PUBLIC COMMENT SUMMARY:
OPACITY PROVISIONS
UNDER
STANDARDS OF PERFORMANCE
FOR NEW STATIONARY SOURCES
OF AIR POLLUTION
Environmental Protection Anency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
"August 1975
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26099
Introduction
On April 22, 1975 (40 FR 17778), the Environmental Protection
Agency (EPA) issued a notice requesting comments from all interested
persons on the opacity provisions under the standards of performance
for new stationary sources of air pollution (40 CFR Part 60). The
opacity provisions are included under 40 CFR 60.11 and Reference
Method 9 of Appendix A. Comments were also requested on the report
entitled "Reevaluation of Opacity Standard of Performance for
Asphalt Concrete Plants."
Table 1 presents the number of persons commenting by affiliation
category and Table 2 lists the name and affiliation of each person
who commented. A summary of the comments and EPA's responses follows
Table 2. Reference has been made in response to several comments to
the "EPA Response to Remand Ordered by U. S. Court of Appeals for the
District of Columbia in Portland Cement Association v. Ruckelshaus
(436 F.2d 375, June 29, 1973)." Copies of this document are available
upon request from the Emission Standards and Engineering Division,
Environmental Protection Agency, Research Triangle Park, North Carolina
27711, Attention: Mr. Don R. Goodwin.
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Comment Summary: Opacity Provisions
Table 1. Number of Commentators by Affiliation Category
Category
State or Local Air Pollution
Control Agency
U. S. Environmental Protection Agency
Other Federal Agencies
Asphalt Concrete Pavement Associations
Asphalt Concrete Companies or Contractors
Asphalt Plant Equipment Manufacturers
Electric Utility Industry
Portland Cement Industry
Iron and Steel Industry
Consulting Firms
Instrument Manufacturers
Air Pollution Control Equipment
Manufacturers
Miscellaneous
Total
Code
A
B
C
D
E
F
G
H
I
J
K
L
M
Number
Received
13
3
1
6
23
. 1
6
6
3
1
4
3
_5
75
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Table 2. List of Commentators on April 22, 1975, Federal Register Notice
Comment
Number
AC-1
AC-2
AC-3
AC-4
AC-5
AC-6
AC-7
AC-8
AC-9
AC- 10
AC-11
AC-1 2
AC-1 3
AC-14
AC-1 5
AC-1 6
AC- 17
AC-18
AC-1 9
AC-20
AC-21
AC-22
AC-23
AC-24
J.
W.
J.
I.
R.
H.
D.
M.
G.
R.
W.
W.
D.
H.
E.
Bi
J.
H.
M.
C.
P.
J.
S.
W.
Commentator
W. Koontz
Simmons
A. Redmond
L. Dickstein
G. Lunche
N. Troy
M. Anderson
C. Cordaro
F. McGowan
W. Heimsoth
Simmons
R. Meyer
M. Thomas
R. Smith
V. Fitzpatrick
11 Stewart
W. Gallion
P. Wolfe
Feaster
E. Minor
E. Todd
P. DiRenzo
W. Simmons
H. Vanderlinden, Or
Affiliation
Prince George's County, Dept. of
Health, Division of Air
Pollution Control
State of Calif., Air Resources
Board
State of Florida, Dept. of
Pollution Control
EPA, Enforcement Region VIII
Los Angeles County APCD
Owens-Illinois
Bethlehem Steel Corp.
Long Island Lighting Co.
Lear Siegler Inc.
Photomation Inc.
State of Calif., Air Resources
Board
Commonwealth of Virginia, State
Air Pollution Control Board
San Bernardino County APCD
U. S. Department of Defense
EPA, Surveillance and Analysis
Division, Region I
Texas Air Control Board
Oklahoma, State Dept. of Health
Limestone Sales, Inc.
Ritchie Construction Co., Inc.
Asphalt Paving Association of
Washington, Inc.
Percy Todd Manufacturing Co.
Ackworth Materials Corp.
Eastern Industries, Inc.
Midstate Contractors, Inc.
Code
A
B
A
K
I
G
K
K
A
A
C
B
A
A
E
E
D
L
E
E
E
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Table 2 (continued)
Comment
Number
AC-25
AC-26
AC-27
AC-28
AC-29
AC-30
AC-31
AC-32
AC-33
AC -34
AC-35
AC^36
ACr37
AC-38
AC-39
AC-40
AC-41
AC-42
AC-43
AC-44
AC-45
AC-46
AC-4.7
AC-48
AC-49
AC -50
AC-51
F.
J.
H.
Wv
R.
J.
w.
B.
E.
C.
E.
E.
F.
W.
E.
T.
J.
L.
C.
B.
J.
D.
M.
H.
R,
R.
J.
Commentator
H. Eller
E. Laird
Ratrie
E. Hooper
G. Lunche
T. Via, Jr.
S. Smith
R. Anthony
M. Allen, Jr.
B. Eller
Bartus
R, Berry
J. Crosby
R. McCormick
F, Arps
D. Parnell
Critehfield
L. Warner
A. Fenet
B. Ross, Jr.
E. Mummert
Y. Maclver
F. L. Stewart, Jr
L. Haddock
J. Bartell
L. Yarbrough
C. Snyder
Affiliation Code
Interstate Equipment Co. L
The Maryland Asphalt Assoc,, Inc. D
Ratrie, Robbins, & Schweizer, Inc. E
Central Paving Co, E
Los Angeles County APCD A
Tucspn Gas & Electric Co. G
Entropy Environmentalists, Inc. J
Washita Construction Co. E
Murray Co., Inc. E
EPA, Surveillance and Analysis B
Division, Region IX
Unknown M
Asphalt Pavers Asspc,, Inc, D
Ward Pavements, Inc. E
Southwestern Portland Cement H
Co., Eastern Division
Tri County Asphalt Corp. E
Hall & Barber, Inc, E
Associated General Contractors E
Southwestern Portland Cement Co., H
Eastern Division
R. E. Heidt Construction Co. E
Carolina Asphalt Pavement D
Assoc., Inc.
Soutjiwes.tern Portland Cement, Southwest H
Division
Southwestern Portland Cement Co. H
Asphalt Manufacturers Assoc. of D
Western Pa.
Crowell Constructors, Inc. E
Iowa Manufacturing Co. F
University Asphalt Co. E
The Buffalo Slag Co., Inc. E
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Table 2 (continued)
Comment
Number
AC-52
AC-53
AC-54
AC-55
AC-56
AC-57
AC-58
AC-59
AC-60
AC-61
AC-62
AC-63
AC-64
AC-65
AC-66
AC-67
AC -68
AC-69
AC-70
AC-71
AC-72
AC-73
AC-74
AC-75
Commentator
F. D. Pickar
W. R. Cady
C. J. Heath
S. J. Acquaviva
D. S. Cahn
V. L. Sewell
R. L. Smith
J. F. Denton
W. R. Meyer
C. M. Brown
H. E. Dunkel burger, Or
and T. L. Garrett
M. C. Cordaro
R. H. Berby
R. Dworek
J. L. Gil Inland
L. V. Earnhardt
W. C. Achinger
H. Wong-Woo
J. R. Jannarone
H. N. Troy
J. B. Moore
T. N. Combs
T. McKie
P. A. Krenkel
Affiliation Code
Arrowhead Blacktop Co. E
Allied Chemical E
Precipitation Assoc. of America, L
Inc.
Golden Glades Materials, Inc. E
Amcord M
Texas Industries, Inc. M
Warren Bros. Co. E
Warren Bros. Co. E
Commonwealth of Virginia, State : A
Air Pollution Control Board
Republic Steel Corp. I
Covington & Burling representing E
Warren Bros. Co.
Long Island Lighting Co. G
Kaiser Cement & Gypsum Corp. H
United States Steel Corp. I
Ideal Basic Industries, Cement H
Division
The Fountain Sand and Gravel Co. M
Wayne County Dept. of Health, A
Air Pollution Control Division
State of California, Air Resources A
Board
Con Edison of New York G
Owens-Illinois K
So. Calif. Edison Co. G
Webster, Kilcullen & Chamberlain D
representing National Asphalt
Pavement Association
Unknown M
Tennessee Valley Authority G
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Comment Summary and EPA Responses
The comments on the opacity provisions are categorized and presented
according to the provisions to which thev primarily pertain. Following
each summarized comment is a coded listing of all commentators who
commented on that issue (see Table 2) and their affiliation (see Table 1)
Section 60.11
1. The provisions of §60.11(e) are a necessary step toward establishment
of reasonable opacity standards. AC-65(I)
Resoonse: No response necessary.
2. EPA should add provisions similar to those of §60.11(e)(2) which
would allow establishment of alternative opacity standards for
fugitive emission sources. Suggest ambient afr sampling around
the facility. A
Response: The suggested alternative provisions are not necessary
and would defeat the nurpose of opacity standards for fugitive
emission sources. Opacity standards are established for fugitive
emission sources to require the owner or operator to direct proper
attention to maintenance and housekeeping practices at the facility
as well as to nroner ducting of all emission points. nnacitv
standards for fugitive emissions are established at a level such that
if the facility is properly designed, and proper maintenance and
housekeeping practices are implemented, the standards can be met
easily.
The provisions of §60.11(e) are meaningless if. State and local air
pollution control agencies do not adopt a similar exception procedure
because the source will still be subject to the more restrictive
local regulation. EPA should deny establishment of special stan-
dards under §60.11(e) if the State or local air pollution control
agency does not also allow such petitions. AC-66(H), AC-68(A)
Response: EPA believes that the provisions of §60.11(e) are necessary
and meaningful without States adopting similar exception procedures.
The EPA regulation bases determination of compliance with opacity
standards of performance on single sets of 24 observations taken
in accordance with Method 9, while most State and local regulations
base compliance on an opacity level which is not to be exceeded
except for allowed time periods. Since the standards and the methods
of determining compliance are not comparable, whether or not a source
requires an exemption from the local regulation is dependent on the
level of the local opacity standard and the duration of the time
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exemption. Obviously, such an analysis must be conducted on a
case-by-case basis and cannot be adequately addressed here. It
is expected that very few special opacity standards will need to
be established under the provisions of §60.11(e) since opacity
standards of performance are established at levels which consider
maximum expected effects of stack diameter, particle diameter,
and other significant variables.
4. Disagree with the provisions of §60.11(e) since it allows the
Administrator to establish alternative opacity standards without
requiring the source to first demonstrate compliance with all
applicable standards. AC-16(A)
Response: The provisions of §60.11(e)(3) clearly require the
owner or operator to demonstrate that the facility was operated
and maintained in a manner to minimize the opacity of emissions
during the performance test; that the performance tests were
properly conducted; and that the facility and its associated
air pollution control equipment cannot be adjusted to meet the
applicable opacity standard.
The provisions of §60.11(el in effect grant waivers from opacity
standards for certain sources. These provisions are in conflict
with existing EPA policies and ignore health effects of pollution
by allowing increased emissions of fine particles. AC-5(A),
AC-29(A)
Response: The provisions of §60.11(e) are not in conflict with
EPA policies, but provide consideration for anomalous sources
which cannot be adjusted to comply with the opacity standard.
Special opacity standards will be established under the provisions
of §60.11(e) only if it can be demonstrated that: (1) the facility
was operated in a manner to minimize the opacity of emissions from
the source, (2) the performance tests were properly conducted and
showed the facility to be in compliance with the applicable mass
or concentration standards, and (3) the facility and control equip-
ment cannot be adjusted to meet the applicable opacity standards.
Establishing special standards under these conditions is consistent
with EPA's policy that where opacity and concentration or mass
standards are applicable to the same source, the opacity standard
will not be more restrictive than the concentration or mass standard.
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The health effects of emissions from a source category are reflected
in the development of the concentration or mass standard and in the
determination of the best system of emission reduction considering
costs. The concentration or mass standard for a given source category
is established at a level which will result in the design, installa-
tion, and operation of the best adequately demonstrated system of
emission reduction. Any associated opacity standard is established
at a level which will require proper operation and maintenance of
the air pollution control system but will not require the design
and installation of a more efficient control system. Establishment
of separate opacity standards for anomalous sources which cannot
be adjusted to comply with the source category opacity standard
does not exempt these sources from compliance with the concentration
or mass standard, which is the more restrictive of the two standards.
The impact of the emission source on ambient air quality, thus,
is minimized to the level achievable by best control technology,
and further reductions are not achievable at a reasonable cost.
Any separate opacity standard established under §60.11(e) will be
set at a level which requires proper operation and maintenance of
the control system. EPA does agree with the commentator that opacity
standards can be a means of regulating fine particulate emissions;
however, EPA also believes that it is preferable to expressly regu-
late these emissions in the size range of interest. Therefore,
opacity standards of performance are not used for the purpose of
regulating fine particle emissions.
6. Section GO.llCe) will make enforcement of opacity standards overly
complex because there will be different opacity standards for
different plants in the same source category. AC-5(A)
Response: Opacity standards of performance are established at
levels such that well-controlled plants with stack diameters and
other parameters in the expected range can comply with the opacity
standard if they comply with the concentration, or mass standard. EPA
believes that the situations where special standards are required
will be very rare. The provisions of §60.11(e), therefore, are not
expected to make enforcement of opacity standards overly complex.
In addition, EPA believes that it is not unreasonable to expect the
enforcement officer to familiarize himself with the applicable
standards for a facility prior to surveillance of that facility.
7. The provisions of §60.11(e)(2) would be unnecessary if EPA obtained
data representative of the entire so.urce category and did not
establish overly stringent opacity standards. AC-52(E), AC-59(E),
AC-62(E), AC-73(D)
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Response: Opacity standards are not established at an overly
restrictive level for facilities using best systems of emission
reduction. EPA establishes opacity standards at a reasonable
level which is based on data from facilities operating within
the known range of variables. The provisions of §60.11(e) were
established to provide accommodation for situations where operating
and design variables are outside of the expected range. As was
indicated in the November 12,1974, Federal Register publication,
the situations where use of the special standards provisions is
necessary are expected to be extremely infrequent.
8. EPA should not allow instrument data to take precedence over
opacity observations by qualified observers. AC-5(A), AC-29(A)
Response: Section 60.11(b) does not allow instrument data to
take precedence over observations by qualified observers, but
rather in certain situations and under certain conditions allows
their use merely as probative, not conclusive, evidence. Obserr
vations taken in accordance with Method 9 by qualified observers
still remains the primary and accepted means of determining com-
pliance with opacity standards of performance.
9. Use of in-stack transmissometers to establish compliance with opacity
standards is an unacceptable approach in cases where condensation of
parti oil ate matter occurs upon emission to the atmosphere (e.g. SO-i
or HC1 in the effluent gas stream). AC-5(A), AC-29(A)
Response: As noted in the discussion of the November 12, 1974 (39 FR
39372), revisions to 40 CFR 60.11 and Reference flethod 9, in-st*ck
transmissometers are not used to establish compliance with opacity
standards. Section 60.11(b) specifies that Reference Method 9 is the
means for determining compliance with opacity standards; however,
data from in-stack transmissometers may be submitted as probative,
but not conclusive, evidence of compliance. EPA agrees that in.-stack
measurements of opacity could possibly be a meaningless indication
of actual plume opacity when the effluent contains condensable com-
pounds. In any submittal of data from continuous monitoring by trans-
missometer, EPA would consider the relevancy of these data to the
question of the plume opacity in addition to reviewing the evidence
submitted by the source owner shoving that the transmissometer meets
Performance Specification 1 in Appendix B, that the transmissometer has
been properly maintained and calibrated, and that the data have not
been tampered with in any way. Obviously, such a review must be
conducted on an individual case basis. Even in situations where the
results from continuous monitoring by transmissometer are accepted as
probative evidence, the results of opacity readings by f'ethod 9
remain presumptively valid and correct.
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For source categories whose emissions contain appreciable amounts
of condensable compounds and have applicable opacity standards, EPA
does not require installation of an in-stack transmissometer.
Should a facility unexpectedly have appreciable quantities of
condensed compounds such that in-stack measurement of opacity
is meaningless, the provisions of §60.11(i) allot'.1 the owner or
operator to request exemption from the monitoring requirement.
10. Method 9 observations should be subordinate to data from in-stack
transmissometers since these data are more accurate than Method 9
observations, in-stack transmissometers are the primary reference
during observer certification, and transmissometer data do not vary
v.'ith illumination and other environmental conditions. Method 9
should be retained only for use at facilities without in-stack
transmissometers. AC-6(K), AC-8(G), AC-56(M), AC-62(E), AC-70(G),
AC-71(K)
Response: Method 9 has been demonstrated to be of sufficient
accuracy for determining compliance with opacity standards when
the positive error is taken into consideration in determining possible
violations. In addition, Method 9 is being retained as the primary
and accepted means for determining compliance in order to have a
consistent regulatory and enforcement approach for all stationary
sources. Data from in-stack transmissometers are not accepted
as the means for demonstrating compliance with opacity standards
because of the difficulties involved for the enforcement agency
in verifying that the transmissometer has been properly calibrated,
operated, and maintained. However, in-stack transmissometer data
may be submitted as probative (but not conclusive) evidence of the
actual opacity of emissions.
11. Since §60.11(b) allows the use of in-stack transmissometers as
probative evidence of compliance, EPA should develop criteria for
reduction of the transmissometer data. Factors that should be
considered include averaging periods, data reduction of transitory
peak periods, correction of the data to stack exit diameter values,
the effects of non-uniform processes, and the effect of air inleakage
after the transmissometer and before the stack exit. AC-63(G)
Response: Such criteria have been developed and are part of the
specifications on continuous monitoring which will be promulgated
in the Federal Register in the future.
12. The provisions of §60.11(e) represent an unnecessarily cumbersome
method of handling a situation which may occur frequently. AC-67(M)
Response: EPA agrees with the commentator that the establishment of
special opacity standards would be a cumbersome approach if many of
these situations occurred. However, as indicated in the responses
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to comments 6 and 7 of this section, EPA does not expect to estahlis1"
many special opacity standards. Obviously, if any given source
category requires a large number of special standards, the opacity
standard would have to be thoroughly reevaluated.
13. The provisions of §60.11(e) unjustifiably shift to the owner or
operator the burden of proving the unachievability of the opacity
standard. This procedure raises serious constitutional questions
particularly when viewed in the context of the Clean Air Act, which
imposes criminal and civil penalties for noncompliance. AC-62(E)
Response: Opacity standards of performance are established at
levels which require proper operation and maintenance of well-
controlled facilities operating within the expected range of
operating variables. The provisions of §60.11(e) provide neces-
sary flexibility for establishment of special standards for faci-
lities operating outside the expected range of operating variables.
EPA expects that situations requiring special opacity standards are
unlikely, but the provisions of §60.11(e) were established to pro-
vide flexibility for any unforeseen situations.
The term "burden of proof" as used in the comment, refers to the dutv
bf a party to Drove affirmatively a claim asserted in a judicial
case, and the constitutional issues of shifting the burden of proof
relate more specifically to criminal actions in a court of law.
The notion of burden of proof, therefore, is not applicable to
section 60.11(e) which is concerned with administrative, not legal,
action. In the event that legal action, whether civil or criminal,
is taken to enforce these standards under section 113 of the Clean
Air Act, as amended, "EPA has the burden of proving that the alleged
violation has in fact occurred.
Section 60.92(a)
1. The available opacity data clearly indicate that a 20 percent
standard is too lenient and a no visible emission standard should
be promulgated. Experience with nine asphalt concrete plants in
Prince George's Co. (Md.) indicate that a no visible emission
standard is a reasonable standard. AC-1(A)
Response: Review and analysis of the opacity data and the con-
ditions under which the data were obtained shows that a no visible
emissions standard (zero percent opacity) is inappropriate. The
opacity standard was established at 20 percent to allow for any
situations where a plant is operating with an atypically large
stack diameter and/or emits particulates with atypically small
mass mean diameters. For such situations, a standard of zero
percent opacity could be more restrictive than the concentration
standard and would be inconsistent with EPA policy. Therefore,
a zero percent opacity standard was not promulgated.
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2. A 20 percent opacity standard for asphalt concrete plants is well
within levels achievable by available control technology. AC-74(M)
Response: ilo response is necessary.
3. The opacity standard has not been demonstrated to be achievable be-
cause it was based on three plants which were arbitrarily selected
for Method 5 testing, on the basis of no visible emissions, from a
total of 64 well-controlled facilities. EPA has never presented a
justification for excluding these other facilities from study which
may have disproved EPA's assumption that well-controlled asphalt
plants should have no visible emissions. EPA also has never ex-
plained why additional data from plants other than those tested by
Method 5 were not obtained. AC-62(E), AC-73(D)
Response: EPA believes that the opacity standard of 20 percent has
been adequately demonstrated by observations and calculations to be
achievable by facilities that use properly designed, installed,
operated, and maintained baghouses or venturi scrubbers. The three
facilities observed by EPA were originally selected for Method 5
testing because they were good examples of well-designed and well-
operated fabric filter collectors and venturi scrubbers, the facili-
ties were amenable to Method 5 testing, and they were available
for testing during the desired period. The facilities were not
arbitrarily selected for emission testing on the basis of no
visible emissions as alleged by the commentators; in fact, one
facility was observed to have visible emissions during the EPA
pre-survey. The bases for selection of the facilities for testing
were discussed in Volume I of "Background Information for New Source
Performance Standards: Asphalt Concrete Plants..." APTD-1352 (a, b,
c) and in response to comment 1-20 in Volume III. EPA would like
to reiterate that these 64 asphalt concrete plants were not all
equally well controlled; in fact, many installations with low-
efficiency collectors were observed at the request of local
asphalt assocations and were presented as examples of "good.
housekeeping" rather than best control technology.
Additional opacity data were not obtained from asphalt concrete
plants other than those previously tested by EPA for several reasons.
The intent of opacity standards is to ensure proper operation and
maintenance of the control systeiu on a continuous basis. The
opacity data were obtained at asphalt concrete plants with known
proper maintenance practices and with a previously established
emission concentration. Observation of control equipment with
unknown levels of emission control and unknown operation and
maintenance practices could have resulted in data which would
not be representative of the desired levels. (The resultant data
may have been too lenient or too stringent.) Such data would not
have fceen useful for establishment of the opacity standard. Since
the opacity standard was established at a level in excess of the
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8
observed levels, and was established at a level which takes into
consideration the maximum expected effects of stack diameter, par-
ticle size, and other significant variables, this process does
not prejudice owners and operators of well-controlled asphalt
concrete plants operating within the expected range of variables.
4. The opacity standard is insufficiently supported by the data bases
which consist of only 15 hours of observations obtained at three
facilities. Such limited data can hardly be considered a typical
cross-section of the industry which operates under widely varying
conditions. Specifically, EPA should have observed asphalt concrete
plants operating with greater than 10 percent minus 200 mesh feed
material. EPA should submit these data for review to the National
Bureau of Standards to determine the appropriateness of use of such
a limited data base. AC-47(D), AC-49(F), AC-52(E), AC-59(E), AC-62(E),
AC-67(M], AC-73(D]
Response: Section 111 of the Clean Air Act requires that standards
of performance "reflect the degree of emission limitation achievable
through application of the best system of emission reduction which
(taking into account the cost of achieving such reduction) the
Administrator determines has been adequately demonstrated." Neither
the language of section 111 nor the legislative history of the Act
provides any guidance on the amount of data necessary for justifica-
tion of a standard of performance. In any case, the Act does not
require the standard to be based on control levels which all existing
plants are capable of achieving. The Act requires that standards
of performance be based on the application of best available tech-
nology; therefore, the data bases of the standard are necessarily
limited. It was the Administrator's judgment that 15 hours of
Method 9 observations on best controlled facilities combined with
additional information provided by State and local air pollution
control agencies was sufficient justification for establishment of
a 20 percent opacity standard. (The revaluation report did not
discuss the information received from State and local air pollution
control agencies or the data summarized in Volume II of the "Back-
ground Information for New Source Performance Standards:..." APTD-
1352 because all the observations were of unknqwn duration or no
information en emission concentrations was available. This infor-
mation was hot the primary basis of the opacity standard.) The data
bases of this standard are sufficient and the opacity standard is
established at a clearly achievable level as evidenced by comments
1 and 2 of this section.
The standards of performance are not intended to reflect performance
of a typical cross-section of the industry. The opacity standard is
established at a level which will ensure continued proper operation
and maintenance of the control systems of interest (baghouses or
venturi scrubbers) and takes into consideration the effects of the
normal range of operating variables on opacity. EPA believes that
asphalt concrete plants operating under typical conditions, and
witti emission concentrations less than 90 mg/dscm, will have plume
opacities significantly less than the level of the standard (20
percent). The opacity standard is also achievable by facilities
operating witlyvariables at the extreme values of their expected
ranges, such as facilities with an effluent with a mass mean diame-
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ter of one micron. Emissions"from an asphalt concrete plant using
greater than 10 percent minus 200 mesh feed material will not have
an average size smaller than one micron since particles smaller
than one micron are not generated by rock crushing and grinding
operations. Therefore, observation of asphalt concrete plants
using large quantities of minus 200 mesh material was not con-
sidered necessary.
5. The parti oil ate matter emission tests and the opacity observations
were conducted approximately two years apart. The data, therefore,
are not comparable and cannot be used to justify the opacity stan-
dard. AC-59CE1, AC*62(EI, AC*66('H), AC-73(D)
Response: In response to comments received on the proposed opacity
standard, additional opacity observations were conducted at three
well-controlled asphalt concrete plants. These data were summarized
in Table 1 of the revaluation report. (Because the data were
already reported in Volume II of the "Background Information for
New Source Performance Standards: ...," the data bases of the
proposed standard were not summarized in the revaluation report.)
The opacity observations were conducted in September 1973 at three
well-controlled facilities after it was determined that no extensive
changes and repairs had been made to their control devices in the
period since the original emission tests. (Facility B, also tested
by EPA in 1971, was not observed because it had shut down for the win-
ter due to insufficient business.) It was believed that at best the
control devices would be performing at the same efficiency demonstrated
during the performance test. EPA also recognized that these control
systems could possibly have been operating less efficiently than dur-
ing the emission tests and could possibly result in opacity data biased
slightly in favor of the source category. Use of such data to establish
an ooacity standard is not ore.iudicial to the source owner nr ooerator.
During the development of the standard of performance, National Asphalt
Pavement Association (NAPA) alleged that older fabric filter collectors
would "seep" particles and thus would emit more particulate matter than
a new filter in optimum condition. Observation of the two fabric fil-
ter collectors two years after the original tests certainly could have
determined if "seepage" was in fact a problem.
EPA used the concentration data from the previous emission tests as
an indication of the probable emission rate of the facility. EPA
recognized that the concentration of emissions from the facility
could have increased over the previously measured levels if the
performance of the control systems had deteriorated.
All three well-controlled facilities had no visible emissions
despite the range of the originally measured concentrations of
particulate matter. Therefore, it was concluded that emission
concentrations less than 90 mg/dscm which are emitted from typical
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10
stack diameters are invisible to a human observer and the exact emi-
sion concentration of these facilities was not a critical question.
This conclusion is somewhat affirmed by a personal communication
with commentator AC-68 which indicated that asphalt concrete plants
with an effluent concentration of about 180 mg/scm (0.08 gr/scf)
were observed to have plumes of 5 to 10 percent opacity. These
observations are consistent with the in-stack transmissometer data
reported in reference 2 of the revaluation report. For the above
reasons, these opacity observations which were obtained two years
after the emission tests were conducted are considered to be repre-
sentative of emission levels achievable by well-maintained and well-
operated fabric filter collectors or venturi scrubbers. The opacity
standard which was developed from these observations is achievable
by well-controlled asphalt concrete plants and is supported by the
opacity data.
The opacity observations conducted at the three facilities in Septem-
ber 1973 are invalid because neither an in-stack transmissometer nor
revised Method 9 was used to obtain the data. Examination of the
field data reveals the observations were not taken at 15-second
intervals and calculation of six-minute average values from these
data is not valid. AC-59(E), AC-73(D)
Response: EPA disagrees with this comment concerning the validity
of the opacity data obtained at the three facilities observed in
September 1973. The opacity observations of emissions from the
control devices of these facilities were taken according to prac-
tices taught at EPA smoke schools and Method 9 as it was then written.
The observation practices employed by the observers are comparable to
those required by the revised Method 9. Specifically, the observers
read the emission points from a position with the sun located in the
quadrant to their back, 90° sun angle (the revised method relaxed
this criterion to 140° sun angle); they read steam plumes at the
point of dissipation or prior to condensation; and the observer's
line of sight was perpendicular to the plume direction. Some of
the observers did not record as much information on weather condi-
tions as required by the revised method. This omission only slightly
affects the ability to assess the contrast conditions and hence any
bias that may exist in the data. However, this omission does not
prejudice asphalt concrete plant owners or operators since no
visible emissions were observed and the standard was established
at a level higher than was observed. In addition, some of the ob-
servers did not record every reading made at 15-second intervals
because the control device consistently had no visible emissions. It
is known that the observers did observe the emissions from the control
device at 15-second intervals and that their conclusion that no visible
emissions from the control device occurred during the entire observa-
tion period is valid.
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11
Observations were also made of fugitive emission sources when emis-
sions were noticed. Some of the observations of fugitive emission;
points were taken at 15-second intervals, and these data were those
used to calculate the six-minute average values. The opacity stan-
dard for fugitive emission points was also based on engineering judgment of
levels achievable at a well-designed and operated asphalt plant.
This judgment is based on inspection by the EPA observers of the
two asphalt concrete plants that had visible fugitive emissions.
These inspections revealed that visible fugitive emissions could
have been prevented by proper enclosure of the emission area, by
proper operation of the dryer (or by adequate sizing of the fan
for the plant), and by operation of the plant at an adequate
draft to prevent escape of emissions. One of the three asphalt con-
crete plants observed had no visible fugitive emissions in addition
to no visible emissions from the control device. Inspection of
this facility revealed that the absence of visible fugitive emis-
sions was due to proper enclosure and ducting of all potential
emission points as well as proper design and operation of the
dryer. EPA, therefore, concluded that all visible fugitive emis-
sions observed at the other facilities could have been prevented
by proper design, operation, and maintenance of the asphalt concrete
plant. For these reasons, the 20 percent opacity standard for
points of fugitive emissions from an asphalt concrete plant is not
an unreasonable requirement, and new facilities can be designed and operated
to comply with this standard.
The reported transmissometer data do not support the standard
because the accuracy of the transmissometer is questionable, and the
data are irrelevant to the actual plume opacity. The study shows
the impossibility of obtaining meaningful opacity measurements'by
any technique. AC-73(D)
Response: The commentator quoted passages from the report "In-
Stack Transmissometer Measurement of Particulate Opacity and Mass
Concentration" (reference 2 of the revaluation report) to prove
the alleged inaccuracy of the transmissometer data. (In addition
to in-stack transmissometer measurements, this study also evaluated
plume opacity measurements by a sun photometer and by a telephoto-
meter.) Review of the quoted passages from the report reveals that
they referred to the difficulties of obtaining measurements by the
sun photometer and in no way reflect on the operation of the in-
stack transmissometer. In-stack transmissometers are calibrated
using neutral density filters and are not calibrated relative to
sun photometer measurements. The accuracy of the transmissometer
is not questioned in the report, and it was recognized in the
report that the instrument very accurately measured in-stack
opacity. For the above reasons, it is believed that the trans-
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12
missometer data are useful for evaluating the opacity standard.
Additionally, the in-stack opacity measurements are not irrele-
vant to plume opacities as claimed by the commentator. Although
only a limited number of plume opacity measurements could be
obtained by the sun photometer due to its operational problems,
the plume opacity data and the inrstack opacity data show good
agreement (Figure 5-3 of the report).
8. Data submitted by the Los Angeles APCD in a comment on the pro-
posed standards of 0,031 gr/dscf and 10 percent opacity showed
that a plant with an emission rate of 0.015 gr/dscf exhibited
opacity levels of 10 and 15 percent. Therefore, the 20 percent
opacity standard is obviously unachievable for any plant with an
emission rate near 0.04 gr/dscf. AC-73(D)
Response: The data from the Los Angeles APCD do not prove or
disprove the achievability of the 20 percent opacity standard for
facilities with an emission rate of 90 mg/dscm because of the
difference in the methods used to determine compliance. Deter-
mination of compliance with the EPA opacity standards is based
on the average of 24 consecutive observations taken at 15-second
intervals. An asphalt concrete plant could have emissions with
single readings in excess of 20 percent opacity and still have a
six-minute average value less than 20 percent opacity. The method
used by the Los Angeles 'APCD involves timing the duration of each
opacity level observed, and emissions in excess of 20 percent opacity
for time periods greater than three minutes per hour are considered
to be in violation of the Los Angeles standard. The Los pngeles
opacity standard allows emissions in excess of £0 percent for three '
minutes per hour to consider the effects of startups, shutdowns,
soot blowing etc. on emissions. Thus, the 10 and 15 percent opacity
levels reported by Los Angeles could have included a startup or
shutdown episode which can result in higher than normal emissions
from the asphalt concrete plant. EPA's procedure is to exclude
emissions during startup and shutdown periods from determination
of compliance with opacity standards. Opacity standards established
by EPA are not based on emissions levels during abnormal operation
periods.
9. EPA has not taken into account all variables that affect apparent
opacity because the analysis is based on a theoretical projection
of a limited amount of data from an incomplete study and from tests
on a limited number of atypical plants. Therefore, EPA has not
demonstrated the 20 percent opacity standard to be achievable.
AC-59(E), AC-62(E)
Response: EPA considers the achievability of the 20 percent opacity
standard for the asphalt concrete plant to be adecuately demon-
strated. A primary basis of the opacity standard is the Method
9 observations at three well-controlled plants; however, the
effects of normal variations in operating variables on plume
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13
opacities were considered in the reevaluation report. The
expected variations in operating variables which would signifi-
cantly affect apparent plume opacity (particulate size, particle
shape, stack diameter, etc.) were determined from review of
available information. This information consisted of data from
the plant in the transaissometer study, particle size data reported
in the literature for asphalt concrete plants with cyclone control
only, fractional collection efficiency curves for baghouses and
for venturi scrubbers (A Pfc20 inches w.g.), some qualitative.
shape data, refractive indices reported in the literature for
specific compounds, and stack diameters given in 30 test reports
which were available. The established range of variables was
used to determine a maximum probable opacity, as well as typical
opacity levels expected, for asphalt concrete plant emissions at
a concentration of 90 mg/dscm using Bouguer's law (AP-30 pp 29-35).
The opacity standard is achievable by any facility with emissions
less than 90 mg/dscm which are discharged from a stack diameter
less than 4.8 meters. Also, comments 1 and 2 of this section in-
dicate that the standard is reasonable and achievable.
10. The 20 percent opacity standard is not as conservative as claimed
by EPA because the possibility of a 7 1/2 percent error in Method
9 observations would make a facility with a 14 percent opacity
plume appear to be in excess of the 20 percent standard. AC-67(M)
Response: The error of the method is considered at .a time of
enforcement of the standard. An opacity value of 21.5 oerr.pnt.
(14 plus 7.5 percent) would not necessarily result in an enforce-
ment action against the source because that level is clearly
within the range of error of the method. Consequently, enforce-
ment action would not be taken until appropriate consideration was
given to the accuracy of the method.
11. EPA's data show that any asphalt plant with a 3.3 meter stack
diameter and emitting particulate matter with a mass mean diameter
of one micron would exceed 20 percent opacity despite use of a
perfectly functioning baghouse. Therefore, the standard should
be revised upward. AC-73[D)
Response: An asphalt concrete plant which discharges the control
device emissions at a concentration of 90 mg/dscm through a 3.3
meter stack and has a mass mean particle diameter of one micron
would have an equivalent opacity less than 20 percent, as calculated
using the equation on page 30 of AP-30. Therefore, the opacity
standard does not require an upward revision.
12. EPA should revise the 20 perdent opacity standard for asphalt
concrete plants upward to account for the greater light scattering
effect of particles in the size range of one to two microns, which
were calculated to be emitted from baghouses and venturi scrubbers.
AC-73CD)
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14
Response: Light scattering properties of irregular particles in
the size range of one to two microns were considered in the cal-
culations in the revaluation and were the basis of the decision
to not revise the standard.
13. The opacity standard for asphalt plants should be greater than that
for Portland cement plants because the concentration standard for
asphalt plants is greater (0.04 vs. 0,03 gr/dscf). AC-73(D)
Response: The opacity standard for asphalt concrete plants should
not be greater than the standard for Portland cement plants. The
equivalent values of the two opacity standards result from the
slightly larger stack diameters (up to 4.6 meters) employed on
control equipment on Portland cement kilns than are Used on asphalt
concrete plant control devices. Another factor that contributes
to the equivalent opacity standards despite different concentration or
mass standards is that particulate matter emitted by Portland cement
kilns is generally spherical while that emitted from asphalt concrete
plants is highly irregular in shape. Conner and Hodkinson in
"Optical Properties and Visual Effects of Smoke Plumes" (AP-30)
stated that -irregular transparent particles smaller than two microns
attenuate less light than spherical particles of the same projected
area. The combination of use of slightly larger stack diameters
and slightly greater amount of light scattering per particle
counterbalances the difference in concentration.
14% Weather conditions frequently can prevent obtaining meaningful
opacity observations. NAPA believes it is unwise to promulgate a
standard that may be enforced in some areas of the country while
other areas are essentially immune from enforcement. The opacity
standard is thus unwise and unfair. AC-73(D)
Response: EPA disagrees that some areas of the country will be
essentially immune from enforcement of opacity standards.
Observations taken under low contrast and luminescence conditions
will have a negative error and negative bias. The existence of
low contrast conditions will not preclude an observer from conducting
an opacity surveillance, but will reduce the possibility of citation
for violation of opacity standards due to observer error. Such
observations are not prejudicial to the owner, or operator. In
addition, it should be remembered that inclement weather conditions
will not prevail at all times, and observations can be conducted
during the high contrast periods when they occur. The purpose of
opacity standards is to ensure continued proper operation and
maintenance of the control device; thus, on occasion opacity
observations might be supplemented by full inspection of the facility
regardless of the observed opacity level. Consequently, EPA believes
that opacity standards can be applied nationwide in a fair manner.
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15
15< The standards of performance for asphalt concrete plants were never
intended to require control of fugitive emissions. EPA never
examined the degree of fugitive dust control feasible in well-
ducted asphalt concrete plants. The data to support this extension
were obtained after promulgation of the standards (March 8, 1974
Federal Register) and just prior to the revaluation of the opacity
standard.In the revaluation report EPA, for the first time,
indicated that fugitive emission sources are regulated by the
opacity standard. AC-59(E), AC-62(E)
Response: The standards of performance for asphalt concrete plants
have always regulated fugitive emissions as shown by designation of
dryers; systems for screening, handling, storing, and weighing hot
aggregate; systems for loading, transferring, and storing mineral
filler; systems for mixing asphalt concrete; and the loading,
t^ansfe.r,. and;storage systems,associated^it^.emigsiQn^control
systems at "affected facilities" in the oromuldated
regulation. EPA's intent to regulate fugitive emission sources
has been clearly stated from the beginning. Efficient ducting and
other fugitive emission control methods were investigated in the
original study on the standard and additional data were obtained
in September 1973 before, not after, promulgation of the regulation.
The memorandum referred to by the commentator merely reconsidered
these data in light of points raised in Warren Brothers et al. v.
Environmental Protection Agency (No. 74-1338")".
16. The revaluation report was the first time EPA had argued that
opacity standards are necessary for regulation of fugitive emissions.
AC-73(D)
Response: The reevaluation report may have been the first time EPA
published a discussion of methods for regulating fugitive emission
sources; however, previous standards of performance have used
opacity standards to regulate fugitive emission sources and the
discussion in the report should not be surprising.. EPA's intent to
regulate ma.ior sources of fugitive emissions in an asphalt concrete
plant was clearly expressed in the proposed and the promulgated
standards. The proposed and promulgated regulations designated
the major sources of fugitive emissions as "affected facilities"
which are subject to the standard of performance. The application
of the opacity standard of performance to fugitive emission sources
was indicated clearly by the discussion in Volume I (p. 9) of the
"Background Information for New Source Performance Standards.:-.."
(APTD-1352 a, c) and in Volume III (p. 13) which discussed control
of fugitive emission points. Much of this discussion was included
in the preamble to the promulgation of the standards of performance
for-asphalt concrete plants in the March 8, 1974, Federal Register.
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16
Fugitive emission points or operations in other source categories
also have been regulated by opacity standards. Examples of such
standards are the standard of performance for Portland cement
plants [§60.62(c)l and the opacity standards regulating fugitive
emissions from electric arc furnaces in the steel industry.
[§60.272 (a)(3)]. "These standards clearly show that EPA has
always regulated fugitive emission sources where necessary arid
where feasible control procedures exist.
17. Examination of the field data which were used as the bases of
the opacity standard revealed the occurrence of readings in
excess of 20 percent opacity. AC-59(E)
Response: It is true that some individual readings in excess of
20 percent opacity were recorded for fugitive emissions; however,
six-minute averages of the observations taken at 15-second intervals
on the fugitive emission sources are all less than 20 percent
opacity (10 percent maximum value). The standard for fugitive
emissions was- not established at greater than 20 percent because
inspection of the two plants having visible emissions, together
with the fact that one plant had no visible emissions, shows that
all of the fugitive emissions observed could have been prevented
by proper design, operation, and maintenance of the asphalt concrete
plant. The -data show no process variations that would cause visible
fugitive emissions during normal operation periods.
18. The field data include observations on emission sources in the
plant yard which are not specified in the regulation. These data
indicate that the opacity standard is applicable to all emission
sources in the yard. AC-59(E)
Response: The opacity standard is only applicable to emissions from
the designated affected facilities which are: dryers; systems for
screening, handling, storing* and weighing hot aggregate; systems
for loading, transferring, and storing mineral filler; systems for
mixing asphalt concrete; and the loading, transfer, and storage
systems associated with emission control systems. Observation of
other points and activities in the plant yard does not indicate that
they are regulated.
19. Fugitive emissions which cannot be shown to be in excess of the
concentration standard should not be used as a justification for
a separate opacity standard. AC-62(E)
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17
Response: Fugitive emissions are not used as a justification for
a separate opacity standard. Opacity standards are used here to
regulate fugitive emission areas in order to assure efficient
ducting and proper design and operation of the plant. Opacity
standards are also established as a means of ensuring continued
proper operation ariu maiiitenance cf the control device.
20. Fugitive emissions should be regulated only if these emissions
cross property lines and create a nuisance for neighboring property
owners. Most fugitive emissions in an asphalt plant are large
particulate that falls out in the plant yard. AC-67(M)
Response: The suggested regulatory approach is essentially that
which operated prior to enactment of the Clean Air Act. Historically,
demonstration of nuisance and injury to an adjoining property owner
has been difficult to prove and has been an unsatisfactory system
for the adjoining property owners and other victims of pollution.
If fugitive emissions contain particulate matter of sizes as large
as alleged by the commentator, then proper design and operation, and
proper ducting of the plant will reduce product losses and reduce
operating costs for the owner.
21. Object to further tightening of the opacity standard. AC-51(E)
Response: The opacity standard has not been tightened by the
revisions to Method 9 (39 FR 39872) or by the revaluation of the
standard (40 FR 17778).
22 The opacity standard for asphalt concrete plants should be based
on observations on asphalt plants alone, not on projections of
data from Portland cement plants. AC-52(E)
Response: The opacity standard for asphalt concrete plants is based
on observations at three well-controlled asphalt concrete plants and
on calculations of expected opacities for the known range of stack
diameters and expected size distributions of effluent from asphalt
concrete plants. Data from Portland cement plants were not used in
the revaluation of the asphalt concrete plant opacity standard.
23. EPA has never satisfactorily considered the oroblems of obtaining
valid opacity observations at asphalt concrete plants where pro-
duction is interrupted by frequent startups and shutdowns. AC-62(E),
AC-73(D)
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18
Response: As provided by the provisions of §60.11(c), opacity
standards of performance do not apply during periods of startup,
shutdown, and malfunction. Valid opacity observations can be
obtained at asphalt concrete plants by the observer recording
the startups and shutdowns as evidenced by the periods of burner
operation. .Verification of these instances of startups and shut-
downs can be accomplished by checking with the owner or operator
before and/or after the observations are made and by checking the
periods of operation from the burner chart. Frequent startups and
shutdowns may complicate determination of compliance with opacity
standards based on six-minute average values. Regardless of the
frequency of startups and shutdowns the observer will have to
observe the process until at least one six-minute period of
continuous observation is recorded; use of a shorter observation
period for determination of compliance is not presently allowed.
24. An asphalt concrete plant operator does not maintain records of
the exact time the dryer is started up or shut down. Thus, in
order to avoid falsely citing a plant for violation of the opacity
standard, the observer should synchronize his watch with the plant
operator. AC-30(=G), AC-49(F)
Response: Absolute synchronization of the observer's watch with
the plant operator's is not necessary because the observer, or an
assistant, can record the periods of observed burner operations.
The observer can also obtain this information from the burner
chart.
General
Prior notification of surveillance should be given before con-
ducting opacity observations in order to provide due process to
the owner or operator. In addition, to allow for meaningful
review of the evidence, the owner or operator should be allowed
to witness the inspection or should be notified of the results
immediately following completion of the inspection. Prior
notification, or witness of the inspection, will also allow synchron-
ization of the observations with asphalt concrete plant operations
to insure that periods of startup, shutdown, or malfunction are not
included and will provide the owner or operator an opportunity to
identify and correct any problems. AC-18(E), AC-19(E), AC-20(D),
AC-21(i), ACr22(E], AC-23CE), AC-24(E), AC-25(L), AC-26(D), AC-27(E),
AC-28CE], AC-31(J), AC-32(E), AC-33(E), AC-35(M), AC-36(D), AC-37(E),
AC-39(E], AC-40(E), AC-41(E), AC-43(E), AC-4*(D), AC-47(D), AC-48(E),
AC-49{F), AC-50(E), AC-52(E), AC-§3(E), AC-55(E), AC-58(E), AC-73(D)
-------
Response: Due process of law does not require that a person who
must .comply with a law be notified in advance that his behavior
during a certain period will be monitored. Due process does require
that the individual be notified of the alleged violation and be per-
mitted to review the evidence against him in a meaningful way. It
is EPA's practice to provide the owner or operator with such an
opportunity for meaningful review.
EPA inspectors will notify the plant owner or operator in advance
of the opacity observations unless there is reason to believe that
such notification could result in modification of emissions. The
usual procedure followed in evaluating a facility for determining
compliance with opacity standards is to request entry to the plant
in order to conduct a complete inspection. If the operations of
the source are such that emissions cannot be modified to be non-
representative of actual emissions or if the layout of the facility
requires observation from within the plant premises, then the owner
or operator is notified prior to conducting observations. However,
if there is reason to believe that prior notification could result
in nonrepresentative emissions, notification is provided by the
inspector immediately following completion of the observations.
Thus the opacity standard and the enforcement procedure provide
the owner or operator an opportunity for meaningful review and do
not violate due process of law.
Prior notification for the purpose of allowing sychronization of the
observer's time records with the plant operator's time is not necessary.
If an observer (or an assistant) observes the burner end of the dryer
of an asphalt concrete plant, the periods of burner operation will
be apparent from the appearance of the flame. Thus, a record may be
made of the occurrence of any startups or shutdowns, and the obser-
ver can exclude observations made during those periods. Inspection
of the burner chart v/ould provide further verification of the occur-
rence of startups and shutdowns. Notification that an inspection is
about to occur or has occurred provides adequate opportunity for the
operator to check for the existence of startups, shutdowns, and
malfunctions during the observation period and to independently re-
cord critical data such as meterological conditions, general operating
conditions, etc.
As is true with any law, the opacity standard and test method could
be applied in a manner which would violate due process of law. In
achieving widespread compliance with these regulations, however, it
will be in the best interest of EPA to anply them in such a way as
to satisfy the requirements of due process of law. Ultimately, the
issue of whether in the application of any law the rights of an
individual to due process have been violated would be a matter for
the court hearing the case to decide.
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20
Opacity standards violate the intent of section 111 of the-Act
which requires that standards represent levels of emission reduction
achievable by application of. best control technology. S.ince-EPA-
has not established a sufficient relationship.between opacity and
concentration of emissions from asphalt concrete plants, the opacity
standard is invalid. AC-62(E)
Response: The argument represented; by. this comment, was set forth in.
the brief of one petitioner in the-U.S. Court of Appea-ls. (D.C. Circuit)
challenge to the asphalt concrete plant, standard; of performance. A
detailed response to the argument may be found in EPA's. reply brief
filed on July 30,. 1975,: copies of which are available, upon written re-
quest from the EPA Public Information Center (PM-215) „ 401 M Street, S.W.,
Washington,. D.C.. 20460 (specify - Supplemental. Brief for Respondent,
National Asphalt Pavement Association, et al'. v. Train Nos. 74-1332,
74-1388). As discussed'in that response and in the revaluation
report, it is EPA's belief that the relationship between, mass emis-
sions and opacity has been amply- demonstrated;, that the opacity
standard of 20% does represent, the level of particulate emission
reduction achievable by the application of the best available control
technology; and'that it therefore^fulfills* the requirements, of section
111 of the Clean Air Act.
Congress did not specify which test metho.ds or which units must be
used by EPA to express its emission standards under section 111 of
the Clean Air Act. Particulate emission standards can be. expressed
in many ways, including pounds per hour, grams per dry standard
cubic meter, and pounds per ton of feed. For a given- category of
well-controlled stationary sources, opacity can be established as
an indicator of oarti'culate matter emissions and proper operation
and maintenance of the control system. Opacity standards established
in this manner are a reasonable indicator of the emission reduction
achievable by application of best control technology. Therefore^,
opacity standards of performance may be: used: as a means of contro-lling
emissions under section 111 of the Clean Air Act.
Opacity standards are established by EPA expressly as a "means of
ensuring that control equipment is properly maintained and operated
at all times when performance tests are not being, conducted (40 FR
17779)." Therefore, opacity standards are maintenance provisions
and their use as legally enforceable staridards violates the intent
of section 111 of the Act. Opacity does n;ot have- to be an enforce-
able standard in order to accomplish the purpose of ensuring proper
operation and maintenance of the control system. AC-58(E), AC-62(E)
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21
Response: Section 111 of the Act requires EPA to set emission
standards, which reflect "the degree of emission limitation achieve-
able through application of the best system of emission reduction which
(taking into account the cost of achieving such reduction) the
Administrator determines has been adequately demonstrated."
Section lll(e) of the Act requires that new sources continue to
be in compliance with the standards throughout their operational
life. To meet this Congressional mandate EPA establishes opacity
standards at a level which will require proper operation and main-
tenance of the control systems on a continuous basis. Use of
concentration or mass standards alone would nnt. accomplish this mandate
because it would be possible for a source to inadequately operate or
maintain pollution control equipment at all times except during periods
of performance testing. It takes two weeks or longer to schedule a
typical performance test. If only small repairs were required (e.g.
pump or fan repair or replacement of fabric filter bags), such remedial
action could be delayed until shortly before the test was conducted.
For some types of air pollution control equipment, such as scrubbers,
the energy input (pressure drop across the system) could be reduced
when performance tests were not being conducted and. could result in
increased emissions of particulate matter. EHA believes that opacity
standards are a necessary supplement to concentration standards. The
use of opacity as legally enforceable standards is clearly within the
intent of the Act.
EPA failed to make available for public comment prior to promulgation
of the standard the data which were relied upon to justify the
opacity standard for asphalt concrete plants. EPA also failed to
provide for meaningful public comment on the revisions to Method 9.
Such actions are unfair and contrary to the spirit, if not the intent,
of the Administrative Procedures Act (APA). Where a federal agency
becomes significantly involved in an issue, the fact that the agency
ultimately decides to take no action or affirm a prior decision does
not shield the agency from the requirements of APA. AC-32(E), AC-59(E),
AC-62(E)
Response: EPA's notice of April 22, 1975 in the Federal Register (40
FR 17778) invited public comment on the Reevaluation of the Opacity
Standard of Performance for Asphalt Concrete Plants, the revisions'to
Reference Method 9, and the revisions to 40 CFR §60.11. There-
fore, the issues relating to administrative procedures are moot.
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22
5. EPA has not shown that separate enforceable opacity standards are
necessary. Use of opacity as a rebuttable presumption, of violation
of the concentration or mass standard should be equally effective
ensuring proper operation and maintenance of the control system.
AC-21(L), AC-23(E), AC-37(E), AC-38(H), AC-42(H), AC-44(D)', AC-49(F),
AC-51(E), AC-59(E), AC-62(E), AC-67(M)
Response: Opacity is used an an independent enforceable standard,
rather than a rebuttable presumption of violation of the applicable
concentration"or mass standard, because opacity standards are the most
practical and' economically sensible means of ensuring that control
equipment is adequately maintained and operated at alii times. A
performance test conducted after a source was observed to be in,
violation of the opacity standard would not in EPA's opinion neces-
sarily resolve the question whether, at the time of the observed
violation, the source was meeting the concentration standard.
During the period between the observed violation of the opacity
standard and the time of the performance test, the owner or opera-
tor in some cases could take remedial action to bring a non-complying
source into compliance. That is, the owner or operator could delay
making small repairs, such as replacement of fabric filter bags, or
pump or fan repair, until, shortly before the performance test is
conducted. For some types of equipment such as scrubbers, the
energy input could be reduced when performance tests were not
being conducted. Therefore, the emission test results obtained from
the performance test v/ould not be indicative of the facility's
actual emission rate at the time of the observed violation. EPA
believes that the only other means of ensuring continued compliance
with the .standards of performance would be through use of a con-
tinuous monitoring system or through performance tests conducted
at SBC{J frequent intervals as to yield similar results.
6. Opacity standards violate the intent of section 111 of the Act
because opacity standards are not subject to an accurate, repro-
ducible, and objective test procedure. AC-73(D)
Response: The United States Court- of Appeals for the District of
Columbia on May 22, 1975, Portland Cement Association v. Ruckelshaus,
513 F.2d 506, Civ. 72-1073 upfield EPA's position that opacity is
sufficiently reliable to be used as a measure of pollution or as
an aid in controlling emissions. This decision was based in part
upon EPA's showing in the remand response that trained observers
were consistently able to read opacity with errors not exceeding
+7.5 percent based on single sets of the average of 24 readings.
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23
Opacity standards can be applied to all regulated parties with
fairness and uniformity. Compliance with opacity standards is
determined by use of a consistent methodology whose error is taken
into account in determining whether violations exist. (See also
response to comment 2 of this section.)
EPA believes that the use of opacity standards to control emissions
is within the intent of the Act and that the standards are subject
to an accurate, reproducible, and objective test procedure,
While for any given set of conditions opacity and concentration of
parti oil ate matter can be related, there are 23 other variables
which affect the accuracy of opacity observations significantly
enough to make apparent plume opacity meaningless as an indicator
of emission concentration. Opacity standards, therefore, should
be deleted from regulations establishing standards of performance.
The commentator recognizes the need for routine reliable measurements
of mass emissions and would be pleased to cooperate with the EPA in
the development of reliable techniques for direct measurement of mass
emissions. AC-72(G)
Response: The commentator discussed 24 variables which allegedly
affect plume apparent opacity'in a manner such that opacity is
a meaningless indicator of emission concentration. The variables
and their effects on plume apparent opacity which were discussed
are: 0) effluent concentration, (2) stack diameter, (3) mean
particle size, [41 polydispersity of emissions, (5) refractive index,
(6) particle density, (7) stack gas temperature, (8) stack exit
velocity, (9) water vapor, (10) ambient temperature and humidity,
(11) color of plume, (12) wind speed, (13) wind direction, (14) wind
turbulence, (15) background, (16) distance of observer from stack,
(17) effect of non-level terrain, (18) sun angle, (19) time of day,
(20) day of year, (21) longitude, (22) latitude, (23) observer-sun
angle, and (24) allowed observer error.
EPA agrees with the commentator that these variables can affect, to
varying degrees, the apparent opacity of plumes. The commentator's
analysis assumed that none of these variables except concentration
are considered in the development of opacity standards, in the method
for determining compliance with opacity standards, or in the analysis
of the data and any consideration of enforcement actions. EPA'contends
that this assumption is in error because the maximum expected effect
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24
of variables which significantly affect apparent plume opacities
are considered, and any source which is meeting the applicable con-
centration or mass standard will also be meeting the applicable
opacity standard. If a source is exceeding the opacity standard, it
is due to the failure of that source to properly maintain its air
pollution control equipment, and if tested the source would have
emissions in excess of the applicable concentration or mass standard.
The 24 variables which allegedly make opacity standards unsuitable
for ensuring continued proper operation and maintenance of air pol-
lution control equipment consist of four types: (1) factors related
to the source category and its operations, (2) factors related to
opacity observations, (3) factors considered in the determination
of compliance, and (4) factors with an insignificant or non-prejudi-
cial effect on apparent plume opacities. The first seven variables
discussed by the commentator (effluent concentration, stack diameter,
mean particle size, polydispersity of emissions, refractive index,
particle density, and stack gas temperature) are factors specific
to the source category and its operations which are considered by
EPA in the development of opacity standards. These factors can
significantly affect apparent plume opacity. The maximum expected
effects of normal variations in these factors on opacity are used
to ensure that the opacity standard for a soiree category is "established
at a level no more restrictive than.the corresponding concentration or
mass standard. In addition to the above consideration of these
factors, .should a source have a stack of larger than expected diameter
or have other anomalous operating conditions which preclude achieving
the opacity standard, the provisions of §60.11(e) allow the owner
or operator to petition EPA for establishment of a separate opacity
standard. Thus, ample consideration of the effects of these factors
is provided under the opacity provisions of standards of performance.
Factors which are considered in the procedure for obtaining opacity
observations include the commentator's variables: distance of
observer from stack, observer-sun angle, wind direction, water vapor,'
and ambient temperature and humidity. Method 9 includes specific
requirements on maximum observer-sun angle, observer's line of sight,
observer orientation with respect to the plume,etc., such that the
effects of the variables mentioned by the commentator on plume apparent
opacity are minimized. In addition, Method 9 provides specific instruc-
tions for reading of steam plumes.
Factors related to any bias and error in the opacity data are viewing
background, plume color, wind turbulence, and observer error. EPA
has determined that the maximum positive error associated with read-
ings made by qualified observers while reading plumes under high con-
trast conditions and using the procedures of Reference Method 9 is
7.5 percent opacity based on single sets of the average of 24 consecu-
tive readings. This maximum positive error considers the combined
effects of the variables related to observer position, bias, and obser-
ver accuracy on opacity observations made under high contrast conditions,
These factors and any other additional errors introduced by viewing
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25
conditions are considered in the determination of compliance with
opacity standards. Therefore, these factors will not result in
citations of a violation due to errors of the method.
The remaining factors (stack exit velocity, wind speed, effect of
non-level terrain, sun angle, time of day, day of year, longitude,
and latitude) have an insignificant effect on apparent plume opacity
or result in readings which are biased low and do not prejudice the
owner or operator (with the exception of the first three, all of these
factors relate to the effect of variations in luminescence contrast
upon plume apparent opacity). The effect of most of the factors in
the four categories and EPA's consideration of them are discussed in
the "EPA Response to Remand Ordered by U.S. Court of Appeals for the
District of Columbia in Portland Cement Association v. Ruckelshaus
(486 F.2d 375, June 29, 1973)."
Opacity standards of performance will be retained in regulations es-
tablishing standards of performance. EPA believes that the opacity
concept is both technically sound and that opacity standards provide
the most practical and inexpensive means to ensure that control
equipment necessary for a source to meet the applicable concentration
or mass standard .is adequately maintained and operated between per-
formance tests. EPA's study on the accuracy of opacity observations
demonstrated that qualified observers are consistently able to read
opacity within +7.5 percent. This field evaluation shows that the
use of observer aids or special monitorinq equipment is not necessary.
For the above reasons, EPA does not consider it necessary to under-
take a special study for development of a monitoring technique to
ensure continued proper operation and maintenance of control equipment.
In addition, other sufficiently accurate and reliable monitoring tech-
niques also presently exist. In-stack transmissometers have been shown
to have sufficiently stable operations and can be sufficiently.related
'to emissions to accomplish this purpose. Other techniques such as sun
photometers, telephotometers, or use of visual comparators by trained
observers measure light scattering by plumes and can compensate for
the effects of variations in ambient lighting and other contrast con-
ditions on apparent plume opacities.
8. Considering the inaccuracies of Method 9 and the large number of
uncontrollable variables, opacity standards are not a reliable means
of ensuring that control equipment is properly maintained and operated.
AC-48(E)
Response: As shown in the response to the remand in Portland Cement
Association v. Ruckelshaus, 486 F.2d 375, June 29, 1973, observers
trained and certified in accordance with procedures of Method 9 are
consistently able to read opacity with positive errors not exceeding
7.5 percent based on single sets of the average of 24 observations.
On the basis of this review, EPA concluded that the error tolerance of
the/nethod is reasonable and is within the limits considered normal
by the scientific and engineering community. EPA believes that
opacity standards are a reliable means of ensuring proper operation
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26
and maintenance of the control system for three reasons. First,
opacity standards are established at levels which are in excess of
observed and expected opacities for facilities operating in com-
pliance with the concentration or mass standard. Second, the posi-
tive error of 7.5 percent associated with Method 9 readings is con-
sidered at the time of enforcement. Finally, the provisions of §60.11(e)
provide a means for an owner or operator to petition for establishment
of a special opacity standard for an affected facility which meets the
mass or concentration standard but fails to meet the opacity standard.
The result of these three factors is that only facilities clearly in
violation of the concentration or mass standard will be in violation
of the applicable opacity standard. Therefore, opacity standards are
a reliable means of ensuring that control equipment is properly main-
tained and operated.
9. Because of technological advances made in recent years to monitoring
equipment and the large number of uncontrollable variables affecting
readings of plume opacity, the validity of opacity as a statutory
requirement has been eliminated. AC-57(T1)
Response: The validity of opacity as a statutory requirement has
not been eliminated by recent advances in monitoring equipment.
There are a large number of industries which do not extensively
monitor process and control equipment variables and whose emissions
cannot be monitored 6y use of an in-stack transmissometer. Opacity
standards are the only economically sensible means available for
routine surveillance of such facilities by a regulatory agency.
Therefore, the need for a consistent methodology for routine
surveillance of all facilities requires that evaluation of proper
operation and maintenance Be determined by use of opacity standards.
10. Emissions from baghouses are not constant but vary throughout the
cleaning cycle. An opacity standard, therefore, is not a reliable
measure of emissions and should not be a legally enforceable standard.
AC-59(E)
Response: Opacity readings are capable of providing more real time
information on emissions than do present concentration or mass measure-
ment techniques. The occurrence of necessary peak emi'ssion periods in a
production or operation cycle is taken into consideration in the
development of the applicable opacity standard for a source category.
Thus, cyclical emission patterns will not result in an overly
restrictive opacity standard. EPA believes that a properly developed
opacity standard is a reliable measure of emissions and
opacity should be a legally enforceable standard.
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27
From EPA's experience a properly sized, well-tuned, and well-
.operated baghouse on an asphalt concrete plant (which is the
application to which the commentator was referring} is clearly
capable of complying with the 20 percent opacity standard.
The standard also clearly does not preclude visible puffs during
the cleaning cycle or at any other time.
11. Opacity as measured by human observers is not scientifically
accepted to be related to mass or concentration of emissions.
EPA's predecessor agency published several documents which dis-
pute EPA's position on opacity as shown by statements on p. 53
of "Air Quality Criteria for Particulate Matter" (AP-49) and the
conclusions of a study on "Optical Properties and Visual Effects
of Smoke-Stack Plumes" (AP-30). A paper authored by H.P. Buetner
in the September 1974 issue of the Journal of the Air Pollution
Control Association also states that opacity regulations chiefly
control visual appearance, not the quantity of emissions. AC-62(E)
Response: The above referenced material does not show the unac-
ceptability of assessments of opacity by human observers. With
respect to the conclusions quoted from "Optical Properties and
Visual Effects of Smoke-Stack Plumes" (AP-30), Method 9 has always
recognized the effects of illumination, background, and viewing
conditions on plume opacity. In order to limit and consider the
effect of these variables Method 9 provides specific instructions
on allowable observer positions and requires the observer to record
the environmental conditions during the observation period. From
this information an independent assessment may be made of the
accuracy and the bias of the data. The effects of the above factors
on apparent plume opacity are considered in Method 9 , development nf
opacity standards, and in determining compliance with opacity stan-
dards of performance.
The discussion quoted from Chapter 3 of "Air Quality Criteria for
Particulate Matter" would be a valid criticism of opacity standards
if variables other than concentration which affect opacity were
ignored in the development of the standards. EPA submits that these
variables (stack diameter, particle size, particle shane, particle
density, particle refractive index, etc.) are not ignored in the
standard setting process, and with proper consideration of these
factors opacity is a reasonable measure of emissions.
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28
Finally, the referenced article from the,?ePtembeF 1974 issue of JAPCA
is irrelevant to the question or acceptability of visual assessments
of opacity. The article discussed in general the author's opinion
of deficiencies of opacity standards. The comments in this article
are not valid criticisms of opacity standards as established by EPA
because the effect of stack diameter and other variables on opacity
are considered in the development of the standard. Opacity standards
which are established considering all relevant factors can be used
as an indication of emissions.
12. Data presented in Table 1 of the revaluation report and part of
the data bases for the Portland cement plant standards show that
in spite of wide variations in concentration levels, the opacity
was consistently reported as being zero percent. These data
illustrate the inappropriateness of opacity as an emission stan-
dard. AC-66(K)
Response: These data do not indicate the inappropriateness
of use of opacity as an indicator of emissions. The variations
in the concentrations associated with no visible emissions for the
various source categories are due to the variations in the light
scattering properties of the particulate matter in the different
plumes, variations in the path lengths observed, and the factor
of the physiological contrast threshold value. For the cited data
the light scattering characteristics of the effluent and the path
lengths were such that reported apparent plume opacities of zero per-
cent are not unreasonable.
13. An opacity standard in addition to the concentration standard is
unnecessary and is merely another method of harassing the operator
of an asphalt concrete plant. The opacity standard should be
deleted. AC-35(M), AC-39[E), AC-42(H)
Response: As discussed in response to comment 5 of this section,
opacity standards are a necessary supplement to concentration or mass
standards and will not be deleted. The intent of the opacity stan-
dard for asphalt concrete plants is to ensure continued proper
operation and maintenance of the plant and the control system
in order to reduce emissions, not harassment of the operator.
Considering the number of new asphalt concrete plants and other
new stationary sources, it is highly improbable that any enforce-
ment agency has sufficient personnel to capriciously harass any
given source category or any given facility.
14. Agree with EPA that opacity standards are a reliable, inexpensive,
and useful means of ensuring that control equipment is properly
maintained and operated. AC-71(K)
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29
Response: No response is necessary.
15. Opacity standards are a necessary enforcement tool and should be
retained for as many sources as possible, including asphalt con-
crete plants. Violation of an opacity standard is indicative,
to a high degree of probability, of violation of the mass Standard.
AC-60(A)
Response: No response is necessary.
16. EPA should establish opacity standards referenced to a stack dia-
meter, and field observations should be corrected to this diameter
by use of a chart. This would result in uniformly equitable opa-
city standards. AC-70(G)
Response: While the suggested approach would result in uniform
opacity standards for all facilities in a given source category,
the approach would be difficult and cumbersome to implement.
Errors in estimates of stack diameters could be made either by
the operator or the observer and could result in significant
errors in the "corrected" opacities. EPA believes that a
preferable approach is to establish the opacity standards at a
level based on the largest expected stack diameter for the source
category. Thus, sources with the largest exoected stack diameters
are not prejudiced by the opacity standard.
17. The definition of opacity in subpart A should be revised to
specify that opacity is the average of 24 consecutive observa-
tions taken at 15-second intervals according to the test method
in Appendix A. AC-70(G)
Response: The revision suggested by the commentator is neither
necessary nor appropriate. The reference method (Method 0) for
determining compliance with opacity standards clearly specifies that
opacity shall be determined as an average of 24 consecutive obser-
vations taken at 15-second intervals. Also, the suggested revision
would preclude the use of "alternative" and "equivalent" methods of
determining the opacity of emissions. Retention of such flexibility
is necessary for reasonable application of the provisions of Part
60. Therefore, the definition of opacity will not be revised as
suggested.
18. The assumption that the properties of the particulate matter emitted
by a source will remain stable over a long time period and that the
functional mass-opacity relationship will remain constant may not
be valid. AC-71(K)
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30
Response: Unless there are major changes in the protess*, the-feed1
materials characteristics', or operation of"the control: device,, sig-
nificant changes in the particulate matter emitted by a-pi ant should
not occur and the mass-opacity relationship will: remain-reasonably
constant. Minor changes intthe operations of the source, w-ill not
meaningfully alter the opacity of emissions. Since'opacity-standards
are established at levels which consider the maximum^effects of'the
normal range of- particle characteristics- and.'stack diameters' at"
well-contriblle'd facilities, minor changes in the characteristics of
particulate matter emissions with: time will not affect the ability
of the source, to comply-with the opacity; standard.
*
19. Refractive index of the participate' in the- effluent'.is- an important
variable in'the mass-opacity relationship.- It'maybe incorrect
to' assume that the refractive index will'be constant fora given
category of stationary sources. AC-71(K)
Response'': For monod.isperse- particles-with' diameters" between O',05 and
2.0 microns, the particle- extinction- coefficient and angular scatter-
• ingf
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31
most commonly occurring transparent materials (AP-30). If neglect
of the refractive indices due to mineral filler and dust adhering to
gravel was in error, the effect on the calculated opacity is believed
to be insignificant. (The commentator did not show how the neglect
of these items resulted in an opacity standard prejudicial to asphalt
concrete plants.)
21. Particle size data obtained at the one asphalt concrete plant
studied showed mass mean diameters of 0.9 and 5 microns for the
two runs for which there were no controlled leaks in the baghouse.
These size data cannot be used as part of the justification of the
opacity standard, considering the disparity between rans and between
the results calculated in the projection analysis. AC-73(D)
Response: ,The use of both the measured particle size data and the
projected size data to establish the range of effluent particle
sizes arid the maximum expected effect on light scattering by the ef-
fluent is reasonable because their use considers both typical and
maximum light scattering conditions. The use of these data, thus,
did not result in an opacity standard prejudicial to asphalt con-
crete plant owners or operators. In the revaluation of the opacity
standard, the opacity associated with mass mean particle diameter
of one micron was calculated to determine the maximum light scatter
expected for asphalt concrete plant plumes. This calculation and
the consideration of the maximum effect of stack diameter variations
were the basis for retaining the 20 percent opacity standard.
It was appropriate to use these particle size data in the reevalua-
tion of the opacity standard because review of all the data obtained
indicated that the run showing a mean size of 0.9 micron was anoma-
lous. In addition to the data mentioned by the commentator, four
other determinations of mean particle size were made. Of this total
of six measurements, five showed a mean particle size of five to six
microns, while the sixth run reported a mean size of 0.9 micron.
There was no correlation between the mean particle size of the ef-
fluent and the amount of controlled alteration (size of the open
area) of the baghouse. Visible emissions (opacities greater than
two percent) were associated with effluent concentrations in excess
of 40 mg per actual cubic meter and with mean particle size diameters
of five microns. It was concluded that typical emissions from this
asphalt concrete plant had a mean size of five microns and that the
0.9 micron value resulted from a sampling error. This conclusion
is consistent with data obtained using a multi-wavelength transmis-
someter. These data showed that light scattering by the effluent
varied with the wavelength of the incident light in close agreement
with the optical characteristics predicted from light scattering
theory for silica particles with mass mean diameter of five to six
microns and geometric standard deviation of 2.5. (Light scattering
efficiency of a particle is a function of the particle's size and
the wavelength of the incident light.)
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32
The discrepancy between the measured size data and the calculated
sizes results from the assumptions and data used in the analysis.
The projection analysis assumed use of less efficient control de-
vices than well-controlled asphalt concrete plants would employ
and finest expected inlet particle size distributions. These assump-
tions may have biased the analysis toward a more lenient opacity
standard. This process did not prejudice the industry. Therefore,
the resultant discrepancy between the values obtained by the procedures
does not invalidate their use in establishing an opacity standard.
22. EPA used a 1967 publication on smoke plumes, a study by Midwest
Research Institute (MRI) on fine particulate emissions, and a highly
theoretical journal article to develop the asphalt "opacity standard.
Extension of the information in these theoretical publications to
asphalt concrete plants is invalid because asphalt concrete plant.
emissions are not specifically addressed and the data are merely
theoretical calculations, not empirical data. AC-59(E)
Response: The cited references are relevant to the question of the
asphalt concrete plant opacity standard. The 1967 study on smoke
plumes also included a discussion on the light scattering properties
of particles, Bouguer's Law, and the solution of Mie theory equations
for several cases. Extension of this material to the evaluation of
the asphalt concrete plant opacity standard is valid since the
theories have not been disproven. The MRI report was used as a
source of information on the particle size distribution of parti-
culate matter emissions from cyclone controlled asphalt concrete
plants. This information is obviously highly relevant to the
question of the asphalt opacity standard. The "highly" theore-
tical journal article was a second source of information on
light scattering properties of particles. This information
was combined with other data to estimate the effect of specific
variables on the opacity of asphalt concrete t>lant emissions and
resulted in 'the decision not to revise the opacity standard to a
lower level.
23. Fugitive emission sources cannot he read as accurately as
sources uitii a stack discharge. EPA anparcntly recognized
this v.'hen establishing the opacity standard for asphalt
concrete plants but ignored it for Portland cere P. t slants
(§GO.G2(b)(2) and §CO;c2(c)). The standards in §G?.C-2(b)(2)
and §60.C2(c) should be raised to 2C percent opacity. AC-4C(H)
Response: The difference in the opacity standards for asphalt
concrete plants and Portland cement plants does not result
fron an inconsistent regulatory approach. In both cases the
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33
accuracy of the method is to be considered at the time of
enforcement. Standards of performance are established on the
basis of demonstrated levels of control achievable by the in-
dustry in question. Information on control of fugitive
emissions at asphalt concrete plants indicated that a 20
percent standard is reasonable. Similarly, information on
control of emissions from the clinker cooler, raw mill system,
etc.. in Portland cement plants indicated that a in.nprrpnt.
opacity standard is reasonable. The opacity standards of
§60.62(b)(2) and §60.62(c) will remain at 10 percent.
24. EPA fails to consider the area of emission from fugitive emission
sources when establishing opacity standards for them. AC-59(E)
Response: The areas of the fugitive emission points were not
considered in the revaluation of the opacity standard because
the intent of the standard is to require adequate enclosure of
these emission points and proper ducting of the collected
emissions. One asphalt concrete plant observed had no visible
fugitive emissions and had no visible emissions from the control
device. Inspection of the two plants with visible fugitive
emissions showed that all visible fugitive emissions could
have been prevented by proper design, operation, and maintenance
of the asphalt concrete plant. Consideration of the fugitive
emission area was not necessary because the intent of the
standard is to discourage open areas and insufficient fan capa-
city for the dryer load.
25. A facility which discharges an effluent of 90 mg/dscm from a
4.8 meter stack would have an opacity greater than 20 percent.
Many Portland cement plants use stack diameters greater than
4.8 meters and thus their opacity standard should be increased.
AC-66(H)
Response: In EPA's study of the Portland cement industry, the largest
expected stack diameter found was 4.6 meters. Larger diameter stacks
are unlikely due to engineering and economic considerations. The
standards of performance for Portland cement plant kilns is approxi-
mately equivalent to 70 mg/dscm, not 90 nig/dscm. This lov;er concen-
tration of particulate matter, a larger mean particle size, and
maximum expected stack diameter of 4.6 meters indicates that the opa-
city standard for Portland cement plants should not be revised upward.
If a stack of diameter greater than 4.8 meters were installed on a
Portland cement plant kiln and the facility is unable to comply with
the opacity standard despite compliance with the mass standard, the
provisions of §60.11(e) allow the owner or operator to request esta-
blishment of a separate opacity standard. For the above reasons, the
opacity standard for Portland cement plants will not be revised to a
level based on the effect of anomalously large stack diameters.
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26. Participate matter emissions from asphalt concrete plants do not
contribute to the endangerment of public health, and local regula-
tions already adequately control these emissions. AC-51(E),
AC-54(L), AC-55(E)
Response: The Clean Air Act, as amended, directs the Administrator
to promulgate standards of performance for new stationary sources
which he determines may contribute significantly to air pollution,
but it does not provide him with specific criteria or guidelines
to determine what is a significant source. Therefore, to make
such a determination, the Administrator must rely upon judgment.
In the case of particulate matter - a pollutant for which national
ambient air quality standards have been established - the Adminis-.
trator considers all sources to contribute to the endangerment
of public health or welfare.
The presence of particulate matter in the air is the result of
numerous diverse mobile and/or stationary sources. Because
ambient concentrations of particulate matter depend upon a
number of factors such as distribution of sources, topography,
height at which the pollutant is emitted, and meteorological
.; conditions, a source may have a significant impact in one loca-
tion and not in another. This makes it meaningless to develop
a firm definition of "significant source" that could be applied
nationwide.
The Act provides the Administrator a variety of regulatory authori-
ties which may be used singly or in combination to achieve the pur-
poses of the Act. For particulate matter, the Administrator has
determined that1 a comprehensive air quality management strategy is
needed to protect public health and welfare and to enhance the
quality of our air resources. This air quality management strategy
is based on the adoption and enforcement of State implementation
plans approved by the Administrator and on standards of performance
for new stationary sources promulgated by the Administrator. State
implementation plans are designed to achieve and maintain national
ambient air quality standards as required under section 110 of the Act,
and standards of performance are established to facilitate the main-
tenance of national ambient air quality standards while allowing
industrial growth. Ideally, the Administrator should issue standards
of performance for all sources of particulate matter at one time.
This would provide the maximum degree of enhancement of the nation's
air resources. Clearly, EPA has neither the resources nor information
to establish standards of performance for all sources of particulate
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35
matter at one time; therefore, a selection process is used.which
helps establish priorities for standard setting. In this selection
process EPA examines uncontrolled emission rates, proximity to urban
areas, stringency of State/local regulations, number of plants, and
growth rates. A comparative analysis of the air quality impact of
emissions from some 80 sources of particulate matter showed asphalt
concrete,pi ants to be ranked within the first 20 source categories.
In an analysis of emission rates and expected impact on air quality
of standards requiring best demonstrated control technology for
114 sources of particul ate matter emissions, the asphalt concrete
industry ranked number 13 in the amount of reduction in particul ate
emissions that would result from application of biest control technology.
The objective of standards promulgated under section 111 of the Act
is to prevent new air pollution problems from developing by requiring
affected sources to use the best systems of emission reduction at a
cost and within a time frame that is reasonable. These standards
are not intended to be directly related to ambient air quality but
are intended to prevent new air pollution problems from developing.
Attainment and maintenance of national ambient air quality standards
is covered by State implementation plans and regulations as provided
under section 110 of the Act*
27. Installation of control equipment with 99.9 percent plus collection
efficiency will result in unbearable costs and will eliminate many
small asphalt firms. AC-52(E), AC-55(E)
Response: This issue was discussed previously in response to com-
ments on the proposed standard of performance. The standard of
performance was promulgated on March 8, 1974. Since putting this
standard into effect, no information has been received that indicates
a need for a reanalysis of the costs and economic impact of the stan-
dard. The discussion of this issue presented in Volume III of
"Background Information for New Source Performance Standards: ..."
(APTD-1352 c) is still applicable and is repeated in full below.
The promulgated standard of 0.04 gr/dscf requires installation of
best available control technology (considering costs) which for
asphalt concrete plants is considered to be well-designed, -operated,
and -maintained baghouses or venturi scrubbers. This concentration
standard of 90 mg/dscm (0,04 gr/dscf) still requires collection
efficiencies of 99.9+ percent. It is our judgment that the incre-
mental investment required by the final standard will generally
not create any serious additional financing problems for new
asphalt concrete plants.
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36
Asphalt concrete plants meeting State emission standards should be
able to increase prices to cover the added cost of pollution control
according to the February 1972 Economics of Clean Air (Annual Report
of the Administrator of the Environmental Protection Agency to Congress,
March 1972). Because the annual costs for a new plant meeting the
final standard closely approximates the cost for an existing plant
meeting a typical State standard, our judgment is that a new plant
will not be placed at a competitive disadvantage. These judgments
have been reinforced by NAPA's public comments that were submitted
to EPA on July 24, 1973. On page 49 of their comments they stated:
The National Asphalt Pavement Association, .as it has
indicated on many occasions to EPA, subm'ts that the
legitimate goal of protecting t!,c environment and
reducing emissions in'11 be achieved !.y the imposition
of a .CO standard rather than the .03.1 standard. It
is submitted by the industry that this 'nil resvlt in
an improvement of the emission levels by 99.C0' and is
consistent with the goal which he.s been stated of ??.7?'
by the Environmental Protection Agenc1'. Further, it is
submitted tiia.t trie reduction is achievable at a rea-
sonable cost without unduly endangering the existence
of the industry or forcing the use of other alternative
products. Thus, it is submitted thc.t it is important
that the standard be .00 and not .031.
It is important that it be recognized that if the
standard is .DC the equipment which will be required to
be purchased will be either a venturi scrubber wi th a
minimum 20-inch pressure drop or a baghouse with a 0
to 1 air-to-clcth ratio. It is submitted that there-
will be a significant itr^rove^crit in the environment
with an .CC standard. The .OC standard will further
require that the plants be kept in good ore-rating
repair and condition or they v.-ill fail to meet the
.06 standard. A .06 standard v.'i 11 avoid the problems
of the size and shape of the participates and also
other problems 'which cannot be answered at the pre-
sent time.
liAPA's conclusion is that the- cost for a venturi scrul. ber with
a 20-inch pressure drop or a baghousc with a 0:1 air-to-cloth
ratio is reasonable. It is EPA's contention that this equip-
ment v.'i 11 achieve the final standard (0.04 gr/dscf). Thus,
IIAPA's conclusion that cost for ti.is type of equipment i?
c-Tc-llfc re info rets, our ^ud'jme'it that t;:e erst to me&t the
l standard is reasonable.
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The costs resulting from the standard to an owner or operator are
considered reasonable for all sizes of plants; there is no economic
penalty to small plants. The standard does not apply to existing
plants. If an operator of a small plant decides to modify an
existing plant or build a new plant, the costs of complying with the
standard of performance will be increased 6 to 10 percent over the
costs of complying with State regulations.
28. EPA should provide some accommodation in regulations to consider
situations where it is impossible to establish opacity standards.
Specifically, for some steam generators opacity can vary markedly
without any change in mass emissions of the facility (as determined
by Method 5 testing.) AC-75(G)
Response: The suggested exemption of specific facilities is not
necessary. During the development (or revaluation) of the opacity
standards of performance for a given source catecjpry, all variables
affecting opacity are thoroughly investigated. If"the analysis
indicates that certain operating (or other) conditions merit sepa-
rate standards, section 111 of the Act allows the Administrator to
distinguish between such situations and establish separate standards
of performance for separate classes of sources.
Method 9
Paragraph 1
1. Restriction of Method 9 to stationary sources reduces the generality
of the method. AC-14(C)
Response: This is true; however, the special Problems such as the
tunnel effect v/hich can occur with plumes from mobile sources re-
quire further consideration and are beyond the scope of Method 9
which is a reference nethod for determining compliance with stan-
dards of performance for stationary sources.
Paragraph 2
1. Paragraph 2.1 should be amended to require the observer to be located
two to three stack heights, but less than a quarter mile, froir the
stack. If the observer is located closer than two stack heinhts
frop the source, the observed opacity will be nreater than the
actual opacity due to the increased path/length through the plume
and the exponential dependence of opacity on path; length. AC-3(A)
AC-14(C), AC-63(G), AC-64(H), AC-69(A), AC-70(G), AC-72(G)
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Response: An observer located near the stack has the potential to
observe opacities which are preat.er than the true opacity. This
effect is not, however, a result of the distance from the stack:
rather it is a result of the ancle between the line of vision
and the direction of the plume. A lew anole wr.-uld produce an
increased path length which', as indicated in the comment, would
result in high readings. Paragraph 2.1 makes clear that obser-
vations are to be approximately perpendicular to the plume direc-
tion. This criterion is sufficient to preclude readings taken
at low angles and consequently longer than actual path lengths.
2. Method 9 should include more explicit instructions regarding
allowable observer positions. Method 9 should require the ob-
server to fully document any compromise (or greater error) posi-
tions used due to physical limitations at the site. AC*3(A),
AC-7(I), AC-43(E)
Response: Method 9 as promulgated on November 12, 1974,
requires the observer to clearly document all Pertinent infor-
mation. The required records include clear identification of
the source of the emissions, nature of the facility, date of
observations, explicit records of the observer's location with re-
spect to the emission source anc1 the sun, description of sky
condition, plume background, wind speed, and wind direction.
This information can be used for"an independent assessment of
whether the observer was located in conformance with the specified
criteria. If the information indicates that the observer was not
located in accordance with the criteria, then the field data can
be used to assess the effect of the nonconformance on the accuracy
of the data.
3. Method 9 should expressly prohibit observers from taking obser-
vations from positions which are outside the maximum range permitted
by the specifications of paragraph 2.1. AC-r46(H)
Response: The criteria governing observer positions are established
to minimize the maximum positive error associated with Method 9
observations. Express prohibition of positions not strictly in
conformance with these criteria is not necessary if the additional
error introduced by nonconformance is considered in determining
possible violations. The magnitude of this increased error can
be estimated only through a careful assessment of the observer
location, background, and other environmental factors. This error
assessment is necessarily done on an individual basis. Obviously,
any error estimate is open to rebuttal.
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4. How is the observer to determine with any accuracy that the sun
is located within a 140° sector tc his back? At the extremes
of this angle, compliance with this specification may be argu-
able. AC-42(H), AC-46(H), AC-56(M)
Response: This criterion is designed to ensure that readings
are not taken from positions which could result in unaccept-
ably high errors. It is true that determination of confor-
mance with the 140° angle specification requires careful
documentation if the observer is located near the extremes
of the range. Hith carefully documented information on the
relative position of the sun, observer and nlume, the cal-
culation of the angle is a straightforward procedure. In
any case, the 140° angle does not represent a sharp break
point beyond which unacceptably large errors occur, and small
errors (+_10°) in the observer-sun-plume position are not critical
Method 9 should be revised to require the observer to keep the
sun at least in a 120° sector and preferably in a 90° sector
to the observer's back. The present specification of 140°
will allow the sun to be within 20° away from beino perpendi-
cular to the observer's line of sight. Observations taken at
the extreme range of the 140° sector will be affected by the
angular scattering patterns of small particles. Specification
of a 90° or 120° sun angle would minimize this probler. AC-45(H)
AC-46(H), AC-56(M), AC-59(E), AC-64(H), AC-70(6)
Response: It is necessary to prevent positive errors which
can result from observation of the forwardly scattered linnt,
as noted in the comment. The forward scatter contribution to
the apparent opacity of a plume can be important at observer-
sun angles greater than 180°. The contribution of forward
scatter is minimal when the observer is positioned with the
sun in a 140° to 160° sector to his back. The 140° sector
requirement is considered-adequate and has been shown in
field tests to preclude significant errors. Specification
of 120° sector or 90° sector angles is more restrictive than
field data indicate is necessary.
6. Method 9 should require two simultaneous observations taken
45° to 90° apart to consider the effect of sun angle on the
plume's apparent opacity. AC-45(H)
Response: See response to above comment.
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40
7. As presently written, Paragraph 2.1 precludes taking opacity
readings when the sun is directly overhead or during overcast
conditions when the position of the sun is relatively unimpor-
tant. AC-16(A)
Response: Paragraph 2.1 as written does not prohibit the taking
of opacity readings when the sun is overhead because the observer
sun angle specification does not prohibit angles greater than
70°. While paragraph 2.1 is not intended to'prohibit taking
readings during overcast conditions, slightly more restrictive
criteria than necessary are established."
8. The requirement to read across the shorter axis of rectangular
stacks should be deleted to preclude usage of rectangular stacks
solely for circumvention of opacit} standards. AC-2(A), AC-ll(A),
AC-34(B)
Response: It is unlikelv that a source would construct a rec-
tangular stack in order to circumvent the opacity standard since
the mass "or concentration standard is more restrictive and must be
met regardless of the level of the opacity standard. Similarly,
it would not be reasonable for EPA to require readings to be
made,.through the longer path length, as this would in some
cases make the opacity standard more restrictive than the con-
centration standard.
9. Method 9 does not provide any guidance on correct observer
location, etc., for situations when the wind is blowing per-
pendicular to the longer axis of a rectangular stack or other
emission area. AC-7(I)
Response: The observer position criteria specified in para-
graph 2.1 are designed to result in data with minimum positive
errors. Like the other methods in Appendix A, Method 9 does
not discuss special situations which may require changes to
the procedures and exercise of judgment by the personnel con-
ducting the test.. If conditions at the time of observation
prevent the observer from positioning himself strictly in
conformance with these criteria, then larger positive errors
will occur. The magnitude of these errors can only be esti-
mated through a careful assessment of the observer's position
on a case-by-case basis. Method 9 requires recording of suffi-
cient information on the contrast conditions, observer location
with respect to the sun and the emission point, meteorological
conditions, emissions sources observed, and plume characteristics
such that an independent assessment of the accuracy of the data
can be made. Any such assessment of the error associated with
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41
the readings is subject to rebuttal by interested parties. In any
case, an observer should not take readings through the length of
the plume. With situations of this type, the observer should con-
sider evaluating the source at another time under different meteoro-
logical conditions or should consider possible compromise orientations
with respect to the stack or sun. If observations are made under the
latter conditions, then the observer should assess the magnitude of
the increased positive errors that may result and consider this error
in determining any possible violations. The validity of any such
error assessment would be subject to challenge by any alleged violator
in any enforcement proceedings that occur.
10. Since all plumes from closely spaced multiple stacks will be dispers-
ing in the same direction, accurate opacity readings are improbable.
AC-57(M)
Response: Under normal meterological conditions, plume rise will
be sufficient to allow observation of each plume individually.
Readings of single plume widths taken in conformance with the
criteria of Method 9 can be assumed to accurately evaluate the
source's emissions within the error of the method. Close-in mix-
ing and co-dispersion of several plumes is possible only during
certain periods of extreme meteorological conditions. The occur-
rence of such meteorological conditions does not justify reading
multiple stacks colinearly. If observations are made during ceriods
when reading of single plumes is not possible, Method 9's record
keeping requirements will provide sufficient information to allow
an independent assessment of the accuracy of the data. Inability
to conform with the criteria of Method 9 will require careful
assessment of the accuracy of the data for that observer-plume-sun
orientation.
11. The type equipment or process responsible for the emissions should
be recorded on the observation sheet. AC-23(E)
Response: Figure 9-1 is considered to provide a record of suffi-
cient information to identify the process and equipment. Note that
records of the facility, control device, and point of emissions
are required on the form.
12. Reading of a plume that has doubled back on itself should be
expressly prohibited (paragraph 2.3). AC-46(H)
Response: Paragraph 2.1 of Method 9 implies that only one plume
width is to be observed. EPA does not agree that an express
prohibition is necessary. Smoke readers are trained to read
apparent plume opacities by viewing perpendicular to the plume
and through one plume width. Experience with qualified observers
has not shown any readings of doubled back plumes or that"
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42
such situations present any problems.
13. The specifications of paragraph 2.3 are arbitrary because the
point of maximum opacity in the plume varies with time. A
single observation point should be used to give a representa-
tive and consistent picture of plume opacity* AC-16(A), AC-45(H)
Response: The requirements of paragraph 2.3 are not arbitrary
and will result in a representative evaluation of emissions.
For stationary sources which do not exhibit a steam plume, ,the
point of greatest opacity will occur in the immediate vicinity
of the point of emission. The plume, consequently, will be eval-
uated at a single observational area. Although unlikely, should
any situations occur in which non-representative evaluation of
the process would result from reading the emissions at the point
of greatest opacity, the emission cycle and process operations
would be considered in the development of an opacity standard
(if any) and application of Method 9 to that source.
14. The provisions of paragraphs 2.3 and 2.3.2 are contradictory.
Paragraph 2;3 should specify that alj observations, except
those for attached plumes, be made on emissions at the stack
exit. AC-42(H), AC-64(H)
Response: The provisions of paragraphs 2.3 and 2.3.2 are not
contradictory. Paragraph 2.3 clearly specifies reading at the
point of maximum opacity where condensed water vapor is not
present. This point will occur someplace near the stack exit be-
fore appreciable cooling and dispersion of the plume has occurred.
For a detached steam plume, the point of maximum opacity will be
near the stack exit, and paragraph 2.3.2 merely clarifies that
readings are to be made at that point.
15. Taking observations of the plume at 15-second intervals places an
undue burden on the observer. Method 9 should require readings
at 30-second or 60-second intervals. AC-13(A)
Response: Method 9 requires observing at 15-second intervals in
order to assure that the emissions are adequately characterized
by the observer. Observation at 30-second or 60-second intervals
would not sufficiently characterize emissions from many sources
with intermittent or rapidly changing emissions. Considering the
need for an accurate and representative assessment of the emissions,
observation at 15-second intervals does not place an undue burden
on the observer.
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43
16. In order for Method 9 to be valid legally, "uncombined water
vapor" must be defined. AC-16(A)
Response: Every term in a regulation or test method is not,
and need not, be specifically defined in order to be legally
valid if the meaning of the term is understood from standard
usage. Terms or phrases are defined in the general provisions
of Part 60 of Title 40 or in the specific subpart when the absence
of a definition could perhaps result in misinterpretation of the
term or regulation. EPA does not believe that definition of "un-
combined water vapor" is necessary because the meaning of the term
is understandable from standard usage. Recent revisions of Method
(39 FR 39872) have clarified the procedures by which "uncombined
water vapor" is to be excluded from evaluation of the source
emissions.
17. Attached water vapor plumes are not amenable to meaningful
opacity observations because of residual water vapor associated
with, the dust nuclei. AC-42(H), AC-51(E), AC-57(M), AC-64(H),
AC-.72CG);
Response: EPA believes that attached steam plumes can be
meaningfully evaluated for the purpose of detemininc com-
pliance with opacity standards. As shovm in "EPA Response
to Remand Ordered by U.S. Court of Appeals For the District
of Columbia in Portland Cement Association v. Ruckelshaus
(486 F.2d 375, June 29, 1973)," steam plumes can be readilv
distinguished from plumes containing particulate natter and
the point of dissipation of the condensed water varor is
easily determined. Method 9 requires the observer to read
attached steam plumes after the condensed water vapor has
dissipated. At the_ point where all water droplets have
evaporated and are no lonaer visible, the concentration of
particulate matter in the plume has been diluted consider-
ably below that at the stack exit. Only if the plume ex-
ceeds the opacity standard at that point can an observer .
consider a citation for violation. This procedure allov-'S
operators of wet processes the benefits of dilution and
does net result in unjustifiable citation of sources for vio-
lation of opacity standards.
Residual particulate matter observed in the plume followirn
evaporation of tiie condensed water vapor will not Le more
visible due to an adhering layer of condensed water on the
particles. Shortly after evaporation of all water droplets
in the plume, any film of v/ater adhering to particles also
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44
will have evaporated to the equilibrium value. For emissions
from most stationary sources, the effect of the equilibrium
residual layer of water on the effective size and the combined
light scattering properties of the parti cul ate in the plume is
insignificant.
18. Method 9 should specify a longer minimum observation period than
six minutes, for example, 15 minutes. One six-minute period is
not necessarily representative of operations of the source and is
unduly influenced by transitory excursions. AC-14(C), AC-42(H),
AC-45(H), AC^46(H], AC-56(M)
Response: In evaluating the accuracy of Method 9, it was determined
that 24 readings taken at 15-second intervals were sufficient to
assure acceptable accuracy and to obtain a representative evalua-
tion of the emissions. Use of longer averaging periods are not
necessary to consider the effects of transitory high emissions.
That is, if brief periods of high concentration emissions are an
inherent, unavoidable feature of the process, the opacity standard
will have been established at a level which considers these emis-
sions. For sources in which transitory high emissions are not an
inherent', unavoidable feature of the process, transitory excursions
are indicative of improper operation and maintenance of the control
system and process and such emissions should not be allowed. An
observation period longer "than six minutes in not considered necessary.
19. Opacity observations should be averaged over the time period re-
quired to conduct a Method 5 test on the source in order to better
relate opacity to mass emissions. This longer averaging period
does not represent an unreasonable burden on the observer. AC-65(I)
Response: Averaging opacity data for the period required for Method
5 tests so as to better relate it to the mass emissions is unnecessary
for facilities with stable emission rates. Method 5 tests are con-
ducted for periods of one hour or longer to assure collection of
sufficient mass to minimize errors due to recovery and weighing of
the collected particulate matter. If the effluent concentration
fluctuates little, averaging the opacity data over the Method 5
test duration would serve no useful purpose and would complicate
enforcement of opacity standards.
While it can be argued that for any batch process opacity observations
should be averaged over the period of a Method 5 test. to better relate
them to mass emissions, EPA does not believe this is necessary for the
purpose of opacity standards. (In-stack transmissometers or other
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45
plume opacity data are averaged over the period of the concurrent
mass measurements in order to develop a functional mass opacity
relationship. Data from such studies serve a different purpose
than do opacity standards.) Opacity standards are established to
insure continued proper operation and maintenance of the control
system. If the opacity standard for a batch process is established
at a level which reflects the level of control required during the
peak emission period by the concentration or mass standard, the opacity
standard will insure proper operation and maintenance of the control
system and the observations need not be averaged over the period of
a Method 5 test.
20. Method 9, specifically paragraph 2.5, should allow use of alternative
averaging periods. Use of 21 consecutive readings taken at 15-second
intervals has proven to be adequate for enforcement purposes and
should be allowed. AC-16(A)
Response: The provisions of Method 9 establish criteria which are
designed to minimize the maximum positive error associated the read-
ings. The maximum positive error associated with single sets of 24
consecutive readings taken at 15-second intervals in accordance with
the criteria of Method 9 has been quantified. EPA is presently evaluat-
ing the maximum positive error associated with averaging opacity obser-
vations for periods less than six minutes and different methods for
determining compliance with opacity standards. Depending upon the
results of this study, revisions may be made to the methods allowable
under Part 52 of Title 40 for determination of compliance with opacity
standards and may be considered for Reference Method 9 of Appendix A
to Part 60. If any of the methods are revised to allow different
averaging periods, any determination of compliance must consider the
maximum positive error associated with the averaging period in deter-
mining possible violations of applicable opacity standards.
Until the appropriate revisions are made to the methods, use of exist-
ing procedures is possible under the general provisions of Part 60.
The provisions of 40 CFR 60.8(b) allow use, upon approval 'by the
Administrator, of "alternative" or "equivalent" methods for determining
compliance with applicable standards. If a State or other air pollution
control agency desires to use a procedure differing from the revised
Method 9, it may do so provided the "alternative" or "equivalent" pro-
cedure can be demonstrated to produce results adequate for determination
of compliance. The use of average values of single sets of 21 obser-
vations taken at 15-second intervals, therefore, could be an allowable
procedure upon an adequate demonstration of the accuracy of the procedure.
21. The method of averaging opacity observations should be clarified for
cases where the applicable opacity standard of performance includes
a time exemption. AC-63(G)
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46
Response: Opacity standards of performance with time exemptions are
being reevaluated and will be revised to levels based on six-minute
average values. If an opacity standard of performance is established
vith a time exemption, procedures will be specified for determining
compliance with such a standard.
Paragraph 3
1. EPA should require the use of Ringelmann charts or other reference
opacity charts for reading opacities because the ability of obser-
vers to remember opacity levels fades with time, and recertifica-
tion every six months does not adequately correct this problem.
AC-70(G)
Response: Method 9 does not preclude field use of observer aids
such as visual comparators; however, field evaluation of the
capability of an observer to accurately read plumes has shown
that such aids are not necessary, decertification every six
months has been found to be of sufficient frequency to ensure
acceotable observer accuracy.
Use of Ringelmann charts is unacceptable because they are not
the basis for opacity observations. Ringelmann charts are used to
measure the relative blackness or grayness of emissions and as such
are not applicable to Method 9.
2. The certification orocedure still fails to require the observer to
Qualify on predominantly low onacity plumes. AC-7(I)
Resoonse: The certification procedure has proven to be adequate
for training observers to read low opacity plumes. The average
observational error associated with plumes of known opacity was
discussed in the "EPA Response to Remand Ordered by the U.S. Court
of Appeals for the District of Columbia in Portland Cement Asso-
ciation v. Ruckelshaus (486 F.2d 375, June 29, 1973)."
3. Method 9 should require that test results on unsuccessful attempts
for certification should be retained. AC-7(I)
Response: Retention of scores on all unsuccessful runs would serve
no aseful purpose.
4. Observational errors of less than 7.5 percent opacity are achieved only
after several hours of practice on plumes of known opacity, even
for previously certified observers. Therefore, Method 9 is not as
reliable as claimed by EPA. Method 9 should be revised to require
preliminary qualification of the observer followed by a 24-hour
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47
delay during which the observer would not again be exposed to known
plume opacities. At the end of the 24 hours, in order to be a cer-
tified smoke reader, the observer would be required to pass the
test for certification.a second time. AC-45(H), AC-46(H), AC-57(M)
..Response: As discussed in the "EPA Response to Remand..."
qualified observers are able to assign ooacitv levels to plumes
v/ith positive errors less than 7.5 percent opacity. This
evaluation.included field assessments of observer accuracies
in addition to tests conducted nsinq a snoke generator. In
none of these field tests did the observers have the benefits
of practice runs. Therefore, the suggested revision is un-
necessarily restrictive in view of the acceptability of result?
present procedures.
5. Method 9 should reouire observers to qualify on wet plumes.
A'C-46(H), AC-57(t') '
Response: EPA is currently investigating technioues which could
be employed in smoke schools to further enhance an observer's
ability to accurately identify contaminated water ^Tunes. Pro-
cedures used by State anr> local regulatory aoencies to observe
contaminated water vanor "lurries are being reviewed also, and the
use <^f such training aids as movies and apprenticeship trainino
'.•-.•ill"be considered.
6. Method 9 should include Procedures for evaluating onacitv at
night, AC-2(A), AC-ll(A). AC-3*(G), AC-C5(A)
Response: EPA recognizes the advantages of obtainina opacity
readings at night; however, sufficient data have not been
obtained to justify extension of Method 9 tc reading at nicht.
Method 9 should require the observer to qualify without the
benefit of practice runs on a different stack diameter than
that on which he was trained. It is a poor assumption that
the observer can read all stack diameters accurately when
trained on one stack diameter alone. AC-46(H), AC-57(M)
Response: Field tests under varying conditions on different
sources and different stack diameters hrtve shown that observers
certified according to Method 9 using a srrroke generator are cap-
able of reading opacity with a maximum positive error of 7.5
percent regardless of the stack diameter. Therefore, the assump-
tion is valid and Method 9 will not be revised.
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48
8. Training and certification on fugitive emission sources should
be part of Method 9. Without such training, Method 9 is an un-
reliable procedure for determining ooacity of fugitive emissions.
AC-46(H), AC-Eff(E), AC-73(D)
Response: Training and certification on fugitive emission sources
is not necessary because the factors affecting apparent plume opa-
city are the same for fugitive emission sources as for emissions
fron a stack. Specifically, as discussed in response to comment 7
- of this section, the path length through which the emissions are
viewed does not affect the capability of observers to accurately
assign opacities. '(The path length does affect the apparent
opacity which a given concentration level effluent will exhibit.)
The effects of luminescence and color contrast between the emis-
sions and the background on apparent plume opacity will be the
same as experienced with observations of erissions from stacks.
The velocity at which the nases move through the observer's lire
of vision has no effect on opacity. Apparent opacity of fugitive
emissions and emissions from stacks are affected in the same manner;
therefore, the existing training procedures are adequate and Method
9 is a reliable and valid procedure for evaluating fugitive emissions
9. EPA should require- the reading of light colored plumes against a
dark background because the errors are reduced. AC-46(H)
Response: Observations made against less contrasting backgrounds
have a negative bias and negative error which increase.- as color
and luminescence contrast decrease toward zero. A negative bias
decreases the possibility that a plant owner will be cited for
violation of opacity standards due to observer error. Readings
taken under such conditions need not be prohibited.
10. Method 9 should not require the observer to repeat all 5^ obser-
vations if he only fails on one set of 25 observations. Comple-
tion of full certification should then only depend on meeting
the criteria for 25 readings on the other color smoke. AC-3(A),
AC-34(B), AC-69(A)
Response: This relaxation of the requirements for certification
has not been proven necessary or to result in equivalent results.
The Method 9 certification criteria have been proven acceptable
and should not be modified unless it can be shown that eouiva.lent
or better quality data are obtained from the revision.
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49
11. Zero and span drift of the smoke meter should be checked after
each run, and any run in which the drift exceeds +4 percent,
instead of the +1 percent specified, should be dropped. AC-2(A),
AC-11CAL ACT-34T&J, AC-69(A)
Response: A zero and span drift of +4 percent is unnecessarily
large and will result in unacceptable errors. The present re-
quirement of +1 percent is capable of being met and will be
retained.
12. Opacity observers should not be trained on equipment less accurate
than in-stack transmissometers used on many sources. AC-14(C)
Response: A transnn'ssometer nee tine the criteria soecifieci
in Table 9-1 of Method 9 is acceptable for use on a smoke
generator. Smoke generators produce very fine particles,
generally less than 0.5 micron. Because there are fewer
significant variations in angular scattering components, the
angle of view and angle of projection criteria can be less
restrictive for snokc ocnerators then for iii-stack trans-
trn'ssonieters installed in industrial sources. The transmisso-
meters wi11 achieve equivalent accuracy.
13. Several of the sr.oke neter specifications ir Table 9-1 do not
apply to either split or dual hean transmissometers. AC-9(K)
Response: The criteria specified in Table 9-1 are applicable
to the large majority of sroke nenerators' smoke meters. Al-
ternative specifications nay be approved for those fe<:' cases
where split or dual beam transmissoneters erf used on smoke
oenerators.
14. A percent rise should be included in the 'response time speci-
fication. AC-1
Response: Kith in the lii'its of visual perception of the
recorder trace, the rise is to be 100 percent one1 f'.us w
not specified.
15. The thirty minute warn-up period for the srol'.e neter is longer
than necessary and wasteful of both time and enernv. AC-12(A),
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50
Response: EPA's experience has shown that drift is common;-
during warmup of the smoke meter. A thirtv minute warm-up
period is required to prevent this and to assure a valid test.
Gene_ra1_Cprnmen_ts_ on Method 9
1. Concur with the Mcvember 12, 1974 federal Register revisions to
Method 9 and the provisions of §GO jT[?yr~lft£WfG"), AC-5G(i1),
Response: ;io response is necessary.
2. Method 9 should establish morp definitive criteria for reeding
opacity and training of bbservers. AC-38(H)
Response: Method 3 has teen demonstrated to produce accurate-
results and, therefore, the criteria are cieeired adenuate.
Method 9 should specify vho may certifv observers. AC-14(C)
Response: The criteria, not the organization performing the
certification, are the important factors. Any organization
may establish a smoke school oroviided it adheres to the
minimum criteria of Method 9.
4. EPA should establish only certification guidelines rather than
mandatory requirements for states which already have established
smoke schools. AC-16(A)
Response: Minimum criteria, not guidelines, are considered
necessary in the reference methods which are applicable to
standards of performance in 40 CFR Part 60.
Method 9 should allow observations to be made only under weather
conditions comparable to those existing during the observer's
certification or the certification procedure should be expanded
to include training under varying conditions of cloud cover and
background, and on industrial plumes. AC-7(I)
Response: It has not been shown necessary to limit observations
to weather (contrast) conditions prevalent during the observer's
certification test. Field evaluation of industrial plumes by
observers trained under a variety of conditions has not shown
that training conditions affect accuracy.
6. Method 9 is a subjective and imprecise procedure. Too many
variables (wind speed, plume color, illumination, background,
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51 ,-
and wet plumes) affect the apparent opacity for the method to
yield reproducible and accurate results. AC-G(K), AC-20(D),
AC-21(L), AC-22(E), AC-23(E), AC-35(M), AC-38(M), AC-48(E),
AC-49(F), AC-50(E), AC-51(E), AC-57(M), AC-58(E), AC-73(D)
Response: EPA's "Response to Remand Ordered by U.S. Court of Appeals
for the District of Columbia in Portland Cement Association v. Ruckel-
shaus (486 F.2d 375, June 29, 1975)" extensively discussed the accuracy
and reliability of Itethod 9 and the effects-of variables on rlune _anna-
rent opacity. Jr.. summarize the relevant sections of the report; '-It
is known that maximum opacities and maximum errors are associated 'with
observations conducted against contrasting backgrounds. Under con-
ditions presenting a less contrasting background, the apparent opacity
of the plume decreases and approaches zero as the color and luminescence
contrast decrease toward zero. Coriseouentlv, a significant bias and
error can be nade when viewing under Jess contrasting conditions.
The positive error associated with readings conducted against a con-
trasting background was determined iv. this study. Based on the results
of a total of 769 sets of 25 readings, it was determined that qualified
observers can (with a very high confidence level, 99.3%.of the readings")
read plumes v/ith an error less than 7.5 rxrcent. EPA, therefore, con-
cluded that Method 9 has a reasonable error tolerance and the netnod
is a valid and reliable basis for deternining compliance with opacity
standards.
Experience with the effect of meteorological conditions, cloud cover,
and ambient lighting on apparent plume opacities for P. light !:lue
plume fron an oil-fired steam generator contradicts the effects
indicated to be expected ir. .the discussion in the November 12, 197^
Federal Register or in the PCA remand response. AC-30(R)
Response: The data presented by the cement at or do not contradict
the discussion and information presented in the "EPA Response to
Remand...". The data siiow that plume visibility and apparent
opacity decrease as color and luminescence contrast decrease. Under
such conditions a negative bias results. The negative bias resulted
in the discussed light blue plune being invisible against light back-
grounds. The pi nine only became visible
;en a sufficiently contrast-
ing background such as hillside or dark clouds war used
Opacity readings taken in the field are not as accurate or repro-
ducible as tiiose taken for certification at a smoke school. In
field observations the sun angle is determined at the observer's
discretion and by the physical limitations of the site. In addi-
tion, vertical observation anoUs vary, snc! multinle sources may
be present. AC-45(H), AC-57(M)
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Response: While all these situations may occur in the field, tests
under field conditions have demonstrated that observations of accent-
able accuracy can t/e obtained i.i ti.e ficlu uy qualified observers.
See "EPA Response to Remand..." for discussion of field tests.
The November 12, 1974 Federal Register revisions to Method 9 are
appropriate in light of experience with the procedure. Method 9
should be further revised to accommodate situations where an
exemption is necessary (e.r. base period opacity and an exemption)
and to avoid inadvertent!/outlawing their use by local agencies.
AC-3(A), AC-15(B), AC-68(A)
Response: EPA, is presently evaluating the maxlraum nositive error
associated with averaging periods other than six-minutes and different
methods for determining compliance with opacity standards. Depending
on the results of this study, revisions may be made to the methods
allowed under Part 52 of Title 40 for determining compliance with
opacity standards and may be considered for f'ethod 9 of Part 60.
The use of opacity standards of performance based .on six-minute
average values should not invalidate existing local procedures and
opacity standards with time exemptions. Existing State opacity
procedures and regulations should continue to be legally valid just
as existing regulations, for NOX, sulfur oxides, and particulate mat-
ter remained legally valid after EPA established different test pro-
cedures than those used by many State agencies. There is no reason
why the different test procedures cannot coexist.
10. An alternative procedure for determining cornltsnce with op.acitv
standards which include a tine exemption cannot he established
because no valid criteria can be developed. Statutory prohibition
of emissions in excess of a standard is the only logical h-asis
for regulation of sources v.'it.'i intermittent periods of
emissions. AC-16(A)
Response: No response is necessar".
11. The averaging concept is not suitable for regulation emissions
fro~ nan;/ industries. Intermittent emissions in excess cf those
^emitted for startups, shutdowns, soot blowing, etc., should not
be allowed. AC-4(E)
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Response: EPA believes that the average opacity concept is suit-
able for regulating most industries when an average standard at an
appropriate level is selected. Opacity standards thus established
will not allow emissions in excess of control levels determined
to be achievable by well-controlled facilities in that industry.
12. The use of sixrminute average values to determine compliance allows
a new source to emit more particulate matter to the atmosphere than an
existing facility is allowed under a SIP regulation. The commentators
strongly disagree with these revisions. AC-17(A), AC-29(A), AC-68(A)
Response: Whether or not an opacity standard of performance will
allow greater emissions than the existing State regulation is depen-
dent on the control systems used to comply with the respective stan-
dards, the levels of the standards, and the length of the time exemp-
tion allowed in the SIP regulation. In general, due to the time
exemptions in State regulations the differences between the two methods
are "largely superficial, and the total amount of particulate matter
emitted is similar or the standard of performance is more restrictive.
Six-minute averages of opacity observations are used to ensure
taking sufficient readings to ensure acceptable accuracy, and to
obtain a more representative picture of the actual emissions from
the source.
13. L'sc of separate opacity standards for each r,c.\: source cateonry and
averaging the opacity observations makes cnforcene.nt of opacity
standards a nightmare. This approach should be. dropped because
this long chain of determination and averaging is far more then v
can be expected from enforcement personnel" AC-5(A); AC-29(A)
Response: Use of separate opacity standard? for each nsv source
category is necessary in order to i;:surc the establishnert of
opacity levels which are reasonable indicators of nropor o^crt-
tion and maintenance of the control system. Adoption of a'single
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54
opacity standard for all nev.1 sources would not accomplish this
purpose and could be unjustifiably restrictive for so™? sources.
Opacity standards should reflect the degree of erissicn reduction,
not establish unrealistic goals. The calculation of six-minute
average values and knov/ledge of applicable standards should not
unduly tax the capabilities of enforcement personnel.
14. The-average opacity approach does net have any court precedence
establishing the legitimacy of its use. These revisions cast
doubt on the legality of existing opacity standards and existing
procedures used bv State and local air pollution control agencies.
AC-39(A)
Response: EPA's use of opacity standards of performance was- affirmed
by the U. S. District Court of Appeals for the District of Columbia
on May 22, 1975, Portland Cement Association v. Ruckelshaus. 513 F.2d
506> Civ. 72-1073"! These revisions to Method 9 do not'invalidate exist-
ing procedures used by State and local air pollution control agencies
since different methods for measuring the same parameter can coexist
legally. For example, existing State procedures for measurement
of particulate matter emissions from stationary sources continue
to be legally valid despite .the fact that some State procedures
differ significantly from EPA's method for measuring particulate
matter.
15. The November 12, 1974, Federal Register revisions to Method 9 will
have an adverse effect on State agencies' regulations and enforce-
ment activities. Owners and operators of stationary sources may
attempt to pressure the agencies into relaxing the standards.
AC-4(B)
Response: These revisions to Method 9 were determined necessary
and appropriate to assure obtaining readings with an acceptable
and known error tolerance for determining compliance with standards
of performance for new stationary sources. Changes to Method 9
should not have an adverse effect upon State regulations and enforce-
ment procedures if Method 9 was not the procedure used bv the State
for determining compliance. Existing State opacity procedures and
regulations should continue to be legally valid just as existing
regulations on NOX, sulfur oxides, and particulate matter emissions
remained legally valid after EPA established different test proce-
dures than those used by most State agencies. The legal validity
of any given test procedure depends on the regulatory intent (and
penalties) of the standards which the procedure enforces, the
appropriateness of the test procedure for determining compliance with
the applicable standard, the error associated with the test procedure,
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55
and the agency's consideration of that error in determining
possible violations. Whether or not the revisions to Method
9 will have an adverse effect on some State procedures is de-
pendent upon a complete review of the above factors. Such a
review must be conducted on a case-by-case basis.
If a State air pollution control agency adopts the provisions of
revised Method 9, there would be no>reason to relax the applicable
opacity standards and in some cases the agency may wish to revise
some opacity standards downward. In order to maintain opacity
standards and test procedures on a consistent basis, State agencies
that do not revise their opacity method should not revise the appli-
cable dpacity standards due to Method 9 changes. The possibility of
source owners or operators pressuring for relaxation of any applicable
standard always exists and should be handled in a realistic manner.
16. The revised Method 9 places restrictions on the use of some opacity
data without improving the quality of documentation. Existing pro-
cedures in Region VIII (and probably other regions) already require
documentation far in excess of that required by the revised method.
AC-4(B)
Response: The revisions of Method 9 improve the quality of the
documentation as well as clarifying certain provisions and assur-
ing minimum error tolerance to the data. Method 9 now requires
that observations be supported by adequate documentation of the
observer's position relative to the sun and plume, the emission
source and facility and an adequate record of environ-
mental conditions. Such record keeping requirements are necessarv
for valid use of the observations in any enforcement proceedings.
The minimum observation period of six minutes may be less than
called for by existing procedures of many regions; however, it
should be recognized that Method 9 does not place any restrictions
on observation periods in excess of six minutes providing all data
are reduced as six-minute averages. In addition, EPA enforcement
guidelines suggest that while observation for six minutes is adequate,
observation for longer periods of time (e.g. 30 or 60 minutes) is
preferable forest sources.
17. Without meaningful documentation, there is no supportable evidence which
can be used to verify the reported results and conclusions. PC-49(F)
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56
Response: Method 9 requires the observer to make detailed
records on the emission source, observation point locations,
meteorological conditions, background and plume description.
Such detailed information can be used to verify the conformance
of the observer with Method 9 criteria and to calculate the
errors associated with any deviations from the specified criteria.
These records do provide meaningful documentation and are adequate
for enforcement purposes.
18. Method 9's subjectivity is further increased by requiring the
observer to calculate the opacity to the stack exit should
meteorological conditions prevent observing the plume at the
stack exit. AC-49(F)
Response: Paragraph 2.3.1 was added to Method 9 to clarify
that for reading attached steam plumes the observer is to
record the readings made at a point in the plume where all
visible water vapor has evaporated and 9nly particulate matter
remains in the plume. The observer is in no case allowed or in-
structed to extrapolate the readings back to any hypothetical
value at the lip of the stack. Method 9 has never instructed
observers to extrapolate the readings on steam plumes back to
the stack exit. Readings of attached steam plumes at the point
of dissipation allows the operator of a wet process the benefits
of dilution of the plume prior to evaluation of the emissions.
This procedure does not unjustly cite the owner or operator
for violations of the applicable opacity standard.
19. Because of the errors associated with reading opacity against a
contrasting background, the owner or operator may be falsely
cited for violation of an applicable opacity standard. AC-55(E)
Response: The probability of an owner or operator being falsely
cited for violation of an applicable opacity standard is low
because the average positive error of the method must be considered
when determining possible violations of the standard.
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