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