 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued February 25, 2015               Decided July 28, 2015

                        No. 11-1302

           EME HOMER CITY GENERATION, L.P.,
                    PETITIONER

                             v.

          ENVIRONMENTAL PROTECTION AGENCY,
                    RESPONDENT

        SAN MIGUEL ELECTRIC COOPERATIVE, ET AL.,
                     INTERVENORS


  Consolidated with 11-1315, 11-1323, 11-1329, 11-1338,
  11-1340, 11-1350, 11-1357, 11-1358, 11-1359, 11-1360,
  11-1361, 11-1362, 11-1364, 11-1365, 11-1366, 11-1367,
  11-1368, 11-1369, 11-1371, 11-1372, 11-1373, 11-1374,
  11-1375, 11-1376, 11-1377, 11-1378, 11-1379, 11-1380,
  11-1381, 11-1382, 11-1383, 11-1384, 11-1385, 11-1386,
  11-1388, 11-1389, 11-1390, 11-1391, 11-1392, 11-1393,
                    11-1394, 11-1395


  On Petitions for Review of a Final Rule Promulgated by
    the United States Environmental Protection Agency


    Bill Davis, Assistant Solicitor General, Office of the
Attorney General for the State of Texas, argued the cause for
                               2
State and Local Petitioners. With him on the briefs on
remand were Ken Paxton, Attorney General, Jon Niermann,
Chief, Environmental Protection Division, Mark Walters,
Assistant Attorney General, Derek Schmidt, Attorney
General, Office of the Attorney General for the State of
Kansas, Jeffrey A. Chanay, Chief Deputy Attorney General,
Pamela Jo Bondi, Attorney General, Office of the Attorney
General for the State of Florida, Jonathan A. Glogau, Chief,
Complex Litigation, Henry V. Nickel, George P. Sibley III,
Luther Strange, Attorney General, Office of the Attorney
General for the State of Alabama, Robert D. Tambling,
Assistant Attorney General, Greg Zoeller, Attorney General,
Office of the Attorney General for the State of Indiana,
Thomas M. Fisher, Solicitor General, David R. Taggart,
Samuel S. Olens, Attorney General, Office of the Attorney of
the State of Georgia, John E. Hennelly and James D. Coots,
Senior Assistant Attorneys General, James D. ABuddy@
Caldwell, Attorney General, Office of the Attorney General
for the State of Louisiana, Megan K. Terrell, Assistant
Attorney General, Herman Robinson, Jackie M. Marve,
Elliott Vega, Donald Trahan, Deidra Johnson, Kathy M.
Wright, Aaron D. Lindstrom, Solicitor General, Office of the
Attorney General for the State of Michigan, Neil David
Gordon, Assistant Attorney General, Sean Peter Manning,
Chief, Environmental, Natural Resources, and Agriculture
Division, Blake Johnson, Assistant Attorney General, Doug
Peterson, Attorney General, Office of the Attorney General
for the State of Nebraska, Harold E. Pizzetta III, Assistant
Attorney General, Office of the Attorney General for the State
of Mississippi, E. Scott Pruitt, Attorney General, Office of the
Attorney General for the State of Oklahoma, Patrick Wyrick,
Solicitor General, P. Clayton Eubanks, Deputy Solicitor
General, J.B. Van Hollen, Attorney General at the time the
brief was filed, Office of the Attorney General for the State of
Wisconsin, Thomas J. Dawson, Assistant Attorney General,
                              3
Michael DeWine, Attorney General, Office of the Attorney
General for the State of Ohio, Dale T. Vitale, Gregg H.
Bachmann and Elizabeth Ewing, Assistant Attorneys General,
Alan Wilson, Attorney General, Office of the Attorney
General for the State of South Carolina, James Emory Smith,
Jr., Deputy Solicitor General, and Leslie Sue Ritts. William J.
Cobb for the State of South Carolina entered an appearance.

     Peter D. Keisler argued the cause for Industry and Labor
Petitioners. With him on the briefs on remand were C.
Frederick Beckner III, Roger R. Martella, Jr., Eric D.
McArthur, Benjamin Beaton, F. William Brownell, P. Stephen
Gidiere III, Grant Crandall, Arthur Traynor III, Eugene M.
Trisko, Ann M. Seha, Daniel J. Kelly, William M. Bumpers,
Joshua B. Frank, Megan H. Berge, Kelly M. McQueen, Janet
J. Henry, Robert A. Manning, Joseph A. Brown, Mohammad
O. Jazil, Bart E. Cassidy, Katherine L. Vaccaro, Todd E.
Palmer, Jordan J. Hemaidan, Valerie L. Green, Jeffrey L.
Landsman, Vincent M. Mele, Richard G. Stoll, Brian H. Potts,
Steven G. McKinney, C. Grady Moore III, Ben H. Stone,
Terese T. Wyly, Karl R. Moor, William L. Wehrum, Jr.,
Margaret Claiborne Campbell, Bryon W. Kirkpatrick,
Hahnah Williams Gaines, James S. Alves, Gary V. Perko,
David M. Flannery, Kathy G. Beckett, Laura M. Goldfarb,
Peter S. Glaser, Andrea Bear Field, Norman W. Fichthorn, E.
Carter Chandler Clements, David R. Tripp, Dennis Lane,
William F. Lane, and Maureen Harbourt.

     Shannon L. Goessling and Michael J. Nasi were on the
brief for intervenor San Miguel Electric Cooperative, Inc. and
Amicus Southeastern Legal Foundation, Inc. in support of
petitioners on remand.      Robert M. Cohan entered an
appearance.
                             4
    Norman L. Rave, Jr. and Jessica O=Donnell, Attorneys,
U.S. Department of Justice, argued the causes for
respondents. With them on the brief were John C. Cruden,
Assistant Attorney General, and Stephanie Hogan, Attorney,
U.S. Environmental Protection Agency.

     Andrew G. Frank, Assistant Attorney General, Office of
the Attorney General for the State of New York, argued the
cause for State and Local Intervenors in support of
respondent. With him on the brief on remand were Eric T.
Schneiderman, Attorney General, Barbara D. Underwood,
Solicitor General, Steven C. Wu, Deputy Solicitor General,
Michael J. Myers, Assistant Attorney General, Brian E.
Frosh, Attorney General, Office of the Attorney General for
the State of Maryland, Mary E. Raivel, Assistant Attorney
General, Roy Cooper, Attorney General, Office of the
Attorney General for the State of North Carolina, Marc
Bernstein, Special Deputy Attorney General, Peter F.
Kilmartin, Attorney General, Office of the Attorney General
for the State of Rhode Island, Gregory S. Schultz, Assistant
Attorney General, George Jepsen, Attorney General, Office
of the Attorney General for the State of Connecticut,
Kimberly P. Massicotte and Scott N. Koschwitz, Assistant
Attorneys General, Matthew Denn, Attorney General, Office
of the Attorney General for the State of Delaware, Valerie M.
Edge, Deputy Attorney General, Lisa Madigan, Attorney
General, Office of the Attorney General for the State of
Illinois, Matthew J. Dunn and Gerald T. Karr, Assistant
Attorneys General, William J. Moore III, Benna Ruth
Solomon, Carrie Noteboom, William H. Sorrell, Attorney
General, Office of the Attorney General for the State of
Vermont, Thea Schwartz, Assistant Attorney General, Maura
Healey, Attorney General, Office of the Attorney General for
the Commonwealth of Massachusetts, Frederick D.
Augenstern, Assistant Attorney General, Karl Racine,
                             5
Attorney General, Office of the Attorney General for the
District of Columbia, Todd Kim, Solicitor General, Scott J.
Schwarz, and William R. Phelan, Jr.

    Graham G. McCahan argued the cause for Public Health
Respondent Intervenors. With him on the brief on remand
were Howard I. Fox, David S. Baron, Josh Stebbins, Vickie L.
Patton, Sean H. Donahue, David Marshall, John Walke, and
Emily Davis. Ann B. Weeks entered an appearance.

    Brendan K. Collins argued the cause for Industry
Respondent Intervenors. With him on the brief on remand
were Robert B. McKinstry, Jr., Lorene L. Boudreau, and
James W. Rubin.

    Before: ROGERS, GRIFFITH, and KAVANAUGH, Circuit
Judges.

   Opinion for      the   Court   filed   by   Circuit   Judge
KAVANAUGH.

     KAVANAUGH, Circuit Judge: The Clean Air Act requires
EPA to set national ambient air quality standards, or NAAQS.
Those standards limit the levels of common pollutants in the
ambient air. See 42 U.S.C. § 7409(a). Under the Act,
individual States are responsible for ensuring attainment
within their States of federal air quality standards. But air
pollution is “heedless of state boundaries.” EPA v. EME
Homer City Generation, L.P., 134 S. Ct. 1584, 1593, slip op.
at 2 (2014). Emissions in upwind States therefore may affect
air quality in downwind States. The Clean Air Act’s “good
neighbor” provision speaks to that problem by proscribing
upwind States from “emitting any air pollutant in amounts”
that will “contribute significantly to nonattainment” of a
NAAQS in a downwind State. 42 U.S.C. § 7410(a)(2)(D)(i).
                             6
This case concerns EPA’s effort to regulate interstate air
pollution pursuant to the good neighbor provision.

     In 2011, EPA promulgated its latest good neighbor
regulation, the Transport Rule, also known as the Cross-State
Air Pollution Rule. A number of States, localities, and
industry groups promptly challenged the Rule. They argued,
among other things, that the Rule’s methodology for
computing the upwind States’ emissions reduction obligations
under the good neighbor provision exceeded EPA’s statutory
authority. As relevant here, they contended that the Rule
imposed uniform pollution reductions on upwind States
regardless of the actual amounts of pollution that individual
upwind States contributed to downwind States. According to
petitioners, this methodology led to over-control of upwind
States’ emissions.     Applying our precedents in North
Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008), and
Michigan v. EPA, 213 F.3d 663 (D.C. Cir. 2000), this Court
issued a 2-1 decision, with Judge Rogers dissenting, that
agreed with petitioners and vacated the Rule. See EME
Homer City Generation, L.P. v. EPA, 696 F.3d 7, 38 (D.C.
Cir. 2012).

     On review, the Supreme Court reversed in a 6-2 decision.
The Court ruled that the over-control problem did not require
invalidation of the Rule “on its face.” EME Homer, 134 S.
Ct. at 1609, slip op. at 31. In doing so, however, the Court
stated that it “agree[d] with the Court of Appeals to this
extent”:     The Transport Rule requires “unnecessary”
emissions reductions when EPA “requires an upwind State to
reduce emissions by more than the amount necessary to
achieve attainment in every downwind State to which it is
linked.” Id. at 1608-09, slip op. at 29-31. The Court stated
that over-control of individual upwind States could be
                               7
contested through “particularized, as-applied challenge[s].”
Id. at 1609, slip op. at 31.

     Now on remand, we consider several as-applied over-
control challenges to EPA’s 2014 emissions budgets.
Petitioners challenge the 2014 SO2 emissions budgets for
Texas, Alabama, Georgia, and South Carolina. Petitioners
also challenge the 2014 ozone-season NOX emissions budgets
for Florida, Maryland, New Jersey, New York, North
Carolina, Ohio, Pennsylvania, South Carolina, Texas,
Virginia, and West Virginia. On this record, petitioners’ as-
applied challenges are meritorious, and those 2014 emissions
budgets are invalid. We therefore grant the petitions to that
limited extent, and we remand without vacatur to EPA for it
to reconsider those 2014 emissions budgets.
     In this opinion, we also must address a number of
petitioners’ broader challenges to the Transport Rule that we
did not have occasion to address in the prior case. We reject
all of those claims and deny the petitions with respect to those
issues.
                               I

     The Transport Rule has been described in exhaustive
detail in earlier phases of this litigation. See EPA v. EME
Homer City Generation, L.P., 134 S. Ct. 1584, 1593-95, slip
op. at 2-6 (2014). We summarize the main points here.

     The Clean Air Act regulates air quality through a federal-
state collaboration.    First, EPA establishes air quality
standards known as NAAQS. See 42 U.S.C. § 7409(a).
Then, EPA identifies areas within the States that have not
attained those NAAQS. See id. § 7407(d). Those are called
“nonattainment” areas. Id. Next, the baton is passed to the
States, which have the first opportunity to enact plans that
                               8
provide for the “implementation, maintenance, and
enforcement” of the NAAQS. Id. § 7410(a)(1). States
typically must enact and submit their plans – called State
Implementation Plans or SIPs – within three years of any new
or revised NAAQS. Id. If a State declines to submit a SIP, or
if EPA finds that the State’s SIP fails to satisfy the minimum
criteria of the Clean Air Act, EPA must promulgate a Federal
Implementation Plan, or FIP, in its stead.              See id.
§ 7410(c)(1).

    Pollution emitted in upwind States can travel to
downwind States. As a result, some “downwind States to
which the pollution travels are unable to achieve clean air
because of the influx of out-of-state pollution.” EME Homer,
134 S. Ct. at 1593, slip op. at 1.

    The Clean Air Act’s good neighbor provision addresses
the issue of interstate air pollution. That provision, as
currently phrased, requires State SIPs to:

    contain adequate provisions –
       (i) prohibiting, consistent with the provisions of this
       subchapter, any source or other type of emissions
       activity within the State from emitting any air
       pollutant in amounts which will –
            (I) contribute significantly to nonattainment in, or
            interfere with maintenance by, any other State
            with respect to any such national primary or
            secondary ambient air quality standard . . . .

42 U.S.C. § 7410(a)(2)(D). 1


    1
       The Rule imposes good neighbor obligations based on
emissions that “contribute significantly to nonattainment” of
                               9
     The Transport Rule at issue here represents EPA’s latest
effort to implement the requirements of the good neighbor
provision. The Rule focuses on three NAAQS. (NAAQS
regulate individual pollutants measured over a specified time
period.) The NAAQS covered by the Transport Rule are the
8-hour ozone NAAQS, the annual particulate matter (or
PM2.5) NAAQS, and the 24-hour PM2.5 NAAQS. See
Transport Rule, 76 Fed. Reg. 48,208, 48,209 (Aug. 8, 2011).

     The Transport Rule does not directly regulate ozone and
PM2.5.     As gases are “carried downwind, they are
transformed, through various chemical processes, into
altogether different pollutants.” EME Homer, 134 S. Ct. at
1594, slip op. at 3. The pollutants that become ozone in
downwind States start out in upwind States as emissions of
nitrogen oxide (NOX). See Transport Rule, 76 Fed. Reg. at
48,209-10. The pollutants that become PM2.5 in downwind
States start out in upwind States as emissions of NOX and
sulfur dioxide (SO2). Id. Therefore, the Transport Rule
promotes downwind attainment of ozone and PM2.5 NAAQS
by limiting NOX and SO2 emissions in upwind States.
    The Transport Rule employed a “two-step approach” to
determine whether and to what extent a State must reduce its
NOX and SO2 emissions pursuant to the good neighbor
provision. EME Homer, 134 S. Ct. at 1596, slip op. at 7.
    In the first step, EPA identified the upwind States that
“contribute significantly” to nonattainment of NAAQS in one


NAAQS in downwind States and emissions that “interfere with
maintenance” of NAAQS in downwind States. For ease of
discussion, we focus on the “contribute significantly to
nonattainment” prong. But our analysis of over-control applies to
both prongs.
                              10
or more downwind States. See id. If a downwind State’s
receptor site is not in attainment and if an upwind State
caused more than 1% of the pollution at that site, then that
upwind State was deemed to have “contributed significantly.”
See id. (Receptor sites are locations in downwind States
where EPA measures ambient air quality for pollutants
regulated by the Clean Air Act. See id.)
     When an upwind State was found to contribute 1% or
more of the relevant pollution at a downwind receptor, that
upwind State was deemed to have a “linkage” to that
downwind location. See Transport Rule, 76 Fed. Reg. at
48,236. Any State with no such linkages was “screened out
and exempted from regulation under the rule.” EME Homer,
134 S. Ct. at 1596, slip op. at 7. Any State that had at least
one linkage was subject to the Transport Rule. See id. EPA
found 27 upwind States to have one or more linkages in
downwind States. See id. Those 27 States were then subject
to the second step of the Transport Rule.
     In the second step, EPA calculated the pollution
reductions necessary for those 27 upwind States to comply
with their good neighbor obligations. Recall that the good
neighbor provision of the Act prohibits upwind States from
emitting “amounts” of pollution that “contribute
significantly” to nonattainment in downwind States. 42
U.S.C. § 7410(a)(2)(D). EPA’s task at this second step was
to decide what “amounts” of pollution each upwind State
needed to reduce.
     But given what it described as the complexity of trying to
assess the relative amount that each upwind State contributes
to nonattainment in each downwind State, EPA decided to
impose uniform emissions reductions on the upwind States
covered by the Rule. See EME Homer, 134 S. Ct. at 1607,
slip op. at 26-27. In other words, once a State was deemed
                               11
subject to the Transport Rule, its obligation to reduce
emissions would no longer depend on the actual amounts it
emitted into individual downwind States.
     Using its uniform approach, EPA calculated how much
pollution each upwind State could eliminate if all of its
sources applied pollution control technologies available at
particular cost thresholds. See id. at 1596, slip op. at 7-8.
Those cost thresholds were expressed in terms of cost per ton
of emissions reduced.
     In the end, EPA adopted four cost thresholds for the 27
upwind States subject to the Transport Rule. For all States
subject to the Rule for annual NOX, EPA set a $500/ton cost
threshold. See Transport Rule, 76 Fed. Reg. at 48,250. For
States subject to the Rule for ozone-season NOX, EPA also set
a $500/ton cost threshold. See id. For States subject to the
Rule for SO2, EPA divided the States into two groups. For
Group 1 States, EPA set a $2,300/ton cost threshold. See id.
at 48,259. 2 For Group 2 States, EPA set a $500/ton cost
threshold. See id. 3
     In the prior round of litigation, petitioners disputed
EPA’s method of calculating emissions budgets for upwind
States, and this Court found three main problems with EPA’s
approach. First, the Rule could lead to over-control of
upwind States – that is, emissions reductions beyond those

    2
        Group 1 States are Illinois, Indiana, Iowa, Kentucky,
Maryland, Michigan, Missouri, New Jersey, New York, North
Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia,
and Wisconsin. See Transport Rule, 76 Fed. Reg. at 48,257.
    3
       Group 2 States are Alabama, Georgia, Kansas, Minnesota,
Nebraska, South Carolina, and Texas. See Transport Rule, 76 Fed.
Reg. at 48,257.
                              12
necessary to achieve attainment in downwind States. Second,
the Rule could require States to reduce even insignificant
contributions to pollution in downwind States. Third, the
Rule did not purport to try to assess each upwind State’s
relative contribution to nonattainment in downwind States.
We therefore concluded that EPA’s methodology violated the
Clean Air Act, and vacated the Transport Rule.
     The Supreme Court largely agreed with this Court on the
first two issues but not on the third. The Court concluded,
moreover, that those first two issues did not support
“wholesale invalidation” of the Transport Rule. EME Homer,
134 S. Ct. at 1608, slip op. at 29.
     Most important for present purposes is the first issue,
over-control. The Supreme Court “agree[d] with the Court of
Appeals to this extent”: The Transport Rule violates the
statute when it “requires an upwind State to reduce emissions
by more than the amount necessary to achieve attainment in
every downwind State to which it is linked.” Id.
     But the Supreme Court concluded that the potential
“over-control” did not “justif[y] wholesale invalidation of the
Transport Rule.” Id. at 1608, slip op. at 28-29. Rather, as
relevant here, if “any upwind State concludes it has been
forced to regulate emissions . . . beyond the point necessary to
bring all downwind States into attainment, that State may
bring a particularized, as-applied challenge to the Transport
Rule.” Id. at 1609, slip op. at 31.
    That’s where we are now.
                               II
     We start by addressing petitioners’ as-applied challenges
to the Transport Rule.
                                13
                                A
     As the Supreme Court stated in EME Homer, the Clean
Air Act authorizes EPA to “prohibit[] only upwind emissions
that contribute significantly to downwind nonattainment.”
EPA v. EME Homer City Generation, L.P., 134 S. Ct. 1584,
1604, slip op. at 21 (2014); see also id. at 1607, slip op. at 27
(EPA may “require the elimination of only those ‘amounts’ of
pollutants that contribute to the nonattainment of NAAQS in
downwind States.”); id. at 1603-04, slip op. at 21 (“EPA’s
task is to reduce upwind pollution, but only in ‘amounts’ that
push a downwind State’s pollution concentrations above the
relevant NAAQS.”). 4
    In EME Homer, the Supreme Court rejected a facial
challenge to EPA’s uniform approach and recognized that
EPA must have some leeway to balance the possibilities of
over-control and under-control of interstate emissions. The
Court stated, however, that an upwind State may bring an as-
applied challenge to EPA’s Transport Rule emissions budgets
when EPA’s uniform approach has gone too far in proscribing
emissions by upwind States. Id. at 1608-09, slip op. at 29-31.
In such an as-applied challenge, how do we determine
whether EPA has gone too far?



    4
       The Supreme Court held that the same was true for upwind
States that “interfere with maintenance” at downwind locations.
See EME Homer, 134 S. Ct. at 1604 n.18, slip op. at 22 n.18 (“Just
as EPA is constrained, under the first part of the Good Neighbor
Provision, to eliminate only those amounts that ‘contribute . . . to
nonattainment,’ EPA is limited, by the second part of the provision,
to reduce only by ‘amounts’ that ‘interfere with maintenance,’ i.e.,
by just enough to permit an already-attaining State to maintain
satisfactory air quality.”).
                               14
     The Supreme Court answered that question in EME
Homer. As relevant here, it stated that EPA may not require
“an upwind State to reduce emissions by more than the
amount necessary to achieve attainment in every downwind
State to which it is linked.” Id. at 1608, slip op. at 29. If EPA
does so, “the Agency will have overstepped its authority,
under the Good Neighbor Provision, to eliminate those
amounts that contribute to nonattainment.” Id. (alterations
and internal quotation marks omitted).
     When can we say that an upwind State has been required,
in the Supreme Court’s words, “to reduce emissions by more
than the amount necessary to achieve attainment in every
downwind State to which it is linked”? The answer again is
clear from the Supreme Court’s EME Homer opinion: when
those downwind locations would achieve attainment even if
less stringent emissions limits were imposed on the upwind
States linked to those locations. Id. at 1609, slip op. at 30-31.
     For example, assume that a downwind location would
meet its NAAQS if the upwind States to which it is linked
implemented emissions reduction technologies available at a
cost of $100/ton. Once those technologies are in place, the
downwind location will be in attainment. If the upwind
States also implemented emissions reduction technologies
available at a cost of $200/ton, the emissions reductions that
flow from those technologies would not help the downwind
location reach attainment because it already reached
attainment when technologies available at a cost of $100/ton
were implemented.
     In evaluating petitioners’ as-applied challenges, we thus
must determine whether a downwind location would still
attain its NAAQS if linked upwind States were subject to less
stringent emissions limits. If we answer in the affirmative,
EPA has overstepped its authority. Importantly, that does not
                                15
mean that every such upwind State would then be entitled to
less stringent emissions limits. Some of those upwind States
may still be subject to the more stringent emissions limits so
as not to cause other downwind locations to which those
States are linked to fall into nonattainment. Otherwise,
however, upwind States in those circumstances should prevail
in their as-applied challenges. 5
                                 B
                                 1
    Invoking EME Homer’s explicit authorization of as-
applied challenges, petitioners challenge the 2014 SO2
emissions budgets for Texas, Alabama, Georgia, and South
Carolina. Recall that SO2 emissions transform (along with
annual NOX) into PM2.5 in downwind States.
    We begin with Texas. At step one of its process for
computing emissions budgets under the Transport Rule, EPA
found Texas to be linked to PM2.5 nonattainment at only one
downwind location, Madison, Illinois (171191007). Air
Quality Modeling Final Rule Technical Support Document
(June 2011), J.A. 2716. At step two, EPA grouped Texas
with six other States and found that collectively those States
must reduce emissions at the $500/ton level in 2014.
Transport Rule, 76 Fed. Reg. 48,208, 48,257 (Aug. 8, 2011).
    5
      What if the downwind location would still reach attainment if
one upwind State’s emissions limits were relaxed, but only so long
as the other upwind States’ emissions limits were kept the same?
We are not certain how the Supreme Court in EME Homer meant to
resolve that question, but that issue is not presented in this case.
Here, as we will explain, we know from EPA’s own data that the
relevant downwind locations could reach attainment even if all of
the relevant upwind States’ emissions limits were relaxed in a
uniform manner.
                                 16
    However, EPA’s Technical Support Document for the
Transport Rule – a document that EPA prepared when it
proposed the Transport Rule – reveals that Madison, Illinois,
would attain its annual PM2.5 NAAQS even if all of the
upwind States linked to it implemented emissions reductions
available at the $100/ton cost threshold. See Technical
Support Document, Analysis to Quantify Significant
Contribution (July 2010), J.A. 2231.6
     Without any good neighbor reductions, Madison’s
maximum pollution level for PM2.5 would be 16.85 μg/m3 in
2012. J.A. 2231. The NAAQS for annual PM2.5 is 15 μg/m3.
See Transport Rule, 76 Fed. Reg. at 48,218. Madison
therefore needed to reduce its pollution by 1.85 μg/m3.
According to EPA’s projections, if every State connected to
Madison implemented pollution controls at a cost of
$100/ton, Madison would reduce its PM2.5 by at least that
amount in 2014. See J.A. 2231.
     Yet EPA required every State connected to Madison to
implement pollution controls available at a cost of $500/ton
or greater. 7 But EPA’s projections showed that if every State

    6
       At oral argument, EPA stated that it “changed the inputs into
the models between proposal and final [Rule], so we don’t know if”
the analysis in the Technical Support Document “still is true.” Tr.
of Oral Arg. 58-59. But in the final Rule, EPA did not provide any
updated analysis regarding cost thresholds below $500/ton.
Therefore, for the purposes of these proceedings, we may and must
rely on EPA’s initial analysis of those lower thresholds. On
remand, EPA may of course update its analysis, but it must
consider cost thresholds below $500/ton and it must justify its final
calculation consistent with the directions set forth by the Supreme
Court and this Court.
     7
       Some States connected to Madison are in Group 1 for SO2,
which must implement pollution controls at $2,300/ton. See
                              17
connected to Madison implemented pollution controls
available at $500/ton, Madison’s PM2.5 would go down by
2.61 μg/m3. J.A. 2231. That is 0.76 μg/m3 more than
Madison needed to reduce in order to comply with its
NAAQS.
    Put another way, by requiring reductions of $500/ton or
greater for the upwind States linked to Madison, EPA
required those States to help Madison overachieve its
NAAQS by at least 0.76 μg/m3.
     Texas is linked only to Madison, Illinois. Therefore, by
requiring Texas to implement pollution controls available at
$500/ton when controls in all contributing upwind States at
$100/ton would bring Madison into attainment, EPA has
required Texas “to reduce emissions by more than the amount
necessary to achieve attainment in every downwind State to
which it is linked,” in clear violation of the Supreme Court’s
directive. EME Homer, 134 S. Ct. at 1608, slip op. at 29.
    EPA similarly required Alabama, Georgia, and South
Carolina to implement unnecessary emissions controls in their
2014 SO2 emissions budgets.
    Alabama is linked to four downwind locations: Fulton,
Georgia (131210039), Hamilton, Ohio (390610014),
Hamilton, Ohio (390610042), and Hamilton, Ohio
(390618001). See J.A. 2715. Note that some counties
contain multiple receptor locations where EPA measures air
quality; each location is demarcated with a unique
identification number. EPA’s projections show that Fulton,
Georgia, will come into attainment even if all States linked to


Transport Rule, 76 Fed. Reg. at 48,259. Texas is in Group 2 for
SO2, which requires pollution controls at $500/ton. Id.
                              18
it implement no good neighbor reductions in 2014.
Moreover, all three locations in Hamilton, Ohio, will come
into attainment even if all upwind States linked to them
implement cost controls at $100/ton. See J.A. 2231. EPA is
requiring Alabama to implement cost controls at $500/ton,
when cost controls at $100/ton would bring every downwind
location to which it is linked into attainment.
     Georgia is connected to two downwind locations:
Jefferson, Alabama (10730023) and Jefferson, Alabama
(10732003). See J.A. 2715. EPA’s projections show that
Jefferson, Alabama (10730023) will come into attainment if
all States linked to it implement cost controls at $400/ton and
Jefferson, Alabama (10732003) will come into attainment if
all upwind States linked to it implement cost controls at
$200/ton. See J.A. 2231. EPA is requiring Georgia to
implement cost controls at $500/ton, when cost controls at
$400/ton would bring every downwind location to which it is
linked into attainment.
     South Carolina is linked to one location, Fulton, Georgia
(131210039). See J.A. 2716. EPA’s projections showed that
that location would come into attainment if all upwind States
linked to it implemented no cost controls. J.A. 2231. Yet
EPA is requiring South Carolina to implement pollution
controls at $500/ton.
     In short, EPA’s 2014 SO2 emissions budgets for Texas,
Alabama, Georgia, and South Carolina require each of those
States “to reduce emissions by more than the amount
necessary to achieve attainment in every downwind State to
which it is linked.” EME Homer, 134 S. Ct. at 1608, slip op.
at 29. The reductions on those four States are “unnecessary to
downwind attainment anywhere.” Id. at 1609, slip op. at 30.
Those emissions budgets are therefore invalid.
                             19
                             2
     Next, we consider as-applied challenges to the Transport
Rule’s 2014 ozone-season NOX emissions budgets related to
the 1997 8-hour ozone NAAQS. Petitioners bring as-applied
challenges to those 2014 budgets for Florida, Maryland, New
Jersey, New York, North Carolina, Ohio, Pennsylvania, South
Carolina, Texas, Virginia, and West Virginia.
     For ozone-season NOX, the only record data showed that
the downwind locations to which 10 of those 11 upwind
States (all but Texas) were linked would comply with their
NAAQS in 2014 even with no good neighbor obligation on
the upwind States. See Transport Rule, 76 Fed. Reg. at
48,246 (linkages); J.A. 2550-76 (2014 Base Case Maximum
Values). The conclusion is therefore simple. The 2014
ozone-season NOX emissions budgets for those upwind States
are invalid.
     For Texas, petitioners acknowledge that some good
neighbor obligation for ozone-season NOX may be
appropriate, but they say that it must be far lower than
$500/ton. The record supports their argument. The evidence
indicates that the two downwind locations to which Texas is
linked for ozone – East Baton Rouge, Louisiana and Allegan,
Michigan – could comply with their NAAQS even if the
upwind States to which those two locations were linked were
subject to cost thresholds far lower than $500/ton. The 2014
ozone-season NOX emissions budget for Texas is therefore
invalid.
                             C

   Despite those rather clear transgressions of the statutory
boundaries as set forth by the Supreme Court in EME Homer,
EPA argues that petitioners’ over-control challenges should
                             20
fail. EPA advances two main arguments, neither of which is
persuasive in light of the Supreme Court’s opinion.

    First, EPA contends that over-attainment in downwind
locations does not mean that there is impermissible over-
control of upwind States. Regarding Texas, for instance, EPA
says that Madison’s over-attainment “reflects incidental
benefits flowing from emission reductions by other upwind
States that are necessary to” achieve attainment at other
downwind locations. EPA Br. at 53-54.

    EPA’s argument directly contravenes the Supreme
Court’s analysis in EME Homer. According to the Supreme
Court, over-attainment in downwind locations is permissible
when it is “incidental to reductions necessary to ensure
attainment elsewhere.” EME Homer, 134 S. Ct. at 1608, slip
op. at 29. That happens, for instance, when “the emissions
reduction required to bring one linked downwind State into
attainment” is “large enough to push other linked downwind
States over the attainment line.” Id.

    The Supreme Court made crystal clear in EME Homer
that over-attainment in downwind locations is impermissible
when that excess attainment is “unnecessary.” Id. at 1609,
slip op. at 29-30. “If EPA requires an upwind State to reduce
emissions by more than the amount necessary to achieve
attainment in every downwind State to which it is linked, the
Agency will have overstepped its authority.” Id. at 1608, slip
op. at 29. That is precisely what we have here.

     Two examples of upwind States’ linkages to Madison,
Illinois, illustrate the difference between permissible and
impermissible over-attainment at downwind locations.

   The upwind State of Indiana is linked to Madison, Illinois,
as well as to 11 other downwind locations for annual PM2.5.
                              21
See J.A. 2715. To reach attainment, one of those downwind
locations in Allegheny, Pennsylvania, needs all upwind States
to which it is linked to implement cost controls at $2,300/ton
or higher. See J.A. 2715-16; Transport Rule, 76 Fed. Reg. at
48,257. Therefore, regardless of the cost threshold that is
necessary to bring Madison into attainment, Indiana must
implement controls available at $2,300/ton in order to satisfy
its good neighbor obligation to Allegheny. As a result, the
benefits that Madison, Illinois, receives from those higher
controls on Indiana are merely incidental to the reductions on
Indiana that are necessary to bring other locations into
attainment.

    The upwind State of Texas, by contrast, is linked only to
Madison, Illinois for annual PM2.5. Madison will come into
attainment for annual PM2.5 if all States linked to it implement
cost controls at $100/ton. If EPA requires Texas to
implement cost controls at $500/ton, the over-attainment that
Madison would achieve because of Texas’s incremental cost
controls would not be an “incidental” benefit of other
necessary good neighbor reductions imposed on Texas.
Texas does not contribute significantly to nonattainment for
PM2.5 at any other downwind location. Therefore, those
$500/ton reductions from Texas cannot be necessary to – or
even aid in – the achievement of attainment at any other
downwind location. Requiring Texas to implement higher
cost controls does not produce benefits that are “incidental” to
attainment elsewhere; it produces benefits that are
“unnecessary to downwind attainment anywhere.” EME
Homer, 134 S. Ct. at 1609, slip op. at 29-30.

     Second, EPA argues that “imposing less stringent
emission budgets” on those upwind States “would be
inequitable and contrary to the rationale underlying uniform
cost thresholds.” EPA Br. at 55. Specifically, EPA says that
                                22
uniform cost thresholds are important because they subject
“to stricter regulation those States that have done relatively
less in the past to control their pollution” and prevent those
States from “free riding on their neighbors’ efforts to reduce
pollution.” Id. (quoting EME Homer, 134 S. Ct. at 1607, slip
op. at 27).
     But EPA’s argument again flatly contradicts the
crystalline holding of the Supreme Court in EME Homer.
The Supreme Court could not have said it more clearly: “If
EPA requires an upwind State to reduce emissions by more
than the amount necessary to achieve attainment in every
downwind State to which it is linked, the Agency will have
overstepped its authority.” EME Homer, 134 S. Ct. at 1608,
slip op. at 29. The Court therefore explicitly authorized as-
applied challenges that, when successful under the principles
outlined by the Court, will necessarily mean a lack of
uniformity in certain circumstances.
    It bears mention, moreover, that the Supreme Court’s
conclusion on this point tracked the affirmative representation
made by the Deputy Solicitor General to the Supreme Court
that as-applied over-control challenges by upwind States
would be permissible – even though such challenges, when
successful, would necessarily mean the cost thresholds would
not be uniform. 8 EPA is now saying something to this Court


    8
       The Supreme Court’s language allowing such as-applied
over-control challenges was no accident, as examination of the oral
argument transcript in that case reveals:
    Justice Sotomayor: . . . [B]elow, the government conceded that
    there was a theoretical possibility that some States could be
    overcontrolled, that they would be implementing measures that
    would reduce their contributions to pollution below the 1
                                23
that is tension with, if not in contravention of, what the
Deputy Solicitor General told the Supreme Court.
     In sum, EPA’s uniform cost thresholds have required
States to reduce pollutants beyond the point necessary to


   percent. Assume that – I think there’s a theoretical possibility
   of that – but that your approach was basically fine.
   What would we do about that? First of all, are there measures
   States can take to get out of the FIP if it’s inappropriate to
   them because of overcontrol? And if not – and how do they do
   it? I mean, what’s the process? If we think there’s a flaw, do
   we vacate the rule? . . . .
   Mr. Stewart [Deputy Solicitor General]: . . . [E]ven if we win
   everything that’s at issue in this Court, the case is not over.
   There are a variety of more specific challenges to the details of
   the rule that the D.C. Circuit found it unnecessary to address.
   And so if we won on the issues that are before the Court, the
   case would be remanded and there would be an opportunity for
   the court below to consider those. And to the extent –
   Chief Justice Roberts: Including – including the overcontrol
   argument, or would that have been done?
   Mr. Stewart: Well, to – to the extent that any State had – and I
   don’t know the – the pending as-applied challenges at this
   level of detail. But to the extent that any State has a properly
   preserved challenge to the effect that it is actually likely to be
   subject to overcontrol, then that could be heard by the court of
   appeals. The court of appeals could determine both whether
   that is, in fact, likely to happen and whether, if it does happen,
   that would render the rule arbitrary and capricious as to that
   State.
Transcript of Oral Argument at 26:24-28:18, EPA v. EME Homer
City Generation, L.P., 134 S. Ct. 1584 (2014) (Nos. 12–1182, 12–
1183) (italics added).
                              24
achieve downwind attainment. That violates the Supreme
Court’s clear mandate in EME Homer.
                              D
     The next question is the remedy for the invalid 2014
emissions budgets. We will remand without vacatur the 2014
emissions budgets that we have found invalid. Although
there have been some critiques of the practice of remanding
without vacatur, this Court’s precedents authorize remand
without vacatur in certain limited circumstances. See, e.g.,
North Carolina v. EPA, 550 F.3d 1176, 1178 (D.C. Cir.
2008); Advocates for Highway and Auto Safety v. Federal
Motor Carrier Safety Administration, 429 F.3d 1136, 1151
(D.C. Cir. 2005). Here, as petitioners themselves note,
vacatur could cause substantial disruption to the trading
markets that have developed around the 2014 emissions
budgets. Cf. NACS v. Board of Governors of Federal Reserve
System, 746 F.3d 474, 493 (D.C. Cir. 2014) (remanding
without vacating where “disruptive effect of vacatur [wa]s
high”) (internal quotation marks omitted). Moreover, as
petitioners have acknowledged, some good neighbor
obligations may be appropriate for some of the relevant
upwind States. In these circumstances, remand without
vacatur is appropriate.
    On remand, EPA, petitioners, or other parties as
appropriate may provide new evidence, data, or calculations.
To be sure, remand without vacatur creates a risk that an
agency may drag its feet and keep in place an unlawful
agency rule. With that in mind, we expect and urge EPA to
move promptly on remand. If not, petitioners may promptly
bring suit against the Administrator for “failure . . . to
perform,” in addition to other appropriate remedies petitioners
may choose to pursue. 42 U.S.C. § 7604(a)(2).
                               25
                               III
     We now address petitioners’ other challenges to the
Transport Rule that we did not have occasion to reach during
petitioners’ last trip to this Court.
                               A
    To begin with, the State and local petitioners contend that
EPA lacked authority to promulgate the Transport Rule FIPs
for 22 of the 27 covered States. Starting in 2007, EPA
approved SIPs for those 22 States. See Transport Rule, 76
Fed. Reg. 48,208, 48,220-21 (Aug. 8, 2011). 9 Those SIPs
sought to fulfill the States’ good neighbor obligations by
complying with the regulatory framework laid out in the 2005
Clean Air Interstate Rule or CAIR.
    But in North Carolina v. EPA in 2008, this Court found
CAIR to be “fundamentally flawed,” and instructed EPA to
build a replacement for CAIR “from the ground up.” North
Carolina v. EPA, 531 F.3d 896, 929 (D.C. Cir. 2008). The
Court did not vacate CAIR. See North Carolina v. EPA, 550
F.3d 1176, 1178 (D.C. Cir. 2008). Our decision in North
Carolina prompted EPA to develop the Transport Rule.
    EPA may promulgate a FIP only if a State declines to
submit a SIP or if EPA finds that the State’s SIP does not
meet all of the applicable requirements of the Clean Air Act.
See 42 U.S.C. § 7410(c)(1). 10 EPA, in other words, may not

    9
       Those States are: Alabama, Arkansas, Connecticut, Florida,
Georgia, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maryland,
Massachusetts, Minnesota, Mississippi, Missouri, New York, North
Carolina, Ohio, Pennsylvania, South Carolina, Virginia, and West
Virginia. See Transport Rule, 76 Fed. Reg. at 48,220-21.
    10
       The full provision provides that:
                                26
promulgate a FIP for a State if it has previously approved a
SIP for that State. Here, EPA had approved SIPs for 22 of the
27 States covered by the Transport Rule. Therefore, in order
to promulgate the Transport Rule FIPs, EPA first needed to
revise its approval for the CAIR SIPs.
     The Clean Air Act allows EPA to “revise” a prior SIP
approval if that approval “was in error.” Id. § 7410(k)(6). In
particular, the Clean Air Act provides that whenever “the
Administrator determines that the Administrator’s action
approving, disapproving, or promulgating any plan or plan
revision (or part thereof) . . . was in error, the Administrator
may . . . revise such action as appropriate without requiring
any further submission from the State.” Id. Here, EPA
invoked its correction powers under Subsection 7410(k)(6) to
“rescind any statements that the [CAIR] SIP submissions
either satisfy or relieve the state of the obligation to submit a
SIP to satisfy the requirements of” the good neighbor
provision. See Transport Rule, 76 Fed. Reg. at 48,220.




    The Administrator shall promulgate a Federal implementation
    plan at any time within 2 years after the Administrator – (A)
    finds that a State has failed to make a required submission or
    finds that the plan or plan revision submitted by the State does
    not satisfy the minimum criteria established under subsection
    (k)(1)(A) of this section, or (B) disapproves a State
    implementation plan submission in whole or in part, unless
    the State corrects the deficiency, and the Administrator
    approves the plan or plan revision, before the Administrator
    promulgates such Federal implementation plan.

42 U.S.C. § 7410(c)(1).
                              27
     Petitioners argue that EPA’s use of its Subsection
7410(k)(6) correction power was invalid. They advance three
distinct contentions.
     First, petitioners argue that EPA’s initial approval of the
CAIR SIPs was not “in error,” and therefore could not be
corrected pursuant to Subsection 7410(k)(6). But when our
decision in North Carolina deemed CAIR to be an invalid
effort to implement the requirements of the good neighbor
provision, that ruling meant that the initial approval of the
CAIR SIPs was in error at the time it was done. As the
Supreme Court stated: “A judicial construction of a statute is
an authoritative statement of what the statute meant before as
well as after the decision of the case giving rise to that
construction.” Rivers v. Roadway Express, Inc., 511 U.S.
298, 312-13 (1994).
     Second, petitioners argue that because we remanded
CAIR without vacatur in North Carolina, we cannot now
conclude that EPA’s SIP approvals under CAIR were “in
error.” But petitioners misunderstand why we declined to
vacate CAIR in North Carolina. We left CAIR in effect
temporarily because doing so was necessary to “at least
temporarily preserve the environmental values covered by
CAIR” until it could be “replaced by a rule consistent with
our opinion.” North Carolina, 550 F.3d at 1178.
     But critically, the decision to remand without vacatur did
not alter the core holding of North Carolina: CAIR contained
“fatal flaws” and needed to be replaced. North Carolina, 531
F.3d at 901. Our decision to remand without vacating,
therefore, does not change the conclusion that EPA’s original
approvals of the CAIR SIPs were “in error” given our
decision in North Carolina.
                               28
     Third, petitioners say that EPA ran afoul of the Clean Air
Act’s requirement that EPA correct SIP approval errors “in
the same manner as the approval.” 42 U.S.C. § 7410(k)(6).
We reject that argument because EPA did correct the SIP
approvals “in the same manner” as it originally issued them.
Both the original SIP approvals and the corrections were
effectuated through rulemaking pursuant to the requirements
of the Clean Air Act.
     It is true that, as petitioners note, EPA approved the
original CAIR SIPs through rulemaking with notice and
comment, but revised them through rulemaking without
notice and comment. See Transport Rule, 76 Fed. Reg. at
48,221. But both actions complied with the Clean Air Act’s
framework for rulemaking.
    Under the Clean Air Act, rulemaking can be
accomplished without notice and comment when EPA has
“good cause” to forgo that extra procedure. See 42 U.S.C.
§ 7607(d)(1). Specifically, the Clean Air Act permits EPA to
conduct rulemaking without notice and comment when doing
so would be appropriate under Subsection 553(b) of the
Administrative Procedure Act, which sets forth a “good
cause” exception. 11


    11
       The Clean Air Act exempts from its notice and comment
requirements “any rule or circumstance referred to in
subparagraphs (A) or (B) of subsection 553(b) of title 5.” 42
U.S.C. § 7607(d)(1); cf. General Motors Corp. v. Ruckelshaus, 742
F.2d 1561, 1565 n.6 (D.C. Cir. 1984). Those subparagraphs, in
turn, provide two exceptions to the notice and comment
requirement: (A) when the agency enacts interpretative rules, and
(B) when the agency has good cause to forgo notice and comment.
See 5 U.S.C. § 553(b)(A)-(B).
                               29
     Subsection 553(b)(B) provides that an agency has “good
cause” to conduct rulemaking without notice and comment
when proceeding through notice and comment would be
“impracticable, unnecessary, or contrary to the public
interest.” 5 U.S.C. § 553(b)(B). This Court has previously
affirmed the use of the “good cause” exception when
rulemaking without notice and comment is “a reasonable and
perhaps inevitable response to” a “court order.” American
Federation of Government Employees, AFL-CIO v. Block,
655 F.2d 1153, 1157 (D.C. Cir. 1981).
     EPA explained here that it invoked the “good cause”
exception because this Court’s decision in North Carolina
invalidated the CAIR SIPs and commentators could not have
said anything during a notice and comment period that would
have changed that fact. See Transport Rule, 76 Fed. Reg. at
48,222 (“EPA must accept the Court’s conclusion that
compliance with CAIR does not satisfy the requirements of
[the good neighbor provision] and lacks discretion to reach a
different conclusion.”). EPA is correct that it would have
been utterly “unnecessary” and wasteful to go through notice
and comment given our decision in North Carolina. See 5
U.S.C. § 553(b)(B).
     In sum, EPA’s initial approval of the CAIR SIPs was “in
error.” And EPA corrected that approval “in the same
manner” as it approved the SIPs – that is, through a valid
rulemaking. 12


    12
       Our conclusion on Subsection 7410(k)(6) is limited to the
unusual circumstances here, in which a federal court says that EPA
lacked statutory authority at the time to approve a SIP. We do not
take a position on use of Subsection 7410(k)(6) in any other
circumstances.
                                 30
                                  B
     Next, petitioners challenge two models used by EPA to
create the Transport Rule. This Court’s review of EPA’s
modeling choices is deferential. It is “only when the model
bears no rational relationship to the characteristics of the data
to which it is applied that we will hold that the use of the
model was arbitrary and capricious.” Appalachian Power Co.
v. EPA, 135 F.3d 791, 802 (D.C. Cir. 1998).
     First, petitioners argue that EPA’s model for creating air
quality projections was arbitrary and capricious because it
used insufficient real-world data.       In order to project
downwind air quality, EPA used real-world data from 2003 to
2007. See Transport Rule, 76 Fed. Reg. at 48,233-36.
Petitioners argue that EPA should have verified its findings
against air quality measured after 2007 as well.
     EPA’s decision not to use post-2007 air quality data in
the model was reasonable. As already discussed, in 2008, this
Court invalidated CAIR, but we left that Rule in place until
the Agency came up with a replacement. See North Carolina,
550 F.3d at 1178. As a result, air quality data after 2007
reflected “large emission reductions from CAIR” that would
ultimately be displaced by the Transport Rule. See Transport
Rule, 76 Fed. Reg. at 48,230.



     Moreover, given our narrow holding here, EPA’s use of its
correction power under Subsection 7410(k)(6) should not be read to
diminish the scope or force of Subsection 7410(k)(5), which
provides that whenever “the Administrator finds that the applicable
implementation plan for any area is substantially inadequate . . . the
Administrator shall require the State to revise the plan as necessary
to correct such inadequacies.” 42 U.S.C. § 7410(k)(5).
                               31
    As EPA reasonably explained, because “the Transport
Rule will replace CAIR, we must model a future year base
case which does not assume that CAIR is in place (a ‘no-
CAIR’ case).” Id.
     Second, petitioners object to the model EPA used to set
State emissions budgets. That model predicted the generation
and emissions produced at electric generating units within the
States covered by the Transport Rule. Petitioners say that
those predictions were arbitrary because EPA knew that there
were “discrepancies” between the predictions and the actual
generation and emissions at those units. EPA contends that
the model’s “discrepancies are small and random and thus do
not result in biases.” Transport Rule Primary Response to
Comments (June 2011), J.A. 2089.
     We will not invalidate EPA’s predictions solely because
there might be discrepancies between those predictions and
the real world. That possibility is inherent in the enterprise of
prediction. The best model might predict that the Nationals
will win the World Series in 2015. If that does not happen,
you can’t necessarily fault the model. As we have said
previously, the fact that a “model does not fit every
application perfectly is no criticism; a model is meant to
simplify reality in order to make it tractable.” Chemical
Manufacturers Association v. EPA, 28 F.3d 1259, 1264 (D.C.
Cir. 1994).
                               C
    Next, petitioners argue that EPA failed to properly
regulate pursuant to the “interfere with maintenance” prong of
the good neighbor provision. The Transport Rule regulates
two different kinds of interstate air pollution. As we have
discussed, the Rule regulates upwind emissions that
“contribute significantly to nonattainment” of NAAQS in
                              32
downwind States. 42 U.S.C. § 7410(a)(2)(D)(i). The Rule
also regulates upwind emissions that “interfere with
maintenance” of NAAQS in downwind States that have
achieved attainment. Id.
     In North Carolina, we held that EPA must give
“independent significance” to those prongs. North Carolina,
531 F.3d at 910. We found that CAIR failed to do that.
CAIR applied the interference with maintenance provision “in
conjunction with the significant contribution to nonattainment
provision and so did not use the maintenance prong to
separately identify upwind States subject to CAIR.” Id.
(quoting 71 Fed. Reg. 25,328, 25,337 (Apr. 28, 2006)). Put
another way, areas that found “themselves barely meeting
attainment . . . due in part to upwind sources interfering with
that attainment ha[d] no recourse under EPA’s interpretation
of the interference prong” in CAIR. Id.
     Petitioners argue that the Transport Rule repeats the same
error. We disagree.
     The Transport Rule’s methodology affords independent
effect to the “interfere with maintenance” prong of the good
neighbor provision. In formulating the Transport Rule, EPA
“evaluat[ed] contributions to identified maintenance receptors
as well as contributions to identified nonattainment
receptors.” Transport Rule, 76 Fed. Reg. at 48,227; see also
id. at 48,212 (“EPA thus identified specific emission
reduction responsibilities for each upwind state found to
significantly contribute to nonattainment or interfere with
maintenance in other states.”) (emphasis added).
    With the Transport Rule, EPA created a distinct category
of maintenance receptors that could independently trigger an
upwind State’s good neighbor obligations. See id. at 48,228.
Therefore, the Transport Rule complied with North
                               33
Carolina’s requirement that EPA give the nonattainment and
maintenance prongs “independent significance.”
                                D
    Petitioners also raise several objections to EPA’s
methodology for identifying upwind States that “interfere
with maintenance” at downwind locations.
     First, petitioners argue that EPA’s methodology for
identifying upwind emissions that “interfere with
maintenance” failed to “identify and analyze only those
upwind emissions that might actually threaten continued
attainment.” State and Local Br. at 20. Second, they argue
that the methodology improperly required emissions
reductions in upwind States without accounting for
maintenance secured by the downwind States’ own
maintenance plans. 13     As a result, it risked requiring
emissions reductions that would be duplicative or
unnecessary. Third, they say that EPA erred by focusing
“exclusively on the utility sector for emissions reductions,”
when that sector may not produce the emissions that interfere
with maintenance at downwind locations. Id. at 21.
     At bottom, each of those claims is an argument that
EPA’s methodology could lead to over-control of upwind
States that are found to interfere with maintenance at a
downwind location. That could prove to be correct in certain

    13
        When a State believes that an area within its borders has
reached a national air quality standard, that State may seek a
“redesignation” of that area from “nonattainment” to attainment.
See 42 U.S.C. § 7505a(a). That request must be accompanied by a
revision to the State’s SIP, which “provide[s] for the maintenance
of the” NAAQS “for at least 10 years after the redesignation.” Id.
That revision is called a “maintenance plan.”
                               34
locations. But the Supreme Court made clear in EME Homer
that the way to contest instances of over-control is not
through generalized claims that EPA’s methodology would
lead to over-control, but rather through a “particularized, as-
applied challenge.” EME Homer, 134 S. Ct. at 1609, slip op.
at 31. And petitioners do not point to any actual such
instances of over-control at downwind locations.
     As the Supreme Court stated, under the “interfere with
maintenance” prong, EPA may only limit emissions “by just
enough to permit an already-attaining State to maintain
satisfactory air quality.” Id. at 1604 n.18, slip op. at 22 n.18.
If States have been forced to reduce emissions beyond that
point, affected parties will have meritorious as-applied
challenges.
                               E
    Finally, petitioners advance three new arguments on
remand that we may not entertain at this time.
     We may hear objections to EPA rules or procedures only
if the objections were “raised with reasonable specificity
during the period for public comment.”               42 U.S.C.
§ 7607(d)(7)(B). If it was “impracticable to raise a particular
objection” or if “the grounds for the objection arose after that
period,” parties still must petition EPA for administrative
reconsideration before raising the issue before this Court. See
Utility Air Regulatory Group v. EPA, 744 F.3d 741, 746 (D.C.
Cir. 2014).      This may sometimes seem a roundabout
procedure, but that is what the statute requires and what we
therefore must insist upon. If EPA fails to conduct a
reconsideration hearing, the party may seek review of that
decision in this Court. See 42 U.S.C. § 7607(d)(7)(B) (“If the
Administrator refuses to convene such a proceeding, such
                              35
person may seek review of such refusal in the United States
court of appeals for the appropriate circuit.”).
     First, petitioners argue that EPA violated the Clean Air
Act’s notice and comment requirements by significantly
amending the Rule between the proposed and final versions
without providing additional opportunity for notice and
comment. Because that argument is an objection to the notice
and comment process itself, petitioners obviously did not and
could not have raised it during the period for public comment.
Under Subsection 7607(d)(7)(B), however, the only
appropriate path for petitioners to raise this issue is through
an initial petition for reconsideration to EPA. At least one
party to the present suit has done just that. See Br. of
Intervenor San Miguel Electric Cooperative, Inc. and Amicus
Southeastern Legal Foundation, Inc. at 27. EPA has not ruled
on that request, and the parties have not asked for judicial
review of EPA’s delay in acting. Id. We are without
authority at this time to reach this question.
     Second, petitioners argue that EPA did not have authority
to promulgate certain Transport Rule FIPs because those FIPs
were signed by the EPA Administrator before EPA published
its disapproval of the CAIR SIPs in the Federal Register.
Petitioners did not raise this issue before the Agency during
notice and comment, and EPA has not denied any petition for
reconsideration raising this objection. We therefore may not
entertain it now.
    Third, petitioners argue that EPA exceeded its authority
by finding linkages based on upwind contributions to
downwind locations that were designated in “attainment” or
“unclassifiable.” See 42 U.S.C. § 7407(d). Petitioners again
did not raise this argument during the notice and comment
period or otherwise comply with 42 U.S.C. § 7607(d)(7)(B).
                             36
This question is therefore not properly before this Court, and
we may not reach it now.
                            ***
     To sum up: We hold invalid the 2014 SO2 emissions
budgets for Alabama, Georgia, South Carolina, and Texas, as
well as the 2014 ozone-season NOX budgets for Florida,
Maryland, New Jersey, New York, North Carolina, Ohio,
Pennsylvania, South Carolina, Texas, Virginia, and West
Virginia. We remand without vacatur to EPA for it to
reconsider those emissions budgets. We reject all of
petitioners’ other challenges to the Transport Rule, including
all of their facial challenges to the Rule. The petitions for
review are therefore granted in part and denied in part.
                                                  So ordered.
