Federal Register, Volume 91 Issue 125 (Wednesday, July 1, 2026)

[Federal Register Volume 91, Number 125 (Wednesday, July 1, 2026)]
[Proposed Rules]
[Pages 39952-39973]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-13263]

[[Page 39952]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2023-0469; FRL-10857-03-OW]
RIN 2040-AG33

Revisions To Establish the Sixth Unregulated Contaminant
Monitoring Rule (UCMR 6) for Public Water Systems

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; notice of public meeting.

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SUMMARY: 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 public water systems (PWSs) to collect
national occurrence data for seven ultrashort organofluorine compounds
(including certain PFAS), three pesticide metabolites, 13 semivolatile
organic compounds, and seven purgeable organic compounds. Subject to
the availability of appropriations, the EPA will require all community
and non-transient non-community water systems (CWSs and NTNCWSs)
serving 3,300 or more people, and a representative sample of PWSs
serving fewer than 3,300 people, to conduct monitoring. These
contaminants are not currently subject to national primary drinking
water regulations (NPDWRs), and the EPA is proposing to require the
collection of drinking water occurrence data to inform agency
decisions. The data collected will be publicly available. The EPA is
also announcing two public meetings (via webinar) to discuss this
proposal of the sixth Unregulated Contaminant Monitoring Rule (UCMR 6).

DATES: Comments must be received on 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: [email protected]
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. 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: [email protected]; 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: [email protected].

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. 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

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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

[micro]g/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 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). This proposed rulemaking would require all
community water systems (CWSs) and non-transient non-community water
systems (NTNCWSs) serving 3,300 or more people, and a representative
sample of smaller PWSs serving fewer than 3,300 people, to conduct
monitoring. The data collected will be publicly available and will
inform decisions by the EPA.
Consistent with the ``U.S. Environmental Protection Agency
Implementation of Gold Standard Science'' (USEPA, 2025a) based on
Executive Order 14303 (White House, 2025), this proposal identifies
four drinking water analytical methods to support PWS monitoring for a
total of 30 contaminants. These contaminants consist of seven
ultrashort organofluorine compounds (including certain PFAS), three
pesticide metabolites, 13 semivolatile organic compounds, and seven
purgeable organic compounds. The proposed inclusion of ultrashort
organofluorine compounds, which include certain PFAS,\1\ is also
consistent with the EPA's priority to address PFAS in drinking water as
established in the 2019 PFAS Action Plan (USEPA, 2019). This proposal
also describes the EPA's evaluation of alternate contaminants and
invites public comment on all aspects of the proposal.
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\1\ The fifth Contaminant Candidate List (CCL 5) (87 FR 68060,
November 14, 2022 (USEPA. 2022)) defines the structural definition
of PFAS to include 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.
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2. Does this action apply to me?
This proposed rule applies to PWSs described in this section. PWSs
are systems that provide water for human consumption through pipes, or
constructed conveyances, to at least 15 service connections, or that
regularly serve an average of at least 25 individuals daily at least 60
days out of the year. A CWS is a PWS that has at least 15 service
connections used by year-round residents or regularly serves at least
25 year-round residents. An NTNCWS is a PWS that is not a CWS and that
regularly serves at least 25 of the same people over six months per
year. Under this proposal, all large CWSs and NTNCWSs serving more than
10,000 people would be required to monitor. In addition, all small CWSs
and NTNCWs serving between 3,300 and 10,000 people and a nationally
representative sample of CWSs and NTNCWS serving fewer than 3,300
people would be required to monitor, subject to the availability of
appropriations and appropriate laboratory capacity (see discussion of
America's Water Infrastructure Act of 2018 (AWIA) in sections I.A.3 and
I.B of this document). (For a description of the statistical approach
for the nationally representative sample see ``Selection of Nationally
Representative Public Water Systems for the Unregulated Contaminant
Monitoring Rule: 2021 Update'' (USEPA, 2021a)). As is generally the
case for UCMR sampling,

[[Page 39954]]

transient non-community water systems (TNCWSs) (i.e., non-community
water systems that do not regularly serve at least 25 of the same
people over six months per year) would not be required to monitor under
UCMR 6.
States, territories, and tribes with primary enforcement
responsibility (primacy) to administer the regulatory program for PWSs
under SDWA (hereinafter referred to in this document as ``states'') can
participate in the implementation of UCMR 6 through voluntary
Partnership Agreements (see discussion of Partnership Agreements in
section III.N in this document). Primacy agencies with Partnership
Agreements can choose to be involved in various aspects of the UCMR 6
monitoring for PWSs they oversee; however, the PWS remains responsible
for all compliance activities.
Potentially regulated categories and entities are identified in the
following table.

------------------------------------------------------------------------
Examples of
Category potentially regulated NAICS \1\
entities
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State, Local, & Tribal governments. State, local, and 924110
tribal governments
that analyze water
samples on behalf of
PWSs required to
conduct such
analysis; state,
local, and tribal
governments that
directly operate CWSs
and NTNCWSs required
to monitor.
Industry........................... Private operators of 221310
CWSs and NTNCWSs
required to monitor.
Municipalities..................... Municipal operators of 924110
CWSs and NTNCWSs
required to monitor.
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\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. 115-270), specifies that,
subject to the availability of appropriations for such purpose and
appropriate laboratory capacity, the EPA's UCMR program must require
all systems serving between 3,300 and 10,000 people to monitor, and
ensure that only a nationally representative sample of systems serving
fewer than 3,300 people are required to monitor. The program will
continue to ensure that all systems serving a population larger than
10,000 people are required to monitor. This AWIA provision became
effective October 23, 2021.

B. Summary of the Regulatory Action

The EPA proposes to require certain PWSs to collect occurrence data
for 30 contaminants. These contaminants may be present in drinking
water but are not yet subject to NPDWRs. More specifically, the UCMR 6
proposal identifies the following: drinking water analytical methods to
measure the UCMR contaminants; monitoring timeframe; sampling
locations; data elements (i.e., information required to be collected
along with the occurrence data); and conforming and editorial changes,
such as those necessary to remove requirements solely related to UCMR
5.
This proposed action, once finalized, will provide the EPA, states,
and communities with scientifically valid data on the national
occurrence of these contaminants in drinking water. The UCMR data are
the primary source of national occurrence data that the EPA uses to
inform other SDWA programs and risk management decisions for drinking
water contaminants. This proposal identifies four drinking water
analytical methods to be used by laboratories analyzing UCMR samples
for the unregulated contaminants. In addition, section III.E of this
document describes how the EPA evaluated other candidate contaminants.
This proposed rulemaking reflects the monitoring approach defined
in the AWIA amendments and describes the UCMR 6 scope as including all
systems serving 3,300 or more people, and a representative sample of
systems serving fewer than 3,300 people. SDWA section 1445(a)(2)(C)(ii)
requires the EPA to ``pay the reasonable cost of such testing and
laboratory analysis'' for all applicable PWSs serving 10,000 or fewer
people. Accordingly, the AWIA conditioned the monitoring scope on the
availability of appropriations and on the availability of adequate
laboratory capacity to analyze the samples.
Based on the EPA's experience implementing the AWIA scope in UCMR 5
and informed by ongoing engagement with the laboratory community, the
EPA anticipates that sufficient laboratory capacity will continue to
support the scope defined by the AWIA. Regarding the EPA's resources,
the agency plans on taking the same approach outlined in UCMR 5 that
enables the agency to adjust the number of small PWSs that serve 10,000
or fewer people to monitor based upon the appropriations received each
fiscal year. Regardless of whether the EPA is able to carry out the
monitoring outlined in the AWIA or reduces the scope of that monitoring
due to availability of appropriations, the small PWS data collection,
coupled with data collection from all large PWSs serving more than
10,000 people under this action, will provide scientifically valid data
on the national occurrence of 30 unregulated contaminants in drinking
water. See ``Selection of Nationally Representative Public Water
Systems for the Unregulated Contaminant Monitoring Rule: 2021 Update''
for further details about the nationally representative sample (USEPA,
2021a).

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II. Public Participation

A. Written Comments

Submit your comments, identified by Docket ID No. EPA-HQ-OW-2023-
0469, at https://www.regulations.gov, (our preferred method), or the
other methods identified in the ADDRESSES section of this document.
Once submitted, comments cannot be edited or removed from the docket.
The EPA may publish any comment received to its public docket. Do not
submit to the EPA's docket at https://www.regulations.gov any
information you consider to be Confidential Business Information (CBI),
Proprietary Business Information (PBI), or other information whose
disclosure is restricted by statute. Contact the EPA if you want to
submit CBI; see FOR FURTHER INFORMATION CONTACT section of this
document. Multimedia submissions (audio, video, etc.) must be
accompanied by a written comment. The written comment is considered the
official comment and should include discussion of all points you wish
to make. The EPA will 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. 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. Commenters should notify
the person identified in the FOR FURTHER INFORMATION CONTACT section of
this document when they pre-register to speak that they will need
specific equipment. If you require the services of an interpreter or
special accommodation such as audio description, please pre-register
for the webinar with the person identified in the FOR FURTHER
INFORMATION CONTACT section of this document and describe your needs by
July 30, 2026. The EPA may not be able to arrange accommodations
without advance notice.

III. General Background Information

A. How are the Contaminant Candidate List (CCL), the UCMR program, the
Regulatory Determination process, and the NCOD interrelated?

Under SDWA, Congress established a multistep, risk-based approach
for determining which contaminants would become subject to drinking
water standards. Under the first step, the EPA is required to publish a
CCL every five years that identifies contaminants that are not subject
to any proposed or promulgated drinking water standards, are known or
anticipated to occur in PWSs, and may require future action under SDWA.
Under the second step, the EPA must require, every five years,
monitoring of unregulated contaminants to determine the frequency 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/

[[Page 39956]]

nationalcontaminant-occurrence-database-ncod 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. 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. Thirty state representatives attended the meeting and
participated in the discussion (USEPA, 2026a).
The EPA hosted the tribal consultation from March 10 to June 20,
2024, with the meeting on May 20, 2024 (USEPA, 2026b), and the ANCSA
consultation from December 6, 2024, to February 10, 2025, with the
meeting on January 15, 2025 (USEPA, 2026c). More details on tribal and
ANCSA consultations can be found in section V.G of this document.

C. What notable changes are being proposed for UCMR 6?

This proposed action updates the existing UCMR (i.e., UCMR 5), by
revising: the list of contaminants for UCMR 6, the drinking water
analytical methods for these new contaminants, the data elements for
reporting, and the monitoring timeframe. A track-changes version of the
rule language, comparing UCMR 5 to the proposed changes for UCMR 6,
(``Proposed Revisions to 40 CFR parts 141.35 and 141.40'' (USEPA,
2026d)), is included in the EPA public docket for this proposed
rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469. The EPA's proposed
approach and rationale for changes are described in the following
sections.

Exhibit 1--Notable Changes Proposed for UCMR 6
--------------------------------------------------------------------------------------------------------------------------------------------------------
CFR rule section
----------------------------------------------------------------------- Current (UCMR 5) Description of change Corresponding preamble
No. Title/description requirement (UCMR 6) section
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sec. 141.40(a)(3)........................... Related specifications UCMR 5 specified 30 Proposes a new list of III.D, III.E.
for the analytes to contaminants for 30 contaminants for
be monitored. monitoring; identified monitoring;
associated drinking water identifies associated
analytical methods, drinking water
Minimum Reporting Levels analytical methods,
(MRLs), and sample MRLs, and sampling
locations. locations.
Sec. 141.40(a)(3)........................... Related specifications UCMR 5 specified the sample Proposes to revise the III.H.
for sampling collection dates from sample collection
timeframe. January 2023 through dates from January
December 2025. 2028 through December
2030 for UCMR 6.
Sec. 141.40(a), Sec. 141.35(c)(4)......... Applicability dates... UCMR 5 specified February Proposes to revise the III.F.
1, 2021, as the date for dates to February 1,
determining which PWSs 2026, and April 26,
were subject to 2027, for UCMR 6.
monitoring, and April 26,
2022, as the date large
PWSs must contact the EPA
or state if they have not
been notified of the
requirements.
Sec. 141.35(c)(1), Sec. 141.35(c)(2), Sec. Reporting and sampling UCMR 5 specified December Proposes to revise the III.G.
141.35(c)(5)(i), Sec. 141.35(d)(2) and requirements. 31, 2022, as the final date to December 31,
Sec. 141.40(a)(4)(i). date for PWSs to report 2027, for UCMR 6.
contact and zip code
information, sampling
location inventory
information, and
scheduling and
rescheduling notification
requirements.
Sec. 141.35(e).............................. Reporting UCMR 5 specified data Proposes changes to III.J.
requirements--Data elements applicable to the the data elements to
elements. contaminants included in be reported to the
that cycle. EPA based on the
contaminants proposed
for monitoring.

[[Page 39957]]

Sec. 141.40(a)(5)(ii)....................... Laboratory approval UCMR 5 specified that Proposes to revise the III.L.
application timeframe. registration and date to August 1,
application materials are 2027, for UCMR 6.
to be submitted to the EPA
by August 1, 2022.
--------------------------------------------------------------------------------------------------------------------------------------------------------

D. How did the EPA identify the contaminants being proposed for UCMR 6?

In establishing the proposed list of contaminants for UCMR 6, the
EPA evaluated unregulated contaminants consistent with the statutory
authorities described in section I.A of this document. The UCMR is one
of the first steps in the SDWA regulatory process and is used to inform
the criteria outlined in SDWA 1412(b) for EPA's regulatory
determinations (see section III.A). Consistent with SDWA section
1445(a)(2) as amended by the AWIA, and the process described in this
document, the EPA is proposing monitoring for the unregulated
contaminants listed in Exhibit 2.

Exhibit 2--Proposed UCMR 6 Contaminants
------------------------------------------------------------------------

------------------------------------------------------------------------
Seven Purgeable Organic Compounds using EPA Method 524.3 Enhanced
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) Perfluoropropanoic acid
\5\. (PFPrA).\5\
Perfluoroethanesulfonic acid (PFEtS) Perfluoro-2-methoxyacetic acid
\5\. (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. Further, the EPA considered the opportunity to collect
occurrence data for contaminants within the scope of the drinking water
analytical methods that already contained a CCL contaminant based on
available health and occurrence information to create a more cost-
effective design (i.e., maximize the number of contaminants in each
drinking water analytical method, to reduce overall cost and burden).
Consistent with the ``U.S. Environmental Protection Agency
Implementation of Gold Standard Science'' (USEPA, 2025a) based on
Executive Order 14303 ``Restoring Gold Standard Science,'' (White
House, 2025), the EPA evaluated candidate UCMR 6 contaminants using a
prioritization process that deprioritized

[[Page 39958]]

contaminants that were previously monitored under a prior UCMR cycle
(unless there was a compelling case to monitor for them again) as well
as contaminants not expected to have a completed, validated drinking
water method in time for rule proposal. The potential contaminants for
the monitoring program were then further evaluated based on health
effects information, if available, to inform public health concern, and
the occurrence information, if available, to inform the likelihood the
contaminant will be found in finished drinking water.
---------------------------------------------------------------------------

\2\ For CCL 5 (USEPA, 2022), the structural definition of PFAS
included 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.
---------------------------------------------------------------------------

While TFMS, TFSI, and TFA are not defined as PFAS under the CCL 5
structural definition, these ultrashort organofluorine compounds are
persistent in the environment, highly mobile, used widely in industry,
and have health effects information (USEPA, 2026g). Due to the
similarities in chemical structure to the CCL 5 defined PFAS, TFMS,
TFSI, and TFA can also be analyzed by EPA Method 563. This allows the
EPA to better understand the frequency and occurrence of this suite of
contaminants without increased costs, and can inform and prioritize
future resource-intensive research. During early stakeholder
engagement, the public provided both written comments and discussions
in support of monitoring for these contaminants in public drinking
water (see section III.B).
Additionally, as a part of the process to identify contaminants for
the monitoring program, the agency identified an alternate contaminant
in the event that one is needed. The agency identified MGK 264 as the
alternate contaminant. MGK 264 is an ingredient used in common
insecticides to enhance the potency of pyrethroid ingredients. This
contaminant has not been monitored under a previous UCMR cycle, is in a
method already proposed for UCMR 6, and has an available 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 [micro]g/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 [micro]g/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 [micro]g/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). However, chlorpyrifos metabolizes into chlorpyrifos
oxon during the chlorination of drinking water, which is a treatment
commonly used in PWSs (USEPA, 2005). As a result, the metabolite has a
higher likelihood of being found in finished drinking water, and
occurrence data is critical to characterizing exposure and a potential
meaningful opportunity for health risk reduction. Therefore, the EPA
proposes to monitor for chlorpyrifos oxon in UCMR 6. Additionally, EPA
Method 540 is being considered for UCMR 6 because it includes the
pesticide metabolites, phorate sulfone and phorate sulfoxide, which are
both tied to the CCL 5 contaminant phorate in EPA Method 525.3.

[[Page 39959]]

E. What other contaminants did the EPA consider for UCMR 6?

This notice describes the 30 contaminants that the agency has
identified as the highest priorities for UCMR 6 monitoring through the
process described in the preceding section of this document. This
process prioritizes the unregulated contaminants, for which nationally
representative data on the frequency and level of occurrence is
critical to characterizing exposure and assessing 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. 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.
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.
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. These actions support the agency's
approach to prioritize specific pharmaceuticals and develop drinking
water analytical methods to support monitoring in a future UCMR.

F. What is the proposed UCMR 6 applicability date?

In CFR 141.40(a), the EPA proposes February 1, 2026, as the date to
determine which PWSs are subject to UCMR 6. That is, the determination
of whether a PWS is required to monitor under UCMR 6 is based on the
type of system (e.g., CWS, NTNCWS) and its

[[Page 39960]]

retail population served, as indicated by the Safe Drinking Water
Information System Federal Reporting Services (SDWIS/Fed) inventory on
February 1, 2026. If a PWS believes its retail population served in
SDWIS/Fed is inaccurate, the system should contact their state
authority to verify its population as of the specified date and request
a correction, if necessary. This applicability date is exactly five
years from the last date published in UCMR 5 (86 FR 73131, December 27,
2021 (USEPA, 2021d)), based on the 5-year cycle of the UCMR program.
In CFR 141.35(c)(4), the EPA proposes April 26, 2027, as the date
large PWSs must contact the EPA or state if the PWS believes they are
subject to UCMR 6 and they have not been contacted by the EPA or the
state. This date is also exactly five years from the last date
published in UCMR 5 (86 FR 73131, December 27, 2021 (USEPA, 2021d)),
based on the 5-year cycle of the UCMR program.

G. What is the proposed UCMR 6 pre-monitoring reporting date?

In five different CFR sections, 141.35 (c)(1), 141.35 (c)(2),
141.35 (c)(5)(i), 141.35 (d)(2) and 141.40 (a)(4)(i), the EPA proposes
December 31, 2027, as the reporting and sampling requirements date, by
which PWSs are required to report contact information, zip code
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.
[GRAPHIC] [TIFF OMITTED] TP01JY26.017

[[Page 39961]]

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. 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.

Exhibit 4--PWSs Expected to Participate in UCMR 6 Monitoring
------------------------------------------------------------------------
Estimated number of
PWS size (number of people Assessment PWSs per size
served) monitoring design category
------------------------------------------------------------------------
Small PWSs \1\ (fewer than 800 randomly 800
3,300). selected CWSs and
NTNCWSs.
Small PWSs \2\ (3,300-10,000).. All CWSs and 5,155
NTNCWSs.
Large PWS \3\ (More than All CWSs and 4,599
10,000). NTNCWSs.
--------------------
Total \4\.................. .................. 10,554
------------------------------------------------------------------------
\1\ The EPA is responsible for all analytical costs associated with
monitoring at small PWSs. If the EPA concludes that it will not have
the resources necessary to support the full AWIA monitoring, the
agency plans to adjust the number of small PWSs that are required to
monitor based upon the available appropriations.
\2\ Small PWS counts are from SDWIS/Fed in January 2025. The EPA is
responsible for all analytical costs associated with monitoring at
small PWSs. If the EPA concludes that it will not have the resources
necessary to support the full AWIA monitoring, the agency plans to
adjust the number of small PWSs required to monitor based upon the
available appropriations.
\3\ All Large PWS are required to monitor; the counts are from SDWIS/Fed
in January 2025.
\4\ The ``Statistical Design and Sample Selection for the Unregulated
Contaminant Monitoring Regulation'' (USEPA, 2001) shows that a
response rate of 82.375% will meet the data quality objectives (DQOs)
for UCMR. The UCMR program has had a high response for the past five
cycles, ranging from 99.8 percent to 100 percent respectively for both
small and large PWSs. If the UCMR program ever experiences a low
response rate, a plan will be considered.

1. Sampling, Frequency, and Timing
The anticipated number of samples collected by each PWS is
consistent with prior UCMR cycles. PWSs would be required to collect
samples based on the published UCMR sampling frequency and timeframe as
follows: for ground water locations, sampling would take place twice
over the course of a single 12-month period (total of two sampling
events). Sampling events would occur five to seven months apart. For
example, if the first sample is taken in April, the second sample would
then occur anytime in September, October, or November. For surface
water, ground water under the direct influence of surface water, and
mixed locations, sampling would take place for four consecutive
quarters over the course of a single 12-month period (total of four
sampling events). Sampling events would occur three months apart. For
example, if the first sample is taken in January, the second would then
occur anytime in April, the third would occur anytime in July, and the
fourth would occur anytime in October. The monitoring frequency is
designed to be spatially and temporally representative of occurrence.
The design ensures that the sample results can be analyzed for
temporal, seasonal, 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.

[[Page 39962]]

GWRMPs approved under prior UCMRs may be used for UCMR 6, presuming no
significant changes in the configuration of the ground water EPTDSs
since the prior approval. PWSs that intend to use previously approved
plans must send the EPA a copy of the approval documents notifying the
EPA that they intend on using the approved plan at least six months
prior to their scheduled sample collection dates. Large ground water
PWSs (and large surface water PWSs with ground water sources) that do
not have an approved GWRMP may submit proposals at least six months
prior to their scheduled sample collection dates. As for past UCMRs,
details are described in CFR section 141.35(c)(3) and are available in
the document, ``Instructions for Preparing a Ground Water
Representative Monitoring Plan for the Unregulated Contaminant
Monitoring Rule,'' (USEPA, 2021e) found in the EPA public docket for
this proposed rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469.
Changes to inventory data in the Safe Drinking Water Accession and
Review System (SDWARS) that impact a PWS's representative plan before
or during the UCMR sampling period must be reported to the EPA within
30 days of the change (e.g., the representative sampling location
closes, and a new representative sampling location needs to be
selected).
The second way for PWSs to reduce their number of EPTDSs that they
must sample is for PWSs that purchase water with multiple connections
from the same wholesaler, to select one representative connection from
that wholesaler. As described in CFR section 141.40(a)(3) this
representative EPTDS must be a location within the purchaser's water
system, after treatment is applied, and represent each non-emergency
water source in routine use over the 12-month period of monitoring. The
EPTDS sampling location must be representative of the highest annual
volume of connections or if the 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. 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. The EPA will also include sample collection
procedures that are specific to the methods in the ``UCMR 6 Laboratory
Approval Manual,'' and will address this point in the agency's outreach
to the PWSs that will be collecting samples.
The structure of the anticipated UCMR 6 laboratory approval program
is similar to that employed in the previous UCMRs and would provide an
assessment of the ability of laboratories to perform analyses using the
methods listed in CFR section 141.40(a)(3), Table 1. PWSs are required
to exclusively use laboratories that have been approved under the
program. The EPA expects to post a list of approved UCMR 6 laboratories
to https://www.epa.gov/dwucmr and will bring this to the attention of
the PWSs in the agency's outreach.
1. What are UCMR MRLs and how were they determined?
The EPA establishes MRLs for contaminants under the UCMR to ensure
consistency in the quality of the information reported to the agency.
As defined in CFR section 141.40(a)(5)(iii), the MRL is the minimum
quantitation level that, with 95 percent confidence, can be achieved by
capable analysts at 75 percent or more of the laboratories using a
specified drinking water analytical method. 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)

[[Page 39963]]

studies. The results from these laboratory LCMRL studies can be found
in the ``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 [email protected] 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. Application Package
Laboratory applicants complete and return a customized application
package that includes the following: IDC data, including precision,
accuracy and results of MRL studies; information regarding analytical
equipment and other materials; proof of current drinking water
laboratory certification (for select compliance monitoring methods);
method specific SOPs; and example chromatograms for each method under
review.
5. The EPA's Review of Application Package
The EPA will review the application packages and, if necessary,
request follow-up information. Laboratories that successfully complete
the application process become eligible to participate in the UCMR 6 PT
program. Based on a January 1, 2028, anticipated start date for UCMR 6
sample collection, the EPA anticipates that the final opportunity for a
laboratory to complete and submit the necessary registration and
application information will be August 1, 2027.
6. Proficiency Testing
A PT sample is a synthetic sample containing a concentration of an
analyte or mixture of analytes that is known to the EPA, but unknown to
the laboratory. To be approved, a laboratory is expected to meet
specific acceptance criteria for the analysis of a UCMR 6 PT sample(s)
for each analyte in each method, for which the laboratory is seeking
approval. The EPA anticipates offering up to three of these studies
prior to the publication of the final rule, and at least two studies
after publication of the final rule. This allows laboratories to
complete their portion of the laboratory approval process prior to
publication of the final rule and receive their approval immediately
following the publication of the final rule. Laboratories must pass a
PT for every analyte in the method to be approved for that method and
may participate in multiple PT studies in order to produce passing
results for each analyte. The EPA does not expect to conduct additional
PT studies after the start of PWS monitoring; however, laboratory
audits will likely be ongoing throughout the implementation of UCMR 6.
Initial laboratory approval is expected to be contingent on successful
completion of PT studies, which includes properly uploading the PT
results to SDWARS. Continued laboratory approval is contingent on
successful completion of the audit process and satisfactorily meeting
all the other stated conditions.
7. Written EPA Approval
After a laboratory successfully completes steps 1 through 6, the
EPA expects to send the laboratory a notification letter listing the
methods for which approval is either ``pending'' (i.e., 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. 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

[[Page 39964]]

more time to receive approval from the EPA prior to the start of
monitoring to ensure laboratory capacity. Lastly, the EPA initially
schedules PWS monitoring equally over the 3-year monitoring period
(2028-2030) to reduce capacity burden on participating laboratories.
The EPA welcomes comments regarding laboratory capacity to support the
proposed UCMR 6 contaminants, sampling design, and other relevant
aspects of the rule.

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. 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. These costs were calculated by summing the
laboratory unit cost of each method, along with the analysis of the
quality control samples, and shipping the kits. Exhibit 1 presents a
breakdown of the total annualized national costs in 2025 dollars. The
EPA invites comment on the proposed UCMR 6 costs identified in Exhibit
5 and throughout this proposal.
The EPA is responsible for the analytical costs for all PWSs
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. The EPA estimated
laboratory unit costs are based on consultations with multiple
commercial drinking water testing laboratories.
State participation in the UCMR program is voluntary; thus, the
level of effort is expected to vary among states and would depend on
their individual agreements with the EPA. The agency expects that
states that choose to participate may incur modest labor costs
associated with voluntary assistance with the implementation of UCMR 6.
The EPA estimated state costs using the relevant assumptions from 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]
------------------------------------------------------------------------
Costs (7%)
Respondent Costs (3%) \1\
------------------------------------------------------------------------
Small PWSs (10,000 or fewer people), including $0.4 $0.4
labor \2\ only (non-labor costs \3\ paid for
by the EPA)..................................
Large PWSs (10,001 or more), including labor $16.7 $16.7
and non-labor costs..........................
States, including labor costs related to $0.5 $0.5
implementation coordination..................
EPA, including labor for implementation and $16.1 $16.1
non-labor for small PWS testing..............
-------------------------
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). 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

[[Page 39965]]

10,000 people--required to monitor would remain the same, as specified
in SDWA.
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. 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 $0.1 $0.1
labor \1\ only (non-labor costs \2\ paid for
by the EPA)..................................
Large PWSs (10,001 or more), including labor 16.7 16.7
and non-labor costs..........................
States, including labor costs related to 0.5 0.5
implementation coordination..................
EPA, including labor for implementation and 4.9 4.9
non-labor for small system testing...........
-------------------------
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. 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. Moreover, formula-fed
infants drink a large amount of water compared to their body weight.
Thus, while children's exposure to contaminants in drinking water may
present a disproportionate health risk (USEPA, 2013b), the objective of
UCMR 6 is to collect nationally representative drinking water
occurrence data on unregulated contaminants. The detailed information
on the 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 select
the proposed analyte list, is contained in ``Information Compendium for
Candidate Contaminants for the Proposed Sixth Unregulated Contaminant
Monitoring Rule (UCMR 6)'' (USEPA, 2026g).
Executive Order 13045 also does not apply to UCMR 6 because the
environmental health or safety risks addressed by this action do not
present a disproportionate risk to children (See V.H. Executive Order
13045 of this document). However, the EPA's Policy on Evaluating Health
Risks to Children, which ensures that the health of infants and
children is explicitly considered in the agency's decision making, is
applicable, see: https://www.epa.gov/children/epas-policy-evaluating-
risk-children.
Using quantitation data from multiple laboratories, the EPA
establishes statistically based UCMR reporting levels that are
projected to be feasible for the national network of approved drinking
water laboratories to quantify accurately. The EPA sets the reporting
levels as low as is practical, even if that level is well below
concentrations that are currently associated with known or suspected
health effects. In doing so, the EPA positions itself to better address
contaminant risk information in the future, including that associated
with unique risks to children. The EPA

[[Page 39966]]

requests comments regarding any further steps that may be taken to
evaluate and address health risks to children that fall within the
scope of UCMR 6.

C. What documents are being incorporated by reference?

The following methods are being incorporated by reference into this
section of the document for the UCMR 6 monitoring. All method material
is available for inspection electronically at http://
www.regulations.gov in the EPA public docket for this proposed
rulemaking, under Docket ID No. EPA-HQ-OW-2023-0469, or from the
sources listed for each method. The EPA has worked to make these
methods and documents reasonably available to interested parties. The
methods that may be used to support monitoring under this rule are as
follows:
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).
(iv) EPA 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.
This is an EPA method for the analysis of selected organic chemicals in
drinking water using SPE and LC/MS/MS and is proposed to measure three
pesticide metabolites during UCMR 6 (Chlorpyrifos oxon, Phorate
sulfone, and Phorate sulfoxide).
(v) EPA 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-
002. Available at https://www.epa.gov/dwanalyticalmethods. This is an
EPA method for the analysis of ultrashort organofluorine compounds in
drinking water using LC/MS/MS and is proposed to measure seven
ultrashort organofluorine compounds during UCMR 6 (PFPrS, PFPrA, PFEtS,
PFMOAA, TFMS, TFSI, and TFA).

V. Statutory and Executive Orders Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

This action is a significant 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). The information collected will inform
other SDWA programs and risk management decisions for drinking water
contaminants. Reporting is mandatory. The data are not subject to
confidentiality protection.
The 5-year UCMR 6 period spans 2027-2031. As proposed, UCMR 6
sample collection begins in 2028 and continues through 2030. Since ICRs
cannot be approved by OMB for a period longer than three years pursuant
to 5 CFR 1320.10, the primary analysis in the ICR only covers the first
three years of the UCMR period (2027-2029). Prior to expiration of the
UCMR 6 ICR, the EPA will seek to extend the ICR and thus receive
approval to collect information under the PRA in the remaining two
years of the UCMR 6 period (2030-2031).
The EPA has reviewed and, as appropriate, revised the cost and
burden figures from UCMR 5 for UCMR 6. This includes using updated unit
cost estimates for sample analysis. The annual burden and cost
estimates described in this section are based on the implementation
assumptions described in section III.O.1 of this document, among them
the inclusion of all PWSs serving 3,300 to 10,000 people and a
representative sample of PWSs serving fewer than 3,300 people. If the
EPA does not receive the necessary appropriations in one or more of the

[[Page 39967]]

collection years--and thus collects data from fewer small PWSs--the
actual costs would be lower than those estimated here (USEPA, 2026l).
Respondents/affected entities: The respondents/affected entities
are small PWSs (those serving 10,000 or fewer people); large PWSs
(those serving more than 10,000 people); and primacy agencies (states,
tribes, and territories).
Respondent's obligation to respond: Mandatory (40 CFR 141.35).
Estimated number of respondents: Respondents to UCMR 6, as
proposed, include approximately 6,000 small PWSs, approximately 4,600
large PWSs, and the 55 primacy agencies (49 states, one tribal nation,
and five territories). There are approximately 10,600 respondents to
UCMR 6 during the 5-year program period.
Frequency of response: The frequency of response varies across
respondents and years. Across the initial 3-year ICR period for UCMR 6,
small PWSs would sample an average of 2.8 times per PWS (i.e., number
of responses per PWS); large PWSs would sample and report and average
of 3.2 times per PWS; and very large PWSs would sample and report an
average of 3.7 times per PWS.
Total estimated burden: 41,291 hours (per year). Burden is defined
at 5 CFR 1320.3(b).
Total estimated cost: $19,670,760, includes $17,451,527 annualized
capital or operation & maintenance costs.
An agency may not conduct or sponsor, and a person is not required
to respond to, a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for the
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
Submit your comments on the agency's need for this information, 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). Details of this analysis are 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 rule, under
Docket ID No. EPA-HQ-OW-2023-0469.
The EPA anticipates drawing on the set aside of $12.0 million each
year from the Drinking Water State Revolving Fund (DWSRF) consistent
with SDWA section 1445(j) and 1452(o) to use DWSRF monies for the
purposes of implementing the monitoring program for unregulated
contaminants. Thus, the costs to these small PWSs will be modest and
limited to the labor associated with collecting a sample and preparing
it for shipping. The estimated average annual burden across the 5-year
UCMR 6 implementation period is 1.4 hours at $69 per small PWS or
approximately $0.4 million in 2025 dollars across all 5,955 small PWSs.
We have therefore concluded that this action will not have a
significant economic impact on a substantial number of small entities
under the RFA.

E. Unfunded Mandates Reform Act (UMRA)

This action does not contain an unfunded mandate as described in
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely 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. 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

[[Page 39968]]

(associated with shipping and laboratory fees) are paid by the EPA.
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. 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. While the EPA identified multiple potential voluntary
consensus standard body (VCSB) methods from ASTM International (ASTM)
and Standard Methods for the Examination of Water as being potentially
applicable, the agency does not propose to use them. The use of these
VCSB would be impractical because of cost and logistics. Additionally,
multiple VCSB methods would need to be used for the analytes included
in one EPA method and this increases the overall cost of the analysis.
The additional methods would also increase the number of bottles, the
weight of the shipping boxes, and the number of boxes that need to be
shipped. All of the EPA methods are free for download on the agency's
website, and both the ASTM and Standard Methods for the Examination of
Water require payment for access to the methods. The EPA welcomes
comments on this aspect of the proposed action and specifically invites
the public to identify potentially applicable VCSB methods and explain
why such standards should be used in this rule.

VI. References

ASDWA. 2020. 2019 Analysis of State Drinking Water Programs'
Resources and Needs: Addressing Emerging Issues and State
Specificity in Program Implementation. July 2020. Available at
https://www.asdwa.org/wp-content/uploads/2020/07/2019-Analysis-of-
State-Drinking-Water-Programs-Resources-and-Needs.pdf.
ASTM. 2020a. ASTM D8332-20_ Standard Practice for Collection of
Water Samples with High, Medium, or Low Suspended Solids for
Identification and Quantification of Microplastic Particles and
Fibers. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Approved August 14, 2020. Available for purchase at astm.org.
ASTM. 2020b. ASTM D8333-20_ Standard Practice for Preparation of
Water Samples with High, Medium, or Low Suspended Solids for
Identification and Quantification of Microplastic Particles and
Fibers Using Raman Spectroscopy, IR Spectroscopy, or Pyrolysis-GC/
MS. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Approved August 14, 2020. Available for purchase at astm.org.
Governors of New Jersey, Delaware, Illinois, Maryland, Michigan,
Wisconsin, and Connecticut. 2025. Re: Request of the Governors of
New Jersey, Delaware, Illinois, Maryland, Michigan, Wisconsin, and
Connecticut under 42 U.S.C. 300j-4(a)(2)(B)(ii) that EPA Include
Microplastics in the Forthcoming Unregulated Contaminant Monitoring
Rule 6 List. Submitted to the U.S. Environmental Protection Agency.
November 26, 2025.
USEPA. 1998a. National Primary Drinking Water Regulations: Consumer
Confidence Reports. Federal Register. Vol. 63, No. 30, p. 7607.
February 12, 1998.
USEPA. 1998b. National Primary Drinking Water Regulations: Consumer
Confidence Reports. Federal Register. Vol. 63, No. 160, p. 44512.
August 19, 1998.
USEPA. 2001. Statistical Design and Sample Selection for the
Unregulated Contaminant Monitoring Regulation (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.

[[Page 39969]]

Vol. 81, No. 222, p. 81099. November 17, 2016.
USEPA. 2016b. Revisions to the Unregulated Contaminant Monitoring
Rule (UCMR 4) for Public Water Systems and Announcement of Public
Meeting. Federal Register. Vol. 81, No. 244, p. 92666. December 20,
2016.
USEPA. 2019. EPA's Per- and Polyfluoroalkyl Substances (PFAS) Action
Plan. EPA 823R180004. Office of Water. February 2019. Available at
https://www.epa.gov/sites/default/files/2019-02/documents/
pfas_action_plan_021319_508compliant_1.pdf.
USEPA. 2020. Chlorpyrifos: Third Revised Human Health Risk
Assessment for Registration Review. September 21, 2020, memo. Office
of Chemical Safety and Pollution Prevention. Available on the
internet at: https://www.regulations.gov/document/EPA-HQ-OPP-2008-
0850-0944.
USEPA. 2021a. Selection of Nationally Representative Public Water
Systems for the Unregulated Contaminant Monitoring Rule: 2021
Update. EPA 815-B-21-012. Office of Water. December 2021.
USEPA. 2021b. Announcement of Final Regulatory Determinations for
Contaminants on the Fourth Drinking Water Contaminant Candidate
List. Federal Register. Vol. 86, No. 40, p. 12272. March 3, 2021.
USEPA. 2021c. MGK-264: Revised Human Health Risk Assessment in
Support of Registration Review. DP No. D460729. Office of Chemical
Safety and Pollution Prevention. 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. Summary of Tribal Consultation and Coordination on the
Development of the Sixth Proposed Unregulated Contaminant Monitoring
Rule (UCMR 6) for Public Water Systems. EPA-815-S-26-005. Office of
Water. February 2026.
USEPA. 2026d. Proposed Revisions to CFR parts 141.35 and 141.40. EPA
815-Z-26-001. Office of Water. February 2026.
USEPA. 2026e. Recommended Parameters to Enhance Sensitivity for the
Analysis of Select Purgeable Organic Compounds using EPA Method
524.3 (EPA 815-B-56-002) in Selected Ion Monitoring (SIM) Mode. EPA-
815-B-26-002. Office of Water. February 2026.
USEPA. 2026f. Method 563: Determination of Selected Ultrashort
Organofluorine Compounds in Drinking Water by Liquid Chromatography/
Tandem Mass Spectrometry. EPA 815-F-26-002. Office of Water. January
2026.
USEPA. 2026g. Information Compendium for Candidate Contaminants for
the Proposed Sixth Unregulated Contaminant Monitoring Rule (UCMR 6).
EPA 815-R-26-009. Office of Water. February 2026.
USEPA. 2026h. Drinking Water Contaminant Candidate List 6-Draft.
Federal Register. Vol. 91, No. 65, p. 17186. April 6, 2026.
USEPA. 2026i. Human Health Benchmarks for Pharmaceuticals (HHB-Rx)
in Drinking Water. Updated April 2, 2026. Available at https://
www.epa.gov/sdwa/2026-human-health-benchmarks-pharmaceuticals-hhb-
rx.
USEPA. 2026j. UCMR 6 Laboratory Approval Manual. EPA 815-B-26-001.
Office of Water. February 2026.
USEPA. 2026k. Draft Economic Analysis of the Sixth Unregulated
Contaminant Monitoring Rule. EPA 815-R-26-007. Office of Water.
February 2026.
USEPA. 2026l. Information Collection Request for the Final
Unregulated Contaminant Monitoring Rule (UCMR 6). EPA 815-D-26-001.
Office of Water. February 2026.
United States Geological Survey (USGS). 2019. Estimated Annual
Agricultural Pesticide Use: Pesticide Use Maps--Chlorpyrifos. United
States Geological Survey (UGSS). Updated February 26, 2024.
Available at https://water.usgs.gov/nawqa/pnsp/usage/maps/
show_map.php?year=2019&map=CHLORPYRIFOS&hilo=L&disp=Chlorpyrifos.
White House. 2025. Restoring Gold Standard Science. May 2025.
Available at https://www.whitehouse.gov/presidential-actions/2025/
05/restoring-gold-standard-science/.

[Revisions to the Unregulated Contaminant Monitoring Rule (UCMR 6) for
Public Water Systems Page XX of XXX]

List of Subjects in 40 CFR Part 141

Environmental protection, Chemicals, Incorporation by reference,
Indian-lands, Intergovernmental relations, Reporting and recordkeeping
requirements, Water supply.

Lee Zeldin,
Administrator.

For the reasons set forth in the preamble, EPA proposes to amend 40
CFR part 141 as follows:

PART 141--NATIONAL PRIMARY DRINKING WATER REGULATIONS

0
1. The authority citation for Part 141 continues to read as follows:

Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-
5, 300g-6, 300j-4, 300j-9, and 300j-11.

Subpart D--Reporting and Recordkeeping

0
2. Amend Sec. 141.35 as follows:
0
a. In paragraph (c)(1), remove the text ``December 31, 2022'' and add,
in its place, the text ``December 31, 2027'';
0
b. In paragraph (c)(2), remove the text ``December 31, 2022'' and add,
in its place, the text ``December 31, 2027'';
0
c. In paragraph (c)(4), remove the text ``April 26, 2022'' and add, in
its place, the text ``April 26, 2027'';
0
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'';
0
e. In paragraph (d)(2), remove the text ``December 31, 2022'' and add,
in its place, the text ``December 31, 2027'';
0
f. Revise paragraph (e).
The revisions read as follows:

Sec. 141.35 Reporting for unregulated contaminant monitoring results.

(e) Data elements. Table 1 defines the data elements that must be
provided for UCMR monitoring.

[[Page 39970]]

Table 1--Unregulated Contaminant Monitoring Reporting Requirements
------------------------------------------------------------------------
Data element Definition
------------------------------------------------------------------------
1. Public Water System The unique code used to identify
Identification Code (PWSID). 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 Assigned by the primacy agency.
Name).
3. Public Water System Facility An identification code used to
Identification Code (PWS Facility identify each unique applicable
ID). 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 Descriptive Facility Name, assigned
Name (PWS Facility Name). once by the PWS, for every PWS
Facility ID (e.g., Maple St.
Treatment Plant).
5. Public Water System Facility That code that identifies that type
Type (PWS Facility Type). of facility as outlined in SDWIS/
Fed as either:
CC = Consecutive connection.
SS = Sampling station.
TP = Treatment plant.
OT = Other (e.g., other facility
types listed in SDWIS/Fed).
6. Water Source Type.............. The type of source water that
supplies a water system facility.
Systems must report one of the
following codes for each sampling
location:
SW = Surface water (to be
reported for water facilities
that are served entirely by a
surface water source during the
12-month period).
GU = Ground water under the
direct influence of surface
water (to be reported for water
facilities that are served all
or in part by ground water under
the direct influence of surface
water at any time during the 12-
month sampling period), and are
not served at all by surface
water during this period.
MX = Mixed water (to be reported
for water facilities that are
served by a mix of surface
water, ground water, and/or
ground water under the direct
influence of surface water
during the 12-month period).
GW = Ground water (to be reported
for water facilities that are
served entirely by a ground
water source during the 12-month
period).
7. Sampling Point Identification An identification code used to
Code (Sample Point ID). 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. 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.

[[Page 39971]]

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. Maximum Daily Flow or Peak Estimate the maximum daily flow at
Daily Flow. this entry point to the
distribution system (e.g., also
called maximum daily production or
peak daily flow, the highest flow
over one day measured within one
year). [Numerical input] Units:
Million gallons per day or
thousands of gallons per day.
15. Treatment Process Design If a treatment process supplies this
Capacity. entry point to the distribution
system, please provide the design
capacity (e.g., also called design
flow or maximum daily treatment
capacity, the maximum amount of
water per day that can be treated
at the treatment plant). [Numerical
input] Units: Million gallons per
day or thousands of gallons per
day.
16. Sample Collection Date........ The date the sample is collected,
reported as 4-digit year, 2-digit
month, and 2-digit day (YYYYMMDD).
17. Sample Identification Code.... An alphanumeric value up to 30
characters assigned by the
laboratory to uniquely identify
containers, or groups of
containers, containing water
samples collected at the same
sampling location for the same
sampling date.
18. Contaminant................... The contaminant for which the sample
is being analyzed.
19. Analytical Method Code........ The identification code of the
drinking water analytical method
used.
20. Extraction Batch Laboratory assigned extraction batch
Identification Code. ID. Must be unique for each
extraction batch within the
laboratory for each method. For CCC
samples report the Analysis Batch
Identification Code as the value
for this field. For methods without
an extraction batch, leave this
field null.
21. Extraction Date............... Date for the start of the extraction
batch (YYYYMMDD). For methods
without an extraction batch, leave
this field null.
22. Analysis Batch Identification Laboratory assigned analysis batch
Code. ID. Must be unique for each
analysis batch within the
laboratory for each method.
23. Analysis Date................. Date for the start of the analysis
batch (YYYYMMDD).
24. Sample Analysis Type.......... The type of sample collected and/or
prepared, as well as the
fortification level. Permitted
values include:
CCCL = MRL level continuing
calibration check; a calibration
standard containing the
contaminant, the internal
standard, and surrogate analyzed
to verify the existing
calibration for those
contaminants.
CCCM = Medium level continuing
calibration check; a calibration
standard containing the
contaminant, the internal
standard, and surrogate analyzed
to verify the existing
calibration for those
contaminants.
CCCH = High level continuing
calibration check; a calibration
standard containing the
contaminant, the internal
standard, and surrogate analyzed
to verify the existing
calibration for those
contaminants.
FS = Field sample; sample
collected and submitted for
analysis under this final rule.
LFB = Laboratory fortified blank;
an aliquot of reagent water
fortified with known quantities
of the contaminants and all
preservation compounds.
LRB = Laboratory reagent blank;
an aliquot of reagent water
treated exactly as a field
sample, including the addition
of preservatives, internal
standards, and surrogates to
determine if interferences are
present in the laboratory,
reagents, or other equipment.
LFSM = Laboratory fortified
sample matrix; a UCMR field
sample with a known amount of
the contaminant of interest and
all preservation compounds
added.
LFSMD = Laboratory fortified
sample matrix duplicate;
duplicate of the laboratory
fortified sample matrix.
QCS = Quality control sample; a
sample prepared with a source
external to the one used for
initial calibration and CCC. The
QCS is used to check calibration
standard integrity.
FRB = Field reagent blank; an
aliquot of reagent water treated
as a sample including exposure
to sampling conditions to
determine if interferences or
contamination are present from
sample collection through
analysis.
25. Analytical Result--Sign....... A value indicating whether the
sample analysis result was: (<)
``less than'' means the contaminant
was not detected, or was detected
at a level below the Minimum
Reporting Level. (=) ``equal to''
means the contaminant was detected
at the level reported in
``Analytical Result--Measured
Value.''
26. Analytical Result--Measured The actual numeric value of the
Value. analytical results for: Field
samples; laboratory fortified
matrix samples; laboratory
fortified sample matrix duplicates;
and concentration fortified.
27. Additional Value.............. 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

0
3. Amend Sec. 141.40 as follows:
0
a. In paragraph (a) introductory text, remove the text ``February 1,
2021'' and add, in its place, the text ``February 1, 2026'';
0
b. Revise paragraphs (a)(3);
0
c. In paragraph (a)(4)(i), remove the text ``December 31, 2022'' and
add, in its place, the text ``December 31, 2027'';
0
d. In paragraph (a)(5)(ii), remove the text ``August 1, 2022'' and add,
in its place, the text ``August 1, 2027'';
0
e. Revise paragraph (c).
The revisions read as follows:

Sec. 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):

[[Page 39972]]

Table 1 to Paragraph (a)(3)--UCMR Contaminat List
--------------------------------------------------------------------------------------------------------------------------------------------------------
6--Period during
4--Minimum 5--Sampling which sample
1--Contaminant 2--CASRN 3--Analytical methods reporting level location 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 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
1,1,1,2-Tetrachloroethane....... 630-20-6 EPA 524.3 Enhanced Sensitivity.............. 0.004 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
1,2,3-Trichloropropane (1,2,3- 96-18-4 EPA 524.3 Enhanced Sensitivity.............. 0.009 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
TCP).
1,2,4-Trimethylbenzene.......... 95-63-6 EPA 524.3 Enhanced Sensitivity.............. 0.004 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
Hexachlorobutadiene............. 87-68-3 EPA 524.3 Enhanced Sensitivity.............. 0.005 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
Naphthalene..................... 91-20-3 EPA 524.3 Enhanced Sensitivity.............. 0.008 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
Total 1,3-Dichloropropene (cis- 542-75-6 EPA 524.3 Enhanced Sensitivity.............. 0.007 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
& trans-).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Semivolatile Organic Compounds
--------------------------------------------------------------------------------------------------------------------------------------------------------
2,4-Dinitrotoluene.............. 121-14-2 EPA 525.3................................... 0.06 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
2,6-Dinitrotoluene.............. 606-20-2 EPA 525.3................................... 0.2 [micro]g/L... EPTDS............ 1/1/2028-12/31/2030
Anthracene...................... 120-12-7 EPA 525.3................................... 0.04 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Chlorothalonil.................. 1897-45-6 EPA 525.3................................... 0.06 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Dichlorvos (DDVP)............... 62-73-7 EPA 525.3................................... 0.05 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Fluorene........................ 86-73-7 EPA 525.3................................... 0.03 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Isophorone...................... 78-59-1 EPA 525.3................................... 0.04 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Metribuzin...................... 21087-64-9 EPA 525.3................................... 0.2 [micro]g/L... EPTDS............ 1/1/2028-12/31/2030
N,N-Diethyl-m-toluamide (DEET).. 134-62-3 EPA 525.3................................... 0.2 [micro]g/L... EPTDS............ 1/1/2028-12/31/2030
Phorate......................... 298-02-2 EPA 525.3................................... 0.02 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Pyrene.......................... 129-00-0 EPA 525.3................................... 0.03 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Tetrachlorvinphos (Stirofos).... 22248-79-9 EPA 525.3................................... 0.09 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Trifluralin..................... 1582-09-8 EPA 525.3................................... 0.02 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pesticide Metabolites
--------------------------------------------------------------------------------------------------------------------------------------------------------
Chlorpyrifos oxon............... 5598-15-2 EPA 540..................................... 0.00007 [micro]g/ EPTDS............ 1/1/2028-12/31/2030
L.
Phorate sulfone................. 2588-04-7 EPA 540..................................... 0.0006 [micro]g/L EPTDS............ 1/1/2028-12/31/2030
Phorate sulfoxide............... 2588-03-6 EPA 540..................................... 0.00007 [micro]g/ EPTDS............ 1/1/2028-12/31/2030
L.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Ultrashort Organofluorine Compounds
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bistriflimide (TFSI)............ 82113-65-3 EPA 563..................................... 0.003 [micro]g/L. EPTDS............ 1/1/2028-12/31/2030
Perfluoro-2-methoxyacetic acid 674-13-5 EPA 563..................................... 0.06 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
(PFMOAA).
Perfluoroethanesulfonic acid 354-88-1 EPA 563..................................... 0.02 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
(PFEtS).
Perfluoropropanesulfonic acid 423-41-6 EPA 563..................................... 0.01 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
(PFPrS).
Perfluoropropanoic acid (PFPrA). 422-64-0 EPA 563..................................... 0.08 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
Trifluoromethanesulfonic acid 1493-13-6 EPA 563..................................... 0.02 [micro]g/L.. EPTDS............ 1/1/2028-12/31/2030
(TFMS).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Trifluoroacetic acid (TFA)...... 76-05-1 EPA 563..................................... 0.2 [micro]g/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. 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 [email protected], 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

[[Page 39973]]

at the National Archives and Records Administration (NARA). For
information on the availability of this material at NARA, email
[email protected], 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