[Federal Register Volume 88, Number 87 (Friday, May 5, 2023)]
[Proposed Rules]
[Pages 29496-29526]
[FR Doc No: 2023-09311]

Vol. 88

Friday,

No. 87

May 5, 2023

Part IV

Environmental Protection Agency

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40 CFR Parts 131, 230 and 233

Federal Baseline Water Quality Standards for Indian Reservations;
Proposed Rule

Federal Register / Vol. 88, No. 87 / Friday, May 5, 2023 / Proposed
Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 131, 230, and 233

[EPA-HQ-OW-2016-0405; FRL-5868-03-OW]
RIN 2040-AF62

Federal Baseline Water Quality Standards for Indian Reservations

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
establish Federal water quality standards (WQS) for Indian reservation
waters that currently do not have WQS in effect under the Clean Water
Act (CWA or the Act), with limited exceptions. These WQS (referred to
as baseline WQS) would establish human health and environmental
objectives as the basis for CWA protections. EPA would implement the
baseline WQS, in consultation with Tribes, in a manner that would
address location-specific water quality conditions and Tribal
circumstances, as appropriate, and consistent with all relevant public
participation requirements to ensure transparency for stakeholders.
Tribes are encouraged to seek authority to administer their own WQS
program under the Act's provision for eligible Tribes to be treated in
a similar manner as states (TAS). Baseline WQS would not apply in
instances where Tribes with TAS authority have EPA-approved WQS now or
in the future. EPA will continue to work closely with, and offer
support to, Tribes that wish to develop their own WQS under the CWA.

DATES: Comments must be received on or before August 3, 2023.
    Public Hearings: The first public hearing will be on Tuesday, June
27 from 2 p.m. to 4 p.m. ET. The second public hearing will be on
Wednesday, July 12 from 2 p.m. to 4 p.m. ET.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2016-0405, at https://www.regulations.gov (our preferred method), or
the other methods identified in this ADDRESSES section. Once submitted,
comments cannot be edited or removed from the docket. EPA will publish
all comments received to its public docket. Do not submit
electronically any information you consider to be Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. 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. 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). For additional submission methods, the full
EPA public comment policy, information about CBI or multimedia
submissions, and general guidance on making effective comments, please
visit https://www.epa.gov/dockets/commenting-epa-dockets.
    EPA is offering two online public hearings so that interested
parties may provide oral comments on this proposed rule. The first
public hearing will be on Tuesday, June 27 from 2 p.m. to 4 p.m. ET.
The second public hearing will be on Wednesday, July 12 from 2 p.m. to
4 p.m. ET. EPA plans to make a transcript of the public hearings
available to the public in the rulemaking docket. EPA will respond to
substantive comments received as part of developing the final rule and
will include comment responses in the rulemaking docket. For more
details on the public hearings and a link to register, please visit
https://www.epa.gov/wqs-tech/promulgation-tribal-baseline-water-quality-standards-under-clean-water-act.

FOR FURTHER INFORMATION CONTACT: James Ray, U.S. EPA, Office of Science
and Technology, Standards and Health Protection Division, 1200
Pennsylvania Avenue NW (MC 4305T), Washington, DC 20460, (202) 566-
1433, [email protected]. Additional information is also available
online at https://www.epa.gov/wqs-tech/promulgation-tribal-baseline-water-quality-standards-under-clean-water-act.

SUPPLEMENTARY INFORMATION: This proposed rule is organized as follows:

I. General Information
    Does this action apply to me?
II. Background
    A. Role of Water Quality Standards Under the Clean Water Act
    B. Clean Water Act-Effective Water Quality Standards Currently
Applicable in Indian Country
III. EPA's Rationale for Proposing Baseline Water Quality Standards
    A. Status of Water Quality Standards Protection in Indian
Country
    B. Benefits of EPA Promulgating Baseline Water Quality Standards
for Indian Reservations Where Clean Water Act-effective Water
Quality Standards are not in Place
    C. History of EPA's Efforts to Establish Baseline Water Quality
Standards
    D. EPA's Authority for Establishing Baseline Water Quality
Standards
IV. Where the Proposed Baseline Water Quality Standards Would Apply
    A. Waters to Which the Proposed Baseline Water Quality Standards
Would Apply and Waters That Would Be Automatically Excluded
    B. Additional Option for Case-by-Case Exclusions From
Application of the Baseline Water Quality Standards
V. Proposed Baseline Water Quality Standards
    A. Proposed Baseline Designated Uses
    B. Proposed Baseline Water Quality Criteria
    C. Proposed Baseline Antidegradation Policy and Implementation
Procedures
    D. Other Proposed Water Quality Standards Provisions of Baseline
Water Quality Standards
VI. Proposed Procedure To Revise a Designated Use, add a Designated
Use, or Establish a Water Quality Standards Variance After the
Proposed Rule is Final
VII. Implementation of Baseline Water Quality Standards in Clean
Water Act Programs
    A. Section 402 NPDES Discharge Permits
    B. Section 404 Permits for Discharges of Dredged or Fill
Material
    C. Section 401 Certifications
    D. Section 303(d) Impaired Water Listings and Total Maximum
Daily Loads
VIII. Effective Date of the Baseline Water Quality Standards
IX. Conditions Under Which Baseline Water Quality Standards Would no
Longer Apply
X. Economic Analysis
    A. Identifying Affected Entities
    B. Method for Estimating Costs
    C. Results
XI. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review;
Executive Order 13563: Improving Regulation and Regulatory Review;
and Executive Order 14094: Modernizing Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132 (Federalism)
    F. Executive Order 13175 (Consultation and Coordination With
Indian Tribal Governments)
    G. Executive Order 13045 (Protection of Children From
Environmental Health and Safety Risks)
    H. Executive Order 13211 (Actions That Significantly Affect
Energy Supply, Distribution, or Use)
    I. National Technology Transfer and Advancement Act of 1995
    J. Executive Order 12898 (Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations)

I. General Information

Does this action apply to me?

    Tribes,\1\ states, local governments, and citizens concerned with
water

quality and how water quality may be defined and protected on Indian
reservations may be interested in this rulemaking. Entities discharging
pollutants to waters of the United States may be indirectly affected by
this rulemaking since water quality standards (WQS) are used to develop
National Pollutant Discharge Elimination System (NPDES) permit limits
and serve as a basis for Clean Water Act (CWA) section 402 permit
decisions. WQS also form the basis for assessing water quality,
identifying impaired waters, and developing total maximum daily loads
(TMDLs). See CWA sections 305(b) and 303(d). In CWA section 404
permits, WQS are used during the review of permits authorizing the
discharge of dredged or fill material. Categories and entities that may
be affected include the following:
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    \1\ ``Tribe'' means an Indian or Alaska Native Tribe, band,
nation, pueblo, village, community, or other entity that the
Secretary of the Interior acknowledges to exist as an Indian Tribe
pursuant to the Federally Recognized Indian Tribe List Act of 1944,
25 U.S.C. 479a.

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          Category             Examples of potentially affected entities
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States, Tribes, and           Federally recognized Tribes with Indian
 Territories.                  reservations currently without CWA-
                               effective WQS and states and authorized
                               Tribes near or bordering such
                               reservations.
Federal Agencies............  Federal agencies with projects or other
                               activities that may affect surface waters
                               on Indian reservations currently without
                               CWA-effective WQS.
Industry....................  Industries discharging pollutants that may
                               affect surface waters on Indian
                               reservations currently without CWA-
                               effective WQS.
Municipalities..............  Publicly owned treatment works and
                               stormwater outfalls discharging
                               pollutants that may affect surface waters
                               on Indian reservations currently without
                               CWA-effective WQS.
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    This table is not exhaustive, but rather it provides a guide that
identifies entities that could be affected by this proposed rule. Other
types of entities not listed in the table could also be affected. If
you have questions regarding the effect of this action on a particular
entity, please consult the person listed in the preceding FOR FURTHER
INFORMATION CONTACT section.

II. Background

A. Role of Water Quality Standards Under the Clean Water Act

    The CWA establishes the basic structure for regulating pollutant
discharges into waters of the United States. In the CWA, Congress
established the national objective to restore and maintain the
chemical, physical, and biological integrity of the Nation's waters.
The CWA also sets forth the interim goal of achieving water quality,
wherever attainable, that provides for both (i) the protection and
propagation of fish, shellfish, and wildlife and (ii) recreation in and
on the water (sections 101(a) and 101(a)(2)). 33 U.S.C. 1251(a),
(a)(2). To help achieve these goals, the CWA created two complementary
structures for regulating discharges in CWA section 402 NPDES permits:
first, technology-based effluent limitations (TBELs) that set a floor
of performance for categories of dischargers, and second, water
quality-based effluent limitations (WQBELs) that are established where
TBELs are insufficient to meet applicable WQS or site-specific water
quality goals. 33 U.S.C. 1342(a). TBELs in NPDES permits are derived
from secondary treatment standards, which are minimum requirements for
municipal wastewater treatment plants (CWA sections 301, 33 U.S.C.
1311), effluent limitations guidelines, which are national regulatory
standards for industrial wastewater discharged to surface waters and
municipal sewage treatment plants (CWA sections 304 and 1314), and new
source performance standards, which are standards for water pollution
discharges of industrial wastewater to surface waters (CWA section 306,
33 U.S.C. 1316) promulgated by EPA. If TBELs are not sufficient to meet
the WQS in the receiving water, the CWA (section 301(b)(1)(c), 33
U.S.C. 1311(b)(1)(c)) and EPA's NPDES regulation, 40 CFR 122.44(d),
require that the permit writer develop more stringent, WQBELs.
    WQS are the foundation of the water quality-based pollution control
programs required by the CWA. Under CWA section 303(c) and EPA's
regulation at 40 CFR part 131, WQS consist of designated uses for water
bodies, water quality criteria to protect those uses, and an
antidegradation policy to maintain water quality. 33 U.S.C. 1313(c).
Such standards serve as a description of the desired water quality for
particular water bodies. In addition, they serve as the basis for
several CWA programs, including:
     WQBELs issued through state or National Pollutant
Discharge Elimination System (NPDES) Program under section 402, 33
U.S.C. 1342;
     Section 303(d), 33 U.S.C. 1313(d), water body assessments
and determinations of TMDLs;
     Section 401, 33 U.S.C. 1341, certifications of Federal
licenses and permits; and
     Section 404, 33 U.S.C., 1344, permits for dredged or fill
material.
    CWA section 303(c) gives states the primary responsibility to
establish, review, and revise WQS applicable to their waters. In 1987,
Congress amended the CWA to add section 518, the CWA provision for
eligible Indian Tribes to be treated in a similar manner as states, or
TAS. 33 U.S.C. 1377. In CWA section 518, Congress expressly delegated
authority to Indian Tribes to administer CWA regulatory programs over
their entire reservations, including over nonmember activities on fee
lands within the reservation of the applicant Tribe, subject to certain
eligibility requirements. For a Tribe to be eligible to obtain TAS
authority and administer a CWA program, the Tribe must be federally
recognized and maintain governmental authority over a reservation,
among other requirements.\2\
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    \2\ Under CWA section 518 and EPA's implementing regulation at
40 CFR 131.8(a), four requirements must be satisfied before EPA can
approve a Tribe's application for treatment in a similar manner as a
state for purposes of administering water quality standards under
CWA section 303(c).
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    EPA's use of ``Tribe'' in the context of this proposed rule refers
to ``Tribal government authority'' that serves as the ultimate
decision-maker for the Tribe.
    Pursuant to CWA section 518, Tribes can obtain TAS under the CWA
for water resources on their reservation. See 33 U.S.C. 1377(e)(2)
(referring to waters ``within the borders of an Indian reservation'');
81 FR 30183, 30191, May 16, 2016. Many named Indian reservations were
established through Federal treaties with Tribes, Federal statutes, or
Executive orders of the President. Such reservations are often referred
to as formal reservations. EPA's longstanding approach under the CWA
and other statutes administered by EPA is that, in accordance with
judicial precedent, the term ``reservation'' includes both formal
reservations and

informal reservations such as trust land that has been validly set
apart for use by a Tribe even if such trust land is located outside of
the exterior boundaries of a formally designated reservation. See 56 FR
64876, 64881, December 12, 1991; see also Oklahoma Tax Commission v.
Citizen Band Potawatomi Indian Tribe of Oklahoma, 508 U.S. 114, 123
(1991) (``Congress has defined Indian country broadly to include formal
and informal reservations, dependent Indian communities, and Indian
allotments, whether restricted or held in trust by the United
States''); HRI v EPA 198 F.3d 1224 (10th Cir. 2000) (same); Arizona
Public Service Co. v EPA, 211 F.3d 1280 (D.C. Cir. 2000) (Upholding
EPA's interpretation of ``reservation'' in the Clean Air Act as
including tribal trust lands and pueblos, and noting that ``[t]his view
is consonant with other Federal court holdings that an Indian
reservation includes trust lands.''). An Indian Tribe that obtains EPA
approval for TAS to administer a WQS program over its reservation is
referred to as an ``authorized Tribe.''
    CWA section 303(c) also provides for EPA to promulgate Federal WQS
in two situations. First, EPA must act if it determines that a state's
or authorized Tribe's new or revised WQS is not consistent with the
requirements of the Act, and the state or authorized Tribe fails to
submit a modified standard within 90 days. In that case, section
303(c)(4)(A) requires EPA to propose and promulgate a revised or new
standard for the waters involved, unless prior to promulgation, the
state or authorized Tribe adopts a WQS that EPA determines to be
consistent with the Act. Second, section 303(c)(4)(B) grants the EPA
Administrator discretion to promulgate standards in any case where the
Administrator determines that a revised or new standard is necessary to
meet the requirements of the Act. A determination pursuant to section
303(c)(4)(B) is referred to as an ``Administrator's Determination.''
See 40 CFR 131.22(b).

B. Clean Water Act-Effective Water Quality Standards Currently
Applicable in Indian Country

    ``Indian country'' is defined by Federal statute at 18 U.S.C.
1151.\3\ Pursuant to that definition, Indian country includes all
territory within an Indian reservation (including land owned in fee
simple by non-Indians). It also includes ``dependent Indian
communities'' (DICs) and Indian allotments, the titles to which have
not been extinguished, regardless of whether those lands are located
within a reservation. EPA generally directly implements Federal
environmental programs in Indian country where it has not approved a
non-Federal entity to implement the program.\4\ See EPA's 1984 Indian
Policy (``EPA Policy for the Administration of Environmental Programs
on Indian Reservations,'' EPA, November 8, 1984); see also Phillips
Petroleum Co. v. EPA, 803 F.2d 545, 556 (10th Cir. 1986) (holding that
EPA had authority to prescribe regulations in Indian country, and
noting that the court's conclusion was ``also consistent with the
presumption that Congress intends a general statute applying to all
persons to include Indians and their property interests.''); 40 CFR
144.2 (Underground Injection Control Program); 40 CFR 123.1(h)
(National Pollution Discharge Elimination System Program); 40 CFR
71.4(b) (Clean Air Act Title V Permit Program); 40 CFR 281.12(a)(2)
(Underground Storage Tanks Program). Because EPA-approved state WQS
generally do not apply in Indian country, in the absence of Federal WQS
or EPA-approved Tribes' WQS, no CWA-effective WQS apply in the many
Indian country waters where Tribes have not yet obtained TAS and
established EPA-approved WQS.\5\
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    \3\ Indian country is defined at 18 U.S.C. 1151 as: (a) All land
within the limits of any Indian reservation under the jurisdiction
of the United States Government, notwithstanding the issuance of any
patent, and, including rights-of-way running through the
reservation; (b) all dependent Indian communities within the borders
of the United States whether within the original or subsequently
acquired territory thereof, and whether within or without the limits
of a state; and (c) all Indian allotments, the Indian titles to
which have not been extinguished, including rights-of-way running
through the same. Indian reservations are thus a subset of the
broader geographic area that comprises Indian country as a whole.
    \4\ In a few instances, EPA has determined that, due to unique
jurisdictional frameworks enacted by Congress, certain states have
jurisdiction to administer WQS on Indian reservations under the CWA.
These include the reservations, including trust lands, of all four
Tribes in Maine (Houlton Band of Maliseet Indians, Mi'kmaq Nation,
Passamaquoddy Tribe, and Penobscot Nation), the reservation of the
Catawba Indian Nation in South Carolina, non-Indian fee lands of the
Puyallup Reservation in Washington, and reservation lands (excluding
Tribal trust lands, Indian allotments, and certain Tribal fee lands)
in Oklahoma. See, e.g., Letter from H. Curtis Spalding, Regional
Administrator, EPA Region 1, to Patricia W. Aho, Commissioner, Maine
Department of Environmental Protection, ``Re: Review and Decision on
Water Quality Standards Revisions'' (February 2, 2015), Attachment A
at 2; Letter from Daniel Opalski to Laura Watson, Director,
Washington Department of Ecology, Re: Clean Water Act Section 401
Implementation within the Puyallup Tribe of Indians 1873 Survey Area
(August 9, 2021) (Noting that the State of Washington is authorized
``to administer all Clean Water Act delegated and authorized
programs on non-trust lands, as defined in the 1988 Lands Claims
Settlement Agreement,'' pursuant to the Puyallup Tribe of Indians
Settlement Act of 1989, 25 U.S.C. 1773); EPA, 87 FR 3673, Air Plan
Approval; South Carolina; Catawba Indian Nation Portion of the
Charlotte-Gastonia-Rock Hill Area Limited Maintenance Plan for the
1997 8-Hour Ozone NAAQS (January 25, 2022) (``Pursuant to the
Catawba Indian Claims Settlement Act, S.C. Code Ann. 27-16-120 . . .
`all state and local environmental laws and regulations apply to the
[Catawba Indian Nation] and Reservation and are fully enforceable by
all relevant state and local agencies and authorities.'''); Letter
from Andrew R. Wheeler to The Honorable J. Kevin Stitt, Governor of
the State of Oklahoma, Re: Approval of State of Oklahoma Request
Under Section 10211(a) of the Safe, Accountable, Flexible, Efficient
Transportation Equity Act of 2005 (October 1, 2020). (On December
22, 2021, EPA publicized a ``Notice of Proposed Withdrawal and
Reconsideration of October 1, 2020 SAFETEA Decision and Opportunity
for Comment.'' EPA's reconsideration is currently ongoing, and
Oklahoma's approval to administer WQS in the stated areas of Indian
reservations remains in place during that process.)
    \5\ Some Tribes may have WQS effective under Tribal law. Such
standards are not effective for CWA purposes, however, until they
are approved by EPA. 40 CFR 131.21.
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    The Federal Government has recognized 574 Tribes.\6\ More than 300
of these Tribes have formal and/or informal reservations: e.g., named
formal reservations, Pueblos, Rancherias, and lands held in trust by
the United States for Tribal governments that are not designated as
formal reservations. With few exceptions,\7\ any of these Tribes may
apply to EPA under CWA section 518 to administer specific environmental
programs, including WQS, for water resources within the boundaries of
the Tribe's reservation. As explained in section II.A. of this
preamble, waters within the boundaries of a Tribe's reservation also
refers to waters on Tribal trust lands not formally designated as
reservations.
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    \6\ See Indian Entities Recognized by and Eligible to Receive
Services from the United States Bureau of Indian Affairs: Notice,
Department of the Interior, 86 FR 7554 (January 29, 2021).
    \7\ See supra note 4.
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    EPA has approved TAS applications for 84 Tribes to administer the
CWA section 303(c) program. Tribes with an approved TAS application may
adopt WQS under section 303(c) of the CWA and submit them to EPA for
review pursuant to CWA section 303(c) and EPA's implementing
regulation. To date, 47 of the 84 Tribes have submitted Tribal WQS that
EPA has approved in this manner. EPA's website, EPA Actions on Tribal
Water Quality Standards and Contacts \8\ lists these Tribes and the
dates their TAS authority and WQS were approved. EPA updates this list
continually. EPA also provides technical assistance to Tribes in
developing TAS applications and WQS.\9\
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    \8\ https://www.epa.gov/wqs-tech/epa-actions-tribal-water-quality-standards-and-contacts.
    \9\ https://www.epa.gov/wqs-tech/water-quality-standards-tools-tribes.

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    In one instance, EPA has promulgated Federal WQS for an Indian
reservation. In 1986, the Confederated Tribes of the Colville
Reservation (CTCR) in Washington requested EPA to promulgate the CTCR's
WQS as Federal standards for waters of the reservation. The CTCR was
concerned that their WQS could not otherwise be recognized under the
CWA at that time. After EPA received the request from the CTCR,
Congress passed the CWA amendments of 1987 to add the TAS provisions of
section 518 described in section II.A of this preamble. Despite the
pending opportunity to qualify for TAS for purposes of administering a
WQS program, the CTCR supported EPA's promulgation of Federal WQS for
the reservation. EPA finalized the CTCR promulgation in 1989 at 40 CFR
131.35. In 2018, the CTCR obtained TAS authority to administer a WQS
program and is in the process of developing its own Tribe-adopted WQS
for CWA purposes.

III. EPA's Rationale for Proposing Baseline Water Quality Standards

A. Status of Water Quality Standards Protection in Indian Country

    As mentioned in section II.B of this preamble, while more than 300
Tribes with Indian reservations are eligible to apply for TAS, only 84
Tribes have applied and been approved to administer a WQS program. Of
these 84 Tribes, only 47 Tribes to date have adopted WQS and submitted
them to EPA for review and approval under the CWA. EPA has generally
excluded Indian reservations from state WQS approvals, subject to
limited exceptions.\10\ EPA estimates that about 76,000 miles of rivers
and streams and 1.9 million acres of lakes, reservoirs, and other open
surface waters within Indian reservations currently lack CWA-effective
WQS; these reservations are home to approximately 550,000 people.\11\
As a result, 50 years after enactment of the CWA, the majority of
Indian reservations do not have this foundational protection laid out
by Congress in the CWA for their waters.
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    \10\ See supra note 4.
    \11\ See EPA's draft analysis, Analysis of Tribal Reservation
Lands without Applicable WQS (Draft), in the docket for this
rulemaking.
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    Tribal interest in obtaining TAS and adopting their own WQS has
increased in recent years, especially after EPA's action in 2016 to
revise its interpretation of CWA section 518, which streamlined aspects
of a Tribe's TAS application.\12\ A total of 27 of the 84 Tribes with
TAS for the WQS program have been approved in the six years since then.
Nonetheless, acquiring TAS authorities and adopting WQS is a time and
resource-intensive process. At the current pace, it could take more
than a decade for CWA-effective WQS to be put in place for all Indian
reservations.
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    \12\ See Revised Interpretation of Clean Water Act Tribal
Provision, final interpretive rule, 81 FR 30183, May 16, 2016.
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    The lack of CWA-effective WQS for most Indian reservations means
that those waters do not have the human health and environmental
objectives in place that form the basis for CWA protections. WQS are
central to implementing the water quality framework of the CWA.
Although it is EPA's preference for Tribes to obtain TAS and develop
WQS tailored to the Tribes' individual environmental goals and
reservation waters, EPA's promulgation of baseline WQS would safeguard
water quality until Tribes obtain TAS and adopt CWA WQS themselves.

B. Benefits of EPA Promulgating Baseline Water Quality Standards for
Indian Reservations Where Clean Water Act-Effective Water Quality
Standards Are Not in Place

    EPA is proposing a national rule to establish baseline WQS to
safeguard water quality for certain Indian reservation waters. The
proposed rule will ensure that the core CWA framework to protect water
quality is in place for these waters until the Tribe applies for TAS to
administer a WQS program and adopts its own Tribal WQS consistent with
CWA section 303(c). EPA is proposing to establish the following WQS:
     designated uses consistent with the CWA protection and
restoration goals for aquatic life and users of surface water;
     a designated use that protects cultural and traditional
uses;
     water quality criteria to protect those uses;
     an antidegradation policy with associated implementation
procedures; and
     general WQS polices such as a mixing zone policy and
compliance schedule authorizing provision.
    EPA recognizes that WQS specific to the site-specific chemical,
physical and biological conditions of each reservation might be more
desirable than Federal baseline WQS. However, developing WQS tailored
to each reservation, and potentially to different categories of waters
within each reservation, would further delay needed protections.
Instead, EPA is relying on its role as both the promulgating entity and
the primary implementing authority to allow a degree of site-specific
tailoring within the regulatory construct of the WQS during subsequent
implementation of the proposed rule. This tailoring would be
accomplished by use of the narrative criteria and binding translation
procedures identified in the rule. For example, a particular Tribe's
fish consumption rates could be used during the implementation stage as
part of the calculation to set the appropriate human health criteria
value for its waters.
    Because no Tribes have yet applied for TAS to administer the CWA
section 402 NPDES permitting program, EPA is typically the NPDES
permitting authority in Indian country. In the absence of CWA-effective
WQS for these waters, EPA permit writers have utilized various tools to
write protective NPDES permits, such as relying on downstream state WQS
to inform relevant permit limits. However, these mechanisms are limited
in their ability to protect Tribal waters reflecting Tribal priorities.

C. History of EPA's Efforts To Establish Baseline Water Quality
Standards

    EPA has been working with Tribes on the concept of promulgating
baseline WQS for over two decades. Between 1998 and 2003, EPA consulted
with Tribes, and sought input from states and the public on the
possibility of EPA promulgating certain Federal WQS referred to as
``core water quality standards'' for Indian country waters without CWA-
effective WQS. On January 18, 2001, EPA Administrator Carol Browner
determined, pursuant to CWA section 303(c)(4)(B), that new or revised
WQS were necessary for certain Indian country waters lacking CWA-
effective WQS. Pursuant to the Determination, Administrator Browner
signed a proposed rule to promulgate the core WQS under CWA section
303(c).\13\ Specifically, the Determination provides as follows:
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    \13\ Federal Water Quality Standards for Indian Country and
Other Provisions Regarding Federal Water Quality Standards. 2001:
https://19january2017snapshot.epa.gov/sites/production/files/2016-08/documents/federal_wqs_for_indian_country_proposal_signed_1-18-01.pdf.

    [E]xcept where the Tribe wants to have its Indian country waters
excluded from this rule and the Tribe and/or EPA has or intends to
develop a plan for establishing water quality standards under the
Clean Water Act within a reasonable time, and for off-reservation
allotments . . . the EPA Administrator finds under the Clean Water
Act sections 303(c)(4)(B) and 501(a) that

water quality standards are necessary to meet the requirements of
the Clean Water Act for all Indian country waters where EPA has not
either (1) promulgated other Federal water quality standards or (2)
explicitly found State or Tribal jurisdiction to adopt water quality
standards (and Tribal or State standards are in effect) under the
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Clean Water Act.

    The proposed rule excepted waters from the Determination where a
Tribe demonstrated to the Regional Administrator that it had a plan in
place, was working to develop such a plan, or the Tribe and Regional
Administrator have agreed on a plan for adopting CWA-effective WQS
within a ``reasonable amount of time.'' On January 22, 2001, EPA
withdrew that proposal prior to its publication in the Federal Register
to allow additional review.
    In 2015, EPA renewed its efforts to engage in rulemaking to provide
WQS protections in Indian country, focusing on Indian reservation
waters that did not have CWA-effective WQS in place. In 2016, EPA
published an advance notice of proposed rulemaking (ANPRM) to initiate
a formal dialogue with Tribes, states, the public, and other
stakeholders regarding whether EPA should initiate a rulemaking and, if
so, what approach EPA should take regarding key policy issues raised by
such a rulemaking. 81 FR 66900, September 29, 2016. EPA engaged in
extensive consultation and coordination with Tribes leading up to the
publication of the ANPRM in the Federal Register. EPA provided a public
comment period on the ANPRM and received comments from 12 Tribal
governments and associations; 11 state officials, agencies, and
associations; 11 private citizens; and the Domestic Energy Producers
Alliance. Refer to Docket ID No. EPA-HQ-OW-2016-0405 to view comments
submitted to EPA on the ANPRM and EPA's website at https://www.epa.gov/wqs-tech/advance-notice-proposed-rulemaking-federal-baseline-water-quality-standards-indian.
    As a general summary, most comments associated with the ANPRM from
Tribal governments expressed support for promulgation of baseline WQS
at the time. However, some Tribes expressed concerns with this effort,
perceiving it as an infringement on Tribal sovereignty, and requested
that EPA not promulgate baseline WQS for Tribes who did not want to be
covered by a WQS baseline rule. Comments raised the need for baseline
WQS to accommodate regional tailoring, fish consumption rates
reflecting individual Tribes' consumption rates, inclusion of
protections for cultural and traditional uses, and reliance on
antidegradation policies to ensure protection of high quality waters.
States raised concerns about EPA's CWA authority and resources to
promulgate and effectively implement baseline WQS on Indian
reservations. States also commented that baseline WQS might differ from
neighboring states' standards and potentially affect upstream
dischargers.
    On June 11, 2021, EPA sent a ``Notification of Consultation and
Coordination'' letter to all 574 federally recognized Tribes to
initiate a 90-day pre-proposal Tribal consultation and coordination
period that began on June 15, 2021, and ended on September 13, 2021. In
addition to two national Tribal listening sessions, EPA presented at 16
meetings with Tribal staff and leadership, held four staff-level
coordination/engagement meetings, and held four government-to-
government meetings. EPA continued outreach and engagement with Tribes
at national and regional Tribal meetings after the end of the
consultation period. For more information on the comments raised during
these meetings and the comment letters received, please refer to EPA's
Summary Report of Tribal Consultation and Coordination for the Proposed
Rule: Federal Baseline Water Quality Standards for Indian Reservations
available in the docket associated with this rulemaking. In addition,
on September 15, 2021, EPA consulted with state representatives from
the Association of Clean Water Administrators (ACWA) to hear their
initial views on the proposed regulatory changes. Participants raised
questions about EPA's implementation of baseline WQS under the CWA,
EPA's prioritization of Tribes obtaining TAS to administer their own
WQS programs, the ability of baseline WQS to be tailored to reflect
regional and location-specific information, and how EPA would reconcile
differences between downstream Federal baseline WQS and upstream state
WQS.
    This proposed rule builds upon the prior initiatives and the
comments and feedback provided to date which directly inform the
baseline WQS articulated in this proposed rule.

D. EPA's Authority for Establishing Baseline Water Quality Standards

    Section 303(c)(4)(B) of the CWA provides that the Administrator
shall promptly prepare and publish proposed regulations setting forth a
revised or new WQS for the navigable waters in any case where the
Administrator determines that a revised or new standard is necessary to
meet the requirements of the CWA. As explained in section III.C. of
this preamble, in 2001 the EPA Administrator made an Administrator's
Determination that new or revised WQS are necessary for certain Indian
country waters.
    EPA is not proposing to amend the Administrator's Determination.
This remains the source of authority for EPA's proposal of WQS for
Indian country waters that lack such standards. As explained further
below in section IV.B of this preamble, this proposed rule would
effectuate a significant portion of that Determination, recognizing
that Tribes' individual circumstances may vary and focusing initially
on Indian reservation waters where EPA and the relevant Tribes agree
that baseline WQS are appropriate at this time. This approach would
ensure that the Tribes themselves have a role in determining the
application of this rule, so that EPA may appropriately target
resources to those Indian reservation waters where the agency and the
Tribes determine the need for baseline WQS is most pressing. EPA will
continue to monitor the development of WQS for Indian reservation
waters and consider future action to effectuate the remainder of the
Determination. This is discussed further in section IV.B of this
preamble.

IV. Where the Proposed Baseline Water Quality Standards Would Apply

A. Waters to Which the Baseline Water Quality Standards Would Apply and
Waters That Would be Automatically Excluded

    EPA is proposing to promulgate baseline WQS for all waters of the
United States in Indian country, with the following automatic
exclusions:

    (1) The baseline WQS would not apply to Indian reservation
waters for which EPA has promulgated other Federal WQS. Currently,
EPA has promulgated WQS for only one Tribe, the Confederated Tribes
of the Colville Reservation (see 40 CFR 131.35). If EPA were to
promulgate other Federal WQS for other Tribes in the future,
consistent with applicable regulations, that rulemaking would result
in the new Federal WQS being CWA-effective, rather than the baseline
WQS.
    (2) The baseline WQS would not apply to Indian reservation
waters where EPA has explicitly found that a state has jurisdiction
to adopt WQS or authorized a Tribe to adopt WQS pursuant to the TAS
regulation and where EPA has approved the applicable state or Tribal
WQS. As mentioned previously, 47 Tribes have adopted WQS approved by
EPA and there are four instances where EPA found states have
jurisdiction to administer WQS under the CWA on reservations or
parts of reservations.
    (3) The baseline WQS would not apply to Indian country waters in
off-reservation allotments or dependent Indian communities (DICs),
which are included in the definition of Indian country under 18
U.S.C. 1151.

    The first two exclusions flow directly from the Administrator's
Determination, excerpted in section III.C of this preamble, where the
agency explicitly found that standards are not necessary for Indian
country waters where EPA has (1) promulgated other Federal water
quality standards, or (2) found that a state or Tribe has jurisdiction
to adopt WQS and EPA has approved the applicable state or Tribal WQS.
    The third exclusion also flows from the Administrator's
Determination, which excepted off-reservation allotments from the scope
of the Determination. EPA believes that the third exclusion, which also
adds an exception for DICs, is warranted because of the infeasibility
of covering these waters at this time. As noted in section II.A of this
preamble, Indian country includes ``allotments,'' which are lands held
in trust by the Federal Government or under a restriction on alienation
for the benefit of individuals. Allotments may be within the boundaries
of a Tribe's reservation, and thus subject to this proposed rule along
with other Indian reservation waters,\14\ or outside of a Tribe's
reservation boundaries. There are likely many thousands of off-
reservation allotments, many of which are scattered throughout the
United States. The Department of the Interior's Bureau of Indian
Affairs and Bureau of Land Management are in the process of identifying
and locating off-reservation allotments in several geographical areas
around the country. Until this information is confirmed, EPA is
concerned that it would not be practical to ensure uniform
implementation of the baseline WQS and would ensure that persons
affected by this proposed rule have a meaningful opportunity to comment
and engage in the process. Thus, EPA is not currently considering a new
Administrator's Determination regarding off-reservation allotments.\15\
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    \14\ As explained in section II.A of this preamble, Indian
reservation refers to both formal reservations and Tribal trust
lands.
    \15\ The Administrator's Determination, see section III.C of
this preamble, explicitly carved out off-reservation allotments due
to ``gaps in information regarding such allotments[.]'' [Federal
Water Quality Standards for Indian Country and Other Provisions
Regarding Federal Water Quality Standards. 2001: https://19january2017snapshot.epa.gov/sites/production/files/2016-08/documents/federal_wqs_for_indian_country_proposal_signed_1-18-01.pdf].
---------------------------------------------------------------------------

    As noted in section II.A. of this preamble, the definition of
Indian country also includes ``dependent Indian communities'' (DICs).
While the term ``dependent Indian communities'' is not further defined
in the statutory definition of Indian country, the Supreme Court has
held that the term dependent Indian communities ``refers to a limited
category of Indian lands that are neither reservations nor allotments,
and that satisfy two requirements--first, they must have been set aside
by the Federal Government for the use of the Indians as Indian land;
second, they must be under Federal superintendence.'' Alaska v. Native
Village of Venetie, 118 S. Ct. 948 (1998). Given the lack of
information regarding the location of dependent Indian communities, the
application of baseline standards to these areas at this time raises
similar implementation concerns as allotments. As explained further in
section IV.B of this preamble, in this proposed rule the agency is
acting on a significant portion of a nationwide Administrator's
Determination and has chosen to focus this initial effort on waters
where the agency is best positioned to implement the baseline WQS in
collaboration with Tribal partners. Thus, the agency is not currently
proposing new or revised WQS for DICs.
    EPA invites comment on the automatic exclusions included in the
proposal. EPA specifically invites comment on whether dependent Indian
communities should be excluded and whether EPA's concerns, outlined
above, are warranted.

B. Additional Option for Case-by-Case Exclusions From Application of
the Baseline Water Quality Standards

    Section 131.XX(a)(4) of the proposed rule enables the Regional
Administrator to exclude additional waters on a case-by-case basis
informed by consultation with Tribes. The Administrator's Determination
explicitly excluded waters where ``the Tribe and/or EPA has or intends
to develop a plan for establishing water quality standards under the
Clean Water Act within a reasonable time.'' Thus, in this proposed
rule, consistent with the Administrator's Determination, the agency is
providing that Tribes may seek exclusion from coverage due to ongoing
efforts toward establishing WQS. In addition, EPA is providing an
option for Tribes to seek exclusion from coverage in the absence of
such a plan to establish WQS at this time, upon approval by the
relevant EPA Regional Administrator. As noted above, in this proposed
rule the agency has chosen to focus this initial effort on Indian
reservation waters where Tribes are best positioned to work with the
agency to implement WQS.
    Although it is important that WQS be established for all Indian
reservation waters currently lacking WQS effective under the CWA, EPA
recognizes that Tribes' individual circumstances may vary. After
consulting over many years with Tribes, and most recently engaging in
coordination and consultation with Tribes to inform this proposal (see
EPA's Summary Report of Tribal Consultation and Coordination for the
Proposed Rule: Federal Baseline Water Quality Standards for Indian
Reservations available in the docket associated with this rulemaking),
EPA understands that, while some Tribes are presently working toward
seeking TAS for WQS and/or the adoption of WQS for submittal to EPA,
other Tribes may not be in a position to do so at this time. EPA also
recognizes that some Tribes may need additional time to gather more
information about baseline WQS and prepare for the partnership
opportunities the WQS would afford.
    To accommodate these considerations, EPA is proposing to allow
Tribes to work with the appropriate Regional Administrator to seek an
exclusion from the applicability of baseline WQS under this rule. This
approach is consistent with the exception in the Administrator's
Determination for Tribes that have a plan in place for establishing WQS
for EPA approval or are working on a plan and do not yet have EPA-
approved WQS for EPA in effect. Specifically, Tribes with such a plan
in place or that are working on a plan are not subject to the
Administrator's Determination. Similar to its approach to DICs, the
agency is proposing to add an exception for coverage under this
proposed rule to allow for potential exclusion from coverage for Tribes
that do not yet have EPA-approved WQS but demonstrate to the Regional
Administrator that baseline WQS are not consistent with Tribal
priorities at this time. This approach would ensure that the Tribes
themselves have a role in determining the application of this rule.
Allowing Tribes to be excluded from applicability of the baseline WQS
at this time will also enable EPA staff to appropriately target current
resources toward working with those Tribes that are ready to partner
with EPA in implementing baseline WQS in the near term. EPA will
continue to work with those Tribes that are excluded from coverage at
this time on ensuring that water quality on their Indian reservations
is protected consistent with the CWA.
    To seek exclusion from the scope of coverage of the baseline WQS
rule, a Tribe should communicate with the Regional Administrator,
explaining the basis of the Tribes' request to be excluded from
coverage at this time and providing any supporting information,
including, where applicable, plans for

developing WQS and the associated timeline for doing so. The timeframe
for a Tribe seeking to be excluded to communicate to the Regional
Administrator begins upon publication of this proposed rule in the
Federal Register and ends no later than 90 days after the final rule is
published in the Federal Register. See the discussion of the effective
date of the final rule in section VIII of this preamble.
    The Regional Administrator, informed by consultation with the
Tribe, would approve or disapprove a Tribe's exclusion from the
baseline WQS rule. In making a decision regarding exclusion from the
initial coverage of the baseline standards, in the absence of a plan to
develop Tribal CWA-effective WQS, the Regional Administrator would
consider the impacts that exclusion from the baseline WQS rule would
have on reservation water quality, including potential impacts to
overburdened communities. The Regional Administrator would document the
decision for the record.
    Under this proposed rule, EPA would maintain a publicly available
list, on a dedicated website, of all Tribes with Indian reservations
for purposes of this proposed rule and would indicate which of those
Tribes are covered by baseline WQS, which are excluded from coverage at
this time, and which Tribes already have CWA-effective WQS in place.
    A Tribe whose waters are excluded from baseline WQS coverage under
the option described above may at any later time request the Regional
Administrator to rescind the exclusion. Rescinding the exclusion will
result in baseline WQS becoming applicable for waters of the Tribe. The
Regional Administrator would document this decision for the record, and
the Tribe would be listed as covered by baseline WQS on the website
above.
    EPA invites comments on the above proposed approach for EPA to
allow exclusions from coverage by the baseline WQS.

V. Proposed Baseline Water Quality Standards

    The CWA specifies that WQS shall protect public health or welfare,
enhance the quality of water, and serve the purposes of the Act. To
``serve the purposes of the Act'' (as defined in sections 101(a)(2),
and 303(c) of the Act), WQS must provide, wherever attainable, water
quality for the protection and propagation of fish, shellfish, and
wildlife, and recreation in and on the water, and must consider the use
and value of the waters for those uses and for public water supplies,
industrial purposes, and navigation. (40 CFR 131.2). Per 40 CFR
131.22(c), when EPA promulgates WQS, it is subject to the ``same
policies, procedures, analyses, and public participation requirements
established for States in these regulations.'' The following sections
describe the designated uses, water quality criteria, antidegradation
implementation methods, and certain other WQS provisions that EPA
proposes to promulgate as the applicable baseline WQS for the Indian
reservation waters discussed in section IV of this preamble.
    Consistent with the EPA Policy on Consultation and Coordination
with Indian Tribes,\16\ the proposed rule would require the Regional
Administrator to initiate Tribal consultation with a Tribe(s) when
taking actions under this proposed rule that may affect Tribal
interests. See proposed 40 CFR 131.XX(b). That is, the Regional
Administrator would notify the Tribe(s) of the opportunity for
government-to-government consultation when taking actions under the
baseline WQS rule.
---------------------------------------------------------------------------

    \16\ The EPA Policy on Consultation and Coordination with Indian
Tribes (https://www.epa.gov/sites/default/files/2013-08/documents/cons-and-coord-with-indian-tribes-policy.pdf) applies to agency
actions and decisions that ``may affect tribal interests.'' Under
Executive Order 13175 (Consultation and Coordination with Indian
Tribal Governments) agencies must have an accountable process to
ensure meaningful and timely input by tribal officials in the
development of regulatory policies that ``have substantial direct
effects on one or more Indian tribes, on the relationship between
the Federal Government and Indian tribes, or on the distribution of
power and responsibilities between the Federal Government and
Tribes.'' See Section XI.F of this preamble for a discussion of E.O.
13175.
---------------------------------------------------------------------------

    EPA defines consultation in its 2011 EPA Policy on Consultation and
Coordination with Indian Tribes as ``a process of meaningful
communication and coordination between EPA and tribal officials prior
to EPA taking actions or implementing decisions that may affect
tribes.'' As a process, consultation includes several methods of
interaction that may occur at different levels. The appropriate level
of interaction is determined by past and current practices, policy
adjustments, the continuing dialogue between EPA and Tribal
governments, and program and regional office consultation procedures
and plans. EPA would seek information and input regarding
implementation of baseline WQS in accordance with the 2011 EPA Policy
on Consultation and Coordination with Tribes, the 2016 EPA Policy on
Consultation and Coordination with Indian Tribes: Guidance for
Discussing Tribal Treaty Rights,\17\ applicable EPA regional
consultation procedures,\18\ or any other applicable EPA Tribal
consultation policies in effect at the time the proposed rule would be
applied. EPA would consider all relevant information obtained through
consultation to help ensure that EPA is fully informed before taking a
WQS action for Tribes covered by the final baseline WQS rule.
---------------------------------------------------------------------------

    \17\ Available online at https://www.epa.gov/tribal/epa-policy-consultation-and-coordination-indian-tribes-guidance-discussing-tribal-treaty.
    \18\ Available online at https://www.epa.gov/tribal/forms/consultation-and-coordination-tribes.
---------------------------------------------------------------------------

    EPA would attempt to honor consultation requests from Tribal
governments considering the nature of the activity, past consultation
efforts, available resources, timing considerations, and all other
relevant factors. EPA would generally agree to consult when such a
request for consultation is made by a Tribal government, assuming the
proposed action may affect the Tribe.
    If a Tribe wishes to consult, EPA would follow the EPA Policy on
Consultation and Coordination with Indian Tribes, and consultation
procedures established by the relevant EPA regional office. If a Tribe
declines consultation or prefers coordination without government-to-
government consultation, the EPA Region would document this in the file
associated with the Regional Administrator's action and consultation
efforts would be concluded. If the Tribe does not respond, and
reasonable efforts to reach out to the Tribe are unsuccessful, the EPA
Region would document this in the file associated with the action and
would conclude efforts to initiate consultation. Even if the EPA Region
concludes such efforts without government-to-government consultation,
EPA will nonetheless consider the potential interests of the Tribe, as
well as EPA's responsibilities under the CWA, in its decision-making,
pursuant to the general trust relationship and other policies.

A. Proposed Baseline Designated Uses

    EPA's WQS regulation at 40 CFR part 131 requires states and
authorized Tribes to specify appropriate water uses to be achieved and
protected (40 CFR 131.10(a)). These uses are referred to as
``designated uses'' and defined at 40 CFR 131.3(f) as designated uses
specified in WQS for each water body or segment whether or not they are
being attained. Designated uses establish, and communicate to the
public, the environmental management objectives and water quality goals
for a

state or authorized Tribe's waters. Clear and accurate designated uses
are essential to meet the ultimate objective of CWA section 101(a) to
restore and maintain the chemical, physical, and biological integrity
of the Nation's waters.
    The CWA distinguishes between two broad categories of uses: uses
specified in section 101(a)(2) of the Act and uses specified in section
303(c)(2) of the Act. The national goal in CWA section 101(a)(2) is
water quality that provides for the protection and propagation of fish,
shellfish, and wildlife and for recreation in and on the water
``wherever attainable.'' CWA section 303(c)(2)(A) also requires states
and authorized Tribes to establish WQS ``taking into consideration
their use and value'' for a number of purposes, including those
addressed in section 101(a)(2) of the Act.
    The term ``uses specified in section 101(a)(2) of the CWA'' as used
in EPA's WQS regulations, refers to uses, including subcategories of
uses, that provide for the protection and propagation of fish
(including aquatic invertebrates), shellfish, and wildlife, and
recreation in and on the water.\19\ In addition, EPA interprets CWA
section 101(a)(2) to refer not only to protecting water quality so that
fish and shellfish and other aquatic life thrive, but also to
protecting aquatic life as a food source.\20\ EPA defines ``non
101(a)(2) uses'' as those uses that are not related to the protection
or propagation of fish, shellfish, wildlife, or recreation in or on the
water (see 40 CFR 131.3(q)). These uses include public water supply,
agricultural activity, industrial activity, and navigation which are
listed in CWA section 303(c)(2)(A) but not in CWA section 101(a)(2).
The CWA requires that states and authorized Tribes take all of the uses
listed in CWA section 303(c)(2)(A) into consideration when designating
uses, but their uses must include 101(a)(2) uses unless the State or
authorized Tribe demonstrates that such uses are unattainable. 40 CFR
131.10(j).
---------------------------------------------------------------------------

    \19\ 80 FR 51024, August 21, 2015. Preamble to the final Water
Quality Standards Regulatory Revisions, 2015.
    \20\ 80 FR 51024, August 21, 2015. Preamble to the final Water
Quality Standards Regulatory Revisions, 2015.
---------------------------------------------------------------------------

    Consistent with CWA section 101(a)(2) and EPA's regulation at 40
CFR 131.10, EPA proposes to promulgate the following designated uses
for Indian reservation waters consistent with section 101(a)(2). Water
quality must provide for:
     Aquatic Life: Protection and propagation of fish,
shellfish, and wildlife, which includes protection of the health of
human consumers of fish, shellfish, and other aquatic life.
     Primary Contact Recreation: Provides for recreation in and
on the water.
    Since 1983, EPA's WQS regulation at 40 CFR 131.10(j) and (k) has
required that WQS protect CWA section 101(a)(2) uses unless states and
authorized Tribes demonstrate that those uses are infeasible to attain
through a use attainability analysis (UAA) consistent with 40 CFR
131.10, effectively creating a rebuttable presumption of
attainability.\21\ If a state or authorized Tribe adopts designated
uses other than the uses specified in section 101(a)(2) of the Act, it
must document how its consideration of the use and value of water for
those uses appropriately supports the state's action (Sec.  131.10(a)).
---------------------------------------------------------------------------

    \21\ EPA's 1983 regulation and ``the rebuttable presumption
stemming therefrom'' have been upheld as a ``permissible
construction of the statute'' (Idaho Mining Association v. Browner,
90 F. Supp. 2d 1078, 1097-98 (D. Idaho 2000)). Also refer to, Water
Quality Standards Regulatory Revision (80 FR 51019, p. 51024 and FN
12), August 21, 2015.
---------------------------------------------------------------------------

    During the Tribal consultation process, many Tribes stressed the
value and importance of protecting water quality at levels appropriate
for use in various cultural and traditional activities of individual
Tribes. CWA section 303(c)(2)(A) provides that uses are to protect the
``public health or welfare'' and consider a water body's use and value
for various enumerated and other purposes.\22\ Cultural and traditional
uses serve to protect the health and welfare of Tribal members
exercising such uses and are thus within the purposes enumerated in the
Act. EPA proposes to promulgate an explicit cultural and traditional
designated use as part of the baseline WQS to ensure full protection of
such uses. Accordingly, the baseline WQS would contain a third
designated use in addition to the two described above:
---------------------------------------------------------------------------

    \22\ CWA section 303(c)(2)(A): Such standards shall be such as
to protect the public health or welfare, enhance the quality of
water and serve the purposes of this chapter. Such standards shall
be established taking into consideration their use and value for
public water supplies, propagation of fish and wildlife,
recreational purposes, and agricultural, industrial, and other
purposes, and also taking into consideration their use and value for
navigation.
---------------------------------------------------------------------------

     Cultural and traditional uses: Protection of cultural and
traditional uses of reservation waters.
    EPA is not proposing to define cultural and traditional uses in
more detail in this rule because they can include a variety of uses
specific to the ceremonies and traditions of each Tribe, and each use
may require different levels of protection. For example, when
developing NPDES permit limits, a separate limit may not be necessary
to protect full body immersion in the water or fishing-related cultural
or traditional practices, if the limit to protect the primary contact
recreation use is sufficient. However, practices that require
protection of aquatic plants used for basket weaving, for example, may
not be adequately covered by an aquatic life use or its protective
criteria. Further, Tribal treaty or other reserved rights to fish,
hunt, and/or gather on Indian reservations could generally be protected
by such cultural and traditional designated uses, to the extent they
are not protected by an aquatic life use or primary contact recreation
use.
    EPA is considering whether to promulgate any non-101(a)(2) uses,
such as public water supply use, agricultural use, or industrial use,
for all waters covered by this baseline WQS rule in light of the
requirements of 303(c) and 40 CFR 131.10(a). Specifically, EPA is
soliciting comment on whether EPA should designate a public water
supply use for all Indian reservation fresh waters \23\ covered by the
scope of this rule or whether this use is best addressed by allowing
Tribes to request such a designation, as explained below. Many states
have established such a use on large numbers of their water bodies, and
EPA anticipates that many Tribes may similarly desire such a use to be
designated on some or most of their waters to help protect public water
supply sources. However, an important consideration is that designating
a public water supply use for all Indian reservation waters in this
rule without accounting for local considerations could result in a
designation on a water body where such a use is not appropriate (e.g.,
waters that may not have enough flow to support public water supply
uses).
---------------------------------------------------------------------------

    \23\ Waters in which the salinity is equal to or less than 1
part per thousand 95% or more of the time. Model Water Quality
Standards Template for Waters on Indian Reservations, June 2020.
https://www.epa.gov/wqs-tech/water-quality-standards-tools-tribes#tab3.
---------------------------------------------------------------------------

    If EPA does not promulgate a public water supply use for all Indian
reservation fresh waters covered by the final baseline WQS rule, a
Tribe may subsequently request the Regional Administrator designate a
public water supply use for its reservation water bodies if available
information indicates that (1) there is use and value for such a use
and (2) it is thus appropriate to be designated after this rule becomes
effective. Conversely, if EPA were to promulgate a public water supply
use for all Indian reservation waters covered by the final baseline WQS
rule, a Tribe

could subsequently request that the Regional Administrator remove such
a designation, consistent with 40 CFR 131.10(a) and (k)(3), from
specific waters if information is available indicating that (1) there
is no use and value for such a designated use; and (2) it is not an
appropriate designated use.
    EPA recognizes that the designated uses proposed in this rule may
not be attainable in all Indian reservation waters because of Tribe-
specific or site-specific factors. In such circumstances, EPA is
proposing a process to subsequently revise designated uses (or
establish WQS variances) in the future or add additional designated
uses consistent with EPA's WQS requirements. Discussion of a Federal
administrative procedure for a Regional Administrator to revise
baseline designated uses for specific Indian reservation water bodies
is provided in section VI of this preamble.
    EPA invites comments on the proposed designated uses. Specifically,
EPA requests comments on establishing an aquatic life use and primary
contact recreation use consistent with CWA section 101(a)(2) for all
Indian reservation waters covered by the final baseline WQS rule. EPA
also requests comments on the explicit inclusion of a cultural and
traditional designated use. Additionally, EPA requests comments on
whether to include any of the designated uses specified in CWA section
303(c)(2)(A) but not included in CWA section 101(a)(2) such as public
water supply use, agricultural use, or industrial use for all Tribal
reservation waters identified for coverage under this baseline WQS
proposed rule.

B. Proposed Baseline Water Quality Criteria

1. Overview of Water Quality Criteria in Standards
    EPA's WQS regulation at 40 CFR 131.11 requires states and
authorized Tribes to adopt water quality criteria that protect
designated uses. These criteria must be based on sound scientific
rationale, must contain sufficient parameters to protect the designated
use, must support the most sensitive use where multiple use
designations apply, and may be expressed in either narrative or numeric
form. (See 40 CFR 131.11(a) and (b)) Special requirements apply to
priority pollutants as discussed below. Narrative criteria are
qualitative descriptions of the conditions necessary to protect a water
body's designated use, while numeric criteria--expressed as levels,
concentrations, toxicity units or other values--are quantitative
descriptions of those conditions. Narrative criteria accompanied by
binding translation procedures, as part of the water quality standards,
provide a basis for determining case-specific numeric values to protect
the applicable designated use. Both narrative and numeric criteria
provide a basis for the development of NPDES permit limits, water
quality assessments, and other CWA purposes.
    CWA section 304(a)(1) requires EPA to develop and publish, and from
time-to-time update, recommended criteria for water quality accurately
reflecting the latest scientific knowledge regarding concentrations of
specific chemicals or levels of parameters in water that protect
aquatic life and human health. These recommended criteria are based on
sound scientific rationale to protect the designated use(s), and are
based solely on data and scientific judgments on the relationship
between pollutant concentrations and environmental and human health
effects. CWA section 304(a)(1) criteria do not reflect consideration of
economic impacts or the technological feasibility of meeting the
concentrations in ambient water.
    CWA section 304(a)(2) requires EPA to develop and publish, and from
time-to-time update, information on the factors necessary to restore
and maintain the chemical, physical, and biological integrity of all
navigable waters and the factors necessary for the protection and
propagation of shellfish, fish, and wildlife for classes of receiving
waters and to allow recreation in and on the water.
    States and authorized Tribes should establish numeric criteria
based on EPA's recommended CWA section 304(a) criteria, CWA section
304(a) criteria modified to reflect site-specific conditions, or other
scientifically defensible methods. See 40 CFR 131.11(b)(1). EPA's
regulation at 40 CFR 131.11(b)(2) provides that states and authorized
Tribes should establish narrative criteria where numeric criteria
cannot be determined or to supplement numeric criteria. EPA must comply
with these requirements when it promulgates Federal WQS (40 CFR
131.22(c)).
    CWA section 303(c)(2)(B) requires states to adopt numeric criteria,
where available, for all toxic pollutants listed pursuant to CWA
section 307(a)(1) for which EPA has published CWA section 304(a)
criteria, as necessary to support the states' and authorized Tribes'
designated uses. ``Priority toxic pollutants'' are identified in 40 CFR
part 423, appendix A--126 Priority Pollutants. As articulated in EPA's
guidance \24\ that addresses the adoption of criteria for priority
toxic pollutants in WQS, one approach to meet this requirement includes
adopting a procedure for applying a narrative WQS provision that
prohibits toxicity in receiving waters. Such a procedure would be used
in calculating derived numeric values, which are to be used for all
purposes under CWA section 303(c). At a minimum, states and authorized
Tribes must develop numeric values for CWA section 307(a) toxic
pollutants for which EPA has published CWA section 304(a) criteria
where these pollutants are discharged or present in the affected waters
and could reasonably be expected to interfere with designated uses.
---------------------------------------------------------------------------

    \24\ Transmittal of Final ``Guidance for State Implementation
for Water Quality Standards under CWA section 303(c)(2)(B).''
December 1988. https://www.epa.gov/sites/production/files/2014-10/documents/cwa303c-hanmer-memo.pdf.
---------------------------------------------------------------------------

    As discussed in more detail below, EPA proposes narrative criteria
with binding numeric translation procedures designed as the applicable
WQS to protect the proposed designated uses for Indian reservation
waters covered by a final rule. EPA would use these procedures to
translate the narrative criteria into numeric values on a case-by-case
basis to best reflect site-specific conditions and consideration of new
and/or available information representing the latest sound science as
discussed in more detail below. These procedures would be used for all
purposes under CWA section 303(c) as necessary to protect the
applicable designated uses. Although not specifically required for non-
priority pollutants, providing the same information for those other
pollutants is helpful toward meeting the CWA goals and increasing
transparency for stakeholders.
2. EPA's Proposed Approach for Baseline Water Quality Criteria
    This rulemaking proposes to establish CWA-effective WQS for waters
on more than 250 Indian reservations nationwide where EPA is the
primary CWA implementing authority. The baseline criteria would provide
scientifically sound criteria, protect the applicable designated uses,
and enable an appropriate degree of customization to best account for
site-specific conditions and water attributes of importance to
individual Tribes.
    Consistent with the requirements of the CWA and EPA's regulation at
40 CFR part 131, EPA proposes to establish the narrative water quality
criteria in proposed 40 CFR 131.XX(d)(1) to protect the applicable
baseline

designated uses proposed in this rule and discussed in section V.A of
this preamble. The proposed narrative criteria are as follows:

    1. All waters shall be free from toxic, radioactive,
conventional, non-conventional, deleterious or other polluting
substances in amounts that will prevent attainment of the applicable
baseline designated uses;
    2. All waters shall be free from adverse impacts to the
chemical, physical or hydrologic, or biological integrity caused by
pollutants or pollution that prevent the attainment of applicable
designated uses;
    3. All waters shall be free from substances attributable to
wastewater or other discharges that:
    A. Settle to form objectionable deposits;
    B. Float as debris, scum, oil, or other matter to form
nuisances;
    C. Produce objectionable color, odor, taste, or turbidity; or
    D. Produce undesirable or nuisance aquatic life.
    4. All waters shall be free from conditions that would likely
jeopardize the continued existence of any threatened or endangered
species listed under the Federal Endangered Species Act or result in
the destruction or adverse modification of such species' critical
habitat.
    5. All waters shall maintain a level of water quality at their
pour points to downstream waters that provide for the attainment and
maintenance of the water quality standards of those waters,
including the waters of another state or a federally recognized
Tribe.

    For the first proposed element of the baseline narrative criteria
under 1., the term ``polluting substances'' includes ``pollutants'' as
defined in CWA section 502(6) and 40 CFR 122.2. The statute defines
``pollutant'' broadly to include dredged spoil, solid waste,
incinerator residue, sewage, garbage, sewage sludge, munitions,
chemical wastes, biological materials, radioactive materials, heat,
wrecked or discharged equipment, rock, sand, cellar dirt and
industrial, municipal, or agricultural waste discharged into water. CWA
section 502(6). For regulatory purposes, pollutants are grouped into
conventional, toxic, and nonconventional pollutant categories under the
National Pollutant Discharge Elimination System (NPDES) program:
    Conventional pollutants are those defined in CWA section 304(a)(4)
and 40 CFR 401.16 (5-day biochemical oxygen demand, total suspended
solids, fecal coliform, pH, and oil and grease).
    Toxic (priority) pollutants are those defined in CWA section
307(a)(1) (and listed in 40 CFR 401.15 and appendix A of 40 CFR part
423) and include 126 metals and predominately manmade organic
compounds.
    Nonconventional pollutants are those that do not fall under either
of the above categories (conventional or toxic pollutants) and include
parameters such as chlorine, ammonia, nitrogen, phosphorus, dissolved
oxygen, temperature, chemical oxygen demand (COD), and whole effluent
toxicity (WET).\25\
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    \25\ See https://www.epa.gov/sites/default/files/2015-09/documents/pwm_chapt_01.pdf.
---------------------------------------------------------------------------

    The second proposed element of the baseline narrative criteria
under 2. relates to adverse impacts, caused by pollutants or pollution,
to the chemical, physical or hydrologic, or biological integrity of the
waters covered under this proposed rule. The term ``pollution'' is
defined in CWA section 502(19) as the man-made or man-induced
alteration of the chemical, physical, biological, and radiological
integrity of water.
    Chemical characteristics of waterbodies include values for
parameters such as ions, hardness, pH, and dissolved organic carbon
(DOC).
    Physical and hydrologic characteristics and physical habitat of
waterbodies, in the broad sense, include all those structural
attributes that influence or provide sustenance to organisms within the
water body, including the characteristic pattern of flow magnitude,
timing, duration, frequency, and rate of change of a water
body.26 27 Hydrology and habitat play a central role in
supporting the chemical, physical, and biological integrity of streams
and rivers and the services they provide. In addition, those
characteristics are critical for addressing resiliency of watersheds in
the face of climate change. EPA recognizes that Tribes are
disproportionately vulnerable to the impacts of climate change, due in
part to their dependence on specific geographic areas for their
livelihoods; unique cultural, economic and political characteristics;
and limited resources to prepare for, respond to and recover from
climate-related hazards.\28\ There is a strong need to develop
adaptation strategies in partnership with Tribes that promote
sustainability and reduce the impact of climate change on Tribes.\29\
Observations, oral and written knowledge, innovations, practices, and
beliefs developed by Tribes through interaction and experience with the
environment contributes to the scientific, technical, social, and
economic advancements of the United States and our collective
understanding of the natural world. This knowledge should be fully
integrated into the adaptation strategies. Adaptive capacity, or the
ability of a stream ecosystem to withstand climate-driven stresses, may
be seen in rivers whose flow patterns more closely resemble the natural
flow regime.\30\
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    \26\ Consolidated Assessment and Listing Methodology, USEPA,
July 2002.
    \27\ USGS-EPA Technical Report: Protecting Aquatic Life from
Effects of Hydrologic Alteration, also called the Hydrologic
Criteria Technical Document. 2016.
    \28\ See https://www.epa.gov/system/files/documents/2021-09/epa-climate-adaptation-plan-pdf-version.pdf.
    \29\ See https://www.epa.gov/sites/default/files/2016-04/documents/ow-climate-change-adaptation-plan.pdf.
    \30\ USGS-EPA Technical Report: Protecting Aquatic Life from
Effects of Hydrologic Alteration, also called the Hydrologic
Criteria Technical Document. 2016.
---------------------------------------------------------------------------

    Biological characteristics of water bodies include the ability of
an aquatic ecosystem to support and maintain a balanced and indigenous
community of organisms having species composition, diversity,
population densities, and functional organization similar to that of
reference conditions.
    The third proposed element of the baseline narrative criteria under
3. relates specifically to the discharge of substances that adversely
affect the waters covered by this proposed rule. This element includes
provisions that would prohibit the discharge of substances that would
limit the enjoyment or utility of these waters.
    The fourth proposed element of the baseline narrative criteria
under 4. would prohibit conditions that would likely jeopardize
endangered or threatened species that are listed under the Endangered
Species Act or result in the destruction or adverse modification of
such species' critical habitat.
    The fifth proposed element of the baseline narrative criteria under
5. would require that all waters maintain a level of water quality at
their pour points to downstream waters that provide for the attainment
and maintenance of the water quality of downstream waters of those
waters, including the waters of another state or a federally recognized
Tribe. In this context, ``pour points'' refers to the points of entry
into downstream water bodies. Pursuant to CWA sections 303 and 101(a),
the Federal regulation at 40 CFR 131.10(b) requires that upstream WQS
ensure the attainment and maintenance of downstream WQS.
    The rationale for establishing a downstream protection narrative
criterion is described in an EPA guidance document entitled
``Protection of Downstream Waters in Water Quality Standards:
Frequently Asked Questions (June 2014).'' In that document, EPA
interprets the term ``downstream'' to include both intra- and
interstate waters, as well as waters that form a boundary between
adjacent

jurisdictions. The document highlights that designated uses and water
quality criteria that ensure attainment and maintenance of downstream
WQS (1) help to avoid situations where downstream segments become
impaired due, either in part or exclusively, to pollution source(s)
located in upstream segments; (2) may help support more equitable use
of any assimilative capacity available to upstream and downstream
pollution sources and/or jurisdictions and may facilitate restoration
of the downstream waters; and (3) prevents the shifting of
responsibility for pollution reductions from upstream sources and/or
jurisdictions to downstream sources and/or jurisdictions.
    The document further notes that state and Tribal designated uses
and criteria that protect downstream waters may increase the resiliency
of the United States' waters to climate change and may help address
environmental justice issues in urban waters. In addition, designated
uses and criteria that ensure attainment and maintenance of downstream
WQS facilitate consistent and efficient implementation and coordination
of water quality-related management actions (e.g., water quality
monitoring and assessment, development of TMDLs; watershed-based
restoration and protection plans; NPDES permitting; and CWA section 401
certifications).
    EPA invites comments on the proposed narrative water quality
criteria.
3. Proposed Numeric Translation Procedures
    EPA is proposing binding numeric translation procedures as part of
the baseline WQS that would be used to develop numeric values, or
``translations,'' of the narrative criteria in local situations to
protect the applicable designated uses. Specifically, the binding
numeric translation procedures in proposed 40 CFR 131.XX(d)(2) would
require the Regional Administrator to use the procedures as necessary
to derive numeric translations for specific water bodies as needed for
all purposes under the CWA. As such, these translations would occur
during CWA implementation and would comply with public participation
requirements of applicable CWA implementation programs. EPA has
included the words ``as necessary'' to recognize not only that numeric
values may be needed for different parameters in different
circumstances, in accordance with EPA regulations, but also to reflect
variations in the way criteria are applied in different CWA
implementation programs.
a. Proposed Numeric Translation Procedures and Derivation of Numeric
Values
    The proposed numeric translation procedures are provided in 40 CFR
131.XX(d)(2) of the proposed rule. The five options established under
the procedures are summarized in Table 1 of this preamble below.

 Table 1--Summary of Proposed Procedures for EPA To Translate Narrative
                       Criteria to Numeric Values
------------------------------------------------------------------------

------------------------------------------------------------------------
                               Option One
------------------------------------------------------------------------
For parameters for which EPA has    Translate the baseline narrative
 section 304(a) criteria             criteria using EPA's national
 recommendations.                    recommended water quality criteria
                                     published under section 304(a).
------------------------------------------------------------------------
                               Option Two
------------------------------------------------------------------------
For parameters for which EPA has    Translate the baseline narrative
 section 304(a) criteria             criteria using EPA's national
 recommendations, and information    recommended water quality criteria
 and/or data are available that      published under section 304(a) of
 more accurately reflect site-       the CWA modified to reflect site-
 specific conditions.                specific conditions and aquatic
                                     communities based on a sound
                                     scientific rationale, including EPA
                                     published methodologies if
                                     available, incorporating where
                                     relevant:
                                     A fish consumption rate
                                     protective of Tribal fish consumers
                                     or EPA's latest default fish
                                     consumption rate, if appropriate,
                                     or
                                        Available ambient
                                        monitoring data reflecting site-
                                        specific water chemistry inputs,
                                        or
                                        Protective default water
                                        chemistry inputs reflecting
                                        published EPA guidance, where
                                        available, or
                                        Indigenous Knowledge,
                                        often referred to as Traditional
                                        Ecological Knowledge, as
                                        appropriate, or
                                        Other scientifically
                                        defensible assessments, for
                                        example, guidance published by
                                        EPA regions, or those related to
                                        Endangered Species Act
                                        consultation.
------------------------------------------------------------------------
                              Option Three
------------------------------------------------------------------------
Where Tribal or state numeric       Translate the baseline narrative
 criteria are available (as          criteria using numeric criteria
 described at right) that are more   available in:
 appropriate, and for parameters     WQS adopted by the Tribe
 for which EPA does not have CWA     but not yet CWA effective, or
 section 304(a) criteria             Applicable CWA-effective
 recommendations.                    WQS in an adjacent or other
                                     relevant state(s) or Tribe(s)
                                    that are in either case based on a
                                     sound scientific rationale, reflect
                                     similar waterbody characteristics,
                                     and ensure protection of the
                                     applicable designated uses
                                     established under this rule, taking
                                     into consideration Indigenous
                                     Knowledge, as appropriate.
------------------------------------------------------------------------
                               Option Four
------------------------------------------------------------------------
For waters of the Great Lakes       Translate the baseline narrative
 System.                             criteria using provisions of the
                                     Water Quality Guidance for the
                                     Great Lakes System (40 CFR part
                                     132), where applicable, to ensure
                                     that the translations are as
                                     protective as required by 40 CFR
                                     part 132.
------------------------------------------------------------------------
                               Option Five
------------------------------------------------------------------------
If none of the above options apply  EPA may rely on existing CWA
 or are available.                   implementation provisions to
                                     translate applicable narrative
                                     criteria, as necessary.
------------------------------------------------------------------------

    Details regarding each of these options are as follows.
    Option One. In translating the narrative criteria for specific
situations, the Regional Administrator could rely on EPA's current
national recommended CWA section 304(a) water quality criteria,\31\
where available, to set appropriate standards to ensure protection of
the applicable baseline designated uses. These water quality criteria
provide guidance for states and authorized Tribes in adopting WQS under
CWA section 303(c). They also provide guidance to EPA when promulgating
WQS.
---------------------------------------------------------------------------

    \31\ See Current Water Quality Criteria Tables at https://www.epa.gov/wqc.
---------------------------------------------------------------------------

    Option Two. The Regional Administrator could rely on Option Two if
information or data are available that more accurately reflect site-
specific

conditions. The second option of the binding translation procedure
provides that EPA would modify the CWA section 304(a) recommended
criteria to protect site-specific conditions based on a sound
scientific rationale, including EPA published methodologies, if
available, and, as appropriate, Indigenous Knowledge (IK), often
referred to as Traditional Ecological Knowledge (TEK), where consistent
with EPA's regulations and CWA statutory requirements,32 33
incorporating where relevant, but not limited to: (1) a fish
consumption rate protective of Tribal fish consumers or EPA's latest
default fish consumption rate, if appropriate, or (2) available ambient
monitoring data reflecting site-specific water chemistry inputs, or (3)
protective default inputs reflecting published EPA guidance where
available, or (4) other scientifically defensible assessments, for
example, those related to Endangered Species Act consultation.
---------------------------------------------------------------------------

    \32\ Guidance for Federal Departments and Agencies on Indigenous
Knowledge. https://www.whitehouse.gov/wp-content/uploads/2022/12/OSTP-CEQ-IK-Guidance.pdf.
    \33\ EPA Policy on Environmental Justice for Working with
Federally Recognized Tribes and Indigenous People (2014). https://www.epa.gov/sites/default/files/2017-10/documents/ej-indigenous-policy.pdf.
---------------------------------------------------------------------------

    This option provides that EPA may consider available data and
information concerning the physical, chemical, and biological quality
of the waters in Indian country and adjacent waters; scientifically
defensible technical and scientific information, including EPA
published methodologies, IK, as appropriate, ambient monitoring data
reflecting site-specific waterbody chemistry and any EPA technical and
regional guidance to inform those calculations; information regarding
Tribal treaty or other reserved rights to aquatic or aquatic-dependent
resources; and any EPA guidance on policy for, and implementation of,
the WQS program, including the Water Quality Standards Handbook.\34\
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    \34\ EPA Water Quality Standards Handbook. https://www.epa.gov/wqs-tech/water-quality-standards-handbook.
---------------------------------------------------------------------------

    EPA has developed several procedures to derive site-specific
aquatic life criteria. The Recalculation Procedure accounts for
relevant differences between the sensitivities of the aquatic organisms
in the national dataset and the sensitivities of organisms that are
present at the site. For more information, refer to EPA's Revised
Deletion Process for the Site-specific Recalculation Procedure for
Aquatic Life Criteria (2013). For fixed and hardness-based metals
criteria (currently metals other than aluminum and copper), the Water-
Effect Ratio (WER) procedure accounts for relevant differences between
the toxicities of a metal in laboratory dilution water and in the site
water. In performing a WER, care must be taken to ensure that samples
and tests are representative of the potential conditions at a site,
such that the WER-derived criteria continue to be protective under
conditions when the metals are highly bioavailable. For more
information, refer to EPA's Interim Guidance on Determination and Use
of Water-Effect Ratios for Metals (1994) and Modifications to Guidance
Site-Specific Criteria (1997). EPA's national recommended CWA section
304(a) criteria for aluminum and copper both take site-specific water
chemistry into account, obviating the need for a separate procedure
like the WER.
    During Tribal consultation, many Tribes expressed support for use
of appropriate fish consumption rates, one of the input parameters used
to calculate human health criteria, to reflect the true rate of
subsistence consumption by a Tribe. EPA recommends that Regional
Administrators calculating human health criteria select a fish
consumption rate based upon local data. Where sufficient data are
available, a fish consumption rate should be selected that reflects
consumption that is not suppressed by fish availability or concerns
about the safety of fish for human consumption. Regional Administrators
could rely on use of the ``Tribal/State Human Health Criteria
Calculator,'' \35\ available on EPA's website, to adjust EPA's CWA
section 304(a) human health criteria recommendations to reflect a
Tribe's fish consumption rate and selected cancer risk level.
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    \35\ See https://www.epa.gov/wqs-tech/water-quality-standards-tools-tribes.
---------------------------------------------------------------------------

    In 2015, EPA revised 94 of the existing CWA section 304(a) human
health criteria recommendations to reflect the latest scientific
information, including updated exposure factors (body weight, drinking
water consumption rate, fish consumption rate), bioaccumulation
factors, and toxicity factors (reference dose, cancer slope factor).
The updated criteria follow EPA's current methodology for deriving
human health criteria (USEPA 2000).\36\ EPA's updated recommended fish
consumption rate (22 g/day) is protective of the general population of
fish consumers. EPA's national default subsistence value of 142 g/day
represents subsistence fishers whose daily consumption is greater than
the general population, as presented in EPA's 2000 Human Health
Methodology. A further discussion of fish consumption rates may be
found in the 2000 Human Health Methodology and EPA's 2016 Guidance for
Conducting Fish Consumption Surveys.
---------------------------------------------------------------------------

    \36\ Methodology for Deriving Ambient Water Quality Criteria for
the Protection of Human Health (2000), EPA-822-B-00-004, October
2000.
---------------------------------------------------------------------------

    When translating the narrative criteria to protect consumers of
fish, EPA would consult with the Tribe and determine the need for a
modified fish consumption rate in those cases where the Tribe or EPA
can support the modified rate with adequate scientifically defensible
data and information,\37\ or establish that Tribes rely on fish
consumption for subsistence (thereby justifying applying the 142 g/day
rate). Applicable treaty or other reserved fishing rights would inform
this determination. In those consultations, EPA would apply its
Guidance for Discussing Tribal Treaty Rights.\38\
---------------------------------------------------------------------------

    \37\ Guidance for Conducting Fish Consumption Surveys. 2016:
https://www.epa.gov/sites/default/files/2016-12/documents/guidance-fish-consumption-surveys.pdf.
    \38\ EPA Policy on Consultation and Coordination with Indian
Tribes: Guidance for Discussing Tribal Treaty Rights. February 2016.
https://www.epa.gov/sites/default/files/2016-02/documents/tribal_treaty_rights_guidance_for_discussing_tribal_treaty_rights.pdf
.
---------------------------------------------------------------------------

    Option Three. The binding translation procedure allows the Regional
Administrator to utilize Option Three where appropriate. Specifically,
the Regional Administrator could utilize this option when WQS adopted
by the Tribe are not yet CWA effective, or CWA-effective WQS applicable
in an adjacent or other relevant state(s) or Tribe(s), are based on a
sound scientific rationale, reflect similar waterbody characteristics,
and ensure protection of the applicable designated uses, taking into
consideration IK, as appropriate.
    EPA proposes Option Three to recognize the feedback received during
the Tribal consultation process. Many Tribes stressed the value and
importance of relying on existing Tribal WQS that, although not yet
EPA-approved, are based on a sound scientific rationale and could fill
gaps or provide more refined coverage than is available under Option
One or Two. Similarly, under Option Three, the Regional Administrator
could also rely on Tribal or state numeric criteria that are more
appropriate because, for example, they protect designated uses not
considered in Options One or Two or consider site-specific factors,
exposure routes, human health

endpoints, or other factors not considered in Option One or Two; or for
parameters for which EPA does not have CWA section 304(a) criteria
recommendations.
    Option Four. The Regional Administrator would use the Water Quality
Guidance for the Great Lakes System (40 CFR part 132) (part 132
Guidance), where applicable, to translate the narrative criteria, as
defined in 40 CFR 132.2, to ensure appropriate protection of Great
Lakes waters. Both the Great Lakes provisions for water quality
criteria discussed here (proposed 40 CFR 131.XX(d)(2)(iv)) and the
broader requirements for baseline WQS decisions to be consistent with
40 CFR part 132 (proposed 40 CFR 131.XX(k)) are designed to reinforce
the requirements in CWA section 118(c)(2) that all WQS, antidegradation
policies, and implementation procedures within the Great Lakes system
must continue to be consistent with the 40 CFR part 132 Guidance.
    Option Five. For those parameters without established CWA section
304(a) water quality criteria recommendations, the Regional
Administrator would follow Option Three or Option Four of the
translation procedures if applicable. In circumstances where none of
the first four options are applicable, Option Five provides that the
Regional Administrator would rely on existing CWA implementation
provisions to translate the baseline narrative criteria, where
necessary. For example, the Regional Administrator could rely on 40 CFR
122.44(d)(1)(vi)(A) and (C) for NPDES permitting purposes. This fifth
option would ensure consistency with the proposed requirement that the
Regional Administrator derive numeric translations of the baseline
narrative criteria for all purposes under CWA section 303(c) for
specific parameters to protect the applicable designated uses for
specific water bodies.
    For all five options, when EPA translates the baseline narrative
criteria for CWA implementation purposes after the final baseline WQS
rule is in effect, the associated numeric values would be used for
purposes of developing CWA section 402 and 404 permits, section 303(d)
lists and TMDLs, and section 401 certifications, where applicable. In
each case, EPA would identify and explain the derived numeric values as
part of the public process associated with the respective CWA
implementation program. EPA would rely on the public participation
requirements associated with the respective CWA implementation programs
to provide for public review of any resulting numeric values. At its
discretion, a Regional Administrator could also provide a specific
public process on EPA's translation of the baseline narrative criteria,
in advance of the public process associated with the respective CWA
implementation program, to solicit input from affected parties
specifically on the derivation of the numeric values. EPA would make
the numeric values, along with the spatial extent (i.e., waterbody
segment) for which the narrative criteria were translated, publicly
available at a website that will be provided in the final rule. At the
request of a Tribe, EPA could also provide this information to the
Tribe in a non-electronic format.
    Making information available to the respective Tribe, the public,
the regulated community, and other stakeholders is important to
ensuring regulatory certainty and clarity. Documents associated with
CWA implementation also provide transparency for the public. For
federally issued NPDES permits, for example, EPA would describe in the
permit fact sheet or statement of basis how it used the numeric values
translated from the applicable baseline narrative criteria to derive
WQBELs.
    EPA solicits comment on EPA's proposed approach to rely on
narrative criteria with an associated binding numeric translation
procedure. EPA also invites comment on other approaches that should be
considered, including reliance on IK, as appropriate.
b. EPA To Translate the Baseline Narrative Criteria
    EPA is the authority responsible for translating the applicable
baseline narrative criteria for use in CWA regulatory actions because
the baseline WQS would be federally promulgated, and the proposed
regulatory text directs EPA to undertake this translation step. The
most common example would be EPA issuance of a NPDES permit for a
discharge to Indian reservation waters where the baseline WQS would
apply. The EPA regional office (including the WQS and implementing
programs) would rely on the binding translation procedures to translate
narrative criteria for pollutants in the discharge to determine if they
have a reasonable potential to cause or contribute to an exceedance of
WQS. EPA would use those numeric values to derive WQBELs for those
pollutants. Other implementation examples are discussed in section VII
of this preamble.
    EPA also notes that if situations arise where there are significant
differences between upstream state WQS and baseline WQS, EPA would
address them similarly to how EPA currently works with two states, or
an authorized Tribe and a state, to address significantly differing
standards set on a shared water body. Early communication among the
potentially affected jurisdiction(s) and EPA is key to help define the
scope of the issue and determine protective endpoints. This process
entails working with the applicable entities to ensure all WQS are
considered. States, Tribes, and EPA are also able to rely on the public
notice and comment opportunities to inform the derivation of numeric
values translated from the applicable baseline narrative criteria and
the establishment of WQBELs as mentioned previously. In addition, EPA's
regulation at 40 CFR 131.7 provides a mechanism for the resolution of
unreasonable consequences that may arise from differing WQS set by
states and authorized Tribes located on common bodies of water.
Although 40 CFR 131.7 does not apply to situations with different
Federal and state WQS on a shared water body, EPA could utilize
procedural steps similar to those laid out in that section where
appropriate to work with the relevant parties in a neutral fashion in
an effort to resolve the issues involved.

C. Proposed Baseline Antidegradation Policy and Implementation
Procedures

    Antidegradation requirements are an essential component of WQS and
play a critical role in maintaining and protecting valuable water
resources. Antidegradation provides a framework for maintaining and
protecting water quality that has already been achieved. This includes
maintaining and protecting existing uses,\39\ high quality waters, and
the water quality of outstanding national resource waters (ONRWs).
Maintaining water quality, particularly high water quality, is critical
to supporting public health, economic growth, community growth, and
high functioning natural systems. It provides a margin of safety that
will afford the water body increased resilience to potential future
stressors, including climate change. It is more cost effective and
resource efficient to keep water clean than to restore or remediate
waters that have been impaired. The Federal antidegradation regulation
in 40 CFR part 131 requires development and adoption of an
``antidegradation policy'' and development of ``antidegradation
implementation methods.'' 40 CFR 131.12.
---------------------------------------------------------------------------

    \39\ 40 CFR 131.3(e). ``Existing uses are those uses actually
attained in the water body on or after November 28, 1975, whether or
not they are included in the water quality standards.''

---------------------------------------------------------------------------

    EPA is proposing an antidegradation policy for Indian reservation
waters consistent with the antidegradation regulation at 40 CFR
131.12(a). The proposed antidegradation policy for Indian reservation
waters would establish three levels of protection: protection for
existing uses, protection for high quality waters, and protection for
ONRWs. Please refer to the proposed antidegradation policy found at 40
CFR 131.XX(e) of this proposed rule.
    Protection for existing uses (Tier 1) would require that the water
quality necessary to protect existing uses be maintained. ``Existing
uses'' are defined at 40 CFR 131.3(e) as those uses actually attained
in the water body on or after November 28, 1975, whether or not they
are included in the water quality standards. Tier 1 protection would
establish the floor of water quality for all Indian reservation waters.
    Protection for high quality waters (Tier 2) would require that
where water quality exceeds the levels necessary to support protection
and propagation of fish, shellfish, and wildlife, and recreation in and
on the water, that quality shall be maintained and protected. A
lowering of water quality could be allowed if the Regional
Administrator finds with written agreement from the Tribe, after public
involvement and intergovernmental coordination, that allowing lower
water quality is necessary to accommodate important economic or social
development in the area in which the waters are located. ``Exceeds'' in
this context refers to water quality being better than necessary to
support CWA section 101(a)(2) uses. The Regional Administrator must
assure that any lowering of high water quality still results in water
quality that protects existing uses. In addition, the Regional
Administrator must assure that no lowering of high water quality is
allowed unless statutory and regulatory requirements for existing point
sources and all Tribal-regulated,\40\ cost-effective, and reasonable
best management practices for nonpoint source controls are achieved.
Tier 2 protection is intended to establish protection for high quality
waters, and to provide a public, systematic decision-making process for
determining whether to allow limited degradation of water quality in
these high quality waters.
---------------------------------------------------------------------------

    \40\ See https://www.epa.gov/sites/default/files/2014-10/documents/davies-regrequire-memo.pdf.
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    This approach is in accordance with 40 CFR 131.12(a)(2) which
provides that water quality shall be maintained and protected unless
``the State'' finds that allowing lower water quality is necessary to
accommodate important economic or social development in the area in
which the waters are located. Here the Regional Administrator, as the
entity implementing the antidegradation policy, would be making such a
finding. In order to ensure that Tribes are able to exercise
appropriate oversight over their waters based on local priorities,
proposed 40 CFR 131.XX(e)(2) provides that the Regional Administrator
would not allow the lowering of high water quality unless the relevant
Tribe agrees in writing that such a lowering is necessary to
accommodate important economic or social development in the area in
which the waters are located. If the Tribe does not provide its written
agreement, then the Regional Administrator will maintain the current
high water quality WQS.
    In determining whether a lowering of high water quality is
necessary, the Regional Administrator and the Tribe would consider the
results of an analysis of practicable alternatives, which is an
analysis of pollution control and pollution prevention
alternatives.\41\ If identified, a less or non-degrading practicable
alternative would be selected for implementation consistent with 40 CFR
131.12(a)(2)(ii). The Regional Administrator and Tribe would also
consider the results of a socio-economic analysis which would assess
the social and economic importance of the activity to the community
impacted by the degraded water quality. These analyses could be
completed by the agency, the Tribe, or a third party (for example, the
discharger affecting water quality). EPA is considering whether these
analyses could be completed by third parties and solicits comment on
whether this rule should include such a requirement, or alternatively
leave open which entity will provide such information.
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    \41\ ``Practicable, in the context of Sec.  131.12(a)(2)(ii),
means technologically possible, able to be put into practice, and
economically viable.'' 40 CFR 131.3(n).
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    Protection for ONRWs (Tier 3) would require that water quality in
water bodies of exceptional recreational, ecological, or cultural
significance would be maintained and protected. The term ``cultural
significance'' is not a part of 40 CFR 131.12(a)(3). EPA is proposing
to include this language at proposed 40 CFR 131.XX(f)(4) to clarify
that Tribes are able to identify highly valued waters on their
reservations based on their cultural significance in keeping with the
intended purpose of this rule. This provision would establish the
highest level of protection for water bodies by prohibiting the
permanent lowering of water quality. However, activities that result in
short-term and temporary changes in the water quality of the ONRW may
be allowed. EPA interprets short-term and temporary as weeks or months,
and not years. The intent is to limit degradation to the shortest
possible time and prohibit any permanent degradation. EPA is not
proposing to classify any water body as an ONRW in the final baseline
standards rule. See the proposed antidegradation implementation method
at proposed 40 CFR 131.XX(f)(4) and the associated preamble discussion
of Tier 3 below for the process to nominate a water to be an ONRW.
    The purpose of this antidegradation policy would be to maintain and
protect the finite public resource of clean water and ensure that a
decision to allow a lowering of high water quality is made in a public
manner and serves the public good.
    EPA invites comments on the proposed antidegradation policy
provisions. EPA is not proposing to revise 40 CFR 131.12 with this
proposal, and thus does not seek comment on the provisions in 40 CFR
131.12. Rather, EPA invites comment on the antidegradation policy as
applied herein to certain Indian reservation waters for Tribal WQS
decisions.
    EPA also proposes to establish legally binding antidegradation
implementation methods consistent with 40 CFR 131.12(b) and proposed 40
CFR 131.XX(e). Please refer to the proposed antidegradation
implementation methods regulatory language found at 40 CFR 131.XX(f) of
this proposed rule.
    Antidegradation implementation methods (AIMs) are a set of
provisions that describe how a state's or authorized Tribe's
antidegradation policy will be implemented. As currently implemented
under 40 CFR 131.12, AIMs can be legally binding or in guidance. As
stated in 40 CFR 131.12(b), all states and authorized Tribes are
required to develop AIMs that are consistent with 40 CFR 131.12(a) and
their own antidegradation policy. States and authorized Tribes must
make these AIMs available to the public and must provide the public an
opportunity to provide input on the AIMs during their development and
any subsequent revision (40 CFR 131.12(b)).
    In addition to EPA's proposed antidegradation policy and consistent
with 40 CFR 131.12, EPA is proposing antidegradation implementation
methods, as provided at proposed Sec.  131.XX(f), which address the
following elements to implement EPA's proposed antidegradation policy:

     Existing use protection (Tier 1): describes how the
Regional Administrator would ensure the maintenance and protection of
existing uses and the water quality to protect the existing uses. EPA
would implement this provision for Tribes covered by this rule, by
reviewing and determining whether a lowering of water quality would
impair an existing use. If the Regional Administrator finds that a
water body has an existing use that has not been designated, such as a
public water supply use, the Regional Administrator would ensure
protection of that undesignated, but existing use. If an undesignated
use is identified as an existing use, then the Regional Administrator
would work with the Tribe to adopt this use as a designated use to
ensure its future protection. At minimum, 40 CFR 131.10(i) would
dictate that the EPA and Tribe determine the best way to revise
designated uses to protect any existing use that is presently being
attained.
     High quality water protection (Tier 2): (1) describes how
the Regional Administrator would identify high quality waters on a
parameter-by-parameter basis; (2) describes how the Regional
Administrator with written agreement from the Tribe, would determine
whether a lowering of high quality water is necessary to accommodate
important economic or social development in the area in which the
waters are located through an analysis of alternatives and a socio-
economic analysis; (3) describes how the Regional Administrator would
provide for public involvement and intergovernmental coordination on
any decision to lower water quality in a high quality water; (4)
describes how the Regional Administrator would assure that any lowering
of high water quality still results in water quality that protects
existing uses fully; (5) describes how the Regional Administrator would
assure that there shall be achieved the highest statutory and
regulatory requirements for all new and existing point sources and all
Tribal-regulated, cost-effective, and reasonable best management
practices for nonpoint source control when allowing a lowering of water
quality.\42\
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    \42\ See Davies, Tudor. 1994. Memorandum: Interpretation of
Federal Antidegradation Regulatory Requirement. https://www.epa.gov/sites/default/files/2014-10/documents/davies-regrequire-memo.pdf.
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     ONRW protection (Tier 3): describes how the Regional
Administrator would ensure the maintenance and protection of water
quality for waters identified as ONRWs. It also describes the
nomination process to assign waters as ONRWs. In this process, any
person or entity may nominate a specific water for such protection by
providing written documentation of the qualifications of the
reservation water to the Regional Administrator and the Tribe. The
Regional Administrator would make a final decision with written
agreement from the Tribe to assign the water as an ONRW and issue a
public notice regarding that decision. EPA would provide a publicly
available list of waters assigned as an ONRW at a website location to
be provided in the final rule.
    The requirements of the antidegradation policy and AIMs will be
triggered by a request from a discharger or entity for authorization
for any new or expanded regulated activity. Regulated activities
include, but are not limited to, any activity that requires a permit,
license, or water quality certification pursuant to sections 401, 402,
and 404 of the CWA. States and authorized Tribes may implement
antidegradation requirements in programs beyond those regulated under
the CWA, such as state- or Tribal-regulated nonpoint source programs or
voluntary programs. As part of the implementation of antidegradation in
CWA section 402 permits, antidegradation protections will also be
addressed in new or reissued general permits authorized, implemented,
or administered by the Regional Administrator either at the time the
permitting authority develops and issues the general permit or upon
review of an applicant's request to be covered by a general permit.
    For further discussion on AIMs, please refer to EPA's WQS Handbook,
Chapter 4 Antidegradation.\43\
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    \43\ EPA Water Quality Standards Handbook. https://www.epa.gov/wqs-tech/water-quality-standards-handbook.
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    EPA solicits comment on the proposed antidegradation implementation
methods.

D. Other Proposed Water Quality Standards Provisions of Baseline Water
Quality Standards

1. Mixing Zone Policy
    The proposed rule contains a detailed mixing zone policy that would
allow the Regional Administrator to establish mixing zones on a case-
by-case basis. But it would prohibit mixing zones for discharges of
bioaccumulative pollutants and for pathogens and pathogen indicators
without adequate evidence that designated uses will be protected. EPA's
proposed mixing zone policy in this proposed rule draws upon the mixing
zone policy included in EPA's Model WQS Template for Waters on Indian
Reservations,\44\ which builds upon mixing zone guidance produced by
EPA over the years and the state of Washington's existing state mixing
zone policy. EPA would follow its regulations regarding public notice
and opportunity for public comment in applying its mixing zone policy
in federally issued NPDES permits.
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    \44\ https://www.epa.gov/wqs-tech/water-quality-standards-tools-tribes#tab3.
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    A mixing zone (sometimes also called a regulatory mixing zone) is
defined through the NPDES permitting process and may be implemented in
any waterbody type or discharge configuration where rapid and complete
mixing does not occur. EPA's current guidance \45\ describes a mixing
zone as an allocated impact zone where certain water quality criteria
may be exceeded, provided that there is no lethality to aquatic
organisms that pass through the mixing zone; there are no significant
health risks to humans; and the designated and existing uses of the
water body as a whole are not impaired as a result of the mixing zone.
Allocated impact zones or mixing zones, if disproportionately large,
could unacceptably impact the integrity of the aquatic ecosystem and
have unanticipated ecological consequences on the water body as a whole
resulting in impairment of the designated or existing uses. A legally
binding mixing zone policy is considered a WQS under EPA's existing
regulations at 40 CFR 131.13. The policy describes the general
characteristics of, and requirements associated with mixing zones
without accounting for site-specific information. EPA's guidance has
emphasized a holistic approach to mixing zone regulation which
considers location, size, shape, outfall design, and in-zone
quality.\46\
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    \45\ EPA Water Quality Standards Handbook. https://www.epa.gov/wqs-tech/water-quality-standards-handbook.
    \46\ EPA's guidance on mixing zones has been detailed in several
agency publications, including the Water Quality Standards Handbook,
August 1994, the Technical Support Document for Water Quality-based
Toxics Control (TSD), March 1991, and EPA's Compilation of Mixing
Zone Documents, 2006.
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Mixing Zone Size
    To protect the designated uses of the water body as a whole, it is
critical that pollutant concentrations within any mixing zone are not
lethal to mobile, migrating, and drifting organisms in the water body
or cause unacceptable human health risks considering likely pathways of
exposure. One means of achieving these objectives is to limit the size
of the mixing zone. EPA is

proposing to limit the size of mixing zones in 40 CFR 131.XX(g)(2)(vii)
of this proposed rule by establishing specific metrics for: how far
upstream and downstream mixing zones may extend: how much of the water
body may be taken up by mixing zones (in terms of percentages); and
prohibiting overlapping mixing zones. These proposed size metrics
represent a balance among three interests: allowing a reasonable amount
of water for mixing; allowing for sufficient space for human health
protection and aquatic life survival, growth, and reproduction; and
recognizing that multiple dischargers may exist on the same water. EPA
solicits comments on the proposed size metrics and whether other
metrics, metric values, or approaches may be more appropriate.
    Mixing zone sizes are often determined using a set of critical
conditions to ensure protection of the receiving water. Examples of
critical conditions are the critical effluent concentration, critical
effluent flow, and the critical low flow of the receiving stream.
Critical low flows commonly used throughout the United States include
these hydrologically-based metrics:
     1Q10 (the lowest one-day average flow event expected to
occur once every ten years) or the biologically-based 1B3 (the lowest
one-day average flow event expected to occur once every three years)
flow rate for acute aquatic life criteria;
     7Q10 (the lowest seven-consecutive-day average flow event
expected to occur once every ten years) or 4B3 (the lowest four-
consecutive-day average flow event expected to occur once every three
years) flow rate for chronic aquatic life criteria with a duration of
less than 30 days and human health criteria based on a short-term
toxicological effect; the 30Q10, 30Q5, or 30B3 flow rate for chronic
aquatic life criteria with a duration of 30 days or longer; and
     harmonic mean flow rate for human health criteria is based
on lifetime exposure.
    Local, regional, and national guidance is available to determine
critical low flows and other critical conditions for mixing zone
calculations. EPA is proposing that for purposes of this rule, critical
low flow will mean the 1Q10 or 1B3 flow rate for acute aquatic life
criteria; the 7Q10 or 4B3 flow rate for chronic aquatic life criteria
with a duration of less than 30 days and human health criteria based on
a short-term toxicological effect; the 30Q10, 30Q5, or 30B3 flow rate
for chronic aquatic life criteria with a duration of 30 days or longer;
and the harmonic mean flow rate for human health criteria based on
lifetime exposure.
    Zones of passage within water bodies that allow for migrating,
free-swimming, or drifting organisms are particularly important when
determining the appropriate size of a mixing zone. Zones of passage are
continuous water routes of such volume, area, and quality as to allow
the passage of free-swimming and drifting organisms without significant
adverse effects on their populations. Many species migrate for spawning
and other purposes. Not only do migrating species (e.g., anadromous and
catadromous species) need to be able to reach suitable spawning areas,
their young (and in some cases the adults) require a safe return route
to their growing and living areas. Within a mixing zone, pollutant
concentrations exceeding the established criteria can create barriers
that hinder or prevent safe migration.
Mixing Zone Shape
    The water body type, outfall design, and characteristics of the
discharge will determine the shape of a mixing zone. The shape should
be a simple configuration that is easy for both the discharger and the
permitting authority to locate in a water body and that avoids
impingement on biologically important areas. In lakes, a circle with a
specified radius is generally preferable, but other shapes might be
appropriate in the case of unusual site configurations. Mixing zone
shapes and sizes may vary depending on the pollutant of concern and the
specific criterion (e.g., acute, chronic, or human health) being
considered. Local, regional, and national guidance is available to
determine mixing zone characteristics. Under EPA's proposal, the
Regional Administrator would be able to adjust the size and extent of
mixing zones within the limits allowable in proposed 40 CFR
131.XX(g)(2)(vii) to establish the desired shape of mixing zones where
appropriate.
Outfall Design
    Many different factors affect how well the outfall design allows
the discharge to mix with the receiving water, including:
     The height of the outfall with respect to the surface and
bottom of the water body. A surface discharge is least favorable for
toxic discharges since it offers the least initial mixing. Submerged
discharges offer greater flexibility in meeting the design goals for
toxic discharges.
     The distance of the end of the pipe to the nearest bank
(i.e., whether the outfall is in the middle of the water body or close
to one side). Discharges at the shoreline of a water body can yield
high surface concentrations along the shoreline when there is
significant cross-flow.
     The angle of the discharge. The initial dilution can be
maximized when submerged discharges direct the effluent at an angle to
the ambient flow. For example, in rivers, the preferred arrangement for
a submerged discharge is to direct the outfall into the current flow
direction or vertically upward.
     The type of submerged discharge that is used (i.e.,
single-port or multi-port diffuser). A multiport submerged discharge,
or diffuser, can help effluent to be mixed more rapidly than a single-
port submerged discharge.