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WATER QUALITY
HANDBOO
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7
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The WQS Handbook does not change or impose any legally binding requirements on the EPA, states, Tribes,
the public, or the regulated community. This document does not constitute a regulation, nor does it change
or substitute for any Clean Water Act (CWA) provision or EPA regulations. In the case of any conflict
between this Handbook and the CWA or EPA regulations, the statute, and regulations control.
DRAFT CHAPTER 4: Antidegradation
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Table of Contents
INTRODUCTION 1
4.1 BACKGROUND 4
4.1.1 History of the Federal Antidegradation Regulation 4
4.1.2 Summary of the Federal Antidegradation Regulation 6
4.1.3 The EPA's Authority to Review Antidegradation Policies and AIMs 12
4.1.4 Applicability of Antidegradation Policies and AIMs 14
4.1.5 Antidegradation in CWA Implementation Programs 16
4.1.6 Tribal Reserved Rights 18
4.1.7 Federal Promulgations for Tribes 18
4.2 PROTECTION OF EXISTING USES - 40 CFR 131.12(a)(1) 20
4.3 PROTECTION OF HIGH QUALITY WATERS - 40 CFR 131.12(a)(2) 22
4.3.1 Identification of High Quality Waters 23
4.3.1.1 Determining Ambient Water Quality 24
4.3.1.2 Parameter-by-Parameter Approach 25
4.3.1.3 Waterbody-by-Waterbody Approach 27
4.3.1.4 Hybrid Approach 33
4.3.1.5 Considerations for Selecting an Approach 34
4.3.2 Antidegradation Tier 2 Review 35
4.3.2.1 Tier 2 Review: Identification of Activities that Potentially
Lower High Water Quality 37
4.3.2.2 Tier 2 Review: Determining Necessity and Importance of ...
an Activity 38
4.3.2.3 Tier 2 Review: Intergovernmental Coordination and Public
Participation 46
4.3.2.4 Tier 2 Review: Assurance of Existing Use Protection 47
4.3.2.5 Tier 2 Review: Point and Nonpoint Sources 47
4.3.3 Use of De Minimis in Antidegradation 48
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4.4 OUTSTANDING NATIONAL RESOURCE WATERS - 40 CFR 131.12(a)(3) 55
4.5 ADDITIONAL PROTECTION ESTABLISHED BY STATES AND
AUTHORIZED TRIBES (TIER 2%) 59
4.6 THERMAL DISCHARGE REQUIREMENTS - 40 CFR 131.12(a)(4) 60
4.7 ANT I DEGRADATION IMPLEMENTATION METHODS 61
4.8 APPLICATION AND IMPLEMENTATION 63
4.8.1 CWA Section 402: NPDES Permits 64
4.8.1.1 General Permits 68
4.8.2 CWA Section 404: Dredged or Fill Material Permits 69
4.8.3 CWA Section 401 Certification 70
4.8.4 CWA Sections 303(d) and 305(b) Assessment, Listing, and TMDLs 71
List of Figures
Figure 4-1 Example of Water Quality that is Better than Necessary to Support a CWA
Section 101(a)(2) Use 23
Figure 4-2 Example of Lowering of High Water Quality 24
Figure 4-3 Example of the Para meter-by-Para meter Approach 26
Figure 4-4 Example of a Water Receiving Antidegradation Tier 2 Protection Using the
Waterbody-by-Waterbody Approach 32
Figure 4-5 Example of a Water Not Receiving Antidegradation Tier 2 Protection Using
the Waterbody-by-Waterbody Approach 33
Figure 4-6 Example of a De Minimis Threshold 50
Figure 4-7 Example of the Cumulative Impact of Multiple De Minimis Activities 51
Figure 4-8 Determining whether a Tier 2 review is needed before issuing an NPDES
permit using eitherthe parameter-by-parameter approach orthe
waterbody-by-waterbody approach 66
DRAFT CHAPTER 4: Antidegradation
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List of Acronyms and Abbreviations
AIMs
Antidegradation implementation methods
BCC
Bioaccumulative chemical of concern
BMP
Best management practice
CFR
Code of the Federal Register
CWA
Clean Water Act
Corps
United States Army Corps of Engineers
EPA
United States Environmental Protection Agency
FERC
Federal Energy Regulatory Commission
NOI
Notice of intent
NPDES
National Pollutant Discharge Elimination System
NPS
Nonpoint source
ONRW
Outstanding National Resource Water
TBEL
Technology-based effluent limit
TMDL
Total Maximum Daily Load
WQBEL
Water quality-based effluent limit
WQS
Water quality standards
DRAFT CHAPTER 4: Antidegradation
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4 INTRODUCTION
Antidegradation policies and antidegradation implementation methods
(AIMs) are essential to the water quality standards (WQS) program. The three core
components of WQS are designated uses, water quality criteria, and an antidegradation
policy. In addition, states and authorized Tribes are required to develop AIMs to describe
how the antidegradation policy will be implemented C40 CFR 131.12(b)). Designated uses
are the uses specified in WQS for each waterbody or waterbody segment whether or
not they are being attained. Designated uses establish the management objectives for a
waterbody. Water quality criteria define the water quality conditions that protect those
designated uses. Antidegradation policies and AIMs complement these elements by
providing a framework for maintaining and protecting water quality that has already been
achieved. This includes maintaining and protecting existing uses1 (Tier 1), maintaining and
protecting high quality waters2 (Tier 2), and maintaining and protecting the water quality
of outstanding National resource waters (ONRWs) (Tier 3). Antidegradation policies
and AIMs play a critical role in helping states and authorized Tribes maintain and protect
the valuable public resource of clean water and ensure that decisions to allow lowering
of high water quality are made in a public manner and serve the public good.3 See Draft
Chapter 2 and Chapter 3 of this Handbook for further discussion of designated uses and
water quality criteria, respectively.
Antidegradation plays an integral role in maintaining and protecting water quality
consistent with the Clean Water Act (CWA). Therefore, the United States Environmental
Protection Agency's regulation requires states and authorized Tribes4 to adopt
antidegradation policies and develop AIMs (see section 4.1.1 for discussion of
antidegradation history and the CWA). Such state and authorized Tribal antidegradation
policies and AIMs provide a framework to maintain a minimum level of water quality
protection and, where water quality exceeds that minimum level of protection, balance
water quality protection with the opportunity for important community growth.5
That framework requires maintenance of water quality already achieved, provides a
mechanism to protect highly valued waters, and requires states and authorized Tribes
to involve the public in decisions that could potentially lower high water quality. This
1 Existing uses are those uses actually attained in the waterbody on or after November 28,1975, whether or not they are
included in the WQS (40 CFR 131.3(e)).
2 The EPA uses the term high quality waters to refer to waters that have water quality that is better than necessary to
support the protection and propagation of fish, shellfish, and wildlife and recreation in and on the water, and thus has
some assimilative capacity for one or more parameters.
3 Water Quality Standards Regulation, 63 Fed. Reg. 36780 (July 7,1998).
4 Hereafter referred to as "states and authorized Tribes". "State" in the CWA and this document refers to a state, the
District of Columbia, the Commonwealth of Puerto Rico, the United States Virgin Islands, Guam, American Samoa,
and the Commonwealth of the Northern Mariana Islands. "Authorized Tribes" refers to those federally recognized
Indian Tribes with authority to administer a CWA WQS program.
? Water Quality Standards Regulatory Clarifications, 78 Fed. Reg. 54528 (September 4, 2013).
DRAFT CHAPTER 4: Antidegradation 1
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framework informs an antidegradation review, which is the process that a state or
authorized Tribe uses to ensure that the appropriate Tier 1, 2, and/or 3 protections
are provided for a waterbody or waterbody segment when considering whether to
allow an activity that would lower water quality. For ensuring Tier 2 protection, a state
or authorized Tribe will conduct a Tier 2 Review, including public participation and
intergovernmental coordination, to decide whether allowing some lowering of water
quality in a high quality water is necessary to accommodate important economic or
social development in the area in which the waters are located.
High water quality is a shared amenity that benefits local communities in a wide
variety of ways. High quality surface waters cart serve as a focal point for recreation
and tourism through community development or redevelopment projects like river
walks, canoe liveries, and boat tours. They can support community health and welfare
by providing opportunities to recreate in and on the water as well as supplemental or
subsistence nutrition through recreational and subsistence fishing. They also increase
property values, lower drinking water costs, create jobs, support commercial fisheries,
and increase the diversity and resilience of aquatic ecosystems.6 Thus, maintaining
high water quality is particularly critical to supporting economic growth, community
growth, and sustainability. Additionally, protecting high water quality, including habitat
and aquatic community structure, will afford the waterbody increased resilience to
potential future stressors, such as atmospherically deposited pollutants, emerging
contaminants, and climate change. The impacts of climate change, such as increased
water temperatures, more frequent and severe droughts, and increases in extreme
weather events, in combination with other anthropogenic stressors, such as stormwater
runoff due to growing urbanization and water withdrawals for agricultural, industrial,
and municipal purposes, can make it more difficult to meet the CWA's objective "to
restore and maintain the chemical, physical, and biological integrity of the Nation's
waters" CCWA Section 1Q1Ca)I Protecting water resources from these adverse impacts
See also https://www.epa.gov/sites/production/files/2015-10/documents/economic benefits factsheet3.pdf:
Economic Benefits of Protecting Healthy Watersheds (EPA 841-N-12-004, April 2012).
DRAFT CHAPTER 4: Antidegradation 2
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depends on maintaining or restoring resilience, i.e., the ability of waterbodies to recover
after a disturbance and their capacity to maintain their ecological functions despite the
disturbance. However, with changing conditions expected to result from climate change,
management strategies of the past may not be adequate to mitigate the impacts of
stressors to a waterbody.7 Using WQS to maintain or build a margin of safety in water
quality affords a waterbody increased resilience in the face of future stressors, including
climate change.
The WQS program provides a
holistic approach to promote system
resilience to climate change and
facilitates efficient coordination
and implementation of water
quality management actions. This
chapter presents ways one can use
antidegradation to maintain and
enhance waterbody resilience to
climate change effects. For example,
section 4.3 discusses how the Tier 2
process of antidegradation can be
used to maintain and protect high
quality waters, including protecting
assimilative capacity, which helps
to maintain waterbody resilience.
While preventing degradation and
maintaining a reliable source of
clean water may involve costs, it
is often less expensive and more
effective and efficient than long-
term restoration efforts or remedial
actions.8
This chapter presents background
information on antidegradation
history, the federal regulation,
EPA authority, and applicability of
antidegradation. It is followed by a
discussion of the three categories,
or tiers, of antidegradation protection, thermal discharge requirements, and application
and implementation of antidegradation.
1 EPA. 2011. Aquatic Ecosystems, Water Quality, and Global Change: Challenges of Conducting Multi-stressor Global
Change Vulnerability Assessments. EPA, Office of Research and Development. Washington, DC 20460. EPA/600/R-
11/011F. August 2011.
? Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51029-51030 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 3
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4.1 BACKGROUND
4.1.1 History of the Federal Antidegradatiori
Regulation
OH February 8,1968, the Secretary of the United States Department of the Interior
released the first antidegradation policy statement in connection with the review
and approval of WQSfor interstate and coastal waters:9
"Waters whose existing quality is better than the established
standards as of the date on which such standards become effective
will be maintained at their existing high quality. Those and other
waters of a State will not be lowered in quality unless and until it
has been affirmatively demonstrated to the State water pollution
control agency and the Department of the Interior that such change
is justifiable as a result of necessary economic or social development
and will not interfere with or become injurious to any assigned uses
made of, or presently possible in, such waters. This will require that
any industrial, public or private project or development which would
constitute a new source of pollution or an increased source of
pollution to high quality waters will be required, as part of the initial
project design, to provide the highest and best degree of waste
treatment available under existing technology, and, since these are
also Federal standards, these waste treatment requirements will be
developed cooperatively."
The EPA refined that statement and included it in the first federal WQS regulation in
1975 (40 Code of the Federal Register CCFR) 130.17Ce^:10
"The State shall develop and adopt a Statewide antidegradation policy
and identify the methods for implementing such policy pursuant
to 5130.10(b)(2). The antidegradation policy and implementation
methods shall, at a minimum, be consistent with the following:
(1) Existing instream water uses shall be maintained and
protected. No further water quality degradation which would
interfere with or become injurious to existing instream water
uses is allowable.
(2) Existing high quality waters which exceed those levels
U.S. Department of the Interior, Federal Water Pollution Control Administration. 1968. Compendium of Department
of the Interior Statement on Non-degradation of Interstate Waters. Washington, DC 2042. August 1968. https://
www.epa.gov/sites/default/files/2014-10/documents/doiwaters.pdf.
Water Quality Standards, 40 Fed. Reg. 55340-55341 (November 28,1975).
9
10
DRAFT CHAPTER 4: Antidegradation
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necessary to support propagation offish, shellfish and wildlife
and recreation in and on the water shall be maintained and
protected unless the State chooses, after full satisfaction of
the intergovernmental coordination and public participation
provisions of the State's continuing planning process, to allow
lower water quality as a result of necessary and justifiable
economic or social development. In no event, however,
may degradation of water quality interfere with or become
injurious to existing instream water uses. Additionally, no
degradation shall be allowed in high quality waters which
constitute an outstanding National resource, such as waters
of National and State parks and wildlife refuges and waters
of exceptional recreational or ecological significance.
Further the State shall assure that there shall be achieved
the highest statutory and regulatory requirements for all
new and existing point sources and feasible management or
regulatory programs pursuant to section 208 of the Act for
nonpoint sources, both existing and proposed.
(3) In those cases where potential water quality impairment
associated with a thermal discharge is involved, the
antidegradation policy and implementing method shall be
consistent with section 316 of the Act."
The 1975 federal WQS regulation was then slightly revised and re-promulgated as part of
the 1983 federal WQS regulation (40 CFR 131.12").11
Several provisions in the CWA form the basis for antidegradation, including the CWA's
principal objective, which is to .. restore and maintain the chemical, physical and
biological integrity of the Nation's waters" (emphasis added) (CWA Section 101(a)) and
the provision that made WQS adopted prior to 1972 the starting point for CWA water
quality requirements CCWA Section 303(a)). Congress explicitly affirmed the principle of
antidegradation through:
An amendment in the Water Quality Act of 1987, codified in CWA Section 303(d)
(4)(B), that requires consistency with antidegradation policies before making
revisions to certain National Pollutant Discharge Elimination System (NPDES)
permits, and
The 1990 Great Lakes Critical Programs Act, codified in CWA Section 118(c)
(2). requiring the EPA to publish Great Lakes water quality guidance including
antidegradation policies and implementation procedures.
In August 2015, as part of a revision of the federal WQS regulation, the EPA revised the
federal antidegradation regulation to promote transparency and public involvement
and provide a better-defined framework for states and authorized Tribes to maintain
11 Water Quality Standards Regulation, 48 Fed. Reg. 51400-51413 (November 8,1983). See page 51402-51403 for a
discussion of revisions to the antidegradation regulation.
DRAFT CHAPTER 4: Antidegradation 5
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and protect high quality waters.12 The revised requirements strengthened the evaluation
states and authorized Tribes must conduct to identify and manage high quality Tier 2
waters, and required increased opportunities for the public and stakeholders to be
involved in the state or authorized Tribal decision-making process.
Timeline of Antidegradation Regulation Development
DOI released first antidegradation policy statement
The EPA refined the antidegradation policy statement and
included it in the first federal WQS regulation
Revised and re-promulgated the federal antidegradation
WQS regulation
Water Quality Act of 1987 required consistency with
antidegradation policies before issuing certain NPDES Permits
Great Lakes Critical Programs Act of 1990 required the EPA to
publish Great Lakes water quality guidance, including
antidegradation policies and implementation procedures
The EPA revised the federal antidegradation regulation to
provide a better-defined framework for states and Tribes,
including greater transparency and public involvement in
antidegradation policies and implementation
4.1.2 Summary of the Federal Antidegradation
Regulation
The federal WQS regulation at 40 CFR 131.12 specifies requirements for states'
and authorized Tribes' antidegradation programs. 40 CFR 131.12 requires states and
develop two elements
for their antidegradation
programs: an
antidegradation policy and
AIMs. The antidegradation
policy establishes the
legal requirements for
protection of existing uses,
high quality waters, and
ONRWs, while the AIMs
explain how the policy will
be carried out by the state
1968
1975
1983
1987
1990
2015
ANTIDEGRADATION REGULATION
131.12 - Antidegradation Policy and Implementation
Methods
131.12(a) - Antidegradation Policy
131.12(a)(1) - Existing Use Protection
131.12(a)(2) - High Quality Water Protection
131.12(a)(3) - ONRW Protection
131.12(a)(4) - Thermal Discharge Requirements
131.12(b)- AIMs
Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51029-51035 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation
6
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or authorized Tribe. Each state's or authorized Tribe's policy and AIMs must be consistent
with 40 CFR 131.12. In addition, a state's or authorized Tribe's AIMs must be consistent
with its policy.
Antidegradation Policies
Antidegradation policies are a set of legally binding requirements included in states'
or authorized Tribes' WQS that describe the expectations for preventing or minimizing
degradation to waters, in a manner consistent with 40 CFR 131.12(a) (e.g., protections
for existing uses, high quality waters, and ONRWs). Although not required, states and
authorized Tribes typically adopt language that is similar to the language of the provisions
at 40 CFR 131.12(a) as their antidegradation policy. Where a state or authorized Tribe
chooses to develop its own antidegradation policy language, the EPA's regulation
requires that any antidegradation policy adopted be consistent with 40 CFR 131.12.13 The
EPA recommends that the state or authorized Tribe include its antidegradation policy in
its WQS regulation for the sake of public transparency. However, a state or authorized
Tribe may choose to include it in another legally binding regulation. When choosing this
path, states and authorized Tribes should specifically reference their antidegradation
policy in their WQS regulation to maintain the clear functional relationship between their
antidegradation policy and their WQS regulation.
Antidegradation Tiers
A state's or authorized Tribe's antidegradation policy must, at a minimum, provide
for protection of the three antidegradation categories specified in 40 CFR 131.12(a).
These categories of protection are commonly referred to as "tiers." It is important to
note that CWA Section 510 gives states and authorized Tribes the discretion to adopt
antidegradation policies more protective than required under the federal regulation.
40 CFR 131.12(a)(1). or "Tier 1," requires the maintenance and protection of "existing
instream water uses," providing the absolute floor for protection of water quality in
all waters of the United States.14 40 CFR 131.3(e) defines existing uses as "those uses
actually attained in the waterbody on or after November 28,1975, whether or not they
are included in the water quality standards."
40 CFR 131.12(a)(2). or "Tier 2," addresses waters where the water quality exceeds
the levels necessary to support the CWA Section 101(a)(2) uses,15 which include the
protection and propagation offish, shellfish, and wildlife and recreation in and on the
13 See question 4.1 of EPA. 2012. What is a New or Revised Water Quality Standard Under CWA 303(c)(3) Frequently
Asked Questions, EPA's Office of Water. Washington, DC 20460. EPA-820-F-12-017. https://www.epa.gov/sites/
production/files/2014-11/documents/cwa303faq.pdf.
14 Water Quality Standards Regulation, 48 Fed. Reg. 51403 (November 8,1983).
15 For purposes of a plain language discussion in this chapter, the EPA uses the term "101(a)(2) use" to refer to any use
that fully supports the uses specified in CWA Section 101(a)(2). including subcategories that support the uses specified
in CWA Section 101(a)(2) (e.g., aquatic life use, recreation use, warm water aquatic life use, cold water aquatic life use,
primary contact recreation). See Draft Chapter 2. section 2.1.1. for additional discussion.
DRAFT CHAPTER 4: Antidegradation
7
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water.16 The EPA refers to these waters as "high quality waters." These high quality waters
can be identified on a parameter-by-parameter basis, where each parameter is evaluated
individually to see if it exceeds the levels necessary to support the CWA Section 101(a)
(2) uses. These waters can also be identified on a waterbody-by-waterbody basis, where
the waterbody is holistically evaluated to see if it is high quality. The water quality of
high quality waters must be maintained and protected unless the state or authorized
Tribe makes a finding that a lowering17 of water quality is necessary to allow important
economic or social development in the area in which the waters are located. The state or
authorized Tribe may only allow a lowering of water quality in a high quality water after
the state or authorized Tribe has followed and met all of the requirements described in
40 CFR 131.12(a)(2).
40 CFR 131.12(a)(3). or "Tier 3," provides the highest level of water quality protection
to ONRWs.18 ONRWs are waters that states and authorized Tribes want to protect from
further degradation because they are highly valued. Any waterbody may be assigned as
an ONRW if the state or authorized Tribe believes it merits such protection. The federal
regulation prohibits lowering of water quality in ON RWs, except on a short-term or
temporary basis.19 Broadly, good candidates for ONRWs include the following:
Waters of National and State parks and wildlife refuges,
Waters with highly intact ecosystems and high levels of biological integrity,
Waters that are important to the protection or restoration of state, Tribal or
federal listed species,
Waters that have unusual or unique ecological or recreational resources,
Waters that are of exceptional recreational significance,
Waters that are of exceptional ecological significance,
^ Waters that have exceptional importance to human health (i.e., drinking water
sources), or
Waters of cultural significance.
States and authorized Tribes must provide Tier 1 protection to all waters of the United
States. Tier 2 protection must be provided to waters that are identified as high quality by
a state or authorized Tribe. States and authorized Tribes can choose which method they
will use to identify high quality waters, either the parameter-by-parameter approach
or waterbody-by-waterbody approach (See sections 4.3.1.2 and 4.3.1.3 of this chapter,
respectively). If the state or authorized Tribe uses a parameter-by-parameter approach,
then Tier 2 protection will be provided to waters where chemical, physical, or biological
parameters exceed the levels necessary to protect CWA Section 101(a)(2) uses. If the
16 Water Quality Standards Regulation, 48 Fed. Reg. 51403 (November 8,1983).
17 Lowering means an increase in pollution, resulting from an activity that would use some of the assimilative capacity in a
high quality water. See also Figure 4-2 in this chapter.
18 Water Quality Standards Regulation, 48 Fed. Reg. 51403 (November 8,1983).
19 Ibid.
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state or authorized Tribe uses a waterbody-by-waterbody approach, then the state or
authorized Tribe will perform holistic evaluations of its waters to determine which waters
will receive Tier 2 protection. Which waters receive Tier 3 protection is at the state's or
authorized Tribe's discretion,
An tidegrada tion Tiers vs. Designated Uses
Antidegradation tiers and designated uses are two distinct concepts in the WQS
program. Antidegradation tiers are categories of protection for water quality while
designated uses20 are an expression of the desired condition or environmental objective
for the water, even if the water quality to protect such uses has not yet been attained.
Antidegradation complements designated uses and criteria by providing a mechanism
whereby consideration of the importance of preserving current water quality is an
explicit requirement before an action that degrades such water quality occurs. As such,
the EPA has two separate sets of regulations addressing the designation of uses C40 CFR
131.10") and antidegradation (40 CFR 131.12).
At times, states and authorized Tribes have adopted antidegradation tiers as designated
uses in their WQS. The EPA does not recommend this practice as it can create confusion
and make the implementation of antidegradation more difficult. For example, Tier 2 only
establishes that high water quality must be maintained unless degradation is necessary
to accommodate important social and economic development. It does not identify a
desired function or activity for the waterbody. Determining whether a water is "high
quality" is dependent upon determining whether the current water quality exceeds
the criteria established to protect designated uses consistent with CWA Section 101(a)
(2). If a state were to adopt "Tier 2" as a designated use, it would be unclear what
function or activity that Tier 2 "use" would be protecting and thus what criteria would
be needed to protect the designated use. In addition, adopting an antidegradation tier
as a designated use could limit the state's or authorized Tribe's ability to change Tier 2
and Tier 3 assignments, because adding or removing a designated use requires revising
the state's or authorized Tribe's WQS (and thus a rulemaking) and the revision must be
consistent with 40 CFR 131.10. If a state or authorized Tribe realizes they unintentionally
* A use is a particular function of, or activity in, a water of the United States that requires a specific level of water quality
to support it (see Water Quality Standards Regulatory Clarifications, 78 Fed. Reg. 54522 (September 4, 2013)).
DRAFT CHAPTER 4: Antidegradation 9
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adopted antidegradation
tiers as designated uses,
it can work with its EPA
regional WQS coordinator
to appropriately revise
its WQS to separate the
two concepts. For more
information on designated
uses, please refer to
Draft Chapter 2 of this
Handbook,
Thermal Discharges
Antidegradation policies
must be consistent with
CWA Section 316. When
authorizing thermal
discharges, states and
authorized Tribes must
provide protection for
waters in any of these
three tiers in a manner
consistent with CWA
Section 316. 40 CFR
131.12(a)(4) addresses potential water quality impairments associated with thermal
discharges. This federal regulation aligns the antidegradation requirements with those
established in CWA Section 316 for setting thermal discharge limitations.
For additional information about Tier 1, Tier 2, and Tier 3 protection, see sections
4.2, 4.3, and 4.4 of this chapter, respectively. For further discussion about thermal
discharges, see section 4.5 of this chapter.
Antidegradation Implementation Methods
AIMs refer to additional documents or provisions in which a state or authorized Tribe
describes methods for implementing its antidegradation policy.21 40 CFR 131.12(b)
requires each state and authorized Tribe to develop AIMs, which must be consistent
with the federal antidegradation regulation and the state's or authorized Tribe's own
antidegradation policy. 40 CFR 131.12(b) also requires states and authorized Tribes
to provide an opportunity for public involvement during the development and any
subsequent revisions of the AIMs and requires AIMs to be publicly available. States
and authorized Tribes have the discretion to adopt their AIMs into rule or other legally
binding form or identify them in non-legally binding guidance. While the EPA does
Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51034 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 10
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not require states and authorized Tribes to adopt AIMs as legally binding provisions, it
encourages states and authorized Tribes to consider doing so. Adopting AIMs as legally
binding provisions provides more transparency to the public and other stakeholders,
increases accountability, and provides a greater degree of regulatory certainty and
consistency to regulated entities.
States and authorized Tribes have the flexibility to engage the public in the development
or revision of their AIMs in a way that best suits them and the public when working to
meet the public involvement requirement at 40 CFR 131.12(b). The public involvement
requirement could be satisfied using a variety of mechanisms such as a public hearing,
public meeting, or public workshop. Online approaches such as webinars or website
postings that include contact information so the public has the opportunity to provide
input could also be used. In 40 CFR 131.12(b), the EPA purposefully uses the phrase
"opportunity for public involvement" to provide for this type of flexibility and to be
different from the "public participation" requirement in 40 CFR 131.20(b). "Public
participation" as it is used in 40 CFR 131.20(b) implements CWA Section 303(c)(1) and
refers to a state or authorized Tribe holding a public hearing, which is a formal meeting
with specific protocols for public engagement, consistent with 40 CFR 25.5 for the
purpose of reviewing or revising WQS at least once every three years.
If a state or authorized Tribe adopted AIMs as part of its WQS rule or in another legally
binding form (e.g., part of permitting regulation), those AIMs are considered WQS.
Therefore, the state or authorized Tribe must hold a public hearing when those AIMs are
initially adopted or revised to meet the public participation requirements for adopting
new WQS in 40 CFR 131.20(b). This public hearing would also satisfy the requirement in
40 CFR 131.12(b) for public involvement.
Where a state or authorized Tribe has its AIMs in guidance or other non-legally
binding form, it must meet the public involvement requirement at 40 CFR 131.12(b),
although the state or authorized Tribe has the discretion to choose the method of
public involvement which will most effectively reach and engage its citizens. States
and authorized Tribes may find that the provisions regarding the Continuing Planning
Process described at CWA Section 303(e) and 40 CFR 130.5 can facilitate the state's or
authorized Tribe's establishment and maintenance of a process for the public to provide
input on its AIMs consistent with the requirements of the federal regulation.22
Antidegradation Requirements for Waters of the Great Lakes System
Because of the documented environmental harm that can arise from pollutants that
bioaccumulate in the Great Lakes basin ecosystem, the EPA's Water Quality Guidance for
the Great Lakes System at 40 CFR Part 132 adds several antidegradation requirements
for those waters with greater specificity and precision compared to the general
antidegradation requirements in 40 CFR 131.12.
22 See 40 CFR 130.5(31 and 40 CFR 130.5(b')(6') for additional provisions regarding the requirements for establishing a
CPP.
DRAFT CHAPTER 4: Antidegradation
11
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As defined in the 40 CFR Part 132 regulation, the Great Lakes system consists of
all streams, rivers, lakes, and other bodies of water within the drainage basin of the
Great Lakes within the United States. The added 40 CFR Part 132 antidegradation
requirements apply to any regulated action or activity that is anticipated to result in an
increased loading of persistent bioaccumulative pollutants termed "bioaccumulative
chemicals of concern" (BCCs).23 Great Lakes states and authorized Tribes must adopt an
antidegradation standard and implementation procedures for BCCs consistent with 40
CFR Part 132 requirements for the Great Lakes system and have the option of applying
them to other pollutants and other state or Tribal waters at their discretion. In the event
of any inconsistencies between the 40 CFR 131.12 and 40 CFR Part 132 requirements
applicable to BCCs, the Great Lakes state or authorized Tribal WQS must comply with
the more stringent provision.
Examples of the antidegradation requirements targeted on BCCs in the Great Lakes
system include the following:
Requiring use of the pollutant-by-pollutant approach for identifying high
quality waters,
Requiring use of any increased mass loading of a BCC as the measure of
lowering water quality,
Assigning antidegradation decisions to the director of the relevant
permitting authority,
Requiring permit conditions that require monitoring of loadings and notifying
the permit authority of any loading increases,
Requ iring the discharger to conduct an antidegradation demonstration
whenever seeking to lower water quality in a Tier 2 water.
Antidegradation decisions by the permitting authority would be subject to
public participation requirements, and
^ Prohibiting "de m/'n/'m/'s" provisions under Tier 2 for BCCs.
4.1.3 The EPA's Authority to Review Antidegradation
Policies and AIMs
As described in section 4.1.2, the federal requirements for antidegradation at 40 CFR
131.12 specifically implement the CWA's objective at 101(a) to "...maintain the chemical,
physical and biological integrity of the Nation's waters". Congress affirmed this principle
by later adding the concept of antidegradation to CWA Sections 303CdX4XB) and 118(c)
(2). Thus, antidegradation, along with designated uses and criteria, make up the core
components of the WQS program.
23 The regulation at 40 CFR 132.2 defines a BCC as a pollutant with a bioaccumulation factor of 1000 or higher
according to methodologies specified in the rule, including but not limited to a list of 22 known BCCs in Table 6A of
the regulation.
DRAFT CHAPTER 4: Antidegradation
12
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40 CFR 131.5(a)(3) specifies that the EPA's review and decision to approve or disapprove
WQS involves a determination of "[w]hether the State has adopted an antidegradation
policy that is consistent with §131.12, and whether any State adopted antidegradation
implementation methods are consistent with §131.12." In addition, while not requiring
that AIMs be adopted as legally binding provisions, 40 CFR 131.12(b) makes clear that
any such developed AIMs shall be "...at a minimum, consistent with the State's policy and
with paragraph (a) of this section." Therefore, when a state or authorized Tribe adopts
or revises its antidegradation policy and when a state or authorized Tribe adopts AIMs as
legally binding provisions, the EPA has the authority24 and the obligation to review and
approve or disapprove the policy or adopted AIMs as a new or revised WQS under CWA
Section 303(c). The EPA can approve a policy or adopted AIMs if they are consistent
with the requirements of the CWA and the federal regulation If the EPA disapproves the
state's or authorized Tribe's policy or adopted AIMs because it is inconsistent with any
of the requirements at 40 CFR 131.12, the state or authorized Tribe has an opportunity
to revise its antidegradation policy
or adopted AIMs to be consistent
with the CWA and the federal
regulation.25 However, if the
state or authorized Tribe does not
make appropriate revisions then,
pursuant to CWA Section 303(c)(4)
(A) and 40 CFR 131.22(a). the EPA
is required by CWA Section 303(c)
(4)(A) to propose and promulgate
an antidegradation policy or
adopted AIMs for the state or
authorized Tribe.
If a state or authorized Tribe
develops AIMs in a non-legally
binding form, the EPA does not
approve or disapprove those AIMs
under its CWA section 303(c)
authority. However, the EPA
will work closely with the state
or authorized Tribe to ensure
its AIMs are consistent with its
corresponding antidegradation policy and 40 CFR 131.12(a). as required by 40 CFR
131.12(b).26 The EPA's evaluation of consistency includes ensuring that the AIMs do not
undermine the antidegradation policy.
24 40 CFR 131.5(3X3) and 40 CFR 131.6(d).
25 See Chapter 6: Procedures for Review and Revision of Water Quality Standards of this Handbook for more information
on WQS review and submittal processes, https://www.epa.aov/wqs-tech/water-quality-standards-handbook
26 Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51033-51034 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 13
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When implementing antidegradation policies and AIMs through mechanisms such as
NPDES permitting, such implementation must be consistent with the applicable (i.e.,
EPA approved) WQS (NPDES: CWA Section 301(b)(1)(C): 40 CFR 122.44(d : 404:
40 CFR 230.10(b)(1)"). In the situation where only the state's or authorized Tribe's
antidegradation policy is legally binding, its antidegradation policy must drive any
CWA implementation decisions. The EPA has the discretionary authority to object to
state or authorized Tribal NPDES permits27 when the effluent limits of a permit do not
meet the requirements of 40 CFR 122.44(d). 40 CFR 122.44(d)(1)(vii)(A) specifies the
need for WQBELs to derive from and comply with all applicable WQS, which include
antidegradation policies. Therefore, if permits are written using antidegradation
implementation methods that are inconsistent with the applicable antidegradation
policy, and thus do not derive from and comply with the applicable WQS, the EPA may
object to the permit.
The EPA encourages states and authorized Tribes to work collaboratively with the EPA
early in the antidegradation policy and AIMs development process. This collaboration can
be most effective if states and authorized Tribes also provide the EPA with early versions
of potential revisions to their antidegradation policy or AIMs for input prior to the state's
or authorized Tribe's adoption or finalization of the antidegradation policy or AIMs.
Developing antidegradation policies and AIMs collaboratively with the EPA allows states
and authorized Tribes to accomplish their antidegradation goals while ensuring that the
new or revised antidegradation policies and state or Tribal adopted AIMs are consistent
with the EPA regulation and approvabie by the EPA.28
4.1.4 Applicability of Antidegradation Policies and AIMs
WQS, including antidegradation policies and state or Tribal adopted AIMs, serve two
purposes. First, they establish the desired condition for a specific waterbody, and second,
they serve as the legal basis to protect water quality for all purposes under the CWA. For
example, WQS are used to derive water quality-based effluent limits (WQBELs) in NPDES
27 As of October 17, 2023, no Tribes have been authorized to administer the NPDES program.
28 See Chapter 6: Procedures for Review and Revision of Water Quality Standards of this Handbook for more information
on WQS review and submittal processes.
DRAFT CHAPTER 4: Antidegradation 14
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permits,29 to assess whether waters are impaired, and to develop Total Maximum Daily
Loads (TMDLs) to restore impaired waters.30 These CWA based programs are aimed at
assessing and achieving the applicable WQS in the receiving water.
Point source means any discernible,
confined, and discrete conveyance,
including but not limited to, any pipe,
ditch, channel, tunnel, conduit, well,
discrete fissure, container, rolling stock,
concentrated animal feeding operation,
landfill leachate collection system,
vessel or other floating craft from which
pollutants are or may be discharged.
This term does not include return flows
from irrigated agriculture or agricultural
storm water runoff. (See 40 CFR 122.3).
(40 CFR 122.2).
Nonpoint source means any source of
water pollution that does not meet the
legal definition of "point source" in
Section 502(14) of the CWA.
States' and authorized Tribes' WQS,
including antidegradation policies and
state or authorized Tribal adopted
AIMs, apply to waterbodies and not
to specific sources of pollution.
However, the CWA only authorizes
the EPA, authorized states, and
authorized Tribes to regulate point
sources of pollution in ways that
are binding under federal law (for
example, through NPDES permits).
Congress leaves the decision of
whether and how to regulate nonpoint
sources to the states and Tribes under
state or Tribal law, respectively.31
Nonpoint source pollution is often
a significant contributor to water
quality degradation32 and, in many
cases, the driving reason why waters
do not achieve their WQS. To address
this issue, in addition to implementing
their antidegradation policies and AIMs through point source control programs, the EPA
recommends that states and authorized Tribes implement their antidegradation policies
and AIMs through nonpoint source control programs as well, such as federal or state
incentive-based programs (e.g., through projects or activities funded with CWA Section
319 grants), state or local regulatory requirements, or through voluntary approaches.
The implementation of antidegradation policies and AIMs through state or federally
issued permits and licenses and through state and authorized Tribal nonpoint source
control programs will further the efforts to achieve the CWA goal to maintain the water
quality of the Nation's waters.
Where states and authorized Tribes regulate activities that affect the hydrology of the
water, such as water withdrawals, flow, diversions, etc., then a state or authorized Tribe
29 CWA Section 402.
30 CWA Sections 305(b) and 303(d).
31 See American Wildlands v. Browner (2001) where the Tenth Circuit United States Court of Appeals held that the
EPA's approval of Montana's Tier II antidegradation policy, which exempted certain nonpoint source discharges from
antidegradation review, was not arbitrary because "the Act nowhere gives EPA authority to regulate nonpoint source
discharges." (260 F.3d 1192 (10th Cir. 2001)).
32 Based on the EPA Nonpoint Source (NPS) Program's analysis of data from the EPA Ask WATERS Expert Query
(conducted in 2016), of all waterbodies that have been assessed and a possible source of impairment identified, 85% of
rivers/streams and 80% of lakes/reservoirs are polluted by nonpoint sources, https://www.epa.gov/sites/production/
files/2016-10/documents/nps program highlights report-508.pdf.
DRAFT CHAPTER 4: Antidegradation
15
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may conduct an antidegradation review before authorizing an activity that could result in
a lowering of water quality.
For additional information about antidegradation application and implementation, see
section 4.7 of this chapter.
4.1.5 Antidegradation in CWA Implementation
Programs
As described in greater detail in section 4.8, antidegradation protections must be
considered and incorporated into authorizations for CWA regulated activities to the
same extent as other WQS requirements. In addition, states and authorized Tribes have
the discretion to implement antidegradation requirements for state or Tribal voluntary
control programs.
Under CWA Section 402, NPDES permits are issued to regulate point source discharges
into waters of the United States. When calculating WQBELs, which are derived from
applicable WQS, permit writers must ensure waters receive their appropriate level of
antidegradation protection (40 CFR 122.44(d)(vii)(A)). Consistent with the state's or
authorized Tribe's antidegradation policy and applicable AIMs, permit writers may need
to adjust WQBELs to ensure appropriate levels of antidegradation protection, and states
and authorized Tribes must conduct Tier 2 reviews to allow a lowering of water quality
in a high quality water.
For more information on
CWA Section 402 Permits,
see section 4.8.1 of this
chapter.
Under CWA Section 404,
dredged and fill permits
regulate the discharge of
dredged or fill material
into waters of the United
States. These permits are
issued by the United States
Army Corps of Engineers
(Corps), with the exception
of those states or Tribes
who have assumed administration of CWA Section 404. Activities regulated by this
program can include discharges of fill for development, water resource projects (such
as dams, water intakes, and levees), infrastructure development (such as highways and
airports), and mining projects. States and authorized Tribes may want to coordinate
with the Corps to ensure that antidegradation protections are appropriately included
ANTIDEGRADATION PROTECTION MUST
BE CONSIDERED IN THE FOLLOWING
CWA REGULATORY PROGRAMS:
CWA Section 303(d) and 305(b) (assessments,
listings, and TMDLs)
CWA Section 401 (state certifications)
CWA Section 402 (NPDES permits)
CWA Section 404 (dredge and fill discharge
permits)
-------
in Corps permits. Existing uses (Tier 1) can be protected by ensuring no "significant
degradation," as defined by the CWA Section 404(b)(1) Guidelines, results from the
dredge and fill activity. Along with Tier 1 protection, states and authorized Tribes must
provide the same level of Tier 2 and Tier 3 protection for jurisdictional wetlands as is
afforded other waters of the United States, consistent with 40 CFR 131.12. Therefore,
where a state or authorized Tribe is the permitting authority, the state or Tribe should
ensure that antidegradation protections are approrpriately included in permits they
issue. See section 4.8.2 of this chapter for more information about CWA Section 404
permits.
Antidegradation protections also need to be considered when a state or authorized Tribe
(or the EPA where a Tribe does not have authority) acts on a request for CWA Section
401 certification. An applicant for a federal license or permit to conduct an activity that
may result in a discharge to waters of the United States must request certification from
the state or authorized Tribe where the discharge originates. A grant of certification
indicates compliance with "water quality requirements." Water quality requirements
include, but are not limited to, EPA approved WQS. Therefore, before granting a
CWA Section 401 certification, part of what states or authorized Tribes (or the EPA)
must ensure is that the federal permit or license is consistent with its antidegradation
policy and adopted AIMs. States or authorized Tribes (or the EPA) where the discharge
originates can either grant, waive, or deny CWA Section 401 certification. Examples
of federal licenses and permits subject to CWA Section 401 certification include the
following:
CWA Section 402 N PDES permits that are issued by the EPA.
CWA Section 404 permits for discharge of dredged or fill material that are issued
by the Corps.
Federal Energy Regulatory Commission (FERC) hydropower licenses.
Rivers and Harbors Act Section 9 and Section 10 permits for activities that have a
potential discharge in navigable waters (issued by the Corps).
For more information about CWA Section 401 certifications see section 4.8.3 of this
chapter.
CWA Sections 303(d) and 305(b) programs also need to consider antidegradation.
Under CWA Section 303(d) and the EPA's supporting regulation at 40 CFR 130.7. states
and Tribes authorized to administer the CWA Section 303(d) program are required to
develop a list of threatened and impaired waters every two years. CWA Section 305(b)
and the EPA's supporting regulation at 40 CFR 130.8 also require states and authorized
Tribes to prepare a report every two years on the water quality of all navigable waters.
The 303(d) list identifies waters that are not meeting applicable WQS, which include
antidegradation. For more information on CWA Sections 303(d) and 305(b) programs,
see section 4.8.4 of this chapter.
Antidegradation also needs to be considered when adopting or revising designated
uses and criteria. 40 CFR 131.10(b) states, "In designating uses of a waterbody and
DRAFT CHAPTER 4: Antidegradation 17
-------
the appropriate criteria for those uses, the State shall take into consideration the
water quality standards of downstream waters and shall ensure that its water quality
standards provide for the attainment and maintenance of the water quality standards
of downstream waters." For example, consideration of Tier 1 protection is critical when
the existing use of the downstream waterbody is more protective than the designated
use currently assigned to that downstream waterbody. In such cases, a more stringent
criterion may be needed to protect the existing use in the downstream waterbody.
States and authorized Tribes should also consider downstream antidegradation
requirements, for both waters within their state or Tribal lands and within downstream
state or Tribal lands, when developing their own antidegradation provisions. For high
quality waters (Tier 2) and ONRWs (Tier 3), upstream and downstream states and
authorized Tribes should coordinate to ensure that these waters are appropriately
protected.33
4.1.6 Tribal Reserved Rights
The EPA promulgated "Water Quality Standards Regulatory Revisions to Protect Tribal
Reserved Rights" on May 2, 2024.34 The contents of this WQS Handbook chapter as it
applies to 40 CFR 131.9 are appropriate for consideration during any state or authorized
Tribe WQS adoption, revision, and implementation, as well as the implementation of
federally promulgated WQS. For more information on protecting Tribal reserved rights,
see the Revising the Federal Water Quality Standards Regulations to Protect Tribal
Reserved Rights website.35
4.1.7 Federal Promulgations for Tribes
As a matter of policy, the EPA prefers that states and authorized Tribes adopt their own
WQS. However, under Section 303(cX4) of the CWA and 40 CFR 131.22. the EPA must
promptly propose federal WQS if either of the following conditions occur:
The EPA determines that a new or revised WQS submitted by a state or
^ authorized Tribe is not consistent with CWA requirements and 40 CFR Part 131.
and the state or authorized Tribe does not adopt the changes the EPA specifies
within 90 days from that disapproval.
In any case where the EPA Administrator determines that a new or revised WQS is
^ necessary to meet CWA requirements and 40 CFR Part 131.
Should the EPA propose federal WQS, it must promulgate those WQS within 90 days of
such a proposal unless the state or authorized Tribe adopts and EPA approves the WQS
33 EPA. 2014. Protection of Downstream Waters in Water Quality Standards: Frequently Asked Questions. EPA, Office
of Water. Washington, DC 20460. EPA-820-F-14-001. June 2014. https://www.epa.gov/sites/default/files/2018-10/
documents/protection-downstream-wqs-faqs.pdf.
34 See 89 FR 35717, https://www.aovinfo.aov/content/pka/FR-2024-05-02/pdf/2024-09427.pdf
35 https://www.epa.aov/wqs-tech/revisina-federal-water-quality-standards-reaulations-protect-Tribal-reserved-riahts
DRAFT CHAPTER 4: Antidegradation
18
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prior to the deadline. The EPA's promulgation of federal WQS for any specific Tribe,36
as well as any other WQS promulgated for Indian reservation waters can be found at 40
CFR Part 131, Subpart D (See Chapter 6: Procedures for Review and Revision of Water
Quality Standards of this Handbook for more information on federal promulgations).
The contents of this WQS Handbook chapter are generally appropriate for any adoption,
revision, and implementation of state, Tribal, or federally promulgated WQS. For more
information specifically on the federal Baseline Water Quality Standards Rule that
promulgated federal WQS for Indian reservation waters that do not have Tribally-
adopted, EPA- approved WQS under the CWA, see the Promulgation of Tribal Baseline
Water Quality Standards Under the Clean Water Act website.37
36 For example, the EPA's promulgation of federal WQS for Colville Confederated Tribes Indian Reservation is at 40 CFR
131.35.
37 https://www.epa.gov/wqs-tech/promulqation-tribal-baseline-water-qualitv-standards-under-clean-water-act
DRAFT CHAPTER 4: Antidegradation 19
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4.2 PROTECTION OF EXISTING USES
40 CFR 131.12(a)(1)
The federal regulation at 40 CFR 131.12(a)(1). or "Tier 1" of antidegradation, requires
the maintenance and protection of existing instream water uses and the level
of water quality necessary to protect existing uses.38 As defined at 40 CFR 131.3(e).
"Existing uses are those uses actually attained in the waterbody on or after November
28,1975, whether or not they are included in the water quality standards."39 A use is an
existing use if it meets the definition at 40 CFR 131.3(e), whether or not it is currently
being attained (i.e., the use has been attained at some point on or after November 28,
1975 but may not be currently attained). To implement the "maintain" component of
CWA Section 101(a). existing uses define the floor of water quality in all waters of the
United States beyond which water quality cannot be lowered. Tier 1 protection provides
the mechanism to ensure existing uses are maintained by applying this minimum level
of protection to all waters of the United States. Tier 2 protection reiterates the need to
provide Tier 1 protection by stating that a state or authorized Tribe "shall assure water
quality adequate to protect existing uses fully" when allowing a lowering of water quality
(40 CFR 131.12(a)(2)).
38 Water Quality Standards Regulation, 48 Fed. Reg. 51403 (November 8,1983).
39 For additional information on existing uses, see section 2.3.3.1 of Draft Chapter 2 of this Handbook.
DRAFT CHAPTER 4: Antidegradation 20
-------
Tier 1 protection applies to the waterbody as a whole. In order to assure that this
protection is maintained when a state or authorized Tribe allows an activity that may
lower water quality, a state or authorized Tribe needs to first identify the existing use
and level of water quality protective of the existing use. To support identification and
protection of existing uses, the EPA recommends that states and authorized Tribes adopt
a definition of the term 'existing uses' that is consistent with the definition at 40 CFR
131.3(e). Then, a state or authorized Tribe needs to review a proposed activity (e.g., new
or increased NPDES discharge) to determine whether the activity will degrade water
quality to the point where the existing uses would no longer be protected. The state
or authorized Tribe cannot allow a proposed activity, as requested, if it will foreseeably
lower water quality to the extent that it is no longer sufficient to protect and maintain
the existing uses in that waterbody. Instead, the state or authorized Tribe has three
choices. First, it could deny an authorization of the proposed activity. Second, it could
require that the entity lowering the water quality implement measures to offset its
pollutant contribution or otherwise protect and maintain existing uses and the water
quality of the waterbody prior to obtaining the authorization. If the state or authorized
Tribe chooses to require a pollution offset, that offset would need to occur in the
waterbody where the degradation would occur. Third, the authorizing authority could
issue the authorization for the proposed activity with conditions or limits stringent
enough to protect the existing uses.
States and authorized Tribes that ensure any lowering of water quality will continue to
protect a waterbody's applicable designated uses can be reasonably assured that the
existing uses are also protected. However, at times, a state or authorized Tribe may not
have yet revised its designated uses to reflect an existing use. Such existing uses must
still be maintained and protected. If, through the antidegradation review process, the
state or authorized Tribe determines that the currently adopted designated uses do not
reflect an existing use that is presently being attained, 40 CFR 131.10(i) requires the state
or authorized Tribe to revise its WQS to reflect the uses actually being attained and adopt
criteria sufficient to protect such uses.40 In addition, if the antidegradation review process
identifies a use specified in CWA Section 101(a)(2) as an existing use that is not protected
by the currently applicable designated uses nor is it presently being attained (i.e., 40 CFR
131.10(i) is not applicable), but the triennial review finds that the existing use is feasible
to attain, 40 CFR 131.20(a) requires the state or authorized Tribe to "revise its standards
accordingly." The EPA encourages communication across state and authorized Tribal water
programs to ensure appropriate designated uses are in place, particularly if the program
performing the antidegradation review is not the same as the program that developed
the water quality standards (e.g., the permitting program vs. the water quality standards
program)
For additional information about antidegradation implementation and application, see
section 4.8 of this chapter.
See Draft Chapter 2. section 2.5.1 of this Handbook.
DRAFT CHAPTER 4: Antidegradation
21
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4.3 PROTECTION OF HIGH QUALITY
WATERS - 40 CFR 131.12(a)(2)
1 is intended to protect the waters in which water quality levels are better than
necessary to support the protection and propagation of fish, shellfish and wildlife, and
recreation in and on the waterbody. This regulation specifies that Tier 2 protection
applies when water quality exceeds the levels needed to protect the CWA Section 101(a)
(2) uses. However, states and authorized Tribes have the discretion to expand Tier 2
protection to water quality that exceeds the levels necessary to protect non-101(a)C2)
uses, as well as 101(a)(2) uses. "Exceeds" in this context refers to water quality being
better than necessary to support CWA Section 101(a)(2) uses or non-101(a)(2) uses.
Generally speaking, water quality levels that are better than necessary to support
the protection and propagation offish, shellfish and wildlife, and recreation in and
on the waterbody (i.e., high water quality) must be maintained and protected unless
the state or authorized Tribe finds that a lowering41 of high water quality is necessary
to accommodate important economic or social development in the area in which the
waters are located. The federal regulation requires a systematic, public decision-making
process for determining whether or not to allow some degradation of water quality in
high quality waters (up to, but not beyond what protects the CWA 101(a)(2) uses).42
The Tier 2 decision-making framework is intended to ensure high water quality is
protected by determining if there are alternatives to proposed activities that would
result in reduced degradation. However, the outcome of a Tier 2 review may be to
authorize degradation of high quality waters, e.g., where an important activity, from an
economic and social development standpoint, would result in water quality degradation
and there is no practicable alternatives that could be implemented to avoid or reduce
such degradation. In such cases, after a Tier 2 review has been completed, high water
quality may only be lowered down to the level that fully protects all the waterbody's
applicable designated and existing uses43 and cannot lead to a use impairment.44
41 Lowering means an increase in pollution, resulting from an activity that would use some of the assimilative capacity in a
high quality water. In this regard, the quality of water is lowered closer to the level of pollution that is protective of the
CWA Section 101(a)(2) uses.
42 Water Quality Standards Regulation, 63 Fed. Reg. 36762 (July 7,1998).
43 The EPA's Response to Comments, Water Quality Standards Regulatory Revisions, Chapter 3 Issue Category:
Antidegradation. Docket # EPA-HQ-OW-2010-0606. August 2015. pg. 3-177 - 3-180, https://www.reaulations.gov/
document/EPA-HQ-QW-2010-0606-0344.
44 Water Quality Standards Regulation, 48 Fed. Reg. 51403 (November 8,1983).
DRAFT CHAPTER 4: Antidegradation 22
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4.3.1 Identification of High Quality Waters
The EPA refers to waters where the quality of water is better than necessary to
support the CWA Section 101(a)(2) uses as high quality waters.45 High quality waters
have assimilative capacity, that is, they can receive additional pollution46 and still meet
the quality necessary to protect the CWA Section 101(a)(2) uses. In the context of
antidegradation, assimilative capacity is the difference in water quality between what
level(s) is needed to protect the CWA Section 101(a)(2) use(s) and the actual, better
water quality that is observed in the waterbody at the time the activity to lower high
water quality is proposed (Figure 4-1).
Designated Use: Aquatic Life
o
fa 120 |Jg/L
<1J
U
C
o
u
u
c
N
¦4-J
"fD
20 ug/L
Cf HS
!_
<1J
-I—'
H3
Assimilative
capacity
Zinc Criterion
^\Ambient Zinc Concentration
Figure 4-1. Example of Water Quality that is Betterthan Necessary to Support a CWA Section
101(a)(2) Use. The current ambient concentration of zinc is lowerthan the criterion forzinc
associated with the aquatic life use, indicating that the water quality is better than necessary
to support a CWA Section 101(a)(2) use. Therefore, this water is high quality and has available
assimilative capacity with regards to zinc.
45 Designated uses may reflect a future goal for a waterbody, so the EPA recommends that states and authorized Tribes
consider designating uses of a waterbody independently from assigning antidegradation tiers to a waterbody.
46 Pollution is defined under the CWA as "the man-made or man-induced alteration of the chemical, physical, biological,
and radiological integrity of water" (CWA Section 502(19)).
DRAFT CHAPTER 4: Antidegradation
23
-------
To identify which waters are high quality waters, states and authorized Tribes may
use a parameter-by-parameter approach, a waterbody-by-waterbody approach, or a
combination of the two approaches. The EPA recognizes that both approaches can be
used in a manner consistent with the CWA and the federal antidegradation regulation
(40 CFR 131.12(a)(2)(i)). Once a waterbody is determined to be high quality using one of
these approaches, the Tier 2 review process proceeds in the same manner, determining
which parameters have assimilative capacity and determining whether the use of that
assimilative capacity (lowering of high water quality) is necessary to accommodate
important economic or social development in the area in which the waters are located
(Figure 4-2).
Designated Use: Aquatic Life
o
fa 120 |Jg/L
<1J
U
C
o
u
u
c
N
¦4-J
"fD
=3
a
!_
a>
-i—>
H3
50 jJg/L
20 jjg/L
Assimilative
capacity
Lowering of
high water
quality
Zinc Criterion
— — Zinc Concentration if Proposed Activity is Allowed
^\^ Ambient Zinc Concentration
Figure 4-2. Example of Lowering of High Water Quality. An activity is being proposed that
utilizes some of the assimilative capacity of zinc in this waterbody. If allowed through a Tier 2
review, this use of assimilative capacity would be a lowering of high water quality.
4.3.1.1 Determining Ambient Water Quality
The first step in determining whether a waterbody is high quality is establishing what
the current ambient water quality is in the waterbody. States and authorized Tribes can
do this by either evaluating existing data or collecting new data to establish current
water quality conditions. The ambient water quality should be determined each time an
authorization for a lowering of water quality is being considered.
DRAFT CHAPTER 4: Antidegradation 24
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This information can then be used for two purposes: (1) determining how much
assimilative capacity47 is in a waterbody for each parameter; and (2) establishing a
baseline for tracking the use of that assimilative capacity cumulatively overtime.
4.3.1.2 Parameter-by-Parameter Approach
States and authorized Tribes using a parameter-by-parameter approach identify
which waters receive Tier 2 protection for a specific chemical, physical, or biological
parameter(s) at the time an entity proposes an activity that could lower the water quality
of that parameter(s). When an activity is proposed, the permitting authority identifies
which parameters are included in the discharge or impacted by the activity. It then
determines whether the ambient water quality for any of those parameters "exceeds
levels necessary to support the protection and propagation of fish, shellfish, and wildlife
and recreation in and on the water" C40 CFR 131.12(a)(2)). In practice, to implement
this provision, the permitting authority would determine for which parameters the
water quality is better than the applicable narrative or numeric criteria that protect the
CWA Section 101(a)(2) uses. Each parameter is considered independently (Figure 4-3).
If the permitting authority determines the ambient concentration of a parameter(s)
is at a level better than the applicable numeric or narrative criterion that protects the
associated CWA Section 101(a)(2) use, the state or authorized Tribe would conduct a
Tier 2 review for that parameter(s) to determine whether the proposed lowering of high
water quality is necessary to accommodate important social and economic development
in the area in which the waters are located. The permitting authority, whether a state,
authorized Tribe, or the EPA, can follow a state's or authorized Tribe's AIMs to determine
whether a waterbody is high quality for a particular parameter. But, if a lowering of that
high water quality is being considered, the state or authorized Tribe has to make the
decision about whether the lowering is necessary to accommodate important social
and economic development in the area in which the waters are located. The parameter-
by-parameter approach provides Tier 2 protection to any parameter with available
assimilative capacity, regardless of whether assimilative capacity exists for other
parameters within the same waterbody/waterbody segment.
When using the parameter-by-parameter approach, the identification of high quality
water occurs at the time an entity proposes an activity that could lower the water
quality. Therefore, the level of protection applied to that waterbody will be subject to
the public involvement requirements associated with that activity. This provides the
public an opportunity to provide input on the provision of Tier 2 protection through the
public involvement requirements of these individual activities, such as the issuance of
NPDES permits.48
47 When determining how much assimilative capacity is available in a waterbody to allocate to an individual activity, a
state or authorized Tribe [or permitting authority] should identify whether any permitted facility on the waterbody
is not yet discharging at its fully authorized level. If so, then the permitting authority would use the maximum
authorization levels for all discharging entities on the waterbody to determine how much assimilative capacity is still
available in the waterbody for a new or expanded activity.
48 Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51030 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 25
-------
Due to evolving science, there may be times at which a state's or authorized Tribe's
numeric or narrative criteria do not reflect the latest science on the water quality
levels that protect the CWA 101(a)(2) uses. When this is the case, the EPA strongly
recommends that a state or authorized Tribe update its criteria as soon as possible,
but no later than its next triennial review (see Chapter 6: Procedures for Review and
Revision of Water Quality Standards of this Handbook for information about the
requirements of a triennial review). This will assure that the criteria appropriately protect
the CWA 101(a)(2) uses when being used for CWA implementation purposes, including
for determining assimilative capacity.
Designated Use: Aquatic Life
o
'¦4—"
03
<1J
U
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o
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!_
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-I—'
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03
!_
03
CL
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-i—>
03
60 |jg/L
52 jjg/L
20 |jg/L
03
=3
a
Assimilative
capacity of
zinc
Zinc Criterion
Ambient Nickel Concentration
Nickel Criterion
Ambient Zinc Concentration
Figure 4-3. Example of the Parameter-by-Parameter Approach. In this example, the ambient
concentration of zinc supports the CWA Section 101(a)(2) uses and assimilative capacity is
available for zinc. However, the ambient concentration of nickel does not support the CWA
Section 101(a)(2) uses and thus no assimilative capacity is available for nickel. In this instance, the
state or authorized Tribe would provide Tier 2 protection for zinc, but not for nickel.
DRAFT CHAPTER 4: Antidegradation 26
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4.3.1.3
Waterbody-by-Waterbody Approach
A waterbody-by-waterbody approach is where a state or authorized Tribe uses a variety
of factors to judge a waterbody's overall quality and identify which waterbodies have
quality that is better than necessary to support the CWA Section 101(a)(2) uses. A
waterbody-by-waterbody approach allows states and authorized Tribes to consider
chemical, physical, biological, and other information (e.g., unique ecological or scenic
attributes) to determine which waters are high quality overall.49 When deciding which
waters are high quality, 40 CFR 131.12(a)(2)(i) specifies that states and authorized
Tribes must provide an opportunity for public involvement on the factors considered
in deciding whether or not to provide Tier 2 protection to a particular waterbody. Such
factors should be rooted in the goals of the CWA. A state or authorized Tribe may
consider a range of factors, including but not limited to the following:
Ambient water quality for all pollutants and parameters,
Factors that affect existing aquatic life uses including aquatic assemblages,
habitat, hydrology, geomorphic processes, and landscape condition,
Existing recreational uses and recreational significance,
Overall value and significance from an ecological, public health, and public-use
perspective, and
The value of retaining ecosystem resilience against future stressors.
It is important that states and authorized Tribes consider all relevant available data when
conducting an overall holistic assessment. Numerous tools, such as biological, habitat,
hydrologic, geomorphic, and landscape assessments or the environmental impact
statement rating system, could be useful to states and authorized Tribes in making and
supporting decisions on whether to provide Tier 2 protection. In instances where states
and authorized Tribes lack data and information on the water quality to make individual
waterbody conclusions, the EPA recommends that they provide all or a subset of their
waters with Tier 2 protection by default. On the other hand, if a state or authorized
Tribe is able to conduct a holistic evaluation with public involvement, it can use that
evaluation to decide whether or not the water is a high quality water and warrants Tier
2 protection.50 Such determinations may be made prior to considering an authorization
of a lowering of water quality (e.g., the state or authorized Tribe may identify a list of
waterbodies classified as "high quality" or "Tier 2" for the purposes of antidegradation)
or at the time of considering an authorization of a lowering of water quality.
For the waterbody-by-waterbody approach, if after conducting an overall holistic
evaluation it is demonstrated that the water quality is better than necessary to support
all the CWA Section 101(a)(2) uses, the state or authorized Tribe must provide that
waterbody with Tier 2 protection. If not, states and authorized Tribes have discretion
49 Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51030 (August 21, 2015).
50 Where a state or authorized Tribe has done a holistic evaluation with public involvement and determined that the
water is not high quality nor does it warrant Tier 3 protection (See section 4.4 for further discussion on Tier 3), it may
identify the waterbody as a waterbody receiving Tier 1 protection only.
-------
to choose whether to apply Tier 2
protection, provided the state or
authorized Tribe does not exclude
a waterbody from Tier 2 protection
solely because water quality does
not exceed levels necessary to
support all the CWA Section 101(a)
(2) uses of the Act (40 CFR 131.12(a)
(2)(i)). A state or authorized Tribe
could not exclude a water from Tier
2 protection solely because it was impaired for a single 101(a)(2) use; either all 101(a)(2)
uses would need to be impaired or other factors from the holistic evaluation, such as
habitat, diversity, or hydrology would also need to indicate that the waterbody was not
high quality.51 In other words, states and authorized Tribes could only decide to exclude
a water from Tier 2 protection if a holistic evaluation of the waterbody was completed
and it demonstrated that overall the waterbody was not high quality. If a waterbody
can be excluded from Tier 2 protection without a holistic evaluation of the waterbody
solely because one of the CWA Section 101(a)(2) uses is not being attained, assimilative
capacity could potentially be lost in a large number of state and Tribal waters for
parameters associated with non-impaired uses without any opportunity for public input.
This approach would not be consistent with the objectives of the CWA to "restore and
maintain the chemical, physical and biological integrity of the nation's waters" nor with
the intent of the antidegradation regulation that implements this objective. Rather, a
state or authorized Tribe would need to consider all the chemical, physical, and biological
characteristics of that waterbody and decide whether overall that waterbody is high
quality or not.
KEY POINT:
A waterbody cannot be excluded from
Tier 2 protection solely because it
does not support ALL CWA Section
101(a)(2) uses. It can still receive Tier 2
protection, even if it only supports one
CWA Section 101(a)(2) use.
st The EPA's Response to Comments, Water Quality Standards Revision, Chapter 3 Issue Category: Antidegradation,
Docket # EPA-HQ-OW-2010-0606. August 2015. pg. 3-154 - 3-176. https://www.reaulatioris.qov/documerit/EPA-HQ
QW-2010-0606-0344.
DRAFT CHAPTER 4: Antidegradation 28
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In addition, a state or authorized Tribe may still identify a water as high quality even if
it went through the regulatory process to remove one of the CWA Section 101(a)(2)
uses because that designated use is not attainable (e.g., a waterbody is designated as
limited aquatic life use rather than aquatic life use). While that waterbody may not have
the ability to attain water quality to fully support the designated use that was or will be
removed, it may still have high water quality supporting a different CWA Section 101(a)
(2) use that warrants Tier 2 protection.
If the state or authorized Tribe has determined that a water is a Tier 2 water, then
whenever a lowering of water quality is proposed for that water, the state or authorized
Tribe would conduct a Tier 2 review (see section 4.3.2). The Tier 2 review will evaluate
all parameters affected by the proposed activity for which assimilative capacity exists in
the waterbody (similar to the review done for the parameter-by-parameter approach)
(Figure 4-4). If the receiving waterbody is not on the Tier 2 list because a holistic
evaluation has demonstrated that as a whole it is not high quality, the state or authorized
Tribe would not need to conduct a Tier 2 review, even if some parameters have
assimilative capacity (Figure 4-5). This is different than the parameter-by-parameter
approach, where a Tier 2 review must evaluate any parameter associated with a CWA
Section 101(a)(2) use with assimilative capacity that may be impacted by the lowering of
water quality. In both approaches, the state or authorized Tribe must still provide Tier 1
protection to the waterbody.
Public Engagement and Transparency
In order to meet the public involvement requirement at 40 CFR 131.12(a)(2)(i), states and
authorized Tribes must involve the public in any decisions pertaining to waters that will
receive Tier 2 protection, including the factors that will be used to decide which waters
will receive Tier 2 protection. With regards to how to involve the public, the requirement
at 40 CFR 131.12(a)(2)(i) uses the phrase "opportunity for public involvement" rather
than "public participation," which is used in 40 CFR 131.20(b). The difference in
terminology is purposeful to provide states and authorized Tribes flexibility in how they
engage the public in this decision-making process.52
States and authorized Tribes may meet the public involvement requirement at 40
CFR 131.12(a)(2)(i) in a number of ways, such as a public hearing, public meeting,
public workshop, webinar or posting the information on a public website with contact
information so the public has the opportunity to provide input. To streamline this
process, the state or authorized Tribe could solicit public input on which waters will
receive Tier 2 protection along with descriptions of the factors they considered in
making those decisions during a triennial review and/or when receiving public input
on an AIMs revision. Obtaining public input during either of these processes has the
advantage of only having to post information for public notice once for two different,
but related, processes. Alternatively, if a state or authorized Tribe adopts a list of
Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51031 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 29
-------
Tier 2 waters into their WQS, then the public involvement requirement will be met by
the public participation requirement associated with the adoption of WQS. As another
example, a state or Tribe authorized to administer the CWA Section 402 program53
could use the public notice process for an NPDES permit to engage the public on its
decision on whether or not the waterbody will be afforded Tier 2 protection.54 This
would be done at the time the state or Tribe proposes a permit that would allow a
lowering of water quality. The state or authorized Tribe could document the relevant
information related to its decision to afford Tier 2 protection to the water in the public
notice for the permit and specifically request comment on that decision and the factors
considered in making that decision. States and authorized Tribes might find it useful for
public engagement to provide water specific rationales for these decisions during the
public involvement process or when responding to comments.
Therefore, the EPA recommends states and authorized Tribes document their overall
assessment in support of their Tier 2 decisions. Doing so builds trust and shows
transparency in decision making. Whichever approach is used, the EPA recommends
that states and authorized Tribes involve the public as early as possible, so stakeholders
have sufficient time to be engaged in the decision -making process.
53 As of September 26, 2023, no Tribes are currently authorized to administer the CWA Section 402 program and the
EPA is the permitting authority. To address the requirement for providing an opportunity for public involvement on
decisions to provide Tier 2 protection, the Tribe may request that the EPA include the information related to this
decision in the permit public notice.
54 Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51031 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 30
-------
The state or authorized Tribe could develop its Tier 2 waters list in one of the two
following ways:
1. The state or authorized Tribe could develop a list prior to considering any
authorizations for lowering high water quality by conducting holistic reviews of all
its waters and creating a list that would be available for when an authorization for
lowering is being considered, or
2. The state or authorized Tribe could evaluate waters as it considers authorizations
for the lowering of water quality, and then add high quality waters to the list as
those evaluations have been completed.
In either instance, the state or authorized Tribe would be required to provide an
opportunity for public involvement in decisions about whether a water should receive
Tier 2 protection, and the factors considered in making those decisions, per 40 CFR
131.12(a)(2Xi) as discussed above. After this list has been created, any changes in the
decisions of which waters receive Tier 2 protection, and thus revisions to this list, would
also require public involvement per 40 CFR 131.12(a)(2Xi).
It is critical for the public to know which waters have been provided Tier 2 protection. 40
CFR 131.12(a)(2) requires that "where the quality of the waters exceeds levels necessary
to support the protection and propagation offish, shellfish, and wildlife and recreation
in and on the water, that quality shall be maintained and protected...." Implementing
programs, such as the permitting authority, can only "maintain and protect" the water
quality of a Tier 2 water if they know which waters the state or authorized Tribe has
identified as high quality waters. In addition, it is critical for the public to have access
to information on which waters the state or authorized Tribe has deemed high quality
so that regulated entities are fully aware of their obligations and the basis for permit
requirements. Such access will also ensure that the public has the necessary information
to hold states and authorized Tribes accountable when implementing WQS. Therefore,
to ensure that high quality waters "shall be maintained and protected" consistent with
40 CFR 131.12(a)(2), the EPA expects states and authorized Tribes to make their Tier 2
lists publicly available. A Tier 2 list could be made publicly available by adopting the list
into rule, posting it on a public website, or by housing it in another location that is easily
accessible to the public. Where a state or authorized Tribe chooses to adopt its Tier 2
waters list into rule, the EPA will review and approve or disapprove those decisions as
new or revised WQS consistent with CWA Section 303(c). However, the EPA recognizes
that making the final list broadly available may not be desired in certain unique instances.
Where a state or authorized Tribe does not wish to make their final list of Tier 2 waters
broadly available, it may specify in its policy or AIMs how interested parties can request
information on which waters are Tier 2 and provide that information upon request.
Making this information publicly available will ensure proper implementation and
oversight of the antidegradation policy consistent with 40 CFR 131.12(a)(2).
Regardless of how a state or authorized Tribe makes the Tier 2 information available
to the public, the EPA recommends periodically revisiting the list of Tier 2 waters to
make sure that waters are appropriately classified and protected. One option may be to
DRAFT CHAPTER 4: Antidegradation 31
-------
revisit this list during a triennial review. If any waterbodies are added or removed from
the list during this time, then the state or authorized Tribe can streamline the public
involvement required by 40 CFR 131.12(a)(2Xi) by pairing it with the public participation
process for the triennial review. As another option, states and authorized Tribes may
choose to provide avenues for ongoing public involvement beyond the triennial review
process by providing structured opportunities for the public to initiate antidegradation
discussions. For example, a state or authorized Tribe could provide a petition process in
which citizens can request Tier 2 protection for specific waters, and those citizens could
provide data and information for a state's or authorized Tribe's consideration.
Designated Use Supported: Aquatic Life
Designated Use Not Supported: Recreation
Antidegradation Protection: Tier 2
Basis: Waterbody-by-Waterbody
Zinc Criterion
— — Zinc Concentration if Lowering of Water Quality
is Allowed
Ambient Zinc Concentration
Assimilative
capacity
Tier 2 review
is required
to determine
if degradation
is necessary to
accommodate
important
economic
and social
development
Figure 4-4. Example of a Water Receiving Antidegradation Tier 2 Protection Using the
Waterbody-by-Waterbody Approach. Waterbody A supports a full aquatic life use, but does not
attain a full recreation use. After completing a holistic assessment of the waterbody, the state
or authorized Tribe has placed this water on the Tier 2 list with support from the public, as this
waterbody is home to several fish species important to commercial and recreational fishing and
is high quality with respect to aquatic life. An entity proposes an activity that would lower water
quality for zinc, a parameter that currently has an instream concentration that is better than
necessary to support the full aquatic life use. Since this water is on the Tier 2 list, a Tier 2 review
must be conducted before the state or authorized Tribe can allow the lowering of high water
quality.
DRAFT CHAPTER 4: Antidegradation
32
-------
Designated Uses Not Supported: Aquatic Life & Recreation
Antidegradation Protection: Tier 1
Basis: Waterbody-by-Waterbody
OQ
O
¦9
O)
4-j
JG
O
O)
-i—'
(T3
120 |Jg/L
¦ir! 50 |Jg/L
(T3
=3
a
20 (Jg/L
Assimilative
capacity
Tier 2 review
is not
required
Zinc Criterion
Zinc Concentration if Lowering of Water Quality is Allowed
Ambient Zinc Concentration
Figure 4-5. Example of a Water Not Receiving Antidegradation Tier 2 Protection Using the
Waterbody-by-Waterbody Approach. The state or authorized Tribe has not listed waterbody B
on the Tier 2 water list after completing a holistic assessment of the waterbody and finding that
it is not high quality. This waterbody does not support its aquatic life and recreation uses. An
entity proposes an activity that would discharge zinc. Since this state or authorized Tribe is using
a waterbody-by-waterbody approach and waterbody B is not on the Tier 2 list, no Tier 2 review
is required to allow this lowering of water quality even though there is assimilative capacity
for zinc. The state or authorized Tribe allows the discharge of zinc and writes the permit to the
current criterion, protecting both the designated and existing uses (Tier 1 protection applied).
4.3.1.4 Hybrid Approach
A handful of states and authorized Tribes use a hybrid approach for identifying waters
that will receive Tier 2 protection. In these instances, states and authorized Tribes
may specify that a certain type or class of water will automatically be afforded Tier 2
protection, while for all other waters, the state or authorized Tribe will assign Tier 2
protection on a parameter-by-parameter basis. The state or authorized Tribe will either
maintain a list of waters assigned Tier 2 protection or will specify the types of waters
that receive Tier 2 protection (e.g., streams that receive annual stockings of trout). Then
during the process of determining whether a waterbody is high quality, the state or
authorized Tribe will first ask if the water has been assigned Tier 2 protection. If not, they
DRAFT CHAPTER 4: Antidegradation
33
-------
will use a parameter-by-parameter approach to determine if they should provide Tier 2
protection to certain water quality parameters.
4.3.1.5 Considerations for Selecting an Approach
Both the parameter-by-parameter and waterbody-by-waterbody approaches have
their advantages and disadvantages. When a state or authorized Tribe is deciding which
approach is best for it, it should consider which approach will allow it to most effectively
use its resources to provide protection for high water quality.
Some states and authorized Tribes have found the parameter-by-parameter approach
more streamlined to implement because the state or authorized Tribe does not need to
conduct a thorough overall, holistic assessment of the waterbody nor provide a separate
opportunity for public input. Decisions are driven strictly by ambient water quality data
rather than judgments concerning a waterbody's overall value or quality. In addition,
since the parameter-by-parameter decisions are based on ambient water quality data,
some states and authorized Tribes consider those decisions easier to explain and thus
may be less susceptible to challenge. The parameter-by-parameter approach may also
result in more waters receiving some degree of Tier 2 protection because the state
or authorized Tribe would provide Tier 2 protection for parameters with assimilative
capacity even if those waters are not supporting any CWA Section 101CaX2^) uses overall.
DRAFT CHAPTER 4: Antidegradation
34
-------
A waterbody-by-waterbody approach allows states and authorized Tribes to identify
which waters are "high quality" as a whole, consistent with the overarching CWA goal
to maintain the chemical, physical and biological integrity of the waters. Thus, where
resources are limited, states and authorized Tribes can focus their efforts on protecting
their higher-value waters based on an assessment of each water's overall chemical,
physical and biological condition.55 This approach also allows for states and authorized
Tribes to make Tier 2 decisions in advance of the antidegradation review, which may
facilitate implementation by providing the public and regulated community with
upfront information and an opportunity to influence which waters will be protected as
Tier 2. Maintaining a list of high quality waters may also be beneficial for water quality
management across programs. For example, nonpoint source programs may be able to
use lists of high quality waters as a resource for developing prioritization frameworks
to target water quality protection work. However, for complicated situations, such
as where the water is meeting some CWA 101(a)(2) uses but not others, some states
and authorized Tribes may find the process of identifying high quality waters using the
waterbody-by-waterbody approach more resource intensive than the parameter-by-
parameter approach. If this is the case, the state or authorized Tribe might consider
whether spending its water quality protection resources performing a Tier 2 review to
determine whether a proposed lowering is necessary to accommodate important social
and economic development in the area might be better than holistically evaluating
waters to identify which waters should be afforded Tier 2 protection.
States and authorized Tribes have discretion when identifying how to provide Tier 2
protection but must do so in a manner consistent with the CWA and 40 CFR 131.12.
Where a state or authorized Tribe decides to change the method used to identify high
quality waters, they may do so, as long as it is in a manner that is consistent with the
CWA and 40 CFR 131.12 and the state or authorized Tribe updates their implementation
methods to reflect the change. The federal regulation does not require states and
authorized Tribes to identify which waters are afforded Tier 2 protection in rule or other
legally binding documents. However, where a state or authorized Tribe identifies waters
for Tier 2 protection in its legally binding WQS (e.g., in its antidegradation policy or
adopted implementation methods), the EPA does have the authority and duty to take a
CWA Section 303(c) action on those categorizations as new or revised WQS. 40 CFR
131.12 also requires that if a state or authorized Tribe uses a waterbody-by-waterbody
approach, the state or authorized Tribe must provide the opportunity for public
involvement in any decisions on which waters are assigned Tier 2 protection and the
factors considered in that decision-making process.
4.3.2 Antidegradation Tier 2 Review
A Tier 2 review is a structured process designed to help a state or authorized
Tribe decide whether the proposed lowering of high water quality is necessary to
accommodate important economic or social development in the area in which the water
55 Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51030 (August 21, 2015).
-------
is located. The finding is based on an analysis of alternatives and a socio-economic
analysis. The analyses may be performed in whichever order the state or authorized Tribe
chooses.
A state or authorized Tribe may conduct the Tier 2 review itself or it may evaluate
analyses submitted by other entities before deciding whether to allow the proposed
degradation. Some states and authorized Tribes rely on the applicant to bear the
burden of performing some components of the Tier 2 review (e.g., the analysis of
alternatives and/or the socio-economic analysis) by requiring the applicant to provide
documentation for the state or authorized Tribe to consider in the Tier 2 review. Some
states and authorized Tribes develop worksheets or application forms for permit/
license/authorization applicants to detail their project information so that the state or
authorized Tribe can perform the Tier 2 review
based on an evaluation of that information.
In all cases, the states and authorized Tribes
remain responsible for making the ultimate
decision to allow or deny a proposed lowering
of high water quality.
When a state or authorized Tribe completes the
Tier 2 review but they are not the entity that
authorizes the lowering of water quality, such
as when the EPA is the permit writing authority,
the state or authorized Tribe provides the
outcome of the Tier 2 review to the authorizing
entity to incorporate into the authorization.
Where the state or Tribe is authorized to
administer the CWA Section 401 program, it
would review whether the results of the Tier 2
review are appropriately incorporated into the authorization during the CWA Section 401
certification process that certifies that the authorization meets the state's or authorized
Tribe's water quality requirements, including antidegradation requirements (see section
4.8.3 of this chapter).
To be consistent with 40 CFR 131.12(a)(2). a state or authorized Tribe must conduct an
antidegradation Tier 2 review before deciding to allow a lowering of higher water quality.
The antidegradation Tier 2 review consists of the following components:
Identification of the proposed activity that, if allowed, could potentially lower
high water quality,
Analysis of alternatives,
Socio-economic analysis,
~> Full satisfaction of all intergovernmental coordination and public participation
provisions,
DRAFT CHAPTER 4: Antidegradation 36
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Assurance that the highest statutory and regulatory requirements for point
sources shall be achieved,
^ Assurance that BMPs for nonpoint source pollutant controls shall be achieved, and
Assurance that the resulting water quality after the lowering of high water quality
will protect existing uses (See section 4.2).
4.3.2.1 Tier 2 Review: Identification of Activities that Potentially
Lower High Water Quality
"Water quality standards serve the dual function of establishing water quality goals for
a specific waterbody and providing the basis for regulatory controls."56 WQS, including
antidegradation policies and state or Tribal adopted AIMs, apply to the waterbody
regardless of the activity, source of degradation (point source or nonpoint source), or
whether there are direct, enforceable, federal implementation mechanisms. Therefore,
states and authorized Tribes should not exempt whole classes of activities from WQS
as it would invalidate "the broader, intended purpose of adopted State water quality
standards."57
The application of WQS is to the waterbody and not limited to activities with
enforceable implementation mechanisms. "Applicability and enforceability are two
distinctly separate functions in the water quality standards program. Water quality
standards are applicable to all waters and in all situations, regardless of activity or source
of degradation. [However,] implementation of those standards may not be possible in all
circumstances."58 A state or authorized Tribe can specify that certain activities have no
control requirements under state or Tribal law, but they cannot specify that WQS do not
apply to those activities.59
The EPA recommends that states and authorized Tribes clearly specify in their
antidegradation policy and AIMs that the activities that could "trigger" enforcement
of the Tier 2 requirements are any proposed activities that could potentially lower high
water quality.
States and authorized Tribes must implement antidegradation policies and AIMs for point
source activities authorized via permits or licenses under CWA Sections 402 or 404
authorities or to which CWA Section 401 certification applies. In addition, where states
and authorized Tribes have nonpoint source control programs, the EPA recommends
that they conduct an antidegradation review before allowing a lowering of water quality
from such activities. The federal regulation would require a Tier 2 review when one of
those activities would potentially "allow" a lowering (with respect to what has previously
been allowed after an antidegradation review) of water quality in a high quality water.
Activities such as a proposed new discharge to a high quality water or a proposed
56 Davies, T. EPA. 1994. Memorandum: Interpretation of Federal Antidegradation Regulatory Requirement. Office of
Water, Washington DC. https://www.epa.gov/sites/production/files/2014-10/documents/davies-rearequire-memo.pdf.
57 Ibid.
58 Ibid.
59 Ibid.
DRAFT CHAPTER 4: Antidegradation
37
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expansion of an existing facility on a high quality water would likely lower high water
quality. Such activities would not be permissible unless the state or authorized Tribe
conducts a Tier 2 review consistent with its antidegradation policy, its AIMs, and the
federal regulation, and finds that the activity is necessary to accommodate important
economic or social development in the area in which the waters are located. In addition,
a proposed permit/license/authorization re-issuance in which the authorization for an
existing facility/activity would allow more pollution to the waterbody than the previous
authorization had allowed (i.e., an expanded discharge) would also trigger a Tier 2 review.
However, an authorization reissued without any changes to its previous limits would not
trigger a Tier 2 review, as long as a Tier 2 review had previously been completed for this
activity.
Where states or authorized Tribes have nonpoint source control programs, states and
authorized Tribes could incorporate antidegradation reviews into these programs to
ensure that any lowering of water quality is consistent with the larger water quality
goals of the state or authorized Tribe. To ensure that the state's or authorized Tribe's
antidegradation policy and AIMs are both effectively implemented and transparent to
the public and the regulated community, the state's or authorized Tribe's antidegradation
policy and AIMs should explicitly describe which activities will trigger a Tier 2 review.
For additional information about the application and implementation of antidegradation
through other proposed regulated activities that could potentially lower water quality,
see section 4.8 of this chapter.
4.3.2.2 Tier 2 Review: Determining Necessity and Importance of an
Activity
Before allowing a proposed activity to
degrade water quality, a state or authorized
Tribe must make a finding that the lowering
is "necessary to accommodate important
economic or social development in the
area in which the waters are located" (40
CFR 131.12(a)(2)). The finding is not based
simply on whether degradation is necessary
to accomplish the proposed activity, but
also whether the lowering of water quality
actually needs to occur for important socio-
economic development that will benefit the
community impacted by the lowering of high
water quality. This finding relies on a multi-
part analysis to examine, at a minimum, the
following two questions (in any order):
Whether "allowing lower water quality is necessary," by examining alternatives to
DRAFT CHAPTER 4: Antidegradation 38
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the proposed degradation through an analysis of alternatives,60 and
Whether the proposed activity that could potentially result in lowering high water
quality will "accommodate important economic or social development in the area
in which waters are located," through a socio-economic analysis that considers
potential harms and benefits to the community where the lowering of water
quality will occur.61
Analysis of Alternatives
An analysis of alternatives answers the question of whether a proposed lowering of
high water quality is "necessary" or whether an alternative to the proposed lowering
is possible and would result in either no or less degradation. An analysis of alternatives
provides a mechanism for the state or authorized Tribe to determine whether non-
degrading or less degrading practicable alternatives to the proposed activity exist.
It is important to note, however, that 40 CFR 131.12(aX2Xii) only requires the entity
conducting the analysis of alternatives to identify a range of practicable alternatives,
not every possible practicable alternative. For the purposes of this requirement, 40
CFR 131.3(n) defines "practicable" as "technologically possible, able to be put into
practice, and economically viable." If the analysis identifies one or more such practicable
alternatives, states and authorized Tribes cannot make a finding that a lowering of high
water quality is necessary unless one of the alternatives resulting in less degradation
than the originally proposed activity is selected for implementation. The entity selecting
the alternative could be the entity requesting the lowering or the state or authorized
Tribe responsible for authorizing any requested lowering. Whichever entity selects the
alternative, it may choose from the range of practicable alternatives identified in the
analysis. The EPA's regulation does not require the entity to select the least degrading
alternative; however, states or authorized Tribes may choose to specify in their policies
60 Water Quality Standards Regulatory Clarifications, 78 Fed. Reg. 54528 (September 4, 2013).
® Ibid.
DRAFT CHAPTER 4: Antidegradation 39
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or AIMs that the least degrading alternative must be selected. The entity must still
select an alternative even if the analysis identifies only one practicable less degrading
alternative. The original proposal can only be selected if no practicable less degrading
alternatives are identified, making that specific proposed activity "necessary." This
structured analysis of alternatives provides states and authorized Tribes with a basis to
make informed and reasoned decisions, ensuring that degradation only occurs where
truly necessary.
Given the variety of available engineering approaches for pollution control and the
importance of pollution prevention, the state or authorized Tribe's finding of necessity
is among the most important and useful aspects of an antidegradation program and
potentially an extremely useful tool in the context of watershed planning. Retaining
additional assimilative capacity in a waterbody by selecting a less or non-degrading
alternative can help retain resiliency in the waterbody to be able to tolerate future
stressors, such as climate change. While the regulation does not specify who must conduct
the analysis of alternatives, the EPA recommends that the applicant for the proposed
activity develop and present to the state or authorized Tribe a range of pollution control/
pollution prevention alternatives for the state or authorized Tribe to consider during the
Tier 2 review. The applicant is in the best position to evaluate options to its own activity
that could achieve its stated purposes but with alternatives that minimize how much that
activity degrades the water quality in the receiving waterbody.
An analysis of alternatives informs the state's or authorized Tribe's decision of whether
the degradation is "necessary." The state, authorized Tribe, or applicant would conduct
its analysis of alternatives by considering a range of available non-degrading and less
degrading practicable alternatives to the proposed activity. The entity could evaluate any
available, practicable alternatives, which might include the following:
Options for no discharge;
Implementation of pollution prevention measures;
Process changes (e.g., treatment process changes, facility process changes);
Reduction in the scale of the project;
Advanced or different treatment technologies;
Water recycling and reuse;
Seasonal or controlled discharge options that would avoid critical water quality
periods; and
Discharging to an alternative location.
Some alternatives may be unique to the type of permit being issued. For example, when
considering alternatives to dredge and fill discharges that may alter the nature of the
waterbody (e.g., changing a stream into a pond for fishing opportunities), the discharger
could evaluate recreational alternatives (e.g., creating a walking path or docks along the
stream to allow fishing rather than creating a pond) that maintain the original hydrology
and habitat of the waterbody. Regardless of the number of alternatives identified, the
DRAFT CHAPTER 4: Antidegradation 40
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The EPA's guidance on
considering economics for
WQS decisions, found in two
main documents: Interim
Economic Guidance for
Water Quality Standards:
Workbook (hereafter
referred to as "1995 Interim
Economic Guidance") and
Clean Water Act Financial
Capability Assessment
Guidance (hereafter referred
to as "FCA Guidance"), can
help states and authorized
Tribes determine whether an
alternative is economically
viable, which is one of the
elements for determining
whether an alternative
is practicable,62'63The
1995 Interim Economic
Guidance provides guidance
to the public and private
sectors on the types of information that a state or authorized Tribe should consider
when determining whether the cost of implementing pollutant reduction alternatives
could result in a substantial impact to the affected community and/or discharger and
potentially not be economically viable. The FCA Guidance supplements the public sector
sections of the 1995 Interim Economic Guidance with additional indicators and analyses
for low-income residents, an Expanded Economic Impact Matrix, and recommendations
m EPA. 1995. Interim Economic Guidance for Water Quality Standards, Workbook, EPA 823-B-95-002. EPA, Office of
Water, Washington, DC 20460. EPA. March 1995. https://www.epa.gov/svstem/files/documents/2024-01/interim-
economic-auidance-water-quality-standards-workbook-1995.pdf:
63 EPA. 2024. Clean Water Act Financial Capability Assessment Guidance. EPA-800-B-24-001. EPA, Office of Water,
Washington, DC 20460. March 2024. https://www.epa.gov/svstem/files/documents/2023-01/cwa-fmancial-
capability-assessment-guidance.pdf.
analysis should provide a
level of detail commensurate
with the significance and
magnitude of the particular
circumstances encountered.
This will provide the
public with the necessary
information to understand
how the state or authorized
Tribe made its decision.
DRAFT CHAPTER 4: Antidegradation 41
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to consider when making WQS decisions. The FCA Guidance does not revise the
recommended methodology in the private sector sections of the 1995 Interim Economic
Guidance. The EPA's Economic Guidance for Water Quality Standards webpage also
provides spreadsheet tools for the public and private sector analysis to help guide the
user through the steps to successfully implement the FCA Guidance and 1995 Interim
Economic Guidance.
The 1995 Interim Economic Guidance suggests a series of financial tests to help
determine whether the cost of pollutant control alternatives could result in a substantial
impact and potentially not be economically viable. For the public sector, the 1995
Interim Economic Guidance recommends to first calculate a municipal preliminary
screener. The municipal preliminary screener evaluates the impact that the cost
of pollutant control alternatives would have on a household and thus "screens" for
situations where additional analyses may not be warranted. A secondary test further
evaluates the potential for a substantial impact by examining indicators related to the
community's ability to obtain financing and the community's socioeconomic health.
For the private sector, the 1995 Interim Economic Guidance recommends evaluating
several indicators related to the potential impact of pollutant control alternatives on
profit, liquidity, solvency, and leverage. Profit is the income to the owner(s) of a company,
liquidity is a measure of how easily a company can pay its short-term bills, solvency is a
measure of a company's ability to meet its fixed and long-term obligations, and leverage
is a measure how much money a company is capable of borrowing. The lowering of water
quality resulting from the original proposal may not be necessary if these tests indicate
that an alternative is economically viable and, in addition, that alternative is also able to
be put into practice and is technologically possible (i.e., "practicable"). If no alternatives
are economically viable, and thus no alternatives are practicable, then the socio-
economic analysis, which incorporates social indicators of a community into the analysis,
must determine whether the originally proposed activity is important for the community
(See the "Socio-economic Analysis" subsection in this section).
Section III of the FCA Guidance recommends an expanded multi-step approach for
public sector entities to determine which pollutant control alternatives could result in
a substantial impact. In addition to the Initial Economic Impact analyses recommended
in the 1995 Interim Economic Guidance, the FCA Guidance recommends states and
authorized Tribes to:
Calculate a Lowest Quintile Poverty Indicator Score: Evaluate a set of six
socioeconomic statistics from the Census Bureau to help identify low income and/or
economically disadvantaged communities and incorporate that information into the
assessment of economic impacts.
Perform a Financial Alternatives Analysis: Investigate a variety of potential
funding sources and alternative financial mechanisms that could minimize financial
impacts to residents living in overburdened and/or low-income communities so
DRAFT CHAPTER 4: Antidegradation 42
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that these residents also enjoy the benefits of infrastructure investments and
improved water quality.
Combine the analysis recommended in the 1995 Interim Economic Guidance
with the additional analyses recommended in the FCA Guidance: Combine the
analytical results from the 1995 Interim Economic Guidance with the additional
analytical results recommended in the FCA Guidance using the expanded
Economic Impact Matrix.
Finally, the FCA Guidance provides recommendations on how to interpret the combined
analytical results to determine if pollution control alternatives would result in a
substantial economic impact and potentially not be economically viable.
Once the evaluating entity identifies a range of practicable alternatives, the state,
authorized Tribe, or applicant would evaluate the alternatives in terms of the resulting
extent of degradation. By initially considering alternatives that range from non-
degrading to less degrading as opposed to simply identifying the single least degrading
practicable alternative, the state, authorized Tribe, or applicant then has the flexibility
to select the alternative among those best suited for the particular situation. The
state, authorized Tribe, or applicant should consider the environmental impacts
and technological and economic feasibility of the alternatives in the context of the
environmental benefits more holistically by considering implications beyond the direct
effects on water quality, such as cross-media impacts. Such impacts may include, for
example, any potential adverse terrestrial impacts due to land application of pollutants
found in water, or any potential adverse impacts to air quality and energy use due to
incinerating pollutants rather than discharging to surface water.
The benefits of high water quality may be jeopardized if states and authorized Tribes
do not consider the long-term consequences of lowering water quality or evaluate the
alternatives that might be available to reduce the need to degrade a high quality water.
This could reduce the resiliency of that ecosystem, making it more difficult for the
ecosystem to endure the impacts of future stressors, like climate change, and retain
its functionality. As mentioned earlier in this section, the analysis of alternatives may
be conducted by the state or authorized Tribe, the permit applicant, or another entity.
Regardless of who conducts the analysis of alternatives, the state or authorized Tribe
remains ultimately responsible for making the finding that a proposed lowering of high
water quality is necessary.
Socio-Economic Analysis
A socio-economic analysis is another component of the state's or authorized Tribe's
Tier 2 review. This analysis answers the question of whether a proposed (either originally
proposed activity or a selected alternative that still results in some degradation) lowering
of high water quality accommodates important economic or social development in the
area in which the waters are located. The state or authorized Tribe, the permit applicant,
or other entity may conduct the socio-economic analysis. Regardless of who conducts the
DRAFT CHAPTER 4: Antidegradation 43
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analysis, the state or authorized Tribe remains ultimately responsible for making the finding
that a proposed lowering of high water quality is socially and economically important.
Approaches for evaluating social and economic importance vary widely. Determining
the social and economic importance of a proposed activity is an essential public question
best addressed by the state, authorized Tribe, or local interests in the larger context of
the local circumstances, perhaps as part of the development of a basin plan. In addition
to helping determine which alternatives are economically viable, the EPA's Interim
Economic Guidance for Water Quality Standards: Workbook and the Clean Water Act
Financial Capability Assessment Guidance also help determine whether a proposed
activity accommodates important social and economic development.64 These guidance
documents can be useful to states and authorized Tribes in determining the relative
economic impacts of various proposed activities and their relationship to WQS. The
EPA also developed supplemental spreadsheet tools65 that can help states, authorized
Tribes, and stakeholders implement the recommendations of the EPA's Interim Economic
Guidance and FCA Guidance.
No specific financial test can indicate definitively whether an activity is important.
Rather, a state or authorized Tribe can examine a number of factors that may be
impacted by the development and use that information to make a judgement call about
the importance of the activity. The socio-economic analysis may address a range of
factors including, but not limited to, the following:
Employment (e.g., increasing, maintaining, or avoiding a reduction in employment),
Improved community tax base,
£> Housing, and
Correction of an environmental or public health problem.
The socio-economic analysis may consider potential benefits of allowing the activity
(e.g., providing new jobs) and potential detriments of allowing the activity (e.g.,
decreasing recreational value, decreasing tourism revenue, or impacting underserved
portions of the community due to the lowering of water quality). States and authorized
Tribes can also consider whether allowing the activity prevents the use of the
waterbody for a non-degrading or less-degrading activity that would also provide
socio-economic benefits (e.g., approving an industrial plant may preclude waterfront
or marina development).66 Finally, the state or authorized Tribe may consider the long-
term plans of the community, and how allowing a loss of high water quality will affect
the community in the future. Overall, implications of the proposed activity should be
considered in a balanced approach that does not overlook the benefits of maintaining
the level of the high water quality.
64 EPA. 1995. Interim Economic Guidance for Water Quality Standards, Workbook, EPA 823-B-95-002. EPA, Office
of Water, Washington, DC 20460. March 1995. https://www.epa.gov/system/files/documents/2024-01/interim-
economic-auidance-water-quality-standards-workbook-1995.pdf
65 http://water.epa.gOv/scitech/swauidance/standards/economics/#spreadsheet.
66 EPA. 1995. Water Quality Guidance for the Great Lakes System: Supplementary Information Document (SID). EPA
820-B-95-001. EPA, Office of Water, Washington, DC 20460. March 1995. https://www.epa.gov/sites/default/
files/2015-12/documents/1995 water quality guidance for great lakes sid.pdf.
DRAFT CHAPTER 4: Antidegradation 44
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Considerations for These Analyses
States and authorized Tribes have the discretion to decide the order in which each
analysis is performed, but the ultimate finding to allow a lowering of high water quality
depends on both an analysis of alternatives and an analysis of the importance of the
economic or social development in the area in which the waters are located. However, if
the analysis of alternatives finds that the lowering of high water quality is not necessary
or the socio-economic analysis finds that the lowering of high water quality is not
important, then the lowering of high water quality cannot be permitted and there is
no need to conduct the second analysis. For example, if the state or authorized Tribe
determines the proposed lowering would not accommodate important economic or
social development in the area in which the waters are located through a socio-economic
analysis, the state or authorized Tribe could not allow the lowering of high water quality,
and therefore no analysis of alternatives would be needed. Similarly, if after the analysis
of alternatives the state or authorized Tribe selects a non-degrading alternative for
implementation, it does not need to proceed with the socio-economic analysis since the
selected alternative would not lower high water quality. Although states have discretion
to perform these analyses in either order, the EPA finds that it is more practical to do
the analysis of alternatives first and then the socio-economic analysis, as the socio-
economic analysis may differ based on the selected alternative.
As states and authorized Tribes consider the results of the analysis of alternatives and
the socio-economic analysis, they are not obligated to allow a proposed activity and
associated lowering of high water quality to move forward. States and authorized Tribes
could make one of the three following decisions:
1. Allow the activity to lower high water quality as originally proposed if the analysis
of alternatives showed that the lowering was necessary and the socio-economic
analysis showed that the lowering was important. This means that no practicable
alternatives were identified, and that the activity will provide an important social
or economic benefit to the community.
2. Allow the activity to lower high water quality to a lesser extent than proposed.
If the analysis of alternatives identified practicable alternatives that lessen the
degradation, the state or authorized Tribe can only allow the lowering of water
quality if one of those practicable alternatives is implemented and the activity is
shown to provide an important social or economic benefit to the community.
3. Not allow the proposed activity and require maintenance of the current high
water quality. The state or authorized Tribe would make this decision if the analysis
of alternatives identified a non-degrading alternative (demonstrating that the
lowering was not necessary) or if the state or authorized Tribe determined, based
on the socio-economic analysis, that the lowering (even by a less degrading
alternative if one was identified) was not important for the community's social or
economic development.
DRAFT CHAPTER 4: Antidegradation
45
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As mentioned previously, while states and authorized Tribes are responsible for making
the finding to allow a lowering of water quality based on a reasonable, credible, and
adequate analysis of alternatives and socio-economic analysis, they do not need to
conduct these analyses themselves. A permit applicant or another entity could perform
the analyses and then provide that information to the state or authorized Tribe to review
and make the decision about whether to authorize the lowering of water quality in a high
quality water.
4,3.2.3 Tier 2 Review: Intergovernmental Coordination and Public
Participation
The federal regulation at 40 CFR 131.12(a)(2) contains an explicit requirement that a
state or authorized Tribe may only allow a lowering of high water quality, "after full
satisfaction of the intergovernmental coordination and public participation provisions
of the State's continuing planning process." States and authorized Tribes may satisfy
these requirements in a variety of ways, provided they are consistent with the state's or
authorized Tribe's continuing planning process.
A state or authorized Tribe needs to follow its own intergovernmental coordination and
public participation provisions. This may include providing public notice of the draft
permit, providing public notice of the proposed activity, and/or holding a public meeting
associated with the proposed activity that would potentially lower high water quality.
The EPA recommends that states and authorized Tribes provide the public and other
affected government entities information on the proposed activity, the analysis of
alternatives, the socio-economic analysis, the state's or authorized Tribe's preliminary
decision on whether to allow the lowering of water quality, and the extent to which
the water quality would be lowered. The EPA recommends engaging the public and
conducting intergovernmental coordination as early as possible in the Tier 2 review
process. This will ensure the most effective intergovernmental coordination and public
participation.
When complying with the requirement for intergovernmental coordination, some states
DRAFT CHAPTER 4: Antidegradation 46
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and authorized Tribes specifically notify downstream states, Tribes, or management
agencies (e.g., Bureau of Land Management, Forest Service) with purview over lands
surrounding the receiving water that may be affected by the proposed activity. They
may also notify local and municipal governments located in the area of the waterbody
impacted by the activity. For example, a state or authorized Tribe could convene specific
meetings with those other governments or entities on the issue or notify them of the
proposed activity and their ability to comment through the avenues available to the
general public (e.g., public notice process for a permit).
4.3.2.4 Tier 2 Review: Assurance of Existing Use Protection
If a state or authorized Tribe has determined that a lowering of high water quality is
both necessary and important, 40 CFR 131.12(a)(2) requires the state or authorized Tribe
also assure that the resulting water quality after allowing the lowering will still "protect
existing uses fully." This requirement reaffirms Tier 1 protection, that in all waters of
the United States the level of water quality necessary to protect existing uses shall be
maintained and protected. Therefore, a state or authorized Tribe cannot allow a lowering
of high water quality beyond the level that fully protects existing uses.
4.3.2.5 Tier 2 Review: Point and Nonpoint Sources
If a state or authorized Tribe decides to allow a lowering of high water quality, the federal
regulation at 40 CFR 131.12(a)(2) requires the state or authorized Tribe to also "assure
that there shall be achieved the highest statutory and regulatory requirements for all
new and existing point sources." This requirement means that states and authorized
Tribes must not allow new or expanded point sources to contribute additional pollution
that could result in degradation of high quality waters to waters with existing point
source control compliance problems until those compliance issues are remedied, or the
discharger provides the state or authorized Tribe an assurance that the compliance issues
will be remedied (e.g., enforcement schedule of compliance).
Similar to the point source pollution control requirement, 40 CFR 131.12(a)(2) also
requires that "all cost-effective and reasonable best management practices for nonpoint
source control" be achieved. This means that where nonpoint sources do not comply
with state or Tribal requirements in high quality waters, states and authorized Tribes
must not allow proposed new or expanded activities to contribute additional pollutants
that could result in degradation until those compliance issues are remedied or there
is assurance that the compliance issues will be remedied. Also, similar to compliance
issues from point sources, allowing additional pollution without first addressing existing
nonpoint source compliance problems would be inconsistent with the intent of the CWA
objective and the federal antidegradation regulation.
The EPA addressed this issue directly in a 1994 memo, explicitly stating that "The
rationale behind the antidegradation regulatory statement regarding achievement of
statutory requirements for point sources and all cost effective and reasonable BMPs for
DRAFT CHAPTER 4: Antidegradation 47
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nonpoint sources is to assure that, in high quality waters, where there are existing point or
nonpoint source control compliance problems, proposed new or expanded point sources
are not allowed to contribute additional pollutants that could result in degradation.
Where such compliance problems exist, it would be inconsistent with the philosophy
of the antidegradation policy to authorize the discharge of additional pollutants in the
absence of adequate assurance that any existing compliance problems will be resolved."67
Note that this language in 40 CFR 131.12(a)(2) only means that nonpoint sources must
achieve adopted state or authorized Tribal nonpoint source control requirements; it does
not require that states or authorized Tribes adopt nonpoint sources control requirements
prior to allowing degradation of a high quality water.68
In addition to assuring proper implementation of required BMPs for nonpoint source
controls, the EPA recommends that states and authorized Tribes explain in their
antidegradation policies and AIMs whether, how, and to what extent, the state or
authorized Tribe will pursue implementation of voluntary BMPs for nonpoint source
controls before allowing point source degradation of high quality waters. For example,
nonpoint source management plans developed under CWA Section 319 (and associated
watershed plans) are likely to identify potential problems and certain voluntary means,
critical areas, and BMPs for nonpoint source controls to correct those problems. The state
or authorized Tribe should consider how these voluntary actions will be implemented and
how they might affect the state's or authorized Tribe's antidegradation program.
4.3.3 Use of De Minimis in Antidegradation
The de minimis concept is not specific to WQS; rather, it is a broader legal principle
used to interpret and implement many environmental statutes and regulations. In
general, it is a tool used to implement a statute in a way that prevents trivial items from
draining government time and resources. The Sixth Circuit has explained that there is an
"administrative law principle which allows an agency to create unwritten exceptions to
a statute or rule for insignificant or 'de minimis' matters."69 The DC Circuit, in Alabama
Power Co. v. Costle,70 ruled that unless Congress has been extraordinarily rigid, there
is likely a basis to use the de minimis authority to provide exemption when the burdens
of regulation yield a gain of trivial or no value.71 The Court went on to explain that
the authority to create a de minimis provision "is not an ability to depart from the
statute, but rather a tool to be used in implementing the legislative design."72 Courts
have explained that the implied de minimis provision authority is "narrow in reach and
tightly bounded by the need to show that the situation is genuinely de minimis or one of
67 Davies, T. EPA. 1994. Memorandum: Interpretation of Federal Antidegradation Regulatory Requirement. Office of
Water, Washington DC. https://www.epa.gov/sites/production/files/2014-10/documents/davies-rearequire-memo.pdf.
68 Davies, T. EPA. 1994. Memorandum: Interpretation of Federal Antidegradation Regulatory Requirement. Office of
Water, Washington DC. https://www.epa.qov/sites/production/files/2014-10/documents/davies-rearequire-memo.pdf
69 Ky. Waterways Alliance v. Johnson, 540 F.3d 466, 483 (6th Cir. 2008).
70 Ala. Power Co. v. Costle, 636 F.2d 323, 360 (D.C. Cir. 1980).
71 Ala. Power Co. v. Costle, 636 F.2d 323, 360-361 (D.C. Cir. 1980).
72 Ala. Power Co. v. Costle, 636 F.2d 323, 361 (D.C. Cir. 1980).
DRAFT CHAPTER 4: Antidegradation 48
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administrative necessity."73
Some states and authorized Tribes apply the de minimis concept to Tier 2 reviews to
prioritize and manage limited resources by not performing Tier 2 reviews for activities
that they believe cause an insignificant lowering of high water quality. This allows
them to focus their resources on activities likely to have significant effects on water
quality to achieve the greatest amount of environmental protection. However, even
de minimis levels of degradation reduce assimilative capacity of the waterbody and
diminish the waterbody's resilience to future stressors. Therefore, some states and
authorized Tribes choose not to employ a de minimis provision in the implementation
of their antidegradation program. The EPA's regulation does not specifically identify
any situations for which states and authorized Tribes can decide not to conduct Tier 2
reviews where such a review would otherwise be required. However, the EPA's regulation
also does not prevent states and authorized Tribes from adopting such de minimis
provisions consistent with the principles set forth by the courts.
To date, states and authorized Tribes have defined "significant degradation" in a variety of
ways. Significance tests range from simple to complex, involve qualitative or quantitative
measures or both, and may vary depending upon the type of pollution or pollutant (e.g.,
the approach may be different for highly toxic or bioaccumulative pollutants). The EPA
does not endorse one specific approach to identifying what constitutes significant
degradation, though the EPA does recognize one potential way a state or authorized Tribe
could describe its de minimis methodology. The state or authorized Tribe could identify
a "significance threshold" as a percentage of assimilative capacity74 lost for a parameter
that would be considered insignificant or de minimis (See Figure 4-6).75 To implement
such an approach, the state or authorized Tribe would specify in its antidegradation policy
and/or AIMs that degradation that utilizes a percentage of the assimilative capacity below
or equal to the significance threshold is considered de minimis and does not require an
antidegradation Tier 2 review prior to authorization.
w Ala. Power Co. v. Costle, 636 F.2d 323, 360-361 (D.C. Cir. 1980).
74 Assimilative Capacity: the difference between the applicable water quality criterion for a pollutant parameter and the
ambient water quality for that pollutant parameter, where it is better than the criterion.
75 King, E. EPA. 2005. Memorandum: Tier 2 Antidegradation Reviews and Significance Thresholds. Office of Water,
Washington DC. https://www.epa.gov/sites/production/files/2014-10/documents/tier2.pdf.
DRAFT CHAPTER 4: Antidegradation 49
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Designated Use: Aquatic Life
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o
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-1—'
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u
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o
u
u
c
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Zinc Criterion
De minimis Threshold: X% of Assimilative Capacity
Ambient Zinc Concentration
Figure 4-6. Example of a De Minimis Threshold. In this example, a state or authorized Tribe
has determined that degradation up to X% of the assimilative capacity is insignificant or de
minimis. Therefore, for a proposed activity that would lower high water quality but would only
use between 0% and X% of the assimilative capacity, the Tier 2 review could be waived. Since
the assimilative capacity in this waterbody is 100 pg/L, X% of the assimilative capacity will
equal X pg/L. If the activity degrades the water quality to the point where more than X% of the
assimilative capacity would be used, then a Tier 2 review would be required before allowing
the activity. See Figure 4-7 for an example of a de minimis threshold with multiple activities.
Note that the use of zinc in this diagram is solely for illustrative purposes. States and authorized
Tribes should evaluate whether the use of a de minimis provision is appropriate for a particular
parameter, taking into consideration any potential bioaccumulative properties.
Legal challenges have raised questions about the extent to which some states and
authorized Tribes use the de minimis concept in the context of antidegradation,
particularly when multiple de minimis degradations of water quality are within the
same waterbody. In the case Ohio Valley Coalition v. Horinko,76 the Court opined that
cumulative, not just individual, effects on assimilative capacity need to be assessed
when determining the appropriateness of de minimis exemptions from Tier 2 review for
activities on high quality waters. The EPA's 2005 recommendation to use a cumulative
76 Ohio Valley Coalition v. Horinko, 279 F. Supp. 2d 732, 746-50 (S.D. W. Va. 2003).
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cap for de minimis exemptions is consistent with the outcome of this case.77 The EPA
recommends that where there are multiple or repeated de minimis activities in one
waterbody, states and authorized Tribes incorporate a cumulative cap on the use of total
assimilative capacity. To do so, a state or authorized Tribe would first establish a baseline
measurement of water quality in a waterbody, and then track the use of assimilative
capacity by each approved activity in that waterbody (Figure 4-7). This approach creates
a backstop so that multiple individual de minimis discharges to a waterbody over time do
not result in a significant amount of the total assimilative capacity being used without a
single antidegradation Tier 2 review. The state or authorized Tribe would thus require a
Tier 2 review for any lowering of water quality beyond the cumulative cap, regardless of
the percentage of assimilative capacity used by that individual activity.
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Figure 4-7. Example of the Cumulative Impact of Multiple De Minimis Activities. In this example
the level of degradation considered insignificant by the state or authorized Tribe, or de minimis,
is X% of the assimilative capacity. This threshold is set as a cumulative cap. In this example,
lowering of the high water quality may be allowed without a Tier 2 review up until the point that
the collective degradation has used up X% of that waterbody's assimilative capacity. After that
point, the state or authorized Tribe must conduct a Tier 2 review before allowing any additional
lowering of water quality. Here, activity 1 used A% of the assimilative capacity and activity 2 used
B% of the assimilative capacity, so collectively X% of the waterbody's assimilative capacity has
77 King, E. EPA. 2005. Memorandum: Tier 2 Antidegradation Reviews and Significance Thresholds. Office of Water,
Washington DC. https://www.epa.qov/sites/production/files/2014-10/documents/tier2.pdf.
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been used. A Tier 2 review could have been waived for these activities. Activity 3 also uses A%
of the assimilative capacity, but since activities 1 and 2 have already used X% of the waterbody's
assimilative capacity, the state or authorized Tribe must perform a Tier 2 review before the
lowering of high water quality is allowed for activity 3. Note that the use of zinc in this diagram
is solely for illustrative purposes. States and authorized Tribes should evaluate whether the use
of a de minimis provision is appropriate for a particular parameter, taking into consideration any
potential bioaccumulative properties.
States and authorized Tribes may see some challenges when implementing the
cumulative cap concept and should consider these challenges prior to deciding whether
to proceed with a de minimis approach. For example, the state or authorized Tribe may
find it difficult to identify a cumulative cap small enough to appropriately be viewed as
"trivial" or "insignificant," while still allowing individual activities considered de minimis
to occur within that margin. The state or authorized Tribe may also find it difficult to
develop appropriate methods for tracking cumulative degradation to a waterbody to
ensure that the cumulative cap is not exceeded without an appropriate Tier 2 review.
Part of this difficulty is establishing baseline water quality, which is the ambient water
quality of the waterbody at the point when the state or authorized Tribe starts tracking
the use of assimilative capacity. States and authorized Tribes may find it easier to
perform Tier 2 reviews on each individual activity that would lower high water quality
than to track the cumulative losses of assimilative capacity.
Alternatively, rather than using a threshold of assimilative capacity, some states have
determined that certain types of activities do not require a Tier 2 review because they
either do not lower high water quality or only result in an insignificant lowering of high
water quality. The EPA cautions against this approach as "States or authorized Tribes that
define a high threshold of significance may be unduly restricting the number of proposed
activities that are subject to a full antidegradation review. Further, the approach
currently used by some States may not adequately prevent cumulative water quality
degradation on a watershed scale."78
In the case Kentucky Waterways Alliance v. EPA,79 the Sixth Circuit Court of Appeals
vacated, among other things, the EPA's approval of Kentucky's use of de minimis to
exempt certain types of discharges from Tier 2 review. The Court held that the EPA
had failed to evaluate whether the individual or cumulative impact of lowering from
the activities that were exempted from Tier 2 review based on the de minimis provision
actually caused a significant impact on the high quality water.
Therefore, the EPA recommends that a state or authorized Tribe only consider
determining that a specific class of activity does not need a Tier 2 review if it can provide
the appropriate technical justification that demonstrates the activity does not cause a
lowering of water quality (or only an insignificant lowering of water quality). In addition,
if the activity can result in insignificant levels of water quality degradation, the state
78 Water Quality Standards Regulation, 63 Fed. Reg. 36742 (July 7,1998).
79 Kentucky Waterways Alliance v. EPA, 540 F.3d 466 (6th Cir. 2008).
DRAFT CHAPTER 4: Antidegradation 52
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or authorized Tribe should demonstrate that cumulative Iowerings will not result in
significant degradation.
Despite these challenges, states and authorized Tribes have the discretion to include
de minimis provisions in their antidegradation programs as long as they use them in a
manner consistent with the CWA and 40 CFR 131.12. This includes demonstrating that
the degradation is truly de minimis and that the use of a de minimis exemption does
not result in significant degradation in the long run (e.g., by the use of a cumulative
cap). Courts have explained that a "determination of when matters are truly de minimis
naturally will turn on the assessment of particular circumstances, and the agency will
bear the burden of making the required showing."80 For any significance threshold, the
state or authorized Tribe should provide appropriate technical justification for how the
loss of that amount of assimilative capacity could be considered to have an insignificant
impact in that particular situation.
"States and authorized tribes should also consider the appropriateness of exemptions
depending on the types of chemical, physical, and biological parameters that would
be affected. For example, if a potential lowering of water quality contains BCCs,
a state or authorized tribe should not apply a categorical de minimis exclusion
because even extremely small additions of such chemicals could have a significant
effect."81 Bioaccumulative chemicals also tend to resist degradation and accumulate
in several different media, such as sediments and biota, leading to the potential for
80 Ky. Waterways Alliance v. Johnson, 540 F.3d 466, 483 (6th Cir. 2008) (quoting Ala. Power Co. v. Costle, 636 F.2d at
360). See also Greenbaum v. U.S. Envtl Prot. Agency, 370 F.3d 527, 534 (6th Cir. 2004) (quoting Ala. Power Co. v.
Costle, 636 F.2d at 360).
81 Water Quality Standards Regulatory Revisions, 80 Fed. Reg. 51035 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 53
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magnified effects.82 For this reason, the EPA did not include a de minimis provision
for bioaccumulative parameters in 40 CFR Part 132. The EPA recommends that states
and authorized Tribes also exclude bioaccumulative parameters from any de minimis
provisions a state or authorized Tribe may choose to include.
If a state or authorized Tribe chooses to employ a de minimis provision in its
antidegradation policy or AIMs, it should be aware of the relevant case law and carefully
consider how to draft and implement de minimis provisions considering the legal
landscape. The EPA has not found a scientific basis to identify a specific percentage
of loss of assimilative capacity or lowering of water quality that could reasonably
be considered insignificant for all situations.83 The EPA recommends that any state
or authorized Tribe intending to employ a de minimis exemption describe in its
antidegradation policy or AIMs any significance thresholds for individual activities and
cumulative caps, methods for establishing baseline water quality, and how it will use de
minimis expemtions in its program.
States and authorized Tribes may also choose not to employ de minimis exemptions in
their antidegradation programs at all. The fundamental intent of antidegradation is to
maintain and protect high quality waters regardless of the significance of impact. Tier 2
reviews provide important public transparency in a state's or authorized Tribe's decision-
making process for how and how much they will protect high quality waters. The EPA
encourages states and authorized Tribes to consider whether more effort and resources
will be required to justify a de minimis exemption than to complete a Tier 2 review for the
activity. The Tier 2 review process need not be onerous, as states and authorized Tribes
have considerable discretion to design processes not only consistent with the federal
requirements, but also intended to minimize administrative burdens. The EPA encourages
states and authorized Tribes to develop ways to streamline Tier 2 reviews, rather than
seeking to exempt activities from review entirely.
Lastly, de minimis provisions that exempt "insignificant" lowering of high water quality
are only appropriate for determining the need for a Tier 2 review and should not be
used to exempt the application of the antidegradation policy as a whole to a waterbody.
De minimis provisions should not be used with the implementation of Tier 1 or Tier 3
protection. Tier 1 protection requires that existing uses be maintained and protected at
all times; therefore, water quality cannot be lowered below the level that protects those
existing uses, even by an insignificant amount. The same holds true for Tier 3 protections.
As ONRWs must be maintained and protected and no permanent degradation can be
allowed in these waters, a de minimis provision is generally not consistent with Tier 3
protection.
82 EPA. 1995. Water Quality Guidance for the Great Lakes System: Supplementary Information Document (SID). EPA
820-B-95-001. EPA, Office of Water, Washington, DC 20460. March 1995. https://www.epa.gov/sites/default/
files/2015-12/documents/1995 water quality guidance for great lakes sid.pdf.
83 Water Quality Standards Regulatory Revisions, 80 Fed, Reg, 51034 (August 21, 2015).
DRAFT CHAPTER 4: Antidegradation 54
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4.4 OUTSTANDING NATIONAL RESOURCE
WATERS - 40 CFR 131.12(a)(3)
The federal regulation at 40 CFR 131.12(a)(3), or "Tier 3" of antidegradation, requires
the maintenance and protection of waters that are outstanding national resources.
Tier 3 protection applies to a waterbody or waterbody segment and provides the highest
level of protection by prohibiting any lowering of water quality in waters that a state
or authorized Tribe identifies as ONRWs. The EPA interprets 40 CFR 131.12(a)(3) to
prohibit new or increased lowerings of water quality both to ON RWs and to tributaries
of ONRWs that would result in a permanent lowering of water quality in the ONRW.84
In addition, since no degradation is allowed in these waters, all improvements in water
quality after a water's classification as an ONRW must also be maintained and protected
once they have been achieved. To ensure that waters with ONRW protection are
maintaining their water quality, states and authorized Tribes can regularly monitor these
waters and discuss protection strategies with stakeholders in the ONRW watershed.
Some states and authorized Tribes choose to specify Tier 3 protection for waters using
a term other than an "ONRW." If doing so, the EPA recommends that the state or
authorized Tribe ensure their regulation is clear that such waters are receiving a level of
protection consistent with 40 CFR 131.12(a)(3).
States and authorized Tribes may allow some limited activities in ONRWs as long as
they only result in temporary and short-term lowerings in water quality and do not
result in any permanent degradation or ultimately result in the improvement of the
long-term water quality.85 For example, some activities that could result in a temporary
lowering of water quality in an ONRW are the degradation that results from road repair
or septic system replacement in a national park. Along with limiting duration, states
and authorized Tribes may also limit lowerings to specific types of activities, such as
restoration.86 Restoration activities may result in the release of sediments or other
contaminants for a short time period during construction (e.g., vegetation planting that
disturbs soils, creation of instream habitat that disrupts sediments, dam removal that
releases sediments), but will ultimately result in the improvement of water quality within
a waterbody.
Deciding what qualifies as "temporary" and "short-term" can be difficult because of the
variety of activities that might cause short-term or temporary degradation. What may
84 EPA. 2012. Water Quality Standards Handbook Chapter 4: Antidegradation. EPA-S23-B-12-002. EPA, Office of Water,
Washington, DC 20460. https://www.epa.aov/sites/default/files/2014-10/documents/handbook-chapter4.pdf.
85 Water Quality Standards Regulation, 63 Fed. Reg. 36786 (July 7,1998).
86 Water Quality Standards Regulation, 48 Fed. Reg. 51403 (November 8,1983).
DRAFT CHAPTER 4: Antidegradation 55
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be considered short-term for one type of activity may be considered long-term for a different
activity, so it is not possible to establish a universal length of time that is considered "short-
term" for all activities. However, in rather broad terms, the EPA's view of "temporary" and
"short-term" for a lowering in an ONRW is weeks and months, not years. Any degradation
allowed in an ONRW should always be limited to the shortest time possible. If a construction
activity is involved, for example, "temporary" would be the length of time necessary to
construct the facility and make it operational. If a state or authorized Tribe allows temporary
degradation in an ONRW (or in one of its tributaries), it should ensure the following:
~> All practical means of minimizing the degradation are implemented,
~> Existing uses are maintained and protected,
£> All essential characteristics that make the water an ONRW are preserved, and
No degradation is permanent.
Tier 3 is a tool states and authorized
Tribes can use to ensure the maintenance
and protection of the water quality in
their high value waters. While states and
authorized Tribes have discretion as to
which waters, if any, they will provide
Tier 3 protection,87 the EPA recommends
that states and authorized Tribes consider
applying this protection to their highly
valued waters. The EPA's regulation at
40 CFR 131.12(a)(3) provides examples
of outstanding national resources (high
value waters), including "waters of
National and State parks" and "wildlife
refuges and waters of exceptional
recreational and ecological significance."
A state or authorized Tribe may assign
Tier 3 protection to any high value
water, including waters of exceptional
ecological, recreational, or cultural
significance. While the water quality of a
waterbody may not be at levels typically
considered pristine, or even high quality,
the state or authorized Tribe may want
to protect a water to maintain its current
water quality and preserve the social,
ecological, or cultural benefit it provides.
87 Diamond, W. EPA. 1989. EPA Designation of Outstanding National Resource Waters. Office of Water, Washington DC. https://
www.epa.gov/sites/default/files/2014-10/documents/diamond-outstanding-memo.pdf
DRAFT CHAPTER 4: Antidegradation 56
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The EPA recommends states and authorized Tribes consider the following types of
additional waters for ONRW protection, including, but not limited to:
^ Waters with federal protection and classification: Wild and Scenic Rivers, National
Water Trails, National Recreational Trails with on-water segments, Wilderness
Areas, National Recreation Areas, National Monuments, National Wildlife Refuges,
Estuarine Research Reserves; and
Waters with state protection classification: State Wild and Scenic Rivers or other
similar designation, State Water Trail or Waterway, Special State Classifications such
as Special Trout Waters.
Ecologically significant waterbodies:
Waters that are ecologically important, unique, or sensitive, such as spawning and
nursery grounds, coldwater refugia, and habitat for threatened or endangered species.
Recreationally significant waterbodies:
Waters that are highly valued waters or heavily visited waters, such as waters that
attract abundant recreation and tourism, waters in national or state parks, and waters
that are economic drivers to the state due to their recreational significance.
Culturally significant waterbodies:
Waters that support water-based cultural and traditional practices.
Waterbodies in National Parks, State Parks, and Wildlife Refuges:
Waters that are located in areas that have been protected in order to conserve and
preserve natural and cultural resources.
To ensure states and authorized Tribes make decisions on which waters to protect as
Tier 3 with as much information as possible and with the support of the community,
the EPA recommends that states and authorized Tribes offer a nomination process for
the public to nominate waters for Tier 3 protection. The EPA also recommends that
states and authorized Tribes provide an opportunity for the public to provide input on
the assignment and removal of waters for Tier 3 protection. For example, a state or
authorized Tribe could outline in its regulation a nomination process in which citizens
could request Tier 3 protection for specific waters, and those citizens could provide
data and information for a state's or authorized Tribe's consideration. Providing such
transparent processes could result in increased public support for the overall state or
authorized Tribal antidegradation program. The EPA also recommends that states and
authorized Tribes periodically review their list of Tier 3 waters to determine whether any
changes may be appropriate.
As states and authorized Tribes assign waters Tier 3 protection, it is critical for the
public to know which waters have this level of protection. 40 CFR 131.12(a)(3) states
that "where high quality waters constitute an outstanding National resource... that
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water quality shall be maintained and protected." Implementing programs, such as the
permit authority, can only "maintain and protect" the water quality of a Tier 3 water
if they know which waters the state or authorized Tribe has identified as ONRWs. In
addition, it is critical for the public to have access to information on which waters the
state or authorized Tribe has assigned as Tier 3 so that regulated entities are fully aware
of their obligations and the basis for permit requirements. Such access will also ensure
that the public has the necessary information to hold states and authorized Tribes
accountable when implementing WQS, Therefore, to ensure that Tier 3 waters "shall be
maintained and protected" consistent with 40 CFR 131.12(a)(3), the EPA expects states
and authorized Tribes to make their Tier 3 lists publicly available. A state or authorized
Tribe could provide this Tier 3 waters list to the public by adopting it into rule, posting
it on a public website, or housing it in another location that is easily accessible to the
public and to state or authorized Tribal programs implementing the CWA. Where a
state or authorized Tribe chooses to adopt its Tier 3 waters list into rule, the EPA will
review and approve or disapprove those decisions as new or revised WQS consistent
with CWA Section 303(c). The EPA strongly recommends states and authorized Tribes
be transparent by providing a broadly accessible Tier 3 waters list; however, the EPA
recognizes that making the list broadly available may not be desired in certain unique
instances. Where a state or authorized Tribe does not wish to make their list of ON RWs
broadly available, it may specify in its policy or AIMs how interested parties can
request information on which waters are ONRWS and then provide that information
upon request. Making the list publicly available will ensure proper implementation and
oversight of the antidegradation policy consistent with 40 CFR 131.12(a)(3).
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4.5 ADDITIONAL PROTECTION
ESTABLISHED BY STATES AND
AUTHORIZED TRIBES (TIER
Several states and authorized Tribes have developed provisions that identify one or
more levels of protection in between Tier 2 (high quality waters) and Tier 3
(ONRWs) as part of their antidegradation policies and AIMs. This additional level of
protection is often referred to by states and authorized Tribes as Tier 2%, and waters
assigned to this additional level of protection are often referred to as outstanding state
or Tribal waters or exceptional state or Tribal waters.88
Waters assigned Tier 2!4 protection receive a greater degree of protection than Tier 2
under these state or authorized Tribal provisions. The level of protection in a Tier 231
water can take a variety of forms, but often states and authorized Tribes use it to put
conditions or restrictions on discharges allowed into such waters. For example, a state or
authorized Tribe may prohibit the discharge of bioaccumulative parameters into Tier 21/2
waters, limit discharges only to those that maintain or improve current water quality, or
require certain types of treatment for discharges before they can be released into these
waters. States and authorized Tribes may also choose to require that when evaluating
alternatives to degradation in Tier 2Vi waters, the least degrading alternative must be
implemented rather than just a less degrading alternative to the originally proposed
activity. All of these examples show how states and authorized Tribes may use the Tier
2Vi approach to provide a stringent level of protection beyond the requirements of Tier
2 but short of prohibiting any permanent lowering as states and authorized Tribes do for
Tier 3 waters.
In using the Tier 2/2 approach, states and authorized Tribes preserve the flexibility
to provide a very high level of water quality protection but also to accommodate
unforeseen, future economic and social development considerations. The EPA has
approved antidegradation policies and state or authorized Tribally adopted AIMs that
include a Tier Th protection level because such additional levels of protection are a more
stringent application of Tier 2 provisions of the federal antidegradation regulation. As
such, these policies and AIMs are permissible under CWA Section 510 unless prohibited
by the state's or authorized Tribe's own law or are inconsistent with 40 CFR 131.12(a)
(2).89 If a state or authorized Tribe assigns Tier 2'/? protection to some of its waters, the
EPA expects states and authorized Tribes to maintain a publicly available list of those
waters for transparency and ease of implementation.
® Water Quality Standards Regulation, 63 Fed. Reg. 36787 (July 7,1998).
89 Ibid.
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4.6 THERMAL DISCHARGE
REQUIREMENTS - 40 CFR 131.12(a)(4)
The federal regulation at 40 CFR 131.12(a)(4) requires that a potential water quality
impairment associated with thermal discharges be handled consistently with CWA
Section 316 (and by extension, the CWA Section 316 implementing regulation at
40 CFR 124.66).90 CWA Section 316(a) allows permit writers to include alternative
thermal discharge limitations ("thermal variances"91) if the permittee can demonstrate
the limitations that would be required under CWA Sections 301 or 306 are more
stringent than necessary to ensure the protection and propagation of a balanced,
indigenous community of shellfish, fish, and wildlife. Most thermal effluent limitations
for temperature contained in NPDES permits are based on applicable state and/or Tribal
WQS for the receiving water. If a discharger is unable to comply with WQBELs at the
point of discharge, applicable WQS may provide specifications for granting thermal
mixing zones which allow portions of the waterbody to exceed the temperature criteria
as long as the mixing zone provisions are met. As with other pollutants, mixing zones
for thermal discharges may be authorized as allowed under applicable state or Tribal
regulations. If the permittee is unable to comply with the applicable thermal limits at the
edge of the regulatory mixing zone or at the point of discharge if a regulatory mixing
zone is not appropriate, a permittee may seek relief from these standards by applying
for a variance in accordance with CWA Section 316(a) and its implementing regulation.
Thus, under Section 316(a) of the Act, if a proper showing is made, NPDES permits may
contain less stringent thermal effluent limitations than what might otherwise be required
under CWA Section 301(b)(1)(C) to implement state antidegradation requirements.
States and authorized Tribes should ensure that their antidegradation policies are not
interpreted or applied to prevent the inclusion of alternative thermal effluent limitations
in NPDES permits under CWA Section 316(a).
90 Water Quality Standards Regulation, 63 Fed. Reg. 36787 (July 7,1998).
91 Thermal variances are alternate thermal discharge limitations that are specifically allowed by Section 316 of the CWA.
These variances differ from a WQS variance issued according to the regulation found at 40 CFR 131.14.
DRAFT CHAPTER 4: Antidegradation 60
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4.7 ANTI DEGRADATION
^3 IMPLEMENTATION METHODS
A I Ms are a set of provisions (legally binding or in guidance) that describe how
a state's or authorized Tribe's antidegradation policy will be executed. 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 policies. States and
authorized Tribes must make these AIMs available to the public and allow the public an
opportunity to provide input on the AIMs during their development and any subsequent
revision (40 CFR 131.12(b)). States and authorized Tribes have considerable discretion
in how they address each of the elements of antidegradation implementation listed in
this section as long as their AIMs are consistent with their antidegradation policy and 40
CFR 131.12(a), and are not otherwise inconsistent with the CWA. The EPA's evaluation
of consistency includes ensuring that the AIMs do not undermine the antidegradation
policy. In addition to the following antidegradation implementation elements, the EPA
recommends that a state or authorized Tribe also describe the scope and applicability
of its antidegradation policy in its AIMs, and make clear that antidegradation protection
applies to the waterbody even if the state or authorized Tribe may only enforce controls
on certain types of dischargers (see section 4.3 and section 4.8). At a minimum, to
be consistent with the federal WQS regulation, the EPA recommends that a state's or
authorized Tribe's AIMs address the following elements:92 (See the cross referenced
sections of this chapter after each element for additional information on what a state or
authorized Tribe may wish to include in its AIMs.)
1. Tier 1 - Existing use protection: Describe how the state or authorized Tribe will
ensure the maintenance and protection of all existing uses and the water quality
necessary to protect the existing uses (see section 4.2).
2. Tier 2 - High quality water protection (see section 4.3):93
a. Identification of high quality waters: Describe how the state or authorized
Tribe will identify high quality waters on a parameter by parameter basis
or a waterbody-by-waterbody basis (or a combination of the two). If using
the waterbody- by- waterbody approach, the state's or authorized Tribe's
implementation methods must ensure that waters are not excluded from Tier
2 protection solely because water quality does not exceed levels necessary to
support all of the CWA Section 101(a)(2) uses (see section 4.3.1).
92 Water Quality Standards Regulatory Clarifications, 78 Fed. Reg. 54530 (September 4, 2013).
93 See section 4.3 of this chapter for additional discussion on the elements related to high quality water protection.
DRAFT CHAPTER 4: Antidegradation 61
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b. Analysis of alternatives and socio-economic analysis: Describe how the state
or authorized Tribe will determine whether a lowering of high water quality 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 (see section 4.3.2.2).
c. Public participation and intergovernmental coordination: Describe how the
state or authorized Tribe will ensure full satisfaction of the public participation
and intergovernmental coordination provisions of the state's or authorized
Tribe's continuing planning process in any finding that will allow the lowering
of high water quality (see section 4.3.2.3).
d. Requirements for point and nonpoint sources: Describe how the state
or authorized Tribe will assure that the highest statutory and regulatory
requirements shall be achieved for all new and existing point sources and
all cost-effective and reasonable BMPs for nonpoint source control when
allowing a iowering of water quality (see section 4.3.2.4 and 4.3.2.5).
3. Tier 3 - ONRW protection: Describe how the state or authorized Tribe will ensure
the maintenance and protection of water quality for waters identified as ON RWs
(see section 4.4).
4. Thermal Discharges: Describe how the state or authorized Tribe will ensure
consistency with CWA Section 316 in cases that involve potential water quality
impairment associated with thermal discharges (see section 4.5).
The EPA's Regional offices94 are available to provide assistance and technical support to
help states and authorized Tribes determine how to develop appropriate AIMs. The EPA
recommends states and authorized Tribes collaborate closely with their EPA Regional office
when developing or revising AIMs not only to ensure AIMs are consistent with regulatory
requirements but also to discuss opportunities to improve efficiency, transparency, and
streamlining of the states' and authorized Tribes' antidegradation programs.
94 See https://www.epa.gov/wqs-tech/forms/contact-us-about-water-quality-staridards-reaulations-and-resources.
DRAFT CHAPTER 4: Antidegradation 62
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4.8 APPLICATION AND IMPLEMENTATION
AS discussed in section 4.1.4, antidegradation is applicable to the waterbody
regardless of pollution source, and as a WQS, is implemented in other CWA
programs to the same extent as other WQS. States and authorized Tribes often specify
that their antidegradation policies and AIMs requirements are only triggered by
the request for authorizations of regulated activities that could lower water quality.
Examples of regulated activities that will trigger an antidegradation review to ensure
protection of Tier 1, 2, and 3 include the request for authorization of a new source of
discharge regulated under the CWA and a request for a change in the discharge of
an existing regulated source, if that change increases the pollutant load or includes
additional new pollutants that were not previously
authorized. As the federal government does not have
CWA authority to regulate nonpoint sources, states
and authorized Tribes determine whether and what
nonpoint source activities trigger an antidegradation
review. States and authorized Tribes have the
discretion to apply their antidegradation policies and
AIMs more broadly to activities not regulated under
state or Tribal law, however this is not required by the
federal WQS regulation.95
For CWA regulated activities, an antidegradation
review is required before a permitting authority can
issue the permit or license. This includes activities that
require: NPDES permits (CWA Section 4021 permits
to discharge dredged or fill material CCWA Section
404), and federal licenses or permits subject to
CWA Section 401 certification.96 On the other hand,
activities that would not iower water quality, such as
a WQS triennial review or adoption of a new or revised WQS (including WQS variances)
do not require an antidegradation review. These activities do not trigger antidegradation
reviews because they do not directly allow for lowering of water quality. Sections
4.8.1, 4.8.2, 4.8.3, and 4.8.4 of this chapter provide some guidance for implementing
antidegradation policies and AIMs for each of these types of activities. States and
authorized Tribes retain discretion to enforce the requirements of their antidegradation
policies and AIMs for other types of activities (such as nonpoint source controls) beyond
those controls already required under a state or authorized Tribal regulation.
96 Water Quality Standards Regulation, 63 Fed. Reg. 36780 (July 7,1998).
96 EPA's Response to Comments, Water Quality Standards Regulatory Revisions, Chapter 3 Issue Category:
Antidegradation, Docket # EPA-HQ-OW-2010 -0606, August 2015, pg. 3-201, pg. 3-212, https://www.regulations.gov/
document/EPA-HQ-OW-2010-0606-0344.
DRAFT CHAPTER 4: Antidegradation 63
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4.8.1 CWA Section 402: NPDES Permits
CWA Section 402 establishes the NPDES permit program, which addresses water
pollution by regulating point sources that discharge pollutants to waters of the United
States. The NPDES regulation includes two types of effluent limits to control pollutant
discharge. The first are technology-based effluent limits (TBELs). TBELs require a
minimum level of effluent quality that is known to be attainable using demonstrated
technologies. TBELs are standardized across an industrial category. The second type of
effluent limits are WQBELs, which are derived from the applicable WQS. The NPDES
regulation requires that WQBELs derive from and comply with ail applicable elements of
WQS, including designated uses, water quality criteria, and the state's
or authorized Tribe's antidegradation policies and any state or Tribal legally adopted AIMs
(40 CFR 122.44(d)! CWA Section 301(b)(1)(C) requires that NPDES permits include
any effluent limitations necessary to meet WQS, even if they are more stringent than
technology-based requirements. Where including technology-based requirements in an
NPDES permit would not be sufficient to meet WQS in the receiving water, the permit
writer develops WQBELs to include in the permit to ensure that WQS are met in the
receiving water.
DRAFT CHAPTER 4: Antidegradation 64
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To meet the antidegradation regulation for Tier 1, which applies to all waters of the
United States, effluent limits must, at a minimum, protect the existing uses of the
waterbody. If the state or authorized Tribe determines that the waterbody has existing
uses requiring more stringent protection than provided by the designated uses, the
WQBELs must be adjusted to protect the existing uses. In addition, where such existing
uses are "presently being attained," the EPA's regulation at 40 CFR 131.10(0 requires
that the state or authorized Tribe revise its WQS to reflect the uses actually being
attained (see Draft Chapter 2 of this Handbook for more information on designated
uses). If a waterbody is impaired97 for a parameter that would be present in the proposed
discharge, the permit writer must identify any relevant TMDLs to ensure that the
effluent limits derived from the applicable water quality criteria are consistent with any
available wasteload allocation for the discharge.98
A new or expanded discharge may trigger an antidegradation Tier 2 review. If the state
or authorized Tribe uses a parameter-by-parameter approach, they would need to
determine whether the receiving waters have high water quality for any parameters
that could be affected by the discharge. If so, a Tier 2 review would be needed. If not,
the permit could proceed without a Tier 2 review. If the state or authorized Tribe uses
a waterbody-by-waterbody approach, they would need to determine if the state or
authorized Tribe maintains a list of Tier 2 waters, and if so, if the receiving water has
been identified as a Tier 2 water. If the state or authorized Tribe does not maintain a
Tier 2 list, then the state or authorized Tribe would need to conduct a holistic review
of the receiving water to determine whether it should be identified as a Tier 2 water. If
the receiving water is identified as a Tier 2 water, then a Tier 2 review would be needed
before the permit is issued. If the receiving water is not identified as a Tier 2 water, then
the permit issuance could proceed without a Tier 2 review.
After the Tier 2 review is conducted for new or expanded facilities or discharges, the
state or authorized Tribe would make a decision on whether the proposed lowering
of high water quality is necessary to accommodate important economic and social
development in the area in which the waters are located. Based on the Tier 2 review,
the state or authorized Tribe could decide to allow the activity to lower high water
quality as proposed, allow the activity to lower high water quality to a lesser extent than
proposed (e.g., for instance if a less degrading practicable alternative is identified), or
not allow the proposed activity to lower high water quality and require maintenance of
the current high water quality (e.g., because the proposed lowering of high water quality
was not necessary, not important, or both). The permit writer will need to make sure
that the permit reflects the state's or authorized Tribe's decision regarding the extent of
degradation allowed. The permit writer may also include additional requirements in the
N PDES permit for that discharge to meet other applicable CWA requirements. For more
information about the components of a Tier 2 review, see section 4.3.1 of this chapter.
97 I.e., those waters that do not meet the WQS set for them, even after point sources of pollution have installed the
minimum required levels of pollution control technologies.
98 40 CFR 122.44(dX1XviiXB).
DRAFT CHAPTER 4: Antidegradation
65
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A NEW OR EXPANDED DISCHARGE MAY TRIGGER AN ANTIDEGRADATION TIER 2 REVIEW
PARAMETER-BY-PARAMETER
APPROACH AND NPDES PERMITS
Before a permit is issued:
Does the receiving waters have high
water quality (as defined by the state or
authorized Tribe's WQS or adopted AIMs)
for parameter(s) affected by the
proposed activity?
YES
NO
a r
Tier 2 review is
needed.
Permit could
proceed without a
Tier 2 review.
J V
WATERBODY-BY-WATERBODY APPROACH AND
NPDES PERMITS
Before a permit is issued:
Does a state or authorized Tribe maintain
a list of Tier 2 waters?
YES
NO
State or authorized Tribe works across its
water program to conduct a holistic review
of the waterbody to determine if it should
be identified as a Tier 2 water.
Is the receiving water for
discharges from the proposed
activity on the state's or authorized
Tribe's list of Tier 2 waters?
Based on the holistic review,
should the waterbody be
identified as a Tier 2 water?
YES
NO
YES
NO
I Tier 2 review is
needed.
Permit could
proceed without
a Tier 2 review.
Tier 2 review is
needed.
Permit could
proceed without|
a Tier 2 review.,
After conducting a Tier 2 review, does the state or authorized Tribe find that the proposed lowering of high water quality
is necessary to accommodate important economic and social development in the area in which the waters are located?
YES
Lowering is important but implementing an
alternative can decrease degradation.
NO
Allow the lowering of high water
quality as proposed.
Allow the lowering of high water quality
to a lesser extent than proposed.
Not allow the lowering of high
water quality and require maintenance
of current high water quality.
Figure 4-8 Determining whether a Tier 2 review is needed before issuing an NPDES permit using either the
para meter-by-para meter approach or the waterbody-by-waterbody approach. A new or expanded discharge
may trigger the need to complete a Tier 2 review consistent with 131.12(a)(2) before issuing a permit. This will
be dependent on whetherthe waterbody is classified as a Tier 2 water using either the parameter-by-parameter
approach or the waterbody-by-waterbody approach. If identified as a Tier 2 water, the Tier 2 review will help to
determine how much degradation may occur in the waterbody.
DRAFT CHAPTER 4: Antidegradation 66
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Where a waterbody is identified as an ONRW, or tributary, wetland, lake, or other
waterbody upstream of an ON RW, the permit writer must consult the state's or
authorized Tribe's antidegradation policy and AIMs to determine whether it is appropriate
to issue an NPDES permit to the waterbody, and if so, to inform the permit requirements
and limits of an N PDES permit issued to Tier 3 waters (e.g., temporary degradation that
results in restoration). In some cases where a waterbody has Tier 3 protection, the permit
writer might find that it is not possible to issue a permit for the proposed activity.
For issuing permits for waterbodies with additional levels of protection, such as Tier 2Vi,
the permit writer should consult the state's or authorized Tribe's antidegradation policy
and AIMs.
Regardless of the tier(s) involved, the EPA recommends that the permit writer clearly
explain the analysis of the antidegradation review and how it affects the calculation of
WQBELs in the fact sheet or statement of basis for the NPDES permit. This is consistent
with the requirements at 40 CFR 124.7.124.8 and 124.56 and will assist the public in
understanding the antidegradation analysis and decisions during the public notice of the
N PDES draft permit. Most states have been authorized by the EPA to implement the
NPDES program through a process defined by CWA Section 402(b) and 40 CFR Part
123. and they are responsible for issuing their own NPDES permits." Where states and
Tribes are not authorized to implement the NPDES program, the EPA implements the
NPDES program, including issuing NPDES permits.
For states that have been authorized to administer the N PDES program, the EPA still
retains an oversight role. If a state issues an NPDES permit that is inconsistent with its
own antidegradation policies and/or state adopted AIMs, that permit could be subject to
a discretionary EPA objection under CWA Section 402(d) and 40 CFR 123.44 or subject
to a citizen challenge.
Where the EPA is responsible for issuing an NPDES permit,100 the EPA will, consistent
with the NPDES regulation, add any additional or more stringent effluent limitations
required to ensure consistency with the state's or authorized Tribe's WQS (including the
state's or authorized Tribe's antidegradation policies and state or Tribally adopted AIMs).
Through the CWA Section 401 certification process, the state or authorized Tribe has
the opportunity to require further permit conditions that it deems necessary to ensure
consistenty with WQS or may deny certification of a permit if it is not consistent with
the state's or authorized Tribe's WQS (see section 4.8.3).
More information for permit writers can be found in the NPDES Permit Writers' Manual.
Chapter 6, September 2010 edition.101
99 https://www.epa.gov/npdes/npdes-state-proaram-information.
100 The EPA issues all NPDES water quality permits in Massachusetts, New Hampshire, New Mexico, District of Columbia,
United States territories, and on federal and Tribal lands.
101 EPA. 2010. NPDES Permit Writers'Manual. EPA 833-K-10-001. EPA, Office of Water, Washington, DC 20460. https://
www.epa.qov/sites/production/files/2015-09/documents/pwm 2010.pdf. For questions regarding anti-backsliding,
please reference Chapter 7 of the NPDES Permit Writers' Manual.
DRAFT CHAPTER 4: Antidegradation 67
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4.8.1.1
General Permits
Many activities regulated under NPDES are authorized under general permits (as opposed
to an individual permit). A general permit is an NPDES permit issued under 40 CFR
122,28 authorizing a category of discharges under the CWA within a geographical area
(40 CFR 122.2"). 40 CFR 122.28 contains the regulation for general permits, including the
specific areas and sources that can be covered by a general permit.
A general permit can streamline the permitting process for entities seeking coverage
for specific activities, provided that the facility meets the requirements for coverage
under the general permit. After a general permit has been issued, facilities seeking
to be covered under the general permit typically submit a notice of intent (NOI) to
the permitting authority. The permitting authority may determine that a general
permit is not appropriate for a facility for which coverage is sought and can require
the facility to apply for an individual permit.102 Like WQBELs for individual NPDES
permits, WQBELs in general permits must derive from and comply with applicable WQS,
including antidegradation policies and state or Tribally adopted AIMs. States and Tribes
authorized to administer the CWA Section 402 program have discretion to decide how
best to ensure the requirements of their antidegradation policies and AIMs are met
when issuing general permits. Some states have used the following approaches to meet
antidegradation requirements when issuing general permits:
The state completes an antidegradation review for the general permit at the time
of issuance,
The state includes requirements in the general permit to ensure the receiving
water is protected consistent with its antidegradation policies and AIMs, or
~> The state specifies in the general permit that if an antidegradation review is
warranted for the receiving water, the state will conduct one when an entity
submits an NOI for coverage under the general permit.
Any of these approaches can be used as long as they are implemented in a manner
consistent with the WQS regulation at 40 CFR Part 131. including the public participation
requirement of 40 CFR 131.12(a)(2). and the NPDES regulation at 40 CFR Part 122.
102 EPA. 2010. NPDES Permit Writers'Manual. EPA 833-K-10-001. EPA, Office of Water, Washington, DC 20460. https://
www.epa.gov/sites/production/files/2015-09/documents/pwm 2010.pdf.
DRAFT CHAPTER 4: Antidegradation 68
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4.8.2 CWA Section 404: Dredged or Fill Material
Permits
CWA Section 404 establishes a program103 to regulate the discharge of dredged or
fill material into waters of the United States. Examples of activities regulated under
this program include discharges of fill for development, water resource projects (such
as dams and levees), infrastructure development (such as highways and airports), and
mining projects. CWA Section 404 requires a permit before dredged or fill material
may be discharged into waters of the United States, unless the activity is exempt from
CWA Section 404 permit requirements (e.g., certain farming and silviculture activities)
pursuant to CWA Section 404(f).
The Corps is responsible for the day-to-day administration of the CWA Section 404
program, including processing Section 404 permits, except where a state or Tribe has
been approved by the EPA and has assumed administration of the permitting program.
The Corps uses the Section 404(b)(1) Guidelines, environmental criteria promulgated
by the EPA in coordination with the Corps, in evaluating permit applications under CWA
Section 404. The Guidelines require, among other things, that a permit authorize only
the least environmentally damaging practicable104 alternative, and that a discharge that
would cause or contribute to "significant degradation" of the aquatic environment not
be permitted.105
A literal interpretation of 40 CFR 131.12(a)(1) could prevent certain physical
modifications to a waterbody that are clearly allowed by CWA Section 404. However,
the EPA's view is that since Congress included CWA Section 404, it intended some
permits for dredged or fill material to be granted within the framework of the CWA. In
the context of fill of wetlands and the antidegradation Tier 1 requirement to maintain
and protect existing uses, the EPA interprets 40 CFR 131.12(a)(1) to be satisfied if the
CWA Section 404 discharge does not result in "significant degradation" of the aquatic
environment as defined in the CWA Section 404(b)(1) Guidelines at 40 CFR 230.10(c).106
The CWA Section 404(b)(1) Guidelines convey that the following effects can contribute
to the significant degradation of the waters of the United States:
"... significant adverse effects [individually or collectively] on (1)
human health or welfare, including, but not limited to, effects
on municipal water supplies, plankton, fish, shellfish, wildlife, and
103 https://www.epa.gov/cwa-404/section-404-permit-proaram.
104 Defined specifically for the CWA Section 404 program at 40 CFR 230.3(1) as "The term practicable means available
and capable of being done after taking into consideration cost, existing technology, and logistics in light of overall
project purposes." Note that for purposes of antidegradation, the WQS regulation includes a specific definition of
"practicable" at 40 CFR 131.3(n) (See section 4.3.2.2).
105 See 40 CFR 230.10(a-d). A state or Tribal program evaluates permit applications utilizing state or Tribal environmental
review criteria that the EPA has approved as consistent with and no less stringent than the 404(b)(1) guidelines
106 40 CFR Part 230. https://www.epa.gov/sites/production/files/2015-03/documents/cwa section404b1 guide
lines 40cfr230 iulv2010.pdf.
DRAFT CHAPTER 4: Antidegradation
69
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special aquatic sites (e.g., wetlands); (2) on the life stages of aquatic
life and other wildlife dependent on aquatic ecosystems, including
the transfer, concentration, or spread of pollutants or their
byproducts beyond the site through biological, physical, or chemical
process; (3) on aquatic ecosystem diversity, productivity, and
stability, including, but not limited to, loss offish and wildlife habitat
or loss of the capacity of a wetland to assimilate nutrients, purify
water, or reduce wave energy; or (4) on recreational, aesthetic, and
economic values."
To determine whether existing uses are protected (Tier 1), states and authorized
Tribes may refer to the CWA Section 404(b)(1) Guidelines to assess the potential
for "significant degradation" from discharges of dredged or fill material. States and
authorized Tribes may also, at their discretion, adopt stricter requirements for dredge
and fill activities in their own antidegradation policies and state or authorized Tribally
adopted AIMs, just as they may adopt any other requirements more stringent than
federal law requires pursuant to CWA Section 510 unless prohibited by their own state or
Tribal law.
States and authorized Tribes must provide the same level of Tier 2 and Tier 3 protection
for jurisdictional wetlands as is afforded other waters of the United States, consistent
with 40 CFR 131.12. However, states and authorized Tribes may determine that
implementation of such protections may need to vary depending on the waterbody type.
Please refer to sections 4.3, 4.4, and 4.7 for additional discussion on the implementation
of each of these levels of protection.
4.8.3 CWA Section 401 Certification
Under CWA Section 401. a federal agency cannot issue a permit or license for an
activity that may result in a discharge into waters of the United States until the state
or authorized Tribe107 where the discharge would originate has granted or waived CWA
Section 401 certification. Where a Tribe does not have the authority to issue 401
certifications, the EPA will issue the 401 certifications for activities discharging to waters
within the Tribe's jurisdiction. States and authorized Tribes (or the EPA) make their
decisions to deny, certify, or condition federal permits or licenses based on compliance
with "water quality requirements,"108 which include but are not limited to EPA approved
WQS. Examples of federal licenses and permits subject to CWA Section 401 certification
include CWA Section 402 NPDES permits issued by the EPA, CWA Section 404 permits
for discharge of dredged or fill material (issued by the Corps), FERC hydropower
licenses, and Rivers and Harbors Act Section 9 and Section 10 permits for activities
that have a potential discharge in navigable waters (issued by the Corps). Many states
107 In this discussion of CWA Section 401. the term "authorized Tribe" refers to a Tribe that has been authorized to
administer CWA Section 401. Under 40 CFR 131.4(c). a Tribe that is eligible to administer WQS is likewise eligible to
administer CWA Section 401 unless it specifically declines that authority.
108 40 CFR 121.1.
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and Tribes rely on CWA Section 401 certification to ensure that point source discharges
from federally licensed or permitted activities, like that of dredged or fill material, into a
water of the United States do not prevent compliance with water quality requirements.
In addition, CWA Section 401 certification may be a state's or authorized Tribe's only
opportunity to review and appropriately condition or object to the federal permitting
or licensing of a project that may result in a discharge into waters of the United States,
including discharges that could violate antidegradation requirements.
In acting on a request for certification, the state or authorized Tribe (or the EPA) will
then need to ensure that the federal permit or license will comply with water quality
requirements, including that it follow its antidegradation policy and adopted AIMs for all
tiers of applicable protection. For example, in the case of Tier 2 protection, the state or
Tribe (or the EPA) needs to make sure that the federal license or permit appropriately
protects assimilative capacity or that a Tier 2 review has been conducted to determine
that lowering water quality in a high quality water is necessary to accommodate
important economic or social development in the area in which the waters are located.
The state or authorized Tribe could either conduct the Tier 2 review themselves or
evaluate a Tier 2 review completed by the licensing or permitting agency. The federal
agency needs to incorporate into it's license or permit any conditions the state or
authorized Tribe deems necessary to ensure compliance with water quality requirements,
including antidegradation
For additional information about CWA Section 401 certifications, see Chapter 8 of this
Handbook, section 8.5.3.
4.8.4 CWA Sections 303(d) and 305(b) Assessment,
Listing, and TMDLs
Under CWA Section 303(d) and the EPA's implementing regulation (40 CFR 130.7).
states and Tribes authorized to administer the CWA Section 303(d) program are
required to develop lists of impaired and threatened waters every two years. These lists,
commonly referred to as "303(d) lists," identify waters for which technology-based
regulations and other required controls are not stringent enough to meet the applicable
WQS. Pursuant to CWA Section 303(d) and the EPA's implementing regulation, states,
and Tribes authorized to administer the CWA Section 303(d) program must establish
priority rankings for waters on the list and develop TMDLs for these waters. A TMDL
includes a calculation of the maximum amount of a pollutant that can be present in a
waterbody and still meet WQS.
Antidegradation policies and adopted AIMs are relevant to the administration of CWA
Section 303(d) programs because CWA Section 303(d) and the EPA's implementing
regulation (40 CFR 130.7(b)(1)) require states and Tribes authorized to administer
the CWA Section 303(d) program to identify on their 303(d) lists waters that are not
meeting any applicable water quality standard. The EPA's implementing regulation
DRAFT CHAPTER 4: Antidegradation 71
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specifies that "applicable water quality standards" refer to criteria, designated uses, and
antidegradation requirements C40 CFR 130.7(b)(3)).
For example, it is possible that available data and information for a waterbody identified
by a state or authorized Tribe as an ONRW indicate degradation in water quality despite
its Tier 3 level protection. If those data and information indicate that the water quality
is degraded and thus does not meet the state's or authorized Tribe's CWA effective
antidegradation policy that the "water quality shall be maintained and protected," the
water must be included on the 303(d) list, even if pollutant concentrations do not
exceed applicable water quality criteria (40 CFR 130.7(b)(1); 40 CFR 103.7(b)(3)).
Under CWA Section 305(b) and the EPA's implementing regulation (40 CFR 130.8).
states109 are required to prepare reports every two years on the water quality of all
navigable waters, a subset of which are waters that belong on the state's 303(d)
lists. To efficiently meet the reporting requirements for both CWA Section 303(d)
and 305(b), the EPA encourages states to submit a single consolidated report (an
Integrated Report). The EPA encourages states to use a consolidated assessment and
listing methodology to develop their Integrated Reports. This methodology describes
the state's approach to assessing water quality against CWA goals and WQS including
antidegradation considerations.
As discussed above, state and tribes authorized to administer the CWA Section 303(d)
program collectively are required to develop TMDLs for waters on their Section 303(d)
lists. TMDLs must include a description of the applicable water quality standards,
including designated uses(s) of the waterbody, the applicable numeric or narrative water
quality criterion, and the antidegradation policy (40 CFR 130.7(c)(1)). EPA needs this
information to review the loading capacity determination, and the load and wasteload
allocations, which are required by regulation.110
For additional information about CWA Sections 303(d) and 305(b) assessments, listings,
and TMDLs, see Chapter 7 of this Handbook.
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