Meeting
The EPA will hold two identical virtual public meetings during the public comment period on August 11, 2026 and August 12, 2026. Topics will include the proposed UCMR 6 monitoring requirements, contaminant selection and rationale, drinking water analytical methods, and the laboratory approval process. To register to attend the meeting or speak, please use the online registration form available at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials or contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this document. The last day to pre-register to speak at the meeting will be July 31, 2026. On August 10, 2026, the EPA will post a general agenda for the meeting that will list pre-registered speakers in approximate order at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials and will concurrently email registered participants the materials that were posted on the website.
The EPA will make every effort to follow the schedule as closely as possible on the day of the meeting; however, please plan for the identical events to run either ahead of schedule or behind schedule.
Each commenter will have the opportunity to provide oral testimony, and the agency will allocate the time available amongst the commenters who registered to speak ( i.e., not to exceed 10 minutes). We ask that only one person present on behalf of a group or organization
le on the day of the meeting; however, please plan for the identical events to run either ahead of schedule or behind schedule.
Each commenter will have the opportunity to provide oral testimony, and the agency will allocate the time available amongst the commenters who registered to speak ( i.e., not to exceed 10 minutes). We ask that only one person present on behalf of a group or organization. The EPA encourages commenters to provide the EPA with a copy of their oral testimony electronically by emailing it to the person identified in the FOR FURTHER INFORMATION CONTACT section of this document. The EPA also recommends submitting the text of your oral comments as written comments to the rulemaking docket.
The EPA may ask clarifying questions during the oral presentations but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral comments and supporting information presented at the public meeting.
Please note that any updates made to any aspect of the meeting will be posted online at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials and will be emailed to those who register to attend the meeting. While the EPA expects the meeting to go forward as set forth above, please monitor our website or contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this document to determine if there are any updates. The EPA does not intend to publish a document in the Federal Register announcing updates. The number of connections available for the meeting is limited and will be available on a first-come, first-served basis. If the number of connections becomes limited, the EPA will post additional dates and times online at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials.
The EPA will not provide audiovisual equipment for presentations unless we receive special requests in advance
quency and level of their occurrence in drinking water systems; this is the UCMR program. Under the third step, the EPA is required to determine, every five years, whether or not to regulate at least five contaminants from the CCL through the regulatory determination process. Under SDWA sections 1412(b)(1)(A), the EPA regulates a contaminant in drinking water if the Administrator determines that:
(1) The contaminant may have an adverse effect on the health of persons;
(2) the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in PWSs with a frequency and at levels of public health concern; and
(3) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by PWSs. Where the Administrator determines that a contaminant meets all three criteria, SDWA requires the EPA to propose and publish a NPDWR. Information on the CCL and the regulatory determination process can be found at https://www.epa.gov/ccl.
The data collected through the UCMR program are made available to the public through the NCOD for drinking water. SDWA section 1445(g)(3) requires that the EPA maintain UCMR data in the NCOD and use the data when evaluating the occurrence of contaminants in drinking water at a level of public health concern. The UCMR results can be viewed at https://www.epa.gov/sdwa/ or via the UCMR web page at https://www.epa.gov/dwucmr.
B. What public engagement opportunities have been held in preparation for UCMR 6?
The EPA incorporates public involvement into each UCMR cycle. Specific to the development of UCMR 6, the EPA sought comments on drinking water method development for emerging contaminants, and held a public meeting, state consultation, tribal consultation, and Alaska Native Claims Settlement Act (ANCSA) consultation. A summary of the public comments for each of these meetings is included in the EPA public docket for this proposed rulemaking, under Docket ID No
ecific to the development of UCMR 6, the EPA sought comments on drinking water method development for emerging contaminants, and held a public meeting, state consultation, tribal consultation, and Alaska Native Claims Settlement Act (ANCSA) consultation. A summary of the public comments for each of these meetings is included in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. Additionally, the EPA is announcing another meeting in this proposal (see section II.B of this document).
On February 8, 2024, the EPA published a Federal Register notice that requested public input on the development of drinking water analytical methods for unregulated contaminants (89 FR 8584, (USEPA, 2024a)). The notice focused on contaminants listed on the fifth Contaminant Candidate List (CCL 5), that might support monitoring under the UCMR 6 and/or other future UCMR cycles. The EPA received 12 public comments throughout the 60-day comment period.
The EPA hosted two identical pre-proposal meetings on April 17 and April 18, 2024, to discuss potential approaches for developing UCMR 6, including: the status of drinking water analytical methods and contaminants being considered; possible sampling design; laboratory approval; other potential aspects of the monitoring approach; and included time for public questions and statements (89 FR 8584, (USEPA, 2024a)). Representatives from state agencies, laboratories, PWSs, environmental organizations, and drinking water associations joined the meeting. The presentation materials can be found on the EPA's Unregulated Contaminant Monitoring Program Meetings and Materials webpage at https://www.epa.gov/dwucmr/unregulated-contaminant-monitoring-rule-ucmr-meetings-and-materials.
The EPA hosted the state consultation from May 30 to July 1, 2024, with the meeting on May 29, 2024, to discuss the early development of UCMR 6, and the voluntary options states have in the implementation of the UCMR program
Sensitivity (P&T GC/MS) 1 1,2,4-Trimethylbenzene 1,2,3-Trichloropropane (1,2,3-TCP). 1,1,2,2-Tetrachloroethane Total 1,3-Dichloropropene (cis- & trans-). Naphthalene Hexachlorobutadiene. 1,1,1,2-Tetrachloroethane 13 Semivolatile Organic Compounds using EPA Method 525.3 (SPE GC/MS) 2 Phorate Chlorothalonil. Dichlorvos (DDVP) Metribuzin. N,N-Diethyl-m-toluamide (DEET) Pyrene. Trifluralin Isophorone. 2,4-Dinitrotoluene 2,6-Dinitrotoluene. Tetrachlorvinphos (Stirofos) Anthracene. Fluorene Three Pesticide Metabolites using EPA Method 540 (SPE LC/MS/MS) 3 Chlorpyrifos oxon Phorate sulfone. Phorate sulfoxide Seven Ultrashort Organofluorine Compounds using EPA Method 563 (LC/MS/MS) 4 Perfluoropropanesulfonic acid (PFPrS) 5 Perfluoropropanoic acid (PFPrA). 5 Perfluoroethanesulfonic acid (PFEtS) 5 Perfluoro-2-methoxyacetic acid (PFMOAA). 5 Trifluoromethanesulfonic acid (TFMS) Bistriflimide (TFSI). Trifluoroacetic acid (TFA) 1 EPA Method 524.3 Enhanced Sensitivity (Purge-and-trap (P&T) capillary column gas chromatography/mass spectrometry (GC/MS)) (USEPA, 2026e). 2 EPA Method 525.3 (Solid phase extraction (SPE) capillary column gas chromatography/mass spectrometry (GC/MS)) (USEPA, 2012a). 3 EPA Method 540 (Solid phase extraction (SPE) liquid chromatography/tandem mass spectrometry (LC/MS/MS)) (USEPA, 2013a). 4 EPA Method 563 (Liquid chromatography/tandem mass spectrometry (LC/MS/MS)) (USEPA, 2026f). 5 Identified as a PFAS in accordance with definition used in CCL 5. 2 SDWA 1445(a)(2) requires the EPA to establish criteria for a monitoring program for unregulated contaminants. As a starting point, the EPA considered the CCL 5, which includes 66 chemicals, three chemical groups and 12 microbes (87 FR 68060, November 14, 2022 (USEPA, 2022)). The agency also evaluated contaminants nominated by the public for potential inclusion on the sixth CCL (CCL 6) (88 FR 10316, February 17, 2023 (USEPA, 2023)) and considered other priority contaminants beyond the CCL
ncluded chemicals that contain at least one of these three structures:
1. R-(CF2)-CF(R′)R″, where both the CF2 and CF moieties are saturated carbons, and none of the R groups can be hydrogen
2. R-CF2OCF2-R′, where both the CF2 moieties are saturated carbons, and none of the R groups can be hydrogen
3. CF3C(CF3)RR′, where all the carbons are saturated, and none of the R groups can be hydrogen.
Additional information on this prioritization process, as well as contaminant-specific information ( e.g., source, use, production, release, persistence, mobility, health effects, and occurrence) that the EPA used to evaluate candidate contaminants, is contained in “ Information Compendium for Candidate Contaminants for the Proposed Sixth Unregulated Contaminant Monitoring Rule (UCMR 6)” (USEPA, 2026g), found in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. The EPA invites comment on the proposed UCMR 6 contaminants (and their associated drinking water analytical methods) identified in Exhibit 2.
PFAS are a diverse group of compounds and the CCL 5 lists PFAS as a group, characterized by a structural definition, which EPA uses as a first step in considering individual compounds. The recently-developed EPA Method 563 3 can capture certain PFAS, as defined by the CCL 5 ( i.e., PFMOAA, PFPrA, PFPrS, PFEtS). As noted in the 2019 PFAS Action Plan (USEPA, 2019), these PFAS, referred to as short-chain PFAS have been less thoroughly studied, but are a concern due to increase global production and use.
3 The organofluorine Method 563 was in the early stages of development at the time of the February 2024 Federal Register Notice (89 FR 8584, (USEPA, 2024a)) and did not have a full analyte list. This method has since been finalized and is available in the UCMR 6 docket for public comment
able health assessment (USEPA, 2021c). If, during the laboratory approval process, the agency determines that laboratories are experiencing analytical difficulties with one of the proposed contaminants, the agency intends to replace that contaminant with MGK 264 a priority alternate from EPA Method 525.3 in the final UCMR 6. The EPA welcomes comments on the potential inclusion of MGK 264 in UCMR 6.
The EPA notes that two contaminants deviate from the prioritization process outlined in this section. 1,2,3-TCP has already been monitored in a previous UCMR cycle and the discussion for that contaminant's inclusion is in section III.D.1 of this document. The parent contaminant to chlorpyrifos oxon, chlorpyrifos, has already been monitored in a previous UCMR cycle and the discussion for that contaminant's inclusion is in section III.D.2 of this document.
1. 1,2,3-Trichloropropane (1,2,3-TCP)
1,2,3-TCP is a likely carcinogenic man-made chemical used as an industrial solvent, cleaning agent, degreasing agent, and synthesis intermediate (USEPA, 2009a, USEPA, 2026g). This contaminant was included on the third, fourth, and fifth CCLs and was monitored during UCMR 3 (USEPA, 2009a, USEPA, 2016a, USEPA, 2022, USEPA, 2012b). The UCMR 3 occurrence data can be found at https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-rule#3. The EPA did not make a regulatory determination for 1,2,3-TCP during Regulatory Determination 4 (86 FR 12272, March 3, 2021 (USEPA, 2021b)), and did not make a preliminary determination in Regulatory Determination 5 (90 FR 3830, January 15, 2025 (USEPA, 2025b)), due in part to the drinking water analytical method minimum reporting level (MRL = 0.03 µg/L) being substantially higher than the level of public health concern, which presents uncertainty when characterizing exposure and a potential meaningful opportunity for health risk reduction
did not make a preliminary determination in Regulatory Determination 5 (90 FR 3830, January 15, 2025 (USEPA, 2025b)), due in part to the drinking water analytical method minimum reporting level (MRL = 0.03 µg/L) being substantially higher than the level of public health concern, which presents uncertainty when characterizing exposure and a potential meaningful opportunity for health risk reduction. To better understand the potential risk of this contaminant in drinking water, the agency developed “ Recommended Parameters to Enhance Sensitivity for the Analysis of Select Purgeable Organic Compounds using EPA Method 524.3 in Selected Ion Monitoring (SIM) Mode” (USEPA, 2026e) that can detect 1,2,3-TCP at lower concentrations (0.009 µg/L) than what was feasible in the method “ Method 524.3: Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry,” (USEPA, 2009b) used during UCMR 3. Monitoring using this optimized method would provide the EPA with occurrence data closer to the levels of public health concern, which will provide the agency with additional information that could inform future regulatory decisions for 1,2,3-TCP through SDWA.
2. Chlorpyrifos and Chlorpyrifos Oxon
Chlorpyrifos and its metabolite, chlorpyrifos oxon, are organophosphate pesticides that are used on crops, animals, in buildings, and in other settings, to kill several pests, including insects and worms (USEPA, 2026g). Chlorpyrifos, which is a neurotoxin (USEPA, 2020), is listed on the CCL 5 (87 FR 68060, November 14, 2022 (USEPA, 2022)), is used across the country on a variety of crops (USGS, 2019), and was monitored during UCMR 4 (MRL = 0.03 µg/L) (81 FR 9266, December 20, 2016 (USEPA, 2016b)). There was limited occurrence of the parent, chlorpyrifos, in UCMR 4 (for data results see https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-rule#archival )
ssing whether there is a meaningful opportunity for health risk reduction. The EPA considers that the primary utility of the UCMR data is to provide data to the other SDWA programs. SDWA requires that the data collected under the UCMR be used to develop the CCL (see SDWA section 1412(b)(1)(B)(i)(I)) and to make regulatory determinations for CCL contaminants (see SDWA section 1412(b)(1)(B)(ii)(II)). The data collected under the UCMR also provides states and PWSs with information that could be used to protect public health in each state.
In developing this UCMR action, the EPA considered the burden that UCMR places upon PWSs to monitor and, consistent with SDWA sections 1445(j) and 1452(o), the availability of funding to pay the cost of small PWS monitoring, the laboratory capacity to support the analysis of UCMR samples, and the utility of the information to be collected. For further information on these contaminants, see “ Information Compendium for Candidate Contaminants for the Proposed Sixth Unregulated Contaminant Monitoring Rule (UCMR 6)” (USEPA, 2026g), found in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469.
The EPA invites comment on the contaminants described in the following sections and any other priority contaminants commenters wish to recommend. In your comments, please identify the following: any new contaminant(s) that you believe should be included in the UCMR 6 monitoring; any contaminant(s) in Exhibit 2 that you believe should be removed from the list; the recommended drinking water analytical method(s) for any new contaminant(s) that you propose; and other relevant details ( e.g., reporting level, sampling location, sampling frequency, analytical cost). Comments that provide supporting data or rationale are especially helpful.
1. Microplastics
On November 26, 2025, the agency received a petition from the Governors of 7 states (Governors' Petition) to include microplastics on UCMR 6
method(s) for any new contaminant(s) that you propose; and other relevant details ( e.g., reporting level, sampling location, sampling frequency, analytical cost). Comments that provide supporting data or rationale are especially helpful.
1. Microplastics
On November 26, 2025, the agency received a petition from the Governors of 7 states (Governors' Petition) to include microplastics on UCMR 6. SDWA section 1445(a)(2)(B)(ii) provides that “[t]he Administrator shall include among the list of contaminants for which monitoring is required under this paragraph each contaminant recommended in a petition signed by the Governor of each of 7 or more states, unless the Administrator determines that the action would prevent the listing of other contaminants of a higher public health concern.” The EPA also received a petition from the Food and Water Watch group with signatures from other organizations supporting monitoring for microplastics in UCMR 6 (a copy of that petition and response, and the Governors' Petition have been placed in the public Docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469).
The EPA has listed microplastics as a group on the draft Contaminant Candidate List (CCL 6) as a first step toward defining and better understanding potential public health risk from exposure via drinking water (USEPA, 2026h). The EPA will collaborate with other federal agencies to evaluate risks and exposures of microplastics to enable future monitoring for those microplastics that present potential health risks. This approach will also enable the EPA to list microplastics on a future UCMR when national monitoring is scientifically feasible through the availability of a validated drinking water analytical method
026h). The EPA will collaborate with other federal agencies to evaluate risks and exposures of microplastics to enable future monitoring for those microplastics that present potential health risks. This approach will also enable the EPA to list microplastics on a future UCMR when national monitoring is scientifically feasible through the availability of a validated drinking water analytical method.
As the Governors' Petition acknowledges, there is no validated EPA or consensus drinking water analytical method with the proper quality control data, accuracy, and precision that could be used for UCMR 6, and it is not feasible to develop a drinking water analytical method within the statutory timeframe ( i.e., December 27, 2026). If microplastics were included on UCMR 6, the PWSs subject to this rulemaking would be unable to successfully monitor for microplastics. Such monitoring is the central purpose of the UCMR as outlined by SDWA section 1445(a)(2). In addition, the agency and the public would lose an opportunity to gain occurrence information on other unregulated contaminants that have a drinking water analytical method available for UCMR 6.
The Governors' Petition asserts that “the variability in methodologies for detecting microplastics poses challenges to data consistency and comparability” and “this variability complicates efforts to standardize findings, underscoring the need for harmonized protocols to ensure reliable data collection and analysis.” The agency will continue to evaluate the existing procedures and techniques (ASTM—D8332-20 and D8333-20) (ASTM, 2020a, ASTM, 2020b) to develop robust and validated methods, as well as adequate laboratory capacity, that would support national monitoring for microplastics in a future UCMR
rdize findings, underscoring the need for harmonized protocols to ensure reliable data collection and analysis.” The agency will continue to evaluate the existing procedures and techniques (ASTM—D8332-20 and D8333-20) (ASTM, 2020a, ASTM, 2020b) to develop robust and validated methods, as well as adequate laboratory capacity, that would support national monitoring for microplastics in a future UCMR.
The agency acknowledges the interest in and concern for microplastics in drinking water, and believes that including these contaminants on the draft CCL 6 as a first step in responding to the petition will prioritize the research that is needed to define and better understand the characteristics of microplastics ( i.e., size, type of plastic, shape, count, etc.) that are associated with the public health risk. This research may inform the development of drinking water analytical methods that can be used to standardize data collection and analysis in the future.
2. Pharmaceuticals
Pharmaceuticals in drinking water have been a public health concern for over a decade. Since 2012, the EPA has led a federal workgroup on pharmaceuticals in water alongside the United States Department of Agriculture (USDA), the United States Food and Drug Administration (FDA), and the United States Geological Survey (USGS) to exchange information on pharmaceuticals in the environment and to support the coordination of joint studies. The agency recently included a pharmaceuticals group on the draft CCL 6 to further prioritize research and information needed to identify which specific pharmaceuticals are occurring in drinking water and may be of greatest public health concern (USEPA, 2026h). The agency also released the “ Human Health Benchmarks for Pharmaceuticals (HHB-Rx) in Drinking Water” (USEPA, 2026i). Human health benchmarks are non-enforceable drinking water levels that provide information about adverse health effects from drinking water exposure to contaminants that have no drinking water standards or health advisories
e information, sampling location inventory information, and scheduling and rescheduling notifications. These updated dates are exactly five years from the last dates published in UCMR 5 (86 FR 73131, December 27, 2021 (USEPA, 2021d)), based on the 5-year cycle of the UCMR program.
H. What is the proposed UCMR 6 timeline of activities?
The proposed rule outlines the monitoring period for UCMR 6. From the date of this proposal until January 1, 2028, the EPA will be conducting a number of activities, including reviewing comments and promulgating the final rule, coordinating laboratory approval, selecting representative small PWSs, organizing Partnership Agreements with states, developing State Monitoring Plans (see III.N of this document), establishing monitoring schedules and inventory, and conducting outreach and training. The EPA proposes that PWSs will collect samples between January 1, 2028—December 31, 2030, and PWSs must complete their monitoring by December 31, 2031. Exhibit 3 illustrates the major activities that the EPA expects will take place in preparation for, and during, the implementation of UCMR 6.
EP01JY26.017
I. What is the proposed UCMR 6 monitoring design?
The proposed rule identifies sampling and analysis for UCMR 6 contaminants based on the Assessment Monitoring framework, which provides the best nationally representative monitoring data set for determining if contaminants occur frequently and at levels of public health concern. Further information on this framework, including a description of the statistical approach for the nationally representative sample, can be found in the “ Statistical Design and Sample Selection for the Unregulated Contaminant Monitoring Regulation” (USEPA, 2001) in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469
y and at levels of public health concern. Further information on this framework, including a description of the statistical approach for the nationally representative sample, can be found in the “ Statistical Design and Sample Selection for the Unregulated Contaminant Monitoring Regulation” (USEPA, 2001) in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. With the addition of AWIA in 2018, the “ Selection of Nationally Representative Public Water Systems for the Unregulated Contaminant Monitoring Rule: 2021 Update” (USEPA, 2021a) also found in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469, expanded the UCMR scope prescribed by AWIA, clarified the monitoring framework, updated the description of the sampling design, and clarified how small PWSs would be selected in the event of insufficient appropriations.
As outlined in SDWA, to minimize the impact of the rule on small PWSs (those serving 10,000 or fewer people), the EPA is responsible for their sample kit preparation, sample shipping fees, and sample analysis. If the EPA concludes that it will not have the appropriations necessary to support the monitoring described by the AWIA, the agency plans to adjust the number of small PWSs that serve 10,000 or fewer people to monitor based upon the available appropriations (see section III.O.2 of this document for more details). Consistent with prior UCMRs, large PWSs serving more than 10,000 people are responsible for any costs associated with their monitoring. Exhibit 4 shows a summary of the estimated number of both small and large PWSs subject to required monitoring
and between-system variability on a national level to support future decisions to protect public health. 4
4 The 36-month schedule produces thousands of monthly results per contaminant. These results can be analyzed for seasonal patterns and annual occurrence. The EPA designed the monitoring frequency to ensure that sample results would yield a high level of confidence and a low margin of error. Further information on the statistical approach for the nationally representative sample, can be found in the “Statistical Design and Sample Selection for the Unregulated Contaminant Monitoring Regulation” (USEPA, 2001) found in the docket.
The EPA expects to consult with the states and draft schedules for large PWSs. Thereafter, these PWSs would have an opportunity to modify this initial schedule for planning purposes or other reasons ( e.g., to spread costs over multiple years, a sampling location will be closed during the scheduled month of monitoring). The EPA proposes to schedule and coordinate small PWS monitoring by working closely with states and small PWSs. State Monitoring Plans provide an opportunity for states to review and revise the initial sampling schedules that the EPA proposes (see discussion of State Monitoring Plans in section III.N of this document).
2. Sampling Locations
The EPA is proposing that sample collection for the UCMR 6 contaminants would take place at the entry point to the distribution system (EPTDS). The following are two ways for PWSs to reduce the number of EPTDSs at which they must sample: submit a GWRMP and/or utilize representative sampling from wholesaler connection.
One way for large ground water PWSs (or large surface water PWSs with ground water sources) that have multiple ground water EPTDSs to reduce their number of sampling locations, is to submit a GWRMP
connection selected as the representative EPTDS is not available for sampling, an alternate highest volume representative connection must be sampled.
J. What are the reporting requirements for UCMR 6?
The EPA proposes changes to the reporting requirements currently established for UCMR 6, as detailed in Table 1 of the CFR section 141.35(e), to account for the UCMR 6 contaminants being proposed. These changes include removing data elements related to the specific contaminants from the previous UCMR, adding and updating data elements based on the proposed list of contaminants to be monitored, and improving data reporting from laboratories and PWSs based on experience from the previous UCMR. Recognizing that data elements are updated each monitoring cycle, the EPA invites comment on the proposed data elements and associated definitions, as well as any other data elements that may provide useful information to inform an assessment of the occurrence information and future actions to protect public health.
K. What are the Consumer Confidence Reporting and Public Notice (PN) Reporting requirements for PWSs that are subject to UCMR?
In addition to reporting UCMR monitoring data to the EPA, PWSs are responsible for addressing UCMR results in their Consumer Confidence Reports (CCRs) (40 CFR 141.153), as described in the Federal Register (89 FR 45980, May 24, 2024, (USEPA, 2024b)), and PN requirements (40 CFR 141.207). More details about the CCR and PN requirements can be viewed by the public at https://www.epa.gov/ccr and https://www.epa.gov/dwreginfo/public-notification-rule, respectively.
L. How do laboratories become approved to conduct the UCMR 6 analyses?
Consistent with prior UCMRs, this proposal maintains the requirement that PWSs use laboratories approved by the EPA to analyze UCMR 6 samples. Interested laboratories are encouraged to apply for EPA approval as early as possible, beginning with the publication of this proposal, to ensure national laboratory capacity
tively.
L. How do laboratories become approved to conduct the UCMR 6 analyses?
Consistent with prior UCMRs, this proposal maintains the requirement that PWSs use laboratories approved by the EPA to analyze UCMR 6 samples. Interested laboratories are encouraged to apply for EPA approval as early as possible, beginning with the publication of this proposal, to ensure national laboratory capacity. This early participation is also necessary, if laboratories are interested in a contract with the EPA to analyze samples from small systems. The contract solicitation will be released prior to the end of the laboratory approval program. The UCMR 6 laboratory approval process is designed to assess whether laboratories possess the required equipment and can meet laboratory-performance and data-reporting criteria described in this action.
The EPA anticipates following its standard approach to approving UCMR laboratories, which would require laboratories seeking approval to: (1) provide the EPA with data that demonstrate a successful completion of an initial demonstration of capability (IDC) as outlined in each method; (2) verify successful performance at or below the MRLs as specified in this action; (3) provide information about laboratory standard operating procedures (SOPs); and (4) participate in an EPA proficiency test (PT) study for the analytes of interest. Audits of laboratories may be conducted by the EPA prior to and/or following approval, and maintaining approval is contingent on timely and accurate reporting. The “ UCMR 6 Laboratory Approval Manual” (USEPA, 2026j) provides more specific details on the EPA laboratory approval program and the specific method acceptance criteria. This document can be found in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469
. A more detailed explanation of the MRL calculation is in the “ Technical Basis for the Lowest Concentration Minimum Reporting Level (LCMRL) Calculator” (USEPA, 2010), available at https://www.epa.gov/dwanalyticalmethods/lowest-concentration-minimum-reporting-level-lcmrl-calculator and can also be found in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469.
The EPA established the proposed MRLs in CFR section 141.40(a)(3), Table 1, for each analyte/method by obtaining data from at least three laboratories that performed “lowest concentration minimum reporting level” (LCMRL) UCMR 6 Laboratory Approval Manual” (USEPA, 2026j) found in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. The EPA considers these to be the lowest reporting levels that can practically and consistently be achieved on a national basis (recognizing that individual laboratories may be able to measure at lower levels). The EPA invites comments on the proposed MRLs and will consider scientific information demonstrating that the proposed MRLs are unattainable for laboratories and laboratory capacity would become a concern for the UCMR program.
2. Request To Participate
Laboratories interested in the UCMR 6 laboratory approval program must first email the EPA at UCMR_Lab_Approval@epa.gov to request registration materials. The EPA expects to accept such requests beginning with the publication of this proposal in the Federal Register .
3. Registration
Laboratory applicants provide registration information that includes: laboratory name, mailing address, shipping address, contact name, phone number, email address, and a list of the UCMR 6 methods for which the laboratory is seeking approval. This registration step provides the EPA with the necessary contact information and ensures that each laboratory receives a customized application package.
4
pending promulgation of the final rule if the PT studies have been conducted prior to that time), or for which approval is “granted” (if after promulgation of the final rule). Laboratories receiving pending approval are expected to be granted approval without further action following promulgation of the final rule if no changes have been made to the rule that impact the laboratory approval program. The EPA expects to contact the laboratory if changes are made between the proposed and final rules that warrant additional action by the laboratory.
As a condition of receiving and maintaining approval, the laboratory will be expected to promptly post UCMR 6 monitoring results and quality control data that meet method criteria (on behalf of its PWS clients) to the EPA's UCMR electronic data reporting system, SDWARS.
M. UCMR 6 Laboratory Capacity
The EPA believes there will be laboratory capacity for the proposed UCMR 6 contaminants. EPA Method 525.3 and EPA Method 524.3 with enhanced sensitivity, both use the same instrumental technology, SPE GC/MS. Laboratory capacity has been well-established for GC/MS instrumentation based on laboratory participation in previous UCMR cycles. Additionally, the technology is routinely used for compliance with NPDWRs.
The other two methods proposed for UCMR 6, EPA Method 563 and EPA Method 540, utilize LC/MS/MS. Laboratories are familiar with the LC/MS/MS instrumentation that both methods utilize since the LC/MS/MS instrumentation was first introduced to drinking water laboratories under UCMR 2, nearly 20 years prior (72 FR 368, (USEPA, 2007)). Since then, every cycle of the UCMR program has included at least one or more LC/MS/MS method(s), and the UCMR program has not experienced any laboratory capacity issues. EPA Method 563 is easier and quicker to run compared to EPA Methods 533 and 537.1, which were used for UCMR 5, since the sample can be directly injected into the instrumentation with limited preparation
72 FR 368, (USEPA, 2007)). Since then, every cycle of the UCMR program has included at least one or more LC/MS/MS method(s), and the UCMR program has not experienced any laboratory capacity issues. EPA Method 563 is easier and quicker to run compared to EPA Methods 533 and 537.1, which were used for UCMR 5, since the sample can be directly injected into the instrumentation with limited preparation. This reduces potential laboratory burden, increases the number of samples that can be analyzed per day, and is ultimately more cost-effective.
The UCMR program engages the drinking water laboratory community early in the action development process and encourages comments regarding proposed methods, contaminants, sampling design, and other aspects of each UCMR cycle. For UCMR 6, laboratories had the opportunity to comment on method development in response to the Federal Register Notice (89 FR 8584, (USEPA, 2024a)), during the public webinars on April 17 and 18, 2024 (see the available summary on the EPA public docket for this proposed rule, under Docket ID No. EPA-HQ-OW-2023-0469), and will have the opportunity to provide input on this proposed action during the public comment period and associated public webinar (see section II of this document for further information).
Another way the EPA has established laboratory capacity is to initiate the UCMR laboratory approval program in concurrence with the proposal, and the agency is committed to this opportunity in the proposal today. This early engagement provides laboratories with
N. What is the state's role in the UCMR?
UCMR is a direct implementation rule ( i.e., the EPA has primary responsibility for its implementation), and state participation is voluntary. Under the previous UCMR cycles, most states have participated in the UCMR and have agreed to carry out or assist with specific activities that are identified and established exclusively through Partnership Agreements
What is the state's role in the UCMR?
UCMR is a direct implementation rule ( i.e., the EPA has primary responsibility for its implementation), and state participation is voluntary. Under the previous UCMR cycles, most states have participated in the UCMR and have agreed to carry out or assist with specific activities that are identified and established exclusively through Partnership Agreements. Through Partnership Agreements, states can help the EPA implement the UCMR and help ensure that the UCMR data are of the highest quality possible to best inform agency decision making. Under UCMR 6, the EPA expects to continue to use the Partnership Agreement process to determine and document the following: the process for review and revision of the State Monitoring Plans; replacing and updating PWS information including inventory; review of proposed GWRMPs; notification and instructions for PWSs; and compliance assistance. The EPA recognizes that primacy agencies often have the best information about their PWSs and encourages them to partner in the UCMR 6 program.
O. Costs and Benefits
1. What is the estimated cost of this proposed action?
The EPA estimates the total annualized national cost of this proposed action in 2025 dollars will be $33.7 million at both a 3 percent and 7 percent discount rate for the years 2027-2031. The EPA has documented the assumptions and data sources used in the preparation of this estimate in the “ Draft Economic Analysis of the Sixth Unregulated Contaminant Monitoring Rule” (USEPA, 2026k). Copies of the Draft Economic Analysis may be obtained from the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. The agency proposes four drinking water analytical methods to analyze samples for 30 chemical contaminants. The EPA's estimate of the analytical cost for the UCMR 6 contaminants is $1,893 per sample set with field blanks
m the State Resource Model developed by the Association of State Drinking Water Administrators (ASDWA) (ASDWA, 2020) to help states forecast resource needs. Model estimates were adjusted to account for actual levels of state participation under UCMR 5.
The EPA assumes that one-third of the PWSs would monitor during each of the three sample-collection years from January 2028 through December 2030. The total estimated annual costs (labor and non-labor) would be incurred as follows:
Exhibit 5—Total Annualized Costs of the Proposed UCMR 6 Using 3 Percent and 7 Percent Discount Rates [In millions of 2025 dollars] Respondent Costs (3%) Costs (7%) 1 Small PWSs (10,000 or fewer people), including labor 2 only (non-labor costs 3 paid for by the EPA) $0.4 $0.4 Large PWSs (10,001 or more), including labor and non-labor costs $16.7 $16.7 States, including labor costs related to implementation coordination $0.5 $0.5 EPA, including labor for implementation and non-labor for small PWS testing $16.1 $16.1 Total Annualized National Cost 4 $33.7 $33.7 1 Please see section III.O.2 of this document, which describes the reduced cost alternative if the funds are not received to implement the monitoring as outlined by AWIA. 2 Labor costs pertain to PWSs, states, and the EPA. Costs include activities such as reading the rule, notifying PWSs selected to participate, sample collection, data review, reporting, and recordkeeping. 3 Non-labor costs will be incurred primarily by the EPA and by large PWSs. They include the cost of shipping samples to laboratories for testing and the cost of the laboratory analyses. 4 Totals may not equal the sum of components due to rounding. 2. What are the costs of alternative approaches to implementing the proposed UCMR 6?
As noted in section I.A.3 of this document, the AWIA amendments to SDWA conditioned the UCMR monitoring scope on the availability of appropriations. See SDWA section 1445(j)(1)
mples to laboratories for testing and the cost of the laboratory analyses. 4 Totals may not equal the sum of components due to rounding. 2. What are the costs of alternative approaches to implementing the proposed UCMR 6?
As noted in section I.A.3 of this document, the AWIA amendments to SDWA conditioned the UCMR monitoring scope on the availability of appropriations. See SDWA section 1445(j)(1). If the EPA concludes that it will not have the resources necessary to support the full monitoring described by the AWIA, the agency will reduce the number of small PWSs serving 10,000 or fewer people that will be required to monitor. The EPA will determine the number of small PWSs whose monitoring is covered by the appropriations and will notify the included small PWSs of their upcoming requirements at least six months prior to their scheduled monitoring ( i.e., by July 1 of each year preceding sample collection). This notification approach was successfully implemented in the previous UCMR cycle. The number of large PWSs—those serving more than
The EPA has documented the alternative assumptions and data sources used in the preparation of this estimate in the “ Draft Economic Analysis of the Sixth Unregulated Contaminant Monitoring Rule” (USEPA, 2026k). The EPA estimates the total annualized national cost of this alternative in 2025 dollars will be $22.1 million at both a 3 percent and 7 percent discount rate for the years 2027-2031. Exhibit 6 presents a breakdown of the estimated annual average national costs.
As outlined in SDWA section 1445, the EPA pays for the analytical costs for all systems serving a population of 10,000 or fewer people. Laboratory analysis and sample shipping account for approximately 77 percent of the total national cost for the implementation of UCMR 6. Under the alternative scenario, this percentage slightly decreases since the number of small PWSs decreases from approximately 6,000 to 800. All other expectations with state participation and years of sampling remain the same
pulation of 10,000 or fewer people. Laboratory analysis and sample shipping account for approximately 77 percent of the total national cost for the implementation of UCMR 6. Under the alternative scenario, this percentage slightly decreases since the number of small PWSs decreases from approximately 6,000 to 800. All other expectations with state participation and years of sampling remain the same. Only the number of small PWSs monitoring will be reduced.
Exhibit 6—Estimated Total Annualized Cost Alternatives of the Proposed UCMR 6 Using 3 Percent and 7 Percent Discount Rates [In millions of 2025 dollars] Respondent Costs (3%) Costs (7%) Small PWSs (10,000 or fewer people), including labor 1 only (non-labor costs 2 paid for by the EPA) $0.1 $0.1 Large PWSs (10,001 or more), including labor and non-labor costs 16.7 16.7 States, including labor costs related to implementation coordination 0.5 0.5 EPA, including labor for implementation and non-labor for small system testing 4.9 4.9 Total annualized national cost 3 22.2 22.2 1 Labor costs pertain to PWSs, states, and the EPA. Costs include activities such as reading the rule, notifying PWSs selected to participate, sample collection, data review, reporting, and recordkeeping. 2 Non-labor costs will be incurred primarily by the EPA and by large PWSs. They include the cost of shipping samples to laboratories for testing and the cost of the laboratory analyses. 3 Totals may not equal the sum of components due to rounding. 3. What are the benefits of this proposed action?
The UCMR program gathers data about unregulated contaminant occurrence in drinking water. This occurrence information benefits consumers by letting them know whether or not unregulated contaminants are present in their drinking water. If contaminants are not found, consumer confidence in their drinking water will improve
mponents due to rounding. 3. What are the benefits of this proposed action?
The UCMR program gathers data about unregulated contaminant occurrence in drinking water. This occurrence information benefits consumers by letting them know whether or not unregulated contaminants are present in their drinking water. If contaminants are not found, consumer confidence in their drinking water will improve. If contaminants are found, PWSs and consumers may be able to take actions to avoid adverse health effects such as treatment optimization or point-of-use filters to reduce or remove those contaminants. While the UCMR program does not result in direct improvements to public health that can be monetized for the purpose of a quantitative benefits analysis, the data gathered under the UCMR program informs other agency actions that could result in quantifiable health risk reduction benefits.
The UCMR program provides a value of information benefit that can be used by federal and state agencies, local governments, water systems, and the public, in their policies and regulatory actions to produce national estimates and quantifiable improvements to public health.
IV. Supporting Information
A. Economic Analysis
The general cost and benefits outlined in the economic analysis for this action are discussed in section III.O of this document. The full analysis is available in the public Docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469.
B. How did the EPA consider children's environmental health?
This action is not subject to the EPA's Children's Health Policy at https://www.epa.gov/children/childrens-health-policy-and-plan, because this is a monitoring rule that does not directly address human health. However, by monitoring for unregulated contaminants that may pose health risks via drinking water, UCMR furthers the protection of public health for all citizens, including children. Children consume more water per unit of body weight compared to adults
1. Methods From the U.S. Environmental Protection Agency
(i) EPA Method 524.3, “Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry,” Version 1.0, June 2009, EPA 815-B-09-009. Available at https://www.epa.gov/dwanalyticalmethods. This is an EPA method for analysis of purgeable organic compounds in drinking water using SPE and LC/MS/MS.
(ii) EPA Method 524.3 “ Recommended Parameters to Enhance Sensitivity for the Analysis of Select Purgeable Organic Compounds using EPA Method 524.3 (EPA 815-B-09-009) in Selected Ion Monitoring (SIM) Mode,” Version 1.0, February 2026, EPA 815-B-26-002. Available at https://www.epa.gov/dwanalyticalmethods. This is an EPA method for the analysis of purgeable organic compounds in drinking water using SPE and LC/MS/MS and is proposed to measure seven purgeable organic compounds during UCMR 6 (1,2,4-Trimethylbenzene, 1,2,3-Trichloropropane (1,2,3-TCP), 1,1,2,2-Tetrachloroethane, Total 1,3-Dichloropropene (cis- & trans-), Naphthalene, 1,1,1,2-Tetrachloroethane, and Hexachlorobutadiene).
(iii) EPA Method 525.3 “ Determination of Semivolatile Organic Chemicals in Drinking Water by Solid Phase Extraction (SPE) and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS),” Version 1.0, February 2012, EPA/600/R-12/01. Available at https://www.epa.gov/dwanalyticalmethods. This is an EPA method for the analysis of semi-volatile organic chemicals in drinking water using SPE and GC/MS and is proposed to measure 13 semi-volatile organic chemicals during UCMR 6 (Phorate, Chlorothalonil, Dichlorvos (DDVP), Metribuzin, N,N-Diethyl-m-toluamide (DEET), Trifluralin, Pyrene, Isophorone, 2,4-Dinitrotoluene, 2,6,-Dinitrotoluene, Stirofos, Anthracene, and Flourene).
gnificant regulatory action that was submitted to the Office of Management and Budget (OMB) for review defined under Executive Order 12866. Any changes made in response to OMB recommendations have been documented in the docket. The EPA prepared an economic analysis of the potential costs and benefits associated with this action that is briefly summarized in sections III.O and IV.A of this document. This analysis, “ Economic Analysis of the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6)” (USEPA, 2026k), is available in the EPA public docket for this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. The EPA estimated that the proposed action would result in annualized costs of $33.7 million in 2025 dollars, at both a 3 percent discount rate and a 7 percent discount rate.
B. Executive Order 14192: Unleashing Prosperity Through Deregulation
This action is expected to be an Executive Order 14192 regulatory action. The expected quantified annualized costs of this rule are $7.68 million in 2024 dollars at a 7 percent discount rate and an in-perpetuity time horizon. Details on the estimated costs of this proposed rule can be found in the EPA's analysis of the potential costs and benefits associated with this action.
C. Paperwork Reduction Act (PRA)
The information collection activities in this proposed rule have been submitted for approval to the Office of Management and Budget (OMB) under the PRA. The Information Collection Request (ICR) document that the EPA prepared has been assigned EPA ICR number 7820.01. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here.
The information that the EPA proposes to collect under this rule fulfills the statutory requirements of SDWA section 1445(a)(2), as amended in 1996, 2018, and 2019. The data will describe the source of the water, location, and test results for samples taken from PWSs as described in 40 CFR 141.35(e)
n, the accuracy of the provided burden estimates and any suggested methods for minimizing respondent burden to the EPA using the docket identified at the beginning of this rule. The EPA will respond to any ICR-related comments in the final rule. You may also send your ICR-related comments to OMB's Office of Information and Regulatory Affairs using the interface at www.reginfo.gov/public/do/PRAMain. Find this particular information collection by selecting “Currently under Review—Open for Public Comments” or by using the search function. OMB must receive comments no later than July 31, 2026.
D. Regulatory Flexibility Act (RFA)
For purposes of assessing the impacts of this rule on small entities, the EPA considered small entities to be PWSs serving 10,000 or fewer people. As required by the RFA, the EPA proposed using this alternative definition in the Federal Register (63 FR 7607, February 13, 1998 (USEPA, 1998a)), sought public comment, consulted with the Small Business Administration (SBA), and finalized the alternative definition in the Consumer Confidence Reports rulemaking (63 FR 44512, August 19, 1998 (USEPA, 1998b)). As stated in that document, the alternative definition would apply to this regulation.
I certify that this action will not have a significant economic impact on a substantial number of small entities under the RFA. The small entities subject to the requirements of this action are PWSs serving 10,000 or fewer people. The Agency has determined that up to 5,955 small PWSs would participate in UCMR 6 if the EPA receives the necessary appropriations. Those entities are not expected to experience an impact greater than 0.4% of median revenue because the EPA assumes all costs for analyses of the samples and for shipping the samples from small PWSs to laboratories contracted by the EPA to analyze the UCMR 6 samples (the cost of shipping is included in the cost of each drinking water analytical method)
ely affect small governments. The action implements mandate(s) specifically and explicitly set forth in SDWA section 1445(a)(2), Monitoring Program for Unregulated Contaminants. The costs involved in this action are estimated not to exceed 100 million in 1995 dollars which is $192.68 million in 2025 dollars (adjusted for inflation using the GDP implicit price deflator) or more in any one year.
F. Executive Order 13132: Federalism
This action does not have federalism implications. The EPA believes, however, that this action may be of significant interest to state governments. Consistent with the EPA's policy to promote communications between the EPA and state and local governments, the EPA consulted with state representatives early in the process of developing the UCMR 6 to permit them to have meaningful and timely input into its development. Please see section II.B of this notice and the summary of the public comments for this meeting included in the EPA public docket for this proposed rule, under Docket ID No. EPA-HQ-OW-2023-0469.
G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments
This action has tribal implications; however, it will neither impose substantial direct compliance costs on federally recognized tribal governments, nor preempt tribal law. As described previously, this proposed rule requires monitoring by all large PWSs. Information in the SDWIS/Fed water system inventory indicates there are 30 large tribal PWSs (ranging in size from 10,100 to 32,000 people served). The EPA estimates the average annual cost to each of these large PWSs, over the 5-year rule period, to be $3,082. This cost is based on a labor component (associated with the collection of samples) and a non-labor component (associated with shipping and laboratory fees). As planned, UCMR 6 is expected to also require monitoring by all small PWSs serving 3,300 to 10,000 people and a nationally representative sample of small PWSs serving fewer than 3,300 people
e PWSs, over the 5-year rule period, to be $3,082. This cost is based on a labor component (associated with the collection of samples) and a non-labor component (associated with shipping and laboratory fees). As planned, UCMR 6 is expected to also require monitoring by all small PWSs serving 3,300 to 10,000 people and a nationally representative sample of small PWSs serving fewer than 3,300 people. Information in the SDWIS/Fed water system inventory indicates there are 77 small tribal PWSs (serving 3,300 to 10,000 people). The EPA estimates that less than 2 percent of small tribal PWSs serving fewer than 3,300 people will be selected as part of the nationally representative sample. The EPA estimates the average annual cost to small tribal PWSs over the 5-year rule period to be $69. Such cost is based on the labor associated with collecting a sample and preparing it for shipping. All other small PWS expenses
The EPA consulted with tribal officials under the EPA Policy on Consultation and Coordination with Indian Tribes early in the process of developing this regulation to permit them to have meaningful and timely input into its development. A summary of that consultation is provided in the EPA public docket for this proposed rule, under Docket ID No. EPA-HQ-OW-2023-0469. The summaries are titled, “ Summary of Tribal Consultation and Coordination on the Development of the Sixth Proposed Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems ” and “ Summary of Alaska Native Claims Settlement Act (ANCSA) Corporations Consultation and Coordination on the Development of the Sixth Proposed Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems” The EPA specifically solicits additional comment on this proposed rule from tribal officials.
H
oposed Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems ” and “ Summary of Alaska Native Claims Settlement Act (ANCSA) Corporations Consultation and Coordination on the Development of the Sixth Proposed Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems” The EPA specifically solicits additional comment on this proposed rule from tribal officials.
H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks
The EPA interprets Executive Order 13045 as applying only to those regulatory actions that concern environmental health or safety risks that the EPA has reason to believe may disproportionately affect children, per the definition of “covered regulatory action” in section 2-202 of the Executive Order.
Therefore, this action is not subject to Executive Order 13045 because this is a monitoring rule, and it does not directly address an environmental health risk or safety risk. Since this action does not directly concern human health, the EPA's Policy on Children's Health also does not apply.
I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use
This action is not a “significant energy action” because it is not likely to have a significant adverse effect on the supply, distribution or use of energy. UCMR 6 has not otherwise been designated by the Administrator of the OMB-OIRA as a significant energy action. This is a national drinking water occurrence study that was submitted to OMB for review.
J. National Technology Transfer and Advancement Act (NTTAA)
This action involves technical standards. The EPA proposes to use the following methods developed by the agency to support UCMR 6 monitoring: EPA Method 563, EPA Method 540, EPA Method 525.3, and EPA Method 524.3
gulation (1999). EPA 815-R-01-004. Office of Water. August 2001. USEPA. 2005. Organophosphate Pesticide Degradation Under Drinking Water Treatment Conditions. EPA/600/R-05/103. Office of Research and Development. August 2005. USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water Systems Revisions. Federal Register . Vol. 72, No. 2, p. 368. January 4, 2007. USEPA. 2009a. Drinking Water Contaminant Candidate List 3-Final. Federal Register . Vol. 74, No. 194, p. 51850. October 8, 2009. USEPA. 2009b. Method 524.3: Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry. EPA 815-B-09-009. Office of Water. June 2009. USEPA. 2010. Technical Basis for the Lowest Concentration Minimum Reporting Level (LCMRL) Calculator. EPA 815-R-11-001. Office of Water. December 2010. Available at https://www.epa.gov/dwanalyticalmethods. USEPA. 2012a. Method 525.3 Determination of Semivolatile Organic Chemicals in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS). EPA/600/R-12/010. Office of Research and Development. February 2012. Available at https://www.epa.gov/dwanalyticalmethods. USEPA. 2012b. Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems. Federal Register . Vol. 77, No. 85, p. 26072. May 2, 2012. USEPA. 2013a. Method 540: Determination of Selected Organic Chemicals in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). EPA/600/R-13/119. Office of Research and Development. September 2013. Available at https://www.epa.gov/dwanalyticalmethods. USEPA. 2013b. America's Children and the Environment, Third Edition: Environments and Contaminants: Drinking Water Contaminants. January 2013. Available at: https://www.epa.gov/sites/default/files/2015-06/documents/ace3_2013.pdf USEPA. 2016a. Drinking Water Contaminant Candidate List 4-Final. Federal Register . USEPA. 2016b
revention. April 2021. USEPA. 2021d. Revisions to the Unregulated Contaminant Monitoring Rule (UCMR 5) for Public Water Systems and Announcement of Public Meetings. Federal Register . Vol. 86, No. 245, p. 73131. December 27, 2021. USEPA. 2021e. Instructions for Preparing a Ground Water Representative Monitoring Plan for the Unregulated Contaminant Monitoring Rule. EPA 815-B-21-013. Office of Water. December 2021. USEPA. 2022. Drinking Water Contaminant Candidate List 5—Final. Federal Register . Vol. 87, No. 218, p. 68060. November 14, 2022. USEPA. 2023. Drinking Water Contaminant Candidate List 6 —Nominations. Federal Register . Vol. 88, No. 33, p. 10316. February 17, 2023. USEPA. 2024a. Unregulated Contaminant Monitoring Rule; Methods Request and Webinar. Federal Register . Vol. 89, No. 27, p. 8584. February 8, 2024. USEPA. 2024b. National Primary Drinking Water Regulations: Consumer Confidence Reports. Federal Register . Vol. 89, No. 102, p. 45980. May 24, 2024. USEPA. 2025a. U.S. Environmental Protection Agency Implementation of Gold Standard Science—Based on Executive Order No. 14303 “Restoring Gold Standard Science.” August 2025. Available at https://www.epa.gov/system/files/documents/2026-01/final-epa-gss-report.pdf. USEPA. 2025b. Announcement of Preliminary Regulatory Determinations for Contaminants on the Fifth Drinking Water Contaminant Candidate List. Federal Register . Vol. 90, No. 9, p. 3830. January 15, 2025. USEPA. 2026a. Summary of the State Consultation on the Development of the Sixth Proposed Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems. EPA-815-S-26-006. Office of Water. February 2026. USEPA. 2026b. Summary of Alaska Native Claims Settlement Act (ANCSA) Corporations Consultation and Coordination on the Development of the Sixth Proposed Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems. EPA 815-S-26-002. Office of Water. February 2026. USEPA. 2026c
porting and Recordkeeping
2. Amend § 141.35 as follows:
a. In paragraph (c)(1), remove the text “December 31, 2022” and add, in its place, the text “December 31, 2027”;
b. In paragraph (c)(2), remove the text “December 31, 2022” and add, in its place, the text “December 31, 2027”;
c. In paragraph (c)(4), remove the text “April 26, 2022” and add, in its place, the text “April 26, 2027”;
d. In paragraph (c)(5)(i), remove the text “December 31, 2022” from wherever it appears and add, in its place, the text “December 31, 2027”;
e. In paragraph (d)(2), remove the text “December 31, 2022” and add, in its place, the text “December 31, 2027”;
f. Revise paragraph (e).
The revisions read as follows:
§ 141.35 Reporting for unregulated contaminant monitoring results. (e) Data elements. Table 1 defines the data elements that must be provided for UCMR monitoring.
Table 1—Unregulated Contaminant Monitoring Reporting Requirements Data element Definition 1. Public Water System Identification Code (PWSID) The unique code used to identify each PWS. The code generally begins with the standard 2-character postal state abbreviation or region code; the remaining 7 numbers are unique to each PWS in the state. Each PWSID is assigned by the primacy agency in the Safe Drinking Water Information System Federal Reporting System (SDWIS/Fed). 2. Public Water System Name (PWS Name) Assigned by the primacy agency. 3. Public Water System Facility Identification Code (PWS Facility ID) An identification code used to identify each unique applicable facility ( i.e., for each source of water, treatment plant, distribution system, or any other facility associated with water treatment or delivery). Each PWS Facility Identification Code is assigned by the PWS, established by the primacy agency, or at the primacy agency's discretion. The PWS Facility ID is unique from the PWSID. 4. Public Water System Facility Name (PWS Facility Name) Descriptive Facility Name, assigned once by the PWS, for every PWS Facility ID ( e.g., Maple St
d water source during the 12-month period). 7. Sampling Point Identification Code (Sample Point ID) An identification code used to identify each unique applicable sample point ( i.e., entry point to the distribution system) at each applicable facility. 8. Sampling Point Name Descriptive Sample Point Name, assigned once by the PWS, for every applicable Sample Point ID ( e.g., Maple St. Entry Point). The Sample Point Name should be more descriptive than the Sample Point ID. 9. Sampling Point Type Code A code that identifies the location of the sampling point as: EP = Entry point to the distribution system. 10. Treatment Information Treatment information associated with the sample point for each sample event. Please select all that apply (including the treatment processes used by your wholesaler). CON = Conventional (non-softening, consisting of at least coagulation/sedimentation basins and filtration). SFN = Softening. RBF = River bank filtration. PSD = Pre-sedimentation. INF = In-line filtration. DFL = Direct filtration. SSF = Slow sand filtration. BIO = Biological filtration (operated with an intention of maintaining biological activity within filter). UTR = Unfiltered surface water source treatment. GWD = Groundwater system with disinfection only. PAC = Application of powder activated carbon. GAC = Granular activated carbon adsorption (not part of filters in CON, SFN, INF, DFL, or SSF). AIR = Air stripping (packed towers, diffused gas contactors). POB = Pre-oxidation with chlorine (applied before coagulation for CON or SFN plants or before filtration for other filtration plants). HMF = High pressure membrane filtration. LMF = Low pressure membrane filtration. IEX = Ionic exchange. DAF = Dissolved air floatation. CWL = Clear well/finished water storage without aeration. CWA = Clear well/finished water storage with aeration. ADS = Aeration in distribution system (localized treatment). OTH = All other types of treatment. NTU = No treatment used. DKN = Do not know. 11
plants). HMF = High pressure membrane filtration. LMF = Low pressure membrane filtration. IEX = Ionic exchange. DAF = Dissolved air floatation. CWL = Clear well/finished water storage without aeration. CWA = Clear well/finished water storage with aeration. ADS = Aeration in distribution system (localized treatment). OTH = All other types of treatment. NTU = No treatment used. DKN = Do not know. 11. Disinfectant Type All of the disinfectant and/or oxidant types that have been added prior to and at the entry point to the distribution system of your finished water for each sample event. Please select all that apply: PEMB = Permanganate. HPXB = Hydrogen peroxide. CLGA = Gaseous chlorine. CLOF = Offsite generated hypochlorite (stored as a liquid form). CLON = Onsite generated hypochlorite. CAGC = Chloramine (formed with gaseous chlorine). CAOF = Chloramine (formed with offsite hypochlorite). CAON = Chloramine (formed with onsite hypochlorite). CLDB = Chlorine dioxide. FERA = Ferrate (VI). OZON = Ozone. ULVL = Ultraviolet light. OTHD = All other types of disinfectant/oxidant. NODU = No disinfectant/oxidant used. 12. Additives Any chemical(s) added to finished water after treatment and before the clear well, finished water storage reservoir, and/or entry point to the distribution system. Please select all that apply: FLU = Fluoride. ORT = Orthophosphate. POL = Polyphosphate. BLD = Blended phosphates. SIL = Silica. OTH = Other. NAU = No additive used. DNK = Do not know. 13. Average or Typical Daily Flow Estimate the typical or average daily flow at this entry point to the distribution system ( e.g., also called daily average production, the average amount of water per day produced by the treatment plant). [Numerical input] Units: Million gallons per day or thousands of gallons per day. 14
lue Represents the true value or the fortified concentration for spiked samples for QC Sample Analysis Types (CCCL, CCCM, CCCH, QCS, LFB, LFSM, and LFSMD). 28. Laboratory Identification Code The code, assigned by EPA, used to identify each laboratory. The code begins with the standard two-character state postal abbreviation; the remaining five numbers are unique to each laboratory in the state. 29. Sample Event Code A code assigned by the PWS for each sample event. This will associate samples with the PWS monitoring plan to allow EPA to track compliance and completeness. Systems must assign the following codes: SE1, SE2, SE3, and SE4—Represent samples collected to meet UCMR Assessment Monitoring requirements; where “SE1” and “SE2” represent the first and second sampling period for all water types; and “SE3” and “SE4” represent the third and fourth sampling period for SW, GU, and MX sources only. 30. Place Name Provide the census place names that are served by the PWS. This is entered by the PWS.
Subpart E—Special Regulations, Including Monitoring
3. Amend § 141.40 as follows:
a. In paragraph (a) introductory text, remove the text “February 1, 2021” and add, in its place, the text “February 1, 2026”;
b. Revise paragraphs (a)(3);
c. In paragraph (a)(4)(i), remove the text “December 31, 2022” and add, in its place, the text “December 31, 2027”;
d. In paragraph (a)(5)(ii), remove the text “August 1, 2022” and add, in its place, the text “August 1, 2027”;
e. Revise paragraph (c).
The revisions read as follows:
§ 141.40 Monitoring requirements for unregulated contaminants. (a) * * *
”;
b. Revise paragraphs (a)(3);
c. In paragraph (a)(4)(i), remove the text “December 31, 2022” and add, in its place, the text “December 31, 2027”;
d. In paragraph (a)(5)(ii), remove the text “August 1, 2022” and add, in its place, the text “August 1, 2027”;
e. Revise paragraph (c).
The revisions read as follows:
§ 141.40 Monitoring requirements for unregulated contaminants. (a) * * *
(3) Analytes to be monitored. Lists 1, 2, and 3 contaminants are provided in table 1 to paragraph (a)(3):
Table 1 to Paragraph ( a )(3)—UCMR Contaminat List 1—Contaminant 2—CASRN 3—Analytical methods 4—Minimum reporting level 5—Sampling location 6—Period during which sample collection to be completed List 1: Assessment Monitoring Purgeable Organic Compounds 1,1,2,2-Tetrachloroethane 79-34-5 EPA 524.3 Enhanced Sensitivity 0.008 µg/L EPTDS 1/1/2028-12/31/2030 1,1,1,2-Tetrachloroethane 630-20-6 EPA 524.3 Enhanced Sensitivity 0.004 µg/L EPTDS 1/1/2028-12/31/2030 1,2,3-Trichloropropane (1,2,3-TCP) 96-18-4 EPA 524.3 Enhanced Sensitivity 0.009 µg/L EPTDS 1/1/2028-12/31/2030 1,2,4-Trimethylbenzene 95-63-6 EPA 524.3 Enhanced Sensitivity 0.004 µg/L EPTDS 1/1/2028-12/31/2030 Hexachlorobutadiene 87-68-3 EPA 524.3 Enhanced Sensitivity 0.005 µg/L EPTDS 1/1/2028-12/31/2030 Naphthalene 91-20-3 EPA 524.3 Enhanced Sensitivity 0.008 µg/L EPTDS 1/1/2028-12/31/2030 Total 1,3-Dichloropropene (cis- & trans-) 542-75-6 EPA 524.3 Enhanced Sensitivity 0.007 µg/L EPTDS 1/1/2028-12/31/2030 Semivolatile Organic Compounds 2,4-Dinitrotoluene 121-14-2 EPA 525.3 0.06 µg/L EPTDS 1/1/2028-12/31/2030 2,6-Dinitrotoluene 606-20-2 EPA 525.3 0.2 µg/L EPTDS 1/1/2028-12/31/2030 Anthracene 120-12-7 EPA 525.3 0.04 µg/L EPTDS 1/1/2028-12/31/2030 Chlorothalonil 1897-45-6 EPA 525.3 0.06 µg/L EPTDS 1/1/2028-12/31/2030 Dichlorvos (DDVP) 62-73-7 EPA 525.3 0.05 µg/L EPTDS 1/1/2028-12/31/2030 Fluorene 86-73-7 EPA 525.3 0.03 µg/L EPTDS 1/1/2028-12/31/2030 Isophorone 78-59-1 EPA 525.3 0.04 µg/L EPTDS 1/1/2028-12/31/2030 Metribuzin 21087-64-9 EPA 525.3 0.2 µg/L EPTDS 1/1/
-12/31/2030 Anthracene 120-12-7 EPA 525.3 0.04 µg/L EPTDS 1/1/2028-12/31/2030 Chlorothalonil 1897-45-6 EPA 525.3 0.06 µg/L EPTDS 1/1/2028-12/31/2030 Dichlorvos (DDVP) 62-73-7 EPA 525.3 0.05 µg/L EPTDS 1/1/2028-12/31/2030 Fluorene 86-73-7 EPA 525.3 0.03 µg/L EPTDS 1/1/2028-12/31/2030 Isophorone 78-59-1 EPA 525.3 0.04 µg/L EPTDS 1/1/2028-12/31/2030 Metribuzin 21087-64-9 EPA 525.3 0.2 µg/L EPTDS 1/1/2028-12/31/2030 N,N-Diethyl-m-toluamide (DEET) 134-62-3 EPA 525.3 0.2 µg/L EPTDS 1/1/2028-12/31/2030 Phorate 298-02-2 EPA 525.3 0.02 µg/L EPTDS 1/1/2028-12/31/2030 Pyrene 129-00-0 EPA 525.3 0.03 µg/L EPTDS 1/1/2028-12/31/2030 Tetrachlorvinphos (Stirofos) 22248-79-9 EPA 525.3 0.09 µg/L EPTDS 1/1/2028-12/31/2030 Trifluralin 1582-09-8 EPA 525.3 0.02 µg/L EPTDS 1/1/2028-12/31/2030 Pesticide Metabolites Chlorpyrifos oxon 5598-15-2 EPA 540 0.00007 µg/L EPTDS 1/1/2028-12/31/2030 Phorate sulfone 2588-04-7 EPA 540 0.0006 µg/L EPTDS 1/1/2028-12/31/2030 Phorate sulfoxide 2588-03-6 EPA 540 0.00007 µg/L EPTDS 1/1/2028-12/31/2030 Ultrashort Organofluorine Compounds Bistriflimide (TFSI) 82113-65-3 EPA 563 0.003 µg/L EPTDS 1/1/2028-12/31/2030 Perfluoro-2-methoxyacetic acid (PFMOAA) 674-13-5 EPA 563 0.06 µg/L EPTDS 1/1/2028-12/31/2030 Perfluoroethanesulfonic acid (PFEtS) 354-88-1 EPA 563 0.02 µg/L EPTDS 1/1/2028-12/31/2030 Perfluoropropanesulfonic acid (PFPrS) 423-41-6 EPA 563 0.01 µg/L EPTDS 1/1/2028-12/31/2030 Perfluoropropanoic acid (PFPrA) 422-64-0 EPA 563 0.08 µg/L EPTDS 1/1/2028-12/31/2030 Trifluoromethanesulfonic acid (TFMS) 1493-13-6 EPA 563 0.02 µg/L EPTDS 1/1/2028-12/31/2030 Trifluoroacetic acid (TFA) 76-05-1 EPA 563 0.2 µg/L EPTDS 1/1/2028-12/31/2030 List 2: Screening Survey Reserved Reserved Reserved Reserved Reserved Reserved List 3: Pre-Screen Testing Reserved Reserved Reserved Reserved Reserved Reserved Column headings are: 1—Contaminant: The name of the contaminant to be analyzed. 2—CASRN (Chemical Abstracts Service Registry Number) or Identification Number: A unique number identifying the chemical contaminants
L EPTDS 1/1/2028-12/31/2030 List 2: Screening Survey Reserved Reserved Reserved Reserved Reserved Reserved List 3: Pre-Screen Testing Reserved Reserved Reserved Reserved Reserved Reserved Column headings are: 1—Contaminant: The name of the contaminant to be analyzed. 2—CASRN (Chemical Abstracts Service Registry Number) or Identification Number: A unique number identifying the chemical contaminants. 3—Analytical Methods: Method numbers identifying the methods that must be used to test the contaminants. The analytical procedures shall be performed in accordance with the documents associated with each method, see paragraph (c) of this section. 4—Minimum Reporting Level (MRL): The value and unit of measure at or above which the concentration of the contaminant must be measured using the approved drinking water analytical methods. The MRL is the minimum concentration of each analyte that must be reported to EPA. If EPA determines, after the first six months of monitoring that the specified MRLs result in excessive resampling, EPA will establish alternate MRLs and will notify affected PWSs and laboratories of the new MRLs. N/A is defined as non-applicable. 5—Sampling Location: The locations within a PWS at which samples must be collected. Sampling must occur at your PWS's entry points to the distribution system (EPTDSs), after treatment is applied, that represent each non-emergency water source in routine use over the 12-month period of monitoring. Systems that purchase water with multiple connections from the same wholesaler may select one representative connection from that wholesaler. The representative EPTDS must be a location within the purchaser's water system. This EPTDS sampling location must be representative of the highest annual volume connections. If the connection selected as the representative EPTDS is not available for sampling, an alternate highest volume representative connection must be sampled
esaler may select one representative connection from that wholesaler. The representative EPTDS must be a location within the purchaser's water system. This EPTDS sampling location must be representative of the highest annual volume connections. If the connection selected as the representative EPTDS is not available for sampling, an alternate highest volume representative connection must be sampled. See 40 CFR 141.35(c)(3) for an explanation of the requirements related to the use of representative GW EPTDSs. 6—Period During Which Sample Collection to be Completed: The time period during which the sampling and testing will occur for the indicated contaminant. PWSs must complete their monitoring by December 31, 2031.
(c) Incorporation by reference. The standards required in this section are incorporated by reference into this section with the approval of the Director of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. All approved material is available for inspection at U.S. Environmental Protection Agency, Water Docket, EPA/DC, EPA West, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004, (202) 566-1744, email Docket-customerservice@epa.gov, or go to https://www.epa.gov/dockets/epa-docket-center-reading-room, and is available from the sources indicated elsewhere in this paragraph. The material is also available for inspection fr.inspection@nara.gov, or go to:
(1) U.S. Environmental Protection Agency, EPA West, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; telephone: (202) 566-1744.
mail Docket-customerservice@epa.gov, or go to https://www.epa.gov/dockets/epa-docket-center-reading-room, and is available from the sources indicated elsewhere in this paragraph. The material is also available for inspection fr.inspection@nara.gov, or go to:
(1) U.S. Environmental Protection Agency, EPA West, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; telephone: (202) 566-1744.
(i) Method 524.3, “ Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry,” Version 1.0, June 2009, EPA 815-B-09-009. Available at https://www.epa.gov/dwanalyticalmethods.
(ii) Method 524.3 “Recommended Parameters to Enhance Sensitivity for the Analysis of Select Purgeable Organic Compounds using EPA Method 524.3 (EPA 815-B-09-009) in Selected Ion Monitoring (SIM) Mode,” Version 1.0, February 2026, EPA 815-B-26-002. Available at https://www.epa.gov/dwanalyticalmethods.
(iii) Method 525.3, “Determination of Semivolatile Organic Chemicals in Drinking Water by Solid Phase Extraction (SPE) and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS),” Version 1.0, February 2012, EPA/600/R-12/01. Available at https://www.epa.gov/dwanalyticalmethods.
(iv) Method 540, “Determination of Selected Organic Chemicals in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS),” Version 1.0, September 2013, EPA/600/R-13/119. Available at https://www.epa.gov/dwanalyticalmethods.
(v) Method 563 “Determination of Selected Ultrashort Organofluorine Compounds in Drinking Water by Liquid Chromatography/Tandem Mass Spectrometry,” Version 1.0, January, 2026, EPA 815-F-26-02. Available at https://www.epa.gov/dwanalyticalmethods.
(2) [Reserved]

[FR Doc. 2026-13263 Filed 6-30-26; 8:45 am] BILLING CODE 6560-50-P

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Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/FR_PRORULE_2026-13263. Check the current official text before relying on it. Not legal advice.