Revised Definition of "Waters of the United States"

Response to Comments Document

Section 10 - Wetlands and Adjacency

See the Introduction to this Response to Comments Document for a discussion of the U.S. Environmental
Protection Agency and the U.S. Department of the Army's (hereinafter, the agencies ) comment response

process and organization of the eighteen sections.

10.0 Wetlands and Adjacency-General	2

10.1	Wetlands-Science/Functions	4

10.1.1	Additional wetlands protections	4

10.1.2	Wetland functions	6

10.1.3	Protection of specific wetland types/geographic areas	8

10.2	Adjacent Wetlands - General Implementation	11

10.2.1 Prior regulatory regime s	15

10.2.2 Regulatory text	17

10.2.3	Subsurface hydrology and distance	17

10.2.4	Bordering, contiguous, neighboring	21

10.2.5	Wetlands adjacent to lakes, ponds, and impoundments	23

10.3	Regulatory Definition of "Wetlands" and Wetland Delineation	24

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

1

-------
10.0 Wetlands and Adjacency-General

A few commenters generally critiqued the proposed rule's criteria for establishing if a wetland is
"adjacent" as "overly-broad and ambiguous." One commenter discussed the importance of a more
specific and clearer definition of wetlands for transportation project funding, planning, scheduling,
permitting, construction, and costs, and also warned of negative impacts (e.g., delays) from the concept of
adjacency as defined. Some of the commenters critiqued the approach to wetlands and adjacency in the
proposed rule claiming it was unclear and/or regulatory over-reach.

Several commenters presented their own suggested approaches to defining adjacency. A few commenters
recommended that the agencies use the best available science that addresses the physical, chemical, and
biological connections of wetlands to "waters of the United States" in finalizing a rule, guidance, and/or
financial assistance at local levels for jurisdictional determinations.

One commenter said the agencies' definition of "adjacent wetlands" is not identical to the pre-2015
regulatory regime, as the agencies indicated, which the commenter stated unravels the long-held
understanding of adjacency.

Agencies' Response: The agencies disagree with the commentors that regard the approach
to adjacency as "overly-broad and ambiguous," unclear, or over-reach. Under the final
rule, the agencies have made no changes to the longstanding definition of "adjacent" as
bordering, contiguous, or neighboring, and includes waters separated from other "waters of
the United States" by constructed dikes or barriers, natural river berms, beach dunes and
the like as "adjacent wetlands." The agencies are not including all adjacent wetlands as
jurisdictional waters. Rather, the agencies conclude that jurisdiction over this longstanding,
familiar category of waters when they meet either the relatively permanent standard or the
significant nexus standard is consistent with the statute, informed by relevant Supreme
Court decisions, and reflects the record before the agencies, including consideration of the
best available science, as well as the agencies' expertise and experience implementing the
pre-2015 regulatory regime. See Technical Support Document (TSD) Section III.B for the
scientific support of wetlands and adjacency; Final Rule Preamble Sections IV.C.5 and
IV.C.10 for additional information. The agencies have not established a specific distance
limitation in the rule beyond which wetlands are never adjacent because whether a wetland
is reasonably close such that the wetland and the jurisdictional water are part of the same
aquatic ecosystem depends on regional variations in climate, landscape, and
geomorphology. But the agencies can state based on nearly 45 years of implementation of
this definition that in a substantial number of cases, adjacent wetlands abut (touch) a
jurisdictional water. And, on the whole, nationwide, adjacent wetlands are within a few
hundred feet from jurisdictional waters (and in the instances where the distance is greater
than a few hundred feet, adjacency is likely supported by a pipe, non-jurisdictional ditch,
karst geology, or some other feature that connects the wetland directly to the jurisdictional
water). While bright-line rules (for example, wetlands that are a specific number of feet
from a jurisdictional water are not "adjacent") are easiest to understand and implement,
convenience is not the only goal the agencies must consider in administering the Clean
Water Act. Because the relationship between a wetland and a proximate jurisdictional
water can depend upon a number of site-specific factors, like climate, geomorphology,
landscapes, hydrology, and size of the jurisdictional water (e.g., the ocean compared to a

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

2

-------
headwater stream), and because the central purpose of the Act is to protect the integrity of
our nation's waters, a more nuanced analysis is required. See Final Rule Preamble Section
IV.C.5 for additional discussion.

The agencies disagree that the proposed definition will contribute significantly to costs for
jurisdiction determinations. The agencies acknowledge that there are indirect costs—both
monetary and temporal—associated with implementation of the final rule. Indeed, there are
indirect costs associated with implementation of all prior rules defining "waters of the
United States." As the final rule is very similar in scope to that of pre-2015 practice, there
will be de minimis new indirect costs associated with the implementation of the final rule.
See also the agencies' response to comments in Section 17 on the Economic Analysis. As
discussed in Final Rule Preamble Section IV.A, the agencies are finalizing a definition of
"waters of the United States" that is within the agencies' authority under the Act; that
advances the objective of the Clean Water Act; that establishes limitations that are
consistent with the statutory text, supported by the scientific record, and informed by
relevant Supreme Court decisions; and that is both familiar and implementable.

The agencies recognize commenters who recommended changes to the proposed approach
to wetlands and adjacency, including use of the best available science. The definition of
"adjacent" is a longstanding and familiar definition that is supported by the text of the
statute, Supreme Court case law, and science. See, e.g., Riverside Bayview1, 474 U.S. at 134
("[T]he Corps' ecological judgment about the relationship between waters and their
adjacent wetlands provides an adequate basis for a legal judgment that adjacent wetlands
may be defined as waters under the Act."). Thus, the longstanding definition of "adjacent"
reasonably advances the objective of the Clean Water Act. In this final rule, the agencies
are exercising their authority to interpret "waters of the United States" to mean the waters
defined by the familiar 1986 regulations, with amendments to reflect the agencies'
determination of the statutory limits on the scope of the "waters of the United States"
informed by the text of the relevant provisions of the Clean Water Act and the statute as a
whole, the scientific record, relevant Supreme Court precedent, and the agencies'
experience and technical expertise after more than 45 years of implementing the
longstanding pre-2015 regulations defining "waters of the United States." Through this
rulemaking process, the agencies have considered all timely public comments on the
proposed rule, including changes that improve the clarity, implementability, and durability
of the definition. The regulations established in this rule are founded on the familiar
framework of the 1986 regulations and are generally consistent with the pre-2015
regulatory regime. The agencies find that this final rule increases clarity and
implementability by streamlining and restructuring the 1986 regulations and providing
implementation guidance informed by sound science, implementation tools, and other
resources. Further, because this rule is founded upon a longstanding regulatory framework
and reflects consideration of the agencies' experience and expertise, as well as updates in
implementation tools and resources, the agencies find that the final rule is generally
familiar to the public and implementable. See Final Rule Preamble Section IV.A.4.

1 United States v. Riverside Bayview Homes, 474 U.S. 121, 131-35 (1985)

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

3

-------
The agencies agree with the need for consistency in the rule's approach to wetlands and
adjacency with Supreme Court precedents. The agencies have included the relatively
permanent and significant nexus standards in the final rule based on their conclusion that
together those standards are consistent with the statutory text, advance the objective and
policies of the Clean Water Act, and are supported by the scientific record. See the
agencies' response to comments in Section 2.3.5 regarding the agencies' legal authority over
adjacent wetlands, including consistency with the Constitution, the Clean Water Act, and
case law.

The agencies disagree that the final rule unravels the long-held understanding of adjacency.
In fact, the agencies have made no changes to the longstanding definition of "adjacent."
Final Rule Preamble Section IV.C.5 explains how the agencies will implement the definition
of "adjacent" consistent with longstanding practice. The regulations established in this rule
are founded on the familiar framework of the 1986 regulations and are generally consistent
with the pre-2015 regulatory regime. They are fully consistent with the statute, informed by
relevant Supreme Court decisions, and reflect a reasonable interpretation based on the
record before the agencies, including the best available science, as well as the agencies'
expertise and experience implementing the pre-2015 regulatory regime. See Final Rule
Preamble Section IV.A.4 for further discussion of the agencies' finding that the final rule is
both familiar and implementable.

10.1 Wetlands-Science/Functions

10.1.1 Additional wetlands protections

Many commenters argued that wetlands can have physical, chemical, and biological connections to other
waters and called for greater jurisdictional protections. Many commenters explicitly connected their
discussions of the science and functions of wetlands with calls for additional protections for wetlands.
Most of these calls for additional protections were set in contrast to the 2020 Navigable Waters Protection
Rule (2020 NWPR) or to the proposed rule. A couple of commenters voiced support for the concept of
"no net loss" of wetlands. One of those commenters encouraged "a management approach that first avoids
the destruction of wetlands, then minimizes wetland loss, and mitigates any loss as the final alternative."
A number of commenters discussed harmful impacts to wetlands including, for example, wetland losses
from development resulting from the 2020 NWPR. A few commenters specifically mentioned negative
impacts to wetlands, including adjacent and/or isolated wetlands, from climate change. One of those
commenters highlighted that the "dynamic interplay between wetlands and climate is extremely
complicated and a primary recommendation by scientists across the globe for addressing climate change
is to avoid disturbing wetlands." Another commenter explained that "wetlands are being substantially
affected by even the smallest changes in climate, including changes in hydrologic regimes due to sea level
rise and decreased surface and ground water levels, air temperature changes, and soil temperature
changes. Reduced precipitation levels are likely to decrease surface water levels and flow, which will
impact the adjacency parameters for their neighboring wetlands, resulting in an increase in isolated
wetlands (e.g., ephemeral wetlands)."

A few commenters discussed local policies and implementation approaches and the associated impacts to
the function of wetlands. One commenter stated, "New York State has developed a regulatory framework

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

4

-------
of planning and guidance to communities throughout the years to reduce or eliminate development in
environmentally sensitive areas to preserve the natural functions and ecosystem benefits that wetlands and
other waters provide," noting several of the functions of wetlands, and recognizing state authorities verses
federal regulatory authority. A number of commenters cited scientific studies to support broader
jurisdiction over wetlands, including regulating subsurface flows. Commenters also cited these studies in
critiques of the 2020 NWPR and associated distance parameters.

One commenter connected arguments about the need for stronger protections for wetlands to the
Infrastructure Investment and Jobs Act, stating, "wetlands naturally provide many of the functions
pursued as water quality improvement and climate resilience measures in the infrastructure law." The
commenter argued that failing to adopt additional protections would undercut infrastructure investments.

A few other commenters argued for stronger wetlands protections based in part on decisions of the
Supreme Court. One commenter stated, "the proposed definition of adjacent wetlands offers better
protection than the [2020] NWPR and is consistent with Supreme Court decisions. However, the
proposed definition is not currently strong enough to include known types of biological, chemical, and
physical connections, as supported by the U.S. Environmental Protection Agency, Connectivity of
Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence (2015)
("Science Report")2 and the best available science." One commenter suggested following the 2015 Clean
Water Rule approach to adjacency, stating:

"As the discussion in the agencies' Technical Support Document demonstrates, [see Proposed
Rule Technical Support Document (TSD) at 173-196] the scientific record shows conclusively
that floodplain wetlands have multiple significant effects on downstream waters. Accordingly,
such wetlands should be protected categorically in recognition of the significant nexus they have
to traditional navigable waters, interstate waters, and the territorial seas ... At a minimum, the
agencies must protect those adjacent waters—ones that are "adjacent" as defined in the 2015
Clean Water Rule—that the agencies previously determined to have a significant nexus."

Another commenter expressed concerns based on major wetland losses in the greater Houston region
while the Rapanos Guidance3 framework was in place. That commenter explained that the Galveston
Army Corps District interprets SWANCC4 and Justice Kennedy's opinion in Rapanos5 incorrectly to
exempt from regulatory jurisdiction almost all regional wetlands outside of FEMA's 100-year
floodplain—an approach which differs from that taken by other Army Corps district offices both in and
out of Texas.

A commenter stated that all adjacent wetlands that significantly affect "downstream waters" must be
protected under the Act.

2 U.S. Environmental Protection Agency, Connectivity of Streams and Wetlands to Downstream Waters: A Review
and Synthesis of the Scientific Evidence (Final Report), EPA/600/R-14/475F (2015), available at
httPs://cfpub.epa.gov/ncea/risk/recordisplav.cfm?deid=296414.

3U.S. EPA&U.S. Army Corps ofEngineers, Clean Water Act Jurisdiction Following the U.S. Supreme Court's
Decision in Rapanos v. United States & Carabell v. United States (June 5, 2007)

4	Solid Waste Agency of Northern Cook County v. U.S. Army Corps ofEngineers, 531 U.S. 159 (2001) ("SWANCC')

5	Rapanos v. United States, 547 U.S. 715 (2006) ("Rapanos")	

Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

5

-------
Agencies' Response: The agencies agree with commenters that the scientific literature
unequivocally demonstrates that wetlands and open waters in riparian areas and
floodplains are chemically, physically, and biologically integrated with rivers via functions
that improve water quality in paragraph (a)(1) waters. Such functions include: the
temporary storage and deposition of channel-forming sediment and woody debris;
temporary storage of local groundwater that supports baseflow in rivers; transformation
and transport of stored organic matter; assimilation, transformation, or sequestration of
pollutants; providing nursery habitat for breeding fish and amphibians; colonization
opportunities for stream invertebrates and maturation habitat for stream insects;
desynchronization of flood waters; and sequestration of pollutants. See TSD Sections I and
III.B. The rule provides for jurisdiction for wetlands adjacent to waters that are not
paragraph (a)(1) waters that meet the relatively permanent standard or the significant
nexus standard, so adjacent wetlands, alone or in combination with similarly situated
waters in the region, that significantly affect the chemical, physical, or biological integrity of
paragraph (a)(1) waters are protected by the Clean Water Act.

Several commenters articulated the linkage of the health of the nation's waters and climate
impacts. The agencies recognize and agree that climate change will impact "waters of the
United States." See Section II.C of the TSD. When the agencies assess whether or not a
water is a "water of the United States," consistent with longstanding practice, they do not
assess future conditions based on potential climatic changes. See also Final Rule Preamble
Section IV.C.9.c.ii for a discussion of how the agencies can consider a changing climate
under the significant nexus standard consistent with the best available science. The agencies
also agree that the protection of wetlands needs to be undertaken at all levels of government
to assure protection of the important functions of these waters on multiple geographic
levels.

The agencies agree that protecting wetlands is an essential part of protecting our nation's
infrastructure and helps to further the objectives of the Infrastructure Investment and Jobs
Act. The agencies are committed to assuring that the rule is implemented consistently
throughout the nation. The final rule does not categorically exclude wetlands outside of
FEMA's 100-year floodplain.

Determinations regarding the jurisdictional status of any specific water are outside the
scope of this rulemaking. The agencies will assess jurisdiction under the final rule on a case-
specific basis.

See Preamble Sections IV.A, IV.C.5.a, and the agencies' response to comments in Section
2.3.5 regarding the agencies' legal authority over wetlands, including consistency with case
law.

10.1.2 Wetland functions

Many commenters discussed the science and beneficial functions of wetlands, noting that wetlands can
improve water quality by filtering out algal blooms, pollution, and sediment. In discussing wetland
protections in the context of science and functions, one commenter called for "additional federal funding

and technical assistance."	

Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

6

-------
Many commenters also discussed other wetland functions and benefits, including:

•	Benefits to wildlife (e.g., birds, fish) and/or habitats, including endangered species;

•	Mitigating floods, storms, and/or related climate change impacts, with some commenters
particularly discussing floodplain wetlands;

•	Carbon storage;

•	Mitigating droughts and/or low flows;

•	Supporting clean drinking water and/or drinking water supplies; and

•	Social benefits such as health, safety, and economy (e.g., recreation, tourism, fisheries).

A few commenters explained that wetlands "retain large volumes of stormwater, floodwater, and
contaminated runoff that would otherwise harm river quality. [Proposed Rule TSD at 30.]." A commenter
shared that "filtering stormwater runoff through the soil profile reduces phosphorus and turbidity
dramatically." Another commenter discussed that "the promotion of subsurface water management
increases production on current farmland, allowing non-cropland to be reserved for other uses, such as
hunting and recreation." The same commenter expressed support for "reasonable, subsurface management
of water on cropland in order to increase the storage of floodwaters in the soil profile, thereby reducing
surface run-off, soil erosion, sediment transfer, and reducing peak-flow discharges downstream."

One commenter stated that floodplain wetlands have the following functional connections to other
jurisdictional waters.:

•	Surface water flows/exchange;

•	Groundwater flows/exchange;

•	Sediment source;

•	Flood control;

•	Pollutant filtration/retention/sequestration; and

•	Wildlife habitat.

Many commenters voiced support for the 2015 Clean Water Rule and its approach to adjacency. Several
commenters cited Supreme Court precedent as recognizing the functions of wetlands, including Justice
Kennedy's statement in the Rapanos case that "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."
Commenters noted that wetlands play a key role in achieving the Clean Water Act's objective to "restore
and maintain the chemical, physical, and biological integrity of the Nation's waters."

Agencies' Response: The agencies agree wetlands play a key role in achieving the Clean
Water Act's objective to "restore and maintain the chemical, physical, and biological
integrity of the Nation's waters." Consistent with the proposal, this rule retains the adjacent
wetlands provision of the 1986 regulations, with amendments to reflect the agencies'
interpretation of the statutory limits on the scope of the "waters of the United States"
informed by the law, the science, and agency expertise.

The agencies agree that wetlands serve valuable functions for receiving waters. As
mentioned in Section 10.1.1, the scientific literature unequivocally demonstrates that
wetlands and open waters in riparian areas and floodplains are chemically, physically, and
biologically integrated with rivers via functions that improve water quality in paragraph
(a)(1) waters. The agencies agree with the commenters who linked the functions provided
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

7

-------
by wetlands to water quality benefits realized by receiving waters. Most of the
biogeochemical functions described by commenters are reflected in the list of key functions
to be assessed and factors to be considered in the significantly affect definition described in
the Final Rule Preamble Section IV.C.9. and the agencies' response to comments in Section
12 on the significant nexus standard. The agencies have modified the factors in response to
public comments and to increase clarity in the final rule. The factors in the final rule
influence the types and strength of chemical, physical, or biological connections and
associated effects that streams, wetlands, and open waters have on paragraph (a)(1) waters.
The functions in the final rule are indicators that are tied to the chemical, physical, or
biological integrity of paragraph (a)(1) waters.

Specific allocations of federal funding and technical assistance are beyond the scope of this
rule.

10.1.3 Protection of specific wetland types/geographic areas

Many commenters connected the science and functions of wetlands either generally or specifically to their
support for protecting specific wetland types, specific wetlands, or wetlands in specific geographic areas,
and to the importance of wetlands to watershed protection. Several commenters called for protections for
particular wetland types (e.g., isolated, adjacent, riparian, floodplain, physically separated). A few
commenters expressed concern over cumulative wetland losses in specific geographic regions, states, or
local areas. A commenter highlighted there has been substantive wetland losses in specific geographic
areas, including that "twenty-two states have lost more than 50% of their wetland acreage, ten states in
the Midwest and coastal areas have lost more than 70%, and California has lost 91%."

A number of commenters identified wetlands in particular geographic areas that warrant protection,
including:

•	The Southeast, especially those that mitigate flooding or serve to filter drinking water;

•	California;

•	Illinois, Mississippi, and Ohio Rivers and the Gulf of Mexico;

•	Florida, including headwaters;

•	Missouri;

•	New York State;

•	North Carolina, particularly pocosins, as well as other coastal and mountain wetlands (e.g.,
headwaters);

•	Texas, particularly coastal (including coastal prairie) wetlands, for example in Harris County,
Montgomery County, Houston, Galveston Bay, Matagorda Bay;

•	The Chesapeake Bay watershed;

•	The Navajo Nation, including the Chaco River, the Puerco River, and the Chinle Wash; and

•	Los Alamos National Laboratory, including the Rio Grande and Colorado River.

In addition to wetland types and geographic areas, commenters raised concerns about inconsistent
jurisdictional decisions. A few commenters were concerned that wetland complexes were vulnerable to
inconsistent decisions and historic disconnections caused by development, and recommended assessing
these in the aggregate as wetland complexes that are functionally integrated through surface, subsurface,
and groundwater connections. One commenter explained that despite scientific research quantitatively

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

8

-------
measuring the hydrological connectivity of Texas coastal prairie wetland complexes to "waters of the
United States," "the Galveston District has categorically excluded most Texas coastal prairie wetlands
from the Clean Water Act's protections."

A few commenters called for consideration of regional differences in wetland jurisdictional approaches
related to adjacency, some citing the Science Report in support of their comments. Another commenter
discussed the importance of wetlands' functions in meeting the goals of the 2014 Chesapeake Watershed
Agreement.

Agencies' Response: The agencies recognize the ecosystem and societal services that
particular wetland types provide, as described in the Science Report and TSD Sections

III.B,	III.D.i, and III.G. In the Final Rule Preamble Section IV.A and the TSD Section III.B,
the agencies acknowledge that the best available science supports that the functions
provided by adjacent wetlands to paragraph (a)(1) waters include valuable flood control
and water quality functions such as interruption and delay of the transport of water-borne
contaminants over long distances, retention of sediment, prevention and mitigation of
drinking water contamination, and assurance of drinking water supply.

The agencies agree that wetlands adjacent to paragraph (a)(1) waters, including lakes,
provide important functions to those waters. Further, the agencies agree wetlands that meet
the definition of "wetland" in the final rule are considered adjacent wetlands if they meet
one of three criteria. First, there is an unbroken surface or shallow subsurface connection to
jurisdictional waters. Second, they are physically separated from jurisdictional waters by
human-made dikes or barriers, or natural breaks (e.g., river berms, beach dunes). Or third,
their proximity to a jurisdictional water is reasonably close. Wetlands that meet one of these
three criteria are considered bordering, contiguous, or neighboring in the final rule. For
more details regarding lakes used for waterborne commerce, see the Final Rule Preamble
Section IV.C.2 and response to comments Section 6. For more details about smaller lakes
and ponds, see the Final Rule Preamble IV.C.4 and IV.C.6 and the agencies' response to
comments in Sections 9 and 11.

The agencies' approach to adjacent wetlands in this rule reflects consideration of regional
differences and is intended to be flexible enough to accommodate these differences, while
not specifically identifying wetlands warranting protections in particular parts of the
country. See the Final Preamble Section IV.C.5.

If the wetland in question does not meet the criteria for an adjacent wetland, then the
agencies will evaluate the wetland under paragraph (a)(5). See Final Rule Preamble Section

IV.C.6.C	and agencies' response to comments Subject 11. Because some wetlands identified
by commenters may be jurisdictional under paragraph (a)(1), see also the agencies'
response to comments in Section 6 and the Final Rule Preamble Section IV.C.5.a.

Most of the biogeochemical functions described by commenters are reflected in the list of
key functions to be assessed and factors to be considered in the significantly affect definition
described in the Final Rule Preamble Section IV.C.9. The agencies have modified the
factors in response to public comments and to increase clarity in the final rule. The factors
in the final rule are readily understood criteria that influence the types and strength of
chemical, physical, or biological connections and associated effects on paragraph (a)(1)

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

9

-------
waters. The functions in the final rule are indicators that are tied to the chemical, physical,
or biological integrity of paragraph (a)(1) waters.

The scientific literature unequivocally demonstrates that wetlands and open waters in non-
floodplain landscape settings (hereafter called "non-floodplain wetlands") can provide
numerous functions that benefit the chemical, physical, and biological integrity of larger
downstream waters, including the paragraph (a)(1) waters, particularly when analyzed in
the aggregate. These functions include: storage of floodwater; recharge of groundwater that
sustains river baseflow; retention and transformation of nutrients, metals, and pesticides;
export of organisms or reproductive propagules (e.gseeds, eggs, spores) to downstream
waters; and habitats needed for stream species. This diverse group of wetlands (e.g., many
prairie potholes, vernal pools, playa lakes) can be connected to downstream waters through
surface water, shallow subsurface water, and groundwater flows and through biological and
chemical connections. Some effects of non-floodplain wetlands on larger downstream waters
are due to their relative isolation, rather than their connectivity. Where the wetland
intercepts materials that otherwise would reach downstream water, wetland "sink"
functions trap materials and prevent their export to downstream waters (e.g., sediment and
entrained pollutant removal, water storage). See TSD Sections I, III.B, and III.D.

The importance of retaining functions of wetlands in specific geographic areas is part of the
agencies' analysis of the significant nexus definition factors and functions. In the TSD, the
agencies note the functions of remaining wetlands in formerly dense wetland landscapes
could become more important. Under the significant nexus standard for adjacent wetlands,
the agencies will determine whether the wetlands, either alone or in combination with
similarly situated waters in the region, significantly affect the chemical, physical, or
biological integrity of paragraph (a)(1) waters. Further details are provided in the Final
Rule Preamble Section IV.C.5. However, unlike the 2015 Clean Water Rule, the agencies
are not establishing a category for certain wetland types in specific geographic areas that
can be considered similarly situated and assessed together on a watershed-basis in a case-
specific significant nexus analysis. In developing the final rule, the agencies thoroughly
considered alternatives to this rule, including the 2015 Clean Water Rule, and have
concluded that this final rule best accomplishes the agencies' goals to promulgate a rule that
advances the objective of the Clean Water Act, is consistent with Supreme Court decisions,
is informed by the best available science, and promptly and durably restores vital
protections to the nation's waters. See Section IV.B.l of the Preamble to the Final Rule for
further discussion of the agencies' grounds for concluding that the 2015 Clean Water Rule
is not a suitable alternative to the final rule.

The agencies have defined "significantly effect" and "material influence" to promote clarity
and implementation consistency. In Final Rule Preamble Section IV.C.9.b, the agencies
clarify the significant nexus standard considers whether wetlands demonstrate a "material
influence" on the chemical, physical, or biological integrity of downstream waters.

The agencies agree that where wetlands in a complex of wetlands have a continuous
physical surface connection to one another such that upland boundaries or dikes, barriers,
or other structures cannot distinguish or delineate them as physically separated, the entire
area is viewed as one wetland for consideration as to whether the wetland meets the terms
of adjacency. See additional clarification in the Final Rule Preamble Section IV.C.5.c.i.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

10

-------
The agencies also recognize there were some important functions identified by commenters
that could not be taken into account in the final rule because the significant nexus analysis
is limited to an assessment of only those functions identified in the final rule that have a
nexus to the chemical, physical, or biological integrity of paragraph (a)(1) waters. There are
a wide variety of functions that streams, wetlands, and open waters provide that translate
into ecosystem services that benefit society that would not be considered in a significant
nexus analysis under the final rule. These include provision of areas for personal enjoyment
(e.g., fishing, hunting, boating, and birdwatching areas); ceremonial or religious uses;
production of fuel, forage, and fibers; extraction of materials (e.g., biofuels, food, such as
shellfish, vegetables, seeds, nuts, rice); plants for clothes and other materials; and medical
compounds from wetland and aquatic plants or animals. While these ecosystem services can
contribute to the economy, they are not relevant to the chemical, physical, or biological
integrity of paragraph (a)(1) waters and would not be considered in a significant nexus
analysis under the final rule. See the agencies' response to comments Section 12 on the
significant nexus standard.

10.2 Adjacent Wetlands - General Implementation

In writing about adjacency, several commenters argued that local governments and Tribal governments
are best suited to assess appropriate protections for waters on their land. A few other commenters
suggested stakeholder involvement or coordination in defining and assessing adjacency.

Many commenters argued that wetlands should only be jurisdictional if they have a direct connection to
and/or abut traditional navigable waters, while other commenters stated that wetlands should only be
jurisdictional if they have a direct connection to and/or directly abut "waters of the United States."

Some commenters asked the agencies to clarify application of the significant nexus standard for adjacent
wetlands. One commenter stated that, "the rule must protect all adjacent and floodplain wetlands as
having a significant nexus."

A few commenters made arguments or recommendations in the context of a final or second rulemaking.
One of these commenters "recommend[ed] that the final Rule 1 preamble and TSD discussion include a
discussion of scientific literature regarding both wetlands and open waters when discussing the concept of
adjacency, providing a strong foundation for proposing "adjacent waters" in Rule 2. Such an approach
would closely reflect peer-reviewed aquatic resource science as well as the goals of the CWA and thus
support the Agencies' goal of creating a 'durable' final rule." The commenter recommended such a
discussion include terms such as "neighboring" and asked the agencies to wait until a second rulemaking
to revise the definition of "adjacent." The commenter went on to suggest the agencies reinforce principles
such as "functional relationships" and "regional variations" in redefining adjacency in the second
rulemaking. Lastly, that commenter argued, "if the agencies conclude adjacent wetlands are not
appropriate as a per se categorical WOTUS in a final Rule 1,... they should be considered during Rule 2
development."

Another commenter "recommend[ed] that quantitative criterion be addressed regionally through guidance
or in the second proposed rulemaking," and another commenter argued for distance considerations for
adjacency in the second proposed rulemaking.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

11

-------
One commenter expressed concern that the agencies will assert jurisdiction over wetlands with only
intermittent, physically remote hydrologic connections, such as asserting jurisdiction based on shallow
subsurface connections or based on "reasonably close" proximity and an inference of ecological
interconnection. The commenter stated that a continuous surface connection must be to a relatively
permanent water connected to a traditional interstate navigable water. The commenter stated that the
agencies have improperly converted the "continuous surface connection" requirement into a "physical
connection or ecological connection" test. The commentor also stated that it is improper to assert
jurisdiction over wetlands adjacent to relatively permanent impoundments if such impoundments are not
themselves connected to a traditional interstate navigable water.

A commenter stated that the scientific knowledge of the benefits of wetlands to downstream waters has
advanced since the Rapanos Guidance, which the commenter suggested should allow for greater wetland
protection under the significant nexus standard.

Agencies' Response: The agencies agree with commenters that local governments and tribal
governments have in depth knowledge of waters within their jurisdiction. States and tribes
may establish more protective standards or limits than the Clean Water Act to manage
waters subject to Clean Water Act jurisdiction or waters that fall beyond the jurisdictional
scope of the Act and may choose to address special concerns related to the protection of
water quality and other aquatic resources within their borders. Nothing in the final rule
limits or impedes any existing or future state or tribal efforts to further protect their waters.

The agencies also agree with the commenters that stakeholder input is critical to defining
adjacency. On June 9, 2021, the agencies announced their intention to revise or replace the
2020 NWPR. The agencies subsequently embarked on an extensive stakeholder outreach
process, including public meetings and federalism and tribal consultations. See Final Rule
Preamble Section III.C. The agencies received over 32,000 recommendation letters from the
public during pre-proposal outreach and over 114,000 comments on the proposed rule
during the public comment period. The agencies also held a public hearing and listening
sessions with state, tribal, and local governments during the public comment period to listen
to feedback on the proposed rule from co-regulators and a variety of stakeholders. The
agencies understand that the scope of Clean Water Act jurisdiction is an issue of great
national importance and appreciate feedback and engagement from all stakeholders.
See Final Rule Preamble Section II.C for a summary of stakeholder outreach conducted for
this rulemaking.

The Clean Water Act sets a baseline of federal protection for waters that meet the definition
of "waters of the United States" and authorizes States to be more protective than the Act
while also leaving substantial responsibility and autonomy to the States over those waters
that do not have a significant nexus to the core waters covered by the Act. The agencies
agree that partnerships with Tribes, States, and local governments are important to meet
the objective of the Act and have worked with these entities to ensure they had
opportunities to provide input on the rule and will continue to work with Tribes and States
to implement the final rule. To the extent commenters suggest delegating the authority to
define the term "waters of the United States" to States, Tribes, or stakeholders, the agencies
conclude that would not be consistent with Congress' intent in enacting the Clean Water
Act.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

12

-------
The agencies disagree with commenters that state there needs to be a direct connection (or
abutment) between adjacent wetlands and traditional navigable waters or other "waters of
the United States." Wetlands that are adjacent to traditional navigable waters, as that term
is defined in the rule, are per se jurisdictional. However, the definition of "adjacent" is not
limited to direct connections or abutting landscape positions for the reasons discussed in
Final Rule Preamble Section IV.A.2.b.ii.

The agencies have provided additional clarification regarding implementation of the
significant nexus standard for adjacent wetlands in the final rule. The agencies have not
made a categorical significant nexus determination for all floodplain and adjacent wetlands
in the rule. As discussed in Final Rule Preamble Section IV.A, the agencies are finalizing a
definition of "waters of the United States" that is within the agencies' authority under the
Act; that advances the objective of the Clean Water Act; that establishes limitations that are
consistent with the statutory text, supported by the scientific record, and informed by
relevant Supreme Court decisions; and that is both familiar and implementable. As the
agencies charged with construing the statute, EPA and the Corps must develop the outer
bounds of the scope of the Clean Water Act. The agencies agree with commenters who
stated that science alone cannot dictate where to draw the line defining "waters of the
United States." But science is critical to understanding what scope of jurisdiction furthers
Congress's objective to restore and maintain the chemical, physical, and biological integrity
of the nation's waters and properly determining which waters are the subject of federal
jurisdiction due to their effects on paragraph (a)(1) waters. Wetlands are also adjacent
when their proximity to a jurisdictional water is reasonably close. Also, see Section III.B.ii
of the TSD for scientific support for the agencies' rationale.

In the preamble to the proposed rule, the agencies stated that they would consider changes
through a second rulemaking that they anticipated proposing in the future, which would
build upon the foundation of this rule. The agencies have concluded that this rule is durable
and implementable because it is founded on the familiar framework of the 1986 regulations,
fully consistent with the statute, informed by relevant Supreme Court decisions, and reflects
the record before the agencies, including consideration of the best available science, as well
as the agencies' expertise and experience implementing the pre-2015 regulatory regime. The
agencies may consider further refinements in a future rule to address implementation or
other issues that may arise.

The agencies are retaining their longstanding definition of "adjacent" unchanged from the
1986 regulations and are not establishing quantitative criteria or numeric standards to
interpret this term, or the term "neighboring." The agencies tie the concept of adjacency to
wetlands in Preamble Section IV.C.5, and this is supported by scientific literature as
reviewed in Section III.B.ii of the TSD and in Chapter 4 of the Science Report. The agencies
discuss how implementation under the final rule of the definition of "adjacent" at
paragraph (a)(4) is consistent with pre-2015 regulatory practice in Preamble Sections
IV.C.5; see also Section III.B of the TSD. Functions are discussed in terms of "significantly
affect" in the regulatory text at paragraph (c)(6) and in Preamble Section IV.C.5. Regional
variations are discussed in Preamble IV.C.5, and further details on this subject can be
found in the agencies' response to comments in Section 18.3.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

13

-------
The agencies in this rule are interpreting "waters of the United States" to mean the waters
defined by the familiar 1986 regulations, with amendments to reflect the agencies'
determination of the statutory limits on the scope of "waters of the United States" informed
by the text of the relevant provisions of the Clean Water Act and the statute as a whole, the
scientific record, relevant Supreme Court precedent, and the agencies' experience and
technical expertise after more than 45 years of implementing the longstanding pre-2015
regulations defining "waters of the United States." It also reflects consideration of extensive
public comment. Final Rule Preamble Section IV.A.3 explains the agencies' conclusion that
utilization of both the relatively permanent standard and the significant nexus standard
gives effect to the Clean Water Act's text, including its objective as well as its limitations.
The significant nexus standard is consistent with the text, objective, and legislative history
of the Clean Water Act, as well as relevant Supreme Court case law and the best available
science. The relatively permanent standard is administratively useful as it more readily
identifies a subset of waters that will nearly always significantly affect paragraph (a)(1)
waters but standing alone is insufficient to meet the objective of the Clean Water Act. See
Final Rule Preamble Section IV.C.5.C for a description of how the standards will be
implemented in determining the jurisdiction adjacent wetlands in the final rule.

The agencies disagree with the commenter who expressed concern that the agencies will
assert jurisdiction over wetlands with only intermittent, physically remote hydrologic
connections. The longstanding definition of "adjacent," by its terms, does not require flow
from the wetland to the jurisdictional water or from the jurisdictional water to the wetland
(although such flow in either direction can be relevant to the determination of adjacency).
Furthermore, while under this rule the agencies are not establishing distance limits for
adjacency, the agencies recognize that as the distance between the wetland and
jurisdictional water increases, the reasonableness of the connection between the waters will
generally decrease, particularly in the absence of surface or shallow subsurface connections,
and a finding of adjacency is less likely. The distance between a jurisdictional water and its
adjacent wetlands may vary by region, as well as based on site-specific factors within
regions. In practice, under this criterion, the agencies have found that adjacent wetlands
are on the whole, nationwide, within a few hundred feet of jurisdictional waters. This can
vary based on site-specific and regional factors. See Final Rule Preamble Section IV.C.5.C
for additional discussion.

The agencies disagree with the commenter who stated that the continuous surface
connection standard only applies to wetlands connected to relatively permanent waters
connected to traditional interstate navigable waters; the agencies interpret this standard as
applicable to wetlands connected to any relatively permanent waters, which are
jurisdictional by virtue of their connection to any paragraph (a)(1) waters. See Final Rule
Preamble Section IV.C.2.b for a discussion of why waters that are connected to any
traditional navigable waters, territorial seas, and interstate waters are jurisdictional. The
agencies also disagree with the commenter who stated that the agencies improperly convert
the "continuous surface connection" requirement into a "physical connection or ecological
connection" test. Adjacent wetlands meet the relatively permanent standard if they have a
continuous surface connection to a relatively permanent impoundment or a jurisdictional
tributary when the jurisdictional tributary meets the relatively permanent standard. See
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

14

-------
Final Rule Preamble Section IV.C.5.c.ii for further discussion of continuous surface
connection.

Finally, the agencies disagree with the commenter who stated that it is improper to assert
jurisdiction over wetlands adjacent to relatively permanent impoundments if such
impoundments are not themselves connected to a traditional interstate navigable water. See
Final Rule Preamble Section IV.C.3.C. The agencies' implementation of the paragraph
(a)(2) impoundments category is based on two primary principles. First, as a matter of
policy, law, and science, impoundments do not render "waters of the United States" no
longer "waters of the United States." Second, as a matter of policy and science, if an
impounded water has the characteristics of another jurisdictional water, then the
impoundment is jurisdictional. Wetlands adjacent to these impoundments are jurisdictional
if they have a continuous surface connection to relatively permanent impoundments or are
adjacent to paragraph (a)(2) impoundments and meet the significant nexus standard. The
final rule protects these adjacent wetlands because of the ecological relationship between
adjacent wetlands and jurisdictional waters.

10.2.1 Prior regulatory regimes

A few commenters wrote in support of the 2020 NWPR and its "categorical" approach to wetlands and
adjacency and said it was easily recognizable to landowners and transportation planners, while consistent
with the original scope of the CWA. A few of these commenters challenged what they characterized as
the agencies' assertion that the 2020 NWPR was difficult to implement. Specifically, "the agencies claim
in the preamble that their staff found it difficult to implement the NWPR adjacency definition, in certain
circumstances. Only a few examples of these 'difficulties' were provided by the agencies in the preamble,
but these difficulties could have been addressed through minor revisions to the NWPR adjacency
definition or inclusion of field-based indicators. Rather than build on to the NWPR's definition to address
the limitations in certain circumstances, the agencies decided to retain the long-standing and ambiguous
1986 definition."

Another commenter critiqued the inconsistent use of the terms "dry land" and "upland," (e.g., in the
context of exclusions or the significant nexus standard). They called for "replacing the term 'dry land'
with the term 'upland,' with a clear definition of 'upland' codified in the rule. These commenters
generally supported the 2020 NWPR's approach to the definition of adjacent wetlands and in defining
upland.

Other commenters critiqued the 2020 NWPR's approach to wetlands and adjacency. Those commenters
called for broader protections and challenged the 2020 NWPR's more narrow approach, particularly
related to subsurface connections and adjacency. Some commenters characterized the 2020 NWPR's
approach as inconsistent with science.

Several commenters wrote in favor of the 2015 Clean Water Rule's approach, stating that it was
consistent with science. A couple of the commenters thought the 2015 Clean Water Rule expanded
jurisdiction for adjacent wetlands and argued that it created "uncertainty." A number of commenters
wrote about the pre-2015 regulatory regime and/or 1986 regulations and approaches to wetlands and/or
adjacency. Some of these commenters critiqued the pre-2015 regulatory regime for not being protective

enough and/or causing confusion, generally citing scientific or regulatory reasons. A number of	

Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

15

-------
commenters generally supported returning to the pre-2015 regulatory regime, with some calling for
additional clarifications and implementation support. Others critiqued the pre-2015 regulatory regime,
citing implementation challenges and regulatory overreach. A few commenters argued that the proposed
rule's approach to wetlands and definitions goes beyond the pre-2015 regulatory regime. A commenter
broadly critiqued the concept of wetland adjacency in both the 2015 Clean Water Rule and the proposed
rule.

Agencies' Response: As the agencies explain in Section IV.B.3 of the preamble to the final
rule, implementing the adjacency definition of the 2020 NWPR posed challenges. The
agencies disagree with the commenter who stated that the implementation problems with
the 2020 NWPR could have been addressed with minor revisions. The "typical year"
concept was fundamental to the 2020 NWPR because it is the only way that the 2020 NWPR
could make its bright line exclusions work. It proved extremely difficult to implement for
the reasons discussed in the preamble and the agencies are not aware of minor revisions
that could have addressed these difficulties. However, the agencies incorporated some
concepts from the 2020 NWPR's interpretation of adjacency in addressing the "continuous
surface connection" component of the relatively permanent standard, as discussed in
Section IV.C.5 of the preamble to the final rule. The agencies are also codifying the
significant nexus standard for the reasons discussed in Section IV.A of the preamble to the
final rule.

The agencies agree that use of the terms "upland" and "dry land" interchangeably may be
confusing and lead to inconsistent implementation of the rule. The proposed rule and the
pre-2015 regulatory regime used the phrases "dry land" and "upland" interchangeably in
their description of features that the agencies considered to be generally non-jurisdictional.
In the final regulatory text for these exclusions, the agencies are consistently using the term
"dry land" rather than "upland." The term "dry land" refers to areas of the geographic
landscape that do not include waters such as streams, rivers, wetlands, lakes, ponds, tidal
waters, ditches, and the like. It is important to note that jurisdictional and non-
jurisdictional waters are not considered "dry land" just because they lack water at a given
time. Similarly, an area may remain "dry land" even if it is wet after a precipitation event.
The agencies are not adopting the 2020 NWPR's definition of "upland" as any area that
does not satisfy the regulatory definition of wetland and that does not lie below the ordinary
high water mark or the high tide line of a jurisdictional water. The agencies have concluded
that defining "upland" as an area that does not satisfy certain regulatory criteria would be
confusing. The agencies prefer to use the more intuitive, plain meaning approach that refers
to dry land as areas that do not include waters, as opposed to the converse of a regulatory
definition.

The agencies agree with commenters who stated that the definition of "adjacent wetlands"
in the 2020 NWPR was inconsistent with science and that the 2015 Rule's protections were
more consistent with science. The agencies ultimately decided to use the familiar framework
of the pre-2015 regulatory regime. The agencies find that this final rule increases clarity
and implementability by streamlining and restructuring the 1986 regulations and providing
implementation guidance informed by sound science, implementation tools, and other
resources. Further, because this rule is founded upon a longstanding regulatory framework
and reflects consideration of the agencies' experience and expertise, as well as updates in
implementation tools and resources, the agencies find that the final rule is generally
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

16

-------
familiar to the public and implementable. Consistent implementation of the final rule will
be aided by improved and increased scientific and technical information and tools that both
the agencies and the public can use to determine whether waters meet the definition of
"waters of the United States." See Final Rule Preamble Section IV.G.

This rule allows for the consideration of shallow subsurface connections in assessing
jurisdiction over adjacent wetlands. The agencies conclude that consideration of shallow
subsurface hydrologic connections is consistent with longstanding agency practice and note
waters that possess a shallow subsurface connection are only jurisdictional where they meet
the requirements under paragraph (a) of the final rule. Further, the agencies find that
consideration of shallow subsurface flow as a factor in determining if waters meet the
applicable standards to be "waters of the United States" is not inconsistent with the long-
recognized understanding that groundwater is not a "water of the United States."

10.2.2	Regulatory text

A number of commenters discussed the parenthetical in the "adjacent wetlands" category (i.e.. "(other
than waters that are themselves wetlands)"). Many commenters argued in favor of removing the
parenthetical, claiming that it created "confusion," with most commenters citing concerns that the
parenthetical could improperly limit jurisdiction of wetlands, for example leading some wetlands "to be
targeted by polluters wishing to exploit the poorly worded parenthetical." A few commenters voiced
support for keeping the parenthetical.

Agencies' Response: The agencies agree with those commenters who supported removing
the parenthetical. The final rule does not alter the long-standing definition of "wetlands" or
"adjacency." As discussed in Preamble Section IV.C.5.b.i, the parenthetical created
unnecessary confusion for the public. Therefore, the agencies deleted the parenthetical in
the final rule in order to streamline the regulation and provide more clarity.

10.2.3	Subsurface hydrology and distance

In calling for "the inclusion of certain subsurface hydrologic connections in the definition of WOTUS"
and highlighting karst geology in New Jersey, one commenter, "urge[d] the agencies to further explore
subsurface hydrology in round two of the rulemaking process." The same commenter voiced support for
"the inclusion of certain subsurface hydrologic connections in the definition of WOTUS," especially
based on karst geology in their state. Several commenters highlighted the importance of subsurface flows.
Some of these commenters critiqued the 2020 NWPR's approach to subsurface flows on scientific
grounds and the fact that it did not consider subsurface flows as establishing connections for purposes of
jurisdiction, other than subterranean rivers.

A few commenters referenced the importance of protecting floodplain wetlands. For example, a
commenter highlighted that "riparian/floodplain wetlands that rarely flood (e.g., lack direct perennial or
intermittent hydrologic surface connections with other WOTUS) can be important because of long-lasting
effects on streams and rivers. Most of the major changes in sediment load and river-channel structure that
are critical to maintaining the health of a river result from large floods that provide infrequent connections
with more distant riparian/floodplain wetlands." A few commenters called for including subsurface flow
as a parameter for regulating adjacent wetlands. One commenter suggested clarifications on subsurface
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

17

-------
and surface flows and more information on hydrologic connections between them. One commenter did
not write specifically about "subsurface" flows but wrote more generally about broad hydrologic
interconnectedness between wetlands and other waterbodies, even if subsurface flow isn't readily
apparent.

Other commenters argued against jurisdiction based on subsurface flows due to a lack of clarity and/or
vagueness and highlighted associated implementation challenges. A few commenters shared that "the
agencies do not define "shallow" subsurface connection or demonstrate how to distinguish such
connections from groundwater. Moreover, the term introduces significant implementation challenges and
establishing adjacency based on such connections comes dangerously close to the "any hydrological
connection" test rejected in Rapanos."

A number of the commenters who wrote about subsurface flows also wrote about distance considerations
for adjacency. One commenter argued that "a scientifically informed definition of 'adjacent' should focus
on functional relationships, informed by proximity, but not be based on distance alone." This commenter
described the approach to distance requirements (or lack thereof) in the pre-2015 regulatory regime, under
the 2015 Clean Water Rule, and under the 2020 NWPR. The commenter suggested "that the final Rule
explanation of the definition of "adjacency" focus[es] on functional relationships, including both surface
and shallow subsurface connections, informed by proximity, but not based on distance alone" and argued
against the 2020 NWPR approach, as well as the 2015 Clean Water Rule approach, unless providing
scientific analysis, including on functionality. Another commenter explained that "the agencies do not
define what it means to be an "unbroken . . . shallow subsurface connection" or how to distinguish such
connections from groundwater. The same commenter asked whether there are any limitations on the
distance of the sub-surface connection between the "adjacent" wetland and the non-navigable water, and
how deep can such connections be and still be considered "shallow."'

Commenters argued that any distance criteria should account for regional differences. One commenter
called for regionally quantitative criteria in the second rulemaking. A few of these commenters critiqued
the use of the terms "reasonably close" as too general and broad, with unclear field application, calling for
clarity. One commenter suggested the final rule assign a range of values for adjacency on the scale of feet
or yards, as opposed to hundreds of yards or miles. Another commenter specifically argued that such
distance criteria are not consistent with the "plurality's test" from the Rapanos case. An additional
commenter called for more objective criteria, arguing "the greater the distance and the more tenuous a
connection to a TNW, the stronger the site-specific evidence is needed to assert jurisdiction."

Agencies' Response: The agencies have determined that certain subsurface hydrologic
connections should be considered when determining if a particular aquatic resource meets
the definition of "waters of the United States." The agencies consider shallow subsurface
hydrologic connections to play an important role in determining adjacency and have
determined that shallow subsurface flow is one of the factors to be considered as part of the
significant nexus analysis. See Sections III.B.ii and of the TSD. The agencies conclude that
consideration of shallow subsurface hydrologic connections is consistent with longstanding
agency practice and note that waters that possess a shallow subsurface connection to other
jurisdictional waters are only themselves jurisdictional where they meet the requirements
under paragraph (a) of the final rule. Further, the agencies find that consideration of
shallow subsurface flow as a factor in determining if waters meet the applicable standards
to be "waters of the United States" is not inconsistent with the long-recognized
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

18

-------
understanding that groundwater is not a "water of the United States." The agencies also
recognize the role of karst geology in conveying subsurface hydrologic flow.

The agencies recognize that wetlands lacking a direct perennial or intermittent hydrologic
surface connection with other jurisdictional waters can still be connected to the waters they
are located near and can have important effects on paragraph (a)(1) waters. For instance,
wetlands with an unbroken shallow subsurface connection to paragraph (a)(1) water, a
paragraph (a)(2) impoundment, or paragraph (a)(3) tributary are "adjacent" under the
final rule, consistent with the pre-2015 regulatory regime. A shallow subsurface hydrologic
connection is predominantly lateral water flow through a shallow subsurface layer. Such
flows may be found, for example, in wetlands on slopes, where water seeps through surface
soils to downstream waters; in soils with a restrictive horizon; in the hyporheic zone; or in
karst systems. A shallow subsurface connection also exists, for example, when the adjacent
wetland and the water to which it is adjacent are in contact with the same shallow aquifer
or with the same shallow water table which fluctuates within the soil profile, sometimes
rising to or near the ground surface. Shallow subsurface connections can also be maintained
as water moves through karst topography and through confined human-made subsurface
conveyance systems such as drain tiles and storm sewers. Shallow subsurface connections
may be found below the ordinary root zone (below 12 inches), where other wetland
delineation factors may not be present. A variety of factors may reflect the presence of a
shallow subsurface connection, including position of the wetland in the landscape (for
example, on a slope above the jurisdictional waters); stream hydrographs; soil surveys (for
example, exhibiting indicators of high transmissivity over an impermeable layer); and
information indicating that the water table in the stream is lower than the shallow
subsurface. Shallow subsurface connections convey water quickly through the soil and
impact surface water directly within hours or days rather than the months or years it may
take long pathways to reach surface waters. However, the agencies note that neither shallow
subsurface connections nor any type of groundwater, shallow or deep, are themselves
"waters of the United States." See TSD section III.B.ii for additional information on surface
and shallow subsurface hydrologic connections.

In Section IV.C.5.C of the Preamble, the agencies clarify the difference between shallow
subsurface hydrologic connections and groundwater. Shallow subsurface hydrologic
connection is predominantly lateral water flow through a shallow subsurface layer, where
the flow maintains the same or very nearly the same flow volume underground and at the
downgradient point where it returns to the surface. Such flows may be found, for example,
in steeply seeping forested areas with shallow soils, soils with a restrictive horizon, in the
hyporheic zone, or in karst systems. However, neither shallow subsurface connections nor
any type of groundwater, shallow or deep, are themselves "waters of the United States."

This rule does not establish specific distance limitations for adjacency, to ensure that site-
specific and regional factors can be considered when a wetland is being evaluated for
adjacency. The agencies have not established a specific distance limitation in the rule
beyond which wetlands are never adjacent because whether a wetland is reasonably close,
such that the wetland and the jurisdictional water are part of the same aquatic ecosystem,
depends on regional variations in climate, landscape, and geomorphology. However, the
agencies can state, based on nearly 45 years of implementation of this definition, that in a
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

19

-------
substantial number of cases, adjacent wetlands abut (/.e., touch) a jurisdictional water. And,
on the whole, nationwide, adjacent wetlands are within a few hundred feet from
jurisdictional waters; in the instances where the distance is greater than a few hundred feet,
adjacency is likely supported by a pipe, non-jurisdictional ditch, karst geology, or some
other feature that connects the wetland directly to the jurisdictional water. While bright-
line rules (for example, wetlands that are a specific number of feet from a jurisdictional
water are not "adjacent") are easiest to understand and implement, convenience is not the
only goal the agencies must consider in administering the Clean Water Act. Because the
relationship between a wetland and a proximate jurisdictional water can depend upon a
number of site-specific factors, like climate, geomorphology, landscapes, hydrology, and size
of the jurisdictional water (e.g., the ocean compared to a headwater stream), and because
the central purpose of the Act is to protect the integrity of our nation's waters, a more
nuanced analysis is required. See Final Rule Preamble Section IV.C.5. For purposes of
determining whether a wetland is "adjacent," artificial structures do not divide a wetland if
a hydrologic connection is maintained between the divided portions of the wetland. Rather,
the wetland is treated as one wetland. For example, if a wetland is divided by a road, a
culvert could maintain a hydrologic connection. The agencies may also consider if a
subsurface hydrologic connection is maintained, using indicators such as hydric soils, the
permeability of the artificial structure, and/or the permeability of the soils below the
artificial structure.

Wetlands are also adjacent when their proximity to a jurisdictional water is reasonably
close. The ecological relationship between jurisdictional waters and their adjacent wetlands
is well-documented in the scientific literature and reflects their physical proximity as well as
shared hydrological and biological characteristics. See TSD section III.B. The close
proximity between an adjacent wetland and a jurisdictional water means the wetland can
modulate water quantity and water quality in the jurisdictional water, and the
jurisdictional water can modulate water quantity and quality in the wetland. For example,
adjacent wetlands typically help to store floodwaters, pollutants, and sediments that could
otherwise reach a jurisdictional water. They also provide flow contributions to the waters
which they are adjacent during high hydroperiods, where water spills from the wetland to
the nearby jurisdictional water, and such contributions of flow are facilitated by their close
proximity to the jurisdictional water. The proximate jurisdictional waters can serve as
important sources of water for adjacent wetlands, for example, through overtopping events
where flow from the jurisdictional waters is stored in the wetlands. A wetland within the
riparian area or floodplain of a jurisdictional water typically has such an interconnection,
though this rule is not establishing a requirement for adjacent wetlands to be located within
a riparian area or floodplain. While under this rule the agencies are not establishing
distance limits for adjacency, the agencies recognize that as the distance between the
wetland and jurisdictional water increases, the reasonableness of the connection between
the waters will generally decrease, particularly in the absence of the type of surface or
shallow subsurface connections described above, and a finding of adjacency is less likely.
The distance between a jurisdictional water and its adjacent wetlands may vary by region,
as well as based on site-specific factors within regions. In practice, under this criterion, the
agencies have found that adjacent wetlands are on the whole, nationwide, within a few
hundred feet of jurisdictional waters. This can vary from site to site and region to region
due to differences in climate, geomorphology, landscape setting, hydrology, soils, vegetation,
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 10 - Wetlands and Adjacency

20

-------
elevation, size of the jurisdictional water, and other site-specific variables. See Final Rule
Preamble Section IV.C.5.C. for further discussion.

In regard to comments relating to a second rulemaking, in the preamble to the proposed
rule, the agencies stated that they would consider changes through a second rulemaking
that they anticipated proposing in the future, which would build upon the foundation of this
rule. The agencies have concluded that this rule is durable and implementable because it is
founded on the familiar framework of the 1986 regulations, fully consistent with the statute,
informed by relevant Supreme Court decisions, and reflects the record before the agencies,
including consideration of the best available science, as well as the agencies' expertise and
experience implementing the pre-2015 regulatory regime. The agencies may consider
further refinements in a future rule to address implementation or other issues that may
arise.

Regarding the term "reasonably close" and its consistency with the Rapanos case, see the
agencies' response to comments in Section 2.3.5 for a response to comments regarding the
agencies' legal authority over wetlands, including consistency with Supreme Court case law.

10.2.4 Bordering, contiguous, neighboring

Some commenters who wrote about adjacency discussed the concepts of bordering, contiguous, and/or
neighboring, including in some cases whether natural and/or artificial barriers (e.g., berms) should be
taken into consideration. For example, some commenters supported inclusion of wetlands separated by
man-made dikes or barriers, natural river berms, beach dunes and the like. A few commenters opposed
this approach and stated that including wetlands physically separated by man-made dikes, barriers or
natural breaks would include wetlands that have no relationship to the adjacent traditional navigable
water.

One commenter wrote in support of "bordering or contiguous" but not "neighboring" because that term
was not defined and would lead to "confusion and/or inconsistent application." Other commenters
suggested the agencies use the "neighboring" concept but more clearly define it to avoid confusion. Some
commenters called for the concept of "neighboring" to be applied in a "uniform" and "consistent" manner
"across all [Corps] Districts," with one commenter arguing, "the application of the term has led to widely
varying interpretation of the limits of 'waters of the United States.'" In some cases, neighboring wetlands
are merely yards away, while other neighboring wetlands may approach a mile from the nearest
jurisdictional water.

Another commenter suggested clarifying distance requirements for "neighboring." One commenter
suggested providing clarification and definition for the term "neighboring" and argued that neighboring
wetlands should include "those wetlands located within a federally regulated 100-year floodplain of a
jurisdictional water and are separated by a man-made or natural barrier from the jurisdictional water or
lack a direct hydrological connection to it." Another commenter suggested defining "bordering,
contiguous, and neighboring," because of "confusion and disagreement during the pre-2015 regulatory
regime." One commenter also suggested clarifications but generally supported the agencies' proposed
approach.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

21

-------
One commenter stated that measuring floodplains by a hydrogeomorphic boundary, such as a 100-year
flood, could be confusing, as constructed barriers, such as levees, could cut off connections to
downstream waters and thereby cut off jurisdiction.

One commenter requested regional guidance regarding jurisdictional determination of flooding that
creates wetland hydrology.

Agencies' Response: The agencies will continue to implement a number of longstanding
interpretations of "adjacent" based on scientific principles and practical administration of
the definition with this rule. The agencies consider wetlands "adjacent" if one of following
three criteria is satisfied. First, there is an unbroken surface or shallow subsurface
connection to jurisdictional waters. All wetlands that directly abut jurisdictional waters
have an unbroken surface or shallow subsurface connection because they physically touch
the jurisdictional water. Wetlands that do not directly abut a jurisdictional water may have
an unbroken surface or shallow subsurface connection to jurisdictional waters. Water does
not need to be continuously present in the surface or shallow subsurface connection.

Second, the wetlands are physically separated from jurisdictional waters by human-made
dikes or barriers, or natural landforms (e.g., river berms, beach dunes). Or third, the
wetlands proximity to a jurisdictional water is reasonably close. Wetlands that meet one of
these three criteria are considered bordering, contiguous, or neighboring for purposes of
this rule. See the Final Rule Preamble Section IV.C.5 for further discussion on the
implementation of these definitions.

While this rule does not explicitly identify regional factors that influence what is
"reasonably close" for purposes of adjacency, the agencies recognize there may be site-
specific factors (e.g., topography) that influence what is "reasonably close." This rule does
not establish specific distance limitations for adjacency, which helps ensure that site-specific
and regional factors can be considered when a wetland is being evaluated (see Section
IV.C.6.C of the Final Rule Preamble). The agencies have not established a specific distance
limitation in the rule beyond which wetlands are never adjacent because whether a wetland
is reasonably close such that the wetland and the jurisdictional water are part of the same
aquatic ecosystem depends on regional variations in climate, landscape, and
geomorphology. However, the agencies can state, based on nearly 45 years of
implementation of this definition, that in a substantial number of cases, adjacent wetlands
abut (/.e., touch) a jurisdictional water. And, on the whole, nationwide, adjacent wetlands
are within a few hundred feet from jurisdictional waters; in the instances where the
distance is greater than a few hundred feet, adjacency is likely supported by a pipe, non-
jurisdictional ditch, karst geology, or some other feature that connects the wetland directly
to the jurisdictional water. While bright-line rules (for example, wetlands that are a specific
number of feet from a jurisdictional water are not "adjacent") are easiest to understand
and implement, convenience is not the only goal the agencies must consider in administering
the Clean Water Act. Because the relationship between a wetland and a proximate
jurisdictional water can depend upon a number of site-specific factors, like climate,
geomorphology, landscapes, hydrology, and size of the jurisdictional water (e.g., the ocean
compared to a headwater stream), and because the central purpose of the Act is to protect
the integrity of our nation's waters, a more nuanced analysis is required. See Final Rule
Preamble Section IV.C.5.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

22

-------
The agencies agree with commenters in support of the 1986 regulation's definition of
"adjacent" to include wetlands even if they are separated by natural landforms or human-
made barriers for the reasons discussed in sections IV.A.3 and IV.C.8.b of the Final Rule
Preamble. The rationale for including these wetlands as adjacent is discussed in sections
IV.A and IV.C.5 of the Preamble for the Final Rule. This approach is also supported by
scientific literature and aligns with the agencies' scientific and technical expertise and
experience, which confirm that wetlands separated by other jurisdictional waters from
constructed dikes or barriers, natural river berms, beach dunes, and the like have chemical,
physical, and biological effects on downstream waters. See TSD section III.B.

Although a wetland within the riparian area or floodplain usually has an interconnection,
this rule is not establishing a requirement for adjacent wetlands to be located within a
riparian area or floodplain as wetlands not located within federally regulated 100-year
floodplain of a jurisdictional water provide numerous functions that benefit downstream
water integrity. The scientific literature unequivocally demonstrates that wetlands and open
waters in non-floodplain landscape settings (hereafter called "non-floodplain wetlands")
can provide numerous functions that benefit the chemical, physical, and biological integrity
of larger downstream waters, including the paragraph (a)(1) waters, particularly when
analyzed in the aggregate. These functions include: storage of floodwater; recharge of
groundwater that sustains river baseflow; retention and transformation of nutrients,
metals, and pesticides; export of organisms or reproductive propagules (e.gseeds, eggs,
spores) to downstream waters; and habitats needed for stream species. This diverse group
of wetlands (e.g., many prairie potholes, vernal pools, playa lakes) can be connected to
downstream waters through surface water, shallow subsurface water, and groundwater
flows and through biological and chemical connections. Some effects of non-floodplain
wetlands on larger downstream waters are due to their relative isolation, rather than their
connectivity. Where the wetland intercepts materials that otherwise would reach
downstream water, wetland "sink" functions trap materials and prevent their export to
downstream waters (e.g., sediment and entrained pollutant removal, water storage). See
TSD Sections I, III.B, and III.D.

As with any final regulation, the agencies will consider developing new guidance to facilitate
implementation of the final rule should questions arise in the field regarding application of
the final rule to regional settings. Nevertheless, the agencies conclude that the final rule,
together with the preamble and existing tools, provides sufficient clarity to allow consistent
implementation of the final rule.

10.2.5 Wetlands adjacent to lakes, ponds, and impoundments

One commenter stated that for wetlands adjacent to jurisdictional lakes and ponds, a case-specific

determination of jurisdiction may be best. The commenter noted that in Wisconsin, many lakes "can be

determined to be foundational6 waters on the basis that they are susceptible of supporting waterborne

6 In the proposed rule, the term "foundational waters" was used to refer to traditional navigable waters, the territorial
seas, and interstate waters. In this response to comments, the agencies will preserve the use of the term

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

23

-------
commerce. Wetlands adjacent to these lakes provide spawning and nursery habitat, while smaller lakes
and ponds that may not be fishing destinations can be key breeding habitat for amphibians and other
aquatic life. These wetlands support the biological integrity of other lakes, streams, and wetlands that are
either foundational waters themselves or have a significant nexus to foundational waters."

Several commenters asked the agencies to protect wetlands adjacent to impoundments because science
shows that wetlands have an effect on downstream traditional navigable waters, the territorial seas, and
interstate waters. Some commenters indicated that the proposed rule was unclear with regard to the
inclusion of impoundments and wetlands adjacent to impoundments.

Agencies' Response: The agencies agree that wetlands adjacent to jurisdictional lakes and
ponds can perform many important functions that support the integrity of paragraph (a)(1)
waters. The agencies also agree that wetlands adjacent to impoundments can have an effect
on the integrity of paragraph (a)(1) waters. Wetlands that are adjacent to lakes, ponds, or
impoundments that are paragraph (a)(1) waters are jurisdictional under the final rule.
Wetlands adjacent to lakes and ponds that are tributaries (e.g., in-stream lakes or ponds) to
paragraph (a)(1) waters are jurisdictional if they meet either the relatively permanent
standard or the significant nexus standard. Additionally, wetlands adjacent to paragraph
(a)(2) impoundments are jurisdictional if they meet either the relatively permanent
standard or the significant nexus standard. Wetlands adjacent only to paragraph (a)(5)
waters would themselves be assessed under paragraph (a)(5) of the final rule, and such
wetlands would be jurisdictional if they meet either the relatively permanent standard or
the significant nexus standard.

When evaluating a wetland adjacent to a paragraph (a)(2) impoundment under the
relatively permanent standard, field staff would assess whether the impounded water is
relatively permanent, standing or continuously flowing, and then determine whether the
wetland has a continuous surface connection to the impoundment. See Final Rule Preamble
Section IV.C.3 for more information about wetlands adjacent to impoundments.

10.3 Regulatory Definition of "Wetlands" and Wetland Delineation

Several commenters discussed the proposed rule's definition of "wetlands." A number of commenters
wrote in favor of using the agencies' longstanding regulatory definition of "wetlands" and/or its three
criteria, which requires that a feature meet the three requirements for delineation criteria: hydrology,
hydrophytic vegetation, and hydric soils. One commenter, in their support of the proposed definition of
"wetlands," noted "it makes no changes from the 1986 and 2020 rules." A few commenters, however,
argued that the agencies' applications of the definition of "wetlands" are not always consistent,
specifically in terms of not requiring all three delineation criteria to be met, or use of the term "dry land."

A number of commenters critiqued the proposed definition of "wetlands," for example as "nearly
unrestrained" or "ill defined." The commenter who used the term "ill defined" also argued that the
proposed definition would require professional jurisdiction determinations, which would "contribute

"foundational waters" as used by commenters; however, responses will use "traditional navigable waters, the
territorial seas, and interstate waters" or "paragraph (a)(1) waters," as the final rule does not use the term

"foundational waters."	

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

24

-------
significantly to costs for jurisdiction determinations regardless of permitting and mitigation requirements,
only to be unnecessary for non-jurisdictional waters/wetlands."

A commenter suggested amending the definition of "wetlands" to accept wetland delineations conducted
by the U.S. Department of Agriculture (USDA). Another commenter asked the agencies to clarify that the
definition of "wetlands" does not apply to engineered facilities, such as constructed wetlands.

In the context of adjacency, a few commenters argued that the agencies' three wetland delineation factors
("hydric soils, hydrophytic vegetation, and hydrology") must be present for wetlands to be jurisdictional.
Several commenters specifically discussed wetland delineations, including different agencies' approaches
to them, although this theme is also relevant to several other themes in this summary (e.g., definition of
"wetlands," wetlands jurisdiction, approach to adjacency, distance parameters). One commenter argued,
"it remains unclear as to which methods would be used to delineate the boundary of jurisdictional
wetlands adjacent to WOTUS," and suggested using the agencies' three factor test for defining
"wetlands."

One commenter recommended that federal agencies take a unified approach to wetland delineations and
different delineation manuals, including the following:

•	USDA's Natural Resources Conservation Service (NRCS) and the Food Security Act of 1985

•	U.S. Department of Interior's U.S. Fish and Wildlife Service and the National Wildlife Refuge
System Administration and Duck Stamp Acts

•	EPA and the Corps and the Clean Water Act

The commenter argued, "[a] unified approach by all agencies of the federal government to wetland
identification, delineation, and mitigation would decrease the burden on regulatory agencies, save
administrative costs to the agencies and the regulated community, and help bring clarity and trust back to
the administrative process." The commenter further "encourage[d] the EPA and the Army Corps to enter
into a Memorandum of Agreement with the U.S. Department of Agriculture and the Department of
Interior concerning delineation of wetlands for purposes of the Clean Water Act, Food Security Act, and
management of waterfowl production area easements under the National Wildlife Refuge System Act."
Another commenter argued "the process of delineating the contours of a wetland must be reasonably clear
to an average landowner and capable of consistent, predictable application by field agents" and suggested
a simple approach and pamphlet that landowners could use, instead of a lengthy wetland delineation
manual. That commenter also suggested limiting wetland jurisdiction more broadly to simplify wetland
delineations. One commenter cited one of their own policies that reads: "Federal and state agencies
should only use the guidance set forth in the 1987 Army Corps of Engineers Wetland Delineation Manual
to determine whether an area is considered a 'wetland.'"

Agencies' Response: The agencies disagree with the commentors that regard the definition
of wetland as ill defined, nearly unrestrained, or unclear. The final rule regulatory text
defines the term "wetlands" and the agencies are not amending this longstanding definition
in this rule. The definition of "wetlands" in the final rule is identical to the definition of this
term in the 1986 regulations, 2019 Repeal Rule, and 2020 NWPR. Thus, under the final
rule, the longstanding definition of "wetlands" will remain as "areas that are inundated or
saturated by surface or ground water at a frequency and duration sufficient to support, and
that under normal circumstances do support, a prevalence of vegetation typically adapted
for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

25

-------
similar areas." The agencies note, however, that the definition of "wetlands" in the final
rule can apply to engineered facilities, such as constructed wetlands, if such aquatic
resources meet the definition of "wetlands" under the final rule.

Comments regarding the process for wetland delineations are outside the scope of the final
rule. The agencies note that, as under prior regimes, wetlands are identified in the field in
accordance with the 1987 U.S. Army Corps of Engineers Wetland Delineation Manual and
applicable regional delineation manuals. Field work is often necessary to confirm the
presence of a wetland and to accurately delineate its boundaries. However, in addition to
field observations on hydrology, vegetation, and soils, remote tools and resources can be
used to support the identification of a wetland.

Revised Definition of "Waters of the United States" - Response to Comments Document

Section 10 - Wetlands and Adjacency

26

-------