Precon Development Corp. v. United States Army Corps of Engineers

PUBLISHED

UNITED STATES COURT OF APPEALS
FOR THE FOURTH CIRCUIT

PRECON DEVELOPMENT 
CORPORATION, INCORPORATED,
Plaintiff-Appellant,
v.
UNITED STATES ARMY CORPS OF
ENGINEERS,
Defendant-Appellee.  No. 09-2239

CHESAPEAKE BAY FOUNDATION;
NATIONAL WILDLIFE FEDERATION;
NATURAL RESOURCES DEFENSE
COUNCIL,
Amici Supporting Appellee.

Appeal from the United States District Court
for the Eastern District of Virginia, at Norfolk.
Rebecca Beach Smith, District Judge.
(2:08-cv-00447-RBS-TEM)

Argued: October 28, 2010

Decided: January 25, 2011

Before SHEDD and DUNCAN, Circuit Judges,
and HAMILTON, Senior Circuit Judge.
2 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
Reversed and remanded by published opinion. Judge Duncan
wrote the opinion, in which Judge Shedd and Senior Judge
Hamilton joined.

COUNSEL

ARGUED: Mark R. Baumgartner, PENDER & COWARD,
PC, Virginia Beach, Virginia, for Appellant. Mary Gabrielle
Sprague, UNITED STATES DEPARTMENT OF JUSTICE,
Washington, D.C., for Appellee. ON BRIEF: Douglas E.
Kahle, PENDER & COWARD, PC, Virginia Beach, Virginia,
for Appellant. Ignacia S. Moreno, Assistant Attorney General,
Katherine W. Hazard, Austin D. Saylor, Kent E. Hanson,
Environmental & Natural Resources Division, Appellate Sec-
tion, UNITED STATES DEPARTMENT OF JUSTICE,
Washington, D.C., for Appellee. Deborah M. Murray,
SOUTHERN ENVIRONMENTAL LAW CENTER, Char-
lottesville, Virginia; James G. Murphy, Ramya Sivasubra-
manian, Alex Phipps, NATIONAL WILDLIFE
FEDERATION, Montpelier, Vermont; Jon Devine, Rebecca
Hammer, NATURAL RESOURCES DEFENSE COUNCIL,
Washington, D.C.; Jon A. Mueller, CHESAPEAKE BAY
FOUNDATION, Annapolis, Maryland, for Amici Supporting
Appellee.

OPINION

DUNCAN, Circuit Judge:

This appeal arises out of a determination made by the Army
Corps of Engineers (the "Corps") that it has jurisdiction,
under the Clean Water Act ("CWA"), 33 U.S.C. § 1251 et
seq., over 4.8 acres of wetlands located on Precon Develop-
ment Corporation’s ("Precon"’s) property, approximately
seven miles from the nearest navigable water. The Corps sub-
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 3
sequently denied Precon’s application for a CWA permit to
impact the wetlands through development. Precon appealed
these determinations to the United States District Court for
the Eastern District of Virginia under the Administrative Pro-
cedure Act ("APA"), 5 U.S.C. § 702, and the parties cross-
moved for summary judgment. The district court granted
summary judgment to the Corps on September 4, 2009,
upholding both its jurisdictional determination and its permit
denial. On appeal, Precon challenges only the Corps’ jurisdic-
tional determination. Because we find the Corps’ administra-
tive record inadequate to support its conclusion that it had
jurisdiction over Precon’s wetlands, we vacate the district
court’s grant of summary judgment and remand to the district
court with instructions to remand to the Corps for reconsider-
ation of its jurisdiction over the wetlands in question.

I.

A.

Precon is the developer of a 658-acre Planned Unit Devel-
opment known as Edinburgh (the "Edinburgh PUD"), located
in Chesapeake, Virginia. The city of Chesapeake is in south-
eastern Virginia, a region historically comprised of forested
wetlands. Many of these wetlands ultimately drain into the
Northwest River, which flows south through the region, pass-
ing within five to ten miles of the Edinburgh PUD.

The Edinburgh PUD is a mixed-use development that con-
tains both residences and retail establishments. Its construc-
tion began in 2001. Precon acquired the Edinburgh PUD from
RGM Corporation ("RGM"), the initial developer, in 2003.
Since 2003, Precon has pursued the development of several
residential areas within the Edinburgh PUD. Between 2004
and 2006, the Corps granted Precon permits to fill 77 acres of
wetlands in order to proceed with these developments, based
in part on an understanding that this was the totality of the
development planned for the Edinburgh PUD.
4 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
In 2006, Precon announced a plan to develop ten additional
residential lots in the Edinburgh PUD. The original plan for
developing these lots required filling 10.7 acres of wetlands.
However, after discussions with the Corps in which the Corps
expressed its displeasure that Precon was separately pursuing
additional residential development, Precon limited its pro-
posed design so that it would only impact 4.8 acres of wet-
lands (the "Site Wetlands"). Precon further suggested that it
did not believe the Corps had jurisdiction over these 4.8 acres.
The Corps disagreed.

A detailed explanation of the geography of the Site Wet-
lands is critical to understanding the parties’ dispute. The Site
Wetlands are in the southwest quadrant of the Edinburgh
PUD and sit adjacent to a man-made drainage ditch approxi-
mately 2,500 feet long (the "2,500-foot Ditch").1 The Site
Wetlands do not, however, abut the 2,500-foot Ditch, because
when the 2,500-foot Ditch was excavated through the sur-
rounding wetlands in 1977, "[m]aterial excavated . . . was
side-cast on the east bank and therefore creates a berm
between the [Site Wetlands] and the ditch."2 J.A. 264.

The 2,500-foot Ditch, which flows seasonally—i.e., from
late winter to early spring—joins a larger, perennial drainage
ditch, the Saint Brides Ditch, approximately 900 feet down-
stream of the Site Wetlands. The Saint Brides Ditch runs
along the western boundary of the PUD for approximately
3,000 feet before continuing to meet a second perennial tribu-
tary about two and one-half to three miles south of the Edin-
burgh PUD. These merged tributaries flow into the Northwest
River approximately three to four miles downstream.
1
Adjacent, per the Corps’ relevant regulations, means "bordering, con-
tiguous, or neighboring. Wetlands separated from other waters of the
United States by man-made dikes or barriers, natural river berms, beach
dunes and the like are ‘adjacent wetlands.’" 33 C.F.R. § 328.3(c).
2
A "berm," as used in this context, is "[a] raised bank or path," or "[a]
mound or bank of earth, used especially as a barrier . . . ." American Heri-
tage Dictionary 171 (4th ed. 2006).
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 5
The 4.8-acre Site Wetlands comprise only a small portion
of the total wetland acreage within the Edinburgh PUD. There
are, in total, 166 acres of wetlands in the PUD that are part
of the Northwest River watershed.3 The remainder of the 166
acres are concentrated along the western edge of the PUD and
surround the 2,500-foot Ditch and the Saint Brides Ditch.

B.

In 2007, Precon applied to the Corps for a jurisdictional
determination as to whether the Site Wetlands were covered
by the CWA, such that a permit would be needed before they
could be impacted by development. Precon further requested
a permit to fill the Site Wetlands if the Corps determined that
a permit was required under the CWA.

On May 31, 2007, the Corps determined that it had jurisdic-
tion over the Site Wetlands, on the ground that the wetlands
sat adjacent to a ditch which qualified as "waters of the
United States." J.A. 202. It subsequently denied Precon’s
request for a CWA permit. Precon administratively appealed
both determinations. Around this same time, the Corps and
the Environmental Protection Agency ("EPA") jointly issued
new guidance (the "Rapanos Guidance," issued June 5, 2007)
on CWA jurisdiction following the Supreme Court’s
jurisdiction-limiting decision in Rapanos v. United States, 547
U.S. 715 (2006). In light of the Rapanos Guidance, a Corps
appeals officer remanded the Corps’ jurisdictional determina-
tion to the Corps’ Norfolk District for reconsideration.

i.

The Rapanos Guidance instructs Corps and EPA personnel
3
The Edinburgh PUD is situated on a drainage divide, meaning that only
a portion of the property drains towards the Northwest River. Additional
acres of wetlands on the Edinburgh PUD, which drain towards the Intra-
coastal Waterway, are not relevant for purposes of this opinion.
6 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
on how to make jurisdictional determinations that comply
with the new rules for CWA jurisdiction announced by the
Supreme Court in Rapanos.4 The Guidance explains that post-
Rapanos, wetlands, such as the Site Wetlands, which are "ad-
jacent to, but not directly abutting, a relatively permanent trib-
utary (e.g., separated from it by uplands, a berm, dike or
similar feature)," are no longer automatically subject to the
Corps’ jurisdiction. J.A. 484. Pursuant to the Supreme Court’s
decision, the Rapanos Guidance instructs the Corps to evalu-
ate such wetlands, along with "similarly situated" wetlands in
the area, in order to determine whether they have a "signifi-
cant nexus" with traditional navigable waters. Id.; see also
Rapanos, 547 U.S. at 780.

The first step in evaluating whether a significant nexus
exists, according to the Rapanos Guidance, is to determine the
region to be evaluated for significance. To do so, the relevant
tributary must first be identified. A "tributary" for these pur-
poses is defined as "the entire reach of the stream that is of
the same order (i.e., from the point of confluence, where two
lower order streams meet to form the tributary, downstream
to the point such tributary enters a higher order stream)." J.A.
486. The pertinent section of the relevant tributary is known
as the "relevant reach." Id. at 261. The Corps must next iden-
tify all wetlands adjacent to the relevant reach. Together, the
relevant reach and its adjacent wetlands constitute the area to
be evaluated for a significant nexus with a traditional naviga-
ble water.
4
The version of the Rapanos Guidance utilized by the Corps, and thus
the one described here, is the version dated June 5, 2007, and included
within the Joint Appendix. The Guidance has since been updated, and the
current version of the Guidance is available on the Corps’ website. See
U.S. Envt’l Prot. Agency & U.S. Army Corps of Eng’rs, Clean Water Act
Jurisdiction Following the U.S Supreme Court’s Decision in Rapanos v.
United States & Carabell v. United States (Dec. 2, 2008), available at
http://www.usace.army.mil/CECW/Documents/cecwo/reg/cwa_guide/cwa
_juris_2dec08.pdf.
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 7
The Rapanos Guidance explains that such evaluation
should focus on the flow and functions of the relevant reach
and adjacent wetlands. It instructs the Corps to specifically
consider "volume, duration, and frequency" of flow in the rel-
evant reach, as well as hydrologic information, physical char-
acteristics, and functions performed by the relevant reach and
its wetlands. Id. at 487. The Guidance then instructs the
Corps, "after assessing the flow characteristics and functions,"
to evaluate whether these factors "are likely to have an effect
that is more than speculative or insubstantial on the chemical,
physical, and biological integrity of a traditional navigable
water." J.A. 487. It emphasizes that "[a]s the distance from
the tributary to the nagivable water increases, it will become
increasingly important to document whether the tributary and
its adjacent wetlands have a significant nexus rather than a
speculative or insubstantial nexus with a traditional navigable
water." Id.

ii.

Upon remand and application of this new guidance, the
Corps upheld its finding of jurisdiction over the Site Wet-
lands. Because the Site Wetlands do not abut—but only sit
adjacent to—the 2,500-foot Ditch, the Corps did not treat
them as automatically subject to jurisdiction, but instead, as
instructed by the Rapanos Guidance, attempted to explain its
rationale for upholding jurisdiction through a "Significant
Nexus Determination."

First, the Corps’ Significant Nexus Determination identi-
fied the relevant reach as the 2,500-foot Ditch and the Saint
Brides Ditch, collectively. The Corps considered these ditches
collectively because the Saint Brides Ditch and the 2,500-foot
Ditch are, historically, part of the same naturally defined wet-
land drainage feature—a feature that was manipulated into
discrete ditches in the late 1970s. Further, the Corps labeled
both the Saint Brides Ditch, which undisputedly has perennial
flow, and the 2,500-foot Ditch as "relatively permanent
8 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
waters." The Corps defines "relatively permanent waters" as
tributaries that "typically flow[ ] year-round or ha[ve] contin-
uous flow at least ‘seasonally’ (e.g., typically 3 months)." Id.
at 242. The Corps found the 2,500-foot ditch to be a relatively
permanent water because photographs supported the conclu-
sion that the tributary flowed from February through April.
Together, these two ditches were labeled as "a man-altered,
first-order tributary to the Northwest River." Id. at 259.

The Corps then determined that the relevant reach of this
tributary extended to the point, downstream 3.11 miles, where
the Saint Brides Ditch joined the Pleasant Grove Swamp. In
making this determination, the Corps ignored "[m]ultiple
man-made or manipulated drainage ditches" that carried
minor flow to the Saint Brides Ditch at various points down-
stream of the Edinburgh PUD, and instead selected the point
where the Saint Brides Ditch converged with another histori-
cally natural drainage. Id.

The Corps next took up the task of identifying "similarly
situated wetlands." It first identified all 166 acres of wetlands
located within the Edinburgh PUD and the Northwest River
watershed as similarly situated. Although the 4.8-acre Site
Wetlands are separated from the remaining approximately
161 acres of wetlands by a road that is unfinished (filled but
not paved), the Corps focused on this larger area because "the
4.8 acres of wetlands function as one with the remainder of
the 166 acres of on site wetlands in the Saint Brides Ditch
drainage area." Id. at 265. A berm separates these 166 acres
of wetlands from the Saint Brides Ditch, but it has several
breaks along its eastern edge.

The Corps then identified 282 more acres of "similarly situ-
ated wetlands" adjacent to the relevant reach but not on Pre-
con’s property. In determining that these 448 acres of
wetlands should be evaluated in the aggregate, the Corps
explained that the 4.8 acres of Site Wetlands and 166 acres of
PUD wetlands are part of a "physical, chemical and biological
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 9
connection of wetlands and streams" that exists, and "has
always existed," in the area. Id. at 267.

Again in accordance with the Rapanos Guidance, the
Corps’ Significant Nexus Determination analyzed the func-
tions and flow of the Saint Brides Ditch and the 2,500-foot
Ditch. With respect to the Saint Brides Ditch, the Corps noted
that the channel has a dynamic storage capacity of approxi-
mately 1.2 million cubic feet of water, a channel slope of 0.04
percent, and water velocities of approximately 1.3 feet per
second—all of which means that it takes a volume of water
approximately four hours to move through the relevant
reach. Based on these observations, the Corps found that the
ditch "greatly moderates the effect of flood flows" on the
Northwest River due to its large storage capacity and slow
release. Id. at 263. Additionally, it concluded that this low
water velocity and extended residence time allowed sus-
pended sediments to settle out of the water. It estimated that
approximately 10,540 cubic yards of sediment is stored in the
relevant portion of the Saint Brides Ditch rather than down-
stream in the Northwest River. It explained that this filtered
sediment likely includes some quantity of dissolved pollutants
that are thus removed from the Northwest River, improving
the drinking water and fishing quality of the river.

With respect to the 2,500-foot Ditch, the Corps found that
its 93,750 cubic feet of water storage capacity and substantial
accumulation of woody debris allowed it to slow water veloc-
ities to 1.13 feet per second, providing "significant flood flow
benefits to downstream traditionally navigable waters." J.A.
265. Its large woody debris also allowed it to trap at least
2,083 cubic yards of sediment and organic material that would
otherwise flow downstream. Decomposed organic matter
from these tributaries, the Corps explained, provides a "sub-
stantial food source" to fish species in the Northwest River.
Id. at 266.

The Corps’ Significant Nexus Determination further
explained that numerous other ditches, similar to the 2,500-
10 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
foot Ditch, drain into the Saint Brides Ditch along the relevant
reach, each serving similar functions. The Corps concluded
that these ditches cumulatively provide significant benefits to
the river below, including "retaining a significant amount of
flood water/flows, removing large volumes of sediments and
pollutants from the system, as well as delivering important
food resources to fish and other species living and spawning
in the Northwest River." Id. at 267.

The Significant Nexus Determination then analyzed the
448 acres of similarly situated wetlands. Most of these wet-
lands are mineral flats, which contain unique hydric soils that
have large amounts of organics at the surface, allowing them
to retain more water than most wetlands. Although berms
"have severed the direct surface water connection" among
these wetlands in many places, the Corps found that "the berm
has a negligible effect on the overall ecological functions that
. . . all of the adjacent wetlands in the [significant nexus]
determination provide to downstream [traditional navigable
waters]." Id. at 271. The Corps found the berms to be neither
a barrier to wildlife functions nor an inhibitor of wetland
functions, and in fact explained that they provide the benefit
of "allow[ing] floodwaters to be retained longer within the
wetlands prior to being discharged downstream thus moderat-
ing and mitigating flood flows." Id. The Corps also found that
subsurface flows exist in the Edinburgh PUD wetlands,
explaining that they slowly release groundwater into the Saint
Brides Ditch.

The Corps then elaborated on the wetlands’ role in flood
mitigation. The 166 acres of on-site wetlands are capable of
storing up to one and one-half feet of water per acre, and
receive approximately 1,222,943 gallons of precipitation a
year. Blackened leaves observed on-site evidence the wet-
lands’ prolonged water storage capabilities. The Corps further
explained that expert testimony from a trial between the
Corps and the previous developer, RGM,5 supported the con-
5
In 2001, the Corps brought a civil enforcement action against RGM for
filling wetlands without a CWA permit. In United States v. RGM Corp.,
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 11
clusion that the wetlands "slow release of water maintains
base flows to the Northwest River and also moderates down-
stream flooding during extreme precipitation events." Id. at
272. Moreover, one expert testified that "loss of wetlands on
the Edinburgh PUD would result in a major change to the tim-
ing and routing of water from the site," and that increased
water velocities downstream "would cause erosion of sedi-
ments, increasing sedimentation and pollution of downstream
waters including the Northwest River." Id.

The Corps further observed that such mineral flat wetlands
rapidly cycle nutrients, sequester carbon, and help denitrify
water, reducing eutrophication.6 The 448 acres of similarly
situated wetlands were found to remove an estimated 448 to
9,403 pounds of nitrogen per acre from the water each year,
and also remove an unquantified amount of pollutants and
particles. Moreover, the 4.8-acre Site Wetlands and similarly
situated wetlands serve as habitat for numerous species,
including State endangered species, at least some of which
can cross the unfinished road separating the Site Wetlands
from remaining wetlands. These species use the area as "a

222 F. Supp. 2d 780 (E.D. Va. 2002), the court found that the Corps had
no jurisdiction over the wetlands on the Edinburgh PUD. However, after
Precon acquired the Edinburgh PUD, Precon and the Corps settled pend-
ing appeal and the district court vacated its earlier judgment. See No. 01-
cv-719, 2005 U.S. Dist. LEXIS 1992 (E.D. Va. Jan. 18, 2005). The partic-
ulars of this suit and settlement have no bearing on the instant litigation.
6
Eutrophication is:
a process by which [a water body’s] nutrient content increases
dramatically due to nitrogen- and phosphorus-rich soil that is
washed into [it]. These nutrients encourage the growth of algae,
which renders the formerly clear blue water green and increas-
ingly opaque. Moreover, the algae depletes oxygen in the water,
jeopardizing the survival of fish and other animal life.
Tahoe Sierra Pres. Council, Inc. v. Tahoe Reg’l Planning Agency, 322
F.3d 1064, 1070 (9th Cir. 2003).
12 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
corridor for movement between the Northwest River and
points to the north and west." Id. at 276.

On the basis of this evidence, the Corps’ Significant Nexus
Determination concluded that the tributaries and their adja-
cent wetlands have "a significant nexus that has more than a
speculative or insubstantial effect on the Northwest River,"
and that loss of these wetlands "would have a substantial neg-
ative impact on water quality and biological communities of
the river’s ecosystem." Id. at 277-78. Accordingly, the Corps
reaffirmed its previous conclusion that it had jurisdiction over
the Site Wetlands, such that Precon would be required to
obtain a CWA permit before filling them.

C.

Precon sought judicial review of this determination, along
with the Corps’ denial of its permit application, in the United
States District Court for the Eastern District of Virginia. The
parties filed cross-motions for summary judgment, which
were referred to a magistrate judge for a Report and Recom-
mendation ("R&R"). The district court adopted this R&R in
full on September 4, 2009, granting the Corps’ motion for
summary judgment and denying Precon’s motion for sum-
mary judgment.

The district court found that the Corps had permissibly
defined the scope of its review area as including 448 acres of
similarly situated wetlands, and that the Corps’ determination
that these wetlands had a significant nexus to the Northwest
River was supported by substantial factual findings. The dis-
trict court also upheld the Corps’ denial of a CWA permit.
This appeal followed.

II.

On appeal, Precon challenges the district court’s finding
that the Corps properly asserted jurisdiction over the Site
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 13
Wetlands under the CWA.7 Precon argues that there are two
major flaws in the Corps’ jurisdictional determination. First,
it contends that the Corps’ decision to aggregate 448 acres of
surrounding wetlands in determining jurisdiction was imper-
missible. Second, it argues that even if all 448 acres were
appropriately included in the Corps’ jurisdictional determina-
tion, the Corps did not provide sufficient evidence that the
connection between these wetlands and the Northwest River
amounted to a significant nexus.

Before reaching Precon’s two substantive arguments, we
provide an overview of the Supreme Court’s jurisprudence
addressing the parameters of CWA jurisdiction. We then turn
to each of Precon’s contentions.

A.

Congress passed the CWA in 1972 "to restore and maintain
the chemical, physical, and biological integrity of the Nation’s
waters." 33 U.S.C. § 1251. To that end, the CWA prohibits
the discharge of pollutants into navigable waters. See id.
§§ 1311(a), 1362(12)(A). The CWA defines navigable waters
as "the waters of the United States, including the territorial
seas." 33 U.S.C. § 1362(7). Although the Corps initially con-
strued this definition to cover only waters navigable in fact,
"in 1975 the Corps issued interim final regulations redefining
‘the waters of the United States’ to include not only actually
navigable waters but also tributaries of such waters" and
"‘freshwater wetlands’ that were adjacent to other covered
waters." United States v. Riverside Bayview Homes, Inc., 474
U.S. 121, 123-24 (1985).

In Riverside Bayview Homes, the Supreme Court upheld
the Corps’ determination that it had jurisdiction over wetlands
adjacent to navigable waters. Id. at 139. Even though the plain
7
Precon does not challenge the Corps’ permit denial, which will accord-
ingly not be discussed further.
14 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
language of the statute did not compel this conclusion, the
Court explained that by including a broad definition of "navi-
gable waters" in the CWA, Congress "evidently intended to
. . . exercise its powers under the Commerce Clause to regu-
late at least some waters that would not be deemed ‘naviga-
ble’ under the classical understanding of that term." Id. at 133.
It further reasoned that the Corps’ decision to include wet-
lands within its jurisdiction was a reasonable one, given wet-
lands’ critical importance to the health of adjacent waters. Id.
at 133-34.

The Supreme Court again interpreted the CWA term "navi-
gable waters" in Solid Waste Agency of Northern Cook
County v. United States Army Corps of Engineers, 531 U.S.
159 (2001) ("SWANCC"). In SWANCC, it considered whether
"isolated ponds, some only seasonal, wholly located within
two Illinois counties, f[e]ll under [the CWA’s] definition of
‘navigable waters’ because they serve[d] as habitat for migra-
tory birds." Id. at 171-72. The Court held that these waters
were simply too far removed from any navigable waters to be
included within that term. Id. To distinguish these isolated
ponds from the wetlands it considered in Riverside Bayview
Homes, the Court explained: "It was the significant nexus
between the wetlands and ‘navigable waters’ that informed
our reading of the CWA in Riverside Bayview Homes." Id. at
167.

Five years later, in Rapanos, the Supreme Court revisited
the issue of the Corps’ jurisdiction over adjacent wetlands.
547 U.S. at 715. Although recognizing the continuing validity
of Riverside Bayview Homes, a majority of the Court found
troubling the Corps’ assertion of jurisdiction over wetlands
adjacent to tributaries far away from, and unimportant to, any
traditional navigable water.8 See id. at 726, 730-33 (plurality
8
In Rapanos, the Court specifically considered the validity of the Corps’
regulation defining "waters of the United States," 33 C.F.R. § 328.3(a).
Section 328.3(a) broadly defines this term to encompass all wetlands "ad-
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 15
opinion); id. at 776, 779-80 (Kennedy, J., concurring in the
judgment). Accordingly, a fractured Court proposed two dif-
ferent ways to limit the reach of its earlier ruling so as not to
allow jurisdiction over wetlands lying alongside "remote and
insubstantial" ditches and drains. Id. at 778 (Kennedy, J., con-
curring in the judgment). The Rapanos plurality suggested
that wetlands should only fall within CWA jurisdiction when
they: (1) are adjacent to a "relatively permanent body of water
connected to traditional interstate navigable waters"; and (2)
have "a continuous surface connection with that water." Id. at
742 (plurality opinion). Justice Kennedy, concurring, found
this test too limiting. Instead, he borrowed language from
SWANCC to establish an alternative new test for jurisdiction
over adjacent wetlands. Id. at 779-80 (Kennedy, J., concurring
in the judgment). Under his formulation, when the Corps
"seeks to regulate wetlands based on adjacency to nonnaviga-
ble tributaries," it must establish that a "significant nexus"
exists "between the wetlands in question and navigable waters
in the traditional sense." Id. at 779, 782. The dissent, which
drew four votes, found both of these tests too stringent. It thus
suggested that in the future, jurisdiction should be established
if either the plurality’s or Justice Kennedy’s test is met. Id. at
810 (Stevens, J., dissenting).

The parties here agree that Justice Kennedy’s "significant
nexus" test governs and provides the formula for determining
whether the Corps has jurisdiction over the Site Wetlands. We
therefore do not address the issue of whether the plurality’s

jacent to waters," including "intrastate lakes, rivers, streams (including
intermittent streams), mudflats, sandflats, wetlands, sloughs, prairie pot-
holes, wet meadows, playa lakes, or natural ponds, the use, degradation or
destruction of which could affect interstate or foreign commerce" and trib-
utaries of such waters. 33 C.F.R. § 328.3(a). A majority of the justices in
Rapanos found this regulation to be overly broad inasmuch as it allowed,
as a matter of course, jurisdiction over wetlands adjacent to nonnavigable
tributaries. See 547 U.S. at 739 (plurality opinion); id. at 781-82 (Ken-
nedy, J., concurring in the judgment).
16 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
"continuous surface connection" test provides an alternate
ground upon which CWA jurisdiction can be established.9

Given that the significant nexus test undisputedly controls,
it bears further elaboration. Justice Kennedy derived this test
from a recognition that while Congress clearly intended to
allow CWA jurisdiction over "at least some waters that are
not navigable in the traditional sense," id. at 767 (Kennedy,
J., concurring in the judgment), some meaning had to be
given to the term "navigable" as used in the statute, id. at 778-
79. To discern this meaning, he returned to Riverside Bayview
Homes, where the Court upheld jurisdiction over some wet-
lands by explaining that "wetlands adjacent to lakes, rivers,
streams, and other bodies of water may function as integral
parts of the aquatic environment . . . ." Id. at 779 (quoting Riv-
erside Bayview Homes, 474 U.S. at 135).

Drawing upon this purposive rationale for including certain
wetlands within the term "navigable waters," Justice Kennedy
explained that "the Corps’ jurisdiction over wetlands depends
upon the existence of a significant nexus between the wet-
lands in question and navigable waters in the traditional
sense." Id. Wetlands possessing this significant nexus are
those that "perform critical functions related to the integrity of
other waters—functions such as pollutant trapping, flood con-
trol, and runoff storage." Id. Accordingly, Justice Kennedy set
forth the following standards for evaluating the existence of
a significant nexus:

[W]etlands possess the requisite nexus, and thus
come within the statutory phrase "navigable waters,"
if the wetlands, either alone or in combination with
similarly situated lands in the region, significantly
9
We note that in any event, the applicability of the continuous surface
connection test is more questionable on these facts, given the presence of
a continuous berm separating the 4.8-acre Site Wetlands from the 2,500-
foot Ditch.
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 17
affect the chemical, physical, and biological integrity
of other covered waters more readily understood as
"navigable." When, in contrast, wetlands’ effects on
water quality are speculative or insubstantial, they
fall outside the zone fairly encompassed by the statu-
tory term "navigable waters."

Id. at 780.

Justice Kennedy further explained that, in accordance with
Riverside Bayview Homes, wetlands adjacent to navigable-in-
fact waters necessarily satisfy this significant nexus test. Id.
However, for wetlands adjacent to non-navigable tributaries,
such as the Site Wetlands we consider here, the Corps must
now "establish a significant nexus on a case-by-case basis."
Id. at 782. As possible indicia of the significance of such wet-
lands, Justice Kennedy noted that the Corps might consider
documenting "the significance of the tributaries to which the
wetlands are connected," a "measure of the significance of
[the hydrological connection] for downstream water quality,"
and/or "the quantity and regularity of flow in the adjacent
tributaries." Id. at 784, 786.

B.

With this framework established, we turn to Precon’s sub-
stantive challenges. We review the district court’s decision to
grant summary judgment de novo, S.C. Green Party v. S.C.
State Election Comm’n, 612 F.3d 752, 755 (4th Cir. 2010),
including its findings on an administrative record, Ohio Val-
ley Envtl. Coal. v. Aracoma Coal Co., 556 F.3d 177, 189 (4th
Cir. 2009).

Precon’s arguments require a careful examination of the
Corps’ application of the language Justice Kennedy has
engrafted into the statutory requirements of the CWA. See
Rapanos, 547 U.S. at 779 (Kennedy, J., concurring in the
judgment). We therefore treat compliance with Justice Kenne-
18 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
dy’s "significant nexus" test as a question of law, as we do
any question of statutory interpretation, and review for com-
pliance de novo. See, e.g., Stone v. Instrumentation Lab. Co.,
591 F.3d 239, 242-43 (4th Cir. 2009); cf. Kentuckians for
Commonwealth Inc. v. Rivenburgh, 317 F.3d 425, 439 (4th
Cir. 2003) ("When reviewing a particular agency action . . .
[t]he court is first required to decide whether the [agency]
acted within the scope of [its] authority." (internal quotations
omitted and alterations in original)). However, recognizing
the Corps’ expertise in administering the CWA, we give def-
erence to its interpretation and application of Justice Kenne-
dy’s test where appropriate.10 See United States v. Mead
Corp., 533 U.S. 218, 234 (2001) ("[A]n agency’s interpreta-
tion may merit some deference whatever its form, given the
‘specialized experience and broader investigations and infor-
mation’ available to the agency . . . ." (quoting Skidmore v.
Swift, 323 U.S. 134, 140 (1944)).

i.

Precon first challenges the Corps’ decision to label 448
acres of surrounding wetlands as "similarly situated" wetlands
for purposes of its significant nexus determination. On this
point, recognizing the deference due the Corps’ factual find-
10
We do not, however, review the Corps’ interpretation of the phrase
"significant nexus" under the greater deference accorded to some agency
interpretations under Chevron U.S.A. Inc. v. Natural Resources Defense
Council, Inc., 467 U.S. 837 (1984), because—although it could—the
Corps has not adopted an interpretation of "navigable waters" that incor-
porates this concept through notice-and-comment rulemaking, but instead
has interpreted the term only in a non-binding guidance document. See
United States v. Mead Corp., 533 U.S. 218, 234 (2001); Rapanos, 547
U.S. at 782 (Kennedy, J., concurring in the judgment) (explaining that
"[a]bsent more specific regulations . . . the Corps must establish a signifi-
cant nexus on a case-by-case basis"); id. at 758 (Roberts, J., concurring)
(noting that the Corps has broad leeway to interpret the CWA, but that in
order to receive Chevron deference, it must engage in rulemaking that
interprets "the broad, somewhat ambiguous, but nonetheless clearly limit-
ing terms Congress employed in the [CWA]").
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 19
ings and interpretation of the phrase "similarly situated," we
uphold the Corps’ finding that 448 acres of wetlands were
"similarly situated" to the Site Wetlands.

Justice Kennedy’s significant nexus test clearly allows
some aggregation of wetlands in determining whether a sig-
nificant nexus exists. He explained that the significant nexus
inquiry should focus on whether "wetlands, either alone or in
combination with similarly situated lands in the region, sig-
nificantly affect the chemical, physical, and biological integ-
rity of other covered waters more readily understood as
‘navigable.’" Rapanos, 547 U.S. at 780 (Kennedy, J., concur-
ring in the judgment) (emphasis added). However, his concur-
rence provided no further explanation of what "similarly
situated," or, for that matter, "region," should be taken to
mean in this context.

To flesh out this concept, the Corps’ Rapanos Guidance
interprets "similarly situated" to mean "all wetlands adjacent
to the same tributary." J.A. 486. A tributary, in turn, is defined
as "the entire reach of the stream that is of the same order (i.e.
from the point of confluence, where two lower order streams
meet to form the tributary, downstream to the point such trib-
utary enters a higher order stream)." Id.

Applying these definitions to the instant case, the Corps
identified the relevant tributary as the 2,500-foot Ditch and
the Saint Brides Ditch, collectively, down to the point where
the Saint Brides Ditch converged with the Pleasant Grove
Swamp. The Corps explained that it considered these ditches
together because they were historically part of the same natu-
rally defined wetland drainage feature before human-made
ditches altered the area. The Corps then identified the 166
acres of wetlands located on the Edinburgh PUD and an addi-
tional 282 acres of wetlands outside of Precon’s property as
wetlands sitting "adjacent" to this "relevant reach." It noted
that all 448 acres were part of a "physical, chemical and bio-
20 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
logical connection of wetlands and streams" that existed, "and
had always existed," in the area. Id. at 267.

Precon acknowledges that the Rapanos Guidance’s inter-
pretation of "similarly situated lands in the region" is entitled
to Skidmore deference. Under Skidmore, an agency’s interpre-
tation merits deference "to the extent that the interpretation
has the power to persuade." U.S. Dep’t of Labor v. N.C.
Growers Ass’n, 377 F.3d 345, 353-54 (4th Cir. 2004) (citing
Skidmore, 323 U.S. at 140). Precon argues, however, that the
Corps’ determination that the 448 acres were "similarly situ-
ated" is unpersuasive because (1) adjacent and abutting wet-
lands cannot reasonably be considered to be "similarly
situated," and (2) the Corps failed to follow its own guidance
here.11

According to Precon, the primary flaw in the Corps’ inter-
pretation of "similarly situated" is its equal treatment of abut-
ting and other adjacent wetlands. Specifically, Precon argues
that the plurality and Justice Kennedy in Rapanos "expressly
recognize[d] that there is a significant difference in the rela-
tionship between abutting and non-abutting wetlands and their
nearest ditches." Appellant’s Br. at 46.

Although the Rapanos plurality clearly found the abut-
ting/adjacent distinction meaningful, see 547 U.S. at 740-42,
we find no evidence that Justice Kennedy, in permitting "sim-
ilarly situated lands" to be included within the significant
nexus analysis, intended to differentiate between abutting and
other adjacent wetlands. To the contrary, his concurrence
explicitly approved of the Corps’ regulatory definition of "ad-
11
Precon also argues that the Corps impermissibly aggregated bottom-
land hardwood wetlands and forested mineral flat wetlands. But as the
Corps notes in response, the bottomland hardwood wetlands only com-
prised three of the 448 acres. Accordingly, there is no indication that
inclusion of these acres, even if improper, had any material impact on the
outcome of the Corps’ significant nexus analysis.
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 21
jacent," which includes both those wetlands that directly abut
waters of the United States and those separated from other
waters "by man-made dikes or barriers, natural river berms,
beach dunes and the like." 33 C.F.R. § 328.3(c). As Justice
Kennedy explained, abutting wetlands are not necessarily any
more important than other adjacent wetlands because "filling
in wetlands separated from another water by a berm can mean
that floodwater, impurities, or runoff that would have been
stored or contained in the wetlands will instead flow out to
major waterways." Rapanos, 547 U.S. at 775 (Kennedy, J.,
concurring in the judgment). He thus concluded that "it may
be the absence of an interchange of waters . . . that makes pro-
tection of the wetlands critical to the statutory scheme." Id.

Here, the Corps adopted this precise rationale in aggregat-
ing abutting and other adjacent wetlands. It explained that the
berm separating the 4.8-acre Site Wetlands from the 2,500-
foot Ditch did not disconnect these wetlands from surround-
ing ones, because it neither inhibited wildlife movement nor
wetland functions. It also explained that the berm in fact pro-
vided the additional benefit of "allow[ing] floodwaters to be
retained longer within the wetlands prior to being discharged
downstream thus moderating and mitigating flood flows."
J.A. 271. Given this reasonable explanation for its actions, we
see no error in the Corps’ decision to aggregate both abutting
and adjacent wetlands in its significant nexus determination.

As for Precon’s second argument, we acknowledge that it
is difficult to determine whether the Corps precisely adhered
to the Rapanos Guidance in identifying "similarly situated"
wetlands. Specifically, it is not clear that the Guidance con-
templates that multiple tributaries might appropriately be
included within the "relevant reach." Although at oral argu-
ment the Corps took the position that its determination to
aggregate these two ditches was merely an application of its
Rapanos Guidance to the unique geography of the area, we
are not convinced that the Guidance is so flexible on this
point.
22 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
However, we conclude that we do not need to determine
whether or not the Corps methodically adhered to its non-
binding guidance document in identifying the "similarly situ-
ated" wetlands here. Cf. J.A. 481 n.16 (footnote in the
Rapanos Guidance explaining that the guidance "does not
impose legally binding requirements . . . and may not apply
to a particular situation depending on the circumstances").
Even if the Corps deviated from its guidance, it provided rea-
soned grounds for doing so.

The Corps explained that it decided to aggregate the wet-
lands surrounding both the 2,500-foot Ditch and the Saint
Brides Ditch because the two ditches were, historically, part
of the same naturally defined wetland drainage feature—a
feature that was manipulated into discrete ditches in the late
1970s. We accept this finding as true, having no reason to
believe it was "arbitrary, capricious, an abuse of discretion, or
otherwise not in accordance with law." 5 U.S.C. § 706(2)(A);
see also Aracoma, 556 F.3d at 192 (explaining that we should
be at our "most deferential" when reviewing findings of fact
based on special expertise). And based on this finding, we are
persuaded that the Corps acted reasonably in aggregating
these two man-made ditches into a single "tributary." There is
both logical and practical appeal to treating man-made ditches
that would naturally be part of the same drainage feature
together. Otherwise, a property owner could avoid CWA
jurisdiction simply by digging a few well-placed drainage
ditches on either side of the wetlands he wished to fill.

We find more questionable the Corps’ decision, after deter-
mining that it would treat these two ditches together, to
include adjacent wetlands stretching over three miles down-
stream as "similarly situated." However, we recognize that
Justice Kennedy’s instruction—that "similarly situated lands
in the region" can be evaluated together—is a broad one, open
for considerable interpretation and requiring some ecological
expertise to administer. On the basis of this recognition, and
with no appropriate limiting principle suggested by Precon as
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 23
to which wetlands could properly have been considered "simi-
larly situated" here, we uphold the Corps’ finding that all 448
acres of non-contiguous wetlands adjacent to the 2,500-foot
Ditch and the Saint Brides Ditch down to Pleasant Grove
Swamp were "similarly situated." However, the Corps’ record
on this point gives us a bare minimum of persuasive reasoning
to which we might defer. It only notes, somewhat conclu-
sorily, that the Site Wetlands "continue to function as part of
the entire" 448 acres. J.A. 271. We urge the Corps to consider
ways to assemble more concrete evidence of similarity before
again aggregating such a broad swath of wetlands.

For the foregoing reasons, we reject Precon’s argument that
the Corps impermissibly identified 448 acres of wetlands as
"similarly situated lands in the region," and uphold the Corps’
findings on this point.

ii.

We now turn to Precon’s argument that the Corps did not
adequately establish the existence of a significant nexus
between the Site Wetlands—along with similarly situated
wetlands—and the Northwest River. The Corps’ factual find-
ings on this point are not in dispute;12 rather, Precon chal-
12
There is one factual dispute between the parties. Precon argues that
the Corps improperly characterized the 2,500-foot Ditch as a "relatively
permanent water," given that the ditch was "substantially dry" in January
2008, which it asserts was the wettest time of year. Appellant’s Reply Br.
at 17. However, the Corps’ determination that the ditch was a reasonably
permanent water, which it defines as a tributary that "has continuous flow
at least ‘seasonally’ (e.g. typically three months)," J.A. 242, rested on its
conclusion that it seasonally flowed from February to April. The Corps’
Significant Nexus Determination also observed that January 2008 was a
period of drought, and that even at this time standing water was observed
in the ditch. Id. at 264. Accordingly, we accept the Corps’ factual determi-
nation that the 2,500-foot Ditch flowed at least seasonally, finding it not
to be "arbitrary, capricious, an abuse of discretion, or otherwise not in
accordance with law." 5 U.S.C. § 706(2)(A); cf. Marsh v. Or. Natural Res.
Council, 490 U.S. 360, 376 (1989) (applying § 706(2)(A) to "a factual dis-
pute the resolution of which implicates substantial agency expertise").
24 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
lenges whether the Corps’ administrative record, if accepted
as accurate, suffices to meet Justice Kennedy’s significant
nexus test. Upon close examination of the record, we find that
it contains insufficient information to allow us to assess the
Corps’ conclusion that these wetlands have a significant
nexus with the Northwest River, a body of water situated
miles away.

Precon’s primary argument is that the Corps’ record lacks
any "measures" of the effects that these wetlands have on the
Northwest River. And, it reasons, without such "measures,"
the wetlands’ significance for the river’s health cannot be
established. The Corps responds that Justice Kennedy’s sig-
nificant nexus test does not require empirical or quantitative
evidence of "significance," and that the evidence it provided
more than sufficed to establish a significant nexus.

We have not yet had occasion to consider the evidentiary
requirements of Justice Kennedy’s significant nexus test. The
Sixth Circuit has most directly addressed the issue. In United
States v. Cundiff, 555 F.3d 200 (6th Cir. 2009), it held that
Justice Kennedy’s significant nexus test does not require
"‘laboratory analysis’ of soil samples, water samples, or . . .
other tests." Id. at 211. Instead, the Sixth Circuit found that
the district court had not clearly erred by finding that a signif-
icant nexus was demonstrated through qualitative, rather than
quantitative, physical evidence. This evidence included expert
testimony that dredging and filling of the wetlands at issue
"undermined the wetlands’ ability to store water which, in
turn, . . . affected the frequency and extent of flooding, and
increased the flood peaks in the Green River," and caused vis-
ible acid mine runoff previously stored in the wetlands to flow
more directly to the Green River. Id. at 210-11.

We agree that the significant nexus test does not require
laboratory tests or any particular quantitative measurements in
order to establish significance. As Justice Kennedy explained,
the significant nexus test is a flexible ecological inquiry into
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 25
the relationship between the wetlands at issue and traditional
navigable waters. See Rapanos, 547 U.S. at 779-80 (Kennedy,
J., concurring in the judgment). However, in announcing this
test, he clearly intended for some evidence of both a nexus
and its significance to be presented. Otherwise, it would be
impossible to engage meaningfully in an examination of
whether a wetland had "significant" effects or merely "specu-
lative or insubstantial" effects on navigable waters. Id. at 780.
Justice Kennedy’s opinion further provides specific examples
of the types of evidence that might support a determination of
significance. For instance, an adequate record might include
documentation of "the significance of the tributaries to which
the wetlands are connected," a "measure of the significance of
[the hydrological connection] for downstream water quality,"
and/or "indication of the quantity and regularity of flow in the
adjacent tributaries." Id. at 784, 786.

The question is thus whether the Corps’ record contained
enough physical evidence—quantitative or qualitative—to
allow us to uphold its determination that a significant nexus
existed here. Relying on the final example described above,
the Corps asserted at oral argument that its documentation of
the flow of the adjacent tributaries sufficed, even standing
alone, to establish that a significant nexus existed here.
According to this theory, a measurement of these tributaries’
flow adequately demonstrated that this area "help[ed] to slow
flows/retain floodwaters, releasing them slowly so that down-
stream waters do not receive as much flow volume and veloc-
ity, all working to diminish downstream flooding and
erosion," which led to the conclusion that a significant nexus
existed. J.A. 265.

We cannot accept this conclusion for two reasons. First, as
Precon points out, the Corps’ administrative record does not
appear to contain any measurements of actual flow. Nor was
counsel able to point to such measurements at oral argument.
Instead, the record reflects measures of the water storage
capacity and the resultant potential flow rates of the Saint
26 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
Brides Ditch and the 2,500-foot Ditch, without any indication
of how often this capacity is reached or how much flow is
typically in the ditches.13

Second, even if the record had sufficiently documented
flow, we do not believe that recitation of the flow of an adja-
cent tributary alone, absent any additional information regard-
ing its significance, would necessarily suffice to establish a
significant nexus. The significant nexus inquiry emphasizes
the comparative relationship between the wetlands at issue,
their adjacent tributary, and traditional navigable waters. Cf.
Rapanos, 547 U.S. at 780 (Kennedy, J., concurring in the
judgment) (drawing a critical distinction between wetlands
with "significant" effects versus only "insubstantial" effects
on navigable waters). We can therefore imagine, for example,
that wetlands next to a tributary with minimal flow might be
significant to a river one quarter mile away, whereas wetlands
next to a tributary with much greater flow might have only
insubstantial effects on a river located twenty miles away.
Accordingly, in this case of wetlands approximately seven
miles from any navigable water, we cannot say that recitation
of the adjacent tributary’s flow, standing alone, would neces-
sarily have sufficed.

We acknowledge that the Corps’ Significant Nexus Deter-
mination did contain other physical observations about the
wetlands and adjacent tributaries.14 However, there is no doc-
13
In fact, the record suggests that the two ditches are not generally at
capacity, such that a measurement of capacity could double as a measure
of flow. At the United States v. RGM Corp. trial, a neighbor testified that
the Saint Brides Ditch perennially has water in it, but that at
times—especially during drought conditions—portions of it have only two
to three inches of water and that it is often not possible to discern which
way it is flowing. J.A. 415-16.
14
Specifically, the Corps’ record documents the Saint Brides Ditch’s
dynamic storage capacity, channel slope, water velocities, and sediment
storage capabilities; the 2,500-foot Ditch’s storage capacity, water veloc-
ity, and estimated sediment and organic material trapping capabilities; and
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 27
umentation in the record that would allow us to review its
assertion that the functions that these wetlands perform are
"significant" for the Northwest River. In particular, although
we know that the wetlands and their adjacent tributaries trap
sediment and nitrogen and perform flood control functions,
we do not even know if the Northwest River suffers from high
levels of nitrogen or sedimentation, or if it is ever prone to
flooding. This lack of evidence places the facts here in stark
contrast to those in Cundiff, upon which the Corps relies.
There, the Sixth Circuit noted that the district court credited
expert testimony about the wetlands "in relation to" the navi-
gable river. 555 F.3d at 210-11 (emphasis added). According
to that testimony, the challenged actions had undermined the
wetlands’ ability to store water, which, in turn, had increased
the flood peaks in the Green River. Id. Additional testimony
established that acid mine runoff that had previously been
stored in the wetlands flowed more directly into the river,
causing "direct and significant impacts to navigation . . . and
to aquatic food webs" in the river. Id. at 211. There is no such
testimony here.

Accordingly, we must conclude that this record does not
support the Corps’ determination that the nexus that exists
between the 448 acres of similarly situated wetlands and the
Northwest River is "significant." Particularly given the facts
of this case, involving wetlands adjacent to two man-made
ditches, flowing at varying and largely unknown rates toward
a river five to ten miles away, we cannot accept, without any
information on the river’s condition, the Corps’ conclusion
that the nexus here is significant. Justice Kennedy created the

the 448 acres of similarly situated wetlands’ foot/acre water storage capac-
ity, annual amount of precipitation received, and estimated amount of
nitrogen stored. These findings support a conclusion that certain amounts
of water, sediment, and pollutants migrate, or are prevented from migrat-
ing, from these wetlands to the Northwest River, and thus establish that
a "nexus" is present here. But they do not speak to the significance of this
nexus.
28 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
significant nexus test specifically because he was disturbed by
the assertion of jurisdiction over wetlands situated along a
ditch "many miles from any navigable-in-fact water," carrying
"only insubstantial flow toward it." Rapanos, 547 U.S. at 786
(Kennedy, J., concurring in the judgment).

In support of our request for further information on these
wetlands’ significance, we observe that the geography of the
wetlands at issue places them squarely in that category of wet-
lands over which jurisdiction is no longer assured. Carabell,
one of the consolidated cases in Rapanos, involved wetlands
similar to, but less remote than, the Site Wetlands. In Cara-
bell, the Corps had asserted jurisdiction over 15.9 acres of for-
ested wetlands, lying along a ditch—but separated from the
ditch by a man-made berm—which eventually drained into
Lake St. Claire approximately one mile downstream. Id. at
764. Both the plurality and Justice Kennedy agreed that more
evidence was needed about these wetlands’ characteristics
before jurisdiction could be established. Id. at 757 (plurality
opinion); id. at 786-87 (Kennedy, J., concurring in the judg-
ment). Given that the Site Wetlands are considerably more
removed from traditional navigable waters than the wetlands
at issue in Carabell, it follows that it would be even more
important for the Corps to fully document the significance of
their effects on navigable water. Indeed, even the Corps’ own
Rapanos Guidance cautions that "[a]s the distance from the
tributary to the navigable water increases, it will become
increasingly important to document whether the tributary and
its adjacent wetlands have a significant nexus rather than a
speculative or insubstantial nexus with a traditional navigable
water." J.A. 487.

Recent Ninth and Sixth Circuit cases provide good exam-
ples of the types of evidence—either quantitative or qualita-
tive—that could suffice to establish "significance." In
Northern California River Watch v. City of Healdsburg, 496
F.3d 993 (9th Cir. 2007), the Ninth Circuit held the significant
nexus test satisfied in part because the district court found
 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS 29
increased chloride levels in the relevant navigable water, from
5.9 parts per million to 18 parts per million, due to chlorine
seepage from the wetlands in question into the navigable
river. Id. at 1001. Alternatively, Cundiff provides an example
of the type of qualitative evidence that can establish a signifi-
cant nexus. As noted earlier, the Sixth Circuit’s opinion in
Cundiff rested on evidence that the wetlands’ acid mine drain-
age storage capabilities and flood storage capabilities had "di-
rect and significant" impacts on navigation in the Green
River, via sediment accumulation, and that the diversion of
water from the wetlands had "increased the flood peaks" in
the Green River. 555 F.3d at 210-11. Thus, in contrast to the
present case, both River Watch and Cundiff included some
evidence not only of the functions of the relevant wetlands
and their adjacent tributaries, but of the condition of the rele-
vant navigable waters.

The Corps argues that we must afford deference to its sig-
nificant nexus finding. We agree that its factual findings are
entitled to deference under the APA, and should be reversed
only if "arbitrary, capricious, an abuse of discretion, or other-
wise not in accordance with law." 5 U.S.C. § 706(2)(A); see
also Marsh v. Or. Natural Res. Council, 490 U.S. 360, 376-77
(1989). The Corps’ factual findings, however, are not in dis-
pute. The question is instead whether the Corps’ findings
were adequate to support the ultimate conclusion that a signif-
icant nexus exists. This legal determination is essentially now
a matter of statutory construction, as Justice Kennedy estab-
lished that a "significant nexus" is a statutory requirement for
bringing wetlands adjacent to non-navigable tributaries within
the CWA’s definition of "navigable waters." See Rapanos,
547 U.S. at 779-80 (Kennedy, J., concurring in the judgment).
As we mentioned at the outset, on this question of statutory
interpretation, absent the promulgation of new regulations, the
Corps’ conclusions are entitled at most to Skidmore defer-
ence. See Mead, 533 U.S. at 234-35; cf. Rivenburgh, 317 F.3d
at 439. Because the Corps’ current administrative record con-
tains no evidence of significance for us to review, we cannot
30 PRECON DEVELOPMENT v. U.S. ARMY CORPS OF ENGINEERS
find its conclusion that significance existed here persuasive.
Cf. Shipbuilders Council of Am. v. U.S. Coast Guard, 578
F.3d 234, 245 (4th Cir. 2009) ("Some indicia of reliability and
reasonableness must exist in order for us to defer to the agen-
cy’s interpretation.").

For these reasons, we reverse the district court’s holding
that the Corps’ administrative record adequately demonstrated
that a significant nexus existed here, and remand to the Corps
for reconsideration of its significant nexus determination. Cf.
Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm Mut.
Auto. Ins. Co., 463 U.S. 29, 52, 57 (1983) (remanding for fur-
ther agency consideration when the agency’s view of the facts
was accepted but the Court "appreciate[d] the limitations of
th[e] record in supporting the agency’s decision"); Cook v.
Heckler, 783 F.2d 1168, 1174 (4th Cir. 1986) (remanding for
further consideration where it was "impossible to conclude
that there [was] substantial evidence to support the Secre-
tary’s determination"). In doing so, we do not intend to place
an unreasonable burden on the Corps. We ask only that in
cases like this one, involving wetlands running alongside a
ditch miles from any navigable water, the Corps pay particu-
lar attention to documenting why such wetlands significantly,
rather than insubstantially, affect the integrity of navigable
waters. Such documentation need not take the form of any
particular measurements, but should include some compara-
tive information that allows us to meaningfully review the
significance of the wetlands’ impacts on downstream water
quality.

III.

For the foregoing reasons, the district court’s grant of sum-
mary judgment is reversed and we remand to the district court
with instructions to remand to the Corps for further consider-
ation in light of this opinion.

REVERSED AND REMANDED