1 (Slip Opin i o n) OCTOBER T ERM, 20 08 Sy llabu s N O TE : Wh er e it i s feas ibl e , a s yllab u s (h ead n ot e) wil lbe rel e as ed , as is bein g d o n e incon n ecti onwithth is cas e , a tth e ti meth e op in i o n is is s u ed

. Th e s yll abu s con s titu tes n o p a rt of th e op in i o nof th eC o u r t bu t h a s be en pre p are dbyt h e Re po rte ro f De ci sio n s fo r t h e co nveni e nce of t h e reade r . Se e United Statesv. Detroit Timbe r& Lumb er Co., 200U. S

. 3 21, 337

. 

# SUPREME CO URT O FTHE UNI TED STATES
Sy llabu s 

### ENTE RGY COR P

. v . R IVERKEEP ER, INC., ET AL


### . CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE SECON D CIRCUIT No. 07–5 88. Ar gu ed Dec e mb er2, 2008—Dec i ded Apr il 1, 2009 * Petitioner s’ p o wer p lants hav e“c oolingwaterintake str u c t ur es” that

threaten the environment b ysquash ing against intake screens (“im

ping ement”) orsuc t ioningi n to th e cooling system (“entrainment”) aquaticor g a ni sms fr om the watersour c e s tappedto c o o lthe plant s . Thus, the facilitie s are subj ect to regulati on under the Clean W a te r Ac t, wh ic h man d ates th at “[a]n ystan da r destabl ish e dpu r s u a n tto sec t ion13 11 .

. . orsec t ion1316

. . . an d applic able to a poin t sou r c e shall require that the locat i on, desi gn, cons t r uct i on, a n d ca pa cit yof c oolingwater intake str u c t ur es r e flec t the best tec hnologyav ailable formin i mizin gadv e r s e env i r o n m en tal impac t .” 33 U. S. C. §1326(b)

. Sec t ion s 1 311 an d 13 16, int u r n , employa v a r i etyof “bes t tec h n o logy” stan dar d s to r e g u late effluen tdisc har g e into the Nation’ s water s . The Enviro nmental Prote c tion Agency (EPA) pro m ulgated the §132 6(b) r e g u lation s atis su e aftern e ar lyth r ee dec a des of m a kin g the “be s t tec hnologyav ailab l e” deter m inat ion on a c a se- b y - c a se b a si s. It s “ P h a s eI” regula t i ons govern new coolin g wa t e r int a ke s t ruct ures , w h ile th e “Phase II” r u les a tissu e a pply to cert a i n la rg e exis t i ng fa

cilities. In the latter rules, the EPA set “ n ational performance stan

dards,” requiring most Pha s e II f a cilitie s to reduce “i mpingement mor t ali t yfor[aqu aticor g a n i sms] by80 to 95 per c e n tfr om th e c a lc u lation ba selin e,” and requi r ing a su bset of facilities t oreduceen tr ain m en t of su c hor g a n i sms by“60 to 90 per c e n tfr om [th a t] ba se line.” 40 CFR §125.94(b)(1), (2 ). Ho wever, the EPA expressly declined to mandate close d -cycle c ooling systems, or equivalent re

-

——————

* Tog e th er with No. 07–5 89, PSEG Fossil LLC et al. v. Riverk eep er, Inc., e tal., and No. 0 7

– 597, Utility Water Act Gro u p v. Riverk eep er, Inc

. , et al. , a l s oon c e rt iora ri t ot h e s a m ecourt
.2 ENTERGY C O RP. v. RIVERKEEPER, I N C. Sy llabu s ductions in impingemen t and entr ainment, as it ha d done in it s Phase I rules, in part becaus e the co st of rendering e x isting facilitie s c l osed-c y c le compliantwould be nine ti mes the est i matedc o st of c o mplianc e with the Phase II per f or man c e stan d a r d s, an d bec a u s e ot her t e ch nologies could a pproa ch t h e pe rf ormance of closed-cycle op

era t ion. The Pha s e II rules a l s operm itsit e -s pecific va ria n ces from the national p e rformance standards, provided that the p e rmit-issuing author ityimp o ses r e med i almea s ur es tha ty i eld r e sul t s “a s c l ose a s pr ac tic able to th e applic ab le per f or man c e stan dar d s.” §125.9 4 (a)(5)(i) , (ii)

. Respondents—environmental gro u ps and vari

ous States—c hallenged the Phase II regulations. Co ncluding that c o st-ben efit a n aly s is i s i m p e r m issible u n d er33 U. S. C

. §132 6(b), th e S e cond Circui tfound t h e s i t e -s pecific cos t -b enefitva riance pro v is ion unlawful and r e manded the r e g u lation s t othe EPA forit to cl arify whether it had relied on cost-benefitan al y s is in se ttingthe nationa l performance s t andards. Held: The EPA perm iss ib l y relied on cos t -b enefit analys is in set t ing the

national performance stand a rds an din providing for cost-benefi t variances from those stand a rds as pa rt o f the Phase II regulations. Pp. 7–16.

(a) Th e EPA’ s v i ew th at § 1 326(b)’ s “b es t tec h n o logyavailable for m i nim i zing a dvers e environ m ent a l impa ct” s t a n da rd perm it s cons id

eration of the technology’s costs an d of the relationship between those costs and the environmental benefits produced governs if it is a rea

sonable inter p r e tation of the st at ute—not necessarily th e only possi

ble interpretation, nor even the interpretation dee m ed mos t reason able byth e c o u r ts. Chevron U. S. A. I n c. v. Natu ral Resources Defense Council, Inc. , 467 U. S. 837, 84 3 –84 4. Th e Sec o n dCir c u it took “be s t tec hnology” to mean the tec hnologythat ac hiev es the gr eatest r e du ctioninadv e r s e env i r o n m en tal impac t s at a r e ason abl e c o st to the industr y , but it may also desc r ib ethe tec hnologythat mos t efficientlyp r o d uces a good, even if it produces a lesse r quantity of th at g ood th anoth e rav ailable tec h n o logi es. Th is r e adin gis n o t pr e c l uded bythe phr a se “forminimizi ng adverse enviro nmental imp a ct.” Minimizing a d mits of degre ea n d is not n e ces s a rily us ed to referex clus ively t ot h e “ grea t es t poss ib le reduct ion.” Ot her Clea n Wa t e r Act provisions show that when Congre ss wished to mandate the gr eatest feasib le reduction in waterpollu tion, it us ed pla i n langua ge , e. g., “elimin a t iono f disc h a r g es of all po llu tan t s,” §1 311(b)(2) ( A). Th u s , §132 6(b)’ s u s e of th e less am bitiou s goal of “minimizing adverse envi

r o nmental im pac t” sug g e sts that the EPA has some d i s c r e tion to de

termine the extent of reduction wa rra nt ed under t h e ci rcum s t a nces , plausibly involving a consideration of the benefits derived from re

du c t ion s an d th e c o sts of ac hiev in gth em. Pp. 7–9.3 Cite as: 55 6 U

. S. ____ (2009) Sy llabu s (b) Con s ider in g§1326(b)’ s te x t , an d c o mpa r in git withth e tex tan d sta t utory factors applicab le to pa ralle l C l ean Water Ac t provisions, prompts the conclusion that it was well within the bounds of reason

able inter p r e t a tion forthe EPA to c o n c lu de th at c o st- b en efit an aly s i s is not ca t e gorica lly forb idden. In t h e Phas e II rules t h e EPA s o ught only to avoid extreme dispar i t ies be tw eencost s and benefits, lim iting va ria n ces fro mPha s e II’s “ n a t iona l perform a nce s t a n da rds ” t ocir

cumstances w h ere the costs are “sig nificantly grea ter tha nthe b e ne fits” of c o mpli an c e . 40 CF R §12 5 .94( a)(5 )(ii). Indefin i n g“n ation a l performance s t andards” the EPA a ssume d the applic at ion of tec h

nologies whose benefits ap proach those estimatedfor closed-cycle cooling systems at a fracti on of th e cost. That the EPA has for over thir tyy e ar s inter p r e ted §13 2 6 (b) to perm it a com p a r is on of cos t s a n d benefits , while not con c lus iv e , als o tends t oshow that its inter p r e ta

tion is reasonable and hence a legiti mate exercise of its discretion. Even res p ond e nt s a n d t h e S e cond Circui tult i m a t e ly recognize t h a t s o m ecom p a r is on of cos t s a n d b e nefit s is perm it t e d. The S e cond Cir

c u it h e ld th at §132 6(b) m a n d ates only those technologie s whose costs c a nbe r e ason ablybor n e byth e in du str y . Bu t wh eth e r it is r e ason ab l e t ob e a ra pa rt icula rcos tca n very well depend on t h e res u lt ing benefits. Lik e wise, respondents concede that the EPA need not re

quire that industry spen d billions to s ave one more fis h

. T h is con

cedes the principle, and there is no statu t ory basis for limit ing the c o mpar isonof c o sts an d ben e fits tosi tuati o ns wher e the benefits ar e de minimisr a th erth ansig n ific an tlydispr o por t ion a te. Pp. 9–16. 475 F. 3d 83, r e v e r s ed an d r e man d ed.

S CALIA , J., delivered the opinion of the Cour t, in whic h R OBERTS , C. J., and K ENNEDY , T HOMA S , andALITO , JJ., joined. B REYER , J., filed a nopinion con c ur ring i npa r ta n d dis s e nting in pa rt. S TEVENS , J., filed a dissent ing o p inion, in whi c h S OUTERand G IN SB U R G , JJ

. , join ed._________________

_________________ Cite as: 55 6 U

. S. ____ (2009) 1 Opinion of theCourt
NOTIC E : Th is op i n ionis subjec t to f o rma lrevi si onbef o r e publicat ioninth e p r eli m in ary p rin t of th e U n it edS t at es R e p o rts
. R e ad ers ar e r e qu es ted to n o tif yth e R e p o rt e rof D e c i s i on s , Su p r em e C o u rt of th e U n ited St at es , Wa s h

ington, D. C. 2054 3, of any typ o gra p hical or other f o rmal err o rs , in or der th atc o rr ect i on sm a y b e mad eb e f o r e th ep r e lim in aryp rin t go es t o p r es s . 

# SUPREME CO URT O FTHE UNI TED STATES
Nos. 07– 58 8, 07–5 89 an d 07

– 597 

### ENTE RGY COR P ORAT ION, PE T I TIONER 07–588 v. RIVER KE E P ER, INC., ET AL


### . PSEG F O SSIL LLC, ET AL 

### ., PETI TIONERS 07–589 v. RIVER KE E P ER, INC., ET AL


### . UTILITY WATER ACT GROUP, PETITIONER 07–597 v. RIVER KE E P ER, INC., ET AL


### . ON WRITS OF CERTIORARI TO THE UNITED STAT ES COURT OF APPEAL S FOR THE SECO ND CIRCUIT [Apr il 1, 200 9] 

### J USTICE 

### S CALIA 

### delivered the opini o n of the Co urt. These cases concern a set of regul a tions adopted bythe Environmental Protection Agency (EPA or agency) under §316(b) of the Clean Water Act, 33 U. S. C. §1326(b). 69 Fed. Reg. 41576 (200 4). Respondents—environmental groups and various States 1 

### —challenged those regulations, and the Sec o nd Circuit set them aside. Riverk eepe r, Inc. v.

——————

1 Th e EPA an d its Adm i n i str a torappear ed as r e spon den t s in su ppor t of petitioners. See Brief for Fede r a l Par t ie s as Respon de n t s Su ppor t in g Petitioner s. Refer e nc es to “r espo ndents ” throughout th e opinion refe r only to those p a rties challenging the EPA r u les at issu e i nth ese c a ses.2 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### EPA , 475 F. 3d 83, 99– 100 (2007). The is sue f o r our deci

sion is whether, as the Second Circuit held, th e EPA is not permitted to use cost- b enefit ana lysis in det e rmining the content of regulations promulgated under §1326(b). I Petitioners operate—or re present those who operate— large powe rplants. I nthe cour se of generating powe r, those plant s also generate larg e amounts of heat. To cool their facilities, petitioners employ “cooling water intake structu res” that extrac twater from nearby water sources. These struc t ures pose various thr e ats to the environment, chief amon g them the squashing against intake screens (elegantly called “impi n gement”) or suction into the cool

ing system (“entrainment”) of aqua tic organis m s that live in the affec t ed water sources. See 69 Fed. Reg. 41586. Accordingly, the facilities are subj ect to regulation under the Clean Water Act, 33 U. S. C. §1251 etse q. , which mandates: “Any stan dard established pursuant to section 1311 of this title or section 1 316 of this title and applicable to a point source shall require that the locat i on, de

sign, constr uction, andcapacit yo f cooling water in

take stru ct ures reflect th e best technology available for minimizing adverse environmental impact. ” §1326(b). Sections 1311 and 1316, in turn, employ a variety of “best technology” standards to regu late the discharge of efflu

ents into the Nation’s waters. The §1326(b) regulati ons at issue here were promul

gated by th e EPA afternearly thr ee decades in which th e determination of the “b est technology available for m i n i

mizing [cooling waterintake str u ctures’] a dverse envi

ronmental impact” wa s made by permit-issuing authori

ties on a case-by-case basis, without benefit of a governing3 Cite as: 55 6 U

. S. ____ (2009) Opinion of theCourt 

### regulation. The EPA’ s initial attempt at sucha regulation came to no ught when the FourthCircuit determined tha t the agency had failed t oadhere to the procedural require

ments of the Administrative Procedure Act. Appalachian Power Co. v. Train , 5 66 F. 2d 45 1, 457 (1977). The EPA withdre wthe regulation, 44 Fed. Reg. 3295 6 (1979), a n d instead published “draft guidance” for use in implement

ing §1326(b)’s requirements via site-specific permit deci

sions under §1342. See EPA, Office of Water Enforcement Permits Di v., {Draft} Guidance fo r Evaluating the Adverse Impact of Cooling Water Intake Structures onthe Aquati c Environment: Section 316(b) P. L. 9 2–500, (May 1, 1977), at http://www.epa.gov/waterscience/316b/file s/1977AEIguid.pdf, (all Internet materials as visited Mar. 30, 2009, and ava il

able inClerk of Court’s case file); 69 Fed. Reg. 4158 4 (describing system of c a se-by-case permits un der the d r af t guidance). In 1995, the EPA ente red into a consent decree which, as subsequ e ntly amended, set a multiphase timetable for the EPA to promulgate regulations under §1326(b). See Rive rk ee per, Inc

. v. Whit man , No . 93 Civ. 0314 (AGS), 2001 WL 1505497, *1 (SDNY, Nov. 27, 2001). In the fir s t phase the EPA adoptedregulations governing certain new, large coolin g water intake structu res. 66 Fed. Reg. 65256 (2001) (Pha se I rules); see 40 CFR §§125.80(a) , 125.81(a) (2008). Those rules require new facilities with wate r intake flow greater than 10 million gallons per day to, among other things, restrict th eir inflow “to a level com

mensurate with that which can be attained by a closed

cycle reci rc ulating cooling wate r s y stem.” 2 

### §125.84(b)(1). New facilities with water-intake flow between 2 million

——————

2 Closed-cycle cooling systems recircu late the waterused to c ool the facility, and consequent ly extract less water from the a d jacent water

way, proportionately red u cing impingement and entrainment. Riverk eep er, I n c. v. EPA , 35 8 F. 3d 174, 1 82, n

. 5 (CA 2 200 4); 6 9Fed. Reg

. 41601, an d n

. 44 (2004).4 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### and 10 million gallons per day ma y alternati v ely comply by, among other things, reducing the volume and velocity of water removal to certain levels. §125.8 4 (c). And all facilities may alternatively comply by demonstrating, among other things, “that the technologies employed will reduce the level of adverse environmental impact .

. . to a comparable level” to what would be achievedby using a closed-cycle cooling system. §125. 84(d). These regulations were upheld in large part by the Second Circuit in Rive rk ee per, Inc

. v. EP A , 358 F. 3d 174 (2004). The EPA then adopted the so-called “Phase II” rules at issue h e re. 3

### 69 Fed. R e g. 41576. They apply to existin g facilities th at are point sources, whose prima ry acti vity i s the generat i on and tra nsmission (or sale for t r ansmission) of electricity, and whos e water-intake flow is more than 50 million gall ons of water per da y, at least 25 percent of which is used for cooling purposes. Ibid. Over 500 faci li

ties, accounting for approximately53 percent of the Na

tion’s electric-power ge neratingca pacity, fall within Pha s e II’s ambit. See EPA, Economic and Benefits Analysis for the Final Section 316(b) Phase II Existing Fa cilities Rule, A3–13, Table A3–4 ( F eb. 2004), onlin e athttp://www. epa. go v/wa ters cien ce/3 1 6b/phase 2 /e conbe nefi ts/f inal/ a3. pdf. Those facili ties remove on average more than 214 billion gallons of water pe r day, causin g impinge m ent and en trainment of over 3.4 billionaqu atic organisms per year. 69 Fed. Reg. 41586. To address those environmental impacts, the EPA se t “national performance standards,” requiring Phase II facilities (with some exceptions) to reduce “i mpingement mortality fo r all life stages of fish and shellfishby 80 to 95

——————

3 The EPA has also adopte d P h ase III rules for facilities not subjectt o th e Ph ase I an d Ph ase II regu lation s. 71 Fed. Reg

. 3500 6 (20 06). A cha llenge t othos e regula t i ons is current ly b e fore t h e Fift h Circuit , whereproceedings have bee nstayed pe nding dispositionof these cases. See ConocoPhi llips Co. v. EPA , No. 06–606 62.Cite as: 55 6 U

. S. ____ (2009) 5 Opinion of theCourt 

### percent from the calculation bas el ine”; a subset of facilities must also reduce entrainment of such aquatic organisms by “60 to 9 0 percent from the calculation b a seline.” 4 0 CFR §125.94(b)(1), (2); see §125.9 3 (defining “calculation baseline”). Those targe t s are based on the environmental improvements achievable through deployment of a mix of remedial technologies, 69 Fed. Reg. 41599, which the EPA determined were “commercially available and economi

cally prac ticable,” id. , at 41602. In its Phase II rules, however, the EPA expressly de

clined to m andate adoption of closed-cycle cooling systems or equivalent reductio n s in impingement and entrain

ment, as it had done for new facilities subject to the Phase I rules. Id. , at 41601. It refused to take that step in part because of the “generally high cost s” of conver ting existing facilities to closed-cycle op eration , and because “other technologie s approach the performance of this option.” Id. , at 41605. Thus, while closed-cycl ecooling systems could reduce impingement and entrainment mortality by up to 98 percent, id. , at 41601, (compared to the Phase II targets of 80 to 95 percent impingement reduction), the cost of rendering all Phase II facilit ies closed-cycle-compliant would be approximately $3.5 billion per year, id. , a t 41605, nine times the estimated cost of compliance with the Phase II performance standards, id., at 41666. More

over, Phase II facilities compelled to convert to closed-cycl e cooling systems “would produce 2. 4 percent to 4.0 percen t less electricity even while burning the sa me amount of coal,” possibly requiring the co nstruction of “20 additional 400–MW plants .

. . to replace the generating capaci ty lost.” Id., at 41605. The EPA thus concluded that “[a]l

though not identical, the range s of impingement and entrainment reduction are similar under both options.

. . . [Benefits of compliance with the Phase II rules] can ap

proach thos e of closed-cycle recir c u lating at l e ss cost wit h fewer implementation problems.” Id., at 41606.6 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### The regulations permit the issu ance of sit e -specific variances from the na tional performance standards if a facility can demonstrate either that the costs of compli

ance are “s ignificantly greater th an” the cos t s considered by the a g ency in setting th e standards, 40 CFR §125.94(a)( 5 )(i), or tha tthe costs of compliance “would b e significantly greater than the benefits of complying wi th the applicable performance standards,” §125.94(a)(5)(ii). Where a variance is warranted, th e permit-issuing author

ity must impose remedi al measures that yield results “as close as practicable to the applicable perfor mance stan

dards.” §125.94(a)(5)(i), (ii)

. Respondents challenged the EPA’s Phase II regulations, and the Se cond Circui tgran te d t h eir petition for review and remanded the reg u lations to the EPA. The Secon d Circuit identified two ways in which the EPA could p e r missibly consider costs under 33 U. S. C. §1326(b): (1) in determining whetherthe costs of remediation “can be ‘reasonably borne’ by the industry,” and (2) in determining which remedial technologies are the most cost-effectiv e , that is, th e technologies that reach a speci f ied level of benefit at th e lowest c o st. 475 F. 3d, at 99–100. See a l s o id., at 98, and n. 10. It concluded, however, that cost

benefit analysis, which “compares the costs and benefits of various ends, and choo ses the endwith the b e st net ben e fits,” id., a t98, is im permissible under §13 26(b), id., at 100. The Court of Appeals held the site-specific cost-benefit variance provision to be unlawful. Id ., at 11 4. Finding it unclear whether the EPA had relied on cost-b enefit analy

sis in setting the na tional performance stan dards, or h a d only used cost-effectiveness analysis, it rema nded to the agency for clarification of that point. Id., at 104–105. (The remand was also based onother grounds which are not at issu e here.) T h e EPA suspended op eration of the Phase II ru les pending further rulemaking. 72 Fed. Reg.7 Cite as: 55 6 U

. S. ____ (2009) Opinion of theCourt 

### 37107 (2007). We then granted certiorari limited to th e following question: “Whether [§1326(b)] .

. . authorizes the [EPA] to compare cost s with be nefits in determining ‘th e best techn o logy available for minimizing adverse envi

ronmental impact’ atcooling water intake structures

. ” 552 U. S. ___ (2008). II In setting the Phase II national performance standards and providi n g for site-specific cost-benefit variances, the EPA relied on its view that §1326(b)’s “best technology available” standard pe rmits co nsideration of the techno l

ogy’s costs, 69 Fed. Reg. 41626, and of the relationship between those costs a n d the environmental benefits pro

duced, id., at 41603. That view governs if it is a reason

able interpretation of the statute—not necessarily the only possible interpretati on, nor even the interpretati on deemed most reasonable by the courts. Che v ron U. S. A. Inc. v. Natural Re sour cesDefens eCouncil, I n c. , 467 U. S. 837, 843–84 4 (1984). 4 

### As we have described, §1326(b) in structs the EPA to set standards f o r cooling water inta ke structu res that reflec t “the best technology available f o r minimiz i ng advers e environmental impact.” The Second Circu it took that

——————

4 Th e dissen tfi n d s it “pu zzl in g” th atwe invoke this proposition (tha t a r e ason able ag en c yin ter p r e tationpr ev ails) at the “ou t set,” omi tting the supposedl y prior inquiry of “ ‘whetherCongres s ha s directly s p oken to the precise ques tion at issue.’ ” Post , a t6, n. 5 (opinion of S TEVENS , J.) (quoting C h evro n , 467 U. S., at 842). Bu t su r e lyif Con gr e ss h a s direct ly s p oken t oa nis s u e t h en a n ya g en cy int e rp ret a t i on co nt ra dict

ing w h a tCongres s ha s s a id would b eun re a s onab le.

What is tr uly“puzzling” i s the dis s en t’ s ac c o mpan y i n gc h ar g eth at the Cour t’ s failur eto c o nduc t the Chevronstep-oneinquiry at the outset “reflect s [its] relucta n ce to co nsider the possib ility .

. . that Congr e ss’ sile nc e mayhav emeant to foreclose cost-be n efit analysi s .” Post , at 6, n

. 5. Ou rdisc u s sionof th at is su e, infra, at 11, s p eaks for itself.8 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### language to mean the technology that achieve s the great

est reduction in advers e environmental impacts at a cost that can reasonably be borne by th e industry. 475 F. 3d , at 99–100. That is certainly a plausible interpretation of the statute. The “best” technology—that wh ich is “most advantageo us,” Webster’s New International Dictionary 258 (2d ed. 1953)—may well b ethe one that produces the most of so me good, h e re a reduction in adverse enviro n mental impact. But “best te chnology” may also describe the technology that most efficien t lyproduces somegood

. In common parlance o n e could ce rtainly use the phras e “best techn o logy” to ref e r to that which produc es a good at the lowest per-unit cost, even if it produces a lesser quan

tity of that good than ot her available technologies. Respondents contend that this l a tter readi n g is pre

cluded by the statute’s use of the phrase “forminimizing adverse environmental impact.” Minimizing, they ar gu e, means reducing to the smallest a m ount poss ible, and th e “best technology available forminimizing adverse envi

ronmental impacts,” must be the economi c ally feasible technology that achieves the gr eatest possible reduction in environmental harm. Brief for Re spondents Riverk eepe r , Inc. et al. 2 5–26. But “minimize” is a term that admits of degree and is not necessarily used to refer exclusively to the “greate s t possible reduction.” For example, els e where in the Clean Water Ac t, Congress declared th at the proce

dures implementing the Act “sha ll encourage the drast i c minimization of paperwor k andinteragency decision procedures.” 33 U. S. C. §1251(f). If respondents’ defini

tion of the term “mini m ize” is cor r ect, the s t atute’s use of the modifier “drasti c” i s superfluous. Other p r ovi s ions in the Clean Water Ac t al so suggest the agency ’s interpret a tion. When Congress wished t o mandate the greatest feasible reduction in water pollution, it did so inplain language: The provision governing th e discharge of toxic po llutants into the Nat i on’s water s9 Cite as: 55 6 U

. S. ____ (2009) Opinion of theCourt 

### requires the EPA to set “efflue nt limitations [which] shall require the eliminatio nof discha rges of all pollutants i f the Admini strator find s . . . that s u ch elimination is tech

nologically and economically achievable,” §1311(b)(2)(A) (emphasis added). See also §1316(a)(1) (mandating “where pra cticable, a standar d [f or new point sources] permitting no dischargeof polluta nts” (emphasis added)). Section 1326(b)’s use of the less ambitious goal of “mini

mizing adverse environmental impact” sug g ests, we think, that the agency retains some discretion to determine the extent of reduction that is warra nted under the circum

stances. That determination cou l d plausibly involve a consideration of the b e nefits derived from reductions an d the costs of achieving them. Cf. 4 0 CFR §125.83 (definin g “minimize” for purpo s es of the Phase I regulations as “reduc[ing] to the s m allest amount, extent, or degr ee reasonably possible”). It seems to us, therefore, that the phrase “best technology available,” even wit hthe adde d specification “for minimizingadverse enviro nmental i m pact,” does not un ambiguousl y preclude cost-benef it analysis. 5 

### Respondents’ alternative (and, alas, also mor ecomplex) argument r e sts upon the structur eof the Clean Water Act

. The Act provided that during its initial im plementation period existing “point s o urces”—di s crete conv eyances from which pollutants are or may b edischarged, 33 U. S. C. §1362(14)—were subject to “effluent limitations .

. . which shall requir ethe applic ation of the best pr ac ti cable control technology currently a v ailable.” §1311(b)(1)(A) (emphasis

——————

5 Respondents concede that the term “av a i l able ” is amb i gu ou s, as it c o uld mean eithertec h nologi c a llyfeas ible o reconomically feasible. Bu t an yambig u ityinth e ter m “ av a ilable” is la rgely irrelev a nt
. Rega rdles s of the criteria that render a techno logy “available,” the E PA would still have to determine which available te c hnologyis the “be s t” one. And a s discussed abo v e, that determinatio n m a y well involve consideration of the tec hnology’ s r e lativ ec o sts and benefits.10 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### added). (W e shall call this the “BPT” test.) Following that transition period, the Act initially mandated adoption, by July 1, 198 3 (later extended to M a rch 31, 1989), of stricter effluent limitations requiring “application of the bes t available technology economically achievab lefor such category or class, which will resul tin reason able further progress toward the national goal of eliminat ing the dis

charge of al l pollutants.” §1311(b)(2)(A) (emph a sis added); see EPAv. National Crushed Stone Assn. , 449 U. S. 64, 69–70 (198 0). (We shall call this the “BATEA” test.) Sub

sequent am endment li mited a ppli c ation of this stan dard to toxic and nonconventional pollutants, and for the remain

der establis hed a (pres u mably la x e r) test of “b est conv en tional-pollu tant control technology. ” §1311(b)(2)(E). 6 

### (We shall call this “BCT.”) Finally, §1316 subjected certai n categories of new pointsources to “the greate st degree of effluent reduction whic h the Admi nistrator de termines to be achievable through applicati o n of the best availa ble demonstrated control technology .” §1316(a)( 1 ) (emphasis added); §1316(b)(1)(B). (We sha l l call this the “BADT” test.) The provision at issue here, applicable not to efflu

ents but to cooling wat e r intake st ructures, requires, as we have descri bed, “the best technology av ailabl e for minimiz

ing adv ers e envi ronmentalimpa ct ,” §1326(b) (emphasis added). (We shall call this the “B TA” test.) The first fo ur of these test s are elucidatedby statutory factor lists that guide their implementation. To take th e standards in (presumed) order of increasing stringency , see Crushed Stone, su pra, a t69– 70: In applying the BPT test the EPA is instru cted to consider, among other fa c tors, “the to tal cost of a pplication of technology in relation

——————

6 The s t a t ute does not conta i n ahy phe nbetween the words “conven

tional” and “ p ollutant.” “Co nv e ntio nal pollutant” is a st atutory term, h o wev e r , see 33 U. S. C. §131 4(a)(4), an d it is c l earth atin §131 1(b)(2)( E) th e adjec t iv e modifies “pol lutant” r a therthan “c ontr ol technology.” The hyp h en m a kes that clear.11 Cite as: 55 6 U

. S. ____ (2009) Opinion of theCourt 

### to the e f fluent redu ctio n bene fits to beachie v e d

. ” §1314 (b)(1)(B). In appl yin g the BCT tes tit is instru cted to consi d e r“th e re aso n a b le n es s of th e re la tion shi p between the cos t s of attainin g a re du ctio n in effluen t s a n d the efflue nt reduction benefi ts de rived. ” §1314 (b)(4)(B) (em p h a sis adde d)

. An d in a p pl yi ng the BAT EA an d BADT tes t s th e E PA i sin stru c t ed t oco n s i d er th e “c os tof ach i e vin g s u ch effluen t reduction. ” §§ 1314 (b)(2)(B), 1316 (b )(1)(B). T h e r e is no such elucidating languag e applicable tothe BTA test at issue here. To facil i tate compa r ison, the texts of these five tests, the clarifying factors applicable to them, and th e entities to which they apply are set forth in the Appendix, infra. The SecondCircuit, in rejectingt h e EPA’ s u s e of cost

benefit analysis, relied in part onthe propositions that (1) cost-benefit analysis is precluded under the BATEA and BADT tests ; and (2) th at, insofar as the per m issibility of cost-benefit analysis is concerned, the BTA tes t(the one at issue here) is to be treated the same as those two. See 475 F. 3d, at 98

. It is not obvious to us that the first of the s e propositions is correct, but we need not pursue that point, since we assuredly do not agree with the second. It is certainly reasonable for the agency to conclude that the BTA test need not be interp reted to permit only what those other two tests permit. Its text is not identical to theirs. It has the relatively modest goal of “minimizing adverse environmental impact” as compar ed with th e BATEA’s goal of “elim inating the discharge of all p o llu t

ants.” And it is un encumbered by specified statutory factors of th e sort pro vided for thos e other two tests, which omissioncan reasonably be inte rpreted to suggest that th e EPA is ac corded gre a ter discre tion in det e rmining its precise content. Respondents and the dissent argue that the mere fact that §1326(b) does n o t expressly authorize cost-benefit analysis for the BTA te st, though i tdoes so for two of the12 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### other tests, displays an intent to forbid its use. This surely prov es too much. For while it is true that two of th e other tests authorize cost-benefit analysis, itis also true that all four of the other tests expressly authorize some consideration of costs. Thus, if respondents’ and the di s sent’s conclusion regarding the import of §1326(b)’s silence is correct, it is a fortiori true that t h e BTA test permits no considera ti on of cost wha t soev e r , not eve nthe “cost

effectiveness” and “fea sibility” analysis that the Second Circuit approved, seesupra, at 6, that the di ssent would approve, po st, at 1–2, and that re spondents acknowledge. The inference that respondents and the dissent would draw from the silenc e is, in an y event, implausible, as §1326(b) is silent not only withrespect to cost-benefit analysis but withrespect to all potentially relevant fac

tors. If silence here implies prohibition, then the EPA could not co nsider any factors in i m plementing §1326(b)— an obvious logical impossibil i ty. It is eminently reason

able to conclude that § 1326(b)’s silence is meant to con v ey nothing more than are fusal to tie the agency’s hands as to whether co st-benefit analysis should be used, and if so to what degree. Contrar yt othe dissent’s sug g estion, seepost , at 3–4, our decisions in Whit manv. Am erican Tru c king Assn s., Inc. , 531 U. S. 457 (2001), and AmericanTextil e Mf rs. Institu t e, I n c. v. Don o van , 452 U. S. 490 (1981), do not undermine this conclusion. In American Truckin g , we held that the text of §109 of the Clean Air Act, “inter

preted in its statutory and hi storical context
. . . unambi

guously bars cost considerations” in setting air quality standards under that provision. 531 U. S., at 471. Th e relevant “st a tutory context” includ ed other pr ovisions in the Clean Air Act tha texpre ssly authorized consideration of costs, whereas §109 did not. Id. , at 467–46 8. America n Truckin g

thus stands for the rather unremarkable propo

sition that sometimes statutory silence, when viewed in13 Cite as: 55 6 U

. S. ____ (2009) Opinion of theCourt 

### context, is best interpreted as limiting agency discreti on. For the reasons discus sed earlier, §1326(b)’s silence cann o t bear that interpretatio n . In Americ a n Tex t ile , t h e Court relied in parton a stat

ute’s failure to mention cost-benefit analysis in holdin g that the relevant agency wa s not required to engage in cost-benefit analysis in setting certain health and safety standards. 452 U. S., at 510–51 2. But un der Che v ro n , that an age n cy is not required to do so does n o t mean that an agency is not permitted to do so. This extended consider ation of th e text of §13 26(b), and comparison of that with the tex tand sta t utory fa cto rs applicable to four parallel provisions of the Clean Water Act, lead us to the conclusion that it was well within the bounds of r e asonable interpretati on for the EPA to con

clude that cost-benefit analysis is not categorically forbid

den. Other arguments may be av ailable to p r eclude such a rigorous form of cost-benefit ana lysis as that which wa s prescribed under the statute’s former BPT standa r d, which requ ired weighing “the to tal cost of application of technology” against “th e. . . bene f i t s t ob ea c h i e v e d

. ” S e e , supra , at 10

. But that question is not before u s . In the Pha s e II requirements challenged here the EPA sought only to avoid extreme disparities between costs and benefits. The agency limited variances from the Phase I I “national performance standards” to circumstances where the costs a r e “significantly greater than the benef i ts” of compliance. 40 CFR §125.94(a)( 5 )(ii). In defining th e “national performance standards ” themselves the EPA assumed th e application of technologies whose benefits “approach those estimated” for closed-cycle cooling sys

tems at a fraction of the cost: $389 million per year, 6 9 Fed. Reg. 41666, as compared with (1) at lea s t $3.5 billion per year to operate compliant closed-cycle co oling systems, id., at 416 05 (or $1 billionperyear to i m pose sim i lar requiremen t s on a subset of Ph ase IIfacil i ties, id., at14ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt 

### 41606), and (2) significant reducti on in the energy output of the altered facilities , id., at 416 05. And fi nally, EPA’s assessmentof the rela tively meager financial benefits of the Phase II regulations that itadopted—reduced im

pingement and entrai n ment of 1.4 billion aquatic organ

isms, id., at 41661, Exh. XII–6, with annualized use

benefits of $83 milli on, id., at 416 62, and non

- use benef i ts of indeterminate value, id., at 41660–41661—when com

pared to an nual costs of $389 million, demon s trates quite clearly thatthe agencydid not select the Pha s e II regula

tory requirements because th eir benefits equaled their costs. While not conclusive, it surely te nds to show tha tth e EPA’s current practice is a reasonable andhence legiti

mate exercise of its discreti on to weigh benefits against costs that the agency has b eenproceeding in essentia ll y this fashionfor over 30 years. See Alaska Dept. of Envi

ronmentalConserv atio nv. EPA , 5 40 U. S. 46 1, 487 (2004); Barnhartv. Walton , 5 35 U. S. 212, 219–220 (2002). As early as 19 77, the agency determined that, while §1326(b) does not re quirecost-b enefit analysis, it is also not reason

able to “interpret Section [1326(b)] as requiring use of technology whose cost is who lly disproporti onate to the environmental benefit to be gained.” In re Public Servic e Co. of New Hamp shir e , 1 E. A. D. 332, 340 (1977). See also In re Central Hu dson Gas a nd Elec tri cCorp. , EPA Decision of the General Counsel, NPDES Pe rmits, No. 63, pp. 371, 381 (July 29, 1977) (“EPA ultimately must de m onstrate that the present value of the cumulative annual cost of mod i fications to coo ling wa ter inta ke structu res is not wholly out of proportion to the magnitude of the esti

mated environmental gains”); Seacoast A n ti-Pollutio n Leagu ev. Cos t le , 597 F. 2d 306, 31 1 (CA1 1979) (rejecting challenge to an EPA permit deci sion that was based in part on th e agency’s determi nation that further restric

tions would be “ ‘wholly disproportionate to any environ

mental benefit’ ”). While the EPA’s prior “wholly dispro

-15 Cite as: 55 6 U

. S. ____ (2009) Opinion of theCourt 

### portionate” standard m a y be somewhat different from its current “significantly greate r than” standard, there is nothing in the statute t hat would indicate tha tthe former is a permissible interpretation while the latter is not. Indeed, in i t s review of the EPA’s Phase I regulations, the Second Circuit seemed to recognize that §1326(b) permits some form of cost-benefit analysis. In considering a challenge to the EPA’s rejec t ion of dryco oling systems 7 

### as the “best technology available” for Phase I facilities the Second Circuit noted that “while it certainly sounds sub

stantial tha tdry cooling is 95 percent more effective than closed-cycle cooling, it is undeniably relevant that th a t difference represents arelatively small impr ovement over closed-cycle cooling at a very signi f icant cos t .” Riverke e pe r , 358 F. 3d, at 194, n. 22. And inthe decision below rejecting the use of cost-benefit analysis in the Phase II regulations, the Second Circuitnonetheless interpreted“best techn o logy available” as mandating only those technologies thatcan “be reasonably b o rne by the industry.” 475 F. 3d, at 99. But whether it is “reasonable” to bear a particular co st may well depend on the resulting benefits; if the only relevant facto r was the f e asibility of the costs, their reasonableness would be irrelevant. In the last analysis, ev en respond e nts ultima tely recog

nize that some form of cost-benefit analysis is permissible. They ack n o w ledge that the st atute’s language is “plainly not so constricted as to requi re EPA to require industry petitioners to spend billion s to save one more fish or plank ton.” Brief for Respondents Riverk eeper, Inc. et al. 29. This concedes the principle—the permissibility of a t least some cost-benefit analysis—and we see no statutory basis for limiting its use to situ ations where the ben e f i ts

——————

7 Dry cooling s y s t em s us e a i r dra f t s t ore m o ve hea t , a n d a ccordin gly rem o ve lit t l e or no wa t e r froms u rroundin g wa t e r s o urce s . S e e 6 6 Fed. Reg

. 65282 (2 0 01).16 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of theCourt


### are de minimisrather than significantly dispro portionate. * * * We conclude that the EPA permi ssibly relied on cost

benefit ana lysis in setting the nati o nal performance stan

dards and in providing for cost-benefit variances from those standards as part of the Ph ase I I regul a tions. Th e Court of Appeals’ reliance in part on the agency’s use of cost-benefit analysis ininvalidatin g the site-s pecific cost

benefit variance provision, 475 F. 3d, at 114, was therefore in error, as was its remand of th e national performance standards for clarification of whether cost-benefit analysis was impermissibly used, id. , at 104–105. We of course express noview on th e remaini n g bases fo r the Second Circuit’s re mand which did no t depend on the permissibil

ity of cost-benefit analysis. See id., at 108, 11 0, 113, 115 , 117, 120. 8

### The judgment of the Court of Appeals is r e versed, andthe cases are re manded for further proceed

ings consistent with thi s opinion. It is so orde red.

——————

8 J US TI CE B REY ERwou l d r e m a n dforth e addition al r e aso nof wh at h e rega rds a s t h e a g ency ’s ina d eq ua t e expl anation of th e change in i t s crit e rion for v a ria n ces
—fromarela t i on ship of cos t s t o b e nefit s t h at is “ ‘wholly disproportionate’ ” to one that is “ ‘ s ignifica ntly gr ea ter.’ ” Po st , at 7–8(opin i o nc o n c u r r i n ginpar tan d dis s en tin ginpar t). Th atqu es tion ca n haveno b e a r ing u p on wh ether the EPA can use cost-benefit analysis, which is the only qu estion presented here. It seems to us, i n an yc a se, th atth e EPA’ s ex plan ationwa s ample. I tex plain e d th a tt h e “wholly out of proportion” standard was i n appropriate f o r the existin g facilitie s subj e c t to the Pha s eII rules beca use those facil i ties lack “ t he greater flexibility available t onew fac ilitie s for selecting the location of their intakes and instal ling technologi es a tlower cos t s rela t ive t ot h e costs as sociat ed with retrofittingexisti ng facilities,” and because
“ e conom i ca lly im pra c t i cable im pa cts onenergy p r ices, production costs, and energy p r oduction .

. . could occur if large numbers of Phase I I exis t i ng fa cilit i es incurred cos t s t h atwere m o re t h a n‘s ignifica nt ly gr eater ’ than but not ‘ w hollyout of pr opor tion’ to the c o sts in the EPA’ s r e c o r d .” 68 Fed. Reg

. 13541 (200 3).Opinion of theCourt 17 Cite as: 55 6 U

. S. ____ (2009) Appendix to opinion of the C ourt 

### APPENDIXTO OPINION OF T H E COURT Statutory Standard Statutorily Mandated Facto r s Entities Subject to Regulation BPT : “[ E]f f l ue nt li mi tatio n s

. . . w h ic h s h all require the ap plicatio n o f the best p ra c ticablecontr o l tec h nology cu rre n t ly available .” 33 U. S. C. §1311(b) (1) (A) (e mpha

sis ad de d)

. “F actors rela ti ng t ot h e assessme n t of best practicabl e control tec h nol o gy c u rre ntly available .

. . shall incl ude consi d era t io n o f th e total cost of ap plicatio n o f tec h nologyin relatio nto t h e eff l ue nt red u c t io n be nef i ts to be achie v e d .” 33 U. S. C. §1314(b) (1) ( B). Existi ng poi n t sou r ces du ri n g th e Clea n W a te r Act’s initial i m p l emen t a t i on ph ase.

BCT : “[ E]f f l ue nt li mi tatio n s

. . . w h ic h s h all require ap plicatio n of the best conv e n tio n al po llut a n t control tec h nol ogy.” 33 U. S. C. §1311(b) (2 )(E) (emph a sis adde d). “F actors rela ti ng t ot h e assessme n t of best co nv e n tion al poll uta n t con t rol tec h nology. . . shall incl ude cons i d era t io n o f th e reas o n ableness o f the relatio n s h ip betw ee n t h e co sts of attai n i n g a red u ctio n i neff l ue nts a n d the efflue nt reduc t io n benefits deriv e d.” 33 U. S. C. §1314(b) (4) ( B). Existi ng poi n t sou r ces that disc harg e “co nve ntio nal poll uta n ts” as def i ne d by t h e EPA und er 33 U. S. C. §1314(a) (4)

.
BAT EA : “[ E]f f l ue nt li mi tatio n s . . . w h i c h .

. . s h a l l requir e ap plica t ion of th e best av aila ble tec h nology econom ically ac hieva b le

. . . w h i c h will result i nre asona b le further prog res s to war d th e na tio n al go al of e l i m in at in gth e d i s char ge of allpo llut

ants.” 33 U. S. C. §1311(b) (2) (A) (e mpha

sis ad de d)

. “F actors rela ti ng t ot h e assessme n t of best available tec h nologyshal l tak eint o acco unt .
. . the cost o f achie v ing s u c heff l ue nt re d u c t io n.” 33 U. S. C. §1314(b )(2 )(B)

. Existi ng poi n t sou r ces that disc harg e toxic poll uta n ts an d no n c o nv en t i ona l poll uta n ts.Opinion of theCourt 18ENTERGY C O RP. v. RIVERKEEPER, I N C. Appendix to opinion of the C o urt 

### Statutory Standard Statutorily Mandated Facto r s Entities Subject to Regulation BADT : “[A] sta n dar df o r th e control of the dischar g e of poll uta n ts w h ic h ref l ects the g r e a test deg r ee of e fflue nt red u c t io n with the A d mi nistra tor deter

mi nes to be achievable th ro ugh a pplic atio n of th e best av aila ble de m o ns tr ate dc o nt rol tec h nology.” 33 U. S. C. §1316(a) (1) (emphasis ad de d). “[T]he Ad mi nis t rato r shall take i n to co nsi d era t io n t h e cost of ac hievi n g suc hefflue nt red u c t io n, an d an y no n- w a ter quality e nviro nme n tal i m pac t a n den e r gyr e qu i r emen t s . ” 3 3 U. S. C. §1316(b) (1 )(B). Ne w poi n t sou r ces withi n the cate gories of sou r ces ide n ti

fied by the E PA und er 33 U. S. C. §1316(b) (1) (A).

BTA : “An ys t a n d a r d

. . . applicable to a poi n t sourc eshall re quire th at t h e loca tio n , desig n , co nstr u c tio n , and cap a city of cooling wate r intake struc t ures ref l ect th e best tec h nol

ogy availabl e fo r mi ni m i zi ng a dvers e enviro nme n tal impac t .” 33 U. S. C. §1326(b )

. N/A Poi n t so u r ces that operate cooling wa ter inta ke str u c tu res._________________

_________________ 1 Cite as: 55 6 U

. S. ____ (2009) Opinion of B RE Y E R , J. 

# SUPREME CO URT O FTHE UNI TED STATES
Nos. 07– 58 8, 07–5 89 an d 07

– 597 

### ENTE RGY COR P ORAT ION, PE T I TIONER 07–588 v. RIVER KE E P ER, INC., ET AL


### . PSEG F O SSIL LLC, ET AL 

### ., PETI TIONERS 07–589 v. RIVER KE E P ER, INC., ET AL


### . UTILITY WATER ACT GROUP, PETITIONER 07–597 v. RIVER KE E P ER, INC., ET AL


### . ON WRITS OF CERTIORARI TO THE UNITED STAT ES COURT OF APPEAL S FOR THE SECO ND CIRCUIT [Apr il 1, 200 9] 

### J USTICE 

### B RE YE R 

### , conc urring in p a rt and dis s enting in part. I agree with the Court that the relevant statutory lan

guage authorizes the Environmental Protection Agency (EPA) to co mpare costs and benefit s . Ante , at 7–13. None

theless the drafting history and legislative history of related provisions, Pub. L. 92–500, §§301, 304, 86 Stat. 844, 850, as amended, 33 U. S. C. §§1311, 1314, make clear that those who sponsored the legislation intended the law’s text to be read as restricting, though not forbid

ding, the u s e of cost-benefit comp arisons. And I would apply that t e xt accordi n gly. I Section 301 provides that, not later than 197 7, effluent2 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of B RE Y E R , J. 

### limitations for point sources shall require the applicatio n of “ best pr acti cableco ntrol technology,” §301(b)(1)(A), 86 Stat. 845 (emphasis added); and that, not later than 198 3 (later extended to 1989), efflue nt limitations for categories and classes of point sources shall require application of th e “ best availabletech nology economically achievable,” §301(b)(2)(A), ibid. (e mphasis added). Secti o n 304(b), in turn, identifies the factors that the Agency sh all take into account in determining (1) “ b e st practicablecontrol tec h

nology” and (2) “ best a v ailabletechnology.” 86 Stat. 851 (emphasis added). With respect to the first, the statute provides that the factors ta ken into acc o unt by th e Agency“ s hall include consideration of the total cost of application of technology in relation to the effluent redu ctio nbenefits to be achieved from such application .

. . and s u ch other factors as the Administra tor deems appropriate

. ” §304(b) (1)(B), ibid. With respect to the s e cond, the statute says that th e Agency “shall take into account . . . the cost of achieving such effluent reduction” and “such other fa ctors as th e Administra tor deems appropriate.” §304(b)(2)(B), ibid. The draftin ghistory makes clear that the statute re

flects a compromise. In the H o use versionof the l e gisla

tion, the A g ency was to consider “the cost and the ec o nomic, social, and environmental impact of achieving such effluent reduction” whe ndetermining both “ best practica

ble” and “ b est availa b le” technol o gy. H. R. 11896, 92d Cong., 2d Sess., §§30 4 (b)(1)(B), (b)(2)(B) (1 972) (as re

ported from committee). The Hous e Report explained that the “ best availabletechnology” standard was needed—as opposed to mandating the elim ination of discharge of pollutants—because “the difference in the cost of 1 0 0 percent elimination of pollutants as compared to the cos t of removal of 97–99 percent of the pollutants in an effluen t can far exceed any reasonable b e nefit to be achieved. In most cases, the cost of remo val of the last fe w percentage3 Cite as: 55 6 U

. S. ____ (2009) Opinion of B RE Y E R , J. 

### points increases expo[n]entially.” H. R. Rep. No. 92–911 , p. 103 (1972). In the Senate version, the Agenc ywas to co nsider “th e cost of achieving such efflue nt reduction” when determin

ing both “ best pr ac ticab le” and “ bestavailable” technology. S. 2770, 92d Cong., 1st Sess., §§304(b)(1)( B), (b)(2)(B) (1971) (as reported fro mcommittee). The Senate Report explains that “the technology must be available at a cos t

. . . which the Adminis trator determines to be reasonable.” S. Rep. No. 92–414, p. 52 (1971) (h ereinafter S. Rep.). But it said nothing about comparing co sts and benefits. The final s t atute reflects a modif i cation of th e H o use’s language with respect to “ best practicable ,” a n d an adop

tion of the Senate’s language wit hrespect to “ best avai l

able .” S. Conf. Rep. No. 92–1236, pp. 124–125 (1972). Th e final statute does n o t requirethe Agency to c o mpare costs to benefits when determining “ best availabletechnology,” but neither does it expressly forbidsuch a comparison. The strongest evidence in thele gislative hi story sup

porting the respondents’ position—namely, that Congre ss intended to forbid comparisons of costs and benefits when determining the “ best available technology”—can be foun d in a written discussion of the Act’s provisions distributed to the Senate by Senator Edmund Muskie, the Act’s prin

cipal sponsor, when h esubmitted the Conf erence Report for the Senate’s consideration. 118 Cong. Rec. 33693 (1972). Th e relevant part of tha tdiscussion points out that, as to “ best practicabletech nology,” th e statute r e quires application of a“balancing test between total cos t and effluent reduction benefits. ” Id. , at 33696; s e e §304(b)(1)(B). But a s to “ best availabletechnology,” it states: “While cost should be a factor in the Administra

tor’s judgment, no bal ancing test will be requ ired.” Ibid.; see §304(b) (2)(B). And Senator Muskie’s discussion lat e r speaks of the agency “evaluat[ing] .

. . what needs to b e done” to eliminate pollutant discharge an d “wha t i s4 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of B RE Y E R , J. 

### achievable,” both “with o ut regard t ocost.” Ibid. As this language sugg ests, the Act’s sponsor s had rea

sons for m i nimizing the EPA’s investigation of, and reli

ance upon, cost-benefit compar isons. The preparation of formal cost-benefit analyses can take too much time, thereby delaying regulation. And the sponsors feared that such analyses would emphasize easily quantifiable factors over more qualitative factors (par ticularly en vironmental factors, for example, the value of pres erving non mark etable species of f i sh). See S. Rep., at 47. Above all, they hoped that minimizing the use of cos t -benefit com

parisons would force the deve lopment of cheaper contr o l technologies; and doin g so, whatever the initial in efficien

cies, would eventually mean cheaper, more effective cleanup. See id. , at 50–51. Nonetheles s, neither the sponsors’ language nor the underlying rationale requires the Act to be re ad in a wa y that would forbid cost-benefit comparisons. Any such total prohibition would be difficult to enforce, for ever y real choice requires a decisi onma ker to weigh advantages against disadvantages, and disadvantages can be s een in terms of (often quantifiable) costs. Moreover, an absolute prohibitionwould bring about irrational res u lts. As the respondents themselv es say, it would make no sense to require plants to “spe nd billions to save one more fish or plankton.” Brief for Respondents Riverkeepe r , Inc., et al. 29. That is so even if the industry might somehow afford those billi ons. And it i s particularly so in an age of limited resources available t odeal withgrave environmental problems, where toomu ch wasteful expenditure devoted to one problem may well mean cons iderably fewer resources available to deal effectively with other (perhaps more serious) problems. Thus Senator Muskie used nuanced langu a ge, which one can read as leaving to the Agency a degree of author

ity to ma ke cost-benefit compariso n s in a ma nner that i s5 Cite as: 55 6 U

. S. ____ (2009) Opinion of B RE Y E R , J. 

### sensitive both to the need for such comparisons and to the concerns th at the law’s sponsors expressed. The relevant statement begins by listing various factors that the statute require s th e Administrator to ta ke into ac count whe n applying th e phrase “practic able” to “classes and catego

ries.” 118 Cong. Rec. 33696. It states that, when doing s o , the Administrator mustapply (as the statute specifies) a “balancing test between total cost and effluent reductio n benefits.” Ibid. At the same time, it seeks to reduce the likelihood that the Administrator will place too much weight upon high costs by adding that the balancing test “is intended to limit the application of tec hnology on l y where the additional degree of efflu e nt reduction is wholly out of proportion to the costs of achieving” a “marginal level of reduction.” Ibid. Senator Musk ie’s statement thenconsiders the “ differ

ent test” th at the statute requires the Administrator to apply whendetermining the “ ‘ b est available ’ ” technology. Ibid. (emphasis added). Under th at test, the Administra

tor “may co nsider a broader range of technological alterna

tives.” Ibid

. And in d e termining what is “ ‘ best available ’ for a categ o ry or clas s, the Adm i nistrator is expected to apply the same principles involv ed in making the deter

mination of ‘ best practicable ’ .

. . e x cept as to cost-benefit analysis.” Ibid. (emph a sis added). That is, “[w]hile cost should be afactor . . . no balancin g test will be required .” Ibid. (emphasis added). Rather, “[t]he Admin i str a tor wil l be bound by a test of reasonabl eness. ” Ibid. (emphasis added). The statement adds that the “ ‘ best available ’ ” standard “is intended to reflect t h e need to press towar d increasingly higher levels of control.” Ibi d

. (emphas is added). An d “the reas onableness of what is ‘economically achievable’ should refle ctan e v aluation of wh at needs to be done to move towar dthe e limination of the discharge of pollutants and what is achiev able through the application of available technology—withoutregardto cost.” Ibid.6 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of B RE Y E R , J. 

### (emphasis added). I believe, a s I said, that this language is deliberately nuanced. The statement says tha twhere the statute uses the term “ best p rac tic a ble ,” the statute requi rescompa r i

sons of costs and benef i ts; but where the stat ute uses th e term “ best available ,” s u ch comparisons are not “ required. ” Ibid. (emphasis added). Senator M u skie does not say tha t all efforts to compare costs and benefits are forbidden. Moreover, the statement points out that where the statute uses the term “ best available ,” the Administrato r “will be bou n d by a tes tof reasona bleness. ” Ibid. (empha

sis added). It adds th at the A d m i nistrator s h ould apply this test in a way tha t refl e c t s its ideal objective, moving as closely as is technologica lly possible to the elimination of pollution. It thereby says th e Administrator should consider, i.e. , take into account, how much pollution would still remai nif the best availabletechnologywere to b e applied everywhere—“ without re gard to cos t .” Ibid. I t does not say thatthe Administra tor mustset the standard based solely on the res u lt of that determination. (It would be difficult to reconcile the alternative, more absolut e reading of this language with the Senator’s earlier “test of reasonableness.”) I say that one may, n o t that one must, rea dSenato r Muskie’s st atement this way. B u t to read it differently would put the Agency in conflict with the test of reason

ableness b ythreatening to impo se massive costs far in excess of any benefit. For 30 yea r s the EPA has read the statute and its history in this way. The EPA has though t that it would not be “reasonable to interpret Section 316(b ) as requiring use of technology wh ose cost is wholly disp ro portionate to the environmental benefit to be gained.” In re Pub. Serv. Co. of N. H. (Se a brook Station, Units 1 and 2) , 1 E. A. D. 3 32, 340 (19 77), remanded on oth e r grounds, Seacoast An ti-PollutionLeague v. Costl e , 57 2 F. 2d 872 (CA1 1978) (emphasis added); see also In re7 Cite as: 55 6 U

. S. ____ (2009) Opinion of B RE Y E R , J. 

### Central Hu dson Gas & Elec. Co rp., EPA Decision of th e General Counsel, NPDES Permits , No. 63, p. 371 (July 2 9 , 1977) (also applying a “wholly disproportionate” test); In re Pub. Serv. Co. of N. H. , 1 E. A. D. 455 (1978) (same). “[T]his Court will normally a ccord particular deference to an agencyinterpretation of ‘longstanding’ dura tion.” Barnhart v. Walton , 535 U. S. 212, 220 (2002). And for th e last 30 year s, the EPA has given th e statute a permissive reading without suggesting that in doing so it was ignor

ing or thwarting the intent of the Congress that wrote the statute. The EPA’s reading of the statute would seemto permit it to describe environmenta l ben e fits in n o n-monetized terms and to evaluate both costs and benefits in accor

dance withits expert judgmentand scientific kno w ledge. The Agency can thereby avoid lengthy formalcost-benefit proceedings and futile attempts at comprehensive moneti

zation, see 69 Fed. Reg. 41661 –41662; take account o f Congress’ technology-forcing objectives; and still prevent results that are absurd or unrea son able in light of extreme disparities between costs and benefits. This approach, i n my view, rests upon a “reasonable interpretation” of th e statute—legislative history incl uded. Hence it is lawf ul. Chevron U. S. A. Inc. v. Natu ral R esource s Defense Coun

cil, Inc. , 46 7 U. S. 837, 844 (1984). Most of what the ma

jority says is consistent with this vi ew, and to that extent I agree with its opinion. II The cases before us, however, present an additional problem. We hereco nsider a ru le that per m its variances from nation a l standards if a facility demonstrates that its costs would be “significantly grea ter thanth e benefits of complying.” 40 CFR §125.94(a)(5)(ii) (2008). The words “significant ly greater” differ from the words t h e EPA has traditionally used to describe its standa r d, namely,8 ENTERGY C O RP. v. RIVERKEEPER, I N C. Opinion of B RE Y E R , J. 

### “wholly disproportionate.” Perhaps the EPA does no t mean to make much of that differe nce. But if it means the new words to set forth a new and different test, the EPA must adequately explain why itha s changed i t s standard. Motor Vehicle Mfrs. A ssn. of United State s , Inc. v. State Farm Mut. Automobile Ins. Co. , 463 U. S. 29, 42–43 (1983); National Cable & Teleco mmunicatio n s Assn. v. Brand X Intern et , 54 5 U. S. 967, 981 (20 05); Thoma s Jefferson Univ. v. Shalala , 512 U. S. 504, 524, n. 3 (1994) (T HOMAS 

### , J., dissentin g). I am not co nvinced the EPA has s u ccessfully explained the basis for the change. It has r e ferred to the fact tha t existing facilities have less fl exibi lity than new facilities with respect to installing new technologies, and it has pointed to special, en ergy-rela te d impacts of regulation. 68 Fed. Reg. 13541 (2003) (proposed rule). But it has not explained why the traditional“wholly disp roportionate” standard ca nnot do the job now, when the EPA has used that standard (for existing fa ciliti e s and otherwise) with apparent success in th e past. S ee, e.g. , Central Hudson , supra . Consequent ly, like the majority, I would rem and these cases to the Court of Appeals. But unlike the majority I would permit that court to re mand the cases to the EPA so that the E PA caneit h er apply its traditio nal “wholly disproporti onate” standard or provide anadequately reasoned ex planation for the change._________________

_________________ 1 Cite as: 55 6 U

. S. ____ (2009) S TEVENS , J., di s s e nting 

# SUPREME CO URT O FTHE UNI TED STATES
Nos. 07– 58 8, 07–5 89 an d 07

– 597 

### ENTE RGY COR P ORAT ION, PE T I TIONER 07–588 v. RIVER KE E P ER, INC., ET AL


### . PSEG F O SSIL LLC, ET AL 

### ., PETI TIONERS 07–589 v. RIVER KE E P ER, INC., ET AL


### . UTILITY WATER ACT GROUP, PETITIONER 07–597 v. RIVER KE E P ER, INC., ET AL


### . ON WRITS OF CERTIORARI TO THE UNITED STAT ES COURT OF APPEAL S FOR THE SECO ND CIRCUIT [Apr il 1, 200 9] 

### J USTICE 

### S TEVEN S 

### , wi th whom J USTICE 

### S OUTER

### and J USTICE 

### G IN S B UR G

### join, dissentin g. Section 316(b) of th e Clean Water Act (CWA), 33 U. S. C. §1326(b), which gove rns industrial powerplant water inta ke structu res, provides that the En vironmental Protection Agency (E PA or Age n cy) “shall require” that such struct ures “reflect the best t e chnology available for minimizing adverse environmental impact.” The EPA has interpretedthat man d ate to au thorize the use of cost

benefit an alysis inpromulga ting regul a tions under §316(b). For instance, under the Agency’s interpretatio n , technology that would otherwise qualify as the best avail

able need n o t be used if its co sts a r e “significantly greater than the be nefits” of co mpliance. 40 CFR §125.94(a)(5)(ii) (2008).2 ENTERGY C O RP. v. RIVERKEEPER, I N C. S TEVENS , J., di s s e nting 

### Like the Co urt of Ap peals, I am convinced tha tthe EPA has misinterpreted the plain text of §316(b). Unless cost s are so highthat the best technology is not “available,” Congress has decided that they are outweighed by the benefits of minimizing adverse environmental impact. Section 316(b) neither expressl y nor implicitly authorizes the EPA to use cost-benefit analysis when set t ing regula

tory standa r ds; fairly read , it prohibits such use. I As typically performed by the EPA, cost-benefit analysis requires the Agency to first monetize the cos t s and bene

fits of a re gulation, b a lance the results, an d then choose the regulati on with the greatestnet benefits. The process is particularly controv e rsial in the environmental contex t in which a regulation’s financial costs are often more obvious an d easier to quantify than its environmental benefits. And cost-b enefit analysis often, if not alwa ys, yields a result that does not maximize environmental protection. For instanc e, although the EPA estimated that wate r intake structures kill 3.4 billion fish and shellfish each year, 1 

### see 6 9 Fed. Reg. 41586, the Agency s truggled to calculate th e value of the aquatic life that wo uld be pro

-

——————

1 To produce e n ergy, i n dustrial po werplants withdraw billions of gallons of water dai l y from our Nati on’ s water w ay s. Ther mo electric powerplants alone demand 39 pe rcent of all freshwater with

drawn nationwide. S ee Dept. of Energy , Addressi ngthe Critical Lin kBetweenFossilEn er gyan d Water2 (Oc t
. 20 05), h ttp :// www. netl.doe. gov/tec hnologi es /coalp ower/e wr/pubs / NETL_Water_Paper _Fin al_Oc t .20 05.pdf ( a ll In t e r n et mater i a l s as v i sited M a r . 18, 20 09 , an d av ail able inCler k of Co u r t’ s c a se file)

. Th e fishan d sh ellfi s har e killed by “i mp ingement” or “entrain ment.” I m pingeme n t occurs whe n aquatic organisms are tr app e d against the screens and grills of water intake str u c t ur es. Entr ainment occurswhe ntheseorganisms are drawn into the intake structures. See Ri verk eep er, Inc

. v. EPA , 475 F. 3d 83, 89 (C A2 20 07); 69 F e d. Reg

. 41586 (2004).3 Cite as: 55 6 U

. S. ____ (2009) S TEVENS , J., di s s e nting 

### tected und er its §316(b) regulations, id. , at41661. T o compensate, the EPA tooka shortcut: Instead of monetiz

ing all aquatic life, the Agency counted only those species that are commercially or recre ationally harvested, a tin y slice (1.8 percent to be precise) of all impacted fish and shellfish. This narrow focus in turn skewedthe Agenc y ’s calculation of benefits. When the EPA a ttem p ted to value all aquatic life, the b e nefits meas ured $735 million. 2 

### Bu t when the E PA decidedto gi ve zer ovalue to t h e 98.2 per

cent of fish not commerciallyor recreationally harvested, the benefit s calculation dropped dramatically—to $83 million. Id. , at 41666. The Agency acknowledged that its failure to monetize the othe r 98.2 percent o f affected s p e cies “ ‘couldresult in s e rious misallocation of resources,’ ” id. , at 416 60, because its “comparison of complete cost s and incomplete benefits does not provide an accura te picture of net benefits t osociety.” 3 

### Because benefits can be mo re accurately m o netized in some indus tries than in others, Congress typically decides whether it is appropriate for an agency to use cost-benefit analysis incrafting regulations. Indeed, this Court has recognized that “[w]he n Congress has inten d ed that an agency engage in cost-benefit analysis, it has clearly indi

cated such intent on the face of the statute.” Americ a n Textil e Mfrs . Institu t e, Inc. v. Donovan , 452 U. S. 490, 510 (1981). Accordingly, we should not treat aprovision’s silence as an implicit source of cost-benefit authority, particularlywhen suc hauthorityis elsewhere expressl y granted an d it has the potential t ofundamen tally alter an

——————

2 EPA, Economic and Benefi ts Ana l ysis for the Proposed Section 316(b) Phase I IEx istingFacilitie s Rule, p. D1–4 (EPA –8 21–R–0 2

– 0 0 1 , Feb. 2002), http://www.epa.gov/waterscience/316b/phase2/ e conbenefits.

3 EPA, Ec on omican d Ben e fits An aly s i s forth e Fin a l Se c t ion316(b) Phase II Ex istingFacilities Rule, p. D1–5 (EPA–8 21

–R–0 4–0 05, Fe b. 2004), http://www.epa.gov/wat erscience/316b/phase2/e conbenefits/final. htm.4 ENTERGY C O RP. v. RIVERKEEPER, I N C. S TEVENS , J., di s s e nting 

### agency’s a p proach to re gulation. C o ngress, we have noted, “does not alter the fundamental details of a regulatory scheme in vague terms or ancill ary pro visions—it does not, one might say, hi de elephants in mouseholes.” Whit

man v. American Trucking Assns., Inc. , 5 31 U. S. 457, 467–468 (2001). When inter p reting statutory silence in the pas t , we have sought gui d ance from a statut e’s other provisions. Evi

dence that Congress confronted an issue in some parts of a statute, wh ile leaving it unaddressed in others, can dem

onstrate th at Congres s meant its silence to be decisive. We concluded as much in American Trucking. I nt h a t case, the Court reviewed the EPA’s claim that §109 of th e Clean Air Act (CAA), 42 U. S. C. §7409(a) (2000 ed.), au

thorized the Agency to consider implementa tion costs in setting ambient air quality standards. We read §109 , which was silent on th e matter, to prohibit Agency reli

ance on cost considerations. After examining other provi

sions in which Congress had given the Agency authority to consider costs, the Court “refuse d to find implicit in am

biguous sec t ions of the CAA an a u thorization to consider costs that has elsewhere, and so often, been expressly granted.” 531 U. S., at 467. Studied silen c e, we thu s concluded, can be as much a prohibition a s an explicit “no.” Further motivating the Court in A m erican Trucking wa s the fact th at incorporating implementation costs into the Agency ’s calculus risked co untermanding Congress’ deci

sion to protect public health. The cost of implementation, we said, “is both so indirectly related to publichealth and so full of potential forcanceling the conclusions drawn from direct health effects that it would surely have been expressly mentioned in [the te xt] had Congress meant itto be consider ed.” Id. , at 469. American Truckin g’s approach should have guided the Court’s reading of §31 6 (b). No wh ere in the text of §316(b)5 Cite as: 55 6 U

. S. ____ (2009) S TEVENS , J., di s s e nting 

### does Congress explicitly authori ze the use of cost-benefit analysis as it does elsewhere in the CWA. An d the use of cost-benefit analysis, like the con s ideration of implemen

tation costs in American Tru c k i ng , “pad[s ]” §316(b)’s environmental mandate with tangential eco n omic effi

ciency conc erns. Id. , at 468. Y e t the maj o rity fails to follow American Trucking despite that case’s obviou s relevance to our inquiry. II In 1972, Congress amended the CWA to strike a careful balance between the country’s en ergy demands and its desire to protect the e nvironment. The Act required in

dustry to a d opt increasingly adva nced technology capable of mitigating its detrimental envi ronmental impact. Not all point sources were subject to s trict rules at once. E x isting plants were granted timeto retrofit with the best technology while new plants we re required to incorporat e such techno logy as a m a tter of desi gn. Al though Congress realized that technology standa r ds would n e cessarily put some firms out of busi n ess, see EP A v. Na t i on a l Cr u s hed Stone A ssn. , 449 U. S. 64, 79 (1980), the statute’s steady march was toward st ricter ru les and poten t ially higher costs. Section §316(b) was a nintegral part of the statutory scheme. The provision ins tructs that “[a]ny standard established pursuant to section 1311 of this title or section 1316 of this title and applicable to a point source shall require that the location, design, constructio n , and capac

ity of coolin g water inta ke structu res reflect the best tech

nology available for minimizing adverse e n vironmental impact .” 33 U. S. C. §1326(b) (2006 ed. ) (emphasis added). 4

### The “best technology available,” or “ B TA,” stan

-

——————

4 Th e two c r o ss-r e fer e nc ed pr ov ision s , §§1 31 1 an d13 16, al so es tablish “bes t tec hnology” standar d s, the fir s t applic ab le t oex istingpoint sources and the second to new facilit ie s. The reference to these provi

-6 ENTERGY C O RP. v. RIVERKEEPER, I N C. S TEVENS , J., di s s e nting 

### dard delivers a clear c o mmand: To minimize the advers e environmental impactof water intake structures, t h e EPA must require industry to ad opt the best technology available. Based largely on the observation that §316(b)’s tex t offers little guidance and therefore delegates some amou nt of gap-filling authority to th e EPA, the Court conclude s that the A g ency has discretion to rely on cost-benefit analysis. See ante , at 11–12. The Court assumes that, by not specifying how the EPA is to determine B TA, Congre ss intended to give considerabl e discretion to the EPA t o decide how to proceed. Silence, in the majority’s view, represents ambiguity and an invitation for the Agency to decide for it self which f a ctors shou ld governit s regulator y approach. The appropriate analysis requires full consid eration of the CWA’s structu re and legislative history t odetermine whether Co ngress contemplated cost-benefit analysis an d, if so, under what cir c u mstances it directed the EPA to utilize it. This appro a ch reveals that Congress grante d the EPA authority to use cost-benefit analysis in some contexts bu t not others , and that Congress intend to con

trol, not delegate, when cost-benefit analysis should be used. See Chevron U. S. A. Inc. v. Nat u ral Re s o ur ces Defen se Co uncil, Inc. , 467 U. S. 837, 842–843 (1984). 5

—————— sions in §3 16 (b) merely requires any rule promulgate d under those provisions, when applied to a point s o urce wit hawa t e r int a ke s t ruc tu r e , to inc o r p or ate §316(b) s t an dar d s.

5 The major i ty announc e s at the outs et that the EPA’s re ading of the BTA s t andard“governs if it is a re asonable interpretati on of the stat

ute—not nece ssarily the o n ly possible i n terpretation, nor even the interpretationdeemed mos tr e ason able byth e c o u r ts.” An t e , at 7. Th is observation is puzzling in light of the co mmonly understood practice that, as a fir s t step, we ask“whetherCongr e ss has dir e c t lyspoken to the precise questi on at issue.” Chevron , 467 U. S., at 84 2

. On lylater , if Congres s ’ intent is not clea r, do weconsider the reasonableness of th e agency’s action. Id. , at 843

. Assu min gambig u ityan d mov i n gto th e7 Cite as: 55 6 U

. S. ____ (2009) S TEVENS , J., di s s e nting 

### Powerful evidence of Congre ss’ decision not to authorize cost-benefit analysis in the BTA standard lies in the series of standards adopted to regulate the outflow, or effluent, from industrial powerplants. Passed at the s a me time as the BTA standard at issue h e re, the effluent limitation standards i m posed increasingl y strict technology require

ments on industry. I neach effluent limitation provision, Congress distinguished its willingn ess to allowthe EPA to consider costs from its willingnes s to all o w the Agency to conduct a cost-benefit analysis. And to the extent Co n gress permitted cost-benefit analysis, its use was intended to be temporary and exceptional. The first tier of technology standar ds applied to existing plants—faci lities f o r which re trofitting wouldbe particu

larly costly

. Congress requi red these plants to adopt “effluent limitations .

. . which shall requir ethe applica

tion of the best prac t i cable control technology cu rrent ly available.” 33 U. S. C. §1311(b)(1)(A). Becau s e this “best practicable, ” or “BPT,” standard was meant to ease indus

try ’s t r ansition to the new techno logy-based regime, Con

gress gave BPT two unique featu r es: First, it would be temporary, remaining in eff e ct only until J u ly 1, 1983

. 6 

### Second, it specified that the EPA was to conduct a cost

benefit ana lysis in setting BPT requirements by consider

ing “the total cost of applicat ion of technology in relation to the effluent reducti on benefits to be achieved from such application.” 7

### §1314(b )(1)(B). Permitting cost-benefit

—————— s e cond s t ep reflect s t h e Court ’ s reluct a n ce t ocons ider t h e pos s ib i lity, which it laterlament s is “ m ore complex,” ante , at 9, th at Con gr e ss’ silenc e mayhav emeant to for e close cost-benefit analysis.

6 Con gr e ss laterex ten d ed th e deadlin e to M a r c h31, 1989. 7 SenatorM u skie, the Senate sponsor of thelegislation, described the cos t -b enefitana l ys is perm itt e d under BP T a s decidedly na rro w, a s s e rt

ingthat “[t]he balanc i ngtest betweent o t a l cos ta n d effluentredu ct ion benefits is int e nded to li mitthe app licati o n of technology only whe r e the addition al degree of effluent reduct ion i s wholly out of proportion to t h e cos t s of a c hieving s u ch m a rgina llevel of reduct ion for a n y cla s s or8 ENTERGY C O RP. v. RIVERKEEPER, I N C. S TEVENS , J., di s s e nting 

### analysis inBPT gave the EPA the ability to cushion the new technology requirement. For a limited time, a tech

nology with costs that exceededits benefits would not be considered “best.” The second tier of technology standards req u ired exist

ing powerp lants to adopt th e “best available technology economically achievable” to advan c e “the nati o nal goal of eliminating the discharge of all pollutants.” §1311(b)(2)(A). In s e tting this “bes t available technology,” or “BAT, ” 8 

### standard, Congress gave the EPA a notably different command for decidi ng what techn o logy would qualify as “best”: The EPA was to consider, among other factors, “ t h ecost of ac hieving suc heffluent reduction,” b u t Congress di d not grant it authority to balance costs with the benefits of stricter regulation. §1314(b)(2)(B). Indeed, in Crushed Stonethis Court expla i ned that the difference between BPT and BAT was the existence of cost-benefit authority in the first and the abs ence of thatauthority in the second. See 449 U. S., at 71 (“Similar directions are given the Administra tor for det e rmining effluent reduc

tions attainable from the BAT except tha tin assessing BAT total cost is no longer to be considered in comparison to effluent reduction benefits”). The BAT standard’s legislativ e hi story strongly supports the view that Congress purposeful ly withheld cost-benefi t authority for this tier of regulation. See ibid. , n. 10. The H o use of Representatives and the Senate split over the role cost-benefit analysis would play in the BAT provision. The House favored the tool, see H. R. Rep. No. 92–911, p. 107 (1972), 1 Leg. His t . 794, while the Senat e rejected it,

—————— ca t e gory of s o urces . ” 1 Legis l a t ive History of the Water Polluti on Con t r o l Ac t Amen dmen ts of 1972 (Com m i ttee Pr in t c o mpiled forth e Senate Co mm ittee on Publ i cWor k s byth e Libr ar yof Con gr e ss), Ser

. No. 93–1, p. 170 (19 73) (h er ein a fterLeg

. Hist.)

8 Althoughthe major i tyc a lls this “BATEA ,” the par t ies r e ferto the provision as “BAT,” and for simpl i city, so will I.9 Cite as: 55 6 U

. S. ____ (2009) S TEVENS , J., di s s e nting 

### see 2 id. , at1183; id. , at 1132. The Senate view ultimately prevailed in the final legislation, resulting in a BAT stan

dard that was “not subject to any test of cost in relation t o effluent reduction benefits orany form of cost/benefi t analysis.” 3 Legislative History of the Clean Water Act of 1977: A Continuationof the Legislative History of the Federal Water Pollution Control Act (Com mittee Print compiled for the Senate Committee on Envir o nment and Public Works by the Library of Congress), Ser. No. 95–14, p. 427 (1978). The third a n d strictestregulatorytier was re served fo r new point sources—facilities thatcould incorporate tech

nology improvements i n to their in itial design. These new facilities were required to adopt “the best available dem

onstrated c o ntrol technology,” or “BAD T,” which Congr e ss described as “a standa r d .

. . whic h reflect[s] the greates t degree of effluent reduction.” §1316(a)(1). In administer

ing BADT, Congress directed the EPA to consider “the cost of achieving such efflu e nt reducti on.” §1316(b)(1)(B). But because BADT was meant to be th e most stringent stan

dard of all, Congress made no mention of cost-benefit analysis. Ag ain, the silence was in tentional. The House’s version of BADT origi nally contained an exemption for point sources for which “the economic, social, and envi

ronmental costs bear no reas onable relationship to the economic, social, and environmental benef i t to be ob

tained.” 1 Leg. Hist. 798. That this exemption did not appear in the final legislation demonstrates that Congre ss considered, and rejected, reliance on cost-benefit analysis for BADT. It is in this light that the BTA standard regulating water intake structure s must be vi ewed. The use of cost

benefit analysis was a critical co mponent of the CWA’s structu re and a key concern in the legislative process. We should therefore conclude that Con gress intended to forbid cost-benefit analysis in one provision of the Act in which i t10 ENTERGY C O RP. v. RIVERKEEPER, I N C. S TEVENS , J., di s s e nting 

### was silent on the mat t er when it expressly authorized its use in another. 9 

### See, e.g. , Alli son Engin eCo

. v. United Sta t esex rel . Sanders , 553 U. S. ___, ___ (2008) (slip op., at 7–8); Russe llo v. United Sta t es , 4 64 U. S. 16 , 23 (1983) (“[W]here Congress includes particular language in one section of a statute but omits it in another .

. . , it is gener

ally presumed that Congress acts intention a lly and pur

posely in th e disparate inclusionor exclusion” (internal quotation marks omit ted)). This is particularly true giv e n Congress’ decision that cost-benefit analysis would play a temporary and exceptional roleinthe CWA to help exist

ing plants transition to the Act’s ambitious environmental standards. 10

### Allowing cost-benefit analysis in the BTA standard, apermanent mandate applicable to all power

plants, serves no such purpose and instead fundamentally

——————

9 Th e Cou r t ar gu es th at, if sil e n c e in§316(b ) sig n als th e p r oh ibitionof cost-benefit a n alysis, it m u st al so foreclose the consi d eration of al l ot her pot e nt ially releva ntdis cret i ona r y fa ct ors in s e tt ing BTA s t a n dards. Ante , at 12. Th is a ll-or -n oth i n g reasoning rests on the deeply flaw ed a ssu m p tionth a tCo n gr e ss tr ea tedcost-benefit analysis as jus t one among many factors upon which the EPA could pot e ntially rely t o establi s hBTA

. Ye t, as ex pl ain e d abov e , t h e str u c t u r e a n d legi slat iv e histor yof the CWA demonstr ate th at Congress viewe dcost-benefit analysis with special skep ticism and cont rolled it s us e a c cordingly

. T h e Court’s assumption of equivalence is thus plainly incorrect. Properly r e ad, Con gr e s s ’ silen c e in§316(b) forb ids r e lian c e onth e c o st-ben efi t tool but does not foreclose rel i ance ona l l other cons idera t ions , s u ch a s a determinationwhether a technology is so costly that itis not “avail

able” for indus t ry to adopt.

10 In1977, Con gr e ss es tab lish e d ana ddit i on al tec h n o logy - baseds t an dar d , c o mmo nlyr e ferr ed to as “be s t c o nv entional pollutant c o ntr o l t e chnology ,” or “ B C T ,” t o govern co nventi onal pol l utan ts previously c o v e r e d byth e BAT s t an dar d

. See 33 U. S. C. §1311(b)( 2 )(E). Th e BCT s t a n da rd required t h e EPA t oco nsider, among other factors, “the relationship between the co sts of at tainin g a reduction i neffluents and the effluent reduction benefits derived.” § 1314(b)(4)( B). That Congress expressly authorized cost-be n efit anal ys is in BCT furt her confi r m s t h at Congres s t r ea t e d cos t -b enefita n a l ys is a s except iona l a n d res e rved for itself the auth ority to decide when it wo uld be us ed in the Act.11 Cite as: 55 6 U

. S. ____ (2009) S TEVENS , J., di s s e nting 

### weakens th e provision’s mandate. 11 

### Accordin gly , I would h o ld that th e EPA is without au

thority to perform cost-benefit analysis in setting BTA standards. To the extent the EPA relied oncost-benefi t analysis in establishin gits BTA regulations, 12

### that action was contrar yto law, for Congress directly for e closed suc h reliance in the statute itself. 13 

### Chev ron , 467 U. S., at 843.

——————

11 The Cour t attempts to c abinits ho lding by suggesting that a “rigor

ous formof co s t -b enefit a n alys is ,” s u ch a s t h e form“ p res crib e d under the sta t ute’ s f o r m erBPT st andar d ,” may not be per m i t ted forset t ing BTA reg u lati ons. Ante , a t1 3

. Thus the Court ha s effectively in

s t ruct ed t h e Agenc yt h a titca n perf orm a cost-benefit analysis so lon g as it does not r e semble the kind of cos t -benefit anal ysis Congress elsewhere authorized in the CWA. The major i ty ’ s sug g e sted li mit o n the Agency’s discretion can only ber e ad as a c o n c essionth at c o st

ben e fit an aly s is, as ty pic a ll yper f or med, maybe inc o nsistent with the BTA manda t e.

12 The “national performance stan dards” the EPA adopted were shaped by economic efficiency co nc e r ns at the expense of finding the tec h n o logythat be st m i n i m i zes adv e rs e environm ent a l im pa ct
. In its final rulemaki ng, the Agency declinedto r e qu ir e in du str i al pl an ts t o adopt closed-c ycle cooling t e chnolo gy , w h ich b yreci rcu la t i ng cooling waterr e qu ir es less waterto be with dr awnan d thu s fewer aqu ati c organisms to be killed. Ri verk eep er, In c. v. EPA , 358 F. 3d 174, 18 2, n . 5 (CA2 20 0 4); 69 Fed. Re g . 41601, an dn . 44. This the Agency de

cided des p it e it s a c knowledgm e ntt h a t“ c los e d-cycle, recirc ula t ing cooling s y s t em s . . . ca n redu ce m o rt a lity from impingement by up to 98 per c e n tan d en tr ain m en t byu p to 98 per c e n t .” Id. , at 4160 1. Th e EPA instead permi tted individual plants tor e s o r tto a “suite ” of options so longas the method used r e duc e d imping ement and entr ainment bythe mor emodest amou n tof 80 an d 60 per c e n t , r e spec tiv e ly

. See 40 CFR §125.9 4 (b). T h e Ag en cyals oper m ittedi n div i du al pla n ts to o b ta ina s i t e -specific va ria n ce fromt h e na t i ona lperform a nce s t a n da rds if t h ey could prove ( 1 ) t h a tcom p lia n ce cos t s would b e“ s ignifica nt ly grea t e r than” those th e Agency cons idered wh en e s tabli s hing the standard s, or (2) that com p liance costs “would bes i g n ific antlygr eaterthan the benefits of c o mply ingwith the applic ab le per f or mance standar d s, ” §125.9 4 (a)(5).

13 Thus , the Agency ’s pa st relia nce on a “wholly dis p roportiona te” s t a n da rd, a m ild va ria n t of cos t -b enefit a n a l ys is , is irreleva nt
. S ee ante , at 14. Bec a u s e “Co n gr ess h a s di rectly spoken to the precise12 ENTERGY C O RP. v. RIVERKEEPER, I N C. S TEVENS , J., di s s e nting 

### Because we granted ce rtiorari to decide only whether t h e EPA has a u thority to conduct cost-benefit analysis, there is no need to define the universe of considerations upon which the EPA can properly re ly i nadministering the BTA standard. I would leav e it to the Agency to d e cide how to proceed in the first instance. III Because th e Court uns ettles the sc heme Congress estab

lished, I res p ectfully di ssent.

—————— question at i s sue,” Chevron , 46 7 U. S., a t 842, lon g stan din gy e t impe r m i s s ib le a g ency pra c t i ce ca n n otripen int o perm is s ib l e a g encypra c t i ce.