United States
Environmental Protection
Agency
Atmospheric Research and Exposure
Assessment Laboratory
Research Triangle Park 27711
Research and Development
EPA/600/S3-90/056 Aug. 1990
SEPA Project Summary
Accuracy and Reliability of
GEMS Subpart Da (Electric
Utilities) Facilities
George Walsh and Kim Mans
This report is a summary of the
information provided in Data
Assessment Reports for calendar
year 1988 and the first two quarters of
calendar year 1989. The reports were
submitted to enforcement agencies
by owners or operators of Subpart Da
Electric Steam Generating units in
response to the requirements of 40
CFR Part 60 Appendix F. Appendix F
establishes minimum quality assur-
ance requirements for continuous
emission monitoring systems when
used as the New Source Performance
Standard performance test method.
Data on Relative Accuracy Test
Audits were obtained for 30 facilities.
Ninety-eight Relative Accuracy Test
Audits were done for SO2; Fifty-four
audits were done for NOX. Ten
continuous emissions monitoring
systems at eight facilities exceeded
the criteria of 20 percent relative ac-
curacy for acceptable perform-ance.
In three cases the audits were re-
peated and relative accuracy was
demonstrated to be less than 20
percent. In the remaining cases the
boilers were taken out-of-service for
maintenance. At two sources,
periods of invalid data were reported
because of excessive inaccuracy
based on Relative Accuracy Test
Audits.
Data for approximately 440
Cylinder Gas Audits were obtained
for SO2, NOX, COfc and O2 analyzers
at 30 facilities. Five continuous
emissions monitoring systems at four
facilities exceeded the criteria of ±15
percent accuracy. All other analyzers
were demonstrated 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. At only one source was a
period of invalid data reported
because of excessive inaccuracy
based on a Cylinder Gas Audit.
Almost 50 percent of the Data As-
sessment Reports contained no
information on Calibration Drift As-
sessment. Seventeen reports in-
cluded days on which one or more
analyzers were found to exceed
Appendix F criteria for excessive
drift. In most cases the criterion ex-
ceeded was for one day's operation.
In many cases, periods of invalid data
because of excessive drift were in-
correctly reported as fractions of a
day.
Corrective actions for excessive
drift were noted in most of the Data
Assessment Reports which included
information on excessive drift. A
majority bf the corrective actions
appear to be items that should be
performed routinely in response to
the facilities quality control plan.
This Project Summary was
developed by EPA's Atmospheric
Research and Exposure Assessment
Laboratory, Research Triangle Park,
WC, to announce 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
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Source Performance Standard (NSPS) for
Electric Utility Steam Generating Units
under 40 CFR Part 60 Subpart Da in
December 1978. Subpart Da applies to
units for which construction was
commenced after September 18, 1978.
For convenience, the term "Da" is used
in this 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. A day is defined as a 24-
hour period from midnight to midnight. A
boiler operating day is defined as a day
during which fuel is burned for the entire
24 hours. The NSPS requires the use of
continuous emission monitoring system
(CEMS's) as the performance test meth-
od.
EPA promulgated minimum quality
assurance (QA) requirements to be
implemented by the source owner when
the GEMS is specified as the
performance test method. The QA
requirements were published in 40 CFR
Part 60 Appendix F and became effective
in December 1987. 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.
QA activities reported under Appendix
F comprise a Data Assessment Report
(DAR). The DAR includes identifying and
descriptive information of the CEMS's,
results of periodic audits, identification of
periods when calibration drift exceeds
specified criteria, identification of periods
when the analyzers or CEMS's are out-of-
control (OOC), and descriptions 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. Criteria
are expressed in terms of GEMS relative
accuracy, analyzer accuracy, and
analyzer drift.
Data generated by a GEMS after it is
found to be OOC cannot be used to meet
the minimum number of measurements
required in Da to calculate 30-day
averages. When minimum data needs are
not met by the GEMS, supplemental
sampling is required.
Appendix F requires an audit of each
GEMS every calendar quarter. These
audits include Relative Accuracy Test
Audits (RATA's). Cylinder Gas Audits
(CGA's), and Relative Accuracy Audits
(RAA's).
The NSPS General Provisions
(Subpart A) and Appendix F require a
daily assessment of drift. In Appendix F
the daily check is called a Calibration
Drift Assessment (CDA).
The principle objective of this study is
an evaluation of the information in DAR's
for the first and second quarters of
calendar year 1988. Secondary study
objectives include: (1) the establishment
of contacts with agency staff who
normally receive the DAR's each quarter
and (2) identification of facilities for which
DAR's were apparently not received, for
follow-up by the appropriate agency.
Summary of Information
Forty Subpart^Da-facilities~owned or
operated by 30 companies were
identified through contacts with personnel
in Federal, State, and local control
agencies. Although an attempt was
made to compile Data Assessment
Reports from all forty facilities, reports
were not obtained for all quarters.
Primary reasons for not obtaining reports
for all quarters are an apparent failure to
communicate the request to agency
contacts and, in some cases, a failure to
establish a viable contact person. Based
on the reports obtained for the report, the
following conclusions are drawn:
1. Continuous emission monitoring
systems on Subpart Da facilities
routinely achieve the quarterly audit
and daily drift criteria for acceptable
performance.
2. The monitoring systems produce
quality-assured data over 95
percent of the time.
3. Some owners/operators report
relative accuracy results in concen-
tration units, not in units of the
standard.
4. Out-of-Control (OOC) periods are
reported frequently as a result of
excessive drift. In many cases,
however, the duration of the OOC
period was reported as less than
one day, which is inconsistent with
the definitions in Appendix F.
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George Walsh and Kim Mans are with Entropy Environmentalists, Inc. , Research
Triangle Park, NC
Dairy/ von Lehmden is the EPA Project Officer (see below).
The complete report, entitled "Accuracy and Reliability of OEMS Subpart Da
(Electric Utilities) Facilities," (Order No. PB 90-250 168/AS; Cost: $17.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The 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
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penally for Private Use $300
EPA/600/S3-90/056
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