United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 2771 1
EPA-450/3-87-009
April 1987
Air
Appendix F — Quality
Assurance Procedures
Procedure 1 — Quality
Assurance Requirements
for Gas Continuous
Emission Monitoring
Systems Used for Compliance
Summary
of Comments and Responses
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EPA-450/3-87-009
Appendix F — Quality Assurance Procedures
Procedure 1 — Quality Assurance
Requirements for Gas Continuous Emission
Monitoring Systems Used for Compliance
Determination
(Proposed March 14, 1984, 49 FR 09676)
Summary of Comments and Responses
Quality Assurance Division
Environmental Monitoring Support Laboratory
Emission Measurement Branch
Emission Standards and Engineering Division
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
April 1987
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This report has been reviewed by the Quality Assurance Division of the Environmental Monitoring Support
Laboratory and the Emission Standards and Engineering Division of the Office of Air Quality Planning and
Standards, EPA, and approved for publication. Mention of trade names or commercial products is not intended
to constitute endorsement or recommendation for use. Copies of this report are available through the Library
Services Office (MD-35), U.S. Environmental Protection Agency, Research Triangle Park NC 27711, or from the
National Technical Information Services, 5285 Port Royal Road, Springfield VA 22161.
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APPENDIX F - QUALITY ASSURANCE PROCEDURES
PROCEDURE 1 - QUALITY ASSURANCE REQUIREMENTS FOR GAS CONTINUOUS
EMISSION MONITORING SYSTEMS USED FOR COMPLIANCE DETERMINATION
(Proposed March 14, 1984, 49 FR 09676)
SUMMARY OF COMMENTS AND RESPONSES
Quality Assurance Division
Environmental Monitoring Support Laboratory
Emission Measurement Branch
Emission Standards and Engineering Division
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
April 1987
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TABLE OF CONTENTS
Page
Chapter 1. Introduction 2
Chapter 2. Summary of Changes Since Proposal,
Chapter 3. Summary of Comments and Responses,
Table 1. List of Acronyms Used in Summary of Comments. ... 1
and Responses
Table 2. List of Commenters 71
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Table 1. LIST OF ACRONYMS USED
CD - Calibration drift.
CEMS - Continuous emission monitoring system.
CGA - Cylinder gas audit.
CRM - Certified reference material.
EPA - Environmental Protection Agency.
FGD - Flue gas desulfurization.
NBS - National Bureau of Standards.
NSPS - New source performance standards.
PS - Performance Specification (e.g., Performance Specification 2 or PS 2).
QA - Quality assurance.
QC - Quality control.
RA - Relative accuracy.
RAA - Relative accuracy audit.
RAT - Relative accuracy test.
RATA - Relative accuracy test audit.
RM - Reference method.
SRM - Standard reference material.
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Chapter 1
INTRODUCTION
On March 14, 1984, the U.S. Environmental Protection Agency (EPA)
published in the federaj RejJJl6! (49 FR 9676) "Appendix F - Quality
Assurance Procedures, Procedure 1 - Quality Assurance Requirements for
Gas Continuous Emission Monitoring Systems for Compliance." This
procedure was proposed under the authority of Sections- 111, 114, and
301(a) of the Clean Air Act, as amended.
Public comments were solicited at the time of proposal. To provide
interested persons the opportunity for oral presentation of data, views, or
arguments concerning the proposed procedure, a public hearing was scheduled
for April 9, 1984, beginning at 9:00 a.m. The hearing was not held because
no one requested to speak. The public comment period was originally
scheduled to end May 14, 1984; however, the comment period was extended to
July 13, 1984 (49 FR 24151), at the request of several commenters to allow
them sufficient time to develop pertinent and informed comments.
Thirty-nine comment letters on the proposed Procedure 1 were received
from industry, Federal agencies, State air pollution control agencies,
trade associations, and equipment manufacturers. The comments that were
submitted along with EPA's responses are summarized in this document. The
summary of comments and responses serves as a basis for the revisions that
have been made to Procedure 1 between proposal and promulgation.
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Chapter 2
SUMMARY OF CHANGES SINCE PROPOSAL
1. Section 60.13(a). The last sentence of this paragraph was changed
to include the specific date of applicability.
2. Sections 60.45 and 60.47a have been revised to allow use of
Methods 3, 3A, 6A, 6B, 6C, 7A, 7C, 7D, or 7E for relative accuracy (RA)
testing.
3. Section 1.1. (Note: All the following section numbers refer to
Procedure 1 as proposed.) The wording in the Applicability section was
expanded to clarify that Procedure 1 applies to evaluation of the
effectiveness of the quality control and assurance procedures and the
quality of data produced by CEMS's used for compliance monitoring.
4. Section 1.2. The language in the Principle section was expanded
to identify the basis for the methods in Procedure 1.
5. Section 2.4. The term span l_ey_el_ and its definition have been
omitted from Procedure 1. Succeeding sections have been renumbered
appropriately.
6. Section 2.5. A sentence has been added to identify the potential
sources of reference values for calibration drift (CD) determination.
7. Section 3. A sixth category, Accuracy Audit Procedure Including
Sampling and Analysis Methods, was added.
8. Section 4. All of Section 4, Assessment of Data Precision, has
been eliminated from Procedure 1.
9. Section 5. The title has been revised to "Calibration Drift
Assessment."
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10. Section b.l. The language of this section has been changed to
address the measurement of both zero (or low-level) and upper-level
CD.
11. Section 5.2. The language was revised to include CD.
12. Section 5.3. The section was divided into two new sections in
order to define the periods of out-of-control operation start and end.
13. Section 5.4. Sections 5.4 and 5.4.1 were combined to define
the condition of out-of-control data.
14. Section 6. The title was changed to "Data Accuracy Assessment."
15. Section 6.1. The section was revised to define three types of
audits: the annual relative accuracy test audit (RATA) that is required
at least once per year, the cylinder gas audit (CGA) that may be used up
to three times per year, and the relative accuracy audit (RAA) that may
be used up to three times per year. The RATA is conducted as defined in
the applicable performance specification. The CGA is a three-run,
two-point audit of each analyzer using certified gases; and the RAA is a
three-run RA check using methods specified in Appendix A.
16. Section 6.2. The title was changed to "Criteria for Excessive
Inaccuracy" and the language was revised to define specifically the
condition of the out-of-control period based on the type of audit
conducted.
17. Section 7. The description of the performance audit for the
sampling method testing was deleted and wording was added to the
description of the RATA to require the performance audit as described in
the sampling methods.
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18. Section 9. The section was divided into three new sections each
defining the procedures required for calculating the respective CEMS
accuracy values.
19. Section 10. References to precision assessment were deleted and
reporting requirements for the three accuracy audit procedures were
defined.
20. Figure 1. The example format for data assessment reporting was
revised to reflect the deletion of the precision assessment.
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Chapter 3
SUMMARY OF COMMENTS AND RESPONSES
Section 1. Applicability.
1.1 Commenters IV-D-6 and 19.
Comment: The quality assurance (QA) procedures should be made
mandatory for all continuous emission monitoring systems (CEMS's) required
to be installed under the provisions of any regulation (e.g., Subpart D),
permit, plan approval, consent order, decree, etc. If the quality of data
from the CEMS is of no concern, a company should not be required to incur
the cost of installing one.
Response: The Agency agrees that quality control (QC) and QA for
CEMS data are important for every application; however, different
applications require different degrees of QA and QC. Present regulations
for CEMS's used as indicators of proper operation and maintenance of emission
control systems include QC measures such as daily calibration drift (CD)
measurements and adjustment limits and the initial performance specification
(PS) tests. With the advent of regulations requiring continuous compliance
monitoring, additional data, as defined in Procedure 1, are needed for the
protection of both the source operator and the regulatory agency. If the
Agency determines that additional QC and QA procedures are needed for
CEMS's intended for other purposes, procedures will be developed and proposed.
1.2 Commenters IV-D-12, 18, 22, and 38.
Comment: Many generating stations, subject to 40 CFR Part 60, Subpart D
regulations and monitoring S02, NOX, C02, and opacity emissions, have no
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computer data reduction systems, and major modifications and expense would
be required to adapt these units to Appendix F. We, therefore, recommend
that applicability of Appendix F be limited to CEMS's installed after the
promulgation of the regulation, if at all.
Response: Appendix F, Procedure 1, has been developed in response to
obligations made when Subpart Da was promulgated in 1979. That is, the
Da regulation required the CEMS to be the compliance method and that
specific procedures must be implemented to assure that data supplied by
CEMS's for compliance be of known accuracy and precision.
The proposal of revisions to Subpart D (48 FR 48964) includes the use
of CEMS's for compliance determination on a 30-day rolling average basis.
This significant change for Subpart D sources will cause major
modifications to computer-operated systems. The proposal includes a 1-year
development period to accommodate such changes. The Agency believes that
addition of Procedure 1 requirements to other changes being considered for
Subpart D sources will not be burdensome and the promulgated Procedure 1,
with the changes included since proposal, is applicable for evaluating
CEMS's on present and future Subpart D sources should they become subject
to continuous compliance requirements.
1.3 Commenters IV-D-21 and 31.
Comment: We recommend that similar regulations be proposed for
Subpart D sources and the public be allowed another opportunity to comment
on this procedure.
Response: As mentioned in the preamble to the proposal, Procedure 1
will apply to Subpart D sources should they become subject to continuous
compliance provisions. Thus, interested persons have had the opportunity
to comment on the application of Procedure 1 to Subpart D. The Agency sees
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no reason to provide further opportunity for comment on this application.
At this time, the Agency has not considered similar QA requirements on
CEMS's that produce data only for operation and maintenance monitoring; if
the Agency determines such a need, the public will be allowed to comment on
proposed procedures.
1.4 Commenters IV-D-23, 25, 31, and 38.
Comment: This proposal is unfair in two ways. (1) It is being
developed to apply to future sources which are currently not identified;
these unidentified sources have no way of knowing whether they will be
affected at some future date. Not knowing they will be affected, they are
precluded from taking part in the rulemaking process to ensure their
interests are appropriately addressed. (2) The burden placed on nonutility
sources will generally be much greater per unit ton of emission than the
burden placed on utility sources.
Response: Procedure 1 affects only Subpart Da sources; at present,
Procedure 1 does not apply to other sources. If the Agency determines that
Procedure 1 should apply to other source categories, the applicability of
Procedure 1 will be proposed with the regulatory revision and subjected to
comment and review by all affected facilities and related organizations.
1.5 Commenter IV-D-32.
Comment: Our four coal-fired units have successfully held emissions
well below established sulfur dioxide limits without the use of scrubbers.
For example, we are able to achieve an emission level of 0.72 Ib/MMBtu when
the standard is 1.2 Ibs/MMBtu. It hardly seems appropriate to apply stringent
QA procedures to companies that burn compliance coal. We do not foresee
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any environmental benefit from the proposed regulations and yet our
rate-payers must subsidize the added requirements.
Response: The commenter may be referring to a fuel analysis option
for determining compliance with emission standards, in which case, the
Procedure 1 requirements are not applicable. Another procedure in
Appendix F would be necessary for such an application and this is not yet
available.
If the commenter is referring to a CEMS applied to a Subpart D source,
the owner/operator may apply to the Agency for approval of an alternative
procedure under provisions in 40 CFR 60.71(i). This is a source specific
issue and is not addressed in Procedure 1.
1.6 Commenters IV-D-33 and 36.
Comment: Six months is insufficient time to educate the different
stations on the QA procedures, to implement the necessary data collection
and reduction (data precision), to write and implement written procedures
(QC requirements), and hire additional personnel. Several of these
requirements will require reprogramming for the CEMS computer systems
(i.e., ability to delete emission data invalidated by out-of-control
periods, ability to add data collected by alternate means). These computer
program changes could be construed as a "major modification" to the CEMS
which would require retests of the CEMS to check compliance with the PS
tests. Each station would have to hire and train personnel to collect and
reduce the data required by the precision checks and additional test
personnel would have to be hired to do the relative accuracy audits (RAA's)
and the cylinder gas audits (CGA's). This would require significant
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additional time to comply with the proposed regulations. We would suggest
that Appendix F be applicable no earlier than 1 year after promulgation.
Response: The requirements of Subpart Da (promulgated in 1979)
already define the capabilities a CEMS must have to handle data reduction.
Procedure 1, as promulgated, does not add to these requirements. There are
some additional reporting requirements for the audits results and
out-of-control descriptions that are a result of implementation of
Procedure 1, but these should not significantly affect work load.
Preparation of a QA plan is the major initiating project for these sources,
and the Agency believes that 6 months is sufficient time to implement the
procedures required to comply with Procedure 1.
The proposed Subpart D revisions include a 1-year preparation period
before implementation. If these revisions promulgate a continuous
compliance provision as proposed, this 1-year period will be sufficient to
complete computer operation changes required by both the Subpart D
revisions and the Procedure 1 requirements.
1.7 Commenter IV-D-35.
Comment: We seek confirmation that Subpart D generating units that use
other methods for demonstrating compliance with emission limits will not be
affected by the Procedure 1 proposal. We also seek confirmation that the
requirements of Procedure 1 are not applicable to opacity monitors.
Response: Procedure 1 applies only to gaseous emissions CEMS's used
for compliance monitoring. It does not apply to opacity monitors
(transmissometers), nor to other means of monitoring emissions, such as
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fuel sampling and analysis or manual methods of emission sampling. The
Agency is reviewing and developing appropriate QA requirements for these
monitoring approaches.
1.8 Commenter IV-D-35.
Comment: We are concerned that the proposed rules may be misconstrued
to apply to CEMS's on generating units not subject to Subpart D or Da. We,
therefore, request that the Agency acknowledge in this rulemaking that
monitoring systems on older generating units may not be capable of complying
with the rigorous testing and criteria in the Procedure 1 proposal. Emphasis
of this point may be valuable in the event that other regulatory agencies
seek to apply the Procedure 1 requirements to CEMS's existing units.
Response: The applicability section of Procedure 1 is very specific
on this point. The preamble to the promulgation also discusses this issue.
The Agency believes that sufficient explanation and clarification are
included.
1.9 Commenter IV-D-39.
Comment: Make it clear that Appendix F is intended to address
minimum QA requirements that should be implemented by sources after the
source initially demonstrates that its CEMS's have met the relevant PS's.
Response: In discussing the applicability, Section 1.1, Procedure 1
is very clear on this point. Procedure 1 states "This procedure specifies
the minimum QA requirements necessary for control and assessment of the
quality of CEMS data submitted to EPA." 40 CFR 60.13(c) is also specific
that all CEMS's shall comply with the provisions of the PS's in Appendix B
within 30 days of performance tests required in 40 CFR 60.8. This
requirement has not been changed.
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1.10 Commenter IV-D-6.
Comment: We would prefer that EPA include language specifically
stating that, since these procedures are minimum requirements, States are
encouraged to develop modifications of the procedures more suitable to
their individual CEM programs.
Response: The introductory section of Procedure 1 includes specific
encouragement to source operators to expand on the QA procedures in order
to address specifically the needs of individual CEMS installations.
Similar encouragement to regulatory agencies is contained in
Section 60.10 of the General Provisions which provides that State or
local agencies may implement additional requirements to new source
performance standards (NSPS).
1.11 Commenters IV-D-35 and 36.
Comment: Low-capacity units which include units that typically
operate on a seasonal cycling mode, units that remain on cold standby for
prolonged periods of time, and units that remain on hot standby (operation
solely to maintain boiler pressure) for several days at a time should not
be subject to Procedure 1 requirements. The Agency should also consider
exempting from Appendix F those units which burn gas and oil, if oil
represents less than 25 percent of the total annual heat input.
Response: Definition of which sources are subject to continuous
monitoring regulations is not within the scope of Procedure 1. This issue
is defined within the applicable regulations which include criteria for
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minimum source operating levels and time for determination of applicability.
Note that if a source is subject to a continuous monitoring requirement and
a CEMS is applied, an initial relative accuracy test (RAT) is required
regardless of the implementation of Procedure 1. If the CEMS data are used
for compliance determination, Procedure 1 would then be applicable.
Source operators do have the opportunity to apply for alternative
procedures under the General Provisions in 40 CFR Part 60. Such alternative
procedures could include alternative QC and QA procedures, as well as,
measurement methods.
1.12 Commenters IV-D-23 and 25.
Comment: The CEMS data should be used only to monitor operation and
maintenance, not to determine compliance.
Response: The decision that CEMS's are appropriate compliance tools
for NSPS is not within the scope of this regulatory action. Such a
determination was made with respect to Subpart Da in the Subpart Da
rulemaking and is a subject of the pending Subpart Da rulemaking.
Procedure 1 provides a basis by which to judge whether the data provided by
a CEMS are valid for compliance determinations.
Section 2. Definitions.
2.1 Commenters IV-D-2, 6, 17, and 20.
Comment: Use of the terms "span value" and "span level" is confusing.
Use of "full scale value" in place of "span value" and "precision check
value" in place of "span level" may help to clarify the definitions. In
addition, all span levels should be within plus or minus 10 percent of the
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Response: Span value is not necessarily the same as instrument range.
Span value is defined in PS 2 as: "The upper limit of a gas concentration
measurement range specified for affected source categories in the
applicable subpart of the regulations." Span value is defined in the
applicable regulations and corresponds to a concentration value about 1.25
times the maximum, expected, pollutant concentration for uncontrolled
emissions or 50 percent of the maximum expected value for controlled
emissions.
The span value, instead of the CEMS range, is used as the basis for
calculation of CD so that the limits of acceptability are equitably
enforced. Also, in this manner the drift specifications are directly
related to applicable emission standard and are more meaningful than
instrument-specific values would be.
Specifying cylinder gas values as percentages of the applicable
emission standard is inappropriate for most CEMS applications. It is
inappropriate because the emission standards are not defined in
concentration units but require calculations using data from more than one
gas analyzer. To deal with this, Procedure 1 requires that the CGA
include a point at 50 to 60 percent of the span value which will approximate
the level of the pollutant concentration corresponding to the emission
standard.
Similarly, defining "normal operating levels" of diluent gases within
10 percent is difficult for most sources. The Agency has defined a range
of diluent gas concentrations for the CGA. This range corresponds to the
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fossil fuel-fired boilers. These values may not apply to other emission
sources and will be reviewed when other EPA regulations require CEMS for
continuous compliance determinations at other sources.
The definitions section of Procedure 1 has been revised to clarify
the use of these terms.
Section 3. QC Requirements.
3.1 Commenter IV-D-11.
Comment: These requirements should include monitor siting criteria
and data validation criteria.
Response: The monitor siting criteria should be addressed prior to
installation and be adequately certified by the PS test results. The
fourth factor in Section 3, data reporting and recording, should include
data validation criteria such as spot checks of calculations and periodic
checks of the integrity of computer manipulations.
The Agency believes the list of QC requirements in Section 3 can and
should be expanded by the source operator to reflect more accurately the
needs of a particular system.
3.2 Commenter IV-D-13.
Comment: The QC requirements of Section 3 should be standard procedure
for all CEMS operators.
Response: The Agency agrees with this sentiment. Some QC procedures
are mandated for CEMS's installed in compliance with 40 CFR Part 60, but
Procedure 1 is the only regulatory section requiring written QC procedures.
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3.3 Commenter IV-D-21.
Comment: Section 3 should require the inclusion of an alternate
method of obtaining emission data when the CEMS is considered out-of-control.
Response: The Agency agrees that a source subject to minimum data
requirements should be prepared if alternate sampling is required.
Procedure 1 includes six major categories for a QC program plan with one
listed as "Program of corrective action for malfunctioning CEMS." The plan
under this category should include alternative emission testing procedures.
3.4 Commenter IV-D-28.
Comment: Procedure 1 specifies that if excessive CEMS inaccuracies
occur two consecutive quarters, the QC procedures must be rewritten to
correct the deficiency. It is generally recognized that the design of the
CEMS's (especially the vintage installed at Subpart D sources) has not
achieved the level at which continuous, reliable operations can be reasonably
expected. Thus, it is the instrument design that is typically the limiting
factor to monitor performance, not QC procedures. While it is recognized
that QC can improve monitor performance, it is erroneous to assume that
simply revising a procedure will fully correct data deficiencies. We
recommend that this requirement be deleted.
Response: If a CEMS fails to meet any of the relative accuracy (RA)
criteria on the first attempt for two quarters in succession, that is good
indication that the CEMS and the QC program are in need of serious review
and revision. The source operator should conduct this review and make
changes necessary to ensure successful operation of the CEMS. The required
action may be to revise the QA/QC procedures, or it may be to replace the
CEMS because of poorly designed equipment.
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The Agency recognizes that the design of a CEMS and its specific
application are important factors in determining whether the CEMS will
operate successfully. The first step in a good QC program is selection of
good, durable, accurate equipment suitable for the intended application.
The source owner/operator is responsible for this selection. The owner/
operator should be as well-informed as possible about CEMS operation and
application. Manufacturer's information, advice from source testing
consultants, technical publications from EPA and others in the industry can
provide excellent guidance in this area.
3.5 Commenter IV-D-34.
Comment: Appendix F should include requirements that plant specific QA
procedures include manufacturer recommendations for assurance of data
precision and accuracy. In addition, Appendix F should give more detail
on establishing a QA program at a given facility. The regulation
guidelines for plant QA programs should be expanded to include as a
minimum:
1. The assignment of CEMS responsibility to specific personnel for
meeting QA objectives.
2. Operator training in all aspects of CEMS operation and
maintenance.
3. The keeping of a service and maintenance log for the CEMS.
4. The establishment of a spare parts inventory for the CEMS.
5. Security for the CEMS and all output data.
6. Implementation of routine weekly, monthly, and quarterly CEMS
maintenance schedules.
7. Periodic audits of CEMS precision and accuracy.
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Response: The Agency agrees with the commenter that these are
important considerations for a QC program. The proposed and promulgated
versions of Procedure 1 include these and other QC issues in the list of
general headings for the required QC program. The Agency has chosen to
recommend several critical elements as the commenter has done and leave
the responsibility to the owner/operator to develop an appropriate QC
program with the help of the manufacturer, if necessary.
Section 4. Assessment of Data Precision.
4.1 Commenters IV-D-4, 6, 11, 13, 19, 20, and 27.
Comment: Assignment of cylinder gas or gas cell concentration values
from CEMS readings should not be allowed. Such a practice could result in
CEMS data that would be precisely wrong. If there is an undetected
analyzer malfunction between the time of certification and the time of
assignment of calibration values, use of the gas or cells would not provide
a valid check of the analyzers. Determination of calibration standard
values should utilize reference method (RM) procedures.
Response: The purpose of the CD checks is to determine whether the
CEMS has the ability to repeat its response to a specific input over known
time intervals. It is, therefore, not necessary to know the input values
with absolute accuracy, only that the value is stable.
The Agency would encourage the CEMS operator to include evaluation of
all calibration gases or cells as part of the QC procedures. Such
additional knowledge can only enhance the quality of the CEMS data; however,
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the Agency believes that, such, rigorous analyses are not required for
the purpose of the CD measurements. The additional analyses should be left
to the discretion of the CEMS operator.
4.2 Commenters IV-D-3, 5, 6, 7, 12, 14, 17, 27, 32, 35, and 36.
Comment: Present regulations require a daily zero and span CD check
in accordance with a written procedure and provide guidelines on when to
adjust the zero and span points. This in itself is QA, and we feel this
procedure most accurately represents instrument precision. Using all of
the daily span checks to calculate analyzer precision would not further the
information on CEMS performance and would impose unnecessary recordkeeping
and reporting requirements. We recommend that Section 4 be deleted.
Response: The Agency agrees that daily drift checks are part of QA,
but these checks alone are insufficient. It is also necessary to conduct
frequent equipment RA checks. The Agency has determined that the
combination of daily drift checks and periodic RA checks provide the
necessary QA for these CEMS's.
The Agency agrees that the precision calculation and reporting are
unnecessary for QA. The precision check section has been removed from
Procedure 1.
4.3 Commenters IV-D-6, 12, and 28.
Comment: The precision of the analyzer zero should also be
determined daily. An error in the analyzer zero can affect CEMS output
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just as much as upscale drift. Zero drift should be treated identically to
span drift. Another determination of instrument drift would be the percent
difference in the CEMS output calibration span value minus the zero value
for successive days.
Response: The Agency agrees that the CEMS zero drift should be
monitored as well as the span drift. Both of these measurements are
indicators of CEMS CD. However, the Agency disagrees that zero drift
should be subtracted before calibration span drift is measured if
calibration span drift is the only indicator of CEMS stability. The
purpose of the drift measurements is to monitor the CEMS response to
repeated reference value inputs. These inputs are intended to simulate
stack gas measurements to some degree, and it would be of less value to
allow adjustment to the CEMS response for the drift check while
measurements of stack gas concentration are unadjusted.
With both measurements required, it would be permissible to measure
an unadjusted zero drift followed by the measurement of an adjusted span
drift. Indication that either CD measurement exceeded the limit would be
cause for corrective action. The promulgated Procedure 1 reflects this
change, including criteria for acceptable limits for both zero and span
CD's.
Section 5. Zero and Span CD.
5.1 Commenter IV-D-5.
Comment: The requirement for an RAA after an "out-of-control" period is
reasonable, especially if major repairs were required. However, in order
to reduce the impact of these audits on the scheduling of other tests, the
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2-week deadline should be extended to a month. We also feel that this
audit should be counted as an annual audit thereby changing the date for
the next required annual audit to 12 months after the out-of-control
audit.
Response: Procedure 1 defines the out-of-control situation for two
CEMS deficiencies. The first results from the CEMS being unable to meet
the excessive drift criteria. The Agency has determined the RATA is
unnecessary following a correction for excessive drift in most cases.
The promulgated Procedure 1 reflects this change from the proposal.
The second CEMS deficiency leading to out-of-control designation is
failure to pass the RA assessment, either the quarterly audit or the annual
RATA. It is necessary to repeat the audit or the RATA following repairs.
The repeated RA assessment is counted as the quarterly or annual audit, as
appropriate, and no other provisions in Procedure 1 are necessary.
5.2 Commenters IV-D-6, 11, and 36.
Comment: Since the 24-hour drift specifications must be met by a
CEMS in order to be certified, it seems appropriate to consider a CEMS
out-of-control when the drift exceeds twice the specification on any day.
Our experience indicates that requiring adjustment whenever the
specification is exceeded is not overly burdensome.
Response: A single measurement in excess of the lower drift limit
may be an indication of CEMS problems, but may also be a result of a
statistical aberration, dirty windows which may be easily cleaned,
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or a nearly empty gas cylinder. Five consecutive excesses would be a
positive indication that a serious problem exists and the CEMS should be
repaired immediately. The Agency believes that declaring a CEMS to be
out-of-control based on one violation of the lower drift limit is
excessive.
5.3 Commenter IV-D-9.
Comment: We recommend that this section be revised so that adjustment
of the zero and span be required whenever the drift exceeds four times the
cell value instead of the proposed criteria of two times the limit which
is unrealistically restrictive.
The criteria for defining monitor out-of-control should be changed
to "four times the applicable PS in Appendix B for five consecutive span
checks." An acceptable alternate would be "3 percent of full scale for
five consecutive span checks."
Response: The commenter has confused instrument scale and the term
"span value" used in Procedure 1. The drift limits in Procedure 1 are
referenced to the span value for that source category, not the calibration
cell value or the instrument full scale value. In this manner, the drift
limits are directly related to the emission limits of the regulation,
rather than the site-specific instruments. The limits in Procedure 1 are
greater than those recommended by the commenter in terms of actual drift.
5.4 Commenters IV-D-11 and 31.
Comment: It seems inconsistent that a monitor is considered
out-of-control only after five consecutive excessive drift measurements
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when the desired goal is the collection of valid, representative data.
Specify a minimum acceptable data capture, general guidelines for
acceptance of data, and the means by which to collect the data. Then allow
operators to use their discretion in meeting data capture requirements.
Response: The Agency has specified minimum data capture requirements
in Subpart Da and has proposed similar requirements in Subpart D for
compliance determinations. Procedure 1 defines the criteria and procedures
by which to determine the validity of the CEMS data and those periods when
the CEMS is to be considered not operating within acceptable bounds. CEMS
operators who must comply with applicable regulations are then expected
to meet the data capture requirements within these criteria.
5.5 Commenters IV-D-9, 11, 12, 23, 25, 27, 35, and 36.
Comment: Conducting an RAA everytime corrective action for excessive
drift is performed is excessive.
Response: The Agency has determined that, in most cases, a CEMS that
shows excessive drift can be returned to proper operation by correction of
the drift problem and that a subsequent RA assessment is unnecessary. The
promulgated version of Procedure 1 reflects this view with a change in the
corrective action needed for exceeding the drift criteria.
5.6 Commenter IV-D-12.
Comment: The definition of "unacceptable data" in Section 5.4
specifies that the previous day's data are unacceptable if an individual
CD exceeds four times the applicable limit. This definition of unacceptable
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data would create numerous recordkeeping and notification problems in that
it would require monthly recalculation of rolling average data. When the
cause or time of drift can be determined, it may not be necessary to
invalidate an entire day of previous data. We recommend that the
definition of unacceptable data be based on a larger drift than 10 percent.
When drift is caused by identified maintenance or the exact time of drift
can be determined, the data should not be invalidated.
Response: The Agency believes that a CD of over 10 percent of the
span value is a strong indication that the CEMS is in need of direct
attention and is probably in need of repair. Data collected under such
conditions are unreliable and should not be included in a set of valid
data. If the cause of the drift problem and the time of its occurrence can
be accurately identified, it would be possible to delete only those data
affected by the change in CEMS response. Such data validation procedures
should be clearly outlined and presented to the Administrator as a request
for alternative procedures.
Further, any recalculation of rolling averages would be for only the
period ending on the day of excessive drift. This would be one 30-day
average for a Subpart Da source with a computer program designed to
calculate the emission rate at the end of a verified boiler operating day
as directed by the regulation.
5.7 Commenter IV-D-7.
Comment: Procedure 1 should recommend (or require) a CEMS calibration
check with a standard other than the daily span source with a frequency
within 90 days.
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Response: The Agency believes that the quarterly audit procedure with
either the RAA or the CGA and the only drift check are sufficient checks of
the CEMS calibration and measurement accuracy. The source owner is
encouraged to incorporate more frequent calibration checks and other CEMS
QC procedures suitable for specific CEMS installations in the introduction
to Appendix F.
5.8 Commenter IV-D-19.
Comment: A sentence should be added requiring that the duration
of zero and span checks be adequate to reflect properly the stabilization
of the monitor. Experience has shown that, in some instances, these checks
are being performed too rapidly to characterize monitor response adequately.
Response: Procedure 1 references procedures for zero and span checks
as set forth by the equipment manufacturers. These procedures should
include criteria for response time and CEMS stabilization that are
applicable for the equipment being tested. The Agency agrees that such
considerations are important in measuring CEMS drift, but the procedures
and criteria are application-specific. Appendix F specifies acceptability
limits for CEMS checks and tests which will prevent loose operation of
CEMS's.
5.9 Commenter IV-D-28.
Comment: Procedure 1 requires that the source operator use alternate
methods of obtaining emission data when the CEMS is out-of-control. It
should be noted that the current requirements for Subpart D sources contain
no provisions for minimum data capture or alternate measurement methods.
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Thus, implementation of Appendix F could require significant expenditures
at Subpart D sources for alternate monitoring. The cost and manpower
requirements associated with the installation and operation of these
alternate systems would be substantial.
Response: Procedure 1 does not require source operators to conduct
alternate monitoring during periods of CEMS out-of-control operation.
This is a provision of the applicable regulations which include minimum
data availability criteria. Testing with an alternate method should be
done only to meet the minimum data availability requirements. Procedure 1
defines the criteria which determine when a CEMS is out-of-control and
the CEMS data are not valid for meeting the minimum data availability
requirements. It is a vital part of any QC program to provide a method(s)
for alternate monitoring and to be prepared to implement such as necessary.
5.10 Commenter IV-D-28.
Comment: Procedure 1 requires that data collected during a monitoring
system breakdown be retained for EPA inspection. The requirement to collect
and store such data will involve significant changes to current data
acquisition system. Currently, information that is known to be faulty is
not retained. Given that such data have no value to the company, and given
that the EPA has not identified any potential value which the data may
have, the company concludes that the requirement to collect and maintain
data files of useless information is not worth the expense involved and
should be deleted.
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Response: This statement in Procedure 1 to retain all CEMS data
is a restatement of the regulatory requirement in 40 CFR 60.7(d). This
paragraph requires the source operator to maintain a file of alj_ CEMS data
for at least 2 years.
5.11 Commenter IV-D-32.
Comment: The proposed rule for corrective action for excessive span
drift, the source owner or operator must use another method of obtaining
the minimum emission data as required and described in the applicable
subpart [e.g., 60.47a(f)]. We suggest that EPA consider the alternative of
allowing a source owner to replace a monitor that is out-of-control with
another CEMS. Many times a source owner has another CEMS 'available. Also,
purchasing an extra CEMS for these situations may be less costly than the
process of stack testing.
Response: Applying another CEMS in place of one that is
out-of-control is certainly a valid alternative monitoring procedure.
The alternate CEMS would be subject to the same PS certification and QA
procedures as any other CEMS used for compliance monitoring.
5.12 Commenter IV-D-33.
Comment: The CD limits and corrective action sections need
clarification. Does "five consecutive span checks" mean five daily span
checks (i.e., over 5 days) or five consecutive span checks on the same day?
It is possible to exceed the PS for span checks and not affect the previous
data. For example, in a computer initiated and compensated span check in
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which the gas cylinder is emptied or has the wrong gas, the span check
would be out of specifications; however, the previous data would not
necessarily be affected. We would recommend more flexibility in
determining out-of-control and system breakdown periods. We would
suggest that each of the incidences must be reviewed to determine the
status.
Response: Procedure 1 references the drift specifications in
PS's 2 and 3 that are stated as measurements of 24-hour drift. The Agency
is aware of various CEMS problems that can cause apparent drift problems
when none exist. The allowance for 5 days of consecutive excess drift
provides time to identify and correct such problems. The Agency believes
that excesses continuing for longer periods indicate serious CEMS
operational problems or poor maintenance, either of which is cause for
immediate critical review and corrections.
5.13 Commenter IV-D-35.
Comment: Under Section 5 of proposed Procedure 1, a monitor is
considered to be .out-of-control if the span drift exceeds "twice the-
applicable PS in Appendix B for five consecutive span checks." For NOX and
SOX CEMS, twice the allowable span drift is only 5 percent. The appropriate
criterion for a particular monitor would be calculated by taking 5 percent
of the span value as that term is defined at Section 2.4 of PS 2 in
Appendix B and Section 2.3 of proposed Procedure 1 ("the upper limit of a
gas concentration measurement range that is specified for affected source
categories in the applicable subpart of the regulations"). Thus, for an
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NOX monitor at a solid fuel-fired Subpart Da generating unit, the criterion
would be 5 percent of the 1000 ppm span value specified at 40 CFR
§60.47a(l)(3), or 50 ppm.
Response: This is correct.
5.14 Commenters IV-D-5, 31, and 35.
Comment: Since NOX and diluent emissions are primarily controlled
by boiler design, it is unlikely that NOX or diluent emission rates would
vary significantly during a monitor outage. We propose that alternative
monitoring requirements for NOX or diluent during CEMS outages be deleted
from the proposed regulations.
Response: The commenter's suggestion to use historical data for
limited periods of CEMS inoperation could be a valid alternative method.
As such it could be considered by the Agency as an acceptable alternative
method if proposed for a specific application and included criteria for
process control and monitoring, data acquisition and reduction, period of
alternative monitoring, and proposed corrective action for CEMS. Such
alternative monitoring could apply not only to NOX emissions, but also
diluent concentration under restricted circumstances. Review by the
Agency of any alternative procedures is necessary before approval for
specific or general use.
5.15 Commenter IV-D-36.
Comment: The proposal states that if the span drift exceeds twice the
applicable monitor drift limit for five consecutive span checks, or four
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times the monitor drift limit for a single span check, the monitor is
out-of-control. Twice the allowable span drift is only 5 percent.
Since EPA has not included in the docket or discussed in the proposal any
analysis of drift data that would support these criteria, EPA has not
demonstrated that available CEMS's could meet this out-of-control
criteria based on span drift. In fact, in an extensive CEM demonstration
project conducted by EPA in 1980-81, CEMS's were unabTe to satisfy these
out-of-control criteria a substantial portion of the time. As a result,
under these proposed criteria, much of the data collected during this
project would have been invalidated.
Response: The Agency reviewed the data analyses provided by the
commenter and disagrees with the commenter's evaluation on a couple of
points. First, the commenter used a span value corresponding to the
value of a cylinder gas used to calibrate the OEMS rather than the
applicable span value. The span value in this case was significantly
greater than the cylinder gas value and would thus produce drift results
lower than those the commenter calculated. Second, the commenter divided
relatively long periods of poor CEMS operation into individual cases of
out-of-control operation. If the procedures in Procedure 1 were
followed, many of the periods exceeding drift limits identified by the
commenter would be consolidated into relatively few out-of-control periods
that would have ended only when corrective action was completed.
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The Agency has reviewed long-term drift data from five other CEMS
installations. These data indicate that the drift specifications in
Procedure 1 will be exceeded less than 1 percent of the CEMS operating
time.
5.16 Commenter IV-D-6.
Comment: Additional criteria should be added to determine
"unacceptable data" status. Examples are pollutant or diluent monitor
malfunction, process not operating, etc. Also, minimum data requirements
for calculation of various time-averaged concentrations or rates should be
specified.
Response: The criteria listed in Appendix F apply to the QC and QA
measurements that are specified in the procedure. It is not within the
scope of Procedure 1 of Appendix F to define acceptable process conditions,
regulatory averaging time, or minimum data requirements. These issues are
addressed in the applicable regulations.
Section 6. Assessment of Data Accuracy and Corrective Action for
Excessive Inaccuracy.
6.1 Commenters IV-D-1, 4, 6, 7, 8, 9, 11, 12, 20, 21, 30, 32,
33, 35, and 36.
Comment: We recognize the need for conducting QA checks on a
CEMS; however, we believe that the quarterly assessment of data accuracy is
far too stringent, costly, and time-consuming. The frequency of audits
should be changed to once per year, as recommended by some commenters, or
less frequent schedules as recommended by others.
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Response: The commenters provided no substantial amount of data
supporting a reduction of audit frequency to less than quarterly. The
quality of CEMS data is a function somewhat of CEMS design and specific
application and more importantly of equipment maintenance which includes
instrument response checks, parts cleaning and repair, and maintenance
of expendable supplies. However, the only measure of the effectiveness of
the QC measures is a periodic accuracy audit. To reduce the testing burden,
Procedure 1 has been revised to require an RAT as per PS 2 once a year and
to allow the use of CGA, where applicable, or a reduced number (three runs
instead of six or nine) of RA method tests for three quarters.
6.2 Commenter IV-D-4.
Comment: If a monitoring system can demonstrate at least a 1-year
period of successful QA audits, we believe that a longer time period
between audits for that particular monitoring system could be allowed
without compromising the overall quality of the data generated by the
monitoring system.
Response: This is an approach worth consideration under an
alternative procedure review on a case-by-case basis. The Agency would
need to review the background data before considering such a relaxation.
6.3 Commenters IV-D-4 and 17.
Comment: Procedure 1 proposes that the appropriate performance audit
sample be analyzed with each RATA performed. We support this position and
recommend that either failure to analyze the performance audit sample or
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unacceptable analytical results on the performance audit sample should be
made grounds for invalidating the RATA. Further discussion in Procedure 1
is necessary.
Response: The promulgated version of Procedure 1 references the
performance audits in the applicable RM's as these have been promulgated
(49 FR 26522) since the proposal of Appendix F. These procedures in the
respective methods include a provision for retesting if the performance
audit limits are not met.
6.4 Commenter IV-D-4.
Comment: We have noted a discrepancy in the CEMS responses produced
by two different audit gases supplied by different sources.
Response: Procedure 1 specifies the use of audit gases directly
comparable to the National Bureau of Standards (NBS) Standard Reference
Materials (SRM), or NBS/EPA approved gas manufacturers' Certified Reference
Materials (CRM) prepared following EPA's Protocol 1, or the direct use of
CRM gases. If gases of this quality are compared, there should be no
significant differences in the produced instrument responses.
6.5 Commenter IV-D-5.
Comment: Analyses of coal samples taken to verify heating value and
sulfur content could be used to check independently the calibration of the
monitor to determine if it is out-of-control in terms of data accuracy.
Response: Review of fuel analysis data for different sampling periods
shows that the imprecision associated with daily samples is much greater
than the limits of drift specified for CEMS. For this reason, comparison
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of the data produced by these two methods on a daily basis would not be
appropriate for determining an out-of-control condition for CEMS's.
6.6 Commenters IV-D-6 and 11.
Comment: For an RAA, a test run of three samples should be sufficient
to identify major problems with the CEMS.
Response: The Agency agrees that comparing the mean results of
three RM test runs would be a good indicator of CEMS performance. The
revised Procedure 1 includes a provision to allow this abbreviated RAA for
three of four quarters with an RAT as per PS 2 required annually.
6.7 Commenter IV-D-6.
Comment: The CGA audit points used should be those specified
for calibration error testing in EPA-450/3-82-026, including the zero
level.
Response: The purpose of the CGA is to audit the accuracy of the
CEMS response at gas concentrations in the range expected during normal
operation. The values specified in Procedure 1 reflect this purpose. The
zero level is not needed.
On the other hand, the purpose of the calibration error test in the
CEMS Guidelines (EPA-450/3-82-026) is to provide a procedure for checking
the calibration linearity or calibration accuracy of the analyzer. This
procedure does not include the entire CEMS sampling system and is not
designed as an auditing technique.
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6.8 Commenters IV-D-6, 7, 13, 26, and 30.
For monitors using gas cells for calibration, cells should be
allowed for the audit.
Response: An independent procedure for determining accurately the
the appropriate instrument response a gas cell should produce has not been
developed. Without independent cell certification, the use of gas cells
for accuracy auditing is uncertain and undesirable.
6.9 Commenter IV-D-6.
Comment: The CEMS should not be considered out-of-control based on
the result of an RAA or CGA. The audits are not, as now specified,
consistent with the complete RA or calibration error test procedures used
for CEMS certification. The audits should be used to trigger repetition of
the certification procedures within a specific time period. Failure to
meet the actual certification specification should be the criteria for
out-of-control status.
Response: The Agency believes that an RAA or a CGA resulting in
failure of the CEMS to meet minimum requirements would be a very strong
indication that the CEMS was in need of corrective action. There would be
no purpose in conducting another audit, RAT, or performance certification
test until the cause of the problem was found and rectified. An additional
certification test or audit before a corrective action would be unnecessary.
6.10 Commenter IV-D-6.
Comment: Use of effluent volumetric flow rate and actual heat input
for the unit should be allowed for determination of S02 in Ib/MM Btu.
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Response: Use of these alternative procedures for the determination
of RA or alternative compliance procedures is not within the scope of this
action, nor is it within the scope to change any RAT requirements in PS's 2
and 3. Review of alternative procedures is conducted by the Agency on a
source specific basis and operators or testers are encouraged to contact
the applicable regulatory agency with requests for such review.
6.11 Commenter IV-D-7.
Comment: We have some concern regarding the auditability of some
nonextractive CEMS. The EPA should require all CEMS manufacturers to have
an EPA-approved method or procedure for effectively auditing CEMS with gas
cylinders, gas cells, or optical filters. New CEMS should be designed to
provide the capability for a cylinder gas, gas cell, or optical filter
audit. All CEMS presently in operation should be required to be
retrofitted to accommodate auditing. We are currently aware of at least
two nonextractive analyzers which could not receive the CGA as described
in the proposed Procedure 1.
Response: Procedure 1 does not require that all CEMS's be auditable
using cylinder gas, but allows the CGA where it is applicable. Procedure 1
includes another audit procedure—the abbreviated, three-run, RAA--which
should be used when other procedures are not applicable.
It is the policy of the Agency not to specify the design of CEMS
equipment if means are available for certifying the proper operation of
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that equipment without a design change. For determining measurement
accuracy, the RATA and the RAA are available and an equipment design
specification is not necessary.
6.12 Commenter IV-D-7.
Comment: The phrase "whichever is greater" should be deleted from
the RA limit statement.
Response: The phase "whichever is greater" is necessary to
distinguish between the conditions for selecting the appropriate limit.
The 25 percent of RM mean value limit applies when emission values are over
40 percent of the applicable standard. The 10 percent of the applicable
standard limit applies when emission values are below 40 percent of the
applicable standard and a more tolerant RA limit is appropriate.
6.13 Commenters IV-D-9 and 11.
Comment: We recommend deleting "During the period the monitor is
out-of-control, the source owner or operator must use another method of
obtaining emission data as required and described in the applicable subpart
[e.g., 60.47a(f)]." Many operators are not required to obtain emission
data through alternate means if a monitor is out-of-control. For those
operations for which such a requirement exists, it is probably adequately
addressed through permit conditions or the applicable subpart. As presently
worded, it appears that all operators are expected to fulfill this
requi rement.
Response: The commenter is correct that not all subparts specify
CEMS's for compliance monitoring, nor do all subparts require alternative
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measurement procedures in the event of a CEMS failure. The purpose of this
paragraph in Procedure 1 is to define the effect of an out-of-control
period in data availability only for those CEMS's specified for continuous
compliance monitoring in the applicable regulation. Procedure 1 has been
revised to emphasize the status of the CEMS data collected during an
out-of-control period rather than the requirement to conduct alternative
testing.
6.14 Commenter IV-D-11.
Comment: Specification of a minimum data capture requirement and
allowing the operators to use their own means to achieve the goal is a
realistic approach. A reasonable data capture requirement is 60 percent
valid data. If a situation develops where data are invalidated, it occurs
after the data are collected and plant operations could not have been
modified to accommodate these time periods. This validation after the
fact serves to enhance the intent of continuous monitoring requirements,
limiting emissions of various compounds. Any organization that would take
advantage of invalid monitoring data would do this no matter what is
required. Any additional requirements to catch these individuals or
organizations will only penalize cooperative parties.
Response: It is not the purpose of Procedure 1 to penalize any source
operator or owner operating within the requirements of the regulations.
Rather, Procedure 1 is designed to establish minimum criteria for accepting
or rejecting CEMS data that will be used to show compliance with emission
limits. These criteria are as beneficial to the owner/operator as to the
regulating agency in assuring that the collected and reported data are valid.
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6.15 Commenters IV-D-11 and 35.
Comment: Why should all audits be conducted within the first 2
months of a calendar quarter? If the intent of this requirement is to
prevent audits from being conducted at the end of one quarter and beginning
of the next, why not simply specify a minimum time frame of 30 days between
audits?
Response: The Agency agrees in principle with this comment but has
revised Procedure 1 to specify a minimum of 60 days between audits.
6.16 Commenter IV-D-11.
Comment: Methods 6A and 6B must be allowed for audit purposes. These
methods will greatly reduce the estimated man years associated with these
audit programs and are less error prone.
Response: This is a good suggestion, and such a change is included in
the promulgation package as revisions to the applicable subparts.
6.17 Commenter IV-D-11.
Comment: The CGA is actually a two-point precision check. It seems
that a more appropriate means of "auditing" would be to use three gases
that cover the entire range of the the instrument. The appropriate
concentrations would be 0-5 percent, 45-55 percent, and 85-95 percent of
full scale.
Response: The Agency disagrees with the commenter's definition of the
CGA. A precision check is a measure of the CEMS's capability to repeat
successively a specific value; whereas, the CGA is a measure of the CEMS's
capability to measure accurately a known value or input. For the CGA, the
CEMS is tested for an average response to each of two cylinder gases.
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The concentrations of gases used in the CGA are intended to represent and
bracket the levels of emissions expected from a source in compliance with
the applicable standard.
The commenter's suggestion of a three-point calibration check would be
a very good QC procedure for preparing the CEMS for operation and for
periodic checks of instrument integrity and linearity. Such a procedure
would be appropriate as part of the QC program required in Section 3 of
Procedure 1.
6.18 Commenters IV-D-11, 17, and 37.
Comment: Methods 6, 3, and 7 should be allowed for use in determining
cylinder gas concentrations. This would be far cheaper than purchasing the
specified gases.
Response: The Agency has determined that an independent analysis of
audits is necessary and has established a policy of traceability to NBS
gaseous SRM or gas manufacturers' CRM for cylinder gas standards used for
independent audits. The Agency does not plan to allow the use of RM's for
these analyses.
6.19 Commenters IV-D-11 and 31.
Comment: If the average percent difference between our audit value
and our monitor value exceeds 20 percent, we consider the CEMS to have been
and to be "out of control." Allowing 25 percent error devaluates the CEMS
data base. It is important to note these same requirements will probably
be used for any monitoring systems used for compliance determination.
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Response: The calculation of RA includes two factors. First is the
mean relative error which is the difference between the mean CEMS value and
the mean RM value. The second is the 95 percent confidence interval based
on the standard deviation and a statistical t-test calculation. The 20
percent limit (25 percent for six-run average) imposed in PS 2 and
Procedure 1 represents an acceptable maximum value for the sum of these two
factors. The limit allows not only for any actual error or difference
between the CEMS response and RM results, but also for the inherent
imprecision in both of the measurement methods. It is misleading to state
that the limit allows for up to 20 or 25 percent difference between the
CEMS response and the RATA when calculation of the RA includes a confidence
interval. Procedure 1 has been revised from the proposal to require one
nine-run RATA per year and the limit of accuracy is 20 percent.
6.20 Commenter IV-D-13.
Comment: The proposed use of cylinder gases as a substitute for the
more expensive RAA creates its own set of problems for both extractive and
probe-type in-situ analyzers. Many extractive systems by-pass the entire
probe assembly so that effects of plugging, condensation, reactions or
leakage are not tested. Probe-type in-situ analyzers face the challenge of
inserting the cal gas quickly enough that the stack gas does not infiltrate
the sample through the porous probe but not so quickly that the gas cannot
temperature-stabilize or becomes pressurized. This is further complicated
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by the fact that the porous probe may or may not be partially clogged,
which of course changes the optimal flow rate. In many applications of
probe-type in-situ analyzers, sealed cells have been found to correlate
with RAA's better than the cylinder gases. A CGA does not directly compare
any values with the existing parameters in the stack gas. A dynamic system
cannot be audited by a static check of precision. Data from the CGA is
totally different from data obtained during an RAA. These data cannot be
compared because they measure different items.
Response: The Agency has performed CEMS evaluations including CGA's,
gas cell audits, and RAT's at many sites. Results of these tests show that
the CGA, where applicable, is a reliable indicator of CEMS performance when
applied as specified in Procedure 1. The results using gas cells were less
conclusive and, thus, gas cells are not included in Procedure 1 as an
acceptable audit.
6.21 Commenter IV-D-13.
Neither a CGA nor the use of gas cells represents an RAA. Neither
checks for changes in stratification or interfering species. Neither lasts
long enough to track the effect of temperature or load changes.
Response: The Agency agrees with this comment on the face of it.
However, the commenter is concerned that the gas cell audit procedure ought
to be allowed if the Agency requires a quarterly accuracy audit and allows
a CGA as a substitute for three of four quarters. The Agency believes
that the CGA procedure has been demonstrated as a reliable indicator of CEMS
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performance where applicable. While the CGA is not the same as an RAA, it
does provide an independent check of most of the active components of the
GEMS and results of comparisons with RAA results have shown this to be
true.
The Agency has found that checks using gas cells are not as reliable
as CGA checks. Agency studies have indicated that successful completion of
a gas cell audit is not assurance that the CEMS is operating properly nor
that it will pass an RAA.
6.22 Commenters IV-D-13 and 30.
Comment: The use of the CGA does not represent a position consistent
with the mandate in the Clean Air Act. The CGA favors technologies that do
not represent advances in spectrographic methods to monitor pollutant
emissions. This discourages research and development for new
instrumentation which could improve the current state-of-the-art.
Exclusive use of RAA procedures would stimulate research for incorporating
advanced spectrographic techniques into CEMS instruments. It would create
a market demand for new and improved equipment.
Response: The Agency believes that the CGA is a technically
acceptable, demonstrated, independent auditing procedure for CEMS's.
Approval of a such a demonstrated alternative procedure is not favoritism
nor is it discouragement of the development of other procedures. The
Agency will continue to review and publish alternative procedures as they
become available.
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6.23 Commenter IV-D-13.
Comment: There is good documentation that, properly designed and
used zero jigs and fixtures provide a good indication of the "stack zero"
for in-situ monitors. Attachment 8 shows typical results in which the
zeros and calibrations found using (1) a purged zero pipe, (2) a zero
jig, (3) the incremental calibration method, all agreed to an accuracy
better than the quality of most cylinder gases.
Response: The material in the commenter's attachment describes
calibration error tests using the three approaches for an in-situ,
cross-stack GEMS. The results of the three calibration approaches agree
fairly well, as indicated by the commenter. However, there are no RAA's
indicating whether these procedures actually indicate the capability of the
CEMS to measure stack gas emissions accurately.
The proper calibration of a CEMS is an important tool for operation
and maintenance of the equipment. Regular calibrations should be included
in every QC program. If gas cell calibration procedures are determined to
be acceptable audit procedures, the Agency will publish them.
6.24 Commenter IV-D-17.
Comment: Section 6.1.2 states that the CGA or "an EPA approved
alternative method" is to be used "instead of the RAA." This prevents the
use of an RAA on a quarterly basis, unless the RAA is approved.
Response: The promulgation version of this requirement is more
clearly worded on this point.
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6.25 Commenter IV-D-17.
Comment: When Methods 7C and 7D are promulgated, will these be
acceptable for RAA and RATA?
Response: These methods have been promulgated and provisions were
made with that promulgation (49 FR 38232, September 27, 1984) to allow
their use for RATA and RAA sampling.
6.26 Commenters IV-D-18, 24, 31, and 32.
Comment: The RATA and CGA are equivalent methods. An RATA is not
necessary when the CGA accomplishes the same task with fewer labor-hours
involved.
Response: While the Agency has determined that the CGA is a reliable
indicator of CEMS performance, the CGA is not a substitute for the RATA.
The RATA is the only means to assess independently the total CEMS as it
measures the pollutant gas concentrations under normal operating conditions,
This independent check is necessary periodically to assure that all parts
of the CEMS are operating and the data produced are accurate.
6.27 Commenters IV-D-18 and 20.
Comment: The performance audit samples received from EPA do
absolutely nothing to audit the CEMS, rather this requirement only
challenges the laboratory performing the analytical services for the CEMS
certification tests.
Response: The commenter is correct that the RM performance audits
apply only to the testing laboratory in the performance of the reference
method. The benefit derived from this audit is the assurance that the
analysis procedures are performed correctly and the quality of the RM
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data used in the RA determination is assured. An audit survey conducted by
EPA/EMSL showed that audits are necessary to assure accurate analyses. As
the GEMS data are to be used for compliance determinations, the quality of
data used to certify the reported results is important to both the operator
and the regulatory agency.
6.28 Commenter IV-D-19.
Comment: To improve the accuracy of the CGA, we would recommend
the procedure require a minimum of three replicate samples for each audit
with the average used to determine the percentage difference.
Response: The Agency agrees with the commenter on this point and has
changed Procedure 1 accordingly.
6.29 Commenters IV-D-20 and 28.
Comment: It is recommended that EPA develop a standard data assessment
report form similar, if not identical, to Figure 1. This would standardize
the reported data throughout the country for ease of comparison.
Response: The Agency recognizes that the responsibility for
enforcing its regulation lies with many different organizations. Each
different enforcing agency can define the data needed for reporting and
the format for those data according to its needs. Procedure 1 offers a
suggested report form for Procedure 1 results and recommends its use
when no other form is provided.
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6.30 Commenter IV-D-21.
Comment: Procedure 1 references performance audit samples for S02
and NOX. What does EPA consider to be acceptable accuracy for analysis of
the samples?
Response: The RM's in Appendix A specify the acceptable limits for
the performance audit results. The procedures also include provisions for
repeating sampling and analysis if the tests are failed.
6.31 Commenter IV-D-21.
Comment: Procedure 1 allows a 25 percent inaccuracy using the RAA.
We believe that the present 20 percent should be maintained. Also, we believe
that the 15 percent inaccuracy for the CGA should be 10 percent, based on
previous performance of CEMS's.
Response: Procedure 1 as promulgated has omitted the 25 percent
inaccuracy value and incorporated an annual RATA consisting of nine runs as
prescribed in PS 2. Procedure 1 also includes an RAA of only three RM
tests for the three quarterly audits between the annual RATA's. For these
three-run audits, only the averages of the RM tests and the CEMS responses
are compared; that is, no confidence interval is calculated or included in
the comparison. Procedure 1 prescribes a limit of 15 percent for
acceptable audit results using the three-run RAA approach.
Results from many audits of installed CEMS's using CGA's indicate that
a 10 percent limit for the CGA result would be too restrictive. The Agency
believes that a 15 percent limit is sufficient indication of CEMS accuracy.
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6.32 Commenter IV-D-27.
Comment: The EPA must be aware that the gaseous matrix may affect
the response for different analytical methods. For instance, 02, C02, CO,
and H2 in mole-percent amounts can reduce the response (relative to
measurement in pure N2) for the chemiluminescence method for NOY. Also,
J\ '
pulsed fluorescence analyzers for S02 will respond much less to S02 in air
(at least 1 percent 02) than to S02 in pure Ng. These "quenching" effects
are not significant in ambient monitoring where the matrix is quite
homogeneous, but can be very significant in process streams that vary
widely in background matrix.
Response: Specification of which gas mixture is appropriate for
calibrating a certain CEMS is the primary concern of the owner/operator of
the CEMS and, of course, the CEMS manufacturer. The Agency is aware of
potential problems regarding the indiscriminate use of calibration gases
with instruments of different designs. However, it is not within the scope
of Procedure 1 to include QC techniques specifically applicable to each
CEMS available. Instead, Procedure 1 specifies QA procedures and criteria
that are independent of CEMS design as much as possible.
For the specific concerns mentioned by the commenter, the initial
PS test of the CEMS, which includes an RAT, would demonstrate whether the
appropriate calibration gases were applied. Subsequent quarterly checks
would be completed using similar mixtures in the audit gases in order to
demonstrate continued proper operation of the CEMS. If other, less
suitable mixtures were used for the quarterly audits, the results would
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indicate a significant CEMS problem and require corrective action. The
corrective action in such a case would be to obtain the appropriate gas
mixture.
6.33 Commenter IV-D-27.
Comment: For chemiluminescent NOX analyzers, a N0£ to NO conversion
efficiency test should be done as part of the quarterly audit and the
efficiency included as part of the report. Since source operators should
be performing periodic efficiency checks as a part of normal QC, this
should not create undue hardship and would ensure at least quarterly checks
of the efficiency. Similar tests should be made whenever a conversion of
species is necessary for detection.
Response: There are a couple of factors that make this conversion
efficiency check less critical for present applications of Procedure 1.
First, there is an initial RAT that would determine whether the converter
is performing properly, and this is-followed by at least an annual RATA.
Second, the sources to which Procedure 1 will be applied initially will be
large boilers which produce small quantities of N02 in relation to the
total NOX. The need for complete conversion is not critical for such
sources. This is evidenced by the large number of CEMS's that measure only
NO and that have passed the RAT's.
6.34 Commenter IV-D-29.
Comment: Procedure 1 specifies the method for checking the accuracy
of a CEMS by performing a CGA. It is our experience the proposed procedure
may introduce calibration errors.
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These errors can be eliminated by first transferring the calibration
gas to a gas sampling bag (e.g., Tedlar). The gas can then be drawn from
the bag, duplicating actual operating pressures.
Response: The commenter offers a good procedure for sampling from
calibration gas cylinders. There are others, some of which are described
in "Gaseous Continuous Emission Monitoring Systems - Performance
Specification Guidelines for S02, NOX, C02, 02, and TRS," EPA-450/3082-026.
A source operator is responsible for the procedures for calibrating the
GEMS. The RATA results performed initially and annually will indicate
whether proper calibration procedures are used.
6.35 Commenter IV-D-30.
Comment: Has EPA investigated the feasibility of using a transportable
system as an audit for in-situ systems? It is reasonable to request that
an alternative audit method be accepted in lieu of the CGA for these systems.
Response: The Agency will review proposed alternative procedures as
indicated in 40 CFR 60.13(i). The use of a transportable measurement
system would be an attractive option for a utility with many installations.
The Agency would invite proposal of such a procedure that included
equipment specifications, calibration techniques and criteria, sampling
criteria, and RA limits. Reports of field experience and RA data should
also be included.
The Agency has evaluated use of instrumental methods as acceptable
reference methods and proposed such methods as additions to 40 CFR Part 60.
Methods 3A, 6C, and 7C were proposed February 28, 1985 (50 FR 8290).
Promulgation of these methods occurred on June 11, 1986 (51 FR 21164).
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The methods have been included in this regulatory revision as suitable for
the RAT and RATA of CEMS's.
6.36 Commenters IV-D-35 and 38.
Comment: Procedure 1 specifies six rather than the usual nine sets
of measurements are required for an RAA. The rule should make clear that
an owner/operator has the option for either six or nine measurements, at
its election, for an RAA. Otherwise, the Agency's attempt to provide
flexibility by allowing only six measurements per RAA could turn out to be
more restrictive in some cases.
Response: Procedure 1 as promulgated defines two types of audits
using RM's. The first is an annual, nine-run relative accuracy (RATA) as
described in PS 2. This is required for every CEMS. The second audit type
is a three-run audit (RAA) which is allowed three of four quarters, if a
CGA is not used or is not applicable. If desired, the nine-run RATA may be
conducted any or all quarters.
6.37 Commenter IV-D-35.
Comment: In regard to the CGA procedure, we believe that the use of
ambient air for Audit Point 2 on 02 diluent monitors with 25 percent full
scale range should be allowed. Additional cost savings would be realized,
without sacrificing accuracy, by not having to purchase additional
calibration gas.
Response: The Agency selected Audit Points 1 and 2 to coincide with
the levels of diluent and pollutant gases normally encountered in fossil
fuel-fired sources' emissions. The purpose of this is to challenge the
CEMS for measurement accuracy at the levels of most measurements. The Q£
level in ambient air, 21 percent, is not within this range.
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6.38 Commenters IV-D-35, 36, and 39.
Comment: Determination of when an out-of-control period begins and
ends may be crucial, as the proposal provides that data obtained from an
out-of-control monitor may not be used to meet minimum daily data-capture
requirements under applicable NSPS subparts. When a monitor is
out-of-control, an alternate method of obtaining the minimum required
emission data is applied. We seek confirmation that an out-of-control
period resulting from excessive span drift begins when the fifth
consecutive drift check for a monitor exceeds twice the applicable PS in
Appendix B. If a monitor fails a quarterly accuracy audit (either RATA,
RAA, or CGA), it is our understanding that the out-of-control period begins
when the audit results are determined. Monitoring data obtained prior to
these points in time would not be invalidated.
Response: The commenters are correct about the beginning of an
out-of-control period resulting from excessive span drift. That is, the
CEMS is determined to be out-of-control when the fifth consecutive excessive
drift measurement occurs or when a single drift determination in excess of
four times the limit occurs. The out-of-control period ends when corrective
action is completed and the CEMS operates within the 24-hour drift
specifications, that is, at the completion of the day during which the CEMS
demonstrates acceptable drift performance.
The CEMS is determined to be out-of-control as a result of excessive
inaccuracy from the time the accuracy audit sampling is completed. This
does not include the time for sample analysis and data reduction. This
approach emphasizes the importance of expediting the sample analysis and
data reduction. The same applies to the determination of the end of the
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out-of-control period; that is, the out-of-control period ends when CEMS
completes the audit successfully. The time for sample analysis and
reporting is not included.
6.39 Commenters IV-D-23, 35, and 36.
Comment: A major component of the cost of complying with the
Procedure 1 proposal relates to the actions required if a monitor goes
out-of-control. Corrective action must be taken, and an RATA, RAA, or C6A
must be performed within 2 weeks of the corrective action. Moreover, an
alternative method of obtaining minimum emission data must be employed
during the out-of-control period.
If backup monitors must be purchased for use as an alternative method,
an initial capital cost of approximately $30,000 to $50,000 would be
incurred for the purchase of each monitor. In addition, each backup
monitor would require installation, maintenance, and, presumably,
certification.
If approved EPA RM tests are selected as the alternative method,
additional testing crews would have to be available for dispatch to a plant
on short notice in the event of monitor malfunction. This could
necessitate hiring a minimum of two additional crew members per utility, at
an approximate annual salary of $30,000 per person, plus other indirect
costs such as employee benefits.
If fuel analysis is chosen as the alternative method for an
oil-fired generating unit, purchases of sampling and analysis equipment
at an approximate cost of $40,000 could be required.
Response: The issues raised by the commenter are related to
Procedure 1, but the costs are not directly attributable to implementation
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of Procedure 1. The applicable regulations specify the minimum data
availability requirements (e.g., Subpart Da), and specify which methods
are appropriate alternatives in the event of CEMS inoperation. Procedure 1
defines criteria to use to judge the operation of a CEMS and the
acceptability of the data produced. Alternative sampling is required to
meet minimum data requirements and planning for this possibility is very
much a part of the CEMS QC plan.
A well-developed QC plan can save money for the source in a couple of
ways. First, good QC procedures will limit the periods of CEMS inoperation
to a minimum and consequently minimize the need for alternative sampling.
Second, good planning can result in the best alternative procedure being
available at the lowest cost. For example, Method 6B is applicable as an
alternative for S02 monitoring for Subpart Da and D sources. This
procedure is relatively inexpensive in terms of equipment and labor. It
is a suitable alternative to CEMS's and fuel monitoring, so no expensive
backup monitors or fuel sampling equipment would be necessary.
6.40 Commenters IV-D-35 and 36.
Comment: The minimum requirement of two RAA's per year may itself
require forced operation for some types of generating units. If RAA's are
required more often because CGA's cannot be performed or because of out-of-
control monitors, the probability of forced operation is increased
considerably. In effect, forced operation would require the use of less
cost-effective generating units in place of more cost-effective generating
units simply in order to create the conditions necessary for an RAA.
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Response: The promulgated Procedure 1 requires only an annual
RATA while quarterly audits can be completed using cylinder gases or an
RAA. The annual audit (RATA) is performed as described in PS 2
and requires that the source be operating at more than 50 percent capacity.
The Agency believes it is not burdensome to require an RATA once per year.
Scheduling of such a test to coincide with operation of the source once per
year should not be difficult or cause the source a serious hardship.
The Agency believes it is important to maintain operation of the GEMS
regardless of the operation of the source if that GEMS is intended to
provide compliance data when the source is operating at production levels.
This means that daily drift analyses and quarterly audits are necessary
for CEMS's subject to Procedure 1 requirements. It is not necessary for
the source to be operating at production loads to conduct a CGA or the
drift analyses.
6.41 Commenter IV-D-36.
Comment: The Agency has recognized that requiring an audit for ambient
monitors at least once per year is adequate to ensure accuracy. The EPA
has demonstrated no reason for more burdensome audit requirements for CEMS.
Response: The continuous compliance programs in 40 CFR Part 60 are
not similar to the ambient monitoring programs defined by other EPA
regulations. The QA procedures in Procedure 1 are designed to address
the particular issues regarding CEMS operation and data production. The
commenter included information in an earlier comment that indicated that
CEMS operation was prone to drift problems and required frequent
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observation, if not maintenance. It appears contradictory now for this
commenter to propose a QA program that requires less frequent auditing.
The Agency believes that quarterly auditing of GEMS operation is necessary
and is promuglating Procedure 1 with this requirement.
6.42 Commenter IV-D-39.
Comment: Include a table in Appendix F which summarizes: (a) those
conditions which indicate that the CEMS is out-of-control, (b) what the
source must do before certifying or recertifying the validity of data from
the CEMS, and (c) any related reporting requirements.
Response: The Agency believes that a summary table is inappropriate
for several reasons: (1) there is a great deal of information that would
have to be in such a table. This table would be very cluttered and
difficult to read in Federal Register type; (2) deleting or abbreviating
some of the necessary information to make a smaller table would cause the
reader to either err in complying with Procedure 1 or cause confusion and
conflict with the specific sections containing the requirements; and
(3) the sections in Procedure 1 are clearly written and are complete as
promulgated. Further, the QA requirements, while they contain several
alternatives for methods and schedules, are not so numerous that technical
representatives of the source operators or the regulatory agency cannot
understand them.
Section 7. EPA Performance Audit Program
7.1 Commenter IV-D-11.
Comment: Can EPA meet the need for RM performance audit samples
required with the implementation of Procedure 1?
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Response: The Agency has promulgated QA provisions in Method 6 or 7
specified for compliance testing. The Agency has made the necessary plans
with suppliers to have a sufficient supply available for these applications
Section 8. Calculations for Monitoring Data Precision
There were comments directed at these calculation procedures, but the
promulgated Procedure 1 does not include any precision calculations making
it unnecessary to address these comments.
Section 9. Calculations for Monitoring Data Accuracy
9.1 Commenter IV-D-6.
Comment: Use of the confidence interval when less than nine tests
are conducted is questionable.
Response: It is correct statistically to include the confidence
interval with any number of data values in calculating RA. The Agency has
reviewed PS test results and determined that the results of RA
determinations using six values is not significantly different from results
where nine values are used. That is, the number of CEMS's meeting the
RA limit was similar for either data set size. However, the Agency has
determined that there is a need to reduce the burden of multiple reference
method tests for those sources whose CEMS's are not amenable to quarterly
audits using cylinder gases. Procedure 1 permits the use of a three-run
average value in determining CEMS audit accuracy for these quarters. The
three-run test will not include the confidence interval but will compare
averages only. The required annual audit for all CEMS's is a nine-run RAT
as prescribed in PS 2. The nine-run test will include the confidence
interval in calculating RA.
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Section 10. Reporting Requirements.
10.1 Commenter IV-D-15.
Comment: The promulgation of Appendix F and Subpart D revisions will
result in annual submittal of 100 CEM reports to this State agency from
Subpart D sources. The engineering review and audit of these reports will
require approximately 300 hours per year. An additional 20 hours per year
will be required to record and track this information. This would not be a
severe economic burden on our Agency.
Response: The burden of implementing Procedure 1 for Subpart D
sources and for the State and local control agencies will be evaluated
at the time of any revisions to the regulation.
10.2 Commenter IV-D-12, 24, 28, 30, and 36.
Comment: The requirements in Appendix F could significantly increase
recordkeeping and reporting requirements at generating plant subject to the
Subparts D or Da NSPS. While we recognize the need for quality emissions
data, we doubt that such an increase in labor and associated cost will
yield a commensurate improvement in data quality.
Response: Sources subject to compliance monitoring are required to
supply all reduced data every quarter, not just for periods of excess
emissions. It is the opinion of the Agency that such data must be
supported by good QA assessments and that these data shall also be
submitted with the compliance data.
A great deal of the data reduction and reporting has been eliminated
from the proposal in the promuglated Procedure 1. The precision assessment
requirements are no longer required. The Agency believes it is not in
conflict with the Paperwork Reduction Act to require the source to supply
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information about audits and periods of out-of-control CEMS operation with
the quarterly data reports. The other CEMS reporting and recordkeeping
requirements are dictated by the applicable, source specific regulations,
as well as the general provisions in Section 60.7. For Subpart Da sources,
there is a requirement to report CEMS data reduced to the form of the
standard, process operation status for the reporting period, calculation
factors used, number of data used, and other CEMS related information
including QA factors [40 CFR 60.49a(b) and (c)]. Procedure 1 does not
significantly increase the reporting requirements as promulgated.
10.3 Commenters IV-D-33 and 36.
Comment: According to EPA, a guideline document entitled
"Interpretation and Application of Precision and Accuracy Data" will be
issued at a later date. By specifying how data will be interpreted and
used, this document will go to the heart of the Appendix F proposal.
Accordingly, before promulgating final rules, EPA must make this document
available to the public for a sufficient period of time to allow analysis
and comment.
Response: The requirement for precision assessment is not included
in the promulgated Procedure 1; therefore, the referenced guideline will
not be prepared. A guideline entitled "Calculation and Interpretation of
CEMS Accuracy Data" has been completed and included as part of the Quality
Assurance Handbook. This document merely describes the calculation
procedures in detail and there is no significant interperative language.
It is not necessary to obtain public comment for such a guideline, nor is
it necessary to delay promulgation of Procedure 1 because of it.
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10.4 Commenter IV-D-39.
Comment: The policy statement in the Federal Register should be
reworded so as not to preclude control agencies from taking into account
the QA results when considering CEMS data, but should clearly forbid sources
from doing so.
Response: The Agency believes strongly that it is technically
incorrect to adjust CEMS results based on RAT information or quarterly audit
data. Audit results, including the RATA, invariably include imprecision as
well as measurement error. The imprecision and error can be associated
with both the CEMS and the audit method results. These measurement factors
are the basis for allowing a range of audit results that indicate acceptable
CEMS operation (e.g., +15 percent for the CGA). In addition, the sample
sizes for either the quarterly audit or the annual RATA are very small and
cover only a brief period of process operation. There is no technical
basis for "taking into account the QA results when considering CEMS data"
beyond assuring that the audit results are within the specifications.
Preamble. Costs of Implementation
P.I Commenters IV-D-12, 23, 24, 25, and 36.
Comment: The impact of this proposed requirement has been greatly
underestimated. The proposal states the impact on utility boilers subject
to Subpart Da will be 80 person-years over the 5-year period from 1984 to
1988. This assumes 77 boilers are subject to the requirements and each
boiler requires 620 person-hours annually to meet the requirements. The
80 person-years is in error and should be 124 person-years.
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Response: The Agency calculated the number of person-years needed to
meet the Procedure 1 requirements recognizing that not all of the Subpart
Da boilers would be operating during the entire 5 years. Some of the
boilers will start operation earlier than others, and some will not be
operating until the very end of that 5-year period. While the commenters'
figures represent the most conservative view, the Agency believes the
80 person-year value is also a conservative figure for the efforts needed
to implement Procedure 1 for Subpart Da sources. The costs assocated with
implementation of Procedure for other source categories will be evaluated
upon promulgation of revisions to those regulations.
P.2 Commenter IV-D-15.
Comment: This State agency recognized the need for a continuing CEMS
QA program. We have already installed provisions in many operating permits
that relate to CEMS QA. The agency has not received a single objection to
these CEMS provisions. The QA requirement would not be a severe economic
burden on the affected facilities.
Response: No response is necessary.
P.3 Commenter IV-D-12, 23, 24, 32, 35, 36, 37, and 38.
Comment: The level-of-effort required by the current proposal has
been substantially understated. For example, EPA based labor estimates on
a unit having one S02 monitor and one NOX monitor. However, Subpart Da
sources also have to monitor flue gas desulfurization (FGD) inlet S02 and
diluent concentrations in order to calculate removal efficiency.
Therefore, EPA has underestimated the number of monitors affected by
Appendix F by a factor of two.
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Response: The Agency agrees that the cost estimates in the proposal
were derived for only an outlet GEMS. However, adding the costs incurred
by the QA requirements imposed on an inlet CEMS will not necessarily
double the costs of applying Procedure 1. The amount of increase would
depend on the degree to which tasks can be consolidated and needless
duplication avoided. The total cost should be considerably less than
twice the conservative costs mentioned in the proposal.
The promulgated Procedure 1 does not include the precision assessment
requirement thereby considerably reducing data reduction and reporting
costs. Further, the RAT audit has been reduced to one per year with CGA or
RAA allowed other quarters.
The preamble to the proposed Procedure 1 included estimated costs of
implementation for one S02 and NOX CEMS to be between 450 to 620 labor-
hours annually. The cost estimate included two RAA's, two CGA's, and
precision assessment efforts. The higher value, 620 labor-hours, was used
in determining the industry resources needed for Subpart Da sources.
The Agency has examined the costs of implementing Procedure 1 more
thoroughly (a report of these studies is in the docket). Using these
latest cost estimates and eliminating the precision assessment efforts
that are no longer required, the Agency has determined that the original
estimates are reasonable. For the example of a Subpart Da source with
an outlet CEMS measuring S02, NOX, and diluent and one CEMS measuring
FGD inlet S02 and diluent, the estimated level of effort for implementing
Procedure 1 as promulgated is from 326 to 704 hours annually depending on
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the type of audit used, CGA or RAA. This level is consistent with the
estimate described in the proposal and does not significantly change the
estimated effect on the industry.
P.4 Commenters IV-D-12, 24, 28, 33, and 36.
Comment: Because of design constraints of our plant's data acquisition
system, significant modifications of the system could be required to
accommodate the requirements of Appendix F. The labor and cost to
implement such modifications are anticipated to be substantial. The EPA
should evaluate labor and cost impacts for modifying data acquisition
systems during the rulemaking process.
Response: The proposed version of Procedure 1 included precision
measurements and calculations that were performed differently from
previously required in NSPS regulations (40 CFR 60.13) and from what is
considered common practice. Such changes would indeed have caused
revisions to many data acquisition systems. However, the promulgated
Procedure 1 has omitted this precision determination procedure. Other
procedures in Procedure 1 for deleting data when the CEMS is not
operating properly and including alternative monitoring capabilities are
presently required by other applicable regulations [e.g., 40 CFR 60.47a(f)
and (h)] and should already be part of the computer capabilities. Computer-
operated CEMS's now meeting NSPS data reduction and reporting requirements
should not need modifications to meet the requirements of implementing
Procedure 1 as promulgated.
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P.5 Commenters IV-D-28 and 36.
Comment: The cost estimates would be realistic if CEMS's in routine
service rarely went out-of-control as defined in the proposal. Based on
our experience with CEMS's (Lear Siegler SM-810 and CM-50), routine span
drift values can often exceed the proposed limits for span drift. From the
proposed requirements, it follows that the requirement to "use another
method of obtaining the minimum emission data as required and described
in the applicable subpart [e.g., paragraph 60.47a(f)]," will come into play
quite often. Using EPA Methods 3, 6, and 7 to provide data when the CEMS
is out-of-control will greatly add to the resources needed to meet the
proposed requirements. This could easily double or triple the required
resources.
Response: The Agency has collected data for drift assessment and
RA assessment for five, different, representative CEMS installations,
including the model mentioned by the commenter. The results of these
studies indicate that CEMS's subjected to reasonable levels of QC and
maintenance efforts rarely exceed the drift or accuracy specifications in
Procedure 1. Each of the CEMS's in this study exceeded the drift
specifications less than 1 percent of the period which included over 2
years worth of data. Reports of these studies are in the docket.
The Agency recognizes that not all CEMS's will operate properly all
of the time and that significant corrective actions will necessarily add
to other operating costs. The Agency also recognizes that good operation
and maintenance practices and a sound QC program will minimize the
occurrences of out-of-control periods. Part of the effectiveness of
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promulgating Procedure 1 and the QA assessments is to encourage the
operator of an affected facility to develop an effective QC plan and to
follow it. The Agency believes that adherence to such a sound program
will not increase significantly the cost of continually operating a CEMS
as required by the regulation and may actually reduce operating costs by
identifying potential problems before expensive repairs are required and
before alternative measurement methods are needed to meet minimum data
requirements.
It is necessary that the Agency define criteria by which to judge
the validity of CEMS data that are to be used to determine compliance.
This is necessary and beneficial for both the source operator and the
regulatory agency.
P.6 Commenter IV-D-36.
Comment: The Agency has made no estimates of the burdens that would
be involved in developing, implementing, and periodically revising QA/QC
programs. Given the potentially significant burdens that are imposed by
the proposed QA/QC package, and the absence of any direct environmental
benefits flowing from these requirements, the Agency should carefully
assess any means of rendering this proposal less burdensome and more
flexible.
Response: The background document supplied by the commenter
recognizes and supports the need for development and implementation of
QC procedures for any CEMS program. Procedure 1 outlines the primary
elements of a QC program and specifies that any deficiencies in the
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program be reviewed and revised as necessary to maintain adequate OEMS
operation. The Agency believes that these are minimum requirements for
QC regardless of the promulgation of Procedure 1; in fact, every OEMS
manufacturer has similar recommendations for QC programs following CEMS
installation. Promulgation of Procedure 1 does not affect the costs of
implementing good QC programs.
The primary concern of the commenter is that the additional QA
procedures required by Procedure 1 not be excessively burdensome to
sources already implementing good QC procedures. While QC programs are
necessary for operation of any CEMS, some additional QA procedures are
mandatory if the CEMS data are to be used for compliance determination.
The promulgated Procedure 1 contains the minimum QA requirements necessary
to produce valid and useable CEMS compliance data. The Agency also
believes that the costs of implementing Procedure 1 will not be excessive.
P.7 Commenter IV-D-36.
Comment: From a broader perspective, these QA/QC procedures are just
a small number of the many existing regulatory requirements that currently
apply to CEMS. If EPA assesses the resource burdens of each portion of the
many CEMS-related requirements independently, it will, of course, project
relatively small impacts. Our estimate of the annualized cost of the
equipment and the labor required for routine operation and maintenance
of CEMS as well as the costs for collection of backup data, PS tests,
QA/QC programs, and recordkeeping and reporting could easily exceed
$100 million annually.
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Response: The commenter does not provide any background data to
support the figure of $100 million. The Agency has discussed the
commenter's cost estimates for CEMS operation in earlier responses. In
general, the Agency believes the commenter has overestimated the costs
and concludes that the actual burden of the implementation of Procedure 1
is not excessive.
The benefit of providing useable, valid compliance data applies both
to the source and the regulatory agency. The Agency views the costs as
worthwhile for the increased confidence in demonstrating compliance and
in instituting any enforcement actions. Source owner/operators further
benefit through the availability of continuous, valid information on the
operation of the control system and can use such data to optimize
operations.
Miscellaneous Issues
M.I Commenters IV-D-4 and 15.
Comment: This State agency has an ongoing QA program for continuous
in-stack monitors within its jurisdiction. Therefore, we support the
establishment of official EPA QA procedures for in-stack monitors.
Response: No response is necessary.
M.2 Commenters IV-D-15.
Comment: Some sources which operate $63 removal devices rely on S02
CEMS to control material usage. Well-calibrated S02 CEMS's will aid in
conserving raw materials. These companies have advised our Agency that
well-maintained instruments are essential to controlling material usage.
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We conclude that many sources would maintain accurate S02 monitors
even without the requirements of Appendix F and Appendix F should not cause
a significant new economic burden. We, therefore, recommend promulgation
of Appendix F as a reasonable and necessary regulatory action.
Response: No response is necessary.
M.3 Commenters 23 and 25.
Comment: The CEMS data should be used only to monitor operation and
maintenance, not to determine compliance.
Response: The decision that CEMS's are appropriate compliance tools
for NSPS is not within the scope of this regulatory action. Procedure 1
provides a basis by which to judge whether the data provided by a CEMS are
valid for compliance determinations.
M.4 Commenters IV-D-10 and 36.
Comment: According to the notice on the above-referenced rulemaking
published at 49 Federal Register 9676 (March 14, 1984), the comment period
for the Agency's Appendix F proposal will close on May 14, 1984. We request
an extension of the comment period.
Response: The comment period was extended to July 13, 1984,
(49 FR 24151).
M.5 Commenter IV-D-36.
Comment: We agree in principle with the desirability of QA and QC
procedures for CEMS. Most utilities already apply some form of QA/QC to
their emission measurement procedures and instruments in order to ensure
that useful data are produced. It is in the source's own interest to
produce accurate and reliable data on source operation and maintenance.
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The types of QA/QC procedures needed at a given utility plant vary
depending on site-specific considerations. For example, the type of
QA/QC procedures applied in a specific case will depend on how the data
generated from CEMS will be used (e.g., whether the data are to be used
for compliance or operation and maintenance purposes), how close to the
standard the source is operating, whether the monitoring equipment is
being used downstream of FGD control equipment, and the type of monitoring
instrumentation that is used.
Response: No response is necessary.
M.6 Commenter IV-D-36.
Comment: Whether monitoring technology can meet EPA's standards will
be determined not by the type of QA/QC procedures that EPA establishes in
these guidelines, but by research and development work with the technology
itself. The Agency should focus its efforts in the research and
development area and adopt a less burdensome and more flexible approach to
QA/QC requirements.
Response: The Agency believes the technology of CEMS has been
developed to the point where it can be applied to continuous compliance
determinations. Numerous demonstrations of successful long-term operation
have been reported both by the Agency and by industrial users. The Agency
is pursuing further study in the areas of alternative auditing procedures
and alternative QA schedules, but these studies are intended to review and
revise QA requirements rather than develop new procedures. There is no
substantive reason for delaying the implementation of Procedure 1 for
CEMS's used for compliance monitoring.
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M.7 Commenter IV-D-36.
Comment: Because of the site-specific nature of QA/QC, any procedures
should be written as guidelines that provide minimum procedures. Although
EPA has used this approach in the past (e.g., guidelines for ambient
monitors), it has only in certain respects reflected in the QA/QC program
required by proposed Appendix F.
Response: The ambient monitoring program is substantially different
from EPA's gaseous emission monitoring requirements. The ambient monitors
are very specifically defined by design and operation characteristics.
Performance criteria are unnecessary if all monitors are of the same design
and design criteria can be specified. The same would apply to QC
procedures for such monitors. Additionally, data supplied by ambient
monitors cannot be used in compliance actions against a specific source.
Procedure 1 applies to CEMS's required under 40 CFR Part 60 regulations
and are used for compliance determinations. These CEMS's are not defined
by design criteria nor are the conditions under which they operate similar
from site-to-site. Performance criteria are necessary for demonstrating
that such CEMS's operate properly and the data are valid representation of
the emissions. These requirements are beneficial and protective of both
the source and the regulatory agency.
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Table 2. LIST OF COMMENTERS
Docket Number A-80-29
Docket Item Number
IV-D-1
IV-D-2
IV-D-3
IV-D-4
IV-D-5
IV-D-6
IV-D-7
Commenter/Affi1i ati on
H. Neal Troy, Manager
Environmental Control Dept.
Owens-Illinois
One Seagate
Toledo, Ohio 43666
Joe Francis, Environmental Spec.
State of Nebraska
Dept. of Environmental Control
Box 94877
Lincoln, Nebraska 68509-4877
Jerry W. Powell, Environmental
Control Chemist
Texasgulf Chemicals Co.
Post Office Box 48
Aurora, North Carolina 27806
Harold E. Hodges, Technical
Secretary
Tennessee Air Pollution Control Board
150 Ninth Avenue, North
Nashville, Tennessee 37203
Robert L. Pearson, Administrator
Environmental Affairs
Public Service Company of Colorado
Post Office Box 840
Denver, Colorado 80201
James K. Hanbright, Director
Bureau of Air Quality Control
Commonwealth of Pennsylvania
Post Office Box 2063
Harrisburg, Pennsylvania 17120
Donald F Theiler, Director
Department of Natural Resources
State of Wisconsin
Post Office Box 7921
Madison, Wisconsin 53707
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Table 2. LIST OF COMMENTERS
(Continued)
Docket Number A-80-29
Docket Item Number Commenter/Aff i1i ati on
IV-D-8 Jack Byrom, Vice President
Engineering
Sierra Pacific Power Company
Post Office Box 10100
Reno, Nevada 89520
IV-D-9 M. S. Litus, Environmental Engineer
Tenneco Minerals
Post Office Box 1167
Green River, Wyoming 82935
IV-D-10 Peter C. Cunningham
Hopping, Boyd, Green, and Sams
P.O. Box 6526
Tallahassee, Florida 32314
IV-D-n Vincent J. Brisini, Environmental
Scientist
Pennsylvania Electric Company
1001 Broad Street
Johnstown, Pennslyvania 15907
IV-°-12 W. F. McGuire, Manager
Environmental Protection Department
Houston Lighting and Power Co.
Post Office Box 1700
Houston, Texas 77001
IV-D-13 Richard L. Meyers, Manager
Thermo Electron Instruments
530 Alpha Drive
Pittsburgh, Pennsylvania 15238
IV-D-14 W. Neal Kocurek, Vice President
Radian Corporation
Post Office Box 9948
Austin, Texas 78766
JV-D-15 J. Michael Valentine, Director
Division of Air Quality
Minnesota Pollution Control Agency
1935 West County Road B2
Roseville, Minnesota 55113-2785
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Table 2. LIST OF COMMENTERS
(Conti nued)
Docket Number A-80-29
Docket Item Number Commenters/Affi 1 i at1 on
IV-D-16 Charles H. Knauss
Hunton and Williams
Post Office Box 19230
Washington, D.C. 20036
IV-D-17 Daniel L. Todd, Senior Air Scientist
Big Rivers Electric Corporation
Post Office Box 24
Henderson, Kentucky 42420
IV-D-18 Terry G. Freeze, Corporate Environmental
Engineer
Mississippi Chemical Corporation
Post Office Box 388
Yazoo City, Mississippi 39194-0388
IV-D-19 Roger B. McCann, Director
Division of Air Pollution Control
Commonwealth of Kentucky
18 Reilly Road
Frankfort, Kentucky 40601
IV-D-20 Dwight K. Wylie, Chief
Air Division
Mississippi Dept. of Natural Resources
Post Office Box 10385
Jackson, Mississippi 39209
IV-D-21 Dana K. Mount, Director
Division of Environmental Engineering
North Dakota State Dept. of Health
Bismarck, North Dakota 58505
IV-D-22 Gary D. Myers, President
The Fertilizer Institute
1015 18th Street, N.W.
Washington, D.C. 20036
IV-D-23 M. E. Miller, Jr., Manager
Environmental Engineering Unit
R. J. Reynolds Tobacco Company
Winston-Salem, North Carolina 27102
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Table 2. LIST OF COMMENTERS
(Continued)
Docket Number A-80-29
Docket Item Number Commenter/Affi1i ati on
IV-D-24 Timothy A. Gustafson, Environmental
Engineer
City of Colorado Springs
Post Office Box 1103
Colorado Springs, Colorado 80947
IV-D-25 William B. Marx, President
Council of Industrial Boiler Owners
11222 Silverleaf Drive
Fairfax Station, Virginia 22039
IV-D-26 Tom King, Vice President, Engineering
Bob Alders, EPA Certification Coordinator
Measurex Corproation
One Results Way
Cupertino, California 95014
IV-D-27 J.A. Stuart, Executive Officer
South Coast Air Quality Management
District
9150 Flair Drive
El Monte, California 91731
IV-D-28 Thomas F. O'Masta, Supervisory
Engineer, Environmental Dept.
Consumers Power Company
212 West Michigan Ave.
Jackson, Michigan 49201
IV-D-29 Jeffery D. Mathews, Supervisor
Environmental Technical Services
Eastman Kodak Company
1669 Lake Ave.
Rochester, New York 14650
IV-D-30 Merlin E. Horn, Director
Environmental Affairs
Wisconsin Power Power and Light Co.
222 West Washington Ave.
Post Office Box 192
Madison, Wisconsin 53701
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Table 2. LIST OF COMMENTERS
(Continued)
Docket Number A-80-29
Docket Item Number Commenter/Affiliation
IV-D-31 J. C. Edwards, Manager
Clean Environment Program
Eastman Kodak Company
Post Office Box 511
Kingsport, Tennessee.37662
IV-D-32 Olon Plunk, Manager
Licensing and Environmental Affairs
Southwestern Public Service Company
Post Office Box 1261
Amarillo, Texas 79170
IV'D-33 Robert V. Tanner, Vice President
Production
South Carolina Public Service
Authority
Post Office Box 398
Moncks Corner, South Carolina 29461
IV"°'34 6- J. Aldina, Stack Systems Specialist
Thermo Electron Instruments
108 South Street
Hopkinton, Massachusetts 01748
IV-D-35 Peter C. Cunningham
Hopping, Boyd, Green, and Sams for
Florida Electric Power Coordinating
Group, Inc.
Post Office Box 6526
Tallahassee, Florida 32314
IV-D-36 F. William Brownell
Charles H. Knauss
Hunton and Williams for The Utility
Air Regulatory Group
Post Office Box 19230
Washington, D.C. 20036
IV-D'37 H. B. Coffman, Manager
Environmental Services
Texas Utilities Generating Company
400 North Olive Street
Dallas, Texas 75201
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Table 2. LIST OF COMMENTERS
(Continued)
Docket Number A-80-29
Docket Item Number Commenter/Affiliation
IV-D-38 Steven P. Lindberg, Supervisor
Environmental Affairs Dept.
Cooperative Power Association
14615 Lone Oak Rd.
Eden Prairie, MN 55344-2287
IV-D-39 Mark S. Siegler, Chief
Technical Support Branch
Stationary Source Compliance Div.
Office of Air, Noise, and Radiation
Environmental Protection Agency
Washington, D.C. 20460
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