F OR P UB LIC AT ION



### U N I TED STA TES C O U R T O F A PPEA LS F O R T H E N IN T H C IR C U IT

R ES I S TI NG E NVI R ONMEN TAL D ES TR UC TI ON ON I NDI GE NOUS L ANDS , R E D O IL ; A LASKA W I LD ER N ESS L EA GUE ; C EN TER F OR B I O LO G I CA L D I VE R S I TY ; N ATUR AL R ESO U RC ES D EF ENS E C O U N C IL ; N OR THER N A LASKA E N V I RO N M EN T A L C ENTER ; O C EA NA ; P A CI FI C E NVI R ONMEN T ; S I ERRA C L UB ; T HE W I LD ER N ESS S OC I E TY , Pe tit ion e rs,

v.
U NI TED S T A T ES E NVI R ONMEN TAL P R OTEC TI ON A G EN CY , Respondent , S H ELL G U LF OF M EX I C O I NC .; S H ELL O F F S HORE I

NC ., Re sp on de nts -I

nte rv e no rs

. No. 12-70518

AMENDED OPI NI ON

On Petition for Review of a n Orde r of the Environmental Protec tion Age ncy Environmental Appe als Boa rd
Argued and Submitted Aug ust 28, 2012—Anchora g e, AlaskaR E D O IL V

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T hi s s ummary cons t i t ut es n o part of t he op i ni on of

t he cour t

. I t ha s * b een p repa red b y co urt s t af f f o r t he co nveni ence o f

t he read er. Filed De cembe r 26, 2012 Amended A

pril 23, 2013

Be fore : Michael Da ly

Hawkins, M. Mar g are t McKeown, and Carl os T. B e a , Ci rc uit

Judg e s. Opinion by

J udg e McK eown

SUMMAR

Y *

Envi ronm ental Law The pa nel denied a

petition for rev i ew, and upheld a decision of the Environmental Protection Ag enc y g ranting tw o a ir pe rm its a

uth or izin g e xplor a tor

y dr ill ingop e ra

tio ns in t he Ar ctic Oc ean by

a drillship and its associated f leet of
su pp or t ve sse ls. The pa nel uphe l d the EPA’s statutory and re g ulatory int e rp re tatio ns

. Spe c if

ic a lly , the pa

ne l he ld t hat th e Cle an A ir Ac t is a mbi g uo us a s to the a pp lic a bil ity of the be st a

va ila ble control emissions to support vessels not attache d to an Outer Continental Shelf source, a nd conclude d under

Chevron U.S.A., Inc . v. NRDC, Inc. , 467 U.S. 837 (1984), defe renc e that the EPA’s construction of the statute was pe rmissible and
rea sonable. The panel also held that the EPA’s g rant of a 500 meter a mbient air exemption was not plainly err oneous or inc on sis te nt w iththe EPA ’s re g ulatio ns

.R E D O IL V

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CO UN SEL

Colin C. O’B rien (a

rgued), Ea

rthjustice, Anchor ag e, Alaska ; Eri c P. J org ensen, Ea rthjustice, J uneau, A laska, for Pe tit ion e rs

.
I g nacia S. Moreno, Danie l Pinks ton (a rgu ed), A lan D. Gre enber g , United States Depa rtment of Jus t i ce , Denve r, Col or a do , f

or Re sp on de nt.

Kathl e e n M . Su lli va

n ( argue d) , Wil liam B. Ad a ms, Da vid S. Mader , Quinn Emanuel Urquha rt & Sulli van L L P, Ne w York, New Y ork; Duane A. Siler, Sarah C. B ordelon, Tony G. Mendoza, Crowell & Moring L L P, W ashing ton, D.C., for I nte rv e no rs -R e sp on de nts

.
L i s a E

. J o n es , S am u el B. Bo x erm an , an d J am es R

. W ed ek i n g, Sidley Austin, L L P, Washing ton, D .C., Ma ra E. Z immerman, Washington, D.C., for A micus Curiae Ame rica n Pe troleum I nstitut e.
Came ro n M . L e on a

rd , O ff ic e of the Attor

ne y Ge ne ra l, Fa irbanks, Alaska , for Amicus Curia e State of A laska.

OP IN ION
McKEOWN, Circuit J udg e: Since 1990, the Environmenta l Protection Ag ency (“EPA” ) has be en re sponsible for re g ulating a ir pollution fr om o ff sh or e so ur c e s o n th e Oute r C on tin e nta l Sh e lf (“ OC S” ) under the C le an A ir Ac t ( “ the Ac t” ). 42 U. S.C. § 7627. We consider he re whether the EPA’s Environmenta lR E D O IL V

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O ut er C ont i nen t al Shel f l eas e bl ocks ar e def i ned g eogr aphi c a r eas over 1 t he o ut er conti nent al sh e lf t hat i d ent i f

y f ed eral l and ow ners hi p and f ac i l i t ate the m an ag em en t o f o f f sho re re so urc es. Ap pe a ls B oa

rd (“ EA B ” ) p ro pe rl y

up he ld t wo a ir pe rm its
a uth or izin g e xplor a tory dr ill ingop e ratio ns in t he Ar c tic Oce an by a drillship and its a ssociated flee t of support vessels. The petition for revie w cha lleng es two aspe cts of the permits: (1) the de termination that support vessels, unlike the drillship it self, do no t require the best available c ontrol tec h n o lo g y

( “ B A CT ” ) to c o n tr o l e mi s s io n s ; a n d ( 2 ) the exemption of the area

wi t h i n a 500-meter ra dius of the dr ill sh ip f ro m ambi e nt a ir

qu a lity sta nd ard s.
Th e a pp lic a tio n o f B AC T t o s up po rt ve sse ls r e qu ir e s u s to
rec oncile conf

licting pr ovisions of the Act. In doing so, under Chevron U.S.A., Inc. v. NR DC
, Inc. , we de fer

to the EAB ’s re asonable i n t erpr etation of those pr ovisions and related re g ulations. 467 U.S. 837 (1984). L ikewise, we
e va luate wh e the r t

he EA B ’s d eci sio n o n th e ambi e nt a ir boundary i s a per

missibl e application of the EPA’s regulations. I n both case s, we uphold the EPA’s statutory and regulatory

interpre tations, and we de ny the petition.

I. B ACKG ROUND Shell Gulf of Mexico, I n c. and Shell Offshore, I nc. (collec tively

“Shell”) pur chase d lease blocks in the Chukchi 1 and B eauf

ort Seas off

th e North Slope of Alaska for oil and g a s explo ratio n. She ll p lans to c on du c t th is e xplor a tio n v ia its drills hip, the Discove rer , along with a n associate d flee t of
su pp or t ve sse ls, inc lud ingic ebreake rs , o il s pil l r e sp on se ve sse ls, and

a su pp ly sh ip. As re qu ir e d b y

the Ac t, S he ll
a pp lie d f or pe rm its to e mit

po llutants i n conne c tio n w ithitsR E D O IL V

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were up h e l d i n t wo a dm in is tr ati ve ap peal s t o t he E AB. Petitioners, Resist i n g E n v i ro n m en tal Destruc tion on I ndige nous L ands, an environmenta l org anization, and other
en v i ro n m en t al gro u

p s (c o l l e c t i v el y

“R E DO I L ”) , ch al l en ge the pe rm its on

the ba sis that the y do no t sat isf y the Ac t’ s a ir permit requir ements. Shell inter vened to oppose REDOI L ’s pe tit ion s. Two per mits ar e at issue, one for operation in the Chukchi Sea and the other for

the B eauf

ort Sea. The permit s allow She ll, su bje c t to c on dit ion s, to c on str uc t and op erat e its Di scove rer

drillship and use its associated f leet for exploratory

drilling a ctivities betwee n J uly 1 and Nove mber 30 eac h y ear

. The Chukchi permit underw ent two rounds of notice-a nd-comment be fore it was iss ued in Marc h 2010. The Be aufor t permit underwe nt one round o f n o ti ce- and-c omment befor e it was issued in April 2010. The E AB addre ssed the two permits toge ther in the a dminist rative p roceeding s that followed.

Under the permits, S hell must apply BA CT—consisting of spec ific tec hnologie s selecte d b y t h e EPA, such a s g ood combustion practice s, a par ticular ve ntilation sy stem, or a ty pe of fu e l—t o li mit

the e mis sio ns of

sp e c if ic po llutants subject to regulation under the Act. Central to this appea l, the EPA deter

mined that BA CT applies to the Discove rer when it i s at t ac hed to the sea

bed at a drill site by

at least one anchor , and to any vessel that is tied to the Di sc ov e re r under that condition

. I n sho rt , the pe rm its re qu ir e She ll t o c omp ly with technolog ical re quirements for the Discove rer

and the supply vessel whe never

it is t ied to the Di

sc ov e re r. Howeve r, the per mits do not presc ribe tec hnologic al re quirements forR E D O IL V

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the re ma ini ng ve sse ls in the a sso c iate d fl e e t be c a us e the y wi ll not be phy sically

attache d to the Discove rer

. REDOI Lappeal ed t he appr oval of the pe rmits to the EAB , seeking to have B ACT applied to the entire associate d flee t wheneve r it is operatingwithin 25 mi les of the Discove rer , reg ar d l es s of whethe r the ve ssels are tied to the drillship. R EDOI Largued that § 7627 esta blis h es an “unambiguous mandate” requiring the EPA to do so. Cit ing ambig uity in § 7627’s re quirements, the EA B de nied re view in Dec ember

2010, but remande d for r easons not at issue here

. In re: Shell Gulf of Mexic o, Inc. & Shell Offshore, Inc. , 2010 WL 5478647 (E.P.A. Dec . 30, 2010).

On re mand , th e EPAiss ue d r e vis e d a ir pe rm its in September 2011. The revised pe rmit s allow the Discove rer an area with a 500-meter radius, measure d from the c enter of the dr ill sh ip, that is e xemp t f ro m “ ambi e nt a ir ” sta

nd ard s. Th e e xemp tio n is c on dit ion e d o n th e Un ite d State s Co a st Gu ard’ s establishment of an e ffe ctive saf ety zone that pr oh ibi ts m e mbe rs of the pu bli c fr om en te ri ngthe are a . Sh e ll
mu s t als o develop a

nd implement a public ac cess c ontrol prog ram to (1) notify

the g ener al public of the prohibition on enter ing the safe ty zone, a nd (2) c ommunicate to North Slope communities releva

nt inform at i o n ab o u t exploration operations, such as timing and loc ation.

RED OI L app eale d th e re vis e d p e rm its to t he EA B , th is time targ eting the ambient air exempt i o n . REDOI Lurg ed that the exemption contra vened both the definit i o n of “ambient air” in the EPA’s regulations a nd the age n cy ’s longsta nding inter

pretation of those regulations. The EAB dismiss ed this second r ou n d o f appe als in a January 2012 order , noting that ambient air e x emptions are de termined onR E D O IL V

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a ca se-by -ca se basis. In re : S he ll G ulf of M e x ic o, In c . &Sh e ll O ff s h o r e, I nc. , 2 012 WL 119962, at *27 (E.P.A. Jan. 12, 2012). The pe rmits be ca m e effective on January 27, 2012. No tic e of Ap pr ov a l of

Cle an Ai r Ac t Oute r Con tin e nta l Sh e lf Pe rm its I ssu e d to She ll G ulf of Me xico , Inc ., and

She ll Of fs h o re , I n c. fo r t h e D i s c o v er er Dr i l l s h i p , 7 7 Fe d

. R eg. 7148, 7148 (F eb. 10, 2012).

REDOI Lnow see ks review of bot h t h e De cembe r 2010 EAB ruling declining to a pply BA CT to the entire associate d flee t a nd the J anuar

y 2012 EAB ruling on the 500-meter ambient air e x emption.

II. A PPLI C A TIO N O F BACT TO THE A S S OCI AT E D F LEET
A. S T AT UT ORY F RAM E W ORK

Enact ed in 1970, the Clean A ir Act e stablished a compre hensive prog ram to protec t and enhance air qua lity by limit ing e missions from both stationary industrial sour ces a

nd mobile sources. 42 U .S.C. § 7401 e t se q

. Ce nt ra l to thi s leg islation are national air standard s , known as “ National Am bie nt A ir Qu a lity Stand ard s” (“NA AQ S” ), se t by the EPA for pollutants consider ed har mful t o p u b lic health and the
env i ro nment. 42 U.S.C. §§ 7408–10. The Act has be en sig nif ic antl y a me nd e d tw ic e , in

19 77 and

19 90. Cle an A ir Act Amendme nts of 1977, Pub

. L . No. 95-95, 91 Stat. 685 (1977); Clean A ir Act Ame ndment s of 1990, Pub. L . No. 101-549, 104 Stat. 2399 (1990). The P re v ention of Significa nt D eter ioration (“PSD”) prog ram and its re l ated BA CT requirement wer e first include d in the 1977
a me ndme nt, wh ic h d e a lt w ithon sh or e so ur c e s o f a ir pollution. 42 U.S .C. §§ 7470–7492. The PSD prog ram wa s later applied to offshore source s on the OCS through the 1990R E D O IL V

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a me ndme nt. 42 U. S.C. § 7 62 7. Th e e xten t to wh ic h B AC T applies to an associated fleet t urns on the i ntera ction betwee n the tw o ame ndme nts

. The 1977 amendment direc ted that major ne w stationary
source s of pollution and major exist ing stationary source s that
are being signific antly modified must obtain preconstruc tion pe rm its thr ou g h a pr oc e ss c a lle d Ne w So ur c e Re vie w. PSD is the Ne w Sourc e Re vie w p ro g ra m f or are a s w ithre lativ e ly
c le an a ir —t hose are a s th a t th e EPAde sig nate s a s in

“ a tta inm e nt” wi th N AA QS o r a s “ un c la ssi fi a ble ” du e to ins uf fi c ie nt d a ta

. 42 U. S.C. § 7 47 1. Th e pr og ra m’ s p ur po se i s to protect the public f

rom any adver se hea lth or welfa

re eff ects of a ir pollution that may occur despite ac hievement of NA AQ S, an d to re qu ir e c are fu l e va luatio n o f a ll
c on se qu e nc e s o f n e w i nd us tr ial de ve lop me nt. 42 U. S.C. § 7470(1), ( 5).

U n d e r t h e P S D p r o g r am , “ [ n ] o m a j o r e m i t t i n g f

a c i l i t y”

“ may be c on str

uc te d” witho ut a

c on fo rm ingpe rm it. 42 U.S.C. § 7475(a) (1). “Major emitting fa cility ” is define d, in part, as a

“stationary

source [] o f ai r pollutants” with the po te nti a l to e mit

c e rt a in t hr eshold le ve ls o f s pe c if

ie d a ir pollutants subject to regul at ion. 42 U.S.C. § 7479(1). To obtain a PSD permit, such a f acilit y must, among othe r thi ngs, satis fy

tw o in de pe nd e nt r e qu ir e me nts . T he fi rs t require ment conce rns emis sions: the owner or operator of the major emitting fac ility must c onduct air qualit y an aly ses de mon str a tin g that e mis sio ns fr om t he fa c ili ty wi ll n ot c a

us e or c on tr ibute to a ir po llutio n in v iol a tio n o f v ari ou s a ir qu a lity sta nd ard s. 42 U. S.C. § 74 75 (a )( 3) . T he se c on d r e qu ir e me nt, and the one at issue here , conce rns technolog y : “the propose d fac ility is subjec t to the best available control tec hnology for
eac h po l l u t ant subject to re g ulation” emitted from suc hR E D O IL V

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fa c ili ty . 4 2 U .S. C. § 74 75 (a )( 4) . The ob lig a tio n to a pp ly BA CT require s the EPA to select e mis s i o n control technolog ies that result in the maxim um redu ction of specifie d pollutants in vi ew o f “ene rg y , environmenta l, and economic impac ts and other c osts.” 42 U.S.C. § 7479(3).

The 1990 amendment extended the appl i ca b ility of the PSD re q u irements beyond major onshore stationary source s of air pollution. As a re sult of the 1990 amendment, the E PA, fo r t he fi rs t ti me , w a s g ive n ju ri sd ic tio n to reg ul a te OC S
source s “located offshore of the States along t h e P acif ic, Ar c tic and

At lanti c Coa sts ” and cert ain a re a s o f t he Gu lf Coast. 42 U.S.C. § 7627(a)(1) . To ac hieve the g oals of the PSD pr og ra

m, C on g re ss d ir e c te d th e EPAto “ e sta bli sh
re qu ir e me nts ” so tha

t O CS so ur c e s w ou ld atta in a nd ma int a in
a mbi e nt a ir

qu a lity sta nd ards and

c omp ly wi th t he PSD prog ram. Id. A key provision of § 7627 is the definitio n o f t h e ter m “Outer Continental Shelf source,” which mea ns “any equipment, ac tivity , or fa cility ” that “(i) e mits or has the potential to emit any

air pollutant, (ii) i s regulated or authorized under the Out er Continental Shelf L ands Ac t [(“OCSL A”) , 43 U.S.C. § 1331 et seq.], and (iii) is located on t h e Ou t er Continental Shelf or in or on wate rs above the Outer Conti n ental Shelf.” 42 U.S.C. § 7627(a)(4) (C). Significa ntly , jurisdiction under OCSL A extends only to “the
su bs oil and se a

be d of the oute r Con tin e nta l She lf and

. . . a ll ins ta llatio ns and

oth e r d e vices pe rm ane ntl y or te mpo ra ri ly attache d to the s eabe d.” 43 U.S.C. § 1333(a) (1). The statut or y de fi nit ion of “ OC S so ur c e ” a dd iti on a lly dir e c ts that, “[f]or purposes of this subsection, emissions from any vessel servicingor assoc iated with an OCS source , including emissions while at the OCS source or en route to or f

rom theR E D O IL V

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OCS source within 25 miles of t h e OCS source , shall be considered di rec t emissions from the OCS source.” 42 U.S.C. § 7627(a)(4) (C)(iii).

I n f oll ow -on re g ulatio ns a do pte d in 19 92 , th e EPA inc o r p o r a te d s e c ti o n s ( i) , ( ii ) an d

( ii i) o f th e s ta tutory definition of “OCS source ” and added that it would include vessels onl y when “(1) [ p]ermanently or tempora rily attache d to t he se a be d, ” or “ (2 ) [p ]hy sic a lly

a tta c he d to an O CS fac ility , in which case only the stationary

source s aspec ts of the vessels will be re g ulated.” 40 C.F .R. § 55.2.

B. T HE C L E AN A I R A C T IS A M B I GUO US AS T O BA CT ’ S A P P L I CAT I ON T O A SS OC I A TED V ESSEL S N OT A T T ACHE D T O AN OCS S OURCE

We next consider wheth er t he Ac t clear ly and unambig uously

require s the application of all aspec ts of the PSD pr og ra

m, i nc lud ingB AC T, to a sso ciate d v e sse ls operating within 25 miles of the OCS s ource , reg ardle ss of whether they are tied to the OCS s o urce , as urg ed by RE DO I L

. I n contra st, the EPA and Shell argue that the statute is ambiguous a

nd that we owe def

ere nce to the E PA’s permissible construc tion that BACT applies to the Di s cove rer , w hic h is a

statio na ry OC S so ur c e , b ut n ot t o mobile support vessels unattac hed to the drillship. To interpre t the statute, we look fir st to the statute’s “languag e itself [and] the specific c ontext in w h i ch that lang uag e is used.” McNeill v. United States , 131 S. Ct . 2218, 2221 (2011) ( quotin g Robinson v. Shell Oil Co. , 5 19 U. S. 337, 341 (1997) (interna l quotation mar ks omitt ed)) . I f “the [ex presse d] i ntent of Cong ress is clear , ” then the court and the a g e nc y

“ mus t g ive e ff

e c t to [that] un a mbi g uo us lyR E D O IL V

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ex presse d intent.” Chevron , 4 6 7 U

. S. a t 8 4 2

– 4 3

. I f, ho we ve r, “ Con g re ss h as no t di re c tly a dd re sse d th e pr e c ise question at issue,” the n we m ust not “simply impose [our] construction on the statute, a s would be nec essar y in the
a bs e n c e o f an a dm i n i s t r a t i v e i n t e r p r e t a t i o n , ” b u t r a t h e r

a sk

“ wh e the r the age nc y ’s ans we r i s b a se d o n a pe rm iss ibl e construction of the statute.” Id. at 843. An additional question is wheth er the EAB ’s int e rp re tatio n deser

ve s Chevron de fe re nc e . Co ng re ss e xplic itl y g ra nte d to the EPA th e a

uth or ity to p ro mul g a te
re g ulatio ns and

g ra nt ai r per mit s f or a c tiv iti e s o n th e OC S. Th e EPAe xer c ise d th a t a uth or ity th ro ug h a

fo rm a l pr oc e ss that in c lud e d mult ipl e ro un ds of pu bli c no tic e and

c omm e nt, various petitions for administ rative review, and two re asoned EA B de c isi on s u

ph old ingthe a ir

pe rm its a t is sue. We j oin
our s ist e r c ir c uit s in

c on c lud ingthat th e EA B pr oc e e din g is a fo rm a l a dju dic a tio n th a t w arr ants Chevron defe renc e. See I n re Ly on Cnt

y . La nd fil l , 406 F.3d 981, 9 8 4 (8t h Cir. 2005) (“ EA B de c isi on s .

. . are fo rm a l adj ud ic a tio ns c on sis te nt w ith th e A dmi n is tr a ti v e Pr o c e d u r e A c t

. . . , an d

due C h evron d ef er en ce

. ”) (c i t i n g United States v. Me ad Corp. , 5 33 U. S. 21 8, 22 8 ( 20 01 )) ; Sultan Chemists, Inc. v. EPA , 281 F.3d 73, 79 (3 d Ci r. 20 02 ) ( ho ldi ngth at an EAB pr oc e e din g is a formal adjudication to which cour ts should defer unde r Mead if th e st a tut or

y langua g e is a

mbi g uo us ); Pi ne

yRu n Pre

s. Ass’n v. Cnty. Com’rs of Carrol l Cnty. , 268 F.3d 255, 267–68 (4th C i r. 2 0 01) (noting that an ea rlier EA B de cision
art ic ulatin g a

re a so na ble statut or

y int e rp re tatio n is e nti tle d to Chevron defe renc e). Chevron d ef er ence also extends to the EA B ’s int e rp re tatio n o f t he Clean A ir

Ac t, whic h is administered by

the EPA.R E D O IL V

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I t is useful to beg in with what is clear and undisputed, both in the statute and by the p arties. Under a

plain rea ding of the statute, the PSD prog ram a nd the B ACT require ment
a pp ly to an “ Oute r Con tin e nta l She lf so ur c e .” 42 U. S.C. § 7627(a) (1) ( The EPA is re q u i red to “ control air pollution from Outer

Continental Shelf sources” by establishing require ments to ensure that s uch sourc es “c omply with the pr ov isi on s o f part C of sub c ha pte r I of thi s c ha

pte r [t he PSD prog ram].” ). The D is c o v e r er , wh en it is attached to the seabe d by

an an ch o r, is an OCS source. Additionally , an associate d vessel that is t ied to the Discove rer wh ile it i s anc ho re d to the se a

be d a lso be c ome s an O CS so ur c e be c a us e it is “[ p]hy sically

attache d to a

n OCS facility ,” an a lternative way to qualify

as an O CS source under

the EPA’s re g ulatory definition. 40 C.F.R. § 55.2. Howeve r, support vesse ls that
are not “[p] erma

nently or t empora

rily attache d to the seabe d,” or “[p]hy sically

attache d to an OC S fa cil ity ,” ar e not

“ re g ula te d o r a uth or ize d und e r t

he Oute r Contin e nta l Sh e lf L ands Ac t” and thus ca

nnot be an OCS source under the statute or under

the EPA’s re g ulatory

d efinition. See 40 C.F .R. § 5 5. 2; 43 U.S.C . § 13 33 (a )( 1) ; 42 U. S.C. § 7627(a) (4)( C)(ii). Cong ress ther efor e did not express an int e nti on to re g ulate a sso c iate d v e sse ls a s O CS so ur c e s, or to
a pp ly B AC T t o a sso c iate d v e sse ls o n th a t ba sis

. Her e i s t h e rub. Sec tion 7627 also provides that “[f]or purposes of this subsec tion, emissions from any v es s el servicingor assoc iated with an OCS source , including emissions while at the OCS source or en route to or from the OCS source withi n 2 5 miles of the OCS source, sha ll be considere d d i rec t emissions from the OCS source.” 42 U. S.C. § 7 62 7( a )( 4) (C )( iii ). RED OI Le lli pti c a lly argue s, ba se d o n th is “ dir e c t e mis sio ns ” c la us e, th a t Co ng re ss int e nd e d to a

pp ly a ll PSD re qu ir e me nts , in c lud ingB AC T, toR E D O IL V

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ve sse ls i nto “ OCS
source s.” Howe ver, t h at conc lusion does not follow
un a mbiguously

from the statutory

lang uag e bec ause the direc t emissions clause does not re define “OCS source .”

Th e statut e do e s not instruct that “any vessel ser vicing or associate d with an OCS source” “while at the OCS source or en route to or from the O CS s o u rc e withi n 25 miles of the OCS source” shall be considered an O CS source . Rather, the direc t emissions clause maintains a distinction betwee n an OCS source, to which a ll PS D re quiremen t s apply , and
v es sels servicingan OCS source , to which unspec ified require ments ap ply

beca use their e missions must be considere d direc t e missions from the OCS sourc e. As noted in the EAB decision, § 7627 provides no further e x planation as to why

emissions from associate d v essels shoul d be considere d direc t emissions from the OCS sourc e or to what eff ect. See I n re: She ll Gulf of Mexico , 2010 WL 5478647, at *12. Thus, Congr ess gave conflicting signa ls by clea rly and unambig uously

exclu d ing the associate d flee t from the definition of “OCS source ” and yet i n cluding the associated flee t’s emissions as direct e missions of the OCS source

. The Act’s structure provides a further wrinkle sug g esting that associate d vessels may be tr ea t ed diffe rently

from an OC S so ur c e . T he PSD pr og ra m is fo un d in T itl e Iof

the Ac t, which g overns major stationary source s such as industrial plants, while mobile source s such as motor vehic les are
re g ulate d s e pa

rate ly by Ti tle I I

. 42 U. S.C. §§ 74 01 –7 51 5; id. at §§ 7521–7590. B y

def i nition, a “stationary

source ” excludes any source of “emissions resulting direc tly from an internal c ombustion engine for tra nsportation purpose s or fr om a no nr oa d e ng ine or

no nr oad ve hic le .” 42 U. S.C.R E D O IL V

. EPA 14 § 7602(z). The EPA’s r egulations in turn d efine “marine
e ng ine ” a s “ a

no nr oa d e ng ine tha

t is ins ta lle d o r int end ed to be installed on a ma

rine ve ssel.” 40 C.F.R. § 89.2. Reading § 7627 within the context of t he P SD provisions points to the conclusion t hat P SD require ments should apply to stationary
s o u r c e s o n th e O CS , b u t n o t m o b il e ma r in e v e s s e ls

. We ag ree with the EAB ruling that this d i s t i n cti on betwee n stationary and mobile source s is consisten t with application of B AC T t o in sta llatio ns a tta c he d to the se a be d but not

to
ve sse ls, su c h a s th os e in t

he a sso c iate d f

le e t, m ov ingfr e e ly

in the wate rs above the OCS. In re: Shell Gulf of Mexic o , 2010 WL 5478647, at *14. Whether Congr es s expressed an intention that BACT we re to apply to associated ve ssels that
are no t atta c he d to an OCS so urc e is, a t th e ve ry le a st,
a mbi g uo us

. REDOI Lironically

resor ts to legis l at i ve history

in an eff ort to av oid

ambig uity . Howeve r, we re the statutory lang uag e cle ar, as REDOI L posits, ref ere nce to the leg islative his tor y wo uld be bo th u

nn e c e ssa ry and ina pp ro pr iate to i l l uminate unambig uous tex t. R a tz la f v

. U n ite d S ta tes , 51 0 U .S. 135, 14 7–48 (1 99 4) (“ [W]e d o n ot r e so rt to leg islative history

to cloud a statutory

text that is clear .”); Barnhill v. J

ohnson , 5 03 U. S. 3 93 , 4 01 (1 99 2) (“ [A]pp e a ls t o statutory history are well taken o n l y

to resolve statutory ambig uity .”) ( internal quotation marks omitted).

Of course, in the case of an a mbiguous statute, we may consider le g islative history

. See, e .g. , N. Cal. Ri ver W atch v. W ilcox , 633 F.3d 766, 773 (9th Cir. 2011) (“I f th e p roper interpr et ation is not clear f rom this tex tual analy sis, the le g isl a tiv e his tor

y of fers va lua ble g uid anc e and

ins ig ht i nto Congr essional intent.”) (inter nal quotation marks and c itation omitted). But in this case, the leg islative history o f § 7627R E D O IL V

. EPA 15

offe rs no useful guidance as t o cong ressional intent. A re port submitt ed d u ri n g the floor de bate in the House of Represe ntatives stated that “[m]arine vessels emissions . . . which ar e assoc iated with an OC S ac tivity , will be included as par t of the OCS fac il ity

emissions for the purpose s of regulation,” so as to “ ensure that the cruisingemissions from marine ve ssels ar e contr olled and off set as if they

wer e par t of the OCS fac ility ’s emiss i o n s .” 136 Cong . Rec. H12,848 (daily ed. Oct. 26, 1990) (re port submitt ed by Re p

. R o bert L a g o m ar s i n o ); see also 136 Cong. Rec . S16,895 (daily ed. Oct. 27, 1990) ( confe renc e re port submitted by Senator Max B a uc us ). With ou t r eferenci ngB AC T o r e xpla ini ngwh a t it means to be r egulated “a s part of the OCS fa cility emissions,” it is i mpossible to discern if Congr ess s pecif ically considere d the qu e sti on

of wh e the r B AC T a

pp lie s to a ssoci ate d v e sse ls in the same manne r and to the sa me deg ree as an O CS source itself. We a g ree with the EAB that the leg islat i v e h istory
mere ly “shows that Cong ress intended vessel emissions to be ‘controlled,’ ‘off

set,’ ‘m i tigated,’ or subje ct to ‘re g ulation,’ all of which are acc omplished to some de g ree ” by the EPA’s interpre tation of § 7627. In re: Shell Gulf of Mexic o , 2010 WL 5478647, at *15.

Neith e r d o e s th e f

a c t t h a t C o n g r e s s e n a c te d

§ 7 6 2 7 a f

ter the D.C. Circuit’s dec ision in NRDC, Inc. v . EPA resolve the provision’s ambig uity , as REDOI Lposits. 7 2 5 F.2d 761 (D.C. C i r. 1984). In that case , the D.C. Circuit upheld the EPA’s revoc ation of regulations tre ating emissions produced by ships moving to or from a mar ine terminal a s “sec ondary emissions” of t he terminal itself, meaning that such emissions would be counte d toward the marine te rminal for various purposes, includingth e PSD progr am’s air quality impact
an a ly s is

. Id. at 766, 772–73. Howe ver, the court’s
acc eptanc e of the EPA’s revoc ation of the “ seconda ryR E D O IL V

. EPA 16

e mis sio ns ” re g ulatio n, wh ic h th e a g e ncy la c ke d a uth or ity to promulg ate in the f

irst place, she ds litt le l ight on Congre ss’s intent i n l at er employ ing the term “dire ct emissions” in the OCS provisions. I t hardly follows that Congr ess’s use of

“ dir e c t e mis sio ns ” a s o pp os e d to “ se c on da ry e mis sio ns ” manifested a clea

r intent to subject “dire ct emissions” to the fu ll s uit e of

PSD re qu ir e me nts

. C. EPA ’ S I N TE R PR ET A TIO N O F 42 U

. S.C. § 7627 IS REASON A BLE

Be cause the Clean Air A ct is ambigu o u s as to the applicability

of B ACT to support vessels not attache d to an OCS source, o u r task is to assess whe ther the a g ency ’s construction of the s t at u t e is “pe rmissible” or “r easona ble.” Chevron , 4 6 7 U. S

. at 8 4 3

– 4 4

. I n i t s De ce mb er 2 0 1 0 ru l i n g, the EA B c on c lud e d th a t it is p e rm issib le to a

pp ly B AC T t o support vessels only

insofar a s they

are attache d to the Discove rer

beca use § 7627 “simply

does not conta i n any wo rd s expr e ssl y , o r b y

imp lic a tio n, e xpla ini ngwhy the statut e distinguishes betwe en the OCS source and vesse ls servicing the OCS source when dire cting that s uch vesse ls’ emissions shall be consider ed dire ct emission s fr o m the OCS source.” In re: Shell Gulf of Mexic o , 2 0 1 0 W L 5 4 7 8 6 4 7 , a t * 2

. We
a g r e e w i t h t h e E A B ’ s c h ar a c t e r i z a t i o no f t h e a mb i g u i ty.
Th e EA B re c on c ile d th is a mbi g uit y in t wo wa y s. Fir st, the associated flee t’s emissions p ro vide a ba seline for trig g eringPSD requirements. Emissio n s from the e ntire associate d flee t and the Dis co vere r wer e used to de termine whether the drillship met the threshold of havingthe potential to e mit tw o hun dr e d a

nd fi ft y ton s o r m or e of

re g ulate d a ir po ll uta nts , th e re by

su bje c tin g the dr ill sh ip t o PSD
re qu ir e me nts . Thi s app ro a c h f oll ow e d th e EPA ’s ratio na le inR E D O IL V

. EPA 17

its OCS rulemaking . Havingdeter mined that, under O CSL A, it c ou ld not re g ulate ve sse ls oth e r tha n dri lls hip s and

ve sse ls attache d to the drillship as “OCS sources,” the EPA explained that emissions from the associated flee t are “ac counted f or by including ve ssel emissions in t he ‘pote ntial to emit.’” Outer Continental Shelf Air Reg ulation s , 5 6 Fe d. Reg . 63,774, 63 ,7 77 (D e c

. 5, 19 91 ). Th is int e rp re tatio n g ive s me anin g to the “dire ct emissions” lang uag e—by including the associate d flee t’s emissions “while at the OCS s ource or en r oute to or from the OCS source within 25 mil es of the OCS source” toward the drillship it self— wh i le re spectingthe limitations imposed by

the def inition of OCS source

. Th e e mis sio ns fr om the e nti re fl e e t we re a lso a ttr ibute d to the OCS source in a

sec o n d wa y

—in assessing whether

the Discove rer

wo uld c a us e a vio latio n of v ari ou s a ir qu a lity sta nd ard s, on e of

the PSD re qu ir e me nts . I n g ra nti ng the PSD permits, the EAB thus imposed conditions that incorporate d the emissions of the associated flee t but found that “the Associated F leet [ex cept f or a supply

v essel] will not be phy sically

attache d to the D i

s c o v e r e r and ther efor e will not be pa rt of the OSC so ur c e and no t subje c t to the B AC T require ments.”

The EAB ’s approa ch is c onsistent with the D.C. Circuit’s decision in Sa nta Ba rb ara Cnty . A ir P olluti on Con tro l D ist

. v. EPA , w hic h u

ph e ld E PA r e g ulatio ns re fu sin g to re g ulate in-transit maritime vessels as OCS sourc es. 31 F. 3 d 1179 (D.C. Cir. 1994). The c ourt held that “it was rea sonable for the EPA to c on c lud e that OC S so ur c e s did no t in c lud e ve sse ls that wer e mer ely

trave ling ove r the OCS.” Id. at 1181.

I n sum, we conc lude that while the B ACT require ment clea rly applies to a

n OCS sourc e, the statute is ambiguous asR E D O IL V

. EPA 18 to application of BA CT to associate d vessels within 25 miles of an OC S so ur c e . We de fe r t o th e EPA ’s re a so na ble construction of the statute, as adopte d by the EAB , that B AC T d oe s n ot ap ply to m ob ile su pp or t ve sse ls u natta c he d to the drillship.

III. EPA ’ S G R ANT OF A 500 M E T E R A M BI ENT A IR E XE M P T I ON I S NOT P L AI NL Y E RRONEO US OR I NCONS I S T E NT WI T H T HE AGE NCY ’ S RE GUL AT I ONS

I n the re vised air pe rmits issued in S eptember 2011, the EPA g rante d Shell’s reque st for a 500- meter r adius “ambient air” exempti o n

. T he EAB , in its J anuar y 2012 decision, up he ld t hi s exemp tio n, wh ic h a llo ws She ll t o a sse ss compliance with air quality standards at a d i s t ance of 500 meters f rom the ce nter of the d ri l l ship. In re: Shell Gulf of Mex ico , 2012 WL 119962. Air qualit y impacts within the 500-meter

radius ar e not subject to ana ly sis or re g ulation. The e x emption is contin gent on t he Coast Guar d’s
e sta bli sh me nt o f a

n e ff e c tiv e sa fe ty

zone p re c lud ingpu

bli c acc ess to the ar ea, a nd Shell’s developm ent and imp le me ntatio n o f a

pu bli c a c c e ss p ro g ra

m.
Acc ording to the S upreme Court, “‘ambient air’ [] i s the statute’s term f

or the outdoor a ir used by the g ener al public.” Train v. NRDC, Inc. , 421 U.S. 60, 65 (1975). Curiously , the Clean Air Ac t does not define “am b i en t air,” but the EPA’s regulations define the term as “that portion of the atmosphere, external to buildings, t o which the g ener al publ ic has acce ss.” 40 C.F.R. § 50.1(e) . The a g ency has occ asionally

exempted
cer tain are as fr om being lab el ed ambient air. The parties
a g re e that th e a g e nc y ’s “lo ngsta nd ingint e rp re tatio n” of

thi s e x emp tion i s d e sc ri be d in a 19 80 le tte r f

ro m f or me r E PA A dmi n is tr a to r D o u g la s Co s tl e

. T h a t le tt e r s tate s th at anR E D O IL V

. EPA 19 “exemption from ambient air is ava ilable only for the atmosphere over land owned or controlled by the s ource and to which public ac cess is pre cluded by a fe nce or

other phy sical bar

riers.” The Supreme Court instructs that an age ncy ’s int e rp re tatio n o f i ts o wn

re g ulatio ns is “ c on trol ling un le ss ‘plainly err oneous or inconsistent with the re g ulation.’” Auer v. Robbins , 5 1 9 U. S

. 4 5 2 , 4 6 1 (1 9 9 7 ) ( qu o t i n g Rob er t s o n v. Me tho w Va lle

yCiti ze ns Cou nc il , 490 U.S. 332, 359 ( 1989)). The rele vant inquiry is w hether the EPA’s g ran t o f t he ambient air e x emption to Shell i s plainly err oneous or inconsistent with its regulatory definition of ambient air

.
I t is obvious t hat t h e exemption here is not “f or the atmosphere over land

owned or controlled by the source and to which public ac cess is pre cluded by a fe nce or

other phy sical bar

riers” (empha sis added). Howeve r, neither is the exemption i nconsistent with the EPA’s regulatory definition of ambient a ir or clea

rly err oneous. The e ssence of the EPA’s
re g ulator y de fi nit ion

links ambi e nt a ir to publi c a c c e ss. B e c a us e the EPAc on dit ion e d Sh e ll’ s p e rm it a nd a mbi e nt a ir exemption on t he esta

blishment of an ef

fec tive safe ty

zone that prec ludes pub l i c ac cess, the g rant is consistent with the regulation.

F ur the r, the EPA ha s not impe rm iss ibl y de pa rt e d f ro m it s longsta nding r egulatory

interpret ati on of “a

mbient air”
w it h o u t e xp la

n a ti o n o r ju s ti f

ic a ti o n , a s RE D O I Lc la im s

. We
are persua ded by t h e EAB ’s re asonable explanation that Costle’s 1980 letter pre scri b i n g a fe nce or other phy sical ba rrier to p re c lud e pu

bli c a c c e ss w a s “ c le arl y

wr itt e n w ith overla nd situations in m ind.” In re: Shell Gulf of Mexic o , 2012 WL 119962, at *2 9. The a g ency did not have theR E D O IL V

. EPA 20

occa sion to consider how it might a pply the exemption in t he
c on te xt of

op e n w a te rs un til te n y ears late r, wh e n Co ng re ss first g ave the EPA jurisdiction to reg ulate air polluti on from OCS sources. T h e EAB ’s assessment that the a g ency “re quires some lee way” in de termining how to apply “the regulation and the interpre tive letter to an ‘ overw ater ’ situation” is just common sense. Id

. Con str uc tin g a fe nc e in the Arc tic Oce an would make l i t t le sense, a nd the EPA has pr e vio us ly re c og nize d a sa fe ty zon e e sta bli sh e d by the Coa st Guar d as evide nce of

sufficien t o wn ership or c ontrol over open water are as to qua lify as a boundary for d ef i ning ambient air. H ere , as in that p re ce d ent, the EPA imposed
c on dit ion s tha t a

pp ro xima te d th e c ri te ri a in t he Cos tle letter—c ontrol of prope rty and limited publi c ac cess—for a marine e nvironment. We conclude that the EPA’s g rant of a n ambient air e x emption to Shell conditi oned o n an ef fec tive
sa fe ty zon e e xclu dingthe pu bli c is a

pe rm iss ibl e interpre tation of its ambi ent air r egulation and ea rlier letter
ru l i n g.

P ETIT ION DENIED.