                        PUBLISHED


UNITED STATES COURT OF APPEALS
              FOR THE FOURTH CIRCUIT


OHIO VALLEY ENVIRONMENTAL               
COALITION, INC.; WEST VIRGINIA
HIGHLANDS CONSERVANCY, INC.;
SIERRA CLUB; COAL RIVER
MOUNTAIN WATCH, INC.,
               Plaintiffs-Appellants,
                 v.
UNITED STATES ARMY CORPS OF
ENGINEERS; ROBERT L. VAN
ANTWERP, Commander and Chief
of Engineers, U.S. Army Corps of
                                           No. 12-1999

Engineers; ROBERT D. PETERSON,
Colonel, District Engineer, U.S.
Army Corps of Engineers,
Huntington District,
             Defendants-Appellees,
                and
HIGHLAND MINING COMPANY,
    Intervenor/Defendant-Appellee.
                                        
        Appeal from the United States District Court
 for the Southern District of West Virginia, at Huntington.
            Robert C. Chambers, District Judge.
                      (3:11-cv-00149)

                  Argued: March 19, 2013

                   Decided: May 15, 2013
2      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
    Before TRAXLER, Chief Judge, and WILKINSON and
               NIEMEYER, Circuit Judges.



Affirmed by published opinion. Judge Niemeyer wrote the
opinion, in which Chief Judge Traxler and Judge Wilkinson
joined. Judge Wilkinson wrote a separate concurring opinion.


                        COUNSEL

ARGUED: Joseph Mark Lovett, APPALACHIAN MOUN-
TAIN ADVOCATES, Lewisburg, West Virginia, for Appel-
lants. Michael Thomas Gray, UNITED STATES
DEPARTMENT OF JUSTICE, Jacksonville, Florida; Robert
G. McLusky, JACKSON KELLY, PLLC, Charleston, West
Virginia, for Appellees. ON BRIEF: James M. Hecker, PUB-
LIC JUSTICE, Washington, D.C., for Appellants. Michael R.
Shebelskie, HUNTON & WILLIAMS, LLP, Richmond, Vir-
ginia; James R. Snyder, M. Shane Harvey, JACKSON
KELLY, PLLC, Charleston, West Virginia, for Appellee
Highland Mining Company. Ignacia S. Moreno, Assistant
Attorney General, UNITED STATES DEPARTMENT OF
JUSTICE, Jacksonville, Florida, for Federal Appellees.


                        OPINION

NIEMEYER, Circuit Judge:

   In connection with a proposed surface coal mine adjacent
to Reylas Fork (a stream) in Logan County, West Virginia,
the West Virginia Department of Environmental Protection
("WVDEP") issued Highland Mining Company a permit
under the Surface Mining Control and Reclamation Act
("SMCRA") to do the mining, finding that the proposed mine
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS           3
would not cause material damage to the hydrologic regime.
The WVDEP also issued a water quality certification under
§ 401 of the Clean Water Act ("CWA"), concluding that the
proposed mine would not cause or contribute to violations of
the State’s EPA-approved water quality standards, as well as
a National Pollutant Discharge Elimination System
("NPDES") permit under CWA § 402, finding that the pro-
posed sediment pond for the mine would not have significant
adverse effects. Finally, the U.S. Army Corps of Engineers
(the "Corps") issued a fill permit under CWA § 404, authoriz-
ing Highland Mining to place rock overburden into the adja-
cent valley of Reylas Fork as part of the mining process. The
Corps issued the permit without an environmental impact
statement, finding that the fill would not have a substantial
cumulative impact on the water quality in the relevant water-
shed.

   Four environmental groups (collectively, the "Environmen-
tal Coalition") commenced this action to challenge the fill
permit issued under CWA § 404. The Environmental Coali-
tion contends that the Corps, in conducting its analysis for the
§ 404 permit, "materially misapprehended" the baseline con-
ditions in the relevant watershed, thus corrupting its analysis
of the cumulative impact that the mine would have on the
streams in the watershed. It also contends that the Corps acted
arbitrarily and capriciously in determining that the valley fill
would not have a significant cumulative impact on the water
quality in the relevant watershed.

   The district court evaluated the data considered by the
Corps, the Corps’ analysis, and the Corps’ conclusions and
found that the Corps did not misapprehend the baseline condi-
tions in the relevant watershed. Ohio Valley Envtl. Coalition,
Inc. v. U.S. Army Corps of Eng’rs ("OVEC"), 883 F. Supp. 2d
627, 642-44 (S.D. W. Va. 2012). It also found that the Corps
analyzed a "wide array of evidence about water quality" to
reach a reasoned decision that the individual and cumulative
environmental impacts of the Corps’ CWA § 404 permit
4       OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
would not rise to the level of significance required to trigger
the need for an environmental impact statement. Id. at 645. As
the district court concluded, "[t]he Corps has analyzed the
cumulative impacts, ‘articulated a satisfactory explanation for
its conclusion,’ and thus has not acted arbitrarily or capri-
ciously." Id. (quoting Ohio Valley Envtl. Coalition v. Ara-
coma Coal Co., 556 F.3d 177, 209 (4th Cir. 2009)).

    For the reasons that follow, we affirm.

                               I

   The mining operation proposed at the Reylas mine would
involve removing mountaintop rock that covers the coal
seams to be mined, placing the rock in the adjacent valley,
extracting the coal, and replacing the rock on the mountain-
top. See Bragg v. W. Va. Coal Ass’n, 248 F.3d 275, 286 (4th
Cir. 2001) (describing the process). Because the rock is bro-
ken up as it is removed from the mountaintop, its volume
swells such that all of the rock would not be needed to restore
the mountaintop. The excess rock, or overburden, would
accordingly be left in the valley as permanent fill. See Ken-
tuckians for the Commonwealth, Inc. v. Rivenburgh, 317 F.3d
425, 431 (4th Cir. 2003). A sediment pond, as was typical,
would be constructed below the valley fill to collect water
until the valley fill is stabilized. See Aracoma Coal, 556 F.3d
at 186. In connection with the Reylas mine, the overburden
rock would be deposited in a valley that includes a stream cal-
led Reylas Fork. Reylas Fork flows into Bandmill Hollow,
which in turn flows into Dingess Run. The Dingess Run
watershed was the relevant area for assessing the mine’s
cumulative impact.

  To operate the Reylas mine, Highland Mining obtained a
SMCRA permit from the WVDEP, a state agency that has
assumed "exclusive jurisdiction over the regulation of surface
coal mining and reclamation operations" on nonfederal lands.
30 U.S.C. § 1253(a). Highland Mining also obtained from the
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS          5
WVDEP a permit under CWA § 401, certifying that the dis-
charge from the mine will be consistent with the State’s
water-quality standards, and a permit under CWA § 402,
authorizing the discharge of pollutants other than dredged or
fill material into navigable waters. Finally, Highland Mining
obtained a permit under CWA § 404 from the Corps to allow
"the discharge of dredged or fill material into the navigable
waters at specified disposal sites." 33 U.S.C. § 1344(a).

   Under guidelines issued by the EPA, the Corps could issue
a § 404 permit only after concluding that the mining activity
would not cause or contribute to violations of the State’s
water-quality standards or to the significant degradation of
waters of the United States. 40 C.F.R. § 230.10(b)(1), (c). In
making that assessment, it had to comply with the National
Environmental Policy Act ("NEPA") and take a "hard look"
at the potential environmental consequences of the activity.
See Robertson v. Methow Valley Citizens Council, 490 U.S.
332, 350 (1989). NEPA required federal agencies such as the
Corps to prepare an environmental impact statement ("EIS")
for major federal actions that significantly affect the quality
of the human environment. 42 U.S.C. § 4332(C). To decide if
an EIS was required, the Corps had to prepare an environmen-
tal assessment. 33 C.F.R. § 230.10; 40 C.F.R. § 1501.3. If,
after conducting the assessment, the Corps found that the pro-
posed project would not, either individually or cumulatively,
have a significant impact on human health or the environ-
ment, it could make a "finding of no significant impact"
("FONSI"), obviating the need for preparing an EIS. 33
C.F.R. § 230.11; see also 40 C.F.R. § 1508.13 (describing the
contents of a FONSI).

   Before evaluating Highland Mining’s application for a
§ 404 permit, the Corps gave public notice of the application
and invited comment. The Environmental Coalition—
consisting of Ohio Valley Environmental Coalition, Inc.;
West Virginia Highlands Conservancy, Inc.; Sierra Club; and
Coal River Mountain Watch, Inc.—submitted comments
6     OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
opposing Highland Mining’s application. The Coalition main-
tained that the disturbance from the Reylas mine would be
ecologically significant, as the "sheer volume of disturbance
in the region had already indicated significant degradation and
would only be made worse by additional mining." The EPA
also submitted comments stating that "this proposal is likely
to cause or contribute to an excursion from the State’s water
quality standards downstream resulting in an impairment of
the aquatic life use." The EPA warned that "the direct and
cumulative impacts from this and future mines will be persis-
tent and permanent and can not be sufficiently or effectively
compensated through the proposed mitigation."

   After receiving the EPA’s comments, Highland Mining
requested that the Corps stay its consideration of the permit
application until Highland Mining had an opportunity to allay
the EPA’s concerns. Thereafter, the Corps, the EPA, and
Highland Mining consulted each other and agreed to modifi-
cations to the conditions of the permit. Under the agreement
reached, Highland Mining would eliminate approximately
400 feet of impact to Reylas Fork and apply a mitigation plan
involving best management practices and monitoring. After
the Corps made these changes, the EPA advised the Corps,
"We believe that with appropriate permit conditions that the
applicant could move forward with the issuance of the per-
mit."

   The Corps released its Combined Decision Document and
§ 404 permit on March 4, 2011, in which it included a FONSI
with respect to the Reylas mine.

   The Environmental Coalition shortly thereafter commenced
this action against the Corps, its Commander, and its District
Engineer, alleging that the Corps’ failure to require an EIS
violated NEPA and was arbitrary and capricious "because the
Corps failed to take a hard look at the environmental impacts
of those projects." The Coalition also alleged that the Corps
arbitrarily and capriciously concluded that the § 404 permit
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS          7
would not result in violations of West Virginia’s water-quality
standards. The district court granted Highland Mining’s
motion to intervene as a defendant.

   On cross-motions for summary judgment, the district court
denied the Environmental Coalition’s motion for summary
judgment; granted the Corps’ and Highland Mining’s cross-
motions for summary judgment; and entered final judgment.
OVEC, 883 F. Supp. 2d at 645. The court rejected the Coali-
tion’s argument that the Corps, in conducting its analysis,
"misapprehended" the baseline conditions of Dingess Run. Id.
at 642-44. It also rejected the Coalition’s NEPA challenge,
finding that the Corps took the requisite "hard look." Id. at
644. It noted that the Corps reasonably relied "on the exper-
tise of the WVDEP, the agency with primary responsibility
for water quality, in determining that impacts on water quality
will be insignificant." Id. at 645.

   The Environmental Coalition filed this appeal and at the
same time requested that the district court issue an injunction
to prevent Highland Mining from filling Reylas Fork valley
pending appeal. When the district court denied the motion, the
Coalition filed a similar motion in this court, which we too
denied, by order dated September 24, 2012.

                              II

   The Environmental Coalition contends first that the Corps,
in determining the baseline conditions of the relevant water-
shed, which was part of its analysis of the cumulative impact
of the proposed mining activity, made "a material factual
error" and "misapprehended" the baseline conditions. It
explains:

    The Corps’ [Combined Decision Document] repeat-
    edly stated that [Dingess Run] had good water qual-
    ity, healthy aquatic life, and no significant mining
    impacts. . . . In fact . . . WVDEP has measured Din-
8     OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
    gess Run as being in "poor" biological condition and
    listed its entire 7.4-mile length as an impaired water
    under § 303(d) of the CWA.

This argument requires us to evaluate both the Combined
Decision Document, in which the Corps makes its baseline
assessment of current conditions in the relevant watershed,
and the § 303(d) document, in which the WVDEP listed Din-
gess Run as among the State’s impaired streams. But our
review is limited to deciding whether the Corps considered
the "relevant factors" when assessing the baseline conditions
of the watershed. See Motor Vehicle Mfrs. Ass’n of U.S., Inc.
v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983).

   In a 2010 report, the WVDEP included Dingess Run on its
list of impaired streams for purposes of complying with CWA
§ 303(d). The WVDEP’s report explained that Dingess Run
was included on the list based on measurements of a portion
of a stream, using six benthic community metrics—i.e., met-
rics evaluating the stream bed for biological life—which were
combined into a "single multi-metric index." A stream scoring
above 68 using that index was categorized as biologically
unimpaired; a stream scoring between 60.6 and 68 fell within
a "gray zone"; and a stream scoring less than 60.6 was consid-
ered biologically impaired. Although the report found that
Dingess Run was "impaired," it cautioned that the scope of its
finding was limited:

    Most streams with low biological scores are listed as
    having an unknown source/cause of impairment on
    the 303(d) List and most are listed, by default, for
    their entire length. It is doubtful that the entire length
    of every stream is impaired, but without further data,
    the exact length of impairment is unknown.

J.A. 327. Thus, the WVDEP § 303(d) list represented, based
on limited data, the assessment that Dingess Run was "im-
       OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS            9
paired" when measured against the "single multi-metric
index" and that the causes for the impairment were unknown.

   This impairment finding undoubtedly raises the question of
whether Dingess Run would be able to assimilate the effects
of the Reylas mine, particularly the effects of the valley fill
that was the subject of the Corps’ § 404 permit. Two distinct
analyses conducted in the Combined Decision Document,
however, convince us that the Corps addressed the question
only after considering the relevant data about baseline condi-
tions and properly assessing them. First, the Corps analyzed
the conditions at the fill site itself. And second, the Corps rec-
ognized and analyzed the impaired conditions of the streams
in the relevant watershed.

   In its analysis of the conditions at the site of Reylas mine
fill, the Corps exhaustively reviewed the relevant data, report-
ing:

    The streams proposed for impact at the site have
    perennial, intermittent and ephemeral flow regimes.
    The perennial and intermittent streams exhibit rela-
    tively good water quality based on analytical meth-
    ods developed and approved by the USEPA and
    WVDEP. . . . Based on USEPA’s Rapid Bioassess-
    ment Protocol, the streams fall in the middle range
    of "fair-good" range for habitat features, and have
    good West Virginia Stream Condition Index
    (WVSCI scores). The ephemeral streams lack suffi-
    cient water flow to conduct these analyses. Within
    the perennial and intermittent streams, the macroin-
    vertebrate analysis indicates a good benthic commu-
    nity [representing the vitality of the stream bed] with
    good diversity with a dominance of shredders.
    Approximately 6% of the species were comprised of
    the sensitive mayfly species. The presence of these
    types of benthic species indicates the stream has the
    ability to provide functions such as transport of
10     OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
     nutrients, decomposition of organic input/detritus,
     and food web support. Overall, the perennial and
     intermittent stream channels located on-site are of
     good quality and do provide several important func-
     tions. The ephemeral streams, due to their lack of
     flow throughout the majority of the year, do not pro-
     vide these same functions.

J.A. 180-81. The Corps followed up this summary by detail-
ing the supporting data collected with respect to "physical
habitat," "water quality," "benthics," and "stream function-
ing."

   With respect to physical habitat, the Corps found that,
overall, five of the eight streams proposed for impact exhib-
ited good physical habitat, despite previous logging and deep
mine activities at the site.

  With respect to water quality, the Corps referred to data
collected in April 2004 and July 2007. The 2004 samplings
were conducted during the rainy season and presented

     overall good water quality for the majority of param-
     eters tested. Two sites, located within the perennial
     segments, had slightly elevated conductivities [dis-
     solved salts], while the site located higher in the
     watershed had a relatively low conductivity reading.

J.A. 203. The samplings revealed that magnesium was higher
than recommended but concluded:

     Although these parameters are slightly high, they do
     not appear to have resulted in adverse effects on the
     benthic communities at the sample sites as the data
     indicates thriving benthic communities.

Id. The 2007 sampling found that the conductivities were
higher, although magnesium levels remained similar to the
        OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS          11
2004 levels. As to the water quality aspect, the Corps con-
cluded:

      Overall, water quality on-site is good with the excep-
      tion of elevated conductivity and magnesium read-
      ings in the lower perennial and intermittent sections
      of Reylas Fork. Based on data obtained in down-
      stream segments of Bandmill Hollow, the receiving
      stream and Dingess Run magnesium levels fall
      within acceptable parameters established by
      WVDEP.

Id.

   With respect to benthics, the Corps noted that, based on
testing conducted in April 2004 and July 2007, "the benthic
community within the perennial and intermittent stream chan-
nels contained good benthic communities although there were
slight differences in species diversity." J.A. 203. The Corps
stated:

      [T]he unnamed first right tributary of Reylas Fork
      presented the most diverse benthic community how-
      ever the WVSCI scores indicated very good biologi-
      cal integrity at each sampling location. The
      remaining streams proposed for impact are ephem-
      eral and did not contain benthic communities. Over-
      all, the intermittent and perennial stream channels at
      the site contain good aquatic habitat despite the
      slightly elevated levels of conductivity and magne-
      sium present in several of the streams at the site.

Id.

   Finally, with respect to stream functioning, the Corps found
that "the majority of streams proposed for impacts are fully
functional and of high quality based primarily on their posi-
tion within the landscape, and how the stream interacts with
12     OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
geology, hydrology and soils, which influence biotic and
physical processes." J.A. 207.

  With the specific water data evaluated and the impairments
noted, the Corps’ Combined Decision Document concluded
with a summary that the streams at the impact site

     are of good quality with good physical aquatic habi-
     tat, good riparian cover, good water quality (with the
     exception of elevated conductivity and magnesium
     levels) and viable benthic communities.

J.A. 209.

   After looking at site-specific factors, the Corps turned its
attention to the Dingess Run watershed as a whole. It recog-
nized, at the outset, that "deep and surface coal mining and
timber removal activities have been on-going within the Din-
gess Fork Watershed . . . for the past 150 years." J.A. 247.
Because most of this activity was unregulated, "many areas
within the Appalachian Coal Fields have been adversely
impacted by these activities." Id. The Corps stressed the
importance of these earlier mining activities:

     These pre-SMCRA and pre-CWA impacts are rele-
     vant as they have set a baseline condition for water
     quality and aquatic habitat values within the water-
     shed. They also provide the context for purposes of
     assessing the significance of impacts in our NEPA
     analysis.

Id. (emphasis added).

   Taking this history into account, the Corps then considered
water-quality testing data provided by Highland Mining "from
eight baseline surface monitoring sites located on Bandmill
Hollow, as well as seven streams which flow into Dingess
Run." J.A. 247.
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS          13
   The Corps’ cumulative analysis thus considered data not
only from the impact area, but also from other tributaries. The
sampling from Bandmill Hollow, the area that would be
directly impacted by the Reylas mine valley fill, indicated ele-
vated levels of conductivity. See J.A. 203; J.A. 254. The sam-
plings from other upstream tributaries of Dingess Run
revealed "slightly elevated selenium levels." J.A. 248; see
also J.A. 253. Thus, the Corps acknowledged that the data
indicated a level of impairment. But it concluded that this
level of impairment did not prevent the streams in the Dingess
Run watershed from absorbing the impacts of past mining:

    [D]espite past unregulated mining, which has
    impacted the relevant environment and provides the
    context for this assessment, the watershed is heavily
    forested and continues to provide a functioning
    aquatic ecosystem with good water quality.

J.A. 256-57. Taking into account the historical damage as
well as current sampling, the Corps found that "[r]ecent water
quality and biological data has indicated the watershed is suf-
ficiently absorbing the impacts without significant aquatic
impairment and/or degradation." J.A. 256.

   These observations and assessments do not support the
Environmental Coalition’s claim that the Corps "misappre-
hended" existing conditions. The Corps’ conclusion that the
Dingess Run watershed had good water quality was a contex-
tual judgment made after considering all relevant data. More-
over, the Corps’ discussion of the baseline conditions was
more exhaustive than that found in West Virginia’s discussion
made in connection with its § 303(d) list and not necessarily
in tension with it. Specifically, the Corps recognized that the
watershed had elevated levels of conductivity and selenium.
See J.A. 203-07 (identifying elevated levels of conductivity);
J.A. 248 (acknowledging "slightly elevated selenium levels");
J.A. 253 ("Several streams have exhibited elevated selenium
levels during some sampling events"); J.A. 254 (recognizing
14     OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
high conductivity levels). The § 303(d) document, on the
other hand, was not pollutant-specific, concluding only that
the Dingess Run was "impaired."

   We thus find no merit to the Environmental Coalition’s
claim that the Corps "misapprehended" the baseline condi-
tions. The Corps considered the relevant factors, evaluating
both the impact site and the entire watershed. Only after this
evaluation did the Corps reach its informed judgment as to the
baseline conditions.

                             III

   For its second argument, the Environmental Coalition con-
tends that the Corps’ finding of cumulative insignificance was
"arbitrary and capricious" because the Corps irrationally dis-
missed the strong correlation between surface coal mining
activities and downstream biological impairment. Under the
Coalition’s reading of the Combined Decision Document, the
Corps failed to take a "hard look" at potential environmental
consequences because the Document is "not supported by any
reasoned analysis of, or expert opinion about, the science on
conductivity and stream impairment." Stated otherwise, the
Coalition challenges the rationality of the Corps’ predictive
judgment that the valley fill from the Reylas mine will not
have a cumulatively significant impact on the streams in the
Dingess Run watershed.

  The district court rejected the Environmental Coalition’s
argument, observing that the Corps had before it

     a wide array of evidence about water quality and the
     effects of conductivity including the SMCRA per-
     mit, the NPDES permit, the § 401 certification, and
     the studies provided by the Plaintiffs and the EPA.
     The [Combined Decision Document] reflects a sub-
     stantive review of these materials, after which the
     Corps concluded that the individual and cumulative
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS            15
    environmental impacts of this permit would not rise
    to the level of significance required to trigger an EIS.

OVEC, 883 F. Supp. 2d at 645. The court thus concluded that
the Corps had "analyzed the cumulative impacts, ‘articulated
a satisfactory explanation for its conclusion,’ and thus has not
acted arbitrarily or capriciously." Id. (quoting Aracoma, 556
F.3d at 209).

   In assessing whether a project’s impacts will be significant,
the Agency must take a "hard look" at potential environmen-
tal consequences. Robertson v. Methow Valley Citizens Coun-
cil, 490 U.S. 332, 350 (1989). "The hallmarks of a ‘hard look’
are thorough investigation into environmental impacts and
forthright acknowledgment of potential environmental
harms." Nat’l Audubon Soc’y v. Dep’t of Navy, 422 F.3d 174,
185 (4th Cir. 2005).

   In this case, the Corps collected the competing views of the
Environmental Coalition, the EPA, the WVDEP, and High-
land Mining and examined them in some detail, along with
the supporting data. Indeed, a substantial portion of the Com-
bined Decision Document is dedicated to addressing water
quality and the cumulative effect of the Reylas mine fill on
water quality. The Corps devoted four years to the effort,
meeting repeatedly with the parties to resolve concerns,
prompting the district court to observe:

    The administrative record documents the extensive
    interaction among the Corps, the EPA, the WVDEP
    and Highland to resolve the EPA’s concerns. Though
    Highland and the WVDEP disputed the EPA’s posi-
    tion on conductivity and cumulative water quality
    impacts of valley fills, the Corps focused on site-
    specific factors which provide at least a rational
    basis for its decision.

OVEC, 883 F. Supp. 2d at 644.
16    OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
   In response to the EPA’s concerns, the Corps adopted mea-
sures agreeable to the EPA as conditions of its § 404 permit,
involving reduction of the fill and post-permit monitoring and
other mitigation requirements. These special conditions incor-
porated a series of best management practices designed to
minimize increases in conductivity and total dissolved solids
associated with the mining activities of Highland Mining. The
conditions also required that if the monitoring showed that the
mining activities were resulting in adverse impacts to water
quality, Highland Mining would be required to initiate reme-
dial actions, provide additional water quality-based mitigation
under the terms of the permit, or both. J.A. 265-66. All of
these conditions were incorporated as conditions of the § 404
permit. This accommodation process was significant and,
indeed, resulted in a two-year delay of the issuance of the
§ 404 permit.

   In addition to these modifications to the § 404 permit, the
Corps’ Combined Decision Document gave a "hard look" at
conductivity and water quality more generally. After reciting
the history of mining in the Dingess Run watershed over the
period of 150 years and its impact, the Document evaluated
the data from various sources which indicated that the water-
shed would still be able to absorb the impacts of the Reylas
mine without significant aquatic impairment or degradation.

   The Document specifically discussed the elevated levels of
conductivity and selenium in the streams. As to the selenium,
it concluded that the source of selenium in that area is located
"in a stratum or strata located in rock formations higher in ele-
vation than those proposed to be mined as part of this proj-
ect," J.A. 248, so that the selenium level would not be
increased by the mine. And as to conductivity, the Document
compared elevated conductivity levels found in areas down-
stream of other valley fills with those of streams containing
no valley fills. It found that "benthic microinvertebrate com-
munities do become established downstream of valley fills
and often are comparable to those communities in un-
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS          17
impacted stream channels." J.A. 254. Indeed, the conclusions
were supported in part by a study that showed that streams
below valley fills sometimes did better than the streams con-
stituting the reference sites. J.A. 262.

   At bottom, the Document reached the conclusion that "the
valley fill, sediment pond, and mine through activities, if con-
ducted in accordance with all applicable state and Federal reg-
ulations, should not contribute to or result in cumulative
significant adverse impacts to the aquatic or human environ-
ment within the Dingess Run Watershed." J.A. 256.

   Thus, contrary to the Environmental Coalition’s contention
that the Corps failed to take a hard look at conductivity and
stream impairment, the record amply shows that the Corps
grappled with the issue extensively, rationally finding that (1)
the connection between conductivity and stream impairment
was not strong enough to preclude a permit and (2) the com-
promise measures agreed to by the EPA and Highland Mining
would successfully mitigate the potential for adverse effects.

   With the inability to demonstrate that the Corps failed to
take a "hard look," the Environmental Coalition’s arguments
are reduced to no more than a substantive disagreement with
the Corps. But our review is limited, and we may not "use
review of an agency’s environmental analysis as a guise for
second-guessing substantive decisions committed to the dis-
cretion of the agency." Nat’l Audubon Soc’y, 422 F.3d at 185
(citing Robertson, 490 U.S. at 350).

   The Corps’ predictive judgment in this case was based on
facts and recommendations, adduced during a lengthy consul-
tation between the Corps, Highland Mining, the EPA, and the
WVDEP, and we conclude that this process satisfies NEPA’s
procedural requirement to take a "hard look." See Hughes
River Watershed Conservancy v. Johnson, 165 F.3d 283, 288
(4th Cir. 1999) ("[A]n agency takes a sufficient ‘hard look’
when it obtains opinions from its own experts, obtains opin-
18       OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
ions from experts outside the agency, gives careful scientific
scrutiny and responds to all legitimate concerns that are
raised" (citing Marsh v. Oregon Natural Resources Council,
490 U.S. 360, 378-85 (1989))). Because the Corps’ analysis
satisfied NEPA’s procedural requirements, the Corps’ finding
of cumulative insignificance is neither arbitrary nor capri-
cious. See Aracoma Coal, 556 F.3d at 209.

     Accordingly, we affirm the judgment of the district court.

                                                    AFFIRMED

WILKINSON, Circuit Judge, concurring:

   Several aspects of the record are troubling in this case: the
EPA’s March 2009 comments, the Dingess Run WVSCI
score of 33, and the WVDEP’s listing of Dingess Run as an
impaired waterway. But, on balance, they are not enough to
reverse in light of the standard of review, the unfolding of the
agency process, and the analysis in the Corps’ Combined
Decision Document. I am thus pleased to concur in the major-
ity opinion. I write separately, however, to underscore two
critical points in the analysis.

                                I.

   First, in March of 2009, the EPA stated that it had "signifi-
cant concern regarding the impact to the human environment"
from the proposed mining project. J.A. 109. The question then
becomes whether a court should seize upon this assessment as
a basis for vacating the later grant of the fill permit under the
Clean Water Act. If we were to do so under these circum-
stances, I fear we would stifle the very agency candor and
applicant responsiveness that is essential to the proper func-
tioning of the administrative process and, ultimately, to the
goal of natural resource protection.

  Here, for instance, the EPA’s March 2009 objections to
Highland Mining’s initial permit application precipitated an
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS          19
extended dialogue among the Corps, the EPA, and Highland.
The product of this discussion was meaningful concessions
from Highland and the Corps that were responsive to the
EPA’s stated apprehensions. Specifically, Highland and the
Corps agreed to a more extensive mitigation plan for the proj-
ect site, additional testing and monitoring of water quality in
and around the site, and a number of best management prac-
tices to be employed in operating the mine. See Maj. Op. at
6, 15-16. Following these modifications, the EPA concluded
in September 2009 that Highland and the Corps "could move
forward with issuance of the permit." J.A. 144. But for the
EPA’s March 2009 comment letter, the foregoing corrective
measures might not have been considered.

   Even after this litigation commenced, the agency dialogue
continued. In April 2011, the Corps determined that the chal-
lenged permit merited "further consideration" and filed an
unopposed motion for voluntary remand in the district court.
The Corps and Highland then engaged in additional commu-
nication regarding the project’s potential environmental
impact and Highland’s associated mitigation efforts. This
exchange led to further evaluation of operating practices at
the proposed mine, with the Corps ultimately concluding that
"[i]mpacts to the waters of the U.S. associated with the pro-
posal have been minimized to the maximum extent practica-
ble regardless of the designated [post-mine land use]." Status
Report, No. 3:11-cv-00149, ECF No. 45, at 7 (S.D.W. Va.
Sept. 20, 2011).

   There is a limit to the extent that courts can direct the CWA
process, given the episodic nature of our involvement, the
standard of review, and the lack of our own extensive scien-
tific expertise. We can, however, try to adjust incentives in a
manner that facilitates the protection of natural resources in
the course of agency deliberation. The administrative process
works best when interested parties are comfortable sharing
information that can shed light on issues affecting the ultimate
outcome. Were we to jump on the EPA’s March 2009 com-
20    OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS
ments, the single low WVSCI score, or the Corps’ earlier
request for voluntary remand as a basis for reversing the
Corps’ decision, it would discourage honest conversation and
meaningful corrective actions in future cases.

   Accordingly, rather than utilize judicial review in a manner
that encourages regulators or those they regulate to sweep
adverse evidence under the rug, our affirmance here encour-
ages them to keep the dialogue above board and disclose even
problematic information so that the appropriate parties can
take steps to address any underlying environmental concerns.
There will, of course, be cases where substantial evidence
fails to support the Corps’ decision to dispense with an envi-
ronmental impact statement, but I cannot conclude the Corps
acted arbitrarily in granting the CWA permit here after pro-
longed, but productive, deliberation.

                               II.

   When an agency is tasked with determining the environ-
mental impact of a project upon an ecological setting that is
already the situs of other activity, there is a real danger that
the agency’s appraisal may fail to take a wide enough view
of the collective impact of all of the environmental effects that
the location has experienced over time. Recognizing the risk
that an agency may proceed with too myopic a focus on the
singular effects of the particular project before it, NEPA calls
for an EIS if a project produces a "cumulatively significant
impact" in tandem with other activity. 40 C.F.R.
§ 1508.27(b)(7) (emphasis added). This cumulative impact
requirement, however, is not one with which agencies always
comply. See Grand Canyon Trust v. FAA, 290 F.3d 339, 342-
43 (D.C. Cir. 2002) (discussing cases where agencies have
failed to consider cumulative impact).

   Here, by contrast, the record demonstrates that the Corps
gave full consideration not just to the incremental effects of
the proposed valley fill, but also to its cumulative effects. See
      OHIO VALLEY ENVIRONMENTAL v. U. S. ARMY CORPS         21
Maj. Op. at 12-13. The CDD thus included an in-depth dis-
cussion regarding the cumulative impacts of the proposed
project. The Corps considered the "impacts associated with
the [project] when added to other past, present, and reason-
ably foreseeable future impacts." J.A. 246. It ultimately con-
cluded that, in light of the evidence in the record, "it is not
expected that the Reylas Surface Mine would, when com-
bined with other mining activities within the Dingess Run
Watershed, result in significant cumulative impacts to the
human and/or aquatic environment." J.A. 256. Again, I cannot
conclude after careful review of this record that the required
cumulative impact assessment was arbitrarily ignored.

                             III.

   The Corps has been tasked with regulating mineral extrac-
tion in West Virginia in a way that respects the extraordinary,
but fragile, environmental and natural resources of that state.
Here, the record demonstrates a frankness in the agency dia-
logue that resulted in a greater respect for NEPA’s basic aims.
Given the corrective measures ultimately taken, I believe it
would be counterproductive to leap upon the earlier EPA and
Corps reservations as a reason to reverse. To do so would pro-
duce darkness in the process, not light. Of course, the judi-
ciary is not a rubber stamp on agency action, and there are
times when contrary evidence will either not support or will
actively undercut an agency’s decision. But this is not one of
those cases. I therefore concur in the majority’s opinion and
in its decision to affirm.
