authority of the Federal government and States, meets its obligation to
provide fair notice to members of the regulated community, and adheres
to the overall structure and function of the CWA by ensuring the
protection of the nation's waters.

III. Proposed Definition of ``Waters of the United States''

    Below is a summary of the key substantive provisions of this
proposed rule. Each subsection describes what the agencies are
proposing, why the agencies are proposing this approach, how the
agencies might implement the approach, and specific issues upon which
the agencies are seeking comment. To assist the reader, the longer
subsections have internal headings.
    As a threshold matter, in this proposal the agencies would
interpret the term ``the waters'' in the phrase ``the waters

of the United States'' to encompass relatively permanent flowing and
standing waterbodies that are traditional navigable waters in their own
right or that have a specific connection to traditional navigable
waters, as well as wetlands abutting or having a direct hydrologic
surface connection to those waters. As the plurality decision in
Rapanos notes, the term ``the waters'' is most commonly understood to
refer to ``streams and bodies forming geographical features such as
oceans, rivers, lakes,'' or ``the flowing or moving masses, as of waves
or floods, making up such streams or bodies.'' 547 U.S. at 732 (citing
Webster's New International Dictionary 2882 (2d ed. 1954)); see also
Riverside Bayview, 474 U.S. at 131 (characterizing ``waters of the
United States'' as ``rivers, streams, and other hydrographic features
more conventionally identifiable as `waters.' ''); see also 118 Cong.
Rec. 33699 (Oct. 4, 1972) (statement of Sen. Muskie) (referring to
``navigable waters'' as ``water bodies''). According to the Rapanos
plurality, however, the ordinary meaning of the term ``waters'' does
not include areas that are dry most of the year, and which may
occasionally contain ``transitory puddles or ephemeral flows of
water.'' See Rapanos, 547 U.S. at 733.
    The agencies are also proposing a definition of ``waters of the
United States'' to align with the intent of Congress to broadly
interpret the term ``navigable waters'' beyond just commercially
navigable-in-fact waters. See, e.g., S. Conf. Rep. No. 92-1236, p. 144
(1972). As proposed, this definition recognizes Congress' intent ``to
exercise its powers under the Commerce Clause to regulate at least some
waters that would not be deemed `navigable' under the classical
understanding of that term,'' Riverside Bayview, 474 U.S. at 133, but
at the same time acknowledges ``[t]he grant of authority to Congress
under the Commerce Clause, though broad, is not unlimited.'' SWANCC,
531 U.S. at 173. The definition also recognizes the constitutional
underpinnings of the CWA, which was Congress exercising ``its commerce
power over navigation.'' Id. at 168 n.3.
    This proposal is intended to establish categorical bright lines
that provide clarity and predictability for regulators and the
regulated community by defining ``waters of the United States'' to
include the following: Traditional navigable waters, including the
territorial seas; tributaries of such waters; certain ditches; certain
lakes and ponds; impoundments of otherwise jurisdictional waters; and
wetlands adjacent to other jurisdictional waters. The agencies propose
to eliminate the case-by-case application of Justice Kennedy's
significant nexus test, proposing instead the establishment of clear
categories of jurisdictional waters that adhere to the basic principles
articulated in the Riverside Bayview, SWANCC, and Rapanos decisions
while respecting the overall structure and function of the CWA.

A. Traditional Navigable Waters and Territorial Seas

    The proposed definition of ``waters of the United States'' would
encompass traditional navigable waters, including the territorial seas.
Since the passage of the CWA, the first paragraph of the agencies'
definition of ``waters of the United States'' has included all waters
that are currently used, or were used in the past, or may be
susceptible to use in interstate or foreign commerce, including all
waters which are subject to the ebb and flow of the tide. See, e.g., 33
CFR 328.3(a)(1). This paragraph of the 1986 and 2015 regulations
encompasses waters that are often referred to as waters more
traditionally understood as navigable or ``traditional navigable
waters.'' The second paragraph of the 1986 and 2015 regulations lists
the territorial seas as jurisdictional. See id. To streamline and
simplify the definition of ``waters of the United States,'' the
agencies propose to include both traditional navigable waters and the
territorial seas as a single category of jurisdictional waters. The
agencies can think of no instance in which a territorial sea would not
also be considered traditionally navigable, and thus the broader term
should suffice. The agencies are proposing no other changes to these
historically regulated categories of waters.
    The agencies note that the term ``territorial seas'' is defined in
CWA section 502(8), 33 U.S.C. 1362(8), as ``the belt of the seas
measured from the line of ordinary low water along that portion of the
coast which is in direct contact with the open sea and the line marking
the seaward limit of inland waters, and extending seaward a distance of
three miles.'' The territorial seas establish the seaward limit of
``waters of the United States.'' The agencies are not proposing to
replicate this definition in this proposed rule, but request comment on
whether adding the definition would improve regulatory clarity.
    The agencies interpret traditional navigable waters as all waters
that are currently defined in 33 CFR part 329, which implements
sections 9 and 10 of the Rivers and Harbors Act, and by numerous
decisions of the federal courts, as well as all other waters that are
navigable-in-fact. The definition of navigable-in-fact originates with
the Supreme Court's decision in The Daniel Ball, 77 U.S. 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.

    In subsequent decisions, the Supreme Court clarified that waters
that are navigable-in-fact include waters beyond those capable of
navigation by large vessels, The Montello, 87 U.S. 430, 441-42 (1874);
as well as waters that are not continuously navigable or are not
navigable in all seasons, Economy Light and Power Co. v. U.S., 256 U.S.
113, 122 (1921); and waters that have never been used in commerce, so
long as they are susceptible for use in commerce. U.S. v. Utah, 283
U.S. 64 (1931); U.S. v. Appalachian Elec. Power Co., 311 U.S. 377
(1940). The proposed rule does not modify the text that supports the
agencies' longstanding interpretation of ``traditional navigable
waters.'' Nonetheless, the pre-proposal recommendations docket received
several comments on how to interpret ``traditional navigable waters,''
including comments about what constitutes navigability for purposes of
that term and what it means to be ``susceptible to use'' in commerce.
    Several pre-proposal commenters, for example, identified confusion
in recent years associated with the agencies' interpretation and field
implementation of the tests for determining navigability. Those
commenters point out that determinations made by the agencies using the
Rapanos Guidance, and in particular Appendix D to that guidance, may
have allowed for the regulation of waters that are not navigable-in-
fact within the legal construct established for such waters by the
courts. The agencies therefore solicit comment on and request specific
examples of where that may be the case. As the agencies consider
whether Appendix D is sufficiently clear regarding the regulation of
these foundational waters, the agencies solicit comment on whether the
existing guidance regarding the scope of traditional navigable waters
should be updated to help improve clarity and predictability of the
agencies' regulatory program. The agencies also solicit comment on
whether the regulation of this category of waters has been or can be
clarified

through existing, modified, or new exclusions to the term ``waters of
the United States,'' or other regulatory changes.

B. Interstate Waters

1. What are the agencies proposing?
    The 1986 regulations define ``waters of the United States'' to
include interstate waters, including interstate wetlands. In this
proposal, the agencies would remove interstate waters and interstate
wetlands as a separate category of ``waters of the United States'' to
more closely align the definition to the constitutional and statutory
authorities reflected in the CWA and judicial interpretations of the
term ``navigable waters,'' while balancing the statute's policy
directives to preserve and protect the rights and responsibilities of
the States.
2. Why are the agencies proposing this approach?
    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 are proposing to
eliminate the category in this rulemaking. The agencies are concerned
that the regulation of interstate waters is a relic of the original
Water Pollution Control Act (WPCA) of 1948 and lacks foundation in
statutory text. 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 declared to
be a public nuisance and subject to abatement as provided by the Act.''
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, 62 Stat. 1161.
    In 1961, Congress amended the statute to substitute the term
``interstate or navigable waters'' for ``interstate waters.'' See
Public Law 87-88, 75 Stat. 208 (1961). In 1965, Congress 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 the continued
enforcement of water quality standards for interstate waters developed
by the States 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 the
agencies have retained it as a separate category ever since, including
in the 2015 Rule.
    The agencies have historically viewed navigable and interstate
waters as having distinct and separate meanings because Congress in
1961 identified both in the statute. The agencies have explained their
continuing 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. 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 position. 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). Finally, the
agencies historically have referred to section 303(c) of the CWA as
further evidence that Congress intended interstate waters to be
retained as an independent category of jurisdictional waters because
that provision allowed the continuing enforcement of water quality
standards for ``interstate waters'' developed following the 1965
amendments. A 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'').\25\
---------------------------------------------------------------------------

    \25\ U.S. EPA and U.S. Army Corps of Engineers. 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.
---------------------------------------------------------------------------

    The agencies note that when Congress enacted the 1972 CWA
amendments, it selected the term ``navigable waters'' to frame the
scope of federal regulatory jurisdiction under the Act. To the extent
interstate waters were viewed by Congress as a separate and distinct
category, the agencies now consider a more natural interpretation of
the 1972 amendments to be an express rejection of that 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.''). Thus, the agencies
are concerned about continuing to rely on congressional acquiescence to
their regulatory definitions, see, e.g., 2015 Rule TSD at 219-220,
following SWANCC.
    The legislative history of the 1972 amendments, in fact, suggest
that Congress may not have considered 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, 92nd Cong. 1st Sess., at 2
(Oct. 28, 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 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 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). This history suggests at a minimum that the
section 303(a) provision relating to existing water quality standards
for ``interstate waters'' may be referring to ``interstate navigable
waters,'' not interstate waters more broadly, at least with respect to
continuing federal enforcement authority over the pre-existing
standards.
    Neither Supreme Court case historically relied on by the agencies,
as discussed in the 2015 Rule TSD, addressed the specific question of
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 would support the notion 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 of a later regulatory determination.
    The agencies therefore propose to eliminate ``interstate waters''
as a separate category of ``waters of the United States.'' 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. By proposing to eliminate a
separate category for interstate waters, the proposed rule adheres to
the agencies' legal principles discussed in Section II 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 ditches that
operate more like traditional navigable waters or were excavated in
tributaries or adjacent wetlands; certain lakes and ponds; impoundments
of otherwise jurisdiction 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. Therefore,
those interstate waters that would satisfy the definitions in this
proposed rule would be jurisdictional; interstate waters without any
connection to traditional navigable waters would be more appropriately
regulated by the States and Tribes under their sovereign authorities.
    The agencies recognize that this proposal marks a shift away from
prior agency positions. In doing so, however, the agencies anticipate
that most waters that would be deemed jurisdictional under the existing
regulatory definition from the 1980s would likely remain jurisdictional
under this proposal as they would likely fall within the proposed
traditional navigable waters category or one of the other proposed
categories, such as tributaries or lakes and ponds. The agencies note
that this proposal likely would reduce the number of interstate waters
that would be jurisdictional under the 2015 Rule given that rule's
broad interpretation of the term ``neighboring'' within its
``adjacent'' definition and its inclusion of ephemeral streams and
related features meeting its ``tributary'' definition. The agencies,
however, 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 and therefore lack the analytical ability to perform a
comparative analysis with precision.
3. What are specific issues upon which the agencies are seeking
comment?
    The agencies welcome comment on this proposed change, including the
rationale for and against having interstate waters as a separate
jurisdictional category. Alternatively, the agencies seek comment on an
approach that would retain interstate waters as a separate category,
reflecting longstanding agency practice. In the event the agencies were
to pursue that alternate approach, the agencies solicit comment on
which waters should remain jurisdictional and on what basis, 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. Finally, if
a commenter believes that the agencies have in the past asserted
jurisdiction over waters based solely on the fact that such waters were
interstate and otherwise not connected to a traditional navigable
water, the agencies solicit examples of such jurisdictional
determinations or other available data that may allow the agencies to
further analyze the differences between the 1986 and 2015 rules and
this proposed rule.

C. Impoundments

    The agencies do not propose to make any changes to the impoundment
category of ``waters of the United States'' as it existed in the 1986
regulations. Impoundments have historically been determined by the
agencies to be jurisdictional because impounding a ``water of the
United States'' generally does not change the water body's status as a
``water of the United States.'' See, e.g., S. D. Warren Co. v. Maine
Board of Environmental Protection, 547 U.S. 370, 379 n.5 (2006)
(``[N]or can we agree that one can denationalize national waters by
exerting private control over them.''). Under this proposal, alteration
of a ``water of the United States'' by impounding it would not change
the water's jurisdictional status, consistent with longstanding agency
practice, unless jurisdiction has been affirmatively relinquished.
    Most impoundments do not cut off a connection between upstream
tributaries and a downstream traditional navigable water or territorial
sea. As a result, the agencies would consider tributaries upstream of
an impoundment to be tributaries to downstream jurisdictional waters
even where the impoundment might impede the flow of water. Impoundments
therefore may serve as one of the waters through which tributaries flow
to a traditional navigable water or territorial sea. However, where
discharge of dredged or fill material into a ``water of the United
States'' transforms a water body into upland through a section 404
permitting action, the water would no longer be jurisdictional,
consistent with longstanding agency practice.
    During the agencies' pre-proposal outreach, most commenters
supported a policy under which impoundments of waters of the United
States remain jurisdictional, while some commenters argued that
impoundments that do not remain hydrologically connected to a
traditional navigable water should not

be jurisdictional. The agencies welcome comment on whether impoundments
are needed as a separate category of ``waters of the United States,''
or whether the other categories of waters in this proposed rule
effectively incorporate the impoundment of other jurisdictional waters,
such as the lakes and ponds category. The agencies also seek comment on
whether there are existing jurisdictional impoundments that would not
be found jurisdictional under an alternate approach that would remove
impoundments as a separate category of ``waters of the United States.''
The agencies also welcome comment on whether certain categories of
impoundments should not be jurisdictional, such as certain types of
impoundments that release water downstream only very infrequently or
impede flow downstream such that the flow is less than intermittent. An
impounded wetland frequently becomes a pond, and the agencies solicit
comment as to whether that pond should remain jurisdictional even if,
for example, it does not meet the elements of the lakes and ponds
category under paragraph (a)(4) in this proposed rule, such as
contributing perennial or intermittent flow to an (a)(1) water. The
agencies solicit comment on these and any other aspects of the proposed
impoundment category.

D. Tributaries

1. What are the agencies proposing?
    In this proposed rule, the agencies would retain tributaries as a
category of jurisdictional waters subject to CWA jurisdiction. This
proposed rule defines ``tributary'' to mean a river, stream, or similar
naturally occurring surface water channel that contributes perennial or
intermittent flow to a traditional navigable water or territorial sea
in a typical year either directly or indirectly through other
jurisdictional waters, such as other tributaries, impoundments, and
adjacent wetlands or through water features identified in paragraph (b)
of this proposal so long as those water features convey perennial or
intermittent flow downstream. Excluded waters and features in this
proposal are not tributaries, but certain excluded waters and features
may convey perennial or intermittent flow from a tributary to
traditional navigable waters or the territorial seas. For example, if a
tributary flows into an excluded ditch or a waste treatment system and
those excluded features convey perennial or intermittent flow to a
tributary downstream, the tributary remains a jurisdictional tributary
upstream and downstream of the excluded feature. However, certain
excluded waters and features are incapable of providing perennial or
intermittent flow as defined in this proposal (e.g., ephemeral
features) and therefore break jurisdiction upstream of the excluded
feature. Under the proposed definition, a tributary does not lose its
status as a jurisdictional tributary if it flows through a culvert,
dam, or other similar artificial break or through a debris pile,
boulder field, or similar natural break so long as the artificial or
natural break conveys perennial or intermittent flow to a tributary or
other jurisdictional water at the downstream end of the break. The
alteration or relocation of a tributary would not modify its status as
a jurisdictional tributary as long as it continues to satisfy the
elements of the tributary definition.
    Regardless of the name they are given locally (e.g., creek, bayou,
branch, brook, run, etc.), or their size (e.g., discharge volume,
width, depth, stream order, etc.), waters that meet the definition of
``tributary'' would be jurisdictional under this proposed rule.
However, tributaries as defined in this proposal do not include surface
features that flow only in direct response to precipitation, such as
ephemeral flows, dry washes, arroyos, and similar features. These
features lack the required perennial or intermittent flow regimes to
satisfy the tributary definition under this proposal and therefore
would not be jurisdictional.
    Though ``perennial,'' ``intermittent,'' and ``ephemeral'' are
commonly used scientific terms, the agencies are proposing to provide
definitions of these terms for purposes of CWA jurisdiction to ensure
that the regulation is clear. The agencies propose to define the term
``perennial'' to mean surface water flowing continuously year-round
during a typical year. The proposed definition of ``intermittent'' is
surface water flowing continuously during certain times of a typical
year, not merely in direct response to precipitation, but when the
groundwater table is elevated, for example, or when snowpack melts.
Continuous surface flow during certain times of the year may occur
seasonally such as in the spring when evapotranspiration is low and the
groundwater table is elevated. Under these conditions, the groundwater
table intersects the channel bed and groundwater provides continuous
baseflow for weeks or months at a time even when it is not raining or
has not very recently rained. The term ``snowpack'' in this definition
is proposed as ``layers of snow that accumulate over extended periods
of time in certain geographic regions and high altitudes (e.g., in
northern climes and mountainous regions).'' Melting snowpack can be the
sole or primary source of perennial or intermittent flow in
tributaries. The agencies recognize that perennial or intermittent flow
in certain mountain streams, for example, may result primarily from
melting snowpack, not groundwater contributions to the channel.
    The phrase ``certain times of a typical year'' is intended to
include extended periods of predictable, continuous, seasonal surface
flow occurring in the same geographic feature year after year. The
agencies are not proposing a specific duration (e.g., the number days,
weeks, or months) of surface flow that constitutes intermittent flow as
the agencies believe the time period that encompasses intermittent flow
can vary widely across the country based upon climate, hydrology,
topography, soils, and other conditions. ``Typical year'' is defined in
the proposed rule to mean within the normal range of precipitation over
a rolling thirty-year period for a particular geographic area. Under
this proposed definition, a typical year would generally not include
times of drought or extreme flooding. The term ``ephemeral'' in the
proposal means surface water flowing or pooling only in direct response
to precipitation, such as rain or snow fall. The agencies intend to
distinguish flow resulting from snow fall from sustained flow resulting
from melting snowpack in these definitions.
    Under the proposed rule a tributary must contribute perennial or
intermittent flow to a traditional navigable water or territorial sea
in typical year. Perennial or intermittent flow would require some form
of discrete and confined flow (as opposed to diffuse overland flow)
forming geographic features such as rivers, streams, or similar
naturally occurring surface water channels. A tributary may contribute
perennial or intermittent flow to downstream traditional navigable
waters through, for example, lakes, impoundments, adjacent wetlands, or
other tributaries. Under the proposed rule, when a tributary flows
through a wetland and into another tributary (sometimes called a ``run-
of-stream'' wetland), the tributary would remain jurisdictional even
though it may be difficult to identify channelized flow through the
wetland. Similarly, such a wetland would be considered ``adjacent'' and
thus jurisdictional under this proposal given the wetland abuts (i.e.,
touches at a point in this case) the tributary. In the case of a
perennial or intermittent stream which flows through ditches excluded
from this proposed definition of ``waters of the United

States,'' the non-jurisdictional ditches would not sever jurisdiction
under the proposed rule as long as the ditches convey perennial or
intermittent flow to tributaries or other jurisdictional waters at the
downstream end of the ditch. However, a perennial or intermittent
stream that flows into a non-jurisdictional ephemeral feature would not
meet the definition of ``tributary'' if the perennial or intermittent
flow does not reach a traditional navigable water or territorial sea;
the ephemeral feature would sever jurisdiction for such perennial and
intermittent streams as it does not convey surface water year-round or
continuously for extended periods of time to a traditional navigable
water or territorial sea.
    Under the proposed rule, tributaries could have certain natural
breaks (such as debris piles, boulder fields, or subterranean rivers)
or man-made breaks (such as bridges, culverts, pipes, or dams) and
remain a tributary. A tributary does not lose its status as a tributary
according to this proposal if it flows through a natural or man-made
break so long as the break conveys perennial or intermittent flow to a
tributary or other jurisdictional water at the downstream end of the
break. To implement the proposed tributary definition, the agencies
would consider the upstream extent of a tributary to be the point at
which the feature ceases to contribute perennial or intermittent flow
to a traditional navigable water or territorial sea.
    The alteration or relocation of a tributary would not modify its
status under the proposed definition of tributary as long as it
continues to satisfy the elements of the definition. The agencies'
longstanding interpretation of the CWA is that tributaries that are
modified waters are jurisdictional, and the agencies are not proposing
to change this interpretation. If a tributary is channelized, its bed
and/or banks are altered in some way, or it is re-routed or its flow
regime is modified, then it would remain jurisdictional under the
proposed rule as long as it continues to meet the definition of
``tributary.'' For example, streams that have been channelized with
hardened banks or otherwise modified may still meet the definition of
``tributary'' under the proposal.
2. Why are the agencies proposing this approach?
    The agencies' proposed definition of ``tributary'' reflects the
authority granted by Congress to regulate navigable waters, the
interconnected nature of the tributary system, as well as the ordinary
meaning of the term ``waters,'' an adherence to 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 the agencies' goal to establish a
clear and easily implementable definition. In the proposed definition
of ``tributary,'' the agencies would set boundaries to the scope of the
regulation to ensure 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 SWANCC, 531 U.S. at 172-73 and
supra Section III.A.
    Limiting the scope of the proposed ``tributary'' definition to
perennial or intermittent fixed waterbodies that contribute flow to
traditional navigable waters or the territorial seas, including through
other jurisdictional waters and through certain excluded waters and
features, would also provide clear and predictable jurisdictional
boundaries to guide the agencies and the regulated community. By
proposing to define perennial and intermittent tributaries of
traditional navigable waters as jurisdictional and ephemeral features
as non-jurisdictional, the agencies seek to balance Congress' intent to
interpret the term ``navigable waters'' broadly, see, e.g., S. Conf.
Rep. No. 92-1236, p. 144 (1972), with the notion 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 agencies believe that limiting jurisdiction to
perennial and intermittent streams most appropriately balances the
Federal government's interest in regulation the nation's navigable
waters while respecting State land use authority over features that are
only episodically wet following precipitation events.
    By including rivers and streams that contribute perennial or
intermittent flow to traditional navigable waters or the territorial
seas, and excluding ephemeral features, the agencies are proposing a
definition of ``tributary'' that is 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.'' Id. 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'' (original emphasis)). 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 (original emphasis);
compare id. at 770 (Kennedy, J., concurring) (``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''). 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.
    Pre-proposal commenters provided various definitions for perennial
flow, including streams which flow continually or which flow for twelve
months of the year other than times of extreme drought. Several
commenters recommended that the agencies only include tributaries with
perennial flow, suggesting that they would broadly protect water
quality and provide a clear line regarding federal jurisdiction without
being overly expansive. Some stakeholders recommended the agencies
include waters that receive water from a spring or other surface
source, such as melting snow. Others recommended including ephemeral
features and washes in the definition of ``tributary'' and relying on
physical features of a stream (e.g., bed and banks and ordinary high
water mark) regardless of flow. Many pre-proposal commenters
recommended the agencies propose a bright line to distinguish between
intermittent and ephemeral flow regimes. A few commenters suggested
specific timeframes for the flow requirement to be a tributary, such as
185 days, with most recommending three continuous months of the year.
Several States submitted comments during the Federalism consultations
recommending a regionalized approach to flow regime, whereby the
agencies could provide regional manuals with examples of jurisdictional
flow regimes in various parts of the country or some other mechanism to
recognize regional differences in waters. The agencies have

considered these comments and have crafted proposed regulatory
definitions designed to address a broad array of interests, while
adhering to the legal principles articulated in this notice and while
providing a predictable, implementable regulatory framework.
    By proposing to define ``tributary'' as rivers and streams that
contribute perennial or intermittent flow to traditional navigable
waters or the territorial seas, the agencies would establish 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 perennial or
intermittent flow to a traditional navigable water. Id. at 732. This
proposed 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. On the other hand, Justice Kennedy challenged the plurality's
requirement that a channel contain ``continuous flow,'' asserting
``[t]he merest trickle, if continuous, would count as a `water' subject
to federal regulation'' under the plurality's test.'' Id. at 769. The
proposed requirement that a tributary be connected to a traditional
navigable water by perennial or intermittent flow also 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.
    The agencies acknowledge the proposed tributary definition contains
no flow volume requirement, but only a flow duration requirement of
perennial or intermittent flow. The agencies believe establishing a
specific flow volume requirement for all tributaries would be
inappropriate given the wide spatial and temporal variability of flow
volume in rivers and streams across the country. While the proposed
definition may in certain instances assert jurisdiction over bodies of
water contributing ``the merest trickle'' to a traditional navigable
water, the agencies believe that regardless of flow volume, such bodies
are `` `waters' in the ordinary sense of containing a relatively
permanent flow.'' Id. at 757. As described in the agencies' Rapanos
Guidance, the agencies currently conduct 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[.]''). This proposed definition of ``tributary'' would
replace existing procedures that may depend on case-specific
``significant nexus'' analyses of the relationship between a particular
stream with downstream waters. The agencies are proposing to eliminate
this case-specific ``significant nexus'' analysis by providing a clear
definition of ``tributary'' that is easier to implement. Indeed,
Justice Kennedy's ``significant nexus'' test for wetlands adjacent to
nonnavigable tributaries was only needed ``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'' proposed today, the agencies propose to
eliminate the case-specific significant nexus review through
categorical treatment of all tributaries, as defined by this proposal,
as ``waters of the United States.'' In doing so, the agencies believe
they avoid interpretation of the CWA that raise significant
constitutional questions. See Rapanos 547 U.S. 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
some courts apply the significant nexus standard articulated in Justice
Kennedy's opinion as the exclusive test of CWA jurisdiction over
certain waters. But the agencies believe that this proposed definition
incorporates the important aspects of Justice Kennedy's opinion,
together with the plurality, to craft a clear and implementable
definition that stays within our statutory and constitutional mandates.
The agencies request comment on this interpretation, and on whether the
agencies have previously overread Justice Kennedy's opinion to mandate
the significant nexus test outside the actual holding of Justice
Kennedy's opinion, which was limited to the wetlands at issue in that
case.
    The proposed definition of ``waters of the United States'' is a
legal and policy decision informed by the statute, its legislative
history, Supreme Court interpretations, and the agencies' respect for
the traditional power of States to regulate their land and water
resources. This proposed definition is also informed by the science. As
part of the rulemaking effort leading up to the promulgation of the
2015 Rule, the EPA's Office of Research and Development developed a
report entitled ``Connectivity of Streams and Wetlands to Downstream
Waters: A Review and Synthesis of the Scientific Evidence''
(``Connectivity Report'').\26\ The report reviews more than 1,200 peer-
reviewed publications and summarizes the current scientific
understanding about the connectivity and mechanisms by which streams
and wetlands affect the physical, chemical, and biological integrity of
downstream waters. Before the Connectivity Report was finalized, the
EPA released a draft version of it in September 2013 (``Draft
Connectivity Report'').\27\ The Draft Connectivity Report was reviewed
by the EPA's Science Advisory Board (``SAB''), a public advisory group
tasked with providing scientific information and advice to EPA. In
October 2014, the SAB completed its peer review (``SAB Review'') of the
Draft Connectivity Report. While the SAB found that ``[t]he literature
review 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,'' at the same time the SAB stressed
that ``the EPA should recognize that there is a gradient of
connectivity.'' \28\ 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.'' \29\
---------------------------------------------------------------------------

    \26\ U.S. EPA. Connectivity of Streams and Wetlands to
Downstream Waters: A Review and Synthesis of the Scientific Evidence
(Final Report). U.S. Environmental Protection Agency, Washington,
DC, EPA/600/R-14/475F, 2015.
    \27\ U.S. EPA. Connectivity of Streams and Wetlands to
Downstream Waters: A Review and Synthesis of the Scientific Evidence
(External Review Draft). U.S. Environmental Protection Agency,
Washington, DC, EPA/600/R11/098B, September 2013.
    \28\ Letter to Gina McCarthy. October 17, 2014. SAB Review of
the Draft EPA Report Connectivity of Streams and Wetlands to
Downstream Waters: A Review and Synthesis of the Scientific
Evidence. Page 3.
    \29\ 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 SAB Review fig. 3 at 54. 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. In other words, the SAB found perennial and
intermittent streams have a greater probability to impact downstream
waters compared to ephemeral streams. 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.
    At the same time, the SAB 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 this proposed 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, but acknowledge that
science cannot be used 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.
    This proposed tributary definition identifies a category of
perennial and intermittent rivers and streams that due to their
relatively permanent flow regime and their contribution of flow to
navigable waters should be federally regulated. Through this proposed
definition of ``tributary,'' the agencies would also acknowledge the
policy direction from 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 proposed approach to defining
``tributary'' is also intended to limit federal jurisdiction over
ephemeral flows and other ordinarily dry land features in order to
``preserve, and protect the primary responsibilities and rights of
States to . . . plan the development and use . . . of land . . .
resources.'' See id. at 738 (Scalia, J., plurality) (``Regulation of
land use, as through the issuance of the development permits sought by
petitioners in both [Rapanos and Carabell], is a quintessential state
and local power.''). With the proposed definition, the agencies seek to
avoid ``impairing or in any manner affecting any right or jurisdiction
of the States with respect to waters (including boundary waters) of
such States.'' 33 U.S.C. 1370. In addition, the agencies are drawing a
line between intermittent and ephemeral flows for administrative
efficiency as they balance the law, science, and stakeholder feedback.
Therefore, ephemeral features, such as dry washes and arroyos, that
lack the required perennial or intermittent flow regime necessary to
satisfy the tributary definition under this proposed rule are excluded
from the definition. However, an ephemeral feature may constitute a
point source that discharges pollutants to a ``water of the United
States.'' See Rapanos, 547 U.S. at 743-44 (Scalia, J., plurality).
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.
3. How might the agencies implement this approach?
    The agencies and our co-regulators have significant experience
identifying flow regime in perennial and intermittent waters and expect
that landowners will have also sufficient knowledge to understand how
water moves throughout their properties. Moreover, the technical
consultants that support the permitting and development community will
be familiar with the basic concept of perennial and intermittent flow
regimes. The agencies, however, have identified several potential
implementation methods and tools that could be used to identify and
distinguish perennial and intermittent flow regimes from ephemeral flow
regimes as defined in this proposal. In conjunction with a field visit,
such methods could include remote and field-based tools, such as visual
observations, photographs, data collection on flow, trapezoidal flumes
and pressure transducers for measuring surface flow and comparing that
to rainfall, StreamStats by the U.S. Geological Survey (USGS)
(available at https://streamstats.usgs.gov/ss/), 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, such as 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 other
publicly available information. There may be other methods which could
be researched and developed by the agencies over time, including the
identification of field indicators, such as vegetation and
macroinvertebrates, which could be regionalized (for example, the
Streamflow Duration Assessment Method for the Pacific Northwest, at
http://www.epa.gov/measurements/streamflow-duration-assessment-method-pacific-northwest, which could be expanded to other regions).
    During the agencies' Federalism consultation, a few States
recommended the agencies identify a variety of methods which may be
employed to identify flow regimes, and that such methods involve tools
readily available to a typical landowner. Some other States recommended
not using the

National Hydrography Dataset (NHD) because they commented that it has
been shown to overestimate flow in certain areas. Some States
recommended using local flow data collected and maps developed by
government agencies, where available. Climatic conditions and
precipitation data are important elements to consider when determining
flow regime given the dependent relationship in many systems between
surface flow and groundwater tables. For example, observing flow
directly after a large rainfall may not be a good indicator of a
stream's typical flow regime, while observing flow in a stream in the
middle of summer in the arid West when no recent rainfall has occurred
may be a good indication that it flows more than ephemerally. Often
multiple data points and multiple sources of information could be used
to determine flow regime.
    The same tools discussed above can also be helpful in establishing
the presence of a tributary. For example, where a USGS topographic map
and/or NHD data display a ``blue line stream,'' there is an indication
of a potential tributary. Combining this information with stream order
can yield greater certainty. For example, higher order streams will
generally be more likely to exhibit relatively permanent flow compared
to lower order streams. This information will vary in validity in
different parts of the country, so care would be taken to evaluate
additional information prior to reasonably concluding a tributary is
present. Supporting information, as well as field work, should also be
used to conclude the presence of a tributary. Other reliable methods
that can indicate existence of a tributary include stream gage data,
elevation data, spillway height, historic water flow records, flood
predictions, statistical evidence, and direct observation. Also, the
agencies recognize that States may have specific, validated tools they
employ to identify perennial or intermittent streams or flow regimes
and are soliciting comment on those approaches which may be useful for
application in this proposed rule. The agencies also solicit comment on
other implementation tools available to determine the flow regime of a
river or stream and its contribution of flow to a traditional navigable
water.
    To determine whether the year in question is a ``typical year,''
the agencies presently use observed rainfall amount and compare it to
tables developed by the Corps using data from the National Oceanic and
Atmospheric Administration (NOAA). The agencies consider a year to be
``typical'' when the observed rainfall from the previous three months
falls within the 30th and 70th percentiles established by a 30-year
rainfall average generated at NOAA weather stations. A typical year
would generally not include times of drought or extreme floods. A
rolling 30-year period would account for variability to provide a
reliable indicator of the climate in a given geographic area without
being confounded by a year or two of unusual climate data for the given
area. The geographic area proposed to be used by the agencies would be
on a watershed-scale basis to ensure specific climatic data are
representative of the landscape in relation to the feature under
consideration for meeting the tributary definition.
    Other potential data sources for obtaining relevant information to
determine typical year could include one or several of the following:
the Web-based Water-Budget Interactive Modeling Program (WebWIMP) for
approximate dates of wet and dry seasons for any terrestrial location
based on average monthly precipitation and estimated evapotranspiration
(http://climate.geog.udel.edu/~wimp/); WETS tables (or similar tools)
which are provided by the NRCS National Water and Climate Center
(http://www.wcc.nrcs.usda.gov/climate/wetlands.html) and are calculated
from long-term (30-year) weather records gathered at National Weather
Service; meteorological stations; or by examining trends in drought
indices, such as the Palmer Drought Severity Index (PDSI) (Sprecher and
Warne 2000), where time-series plots of PDSI values by month or year
are available from the National Climatic Data Center (http://www.ncdc.noaa.gov/oa/climate/onlineprod/drought/xmgr.html#ds). The
agencies are not proposing to codify specific tools or resources in the
regulation to determine a ``typical year.''
    Sources of information on ``snowpack'' can be found in the NOAA
national snow analyses maps (https://www.nohrsc.noaa.gov/nsa/), Natural
Resources Conservation Service sources (https://www.wcc.nrcs.usda.gov/snow/), or by using hydrographs of subject locations as a potential
guide to alert the regulated public and regulators as to which regions
of the country have to consider snowpack scenarios. In these regions,
for example, a hydrograph could indicate a large increase in discharge
volume due to the late spring/early summer thaws of melting snowpack.
Such indications are a regular, predictable, seasonal occurrence of
flow. The large water contribution source for those northern and
mountainous geographic regions which do not have significant elevation
changes but which do have a consistent, predictable snowfall that
accumulates on the ground for extended periods of time would be covered
in a proposed definition of ``snowpack.''
4. What are specific issues upon which the agencies are seeking
comment?
    While the public may comment on all aspects of the agencies'
proposed rule, the agencies have identified several specific areas
related to the proposed tributary definition for which they seek
comment. As a threshold matter, the agencies solicit comment on their
interpretation of the Rapanos opinions and whether the significant
nexus standard, articulated by a single justice, must be a mandatory
component of any future definition of ``waters of the United States.''
Or, may the agencies apply the principles and rationale of the
plurality and concurring opinions to craft a new standard established
by rule?
    The agencies also solicit comment on whether the definition of
``tributary'' should be limited to perennial waters only. The agencies
also request comment whether the definition of ``tributary'' as
proposed should indicate that the flow originate from a particular
source, such as a requirement for groundwater interface, snowpack, or
lower stream orders that contribute flow. The agencies also solicit
comment on how effluent-dependent streams (e.g., streams that flow
year-round based on wastewater treatment plant discharges) should be
treated under the tributary definition. As proposed, effluent-dependent
streams would be included in the definition of ``tributary'' as long as
they contribute perennial or intermittent flow to a traditional
navigable water or territorial sea in a typical year.
    The agencies also solicit comment on whether the tributary
definition should include streams that contribute less than
intermittent flow to a traditional navigable water or territorial sea
in a typical year. Additionally, the agencies request comment on
whether less than intermittent flow in a channel breaks jurisdiction of
upstream perennial or intermittent flow and under what conditions that
may happen. The agencies recognize that the proposed definition may
present a challenge for certain landowners upstream of an ephemeral
feature. For example, landowners may find it difficult to determine
whether there is a jurisdictional break downstream of a feature on
their property. The agencies therefore solicit comment on this issue.

The agencies also seek comment on the proposed treatment of natural and
man-made breaks regarding the jurisdictional status of upstream waters,
including whether these features can convey perennial or intermittent
flow to downstream jurisdictional waters. The agencies also seek
comment on the jurisdictional status of the breaks themselves.
    The agencies are also soliciting comment on an alternate definition
that would change the focus of the proposed definition from
intermittent flow occurring during certain times of the year to
``seasonal flow.'' Under this alternative definition, a tributary would
be a river, stream, or similar naturally occurring surface water
channel that contributes flow at least seasonally to a traditional
navigable water or territorial sea in a typical year. The alternate
definition could add that ``seasonal flow is predictable, continuous
surface flow that generally occurs at the same time in a typical
year.'' The agencies welcome comments on the concept of a ``seasonal''
flow regime, what that term may include, and how it may be implemented,
including tools to identify ``seasonal'' flow.
    As an alternative to the proposed definition of ``intermittent,''
the agencies are soliciting comment on whether the term could instead
mean ``water flowing continuously during certain times of a typical
year as a result of melting snowpack or when the channel bed intersects
the groundwater table.'' Although the identification of groundwater
input is found in most definitions for intermittent flow,\30\ the
agencies note that identifying whether the channel bed intersects the
groundwater table may be challenging to accomplish in the field, that
gathering the relevant data could be time consuming, and could require
new tools and training of field staff and the regulated public. Some
options for identifying whether groundwater is providing a source of
water to the tributary may involve the installation of monitoring wells
or staff gauges to identify the presence of the water table and/or to
estimate the base flow using a hydrograph. Identifying the appropriate
depth of installation for a monitoring well can be challenging,
especially in the case of intermittent streams that have seasonally
fluctuating water tables. Installing these devices in certain
substrates, such as rocky substrates, can also be challenging. There
may be other methods which could be researched and developed by the
agencies over time, including the identification of field indicators,
which could be regionalized, as well as the development of modeling
tools. However, both of these methods (field indicators and modeling
tools) would only provide an indication of groundwater generated base
flow and would not directly measure its presence. The agencies are
soliciting comment on whether these or other methods may be most
appropriately used to identify groundwater in the field.
---------------------------------------------------------------------------

    \30\ See, e.g., 82 FR 2006 (Jan. 6, 2017) (Corps nationwide
permit program); National Research Council. 2002. Riparian Areas:
Functions and Strategies for Management. Washington, DC: The
National Academies Press. https://doi.org/10.17226/10327.
---------------------------------------------------------------------------

    The agencies are also soliciting comment on whether the definition
of ``intermittent'' should contain the requirement of continuous flow
for a specific duration, such as ``at least one month of the calendar
year,'' instead of the phrase ``during certain times of a typical
year.'' See, e.g., 30 CFR 710.5 (definition of ``intermittent'' used in
a U.S. Department of the Interior regulation). The agencies note that
such an approach would provide for national consistency but may not
offer a more regionalized implementation of intermittent tributaries as
some States recommended (i.e., intermittent would be viewed the same
across the country, from the arid West to the Southeast). Some pre-
proposal commenters recommended this approach to provide certainty for
determining flow regime. The agencies are also soliciting comment on
whether the seasonal continuous surface flow consideration (e.g.,
typically three months) from the Rapanos Guidance could be used as a
definitional flow regime in the regulation. Rapanos Guidance at 6.
Several commenters recommended this approach be used to define
tributaries. The seasonal ``typically three month'' approach is current
practice, subject to case-by-case analysis, and is therefore familiar
to agency staff and the regulated public, but like a one-month
limitation, it may not provide for regional variation in the
implementation of flow regime.
    The agencies therefore seek comment as to whether the tributary
definition should include specific flow characteristics (e.g., timing,
duration, frequency, or magnitude), and if so, what flow values or
ranges of values (including supporting rationale) would satisfy the
tributary definition and what methods, tools, or data could be used to
determine such values. Certain flow requirements might include, for
example, an average annual flow volume of five or more cubic feet per
second in a typical year and/or that a river or stream flow
continuously for a certain number of days (e.g., 30, 60, or 90 days) in
a typical year.
    The agencies are also soliciting comment on whether the concepts of
bed and banks and ordinary high water mark should be added to the
definition of tributary, and if so, how. Several commenters recommended
including these characteristics in the proposed definition of
``tributary,'' similar to the definition of tributary in the 2015 Rule,
while others opposed the addition, stating that it would
inappropriately result in regulation over certain waters that should
not be jurisdictional under the CWA, such as ephemeral features.
    The lateral jurisdictional limit of a tributary currently is
established by a tributary's ordinary high water mark. The agencies
solicit comment on the usefulness of incorporating into the tributary
definition the following sentence: ``the lateral extent of a tributary
is established by its ordinary high water mark.'' The agencies note
that the Corps has existing regulations at 33 CFR 328.4 regarding the
limits of jurisdiction for categories of ``waters of the United
States.'' The agencies solicit comment on including these Corps
regulations in the EPA's regulations or simply cross-referencing the
Corps regulations in EPA's to apply to the definition of ``waters of
the United States.''
    The agencies are proposing to define a typical year as ``within the
normal range of precipitation over a rolling 30-year period for a
particular geographic area.'' The agencies solicit comment on whether
it is necessary to define ``typical year'' given the agencies'
understanding that it is a commonly understood term in field
application. Alternatively, the agencies seek comment on whether they
should provide additional details in the rule text about what
constitutes a typical year or provide further guidance in a final
preamble about appropriate tools for determining whether a year is
``typical.'' Finally, the agencies solicit comment on alternative
approaches in the rule text to convey that times of drought or extreme
floods would not be a factor when determining if a river or stream
meets the conditions of the definition of ``tributary.''
    The agencies are also soliciting comment on implementation methods
and tools that could be used to identify and distinguish perennial and
intermittent flow regimes from ephemeral flow regimes as defined in
this proposal. As mentioned above, such tools could include field-based
tools, such as visual observations, or remote desktop tools, such as
aerial photos. The agencies are also soliciting comment on

the appropriate watershed scale for use in the geographic area as
defined in a ``typical year'' of the proposed rule, for example,
hydrologic units at the level of Hydrological Unit Code (HUC)-8s, HUC-
10s, or HUC-12s could be used. A broad geographic area may include
multiple micro-climates and may not be representative of precipitation
conditions on the ground for the subject tributary. The agencies are
soliciting comment on other approaches to determine the geographic
area.

E. Ditches

1. What are the agencies proposing?
    The agencies propose to add a new category to the definition of
``waters of the United States'' to provide regulatory clarity and
predictability regarding the regulation of ditches and similar
artificial features. 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. In an effort to reduce that confusion, the
agencies propose to delineate the categories of ditches that would be
``waters of the United States,'' and are proposing to exclude all other
ditches from that definition.
    The agencies also propose to define ditches for purposes of this
proposed rule as simply artificial channels used to convey water.
Ditches perform a variety of functions including conveying irrigation
water, draining water from farm fields, capturing runoff from roads, or
use for transporting goods and services in interstate or foreign
commerce, such as the Erie Canal and the Great Lakes Waterway. The
status of ditches as ``point sources'' under the CWA, 33 U.S.C.
1362(14), would not be affected by this proposed rule. One of the goals
of this proposal is to address the confusion regarding whether ditches
are point sources or ``waters of the United States'' more generally,
and to provide clear categories for regulators and the regulated
community for distinguishing between the two.
    The agencies propose to include ditches as ``waters of the United
States'' if they (1) satisfy any of the conditions identified in
paragraph (a)(1) of this proposed rule; (2) are ditches constructed in
a tributary as defined in paragraph (c)(11) of the proposal as long as
those ditches also satisfy the conditions of the tributary definition;
or (3) are ditches constructed in an adjacent wetland as defined in
paragraph (c)(1) of the proposal as long as those ditches also satisfy
the conditions of the tributary definition. The agencies propose to
exclude all other ditches from the definition of ``waters of the United
States.'' Ditches not covered by this proposed category could still be
regulated by States and Tribes and would be subject to CWA permitting
if they meet the definition of ``point source'' in CWA section 502(14).
2. Why are the agencies proposing this approach?
    During the 1970s, the Corps interpreted its authorities under the
CWA as not including drainage and irrigation ditches in 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 and clarified as applying to ditches excavated
in dry land. 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 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).\31\ 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, 12823-24 (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. Essentially, the
agencies have found that a ditch becomes part of the tributary network
because of the presence of the ordinary high water mark in the ditch.
---------------------------------------------------------------------------

    \31\ 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).
---------------------------------------------------------------------------

    In the 2015 Rule, the agencies promulgated a definition of ``waters
of the United States'' that expressly included man-made features such
as ditches and canals in the definition of tributaries, but excluded
ditches with ephemeral flow if those ditches are not a relocated
tributary or were not constructed in a tributary. 80 FR 37105 (June 29,
2015). That definition also excluded ditches with intermittent flow, as
long as those ditches are not a relocated tributary, are not
constructed in a tributary, or do not drain wetlands. Id. Ditches that
do not contribute flow, either directly or through another ``water of
the United States,'' are also excluded from the definition of ``waters
of the United States'' under the 2015 Rule. Id.
    The agencies today propose to clarify the regulatory status of
ditches in a manner that would be 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
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.'' 33 U.S.C. 1362(16).
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. (defining ``discharge of pollutants'' as ``any addition
of any pollutant to navigable waters from any point source''). The
agencies today propose to

better demarcate navigable waters and point sources that can discharge
pollutants into those waters, as established by Congress in 1972. See,
e.g., Rapanos, 547 U.S. at 735-36 (Scalia, J., concurring) (``The
definition of `discharge' would make little sense if the two categories
were significantly overlapping''). To do so, the agencies evaluated the
treatment of ditches in the CWA 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). One possible
interpretation of these exemptions is 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 section 404 permitting. Another
interpretation, and one that may more closely align with the pre-
existing CWA definition of ``point source,'' is that dredged or fill
material is 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).\32\ 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).
---------------------------------------------------------------------------

    \32\ 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.
---------------------------------------------------------------------------

    The permitting exemption for drainage ditches, by contrast, is
limited to the maintenance of such ditches. 33 U.S.C. 1344(f)(1)(C).
That is because an alternate formulation would have allowed the
drainage of wetlands subject to CWA jurisdiction without a permit.
Congress' concern for 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'').
    Thus, 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.'' The agencies have not been able to identify any
legislative history, however, that signals the clear intent of Congress
on this complex topic. The agencies also recognize that this
interpretation of the statutory structure has not been articulated
previously, and solicit comment on which this formulation adheres more
closely to the language of the Act and the positions articulated by the
plurality opinion in Rapanos. See, e.g., 547 U.S. at 735-36 and n.7. To
be clear, the agencies are not saying that in all circumstances a ditch
may be a water of the United States or a point source, but not both.
The agencies are, however, attempting to more clearly establish
demarcations between the two to reduce regulatory uncertainty.
    The agencies today propose to limit the term ``waters of the United
States'' to apply to clearly defined categories of ditches and related
features. The agencies propose to include their longstanding
interpretation that ditches that satisfy any of the conditions of a
category (a)(1) water are ``waters of the United States.'' This also
includes tidal ditches and ditches that transport goods and services in
interstate and foreign commerce, as those ditches--more commonly
referred to as ``canals''--provide important commercial navigation
services to the nation and operate more like natural waters
traditionally understood as navigable. See, e.g., id. at 736 (Scalia,
J., plurality) (``a permanently flooded man-made ditch used for
navigation is normally described, not as a `ditch,' but a `canal' '').
The Los Angeles River, for example, is a ``water of the United States''
(having been determined to be a traditional navigable water) and would
not be excluded under paragraph (b) even where it has been channelized
or concreted. Other examples include the St. Lawrence Seaway, the
Sturgeon Bay Ship Canal, and the Chesapeake and Delaware Canal.
    In addition, the agencies propose to include ditches that were
constructed in a water that meets the proposed definition of
``tributary'' and continues to meet the definition of ``tributary.''
This provision is consistent with the agencies' longstanding, historic
position that non-tidal ditches excavated in upland (and historically
described as ``dry land'') are not jurisdictional. Features, including
ditches, that are not waters under paragraph (a)(1) and that are
constructed in upland are not ``waters of the United States'' because
areas that are naturally dry land do not meet the ordinary meaning of
the term. As discussed in the introduction to Section III, ``waters of
the United States'' are waters within the ordinary meaning of the term,
such as oceans, rivers, streams, lakes, ponds, and wetlands; ditches
artificially excavated in upland do not fit into this category. This
proposal would also align the treatment of ditches to that of
tributaries in this proposal, which retains the agencies' longstanding
position that the alteration or relocation of a ``water of the United
States'' does not modify the jurisdictional status of that water, and
as such, ditches that alter or relocate a water of the United States
would be jurisdictional.
    The agencies also propose to include ditches as ``waters of the
United States'' if they were constructed in a wetland that meets this
proposed definition of ``adjacent wetland,'' as long as the ditch also
satisfies the conditions of the tributary definition in this proposed
rule. Such an approach would align the proposed rule with the section
404(f) permitting exemption for the maintenance but not construction of
drainage ditches, and the associated concern expressed during the
legislative process for the 1977 amendments related to draining swamps
and wetlands. The provision would also be restricted to ditches that
satisfy this proposed definition of ``tributary,'' as such ditches
likely functionally maintain some of the same interconnected
relationship between the drained wetland and navigable water that
supported federal jurisdiction over

the adjacent wetland in the first instance.
    Ditches used to drain surface and shallow subsurface water from
cropland are a quintessential example of the interconnected
relationship between land and water resource management, as is managing
water resources in the Western United States, conveying irrigation
water to and from fields, and managing surface water runoff from lands
and roads following precipitation events--all activities that rely on
ditches. See, e.g., FERC v. Mississippi, 456 U.S. 742, 768 n.30 (1982)
(characterizing ``regulation of land use [as] perhaps the
quintessential state activity''). This proposal therefore effectuates
the clear policy directive from Congress to preserve and protect the
primary authority of States over land and water resources within their
borders. See 33 U.S.C. 1251(b), 1370.
3. How might the agencies implement this approach?
    In order to be a jurisdictional ditch under this proposed rule, a
feature would first need to meet the definition of ``ditch'' as
proposed (i.e., an artificial channel used to convey water). An
``artificial'' channel is not a natural feature, rather it has been
constructed in some manner. Also, to meet the proposed definition of
``ditch,'' the artificial channel must be used to convey water. Once a
feature has been determined to meet the proposed definition of
``ditch,'' a ditch would be considered ``waters of the United States''
if it meets any of the conditions in paragraph (a)(1). This would
include ditches which are currently used, or were used in the past, or
may be susceptible to use in interstate or foreign commerce, as well as
ditches which are subject to the ebb and flow of the tide. This may
include waters such as navigable canals and tidal drainage ditches. See
Section III.A for further discussion on paragraph (a)(1) waters.
    A ditch would also be considered a ``water of the United States''
if it was constructed in a tributary as defined in paragraph (c)(11)
and also satisfies the conditions of the tributary definition. A
tributary that was channelized or straightened because its natural
sinuosity has been altered, cutting off the meanders, may or may not
meet the definition of ``ditch'' but nonetheless would remain a
tributary as long as it meets the conditions of the tributary
definition provided in this proposed rule. If these ditches were
tributaries prior to their construction and continue to meet the
conditions of the tributary definition after construction, they would
remain jurisdictional under the proposed rule. However, if the evidence
does not demonstrate whether a ditch was constructed in a tributary as
defined in the proposed rule, that ditch would be considered to be non-
jurisdictional by the agencies under this proposal.
    For example, if the agencies are not sure whether a ditch was
constructed in a tributary given the physical appearance and
functionality of the current ditch, the agencies would look at the
available evidence to attempt to discern when the ditch was constructed
and the nature of the landscape before and after construction. If the
evidence does not demonstrate that the ditch was located in a natural
waterway, the agencies would consider the ditch non-jurisdictional
under this proposed rule. If the evidence suggests that the ditch may
have been constructed in a natural waterway, the agencies would review
the available evidence to attempt to discern whether that natural
waterway would qualify as a tributary under this proposed rule. Absent
such evidence, the agencies would determine the ditch is non-
jurisdictional. If the evidence demonstrates that a ditch was
constructed in a tributary, then the ditch would be a ``water of the
United States'' as long as it still satisfies the conditions of the
proposed definition of ``tributary.'' See Section III.D for further
information about tributaries under this proposed rule.
    A ditch would be considered a ``water of the United States'' if it
was constructed in an adjacent wetland as defined in this proposed rule
(see Section III.G for a discussion of adjacent wetlands under this
proposed rule), but only if that ditch also satisfies the conditions of
the proposed definition of ``tributary.'' The same scenarios above for
ditches constructed in a tributary would apply when determining the
jurisdictional status of a ditch constructed in an adjacent wetland. If
there is evidence to indicate that a ditch was constructed in an
adjacent wetland as defined in the proposal, the agencies would
consider the ditch to be jurisdictional if it also satisfies the
conditions of the tributary definition as proposed. Absent such
evidence, the agencies would determine the ditch is non-jurisdictional.
    Along with field data and current information on the subject water,
historic tools and resources may also be used to determine the presence
of a tributary or adjacent wetland at the time of ditch construction,
and several sources of information may be required to make such
determination. This may include historic topographic maps, historic
aerial photographs, local and state records and surface water
management plans, agricultural records, street maintenance data,
precipitation records, historic permitting and jurisdictional
determination records, certain hydrogeomorphological or soil
indicators, wetlands and conservation programs and plans, and
functional assessments and monitoring efforts. For example, when a USGS
topographic map displays a tributary located upstream and downstream of
a ditch, this may indicate that the ditch was constructed in a
tributary.
    In addition, high resolution aerial photographs may be used to
identify whether there are or were characteristics of a tributary
upstream or downstream of a ditch, indicating that a ditch may have
been constructed in a tributary. In some cases, stream channel
morphology is visible on the aerial photograph along with visible
persistent water (e.g., multiple dates of aerial photography showing
visible water) providing evidence of the flow regime necessary to
identify a tributary under this proposed rule at the time of ditch
construction. However, characteristics of tributaries may not be
visible in aerial photographs taken in areas with high shrub or tree
cover, in which case aerial photographs taken during ``leaf off'' may
provide the most beneficial information. National Wetlands Inventory
maps may indicate the presence of a ditch constructed in an adjacent
wetland; however, it may be challenging to identify the historic status
of a wetland where a ditch has drained the wetland such that it would
no longer meet the definition of ``adjacent wetland'' under this
proposed rule. In general, the burden of proof would be on the agencies
to determine the historic status of the ditch construction, and if
field and remote-based resources do not provide sufficient evidence to
show that the ditch was constructed in a tributary or an adjacent
wetland then a determination would be made that the ditch is not
jurisdictional under this proposed rule.
4. What are the specific issues upon which the agencies are seeking
comment?
    While the public may comment on all aspects of the agencies'
proposed rule, the agencies are proposing a number of ways to address
and clarify jurisdiction over ditches as described above and are
seeking comment. The agencies seek comment on the utility and clarity
of proposing a separate category of jurisdictional ditches and how the
agencies have delineated those ditches that would be ``waters of the
United States'' and those that would be

excluded. In the alternative, the agencies seek public comment on
whether the agencies should retain the historical treatment of
jurisdictional ditches within the definition of ``tributary'' and not
in a separate category. The agencies also seek comment on their
proposed definition of ``ditch.''
    As the agencies consider how to implement this provision, the
agencies seek comment on whether they should add a temporal component
to distinguish jurisdictional ditches when evaluating ditches that may
have been constructed in tributaries or adjacent wetlands. For example,
the agencies could consider a ditch that appears to have been
constructed in upland to be non-jurisdictional unless there is evidence
that the ditch was in fact constructed in a natural waterway prior to
the adoption of the 1972 CWA amendments. The agencies also solicit
comment as to what tools can be used to help identify whether a ditch
is constructed in upland or whether it was constructed in a tributary
or adjacent wetland that meets the respective proposed definitions, and
in particular what sort of showing would constitute evidence that a
ditch was constructed in upland or in a jurisdictional tributary or
adjacent wetland. The agencies seek comment as to whether there are
other approaches for addressing the evidentiary concerns that may arise
in a permitting context for historic ditches. For example, the agencies
solicit comment on the role of historic photographs and records, in
determining whether a ditch was built in a tributary and more generally
what constitutes evidence that a ditch was constructed in a tributary
or an adjacent wetland.
    In addition, the agencies solicit comment on the exclusion of all
ditches constructed in upland, regardless of flow regime, and whether
that is consistent with the plurality and concurring opinions in
Rapanos. For example, ditches constructed in upland that flow
perennially would be presumed non-jurisdictional under this proposal,
even if they would also satisfy the conditions of the proposed
tributary definition. Finally, the agencies solicit comment on whether
a ditch can be both a point source and a ``water of the United
States,'' or whether these two categories as established by Congress
are mutually exclusive.

F. Lakes and Ponds

1. What are the agencies proposing?
    The agencies are proposing a separate category of waters of the
United States to include certain lakes and ponds. The agencies are
proposing three instances where lakes and ponds would meet the
definition of ``waters of the United States.'' First, lakes and ponds
that satisfy any of the conditions in paragraph (a)(1) are proposed to
be included. Such lakes and ponds would be jurisdictional as an (a)(1)
water, as well as an (a)(4) water.
    Second, lakes and ponds that contribute perennial or intermittent
flow to an (a)(1) water in a typical year through an (a)(2)-(6) water
would also be considered waters of the United States. This second
category of lakes and ponds can contribute flow to an (a)(1) water
either directly or through a tributary, jurisdictional ditch, another
jurisdictional lake or pond, an impoundment, an adjacent wetland, or
through a combination of these waters. The contribution of perennial or
intermittent flow to an (a)(1) water from such lakes and ponds may also
occur through water features identified in paragraph (b) of this
proposal so long as those water features convey perennial or
intermittent flow downstream and ultimately to an (a)(1) water. The
term ``typical year'' as used in the proposed lakes and ponds category
of ``waters of the United States'' would be implemented using the
proposed definition of the term in paragraph (c)(12).
    Third, the agencies propose that lakes and ponds flooded by an
(a)(1)-(5) water in a typical year would be waters of the United
States. These lakes and ponds would receive flood waters from (a)(1)-
(5) waters via overtopping in a typical year.
2. Why are the agencies proposing this approach?
    The agencies propose to include certain lakes and ponds as waters
of the United States because lakes and ponds are waters within the
ordinary meaning of the term. As discussed in Section II, the plurality
decision in Rapanos explains that the term ``the waters'' is most
commonly understood to refer to ``streams and bodies forming
geographical features such as oceans, rivers, lakes,'' or ``the flowing
or moving masses, as of waves or floods, making up such streams or
bodies.'' 547 U.S. at 732. The plurality also noted that its reference
to ``relatively permanent'' waters did ``not necessarily exclude
streams, rivers, or lakes that might dry up in extraordinary
circumstances, such as drought,'' Id. at 732 n.5. The agencies focus in
large part on the lake or pond's contribution of flow to and connection
with traditional navigable waters to remain consistent with the overall
structure and function of the CWA. See, e.g., SWANCC, 531 U.S. at 168
n.3.
    Many commenters in the Federalism consultation with the agencies
stated that the rule should include permanent lakes. Some commenters
also stated that the rule should not include isolated lakes, which this
proposal does not unless the lake satisfies the conditions in paragraph
(a)(1). The agencies are proposing a distinct category for lakes and
ponds because they are distinct water features; they are lentic systems
(i.e., still waters) as opposed to tributaries, which are typically
lotic features (i.e., flowing waters). In addition, the agencies view
the establishment of a separate category for lakes and ponds as
providing greater clarity and predictability for Federal agencies,
States, Tribes, the regulated community, and the public, rather than
including these waters in the definition of ``tributaries'' or with
adjacent wetlands.
    As discussed in Section II, the agencies' authority to regulate
``the waters of the United States'' is grounded in Congress' commerce
power over navigation. The agencies can choose to regulate beyond
waters more traditionally understood as navigable given the broad
purposes of the CWA, but must provide a reasonable basis for doing so.
The agencies are proposing that lakes and ponds that contribute
perennial or intermittent flow to those traditional navigable waters,
in any of the manners described above, fall within Congress' commerce
power and are consistent with the ordinary meaning of ``waters of the
United States,'' and that regulating them effectuates the goals and
policies of the CWA.
    Lakes and ponds that satisfy any of the conditions in paragraph
(a)(1) are traditionally navigable waters and as such should be
considered waters of the United States for the same reasons discussed
under the rationale for (a)(1) waters in this proposal. Lakes and ponds
that contribute perennial or intermittent flow to an (a)(1) water in a
typical year either directly or indirectly through an (a)(2)-(6) water
or through water features identified in paragraph (b) of this proposal
so long as those water features convey perennial or intermittent flow
would also be considered waters of the United States. Such lakes and
ponds would contribute flow in a manner similar to a tributary and
would be jurisdictional for the same reasons that a tributary would be
jurisdictional. Lakes and ponds that contribute flow to traditional
navigable waters through ephemeral flow would be excluded for the same
reasons that

ephemeral features are proposed to be not jurisdictional. The agencies
believe that this proposed category of lakes and ponds better reflects
the limits to the agencies' authority that the plurality and concurring
opinions recognized in Rapanos.
    By requiring that a contribution of flow exists as perennial or
intermittent flow between lakes and ponds and traditional navigable
waters, including the territorial seas, in the proposed definition, the
agencies would establish that a mere hydrologic connection cannot
provide the basis for CWA jurisdiction; the connection must be
perennial or intermittent flow from the lake or pond. This proposed
requirement is informed by Rapanos wherein the plurality rejected the
Federal government's hydrologic connection theory in deciding 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. It also
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 (emphasis added).
    Lakes and ponds that are flooded by an (a)(1)-(5) water in a
typical year would be considered waters of the United States under this
proposal. See Rapanos, 474 U.S. at 732 (Scalia, J., plurality)
(recognizing that the term ``the waters'' within ``the waters of the
United States'' includes ``the flowing or moving masses, as of waves or
floods, making up . . . streams or bodies,'') (emphasis added)
(internal quotations omitted); id. at 770 (Kennedy, J., concurring)
(``the term `waters' may mean `flood or inundation' events that are
impermanent by definition'') (emphasis added) (internal citations
omitted). During times of inundation occurring from a jurisdictional
water to a lake or pond in a typical year, such lake or pond is
indistinguishable from and inseparably bound up with other waters of
the United States.
    Flooding from a water of the United States to a jurisdictional lake
or pond can occur as a result of seasonal or permanent flooding, for
example, so long as flood waters connect such lakes or ponds to other
waters of the United States in a typical year and have as their source
a jurisdictional water. A mere hydrologic connection between a
nonnavigable, isolated, intrastate lake or pond and a jurisdictional
water, however, may be insufficient to establish jurisdiction under the
proposed rule. For instance, a lake or pond that may be connected to a
``water of the United States'' by flooding, on average, once every 100
years would not be jurisdictional under this proposal. To be
jurisdictional, a lake or pond that is otherwise physically separated
from a ``water of the United States'' would need to be flooded by a
jurisdictional water during a typical year; ecological connections
between physically separated lakes and ponds and otherwise
jurisdictional waters cannot be used to assert jurisdiction according
to this proposal. See 547 U.S. at 741-42 (Scalia, J., plurality)
(``SWANCC found such ecological consideration irrelevant to the
question whether physically isolated waters come within the Corps'
jurisdiction.'').
    The proposed lakes and ponds category would replace existing
procedures that may depend on case-specific ``significant nexus''
analyses of the relationship between a particular lake or pond with
downstream waters. The agencies are proposing to eliminate this case-
specific ``significant nexus'' analysis by providing a clear category
of ``waters of the United States'' that is easier for members of the
public and regulatory agencies to implement. In light of the clearer
lakes and ponds category proposed today, the agencies propose to
eliminate the case-specific significant nexus review through
categorical treatment of certain lakes and ponds as ``waters of the
United States.''
    This proposed rule identifies a category of certain lakes and ponds
that due to their contribution of perennial or intermittent flow to
navigable waters should be federally regulated. Through this proposed
category, the agencies would also acknowledge the policy direction from
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 proposed approach to lakes and ponds is also
intended to avoid ``impairing or in any manner affecting any right or
jurisdiction of the States with respect to waters (including boundary
waters) of such States.'' 33 U.S.C. 1370. For example, lakes and ponds
which contribute ephemeral flow, such as through dry washes and
arroyos, that lack the required perennial or intermittent flow regime
necessary to satisfy the conditions of jurisdictional lakes and ponds
under this proposed rule would not be ``waters of the United States.''
Those features are, however, water resources of the States, and
therefore, States have an inherent interest in regulating such features
pursuant to the powers reserved to the States under the Constitution.
See., e.g., North Dakota, 127 F. Supp. 3d at 1059. States and Tribes
may therefore address such features under their own laws to the extent
they deem appropriate. Lakes and ponds that contribute flow through
ephemeral features may also constitute point sources that discharge
pollutants to a ``water of the United States.'' See Rapanos, 547 U.S.
at 743-44 (Scalia, J., plurality). In those instances, authority to
regulate water quality in downstream waters under the CWA is not lost
to either Federal or State governments.
3. How might the agencies implement this approach?
    Most lakes and ponds are formed through a variety of events,
including glacial, tectonic, and volcanic activity. Lakes and ponds can
also be man-made features for industrial and agricultural uses, power
generation, domestic water supply, or for aesthetic or recreational
purposes. Most lakes and ponds have at least one natural outflow in the
form of a river or stream, which maintain a lake's average level by
allowing the drainage of excess water. Some lakes do not have a natural
outflow and lose water solely by evaporation or underground seepage or
both. Individual lakes and ponds range in size. Ponds are generally
smaller in size than lakes but regional naming conventions vary. Lakes
are also generally deeper than ponds.
    The tools and guidance which are described in Section III.A can be
used to determine whether a lake or pond meets the terms of an (a)(1)
water and as such would be jurisdictional under this proposed rule as
an (a)(1) water, as well as an (a)(5) water. The same tools discussed
in Section III.C can also be helpful in establishing the presence of a
lake or pond. For example, where an enclosed body of water is displayed
on a USGS topographic map or in NHD data it may indicate a lake or pond
is present. USGS maps often include different symbols to indicate
perennial or intermittent lakes and ponds and even a different symbol
to indicate dry lakes and ponds, which may be helpful in determining
whether such lakes and ponds satisfy the proposed definition of
``waters of the United States.'' Waterbodies such as lake and pond
features are also represented in NHDWaterbody. The NHD portrays the
spatial geometry and the attributes of the feature. These water
polygons may

also have NHDFlowline artificial paths drawn through them to allow the
representation of water flow direction. Combining this information with
climate and surrounding hydrology information can yield greater
certainty as to the presence of a lake or pond and the flow regime the
lake or pond contributes downstream. These tools may also be helpful in
indicating whether the lake or pond is part of the ``waters of the
United States'' network because they may identify whether it
contributes perennial or intermittent flow downstream. For example, the
presence of a ``blue line stream'' on USGS topographic or NHD maps
which extends from the lake or pond may indicate the lake or pond
contributes perennial or intermittent flow, directly or indirectly
through an (a)(2)-(6) water, to the (a)(1) water in a typical year,
which may indicate that the lake or pond is jurisdictional. Other
reliable methods that can indicate existence of a lake or pond and
potential jurisdictional status include gage data, bathymetry data,
elevation data, spillway height, historic water flow records, flood
predictions, statistical evidence, and direct observation.
    The agencies are proposing that lakes and ponds that are flooded by
a water identified in paragraphs (a)(1)-(5) in a typical year would
also be waters of the United States. The agencies propose to use flood
records, precipitation data, elevation data, aerial photography, and
field observations to help identify when a lake or pond may be flooded
by an (a)(1)-(5) water in a typical year. Oxbows may be jurisdictional
under this category.
    The information provided by the tools described above will vary in
validity in different parts of the country, so care would be taken to
evaluate the information prior to reasonably concluding a lake or pond
is jurisdictional. Supporting information, as well as field work, may
also be used to conclude the presence of a jurisdictional lake or pond.
4. What are specific issues upon which the agencies are seeking
comment?
    The agencies welcome comment on the proposal to establish a
distinct jurisdictional category for lakes and ponds and whether this
provides additional clarity and regulatory certainty. In the
alternative, the agencies solicit comment on incorporating
jurisdictional lakes and ponds into another category, such as
tributaries. The agencies note that there is considerable uncertainty
about defining the difference between lakes and ponds, and no current
accepted definition of either term across scientific disciplines
exists. The agencies are soliciting comment on whether a specific
definition of lakes and ponds should be provided in the rule language
or whether any such definition is necessary. For example, the Corps has
a definition of ``lake'' provided at 33 CFR 323.2, which includes,
``The term lake means a standing body of open water that occurs in a
natural depression fed by one or more streams from which a stream may
flow, that occurs due to the widening or natural blockage or cutoff of
a river or stream, or that occurs in an isolated natural depression
that is not a part of a surface river or stream. The term also includes
a standing body of open water created by artificially blocking or
restricting the flow of a river, stream, or tidal area. . . .''
Alternatively, other definitions could be used to define lakes and
ponds, such as the Cowardin classification system developed by the U.S.
Fish and Wildlife Service which could use the permanently flooded and
semi-permanently flooded for non-tidal waters categories. Such
definition could be, ``Lakes and ponds are either semi-permanently or
permanently flooded during a typical year and may or may not exhibit
hydrophytic vegetation.'' There may also be other parameters used to
define lakes and ponds, such as size and depth. For example, in the
1975 regulations, the Corps had proposed a minimum size requirement on
lakes of five acres to be waters of the United States. See 40 FR 31321.
However, such size requirement received many negative comments that the
size was too small or too large or did not account for seasonal changes
in sizes of lakes, while others commented on the legality of imposing
size limitations on lakes. See 42 FR 37129. Also, the agencies
recognize that States and Tribes may have specific, validated tools
they employ to identify lakes or ponds and are soliciting comment on
those approaches which may be useful for application in this proposed
rule.
    The agencies solicit comment on whether more specific parameters
should be included for the type of flooding that should be included for
lakes and ponds when flooded by an (a)(1)-(5) water in a typical year.
For example, the agencies request comment as to whether to establish a
specific flooding periodicity or magnitude or frequency. The agencies
also solicit comment on other implementation tools available to
determine the presence of a contribution of perennial or intermittent
flow from the lake or pond in a typical year. Additionally, the
agencies request comment on whether less than intermittent flow from
lakes and ponds to an (a)(1) water in a typical year could be
sufficient to extend jurisdiction to such lakes and ponds.

G. Wetlands

1. What are the agencies proposing?
    The agencies propose a category of ``waters of the United States''
to include all adjacent wetlands to: Traditional navigable waters,
including the territorial seas; tributaries to those waters;
jurisdictional ditches; jurisdictional lakes and ponds; and
impoundments of otherwise jurisdictional waters. The agencies propose
to maintain their longstanding regulatory definition of ``wetlands'' to
mean ``those areas that are inundated or saturated by surface or ground
water at a frequency and duration sufficient to support, and that under
normal circumstances do support, a prevalence of vegetation typically
adapted for life in saturated soil conditions. Wetlands generally
include swamps, marshes, bogs, and similar areas.'' The presence and
boundaries of wetlands are determined based upon an area satisfying all
three of the definition's criteria (i.e., hydrology, hydrophytic
vegetation, and hydric soils) under normal circumstances.
    The agencies propose to define the term ``adjacent wetlands'' to
mean wetlands that abut or have a direct hydrologic surface connection
to other ``waters of the United States'' in a typical year. ``Abut'' is
proposed to mean when a wetland touches a water of the United States at
either a point or side. A ``direct hydrologic surface connection'' as
proposed occurs as a result of inundation from a jurisdictional water
to a wetland or via perennial or intermittent flow between a wetland
and a jurisdictional water.
    The agencies propose that when wetlands are physically separated
from jurisdictional waters by upland or by dikes, barriers, or similar
structures and also lack a direct hydrologic surface connection to
jurisdictional waters, those wetlands are not adjacent. ``Upland'' in
the proposed rule refers to any land area above the ordinary high water
mark or high tide line that does not satisfy all three wetland
delineation factors (i.e., hydrology, hydrophytic vegetation, and
hydric soils) under normal circumstances, as described in the Corps'
1987 Wetland Delineation Manual. Features that were once wetlands but
have been naturally transformed or lawfully converted to upland (e.g.,
in compliance with a section 404 permit) would be

considered upland. A ``typical year'' means within the normal range of
precipitation over a rolling 30-year period for a particular geographic
area. For convenience, the agencies propose to include the existing
Corps definitions for ``ordinary high water mark'' and ``high tide
line'' from 33 CFR 328.3, as those terms are used in the proposed
definition of ``upland.''
    Wetlands that have a direct hydrologic surface connection to a
``water of the United States'' via inundation by a jurisdictional water
during a typical year would be adjacent wetlands under the proposal.
Similarly, a wetland has a direct hydrologic surface connection to a
jurisdictional water and is an adjacent wetland if the wetland and
jurisdictional water are connected via perennial or intermittent flow
in a typical year. The perennial or intermittent flow constituting the
direct hydrologic surface connection may occur in either direction
(i.e., jurisdictional water to wetland or wetland to jurisdictional
water). Perennial or intermittent flow between a wetland and
jurisdictional water may occur through upland or through a dike,
barrier, or similar structure via a culvert, tide gate, or other
feature. Perennial or intermittent flow between a wetland and
jurisdictional water may also occur as a result of a wetland
overtopping upland or overtopping a dike, barrier, or similar structure
and flowing directly into a jurisdictional water.
2. Why are the agencies proposing this approach?
    The agencies are proposing the definition of ``adjacent wetlands''
based on the core principles and concepts set forth in the three major
Supreme Court cases addressing the scope of the phrase ``the waters of
the United States,'' as discussed at length in Section II.E.2. In
summary, adjacent wetlands as proposed form part of the ``waters of the
United States''; otherwise they are isolated from ``waters of the
United States'' and not jurisdictional. The agencies' proposed
definition is consistent with the ordinary meaning of the term
``waters'' described in those cases and is intended to implement the
CWA policy directive of preserving the ability of the States to
regulate land and waters within their boundaries. The agencies view the
proposed definition as establishing a clear, predictable regulatory
framework that can be efficiently implemented in the field.
    This proposed definition of ``adjacent wetlands'' as wetlands
abutting or having a direct hydrologic surface connection to other
jurisdictional waters in a typical year rests on several key factors
and considerations. As a threshold matter, the proposed definition is
informed by the Supreme Court decisions in Riverside Bayview, SWANCC,
and Rapanos. For example, the agencies considered the holding in
Riverside Bayview ``that a definition of `waters of the United States'
encompassing all wetlands adjacent to other bodies of water over which
the Corps has jurisdiction is a permissible interpretation of the
Act.'' 474 U.S. at 135. The proposed definition is consistent with the
holding in Riverside Bayview and with the Supreme Court's subsequent
interpretation of Riverside Bayview and the scope of CWA jurisdiction
over wetlands in Rapanos, in which both the plurality and concurring
opinions agreed that waters of the United States encompass wetlands
closely connected to navigable waters. As discussed in Section II.E.2,
the plurality characterized the scope of CWA jurisdiction over wetlands
as encompassing wetlands, like those at issue in Riverside Bayview,
with a ``continuous surface connection'' or a ``continuous physical
connection'' to a navigable water, Rapanos, 547 U.S. at 742, 751 n.13.
Justice Kennedy's concurrence recognized that ``the connection between
a nonnavigable water or wetland and a navigable water may be so close,
or potentially so close, that the Corps may deem the water or wetland a
`navigable water' under the Act.'' Id. at 767. The concepts of
``abutting'' and a ``direct hydrologic surface connection'' in this
proposal are consistent with the Rapanos plurality's continuous surface
connection requirement. Because the concept of ``abutting'' in this
proposal does not require the existence of a hydrologic connection
between wetlands that physically touch jurisdictional waters, this
concept is also consistent with Justice Kennedy's statement that
``[g]iven the role wetlands play in pollutant filtering, flood control,
and runoff storage, it may well be the absence of hydrologic connection
(in the sense of interchange of waters) that shows the wetlands'
significance for the aquatic system.'' Id. at 786. The agencies
acknowledge, however, that non-abutting wetlands may also lack a
hydrologic connection. Those non-abutting wetlands would not be
considered adjacent under this proposal because the agencies believe
they do not implicate the line-drawing concerns articulated in
Riverside Bayview, SWANCC, and the Rapanos plurality, and because this
proposed definition will provide clear, understandable delineation
between Federal waters and state land and water resources.
    The limits to this proposed definition, i.e., the categories of
wetlands that the proposed definition would not encompass, are
consistent with the principles articulated in the three key Supreme
Court decisions. The inquiry as to where to draw the line between
jurisdictional and non-jurisdictional wetlands is laid out in Riverside
Bayview: ``[i]n determining the limits of its power to regulate
discharges under the Act, the Corps must necessarily choose some point
at which water ends and land begins . . . . Where on this continuum to
find the limit of `waters' is far from obvious.'' 474 U.S. at 132.
While the Court in Riverside Bayview identified this inquiry as a task
for the Corps and deferred to the Corps' judgment under Chevron
principles, the Supreme Court has subsequently recognized outer bounds
for the scope of ``waters of the United States.''
    In SWANCC, the Supreme Court held that the agencies do not have
authority to regulate nonnavigable, isolated, intrastate waters that
lack a sufficient connection to a traditional navigable water, as
regulation of those waters would raise constitutional questions
regarding the scope of CWA authority. 531 U.S. at 172. The plurality
opinion in Rapanos elaborated further on the wetlands that it did not
consider jurisdictional under the Act, specifically, wetlands with only
an ``intermittent, physically remote hydrologic connection to `waters
of the United States,' '' as those ``do not implicate the boundary-
drawing problem of Riverside Bayview.'' 531 U.S. at 742. The proposed
definition also reflects Justice Kennedy's concurring opinion in
Rapanos that in some instances, as exemplified by the ``ponds and
mudflats that were isolated in the sense of being unconnected to other
waters covered by the Act,'' ``there may be little or no connection''
``between a nonnavigable water or wetland and a navigable water.'' Id.
at 766-67. The proposal is consistent with SWANCC and the Rapanos
plurality opinion in that it would exclude isolated wetlands with only
physically remote hydrologic connections to jurisdictional waters.
Under the proposed definition, ecological connections alone would not
provide a basis for including physically isolated wetlands within the
phrase ``the waters of the United States.'' See, e.g., id. at 741-42
(Scalia, J., plurality) (``SWANCC rejected the notion that the
ecological considerations upon which the Corps relied in Riverside
Bayview--and upon which the dissent repeatedly relies today . . .--
provided an

independent basis for including entities like `wetlands' (or `ephemeral
streams') within the phrase `the waters of the United States.' SWANCC
found such ecological considerations irrelevant to the question whether
physically isolated waters come within the Corps' jurisdiction.''
(original emphasis)).
    In assessing the appropriate ``limits of `waters' '' on the
continuum between water and land, the proposed definition balances the
inclusion of wetlands that have a direct hydrologic surface connection
to otherwise jurisdictional waters during a typical year with the fact
that ``a mere hydrologic connection should not suffice in all cases.''
Id. at 784 (Kennedy, J., concurring). For example, the Rapanos
plurality questioned the Corps' broad interpretation of its regulatory
authority to ``conclude that wetlands are `adjacent' to covered waters
if they are hydrologically connected through directional sheet flow
during storm events or if they lie within the 100-year floodplain of a
body of water.'' Id. at 728 (internal citations and quotations
omitted). Similarly, Justice Kennedy believed that ``possible
flooding'' was an unduly speculative basis for a jurisdictional
connection between wetlands and other jurisdictional waters as applied
to the facts of Carabell. 547 U.S. at 786. In other words, wetlands
separated from otherwise jurisdictional waters by upland or by dikes,
barriers, or other similar structures are not adjacent simply because a
surface water connection between the two is possible or if, for
example, wetlands ``are connected to the navigable water by flooding,
on average, once every 100 years'' or by directional sheet flow during
an individual storm event. Id. In order to satisfy this proposed
``adjacent wetlands'' definition, a wetland separated from other waters
of the United States by upland or by dikes, barriers, or other similar
structures would have to have a direct hydrologic surface connection to
an otherwise jurisdictional water in a typical year.
    As proposed, a direct hydrologic surface connection occurs as a
result of inundation from a jurisdictional water to a wetland or via
perennial or intermittent flow between a wetland and a jurisdictional
water. Inundation can occur as a result of seasonal or permanent
flooding, for example, so long as inundation occurs in a typical year
and has as its source a jurisdictional water. A direct hydrologic
surface connection that occurs as a result of perennial or intermittent
flow between a wetland and a jurisdictional water must satisfy the
definitions of ``perennial'' or ``intermittent'' in this proposal and
can occur either from a jurisdictional water to a wetland or from a
wetland to a jurisdictional water. Ephemeral flow or ephemeral pooling