MEMORANDUM

SUBJECT: Use of Acid Rain CEMS as NSPS CEMS

FROM:    John B. Rasnic, Director
         Stationary Source Compliance Division
         Office of Air Quality Planning and Standards

TO:      Air, Pesticides, and Toxics Management Division
          Directors
         Regions I and IV

         Air and Waste Management Division Director  
         Region II

         Air, Radiation, and Toxics Division Director
         Region III
 
         Air and Radiation Division Director
         Region V

         Air, Pesticides, and Toxics Division Director
         Region VI

         Air and Toxics Division Directors
         Regions VII, VIII, IX, and X   


     The Stationary Source Compliance Division (SSCD) has
recently received a number of questions pertaining to using 40
CFR Part 75 (Acid Rain) continuous emission monitoring systems
(CEMSs) to meet the SO2 and NOx CEMS requirements of New Source
Performance Standards (NSPS), 40 CFR Part 60, Subparts D, Da, and
Db.  In the near future, electric utilities operating CEMSs to
comply with the requirements of Part 60 must also install CEMSs
to meet the requirements of Part 75.  These utilities wish to use
the same CEMSs to comply with both Acid Rain and NSPS programs. 
Representatives from the Regions, States, and regulated community
requested a clarification on whether the Acid Rain CEMSs can be
used as the NSPS CEMSs, and if during the replacement period of
the existing NSPS CEMSs by the Acid Rain CEMSs, NSPS monitoring
and reporting could be curtailed.





     SSCD realizes that the requirements of Part 75 directly
affect CEMS performance, data collection, and reporting for the 
purposes of Part 60, and that there may be a conflict when the
NSPS CEMSs are replaced by Acid Rain CEMSs.  The possibility of
this conflict has also been identified in the Acid Rain CEMS
Implementation Team Approach paper.      

     SSCD has determined that since the CEMS requirements of 40
CFR Part 75 are equivalent to or more stringent than the
requirements of 40 CFR Part 60, EPA can accept Acid Rain CEMSs as
NSPS CEMSs provided that the utility demonstrates compliance with
all applicable NSPS regulations.  However, while authorizing the
use of Acid Rain CEMSs as NSPS CEMSs, we determined that a
blanket "grace period" from complying with the requirements of
Part 60 when installing CEMSs for Part 75 is not an appropriate
option. 

     SSCD recommends that, whenever possible, a utility operate
the existing NSPS CEMSs until the new Part 75 CEMSs are
operational and certified according to the requirements of Parts
60 and 75 (except for the DAHS certification).  The field test of
the Part 75 certification process should be scheduled as soon as
possible after the CEMSs become operational.  If there is an
unavoidable changeover time, the utility must minimize that time
since all periods of missing data will count as monitor downtime
for NSPS reporting purposes.  

     SSCD also recommends that, to meet the monitor data
availability during a changeover time, a utility use an approach
consistent with the requirements of Part 60.  To collect data for
SO2 and NOx from Subpart Da and Db boilers, a utility shall use
methods, procedures, and alternatives specified in Part
60.47a(h),(j), Part 60.47b(b), and in Part 60.48b(f).  The
utility must notify EPA when using this approach.  The Regions,
at their discretion, may require additional monitoring
procedures.  To meet the monitoring requirements when a Subpart D
boiler is involved, a utility should apply to the Region for a
short-term alternative to operating CEMS consistent with the
applicable requirements of 40 CFR Part 60.  The EPA Regional
Offices may allow using the requested alternative to operating
CEMS that meets the general criteria of this memorandum.  Every
petition for an approval of a temporary alternative to operating
CEMS should:

      Justify the request.

      Present the alternative.

      Present the approach to monitoring compliance with the     
      NSPS emission limitations.

      Provide a monitoring schedule.  




Examples of acceptable temporary alternatives to operating CEMS
include instrumental, analytical, and parametric approaches;
e.g., fuel sampling and analysis, periodic stack testing using a
reference method, control device parametric monitoring, visible
emission observation, or a backup monitor.  These alternatives
must be capable of clearly indicating compliance with applicable
regulations.  

     If the utility-proposed alternative to operating CEMS does
not meet the above listed conditions, the request must be denied. 
The use of any alternative must be short-term, not to exceed
eight weeks.  The Regions may grant an extension of this term
only in extreme fully justifiable circumstances.  We also suggest
that the Regions take a similar approach to other federally-
mandated programs that require SO2/NOx CEMSs; e.g., SIPs.     

     The Regions will approve in writing a successfully completed
field test of the acid rain CEMS certification procedure as an
equivalent to NSPS CEMS certification if a utility can
demonstrate compliance with the NSPS relative accuracy
requirements (by using data from Part 75 relative accuracy test,
diluent CEMS, and reference method) and the 7-day calibration
drift test (may involve a recalculation of the drift results as a
percentage of the NSPS span value rather than the Part 75 value).

     If you have any questions, please call Zofia Kosim of my
staff at 703-308-8733.

cc:  John Seitz
     Larry Kertcher, ARD

bcc:  Richard Biondi
      Steven Hoover
      Mamie Miller
      Linda Lay  
      Sally Mitoff
      Peter Westlin
      Anthony Wayne
      Daniel Bivins
      Zofia Kosim
      Richard Copland
      Judy Tracy
      Ken Harmon      
      Regional CEMS Coordinators
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