 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued April 4, 2017                 Decided May 23, 2017

                       No. 16-1092

    DELAWARE RIVERKEEPER NETWORK AND MAYA VAN
        ROSSUM, THE DELAWARE RIVERKEEPER,
                    PETITIONERS

                             v.

       FEDERAL ENERGY REGULATORY COMMISSION,
                    RESPONDENT

    TRANSCONTINENTAL GAS PIPE LINE COMPANY, LLC,
                   INTERVENOR


          On Petition for Review of Orders of the
          Federal Energy Regulatory Commission


     Aaron Stemplewicz argued the cause and filed the briefs
for petitioners.

     Holly E. Cafer, Senior Attorney, Federal Energy
Regulatory Commission, argued the cause for respondent.
With her on the brief were Robert H. Solomon, Solicitor, and
Lisa B. Luftig, Attorney. Karin L. Larson, Attorney, Federal
Energy Regulatory Commission, entered an appearance.
                              2
    John F. Stoviak argued the cause for intervenor. With him
on the brief were Pamela S. Goodwin, Elizabeth U. Witmer,
and Patrick F. Nugent.

    Before: GARLAND, Chief Judge, GRIFFITH, Circuit Judge,
and EDWARDS, Senior Circuit Judge.

     EDWARDS, Senior Circuit Judge: This case involves three
federal statutes: the Natural Gas Act (“NGA”), 15 U.S.C.
§ 717, et seq.; the Clean Water Act (“CWA”), formally titled
the Federal Water Pollution Control Act Amendments of 1972,
33 U.S.C. § 1251, et seq.; and the National Environmental
Policy Act (“NEPA”), 42 U.S.C. § 4321, et seq. Although the
Federal Energy Regulatory Commission (“FERC” or
“Commission”) administers only the NGA, all three statutes
apply to the disputed actions taken by the Commission in this
case.

     On September 30, 2013, Transcontinental Gas Pipe Line
Company, LLC (“Transco”) filed an application with FERC to
construct and operate its proposed Leidy Southeast Project
(“Leidy Project”). The project was designed to expand the
capacity of Transco’s existing natural gas pipeline and add new
facilities in Pennsylvania and New Jersey. Pursuant to the
requirements of NEPA, FERC conducted an environmental
review of the project and issued an environmental assessment
(“EA”) on August 11, 2014. The EA found, with appropriate
mitigating measures, “no significant impacts” associated with
the Leidy Project. However, it required Transco to obtain “all
applicable authorizations required under federal law” prior to
FERC authorizing construction. Because it was understood that
the Leidy Project might result in discharges into navigable
waters, Transco was obligated by § 401 of the CWA to obtain
a water quality certification from the state in which the
discharge would originate before FERC could authorize any
                               3
activity that “may result” in such a discharge. See 33 U.S.C.
§ 1341(a)(1). The EA thus in turn required Transco to obtain
this state certification before FERC would authorize any
construction.

     On June 10, 2014, Transco applied for a § 401 certification
from Pennsylvania’s Department of Environmental Protection.
On December 18, 2014, before Pennsylvania had acted on
Transco’s application, FERC issued a Certificate of Public
Convenience and Necessity (“Certificate Order”) under the
NGA conditionally approving the Leidy Project. The
Certificate Order made it clear that FERC would not authorize
any construction until Transco had obtained a § 401
certification from Pennsylvania. Delaware Riverkeeper
Network, a nonprofit organization, timely sought rehearing of
the Certificate Order before the Commission. FERC denied the
request for rehearing. Delaware Riverkeeper Network and
Maya van Rossum, the current Delaware Riverkeeper (together
“Riverkeeper”), then petitioned for review in this court.
Transco intervened in support of the Commission.

     Before this court, Riverkeeper contends that the
Commission violated the CWA because it granted Transco’s
request to construct and operate the Leidy Project prior to the
issuance of Pennsylvania’s § 401 water quality certification.
Riverkeeper also claims that the Commission violated NEPA
in failing to establish an accurate baseline from which to
conduct its environmental review of the Leidy Project. In
particular, Riverkeeper argues that FERC misidentified
numerous specially protected wetlands, and miscalculated both
the cover type categorization of those wetlands and the total
acreage of those wetlands. We find no merit in these claims
and, therefore, reject the petition for review.
                                4
                      I.   BACKGROUND

A. Statutory Background

     Under the NGA, a natural gas pipeline company must
obtain a Certificate of Public Convenience and Necessity from
FERC prior to “undertak[ing] the construction or extension” of
any natural gas facility for the transportation of natural gas in
interstate commerce. 15 U.S.C. § 717f(c)(1)(A). FERC may
place any reasonable conditions on the issuance of such a
certificate “as the public convenience and necessity may
require.” Id. § 717f(e). This court has jurisdiction to review
challenges to certificates granted under the NGA, but
petitioning parties must first seek rehearing before the
Commission and may not raise any argument before this court
that was not raised on rehearing. See 15 U.S.C. § 717r(b).
Letter orders issued by FERC are also subject to review in this
court subject to the same rehearing requirement. See 18 C.F.R.
§ 385.1902.

     In addition to the requirements of the NGA, § 401 of the
CWA requires “[a]ny applicant for a Federal license or permit
to conduct any activity including . . . the construction or
operation of facilities, which may result in any discharge into
the navigable waters,” to “provide the licensing or permitting
agency a certification from the State in which the discharge
originates or will originate.” 33 U.S.C. § 1341(a)(1). The state
must certify “that any such discharge will comply” with the
CWA’s effluent limitations and other pollutant control
requirements, including state-administered water quality
standards. Id. The state may certify that there are no applicable
limitations or standards for the discharge activity, or it may
deny certification or waive the certification requirement. Id.
But “[n]o license or permit shall be granted until the
certification . . . has been obtained or has been waived.” Id. Any
                                5
limitation in a § 401 certification “shall become a condition” of
the federal license or permit requiring such certification. Id.
§ 1341(d).

     Section 401 is an important part of the CWA, in which
“Congress sought to expand federal oversight of projects
affecting water quality while also reinforcing the role of States
as the prime bulwark in the effort to abate water pollution.”
Alcoa Power Generating Inc. v. FERC, 643 F.3d 963, 971
(D.C. Cir. 2011) (citation and internal quotation marks
omitted). The state certification authority under § 401 is “‘[o]ne
of the primary mechanisms’ through which [states] may
exercise this role, as it provides them with ‘the power to block,
for environmental reasons, local water projects that might
otherwise win federal approval.’” Id. (quoting Keating v.
FERC, 927 F.2d 616, 622 (D.C. Cir. 1991)).

     The last statute at issue in this case is NEPA, which was
enacted in part to “promote efforts which will prevent or
eliminate damage to the environment and biosphere . . . [and]
enrich the understanding of the ecological systems and natural
resources important to the Nation.” 42 U.S.C. § 4321. As we
recently explained:

      The Commission, in exercising its . . . authority,
    must comply with NEPA and its implementing
    regulations, which require that all federal agencies
    include an environmental impact statement (“EIS”)
    “in every recommendation or report on . . . major
    Federal actions significantly affecting the quality of
    the human environment.” 42 U.S.C. § 4332(2)(C); see
    also 40 C.F.R. § 1508.11. To determine whether an
    EIS is necessary, an agency first prepares an
    environmental assessment, 40 C.F.R. § 1508.9, which
    must include, among other information, a discussion
                                6
    of “the environmental impacts of the proposed
    action,” id. § 1508.9(b). “Indirect effects . . . are
    caused by the action and are later in time or farther
    removed in distance, but are still reasonably
    foreseeable.” Id. § 1508.8(b). “Cumulative impact is
    the impact on the environment which results from the
    incremental impact of the action when added to other
    past, present, and reasonably foreseeable future
    actions regardless of what agency (Federal or non-
    Federal) or person undertakes such other actions.” Id.
    § 1508.7; see also id. § 1508.8. After preparing an
    environmental assessment, an agency may conclude
    that the proposed action would have no significant
    impact (often referred to as a “FONSI,” for “finding
    of no significant impact”) in lieu of issuing an EIS. Id.
    §§ 1508.9(a)(1), 1508.13.

Sierra Club v. FERC, 827 F.3d 59, 63 (D.C. Cir. 2016). For
either an EA or an EIS, the purposes of NEPA require the
Commission to “consider and disclose” the environmental
effects of the actions it certifies. Balt. Gas & Elec. Co. v. Nat.
Res. Def. Council, Inc., 462 U.S. 87, 96 (1983). So long as the
agency takes a hard look at the environmental consequences,
NEPA “does not mandate particular results.” Robertson v.
Methow Valley Citizens Council, 490 U.S. 332, 350 (1989).

B. Factual and Procedural Background

     Transco maintains an interstate natural gas pipeline that
runs from Texas to New York City, passing through
Pennsylvania. In September 2013, Transco applied to FERC
for a Certificate of Public Convenience and Necessity for the
Leidy Project, which would add approximately thirty miles of
looping to Transco’s existing pipeline in Luzerne and Monroe
Counties, Pennsylvania and parts of New Jersey, to meet
                               7
increasing energy demands. On August 11, 2014, FERC issued
a finding of no significant impact and published its review of
the environmental consequences of the Leidy Project in a 217-
page EA. Environmental Assessment, Joint Appendix (“JA”)
168–331. Among a number of conditions, Environmental
Condition No. 9 of the EA required Transco to obtain and file
with the Secretary of the Commission “all applicable
authorizations required under federal law (or evidence of
waiver thereof)” prior to FERC authorizing construction. Id. at
324. The EA identified § 401 state water quality certifications
as required authorizations. The EA also discussed mitigation
for the Leidy Project’s impact on Pennsylvania wetlands and
concluded that the project’s proposed pipeline gas flow
velocities were safe.

     Transco had timely applied for a § 401 certification from
Pennsylvania’s Department of Environmental Protection on
June 10, 2014. However, on December 18, 2014, FERC issued
a Certificate Order to Transco, conditionally approving the
Leidy Project, before Pennsylvania had acted on Transco’s
§ 401 request. The Certificate Order adopted the conditions of
the EA, including Environmental Condition No. 9, which
clearly stated that Transco was required to obtain all applicable
federal authorizations, including a § 401 certification from
Pennsylvania. FERC was thus clear that it would not authorize
any construction before the necessary § 401 certifications had
been obtained. On January 16, 2015, Riverkeeper sought
rehearing of the Certificate Order before the Commission.

     During the early months of 2015, after the conditional
Certificate Order had been issued, the Commission authorized
Transco via letter orders to conduct certain “pre-construction”
activities, including tree-felling. Riverkeeper moved the
Commission to stay the tree-felling activity. FERC denied this
request. Riverkeeper never sought rehearing of this action or of
                                8
any of FERC’s letter orders. Instead, on March 15, 2015,
Riverkeeper filed a petition for an emergency stay with this
court. The Petition was denied on March 19, 2015. Del.
Riverkeeper Network v. FERC, No. 15-1052 (D.C. Cir. Mar.
19, 2015), ECF No. 1543345. By the end of March 2015,
Transco had begun felling trees, as authorized, along a right-
of-way by the projected pipelines, including in Pennsylvania
wetlands.

     On April 6, 2015, Pennsylvania’s Department of
Environmental Protection issued a § 401 certification for the
Leidy Project. Riverkeeper challenged the Pennsylvania
certification by filing a petition for review in the Third Circuit,
but the petition was denied. Del. Riverkeeper Network v. Sec’y
Penn. Dep’t of Envtl. Prot., 833 F.3d 360, 385–88 (3d Cir.
2016) (upholding Pennsylvania’s decision to issue the § 401
certification).

    On March 3, 2016, FERC denied Riverkeeper’s request for
rehearing. Riverkeeper timely petitioned this court for review
of FERC’s EA, Certificate Order, and order denying rehearing.
Transco intervened.

                         II. ANALYSIS

A. Standard of Review

    “[I]n evaluating the Commission’s authority to issue [a]
challenged certificate of public convenience and necessity[,]
[w]e . . . review[] the Commission’s interpretation of its
authority to issue such a certificate by applying the two-step
analytical framework of Chevron.” Myersville Citizens for a
Rural Cmty., Inc. v. FERC, 783 F.3d 1301, 1315 (D.C. Cir.
2015) (citing Chevron, U.S.A. Inc. v. Nat. Res. Def. Council,
467 U.S. 837 (1984)). Under the Chevron framework,
                               9
   an agency’s power to regulate “is limited to the scope
   of the authority Congress has delegated to it.” Am.
   Library Ass’n v. FCC, 406 F.3d 689, 698 (D.C. Cir.
   2005). Pursuant to Chevron Step One, if the intent of
   Congress is clear, the reviewing court must give effect
   to that unambiguously expressed intent. If Congress
   has not directly addressed the precise question at issue,
   the reviewing court proceeds to Chevron Step Two.
   Under Step Two, “[i]f Congress has explicitly left a
   gap for the agency to fill, there is an express delegation
   of authority to the agency to elucidate a specific
   provision of the statute by regulation. Such legislative
   regulations are given controlling weight unless they are
   . . . manifestly contrary to the statute.” Chevron, 467
   U.S. at 843–44. Where a “legislative delegation to an
   agency on a particular question is implicit rather than
   explicit,” the reviewing court must uphold any
   “reasonable interpretation made by the administrator
   of [that] agency.” Id. at 844. But deference to an
   agency’s interpretation of its enabling statute “is due
   only when the agency acts pursuant to delegated
   authority.” Am. Library Ass’n, 406 F.3d at 699.

EDWARDS, ELLIOTT, & LEVY, FEDERAL STANDARDS                     OF
REVIEW 166–67 (2d ed. 2013).

     A court does not defer to an agency’s interpretation of a
statute that it is not charged with administering. See Metro.
Stevedore Co. v. Rambo, 521 U.S. 121, 138 n.9 (1997).
Therefore, we do not accord Chevron deference to the
Commission’s interpretation of the CWA because the
Environmental Protection Agency, not FERC, administers the
statute. See Alcoa Power, 643 F.3d at 972. Our review of the
requirements of the CWA is de novo. Id.
                               10
     Finally, we apply “a ‘rule of reason’ to an agency’s NEPA
analysis and ha[ve] repeatedly refused to ‘flyspeck’ the
agency’s findings in search of ‘any deficiency no matter how
minor.’” Myersville, 783 F.3d at 1322–23 (citations omitted).
Because “NEPA’s requirements are ‘essentially procedural,’”
so “long as the agency’s decision is ‘fully informed’ and ‘well-
considered,’ it is entitled to judicial deference.” Nat. Res. Def.
Council v. Hodel, 865 F.2d 288, 294 (D.C. Cir. 1988) (citations
omitted). Especially “[w]hen considering FERC’s evaluation
of ‘scientific data within its technical expertise,’ we afford
FERC ‘an extreme degree of deference.’” Myersville, 783 F.3d
at 1308 (citation omitted).

B. Jurisdiction

     FERC argues that Riverkeeper’s Clean Water Act claim
“may no longer present an ongoing case or controversy” as “[i]t
is not clear what relief would be available to remedy
Riverkeeper’s sequencing claims—if they prevailed—where
the [state] water quality certifications have been issued and
affirmed on appeal [by the Third Circuit].” Br. for FERC at 22
n.3. In other words, according to FERC, even if the agency
issued the conditional Certificate Order prematurely, no
remedy is needed for the sequencing error because the state
water quality certifications have been issued and found lawful.
FERC’s argument is misguided.

    First, the principal issue before the Third Circuit was
whether Pennsylvania “was required to engage in an
environmental review prior to issuing a Water Quality
Certification.” Del. Riverkeeper, 833 F.3d at 385. Here, in
contrast, the question raised by Riverkeeper is whether the
Commission (not Pennsylvania) violated the sequencing
requirement of the CWA by issuing its Certificate Order before
Pennsylvania issued its § 401 certification. These are entirely
                               11
distinct issues and the former does not subsume the latter.
FERC does not argue otherwise.

     Furthermore, Riverkeeper’s claim is not moot because
once the CWA’s sequence has been flouted, the only fix is to
start the process over. Riverkeeper asks this court to “rescind[]
the Commission’s Orders, or remand[] the decision to ensure
that the Orders comply with the [Clean Water Act] and NEPA.”
Br. for Pet’rs at 15. We could provide Riverkeeper the remedy
it seeks by rescinding the conditional Certificate Order. That
would halt the project and force FERC to follow the proper
sequence of action. See Gunpowder Riverkeeper v. FERC, 807
F.3d 267, 272 (D.C. Cir. 2015) (rejecting similar mootness
argument because granting relief on the NEPA claim would
undo the conditional certificate, which could start the CWA
sequence over).

     Perhaps FERC means to suggest that no effectual relief can
be granted because vacating the Certificate Order and
remanding the matter to the agency would almost certainly
have no real world consequences. In other words, in FERC’s
view, even if the court were to remand the case, the agency
could immediately re-issue the conditional Certificate Order
because the state water quality certifications have been issued.
Such a response by FERC is not unlikely, but it is surely not
guaranteed. In any event, “[c]ourts often adjudicate disputes
where the practical impact of any decision is not assured.”
Chafin v. Chafin, 568 U.S. 165, 133 S. Ct. 1017, 1025 (2013).
Therefore, we could grant Riverkeeper vacatur of FERC’s
conditional Certificate Order even if its victory might be short
lived. “Such relief would of course not be ‘fully satisfactory,’
but with respect to the case as whole, ‘even the availability of
a partial remedy is sufficient to prevent [a] case from being
moot.’” Id. at 1026 (quoting Calderon v. Moore, 518 U.S. 149,
150 (1996) (per curiam)).
                                12
     In sum, we agree with Riverkeeper that we have
jurisdiction to consider its challenge to the Certificate Order on
the ground that FERC violated the sequencing requirement of
the CWA by issuing its Certificate Order before Pennsylvania
issued its § 401 certification. We therefore proceed to the
merits of Riverkeeper’s claims under both the CWA and
NEPA.

C. Riverkeeper’s Challenges Under the CWA

     Riverkeeper argues that the Commission violated § 401 of
the CWA by “issu[ing] its approval of the [Leidy] Project prior
to Pennsylvania’s issuance of its Clean Water Act Section 401
water quality certificat[ion].” Br. for Pet’rs at 19. We disagree.
We hold that the sequencing requirement of § 401 was not
triggered because the Commission’s conditional approval of
the Leidy Project construction did not authorize any activity
which might result in a discharge in navigable waters.

     We decline to review Riverkeeper’s alternative CWA
challenge to the letter orders approving pre-construction tree-
felling. The NGA requires that, prior to challenging an order
before this Court on review, a party first must file a petition for
rehearing with the Commission and then specify the challenged
orders in a petition for judicial review. 15 U.S.C. §§ 717r(a),
(b). Because Riverkeeper failed to seek rehearing of any of the
disputed letter orders authorizing pre-construction activities,
those individual decisions are not properly before this court.
                                13
    1. The Sequencing of the Certificate Order and the
       § 401 Certification

      Section 401 of the CWA requires that “[a]ny applicant for
a Federal license or permit to conduct any activity . . . which
may result in any discharge into the navigable waters” must
first obtain a water quality certification from the state in which
the discharge will originate, and that “[n]o license or permit
shall be granted until the certification required by this section
has been obtained or has been waived.” 33 U.S.C. § 1341(a)(1).

     Transco argues preliminarily that the Commission’s
Certificate Order is not a “license or permit” subject to the
CWA because it is a “certificate[] of public convenience and
necessity.” Br. for Transco at 16; see id. at 15–19. We reject
this argument out of hand. The Commission agrees with
Riverkeeper that its Certificate Order was a “license or permit”
potentially subject to the requirements of § 401. Furthermore,
Transco’s assertion comes too late: before the Commission,
Transco never claimed that § 401 was inapplicable and the
company applied to Pennsylvania for the certification without
protest. Finally, it is clear that Congress intended § 401 to apply
broadly to federal approval of potential pollution activity.

    The Supreme Court has noted that:

    State certifications under § 401 are essential in the
    scheme to preserve state authority to address the broad
    range of pollution, as Senator Muskie explained on the
    floor when what is now § 401 was first proposed:

         “No polluter will be able to hide behind a Federal
         license or permit as an excuse for a violation of
         water quality standard[s]. No polluter will be able
         to make major investments in facilities under a
                              14
         Federal license or permit without providing
         assurance that the facility will comply with water
         quality standards. No State water pollution
         control agency will be confronted with a fait
         accompli by an industry that has built a plant
         without consideration of water quality
         requirements.” 116 Cong. Rec. 8984 (1970).

    These are the very reasons that Congress provided the
    States with power to enforce “any other appropriate
    requirement of State law,” 33 U.S.C. § 1341(d), by
    imposing conditions on federal licenses for activities
    that may result in a discharge, ibid.

S.D. Warren Co. v. Me. Bd. of Envtl. Prot., 547 U.S. 370, 386
(2006).

    The CWA in its entirety “provides for a system that
respects the States’ concerns” in application to all federal
agencies. Id. And the act of “licensing” or “permitting” clearly
extends to “certifying,” which is merely a different name for
the stamp of federal approval Congress intended to capture.
Transco’s reliance on the doctrine of expressio unius, that
Congress’s selection of “license or permit” excludes a
“certificate,” is misplaced because that doctrine applies “only
when ‘circumstances support[] a sensible inference that the
term left out must have been meant to be excluded.’” NLRB v.
SW Gen., Inc., 137 S. Ct. 929, 933 (2017) (citation omitted).
Here, the broad sweep of the statute raises no such inference.

    The principal issue here is not whether FERC’s disputed
Certificate Order is a “license or permit” covered by the CWA,
but whether it approved “activity . . . which may result in any
discharge” and thus triggered the requirements of the CWA. 33
U.S.C. § 1341(a)(1). We have previously stated that the
                               15
“logically antecedent” question under § 401 is whether the
disputed federal permit or license “is subject to the provisions
of Section 401(a)(1)” in the first place. North Carolina v.
FERC, 112 F.3d 1175, 1186 (D.C. Cir. 1997). If the activity
that FERC approved would not result in a discharge, then the
sequencing requirement of § 401 was not “trigger[ed].” See id.
at 1188.

     Here, the record indicates that the Certificate Order did not
authorize any activity that could result in a discharge. Instead,
the conditional Certificate Order was merely a first step for
Transco to take in the complex procedure to actually obtaining
construction approval. Br. for FERC at 25–28. And, as
explained above, FERC required Transco to obtain the
appropriate state agency permits, including a § 401
certification from Pennsylvania, prior to FERC granting
Transco permission to proceed with activity that could result in
a discharge.

     Judge Rogers’ concurring statement in Gunpowder
Riverkeeper, which we adopt, disposes of Riverkeeper’s claim
in this case:

    The plain text of the Clean Water Act does not appear
    to prohibit the kind of conditional certificate the
    Commission issued here. On its face, section
    401(a)(1) does not prohibit all “license[s] or
    permit[s]” issued without state certification, only
    those that allow the licensee or permittee “to conduct
    any activity . . . which may result in any discharge into
    the navigable waters.” 33 U.S.C. § 1341(a)(1).
    Petitioner has pointed to no activities authorized by
    the conditional certificate itself that may result in such
    discharge prior to the state approval and the
    Commission’s issuance of a Notice to Proceed.
                               16
807 F.3d at 279 (Rogers, J., dissenting in part and concurring
in the judgment) (second emphasis added); see also Myersville,
783 F.3d at 1320–21 (upholding FERC’s conditional approval
of a natural gas facility construction project where FERC
conditioned its approval on the applicant securing a required
federal Clean Air Act air quality permit from the state); Del.
Dep’t. of Nat. Res. & Envtl. Control v. FERC, 558 F.3d 575,
578–79 (D.C. Cir. 2009) (holding Delaware suffered no
concrete injury from FERC’s conditional approval of a natural
gas terminal construction despite statutes requiring states’ prior
approval because FERC conditioned its approval of
construction on the states’ prior approval).

     Because the Certificate Order expressly conditioned
FERC’s approval of potential discharge activity on Transco
first obtaining the requisite § 401 certification, and was not
itself authorization of any potential discharge activity, the
issuance of the Certificate Order before Pennsylvania’s
issuance of its § 401 certificate did not violate § 401 of the
CWA.

    2.   The Letter Orders

     Riverkeeper alternatively contends that the Commission’s
letter orders authorizing pre-construction tree-felling
impermissibly approved activity that might have resulted in a
proscribed discharge before Pennsylvania could issue its water
quality certification. In response, the Commission contends
that its letter orders did not trigger the requirements of § 401
because the U.S. Army Corps of Engineers determined that
Transco’s “proposed tree cutting activities would not result in
a discharge,” JA 638, and FERC relied on the Corps’
determination, JA 644–45. We need not decide this issue,
however, because Riverkeeper did not independently challenge
the letter orders. Neither FERC nor Riverkeeper dispute that
                               17
the letter orders reflected final agency action and were
separately appealable after rehearing before the Commission.
See 18 C.F.R. § 385.1902(a)–(b). But as it conceded at oral
argument and in its briefing, Reply Br. for Pet’rs at 3–5,
Riverkeeper did not request rehearing of the letter orders, so
the letters are not properly before us for review. See 15 U.S.C.
§ 717r(a)–(b); see also Darby v. Cisneros, 509 U.S. 137, 145
(1993) (recognizing the statutory rehearing requirement of
§ 717r as mandatory).

    In sum, we need not decide whether the letter orders
impermissibly approved activity that might have resulted in a
discharge before Pennsylvania issued its § 401 certification.

D. The Commission’s Wetlands Analysis

     Riverkeeper contends that FERC violated NEPA by
misclassifying wetlands in two ways: (1) under Pennsylvania’s
own state classification system; and (2) under the “Cowardin”
classification system. We reject both challenges. FERC did not
purport to rely on Pennsylvania’s classification system and
Riverkeeper does not show how any misclassification under the
Cowardin system was prejudicial error.

     Nowhere in the EA does FERC even discuss, much less
rely on, the application of Pennsylvania’s system. In Appendix
I, the EA includes a secondary reference to wetlands as either
“exceptional” or “other,” which is pursuant to the Pennsylvania
Administrative Code. 25 Penn. Admin. Code § 105.17. See JA
330–31. But the wetlands discussion in the EA itself does not
use the terms “exceptional” or “other,” and does not refer to the
Pennsylvania system at all.

    As Riverkeeper concedes, FERC was not bound to use
Pennsylvania’s classification system. And the EA clearly
                               18
explains that the “field delineations of wetlands” in
Pennsylvania were performed according to the U.S. Army
Corps of Engineers’ “Wetlands Delineation Manual (COE,
1987),” JA 202, and that delineated wetlands “were classified
as described in Cowardin, et al., (1979),” JA 203. The EA thus
classifies the wetlands as either Palustrine Forested, Palustrine
Scrub-Shrub, or Palustrine Emergent wetlands. These three
Palustrine wetland types are consistent with the Cowardin
classification system referenced in the Corps’ delineation
manual. See U.S. ARMY CORPS OF ENG’RS, WETLANDS
DELINEATION MANUAL 3 (1987); LEWIS M. COWARDIN, ET AL.,
CLASSIFICATION OF WETLANDS AND DEEPWATER HABITATS OF
THE UNITED STATES 10–13 (1979).

     On rehearing, FERC again rejected Riverkeeper’s
contention that the agency had used Pennsylvania’s system:
“As indicated in the EA and the December 18 [Certificate]
Order, Transco’s wetlands delineations were conducted using
the Corps’ Wetlands Delineation Manual.” JA 716. Moreover,
FERC made it clear that each state was to oversee its own
delineation, clearly implying this was to be done for purposes
of classification: “It is at the discretion of the Corps [and] the
Pennsylvania Department of Environmental Protection . . . to
determine whether Transco’s wetland delineations comply
with each agency’s permit application process, prior to issuing
the appropriate water quality permit.” JA 514; see also JA 203
(using “delineate[]” in reference to identifying cover types).
There is no evidence the secondary wetlands identifications in
Appendix I as “exceptional” or “other,” even if erroneous, had
any effect on FERC’s consideration of the environmental
impact of the Leidy Project. Accordingly, there is no NEPA
violation here.

   Riverkeeper’s second wetlands argument attacks the
Cowardin classification system that the Commission actually
                                19
used. Riverkeeper contends that FERC “failed to accurately
account for the expected ground disturbance impacts that will
result from the [Leidy] Project’s construction and operational
activity,” Br. for Pet’rs at 44, because it misidentified the cover
types of fourteen wetlands – totaling approximately 3.8 acres
that would be impacted by operation or construction – pursuant
to the Cowardin system, see id. at 44–49. For example,
Riverkeeper argues that aerial photographs show that a wetland
classified as Palustrine Emergent (non-forested) was “clearly”
forested and therefore should have been classified as Palustrine
Forested. Id. at 46. However, Riverkeeper does not explain
how this inexorably leads to the conclusion that FERC failed
to accurately account for the Leidy Project’s impact on the
environment. Indeed, the ultimate implication Riverkeeper
raises for this alleged erroneous classification is an “alteration
of wetland value due to vegetation clearing.” Id. at 45 (quoting
JA 205). But the EA identifies only one difference in
vegetation clearing: the time it takes for the three different
types of wetlands to re-vegetate. See JA 205. Riverkeeper does
not raise any unaccounted-for consequences of this. In other
words, even assuming FERC misclassified a small area of
Pennsylvania wetlands, this merely means the Leidy Project
will result in a longer re-vegetation process for some wetlands,
and a shorter re-vegetation process for others. Riverkeeper fails
to explain how this caused FERC’s mitigation plan to be
significantly deficient.

    What we see from the record in this case is that FERC
responsibly addressed Riverkeeper’s misclassification
argument in its Certificate Order. The Commission stated that
it relied on its classification only to “disclose and evaluate
potential impacts on wetlands and to serve as a starting point
for the development of protective mitigation.” JA 514. FERC
thus disclosed its methodology and purpose as a starting point
for mitigation, which would subsequently involve the Corps
                                20
and state agencies to further oversee mitigation. See id.; JA
716–17 (order denying rehearing). It seems clear here that
FERC took the requisite “hard look” at the impact of the Leidy
Project on the environment. Hodel, 865 F.2d at 294 (quoting
Izaak Walton League of America v. Marsh, 655 F.2d 346, 371
(D.C. Cir. 1981)). Even if FERC technically erred in some of
its classifications, Riverkeeper has not shown any prejudice by
virtue of the agency “fail[ing] to comply precisely with NEPA
procedures.” Nevada v. Dep’t of Energy, 457 F.3d 78, 90 (D.C.
Cir. 2006); see also Hodel, 865 F.2d at 295–97 (refusing to
remand despite an agency error because it had “serve[d]
NEPA’s informational function”).

E. The Commission’s Gas Flow Velocity Analysis

    In its final challenge, Riverkeeper contends that FERC
“repeatedly failed to disclose information addressing both the
safety and independent viability” of the Leidy Project’s
projected pipeline gas flow velocities. Br. for Pet’rs at 57. This
argument rests on Riverkeeper’s claims that FERC failed to
consider and disclose (1) key information about Transco’s
projected gas flow velocities, (2) the project’s interdependence
on past or future pipeline projects, and (3) the safety risks of its
gas flow velocities. Id. at 50–60. Riverkeeper also contends
that FERC treated the Leidy Project differently than a similarly
situated project. We find no merit in these claims.

    First, the record belies Riverkeeper’s claim that FERC
withheld critical information regarding the projected gas flow
velocities. Riverkeeper asserts that it never received answers to
nine questions it asked, regarding, inter alia, data about the
pipe diameter, grade, wall thickness, and gas flow rates and
pressures. Id. at 54–55. The record shows, however, that FERC
and Transco responded to Riverkeeper’s queries and made it
clear that the flow diagrams contained in Exhibits G and G-II
                              21
answered the questions that had been raised. JA 159. On
appeal, Riverkeeper summarily asserts that the cited exhibits
were non-responsive to its questions, but it does not explain
how so.

    In fact, the record before us shows that Riverkeeper was
invited to view Transco’s hydraulic flow modeling software,
used to project gas flow velocity, via video conference or in
person (due to the software’s proprietary nature). Riverkeeper
concedes that this offer was made but asserts it “made the
decision” to “not waste . . . limited time and resources to fly
their expert from Washington to Texas” to view the software.
Reply Br. for Pet’rs at 24–25. This is hardly a compelling
response, especially since Riverkeeper could have viewed the
modeling software via video conferencing.

    In sum, on the record before us, we have no basis upon
which to credit Riverkeeper’s vague and unsubstantiated
assertions that FERC withheld key data from the public.
Indeed, the record reflects that FERC made every effort to
comply with requests for information and no information was
withheld from Riverkeeper.

    Second, Riverkeeper contends that the EA’s data on the
projected gas flow velocity was insufficient and, therefore, it
could not review the dependence of the Leidy Project on future
pipeline expansions. Riverkeeper says the information is
important because FERC’s regulations require the agency to
review connected, cumulative, or similar actions. See 40 C.F.R.
§ 1508.25(a); Del. Riverkeeper Network v. FERC, 753 F.3d
1304, 1309 (D.C. Cir. 2014). In support of this claim,
Riverkeeper points to this court’s decision in Delaware
Riverkeeper Network. That case is plainly distinguishable,
however. There, the court determined that FERC had
impermissibly segmented NEPA review by approving one of
                               22
four “indisputably related and significantly ‘connected’”
pipeline upgrade projects without looking at the projects’
cumulative impact. Id. at 1313–14. Here, in contrast, FERC
evaluated the cumulative impact of recent related projects, see
JA 320, and found that “[t]he location of any future expansion
facilities is entirely speculative.” JA 499. Riverkeeper offers no
evidence to the contrary.

    Third, Riverkeeper alleges that it presented expert evidence
to FERC that Transco’s proposed gas flow velocities were
potentially unsafe, and these concerns were left “wholly
unanswered and unrebutted.” Br. for Pet’rs at 57. The record
indicates otherwise. The EA concluded that Transco’s
proposed gas flow velocities, not to exceed 60-61 feet per
second, were safe based on an American Petroleum Institute
report that gave a conservative guideline for maximum flow
velocity as 100 feet per second for pipelines exposed to liquid
droplet erosion. The Commission concluded that Transco’s 60-
61 feet per second maximum flow velocity was safe, especially
since Transco’s pipelines would not be subject to liquid
droplets. JA 498. In both instances, FERC highlighted the fact
that Riverkeeper did not “cite any industry or government
standard, regulation, or study to support its position” when
expressing its concern that gas flow velocities beyond 50 feet
per second would be unsafe. JA 315; see JA 496. We therefore
reject Riverkeeper’s claims, which are based on sheer
speculation, that FERC erred in its determinations regarding
the safety of the Leidy Project’s gas flow velocities.

    Finally, we reject Riverkeeper’s contention that FERC
treated similarly situated parties differently and, therefore, the
agency’s determinations on gas flow velocity are arbitrary and
capricious. Br. for Pet’rs at 57–60. In 2011, FERC determined
that a pipeline project, the Northeast Upgrade Project, was not
hydraulically feasible because its gas flow velocity would
                              23
exceed 40 feet per second. Riverkeeper thus asserts that
FERC’s approval of the Leidy Project’s gas flow velocity of 60
feet per second is unjustified. The two projects are quite
different, however. The Northeast Upgrade Project proposed
adding compression to an existing 24-inch diameter pipeline,
without adding additional looping. See Br. for FERC at 44. In
contrast, the Leidy Project proposed to add looping of 42-inch
diameter pipeline, nearly double that of the Northeast Upgrade
Project. Riverkeeper is conspicuously silent as to these salient
differences.

    The Commission’s NEPA review of the Leidy Project’s
proposed gas flow velocities appears to be fully informed and
well-considered. Riverkeeper presents no countervailing
evidence. As such, the Commission’s judgment is “entitled to
judicial deference.” Hodel, 865 F.2d at 294.

                      III. CONCLUSION

    For the foregoing reasons, we deny the petition for review.

                                                  So ordered.
