The agencies have not changed their interpretation of traditional
navigable waters in this final rule, and the agencies are retaining
Appendix D to help inform implementation of this provision with
additional clarification in this notice in response to comments. As
discussed in Section II.E, the definition of navigable-in-fact waters
originates with the Supreme Court's decision in The Daniel Ball, 77
U.S. (10 Wall.) 557 (1870). In that case, the Supreme Court stated:

    Those rivers must be regarded as public navigable rivers in law
which are navigable in fact. And they are navigable in fact when
they are used, or are susceptible of being used, in their ordinary
condition, as highways for commerce, over which trade and travel are
or may be conducted in the customary modes of trade and travel on
water.

    Id. at 563. As explained by the Supreme Court in 2012, ``[t]he
Daniel Ball formulation has been invoked in considering the
navigability of waters for purposes of assessing federal regulatory
authority under the Constitution, and the application of specific
federal statutes, as to the waters and their beds.'' PPL Montana, LLC
v. Montana, 565 U.S. 576, 592 (2012). ``With respect to the federal
commerce power, the inquiry regarding navigation historically focused
on interstate commerce.'' Id. at 593. The Supreme Court further
explained that, ``of course, the commerce power extends beyond
navigation'' and cautioned ``that the test for navigability is not
applied the same way'' in all cases. Id. at 592-93; see also Kaiser
Aetna v. United States, 444 U.S. 164, 171 (1979) (``[A]ny reliance upon
judicial precedent [in this area] must be predicated upon careful
appraisal of the purpose for which the concept of navigability was
invoked in a particular case.'' (internal quotation marks, citation
omitted, and emphasis in original)). But generally, navigability for
purposes of federal regulatory authority under the federal commerce
power encompasses waters that were ``once navigable but are no
longer,'' PPL Montana, 565 U.S.at 592 (citing Economy Light & Power Co.
v. United States, 256 U.S. 113, 123-24 (1921)), ``waters that only
recently have become navigable,'' id. (citing Philadelphia Co. v.
Stimson, 223 U.S. 605, 634-35 (1912)), and waters that ``are not
navigable and never have been but may become so by reasonable
improvements,'' id. at 592-93 (citing United States v. Appalachian
Elec. Power Co., 311 U.S. 377, 407-08 (1940)). The agencies note that
this summary articulated by the Supreme Court in 2012 generally
reflects the basic structure of the longstanding jurisdictional test
for ``traditional navigable waters'' retained in paragraph (a)(1) of
the final rule.
    Many commenters expressed support for the agencies' decision to
retain the existing regulatory text describing traditional navigable
waters. These

commenters stated that the existing text is clear, concise,
predictable, and well understood by the public. Other commenters
expressed concern about implementation of the regulation and guidance
and suggested modifications to the regulation. Some commenters
suggested clarifying that traditional navigable waters must be used to
``transport commerce,'' as that is the phrase Congress used to describe
the waters over which the Corps retains permitting authority when
States and Tribes assume CWA section 404 permitting. See 33 U.S.C.
1344(g). As discussed in Section II.E, and consistent with a technical
advisory committee report submitted to EPA as part of an effort to
modernize the section 404(g) assumption process (see n.28), section
404(g) refers to RHA section 10 waters. Some commenters recommended
that the agencies adopt the RHA section 10 definition and the two-part
legal test established by The Daniel Ball for ``navigable waters of the
United States'' as the test for ``traditional navigable waters'' for
purposes of implementing the term ``waters of the United States'' under
the CWA. That test requires first that a water be navigable-in-fact,
and second that commerce be transported across State or foreign lines
on those waters. The Daniel Ball, 77 U.S. (10 Wall.) at 563.
    The Supreme Court has not spoken directly to the precise meaning of
the phrase ``traditional navigable waters'' as that term applies in the
CWA context, but it has stated that the statutory ``term `navigable'
has at least the import of showing us what Congress had in mind as its
authority for enacting the CWA: Its traditional jurisdiction over
waters that were or had been navigable in fact or which could
reasonably be so made.'' SWANCC, 531 U.S. at 172. In the agencies'
view, the Supreme Court has therefore signaled an acceptance of the
first prong of The Daniel Ball test. Whether the second prong applies
in full to the administrative definition of ``traditional navigable
waters'' is less clear, but the legislative history suggests that
Congress had in mind a more expanded notion of interstate commerce when
enacting the CWA, including overland links to commercial navigation on
navigable-in-fact waters.\40\ As described in Section II.E, the Supreme
Court has stated that nothing in the legislative history of the Act
suggests ``that Congress intended to exert anything more than its
commerce power over navigation.'' SWANCC, 531 U.S. at 168 & n.3. The
agencies therefore are not modifying the longstanding regulatory text
for traditional navigable waters to specifically align it with the RHA
test for jurisdiction, as some commenters suggested.
---------------------------------------------------------------------------

    \40\ See Section II.E for additional discussion of the complex
legislative history on this topic, as well as the detailed
discussion of the same in the Albrecht & Nickelsburg article cited
in note 25.
---------------------------------------------------------------------------

    The agencies acknowledge that some commenters suggested that
Appendix D as-applied in certain circumstances has led to confusion.
For example, some commenters expressed concern that Appendix D could be
read to support a conclusion that any water that can float a boat, even
very shallow draft vessels like canoes and kayaks, is by definition
``susceptible'' to use in interstate commerce and therefore may be
deemed a traditional navigable water. The agencies believe that this
interpretation is inconsistent with the cases summarized in Appendix D
and sweeps too broadly. For example, whether a water is susceptible to
use in interstate commerce requires more than simply being able to
float a boat to establish jurisdiction over navigable-in-fact waters
under paragraph (a)(1); it requires evidence of physical capacity for
commercial navigation and that it was, is, or actually could be used
for that purpose. See, e.g., Appendix D (citing The Montello, 87 U.S.
430, 441-42 (1874); United States v. Holt State Bank, 270 U.S. 49, 56
(1926); United States v. Utah, 283 U.S. 64 (1931); United States v.
Appalachian Elec. Power Co., 311 U.S. 377, 416 (1940)).
    Other commenters provided examples of traditional navigable water
determinations about which the commenters asserted that the capacity to
float a boat in a water that is near an interstate highway was deemed
sufficient to make a traditional navigable water determination under
the paragraph (a)(1) standard. This interpretation is inconsistent with
the applicable case law, including the cases discussed in Appendix D.
Simply driving across a State line and using a waterbody, or having the
potential to use a waterbody, is similar to the theory of jurisdiction
that the Supreme Court specifically rejected in SWANCC. One of the
arguments raised in support of the ``Migratory Bird Rule'' for CWA
jurisdiction was that individuals cross State lines and engage in
commercial activity to hunt or observe migratory birds that use
isolated waters as habitat. See SWANCC, 531 U.S. at 166; id. at 195 &
n.17 (Stevens, J., dissenting). The SWANCC Court rejected this
interpretation of CWA jurisdiction because it raised ``significant
constitutional questions'' that would require the agencies to
``evaluate the precise object or activity that, in the aggregate,
substantially affects interstate commerce.'' Id. at 173-74. The
``substantial effects'' test is the most expansive of the three primary
bases for exercising congressional authority under the Commerce Clause
articulated by the Supreme Court in United States v. Lopez, 514 U.S.
549, 558-59 (1995). This application of the ``substantial effects''
test to assert CWA jurisdiction over waters beyond those more
traditionally understood as navigable was not intended by Appendix D
and has been rejected by the SWANCC Court because it was inconsistent
with Congress' intent to exercise its more traditional ``commerce power
over navigation.'' SWANCC, 531 U.S. at 173 & n.8. Thus, the legal
principles summarized in Appendix D were not intended to endorse, and
should not be interpreted as endorsing, the application of the
``substantial effects'' test to CWA jurisdiction, or otherwise
suggesting that the mere capacity to float a boat makes a waterbody
susceptible to commercial navigation.
    The agencies intend to update their guidance materials, if and as
necessary, as the agencies begin to implement the revised tests for
jurisdiction established by the final rule, both initially and as the
agencies gain field experience to address implementation questions that
may arise. As part of that process, the agencies will continue to
evaluate prior guidance on how to apply established case law principles
to traditional navigable water determinations. The agencies will also
implement field elevation procedures should difficult legal questions
arise, including requiring such interpretations to be reviewed by
senior legal staff at each of the agencies' respective headquarters.
Implementation of this section of the traditional navigable waters
provision of paragraph (a)(1) in the final rule will be case-specific,
as it has always been. This case-specific analysis will include
relevant portions of EPA and Corps regulations, prior determinations by
the Corps and by the federal courts, and case law. Should the agencies
determine that additional, more formal guidance on traditional
navigable waters is warranted, the agencies will develop any such
guidance in compliance with Executive Order 13891, and with any
applicable public participation requirements.

C. Interstate Waters

1. What are the agencies finalizing?
    Consistent with the proposal, this final rule removes interstate
waters, including interstate wetlands, as a separate category of
``waters of the

United States.'' The agencies are finalizing this aspect of the
proposal to more closely align the regulatory definition with the
constitutional and statutory authorities reflected in the CWA and
judicial interpretations of the term ``navigable waters,'' while
balancing the statute's objective to restore and maintain the integrity
of the nation's waters and its policy directives to preserve and
protect the rights and responsibilities of the States.
    Many commenters supported the removal of interstate waters and
wetlands as an independent category of ``waters of the United States.''
Those commenters stated that such a category was not authorized by the
CWA and that, as proposed by the agencies, waters must be connected to
traditional navigable waters to be jurisdictional under the CWA.
Commenters also stated that interstate waters and wetlands that
actually fall within the scope of CWA jurisdiction would be covered by
the other categories of waters as proposed. Other commenters opposed
removing interstate waters as an independent jurisdictional category.
Those commenters stated that any water that crosses a State line is by
definition a ``water of the United States.'' The same is true, some
commenters added, for waters that cross tribal boundaries. Additional
commenters added that the proposed rule would arbitrarily narrow the
scope of CWA jurisdiction over ecologically important waters and
recommended that the agencies continue to regulate interstate waters.
Other commenters suggested that the exclusion for ephemeral features,
if finalized, would help balance the inclusion of interstate waters as
a category.
    The agencies have considered this diverse range of opinions, and
for the reasons discussed below, have concluded that the best
interpretation of the CWA and its legislative history is to finalize
the regulatory text as proposed, without a separate interstate waters
category. Interstate waters and interstate wetlands remain subject to
CWA jurisdiction under the final rule if they are waters identified in
paragraph (a)(1), (2), (3), or (4) (generally referred to as
``paragraph (a)(1) through (4) waters'' or ``a paragraph (a)(1) through
(4) water'' in this notice).
2. Summary of Final Rule Rationale and Public Comment
    The agencies have evaluated their earlier legal and policy
rationales supporting the inclusion of interstate waters as a separate
category of ``waters of the United States'' and comments on the
proposed rule and are not including this category in the final rule.
The agencies have concluded that the regulation of interstate waters as
a standalone category is based on an overly broad reading of the
original Water Pollution Control Act (WPCA) of 1948 and lacks
foundation in statutory text of the 1972 CWA amendments. The WPCA
stated that the ``pollution of interstate waters in or adjacent to any
State or States (whether the matter causing or contributing to such
pollution is discharged directly into such waters or reaches such
waters after discharge into a tributary of such waters), which
endangers the health or welfare of persons in a State other than that
in which the discharge originates, is hereby declared to be a public
nuisance and subject to abatement as herein provided.'' WPCA of 1948,
2(d)(1), (4), 62 Stat. 1155, 1156-57. The statute defined ``interstate
waters'' as ``all rivers, lakes, and other waters that flow across, or
form a part of, State boundaries.'' Id. at 10(e), 62 Stat. 1161.
    In 1961, Congress amended the statute to substitute the term
``interstate or navigable waters'' for ``interstate waters'' in the
statute's enforcement provision while making minor changes to the
definition of ``interstate waters.'' See Public Law 87-88, 75 Stat. 208
(1961). In 1965, Congress again amended the statute to require states
to develop water quality standards for all ``interstate waters'' within
their borders. See Public Law 89-234, 79 Stat. 908 (1965). In 1972,
Congress amended the statute again and selected the term ``navigable
waters'' as the operative term for the major regulatory programs
established by the 1972 amendments, dropping the definition of
``interstate waters'' from the statute. See, e.g., 33 U.S.C. 1362(7)
(defining ``navigable waters'' as ``waters of the United States''). In
doing so, however, Congress allowed States to retain existing water
quality standards for interstate waters developed under the pre-1972
statutory program. See 33 U.S.C. 1313(a).
    The EPA promulgated its first regulatory definition for the term
``waters of the United States'' in 1973. 38 FR 13528 (May 22, 1973). In
that regulation, the EPA administratively determined that ``interstate
waters'' should be a separate category of ``waters of the United
States,'' distinct from the traditional navigable waters category, and
until this final rule the agencies had retained it as a separate
category.
    The agencies previously viewed navigable and interstate waters as
having distinct and separate meanings because Congress in 1961 used
both terms in the statute. The agencies explained their prior
interpretation in part through the doctrine of congressional
acquiescence, in that Congress was aware of the EPA's retention of
``interstate waters'' as a separate category when amending the CWA in
1977 (making no amendments to remove the agencies' regulatory inclusion
of interstate waters), and therefore acquiesced to its inclusion as a
separate category. The agencies have also historically relied on two
Supreme Court cases--Illinois v. City of Milwaukee, 406 U.S. 91 (1972)
and City of Milwaukee v. Illinois, 451 U.S. 304 (1981)--addressing
interstate water pollution to further support their prior
interpretation. In the 1972 case, which was decided prior to the date
of the 1972 CWA amendments, the Supreme Court referred to the two
categories in the disjunctive, implying that the Court viewed the pre-
1972 statutory program as encompassing two separate categories. See
Illinois, 406 U.S. at 102 (``it is federal, not state, law that in the
end controls pollution of interstate or navigable waters'') (emphasis
added). The 1981 case is described further below. The agencies also
have referred to section 303(a) of the CWA as further evidence that
Congress intended ``interstate waters'' to be retained as an
independent category of jurisdictional waters because that provision
authorized water quality standards for ``interstate waters'' developed
following the 1965 amendments to remain in effect, subject to revision
under the new statutory program. A more complete summary of the
agencies' prior legal position with respect to interstate waters was
included in a Technical Support Document prepared in support of the
2015 Rule (``2015 Rule TSD'').\41\ The agencies now conclude that their
prior interpretation is inconsistent with the text and structure of the
CWA.
---------------------------------------------------------------------------

    \41\ U.S. EPA and U.S. Department of the Army. Technical Support
Document for the Clean Water Rule: Definition of Waters of the
United States (May 2015) (Docket ID: EPA-HQ-OW-2011-0880-20869),
available at https://www.regulations.gov/document?D=EPA-HQ-OW-2011-0880-20869.
---------------------------------------------------------------------------

    When Congress enacted the 1972 CWA amendments, it selected the term
``navigable waters'' to frame the scope of federal regulatory
jurisdiction under the Act. Rather than interpreting those amendments
as retaining ``interstate waters'' as a separate and distinct category
of ``waters of the United States,'' the agencies now conclude that a
more natural interpretation of the 1972 amendments is an express
rejection of that independent category, as Congress had before it both
options within the scope of the statute it was modifying. Congress
specifically did not carry that term forward as the operative phrase
for

federal jurisdiction. Under basic canons of statutory construction, the
agencies begin with the presumption that Congress did so intentionally.
See, e.g., Stone v. INS, 514 U.S. 386, 397 (1995) (``When Congress acts
to amend a statute, we presume it intends its amendment to have real
and substantial effect.'').
    Congressional acquiescence is a doctrine of limited application and
was specifically rejected as a basis for expansive federal jurisdiction
in SWANCC in the context of analyzing the Corps' 1977 regulations.
SWANCC, 531 U.S. at 170-71 (``Although we have recognized congressional
acquiescence to administrative interpretations of a statute in some
situations, we have done so with extreme care.''). The plurality
opinion in Rapanos further elaborated, when also rejecting the notion
that Congress acquiesced to the Corps' 1977 regulations, that
``Congress takes no governmental action except by legislation. What the
dissent refers to as `Congress' deliberate acquiescence' should more
appropriately be called Congress's failure to express any opinion.''
Rapanos, 547 U.S. at 750 (Scalia, J., plurality). The plurality
explained that we cannot know whether Congress' inaction resulted from
their belief that the Corps' regulations were correct, or from other
reasons, such as confidence that courts would correct excesses or
political considerations. See SWANCC, 531 U.S. at 169-70, 178 n.5
(``Absent such overwhelming evidence of acquiescence, we are loath to
replace the plain text and original understanding of a statute with an
amended agency interpretation.''). The agencies now conclude,
consistent with the admonitions of SWANCC and the Rapanos plurality,
that the doctrine of congressional acquiescence is not a sound basis to
guide the agencies' decision regarding the scope of federal
jurisdiction over certain waters in this final rule, particularly as it
applies to interstate waters divorced from any notion of commercial
navigability.
    The legislative history of the 1972 amendments, in fact, supports
the agencies' conclusion that Congress did not consider interstate
waters and navigable waters to be two separate and distinct categories,
and instead referred to terms in the pre-1972 statutory regime
conjunctively as ``interstate navigable waters.'' S. Rep. No. 92-414,
at 2 (1971) (``Each State was required by the 1965 Act to develop
standards for water quality within its boundaries. These standards were
to be applied to all interstate navigable waters flowing through the
State; intrastate waters were not included.'') (emphasis added); id. at
4 (``The setting of water quality standards for interstate navigable
waters . . . is the keystone of the present program for control of
water pollution.'') (emphasis added); id. (``The States have first
responsibility for enforcement of their standards. When approved by the
[EPA], however, the standards for interstate navigable waters become
Federal-State standards.'') (emphasis added). In fact, the legislative
history suggests that Congress modified the text of the statute in 1972
in part because the States had narrowly interpreted the phrase
``interstate'' to apply only to interstate navigable waters and had
failed to establish water quality standards for the intrastate
tributaries to such waters. See, e.g., id. at 77 (``The control
strategy of the Act extends to navigable waters . . . . Through a
narrow interpretation of the definition of interstate waters the
implementation [of the] 1965 Act was severely limited.''); 118 Cong.
Rec. 10240 (1972) (the amendment ``expands the coverage of the law to
intrastate, as well as interstate navigable waterways'') (emphasis
added). In 1976, the Supreme Court shared the same view of the pre-1972
statutory scheme: ``Before it was amended in 1972, the Federal Water
Pollution Control Act employed ambient water quality standards
specifying the acceptable levels of pollution in a State's interstate
navigable waters as the primary mechanism in its program for the
control of water pollution.'' EPA v. California, 426 U.S. 200, 202
(1976) (emphasis added) (footnote omitted). This history suggests that
the section 303(a) provision relating to existing water quality
standards for ``interstate waters'' was referring to ``interstate
navigable waters,'' not interstate waters more broadly.
    Neither Supreme Court case previously relied on by the agencies and
discussed in the 2015 Rule TSD addressed the specific question whether
``interstate waters'' and ``navigable waters'' are separate and
distinct categories of jurisdictional waters under the CWA. They
instead addressed interstate water pollution generally, and the water
at issue in those cases was Lake Michigan, an interstate navigable-in-
fact water. The 1981 decision, however, did recognize that the 1972
amendments ``were viewed by Congress as a `total restructuring' and
`complete rewriting' of the existing water pollution legislation
considered in that case.'' Milwaukee, 451 U.S. at 317 (citing
legislative history of the 1972 CWA amendments). This supports the
agencies' conclusion that prior iterations of the statute, referring to
both interstate waters and navigable waters, were replaced with a
completely new program in 1972, not that certain aspects of that
program continued through congressional acquiescence in a later
regulatory determination. The final rule therefore eliminates
``interstate waters'' as a separate category of ``waters of the United
States.''
    By eliminating a separate category for interstate waters, the final
rule adheres to the legal principles discussed in Section II.E by
including within the definition of ``waters of the United States''
traditional navigable waters, the territorial seas, and waters subject
to the ebb and flow of the tide; tributaries to such waters; certain
lakes, ponds, and impoundments of otherwise jurisdictional waters; and
wetlands adjacent to jurisdictional waters. Because the agencies'
authority flows from Congress' use of the term ``navigable waters'' in
the CWA, the agencies lack authority to regulate waters untethered from
that term. Nothing in the legislative history of the 1972 CWA
amendments ``signifies that Congress intended to exert anything more
than its commerce power over navigation.'' SWANCC, 531 U.S. at 168 n.3.
    Therefore, those interstate waters that would satisfy the
definitions in this final rule are jurisdictional; interstate waters
without any surface water connection to traditional navigable waters or
the territorial seas are not within the agencies' authority under the
CWA and are more appropriately regulated by the States and Tribes under
their sovereign authorities.
    The agencies' rationale is supported by the U.S. District Court for
the Southern District of Georgia's remand order. Georgia v. Wheeler,
No. 2:15-cv-00079, 2019 WL 3949922 (S.D. Ga. Aug. 21, 2019). There, the
court directly addressed the 2015 Rule's assertion of authority over
all interstate waters, including nonnavigable interstate waters. Id. at
*10-13. The court found that ``the inclusion of all interstate waters
in the definition of `waters of the United States,' regardless of
navigability, extends the Agencies' jurisdiction beyond the scope of
the CWA because it reads the term navigability out of the CWA.'' Id. at
*12. The court also found that, because the 2015 Rule would assert
jurisdiction over tributaries, adjacent waters, and case-by-case waters
based on their relationship to non-navigable isolated interstate
waters, it would result in federal jurisdiction over even the most
remote and isolated waters that the Supreme Court held in SWANCC are
beyond the

reach of the CWA. Id. at *13. The agencies agree with the court's
analysis and conclusion.
    This final rule marks a shift away from prior agency positions. The
agencies received public comment that the proposal had failed to
analyze potential impacts resulting from the removal of ``interstate
waters'' as a separate category, but as noted in the preamble to the
proposed rule, the agencies are not aware of any database that
identifies the jurisdictional status of interstate waters based solely
on the fact that they cross state lines, or any other resource that
would identify these waters. The agencies therefore lack the ability to
perform a comparative analysis with any precision. Some commenters
provided examples of interstate waters that may lose jurisdictional
status if the separate category is eliminated; however, the Corps' ORM2
database does not contain any jurisdictional determinations based
solely on a water's status as an interstate water. Since issuance of
the Rapanos Guidance, the Corps has not tracked this category
separately for approved jurisdictional determinations conducted under
the Guidance in ORM2.
    The agencies requested comment on the rationales in favor of and
opposed to a separate jurisdictional category for ``interstate
waters.'' Some commenters supported the proposal to remove ``interstate
waters'' as a separate category, noting that there is no statutory or
constitutional basis to regulate interstate waters that would not
otherwise be jurisdictional and suggesting that the agencies lacked the
authority to include a separate ``interstate'' category in earlier
versions of the regulations. Other commenters opposed the proposal,
asserting that the text and structure of the CWA, legislative history,
and prior court cases, including Justice Scalia's discussion in
Rapanos, demonstrate that the CWA applies to interstate waters
regardless of navigability. The agencies considered these comments and,
for the reasons explained above, conclude that the final rule most
closely aligns with the agencies' constitutional and statutory
authorities reflected in the CWA and relevant judicial interpretations
of the term ``navigable waters'' and the legislative history of the
CWA, while balancing the statute's objective to restore and maintain
the integrity of the nation's waters and its policy directives to
preserve and protect the rights and responsibilities of the States.
    Some commenters stated that the agencies did not provide sufficient
rationale for deviating from their prior analysis and interpretation,
as provided in the 2015 Rule TSD. The agencies disagree, as the
proposal clearly identified independent reasons questioning the
validity of the agencies' prior interpretation. The agencies' 2015 Rule
TSD, for example, included three primary arguments supporting the prior
interpretation: First, the language, structure, and history of the CWA
demonstrate that Congress intended to include interstate waters in
addition to navigable waters; second, the Supreme Court decisions in
Rapanos and SWANCC did not constrain CWA jurisdiction over isolated,
nonnavigable, interstate waters; and third, Supreme Court precedent
supports jurisdiction over interstate waters, regardless of
navigability. These arguments are addressed in the proposal and in
earlier sections of this notice, but the agencies provide additional
detail to respond to comments received as follows.
    The 2015 Rule TSD analyzed two Supreme Court decisions to support
its conclusion that interstate waters should be a separate category of
jurisdiction under the CWA. The first decision was issued in 1972, just
prior to the 1972 CWA amendments, and concluded that federal common law
was appropriate to resolve a cross-border water pollution dispute among
states where existing statutes did not address the dispute. Illinois,
406 U.S. 91. The Court found that where ``no fixed rules'' govern
cross-boundary pollution disputes, ``these will be equity suits in
which the informed judgment of the chancellor will largely govern.''
Id. at 107-08.
    The second decision was issued in 1981, and it analyzed the effect
of the 1972 amendments on a federal common law claim concerning the
same cross-border water pollution dispute that was presented the 1972
case. City of Milwaukee, 451 U.S. 304. In that case, the Court
acknowledged the 1972 amendments and noted that ``[t]he establishment
of such a self-consciously comprehensive program by Congress, which
certainly did not exist when Illinois v. Milwaukee was decided,
strongly suggests that there is no room for courts to attempt to
improve on that program with federal common law.'' Id. at 319 (emphasis
added).
    Contrary to the assertions in the 2015 Rule TSD, however, the Court
did not conclude that the CWA occupies the field with regard to all
interstate waters.\42\ Instead, the Court considered the facts of the
case before it--whether NPDES permits issued by an authorized State in
compliance with the CWA could be modified or augmented by federal
common law claims brought by a downstream State. Focusing on
respondents' claims that discharges from the facilities were causing a
public nuisance, the Court observed that, ``the action of Congress in
supplanting the federal common law is perhaps clearest when the
question of effluent limitations for discharges from the two treatment
plants is considered.'' City of Milwaukee, 451 U.S. at 319-20. The
Court identified the numerous provisions of the permits that addressed
discharges and overflows from the facilities, and the State-initiated
enforcement action contemplated by the CWA, and concluded that
``[t]here is no `interstice' here to be filled by federal common law:
Overflows are covered by the Act and have been addressed by the
regulatory regime established by the Act. Although a Federal court may
disagree with the regulatory approach taken by the agency . . . such
disagreement alone is no basis for the creation of federal common
law.'' Id. at 323.
---------------------------------------------------------------------------

    \42\ See U.S. EPA and Department of the Army, Technical Support
Document of the EPA-Army Clean Water Rule at 210 (May 20, 2015)
(``2015 Rule TSD'') (Docket ID: EPA-HQ-OW-2011-0880-20869) available
at https://www.regulations.gov/document?D=EPA-HQ-OW-2011-0880-20869.
(``In City of Milwaukee, the Court found that the CWA was the
`comprehensive regulatory program' that `occupied the field' (451
U.S. 317) with regard to interstate water pollution, eliminating the
basis for an independent common law of nuisance to address
interstate water pollution.''). The 2015 Rule TSD also asserts that
the Court ``expressly overruled'' its decision in Illinois; however,
a more precise statement would be that the Court found no federal
common law remedy available ``at least so far as concerns the claims
of respondents'' because Congress occupied the field with a federal
regulatory program that establishes effluent limits and other
specific requirements that supersede the ``often vague and
indeterminate nuisance concepts and maxims of equity
jurisprudence.'' City of Milwaukee, 451 U.S. at 317 (emphasis
added).
---------------------------------------------------------------------------

    The Court also noted that in its 1972 decision, the Court was
concerned that the downstream State ``did not have any forum in which
to protect its interests unless federal common law were created,'' City
of Milwaukee, 541 U.S. at 325, but that the NPDES permitting provisions
of the 1972 amendments ``provided ample opportunity for a State
affected by decisions of a neighboring State's permit-granting agency
to seek redress.'' Id. at 325-26 (identifying the CWA requirement to
provide notice to affected States and opportunity to comment and
request public hearings, the Wisconsin law that provides the same,
affected States' opportunity under the CWA to petition the EPA to
object to a NPDES permit, and noting that respondents did not take
advantage of these provisions). The case therefore presented a dispute
between States concerning NPDES permits lawfully issued for discharges
into an otherwise

navigable water--Lake Michigan. The Supreme Court did not consider
disputes outside of the NPDES permit program or those concerning non-
navigable interstate waters, and the Court did not broadly conclude
that the CWA occupies the field of all interstate water pollution.\43\
All it had before it was the CWA, and as discussed in Section II,
Congress chose not to exercise its full powers under the Commerce
Clause when enacting the 1972 amendments. Congress specifically
recognized that there are other land and water resources that are more
appropriately regulated by the States and Tribes under their sovereign
authorities. Field preemption cannot extend beyond the field. Hines v.
Davidowitz, 312 U.S. 52, 78-79 (1941) (``[e]very Act of Congress
occupies some field, but we must know the boundaries of that field
before we can say that it has precluded a state from the exercise of
any power reserved to it by the Constitution''); see also Gonzales v.
Oregon, 546 U.S. 243, 275 (2006); Medtronic, Inc. v. Lohr, 518 U.S.
470, 475 (1996); Metropolitan Life Ins. Co. v. Massachusetts, 471 U.S.
724, 756 (1985)).
---------------------------------------------------------------------------

    \43\ In a footnote, the 2015 Rule TSD identifies two other
Supreme Court decisions and concludes that ``[n]othing in either
decision limits the applicability of the CWA to interstate water
pollution disputes involving navigable interstate waters or
interstate waters connected to navigable waters.'' 2015 Rule TSD at
211 n.16 (referencing International Paper v. Ouellette, 479 U.S. 481
(1987), and Arkansas v. Oklahoma, 503 U.S. 91 (1992)). Similar to
the facts of City of Milwaukee, both of these cases addressed
disputes that arose in the CWA's NPDES permitting context for waters
that would otherwise be jurisdictional--Lake Champlain and the
Illinois River. In neither case was the Court asked to consider
whether or how the CWA may apply to non-navigable interstate waters,
and these cases do not provide useful context or precedent on that
issue. The 2015 Rule TSD similarly concluded that neither SWANCC nor
Rapanos addressed or limited CWA jurisdiction over non-navigable
interstate waters. See Section II.E of this notice for the agencies'
detailed analysis of the SWANCC and Rapanos decisions.
---------------------------------------------------------------------------

    The agencies also requested comment on an alternative approach that
would retain ``interstate waters'' as a separate category, reflecting
longstanding agency practice, and whether the term ``interstate''
should be interpreted as crossing between States, between States and
tribal lands, between States and/or tribal lands and foreign countries,
or other formulations. Some commenters opposed this alternative
approach, stating that the agencies lacked the authority to codify or
implement it. Other commenters supported retaining ``interstate
waters'' as a separate category and expressed concern that removing it
would eliminate the EPA's role as a co-regulator in cross-boundary
disputes over water quality.
    The CWA provides two opportunities for the EPA to mediate disputes
among States: The section 401(a)(2) neighboring jurisdiction
notification provisions for federally permitted projects that may
discharge to navigable waters and the section 319(g) provisions
allowing the EPA to convene an interstate management conference to
address cross-boundary nonpoint pollution in navigable waters. In the
past, these provisions have been invoked infrequently by States, and
the agencies do not expect a significant increase in cross-boundary
disputes as a result of this rulemaking. In addition, the EPA can
address concerns of States whose waters may be affected by the issuance
of a permit in another State through the permit objection process
pursuant to CWA sections 402(b)(5), 402(d)(d), and 40 CFR 123.44(c)(2).
As demonstrated in City of Milwaukee, if a cross-boundary dispute is
one that is contemplated and addressed by the CWA, such as the
sufficiency of effluent limits in a NPDES permit, the statute has
occupied the field and federal common law does not provide a remedy.
451 U.S. at 317. However, if a State NPDES permit or a section 401
certification is not required, the EPA does not have a role within the
CWA permitting framework to address cross-boundary disputes; similarly,
if a water is not a ``water of the United States,'' then the EPA's
conference convening authorities under section 319(g) would not apply.
In addition, and as described in the Section II.B of this notice, the
CWA provides the EPA with numerous other authorities to provide
technical assistance to States and Tribes to facilitate the management
of non-jurisdictional waters.\44\
---------------------------------------------------------------------------

    \44\ In addition, the notion that categorical federal regulation
of interstate waters is necessary to end water pollution disputes
between States would call into the question the need for CWA section
103 (``Interstate Cooperation and Uniform Laws''), 33 U.S.C. 1253,
which establishes a framework for the Administrator to encourage
cooperation between States for the prevention and control of
pollution.
---------------------------------------------------------------------------

    Under the current framework, the remedies available for cross-
boundary water pollution disputes over non-jurisdictional waters
depends upon the parties and the issues in the case. As an initial
matter, many State programs regulate more waters than are covered by
the federal definition of ``waters of the United States'' and may have
similar notification provisions in place for States affected by a
State-issued NPDES permit. See e.g., Wis. Stat. 281.33 (authorizing
Wisconsin to issue NPDES permits for all waters of the State); Wis.
Admin. Code. 203.03 (providing notice during the NPDES process to other
agencies, including other States potentially affected by the
discharge). This important fact supports the agencies' conclusion that
all States protect their water resources under State law and many have
the ability and expertise to do so in the absence of federal
regulation, as discussed in more detail in the Resource and
Programmatic Assessment for the final rule. As they do today, remedies
for pollution disputes among States that do not implicate CWA sections
319(g), 401, or 402 would likely derive from federal common law under
the Supreme Court's original jurisdiction. See, e.g., Illinois, 406
U.S. at 98-99. Remedies for disputes between a State and a public or
private party would likely derive from State or federal common law and
be heard by State or Federal courts. See id. at 100, 107-08;
International Paper, 479 U.S. at 497-500.

D. Tributaries

1. What are the agencies finalizing?
    In this final rule, the agencies retain ``tributaries'' as a
category of jurisdictional waters subject to CWA jurisdiction. The
final rule defines ``tributary'' to mean a river, stream, or similar
naturally occurring surface water channel that contributes surface
water flow to the territorial seas or traditional navigable waters
(paragraph (a)(1) waters) in a typical year either directly or through
one or more tributaries (paragraph (a)(2) waters), lakes, ponds, and
impoundments of jurisdictional waters (paragraph (a)(3) waters), or
adjacent wetlands (paragraph (a)(4) waters). A tributary must be
perennial or intermittent in a typical year. The alteration or
relocation of a tributary does not modify its jurisdictional status as
long as it continues to satisfy the flow conditions of this definition.
A tributary does not lose its jurisdictional status if it contributes
surface water flow to a downstream jurisdictional water in a typical
year through a channelized non-jurisdictional surface water feature,
through a subterranean river, through a culvert, dam, tunnel, or
similar artificial feature, or through a debris pile, boulder field, or
similar natural feature.
    As discussed in greater detail in Section III.E, the term
``tributary'' includes a ditch that either relocates a tributary, is
constructed in a tributary, or is constructed in an adjacent wetland as
long as the ditch satisfies the flow conditions of the ``tributary''
definition. A ditch can also be a traditional navigable water if it
meets the

conditions of that category. The agencies are excluding all other
ditches from the definition of ``waters of the United States,'' other
than those identified in paragraph (a)(1) or (2) and ditches any
portion of which are constructed in an adjacent wetland that lack
perennial or intermittent flow (meaning they do not satisfy the
``tributary'' definition in paragraph (c)(12)) but that develop
wetlands in all or portions of the ditch that satisfy the ``adjacent
wetlands'' definition in paragraph (c)(1). Excluded ditches may be
subject to regulation under State or tribal law and could potentially
be conveyances of discharges of pollutants from ``point sources''
subject to CWA permitting (see 33 U.S.C. 1362(14)) if they convey
pollutants from a discharger to jurisdictional waters.
    Regardless of the name they are given locally (e.g., creek, bayou,
branch, brook, run), or their size (e.g., discharge volume, width,
depth, stream order), waters that meet the definition of ``tributary''
are jurisdictional under this final rule. Surface features that flow
only in direct response to precipitation, such as ephemeral streams,
swales, gullies and rills, are not tributaries. These features lack the
required perennial or intermittent flow to satisfy the ``tributary''
definition and therefore are not jurisdictional. However, such features
may convey surface water flow from an upstream jurisdictional water to
a downstream jurisdictional water without severing jurisdiction of the
tributary.
    The regulatory status of tributaries has evolved over the last
several decades, resulting in confusion for the regulated community and
regulators alike. Some commenters said that all channels on the
landscape that convey water, regardless of flow regime, should be
subject to CWA regulation, including both natural and artificial
channels. Others asserted that Congress intended to regulate only
traditional navigable waters, and navigable tributaries to those
waters. Some would regulate all ditches, while others would exclude all
ditches from CWA jurisdiction. Some stated that all ephemeral washes
should be regulated, while others viewed ephemeral features as more
like land that is wet after it rains. Some would extend jurisdiction to
perennial rivers and streams and cut off jurisdiction for intermittent
or seasonal waters. Others would regulate intermittent waters based on
a minimum number of days of continuous flow, such as 30, 90, or 185.
Even the Supreme Court has struggled with articulating clear principles
governing which tributaries to traditional navigable waters should be
subject to CWA jurisdiction, as evidenced by the fractured opinion in
Rapanos. What is clear from that opinion, however, is that a majority
of the Court believed the agencies' existing standard for tributaries
at that time raised serious questions regarding the scope of the
agencies' authority under the CWA. See Section II.E.2.
    The agencies proposed a definition for ``tributary'' that they
believed respected their statutory and constitutional authorities,
consistent with principles established in Riverside Bayview, SWANCC,
and Rapanos. Many commenters agreed with the proposal, indicating that
it balanced federal authority over the core waters targeted by Congress
under the CWA with waters that are more appropriately regulated solely
by the States and Tribes. Others argued that the proposed ``tributary''
definition regulated too broadly, preferring instead that the agencies
restrict jurisdiction to perennial tributaries only. Others argued that
the agencies failed to regulate ecologically important ephemeral
reaches and cut off jurisdiction to headwater reaches that are
important to the tributary network.
    The agencies have considered all comments received and have crafted
a final regulatory definition of ``tributary'' designed to adhere to
the legal principles articulated in this notice and that provides a
predictable, implementable regulatory framework. The agencies are
finalizing their proposal to regulate perennial and intermittent
tributaries to traditional navigable waters, while excluding ephemeral
streams from CWA jurisdiction as those features are more appropriately
regulated by States and Tribes under their sovereign authorities.
However, the agencies have modified the final rule to reduce the
instances in which natural and artificial features and structures sever
jurisdiction of upstream waters, as discussed in Section III.A.3 and in
more detail below. The agencies conclude that interpreting upstream
waters that contribute surface water flow in a typical year to a
paragraph (a)(1) water to be part of the regulated tributary network
better balances the CWA's objective in section 101(a) with the need to
respect State and tribal authority over land and water resources as
mandated by Congress in section 101(b).
2. Summary of Final Rule Rationale and Public Comment
    The definition of ``tributary'' in the final rule reflects the
authority granted by Congress to regulate navigable waters and the
interconnected nature of the tributary system, as well as the ordinary
meaning of the term ``waters.'' In addition, the agencies are adhering
to their constitutional and statutory authority regarding the role of
the Federal government and limits on its authority to regulate the use
of land and waters within State and tribal boundaries, and their
intention to establish a clear and easily implementable definition. The
definition of ``tributary'' in the final rule sets a boundary on the
scope of the regulation to ensure that it is consistent with the role
of the Federal government under the Constitution and the CWA. As the
Supreme Court recognizes, States traditionally exercise ``primary power
over land and water use,'' SWANCC, 531 U.S. at 174. The Federal
government should avoid pressing against the outer limits of its
authority when doing so would infringe upon the traditional rights and
responsibilities of States to manage their own waters. See id. at 172-
73 and supra Section II.E.
    Under this final rule, a tributary must be perennial or
intermittent, and it must contribute surface water flow in a typical
year to a traditional navigable water or territorial sea directly or
through one or more waters identified in paragraph (a)(2), (3), or (4)
(generally referred to as ``paragraph (a)(2) through (4) waters'' or
``a paragraph (a)(2) through (4) water'' in this notice), or through
one or more of the features described in Section III.A.3. The
``tributary'' category includes waters that, due to their relatively
permanent flow classifications and their contribution of surface water
flow to paragraph (a)(1) waters, are appropriately regulated under the
Commerce Clause powers that Congress exercised when enacting the CWA.
The agencies have concluded that their regulatory authority under the
CWA and Supreme Court precedent is most appropriately interpreted to
encompass the perennial and intermittent flow classifications provided
in the definition of ``tributary,'' and that this approach also
balances the regulation of the Federal government with the authority of
States and Tribes to more appropriately regulate certain waters within
their jurisdiction, such as ephemeral streams. The agencies have also
concluded that this definition effectively furthers both the objective
of the Act to ``restore and maintain the chemical, physical, and
biological integrity of the nation's waters'' and the ``policy of
Congress to recognize, preserve, and protect the primary
responsibilities and rights of States to prevent, reduce, and eliminate
pollution [and] to plan for the development and

use (including restoration, preservation, and enhancement) of land and
water resources . . . .'' 33 U.S.C. 1251(b); see also Rapanos, 547 U.S.
at 737 (Scalia, J., plurality). The agencies' approach to defining
``tributary'' is also intended to ensure that federal regulatory
jurisdiction does not intrude upon State, tribal, and local control of
land and water use decisions. See Rapanos, 547 U.S. at 738 (Scalia, J.,
plurality) (``Regulation of land use, as through the issuance of the
development permits . . . is a quintessential state and local
power.''). With this final definition, the agencies seek to avoid
``impairing or in any manner affecting any right or jurisdiction of the
States with respect to the waters (including boundary waters) of such
States.'' 33 U.S.C. 1370.
    A clear regulatory line between jurisdictional and excluded waters
has the additional benefit of being less complicated than prior
regulatory regimes that required a case-specific significant nexus
analysis. Ephemeral features, such as dry washes and arroyos, that lack
the perennial or intermittent flow necessary to satisfy the
``tributary'' definition under this final rule are excluded from the
definition. Although the agencies are not regulating features that flow
only in direct response to precipitation, certain ephemeral features
can convey surface water flow that is sufficient to maintain the
jurisdictional status of the upstream tributary reach, as discussed in
Section III.A.3. States and Tribes may also address ephemeral features
as ``waters of the State'' or ``waters of the Tribe'' under their own
laws to the extent they deem appropriate, as envisioned under section
101(b) of the CWA. In addition, an ephemeral feature may convey a
discharge of pollutants from a point source to a water of the United
States. See Rapanos, 547 U.S. at 743-44 (Scalia, J., plurality).
    Some commenters stated that the agencies' proposal for tributaries
is not supported by science and is inconsistent with the CWA and
judicial precedent. The agencies disagree. As discussed in the preamble
to the proposed rule, the agencies relied on the available science to
help inform where to draw the line of federal jurisdiction over
tributaries, consistent with their statutory authorities. See 84 FR
4175 (``This proposed definition [of tributary] is also informed by the
science.'') As noted in that preamble, while the SAB found that the
draft Connectivity Report ``provides strong scientific support for the
conclusion that ephemeral, intermittent, and perennial streams exert a
strong influence on the character and functioning of downstream waters
and that tributary streams are connected to downstream waters,'' the
SAB stressed that ``the EPA should recognize that there is a gradient
of connectivity.'' SAB Review at 3. The SAB recommended that ``the
interpretation of connectivity be revised to reflect a gradient
approach that recognizes variation in the frequency, duration,
magnitude, predictability, and consequences of physical, chemical, and
biological connections.'' Id. at 2 (emphasis added). To describe the
``connectivity gradient'' and the probability that impacts occurring
along the gradient will be transmitted downstream, the SAB developed a
figure as part of its review of the Draft Connectivity Report. See id.
at 54 figure 3. The figure illustrates the connectivity gradient and
potential consequences between perennial, intermittent, and ephemeral
streams and downstream waters and depicts a decreased ``probability
that changes . . . will be transmitted to downstream waters'' at flow
regimes less than perennial and intermittent. Id. While the SAB stated
that ``at sufficiently large spatial and temporal scales, all waters
and wetlands are connected,'' it found that ``[m]ore important are the
degree of connection (e.g., frequency, magnitude, timing, duration) and
the extent to which those connections affect the chemical, physical,
and biological integrity of downstream waters.'' Id. at 17.
    The SAB, however, recognized that ``[t]he Report is a science, not
policy, document that was written to summarize the current
understanding of connectivity or isolation of streams and wetlands
relative to large water bodies such as rivers, lakes, estuaries, and
oceans.'' id. at 2. ``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.'' 80 FR 37065. And in issuing the
2015 Rule, the agencies stated, ``the science does not provide a
precise point along the continuum at which waters provide only
speculative or insubstantial functions to downstream waters.'' Id. at
37090. Thus, the agencies use the Connectivity Report to inform certain
aspects of the revised definition of ``waters of the United States,''
such as recognizing the ``connectivity gradient'' and potential
consequences between perennial, intermittent, and ephemeral streams and
downstream waters within a tributary system. The ``tributary''
definition that the agencies are finalizing, which takes into
consideration the connectivity gradient, ``rests upon a reasonable
inference of ecological interconnection'' between those tributaries and
paragraph (a)(1) waters. 547 U.S. at 780 (Kennedy, J., concurring in
the judgment). The agencies acknowledge that science alone cannot
dictate where to draw the line between Federal and State waters, as
those are legal distinctions that have been established within the
overall framework and construct of the CWA.
    The agencies also relied on scientific principles, as appropriate
and within the agencies' statutory limits, to inform several other
aspects of this final rule, including, for example, how the agencies
define the flow classifications (perennial, intermittent, ephemeral)
used throughout the regulation, the incorporation of inundation and
flooding to create surface water connections, and the use of the
typical year concept that relies upon a large body of precipitation and
other climatic data to inform what may be within a normal range for a
particular geographic region. The agencies will also rely on science to
implement the final rule, such as with the development of tools and
scientific-based approaches to identify flow classification and typical
year conditions.
    Thus, contrary to the assertions of some commenters, the agencies'
decisions in support of this final rule have been informed by science.
The agencies therefore agree with other commenters who stated that the
agencies appropriately balanced science, policy, and the law when
crafting the proposed rule. But to be clear, as discussed in the
preamble to the proposed rule, 84 FR 4176, and in Section II.E of this
notice, science cannot dictate where to draw the line between Federal
and State or tribal waters, as those are legal distinctions that have
been established within the overall framework and construct of the CWA.
The definition of ``waters of the United States'' must be grounded in a
legal analysis of the limits on CWA jurisdiction reflected in the
statute and Supreme Court guidance.
    By defining perennial and intermittent tributaries of traditional
navigable waters as jurisdictional and ephemeral features as non-
jurisdictional, the agencies balance Congress' intent to interpret the
term ``navigable waters'' more broadly than the classical understanding
of that term, see Riverside Bayview, 474 U.S. at 133, with the fact
that nothing in the legislative history of the Act ``signifies that
Congress intended to exert anything more than its commerce power over
navigation.'' SWANCC, 531 U.S. at 168 n.3. The final rule's definition
of ``tributary'' is also consistent with the Rapanos plurality's
position that `` `the

waters of the United States' include only relatively permanent,
standing, or flowing bodies of waters . . . as opposed to ordinarily
dry channels . . . or ephemeral flows of water.'' Rapanos, 547 U.S. at
732-33 see also id. at 736 n.7 (``[R]elatively continuous flow is a
necessary condition for qualification as a `water,' not an adequate
condition'' (emphasis in original)). Perennial waters, by definition,
are permanent. And while the plurality did note that waters of the
United States do not include ``ordinarily dry channels through which
water occasionally or intermittently flows,'' id. at 733, the plurality
would ``not necessarily exclude 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); compare id. at 770
(Kennedy, J., concurring in the judgment) (``an intermittent flow can
constitute a stream . . . while it is flowing . . . [i]t follows that
the Corps can reasonably interpret the Act to cover the paths of such
impermanent streams''). The agencies note that intermittent waters may
occur seasonally, for example, during times when groundwater tables are
elevated or when snowpack runoff produces relatively permanent flow,
returning on an annual basis in known, fixed geographic locations.
    By defining ``tributary'' as perennial or intermittent rivers and
streams that contribute surface water flow to traditional navigable
waters or the territorial seas in a typical year, the agencies are
establishing that a mere hydrologic connection cannot provide the basis
for CWA jurisdiction; the bodies of water must be ``geographical
features'' (i.e., rivers and streams) that are ``relatively permanent''
(i.e., perennial or intermittent) and that contribute surface water
flow to a traditional navigable water or the territorial seas in a
typical year. Rapanos, 547 U.S. at 732. This requirement is informed by
Rapanos, wherein the plurality determined that the phrase ``the waters
of the United States'' ``cannot bear the expansive meaning that the
Corps would give it,'' id. at 732, and challenged the notion that
``even the most insubstantial hydrologic connection may be held to
constitute a `significant nexus.' '' Id. at 728. Similarly, Justice
Kennedy noted, ``mere hydrologic connection should not suffice in all
cases; the connection may be too insubstantial for the hydrologic
linkage to establish the required nexus with navigable waters as
traditionally understood.'' Id. at 784-85. The agencies believe that
the requirement that a tributary be perennial or intermittent and be
connected to a traditional navigable water is reasonable and reflects
the plurality's description of a `` `wate[r] of the United States' ''
as ``i.e., a relatively permanent body of water connected to
traditional interstate navigable waters.'' Id. at 742.
    Under the proposed definition of ``tributary,'' an artificial or
natural ephemeral feature would have severed jurisdiction upstream of
the feature, because the waterbody would not contribute surface water
to a paragraph (a)(1) water on a perennial or intermittent basis.
Several commenters supported this approach, noting that waters above
ephemeral breaks are more appropriately subject to State or tribal
jurisdiction. Others criticized the approach as too restrictive and
raised concerns regarding the importance of those upstream waters to
the tributary system. The agencies recognize that the proposed rule's
treatment of ephemeral features would have severed jurisdiction for
certain relatively permanent bodies of water that are regularly
``connected to'' traditional navigable waters in a typical year via
channelized surface water flow through those features. The final rule
has been modified to address these concerns regarding ephemeral breaks
between two relatively permanent waters while remaining faithful to the
text, structure, and legislative history of the CWA and Supreme Court
guidance.
    As discussed in Section III.A.3, the final rule provides that
channelized non-jurisdictional surface water features do not sever
jurisdiction of upstream perennial or intermittent waters so long as
they convey surface water from such upstream waters to downstream
jurisdictional waters in a typical year. The use of ``channelized'' in
this context generally indicates features with a defined path or
course, such as a ditch or the bed of an ephemeral stream. The flow
must be channelized in the sense of being discrete and confined to a
channel, as opposed to diffuse, non-channelized flow. Channelized non-
jurisdictional surface water features are generally continuously
present on the landscape as geomorphic features and may regularly
``connect'' the upstream tributary to the downstream jurisdictional
water such that those waters can mix and become indistinguishable in a
typical year. This may occur, for example, where managed water systems
alter the flow classification of a perennial or intermittent tributary
to ephemeral but the perennial or intermittent flow returns farther
downstream. It could also occur as a result of natural conditions, such
as a tributary that becomes a losing stream for a reach, but then
becomes perennial again downstream of the losing reach. The losing
reach could occur because of water infiltrating into the ground and
recharging groundwater, where the water table is below the bottom of
the channel bed.
    The final rule also allows for other types of artificial or natural
features, such as dams or boulder fields, which may maintain
jurisdiction so long as they convey surface water flow from an upstream
tributary to a downstream jurisdictional water in a typical year. The
agencies have determined in this final rule that such conditions do not
sever jurisdiction for the upstream reach of the tributary if a
channelized non-jurisdictional surface water feature conveys surface
water flow to a downstream jurisdictional water in a typical year. The
agencies have concluded that water flowing through features such as
dams or boulder fields can sustain a regular and predictable surface
water connection between upstream and downstream waters and therefore
can maintain jurisdiction between such waters. In all cases, however,
the excluded or ephemeral feature remains non-jurisdictional. Certain
other excluded features are incapable of providing channelized surface
flow (e.g., groundwater, diffuse stormwater run-off, or directional
sheet flow over upland) and therefore sever jurisdiction upstream of
such excluded features.
    The Supreme Court has not spoken directly to the question of
whether an ephemeral reach along or downstream of an otherwise
jurisdictional tributary severs jurisdiction, and the agencies believe
that the final rule appropriately reflects their statutory authority.
In particular, the plurality decision in Rapanos emphasized that
jurisdictional waters themselves must be relatively permanent and
connected to traditional navigable waters, 547 U.S. at 742, but did not
specify the type of connection necessary between the relatively
permanent waters and downstream traditional navigable waters. Justice
Kennedy's opinion stated that the Corps could identify by regulation
categories of tributaries based on ``their volume of flow (either
annually or on average), their proximity to navigable waters, or other
relevant considerations,'' id. at 780-81, but fails to provide further
guidance. The agencies conclude that the final rule appropriately
reflects and balances these general guiding principles by exercising
jurisdiction over perennial and intermittent tributaries but not
ephemeral streams

and dry washes, while under certain circumstances allowing such
channelized features to maintain jurisdiction between upstream and
downstream more permanent waters.
    Some commenters agreed with the agencies' proposal that ephemeral
reaches should sever jurisdiction of upstream waters because those
waters no longer have a continuous hydrologic surface connection of
relatively permanent flow to a downstream jurisdictional water. Other
commenters stated that the proposed definition of ``waters of the
United States'' was inconsistent in that some forms of natural or
artificial features could connect upstream tributaries with downstream
jurisdictional waters, whereas ephemeral reaches would have severed
jurisdiction of upstream perennial and intermittent streams. In
addition, many commenters raised concerns about implementing a
definition of ``tributary'' in which an ephemeral feature would sever
jurisdiction of upstream reaches, indicating that it may be difficult
to apply in the field. Commenters also stated that if ephemeral
features severed jurisdiction of perennial and intermittent waters
upstream, many waters in certain regions, such as the arid West, would
be non-jurisdictional. Some commenters expressed concern that the
proposed definition would place a burden on project applicants to
identify and anticipate such ephemeral breaks to avoid potential
responsibility for compensatory mitigation of upstream losses. The
agencies have modified the final rule language in a manner that
addresses these concerns. Under the final rule, tributaries that
contribute surface water flow to a downstream jurisdictional water in a
typical year through certain natural features (such as debris piles or
boulder fields) or artificial features (such as culverts or dams) are
tributaries, even though these features may result in an interruption
in the surface water channel. A perennial or intermittent tributary
above the natural or artificial feature does not lose its
jurisdictional status as long as the natural or artificial feature
continues to convey surface water flow from the upstream reach to a
downstream jurisdictional water in a typical year.
    Commenters also requested clarification on whether a natural
feature through which a tributary flows could be considered a
jurisdictional feature as part of the tributary itself, such as a
boulder field or subterranean river. Natural or artificial features
that do not satisfy the surface water flow conditions of the
``tributary'' definition are not tributaries under this rule, even if
they convey surface water flow from upstream relatively permanent
waters to downstream jurisdictional waters in a typical year. See
Section III.A.3 for additional discussion.
    Some commenters asked for clarification on whether tributaries are
viewed as reaches or as an entire network. The agencies are using the
term ``reach'' in this preamble to the final rule to mean a section of
a stream or river along which similar hydrologic conditions exist, such
as discharge, depth, area, and slope.\45\ If a perennial tributary
becomes intermittent and then ephemeral and then perennial again, it
may be viewed as four separate reaches (e.g., perennial reach,
intermittent reach, ephemeral reach, perennial reach), especially if
they also share other similarities with respect to depth, slope, or
other factors. In general, a reach can be any length of a stream or
river, but the agencies are clarifying for implementation purposes that
such length is bounded by similar flow characteristics.
---------------------------------------------------------------------------

    \45\ See Connectivity Report at A-10, defining ``reach'' as ``a
length of stream channel with relatively uniform discharge, depth,
area, and slope.'' A similar definition is used by the USGS, at
https://www.usgs.gov/faqs/what-a-reach.
---------------------------------------------------------------------------

    Commenters suggested that flow classification and jurisdictional
status could be determined based on the flow in the majority of a reach
(i.e., whether it is perennial, intermittent, and ephemeral), which
they said would be simpler than differentiating various segments from
the broader stream reach. The agencies are not determining flow
classification using the majority of the reach. Under the Rapanos
Guidance, a tributary ``reach'' was identified by a stream order
classification system where the relevant reach was used for purposes of
a significant nexus determination. However, stream order is not
directly relevant to stream and river jurisdiction under this final
rule, and instead flow classification is a key aspect in determining
the jurisdictional status of a tributary. The agencies conclude that
such an approach is easier to implement in light of the final rule's
``tributary'' definition and is more consistent with the legal and
scientific foundation for the rule. Along the length of a tributary,
the flow classification may fluctuate, and the points at which flow
classifications change are the points at which a reach is bounded. If a
tributary flows through a non-jurisdictional ephemeral reach to
downstream jurisdictional waters, the point at which a tributary
becomes ephemeral may fluctuate upstream and downstream in a typical
year based on climatic conditions, changes in topography and
surrounding development, water input, and water withdrawals. When such
a transition zone of flow classification occurs, the agencies will use
best professional judgment and various tools to identify where the
change in flow classification occurs. The agencies have historically
implemented comparable approaches at transition zones, for example with
the identification of the extent of tidal influence (also referred to
as the head of tide). This generally occurs where a river flows into
tidal waters and the agencies must identify the farthest point upstream
where a tributary is affected by tidal fluctuations in order to
determine which lateral extent to apply for the limits of jurisdiction
(i.e., high tide line or ordinary high water mark), permitting
requirements, and similar factors. There is generally not a hard
demarcation distinguishing where a waterbody ceases to be tidal, so the
agencies must use best professional judgment utilizing all available
information and tools which may assist in making the determination. See
Section III.B.3 for additional information.
    Many commenters recommended that tributaries that were altered or
relocated should remain tributaries. The agencies agree with those
comments and, consistent with the proposal, have included that
provision in the final rule. Many commenters expressed concern about
the challenges of implementing a flow-based ``tributary'' definition
where many systems have been modified by human actions. Some commenters
also stated that the use of ``naturally occurring'' in the proposed
``tributary'' definition was unclear and questioned how it would apply
to modified systems. The agencies disagree with the proposition that
identifying flow conditions would be challenging in modified systems.
An altered tributary is one in which the flow or geomorphic conditions
have been modified in some way, for example, by straightening a sinuous
tributary, adding concrete or riprap to stabilize the banks of a
tributary, reducing flow conditions from perennial to intermittent flow
due to water withdrawals, or widening or adding physical features (such
as riffle/pool complex restoration or check dams) to the tributary to
reduce the velocity of flow. A relocated tributary is one in which an
entire portion of the tributary may be moved to a different location,
as when a tributary is rerouted around a city center to protect it from
flooding or around a mining complex to enable extraction of
commercially

valuable minerals. To be considered a tributary, such features must
continue to meet the flow conditions of the ``tributary'' definition.
The agencies conclude that identifying flow conditions in these
features would be no more challenging than identifying flow conditions
in other tributaries, which the agencies have been doing to apply the
Rapanos Guidance since 2008. In a relocated tributary, the reach that
has been relocated may meet the definition of ``ditch'' or may be
colloquially called a ditch, which is why, for simplicity and clarity,
the agencies have included these ditches in the definition of
``tributary.'' The agencies also believe that retaining jurisdiction
over the relocated tributary is consistent with its legal authorities
and the agencies' treatment of impoundments of jurisdictional waters
(see Section III.F), which may alter the course or form of a water of
the United States but maintains sufficient surface water connection to
a traditional navigable water in a typical year.
    Some commenters requested clarification on how water diversions may
affect the jurisdictional status of tributaries. A water diversion that
completely reroutes a tributary through a tunnel would be considered an
artificial feature that would not sever jurisdiction under this final
rule. The tunnel itself is not a tributary under the rule, however,
because it is not a surface water channel. This final rule clarifies
that jurisdiction applies based on current flow classification in a
typical year. When completing jurisdictional determinations in managed
systems, just as in natural systems, the agencies will consider whether
features meet the flow conditions of the ``tributary'' definition in a
typical year. Managed systems are jurisdictional as long as they
satisfy the definition of ``tributary,'' including the flow conditions.
If a stream is ephemeral in a typical year due to managed water
withdrawals, the feature is an excluded ephemeral stream. Tributaries
that have been altered via water management systems, or whose
morphology has been altered in some manner, maintain their tributary
status as long as they are perennial or intermittent and contribute
surface water flow to the territorial seas or a traditional navigable
water in a typical year.
    Under the pre-existing regulatory regime (recodified in the 2019
Rule), the agencies conducted a significant nexus analysis for certain
types of waters referred to as ``non-relatively permanent waters,''
which includes ephemeral features and some intermittent streams. See
Rapanos Guidance at 7 (`` `[R]elatively permanent' waters do not
include ephemeral tributaries which flow only in response to
precipitation and intermittent streams which do not typically flow
year-round or have continuous flow at least seasonally. However, CWA
jurisdiction over these waters will be evaluated under the significant
nexus standard[.]''). The definition of ``tributary'' in the final rule
replaces existing procedures that utilize a case-specific ``significant
nexus'' analyses of the relationship between a particular stream and
downstream traditional navigable water. The agencies are eliminating
this case-specific ``significant nexus'' analysis by providing a clear
definition of ``tributary'' that is easier to implement. Justice
Kennedy's ``significant nexus'' test for wetlands adjacent to
nonnavigable tributaries was needed only ``absent more specific
regulations,'' Rapanos, 547 U.S. at 782, because ``the breadth of [the
Corps' existing tributary] standard . . . seems to leave wide room for
regulation of drains, ditches, and streams remote from any navigable-
in-fact water and carrying only minor water volumes towards it'' and
thus ``precludes its adoption as the determinative measure of whether
adjacent wetlands are likely to play an important role in the integrity
of an aquatic system comprising navigable waters as traditionally
understood.'' Id. at 781. In light of the ``more specific [tributary]
regulations'' finalized in this rule, the agencies are eliminating the
case-specific significant nexus review through categorical treatment,
as ``waters of the United States,'' of all tributaries with perennial
or intermittent flow that contribute surface water flow to downstream
navigable-in-fact waters in a typical year. See id. at 780-81 (Kennedy,
J., concurring in the judgment) (``Through regulations or adjudication,
the Corps may choose to identify categories of tributaries that, due to
their volume of flow (either annually or on average), their proximity
to navigable waters, or other relevant considerations, are significant
enough that wetlands adjacent to them are likely, in the majority of
cases, to perform important functions for an aquatic system
incorporating navigable waters.'') (emphasis added). In doing so, the
agencies believe they avoid interpretations of the CWA that raise
significant constitutional questions. See id. at 738 (plurality)
(``Even if the term `the waters of the United States' were ambiguous as
applied to channels that sometimes host ephemeral flows of water (which
it is not), we would expect a clearer statement from Congress to
authorize an agency theory of jurisdiction that presses the envelope of
constitutional validity.'').
    The agencies recognize that this is a departure from prior
positions of the Federal government. The agencies also recognize that
prior to the finalization of this rule, some courts applied the
significant nexus standard articulated in Justice Kennedy's opinion as
the exclusive test of CWA jurisdiction over certain waters. As
described in detail in Section II.E, the agencies have analyzed the
text, structure, and legislative history of the CWA in light of Supreme
Court guidance and conclude that this final rule incorporates important
aspects of Justice Kennedy's opinion, together with those of the
plurality, to craft a clear and implementable definition that stays
within their statutory and constitutional authorities.
    The final ``tributary'' definition contains no flow volume
requirement, but only a requirement of perennial or intermittent flow
and a contribution of surface water flow to a paragraph (a)(1) water in
a typical year. The agencies believe that establishing a specific flow
volume requirement for all tributaries is inappropriate, given the wide
spatial and temporal variability of flow volume in rivers and streams
across the country. While the definition may in certain instances
assert jurisdiction over bodies of water contributing ``the merest
trickle,'' 547 U.S. at 769 (Kennedy, J., concurring in the judgment),
to a traditional navigable water during certain times of the year, the
agencies conclude that such bodies are `` `waters' in the ordinary
sense of containing a relatively permanent flow'' regardless of flow
volume. Id. at 757 (Scalia, J., plurality).
    Some commenters suggested that using stream flow volumes rather
than flow duration classifications for the definition of ``tributary''
would be easier to implement. The agencies disagree with this
suggestion based on their experience. In 1977, the Corps proposed to
use flow volumes (i.e., five cubic feet per second) to define
``headwaters'' in the definition of ``waters of the United States,''
and instead finalized the use of flow volumes for implementation of
their general permit program. 42 FR 37129 (July 19, 1977). Stream flow
volume is challenging to measure directly, in particular in an
intermittent stream where flow is not always present and may require
multiple field-based measurements that can make implementation
inefficient and result in delays in making a jurisdictional
determination. While flow duration classifications may also require
field measurements, in certain instances

remote tools, such as remote sensing and aerial photography, can be
used to observe presence or absence of flow and identify flow duration
classifications, but cannot also assess flow volumes. In addition, the
agencies have not identified a reasonable or appropriate rationale or
justification for specific flow volumes that should establish
jurisdiction given the broad nationwide applicability of the final
rule.
    A few commenters requested a flow duration metric (e.g., 30, 90, or
185 days) to determine a jurisdictional tributary. Several commenters
recommended the agencies adopt a definition of ``intermittent'' that
contains the requirement of continuous flow for a specific duration,
such as ``at least one month of the calendar year'' to provide
certainty for determining flow classification. See e.g., 30 CFR 710.5
(definition of ``intermittent'' used in a U.S. Department of Interior
regulation). Several commenters also recommended a regionalized
approach to flow classification. The agencies have finalized an
approach that considers streamflow duration in the flow classification
definitions generally (e.g., ``flowing continuously year-round,''
``flowing continuously during certain times of the year and more than
in direct response to precipitation,'' and ``flowing . . . only in
response to precipitation'') but without specifying an exact number of
days of flow. The agencies are not providing a specific duration (e.g.,
the number of days, weeks, or months) of surface flow that constitutes
intermittent flow, as the time period that encompasses intermittent
flow can vary widely across the country based upon climate, hydrology,
topography, soils, and other conditions. The ``typical year'' construct
captures that variability, however, and provides for regional and local
variations in the actual application of a uniform nationwide
definition. The agencies acknowledge that an approach utilizing a
specific duration would provide for enhanced national consistency, but
it would also undermine the regionalized implementation of intermittent
tributaries as provided for under this final rule. Some commenters
cautioned the agencies against treating intermittent streams similarly
across the country based on a prescriptive flow duration metric, as
intermittent streams in the arid West are fundamentally different from
intermittent streams in the Southeast, for example. A specific duration
requirement would also be challenging to implement--even landowners
familiar with their properties may not know the number of days a stream
flows per year.
    Other commenters recommended the use of physical indicators of
flow, such as ordinary high water mark and bed and banks, which could
be regionalized for a field-based approach. These commenters stated
that physical indicators can be more readily observable and can
indicate flows of sufficient magnitude and duration to qualify as a
tributary. The agencies disagree with these comments and conclude that
physical indicators of flow, absent verification of the actual
occurrence of flow, may not accurately represent the flow
classifications required for tributaries under this rule. See, e.g.,
547 U.S at 781 (Kennedy, J., concurring in the judgment) (expressing
concerns that a the Corps' existing tributary standard based, in part,
on the ``possess[ing]'' of ``an ordinary high water mark, defined as a
`line on the shore established by the fluctuations of water and
indicated by [certain] physical characteristics,' . . . seems to leave
wide room for regulation of drains, ditches, and streams remote from
any navigable-in-fact water and carrying only minor water volumes
towards it''). For example, ephemeral streams can have an ordinary high
water mark and bed and banks, which would not allow for the agencies or
the public to distinguish between a non-jurisdictional ephemeral stream
and a jurisdictional intermittent or perennial tributary using those
physical indicators. Ephemeral streams in the arid West, for example,
may have ordinary high water marks that were incised years ago
following a single large storm. It makes more practical sense for a
feature to be first assessed as a tributary, after which the lateral
extent of that tributary can be identified using the ordinary high
water mark.
    Physical indicators, however, may be one line of evidence the
agencies could use to evaluate whether a stream meets the flow
requirements to be a tributary under this definition. These indicators
could be regionalized to obtain a practical field-based approach for
identifying the flow classification of a stream which is a required
component of identifying a tributary. Such physical indicators are
further discussed in Section III.D.3 of this notice. In addition, the
agencies cannot always rely on field-based physical indicator methods--
for example, when evaluating a site at a time that does not meet the
definition of ``typical year.'' In some instances, completing a desktop
determination with remote tools may supplement or substitute for field-
based indicators.
3. How will the agencies implement the final rule?
    The agencies will employ many different methods and tools to
identify and determine whether a feature meets the definition of
``tributary'' under this final rule. A few commenters recommended that
the agencies identify a variety of methods which may be employed to
identify flow classifications, and that such methods involve tools
readily available to a typical landowner. Methods and tools used by the
agencies are generally available for the public to use so that they can
make an informed decision about how to proceed with requests for
jurisdictional determinations or authorization for activities under the
CWA. The agencies believe that there are numerous cases where an
informed decision can save valuable time and money by avoiding
unnecessary jurisdictional determination requests. This can be done,
for example, where landowners are familiar with the water features on
their property and know that they only flow in response to a rain
event, or that an isolated wetland in the middle of a ranch is not
flooded by a nearby perennial river in a typical year. However, in
cases where a member of the general public makes an informed decision
to not request a jurisdictional determination and discharges pollutants
into a waterbody that is, in fact, jurisdictional without required
permits, the individual could be subject to the agencies' enforcement
authorities under the CWA.
    One of the first steps in determining whether a feature is a
tributary is to identify relevant features on the landscape, such as
rivers, streams, or similar naturally occurring surface water channels,
as well as ditches. Field work to include direct observation and other
reliable methods can indicate the existence of a tributary, such as
stream gage data, elevation data, historic or current water flow
records, flood predictions, statistical evidence, aerial imagery, and
USGS maps.
    Another step in determining whether a feature is a tributary is to
identify whether the feature contributes surface water flow to a
paragraph (a)(1) water either directly or through one or more paragraph
(a)(2) through (4) waters in a typical year. The agencies intend to use
several sources to identify the flow path of a potential tributary to
determine whether surface water flow is being contributed eventually to
a paragraph (a)(1) water. The agencies can use USGS maps, State and
local knowledge or maps, aerial photography, or other remote sensing
information so long as

the tools the agencies use have been verified to be reliable (see,
e.g., Section IV of this notice regarding limitations of existing
aquatic resource mapping datasets) to assess a feature's flow path. The
agencies can also use available models, including models developed by
Federal, State, tribal and local governments, academia, and the
regulated community. One such model includes the ``Flow (Raindrop)
Path'' GIS tool which allows the user to click a point on a map to
signify a falling raindrop on that point, after which a flow path is
drawn to estimate where the raindrop may flow, eventually making its
way to the ocean if the tributary network allows for it (https://streamstats.usgs.gov/ss/). The StreamStats tool may potentially be used
to identify the flow path from the subject water to the downstream
paragraph (a)(1) water using the ``Flow (Raindrop) Path'' component of
the tool. These tools could be used in conjunction with field
observations, data, and other desktop tools to evaluate whether a
specific point on a potential tributary may have a surface water
connection to a downstream paragraph (a)(1) water in a typical year.
    In addition to identifying the presence of rivers, streams, or
similar naturally occurring surface water channels which contribute
surface water flow to a downstream paragraph (a)(1) water, the agencies
must assess the feature's flow classification. The agencies have
substantial experience using visual hydrologic observations, field data
and indicators, and remote tools to determine flow classification.
Commenters expressed several key concerns about the flow classification
concept. Some commenters noted that there is no established or
universally accepted methodology to identify flow classification. The
agencies agree that there is no universally accepted methodology;
however, scientists, environmental consultants, and other water
resource professionals, including agency staff, have used the terms
``perennial,'' ``intermittent,'' and ``ephemeral'' for decades in the
field. Indeed, the agencies have used these terms to evaluate the
jurisdictional status of waters for more than a decade, in accordance
with the 2008 Rapanos Guidance.\46\ More recently, the Corps has
applied these terms in its Nationwide Permit Program (NWP). See 82 FR
1860, 2005 (January 6, 2017). The terms are used in the NWP in a manner
similar to the definitions in this final rule, but in the NWP the terms
adhere more closely to the generally-accepted scientific definitions
that focus on groundwater rising above the bed of the stream channel as
differentiating between ephemeral features and perennial and
intermittent waters. See id. at 2006. For the reasons explained in
Section III.A.2, however, the agencies have finalized definitions for
the three flow classification terms in this rule that better align with
the scope of CWA jurisdiction, while improving clarity of the rule and
transparency of the agencies' implementation. These flow classification
terms can be implemented using readily available resources in addition
to visual assessments.
---------------------------------------------------------------------------

    \46\ Under the Rapanos Guidance, the agencies applied a
different jurisdictional test based upon a tributary's flow regime.
``The agencies will assert jurisdiction over relatively permanent
non-navigable tributaries of traditional navigable waters without a
legal obligation to make a significant nexus finding.'' Rapanos
Guidance at 7. Relatively permanent tributaries were described in
the guidance as tributaries that ``typically flow year-round or have
continuous flow at least seasonally (e.g., typically three
months)[.]'' Id. at 1. At the same time, the guidance established
that `` `relatively permanent' waters do not include ephemeral
tributaries which flow only in response to precipitation and
intermittent streams which do not typically flow year-round or have
continuous flow at least seasonally. . . . CWA jurisdiction over
these waters will be evaluated under the significant nexus [test.]''
Id. at 7. The agencies also note that in June 2009, the Corps added
a classification code ``R6,'' entitled ``Riverine Ephemeral,'' to
identify ephemeral aquatic resources. The Corps created the ``R6''
code to provide clarity to field staff when identifying ephemeral
waters for entry into the ORM2 database. See https://www.spa.usace.army.mil/Portals/16/docs/civilworks/regulatory/Bulk%20Upload/Bulk%20Data%20Cowardin.pdf.
---------------------------------------------------------------------------

    Some commenters expressed concern that the information needed to
determine flow classification would require a high burden of proof and
would result in significantly longer processing times for
jurisdictional determinations. The agencies will continue to bear the
burden of proof for determinations and, as noted above, have already
implemented a version of the flow classification concept under the
Rapanos Guidance and the Corps' NWP. The agencies disagree with the
suggestion that the use of these flow classifications will result in a
lengthier process for jurisdictional determinations. With the clear and
categorical definition as to the scope of CWA jurisdiction included in
this final rule, the elimination of the significant nexus determination
requirement for tributaries, the use of existing tools, and the
development of new tools, jurisdictional determinations for tributaries
should be more efficient under this final rule than under prior
regulatory regimes.
    Some commenters also noted that the data and resources identified
in the preamble to the proposed rule to evaluate flow classification
have limited availability. The agencies agree that some data and
resources have significant limitations and other national-level tools
and methods may not be readily available or accurate for use in many
areas of the country, including in rural or remote areas and in heavily
modified systems. The agencies will continue to rely on local
knowledge, information provided by the landowner, and local, State, and
tribal agencies, and a variety of additional tools and resources to
evaluate flow classification in such systems. The final rule language
on flow classifications allows for consistent implementation approaches
for modified systems and more natural systems.
    Visual observations of surface hydrology are a useful primary
method to identify flow classifications. The agencies expect that
landowners will often have sufficient knowledge to understand how water
moves through their properties, although visual observations could be
conducted by Federal, State, tribal and local agencies, and other
public or private organizations, as appropriate. The agencies also
recognize that a single visual observation may not always be sufficient
to accurately determine flow classification, and visual observations
should generally be combined with precipitation and other climate data
and expected flow seasonality to accurately determine flow
classification. For example, observing flow directly after a large
rainfall or observing no flow during a dry season may not be good
indicators of a stream's typical flow classification.
    In addition to visual observations of surface hydrology, the
agencies may use field-based indicators and tools as another line of
evidence to determine flow classification. Some commenters recommended
using local flow data collected by government agencies, where
available, and the agencies acknowledge that this could be a useful
source of data. The agencies have also used methods such as trapezoidal
flumes and pressure transducers for measuring surface flow. During the
public comment period, many commenters mentioned the availability of
existing rapid, field-based, streamflow duration assessment methods
that have been developed for use across various States or geographic
regions and suggested that these existing methods could be used to
distinguish between streams with perennial, intermittent, and ephemeral
flow classifications. Many commenters also recommended that the
agencies develop

similar methods for use across the United States, with input from the
public and the scientific community.
    The agencies recognize that some States have developed streamflow
duration assessment methods (SDAMs) that use physical and biological
field indicators, such as the presence of hydrophytic vegetation and
benthic macroinvertebrates, to determine the flow duration class of a
stream reach as perennial, intermittent, or ephemeral (e.g., the
Streamflow Methodology for Identification of Intermittent and Perennial
Streams and Their Origins, developed by the North Carolina Division of
Water Quality, available at http://portal.ncdenr.org/c/document_library/get_file?uuid=0ddc6ea1-d736-4b55-8e50-169a4476de96&groupId=38364). The EPA, the Corps, and the State of
Oregon also previously developed a regionalized SDAM that has been
validated for use throughout the Pacific Northwest since 2015
(available at http://www.epa.gov/measurements/streamflow-duration-assessment-method-pacific-northwest).
    Because SDAMs use indicators that are robust to seasonal and short-
term climatic variability, these methods can be applied in a single
site visit to distinguish streamflow duration when a channel is flowing
or in the absence of flow. The agencies agree with commenters that
these methods are useful and practical tools that could be used to help
inform timely and predictable jurisdictional determinations, for
implementation of the final ``tributary'' definition, in the States and
regions where previously developed SDAMs are available. The agencies
also agree with commenters that developing similar methods for use
across the United States would promote consistent implementation of the
final tributary definition and note that the agencies are currently
working to develop regionally-specific SDAMs for nationwide coverage.
The agencies believe that developing regionally-specific SDAMs is
important to account for the differences in climate, geology, and
topography that can influence relationships between physical and
biological indicators and streamflow permanence.
    A variety of remote, desktop tools could be used to determine flow
classification of potential tributaries, particularly when coupled with
site specific information. In meetings with stakeholders, some local
government officials recommended using local maps developed by
government agencies, where available, as opposed to national maps,
noting for example that the National Hydrography Dataset (NHD) has been
shown to overestimate flow in certain areas. The agencies will assess
flow classification using a compilation of the best available mapping
sources, which may include the NHD \47\ or local maps, as well as other
remote tools such as photographs, StreamStats by the USGS (available at
https://streamstats.usgs.gov/ss/), Probability of Streamflow Permanence
(PROSPER) by the USGS (available at https://www.usgs.gov/centers/wy-mt-water/science/probability-streamflow-permanence-prosper), Natural
Resources Conservation Service (NRCS) hydrologic tools and soil maps,
desktop tools that provide for the hydrologic estimation of a discharge
sufficient to generate intermittent or perennial flow (e.g., a regional
regression analysis or hydrologic modeling), USGS topographic data, or
modeling tools using drainage area, precipitation data, climate,
topography, land use, vegetation cover, geology, and/or other publicly
available information. The agencies will continue to rely on field
observations and field data to verify desktop assessments as
appropriate, and will also consider data and tools developed by
academia, the regulated community, and other stakeholders.
---------------------------------------------------------------------------

    \47\ As described in the RPA for the final rule, the agencies
note that NHD at High Resolution does not distinguish intermittent
from ephemeral features in most parts of the country and may not
accurately identify on-the-ground flow conditions.
---------------------------------------------------------------------------

    Ultimately, multiple data points and multiple sources of
information should be used to determine flow classification. For
example, a ``blue line stream'' on a USGS topographic map and/or mapped
in the NHD may indicate a potential tributary. Combining this
information with stream order can further inform determinations of flow
classification, as higher order streams may be more likely to exhibit
perennial or intermittent flow compared to lower order streams, though
some headwater streams are perennial or intermittent. The agencies
could further determine whether flow data, field indicators, or visual
observations of surface hydrology are available to confirm a stream's
flow classification. Field-based and remote information may vary in
availability and accuracy in different parts of the country, so care
will be taken to evaluate additional information prior to reasonably
determining the presence or absence of a tributary. Also, the agencies
will continue to use the specific, validated tools developed by States
to identify stream flow classifications.
    As noted previously, the agencies will use best professional
judgment and various tools to identify where the change in flow
classification occurs (e.g., from intermittent to ephemeral and vice-
versa). The tools described above can assist in the identification of
that transition in flow classification and therefore the delineation of
a reach as used in this final rule. The primary distinction necessary
under this rule is the identification of when a perennial or
intermittent reach transitions to an ephemeral reach and vice-versa.
The agencies acknowledge that there are spatial and temporal variations
in stream attributes such that there may not always be a distinct point
demarcating the flow classification changes. For example, a single
distinct point may occur at the confluence of two ephemeral streams,
which become intermittent at the confluence. However, in some
situations between stream confluences, there may be a transition zone
where the flow classification change fluctuates within that zone
throughout a typical year. The agencies will gather information from
upstream and downstream of the transition zone as far as needed to get
an accurate assessment of the conditions on the ground when it may be
necessary for a decision point. This transition zone where the change
in flow classification occurs will be evaluated by the agencies using
the tools described above, as well as best professional judgment, to
identify the most appropriate point at which to distinguish flow
classifications.
    In addition to determining the flow classification of a potential
tributary, the agencies will also determine whether climatic conditions
are typical to determine whether the water feature meets the definition
of ``tributary'' under the final rule. As discussed in Section III.A.1,
the final rule defines the term ``typical year'' to mean ``when
precipitation and other climatic variables are within the normal
periodic range (e.g., seasonally, annually) for the geographic area of
the applicable aquatic resource based on a rolling thirty-year
period.'' The agencies will use readily available climatic data and
tools to evaluate normal precipitation and climatic conditions for the
region at issue and will ensure that the time period of evaluation is
representative of the normal characteristics of the subject waterbody
(i.e., it is neither too wet nor too dry). A detailed discussed of how
the agencies intend to implement this definition is provided in Section
III.A.1.
    In utilizing the data sources described above and determining the
flow classifications of tributaries under typical climatic conditions,
the agencies recognize the need to consider seasonality and timing of
tributary

flows. For instance, in some geographic areas, intermittent streams may
typically flow only at certain times, such as during seasonally wet
conditions. Thus, the agencies would not expect to observe streamflow
in seasonally dry conditions, even if precipitation during those dry
conditions is considered typical for the dates of interest. The
agencies may need to use the multiple tools described above to
determine the flow classification for a tributary that is not flowing
because of seasonally dry conditions, including remote- and field-based
hydrologic and non-hydrologic indicators of the flow classification
that would occur during seasonally wet conditions. For example, remote
indicators might include a series of aerial and satellite images,
spanning multiple years and taken under normal climatic conditions, the
majority of which depict water flowing in the channel.
    In the field, evidence of recent flow can be observed through the
presence of multiple or abundant signs of certain ordinary high water
mark indicators for the region, such as the presence of point bars,
concentrations of drift deposits, or the destruction of terrestrial
vegetation. Furthermore, certain wetland hydrology indicators can help
clarify whether water is present in the area only immediately following
precipitation events, or whether longer-term saturation has likely
occurred. An example of an indicator is the presence of oxidized
rhizospheres along living root channels, which can take four to eight
weeks of continuous saturation to form. This indicator alone cannot be
conclusive of water flowing above the surface, but multiple positive
indicators could provide an increased degree of confidence in these
situations. Conversely, the agencies may observe flow during wetter
than normal precipitation conditions. In this case, the agencies can
use other lines of evidence, including remote- and field-based
hydrologic and non-hydrologic indicators of flow classification as
appropriate. Streams that contain flowing water during wetter than
normal climatic conditions, but which lack an ordinary high water mark
or hydrology indicators may be less likely to flow during normal
climatic conditions. This assessment is further supported if the
majority of wet season aerial and satellite images taken during normal
climatic conditions depict a dry channel. In addition, a landowner's
specific information indicating whether a water feature meets the
definition of a ``tributary'' under ``typical year'' conditions may
also aid in determining flow classification.
    In addition to requesting clarification about when a surface water
feature meets the definition of ``tributary,'' some commenters also
stated that it would be helpful to incorporate the lateral limits of
jurisdiction directly into the ``tributary'' definition and questioned
how such limits would be determined. In addition, some commenters
expressed concern regarding the status of braided rivers that migrate
and have multiple channels where the jurisdictional limits would be
identified. The lateral limits of jurisdiction for tributaries extends
to the ordinary high water mark, as indicated by the physical
characteristics provided in the definition. Consistent with existing
practice, the agencies intend to continue to use the Corps' ordinary
high water mark manuals, as well as Regulatory Guidance Letter 05-05,
when making ordinary high water mark determinations.\48\ The outer
limits of a braided channel may be used to identify the lateral extent
when appropriate, which may encompass multiple low-flow channels and
the migratory islands that separate them. Adding the ordinary high
water mark concept to the definition of ``tributary'' is unnecessary
because it is already located in the Corps' regulations at 33 CFR 328.4
to identify the lateral extent of jurisdiction. The agencies are
finalizing the rule with the definition of ``ordinary high water mark''
as proposed, however, to improve consistency between the corresponding
regulations and also because the term ``ordinary high water mark'' is
used in the final rule's definition of ``upland.''
---------------------------------------------------------------------------

    \48\ The Corps' ordinary high water mark manuals are available
at: https://www.erdc.usace.army.mil/Media/Fact-Sheets/Fact-Sheet-Article-View/Article/486085/ordinary-high-water-mark-ohwm-research-development-and-training/. Regulatory Guidance Letter 05-05 is
available at: https://usace.contentdm.oclc.org/utils/getfile/collection/p16021coll9/id/1253.
---------------------------------------------------------------------------

E. Ditches

1. What are the agencies finalizing?
    The regulatory status of ditches has long created confusion for
farmers, ranchers, irrigation districts, municipalities, water supply
and stormwater management agencies, and the transportation sector,
among others. To address this confusion, the agencies proposed to add a
new category to the definition of ``waters of the United States'' for
jurisdictional ditches and similar artificial features. The agencies
proposed to include in that category: (1) Ditches that are traditional
navigable waters or that are subject to the ebb and flow of the tide
(e.g., paragraph (a)(1) waters); (2) ditches that are constructed in
tributaries or that relocate or alter tributaries as long as the ditch
satisfies the flow conditions of the tributary definition; and (3)
ditches constructed in adjacent wetlands as long as the ditch likewise
satisfies the conditions of the tributary definition. 84 FR 4203. All
other ditches were excluded from CWA jurisdiction under the proposal.
    Many commenters did not find that the separate jurisdictional
category of ``ditches'' provided the regulatory clarity and
predictability that the agencies had sought. They instead stated that
the separate category created confusion. Other commenters said that the
proposed separate category provided additional clarity, while others
argued that all ditches should be excluded. Other commenters stated
that the proposal was too limiting and should include more ditches as
jurisdictional, including any ditch that contributes perennial,
intermittent, or ephemeral flow to other ``waters of the United
States.''
    In response to these diverse comments, the final rule does not
include the separate category of ``ditches'' under paragraph (a)(3) as
proposed and instead incorporates the elements of the proposal into the
``tributary'' category, with some additional clarifying edits. Ditches
that are paragraph (a)(1) waters do not need to be identified in
another jurisdictional category, so that aspect of the proposal has
been eliminated as unnecessary and redundant. Ditches that are
constructed in or that relocate a tributary are included in the final
rule as tributaries, as long as the ditch satisfies the flow conditions
of the ``tributary'' definition. The same is true for ditches that are
constructed in adjacent wetlands.
    The agencies did not retain the term ``alter'' from the proposed
rule given the potential confusion associated with the use of that
term. As some commenters noted, most, if not all, ditches may have some
effect on and therefore may ``alter'' a tributary or some portion of
the tributary system. As described throughout this notice, the CWA does
not authorize the agencies to regulate all waters, nor does it
authorize the agencies to regulate all ditches that exist across the
landscape to assist in water management activities. The agencies
conclude that ditches that are ``constructed in'' or that ``relocate''
a tributary, and that satisfy the flow conditions of the ``tributary''
definition, are appropriately within the authority granted to the
agencies under the CWA, consistent with the legal principles outlined
in Section II.E. The regulation

and management of all other ditches is appropriately left to States and
Tribes as part of their primary authority over land and water resources
within their border. See 33 U.S.C. 1251(b), 1370.
    The agencies consider it to be clearer to include in the definition
of ``tributary'' that the alteration of a tributary does not modify its
jurisdictional status as a tributary as long as it continues to meet
the flow conditions of the definition, rather than to classify the
alteration of a tributary as a ditch. This is also consistent with
longstanding agency practice. The agencies have modified the exclusion
for ditches in paragraph (b)(5) to reflect these changes. The agencies
also recognize that in certain circumstances, ditches that are
constructed in adjacent wetlands that lack sufficient flow to be
considered tributaries under this final rule may develop wetland
characteristics if not maintained. As discussed below, in limited
circumstances, those wetlands may be treated as adjacent wetlands,
subject to the permitting exemptions in 33 U.S.C. 1344(f). All other
ditches are excluded under the final rule.
    The agencies believe that this approach to ditches best addresses
the comments received and provides clarity and regulatory certainty to
determine when a ditch may be a jurisdictional water and when a ditch
may be excluded, consistent with the agencies' authority under the CWA.
Finally, as discussed in Section III.A.3, non-jurisdictional ditches
under this final rule may be capable of conveying channelized surface
water flow between upstream relatively permanent jurisdictional waters
and downstream jurisdictional waters in a typical year. In this
example, the ditch itself, however, would remain non-jurisdictional.
2. Summary of Final Rule Rationale and Public Comment
    During the 1970s, the Corps interpreted its authorities under the
CWA as excluding drainage and irrigation ditches from the definition of
``waters of the United States.'' See, e.g., 40 FR 31320, 31321 (July
25, 1975) (``Drainage and irrigation ditches have been excluded.'').
The ditch exclusion was expressly stated in regulatory text in the
Corps' 1977 regulations. 33 CFR 323.2(a)(3); 42 FR 37122, 37144 (July
19, 1977) (``manmade nontidal drainage and irrigation ditches excavated
on dry land are not considered waters of the United States under this
definition''). As the Corps explained in 1977: ``nontidal drainage and
irrigation ditches that feed into navigable waters will not be
considered `waters of the United States' under this definition. To the
extent that these activities cause water quality problems, they will be
handled under other programs of the FWPCA, including Section 208 and
402.'' 42 FR at 37127 (July 19, 1977). Similar statements in preambles
to the proposed rules from the early 1980s confirmed this
interpretation: ``man-made, non-tidal drainage and irrigation ditches
excavated on dry land are not considered waters of the United States.''
45 FR 62732, 62747 (September 19, 1980); see also 48 FR 21466, 21474
(May 12, 1983) (``Waters of the United States do not include the
following man-made waters: (1) Non-tidal drainage and irrigation
ditches excavated on dry land, (2) Irrigated areas which would revert
to upland if the irrigation ceased.'').
    The general exclusion for non-tidal drainage and irrigation ditches
excavated in dry land continued through 1986, although the Corps
modified its earlier statements that year by noting in preamble text
that ``we generally do not consider'' such features to be ``waters of
the United States,'' and indicating that the agency would evaluate
certain ditches on a case-by-case basis. 51 FR 41206, 41217 (November
13, 1986).\49\ The EPA also included similar language in a Federal
Register notice in 1988. 53 FR 20764 (June 6, 1988). The Corps further
clarified the regulation of ditches in its nationwide permit regulation
in March 2000, stating that ``non-tidal drainage ditches are waters of
the United States if they extend the [ordinary high water mark] of an
existing water of the United States.'' 65 FR 12818, 12823 (March 9,
2000). In other words, if flow or flooding from a jurisdictional non-
tidal river or stream inundated an upland ditch, the agencies would
assert jurisdiction over that upland ditch because the ordinary high
water mark of the river or stream extends into the ditch, and the
agencies would then assert jurisdiction over the entire reach of that
ditch.
---------------------------------------------------------------------------

    \49\ The Corps also moved the ditch exclusion from rule text to
preamble language in 1986 but stated that this was not a substantive
change and that jurisdiction was not expanded. 51 FR 41206, 41216-17
(November 13, 1986).
---------------------------------------------------------------------------

    This final rule clarifies the regulatory status of ditches in a
manner that is more consistent with the Corps' regulations following
the 1972 and 1977 CWA amendments, with some modifications to provide a
clear definition that also falls within the scope of the agencies'
authority under the CWA. When Congress enacted the 1972 amendments, it
specifically included ditches and related artificial features as
``point sources,'' declaring them to be ``discernible, confined, and
discrete conveyances . . . from which pollutants are or may be
discharged.'' Public Law 92-500, 86 Stat. 816, 887 (1972) codified at
33 U.S.C. 1362(14). Congress envisioned protecting the quality of the
navigable waters, defined as ``waters of the United States'' at that
time, by regulating the discharge of pollutants from conveyances like
pipes, ditches, channels, tunnels and similar features into waters of
the United States. Id. at 1362(12) (defining ``discharge of pollutant''
as ``any addition of any pollutant to navigable waters from any point
source'').
    The agencies evaluated the treatment of ditches in the CWA and its
legislative history to discern whether Congress intended ditches to be
point sources, navigable waters, or both. For example, Congress
exempted the discharge of dredged or fill material into waters of the
United States when that discharge occurs as a result of the
construction or maintenance of irrigation ditches, the maintenance of
drainage ditches, or minor drainage associated with normal farming
activities. 33 U.S.C. 1344(f)(1)(A), (C) (exempting such activities
from sections 301, 402, and 404 of the Act). One possible
interpretation of these exemptions is that they function as an implicit
acknowledgement that there may be some irrigation or drainage ditches
that are waters of the United States, thus the need to exempt common
agricultural and related practices in those waters from CWA section 404
permitting. Another interpretation is that dredged or fill material or
other pollutant discharges arising from such activities are not subject
to federal permitting if those materials get washed down the ditch into
a connected water of the United States.
    For irrigation ditches, which typically are constructed in upland
but frequently must connect to a water of the United States to either
capture or return flow, Congress exempted both the construction and
maintenance of such facilities. 33 U.S.C. 1344(f)(1)(C); see also 33
U.S.C. 1362(14) (excluding agricultural stormwater discharges and
irrigation return flows from the definition of ``point source'').\50\
The

construction activities performed in upland areas are beyond the reach
of the CWA, but the permitting exemption applies to the diversion
structures, weirs, headgates, and other related facilities that connect
the irrigation ditches to jurisdictional waters. See, e.g., Corps,
Regulatory Guidance Letter No. 07-02, at 1-2 (July 4, 2007).
---------------------------------------------------------------------------

    \50\ The agencies also note that Congress exempted the discharge
of irrigation return flows into waters of the United States from the
section 402 permit program. 33 U.S.C. 1342(l). This exemption
potentially would not be needed if agricultural drainage ditches
carrying irrigation return flow were themselves waters of the United
States, as the entry point of the irrigation return flow into the
drainage ditch might then lack the requisite point source
discharging mechanism given the diffuse overland flow entry point
from the field to ditch in most circumstances.
---------------------------------------------------------------------------

    For drainage ditches, by contrast, the permitting exemption is
limited to only maintenance of such ditches. 33 U.S.C. 1344(f)(1)(C).
That is because a parallel exemption for construction would allow the
drainage of wetlands subject to CWA jurisdiction without a permit.
Congress' intent to prevent such a result is evident in the
``recapture'' provision of 33 U.S.C. 1344(f)(2). See, e.g., Sen. Rpt.
95-370, 95th Cong. 1st Sess., at 76-77 (July 19, 1977) (noting that
exempted ``activities should have no serious adverse impact on water
quality if performed in a manner that will not impair the flow and
circulation patterns and the chemical and biological characteristics of
the affected waterbody'' and noting that the ``exemption for minor
drainage does not apply to the drainage of swampland or other
wetlands'').
    In summary, Congress may have envisioned the interconnection
between the irrigation and drainage ditches and down-gradient waters of
the United States as creating the need for the section 404(f)
permitting exemptions, not necessarily that those ditches themselves
are waters of the United States. Or Congress could have envisioned that
some drainage ditches constructed in jurisdictional wetlands become
waters of the United States themselves and thus require section 404(f)
permitting exemptions for maintenance work performed in them. The
agencies have not been able to identify any legislative history that
signals the clear intent of Congress on this complex topic, and
commenters provided a diverse range of viewpoints that failed to
provide a clarifying position. To resolve the ambiguity, the agencies
are interpreting the statutory text in section 404(f) and its
legislative history as an indication that Congress may have intended,
in certain limited circumstances, that ditches constructed in
jurisdictional wetlands could become jurisdictional waters themselves.
The agencies believe that the final rule formulation adheres more
closely to the language of the statute and the positions articulated by
the plurality opinion in Rapanos. See, e.g., 547 U.S. at 735-36 and
n.7.
    Many commenters requested the agencies clarify that a water of the
United States and point source are mutually exclusive. Some commenters
expressed concern about features which may be considered point sources
rather than waters of the United States under the proposed rule, and
whether such features would require section 402 permits to convey
pollutants downstream. Other commenters stated that permit requirements
may need to be modified by sampling at the downstream end of the ditch
to demonstrate that pollutants are being added to a water of the United
States. The final rule does not make any changes to the agencies'
interpretation of the definition of ``point source'' in CWA section
502(14). The agencies believe that this final rule will help clarify
whether a ditch is a water of the United States or a point source.
Either it is a water of the United States that subjects a discharger to
sections 402 and 404 permitting requirements for direct discharges into
the ditch, or, if it is non-jurisdictional but conveys pollutants to
downstream jurisdictional waters, it may be a point source that
subjects a discharger into a ditch to section 402 permitting
requirements. Both scenarios could also be subject to statutory
exemptions that would obviate the need for a permit. In addition, if
the ditch is a non-jurisdictional water that does not convey
pollutants, it would not require a permit.
    The agencies recognize that a change in jurisdiction resulting from
this rule may change the scope of application of the CWA regulatory
programs to a particular water, but the longstanding approach that the
agencies have taken to implementing and enforcing those programs would
remain the same. If a CWA section 402 permit is not currently required
for a discharge to a water, it is unlikely that this final rule will
create a requirement for a new CWA permit. If a section 402 permit is
currently required for a discharge to a water that is no longer
jurisdictional under this final rule, that permit may no longer be
required; it may still be required if the non-jurisdictional feature
conveys a discharge of pollutants from a point source to a water of the
United States; or it may still be required but the conditions
associated with the permit may need to be modified, subject to
applicable anti-backsliding permit requirements.
    This final rule includes the agencies' longstanding interpretation
that ditches that satisfy any of the conditions of a paragraph (a)(1)
water are waters of the United States as paragraph (a)(1) waters. This
also includes tidal ditches and ditches that transport goods and