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### Document

Number: 

# 93 ) IV-B- 1

Docket Number: 

# A-84-2 2

Printed 4/18/2008 10:52:09 AM Sheet 93 of 94 p. 1P. 2 

# RADIA N CORPORATIO N MEMORANDU M 

# A-84-2 2 IV-B- 1

TO : FROM : DATE : Opacit y

Metho dProjec t Fil e Ki m S . Kepford , Radia nCorporatio n Februar y 6 , 199 1 

# jjUaJLUj /

i H !



# 1 " - j L EP A AI R DOCKE T

SUBJECT : Consideration s o f Opacit y Erro r i n Visibl e Emission s Testin g

1. 0 INTRODUCTIO N Thi s memorandum

discusse s th e concept s o f erro r and bias . I t include s section s o n ho w

thes e concept s ar e characterize di n eac ho f th e thre e propose d method s fo r measurin g opacity , an d ho w the y influenc e complianc e determination . Th e thre e method s referre dt o in thi s memorandum ar e a s follows : (1 ) Metho d203 A

- - Visua l Determinatio no f Opacit y Emission s Fro

m Stationar y

Source s fo r Time-Average dRegulations ; (2 ) Metho d203 B - - Visua l Determinatio no f Opacit y Emission s Fro

m Stationar y

Source s fo r Time-Exceptio nRegulations ; an d (3 ) Metho d203 C - - Visua l Determinatio no f Opacit y Emission s Fro

m Stationar y

Source s fo r Instantaneous-Limitatio nRegulations . Section s 2.0 , 2.1 , an d 2. 2 provid e genera l discussion s o f decisio nan d metho derrors . Sectio n2. 0 i s a n introductio nt o th e type s o f erro r discusse d i nth e memorandum . Sectio n2. 1 present s th e description s an d theoretica l consideration s o f decisio nerrors . Sectio n2. 2 provide s a descriptio no f possibl e metho derror s an d th e relativ e importanc e o f each . Sectio n3. 0 discusse s bias , alon g wit hth e concept s o f precisio nan d accuracy . Als o include di s an*explanatio no f how bia s an d erro r ar e related . Sectio n4. 0 present s a brie f descriptio no f th e propose dopacit y measuremen t methods . Section s 4.1 , 4.2 , an d 4. 3 discus s th e erro r an d bia s associate dwit heac ho f th e thre e methods . Informatio nprovide di n thes e section s include s th e positiv e and negativ e erro r estimate s fo r eac ho f th e methods . Sectio n5. 0 provide s a discussio non how th e erro r an

d bia s associate dwit heac hmetho d shoul db e considere dwhe nchoosin g a standar dfo r th e regulatio no f opacity . Particula r attentio ni s pai dt o ho w thes e value s affec t complianc e determination .

Progres s Center/320 0 E

. Chape l Hil l Rd./Nelso n Hwy./P.O

. Bo x13000/Researc h Triangl e Park

. N. C 27709/(919)54 1 910 0P. 3

2. 0 INTRODUCTIO N

T O ERRO R Erro r ca nb e though t o f a s uncertaint y o r variabilit y

i na give nmetho d
o r i nth e us e o f tha t method . Ther e ca nbe erro r inth e procedure s withi na tes t metho do r i nth e applicatio no f metho dresults , and thes e source s o f
erro r wil l b e considere dseparately . Sectio n2. 1 discusse s error s i nth e decision-makin g process . Error s inth e tes t metho dresul t i neithe r a nover o r underestimatio no f th e actua l opacity , an d wil l b e discusse di n Sectio n2.2 .
2. 1 Decisio nErro r Inth e decision-makin g process , tw o type s o f erro r ar e possible . Th e firs t typ e o f erro r ("Typ e I" ) woul db e t o falsel y cit e a sourc e a s a violatio nwhe ninfac t i t i s no t ou t o f compliance . Th e secondtyp e o f erro r ("Typ e II") woul db

e t o fai l t o cit e a sourc e tha t actuall y i s ou t o f compliance . Th e tw

o type s o f erro r ar e inversel y related , an

d a Stat e mus t decid e whic htyp e o f erro r i t wishe s t o reduc e th e most . Th e amoun t o f negativ e o r positiv e erro r withi na tes t metho daffect s th e erro r mad e inth e decision-makin g process . Thus , whe nconsiderin g th e relativ e amoun t o f eac htyp e o f decision-makin g erro r t o accept , i t i s importan t t o hav e informatio nonbot hth e negativ e an d positiv e erro r resultin g fro

m th e tes t method . Sectio n5. 0 discusse s ingenera l term s ho w th e erro r associate dwit heac ho f th e method s affect s complianc e determination .
2. 2 Metho dErro r Ther e ar e severa l type s o f metho derro r whic hcontribut e t o th e tota l possibl e erro r fo r eac ho f th e opacit y tes t methods . Thi s memorandum discusse s erro r resultin g fro m th e sampling , measurement , an d observatio n processes , alon g wit hgros s error s (mistakes ) inan y aspec t o f thes e procedures . Samplin g erro r i s tha t erro r du e t o th e sampl e selectio nprocess . I t result s fro

m th e natura l variatio ni nopacit y an d th e fac t tha t measurement s ar e no t take ncontinuously . A s inMetho d9 , eac ho f th e observation s i s intende dt o represen t th e "average " opacit y ove r th e 1 5 secon dinterval. - Sinc e opacit y

i s no t constantl y

monitored , th e value s reporte dar e actuall y onl y a subse t o f th e tru e opacity , whic hi s continuous . Constan t monitorin g i s no t economicall y

feasible , an

d th e natura l variatio ni nopacit y canno t b e
dkd.12 7 2P. 4

eliminated

. Effor t wa s mad e t o reduc e thi s typ e o f erro r durin g th e developmen t o f th e thre e propose d tes t methods
. Thus , th e smal l amoun t o f samplin g erro r wil l no t b e discusse d further
. Measuremen t error s resul t fro mth e collectio n process , and ar e du e t o suc h factor s a s environmenta l conditions , equipmen t characteristics , o r th e locatio n o f th e opacit yobserver
. Measuremen t error s ca n b e eithe r rando mo r systematic

. I f a certai n piec e o f equipmen t i s calibrate d incorrectly , th e error s ma yb e systematic

. I f th e equipmen t i s malfunctioning , th e resultin g error s coul d b e random
. Measuremen t error s ca n b e reduce d b yth e standardizatio n o f equipmen t and monitorin g procedures
. Ever yeffor t wa s mad e t o reduc e thes e error s durin g th e developmen t o f th e propose d tes t methods
. Thi s typ e o f erro r wil l no t affec t a State' s decisio n o n whic h metho d t o implement , an d wil l no t b e discusse d further
. Gros s error s ar e mistake s i n anyo f th e step s i n dat a collectio n o r analysis

. The yrang e fro m incorrectl yplace d decima l point s t o th e applicatio n o f invali d statistica l procedures
. Gros s error s ca n b e reduce d b ycarefull y checkin g al l dat a recordin g and transferrin g steps , alon g wit h th e appropriatenes s o f eac h statistica l procedure
. Th e reductio n o f thes e error s ha s als o bee n deal t wit h durin g th e developmen t o f th e tes t methods , an d ca n b e achieve d b

ystandar d qualit yassuranc e methods
. Th e majo r sourc e o f erro r i n th e opacit ytes t method s i s observational

. Observatio n erro r i s th e discrepanc ybetwee n observe d opacit yand actua l opacit y(a s measure d b ya transmissometer)

. I t i s du e t o th e us e o f observer s wh o estimat e th e opacit yo f a plum e base d o n thei r ow n judgement

. Effort s t o reduc e observationa l erro r includ e th e certificatio n o f al l observers , and th e us e o f averagin g technique s o n repeate d observations

. Certificatio n ensure s tha t observer s hav e bee n expose d t o prope r observationa l technique s an d tha t the yhav e me t require d proficienc ylevel s fo r estimatin g opacity

. Takin g multipl e observation s increase s th e siz e o f th e sampl e population , whic h reduce s th e differenc e betwee n observe d an d actua l opacit ylevels
. However , du e t o th e huma n judgemen t involved , observatio n erro r remain s th e larges t contributo r t o th e tota l erro r i n al l thre e tes t procedures
.

died . 12 7P. 5

3. 0 BIAS , PRECISION , AN D ACCURAC Y Bia s ca nb e define da s a consisten t under - o r overestimatio no f a value . Fo r opacity , positiv e bia s i s a resul t o f estimation s tha t ar e greate r tha n th e actua l opacit y

an dnegativ e bia s i s a resul t o f observation s tha t ar e consistentl y

les s tha nactua l opacity . Thi s memorandum consider s tw

o type s o f bias , (1 ) statistica l bias , an d(2 ) measuremen t bias . Statistica l bia s i s th e differenc e betwee nth e expecte dvalu e o f th e estimato r (observatio nvalue ) an dth e populatio nparamete r bein g estimated (actua l value) . Often , i t i s th e resul t o f th e incorrec t us e o f a statistica l procedur e suc ha s averaging . I nmos t cases , statistica l bia s ca nbe reduce d
o r eliminate db

y increasin g th e numbe r o f observations . Al l o f th e test s performe do nth e thre e opacit y measuremen t method s contai na sufficien t numbe r o f observation s t o sufficientl y reduc e statistica l bias ; a s d o the.method s themselves . Measuremen t bia s i s anothe r typ e o f consisten t under - o r overestimatio n o f th e populatio nparameter . I t ca nresul t fro m an y o f th e error s discusse d i nSectio n2.2 . Th e larges t potentia l sourc e o f bia s i nth e thre e tes t method s i s observe r error . Al l o f th e opacit y tes t method s showe da negativ e bias . Bia s i s a

nimportan t consideratio nwhe ndeterminin g compliance , an d Sectio n5. 0 discusse s i t fo r eac ho f th e methods . Precisio ni s a measur e o f th e closenes s o f agreemen t betwee ntw o individua l observations . Precisio nca nb e calculate dfo r th e observation s mad e b y on e individual , o r betwee ntw o differen t observer s measurin g th e same plume . Bia s an

dprecisio ncombin e t o giv e accuracy . Th e classi c exampl e showin g th e relationshi pbetwee nbias , precision , an daccurac y

i s t o describ e shot s a t a target , a s see ninFigur e 3-1 . Figure s 3-l(a ) an d3-l(c ) show

th e effect s o f bia s o

nth e estimation . Althoug hFigur e 3-l(c ) i s precise , intha t eac ho f th e shot s i s clos e t o th e others , i t i s no t accurat e du e t o th e presenc e o f bias . Figur e 3-1(b ) i s unbiased , bu t 1 s no t accurat e du e t o th e lac k o f precision . Figur e 3-1(d ) is . bot hprecise , an dunbiased , an

di s therefor e accurate . Th e precisio no f eac hobserve r i s measure da s par t o f th e Stat e certificatio nprocess . Observer s mus t b e recertifie dperiodicall y t o ensur e thei r precisio ni s kep t withi nth e standar dse t b y tha t State . Ensurin g th e

died . 12 7P. 6

' • -J-T - n-^ja-ja^fr, -



## (a ) (b )

(c ) (d )

Figur e 3-1 . Bia s an d Precision .

Pattern s o f shot s a t a targe t (afte r Jessen , 1978 , Fig . 1)2 . (a) : hig hbia s + low precisio n= lo

w accuracy ; (b) : lo

w bia s + low

precisio n=

• low accuracy ; (c) : hig hbia s + hig hprecisio n- low accuracy ; (d) : lo w

bia s + hig hprecisio n

= hig haccuracy .

dkd.12 7P. 7

precisio nan

dabilit y

o f certified , observer s i s th e responsibilit y o f eac h state , an

d1 s on e o f th e primar y way s t o reduc e erro r 1nestimates .
4. 0 METHO D DESCRIPTIO N Thi s sectio nbriefl y

describe s opacit y

measuremen t Method s 203A , 203 B an d203C . Fo r a mor e detaile ddescriptio no f thes e methods , th e reade r i s referre dt o th e preambl e t o th e propose dMethods . Th e statistic s onerro r an d bia s discusse dinthi s memorandu m ar e derive dfro

m fiel dstudie s performe db y EP A fo r us e wit hMetho d9. 3 Metho d203 A

i s use dwit htime-average dregulations . Fiel dstudie s on thi s metho dinvolv e calculatin g th e averag e opacit y valu e fo r observation s take ni n15-secon dinterval s fo r time period s rangin g fro m 1 5 second s t o 8 minutes . Fo r time-average dregulations , complianc e woul dbe me t b y no t exceedin g a specifie daverag e opacit y level . Metho d203 B 1 s use dfo r determinin g complianc e fo r time-exceptio n regulations . I t consist s o f aggregatin g th e amoun t o f time correspondin g t o th e numbe r o f opacit y reading s (take na t 1 5 secon dinterval s ove r a specifie d time period ) whic har e ove r a specifie d level . Time-exceptio nregulation s limi t th e tota l time opacit y ca nb e abov e th e specifie dlevel , an d complianc e woul db e me t b

y keepin g th e time abov e th e specifie dopacit y a t o r below

thi s 1imit . Metho d203 C i s use dfo r instantaneous-limitatio nregulations . Observation s ar e take na t 5-secondinterval s average dove r a on e minut e time period . Instantaneous-limitatio nregulation s prohibi t opacit y value s abov e th e give nlimi t a t an y time .
4. 1 Erro r an

dBia s 1nMetho d 203 A A s mentione di nSectio n4.0 , th e fiel d studie s use d t o evaluat e th e opacit y erro r fo r Metho d203 A wer e originall y

performe dt o tes t Metho d9. * Fo r studie s o ntime-average dmethods , th e ra w dat a containe dindividua l 15 - secondobservations , wit hcorrespondin g transmissomete r readings . Th e observation s wer e recorde dsequentiall y an drollin g average s wer e calculate d
ove r time period s rangin g fro m 1 5 second s t o 8 minutes . Th e percen t erro r wa s the ndetermine dfo r eac ho f th e averages . Th e averag e erro r (1 nterm s o f percen t opacity ) wa s the ngroupe dInt o eleve nclasse s t o determin e frequenc y distributions .

dkd.12 7P. 8

Tabl e 4- 1 summarize s th e percentag e distributio no f opacit y error s b

y averagin g time . Th e tabl e show s ther e i s bot hpositiv e an dnegativ e erro r a t al l o f th e averagin g times . I t als o reveal s tha t a s averagin g time increases , th e percentag e o f positiv e an dnegativ e erro r decreases . Thi s reflect s th e concep t tha t a s sampl e siz e increases , th e expecte d valu e o f th e sampl e approache s th e tru e populatio nvalu e (a s measure db y transmissometer) . Tabl e 4- 2 show s th e percentag e o f dat a wit hnegativ e opacit y error . Th e number s indicat e a sligh t negativ e bia s fo r al l o f th e averagin g times , wit h
a t leas t 5 5 percen t o f al l dat a havin g negativ e error . Figur e 4- 1 show s a sampl e frequenc y

distributio nfo r percen t erro r fo r a six-minut e averagin g time . Th e error s appea r t o follow a norma l distribution , an d5 2 percen t o f al l dat a ar e withi n+ 5 percen t an d- 5 percen t opacit y

error . Approximatel y 9 5 percen t o f al l dat a sho w les s tha n+1 5 percen t opacit y error . Jhi s mean s tha t i f a give nobservatio n(average dove r si xminutes ) reveal s a nopacit y

o f 5 0 percent , the n9 5 time s ou t o f 100 , th e tru e opacit y i s withi nthe rang e o f 3 5 t o 6 5 percent . However , i t als o mean s tha t i f th e tru e opacit y i s 2 0 percent , the nth e confidenc e interva l i s fro m 5 t o 3 5 percen t opacity . Thi s indicate s tha t th e influenc e o f erro r i s greate r fo r low opacit y readings . Th e effec t thi s ha s oncomplianc e determinatio ni s discusse dinSectio n5.0 .
4. 2 Erro r an

dBia s inMetho d203 B Fiel dstudie s don e onth e erro r intime-aggregate dmethod s summe dtota l time tha t opacit y

exceede da standar d durin g a give naveragin g period. 5 Observation s wer e take n1 n15-secondintervals . Th e standar duse dwa s 2 0 percen t opacity , an dth e averagin g time wa s 6 minutes . Th e aggregate dtime th e observe r indicate dopacit y exceede d2 0 percen t wa s compare dt o th e actua l time opacit y

exceede dthi s leve l a s measure db y a transmissometer . Th e erro r wa s reporte d1nsecond s ove r o r unde r th e actua l numbe r measure db

y th e transmissometer . Erro r wa s groupe din15-secon dincrements , an drange dfro

m +36 0 second s t o -36 0 seconds . A nerro r o f -36 0 second s mean t tha t th e observe r di dno t recor dan y observation s a s ove r 2 0 percen t opacit y whe nth e transmissomete r measure d th e entir e 6 minute s a s exceedin g 2 0 percent . Tabl e 4- 3 show s th e cummulativ e distributio no f opacit y errors . Figur e 4- 2 show s th e distributio no f th e numbe r o f dat a set s b y erro r (i nseconds) . Al l fiel dstudie s hav e bot hnegativ e andpositiv e error , an d 6 7 percen t o f al l dat a set s hav e a nerro r o f betwee n-1 5 an d+1 5 seconds .

dkd.12 7P. 9

TABL E 4-1 . PERCENTAG E DISTRIBUTIO N O F OPACIT YERROR S BYAVERAGING TIME** *

Erro r Directio n and Rang e
Positiv e error :
Mor e tha n+1 5 % + 1 5 % o r les s + 1 0 % o r les s + 7. 5 % o r les s + 5 % o r les s + 1 % o r les s Negativ e error :
Mor e tha n0 %

- 1 % o r mor e

- 5 % o r mor e -1 0 % o r mor e -1 5 % o r mor e 

### 15

s

4 9 6 9 1 8 6 8 0 65

55 5 5 3 4 1 9 8 30s

4 9 6 9 1 8 7 8 0 6 4

56 5 4 3 3 1 7 7 l m

3 9 7 9 1 8 7 8 1 6 3

5 7 5 3 3 2 1 6 6 Averagin g Tim e 

### 2 m

2 9 8 9 3 8 7 8 1 63

5 7 5 2 3 2 1 5 5 3 m .



### 2 9 8 9 3 8 8 8 1 6 3

5 7 5 2 3 1 1 4 5 4 mCM 

### 9 8 9 3 8 8 8 1 6 3

5 7 5 2 3 1 1 4 5 5 m

2 9 8 9 3 8 8 8 1 6 3

5 7 5 2 3 1 1 3 4 6 m

2 9 9 9 4 8 9 8 2 6 3

5 7 5 1 3 1 1 3 4 7 m

2 9 8 9 4 89 8 2 6 3

- 5 7 

### 5 1 3 1 1 3 4 8 m

1 9 9 9 4 8 9 8 2 63

56 5 1 3 1 1 3 4

TABL E 4-2 . PERCEN T O F DATA WIT H NEGATIV E ERROR ?
Averagin g Tim e


### 15 s 30s l m 2 m 3 m 4 m 5 m 6 m 7 m j . 8 m Percen t o f Dat a wit hNegativ e Erro r



### 5 5 5 6 5 7 57 57 5 7 5 7 5 8 5 7 5 6 |



### 8

### 2 5

2 0 27

25

1 5 1 8

SO c 3 c r t u s 

### 1

0 1 1

-1 5 -1

0 - 5 0 5

Erro r ( % opacity ) 

### 1 0 1

5

Figur e 4-1 . Freguenc y distributio nfo r percen t erro r fo r time-average d methods .P.1 1

TABL E 4-3 .

Erro r Second s -36 0 -34 5 -33 0 -31 5 -30 0 -28 5 -27 0 -25 5 -24 0 -22 5 -21 0 -19 5 -18 0 -16 5 -15 0 -13 5 -12 0 -10 5 

### -9 0 -75 -60 -4 5 -3 0 -1 5 0 1 5 3 0 45 6 0 75 9 0 105 12 0 13 5 150 165 18 0 19 5 21 0 225 24 0 255 27 0 28 5 30 0 31 5 33 0 345 36 0 CUMULATIVE PERCENTAG E DISTRIBUTIO N O F TIM E AGGREGATIO N ERROR S FO

R ESTIMATIN

G PLUME OPACIT YDURATION OVE RA S

No . o f Dat a Set s b

y F i RTP B



### 7 2 3 14 2 46 9 6 2 TP W

1 1 6 197 5 9 33 1 6 6 5 1 1 FL1 B 

### 1 2 2 2 2 5 3 1 4 5 1 2 1 5 5 5 3 2 2 2 8 2 2 2 6 7 0 1

2 1 2

1

1 el d Evaluation - Stud y 

## ^ L 

## i w 3

1 1 3 2 1 2 3 3 1 1 3 2 2 2 1 5 9 1 3 5 1 2 2 2 1 5 2 6

4 2 3 2 7 1

1 1 3 FL2 B



### 1 1

1 1

1 2 1 2 1 1 4 2 1 2 2 4 2 26 1 1 2 3 6 4 2

1 6 FL2 W



### 42 1 1 1 1 3 2 3 1 9 1 1

2 4

TOTA L XMINU T E PERIOD 8

Sure ! %J. Cum

%


### 1 5 3 3 2 5 2 4 1 5 8 3 3 18 1 0 6 8 4 4 9 4 1 1 6 4 1 5 52 56 8 12 1 50 3 7 2 1 1 4 8 23 6 4 1 2 1 2 4 4 2 4 2 7 1 0 0 1 1 3 

## 1 111 0 1

0 0 0 0 0 0 1 1 0 0 2 1 - 1 1 0 0 1 0 1 1 0 1 5 5 1 1 1 5 3 2 1 1 2 1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 2 2 2 3 3 3 4 5 5 6 7 8 9 9 1 0 1 0 1 1 1 1 1 2 1 3 1 3 2 5 29 7 0 8 1 8 6 8 9 9 1 9 2 93 9 5 9 6 9 6 9 7 9 7 9 7 9 8 9 8 9 8 9 9 9 9 9 9 10 0 10 0 10 0 10 0 10 0 10 0 

# 1a * >» 5 0

4 0

3 0

2 0

1 0

1 1 1 2 2 1 1 1 1 51 %

6 hav e zer o erro r

1 6

5

2 '

3

1 1 -36 0 -33 0 -30 0 -27 0 -24 0 -21 0 -18 0 -15 0 -12 0 -9 0 -6 0 -3 0 0 3 0 6 0 9 0 12 0 15 0 18 0 21 0 24 0 27 0 30 0 36 0

erro r i n second s Fgur e 4-2

. Frequenc ydistributio n fo rpercen t erro rfo rtime-aggregate d methods

.P.1 3

i s a percen t frequenc y distributio nfo r error . I t show s th e precisio no f th e method , wit h5 1 percen t o f th e dat a set s havin g n o error . Althoug hth e dat a set s show

a stron g centra l tendency , ther e i s a larg e sprea do f extrem e values . Th e rang e fo r erro r t o includ e 9 5 percen t o f th e dat a 1 s betwee n-24 0 second s an

d+12 0 second s (-4 minute s t o + 2 minutes) . Thi s larg e sprea d1 n erro r i s importan t whe nsettin g complianc e levels , an dwil l b e discusse d furthe r inSectio n5.0 .
4. 3 Erro r an

dBia s InMetho d203 C Referenc e Metho d9 specifie s tha t opacit y observation s b e take na t 15 - secondintervals ; 2 4 consecutiv e observation s ar e the naverage dt o yiel da 6 - minut e averag e fo r complianc e determination. 3 Man y stat e implementatio nplan s (SIPs ) includ e opacit y standard s wher e thi s 6-minut e averag e i s no t appropriate . On e exampl e o f wher e thi s typ e o f opacit y measuremen t metho d doe s no t appl y

i s fo r a

ninstantaneous-limitatio nregulation . Metho d203 C i s th e propose dmetho dfo r determinin g complianc e wit h instantaneous-limitatio nregulations . A s mentione dinSectio n4.0 , i t involve s observation s take na t 5-secondinterval s average dove r a 1-minut e time period . Takin g observation s a t shorte r interval s an daveragin g ove r a shorte r time perio di s intende dt o mor e accuratel y reflec t th e concep t o f "instantaneous " opacity . A fiel dstud

y wa s conducte d t o determin e th e abilit y o f observer s t o accuratel y

measur e opacit y

a t 5-second intervals . Th e stud y consiste do f eigh t observer s participatin g intenruns . Eac hobserve r recorde dthirtee n5 - secondobservation s ove r a 1-minut e averagin g period . Observe r opacit y estimate s wer e compare dwit hactua l value s a s measure db y a transmissomete r t o determin e error . Dat a set s wer e groupe daccordin g t o thei r error , and compare dt o th e erro r result s fro m previou s method s (Metho d9 , an dpropose d Metho dF-1) . Tabl e 4. 4 show s th e distributio no f opacit y errors . Th e observation s showe d a sligh t negativ e bias , wit h5 3 percen t o f th e average s havin g negativ e error . Figur e 4- 3 show s th e frequenc y distributio n fo r error . Th e negativ e bia s ca nbe see ninth e skewe ddistributio no f th e frequenc y

bar s towar dth e negativ e sid e o f th e graph . Th e dat a showe da stron g centra l tendency , wit h5 6 percen t o f th e error s betwee n+ 5 an d- 5 percen t opacity . Fo r thi s study , 9 5 percen t o f th e erro r wa s betwee n+1 5 an d -1 5 percen t opacity .

dkd.12 7 1 2

### TABL E 4-4 . DISTRIBUTIO N O F OPACIT YERROR* *

t o Opacity

Error Percent Leve l Number o f Set s Cumulativ

e Numbe r o f Set s Cumulativ

e Percent o f Set s 

### >1

5 3

3

3 >1 0 2

5

6. 3 >7. 5



### 1

6

7. 5 >

5 7

1 3

16. 3 

### >

1 18

3 1

38. 8 

### >0

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3 6

45. 0 

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l 8

4 4

55. 0 

### >-5

1 4

5 8

72. 5 >-1 0



### 1 0

5 8

85. 0 >-1 5



### 1 1

7 9

98. 8 <-1 5



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### 8 0 1
100. 0 1

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2 4 2 4

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-1 0 - 5 0 5 1 0 Erro r ( % opacity ) Figur e 4-3
. FrequencyDistributio n fo r percen t erro r for time-exception methods
. 

### 1 5

U lP.1 6

Thes e result s ar e quit e simila r t o thos e foun dinth e previousl y mentione dfiel dstudies , usin g th e 15-secondobservatio ninterva l methods . Ther e doe s no t appea r t o b e an y significan t increas e inerro r whe nusin g 5-secondobservatio nintervals .
5. 0 REGULATIO N

AN D COMPLIANC E DETERMINATIO N I t i s Importan t t o hav e a nunderstandin g o f th e sig n( + o r - ) an d relativ e magnitud e o f th e erro r involve d ineac ho f th e propose dopacit y measuremen t methods . Th e amoun t o f erro r o r th e presenc e o f bia s i na measuremen t methodaffect s complianc e determination . Thus , State s shoul d conside r th e sig nan

dmagnitud e o f an

y erro r o r bia s whe nchoosin g th e metho d
o f regulatio nan

dwhe ndeterminin g compliance . Anunderstandin g o f th e sprea d (an ddistribution ) o f erro r is . importan t whe nmakin g complianc e determinations . I f th e erro r show s a stron g centra l tendency , meanin g i t i s concentrate daroundzero , the nth e amoun t o f uncertaint y

involve dina

nobservatio ni s less . I nthi s case , a Stat e ma y decid e t o see k enforcemen t agains t al l source s slightl y ove r th e standard . Wherea s i f th e sprea do f erro r i s large , th e Stat e ma y see k enforcemen t agains t onl y

thos e source s whic har e ove r th e standar d b y a nobviousl y

large r amount . Th e distributio no f erro r allow s a Stat e t o determin e th e rang e o f opacit y observation s i t woul dconside r t o b e inclea r violatio no f th e standard . A nare a wher e additiona l study i s neede di s t o determin e th e relationshi pbetwee nopacit y erro r an

dactua l opacit y

level . Thi s woul dgiv e State s a nunderstandin g o f ho w opacit y erro r change s wit hth e leve l o f opacit y bein g estimate d(o r i f i t doe s no t change) . Thi s become s Increasingl y importan t a s th e standar dfo r opacit y decreases . I t woul db e mos t usefu l fo r State s t o hav e a

nestimat e o f th e percentag e erro r a s a functio no f opacit y level . A s mentione dinSectio n4.1 , a +1 5 o r -1 5 percen t opacit y erro r ca nbe significan t 1 f th e standar d1 s se t a t 2 0 percen t opacity . Sectio n2. 1 discusse dth e concep t o f decisio nerror . I t presente dth e tw o type s o f erro r a Stat e mus t accep t whe nsettin g a standard . I t i s upt o th e Stat e t o determin e whic htyp e o f erro r I t find s mos t acceptabl e o r defensibl e (1 nlega l terms) . Previou s erro r analyse s hav e deal t onl y 1nterm s o f th e positiv e erro r fro m measuremen t methods . Thi s Informs-th e Stat e o f th e probabilit y

o f makin g a Typ e I erro r (falsel y citin g a sourc e tha t 1 s no t trul y ou t o f compliance) . dkd.12 7 1 5P.1 7

Definin g a metho d i n term s o f it s positiv e erro r allow s a Stat e t o se t standard s fo r eac h typ e o f regulatio n a t level s whic h minimiz e Typ e I error . Fo r example , i f a Stat e know s tha t th e 9 5 percen t confidenc e Interva l fo r averag e erro r fo r a time-averag e regulatio n i s 1 0 percent , (usin g a n observe r wh o 1 s State

- certifie d t o rea d opacit ywithi n 7. 5 percent ) the yma ydecid e t o defin e complianc e wit h a 2 0 percen t opacit ystandar d a s anyaverag e whic h 1 s unde r 2 3 percen t opacity

. However , i t shoul d b e note d tha t th e probabilit yo f a Typ e I I erro r increase s a s th e probabilit yfo r Typ e I decreases
. State s wil l eventuall yb e calle d upo n bypubli c interes t o r environmenta l group s t o defen d Typ e I I error s (failin g t o cit e a sourc e whic h i s ou t o f compliance)

. Thus , i t 1 s importan t fo r State s t o understan d th e amoun t o f negativ e error , o r underestimatio n o f opacit ycontaine d i n eac h o f th e methods
. A t present , observe r erro r canno t b e eliminate d fro mopacit ytes t methods
. Stric t adherenc e t o prescribe d methodologies , an d rigorou s Stat e certificatio n program s ar e recommende d t o reduc e observe r error . State s shoul d se t and enforc e standard s withi n th e rang e o f positiv e an d negativ e erro r fo r th e chose n measuremen t methodology
. I t 1 s recommende d tha t State s specif yth e opacit yleve l a t whic h a citatio n wil l b e Issue d (se e Appendi x A : Section s o f Tennesse e regulations)

. I f th e averag e o r aggregat e opacit yo f a sourc e exceed s thi s level , the n th e sourc e woul d b e considere d ou t o f compliance , unles s i t ca n b e shown tha t th e individua l observe r show s a n erro r outsid e th e expecte d range .

dkd.12 7 1 6P.1 8

! « • a

REFERENCE S

1
. 4 0 CF R 60
. Appendi x A , Metho d 9
. 1987 , a s amended
. Visua l Determinatio n o f th e Opacit yo f Emission s fro m Stationar ySources
.
2
. Gilbert , Richar d 0
. Statistica l Method s fo r Environmenta l Pollutio n Monitoring

. Va n Noshan d Reinhol d Company , Inc
. Ne wYork
. 1987
. pg . 11
.
3
. U.S
. Environmenta l Protectio n Agency , Offic e o f Ai r Qualit yPlannin g and Standards
. Opacit yError s fo r averagin g an d Nonaveragin g Dat a Reductio n and Reportin g Techniques

. Fina l Repor t SR-1-6-85
. Researc h Triangl e Park , Nort h Carolina

. Jun e 1985
.

/
4'
. Se e Referenc e 3
.
5
. Se e Referenc e 3
.
6
. Se e Referenc e 3
. pg . 12
.
7
. Se e Referenc e 3
. pg . 13
.
8
. Se e Referenc e 3
. pg . 17
.
9
. Se e Referenc e 1
. 10
. Rose , Thoma s H. , Easter n Technica l Associates , Raleigh , Nort h Carolin a Collaborativ e Studyo f Opacit yObservation s a t Five-secon d Interval s b y Certifie d Observers
. Prepare d fo r U.S
. Environmenta l Protectio n Agency , Stationar ySourc e Complianc e Division , Washington , D.C
. Septembe r 1990
.
11
. Se e Referenc e 10
.
12
. Tennesse e Visibl e Emissio n Evaluatio n Metho d 1
. 1984 , a s amended
.
13
. Tennesse e Visibl e Emissio n Evaluatio n Metho d 2
. 1984 .

dkd.12 7 1 7P.1 9

a » a »

APPENDI X AP.2 0

t (f r»

APPENDI XAl2,1 3

TVE E Metho d1 Sectio nNo . 4 Revisio nNo . 3 Dat e Ma y 29 , 198 4 Pag e 1 o f 1 Page s
Opacit y o f Emission s Fro

m Nontraditiona l source s (Road s an

dParkin g Areas )

4. 0 Observatio nErro r
4. 1 A positiv e observationa l erro r o f 8. 8 percen t opacit y shal l be take n int o accoun t prio r t o issuin g a Notic e o f Violatio nonnontraditiona l source s (road s an

dparkin g areas) .

TVE E Metho d2 Sectio nNo . 3 Revisio nNo . 0 Dat e Ma y 18 , 198 4 Pag e 1 o f 1 Page s

Visua l Determinatio no f Opacit y Fo r Aggregat e Coun t Visibl e Emissio nStandard s

Observatio nErro r
Inorde r fo r a Notic e o f Violatio nt o be issue d exces s visibl e emission s mus t b e recorde dtha t ar e equa l t o o r greate r tha n15 % opacit y abov e th e allowabl e opacit y

standard .

ddk.12 7 . i