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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