under paragraph (a)(6) and no case-specific significant nexus is
required. Waters that do not fall within the six categorically
jurisdictional waters identified in paragraph (a)(1) through

(a)(6) of the rule or within these two case-specific provisions are not
``waters of the United States.''
    This section first discusses the five subcategories of waters that
the agencies determine are ``similarly situated'' for purposes of a
significant nexus determination; second, the 100-year floodplain and
4,000 foot boundaries under which waters will be subject to a case-
specific significant nexus determination but for which the agencies
have not made a ``similarly situated'' determination; third, the
definition of ``significant nexus'' and how the case-specific
significant nexus determinations will be made under these two
provisions; and, finally, the revisions made to the rule with respect
to case-specific determinations and major comments.
1. Waters Determined To Be ``Similarly Situated'' by Rule for Which a
Case-Specific Significant Nexus Determinations Is Required
    In the rule, paragraph (a)(7) specifies the subcategories of waters
(Prairie potholes, Carolina and Delmarva bays, pocosins, western vernal
pools in California, and Texas coastal prairie wetlands) that, if they
are not otherwise jurisdictional under paragraphs (a)(1) through
(a)(6), the agencies determine to be ``similarly situated'' by rule. In
the proposal the agencies sought comment on a number of options to
address remaining waters that did not fit within the jurisdictional
categories, including whether to conclude that other waters were
``similarly situated'' in certain areas of the country or whether to
conclude that specified subcategories of waters were jurisdictional. 79
FR 22215, 22216. The agencies concluded that waters within the five
subcategories were ``similarly situated'' in the areas of the country
in which they are located. The rationale for this determination is
discussed above in Section III. Under paragraph (a)(7), Prairie
potholes, Carolina and Delmarva bays, pocosins, western vernal pools in
California, and Texas coastal prairie wetlands are jurisdictional when
they have a significant nexus to a traditional navigable water,
interstate water, or the territorial seas. Waters subject to normal
farming, silviculture, and ranching activities that are within these
subcategories will be assessed consistent with this provision of the
rule. Waters in these subcategories are not jurisdictional as a class
under the rule. However, because the agencies determined that these
subcategories of waters are ``similarly situated,'' the waters within
the specified subcategories that are not otherwise jurisdictional under
paragraph (a)(6) of the rule must be assessed in combination with all
waters of the same subcategory in the region identified by the
watershed that drains to the nearest point of entry of a traditional
navigable water, interstate water, or the territorial seas (hereinafter
referred to as the point of entry watershed).
    When performing a case-specific significant nexus evaluation for a
water in the paragraph (a)(7) subcategories, the rule establishes which
waters must be considered in combination. The similarly situated waters
identified in the subparagraphs will be combined with other waters in
the same subparagraph located in a single point of entry watershed. For
example, under paragraph (a)(7) only western vernal pools can be
analyzed with other western vernal pools in the same point of entry
watershed. Waters identified in the subparagraphs that are otherwise
jurisdictional under the rule cannot be considered in combination with
paragraph (a)(7) waters for purposes of a case-specific significant
nexus determination under paragraph (a)(7). Individual waters of the
specified subcategories may be jurisdictional under other paragraphs of
this rule (e.g., a Prairie pothole that sits on a state border is an
interstate water under paragraph (a)(2) or a western vernal pool that
meets the definition of adjacent under paragraph (a)(6)). Where those
individual waters are jurisdictional under paragraph (a)(1) through
(a)(6) by rule, no case-specific significant nexus analysis is
required. The rule also states that waters in paragraph (a)(7) shall
not be combined with waters jurisdictional under paragraph (a)(6).
Essentially, while Prairie potholes are an identified subcategory under
paragraph (a)(7), that identification does not affect a Prairie pothole
that borders a covered tributary and is jurisdictional as an adjacent
water under paragraph (a)(6). Additionally, a Prairie pothole that is
jurisdictional under paragraph (a)(6) cannot be combined with Prairie
potholes that require a case-specific jurisdictional analysis under
paragraph (a)(7) since ``adjacent waters'' have already been determined
to have a significant nexus by rule. Finally, waters within the
specified subcategories in paragraph (a)(7) are assessed under
paragraph (a)(7) not under paragraph (a)(8); waters within the
specified subcategories that are within the 100-year flood plain of a
traditional navigable water, interstate water, or the territorial seas
or within the 4,000 foot boundary established for case-specific
determinations under paragraph (a)(8) remain ``similarly situated''
waters under paragraph (a)(7). These similarly situated waters are
evaluated in combination for their effect on the chemical, physical, or
biological integrity of traditional navigable waters, interstate
waters, or the territorial seas. Additional details about the case-
specific significant nexus analysis are found in section 4 below.
2. Waters Within the 100-Year Floodplain of a Traditional Navigable
Water, Interstate Water, or the Territorial Seas and Waters Within
4,000 Foot Boundary for Which a Case-Specific Significant Nexus
Determination Is Required
    Paragraph (a)(8) in the rule specifies that a water that does not
otherwise meet the definition of adjacency is evaluated on a case-
specific basis for significant nexus under this paragraph where it is
located within the 100-year floodplain of a traditional navigable
water, interstate water, or the territorial seas or within 4,000 feet
of the high tide line or ordinary high water mark of a traditional
navigable water, interstate water, the territorial seas, impoundment,
or covered tributary. Although these waters are not considered
similarly situated by rule, waters under this paragraph can be
determined on a case-specific basis to be similarly situated. This is a
change from the proposal which would have allowed for a similarly
situated analysis and significant nexus determination for any water,
anywhere in the region. Under the rule, the waters specified in
paragraph (a)(7) and waters that meet the requirements in paragraph
(a)(8) are the only waters for which a case-specific significant nexus
determination may be made.
    Under paragraph (a)(8), only waters that are within the 100-year
floodplain of a traditional navigable water, interstate water, or the
territorial seas or within the 4,000 foot boundary can be evaluated on
a case-specific basis for significant nexus to a traditional navigable
water, interstate water, or the territorial seas. If a portion of the
water is located within the 100-year floodplain of a traditional
navigable water, interstate water, or the territorial seas or 4,000
feet of the ordinary high water mark or high tide line of a traditional
navigable water, interstate water, the territorial seas, impoundment,
or covered tributary, the entire water will be considered to be within
the boundaries for paragraph (a)(8) and will undergo a case-specific
significant nexus determination. Under this provision, if the 100-year
floodplain of a traditional navigable water,

interstate water, or the territorial seas extends beyond 4,000 feet of
the ordinary high water mark, a water, that is not otherwise
jurisdictional under the rule, within that floodplain will be evaluated
under the 100-year floodplain boundary of paragraph (a)(8). A water
within the boundaries must be evaluated on a case-specific basis for
not only a significant nexus but also for a determination of whether
there are any waters with which the waters is similarly situated.
Waters identified in paragraph (a)(8) may not be combined with waters
identified in paragraph (a)(6) for purposes of the significant nexus
analysis, but may be combined with similarly situated waters located in
the same point of entry watershed. If waters identified in paragraph
(a)(8) also meet the definition of adjacency under paragraph (a)(6),
they are jurisdictional as ``adjacent waters'' and do not need a case-
specific significant nexus analysis. Under paragraph (a)(8), for
example, the agencies would evaluate on a case-specific basis whether a
low-centered polygonal tundra and patterned ground bog in an area with
a small floodplain and located beyond the 1,500 foot boundary but
within the 100-year floodplain of a traditional navigable water,
interstate water, or the territorial seas or within the 4,000 foot
boundary, or a wetland in which normal farming, ranching, or
silviculture activities occur, as those terms are used in section
404(f) of the Clean Water Act and its implementing regulations, has a
significant nexus as defined in the rule.
    Waters identified in the subcategories in paragraph (a)(7) are
evaluated under paragraph (a)(7) only; the provisions of paragraph
(a)(8), including the boundaries in paragraph (a)(8), do not apply to
paragraph (a)(7) waters. The significant nexus analysis for waters
under paragraph (a)(8) will then consider the waters individually or,
if it is determined that there are similarly situated waters, as a
group of waters within a point of entry watershed for their effect on
the chemical, physical, or biological integrity of traditional
navigable waters, interstate waters, or the territorial seas.
    Some commenters asked how wetlands underlain by permafrost would be
treated under this rule. Waters subject to case-specific review under
paragraph (a)(8) will include areas determined to meet the technical
definition of ``wetlands'' because they have the required hydrology,
vegetation, and soils. The presence of permafrost is not itself
determinative of whether a particular area satisfies the three
parameter requirement needed to be wetlands under the rule. This is
true under existing regulations and remains unchanged in this rule.
Because the definition of wetland does not change under the rule, the
agencies do not anticipate the rule will alter the current scope of CWA
jurisdiction over wetlands underlain by permafrost.
a. Summary of Rationale for Case-Specific Significant Nexus Analysis
Within 100-Year Floodplain of a Traditional Navigable Water, Interstate
Water, or the Territorial Seas
    As discussed in Section III, above, the scientific literature
supports that wetlands and open waters in floodplains are physically,
chemically, and biologically connected to downstream traditional
navigable waters, interstate waters, or the territorial seas and
significantly affect the integrity of such waters. The Science Report
concludes that wetlands and open waters located in ``floodplains are
physically, chemically and biologically integrated with rivers via
functions that improve downstream water quality, including the
temporary storage and deposition of channel-forming sediment and woody
debris, temporary storage of local ground water that supports baseflow
in rivers, and transformation and transport of stored organic matter.''
Science Report at ES-2 to ES-3. As described in the Science Report and
the Technical Support Document, such waters act as the most effective
buffer to protect downstream waters from nonpoint source pollution
(such as nitrogen and phosphorus), provide habitat for breeding fish
and aquatic insects that also live in streams, and retain floodwaters,
sediment, nutrients, and contaminants that could otherwise negatively
impact the condition or function of downstream waters. As discussed
above, in defining waters as adjacent, and therefore categorically
jurisdictional, the agencies established a 1,500 foot boundary for
waters located within the 100-year floodplain of a traditional
navigable water, interstate water, the territorial seas, impoundment,
or covered tributary in order to protect vitally important waters while
at the same time providing a practical and implementable rule. In light
of the science on the functions provided by floodplain waters and
wetlands, waters and wetlands within the 100-year floodplain of
traditional navigable waters, interstate waters, or the territorial
seas are likely to provide those functions for traditional navigable
waters, interstate waters, or the territorial seas. However, because
the 100-year floodplain of a traditional navigable water can, in some
case be quite large, the agencies concluded it was reasonable to
subject waters and wetlands in the 100-year floodplain that are beyond
1,500 feet of the ordinary high water mark, and therefore do not meet
the definition of ``neighboring,'' to a case-specific significant nexus
analysis rather than concluding that such waters are categorically
jurisdictional. This inclusion of a case-specific analysis for such
floodplain waters is supported by the SAB. The SAB concluded that
``distance should not be the sole indicator used to evaluate the
connection of `other waters' to jurisdictional waters.'' SAB 2014b at
3. In allowing the case-specific evaluation of waters within the 100-
year floodplain of a traditional navigable water, interstate water, or
the territorial seas that do not meet the definition of adjacency, the
agencies are allowing for the functional relationship of those
floodplain waters to be considered regardless of distance. The SAB also
supported the Science Report's conclusion that ``the scientific
literature strongly supports the conclusions that streams and
`bidirectional' floodplain wetlands are physically, chemically, and/or
biologically connected to downstream navigable waters; however, these
connections should be considered in terms of a connectivity gradient.''
SAB 2014a at 1. In addition, the SAB noted, ``the literature review
does substantiate the conclusion that floodplains and waters and
wetlands in floodplain settings support the physical, chemical, and
biological integrity of downstream waters.'' Id. at 3.
    The agencies do not anticipate that there will be numerous
circumstances in which this provision will be utilized because
relatively few traditional navigable waters will have floodplains
larger than 4,000 feet (the other threshold in paragraph (a)(8) for
waters regardless of floodplain). Further, the agencies recognize that
extensive areas of the nation's floodplains have been affected by
levees and dikes which reduce the scope of flooding. In these
circumstances, the scope of the 100-year floodplain is also reduced and
is reflected in FEMA mapping used by the agencies. In circumstances
where there is little or no alteration of the floodplain and it remains
relatively broad, the agencies will explicitly consider distance
between the water being evaluated and traditional navigable water,
interstate water, or the territorial seas when making a case-specific
significant nexus determination. Based on the science concerning the
important functions provided by floodplain waters and wetlands, the
agencies established this provision to ensure that truly

important waters may still be protected on a case-specific basis. By
using the 100-year floodplain and limiting the provision to traditional
navigable waters, interstate waters, or the territorial seas, the
agencies are reasonably balancing the protection of waters that may
have a significant nexus with the goal of providing additional
certainty.
b. Summary of Rationale for Case-Specific Significant Nexus Analysis
Within 4,000 Foot Boundary
    The agencies establish a provision in the rule for case-specific
significant nexus determinations because the agencies concluded that
some waters located beyond the distance limitations established for
``adjacent waters'' can have significant chemical, physical, and
biological connections to and effects on traditional navigable waters,
interstate waters, or the territorial seas. The agencies reasonably
identified the 4,000 foot boundary for these case-specific significant
nexus determinations by balancing consideration of the science and the
agencies' expertise and experience in making significant nexus
determinations with the goal of providing clarity to the public while
protecting the environment and public health. The agencies' experience
has shown that the vast majority of waters where a significant nexus
has been found, and which are therefore important to protect to achieve
the goals of the Act, are located within the 4,000 foot boundary.
Moreover, because of the unique status under the CWA of traditional
navigable waters, interstate waters, and the territorial seas, the 100-
year floodplain boundary for these waters provides another means of
identifying on a case-specific basis those waters that significantly
affect traditional navigable waters, interstate waters or the
territorial seas. The agencies' balancing of these considerations is
consistent with the statute and the Supreme Court opinions. The
agencies decided that it is important to promulgate a rule that not
only protects the most vital of our Nation's waters, but one that is
practical and provides sufficient boundaries so that the public
reasonably understands where CWA jurisdiction ends.
    The agencies' decision to establish a provision that authorizes
case-specific significant nexus analysis for waters within 4,000 feet
is based on a number of factors. These waters may be located within the
floodplain of a traditional navigable water, interstate water, the
territorial seas, impoundment, or covered tributary. Section IV.G. and
the Technical Support Document discuss the importance of floodplain
waters on the chemical, physical, and biological integrity of
downstream traditional navigable waters, interstate waters, or the
territorial seas. For purposes of clarity and to provide regulatory
certainty, the agencies decided to use distance boundaries within the
100-year floodplain to define adjacency for floodplain waters. Under
the rule, the only floodplain waters that are specifically identified
as being jurisdictional as ``adjacent'' are those located in whole or
in part within the 100-year floodplain and not more than 1,500 feet of
the ordinary high water mark of jurisdictional waters.
    Similarly, due to the many functions that waters located within
4,000 feet of the high tide line of a traditional navigable water or
the territorial seas provide and their often close connections to the
surrounding traditional navigable waters, science supports the
agencies' determination that such waters are rightfully evaluated on a
case-specific basis for significant nexus to a traditional navigable
water or the territorial seas. Waters within 4,000 feet of the ordinary
high water mark of a traditional navigable water, interstate water, the
territorial seas, impoundment, or covered tributary may fall within the
riparian areas of such waters. As discussed in section IV.G., in
response to comments regarding the uncertainty of the term ``riparian
area,'' the agencies removed the term from the definition of
``neighboring.'' However, the agencies continue to recognize that
science is clear that wetlands and open waters in riparian areas
individually and cumulatively can have a significant effect on the
chemical, physical, or biological integrity of downstream waters. Thus,
the rule allows for a case-specific determination of significant nexus
for waters located within 4,000 feet of the high tide line or the
ordinary high water mark of a traditional navigable water, interstate
water, the territorial seas, impoundment, or covered tributary.
    The agencies have always recognized that adjacency is bounded by
proximity, and the rule adds additional clarity to adjacency by
bounding what can be considered neighboring. The science is clear that
a water's proximity to downstream waters influences its impact on those
waters. The Science Report states, ``[s]patial proximity is one
important determinant of the magnitude, frequency and duration of
connections between wetlands and streams that will ultimately influence
the fluxes of water, materials and biota between wetlands and
downstream waters.'' Science Report at ES-11. Generally, waters that
are closer to a jurisdictional water are more likely to be connected to
that water than waters that are farther away. A case-specific analysis
for waters located within 4,000 feet of the high tide line or the
ordinary high water mark of a traditional navigable water, interstate
water, the territorial seas, impoundment, or covered tributary allows
such waters to be considered jurisdictional only where they meet the
significant nexus requirements. Even where not within a 100-year
floodplain, waters within 4,000 feet of the high tide line or the
ordinary high water mark of a traditional navigable water, interstate
water, the territorial seas, impoundment, or covered tributary can have
significant chemical, physical, and biological connections with
traditional navigable waters, interstate waters, or the territorial
seas.
    As noted previously, in response to comments concerned that there
were no bounds in the proposed rule on how far a surface hydrologic
connection could be for purposes of adjacency, the agencies did not
include surface hydrologic connections as its own factor for
determining adjacency in the final rule. Such connections, however, are
relevant in a case-specific significant nexus determination under
paragraph (a)(8). For example, waters located within 4,000 feet of the
high tide line or the ordinary high water mark of a traditional
navigable water, interstate water, the territorial seas, impoundment,
or covered tributary that contribute confined surface flow to a
downstream water can have important hydrologic connections to and
effects on that downstream water such as the attenuation and cycling of
nutrients that would otherwise effect downstream water quality.
    The agencies' decision to establish the case-specific provision at
paragraph (a)(8), including the boundaries, was also informed by the
knowledge that waters located within 4,000 feet of the high tide line
or the ordinary high water mark of a traditional navigable water,
interstate water, the territorial seas, impoundment, or covered
tributary can have a confined surface or shallow subsurface connection
to such a water. In order to provide the clarity and certainty that
many commenters requested regarding ``adjacent waters,'' the rule does
not define ``neighboring'' to include all waters with confined surface
or shallow subsurface connections.
    However, the agencies recognize that the science demonstrates that
waters with a confined surface or shallow subsurface connection to
jurisdictional

waters can have important effects on downstream waters. For purposes of
a case-specific significant nexus analysis under the rule, a shallow
subsurface hydrologic connection is lateral water flow over a
restricting layer in the top soil horizons, or a shallow water table
which fluctuates within the soil profile, sometimes rising to or near
the ground surface. In addition, water can move within confined man-
made subsurface conveyance systems such as drain tiles and storm
sewers, and in karst topography. Confined subsurface systems can move
water, and potential contaminants, directly to surface waters and
rapidly without the opportunity for nutrient or sediment reduction
along the pathway.
    Shallow subsurface connections move quickly through the soil and
impact surface water directly within hours or days rather than the
years it may take long pathways to reach surface waters. See Technical
Support Document. Tools to assess shallow subsurface flow include
reviewing the soils information from the NRCS Soil Survey, which is
available for nearly every county in the United States. When assessing
whether a water within the 4,000 foot boundary performs any of the
functions identified in the rule's definition of significant nexus, the
significant nexus determination can consider whether shallow subsurface
connections contribute to the type and strength of functions provided
by a water or similarly situated waters. However, neither shallow
subsurface connections nor any type of groundwater, shallow or deep,
are themselves ``waters of the United States.''
    The proposed rule did not set a distance threshold for case-
specific waters to be evaluated for a significant nexus. Some
commenters argued that there should be a limitation on areas subject to
case-specific analysis while others contended that the agencies lack
discretion to set regulatory limits that would exclude from
jurisdiction any water meeting the significant nexus test. The agencies
disagree that the agencies lack the authority to establish reasonable
boundaries to determine what areas are subject to case-specific
significant nexus analysis. Nothing in the CWA or case law mandates
that the agencies require every water feature in the nation be subject
to analysis for significant nexus. The Supreme Court has made clear
that the agencies have the authority and responsibility to determine
the limits of CWA jurisdiction, and establishing boundaries based on
agency judgment, expertise and experience in administering the statute
is at the core of the agencies authority and discretion.
    After weighing the scientific information about these waters'
connectivity and importance to protecting downstream waters, the
agencies' considerable experience making jurisdictional determinations,
the objective of enhancing regulatory clarity and consistent with the
statute and the caselaw, the agencies decided to set a boundary of
4,000 feet for case-specific significant nexus analysis for waters that
do not otherwise meet the requirements of paragraphs (a)(1) through
(a)(7). Tying this provision for case-specific significant nexus
analysis to distance informed by the science, and the agencies'
experience and expertise, as spatial proximity is a key contributor to
connectivity among waters. Science Report at ES-11. Distance is by no
means the sole factor, and aquatic functions will play a prominent role
in determining whether specific waters covered under this aspect of
paragraph (a)(8) have a significant nexus. In light of the role spatial
proximity plays in connectivity and the objective of enhancing
regulatory clarity, predictability and consistency, the agencies
conclude that establishing a boundary for this aspect of waters subject
to case-specific significant nexus analysis based on distance is
reasonable.
    While, for purposes of this national rule, distance is a reasonable
and appropriate measure for identifying where this case-specific
significant nexus analysis will be conducted, the science does not
point to any particular bright line delineating waters that have a
significant nexus from those that do not. The Science Report concluded
that connectivity of streams and wetlands to downstream waters occurs
along a gradient. The evidence unequivocally demonstrates that the
stream channels and floodplain wetlands or open waters that together
form river networks are clearly connected to downstream waters in ways
that profoundly influence downstream water integrity. The connectivity
and effects of non-floodplain wetlands and open waters are more
variable and thus more difficult to address solely from evidence
available in peer-reviewed studies. Science Report at ES-5. Because of
this variability, with respect to waters that are not covered by
paragraphs (a)(1) through (a)(7) of the rule, the science does not
provide a precise point along the continuum at which waters provide
only speculative or insubstantial functions to downstream waters.
    Like connectivity itself, there is also a continuum of outcomes
associated with picking a distance threshold. A smaller threshold
increases the likelihood that waters that could have a significant
nexus will not be analyzed and therefore not subject to the Act; a
larger threshold reduces that possibility, but also means that agency
and the public's resources are expended conducting significant nexus
analyses on waters that have a lower likelihood of meriting the Act's
protection.
    Recognizing that there is no optimal line, in selecting both the
100-year floodplain for and the 4,000 foot boundaries the agencies
looked principally to the extensive experience the Corps has gained in
making significant nexus determinations since the Rapanos decision. As
noted in Section III above, since the Rapanos decision, the agencies
have developed extensive experience making significant nexus
determinations, and that experience and expertise informed the judgment
of the agencies in establishing both the 100-year floodplain boundary
and the 4,000 foot boundary. The agencies have made determinations in
every state in the country, for a wide range of waters in a wide range
of conditions. The vast majority of the waters that the Corps has
determined have a significant nexus are located within 4,000 feet of a
jurisdictional tributary, traditional navigable or interstate water, or
the territorial seas. Therefore, the agencies conclude that the 100-
year floodplain and 4,000 foot boundaries in the rule will sufficiently
capture for analysis those waters that are important to protect to
achieve the goals of the Clean Water Act.
    The agencies acknowledge that, as with any meaningful boundary,
some waters that could be found jurisdictional lie beyond the boundary
and will not be analyzed for significant nexus. The agencies minimize
that risk by also establishing a provision in paragraph (a)(8) for
case-specific significant nexus analysis of waters located within the
100-year floodplain of a traditional navigable water, interstate water,
or the territorial seas. While in the agencies' experience the vast
majority of wetlands with a significant nexus are located within the
4,000 foot boundary, it is the agencies' experience that there are a
few waters that have been determined to be jurisdictional that are
located beyond this boundary, typically due to a surface or shallow
subsurface hydrologic connections. Nonetheless, the agencies have
weighed these considerations and concluded that the value of enhancing
regulatory clarity, predictability and consistency through a distance
limit outweigh the likelihood that a distinct minority of waters that
might be shown

to meet the significant nexus test will not be subject to analysis. In
the agencies' experience, requiring an evaluation of significant nexus
for waters covered by paragraph (a)(8) should capture the vast majority
of waters having a significant nexus to the downstream waters. The
agencies therefore conclude that that adoption of the 4,000 foot
boundary is reasonable.
    The rule's requirements for these waters, coupled with those for
``adjacent waters,'' create an integrated approach that tailors the
regulatory regime based on the science and the agencies' policy
objectives. Determining by rule that covered adjacent waters have a
significant nexus follows the science, achieves regulatory clarity and
predictability, and avoids expenditure of agency and public resources
on case-specific significant nexus analysis. Similarly, providing for
case-specific significant nexus analysis for waters that are not
adjacent but within the 4,000 foot distance limit, as well as those
within the 100-year floodplain of a traditional navigable water,
interstate water, or the territorial seas, is consistent with science
and agency experience, will ensure protection of the important waters
whose protection will advance the goals of the Clean Water Act, and
will greatly enhance regulatory clarity for agency staff, regulated
parties, and the public.
    For these reasons, the agencies decided to allow case-specific
determinations of significant nexus for waters located within the 100-
year floodplain of a traditional navigable water, interstate water, or
the territorial seas and for waters located within 4,000 feet of the
high tide line or the ordinary high water mark of a traditional
navigable water, an interstate water, the territorial seas, an
impoundment, or a covered tributary. Under the rule, these waters are
jurisdictional only where they individually or cumulatively (if it is
determined that there are other similarly situated waters) have a
significant nexus to traditional navigable waters, interstate waters,
or the territorial seas. Additional scientific and policy rationale for
including such waters as waters that can be evaluated on a case-
specific basis can be find in the Technical Support Document.
    The agencies emphasize that they fully support efforts by States
and tribes to protect under their own laws any additional waters,
including locally special waters that may not be within the
jurisdiction of the CWA as the agencies have interpreted its scope in
this rule. Indeed, the promulgation of the 100-year floodplain and 4000
foot boundaries for purposes of a case-specific analysis of significant
nexus does not foreclose states from acting consistent with their state
authorities to establish protection for waters that fall outside of the
protection of the CWA. In promulgating the 4,000 foot boundary, the
agencies have balanced protection and clarity, scientific uncertainties
and regulatory experience, and established a line that is, in their
judgment, reasonable and consistent with the statute and its goals and
objectives.
3. Case-Specific Significant Nexus Determinations
    Only waters identified in paragraphs (a)(7) or (a)(8) of the rule
require a case-specific determination of significant nexus. This
section discusses the definition of significant nexus in the rule and
how the agencies will make case-specific significant nexus
determinations under the rule.
a. Definition of Significant Nexus
    Paragraph (c)(5) of the rule defines the term ``significant nexus''
to mean a significant effect (more than speculative or insubstantial)
on the chemical, physical, or biological integrity of a traditional
navigable water, interstate water, or the territorial seas. 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. Functions to be considered for the
purposes of determining significant nexus are sediment trapping,
nutrient recycling, pollutant trapping, transformation, filtering and
transport, retention and attenuation of floodwaters, runoff storage,
contribution of flow, export of organic matter, export of food
resources, and provision of life-cycle dependent aquatic habitat (such
as foraging, feeding, nesting, breeding, spawning, or use as a nursery
area) for species located in traditional navigable waters, interstate
waters, or the territorial seas.
    The agencies' definition of significant nexus is based upon the
language in SWANCC and Rapanos. The definition is also consistent with
current practice, where field staff evaluate the functions of the
waters in question and the effects of these functions on downstream
waters. In order to add clarity and transparency to the definition of
significant nexus, the agencies have listed in the definition the
functions that will be considered in a significant nexus analysis.
These functions are consistent with the agencies' scientific
understanding of the functioning of aquatic ecosystems. A water does
not need to perform all of the functions listed in paragraph (c)(5) in
order to have a significant nexus. Depending upon the particular water
and the functions it provides, if a water, either alone or in
combination with similarly situated waters, performs just one function,
and that function has a significant impact on the integrity of a
traditional navigable water, interstate water, or the territorial seas,
that water would have a significant nexus.
    Case-specific determinations of significant nexus require paragraph
(a)(7) or (a)(8) waters to be evaluated either alone, or in combination
with other similarly situated waters in the region. In the rule, the
agencies interpret the phrase ``in the region'' to mean the watershed
that drains to the nearest traditional navigable water, interstate
water, or the territorial seas through a single point of entry. See
Section III. In circumstances where the single point of entry watershed
includes waters that are identified under paragraph (a)(7) and waters
that are subject to analysis under paragraph (a)(8), those waters will
be analyzed separately under the provisions of those paragraphs.
    In a case-specific analysis of significant nexus, the agencies
determine whether the water they are evaluating, in combination with
other similarly situated waters in the region, has a significant effect
on the chemical, physical, or biological integrity of the nearest
traditional navigable water, interstate water, or the territorial seas.
As noted previously, the agencies evaluate the listed functions in
paragraph (c)(5) as part of that evaluation to determine if the water
has an impact that is more than speculative or insubstantial.
b. Conducting Case-Specific Significant Nexus Determinations Under
Paragraphs (a)(7) and (a)(8)
    The significant nexus analysis for waters assessed under paragraphs
(a)(7) and (a)(8) is a three-step process: First, the region for the
significant nexus analysis must be identified--under the rule, it is
the watershed which drains to the nearest traditional navigable water,
interstate water or territorial sea; second, any similarly situated
waters must be identified--under the rule, that is waters that function
alike and are sufficiently close to function together in affecting
downstream waters; and third, the waters are evaluated individually or
in combination with any identified similarly situated waters in the
single point of entry watershed to determine if they significantly
impact the chemical, physical or biological integrity of the
traditional navigable water, interstate water or the territorial seas.

i. ``In the Region''--The Point of Entry Watershed
    As discussed in Section III of the preamble and established in the
definition of ``significant nexus,'' the region for purposes of a
significant nexus analysis is the watershed that drains to the nearest
traditional navigable water, interstate water, or the territorial seas.
The first step of the analysis is to identify the point of entry
watershed that the water being evaluated under paragraphs (a)(7) or
(a)(8) drains to. This point of entry approach identifies the nearest
traditional navigable water, interstate water, or the territorial seas
that the water being evaluated and any similarly situated waters flow
to and delineates the watershed of that nearest traditional navigable
water, interstate water, or the territorial seas. The point of entry
watershed is the area drained by the nearest traditional navigable
water, interstate water, or the territorial seas and is typically
defined by the topographic divides between one traditional navigable
water, interstate water, or the territorial seas and another.
    Available mapping tools, such as those that are based on the NHD,
topographic maps, and elevation data, can be used to demarcate
boundaries of the single point of entry watershed. As discussed in
Section III and in the Technical Support Document, the single point of
entry watershed represents the scientifically appropriate sized area
for conducting a case-specific significant nexus evaluation in most
cases.
    In the arid West, the agencies recognize there may be situations
where the single point of entry watershed is very large, and it may be
reasonable to evaluate all similarly situated waters in a smaller
watershed. Under those circumstances, the agencies may demarcate
adjoining catchments surrounding the water to be evaluated that,
together, are generally no smaller than a typical 10-digit hydrologic
unit code (HUC-10) watershed in the same area. The area identified by
this combination of catchments would be the ``region'' used for
conducting a significant nexus evaluation under paragraphs (a)(7) or
(a)(8) under those situations. The basis for such an approach in very
large single point of entry watersheds in the arid West should be
documented in the jurisdictional determination.
ii. ``Similarly Situated''
    Second, the agencies determine if the water or waters to be
evaluated are similarly situated. The waters identified in paragraph
(a)(7) are similarly situated by rule and shall be combined with other
waters of the same category located in the same watershed that drains
to the nearest traditional navigable water, interstate water, or the
territorial seas with no need for a case-specific similarly situated
finding. Under paragraph (a)(7), only waters of the same subparagraph
in the point of entry watershed can be considered as similarly
situated. For example, only pocosins may be evaluated with other
pocosins in the same point of entry watershed. Pocosins in different
point of entry watersheds cannot be combined, and pocosins cannot be
combined with Carolina bays under paragraph (a)(7), even where they
occur in the same point of entry watershed.
    Unlike waters evaluated under paragraph (a)(7), the waters
specified at paragraph (a)(8) require a determination whether they are
similarly situated. Under this step, the agencies apply factors in the
determination of when waters evaluated under paragraph (a)(8) should be
considered either individually or in combination for purposes of a
significant nexus analysis. A determination of ``similarly situated''
requires an evaluation of whether a group of waters in the region that
meet the distance thresholds set out under paragraph (a)(8) can
reasonably be expected to function together in their effect on the
chemical, physical, or biological integrity of downstream traditional
navigable waters, interstate waters, or the territorial seas.
    Similarly situated waters can be identified as sufficiently close
together for purposes of this paragraph of the regulation when they are
within a contiguous area of land with relatively homogeneous soils,
vegetation, and landform (e.g., plain, mountain, valley, etc.). In
general, it would be inappropriate, for example, to consider waters as
``similarly situated'' under paragraph (a)(8) if these waters are
located in different landforms, have different elevation profiles, or
have different soil and vegetation characteristics, unless the waters
perform similar functions and are located sufficiently close to a
``water of the United States'' to allow them to consistently and
collectively function together to affect a traditional navigable water,
interstate water, or the territorial seas. In determining whether
waters under paragraph (a)(8) are sufficiently close to each other the
agencies will also consider hydrologic connectivity to each other or a
jurisdictional water.
    In determining whether groups of waters under paragraph (a)(8)
perform ``similar functions'' the agencies will consider functions such
as habitat, water storage, sediment retention, and pollution
sequestration. In addition, consideration of wetland/water type and
landscape location are relevant for determining if the waters are
similarly situated. For example, Texas coastal sand sheet wetlands that
form a complex of wetlands with other wetlands of the same type on the
landscape and are densely located may very well be similarly situated
and considered in combination with other Texas coastal sand sheet
wetlands in the same single point of entry watershed. However, under
paragraph (a)(8), waters do not need to be of the same type (as they do
in paragraph (a)(7)) to be considered similarly situated. As described
above, waters are similarly situated under paragraph (a)(8) where they
perform similar functions or are located sufficiently close to each
other, regardless of type. The agencies will consider the hydrologic,
geomorphic, and ecological characteristics and circumstances of the
waters under consideration. Examples include: Documentation of
chemical, physical, or biological interactions of the similarly
situated waters; aerial photography; USGS and state and local
topographical or terrain maps and information; NRCS soil survey maps
and data; other available geographic information systems (GIS) data;
National Wetlands Inventory maps where wetlands meet the CWA
definition; and state and local information. The evaluation will use
any available site information and pertinent field observations where
available, relevant scientific studies or data, or other relevant
jurisdictional determinations that have been completed in the region.
    Only those waters that do not meet the requirements in paragraph
(a)(1) through (a)(6) are to be considered in case-specific significant
nexus determinations; subcategory waters that meet the provisions in
paragraph (a)(1) through (a)(6) are per se jurisdictional without the
need for a significant nexus determination. For example, waters that
are identified under paragraph (a)(6) are adjacent and are not subject
to a case-specific significant nexus evaluation under paragraph (a)(7)
or (a)(8). Waters evaluated under paragraph (a)(7) cannot be combined
with waters identified in paragraph paragraph (a)(6) or (a)(8), and
waters evaluated under paragraph (a)(8) cannot be combined with waters
identified in paragraph (a)(6) or (a)(7). For example, Prairie potholes
being evaluated under paragraph (a)(7) may not be combined with Prairie
potholes that are per se jurisdictional under paragraph (a)(6) that
meet the definition

of adjacent. When a water meets the specifications at both paragraphs
(a)(7) and (a)(8), it can only be evaluated under paragraph (a)(7).
That is, for example, if a wetland is a Western vernal pool and is also
within 4,000 feet of the ordinary high water mark of a covered
tributary, it can only be assessed for significant nexus under
paragraph (a)(7) in combination with other Western vernal pools in the
point of entry watershed. Unlike paragraph (a)(8), there is no distance
threshold for waters evaluated under paragraph (a)(7)--that is, waters
in the paragraph (a)(7) subcategories that are more than 4,000 feet
from the high tide line or the ordinary high water mark of a
traditional navigable water, interstate water, the territorial seas,
impoundment, or covered tributary or are beyond the 100-year floodplain
of an traditional navigable water, interstate water, or the territorial
seas are to be included in combination in a significant nexus analysis.
iii. Significant Nexus Analysis for Paragraph (a)(7) and (a)(8) Waters
    Third, the agencies evaluate waters individually or in combination
with any identified similarly situated waters in the single point of
entry watershed to determine if they significantly impact the chemical,
physical, or biological integrity of the traditional navigable water,
interstate water, or the territorial seas. For purposes of determining
significant nexus under paragraph (a)(7), all waters of the specified
subcategory are to be considered in combination in the point of entry
watershed, as those waters are similarly situated. For purposes of
determining significant nexus under paragraph (a)(8), depending on the
results of step two, a water within the boundaries in paragraph (a)(8)
is evaluated either alone or in combination with other similarly
situated waters in the region. For example, in the case where the
agencies have determined that a particular water under paragraph (a)(8)
is not similarly situated, it is evaluated individually for significant
nexus; the water cannot be aggregated if it is not similarly situated
with other such waters.
    The analysis will include an evaluation of the functions listed in
paragraph (c)(5) of the rule, which defines significant nexus. A water
has a significant nexus when any single function or combination of
functions performed by the water, alone or together with similarly
situated waters in the region, contributes significantly to the
chemical, physical, or biological integrity of the nearest traditional
navigable water, interstate water, or the territorial seas. A water may
be determined to have a significant nexus based on performing any of
the following functions: sediment trapping, nutrient recycling,
pollutant trapping, transformation, filtering, and transport, retention
and attenuation of floodwaters, runoff storage, contribution of flow,
export of organic matter, export of food resources, or provision of
life cycle dependent aquatic habitat (such as foraging, feeding,
nesting, breeding, spawning, or use as a nursery area) for species
located in a traditional navigable water, interstate water, or the
territorial seas.
    For purposes of paragraph (c)(5)(ix), a species is located in a
traditional navigable water, interstate water, or the territorial seas
if such a water is a typical type of habitat for at least part of the
life cycle of the species. For example, amphibians and many reptiles
can use a traditional navigable water, interstate water, or the
territorial seas for part of their life cycle needs.
    When evaluating a water individually or in combination with other
similarly situated waters for the presence of a significant nexus to a
traditional navigable water, interstate water, or the territorial seas,
a variety of factors will influence the chemical, physical, or
biological connections the water has with the downstream traditional
navigable water, interstate water, or the territorial seas, including
distance from a jurisdictional water, the presence of surface or
shallow subsurface hydrologic connections, and density of waters of the
same type (if it has been concluded that such waters can be evaluated
in combination). The likelihood of a significant connection is greater
with increasing size and decreasing distance from the identified
traditional navigable water, interstate water, or the territorial seas,
as well as with increased density of the waters for such waters that
can be considered in combination as similarly situated waters. In
addition, the presence of a surface or shallow subsurface hydrologic
connection can influence the impact that a water has with downstream
waters.
    In many cases, the presence of a hydrologic connection increases
the strength of the impact of the downstream traditional navigable
water, interstate water, or the territorial seas. However, a hydrologic
connection is not necessary to establish a significant nexus, because,
as Justice Kennedy stated, in some cases the lack of a hydrologic
connection would be a sign of the water's function in relationship to
the traditional navigable water, interstate water, or the territorial
seas. These functional relationships include retention of floodwaters
or pollutants that would otherwise flow downstream to the traditional
navigable water, interstate water, or the territorial seas. See 547
U.S. at 775 (citations omitted) (J. Kennedy) (``it may be the absence
of an interchange of waters prior to the dredge and fill activity that
makes protection of the wetlands critical to the statutory scheme'').
The Science Report concludes, ``[s]ome effects of non-floodplain
wetlands on downstream waters are due to their isolation, rather than
their connectivity. Wetland `sink' functions that trap materials and
prevent their export to downstream waters (e.g., sediment and entrained
pollutant removal, water storage) result because of the wetland's
ability to isolate material fluxes.'' Science Report at ES-4. For
example, a report that reviewed the results of multiple scientific
studies concluded that depressional wetlands lacking a surface outlet
functioned together to significantly reduce or attenuate flooding. See
Science Report and Technical Support Document. Even when they lack a
surface hydrologic connection to downstream traditional navigable
waters, interstate waters, or the territorial seas, Prairie potholes,
for instance, cumulatively can store large volumes of water, impacting
streamflow and reducing flooding downstream, and several studies have
quantified the large storage capacity of Prairie pothole complexes.
This water storage function is estimated to hold tens of millions of
cubic meters of water, including for example Prairie potholes located
in the watersheds of Devils Lake and the Red River of the North, which
have both had a long history of flooding. Where Prairie potholes lack a
surface hydrologic connection, this water storage capacity is
particularly effective in reducing downstream flooding and can have a
significant effect on downstream traditional navigable waters,
interstate waters, or the territorial seas. Thus, even when lacking a
surface hydrologic connection, a water can still have a significant
effect on the chemical or the biological integrity of downstream
traditional navigable waters, interstate waters, or the territorial
seas.
    The rule recognizes that not all waters have the requisite
connection to traditional navigable waters, interstate waters, or the
territorial seas sufficient to be determined jurisdictional. Waters
with a significant nexus must significantly affect the chemical,
physical, or biological integrity of a downstream traditional navigable
water,

interstate water, or the territorial seas, and the requisite nexus must
be more than ``speculative or insubstantial.'' Rapanos at 780.
    Evidence of chemical connectivity and the effect on waters can be
found by identifying the properties of the water in comparison to the
identified traditional navigable water, interstate water, or the
territorial seas; signs of retention, release, or transformation of
nutrients or pollutants; and the effect of landscape position on the
strength of the connection to the nearest ``water of the United
States,'' and through it to a traditional navigable water, interstate
water, or the territorial seas. In addition, relevant factors
influencing chemical connectivity include hydrologic connectivity (see
physical factors, below), surrounding land use and land cover, the
landscape setting, and deposition of chemical constituents (e.g.,
acidic deposition).
    Evidence of physical connectivity and the effect on traditional
navigable waters, interstate waters, or the territorial seas can be
found by identifying evidence of physical connections, such as flood
water or sediment retention (flood prevention). Presence of indicators
of hydrologic connections between the other water and jurisdictional
water are also indicators of a physical connection. Factors influencing
physical connectivity include rain intensity, duration of rain events
or wet season, soil permeability, and distance of hydrologic connection
between the paragraph (a)(7) or (a)(8) water and the traditional
navigable water, interstate water, or the territorial seas, depth from
surface to water table, and any preferential flowpaths.
    Evidence of biological connectivity and the effect on waters can be
found by identifying: Resident aquatic or semi-aquatic species present
in the case-specific water and the tributary system (e.g., amphibians,
aquatic and semi-aquatic reptiles, aquatic birds); whether those
species show life-cycle dependency on the identified aquatic resources
(foraging, feeding, nesting, breeding, spawning, use as a nursery area,
etc.); and whether there is reason to expect presence or dispersal
around the case-specific water, and if so whether such dispersal
extends to the tributary system or beyond or from the tributary system
to the case-specific water. Factors influencing biological connectivity
include species' life history traits, species' behavioral traits,
dispersal range, population size, timing of dispersal, distance between
the case-specific water and a traditional navigable water, interstate
water, or the territorial seas, the presence of habitat corridors or
barriers, and the number, area, and spatial distribution of habitats.
Non-aquatic species or species such as non-resident migratory birds do
not demonstrate a life cycle dependency on the identified aquatic
resources and are not evidence of biological connectivity for purposes
of this rule.
    For practical administrative purposes, the rule does not require
evaluation of all similarly situated waters under paragraph (a)(7) or
(a)(8) when concluding that those waters have a significant nexus to a
traditional navigable water, interstate water, or territorial sea. When
a subset of similarly situated waters provides a sufficient science-
based justification to conclude presence of a significant nexus, for
efficiency purposes a significant nexus analysis need not unnecessarily
require time and resources to locate and analyze all similarly situated
waters in the entire point of entry watershed. For example, if a single
Carolina bay or a group of Carolina bays in a portion of the point of
entry watershed is determined to significantly affect the chemical,
physical, or biological integrity of a traditional navigable water,
interstate water, or the territorial seas, the analysis does not have
to document all of the similarly situated Carolina bays in the
watershed in order to conduct the significant nexus analysis. A
conclusion that significant nexus is lacking may not be based on
consideration of a subset of similarly situated waters because under
the significant nexus standard the inquiry is how the similarly
situated waters in combination affect the integrity of the downstream
water.
    While the rule is clear that waters that are jurisdictional by rule
cannot be combined with waters subject to a case-specific significant
nexus analysis, the analysis may appropriately include the evaluation
of functions of paragraph (a)(8) waters that reach covered waters
through paragraph (a)(6) waters without consideration of the functions
contributed by those paragraph (a)(6) waters. The hydrologic
connections between paragraph (a)(8) waters and a covered tributary and
eventually to a traditional navigable water, interstate water, or the
territorial seas, can often occur through an adjacent water. This
hydrologic connection is an appropriate part of the case-specific
analysis as to whether the paragraph (a)(8) waters, alone or in
combination with any similarly situated paragraph (a)(8) waters in the
point of entry watershed, provide those functions downstream such that
they significantly affect the chemical, physical or biological
integrity of the traditional navigable water, interstate water, or the
territorial seas. For example, when evaluating a wetland that is 2,500
feet from the ordinary high water mark of an paragraph (a)(5) water and
that has surface or shallow subsurface connections to downstream
traditional navigable waters, interstate waters, or the territorial
seas via a wetland that is adjacent to an paragraph (a)(4) water, the
existence of those connections is not ignored. However, while a water's
connections to the traditional navigable water, interstate water, or
the territorial seas through paragraph (a)(5) through (a)(7) waters can
be considered in the significant nexus analysis in order to determine
whether the functions of the paragraph (a)(8) waters are provided
downstream, only the functions of the water, along with any similarly
situated waters, being evaluated under paragraph (a)(8) on downstream
water integrity can be included in the significant nexus analysis.
    The administrative record for a jurisdictional determination for a
water under paragraph (a)(7) or (a)(8) will include available
information supporting the determination. In addition to location and
other descriptive information regarding the water at issue, the record
will include an explanation of the rationale for the jurisdictional
conclusion and a description of the information used. Relevant
information can come from many sources, and need not always be specific
to the water whose jurisdictional status is being evaluated. Studies of
the same type of water or similarly situated waters can help to inform
a significant nexus analysis as long as they are applicable to the
water being evaluated. In the case of paragraph (a)(8) waters, the
administrative record will include the rationale behind the similarly
situated analysis, including an explanation of the data or information
examined.
    The agencies expect that where waters are determined to be
similarly situated in a single point of entry watershed, such similarly
situated waters will often be found jurisdictional through the case-
specific analysis of significant nexus. However, case-specific factors
such as distance to the traditional navigable water, interstate water,
or the territorial seas; density or number of similarly situated
waters; individual and cumulative size of the similarly situated
waters; soil permeability; climate; etc., may be considered in the
determination, and there could be cases where even considering these
waters in combination with similarly situated waters will not

be sufficient for waters to have a significant nexus.
    Within a single point of entry watershed, over a period of time
there will likely be multiple jurisdictional determinations. For
paragraph (a)(7) waters, if a case-specific significant nexus
determination has been made in the point of entry watershed, all waters
in the subcategory in the point of entry watershed are jurisdictional.
For paragraph (a)(8) waters, the case-specific significant nexus
analyses must use information used in previous jurisdictional
determinations, and if a significant nexus has been established for one
water in the watershed, then other similarly situated waters in the
watershed would also be found to have a significant nexus. This is
because under Justice Kennedy's test, similarly situated waters in the
region should be evaluated together. A positive significant nexus
determination would then apply to all similarly situated waters within
the point of the watershed. A negative case-specific significant nexus
evaluation under paragraph (a)(7) or (a)(8) of all similarly situated
waters in the point of entry watershed applies to all similarly
situated waters in that watershed. However, as noted above, a
conclusion that significant nexus is lacking may not be based on
consideration of a subset of similarly situated waters, because under
the significant nexus standard the inquiry is how the similarly
situated waters in combination affect the integrity of the downstream
water. The documentation for each case should be complete enough to
support the specific jurisdictional determination, including an
explanation of which waters were considered together as similarly
situated and in the same region.
4. Summary of Revisions to Case-Specific Determinations of ``Waters of
the United States'' and Major Comments
a. Significant Nexus
    Some commenters stated concerns over the potential for inconsistent
application of the significant nexus analysis in a jurisdictional
determination. To address this concern within the regulatory framework,
the agencies provide more detail regarding the definition of
significant nexus in the rule and list the specific functions that will
be considered in the analysis. This approach provides individual
regulators who conduct the analysis clear and consistent parameters
that they will consider during their review in making jurisdictional
determinations and provides transparency to the regulated public over
which factors will be considered.
    Overall, there was support for the concept of the single point of
entry watershed as the interpretation of ``in the region.'' Several
commenters supported the approach that the single point of entry
watershed was an appropriate scale to use to measure effect on
traditional navigable waters, interstate waters, or the territorial
seas. Other commenters felt the single point of entry watershed was too
small to capture all the benefits that waters that do not meet the
definition of adjacency contribute. Some of the SAB panel members
thought that because surface and ground-watershed units may not align,
watersheds might be problematic for defining ``in the region.'' These
panel members suggested that a more scientifically justified approach
would include surface and subsurface waters in a watershed delineation.
The agencies have retained the single point of entry watershed from the
proposed rule as the appropriate unit of analysis for significant nexus
in the final rule as these watersheds are more easily understood and
easier to delineate than those that map subsurface waters as the SAB
suggested.
    With respect to the agencies' approach to ``similarly situated
waters,'' commenters offered support for assessing waters in
combination based on their type and function, particularly waters such
as Prairie potholes. Conversely, several commenters found that the
ability to aggregate waters that do not meet the definition of
adjacency is over-reaching and causes uncertainty to the regulated
public. Some commenters also attributed uncertainty in which waters
were regulated to subjectivity in review by Federal regulator(s).
Similarly, some commenters were concerned that waters eligible for
protection were based on an individual analyst's interpretation and
wanted to know how the agencies would address consistency and potential
bias. In response, the rule lists in paragraph (a)(7) a limited number
of subcategories of waters where waters of the specified types have
been determined by rule to be similarly situated for a significant
nexus analysis. This will add consistency, predictability, and clarity,
as the rule explicitly states that such waters are similarly situated
for purposes of the significant nexus analysis. For waters identified
under paragraph (a)(8), the agencies have established two limitations:
Waters within the 100-year floodplain of a traditional navigable water,
interstate water, or the territorial seas, and waters within 4,000 foot
feet of a traditional navigable water, interstate water, the
territorial seas, impoundment, or covered tributary. The agencies also
have established within the definition of significant nexus at
paragraph (c)(5) criteria for determining whether waters are similarly
situated and should therefore be analyzed in combination. Waters
identified under paragraph (a)(8) are similarly situated when they
function alike and are sufficiently close to function together in
affecting downstream waters. The agencies have not determined that such
waters are categorically similarly situated, so the agencies will base
their case-specific determinations of whether a particular water has
any similarly situated waters on the available information and science.
The rule also clarifies that paragraph (a)(8) waters cannot be
considered similarly situated with ``adjacent waters,'' which are
jurisdictional by rule, and paragraph (a)(7) waters, which have been
determined to be similarly situated by rule. These parameters will
reduce inconsistency in reviews and add clarity.
    Similarly, several commenters expressed concern that landowners
would not know which water bodies on their property are subject to CWA
jurisdiction due to aggregation, as waters on their property may be
considered similarly situated with waters located off-site. While the
rule does not eliminate the use of case-specific significant nexus
analyses, and the concern arises from Justice Kennedy's phrase
``similarly situated,'' the parameters placed on waters requiring a
case-specific determination and the clearer definition of significant
nexus address the concerns about uncertainty and inconsistencies in
reviews. In particular, waters that are not either one of the five
identified subcategories in paragraph (a)(7) or within the thresholds
in paragraph (a)(8) cannot be subject to a case-specific significant
nexus analysis under the rule. Generally, jurisdictional determinations
are conducted at the request of an applicant or landowner for specific
waters. While the agencies cannot arbitrarily depart from a
determination that waters are ``similarly situated,'' landowners may
provide new information to inform subsequent jurisdictional
determinations. In addition, owners with questions regarding
jurisdiction of waters on their property may always consult their local
Corps District or EPA Regional Office, which is not a change from
longstanding practice.

b. Case-Specific Determinations
    The rule provides more regulatory certainty by narrowing the scope
of waters that can be assessed under a case-specific significant nexus
evaluation as compared to the proposal. These changes still allow the
scientific value of specific waters not covered in paragraph (a)(1)
through (a)(6) to be evaluated on a case-specific basis.
    In the proposal, the agencies solicited comment regarding a variety
of approaches to the category of waters subject to a case-specific
significant nexus analysis. In addition, the agencies solicited comment
on additional scientific research and data that might further inform
decisions about these waters. In particular the agencies solicited
information about whether current scientific research and data
regarding particular types of waters are sufficient to support the
inclusion of subcategories of types of waters, either alone or in
combination with similarly situated waters, that can appropriately be
identified as always lacking or always having a significant nexus. One
of these alternate approaches in the preamble to the proposed rule was
to determine by rule that certain additional subcategories of waters
would be jurisdictional rather than addressed with a case-specific
basis for determining significant nexus.
    Many commenters expressed support for the agencies' proposed
approach to case-specific waters, included additional references to
support these waters being protected by rule, and supported the
treatment of certain categories of waters as similarly situated (that
is, evaluating them in combination with similarly situated waters for
the purposes of the significant nexus analysis). Some suggested the
agencies establish jurisdiction over case-specific waters by rule and
provided detailed information in support of their position. Other
commenters suggested additional subcategories of waters be considered
as jurisdictional or as similarly situated by rule, such as playa
lakes, kettle lakes, and woodland vernal pools.
    However, there was a concern raised by other commenters about what
was termed regulatory overreach and uncertainty created by the ``other
waters'' category in the proposal. Some commenters stated that the
``other waters'' category in the proposal would allow the agencies to
regulate virtually any water. To address this concern, the rule places
limits on which waters could be subject to a case-specific significant
nexus determination, in recognition that case-specific analysis of
significant nexus is resource-intensive and based on the body of
science that exists. As noted above, the agencies also establish by
rule subcategories of waters that are ``similarly situated'' for the
purposes of a significant nexus analysis because science supports that
the subcategory waters fall within a higher gradient of connectivity.
By not determining that any one of the waters available for case-
specific analysis is jurisdictional by rule, the agencies are
recognizing the gradient of connectivity that exists and will assert
jurisdiction only when that connection and the downstream effects are
significant and more than speculative and insubstantial.
    Waters are covered under the rule only where they are identified as
jurisdictional in paragraphs (a)(1) through (a)(6), where they are not
excluded under paragraph (b), or where they are within the limited
number of subcategories listed in paragraphs (a)(7) and (a)(8) and have
a case-specific significant nexus to a traditional navigable water,
interstate water, or the territorial seas. These limits on jurisdiction
reflect the case law and are in response to comments requesting greater
regulatory certainty. Although some commenters suggested additional
subcategories of waters for consideration, such as playa lakes and
kettle lakes, the agencies at this time are not able to determine that
the available science supports that the suggested additional
subcategories of waters as a class have a significant nexus to
traditional navigable waters, interstate waters, or the territorial
seas. However, to be clear, under the rule, individual waters of the
suggested additional subcategories are jurisdictional where they meet
the requirements of paragraphs (a)(1) through (a)(6) or (a)(8) (e.g., a
playa lake that is an interstate water, a kettle lake that is an
adjacent water, or a woodland vernal pool that is less than 4,000 feet
from a jurisdictional tributary and is determined on a case-specific
basis to have a significant nexus to a traditional navigable water,
interstate water, or the territorial seas).
    In consideration of the variety of views of the commenters, the
Science Report, the input from the SAB, and the developing state of the
science, the agencies reasonably decided not to establish jurisdiction
over all waters that do not meet the requirements of paragraph (a)(1)
through (a)(6) by rule. Instead, the agencies established case-specific
provisions for some specified waters at paragraph (a)(7) and waters
within the boundaries at paragraph (a)(8). This approach strikes a
balance between requests for clear boundaries and limited case-specific
reviews with scientific support.

I. Waters and Features That Are Not ``Waters of the United States''

    In the rule, the agencies identify a variety of waters and features
that are not ``waters of the United States.'' Prior converted cropland
and waste treatment systems have been excluded from this definition
since 1992 and 1979, respectively, and they remain substantively and
operationally unchanged. Only ministerial changes to delete an outdated
cross reference are made to the exclusion for waste treatment systems.
The agencies add exclusions for all waters and features identified as
generally exempt in preamble language from Federal Register documents
by the Corps on November 13, 1986, and by EPA on June 6, 1988. This is
the first time these exclusions have been established by rule. In
addition, under prior preamble language, the agencies retained the
authority to determine that a particular feature generally considered
non-jurisdictional was in fact a ``water of the United States.'' The
agencies do not retain that authority for features excluded under the
rule. The agencies for the first time also establish by rule that
certain ditches are excluded from jurisdiction. The agencies add
exclusions for groundwater and erosional features, as well as
exclusions for some waters that were identified in public comments as
possibly being found jurisdictional under proposed rule language where
this was never the agencies' intent. These exclusions are reflective of
current agencies' practice, and their inclusion in the rule furthers
the agencies' goal of providing greater clarity over what waters are
and are not protected under the CWA. Importantly, under the rule all
waters and features identified in paragraph (b) as excluded will not be
``waters of the United States,'' even if they otherwise fall within one
of the categories in paragraphs (a)(4) through (a)(8). For example, a
ditch that is excluded under paragraph (b)(3)(i) or (b)(3)(ii) is not
jurisdictional even when the ditch connects directly or through another
water to a traditional navigable water, interstate water, or the
territorial seas. The proposed rule referenced paragraphs (a)(1)
through (a)(8), but the agencies did not intend to exclude any
traditional navigable waters, for example, and the revision clarifies
that. Finally, nothing in the rule is intended to change the way in
which the Corps applies individual or nationwide permits.
    The exclusions reflect the agencies' long-standing practice and
technical judgment that certain waters and

features are not subject to the CWA. The exclusions are also guided by
Supreme Court cases. The significant nexus standard arises from the
case law and is used to interpret the terms of the CWA. Thus, a
significant nexus determination is not a purely scientific inquiry, but
rather is a determination by the agencies in light of the statutory
language, the statute's goals, objectives and policies, the case law,
the relevant science, and the agencies' technical expertise and
experience. The plurality opinion in Rapanos also noted that there were
certain features that were not primarily the focus of the CWA. See 547
U.S. at 734. In this section of the proposed rule, the agencies are
drawing lines and concluding that certain waters and features are not
subject to the jurisdiction of the Clean Water Act. The Supreme Court
has recognized that clarifying the lines of jurisdiction is a difficult
task: ``Our common experience tells us that this is often no easy task:
The transition from water to solid ground is not necessarily or even
typically an abrupt one. Rather, between open waters and dry land may
lie shallows, marshes, mudflats, swamps, bogs--in short, a huge array
of areas that are not wholly aquatic but nevertheless fall far short of
being dry land. Where on this continuum to find the limit of `waters'
is far from obvious.'' Riverside Bayview at 132-33. The exclusions are
an important aspect of the agencies' policy goal of providing clarity
and certainty. Just as the categorical assertions of jurisdiction over
covered tributaries and covered adjacent waters simplify the
jurisdiction issue, the categorical exclusions will likewise simplify
the process, and they reflect the agencies' determinations of the lines
of jurisdiction based on science, the case law and the agencies'
experience and expertise.
    The existing exclusion for waste treatment systems moves to
paragraph (b)(1) with no substantive changes. One ministerial change is
the deletion of a cross-reference in the current language to an EPA
regulation that no longer exists. Because the agencies are not
addressing the substance of the exclusion, the agencies do not make
conforming changes to ensure that each of the existing definitions of
the ``waters of the United States'' for the various CWA programs have
the exact same language with respect to the waste treatment system
exclusion, with the exception of deleting the cross-reference.
    Many commenters expressed concern about whether the agencies'
insertion of a comma following this ministerial change unintentionally
narrowed the exclusion such that all excluded waste treatment systems
must be designed to meet the requirements of the Clean Water Act. The
commenters indicated concerns that waste treatment systems built before
the Clean Water Act or primarily for purposes of other environmental
laws could not be exempt. The agencies do not intend to change how the
waste treatment exclusion is implemented and have deleted this proposed
comma. Continuing current practice, any waste treatment system built in
a ``water of the United States'' would need a section 404 permit to be
constructed and a section 402 permit for discharges from the waste
treatment system into ``waters of United States.''
    A number of commenters suggested the agencies clarify how the waste
treatment system exclusion is currently implemented. Many comments
raised questions about stormwater systems and wastewater reuse and
whether such facilities qualified under the waste treatment system
exclusion as part of a complete waste treatment system. For clarity,
the agencies have identified related exclusions in paragraphs (b)(6)
and (b)(7). Many commenters also suggested making substantive changes
to the existing exclusion for waste treatment systems. Because the
agencies are not making any substantive changes to the waste treatment
system exclusion and these comments are outside the scope of the
proposed rule, the final rule does not reflect changes suggested in
public comments.
    The existing exclusion for prior converted cropland moves to
paragraph (b)(2) of the rule and is unchanged. A number of commenters
suggested changes to the existing exclusion for prior converted
cropland. As with waste treatment systems, the preamble to the proposed
rule stated this rulemaking was not making changes to the exclusion for
prior converted cropland. As a result, comments requesting changes to
the prior converted cropland exclusion or seeking clarification of how
the exclusion is implemented in the field are outside the scope of this
rulemaking, and the rule does not reflect changes or respond to issues
raised in public comments. The agencies will continue to implement this
exclusion consistent with current policy and practice.
    The agencies identify excluded ditches in paragraph (b)(3).
Jurisdictional ditches are discussed at more detail in section IV.F.
The rule excludes all ditches with ephemeral flow that are not
excavated in or relocate a tributary. The rule also excludes ditches
with intermittent flow that are not a relocated tributary, excavated in
a tributary, or drain wetlands, regardless of whether or not the
wetland is a jurisdictional water. Finally, ditches that do not connect
to a traditional navigable water, interstate water, or territorial sea
either directly or through another water are excluded, regardless of
whether the flow is ephemeral, intermittent, or perennial. These ditch
exclusions are clearer for the regulated public to identify and more
straightforward for agency staff to implement than the proposed rule or
current policies. The ditch exclusions do not affect the possible
status of a ditch as a point source.
    Many comments addressed ditches, and many of these comments are
reflected in the approach to ditches articulated in the rule. The
majority of commenters requested that the agencies' ditch exclusion be
clarified or broadened. Many commenters were confused by the term
``uplands'' and did not feel the term had a common understanding. For
example, some commenters felt the term referred only to areas at higher
elevations in the landscape. Many expressed concerns that all ditches
would be jurisdictional under the proposed rule. Many groups especially
called for exclusions of roadside ditches.
    The revised exclusions reflect the agencies' careful consideration
of these comments. First, the agencies have eliminated the term
``uplands'' in response to the questions the term created. Second, the
agencies have instead provided a clearer statement of the types of
ditches that are subject to exclusion--ditches that are not excavated
in or relocate a tributary and ditches that do not drain a wetland.
Eliminating the term ``uplands'' with this more straightforward
description should improve clarity. Finally, the agencies have more
clearly stated the flow regimes in ditches that are subject to the
exclusions; these flow regimes are described earlier and have been used
by the agencies consistently and are readily understood by field staff
and the public.
    As noted, the agencies received many comments asking that roadside
ditches be addressed, and more specifically excluded, in the final
rule. Like the proposed rule, the final rule does not include an
explicit exclusion for roadside ditches, but the agencies believe the
exclusions included in the final rule will address the vast majority of
roadside and other transportation ditches. Moreover, since the agencies
have focused in the final rule on the physical characteristics of
excluded ditches, the exclusions will address all ditches that the
agencies have

concluded should not be subject to jurisdiction, including certain
ditches on agricultural lands and ditches associated with modes of
transportation, such as roadways, airports, and rail lines.
    As discussed in Section IV.F.1., the definition of tributary
includes natural, undisturbed waters and those that have been man-
altered or constructed, but which science shows function as a
tributary. In addition, natural streams and rivers that are altered or
modified for purposes as flood control, erosion control, and other
reasons does not convert the tributary to a ditch. A stream or river
that has been channelized or straightened because its natural sinuosity
has been altered, cutting off the meanders, is not a ditch. A stream
that has banks stabilized through use of concrete or rip-rap (e.g.,
rocks or stones) is not a ditch. The Los Angeles River, for example, is
a ``water of the United States'' (and, indeed, a traditional navigable
water) and remains a ``water of the United States'' and is not a
excluded under paragraph (b)(3), even where it has been ditched,
channelized, or concreted.
    The rule excludes ditches with ephemeral flow except where a ditch
is excavated in or relocates a covered tributary. Under the rule, that
portion of a ditch with ephemeral flow actually excavated in or
relocating the covered tributary would be considered jurisdictional.
The jurisdictional status of upstream and downstream portions of the
same ditch would have to be assessed based on the specific facts and
under the terms of the rule to determine flow characteristics and
whether or not the ditch is excavated in or relocates a tributary. This
approach reasonably balances the exclusion with the need to ensure that
covered tributaries, and the significant functions they provide, are
preserved. A ditch that relocates a stream is not an excluded ditch
under paragraph (b)(3), and a stream is relocated either when at least
a portion of its original channel has been physically moved, or when
the majority of its flow has been redirected. A ditch that is a
relocated stream is distinguishable from a ditch that withdraws water
from a stream without changing the stream's aquatic character. The
latter type of ditch is excluded from jurisdiction where it meets the
listed characteristics of excluded ditches under paragraph (b)(3). The
agencies will determine historical presence of tributaries using a
variety of resources, such as USGS and state and local maps, historic
aerial photographs, local surface water management plans, street
maintenance data, wetlands and conservation programs and plans, as well
as functional assessments and monitoring efforts.
    The rule also excludes ditches with intermittent flow except where
a ditch is excavated in or relocates a covered tributary, or drains
wetlands. Where an excluded ditch drains a wetland, the segment of the
ditch that physically intersects the wetland would be considered
jurisdictional. The jurisdictional status of upstream and downstream
portions of the same ditch would have to be assessed based on the
specific facts and under the terms of the rule to determine flow
characteristics and whether or not the ditch drains a wetland. The
provision of paragraph (b)(3) addressing draining of wetlands is
specific to ditches with intermittent flow. As discussed previously,
features that are ephemeral will flow only in response to precipitation
events, such as rainfall or snowmelt. Ditches with ephemeral flow,
therefore, do not typically have the flow characteristics
characteristic of ditches that drain wetlands. The agencies have
accordingly focused on intermittent ditches that drain wetlands.
    In addition, the agencies clarify that a ditch drains a wetland
when it physically intersects the wetland. If the ditch has been cut to
carry only ephemeral flows, such as those following a storm event, the
effect of the ditch is minimal as it carries only that flow that
overtops the wetland during and immediately following the rain event.
However, if the ditch has been cut to carry intermittent or perennial
flows from the wetland, the ditch is serving as a conduit for
transferring flow from the wetland to a downstream tributary. As a
result of the cut ditch, the wetland's hydrologic regime is modified
and can generally affect the natural functions performed by the
wetland. When the ditch has been cut to carry intermittent or perennial
flow from the wetland to the downstream tributary, the wetland soils
and vegetation can shift into a community that supports less hydric
soils and a mix of riparian or upland vegetation. Consequently, the
ditch is draining the wetland and the wetland quality degrades and may
cease to exist over time. Therefore, a ditch that carries intermittent
flow and physically intersects with a wetland is not excluded under
this provision.
    A number of commenters expressed concern that a ditch could be
viewed as both a point source and a ``water of the United States.''
However, the approach that ditches can be considered both reflects the
CWA itself as well as longstanding agency policy.
    Paragraph (b)(4) of the rule identifies features and waters that
the agencies have identified as generally not ``waters of the United
States'' in previous preambles or guidance documents. Codifying these
longstanding practices supports the agencies' goals of providing
greater clarity, certainty, and predictability for the regulated public
and the regulators. The agencies' 1986 and 1988 preambles indicated
that these waters could be determined on a case-specific basis to be
``waters of the United States.'' This rule does not allow for this
case-specific analysis to be used to establish jurisdiction--these
waters are categorically excluded from jurisdiction. Some of the
exclusions have been modified slightly to address public comments and
improve clarity. The following features are not ``waters of the United
States'':
     Artificially irrigated areas that would revert to dry land
should application of irrigation water to that area cease
     Artificial, constructed lakes or ponds created by
excavating and/or diking dry land such as farm and stock watering
ponds, irrigation ponds, settling basins, log cleaning ponds, cooling
ponds, or fields flooded for rice growing
     Artificial reflecting pools or swimming pools created by
excavating and/or diking dry land
     Small ornamental waters created by excavating and/or
diking dry land for primarily aesthetic reasons
     Water-filled depressions created in dry land incidental to
mining or construction activity, including pits excavated for obtaining
fill, sand or gravel that fill with water
     Erosional features, including gullies, rills, and other
ephemeral features that do not meet the definition of tributary, non-
wetland swales, and lawfully constructed grassed waterways
     Puddles
    Several of these exclusions use the phrase ``dry land.'' This
phrase appears in the 1986 and 1988 preambles, and the agencies believe
the term is well understood based on the more than 30 years of practice
and implementation. But in keeping with the goal of providing greater
clarity, the agencies state that ``dry land'' refers to areas of the
geographic landscape that are not water features such as streams,
rivers, wetlands, lakes, ponds and the like. However, it is important
to note that a ``water of the United States'' is not considered ``dry
land'' just because it lacks water at a given time. Similarly, an area
remains ``dry land'' even if it is wet after a rainfall event. The
agencies received comments suggesting that the

final rule provide a definition of ``dry land'' as it relates to the
exclusion for stormwater control features. The agencies considered the
request and determined that there was no agreed upon definition given
geographic and regional variability. The agencies concluded that
further clarity on this issue can be provided during implementation.
    In the exclusion for artificial lakes or ponds, the agencies have
removed language regarding ``use'' of the ponds, including the term
``exclusively.'' In most cases, the ``use'' of the pond is captured in
its name. More importantly, the agencies recognize that artificial
lakes and ponds are often used for more than one purpose and can have
other beneficial purposes, such as animal habitat, water retention or
recreation. For example, rice growing is typically facilitated by land
leveling and inundation that floods vast areas. The fields are flooded
for the purpose of weed control and to facilitate rice cultivation, but
these rice fields are often extensively used by waterfowl and other
wildlife. The agencies agree with commenters who raised concern that
rice fields ``used'' both for rice growing and waterfowl habitat should
continue to be excluded even where they are not used ``exclusively''
for a single purpose. The change to the exclusion reflects the
agencies' practice and ensures that waters the agencies have
historically not treated as jurisdictional do not become so because of
another incidental beneficial use.
    The agencies have also added farm ponds, log cleaning ponds, and
cooling ponds to the list of excluded ponds in the rule based on public
comments. The list of ponds has always been illustrative rather than
exhaustive, and the additions respond to requests to clarify that farm
ponds, and log cleaning ponds \12\ created in dry land are excluded.
The agencies have also added cooling ponds created in dry land to the
list of excluded waters. The agencies also note that cooling ponds that
are created under section 404 in jurisdictional waters and that have
NPDES permits are subject to the waste treatment system exclusion,
which is not changing. Cooling ponds created to serve as part of a
cooling water system with a valid state permit constructed in waters of
the United States prior to enactment of the Clean Water Act and
currently excluded from jurisdiction remain excluded under the new
rule. Additional ponds will also likely fall under the exclusion based
on site specific evaluation, including, for example, fire control ponds
and fishing ponds excavated from dry land. Artificial lakes and ponds
created in dry land that do not connect to jurisdictional waters are
covered by this exclusion. Where these ponds do connect and discharge
to jurisdictional waters, the agencies will evaluate factors such as
the potential for introduction of pollutants and coverage under an
issued NPDES permit. As a general matter, ponds created in dry land
that discharge to ``waters of the United States'' are covered by the
exclusion where such discharge is regulated under a NPDES permit.
Conveyances created in dry land that are physically connected to and
are a part of the excluded feature are also excluded. These artificial
features are working together as a system, and it is appropriate to
treat them as one functional unit. The agencies emphasize that ponds
excluded from ``waters of the United States'' can, in some
circumstances, be point sources of pollution subject to section 301 of
the Act.
---------------------------------------------------------------------------

    \12\ Log cleaning ponds are used to float logs for removal of
twigs, branches, and large knots.
---------------------------------------------------------------------------

    The rule includes several refinements to the exclusion for water-
filled depressions created as a result of certain activities. In
addition to construction activity, the agencies have also excluded
water-filled depressions created in dry land incidental to mining
activity. This change is consistent with the agencies' 1986 and 1988
preambles, which generally excluded pits excavated for obtaining fill,
sand or gravel, and there is no need to distinguish between features
based on whether they are created by construction or mining activity.
    The agencies also here clarify their longstanding view that only
the specific land being directly irrigated that would revert to dry
land should irrigation cease is exempt; it is not the case that all
waters within watersheds where irrigation occurs are exempt.
    The rule identifies all erosional features, including gullies and
rills, as non-jurisdictional features. While the proposed rule
specifically identified gullies and rills, the agencies intended that
all erosional features would be excluded. The final rule makes this
clear. Erosional features are not jurisdictional under the terms of
paragraph (a) and the definitions in paragraph (c), especially the
definition of tributary. These features are specifically excluded in
the rule to avoid confusion, because preceding guidance identified them
as non-jurisdictional and many commenters stated these exclusions were
important to maintain in the rule.
    Tributaries can be distinguished from erosional features by the
presence of bed and banks and an ordinary high water mark. Concentrated
surface runoff can occur within erosional features without creating the
permanent physical characteristics associated with bed and banks and
ordinary high water mark. See Technical Support Document. It should be
noted that some ephemeral streams are colloquially called ``gullies''
or the like even when they exhibit a bed and banks and an ordinary high
water mark; regardless of the name they are given locally, waters that
meet the definition of tributary are not excluded erosional features.
    The rule also excludes lawfully constructed grassed waterways.
Grassed waterways are lawfully constructed for purposes of this rule
either where they are on dry land and replace non-jurisdictional
erosional features or, more commonly, where they have been lawfully
converted from an intermittent or ephemeral stream under a CWA permit.
Once converted to grassed waterways, these former streams segments no
longer exhibit a bed and banks or ordinary high water mark and are
excluded because they do not meet the definition of ``tributary.''
However, such conversion does not sever jurisdiction over the entire
length of the tributary above and below the grassed waterway. Instead,
the grassed waterway is considered a constructed break in the bed and
banks and ordinary high water mark. This is reflected in the definition
of tributary, which specifically addresses natural or man-made breaks
in bed and banks and ordinary high water mark.
    The final rule adds an exclusion for puddles. The proposed rule did
not explicitly exclude puddles because the agencies have never
considered puddles to meet the minimum standard for being a ``water of
the United States,'' and it is an inexact term. A puddle is commonly
considered a very small, shallow, and highly transitory pool of water
that forms on pavement or uplands during or immediately after a
rainstorm or similar precipitation event. However, numerous commenters
asked that the agencies expressly exclude them in a rule. The final
rule does so.
    The agencies include an exclusion for groundwater, including
groundwater drained through subsurface drainage systems. As discussed
in the preamble to the proposed rule, the agencies have never
interpreted ``waters of the United States'' to include groundwater. The
exclusion does not apply to surface expressions of groundwater, as some
commenters requested, such as where groundwater emerges on the surface
and

becomes baseflow in streams or spring fed ponds.
    The final rule includes a new exclusion in paragraph (b)(6) for
stormwater control features constructed to convey, treat, or store
stormwater that are created in dry land. The agencies stated in the
proposed rule that the exclusions were guided by decisions of the
Supreme Court and were intended to further the agencies' goal of
providing clarity and certainty. The agencies in the proposed rule
sought to provide a ``full description'' of the waters that will not be
``waters of the United States.'' 79 FR at 22218. In response to the
agencies' proposal, several commenters indicated additional clarity was
needed, particularly with respect to stormwater control features and
wastewater recycling facilities. This exclusion responds to numerous
commenters who raised concerns that the proposed rule would adversely
affect municipalities' ability to operate and maintain their stormwater
systems, and also to address confusion about the state of practice
regarding jurisdiction of these features at the time the rule was
proposed.
    The agencies' longstanding practice is to view stormwater control
measures that are not built in ``waters of the United States'' as non-
jurisdictional. Conversely, the agencies view some waters, such as
channelized or piped streams, as jurisdictional currently even where
used as part of a stormwater management system. Nothing in the proposed
rule was intended to change that practice. Nonetheless, the agencies
recognize that the proposed rule brought to light confusion about which
stormwater control features are jurisdictional waters and which are
not, and agree that it is appropriate to address this confusion by
creating a specific exclusion in the final rule for stormwater controls
features that are created in dry land.
    Many commenters, particularly municipalities and other public
entities that operate storm sewer systems and stormwater management
programs, expressed concern that various stormwater control measures--
such as stormwater treatment systems, rain gardens, low impact
development/green infrastructure, and flood control systems--could be
considered ``waters of the United States'' under the proposed rule,
either as part of a tributary system, an adjacent water, or as a result
of a case-specific significant nexus analysis. This exclusion should
clarify the appropriate limits of jurisdiction relating to these
systems. A key element of the exclusion is whether the feature or
control system was built in dry land and whether it conveys, treats, or
stores stormwater. Certain features, such as curbs and gutters, may be
features of stormwater collection systems, but have never been
considered ``waters of the United States.''
    Stormwater control features have evolved considerably over the past
several years, and their nomenclature is not consistent, so in order to
avoid unintentionally limiting the exclusion, the agencies have not
included a list of excluded features in the rule. The rule is intended
to exclude the diverse range of control features that are currently in
place and may be developed in the future.
    Traditionally, stormwater controls were designed to direct runoff
away from people and property as quickly as possible. Cities built
systems to collect, convey, or store stormwater, using structures such
as curbs, gutters, and sewers. Often, cities used existing stream
networks as part of the stormwater drainage network. Retention and
detention stormwater ponds were built to store excess stormwater until
it could be more safely released.
    Recently, treatment of stormwater has become more prevalent to
remove harmful pollutants before the stormwater is discharged. Even
more recently, cities have turned to green infrastructure, using
existing natural features or creating new features that mimic natural
hydrological processes that work to infiltrate or evapo-transpirate
precipitation, to manage stormwater at its source and keep it out of
the conveyance system. These engineered components of stormwater
management systems can address both water quantity and quality
concerns, as well as provide other benefits to communities. This rule
is designed to avoid disincentives to this environmentally beneficial
trend in stormwater management practices. This exclusion does not cover
transportation ditches; those ditches are addressed under paragraph
(b)(3) of the rule. As discussed above, the exclusion in paragraph
(b)(6) is intended to address engineered stormwater control structures
in municipal or urban environments. Stormwater control features are
designed to address runoff that occurs during and shortly after
precipitation events; as a result, stormwater features that convey
runoff are expected to only carry ephemeral or intermittent flow. For
ease of implementation, the agencies want water features to be dealt
with under only one provision of the rule. However, the agencies do not
expect the scope of ditches excluded to be different under paragraphs
(b)(3) and (b)(6), so there should be little practical need to
distinguish between the two.
    Paragraph (b)(7) of the rule clarifies that wastewater recycling
structures constructed in dry land are excluded. This new exclusion
clarifies the agencies' current practice that such waters and water
features used for water reuse and recycling are not jurisdictional when
constructed in dry land. The agencies recognize the importance of water
reuse and recycling, particularly in areas like California and the
Southwest where water supplies can be limited and droughts can
exacerbate supply issues. This exclusion responds to numerous
commenters and encourages water reuse and conservation while still
appropriately protecting the chemical, physical, and biological
integrity of the nation's water under CWA.
    The agencies specifically exclude constructed detention and
retention basins created in dry land used for wastewater recycling as
well as groundwater recharge basins and percolation ponds built for
wastewater recycling. Many commenters noted the growing interest in and
commitment to water recycling and reuse projects. Detention and
retention basins can play an important role in capturing and storing
water prior to beneficial reuse. Similarly, groundwater recharge basins
and percolation ponds are becoming more prevalent tools for water reuse
and recycling. These features are used to collect and store water,
which then infiltrates into groundwater via permeable soils. Though
these features are often created in dry land, they are also often
located in close proximity to tributaries or other larger bodies of
water. The exclusion also covers water distributary structures that are
built in dry land for water recycling. These features often connect or
carry flow to other water recycling structures, for example a channel
or canal that carries water to a percolation pond. The agencies have
not considered these water distributary systems jurisdictional where
they do not have surface connections back into, and contribute flow to,
``waters of the United States.'' In contrast, the agencies have
consistently regulated aqueducts and canals as ``waters of the United
States'' where they serve as tributaries, removing water from one part
of the tributary network and moving it to another. The exclusion in
paragraph (b)(7) codifies long-standing agency practice and encourages
water management practices that the agencies agree are important and
beneficial.
    The agencies also received other suggestions for new exclusions
that

were not adopted in the final rule. The agencies determined that it was
not appropriate or necessary to add certain requested exclusions for
one or more reasons, including: (1) The requested exclusion was so
broadly characterized as to introduce significant confusion and
potentially have the effect of excluding waters that the agencies have
consistently determined should be covered as ``waters of the U.S.,''
(2) the requested exclusion was so site-specific or activity-based as
to lack illustrative value, or (3) the requested exclusion was likely
covered by another exclusion in the final rule.
    It is important to note that while the waters listed in the
exclusions are not ``waters of the United States,'' they can serve as a
hydrologic connection that the agencies would consider under a case-
specific significant nexus under paragraphs (a)(7) and (a)(8). For
example, a wetland may be directly hydrologically connected to a
covered tributary via flow through an excluded non-wetland swale. While
the swale itself is excluded from jurisdiction, the connection of the
wetland to the tributary is relevant for determining whether the
wetland has a significant nexus to downstream traditional navigable
waters, interstate waters, or the territorial seas. In addition, these
geographic features may function as ``point sources'' under CWA section
502(14), such that discharges of pollutants to waters through these
features would be subject to other CWA regulations (e.g., CWA section
402).

V. Economic Impacts

    This rule establishing the definition of ``waters of the United
States,'' by itself, imposes no direct costs. The potential costs and
benefits incurred as a result of this rule are considered indirect,
because the rule involves a definitional change to a term that is used
in the implementation of CWA programs (i.e., sections 303, 305, 311,
401, 402, and 404). Entities currently are, and will continue to be,
regulated under these programs that protect ``waters of the United
States'' from pollution and destruction. Each of these programs may
subsequently impose direct or indirect costs as a result of
implementation of their specific regulations.
    While the rule imposes no direct costs, the agencies prepared an
economic analysis for informational purposes. In preparing the economic
analysis to accompany the final rule, the agencies considered what
should be the appropriate baseline for comparison. Existing regulations
and historic practice in implementing them represent one appropriate
baseline for comparison, and because the final rule is narrower in
jurisdictional scope than the existing regulations, there would be no
additional costs in comparison to this baseline. A comparison to recent
field practice following the 2008 guidance is also an appropriate
baseline, and the agencies prepared illustrative estimates of how the
costs and benefits of various CWA programs may change with an increase
in positive jurisdictional determinations relative to that baseline.
    To estimate changes in potential costs and benefits of different
CWA programs, the economic analysis utilizes available program data to
estimate the extent to which assertion of jurisdiction might change
under the associated final policies. The proposed rule analysis
utilized CWA Section 404 jurisdictional determination and permit data
from fiscal years 2009-2010 (post SWANCC and Rapanos), following
issuance of program guidance in 2008 by the EPA and the Corps. The
analysis for the final rule has been updated using data from fiscal
years 2013-2014, providing a comparison to a more recent year of data,
which responds to public comments. An estimate of how assertion of
jurisdiction may change compared to the recent practice baseline,
developed using updated data from fiscal years 2013-2014 jurisdictional
determinations, is then applied to cost and benefit information for
affected CWA programs. Additional updates to the economic analysis
include a refined approach to calculating benefits from section 404
compensatory mitigation, differentiating between emergent and forested
wetlands, as well as presenting results in ranges to reflect
uncertainty. The agencies' economic analysis yielded the following key
conclusions:
     Compared to the current regulations and historic practice
of making jurisdictional determinations, the scope of jurisdictional
waters will decrease, as would the costs and benefits of CWA programs.
     Compared to a baseline of recent practice, the agencies
assessed two scenarios. Those scenarios result in an estimated increase
of between 2.84 and 4.65 percent in positive jurisdictional
determinations annually.
     The agencies' analysis indicates that for both scenarios,
the change in benefits of CWA programs exceed the costs by a ratio of
greater than 1:1.
     The economic analysis estimates that incremental annual
costs for scenario 1 will range from $158M-$307M and incremental annual
benefits will range from $339M-$350M and, for scenario 2, costs will
range from $237M-$465M and benefits will range from $555M-$572M.

The agencies conducted this economic analysis to provide the public
with information on the potential changes to the costs and benefits of
various CWA programs that may result from a change in the number of
positive jurisdictional determinations. The economic analysis was done
for informational purposes only, and the final decisions on the scope
of ``waters of the United States'' in this rulemaking are not based on
consideration of the information in the economic analysis. The economic
analysis fulfills the requirements of Executive Orders 13563 and 12866.
An explanation of the data, methods, and assumptions used to estimate
indirect costs and benefits can be found in the Economic Analysis for
the Clean Water Rule; Definition of ``Waters of the United States''
Under the Clean Water Act (Final Rule) in the accompanying docket.

VI. Related Acts of Congress, Executive Orders, and Agency Initiatives

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this
action is a ``significant regulatory action.'' Accordingly, EPA and the
Army submitted this action to the Office of Management and Budget (OMB)
for review under Executive Orders 12866 and 13563 (76 FR 3821, January
21, 2011) and any changes made in response to OMB recommendations have
been documented in the docket for this action.
    In addition, EPA and the Army prepared an analysis of the potential
costs and benefits associated with this action. This analysis is
contained in Economic Analysis of the EPA-Army Clean Water Rule. A copy
of the analysis is available in the docket for this action.

B. Paperwork Reduction Act

    This action does not impose any information collection burden under
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq.
Burden is defined at 5 CFR 1320.3(b). An agency may not conduct or
sponsor, and a person is not required to respond to, a collection of
information unless it displays a currently valid OMB control number.
The OMB control numbers for the CWA section 402 program may be found at
40 CFR 9.1. (OMB Control No. 2040-0004, EPA ICR No. 0229.19). For the
CWA section 404 regulatory

program, the current OMB approval number for information requirements
is maintained by the Corps of Engineers (OMB approval number 0710-
0003). However, there are no new approval or application processes
required as a result of this rulemaking that necessitate a new
Information Collection Request (ICR).

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice-and-comment rulemaking requirements under the Administrative
Procedure Act or any other statute unless the agency certifies that the
rule will not have a significant economic impact on a substantial
number of small entities. Small entities include small businesses,
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of this final action on small
entities, ``small entity'' is defined as: (1) A small business that is
a small industrial entity as defined in the U.S. Small Business
Administration's size standards (see 13 CFR 121.201); (2) a small
governmental jurisdiction that is a government of a city, county, town,
school district, or special district with a population of less than
50,000; or (3) a small organization that is any not-for-profit
enterprise that is independently owned and operated and is not dominant
in its field.
    After considering the economic impacts of this rule on small
entities, we certify that this final rule will not have a significant
economic impact on a substantial number of small entities. See, e.g.,
Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855 (D.C. Cir. 2001);
Michigan v. EPA, 213 F.3d 663 (D.C. Cir. 2000); Am. Trucking Ass'n v.
EPA, 175 F.3d 1027 (D.C. Cir. 1999); Mid-Tex Elec. Co-op, Inc. v. FERC,
773 F.2d 327 (D.C. Cir. 1985).
    Under the RFA, the impact of concern is any significant adverse
economic impact on small entities, because the primary purpose of the
initial regulatory flexibility analysis is to identify and address
regulatory alternatives ``which minimize any significant economic
impact of the proposed rule on small entities.'' 5 U.S.C. 603. The
scope of jurisdiction in this rule is narrower than that under the
existing regulations. See 40 CFR 122.2 (defining ``waters of the United
States''). Because fewer waters will be subject to the CWA under the
rule than are subject to regulation under the existing regulations,
this action will not affect small entities to a greater degree than the
existing regulations. As a consequence, this action will not have a
significant adverse economic impact on a substantial number of small
entities, and therefore no regulatory flexibility analysis is required.
    This rule is not designed to ``subject'' any entities of any size
to any specific regulatory burden. Rather, it is designed to clarify
the statutory scope of ``the waters of the United States, including the
territorial seas,'' section 502(7), consistent with Supreme Court
precedent. This question of CWA jurisdiction is informed by the tools
of statutory construction and the geographical and hydrological factors
identified in Rapanos v. United States, 547 U.S. 715 (2006), which are
not factors readily informed by the RFA.
    Nevertheless, the scope of the term ``waters of the United States''
is a question that has continued to generate substantial interest,
particularly within the small business community, because permits must
be obtained for many discharges of pollutants into those waters. In
light of this interest, the EPA and the Army determined to seek wide
input from representatives of small entities while formulating the
proposed and final definition of this term that reflects the intent of
Congress consistent with the mandate of the Supreme Court's decisions.
Such outreach, although voluntary, is also consistent with the
President's January 18, 2011 Memorandum on Regulatory Flexibility,
Small Business, and Job Creation, which emphasizes the important role
small businesses play in the American economy. This process has enabled
the agencies to hear directly from these representatives, throughout
the rule development, about how they should approach this complex
question of statutory interpretation, together with related issues that
such representatives of small entities may identify for possible
consideration in separate proceedings. The agencies have prepared a
report summarizing their small entity outreach, the results of this
outreach, and how these results have informed the development of this
rule. This report, Report of the Discretionary Small Entity Outreach
for the Revised Definition of Waters of the United States (Docket Id.
No. EPA-HQ-OW-2011-0880-1927), is available in the docket.

D. Unfunded Mandates Reform Act

    This action does not contain any unfunded mandate under the
regulatory provisions of Title II of the Unfunded Mandates Reform Act
of 1995 (UMRA) (2 U.S.C. 1531-1538), and does not significantly or
uniquely affect small governments. The action imposes no enforceable
duty on any state, local, or tribal governments, or the private sector,
and does not contain regulatory requirements that might significantly
or uniquely affect small governments. The definition of ``waters of the
United States'' applies broadly to CWA programs.

E. Executive Order 13132: Federalism

    This rule does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the national government and the states, or on the distribution of power
and responsibilities among the various levels of government.
    Keeping with the spirit of Executive Order 13132 and consistent
with the agencies' policy to promote communications with state and
local governments, the agencies consulted with state and local
officials throughout the process and solicited their comments on the
proposed action and on the development of the rule.
    For this rule state and local governments were consulted at the
onset of rule development in 2011, and following the publication of the
proposed rule in 2014. In addition to engaging key organizations under
federalism, the agencies sought feedback on this rule from a broad
audience of stakeholders through extensive outreach to numerous state
and local government organizations.
    Early in the rulemaking process, EPA held two in-person meetings
and two phone calls in the fall and winter of 2011. Organizations
involved include the National Governors Association, the National
Conference of State Legislatures, the Council of State Governments, the
National Association of Counties, the National League of Cities, the
U.S. Conference of Mayors, the County Executives of America, the
National Associations of Towns and Townships, the International City/
County Management Association, and the Environmental Council of the
States. Additionally, the National Association of Clean Water Agencies
and the Association of Clean Water Administrators were invited to
participate. The agencies held many additional calls and meetings with
state and local governments and their associations, in preparation for
the development of a proposed rule.
    Similarly to the outreach conducted prior to the development of the
rule, the agencies committed themselves to providing a transparent,
comprehensive, and effective process for taking public comment on the
proposed rule. As part of this consultation, EPA held a meeting on May
13, 2014 to seek technical input on the proposed rule from the largest

national representative organizations for State and local governments.
During this process the agencies also extended its focused outreach to
include a series of meetings with the Local Government Advisory
Committee, and the Environmental Council of the States in conjunction
with the Association of Clean Water Administrators and the Association
of State Wetland Managers. In addition to engaging these key
organizations, the agencies sought additional feedback on the proposed
rule through broader public outreach to state and local government
organizations during the public comment period.
    During the consultation process, some participants expressed
concern that the proposed changes may impose a resource burden on state
and local governments. Some participants urged EPA to ensure that
states are not unduly burdened by the regulatory revisions.
    The agencies have prepared a report summarizing their voluntary
consultation and extensive outreach to State, local, and county
governments, the results of this outreach, and how these results have
informed the development of today's rule. This report, Report on the
Discretionary Consultation and Outreach to State, Local, and County
Governments on the Clean Water Rule: Definition of ``Waters of the
United States;'' Final Rule (Docket Id. No. EPA-HQ-OW-2011-0880) is
available in the docket for this rule.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    Subject to the Executive Order (E.O.) 13175 (65 FR 67249, November
9, 2000), agencies generally may not issue a regulation that has tribal
implications, (1) that imposes substantial direct compliance costs, and
that is not required by statute, unless the Federal government provides
the funds necessary to pay the direct compliance costs incurred by
tribal governments, or the agencies consult with tribal officials early
in the process of developing the proposed regulation and develop a
tribal summary impact statement, or (2) that preempts tribal law unless
the agencies consult with tribal officials early in the process of
developing the proposed regulation and develops a tribal summary impact
statement.
    This action does not have tribal implications as specified in E.O.
13175. In compliance with the EPA Policy on Consultation and
Coordination with Indian Tribes (May 4, 2011), the agencies consulted
with tribal officials throughout the rulemaking process to gain an
understanding of tribal views and solicited their comments on the
proposed action and on the development of this rule. In the course of
this consultation, EPA and the Corps jointly participated in aspects of
the process.
    The agencies began consultation with federally-recognized Indian
tribes on the Clean Water Rule defining ``waters of the United States''
in October 2011. The consultation and coordination process, including
providing information on the development of an accompanying science
report on the connectivity of streams and wetlands, continued, in
stages, over a four year period, until the close of the public comment
period on November 14, 2014. EPA invited tribes to provide written
input on the rulemaking throughout both the tribal consultation process
and public comment period.
    EPA specifically consulted with tribal officials to gain an
understanding of, and to address, the tribal views on the proposed
rule. In 2011, close to 200 tribal representatives and more than 40
tribes participated in the consultation process, which included
multiple webinars and national teleconferences and face-to-face
meetings. In addition, EPA received written comments from three tribes
during the initial consultation period.
    EPA continued to provide status updates to the National Tribal
Water Council and the National Tribal Caucus during 2012 through 2014.
The final consultation event was completed on October 23, 2014 as a
national teleconference with the Office of Water's Deputy Assistant
Administrator. Ultimately, EPA received an additional 23 letters from
tribes/tribal organizations by the completion of the consultation