**NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FROM COAL**  

** AND OIL** **- FI**  **RED ELECTRIC UTILITY STEAM GENERATING UNITS --**  **RECONSIDERATION ;**  **SUMMARY OF PUBLIC COMMENTS AND RESPONSES** 

U.S. Environmental Protection Agency Office of Air Quality

Planning and Standards Sector Policies and Programs Division Research Triangle Park, North Carolina 27711

March 2 0132 THI S PAGE INTENT IONALLY LEFT BLANK3 

### Table	of	Contents 1.0 LEGAL ................................ ................................ ................................ ................................ ................. 8 1.1 New Source Trigger Date: May 3, 2011 ................................ ................................ ........................... 8 1.2 Comments on issues which were not reconsidered in this notice ................................ ..................... 8 1.3 Other legal ................................ ................................ ................................ ................................ ....... 14 **2.0 NEW SOURCE EMISSION LIMITS** ................................ ................................ ............................. 17 2.1 New coal - fired unit ................................ ................................ ................................ ......................... 17 2.1. 1 Filterable PM (9.0E - 02 lb/MWh) ................................ ................................ ............................ 17 2.1.2 Hydrogen Chloride (1.0E - 02 lb/MWh) ................................ ................................ .................... 24 2.1.3 Sulfur dioxide (1.0 lb/MWh) ................................ ................................ ................................ ... 26 2.1.4 L ead (3.0E - 02 lb/GWh) ................................ ................................ ................................ ........... 32 2.1.5 Selenium (5.0E - 02 lb/GWh) ................................ ................................ ................................ .... 33 2.2 New coal - fired unit, not low rank virgin coal ................................ ................................ ................. 34 2.2.1 Mercury

(3.0E - 03 lb/GWh) ................................ ................................ ................................ ..... 34 2.3.1 Mercury

(possible revision) ................................ ................................ ................................ ..... 53 2.4 IGCC unit ................................ ................................ ................................ ................................ ........ 55 2.4.1 Sulfur dioxide (4.0E - 01 lb/MWh) ................................ ................................ ............................ 56 2.5 Solid oil - derived fuel - fired unit ................................ ................................ ................................ ...... 56 2.5.1 Filterable PM (3.0E - 02 lb/MWh) ................................ ................................ ............................ 58 2.5.2 Sulfur dioxide (1.0 lb/MWh) ................................ ................................ ................................ ... 58 2.6 Liquid oil - fired unit

—continental ................................ ................................ ................................ ... 59 2.6.1 Filterable PM (4.0E - 01 lb/MWh) ................................ ................................ ............................ 59 2.7 Other ................................ ................................ ................................ ................................ ............... 59 3.0 BEYOND - THE - FLO OR (BTF) ANALYSI S ................................ ................................ ..................... 73 3.1 New coal - fired unit ................................ ................................ ................................ ......................... 74 3.1.1 Filterable PM ................................ ................................ ................................ ........................... 74 3.1.2 Hydrogen chloride ................................ ................................ ................................ ................... 75 3.2 Other beyond - the - flo or ................................ ................................ ................................ ................... 76 4.0 FILTERABLE PM MONITORING ................................ ................................ ................................ ... 79 4.1 Quarterl y stack testing ................................ ................................ ................................ .................... 79 4.2 PM CEMS ................................ ................................ ................................ ................................ ....... 81 4.3 PM CPMS ................................ ................................ ................................ ................................ ....... 84 4.3.1 First Approach for establishing the operating limit for PM CPMS

– Requiring use of the highest parameter value obtained during any run of an individual emissions test as the operating4

limit, provided that the result of that individual emissions test met the emission limit. .................. 88 4.3.2 Second Approach for establishing the operating limit for PM CPMS

– Requiring use of the average parameter value obtained from all runs of an individual emissions test as the operating limit, provided that the result of the individual emissions test met the emissions limit. .................. 89 4.3.3 Third Approach for establishing the operating limit for PM CPMS

– Requiring use of the higher of a parameter scaled from all values obtained during an individual emissions test to 75 percent of the emissions limit or th e average parameter value obtained from all runs of an individual emissions test as the operating limit, provided that the result of the individual emissions test met the emissions limit. ................................ ................................ ................................ .............. 90 4.3.4 Emissions Testing After Each Exceedance ................................ ................................ .............. 93 4.3.5 Exceedances Leading to Violation ................................ ................................ ........................... 93 5.0 TECHNI CALCORRECTI ONS AND CLARIFICATIONS ................................ .............................. 97 5.1 Definitions (existing) ................................ ................................ ................................ ...................... 97 5.2 Definitions (new) ................................ ................................ ................................ ............................ 98 5.3 Rule language ................................ ................................ ................................ ................................ .. 98 5.4 Other technical corrections and clarifications ................................ ................................ ................. 99 6.0 IMPACTS AND COST ANALYSI S ................................ ................................ ................................ 102 6.1 Air Impacts ................................ ................................ ................................ ................................ .... 102 6.2 Energy

Impacts ................................ ................................ ................................ ............................. 103 6.3 Economic Impacts/Employ ment Impacts ................................ ................................ ..................... 103 6.4 Health Co - Benefits ................................ ................................ ................................ ........................ 104 6.5 Other impacts and cost analy sis ................................ ................................ ................................ .... 105 7.0 GENERAL COMMENTS ................................ ................................ ................................ ................ 107 8.0 OUT OF SCOPE ................................ ................................ ................................ ............................... 108 9.0 INCORPORATE BY REFERENCE ................................ ................................ ................................ 110 10.0 OTHER COMMENTS NOT COVERED ................................ ................................ ...................... 112 11.0 DUPLICATE COMMENTS ................................ ................................ ................................ ........... 1135 LIST OF COMMENTERS **Commenter Name Commenter Organization**  **Docket ID** Floyd Gilzow Missouri Joint Municipal Electric Utility Commission EPA - HQ - OAR - 2009 - 0234 - 20238 Cecile M. Conroy International Brotherhood of Boilermakers (IBB) EPA - HQ - OAR - 2009 - 0234 - 20241 David Ussery Platte River Power Authority EPA - HQ - OAR - 2009 - 0234 - 20242 Terry M. Hogan Wabash Valley Power Association, Inc. EPA - HQ - OAR - 2009 - 0234 - 20243 Karen Jackson Grand Parents Second Time Around EPA - HQ - OAR - 2009 - 0234 - 20244 Eric Redman Summit Power EPA - HQ - OAR - 2009 - 0234 - 20245 Bart Sponseller Wisconsin Department of Natural Resources (WDNR) EPA - HQ - OAR - 2009 - 0234 - 20246 Claire M. Olson Basin Electric Power Cooperative EPA - HQ - OAR - 2009 - 0234 - 20247 Walter Stone NRG Energy, Inc. EPA - HQ - OAR - 2009 - 0234 - 20248 Todd Parfitt Wyoming Department of Environmental Quality EPA - HQ - OAR - 2009 - 0234 - 20249 Kim berly A. Scarborough PSEG Services Corporation EPA - HQ - OAR - 2009 - 0234 - 20250 Bob Holmes Omaha Public Power District (OPPD) EPA - HQ - OAR - 2009 - 0234 - 20251 Lisa Jaeger Edgecombe Genco LLC and Spruance Genco LLC EPA - HQ - OAR - 2009 - 0234 - 20252 Gregory C. Staple American Clean Skies Foundation (ACSF) EPA - HQ - OAR - 2009 - 0234 - 20253 Jo e L. Citta, Jr. Nebraska Public Power District (NPPD) EPA - HQ - OAR - 2009 - 0234 - 20254 Patrick O ’ Loughlin Buckeye Power, Inc. EPA - HQ - OAR - 2009 - 0234 - 20255 Raymond L. Evans FirstEnergy Corp. EPA - HQ - OAR - 2009 - 0234 - 20256 Kenneth J. Anderson Ameren Corporation EPA - HQ - OAR - 2009 - 0234 - 20257 Frank L. Kohlasch Minnesota Pollution Control Agency EPA - HQ - OAR - 2009 - 0234 - 20258 Anonymous Individual EPA - HQ - OAR - 2009 - 0234 - 20259 Anonymous Individual EPA - HQ - OAR - 2009 - 0234 - 20260 Paul Chu Electric Power Research Institute (EPRI) EPA - HQ - OAR - 2009 - 0234 - 20261 Mark Thoma Otter Tail Power Company EPA - HQ - OAR - 2009 - 0234 - 20262 Bob Davis Airgas, Inc. EPA - HQ - OAR - 2009 - 0234 - 20263 Catharine Fitzsimmons Io wa Department of Natural Resources EPA - HQ - OAR - 2009 - 0234 - 20264 Paul Bailey American Coalition for Clean Coal Electricity (ACCCE) EPA - HQ - OAR - 2009 - 0234 - 20265 Lindil C. Fowler, Jr. Railroad Commission of Texas (RRC) EPA - HQ - OAR - 2009 - 0234 - 20266 PJ Becker City of Springfield, City Water Light and Power EPA - HQ - OAR - 2009 - 0234 - 20267 Betsy Natz Institute of Clean Air Companies (ICAC) EPA - HQ - OAR - 2009 - 0234 - 20268 Debra J. Jezouit Baker Botts L.L.P. et al. on behalf of The Class of ‘ 85 Regulatory Response Group EPA - HQ - OAR - 2009 - 0234 - 20269 Chris M. Hobson Southern Company EPA - HQ - OAR - 2009 - 0234 - 20270 Cathy S. Woollums MidAmerican Energy Holdings Company EPA - HQ - OAR - 2009 - 0234 - 20271 Jay Hudson Santee Cooper EPA - HQ - OAR - 2009 - 0234 - 20272 John A. Riley Bracewell & Giuliani LLP, on behalf of Las Brisas Energy Center, LLC EPA - HQ - OAR - 2009 - 0234 - 20273 Susan Ecke rly National Federation of Independent Businesses (NFIB) EPA - HQ - OAR - 2009 - 0234 - 202746

Michael J. Nasi Jackson Walker, LLP, on behalf of Gulf Coast Lignite Coalition (GCLC) EPA - HQ - OAR - 2009 - 0234 - 20275 Jon Madison Montana - Dakota Utilities Company EPA - HQ - OAR - 2009 - 0234 - 20276 Greg F. Myers Consumers Energy EPA - HQ - OAR - 2009 - 0234 - 20277 Myra Glover Entergy Services, Inc. EPA - HQ - OAR - 2009 - 0234 - 20279 Kelly J. Barr Salt River Project (SRP) EPA - HQ - OAR - 2009 - 0234 - 20280 J. Michael Geers Duke Energy EPA - HQ - OAR - 2009 - 0234 - 20281 Lee B. Zeugin, et al. Utility Air Regulatory Group (UARG) EPA - HQ - OAR - 2009 - 0234 - 20282 Alex Bond National Mining Association (NMA) EPA - HQ - OAR - 2009 - 0234 - 20284 Jeffrey A. McNelly ARIPPA EPA - HQ - OAR - 2009 - 0234 - 20285 Zak Covar Texas Commission on Environmental Quality (TCEQ) EPA - HQ - OAR - 2009 - 0234 - 20286 Chet Thompson Crowell & Moring LLP, on behalf of Homer City Generation, L.P. EPA - HQ - OAR - 2009 - 0234 - 20287 Stephen Fotis Generators for Clean Air (GCA) EPA - HQ - OAR - 2009 - 0234 - 20288 Henry E. Eby Lower Colorado River Authority (LCRA) EPA - HQ - OAR - 2009 - 0234 - 20289 Daniel R. Wilkus Westar Energy, Inc. EPA - HQ - OAR - 2009 - 0234 - 20290 Paul M. Ling Kansas City Power & Light Company (KCP&L) EPA - HQ - OAR - 2009 - 0234 - 20291 Mark J. Sedlacek Los Angeles Department of Water and Power EPA - HQ - OAR - 2009 - 0234 - 20292 Arthur N. Marin Northeast States for Coordinated Air Use Management (NESCAUM) EPA - HQ - OAR - 2009 - 0234 - 20293 J. Michael Brown Ohio Valley Electric Corporation EPA - HQ - OAR - 2009 - 0234 - 20294 Quinlan J. Shea Edison Electric Institute (EEI) EPA - HQ - OAR - 2009 - 0234 - 20295 Peter Glaser Troutman Sanders, LLP, for New Unit Developers EPA - HQ - OAR - 2009 - 0234 - 20296 Brian Brazil TransAlta Centralia Generation, LLC EPA - HQ - OAR - 2009 - 0234 - 20297 Gary S. Rose Connecticut Department of Energy and Environmental Protection EPA - HQ - OAR - 2009 - 0234 - 20298 Norman Schilling General Electric Company (GE) EPA - HQ - OAR - 2009 - 0234 - 20299 David Woodsmall Sierra Club, et al. EPA - HQ - OAR - 2009 - 0234 - 20300 Donna Nelson Public Utility Commission of Texas EPA - HQ - OAR - 2009 - 0234 - 20301 Michael L. Krancer Pennsylvania Department of Environmental Protection (PDEP) EPA - HQ - OAR - 2009 - 0234 - 20302 Jo seph G. Eutizi San Miguel Electric Cooperative EPA - HQ - OAR - 2009 - 0234 - 20303 Melvin E. Keener Coalition for Responsible Waste Incineration (CRWI) EPA - HQ - OAR - 2009 - 0234 - 20304 David Woodsmall Sierra Club, et al. EPA - HQ - OAR - 2009 - 0234 - 20305 Gregory Ryan DTE Energy EPA - HQ - OAR - 2009 - 0234 - 20306 Holly Rachel Smith, Esq. National Association of Regulatory Utility Commissioners (NARUC) EPA - HQ - OAR - 2009 - 0234 - 20307 John M. McManus American Electric Power (AEP) EPA - HQ - OAR - 2009 - 0234 - 20308 Terrance Stanton Individual EPA - HQ - OAR - 2009 - 0234 - 20309 David Low Individual EPA - HQ - OAR - 2009 - 0234 - 20310 Nancy Barta - Smith Individual EPA - HQ - OAR - 2009 - 0234 - 203117

Jay Sweeney Individual EPA - HQ - OAR - 2009 - 0234 - 20312 Mass comment campaign sponsoring organization unknown (email) Mass mail EPA - HQ - OAR - 2009 - 0234 - 20313 Berdell Knowles JEA EPA - HQ - OAR - 2009 - 0234 - 20321 Jo aquin C. Flores Guam Power Authority EPA - HQ - OAR - 2011 - 0044 - 5785 Megan Murphy PPL Services Corporation EPA - HQ - OAR - 2011 - 0044 - 58038

**1.0 LEGAL**  1.1 New Source Trigger Date: May 3, 2011 **Comment:** Commenters (20251 and 20308) stated that the meaning of paragraph 63.9982(c) in the proposed reconsideration is not clear. The Commenter s agreed that applicability for n ew and reconstructed electric utility steam generating units ( EGUs ) rely on the 5/3/2011 date. The Commenter s recommended that the “ or if ” in 40 CFR §63.9982(c) should be “ and” because you must meet the reconstruction criteria and begin reconstruction after 5/3/2011. The Commenter s noted that otherwise this is retroactive to any work that causes a source to meet the reconstruction criteria, even if the changes were made prior to the effective date in 40 CFR §63.9982(b). The Commenter s suggested the following change to the language: An EGU is reconstructed if you meet the reconstruction criteria as defined in §63.2, or and if you commence reconstruction after May 3, 2011. Commenter (20282) disagreed that the EPA ’ s proposed change to correct the discrepancy between 40 CFR §63.9982(c) and §63.9985(a) is a technical correction that may be undertaken without additional anal ys is. The Commenter stated that with the correction, the EPA proposes, contrary to CAA §112 and the existing rule, to apply the more stringent emission limits for new EGUs that were not constructed or reconstructed after May

3, 2011. The Commenter stated that to avoid this result, and limit the change to a technical correction, the EPA should substitute the word “ and” in place of the word “ or. ” Commenter (20282) stated that in the event that the Agency ’ s use of the word “ or” was intentional, and not a drafting error, the Commenter reminds the Agency that it lacks the statutory authority to trigger the reconstruction rule for activities that occurred before May 3, 2011. The Commenter discussed this point. **Response:** The EPA has made the change suggested by the Commenter in the final rule. 1.2 Comments on issues which were not reconsidered in this notice **Comment:** Commenters (20273, 20286, 20295, 20296 , 20302, and 20308 ) disagree with the EPA ’ s pollutant - by-pollutant approach to setting MACT standards. Commenter (20273) stated that EPA ’ s reconsidered MATS are still based on the erroneous premise that EPA can establish limits through a pollutant - by- pollutant methodology an d not based on the performance of a single source. The Commenter stated that EPA ’ s Reconsidered MATS, although improved over the promulgated MATS, are contrary to the explicit language of CAA §112(d)(3) because they

were established using a pollutant - by -po llutant approach where different EGUs were selected as the best controlled source for each individual pollutant to be regulated. The Commenter observed that the statutorily prescribed method for determining these standards requires EPA to identify the sing le “best controlled similar source ” for all of the pollutants to be regulated. The Commenter stated that because EPA deviated from the statutorily mandated method, it is unclear as to whether the reconsidered MATS standards are “ achievable ” by any new soli d oil - derived fueled EGUs. The Commenter stated that the Joint Brief of Petitioners filed in the United States Court of Appeals for the District of Columbia Circuit ( “ D.C. Circuit” ) on July 27, 2012 in Case No. 12 - 1272, Document No.9

1386256, correctly

sets forth the legal constraints on EPA in setting the MATS and the points made in Section II of that brief, of which EPA is unquestionably aware, are incorporated by reference into these comments , the EPA ’ s statements to the contrary notwithstanding. Comment er (20286) stated that the hazardous air pollutant (HAP ) - by- HAP approach used by the EPA to develop numerical emission standards does not consider overall technical feasibility . The Commenter stated that EPA ’ s arbitrary acceptance of the results of the HAP - by- HAP analy sis when establishing MACT emission standards is contrary to the federal Clean Air Act (CAA) § 112. The Commenter suggests an alternate MACT analy sis approach using the HAP - by- HAP approach initial ly to screen facilities to determine the “best controlled similar source ” while basing the final MACT floor determination on a holistic approach. The Commenter provided justification for why they believe that EPA ’ s HAP by

HAP approach is arbitrary and capricious, highlighting The Logan Generating Plant, previous litigation, and the CAA. Commenter (20295) stated that the pollutant - by-pollutant approach to setting MACT standards for existing EGUs is contrary to CAA § 112(d)(3). Commenter (20296) disagreed that the EPA ’ s pollutant - by- pollutant approach is a correct method of implementing CAA §112(d)(3) and maintain that EPA instead must set the standard based on the single unit that emits the lowest level of all of the pollutants to be regulated. The Commenter attached a court brief with more details. Commenter (20302) stated that in the development of new emission standards for certain pollutants emitted by

new and reconstructed EGUs, the EPA cherry- picked one of the best performing EGUs for each particular pollutant and statistically derived an emission limit based on that one unit. The Commenter disagreed with this approach, and stated that a more appropriate approach would be to identify the best performing EGU or EGUs for total HAP and statistically deriv e all emission limits based on those EGUs . The Commenter referred to the language of CAA § 112(d)(3) , and noted that the CAA requires that emissions limitations for new EGUs may not be less stringent ‘‘ than the emission control that is achieved in practice by the best controlled similar source, ” not the best controlled sources. The Commenter stated that the rulemaking docket does not support a conclusion that the standards are in fact achievable. Commenter (20308) objected to proposed standards for individual HAP or surrogates for HAP based on the performance of a different set of EGUs for each different HAP standard, which establishes emission limits that are not indicative of what a single source has demonstrated or could demonstrate to be achieved or achievable in practice. The Commenter stated that EPA ’ s methodology fails to provide appropriate consideration of the potential impact on the ability to effectively

control other HAP when choosing th e “best performing ” results for a given HAP. The Commenter suggested that the EPA follow the language of CAA § 112(d)(3) for setting new source MACT limits. The Commenter encouraged the EPA to re - evaluate the emissions data for HAP in their entirety to deve lop new source emission limits that can be met b y the best performing EGUs in accordance with the CAA language. **Response:** The EPA addressed comments on the pollutant - by-pollutant approach to establishing standards in the final rule and we incorporate our responses to those comments herein. See, e.g. , 77 FR10

9304, 9386 - 88 (February 16, 2012) ; Response to Comments document for the final MATS rule (RTC, Docket ID EPA - HQ - OAR - 2009 - 0234 - 20126) Vol. 1, pp. 423 - 433 . Furthermore we note that there are a number of existing coal - fired EGUs whose test data available to the EPA at the time of rule development demonstrate that these EGUs have in practice achieved the new source limits proposed in this notice (considering all of their submitte d data) . In the reconsideration proposal notice, the EPA indicated that “based on our review of the data EPA collected as part of the 2010 In formation Collection Request ( IC R) process, at least eight existing non - low rank virgin coal fired EGUs and one low rank virgin coal - fired EGU ” in this category meet the new source limits for Hg, PM, and HCl (see 77 FR 71329) . Because this analysis was based on a review of the same 2010 ICR data available to the public (and, thus, the analysis could also have been done by the public), the EPA did not identify

these EGUs. Further, the statute does require that any source be able to achieve the level of all the new source limit s as the C ommenters imply . However, the EPA conducted the analy sis as one means of indicating th at the new source limits are reasonable. The nine EGUs that have short- term stack test data that demonstrate that these EGUs have in practice achieved the new source limits for Hg, PM, and HCl are: Lo gan Unit 1 Elm Road Unit 1 Clover Units 1 and 2 Chamber s Units 1 and 1 Mount Tom Unit 1 H.L . Spurlock Unit 3 Sandow Unit 5A In addition, c ontrary

to both the language of CAA section 112(d)(2) and the broader purpose it reflects, Commenter s’ approach to setting MACT floors based on a single source could result in standards that reflect emissions levels achieved b y an existing EGU that is not a best performer in regard to any HAP

– a result the EPA has aptly stated that such an approach would lead to “least common denominator floors.” See 77 FR 9387. In fact, utilizing the single - unit theory put forward by Commenter s could result in the EPA setting standards at levels that would, for some pollutants, actually be based on emissions data from lower performing EGUs (as a poorl y-performing source for a particular pollutant could nevertheless be identified as having the best overall performance), rather than the best -performing EGU , as required b y the statute. For example, Hatfield’s Ferry Unit 1 is number 5 on the acid gas list but only number 255 on the H g list; Rawhide Unit 101 is number 14 on the acid gas list but only number 314 on the Hg list; Dunkirk Unit 1 is number 2 on the PM list but only number 166 on the Hg list; and Sheldon Station Unit 2 is number 5 on the PM list but only number 102 on the Hg list. We do not believe such a result is consistent with the statute and we maintain that the approach taken by the Agency provides a reasonable mechanism for ensuring that each new source limit is based on the best controlled similar source. **Comment:** Commenter (20286) stated that the EPA has not properl y considered the impacts of its approach for establishing MACT emission standards on reconstructed EGUs . The Commenter stated that there is no documentation in the proposed MATS rule that EPA considered the technical feasibility of the proposed new source standards to reconstructed sources. The Commenter stated that the HAP - byHAP approach used b y the EPA is incompatible with reconstructed sources, because it does not consider11

technical feasibility

to a s pecific emission source because the selection of emission rates from multiple sources draws from multiple unique designs and specific fuel characteristics. Commenter (20286) stated that the unit design and other unique aspects already exist and the recons truction of those sources may not fundamentally

change the existing reconstructed source into the newly constructed source. The Commenter stated that the EPA either needs to apply a “whole -plant” view in establishing emission standards (i.e., look at the p erformance of all pollutants from one single reconstructed unit) or if EPA wants to continue a piecemeal approach to establishing the standards, it must further subcategorize emission standards to consider specific emission source designs and fuel ty pe, which have significant effects on emission performance. **Response:** The EPA does not agree with the Commenter . The EPA has broad discretion in making decisions concerning subcategorization, and the Commenter has not provided data to support an argument that additional new source categories are necessary or supportable for reconstructed EGUs . See CAA section 112(d)(1) (stating that the Agency “may” establish subcategories). In any case, this issue is outside the scope of this rulemaking. Subcategorization was addressed in the final rule (see , e.g. , 77 FR 9378 - 9379, 9394 - 9402). The EPA did not solicit comment in the reconsideration proposal on additional subcategories . In addition, as noted in response to comments above, the EPA did not open for comment the pollutant - by- pollutant approach to establishing new source MACT limits. Furthermore, the EPA ’ s understanding of reconstructions is based primarily on the enforcement actions brought against power plants and on self - reporting b y power plants. Over the lengthy history of the Agency ’ s programs, such actions have been too few in number to allow us to develop a sufficiently robust base of knowledge. The EPA is aware of the KCP&L situation at the Hawthorn Station (i.e., Unit 5 boiler explosion in 1999 and subseq uent rebuilding) and data from Hawthorn Unit 5 are in the 2010 ICR database and were, thus, considered in the analyses. Further, data from any other reconstructed EGU s would also be in the 2010 I CR database and anal ys es. In any case, if an owner or operato r intends to reconstruct an EGU, the reconstruction will need to occur in a manner that ensures that the reconstructed unit will be able to comply with the final MATS rule. The Commenter s have not demonstrated that reconstructed units will be unable to comply with the applicable new source limits. Nothing in the statute requires the EPA to consider every potential scenario in establishing new source MACT standards and the Agency maintains that it s approach is consistent with the statute and no information provided b y the Commenter s supports a different conclusion . **Comment:** Commenter (20246) stated the EPA should develop separate emission limit categories for EGUs using different ty

pes of coal - fired boiler technologies, such as super cri tical pulverized boilers (SPC), fluidized bed combustion (FBC) boilers, conventional pulverized coal (PC), and advanced stoker boilers . The Commenter said the EPA is proposing new source emission limitations for all coal - fired power plants based on the bes t emission rate (b y pollutant) demonstrated by either a SPC boiler or a FB boiler . The Commenter stated it is not clear that the resulting set of hy brid emission limits can be achieved at all ty

pes of new coal - fired EGUs at the cost levels considered in EP A ’ s anal ys is . The Commenter also stated that the EPA appears to believe that these two specific boiler ty pes are interchangeable and can meet requirements for all different types of EGU configurations and projects . The Commenter stated this is not true . Th e Commenter said SPC boilers are exclusive to large base - load power plant applications, whereas FB boilers are utilized for smaller generation or co - generation projects . The Commenter said another factor to consider is that different boiler ty pes, such as advanced12

stoker boilers, may

serve a project more efficiently or allow the use of alternative fuel combinations which results in lower overall emissions . The Commenter stated more efficient options should not be precluded b y the new source emission limits. **Response:** The EPA does not agree with the Commenter . The EPA has broad discretion in making decisions concerning subcategorization. See CAA section 112(d)(1) (stating that the Agency “may” establish subcategories). In any case, this issue is outside the scope of this rulemaking. Subcategorization was addressed in the final rule (see , e.g. , 77 FR 9378 - 9379, 9394 - 9402). The EPA did not solicit comment in the reconsideration proposal on additional subcategories . Furthermore, the Commenter has provided no data that would support its contention that additional subcategories are warranted or necessary . The EPA maintains that without such demonstration it would be unreasonable to establish additional subcategories for new sources. **Comme nt:**  Commenter (20273) stated the MATS limit for solid oil - derived fuel for hydrochloric acid (hydrogen chloride, HCl) is too stringent. The Commenter noted there was no change in the MATS limit for HCl emissions (4.0 x 10 - 4 pounds per megawatt - hour, lb/MWh) for new solid oil - derived fuel - fired units. The Commenter stated that based on discussions with equipment manufacturers, the HCl limit of 0.0004 lb/MWh is too low to provide a guarantee. The Commenter said this limit represents a very low concentration of HCl where the accuracy of the test methods is questioned by the vendors. The Commenter continued that one potential vendor confirmed to the Commenter ’ s consultants that without a reliable method to me asure emissions at the proposed levels, it is unlikely to provide a guarantee. The Commenter stated, nonetheless, with the alternate limit for sulfur dioxide ( SO 2 ) emissions as a surrogate for compliance with the HCl MATS appropriately raised from 0.4 to 1 .0 lb/MWh in the proposed reconsidered MATS for solid oil - derived fuel - fired EGUs , and that compliance with the reconsidered MATS is possible. **Response:** The HCl limit for solid oil - derived fuel - fired EGUs was not among those limits revised and proposed for comment in the reconsideration notice . As identified in the reconsideration proposal, the EPA will not respond to any comments addressing any provisions of the MATS rule not specifically identified as being revised and proposed for comment ( see 77 FR 71325 ). Moreover, the EPA is under no obligation to review HCl limit for solid oil - derived fuel because the deadline for commenting on the RDLprocedure for HCl in the petition for reconsideration is long past. Should a soli d oil - derived fuel fired EGU owner or operator believe HCl CEMS incapable of providing accurate measurements for compliance purposes, he can choose to use quarterly testing, along with continuous monitoring of one or more parameters. Further, as Commenter notes, such EGUs with add - on SO 2 controls in -place are eligible for the alternate SO 2 emission limit. **Comment:** Commenter (20273) stated the MATS standard for solid oil - derived fuel for mercury (Hg) is too stringent. The Commenter noted, as with HCl, the reconsidered MATS standard has not changed for Hg emissions for solid oil - derived fuel - fired EGUs and remains at 2.0 x 10 - 3 pounds per gigawatt - hour ( lb/GWh) . The Commenter stated that to achieve this standard, the Hg removal effic iency requirements are approximately

99.6 percent for some petroleum coke fuel to stack. Commenter (20273) stated, furthermore, although the proposed Hg limit for new coal EGUs (0.003 lb/GWh) is considered very aggressive and compliance will present a significant challenge with current control technologies and require an improved understanding of removal performance for these13

technologies, the proposed MATS standard for Hg for solid oil - derived fuel - fired EGUs is even more aggressive at 0.002 lb/GWh. The C ommenter ’ s consultants have advised that with application of a combination of different technologies, at least one vendor suggests that it would guarantee the reconsidered MATS Hg limits for new coal EGUs . The Commenter stated that with the suite of contro ls planned for the LBEC, there is growing operating experience that helps them understand the mechanisms for Hg capture and, over time, may provide a sufficient basis for vendors to provide a guarantee at the lower reconsidered MATS standard applicable to petroleum coke fuel. The Commenter stated, however, the detectability , operability , and practicality concerns that EPA accepted and endorsed in justifying the higher Hg MATS standard for coal EGUs are equall y applicable to solid oil - derived f uel - fired EGUs . The Commenter stated that the EPA must be consistent and apply the same considerations and reasoning in setting standards for all ty pes of EGUs . The Commenter stated that they are advised that the use of PAC in conjunction with circulating semi - dry scrubber flue gas desulfurization ( CDS - FGD ) technology for control of Hg can support guarantees at the reconsidered MATS limits for new coal EGUs , 0.003 lb/GWh. Commenter (20273), based on the above, requested that EPA reset the proposed limit fo r Hg for solid oil - derived fuel - fired units where it sets the limit for coal. The Commenter stated, as EPA explains in its overarching justification for the reconsideration of the promulgated MATS rule , the reconsidered MATS rule will not lead to the appli cation of different controls and that is certainly true for Hg in the LBEC context. **Response:** The EPA did not propose to revise the Hg limit for solid oil - derived fuel fired EGUs, and, for that reason, the Agency

is under no obligation to respond to this comment. In any case, because of the concerns with measurement capabilities associated with Hg emissions from non - low rank virgin coal fired EGUs , the EPA determined it was reasonable in this case to compare the calculated Hg limit with the level 3XRDL for solid - oil fired units to ensure that the final standard could be continuously monitored. The EPA conducted the same ty pe of three times the representative detection level (3XRDL) anal ys is for the solid oil - derived fuel Hg limit as was conducted for the co al Hg limit using the Hg data from the solid - oil fired EGUs . The EPA found the average RDL from the best performing solid oil derived fuel fired EGUs for which data were available to be 1.2 nanograms. Using that value, as well as the heat rate and F - factor for solid oil - derived fuel (8,900 British thermal units per kilowatt - hour ( Btu/kWh) and 9,830 cubic meters per million Btu (m 3 /MM Btu) , respectively) in calculations to express the 3XRDLvalue in terms of an emissions limit, the EPA found the 0.002 0 lb/GWh limit finalized in MATS to be appropriate for those EGU owners or operators who believe frequent sampling times (30 minutes of sample collection) over short periods of load or process transition is necessary. EGU owners or operators who choose to sample f or longer periods should have no problems using sorbent monitoring systems for compliance purposes. **Comment:** Commenter (20303) stated that the beyond - the - floor (BTF) limit for existing low - rank virgin coal EGUs , established at 4.0 pounds per trillion Btu ( lb/TBtu) in the rulemaking, cannot be attained by existing EGUs . The Commenter stated that the BTF limit was based on the lowest data point from a single unit rather than the group of EGUs required by the CAA, and that this is a violation of the CAA. The Commenter noted that the one newest unit could not consistently meet the proposed 4.0 lb/TBtu limit. The Commenter concluded that the Hg BTF limit for low - rank virgin coal EGUs should be struck from the rule or at a minimum be revised to an achievable limit. The Commenter suggested a limit of 7.0 lb/TBtu.14

**Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the existing - source emission limits. **Comment:** Commenter (20282) asked that the EPA further revise portions of the MATS rule to address issues in its petition for reconsideration (incorporated b y reference in their comment) that were not addressed in the proposed reconsideration. **Response:** This issue is outside the scope of this rulemaking. The EPA specificall y identified the issues being proposed for reconsideration in the November 30, 2012 , notice (77 FR 71323) ; other issues contained in the petitions for reconsideration are being address ed outside of this rulemaking. 1.3 Other legal **Comment:** Commenters (20265 and 20296) urged EPA to finalize the proposed rule as quickl y as possible. Commenter (20265) stated the combination of the new source standards in the MATS rule and EPA ’ s proposed greenhouse gas (GHG) New Source Performance Standards (NSPS) for new coal - fueled EGUs has created a regulatory

Catch - 22 for new EGUs . The Commenter stated that on the one hand, under the proposed GHG NSPS, new EGUs having PSD permits must commence construction by April 12, 2013 , in order to avoid being subject to the proposed NSPS (which new coal EGUs cannot meet). On the other hand, according to the Commenter , the EPA ’ s MATS rule new source standards, because they also could not be met, effectively prevented new EGUs from commencing construction. The Commenter stated because of the time EPA has taken to reconsider the new source MACT standards, the 1 - ye ar deadline to co mmence construction under the GHG NSPS is about to expire. Commenter (20265) noted that EPA stated that it intends to finalize the reconsidered new source MACT standards b y “ March. ” The Commenter stated, however, new EGUs cannot commence construction immediately

after new source MACT standards are published because time will be needed to evaluate the final standards, to negotiate equipment purchase contracts with vendors, and to take other necessary steps that are a prerequisite to commencing construction. The Commenter said, therefore, March may be too late to ensure that new EGUs can commence construction by April 12. The Commenter concluded that to give new unit developers at least some chance to meet the April 12 deadlin e , the EPA must issue the final standard as early in March as possible. Commenter (20296) further asked that the EPA extend the transitional source period for the GHG NSPS rule by an amount of time equal to the period of time between publication of the initial MATS rule and publication of the reconsidered MATS rule. **Response:** Comments on the GHG NSPS rule are outside the scope of this rulemaking. The remaining comments concerning finalization of the new source limits are moot. **Comment:** Commenter (20251) stated that the MATS rule should clearl y s tate that it does not apply to stationary CTs that are not associated with an IGCC unit. The Commenter stated that there is a statement on page 9309 of the preamble to the February 16, 2012 , final rule that indicates that EPA does not15

consider stationary

CTs to be EGUs for the purpose of the final MATS rule, and a footnote to this statement states that the CT NESHAP regulates HAP emissions from all simple - cycle and combined cycle stationary

CTs producing electricity or steam for any purpose. The Commenter stated that this is not correct, as the CT NESHAP only applies to CTs located at major sources. The Commenter asked that this be clarified b y revising paragraph 63.9983(a) of the MATS rule, which specifies EGUs not subject to the rule, to read as follows: (a) Any unit designated as a stationary combustion turbine, other than an integrated gasification combined cycle (IGCC) unit. , covered by 40 CFR part 63, subpart YYYY. **Response:** This issue is outside the scope of this rulemaking. The EPA did not receive petitions for reconsideration on this issue and it was not open for reconsideration in the November 30, 2012 , notice . **Comment:** Commenter (20286) stated that although the EPA in this action is reconsidering the SO 2 limit for new coal - fired EGUs based on its original inclusion of a unit that is actuall y an industrial boiler, and therefore, not subject to MATS, the EPA also states in the preamble (77 FR 71326) to the proposed rule that “ As an initial matter, nothing in the CAA precludes the EPA from identifying a source in another source category as the best controlled similar source. ” The Commenter disagreed with this statement, stating that it is clearly in opposition to the decision of the U.S. Court of Appeals for the District of Columbia regarding the Portland Cement NESHAP. ( Portland Cement Association v. EPA, 665 F.3d 177 (D.C. Cir. 2011)) . The Commenter provided discussion regarding other court rulings pertaining to this approach. Commenter (20296) disagreed with EPA ’ s assertion that “nothing in the CAA precludes the EPA from identifying a source in another source category as the best controlled similar source. ” The Commenter stated that by

definition, a source in a different category cannot be deemed to be “ similar” to sources in a different category . Commenter (20249) stated in Item 2 of Section IV, when addressing whether a boiler used to establish the SO 2 standard for new coal - fired EGUs qualified as an EGU , the EPA states: As an initi al matter, nothing in the CAA precludes the EPA from identifying a source in another source category

as the best controlled similar source. However, they believe that it is appropriate in this case, where we have considerable data on EGUs, to base the new source standard on the best performing unit that is an EGU. ” Commenter (20249) stated that when EPA establishes NSPS , the EPA must consider whether the standards are achievable given the typ e and operation of the source. The Commenter stated, when identifying sources in other source categories for consideration in establishing a new performance standard , the EPA should provide an analysis demonstrating similarity between the source from another category and sources affected by

the new standard. The Commenter added that this analysis must also address whether the data used by the similar source applies to all modes of operation or just specific operating times.16

**Response:** Although we disagree with the Commenters’ assertions concerning th e term “similar source” as it appears in CAA section 112(d)(3), we need not address this issue as the Agency established all of the final MATS MACT standards based on EGUs.17

**2.0 NEW SOURCE EMISSION LIMITS**  2.1 New coal - fired unit 2.1.1 Filterable PM (9.0E - 02 lb/MWh) **Filterable PM emission standard Comment:**  Commenter (20293) stated that EPA finalized a filterable particulate matter ( fPM ) limit of 0.007 lb/MWh, which should be revised on reconsideration because it is not feasible and appears to be the result of an error in interpreting or transcribing test results from one facility . The Commenter stated that the 0.09 lb/MWh limit that EPA now proposes is higher than would be warranted based on the data in the record. The Commenter stated that the resul t of EPA ’ s calculation was 8.23 x 10 - 2 lb/MW. Expressed to two significant digits, this result properly rounds to 8.2 x10 - 2 lb/MW or, arguably 8.3 x10 - 2 lb/MW, but not to 9.0 x10 - 2 lb/MW, as proposed by EPA. **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the rounding convention used in determining the final emission limits. The EPA used the same rounding convention for fPM as was used in the MATS proposal and final (see , e.g. , RTC, Vol. 1, pp. 463 - 465) , and we maintain that the approach is reasonable for the reasons stated in the entire MATS record . **Comment:** Commenter (20305) stated that the proposed reconsidered fPM standards are extraordinarily lenient. The Commenter stated that the numeric emissions rate is well in excess of emissions demonstrated b y the best -performing plants. The Commenter noted that the Agency has already

relaxed the stringency

of its limits by extending compliance to 30 operating day s. **Response:** The EPA used the same approach for selecting the “best performing similar source ” and in conducting the MACT floor anal ys es in the proposed reconsideration as was used at proposal and final (see , e.g. , Docket ID EPA - HQ - OAR - 2009 - 0234 - 9858, National Emission Standards for Hazardous Air Pollutants (NESHAP) Maximum Achievable Control Technology (MACT) Floor Analysis for Coal- and Oil- fired Electric Utility Steam Generating Units

– REVISED ; Docket ID EPA - HQ - O AR- 2009 - 0234 - 20132, National Emission Standards for Hazardous Air Pollutants (NESHAP) Maximum Achievable Control Technology (MACT) Floor Analysis for Coal- and Oil- fired Electric Utility Steam Generating Units for Final Rule ; “MATS MACT Floor Memos” ). That is, the EPA selected the best controlled EGU for the MACT floor analysis after ranking the EGUs based on their single best 3 - run test average. The EPA then incorporated any other data from the EGUs selected for the MACT floor anal ys is into the variability anal ys es. Issues related to the incorporation of variability were addressed at final (see , e.g. , RTC, Vol. 1, p. 662). The EPA recognizes that other approaches to selecting the best performing source exist, but the Agency

maintains that its approach is re asonable and consistent with the statute. The Commenter has not demonstrated that the Agency erred in calculating the final fPM limit using the approach for establishing MACT limits in the MATS rule. **Comment:** Commenter (20305) stated that the 30 - day rolling average was originall y developed to account for variability during periods of startup and shutdown, but EPA failed to explain in the final18

Rule why the standard was not made more stringent based on EPA ’ s decision to exclude periods of startup, shutdown, and maintenance from compliance calculations. **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding adjustments to the filterable PM standard based on exclusion during periods of startup or shutdown. In any event, the EPA disagrees with the Commenter’s suggestion that the 30 - boiler operating day rolling average was developed primaril y to account for vari ability during periods of startup and shutdown and that the emission limit should become more stringent when periods of startup or shutdown are excluded. Comments regarding variability were received after publication of the proposed rule, and those comment s were addressed at final. As mentioned in the RTC, the 30 - boiler operating day

rolling average was designed to incorporate a variety of sources of variability , including, but not limited to, load, operational, fuel, and CEMS use (see , e.g. , RTC, Vol. 1, p . 564) . Removal of just one component of potential variability in no way diminishes the other components of variability . The Commenter has provided no data or information to suggest that the possible variability associated with periods of startup and shutdown is sufficiently great such that a less robust variability analysis is necessary . In fact, the Agency did not have startup and shutdown data when developing the rule, so the impact of those periods on HAP emissions is unknown. The EPA explained its approach to assessing variability in the proposed MATS rule, and the Agency did not revise its approach to assessing variability in this reconsideration of certain new source MACT standards. See 76 FR 25041; EPA - HQ - OAR - 2009 - 0234 - 20062 (explaining the UPLanalysis). The EPA relies on the prior discussions of variability in the MACT standard setting process and further notes the following about the variability anal ys is in the MACT standard setting process. The EPA’s overall methodological approach to setting n ew source standards that reflect the “level of emission control achieved in practice” (CAA section 112(d)(3)) b y the best controlled source for each of the HAP at issue was reasonable. See Sierra Club v. EPA , 479 F.3d 875, 880 (D.C. Cir. 2007) (“EPA may no t deviate from section 7412(d)(3)’s requirement that floors reflect what the best performers actuall y achieve ... ”). When setting MACT floors, the EPA considers variability in operations in estimating the degree of emission reduction that has been achieve d by the best -performing sources . See Mossville Environmental Action Now v. EPA , 370 F.3d 1232, 1242 (D.C. Cir. 2004) (EPA may consider variability

of emissions of the best performing source when setting the MACT floor). However, the EPA has considerable discretion in determining the appropriate way to account for variability . See 370 F.3d at 1242. In this rulemaking, the EPA took multiple steps to account for variability in operations in estimating the degree of emission reduction that was achieved b y the best -performing source s. Variability

in performance comes from a number of causes. Run - to - run variability is variability

in each test, and includes uncertainties in c orrelation of monitoring parameters and emissions, and imprecision of stack test methods. Test - to - test variability results from varying efficiencies of control equipment over time (including variations in routine maintenance cycles), and is a longer- term variability. Additional sources of variable performance come from different level of HAP in raw materials, fuels, and other process inputs.19

The EPA assessed these ty pes of short - and long - term variability b y means of a statistical tool, an “Upper Prediction Limit” or “UPL” anal ys is which was applied to actual stack test data from the best performing sources. The UPLanal ys is is used in order to provide an appropriate margin for the variability

in a best performing source’s operations. The UPLanal ys is estimates what the upper bound of future values will be, based upon present or past s amples taken and specificall y estimates a level that future 3 - run stack averages from the best performing source would achieve 99 percent of the time. The UPLformula uses a pooled variance (in the s 2 term) that encompasses all the data -point to data -point variability

in the best performing source used to establish the MACT floor for each HAP. The UPL formula thus accounts for both short - term and long - term variability. See 76 FR 25041 - 48 ; EPA - HQ OAR- 2009 - 0234 - 20062. By appl ying this statistical tool, the EP A reasonably accounted for sources’ variability . S ee Kennecott v. EPA , 780 F.2d at 450 (upholding technology- based standards where long term limits were derived from short term data b y application of statistical procedures) . Next, to assure that a potenti al standard can be measured to a relative imprecision similar to that of EPA test methods reliably , the EPA compared the value resulting from the UPLanal ys is with the value equivalent to level 3 times the “Representative Detection Limit” (“RDL”) of the st ack test laboratory emissions measurement methodology for each pollutant. 76 FR 25044 . To identify the RDL, the EPA identifies the “method detection level” (“MDL”), which is the smallest quantity of a pollutant that can be accuratel y measured (i.e., that c an be distinguished from a reading of zero). The MDL for any EP A test method will vary

among testing contractors and the laboratories they use for any number of reasons (e.g., different testing equipment, sampling volumes, laboratory equipment, etc.). In o rder to determine the RDL , the EPA averages the MDLs from all individual tests from the best performing units to provide a reasonable representation of the level at which a competent testing contractor, along with its laboratory , can measure emissions. See EPA - HQ - OAR - 2009 - 0234 - 20062. The RDL thus accounts for intra - and inter - laboratory variability . As mentioned earlier, once it determined the RDL , the EPA multiplied the RDLby

a factor of three and compared that value (3XRDL) number to the value from the UPLcalculation. If the 3XRDLcalculation resulted in a value greater (i.e., less stringent, emissions wise) than the value resulting from the UPL calculation, then the floor was determined to be equivalent to the 3XRDLvalue. 76 FR 25044 . Finally , in order to provide regulated sources with a “more flexible and less costly alternative” for demonstrating compliance with the emission standards set in the MATS Rule (77 FR 9385) , the EPA allows sources to average their emissions, as measured b y a continuous emissions monitoring sy stem (“CEMS”) or, in the case of Hg , a sorbent trap monitoring s ys tem, over a rolling 30 - boiler operating day period. 1 77 FR 9371 , 9384 - 85. Thus, even if a source experiences a short - term spike in emissions, it will not necessaril y be deemed to have violated the applicable emissions limit so long as the 30 - day rolling average remains below the limit. The 30 - boiler operating day averaging period can thus effectivel y dampen short - term perturbations or upsets to the sy stem because a unit’ s emissions performance, averaged over 30 days, will not be as good as its single best performance within that time frame. However, increasing the averaging period beyond the duration associated with conducting a performance test (typically 3 hours) to 30 days normally makes a standard more lenient because there is more opportunity

to average out individual results.

1 Existing EGUs that use non - low rank virgin coal as fuel have the option of using a longer averaging period (90 - boiler operating days) coupled with a more stringent emissions limit (1.0 lb/TBtu or 1.1E - 02 lb/GWh) for Hg (see 40 CFR 63.10009(a)(2)).20

Therefore, the EPA’s use of the 99 th percentile UPL calculation, its comparison of the results of that calculation to the 3XRDL value, and th e 30 - boiler operating day emissions average compliance option adequatel y accounts for variability in the operations of the best performing sources identified for the MACT floor anal ys es for each HAP. **Best performing source Comment:**  Commenter (20293) stated that EPA is proposing to base the new source MACT floor for fPM on the performance of Springerville Unit 3, because that unit has the next lowest test run after the Dunkirk plant. The Commenter stated that at least five other EGUs in EPA ’ s data set have lower average emission test results and lower standard deviation than Springerville Unit 3. The Commenter stated that the Springerville Unit 3 test results average 1.91 x10 - 3 lb/MW with a standard deviation of 1.48 x 10 - 3 lb/MMBtu and a 99 th percentile UPLof 8.23 x10 - 2 lb/MW. The Commenter stated that Mercer Unit 2 ’ s average test results were 1.23 x10 - 3 lb/MW with a standard deviation of 6.68 x10 - 4 lb/MW and 99 th percentile UPL of 6.0 x10 - 2 lb/MMBtu. The Commenter stated that EPA ’ s estimate of the performance of the number two performing unit, at 6.0 x10 - 2 lb/MMBtu, is much higher than the 2.5 x 10 - 2 lb/MMBtu that the agency

would calculate as the average performance of that unit and the next higher emitting unit. **Response:** The EPA used the same approach for selecting the “best performing similar source ” in the proposed reconsideration as was used at proposal and final (see , e.g. , MATS MACT Floor Memos - Docket ID EPA - HQ - OAR - 2009 - 0234 - 9858 , Docket ID EPA - HQ - OAR - 2009 - 0234 - 2013 2 ). CAA section 112(d)(3) requires EPA to establish the new source limits based on the performance of the best controlled “similar source.” The statute does not define the term “similar source” and, for that reason, the Agency

has discretion to evaluate the sources for which the Agency has data and make a selection as long as the Agency has a reasoned basis for it selection. In this case, the EPA acknowledges that there are various approaches that can be used for selecting the “best performer,” including that noted by Commenter. However, for consistency the EPA has used the same approach as was used at both proposal and final

– i.e., ranking of sources based on their lowest 3 - run average. The EPA decided upon this approach of selecting the “best performing ” sources on the premise that the lowest 3 - run average was indicative of the best the source could perform; the additional data from the sources in the MACT floor pool were then used to assess variability . Issues with this approach were not raised in comment on the proposed MATS rule , and EPA did not open that issue for reconsideration in this rule . However, the Commenter also questions why the Agency

did not select other sources with a lower 3 - run average . As discussed in the final MATS MACT Floor M emo (Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132), there were situations for some pollutants from certain EGUs where only a single test average , and no individual run - level data , w as available for the EGU identified as the best - controlled source. In these cases, no emission variability could be determined based on a single data point. Therefore, the next best - controlled similar source with sufficient data to account for variability was used to determine the new source MACT . With the exception of the Stanton data s et noted elsewhere in this document, the EPA knows of no instance where an EGU with a lower single 3 - run average meeting the above criteria was not considered the “best performing similar source” for the MACT floor anal ys es.21

**Comment:** Commenter (20305) que stioned why the EPA has not gathered or examined PM continuous emission monitoring system ( CEMS ) data from the nearl y 100 plants with PM CEMS to determine what emission limits might be achieved on a 30 - day rolling average basis. The Commenter provided as an attachment PM CEMS data for two coal - fired electric generating plants reporting 30 - day rolling averages that are lower than the proposed new plant limits. **Response:** As a part of the 2010 I CR, the EPA required all coal - and oil - fired EGUs to provide all emission data gathered in the period January 1, 2005, to the issuance of the ICR itself. The EPA received no PM CEMS data through the ICR ; however, the EPA reviewed the provisions of three publicly available consent decrees (not among the data provided b y Commenter) that required the installation of PM CEMS on coal - fired EGUs. 2 , 3 , 4 The EPA notes that though the consent decrees require the companies to “ install , correlate , maintain , and operate PM CEMS , ” the consent decrees also state that each company “maintains that its agreement in this Consent Decree to install , correlate , maintain , and operate PM CEMS shall not prevent ... in any future proceedings from challenging the relationship between the data generated from such PM CEMS , including the averaging period for which such data is reported ... and the results of performance tests for PM ... ” or “ may attempt to demonstrate that it is infeasible to continue operating PM CEMS ... ” Thus, the CEMS data these EGUs would generate pursuant to the Consent Decrees would have been questionable from a reliability perspective and thus of limited utility in establishing MACT limits. Given the limited value of these three CEMS installations, the EPA does not believe that Commenter has provided any information that would lead us to believe the other data alluded to would be of any more use. Moreover, most, if not all, of the PM CEMS data were unavailable for rule - making review, because installation dates in most consent decrees that required PM CEMS were to o late to provide information in the timeframe necessary to develop the rule , and EPA did not undertake an additional information collection process prior to issuing the reconsideration notice . Concerning the data provided by the Commenter , the data w ere not certified by the EGU owner or operator as to being true, accurate, or complete , and, for that reason, the data were not considered as reliable as those data collected pursuant to the I CR . The EPA required EGU owners and operators to certify the data s ubmitted in response to the MATS IC R , and the EPA determined in the MATS rule that it was reasonable to consider only th ose data certified as accurate (or data the Agency could independentl y verif

y through, for example, review of test reports provided with the data) in the rulemaking effort, given the considerable certified data the EPA collected pursuant to the IC R . In addition, other data suggested by the Commenter as being available also has credibility concerns, as 2 Unite d States District Court , Eastern District of Kentucky , Central Division , Lex ington. United States of America , Plaintiff

, v. East Kentucky Power Cooperative , In c. , Defendant. Civil Action No. 04 - 34 - KSF. Consent Decree . 3 United States District Court for the District of Arizona. United States of America , Plaintiff , v. Salt River Project Agricultural Improvement and Power District , Defendant. Civil Action No. 2:08 - cv - 1479 - JAT. Consent Decree. 4 United States Environmental Protection Agency . In the matter of: T ennessee Valley Authority , 400 West Summit Hill Drive , Knoxville , Tennessee 37902. Allen , Bull Run , Colbert , Cumberland , Gallatin , Johnsonville , John Sevier , Kingston , Paradise , Shawnee , and Widows Creek Fossil Plants. Federal Facilities Compliance Agreement Between the United States Environmental Protection Agency and the Tennessee Valley

Authority . Docket No. CAA - 04 - 2010 - 1760.22

most owners or operators of EGUs subject to consent decrees were not required to install the PM CEMS according to PS - 11 requirements, and, as mentioned earlier, could challenge any data collected b y P M CEMS if the source questioned the validity of the data . Although it is possible that some value could be extracted from PM CEMS operated to provide indicator or trend information, the EPA decided that a mere collection of data with suspect quality assurance, suspect correlation to emissio ns of concern, and lack of certification is inappropriate for consideration in establishing MACT floors. Moving forward, as those PM CEMS are installed to meet PS - 11 and ongoing quality assurance criteria, and as compliance with those data are certified and reported, the EPA will be able to use those data in future rule reviews. **Comment:** Commenter (20265) stated that the EPA appears to have corrected errors by using all the available test results in setting the f PM standard. The Commenter pointed out that the data the EPA relied on in setting the re -proposed standard were obtained under well - controlled conditions. The Commenter concluded, however , the re -proposed emission limit could still be difficult to meet “ in practice, ” that is, under real - world operating conditions. **Response:** The EPA agrees that the fPM limit was established using all the data available for the best performing source and consistent with the statute . The Agency explained why its variability analysis is valid and accounts for different real - world operating conditions (see , e.g. , RTC, Vol. 1, pp. 493 - 496) . The EPA explained its approach to assessing variability in the proposed MATS rule, and further discussion is provided elsewhere in this document . **Comment:** Commenter (20305) stated that the EPA may not distinguish between sources based on the pollution control technology they employ . The Commenter ’ s concern was based on EPA elimination from consideration any best performing source that did not employ an advanced scrubber. The Commenter stated that CAA § 112(d) requires that MACT standards be set to reflect the performance actuall y achieved b y the best performer, however that performance is achieved, including through upgraded control technology . See Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855, 861 (D.C. Cir. 2001). The Commenter stated that for the same reason, the Act does not permit EPA to exclude sources from consideration as not “ similar” because they use different control technology . The Commenter provided discussion about the term “ similar source. ” The Commenter stated that a source may be discarded as dis - similar only if other sources are incapable of achieving its level of control because of differences in their design, capacity , or emissions. The Commenter stated that 40 CFR §63.41 does not permit the EPA to discard sources based on the control technology that they employ , and doing so would violate CAA §112(d). Commenter (20305) stated that the EPA provided no record evidence that sources empl oying state - ofthe - art scrubbers are not capable of achieving the PM emission reductions achieved by the best performing sources without such scrubbers. The Commenter stated that this rule does not present a situation where the Act could impose incompatibl e obligations. The Commenter stated that assuming arguendo that the Act would permit EPA to exclude best performers to accommodate other sources using control technology

that both 1) is required for compliance with another CAA requirement and 2) renders th ose sources incapable of achieving of the level of control of the best performer and the Commenter asserts that the Act does not permit EPA to do so where, as here, the record does not show, and EPA does not claim, that required controlled technology makes sources incapable of achieving of the level of control of the best performer. The Commenter observed that a contrary interpretation would violate CAA §112(d)(2) and §112(d)(3), because it would render the floor setting process under (d)(3),23

which does not even permit consideration of cost, even more accommodating of cost than section (d)(2), which does, but only

for the purpose of determining “the maximum degree of reduction in emissions . . . that the Administrator . . . determines is achievable[.] ” Comm enter (20305) stated that discarding sources without advanced scrubbers because some state - ofthe - art scrubbers can add PM to the flue stream is arbitrary . The Commenter stated that the EPA does not provide an explanation why there is sufficient reason to eliminate all sources without advanced scrubbers from consideration as the best performer for particulate matter. The Commenter stated that it is arbitrary

for EPA to discard data from best performers without determining whether sources with advanced scrubbers are achieving an emission level consistent with a standard based on the emissions of the best performer without an advanced scrubber. Commenter (20305) stated that at least two scrubbed EGUs are achieving lower fPM emissions than the unit selected as the “best performer” in EPA ’ s reconsidered proposal, and the Commenter provided stack test from those EGUs as attachments. Commenter (20293) stated that in regards to fPM for new oil - , coal - , and low rank virgin coal - fired EGUs, the EPA is proposing in its reconsideration to eliminate two plants, the Dunkirk and Martin Drake plants, as the best - performing EGUs on the basis that these plants do not employ a FGD for SO 2 control. The Commenter stated that this would only be relevant if FGDs consistently increased fPM emissions, which Commenter understands not to be the case. The Commenter stated that in many applications, the FGD is considered part of the PM control system as the wet spray captures a portion of the PM pres ent in the exhaust stream. The Commenter stated that the Martin Drake plant does not have any SO 2 control s ys tem and so, it is at least possible that the PM loading to the control device may be somewhat lower than if an FGD were in place. The Commenter stated that the Dunkirk plant employ s low sulfur coal and dry

spray and has the capability

to use activated carbon injection (ACI) enabling it to meet its Hg limit of 0.6 lb/TBtu in 2015. The Commenter stated that each of these technologies adds to the load that the PM controls must be capable of addressing. The Commenter stated that the PM control system at this facility

is a fabric filter system installed in 2009. The Commenter stated that there is no thing in the design of this sy stem that would warrant disqualifying it as a best -performing unit. **Response:** The EPA did not distinguish between sources based on the pollution control technology they employ . However, as noted in the final rule, the EPA be lieves it may consider both the ty

pes of EGUs likely to be built in the future and the regulations those EGUs would need to comply with in the selection of an EGU as the “best performing similar source ” (see , e.g. , 77 FR 9390; RTC, Vol. 1, pp. 441 - 446, 446 - 448, 590 - 593, 622, 623 - 624) . That is, the EPA determined it appropriate to select as the basis for the new source MACT limits an EGU that would be configured to comply with the NSPS (i.e., employ

a full suite of controls). The highest performing EGU meetin g these criteria was selected. Further, a s discussed in the final MATS MACT F loor M emo (Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132), there were situations for some pollutants where onl y a single test average and no individual run level data were available for the EGU identified as the best - controlled source. In these cases, no emission variability

could be determined based on a single data point. Therefore, the next best controlled similar source with sufficient data to account for variability was used to determine the new source MACT . With the exception of the Stanton data set noted elsewhere in this document, the EPA believes that all the other new source MACT floor anal ys es were based on the EGU with the lowe st single 3 - run average. The EPA believes that Commenter’s allegations that the EPA discarded sources24

without advanced scrubbers is misplaced as we did not eliminate from “consideration any best performing source” based on the fact that it did not employ an advanced scrubber. The data were sorted in the same manner as was done at MATS proposal and final and then the above criteria were applied. The Commenter s have provided no additional information or rationale that would cause the EPA to change its approach. The data Commenter provided related to “at least two scrubbed EGUs” that are “achieving lower fPM emissions” than the EGU selected as the “best performer” was insufficient for the EPA to conduct an anal ys is to confirm that allegation. The Commenter provided no process data for the tw o EGUs for the emission tests by

which the input - based data (lb/MMBtu) could be converted to the output - based format (lb/GWh) of the new source MATS limits. The Dunkirk EGU may , as Commenter notes, have the ability to use dry

spray injection and ACI but the information available to the EPA indicates that neither process was operational during the emission tests that were used for the 2010 I CR submittal and, thus, it could not be confirmed that this EGU was operating with the requisite full suite of control s . 2.1.2 Hydrogen Chloride (1.0E - 02 lb/MWh) **Monitoring Comment:**  Commenter (20261) stated that they are currently

evaluating continuous HCl monitoring technologies for their capabilities at or below the proposed emission limits for new coal plants. The Commenter described one of the most promising technologies, the in situ tunable diode laser (TDL). The Commenter stated that in a laboratory study conducted in 2011, detection limits of 1 ppm per meter of absorption path length were obtained, indicating that a cross - stack in situ TDLwould likely have a detection level of 0.1 ppm (approximately 0.0002 lb/MMBtu or 0. 002 lb/MWh), making the proposed limit for new coal EGUs of 0.01 lb/MWh measurable by these monitors. The Commenter listed similar studies of other technologies such as Fourier transform infrared (FTIR), non - dispersive infrared (NDIR), and Cavity

Ring - Down Spectroscopy (CRDS) that are underway . The Commenter concludes that there are insufficient data to suggest that continuous HCl monitors are either capable or reliable enough for compliance measurements on coal - fired applications at the proposed new source limits. The Commenter noted that until EPA finalizes PS - 18, it is unclear which technologies are viable candidates for application to coal - fired power plants. **Response:** The EPA appreciates the Commenter ’s participation in HCl monitoring technology evaluation and shares the Commenter ’s agreement that HCl CEMS based on one or more technology approaches will be able to measure emissions from coal - fired EGUs. Much ground has been covered since 2011, and while PS - 18, the performance specification for HCl CEMS, remains on track to be promulgated well in advance of the compliance date for existing EGUs, other compliance options such as use of SO 2 CEMS for EGUs equipped with flue gas desulfurization or quarterl y HCl testing are viable now. Owners or operators who are concerned about the availability or reliability

of HCl CEMS should choose from one of these other compliance approaches. In addition, if an owner or operator determines that a technology

different from the promulgated CEMS performance specification PS - 15 seems more appropriate for their HCl monitoring then application for an alternative HCl monitoring approach can be made under the general provisions for alternative test methods (see 40 CFR 63.7(f)).25

**Calculation of Standards Comment:**  Commenter (20293) stated that EPA identified the Logan Generating plant as the best performing new unit for HCl emissions on the basis of the single lowest test. The Commenter stated that the average tested emission rate at this unit was 1.87 x 10 - 4 lb/MMB tu and the standard deviation of the test results is 1.4 x 10 - 4 lb/MMBtu. The Commenter stated that the Walter Scott Energy Center unit, among others, showed better and less variable performance

– the average tested emission rate for this unit was 5.69 x 1 0 - 5 lb/MMBtu (5.14 x 10 - 4 lb/MWh) and the standard deviation of the test results is 1.79 x 10 - 5 lb/MMBtu (1.6 x 10 - 4 lb/MWh). The Commenter stated that application of EPA ’ s 99 th percentile UPL to the Walter Scott Energy Center test results yields a MACT fl oor of 5.8 x 10 - 3 lb/MWh, substantially

less than the proposed “beyond the floor” limit of 1.0 x 10 - 2 lb/MWh. **Response:** This issue is outside the scope of this rulemaking. The EPA specificall y identified the issues being proposed for reconsideration, inc luding use of all of the data when establishing the new source limits. The approach used in selecting the “best performing similar source” was not among the issues for which reconsideration was granted. As noted elsewhere in this document, the EPA used the same approach for selecting the “best performing similar source ” in the proposed reconsideration as was used at proposal and final. CAA section 112(d)(3) requires EPA to establish the new source limits based on the performance of the best controlled “similar source.” The statute does not define the term “similar source” and, for that reason, the Agency

has discretion to evaluate the sources for which the Agency has data and make a selection as long as the Agency has a reasoned basis for it selection. In this case, the EPA acknowledges that there are various approaches that can be used for selecting the “best performer,” including that noted by Commenter. However, the EPA determined its approach is reasonable and consistent with the statute and has used the same approach as was used at both proposal and final

– i.e., ranking of sources based on their lowest 3 - run average. The EPA decided upon this approach of selecting the “best performing” sources on the premise that the lowest 3 - run average was indicative of the best the source could perform; the additional data from the sources in the MACT floor pool were then used to assess variability . Issues with this approach were not raised in comment on the proposed MATS rule. In addition, the EPA has not been able to recreate or identify in the MACT floor spreadsheets the emission rates cited b y the Commenter . Those available to the EPA and used in the MACT floor anal ys es are identified in the MACT floor spreadsheet (see Docket ID EPA - HQ - OAR - 2009 - 0234 - 20220, attachment “UPL _Coal_HCl_Logan_111612”) .The Commenter has not provided sufficient information to resolve the differences. **Comment:** Commenter (20265) stated that the EPA appears to have corrected errors by using all the available test results in se tting the HCl standard. The Commenter said, however, it is still important to point out that the data EPA relied on in setting the re -proposed standard was obtained under well controlled conditions. The Commenter concluded, therefore, the re -proposed emission limit could still be difficult to meet “ in practice, ” that is, under real - world operating conditions. **Response:** The EPA appreciates the Commenter ’ s overall support. The issue of the use of short - term emissio n test data to establish 30 - day rolling average emission limits was addressed in the final RTC (see , e.g. , Vol. 1 , pp. 462 - 463 , 468 - 469, 494 - 496 , 500 , 549 - 551) and is outside the scope of this26

rulemaking . This issue was not one of the issues being reconsidered and the EPA did not solicit comment in the reconsideration proposal regarding the use of short - term data. In addition , the Agency also explained why

its variability

anal ys is is valid and accounts for different real - world operating conditions (see , e.g. , RTC, Vol. 1, pp. 493 - 496). The EPA explained its approach to assessing variability

in the proposed MATS rule, and further discussion is provided elsewhere in this document . 2.1.3 Sulfur dioxide (1.0 lb/MWh) **Calculation of standards Comment:**  Commenter (20246) stated the EPA needs to more fully account for operating and fuel variability

in setting achievable new source emission limitations . The Commenter said, in particular, the EPA is proposing a sulfur dioxide (SO 2 ) emission limit for controlling acid gases based on the emission rate achieved b y a single plant demonstrating 98 percent control efficiency during a testing sequence . The Commenter stated, i n applying 98 percent control, the EPA should account for all possible fuel and operating variability

that may occur across all ty

pes of new coal - fired plants. **Response:** The EPA has accounted for variability to the extent the EPA determined was reasonable and sufficient consistent with the requirements of CAA § 112. The incorporation of variability was addressed in the final rule (see , e.g. , RTC, Vol. 1, pp. 457 - 463). The Commenter has provided no data or other information to support its contention that the variability anal ys is is incorrect and the EPA maintains that the approach to accounting for variability is valid for the reasons set forth in MATS record. The EPA explained its a

pproach to assessing variability in the proposed MATS rule, and further discussion is provided elsewhere in this document . **Comment:** Commenter (20296) endorsed the EPA ’ s proposed revision of the SO 2 limit because the as adopted MATS rule new source SO 2 lim it was based on a facility that was only

25 MW in capacity. **Response:** This comment requires no response . **Available facility data Comment:**  Commenter (20305) stated that it is unlawful and arbitrary for EPA to not use the available data it has for some of the best performing EGUs in setting the SO 2 limit. The Commenter discussed as an example, the Stanton unit. **Response:** Commenter is correct in that the EPA inadvertentl y overlooked the Stanton Unit 10 data. In the final rule, the EPA used the Stanton data to calculate the MACT floor using the same statistical anal ys es used in the proposed rule (i.e., 99 percent upper predictive limit (UPL)), and the resulting MACT floor emission limit is 1.3 lb/MWh. Because this limit is less stringent than the new source performance standard (NSPS) finalized in the Utility NSPS (77 FR 9451; February 16, 2012), the EPA is finalizing a beyond - the - floor (BTF) MA CT standard of 1.0 lb/MWh, which is the same level required by the CAA section 111 NSPS for these same sources. See 40 CFR 60.43Da(l)(1)(i). As cost is a required consideration in establishing CAA section 111 rules and in going BTF in establishing CAA section 112 rules, we are adopting the cost evaluation of the NSPS. In any case, because the NSPS limit is in place and all new source coal - fired EGUs will be required to comply with that limit, there is no27

additional cost to these sources. Furthermore, we hav e not identified any non - air quality health or environmental impacts or energy requirements associated with the final standard set at this level. For these reasons, we are finalizing 1.0 lb/MWh as the new source MATS NESHAP limit, which is the same limit required for SO 2 emissions from for new coal - fired EGUs under the Utility NSPS. The CAA section 111 standard is based on the performance of EGUs with the best performing SO 2 controls, at a reasonable incremental cost effectiveness (over the NSPS requirement s in existence prior to the February 16, 2012, rule) of less than $1,000 per ton of SO 2 controlled, and controls that result in minimal secondary

environmental and energy impacts. **Comment:** Commenter (20293) stated that EPA set the new source SO 2 limits based on the performance of an EGU , but received a comment that this EGU is rated at 25 MW, and the regulations onl y appl y to EGUs whose capacity

is greater than 25 MW. The Commenter stated that EPA then chose the Sandow 5 Unit as its best performer, but that unit ’ s test results are highl y variable and the new source performance limit is well above permitted limits for several existing EGUs and has been met by 40 percent of existing EGUs . The Commenter stated that there appear to be at least six EGU s that have demonstrated substantially

better consistent performance than the Sandow Unit selected by EPA. The Commenter stated that these are the Gallagher, Coffeen, Stanton, AES Puerto Rico Units 1 and 2, Elm Road, and two Rio Bravo Poso units . The Commenter stated that the 99 th percentile UPLof one Rio Bravo Unit is 0.35 lb/MWh, whereas the other Rio Bravo unit ’ s 99 th percentile UPLis 0.38 lb/MWh. The Commenter noted that EPA states that it does not have run - level data for several of these EGUs , but this information is presumably

available to the agency . The Commenter noted that EPA Region 2 was the permitting agency for the AES Puerto Rico facility and presumably

has the initial NSPS performance testing, additional ongoing CEM data, and other emissions information needed to determine the performance of this unit. Commenter (20293) stated that the two AES Puerto Rico EGUs are subject to an SO 2 emission limit of 0.022 lb/MMBtu ( 3 - hour) limit, approximately equal to a 0.2 lb/MWh limit, whereas the Virginia City Hy brid Energy

Center is subject to a 30 - day limit at the same level. The Commenter stated that “ individual test information ” is at least as “ available ” as information obtained under EPA ’ s CAA § 114 information request and clearl y “ availab le ” to the agency where (1) the agency

is the permitting authority , (2) the permitting authority acts under a delegation from EPA, or (3) EPA has an interagency cooperative agreement. The Commenter stated that where individual run data are not available , the EPA must consider the performance of these EGUs in setting a new source MACT floor. The Commenter stated that the hourly CEM data in the record for the AES Puerto Rico EGUs show a 30 - day average SO 2 emission rate of 0.011 and 0.012 lb/MMBtu and a standard deviation of 0.009 and 0.007 lb/MMBtu. The Commenter stated that there are far more data available documenting the performance of these units than any other units in EPA ’ s data set and these units have complied with an SO 2 limit for over 10 years that is one - fifth the level proposed b y the EPA on reconsideration. Commenter (20305) stated that the proposed SO 2 limit does not reflect the performance of the best controlled similar source. The Commenter stated that the EPA ’ s own data identifies six better performing EGUs that have achieved SO 2 emission levels significantly below those achieved by the Sandow Unit 5 that EPA selected as the best performer. The Commenter stated that because CAA § 112(d)(3) unambiguously requires floors for new EGUs to reflect the emission level achieved b y the single best performing unit, the agency ’ s decision to exclude the top six EGUs from its floor anal ys is28

and base floors on the seventh best performing unit is unlawful. See Northeast Marylan d, 358 F.3d at 954 - 955; Sierra Club , 479 F.3d at 880. Commenter (20305) stated that the EPA ’ s rationale for excluding the Elm Road Generating Station is unlawful and arbitrary , because floors must reflect the emission level that the relevant best sources actuall y “ achieved ” not the levels EPA thinks are “ achievable. ” See , e .g., Sierra Club , 479 F.3d at 880. The Commenter stated that even if this approach was relevant to setting floors, which the Commenter disagreed with, the EPA has frequently used data fo r EGUs for which it has only one test to set floors and the agency

uses its UPLanal ys is to account for variability in such situations. The Commenter stated that the EPA does not explain why it cannot use the data for the Elm Road unit even though it has n ot hesitated to base other floors on the performance of EGUs for which it has only one emissions test. The Commenter stated that by treating similar situations differentl y without explanation , the EPA acts arbitraril y. Commenter (20293) stated that in determining the new source MACT floor for SO 2 , the EPA rejected low - emitting EGUs (LE Es) at Gallagher and Coffeen plants, as well as CEM data for AES Puerto Rico, because it did not have run - level data for those plants. The Commenter stated that the run - level data for Springerville 3 yi elds a UPLof 0.009 lb/MWh, but EPA decided to include additional testing, where run - level data were not available in its calculation. The Commenter stated that this resulted in an order of magnitude increase in the calculate d MACT floor. The Commenter stated that if one includes test results where run - level data are not available, this unit is not the best -performing unit. The Commenter stated that it appears that the Mercer 1 and 2 units are better performers. The Commenter stated that EPA should include in its anal ys is all EGUs where reliable emissions data are available and determine the variability

factor using a process that employ s a sufficient number of data points. Commenter (20305) stated that the EPA ’ s exclusion of five out of the top six performing EGUs based on its claim to lack “run - level ” data is also both unlawful and arbitrary . The Commenter provided five reasons: (1) CAA § 112(d)(3) requires EPA to base floors on the best performing unit, not the best performing unit for which EPA happens to have run - level data; (2) The EPA ’ s desire to use run - level data for variability anal ys is does not override the agency ’ s obligation to assure that its standards for new EGUs reflect the emission level actuall y achieved b y the single best performer. The Commenter stated that CAA § 112 requires floors to reflect the performance of the best performing unit, not the best performing unit for which EPA can perform a UPLanal ys is. (3) The EPA does not provide any explanation for excluding the top performing EGUs from its analysis just because it lacks run - level data for them. CAA § 112(d)(3) unambiguously requires floors for new EGUs to reflect the emission level achieved b y the single best performing unit . The EPA cannot avoid this statutory

duty just because it wishes to use a particular method to account for variability, UPL anal ys is, in setting floors. (4) The EPA has an obligation to make reasonable efforts to obtain emissions data for EGUs that are, by the ag ency ’ s own estimation, the best performing EGUs . If EPA does not have the run - level data for the29

best performers and believes that run - level data is necessary , it is EPA ’ s responsibility to obtain the run level data for those EGUs . (5) The EPA ’ s failure to provide a rational basis for not obtaining and considering run - level data from the six best performing EGUs identified b y EPA in setting the SO 2 limit for new sources is arbitrary and capricious. **Response :**  As noted elsewhere in this document, the EPA us ed the same approach for selecting the “best performing similar source” in the proposed reconsideration as was used at proposal and final. That is, the EPA selected the MACT floor pool of EGUs based on their lowest emission test result , ranking the EGUs on this lowest emission test result (the lowest emitting source becoming the basis for the new source limits provided the stated criteria were met), and then incorporated any other data from these floor EGUs (or single EGU in the case of the new source limit s) into the variability anal ys es. This approach included rejection, for the new source analysis, of any EGU selected as the “best performer” where there was onl y a single data set that did not include run - level data and that did not have additional data sets for inclusion in the anal ys es (“For the new source MACT floors, the best - controlled source was identified for which there were individual source test run data in the ICR data set.” 5 ). Variability anal ys es cannot be conducted on a single data point; therefore, if no individual run data were available, no variability

anal ys is could be conducted on an EGU. The EPA used data that were provided to it by the companies through the 2010 I CR. As a part of the 2010 ICR, the EPA required all coal - and oil - fire d EGUs to provide all emission data gathered in the period January 1, 2005, to the issuance of the ICR itself. The data noted b y Commenter were not submitted b y the company and, thus, were not made available to the EPA. Commenters have noted that the propo sed limits are less stringent than the permitted limits for “several existing EGUs.” However, Commenters did not provide the permits. In addition, for one of the EGUs cited by Commenter (20293) (i.e., AES Puerto Rico) the limit is for a 3 - hour period rather than for a 30 - day period and, thus, is not directl y comparable. Further, the EPA has data for the two AES Puerto Rico EGUs in the MACT floor data set; these data are actuall y lower (i.e., more stringent) than what Commenter reports as being the permitted level on an input basis (i.e., 0.00871 and 0.0090 lb/MMBtu vs. 0.022 lb/MMBtu). Commenter does not provide any process information with which the input - based limit (0.022 lb/MMBtu) can be converted to the requisite output basis for the new source standard s (i.e., lb/MWh) and the EPA does not find Commenter’s statement that this input- based permit limit is “approximately

equal to a 0.2 lb/MWh limit” convincing without supporting information. In addition, the two AES Puerto Rico EGUs fall at numbers 4 and 6 on the list of “best performers.” We have acknowledged elsewhere in this document that we are using Stanton Unit 10 as the basis for the new source limits; Stanton Unit 10 is number 3 on the list of “best performers” and, thus, takes precedence over the AE S Puerto Rico EGUs in our anal ys is. 6 The other EGU cited (Virginia City H ybrid Energy Center) did not begin commercial operation until July 2012, and, thus, its data were not available to the EPA.

5 See , e.g. , MATS MACT Floor Memos - Docket ID EPA - HQ - OAR - 2009 - 0234 - 9858, Docket ID EPA HQ - OAR- 2009 - 0234 - 20132 . 6 EGUs numbered 1 and 2 on the MACT floor list (Gallagher Unit 2 and Coffeen Unit 1) onl y provided a single data set and that data set did not include any individual run data.30

The EPA also does not agree that the approach for selectin g the best performing source suggested by the Commenter is mandated under the statute and the EPA maintains that its approach is reasonable. CAA section 112(d)(3) requires the EPA to establish the new source limits based on the performance of the best controlled “similar source.” The statute does not define the term “similar source” and, for that reason, the Agency

has discretion to evaluate the sources for which the Agency has data and make a selection as long as the Agency has a reasoned basis for it sele ction. In this case, the EPA acknowledges that there are various approaches that can be used for selecting the “best performer,” including that noted by Commenter. However, for consistency the EPA has used the same approach as was used at both proposal and final

– i.e., ranking of sources based on their lowest 3 - run average. The EPA decided upon this approach of selecting the “best performing” sources on the premise that the lowest 3 - run average was indicative of the best the source could perform; the additional data from the best performing source in the MACT floor for each standard was then used to assess variability in the new source limit anal ys es . Issues with this approach were not raised in comment on the proposed MATS rule. However, the Commenter ques tions why the Agency

did not select other sources with a lower 3 - run average. As discussed in the final MATS MACT F loor M emo (Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132), there were situations for some pollutants where onl y a single test average and no individual run - level data were available for the EGU identified as the best - controlled source (e.g., R. Gallagher Unit 2, Coffeen Unit 1). In these cases, no emission variability could be determined based on a single data point. Therefore, the next best - controlled similar source with sufficient data to account for variability was used to determine the new source MACT. With the exception of the Stanton data set noted elsewhere in this document, the EPA knows of no instance where an EGU with a lower single 3 - run avera ge and meeting the above criteria was not considered the “best performing similar source” for the MACT floor analyses. We also question C ommenters’ assertions that the permit data are a better reflection of the performance of the existing sources (which are used to establish the new source limits) as those assertions are not supported by

available data and commenters have not demonstrated that they are in fact a better representation (see , e.g. , RTC, Vol. 1, pp. 460 - 462 ) . The EPA may use permit information only if the permit information allows EPA to make a reasonable estimate of emissions. See Northeast Maryland Waste Disposal Authority v. EPA , 358 F.3d 936, 953 (D.C. Cir. 2004). We do not believe at this time that the permit information provide a reasonable estimate of emissions as they represent allowable emissions, and we have actual HAP emissions data on which to establish the standards. The data available to the EPA on Elm Road Unit 1 places it at number 5 on the list of “best performers.” As noted above, Stanton Unit 10 is number 3 on the list of “best performers” and, thus, takes precedence over Elm Road Unit 1 in our anal ys is. **Comment:** Commenter (20305) noted that the EPA has extensive continuously monitored data for SO 2 in the Clean Air Markets Data - base (CAMD). The Commenter stated that with that data, the EPA cannot discard potential best -performers based on lack of data. The Commenter discussed several facilities that have emissions below the proposed standard, and attached emissions information for those facilities. The Commenter stated that the EPA does not need to limit analysis to the stack tests provided by industry . The Commenter concluded that in light of the availability of the CAMD data, the EPA proposed approach using a stati stical sample and based on a constrained set of data is neither necessary nor legally

defensible.31

**Response:** The EPA opted to use the SO 2 data obtained through the 2010 ICR rather than data gathered through other means (including data available through CAM D) so as to be better able to correlate such data with the concurrently acquired HCl data (the EPA has discussed the Stanton data elsewhere in this document) . In developing the 2010 IC R, the EPA required EGUs to conduct concurrent HCl and SO 2 testing so as to be better able to correlate the data acquired. Such a comparison would not be possible between HCl data acquired through the 2010 ICR and SO 2 data acquired through the (e.g.) Acid Rain program. Therefore, the EPA opted not to use the Acid Rain database in its anal ys es. **SO 2**  **as a surrogate for HCl Comment:**  Commenter (20293) provided a graphic of the top 100 SO 2 emissions rates for coal - and low rank virgin coal - fired EGU ’ s. The Commenter stated that this figure demonstrates the wide disparity between the emission rate achieved b y the top 10 sources and the proposed rate on reconsideration. The Commenter stated that at the SO 2 emission levels that are now being proposed, it is not clear that SO 2 is a reliable surrogate for MACT level of control of hazardous acid gas emissions. The Commenter stated that EPA should provide an anal ys is documenting the relationship between the emission levels of the different pollutants at the proposed level of SO 2 control. Commenter (20300) stated that the EPA has not demonstrated that SO 2 is an adequate surrogate for inorganic acid gas HAP under the stringent standards set forth in Sierra Club v. EPA, 353 F.3d 976, 982 - 85 (D.C. Cir. 2004). The Commenter referred to their comments for the proposed MATS rule submitted in 2011 for discussion of the topic. The Commenter stated that SO 2 emissions from EGUs are poorl y correlated with HCl, and are not correlated at all with hydrogen fluoride ( HF ) or cyanide ( HCN) ; the precursors for acid gas emissions are not found in uniform proportions to sulfur in the coal used to fuel EGUs; and, as shown in the data EPA presented in the proposed MATS, FGD sy stems control emissions of HCl and HF at wildly

inconsistent rates. The Commenter further noted that because the reaction chemi stry that FGD s ys tems employ for SO 2 varies from that of HCl and other acid gases, a FGD system that is optimized for SO 2 removal is unlikely to achieve maximum removal of acid gas HAP. Moreover, the Commenter stated, FGD s ys tems are but one possible metho d for controlling acid gas HAP

— other methods include the use of low - chlorine coal, chloride prescrubbers, and the use of reagents specifically

targeted at neutralizing HCN. Commenter (20300) stated that the best - controlled EGU for SO 2 (Sandow) is only the eighth - best controlled for HCl

— and emits HCl at a rate almost twice that of the best - controlled EGU for HCl. The Commenter recommended that the EPA reconsider the use of SO 2 as a surrogate for acid gas HAP. **Response:** This issue is outside the scope o f this rulemaking. The issue of the use of SO 2 as a surrogate for acid gas HAP was addressed in the final RTC (see , e.g. , Vol. 1 , pp . 715, 717, 718 , 726 - 727, 758 - 761 ). The EPA did not solicit comment in the reconsideration proposal regarding the use of SO 2 as a surrogate. In addition, the Commenter maintains that the EPA must comply with a specific three -part test for surrogacy that the D.C. Circuit applied when evaluating whether PM was a valid surrogate for non - Hg metal HAP in another CAA section 112 standard. See Sierra Club v. EPA , 353 F.3d 976, 984 (D.C. Cir 20 04) (“this court established a three -part anal ys is for determining whether the use of PM as a surrogate for HAP is reasonable...”). However, the EPA maintains that the only standard from that case that32

expressly applies to the EPA’s establishment of a surrogate standard for acid gas HAP is that the surrogate be reasonable. We maintain that HCl and SO 2 are reasonable surrogates for all acid gas HAP when the unit is using a flue gas desulfurization technology to compl y with the surrogate standard. The EPA maintains in the MATS rule that the control of the surrogate (in this case HCl or SO 2 ) also indiscriminately

captures the air toxic acid gases along with the surrogate (see , e.g. , 76 FR 25014, 25023 , 25039, 25040 ) . The EPA explained that, based on the known chemical and phys ical properties of the compounds, ty

pical flue gas desulfurization systems (e.g., wet scrubbers, dry scrubbers, dry

alkaline sorbent injection) will effectivel y reduce the emissions of the acidic gas HAP. The emissions of all of the acid g as HAP will be reduced due to their solubility or their acidity

(or both) (see , e.g. , 76 FR 25014, 25017; RTC, Vol. 1, p. 717, 758

– 761) . 2.1.4 Le ad (3.0E - 02 lb/GWh) **Comment:** Commenter (20293) stated that in determining the new source lead (Pb) limit for coal - or low rank virgin coal - fired EGUs , the EPA had selected the Weston unit as the best -performing unit. The Commenter stated that on reconsideration , the EPA has included a test result that is 60 times greater than the test that it used to identify this unit as a best -performing unit. The Commenter stated that it appears that the Dallman unit is a far better performer in that data set because its average emiss ion rate is close to that of the Weston unit, but the test - to - test variability is far less. The Commenter stated that these data also show that a number of other sources have apparentl y identified highly differing test results. The Commenter stated that Fi gure 4 (refer to Docket ID EPA - HQ - OAR - 2009 - 0234 - 20293 - A2) sets out the lowest emission rate for each of the EGUs in EPA ’ s data set and also shows the additional test results for the unit. The Commenter stated that the Logan Unit, is the #11 source in this figure. The Commenter stated that the 75 - fold increase in fPM emissions during a 2005 stack test was accompanied by a 238 - fold increase in Pb emissions. The Commenter stated that these results are of concern as they may suggest that (1) even EPA ’ s proposed reconsidered limit cannot be consistently met by well - controlled EGUs or (2) annual Reference Method testing will not provide a reasonable assurance of compliance with (any) limit. The Commenter stated that these results may reflect the fact that permitte d PM control limits often provide a substantial compliance margin for such EGUs and the higher emission levels may not reflect the full performance of the unit. The Commenter recommended that EPA examine this issue in more detail before acting on its propo sed reconsideration limits. **Response:** As noted elsewhere in this document, the EPA used the same approach for selecting the “best performing similar source ” in the proposed reconsideration as was used at proposal and final. That is, the EPA selected the MACT floor pool of EGUs based on their lowest emission test result and then incorporated any other data from these floor EGUs into the variability analyses. The EPA used the data provided b y the companies through the 2010 ICR in conducting the anal ys es . The EPA note s that the individual HAP metal limits are an alternative compliance option and we do not expect many EGUs to use that approach to demonstrate compliance given that the costs of measuring individual metal will far exceed the other compliance op tions (e.g., total HAP metals, fPM). The EPA acknowledges that there are various approaches that can be used for selecting the “best performer,” including that noted by Commenter. However, in part for consistency with the initial MATS rulemaking, the EPA has used the same approach as was used at both proposal and final

– i.e., ranking of sources based on their lowest 3 - run average. The EPA decided upon this approach of selecting the33

“best performing” sources on the premise that the lowest 3 - run average was indicative of the best the source could perform; the additional data from the sources in the MACT floor pool were then used to assess variability . I ssues with this approach were not raised in comment on the proposed MATS rule even though the issue could h ave been raised . **Comment:** Commenter (20293) stated that EPA ’ s proposed new source MACT limit for Pb for coal and low rank virgin coal - fired EGUs (3.0 x 10 - 2 lb/GWh) is higher than the adopted existing source limit for this category

(2.0 x 10 - 2 lb/GWh) an d remains unchanged b y this proposal. The Commenter stated that in the past , the EPA has used the agency ’ s “beyond the floor authority” to establish a new source limit that is at least as stringent as the limit applicable to existing sources, but does not propose to do so in this rulemaking. Commenter (20298) stated that the Pb limit for coal - fired EGU and the filterable PM limit for liquid oil (continental) - fired EGU are too lenient and less stringent that the applicable limits on the existing EGUs . The Commenter stated that the problem is that EPA uses the variability in performance of each individual unit where sufficient data do not exist. According to the Commenter , the EPA ’ s approach estimates the variability

of the unit that is a function of the limited number of tests rather than the variability

that one would expect from the combustion technology and fuel, which leads to erroneous results such as the calculation of new source MACT floor that are higher than the existing source MACT floor. The Commenter recommended that EPA develop a variability factor based on the variability in performance of a larger data set comprised of EGUs employing similar designs. Such an evaluation would be based on all relevant information, including engineering information, continuous emissions monitoring data and the variability in performance of EGUs of similar design. **Response:** The EPA has adjusted the limit proposed in the reconsideration notice to the more stringent level of the existing - source limit in this final rule for the reasons set forth in the record (see , e.g. , final MATS MACT Floor Memo, Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132

– “Additionally , similar to the approach used in the HMIWIrulemaking, if the emission limit for new sources was less stringent than the emission limit for existing sources in the same subcategory , the EPA decided to use existing source limits for new sources . ” ). Although CAA section 112(d)(3) allows existing source MACT floor limits to be less stringent than new source limits, the EPA interprets this provision as precluding new source limits from being less stringent than existing source limits. See CAA secti on 112(d)(3). Further, in this specific instance, the data support setting the new source limit being equivalent to the existing source limit. Thus, the EPA is finalizing new source limits that are equivalent to the final existing - source limits. The new so urce limit for Pb from coal - fired EGUs has been corrected to the existing - source limit of 2.0 x 10 - 2 lb/GWh . 2.1.5 Selenium (5.0E - 02 lb/GWh) **Comment:** Commenter (20293) stated that EPA had selected the Logan Generating Station as its best performing unit for selenium on the basis of the lowest single run even though other EGUs in its data set had lower average emissions. The Commenter stated that EPA was then informed of an earlier test result reporting an emission rate 75 times higher than the testing conducted in response to the agency ’ s survey . The Commenter stated that such variations in performance are not expected in properl y functioning PM control systems, and so , the EPA should contact the source and the appropriate permitting authority to determine the circumstances surrounding this test. The Commenter stated that if the earlier test result is34

representative of the current controls and operations at the Logan Generating Station, it would be appropriate for EPA to consider this data and determine that the emissions performance of this unit is not as good as it had previously appeared. The Commenter stated that this should also be accompanied by a determination that this unit is not the best -performing unit in the set. Commenter (20293) stated that the average emission test result for this EGU now ranks 70 th out of approximately

200 test results in EPA ’ s data set. The Commenter stated that because the newl y considered test result is so much greater than the initial result considered , the EPA ’ s 99 th percentile UPL calculation generates a result that is exceedingly high

– substantiall y higher than the top 100 test results in the data set. The Commenter stated that a single test run is not the appropriate measure of the best performing EGU . The Commenter stated that where EPA receives credible information that a particular EGU is not the best -performing EGU , the EPA should look to o ther well performing EGUs rather than simply recalculating the emission rate for the EGU it had thought to be the best -performing EGU . Commenter (20293) stated that Figure 3 (refer to Docket ID EPA - HQ - OAR - 2009 - 0234 - 20293 - A2) sets out the emission rate in lb/MWh for each of the top 100 results in EPA ’ s data set, the final limit and the limit as proposed on reconsideration. The Commenter stated that these data show how much higher the added Logan test result is than what was routinel y demonstrated b y the better performing EGUs and that the proposed increase is unwarranted . The Commenter stated that 135 of the 260 EGUs in EPA ’ s data set have demonstrated that they can meet EPA ’ s proposed limit for new sources **Response:** As noted elsewhere in this document, the EPA used the same approach for selecting the “best performing similar source ” in the proposed reconsideration as was used at proposal and final. The EPA acknowledges that there are various approaches that can be used for selecting the “best performer.” In addition, the EPA conducted standard outlier analyses on the data in the MACT floor pool (see , e.g. , Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132). That is, the EPA selected the MACT floor pool of EGUs based on their lowest emission test result and then incorpo rated any other data from these floor EGUs into the variability

analyses. CAA section 112(d)(3) requires EPA to establish the new source limits based on the performance of the best controlled “similar source.” The statute does not define the term “similar source” and, for that reason, the Agency

has discretion to evaluate the sources for which the Agency has data and make a selection as long as the Agency has a reasoned basis for it selection. In this case, the EPA acknowledges that there are various approaches that can be used for selecting the “best performer,” including that noted by Commenter. However, for consistency the EPA has used the same approach as was used at both proposal and final

– i.e., ranking of sources based on their lowest 3 - run average. The EPA decided upon this approach of selecting the “best performing” sources on the premise that the lowest 3 - run average was indicative of the best the source could perform; the additional data from the sources in the MACT floor pool were then u sed to assess variability . Issues with this approach were not raised in comment on the proposed MATS rule. Further, the EPA would note that the data submitted by each 2010 I CR respondent were certified and did not violate the standard outlier anal ys es perf ormed during the MACT floor anal ys es. 2.2 New coal - fired unit, not low rank virgin coal 2.2.1 Mercury

(3.0E - 03 lb/GWh)35

**Monitoring Comment:**  Commenter (20261) stated that they conducted two evaluations of continuous Hg monitors (CMMs) on a pilot combustor to quantify low level Hg measurement capabilities. The Commenter discussed the results of these tests. The Commenter stated that the results of the study showed that depending on the instrument used, the quantitation level may be slightl y above or below the proposed limit for new coal EGUs > 8,300 Btu/lb of 0.003 lb/GWh. The Commenter observed that due to the proximity of these quantitation levels to the proposed limit, facilities are likely to choose sorbent tubes rather than CMMs for compliance monitoring purposes. The Commenter expressed concern over the ability to maintain the certification of CMMs at such low levels given the lack at this time of NI ST traceable standards at that level. The Commenter concluded that at present, due to instrument drift, lack of low - level standards, and the need to maintain a safety margin between emissions and the limit, CMMs are not sensitive enough for monitoring compliance at the proposed limits for coal EGUs > 8,300 Btu/lb or at the MATS rule limits for liquid oil. The Commenter stated that sorbent tubes have the sensitivity

required for coal EGUs (with a higher flow rate as discussed earlier), but cannot provide the real - time process control feedback that facilities need to adjust op erating conditions for compliance with emissions limits. The Commenter stated that for effective process control using a CMM, the emissions limit would have to rise above the currentl y proposed 0.003 lb/GWh. Commenter (20265) stated that the EPA ’ s methodo logy for setting the Hg standard appears to be a step in the right direction to the extent a sorbent trap monitoring system is used to determine compliance. The Commenter noted that although EPA states that utilities also have the option to determine compl iance with the Hg limit using a CEMS, CEMS technology is not capable of reliably measuring Hg emissions at the level of the re -proposed standard, as other comments show The Commenter stated that the level of the Hg standard would need to be increased for s ources to realistically use CEMS to measure emissions and adjust emission controls to maintain compliance with a standard. **Response:** If f

or a particular EGU , an owner or operator believes that a Hg CEMS cannot achieve the performance requirements needed to satisfy the final standards, the owner or operator may elect to install and use a sorbent trap monitoring s ys tem to monitor for continuous compliance. Moreover, in order to better track emissions and allow process control during transitional periods, such as load swings, an owner or operator may choose to use a more frequent sampling period, e.g., 30 minutes, instead of several days, over short periods. An owner or operator is also free to use a Hg CEMS for control operations and use the sorbent trap monitoring for compliance if he feels that such operational data is sufficientl y critical to the EGU ’ s control operations. As noted in the Reconsideration proposal, the EPA believes the proposed change in th e non - low rank virgin coal Hg limit for new EGUs will also allow the option of using a Hg CEMS for process control and for determining compliance based on information provided b y the Commenter s, our experience, and the National Institute of Standards and T echnology ’ s (N IS T) recently confirmed capability

to certify Hg calibration gas generators down to 0.2 micrograms per cubic meter ( μg/ m 3 ) . 7 **Comment:** Commenter (20268) expressed support of a shorter sampling period.

7 See Status 0.2 μg/m 3 Hg Reference Gas for Compliance Monitoring in rulemaking docket EPA - HQ OAR- 2009 - 0234.36

**Response:** The EPA is finalizing the allowance for shorter sampling periods . **Comment:** Commenter (20268) expressed support for the option of using CEMS for monitoring Hg compliance. The Commenter noted that for process control and optimization of Hg control, onl y a certified electronic (i.e. , real - time) Hg CEMS can provide the feedback information quickly enough to respond to critical changes impacting Hg emissions. **Response:** As noted in response to other comments, an EGU owner or operator can use an Hg CEMS for compliance, or an EGU owner or operator is free to use a Hg CEMS for control operations and use the sorbent trap monitoring for compliance or the sorbent trap monitoring alone for shorter time periods if it feels that such operational data is sufficientl y critical to its control operations. The EPA maintains that these shorter sampling periods will allow sources to obtain the information quickly enough to respond to changes that may affect Hg emissions, contrary to the Commenter’s statements. **Comment:** Commenters (20258 and 20293) state d that EPA ’ s calculation of the Hg MACT floor is based on several assumptions about how sources in the future may choose to monitor the ongoing performance of their EGUs in lieu of the actual documented performance of the best EGUs . The Commenter s stated that these assumptions are unsupported and unrealistic and bear no relationship to the performance of the unit. The Commenter s also suggested that the se assumptions concerning which ty pe of Hg monitoring approach

– Hg CEMS or sorbent trap monitoring s ys tems

– would be used are unrelated to the compliance demonstration required by the final rule. The Commenter s asserted that EPA ’ s assumptions result in a proposed limit that is 100 times greater than the measured performance of the best unit and 15 times greater than would be calculated using EPA ’ s procedure for assigning variability

to the performance of that unit. **Response:** The EPA disagrees with the Commenters’ assertions that an EGU owner or operator may choose either Hg CEMS or sorbent trap monitoring s ys tem without regard as to how frequently reliable data can be provided seem incorrect. As explained in the Segall and Parker memo, 8 the EPA agreed with the concerns of other commenters who wanted to be able to use sorbent trap monitoring systems to provide data on a more frequent basis, so that issues with emissions control equipment or plant operation could be adjusted more quickly than under traditional uses which involved longer sampling periods. Such frequent monitoring sample collection and an alysis, coupled with EGU owner or operation action to return equipment or processes to normal operation, would minimize Hg emissions and is consistent with the EPA’s goals of vigilance and quick corrective action when necessary . The EPA notes that that mem o has been revised based on comments received to clarify that the calculation relies on 30 minutes of sampling time. The memo continues to explain how the shortest reasonable amount of time for sample collection using a Hg sorbent trap monitoring s ys tem wa s determined. Namel y, that the 3XRDL value is calculated using the average of the method detection levels (MDL) identified from the best performing EGUs, and that 3XRDLvalue is then included in calculations using the shortest reasonable amount of time

– 4 0 minutes - available for collecting and changing sorbent tubes. This amount of time addresses industry

concerns that quick, reliable feedback may be needed for brief durations to ensure proper control device operation during certain operational periods. Rather than being unsupported, 8 Determination of Representative Detection Level (RDL) and 3 X RDL Values for Mercury Using Sorbent Trap Technology” ( Docket ID EPA - HQ-OAR - 2009 - 0234 - 20222).37

unrealistic, and unrelated, the emissions limit determined from the 3XRDL value and a 30 - minute sample collection time, coupled with recentl y confirmed calibration gas generator capability, will allow companies not only

to pro vide commercial guarantees but also to provide a value whose estimated measurement imprecision is comparable to that documented in ASME’s ReMAP study . 9 **Support for proposed standard Comment:**  Commenter (20268) expressed full support of the proposed Hg standard for new coal fired EGUs burning non - low rank coal. The Commenter discussed the standard, and agreed that a change from the final rule will not change the air pollution control equipment configurations and choices that will be made to comply

with the revised standard as Hg reductions will still be greater than 97 percent . The Commenter supplied a table showing the emissions control equipment being used for recently- built coal - fired power plants to show that these configurations represent essentially all of the commercially available equipment and technologies available for limiting Hg emissions. The C ommenter stated that the proposed revised limit combined with the recently confirmed capability of NI ST to certify Hg calibration gas generators down to 0.2 μg/m 3 will allow its member companies to provide commercial guarantees, and allow sources to continuously monitor emissions which is necessary to ensure compliance with the 30 - day rolling average Hg emission limit. Commenter (20279) supported the proposed increase in the emission limit for Hg for new coal - fired EGUs designed for non - low rank virgin coal. The Commenter stated that the original limit, as finalized, was too low for emissions to be reliabl y measured. The Commenter noted that the increased limit would improve owners ’ and operators ’ ability to track emissions and ensure compliance. Commenter (20269) supported the increase in the Hg emission limit for new coal - fired EGUs designed for non - low rank virgin coal. The C ommenter noted that the original limit was too low for emissions to be reliabl y measured. **Response:** The EPA acknowledges the Commenter’s support. Please see section IV of the preamble to the final reconsideration rule for further discussion of EPA’s basis for finalizing these limits. **Comment:** Commenter (20284) was pleased that EPA has proposed to reconsider certain new source MATS limits . The Commenter appreciated that EPA has recognized the need to consider all of the data collected in the Information Collection Request as a basis for determining the appropriate level of the emissions standards for the regulated pollutants. The Commenter noted that it now appears there are several sources that have demonstrated, through short term emissions testing, that they are able to achieve the emission rates that have been proposed. However, the Commenter stated these sources achieved the proposed emission rates under the best operatin g conditions possible and that long term on going compliance will still prove to be challenging during regular operation of the EGUs . Commenter (20284) supported the proposed revisions to the emission standards for new EGUs because they are more achievable and may allow new unit developers to better consider the construction of new coal - fueled EGUs. However, the Commenter urged EPA to fully consider the ability

of these new sources to continuously

demonstrate compliance with the proposed emission limits over the long period 9 Docket ID EPA- HQ - OAR - 2011 - 0817 - 0225.38

of time that they

will operate. The Commenter discussed the limitations of CEMS and carbon (i.e., sorbent) trap s ys tems. The Commenter noted that CEMS cannot reliably measure Hg emissions at the 3.0 x 10 - 3 lb/GWh level of the proposed standard, and a carbon trap s ys tem does not provide real - time feedback on a unit ’ s level of Hg emissions, which the Commenter believes it is important for Hg control. The Commenter stated it is impractical to conduct 30 - minute sorbent trap runs as EPA assumed in setting the new source Hg limit. The Commenter stated that the Hg standard for new EGUs should be adjusted to provide EGUs with the true option of demonstrating compliance using either a Hg carbon trap system or a Hg CEM S. The Commenter stated that increasing the new source Hg limit would allow EGUs flexibility

in showing continuous compliance with the standard in real time and improve the long term viability

of construct well controlled, high efficiency and high technolo gy

coal EGUs . Commenter (5803) expressed concern regarding the ability to accuratel y measure emissions (specifically Hg ) at the Reconsideration ’ s propo se d levels. **Response:** As mentioned earlier, if f or a particular EGU , an owner or operator believes that a Hg CEMS cannot achieve the performance requirements needed to satisfy the final standards, the owner or operator may elect to install and use a sorbent trap monitoring s ys tem to monitor for continuous compliance. Moreover, in order to bett er track emissions and allow process control during transitional periods, such as load swings, an owner or operator may choose to use a more frequent sampling period, e.g., 30 minutes, instead of several days, over short periods. The EPA notes that a 30 minute sample collection period, coupled with a 10 minute period for sorbent tube insertion and removal, is the shortest reasonable period for sorbent tube cycling, especially for brief durations lasting fewer than one or two days; such a collection frequenc y may prove arduous, but achievable, b y persons desirous of such information. Although sampling over such brief periods may provide relevant information, it is not necessary to meet the 30 - (or 90 - ) boiler operating day rolling average contained in the rul e. An owner or operator is also free to use a Hg CEMS for control operations and use the sorbent trap monitoring for compliance if it feels that such operational data is sufficiently critical to the EGU ’ s control operations. As noted in the Reconsideration proposal, the EPA believe s the proposed change in the non - low rank virgin coal Hg limit for new EGUs will also allow the option of using a Hg CEMS for process control and for determining compliance based on information provided by the Commenter s, our experience, and the NI ST ’ s recentl y confirmed capability to certify Hg calibration gas generators down to 0.2 μg/ m 3

. The Commenter s have provided no data or information to suggest that the available compliance demonstration methodologies are inadeq uate. **Calculation of standards Comment:**  Commenter (20286) expressed concerns about this emission standard ’ s feasibility . The Commenter stated that although the EPA ’ s MACT anal ys is data for the proposed revision to the Hg emission standard for new coal - fired EGUs designed to burn coal with ≥ 8,300 Btu/lb indicates that 62 EGUs would be able to comply with the proposed Hg standard of 0.0030 lb/GWh, the Hg emissions data that the EPA is relying upon is based on relativel y short term testing. The Commenter stated that in many cases (approximately

70 percent of the EGUs ), the results are based on a single test series. The Commenter is concerned that even a newl y constructed EGU and in particular a reconstructed EGU may not be able to reliabl y meet the proposed Hg emission standard given the significant variability that can occur in Hg emissions from a coal - fired EGUs, and the Commenter stated that EPA ’ s own test data demonstrates the variability that can occur in Hg emissions. The Commenter stated that th e EPA39

excluded many EGUs from the EGUs considered to meet the proposed standard due to this variability. The Commenter provided examples of the variability in Hg emissions from EPA ’ s data. **Response:** This issue is outside the scope of this rulemaking. The issue of the use of short - term emission test data to establish 30 - boiler operating day rolling average emission limits was addressed in the final RTC (see , e.g. , Vol. 1 , pp. 462 - 463 , 468 - 469, 494 - 496 , 500 , 549 - 551). This issue was not one of the is sues being reconsidered and the EPA did not solicit comment in the reconsideration proposal regarding the use of short - term data. In any case, the Agency maintains that the approach to accounting for variability is valid for the reasons set forth in MATS record. The EPA explained its approach to assessing variability

in the proposed MATS rule, and further discussion is provided elsewhere in this document . Further, the EPA believes Commenter is misguided in focusing on any “ alleged” exclusions from the anal ys es. By

statute, the new source MACT is to be based on the “best performing similar source ” (singular) and, thus, may

in fact be met by

onl y one source within the population of sources. The fact that 62 EGUs have demonstrated the ability to achieve the level of the standard indicates that the limit has adequately addressed consistent with the statute. In addition, the proposed limit is based on use of the 3XRDL approach (see , e.g. , 77 FR 71326) which is a higher (less stringent) number than the calculated limit and, therefore, we maintain the final limit provides a sufficient margin to address variability of the emissions . **Comment:** Commenter (20286) stated that an analysis of the EPA ’ s Hg MACT anal ys is data for coal fired EGUs indi cates an inherent bias towards FBC EGUs . The Commenter stated that of the 38 FBC EGUs included in the entire data set, 58 percent (22 EGUs ) are in the group that the EPA considers as meeting the proposed standard. The Commenter stated that approximately 90 percent of those 22 FBC EGUS are less than 25 percent of the proposed standard. The Commenter stated that of the 347 conventional boilers in the data set, only 12 percent (40 EGUs ) are in the group considered to be meeting the standard. The Commenter st ated that the Hg emission performance of coal-fired FBC EGUs is in contrast to the emission performance of FBC EGUs for acid gases. The Commenter stated that approximately 20 percent of the FBC EGUS in the respective data sets would be considered as possib ly meeting the HCl and SO 2 standards for coal - fired EGUs. The Commenter also stated that this analysis indicates a performance difference in Hg emissions between FBC EGUs and conventional boilers. The Commenter stated that the EPA should reanalyze the Hg MACT floor for coal - fired EGUs with separate categories for FBC EGUs and conventional boilers to ensure that the standard is achievable as required by CAA § 112. **Response:** This issue is outside the scope of this rulemaking. Subcategorization was addressed in the final rule (see , e.g. , 77 FR 9378 - 9379, 9394 - 9402). The EPA did not solicit comment in the proposed reconsideration rule on additional subcategories, including subcategorizing FBC EGUs. The specific issue of alleged “ overrepresentation ” of FBC E GUs in the database was also addressed at final (see , e.g. , RTC, Vol. 1, pp. 358 - 365). Commenter asserts that FBC units are disproportionately represented among the best performers for Hg . However, FBC EGUs were not specifically selected in the 2010 I CR as best performers for Hg, as the40

EPA did not select any EGUs based on a determination that they were best performers for Hg, and to the extent CFB units were selected in the 2010 ICR, they were selected because we determined they were best performers for non - mercury metallic HAP, acid gas HAP, or organic HAP or because they were randomly selected among the non - best performers for those three HAP groupings. Thus, the FBCs were selected for testing under the 2010 I CR based not on their boiler design but, rather, based on the age and on their PM and FGD control sy stems. As many FBC EGUs are relativel y new, they were included in the non - mercury

metallic HAP group selected for testing (because their PM controls were among the 175 newest) and the acid gas HAP group selected for testing (because FBC was considered to be an FGD s ys tem and the units were among the 175 newest). Although FBC units may be found among the better performers (among the top 10 EGUs) on the Hg MACT floor spreadsheet, they are also found in the range of 221 to 226 EGUs (of 393 data points). Thus, the EPA disagrees that FBC units are disproportionately represented in the Hg floor and that their inclusion is somehow inappropriate or leads to skewing of the anal ys is. FBC EGUs are not an excepti on and such EGUs are found across the range of top performing EGUs for all of the HAP categories. **Comment:** Commenter (20286) stated that the EPA indicates that “ at least eight existing non - low rank virgin coal - fired EGUs and one low rank virgin coal - fired EGUs have reported short - term stack test data that demonstrate that these EGUs have in practice achieved the new source limits proposed” (77 FR 71329). The Commenter stated that the EPA does not identify these EGUs to allow Commenter s to evaluate the validity

of this claim nor does the EPA explain whether these EGUs literally meet all of the emission standards applicable to the EGU including the primary pollutants and surrogate standards (e.g., meet the f PM standard, total non - mercury metal HAP standard, and each speciated non - mercury metal HAP standard) or if the EGUs would only be able to meet the rule requirements via surrogate standards. **Response:** As Commenter has indicated, we note in the reconsideration proposal that there are a number of existing coal - fired EGUs whose test data available to the EPA at the time of rule development demonstrate that these EGUs have in practice achieved the new source limits proposed in this notice (considering all of their submitted data) . In the reconsideration proposal notice, the EPA indicated that “based on our review of the data EPA collected as part of the 2010 In formation Collection Request ( IC R) process, at least eight existing non - low rank virgin coal - fired EGUs and one low rank virgin coal fired EGU ” in this category meet the new source limits for Hg, PM, and HCl (see 77 FR 71329) . Because this anal ys is was based on a review of the same 2010 ICR data available to the public (and, thus, the analysis could also have been done by the public), the EPA did not identify these EGUs. Further, the statute does require that any source be able to achieve the level of all the new source limits as the Commenter s imply . However, the EPA conducted the analy sis as one means of indicating that the new source limits are reasonable. The nine EGUs that have short - term stack test data that demonstrate that these EGUs have in practice achieved the new source limits for Hg, PM, and HCl are: Lo gan Unit 1 Elm Road Unit 1 Clover Units 1 and 2 Chambers Units 1 and 1 Mount Tom Unit 1 H.L . Spurlock Unit 3 Sandow Unit 5A41

These EGUs all meet the Hg, fPM, and HCl or SO 2 limits with all of the data available to the EPA at the time of rule development. Sources meeting these limits or alternate limits are meeting the standards so there is no need to evaluate the other alternate standards. **Comment:** Commenter (20293) stated that in the EPA ’ s memorandum describing how it arrived at the proposed Hg limit for new coal - and low rank virgin coal - fired EGUs, the EPA sets out th e formula and each of the values that it employs to calculate the MACT floor. The Commenter stated that the EPA does not report the actual results of the calculation, rather that “when rounded, ” this calculation results in a limit of 3.0 x 10 - 3 lb/GWh. The Commenter stated that when the calculation is performed using each of the EPA ’ s assumptions, the result is 2.103 x 10 - 3 lb/GWh, which properly rounds to 2.1 x 10 - 3 lb/GWh. The Commenter stated that the EPA ’ s guidance requires that standards be established at no less than two significant digits. The Commenter stated that the result of the EPA ’ s calculation is no higher than 2.2 x 10 - 3 lb/GWh, not the 3.0 x 10 - 3 lb/GWh that it reports and proposes as the recon sidered Hg emission rate for new coal - fired EGUs. **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the rounding convention used in determining the final emission limits. The EPA used the same rounding convention as was used at final (see , e.g. , RTC, Vol. 1, pp. 463

- 465) . The full equation is presented in the subject memo; the equation is carried out to the result in the revised memo in the rulemaking docket. 10 Two significant digits have been used in the limit. **Comment:** Commenter (20293) stated that in the course of case - by- case new source MACT permitting, it was recently

determined based on reference testing of similar sources and the application of a reasonable compliance margin , that a limit of 0.00088 lb/GWh, was appropriate. The Commenter stated that this rate is approximately 4.5 times higher than the EPA final limit. The Commenter stated that the y do not believe that the Hg limit in the final rule is technicall y feasible, but they also believe that EPA ’ s proposed limit of 0.003 lb/GWh is not based on a robust consideration of all the data. The Commenter recommended that EPA examine the emissions data reviewed in that permitting process as well as for the Logan, Nucla, Seward, AES Greenidge, and Roanoke Valley I EGUs to determine which of those EGUs represents the best -performing unit and set an appropriate limit

– on the basis of all available data , not just the single lowest run. **Response:** The EPA disagr ees with Commenter ’ s assertion. As noted elsewhere in this document, the EPA used the same approach for selecting the “best performing similar source ” and establishing the MACT limits in the propos ed reconsideration as was used at proposal and final. The EPA maintains that it has conducted a robust anal ys is of all of the data available to it (see , e.g. , RTC, Vol. 1, pp. 460 - 463). To the extent the Commenter is asserting that the EPA did not consider all of the available data for the EGU s selected as the best performers, that assertion is incorrect . The Agency used all the data available for the best performing sources when determining variability . **Three -** **times -** 

**RDL (**  **3XRDL )**  **approa ch and detection levels** 

10 Determination ofRepresentative Detection Level (RDL) and 3 X RDL Values for Mercury Measured Using Sorbent Trap Technologies , February 8, 2013 .42

**Comment:** Commenter (20286) stated that in technical support documents (TSDs) for the proposed reconsideration of the MATS rule as well as other recent rulemaking, the EPA has attempted to use the 2001 ASME ReMAP study to support the use of the 3XRDL approach. The Commenter stated that for the Portland Cement NESHAP reconsideration, the EPA claimed that using the 3XRDL approach would result in “ a standard where the method would produce measurement accuracy on the order of 10 to 20 percent, similar to other EPA test methods and the results found in the ASME ReMAP study” ( Docket ID EPA - HQ - OAR- 2011 - 0817 - 0225) . Commenter (20286) stated that for the MATS rule reconsideration proposal, the EPA makes similar claims regarding precision of the methods at a level 3XRDL of the method in the TSD Determination of Representative Detection Level (R DL) and 3 X RDL Values for Mercury Using Sorbent Trap Technology ( Docket ID EPA - HQ- OAR - 2009 - 0234 - 20222). The Commenter stated that the ReMAP study onl y evaluated a limited set of EPA reference methods. The Commenter stated that although the ReMAP study included some methods for Hg measurement, these methods are impinger- based methods and significantl y different from the sorbent trap - based methodology of Method 30B which is the basis of the EPA ’ s anal ys is and the 3XRDL - based Hg emission s tandard for coal - fired EGUs designed to burn coal with ≥ 8,300 Btu/lb. The Commenter stated that the EPA is extrapolating the results of the ReMAP study to appl y to all EPA reference methods, yet the EPA has provided no technical basis fo r making such an e xtrapolation. Commenter (20286) stated that even for methods that were included in the ReMAP or are similar to those methods, the data presented in the study shows no indication that the study evaluated the methods at concentration levels near 3XRDL . The Commenter stated that the EPA TSD on determining the 3XRDL values shows the 3XRDL value for a Method 26 test to be between 83 - 250 micrograms per dry standard cubic meter (ug/dscm ) . Commenter (20286) stated that the EPA ’ s approach of setting MACT emissio n standards based on 3XRDL of the reference methods is arbitrary and capricious. The Commenter stated that the EPA has failed to consider the practical enforceability of emission standards set at levels so close to the MDL. The Commenter stated that the EP A has not adequately demonstrated the reliability and accuracy

of the EPA test methods at such a narrow margin above the MDL of the methods. Commenter (20286) stated that the 3XRDL approach can set the emission standards close to or even significantl y less than the practical quantitation limit (PQL) and that the EPA ’ s own technical experts recognize the need for an additional margin between an emission standard and the PQL of method s used to demonstrate compliance. The Commenter stated that the EPA should determine the PQL of the required methods before assuming that the methods are sufficiently accurate to demonstrate compliance with an emission standard established using the 3XRDL approach. The Commenter stated that the EPA cannot ensure that an arbitrary factor of three will establish an emission standard greater than the PQLof such methods. Commenter (20286) stated that the TSD s contained in the docket for the recently proposed reconsideration of the Portland Cement NESHAP rule indicated that the margin between an emission standard and the MDL of the method should be greater than the factor of three that the EPA is using in the 3XRDL approach to set MACT limits. The Commenter re ferred to EPA ’ s technical memorandum regarding the capabilities of PM CEMS and Method 5 ( Docket ID EPA - HQ - OAR - 2011 - 0817 - 0187,43

Particulate Matter Continuous Emissions Monitoring System (PM CEMS) Capabilities , dated June 13, 2012). The Commenter stated (and cites data from) the anal ys is in the EPA technical memorandum indicates that the overall recommended margin between the Method 5 MDL and the emission standard should be at least a factor of 6 - 9 and not an arbitrary factor of 3 that the EPA is using in th e MATS rule, Portland cement NESHAP, and other NESHAP rulemakings. Commenter (20286) stated that the EPA is relying upon the 3XRDL approach for setting some of the other emission standards and the statements made by EPA technical staff regarding the margin necessary between emission standards and method PQL are relevant to other EPA test methods. **Response:** The EPA believes the Commenter may misunderstand the 3XRDL approach as described in the December 13, 2011 , memorandum from Peter Westlin and Ray Merrill ( Docket ID EPA - HQ - OAR 2011 - 0817 - 0142). When the EPA set an emission limit using the 3XRDL process, it is because the UPL calculation, designed to assess source and operational variability , has determined that the floor would otherwise be set below the level of quantitation reasonabl y achieved in practice b y the test method. By using the 3XRDL value , the EPA has determined that a level of quantitation reliabl y measured b y the test method is the suitable emissio n floor as that test method is the determination of compliance necessary to write and enforce the rule. The EPA do es believe that measured values reported above the MDL but below the 3XRDL value are useful information, but hold s that they have higher degre es of uncertainty than those values at or above the 3XRDL level. Guidance to respondents for reporting pollutant emissions used to support the data collection specified the criteria for determining test - specific MDL s. Those criteria insure that there is o nl y about a 1 percent probability

of an error in deciding that the pollutant measured at the MDL is pre sent when in fact it was absent (per the ReMAP Study). S uch a probability is also called a false positive or the alpha, Ty pe I, error. This means specifi cally that for a normally

distributed set of measurement data, 99 out of 100 single measurements will fall within ±2.54 σ of the true concentration. The anticipated range for the average of repeated measurements comes progressively closer to the true concentration. More precisely , the anticipated range varies inversel y with the square root of the number of measurements. Thus, if σ is the standard deviation of anticipated single measurements, the anticipated range for 99 out of 100 future triplicate measurem ents will fall within ± 2.54 σ/√3 of the true concentration. This relationship translates to an expected measurement imprecision for an emissions value occurring at or near the MDL of about 40 to 50 percent (per the ReMAP Study). By assuming a similar distribution of measurements across a range of values and increasing the mean value to a representative higher value (e.g., 3xMDL), the EPA can estimate measurement imprecision at other levels. For an assumed 3XRDL , the estimated measurement imprecision for a three test run average value would be on the order 10 to 20 percent. The 3XRDL process is based on the widel y accepted definition of quantitation limit being 10 times the standard deviation of 7 measurements of a sample blank or 3.33 times the MDL. Refer to: http://www.epa.gov/fem/pdfs/Env_Measurement_Glossary _Final_Jan_2010.pdf

. The EPA acknowledges that the Commenter makes the point that the ReMAP study did not specifically address Method 30B. Although this is true, Method 30B performance criteria assure the test data 1) have44

a precision of less than 10 percent for Hg concentrations of less than one μg/m 3 and less than 20 percent for Hg concentrations less than or equivalent to one μg/m 3 , and 2) have an accuracy in terms of spike recovery of ± 15 percent. The EPA believe s these criteria address the qual ity of data at the low levels. Also, a s such, these test methods are co nsidered to be self - validating and limited by the QA and QC information determined through the individual sample anal ys is, not by independent study

such as ReMAP. **Comment:** Commenter (20305) stated that setting new source Hg floors at 3XRDL contravenes CAA § 112(d)(3). The Commenter stated that from the text of CAA § 112(d)(3) and well established in binding D.C. Circuit precedent, floors for new sources must reflect the emission level achieved b y the single best performing source in the category or subcatego ry . The Commenter cited court cases to support its point. The Commenter stated that the floors set at 3XRDL do not purport to reflect the emission level actually achieved b y the single best performing source, and that the EPA must demonstrate that floors s et at 3XRDL reflect the emission level achieved by the single best performing source. Commenter (20305) noted that the EPA does not even claim that the new source Hg floor it proposes to set at 3XRDL reflects or even estimates the emission level achieved in practice by the single best performing coal - fired EGU designed for coal with greater than 8,300 Btu/pound . The EPA has estimated the uncertainties for an emissions value occurring at or near the MD L at about 40 to 50 percent, and at 30 percent, at different places. The C ommenter stated that taking the higher number, the maximum actual emissions of a plant whose pollution is measured at or below the detection level would be 1.5 times the detection level. **Response:** The EPA disagrees with the Commenter and has established the RDLand 3XRDL evaluation process as part of MACT floor development to address measurement variability and reliability . The RDLis determined from the average of MDL ’ s reported in the MACT floor data set. This is not the best MDLreported for the MACT floor . The EPA believe s that the outcome should minimize the effect of a test(s) with an inordinately high MDL (e.g., the sample volume was too small, the laboratory technique was insu fficientl y sensitive, or the procedure for determining the minimum value for reporting was other than the detection level). The EPA then call s the resulting mean of the MDLs the RDL because it is characteristic of accepted source emissions measurement perf ormance. The RDLprocess was developed in this way

in part to promote better MDLs moving forward b y not considering the higher half, and in part to provide the flexibility for sources to select testers and labs that are competitive and local rather than forcing the selection of the single best performing laboratory and/or tester. MDL i s commonly defined as 3x the standard deviation of 7 measurem ents of a sample blank. The 3XRDL process is based on the widely

accepted definition of quantitation limit being 10 times the standard deviation of 7 measurements of a sample blank or 3.33 times the MDL. Refer to: http://www.epa.gov/fem/pdfs/Env_Measurement_Glossary _Final_Jan_2010.pdf. As mentioned in the RTC for Portland cement (see response to comment 3.22 , pp. 45 - 46; Docket ID EPA - HQ - OAR- 2011 - 0817 - 0846) , 11 when the EPA set an emission limit using 3XRDL it is because the UPLcalculation, designed to assess source and operational variability , has determined that the floor would otherwise be set below the level of quantitation reasonabl y achieved in practice b y the

11 See also National Emissions Standards For Hazardous Air Pollutants: Portland Cement Summary Of Public Comments And Responses in rulemaking docket EPA - HQ - OAR- 2009 - 0234.45

compliance test method. By using the 3XRDL value the EPA ha s determined that a level of quantitation reliably measured by

the test method is the suitable emission floor as that test method is the determination of compliance necessary to write and enforce the rule. **Comment:** Commenter (20305) stated that the detection level used to set the 3 x detection level emission standard does not reflect readil y available methods. The Commenter noted that the rule requires compliance, first, over emissions averaged over 30 days. The Commenter stated that the EPA has selected standards that the best performing unit would never exceed. The Commenter observed that monitoring requirements elsewhere in the rule bely any assertion that the rules ’ standards are dependent upon hourly

variations in “process and operational ” characteristics; for most pollutants, the Agency requires a single quarterly stack test, with no monitoring of process and operational characteristics at all between tests. The Commenter stated that stack testing of such infrequency could not ensure compliance if hourly process and operational characteristics threaten emissions sufficient to push the 30 - operating day average above the applicable limit. The Commenter stated that neither the EPA nor industry has demonstrated any

reason able basis for feedback on a 30 - minute basis, and the proposed rule ’ s emissions calculations require hourl y measurements. The Commenter cited the EPA ’ s Reconsideration Beyond the Floor Memorandum to assert that plant - operators cannot adjust operations to m ake use of half - hourly sampling. The Commenter discussed the logistical difficulties of processing sorbent tubes at 30 - minute intervals. The Commenter concluded that absent a requirement to use continuous emissions monitors, as well as a short - term averaging period sufficient to demand fine - grained emissions control, the Agency has failed to demonstrate any rational basis for its 20 - minute testing period. **Response:** As explained above , the EPA determined the RDL (and the 3XRDL) value based on data submitted to the EPA by

the best performing EGUs. As the average of those individual detection levels, the RDL(and the 3XRDL) certainly reflect readily

available methods. The EPA finds the Commenter’s allegations concerning standards other than those identified as issues in the Reconsideration irrelevant; no response is necessary . With respect to the issue of concern

– the non - low rank virgin coal - fired EGU Hg emission limit

– either Hg CEMS or sorbent trap monitoring s ys tems, both of which collect a continuous sample, are compliance options, whereas quarterl y testing is not a compliance option. The EPA has determined that a short - term sorbent trap monitoring sampling approach involving 30 - minute sample collection periods is a feasible option for evaluating process and operational controls during different operating levels to ensure compliance, and represents the shortest interval at which such measurements can occur to obtain data relativel y comparable to a Hg CEMS. Having determined this monitoring approach as an option that is permissible under the rule, the rule sets the emission standard on the same basis in this Reconsideration rulemaking as the EPA used in setting standards for the proposed and final rules. That standard setting methodology is fully explained and supported in the rulemaking record. In evaluating detection levels over shorter sorbent trap sampling periods, the EPA shared Commenter s ’ concerns with source owners or operators having the ability to identify

and react to emission problems in as expeditious a time frame as possible, and providing the ability to demonstrate compliance with the emission limit on a short - term basis. **Comment:** Commenter (20305) stated that the detection level used in the 3XRDL emission standard does not reflect the level at which Hg can be reliably detected b y available test methods. The46

Commenter stated that the EPA ’ s average of 24 EGU - level results from the 43 EGUs used does not reflect a reasonable estimate of the level at which Hg emissions can be reliably detected. The Commenter questioned why the anal ys is was limited to the EGUs that were used, and stated that the record does not support that the measurements were from the best performing testing companies and laboratori es using the most sensitive analy tical procedures. The Commenter stated that the most sensitive anal ytic procedures are those with the lowest detection limits provided in response the Agency ’ s information collection request, which is not the sample used by the EPA. Commenter (20305) stated that by counting each unit, used to determine the average detection limit, rather than each laboratory- specific detection level , the EPA has biased its “representative ” average. The Commenter stated that by including outlying detection levels, and counting them repeatedly (once for each unit), the Agency

has failed to produce a number that is the mean value of the available reported pollutant - specific MDLs from the best performing testing comp anies. Commenter (20305) stated that the EPA underestimates the performance of sorbent tube technology used for the 3XRDL emission standard. The Commenter stated that the EPA assumes a MDL of 1 ng/section under Method 30B but vendors report much lower detection levels. **Response:** The EPA did not assume an MDL, but determine d the RDL from the average of MDLs reported in the MACT floor data set that used Method 30B . The EPA believe s that by using MDLs reported for best performing EGUs, the outcome should minimize the effect of a test with an inordinately

high MDL (e.g., the sample volume was too small, the laboratory technique was insufficiently

sensitive, or the procedure for determining the minimum value for reporting was other than th e detection level). The EPA then call s the resulting mean of the MDLs the RDL because it is characteristic of accepted source emissions measurement performance. The 3XRDLprocess was developed in lieu of the 3XMDL in this way in part to promote better MDLs moving forward b y not considering the higher half, and in part to provide the flexibility for sources to select testers and labs that are competitive and local rather than forcing the selection of the single best performing laboratory and/or tester. **Comm ent:**  Commenters (20258 and 20293) stated that EPA ’ s 3XRDL calculation should have no impact on the determination of the standard for this subcategory . The Commenter s ’ Chart No. 5 [see originals for figure] showed the lowest emission test result for the 158 EGUs in EPA ’ s data set. The Commenter s stated that these data demonstrate that EPA ’ s calculation leads to a result that is not consistent with the ongoing improvement in control technologies

– a limit for Hg for new sources that is less than the measured emission rates of about one - third of existing EGUs . Commenters (20258 and 20293) stated that the proposed Reconsideration will relax the final standard for Hg emissions from coal - fired EGUs b y a factor of 15. The Commenter s said that this proposal is not based on any new information concerning the emissions performance of the best -performing unit, but is in response to petitions received from industry members that they

need to be able to determine compliance on an ongoing b asis. The Commenter s noted that in its initial testing request, the EPA had advised sources that it anticipated that the sampling period might need to be extended to up to two weeks to obtain the required precision. The Commenter s stated that because EPA h as multiplied the results from the best -performing unit by a factor of 3.5, that length of sampling should no longer be required to ascertain compliance with the standard. The Commenter s noted that because of QA47

requirements, most users replace sorbent tra ps every four to seven day s, which limits the amount of data lost if a sample is rejected for QA reasons. The Commenter s noted in response to Petitioners ’ representations , the EPA has proposed to assume that the time for sorbent trap sampling is reduced from the normal period of several day s to a week to just 30 minutes . The Commenter s stated that the selection of 30 minutes is intended by EPA to reflect the sampling time available with the use of Hg CEMs. The Commenter s stated that EPA then makes a number of assumptions about the use of sorbent traps to calculate its 3XRDL “ alternate ” approach to setting standards. The Commenter s stated that this approach leads the agency to propose a limit that may be higher than would have resulted from P etitioners ’ sugge stion to raise the emission limit to facilitate the use of Hg CEMs. Commenters (20258 and 20293) noted, in the first instance, that it may be possible for new EGUs to employ Hg CEMs that have sufficientl y low detection levels to allow their use in ascertaining compliance. The Commenter s stated that tests conducted on the newest generation of Hg CEMs demonstrate an ability

to detect and to quantify Hg emissions at or below the final Hg emission limit for coal - fired EGUs. The Commenter s noted that the manufacturers of the Tekran Hg CEM assert that their system has a quantification level of approximately 0.033μg/m3. The Commenter s noted that for internal compliance assurance purposes a measurement greater than the detection level, but le ss than the quantification level, should be sufficient to alert the operator that corrective action is required. The Commenter s noted further, there is no reason why sampling times in Hg CEMs cannot be extended beyond 15 minutes and sampling volumes increa sed to provide for lower detection levels as desired. Commenters (20258 and 20293) stated secondl y, that it is reasonable to assume that over the next several ye ars operators can develop and implement continuous parametric operating plans to assure compli ance with operating limits. The Commenter s added that these plans are in addition to, and not in lieu of, the enforceable compliance demonstration requirements. Commenters (20258 and 20293) stated thirdly , there is no documentation that the performance of affected EGUs is so variable that sources must be able to determine emission levels on either a 15 minute or 30 minute basis to maintain compliance with a 30 operating - day average. The Commenter s stated that the scenario posed by EPA is economically

unrealistic. The Commenter s continued, that given the available alternatives, they find it difficult to believe that sources will routinely volunteer to change sorbent traps every half hour and then pay for laboratory

anal ys es of the 17,520 samples per year that would result from such an exercise and with the short - term turnarounds that would be required to use such samples as a short - term monitoring s ys tem. The Commenter s stated that the EPA has selected 30 minutes in an attempt to duplicate the frequency of me asurement of Hg CEMs, but Hg CEMs have much higher sampling flow rates than cited b y EPA for sorbent traps. The Commenter s concluded, for this reason , the EPA ’ s assumption of extremely short sampling times and low flow sampling rates for sorbent traps lead s to levels of quantification far higher (less precise) than ordinarily achieved by

either Hg CEMs or sorbent traps. Commenters (20258 and 20293) asserted that EPA has not explained why a determination of ongoing emission rates 5 to 10 times per month

– o r 100 times per month

– will not suffice to complement ongoing parametric monitoring. The Commenter s stated that sources are, of course, free to conduct additional monitoring as they see fit, and can generate hourl y updates to the rolling monthly average b y employing more than one trap at a time and staggering the start times of the sampling by different traps.48

Commenters (20258 and 20293) stated that the EPA ’ s 3XRDL calculation contains several key errors and incorrect assumptions. The Commenter s noted th at this calculation employs four factors: (1) the MDLof the test, (2) the sample collection time, (3) the sample collection rate and (4) the heat rate of the unit. The Commenter s stated, that with respect to the MDL , the EPA asserts that it has calculated the average MDL for measuring mass from a number of tests of the best -performing EGUs , included multiple results from three sources owned b y a single operator that are several times higher than other values in the set. The Commenter s stated there is no re ason why EPA should base its determination of the detection level that can be achieved b y new sources in the future on the basis of the choice of MDL where there was no obligation or incentive to employ more accurate methods to determine the mass of the sample in the sorbent trap. The Commenter s stated that the EPA should use either the best, or at least one of the best MDLs reported by a lab in the group. The Commenter s stated that if EPA were to do this, the applicable limit would be unaffected b y the 3XRDL test. Commenters (20258 and 20293) stated that EPA uses a sample collection time of 30 minutes and noted that the EPA intended to use a sample collection time of 20 minutes, but erred. The Commenter s stated, as explained above, this choice is arbitrary and unrealistic. The Commenter s stated that if EPA assumes a sample collection time of 360 minutes ( 6 hours) and makes no other change to its assumed values, the 3XRDL level is less than the final stan dard and so the applicable limit would not affected by the 3XRDL test. The Commenter s stated that sources that employed sample collection times of six hours would be able to determine their compliance status 120 times per month. The Commenter s stated that this should be more than sufficient to assure compliance with applicable standards, especiall y because sources should be assumed to establish a baseline emission rate that takes into account the level of emissions variation shown b y EPA ’ s 99 th percentile UPLprocedure. Commenters (20258 and 20293) stated that EPA assumes a sample collection rate of 0.5 liters per minute, based on “ an informal survey on the normal sampling rates. ” The Commenter s stated this rate of sample collection may

be the practice today , but there is no reason why, if the final rule remains in place, sources cannot elect to sample at the rates available with commercially available equipment. The Commenter s stated that if th e EPA assumes that the source samples at the maximum rate of commerciall y available units, and makes no other change to its assumed values, the final limit is not affected b y the 3XRDL test. **Response :**  One Commenter’s concern appear s to arise not from the 3XRDL calculation, but from the calculation used to express the 3XRDLvalue into its corresponding electrical output rate (in lb/MWh). With respect to the Commenter’s claims that data it submitted demonstrate an emission limit that is not consistent with the ongoing improvement in control technologies, the EPA is unable to assess the data’s relevance, particularl y with respect to the sampling periods over which the data were collected. In order to make a reasoned comparison between the limit and the data, i f indeed that were necessary , the Commenter’s data sample collection period would need to be consistent with that of the rule

– 30 minutes. As the Commenter has not provided this critical piece of information, the EPA finds the comment not relevant. The E PA agrees with Commenters that the EPA developed the revised Hg limit in response to EGU owner or operator concerns about having the ability to identify

and react to emission problems in as expeditious a time frame as possible, and providing the ability to demonstrate compliance with the emission limit on a short - term basis, yet the EPA disagrees with the Commenters’ implication that the49

revised Hg limit does not represent the ability of best -performers over the reduced sampling period. Although the EPA agrees that compliance is to be determined over 30 days, the EPA does not believe it prudent to bar an EGU owner or operator from conducting more frequent sampling on his own, particularl y when the EGU owner or operator is monitoring control devices more care full y via the more frequent monitoring. With respect to the Commenter’s concerns over a shorter sampling period than 4 to 7 days, as mentioned earlier, the EPA has determined that a short - term sorbent trap monitoring sampling approach involving 30 - minute sampling periods is a feasible option for evaluating process and operational controls during operational changes to ensure compliance, and represents the shortest interval at which such measurements can occur to obtain data relativel y comparable to a Hg CE MS. Having determined this monitoring approach as an option that is permissible under the rule, the rule sets the emission standard on the same basis in this Reconsideration rulemaking as the EPA used in setting standards for the proposed and final rules. That standard setting methodology is fully explained and supported in the rulemaking record (see , e.g. , MATS MACT Floor Memos - Docket ID EPA - HQ - OAR - 2009 - 0234 - 9858 , Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132 ) . The EPA agrees with the Commenter who asserts that it may be possible to employ

Hg CEMS as a compliance option, and the rule continues to allow Hg CEMS use. The EPA agrees with the Commenter that Hg CEMS could be used in a corrective action, not compliance, mode as long as a compliance determination method for Hg emissions is selected and used. The EPA disagrees with the Commenter’s assertion regarding extending Hg CEMS sampling times or increasing sampling volumes, as neither the sampling time nor the sampling volume appear problematic for Hg CEMS, especi all y based on the aforementioned information from other Commenters, our experience, and NIST’s confirmed Hg calibration gas generation capability. With respect to the Commenter’s second assertion, although the EPA agrees such continuous parametric operating plans could be developed and used b y EGU owners or operators for their ongoing, internal operations, the rule does not require their development or use. For the reasons given above, the EPA disagrees with the Commenter’s third assertion, noting that the sampling period identified and used represents the shortest interval at which such measurements can occur to obtain data relativel y comparable to a Hg CEMS . With respect to the Commenters’ concerns that longer sampling periods could complement ongoing mo nitoring, the EPA does not disagree, but, such longer sampling periods are not consistent with the shortest reasonable period determined to be sufficient for compliance purposes. The EPA disagrees with the Commenter who suggests key errors and incorrect a ssumptions regarding the newl y- calculated non - low rank virgin coal - fired Hg emission limit. As mentioned elsewhere, the RDLis the average of individual MDL s of the best -performing EGUs that provided data; the sample collection time represents the shortest reasonable interval over which measurements can occur; the sample collection rate represents a typical value observed and available today; and the heat rate is the same value used for other Hg floor calculations.50

As explained in the preamble, the EPA ack nowledged the sample collection time error in the Determination of Representative Detection Level (RDL) and 3 X RDL Values for Mercury Measured Using Sorbent Trap Technologies memorandum and revised the memorandum to make the sample collection period a con sistent 30 minutes. As mentioned earlier, the EPA found that 30 minutes - not 360 minutes, as suggested b y the Commenter

– to be the s hortest interval at which such measurements can occur to obtain data relatively comparable to a Hg CEMS . Although the EPA agrees with the Commenter that nothing prevents sample collection rates in excess of 0.5 liters per minute in the future, nothing in today’s rule requires a change in this normal sorbent trap monitoring sampling rate. **Comment:** Commenters (20258 and 20293) stated that EPA assumes that the heat rate of new coal - fired boilers using high Btu coal will be 11,180 Btu/kWh. The Commenter s said that the Agency argues that this number represents the average of the EGUs that it selected fo r evaluation for this purpose. The Commenter s stated that this rate is substantially greater than one would anticipate for a new coal - fired plant burning high Btu coal and is higher than the average of all coal - fired EGUs in EPA ’ s data set (10,478 Btu/kWh) . The Commenter s stated it is also somewhat higher than the average of the top 29 EGUs in EPA ’ s data set (8,449 Btu/kWh). The Commenter s noted that these somewhat smaller differences turn out to be more significant than might be apparent. Commenter (20305 ) also stated that the EPA used a very high and inefficient heat - rate of 11,180 Btu/kWh in its calculation of detection levels to create an output - based standard. The Commenter disagreed with having the detection level depend upon the “ average heat rate of the EGUs used to determine the RDL value. ” The Commenter noted that the testing laboratories would have reported the same detection levels regardless of the heat rate. The Commenter stated that the EPA used a heat rate that is non - representative of the he at rates likel y ata newl y constructed coal - fired power plant, and by doing so, inflated its detection level well beyond what could be reasonabl y described as “representative. ” **Response:** The EPA dis agree s with the Commenter s with respect to the use of more efficient heat rates for Hg. Similar concern s with the heat rate were raised by Commenters in the MATS rulemaking and addressed in the RTC (Vol. 1, pp 466 - 467) . As mentioned there , the EPA utilized the average heat rate be cause of the antagonistic relationship between low Hg emissions and high thermal efficiency in coal combustion . This antagonistic relationship is attributable to the high carbon content (i.e., high loss on ignition (LOI)) ty

pical of inefficient combustion units and the affinity of this high - carbon flue gas stream for Hg. For the conversion of the Hg emission rates for the best performing (lowest emitting) sources, the EPA utilized the average heat rate for the sources in the input based floor pool (i.e., th e 47 sources used to set the lb Hg/MMBtu standard) and maintained the same EGUs and their rankings between the input - and output - based standards. The numerical value of this average heat rate is 11.18 MMBtu/MWh. These are the same EGUs that were used to determine the RDLvalue and, thus, the use of the average heat rate is appropriate. 2.3 New coal - fired unit, low rank virgin coal51

**Existing coal refuse -** 

**fired EGUs**  **Comment:** Commenters (20285 and 20302) stated that in the final MATS Rule, the EPA did not consider the effects of the MATS HCl emission limit on existing coal refuse - fired circulating fluidized bed (CFB) boilers, also known as FBC. Commenter (20285) stated that because the EPA has decided to reconsider the HCl limit for new coal fired EGUs, and because EPA has also concluded that FBC EGUs should be regulated differently from traditional coal - fired EGUs under the MATS rule , the EPA should also revise, through the current reconsideration process, the HCl limit for coal refuse - fired FBC EGUs . Commenter (20302) noted that facilities using this technology serve as a remedy

to abandoned coal mines and coal refuse piles. The Commenter st ated that the final Utility MATS rule should not establish HCl limits that would adversel y impact the environmental beneficial use of waste coal. The Commenter discussed the difficulties for well - controlled CFB EGUs in meeting the HCl limits in the final MATS Rule. The Commenter urged the EPA to reconsider the proposed HCl and surrogate SO 2 limits, which are not achievable for certain EGUs including EGUs operating with acid gas controls. Commenter (20302) stated that fuel switching is not an option for co al refuse - fired CFB boilers. Commenter (20285) asked that the EPA create a subcategory- specific HCl emission limit for coal refuse - fired FBC boilers that is technically and economically

achievable in consideration of the distinct characteristics of this source category . Commenter (20285) provided discussion regarding the determination of a MACT floor for HCl emissions from coal refuse - fired CFBs, including an attachment deriving an example HCl limit based on existing EGUs , and attachments that list the c osts for HCl control using SDA for an existing unit, and ash generation at multiple facilities. Commenter (20285) stated that existing coal refuse - fired FBC EGUs injecting limestone to control SO 2 and other acid gases are not capable of yi elding the HCI emission reductions necessary to comply

with the applicable limit under the Final MATS Rule. The Commenter provided discussion of available controls that could be used by existing EGUs , and a discussion of the Final Rule ’ s approach to setting standards for existing coal refuse - fired FBC EGUs . **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the existing - source emission limits. The issue of establishing a separate subcategory for coal refuse - fired CFB EGUs , essentiall y Commenter ’ s main point, was addressed in the final rule (see , e.g. , 77 FR 9378 - 9379, 9394 - 9402; RTC, Vol. 1 , pp. 358 - 365). The issue of a separate HCl limit for coal refuse - fired EGUs was also addressed in the final rule (see , e.g. , RTC, Vol. 1 , pp. 584 - 587). The issue relating to the alleged inability of coal refuse - fired EGUs to add on additional controls was also addressed in the final rule (see , e.g. , RTC, Vol. 1 , p. 761). The issue of the impact of sodium - based sorbents on the ability of coal refuse - fired EGUs to reuse their ash was also addressed in the final rule (see , e.g. , RTC, Vol. 2 , pp. 509 - 511).52

As noted in the RTC (Vol. 1, p. 761), the EPA is aware of at least two coal refuse - fired CFB EGUs that reported add - on “polishing ” technologies for SO 2 (or, at least, technologies beyond the CFB itself) in their responses to the 2010 I CR. One of these EGUs had the additional equipment installed during initial construction; however, the other EGU retrofitted the equipment. Thus, the EPA does not believe (as Commenter implies) that the cost of such add on (or additional) “polishing ” equipment is prohibitive f or coal refuse - fired EGUs. The EPA has found that at least one control device vendor markets such technology

(including installations on a coal refuse - fired CFB EGU, on CFB EGUs using other coal ranks, and on retrofit applications) that will lower HCl (and HF) emissions to the 1 part per million level. 12 , 13 Therefore, the EPA does not agree , as Commenter also implies, that the HCl limit in the final rule is unachievable for such EGUs. One unique feature of the technology when employed on CFB EGUs is the “ abil ity

to use the ash (which contains surplus lime) supplied by the CFB (via the flue gas stream) ” for enhanced SO 2 control. 14 , 15 The EPA believes that this “ left over” lime in the ash will lessen or eliminate the need to add lime, thus lessening the overall co st of the technology . Although not specificall y installed for HCl control, the EPA believes that the humidification step inherent in the process will further remove HCl. Further, such coal refuse - fired EGUs are eligible for the alternate SO 2 emission limi t in lieu of the HCl limit. The EPA does not believe that there is any confusion in the definition of “ dry flue gas desulfurization technology, or dry FGD, or spray

dryer adsorber (SDA), or spray dryer, or dry

scrubber” and that the definition clearly indi cates that FBC and CFB boilers qualify the respective EGU for the alternate SO 2 emission limit. The EPA has reviewed a number of Title V permits for coal refuse - fired EGUs and, based on those permits, believes that the alternate SO 2 emission limit is achievable by such EGUs if they

believe that they

cannot achieve the HCl emission limit. **Comment:** Commenter (20285) requested that the language of the Final MATS Rule be revised to clearl y reflect that limestone injection within the FBC combustion zone qualities as DSI , and therefore would allow plants with existing coal refuse - fired FBC EGUs to utilize the SO2 emission surrogate as a compliance demonstration method. The Commenter noted that the Commenter ’ s coal refuse - fired FBC EGUs would be no more able to demonstrate compliance with the surrogate SO 2 emission limit under MATS than the stringent HCl emission limitation in the same regulation. **Response:** This issue is outside the scope of this rulemaking. The issue of clarifying the definitions of FGD was raised in public comments submitted in response to the May 3 , 2011 , proposed MATS rule (76 FR 24976). The EPA ’ s responses to the comments are in the RTC (see , e.g. , Vol. 2, p . 715 ). As noted in the RTC, the definition in 40 CFR 63.10042 for “Dry flue gas desulfurization technology , or dry FGD , 12 Gatton, Lawrence, Principal Engineer, Alstom Power ECS. Next Generation NID for PC Market . Presented at Coal - Gen Conference and Exposition, Columbus, Ohio. August 17 - 19, 2011. 13 Alstom. NID Flue Gas Desulphurization System for the Power Industry . 14 Morin, Jean - Xavier, Alstom. Recent Alstom Power Large CFB and Scale up aspects including steps to Supercritical. Presented at 47 th International Energy Agency Workshop on Large Scale CFB , Zlotnicki , Poland . October 13 , 2003 15 Ahman, Stefan, et al. Alston Power’s Flash Dryer Absorber For Flue Gas Desulfurization. Proceedings of the 2002 International Joint Power Generation Conference. Phoenix, Arizona. June 24 - 26, 2002.53

or spray dryer , or dry scrubber” indicates that CFB technology is considered to be an “ FGD s ys tem ” ( “ [a]kaline sorbent injection systems in FBC or CFB boilers are in cluded in this definition ” ). The EPA believes that the definition, when taken as a whole, adequatel y addresses Commenter ’ s concerns. **Comment:** Commenter (20285) stated that establishing an HC l emission limit of 0.034 lb/MMBtu for coal refuse - fired FBCs would not result in unacceptable adverse health impacts. The Commenter provided an attachment reviewing the health impact of an example unit, using EPA methods. **Response:** This issue is outside th e scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding additional health impacts. 2.3.1 Mercury

(possible revision) **Existing units Comment:**  Commenter (20275) was concerned with the impact that the Final MATS Rule and the proposed MATS Rule Reconsideration will have on low rank virgin coal - fired power plants. The Commenter referred to previously filed comments outlining its position on the MAT S Rule during the proposal phase, including their comments on the burdensome emissions limitations placed on existing and new low - rank virgin coal EGUs , particularl y the establishment of a BTF limit for Hg emissions from existing EGUs . The Commenter referr ed to comments to the proposed MATS rule: Docket ID EPA - HQ - OAR- 2009 - 0234 - 17930; Docket ID EPA - HQ - OAR - 2011 - 0044 - 5240. Commenter (20275) stated that the limits cannot be met by new EGUs , thus, for the reasons in the referenced data and comments, the BTF limit for existing low - rank virgin coal EGUs , established at 4.0 lb/TBtu in the rulemaking, cannot be attained by existing EGUs . The Commenter said, in violation of CAA §112(d)(3), the limit was based on the lowest data point from a single unit rather than t he group of units required b y the CAA . The Commenter added that the one newest unit used for the limit could not consistently

meet the proposed 4.0 lb/TBtu limit. The Commenter concluded that the Hg BTF limit for low - rank virgin coal EGUs should be struck from the rule. **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the existing - source emission limits. **New EGUs**  **Comment:** Commenter (20275) stated that the data and comments filed b y affected parties during this rulemaking clearl y demonstrate that the MATS Rule ’ s Hg limits for new low - rank virgin coal EGUs are not consistently

achievable at the newest existing low - rank virgin coal EGU nor do the limits account for low rank virgin coal variability The Commenter stated the Hg limit should therefore be set at a higher level, one consistently achievable b y the newest existing low - rank virgin coal EGUs . Commenter (20303) stated that the MATS Hg limits for new low - rank virgin coal EGUs are not consistently

achievable at the newest existing low - rank virgin coal unit nor do the limits account for low rank virgin coal variability . The Commenter stated that the Hg limit should therefore be set at a higher level, one consistentl y achievable b y the newest existing low - rank virgin coal EGUs .54

**Response:** The EPA disagrees with Commenters ’ allegation that the subject emission limit is not achievable or being achieved in practice. Based on data in the record (Docket ID EPA - HQ - OAR - 2009 - 0234) and available to Commenters, the EPA has determined that three of the four low rank virgin coal EGUs tested that had mercury- specific controls were meeting the BTF limit established (see 77 FR 9393). As the final new - and existing - source Hg limits for low rank virgin coal - fired EGUs are the same, the EPA believes the new source limit to be reasonable and achievable. **Comment:** Commenter (20285) stated that reduction of chlorine through the use of DSI f or coal refuse fired EGUs could also result in a reduction in the amount of Hg oxidized and, in turn, cause a corresponding increase in Hg emissions. The Commenter suggested that to the extent that EPA determines to continue to impose a numeric emission limit for HC l on coal refuse - fired FBC boilers through the MATS rule , the EPA should establish a revised emission limit for HC l that applies only to coal refuse - fired FBC EGUs . **Response:** The EPA understands that flue gas halogens will promote the oxidation of Hg which enhances its control. The EPA also understand s that DSIcan be used to capture HCl and thus make it relativel y unavailable for reaction with gas phase Hg . However, the EPA is also aware of several commerciall y available control options that have been specificall y developed to control Hg that is present in the flue gas stream as elemental Hg vapor. Those technologies

– which may include injection of halogen or halogenated activated carbon

– assist in the oxidation of elemental Hg. The location of the halogen or halogenated - AC injection can be optimized to avoid interference b y the DSI s ys tem. Western subbituminous and many low rank virgin coals have inherentl y low chlorine levels and tend to produce elemental Hg vapor in the post combustion flu e gas. Facilities burning those fuels may need to use those technologies ( e.g., bromine injection, halogenated activated carbon, etc.) to control Hg emissions . **Comment:** Commenter (20286) stated that revisions to the Hg emission standard for new low rank v irgin coal - fired EGUs are not clearl y explained in the preamble discussion in the Federal Register or the TSD . The Commenter stated that if the EPA is considering making an emission standard more stringent with this proposal, it must be clearl y presented, explained, and justified so that interested parties have full opportunity to comment on such a change. The Commenter stated that the TSD only includes a footnote for the revised MACT anal ys is results for Hg , which appears to indicate that the EPA is considering reducing the Hg emission standard for Subcategory 2 from 0.040 lb/GWh to 0.030 lb/GWh. **Response:** The EPA did not prop ose to revise the Hg limit for low - rank virgin coal - fired EGUs. Instead, as Commenter notes , the EPA referenced a potential data availability issue for such units. The fact that Commenter has identified the information indicates that it was clearly present ed and full y available for comment. Further, as the EPA received no comments supporting a revision to the low rank virgin coal Hg limit, the limit will remain as promulgated in the final MATS rule . **Comment:** Commenter (20286) stated that the EPA indicates that the proposed new source limits for Hg are consistent with the levels suggested b y a number of control vendors (77 FR 71329), yet the EPA does not provide the vendor information with the proposed rule or provide a comparative anal ys is to support its claim. The Commenter stated that the vague discussion regarding vendor “ suggestions ” does not provide adequate justification to support achievability as required b y CAA § 112.55

**Response:** The EPA is not using vendor “ suggestions ” as a justification supporting its rulemaking as suggested b y Commenter. Rather, the EPA is noting that its independent analysis (see Docket ID EPA HQ - OAR- 2009 - 0234 - 20222) happens to also be in the same range as in dicated by vendors (see , e.g. , Docket ID EPA - HQ - OAR - 2009 - 0234 - 20176), one indication of the reasonableness of the anal ys is. 2.4 IGCC unit **Calculation of standards Comment:**  Commenter (20293) stated that the EPA established the MACT limits for Integrated Gas Combined Cycle (IGCC) EGUs on the basis of the permitted EPA emission limits for new EGUs . The Commenter recommended that EPA consider permitted emission levels for all s ubcategories and all pollutants, not just I GCCs. The Commenter stated that the EPA is obliged to set MACT standards on the basis of all of the information that is available to it, including permit determinations, specifically those in the RBLClearinghouse . The Commenter stated that pre - construction permitting is based on conservative engineering assumptions and such limits should be considered an upper bound on the actual performance of the unit and should be considered in determining the performance of th e unit. The Commenter stated that EPA seeks to rel y solel y on permitted limits in establishing MACT limits for IGCCs, yet EPA proposes to set MACT limits for Hg, SO 2 and other pollutants that are higher than permitted levels that sources have complied with for many years. **Response:** The EPA has stated earlier that generally where sufficient emissions data are available, it believes it appropriate to use such data ins tead of permit data (see , e.g. , RTC, Vol. 1, pp. 460 - 463). As Commenter notes, the EPA followed this practice for all subcategories except for the new source limits for IGCC EGUs where we had very limited data (and none from current generation IGCC EGUs) . The EPA has provided its rationale for the use of permits for IGCC EGUs under construction in the record (see , e.g. , 77 FR 9394). For other subcategories, the EPA is not aware of a universal set of permits that contain consistent information and/or data that could be used to set nationwide emission limits. For example, many

Hg permits contain provisions whereb y the source may return to the permitting agency after a period of time and renegotiate the permit level if the o riginal level was determined to be unachievable. Other permits only required the use of a certain level of ACI injection with no emission limit stipulated. For other HAP , there are onl y a limited set of permits (e.g., HCl). Thus, the EPA determined to only use permits for the new source IGCC limits. **Comment:** Commenter (20308) stated that EPA ’ s use of data from the only two IGCC EGUs operating in the United States misrepresents the design and potential performance of future IGCC EGUs . The Commenter stated that if the final reconsideration rule remains applicable to IGCC EGUs , then EPA should consider a broader scope of IGCC technologies, the inherent uncertainties with technology development, and the use of first - of - a - kind technologies for new IGCC units. The Commenter noted that the air permits used for proposed MATS standards for IGCC units are for facilities that have not begun operation. **Response:** In response to comments on the proposed MATS rule that application of emission limits for IGCC EGUs based on those of pulverized coal EGUs was inappropriate and that the use of permit levels from IGCC EGUs was preferable, the EPA followed this new approach at final. The reconsideration of56

the IGCC EGU limits served to address a notice - and - comment issue. The Commenter has not provided any information to suggest where outside the subcategory (i.e., the two existing IGCC EGUs or permits for IGCC EGUs under con struction) the EPA should look to consider “ a broader scope of IGCC technologies ” in establishing IGCC EGU emission limits or how the EPA ’ s use of permits for IGCC EGUs under construction is not “representative of both current technologies and of IGCC EGUs that will b e built in the near- term future ” (77 FR 9394) . The Commenter has not provided any new information that was not available at final. The issue of the use of only two data points for existing IGCC EGUs was addressed at final (see , e.g. , RTC, Vol. 1, pp . 482 - 483 ) and was not an issue subject to reconsideration . 2.4. 1 Sulfur dioxide (4.0E - 01 lb/MWh) **Comment:** Commenter (20299) asked that the MATS eligibility requirement for IGCC to use SO 2 as an alternative for HCl be clarified. The Commenter stated that IGCC EGUs do not employ flue gas desulfurization (FGD) as flue gas strictl y pertains to the final product of combustion which for an IGCC, is that at the HRSG stack following the gas turbine. The Commenter noted that an IGCC EGU is the combine d cycle gas turbine using solids derived fuel (sy ngas). The Commenter stated that for IGCC, acid gas control is outside of the scope of the EGU with all of the scrubbing of acid gas species (SO 2 , HCl) performed prior to the EGU. The Commenter stated that requiring the use of an FGD would essentially

constitute a polishing step which is neither practical nor economically justified because the primary control is designed to be adequate to meet the HCl and corresponding alternative SO 2 performance standard. C ommenter (20299) recommended that the proposed provision be modified to read as follows: For coal - fired and solid oil - derived fuel - fired units that employ FGD technology and new or reconstructed IGCC units that employ FGD technology and elect to meet the alternative SO 2 limit in place of the HCl limit, you need not conduct an initial stack test for HCl or SO 2 . Instead, the 30 boiler operating day s of data collected with the certified SO 2 CEMS by

the initial compliance demonstration date specified in § 63.10005 are used to determine initial compliance, and the SO 2 CEMS is used thereafter to demonstrate continuous compliance. **Response:** The EPA agrees that some clarification is warranted and has included the appropriate language in footnote 3 of table 1 to subpart UUUUU of Part 63. 2.5 Solid oil - derived fuel - fired unit **Other pollutant standards Comment:**  Commenter (20286) stated that although the EPA has not proposed revisions to the HCl emission standard for new petroleum coke - fired EGUs, the Commenter questioned the EPA ’ s HC l MACT floor anal ys is for the petroleum coke - fired subcategory . The Commenter stated that the new unit floor for HCl wa s set by

AES Deepwater in Houston, Texas (the only conventional boiler included in the data set for the MACT floor anal ys is of petroleum coke - fired EGUs), whereas the other seven EGUs included in the data set are FBC EGUs .57

Commenter (20286) stated that AES Deepwater ’ s HCl emission performance does not appear representative of the petroleum coke - fired EGU category because of its design and the low chlorine content in its fuel. The Commenter urged the EPA to reevaluate the petroleum coke - fired EGU MACT anal ys is for HCl and select a unit that is more representative of the category . The Commenter stated that the EPA excluded certain EGUs for similar reasons from the Hg MACT analysis for coal - fired EGUs and the f PM MACT analy sis for petroleum coke - fired EGUs. **Response:** This issue is outside the scope of this rulemaking. Subcategorization was addressed in the final rule (see , e.g. , 77 FR 9378 - 9379, 9394 - 9402). This issue was not one of the issues being reconsidered and the EPA did not solicit comment in the reconsideration proposal on additional subcategories, including subcategorizing solid oil - derived fuel - fired EGUs. **Calculation of standards Comment:**  Commenter (20273) stated that EPA ’ s reliance on limited short - term testing data has not been adequatel y c orrected in the reconsidered MATS for solid oil - derived fuel EGUs. The Commenter stated that although EPA has reconsidered the promulgated MATS and proposed slightly less stringent limits for solid oil - derived fuel EGUs based on additional data , the EPA has not corrected the flaws in its methodology

stemming from an inadequate data set and unsupported extrapolation of its limited data. The Commenter noted that the EPA ’ s upper prediction limit ( “UPL” ) analysis cannot predict a facility ’ s continuous emissi ons performance based on an hours - long emissions test, unless that test is representative of continuous performance. The Commenter continued that because EPA continues to exclude data from its calculations of standards, the revised solid oil - derived fuel l imits are still too low. The Commenter said it is axiomatic that EPA ’ s statistical analysis is only as valid as the data that supports it and EPA does not have sufficient data available from 100 percent solid oil - derived fuel - fired EGUs across varying operational conditions to form a basis for MATS for these facilities. The Commenter stated if EPA is determined to set limits for solid oil - derived fuel EGUs , the EPA should set the solid oil - derived fuel standards at the same reconsidered limits as it has proposed for new coal EGUs not designed for low rank coal (hereinafter referred to as “ coal ” ) because the same considerations expressed by

EPA in setting the coal standards, including fuel content variability , control performance, measurement constraints, and operating condition variations are present for EGUs using onl y solid oil derived fuel. The Commenter said, in short , the EPA ’ s failure to give equal consideration to solid oil derived fuel - fired EGUs as coal EGUs is arbitrary and EPA should adjust the standards applicable to petroleum coke fueled EGUs , such as the LBEC, to the reconsidered MATS applicable to coal EGUs . The Commenter stated that there is no reasoned justification for disparate treatment. **Response:** The issue of the use of short - term emission test data to establish 30 - day rolling average emission limits was addressed in the final RTC (see , e.g. , Vol. 1 , pp. 462 - 463 , 468 - 469, 494 - 496 , 500 , and 549 - 551). Further, the Commenter has not identified the data alleged to have been excluded so the EPA cannot address that comment. Inany case, the Agency

maintains that the approach to accounting for variability is valid for the reasons set forth in MATS record. The Commenter has also failed to explain ho w solid oil - derived fuel fired EGUs are sufficientl y similar to low - rank virgin coal fired EGUs and, in any case, the EPA did not open this issue for reconsideration.58

**Comment:** Commenter (20273) disagreed with the EPA ’ s accounting for variability through the RDL multiplier. **Response:** This issue is outside the scope of this rulemaking. Comments concerning EPA’s accounting for variability through the RDLmultiplier were raised in public comments submitted in response to the May 3, 2011, proposed MATS rule ( 76 FR 24976). The EPA’s responses to the comments are in the RTC (see , e.g. , Vol. 1, p.523). 2.5.1 Filterable PM (3.0E - 02 lb/MWh) **Comment:** Commenter (20273) stated the reconsidered MATS for solid oil - derived fuel for fPM is too stringent. The Commenter stated that although the new proposed fPM emission limit for new solid oil derived fuel - fired EGUs is higher than the limit of 2.0x10 - 2 lb/MWh in the promulgated MATS, it is still much lower than what has been guaranteed b y qualified vendors in practice. The Commenter noted that once EPA reconsidered the fPM limit for coal, it proposed a limit that is three times higher (9.0x10 - 2 lb/MWh) than the newly

proposed limit for solid oil - derived fuel - fired EGUs . The Commenter stated that because the same technology (i.e. , fabric filtration) is accepted as the best technology for control of fPM emissions for both ty pes of EGUs , the difference in the standards cannot be justified on a technological level and evidences that EPA has not taken into consideration that the control technology functions with essentially the same level of control for both coal and solid oil - derived fuel. Commenter (20273) stated that the reconsidered MATS coal fPM proposed limit has been guaranteed by equipment manufacturers and has been achieved in practice. The Commenter stated that in discussions with equipment vendors, vendors explained that they are providing operator - acceptable guarantees for fPM at levels at approximating the reconsidered coal MATS of 0.01 lb/M M Btu and could provide a similar operator- acceptable guarantee in that range for a petroleum coke fueled EGU . The Commenter added that given the relative difference in the number of coal EGUs likel y t o be proposed versus the number of solid oil - derived fuel - fired units, it is unlikely that vendors will be incentivized to develop a different performance level for 100 percent petroleum coke fueled EGUs . Commenter (20273) said that even if a vendor were to offer an initial performance warranty , typically 12 to 18 months, the challenges in maintaining the proposed fPM limit to an operator that come later in the life of an EGU as the controls wear and the EGU degrades are significant. The Commenter stated that the proposed solid oil - derived fuel - fired EGU reconsidered fPM MATS would effectivel y preclude new 100 percent petroleum coke fired EGUs from being proposed and constructed. **Response:** The EPA disagrees with the Commenter’s assertions. The revised fPM limit was based on review of the performance of solid oil - fired EGUs and their control devices, and is independent of the review of the performance of coal - fired EGUs or their control devic es. The statute does not allow emissions limits to be established based on perceived control capabilities or EGU market share. The EPA agrees with the Commenter that EGU owners or operators need to be cognizant of potential control device and process degra dation and ensure that the EGU continues to meet emissions limitations. 2.5.2 Sulfur dioxide (1.0 lb/MWh)59

**Comment:** Commenter (20273) stated that with the alternative limit for SO 2 emissions as a surrogate for compliance with the HCl MATS appropriately raised from 0.4 to 1.0 lb/MWh in the proposed reconsidered MATS for solid oil - derived fuel - fired EGUs , the Commenter stated that compliance with the reconsidered MATS is possible. The Commenter stated that one vendor contacted explained that using compliance with the revised SO 2 standard as a surrogate for compliance with the HCl MATS is feasible and can be guaranteed. The Commenter consequently stated that the reconsidered MATS for SO 2 emissions as a surrogate for compliance with HCl emissions standard can b e supported b y vendor guarantees. **Response:** This comment requires no response . 2.6 Li quid oil - fired unit

—continental 2.6.1 Filterable PM (4.0E - 01 lb/MWh) **Comment:** Commenter (20293) stated that EPA ’ s proposed new source MACT limit for fPM for liquid oil - fired EGUs (4.0 x 10 - 1 lb/MWh) is higher than the adopted existing source limit for this category (3.0 x 10 - 1 lb/MWh) and which remains unchanged b y this proposal . The Commenter stated that an error of this magnitude demonstrates once again that EPA ’ s statistical methodology is flawed as described in this and earlier comments . The Commenter stated that in the past , the EPA has attempted to use the agency ’ s “beyond the floor authority” to establish a new source limit that is at least as stringent as the limit applicable to existing sources, but does not propose to do so in this rulemaking. **Response:** The EPA has adjust ed the limit proposed in the reconsideration notice to the more stringent level of the existing - source limit in this final rule for the reasons set forth in the record (see , e.g. , final MATS MACT Floor Memo, Docket ID EPA - HQ - OAR - 2009 - 0234 - 20132

– “Additionally , similar to the approach used in the HMIWIrulemaking, if the emission limit for new sources was less stringent than the emission limit for existing sources in the same subcategory , the EPA decided to use existing source limits for new sources. ” ). Although CAA section 112(d)(3) allows existing source MACT floor limits to be less stringent than new source limits, the EPA interprets this provision as precluding new source limits from being less stringent than existing source limits. See CAA section 112(d)(3). Further, in this specific instance, the data support setting the new source limit being equivalent to the existing source limit. Thus, the EPA is finalizing new source limits that are equivalent to the final existing - source limits. The new source limit for fPM from liquid oil - fired EGUs in the continental subcategory has been corrected to the existing - source limit of 3.0 x 10 - 1 lb/MWh . 2.7 Other **Support for new limits Comment:**  Commenter (20241) expressed support for the revised standards for Hg, f PM and HCl. Commenter (20281 , 5803 ) expressed support for the revised new source limits. Commenter (20296) expressed support for the new Hg limits.60

Commenters (29281 and 20282) stat ed that the revised new source limits make it likely that properl y designed and equipped new EGUs will be able to meet the limits with at least one of the compliance monitoring options currently provided under the rule. Commenter (20282) expressed suppor t for the new source limits in the proposed reconsideration rule as long as EPA provides appropriate compliance methods. Commenter (20265) stated that the EPA ’ s re -proposed new source limits appropriatel y reflect the use of the best control technology equipment available on the market. The Commenter agreed with EPA that these reconsidered limits do not represent a relaxation of the emissions control requirements originally promulgated in the MATS rule. The Commenter noted that as the EPA states, the same c ontrol equipment will be required to meet the reconsidered limits as would have been required to meet the limits promulgated in the MATS rule. However, the Commenter observed , the EPA has now estimated more accurately

the emissions reductions the same emis sions control equipment can actually achieve in practice. Commenter (20276) stated that in the final April 2012 MATS Rule , the EPA established limits for new EGUs that were too stringent. The Commenter said the limits could not be achieved b y new EGUs and would not have been able to be measured adequately because the limits were set below the detection limits of monitoring devices/methods. The Commenter agreed with lowering the standards as EPA has done in this rule revision, to the extent that these limits can be achieved and measured consistently with current technologies. **Response:** The EPA understand s that Commenter 20276 is referring to the February 16, 2012 (77 FR 9304) final MATS rule and notes that the Commenters ’ support for the reconsidered limits requires no response . Comments on the ability to measure the limits are addressed elsewhere in this document. **Compliance demonstration –**  **Hg limits Comment:**  Commenters (20281, 20282, and 20296) expressed concern that the proposed Hg limits are not achievable in all circumstances. The Commenter s stated that Hg sorbent trap monitoring s ys tems can reliably demonstrate compliance, but the proposed Hg limits are too low for Hg CEMS. Commenter s (20281 and 20282) cited Hg CEMS research supported b y the EPRIand the U.S. DOE, and stated that the two most prominent Hg CEMS monitors have level of quantifications of 0.3 and 0.5 μg/m 3 , which are values at or above the proposed limit. Commenter (20282 ) provided an attachment that stated that these levels of quantification are sufficient to disqualify Hg CEMS from consideration as a continuous compliance option. Commenter (20282) noted in Attachment 1 of their comment that the Hg emission limit is too low to use a Hg CEMS for compliance, but some owner/operators may choose to install a Hg CEMS to provide near real time feedback or process control information. **Response:** As mentioned earlier, if f or a particular EGU , an owner or operator believes that a Hg CEMS cannot achieve the performance requirements needed to satisfy the final standards, the owner or operator may elect to install and use a sorbent trap monitoring s ys tem to monitor for continuous compliance.61

Moreover, in order to better track emissions and allow process control during transitional periods, such as load swings, an owner or operator may choose to use a more frequent sampling period, e.g., 30 minutes, instead of several days, over short periods. An owner or operator is also free to use a Hg CEMS for control operations and use the sorbent trap monitoring for compliance if he feels that such operational data is sufficiently critical to the EGU ’ s control operations. As noted in the Reconsideration proposal, the EPA believe s the proposed change in the non - low rank virgin Hg limit for new EGUs will also allow the option of using a Hg CEMS for process control and for determining compliance based on information provided b y the Commenter s, our experience, and the NI ST ’ s recentl y confirmed capability to certify Hg calibration gas generators down to 0.2 μg/m 3

. **Comment:** Commenters (20281 and 20282) noted that the EPA has set the performance criteria for the permissible inaccuracy

of a RATA and the quarterly linearity check at levels several times higher than the 0.3 μg/m 3 limit for Hg emissions. The Commenter s concluded that one of the two methods designated b y EPA for demonstrating compliance with the new source Hg limits is unable to measure emissions accurately

at the proposed limit. The Commenter s discussed the differences between a Hg carbon trap sy stem and a Hg CEMS. The Commenter s stated that a carbon trap s ys tem does not provide real - time feedback on a unit ’ s level of Hg emissions, and that it is impractical to conduct 30 - minute sorbent trap runs as EPA assumed in setting the new source Hg limit. Commenter (20282) cited in Attachment 1 of their comment a power plant study , in which it was observed that the 24 - hour zero drift of the Hg CEMS monitors could commonly be 0.2 μg/m 3 . The Commenter noted the difficulty of a 24 - hour zero drift that is two - thirds of the emission limit. They also noted that the allowable Hg CEMS error of the quarterl y linearity check is greater than the proposed new - unit limit of approximately 0.3 μg/m 3

. **Response:** The EPA recognizes the concerns with the performance criteria for Hg CEMS identified by the Commenter s, and will consider tightening the criteria in the future. B ased on information provided by the Commenter s, our experience, and the NI ST ’ s recently confirmed capability

to certify Hg calibration gas generators down to 0.2 μg/m 3 , the EPA believe s some Hg CEMS may be used for determining compliance with the final new source Hg limit . **Comment:** Commenters (20281 and 20282) recommended that the Hg standard for new EGUs of 5 x 10 - 3 lb/GWh would allow EGUs flexibility in demonstrating compliance using either a Hg carbon trap system or a Hg CEMS to show continuous compliance with the MACT limit. **Response:** As mention ed earlier, based on information provided by the Commenter s, our experience, and the NI ST ’ s recently

confirmed capability

to certify Hg calibration gas generators down to 0.2 μ g/m 3 , the EPA believe s some Hg CEMS may be used for determining compliance. Should a particular EGU , an owner or operator believe that a Hg CEMS cannot achieve the performance requirements needed to satisfy the final standards, the owner or operator may elect to install and use a sorbent trap monitoring system to monitor for continuous compliance. Moreover, in order to better track emissions and allow process control during transitional periods, such as load swings, an owner or operator may choose to use a more frequent sampling period, e.g., 30 minutes, instead of several day s, ov er short periods. An owner or operator is also free to use a Hg CEMS for control operations and use the sorbent trap monitoring for compliance if he feels that such operational data is sufficiently critical to the EGU ’ s control operations and shorter sorbent trap sampling times are not practical.62

**Comment:** Commenter (20296) stated that the sorbent trap monitoring s ys tem can provide a reasonable measure of compliance and should continue to be an option in the final rule; however, the sorbent trap monitoring system does not necessaril y provide the type of process control feedback that some operators will need to activel y manage their Hg emissions to the very low levels required under MATS. The Commenter stated that the final rule should ensure that CEMS will be a feasible option for demonstrating compliance with the new source Hg limits. The Commenter stated that the Hg limit should be further adjusted to allow the use of CEMS and should not delay the is suance of a final rule. C ommenter (20296) stated that if EPA does not increase the Hg limit and instead promulgates a limit that cannot be reliably

detected with a CEMS, the final rule should provide that sources electing to demonstrate compliance with that limit using a sorbent trap cannot be held to violate the MATS rule based on CEMS data that they may generate. The Commenter noted that this is an important point because even those electing to demonstrate compliance with a sorbent trap may nevertheless elect to install a CEMS to monitor emissions or may be required to do so by

permit terms or other rule requirements that set higher Hg limits. The Commenter stated that without this qualification, these sources ’ CEMS emissions data could conceivabl y be argued to constitute “ credible evidence ” of a violation. **Response:** The EPA agree s with the Commenter that sorbent trap monitoring can be a useful means of demonstrating compliance, but as mentioned earlier, disagree that sorbent trap monitoring does not nec essarily

provide the ty

pe of process control feedback that some Commenter s desire, particularl y over the short - term. The EPA note s that Hg CEMS or any other typ e of data relevant to compliance with the emissions limit may

or may not be found to be credible evidence of compliance or violation, as the determination of whether data provide credible evidence of a violation of a standard is an issue beyond the scope of this rulemaking, and is a matter for a court to determine in a specific proceeding. Generally , under the CAA , the EPA (and other agencies with enforcement authorities) has the authority and the ability to determine whether any data constitutes credible evidence of a violation. Also, responsible officials that certify

compliance must make that certification on the basis of all available information. Nothing in this rule affects those underlying provisions. **Compliance demonstration –**  **other pollutants Comment:**  Commenter (20255) stated that EPA should retain the quarterl y testing option for HCl a s CEMS for HCl are not viable for all EGUs and data are lacking on the reliability and accuracy

of CEMS at the established emission limits. Given that EPA acknowledges that HCl monitors are not currently commerciall y available but are expected within 3 years, the Commenter stated that EPA should not issue rules with the expectation that industry and vendors will find a way to develop technology

to meet compliance deadlines. The Commenter stated that quarterl y testing may be the most economic compliance demo nstration method for many EGU at an annual cost, on average, of $50,000. **Response:** The subject of this comment is not within the scope of this rulemaking; therefore, no response is necessary . That said, the EPA disagree s with the C ommenters ’ contention that continuous HCl monitoring is premature or not available for the measurement at the limits set in the proposed standard ; however, the rule provides several options for HCl monitoring including: 1) using HCl CEMS for compliance, 2) seeking a pproval for an alternative HCl monitoring procedure through section63

63.7 (f) , 3) monitoring SO 2 continuously as a surrogate for HCl at facilities equipped with wet scrubber control technology

for SO 2 , 4) quarterl y reference method testing , and for certain liquid oil - fired EGUs, 5) use of fuel moisture measurements as an alternative to HCl monitoring . Including these options in the rule provides flexibility

to adopt CEMS monitoring options as the technology continues to mature and EPA performance specificati ons become available. **Comment:** Commenter (20254) stated that the lack of reliable HCl CEMS will necessitate that units without SO 2 controls perform quarterly stack testing to show compliance with the HCl limit. **Response:** The subject of this comment is no t within the scope of this rulemaking; therefore, no response is necessary . As mentioned earlier, however, the EPA disagree s with the Commenter s ’ contention that continuous HCl monitoring is premature or not available for the measurement at the limits set in the proposed standard. As the Commenter notes , the rule allows the compliance determination option of quarterl y performance testing, and that provides flexibility to initially comply in that manner and to adopt CEMS monitoring options as the technology continues to mature and EPA performance specifications become available if the source determines it is appropriate . **Comment:** Commenter (20295) s tated that the reconsideration proposal would revise many of the new source standards to levels that are more in line with what is achievable b y s ome of the newest coal - fired EGUs. But, the Commenter stated that there are concerns that all existing measurement technology options may

not be adequate to demonstrate continuous compliance with the MATS for new units, particularl y the revised Hg standards. Commenter (20282) expressed concern that the proposed limits are not achievable in all circumstances, stating that demonstrating actual compliance may not be achievable. The Commenter cited discussion in an attachment in their comment (20282 , Attachment 1) regarding compliance issues. **Response:** The first Commenter expresses specific concerns about the Hg emission limit and mentions repeating its generic concerns over emissions limits provided in comments on the proposed rule. The second Commenter expresses specific concerns about the Hg and PM emissions limits. As mentioned in the Preamble to the final rul e and RTC (see 77 FR 9389/3 , February 16, 2012; 77 FR 9390/1,2 , 77 FR 9391/3; and RTC, Vol.1, pp. 522 - 524), the EPA believes every emissions limit has been designed so that it can be measured with an acceptable level of accuracy with at least one compliance approach. As mentioned earlier, if f

or a particular EGU , an owner or operator believes that a Hg CEMS cannot achieve the performance requirements needed to satisfy the final standards, the owner or operator may elect to install and use a sorbent trap m onitoring s ystem to monitor for continuous compliance. As mentioned later, an EGU owner or operator who believes PM CEMS may not be sufficient to demonstrate compliance for his EGUs may choose to use a PM CPMS instead. The EPA notes that the latter Comment er anal yz ed about 6 months of data from three PM CEMS, all of which had successful correlations according to PS - 11, found no exceedances of the new EGU emission limit, thus showing for that EGU, PM CEMS worked very well (see EPA - HQ - OAR - 2009 - 0234 - 20282, Att achment 8, page 3). **Comment:** Commenter (20286) claim s that the EPA has made significant errors in determining the method RDLvalues in the TSD entitled Data and procedure for handling below detection limit data in analyzing various pollutant emissions databases for MACT and RTR emission limits ( Docket ID EPA HQ - OAR- 2009 - 0234 - 20062) by failing to consider the effect of additional moisture vapor condensation64

that occurs when Method 26A test runs collecting 3 to 4 dry s tandard cubic m eters (dscm) of sample gas are conducted to demonstrate compliance with the new petroleum coke HCl standard . The Commenter asserts that in the RDL determination for Method 26A for HCl and chlorine (Cl 2 ) , the EPA assumed a total mass RDLfor a Method 26A test of 60 micrograms ( μ g) , which the Commenter presumes is calculated using the documented anal ytical detection limit in Method 26A of 0.2 μ g/ml and the impinger volume of 300 milliliters (ml) assumed in Section 13.3 of Method 26A . This impinger volume appears to be based on a relative gain of approximately 100 ml of liquid from moisture vapor condensation in the impingers , occurring over a sample collection volume of 1 dscm . The Commenter believes that significantl y more liquid will be gained from moisture vapor condensation for test runs collecting 3 or 4 dscm of sample gas necessary for demonstrating compliance with the new petroleum coke - fired EGU standard and that because the anal ytical procedures of Method 26A do not allow concentration or extraction of the impinger solution before anal ys is as some other EPA methods (e.g., Method 29) , the RDLvalue assumed by

the EPA is biased low. Commenter (20261) claims the volume of moisture data submitted b y a liquid oil - fired EGU in response to the Information Collection Request (I CR) is not consistent with the volume that the Commenter believes should have been reported , and the Commenter recommends the EPA follow up on the data. The Commenter also suggests the use of Method 26A on wet stacks is problematic, in that the increased stack gas moisture leads to greater capture of condensed water and to elevated detection levels for HCl and HF. **Response:** Neither the HCl nor the HF limit for solid oil - derived fuel - fired EGUs was among those limits revised and proposed for comment in the reconsideration notice . As identified in the reconsideration proposal, the EPA will not respond to any comments addressing any provisions of the MATS rule not included in those issues (see 77 FR 71325). Moreover, the EPA is under no obligation to review HC l limit for solid oil - derived fuel because the deadline for commenting on the RDL procedure for HCl in the petition for reconsideration is long past. Although the EPA understands the concept asserted b y the Commenters

– additional moisture raises the detec tion level

– based on the information provided b y the Commenters, the EPA cannot ascertain that the RDL value was determined in error. Moreover, the EPA disagrees with the Commenter that additional investigation of the data need occur: the EPA used the dat a collected, submitted, and certified by EGU owners or operators as being accurate for their EGUs. Should a solid oil - derived fuel - fired EGU owner or operator believe HCl or HF CEMS incapable of providing accurate measurements for compliance purposes, he c an choose to use quarterly testing, along with continuous monitoring of one or more parameters. Further, as Commenter notes, EGUs with add - on SO 2 controls and SO 2 CEMS are eligible for the alternate SO 2 emission limit. **Comment:** Commenter (20308) stated that the Reconsideration Rule limits will require an operator to test below a limit one time and then test above the limit the next without knowing what actions to take to change the emission rate. The Commenter stated that when emission limits become so stringent that they are below the levels that can be measured with current testing methodologies (as the proposed limits are), the ability

to effectively

manage known and controllable variables in operating conditions and fuel qual ity is effectivel y eliminated. The Commenter stated that the risk of non - compliance due to unknown and uncontrollable variables, especiall y for elements present in trace quantities for which no detailed operational history

exists, is significantl y increase d. The Commenter stated that the new source emission limits in the proposed rule are so low that they do not accommodate the full range of unit operating65

conditions, and currentl y available monitoring methods lack the precision and accuracy necessary

to co nfidently

assure compliance. Commenter (20308) stated that EPA ’ s proposed limits do not provide sufficient flexibility to allow compliance demonstrations to be made during reasonably foreseeable operating scenarios, and must be reevaluated. The Commenter stated that the EPA should give greater consideration to the diversity of issues that impact the emissions from coal - based generation and to the process that state agencies have undertaken to issue air permit limits so that the final rule contains MACT st andards that are practical and achievable. The Commenter suggested that the resulting new source limits in the final Reconsideration Rule should be designed with greater flexibility so that sources can have reasonable assurance that compliance can be achieved across the entire range of operations a unit would experience. **Response:** The EPA disagrees with the Commenter’s assertions regarding emission limits being so stringent that they

are below the levels than can be measured with current testing methodolog ies and emission limits not providing sufficient operational flexibility . As mentioned in the preamble to the final rule and in the RTC, the emission limits have been designed so that the higher of the 3XRDL approach, which ensures values can be measured accurately , or the 99 UPLapproach, which takes operational variability

into account, is used. Therefore, the emissions limit accounts for both measurement and operational uncertainty. The EPA notes that responses to similar comments on our approach to developing the MACT standards were prepared and can be found in Section VII.A., MACT Floor Analysis of the final MATS preamble, and the RTC (see 77 FR 9389/3 , February 16, 2012; 77 FR 9390/1,2; 77 FR 9391/3; RTC, Vol. 1, pp. 522 - 524). The Commenter present s no new information that requires further response. **Calculation of standards Comment:**  Commenter (20293) recommended that EPA provide a more transparent and robust explanation for its methodology and data used in determining applicable MACT floor, which is particularl y crucial in instances where the new source floor is higher than the existing source floors. The Commenter stated that based on their general experience with existing facilities, that some increase in several of the final limits for new facilities may be warranted, any such increase should be based on the performance of the best facilities and control devices. The Commenter stated that due to the short comment period, the Commenter has not attempted to examine either the engineering or the long - term emission test results of specific “best -performing plants ” in each of the subcategories to determine the extent to which the reported test results are consistent with the long - term performance of those plant s or the technologies that have been employed. The Commenter recommended that EPA undertake such an effort before making a final decision on the proposed reconsideration of the standard. Commenter (20293) stated that EPA has not provided a rationale that can be evaluated to determine whether the proposed MACT levels are appropriate. The Commenter stated that the approach utilized by EPA several ye ars ago (where it evaluated the performance of the best available technology) produced a more reliable result than the agency ’ s current reliance on a method that is overly sensitive to a small number of statistics. The Commenter stated that the Court rejected the earlier EPA approach, not because o f its consideration of technology , but because the agency did not consider best -performing EGUs that did not employ a technology . The Commenter stated that in this source category all of the best -performing EGUs employ technologies; some also use cleaner f uels. The Commenter urges EPA to66

evaluate in detail the plants that show the best, consistent performance and determine the factors that led to this performance. The Commenter stated that EPA should then evaluate whether those factors are unique to that pl ant, or are of general applicability . The Commenter stated that EPA should then use ye ar- over- ye ar data of better performing plants to apply an objectivel y determined compliance margin for those plants. The Commenter stated that this compliance margin should then be applied to the best performing plant to establish the new source MACT. **Response:** The EPA disagrees with Commenter ’ s assertion that an adequate explanation of its methodology

and data used was not provided for the proposed reconsideration. The E PA believes the discussion in the reconsideration proposal preamble (77 FR 71323) and reconsideration MACT floor memo ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20220) adequately describe and explain its methodology . Further, the EPA disagrees with Commenter ’ s assess ment of the Court ’ s decision and believes it has followed both the statute and the Court ’ s mandate in its approach. The approach suggested b y the Commenter is not compelled by either the statute or applicable case law. The EPA maintains that its approach to establishing MACT standards is reasonable as explained in the rulemaking record. **Comment:** Commenter (20296) stated that the EPA has not rectified all of the flaws of the final MATS standards. The Commenter stated that EPA continues to use short - term “ s nap shot” test results to establish standards that must be met continuously and over the long - term. The Commenter attached a court brief in the White Stallion case explaining that these short - term data are not representative of long term performance. The C ommenter stated that on reconsideration, although EPA uses data from different EGUs than it used to establish the limits in the initial MATS rule, that data still comes from the short - term ICR stack tests, and the Commenter reasserted their argument that the EPA is relying on unrepresentative data that results in overly stringent standards. **Response:** The issue of the use of short - term emission test data to establish 30 - day rolling average emission limits was addressed in the final RTC (see , e.g. , Vol. 1 , pp. 462 - 463 , 468 - 469, 494 - 496 , 500 , 549 - 551). The EPA maintains that its approach is reasonable and adequatel y accounts for variability

for the reasons set forth in MATS record. **Comment:** Commenter (20305) stated that the reconsidered standards are unlawful and arbitrary . The Commenter provided discussion with citations to court cases, supporting the assertion that CAA §112(d)(3) requires that EPA ’ s standards for new sources be “no less stringent than the emission control that is achieved in practice by the best controlled similar source, ” the EPA ’ s proposed floors do not reflect the emission levels achieved b y the best performing EGU, and the EPA has not demonstrated that they are reasonab le estimates of such emissions levels. **Response:** The EPA does not agree that the approach for selecting the best performing source suggested by the Commenter is mandated under the statute and EPA maintains that its approach is reasonable. CAA section 112(d)(3) requires the EPA to establish the new source limits based on the performance of the best controlled “similar source.” The statute does not define the term “similar source” and, for that reason, the Agency

has discretion to evaluate the sources fo r which the Agency has data and make a selection as long as the Agency has a reasoned basis for it selection. The EPA acknowledges that there are various approaches that can be used for selecting the “best performer.” However, for consistency the EPA has u sed the same approach as was used at both proposal and final

– i.e., ranking of sources based on their lowest 3 - run average. The EPA decided upon this approach of selecting the “best performing”67

sources on the premise that the lowest 3 - run average was indi cative of the best the source could perform; the additional data from the sources in the MACT floor pool were then used to assess variability . I ssues with this approach were not raised in comment on the proposed MATS rule. **Comment:** Commenter (20293) state d that EPA has not to date provided an objective rationale for the 99 th percentile, as opposed to the 99.9 th percentile, the 90 th percentile or any other choice and they urge EPA to do so in the final rule. **Response:** The use of the 99 th percentile was addressed in the RTC document ( Docket ID EPA - HQ OAR- 2009 - 0234 - 20126 ; see , e.g. , Vol. 1, pp. 490 - 491, 508). This issue was not one of the issues being reconsidered and the EPA did not solicit comment in the reconsideration proposal regarding the use of the 99 th percentile in the anal ys es , but maintains that it is reasonable for the reasons set forth in the MATS record . **Best performing Comment:**  Commenter (20293) stated that the procedure used by EPA to identify

the best -performing sources that are the subje ct of the Reconsideration notice uses inconsistent definitions of the performance of the unit. The Commenter stated that EPA uses the single best run to identify what it calls the best -performing EGU , but then uses all test runs, including test runs from tests conducted at other times, to determine the performance of the EGU . The Commenter stated that the best -performing plant is not the plant that has a single low test run because a single test run does not constitute an acceptable reference method test an d provides no measure of the consistency in the performance of that plant that is then employed in the standard - setting process. The Commenter stated that the best -performing source is the plant that demonstrates the lowest consistent performance on the basis of all available testing, which should include at least one full Federal Reference Method (FRM) test with the three test runs that are required for such testing. The Commenter stated that new source MACT floor calculations are particularly susceptibl e to high statistical variability

under the procedure employed by EPA because there may

onl y be one or two FRM tests of the better performing EGUs . The Commenter stated that EPA ’ s inconsistent process for (1) identifying the best -performing unit and (2) calculating the performance of that unit leads to selection of EGUs whose emissions are variable and, on average, high, rather than the unit that demonstrates the best consistent performance. Commenter (20305) stated that the EPA was inconsistent in its approaches to calculating the revised standards and to selecting the best performing plants for its floors. The Commenter stated that if, as the Agency claims, the “ emission control . . . achiev ed in practice b y the best controlled similar source ” is best estimated by

a UPL applied to all stack tests in the Agency ’ s record, the “best controlled similar source ” must be the plant with the lowest emissions, by that measure of “ emission control. ” The Commenter added that by that measure of emission control, the Agency ’ s proposed “best performers ” are not the plants with the lowest emissions. The Commenter cited the November 15, 2012 Reconsideration Floor Memorandum. The Commenter discussed how specifi c plants ’ emissions determined b y the EPA ’ s UPL - adjusted, all - tests method, that are lower than the Agency ’ s proposed standard, and provided summaries of UPL calculations in several attachments. The Commenter stated that if the “ emission control achieved in practice ” by the best performing plant is best estimated by that68

plant ’ s single, lowest stack test, its standards must, in turn, be based on that measure of emission control (rather than the “pooled UPLvariance ” used b y the Agency to generate its standards). The Commenter concluded that the EPA has not met CAA § 112 ’ s requirements; by its measure of the emission control achieved in practice

– an Upper Prediction Limit of all stack tests in EPA ’ s data - set

– its limits do not reflect the emission control o f the best performing source. **Response:** As noted elsewhere in this document, the EPA used the same approach for selecting the “best performing similar source ” in the proposed reconsideration as was used at proposal and final. That is, the EPA selected the MACT floor pool of EGUs based on their lowest 3 - run emission test result and then incorporated any other data from these floor EGUs into the variability anal yses. Where onl y a single 3 - run average data point was available, the individual run data were used. CAA section 112(d)(3) requires the EPA to establish the new source limits based on the performance of the best controlled “similar source.” The statute doe s not define the term “similar source” and, for that reason, the Agency

has discretion to evaluate the sources for which the Agency has data and make a selection as long as the Agency has a reasoned basis for it selection. In this case, the EPA acknowledge s that there are various approaches that can be used for selecting the “best performer,” including that noted by the Commenter. However, for consistency the EPA has used the same approach as was used at both proposal and final

– i.e., ranking of sources ba sed on their lowest 3 - run average. The EPA decided upon this approach of selecting the “best performing” sources on the premise that the lowest 3 - run average was indicative of the best the source could perform; the additional data from the sources in the MACT floor pool were then used to assess variability . Issues with this approach were not raised in comment on the proposed MATS rule. As discussed in the final MATS MACT Floor M emo (Docket ID EPA - HQ - OAR- 2009 - 0234 - 20132), there were situations for some pollutants where onl y a single test average and no individual run - level data were available for the EGU identified as the best - controlled source. In these cases, no emission variability could be determined based on a single data point. Therefore, the next best - controlled similar source with sufficient data to account for variability was used to determine the new source MACT . **Achievability Comment:**  Commenter (20308) stated that the proposed standards erroneously rel y on short - term test results that are not representative of what has been or can be achieved in practice for the range of reasonabl y expected operating conditions experienced over the life of the unit. The Commenter suggested that the EPA obtain additional data to establish standards that can be achieved on an ongoing basis by the best performing EGUs , or revise the standards to address the full range of operating conditions, especiall y when attempting to regulate substances present in trace quantities and for which control performance can more strongly be influenced by

unknown and uncontrollable factors. Commenter (20308) stated that the revised new source standards in the proposed Reconsi deration Rule, although at a level that a modern well - controlled unit could potentially achieve for certain periods, have not been demonstrated to be achievable across the range of operating scenarios expected over the life of a unit. The Commenter referen ced earlier comments for the proposed MATS rule for discussion of this issue.69

Commenter (20308) stated that a coal - based generating unit is not a steady- state operation, and efficiency , performance, and emissions profile vary with operating conditions. Factors such as ambient conditions, the age of equipment, and changes in coal characteristics also influence operations. The Commenter stated that there is little operating data to base the HAP standards, and the ICR data was collected during stable full - load operations. **Response:** The issue of the use of short - term emission test data to establish 30 - day rolling average emission limits was addressed in the final RTC (see , e.g. , Vol. 1 , pp. 462 - 463 , 468 - 469, 494 - 496 , 500 , 549 - 551). This issue was not one of the issues being reconsidered and the EPA did not solicit comment in the reconsideration proposal regarding the use of short - term data. As mandated b y CAA § 112, the EPA has used the data available to it with which to establish the emission limits. These data reflect EGUs, and controls, of varying ambient conditions, age of equipment, and coal characteristics; thus, the EPA continues to believe that variability has been accounted for to the extent necessary and consistent with the statute . The Agency maintains that the approach to accounting for variability is valid for the reasons set forth in MATS record. **Comment:** Commenter (20308) stated that the most advanced controlled and the most stringently regulated existing coal - based EGUs have not been demonstrated to meet the proposed new source Reco nsideration Rule limits across the range of operating scenarios expected over the life of a unit . The Commenter stated that in prior comments, the Commenter included an analysis of 40 new coal - based generation projects which would be significantly challenged to meet all the proposed new source MACT standards based on the existing requirements in their air permits. The Commenter suggested that the EPA review C AA §112(g) case - by- case MACT determinations. **Response:** The Commenter’s repetition of comments it submitted in response to the proposed rule on emissions limits not subject to reconsideration are not relevant, and the EPA is not addressing them. Then, as now, the EPA disagreed with the commenter, and responses to those comments can be found the RTC to the proposed rule. Regarding the Commenter’s assertion that the proposed reconsidered emissions limits have yet to be demonstrated across the range of operating scenarios expected over the life of a unit, the EPA also disagrees. As explained elsewhere in this document, the EPA established emissions limits that take into account the potential variability , as expressed by these Commenters, such that the best -per forming EGU is or EGUs are expected to be able to meet 99 times out of 100 times. The EPA has based the new source limits in the proposed MATS reconsideration on all of the data available to it; whereas many of the case - by- case determinations were based on a much more limited data set and in a different manner than required under section 112(d)(2) and (3), the EPA believes the reconsidered limits for new EGUs are achievable. **Test methods Comment:**  Commenter (20261) stated that they reviewed the final MATS and proposed reconsideration emission limits for coal and liquid oil EGUs with respect to the capabilities of manual stack test methods. The methodology used in the review was the same as described in their comments on the proposed MATS rule. Considering onl y those limits that were revised in the reconsideration proposal, f PM, Hg, selenium, and Pb should be measurable for all coal EGUs with acceptable accuracy using standard EPA manual test methods. Hydrochloric acid (HCl) will be measurable at the beyond - the floor limit in most coal units; however, it may not be measurable in w et stacks with very low emissions, due70

to dilution of the sample with condensed water. However, the Commenter asserts that the MATS rule includes limits on other substances and EGU types that were not addressed in the reconsideration proposal. Based on pas t work, the Commenter concluded that some of the regulated substances still may not be measured accurately at the proposed limits with present methods. The new EGU limits that are of concern are as follows: New Coal EGUs : Non - Hg metals b y EPA Method 29: arsenic, beryllium, cadmium New Continental Liquid Oil EGUs : Mercury by EPA Method 30B Non - Hg metals b y EPA Method 29: arsenic, beryllium, cadmium HCl and HF b y EPA Method 26A New Non - continental Liquid Oil EGUs : Mercury by EPA Method 30B HF b y EPA Method 26A The Commenter (20261) stated that EPA attempted to account for method sensitivity by calculating RDL s and using those in some cases as MACT floors for the final Rule. However, for metals , the EPA derived the RDLs b y multiplying published anal ytical detection limits for clean water samples by three. Based on the Commenter ’ s evaluation of the measurements performed for the I CR, reporting limits for the filter and impinger fractions of a Method 29 train are frequently much higher than the RDLs. Th e Commenter (20261) stated that for Hg using Method 30B , the EPA adjusted the limit for new coal EGUs burning coal with a heating value > 8,300 Btu/lb to allow plant owners to collect half - hour samples with adequate method sensitivity . At the proposed emis sion limit, the amount of Hg collected on the first sorbent trap bed during a 30 - minute sample with a 1 liter/minute flow rate will be approximately

10 ng. This amount can be measured accuratel y if the background Hg concentration in the sorbent is low. How ever, a footnote to the sampling requirements in the proposed rule (and in the Final MATS rule) states that the Method 30B estimated mass must be one - half of the target emission rate. The Commenter understands this to imply that the method must be capable of quantifying Hg at an emission rate of 0.0015 lb/GWh, or approximately 0.15 lb/TBtu. Assuming that Hg loading on the trap is proportional to sample volume, a longer sampling duration (e.g., 1 hour) or higher sampling rate (2 liters/min) is required to achieve this level of sensitivity . The EPA should clarify this point in the final rule and consider allowing higher flow rates. The Commenter (20261) stated that EPA did not adjust Hg limits for other source types using the same approach; thus, very

long sampling times will be required to measure accurately at the limits for new continental and offshore oil EGUs (approximately 3.5 and 14 hours, respectively). The Commenter71

recommends that EPA consider using the same approach to deriving the limit for all source types as was used for coal EGUs > 8,300 Btu/lb. The Commenter (20261) stated that for HCl measurements at liquid oil EGUs by EPA Method 26A, only one facility

that participated in the ICR reported a detection limit below the limit for new continental oil EGUs , which is based on a calculated RDLof 4 x 10 - 5 lb/MMBtu. In fact, only one facility (East River, ORIS 2493) was repre sented in the EPA ’ s database as having HCl detection limits below the RDL. The Commenter reviewed the test report for that facility which the EPA did not have access to prior to the issuance of the Final Rule. The Commenter ’ s conclusion is that the data qu ality for those results is questionable. The tests were run at three times the normal sampling rate. The impinger volume collected (10 - 12 ml condensed moisture) is not consistent with the volume that should have been collected at the reported moisture content (7.5 percent) and sample volume (approximately 240 dscf). The information in the test report is not sufficient to determine the reason for the discrepancy , but the Commenter recommends that EPA follow up on these data . The EPA did not report on the bas is of the RDLcalculation for HF; however, for measurements at both continental and non - continental liquid oil EGUs by

EPA Method 26A, the same issue applies for HF as for HCl. As discussed in their previous comments, Commenter (20261) stated that the use of Method 26A on wet stacks is problematic for compliance monitoring, because, as observed in the ICR tests, increased stack gas moisture leads to greater capture of condensed water, and consequently to elevated detection limits. Another potential measurement issue is for EGUs that inject ammonia for flue gas conditioning or NO X control; researchers have reported that ammonia salts formed in the stack gas can dissociate in the Method 26A impingers under some conditions to form HCl, thus creating a high bia s for this parameter. This potential bias requires further investigation, and EPA should consider discussing it as a potential source of inaccuracy

in the methods requirements in the final rule. **Response:** The EPA finds the Commenter agrees that the test m ethods are sufficient for the new coal fired EGU PM, Hg, Se, and Pb emission limits, the Commenter expresses concerns over the test method for new coal - fired HCl emission limits, and the Commenter acknowledges that its concerns over the test methods for th e other pollutant emission limits were not among the issues opened for reconsideration. As identified in the reconsideration proposal, the EPA will not respond to any comments addressing any provisions of the MATS rule not proposed for comment in the reconsideration notice (see 77 FR 71325). The EPA also notes that it has reviewed and responded to similar concerns in the final rulemaking (see , e.g. , RTC, Vol.1 , Section 4A03, and Vol. 2, Section 5A). The EPA believe s that our procedure for establishing the floor and the emissions limit ensures that the Methods identified in the rule, along with their requisite sampling times, are appropriate for determining compl iance with the emissions limits. With respect to concerns about sampling rates or periods for Hg, the EPA notes that the value used represents what we believe can be achieved now ; should an EGU owner or operator believe other sampling rates or periods are appropriate, he can increase the sampling period as desired and he should seek EPA approval before increasing the sampling rate. With respect to the concern about HCl detection levels, see the earlier response. **Other Comment:**  Commenter (20305) disagreed with the EPA ’ s statement that new power plants would choose to install and operate the same or similar air pollution control technologies in order to meet the72

revised emission limits as would have been necessary to meet the previously

finalized standards. The Commenter stated that emissions of toxic pollution depend not just on the control technology installed but also on the way

the technology

operated and maintained, the way the EGUs are operated and maintained, raw material inputs, and other factors. The Commenter stated that two sources with “the same or similar air pollution control technolo gi es ” can and often do emit different quantities of toxic air pollution at different rates. **Response:** The EPA disagrees with Commenter ’ s assertions and stands by its discussion in the reconsideration proposal preamble . Sources will have to be designed in a manner that assures compliance with the final rule and the Commenter has provided no data to support its assertions.73

**3.0 BEYOND**  **- THE**  **- FLOOR**  **(BTF) ANALYSIS**  **Comment:** Commenter (20305) stated that the EPA ’ s BTF analysis inexplicabl y and arbitraril y excludes reductions that that the Agency already assumes facilities will be able to meet. The Commenter stated that the Agency

has violated the Act. The Commenter disagreed with the EPA ’ s anal ys is of incremental cost effectiveness between 75 percent and 50 percent of the proposed floors, stating that industry ’ s statements that industry targets such emission levels to allow for a margin of error were unbinding and unenforceable. The Commenter stated that the effect of the EPA ’ s anal ys is creates an unlawful 25 percent “ compliance margin ” which ignores the achievability of BTF standards between 75 and 100 percent of the proposed floor. The Commenter stated that the EPA ’ s determination that a CAA §112(d)(3) standard 50 percent below the proposed floor was not achievable due to cost does not mean that such a standard at 75 percent (or between 75 percent and 100 percent of the floor) is also not achievable. The Commenter stated that the EPA already accounted for sources ’ variability in its floor calculations by appl ying the UPL to the best performers ’ stack tests (November 30, 2012 Reconsideration MACT Floor Memorandum, and December 16, 2011 MACT Floor Memorandum). The Commenter stated that the UPL statistical formula and the 30 day averaging period provide for variability that new EGUs may experience as compared to the best performer. The Commenter concludes that the Agency ’ s use of a 25 percent compliance margin as ye t another measure to account f

or variability

is unlawful. The Commenter stated that by focusing onl y on the cost effectiveness of a standard between 75 and 50 percent of the proposed floor, the Agency ignored the achievability , or even the possibility, of a standard between 75 and 100 percent of the proposed floor. The Commenter stated that the EPA therefore violated its duty to determine the maximum reductions that are achievable under CAA §112(d)(2). **Response:** The EPA is confident in our approach for evaluating BTF emission limits fo r new sources in the reconsideration proposal. Because the BTF analyses for this reconsideration proposal were for emission limits for new , yet - to - be constructed , units, the EPA had to make assumptions about such a new hypothetical plant. When setting MACT emission limits for the new source categories , the EPA determined the emission limitation achieved in practice by the best performing existing source within that category for each regulated HAP or HAP surrogate . The EPA then incorporated inherent variability (e.g., process, fuel, operational) using the “upper predictive limit” methodology that has been explained elsewhere. The EPA believes that it has appropriately considered variability in establishing standards that apply at all time s . See Mossvi lle Environmental Action Now v. EPA , 370 F.3d 1232, 1242 (D.C. Cir. 2004) (holding that MACT floors may legitimately

account for variability

because “ each [source] must meet the [specified] standard every day and under all operating conditions. ” ). The EPA believe s that our methodology

for incorporating inherent variability is consistent with past practice and with Court interpretations of the statute. The control equipment associated with the best performing existing source must be designed to meet an emiss ion standard at optimum operating conditions. That level of performance at optimum conditions would be expected to be the highest level of performance

– a level of performance that exceed s that necessary to meet the actual emission standard which the sourc e would need to meet under all operating conditions. In petitions for reconsideration, petitioners stated that operators usuall y target emissions that are 50 to 75 percent of the emission limitation to provide for a74

margin of error and unexpected spikes in emissions . The Commenter indicates that this level is unbinding and unenforceable . The EPA agree s, but acknowledge s that it represents the reality of how control technology

equipment are designed and operated by sources that must comply at all times with the promulgated standard . Inconducting the BTF anal ys is , the EPA assumed that the installed controls were de signed to achieve a level of 75 percent of the floor emission standard at optimum conditions and to not exceed the floor e mission standard during non - optimum conditions. The EPA then assumed that a BTF emission limit would require some level of investment in additional, larger, or better performing control technology

(e.g., installation of downstream “polishing ” baghouses for fPM). For our anal ys i s , the EPA assumed a BTF level of 50 percent of the floor emission level for the hy pothetical new plant. The EPA believe s this is a realistic approach and feel s confident in our conclusions drawn from the anal ys is. **Comment:** Commenter (20305) stated that the EPA ’ s rejection of various BTF standards because they are not “ cost - effective ” or their cost is not “reasonable ” is unlawful. The Commenter stated that in these cases, the EPA has used the wrong legal test. The Commenter stated that CAA §112(d)(2) requires the “maximum ” degree of reduction that can be achieved considering cost and the other statutory factors, but that the EPA ’ s rejection of BTF standards merely because it views their cost - effectiveness as unreasonable contravenes Congress ’ s plainly expressed intent. Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837, 842 - 43 (1984); New Jersey v. EP A , 517 F.3d 574, 582 (D.C. Cir. 2008). The Commenter further stated that because EPA bases its rejection of BTF standards on cost effectiveness claims without making any effort to explain how its rationale comports with the statutory language, and because its reading of CAA §112 “ diverges from any realistic meaning of the statute, ” the agency ’ s reading is also unreasonable under Chevron step two. **Response:** CAA §112(d)(2) requires that the Agency promulgate standards that “ shall require the maximum degree of reduction in emissions...that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non - air quality

health and environmental impacts and energy requirements, determines is achievable... ” The EPA has, as directed by Congress, considered the cost of achieving “the maximum degree of reduction ” and in all cases , ex cept one, found the costs of achieving a BTF level of control to be not cost - effective or for the costs to be unreasonable. The Commenters believe that the EPA should have continued to examine, in detail, the “non - air quality health and environmental impac ts ” and “ energy requirements ” associated with the considered BTF emission limit. The EPA did consider these factors but agrees with the Commenter that it was not adequatel y described in the BTF TSD. The final BTF TSD has been edited to more completel y desc ribe the full range of factors considered in the BTF analysis. In any case, the Agency maintains that a decision to deny

a BTF level of control on costs alone would be valid if the conclusion reached (i.e. , that the BTF level of control is not cost effective) is valid because even assuming no non - air quality health or environmental impacts or adverse energy requirement, the costs will remain unreasonable. 3.1 New coal - fired unit 3.1.1 Filterable PM **Comment:** Commenter (20305) stated that the EPA ’ s standards must reflect the maximum degree of reduction of emissions of HAP achievable, as stated in CAA § 112. The Commenter stated that the CAA § 112 language demands consideration of all available methods of reducing pollution, including75

alternative “ size[s] and [c]onfiguration[s] ” of various pollution - control technologies . In re. Knauf Fiber Glass, GmbH, 8 E.A.D. 121, 141(E.A.B. 1999). The Commenter stated that the EPA has not followed that command in its BTF anal ys is for fPM , by failing to assess fabric filters providing superior pollution - control than EPA ’ s floor- based limit. The Commenter provided as an attachment examples of EGUs with fabric filters and emissions below the EPA ’ s limit. **Response:** The EPA believes that it has adequately conducted a BTF analysis for fPM for new coal fired EGUs. In setting the MACT floor (the emission standard), the Agency selected the best performing source for fPM. The Agency had insufficient information on the specific filter material used by the best performing source and, therefore, the EPA was unable to assess whether or not additional reductions could have been possible with better performing filters. However, the EPA stated in the BTF TSD ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20221) that “ it is reasonable to expect that the very best performing source is achieving that level of control through the application of well -performing control technologies, by

following a disciplined and routine maintenance schedule, and by operating in an efficient mann er. ” And, as with the floor emission standard, any BTF emission standard would need to be one that is achievable “under all operating conditions , ” not just under optimum conditions. In addition, the Environmental Appeals Board case cited by the Commenter c oncerns development of a Prevention of Significant Deterioration permit applicable to a specific units, and not development of a nationally applicable MACT standards under section 112; thus, we do not find the anal ys is in that case to be directl y applicabl e to development of the new source standards. 3.1.2 Hydrogen chloride **Comment:** Commenter (20249) does not support the establishment of a BTF standard for HCl of 1.0E 02 lb/MWh. The Commenter stated the anal ys is performed is based on chlorine content of the fuel and control efficiencies of a high efficiency spray dryer absorber or wet - flue gas desulfurization scrubber . The Commenter said that the EPA believes a BTF emission HCl limit is cost - effective because it does not involve additional cost. The Commenter stated EPA did not evaluate the impact of additional controls on the cost of HCl control. The Commenter said, when controlling Hg emissions, the chlorine content of the coal can impact the removal efficiency of sorbent injection. It is the Commenter s ’ understanding that one option to improve Hg control is to inject chloride, which may increase HCl emissions. The Commenter stated that improving the efficiency of one emission control while adversely impacting another isn ’ t limited to just Hg and HCl, it is also true of sorbent injection and particulate matter emissions. The Commenter stated, often the collateral increases in one pollutant are trivial when compared to the beneficial reduction in another. The Commenter concluded, nonetheless , the EPA should consider the impact of Hg control when establishing a BTF standard for HCl. **Response:** The EPA believes that is has adequately and correctl y performed the BTF anal ys is for HCl and stands by

the conclusion described in the BTF TSD and in the reconsideration preamble. As stated in the BTF TSD, the EPA believes that is it reasonable to assume that a new coal - fired EGU will install either a wet flue gas desulfurization (wet - FGD) scrubber or a high - efficiency spray drier absorber (SDA) for SO 2 control and the EPA believe s that the level of HCl control that can be achieved by these equipment exceeds the calculated MACT floor emission limit. Because the FGD is installed for SO 2 control and the increased HCl control is achieved as a “ co - benefit , ” there are not additional cost s for the BTF HCl control. Regarding the interactions affecting HCl and Hg control, the EPA is aware of these interactions as has been discussed in great length in the rule proposal and in response to comments on76

the rule proposal (see , e.g. , 76 FR 25014; RTC, Vol . 1, pp. 315, 588; RTC, Vol . 2, pp. 526 - 52 7) . T he EPA understands that flue gas halogens will promote the oxidation of Hg which enhances its control. However, the EPA is also aware of several commerciall y avai lable control options that have been specificall y developed to control Hg that is present in the flue gas stream as elemental Hg vapor. Western subbituminous and many low rank virgin coals have inherentl y low chlorine levels and tend to produce elemental Hg vapor in the post combustion f lue gas. Fac ilities burning those fuels may also use those technologies ( e.g., bromine injection, halogenated activated carbon, etc.). Although injection of chloride for Hg control is an option (injection of bromide is the more likely option), it would be unlikely to increase HCl emissions for a new coal - fired EGU with a high - efficiency SDA or a wet - FGD scrubber. Both of these acid gas removal technologies are very efficient for removal of HCl , which is both a strong acid and is highl y water soluble , which means its removal in those controls is greater than SO 2 . **Comment:** Commenter (20305) stated that the EPA ’ s failure to consider further measures for HCl controls, such as requiring the use of low - chlorine coal, violates the Act. The Commenter stated that 42 U.S.C. §7412(d)(2)(A) requires the EPA to consider the “ application of measures, processes, methods, systems or techniques including...process changes [or] substitution of materials.... ” The Commenter stated that the EPA did not consider low - chlorine coal or coal blending, and did not offer any rationale as to why it did not do so, or why

it would be infeasible for facilities to use low - chlorine coal. **Response:** As stated in the BTF TSD, the EPA believes that is it reasonable to assume that a new coal fired power plant will install either a wet - FGD scrubber or a high - efficiency SDA for SO 2 control and the EPA believe s that the level of HCl control that can be achieved by these equipment exceeds the calculated MACT floor emission limit. The EPA did not consider a requirement to use low - chlorine coal because, when applying these FGD control technologies, the chlorine content of the coal does not affect the emission level. Coals containing very high chlorine levels can see greater than 99+ percent control and very low emission levels while coal containing inherently very low chlorine levels (and usually high alkalinity) can see a relatively low HCl control percentage, but a very similar emission level. HCl is very easily removed in these control technologies due t o its strong acidity and its high solubility . 3.2 Other beyond - the - floor **Comment:** Commenter (20253) stated that the EPA should consider fuel switching from coal and oil to natural gas at new EGUs as a beyond the floor option, which is an option that reli es upon cleaner fuels to lower emissions beyond the baseline that can be achieved b y appl ying the best pollution controls to existing fuels. The Commenter stated that, if necessary , the EPA should re -propose the MATS rule for new EGUs to incorporate fuel s witching as such a beyond the floor option. The Commenter stated that by not considering fuel switching as a beyond the floor option , the EPA will not achieve the health and environmental benefits required by the CAA. The Commenter stated EPA can correct its failure to achieve it s statutory

mandate by

requiring emission limits consistent with fuel switching using natural gas because the reconsideration proposal requested comments on all aspects of EPA ’ s beyond the floor anal ys is including any

technologies o r practices demonstrated to consistently reduce HAP emissions below the standards proposed and in a cost - effective manner. Specificall y, the Commenter (20253) stated that EPA erred in the reconsideration by not basing emission limits on fuel switching to natural gas as a beyond the floor requirement for new sources. The Commenter referred to clear legal precedent and applicable statutory criteria that m andate the EPA set77

emission limits based on fuel switching to natural gas as a beyond the floor requirement for new EGUs as a means of reducing HAP to the maximum extent possible. The Commenter stated that EPA is correctly reconsidering the BTF provisions as CAA § 112(d)(2) (the BTF provision) provides that EPA must require the “maximum degree of reduction ” in HAP. Furthermore, CAA § 112(d)(2) specifies that eligible compliance options include process changes, substitution of materials or other modifications, which clearly

include changes to cleaner fuels such as natural gas. Furthermore, fuel switching has been identified as a means of reducing emissions that EPA must consider in reaching the “maximum degree of reduction ” in emissions. See Nat ’l Lime Ass ’n v. EPA , 233 F.3d 625,635 (D.C. Cir. 2000). The Commenter (20253) stated that in the original MATS proposed rule , the EPA recognized that emissions from natural gas power plants are negligible and offers a greater degree of reduction than other compliance options and, therefore, offers the maximum degree of reduction and must be selected as the beyond the floor technology unless some other statutory criterion rules it out. The Commenter stated that this analysis is consistent with other EPA rulemakings such as the Power Plant GHG NSPS, which set emission levels for fossil - fueled new power plants consistent with natural gas combined cycle (NGCC) EGUs as these gas EGUs are the best s ystem of emission reduction. According to the Commenter (20253), natural gas c ombined cycle plants are less expensive than natural gas combined cycle plants with lower capital and annual operating costs. The Commenter also stated that EPA ’ s argument that natural gas is not widel y available is inaccurate and unsupported and inconsistent with EPA ’ s pronouncements in other rules. For example, the Power Plant GHG NSPS recognized that NGCC EGUs will be the predominant choice for new fossil fuel - f ired generation. Citing non - air quality health and environmental benefits, the Commenter stated that modern NGCC plants use less water for cooling than coal fired power plant and do not generate coal ash for disposal. The Commenter (20253) cited current l itigation over the MATS rule ’ s failure to properl y assess natural gas as a beyond the floor requirement. The Commenter (20253) stated that the beyond the floor requirements for new sources need not be burdensome. For example, the Commenter observed, emis sion limits consistent with use of natural gas would be required unless a permit applicant can demonstrate that natural gas is unavailable. The Commenter stated that another option would be to consider natural gas on a case b y case basis for all new coal and oil - fired EGUs whereb y each potential emission control technology would be anal yz ed with EPA determining what the maximum emission reductions should be for that unit. The Commenter suggested that fossil fuel plants where natural gas is available could b e considered as a “ subcategory” for MACT standard - setting purposes. The Commenter stated that in this subcategory of EGUs (where natural gas is available), the MACT BTF limits would be based on the emissions of NGCC EGUs . The Commenter stated that none of these approaches is a prohibition on new coal plants. The Commenter stated that i f natural gas is available and cost effective in a particular location, then a new EGU at that location must meet the emission standard achieved by a NGCC unit. Otherwise, stated that Commenter , the standard for the new EGU could be set based on MACT floor separately established for the particular subcategory

of EGU. **Response:** The EPA determined it unreasonable to mandate fuel switching because that approach would prohibit new construction of coal - fired EGUs. See 76 FR 25049/1. For existing EGUs, the EPA reasonabl y rejected a fuel switching standard as not being “achievable” because natural gas supplies78

might be inadequate during peak demand, id. at 25046/2 - 3. The EPA also conc luded for existing sources that fuel switching would not be a cost - effective way to achieve HAP reductions. The Commenter claims that EPA’s position is inconsistent with the proposed NSPS for GHG emissions from new EGUs issued pursuant to CAA section 111 (the Carbon Pollution Rule). There, the EPA proposed that new coal - fired EGUs meet the same emission as natural gas combined cycle (NGCC) plants for GHG emissions only , because such coal - fired EGUs could install a control technology

– carbon capture and s torage

– that “is technically feasible and sufficientl y available” and can reduce emissions to levels emitted by NGCC EGUs. See 77 FR 22392, 22414 (April 13, 2012). The EPA went on to provide an alternative compliance method

– allowing new coal - fired EGUs to meet the proposed standard on an average basis over a 30 - ye ar period

– which was intended to provide compliance flexibility to assure that such EGUs could continue to be built. Id. at 22406 - 07. Importantly , however, in the Carbon Pollution Rule proposal, the EPA did not propose to require new coal - fired EGUs to meet the same standards as natural gas plants for any pollutants other than CO 2 . See 77 FR 22411/3. For example, coal - fired boilers and NGCC EGUs have separate NSPS emission limits for criteria pollutants. In fact, in the Carbon Pollution Rule proposal, the EPA explained

– [A]t this time, we do not consider it appropri ate to [apply the same §111 standards for conventional pollutants emitted by NGCC EGUs to criteria and air toxic pollutants emitted by

coal - fired EGUs]. This is because although coal - fired EGUs have an array of control options for criteria and air toxic air pollutants to choose from, those controls generall y do not reduce their criteria and air toxic emissions to the level of conventional emissions from natural gas - fired EGUs. Id. Accordingl y, the EPA’s actions in the GHG (and criteria pollutant) NSPS context retain a viable path for construction of new coal - fired EGUs.79

**4.0 FILTERABLE PM MONITORING**  4.1 Quarterl y stack testing **Retain Quarterly Stack Testing Comment:**  Commenters (20242, 20246, 20247, 20248, 20249, 20250 20254, 20255, 20267, 20272 , 20275, 20280, 20281, 20282, 20285, 20290, 20291, 20294, 20295, 20303, 20304, 20308 , and 5803 ) requested that the EPA retain the PM quarterl y stack testing compliance option. Commenters (20242, 20246, 20248, 20249, 20255, 20276, 20281, 20282, 20290, and 20292) provided general comment that stated that there will be sources that will need to rely on stack testing for various reasons including cost - effectiveness, LEE qualification, a shortage of PM CEMS hardware or qualified installers, PM CEMS improper functioning or PM CEMS inability to pass performance specification testing . The Commenter s stated that the quarterly testing option allows avoidance of the installation, operation, and maintenance concerns associated with PM CEMS and PM CPMS for sources that can demonstrates compliance with the standards using the same method

– testing

– that was used to set the standard. Commenters (20242, 20246, 20281, and 20294) stated that quarterly stack testing provides an essential fall - back option should PM CEMS or P M CPMS not meet source or agency expectations and provides flexibility for sources where one PM monitoring option may be difficult to implement due to site specific issues. Commenter (20285) stated that smaller facilities would be forced to incur signific ant costs, and would not yield any environmental benefit if they were expected to use either PM CEMS or PM CPMS. Commenters (20254, 20267, 20272, 20282, and 20291) stated that EPA should retain the quarterl y stack testing option because many facilities wil l have no interests in demonstrating compliance using CEMS, especiall y for EGUs with very low PM and Hg levels for which there is no need for the “ frequent feedback” of PM CEMS . The Commenter s stated that it is presumptuous for EPA to assert that because direct measurement of f

PM or a correlated parameter is available, quarterl y stack testing is not necessary . Commenters (20269, 20271, 20275, 20276, 20279, 20280, and 20303) stated that it appeared that the EPA asked for comment on the use of quarterl y stac k testing for new EGUs only . The Commenter s believed that quarterl y stack testing should be an option for both existing and new sources . The Commenter s provided various reasons (economic, operational, and other considerations) for why existing EGUs should be allowed the use of quarterly stack testing. Commenter (20247) stated that EPA should retain the quarterl y stack testing compliance option until PM CEMS technology

advances and consistently provides reliable continuous emissions monitoring. **Response:** The EPA acknowledges the Commenters’ support for retaining quarterl y testing. For the reasons set forth in the preamble to this final rule and below, the rule does not retain the quarterl y PM performance testing option for new units.80

**Do not reta in the quarterly stack testing option**  **Comment:** Commenters (20258 and 20293) stated that they do not support retaining quarterly stack testing in lieu of PM CEMs because this option reduces the quality of the information provided to operators of these sources and increases the risk of inadvertent excess emissions . The Commenter stated that it provides no meaningful cost savings or other benefit to operators of EGUs, but poses a significant resource burden on state and local permitting authorities. Commenter (20305) stated there is no reason to retain the quarterly stack testing option because the results provided b y quarterly tests are not sufficient to ensure continuous compliance with the standards, if the variability

assumed by

the Agency

in crafting its standards exists. The Commenter noted that the Agency ’ s rationale for the extended 30 - day averaging period was to “provid[e] an additional allowance of variability

for CEMS use. ” See RTC, Vol. 1 , p. 564. **Response:** G iven that continuous, direct measurement of f ilterable PM (fPM) or a correlated parameter is available, is preferable to quarterl y stack testing for determining compliance on a continuous basis, and is likely

to be used by

most new EGUs to monitor compliance with the proposed new source standards , the rule does not retain the quarterl y PM stack testing option for new units. New EGUs can be designed to incorporate PM CEMS or PM CPMS from the outset, without being impeded b y retrofit location installation constraints that could impact existing EGUs. This final action now requires new sources to use either PM CEMS or PM CPMS as options for determining compliance with the new source PM limits; data from the PM CEMS or PM CPMS are suitable to provide air operating permit compliance certificatio ns. **Other questions and concerns Comment:**  Commenter (20272) requested guidance on the obligation to perform the quarterl y stack tests in the case of affected coal - fueled EGUs that do not operate or operates for de minimis periods of time during any parti cular calendar period . The Commenter stated that EPA has defined a Quality Assurance (QA) Operating Quarter as calendar quarter in which there are at least 168 unit or stack operating hours for purposes of Hg CEMS . The Commenter stated that EPA should foll ow same approach with PM stack testing, and confirm that the quarterly stack test requirement does not appl y to low - utilization EGUs that are below the Operating Quarter threshold as defined by the Hg CEMS regulations. **Response:** As the rule no longer cont ains quarterly PM testing for new EGUs, no response is necessary . Further, EPA did not propose to revise PM testing requirements for existing sources. However, in regard to existing EGUs which still have the option to conduct quarterl y stack testing, the final MATS rule in 40 CFR § 63.10021(d)(1) allows EGU owners or operators not to conduct performance testing in those quarters during which less than 168 boiler operating hours occur, except that a performance test must be conducted at least once every calendar ye ar. **Comment:** Commenter (20290) stated that quarterly stack testing is currently how sources determine if they qualify for Low Emitting EGUs and the relaxed requirements that come with that qualification.81

Commenter (20248) stated that the elimination of quarterl y stack testing would also eliminate the LEE compliance option. The Commenter stated that i f a unit exceeds the LEE emission rate during the qualifying 3 - ye ar period, it is unclear what this unit ’ s compliance status would be and how compliance would be demonstrated if the quarterl y testing option were eliminated. **Response:** The subject of this comment is not within the scope of this rulemaking , as the LEE program does not apply

to new, EGUs. Therefore, no response is necessary . **Comment:** Commenter (20262) stated that the requirement for quarterl y performance tests to be conducted every

80 to 100 calendar day s is restrictive and needs to be changed to “boiler operating days. ” Commenter stated that in addition to normal scheduled plant outages, there are many uncontrollable factors that can prevent an EGU from operating on short notice for an extended period of time (storms that cause transmiss ion line outages and loss of plant equipment). In absence of making this change to boiler operating day s, the Commenter stated that the quarterly testing is not a realistic option for any EGU due to the uncertain factors outside of the owner or operator ’ s control. Commenter (20262) stated that unforeseen situations can arise at EGUs that derate a unit, thus preventing it from being able to operate at a high load for a period of time. The Commenter noted that this may cause an EGU to have to reschedule the quarterl y test and potentially miss the 20 - day window that EPA requires. The Commenter stated that s tack testing scheduling is typically done well in advance of the actual test date and coupled with the higher demand for stack testers because of the added testing requirements from MATS, it will be difficult to reschedule a tester on short notice and still be within the required 20 - day

window. To account for these situations, the Commenter recommends that a 10 - day grace period needs to be added. Alternatively , the Commenter suggests that the 20 - day window simply be expanded to 30 days. **Response:** As the rule no longer contains quarterly PM performance testing for new EGUs, no response is necessary . Further, EPA did not propose to revise the performance testing requirements for existing sources. 4.2 PM CEMS **Comment:** Commenter (20248) has concerns with certifying and operating PM monitors in accordance with PS - 11 and Appendix F, Procedure 2 for EGUs where PM monitors are currentl y not installed and operating . The Commenter’ s primary concern is relying on PM CEMS to demonstrate compliance with low PM standards. The Commenter stated that with low PM emission limits (<0.03 lb/MMBtu) the spread for the c orrelation curves will be small and the annual relative response audit ( “ RRA ” ) may fall outside of the acceptable range for the existing correlation curve. The Commenter stated that this result would require the development of a new correlation curve on an annual basis (minimum of 12, Method 5 tests). The Commenter expects that a ty pical correlation curve would be based on filterable particulate concentrations of 0 - 20 mg/m3 in order to remain below the equivalent standard of 0.03 lb/MMBtu. The Commenter s tated that this design presents enormous challenges for current control technologies and for maintaining emissions at set levels for the duration required to develop the PS - 11 correlation curves. The Commenter stated that they have explored the use of quantitative aerosol generator s ys tems to produce NI ST traceable particulate masses for correlation purposes but stated that they are not reliable in wet stacks and do not correlate well with currently used light scattering devices.82

Commenter (20290) stated that the inherent PM CEMS response variability and the uncertainty associated with the representative sampling at low emission levels make it problematic to satisfy the ±25 percent of the applicable PS 11 acceptance threshold without extraordinarily long M ethod 5 test runs; and having to use increased Method 5 sampling runs to demonstrate compliance with PS 11 make it potentially

far less economical than using the quarterly stack testing option. Commenter (20261) stated that the accuracy of continuous PM m onitors is limited by the sensitivity

of EPA Method 5, which is used to establish a calibration curve under EPA ’ s PS - 11. The Commenter stated that b ased on gravimetric precision alone, Method 5 should be able to quantify filterable particulate mass accurat ely at the new coal unit limit of 0.09 lb/MWh; however, the overall accuracy of the method at these low levels needs to be evaluated further. The Commenter stated that currentl y installed PM monitors are used routinel y to measure emissions in the range of 0.005 to 0.04 lb/MMBtu (approximately

0.05 to 0.4 lb/MWh for coal). The Commenter concluded that fPM can be measured accuratel y using continuous PM analy zers at the proposed new unit limits. Commenters (20281 and 20282) provided discussion about the diffi culties of correlating PM CEMS response to those that would be obtained with Method 5. Commenter (20282) noted that the PS 11 performance criteria become more difficult to meet as the emission limit gets lower, simply as a matter of application of the st atistics. The Commenter stated that lower emission limits also mean greater influence of reference method measurement uncertainty and variability . The Commenter provided discussion about these topics, citing other EPA rules, an EPA memorandum, and permit determinations. Commenter (20242) discussed their evaluation of existing PM CEMS technologies, stating that these technologies either have significant field condition limitations or have only been deployed in limited utility scale applications. The Comment er stated concerns that if a beta gauge typ e PM CEMS were located in their CEMS building, there would be problems with sample moisture, transport distance and associated particulate fallout. The Commenter discussed th e alternative, locating the PM CEMS at the stack sampling location half way up the 500 foot stack. The Commenter stated that at this time there appears to be no proven PM CEMS instrumentation that accuratel y and reliably measures PM and meet all the QA/QC testing requirements. Commenter (20282 ) discussed the uncertain accuracy of PM CEMS. The Commenter noted that an owner/operator choosing PM CEMS as the compliance method must bear any risk. Commenters (20282 and 20296) stated that PM CEMS technology is different from the test methods EPA used to set the s ubpart UUUUU standards. Commenter (20296) stated that the EPA erred in basing the requirement that sources demonstrate compliance with the revised PM standard us ing a PM CEMS on emission performance data gathered using an entirely different measurement method. The Commenter cited Portland Cement Ass ’n v. Ruckelshaus , 486 F.2d 375, 396 - 97 (D.C. Cir. 1973). The Commenter concluded that the final rules should allow a source to undertake a demonstration of compliance with the PM limits using the same measurements on which EPA bases the PM emissions limit.83

Commenter (20282) noted that a PM CEMS ’ single sampling point may not provide representative concentrations across the stack of a stratified gas stream. **Response:** These comments concerning use of PM CEMS are not relevant . The EPA sought comment in the proposed reconsideration only on retaining quarterl y testing as an option for performance testing and on approaches f

or establishing PM CPMS operating limits for new EGUs, and, as explicitly stated in the proposal, the EPA is not responding to any comments addressing any provisions of MATS beyond those identified as issues for reconsideration, including comments regardin g the use of PM CEMS. Therefore, this comment is not addressed . The EPA notes that PM CEMS continue to be installed and operational at existing EGUs; moreover, their use is included in recentl y- completed existing EGUs that have emissions limits at levels n ear those contained in the standards. In addition, as mentioned in the Portland cement source rule preamble, fossil - fueled EGUs may be more suited to use PM CEMS than Portland cement plants, as EGU emissions have more uniform particle characteristics. See 77 FR 42375/2, July 18, 2012. The EPA notes and appreciates the comment from the Electric Power Research Institute, based on its anal ys is of PM CEMS and repeated from comments on the proposed rule, that PM can be measured accuratel y using continuous PM analy zers at the proposed new unit limits. The EPA also notes that the final rule provides the option to use a certified PM CEMS for direct compliance, but also allows the use of PM CPMS. For Commenter s that believe the PM CEMS option is too unreliable as applied to their EGUs , those Commenter s are free to choose the other option specified in the rule . Finally , the EPA notes that one Commenter who anal yz ed about 6 months of data from three PM CEMS all o f which had successful correlations according to PS - 11, found no exceedances of the EGU new source emission limit, thus showing that PM CEMS, calibrated as required b y PS 11, was capable of measuring to the level of the standard. These data thus at least p artially refute those comments indicating that PM CEMS could not reliably

measure to the level of the standard (see EPA - HQ - OAR - 2009 - 0234 - 20282, Attachment 8, page 3). The issue of the use of short - term emission test data to establish 30 - day rolling averag e emission limits was addressed in the final RTC (see , e.g. , Vol. 1 , pp. 462 - 463 , 468 - 469, 494 - 496 , 500 , 549 - 551) and is outside the scope of this rulemaking . This issue was not one of the issues being reconsidered and the EPA did not solicit comment in the reconsideration proposal regarding the use of short - term data. In addition, the Agency

also explained why

its variability

anal ys is is valid and accounts for different real world operating conditions (see , e.g. , RTC, Vol. 1, pp. 493 - 496). The EP A explained its approach to assessing variability

in the proposed MATS rule, and further discussion is provided elsewhere in this document . **Comment:** Commenter (20282) recommended that the EPA set limits based on PM CEMS data collected at sources representative of the range of EGUs subject to the standard, and over a sufficient period of time to ensure that any lack of stability in the calibration is taken into account. **Response:** The EPA maintains that its approach to establishing the MACT standards in the final rule is reasonable and consistent with the statute. The issue of the use of short - term emission test data to establish MACT emission limits wa s addressed in the final RTC (see , e.g. , RTC Vol. 1 , pp. 462 - 463 , 494 - 496 , 500 , 549 - 551). **Comment:** Commenter (20282) stated that there is not any significant helpful feedback provided b y stack- mounted PM CEMS for process control.84

**Response:** The EPA disagree s with the Commenter and feel s that information from a PM CEMS monitor that allows a source to maintain compliance with their emission limit is providing helpful feedback to the source and supporting the overall aim of this rule **.** The same is true of measurements from a CPMS, which indicated whether the operating parameter has been exceeded. **Comment:** Commenter (20308) stated that for most coal - fired generation that will be built to meet the requirements of this proposed reconsideration rule, the po llution control equipment necessary to meet the emission limits will likely require operation of a wet stack. The Commenter noted that the ability to measure the particulate emission levels with a continuous emissions monitor in a wet stack are unknown or in its infancy , and noted that the emissions low in the span of measurements does not provide usable data for compliance or operational decisions. **Response:** The EPA disagrees with the Commenter, for PM CEMS employing beta gauge technology are unaffected b y moisture in stacks (i.e., wet stacks). The EPA recognizes that a pplying a technology suitable for a particular application would naturally take some planning , but do not agree with the Commenter’s view regarding usability of data . Current guidance given in Section 2.4(1) of PS - 11 states that an owner or operator should select a PM CEMS that is appropriate for its source. For Commenter s who believe the PM CEMS option is too unreliable as applied to their EGUs , those Commenter s are free to choose the other compliance option specified in the rule . **Comment:** Commenters (20258 and 20293) stated that they do not support the proposal to reduce or eliminate Relative A ccuracy T est Audit (RATA) testing for CEMs; if such CEMs are to be installed, they should be calib rated so that the reported results accuratel y reflect the performance of the EGU. **Response:** The EPA agrees with the Commenters and notes that PM CEMS used for direct compliance will need to meet PS - 11 performance specifications and Procedure 2 on an annual basis. **Comment:** Commenter (20280) cited their comments on the proposed rule where they expressed their concern about PM CEMS. The Commenter attached those comments for reference. **Response:** This comment concerning use of PM CEMS is not relevant. The EPA sought comment in the proposed reconsideration only on retaining quarterly

testing and on approaches for establishing PM CPMS operating limits, and, as explicitly stated in the proposal, the EPA is not responding to any comments addressing any provisions of MATS not identified as issues for reconsideration, including comments concerning the use of PM CEMS. Further, in this case, commenters simply reference comments they

provided on the 2011 proposed MATS rule, to which EPA responded in its final action on that proposal. The EPA notes that the final rule provides the option to use a certified PM CEMS for direct compliance, but also allows compliance demonstration by establishing operating parameters, measured b y a CPMS, should a source elect that compliance alternative . Therefore, EGU owners or operators who do not believe PM CEMS option is the best approach could choose the other option allowed in the rule . 4.3 PM CPMS85

**Comment:** Commenter (20242) stated that the existing method and two proposed options for setting the PM CPMS operating limit are arbitrary , likel y non - representative, and potentially too restrictive. The Commenter stated that the proposed methodologies for establishing operating limits are likel y non representative because the time period nece ssary to perform the PM performance test is relativel y s hort and does not represent typical PM control efficiencies. Commenter (20281) stated that the PM CPMS option proposed b y the EPA offers no advantage, but adds potential cost and risk, over PM CEMS for most EGUs. Commenter (20282) objected to the proposed revisions to the new unit PM CPMS option, if it is in anticipation of requiring new EGUs to use PM CPMS (or PM CEMS). The Commenter stated that the proposed PM CPMS option is seriously flawed, even with the proposed new unit revisions. Commenter (20242) stated that the PM CPMS operating limit determination methods are potentiall y subjective. The Commenter stated that a facil ity may be penalized if their control system is very effective during performance testing, and result in operating limit exceedances that the source will then need to rebut. The Commenter observed that with this concern, performing quarterl y compliance PM stack testing seems to be the most reasonable and objective option. Commenter (20282) stated that although the option has the advantage of avoiding the testing issues associated with PS 11 correlations, absent that correlation the parameter is nothing more than an indicator that PM may

be increasing or decreasing. The Commenter stated that CPMS could be useful to identify the need for investigation and action, but not to establish an enforceable limit. Commenter (20282) stated that an EGU establishing a P M CPMS operating limit could be testing well below the applicable emission limit, and there is no basis to assume that an exceedance (or multiple exceedances) of a 30 - boiler operating day rolling average parameter limit indicates an emission limit was exce eded, or that controls were not operated properl y. The Commenter stated that it means that emissions on average were above the level of emissions during the last performance test. The Commenter stated that unless the EGU has collected data to determine what PM CPMS parameter level is equivalent to a violation of the emission standard, there is no basis to suggest that any parameter exceedance is a violation. The Commenter stated that requiring an EGU to attempt to collect data to establish such an equivalent value would require just the sort of PS 11 correlation that the option is intended to avoid. Commenter (20282) suggested that for the approach to be useful as an alternative to quarterl y stack testing or PM CEMS , the EPA would have to (1) allow reasonab le scaling (Option 3), and (2) abandon its arbitrary

definition of a violation in favor of a pure investigation and corrective action approach. The Commenter suggested that PM CPMS would be more appropriate as a part of a Compliance Assurance Monitoring (C AM) approach rather than as a direct indication of compliance. Commenter (20304) stated that the language in paragraph (2)(i) of the docket memo is confusing. The Commenter stated that it appears to require the use of option 2 (averaging) but the following paragraphs (A) through (D) describe the method to extrapolate up to 75 percent of the standard (option 3). The Commenter suggested that the Agency clarify the language in (2)(i) to make it clear that the facility is allowed to use option 3 when the test shows the emissions are below 75 percent of the standard. The86

Commenter stated that four additional paragraphs (iii, iv, v, and vi) are not needed and could be dropped. Commenter (20242) supported adding the two new proposed methods/options to establish PM CPMS operating limits because this flexibility provides some minor improvement. Commenter (20304) stated that all three options for PM CPMS should be included in the final rule. Commenter (20308) stated that the costs of a PM CPMS are offset b y the c osts of stack testing procedures. **Response:** The rule requires the third of the three proposed approaches based on the 3 - run average operating parameter value determined from performance test results, and scaling for units with emissions below 75 percent o f the limit. The EPA selected the third approach as the most reasonable here. It avoids penalizing the lower emitting sources by allowing the parameter value obtained from the performance test to be scaled up to 75 per cent of the limit. Higher emitters mu st establish operating parameters reflecting the average values of their (successful) performance test, and the CPMS is highly reliable at detecting exceedances of that operating parameter. As mentioned earlier, th e third approach was selected because it appropriatel y balances the competing concerns considered b y the Agency and raised b y commenters. Specificall y, this approach provides the greatest amount of flexibility while still demonstrating continuous operating parameter compliance for lower- emitting EGUs , at the same time holding higher emitters to parametric limits representative of values below the emission standard. With this parametric monitoring approach in place , the EPA expect s EGU owners or operators to evaluate control options that provide excellent PM emissions control and provide them greater operational flexibility . Every EGU using PM CPMS will need to conduct an annual Method 5 test to determine compliance with the PM emissions limit, and during this testing will also monitor its PM CPMS milliamp output. An EGU which emit s PM less than 75 percent of their emission limit will be able to scale its PM CPMS milliamp output to determine where its PM CPMS would intersect 75 percent of their allowed f PM emissions, and set its operating level at that milliamp output. This alleviates many re - testing concerns for EGUs that operate well below the emission limit (where a source could exceed the parametric limit established from the performance test but still be operating at a level well below the leve l of the standard) and provides them with greater operational flexibility while still assuring continuous compliance with the PM parametric limit . It also creates an incentive for EGU owners or operators to select high efficiency

PM controls when evaluating potential compliance strategies. For EGU s whose Method 5 compliance tests place them at or above 75 percent of the emission standard, their operating limit level s will be the average PM CPMS milliamp output during the three Method 5 test runs. This means their operating level s are the milliamp output s that correlate to their PM compliance determination, and not the highest average 1 hour run value that was identified as Option 1, as discussed in the preamble to the proposed Reconsideration rulemaking notice . Now that the rule adopt s a scaling factor for new EGUs , the EPA no longer believe s that it is also appropriate to establish the parametric limit based on the highest value of the three runs .87

The scaling option provides flexibility for low emitting , well - operated sources, and it was determined to be a reasonable compromise of flexibility and protection of the emission standard. Seventy- five percent of the emission limit is an already- established threshold in the Standards of Performance for New Stationary

Sources and Emission Guidelines for Existing Sources: Commercial and Industrial Solid Waste Incineration Unit (76 FR 15757) to determine the frequency of subsequent compliance testing. In that rule, owners or operators of sources were able to reduc e their performance test frequency when emissions were equivalent with or below 75 percent of the limits. Otherwise, performance testing was to occur at the normal frequency prescribed in the rule. See also 78 FR at 10019 - 10020 (Feb. 12, 2013) where EPA adopted a similar approach for parametric monitoring for the PM stan dard in the NESHAP for the P ortland cement source category . The EPA believe s this threshold can be used in conjunction within a PM CPMS scaling factor, as results above 75 percent of the equivalent emissions limit would be ineligible for scaling factor use and could lead to increased performance testing, while results equivalent with or below 75 percent of the equivalent emissions limit would be eligible for scaling factor use. Adherence to an operating limit with a 25 percent (1 - 0.75) margin of compliance should demonstrate continuous, qualitative compliance with an operating limit below the PM standard. Moreover, the EPA believe s that on balance the 30 days of averaged CPMS measurements provides ample operating cushion to incorporate operational variability . The issue of more than four exceedances of the parameter operating limit over a 12 month period as being a presumptive violation of the emission limit is discussed in Section 4.3.5 of this RTC. **Comment:** Commenter (20305) stated that rather than retaining the CPMS alternative , the EPA should require sources to use PM CEMS to determine compliance, but the EPA has provided no rationale for not requiring the use of PM CEMS. The Commenter stated that requiring PM CEMS would eliminate the problems associated with the CPMS method for determining compliance, and would provide a compliance method that correlates to methods used by EPA to set the applicable emissions limit. **Response:** This comm ent concerning use of PM CEMS as the exclusive means of demonstrating compliance is not relevant. The EPA sought comment on retaining quarterly testing and on approaches for establishing PM CPMS operating limits in the reconsideration, and, as explicitly s tated in the proposal, the EPA will not respond to any comments addressing any provisions of MATS not identified as issues for reconsideration. Therefore, this comment is not addressed . Moreover, this Commenter raised the same issue in comments on the 2011 proposed rule, and the EPA considered those comments and decided in its final action on that proposed rule not to require PM CEMS as the exclusive means of compliance (see pg. 177, RTC Vol. 2). The EPA notes that the final rule provide s for the use of a P M CEMS to determine compliance with the filterable PM emission limit if the source owner or operator elects to use this approach . Finally , the EPA maintains that the compliance demonstration options (PM CPMS and PM CEMS) both assure compliance with the fin al standards, and the Commenters have provided no data or information to demonstrate otherwise. **Comment:** Commenter (20291) stated that allowing opacity , pressure drop across baghouse, or electrostatic precipitator (ESP) voltage to be linearly correlated to PM emissions pursuant to 40 CFR Part 64 (CAM Plans) should be allowed as a compliance method in MATS. The Commenter explained that pursuant to CAM Plan methodology , a battery of typically three method 5 tests is run at three differing ESP voltage setting s during unit steady state for a total of nine method 5 benchmarks. The Commenter stated that d

uring each test the opacity is noted from the installed continuous opacity88

monitoring system (COMS). The Commenter continued that u sing the results of the method 5 tests and COMS readings a linear curve fit correlation is drawn with requisite criteria of acceptability. Hence, the Commenter stated, equivalent PM reading can be extrapolated from a COMS reading in the range of compliance up to the PM limit for the unit without artificially placing the compliance limit at the highest source test result under the requisite regulatory limit. The Commenter stated that the regulatory limit is the limit and there is no penalization. The Commenter noted that in many of the C ommenter’ s federal Part 70 permits this is a PM compliance option already in place. The Commenter stated that allowing this method would reduce regulatory overlap, redundancy

and confusion as well as providing a flexible cost effective avenue to compliance for EGUs with already installed equipment and approved plans. **Response:** The EPA does not agree with these comments. As explained in the Portland cement rule preamble (78 FR 10019; February 12, 2013), the PM CPMS is considerably more sensitive than an opacity monitor at detecting fluctuations in PM level. An opacity monitor determines the percent of a light signal that is occluded across the stack diameter. Opacity anal yz ers operate on a zero to 100 percent sc ale, meaning they are capable of registering PM that completel y occludes the far stack wall from the instrument light source. This amount of PM is roughly equivalent to a complete failure of the emission control device. A properl y operating control device will emit five percent opacity or less, which is barel y visible to the naked eye and on the low end of the opacity monitor capability. PM emissions that increase opacity two percent at this level may well exceed the emission standard, yet they only mildly deflect the opacity monitor output. However, this same 2 percent opacity increase will register changes of several milliamps on a PM CPMS when operating on the scale provided in this final rule. Further, the PM CPMS has several decimal fractions available between each milliamp to track signal output, and three or four milliamps represent 1 percent change in opacity . Therefore, a small increase in PM emissions at low PM concentrations

– which could represent an exceedance of the standard

– is more easily

read using PM CPMS has a clear advantage than through opacity monitoring systems. **Comment:** Commenter (20304) recommended that the PM CPMS language should allow new and existing sources to use all three options . Commenters (20262, 20267, 20282) encouraged EP A to allow existing EGUs to benefit from these slightly more flexible provisions. Commenter (20262) stated that EGUs that have, or choose to install, high performing PM control equipment cannot take advantage of the linear scale approach; extending this approach to existing EGUs would provide an incentive to install and operate technologies that control PM emissions well below the MATS limit. **Response:** These comments concerning use of alternative PM CPMS monitoring approaches for existing EGUs are not relevant to today ’s action. The EPA neither proposed nor requested comments in the proposed reconsideration on the operating limit for PM CPMS at existing EGUs, and, as explicitly stated in the proposal, the EPA is not responding to any comments addressing any provisions of MATS beyond those identified as issues for reconsideration. 4.3.1 First Approach for establishing the operating limit for PM CPMS

– Requiring use of the highest parameter value obtained during any run of an individual emissions test as the operating limit, provided that the result of that individual emissions test met the emission limit.89

**Comment:** Commenter (20305) stated that the provision of the first approach does not suffice to secure compliance with the standard. The Commenter stated that the first approach demands compliance with a “parameter, ” but fails to ensure that the parameter correlates with the applicable emissions limit. The Commenter stated that an emissions test may , on average, be below the limit, even while individual test runs yield emissions above the limit. The Commenter stated that the “highest parameter value ” associated with one test among a test run may therefore exceed the limit, even while the average of all test values does not. The Commenter stated that monitoring compliance with a parameter thus derived will not ensure compliance with the standards, and does not ensure compliance with the law. The Commenter suggested that the EPA should require plant - owners to define their operating parameters only according to “the average parameter value obtained from all runs pertaining to an individual emissions test” demonstrating compliance with the PM limit. Commenter (20305) stated that allowing plant owners to combine the data collected over multiple performance tests to establish a more representative value for the monitored parameter invites plant owners to further distance their parametric monitoring from plant ’ s actual emissions. The Commenter stated that combining multiple stack tests may result in a set of characteristics that do not reflect any of the plant ’ s actual operating characteristics. The Commenter stated that this difficulty is exacerbated if the Agency

continues to establish, as its governing parameter, the highest test - run amongst stack tests whose averag e meets the underlying standard; the distance between the highest test and the average value is likely

to increase as a greater number of stack tests are combined together. Commenter (20269) supported the use of the first approach due to the amount of operational flexibility . **Response:** As mentioned earlier, the rule requires the third approach based on the three run average operating parameter value determined from performance test results, and scaling for units with emissions below 75 percent of the limit; not the highest operating parameter value determined from performance test results approach . Scaling alleviates many re - testing concerns for EGU s that operate well below the emission limit , and provides them with greater operational flexibility while still assuring continuous compliance with the PM stack emission standard. 4.3.2 Second Approach for establishing the operating limit for PM CPMS

– Requiring use of the average parameter value obtained from all runs of an individual emissions test as the operating limit, provided that the result of the individual emissions test met the emissions limit. **Comment:** Commenters (20258 and 20293) stated that they agree with EPA ’ s proposal to index parametric monitoring to the average of the parameters in three run reference method tests rather than to the parameters in the highest emitting run. The Commenter s stated that because the highest emitting run would show emissions greater than the average of the three runs, the parameters associated with the highest run would not be sufficient to assure compliance with the applicable limit. Regarding Option 2, Commenter (20267) stated that it is obvious that increasing the sample duration increases the accuracy

of any measurement. It is no less true for the CPMS parameter vs. actual emissions correlation. The Commenter stated that inclusion of multiple runs into an average parameter value will strengthen that correlation.90

**Response:** Consistent with the Comment ers’ concerns and, as mentioned earlier, the rule requires the third approach based on the 3 - run average operating parameter value determined from performance test results, and scaling for units with emissions below 75 percent of the limit; not the first a pproach . 4.3.3 Third Approach for establishing the operating limit for PM CPMS

– Requiring use of the higher of a parameter scaled from all values obtained during an individual emissions test to 75 percent of the emissions limit or the average parameter value obtained from all runs of an individual emissions test as the operating limit, provided that the result of the individual emissions test met the emissions limit. **Comment:** If the first approach is rejected, Commenter (20269) supports the third appro ach. The Commenter noted that the third approach does not provide as much operational flexibility as the Commenter would prefer. **Response:** As mentioned earlier, the rule requires the third approach based on the 3 - run average operating parameter value determined from performance test results, and scaling to 75 percent for units with emissions below 75 percent of the limit; not the first approach . Scaling alleviates many re - testing concerns for EGU s that operate well below the emission limit , and provides th em with greater operational flexibility

while still assuring continuous compliance with the PM stack emission standard. This approach is discussed more fully in Section 4.3 of this RTC. **Comment:** Commenter (20269) asked that EPA clarify (in the third optio n) whether a 30 - day rolling average or a 30 - day

average is intended. **Response:** The operating limit is based on a 30 - boiler operating day rolling average. **Comment:** Commenter (20282) expressed appreciation for EPA ’ s proposed scaling option, but the Commenter stated that EPA ’ s proposed use of 75 percent of the emission level as the upper point is arbitrary , and still would put sources that are operating with significant compliance margin at risk of a violation. The Commenter stated that for a scaled l imit to justify a violation , the EPA must establish not only the consistency

of the uncorrelated measurements over time, but allow scaling up to 100 percent of the emission limit. The Commenter stated that the EPA ’ s reliance on the extended averaging time to ensure that compl ying sources are not deemed in violation is based on the incorrect assumption that, at an EGU with properl y operated PM controls, hourly parameter values above the average (or highest) value during the performance test will always be th e result of normal variability that will automatically smooth out over time. The Commenter stated that such values, however, could just as easily be the result of an actual change in condition that does not result in emissions above the applicable emission limit. The Commenter illustrated this point with a memorandum anal yz ing raw PM CEMS output data, provided as Attachment 8 to the comment letter. The Commenter concludes, based on this anal ys is, that neither the average nor the maximum 1 - hour average PM CE MS raw output during a performance test provides a reasonable basis for setting an operating limit for any facility with any compliance margin. Commenter (20282) also included in Attachment 8 of their comment a comparison of the three options proposed to develop an operating limit using PM CPMS for new sources and an approach for existing sources using the 75 percent scaling approach. In the Commenter’ s study , the first and second options produced false positives; the scaled approach produced better results. The Commenter reiterated that 75 percent is not the appropriate end point for scaling.91

Commenter (20262) supports the approach to allow an EGU owner or operator whose PM emissions do not exceed 75 percent of the limit to set a PM CPMS operating limit by linearl y scaling the average operating value obtained during all the performance testing runs to be equivalent to the value at 75 percent of the limit. The Commenter encourages EPA to allow scaling up to 100 percent of the limit . Commenter (20267) stated that without Option 3, there is no mechanism to reduce the compliance burden on very

low - emitting EGUs. The Commenter stated that those EGUs would be forced to over comply with the MATS PM standard as the CPMS operating limits would be set at a level c ommensurate with tested PM emissions that are under that standard. Otherwise, the Commenter observed, a utility

might be compelled to perform a science experiment of graduall y detuning PM controls during multiple stack tests in order to achieve the most fl exibility and a margin of safety in daily operation. The Commenter stated that the exact scaling method and the 75 percent target should be up for debate as well. The Commenter stated that in addition, ruling that four exceedances of the EGU operating limi t violate the standard unnecessarily burdens low - emitting EGUs that operate at or below 75 percent of the standard. **Response:** As mentioned earlier, the rule requires the third approach based on the 3 - run average operating parameter value determined from performance test results, and scaling for units with emissions below 75 percent of the limit; not the highest operating parameter value determined from performance test results approach . Scaling alleviates many re - testing concerns for EGU s that operate well below the emission limit , and provides them with greater operational flexibility while still assuring continuous compliance with the PM stack emission standard. The EPA believe s that the 30 - boiler operating day rolling averaging feature plus the 75 -percent scaling feature for the lower emitting sources provides a sufficient operating cushion . Also see the response to comments on the chosen approach in Section 4.3 on PM CPMS, and see Section 4.3.5 on the issue of four exceedances leading to violation. In response to the Commenter who sought use of a 100 percent scaling factor, the Agency disagrees. A parameter level scaled lower than the emissions limit is appropriate because neither the EPA nor the EGU owner or operator knows with certainty what the emissions are at any untested parameter value. Over time, an EGU owner or operator may develop enough data to provide a better prediction and then submit such information to the Administrator in a request for an alternative standard. An EGU owner or operator who is concerned about not having enough operating limit flexibility could always switch to PM CEMS use, as those instruments report values in terms of the emissions limit The EPA notes that the term false positive, as claimed by one Commenter in its rev iew of PM data collected over a period of about six months from three PM CEMS operated as PM CPMS may be incorrect. As the data were reviewed well after the instances occurred, there was no ability of the EGU owner or operator to take corrective action or to perform stack testing and reset the operating limit to demonstrate that the value recorded did not indicate non - compliance with the emissions limit. The EPA also notes that the Commenter was able to successfully perform a correlation for each of the thr ee PM CEMS under PS - 11 and that the Commenter found no exceedances of the new source emissions limit, thus showing for this EGU that PM CEMS, calibrated as required b y PS 11, was capable of measuring to the level of the standard. These data thus at least p artially refute those comments indicating that PM CEMS could not reliably measure to the level of the standard .92

**Comment:** Commenter (20305) stated that the third approach would permit emissions in excess of the limits. The Commenter expressed concern that plant owners are given leeway to select an indicator of convenience, and the rule does not indicate that the “parameters ” available to power-plant operators all have a linear relationship to PM emissions. The Commenter noted that most facilities will be co ntrolled with fabric filters, which are constant - output devices. The Commenter stated that a properl y maintained and operating fabric filter will either meet a specified emissions limit or not; its emissions will not vary , and certainly

not linearly, over a wide range. Commenter (20305) stated that parametric options for the performance of fabric filters do not show a functional or linear correlation, as a small change in any of the parameters

– e.g., a reduction in pressure or amperage below the threshold at which the f ilter is designed to function

– could result in a very large increase in particulate emissions. The Commenter stated that the EPA cannot rely on “ linear scaling ” to ensure that emissions will remain below the limit **Response:** The EPA does not agree that th e PM CPMS output is an indicator of convenience and maintain s that PM CPMS monitoring provides for continuous qualitative assessment of source PM emission controls and is protective of the emission standard

– i.e. given the instrument sensitivity to detecting and reporting increases in the PM signal, there is virtually no likelihood of false negatives. Where PM controls are failing, the PM CPMS signal will indicate the increasing concentration of PM in the stack gas . The EPA recognize s this as a significant step forward in emissions measurement related to PM standards. Indeed, the sensitivity of the PM CPMS is why the EPA introduced the scaling factor to accommodate the situation of lower- emitting facilities, to avoid what in effect would be false positives

– CPMS measurements where an increase in PM emissions would not implicate the emission standard itself. The scaling option provides flexibility for low emitting and well - operated sources, and was determined to be a reasonable compromise of flexibility an d protection of the emission standard. Seventy- five percent of the emission limit is an already- established threshold in the Standards of Performance for New Stationary

Sources and Emission Guidelines for Existing Sources: Commercial and Industrial Solid W aste Incineration Unit (76 FR 15757) to determine the frequency of subsequent compliance testing. In that rule, owners or operators of sources were able to reduce their performance test frequency when emissions were equivalent with or below 75 percent of the limits. Otherwise, performance testing was to occur at the normal frequency prescribed in the rule. The EPA believe s this threshold can be used in conjunction within a PM CPMS scaling factor, as results above 75 percent of the equivalent emissions limit would be ineligible for scaling factor use and could lead to increased performance testing, while results equivalent with or below 75 percent of the equivalent emissions limit would be eligible for scaling factor use. Adherence to an operating limit with a 25 percent (1 - 0.75) margin of compliance should ensure continuous, qualitative compliance with an operating limit below the PM standard. Moreover, use of a scaling factor limited to 75 percent reduces concerns about non - linearity of emissions relative to PM CPMS signal. As explained in the Establishing an Operating Limit for PM CPMS memorandum, 16 although the EPA may not know the specific sh ape of the emissions/PM CPMS signal relationship prior to data collection, an assumption of linearity from zero to 75 percent of the emissions limit focuses attention on the lower part of the relationship which is more linear that the upper 16 See item number EPA - HQ - OAR - 2011 - 081 7 in the Portland cement rule docket93

part of the rel ationship. Moreover, stopping the scaling at 75 percent of the emissions limit provides a margin of safety

or reserve such that emissions values from non - linear relationships near the scaling endpoint do not exceed the emissions limit. 4.3.4 Emissions Te sting After Each Exceedance **Comment:** Commenter (20282) stated that it is not reasonable for the EPA to require sources to (1) conduct performance tests, perhaps as often as every 45 days, in order to demonstrate compliance and reassess its parameter level and (2) be labeled a violator as a result of its fourth successful performance test in a 12 - month period. The Commenter stated that if an EGU that has invested in a PM CPMS is conducting appropriate investigations and corrective action in response to parameter exceedances, there is no basis to label that poor control device performance. **Response:** We understand the Commenter is concerned about the relationship of testing after each exceedance and still being labeled as in vio lation after four exceedances. See response to comments under Section 4.3.5., below, for EPA ’ s response to concerns with the four exceedance provisions. **Comment:** Commenter (20304) supported allowing a facility to retest when the limit established during the annual test is exceeded. **Response:** The EPA appreciates Commenter’s support. 4.3.5 Exceedances Leading to Violation **Comment:** Commenter (20282) disagreed with the proposed presumptive violation after more than four tests. The Commenter asked what evidence is the source supposed to rebut if the rule defines the violation based on the triggering of a fifth test in 12 months, and not based on any evidence that the exceedance that triggered the fifth test resulted from emissions that were actually above the emission limit. **Response:** The Commenter objected to the proposal that four calendar ye ar exceedances from the parametric limit would be a presumptive violation of the emission standard. The EPA does not agree. First, the EPA may

permissibly

establish such a presumption by rule, assuming there is a reasonable factual basis to do so. See Hazardous Waste Treatment Council v. EPA , 886 F. 2d 355, 367 - 68 (D.C. Cir. 1989) explaining that such presumptions can legitimatel y establish the elements of the agency ’ s prima facie case in an enforcement action. Second, there is a reasonable basis for the presumption that four exceedances (i.e. increases over the parametric operating limit) of the 30 - boiler operating day rolling averages in excess of the operating limit are a violation of the emission standard. The parametric monitoring limit is established as a 30 - boiler operating day rolling average of the averaged test value in the performance test, or the 75 th percentile value if that is higher. In either instance, the 30 - boiler operating day rolling averaging feature provides significant leeway to the owner or operator not to deviate from the parametric operating level because the 30 mea surement days will significantly dampen variability

in the single measurement (average of three test runs) that produced the parametric value. See 77 FR 42377/2 and sources there cited. The EPA acknowledge s that the difference was even greater between the parametric level and the94

emission standard in the proposed rule (which was based on the highest value measured during the test run s ). The EPA believe s that the 30 - boiler operating day rolling averaging feature plus the 75 -percent scaling feature for the lo wer emitting sources now provides a sufficient operating cushion for those EGU owners or operators who choose to use PM CPMS . See 77 FR 42377 and the Final Portland Cement Reconsideration Preamble (78 FR 10015, 10019; February , 12, 2013). Moreover, for ev en a single exceedance to occur, the 30 day average would have to be higher than the operating limit established for the PM CPMS during normal EGU operation. If that occurs, then the EGU owner or operator is required to conduct an inspection to determine any abnormalities and an emissions test to re - establish or generate a new operating limit. Given that EGUs and their emissions control devices are designed to operate at known, specific conditions, deviations from these conditions are not expected and are indicative of problems with load, controls, or some combination of both. Continued operation outside these known, specific conditions will require an EGU owner or operator to identify and then correct problems. More than four such exceedances of the 30 day average would mean that the EGU owner or operator was unable to determine or correct the problem, since inspection and re calculation of the operating limit is required after each exceedance. This indicates an ongoing problem with maintaining process control and /or control device operation, which would be the basis for a presumptive violation of the emissions standard. The EPA notes that emissions tests conducted by an EGU owner or operator to better define or reassess the operating limit that are not the result of an exceedance of the operating limit are not included as counting towards the 4 test limit over a 12 month period that constitutes a presumptive violation of the emission standard. The EPA further notes that the presumptive violation is just a presumption, which can be rebutted. There are a number of items a court may find credible as evidence that an EGU did not exceed its emissions limit even though the EGU did exceed its PM CPMS operating limit. For example, an EGU owner or operator might pro vide sufficient information to show that the EGU remained in process control, or that the operation and maintenance conducted on the EGU ensured the control devices remained in proper operating condition, or that emissions tests results conducted while rep licating the conditions showing exceedance of the 30 - boiler operating day rolling average showed compliance with the emissions limits. What would be sufficient information for credible evidence to rebut non - compliance remains a case - bycase determination b ased on specific facts. **Comment:** Commenter (20269) asked that EPA clarify that a “ single equipment problem that spans two or more days that causes the average emissions to exceed the limit over multiple day s will be treated as a single episode of exceedance, triggering the requirement to conduct a single performance test. ” The Commenter (20269) asked that “ any enforcement action taken in response to a fifth performance test in a 12 - month process operating period” be treated as a single violation of the standard. **Response:** The EPA disagrees that the rule needs the additional clarification sought b y the Commenter. The rule is clear that an exceedance occurring between the first exceedance and the performance test is considered part of the initial exceedance (see 40 CFR § 63.10021(c)(1)(iii)) as long as no more than four performance tests are conducted over a 12 - month period (rolling monthl y). Should an exceedance of the operating limit occur after the fourth performance test conducted over a 12 - month period, a violation of the 30 - boiler operating day rolling average occurs on the day of the exceedance. Further, each day in95

which an exceedance continues to occur (or a new one occurs) creates a rebuttable presumption of a separate violation of the 30 - boiler operating day rolling average. **Comment:** Commenters (20258 and 20293) stated that EPA proposes to define a separate violation when more than four reference method tests result in a year because of exceedances of 30 - day PM Continuous Parametric Monitoring Sy stem ( “ CPMS ” ) parameters. The Commenter s stated that this limit is a 30 - day

limit, rolled monthly, and the source has 45 day s to conduct the reference method test. The Commenter s stated that during this time period additional exceedances of the CPMS parameters do not count and there is no violation unless the source is required to conduct more than four reference method tests in a year. The Commenter s stated that up to 375 day s of continuous noncompliance may elapse before a fifth reference method test occurs. Commenters (20258 and 20293) stated that EPA undercuts its establishment of a separate violation by asserting that this provision merel y creates a rebuttable presumption. The Commenter s stated that this “ separate violation” therefore is illusory and of no particular benefit. The Commenter s stated that instead, it can be read to limit the authority of permitting agencies to prove a violation bas ed on a single gross exceedance of a parametric limit

– such as data showing that the ESP has been turned off. Commenters (20258, 20264, and 20293) stated that 40 CFR § 63.10021(c)(2) is unnecessary and unhelpful and they

suggest that it be removed. Commenter (20264) said it is unclear what is meant by “ separate violation ” in the proposed new paragraph 63.10021(c)(2). The Commenter stated that EPA is proposing to take away the enforcement authorities ’ discretion in deciding what is and what is not a viol ation when there has been a deviation from the CPMS operating limit. The Commenter stated that by explicitly

stating that exceedances leading to more than four performance tests per ye ar will be considered a violation, this paragraph implies that exceedanc es leading to four or fewer tests in a year cannot be considered a violation . The Commenter stated the enforcement authority ’ s ability to determine whether a CPMS deviation is a violation should not be limited in this way . Commenters (20258 and 20293) stated that if EPA intends to address those who chronicall y exceed their CPMS parameters, the Commenters suggest that the EPA identify a number of months in a year, perhaps two or three, where exceedances of a monthl y CPMS parameter will require co nversion of the monitoring system to a PM CEMS. The Commenter s stated that EPA should also make clear that the permitting agency

has the authority

and the ability

under the Credible Evidence rule to determine whether a CPMS deviation is a violation of the underlying limit. Commenter s (20258, 20264, and 20293) stated that if a facility reports, for example, that it has been operating at a level twice as high as its operating limit, the enforcement authority should be able to determine that there has been a violation of the standard. Commenter (20305) stated that the consequences for an exceedance of an indicator remain inadequate. The Commenter stated that the Agency would permit nearly

six months (4 periods of 45 day s, 180 day s in total) of exceedances out of every 12 months

– without finding a violation of the underl ying standard. The Commenter stated that by permitting exceedances of the specified parameters

– even with those provisions in place, and with an opportunity to rebut the presumed violation

– the Agency is permitting96

plants to emit particulate matter at levels exceeding the emission control of the best performing similar source, in violation of the Act. 42 U.S.C. §7412(d)(3). **Response:** The EPA disagrees with the Commenters concerns that the approach is inadequate for ensuring continuous compliance because the time period between an exceedance and testing could be long, thus leading to potential additional exceedances, and permits plants to emit particulate matter at levels exceeding the emissio n limit in violation of the CAA. The final rule requires an EGU owner or operator to visuall y inspect the APCD within 48 hours of the exceedance, and to take corrective action as soon as possible to return the PM CMPS measurement to within the established value. In addition, an EGU owner or operator is required to conduct a performance test within 45 days of the exceedance to determine compliance and verify or re - establish the PM CMPS limit. The EPA finds it unlikely that there will be long periods of nonco mpliance with the underl ying PM standard as estimated in some of the comments given the inspection and performance testing requirements. Moreover, the Credible Evidence rule still applies, and is not restricted b y this approach. This approach does not limit in any

way a permitting or enforcement authority ’s ability to proceed with an enforcement action resulting from exceedances that do not trigger more than four performance tests in a 12 month period under this approach.97

**5 .0**  **TECHNICAL CORRECTIONS AND CLARIFICATIONS**  5 .1 Definitions (existing) **Comment:** Commenter (20285) asked that the EPA revise the definition of “ coal refuse ” in the Final MATS Rule. The Commenter stated that the definition of coal refuse in the MATS rule includes some additional qual ifying language that is not included in the referenced NSPS provisions. The Commenter stated that these criteria are not supported b y available data. The Commenter stated that coal refuse can be variable in many relevant characteristics, and provided discu ssion concerning that point. The Commenter requested that the EPA revise the definition for coal refuse to be consistent with the definition previously

promulgated b y EPA through the NSPS, at 40 CFR §60.41 and § 60.41 Da. The Commenter suggested the following changes:

“ Coal refuse means any by-product of coal mining, phy sical coal cleaning, and coal preparation operations (e.g., culm, gob, etc.) containing coal, matrix material, clay , and other organic and inorganic material with an ash content greater than 50 percent (by weight) and a heating value less than 13,900 kilojoules per kilogram (6,000 Btu per pound) on a dry

basis . ” The Commenter discussed a further advantage to removing the heating value qualifier clarifies that coal refuse - fired FBC EGUs would be classified as units not combusting low rank virgin coal. The Commenter stated that if the EPA does not revise the definition of coal refuse by eliminating the restriction on heating value, then the EPA should clarify which of the two subcategories for coal - fired EGUs under the MATS rule applies to coal refuse - fired FBC EGUs . The Commenter noted that the definition of coal refuse in the relevant NSPS references the word “waste . ” The Commenter recommended the exclusion of this word from the definition o f coal refuse in the Final MATS Rule, because currentl y- mined coal refuse is not a waste at the point of generation, and in general, coal refuse is not a waste at the point of combustion. **Response:** This issue is outside the scope of this rulemaking. The definition of “ coal refuse ” was addressed in the final rule (see , e.g. , RTC, Vol. 2, pp. 709 - 710). The EPA did not solicit comment in the reconsideration proposal on the definition of “ coal refuse . ” **Comment:** Commenter (20285) stated that the EPA should revise the second sentence of the definition of dry FGD to clarify

that the sorbent injection sy stem in an FBC boiler need not be a separate, add - on air pollution control system located downstream of the steam generating unit, in order to qualify as FGD. The Commenter requested that the EPA revise the definition of FGD by either eliminating the reference to a required back- end pollution control device, or clarifying that such reference does not apply to sorbent injection systems associated with FBC boilers. **Response:** This issue is outside the scope of this rulemaking. The EPA does not believe that there is any ambiguity in the definition of “ dry flue gas desulfurization technology , or dry FGD, or spray

dryer ads orber (SDA), or spray dryer, or dry scrubber” and that the definition clearly indicates that FBC and CFB boilers qualify

the respective EGU for the alternate SO 2 emission limit.98

**Comment:** Commenter (20304) stated that multiple definitions of natural gas are not needed. The Commenter noted that the EPA has defined natural gas in 40 CFR Part 60, subpart Db , and 40 CFR Part 63, subpart DDDDD. The Commenter discussed the varying caloric values of natural gas, and suggested that the EPA allow for averaging the gross caloric value over time (e.g., quarterl y) to meet the 910 to 1,150 Btu/dscf range. The Commenter recommended that the EPA revise the definition of natural gas to expand the range of gross caloric values to match the definition in Db. The Commenter stated that facilities do not have control over whether a pipeline company would add landfill gas if that material was available, and may

not be informed about the addition of landfill gas. The Commenter stated that the facility

may be liable for a deviation in that case. Commenter (20304) disagreed with the exclusion of the gases listed in the last part of the natural gas definition. The Commenter noted that the majority of these gases would not meet the minimum gross caloric value, but if they

did and would meet the maximum sulfur content, there are no practical or technical reasons why these fuels would not create as clean a flame as would natural gas, and provide the facility

with additional operating flexibility . **Response:** This issue is outside the scope of this rulemaking. The definition of “natural gas ” was addressed in the final rule (see , e.g. , RTC, Vol. 2, p. 700). The EPA did not solicit comment in the reconsideration proposal on the definition of “natural gas . ” 5 .2 Definitions (new) **Comment:** Commenters (20258 and 20293) noted that EPA has proposed more lenient limits for certain pollutants for sources that are designed to burn “nonagglomerating virgin coal ” having a heat value of less than 8,300 Btu/lb “ that are construc ted and operated at or near the mine that produces such coal” [emphasis added]. The Commenter s noted that the term “ at or near” is not defined and new coal - fired facilities could still claim the more lenient standard if they burn nominal amounts of low rank virgin coal and are within a short distance of the low rank virgin coal mine where they purchase the nominal amount of low rank virgin coal . The Commenter s stated that one potential solution to this issue would be to write the rule so that only those EGUs that combust a minimum percentage of low rank virgin coal would qualify

for the more lenient standard. The Commenter s suggested that this percentage would be a reasonabl y high figure based on the fuel - use of the EGUs that were the basis of the standard. The Commenter s stated that the rule should be written to ensure that there is not a third class, such as low rank virgin coal - fired EGUs that are not near the mine, for which no standards are applicable. **Response:** This issue is outside the scope of thi s rulemaking and, therefore EPA need not respond to the comment. The EPA maintains, however, that consideration of the “ at or near” term is best left for specific implementation determinations. EGUs such as noted by Commenters would need to meet the “ designed to burn ” part of the definition in addition to the “ at or near” portion. 5 .3 Rule language **Comment:** Commenter (20282) supported the change to the term Rti in 40 CFR §63.10009(b)(2) (Eq. 2a) and (3) (Eq. 3a).99

Commenter (20282) supported the correction to a reference in Appendix A §4.1 to the deadline for initial compliance demonstration (replacing 40 CFR §63.10005(g) with §63.99849(f)). **Response:** The EPA appreciates the Comment er ’ s support for the corrections . **Comment:** Commenters (20282, 20294, and 20308) request that the EPA retain the 30 - day notice for a performance test, as a 60 - day notice is not reasonable for facilities conducting quarterl y tests. The Commenter s provided discussion about the importance of a 30 - day notification period. Commenter (20308) disagreed with the changes to notification time frames in 40 CFR §63.10030 paragraphs (b), (c), and (d). The Commenter noted that this may be in line with other parts of 40 CFR Part 63 and 40 CFR Part 60, but longer than the EPA ’ s current philosophy . The Commenter stated that 40 CFR 75 has allowed reduced times of <30 day s, not increased times. The Commenter stated that the requirement to make notifications 60 days prior to a test when quarterl y testing may be utilized as the monitoring method does not allow flexibility of scheduling and will increase the notifications for changes that may

occur on such a short time frame for compliance testing. The Commenter recommended keeping this time at 30 day s. Commenter (20294) opposed changing the performance test notification period from 30 days to 60 day s. According to the Commenter , a 30 - day notification allows greater flexibility to take advantage of testing opportunities when system demand, equipment and contractor availability are in alignment with the Commenter ’ s testing needs. The Commenter noted that a 30 - day notification will also reduce the occurrence of performance test rescheduling due to unforeseeable events such as emergency and/or unscheduled equipment repair, maintenance and malfunctions that may be more likely

with multiple EGUs that share common pollution control equipment. **Response:** The EPA notes that the proposed 60 day notification requirement technical correction was provided to address previous concerns from some of the same Commenter s that different advance notice of performance testing periods existed in the rule. Upon consideration of the Commenter ’s concerns, and in concert with timelines allowed b y the acid rain program, the rule has been changed to allow 30 - day notices f or performance tests. 5 .4 Other technical corrections and clarifications **Comment:** Commenter (20263) is fully supportive of EPA ’ s proposed revision of the new unit Hg standard to 3.0E - 3 lb/GWh. The Commenter stated the proposed revised limit combined with the recently confirmed capability

of NI ST to certify

Hg calibration gas, and generators down to 0.2 μg/ as well NI ST has the capacity to create a Zero gas for Hg by 2014. The Commenter asked that Hg gas calibration cylinders for both the pollutant and the zero gas be included in the reconsideration. Commenter (20263) noted an inconsistency between the requirements of 40 CFR Part 72.2 ( “ Definitions ” ) and the discussion on continuous compliance within the proposed reconsideration: 1) **“ Continuous emission monitoring system or CEMS**  means the equipment required by part 75 of this chapter used to sample, anal yz e, measure, and provide, by means of100

readings recorded at least once every 15 minutes (using an aut omated data acquisition and handling s ys tem (DAHS)). 2) **“ Calibration error**  means the difference between: (1) The response of a gaseous monitor to a calibration gas and the known concentration of the calibration gas; (2) The response of a flow monitor to a ref erence signal and the known value of the reference signal. 3) “ **Calibration gas** means: (1) A standard reference material; (2) A standard reference material - equivalent compressed gas primary reference material; (3) A NIST traceable reference material; (4) NI ST/EPA - approved certified reference materials; (5) A gas manufacturer ’ s intermediate standard; (6) An EPA protocol gas; (7) Zero air material; or (8) A research gas mixture. 4) **“ Alternative monitoring system**  means a sy stem or a component of a s ys tem designe d to provide direct or indirect data of mass emissions per time period, pollutant concentrations, or volumetric flow, that is demonstrated to the Administrator as having the same precision, reliability , accessibility , and timeliness as the data provided b y a certified CEMS or certified CEMS component in accordance with part 75 of this chapter. ” Commenter (20263) stated, in summary to the above excerpts from 40 CFR § 72.2: 1) It is evident that for a CEMS to qualify for Part75 the unit must be challenged with a traced “ compressed gas primary reference ” of some manner. Itis therefore that the Zero Gas should also be included in the MATS as a requirement to zero out the anal yz ers for the daily

calibration check process. Gas generators cannot be used for CGAs an d RATAs. 2) Based on the criteria set in § 72.2 a CEMS must be able to provide continuous data points at a minimum of every 15 minutes. 3) If the monitoring s ys tem does not have the capability to be challenged b y a traceable gas or cannot provide a minimum data s et of every 15 minutes then it must be qualified as an Alternative Monitoring S ys tem (AMS) and will be subject to the requirements of 40CFR Part75; subpart - E in order to be used as a compliance device. Commenter (20263) concluded, these points are needed to be added to the MATS such that it will remain compliant with the Clean Air Management [sic] Division (CAMD) requirement. Commenter (20268) noted an inconsistency between the requirements of 40 CFR Part 72.2 ( “ Definitions ” ) and the discussion on continuous compliance within the proposed reconsideration. The Commenter stated that if the monitoring s ys tem does not have the capability to be challenged b y a traceable gas or cannot provide a minimum data set of every 15 minutes then it must be qualified as an Alternative Monitoring System (AMS) and will be subject to the requirements of 40 CFR Part 75;101

subpart - E in order to be used as a compliance device, and sorbent traps may fall in this category . The Commenter stated that this is not clear in the proposed reconsideration. **Response:** The Commenter requests that Hg gas cylinders and zero gas be addressed in the reconsideration; the EPA sees no rationale for this. Inthe case of Hg cylinder gases, they are already addressed in sev eral places both within Part 63, subpart UUUUU and within associated documents. In Section 3.1.4 of Appendix A of Subpart UUUUU, compressed gases are mentioned as suitable calibration standards if prepared according to the “EPA Traceability Protocol for As say

and Certification of Gaseous Calibration Standards” and though Hg gas cylinders are not specifically mentioned in the document, it would clearly be possible and appropriate to certify Hg gas cylinders through an unbroken chain of comparisons using NI ST - traceable ‘vendor prime’ Hg gas generators (as defined in the “ Interim EPA Traceability Protocol for Qualification and Certification of Elemental Mercury Gas Generators ” 17 ). The appropriate target uncertainty would be the same as that specified in the late st version of this interim p rotocol (currently 5 percent). Cylinder gases are also mentioned in the interim protocol as reference gases (see Section 3.20) and to perform periodic assessments of certified generators (see Section 7.1.4). The EPA sees no rati onale for defining zero gases beyond what is specified in Section 3.1.8 of Appendix A of Subpart UUUUU which specifies ‘calibration gas containing a Hg concentration that is below the level detectable b y the Hg gas anal yz er in use. The EPA finds irrelevant the Commenter’s concerns regarding monitoring s ys tem inconsistencies between this rule and the acid rain rules. It is not unreasonable that the MACT program has differing requirements than the acid rain program given the different mandates of the programs . The requirements for this rule’s Hg monitoring and HCl/HF monitoring s ys tems are provided in Part 63, subpart UUUUU, Appendices A and B , while the concerns mentioned by the Commenter are found in Parts 72 and 75. The Commenters’ assertion that complete c onsistency with Part 72 and 75 monitoring requirements must be achieved for this rule’s unique monitoring s ys tems is inappropriate and beyond the scope of this rulemaking.

17 http://www.epa.gov/ttnemc01/metals/ElemHgProtocol.pdf, from July 1, 2009. Also available in Docket ID EPA - HQ - OAR - 2009 - 0234.102

**6 .0**  **IMPACTS AND COST ANALYSIS** 6 .1 Air Impacts **Comment:** Commenter (20249) stated EPA addresses control technologies needed to meet the NESHAP and NSPS emission limits for a new source in Item 7 of Section IV . The Commenter said, based on an anal ys is of control requirements for a new hy pothetical 500 MW facility , the EPA concluded that new EGUs would need to be designed to use the same types of emission control technologies to meet the proposed new source limits as would hav e been needed to meet the final MATS new source limits. The Commenter stated, however, that EPA chose a hyp othetical unit of roughly median size (500 MW). The Commenter said this approach may not address design and operation limitations of such controls wh en unit sizes approach either the minimum and maximum size. **Response:** The EPA evaluated the types of emission controls that would generall y be necessary to meet the final new source limits and compared those to the ty pes of emission controls that would generall y be necessary to meet the proposed reconsideration new source limits. The EPA chose to examine the level of control needed at a hypothetical 500 MW plant. However, the size of the unit is irrelevant

– the EPA could have just as easily

compared the c ontrols needed at a 100 MW plant or at a 900 MW plant. In each case, the comparison would have been between the controls needed to meet the final new source limits and the controls needed to meet the proposed reconsideration new source limits. Our conclusi on would have been the same. Any “ design and operation limitations ” of the controls would have been present whether the unit was attempting to meet the final limits or the proposed reconsideration lim i ts. **Comment:** Commenter (20249) stated when addressing control technologies in Item 7 of Section IV , the EPA also anal yz ed controls on existing sources to determine whether existing sources can meet standards for new sources. The Commenter said EPA performed this analysis even though it asserts that nothing in the statute (CAA) requires the EPA to make such a demonstration. The Commenter stated, as evidenced b y Figure 1, Example sorbent injection performance curve, in the November 16, 2012 , EPA Memorandum from Nick Hutson, the effectiveness of controls can diminish as higher removal rates are targeted. The Commenter stated there can be inordinate costs associated with achieving an incremental amount of additional emissions reduction. **Response:** The EPA agrees that the effectiveness of controls can diminish as higher removal rates are targeted and that there can be inordinate costs associated with achieving an incremental amount of additional emissions reduction. The cost effectiveness for incremental levels of control was examined in the BTF anal ys is (see Secti on 3.0 of this document for additional detail). When setting MACT emission limits for the new source categories , the EPA determined the emission limitation achieved in practice by the best performing existing source within that category . The EPA then incor porated inherent variability (e.g., process, fuel, operational) using the “upper predictive limit” methodology that has been explained elsewhere. CAA §112(d)(2) requires that the Agency promulgate standards that “ shall require the maximum degree of reduc tion in emissions...that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non - air quality health and environmental impacts and energy requirements, determines is achievable... ” This is referred to as the BTF analysis. The EPA has, as directed by103

Congress, considered the cost of achieving “the maximum degree of reduction ” and in all cases, except one, found the costs of achieving a BTF level of control to be not cost - effective or unreasonable. 6 .2 Energy Impacts **Comment:** Commenter (20266, 20286, and 20301) stated that the EPA has not addressed how the proposed issues under reconsideration will impact electric power grid reliability . Commenters (20266, 20286, and 20301) stated that they expressed these co ncerns in previous comments on the proposed rule regarding the EPA ’ s erroneous assumptions regarding the Electric Reliability Council of Texas (ERCOT) and the Texas electric power grid. The Commenter s expressed concerns that EPA had significantly

understat ed the effects of the rule on electric reliability and electricity prices in Texas, and had made incorrect assumptions regarding the Electric Reliability Council of Texas (ERCOT) and the Texas power grid in the rule. Commenter (20286) stated that the EPA c ontinued to perpetuate those errors in the final rule, relying on incorrect information when evaluating the potential effects of the final rule on electric reliability . The Commenter s stated that in its final rule , the EPA acknowledged and corrected one of its errors, but otherwise failed to revise its analysis to correct the numerous other errors and invalid assumptions enumerated by their earlier comments. The Commenter s stated that by

failing to address how the proposed reconsideration would impact electric reliability, the EPA compounds these errors further, while refusing to provide transparent information to the public for review and comment. **Response:** This issue is outside the scope of this rulemaking. The EPA has addressed the issue of reliability in the final rule (see , e.g. , 77 FR 9406 - 9411). The impacts of this rulemaking are further minimized because it only addresses new sources. 6 .3 Economic Impacts/Employ ment Impacts **Comment:** Commenter (20273) stated that the reconsidered MATS will discourage the use of an abundant, affordable, and renewable fuel

– petroleum coke. The Commenter noted that regardless of whether the Commenter ’ s facility is built, petroleum coke will continue to be produced in large quantities as part of the oil refining process. The Commenter stated that they are developing a new, petroleum coke - fueled electric generation project in Corpus Christi, Texas. The Commenter stated that if this facility

is brought on - l ine, it will serve a vital role in addressing the shortfall in electric generating capacity facing Texas. The Commenter noted that the new facility ’ s EGUs will burn 100 percent solid oil - derived fuel, i.e., petroleum coke, a product of nearb y refineries. The Commenter stated that using CFB boiler technology

to generate approximately 1,200 net megawatts of electricity , the new facility would generate enough electricity to power more than 850,000 Texas homes. Commenter (20273) stated that each ye ar, approxim ately 1.7 million tons of petroleum coke are produced in Corpus Christi and approximately 35 million tons are produced throughout other parts of the Gulf Coast region. The Commenter says that presentl y, the majority of Gulf Coast petroleum coke is transported to remote international markets where it is burned in cement kilns, power plants, and other processes. The Commenter stated that because petroleum coke will continue to be generated as part of the petroleum refining process and, because this fuel will continue to be shipped abroad and burned for energy recovery in the absence of a local consumer, operation of the well - controlled new facility would104

result in a net decrease in air emissions, including global Hg and GHG emissions versus the present alternative uses. The Commenter noted that the new facility will use CFB boilers for steam generation where limestone is injected into the CFB for in - bed desulfurization, and a CDS - FGD s ys tem and a fabric filter located downstream of the CFB boilers. The Commenter stated that injection of powdered activated carbon ( “ PAC ” ) for Hg capture will be employed upstream of the CDS - FGD s ys tem. The Commenter noted that using this fuel locall y will eliminate the GHG emissions associated w ith the transportation of petroleum coke to international markets, the new facility will more efficientl y convert the petroleum coke into useful energy relative to other users, and it will employ emission controls that will result in significantly lower am ounts of Hg and other air emissions relative to other users. Commenter (20273) stated that despite the obvious benefits to the environment from using domesticallyproduced solid oil - derived fuel at the Commenter ’ s new facility and even as revised, the EPA ’ s proposed reconsidered MATS, will likely cause the Commenter to abandon development of its new facility and the unique opportunity of locating a significant and much - needed power generation facility near an abundant, affordable, and renewable fuel supply will be lost. The Commenter disagreed with the revised standards as a matter of policy . The Commenter stated that EPA should modify the reconsidered MATS applicable to solid oil - derived fuel for EGUs because the proposed standards will discourage, if not preclude, the use of these EGUs . **Response:** The EPA disagrees with Commenter ’ s allegation that the proposed reconsidered limits will discourage or preclude construction or use of solid oil - derived fuel - fired EGUs as the data used to establish the emission limits came from such EGUs and the Commenter has provided no information to support an argument that the final limits cannot be achieved on a new solid oil - derived fuel - fired EGU . **Comment:** Commenter (20274) stated that the price of energy is a significant concern to the Commenter ’ s members, and that small - business owners depend on energy supplies at globall y competitive prices to operate and effectivel y run their businesses. The Commenter c ited the most recent edition of NFIB ’ s Small Business Problems and Priorities, published earlier this year, and stated that the cost of energy

was reported by

NFIB members to be the third most important problem facing their company. The Commenter stated th at nearl y 35 percent of survey respondents cited the issue as a “ critical ” problem. Commenter (20274) stated the way that the Utility

MACT rule is structured will mean significant increases in energy

rates. The Commenter stated that the Final Rule finaliz ed in February is the most expensive in U.S. history and the Reconsideration has done little to alleviate this burden. The Commenter stated that small businesses cannot afford to spend more on energy , and that the rule threatens energy

reliability . Commenter (20274) asked that the EPA issue a rule that addresses the target pollutants commensurate with the benefits of reducing the target pollutants. **Response:** This issue is outside the scope of this rulemaking. The EPA has addressed the price of electrici ty and the potential impact of MATS in the final rule (see , e.g. , 77 FR 9414). The impacts of this rulemaking are further minimized because it only addresses new sources. 6 .4 Health Co - Benefits105

**Comment:** Commenter (20305) stated that recent studies continue to demonstrate that methylmercury impacts are widespread and significant, impact more wildlife species than previously recognized, and adversel y affect fish and wildlife at lower concentrations. The Co mmenter cited several recent studies that discuss the extent of Hg in the environment. The Commenter stated that research continues to confirm that coal - fired power plants contribute to significant local Hg contamination and exposure. The Commenter cited a recent study of Hg levels in infants, and cited a recent study on the widespread health effects to all organ s in the human body . Commenter (20305) discussed the role of PM2.5 and toxic metal content on human health, citing several journal articles, and discussed carcinogenic emissions and cancer risks, citing three studies. **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding additional health impacts. 6 .5 Other impacts and cost analysis **Comment:** Commenter (20247) stated that the use of powdered activated carbon (PAC) injection for Hg control has been linked to fires in baghouse hoppers. According to the Commenter , loss on ignition (LOI) is one of the key

parameters in assessing the risk of fire and although not all the factors affecting auto - ignition potential are known, a target LOI level in the fly ash of 10 percent provides a reasonable margin from the level of 15 percent identified b y the Institute of Clean Air Companies (ICAC) as a level at which auto - ignition did not occur. The Commenter stated that the LOI should be taken into account in evaluating the PAC and Hg emission limits on newly constructed EGUs and recommends that EPA allow the regulating agency with primacy

over the program to consider LOI levels on a case - by- case basis and use a target LOI level in the fl y ash of 10 percent to provide a reasonable margin from the value determined b y IC AC. **Respons e:**  The EPA is aware of such instances as Commenter notes in early installations of activated carbon injection. However, the EPA believes these issues have been resolved and ACI is installed and being used successfully , without fire issues, on a wide range of EGUs. Individual companies and their engineering firms should always consider safety in the design of all of their emission controls. **Comment:** Commenter (20307) stated that the purpose of the Commenter ’ s filing is to express an interest in these matter s and to note some consistencies between the Agency ’ s action in reconsidering some provisions of previously proposed rules with the Commenter ’ s studies on regulatory policy . The Commenter cited: Resolution on the Role of State Regulatory Policies in the Development of Federal Environmental Regulation and subsequent Resolution on Increased Flexibility for the Implementation of EPA Rulemakings . The Commenter emphasized the need for environmental and energy policies that ensure continued emission reduction pro gress that also enhances energy reliability

and lower costs. Commenter (20307) cited Resolution on the Role of State Regulatory Policies in the Development of Federal Environmental Regulation , stating that this resolution set forth the Commenter ’ s initial position on the development of public health and environmental regulations that will directly affect the electric power sector. In this resolution the Commenter acknowledged that such regulations could pose economic, feasibility

and reliability

challenges. The Commenter stated that state utility regulators are106

well positioned to evaluate risks and benefits of various resource options through policies that appropriatel y account for and mitigate the risks arising from compliance with pending regulations. The Commenter said that state utility regulators, by

working with the power sector and State and federal environmental regulators, can help to facilitate least - cost compliance with public health and environmental goals. Commenter (20307) stated the Resolution on the Role of State Regulatory Policies in the Development of Federal Environmental Regulation includes several policy resolves that pertain specificall y to the Agency in developing public health and environmental programs such as MATS. The Commenter urged the Agency

through this resolution to: 1) seek ways to minimize cost impacts to consumers, 2) ensure that its actions do not impair the availability of adequate electricity and natural gas resources, and 3) recognize the needs of states and re gions to deploy a diverse portfolio of cost - effective supply- side and demand - side resources based on the unique circumstances of each state and region. Commenter (20307) recognized the need for increased flexibility for the implementation of Agency rulemakings. The Commenter stated that there are many strategies available to states and utilities to comply with EPA regulations, including 1) retrofits and installation of pollution control equipment, 2) construction of new power plants, 3) transmission upgrades to provide resources adequacy and s ys tem security where needed when power plants retire, 4) purchases of power from wholesale markets, 5) demand response, 6) energy efficiency , and 7) renewable energy policies -- the collection of which can be implement ed at different time frames b y different interested parties and may constitute lower- cost options that provide benefits to ratepayers. The Commenter stated that the proposed revisions to the new sources standards represent changes that may assist with pres erving the multitude of options available to comply with the Agency ’ s hazardous air pollution standards. **Response:** This comment requires no response .107

**7 .0**  **GENERAL COMMENTS**  **Comment:** C ommenters (20244, 20259, and 20260) stated that EPA should eliminate the use of coal. **Response:** This comment is outside the scope of this rulemaking as the EPA is only establishing certain revised emission limits for new sources rather than setting national energy policy . **Comment:** Commenter s (20309, 20310, 20311, 20312, and 20313) stated that EPA should not weaken the Mercury

and Air Toxics Standard. The Commenter s opposed loosening of the Hg and other emission standards while reclassifying s ynthetic natural gas derived from coal, ULSD fuel and propane as clean fuels as this designation places those pollutants outside of EPA ’ s rule. The Commenter s stated that such fuels emit GHG s , are not clean fuels and that EPA is putting industry interests ahead of protecting public health. **Response :**  The EPA does not believe that the MATS rule is being weakened as alleged b y Commenters. Further, as this rulemaking addresses hazardous air pollutants (HAP), comments on GHG issues are outside the scope of the rulemaking.108

**8 .0**  **OUT OF SCOPE Comment:**  Commenter (20256) stated that, similar to its recalculation of the new source MACT floors based on all of the emissions data in the record , the EPA must be consistent it its approach in the establishment of the MACT limits for existing sources as well. In particular, the Commenter stated that the input based emissions standard for particulate matter for existing “petroleum coke units ” should similarly be revised b y EPA based on all of the emissions data in the record from the “best performing ” EGUs . The Commenter ’ s February 17, 2012 , petition seeking reconsideration includes a detailed anal ys is of data from the “best performing ” petroleum coke EGUs . **Response:** This issue is outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the existing - source emission limits. **Comment:** Commenter (20248) requested that EPA reconsider the stack testing requirements related to demonstrating compliance for non - mercury metals and acid gases and provide the opportunity to scale back testing after a demonstration period. The Commenter stated that the EPA should recognize the difficulty in planning stack tests for EGUs that are not base load. The Commenter noted that s tack tests require coordinating schedules with the regional Independent S ys tem Operator (I SO), state agencies, stack test contractors, and plant operations. The Commenter stated that i t is very difficult to align schedules and as a result EGUs will be forc ed on for the sole purpose of stack testing. The Commenter observed that r educing the frequency of testing will satisfy the EPA ’ s desire for EGUs to demonstrate consistent emissions profiles, while eliminating unnecessary emissions and minimizing the burden on resources. The Commenter requests that the EPA reduce the LEE demonstration period to quarterl y testing for 1 ye ar and that the EPA revert back to the original MATS proposal for subsequent LEE tests to be conducted every

5 years. For EGUs not eligible for LEE, the Commenter requests quarterl y testing for 1 year and , provided each quarterl y test nets a compliant result, test frequency would be reduced to annually . **Response:** These issue s are outside the scope of this rulemaking. The EPA did not solicit comment in the reconsideration proposal regarding the existing - source emission limits or on monitoring issues related to existing sources. **Comment:** Commenter (20262) stated that they were confused about when and how to demonstrate comp liance with several of the tune - up provisions of 40 CFR §63.10005(e - f) and §63.10021(e) and encourage d EPA to issue more guidance or make clarifications within the rule. The Commenter provided several examples of tune - up provisions in need of additional guidance or clarification. **Response:** Issues such as those noted by Commenter are outside the scope of this rulemaking. If there are questions or concerns about the implementation of the final MATS rule for existing sources, the owners or operators should co ntact EPA or the appropriate state authority . **Comment:** Commenter (20262) stated that EPA should allow the use of the diluent cap for all hours outside of these thresholds, not just for hours that fit within EPA ’ s narrow definition of startup and shutdown. The Commenter stated that this would be consistent with 40 CFR Part 75 Appendix F Section 3.3.4.1 for calculating lb NO X/MMBtu . The Commenter stated that this concept should likewise be applied to calculating HCl (Appendix B to s ubpart UUUUU) emissions.109

**Response:** This issue , expansion of diluent cap use, is outside the scope of this rulemaking. The EPA neither proposed nor requested comments on this issue; thus, this comment is not addressed .110

**9 .0**  **INCORPORATE BY REFERENCE Comment:**  Commenter (20243) incorporated by reference comments from NRECA (no docket number) and UARG ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20282 ). Commenter (20253) stated that they incorporated by

reference comments submitted to EPA during the initial MATS rulemaking that provi de support for its arguments regarding the availability of natural gas, cost effectiveness, non - air quality health and environmental impacts, the need for EPA to consider the use of cleaner fuels under the MACT standards, and the BTF requirements. The Comm enter also incorporated b y reference comments including those of America ’ s Natural Gas Alliance ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 17810), Julander Energy Company

( Docket ID EPA - HQ - OAR- 2009 - 0234 - 18423), and the comments originall y submitted by the Commenter (20253) ( Docket ID EPA - HQ - OAR 2009 - 0234 - 17852). Commenter (20255) stated that they endorse and adopt the comments submitted by American Electric Power Company

( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20308). Commenter (20281) incorporated b y reference comments from UARG ( Docket ID EPA - HQ - OAR 2009 - 0234 - 20282). Commenter (20285) incorporated b y reference and reasserted, b y the extent applicable, their comments in their Petition for Reconsideration of the Final MATS Rule. Commenter (20295) supports the comments o f UARG ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20282), and incorporated b y reference their own comments submitted for the 2011 proposed MATS rule. Commenter ( 20305 ) incorporated b y reference 10 scientific article s concerning the dangers of Hg , three articles about particulate matter and toxic metals and human health, and three articles about airborne carcinogens. Commenter (20266) has reviewed and full y endorses the comments of Public Utility Commission of Texas ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20301) and TCEQ ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20286). Commenter (20277) fully supports and incorporates by reference the comments of UARG ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20282) including its attachment prepared b y RMB Consulting and Research, In c., and EE I ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20295). Commenter (20276) stated that they support and incorporate by reference the comments made b y the Edison Electric Institute (EEI) ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20295) and the UARG ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20282) . Comm enter (20308) incorporated b y reference comments from UARG (Docket ID EPA - HQ - OAR 2009 - 0234 - 20282). The Commenter also incorporated b y reference their comments submitted on the proposed MATS rule (Docket ID EPA - HQ - OAR - 2009 - 0234 - 19114) regarding long - term achievability of the standards and IGCCs.111

Commenter (20306) incorporated b y reference comments from EEI (Docket ID EPA - HQ - OAR - 2009 - 0234 - 20295), GCA ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20288), and UARG ( Docket ID EPA - HQ OAR- 2009 - 0234 - 20282). Commenter (20303 ) incorporated b y reference comments from NRECA and GCLC ( Docket ID EPA HQ - OAR- 2009 - 0234 - 20275). Commenter (20301) agreed with and supported the comments made b y TCEQ ( Docket ID EPA - HQ OAR- 2009 - 0234 - 20286). Commenter (20300) incorporated b y reference co mments submitted for the proposed MATS rule in 2011 ( Docket ID EPA - HQ - OAR - 2011 - 0044 - 5715) . Commenter (20256) endorsed and incorporated by reference comments submitted by the UARG ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20282) that comment ’ s attachment, prepared b y RMB Consulting & Research, Inc. (RMB). The Commenter also incorporated b y reference the relevant portions of their earlier, more extensive comments on the proposed rule dated August 4, 2011. C ommenters (20257 and 20270) supported and endorsed the comments submitted by UARG ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20282). C ommenters (20262 and 20291) endorsed the comments submitted by the EEI( Docket ID EPA - HQ OAR- 2009 - 0234 - 20295) and UARG ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20282). Commenter (20271) stated that they support and incorporate by reference the comments of EEI ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20295). Commenter (20294) stated that they support and incorporate by reference the comments of EEI ( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20295), EPRI( Docket ID EPA - HQ - OAR- 2009 - 0234 - 20261) and AEP ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20308). Commenter (20275) incorporated b y reference, as applicable, comments submitted to the proposed MATS rule: Docket ID EPA - HQ - OAR- 2009 - 0234 - 17930; Docket ID EPA - HQ - OAR- 2011 - 0044 - 5240. Commenter (20321) stated that they support the comments of the Class of ‘ 85 Regulatory Response Group ( Docket ID EPA - HQ - OAR - 2009 - 0234 - 20269 ) . **Response:** The comments have been addressed elsewhere in this document. Note that the National Rural Electric Cooperative (NRECA) did not submit comments on the reconsideration proposal.112

**1 0**  **.0 OTHER COMMENTS NOT COVERED**  **Comment:** Commenter (20238) stated that had E PA indicated in any way that the Agency planned to use CAA §111(d) to require states to draft and seek approval from the Agency for a SIP requiring existing emission sources to comply with the emission limits set forth in this and in the original rules on whi ch the reconsideration is based, the Commenter would have submitted substantial comments. **Response:** No response is required as this rulemaking is under CAA § 112. **Comment:** Commenter (20270) recommended that EPA consider all of the items addressed in petitions for reconsideration and provide further opportunity to comment on those issues as well. The Commenter stated that utilities are in the process of planning for compliance and nee d further clarification and/or revisions in order to proceed. **Response:** The EPA is still evaluating the reconsideration issues that were not addressed in the November 30, 2012, reconsideration notice.113

**1 1**  **.0 DUPLICATE COMMENTS**  Docket entries identified as duplicate comments are: 20278, 20283, 20314, 20317 .