p. 1



# OAR Box 1168

Prepped by Ollie Stewart



### Document

Number: 

# 92 ) ll-C-2 1

Docket Number: 

# A-89-1 0

Printed 4/29/2008 11:23:20 AM Sheet 92 of 131P. 2

•i ^ ° S, 4r*. 

# jm.

*>' i 4 < PHO' * UNITE D STATE S ENVIRONMENTA L PROTECTI C Offic e o f Ai rQualit yPlannin g an d Stan d Researc h Triangl e Park , Nort h Carolin a 2 

# A-89-1 0

II-C-2 1



### Apri l 10 , 199

0 

### FE B I f

. 199 1
1 EP A AI R DOCKE T Dea r Re g Ne g Committe e Member :
A t th e las t Re g Ne g meeting , i t wa s requeste dtha t w e provid e a write-u p describin g th e revision s tha t w e hav e mad e t o th e databas e a s presente db y Rober t Pahel-Short . Hi s presentatio ni s Attachmen t 7 o f th e Meetin g Minutes . Thi s lette r describe s th e tw o refinement s w e hav e mad e t o th e previou s versio n(2/14/90 ) o f th e ethylen e oxid e (EO) an dbutadien e (BD ) databases . First , w e hav e identifie dsevera l screenin g value s tha t shoul dhav e bee n marke da s "pegged" , bu t wer e not . We identifie dthes e by revie w o f th e raw data , an

d comparin g them

wit hth e computerize ddatabases . Thes e correction s had1ittl e impact . Th e secondan

dmor e significan t chang e i s relate dt o th e emissio n factor s use dwit hscreenin g value s greate r tha n10,00 0 ppm . Inth e origina l CM A reportin g o f th e E 0 an d B D dat a an

d i nth e 2/14/9 0 database , th e SOCM I lea kfactor s wer e use dfo r al l screenin g value s greate r tha no r equa l t o 10,00 0 ppm . Thi s wa s don e becaus e th e dat a a t a majorit y o f th e plant s include dvalue s wher e th e screenin g instrumen t wa s "pegged " a t 10,00 0 ppm . Sinc e th e SOCM I lea kfactor s wer e derive dfro m plant s wit hhighe r lea k frequencies , thi s facto r ver y likel y overstate s th e emission s from component s a t th e E O an

dB D plant s which , a s a group , hav e muc hlowe r lea kfrequencies . Therefore , fo r th e plant s wher e screenin g value s wer e equa l t o o r greate r tha n 10,00 0 pp

m an d wer e no t pegged , w e recalculate demission s fro m th e correlatio n curve . Also , w e use dthes e dat a t o deriv e a new lea kfacto r an

dapplie dit , instea do f th e SOCM I lea kfactor , t o thos e component s screene da s bein g pegged . Thi s result s i nlea kfactor s tha t ar e lowe r fo r al l components , excep t flanges . Inaddition , w e considere dhow dat a woul db e generate da t plant s tha t wil l b e subjec t t o th e standar di nth e future . I t i s reasonabl e t o expect , a t plant s tha t ar e runnin g LDA Rprograms , tha t th e screenin g dat a collecte di n th e LDA Rprogram s wil l b e use dt o estimat e emissions . However , i t appear s tha t thi s approach , alon g wit hcurrentl y availabl e emissio nfactors , may overstat e emissions . Th e reaso ni s tha t screenin g value s i nLDA Rprogram s ar e obtaine dbefor e repair s ar e made . Sinc e repair s ar e mad e immediatel y afte r th e screening , th e before-repai r reading s overstat e averag e emission s fo r th e period . Fo r example , i f reading s an drepair s ar e mad e a t th e en do f th e quarter , a t day

90 , th e emissio nestimate s wil l represen t th e emission s d nday 90 . O nda y 91 , emission s wil l b e lowe r du e t o th e repairs . Emission s wil lP. 3 

# 1

increas e ove r time unti l th e nex t roundo f screening s an drepairs , whic hwoul d occu r o nda y 18 0 i na quarterl y

program . Averag e emission s wil l depen do nth e progressio no f leak s durin g th e quarter . However , it seem s reasonabl e t o assume tha t th e emission s correspon dapproximatel y t o th e averag e o f befor e an dafter-repai r screenin g values . T o examin e th e effec t o f this , w e looke da t th e E O an dB D data . Sinc e w e hav e no after-repai r data , w e hadt o estimat e th e effec t o f repair . Severa l option s wer e possible . On e i s t o assum e repaire dcomponent s hav e n o detectabl e emissions . Anothe r i s t o assume tha t component s ar e repairedt o jus t belo w

th e leakdefinition . A third , an

dth e on e w e used , i s t o assume tha t th e distributio no f emissio nrate s amon g repaire dcomponent s mirror s th e distributio namon g non-leakin g components . Robert' s las t 2 overhead s illustrate dthi s result . Thi s seem s reasonable , give ntha t repaire d component s woul dexhibi t variatio ni nthei r degre e o f repai r dependin g onth e component' s physica l condition . Base donou r assumptio ntha t th e repairedcomponent s emi t a t th e sam e rat e a s th e averag e non-leakin g components , w e ca ncalculat e anafter-repai r emissio nfactor . We coul dthe naverag e th e before-repai r factor s tha t wer e calculate ddirectl y

from th e E O an

dB D data , wit hth e after-repai r factor s t o determin e a

nestimat e o f wha t averag e emission s ove r th e quarte r woul dbe . We believ e thi s i s a reasonabl e approac hfo r estimatin g th e averag e emission s fo r a uni t tha t i s meetin g a specifie dpercen t lea klevel . I f yo u hav e an

y questions , o r woul dlik e a copy o f th e update ddatabas e pleas e cal l me a t (919 ) 541-5262 . Sincerely , 

## AC^tJZ LdZy£- — Ric kColye r Standard s Developmen t Branc h

cc : Intereste dpartie s