^,,£Dsr^^ ^ UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y REGIO N 8 ^^KKi> y g 159 5 Wynkoo

p Stree t ^.'iwlWfc' /

DENVER , C O 80202-112 9 '^^ i PR0^^ ^ ^^°^ ^ 800-227-891 7 http://www.epa.gov/region0 8 

## JUM1 0 201 1 Ref : 8P-A R Brian Gustafson , Administrato r Ai r Quality Progra m South Dakot aDepartmen t o f Envirormien t

an dNatural Resource s 52 3 Eas t Capito l Avenu e Pierre , Sout

h Dakot a57501-318 2 RE : EP A Respons e t o Jim e 1 , 201 1 Letter o n Regiona l Haz e Stat e Implementatio n Pla n
Dea r Mr , Gustafson : W e ar e providin g thi s correspondenc e i n respons e t o you r lette r date dJun e 1 , 2011
. W e appreciat e you r

ongoin g effort s t o wor

k with u s t o enhanc e you r

Regiona l Haz e Stat e Implementatio n Plan (SIP)
. A t thi s stag e i n th e SI P process , w e recogniz e th e nee dt o reac h resolutio n o n aSI P revisio n an dwil l addres s onl y critica l point s fromyou r Jun e letter
. Emissio n limit s fo

r Bi g Ston e I : W e appreciat e C>tte r Tai l Powe r

Company' s willingnes s to accep t th e emissio n limit s w e hav e recommended
. W e understan dtha t th e emissio n limit s for NO x an dSO 2 presente di n you r

draf t revisio n for

th e Administrativ e Rule s o f Sout h Dakota , chapte r 74:36:2 1 wil l appl y at

al l times , includin g startu p an dshutdown , an db e include di n you r nex t SI P submittal
. Complianc e tes t

metho dfor

particulat e matter : W e continu e t o prefe r anarrowe r

lis t o f tes t metho doption s a s detaile din ou r May 16 , 201 1 email , however , w e ar e satisfie dthat your suggeste dapproac h t o includ e th e referenc e t o th e Sout h Dakot aperformanc e testin g method s rul e wil l ensur e adequat e enforceability o f th e particulat e matte r

emission s limits
. T o eliminat e possibl e confusio n an denforcemen t challenge s with th e inclusio n o f separat e irrelevan t

sub

section s o f

chapte r 74:36:11 , w e sugges t

yo u revis e th e referenc e t o 74:36.11.0 1 whic h w e suspec t wa s you r origina l intent
. Continuou s emissio n monitorin g syste m(CEMS ) requirements : W e appreciat e you r agreemen t t o chang e th e referenc e i n 74:36:21:0 9 t o 4 0 CF RPart 75 , Ou r recommendatio n i n thi s regard result s in certai n reportin g dilemma s tha t wer e no t fiilly detaile di n ou r

May email
. 4 0 CFR75,6 4 require s submitta l o f

quarterl y Electroni c Dat aReport s directl y t o th e EP A Administrato r wit hn o cop y t o th e state
. Th e genera l approac h othe r state s hav e use dan dwhic h w e findacceptabl e involve s providin g clarificatio n in th e states ' Regiona l Haz e rules
. Fo r South Dakota , thi s woul d involv e fiirther

revisin g th e referenc e i n 74:36:21:0 9 a s w e offe r below : "Monitorin g o f

sulfij r dioxid e an dnitroge n oxid e emission s fromth e mai n stac k o f a BART-eligibl e sourc e shal l b e conducte dusin g acontinuou s emissio n monitorin g syste m whic h complie s wit h th e followin e specifi c continuou s emissio n monitorin g requirement s i n 4 0 CF RPart

7 5 (Jul y 1 , 2009 ) an d4 0 CF RPart 6 0 (Jul y 1
. 2009^ :
• BAR T CEMS s shal l b e certified , maintained , calibrate dan doperate d i n accordanc e with 4 0 CFRPar t 75
. Continuou s monitorin g o f SO ? emission s shal l mee t

th e requirement s o f

4 0 CF R75.11
. Continuou s monitorin g o f

NO v emission s shal l mee t

th e requirement s o f

4 0 CF R 75.12
. • BAR T CEMS s recordkeepin g an dreportin g shal l b e i n accordanc e wit h th e requirement s o f

4 0 CF R60.7
. Vali dCEM S dat ashal l mee t th e requirement s o f

4 0 CF R60,13
. Emission s i n Ib/MMBtu for BAR T complianc e shal l b e calculate da s specifie di n th e definitio n o f

30-da v rollin g average a t 74:36:21:02(10). " Reasonabl e Progres s four-facto r analysis : W e woul dlik e t o acknowledg e th e additiona l effor t require dt o performarevise dfour-facto r analysi s for

GC C Dacotah an dar e please dwith you r willingnes s t o procee dwit h this
. W e offe r ou r assistanc e t o revie w adraf t o f thi s analysi s whe n i

t i s availabl e before yo u mov e forwardwith processin g arevise dSIP
. Your genera l approac h o n al l othe r item s discusse din you r

Jun e lette r

appear s satisfactory ; however , w e wil l onl y reac h afinal conclusion , an dperfor mou r complet e review , regardin g th e adequac y o f

Sout h Dakota' s Regiona l Haz e SI P whe n w e ac t o n th e Sout

h Dakot aRegional Haz e SI P revisio n throug h ou r owo i publi c notic e an dcommen t rulemaking
. We are availabl e t o discus s an y remainin g concem s yo u ma y hav e wit

h th e Regional Haz e SIP
. I f yo u hav e an y question s o n EPA' s comments , pleas e contac t m e a t (303 ) 312-6416 , o r

you r staf f may contac t

Gai l Fallo n at

(303 ) 312-6281 , Sincerely , 

# OJ 6

Car l Daly , Directo r Ai r Program