                       RECOMMENDED FOR FULL-TEXT PUBLICATION
                           Pursuant to Sixth Circuit I.O.P. 32.1(b)
                                   File Name: 13a0115p.06

                 UNITED STATES COURT OF APPEALS
                                FOR THE SIXTH CIRCUIT
                                  _________________


                                                   X
                                                    -
 KENTUCKY RIVERKEEPER, INC.;
                                                    -
 KENTUCKIANS FOR THE COMMONWEALTH,
 INC.; KENTUCKY WATERWAYS ALLIANCE,                 -
                                                    -
                                                       No. 11-6083
 INC.,
                           Plaintiffs-Appellants, ,>
                                                    -
                                                    -
                                                    -
             v.
                                                    -
                                                    -
                                     Defendants, -
 ROBERT A. ROWLETTE, JR., et al.,

                                                    -
                                                    -
                                                    -
 CARL A. STROCK, Lieutenant General, Chief
 of Engineers and Commander of the U.S.             -
                                                    -
                                                    -
 Army Corps of Engineers; RAYMOND G.

 Army Corps of Engineers, Louisville District; -
 MIDKIFF, Colonel, District Engineer, U.S.
                                                    -
 DANA R. HURST, Colonel, District Engineer,         -
                                                    -
                                                    -
 U.S. Army Corps of Engineers, Huntington
                                                    -
 District; STEVEN J. ROEHMHILDT, Colonel,
                                                    -
 District Engineer, U.S. Army Corps of
 Engineers, Nashville District,                     -
                          Defendants-Appellees. N
                     Appeal from the United States District Court
                   for the Eastern District of Kentucky at Pikeville.
                No. 7:05-cv-181—David L. Bunning, District Judge.
                                 Argued: October 4, 2012
                           Decided and Filed: April 22, 2013
            Before: SILER and COOK, Circuit Judges; STEEH, District Judge.*




        *
        The Honorable George C. Steeh, United States District Judge for the Eastern District of
Michigan, sitting by designation.


                                              1
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                     Page 2


                                  _________________

                                       COUNSEL
ARGUED: James M. Hecker, PUBLIC JUSTICE, Washington, D.C., for Appellants.
Tamara N. Rountree, UNITED STATES DEPARTMENT OF JUSTICE, Washington,
D.C., for Appellees. ON BRIEF: James M. Hecker, PUBLIC JUSTICE, Washington,
D.C., Stephen A. Sanders, APPALACHIAN CITIZENS LAW CENTER, Whitesburg,
Kentucky, Joseph M. Lovett, APPALACHIAN MOUNTAIN ADVOCATES,
Lewisburg, West Virginia, for Appellants. Tamara N. Rountree, UNITED STATES
DEPARTMENT OF JUSTICE, Washington, D.C., for Appellees.
                                  _________________

                                        OPINION
                                  _________________

        COOK, Circuit Judge.        Plaintiffs-Appellants Kentucky Riverkeeper, Inc.,
Kentucky Waterways Alliance, Inc., and Kentuckians for the Commonwealth, Inc.
(collectively “Riverkeeper”) sued the Army Corps of Engineers alleging violations of
the Clean Water Act (CWA), 33 U.S.C. § 1344(e), the National Environmental
Protection Act (NEPA), 42 U.S.C. § 4332(2)(C), and the Administrative Procedure Act
(APA), 5 U.S.C. § 706, during the Corps’ issuance of two nationwide coal-mining
waste-discharge permits in 2007. The district court granted summary judgment to
the Corps, and Riverkeeper appeals. During Riverkeeper’s appeal, the two permits at
issue expired. For the following reasons, the case remains in controversy and we
REVERSE the district court’s judgment in part.

                                             I.

A. The Nationwide Permits: NWP 21 and NWP 50

        The Clean Water Act requires the Army Corps of Engineers to issue permits for
mining activities that discharge dredged or fill material into United States waterways.
33 U.S.C. § 1344. The Corps engages in two permitting options, each different in scope.
It issues either individual permits that allow an individual applicant’s project to proceed
or general permits that authorize a specific category of activities on a state, regional, or
nationwide basis. For activities covered by a general permit, operators may forgo the
No. 11-6083      Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                   Page 3


more burdensome process for obtaining an individual permit and instead seek
authorization under the general permit. See Ohio Valley Envtl. Coal. v. Bulen, 429 F.3d
493, 503 (4th Cir. 2005) (“The process for obtaining authorization under a general
permit . . . is significantly more expeditious than the process for obtaining an individual
permit under section 404(a).”). The Corps issues a general permit only if the regulated
activities are similar in nature, will “cause only minimal adverse environmental effects
when performed separately,” and will cause “only minimal cumulative adverse effect on
the environment.” 33 U.S.C. § 1344(e)(1).

       In 2007, the Corps issued two nationwide general permits (hereinafter the
“nationwide permits”): permit 21 and permit 50. Permit 21 authorized surface coal-
mining operations to discharge dredged and fill material into waters of the United States
(i.e., streams); permit 50 allowed underground coal-mining operations to do the same.
Before issuing each permit, the Corps conducted a public notice-and-comment period
and completed required environmental analyses, including a cumulative-impacts
analysis.     Each cumulative-impacts analysis projected the permits’ respective
environmental impacts before determining that compensatory mitigation would reduce
adverse impacts to a minimal level. The Corps disclosed its analyses and findings in
each nationwide permit’s Environmental Assessment (hereinafter “the Assessment(s)”),
prepared for NEPA purposes in lieu of an environmental impact statement. The
nationwide permits became effective on March 19, 2007.

       Projects seeking authorization under the nationwide permits faced two additional
layers of Corps oversight. First, a proposal needed to pass muster under any regional
“public interest” requirements imposed by the Corps’ division engineers in their
discretion. 33 C.F.R. § 330.5(c)(1). Second, the Corps’ local district engineers had to
approve a project’s pre-construction notification. Id. § 330.5(c)(2). A district engineer
could authorize or suspend projects, or impose project-specific special conditions to
ensure that the project has only minimal cumulative net impacts. See id. § 330.5(d).
No. 11-6083        Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                                Page 4


         The nationwide permits expired on March 18, 2012, but the Corps extended the
permits until March 18, 2013 for projects started before the 2012 expiration date.
77 Fed. Reg. 10,184, 10,184 (Feb. 21, 2012). Additionally, in order to “provide an
equitable and less burdensome transition” and avoid a “significant hardship” for coal
operators, id. at 10,209, the Corps granted a five-year accommodation (until 2017) to
activities authorized under permit 21 “without applying the new limits imposed [by 2012
amendments to the permit],” id. at 10,184. The Corps estimates that approximately
70 surface coal-mining activities authorized under permit 21 qualify for this five-year
reauthorization. Id. at 10,209.

B. District Court Proceedings

         Riverkeeper sued the Corps, alleging that the cumulative-impacts analyses
prepared for the Assessments authorizing the nationwide permits violated the CWA,
NEPA, and the APA.1 Riverkeeper advanced two primary challenges to the permits’
Assessments: (1) that the Corps bypassed a necessary NEPA consideration, the present
effects of past permit authorizations, see 40 C.F.R. § 1508.7–.9; and (2) that the Corps
failed—in violation of the CWA, NEPA, and the APA—to properly explain how
compensatory mitigation would ensure cumulatively minimal impacts.                               See Ky.
Riverkeeper, Inc. v. Midkiff, 800 F. Supp. 2d 846 (E.D. Ky. 2011). In making these
arguments, Riverkeeper relied on a district court decision from West Virginia, Ohio
Valley Environmental Coalition v. Hurst, 604 F. Supp. 2d 860 (S.D. W. Va. 2009), that




         1
           Kentucky Riverkeeper, Inc., Kentucky Waterways Alliance, Inc., and Kentuckians for the
Commonwealth, Inc. collectively challenged nationwide permits 21, 49, and 50 (2007). The district court
held that each plaintiff lacked standing to challenge permit 49, and the parties did not appeal this ruling.
The court determined that Kentucky Waterways Alliance and Kentuckians for the Commonwealth—but
not Kentucky Riverkeeper—could pursue their claims against permits 21 and 50 because “prior
authorizations remain effective and filling activities can continue under those authorizations until March
2013.” Ky. Riverkeeper, Inc. v. Midkiff, 800 F. Supp. 2d 846, 859–60, 863 (E.D. Ky. 2011).
          Appellants argue that the court erred in dismissing Kentucky Riverkeeper, Inc. from the litigation
below. The Corps does not defend Kentucky Riverkeeper, Inc.’s dismissal. (Appellee Br. at 2 n.2.) Yet,
because the district court found that Kentucky Waterways Alliance, Inc. and Kentuckians for the
Commonwealth, Inc. have standing, we need not inquire whether Kentucky Riverkeeper, Inc. also had
standing. See, e.g., Clinton v. City of New York, 524 U.S. 417, 431 n.19 (1998); Bowsher v. Synar,
478 U.S. 714, 721 (1986); Chabad of S. Ohio & Congregation Lubavitch v. City of Cincinnati, 363 F.3d
427, 432 n.1 (6th Cir. 2004) (“[I]n a facial challenge such as this where one party has standing, we need
not consider the issue of standing of other parties to the action.”).
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                   Page 5


invalidated permit 21 “for the very same reasons.” Ky. Riverkeeper, 800 F. Supp. 2d at
865.

       The district court rejected Hurst’s reasoning and granted summary judgment to
the Corps, finding that the Corps adequately reviewed the present effects of past
nationwide permit authorizations and properly relied on compensatory mitigation to
ensure minimal cumulative impacts. Riverkeeper timely appeals, advancing the same
arguments presented to the district court. We have jurisdiction under 28 U.S.C. § 1291.

                                             II.

       Before we consider the merits of Riverkeeper’s claims, we address the Corps’
argument that the nationwide permits’ expiration renders Riverkeeper’s claims moot.

       “It is a basic principle of Article III that a justiciable case or controversy must
remain extant at all stages of review, not merely at the time the complaint is filed.”
Decker v. Nw. Envtl. Def. Ctr., 133 S. Ct. 1326, 1335 (2013). “A case becomes moot
only when it is impossible for a court to grant any effectual relief whatever to the
prevailing party,” id., and a change in circumstances that renders a court unable to grant
petitioners meaningful relief may prudentially moot an action, see Greenbaum v. EPA,
370 F.3d 527, 534–35 (6th Cir. 2004). The Corps argues that the March 18, 2012
expiration of the nationwide permits prudentially moots Riverkeeper’s appeal. But when
an expired permit’s conditions remain in effect, so too does the case and controversy.
In Kescoli v. Babbitt, the Ninth Circuit distinguished challenges to agency action that
“had already begun and ended” from challenges where the issuance of a renewal permit
sustains the controversy.     101 F.3d 1304, 1309 (9th Cir. 1996).         If “the same
[challenged] condition [remains] in effect and continues to govern [defendant’s] coal
mining operations[,] . . . [t]he same controversy exists after the issuance of the renewal
permit.” Id.

       Though the permits here expired, the Corps grandfathered mining activities
authorized by permit 21 for five years, allowing project reauthorization “without
applying the new limits imposed on [2012 permit 21].” 77 Fed. Reg. at 10,184 (titled
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                    Page 6


“Grandfather Provision for Expiring NWPs”). These reauthorizations, effective until
2017, allow projects authorized in reliance on permit 21’s challenged cumulative-
impacts analysis to evade considerably tighter restrictions on surface coal mining. See
id. It matters not that “the 2012 versions of [permits] 21 and 50 are significantly
different from the [permits] challenged here” (Appellee Br. at 29), because the Corps
incorporated permit 21 into its 2012 amended form and therefore extended its reliance
on the challenged cumulative-impacts analysis. See Kescoli, 101 F.3d at 1309.

       We do not consider Riverkeeper’s challenges to permit 50, however, because
projects authorized under permit 50 were extended only for one year, until March 18,
2013. 77 Fed. Reg. at 10,184. Because the Corps no longer relies on that now-expired
permit’s challenged cumulative-impacts analysis, we analyze only the live controversy
concerning projects reauthorized under permit 21.

                                            III.

A. Standard of Review

       We review the district court’s summary judgment rulings de novo and the Corps’
permitting decisions under the APA’s arbitrary and capricious standard. Ky. Waterways
Alliance v. Johnson, 540 F.3d 466, 473 (6th Cir. 2008). Summary judgment is proper
if the record shows that no genuine dispute exists as to any material fact, and the movant
is entitled to judgment as a matter of law. Fed. R. Civ. P. 56(a). The APA directs courts
to “hold unlawful and set aside agency action, findings, and conclusions found to be
arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.”
5 U.S.C. § 706(2)(A). An agency’s decision is arbitrary and capricious when the agency
has:

       relied on factors which Congress had not intended it to consider, entirely
       failed to consider an important aspect of the problem, offered an
       explanation for its decision that runs counter to the evidence before the
       agency, or is so implausible that it could not be ascribed to a difference
       in view or the product of agency expertise.

Nat’l Ass’n of Home Builders v. Defenders of Wildlife, 551 U.S. 644, 658 (2007).
No. 11-6083       Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                 Page 7


          “Judicial review of NEPA compliance is limited in scope.” Cmtys., Inc. v. Busey,
956 F.2d 619, 623 (6th Cir. 1992). We “ensure that the agency has adequately
considered and disclosed the environmental impacts of its actions and that its decision
is not arbitrary or capricious.” Balt. Gas & Elec. Co. v. Nat’l Res. Def. Council, 462
U.S. 87, 97–98 (1983); see also Robertson v. Methow Valley Citizens Council, 490 U.S.
332, 350 (1989) (explaining that NEPA “does not mandate particular results, but simply
prescribes the necessary process”). In reviewing challenges to NEPA compliance, we
give “substantial deference” to the regulations promulgated by the Council on
Environmental Quality (CEQ), the federal agency established to fill in the gaps of
NEPA’s regulatory scheme. Marsh v. Or. Natural Res. Def. Council, 490 U.S. 360, 372
(1989).

B. The NEPA Regulations & The Cumulative Impact of Past Actions

          NEPA employs a “set of ‘action-forcing’ procedures that require agencies to take
a ‘hard look at environmental consequences.’” Robertson, 490 U.S. at 350 (internal
quotation marks omitted) (citing Kleppe v. Sierra Club, 427 U.S. 390, 410 n.21 (1976)).
One of these action-forcing procedures requires federal agencies to prepare an
environmental impact statement for all “major Federal actions significantly affecting the
quality of the human environment.” 42 U.S.C. § 4332(C). To spare agencies the
hardship of conducting exhaustive review of every NWP proposal’s environmental
impact, CEQ authorized agencies to first prepare a less burdensome environmental
assessment as a method for determining whether a proposal needed an environmental
impact statement. See 40 C.F.R. § 1508.9. The Corps did that here, deeming an EIS
unnecessary. Though less demanding than an environmental impact statement, an
environmental assessment still required the authorizing agency to consider the
environmental impacts of its proposals. See id. § 1508.9(b); Ctr. for Biological Diversity
v. Nat’l Highway Traffic Safety Admin., 538 F. 3d 1172, 1215 (9th Cir. 2008) (explaining
that environmental assessments “need not conform to all the requirements” of an
environmental impact statement) (internal quotation marks omitted).
No. 11-6083         Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                                 Page 8


         The NEPA regulations provide that environmental assessments “[s]hall include
brief discussions of the . . . environmental impacts of the proposed action and
alternatives,” 40 C.F.R. § 1508.9(b), including “cumulative impact,” see id.
§ 1508.7–.8.2 Cumulative impact refers to “the impact on the environment which results
from the incremental impact of the [proposed] action when added to other past, present,
and reasonably foreseeable future actions.” Id. § 1508.7.

         The Corps concedes that these regulations required it to assess the impact of past
actions, but cites a CEQ advisory memorandum for the proposition that it could satisfy
this obligation by considering past actions’ impact “in the aggregate.” (Appellee Br. at
31–32        (citing    Council       on    Environmental           Quality,      Guidance         on    the
Consideration           of     Past     Actions        in     Cumulative          Effects        Analysis
(2005)          [hereinafter             “Guidance”]               at     2–3,        available           at
http://energy.gov/sites/prod/files/nepapub/nepa_documents/RedDont/G-CEQ-PastAct
sCumulEffects.pdf).) The Ninth Circuit has already adopted this view from the
Guidance, see League of Wilderness Defenders-Blue Mountains Biodiversity Project v.
U.S. Forest Serv., 549 F.3d 1211, 1217 (9th Cir. 2008), and we have no qualms agreeing.
The Corps’ argument runs aground, however, because the Assessment failed to identify
any impact—aggregate or otherwise—of past actions.

         Not so, says the Corps, because the Assessment reflects its consideration of the
“national environmental baseline,” a term it uses to refer to a compilation of statistical
surveys regarding available aquatic natural resources throughout the United States.
Indeed, pages 12 to 17 of the Assessment include portions of various national surveys
in discussing available resources, but the Assessment’s discussion of these surveys
makes no mention of the impact of prior actions. In fact, section 4.0 of the Assessment,
titled “Environmental Consequences,” expressly disclaims consideration of past impacts:
“Only the reasonably foreseeable direct or indirect effects [of the proposed nationwide



         2
           The NEPA regulations synonymously use the words “impacts” and “effects.” “Effects”
encompass a variety of factors, including “ecological . . . , aesthetic, historic, cultural, economic, social,
or health, whether direct, indirect, or cumulative.” 40 C.F.R. § 1508.8.
No. 11-6083       Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                           Page 9


permit] are included in the environmental assessment.” (NWP 21 Decision Doc. at 20.)3
Given this statement, we may not infer that surveys discussing the availability of
national resources reflect the Corps’ consideration of the cumulative impact of past
actions. This “baseline” argument also comes as a surprise because, as Riverkeeper
points out, the Corps did not so argue before the district court in Hurst. Rather, it
appears that the Corps defended permit 21’s Assessment in that case by categorically
denying that the NEPA regulations required consideration of past impacts. Hurst, 604
F. Supp. 2d at 885–86 & n.19 (rejecting the Corps’ conclusory argument that past
activities authorized under permit 21 have no bearing on its cumulative-impact analysis).

        The Corps provides a nonresponsive argument with its three-tier review process
for individual activities seeking approval under permit 21. The Corps notes that its
divisions and districts will add regional conditions that enhance environmental
protections and address local concerns. It maintains that its division engineers “consider
. . . the present effects of past actions in greater detail than is possible for the nationwide
analysis.” But these additional assessments occur after the reauthorization of the
nationwide permit—itself an alternative to an individual permitting system—and
therefore presume that the Assessment satisfied the NEPA regulations’ prerequisites for
reauthorization. Though the Corps argues that “the nationwide level of review is only
the preliminary stage” of review, it acknowledges that the relevant NEPA regulations,
40 C.F.R. § 1508.7–.9, mandate that the Assessment include a cumulative-impact
analysis encompassing a review of past impacts. (Appellee Br. at 31–32.)

        Despite conceding its obligation under the NEPA regulations to consider past
impacts in the aggregate (Appellee Br. at 39–40), the Corps appears to read the CEQ
Guidance as overriding the § 1508.7 requirement to consider past impacts. Cf. 40 C.F.R.
§ 1508.7 (defining “cumulative impact” as “the impact on the environment which results
from the incremental impact of the [proposed] action when added to other past, present,
and reasonably foreseeable future actions.” (emphasis added)). Yet, the Corps offers no

        3
           Matching this exclusionary language, the same section of the Assessment states that “[t]he
following evaluation comprises the NEPA analysis,” thereby omitting the prior sections’ discussion of
available resources. (NWP 21 Decision Doc. at 19 (emphasis added).)
No. 11-6083      Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                  Page 10


authority that allows an interpretive guidance to work such a substantive change to a
duly promulgated regulation.

        The Guidance itself belies such a narrow reading. Issued by CEQ’s Chairman
in 2005, it states in pertinent part:

        The environmental analysis required under NEPA is forward-looking, in
        that it focuses on the potential impacts of the proposed action that an
        agency is considering. Thus, review of past actions is required to the
        extent that this review informs agency decisionmaking regarding the
        proposed action. This can occur in two ways:
        First, the effects of past actions may warrant consideration in the analysis
        of the cumulative effects of a proposal for agency action. CEQ interprets
        NEPA and CEQ’s NEPA regulations on cumulative effects as requiring
        analysis and a concise description of the identifiable present effects of
        past actions to the extent that they are relevant and useful in analyzing
        whether the reasonably foreseeable effects of the agency proposal for
        action and its alternatives may have a continuing, additive and significant
        relationship to those effects. In determining what information is
        necessary for a cumulative effects analysis, agencies should use scoping
        to focus on the extent to which information is “relevant to reasonably
        foreseeable significant adverse impacts,” is “essential to a reasoned
        choice among alternatives,” and can be obtained without exorbitant cost.
        40 CFR 1502.22. Based on scoping, agencies have discretion to
        determine whether, and to what extent, information about the specific
        nature, design, or present effects of a past action is useful for the
        agency’s analysis of the effects of a proposal for agency action and its
        reasonable alternatives.
        Agencies are not required to list or analyze the effects of individual past
        actions unless such information is necessary to describe the cumulative
        effect of all past actions combined. Agencies retain substantial discretion
        as to the extent of such inquiry and the appropriate level of explanation.
        Marsh v. Or. Natural Res. Council, 490 U.S. 360, 376–77 (1989).
        Generally, agencies can conduct an adequate cumulative effects analysis
        by focusing on the current aggregate effects of past actions without
        delving into the historical details of individual past actions.
        Second, experience with and information about past direct and indirect
        effects of individual past actions may also be useful in illuminating or
        predicting the direct and indirect effects of a proposed action. However,
        these effects of past actions may have no cumulative relationship to the
        effects of the proposed action. Therefore, agencies should clearly
        distinguish analysis of direct and indirect effects based on
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                  Page 11


       information about past actions from a cumulative effects analysis of past
       actions.

Guidance at 1–2.

       In our view, two aspects stand out. First, though reviewing agencies retain
considerable discretion to determine the “scop[e]” and “relevan[ce]” of past actions, and
may “focus[] on the current aggregate effects of past actions without delving into . . .
individual past actions,” this discretion coincides with their obligation to provide “a
concise description of the identifiable present effects of past actions to the extent that
they are relevant and useful in analyzing whether the reasonably foreseeable effects of
the agency proposal for action and its alternatives may have a continuing, additive and
significant relationship to those effects.” Id. at 1 (emphasis added). An environmental
assessment that omits consideration of past impacts, followed by a conclusory
suggestion that past impacts did not matter, cannot be in conformance. This is especially
true where the reviewing agency reauthorizes a nationwide permit involving the same
type of mining activities that cause the same type of environmental impacts. Second, the
Guidance instructs the reviewing agency to “distinguish” the use of past impacts to
forecast future impacts from the use of past impacts to assess cumulative impacts.

       The Corps did not do this. It used past impacts to forecast future impacts, but not
to assess cumulative impacts.         While taking advantage of the more lenient
environmental-assessment method (instead of the intensive environmental-impact-
statement method), the Corps short-circuited the “cumulative impact” analysis by
confining its review to an estimate of future impacts. The Corps reasonably relied on
data regarding past impacts to project future impacts, but it failed to combine the two to
gauge the cumulative impact of reauthorizing permit 21. Its Assessment offered no
explanation for this shortcoming. Such limited review not only avoids the NEPA
regulation’s definition of “cumulative impact,” but also the ordinary meaning of
“cumulative.” See Webster’s II New College Dictionary 275 (2d ed. 2001) (defining
“cumulative” as “[e]nlarging or increasing by successive addition”).
No. 11-6083       Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                Page 12


       The Corps directs us to its final decision reissuing permit 21. See 72 Fed. Reg.
11,092 (Mar. 12, 2007). There, the Corps responded to objections that the Assessment
neglected past-impacts analysis, id. at 11,094–96, by (i) invoking the CEQ Guidance’s
instruction “that agencies look at the present effects of past actions that are relevant
because of significant cause-and-effect relationships with the effects for the proposed
action,” and (ii) explaining that, because nationwide permits rarely authorize “activities
of a continuing nature . . . [t]he cumulative effects analysis is more properly focused on
the permits that can be used to authorize regulated activities, not past permits that have
expired.” Id. at 11,096. Thus, it would seem, the Corps deemed past-impacts analysis
irrelevant to a determination of cumulative impact—the same position it took in the
Hurst litigation. But the Corps fails to explain how prior similar mining projects
authorized under the same permit have no environmental impact, such that a cumulative-
impact analysis should properly exclude them. As the Hurst court explained, “Even if
the individual projects (i.e. the dredging and filling) authorized under past [versions of
permit 21] were complete, the regulations require the Corps to assess the ‘present effects
of past actions.’ Whether the project is complete has no bearing on whether that project
results in present effects to the environment.” Hurst, 604 F. Supp. 2d at 885–86 (citing
Guidance at 1).

       The district court recognized that the Corps “did not provide a detailed
explanation for its belief that [past permit 21 activities] would not have a continuing
effect,” but excused this because the “Corps’ path can reasonably be discerned.” Ky.
Riverkeeper, 800 F. Supp. 2d at 868 (citing Motor Vehicle Mfrs. Ass’n of the U.S., Inc.
v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983)). The district court primarily
relied on the Corps’ final-decision statements, as well as the Corps’ assurance that
compensatory mitigation would offset past environmental impacts. Id. at 867–69. These
justifications do not satisfy the Corps’ obligation to include a cumulative-impact analysis
where the Assessment completely neglects past impacts from that calculus.

       In simultaneously arguing that it did and did not need to consider past impacts
(Appellee Br. at 31–32 vs. final-decision statements and Hurst position), and that it did
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                 Page 13


and did not do so (the “baseline” argument vs. the final-decision statements), the Corps
stakes no position. This much is clear from the administrative record: the Assessment
omitted the present effects of past actions from its cumulative-impact analysis, as
required by 40 C.F.R. § 1508.7, and its conclusory final-decision statements do not cure
this defect. Though we conduct “limited” NEPA review, Cmtys., Inc., 956 F.2d at 623,
we have a duty to set aside the Corps’ action when it eschews its NEPA obligation to
“adequately consider[] and disclose[] the environmental impact of its actions.” Balt. Gas
& Elec. Co., 462 U.S. at 97–98. Because the Assessment failed to comply with the
NEPA regulations’ requirements, we set aside the Corps’ reauthorization of permit
21 as arbitrary and capricious. See 5 U.S.C. § 706(2)(A); Motor Vehicles Mfrs. Ass’n,
463 U.S. at 43 (reviewing agency action to “consider whether the decision was based on
a consideration of the relevant factors”); Citizens to Preserve Overton Park v. Volpe,
401 U.S. 402, 416–17 (1971) (same).

C. Permit 21’s Reliance on Compensatory Mitigation

       We find similarly troubling the Corps’ defense to Riverkeeper’s compensatory-
mitigation claims under the CWA and NEPA. Citing CWA regulations, Riverkeeper
specifically faults the Corps’ failure to provide “analysis or documentation” for the
Assessment’s determination that compensatory mitigation will ensure cumulatively
minimal adverse effects. (Appellant Br. at 27–28 (citing 40 C.F.R. §§ 230.7(b),
230.11).) Though the Corps disputes its failure to provide an explanation for its
decision, it offers no response to Riverkeeper’s no-documentation charge.

       Under the CWA, the issuance of a nationwide permit hinges on the reviewing
agency’s finding that a proposal has only a “minimal cumulative adverse effect on the
environment.” 33 U.S.C. § 1344(e)(1); see also 40 C.F.R. § 230.7(a)(3). In making this
finding, the relevant CWA regulations require an agency to (i) “set forth in writing an
evaluation of the potential . . . cumulative impacts of the category of activities to be
regulated” by the proposal, 40 C.F.R. § 230.7(b), and (ii) provide “documented
information supporting each factual determination [required by § 230.11],” id.
No. 11-6083        Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                            Page 14


§ 230.7(b)(1) (emphasis added), including a determination of cumulative impacts, id.
§ 230.11(g).4 The Corps, in reauthorizing permit 21, made the following factual finding:

         Using the current trend, approximately 1,085 activities could be
         authorized over a five year period until [permit 21] expires, resulting in
         impacts to approximately 320 acres of waters of the United States,
         including jurisdictional wetlands. Approximately 540 acres of
         compensatory mitigation would be required to offset those impacts. The
         required compensatory mitigation will attenuate cumulative impacts on
         the Nation’s aquatic resources, so that the net effects on the aquatic
         environment resulting from the activities authorized by [permit 21] will
         be minimal.

(NWP 21 Decision Doc. at 22.) Absent from this discussion is any mention of the
Corps’ factual underpinnings for this determination. Both in its briefing and at oral
argument, the Corps relied on its procedures overseeing individual projects’ success in
mitigating environmental impacts. (Appellee Br. at 52–53; Oral Arg. at 30:40–32:36.)5
Yet these post-issuance mechanisms do not explain how the Corps arrived at its pre-
issuance minimal cumulative-impact findings. The Corps fails to make this showing
despite Hurst’s earlier adverse decision on the point. See Hurst, 604 F. Supp. 2d at 887
(deeming “conclusory” the Corps’ “unsupported belief in the success of mitigation
measures” and explaining that the Corps’ “‘mere listing’ of mitigation measures and
processes, without any analysis, cannot support a cumulative impacts determination”).

         Citing our decision in Sierra Club v. Slater, 120 F.3d 623, 636 (6th Cir. 1997),
the district court noted that “it is not necessary to have a final, detailed mitigation plan
prior to the issuance of [nationwide permit],” and held that a “permit conditioned on the
future implementation of a mitigation plan complies with the requirements of the CWA.”

         4
          Riverkeeper appears to acknowledge that the NEPA regulations do not require the same
documentation, but asserts that the baseline APA procedures impose a similar requirement. Because the
CWA regulations provide a direct path for resolution, we need not reach this part of Riverkeeper’s
challenge.
         5
           Specifically, the Corps relies on the Eastern Kentucky Stream Assessment Protocol as an
“objective, scientific methodology” used “to assess the appropriate quantity and quality mitigation [sic]
and assist the Corps in ensuring” minimal environmental impacts. While this tool conceivably could have
supported a specific mitigation finding in its determination of minimal cumulative impacts, it did not do
so here. The Corps admits that its use of the Protocol in permit 21’s Supplemental Decision Document
extended no further than prospectively requiring individual Kentucky-based projects to “ensure minimal
impacts.” (Appellee Br. at 18; see also NWP 21 Supp. Decision Doc. at 2.)
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                  Page 15


Ky. Riverkeeper, 800 F. Supp. 2d at 876; see also Bulen, 429 F.3d at 502 (“[S]ection
404(e) does not unambiguously forbid the Corps from making the minimal-
environmental-impact determinations by relying in part on the availability of
post-issuance procedures, and such reliance is a reasonable way for the Corps to ensure
that the projects it authorizes under general permits will have only minimal impacts.”).
No quarrel there, but Sierra Club did not involve the same issue. Whereas the plaintiffs
in Sierra Club advanced a broader challenge that the “[CWA] permit was invalid
because the Corps did not previously prepare a final, detailed mitigation implementation
plan,” 120 F.3d at 636, Riverkeeper specifically challenges the Corps’ compliance with
40 C.F.R. § 230.7(b)’s documentation requirement in making its minimal cumulative-
impacts findings. In other words, Riverkeeper does not dispute that the Corps can rely
on mitigation; rather, it contests the Corps’ failure to “provid[e] any explanation or
documentation to support th[e] presumption” that compensatory mitigation will ensure
minimal cumulative effects. Further, the Corps’ “quite specific” mitigation plan in
Sierra Club belied the plaintiffs’ assertion of “vague mitigation goals.” 120 F.3d at 636.
Tellingly, the Corps does not rely on Sierra Club, Bulen, or this feature of the district
court’s decision.

       We acknowledge that the Corps may rely on post-issuance mitigation procedures
to minimize environmental impacts, but in making a minimal-cumulative-impact finding,
it must, at a minimum, provide some documented information supporting that finding.
40 C.F.R. §§ 230.7(a)–(b), 230.11(g).

D. Conclusion

       Though we generally give greatest deference to an agency’s “complex scientific
determination[s] within its area of special expertise,” Balt. Gas & Elec. Co., 462 U.S.
at 103, we may not excuse an agency’s failure to follow the procedures required by duly
promulgated regulations, see, e.g., Motor Vehicles Mfrs. Ass’n, 463 U.S. at 43. During
oral argument, the Corps repeatedly objected to the feasibility of Riverkeeper’s demands.
This policy argument misses the point. After opting for streamlined nationwide
permitting, the Corps took the easier path of preparing an environmental assessment
No. 11-6083     Ky. Riverkeeper Inc., et al. v. Rowlette, et al.                  Page 16


instead of an environmental impact statement. Having done so, it needed to follow the
applicable CWA and NEPA regulations by documenting its assessment of environmental
impacts and examining past impacts, respectively. Failing these regulatory prerequisites,
the Corps leaves us with nothing more than its say-so that it meets CWA and NEPA
standards. We may not supply a reasoned basis for the agency’s action that the agency
itself has not given. See SEC v. Chenery Corp., 332 U.S. 194, 196 (1947).

       We hereby invalidate permit 21 as arbitrary and capricious, 5 U.S.C. § 706(2)(A),
but stay this ruling for 60 days to allow the parties and the district court an opportunity
to assess the ramifications of this ruling on existing projects and potential remedies.

                                            IV.

       We REVERSE and REMAND for further proceedings consistent with this
opinion. We STAY this ruling for 60 days as explained.
