The agencies received many comments on the proposed rule's reliance
on and approach to the significant nexus standard. As explained in
section IV.A.3.a of this preamble, the agencies have concluded that the
significant nexus standard is consistent with the statutory text and
legislative history, advances the objective of the Clean Water Act, is
informed by the scientific record and Supreme Court case law, and
appropriately considers the policies of the Act. The agencies have the
authority to define the scope of the term ``navigable waters,'' and
they are exercising that authority in this rule. A principal advantage
of the significant nexus standard is that it focuses directly and
specifically on protecting the integrity of those waters in which the
Federal interest is indisputable--traditional navigable waters, the
territorial seas, and interstate waters. Further, while the agencies
disagree that this rule's significant nexus standard is inconsistent
with Justice Kennedy's concurring opinion in Rapanos (as some
commenters had suggested), this rule represents the agencies'
interpretation of the statute, not an interpretation of Rapanos. The
agencies have concluded that the significant nexus standard as
established in this rule is the best interpretation of the statute and
that the relatively permanent standard in the rule provides important
efficiencies and additional clarity for regulators and the public.
Thus, the rule gives effect to the Clean Water Act's broad terms and
environmentally protective aim as well as its limitations.
    Some commenters suggested that the significant nexus standard is
unclear or produces inconsistent results. In response to this concern,
the agencies have established a definition of ``significantly affect''
in this rule, provided additional guidance on applying the significant
nexus standard, and identified implementation tools and resources that
will work together to provide clarity and further consistency in
implementing the significant nexus standard (see section IV.C.9 and
section IV.G of this preamble). The agencies have concluded that these
actions, along with the agencies' extensive experience making
determinations under the significant nexus standard, will increase the
clarity and consistency of determinations of jurisdiction.
    Several commenters discussed whether the proposed rule is
consistent with Justice Scalia's plurality opinion in Rapanos and
expressed various views about the proper interpretation of that
opinion. As discussed in section IV.A.3.a of this preamble, the
agencies have concluded that use of the plurality's approach alone has
no grounding in the Clean Water Act's text, structure, or history and
would upend an understanding of the Act's coverage that has prevailed
for decades. Similarly, no Court of Appeals has held that the
plurality's relatively permanent standard is the sole test that may be
used to establish Clean Water Act jurisdiction. Additionally, requiring
a continuous surface water connection, as suggested by some commenters,
would add a requirement and language that do not exist in the text of
the plurality opinion. The plurality opinion states that ``continuous
surface connection'' is a ``physical-connection requirement.'' Rapanos,
547 U.S. at 742, 751 n.13 (referring to ``our [the plurality's]
physical-connection requirement'' and asserting that Riverside Bayview
does not reject ``the physical-connection requirement''). The plurality
does not state that this standard is a continuous surface water
requirement. Therefore, the agencies disagree that their longstanding
implementation of the continuous surface connection requirement (see
Rapanos Guidance at 7 n.28), which does not require a continuous flow
of water between the wetland and the jurisdictional water, is
inconsistent with the plurality opinion. In addition, a continuous
surface water connection for wetlands is illogical when many wetlands
have surface water only seasonally or intermittently or meet the
wetland hydrology factor through saturated soils, a high water table,
or other indicators of hydrology, and no scientific or regulatory
definition of wetlands demands year-round surface water. See, e.g., 33
CFR 328.3(b) (2008); NRC Report 3-5; see also 85 FR 22309 (explaining
that ``not all abutting wetlands display surface water as the wetland
hydrology factor but rather may have saturated soils, a high water
table, or other indicators of hydrology''). See section IV.C.5.c.ii of
this preamble for further discussion of the basis for the agencies'
implementation of the continuous surface connection requirement in this
rule.
    Additionally, multiple commenters suggested that the relatively
permanent

standard is easier to apply than the significant nexus standard. While
the agencies recognize that the relatively permanent standard can be
easier to apply in many instances, that is not always the case. For
example, in the case of a tributary that flows directly into a
traditional navigable water, it may be easier to demonstrate that the
tributary significantly affects the chemical, physical, or biological
integrity of that paragraph (a)(1) water due to its direct contribution
of flow, woody debris, and other materials and its close distance to
the traditional navigable water than it would be to demonstrate that
the flow in that tributary meets the relatively permanent standard.
More importantly, greater simplicity that comes at the expense of a
profound mismatch with the Clean Water Act's design is not a valid
basis for determining the jurisdictional scope of the Act. Cf. Maui,
140 S. Ct. at 1470, 1476 (rejecting similar arguments about a need for
bright-line certainty in favor of a fact-specific test). Further,
treating the relatively permanent standard as the exclusive criterion
for Clean Water Act coverage would lead to arbitrary and illogical
results. The 2020 NWPR did rely primarily on the relatively permanent
standard and, in doing so, introduced new implementation uncertainties,
including uncertainties related to the rule's case-specific typical
year analysis, which the 2020 NWPR required for most categories of
jurisdictional waters and that proved challenging to implement and
yielded arbitrary results (see section III.B.3 and IV.B.3 of this
preamble). In contrast, as discussed above, the agencies now have over
a decade of nationwide experience with the significant nexus standard,
and it has proven to be eminently administrable. Moreover, the agencies
have made changes to this rule to increase the ease of implementation
of the significant nexus standard.
    Commenters also provided a variety of views on the consistency of
the proposed rule with the SWANCC Supreme Court decision. Some
commenters expressed concern that the proposed rule would expand
Federal jurisdiction over potentially all State waters, contrary to the
Supreme Court's holding in SWANCC that--absent a clear statement from
Congress--the Clean Water Act must be construed in a manner that avoids
federalism and constitutional questions. The agencies disagree that
this rule is contrary to the Supreme Court's holding in SWANCC and note
that a principal advantage of the significant nexus standard is that it
focuses directly and specifically on protecting traditional navigable
waters, the territorial seas, and interstate waters. By design, the
significant nexus standard thereby permits jurisdiction over waters
only if they significantly affect the waters over which Congress has
unquestioned authority. See, e.g., United States v. Lopez, 514 U.S.
549, 558-59 (1995); Hodel v. Va. Surface Mining & Reclamation Ass'n,
452 U.S. 264, 282 (1981). Thus, an affirmative finding under the
significant nexus standard is, by definition, a finding that Congress's
core purpose is implicated. Commenters' constitutional concerns are
therefore fully addressed by this rule.
    In addition, a few commenters asserted that the Supreme Court in
SWANCC rejected the notion that a biological or ecological connection
alone is sufficient to support a finding of significant nexus. This
reading of SWANCC is not correct. The Court in SWANCC did not hold that
the particular ``ecological considerations upon which the Corps relied
in Riverside Bayview,'' Rapanos, 547 U.S. at 741--i.e., the potential
importance of wetlands to the quality of adjacent waters--were
irrelevant to Clean Water Act jurisdiction. Rather, the Court held that
a different ecological concern--namely, the potential use of the
isolated ponds as habitat for migratory birds--could not justify
treating those ponds as ``waters of the United States.'' See SWANCC,
531 U.S. at 164-65, 171-72. The Court found that this specific
ecological concern was not cognizable because it was unrelated to
``what Congress had in mind as its authority for enacting the CWA: its
traditional jurisdiction over waters that were or had been navigable in
fact or which could reasonably be so made.'' Id. at 172. In contrast,
in this rule, the agencies, through application of the significant
nexus standard, provide Federal protections for adjacent wetlands and
other categories of waters based on their importance to the chemical,
physical, or biological integrity of traditional navigable waters, the
territorial seas, and interstate waters. In addition, the objective of
the Clean Water Act is ``to restore and maintain the chemical,
physical, and biological integrity of the Nation's waters.'' 33 U.S.C.
1251(a) (emphasis added). Among the means to achieve the Clean Water
Act's objective, Congress established an interim national goal to
achieve wherever possible ``water quality which provides for the
protection and propagation of fish, shellfish, and wildlife and
provides for recreation in and on the water.'' 33 U.S.C. 1251(a)(2).
Therefore, the agencies disagree that consideration of biological
effects on paragraph (a)(1) waters is inconsistent with the Clean Water
Act.
    Finally, several commenters asserted that the Clean Water Act
requires broader protections than those afforded by the significant
nexus standard and relatively permanent standard. The agencies agree
that the Clean Water Act requires broader protection than the
relatively permanent standard, but have concluded, as explained in
section IV.A.3 of this preamble, that the significant nexus standard is
the best construction of the scope of the Clean Water Act.
c. Comments Regarding Categories of Waters in This Rule
    Multiple commenters expressed concern that the proposed rule would
exceed the agencies' statutory authority by providing for jurisdiction
over broad categories of waters (for example, tributaries) that the
commenters asserted are not within the limits of the Clean Water Act
pursuant to Rapanos. The agencies disagree. As explained above, this
rule reflects the agencies' independent judgment on the scope of
``waters of the United States'' based on the text of the relevant
provisions of the Clean Water Act and the statute as a whole, the
objective and history of the Clean Water Act, the scientific record,
the agencies' experience and technical expertise, and other relevant
Supreme Court cases. This rule reflects carefully tailored
modifications to the 1986 regulations to incorporate both the
relatively permanent standard and the significant nexus standard such
that the waters covered by the definition are within the limits of the
Clean Water Act.
    Many commenters discussed the agencies' legal authority to assert
jurisdiction over tributaries, including specific types of tributaries
(e.g., ephemeral, intermittent, and perennial). Some commenters
asserted that providing for jurisdiction over ephemeral and
intermittent streams in the definition of ``waters of the United
States'' is not supported by Rapanos. In this rule, the agencies are
neither categorically including nor categorically excluding ephemeral
and intermittent tributaries. Nor are the agencies codifying the
opinions in Rapanos. Rather, the agencies are interpreting the phrase
``waters of the United States'' to include tributaries that meet either
the significant nexus standard or the relatively permanent standard
based on their conclusions in section IV.A of this preamble. Further,
there is nothing in the text of the statute or its legislative history
that excludes some categories of

tributaries based on their flow regime. Indeed, as discussed further
below, the best available science demonstrates that ephemeral and
intermittent streams can significantly affect the chemical, physical,
and biological integrity of paragraph (a)(1) waters--i.e., traditional
navigable waters, the territorial seas, and interstate waters.
    Multiple commenters suggested that, pursuant to Supreme Court
precedent and the Clean Water Act, jurisdiction over non-navigable
tributaries should be limited to tributaries (1) containing clearly
discernible features and contributing consistent flow into traditional
navigable waters; or (2) that carry a volume of water needed for
navigable capacity of a traditional navigable water; or (3) of a
quality needed for interstate commerce, where impairment of water
quality would have a negative effect on interstate commerce. The
agencies disagree that the case law, the statute, or the Constitution
provide these precise limitations on the scope of tributaries covered
by the Clean Water Act. The text of ``navigable waters,'' and of its
specialized definition, does not include particular flow requirements.
As discussed further below, the agencies have concluded that
tributaries that meet either the relatively permanent standard or the
significant nexus standard are ``waters of the United States,'' and
flow is a consideration under both standards. These limitations are
informed by Supreme Court case law and designed to be well within
constitutional limits.
    In contrast, other commenters asserted that tributaries should be
categorically jurisdictional rather than subject to a case-specific
analysis and that the Rapanos decision supports a categorical approach.
The agencies agree that Justice Kennedy's concurring opinion in Rapanos
did not reject the agencies' then-existing regulations governing
tributaries, which were more categorical than this rule. 547 U.S. at
781; see also id. at 761. More broadly, it is a well-established
principle of administrative law that agencies may choose to proceed via
rulemaking or adjudication. NLRB v. Bell Aerospace Co. Div. of Textron,
Inc., 416 U.S. 267, 294 (1974) (``[T]he choice between rulemaking and
adjudication lies in the first instance within the [agency's]
discretion.''). With respect to the significant nexus standard in
particular, Justice Kennedy stated that the agencies could proceed to
determine tributaries and their adjacent wetlands jurisdictional
through regulations or adjudication. See Rapanos, 547 U.S. at 780-81.
As explained in section IV.A.3.a.iii of this preamble, the agencies
have concluded that adjudication of which tributaries are within Clean
Water Act protections, through case-specific application of the
significant nexus standard or the relatively permanent standard under
this rule, is appropriate. See section IV.C.10 of this preamble for
additional guidance to landowners on determinations of jurisdiction and
the appeals process for such determinations.
    Many commenters also discussed the agencies' legal authority to
assert jurisdiction over adjacent wetlands. Some commenters stated that
the proposed rule's relatively permanent standard was inconsistent with
the Rapanos plurality opinion, asserting that the plurality opinion
requires a continuous surface connection for adjacent wetlands to be
jurisdictional. As stated elsewhere, the agencies disagree that the
relatively permanent standard as applied in this rule is inconsistent
with the plurality opinion. Under this rule, an adjacent wetland is
jurisdictional if there is a continuous surface connection between that
adjacent wetland and a paragraph (a)(2) impoundment or jurisdictional
tributary when the paragraph (a)(2) impoundment or jurisdictional
tributary is relatively permanent.
    In addition, some commenters expressed concern that the proposed
rule's aggregation of wetlands and the relevant reach approach would be
contrary to Justice Kennedy's significant nexus standard, which the
commenters suggested requires that each wetland be judged in its own
right. The agencies disagree that aggregation of wetlands and their
tributaries is inconsistent with the significant nexus standard. First,
Justice Kennedy explicitly stated that similarly situated waters should
be assessed for a significant nexus ``alone or in combination.''
Rapanos, 547 U.S. at 780. Justice Kennedy understood that waters
provide critical functions to downstream waters in combination,
explaining: ``With respect to wetlands, the rationale for Clean Water
Act regulation is, as the Corps has recognized, that wetlands can
perform critical functions related to the integrity of other waters--
functions such as pollutant trapping, flood control, and runoff
storage. Accordingly, wetlands possess the requisite nexus, and thus
come within the statutory phrase `navigable waters,' if the wetlands,
either alone or in combination with similarly situated lands in the
region, significantly affect the chemical, physical, and biological
integrity of other covered waters more readily understood as
`navigable.' '' Id. at 779-780 (citing 33 CFR 320.4(b)(2)). And Justice
Kennedy's understanding is scientifically correct--though filling in a
single wetland might not on its own materially influence a paragraph
(a)(1) water, its impact is more likely to be significant when
evaluated in combination with other similarly situated waters. Second,
the agencies interpret ``waters of the United States'' to include
waters that meet the significant nexus standard as codified in this
rule because the agencies have determined, informed by the best
available science and the text, structure, and legislative history of
the Clean Water Act, that this standard, including the aggregation of
waters authorized by it, advances the objective of the Act. The
agencies have also established a definition of ``significantly affect''
in this rule that identifies the factors and the functions for
determining whether the significant nexus standard is met, thus
ensuring that the agencies' determinations of jurisdiction are based on
consistent application of sound scientific principles.
    Further, several commenters stated that the agencies should assert
jurisdiction only over those wetlands that directly abut other ``waters
of the United States.'' These commenters asserted that doing otherwise
would exceed the constitutional limits of the agencies' Clean Water Act
jurisdiction. For the reasons discussed above, the agencies disagree
that only wetlands that directly abut other ``waters of the United
States'' should be jurisdictional. Moreover, as discussed elsewhere in
this preamble, the addition of the significant nexus standard in this
rule ensures that the definition of ``waters of the United States''
does not exceed constitutional limits.
    In contrast, several commenters asserted that all adjacent
wetlands--not just those adjacent to the paragraph (a)(1) waters--
should be categorically jurisdictional. Some of these commenters
suggested that providing categorical protection for such wetlands is
necessary to achieve the Clean Water Act's statutory objective. The
agencies agree that providing categorical protection of adjacent
wetlands can be a means of achieving the Act's objective but disagree
that it is the only means. As noted by Justice Kennedy, the agencies
can reasonably proceed to determine which tributaries and their
adjacent wetlands are jurisdictional through regulations or
adjudication, see 547 U.S. at 780-81; see also NLRB v. Bell Aerospace
Co. Div. of Textron, Inc., 416 U.S. at 294. With respect to wetlands
adjacent to tributaries, the agencies are requiring case-specific
determinations

of whether such wetlands meet the relatively permanent standard or the
significant nexus standard to be jurisdictional under this rule.
    Many commenters also addressed the agencies' legal authority to
assert jurisdiction over paragraph (a)(5) waters (the category of
waters described in paragraph (a)(3) of the proposed rule). Some
commenters suggested that, per the Supreme Court's decision in SWANCC,
the agencies lack authority to assert jurisdiction over paragraph
(a)(5) waters or that, under Rapanos, the significant nexus standard
should be applied only to tributaries or wetlands adjacent to
tributaries, not to paragraph (a)(5) waters. First, as explained
further in section IV.A.1 of this preamble, in this rule the agencies
are exercising the authority granted to them by Congress to construe
and implement the Clean Water Act and to interpret an ambiguous term
and its statutory definition. Therefore, while the agencies'
interpretation of the statute is informed by Supreme Court decisions,
including Rapanos, it is not an interpretation of SWANCC or the
multiple opinions in Rapanos, nor is it based on an application of the
Supreme Court's principles as set forth in Marks to derive a governing
rule of law from a decision of the Court in a case such as Rapanos
where no opinion commands a majority. Furthermore, the agencies
disagree that asserting jurisdiction over any waters that meet the
significant nexus standard, including any paragraph (a)(5) waters, is
inconsistent with SWANCC or Rapanos. Based on the law, the science, and
agency expertise, the agencies conclude that the significant nexus
standard applies to tributaries, adjacent wetlands, and intrastate
lakes and ponds, streams, or wetlands not covered by other categories
(i.e., paragraphs (a)(3), (a)(4), and (a)(5) waters under this rule).
Justice Kennedy's explication of the significant nexus standard applies
to each of these types of waters. In Rapanos, Justice Kennedy reasoned
that Riverside Bayview and SWANCC ``establish the framework for''
determining whether an assertion of regulatory jurisdiction constitutes
a reasonable interpretation of ``navigable waters''--``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;'' and ``[a]bsent a
significant nexus, jurisdiction under the Act is lacking.'' 547 U.S. at
767. Justice Kennedy further explained that ``[t]he required nexus must
be assessed in terms of the statute's goals and purposes. Congress
enacted the law to `restore and maintain the chemical, physical, and
biological integrity of the Nation's waters,' and it pursued that
objective by restricting dumping and filling in `navigable waters'.''
Id. at 779 (citing 33 U.S.C. 1251(a), 1311(a), 1362(12)). Justice
Kennedy then concluded that the term ``waters of the United States''
encompasses wetlands and other waters that ``possess a `significant
nexus' to waters that are or were navigable in fact or that could
reasonably be so made.'' Id. at 759 (citation omitted). While Justice
Kennedy's discussion of the application of the significant nexus
standard focused on adjacent wetlands in light of the facts of the
cases before him, his opinion is clear that he does not conclude that
the significant nexus analysis applies only to adjacent wetlands. As he
explicitly states, ``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 (emphasis added). Fundamentally, Justice
Kennedy's significant nexus analysis is about the fact, long
acknowledged by Supreme Court case law, that protection of waters from
pollution can be achieved only by controlling pollution of upstream
waters. In addition, the Court in SWANCC did not hold that ``other
waters'' (a category that has been modified and codified in this rule
as paragraph (a)(5) waters) could never be jurisdictional; rather it
held that the potential use of isolated ponds as habitat for migratory
birds could not be used as the sole basis to justify treating those
ponds as ``waters of the United States.'' See 531 U.S. at 164-65, 171-
72. Indeed, the SWANCC Court in describing Riverside Bayview stated
that ``it was the significant nexus between the wetlands and `navigable
waters' that informed our reading of the CWA'' in that case. Id. at
167. In this rule, the agencies are not protecting paragraph (a)(5)
waters based on their potential use as habitat for migratory birds or
based on their use broadly in interstate commerce as the 1986
regulations did. Instead, this rule includes paragraph (a)(5) waters on
a case-specific basis based on their importance to the integrity of
traditional navigable waters, the territorial seas, and interstate
waters because they meet either the relatively permanent standard or
the significant nexus standard.
    Other commenters stated that the proposed rule does not go far
enough in protecting paragraph (a)(5) waters. The agencies have
concluded that this rule's reliance on the relatively permanent
standard and significant nexus standard properly balances the Clean
Water Act's broad statutory objective, while giving meaning to the word
``navigable.'' Accordingly, the agencies are not asserting jurisdiction
over waters and wetlands simply where ``the use, degradation or
destruction of [such waters] could affect interstate or foreign
commerce.'' Cf. 33 CFR 328.3(a)(3) (1999).

B. Alternatives to This Rule

    In promulgating a rule to repeal existing regulations, agencies
must address and consider alternative ways of achieving the relevant
statute's objectives and must provide adequate reasons to abandon those
alternatives. Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins.
Co., 463 U.S. 29, 48 (1983); see also FCC v. Fox Television Stations,
Inc., 556 U.S. 502, 515 (2009). As discussed below, the agencies have
thoroughly considered alternatives to this rule and have concluded that
this final rule best accomplishes the agencies' goals to promulgate a
rule that advances the objective of the Clean Water Act, is consistent
with Supreme Court decisions, is informed by the best available
science, and promptly and durably restores vital protections to the
nation's waters. The agencies have reconsidered the policies,
interpretations, and conclusions of the 2020 NWPR. Although the 2020
NWPR has been vacated, it is the text currently in the Code of Federal
Regulations. For the reasons articulated in this preamble, the agencies
are changing their approach from that of the 2020 NWPR to interpreting
the scope of ``waters of the United States.''
1. 2015 Clean Water Rule
    The agencies are not repromulgating the 2015 Clean Water Rule.
Unlike aspects of the 2015 Clean Water Rule, this rule is not based on
categorical significant nexus determinations. Rather, this rule
generally restores the longstanding and familiar categories of the 1986
regulations and establishes jurisdictional limitations based on case-
specific application of the relatively permanent standard and the
significant nexus standard to certain categories of waters in the rule.
    Many commenters expressed support for the 2015 Clean Water Rule
because they viewed it as informed by science, and because under that
rule certain types of waters were categorically jurisdictional, which
eliminated the need for extensive case-by-case

jurisdictional determinations. Many other commenters asserted that they
did not support the 2015 Clean Water Rule because they viewed that rule
as expanding Federal jurisdiction over waters that should not be
jurisdictional. The agencies have concluded that the 2015 Clean Water
Rule, while designed to advance the objective of the Clean Water Act,
is not the best alternative to meet the policy goals of the agencies:
to quickly promulgate a durable rule that retains the protections of
the longstanding regulatory framework and avoids harms to important
aquatic resources, informed by the best available science and
consistent with the agencies' determination of the statutory limits on
the scope of the ``waters of the United States,'' informed by relevant
Supreme Court case law. Moreover, agencies may choose to proceed via
rulemaking or adjudication. NLRB v. Bell Aerospace Co., 416 U.S. 267,
294 (1974) (``[T]he choice between rulemaking and adjudication lies in
the first instance within the [agency's] discretion.''). With respect
to the significant nexus standard in particular, Justice Kennedy also
stated that the agencies could proceed to determine tributaries and
their adjacent wetlands jurisdictional through regulations or
adjudication. See 547 U.S. at 780-81. As explained in section
IV.A.3.a.iii of this preamble, the agencies have concluded that the
approach in this rule--i.e., providing categorical jurisdiction for
paragraph (a)(1) waters and for wetlands adjacent to paragraph (a)(1)
waters, and adjudicating which waters in paragraphs (a)(2) through (5)
are ``waters of the United States'' through case-specific application
of the significant nexus standard or the relatively permanent standard
under this rule--is appropriate and fulfills the goals of the agencies
and the objective of the Clean Water Act.
2. 2019 Repeal Rule
    The agencies agree with the concept in the 2019 Repeal Rule of
returning to the pre-2015 regulatory framework as a means of restoring
a longstanding and familiar regulatory regime,\67\ but find that this
rule is preferable to the 2019 Repeal Rule for several reasons. As an
initial matter, like the 2019 Repeal Rule, this rule seeks to return
generally to the longstanding regulatory framework that existed prior
to the 2015 Clean Water Rule, but this rule also restores those
regulations with necessary limitations to ensure the definition of
``waters of the United States'' reflects consideration of the agencies'
statutory authority under the Clean Water Act and relevant Supreme
Court decisions. Additionally, compared to the 2019 Repeal Rule, this
rule provides greater clarity by adding a new definition of
``significantly affect'' and by streamlining and restructuring the 1986
regulations, including by consolidating certain provisions. This rule
also codifies a number of exclusions for features that were generally
considered non-jurisdictional under the pre-2015 regulatory regime and
thus provides more clarity and certainty than the 2019 Repeal Rule.
---------------------------------------------------------------------------

    \67\ 2019 Repeal Rule, Response to Comments at 9 (``The agencies
find that reinstating the longstanding and familiar pre-2015 Rule
regulatory regime will provide regulatory certainty in this interim
period . . . .''), 15 (``[T]his final rule to recodify the 1986
regulations will provide greater regulatory certainty and nationwide
consistency while the agencies consider public comments on the
proposed revised definition of ``waters of the United States.'').
---------------------------------------------------------------------------

    Moreover, the agencies have substantial concerns regarding the
legal rationale underpinning the 2019 Repeal Rule. In particular, the
agencies are concerned that the interpretation of relevant Supreme
Court case law in the 2019 Repeal Rule is flawed and thereby led to an
erroneous assessment of the legality of the approach to the significant
nexus standard in the 2015 Clean Water Rule. See, e.g., 84 FR 56638-52
(October 22, 2019). The agencies' reading of the Clean Water Act in the
2019 Repeal Rule is also inconsistent with the agencies' considered
interpretation, at this time, of the Act. For these reasons, the
agencies find that the 2019 Repeal Rule is not an appropriate
alternative to this rule.
3. 2020 NWPR
    The agencies have also evaluated the 2020 NWPR as an alternative to
this rule. After carefully considering the 2020 NWPR in light of the
text, objective, and legislative history of the Clean Water Act,
Supreme Court case law, the best available scientific information, and
the agencies' experience in implementing it for over a year, the
agencies do not find that the 2020 NWPR is a suitable alternative to
this rule.
a. The 2020 NWPR Failed To Advance the Objective of the Clean Water Act
    The agencies do not consider the 2020 NWPR to have advanced the
statutory objective of the Clean Water Act, which the Supreme Court
recently emphasized is an important aspect of defining the
jurisdictional scope of the Act. See, e.g., Maui, 140 S. Ct. at 1468-69
(emphasizing the importance of considering the Clean Water Act's
objective when determining the scope of the Act and finding that
``[t]he Act's provisions use specific definitional language to achieve
this result,'' including the phrase ``navigable waters''). One critical
example of the 2020 NWPR's failure to advance the Clean Water Act's
objective is its removal of the significant nexus standard without
considering an alternative approach to protecting waters that
significantly affect paragraph (a)(1) waters. To be clear, while the
agencies view the significant nexus standard as the best interpretation
of section 502(7) of the Clean Water Act, the agencies do not view the
Supreme Court's interpretations of the scope of ``waters of the United
States'' as requiring adoption of that approach. Rapanos, 547 U.S. at
758 (Roberts, C.J., concurring). Yet the 2020 NWPR's rejection of the
significant nexus standard while failing to adopt any alternative
standard for jurisdiction that adequately addresses the effects of
degradation of upstream waters on paragraph (a)(1) waters, fails to
advance the Clean Water Act's objective.
    The significant nexus inquiry reflects and furthers the objective
of the Clean Water Act by allowing for a scientific evaluation of the
effect of wetlands, tributaries, and other types of waters on paragraph
(a)(1) waters. For that reason, evolving forms of this inquiry are
present in Riverside Bayview, SWANCC, and Justice Kennedy's concurring
opinion in Rapanos. The 2020 NWPR rejected this scientific approach and
instead, for example, categorically excluded ephemeral features without
appropriately considering scientific information about their important
effects on the integrity of paragraph (a)(1) waters. In addition, in
limiting the scope of protected wetlands to those that touch other
jurisdictional waters or demonstrate evidence (which could include a
natural berm, bank, dune, or similar natural feature) of a regular
surface water connection to other jurisdictional waters, the 2020 NWPR
failed to appropriately consider the many effects of other categories
of wetlands on paragraph (a)(1) waters. For example, ephemeral streams
that flow directly into the Rio Grande (a traditional navigable water)
and wetlands separated from the Mississippi River (a traditional
navigable water) by artificial levees and that lack a direct hydrologic
surface connection to the river in a typical year, would be non-
jurisdictional under the 2020 NWPR, yet both can have significant
effects on these traditional navigable waters.
    The 2020 NWPR contended that the drastic reduction in the scope of
Clean Water Act jurisdiction ``pursues'' the objective of the Act
because it would be

supplemented by the Act's non-regulatory programs as well as Tribal,
State, and local efforts. The 2020 NWPR explained: ``The CWA's
longstanding regulatory permitting programs, coupled with the controls
that States, Tribes, and local entities choose to exercise over their
land and water resources, will continue to address the discharge of
pollutants into waters of the United States, and the CWA's non-
regulatory measures will continue to address pollution of the nation's
waters generally. These programs and measures collectively pursue the
objective of restoring and maintaining the chemical, physical, and
biological integrity of the nation's waters.'' 85 FR 22269 (April 21,
2020). The agencies disagree with the 2020 NWPR's assertion that such
``collective pursuit'' of the objective of the Clean Water Act based on
these programs and measures appropriately considers the objective of
the Act and have concluded that the 2020 NWPR did not advance the
objective of the Act, the proper measure under the statute and Supreme
Court case law of a rule defining ``waters of the United States.''
    The agencies agree with the 2020 NWPR's position that the Clean
Water Act's non-regulatory measures, such as grantmaking and technical
assistance authorities, advance the objective the Act. However, the
agencies do not view these authorities as limiting the scope of
``waters of the United States,'' or as relevant to determining whether
a definition of ``waters of the United States'' advances the objective
of the Clean Water Act. The non-regulatory Clean Water Act programs
cited by the 2020 NWPR complement and support the permitting programs
at the core of the Act, rather than limiting their geographic scope.
For example, the 2020 NWPR cited the Clean Water Act's provisions to
address pollution into key waters in its discussion, including the
Great Lakes, 33 U.S.C. 1258, the Chesapeake Bay, see id. at 1267(a)(3),
Long Island Sound, see id. at 1269(c)(2)(D), and Lake Champlain, see
id. at 1270(g)(2). These resources are ``waters of the United States''
to which regulatory programs apply, and the technical assistance and
grants in the cited sections assist States and others in achieving the
requirements of the Clean Water Act, but they do not limit the
regulatory programs' scope. To the extent there is ambiguity as to the
effects of these non-regulatory programs on the scope of the ``waters
of the United States,'' the agencies have concluded based on the text
and structure of the statute that they are complementary, rather than
limiting.
    As discussed in section III.A of this preamble, the Clean Water
Act's fundamental innovation in 1972 was to ``establish an all-
encompassing program of water pollution regulation,'' Int'l Paper Co.
v. Ouellette, 479 U.S. 481, 492-93 (1987). The definition of ``waters
of the United States'' establishes the scope of that program. The
agencies therefore find that it is appropriate to consider whether the
definition of the scope of waters to which the Clean Water Act's water
pollution regulations apply helps to achieve that objective. Thus, the
2020 NWPR's statement that this rule ``pursues'' the objective of the
Act if Clean Water Act and non-Clean Water Act programs are viewed in
``combination'' is not consistent with the better reading of the text
and structure of the Act, its legislative history, or Supreme Court
decisions concerning the effect of enactment of the Clean Water Act in
1972, nor does it fulfill the agencies' obligation to consider the
objective of the Clean Water Act by assessing the water quality effects
of revising the definition of ``waters of the United States.''
    The preamble to the 2020 NWPR also cited the introductory policy
provision of the Clean Water Act in section 101(b), to protect the
``primary responsibilities and rights of States to prevent, reduce, and
eliminate pollution'' as a justification, in part, for its line-
drawing. For example, one of the most environmentally significant
decisions in the 2020 NWPR was its categorical exclusion of all
ephemeral features from Clean Water Act jurisdiction. The agencies
cited section 101(b) as a basis for this exclusion, because the
exclusion would ``respect[] State and Tribal land use authority over
features that are only episodically wet during and/or following
precipitation events.'' 85 FR 22319. Nothing in the agencies'
explanation, however, links the agencies' line-drawing to the text or
purpose of section 101(b). Nor do the agencies, at this time, see any
linkage between the flow regime of ephemeral features and the nature or
extent of State authorities referenced in section 101(b). Indeed, as
discussed in section IV.A.c.i of this preamble, available science
unequivocally demonstrates that ephemeral features can implicate the
important Federal interest in the protection of the integrity of
traditional navigable waters, the territorial seas, and interstate
waters. Likewise, the 2020 NWPR cited section 101(a) as support for
categorically excluding ephemeral features, but again did not explain
how this decision relates to or advances the Clean Water Act's
objective. 85 FR 22277 (April 21, 2020).
    The 2020 NWPR similarly relied upon the policy provision in section
101(b) as a basis for its definition of adjacent wetlands, in
particular the decision to exclude from consideration subsurface
hydrologic connections between a wetland and an adjacent water when
determining jurisdiction. It stated, ``balancing the policy in CWA
section 101(a) with the limitations on Federal authority embodied in
CWA section 101(b), the agencies are finalizing the definition of
`adjacent wetlands' that does not include subsurface hydrologic
connectivity as a basis for determining adjacency.'' Id. at 22313.
Again, the 2020 NWPR did not explain how excluding consideration of
subsurface hydrologic connections relates to or derives from the text
of section 101(b), and the agencies do not now discern such a linkage.
And as with the definition of ``tributaries,'' the 2020 NWPR did not
explain how this choice relates to or advances the objective of the
Clean Water Act.
    In sum, based on the text and structure of the statute and Supreme
Court case law, the agencies have determined that the 2020 NWPR is not
a suitable alternative to this rule because it fails to advance the
objective of the Clean Water Act. The 2020 NWPR does not establish
either the significant nexus standard or an alternative standard that
similarly advances the objective of the Clean Water Act by protecting
waters, including ephemeral features, wetlands, and paragraph (a)(5)
waters where they have a significant effect on the chemical, physical,
or biological integrity of traditional navigable waters, the
territorial seas, and interstate waters. Nor does the 2020 NWPR
appropriately value the importance of Federal programs in achieving the
objective of the Clean Water Act.
b. The 2020 NWPR Was Inconsistent With the Best Available Scientific
Information
    The 2020 NWPR's exclusion of major categories of waters from the
protections of the Clean Water Act, specifically in the definitions of
``tributary'' and ``adjacent wetlands,'' runs counter to the scientific
record demonstrating how such waters can affect the integrity of
downstream waters. Specifically, as many commenters on the proposed
rule noted, its categorical exclusion of ephemeral features and large
categories of wetlands was inconsistent with the scientific record
before the agencies. In addition, the 2020 NWPR's limits on the scope
of protected wetlands to those

that touch or demonstrate evidence of a regular surface water
connection to other jurisdictional waters run counter to the ample
scientific information demonstrating the effects of wetlands on
downstream waters, including paragraph (a)(1) waters, when they have
other types of connections.
    First, the definition of the term ``tributary'' in the 2020 NWPR
categorically excluded ephemeral features from the regulatory
protections of the Clean Water Act, contrary to scientific information
conclusively demonstrating the vital role these streams can play in
protecting the integrity of downstream waters, including paragraph
(a)(1) waters. The science is clear that aggregate effects of ephemeral
streams ``can have substantial consequences on the integrity of the
downstream waters'' and that the evidence of such downstream effects is
``strong and compelling,'' as discussed above. Science Report at 6-10,
6-13. EPA's SAB Review of the draft Science Report explains that
ephemeral streams ``are no less important to the integrity of the
downgradient waters'' than perennial or intermittent streams. 2014 SAB
Review at 22-23, 54 fig. 3. While in the arid Southwest, streams flow
into downstream waters less frequently than they do in the wetter East,
the Science Report emphasizes that short duration flows through
ephemeral streams can transport large volumes of water to downstream
rivers. Science Report at 6-9. For instance, the report notes that
ephemeral streams supplied 76% of flow to the Rio Grande following a
large rainstorm. Id. at 3-8. The 2014 SAB Review emphasizes that the
``cumulative effects'' of ephemeral flows in arid landscapes can be
``critical to the maintenance of the chemical, physical, and biological
integrity'' of downstream waters. 2014 SAB Review at 22.
    Similarly, the 2020 NWPR's definition of ``adjacent wetlands''
excluded many categories of wetlands that can play a vital role in
protecting the integrity of waters to which they are connected,
including paragraph (a)(1) waters. In defining ``adjacent wetlands,''
the 2020 NWPR limited the scope of wetlands protected by the Clean
Water Act's regulatory programs to those that either abut or have
evidence of certain surface water connections to other protected waters
in a typical year. 85 FR 22340. Specifically, the rule encompassed
wetlands that (i) abut, meaning to touch, another jurisdictional water;
(ii) are flooded by a jurisdictional water in a typical year; (iii) are
separated from a jurisdictional water only by a natural feature, such
as a berm, which provides evidence of a direct hydrologic surface
connection with that water; or (iv) are separated from a jurisdictional
water only by an artificial structure so long as that structure allows
for a direct hydrologic surface connection between the wetlands and the
water in a typical year. Id. As with the tributary definition, the 2020
NWPR stated that the definition of ``adjacent wetlands'' is ``informed
by science.'' Id. at 22314. Yet the 2020 NWPR's limits on the scope of
protected wetlands to those that touch or demonstrate evidence of a
regular surface water connection to other jurisdictional waters
contradicted the ample scientific information before the agencies
conclusively demonstrating the effects of wetlands on downstream waters
when they have other types of surface connections, such as wetlands
that overflow and flood jurisdictional waters or wetlands with less
frequent surface water connections; wetlands with shallow subsurface
connections to other protected waters; or other wetlands proximate to
jurisdictional waters. See Rapanos, 547 U.S. at 786 (Kennedy, J.,
concurring in the judgment) (``Given the role wetlands play in
pollutant filtering, flood control, and runoff storage, it may well be
the absence of a hydrologic connection (in the sense of interchange of
waters) that shows the wetlands' significance for the aquatic
system.''). As commenters noted, under the 2020 NWPR's approach, if a
river were surrounded by hundreds of acres of wetland, building a road
or levee between a river and a wetland complex could potentially sever
Clean Water Act protections for the entire wetland complex.
    The overwhelming scientific information before the agencies weighs
decisively against the limited definition of ``adjacent wetlands'' in
the 2020 NWPR. Available scientific information demonstrates the
significant effects of categories of wetlands excluded by the 2020 NWPR
on the chemical, physical, and biological integrity of paragraph (a)(1)
waters. For example, whereas the 2020 NWPR provided that wetlands
flooded by jurisdictional waters are only protected if the flooding
occurs in a ``typical year,'' the Science Report states that wetlands
that are ``rarely'' or ``infrequently'' flooded by streams and rivers
can be ``highly connected'' to those waters and have ``long-lasting
effects'' on them. Science Report at 4-39. The Science Report notes
that effects ``critical to maintaining the health of the river'' result
from large floods that provide ``infrequent connections'' with more
distant wetlands. Id. Reflecting these concerns, the October 16, 2019
SAB Draft Commentary on the proposed 2020 NWPR states that the narrow
definition of ``adjacent wetlands'' in the 2020 NWPR as it was proposed
``departs from established science.'' The agencies have weighed these
statements and in light of the information about the importance of
``infrequently'' flooded wetlands to downstream waters, have concluded
that excluding wetlands that lack the limited types of surface water
connections to other jurisdictional waters required by the 2020 NWPR
lacks scientific support.
    The SAB's assessment of the 2020 NWPR proposal recognizes that the
proposal was not consistent with the scientific information in the
record, including the Draft Science Report that the SAB had previously
reviewed. SAB Commentary on the Proposed Rule Defining the Scope of
Waters Federally Regulated Under the Clean Water Act (February 27,
2020) (hereinafter, ``SAB Commentary''). The SAB Commentary emphasizes
that the proposal does not ``fully incorporate the body of science on
connectivity'' that the SAB had reviewed in the Draft Science Report
and offers ``no scientific justification for disregarding the
connectivity of waters accepted by current hydrological science.'' Id.
at 2.
    The 2020 NWPR stated that the ``agencies' decisions in support of
this rule have been informed by science.'' 85 FR 22288 (April 21,
2020). For example, the 2020 NWPR cited the concept of a ``connectivity
gradient'' as a basis for excluding ephemeral features. Id. (citing the
SAB Commentary). The 2020 NWPR referred to the SAB Commentary's
recommendation that the agencies recognize that connectivity occurs
along a gradient allowing for variation in chemical, physical, and
biological connections. Id. (citing the SAB Commentary at 3). The 2020
NWPR asserted that there is a ``decreased'' likelihood that waters with
``less than perennial or intermittent'' flow, i.e., ephemeral streams,
will affect the chemical, physical, and biological integrity of
downstream waters. 85 FR 22288 (April 21, 2020).
    Upon careful review, the agencies have concluded that the 2020
NWPR's reliance on the SAB's recommendation is out of context and is
inconsistent with the information in the SAB Commentary as a whole. The
connectivity gradient the 2020 NWPR cited was just a hypothetical
example \68\

meant to illustrate a single aspect of connectivity--hydrological, or
physical connectivity--and sheds no light on the many other ways that
features connect to and affect downstream waters. According to the SAB
itself, the scientific information the agencies provided in support of
categorically excluding ephemeral features does not fully represent the
discussion in the cited SAB Commentary and runs counter to key elements
of the scientific record before the agencies. SAB Commentary at 2.
---------------------------------------------------------------------------

    \68\ The figure cited is captioned in part as ``Hypothetical
illustration of connectivity gradient and potential consequences to
downstream waters.'' 2014 SAB Review at 54 (emphasis added). Nowhere
in its review does the 2014 SAB Review indicate that this is the
actual or only connectivity gradient.
---------------------------------------------------------------------------

    The 2020 NWPR also stated that the line it drew between regulated
and non-regulated wetlands, which excluded large categories of wetlands
covered by previous regulatory regimes is ``informed by science.'' 85
FR 22314 (April 21, 2020). The 2020 NWPR cited statements from the 2014
SAB Review to the effect that wetlands situated alongside other waters
are likely to be connected to those waters, whereas ``those connections
become less obvious'' as the distance ``increases.'' Id. (citing the
2014 SAB Review at 55); see also id. at 22314 (citing the 2014 SAB
Review at 60 (stating ``[s]patial proximity is one important
determinant [influencing the connections] between wetlands and
downstream waters'')). In addition, the 2020 NWPR cited a statement in
the Science Report that explained, ``areas that are closer to rivers
and streams have a higher probability of being connected than areas
farther away.'' Id. at 22314 (citing the Science Report at ES-4).
    Despite these citations, the 2020 NWPR's definition of ``adjacent
wetlands'' was not based on proximity, but instead on a ``direct
hydrologic surface connection,'' a factor that is distinct from
proximity. See id. at 22340. The 2020 NWPR's definition of ``adjacent
wetlands'' may exclude wetlands fifteen feet away from jurisdictional
waters if they are separated by a levee that does not convey flow in a
typical year, but include wetlands much further away so long as they
are inundated by flooding from the jurisdictional water in a typical
year. Therefore, neither of the two scientific rationales the 2020 NWPR
cited for its conclusions actually support the lines drawn in that
rule.
    Many commenters agreed with the agencies that the 2020 NWPR was
inconsistent with the best available science. Some commenters asserted,
however, that the definition of ``waters of the United States'' is a
policy interpretation that may be informed by science but cannot be
based on science alone. As discussed in section IV.A.2 of this
preamble, the agencies agree that science alone cannot dictate where to
draw the line defining ``waters of the United States.'' But science is
critical to determining how to attain Congress's plainly stated
objective to restore and maintain the chemical, physical, and
biological integrity of the nation's waters and properly evaluating
which waters are the subject of Federal jurisdiction due to their
effects on paragraph (a)(1) waters. Only by relying upon scientific
principles to understand the way waters affect one another can the
agencies know whether they are achieving that objective. The 2020 NWPR
is not a suitable alternative to this rule because it cannot advance
the objective of the Act given its lack of scientific support.
c. The 2020 NWPR Was Difficult To Implement and Yielded Inconsistent
Results
    In addition to the above concerns, the agencies' experience
implementing the 2020 NWPR for over a year made clear that foundational
concepts underlying much of the 2020 NWPR were confusing and difficult
to implement. While any rule that draws lines between jurisdictional
waters and non-jurisdictional waters will involve some implementation
challenges, the agencies have found the challenges imposed by the 2020
NWPR to be impracticable in important respects.
    Many commenters stated that the agencies should retain the 2020
NWPR because it was clear, pragmatic, and easy to implement. For
example, commenters stated that the rule provided ``bright lines,'' was
based on readily observable surface features, and categorically
excluded certain categories of waters. The agencies recognize that the
regulatory text of the 2020 NWPR contained categorical language and
referred to observable surface features. However, the ``bright lines''
and surface feature tests relied upon the concept of ``typical year,''
which, as other commenters pointed out, and as discussed further below,
was extremely challenging to implement and led to arbitrary results. As
a commenter emphasized, contrary to statements often made about the
2020 NWPR, under that rule landowners could not determine whether a
stream or wetland is jurisdictional by standing on their property.
Rather, the commenter stated that property owners would need to
determine the source and timing of flow, whether the stream flowed into
a navigable water off-property, whether wetlands abutted a
jurisdictional water, and whether a downstream segment lacked
sufficient flow or otherwise broke jurisdiction. The commenter asserted
that many of these inquiries would require the decision-maker to
trespass onto properties of others, or guess. Furthermore, the
commenter stated that in many cases, critical information that the rule
required the property owner to know--such as whether a wetland is
inundated by flooding from a jurisdictional water in a typical year--is
not normally recorded. This comment is consistent with the agencies'
experience that the 2020 NWPR did not ``provide[ ] clarity and
predictability for Federal agencies, States, Tribes, the regulated
community, and the public.'' See 85 FR 22252 (April 21, 2020). With
respect to categorical exclusions, this rule retains and codifies a
list of categorical exclusions, as did the 2020 NWPR and the 2015 Clean
Water Rule. See further discussion in section IV.C.7 of this preamble.
The challenges that the 2020 NWPR imposed to establish jurisdiction for
features that it appears to define as jurisdictional, and that
significantly affect the integrity of paragraph (a)(1) waters, further
undermine the 2020 NWPR's viability as an alternative to this rule.
i. ``Typical Year'' Metric
    The ``typical year'' is a concept fundamental to many of the 2020
NWPR's definitions. 85 FR 22273 (April 21, 2020). Under the rule,
tributaries and lakes, ponds, and impoundments of jurisdictional waters
were only jurisdictional if they had certain surface water connections
with a traditional navigable water or the territorial seas at least
once in a typical year. 33 CFR 328.3(c)(6), (12). Two categories of
wetlands only met the adjacency test for jurisdiction if they had a
surface water connection with other jurisdictional waters once in a
typical year. 33 CFR 328.3(c)(1). As a scientific matter, the concept
of ``typical year conditions,'' including precipitation normalcy, may
be relevant to ensuring that certain surface water connections in
natural streams are not being observed under conditions that are
unusually wet or dry. In terms of implementation, the concept of
precipitation normalcy is valid in certain contexts, such as to inform
determinations as to the presence of a wetland. However, in many
important contexts, available tools, including the tools the 2020 NWPR
recommended, cannot reliably demonstrate the presence of surface water
connections in a typical year, which are a necessary element of most
categories of jurisdictional waters under the 2020 NWPR. For example, a
recent

study by the Corps found that precipitation normalcy (as calculated
based on the methodology described in the preamble to the 2020 NWPR)
was neither a reliable predictor of streamflow normalcy, nor was it a
precise predictor of streamflow percentiles, in an analysis of
watersheds across the United States.\69\ These challenges undermine the
2020 NWPR's claim that it enhanced the ``predictability and consistency
of Clean Water Act programs.'' See 85 FR 22250 (April 21, 2020).
---------------------------------------------------------------------------

    \69\ Sparrow, K.H, Gutenson, J.L., Wahl, M.D. and Cotterman,
K.A. 2022. Evaluation of Climatic and Hydroclimatic Resources to
Support the US Army Corps of Engineers Regulatory Program. Engineer
Research and Development Center (U.S.) Technical Report no. ERDC/CHL
TR-22-19.
---------------------------------------------------------------------------

    One of the significant implementation challenges of the typical
year metric is that it can be difficult and sometimes impossible to
identify the presence of a surface water connection in a typical year.
Such connections are often not apparent from visual field observation
alone. For example, on the day of a visit to an intermittent stream
that flows only several months or several weeks a year, it is very
unlikely that an observer would see surface water flows connecting to a
downstream jurisdictional water. Similarly, though many ponds or
wetlands may be frequently inundated by flooding from another water, in
arid areas those features may be inundated only a few times every year,
and sometimes the inundation occurs on a single day or within a matter
of hours. While these waters satisfy the 2020 NWPR's jurisdictional
test, agency staff would probably not be able to determine that they
do, given how unlikely they would be to observe these infrequent
connections. The difficulty of finding the direct hydrologic
connections required by the typical year concept during a field visit
is exacerbated by the fact that the 2020 NWPR discouraged reliance on
field indicators. See, e.g., id. at 22292 (``The agencies . . .
conclude that physical indicators of flow, absent verification of the
actual occurrence of flow, may not accurately represent the flow
classifications required for tributaries under this rule.'').
    Given the insufficiency of visual field observations to assess the
presence of a surface water connection as specified in the 2020 NWPR,
under that rule agency staff often needed to expend substantial time
and resources to try to obtain ancillary data to determine flow
conditions at a particular site in a typical year. Hydrologic modeling
tools and advanced statistical analyses could be employed where
sufficient flow data are available, but often data needed to conduct
such analyses is limited or lacking altogether, especially for smaller
streams. Few streams across the country have hydrologic gages that
continuously measure flow, as most such gages are located on larger
rivers with perennial flow. Moreover, ``typical year conditions'' are
often irrelevant to the extent of flow in human-altered streams,
including effluent-dependent streams. The 2020 NWPR did not explain why
human-altered hydrology should be subject to the same typical year
requirement as natural streams.
    For the same reasons that agency staff are unlikely to witness the
specific surface water connections required under the 2020 NWPR during
a site visit in dry regions or during the dry season, they are also
unlikely to capture evidence of a surface water connection between a
stream and a downstream traditional navigable water or the territorial
seas using available aerial photographs taken during typical year
conditions. Aerial photographs are often taken just once per year or
once every other year and staff have no way of ensuring that they were
taken during a typical year. High-resolution satellite imagery can
serve as a reliable source to demonstrate specific surface water
connections. But the availability and usability of such imagery varies
across the country, depending on access, update intervals, cloud cover,
and land cover (i.e., vegetation or trees that obscure aerial views of
stream channels, requiring the use of advanced tools to detect features
of interest or the presence of water), so that such tools may be
unlikely to demonstrate that specific surface water connections are
occurring in a typical year. Moreover, as the 2020 NWPR acknowledged,
``characteristics of tributaries may not be visible in aerial
photographs'' taken during periods of ``high shrub or tree cover,'' 85
FR 22299 (April 21, 2020). Commenters on the proposed rule stated that
Tribes and States lacked sufficient data, aerial photography and access
to other tools required to support the use of the typical year test in
many locations. They expressed concern that under-resourced communities
suffer a particular lack of data necessary to support this test. New
satellites are expected to surmount some of these issues in the future,
but as this information is not yet available, regulators could not use
it to inform jurisdiction based on the requirements in the 2020 NWPR.
Remote tools, such as aerial or satellite imagery, are often useful in
implementing any definition of ``waters of the United States,'' but the
2020 NWPR's typical year criteria made use of these resources
particularly challenging.
    The same difficulties created challenges in detecting surface
hydrologic connections that occurred in a typical year to meet the 2020
NWPR's definition of ``adjacent wetlands'' or ``lakes and ponds, and
impoundments of jurisdictional waters.'' The 2020 NWPR's standard of
inundation by flooding in a typical year was not tied to any commonly
calculated flood interval, such as flood recurrence intervals, and the
agencies are not aware of a tool capable of collecting the type of
inundation data the 2020 NWPR required. Demonstrating that a wetland,
lake, pond, or impoundment is inundated by flooding once in a typical
year would require a field visit or a high-quality aerial photograph or
satellite image coinciding with the exact time that the flooding occurs
from a tributary to a wetland, lake, pond, or impoundment, as well as
being able to demonstrate that this flooding occurred in a typical
year. Determining that inundation by flooding occurs in a typical year
was therefore extremely difficult, and sometimes impossible.
Demonstrating that an artificial feature allows for a direct hydrologic
surface connection between a wetland and a tributary in a typical year
posed similar obstacles, requiring either auspiciously timed field
visits, aerial photography, high-resolution satellite imagery, or data
that the agencies may not be able to access, such as construction plans
or operational records for an artificial levee.
    The 2020 NWPR suggested the agencies ``will generally use''
precipitation data from the National Oceanic and Atmospheric
Administration (NOAA) to help determine the presence of a surface water
connection in a typical year, see 85 FR 22274 (April 21, 2020), but the
methodology described in the 2020 NWPR preamble for determining
precipitation in a typical year made it difficult to use these data to
inform jurisdiction. NOAA precipitation totals over the three months
prior to a site observation are compared to precipitation totals
observed over the preceding 30 years to determine if conditions were
wetter than normal, drier than normal, or normal (``typical''). Using
the methodology in the preamble of the 2020 NWPR, only 40% of
observations over a rolling 30-year period of record are considered
``normal,'' while 30% of observations are considered to be ``wetter
than normal'' and 30% of observations are considered to be ``drier than
normal.'' If

surface water flow was observed during normal or dry conditions, the
agencies could have higher confidence that the surface water
observations represented flow in a ``typical year.'' However, if flow
was observed during the 30% of conditions that are ``wetter than
normal,'' the surface water observations did not reveal whether flow
would occur during a typical year. And if flow was not observed,
precipitation data from the previous three months did not indicate
whether flow might occur in that particular water feature under typical
year conditions at a different point in the year. Therefore, if a site
visit was conducted when surface water flow was not present, the
agencies' suggested approach for evaluating whether a feature meets the
typical year test often did not provide meaningful and relevant
information for the agencies to make accurate determinations of
jurisdiction. Indeed, a commenter on the proposed rule emphasized that
Tribes and States have found the ``typical year'' requirement to
require extensive hydrologic modeling and advanced statistical analyses
in complex conditions. Under any regulatory regime, the agencies use a
weight of evidence approach to determine jurisdiction, but the 2020
NWPR typical year requirement placed onerous and, in many instances,
arbitrary constraints on the data that can be used as evidence.
    Furthermore, the typical year concept as applied to the 2020 NWPR
does not account for the increasing number of recurrent heat waves,
droughts, storms, and other extreme weather events in many parts of the
country. These events can have profound impacts on local and regional
hydrology, including streamflow. Commenters noted that determining what
is ``typical'' under the 2020 NWPR in light of increased drought and
floods was not simple for Tribal or State agencies; such determinations
required expert analysis and left much to interpretation, undermining
the assertion by the agencies that the 2020 NWPR would establish a
clear, predictable regulatory framework that can be implemented in the
field.
    The concept of ``typical year'' in the 2020 NWPR sought to factor
in long-term climatic changes over time to some degree by considering a
thirty-year rolling period of data, see 33 CFR 328.3(c)(13). However,
the 2020 NWPR did not allow the agencies flexibility to consider other
time intervals when appropriate to reflect effects of a rapidly
changing climate, including positive trends in temperature, increasing
storm events, and extended droughts. In response to more rapid recent
changes in climate, NOAA has developed alternative approaches for
estimating climate normals, including seasonal averages computed using
shorter, annually updated averaging periods for temperature (10-year
seasonal average) and total precipitation (15-year seasonal average).
The rigid rolling thirty-year approach to determining typical year in
the 2020 NWPR did not allow the agencies to use these updated methods.
    The 2020 NWPR noted that the agencies can look to sources of
information other than site visits, aerial photographs, and
precipitation data to assess whether a feature has surface water flow
in a typical year. It identified the Web-based Water-Budget Interactive
Modeling Program, Climate Analysis for Wetlands Tables, and the Palmer
Drought Severity Index, 85 FR 22275 (April 21, 2020). These methods,
which provide information useful in many other contexts, often only
look at climate-related conditions generally and often did not answer
the jurisdictional questions posed by the 2020 NWPR. For example, they
did not address whether surface water flow might connect a particular
stream to a downstream traditional navigable water or the territorial
seas, whether a particular wetland was inundated by or connected to a
jurisdictional water as required under the 2020 NWPR, or how
uncertainties at different locations and in different months affected
the accuracy of condition estimates. While precipitation is an
important factor, other information is also relevant to streamflow and
surface water connections in a typical year, including the
contributions of flow from wetlands, upgradient streams, and open
waters in the watershed, evapotranspiration rates, water withdrawals
including groundwater pumping, and other climatic conditions. Yet
collecting this information from a variety of sources and interpreting
it can be extremely time- and resource-intensive and may require
special expertise. While the agencies have substantial experience using
a weight of evidence approach to determine jurisdiction, for example as
part of the significant nexus analysis, the typical year requirement
makes it substantially more difficult to interpret available data and
narrows the scope of data that can be used to determine jurisdiction.
    Finally, the challenges presented by determining the presence of
surface water flow in a typical year are even greater when evaluating a
tributary at a distance from the downstream traditional navigable water
or the territorial seas. Even streams that flow perennially or
intermittently often travel many miles prior to reaching the closest
traditional navigable water or the territorial seas, meaning many
downstream reaches may need to be assessed. Under the 2020 NWPR, any
ephemeral reaches along that pathway that did not carry surface water
flow once in a typical year would render all upstream waters non-
jurisdictional. 85 FR 22277 (April 21, 2020). The need to assess
lengthy tributary systems imposed an extraordinarily high burden of
proof on the agencies to evaluate surface water flow in a typical year
along the flow path from a stream of interest to a downstream
traditional navigable water or the territorial seas. The longer the
pathway, the more challenging the analysis. As a commenter noted, in
adopting the test, the 2020 NWPR inserted case-by-case analyses for
every jurisdictional determination despite the rule's claim that it
``provide[s] a predictable framework in which to establish federal
jurisdiction.'' Id. at 22273-22274. The uncertainty and implementation
challenges generated by the 2020 NWPR's foundational typical year test
are yet another basis to replace that rule.
ii. Determining Adjacency
    The 2020 NWPR provided that wetlands are ``adjacent'' when they:
(1) abut a traditional navigable water or the territorial seas; a
tributary; or a lake, pond, or impoundment of a jurisdictional water;
(2) are inundated by flooding from one of these waters in a typical
year; (3) are physically separated from one of these waters only by a
natural berm, bank, dune, or similar natural feature; or (4) are
physically separated from one of these waters only by an artificial
dike, barrier, or similar artificial structure so long as that
structure allows for a direct hydrologic surface connection between the
wetlands and the water in a typical year, such as through a culvert,
flood or tide gate, pump, or similar artificial feature. 85 FR 22338;
33 CFR 328.3(c)(1). In practice, agency staff have found several of
these criteria for adjacency extremely difficult to implement in
certain circumstances.
    The artificial barrier provision led to arbitrary results. For
example, under the fourth way to meet the adjacency definition, a
wetland may be jurisdictional if it is separated from a jurisdictional
water by an artificial structure, such as a levee, that allows for a
direct hydrologic surface connection in a typical year through a
culvert. However, the same wetland would not be jurisdictional if there
was no levee present, even if there was a direct

hydrological surface connection in a typical year through a culvert
(assuming the wetland did not meet another criterion for adjacency).
The 2020 NWPR therefore established that certain wetlands with a direct
hydrologic surface connection to a jurisdictional water are only
jurisdictional due to the presence of an artificial barrier. This
discrepancy bears no relationship to the actual connections between the
features at issue and is not supported by science or the agencies'
experience.
    Moreover, the provision establishing that a wetland is ``adjacent''
if a jurisdictional water inundates it by flooding in a typical year
was extremely difficult to implement. See 33 CFR 328.3(c)(1)(ii).
Inundation by flooding in a typical year is not a metric that is
normally recorded either by implementing agencies or the regulated
community. Available models generally focus on flood recurrence
intervals, which do not necessarily correspond to the likelihood of
inundation by flooding in a given or typical year, and the agencies
would typically be unable to demonstrate that these indicators reflect
typical year conditions. Indeed, the 2020 NWPR acknowledged that
inundation by flooding in a typical year could correspond to a variety
of flood recurrence intervals depending on location, climate, season,
and other factors. 85 FR 22311. Given the absence of existing records
of inundation by flooding, determining whether inundation by flooding
has occurred in a typical year is challenging in many circumstances.
    Compounding the challenge, the 2020 NWPR provided that wetlands can
be jurisdictional if they are inundated by flooding from a
jurisdictional water in a typical year--but inundation in the other
direction, from the wetlands to the jurisdictional water, is not
grounds for jurisdiction. Not only is there no scientific or legal
basis for distinguishing between inundation of the wetland as opposed
to inundation from the wetland, see Riverside Bayview, 474 U.S. at 134
(upholding the Corps' assertion of jurisdiction over ``wetlands that
are not flooded by adjacent waters [but] may still tend to drain into
those waters''), but determining whether the limited available
photographs or other evidence of inundation reflects flooding in one
direction as opposed to another adds to the difficulty in evaluating
whether this standard is met. The same challenges apply to determining
whether lakes, ponds, or impoundments of jurisdictional waters are
inundated by flooding in a typical year, one basis for demonstrating
Clean Water Act jurisdiction over these features. 85 FR 22338-39 (April
21, 2020); 33 CFR 328.3(c)(vi).
iii. Ditches
    Among other requirements, the 2020 NWPR provided that a ditch \70\
is jurisdictional as a tributary if it was originally built in a
tributary or adjacent wetland, as those terms are defined in the 2020
NWPR, and emphasized that the agencies bear the burden of proof to
determine that a ditch was originally constructed in a tributary or
adjacent wetland. 33 CFR 328.3(a)(2), (c)(12); 85 FR 22299. In other
words, in order to find a ditch jurisdictional, the agencies had to
demonstrate that a ditch was (1) originally constructed in a stream (2)
that, at the time of construction, had perennial or intermittent flow
and (3) a surface water connection to a downstream traditional
navigable water or the territorial seas (4) in a ``typical year.''
Alternatively, the agencies had to show that a ditch was (1) originally
constructed in a wetland (2) that either abutted or had certain surface
hydrologic connections to a jurisdictional water at the time the ditch
was constructed (3) in a ``typical year,'' in order to demonstrate that
the ditch is jurisdictional. Americans have been building ditches,
straightening streams, and draining wetlands for hundreds of years. And
while under earlier guidance and practice, the agencies generally
assessed whether a ditch was excavated in dry land when making a
jurisdictional determination, that involved an assessment simply of
whether the ditch was excavated in a stream, a wetland, or other
aquatic resource. By contrast, to determine whether a ditch was
jurisdictional under the 2020 NWPR, the agencies had to determine if it
was originally built in a tributary or adjacent wetland that would have
been jurisdictional under the 2020 NWPR, and therefore had to address
all of the implementation challenges discussed in the preceding
sections involved in determining surface water connections and wetland
adjacency in a typical year--but often for ditches built twenty, one
hundred, or even several hundred years ago. To the extent that sparse
evidence is available to demonstrate a surface water connection in a
typical year for tributaries using tools available today, evidence is
even more difficult to find when looking so far back in time. States
approached the agencies seeking assistance in assessing the
jurisdictional status of ditches, but the agencies were often unable to
provide meaningful help given the burdens imposed by the 2020 NWPR's
ditch definition.
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    \70\ Ditches perform many of the same functions as natural
tributaries. For example, like natural tributaries, ditches that are
part of the stream network convey water that carries nutrients,
pollutants, and other constituents, both good and bad, to downstream
traditional navigable waters, the territorial seas, and interstate
waters.
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    The 2020 NWPR also provided that ditches are jurisdictional if they
relocate a tributary, as that term was defined in the rule, 85 FR 22341
(April 21, 2020); 33 CFR 328.3(a)(2), (c)(12), but this standard as
defined by the 2020 NWPR was also often extremely difficult to assess.
The 2020 NWPR explained that a relocated tributary is ``one in which an
entire portion of the tributary may be moved to a different location.''
85 FR 22290 (April 21, 2020) (emphasis added). In other words, the 2020
NWPR appeared to require a ditch to divert 100% of the tributary's flow
to meet the ``relocate a tributary'' test. While prior rules have
defined relocated tributaries as jurisdictional, the requirement that
the entire portion be relocated is new and has created substantial
implementation challenges. As a practical matter, when a tributary is
relocated it often reroutes just a portion of its flow to the ditch.
Assessing whether a ditch relocated 100% of a tributary's flow, as
opposed to 80% or 50% of its flow, is extremely difficult and may not
be possible in some circumstances. The scientific literature indicates
that features like ditches that convey water continue to connect to and
affect downstream waters. See section III.A.iv of the Technical Support
Document for additional information. By establishing a jurisdictional
standard that is extremely difficult to meet, the 2020 NWPR effectively
removed from the protections of the Clean Water Act large numbers of
ditches that function as tributaries and that significantly affect the
integrity of downstream traditional navigable waters, the territorial
seas, and interstate waters. As is the case with tributaries, lakes and
ponds, impoundments, and wetlands, the 2020 NWPR's impracticable
approach to ditches made it extremely difficult to implement. In the
agencies' judgment, any efficiencies the 2020 NWPR may have achieved
through categorical exclusions are outweighed by the challenges the
agencies encountered in implementing the rule, coupled with its failure
to implement the objective of the Clean Water Act by removing
protections for waters that are properly within the statute's scope.

d. The 2020 NWPR Substantially Reduced Clean Water Act Protections Over
Waters
    The failure of the 2020 NWPR to advance the objective of the Clean
Water Act, as well as its inconsistency with science and the challenges
it presents in implementation, have had real-world consequences. The
agencies have found that substantially fewer waters were protected by
the Clean Water Act under the 2020 NWPR compared to under previous
rules and practices. It is important to note that the definition of
``waters of the United States'' affects most Clean Water Act programs
designed to restore and maintain water quality--including not only the
section 402 NPDES and section 404 dredged and fill permitting programs,
but also water quality standards under section 303, identification of
impaired waters and total maximum daily loads under section 303,
section 311 oil spill prevention, preparedness, and response programs,
and the section 401 Tribal and State water quality certification
programs--because the Clean Water Act provisions establishing such
programs use the term ``navigable waters'' or ``waters of the United
States.'' While the 2020 NWPR was promulgated with the expressed intent
to decrease the scope of Federal jurisdiction, the agencies now are
concerned that the actual decrease in water resource protections was
more pronounced than the qualitative predictions in the 2020 NWPR
preamble and supporting documents anticipated and acknowledged to the
public. These data support the agencies' conclusion that the 2020 NWPR
is not a suitable alternative to this rule.
i. Jurisdictional Determination and Permitting Data Show a Large Drop
in the Scope of Waters Protected Under the Clean Water Act
    Through an evaluation of jurisdictional determinations completed by
the Corps between 2016 and 2021,\71\ EPA and the Army have identified
consistent indicators of a substantial reduction in waters protected
under the Clean Water Act by the 2020 NWPR (see Technical Support
Document section II.B.i for additional discussion on methods and
results of the agencies' analyses). These indicators include an
increase in the number and proportion of jurisdictional determinations
completed where aquatic resources were found to be non-jurisdictional,
an increase in determinations made by the Corps that no Clean Water Act
section 404 permit is required for specific projects, and an increase
in requests for the Corps to complete approved jurisdictional
determinations (AJDs), rather than preliminary jurisdictional
determinations (PJDs) which treat a feature as jurisdictional. These
trends all reflect the narrow scope of jurisdiction in the 2020 NWPR's
definitions. Additionally, the agencies find that these indicators
likely account for only a fraction of the 2020 NWPR's impacts, because
many project proponents did not seek any form of jurisdictional
determination for waters that the 2020 NWPR categorically excluded,
such as ephemeral features, and the Corps would not have knowledge of
or ability to track such projects. A closer look at each of these
indicators will help demonstrate some of the more pronounced impacts of
the 2020 NWPR on paragraph (a)(1) waters than were identified for the
public in the 2020 NWPR and its supporting documents. As explained in
detail above, when a water falls outside the scope of the Clean Water
Act, that means, among other things, that no Federal water quality
standards will be established, and no Federal permit will be required
to control the discharge of pollutants, including dredged or fill
material, into such waters unless the pollutants reach jurisdictional
waters. And since many entities did not believe that they would need to
seek a jurisdictional determination under the 2020 NWPR, it is
impossible to fully understand the scope of degradation the 2020 NWPR's
definition caused to paragraph (a)(1) waters.
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    \71\ A jurisdictional determination is a written Corps
determination that a water is subject to regulatory jurisdiction
under section 404 of the Clean Water Act (33 U.S.C. 1344) or a
written determination that a water is subject to regulatory
jurisdiction under section 9 or 10 of the Rivers and Harbors Act of
1899 (33 U.S.C. 401 et seq.). Jurisdictional determinations are
identified as either preliminary or approved, and both types are
recorded in determinations through an internal regulatory management
database, called Operation and Maintenance Business Information
Link, Regulatory Module (ORM2). This database documents Department
of the Army authorizations under Clean Water Act section 404 and
Rivers and Harbors Act section 10, including permit application
processing and jurisdictional determinations. This database does not
include aquatic resources that are not associated with a
jurisdictional determination or that are not associated with
alternatives to jurisdictional determinations (such as delineation
concurrences or ``No jurisdictional determination required''
findings, where the Corps finds that a jurisdictional determination
is not needed for a project), or permit request or resource impacts
that are not associated with a Corps permit or enforcement action.
An approved jurisdictional determination (AJD) is an official Corps
document stating the presence or absence of ``waters of the United
States'' on a parcel or a written statement and map identifying the
limits of ``waters of the United States'' on a parcel. A preliminary
jurisdictional determination (PJD) is a non-binding written
indication that there may be ``waters of the United States'' on a
parcel; an applicant can elect to use a PJD to voluntarily waive or
set aside questions regarding Clean Water Act jurisdiction over a
particular site and thus move forward assuming all waters will be
treated as jurisdictional without making a formal determination.
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    Consistent with Executive Order 13990, EPA and Army staff have
reviewed jurisdictional determinations as recorded in the Corps'
internal regulatory management database, referred to as the ORM2
database,\72\ to identify any noticeable trends in jurisdictional
determinations under the past recent rules defining ``waters of the
United States.'' The agencies found within the AJDs completed under the
2020 NWPR, the probability of finding resources to be non-
jurisdictional increased precipitously. Of the 9,399 AJDs completed by
the Corps under the 2020 NWPR during the first 12 months in which that
rule was in effect,\73\ the agencies found approximately 75% of AJDs
completed had identified non-jurisdictional water resources and
approximately 25% of AJDs completed identified jurisdictional
waters.\74\ Conversely, when the 1986 regulations and applicable
guidance were in effect (including following the 2019 recodification of
those regulations), substantially more jurisdictional waters were
identified in AJDs on average per year than compared to the first
twelve months of the 2020 NWPR.\75\ During similar one-year calendar
intervals when the 1986 regulations and applicable guidance were in
effect, approximately 28% to 45% of AJDs completed identified non-
jurisdictional aquatic resources, and 56% to 72% of AJDs identified
jurisdictional resources.

The change from a range of 28% to 45% non-jurisdictional AJD findings
prior to the 2020 NWPR to 75% non-jurisdictional findings after
issuance of the 2020 NWPR indicates that substantially fewer waters
were protected by the Clean Water Act under the 2020 NWPR (see
Technical Support Document section II.B.i for additional discussion).
Again, as commenters on the proposed rule noted, these numbers do not
account for the many entities that did not seek AJDs because they
believed their features were excluded under the 2020 NWPR.
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    \72\ See supra note 71.
    \73\ These AJDs were completed by the Corps between the 2020
NWPR's effective date of June 22, 2020, and June 21, 2021.
    \74\ This excludes dryland AJDs and waters identified as
jurisdictional only under section 10 of the Rivers and Harbors Act.
In addition, under the 2020 NWPR, a single AJD in the Corps'
database can include both affirmative and negative jurisdictional
determinations. Under prior regulatory regimes, the Corps' database
was structured such that a single AJD could be either affirmative,
or negative, but not both. To account for this change in the
structure of the database, a 2020 NWPR jurisdictional determination
that includes both affirmative and negative jurisdictional resources
was normalized and counted as two separate AJDs, one affirmative and
one negative. The total number of AJDs considered after this process
was carried out was 9,399. Prior to this normalization, the total
number of AJDs considered was 7,769. More details on the agencies'
analysis can be found in the Technical Support Document section
II.B.i.
    \75\ The time periods evaluated were June 22, 2016 to June 21,
2017; June 22, 2017 to June 21, 2018; and December 23, 2019 to June
21, 2020. The date ranges here constitute periods of time when the
1986 regulations (including the 2019 Repeal Rule's recodification of
those regulations) and applicable guidance were in effect
nationally. 2015 Clean Water Rule determinations were not part of
this analysis.
---------------------------------------------------------------------------

    When evaluating the effect of the 2020 NWPR on the number of
individual aquatic resources (as opposed to the AJDs completed), the
agencies found a similar substantial reduction in protections provided
by the Clean Water Act. Within the first twelve months of
implementation of the 2020 NWPR, between June 22, 2020, and June 21,
2021, the Corps documented the jurisdictional status of 48,313
individual aquatic resources or water features through AJDs completed;
of these individual aquatic resources, approximately 75% were found to
be non-jurisdictional by the Corps. More specifically, 70% of streams
and wetlands evaluated were found to be non-jurisdictional, including
11,044 ephemeral features (mostly streams) and 15,675 wetlands. Ditches
were also frequently found to be non-jurisdictional (4,706 individual
exclusions), which is likely the result of the narrowed definition of
tributary under the 2020 NPWR and the requirement that a ditch was only
jurisdictional as a tributary if it was originally built in a tributary
or adjacent wetland, as those terms are defined in the 2020 NWPR. By
comparison, only 45% of aquatic resources were found to be non-
jurisdictional during similar year-long calendar intervals between 2016
and 2020 under the pre-2015 regulatory regime.\76\ This increase in
non-jurisdictional determinations, so that approximately 75% of water
bodies are non-jurisdictional under the 2020 NWPR as opposed to only
45% under the prior regulations, undermined the agencies' ability to
provide a baseline of Federal protection for the integrity of the
nation's waters.
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    \76\ Based on the average annual percentage of non-
jurisdictional findings.
---------------------------------------------------------------------------

    Of particular concern to the agencies is the 2020 NWPR's
disproportionate effect on arid regions of the country, as the aquatic
resources in these regions predominantly consist of ephemeral features.
Under the 2020 NWPR, more permittees across the country, including in
the arid West, sought AJDs rather than PJDs, particularly for ephemeral
features. Many more streams were evaluated and determined to be non-
jurisdictional through AJDs in the arid West, while the number of
individual stream reaches considered under PJDs declined precipitously.
As mentioned previously, project proponents who request an AJD obtain
an official Corps document that states either that there are no
``waters of the United States'' present on a parcel, or a statement
that ``waters of the United States'' are present, accompanied by a map
identifying their extent. In contrast, an applicant can elect to use a
PJD to voluntarily waive or set aside questions regarding Clean Water
Act jurisdiction over a particular site and thus move forward assuming
all waters will be treated as jurisdictional without making a formal
determination. There are time savings and sometimes cost savings
associated with requesting a PJD in lieu of an AJD. A decline in the
proportion of PJDs being requested under the 2020 NWPR indicates that
fewer project proponents requested that aquatic resources on their
project site be treated as if they were jurisdictional.
    In Arizona, the annual average number of individual stream reaches
considered under PJDs and similar alternatives to AJDs between 2016 to
2020 was 941, while under the 2020 NWPR in 2020-2021 it was only
45.\77\ Compared to pre-2015 regulatory practice, under the 2020 NWPR,
Arizona experienced an approximate 95% decrease in individual stream
reaches being considered via PJDs and a 9-fold increase in individual
stream reaches being considered via AJDs. Similar metrics for New
Mexico show an 84% decrease in individual streams being considered via
PJDs and a 28-fold increase in individual streams being considered via
AJDs under the 2020 NWPR.
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    \77\ The AJD values associated with the 2020 NWPR fall outside
of the 95% confidence interval calculated for annual data from 2016-
2020. Note that in New Mexico and Arizona, the 2015 Clean Water Rule
was never implemented due to litigation stays. The PJD values
associated with the 2020 NWPR do not fall outside of the 95%
confidence interval calculated for annual data from 2016-2020; this
is likely a product of scale. See the Technical Support Document
section II.B.i for more analysis.
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    The number of stream reaches assessed in Arizona under AJDs
compared to the number of evaluations completed nationwide was
disproportionately high under the 2020 NWPR. The number of stream
reaches assessed in Arizona constituted 9% of the total stream reaches
assessed nationally and 13% of the ephemeral reaches assessed
nationally over the first twelve months in which the 2020 NWPR was
implemented.\78\ This increase in the number of AJDs sought in Arizona
under the 2020 NWPR compared to the number of AJDs sought in Arizona
between 2016 and 2020 likely reflects the desire of landowners to
confirm that features on their property were ephemeral or otherwise
excluded under that rule, though it is possible the pace of landowners
seeking AJDs would have slowed to some extent over time. The agencies
understand the drastic decline in the number of PJDs requested compared
to AJDs in the arid West, and the simultaneous increase in the number
of AJD non-jurisdictional findings in the arid West, to have been
driven largely by the categorical exclusion of ephemeral streams from
jurisdiction. PJDs assume jurisdiction, and under the 2020 NWPR project
proponents were less likely to assume that ephemeral streams were
jurisdictional.
---------------------------------------------------------------------------

    \78\ There were a total of 16,787 stream reaches assessed via
AJDs nationwide between June 22, 2020 and June 21, 2021.
---------------------------------------------------------------------------

    The Corps' data show that in New Mexico, of the 263 streams
assessed via AJDs in the first twelve months of implementation of the
2020 NWPR (i.e., between June 22, 2020, to June 21, 2021), 100% were
found to be non-jurisdictional ephemeral features.\79\ In Arizona, of
the 1,525 streams assessed in AJDs in the first year of implementation
of the 2020 NWPR, 1,518, or 99.5%, were found to be non-jurisdictional
ephemeral resources. Eliminating these streams from jurisdiction under
the 2020 NWPR also typically eliminated jurisdiction over wetlands
which otherwise might meet adjacency criteria.
---------------------------------------------------------------------------

    \79\ These non-jurisdictional ephemeral resources are
predominantly ephemeral streams, but a small portion may be swales,
gullies, or pools.
---------------------------------------------------------------------------

    Some commenters asserted that the low percentage of jurisdictional
AJD findings in Arizona under the 2020 NWPR does not have a
statistically significant difference from the percentages of
jurisdictional findings under the pre-2015 regulatory regime. The
agencies agree that of Corps AJDs completed between 2016 and 2020, high
percentages of streams in Arizona were found to be non-jurisdictional
between 2016 and 2020. Proportionally, the non-jurisdictional findings
via AJDs between 2016-2020 and the 2020 NWPR are similar. However,
because the volume of streams assessed under AJDs in the arid West
increased so substantially, there was a 10-fold increase in non-
jurisdictional findings for streams in Arizona and a 36-fold increase
in non-jurisdictional findings for streams in

New Mexico following implementation of the 2020 NWPR. The average
annual number of individual stream resources considered in AJDs in
Arizona between 2016-2020 was 147 (of which 138 were determined non-
jurisdictional), compared to 1,525 stream reaches assessed under the
2020 NWPR (of which 1,521 were determined non-jurisdictional accounting
for all exclusions). Assessed together, the statistically significant
increase in overall resources assessed via AJD combined with the shift
away from requests for PJDs, as well as the consistent proportion of
AJDs with non-jurisdictional findings indicates that many more project
proponents viewed resources on their land as no longer ``waters of the
United States'' under the 2020 NWPR. The agencies' analysis also
reflects the scope of the streams that the 2020 NWPR left unprotected,
which in many cases are vitally important to desert aquatic ecosystems
and to the hydrologic integrity of watersheds. See section IV.A.2.c.i
of this preamble.
    The Corps identified at least 368 projects from June 22, 2020, to
June 21, 2021, through its ORM2 database that would have needed a Clean
Water Act section 404 permit prior to the 2020 NWPR, but no longer did
under the 2020 NWPR's definition of ``waters of the United States.''
\80\ Moreover, in comparing 2020-2021 to similar annual data from 2016-
2020 from implementation of the 1986 regulations consistent with
Supreme Court case law, there was an average increase of over 100% in
the number of projects determined to not require section 404 permits
under the Clean Water Act due to activities not occurring in ``waters
of the United States'' or activities occurring in waters that were
deemed no longer ``waters of the United States'' due to the 2020 NWPR.
The number of projects that did not require a section 404 permit under
the 2020 NWPR was likely much greater than these numbers indicate
because project proponents did not need to notify the Corps if they had
already received an AJD that concluded waters in the review area were
not ``waters of the United States,'' and because many project
proponents would not have sought a jurisdictional determination or
applied for a permit at all if they believed their aquatic resources
were non-jurisdictional under the 2020 NWPR. Many projects could have
occurred without consultation with the Corps due to the 2020 NWPR's
narrow definition of ``waters of the United States'' and expansive non-
jurisdictional categories. Therefore, while the Corps' ORM2 data shed
light on the trend and magnitude of impacts to the scope of
jurisdiction under the 2020 NWPR, it is fair to assume that these
impacts are an underestimate.\81\
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    \80\ This tracking method only applies when 100% of jurisdiction
is lost under the 2020 NWPR (i.e., if even 1 aquatic resource out of
100 that is proposed to be impacted remains jurisdictional, this
method is not used). Additionally, this tracking method was a new
database feature, which was not yet implemented uniformly across the
United States, and is likely under-representative even for those
cases in which 100% of jurisdiction was lost under the 2020 NWPR.
    \81\ Requests for AJDs and the jurisdictional dispositions of
the aquatic resources evaluated as part of those AJDs are imperfect
measures of activities that might affect those jurisdictional or
non-jurisdictional aquatic resources. The AJD data in the Corps ORM2
database generally contain only records for situations in which
landowners or project proponents have requested jurisdictional
determinations from the Corps or that are associated with an
enforcement action, and thus do not represent all aquatic resources
that exist within the United States. The proportion and specific
types of aquatic resources evaluated for jurisdiction via AJDs
varies both geographically and from year to year. In addition, the
ORM2 data collected from AJDs conducted under different regulatory
regimes have some metrics that are not directly comparable.
Notwithstanding these limitations, the volume of ORM2 data on AJDs
and associated aquatic resources is large and is tracked in a
reasonably accurate fashion, and thus provides a reasonable estimate
of overall trends and conditions on the ground. It represents the
best data available to the agencies at this time.
---------------------------------------------------------------------------

    Many commenters cited the impacts referenced above as reasons to
reject the 2020 NWPR's definition of ``waters of the United States.''
In addition, many commenters cited national-scale assessments of the
number of waterbodies that lost protection under the 2020 NWPR as
evidence of environmental harm. Some commenters noted that 51% of
wetlands and 18% of streams lost protections.\82\ Other commenters
stated that 4.8 million miles of streams and 16.3 million acres of non-
floodplain wetlands would be left without Federal level protections
under the 2020 NWPR.\83\
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    \82\ Contained in the Resource and Programmatic Assessment for
the Proposed Revised Definition of ``Waters of the United States''
(Docket ID No. EPA-HQ-OW-2021-0602-0039).
    \83\ Commenters cited to the following scientific paper as
support: C.R. Lane and E. D'Amico. Identification of putative
geographically isolated wetlands of the conterminous United States,
52 J Am Water Resource Association 705(2016); K. Fesenmyer et al.,
Large portion of USA streams lose protection with new interpretation
of Clean Water Act. February 2021. Freshwater Science 40(1).
---------------------------------------------------------------------------

    Commenters provided many potential examples of the harms caused by
the 2020 NWPR around the country. One commenter stated that in the
Northwest, an estimated 9,165 miles of ephemeral streams in Oregon's
Rogue River Basin that provide drinking water for the region, as well
as habitat and spawning grounds for Federal threatened Southern Oregon/
Northern California Coast coho salmon and steelhead, would have lost
protection under the 2020 NWPR. Another commenter stated that in the
Midwest, protection would have been lost for an estimated 500 to 1,000
miles of ephemeral and ditched streams that flow into the Niagara
River, the channel that connects Lake Erie and Lake Ontario. The
commenter also noted that following promulgation of the 2020 NWPR, two
Great Lakes states finalized legislative action to further reduce
protections under State law for waters excluded by the 2020 NWPR. One
commenter asserted that up to 202,244 acres of wetlands located behind
levees in Missouri would have been excluded from jurisdiction under the
2020 NWPR because they are separated from jurisdictional waters by
``upland or by dikes, barriers, or similar structures.'' The commenter
stated that these wetlands provide flood control, habitats, and improve
water quality. In the Mountain West, a commenter stated that over half
of Colorado's streams and 22% of that State's remaining wetlands would
have been excluded from jurisdiction under the 2020 NWPR. With respect
to the Southeast, a commenter cited analyses demonstrating that 162,149
acres of wetlands in Georgia's Chattahoochee watershed were vulnerable
to losing protection under the 2020 NWPR. The same commenter noted
that, in the Mid-Atlantic, over 100,000 acres of wetlands would have
lost protection under the 2020 NWPR in Virginia's James River and
Rappahannock River watersheds, which are vital to water quality in the
Chesapeake Bay. Finally, in the Southwest, comments from the State of
New Mexico estimated that under the 2020 NWPR, 25-45% of its Clean
Water Act stormwater general permits and 50% of its individual permits
would no longer be required. In Arizona, a commenter stated that 94% of
all wetlands and flowlines in Arizona's Upper San Pedro Watershed would
have lost protection under the 2020 NWPR.
    The agencies have not conducted an independent analysis to verify
each of these comments but have carefully reviewed the concerns
identified and the underlying analyses that commenters cited and found
them generally consistent with the agencies' own findings about the
impacts of the 2020 NWPR. These examples illustrate the quality and
importance of the waters that lost protection under the 2020 NWPR. As
commenters emphasized, waters that the 2020 NWPR categorically
excluded, such as ephemeral streams and their associated wetlands and
wetlands that did not

meet the 2020 NWPR's adjacency criteria, provide critical ecosystem
services. The absence of Clean Water Act protections for such resources
and any subsequent unregulated and unmitigated impacts to such
resources would have caused cascading, cumulative, and substantial
downstream harm. Commenters stated that, specifically, the 2020 NWPR
would have reduced the extent to which waters filter out pollutants
before they reach traditional navigable waters; reduced flood
protections and water storage services, and increased flooding; harmed
fisheries and hunting sites; destroyed bird and wildlife habitat,
including habitats relied on by endangered species; and reduced the
quality of drinking water. Commenters also stated that the reduction in
federally protected waters under the 2020 NWPR could increase water
pollution near low-income communities and communities of color in
particular and that they could experience associated increases in
health risk.
    The 2020 NWPR's removal of Federal protections from the nation's
waters, and the resulting detriment to the services they provide,
undermines the objective of the Clean Water Act, as discussed in
section IV.A.2 of this preamble.
ii. Tribes and States Did Not Fill the Regulatory Gap Left by the 2020
NWPR
    Some commenters asserted that the diminished scope of ``waters of
the United States'' would not necessarily reduce protections for waters
because Tribes, States, and local entities may regulate discharges even
in the absence of Clean Water Act regulation. See section IV.A.3.b of
this preamble. This perspective is consistent with the 2020 NWPR's
emphasis that, in the face of a narrower scope of ``waters of the
United States,'' ``the controls that States, Tribes, and local entities
choose to exercise over their land and water resources'' would help to
achieve the objective of the Clean Water Act. 85 FR 22259 (April 21,
2020). Yet while some Tribes and States regulate ``waters of the
Tribe'' or ``waters of the State'' more broadly than the Federal
Government under their own laws, many newly non-jurisdictional waters
under the 2020 NWPR were on Tribal lands or in States that do not
regulate waters beyond those covered by the Clean Water Act. Under the
2020 NWPR, discharges into these waters could have occurred without any
restriction.
    As discussed in the Economic Analysis for the Final Rule, many
Tribes and States do not regulate waters more broadly than the Clean
Water Act. See Economic Analysis for the Final Rule, Chapter II; 2020
NWPR Economic Analysis at 30-31. Contrary to the predictions made in
the 2020 NWPR Economic Analysis, during the year in which the 2020 NWPR
was in effect, the net change made by States was deregulatory in
nature. Two States which had previously protected State waters beyond
the scope of ``waters of the United States'' removed these expansive
protections, and no States that lacked these broader protections
established them. See 2020 NWPR Economic Analysis at 39-41 (estimating
that certain States are likely to continue their current permitting
practices for dredged and fill material) and the Economic Analysis for
the Final Rule, Chapter II (indicating that two of those States reduced
the scope of State clean water protections after the 2020 NWPR was
finalized, and none of them formally expanded protections as a direct
result of the 2020 NWPR).
    The agencies understand that revising State regulations and/or laws
takes time, and the agencies do not know how some States might have
responded if the 2020 NWPR had been in place for more than a year, but
the agencies have no basis to expect that more States that currently
lack protections beyond the 2020 NWPR Federal floor would have
established them. Indeed, the External Environmental Economics Advisory
Committee has stated that the model that the 2020 NWPR used to forecast
State responses to that rule was overly optimistic with respect to the
likelihood that States would address a Federal regulatory gap, in part
based on the agencies' failure to fully consider States' responses to
past changes to the definition of ``waters of the United States''
(e.g., only three States directly increased protective regulations in
response to the decision in SWANCC that the use of ``isolated'' non-
navigable intrastate ponds by migratory birds was not by itself a
sufficient basis for the exercise of Federal authority under the Clean
Water Act, and the agencies' resulting change in implementation of the
Act).\84\ Moreover, commenters, including State entities, asserted that
the Federal Government provided no assistance or support for
overburdened State agencies trying to compensate for the sudden
suspension in Federal protections under the 2020 NWPR. Finally, States
asserted that in the absence of robust Federal protections, even if
they were to expend substantial resources addressing discharges within
their borders, they would not be able to limit pollutants flowing in
from other States that may not have established such controls.
---------------------------------------------------------------------------

    \84\ Prior to the 2016 Trump Administration, EPA's Science
Advisory Board (SAB) had a subcommittee on environmental economics
known as the Environmental Economics Advisory Committee (EEAC). When
this committee was disbanded under the 2016 Administration, its
members created an ad-hoc external committee. This External
Environmental Economics Advisory Committee (E-EEAC) carried out an
assessment of the economic analysis associated with the 2020 NWPR.
See Keiser, D., S. Olmstead, K. Boyle, V. Flatt, B. Keeler, D.
Phaneuf, J. Shapiro, and J. Shimshack (2020). Report on the Repeal
of the Clean Water Rule and its Replacement with the Navigable
Waters Protection Rule to Define Waters of the United States
(WOTUS). December 2020. As of today, the EPA's SAB has reinstated
the EEAC, which assessed the proposed rule's economic analysis as
part of the SAB's review of the rule.
---------------------------------------------------------------------------

    The agencies are also not aware of any Tribes that expanded their
clean water protections to compensate for a reduction in protections
under the 2020 NWPR. During the agencies' Tribal consultation and
coordination for this rulemaking process, Tribes overwhelmingly
indicated they lack the independent resources and expertise to protect
their waters and therefore rely on Clean Water Act protections. See
Summary of Tribal Consultation and Coordination, available in the
docket for this rule. This feedback is consistent with the concerns
expressed during the 2020 NWPR rulemaking process. See, e.g., 85 FR
22336-22337, April 21, 2020 (``[M]any Tribes may lack the capacity to
create a [T]ribal water program under [T]ribal law, to administer a
program, or to expand programs that currently exist. Other Tribes may
rely on the Federal government for enforcement of water quality
violations . . . .'').
    Given the limited capacity of many Tribes and States to regulate
waters more broadly than the Federal Government and limited authority
under Tribal and State law, the narrowing of Federal jurisdiction would
mean that many discharges into the newly non-jurisdictional waters
would no longer be subject to regulation, including permitting
processes and mitigation requirements designed to protect the chemical,
physical, and biological integrity of the nation's waters. The agencies
have heard concerns from a broad array of co-regulators and
stakeholders, including Tribes, States, scientists, and non-
governmental organizations, that corroborated the agencies' data and
indicated that the 2020 NWPR's reduction in the jurisdictional scope of
the Clean Water Act would cause substantial environmental harms,
including to the quality of paragraph (a)(1) waters, that Tribes and
States lack the authority or resources to address.

    In conclusion, the agencies do not find that the 2020 NWPR is a
suitable alternative to this rule.

C. This Rule

1. Summary of This Rule
    This rule establishes the definition of ``waters of the United
States'' for purposes of the Clean Water Act. For clarity, this rule is
divided into three parts: jurisdictional waters, exclusions, and
definitions. This section of the preamble addresses each provision of
the rule and provides an explanation of the rule text, a response to
significant comments, and the agencies' interpretation and
implementation of the provisions of the rule.
    The ``waters of the United States'' are defined in paragraph (a) of
this rule: (1) traditional navigable waters, the territorial seas, and
interstate waters (``paragraph (a)(1) waters''); (2) impoundments of
``waters of the United States'' (``paragraph (a)(2) impoundments'');
(3) tributaries to traditional navigable waters, the territorial seas,
interstate waters, or paragraph (a)(2) impoundments when the
tributaries meet either the relatively permanent standard or the
significant nexus standard (``jurisdictional tributaries''); (4)
wetlands adjacent to paragraph (a)(1) waters; wetlands adjacent to and
with a continuous surface connection to relatively permanent paragraph
(a)(2) impoundments or to jurisdictional tributaries when the
jurisdictional tributaries meet the relatively permanent standard; and
wetlands adjacent to paragraph (a)(2) impoundments or jurisdictional
tributaries when the wetlands meet the significant nexus standard
(``jurisdictional adjacent wetlands''); and (5) intrastate lakes and
ponds, streams, or wetlands not identified in paragraphs (a)(1) through
(4) that meet either the relatively permanent standard or the
significant nexus standard (``paragraph (a)(5) waters'').
    The ``relatively permanent standard'' means relatively permanent,
standing or continuously flowing waters connected to paragraph (a)(1)
waters, and waters with a continuous surface connection to such
relatively permanent waters or to paragraph (a)(1) waters. The
``significant nexus standard'' means waters that, either alone or in
combination with similarly situated waters in the region, significantly
affect the chemical, physical, or biological integrity of traditional
navigable waters, the territorial seas, or interstate waters.
    Paragraph (b) of this rule contains the longstanding exclusions
from the pre-2015 regulations, as well as additional exclusions based
on well-established practice, from the definition of ``waters of the
United States.'' Paragraph (c) of this rule provides definitions for
terms used in this rule.
Paragraph (a): Jurisdictional Waters
    Paragraph (a)(1). This rule defines ``waters of the United States''
to include traditional navigable waters, the territorial seas, and
interstate waters. The agencies are not making changes to the text or
substance of the provisions of the 1986 regulations covering
traditional navigable waters, the territorial seas, and interstate
waters. The agencies are consolidating these three categories of waters
into one paragraph at the beginning of the regulatory text. While
combined into one paragraph, each category will remain distinct in
separate subparagraphs. The agencies have concluded that this non-
substantive change streamlines the regulatory text and increases
clarity. This streamlining is not a substantive change and does not
alter the agencies' longstanding interpretation and implementation of
these provisions.
    Paragraph (a)(2). This rule defines ``waters of the United States''
to include impoundments of ``waters of the United States.''
Impoundments are created by discrete structures (often human-built)
like dams or levees that typically have the effect of raising the water
surface elevation, creating or expanding the area of open water, or
both. In this rule, the paragraph (a)(2) impoundments category provides
that ``waters of the United States'' do not lose their jurisdictional
status simply because they are impounded. In a change from the 1986
regulations, waters that are jurisdictional under paragraph (a)(5) and
that are subsequently impounded do not retain their jurisdictional
status by rule under the paragraph (a)(2) impoundments provision, but
may still be determined to be jurisdictional if they meet the
requirements of a category of ``waters of the United States'' other
than paragraph (a)(2) at the time of assessment (i.e., as a traditional
navigable water, the territorial seas, interstate water, jurisdictional
tributary, jurisdictional adjacent wetland, or paragraph (a)(5) water).
    Paragraph (a)(3). This rule defines ``waters of the United States''
to include tributaries of traditional navigable waters, the territorial
seas, interstate waters, or paragraph (a)(2) impoundments when the
tributaries meet either the relatively permanent standard or the
significant nexus standard. As compared to the 1986 regulations, this
rule adds the territorial seas to the list of waters to which a water
may be a tributary and deletes intrastate lakes and ponds, streams, or
wetlands not identified in paragraphs (a)(1) through (4) (the (a)(3)
``other waters'' provision under the 1986 regulations) from the list.
    Paragraph (a)(4). Aquatic resources that meet this rule's
definitions of ``wetlands'' and ``adjacent'' with regard to another
jurisdictional water are assessed under this provision. The rule
defines ``waters of the United States'' to include: (1) wetlands
adjacent to traditional navigable waters, the territorial seas, or
interstate waters; (2) wetlands adjacent to and with a continuous
surface connection to relatively permanent paragraph (a)(2)
impoundments or jurisdictional tributaries when the jurisdictional
tributaries meet the relatively permanent standard; or (3) wetlands
adjacent to paragraph (a)(2) impoundments or jurisdictional tributaries
when the wetlands meet the significant nexus standard (``jurisdictional
adjacent wetlands'').
    Paragraph (a)(5). This rule defines ``waters of the United States''
to include intrastate lakes and ponds, streams, or wetlands not
identified in paragraphs (a)(1) through (4) that meet either the
relatively permanent standard or the significant nexus standard. In
this paragraph, the agencies are retaining the category from the 1986
regulations sometimes referred to as ``(a)(3) waters'' or ``other
waters,'' but with changes to reflect the agencies' determination of
the statutory limits on the scope of ``waters of the United States''
informed by the law, the science, and agency expertise, in addition to
consideration of extensive public comment on the proposed rule. Of
particular importance, the agencies have replaced the 1986 regulation's
broad Commerce Clause basis for jurisdiction for waters not identified
in other provisions of the definition, with the relatively permanent
standard and the significant nexus standard. In addition, the agencies
have deleted the non-exclusive list of ``other waters'' in the 1986
regulation. Under this provision in the rule, only ``intrastate lakes
and ponds, streams, or wetlands not identified in paragraphs (a)(1)
through (4)'' can be assessed for jurisdiction under the relatively
permanent standard or significant nexus standard.
Paragraph (b): Exclusions
    The agencies are promulgating a number of exclusions from the
definition of ``waters of the United States,'' including longstanding

exclusions for prior converted cropland and waste treatment systems,
and exclusions for features that were generally considered non-
jurisdictional under the pre-2015 regulatory regime. The agencies are
listing these exclusions in the regulatory text in a new paragraph (b),
which consolidates the exclusions together in a single regulatory
section. Under this rule, where a feature satisfies the terms of an
exclusion, it is excluded from jurisdiction even where the feature
would otherwise be jurisdictional under paragraphs (a)(2) through (5)
of this rule. Paragraph (a)(1) waters are not subject to the
exclusions. The exclusions are:
    (1) Waste treatment systems, including treatment ponds or lagoons,
designed to meet the requirements of the Clean Water Act;
    (2) Prior converted cropland designated by the Secretary of
Agriculture. The exclusion would cease upon a change of use, which
means that the area is no longer available for the production of
agricultural commodities. Notwithstanding the determination of an
area's status as prior converted cropland by any other Federal agency,
for the purposes of the Clean Water Act, the final authority regarding
Clean Water Act jurisdiction remains with EPA;
    (3) Ditches (including roadside ditches) excavated wholly in and
draining only dry land and that do not carry a relatively permanent
flow of water;
    (4) Artificially irrigated areas that would revert to dry land if
the irrigation ceased;
    (5) Artificial lakes or ponds created by excavating or diking dry
land to collect and retain water and which are used exclusively for
such purposes as stock watering, irrigation, settling basins, or rice
growing;
    (6) Artificial reflecting or swimming pools or other small
ornamental bodies of water created by excavating or diking dry land to
retain water for primarily aesthetic reasons;
    (7) Waterfilled depressions created in dry land incidental to
construction activity and pits excavated in dry land for the purpose of
obtaining fill, sand, or gravel unless and until the construction or
excavation operation is abandoned and the resulting body of water meets
the definition of waters of the United States; and
    (8) Swales and erosional features (e.g., gullies, small washes)
characterized by low volume, infrequent, or short duration flow.
Paragraph (c): Definitions
    Paragraph (c) of this rule provides definitions for purposes of the
rule. This rule contains several defined terms unchanged from the 1986
regulations: the definitions of ``wetlands,'' ``adjacent,'' ``high tide
line,'' ``ordinary high water mark,'' and ``tidal water.'' This rule
defines the term ``significantly affect'' for purposes of determining
whether a water meets the significant nexus standard to mean ``a
material influence on the chemical, physical, or biological integrity
of'' a paragraph (a)(1) water. Under this rule, waters, including
wetlands, are evaluated either alone, or in combination with other
similarly situated waters in the region, based on the functions the
evaluated waters perform. This rule identifies specific functions that
will be assessed and identifies specific factors that will be
considered when determining whether the functions provided by the
water, either alone or in combination, have a material influence on the
integrity of a traditional navigable water, the territorial seas, or an
interstate water. These factors include the distance from a paragraph