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Prepped by Keeia Richards 

Document Number: 

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Docket Number: 

A-84-22 

Printed 10/30/2008 1:19:24 PM Sheet 22 of 82 

P.1 
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# ~f</^ UT-jfrr 3 

United States Office of Air Quality Special Report 

Environmental Protection Planning and Standards November, 1983 

Agency Washington DC 20460 Final Draft 

Stationary Source Compliance Series 

v°/EPA Evaluation of 

Visible Fugitive 

Emission Data 
P.3 

This document has not been formally released by EPA and should not be construed to represent Agency 

policy. It is being circulated for comment on its technical accuracy and policy implications. 

Final Draft 

Evaluation of Visible Fugitive 

Emission Data 

Prepared by: 

DEL GREEN ASSOCIATES, INC. 

1465 State Street 

P.O. Box 13446 

Salem, Oregon 97309 

Contract No. 68-01-5110 

Task Order #54 

EPA Task Manager: Kirk Foster 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

Office of Air Quality Planning and Standards 

Stationary Source Compliance Division 

Washington, DC 20460 

November 1983 
P.4 

ACKNOWLEDGMENT 

Del Green Associates, Inc. (DGA) wishes to acknowledge Research Triangle 

Institute for assistance in conducting all the statistical analyses on 

the fugitive emissions data base and on the smoke generator data base from 

the alternative opacity methods study; their analyses were utilized in preparing this report. The cooperation and efforts the of air programs staff in 

Region III to provide the data for evaluation are greatly appreciated. 

Finally, the assistance and guidance provided by Mr. Kirk Foster throughout 

the conduct of this study are appreciated and acknowledged. 

n 
P.5 

TABLE OF CONTENTS 

Page 

List of Tables iv 

List of Figures v 

1.0 Introduction 1 

2.0 Technical Approach 3 

2.1 Emissions Data Base 3 

2.2 Analysis Approach 3 

3.0 Results 9 

3.1 Between-Observer Precision 9 

3.2 Comparison of Methods 13 

4.0 Summary and Conclusions 18 

References 19 

Appendices 

Appendix 1 — List of Inspectors 

Appendix 2 — Data Base 

m 
P.6 

LIST OF TABLES 

Page 

Table 1 Facilities and Emission Sources 4 

Table 2 Difference Between Observers: Opacity 10 

Averaging Method 

Table 3 Difference Between Observers: Aggregate- 11 

Time Method 

Table 4 Parameters Chosen for Relative Stringency 14 

Evaluation 

Table 5 Relative Stringency of Three Methods 15 

Table 6 Opacity Averaging Methods Compared to the 17 

Aggregate-Time Method 

iv 
P.7 

LIST OF FIGURES 

Figure 1 Comparison of Noncompliance by Three 

Methods. 

Page 

17 
P.8 

1.0 INTRODUCTION 

Reference Method 9 — Visual Determination of Emissions from 

Stationary Sources — provides for the determination of the opacity 

of emissions by qualified observers. When Method 9 was revised and 

repromulgated in 1974, the procedure for calculating average opacity 

for six-minute periods was established. However, the Preamble to 

Method 9 recognized that the opacity averaging approach was not 

appropriate for evaluating certain sources of particulate matter with 

intermittent emissions. The Preamble also indicated that alternative 

procedures for evaluating emissions from intermittent sources would be 

investigated. 

The Stationary Source Compliance Division (SSCD) of EPA recently 

has investigated the need for an alternative opacity measurement 

procedure based on nonaveraging or short-term averaging techniques 

(e.g., 3-minute periods). During SSCD's investigation, several 

technical studies ^,2,3 ) were conducted to evaluate various opacity 

measurement techniques. This report presents the results of a study 

made to examine and evaluate different opacity data reduction 

techniques (i.e. , aggregate-time, 3-minute averaging) on visible 

emissions data from fugitive emission sources. The principal purposes 

of this study were to estimate between-observer precision for inspectors 

observing fugitive emissions and to compare the estimate to similar 

precision measurements obtained during evaluation of data from nonfugitive sources. Also, between-observer precision estimates for the 

fugitive data obtained by various data reduction methods (e.g., 3-minute, 

6-minute averaging) were determined. 

As this study proceeded, another purpose was identified: to 

evaluate the relative stringency of various visible emission data reduction 

methods. As a part of this effort, the effect on a source's status of 

compliance with a given standard was examined when the emission levels 

were determined using different data reduction methods (e.g., 3-minute 

averaging, 6-minute averaging, or aggregate-time). 

The scope of this study was limited to evaluating existing fugitive 

emissions data. Since the primary objective of this study was to examine 

between-observer precision, the major criterion for choosing the fugitive 

1 
P.9 

emissions data set to be evaluated was the need for observations obtained 

simultaneously by multiple inspectors. The data set evaluated included 

emissions data obtained from 16 different sources during the period 

October, 1979 to June, 1980. Data obtained from the Iron and Steel 

Industry and the Nonmetallic Mineral Industry were examined. The data 

set included a total of 310 hours of data (approximately 74,400 15-second 

observations) obtained by each inspector. 

Section 2.0 of this report presents a summary of the data set 

examined and the technical approach followed during this study. Section 

3.0 presents a summary and discussion of the results of the study. 

Section 4.0 presents conclusions. 
P.10 

2.0 TECHNICAL APPROACH 

2.1 Emissions Data Base 

Since conducting an actual field study at fugitive sources was 

outside the scope of this study, data on file were obtained and evaluated. 

Data were obtained from the Office of Air Quality Planning and Standards 

(OAQPS) and from EPA Region III. The OAQPS data were obtained from 

inspections of basic oxygen furnace (BOF) roof monitors and nonmetallic 

mineral (NMM) processing facilities; these data had been collected in 

support of developing New Source Performance Standards (NSPS) for those 

source categories. Data from the final test reports obtained from OAQPS 

were coded and loaded on the computer for analysis. Table 1 lists the 

facilities from which regional inspection data were obtained and analyzed. 

The data obtained from Region III were collected by regional personnel 

(or contractor personnel under regional authority) from various iron and 

steel sources in several EPA regions during routine inspection and 

enforcement activities. These data had been included in the Visible 

Emission Information System (VEIS), a visible emission data base management 

system maintained for EPA. The regional data selected for analysis during 

this study were limited to data that had been archived in the VEIS Data 

Base Management System. Furthermore, regional data were used only from 

those facilities where simultaneous observations by company inspectors 

were available since observations were obtained only by a single regional 

observer. In most cases, company personnel observed emissions simultaneously with the regional observer, and these data were submitted to EPA 

and maintained as part of the inspection record. During this study, 

the data obtained by company inspectors were coded directly from the field 

data records. The coded data were loaded into the computer for analysis 

by Research Triangle Institute (RTI). 

2.2 Analysis Approach 

The primary objective of this study was to evaluate the observer 

precision associated with opacity readings obtained by certified observers 

at intermittent fugitive emission sources. During the study, the effect 

of different data reduction methods (e.g., 3-minute versus 6-minute opacity 

averaging) on determining the compliance status of a source with respect 

to a given emission standard also was investigated. 

3 
TABLE 1. FACILITIES AND EMISSION SOURCES 

p.11 

Facility 

Bethlehem Steel Corp. 

Bethlehem, PA 

Republic Steel Co. 

Cleveland, OH 

Republic Steel Co. 

South Chicago, IL 

Inland Steel 

East Chicago, IN 

Date 

6/23-26/80 

6/09-13/80 

6/02-06/80 

5/12-16/80 

Source(s) 

BOF Monitor 

BOF Monitor 

BOF Monitor 

BOF Monitor 

Data 

Reference 

Emission Test Report:* 

EMB 80-B0F-9 

October, 1980 

Emission Test Report:1 

EMB 80-B0F-8 

October, 1980 

Emission Test Report:* 

EMB 80-B0F-7 

October, 1980 

Emission Test Report:1 

EMB 80-B0F-6 

Vulcan Materials Co. 

Garrisonville, VA 

10/22/79 Crusher 

September, 1980 

Emission Test Report: 

EMB 79-NMM-11D 

April, 1980 

Vulcan Materials Co. 

Helena, AL 

Castle Concrete Co. 

Colorado Springs, CO 

Brannan Sand and 

Gravel Co. 

Denver, CO 

Wheeling Pittsburgh 

Steel 

U.S. Steel 

Duquesne, PA 

U.S. Steel 

Edgar Thompson Works 

Flintkote Corporation 

Frederick, MD 

10/02-03/79 

10/08-11/79 

10/15-22/79 

3/02/80-

4/10/80 

6/11-15/79 

9/02-05/80 

6/25/79-

7/26/79 

10/26-30/79 

Crusher 

Screens 

Crusher 

Screens 

Transfer 

Crusher 

Transfer 

Blast Furnace 

Cast House 

BOF Monitor 

BOF Monitor 

Crusher 

Emission Test Report: 

EMB 79-NMM-11A 

April, 1980 

Emission Test Report: 

EMB 79-NMM-11B 

April, 1980 

Emission Test Report 

EMB 79-NMM-11C 

April, 1980 

VEIS2 

VEIS2 

VEIS2 

Emission Test Report: 

EMB 79-NMM-llE 

April, 1980 

r 

Emission Test Report, U.S. EPA Office of Air Quality Planning and Standards, 

Research Triangle Park, NC. 

> 

VEIS — Visible Emission Inventory System 
P.12 

In the case of industrial process fugitive sources, no true opacity 

measurement is available to which observer opacity measurements may be 

compared; i.e. , no transmissometer or stack continuous opacity monitor is 

present. Consequently, the only measure that can be used to assess observer 

error is between-observer precision. The need for data obtained simultaneously 

by multiple observers is apparent, and this criterion was the primary factor 

in determining the fugitive data base to be studied. 

All the data to be studied where coded by facility , date, run number, 

clock time, and inspector. This permitted analyses to be conducted in a 

number of different ways; for example, by comparison of individual 15-second 

readings, by comparison of the mean opacity 6-minute period, or by comparison 

of the emissions for each one-hour "run". 

The between-observer precision was estimated by calculating the standard 

deviation of the difference between observations obtained by different inspectors according to Equation 1: 

/ N M 

/ 1-1 j= i 

/ N - 1 

- X-- )2 

A SD = (Var) V2 = / 1= 1 j= 1 ^i (1 j ' ) 

V 

where: 

SD = Standard Deviation; 

Var = Variance; 

N = Number of observations (depending upon the analysis 

being conducted, an observation is defined as a 3-minute 

opacity average, a 6-minute opacity average, etc.); 

M = Number of inspectors; 

Xj = Observed value for inspector j (1 M) for run i 

(1 N); and 

X-j = Mean observed value for all inspectors for run i. 

The standard deviation of the difference between observers was calculated 

for several different cases, including: 
P.13 

1) Time-Averaged opacity -- a) individual 15-second opacity reading, b) 

3-minute average opacity, and c) 6-minute average opacity; and 2) 

Aggregate-Time -- a) observed time (seconds) greater than 15% opacity; b) 

observed time (seconds) greater than 20% opacity; c) observed time 

(seconds) greater than 25% opacity; and d) observed time (seconds) greater 

than 30% opacity. 

A frequency distribution also was calculated to assess the difference 

between observers. The percent of total determinations (individual 15-

second readings, 3-minute averages, etc.) with a between-observer 

difference of less than or equal to 7.5% opacity was calculated and reported. 

In order to compare the "applicability" of potential test methods, the 

relative stringency of the methods in determining noncompliance with a typical 

emission standard was compared for three methods of data reduction: 1) aggregatetime, 2) 3-minute opacity average, and 3) 6-minute opacity average. For the 

aggregate-time method, the discrete 15-second measurements are aggregated to 

determine the accumulated time during which opacity exceeds a standard; 15-

seconds of time are accumulated for each reading that exceeds the standard. 

For 3-minute (6-minute) opacity averaging, the arithmetic mean of the 12 

(24) individual 15-second opacity observations is calculated to determine 

the average opacity for the time period. 

In conducting the relative stringency analysis, the data were analyzed 

by all the different test methods and then the numbers of noncompliance 

periods indicated by each method were compared. When performing the relative stringency analysis, an allowance for "observer error" was sometimes included by adjusting the noncompliance level by a given amount. 

For example, i f the standard was established at less than or equal to 20% 

opacity, but an observer error allowance of 7.5% opacity was desired, then 

noncompliance would not be indicated until an opacity measurement in excess 

of 27.5% was obtained. During this study, the relative stringency of various 

methods was evaluated both with and without an observer error allowance. 

Furthermore, two separate analyses were conducted using different allowance 

levels for observer error. 
P.M 

During one evaluation, an opacity level not to equal or exceed 20% was 

chosen as the basis for the standard. For a given observation period, the 

source was considered in noncompliance by the aggregate-time method i f the 

opacity was greater than or equal to 20% for more than 3 minutes (180 seconds) 

per hour or 1.5 minutes (90 seconds) per one-half hour observation period. For 

the opacity averaging methods, the source was considered in noncompliance i f 

any 3- or 6-minute average during the observation period was equal to or greater 

than 20% than 20% opacity. The number of noncompliance periods obtained by each 

method was tabulated and compared. 

For the relative stringency analysis where an allowance for observer error 

was included, the error allowance for the aggregate-time method was a combination of observed time and opacity. The error allowance used was 10% opacity 

for each individual 15-second reading, plus a time error allowance of 15 seconds 

for each 6-minute observation period used to accumulate time above the standard. 

This observer error allowance is based on four field test conducted by EPA.(5) 

The example time-exemption opacity limi t chosen for this relative stringency 

evaluation specified that emissions could not equal or exceed 20% opacity for 

more than three minutes per hour (or 1.5 minutes per half-hour). Using the 

opacity and time error margins just described, the data was evaluated as follows: 

- For each data set (30 or 60 minute reading), only individual 15-second 

readings equal to or greater than 30% were counted (20% opacity limi t 

plus 10% opacity error margin). 

- For a 30 minute data set, a "violation" was declared i f the opacity 

limi t (with opacity error margin) was exceeded for more than 1 1/2 

minutes plus the time error margin. For a 60 minute data set, a 

violation was declared i f the opacity limi t (with opacity error margin) 

was exceeded for more than 3 minutes plus the time error margin. 

- The time error margin allowed per 30 minute or 60 minute data set varied 

depending on whether enough 15-second readings in excess of the opacity 

standard to demonstrate a violation were contained in one 6-minute 

segment of the data set, or whether more than one 6-minute segment within the data set was required to demonstrate the violation. For example, 
P.15 

in a 60 minute data set, there is one six-minute segment where each 15-

second reading was over 30% opacity. A violation is demonstrated with 

only that one 6-minute segment. The given time error margin would 

therefore be 15 seconds, since only one 6-minute segment was needed 

to show a violation. I f two 6-minute segments within a data set were 

needed to show a violation, then 2X1 5 seconds or 30 seconds time 

error margin would be required. 

- In this study, each 30- or 60-minute data set was broken into 6-minute 

segments. The 6-minute segment with the most number of 15-second readings at or above 30% opacity were counted, and multiplied by 0.25 minute/ 

readings. I f the time at or above 30% was more than the time exemption 

in the rule plus 15 seconds for the time error margin, then the data 

set was ruled a violation. I f the time was not more than the time 

exemption after evaluating the firs t 6-minute segment, then the next 

worst 6-minute segment was evaluated, and so on until either a violation 

was shown, or al l 6-minute segments were evaluated and compliance was 

shown. A 15-second time error margin is required for each 6-minute 

segment in a data set that is used to establish a violation. 

For the opacity averaging methods, the observer error used was 11.8% (12%) 

opacity for the 3-minute opacity averaging method and 7.5% opacity! for the 6-

minute opacity averaging method. The 12% opacity error is based on smoke generator 

data (white smoke) obtained during the RTP fiel d test C) from the alternative 

opacity method study. The value of 12% is based on the observed 95th percentile 

error distribution for the smoke generator test. In other words, for al l observers 

and al l test runs, the measured error was less than 12% opacity 95% of the time. 

Thus, for the 3-minute opacity averaging method, the noncompliance level with 

allowance for observer error was established at greater than 31.8% opacity (i.e. , 

31.9%); the noncompliance level with observer error for the 6-minute opacity 

averaging method was established at greater than 27.5% opacity (i.e. , 27.6%). 

1 This error margin for the 6-minute average was established during 

tests for the 1974 re-promulgation of Method 9.(4) 
P.16 

3.0 RESULTS 

3.1 Between-Observer Precision 

Table 2 summarizes the results of the analyses to determine the difference 

between observers for opacity averaging methods. The standard deviation of the 

difference between observers was calculated to estimate between-observer precision. In addition, the cumulative frequency of observations with a difference 

between observers of less than or equal to 7.5% opacity was also tabulated. The 

value of 7.5% opacity was used because this is the maximum observer error typically associated with Method 9 6-minute opacity averaging. 

Table 3 presents the results of the between-observer error analysis for the 

aggregate-time data reduction method. For the aggregate-time method, the 

parameter of interest is the aggregate seconds of observed emissions that exceed the level of the opacity standard; consequently, the standard deviation 

between observers is expressed as seconds. 

The results presented in Table 2 indicate that for over 90% of the total 

observations for 2-minute, 3-minute, and 6-minute opacity averaging, the 

readings of two observers compared within 7.5% opacity. Only a small in -

crease in between-observer precision is noted when the averaging time is 

decreased from 6 minutes to 2 minutes. The standard deviation used to 

estimate between-observer precision ranges from 2.6% opacity for a 2-minute r\ 

average to 2.1% opacity for a 6-minute average. The measiixeiLdifference C-pi^^ 

between observers is at a level that compares with data obtained during >^JAX- r. 

•• • ~~~ — ' ~ -7-v-v —*"* ^ 'if I A 

the panel study conducted prior to reprpmulgation of Method 9 {*>. During *> -

llu v 

"fJfiFTRTtFibd 9 study, the composite between-observer standard deviation for 

6-minute opacity averaging was estimated at 2.6% opacity. During the smoke 

generator studies, the between-observer bias was not estimated for timeaveraged opacity. 
TABLE 2. DIFFERENCE BETWEEN OBSERVERS: OPACITY AVERAGING METHOD 

Opacity 

Averaging 

Period 

2 minutes 

3 minutes 

6 minutes 

15-second 

single reading 

Number 

of 

Observations 

17,694 

11,836 

5,954 

140,250 

Standard 

Deviation 

(% Opacity) 

2.6 

2.4 

2.1 

3.4 

Frequency of 

Difference 

Between 

Observers 

< 7.5% Opacity 

Tpercent of 

observations) 

92 

92 

93 

87 

10 
TABLE 3. DIFFERENCE BETWEEN OBSERVERS: AGGREGATE-TIME METHOD 

Parameter 

Observed Time > 15% opacity 

Observed Time >^ 20% opacity 

Observed Time >^ 25% opacity 

Observed Time > 30% opacity 

Mean 

Aggregate Time 

(seconds) 

520 

296 

183 

129 

Standard 

Deviation 

(seconds) 

239 

190 

130 

104 

Relative Standard 

Deviation1 

(percent) 

46 

64 

71 

81 

MEAN VALUE 166 66 

^Standard Deviation/Mean) x 100 

11 
P.19 

For comparison, results for 15-second single observation periods are 

also reported in Table 3. The measure of variation between observers (SD) 

does increase to 3.4 seconds from the 2.1 seconds measured for 6-minute 

opacity averaging. As expected, the percentage of observations with a 

difference between observers exceeding 7.5% opacity also increases. 

The results presented in Table 3 indicate that the mean betweenobserver error for the fugitive emissions data analyzed during this study 

was 166 seconds, with a range of 104-239 seconds, when determining the 

aggregate time exceeding standards of from 10% to 25% opacity. Although 

the between-observer precision appears to decrease as the opacity decision 

level increases (i.e., SD goes from 239 seconds for the observed time 

greater than 15% opacity to 104 seconds for the observed time greater 

than 30% opacity), the between-observer precision actually increases if it 

is determined on a basis relative to the mean aggregate emission time. 

The mean between-observer error of 166 seconds compares favorably to the 

between-observer error of 159 seconds determined during the RTP smoke 

generator study (*'. This is an indication that the observers performed 

about as well in the field observing the fugitive emissions as they did 

observing the smoke generator emissions. In_oth.er words. the Jiariaticm 

between different inspectors observing the fuqiti've_emj^.sJ-aas-jyas_ab.o.u.t 

fJHe~same~as "the variation among inspectors observing smoke generator^ 

•enri"sTi"orrs":—" """ ~~~ 

It is important to remember that no measurement of observer bias 

(error) can be obtained for the fugitive data, since no "true value" is 

available to which the observers' measurements can be directly compared. 

12 
P.20 

3.2 Comparison of Methods 

A major consideration in evaluating an opacity regulation/reading 

method combination is how stringent the combination is, compared to other 

possible opacity regulation/reading methods. For example, for a given 

emission source, will more violations occur with a £20 % opacity level and 

a 3-minute time exemption regulation (aggregate-time reading method), or 

with a <• 20% opacity level regulation (3-minute average), or with a £ 20% 

opacity level regulation (6-minute average)? 

The fugitive emission data set was used to represent typical fugitive 

emission sources, and a relative stringency analysis was conducted using three 

opacity regulation/reading method combinations. The relative stringency 

when determining noncompliance with a typical emission standard was compared 

for three methods: 1) aggregate-time, 2) 3-minute opacity averaging, and 3) 

6-minute opacity averaging. For the same fugitive emissions data set, the 

numbers of noncompliance periods obtained by each method were tabulated and 

compared. Noncompliance was determined for the case where allowance was made 

for observer error in determining opacity levels, as well as for the case where 

the noncompliance level was not adjusted for observer error. Table 4 summarizes 

the parameters used during the noncompliance comparisons. Section 2.0 above 

provided a more detailed explanation of the error allowance parameters chosen 

and the reasons for the choices. 

Table 5 presents the results of the relative stringency analysis. The 

methods are listed according to the level of noncompliance with the chosen 

standard; the most stringent method is listed first. Figure 1 presents the 

results graphically, with the stringency expressed relative to the aggregate 

time noncompliance without observer error (i.e., aggregate-time with no error 

allowance is equivalent to a noncompliance level of 1). The results indicate 

that without error allowance, the aggregate-time method is the most stringent. 

However, with error allowance, the aggregate-time method and the 3-minute opacity averaging method indicate noncompliance with about the same frequency. 

Six-minute opacity averaging is the least stringent method for this data set. 

13 
P.21 

TABLE 4. PARAMETERS CHOSEN FOR RELATIVE STRINGENCY EVALUATION 

Parameter 

Aggregate-Time 

Method 

3-Minute Averaging 

Method 

6-Minute Averaging 

Method 

Regulations 

Compared: 

Error Margin: 

Noncompliance 

Level without 

Error Allowance: 

Noncompliance 

Level with 

Error Allowance 

Not equal to or 

in excess of 20% 

opacity except 

for three minutes 

per hour 

10% opacity plus 

15 seconds exemption per 6-minute 

observation period1 

(up to 2.5 

minutes per hour) 

where excess emissions are noted 

3.25 minutes (13 

readings) >_ 20% 

opacity for onehour period or 1.75 

minutes (7 readings) 

>_ 20% opacity for 

one-half hour period 

3.50 minutes (14 

readings) >_ 30% 

opacity for onehour periods ("•' 

or 2.00 minutes (8 

readings) >_ 30% 

opacity for onehalf hour periods^1

' 

Not to exceed 20% 

opacity 

Not to exceed 20% 

opacity 

11.8% Opacity 7.5% Opacity 

20.1% Opacity 20.1% Opacity 

31.9% Opacity 27.6% Opacity 

1

 One extra reading (0.25 minute) is allowed for observer error for each additional 

6-minute observation period where 15-second readings are in excess of the opacity 

noncompliance level, i.e. , > 30% opacity. 

14 
P.22 

TABLE 5. RELATIVE STRINGENCY OF THREE METHODS 

Method Noncompliance 

(percent of runs)1 

Aggregate-time, without error margin 

3-Minute opacity average, without error margin 

6-Minute opacity average, without error margin 

Aggregate-time, with error margin2 

3-Minute opacity average, with error margin3 

6-Minute opacity average, with error margin* 

97 

75 

56 

46 

45 

36 

1 Percent of runs where noncompliance occurred by at least one method 

2 10% Opacity plus 0.25 minute additional time exemption 

3 11.8% Opacity 

4 7.5% Opacity 

15 
P.23 

100* 

ERROR ALLOWANCE, percent 

' 10 % OPACITY, 0.25 min FOR AGGREGATE TIME; 

11.8% OPACITY FOR 3-min AVERAGING; AND 

7.5% OPACITY FOR 6-min AVERAGING 

Figure 1. Comparison of noncompliance by three methods. 

16. 
P.24 

TABLE 6. OPACITY AVERAGING METHODS COMPARED TO THE AGGREGATE-TIME METHOD1 

**%• ••• 

Opacity Reading Method 

•* 

Aggregate-Time Method 

With no error margin 

With error margin 

Three-Minute Average 

With no error margin 

With error margin 

Six-Minute Average 

With no error margin 

With 7.5% error 

margin 

Nonmetallic 

Mi neral 

Sources 

(21 sets) 

# Sets 

21 

3 

6 

2 

5 

2 

% Sets 

100 

14 

29 

10 

24 

10 

Iron & Steel 

Sources 

(137 sets) 

# Sets 

133 

69 

113 

69 

84 

55 

% Sets 

97 

50 

82 

50 

61 

40 

All Sourcesobservation 

period < 30 

minutes 

(89 sel 

# Sets 

86 

31 

56 

26 

36 

15 

is) 

% Sets 

97 

35 

63 

29 

40 

17 

All Sources— 

60-minute 

obsevation 

peri od 

(69 sel 

# Sets 

68 

41 

63 

45 

53 

42 

:s) 

% Sets 

99 

59 

91 

65 

77 

61 

TOTAL All 

Sourcesall readings 

(158 sets) 

# Sets 

154 

72 

119 

71 

89 

57 

% Sets 

97 

46 

75 

45 

56 

36 

1 356 data sets total, with two readings (two observers) for each of the 356 data sets. The 

first reading of each pair was chosen for evaluation. Only those readings showing a 

'violation by any of the three method/standard combinations were included in the 158 sets. 

17 
P.25 

Table 6 provides a more detailed comparison of opacity averaging methods 

wi ith the aggregate-time method. 

4.0 SUMMARY AND CONCLUSIONS 

Actual fiel d data from fugitive-type emission sources were evaluated in 

order to determine how observer error for the 3-minute opacity averaging method 

compared to observer error associated with the 6-minute opacity averaging method. 

In addition, the degree to which the three methods (aggregate-time, 3-minute 

opacity averaging, and 6-minute opacity averaging) indicated noncompliance in 

relation to a specified standard was also examined to illustrate the relative 

stringency of the methods. Results of this study indicate the following: 

a) The between-observer error for the 3-minute opacity averaging method 

is essentially equivalent to the observer error for the 6-minute opacity averaging 

method; results obtained from other studies (1.4) a - ] S 0 SUpport this conclusion. 

b) The difference in measured opacity by two observers was less than or 

equal to 7.5% opacity for 92% and 93% of the total observations using the 3-

minute opacity averaging method and the 6-minute opacity averaging method, 

respectively. 

c) Between-observer error for observation of fugitive intermittent 

emissions using the aggregate-time method has been estimated and is of the 

same order of magnitude as the error estimate obtained from the RTP smoke 

generator study (D . 

d) For the data set examined, the 6-minute opacity averaging method is not 

as stringent as either the 3-minute opacity averaging or aggregate-time methods.; 

this is true regardless of whether or not error margins are used. 

e) For the data set examined, the aggregate-time and 3-minute opacity 

averaging methods are about equally stringent when error margin is used. 

f) When no error margins are used, the aggregate-time method is the 

most stringent of the three methods compared during this study. 

18 
P.26 

REFERENCES 

1. Field Evaluation of Opacity Reading Methods for Intermittent Plumes, 

Del Green Associates, Inc., December, 1981. 

2. Evaluation of Opacity Frequency Method on Continuous Plumes, Del 

Green Associates, Inc., December, 1981. 

3. Evaluation of Opacity Frequency Method on Slowly Changing Plumes, 

Del Green Associates, Inc., December, 1981. 

4. Evaluation and Collaborative Study of Method for Visual Determination of 

Opacity of Emissions from Stationary Sources. U.S. Environmental Protection 

Agency. EPA 650/4-75-009, January, 1975. 

5. Statistical Analysis of Visible Emissions Field Tests, Research Triangle 

Institute, February, 1982. 

19 
4, i* 

United States 

Environmental Protection 

Agency 

Office of Air Quality Planning and Standards 

Stationary Source Compliance Division 

Washington D.C. 20460 

Official Business 

Penalty for Private Use 

S300 

Publication No. Special Report Postage and 

Fees Paid 

Environmental 

Protection 

Agency 

EPA 335 

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