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# y UNITE D STATE S ENVIRONMENTA LPROTECTIO N AGENC Y Offic e ofAi rQualityPlannin g an d Standard s Research Triangl e Park , Nort h Carolin a 2771 1 

## Pt- 70-37

MA Yi9ag Mr
. Joh nPau l Supervisor , Regiona l Ai r Pollutio n Contro l Agency 45 1 W . Third Stree t P.O . Bo x97 2 Dayton , Ohi o 4542 2 Dea r Mr . Paul : }2 A .\.ii')•>

A s w e agreed , I a

mproviding yo u wit ha draf t cop yfo r revie wb

yth e STAPPA/ALAPC O NS RSubcommitte e o f a summaryo f "top-down " BAC T guidance . Th e draf t i s als o being concurrentl y reviewe d b

yth e EPARegiona l Offices . Pleas e hav e the Subcommitte e submi t thei r comment s b yJun e 19 , 1989 . W e ar e currentl yworking o ndeveloping mor e detaile d "top-down " BAC T guidanc e material . However , i nrespons e t o some o f th e broade r question s an d issue s raise d b

yStat e an

d loca l agencie s an

d permi t applicant s regarding th e implementatio n o f "top-down " BACT , w e hav e prepare d th e attache d summarydocument . Th e purpos e o f th e documen t i s t o ac t a s a genera l guid e through th e "top-down " proces s unti l th e mor e detaile d guidanc e become s available . I f yo u hav e an

yquestion s abou t th e draf t document , pleas e contac t me a t FT S 629-562 1 o r Mr . Davi d Solomo no f th e NewSourc e Revie wSectio na t (FTS ) 629-5375 . Sincere ]

Ai r Johncaacagn i / Directo r (lit yManagemen t Divisio n Enclosur e cc : G . Emiso n(w/enclosure ) W . Becke r (w/enclosure ) Ai r Divisio n Director , Region s I-X(w/enclosure )P. 3

* •* • •*•-rA r * DRAF T •*••*••*••*•*

"TOP-DOWN " BES T AVAILABLE CONTROL TECHNOLOGY :

A SUMMAR Y

Environmenta l Protectio nAgenc y Offic e o f Ai r Qualit yPlanning and Standard s

Ai r Managemen t Divisio n Noncriteri a Pollutant s ProgramBranc h Ne wSourc e Revie wSectio n

May25 , 198 9P. 4

•*•*•*•*•* • DRA.F T •**••*•* *

TOP-DOW N BACT : A

SUMMAR Y
I . BACKGROUN

D O nDecembe r 1 , 1987 , th e Environmenta l Protectio nAgency' s (EPA ) Assistan t Administrato r fo r Ai r an d Radiatio n issue d a memorandu

mtha t establishe d certai nprogra m initiative s designe d t o improv e th e effectivenes s o f th e ne wsourc e revie wprograms . Amon g thes e wa s th e "top-down " methodologyfo r determining bes t availabl e contro l technology(BACT) . Th e Offic e o f Ai r Qualit y Planning an

d Standard s i s responsibl e fo r implementing man yo f thes e initiatives , including th e developmen t o f specifi c guidanc e o nth e "top-down " approac ht o determining BACT . Recently , thi s offic e ha s receive d numerou s inquirie s from th e EPARegiona l Offices , Stat e an

d loca l agencie s an d permi t applicant s requesting guidanc e o n th e implementatio no f "top-down " BACT . Th e purpos e o f thi s overvie wi s t o provid e a genera l summaryo f th e "top-down " methodologyi norde r t o assis t permitting authoritie s an

d preventio no f significan t deterioratio n(PSD ) applicant s i nconducting BAC T analyses . Th e EPAi s als o currentl yworking o n additiona l guidanc e material . I ncalling fo r th e us e o f th e "top-down " approac hi nBAC T determinations , EPAha s no t change d th e BAC T requiremen t fo r an y specifi c sourc e o r categoryo f source . Th e definitio n o f BAC T a s containe d i n th e Clea n Ai r Act , th e PS D regulation s an d th e Stat e implementatio nplan s o f individua l State s ha s no t changed . Rather , th e "top-down " approac hi s a chang e i nth e methodologyo f th e BAC T selectio n process . Ther e ar e tw o keycriteri a tha t mus t b e satisfie d i nan yBAC T analysi s unde r th e Clea nAi r Act . First , th e permi t applican t mus t conside r the mos t stringen t contro l technologie s available . Second , i f th e applican tP. 5

••* ? •*• • * -*e •*• DRAF T •*•*•*••*•• * propose s les s stringen t controls , i t mus t demonstrate , usin g objectiv e data , tha t th e mos t stringen t control s ar e no t achievabl e du e t o source-specifi c energy , environmental , o r economi c impacts , an d th e permitting authorit ymus t exercis e it s informe d judgmen t befor e accepting tha t determination . Th e EPA' s experienc e wa s tha t prio r BAC T methodologie s wer e deficien t i n fulfillin g th e cor e BAC T requirements . Th e EPAexpect s tha t th e top-down approac hwil l b e mor e effectiv e i nassuring tha t BAC T analyse s compl ywit hthes e requirements . II . TH E "TO P DOWN " PROCES S Th e firs t ste p i na "top-down " analysi s i s t o identify , fo r th e emission s uni t i nquestion , al l "available " contro l options . Availabl e contro l option s ar e thos e ai r pollutio ncontro l technologie s wit ha practica l potentia l fo r applicatio nt o th e emission s uni t and th e regulate d pollutan t unde r evaluation . Th e contro l alternative s shoul d includ e no t onl yexisting control s fo r th e sourc e categoryi nquestion , bu t als o (throughtechnology transfer ) control s applie d t o simila r sourc e categorie s and ga s streams , an

d innovativ e contro l technologies . Technologie s require d unde r lowes t achievabl e emissio nrat e (LAER ) determination s ar e availabl e fo r BAC T purpose s an d mus t als o b e include d a s contro l alternatives . Late r i nth e BAC T analysis , on e o r mor e o f th e option s may b e eliminate d from consideratio nbecaus e the yar e determine d t o b e technicall yinfeasibl e o r hav e unacceptabl e energy , economic , an d environmenta l impact s o na case-by-cas e basis . However , a t th e outset , applicant s shoul d identif y(bu t not , a t thi s time , conduc t a detaile d stud yof ) al l contro l option s wit hpotentia l applicatio n t o th e emission s uni t unde r review .P. 6

-*-•*--*•*-•*

- DRAF T

I nth e second step , th e technica l feasibilit yo f th e contro l option s identifie d i nstep on e i s evaluate d wit hrespec t t o th e source-specifi c factor s a t th e emission s unit . I ngeneral , a demonstratio no f technica l infeasibilit yshoul d b e clearl y documente d an

d shoul d show , base d o nphysical , chemical , an d engineering principles , tha t technica l difficultie s woul d preclud e th e successfu l us e o f th e contro l optio no nth e emission s uni t unde r review . Technicall yinfeasibl e contro l option s ar e the n eliminate d fro mfurthe r consideratio ni nth e BAC T analysis . Fo r example , i ncase s wher e th e leve l o f contro l i na permi t ha s no t ye t bee nachieve d i npractic e (e.g. , a sourc e committe d t o a permitte d leve l bu t th e projec t wa s cancelle d o r th e permitting agenc yha s foun d tha t th e permi t limitation s ar e unachievabl e b

yth e permitte d source) , and supporting documentatio nshowing wh ysuc hlimit s ar e no t technicall y feasibl e i s provided , th e optio nmayb e eliminate d fromfurthe r consideration . I nstep three , al l remaining contro l alternative s no t eliminate d i nste p tw o ar e ranke d i norde r o f contro l effectiveness , wit hth e mos t effectiv e contro l alternativ e a t th e top . Th e lis t shoul d presen t th e arrayo f contro l alternative s an d includ e th e following :

- contro l efficiencie s (percen t pollutan t removed) ;

- expecte d emissio nrat e (ton s pe r year) ;

- expecte d emission s reductio n(ton s pe r year) ;P. 7

-*• * •*• •*• •*• DRAF T •*••*••*•*••* •

- economi c impact s (e.g., ; cos t pe r ton , incrementa l and tota l costs) ;

- environmenta l impact s (include s an ysignifican t o r unusua l othe r medi a impact s (e.g. , wate r o r soli d waste) , and , a t a minimum , th e relativ e abilit yo f eac hcontro l alternativ e t o contro l emission s o f toxi c o r hazardou s ai r contaminants) ;

- energ yimpacts . Alis t shoul d b e prepare d fo r eac hpollutan t an d fo r eac h emission s uni t (o r groupin g o f simila r units ) subjec t t o a BAC T analysis . A t thi s poin t th e analysi s validate s th e suitabilit yo f th e to p contro l optio ni nth e listing fo r selectio na s BACT , o r provide s clea r justificatio ntha t th e to p candidat e i s inappropriat e a s BACT . I f th e applican t accept s th e to p alternativ e i nth e listing a s BAC T froman economi c (an d energy ) standpoint , th e applican t proceed s t o conside r whethe r impact s o f unregulate d ai r pollutant s o r impact s i nothe r medi a woul d justif yselectio no f a nalternativ e contro l option . I f ther e ar e n o outstandin g issue s regarding collatera l environmenta l impacts , th e analysi s i s ende d and th e result s accepte d a s BACT . I n th e even t tha t th e to p candidat e i s show nt o b e inappropriate , du e t o energy , environmental , o r economi c impacts , th e rational e fo r thi s finding need s t o b e full yan d carefull ydocumente d fo r th e publi c record . The n th e nex t mos t stringen t alternativ e i nth e listing become s th e ne wcontro l candidat e an d i s similarl y evaluated . Thi s proces s continue s unti l th e technologyunde r consideratio n canno t b e eliminate d b yan ysource-specifi cP. 8

•*•*••*••*•• * DRAF T •*•*••*•*••* • environmental , energy , o r economi c impact s whic hdemonstrat e tha t alternativ e t o b e inappropriat e a s BACT . Th e cor e o f a BAC T analysis , afte r identificatio no f availabl e contro l options , i s th e consideratio no f energy , environmental , an

d economi c impact s t o selec t th e fina l leve l o f control . Th e applican t i s responsibl e fo r presenting a n objectiv e evaluatio no f eac himpact . Consequently , bot h beneficia l an

d advers e impact s shoul d b e discusse d and , wher e possible , quantified . I ngeneral , th e BAC T analysi s shoul d focu s o nth e direc t impac t o f th e contro l alternative . Th e following discussion , unde r eac ho f th e thre e heading s o f energy , environmental , an

d economi c impacts , briefl ytouche s o na numbe r o f factor s whic hmayb e considere d i n th e respectiv e impact s analyses . Thes e factor s provid e genera l guideline s onl yan d ar e no t intende d a s a nexclusiv e lis t o f consideration s fo r BACT . A . EnergyImpact s Applicant s shoul d examin e th e energ yrequirement s o f th e contro l technolog

yan d determin e whethe r th e us e o f tha t technologyresult s i nan ysignifican t o r unusua l energ ypenaltie s o r benefits . Asourc e may , fo r example , benefi t fromth e combustio no f a concentrate d ga s strea mric hi nvolatil e organi c compounds ; o n th e othe r hand , mor e ofte n extr a fue l o r electricit yi s require d t o powe r a contro l devic e o r incinerat e a dilut e ga s stream . I f suc hpenaltie s o r benefit s exist , the y shoul d b e quantified . Certai ntype s o f contro l technologie s hav e inheren t energ

ypenaltie s associate d wit hthei r use . Whil e thes e penaltie s shoul d b e quantified , s o long a s theyar e withi nth e norma l rang e fo r th e technologyi nquestion , suc hpenaltie s shoul d not , i ngeneral , b e considere d adequat e justificatio nfo r nonus e o f tha t technology ._ p ^

•* r • * •* • *c •* • DRAF T •*••*••*••*••* •

Energyimpact s shoul d conside r onl ydirec t energy consumptio nan

d no t indirec t energyimpacts . Fo r example , th e applican t coul d estimat e th e direc t energyimpact s o f th e contro l alternativ e i nunit s o f energ yconsumptio na t th e sourc e ( e.g. , Btu , kWh , barrel s o f oil , ton s o f coal) . Th e energyrequirement s o f th e contro l option s shoul d b e show ni nterm s o f tota l and incrementa l (unit s o f energ ype r to no f reduction ) energycosts . Th e energyimpac t analysi s mayals o addres s th e concer nove r th e us e o f locall yscarc e fuels . Th e designatio no f a scarc e fue l mayvaryfrom regio nt o region , bu t i ngenera l a scarc e fue l i s on e whic hi s i nshor t suppl ylocall yan d ca nb e bette r use d fo r alternativ e purposes , o r on e whic hmayno t b e reasonabl y availabl e t o th e sourc e eithe r a t th e presen t tim e o r i nth e nea r future . B . Environmenta l Impact s Th e environmenta l impact s analysi s i s no t t o b e confuse d wit hth e ai r qualit yimpac t analysis , whic hi s conducte d t o demonstrat e tha t th e sourc e (using th e leve l o f contro l eventuall yselecte d a s BACT ) wil l no t caus e o r contribut e t o a violatio no f an

yapplicabl e nationa l ambien t ai r qualit ystandar d o r PS D increment . Th e environmenta l impact s analysis , i n contrast , concentrate s o nimpact s othe r tha nimpact s o n ai r qualit y(i.e. , ambien t concentrations ) du e t o emission s o f th e regulate d pollutan t i n question , suc ha s soli d o r hazardou s wast e generatio no r discharge s o f pollute d wate r froma contro l device , visibilit yimpacts , o r emission s o f unregulate d pollutants .P.1 0

**** * DRAF T *•**•* * Th e applican t shoul d identif yan ysignifican t o r unusua l environmenta l impact s associate d wit ha contro l alternativ e tha t hav e th e potentia l t o affec t th e selectio no r rejectio no f a contro l alternative . Some contro l technologie s mayhav e potentiall ysignifican t secondaryenvironmenta l impacts . Scrubbe r effluent , fo r example , mayaffec t wate r qualit yan d lan d use , and , similarly , technologie s using cooling tower s mayaffec t visibility , othe r example s o f secondaryenvironmenta l impact s coul d includ e hazardou s wast e discharges , suc ha s spen t catalyst s o r contaminate d carbon . Generally , thes e type s o f environmenta l concern s become importan t whe nsensitiv e site-specifi c receptor s exis t o r whe n th e incrementa l emission s reductio npotentia l o f th e to p contro l i s onl ymarginall ygreate r tha nth e nex t mos t effectiv e option . However , th e fac t tha t a contro l devic e create s liqui d and soli d wast e tha t mus t b e dispose d o f doe s no t necessaril yargu e agains t selectio no f tha t technologya s BACT , particularl yi f th e contro l devic e ha s bee napplie d t o simila r facilitie s elsewher e an d th e soli d o r liqui d wast e problemunde r revie wi s no t significantl ygreate r tha ni nthos e othe r applications . O n th e othe r hand , wher e th e applican t ca nsho w tha t unusua l circumstance s a t th e propose d facilit ycreat e greate r problem s tha nexperience d elsewhere , thi s mayprovid e a basi s fo r th e rejectio no f th e to p contro l alternativ e a s BACT . Th e generatio no r reductio no f toxi c an d hazardou s emissions , including compound s no t regulate d unde r th e Clea nAi r Act , ar e considere d a s par t o f th e environmenta l impact s analysis . O nJun e 23 , 1986 , th e EP AAdministrato r remande d th e PS D permi t decisio nfo r th e Nort hCount yResourc e Recovery projec t i nCaliforni a t o EPARegio nX I fo r reconsideration . A t issu e i nth e remand wa s whethe r appropriat e consideratio nha d bee ngiven , withi nth e BAC T determination , t o th e contro l o f ai rp.1 1

* • * * • • * * • DRAF T *•*••**• * pollutant s no t subjec t t o regulatio nunde r th e Clea nAi r Act . Th e remand strongl yaffirme d tha t th e permittin g authorit yshoul d tak e int o accoun t th e abilit yo f a give ncontro l alternativ e fo r regulate d pollutant s t o reduc e emission s o f unregulate d pollutant s i nmakin g BAC T decisions . Consequently , th e abilit y o f a give ncontro l alternativ e t o contro l toxi c o r hazardou s ai r contaminant s mus t b e considere d i nth e BAC T analysi s and , a s appropriate , raayaffec t th e outcome o f th e analysis . C . Economi c Impact s I nth e economi c impac t analysis , primaryconsideratio n shoul d b e give n t o quantifying th e cos t o f contro l (e.g. , tota l cost , dollar s pe r to n o f pollutan t removed , incrementa l cost s pe r to no f pollutan t removed ) an d no t th e economi c situatio no f th e individua l source . Fo r contro l alternative s tha t hav e bee n effectivel yemploye d i n th e same sourc e category , th e economi c impac t o f suc halternative s o nth e particula r sourc e unde r revie w shoul d b e no t nearl ya s pertinen t t o th e BAC T decisio nmakin g proces s a s th e tota l an d incrementa l cos t effectivenes s o f th e alternative . Thus , wher e a contro l technologyha s bee n successfull yapplie d t o simila r source s i na sourc e category , an applican t shoul d concentrat e o ndocumenting significan t cos t differences , i f any , betwee nthos e othe r source s and th e particula r sourc e unde r review . Normall yth e submitta l o f verydetaile d and comprehensiv e projec t cos t dat a i s no t necessary . However , wher e initia l contro l cos t projection s o nth e par t o f th e applican t appea r excessiv e o r unreasonabl e (i nligh t o f recen t cos t data ) mor e detaile d an

d comprehensiv e cos t dat a mayb e necessaryt o documen t th e applicant' s projections .P.1 2

* * * * * DRAF T •*•*•* * •*• I t i s importan t t o kee p i nmind tha t BAC T i s a primaril y technology-base d standard . However , unusua l circumstance s may greatl yaffec t th e cos t o f control s i na specifi c applicatio nan d shoul d b e documented . A nexampl e o f anunusua l circumstanc e migh t b e th e unavailabilit yi na nari d regio no f th e larg e amount s o f wate r neede d fo r a scrubbing system . Shipping wate r froma distan t locatio nmigh t add unreasonabl e cost s t o th e alternative , thereb yjustifying it s rejectio no neconomi c grounds . Wher e unusua l factor s exis t tha t resul t i n cost/economi c impact s beyond th e rang e normall yincurre d b yothe r source s i ntha t category , th e technologycanb e rejecte d provide d th e applican t ha s adequatel yidentifie d th e circumstances , including th e cos t o r othe r analyses , tha t sho wwha t i s significantl ydifferen t abou t th e propose d source . Wher e th e cos t o f a contro l alternativ e fo r th e specifi c sourc e being reviewe d i s withi nth e rang e o f norma l cost s fo r tha t contro l alternative , th e alternativ e mayals o b e eligibl e fo r rejectio ni n limite d circumstances . Thi s mayoccur , fo r example , wher e th e contro l alternativ e ha s no t bee nrequire d a s BAC T (o r it s applicatio na s BAC T ha s bee n extremel ylimited) , an d ther e i s a clea r demarcatio nbetwee nrecen t BAC T contro l cost s i n tha t sourc e categoryan d contro l cost s fo r source s i nth e categorywhic hhav e bee ndrive nb yothe r constraining factors . T o justif yrejectio no f a nalternativ e o nthes e grounds , th e applican t mus t demonstrat e t o th e satisfactio no f th e permittin g agenc ytha t cost s o f pollutan t remova l (e.g. , dollar s pe r tota l to nremove d an

d i nsome instance s incrementa l to nremoved ) fo r th e contro l ar e disproportionatel yhighwhe ncompare d t o th e cos t o f contro l fo r th e pollutan t i nrecent , acceptabl e BAC T determinations . Specifically , th e applican t mus t documen t tha t th e cos t t o th e applican t o f th e contro l alternativ e i s


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**-** * DRAF T ***** * significantl ybeyond th e rang e o f recen t cost s normall y associate d wit hBAC T fo r th e typ e o f facilit y(o r BAC T contro l cost s i n general ) fo r th e pollutant . Thi s typ e o f analysi s shoul d essentiall ydemonstrat e tha t a technicall yan d economicall yfeasibl e contro l optio ni s nevertheless , b yvirtu e o f th e magnitud e o f it s associate d cost s an d limite d application , unreasonabl e o r otherwis e no t "achievable " a s BAC T i nth e particula r case . Tota l cos t an d cos t effectivenes s number s shoul d b e factore d int o thi s analysis . However , suc heconomi c informatio n mus t b e couple d wit ha comprehensiv e demonstration , base d o nth e othe r objectiv e factor s describe d i nthi s document , tha t th e technologyi s inappropriat e i n th e specifi c circumstance . Also , th e BAC T analysi s shoul d no t focu s o nonl yon e elemen t o f th e economi c analysis , a s th e result s mayb e misleading . I n particular , undu e focu s o nincrementa l cos t effectivenes s ca n giv e a nimpressio ntha t th e cos t o f a contro l alternativ e i s unreasonabl yhighwhe ni nfac t th e tota l cos t effectivenes s i s wel l withi nth e norma l range . Fo r anothe r example , ther e mayb e a cas e wher e th e capita l cos t o f a contro l optio nappear s excessiv e whe npresente d a s a percen t o f th e tota l projec t cost . However , i f i n thi s cas e a larg e emission s reductio ni s projected , lowo r reasonabl e cos t effectivenes s number s ma y validat e th e optio n a s a nappropriat e BAC T alternativ e irrespectiv e o f th e hig hcapita l costs . D . Othe r Consideration s Example s o f othe r possibl e circumstances , no t necessaril y economi c i nnature , whic hmigh t affec t a BAC T analysi s are :



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•*•*•*•* * DRAF T *•*•*•*• * 1 ) Whe nexceeding otherwis e appropriat e cost s b ya moderat e amoun t woul d resul t i na substantia l additiona l emission s reduction . 2 ) Whe na contro l technolog ywoul d achiev e control s o f mor e tha non e pollutan t (including toxi c pollutants) . 3 ) Wher e th e propose d BAC T leve l woul d caus e a violatio no f a napplicabl e ai r qualit ystandar d o r increment . Apermi t canno t b e issue d t o a sourc e tha t woul d caus e o r contribut e t o suc ha violation . 4 ) Whe nther e ar e lega l constraint s outsid e o f th e Clea nAi r Ac t requiring th e applicatio no f a mor e stringen t technology tha non e whic hotherwis e woul d hav e bee ndetermine d t o b e ; BACT . I nal l cases , a complet e BAC T analysi s mus t conside r environmenta l an

d energy , a s wel l a s economi c impact s i nth e BAC T analysis . III . SUMMARY
I nsummary , al l availabl e contro l technologie s ar e ranked , an d th e mos t stringen t alternativ e i s considere d initiall yi nth e BAC T analysis . However , whe nsupporte d b ya complet e an

d objectiv e review , technologie s tha t ca n b e demonstrate d t o b e infeasible , unreasonable , o r otherwis e no t achievabl e considering source-specifi c energy , economic , environmental , o r technologica l reason s ca nb e se t aside .

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