1 

## Standards of Performance for Fossil-Fuel-Fired Steam Generating Units for Which

Construction Is Commenced After August 17, 1971 (40 CFR 60 subpart D)

Standards of Performance for Electric Utility Steam Generating Units for Which

Construction Is Commenced After September 18, 1978 (40 CFR 60 subpart Da)

Standards of Performance for

Industrial-Commercial-Institution al Steam Generating Units (40 CFR 60 subpart Db)

Standards of Performance for Small

Industrial-Commercial-Institution al Steam Generating Units (40 CFR 60 subpart Dc)

Response to Public Comments on Rule Amendments Proposed May 3, 2011 (73 FR 33642)

US Environmental Protection Agency Office of Air Quality Planning and Standards Sector Policies and Programs Division

Research Triangle Park, NC 27711

December 2011Introduction

ii 

### Table of Contents

1. Introduction

............................................................................................................................... ................................ v

2. Response to Comments on Proposed NSPS Amendments to

................................................................................... 1

Subparts D and Da

............................................................................................................................... ......................... 1

2.1 General NSPS Rule Development

................................................................................................................... 1

2.1.1 Fuel and Technology Neutral Ap proach for Rule Development ........................................................... 1

2.1.2 Selection of Best System of Emission Re duction (BSER) ................................................................... . 3

2.1.2.1 Consideration of EGU Energy Efficiency in Selection of BSER

............................................... 3

2.1.2.2 Consideration of IGCC Technology in Selection of BSER

........................................................ 4

2.1.3 Net Energy Output Based Emissions Standards Format ...................................................................... .. 4

2.1.4 Standards for Reconstructed and Modified EGUs ........................................................................... ...... 5

2.1.5 Standards for Combined Heat and Power (CHP) Units S ubject to NSPS ............................................. 6

2.1.6 NSPS during Periods of EGU St artup, Shutdown, a nd Malfunc tion ..................................................... 6

2.1.7 Facility-Wide Em issions Av eraging ....................................................................................... ............... 7

2.1.8 Interrelationship of NSPS with ot her EPA Rulemakings Affecting EGUs ........................................... 8

2.1.8.1 Source Category Impact Analysis

............................................................................................... 8

2.1.8.2 Delay of NSPS Rulemaking until NESHAP Affecting EGUs is Finalized

................................ 8

2.1.8.3 Proposal of EGU NSPS Amendments with EGU NESHAP

...................................................... 8

2.2 Rule Applicability

............................................................................................................................... ............. 9

2.2.1 Regulation of IGCC facilities under 40 CFR 60 subpart KKKK .......................................................... 9

2.2.2 Exemption of EGUs Usin g “Innovative T echnologi es” ....................................................................... . 9

2.2.3 Applicability to Permitt ed EGUs for which Construc tion Has Not Co mmenced ................................ 10

2.3 Particulate Matter (PM) Emissions Standards

............................................................................................... 10

2.3.1 Selection of BSER for PM Emissions ...................................................................................... ........... 10

2.3.2 Regulation of Comb ined PM Emissions ..................................................................................... ......... 11

2.3.3 Regulation of PM 2.5 Emissions ............................................................................................................ 12

2.3.4 Selection of PM Emissions Li mit Value.................................................................................... .......... 12

2.3.5 PM Control Cost Analysis ................................................................................................ ................... 13

2.3.6 PM Standards Exemptions ................................................................................................. .................. 13

2.3.6.1 Opacity Standard Exemption for EGUs Using PM CEMS

....................................................... 13

2.3.6.2 Opacity Standard Exemption for EGUs Complying with a Combined PM Standard

............... 14

2.3.6.3 PM and Opacity Standard Exemptions for Natural Gas Fired EGUs

....................................... 14

2.3.6.4 PM and Opacity Standards Exemption for Low-Sulfur Fuel Fired EGUs

................................ 14

2.4 Sulfur Dioxide (SO 2 ) Emissions Standards

................................................................................................... 15

2.4.1 Selection of BSER for SO 2 Emissions ................................................................................................. 15

2.4.2 Selection of SO 2 Emissions Limit Value ............................................................................................. 15

2.3.3 SO 2 Control Cost Analysis ........................................................................................................ .......... 16

2.4.4 Coal Refuse-Fired EGU Exemption from SO 2 Standards ................................................................... 16

2.5.1 Selection of BSER for NO X Emissions ............................................................................................... 17

2.5.2 Combined NO X + CO Emissions Limit ............................................................................................... 17Introduction

iii 2.5.3 NO X Emissions Limit .............................................................................................................. ............ 18

2.6 Compliance Requirements

............................................................................................................................. 20

2.6.1 Opacity Monito ring

...................................................................................................... ....................... 20

2.6.2 PM Continuous Emission Mo nitori ng ....................................................................................... .......... 20

2.6.3 Electronic Reporting of Performance Test Data ........................................................................... ....... 21

2.6.4 Monitoring PM an d Opacity Emissions from EGUs Using ESPs ....................................................... 23

2.7 Other Proposed Amendments

........................................................................................................................ 23

2.7.1 Rule Definitions ........................................................................................................ ........................... 23

2.7.1.1 Definition of “Affected Facility”

.............................................................................................. 23

2.7.1.2 Definition of “Gaseous Fuel”

................................................................................................... 23

2.7.1.3 Definition of “IGCC Electric Utility Steam Generating Unit”

................................................. 24

2.7.1.4 Definition of “Natural Gas”

...................................................................................................... 24

2.7.1.5 Definition of “Petroleum Coke”

............................................................................................... 24

2.7.2 General Duty ............................................................................................................ ........................... 25

2.7.3 Affirmative Defense Provisions .......................................................................................... ................ 25

2.7.4 Subpart Da Mercury Provisions ........................................................................................... ............... 27

2.7.5 Removal of References to 30-Day Rollin g Averages ........................................................................ .. 27

2.7.6 Deletion of Obsolete Provi sion References in Rule ....................................................................... ..... 27

2.7.7 Proposed Rule Language Co rrections and Cl arifica tions ................................................................... . 27

3. Response to Comments on Proposed NSPS Amendments to Subparts Db and Dc

................................................ 28

3.1 Definition of “Distillate Oil” ............................................................................................ ...................... 28

3.2 Exemption of Steam Generating Units Subject to Other NSPS .............................................................. 28

3.3 Applicability to Temporary Boilers ........................................................................................ ................ 28

3.4 Site-Specific M onitoring Plan ............................................................................................. ................... 29

3.5 Opacity Monito ring

........................................................................................................ ........................ 29



### List of Tables

Table 1. List of Commenters Cited in this Summary Document Submitting Comments to EPA Air and Radiation Docket Number EPA-HQ-OAR-2011-0044 Regarding NSPS Rule Amendments Proposed May 3, 2011 (76 FR 24976)

..... viIntroduction

iv 

### Acronyms and Abbreviations

BACT Best Available Control Technology

BSER

BLD Best System of Emission Reduction Bag leak detection

Btu British thermal unit

CAA Clean Air Act CCS Carbon capture and storage CEMS Continuous emissions monitoring system CFB Circulating fluidized bed CHP Combined heat and power

CO Carbon monoxide COMS Continuous opacity monitoring system CROMERR Cross-Media Electronic Reporting Regulation DOE U.S. Department of Energy EGU Electric steam generating unit EPA U.S. Environmental Protection Agency

ERT 

### Electronic Reporting Tool ESP Electrostatic precipitator FGD Flue gas desulfurization GHG Greenhouse gas IGCC Integrated gasification combined cycle

kWh Kilowatt-hour MW Megawatt MWC Municipal waste combustor MWh Megawatt-hour NAAQS National Ambient Air Quality Standard

NO 2 Nitrogen dioxide

NO

x Nitrogen oxides

NSPS New Source Performance Standards

NSR New Source Review OMB Office of Management and Budget

PM Particulate matter PRA Paperwork Reduction Act PSD Prevention of Significant Deterioration SCR Selective catalytic reduction SNCR Selective non-catalytic reduction SIP State Implementation Plan

SO 2 Sulfur dioxide

SO

x Sulfur oxidesIntroduction

v 

## 1. Introduction

On February 27, 2006, the United States Environmental Protection (EPA) promulgated amendments (71 FR 9866) to the new source performance standards (NSPS) for el ectric utility steam generating units (EGUs) under 40 CFR part 60 subparts D and Da. EPA was subsequently sued by the offices of multiple state Attorneys General and environmental organizations on these amendments. On Se ptember 2, 2009, EPA was granted a voluntary remand without vacatur of the 2006 amendments. On May 3, 2011, EPA proposed amendm ents (76 FR 24976) in response to the voluntary remand. These amendments incl uded proposed new emissions limits for particulate matter (PM), sulfur dioxide (SO 2 ), and nitrogen oxides (NO X ) for EGUs that commence construction, reconstruction, or modification on or af ter May 3, 2011. As part of this action, the Agency also proposed several minor amendments, technical clarifications, and corrections to existing provisions applicable to the fossil fuelfired EGUs under 40 CFR 60 subparts D and Da, as well as large and small industrial-commercial-institutional steam generating units NSPS under 40 CFR part 60 subparts Db and Dc.

A 90-day period ending August 4, 2011 was provided for th e public to submit comments regarding the proposed subparts D, Da, Db, and Dc amendments. Approximately 200,000 comments were entered into EPA’s Air and Radiation docket assigned for this NSPS rulemaking (number 

### EPA-HQ-OAR-2011-0044 ). Many of these comments were duplicative of comments submitted to EPA’s Air and Radiation docket assigned for the development of the proposed national emission standa rds for hazardous air pollutant (NESHAP) from coal- and
oil-fired EGUs under CAA section 112 (number 

### EPA-HQ-OAR-2009-0234 ).

EPA reviewed all of the comments entered into do cket EPA-HQ-OAR-2011-0044 and grouped the commenters into three general categories. The first category is commenters submitting duplicative copies of comments also submitted to docket EPA-HQ-OAR-2009-02 34 regarding the proposed NESHAP rulemaking, and which do not contain any comments specifically related to the prop osed NSPS amendments. The second category consists of commenters stating only general support or opposition to the NSPS rulemaking. Commenters supporting the amendments frequently included statements requesting that EPA establish the most stringent air emissions standards possible for EGUs. Commenters opposing the am endments frequently stated that the proposed NSPS amendments are overly stringent and bur densome and would inhibit or preven t the construction of new coal-fired EGUs, thereby increasing costs for electricity. The thir d and final category of public commenters are those providing comments regarding specific issues and topics re lated to the rule development and proposed rule language for amendments to 40 CFR 60 subparts D, Da, Db, and Dc.

This document presents a summary of the public comments entered into docket 

### EPA-HQ-OAR-2011-0044 regarding specific issues and topics related to the deve lopment of the proposed NSPS amendments to 40 CFR 60 subparts D, Da, Db, and Dc (i.e., comments submitted by commenters in the third category) and EPA’s responses to those comments. The comment summaries pertaining to subparts D and Da are grouped by topic in Section 2 of this document. Comments pertaining to proposed amendmen ts specific to subparts Db and Dc are included in

Section 3. Tables 1 and 2 match the commenter to the doc ket entry number cited in Sections 2 and 3 for specific legal or technical comments. Some of the comment sets were signed or subm itted on behalf of multiple

commenters.Introduction

vi Table 1. List of Commenters Cited in this Summary Document Submitting Comments to EPA Air and Radiation Docket Number EPA-HQ-OAR-2011- 0044 Regarding NSPS Rule Amendments Proposed May 3, 2011 (76 FR 24976)

EPA

‐ HQ

‐ OAR

‐ 2011

‐ 0044

Document No. Date Submitted Name and Affiliation

4634 August 4, 2011 James S. Pew Earthjustice

4635 August 4, 2011 Thomas C. Perry

National Mining Association

4656 August 4, 2011 William D. Bissett Kentucky Coal Association

4673 August 4, 2011 Reid T. Clemmer

PPL Services Corporation

4674 August 4, 2011 Martha E. Rudolph

State of Colorado

Colorado Department of Public Health and Environment

4686 August 4, 2011 John T. Heard

The Virginia Coal Association

4698 August 2, 2011 Ronald A. Amirikian

State of Delaware

Department of Natural Resources & Environmental Control

4712 August 4, 2011 John M. McManus

American Electric Power

4713 August 4, 2011 William O’Sullivan

State of New Jersey

Division of Environmental Protection

4714 August 4, 2011 Mark R. Vickery

State of Texas

Texas Commission on Environmental Quality

4715 August 4, 2011 Erika Padgett

Elizabeth Wheeler

Clean Wisconsin

Kim Wright

Midwest Environmental Advocates

Peter Bakken

Wisconsin Interfaith Power and Light
George Meyer

Wisconsin Wildlife Federation

4760 August 3, 2011 Jolene M. Thompson

American Municipal Power, Inc.

4765 August 4, 2011 Alex Hofmann

Theresa Pugh

American Public Power Association

4766 August 4, 2011 Chris M. Hobson

Southern Company

4768 August 3, 2011 James A. Landreth

SCE&G

4770 August 3, 2011 Desi M. Chari

The Dow Chemical Company

4830 August 4, 2011 Rae E. Cronmiller

National Rural Electric Cooperative Association

4832 August 4, 2011 Kathleen L. Barrón

Exelon CorporationIntroduction

vii EPA

‐ HQ

‐ OAR

‐ 2011

‐ 0044

Document No. Date Submitted Name and Affiliation

4833 August 4, 2011 JoAnne Rau

Randal Griffin

Dayton Power and Light Company

4834 August 4, 2011 Jay Hudson

Santee Cooper

4836 August 4, 2011 F. William Brownell
Craig S. Harrison

Lauren Freeman

Hunton & Williams LLP

Counsel to the Utility Air Regulatory Group (UARG)

4839 August 4, 2011 Verne Shortell

NRG Energy, Inc.

4841 August 4, 2011 Robert D. Bessette

Council of Industrial Boiler Owners

4893 August 4, 2011 Tom Thompson,

Eco Power Solutions (USA) Corp

4926 August 4, 2011 Lisa Jacobson

The Business Council for Sustainable Energy

4984 August 4, 2011 Brian H. Moeck

The Large Public Power Council

4985 August 4, 2011 Raymond L. Evans
FirstEnergy Corporation

4989 August 4, 2011 John M. McManus

American Electric Power

4997 August 4, 2011 Les Oakes Cynthia AM Stroman
King & Spalding LLP

Counsel to The IPP Coalition

5000 August 4, 2011 John L. Stowell

Duke Energy

5074 August 4, 2011 David Gardiner

Alliance for Industrial Efficiency

5075 August 4, 2011 Caroline Choi
Progress Energy

5077 August 4, 2011 John W. Myers

Tennessee Valley Authority

5087 August 4, 2011 Raymond L. Evans
FirstEnergy

5089 August 4, 2011 Thomas C. Perry

National Miming Association

5208 August 3, 2011 G. Vinson Hellwig

State of Michigan
Department of Environmental Quality

5195 August 4, 2011 Kerry Kelly

Waste Management

5210 August 4, 2011 Susanne Brooks

Elena Craft

Mark MacLeod Hilary Sinnamon Mandy Warner

Peter Zalzal

Environmental Defense FundIntroduction

viii EPA

‐ HQ

‐ OAR

‐ 2011

‐ 0044

Document No. Date Submitted Name and Affiliation

5240 August 4, 2011 Michael J. Nash

Gulf Coast Lignite Coalition

5279 August 3, 2011 Eric Redman

Summit Texas Clean Energy, LLC

5470 August 3, 2011 Mark J. Sadlacek

Los Angeles Department of Water and Power

5477 August 15, 2011 Williw R. Taylor

U.S. Department of the Interior

5715 August 4, 2011 Ann Brewster Weeks

Clean Air Task Force
Sanjay Narayan

Sierra Club

James S. Pew Earthjustice

John Walke

Natural Resources Defense Council

Janice E. Nolen

American Lung Association

John Suttles

Southern Environmental Law Center Joseph Mendelson III

National Wildlife Federation

Justin Bloom

Scott Edwards Waterkeeper Alliance

5749 July 20, 2011 Myra C. Reece

State of South Carolina

Bureau of Air Quality, South Carolina Department of Health

and Environmental Control

17620 in

Docket No. EPA–HQ–

OAR–2009–0234 August 4, 2011 S. William Becker

National Association of Clean Air Agencies

17622 in

Docket No. EPA–HQ–

OAR–2009–0234 August 4, 2011 David Foerter

Institute of Clean Air Companies

17711 in

Docket No. EPA–HQ–

OAR–2009–0234 August 4, 2011 Paul Noe and Robert Glowinski

American Forest & Paper Association (AF&PA) and

American Wood Council (AWC)

17755 in

Docket No. EPA–HQ–

OAR–2009–0234 August 3, 2011 Eddie Terrill

State of Oklahoma

Oklahoma Department of Environmental Quality

17852 in

Docket No. EPA–HQ–

OAR–2009–0234 August 4, 2011 Gregory C. Staple

American Clean Skies Foundation (ACSF)

17878 in

Docket No. EPA–HQ–

OAR–2009–0234 August 4, 2011 Ben Yamagata

Coal Utilization Research Council

17975 in

Docket No. EPA–HQ–

OAR–2009–0234 August 4, 2011 Environmental Integrity Project

Eric SchaefferResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

1 

## 2. Response to Comments on Pr oposed NSPS Amendments to Subparts D and Da

2.1 General NSPS Rule Development

2.1.1 Fuel and Technology Neutral Approach for Rule Development

Comment: One commenter (4698) stated support for EPA’s decision to adopt a fuel and technology neutral approach to developing the NSPS for new EGUs because it potentially facilitates the selection of a cleaner fuel as part of the overall integrated emissions compliance strate gy, and provides flexibility in the design, construction, and operation of the unit in a configuration optimized for a given EGU. One commenter (5210) stated that “fuel neutral” standards should be based on the cleanest burning fuels instead of EGUs that burn pulverized coal, which EPA has used as the basis for the proposed emissions limit s. According to the commenter, this approach violates the intent of Congress under Clean Air Act (CAA) secti on 111 that NSPS for new sources be forward looking and technology forcing. 

### Many commenters (4766, 4830, 4834, 4948, 5077, 17878 

### ) oppose using a fuel and technology neutral approach to developing NSPS for EGUs, and instead recommend developing standards based on technology that account for the type of fuel burned. One commenter (4766) stated that 

### EPA has no basis for developing “fuel neutral” standards in which all coal-, gas-, and oil-fired EGUs are subject to identical NSPS emissions limits. This approach unlawfull y fails to consider the differences among boilers using different fuel types. Congress gave EPA the aut hority to “distinguish among classes, types, and sizes” when establishing standards; EPA, therefore, has an obligation to explain how it is applying the CAA Section 111 criteria to each fuel type, and to explain the national policy implications of its choices. A third commenter (4830) stated that it is bad public policy fo r NSPS to effectively eliminate whole categories of generation types, pollution control devices, and fuels. Diversities in generation design are critical to optimizing a facility for its specific and intended use. For example, fluidized bed combustion (FBC) is an ideal technological choice for intermediate-sized generation, and can utilize a broad array of fuels, from biomass to coal of different ranks. On the other hand, pulverized coal (PC) units have generally less fuel flexibility but are better suited for larger generation uses and can be designed to have superior thermal efficiency. An NSPS that effectively precludes coal, a pa rticular coal rank, or combustion design is in effect tailoring the nation’s future options for electric ge neration. CAA Section 111’s statutory provisions are directed at disseminating the best system of emi ssion reduction (BSER) throughout an identified source category and not for the purposes of significantly narrowing the nation’s choices for types of steam electric generation and fuel to power it.

Response: The vast majority of subpart Da affected facilities burn coal as the primary fuel. It is within EPA’s authority under the CAA to establish fuel and technology neutral standards. (See, for example, Lignite Energy

Council v. EPA , 198 F.3d 930 (D.C. Cir. 1999)). It is also within EPA’s authority to subcategorize standards based on fuel and boiler type. Whichever approach EPA c hooses, it is appropriate for it to establish standards for EGUs that allow the use of inherently cleaner burning fuels to comply with th e standards. The amended NO X and PM standards for EGUs are largely fuel neutral, since the achievable emissions rate for the best system of emission reduction (BSER) is similar across boiler and fuel types. While the amended SO 2 standard does not establish separate standards based on coal rank, it does account for the impact of fuels with inherently high sulfur concentrations on the performance of the BSER technology by providing an alternate percent reduction standard.

EPA has concluded that the amended st andards allow affected EGUs the flex ibility to use the boiler design and fuel types that best meet the site-specific needs of the EGU owner and operator. All of the amended standards have been achieved by primary boiler types (pulverized coal and fluidized beds) and across all coal ranks. Under the adopted fuel neutral approach, ow ners/operators of affected EGUs ha ve the flexibility to build new units designed to use a cleaner burning fuel as an alternative to installing post-combustion emission control technology or to co-fire cleaner burning fuels with coal and install slightly less-efficient post combustion control technology.

Neither natural gas nor distillate oil is typically used in new baseload stea m generating units (e.g., boilers with steam turbines). Basing the standards on either of these fuel s would result in standards that are neither technicallyResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

2 or economically achievable for a coal-fired EGU. Basing th e amended standards on the use of natural gas would preclude the development of new coal-fired EGUs since th e standards would not be technically achievable, even with the application of IGCC technology. Natura l gas-fired EGUs have demonstrated annual NO X emission rates of less than 0.40 lb/MWh gross output without the use of post combustion controls. This level has not been demonstrated to be achievable for any coal-fired EGUs even when using the best controls. In addition, natural gas

and distillate oil have trace amounts of ash and sulfur and correspondingly low PM and SO 2 emission rates. Therefore, basing the NSPS on these PM and SO 2 emission rates would not be achievable for coal-fired EGUs with any technology EPA is aware of. If the NSPS were to essentially prohibit the construction of new coal-fired EGUs, the regulated community might stop developmen t of promising control technologies, including carbon capture and storage, which can be used on existing coal-fired EGUs in addition to new coal-fired EGUs.

EPA has concluded that it is appropria te to continue to allow the constr uction of properly controlled coal-fired baseload EGU since, such an approach to generating elect ricity may be the most appropriate approach, from both a technical and financial perspective, in specific circum stances. Basing the standards on what is achievable by BSER employed on a coal-fired unit accomplishes this. EPA has concluded that the use of natural gas and distillate oil will play a dominant role in the future ge neration of electricity. Rather than burning natural gas or distillate oil in a boiler based EGU, however, we believe that any new baseload electric generation based on the use of either of these fuels would use combined cycle combustion turbines. Combustion turbines burning natural gas and distillate oil generate power more efficiently and economically than a boiler burning natural gas or distillate oil. The efficiency and capital cost benefits of combined cycle facilities outweigh the fact that natural gas and distillate oil are significantly more e xpensive per unit heat input than coal.

Comment: Several commenters (4836, 4997) stated that IGCC te chnology is inherently different from other coalbased electric generation technologies and should be regul ated separately. The NSPS applicable to IGCC EGUs should address the unique characteristics of IGCC technology. Factors that should be examined to properly consider the design and operational characteristics of IG CC technology include: 1) operating scenarios in which the IGCC EGUs (combustion turbines and duct burner) are co mbusting different fuels or a combination of fuels, such as natural gas, coal or other carbonaceous compound (p etroleum coke, biomass, municipal solid waste, etc.), derived syngas, and/or syngas produced off-site; 2) the applicability of any work practice and fuel sampling provisions as they relate to the design and operation of IGCC EGUs; and 3) the use of heat input and generation output terminology specific to IGCC EGUs.

Response: EPA has concluded that the language is sufficiently clear that the output from an IGCC facility is the combination of the output from the combustion turbine, st eam turbine, and any useful thermal output. The heat input to an IGCC facility is the combined heat input to the combustion turbine engine and any fuel input to the duct burners in the heat recovery steam generator. Fo r an IGCC facility that does not coproduce hydrogen or carbon containing chemicals, this value should be close to the energy content of the raw coal input to the gasification system (greater than 95%).

The gasification/purification system should be designed to provide a uniform syngas regardless of the feedstock so it is unclear how the feedstock would impact emissions . The commenter did not provide data indicating that the use of natural gas during periods when the gasification system is not providing syngas would create compliance problems. On the contrary, combined cycle facilities would only need to maintain a NO X emissions rate of 25 ppm to comply with the amended NO X standard. This emissions rate is routinely achieved by both combustion turbines using dry low NO X combustion controls and natural gas-fire d diffusion flame combustion turbines using water or steam injection. The combustion of natural gas also results in minimal SO 2 and PM emissions. Post combustion controls would not be required to mainta in compliance with any of the emission standards.

Comment: One commenter (5210) stated that high thermal efficiency should be used to establish standards, instead of being considered a control technology. In EPA’ s current proposed amendments to the NSPS, there is no discussion of thermal efficiency or what efficiency rate was used by the Agency to determine the new standards. The commenter requests that EPA explain in the final ru le what thermal efficiency assumptions were used in determining the new NSPS, and whether they are differe nt from the assumptions used in the last amendments. The commenter also recommends that EPA use the greatest feasible thermal efficiency for EGUs as an input to

determine the NSPS.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

3 Response: The facilities used to establish the output-based sta ndards included some of the most thermal efficient facilities. Therefore, the emission standards account for bot h high thermal efficiency and the efficiency of the emissions control equipment. This is the preferred approach when sufficient data is available, and simultaneously accounts for both the thermal efficiency and control equipm ent efficiency under various operating conditions. We consequently concluded it is not necessary to measure em issions on a heat input basis and then use an assumed efficiency to convert to an output-based standard, but rather directly established output-based standards based on the performance of the best performing facilities.

Comment: One commenter (5240) stated that separate NSPS must be established for the subcategory of EGUs burning coal with a heat input of less than 8,300 Btu/ lb as was the case in EPA’s proposed NESHAP standards. According to the commenter, emissions of air pollutants, especially PM and SO 2, are significantly different when burning these types of coal and must be reflected in any applicable NSPS.

Response: The proposed NESHAP subcategory mentioned by the commenter was for Hg and not acid gases or total metals. The commenter provided neither emissions da ta indicating a subcategory for low Btu fuel such as lignite would be appropriate nor data indicating that SO 2 and PM controls do not work effectively with all types of coal. Fabrics filters, the selected BSER for control of PM emissions, are designed to control emissions to a specified outlet concentration and operate relatively in dependent of the PM concentration coming into the baghouse. The SO 2 standard has an alternate percent reduction re quirement that specifically accounts for the use of high sulfur fuels. In addition, various coal cleaning, upgrading, and drying technologies for low rank coals reduce the ash, sulfur, and moisture content of these coals r esulting in a fuel with characteristics similar to that of higher rank coals.

The following are several examples of existing EGUs which demonstrate that the amended SO 2 and PM standards

are achievable for low rank coals:

1. The Sandow 5B facility is a subcritical lignite-fire d fluidized bed EGU and is presently operating below the

amended SO 2 % reduction alternative. Furthermore, both Sa ndow 5A and 5B are operating below the amended

PM standard of 0.090 lb/MWh.

2. The Oak Grove 1 and 2 facilities are supercritical li gnite-fired pulverized coal EGUS. Both are presently operating below the amended numerical SO 2 standard, and the Oak Grove 2 fac ility is also operating below the

amended SO 2 % reduction requirement.

3. The Milton R. Young B1 and B2 facilities are subcr itical lignite-fired cyclone boiler EGUs. Both are operating

below the amended PM standard of 0.090 lb/MWh.


## 2.1.2 Selection of Best System of Emission Reduction (BSER)

2.1.2.1 Consideration of EGU Energy E fficiency in Selection of BSER

Comment: One commenter (4634) stated that EPA’s failure to set NSPS emissions limits for PM, SO 2 , and NO X reflecting the use of energy-efficient design is unlawful and arbitrary. New coal-fired EGUs can significantly reduce emissions of all pollution emitted by incorporati ng energy-efficient design (e.g., use of supercritical boilers), allowing them to produce more electricity from burning a given amount of coal. To satisfy the directives of CAA section 111, EPA must assume a higher efficiency in combination with emissions controls to impose more stringent emissions limits for PM, SO 2 and NO X

. The commenter questions EPA basing the proposed output-based emissions limits on gross electrical generati ng efficiency of 36 percent, which the commenter contends is not BSER as required by the CAA. The comme nter states that 25 percent of existing EGUs achieve this generating efficiency, or higher and new EGUs can achieve net efficiencies as high as 45 percent.

Response: Efficiency has already been accounted for b ecause the facilities used to establish the amended standards include some of the highest efficiency supe rcritical facilities and the output-based standards were directly established based on the performance of the b est performing facilities. The comment referring to an assumed efficiency of 36% is unclear and appears to refe r to the approach taken in previous amendments to subpart Da. The analysis in this rulemaking looked at act ual out-put based emissions data and, therefore, it was not necessary to assume a gross efficiency.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

4 

### 2.1.2.2 Consideration of IGCC Techno logy in Selection of BSER

Comment: One commenter (5715) stated that integrated gasification combined cycle (IGCC) technology is a demonstrated system of emissions control for EGUs and EPA should consider it in de termining BSER to control PM, SO 2 and NO X emissions from coal-fired EGUs. Another comment er (4997) stated that integrated gasification IGCC technology is a power generation technology and should not be identified as EGU emissions control.

Response: As stated in the proposal preamble, the benefits resulting from reduced emissions of criteria pollutants are not sufficient in all instances to ju stify the higher capital costs of today' s IGCC units. According to the costs and emissions data available from the DOE, the annual costs of a 500 MW IGCC would be $71 million more than a comparable supercritical PC EGU. Even though the IGCC facility would reduce SO 2 , NO X , and PM emissions by 1,156 tons, 264 tons, and 102 tons respectively, the incremental costs are not justified as a basis for national requirements.


## 2.1.3 Net Energy Output Based Em issions Standards Format

Comment: Comments were received in support of and in opposition to EPA’s proposal to require affected EGUs to meet the proposed NSPS for PM, SO 2 , and NO X using an emissions standards format that expresses limits as the allowable amount of pollutant emitted per net energy output by the affected E GU. Several commenters (5715, 5074, 5210) supporting the proposal stated that use of th is format will encourage improvements in overall EGU facility energy efficiency, which results in lower air pollutant emissions and 

### is an incentive to minimize parasitic energy demands from pollution control equipment (auxiliary energy demands is synonymous with parasitic energy demands). Many other commenters (4673, 4698, 4712, 4765, 4830, 4836, 4989, 4997, 5000, 5077, 5089, 5208, 17878) oppose the mandatory use of this format, stating that the NSPS should be based on limits on the allowable amount of air pollutant emitted per gross energy output by the affected EGU or on allowable amounts of air pollutants emitted per energy input to the affe cted EGU. Reasons cited by the commenters for their opposition to requiring mandatory compliance with net ener gy output based emissions standards include: 1) a significant amount of the parasitic power demands at coal-fi red power plants is needed to operate the air pollution control equipment required to comply with air emission s standards; 2) there are monitoring difficulties in measuring net output, especially at facilities operating mu ltiple EGUs; 3) parasitic loads vary on a individual EGU-by-EGU basis and, for a given EGU, on a duty cycle basis (e.g. as the load decr eases on a typical EGU, the percent of parasitic power increases: 4) EGUs are not as thermally efficient at lower loads and consequently the

amount of fuel that must be used increases on an electri cal output basis; 5) at facilities with affected EGUs and also at older, less efficient EGUs which supply power to various auxiliaries throughout the plant, requiring the proposed net output-based NSPS on the affected EGU could actually decrease overall plant efficiency; and 6) a net output approach will be problematic with emer ging technologies such as IGCC and certain greenhouse reduction technologies such as carbon capture and sequestration (CCS).

Response: One of the primary benefits of using net output-b ased standards is that it provides a more accurate measurement of the environmental impacts of speci fic EGUs. Net output-based standards recognize the

environmental benefit of the minimiza tion of auxiliary loads and operating the facility as efficiently as possible under all conditions. The comment about net output-based standards resulting in less efficient EGUs operating more than higher efficiency EGUs at locations with multiple facilities is unclear. The net output would be measured on an EGU-specific basis as the gross output fro m the EGU minus auxiliary lo ads specific to that EGU. If electric power from one EGU were being used to power the auxiliary equipment of a separate EGU then that power would have to be measured and properly accounted for. Due to the lack of net output-based emission rates for multiple types of EGUs with various control configur ations over a range of operating conditions, the final rule allows, but does not require, the use of a net-output based standard as an alternativ e to the gross-output based standard. While gross output-based emission standards are not as accurate a measure of environmental impact as net output-based emission standards, they are s uperior to input-based emission standards.

The use of a gross output-based standard as it is presently defined does not provide sufficient monitoring to allow an accurate comparison of the environmental impact between different EGUs and recognize efficiency improvements. An EGU with electrically driven boiler feed pumps would have higher gross output than a facility that uses steam driven boiler feed pumps (steam driven feed pumps extract energy from the boiler steam prior to the generator). Consequently, the present definition could po tentially drive the installation of electrically drivenResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

5 boiler feed pumps instead of steam driven boiler feed pumps . From an overall net efficiency basis, it is often more efficient to use steam driven boiler feed pumps. Electri cally driven boiler feed pumps could account for as much as 3% of the gross electric output of a coal-fired EGU, substantially increasing the parasitic power requirements. Therefore, we are amending the definition of gross out put for new facilities to be the gross output from the generator(s) minus any electric power requirements to dr ive the boiler feed pumps. Without this amendment, switching to a steam driven feed pump to improve net effi ciency could appear to decr ease gross efficiency. Since boiler feeds pumps are specific to individual boilers, the monitoring issues mentioned by the commenters are no longer applicable. In addition, the majority of larger E GUs use steam driven boiler feed pumps and would not be impacted by the amendment.

Furthermore, the primary parasitic power requirements for an IGCC facility that account for the primary differences between the net and gross efficiency with a PC boiler are the gas compressors (air separation unit main compressor, oxygen compressor, and nitrogen co mpressor). Correspondingly, the gross parasitic power requirements for an IGCC facility would also subtract out the electric power required to run these compressors. For facilities that coproduce chemicals, only a portion of the power would be subtracted from the gross output.

The use of net out-based standards is only an alterna tive. The comment about net output-based standards being problematic when use in conjunction with CCS is no longer relevant.

Comment: Several commenters (4698, 4766, 4768, 5000) disag ree with EPA’s proposal to calculate the net energy output for an EGU from the EGU’ s gross energy output, assuming a 5% parasitic electric load loss factor. Actual parasitic load can vary across EGUs depending on site-specific factors such as geographic location, EGU operating mode, and equipment selection. All of these fact ors affect a facility’s overall auxiliary power load and hence its net energy output. Therefore, a uniform 5% assumption is inappropriate. One commenter (4698) recommends that EPA solicit input from EGU architect a nd engineering companies to develop auxiliary load estimates for a range of EGU sizes and configurations. Another commenter (4768) states that a 10% parasitic electric load loss factor would be a more representativ e value. One commenter’s (5000) experience is that approximately 7 to 8% of a conventional coal fired station’s power is required to run auxiliary equipment. The commenter believes that this is a more representative va lue across the industry considering that units generally will be operating with SCR, FGD, and PM emissions contro ls, all of which require auxiliary power. Also, if a CCS is used in the future, the amount of auxiliary power will dramatically increase.

Response: According to the National Energy Technology Laboratory in the document “Cost and Performance Baseline for Fossil Energy Plants,” parasitic power requirements for pulverized coal-fired boilers using supercritical steam conditions varies from 5.2% for high rank coals to 5.9% for low rank coals. These estimates are based on detailed designs and are the best estimates av ailable to EPA. However, in recognition that parasitic power requirements can increase in terms of percentage of lo ad at lower loads the final rule uses a 7.5% parasitic load assumption.

Comment: One commenter (5210) states that output-based standards are only truly effective when determined by using output based data. The commenter requests that EPA not use input based data to set the NSPS standards and then simply convert those standards to output based numbers. Instead, the commenter recommends that EPA finalize output-based standards, based on output data, for a ll pollutants, regardless of whether compliance is based on performance tests or continuous emissions monitoring systems (CEMS).

Response: Output-based emissions data was used to establish the amended emissions standards.



## 2.1.4 Standards for Reconstructed and Modified EGUs

Comment : One commenter (5715) states that EPA’s proposal to allow modified and reconstructed EGUs to meet less stringent NSPS emission limits than those required fo r new EGUs is not authorized by the CAA, and is therefore unlawful. The proposed NSPS for reconstructe d and modified EGUs contradict Congressional intent that as existing sources are upgraded, they control their em issions to a rate reflecting best system of emission reduction for the industry. The commenter cites specific CAA sections and p ast court decisions to support this

comment.

Response: Standards under section 111 of the Clean Air Act must be achievable See, National Lime Association

v. EPA , 627 Fed. 2d 416 (D.C. Cir. 1980). With this in mind, we have concluded that section 111(b)(2)’sResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

6 authorization to distinguish among classes, types and sizes when establishing NSPS allows us to establish a subcategory for modified sources in appropr iate circumstances. See, Asarco v. EPA , 578 F.2d 319, 330 (D.C. Cir. 1978) (Leventhal, J. concurring) (explaining why the stat ute permits subcategorizing modified sources). Here, certain existing facility designs are not capable of oper ating combustion controls as effectively as newly designed facilities and, therefore, cannot achieve the same leve l of emissions reductions as newly designed facilities through the use of combustion controls. Further, even using the most efficient post combustion controls, these

facilities are not able to achieve the same NO X emissions rate as a newly designed facility. In determining what is achievable, EPA must consider costs and for modified facilities, the incremental cost effectiveness of adding a

second scrubber to reduce SO 2 emissions beyond what is achievable by cu rrently installed technology is not cost

effective. The new source PM standard is based on the u se of a fabric filter. Existing facilities potentially don’t have adequate space available to cost effectively retrofit an existing ESP with a fabric filter.



## 2.1.5 Standards for Combined Heat a nd Power (CHP) Units Subject to NSPS

Comment: One commenter (5074) states that the net output-based standards in the NSPS should be modified in

the final rule to account for both the thermal and elect ric generation from combined heat and power (CHP) and waste heat recovery systems subject to the NSPS. Absen t this, the net output-based standards fail to account for (and incentivize) the full efficiency ga ins associated with such systems.

Response: Based upon comparison of the criteria pollutant emissions that would result from generating the thermal and electric output in separate facilities, EPA in creased the thermal credit from 50% to 75% in 2006 (71 FR 9866). The definition is as follows:

Gross output means the gross useful work pe rformed by the steam generated and, for an IGCC electric utility steam generating unit, the work performed by the stat ionary combustion turbines. For a unit generating only electricity, the gross useful work perfo rmed is the gross electrical output from the unit's turbine/generator sets. For a cogeneration unit, the gross useful work perform ed is the gross electrical or mechanical output plus 75 percent of the useful thermal output measured relative to ISO conditions that is not used to generate additional electrical or mechanical output or to enhance the performance of the unit ( i.e. , steam delivered to an industrial process).

Comment: EPA requested comment on, “whether it is appropr iate to recognize the environmental benefit of electricity generated by CHP units by accounting for the benefit of on-site generati on, which avoids losses from the transmission and distribution of the electricity.” One commenter (5074) states that these avoided losses should be recognized because such savings are one of the key benefits of distributed generation. Several commenters (4926, 5074) state that that for CHP units subject to the NSPS, a 5% benefit for avoided transmission and

distribution losses is too low. EPA should 

### adopt a higher multiplier that fully credits the transmission and distribution savings of CHP and therefore incentivizes such investments.

Response: EPA acknowledges that overall transmission and li ne losses are closer to 10%. However, the CHP facilities typically covered by subpart Da are large fa cilities with relatively large amounts of the generated electricity being transmitted to other end users, and th e benefits are reduced. Therefore, the 5% credit is reasonable and adequately recognizes the environmental benefit of CHP compared to separate electric and thermal generation.


## 2.1.6 NSPS during Periods of EGU Startup, Shutdown, and Malfunction

Comment: Comments were received in support of and in opposition to EPA’ s proposal that NSPS emission limits apply at all times, including start up, shut dow n and malfunction (SSM). Commenters (4698, 5210) support the proposal for a number of reasons. The commenters st ate that startup and shutdown periods are normal phases of EGU operation and should not be held separate fro m other normal operating activities. Reasons stated by commenters (4832, 4834, 4839, 4841, 4984, 5077, 5470) opposing the proposal were varied. One commenter (4714) states that the DC Circuit Court decision regard ing emission limits during SSM periods (Sierra Club vs. EPA, DC Circuit Court, 2008) was specifically regard ing NESHAP rules and not NSPS rules. EPA has not provided any reasoned explanation or justification for wh y it is applying the same approach for new, modified, and reconstructed sources in the propo sed NSPS rule revisions. Furthermore, EPA has not appropriately evaluated applying the same emission limits for normal operations and for SSM periods. Another commenter (4836) statesResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

7 that coal-fired EGUs co-fire other fuels (typically natu ral gas or oil) during certain operating modes, such as startup, shutdown, and flame stabilization operations. The proposed NSPS do not address the potential emissions from these co-fired fuels, which will have different emi ssions profiles from the times the EGU burns coal only. One commenter (4834) states that instead of emission lim its, work practices should be proposed for the NSPS to control emissions during SSM periods. Another commenter (4839) states that provisions for SSM periods should follow precedent in the Industrial Bo iler MACT Rule. Many of the commenters opposing the proposal state that work practices should be used to control emissions fr om EGUs during startup and shutdown. For malfunctions, a source should have to address the malfunction as soon as safely practicable. One commenter (17975) states that since maintenance activities are generally carried out for EGU boilers after they have been turned off, the distinction between “maintenance” and “startup/shutdown” is meaningless.

Response: EPA has determined that under the circumstances of this rulemaking it is not appropriate to treat periods of startup and shutdown differently for purpose of complying with the NO X and SO 2 standards. The NO X and SO 2 CEMS data used to establish the standards include a ll periods of operation and thus demonstrate that the standards can be met during periods of startup and shutdown. As a result, it is not necessary to attempt to separate the data and establish separate numerical standards during norm al operation and periods of startup and shutdown.

However, for PM it is not practicable to measure emissi ons during periods of start up and shutdown and we do not have data upon which to base numerical emission limits dur ing periods of startup and shutdown. Therefore, EPA is finalizing work practice standards instead of numeric emission limits for PM during periods of startup and shutdown. These work practices take into account operati on of PM control devices. The NSPS requirements will be identical to the NESHAP requirements and are descri bed in Table 3 to Subpart UUUUU of Part 63. See the relevant startup/shutdown sections of the NESHAP por tion of the preamble for additional discussion. EPA is committing to reevaluating this approach during the 8-year review when sufficient PM CEMS data is expected to be available from the EGU population

For malfunctions, EPA is finalizing the proposed affirma tive defense language for exceedances of the numerical emission limits that are caused by malfunctions. As EPA explained in the preamble to the proposed rule, EPA recognizes that even equipment that is properly designed and maintained can fail and that such failure can cause

an exceedance of the relevant emission standard. EPA incl uded an affirmative defense in the final rule in an attempt to balance a tension, inherent in many types of air regulation, to ensure adequate compliance while simultaneously recognizing that despite the most dilig ent of efforts, emission limits may be exceeded under circumstances beyond the control of the source. The affi rmative defense simply provi des for a defense to civil penalties for excess emissions that are proven to be beyo nd the control of the source and appropriately balances competing concerns.


## 2.1.7 Facility-Wide Emissions Averaging

Comment: One commenter (4839) stated that facility-wi de emissions averaging should be allowed as a compliance alternative in certain circumstances. EPA should reconsider and supp ort including facility-wide averaging in emission limitations for existing sources subj ect to the NSPS as an additio nal compliance alternative. By including this type of flexibility mechanism, EPA will ensure that facilities will retain some degree of flexibility when complying with the ru le requirements. Similarly, varying operational modes or combination of systems (e.g., wet/dry scrubber, ESP or fabric filter) c ould be employed to provide the greatest potential for economically reducing emissions to meet compliance requirements. EPA’s averaging formula should be constructed so that the average emissions by a group of E GUs subject to the NSPS will be no more than what is permitted on an aggregated individual basis. From a practi cal standpoint, the ability to monitor units with shared stacks may present technical difficulties to the point where separate monitoring is simply not feasible.

Response: While the suggested approach could provide additi onal flexibility without an increase in emissions to the atmosphere, the present applicability of the NSPS is on a boiler by boiler basis and no change to that approach was proposed. As a result, facility-wide averaging woul d require a notice and comment rulemaking to at a minimum clearly identify the affected facility, how the averaging would be done, and how modifications and

reconstructions woul d be determined.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

8 

## 2.1.8 Interrelationship of NSPS with other EPA Rulemaking s Affecting EGUs

2.1.8.1 Source Category Impact Analysis

Comment : One commenter (4760) states that EPA needs to analyze the combined impacts of all regulatory proposals to the electric industry. Decisions by U.S. elect ric utilities to add needed electricity generating capacity are being impacted by the breadth and complexity of the numerous rules-- including the NSPS amendments that EPA is implementing to regulate EGU.

Response: The amendments to the NSPS would have a negligible incremental impact on the cost of new coalfired generation. Annual costs, compared to the exis ting NSPS requirements, will increase less than 0.3%. In addition, the various regulatory actions impacting air emissions from EGUs require similar controls such that the actual impacts of the NSPS amendments would be even less.

Comment : One commenter (4832) states that EPA proposing s ubstantive changes to 40 CFR 60 subpart Da is outside the scope of the proposed NESHAP rulemaking and the changes have not been properly analyzed or justified. Specifically, EPA is proposing to demonstrat e compliance with certain HAP emissions limits under the NESHAP by proxy methods that refer back to SO 2 or PM limits established in 40 CFR 60 subpart Da.

Response: While the proposed SO 2 and PM NSPS amendments are not expected to have any benefits or costs due

to the similar benefits and costs in the new source EGU NESHAP requirements, they would be cost effectively

achievable in the absence of the NESHAP. Docket entry EPA-HQ-OAR-2011-0044-0002 includes detailed incremental cost effectiveness calculations for each pollu tant and EPA has concluded the amended standards are justified in the absence of the NESHAP. If cost and benef its of the proposed amendments were included, it would double count the impacts of the rules.

The NESHAP allows, but does not require, the use of SO 2 and filterable PM as surrogates for acids gases and non mercury metals respectively. Owners/operators that el ect to demonstrate compliance with the NESHAP HAP requirements using these surrogates could also concurren tly demonstrate compliance with the NSPS standards for those pollutants.



### 2.1.8.2 Delay of NSPS Rulemaking until NE SHAP Affecting EGUs is Finalized

Comment : One commenter (4839) states that the substantial technical comments submitted for the EGU NESHAP warrants a delay of the proposed NSPS to allow EPA sufficient time to consider the more comprehensive affect these revised rules will have on the utility sector. In addition, there are some commonalities in the controls needed to comply w ith the requirements of the two rules. Syncing the two rules such that they apply to the same set of new sources will allow owners/ operators of those sources to better plan for compliance. Finally, since EPA is not under any judicial timelin e to promulgate the proposed NSPS, the commenter recommends a delay to account for the considerable tim e EPA will need to revise the EGU NESHAP and respond to any potential judicial challenges.

Response: While the EGU NSPS amendments and NESHAP were included in the same package and are related in terms of the types of required controls, they are independent rulemakings that both serve the purpose of reducing emissions of pollutants. EPA has sufficientl y replied to comments submitted on both proposals. The purpose of the comment referring to syncing the two rules in unclear. For the most part, the comment argues for delaying finalizing the NSPS. The comment referring to syncing the two, however, addresses the issue of which EGU will be subject to the final NSPS standards and the final NESHAP standards for new sources. The universe of EGU subject to both standards was identified on the date the proposed rule was published in the Federal Register. Consequently, new sources are the same for the NESHAP and NSPS and those sources will be subject

to both sets of standards. If the commenter’s intent is to address the relationship between compliance with the NSPS by reconstructed and modified sources and complia nce with the NESHAP by existing sources, compliance with the two sets of requirements cannot be synced.



### 2.1.8.3 Proposal of EGU NSPS Amen dments with EGU NESHAP

Comment : Several commenters (4839, 5087) state that the inclusion of a proposed NSPS rule within the extensive and comprehensive proposed EGU NESHAP is in appropriate and circumvents the appropriate commentResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

9 period that should be afforded each rule individually. The release of NSPS and EGU NESHAP in the same proposal notice with one 60-day comment period suggests th at EPA is rushing its regulatory agenda and shortcircuiting the regulatory process. Since EPA is not unde r a court ordered deadline to develop NSPS amendments, each of these rulemakings should have been propo sed separately with their own comment period.

Response: The proposed 60 day comment period was extended an additional 30 days to provide sufficient time for the public to review and comment on both proposals. 

## 2.2 Rule Applicability

2.2.1 Regulation of IGCC fac ilities under 40 CFR 60 subpart KKKK

Comment : EPA requested comment on whether or not an IGCC EGU that co-produces hydrocarbons or hydrogen should be subject to the combustion turb ine NSPS under 40 CFR 60 subpart KKKK instead of the EGU NSPS under 40 CFR 60 subpart Da. Several commenters (4836, 5715) state that an IGCC EGU that coproduces hydrocarbons or hydrogen should be subject to subpart Da. One commenter (4836) states that IGCC EGUs are designed and structured differently than natural gas-fi red combined cycle EGUs. For the sake of clarity and regulatory certainty, there should not be a mechanism that would require a particular EGU to switch back and forth between different NSPS standards, even if an IGCC is capable of using natural g as as a fuel. Such units that may co-produce hydrocarbons or hydrogen still convert coal or oil into electricity, and apportioning the parasitic load would be difficult. The commenter requests that EPA provide a heat input-based alternative based on the raw feed stock to the gasifier for these units instead of struggling to make them demonstrate compliance with an output-based standard. Another commenter (5715) states that not applying subpart Da to certain IGCC EGUs that co-produce hydrocarbons or hydrogen is not logical. A ll IGCC facilities that sell more than one third their potential electric output capacity and more than 25 megawatts of electricity (MWe) to the grid are and should be classified as an EGU subject to 40 CFR 60 subpart Da wh ether the EGU produces other useful byproducts or not, consistent with the applicability of EGUs to 40 CFR 60 s ubpart Da that are classified as combined heat and power

units.

Response: The IGCC facilities that meet the existing applicab ility criteria will continue to be regulated under subpart Da. EPA concluded that a gross output based sta ndard, using the revised definition of gross output, is appropriate and can be relatively easily measured for all affected facilities, including IGCC facilities. A heat input based standard would require an IGCC facility owner/operato r to measure the coal input to the gasification system and assume all of the energy is input to the stationary combustion turbine and heat recovery steam generator, and calculate a site specific f-factor and employ a stack flow meter and CO 2 CEMS or a fuel flow meter. EPA has concluded that the additional complexity associated with such an approach would not yield improved results compared to an output-based standard.


## 2.2.2 Exemption of EGUs Us ing “Innovative Technologies”

Comment : One commenter (5715) states that EPA is not au thorized under the CAA to allow the proposed exemption of certain EGUs using “i nnovative technologies” from complying with the NSPS emissions standards. The CAA only allows EPA to grant a compliance time ex tension for such affected EGUs on a case-by-case basis that meet certain conditions specified in the statute. Several commenters (4839, 4893, 4984) support the proposed exemption. One commenter (4839) requests that to avoi d precluding the development of new technologies, EPA should consider a broader applicability of the exempti on to include all DOE-funded commercial-scale technology demonstration projects.

Response : As explained in the proposal preamble, the comp liance time extensions under section 111(j) of the Act are not adequate for owners/operators of new EGUs that would be affected facilities subject to subpart Da to secure the funding necessary for construction. As such, the development of promis ing technologies that offer potential reductions in criteria, hazar dous, and GHG emissions could be restri cted. The permits will be granted on a case-by-case basis and depend on the anticipated emissions performance of the specific technology. Since nether multi-pollutant controls or pressurized fluidized bed boilers have demonstrated at the size necessary for applicability to subpart Da we cannot do a separate anal ysis to determine an a ppropriate emissions rate.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

10 To facilitate development of emerging technologies that offer potential for future emissions reductions, the commercial demonstration permit exemption will be mainta ined as proposed for pressurized fluidized beds and multi-pollutant control technologies. Neither of these tec hnologies is generally applicable to existing facilities, and overly stringent standards could impede their fu ture development and make financing projects cost prohibitive. The majority of existing facilities already have some form of emissions control technology. Installing a multi-pollutant control technology is not necessary and pr essurized fluidized beds are sufficiently different from traditional designs that retrofits are unlikely. However, advanced combustion controls are applicable to existing facilities and the exemption is not necessary to further the development of the technolog y. That exemption is not

included in the final amendments.

DOE-funded technology demonstration projects are typically installed at existing EGUs and would not trigger applicability of the NSPS requirements. Therefore, the exemption would not be applicable. If DOE were to request that EPA evaluate the appropriateness of an exemption for DOE-funded tec hnology demonstrations at some point in the future, such an exemption could be considered in a future rulemaking.


## 2.2.3 Applicability to Permitted EGUs for which Construction Has Not Commenced

Comment: One commenter (4830) states that EPA must appropriately accommodate permitted facilities for which construction will not have commenced prior to th e date of the NSPS regulation. Several electric utility entities have recently obtained air permits authorizing the construction of new units. Howe ver, they were not in a position to commence construction on these new units prior to the date that EPA intends to apply the proposed NSPS to facilities that have not commenced construction (M ay 4, 2011). As a result, these units will be regulated as new sources under this proposed rule. This situation creates significant inequities for the projects that are permitted but have not commenced cons truction prior to the proposed NSPS, and ultimately, this proposal may prevent the projects from being implemented, depending on the NSPS adopted in the final rule.

Response: Section 111(a) of the CAA defines a new sour ce as one for which construction or modification commences after the publication of proposed regulations appli cable to the source. In this case, the relevant date is May 4, 2011 and any source which comme nces construction or modification af ter that date is a new source for purposes of the final regulations. EPA has long defined “comme nced” in this context to mean “that an owner or operator has undertaken a continuous program of construc tion or modification or that an owner or operator has entered into a contractual obligation to undertake and co mplete, within a reasonable time, a continuous program of construction or modification.” (40 CFR 60.2). Merely obtaining an air permit authorizing construction does not meet this requirement. EPA disagrees that the NSPS am endments will prevent projects from going forward. While amended NSPS typically require th e installation of improved emissions control equipment, the impacts of complying with the amended standards would not ulti mately change the investment decisions of the owner/operator of an affected facility. On average, the st andards have minimal impact on the capital cost of a new EGU, cost less than $10/kW (less than a 1% increase). Furthermore, the fina l standards are achievable for a range of technologies and coal types and, therefore, would no t require significant redesign of already permitted facilities or impact the decision on the type of boiler used or fuel selection.


## 2.3 Particulate Matter (PM) Emissions Standards

2.3.1 Selection of BSER for PM Emissions

Comment: Several commenters (4765, 4836, 5089, 5715) state that the proposed NSPS for PM emissions does not reflect the application of the BSER. Commenters di ffer as to which PM emissions control technologies should be used as BSER for establishing the NSPS emission limits. One commenter states that EPA’s proposal to require new facilities to meet the same limits already achieve d by many existing sources is contrary to the clear requirements of the statute and Congressional purpose to require new sources to apply the best demonstrated systems of pollution control. Instead, EPA sets PM sta ndards that are “achievable” by all new sources (and even many existing sources) rather than standards that are “achie vable” through the application of the best adequately demonstrated system of emissions control, as the CAA requires. One commenter (4765) states that CAA §111(a)(1) does not allow EPA to base an NSPS on a BSER that is a combination of technologies and EPA has not attempted to do so in the past.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

11 Response: The amended PM standard is a filterable only standa rd. As a result, a fabric filter was identified as BSER. The BSER can take into account multiple factor s including, but not limited to, choice of generation technology, fuel selection, and multiple emission contro l technologies. Nothing in the CAA limits BSER to a single emissions control technology.


## 2.3.2 Regulation of Combined PM Emissions

Comment : Many comments were received in support of a nd in opposition to the proposal to establish a new

combined PM emissions limit for EGUs that is determin ed by adding the measured condensable PM plus the measured filterable PM. Commenters’ (4698, 4710, 5715, 5210) reasons for supporting the proposal include 1) some state permitting agencies already regulate condensable PM for steam ge nerating; and 2) methods now exist

to both measure and control condensable PM. One commenter (4714) notes that the State of Texas has regulated condensable PM through permitting for more than three decades.

Commenters (4712, 4766, 4836, 4989, 5 075, 5077, 5089, 5208) oppose the pr oposal for a number of reasons.

C 

### hanging the existing NSPS for PM from a filterable PM st andard to a combined PM standard by basing the proposed emissions limit on the performance of the top 20% best performing units is unlawful and arbitrary.

EPA cannot establish a combined PM emissions limit b ecause the Agency failed to follow the CAA statutory requirements for establishing a standard by not identifying the condensable PM component, how to control condensable PM, or what BSER is for reducing cond ensable PM emissions. Also, BSER for filterable and condensable PM components are separate. 

### There is no basis for establishing an emissions limit at the emission rate expected by the best performing 20% of the industry, when EPA has not provided any guidance on how the rest of the industry might seek to comply. Commenters also state that th e proposed compliance procedures

for the combined PM standard are unworkable because EPA Test Method 2 02 is inadequate to measure the condensable PM component.

Response: EPA Test Method 202 was promulgated in December 2010. The revised test method is as precise and accurate in measuring condensable PM as Method 5 or 17 are at measuring filterable PM. We have concluded it would be possible to establish and determine compliance with a combined PM standard (Method 5 plus Method 202), but based on comments received and on further consid eration since the proposal, we have concluded it is appropriate to amend only the filterable PM standard at this time. Post pr oposal, EPA has become aware of the complex interactions between control eq uipment configurations and the combin ed PM emissions rate that make it

difficult to set a nationwide standard for combined emi ssions at this time. In a future rulemaking, we will specifically request comment on the following factors necessary to establish a nationwide standard: i) the appropriate monitoring procedures, ii) whether separate st andards for condensable PM and filterable PM have any benefit over a combined PM standard, and; iii) the appropria te numerical standards in each case. To gather a basis for the rule, subpart Da is amended for new facilities to require Method 202 testing and reporting of those emissions each time a Method 5 or 17 performance test is performed. This approach minimizes the burden to the regulated community, while at the same time collecting su fficient data for evaluation of a nationwide standard. If appropriate, EPA will include condensable PM in the PM standard in a future rulemaking that accounts for annual variability. The incremental cost of Method 202 over Method 5 or 17 is less than $700 (10% of PM testing cost).

While EPA plans on evaluating separate filterable and condensable PM standards, we support the present approach that recent permits have taken in establishing a combined PM standard that includes both filterable and condensable PM. Controls required by an NSPS help in achieving and protecting the NAAQS. In the context of a PM standard, the relevant NAAQS is for PM 10 and PM 2.5 . For this source category, a combined PM measurement represents mostly PM 2.5 emissions since the filterable controls remove the larger sized PM. The primary

distinction between filterable and conden sable PM is based on temperature, not the form of the PM in the ambient air. The NSPS establishes standards that can be met throug h the use of the best controls for managing the ambient air pollutant. With regard to setting an NSPS for PM emissi ons, we chose to issue a filterable only standard, rather than a combined PM standard, in part because of the difficulties that may exist in quantifying particle size in a wet stack environment and recognition that many new EGU w ill employ wet scrubbers. Further, while the technology that best controls filterable PM may be different from that which best controls condensable PM, the available data

do not establish a distinct line that differentiates the filterable PM and condensable PM across a number of sources. This is demonstrated by the fact that the Part III EGU NESHAP ICR data, indicates that some units withResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

12 lower combined PM emissions had relatively low filterabl e PM emissions with somewhat higher condensable PM emissions, while other units had a more balanced control of filterable and condensable PM.

In the proposal, we identified dry sorbent injection (DSI) to neutralize SO 3 to sulfate prior to removal by a mist eliminator or particulate control and a wet ESP as cont rol technologies for condensable PM. However, there are

several additional measures that control condensable PM. These include, but are not limited to, (1) the selection of catalysts which minimize the formation of SO 3 from SO 2 , (2) minimizing the temperature at which the particulate matter control device operates, (3) minimizing the ammoni a slip when SCR or SNCR is used, and (4) a more efficient mist eliminator. In addition, the sulfuric aci d mist portion of condensable PM emissions is strongly dependent on the sulfur content of the incoming coal. All of these factors need to be taken into consideration in establishing a meaningful national standard. At this time we do not have sufficient knowledge to determine the combination of control technologies which will achieve the best level of control of both filterable PM and condensable PM across a number of sources and, thus, cannot establish a technical basis for an appropriate

national combined PM emissions standard. The additional c ondensable PM test data will allow us to evaluate the capabilities of a combination of techniques to reduce PM emissions. One potential outcome could be a national

PM standard that is based on the sulfur conten t of the coal, similar to the format for the SO 2 emissions standard. Since we did not propose that approach, we plan on doing a future notice/comment rule that specifically requests comment on the best approach for setting a national standa rd that achieves the best level of control of both filterable and condensable PM across many sources.

Even though we are not establishing a national PM sta ndard that includes condensable PM, emissions of condensable PM by facilities subject to the amended requi rements in subpart Da would not be uncontrolled. All new facilities in this source category would be subject to PSD and be required to account for condensable PM in performing the required analysis under that program. In addition, condensable PM em issions are generally lower for facilities with lower filterable PM emissions and high SO 2 control rates. Since the amended NSPS will require greater control of the emission of these pollutants, ther e should be some reduction in emissions of condensable

PM.


## 2.3.3 Regulation of PM 2.5 

## Emissions

Comment : One commenter (4841) states that a separate filterable PM 2.5 standard should not be established due to both measurement issues with respect to wet stacks and al so because control technologi es installed for combined PM, NO X , and HCl/SO 2 will result in reductions of both direct PM 2.5 and PM 2.5 precursors.

Response: Due to monitoring limitations and the commonality of controls for PM 10 and PM 2.5 , the amendments do not include a separate standard for PM 2.5

. 

## 2.3.4 Selection of PM Emissions Limit Value

Comment: Several commenters (4714, 4765, 4836, 5075) state that the proposed PM emissions limit is not achievable on a nationwide basis, and as a result the final ru le needs to be revised upwards to reflect the actual levels of performance achievable. Seve ral commenters (4673, 4836) state that the proposed PM emissions limit is so stringent that it would effectively preclude constr uction of new coal-fired EGUs. Several commenters (4712, 4989) state that the methodology EPA used to select the proposed PM emissions standard does not sufficiently address variability in EGU fuel use, equipment design, and operation. One commenter (4713) states that PM

emission limits for new source EGUs should be the same in the NSPS and NESHAP. One commenter (5210)

examined the emissions limits in 27 permits and permit applications for pr oposed coal-fired EGUs and concludes

that a combined PM standard of 0.030 lb/MMBtu best reflects BSER for new EGUs. Moreover, of the 27 permit and permit application limits reviewed, 14 listed both a filterable PM limit and a combined PM limit. The commenter also requests that EPA either adopt the most stringent feasible filterable PM standard for modified

EGUs or finalize a combined PM standard that reflects a BSER requiring additional c ontrols for condensable PM

for these units.

Response: For the reasons explained previously, EPA is issu ing a final standard for filterable PM only. The amended standard is appropriate for a national require ment as it represents BSER for both new and modified facilities and takes variability into acc ount. Data submitted as part of the EGU NESHAP ICR for pulverized coal EGUs burning bituminous and subbituminous coals and flui dized bed EGUs burning lignite, petroleum coke, andResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

13 bituminous coal with multiple performance tests show that the amended PM standa rd is demonstrated and

achievable. The data also show that an ESP can be used with coals with ash contents of up to 9 lb/MMBtu to achieve the standard. Data for EGUs that only reported a single performance test as part of the EGU NESHAP ICR, demonstrate that the amended standard is achievabl e by EGUs equipped with an ESP when using coals with ash contents of up to 14 lb/MMBtu. That data also dem onstrate that the amended standard is achievable by EGUs equipped with a fabric filter when using coals with ash contents of up to 68 lb/MMBtu. Further, the amended new source standard of 0.090 lb/MWh, wh ich is consistent with the EGU NESHAP standard, accommodates IGCC facilities in multiple operating modes. We are not changing the PM standard for modified facilities finalized in

2006 because modified facilities would have to increase th e size of any existing ESP or retrofit a fabric filer beyond what the present standard requires to meet the am ended new source standard and some existing facilities would be unable to do this because of space constraints.

Commenter 5210 misinterpreted the proposed combined PM standard of 0.055 lb/MWh as being 0.055 lb/MMBtu. The proposed standard is actually an order of magnitude more stringent than the comment suggests. In addition, if we were establishing a combined PM standard , which we are not, it does not appear that the suggested standard of 0.030 lb/MMBtu (~0.30 lb/MWh) combined PM would reflect BSER for combined PM. Since the amended filterable PM standard is 0.090 lb/MWh, the suggested standard would result in an approximate

allowable condensable PM emissions rate of 0.21 lb/M Wh (the resultant combined standard would be 0.30 lb/MWh). 206 of the 272 condensable PM data points in the EGU NESHAP ICR are below this value, indicating that a more stringent standard would be indicative of the BSER.

Comment : One commenter (5279) states that the proposed PM emissions limit should be revised to address the use of duct burners at IGCC facilities when fired using syngas and using natural gas. The commenter states that higher PM emission limits than the proposed limit are required when operating under either of these two

scenarios.

Response: The PM standard is based on the permit cond itions for an IGCC and accounts for both operating

conditions.


## 2.3.5 PM Control Cost Analysis

Comment : Many commenters (4635, 4656, 4765, 4766, 4686, 4830, 4836, 5075, 5089, 5240) state that EPA failed to independently calculate the control costs for im plementing the proposed PM emissions limit as required by the CAA § 111(a)(1). It specifies that EPA 

### “tak[e] into account the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirements...” when establishing NSPS.
Instead, EPA 

### has unlawfully relied on the PM emissions reductions that it anticipates to occur through implementation of the proposed NESHAP for EGUs. EPA 

### concludes that the proposed NSPS PM emissions

standard 

### will not result any costs or benefits attributable to implementing the NSPS.

Response: Docket item EPA-HQ-OAR-2011-0044-0002 includes an independent incremental cost analysis and a secondary environmental impacts analysis for the propo sed NSPS PM emissions standard. EPA concluded that these costs and benefits would support the am ended NSPS in the absence of the NESHAP.


## 2.3.6 PM Standards Exemptions

2.3.6.1 Opacity Standard Exemption for EGUs Using PM CEMS

Comment : Several commenters (4673, 4766, 4836) state that EPA should exempt EGUs subject to 40 CFR 60 subpart D and using PM CEMS from the opacity standard requirements. For affected EGUs that monitor PM emissions directly with a method EPA has determined as “su fficiently accurate,” the surrogate opacity standard is no longer necessary to assure compliance with the appli cable PM emissions limit. EPA should finalize the exemption proposed in 2008 for any EGU subject to 40 CFR 60 subpart D that demonstrates continuous compliance with the applicable PM emissions limit on a 24-hour (not 3-hour) average basis.

Response: We agree with the commenters that using PM CEMS provides not only a continuous check on the ability of the PM control device to minimize filterable PM emissions but also a direct, continuous measure of compliance with the filterable PM emissions standard. Ho wever, PM and opacity are separate standards. Should source owners/operators want a different averaging time under subpart D, they can petition the Administrator inResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

14 accordance with the requirements in 40 CFR 60.42(c). Fu rthermore, the EGU NESHAP includes an existing

source filterable PM standard of 0.030 lb/MMBtu as an a lternate to measuring total metals. Therefore, the vast majority of subpart D facilities will be installing controls that would allow them to control PM emissions to such an extent that the opacity standard would no longer be applicable.



### 2.3.6.2 Opacity Standard Exemption for EGUs Co mplying with a Combined PM Standard

Comment : One commenter (4836) supports EPA’s proposed op acity standard exemption for affected EGUs complying with a combined PM emissions limit.

Response: The final rule amendments do not include a combined PM emissions limit (see Section 2.3.3) and, therefore, the proposed exemption is no longer relevant.



### 2.3.6.3 PM and Opacity Standard Exemptions for Natural Gas Fired EGUs

Comment : Several commenters (4836, 4841, 17711, 17852) sup port EPA’s proposed opacity standard exemption for natural gas fired EGUs. However, one commenter (4836) does not understand why EPA proposes to limit the Subpart D exemption to those facilities subject to a fe derally enforceable permit limiting fuel use. No such condition is attached to the proposed Subpart Da exem ption. The commenter also does not understand why EPA has not proposed to exempt Subpart Da facilities that co mbust only natural gas from the filterable PM standards. Those facilities also will have negligible filterable emi ssions. As long as the facility is actually combusting only natural gas, it should be exempt from filterable PM a nd opacity standards regardless of a pre-existing permit

restriction.

Response: The “federally enforceable permit” requirement has been removed from subpart D so that the exemption applies to facilities that elect to switch to natu ral gas, but that maintain the ability to burn other fuels without a permit modification in the future. The opacity st andard would be effective immediately if the facility switches back to other fuels. The second part of the comment is unclear since the proposed language in paragraphs §60.42Da(a)(4), (e), and (g) exempt natural gas-fired EGUs from the PM standard.

Comment : One commenter (5749) states that EPA should clarify the circumstances under which 40 CFR 60 subpart Da may apply to gaseous fuel firing, where such gaseous fuel is not a fossil fuel (for example, where a non fossil gaseous fuel is combusted in combination and/or alternately with a fossil fuel). To the extent that Subpart Da would apply under any such circumstance, EPA should extend the Subpart Da exemption from PM and opacity limits for natural gas units to also apply to gaseous fuel fired units, such as those firing landfill gas. The commenter believes that landfill gas and other non foss il gaseous fuels have emission profiles similar to those of natural gas, and should be encouraged as viable alternatives to fossil fuels, including natural gas.

Response: A facility that only burns non foss il gaseous fuels would not be subject to subpart Da even if it met the applicability criteria of being capable of combusting more than 250 MMBtu/h of fossil fuel and supplying more than one-third of its potential electric output capacity and more than 25 MW net-electrical output to any utility power distribution system for sale. Owners/operators of units that are capable of combusting more than 250 MMBtu/h of fossil fuel that co-fire non fossil fuels would, however, be subject to subpa rt Da. We have concluded it is not appropriate to provide an outright exemption for all co-fired gaseous fuels since they can potentially contain contaminants that result in PM emissions and opacity . However, the amount of sulfur in a gaseous fuel is a general indication of the amount of impurities. Th erefore, gaseous and liquid fuels with potential SO 2 emissions

rates of less than 0.060 lb/MMBtu are included in the PM exemption, but not the opacity exemption. Other gaseous fuels do not necessarily burn as completely as natu ral gas. Subpart Da already includes reduced opacity monitoring for owners/operators burning gaseous fuels other than natural gas.



### 2.3.6.4 PM and Opacity Standards Exemption for Low-Sulfur Fuel Fired EGUs

Comment : One commenter (4836) supports EPA’s proposal to exempt EGUs that combust only gaseous or liquid fossil fuel with potential SO 2 emission rates of 0.060 lb/MMBtu or less from the otherwise applicable filterable PM standard, provided the EGU does not use post-combustion SO 2 or NO X controls. One commenter does not support this option for other forms of oil, especially fo r No. 4 oil and other grades. Another commenter (4698) opposes the exemption because opacity emissions from EGU firi ng such fuels is not generally due to fuel ash and impurities but rather is more a functi on of incomplete fuel combustion.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

15 Response: EPA agrees that opacity and filterable PM emissions from low sulfur oil-fired boilers are a result of incomplete combustion and do not result from fuel ash or impurities. However, EPA believes that 20% opacity would rarely occur at facilities burning these fuels. Theref ore, subparts D, Da, and Db are amended to include a provision providing state permitting authorities the flexibilit y to approve site-specific monitoring requirements for distillate oil containing less than 500 ppm sulfur, while still maintaining the opacity standard itself. This flexibility will be especially beneficial to owners/operato rs who only burn distillate oil as a backup fuel. The state would then have the flexibility to approve a site specifi c plan, or (?) require the use of the opacity monitoring procedure set forth in the rule, or the owne r/operator could monitor carbon monoxide emissions.


## 2.4 Sulfur Dioxide (SO 2 

## ) Emissions Standards

2.4.1 Selection of BSER for SO 2 

## Emissions

Comment : Many commenters (4712, 4715, 4765, 4836, 5715, 4989) state that EPA failed to state the BSER that the Agency selected as the b asis for establishing the proposed SO 2 emissions standards. One commenter (5715) states that the proposed SO 2 emissions rates are not the result of an analysis of the application or performance of

the BSER for SO 2 emissions – instead they are based on the SO 2 emissions rates that are already being achieved by existing EGUs. EPA’s BSER determination analysis was not based on the application of new and innovative multi-pollutant control options nor the application of sy stems of emissions reductions that allow control of greenhouse gas emissions (which EPA is regulating u nder a separate rulemaking) along with control of SO 2

. Response: The BSER for SO 2 is the same as in the 2006 final amendments, low sulfur coal and a spray dryer or high sulfur coal and a wet scrubber. In this remand, the achievable standards were reevaluated, but no new technology developments have taken place so the BSER technologies were not changed. The facilities used to

establish the numerical standard used low sulfur coal a nd a spray dryer, and the facilities used to establish the percent reduction requirement burned high sulfur coal and used a wet scrubber. EPA has concluded it is not appropriate to base the amended SO 2 standard on potential GHG requirements that have not been proposed.



## 2.4.2 Selection of SO 2 

## Emissions Limit Value

Comment : Many commenters (4715, 4765, 4768, 4836, 5715, 4989, 5075, 5077) state that the proposed NSPS

SO 2 emissions limit does not reflect the application of th e BSER, and that the methodology EPA used to select the proposed SO 2 emissions limit value does not sufficiently address va riability in EGU fuel use, equipment design, and operation. One commenter (4836) included an analysis of the data set used by the Agency in evaluating the achievability of the proposed SO 2 emissions limit using the BSER. Based on this analysis, the commenter states that an appropriate SO 2 emissions limit is 1.25 lb/MWh for new units with an optional reduction limit of 96%. In contrast, another commenter (4715) states that EPA did not set the NSPS SO 2 emissions limit based on the best demonstrated unit in its data set. According to the comment er, nearly all of EPA’s sample units (12 of 15 units) could meet the proposed NSPS of a 97% reduction in SO 2 , and a third of the units (5 of 15 units) could meet a 98% reduction. Furthermore, all of the units in the data set that tested in the 97% reduction range, excepting one, tested in the upper limits of the 97% range. This f act indicates that a 98% reduction limit is achievable. EPA should incentivize the most efficient use of control technologies to achieve the maximum amount of SO 2 reduction. The reduction limit for SO 2 should be set at 98% for this NSPS. One commenter (5210) examined emissions limits of six existing coal un its (at Intermountain Power, Colstrip , and Navajo) and the emissions limits in 29 permits and permit applications. Based on those data, the commenter recommends setting a SO 2 standard of

at least 0.7 lb/MWh to reflect BSER for all EGUs.

Response: Emissions data for both fluidized bed and pulverized coal EGUs demonstrate that a 97% reduction in potential SO 2 emissions is achievable. While short term data indicates that greater than 97% reduction may at times be achievable, that level of reduction has not been demonstrated to be achievable on a long term basis. Furthermore, even a 97% reduction in potential emissions has only been demonstrated to be achievable for coals

with nominal uncontrolled SO 2 emissions of greater than approximately 3.5 lb/MMBtu. Assuming a gross efficiency of 36%, this correlates to a numerical emis sions rate of 1.0 lb/MWh. Setting a numerical standard below 1.0 lb/MWh, which would be the result of requiri ng a emissions reduction of more than 75%, could limit the ability to use medium sulfur coals in new EGUs a nd drive the market toward subbituminous and low-sulfur

bituminous coals.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

16 While subbituminous coal and low-sulfur bituminous coal have inherently low sulfur content and thus low SO 2 emission rates, neither is a viable option for establishing a na tional standard as the use of these ranks of coal is not practicable for some facilities due to transportation constr aints, costs, and supply limitations. The transportation logistics and costs render the use of subbituminous coal by all new coal-fired generation unfeasible.

Subbituminous coal is mined in the western states and re quires long distance transportation, resulting in increased emissions from locomotives, increased energy consumption, and potential additional ra il line construction due to existing rail system limitations. The use of lower sulfur easter n bituminous coal is also problematic as it is in high

demand across the eastern United States and abroad. The increased demand does not just come from the electric generation sector, the coal is also in demand for use as a raw material in manufacturing. In addition, available veins of low-sulfur eastern bituminous coals are being e xhausted. In addition, addi ng a subbituminous-fired boiler at an existing site designed to burn bituminous coal woul d require significant design changes to the coal material handling equipment and other ex isting ancillary equipment.

Comment : One commenter (17622) states that Table 17- SO 2 Emissions Performance Data in the proposal notice (76 FR 25065) used by EPA to select the SO 2 performance level for EGUs lists th e best performing units in terms of percentage SO 2 control and the subsequent commentary incorrec tly indicates that with the exception of the HL Spurlock Units 3 and 4, all utilize wet limestone scrubbing technology. The three units at the Harrison Station utilize wet magnesium on demand lime scrubbing technology, not wet limestone technology.

Response: The Harrison technology description has been corrected.



## 2.3.3 SO 2 

## Control Cost Analysis

Comment : Many commenters (4635, 4656, 4765, 4766, 4686, 4830, 4836, 4989, 5075, 5240) state that EPA failed to independently calculate the cont rol costs for implementing the proposed SO 2 emissions limit as required by CAA §111(a)(1). It specifies that EPA, 

### “tak[e] into account the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirements...” when establishing NSPS.
Instead, EPA 

### has unlawfully relied on the SO 2 

### emissions reductions that the Agency anticipates from implementation of the proposed NESHAP for EGUs. EPA 

### concludes that the proposed NSPS SO 2 emissions

limit 

### will not result any costs or benefits attributable to implementing the NSPS.

Response: In proposal docket item EPA-HQ-OAR-2011-0044-0002 an incremental cost analysis and a secondary environmental impacts analysis include c ontrol costs for implementing the proposed SO 2 emissions limit. On the basis of that information, EPA concludes the SO 2 limits are achievable and cost effective independent of the

NESHAP.



## 2.4.4 Coal Refuse-Fired EGU Exemption from SO 2 

## Standards

Comment : One commenter (5715) states that EPA’s proposal to exempt EGUs burning more than 75% coalrefuse on an annual basis from the proposed NSPS for SO 2 emissions and instead allow such units to meet the existing NSPS for SO 2 emissions is unlawful. The commenter stat es that in proposing to establish such an exemption, EPA failed to distinguish these EGUs as a s ubcategory warranting separate emissions standards in accordance with the proper statutory requirements as provi ded by 42 U.S.C. §7411(b )(2) (“the Administrator may distinguish among classes, types and sizes within categor ies of new sources for the purpose of [setting NSPS]. One commenter (5210) states that new coal refuse-fired EGUs can meet the same standard as other EGUs. The commenter recommends that EPA adopt a SO 2 standard of 0.07 lb/MWh output for units burning 75% or more

coal refuse.

Response: Coal refuse-fired EGU is a subcategory for the purposes of the SO 2 standard under the existing NSPS. We neither proposed to eliminate the subcategory, no r in any other way reopened the issue of whether the subcategory is appropriate.

Coal refuse-fired EGU is not a subcategory for other po llutants. The Northeastern 31 EGU is the best performing

coal-refuse-fired EGU in terms of NO X . The facility has demonstrated a NO X emissions rate of 0.85 lb/MWh and we are therefore amending the standard accordingly. Furt hermore, the previous 8 PM performance tests at the Northampton NGC01 coal refuse-fired EGU have been under the amended PM standard of 0.090 lb/MWh.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

17 

## 2.5 Nitrogen Oxides (NO X 

## ) Emissions Standards

2.5.1 Selection of BSER for NO X 

## Emissions

Comment : One commenter (5715) states that the proposed NSPS to control NO X emissions (a combined

NO X /CO standards and an alternative NO X standard) does not reflect the application of BSER. EPA’s selection of selective catalytic reduction (SCR) and selective noncatal ytic reduction (SNCR) with advanced combustion controls does not represent BSER for control of NO X emissions. Furthermore, EPA failed to state the BSER that the Agency selected for controlling CO emissions. The commenter states that EPA’s BSER analysis did not

evaluate the NO X and CO emissions reductions achievable by all available NO X and multipollutant control technologies.

Response: The available data does not demonstrate that SCR can be applied to fluidized bed boilers in all circumstances. As a result, EPA believes that SNCR in combination with good combustion controls achieve the

lowest NO X emissions rate, and are, therefore, considered BSER for such boilers. While it may be possible to apply regenerative SCR to fluidized bed boilers, it is a relatively new technology and emissions rates are not yet available. For pulverized coal boilers, BSER was determin ed to be the use of advanced combustion controls and SCR. The only currently viable CO controls on EGUs ar e combustion controls as thermal oxidation and catalytic

reduction have not been demonstrated on EGUs.



## 2.5.2 Combined NO X 

## + CO Emissions Limit

Comment: Many commenters (4673, 4712, 4836, 4989) object to establishing a mandatory NO X + CO NSPS

emissions limit for EGUs at this time because of limited CO emissions data and the inadequate methodology used to determine the emissions limit. An analyses prepared by one commenter concludes that such a standard is unachievable for many EGUs much of the time. Howeve r, several of these commenters (4673, 4836, 4839, 5470)

also state that a combined NO X and CO emissions limit could provide an advantage in terms of compliance flexibility. These commenters do not object to establishing an NO X + CO emission limit that EGU owners/operators could chose to comp ly with as an alternative to a NO X emissions limit. Other commenters (4715, 5715) support EPA establishing a mandatory NO X + CO NSPS emissions limit for EGUs. However, one commenter states that EPA failed to explain why the Agency believes that a NO X + CO emissions limit of 1.2 lb/MWh for new sources reflects application of the BSER, when it is at a significantly higher emissions rate than

its NO X -only emissions limit proposed alternative. The comme nter concludes that the NSPS emissions limit for

NO X + CO should be lowered to reflect BSER, or at the very least, EPA must select a standard at the low end of the proposed range. Another commenter (17620) states th at setting a sufficiently stringent CO standard that avoids poor combustion would be a better op tion than adopting a combined limit for NO X + CO. Allowing inappropriately high CO levels by establishing a comb ined standard will simply permit sources to use less effective SCR controls and emit higher levels of organic HAPs than would lim its that are based on the level of

NO X reduction and CO levels achievable by high efficiency SCRs controls.

Response: While EPA believes that the limited data availabl e supports the achievability of a combined NOx/CO standard in at least some circumstance, it does not sup port the imposition of such a standard across the board. As a result, the combined NO X /CO standard will be provided as an alternative to the amended NO X standard. The alternative standard will be 1.1 lb/MWh, as that is the lo west standard that has been demonstrated as achievable for both pulverized coal and fluidized bed technologies. This combined standard is much more stringent than recent separate NO X and CO limits in BACT permits. The majority of BACT-based CO standards are 0.10 lb/MMBtu or greater. This translates to an approximat e CO emissions rate of 1.0 lb/MWh. With corresponding

BACT-based NO X standards of 0.70 lb/MWh, this corresponds to an equivalent combined standard of 1.7

lb/MWh. The combined standards for coal refuse-fired and modified EGUs were determined by adding a CO factor, 0.4 lb/MWh, to the NO X standard. This is the best CO emissions rate that has been demonstrated for both fluidized bed and pulverized coal boilers.

Comment : One commenter (5210) states that EPA must set the most protective NO X standard. While supporting EPA’s suggested benefits of a combined NO X + CO standard, the commenter states concern over if and how the Agency weighed the different health and environmental impacts of NO X and CO in determining the proposed combined standard. It appears the Agency weighed them equally, which the commenter believes is notResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

18 appropriate, given the greater health and environmental impacts of NO X and its contribution to ozone. While the commenter does not want CO emissions to significantly increase as a result of NO X controls, the commenter is

concerned that the flexibilities of a combined NO X + CO standard will provide for an ultimately more lenient NO X standard, resulting in fewer reductions. Therefore, the co mmenter recommends that EPA at the least set the most stringent standard feasible for NO X , in order to protect public health and the environment from the harmful impacts of ozone, PM, and other NO X related emissions. Another commenter (5208) states that a combined NO X + CO standard potentially would allow higher NO X emissions that would not protect the more stringent nitrogen dioxide (NO 2 ) National Ambient Air Quality Standard (NAAQS).

Response: The combined standard is based on the best perfo rming facilities. New facilities would, at a minimum, have to reduce emissions to below the existing subpart Da NO

x standard established in 2006 to comply with the standard. Therefore, it is a tightening and not a relaxa tion of the existing requirements and would not result in

increased NO X emissions.

Other federal and state permitting programs are design ed to take into account the specific health and environmental issues. In regions where reductions in NO X emissions would result in more significant health and environmental benefits the permit coul d require the maximum reductions in NO X . However, as described in the preamble this could lead to significant increases in CO em issions such that the combined standard would not be

achievable.



## 2.5.3 NO X 

## Emissions Limit

Comment : Several commenters (4712, 4765, 4768, 4836, 5075) state that the proposed NO X emissions limit is not achievable on a nationwide basis, and the final rule shoul d, therefore, be revised upwards to reflect the actual levels of performance achievable. In addition, a separate NO X emissions limit should be set for modified EGUs subject to the NSPS. Several commenters (4712, 4768) state that the methodology EPA used to select the proposed NO X emissions limit value does not sufficiently address variability in EGU fuel use, equipment design, and operation. One commenter (4768) includes their analys is of the data on which EPA based its determination that the proposed NO X emissions limit is achievable using BSER. Based on this analysis, the commenter asserts that an appropriate NO X emissions limit is 0.83 lb/MWh for new units and 1.1 lb/MWh for modified or

reconstructed units. The commenter states that the NO X emissions standard for modified units should be based on the performance of cell burners, wet-bottom boilers, and cyclone fired EGUs. The commenter further notes that recent consent decrees for SCR-equi pped cyclone boile rs require NO X emissions between 0.100 to 0.120

lb/MMBtu.

Response: The available data demonstrates that the proposed standard of 0.70 lb/MWh is achievable by both new and retrofit pulverized coal and fluidized bed boilers burning various coal types. This is true for modified units as well as new and reconstructed units; however, in recogniti on of the difficulties of retrofitting certain modified facilities with advanced combustion controls, the final NO X standard for modified facilities is 1.1 lb/MWh. Since the CEMS data used in establishing the standards in cluded long term data, vari ous operating conditions and variability are inherently accounted for. I The comment a bout cell burners and wet-bottom boilers is unclear. The Cardinal 1, 2, and 3, Muskingum River 5, and Belews Creek 1 EGUs are cell burners retrofit with SCR and have

demonstrated emission rates below 0.70 lb/MWh. In add ition, the Dallman 4 EGU is a wet-bottom boiler with SCR operating below 0.70 lb/MWh. Cyclone boilers are th e only EGU design that has not been demonstrated to be able to achieve the proposed standard. Subbituminous cyclone-fired EGUs (Coffeen, Baldwin, and Allen S. King) have demonstrated NO X emission rates of less than 0.95 lb/MWh are achievable. However, no bituminous or lignite-fired cyclone EGUs have achieved comparable emission rates. The best performing bituminous and lignite-fired cyclone EGUs without SCR are the Merri mack and Leland Olds facilities. These EGUs have demonstrated that cyclone EGUs can maintain NO X emission rates to less than 4.0 lb/MWh. The addition of 75% efficient SCR (or a multi-pollutant control technology) to these facilities would reduce NO X emissions to less than

1.1 lb/MWh.

The differences in the calculated 30-day emission rates betw een the commenter and the EPA is attributed to the procedure used to calculate the 30-day averages. The EPA 30-day averages are calculated using the procedures described in the proposal (sum of emissions of the appli cable pollutant divided by the sum of the gross output), while the commenter used the average of the hourly em ission rates for the 30-day period. As stated in theResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

19 proposal, the EPA procedure results in lower numerical em ission rates because hours with high emission rates but low heat inputs (typical of startup, shutdown, and low load operation) are not weighted as heavily.

Comment : One commenter (5077) states that emissions during st artup and shutdown periods have a particularly large impact on NO X emissions, even after taking into account the compensating effect of a 30

‐ day rolling average. Hence, these periods need to be excluded in the evaluation of co mpliance with the standard. Further, EPA should set a higher NO X NSPS standard for modified units, since ol der modified units typically have higher

heat rates than new units.

Response: The CEMS data used to establish the standards includes emissions during startup and shutdown, so there is no reason to separately evaluate those periods. The standard accounts for emissions typically being higher during periods of startup and shutdown and at the same time is sufficiently stringent to require owners/operators to minimize emissions during all periods of operation to comply with the 30-day standard. The final standard for modified units (1.1 lb/MWh) is based on CEMS data from facilities using subcritical steam conditions and accounts for the higher heat rates of older facilities.

Comment : One commenter (4830) states that the proposed NO X NSPS of 0.70 lb/MWh appears to eliminate the further use of lignite coal for new EGUs. Section 11 1(a) requires EPA to explain the economic and energy impacts when establishing NSPS. Lignite coal is an abundant resource in the upper mid-west and Gulf Coast areas and elimination of it as an energy source would ha ve significant regional economic impacts. EPA has the discretionary authority to subcategorize EGUs such that lignite-fired EGUs could have different NO X standards based on BSER for lignite. Thus, EPA should subcategorize the lignite NO X NSPS for new units. In addition, EPA has not demonstrated that non-lignite-fired units can meet the preferred 0.70 lb/MWh considering the inclusion of startup and shutdown periods into the compliance period. Accordingly, the alternative standard of 0.80 lb/MWh is more representative of what can be realis tically achieved for non-lignite units, and no level lower

than that should be considered for the NO X NSPS for new units.

Response: While the lignite-fired Oak Grove pulverized coal facilities use supercritical steam conditions (3,535 psi and 1,010 o F), increasing the steam temperature and pressure to those used at the Weston 4 facility (3,775 psi and 1,085 o F) would reduce fuel use and emission rates by approximately 2.5%. The figure below shows the impact of various steam conditions on the relative heat rate of an EGU. In addition, upgrading the heating value of the lignite from 6,800 Btu/lb to 10,000 Btu/lb would improve the efficiency of the EGU by almost 4%. Designing either of these things into a new lignite-fired EGU us ing the same control configur ation as Oak Grove 1 would theoretically reduce the NO X emissions rate to less than the 0.70 lb/MWh amended NO X standard. The permit for Oak Grove requires an NO X emissions rate of 0.080 lb/MMBtu. Using the same control configuration, a gross efficiency of 39% would be required to comply with the amended NO X emissions rate. This level of efficiency has been widely demonstrated for supercritical boilers burning subbituminous coals. A facility burning upgraded lignite would be expected to similar efficiencies as a subbitumous-fired EGU.

The Sandow 5B facility is a subcritical (2,420 psi and 1,005 o F) lignite-fired fluidized bed EGU and is presently operating below the combined NO X /CO standard. Furthermore, increasing the steam temperature and pressure to those used at the Weston 4 facility would reduce fuel u se and emission rates by approximately 5%. In addition, upgrading the heating value of the lignite from 6,300 Btu/lb to 10,000 Btu/lb would improve the efficiency of the EGU by almost 5%. Implementing both of these for a newl y designed EGU using the same control configuration as Sandow 5B would theoretically reduce the NO X emissions rate to below the 0.70 lb/MWh amended NO X standard. Fluidized bed boilers are not limited in application since they are available in various sizes, the largest individual unit is 460 MW, and are able to utilize supercritical steam conditions.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

20 As described elsewhere in the res ponse to comments, the 0.70 lb NO X /MWh is achievable for all of the primary coal (and petroleum coke)-fired EGUs. 

## 2.6 Compliance Requirements

2.6.1 Opacity Monitoring

Comment : Many commenters (4712, 4836, 4989) support EPA’s proposal to allow affected EGUs using a PM continuous monitoring system (CEMS), a fabric filter ba g leak detection system (BLDS), or an electrostatic precipitator (ESP) predictive model to be exempted from the existing requirement to install a continuous opacity monitoring system (COMS).

Response: The final rule amendments include a provision a llowing affected EGUs using a PM CEMS, a fabric filter BLDS, or an electrostatic precipitator (ESP) pred ictive model to be exempted from installing a COMS.

Comment: Several commenters (4673, 4836) support EPA’s proposal to reduce the frequency of visible emissions testing for affected EGUs that are subject to an opacity standard, but are not required to use a COMS.

The commenters further note that when EGUs are subject to state air permit requirements to conduct Method 9 visible opacity tests, visible emissions testing requi rements under the NSPS are redundant and may conflict with the state requirements. The commenter recommends that EPA add a provision in the rule explicitly allowing permitting authorities the discretion to waive any NSPS visi ble emissions testing as long as the state testing is at least as frequent.

Response: All the boiler rules have been amended to allo w the permitting authority the discretion to establish site-specific monitoring plans for owners/operators of f acilities burning fuels that typically result in low opacity. The frequency of Method 9 performance testing for owners /operators of facilities with some visible emissions, but with all 6-minute readings of less than 5%, has b een reduced from every 6 months to every 12 months. The frequency of opacity monitoring for ow ners/operators of facilities with hi gher opacity is unchanged. The additional testing frequency for facilities with opacities of 5% and higher is necessary to adequately assure compliance with the opacity standard.


## 2.6.2 PM Continuous Emission Monitoring

Comment: Several commenters (4989, 5077) oppose removal of the option to use Method 19 of Appendix A

when the PM CEMS minimum data availability conditions are not met. One commenter (5077) states that removal of the option to use Method 19 of Appendix A elim inates a credible option to provide data when monitor availability falls below a required threshold. Without the Method 19 option, a source that does not meet the dataResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

21 availability requirements would have to obtain data usi ng “other monitoring systems.” EPA provides no reason in the proposed rule for removing the Method 19 option.

Response: The redline included the intended edits and the ame ndatory language was in error. The option to use

Method 19 has not been removed in the final rule.

Comment: Several commenters (4989, 5077) stated concerns about the ability of PM CEMS to meet the proposed 90% availability requirement on a 30-day rolli ng average basis because of the limited number of installations of PM CEMS on EGUs. One commenter ( 5077) requests that EPA consider using a 75% data availability requirement when validating a require d reporting duration (i.e., 30 day rolling average).

Response: We find the commenter's concern about a limited num ber of PM CEMS installations on utility units to be misplaced, as over 100 EGUs have installed and are opera ting PM CEMS. As we are unaware of situations that have caused or may cause data availab ility from these units with PM CEMS to be below ninety percent, we find

that that level is achievable in the field and that there is no need to lower it.

Comment: One commenter (4989) states that for the PM CEMS missing data procedures EPA is proposing to replace references to “valid” data with the phrase “non-out-o f-control” data. Neither of these terms are defined in Subpart Da.

Response: The part 63 definition for “out-of-control” has been added to subpart Da. This amendment improves consistency for reporting and reduces bu rden to the regulated community.


## 2.6.3 Electronic Reporting of Performance Test Data

Comment: Several commenters (4712, 4836, 4989, 5077) opposes EPA’s proposal specifying mandatory electronic reporting of PM CEMS performance data and Relative Accuracy Test Audit (RATA) data to EPA’s Central Reporting Data Exchange (CDX) using the Electr onic Reporting tool (ERT). The commenters state that this proposed requirement is unlawfu l, unsupported, and incomp rehensible for the following reasons: 1) EPA has not articulated the purpose of the submission and reconcile d that with existing reporting requirements, 2) EPA has not used appropriate terms to identify the data required to be submitted, 3) EPA has not submitted an Information Collection Request (ICR) and obtained Office of Mana gement and Budget(OMB) approval as required by the Paperwork Reduction Act (PRA) for the data to be reported, and (4) EPA has not provided a reporting format compliant with EPA's Cross-Media Electronic Reporting Regulation (CROMERR) requirements.

Response: EPA strongly disagrees with the statement that th e submittal of performance data using the ERT is unlawful, unsupported, and incomprehensible. Section 114 of the Clean Air Act specifically allows EPA to require the submittal of emissions (and ot her environmental data) to develop regu lations. In fact, in support of this rulemaking, there was an information collection request (ICR) that affected many facilities. If EPA had had these performance data prior to the rulemaki ng, then an extensive ICR would not have been needed. We believe that requiring that such data be routinely submitted using the ERT will eliminate, or at least reduce, the need for such an extensive ICR in conjunction with future rulemaking. In answer to item 1 above, the purpose of requiring the submission of the results of performance tests is to support the development of regulations. In addition, performance test data will be used to improve emissions factors, develop control strategies, determine rule effectiveness, and support other air pollution control activities. Assuming the commenters meant performance test reports, rather than performance data, EPA disagrees with the statement that the requirements to submit performance test reports to EPA using the ERT are unsuppor ted. EPA has already required the use of the ERT for several information collection requests and has promulgated several other rules that require its use. Further, EPA as a whole has been working toward electronic submittal of environmental data and information for some time; see, for example, the Risk Management Plan informat ion required in 40 CFR part 68 and the Toxics Release Inventory requirements in the Emergency Planning and Community Right-to-Know Act of 1986. Electronic reporting allows for easier submission and storage of da ta and will provide stakeholders easier access to the information, thereby facilitating easier review of that information. If the commenters meant the submittal of the PM CEMS data, EPA also disagrees with the commenters on that point. EPA has concluded that the data are important in determining whether a facility is being properly operated. The data are also important for determining compliance with this regulation. Thus, EPA is establishing a system to more readily facilitate the collection and analysis of the data.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

22 EPA is not sure what the commenters intend in stating th at the requirements are incomprehensible. The electronic reporting requirement is clear on its face and, for the r easons stated above, electronic reporting of data is a very good solution, both for EPA and for industry, for the collection and review of air quality data. If the incomprehensible comment pertains to the ERT, our r esponse is that the ERT has been used by many source testing companies and is steadily improving. EPA has work ed very closely with the source samplers and industry to identify and correct problems encountered with its u se. In response to item 2, EPA is not sure what the commenters are asking. EPA developed the ERT using/in collaboration with former s ource testing personnel and in conjunction with source testing companies. The model for the ERT was and is the performance test requirements in the parts 60 and 61 general provisions. Th e input of source testing companies was integral to the development of this tool and we are continuing to work closely with source samplers. Thus, common source testing terms are used in the ERT and most of the users of this tool have had little tr ouble in understanding what is required. The response to item 3 is that EPA will be ac counting for ERT use in the ICR for the final regulation. EPA has concluded that requiring the use of this tool will not significantly increase any costs in the reporting of performance test data and will probably eventually result in a reduction in costs. Many source testing companies and most major facilities already use their own systems to gather performance test data electronically. EPA believes that the ERT works well and is ready for general use. EPA also disagrees with the statement in item 4. EPA is working closely with the Office of Environmen tal Information to establish the procedures necessary to ensure that ERT submittals through EPA’s Central Data Exchange are compliant with the Cross-Media Electronic Reporting Regulation. EPA w ill have this process completed prior to the time when the ERT submittals are required.

Comment: One commenter (4674), a state air regulatory agency, in tends to continue to request affected owner or operators to submit hard copies of stack test reports to th e State, in addition to EPA’s collection of stack testing data via the Electronic Reporting Tool (ERT), and ther efore supports EPA’s preservation of related requirements

in 40 CFR 60.8 and 60.11. The commenter believes that th e stack test data reported must be considered along with additional, specific information for each source’s operations. This evaluation cannot be easily conducted with the limited data reported in the ERT. The State believ es that the stack test data submitted in the ERT, taken at face value, may be misleading unless the context in which the testing was completed is understood. Until the number and degree of source configura tion and operation variables can be ad equately accounted for and reported in one reporting tool, allowing the associated test data to be wholly considered, the State relies heavily upon the submission of written stack test reports. Thus, the co mmenter supports EPA’s preservation of the submittal of written performance testing reports to state agencies, and re quests that EPA consider a way for states to report to EPA via the ERT that the test is not approvable or was not representative.

Response: EPA agrees that the State and Local Air Pollution Cont rol Agencies (S/Ls) should be able to continue to require stack test reports to be submitted in the form at that best suits their n eeds. However, EPA encourages S/Ls to consider requiring the submission of stack test data electronically as well and the ERT is a readily available tool for S/Ls use. In response to the comment that the stack test data taken at face value may be misleading, EPA disagrees. EPA believes that the data and information required to be submitted in the ERT is the

same data and information that is included in written performance test reports and will allow for an adequate

review of the stack test and its conduct. The ERT was designed using existing performance test reports. All the data in test reports is also clearly required in the ER T. EPA does believe that the S/Ls have the expertise and knowledge of their sources, such as operation variables a nd source configuration, and would generally be better able to evaluate stack test reports. Thus, we have desi gned the ERT, in conjunction w ith WebFIRE (the repository for ERT data), to allow for S/Ls to conduct a third-part y review of the performance test reports. Regarding the comment to have the S/Ls submit the data, EPA is designi ng the reporting to be submitted by the sources. Where the S/Ls have comments concerning a particular performance test, they need to discuss with the source and have the source resubmit the test report. We have concluded that having the source resubmit their performance test report electronically will eliminate the burden associated w ith tracking different versions of the test report in

different formats.



### Comment: One commenter (4770) requests that the reporting requirements in rules Da, Db and Dc be amended to commence on January 1, 2013 so that affected owne rs and operators have ad equate time to familiarize themselves with the requirements and procedures for us ing the CDX and ERT. Until then, affected facilities

should be allowed to continue to subm it paper copies of test data to EPA. In addition, the reporting requirementsResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

23 should be changed to 90 days after comp letion of correlation and performance te sts so that affected facilities have adequate time to gather required data and make adequate resources available to submit the data.

Response: EPA does not agree that the electronic reporting of performance test data through the Central Data Exchange using the Electronic Reporting Tool (ERT) n eeds to be extended for one year because the ERT is difficult to use. EPA believes that the source testing commun ity, for the most part, has had plenty of experience in the past year using the ERT. EPA h as also worked closely with the source testing community to understand and address their concerns with ease of use, so there is no need to extend the commencement date. We agree that it is appropriate to allow the required repor ts to be submitted 90 days after co mpletion of correlation and performance tests. Among other things, this will pr ovide time for owners/operators to fa miliarize themselves with ERT. Thus, we are extending the date for submitting the ERT report to 90 days.


## 2.6.4 Monitoring PM and Opacity Emissions from EGUs Using ESPs

Comment: One commenter (17755) states that the rule is not clear regarding how PM emissions will be monitored for EGUs using ESPs if and when the ESP is not running, e.g., during SSM or offline activities, and if the ESP is not running, commenter asks how these excess em issions will be detected using the ESP Predictive Model. The commenter states concerns that determining compliance with opacity and PM standards will be more complicated without some kind of continuous emission monitor in place. The commenter requests information and guidance on what constitutes an excess emission if there is no continuous emission monitor, and asks the following: how does the EPA anticipat e that compliance with the emission limit be determined, would an inspector simply monitor and check all of the parameters established for the ESP Predictive Model, and if the ESP is operating outside the defined parameters is that considered an excess emission.

Response: During periods of startup and shutdown, th e ESP predictive model would not apply and the owner/operator would be required to follow the specifi ed work practice standards to minimize emissions. 

## 2.7 Other Proposed Amendments

2.7.1 Rule Definitions

2.7.1.1 Definition of “Affected Facility”

Comment : One commenter (4836) stated that EPA’s rationale for proposing to revise the definition of “affected facility” by adding integrated combustion turbines and fuel cells is vague and ambiguous, and the existing definition should not be revised. Another (4766) stated that EPA should provide additional clarification regarding the proposed expanded definition of “affected facility” under subpart Da to include “integrated” combustion turbines and fuel cells. Although discussed briefly in the prea mble, the word “integrated” is still unclear and is not well-defined in the rule. In addition, although EPA suggests that its intent is to encourage and promote the use of such units, it is unclear how EPA’s pr oposed regulation would accomplish that goal. Without further explanation, the new definition of “affected facility” remains vague and ambiguous and should be eliminated. One commenter (17852) also states that the option to integrate combustion turbines and/or fuel cells with steam generating units is another good way to reduce emissions. The commenter also states that if an owner chooses to integrate and

connect a fuel cell or combustion turbine to a steam boiler to use waste heat to improve efficiency, they should be

able to elect to consider them an integrated unit for compliance purposes.

Response: The definition has been clarified to specify that “integrated” means the device either supplies useful thermal output to the boiler or electrical output to power auxiliary equipment of the EGU. If the definition were not expanded to include integrated equipment, the intent of subpart Da could be circumvented by having auxiliary equipment provide steam to the EGU to increase the ou tput of the EGU and decrease the corresponding outputbased emissions rate without accounting for the emissions from the integrated equipment. The revised definition provides additional flexibilities to reduce emissions.



### 2.7.1.2 Definition of “Gaseous Fuel”

Comment : One commenter (5195) stated that EPA should clarify within subpart Da that the definition of “fossil fuel” does not include landfill gas, biogases or other mate rials such as engineered fuels that are produced from processing components of municipal solid waste. Becau se landfill gas and biogas are included under the proposedResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

24 definition of “gaseous fuel,” and the term “gaseous fuel” is included in the definition of “fossil fuel,” there may be an ambiguity with respect to how these definitions re late to each other in implementing subpart Da. The commenter requests that EPA clarify the circumstances unde r which subpart Da may apply to gaseous fuel firing, where such gaseous fuel is not a fossil fuel (for example, where a non

‐ fossil gaseous fuel is combusted in combination and/or alternately with a fossil

‐ fuel).

Response: The definition of fossil fuel under subpart Da only includes fuels “created fo r the purpose of creating useful heat.’ Since landfill gas and other fuels derived from municipal solid waste are not derived for the purpose of creating useful heat they are not considered foss il fuels under subpart Da. The definition of gaseous fuel includes these fuels strictly to determine the appropria te monitoring requirements in circumstances where nonfossil fuel gaseous fuels are burned in combination with fossil fuels. EGU are subject to the requirements of subpart Da when non-fossil fuel gaseous fuels are burned in combination with fossil fuels.



### 2.7.1.3 Definition of “IGCC Electric U tility Steam Generating Unit”

Comment : One commenter (4836) stated that EPA’s proposed revised definition of “IGCC Electric Utility Steam Generating Unit” should be reworded to read “The Admi nistrator may waive the 50 percent solid-derived fuel requirement during periods of the gasification system construction, startup and commissioning, shutdown or repair.” Adding startup and commissioning would provide the EPA Administrator with additional authority to resolve any regulatory problems associ ated with the construction and initia l operations of an IGCC EGU. Adding shutdown would allow an operator to combust na tural gas for safety reasons during shutdown.

Response: The definition has been amended as suggested.



### 2.7.1.4 Definition of “Natural Gas”

Comment : One commenter (4836) notes that the proposed Subp art D definition of” natural gas”, and the existing definitions of “natural gas” in 40 CFR 60 subparts Da, Db, and Dc, are slightly different from the definition of “natural gas” in Part 75. Another commenter (5749) stated that the definitions of “natural gas” used for the NSPS are different from the proposed definition of “natural gas” for the EGU NESHAP. The commenters recommend that EPA use this NSPS amendment rulemaking to make the definitions consistent in all of the rules to avoid

confusion and unintended results.

Response: In an effort to make the definitions as consistent as possible, the definition of “natural gas” under the NSPS has been amended as follows: i) “maintains a gase ous state under ISO conditions” has been added; ii) the heating value range has been amended to 950 to 1,100 Btu/scf; iii) a statement that natural gas does not include “any gaseous fuel produced in a process which might result in highly variable sulfur content or heating value,” has been added; and, iv) a provision that the “maximum sulfur content is 20 grains per 100 standard cubic feet”

has been added. The definition for industrial sources has historically included liquefied petroleum gas and will continue to do so. However, it will be removed for subpart Da affected EGUs to make it more consistent with that used in part 75.



### 2.7.1.5 Definition of “Petroleum Coke”

Comment : Several commenters (4765, 4836) object to including petroleum coke in the definition of “coal” for purposes of NSPS subpart Da. Reasons cited by the comme nters are 1) EPA acknowledged in its NSPS Subpart Y rulemaking that petroleum coke “is a by-product residual from the thermal cracking of heavy residual oil during the petroleum refining process,”(74 FR 25,304, 25,316/1), a nd therefore is not coal at all; and as a result, the nature of the analysis required for setting NSPS would be different for petr oleum coke as compared to coal; 2) EPA has failed to provide emissions data as to whether EPA’s proposed NSPS for PM, NO X or SO 2 are achievable when petroleum coke is burned in a EGU, eith er during periods of normal operation or during periods of startup and shutdown.

Response: When subpart Da was originally promulgated, pe troleum coke was not as commonly used in utility boilers. Subsequently, when EPA finalized the indus trial boiler NSPS, subpart Db, petroleum coke was recognized as a valuable fuel that has characteristics similar to coal and was therefore included in the definition of coal. From analysis of emissions data from facilities burning petroleum coke EPA has concluded that EGUs burning petroleum coke are able to achieve the amen ded criteria pollutant standards for coal-fired units.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

25 The Northside 1A and 1B EGUs and the Manitowoc 9 pe troleum coke-fired EGUs are achieving the PM standard, the AES Deepwater petroleum coke-fired EGU is achieving the NO X standard, and the Northside 1A facility is achieving the combined NO X + CO standard. While none of the petroleum coke-fired EGUs are achieving the

amended SO 2 standard, the SO 2 technology is directly transferrable and other facilities burning high sulfur fuels have demonstrated that 97% reduction in potential SO 2 emissions is achievable. Furthermore, the recent permit for the proposed Las Brisas Energy Center indicates that the amended NO X and SO 2 standards are achievable for a new petroleum coke-fired EGU. The proposed Las Bri sas Energy Center would burn petroleum coke in a fluidized bed using subcritical steam conditions. The permit conditions for NO X and SO 2 are 0.070 lb/MMBtu and 0.114 lb/MMBtu respectively. The gross EGU efficiency wo uld only have to be 34% (achievable using subcritical steam conditions) and 38% (achievable with supercriti cal steam conditions) to comply with the amended NO X and

SO 2 standards, respectively. In addition, based on the sulfur content of the petroleum coke, the SO 2 control is designed to control over 97% of the potential SO 2 emissions.


## 2.7.2 General Duty

Comment : One commenter (4836) stated that EPA’s proposal to add to Subpart Da a provision imposing a “general duty to minimize emissions” is neither neces sary nor appropriate. Subpar t Da facilities already are subject to the general duty under 40 CFR 60.11(d).

Response: EPA agrees that it is not necessary to include a specific provision imposing a “general duty to minimize emissions” in Subpart Da for the reason the comme nter articulates. The provision has, therefore, been

removed.



## 2.7.3 Affirmative Defense Provisions

Comment: One commenter (5210) stated that EPA’s proposed inclusion of the “affirmative defense” for

malfunctions is unlawful and contravenes the CAA. The co mmenter states that the CAA clearly sets forth how the courts are to assess civil penalties, whether the case is brought by a citizen or EPA. 42 U.S.C. § 7413(e). By allowing an affirmative defense in the case of malfunction, EPA goes directly against two expressed intentions of Congress: 1) the burden it places on citizens makes it less likely that they will enforce the CAA, see, e.g., Pennsylvania v. Del. Valley Citizens' Council for Clean Air, 478 U.S. 546, 560 (1986);and 2) several of the factors at issue in the affirmative defense undercut Congr ess's intent that citizen suit enforcement should avoid redelving into "technological or other considerations, "NRD C v. Train, 510 F.2d 692, 700 (D.C. Cir. 1974). Both result from the technical burden EPA imposes on citizens with the affirmative defense, and both render the defense impermissible. In addition to these problems, th ere is simply no need for an affirmative defense to penalties to be written into the regulations. EPA has discr etion to decide what cases to prosecute, to consider settlements, and to request civil penalties in a case-by- case manner, as long as it acts consistent with the CAA to protect clean air as its top priority, see U.S.C. § 7401. If EPA has the authority to promulgate any type of “affirmative defense”, then the commenter made specific recommendations for the provisions of such “affirmative defense”. Several commenters (4714, 4770, 4830, 4997) stat ed that the proposed “affirmative defense” provisions to be added to subpart Da need clarif ications, are vague or contradictory, and impose requirements that mean that the defense will be entirely useless as a practical matter. Some of the nine requirements that EPA proposed be met in order for a facility to claim an affirmative defense for a malfunction are unreasonable, difficult to demonstrate, and subject to varying interpretation. EPA should revise the affirmative defense provisions in the rule so that the requirements are meaningful to implement. The co mmenters provided specific recommended changes to the proposed rule language to address these issues. Another co mmenter (17975) states that EPA has not determined whether some emission control technologies are prone to ma lfunctions, or explained why EGUs that rely on such equipment should be entitled to an affirmative defense when it breaks down. Requiring government agencies to evaluate and rebut affirmative defenses on a case by case basis is impractical and has proved ineffective.

Response: EPA is finalizing emission standards that apply at all times, including during periods of malfunction. For malfunctions, the EPA is finalizing the proposed affirmative defense language for exceedances of the numerical emission limits that are caused by malfunctions. As EPA explained in the preamble to the proposed rule, EPA recognizes that even equipment that is properly designed and maintained can fail and that such failure

can cause an exceedance of the relevant emission standard . The EPA included an affirmative defense in the final rule in an attempt to balance a tensi on, inherent in many types of air regulation, to ensure adequate complianceResponse to Comments on Proposed NSPS Amendments to Subparts D and Da

26 while simultaneously recognizing that despite the most d iligent of efforts, emission limits may be exceeded under circumstances beyond the control of the source.

With respect to the Affirmative Defense and the comment that the provisions are vague or contradictory, the

EPA’s view is that the affirmative defense is consistent with CAA sec tions 113(e) and 304 and the EPA has concluded that courts are well equippe d and often do evaluate and apply the type of criteria set forth in the affirmative defense. Many of the conditions were mode led after the conditions of the affirmative defense in EPA’s SIP SSM policy, which several states have adopted in to their SIPs. (See, e.g., State Implementation Plans: Policy Regarding Excessive Emissions During Malfunctions, Startup, and Shutdown (Sep t. 20, 1999); Policy on Excess Emissions During Startup, Shutdown, Maintenance, and Malfunctions (Feb. 15 , 1983)). We do not have any indication that parties to enforcement proceedings ha ve had any significant difficu lties applying the terms of these SIP affirmative defenses. In addition, EPA’s view is that use of consistent terms in establishing affirmative defense regulations and policies acro ss various CAA programs will promote c onsistent implementation of those rules and policies. The affirmative defense does not requir e a facility to prove its innocence rather than requiring an enforcement authority to prove a violation of the CAA or change the burden of proof with respect to establishing a violation. The affirmative defense applies to penalties and thus is only utilized where a violation has been established. The burden of proo f remains with the plaintiff in an en forcement action. See, e.g., 40 C.F.R.

22.24. If a violation has been established and a source wi shes to assert the affirmative defense with respect to penalties, the source does bear the burden of establishing that the elements of the affirmative defense have been met. This burden-shifting is appropriate because the source is in a better position to determine the facts required to establish the defense. See, e.g., Arizona Pub. Serv. Co . v. EPA, 562 F.3d 1116, 1120, 1129-30 (10th Cir. 2009) (rejecting industry challenge to EPA’s use of an affirmative defense to address excess emissions during malfunction events.).

Comment: One commenter (4714) states that the proposed rules should be revised to enable EPA to allow state rules for affirmative defense that are EPA-approved as part of a state implementation plan (SIP) to be used in lieu of the federal procedures. This flexibility would eliminat e duplicative or potentially even conflicting requirements for both state agencies and regulated entities.

Response: As a general matter, state SIP provisions do not a pply in the context of an EPA promulgated NSPS. States can, and in fact are encouraged to, take dele gation of the authority to implement and enforce the requirements of NSPS; however, in such circumstances, it is still the provisions of the NSPS that apply, not EPAapproved SIP provisions. EPA, therefore, concludes that inclusion of the Affirmative Defense in the NSPS is appropriate.

Comment: One commenter (4714) states that an initial notifi cation is required if an affected owner/operator

wishes to claim an affirmativ e defense and the proposed rule allows notif ication by either telephone or facsimile. The commenter states that an electronic reporting mech anism should be allowed for this initial notification. However, telephone notifications shoul d not be allowed because such notifications are difficult to verify and enforce. At a minimum, electronic notification that complies with EPA’s Cross-Media Electronic Reporting Regulation (CROMERR) standards could provide for quick and durable reporting that may be relied upon for investigative and enforcement purposes.

Response: The EPA accepts documents in electronic format, as long as the format is compatible with the requirements of the standards. For the affirmative de fense provisions, the owner or operator of a facility experiencing an exceedance of its emission limit(s) during a malfunction must notify the Administrator by telephone or facsimile (FAX) transmission as soon as possibl e, but no later than two business days after the initial occurrence of the malfunction, or if it is not possible to determine within two business days after the malfunction caused or contributed to an exceedance, no later than two business days after the owner or operator knew or

should have known that the malfunction caused or contributed to an exceedance, but, in no event later than two business days after the end of the averaging period. The written reports required to demonstrate that the affirmative defense provisions have been met and requ ests for an extension of the deadline for submitting these reports may also be submitted electronically. EPA has concluded that notificatio n by telephone is appropriate since that notification must by followed by submission of a written report demonstrating that the affirmative defense provisions, including the notifi cation requirement, have been met.Response to Comments on Proposed NSPS Amendments to Subparts D and Da

27 

## 2.7.4 Subpart Da Mercury Provisions

Comment : Several commenters (4836, 5715) state that it is appropriate to remove the applicable mercury emissions standards provisions vacated by a federal c ourt ruling from the NSPS under 40 CFR 60 subpart Da).

Response: The provisions have been removed. In addition, th e amendments to subpart B that occurred as part of the Clean Air Mercury Rule have also been removed.


## 2.7.5 Removal of References to 30-Day Rolling Averages

Comment : One commenter (4836) stated that EPA’s proposed removal of references to 30-day rolling averages in Subpart Da provisions establishing emission limitations and the addition of new provisions stating that compliance with emission limits in various sections “a re determined on a 30-day rolling average basis” does not appear to be intended to change the averaging time of any provision, but could cau se confusion and should be better explained.

Response: The revisions are only intended to make the rules easi er to read and are not intended to change any of the existing provisions.



## 2.7.6 Deletion of Obsolete Pr ovision References in Rule

Comment : One commenter (4698) supports EPA proposal to delete “emergency condition” requirements for the

SO 2 standard exemption, referenc es to percent reductions for NO X and PM, references to the term “solvent refined coal,” and the existing commercial demonstration permit references.

Response: The provisions have been removed


## 2.7.7 Proposed Rule Language Corrections and Clarifications

Comment : One commenter (4698) states that in §60.48Da(k)(1)(i) the term “O sg ” in Equation 2 should be defined as “Average hourly gross energy output from electric utility st eam generating unit” to be c onsistent with the rule’s

definitions.

Response: A “steam generating unit” is a subset of an “elect ric utility steam generating” and EPA has concluded that the suggested change is not necessary.Response to Comments on Proposed NSPS Amendments to Subparts Db and Dc

28 

## 3. Response to Comments on Prop osed NSPS Amendments to Subparts

Db and Dc

3.1 Definition of “Distillate Oil”

Comment : Several commenters (4698, 4770 , 4841) support EPA’s proposal to expand the definition of “Distillate oil” in both 40 CFR 60 subparts Db and Dc to include biodiesel and kerosene because it is appropriate to have the same requirements for units burning biodiesel or kerosene as those un its firing distillate fuel oil. One commenter (5749) requested that EPA explain why the defi nition for “distillate oil” in 40 CFR 60 subpart Db of

the NSPS includes a limitation on the we ight percent nitrogen, while the proposed definition for “distillate oil” in

the EGU NESHAP does not.

Response: The definition of distillate oil has been amende d as proposed. When the industrial boiler NSPS was originally promulgated, certain provi sions in the NSPS assumed low fuel NO X formation and that requires low fuel nitrogen content. This is not necessary for purposes of the EGU NSPS.


## 3.2 Exemption of Steam Generating Units Subject to Other NSPS

Comment : One commenter (4841) supports EPA’s proposal to i) exempt owners and operators of affected facilities subject to 40 CFR 60 subpart Eb (standards of performance for large municipal waste combustors (MWCs) and 40 CFR 60 subpart CCCC (standards of perfo rmance for commercial and industrial solid waste incineration) from 40 CFR part 60, subpart Da; ii) exempt owners/operators of affected facilities subject to 40 CFR part 60, subpart BB (standards of performance fo r Kraft pulp mills) from the PM standards under subpart Db; and, iii) exempt owners/operators of fuel gas co mbustion devices subject to 40 CFR 60 subpart Ja (standards of performance for petroleum refineries) from the SO 2 standard under 40 CFR 60 subpart Db.

Response: The exemptions are included in the final rule.


## 3.3 Applicability to Temporary Boilers

Comment: One commenter (4766) stated that EPA appears to suggest that separate NSPS requirements should apply to temporary boilers that are on-site for 30 days or less. However, temporary boilers, especially those brought on-site on skids or trucks for construction project s, are not stationary equipment and therefore do not fall under NSPS. In any event, even if su ch temporary sources could be consider ed “stationary,” 30 days is not enough time to implement the NSPS.

Response: Section 111(a)(3) defines a "stationary source" as "a ny building, structure, facility or installation which emits or may emit any air pollutant." Temporary boilers as described by the commenter are stationary sources within the meaning of this definition and are, th erefore, subject to the NSPS requirements applicable to boilers in the relevant size category. This conclusion is supported by section 302(z) of the CAA which defines stationary source emissions to include all emissions except those resulting directly from internal combustion engines for transportation purposes or from nonroad engin es or nonroad vehicles as defined in section 7550 of the CAA. Temporary boilers are not internal combustion engines and as such are not nonroad engines or nonroad vehicles as defined in section 7550. The fact that they may only be on site for a period of 30 days or less does not alter their status as stationary sources as there is no tempor al aspect to section 111(a)(3)'s definition of "stationary source.” In recognition of the special considerations asso ciated with temporary boilers the final rule exempts temporary boilers that burn natural gas and/or low sulf ur distillate oil from the NSPS. The requirement to limit temporary boilers fuels to inherently cleaner burning fu els minimizing emissions while providing flexibility to the regulated community.

The definition added to 40 CFR 60 s ubparts Db and Dc is as follows:

Temporary boiler means any generating unit that combusts natu ral gas and/or distillate oil with a potential

SO 2 emissions rate of 26 ng/J (0.060 lb/MMBtu) or less, and that is designed to, and is capable of, being carried or moved from one location to another by mean s of, for example, wheels, skids, carrying handles, dollies, trailers, or platforms. A steam generating unit is not a temporary boiler if any one of the following

conditions exists:Response to Comments on Proposed NSPS Amendments to Subparts Db and Dc

29 (1) The equipment is attached to a foundation.

(2) The steam generating unit or a replacement remain s at a location for more than 180 consecutive days. Any temporary boiler that replaces a temporary boiler at a location and performs the same or similar

function will be included in calcu lating the consecutive time period.

(3) The equipment is located at a seasonal facility an d operates during the full annual operating period of the seasonal facility, remains at the facility for at least 2 years, and operates at that facility for at least 3 months each year.

(4) The equipment is moved from one location to anothe r in an attempt to circumvent the residence time requirements of this definition.


## 3.4 Site-Specific Monitoring Plan

Comment: One commenter (4674) requests that EPA provide further guidance on the “written site-specific monitoring plan approved by the permitting authority, ” under 40 CFR 60.47c(h). Specifically, the commenter requests that EPA allow permitting authorities to authorize less stringent opacity or other monitoring requirements than identified in the rule. For example, a permitting ag ency could require affected owners and operators to conduct opacity testing only upon using a fuel for operati onal reasons rather than for compliance demonstrations. Further, a permitting agency could specify that each periodi cally required Method 9 does not have to adhere to the 40 CFR part 60 notification and reporting requirements associated with performance tests found in §60.8 and §60.11, but rather the affected owner or operator woul d be required to submit any deviations with the excess emissions report required under §60.48c(c).

Response: There are no specific requirements in §60.47c(h). Th e permitting authority for the owner/operator of the affected steam generating unit de termines appropriate procedures and cr iteria for establishing and monitoring specific parameters for the affected fa cility indicative of compliance with th e opacity standard on a site-specific basis. The source specific requirements could be as descr ibed in the comment as long as the permitting authority has determined they are appropriate for a specific affected facility.


## 3.5 Opacity Monitoring

Comment: One commenter (4674), a state air pollution control agency, recommends that EPA consider removing the requirement to complete subseque nt Method 9 opacity performance tests af ter the initial performance test is completed, if the affected owner or operator is able to show in the initial reading that the opacity complies with the standard. It is the experience of the commenter that subsequent opacity readings for sources which have not exceeded the standard are onerous and may actually disc ourage good air pollution contro l practices. Alternately, the State suggests that EPA consider expanding the extension associated with proposed changes to 40 CFR 60.47c(a)(1)(i). EPA proposed a change to allow affected owners and operators to extend the time frame to complete a Method 9 performance test from a minimum of every 12 months for sources where the initial performance test showed that there were no visible em issions. EPA proposes to allow those sources to either repeat the performance test every month or within 45 days of using a fuel with an opacity standard. Without the latter option, sources which primarily combust natural g as are often required to undergo a special startup using diesel fuel solely to satisfy the current compliance requ irement to complete a Method 9 performance test every 12 months. As proposed, those sources will now only be require d to complete a Method 9 performance test within 45 days of using diesel fuel, which w ill be dependent on the sources’ ope rational needs and not a compliance requirement. The State is in agreement with EPA’s pr oposed revision to 40 CFR 60.47c(a)(1)(i). However, this proposed extension is only available to facilities that have no visible emissions observed during the initial 60 minute Method 9 performance test. Pursuant to 40 CFR 60.47c(a)(1)(ii-iv), sources which have any 6-minute opacity average greater than 0% must conduct another Method 9 performance test fo r compliance purposes in the near term (every 6 months, 3 months , or more frequently). It is the commenter’s experience that all boilers running on diesel experience some degree of opacity durin g operation, which typically subsides quickly. At least one 6-minute opacity average is likely to exceed 0%. For ma ny of the State’s sources, the primary fuel used is natural gas, and diesel fuel is used only as a backup. Becau se these sources are likely to have at least one 6-minute opacity average greater than 0% while using diesel fuel, th ey are required to repeat the Method 9 performance test even if they have ceased using diesel fuel in the interi m. Repeating this performance test requires the affectedResponse to Comments on Proposed NSPS Amendments to Subparts Db and Dc

30 owner or operator to shut down the boiler and restart us ing diesel fuel, only to shut down once again to restart using natural gas. It is the State’s experience that, left to the operational needs of the source, a boiler may only utilize diesel fuel once every few years as opposed to the compliance requirement to use diesel fuel every few months. It appears that the 45-day allowance, while in tending to limit unnecessary opacity monitoring for sources with no visible emissions, was not extended to sources wh ich may have some visible emissions during operation. Therefore, such sources are required to regularly shutdown their equipment and restart on diesel just to complete the necessary opacity readings. The St ate suggests that either EPA extend the 45-day allowance to 40 CFR 60.47c(a)(1)(ii-iv), or that a permitting agency may aut horize an alternative opacity monitoring schedule by means of the site-specific monito ring plan as discussed §60.47c(h).

Response: Under subpart Dc §60.47c(h), state permitting auth orities have the ability to develop an alternate opacity monitoring plan to alleviate the above concerns . To minimize burden, the 45 day testing allowance has been added to all subparts.