Harmonization of Part 60 and Part 75 CEM Requirements Robert Vollaro U.S. EPA Clean Air Markets Division

Background On February 28, 2005, EPA proposed amendments to the SO2 , NOx, and PM emission limits in three NSPS boiler regulations---Subparts Da, Db and Dc. As part of that rule package, the Agency also proposed revisions to: Certain CEM provisions in Subparts D, Da, Db, and Dc; §60.13(h) of the NSPS General Provisions; and Appendices B and F of Part 60. The purpose of these additional rule changes was to harmonize, to the extent possible, the CEM provisions of Parts 60 and 75, for sources subject to both sets of regulations.

Background (cont’d) The proposed revisions would: Make the method of calculating hourly emissions averages from CEMS data consistent between Parts 60 and 75 Allow Part 75 span values to be used for Part 60 monitoring applications; Allow the 7-day calibration drift test in Part 60 to be done on 7 consecutive unit operating days, rather than 7 consecutive calendar days Allow the CEMS Quality Assurance provisions of Part 75, Appendix B to be substituted for the procedures in Part 60, Appendix F, for sources subject to both sets of QA requirements

Background (cont’d) Comments received on the proposed CEMS rule changes were generally supportive. However, a number of adverse comments were received on the proposed revisions to the Subpart Da, Db and Dc emission limits. Issues regarding the impact of the emission limits were also raised by the Office of Management and Budget (OMB) and the Department of Energy (DOE). But EPA was under a court-ordered deadline to finalize the Subpart Da, Db, and Dc emission limits by February 9, 2006. Therefore, to meet the deadline, the Agency’s legal and technical staff focused exclusively on resolving the controversy over the Subpart Da, Db, and Dc emission limits

Background (cont’d) Consequently, there was insufficient time to properly review the CEMS amendments, and they were not included in the final rule that appeared in the Federal Register on February 27, 2006. EPA subsequently received petitions to reconsider the Subpart Da, Db, and Dc emission limits On February 9, 2007, EPA published a proposed response to the petitions to reconsider (72 FR 6320). In that Federal Register notice, the Agency stated its intention to finalize the Part 60 vs. 75 CEM harmonization amendments along with the final Subpart Da, Db, and Dc emission limits Under a court order, the final rule was signed by the EPA Administrator on April 13, 2007. As of May 7, 2007, the final rule has not yet been published in the Federal Register.

What Changes Have Been Made to the Part 60 CEM Requirements ? Based on comments received and internal discussion and deliberation within the Agency during the rulemaking process, the final CEM rule revisions will differ somewhat from the proposal. Despite this, EPA believes that the revisions go a long way toward accomplishing the intended purpose, which is to simplify and reduce the cost of compliance for sources under both Parts 60 and 75. The revisions to §60.13(h), concerning the validation of CEM hourly averages, were finalized with only minor edits. The revision to PS 2, allowing the 7-day drift test to be done on 7 consecutive unit operating days was finalized

What Changes Have Been Made to the Part 60 CEM Requirements ? (cont’d) Revisions to Subparts D, Da, and Db, allowing the site-specific Part 75 SO2 and NOx span values to be used in lieu of the more prescriptive Part 60 span values, were finalized The proposed revisions to Part 60, Appendix F were withdrawn. Instead, Subparts Da and Db were revised to allow: Data from certified Part 75 monitors (SO2, NOx, CO2, O2, and flow rate) to be used to demonstrate compliance with the Part 60 emission limits The QA/QC procedures in Part 75, Appendix B to be followed instead of the procedures in Part 60, Appendix F

What Changes Have Been Made to the Part 60 CEM Requirements ? (cont’d) However, the use of Part 75 CEM data and QA/QC procedures for Subpart Da and Db compliance is not unconditional: Part 75 bias-adjusted data and substitute data are not to be used for Part 60 compliance determinations For units subject to a lb/mmBtu SO2 standard, the RATA of the SO2 CEMS must be done on a lb/mmBtu basis and meet the RA specification in PS 2, in addition to meeting the Part 75 RA specification on a ppm basis If the span value of an SO2 or NOx monitor is < 100 ppm, the calibration drift and out-of-control provisions in section 4.3 of Appendix F must be followed for Part 60 data validation If the span value of an SO2 or NOx monitor is ≤ 30 ppm, cylinder gas audits (CGAs) must be performed according to section 5.1.2 of Appendix F

What Changes Have Been Made to the Part 60 CEM Requirements ? (cont’d) For the RATA of a NOx–diluent CEMS, if the average NOx emission rate measured by the reference method is < 0.100 lb/mmBtu, the RA specification in PS 2 must be met in addition to the Part 75 RA specification The last three conditions above pertain to low-emitting sources. The reason for these conditions is that there are a few “cut points” at which the Part 60, Appendix F specifications actually become more stringent than those in Part 75, Appendix B: For SO2 and NOx span values < 100 ppm, the highest single-day calibration error allowed by Appendix F (i.e., 10% of span) is more stringent than Part 75 For SO2 and NOx span values ≤ 30 ppm, Part 75 does not require linearity checks, but Appendix F requires CGAs For NOx emission rates < 0.100 lb/mmBtu, the relative accuracy specification in PS 2 becomes more stringent than the alternative Part 75 RA specification (0.020 lb/mmBtu mean difference)

What Changes Have Been Made to the Part 60 CEM Requirements ? (cont’d) Two commenters on the harmonization amendments asked EPA to consider making revisions beyond those that were proposed. Most of the requested revisions were considered to be too controversial and were not incorporated. However, the following additional revisions were made based on comments received: The requirement for the unit to be operating at > 50% of normal load during the 7-day drift test has been removed. The unit needs only to be on-line during the measurements. Sections 5.1.1 and 5.1.4 of Appendix F have been revised. In a non-operating quarter (i.e., zero hours of unit operation): CGAs are not required; and If a RATA is due, its deadline is automatically extended to the end of the next operating quarter.

Next Steps The amendments to Part 60 that were signed on April 13, 2007 represent a significant step forward. However, the Part 60 and Part 75 CEM provisions can (and, we believe, should) be further harmonized. CAMD will look for opportunities to work with OAQPS to bring about the necessary rule revisions. Some recommended items for discussion: The adequacy of the CEM performance specifications in both Parts 60 and 75 for very low-emitting sources Possibly adding more flexibility (e.g., grace periods, the “QA operating quarter” concept, etc.) to Appendix F

Next Steps (cont’d) Inconsistent opacity monitoring requirements Possibly allowing a wider application of Part 75 QA/QC procedures to other sources that are subject to Appendix F, either by permit or regulation Possibly extending the procedural aspects of the Part 75 QA/QC (i.e., the types of tests performed, test frequency, etc.) to other CEMS that are not subject to Part 75 (e.g., CO monitors).