United States
Environmental Protection
Agency
Atmospheric Research and Exposure ;-^
Assessment Laboratory """"^
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-89/027 Aug. 1989
Project Summary
Data Assessment Reports for
CEMS at Subpart Da Facilities
George Walsh
The full report is a summary of the
information provided in Data Assess-
ment Reports for the first two
quarters of calendar year 1988. The
reports were submitted to enforce-
ment agencies by owners or opera-
tors of Subpart Da Electric Steam
Generating units in response to the
requirements of 40 CFR Part 60 Ap-
pendix F. Appendix F establishes
minimum quality assurance require-
ments for continuous emission mon-
itoring systems when used as the
New Source Performance Standard
performance test method.
Data on Relative Accuracy Test
Audits (RATA) were obtained for 24
facilities. Fifty-three RATAs were
done for SO2; 31 audits were done for
NOX. Eight continuous emission
monitoring systems at six facilities
exceeded the criteria of 20 percent
relative accuracy for acceptable per-
formance. In three cases the audits
were repeated and relative accuracy
was demonstrated to be less than 20
percent. In the remaining cases the
boilers were taken out-of-service for
maintenance. No periods of invalid
data were reported because of
excessive Inaccuracy based on
RATAs. A comparison of audit results
with data from a prior study suggests
an improved distribution of Relative
Accuracy values for the Da monitor-
ing systems.
Data for approximately 190 Cylinder
Gas Audits (CGAs) were obtained for
SO2, NOX, CO2, and 02 analyzers at 19
facilities. With the exception of one
audit, all analyzers were demon-
strated to be operating within the
specified plus or minus 15 percent
accuracy. Approximately 60 percent
of the results were within plus or
minus three percent accuracy. No
periods of invalid data were reported
because of excessive inaccuracy
based on CGAs.
Almost 50 percent of the Data As-
sessment Reports (DAR) contained
no information on Calibration Drift
Assessment Nine DARs indicated no
excessive calibration drift Fourteen
reports included days on which one
or more analyzers were found to
exceed Appendix F criteria for exces-
sive drift In all cases the criterion ex-
ceeded was for one day's operation.
In almost all cases, periods of invalid
data because of excessive drift were
incorrectly reported in fractions of a
day.
Corrective actions for excessive
drift were noted in the 14 DARs which
included information on excessive
drift. A majority of the corrective ac-
tions appear to be items that should
be performed routinely in response
to the facilities quality control plan.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Background
The U.S. Environmental Protection
Agency (EPA) promulgated a New
Source Performance Standards (NSPS)
for Electric Utility Steam Generating Units
under 40 CFR Part 60 Subpart Da in
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December, 1978. Subpart Da applies to
units for which construction was
commenced after September 18, 1978.
For convenience, the term "Da" is used
in the full report as a short-hand for
"Subpart Da.
The Da emission standards for sulfur
dioxide (S02) and nitrogen oxides (NOX)
are based on an average emission rate
for 30 consecutive boiler operating days;
a new 30-day performance test is
completed at the end of each boiler
operating day. The NSPS requires the
use of continuous emission monitoring
systems (GEMS) as the performance test
method.
The EPA promulgated minimum quality
assurance (QA) requirements for the
GEMS in 40 CFR Part 60 Appendix F.
Appendix F requires Da source owners to
develop site-specific QA plans and to
report the results of EPA specified QA
activities each calendar quarter. The first
calendar quarter for which a report was to
be submitted is January through March,
1988.
The report of QA activities under
Appendix F is called a Data Assessment
Report (DAR). The DAR includes iden-
tifying and descriptive information for the
GEMS, results of periodic audits, identi-
fication of periods when calibration drift
exceeds specified criteria, identification
of periods when the analyzers or GEMS
are out-of-control (OOC), and descrip-
tions of corrective actions in response to
OOC conditions. An OOC period occurs
when an analyzer or a GEMS fails to
meet criteria specified in Appendix F.
The criteria are expressed in terms of
GEMS relative accuracy, analyzer accu-
racy, and analyzer drift.
The names of the quarterly audits are:
(a) Relative Accuracy Test Audit (RATA),
(b) Cylinder Gas Audit (CGA), and (c)
Relative Accuracy Audit (RAA).
The principle objective of this study is
an evaluation of the information in DARs
for the first and second quarters of
calendar year 1988. Secondary study ob-
jectives include: (1) the establishment of
contacts with agency staff who normally
receive the DARs each quarter and (2)
identification of facilities for which DARs
were apparently not received, for follow-
up by the appropriate agency.
Summary of Information
Thirty-six facilities operated by 28
companies were identified as operating
Da units at the start of this study. DARs
were obtained for 27 facilities. Data on
RAT As were obtained for 24 Da facilities.
The minimum RA for 53 S02 RATAs is
Da units at the start of this study. DARs
were obtained for 27 facilities. Data on
RATAs were obtained for 24 Da facilities.
The minimum RA for 53 S02. RATAs is
0.9 percent; the maximum is 34.8
percent. The distribution of S02 RA val-
ues is different for the inlet and outlet
monitors. A comparison of S02 RA
values with a previous EPA study
appears to indicate an improvement in
GEMS performance.
The minimum RA for 31 NOX RATAs is
2.2 percent; the maximum is 47.1
percent. A comparison of NOX RA values
with a previous EPA study clearly
indicates an improvement in GEMS
performance.
No correlation is evident between S02
or NOX RA and GEMS type or manu-
facturer. The data suggest improved
results when EPA instrumental methods
are used as the reference test method.
Data on CGAs were obtained for 21 Da
facilities. For SO2 and NOX, the values
appear to be distributed normally arounc
a central value of zero percent. The dat<
for the inlet and outlet S02 monitors
appear to have slightly differen
distributions, with the data for the outle
monitors showing a greater range fron
maximum to minimum values. There i:
insufficient data to warrant furthe
analysis of this possibility, although it ii
consistent with the RATA results.
No correlation is evident between th(
results of the CGAs and other parameter:
such as CEMS type, manufacturer, o
reported OOC periods.
Copies of DARs with information 01
Calibration Drift Assessments (CDA) wer<
obtained for 15 facilities. Ten of the 1!
facilities defined at least one out-of
control (OOC) period. Seven of th<
facilities listed on OOC period for mon
than one analyzer.
Appendix F requires a reporting o
corrective actions for OOC periods. Thi
two corrective actions mentioned thi
most often are manual calibration an<
resetting of the automatic drift compen
sator. Replacement of analyzer lamp;
and calibration gas are the next mos
frequent corrective actions. More than 61
percent the corrective actions are in tru
category of Periodic Maintenance an<
Calibration.
Appendix F includes an example for
mat for a DAR. Except for a few cases
the example or slight modifications of thi
example was followed. In those case:
where the example format was no
followed, the audit results appear to b<
included as portions of more compre
hensive quarterly reports.
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George Walsh is with Entropy Environmentalists, Inc., Research Triangle Park, NC
27709.
Darryl von Lehmden is the EPA Project Officer (see below).
The complete report, entitled "Data Assessment Reports for OEMS at Subpart Da
Facilities," (Order No. PB 89-169 866/AS; Cost: $15.95, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
Tne EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S33-89/027
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