[Federal Register Volume 80, Number 124 (Monday, June 29, 2015)]
[Unknown Section]
[Pages 37053-37127]
[FR Doc No: 2015-13435]

Vol. 80

Monday,

No. 124

June 29, 2015

Part II

Department of Defense

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Department of the Army, Corps of Engineers

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33 CFR Part 328

Environmental Protection Agency

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40 CFR Parts 110, 112, 116, et al.

Clean Water Rule: Definition of ``Waters of the United States''; Final
Rule

Federal Register / Vol. 80 , No. 124 / Monday, June 29, 2015 /
Rules

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DEPARTMENT OF DEFENSE

Department of the Army, Corps of Engineers

33 CFR Part 328

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 110, 112, 116, 117, 122, 230, 232, 300, 302, and 401

[EPA-HQ-OW-2011-0880; FRL-9927-20-OW]
RIN 2040-AF30

Clean Water Rule: Definition of ``Waters of the United States''

AGENCY: U.S. Army Corps of Engineers, Department of the Army,
Department of Defense; and Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) and the U.S. Army
Corps of Engineers (Corps) are publishing a final rule defining the
scope of waters protected under the Clean Water Act (CWA or the Act),
in light of the statute, science, Supreme Court decisions in U.S. v.
Riverside Bayview Homes, Solid Waste Agency of Northern Cook County v.
U.S. Army Corps of Engineers (SWANCC), and Rapanos v. United States
(Rapanos), and the agencies' experience and technical expertise. This
final rule reflects consideration of the extensive public comments
received on the proposed rule. The rule will ensure protection for the
nation's public health and aquatic resources, and increase CWA program
predictability and consistency by clarifying the scope of ``waters of
the United States'' protected under the Act.

DATES: This rule is effective on August 28, 2015. In accordance with 40
CFR part 23, this regulation shall be considered issued for purposes of
judicial review at 1 p.m. Eastern time on July 13, 2015.

FOR FURTHER INFORMATION CONTACT: Ms. Donna Downing, Office of Water
(4502-T), Environmental Protection Agency, 1200 Pennsylvania Avenue
NW., Washington, DC 20460; telephone number<PHONE_NUMBER>; email
address<EMAIL_ADDRESS>v. Ms. Stacey Jensen, Regulatory Community of
Practice (CECW-CO-R), U.S. Army Corps of Engineers, 441 G Street NW.,
Washington, DC 20314; telephone number<PHONE_NUMBER>; email address:
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: This final rule does not establish any
regulatory requirements. Instead, it is a definitional rule that
clarifies the scope of ``waters of the United States'' consistent with
the Clean Water Act (CWA), Supreme Court precedent, and science.
Programs established by the CWA, such as the section 402 National
Pollutant Discharge Elimination System (NPDES) permit program, the
section 404 permit program for discharge of dredged or fill material,
and the section 311 oil spill prevention and response programs, all
rely on the definition of ``waters of the United States.'' Entities
currently are, and will continue to be, regulated under these programs
that protect ``waters of the United States'' from pollution and
destruction.
    State, tribal, and local governments have well-defined and
longstanding relationships with the Federal government in implementing
CWA programs and these relationships are not altered by the final rule.
Forty-six states and the U.S. Virgin Islands have been authorized by
EPA to administer the NPDES program under section 402, and two states
have been authorized by the EPA to administer the section 404 program.
All states and forty tribes have developed water quality standards
under the CWA for waters within their boundaries. A federal advisory
committee has recently been announced to assist states in identifying
the scope of waters assumable under the section 404 program.
    The scope of jurisdiction in this rule is narrower than that under
the existing regulation. Fewer waters will be defined as ``waters of
the United States'' under the rule than under the existing regulations,
in part because the rule puts important qualifiers on some existing
categories such as tributaries. In addition, the rule provides greater
clarity regarding which waters are subject to CWA jurisdiction,
reducing the instances in which permitting authorities, including the
states and tribes with authorized section 402 and 404 CWA permitting
programs, would need to make jurisdictional determinations on a case-
specific basis.

Table of Contents

I. General Information
    A. How can I get copies of this document and related
information?
    B. Under what legal authority is this rule issued?
II. Executive Summary
III. Significant Nexus Determinations
    A. The Significant Nexus Standard
    B. Science Report
    C. Significant Nexus Conclusions
    1. Scope of Significant Nexus Analysis
    2. Categories of Waters Determined to Have a Significant Nexus
    3. Case-Specific Significant Nexus Determinations
IV. Definition of ``Waters of the United States''
    A. Summary of Rule
    B. Traditional Navigable Waters
    C. Interstate Waters
    D. Territorial Seas
    E. Impoundments
    F. Tributaries
    G. Adjacent Waters
    H. Case-Specific ``Waters of the United States''
    I. Waters and Features That Are Not ``Waters of the United
States''
V. Economic Impacts
VI. Related Acts of Congress, Executive Orders, and Agency
Initiatives
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in
    Minority Populations and Low-Income Populations
    K. Congressional Review Act
    L. Environmental Documentation
    M. Judicial Review

I. General Information

A. How can I get copies of this document and related information?

    1. Docket. An official public docket for this action has been
established under Docket Id. No. EPA-HQ-OW-2011-0880. The official
public docket consists of the documents specifically referenced in this
action, any public comments received, and other information related to
this action. The official public docket also includes a Technical
Support Document that provides additional legal and scientific
discussion for issues raised in this rule, and the Response to Comments
document. Although a part of the official docket, the public docket
does not include Confidential Business Information or other information
whose disclosure is restricted by statute. The official public docket
is the collection of materials that is available for public viewing at
the OW Docket, EPA West, Room 3334, 1301 Constitution Ave. NW.,
Washington, DC 20004. This Docket Facility is open from 8:30 a.m.

to 4:30 p.m., Monday through Friday, excluding legal holidays. The OW
Docket telephone number is<PHONE_NUMBER>. A reasonable fee will be
charged for copies.
    2. Electronic Access. You may access this Federal Register document
electronically under the ``Federal Register'' listings at http://www.regulations.gov. An electronic version of the public docket is
available through EPA's electronic public docket and comment system,
EPA Dockets. You may access EPA Dockets at http://www.regulations.gov
to view public comments, access the index listing of the contents of
the official public docket, and access those documents in the public
docket that are available electronically. For additional information
about EPA's public docket, visit the EPA Docket Center homepage at
http://www.epa.gov/epahome/dockets.htm. Although not all docket
materials may be available electronically, you may still access any of
the publicly available docket materials through the Docket Facility.

B. Under what legal authority is this rule issued?

    The authority for this rule is the Federal Water Pollution Control
Act, 33 U.S.C. 1251, et seq., including sections 301, 304, 311, 401,
402, 404 and 501.

II. Executive Summary

    In this final rule, the agencies clarify the scope of ``waters of
the United States'' that are protected under the Clean Water Act (CWA),
based upon the text of the statute, Supreme Court decisions, the best
available peer-reviewed science, public input, and the agencies'
technical expertise and experience in implementing the statute. This
rule makes the process of identifying waters \1\ protected under the
CWA easier to understand, more predictable, and consistent with the law
and peer-reviewed science, while protecting the streams and wetlands
that form the foundation of our nation's water resources.
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    \1\ The agencies use the term ``water'' and ``waters'' in
categorical reference to rivers, streams, ditches, wetlands, ponds,
lakes, oxbows, and other types of natural or man-made aquatic
systems, identifiable by the water contained in these aquatic
systems or by their chemical, physical, and biological indicators.
The agencies use the terms ``waters'' and ``water bodies''
interchangeably in this preamble.
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    Congress enacted the CWA ``to restore and maintain the chemical,
physical, and biological integrity of the Nation's waters,'' section
101(a), and to complement statutes that protect the navigability of
waters, such as the Rivers and Harbors Act. 33 U.S.C. 401, 403, 404,
407. The CWA is the nation's single most important statute for
protecting America's clean water against pollution, degradation, and
destruction. To provide that protection, the Supreme Court has
consistently agreed that the geographic scope of the CWA reaches beyond
waters that are navigable in fact. Peer-reviewed science and practical
experience demonstrate that upstream waters, including headwaters and
wetlands, significantly affect the chemical, physical, and biological
integrity of downstream waters by playing a crucial role in controlling
sediment, filtering pollutants, reducing flooding, providing habitat
for fish and other aquatic wildlife, and many other vital chemical,
physical, and biological processes.
    This final rule interprets the CWA to cover those waters that
require protection in order to restore and maintain the chemical,
physical, or biological integrity of traditional navigable waters,
interstate waters, and the territorial seas. This interpretation is
based not only on legal precedent and the best available peer-reviewed
science, but also on the agencies' technical expertise and extensive
experience in implementing the CWA over the past four decades. The rule
will clarify and simplify implementation of the CWA consistent with its
purposes through clearer definitions and increased use of bright-line
boundaries to establish waters that are jurisdictional by rule and
limit the need for case-specific analysis. The agencies emphasize that,
while the CWA establishes permitting requirements for covered waters to
ensure protection of water quality, these requirements only apply with
respect to discharges of pollutants to the covered water. In the
absence of a discharge of a pollutant, the CWA does not impose
permitting restrictions on the use of such water.
    Additionally, Congress has exempted certain discharges, and the
rule does not affect any of the exemptions from CWA section 404
permitting requirements provided by CWA section 404(f), including those
for normal farming, ranching, and silviculture activities. CWA section
404(f); 40 CFR 232.3; 33 CFR 323.4. This rule not only maintains
current statutory exemptions, it expands regulatory exclusions from the
definition of ``waters of the United States'' to make it clear that
this rule does not add any additional permitting requirements on
agriculture. The rule also does not regulate shallow subsurface
connections nor any type of groundwater, erosional features, or land
use, nor does it affect either the existing statutory or regulatory
exemptions from NPDES permitting requirements, such as for agricultural
stormwater discharges and return flows from irrigated agriculture, or
the status of water transfers. CWA section 402(l)(1); CWA section
402(l)(2); CWA section 502(14); 40 CFR 122.3(f); 40 CFR 122.2.
    Finally, even where waters are covered by the CWA, the agencies
have adopted many streamlined regulatory requirements to simplify and
expedite compliance through the use of measures such as general permits
and standardized mitigation measures. The agencies will continue to
develop general permits and simplified procedures, particularly as they
affect crossings of covered ephemeral and intermittent tributaries
jurisdictional under this rule to ensure that projects that offer
significant social benefits, such as renewable energy development, can
proceed with the necessary environmental safeguards while minimizing
permitting delays.
    The jurisdictional scope of the CWA is ``navigable waters,''
defined in section 502(7) of the statute as ``waters of the United
States, including the territorial seas.'' The term ``navigable waters''
is used in a number of provisions of the CWA, including the section 402
National Pollutant Discharge Elimination System (NPDES) permit program,
the section 404 permit program, the section 311 oil spill prevention
and response program,\2\ the water quality standards and total maximum
daily load programs (TMDL) under section 303, and the section 401 state
water quality certification process. However, while there is only one
CWA definition of ``waters of the United States,'' there may be other
statutory factors that define the reach of a particular CWA program or
provision.\3\

Existing regulations (last codified in 1986) define ``waters of the
United States'' as traditional navigable waters, interstate waters, all
other waters that could affect interstate or foreign commerce,
impoundments of waters of the United States, tributaries, the
territorial seas, and adjacent wetlands. 33 CFR 328.3; 40 CFR 122.2.\4\
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    \2\ While section 311 uses the phrase ``navigable waters of the
United States,'' EPA has interpreted it to have the same breadth as
the phrase ``navigable waters'' used elsewhere in section 311, and
in other sections of the CWA. See United States v. Texas Pipe Line
Co., 611 F.2d 345, 347 (10th Cir. 1979); United States v. Ashland
Oil & Transp. Co., 504 F.2d 1317, 1324-25 (6th Cir. 1974). In 2002,
EPA revised its regulatory definition of ``waters of the United
States'' in 40 CFR part 112 to ensure that the language of the rule
was consistent with the regulatory language of other CWA programs.
Oil Pollution Prevention & Response; Non-Transportation-Related
Onshore & Offshore Facilities, 67 FR 47042, July 17, 2002. A
district court vacated the rule for failure to comply with the
Administrative Procedure Act, and reinstated the prior regulatory
language. American Petroleum Ins. v. Johnson, 541 F. Supp. 2d 165
(D. D.C. 2008). However, EPA interprets ``navigable waters of the
United States'' in CWA section 311(b), in the pre-2002 regulations,
and in the 2002 rule to have the same meaning as ``navigable
waters'' in CWA section 502(7).
    \3\ For example, the CWA section 402 (33 U.S.C. 1342) program
regulates discharges of pollutants from ``point sources'' to
``waters of the United States,'' whether these pollutants reach
jurisdictional waters directly or indirectly. The plurality opinion
in Rapanos noted that ``there is no reason to suppose that our
construction today significantly affects the enforcement of Sec.
1342. . . . The Act does not forbid the `addition of any pollutant
directly to navigable waters from any point source,' but rather the
`addition of any pollutant to navigable waters.' '' 547 U.S. at 743.
    \4\ There are numerous regulations that utilize the definition
of ``waters of the United States'' and each is codified consistent
with its place in a particular section of the Code of Federal
Regulations. For simplicity, throughout the preamble the agencies
refer to the rule as organized into (a), (b), (c) provisions and
intend the reference to encompass the appropriate cites in each
section of the Code of Federal Regulations. For example, a reference
to (a)(1) is a reference to all instances in the CFR identified as
subject to this rule that state ``All waters which are currently
used, were used in the past, or may be susceptible to use in
interstate or foreign commerce, including all waters which are
subject to the ebb and flow of the tide.''
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    However, the Supreme Court has issued three decisions that provide
critical context and guidance in determining the appropriate scope of
``waters of the United States'' covered by the CWA. In United States v.
Riverside Bayview Homes, 474 U.S. 121 (1985) (Riverside), the Court, in
a unanimous opinion, deferred to the Corps' ecological judgment that
adjacent wetlands are ``inseparably bound up'' with the waters to which
they are adjacent, and upheld the inclusion of adjacent wetlands in the
regulatory definition of ``waters of the United States.'' Id. at 134.
The Court observed that the broad objective of the CWA to restore and
maintain the integrity of the Nation's waters ``incorporated a broad,
systemic view of the goal of maintaining and improving water quality. .
. . Protection of aquatic ecosystems, Congress recognized, demanded
broad federal authority to control pollution, for `[w]ater moves in
hydrologic cycles and it is essential that discharge of pollutants be
controlled at the source.' In keeping with these views, Congress chose
to define the waters covered by the Act broadly.'' Id. at 132-33
(citing Senate Report No. 92-414, p. 77 (1972)).
    In Solid Waste Agency of Northern Cook County v. U.S. Army Corps of
Engineers, 531 U.S. 159 (2001) (SWANCC), the Supreme Court held that
the use of ``isolated'' non-navigable intrastate ponds by migratory
birds was not by itself a sufficient basis for the exercise of federal
regulatory authority under the CWA. Although the SWANCC decision did
not call into question earlier decisions upholding the CWA's coverage
of wetlands or other waters ``adjacent'' to traditional navigable
waters, it created uncertainty with regard to the jurisdiction of other
waters and wetlands that, in many instances, may play an important role
in protecting the integrity of the nation's waters. The majority
opinion in SWANCC introduced the concept that it was a ``significant
nexus'' that informed the Court's reading of CWA jurisdiction over
waters that are not navigable in fact.
    Five years later, in Rapanos v. United States, 547 U.S. 715 (2006)
(Rapanos), all Members of the Court agreed that the term ``waters of
the United States'' encompasses some waters that are not navigable in
the traditional sense. In addition, Justice Kennedy's opinion indicated
that the critical factor in determining the CWA's coverage is whether a
water has a ``significant nexus'' to downstream traditional navigable
waters such that the water is important to protecting the chemical,
physical, or biological integrity of the navigable water, referring
back to the Court's decision in SWANCC. Justice Kennedy's concurrence
in Rapanos stated that to constitute a ``water of the United States''
covered by the CWA, ``a water or wetland must possess a `significant
nexus' to waters that are or were navigable in fact or that could
reasonably be so made.'' Id. at 759 (Kennedy, J., concurring in the
judgment) (citing SWANCC, 531 U.S. at 167, 172). Justice Kennedy
concluded that wetlands possess the requisite significant nexus if the
wetlands ``either alone or in combination with similarly situated
[wet]lands in the region, significantly affect the chemical, physical,
and biological integrity of other covered waters more readily
understood as `navigable.''' 547 U.S. at 780.
    In this rule, the agencies interpret the scope of the ``waters of
the United States'' for the CWA using the goals, objectives, and
policies of the statute, the Supreme Court case law, the relevant and
available science, and the agencies' technical expertise and experience
as support. In particular, the agencies looked to the objective of the
CWA ``to restore and maintain the chemical, physical, and biological
integrity of the Nation's waters,'' and the scientific consensus on the
strength of the effects of upstream tributaries and adjacent waters,
including wetlands, on downstream traditional navigable waters,
interstate waters, and the territorial seas. An important element of
the agencies' interpretation of the CWA is the significant nexus
standard. This significant nexus standard was first informed by the
ecological and hydrological connections the Supreme Court noted in
Riverside Bayview, developed and established by the Supreme Court in
SWANCC, and further refined in Justice Kennedy's opinion in Rapanos.
The agencies also utilized the plurality standard in Rapanos by
establishing boundaries on the scope of ``waters of the United States''
and in support of the exclusions from the definition of ``waters of the
United States.'' The analysis used by the agencies has been supported
by all nine of the United States Courts of Appeals that have considered
the issue.
    The agencies assess the significance of the nexus in terms of the
CWA's objective to ``restore and maintain the chemical, physical, and
biological integrity of the Nation's waters.'' When the effects are
speculative or insubstantial, the ``significant nexus'' would not be
present. The science demonstrates that the protection of upstream
waters is critical to maintaining the integrity of the downstream
waters. The upstream waters identified in the rule as jurisdictional
function as integral parts of the aquatic environment, and if these
waters are polluted or destroyed, there is a significant effect
downstream.
    In response to the Supreme Court opinions, the agencies issued
guidance in 2003 (post-SWANCC) and 2008 (post-Rapanos). However, these
two guidance documents did not provide the public or agency staff with
the kind of information needed to ensure timely, consistent, and
predictable jurisdictional determinations. Many waters are currently
subject to case-specific jurisdictional analysis to determine whether a
``significant nexus'' exists, and this time and resource intensive
process can result in inconsistent interpretation of CWA jurisdiction
and perpetuate ambiguity over where the CWA applies. As a result of the
ambiguity that exists under current regulations and practice following
these recent decisions, almost all waters and wetlands across the
country theoretically could be subject to a case-specific
jurisdictional determination.
    Members of Congress, developers, farmers, state and local
governments, energy companies, and many others requested new
regulations to make the process of identifying waters protected under
the CWA clearer, simpler, and faster. Chief Justice Roberts'
concurrence in Rapanos underscores

the importance of this rulemaking effort.\5\ In this final rule, the
agencies are responding to those requests from across the country to
make the process of identifying waters protected under the CWA easier
to understand, more predictable, and more consistent with the law and
peer-reviewed science.
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    \5\ Chief Justice Roberts' concurrence in Rapanos emphasized
that ``[a]gencies delegated rulemaking authority under a statute
such as the Clean Water Act are afforded generous leeway by the
courts in interpreting the statute they are entrusted to
administer.'' Id. at 758. Chief Justice Roberts made clear that, if
the agencies had undertaken such a rulemaking, ``the Corps and the
EPA would have enjoyed plenty of room to operate in developing some
notion of an outer bound to the reach of their authority.'' Id.
(Emphasis in original.)
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    The agencies proposed a rule clarifying the scope of waters of the
United States April 21, 2014 (79 FR 22188), and solicited comments for
over 200 days. This final rule reflects the over 1 million public
comments on the proposal, the substantial majority of which supported
the proposed rule, as well as input provided through the agencies'
extensive public outreach effort, which included over 400 meetings
nationwide with states, small businesses, farmers, academics, miners,
energy companies, counties, municipalities, environmental
organizations, other federal agencies, and many others. The agencies
sought comment on a number of approaches to specific jurisdictional
questions, and many of these commenters and stakeholders urged EPA to
improve upon the April 2014 proposal, by providing more bright line
boundaries and simplifying definitions that identify waters that are
protected under the CWA, all for the purpose of minimizing delays and
costs, making protection of clean water more effective, and improving
predictability and consistency for landowners and regulated entities.
    The agencies' interpretation of the CWA's scope in this final rule
is guided by the best available peer-reviewed science--particularly as
that science informs the determinations as to which waters have a
``significant nexus'' with traditional navigable waters, interstate
waters, or the territorial seas.
    The relevant science on the relationship and downstream effects of
waters has advanced considerably in recent years. A comprehensive
report prepared by the EPA's Office of Research and Development
entitled ``Connectivity of Streams and Wetlands to Downstream Waters: A
Review and Synthesis of the Scientific Evidence'' \6\ (hereafter the
Science Report) synthesizes the peer-reviewed science.
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    \6\ U.S. Environmental Protection Agency, Connectivity of
Streams and Wetlands to Downstream Waters: A Review and Synthesis of
the Scientific Evidence (Final Report), EPA/600/R-14/475F,
(Washington, DC: U.S. Environmental Protection Agency, (2015)).
http://www.epa.gov/ncea.
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    The Science Report provides much of the technical basis for this
rule. The Science Report is based on a review of more than 1,200 peer-
reviewed publications. EPA's Science Advisory Board (SAB) conducted a
comprehensive technical review of the Science Report and reviewed the
adequacy of the scientific and technical basis of the proposed rule.
The Science Report and the SAB review confirmed that:
     Waters are connected in myriad ways, including physical
connections and the hydrologic cycle; however, connections occur on a
continuum or gradient from highly connected to highly isolated.
     These variations in the degree of connectivity are a
critical consideration to the ecological integrity and sustainability
of downstream waters.
     The critical contribution of upstream waters to the
chemical, physical, and biological integrity of downstream waters
results from the accumulative contribution of similar waters in the
same watershed and in the context of their functions considered over
time.

The Science Report and the SAB review also confirmed that:
     Tributary streams, including perennial, intermittent, and
ephemeral streams, are chemically, physically, and biologically
connected to downstream waters, and influence the integrity of
downstream waters.
     Wetlands and open waters in floodplains and riparian areas
are chemically, physically, and biologically connected with downstream
waters and influence the ecological integrity of such waters.
     Non-floodplain wetlands and open waters provide many
functions that benefit downstream water quality and ecological
integrity, but their effects on downstream waters are difficult to
assess based solely on the available science.
    Although these conclusions play a critical role in informing the
agencies' interpretation of the CWA's scope, the agencies' interpretive
task in this rule--determining which waters have a ``significant
nexus''--requires scientific and policy judgment, as well as legal
interpretation. The science demonstrates that waters fall along a
gradient of chemical, physical, and biological connection to
traditional navigable waters, and it is the agencies' task to determine
where along that gradient to draw lines of jurisdiction under the CWA.
In making this determination, the agencies must rely, not only on the
science, but also on their technical expertise and practical experience
in implementing the CWA during a period of over 40 years. In addition,
the agencies are guided, in part, by the compelling need for clearer,
more consistent, and easily implementable standards to govern
administration of the Act, including brighter line boundaries where
feasible and appropriate.

Major Rule Provisions

    In this final rule, the agencies define ``waters of the United
States'' to include eight categories of jurisdictional waters. The rule
maintains existing exclusions for certain categories of waters, and
adds additional categorical exclusions that are regularly applied in
practice. The rule reflects the agencies' goal of providing simpler,
clearer, and more consistent approaches for identifying the geographic
scope of the CWA. The rule recognizes jurisdiction for three basic
categories: Waters that are jurisdictional in all instances, waters
that are excluded from jurisdiction, and a narrow category of waters
subject to case-specific analysis to determine whether they are
jurisdictional.
    Decisions about waters in each of these categories are based on the
law, peer-reviewed science, and the agencies' technical expertise, and
were informed by public comments. This rule replaces existing
procedures that often depend on individual, time-consuming, and
inconsistent analyses of the relationship between a particular stream,
wetland, lake, or other water with downstream waters. The agencies have
greatly reduced the extent of waters subject to this individual review
by carefully incorporating the scientific literature and by utilizing
agency expertise and experience to characterize the nature and strength
of the chemical, physical, and biological connections between upstream
and downstream waters. The result of applying this scientific analysis
is that the agencies can more effectively focus the rule on identifying
waters that are clearly covered by the CWA and those that are clearly
not covered, making the rule easier to understand, consistent, and
environmentally more protective.
    The jurisdictional categories reflect the current state of the best
available science, and are based upon the law and Supreme Court
decisions. The agencies will continue a transparent review of the
science, and learn from on-going

experience and expertise as the agencies implement the rule. If
evolving science and the agencies' experience lead to a need for action
to alter the jurisdictional categories, any such action will be
conducted as part of a rule-making process.
    The first three types of jurisdictional waters, traditional
navigable waters, interstate waters, and the territorial seas, are
jurisdictional by rule in all cases. The fourth type of water,
impoundments of jurisdictional waters, is also jurisdictional by rule
in all cases. The next two types of waters, ``tributaries'' and
``adjacent'' waters, are jurisdictional by rule, as defined, because
the science confirms that they have a significant nexus to traditional
navigable waters, interstate waters, or territorial seas. For waters
that are jurisdictional by rule, no additional analysis is required.
    The final two types of jurisdictional waters are those waters found
after a case-specific analysis to have a significant nexus to
traditional navigable waters, interstate waters, or the territorial
seas, either alone or in combination with similarly situated waters in
the region. Justice Kennedy acknowledged the agencies could establish
more specific regulations or establish a significant nexus on a case-
by-case basis, Rapanos at 782, and for these waters the agencies will
continue to assess significant nexus on a case-specific basis.
    The major elements of the final rule are briefly summarized here.

Traditional Navigable Waters, Interstate Waters, Territorial Seas, and
Impoundments of Jurisdictional Waters

    Consistent with existing regulations and the April 2014 proposed
rule, the final rule includes traditional navigable waters, interstate
waters, territorial seas, and impoundments of jurisdictional waters in
the definition of ``waters of the United States.'' These waters are
jurisdictional by rule.

Tributaries

    Previous definitions of ``waters of the United States'' regulated
all tributaries without qualification. This final rule more precisely
defines ``tributaries'' as waters that are characterized by the
presence of physical indicators of flow--bed and banks and ordinary
high water mark--and that contribute flow directly or indirectly to a
traditional navigable water, an interstate water, or the territorial
seas. The rule concludes that such tributaries are ``waters of the
United States.'' The great majority of tributaries as defined by the
rule are headwater streams that play an important role in the transport
of water, sediments, organic matter, nutrients, and organisms to
downstream waters. The physical indicators of bed and banks and
ordinary high water mark demonstrate that there is sufficient volume,
frequency, and flow in such tributaries to a traditional navigable
water, interstate water, or the territorial seas to establish a
significant nexus. ``Tributaries,'' as defined, are jurisdictional by
rule.
    The rule only covers as tributaries those waters that science tells
us provide chemical, physical, or biological functions to downstream
waters and that meet the significant nexus standard. The agencies
identify these functions in the definition of ``significant nexus'' at
paragraph (c)(5). Features not meeting this legal and scientific test
are not jurisdictional under this rule. The rule continues the current
policy of regulating ditches that are constructed in tributaries or are
relocated tributaries or, in certain circumstances drain wetlands, or
that science clearly demonstrates are functioning as a tributary. These
jurisdictional waters affect the chemical, physical, and biological
integrity of downstream waters. The rule further reduces existing
confusion and inconsistency regarding the regulation of ditches by
explicitly excluding certain categories of ditches, such as ditches
that flow only after precipitation. Further, the rule explicitly
excludes from the definition of ``waters of the United States''
erosional features, including gullies, rills, and ephemeral features
such as ephemeral streams that do not have a bed and banks and ordinary
high water mark.

Adjacent Waters

    The agencies determined that ``adjacent waters,'' as defined in the
rule, have a significant nexus to traditional navigable waters,
interstate waters, and the territorial seas based upon their
hydrological and ecological connections to, and interactions with,
those waters. Under this final rule, ``adjacent'' means bordering,
contiguous, or neighboring, including waters separated from other
``waters of the United States'' by constructed dikes or barriers,
natural river berms, beach dunes and the like. Further, waters that
connect segments of, or are at the head of, a stream or river are
``adjacent'' to that stream or river. ``Adjacent waters'' include
wetlands, ponds, lakes, oxbows, impoundments, and similar water
features. However, it is important to note that ``adjacent waters'' do
not include waters that are subject to established normal farming,
silviculture, and ranching activities as those terms are used in
Section 404(f) of the CWA.
    The final rule establishes a definition of ``neighboring'' for
purposes of determining adjacency. In the rule, the agencies identify
three circumstances under which waters would be ``neighboring'' and
therefore ``waters of the United States'':
    (1) Waters located in whole or in part within 100 feet of the
ordinary high water mark of a traditional navigable water, interstate
water, the territorial seas, an impoundment of a jurisdictional water,
or a tributary, as defined in the rule.
    (2) Waters located in whole or in part in the 100-year floodplain
and that are within 1,500 feet of the ordinary high water mark of a
traditional navigable water, interstate water, the territorial seas, an
impoundment, or a tributary, as defined in the rule (``floodplain
waters'').
    (3) Waters located in whole or in part within 1,500 feet of the
high tide line of a traditional navigable water or the territorial seas
and waters located within 1,500 feet of the ordinary high water mark of
the Great Lakes.
    The agencies emphasize that the rule has defined as ``adjacent
waters'' those waters that currently available science demonstrates
possess the requisite connection to downstream waters and function as a
system to protect the chemical, physical, or biological integrity of
those waters. The agencies also emphasize that the rule does not cover
``adjacent waters'' that are otherwise excluded. Further, the agencies
recognize the establishment of bright line boundaries in the rule for
adjacency does not in any way restrict states from considering state
specific information and concerns, as well as emerging science to
evaluate the need to more broadly protect their waters under state law.
The CWA establishes both national and state roles to ensure that states
specific circumstances are properly considered to complement and
reinforce actions taken at the national level.
    ``Adjacent'' waters as defined are jurisdictional by rule. The
agencies recognize that there are individual waters outside of the
``neighboring'' boundaries stated above where the science may
demonstrate through a case-specific analysis that there exists a
significant nexus to a downstream traditional navigable water,
interstate water, or the territorial seas. However, these waters are
not determined jurisdictional by rule and will be evaluated through a
case-specific analysis. The strength of the science and

the significance of the nexus will be established on a case-specific
basis as described below.

Case-Specific Significant Nexus

    The rule identifies particular waters that are not jurisdictional
by rule but are subject to case-specific analysis to determine if a
significant nexus exists and the water is a ``water of the United
States.'' This category of case-specific waters is based upon available
science and the law, and in response to public comments that encouraged
the agencies to ensure more consistent determinations and reduce the
complexity of conducting jurisdictional determinations. Consistent with
the significant nexus standard articulated in the Supreme Court
opinions, waters are ``waters of the United States'' if they
significantly affect the chemical, physical, or biological integrity of
traditional navigable waters, interstate waters, or the territorial
seas. This determination will most typically be made on a water
individually, but can, when warranted, be made in combination with
other waters where waters function together.
    In this final rule, the agencies have identified by rule, five
specific types of waters in specific regions that science demonstrates
should be subject to a significant nexus analysis and are considered
similarly situated by rule because they function alike and are
sufficiently close to function together in affecting downstream waters.
These five types of waters are Prairie potholes, Carolina and Delmarva
bays, pocosins, western vernal pools in California, and Texas coastal
prairie wetlands. Consistent with Justice Kennedy's opinion in Rapanos,
the agencies determined that such waters should be analyzed ``in
combination'' (as a group, rather than individually) in the watershed
that drains to the nearest traditional navigable water, interstate
water, or the territorial seas when making a case-specific analysis of
whether these waters have a significant nexus to traditional navigable
waters, interstate waters, or territorial seas.
    The final rule also provides that waters within the 100-year
floodplain of a traditional navigable water, interstate water, or the
territorial seas and waters within 4,000 feet of the high tide line or
the ordinary high water mark of a traditional navigable water,
interstate water, the territorial seas, impoundments, or covered
tributary are subject to case-specific significant nexus
determinations, unless the water is excluded under paragraph (b) of the
rule. The science available today does not establish that waters beyond
those defined as ``adjacent'' should be jurisdictional as a category
under the CWA, but the agencies' experience and expertise indicate that
there are many waters within the 100-year floodplain of a traditional
navigable water, interstate water, or the territorial seas or out to
4,000 feet where the science demonstrates that they have a significant
effect on downstream waters.
    In circumstances where waters within the 100-year floodplain of a
traditional navigable water, interstate water, or the territorial seas
or within 4,000 feet of the high tide line or ordinary high water mark
are subject to a case-specific significant nexus analysis and such
waters may be evaluated as ``similarly situated,'' it must be first
demonstrated that these waters function alike and are sufficiently
close to function together in affecting downstream waters. The
significant nexus analysis must then be conducted based on
consideration of the functions provided by those waters in combination
in the point of entry watershed. A ``similarly situated'' analysis is
conducted where it is determined that there is a likelihood that there
are waters that function together to affect downstream water integrity.
To provide greater clarity and transparency in determining what
functions will be considered in determining what constitutes a
significant nexus, the final rule lists specific functions that the
agencies will consider.
    In establishing both the 100-year floodplain and the 4,000 foot
bright line boundaries for these case-specific significant nexus
determinations in the rule, the agencies are carefully applying the
available science. Consistent with the CWA, the agencies will work with
the states in connection with the prevention, reduction and elimination
of pollution from state waters. The agencies will work with states to
more closely evaluate state-specific circumstances that may be present
within their borders and, as appropriate, encourage states to develop
rules that reflect their circumstances and emerging science to ensure
consistent and effective protection for waters in the states. As is the
case today, nothing in this rule restricts the ability of states to
more broadly protect state waters.

Exclusions

    All existing exclusions from the definition of ``waters of the
United States'' are retained, and several exclusions reflecting
longstanding agency practice are added to the regulation for the first
time.
    Prior converted cropland and waste treatment systems have been
excluded from the definition of ``waters of the United States''
definition since 1992 and 1979 respectively, and continue to be
excluded. Ministerial changes are made for purposes of clarity, but
these two exclusions remain substantively and operationally unchanged.
The agencies add exclusions for waters and features previously
identified as generally exempt (e.g., exclusion for certain ditches
that are not located in or drain wetlands) in preamble language from
Federal Register documents by the Corps on November 13, 1986, and by
EPA on June 6, 1988. This is the first time these exclusions have been
established by rule. The agencies for the first time also establish by
rule that certain ditches are excluded from jurisdiction, including
ditches with ephemeral flow that are not a relocated tributary or
excavated in a tributary, and ditches with intermittent flow that are
not a relocated tributary, or excavated in a tributary, or drain
wetlands. The agencies add exclusions for groundwater and erosional
features, as well as exclusions for some waters that were identified in
public comments as possibly being found jurisdictional under proposed
rule language where this was never the agencies' intent, such as
stormwater control features constructed to convey, treat, or store
stormwater, and cooling ponds that are created in dry land. These
exclusions reflect the agencies' current practice, and their inclusion
in the rule as specifically excluded furthers the agencies' goal of
providing greater clarity over what waters are and are not protected
under the CWA.

Role of States and Tribes Under the Clean Water Act

    States and tribes play a vital role in the implementation and
enforcement of the CWA. Section 101(b) of the CWA states that it is
Congressional policy to preserve the primary responsibilities and
rights of states to prevent, reduce, and eliminate pollution, to plan
the development and use of land and water resources, and to consult
with the Administrator with respect to the exercise of the
Administrator's authority under the CWA.
    Of particular importance, states and tribes may be authorized by
the EPA to administer the permitting programs of CWA sections 402 and
404. Forty-six states and the U.S. Virgin Islands are authorized to
administer the NPDES program under section 402, while two states
administer the section 404 program. The CWA identifies the waters over
which states may assume section 404 permitting jurisdiction. See CWA
section 404(g)(1). The scope of waters

that are subject to state and tribal permitting is a separate inquiry
and must be based on the statutory language in CWA section 404. States
administer approved CWA section 404 programs for ``waters of the United
States'' within the state, except those waters remaining under Corps
jurisdiction pursuant to CWA section 404(g)(1) as identified in a
Memorandum of Agreement between the state and the Corps. 40 CFR 233.14;
40 CFR 233.70(c)(2); 40 CFR 233.71(d)(2). EPA has initiated a separate
process to address how the EPA can best clarify assumable waters for
dredged and fill material permit programs pursuant to the Clean Water
Act section 404(g)(1). 80 FR 13539 (Mar. 16, 2015). Additional CWA
programs that utilize the definition of ``waters of the United States''
and are of importance to the states and tribes include the section 311
oil spill prevention and response program, the water quality standards
and total maximum daily load (TMDL) programs under section 303, and the
section 401 state water quality certification process.
    States and federally-recognized tribes, consistent with the CWA,
retain full authority to implement their own programs to more broadly
and more fully protect the waters in their jurisdiction. Under section
510 of the CWA, unless expressly stated, nothing in the CWA precludes
or denies the right of any state to establish more protective standards
or limits than the Federal CWA. Congress has also provided roles for
eligible Indian tribes to administer CWA programs over their
reservations and expressed a preference for tribal regulation of
surface water quality on Indian reservations to ensure compliance with
the goals of the CWA. See 33 U.S.C. 1377; 56 FR 64876, 64878-79 (Dec.
12, 1991)). Tribes also have inherent sovereign authority to establish
more protective standards or limits than the Federal CWA. Where
appropriate, references to states in this document may also include
eligible tribes. Many states and tribes, for example, regulate
groundwater, and some others protect wetlands that are vital to their
environment and economy but outside the jurisdiction of the CWA.
Nothing in this rule limits or impedes any existing or future state or
tribal efforts to further protect their waters. In fact, providing
greater clarity regarding what waters are subject to CWA jurisdiction
will reduce the need for permitting authorities, including the states
and tribes with authorized section 402 and 404 CWA permitting programs,
to make jurisdictional determinations on a case-specific basis.

Overview of the Preamble

    The remainder of this preamble is organized as follows. Section III
(Significant Nexus Standard) provides additional background on the
rule, including a discussion of Supreme Court precedent, the science
underpinning the rule, and the agencies' overall interpretive approach
to applying the significant nexus standard. Section IV (Definition of
Waters of the United States) explains the provisions of the final rule,
including subsections on each of the major elements of the rule.
Section V summarizes the economic analysis of the rule and Section VI
addresses Related Acts of Congress, Executive Orders and Agency
Initiatives.

III. Significant Nexus Standard

    With this rule, the agencies interpret the scope of the ``waters of
the United States'' for the CWA in light of the goals, objectives, and
policies of the statute, the Supreme Court case law, the relevant and
available science, and the agencies' technical expertise and
experience. The key to the agencies' interpretation of the CWA is the
significant nexus standard, as established and refined in Supreme Court
opinions: Waters are ``waters of the United States'' if they, either
alone or in combination with similarly situated waters in the region,
significantly affect the chemical, physical, or biological integrity of
traditional navigable waters, interstate waters, or the territorial
seas. The agencies interpret specific aspects of the significant nexus
standard in light of the science, the law, and the agencies' technical
expertise: The scope of the region in which to evaluate waters when
making a significant nexus determination; the waters to evaluate in
combination with each other; and the functions provided by waters and
strength of those functions, and when such waters significantly affect
the chemical, physical, or biological integrity of the downstream
traditional navigable waters, interstate waters, or the territorial
seas.
    In the rule, the agencies determine that tributaries, as defined
(``covered tributaries''), and ``adjacent waters'', as defined
(``covered adjacent waters''), have a significant nexus to downstream
traditional navigable waters, interstate waters, and the territorial
seas and therefore are ``waters of the United States.'' In the rule,
the agencies also establish that defined sets of additional waters may
be determined to have a significant nexus on a case-specific basis: (1)
Five specific types of waters that the agencies conclude are
``similarly situated'' and therefore must be analyzed ``in
combination'' in the watershed that drains to the nearest traditional
navigable water, interstate water, or the territorial seas when making
a case-specific significant nexus analysis; and (2) waters within the
100-year floodplain of a traditional navigable water, interstate water,
or the territorial seas, or waters within 4,000 feet of the high tide
line or ordinary high water mark of traditional navigable waters,
interstate waters, the territorial seas, impoundments or covered
tributaries. The rule establishes a definition of significant nexus,
based on Supreme Court opinions and the science, to use when making
these case-specific determinations.
    Significant nexus is not a purely scientific determination. The
opinions of the Supreme Court have noted that as the agencies charged
with interpreting the statute, EPA and the Corps must develop the outer
bounds of the scope of the CWA, while science does not provide bright
line boundaries with respect to where ``water ends'' for purposes of
the CWA. Therefore, the agencies' interpretation of the CWA is informed
by the Science Report and the review and comments of the SAB, but not
dictated by them. With this context, this section addresses, first, the
Supreme Court case law and the significant nexus standard, second, the
relevant scientific conclusions reached by analysis of existing
scientific literature, and third, the agencies' significant nexus
determinations underpinning the rule. Section IV of the preamble
addresses in more detail the precise definitions of the covered waters
promulgated by the agencies to provide the bright line boundaries
identifying ``waters of the United States.''

A. The Significant Nexus Standard

    Congress enacted the CWA ``to restore and maintain the chemical,
physical, and biological integrity of the Nation's waters.'' Section
101(a). The agencies' longstanding regulations define ``waters of the
United States'' for purposes of the Clean Water Act, and the Supreme
Court has addressed the scope of ``waters of the United States''
protected by the CWA in three cases. The significant nexus standard
evolved through those cases.
    In United States v. Riverside Bayview Homes, 474 U.S. 121 (1985)
(Riverside), which involved wetlands adjacent to a traditional
navigable water in Michigan, the Court, in a unanimous opinion,
deferred to the Corps' ecological judgment that adjacent wetlands are
``inseparably bound up'' with the waters

to which they are adjacent, and upheld the inclusion of adjacent
wetlands in the regulatory definition of ``waters of the United
States.'' Id. at 134. The Court observed that the broad objective of
the CWA to restore and maintain the integrity of the Nation's waters
``incorporated a broad, systemic view of the goal of maintaining and
improving water quality . . .. Protection of aquatic ecosystems,
Congress recognized, demanded broad federal authority to control
pollution, for `[w]ater moves in hydrologic cycles and it is essential
that discharge of pollutants be controlled at the source.' In keeping
with these views, Congress chose to define the waters covered by the
Act broadly.'' Id. at 132-33 (citing Senate Report No. 92-414). The
Court also recognized that ``[i]n determining the limits of its power
to regulate discharges under the Act, the Corps must necessarily choose
some point at which water ends and land begins. Our common experience
tells us that this is often no easy task: The transition from water to
solid ground is not necessarily or even typically an abrupt one.
Rather, between open waters and dry land may lie shallows, marshes,
mudflats, swamps, bogs--in short, a huge array of areas that are not
wholly aquatic but nevertheless fall far short of being dry land. Where
on this continuum to find the limit of `waters' is far from obvious.''
Id. The Court then deferred to the agencies' interpretation: ``In view
of the breadth of federal regulatory authority contemplated by the Act
itself and the inherent difficulties of defining precise bounds to
regulable waters, the Corps' ecological judgment about the relationship
between waters and their adjacent wetlands provides an adequate basis
for a legal judgment that adjacent wetlands may be defined as waters
under the Act.'' Id. at 134.
    The issue of CWA jurisdiction over ``waters of the United States''
was addressed again by the Supreme Court in Solid Waste Agency of
Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159
(2001) (SWANCC). In SWANCC, the Court (in a 5-4 opinion) held that the
use of ``isolated'' non-navigable intrastate ponds by migratory birds
was not by itself a sufficient basis for the exercise of federal
regulatory authority under the CWA. The SWANCC Court noted that in
Riverside it had ``found that Congress' concern for the protection of
water quality and aquatic ecosystems indicated its intent to regulate
wetlands `inseparably bound up' with the `waters' of the United
States'' and that ``[i]t was the significant nexus between the wetlands
and `navigable waters' that informed our reading of the CWA'' in that
case. Id. at 167. SWANCC did not invalidate any parts of the regulatory
definition of ``waters of the United States.''
    Five years after SWANCC, the Court again addressed the term
``waters of the United States'' in Rapanos v. United States, 547 U.S.
715 (2006) (Rapanos). Rapanos involved two consolidated cases in which
the CWA had been applied to wetlands adjacent to non-navigable
tributaries of traditional navigable waters. All Members of the Court
agreed that the term ``waters of the United States'' encompasses some
waters that are not navigable in the traditional sense. A four-Justice
plurality in Rapanos interpreted the term ``waters of the United
States'' as covering ``relatively permanent, standing or continuously
flowing bodies of water . . .,'' id. at 739, that are connected to
traditional navigable waters, id. at 742, as well as wetlands with a
``continuous surface connection . . .'' to such water bodies, id.
(Scalia, J., plurality opinion). The Rapanos plurality noted that its
reference to ``relatively permanent'' waters did ``not necessarily
exclude streams, rivers, or lakes that might dry up in extraordinary
circumstances, such as drought,'' or ``seasonal rivers, which contain
continuous flow during some months of the year but no flow during dry
months. . . .'' Id. at 732 n.5 (emphasis in original).
    Justice Kennedy concurred that the cases should be remanded for
further decision making, and stated that ``to constitute `navigable
waters' under the Act, a water or wetland must possess a `significant
nexus' to waters that are or were navigable in fact or that could
reasonably be so made.'' Id. at 759 (citing SWANCC, 531 U.S. at 167,
172). Justice Kennedy concluded that ``The required nexus must be
assessed in terms of the statute's goals and purposes. Congress enacted
the law to `restore and maintain the chemical, physical, and biological
integrity of the Nation's waters,' 33 U.S.C. 1251(a), and it pursued
that objective by restricting dumping and filling in `navigable
waters,' Sec. Sec.  1311(a), 1362(12).'' Id. at 779. He concluded that
wetlands possess the requisite significant nexus if the wetlands
``either alone or in combination with similarly situated [wet]lands in
the region, significantly affect the chemical, physical, and biological
integrity of other covered waters more readily understood as
`navigable.' '' 547 U.S. at 780. Justice Kennedy's opinion notes that
such a relationship with navigable waters must be more than
``speculative or insubstantial.'' Id. at 780.
    While Justice Kennedy's opinion focused on adjacent wetlands in
light of the facts of the cases before him, his opinion is clear that a
significant nexus is the basis for jurisdiction to protect non-
navigable waters and wetlands under the CWA (id. at 759), and there is
no indication in his opinion that the analytical framework his opinion
provides for determining significant nexus for adjacent wetlands is
limited to adjacent wetlands. In addition, the four dissenting Justices
in Rapanos, who would have affirmed the court of appeals' application
of the agencies' regulation, also concluded that the term ``waters of
the United States'' encompasses, inter alia, all tributaries and
wetlands that satisfy ``either the plurality's [standard] or Justice
Kennedy's.'' Id. at 810 & n.14 (Stevens, J., dissenting). Neither the
plurality nor the Kennedy opinion invalidated any of the current
regulatory provisions defining ``waters of the United States.''
    Chief Justice Roberts' concurrence in Rapanos emphasized that
``[a]gencies delegated rulemaking authority under a statute such as the
Clean Water Act are afforded generous leeway by the courts in
interpreting the statute they are entrusted to administer.'' Id. at
758. Chief Justice Roberts made clear that, if the agencies had
undertaken such a rulemaking, ``the Corps and the EPA would have
enjoyed plenty of room to operate in developing some notion of an outer
bound to the reach of their authority.'' Id. (Emphasis in original.)
    The agencies utilize the significant nexus standard, as articulated
by Justice Kennedy's opinion and informed by the unanimous opinion in
Riverside Bayview and the plurality opinion in Rapanos which all
recognize that the Act and the agencies must identify the scope of CWA
jurisdiction ``on this continuum to find the limit of `waters,' ''
Riverside Bayview at 132, to interpret the scope of the statutory term
``waters of the United States.'' While a significant nexus
determination is primarily weighted in the scientific evidence and
criteria, the agencies also consider the statutory language, the
statute's goals, objectives and policies, the case law, and the
agencies' technical expertise and experience when interpreting the
terms of the CWA.

B. Science Report

    EPA's Office of Research and Development prepared the Science
Report, a peer-reviewed compilation and analysis of published peer-
reviewed scientific literature summarizing the current scientific
understanding of the

connectivity of and mechanisms by which streams and wetlands, singly or
in combination, affect the chemical, physical, and biological integrity
of downstream waters. The final Science Report is available in the
docket and at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=296414.
    The process for developing the Science Report followed standard
information quality guidelines for EPA. In September 2013, EPA released
a draft of the Science Report for an independent SAB review and invited
submissions of public comments for consideration by the SAB panel. In
October 2014, after several public meetings and hearings, the SAB
completed its peer review of the draft Science Report. The SAB was
highly supportive of the draft Science Report's conclusions regarding
streams, riparian and floodplain wetlands, and open waters, and
recommended strengthening the conclusion regarding non-floodplain
waters to include a more definitive statement that reflects how
numerous functions of such waters sustain the integrity of downstream
waters.\7\ The final peer review report is available on the SAB Web
site, as well as in the docket for this rulemaking. EPA revised the
draft Science Report based on comments from the public and
recommendations from the SAB panel.
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    \7\ U.S. EPA. 2014. SAB review of the draft EPA report
Connectivity of Streams and Wetlands to Downstream Waters: A Review
and Synthesis of the Scientific Evidence. EPA-SAB-15-001, U.S.
Environmental Protection Agency, Washington, DC. (``SAB 2014a.'')
---------------------------------------------------------------------------

    The SAB was established in 1978 by the Environmental Research,
Development, and Demonstration Authorization Act (ERDDAA), to provide
independent scientific and technical advice to the EPA Administrator on
the technical basis for Agency positions and regulations. Advisory
functions include peer review of EPA's technical documents, such as the
Science Report. At the time the peer review was completed, the
chartered SAB was comprised of more than 50 members from a variety of
sectors including academia, non-profit organizations, foundations,
state governments, consulting firms, and industry. To conduct the peer
review, EPA's SAB staff formed an ad hoc panel based on nominations
from the public to serve as the primary reviewers. The panel consisted
of 27 technical experts in an array of relevant fields, including
hydrology, wetland and stream ecology, biology, geomorphology,
biogeochemistry, and freshwater science. Similar to the chartered SAB,
the panel members represented sectors including academia, a federal
government agency, non-profit organizations, and consulting firms. The
chair of the panel was a member of the chartered SAB.
    The SAB process is open and transparent, consistent with the
Federal Advisory Committee Act, 5 U.S.C., App 2, and agency policies
regarding Federal advisory committees. Consequently, the SAB has an
approved charter, which must be renewed biennially, announces its
meetings in the Federal Register, and provides opportunities for public
comment on issues before the Board. The SAB staff announced via the
Federal Register that they sought public nominations of technical
experts to serve on the expert panel: SAB Panel for the Review of the
EPA Water Body Connectivity Report (via a similar process the public
also is invited to nominate chartered SAB members). 78 FR 15012 (Mar.
8, 2013). The SAB staff then invited the public to comment on the list
of candidates for the panel. Once the panel was selected, the SAB staff
posted a memo on its Web site addressing the formation of the panel and
the set of determinations that were necessary for its formation (e.g.,
no conflicts of interest). In the public notice of the first public
meetings interested members of the public were invited to submit
relevant comments for the SAB Panel to consider pertaining to the
review materials, including the charge to the Panel. Over 133,000
public comments were received by the Docket. Every meeting was open to
the public, noticed in the Federal Register, and had time allotted for
the public to present their views. In total, the Panel held a two-day
in-person meeting in Washington, DC, in December 2013, and three four-
hour public teleconferences in April, May, and June 2014. The SAB Panel
also compiled four draft versions of its peer review report to inform
and assist the meeting deliberations that were posted on the SAB Web
site. In September 2014, the chartered SAB conducted a public
teleconference to conduct the quality review of the Panel's final draft
peer review report. The peer review report was approved at that
meeting, and revisions were made to reflect the chartered SAB's review.
The culmination of that public process was the release of the final
peer review report in October 2014. All meeting minutes and draft
reports are available on the SAB Web site for public access.
    The final Science Report states that connectivity is a foundational
concept in hydrology and freshwater ecology. Connectivity is the degree
to which components of a system are joined, or connected, by various
transport mechanisms and is determined by the characteristics of both
the physical landscape and the biota of the specific system.
Connectivity for purposes of interpreting the scope of ``waters of the
United States'' under the CWA serves to demonstrate the ``nexus''
between upstream water bodies and the downstream traditional navigable
water, interstate water, or the territorial sea. The scientific
literature does not use the term ``significant'' as it is defined in a
legal context, but it does provide information on the strength of the
effects on the chemical, physical, and biological functioning of the
downstream water bodies from the connections among covered tributaries,
covered adjacent waters, and case-specific waters and those downstream
waters. The scientific literature also does not use the terms
traditional navigable waters, interstate waters, or the territorial
seas. However, evidence of strong chemical, physical, and biological
connections to larger rivers, estuaries, and lakes applies to that
subset of rivers, estuaries, and lakes that are traditional navigable
waters, interstate waters, or the territorial seas.
    The Science Report presents evidence of those connections from
various categories of waters, evaluated singly or in combination, which
affect downstream waters and the strength of that effect. The
objectives of the Science Report are (1) to provide a context for
considering the evidence of connections between downstream waters and
their tributary waters, and (2) to summarize current understanding
about these connections, the factors that influence them, and the
mechanisms by which the connections affect the function or condition of
downstream waters. The connections and mechanisms discussed in the
Science Report include transport of physical materials and chemicals
such as water, wood, sediment, nutrients, pesticides, and mercury;
functions that covered adjacent waters perform, such as storing and
cleansing water; movement of organisms or their seeds and eggs; and
hydrologic and biogeochemical interactions occurring in and among
surface and groundwater flows, including hyporheic zones \8\ and
alluvial aquifers.
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    \8\ The hyporheic zone is the subsurface area immediately below
the bed of intermittent and ephemeral streams that remains wet even
when there is no surface flow. These areas are extremely important
to macro-benthic organisms critical to the bio-chemical integrity of
streams.
---------------------------------------------------------------------------

    The Science Report presents five major conclusions:

Conclusion 1: Streams
    The scientific literature unequivocally demonstrates that streams,
individually or cumulatively, exert a strong influence on the chemical,
physical, and biological integrity of downstream waters. All tributary
streams, including perennial, intermittent, and ephemeral streams, are
chemically, physically, and biologically connected to downstream rivers
via channels and associated alluvial deposits where water and other
materials are concentrated, mixed, transformed, and transported.
Streams are the dominant source of water in most rivers, and the
majority of tributaries are perennial, intermittent, or ephemeral
headwater streams. Headwater streams also convey water into local
storage compartments such as ponds, shallow aquifers, and floodplains,
and into regional and alluvial aquifers; these local storage
compartments are important sources of water for maintaining baseflow in
rivers. In addition to water, streams transport sediment, wood, organic
matter, nutrients, chemical contaminants, and many of the organisms
found in rivers. The scientific literature provides robust evidence
that streams are biologically connected to downstream waters by the
dispersal and migration of aquatic and semiaquatic organisms, including
fish, amphibians, plants, microorganisms, and invertebrates, that use
both upstream and downstream habitats during one or more stages of
their life cycles, or provide food resources to downstream communities.
In addition to material transport and biological connectivity,
ephemeral, intermittent, and perennial flows influence fundamental
biogeochemical processes by connecting channels and shallow groundwater
with other landscape elements. Chemical, physical, and biological
connections between streams and downstream waters interact via
integrative processes such as nutrient spiraling. This occurs when
stream communities assimilate and chemically transform large quantities
of nitrogen and other nutrients that otherwise would be transported
directly downstream, thereby increasing nutrient loads and associated
impairments due to excess nutrients in downstream waters. Science
Report at ES-2.
Conclusion 2: Riparian/Floodplain Wetlands and Open Waters
    The scientific literature clearly shows that wetlands and open
waters in riparian areas and floodplains are chemically, physically,
and biologically integrated with rivers via functions that improve
downstream water quality, including the temporary storage and
deposition of channel-forming sediment and woody debris, temporary
storage of local groundwater that supports baseflow in rivers, and
transformation and transport of stored organic matter. Riparian/
floodplain wetlands and open waters improve water quality through the
assimilation, transformation, and sequestration of pollutants,
including excess nutrients and chemical contaminants such as pesticides
and metals that can degrade downstream water integrity. In addition to
providing effective buffers to protect downstream waters from point
source and nonpoint source pollution, these systems form integral
components of river food webs, providing nursery habitat for breeding
fish and amphibians, colonization opportunities for stream
invertebrates, and maturation habitat for stream insects. Lateral
expansion and contraction of the river in its floodplain result in an
exchange of organic matter and organisms, including fish populations
that are adapted to use floodplain habitats for feeding and spawning
during high water, that are critical to river ecosystem function.
Riparian/floodplain wetlands and open waters also affect the integrity
of downstream waters by subsequently releasing (desynchronizing)
floodwaters and retaining large volumes of stormwater, sediment, and
contaminants in runoff that could otherwise negatively affect the
condition or function of downstream waters. Science Report at ES-2 to
ES-3.
Conclusion 3: Non-Floodplain Wetlands and Open Waters
    Wetlands and open waters in non-floodplain landscape settings
(``non-floodplain wetlands'') provide numerous functions that benefit
downstream water integrity. These functions include storage of
floodwater; recharge of groundwater that sustains river baseflow;
retention and transformation of nutrients, metals, and pesticides;
export of organisms or seeds to downstream waters; and habitats needed
for stream species. This diverse group of wetlands (e.g., many Prairie
potholes or vernal pools) can be connected to downstream waters through
surface water, shallow subsurface water, and groundwater flows, and
through biological and chemical connections.
    In general, connectivity of non-floodplain wetlands occurs along a
gradient, and can be described in terms of the frequency, duration,
magnitude, timing, and rate of change of water, material, and biotic
fluxes to downstream waters. These descriptors are influenced by
climate, geology, and terrain, which interact with factors such as the
magnitudes of the various functions within wetlands (e.g., amount of
water storage or carbon export) and their proximity to downstream
waters to determine where wetlands occur along the connectivity
gradient. At one end of this gradient, the functions of non-floodplain
wetlands clearly affect the condition of downstream waters if a visible
(e.g., channelized) surface water or a regular shallow subsurface-water
connection to the river network is present. For non-floodplain wetlands
lacking a channelized surface or regular shallow subsurface connection
(i.e., those at intermediate points along the gradient of
connectivity), generalizations about their specific effects on
downstream waters from the available literature are difficult because
information on both function and connectivity is needed. Science Report
at ES-3.
Conclusion 4: Degrees and Determinants of Connectivity
    Connectivity of streams and wetlands to downstream waters occurs
along a gradient that can be described in terms of the frequency,
duration, magnitude, timing, and rate of change of water, material, and
biotic fluxes to downstream waters. These terms, which we refer to
collectively as connectivity descriptors, characterize the range over
which streams and wetlands vary and shift along the connectivity
gradient in response to changes in natural and anthropogenic factors
and, when considered in a watershed context, can be used to predict
probable effects of different degrees of connectivity over time. The
evidence unequivocally demonstrates that the stream channels and
riparian/floodplain wetlands or open waters that together form river
networks are clearly connected to downstream waters in ways that
profoundly influence downstream water integrity. The connectivity and
effects of non-floodplain wetlands and open waters are more variable
and thus more difficult to address solely from evidence available in
peer-reviewed studies. Science Report at ES-3 to ES-4.
Conclusion 5: Cumulative Effects
    The incremental effects of individual streams and wetlands are
cumulative across entire watersheds, and therefore, must be evaluated
in context with other streams and wetlands. Downstream waters are the
time-integrated result of all waters contributing to them. For example,
the amount of water or biomass contributed by a specific

ephemeral stream in a given year might be small, but the aggregate
contribution of that stream over multiple years, or by all ephemeral
streams draining that watershed in a given year or over multiple years,
can have substantial consequences on the integrity of the downstream
waters. Similarly, the downstream effect of a single event, such as
pollutant discharge into a single stream or wetland, might be
negligible but the cumulative effect of multiple discharges could
degrade the integrity of downstream waters.
    When considering the effect of an individual stream or wetland, all
contributions and functions of that stream or wetland should be
evaluated cumulatively. For example, the same stream transports water,
removes excess nutrients, transports pollutants, mitigates flooding,
and provides refuge for fish when conditions downstream are
unfavorable; if any of these functions is ignored, the overall effect
of that stream would be underestimated. Science Report at ES-5 to ES-6.
SAB Review of the Proposed Rule
    In addition to its peer review of the draft Science Report, in a
separate effort the SAB also reviewed the adequacy of the scientific
and technical basis of the proposed rule and provided its advice and
comments on the proposal in September 2014.\9\ The same SAB Panel that
reviewed the draft Science Report met via two public teleconferences in
August 2014 to discuss the scientific and technical basis of the
proposed rule. The Panel submitted comments to the Chair of the
chartered SAB. A work group of chartered SAB members considered
comments provided by panel members, agency representatives, and the
public on the adequacy of the science informing the rule. This work
group then led the September 2014 public teleconference discussion of
the chartered SAB. The public had an opportunity to submit oral or
written comments during these two public meetings. The SAB's final
letter to the EPA Administrator can be found on the SAB Web site and in
the docket for this rule.
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    \9\ U.S. EPA. 2014. SAB Consideration of the Adequacy of the
Scientific and Technical Basis of the EPA's Proposed Rule titled
``Definition of Waters of the United States under the Clean Water
Act.'' EPA-SAB-14-007, U.S. Environmental Protection Agency,
Washington, DC. (``SAB 2014b.'')
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    The SAB found that the available science provides an adequate
scientific basis for the key components of the proposed rule. The SAB
noted that although water bodies differ in degree of connectivity that
affects the extent of influence they exert on downstream waters (i.e.,
they exist on a ``connectivity gradient''), the available science
supports the conclusion that the types of water bodies identified as
``waters of the United States'' in the proposed rule exert strong
influence on the chemical, physical, and biological integrity of
downstream waters. In particular, the SAB expressed support for the
proposed rule's inclusion of tributaries and ``adjacent waters'' as
categorical waters of the United States and the inclusion of ``other
waters'' on a case-specific basis, though noting that certain ``other
waters'' can be determined as a subcategory to be similarly situated.
    Regarding tributaries, the SAB found, ``[t]here is strong
scientific evidence to support the EPA's proposal to include all
tributaries within the jurisdiction of the Clean Water Act.
Tributaries, as a group, exert strong influence on the physical,
chemical, and biological integrity of downstream waters, even though
the degree of connectivity is a function of variation in the frequency,
duration, magnitude, predictability, and consequences of physical,
chemical, and biological processes.'' The Board advised EPA to
reconsider the definition of tributaries because not all tributaries
have ordinary high water marks (e.g., ephemeral streams with arid and
semi-arid environments or in low gradient landscapes where the flow of
water is unlikely to cause an ordinary high water mark). The SAB also
advised EPA to consider changing the wording in the definition to
``bed, bank, and other evidence of flow.'' SAB 2014b at 2. The agencies
did not make this change because this recommendation seemed to suggest
that any hydrologic connection is sufficient for CWA jurisdiction. The
definition of ``tributary'' in the rule better identifies tributaries
that have a significant nexus to downstream traditional navigable
waters, interstate waters, or the territorial seas. In addition, the
SAB suggested that EPA reconsider whether flow-through lentic systems
should be included as ``adjacent waters'' and wetlands, rather than as
tributaries.
    Regarding ``adjacent waters'' and wetlands, the SAB stated, ``[t]he
available science supports the EPA's proposal to include ``adjacent
waters'' and wetlands as a waters of the United States. . . . because
[they] have a strong influence on the physical, chemical, and
biological integrity of navigable waters.'' Id. In particular, the SAB
noted, ``the available science supports defining adjacency or
determination of adjacency on the basis of functional relationships,''
rather than ``solely on the basis of geographical proximity or distance
to jurisdictional waters.'' Id. at 2-3. The agencies have determined
which waters are adjacent, and thus jurisdictional under the rule,
based on both functional relationships and proximity because those
factors identify the waters that have a strong influence on the
chemical, physical, or biological integrity of traditional navigable
waters, interstate waters, or the territorial seas. Section C. and IV.F
below. The agencies' determination is informed by the science, and
consideration of proximity is reasonable in interpreting the scope of
adjacency.
    In the evaluation of ``other waters,'' the SAB found that
``scientific literature has established that `other waters' can
influence downstream waters, particularly when considered in
aggregate.'' Id. at 3. The SAB thus found it ``appropriate to define
`other waters' as waters of the United States on a case-by-case basis,
either alone or in combination with similarly situated waters in the
same region.'' Id. The SAB found that distance could not be the sole
indicator used to evaluate the connection of ``other waters'' to
jurisdictional waters. The agencies' identification of the areas within
which a water is assessed on a case-specific basis for a significant
nexus is informed by the science and the agencies' experience and
technical expertise, and consideration of proximity is reasonable in
interpreting the scope of the statute. The SAB also expressed support
for language in one of the options discussed in the preamble to the
proposed rule. Specifically, the SAB stated there is ``also adequate
scientific evidence to support a determination that certain
subcategories and types of `other waters' in particular regions of the
United States (e.g., Carolina and Delmarva Bays, Texas coastal prairie
wetlands, prairie potholes, pocosins, western vernal pools) are
similarly situated (i.e., they have a similar influence on the
chemical, physical, and biological integrity of downstream waters and
are similarly situated on the landscape) and thus could be considered
waters of the United States.'' Id. The Board noted that other sets of
wetlands could be identified as ``similarly situated'' as the science
continues to develop and that science does not support excluding groups
of ``other waters'' or subcategories thereof from jurisdiction.
    The exclusions paragraph of the proposed rule generated the most
comments from the SAB. The SAB noted, ``[t]he Clean Water Act
exclusions of groundwater and certain other exclusions listed in the
proposed rule and the current regulation do not

have scientific justification.'' Id. With regard to ditches, the Board
found that there is a lack of scientific knowledge to determine whether
ditches should be categorically excluded. For example, some ditches
that would be excluded in the Midwest may drain Cowardin wetlands and
may provide certain ecosystem services, while gullies, rills, and non-
wetland swales can be important conduits for moving water between
jurisdictional waters. The SAB also noted that artificial lakes or
ponds, or reflection pools, can be directly connected to jurisdictional
waters via either shallow or deep groundwater. The SAB also recommended
that the agencies clarify in the preamble to the final rule that
``significant nexus'' is a legal term, not a scientific one.

C. Significant Nexus Conclusions

    As noted earlier, the agencies interpret the scope of ``waters of
the United States'' protected under the CWA based on the information
and conclusions in the Science Report, other relevant scientific
literature, the Technical Support Document that provides additional
legal and scientific discussion for issues raised in this rule, the
relevant Supreme Court decisions, the agencies' technical expertise and
experience, and the objectives and requirements of the CWA. In light of
this information, the agencies made scientifically and technically
informed judgments about the nexus between the relevant waters and the
significance of that nexus and conclude that ``tributaries'' and
``adjacent waters,'' each as defined by the rule, have a significant
nexus such that they are ``waters of the United States'' and no
additional analysis is required. The agencies also determined that
additional waters may, on a case-specific basis, have a significant
nexus to traditional navigable waters, interstate waters, and the
territorial seas, either alone or in combination with similarly
situated waters. The agencies' interpretation of the scope of ``waters
of the United States'' is informed by the Science Report and the review
and comments of the SAB. The rule reflects the judgment of the agencies
in balancing the science, the agencies' expertise, and the regulatory
goals of providing clarity to the public while protecting the
environment and public health, consistent with the law.
    Since the Rapanos decision, the agencies have gained extensive
experience making significant nexus determinations, and that experience
and expertise has informed the judgment of the agencies as reflected in
the provisions of the rule. The agencies, most often the Corps, have
made more than 400,000 CWA jurisdictional determinations since 2008. Of
those, more than 120,000 are case-specific significant nexus
determinations. The agencies made determinations in every state in the
country, from the arid West to the tropics of Hawaii, from the
Appalachian Mountains in the East to the lush forests of the Northwest.
With field staff located in 38 Corps District offices and 10 EPA
regional offices, the agencies have almost a decade of nationwide
experience in making significant nexus determinations. These individual
jurisdictional determinations have been made for waters ranging from an
intermittent stream that provides flow to a drinking water source, to a
group of floodplain wetlands in North Dakota that provide important
protection from floodwaters to downstream communities alongside the Red
River, to headwater mountain streams that provide high quality water
that supplies baseflow and reduces the harmful concentrations of
pollutants in the main part of the river below. Through this
experience, the agencies developed wide-ranging technical expertise in
assessing the hydrologic flowpaths along which water and materials are
transported and transformed that determine the degree of chemical,
physical, or biological connectivity, as well as the variations in
climate, geology, and terrain within and among watersheds and over time
that affect the functions (such as the removal or transformation of
pollutants) performed by streams and wetlands for downstream
traditional navigable waters, interstate waters or the territorial
seas.
    The agencies utilize many tools and many sources of information to
help make jurisdictional determinations, including U.S. Geological
Survey (USGS) and state and local topographic maps, aerial photography,
soil surveys, watershed studies, scientific literature and references,
and field work. For example, USGS and state and local stream maps and
datasets, aerial photography, gage data, watershed assessments,
monitoring data, and field observations are often used to help assess
the contributions of flow of tributary streams, including intermittent
and ephemeral streams, to downstream traditional navigable waters,
interstate waters or the territorial seas. Similarly, floodplain and
topographic maps of federal, state and local agencies, modeling tools,
and field observations can be used to assess how wetlands are trapping
floodwaters that might otherwise affect downstream waters. Further, the
agencies utilize the large body of scientific literature regarding the
functions of tributaries, including tributaries with ephemeral,
intermittent and perennial flow and of wetlands and open waters to
inform their evaluations of significant nexus. In addition, the
agencies have experience and expertise for decades prior to and since
the SWANCC and Rapanos decisions with making jurisdictional
determinations, and consider hydrology, ordinary high water mark,
biota, and other technical factors in implementing Clean Water Act
programs. This immersion in the science along with the practical
expertise developed through case-specific determinations across the
country and in diverse settings is reflected in the agencies'
conclusions with respect to waters that have a significant nexus, as
well as where the agencies have drawn boundaries demarking where
``waters of the United States'' end.
1. Scope of Significant Nexus Analysis
    Under the significant nexus standard, waters possess the requisite
significant nexus if they ``either alone or in combination with
similarly situated [wet]lands in the region, significantly affect the
chemical, physical, and biological integrity of other covered waters
more readily understood as `navigable.' '' Rapanos at 780. Several
terms in this standard were not defined. In this rule the agencies
interpret these terms and the scope of ``waters of the United States''
based on the goals, objectives, and policies of the statute, the
scientific literature, the Supreme Court opinions, and the agencies'
technical expertise and experience. Therefore, for purposes of a
significant nexus analysis, the agencies have determined (1) which
waters are ``similarly situated,'' and thus should be analyzed in
combination, in (2) the ``region,'' for purposes of a significant nexus
analysis, and (3) the types of functions that should be analyzed to
determine if waters significantly affect the chemical, physical, or
biological integrity of traditional navigable waters, interstate
waters, or the territorial seas. These determinations underpin many of
the key elements of the rule and are reflected in the definition of
``significant nexus'' in the rule.
a. Similarly Situated Waters
    As reflected in the rule's definition of ``significant nexus,'' the
agencies determined that it is reasonable to consider waters as
``similarly situated'' where they function alike and are sufficiently
close to function together in affecting the nearest traditional

navigable water, interstate water, or the territorial sea. Since the
focus of the significant nexus standard is on protecting and restoring
the chemical, physical, and biological integrity of the nation's
waters, the agencies interpret the phrase ``similarly situated'' in
terms of whether particular waters are providing common, or similar,
functions for downstream waters such that it is reasonable to consider
their effect together. Regarding covered tributaries and covered
adjacent waters, the agencies define each water type such that the
functions provided are similar and the waters are situated so as to
provide those functions together to affect downstream waters.
    The science demonstrates that covered tributaries provide many
common vital functions important to the chemical, physical, and
biological integrity of downstream waters, regardless of the size of
the tributaries. The science also supports the conclusion that
sufficient volume, duration, and frequency of flow are required to
create a bed and banks and ordinary high water mark. The science also
supports the conclusion that tributaries function together to affect
downstream waters. The agencies conclude that covered tributaries with
a bed and banks and ordinary high water mark are similarly situated for
purposes of the agencies' significant nexus analysis.
    For covered adjacent waters, the science demonstrates that these
waters provide many similar vital functions to downstream waters, and
the agencies defined ``adjacent waters'' with distance boundaries to
ensure that the waters are providing similar functions to downstream
waters and that the waters are located comparably in the region such
that the agencies' reasonably judged them to be similarly situated.
    For waters for which a case-specific significant nexus
determination is required the agencies have determined that some waters
in specific regions are similarly situated; for other specified waters,
the determination of whether there are any other waters providing
similar functions in a similar situation in the region must be made as
part of a case-specific determination. See section IV.H.
    Assessing the functions of identified waters in combination is
consistent not only with Justice Kennedy's significant nexus standard,
but with the science. Scientists routinely combine the effects of
groups of waters, aggregating the known effect of one water with those
of ecologically similar waters in a specific geographic area, or to a
certain scale. This is because the chemical, physical, and biological
integrity of downstream waters is directly related to the aggregate
contribution of upstream waters that flow into them, including any
tributaries and connected wetlands. As a result, the scientific
literature and the Science Report consistently document that the health
of larger downstream waters is directly related to the aggregate health
of waters located upstream, including waters such as wetlands that may
not be hydrologically connected but function together to ameliorate the
potential impacts of flooding and pollutant contamination from
affecting downstream waters. See Technical Support Document.
    For example, excess nutrients discharged into small tributary
streams in the aggregate can cause algal blooms downstream that reduce
dissolved oxygen levels and increase turbidity in traditional navigable
waters, interstate waters, and the territorial seas. Water low in
dissolved oxygen cannot support aquatic life. This widely-recognized
phenomenon, known as hypoxia, has impacted commercial and recreational
fisheries in the northern Gulf of Mexico. In this instance, the
cumulative effects of nutrient export from the many small headwater
streams of the Mississippi River have resulted in large-scale
ecological and economically harmful impacts hundreds of miles
downstream. See Technical Support Document.
    In review of the scientific and technical adequacy of the rule, the
SAB panel members ``generally agreed that aggregating `similarly
situated' waters is scientifically justified, given that the combined
effects of these waters on downstream waters are often only measurable
in aggregate.'' \10\ As stated in section III.B. above, one of the main
conclusions of the Science Report is that the incremental contributions
of individual streams and wetlands are cumulative across entire
watersheds, and their effects on downstream waters should be evaluated
within the context of other streams and wetlands in that watershed. For
example, the Science Report finds, ``[t]he amount of nutrients removed
by any one stream over multiple years or by all headwater streams in a
watershed in a given year can have substantial consequences for
downstream waters.'' Science Report at 1-11. Cumulative effects of
streams, wetlands, and open waters across a watershed must be
considered because ``[t]he downstream consequences (e.g., the amount
and quality of materials that eventually reach a river) are determined
by the aggregate effect of contributions and sequential alterations
that begin at the source waters and function along continuous flowpaths
to the watershed outlet.'' Id. at 1-19.
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    \10\ September 2, 2014. Memorandum from Dr. Amanda Rodewald to
Dr. David Allen. Comments to the chartered SAB on the Adequacy of
the Scientific and Technical Basis of the EPA's Proposed Rule titled
``Definition of `Waters of the United States' under the Clean Water
Act.'' (``SAB 2014c.'')
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    The agencies conclude that it is appropriate to assess the effects
of waters in combination based on the similarity of the functions they
provide to the downstream water and their location in the watershed.
This is consistent with the science and effectively meets the goals of
the CWA.
b. In the Region
    Since Justice Kennedy did not define the ``region,'' the agencies
determined that the single point of entry watershed is a reasonable and
technically appropriate scale for identifying ``in the region'' for
purposes of the significant nexus standard. A single point of entry
watershed is the drainage basin within whose boundaries all
precipitation ultimately flows to the nearest single traditional
navigable water, interstate water, or the territorial sea. The agencies
determined that because the movement of water from watershed drainage
basins to coastal waters, river networks, and lakes shapes the
development and function of these systems in a way that is critical to
their long-term health, the watershed is a reasonable and technically
appropriate way to identify the scope of waters that together may have
an effect on the chemical, physical, or biological integrity of a
particular traditional navigable water, interstate water, or
territorial sea. The watershed includes all streams, wetlands, lakes,
and open waters within its boundaries. Using the watershed that flows
to the nearest single traditional navigable water, interstate water, or
territorial sea is consistent with court decisions that these waters
are the ultimate focus of CWA protections. Using the single point of
entry watershed ensures that any analysis of significant nexus is
appropriately connected to these touchstone waters.
    Because the movement of water from watershed drainage basins to
coastal waters, river networks, and lakes shapes the development and
function of these systems in a way that is critical to their integrity,
using a watershed as the framework for conducting significant nexus
evaluations is scientifically supportable. Watersheds are generally
regarded as the most appropriate spatial unit for water resource
management. Anthropogenic actions and natural events can have
widespread effects within the watershed that collectively

impact the integrity and quality of the relevant traditional navigable
water, interstate water, or the territorial sea. The functions of the
contributing waters are inextricably linked and have a cumulative
effect on the integrity of the downstream traditional navigable water,
interstate water, or the territorial sea. For these reasons, it is more
appropriate to conduct a significant nexus analysis at the watershed
scale than to focus on a specific site, such as an individual stream
segment. See proposal Appendix A, Scientific Analysis, 79 FR 22246,
April 21, 2014, Science Report, and Technical Support Document.
    Concluding that the watershed is the reasonable and appropriate
region for purposes of a significant nexus analysis is also consistent
with the agencies' longstanding practice and experience. To restore or
maintain the health of the downstream affected water, the agencies'
standard practice is to evaluate the condition of the waters that are
in the contributing watersheds and to develop a plan to address the
issues of concern. The Corps has used watershed framework approaches
for water sources, for navigation approaches for more than 100 years,
and in the regulatory program since its inception. Also, using a
watershed framework is consistent with more than two decades of
practice by EPA and many other governmental, academic, and additional
entities that recognize that a watershed approach is the most effective
framework to address water resource challenges. Finally, the watershed
that drains to the nearest (i.e., first downstream) traditional
navigable water, interstate water, or the territorial seas is likely to
be of a size commonly understood as a ``region.''
    In light of the scientific literature, the longstanding approach of
the agencies' implementation of the CWA, and the statutory goals
underpinning Justice Kennedy's significant nexus framework, the
watershed draining to the nearest traditional navigable water,
interstate water, or the territorial sea, is the appropriate ``region''
for a significant nexus analysis. See the proposed rule preamble and
Technical Support Document.
c. Significantly Affect Chemical, Physical, or Biological Integrity
    The agencies' definition of the term ``significant nexus'' in the
rule is consistent with language in Riverside Bayview, SWANCC, and
Rapanos, and with the goals, objectives, and policies of the CWA. The
definition reflects that not all waters have a requisite connection to
traditional navigable waters, interstate waters, or the territorial
seas sufficient to be determined jurisdictional. Justice Kennedy was
clear that to be covered, waters must significantly affect the
chemical, physical, or biological integrity of a downstream navigable
water and that the requisite nexus must be more than ``speculative or
insubstantial,'' Rapanos, at 780. The agencies define significant nexus
in precisely those terms. Under the rule a ``significant nexus'' is
established by a showing of a significant chemical, physical, or
biological effect. In characterizing the significant nexus standard,
Justice Kennedy stated: ``[t]he required nexus must be assessed in
terms of the statute's goals and purposes. Congress enacted the [CWA]
to `restore and maintain the chemical, physical, and biological
integrity of the Nation's waters'. . . .'' 547 U.S. at 779. It is clear
that Congress intended the CWA to ``restore and maintain'' all three
forms of ``integrity,'' Section 101(a), so if any one is compromised
then that is contrary to the statute's stated objective. It would
subvert the objective if the CWA only protected waters upon a showing
that they had effects on every attribute of the integrity of a
traditional navigable water, interstate water, or the territorial sea.
    In the rule's definition of ``significant nexus,'' the agencies
identify the functions that waters provide that can significantly
affect the chemical, physical, or biological integrity of traditional
navigable waters, interstate waters and the territorial seas. In
identifying the functions to be considered the agencies were informed
by the goals of the statute and the available science. Among the means
to achieve the CWA's objective to restore and maintain the chemical,
physical, and biological integrity of the Nation's waters, Congress
established an interim national goal to achieve wherever possible
``water quality which provides for the protection and propagation of
fish, shellfish, and wildlife and provides for recreation in and on the
water.'' Section 101(a)(2). Functions to be considered for the purposes
of determining significant nexus are sediment trapping; nutrient
recycling; pollutant trapping, transformation, filtering, and
transport; retention and attenuation of floodwaters; runoff storage;
contribution of flow; export of organic matter; export of food
resources; and provision of life-cycle dependent aquatic habitat (such
as foraging, feeding, nesting, breeding, spawning, and use as a nursery
area) for species located in traditional navigable waters, interstate
waters, or the territorial seas. The effect of an upstream water can be
significant even when a water, alone or in combination, is providing a
subset, or even just one, of the functions listed.
    Science demonstrates that these aquatic functions provided by
smaller streams, ponds, wetlands and other waters are important for
protecting the chemical, physical, and biological integrity of
downstream traditional navigable waters, interstate waters, and the
territorial seas. For example, States identify sediment and nutrients
as the primary contaminants in the nation's waters. Sediment storage
and export via streams to downstream waters is critical for maintaining
the river network, including the formation of channel features.
Although sediment is essential to river systems, excess sediment can
impair ecological integrity by filling interstitial spaces, reducing
channel capacity, blocking sunlight transmission through the water
column, and increasing contaminant and nutrient concentrations. Streams
and wetlands can prevent excess deposits of sediment downstream and
reduce pollutant concentrations in downstream waters. Thus the function
of trapping of excess sediment, along with export of sediment, have a
significant effect on the chemical, physical, and biological integrity
of downstream waters.
    Nutrient recycling results in the uptake and transformation of
large quantities of nitrogen and other nutrients that otherwise would
be transported directly downstream, thereby decreasing nutrient loads
and associated impairments due to excess nutrients in downstream
waters. Streams, wetlands and open waters improve water quality through
the assimilation, transformation, or sequestration of pollutants,
including excess nutrients and chemical contaminants such as pesticides
and metals that can degrade downstream water integrity. Nutrient
transport exports nutrients downstream and can degrade water quality
and lead to stream impairments. Nutrients are necessary to support
aquatic life, but excess nutrients lead to excessive plant growth and
hypoxia, in which over-enrichment causes dissolved oxygen
concentrations to fall below the level necessary to sustain most
aquatic animal life in the downstream waters. Nutrient recycling,
retention, and export can significantly affect downstream chemical
integrity by impacting downstream water quality.
    The contribution of flow downstream is an important role, as
upstream waters can be a cumulative source of the majority of the total
mean annual flow to bigger downstream rivers and waters, including via
the recharge of baseflow.

Streams, wetlands, and open waters contribute surface and subsurface
water downstream, and are the dominant sources of water in most rivers.
Contribution of flow can significantly affect the physical integrity of
downstream waters, helping to sustain the volume of water in larger
waters.
    Small streams and wetlands are particularly effective at retaining
and attenuating floodwaters. By subsequently releasing
(desynchronizing) floodwaters and retaining large volumes of stormwater
that could otherwise negatively affect the condition or function of
downstream waters, streams and adjacent wetlands and open waters affect
the physical integrity of downstream traditional navigable waters,
interstate waters, or the territorial seas. This function can reduce
flood peaks downstream and can also maintain downstream river baseflows
by recharging alluvial aquifers.
    Streams, wetlands, and open waters supply downstream waters with
dissolved and particulate organic matter (e.g., leaves, wood), which
support biological activity throughout the river network. In addition
to organic matter, streams, wetlands, and open waters can also export
other food resources downstream, such as aquatic insects that are the
food source for fish in downstream waters. The export of organic matter
and food resources downstream is important to maintaining the food webs
and thus the biological integrity of traditional navigable waters,
interstate waters, and the territorial seas.
    Streams, wetlands, and open waters provide life-cycle dependent
aquatic habitat (such as foraging, feeding, nesting, breeding,
spawning, and use as a nursery area) for species located in traditional
navigable waters, interstate waters, or the territorial seas. Many
species require different habitats for different resources (e.g., food,
spawning habitat, overwintering habitat), and thus move throughout the
river network over their life-cycles. For example, headwater streams
can provide refuge habitat under adverse conditions, enabling fish to
persist and recolonize downstream areas once conditions have improved.
These upstream systems form integral components of downstream food
webs, providing nursery habitat for breeding fish and amphibians,
colonization opportunities for stream invertebrates, and maturation
habitat for stream insects, including for species that are critical to
downstream ecosystem function. The provision of life-cycle dependent
aquatic habitat for species located in downstream waters significantly
affects the biological integrity of those downstream waters.
    Tributaries, adjacent wetlands, and open waters can perform
multiple functions, including functions that change depending upon the
season. For example, the same stream can contribute flow when
evapotranspiration is low and can retain water when evapotranspiration
is high. These functions, particularly when considered in aggregate
with the functions of similarly situated waters in the region, can
significantly affect the chemical, physical, or biological integrity of
a traditional navigable water, interstate water, or the territorial
seas. When considering the effect of an individual stream, wetland, or
open water, all contributions and functions that the water provides
should be evaluated cumulatively. For example, the same wetland retains
sediment, removes excess nutrients, mitigates flooding, and provides
habitat for amphibians that also live downstream; if any of these
functions is ignored, the overall effect of that wetland would be
underestimated. It is important to note, however, that a water or
wetland can provide just one function that may significantly affect the
chemical, physical or biological integrity of the downstream water.
2. Categories of Waters Determined to Have a Significant Nexus
    In this rule, the agencies determine that: (1) Covered tributaries,
in combination with other covered tributaries located in a watershed
that drains to a traditional navigable water, interstate water, or the
territorial seas, significantly affect the chemical, physical, and
biological integrity of that water; and (2) covered adjacent waters, in
combination with other covered adjacent waters located in a watershed
that drains to a traditional navigable water, interstate water, or the
territorial seas, significantly affect the chemical, physical, and
biological integrity of that water.
a. Covered Tributaries
    The agencies determine based on their scientific and technical
expertise that waters meeting the definition of ``tributary'' in a
single point of entry watershed are similarly situated and have a
significant nexus because they significantly affect the chemical,
physical, or biological integrity of traditional navigable waters,
interstate waters, and the territorial seas. As such, it is appropriate
to conclude covered tributaries as a category are ``waters of the
United States.'' See Technical Support Document. The agencies limited
the tributaries that are ``waters of the United States'' to those that
have both a bed and banks and another indicator of ordinary high water
mark. That limitation served as a reasonable basis to consider covered
tributaries similarly situated because those physical characteristics
indicated sufficient flow that the covered tributaries are performing
similar functions and located such that they are working together in
the region to provide those functions to the nearest traditional
navigable water, interstate water, or the territorial seas. Justice
Kennedy noted that the requirement of a perceptible ordinary high water
mark for tributaries, a measure that had been used by the Corps, ``may
well provide a reasonable measure of whether specific minor tributaries
bear a sufficient nexus with other regulated waters to constitute
`navigable waters' under the Act.'' 547 U.S. at 781, see also id. at
761. The science supports this.
    The agencies analyzed the Science Report and other scientific
literature to determine whether tributaries to traditional navigable
waters, interstate waters, or the territorial seas have a significant
nexus to constitute ``waters of the United States'' under the Act such
that it is reasonable to assert CWA jurisdiction over all such
tributaries by rule. Covered tributaries have a significant impact on
the chemical, physical, or biological integrity of waters into which
they eventually flow--for CWA purposes, traditional navigable waters,
interstate waters, and the territorial seas. The great majority of
covered tributaries are headwater streams, and whether they are
perennial, intermittent, or ephemeral, they play an important role in
the transport of water, sediments, organic matter, nutrients, and
organisms to downstream waters. Covered tributaries serve to store
water, thereby reducing flooding; provide biogeochemical functions that
help maintain water quality; trap and transport sediments; transport,
store and modify pollutants; provide habitat for plants and animals;
and sustain the biological productivity of downstream rivers, lakes,
and estuaries. Such waters have these significant effects whether they
are natural, modified, or constructed.
    Covered tributaries significantly affect the chemical integrity of
traditional navigable waters, interstate waters, and the territorial
seas. Covered tributaries influence the chemical composition of
downstream waters, through the transport and removal of chemical
elements and compounds, such as nutrients, ions, organic matter and
pollutants. Ecosystem processes in

covered tributaries transform, remove, and transport these substances
to downstream waters. In turn, these chemical compounds can influence
water quality, sediment deposition, nutrient availability, and biotic
functions in rivers. Because water flow transports chemical substances
downstream, chemical effects are closely related to hydrological
connectivity. Within covered tributaries, there are processes that
occur that transform and export nutrients and carbon to downstream
waters, serving important source functions that influence the chemical
integrity of downstream waters. Organic carbon, in both dissolved and
particulate forms, exported from covered tributaries is consumed by
downstream organisms. The organic carbon that is exported downstream
thus supports biological activity throughout the river network.
    Covered tributaries act as both sinks and sources of chemical
substances, further affecting the chemical integrity of traditional
navigable waters, interstate waters, and the territorial seas. Covered
tributaries provide sink functions by trapping chemicals through
absorption to sediments in the stream substrate (e.g., phosphorous
adsorption to clay particles). They provide source functions by
transporting chemicals to downstream traditional navigable waters,
interstate waters, and the territorial seas as chemicals dissolved in
the waters or as chemicals attached to suspended sediments.
    Covered tributaries significantly affect the physical integrity of
traditional navigable waters, interstate waters, and the territorial
seas. Physical connections between covered tributaries and traditional
navigable waters, interstate waters, and the territorial seas result
from the hydrologic transport from covered tributaries to downstream
waters of numerous materials, including water, sediment and organic
matter such as leaves and wood. This transport affects the physical
characteristics of downstream waters. Covered tributaries, even when
seasonally dry, are the dominant source of water in most rivers, rather
than direct precipitation or groundwater input to main stem river
segments. One of the primary functions of covered tributaries is
transporting sediment to downstream waters. Covered tributaries,
particularly headwaters, shape and maintain river channels by
accumulating and gradually or episodically releasing sediment and large
woody debris into river channels. These effects occur even when the
covered tributaries flow infrequently (such as ephemeral covered
tributaries), and even when the covered tributaries are great distances
from the traditional navigable water, interstate water, or the
territorial sea (such as some headwater covered tributaries).
    Covered tributaries significantly affect the biological integrity
of traditional navigable waters, interstate waters, and the territorial
seas. Covered tributaries, including intermittent and ephemeral
streams, are critical in the life-cycles of many organisms capable of
moving throughout river networks. In fact, many organisms, such as
anadromous salmon, have complex life-cycles which involve migration
through the river network, from headwaters to downstream rivers and
oceans and back, over the course of their lives. In addition to
providing critical habitat for complex life-cycle completion, covered
tributaries provide refuge from predators and adverse physical
conditions in rivers, and are reservoirs of genetic- and species-level
diversity. Covered tributaries contribute materials to downstream food
networks and supporting populations for aquatic species, including
economically important species such as salmon. These effects occur even
when the covered tributaries flow infrequently (such as ephemeral
covered tributaries), and even when the covered tributaries are large
distances from the traditional navigable waters, interstate waters, and
the territorial seas (such as some headwater covered tributaries).
    Similarly, modified and constructed tributaries perform the same
functions as natural tributaries, especially the conveyance of water
that carries nutrients, pollutants, and other constituents, both good
and bad, to traditional navigable waters, interstate waters, and the
territorial seas. Modified and constructed covered tributaries also
provide corridors for movement of organisms between headwaters and
traditional navigable waters, interstate waters, and the territorial
seas. The important effect--and thus the significant nexus--between a
covered tributary and a traditional navigable water, interstate water,
and the territorial sea is not broken where the covered tributary flows
through a culvert or other structure. The scientific literature
recognizes that features that convey water, whether they are natural,
modified, or constructed, provide substantial connectivity between
streams and downstream waters. For example, ditches that meet the
definition of tributary and are not excluded quickly move water
downstream to traditional navigable waters, interstate waters, and the
territorial seas due to their often straightened and channelized
nature, transporting downstream sediment, nutrients, and other
materials.
    The CWA regulates and controls pollution at its source, in part
because most pollutants do not remain at the site of the discharge, but
instead flow and are washed downstream through the tributary system to
endanger drinking water supplies, fisheries, and recreation areas.
These fundamental facts about the movement of pollutants and the
interconnected nature of the tributary system demonstrate why covered
tributaries of traditional navigable waters, interstate waters, and the
territorial seas, alone or in combination with other covered
tributaries in a watershed, have a significant nexus with those
downstream waters. Thus, in the rule the agencies assert CWA
jurisdiction over all covered tributaries as defined. Those covered
tributaries are ``waters of the United States'' without the need for
further analysis.
b. Covered Adjacent Waters
    Based on the agencies' review of the scientific literature and the
law, the agencies determine that covered adjacent waters, as defined,
have a significant nexus and are ``waters of the United States.'' The
scientific literature, including the Science Report, consistently
supports the conclusion that covered adjacent waters provide similar
functions and work together to maintain the chemical, physical, and
biological integrity of the downstream traditional navigable waters,
interstate waters, and the territorial seas because of their
hydrological and ecological connections to, and interactions with,
those waters. Science demonstrates that this functional connectivity is
particularly evident where covered adjacent waters are located within
the floodplain of the traditional navigable water, interstate water,
the territorial seas, covered tributary, or impoundment to which they
are adjacent or are otherwise sufficiently proximate to waters with no
floodplain, such as lakes and ponds. Location within the floodplain and
proximity ensure that the aquatic functions performed by covered
adjacent waters are effectively and consistently provided to downstream
waters. See Technical Support Document.
    The agencies conclude that all waters meeting the definition of
``adjacent'' in the rule are similarly situated for purposes of
analyzing whether they have a significant nexus to a traditional
navigable water, interstate water, or the territorial sea. Based on a
review of the scientific literature, the agencies conclude that these
bordering, contiguous, or neighboring waters

provide similar functions and function together to significantly affect
the chemical, physical, or biological integrity of traditional
navigable waters, interstate waters, or the territorial seas. Further,
because the definition of ``adjacent'' considers both the functional
relationships and the proximity of the waters (i.e., those that are
located near traditional navigable waters, interstate waters, the
territorial seas, impoundments, and covered tributaries), interpreting
the term ``similarly situated'' to include all covered adjacent waters,
as defined in the rule, is informed by the science and is a reasonable
interpretation of the scope of the statute. The geographic proximity of
an ``adjacent'' water relative to the traditional navigable waters,
interstate waters, the territorial seas, impoundments, and covered
tributaries is indicative of the relationship to it, with many of its
defining characteristics resulting from the movement of materials and
energy between the categories of waters. The scientific literature
supports that waters, including wetlands, ponds, lakes, oxbow lakes,
and similar waters, that are ``adjacent,'' as defined in the rule, to
traditional navigable waters, interstate waters, the territorial seas,
impoundments, and covered tributaries, are integral parts of stream
networks because of their ecological functions and how they interact
with each other, and with downstream traditional navigable waters,
interstate waters, or the territorial seas.
    Covered adjacent waters function together to maintain the chemical,
physical, or biological health of traditional navigable waters,
interstate waters, and the territorial seas to which they are directly
adjacent or to which they are connected by the tributary system. This
functional interaction can result from hydrologic connections or
because covered adjacent waters can act as water storage areas holding
damaging floodwaters or filtering harmful pollutants. These chemical,
physical, and biological connections affect the integrity of downstream
traditional navigable waters, interstate waters, and the territorial
seas through the temporary storage and deposition of channel-forming
sediment and woody debris, temporary storage of local groundwater
sources of baseflow for downstream waters and their tributaries, and
transformation and transport of organic matter. Covered adjacent waters
improve water quality through the assimilation, transformation, or
sequestration of pollutants, including excess nitrogen and phosphorus,
and chemical contaminants such as pesticides and metals that can
degrade downstream water integrity. In addition to providing effective
buffers to protect downstream waters from pollution, covered adjacent