U.S. ENVIRONMENTAL PROTECTION AGENCY
Region 9
Guidance on
Implementing the Antidegradation Provisions
of 40 CFR 131.12
RICHARD A. CODDINGTON
Acting Director
Water Management
7
EPA
909/S
87-100x
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PURPOSE
This document provides general program guidance for the States
of Region 9 on the development of procedures for implementing
State antidegradation policies. The focus of this guidance is
on 40 CFR 131.12 of the water quality standards regulation
(promulgated in 48 FR 51407, dated November 8, 1983) which
sets out requirements to be met before any action is taken
that would lower the quality of the Nation's waters.
BACKGROUND
Section 101(a) of the Clean Water Act defines the national
goal of restoring and maintaining the chemical, physical and
biological integrity of the Nation's waters. Section 303(a)(4)
of the Clean Water Act explicitly refers to satisfaction of the
antidegradation requirements of 40 CFR 131.12 prior to taking
various actions which would lower water quality. 40 CFR 131.12
requires that antidegradation provisions at least as stringent
as those specified in that regulation be adopted by States as
part of their water quality standards.
This guidance identifies the tasks to be performed by States
to implement Section 131.12 of the water quality standards
regulation. Those tasks that need the development of decision
criteria by the States are identified. Such criteria are
necessary to define those actions which require detailed
economic or water quality impact analyses. The Agency expects
States to develop and document these criteria in their
antidegradation implementation procedures, for review and
approval by EPA regional offices. The Agency's objective is
to achieve the goals of the Act through an integrated approach
to eliminating water pollution which includes the consistent
application of State antidegradation policies. Figure 1 lays
out the decision making process of an antidegradation analysis.
Many of the procedures identified herein are already performed
by States as part of their regulatory programs. Consequently,
this document primarily serves to delineate, in a consistent
manner, the criteria EPA Region 9 will be using to evaluate
both State and EPA decisions, for compliance with
40 CFR 131.12.
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TIER III WATERS - Outstanding National Resource Waters
40 CFR 131.12(a)(3) prohibits any action which would lower
water quality in waters designated as Outstanding National
Resource Waters (ONRWs). Examples of such waters include,
but are not limited to, waters of National and State parks and
wildlife refuges, and waters of exceptional recreational or
ecological significance.
TIER I WATERS
40 CFR 131.12(a)(l) prohibits any action which would lower
water quality below that necessary to maintain and protect
existing uses. In cases where water quality is just adequate
to support the propagation of fish, shell fish and wildlife
and recreation in and on the water, such water quality must
be maintained and protected. In cases where water quality is
lower than necessary to support these uses, the requirements
in Section 303(d) of the Act, 40 CFR 131.10 and other
pertinent regulations must be satisfied. Guidance concerning
actions affecting these waters has been published elsewhere
and will not be repeated here.
TIER II WATERS - High Quality Waters
Applicability
40 CFR 131.12 establishes certain minimum requirements for
States to adopt regulating actions which would lower water
quality in high quality waters. These waters "are defined as
those in which water quality exceeds that necessary to support
propagation of fish, shellfish and wildlife and recreation in
and on the water. Any action which would result in, or which
would permit, a lowering of water quality must be addressed in
State implementation procedures. Actions covered by
antidegradation provisions include, but are not limited to the
following:
Permit Actions
1. Issuance/Re-issuance/Modification of NPDES permits
2. Issuance of variances (e.g. 30l(h), 301(m), etc.)
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3. Issuance of permits for urban runoff
4. Issuance of Section 404 permits
5. Adoption of or alteration of mixing zones
6. Relocation of discharge
7. Commencement of discharge from a new source
8. Increases in the discharge of pollutants from point
sources due to:
a. Industrial production increases
b. Municipal growth
c. New sources
d. Etc.
Standards/Load Allocation Actions
1. Water quality standards revisions
2. Revision of wasteload allocations
3. Reallocation of abandoned loads
4. Section 401 certifications (for example; concerning FERC
licenses, Corps' actions, etc.)
5. Section 208 or Section 303(e) approvals
6. WQM plan approvals
"Non-point Source" Actions
1. Changes in BMPs
2. Resource management plan approvals
3. Land Management (e.g. Forest) plan adoptions, certifica-
tions or approvals
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4. Changes in regulated agricultural activities
5. Changes in regulated silvicultural activities
6. Changes in regulated raining activities
7. Construction and operation of roads, dams, etc.
Other Actions
1. RCRA/CERCLA actions
2. Construction grant activities
3. Other "major Federal actions" (pursuant to NEPA and the
Endangered Species Act)
4. Water quantity/water rights actions which affect water
quality
5. Federal actions regulated by Section 313 of the Clean
Water Act
Prior to proceeding with a detailed analysis of these or
similar actions, the affected water body should be assessed to
determine whether or not it falls into either Tier I or
Tier III. If so, actions which would lower water quality in
such waters are prohibited. Otherwise, the water body should
be assessed to determine the adequacy of the beneficial uses
and water quality criteria designated for that water body.
Adequate water quality standards must be adopted and approved
for an affected water body, pursuant to 40 CFR 131 prior to
allowing any action to proceed which would lower water quality
in that water body.
The first step in any antidegradation analysis is to determine
whether or not the proposed action will lower water quality
(see Figure 1). If the action will not lower water quality, no
further analysis is needed and EPA considers 40 CFR 131.12 to
be satisfied. If the action could or will lower water quality,
and the affected water is not a Tier I or Tier III water, then
the steps to be followed to determine whether or not 40 CFR
131.12 is satisfied are described in the following sections of
this guidance.
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Both point and non-point sources of pollution are subject to
antidegradation requirements. While point sources are generally
well regulated, procedures for controlling non-point source
pollution have not been as extensively defined. Cost-effective
and reasonable best management practices for non-point source
controls must be designed to meet water quality standards. EPA
policy, first issued as SAM-32 on November 14, 1978, states
that where applicable water quality standards are not met,
revised or additional best management practices (BMPs) should
be applied in an iterative process to improve water quality
to the point that standards are attained, and that designated
uses are maintained and protected. In Region 9, States
generally have broad authority to regulate non-point sources.
As part of their implementation methodologies, States must
adopt procedures which adequately assure that non-point sources
of water pollution will comply with the antidegradation
requirements of 40 CFR 131.12.
Implementation Procedures
Four basic elements should be included in State implementation
procedures to ensure that actions affecting water quality are
consistent with the provisions of 40 CFR 131.12. They are:
0 Task A - Identify Actions that Require Detailed Water Quality
and Economic Impact Analyses
0 Task B - Determine that Lower Water Quality Will Fully
Protect Designated Uses
0 Task C - Determine That Lower Water Quality is Necessary to
Accommodate Important Economic or Social Development
in the Area in which the Waters are Located
0 Task D - Complete Intergovernmental Coordination and Public
Participation
Task A - Identify Actions that Require Detailed Water Quality
and Economic Impact Analyses
This task established the types of analyses required for all
actions that lower water quality in Tier II waters and decision
criteria that define the degree of water quality and economic
analysis required.
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State procedures should include three parts. First, the State
should develop procedures to document the degree to which water
quality exceeds that necessary to protect the uses. Ambient
monitoring data can be used to provide this documentation.
States must adopt procedures to assure that, where little or no
data exists, adequate information will be available to determine
the existing quality of the water body or bodies, which could
be adversely affected by the proposed action. Such procedures
should include both an assessment of existing water quality and
a determination of which water quality parameters and beneficial
uses are likely to be affected. These assessments and determin-
ations could be performed either by the State or the party
proposing the action in question.
Second, the State should develop procedures that quantify the
extent to which water quality will be lowered as a result of
the proposed action. Simple mass balance calculations or more
detailed mathematic modelling, such as that contained in waste-
load allocations, can provide this information. Third, the
State should develop decision criteria to define the degree of
water quality change that warrants detailed water quality and
economic impact analyses. Decision criteria could be based on
direct measures, such as an absolute or percent change in
ambient concentrations of the affected parameter or indirect
measures such as changes in primary productivity caused by
nutrients or changes in diurnal dissolved oxygen fluctuations.
Repeated or multiple small changes in water quality (such as
those resulting from actions which do not require detailed
analyses) can result in significant water quality degradation.
To prevent such cumulative adverse impacts, a baseline of water
quality must be established for each potentially affected water
body, prior to allowing any action which would lower the quality
of that water. This baseline should remain fixed unless some
action improves water quality. At such time, the baseline
should be adjusted accordingly.
Proposed actions to lower water quality should then be evaluated
with respect to the baseline and the resultant water quality
change should be determined. This determination should include
the cumulative impacts of all previous and proposed actions
and reasonably foreseeable actions which would lower water
quality below the established baseline. Should the cumulative
impact of actions significantly degrade water quality, more
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detailed water quality and economic impact analyses would be
necessary.
In any case, whether or not water quality is significantly
lowered (thus leading to an economic analysis), the State must
find that any action which would lower water quality is
necessary to accommodate important economic and social
development. Such a finding must include, at a minimum, the
following determinations:
1. That economic and social development will occur, e.g.
there will be new or increased production of goods or
services by the party proposing the change, population will
grow in the service area of a sewage treatment plant, etc.
2. That this economic or social development requires the
lowering of water quality which cannot be mitigated through
reasonable means.
3. That the lower water quality does not result from inadequate
wastewater treatment facilities, less-than-optimal operation
of adequate treatment facilities, or failure to implement
or comply with methodologies to reduce or eliminate non-
point source pollution.
Task B - Determine that Lower Water Quality Will Fully Maintain
and Protect Designated Uses
All actions that could lower water quality in Tier II
waters require a determination that existing uses will be fully
maintained and protected. States should develop methodologies
for making this determination.
Tier II waters, by definition, are those in which the water
quality is better than necessary to support and maintain the
biota and beneficial uses of the water. In most cases, specific
numerical standards do not exist to protect these uses. Where
such standards do exist, they are generally established to
provide the minimum acceptable quality to protect the beneficial
uses of the water. Often, such standards are established on a
statewide or drainage basin-wide basis and thus may not adequately
protect the biota or the uses of specific reaches. Consequently,
comparing existing or projected water quality with adopted
standards may not adequately define whether or not beneficial
uses will be fully maintained and protected.
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Water quality must also meet any applicable public health
standards as well as maintain and protect the existing growth
and reproduction of resident species. The water quality
criteria guidance developed by EPA per §304(a) of the Clean
Water Act provides a basis for this assessment. However,
national water quality criteria (such as those contained in the
"Gold Book") may not fully protect resident species. The
criteria may not protect locally occurring species that either
may not have been tested, or that have been tested, but require
greater protection than the criteria provide. This determina-
tion involves a comparison of the species upon which biological
testing has been completed in the criteria development documents
with the species resident to the water body where water quality
may be lowered. If the resident species are not adequately
represented in the database, additional testing should be
completed before lower water quality is allowed. Implementation
methods should include procedures for making this comparison
and define the circumstances (e.g., in terms of water quality
change or extent of the biological testing database) that would
require additional biological testing before water quality can
be lowered.
Water quality criteria for dissolved oxygen or
conventional and non-conventional pollutants may be subject to
the same limitations and should be considered in the same way.
For parameters for which no criteria guidance has been
developed, biological testing or acceptable site specific
criteria may be used to determine that lower water quality will
fully maintain and protect designated uses.
The lowering of water quality through the discharge of
conservative or persistent pollutants merits more intensive
consideration by States, due to the bioacculumative potential
of these pollutants. These pollutants, particularly
carcinogens, which are considered to have no safe "threshold"
concentration, should have more stringent antidegradation
requirements established for their analysis.
Other methods of determining whether or not beneficial uses are
being maintained and protected include biological assessments,
such as the aquatic ecoregions procedure, or ambient toxicity
testing using standardized species. In some cases, assessing
the quality of water bodies on a pollutant-specific basis could
prove costly, particularly for waters in which a number of
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discharges are located or for complex effluents. EPA's recently
developed acute and chronic toxicity methodologies for assessing
the toxicity of effluents or receiving waters could provide a
more comprehensive and affordable alternative.
Task C - Determine that Lower Water Quality is Necessary to
Accommodate Important Economic or Social Development
Actions which the State determines in Task A to significantly
lower water quality require a determination that such actions
are necessary for important economic or social development.
40 CFR 131.12(a)(2) and the August 1985 "Questions and Answers
on Antidegradation", give general guidance on how to make this
determination. Explicit criteria defining "important economic
or social development" have purposely not been developed by EPA
Headquarters, because of the varying environmental, economic
and social conditions of localities throughout the country.
Further explication of EPA Region 9's expectation concerning
these determinations is appropriate and is presented below.
The fundamental requirement of this task is to establish a
strong tie between the proposed lower water quality level and
"important" economic or social development. If the party
seeking the change in water quality cannot demonstrate the
relationship between such development and water quality, then
the proposed action is prohibited.
Demonstration of important economic or social development
entails two steps. First, the party should describe and analyze
the current state of economic and social development in the
area that would be affected. The purpose of this step is to
determine the "baseline" economic and social status of the
affected community, i.e., the measure against which the effect
of the water quality downgrade is judged. The area's use or
dependence upon the water resource affected by the proposed
action should be described in the analysis. The following
factors should normally be included in the baseline analysis:
0 Population
0 Area employment (numbers employed, earnings, major
employers);
0 Area income (earnings from employment and transfer
payments, if known);
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0 Manufacturing profile: types, value, employment, trends;
0 Government fiscal base: revenues by source (employment
and sales taxes, etc.)
Second, the party seeking the change in water quality should
then demonstrate the extent to which the sought-for level of
water quality would create an incremental increase in the rate
of economic or social development and why the change in water
quality is necessary to achieve such development. The party
should provide analysis, along with the supporting data used in
its preparation, showing the extent to which the factors listed
above will benefit from the change in water quality requested.
The analysis should demonstrate why such economic and social
development requires the lower water quality. Other alterna-
tives or changes in the project or other mitigation measures
which would prevent degradation of water quality should be
identified in this analysis. The following factors may be
included in the analysis of incremental effects expected to
result from the degradation in water quality:
0 Expected plant expansion;
0 Employment growth;
0 Direct and indirect income effects;
0 Increases in the community tax base
Other components of this analysis could include an assessment
of the overall environmental benefits to be achieved by the
proposed action and the tradeoffs to be considered among the
various media. The relative costs of various alternatives to
the proposed action could also be analyzed.
The requirements for a given analysis will be site-specific,
depending upon factors such as data availability, conditions
specific to the relevant water body, the area of impact (city,
county, State-wide), etc. The economic analysis may include
estimation of the treatment costs necessary to maintain existing
water quality; e.g. land treatment or advanced treatment.
Staff of the EPA Regional office are available to assist States
in determining the exact requirements of an analysis of
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specific proposals to lower water quality. In addition, the
Economic Analysis Branch in EPA Headquarters' Office of Water
can assist State and Regional staff, when necessary.
Task D - Complete Intergovernmental Coordination and Public
Participation
Public notification pursuant to 40 CFR 131.12 is
required for all actions that lower water quality in Tier II
waters. EPA requires that proposed actions which degrade water
quality be reviewed by other appropriate agencies and that the
public be given an opportunity to comment.
Documentation and public notification under antidegradation
need not be a lengthy process in many cases and can be combined
with other actions that require public notification. The
public participation requirement may be met by holding a public
hearing, e.g., as part of the adoption of an NPDES permit, as
long as proper notice of a standards action is provided to the
public (see WQS Handbook). Intergovernmental coordination
consists of requests for review of proposed actions by affected
local, State and Federal agencies, such as area-wide planning
agencies, fish and wildlife agencies, etc.
The following is a summary of the public notification required
to comply with the antidegradation provisions of the WQS
regulation:
0 A statement that the action must comply with the State's
antidegradation policy and a description.of the policy.
0 A determination that existing uses will be maintained and
protected. This will require an assessment and documen-
tation for public review of (a) the amount the water
quality currently exceeds that necessary to protect the
existing and designated uses, and (b) the amount that
water quality will be lowered as a result of the proposed
action (see Task A).
0 A summary of other actions, if any, that have lowered
water quality and a determination of any cumulative
impacts.
0 A determination that lower water quality is necessary to
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accommodate important economic or social development.
This will require a detailed analysis or the rationale
used to determine that a detailed analysis is not' required
(see Tasks A and C).
A description of the intergovernmental coordination that
has taken place.
A determination that there has been achieved the highest
statutory and regulatory requirements for all new and
existing point sources and all cost-effective and reason-
able best management practices for non-point sources.
OTHER CONSIDERATIONS
1. The decision criteria for determining that detailed water
quality and economic analyses are needed may vary with the
types of chemical pollutants. Some chemicals are believed
to elicit an effect at a certain concentration (i.e.,
threshold chemicals). Other chemicals (i.e., non-threshold
chemicals) have no safe level. Non-threshold chemicals
include carcinogens, mutagens and teratogens. States are
urged to apply more stringent review procedures to
non-threshold chemicals.
2. NPDES permits do not routinely contain numerical limits
for all of the substances found, in a discharger's effluent.
Nevertheless, all substances are subject to antidegradation
policy implementation, whether or not they are specifically
limited in the permit. To apply antidegradation to
substances not currently limited in the permit, the State
can utilize the notification procedures specified in 40 CFR
122.42, requiring dischargers to notify the State pollution
control agency of any actual or anticipated change in
effluent characteristics, as compared with those existing
at the time the permit was issued.
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FIGURE 1
Antidegradation Flow Chart
Will the regulated action lower
water quality?
YES
NO
Is the water an ONRW?
NO
YES
Is water quality better than
necessary to support designated
uses?
YES
NO
Will the action
significantly*
lower water
quality?
(Task A)
YES
NO
Will designated
uses be fully
maintained
and protected?
(Task B)
NO
Will designated
uses be fully
maintained and
protected?
(Task B)
NO
Action is
prohibited
YES
Is action
necessary to
accommodate
economic or
social
development**
(Task C)
NO
YES
No antidegration analysis is
required '
Action is prohibited
Action is prohibited
YES
State/EPA make
finding that lower
water quality is
necessary to acco-
modate important
economic or social
development
State/EPA determine
that highest statu-
tory/regulatory
requirements are met
Complete public
participation
requirements (Task D)
Perform action
*Significance level and effect of cumulative impacts as defined by State
**Based on criteria defined by State
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