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-Institutional Steam Generating Units 

(40 CFR 60 subpart Db) 

Standards of Performance for Small 

Industrial-Commercial-Institutional 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 2011 
Introduction 

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 Approach for Rule Development ........................................................... 1

2.1.2 Selection of Best System of Emission Reduction (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 Subject to NSPS ............................................. 6

2.1.6 NSPS during Periods of EGU Startup, Shutdown, and Malfunction ..................................................... 6

2.1.7 Facility-Wide Emissions Averaging ...................................................................................................... 7

2.1.8 Interrelationship of NSPS with other 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 Using “Innovative Technologies” ........................................................................ 9

2.2.3 Applicability to Permitted EGUs for which Construction Has Not Commenced ................................ 10

2.3 Particulate Matter (PM) Emissions Standards............................................................................................... 10

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

2.3.2 Regulation of Combined PM Emissions .............................................................................................. 11

2.3.3 Regulation of PM2.5 Emissions ............................................................................................................ 12

2.3.4 Selection of PM Emissions Limit 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 (SO2) Emissions Standards ................................................................................................... 15

2.4.1 Selection of BSER for SO2 Emissions ................................................................................................. 15

2.4.2 Selection of SO2 Emissions Limit Value ............................................................................................. 15

2.3.3 SO2 Control Cost Analysis .................................................................................................................. 16

2.4.4 Coal Refuse-Fired EGU Exemption from SO2 Standards ................................................................... 16

2.5.1 Selection of BSER for NOX Emissions ............................................................................................... 17

2.5.2 Combined NOX + CO Emissions Limit ............................................................................................... 17
Introduction 

iii 

2.5.3 NOX Emissions Limit .......................................................................................................................... 18

2.6 Compliance Requirements............................................................................................................................. 20

2.6.1 Opacity Monitoring ............................................................................................................................. 20

2.6.2 PM Continuous Emission Monitoring ................................................................................................. 20

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

2.6.4 Monitoring PM and 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 Rolling Averages .......................................................................... 27

2.7.6 Deletion of Obsolete Provision References in Rule ............................................................................ 27

2.7.7 Proposed Rule Language Corrections and Clarifications .................................................................... 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 Monitoring Plan ................................................................................................................ 29

3.5 Opacity Monitoring ................................................................................................................................ 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) .....vi

   
Introduction 

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 

NO2 Nitrogen dioxide 

NOx 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 

SO2 Sulfur dioxide 

SOx Sulfur oxides 
Introduction 

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 electric 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 September 2, 2009, EPA was granted a voluntary remand 

without vacatur of the 2006 amendments. On May 3, 2011, EPA proposed amendments (76 FR 24976) in 

response to the voluntary remand. These amendments included proposed new emissions limits for particulate 

matter (PM), sulfur dioxide (SO2), and nitrogen oxides (NOX) for EGUs that commence construction, 

reconstruction, or modification on or after 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 the 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 standards 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 docket 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-2009-0234 regarding the proposed NESHAP rulemaking, and which do not 

contain any comments specifically related to the proposed 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 amendments frequently stated that the proposed NSPS 

amendments are overly stringent and burdensome and would inhibit or prevent the construction of new coal-fired 

EGUs, thereby increasing costs for electricity. The third and final category of public commenters are those 

providing comments regarding specific issues and topics related 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 development 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 amendments specific to subparts Db and Dc are included in 

Section 3. Tables 1 and 2 match the commenter to the docket entry number cited in Sections 2 and 3 for specific 

legal or technical comments. Some of the comment sets were signed or submitted 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 Corporation
Introduction 

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 Fund
Introduction 

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 Schaeffer
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

1 

2. Response to Comments on Proposed 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 strategy, 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 limits. According to the commenter, this approach violates 

the intent of Congress under Clean Air Act (CAA) section 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 unlawfully fails to consider the differences among boilers 

using different fuel types. Congress gave EPA the authority 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 for 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 particular coal rank, or combustion design is in effect 

tailoring the nation’s future options for electric generation. CAA Section 111’s statutory provisions are 

directed at disseminating the best system of emission 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 chooses, it is appropriate for it to establish standards for 

EGUs that allow the use of inherently cleaner burning fuels to comply with the standards. The amended NOX 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 SO2 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 standards allow affected EGUs the flexibility 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, owners/operators of affected EGUs have 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 steam generating units (e.g., boilers with 

steam turbines). Basing the standards on either of these fuels would result in standards that are neither technically 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

2 

or economically achievable for a coal-fired EGU. Basing the amended standards on the use of natural gas would 

preclude the development of new coal-fired EGUs since the standards would not be technically achievable, even 

with the application of IGCC technology. Natural gas-fired EGUs have demonstrated annual NOX 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 SO2 emission rates. 

Therefore, basing the NSPS on these PM and SO2 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 development 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 appropriate to continue to allow the construction of properly controlled coal-fired 

baseload EGU since, such an approach to generating electricity may be the most appropriate approach, from both 

a technical and financial perspective, in specific circumstances. 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 generation 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 expensive per unit heat input than coal. 

Comment: Several commenters (4836, 4997) stated that IGCC technology is inherently different from other coalbased electric generation technologies and should be regulated 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 IGCC technology include: 1) operating scenarios in which 

the IGCC EGUs (combustion turbines and duct burner) are combusting different fuels or a combination of fuels, 

such as natural gas, coal or other carbonaceous compound (petroleum 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, steam 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. For 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 NOX emissions rate of 25 

ppm to comply with the amended NOX standard. This emissions rate is routinely achieved by both combustion 

turbines using dry low NOX combustion controls and natural gas-fired diffusion flame combustion turbines using 

water or steam injection. The combustion of natural gas also results in minimal SO2 and PM emissions. Post 

combustion controls would not be required to maintain 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 rule what thermal efficiency assumptions were used in 

determining the new NSPS, and whether they are different 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 standards included some of the most thermal efficient 

facilities. Therefore, the emission standards account for both 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 equipment efficiency under various operating conditions. We 

consequently concluded it is not necessary to measure emissions 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 SO2, 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 data indicating a subcategory for low Btu fuel such as 

lignite would be appropriate nor data indicating that SO2 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 independent of the PM concentration coming into the 

baghouse. The SO2 standard has an alternate percent reduction requirement 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 resulting 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 SO2 and PM standards 

are achievable for low rank coals: 

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

amended SO2 % reduction alternative. Furthermore, both Sandow 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 lignite-fired pulverized coal EGUS. Both are presently 

operating below the amended numerical SO2 standard, and the Oak Grove 2 facility is also operating below the 

amended SO2 % reduction requirement. 

3. The Milton R. Young B1 and B2 facilities are subcritical 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 Efficiency in Selection of BSER 

Comment: One commenter (4634) stated that EPA’s failure to set NSPS emissions limits for PM, SO2, and NOX

reflecting the use of energy-efficient design is unlawful and arbitrary. New coal-fired EGUs can significantly 

reduce emissions of all pollution emitted by incorporating 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, SO2 and NOX. The commenter questions EPA basing the proposed 

output-based emissions limits on gross electrical generating efficiency of 36 percent, which the commenter 

contends is not BSER as required by the CAA. The commenter 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 because the facilities used to establish the amended 

standards include some of the highest efficiency supercritical facilities and the output-based standards were 

directly established based on the performance of the best performing facilities. The comment referring to an 

assumed efficiency of 36% is unclear and appears to refer to the approach taken in previous amendments to 

subpart Da. The analysis in this rulemaking looked at actual 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 Technology 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 determining BSER to control 

PM, SO2 and NOX emissions from coal-fired EGUs. Another commenter (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 justify 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 SO2, NOX, 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 Emissions 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, SO2, and NOX using an emissions standards format that expresses limits as 

the allowable amount of pollutant emitted per net energy output by the affected EGU. Several commenters (5715, 

5074, 5210) supporting the proposal stated that use of this 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 affected EGU. Reasons cited by the commenters for their 

opposition to requiring mandatory compliance with net energy output based emissions standards include: 1) a 

significant amount of the parasitic power demands at coal-fired power plants is needed to operate the air pollution 

control equipment required to comply with air emissions standards; 2) there are monitoring difficulties in 

measuring net output, especially at facilities operating multiple 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 decreases 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 electrical 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 emerging 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-based standards is that it provides a more accurate 

measurement of the environmental impacts of specific EGUs. Net output-based standards recognize the 

environmental benefit of the minimization 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 from the EGU minus auxiliary loads 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 configurations over a range of operating conditions, the final rule 

allows, but does not require, the use of a net-output based standard as an alternative 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 superior 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 potentially drive the installation of electrically driven 
Response 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. Electrically 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 output for new facilities to be the gross output from the 

generator(s) minus any electric power requirements to drive the boiler feed pumps. Without this amendment, 

switching to a steam driven feed pump to improve net efficiency could appear to decrease 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 EGUs 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 compressor). 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 alternative. 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) disagree 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 factors 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 and 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 representative 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 value across the industry considering that units generally 

will be operating with SCR, FGD, and PM emissions controls, 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 available to EPA. However, in recognition that parasitic 

power requirements can increase in terms of percentage of load 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 all 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 for new EGUs is not authorized by the CAA, and is 

therefore unlawful. The proposed NSPS for reconstructed and modified EGUs contradict Congressional intent 

that as existing sources are upgraded, they control their emissions to a rate reflecting best system of emission 

reduction for the industry. The commenter cites specific CAA sections and past 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)’s 
Response 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 appropriate circumstances. See, Asarco v. EPA, 578 F.2d 319, 330 (D.C. Cir. 

1978) (Leventhal, J. concurring) (explaining why the statute permits subcategorizing modified sources). Here, 

certain existing facility designs are not capable of operating combustion controls as effectively as newly designed 

facilities and, therefore, cannot achieve the same level 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 NOX 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 SO2 emissions beyond what is achievable by currently installed technology is not cost 

effective. The new source PM standard is based on the use 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 and 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 electric generation from combined heat and power (CHP) and 

waste heat recovery systems subject to the NSPS. Absent this, the net output-based standards fail to account for 

(and incentivize) the full efficiency gains 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 increased the thermal credit from 50% to 75% in 2006 (71 

FR 9866). The definition is as follows: 

Gross output means the gross useful work performed by the steam generated and, for an IGCC electric utility 

steam generating unit, the work performed by the stationary combustion turbines. For a unit generating only 

electricity, the gross useful work performed is the gross electrical output from the unit's turbine/generator sets. For 

a cogeneration unit, the gross useful work performed 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 appropriate to recognize the environmental benefit of 

electricity generated by CHP units by accounting for the benefit of on-site generation, 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 line losses are closer to 10%. However, the CHP 

facilities typically covered by subpart Da are large facilities with relatively large amounts of the generated 

electricity being transmitted to other end users, and the 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 down and malfunction (SSM). Commenters (4698, 5210) support 

the proposal for a number of reasons. The commenters state that startup and shutdown periods are normal phases 

of EGU operation and should not be held separate from 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 regarding emission limits during SSM periods (Sierra Club vs. 

EPA, DC Circuit Court, 2008) was specifically regarding NESHAP rules and not NSPS rules. EPA has not 

provided any reasoned explanation or justification for why it is applying the same approach for new, modified, 

and reconstructed sources in the proposed NSPS rule revisions. Furthermore, EPA has not appropriately evaluated 

applying the same emission limits for normal operations and for SSM periods. Another commenter (4836) states 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

7 

that coal-fired EGUs co-fire other fuels (typically natural 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 emissions profiles from the times the EGU burns coal only. 

One commenter (4834) states that instead of emission limits, 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 Boiler MACT Rule. Many of the commenters opposing the proposal state that 

work practices should be used to control emissions from 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 NOX and SO2 standards. The NOX

and SO2 CEMS data used to establish the standards include all 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 normal operation and periods of startup and shutdown. 

However, for PM it is not practicable to measure emissions during periods of startup and shutdown and we do not 

have data upon which to base numerical emission limits during 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 operation of PM control devices. The NSPS requirements will 

be identical to the NESHAP requirements and are described in Table 3 to Subpart UUUUU of Part 63. See the 

relevant startup/shutdown sections of the NESHAP portion 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 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. EPA included 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 diligent of efforts, emission limits may be exceeded under 

circumstances beyond the control of the source. The affirmative defense simply provides for a defense to civil 

penalties for excess emissions that are proven to be beyond the control of the source and appropriately balances 

competing concerns. 

2.1.7 Facility-Wide Emissions Averaging 

Comment: One commenter (4839) stated that facility-wide emissions averaging should be allowed as a 

compliance alternative in certain circumstances. EPA should reconsider and support including facility-wide 

averaging in emission limitations for existing sources subject to the NSPS as an additional compliance alternative. 

By including this type of flexibility mechanism, EPA will ensure that facilities will retain some degree of 

flexibility when complying with the rule requirements. Similarly, varying operational modes or combination of 

systems (e.g., wet/dry scrubber, ESP or fabric filter) could 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 EGUs subject to the NSPS will be no more than what is 

permitted on an aggregated individual basis. From a practical 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 additional 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 would 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 would be determined. 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

8 

2.1.8 Interrelationship of NSPS with other EPA Rulemakings 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. electric 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 existing 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 substantive 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 demonstrate compliance with certain HAP emissions limits under the 

NESHAP by proxy methods that refer back to SO2 or PM limits established in 40 CFR 60 subpart Da. 

Response: While the proposed SO2 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 pollutant and EPA has concluded the amended standards are 

justified in the absence of the NESHAP. If cost and benefits 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 SO2 and filterable PM as surrogates for acids gases and non 

mercury metals respectively. Owners/operators that elect to demonstrate compliance with the NESHAP HAP 

requirements using these surrogates could also concurrently demonstrate compliance with the NSPS standards for 

those pollutants. 

2.1.8.2 Delay of NSPS Rulemaking until NESHAP 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 with 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 timeline to promulgate the proposed NSPS, the commenter 

recommends a delay to account for the considerable time 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 sufficiently 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 compliance with the NESHAP by existing sources, compliance 

with the two sets of requirements cannot be synced. 

2.1.8.3 Proposal of EGU NSPS Amendments 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 inappropriate and circumvents the appropriate comment 
Response 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 that EPA is rushing its regulatory agenda and shortcircuiting the regulatory process. Since EPA is not under a court ordered deadline to develop NSPS amendments, 

each of these rulemakings should have been proposed 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 facilities 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 turbine 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-fired 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 gas 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. All 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 whether the EGU produces other useful byproducts or not, 

consistent with the applicability of EGUs to 40 CFR 60 subpart Da that are classified as combined heat and power 

units. 

Response: The IGCC facilities that meet the existing applicability criteria will continue to be regulated under 

subpart Da. EPA concluded that a gross output based standard, 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/operator 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 CO2 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 Using “Innovative Technologies” 

Comment: One commenter (5715) states that EPA is not authorized under the CAA to allow the proposed 

exemption of certain EGUs using “innovative technologies” from complying with the NSPS emissions standards. 

The CAA only allows EPA to grant a compliance time extension 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 avoid precluding the development of new technologies, EPA 

should consider a broader applicability of the exemption to include all DOE-funded commercial-scale technology 

demonstration projects. 

Response: As explained in the proposal preamble, the compliance 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 promising technologies that offer 

potential reductions in criteria, hazardous, and GHG emissions could be restricted. 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 analysis to determine an appropriate 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 maintained as proposed for pressurized fluidized beds and 

multi-pollutant control technologies. Neither of these technologies is generally applicable to existing facilities, 

and overly stringent standards could impede their future 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 pressurized 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 technology. 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 technology 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 the date of the NSPS regulation. Several electric utility 

entities have recently obtained air permits authorizing the construction of new units. However, 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 (May 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 construction 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 source as one for which construction or modification 

commences after the publication of proposed regulations applicable to the source. In this case, the relevant date is 

May 4, 2011 and any source which commences construction or modification after that date is a new source for 

purposes of the final regulations. EPA has long defined “commenced” in this context to mean “that an owner or 

operator has undertaken a continuous program of construction or modification or that an owner or operator has 

entered into a contractual obligation to undertake and complete, 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 amendments will prevent projects from going forward. 

While amended NSPS typically require the installation of improved emissions control equipment, the impacts of 

complying with the amended standards would not ultimately change the investment decisions of the 

owner/operator of an affected facility. On average, the standards have minimal impact on the capital cost of a new 

EGU, cost less than $10/kW (less than a 1% increase). Furthermore, the final standards are achievable for a range 

of technologies and coal types and, therefore, would not 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 differ 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 achieved 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 standards that are “achievable” by all new sources (and even 

many existing sources) rather than standards that are “achievable” 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 standard. As a result, a fabric filter was identified as 

BSER. The BSER can take into account multiple factors including, but not limited to, choice of generation 

technology, fuel selection, and multiple emission control 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 and in opposition to the proposal to establish a new 

combined PM emissions limit for EGUs that is determined 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 generating; 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, 5075, 5077, 5089, 5208) oppose the proposal for a number of reasons. 

Changing the existing NSPS for PM from a filterable PM standard 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 because 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 condensable 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 the proposed compliance procedures 

for the combined PM standard are unworkable because EPA Test Method 202 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 consideration since the proposal, we have concluded it is 

appropriate to amend only the filterable PM standard at this time. Post proposal, EPA has become aware of the 

complex interactions between control equipment configurations and the combined PM emissions rate that make it 

difficult to set a nationwide standard for combined emissions 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 standards for condensable PM and filterable PM have any 

benefit over a combined PM standard, and; iii) the appropriate 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 sufficient 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 PM10 and PM2.5. For this source category, a combined PM measurement 

represents mostly PM2.5 emissions since the filterable controls remove the larger sized PM. The primary 

distinction between filterable and condensable PM is based on temperature, not the form of the PM in the ambient 

air. The NSPS establishes standards that can be met through the use of the best controls for managing the ambient 

air pollutant. With regard to setting an NSPS for PM emissions, 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 will 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 with 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

12 

lower combined PM emissions had relatively low filterable 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 SO3 to sulfate prior to removal by a mist 

eliminator or particulate control and a wet ESP as control 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 SO3 from SO2, (2) minimizing the temperature at which the particulate 

matter control device operates, (3) minimizing the ammonia slip when SCR or SNCR is used, and (4) a more 

efficient mist eliminator. In addition, the sulfuric acid 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 condensable 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 content of the coal, similar to the format for the SO2 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 standard 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 standard that includes condensable PM, emissions of 

condensable PM by facilities subject to the amended requirements 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 emissions are generally lower 

for facilities with lower filterable PM emissions and high SO2 control rates. Since the amended NSPS will require 

greater control of the emission of these pollutants, there should be some reduction in emissions of condensable 

PM. 

2.3.3 Regulation of PM2.5 Emissions 

Comment: One commenter (4841) states that a separate filterable PM2.5 standard should not be established due to 

both measurement issues with respect to wet stacks and also because control technologies installed for combined 

PM, NOX, and HCl/SO2 will result in reductions of both direct PM2.5 and PM2.5 precursors. 

Response: Due to monitoring limitations and the commonality of controls for PM10 and PM2.5, the amendments 

do not include a separate standard for PM2.5. 

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 rule needs to be revised upwards to reflect the actual 

levels of performance achievable. Several commenters (4673, 4836) state that the proposed PM emissions limit is 

so stringent that it would effectively preclude construction 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 proposed 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 controls for condensable PM 

for these units. 

Response: For the reasons explained previously, EPA is issuing a final standard for filterable PM only. The 

amended standard is appropriate for a national requirement as it represents BSER for both new and modified 

facilities and takes variability into account. Data submitted as part of the EGU NESHAP ICR for pulverized coal 

EGUs burning bituminous and subbituminous coals and fluidized bed EGUs burning lignite, petroleum coke, and 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

13 

bituminous coal with multiple performance tests show that the amended PM standard 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 achievable by EGUs equipped with an ESP when using coals with 

ash contents of up to 14 lb/MMBtu. That data also demonstrate 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, which 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 the size of any existing ESP or retrofit a fabric filer 

beyond what the present standard requires to meet the amended 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/MWh (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 conditions 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 implementing 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 proposed NSPS PM emissions standard. EPA concluded that 

these costs and benefits would support the amended 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 “sufficiently accurate,” the surrogate opacity standard is 

no longer necessary to assure compliance with the applicable 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. However, PM and opacity are separate standards. Should 

source owners/operators want a different averaging time under subpart D, they can petition the Administrator in 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

14 

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

source filterable PM standard of 0.030 lb/MMBtu as an alternate 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 Complying with a Combined PM Standard 

Comment: One commenter (4836) supports EPA’s proposed opacity 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) support 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 federally enforceable permit limiting fuel use. No such 

condition is attached to the proposed Subpart Da exemption. The commenter also does not understand why EPA 

has not proposed to exempt Subpart Da facilities that combust only natural gas from the filterable PM standards. 

Those facilities also will have negligible filterable emissions. As long as the facility is actually combusting only 

natural gas, it should be exempt from filterable PM and 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 natural gas, but that maintain the ability to burn other fuels 

without a permit modification in the future. The opacity standard 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 fossil 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 fossil 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 subpart 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. Therefore, gaseous and liquid fuels with potential SO2 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 natural 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 SO2 emission rates of 0.060 lb/MMBtu or less from the otherwise applicable filterable 

PM standard, provided the EGU does not use post-combustion SO2 or NOX controls. One commenter does not 

support this option for other forms of oil, especially for No. 4 oil and other grades. Another commenter (4698) 

opposes the exemption because opacity emissions from EGU firing such fuels is not generally due to fuel ash and 

impurities but rather is more a function 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. Therefore, subparts D, Da, and Db are amended to include a 

provision providing state permitting authorities the flexibility 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/operators who only burn distillate oil as a backup fuel. The state 

would then have the flexibility to approve a site specific plan, or (?) require the use of the opacity monitoring 

procedure set forth in the rule, or the owner/operator could monitor carbon monoxide emissions. 

2.4 Sulfur Dioxide (SO2) Emissions Standards 

2.4.1 Selection of BSER for SO2 Emissions 

Comment: Many commenters (4712, 4715, 4765, 4836, 5715, 4989) state that EPA failed to state the BSER that 

the Agency selected as the basis for establishing the proposed SO2 emissions standards. One commenter (5715) 

states that the proposed SO2 emissions rates are not the result of an analysis of the application or performance of 

the BSER for SO2 emissions – instead they are based on the SO2 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 systems of emissions reductions that allow control of 

greenhouse gas emissions (which EPA is regulating under a separate rulemaking) along with control of SO2. 

Response: The BSER for SO2 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 and 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 SO2 standard on potential GHG requirements that have not been proposed. 

2.4.2 Selection of SO2 Emissions Limit Value 

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

SO2 emissions limit does not reflect the application of the BSER, and that the methodology EPA used to select the 

proposed SO2 emissions limit value does not sufficiently address variability 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 SO2 emissions limit using the BSER. Based on this analysis, the commenter states 

that an appropriate SO2 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 SO2 emissions limit based on the best 

demonstrated unit in its data set. According to the commenter, nearly all of EPA’s sample units (12 of 15 units) 

could meet the proposed NSPS of a 97% reduction in SO2, 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 fact indicates that a 98% reduction limit is achievable. EPA 

should incentivize the most efficient use of control technologies to achieve the maximum amount of SO2

reduction. The reduction limit for SO2 should be set at 98% for this NSPS. One commenter (5210) examined

emissions limits of six existing coal units (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 SO2 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 SO2 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 SO2 emissions of greater than approximately 3.5 lb/MMBtu. Assuming a gross 

efficiency of 36%, this correlates to a numerical emissions rate of 1.0 lb/MWh. Setting a numerical standard 

below 1.0 lb/MWh, which would be the result of requiring a emissions reduction of more than 75%, could limit 

the ability to use medium sulfur coals in new EGUs and 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 SO2

emission rates, neither is a viable option for establishing a national standard as the use of these ranks of coal is not 

practicable for some facilities due to transportation constraints, 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 requires long distance transportation, resulting in increased 

emissions from locomotives, increased energy consumption, and potential additional rail line construction due to 

existing rail system limitations. The use of lower sulfur eastern 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 exhausted. In addition, adding a subbituminous-fired boiler 

at an existing site designed to burn bituminous coal would require significant design changes to the coal material 

handling equipment and other existing ancillary equipment. 

Comment: One commenter (17622) states that Table 17- SO2 Emissions Performance Data in the proposal notice 

(76 FR 25065) used by EPA to select the SO2 performance level for EGUs lists the best performing units in terms 

of percentage SO2 control and the subsequent commentary incorrectly 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 SO2 Control Cost Analysis 

Comment: Many commenters (4635, 4656, 4765, 4766, 4686, 4830, 4836, 4989, 5075, 5240) state that EPA 

failed to independently calculate the control costs for implementing the proposed SO2 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 SO2 emissions reductions that the Agency anticipates from 

implementation of the proposed NESHAP for EGUs. EPA concludes that the proposed NSPS SO2 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 control costs for implementing the proposed SO2 emissions limit. On the 

basis of that information, EPA concludes the SO2 limits are achievable and cost effective independent of the 

NESHAP. 

2.4.4 Coal Refuse-Fired EGU Exemption from SO2 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 SO2 emissions and instead allow such units to meet the 

existing NSPS for SO2 emissions is unlawful. The commenter states that in proposing to establish such an 

exemption, EPA failed to distinguish these EGUs as a subcategory warranting separate emissions standards in 

accordance with the proper statutory requirements as provided by 42 U.S.C. §7411(b)(2) (“the Administrator may 

distinguish among classes, types and sizes within categories 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 SO2 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 SO2 standard under the existing NSPS. 

We neither proposed to eliminate the subcategory, nor in any other way reopened the issue of whether the 

subcategory is appropriate. 

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

coal-refuse-fired EGU in terms of NOX. The facility has demonstrated a NOX emissions rate of 0.85 lb/MWh and 

we are therefore amending the standard accordingly. Furthermore, 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 (NOX) Emissions Standards

2.5.1 Selection of BSER for NOX Emissions 

Comment: One commenter (5715) states that the proposed NSPS to control NOX emissions (a combined 

NOX/CO standards and an alternative NOX standard) does not reflect the application of BSER. EPA’s selection of 

selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR) with advanced combustion 

controls does not represent BSER for control of NOX 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 NOX and CO emissions reductions achievable by all available NOX 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 NOX 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 determined to be the use of advanced combustion controls and 

SCR. The only currently viable CO controls on EGUs are combustion controls as thermal oxidation and catalytic 

reduction have not been demonstrated on EGUs. 

2.5.2 Combined NOX + CO Emissions Limit 

Comment: Many commenters (4673, 4712, 4836, 4989) object to establishing a mandatory NOX + 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. However, several of these commenters (4673, 4836, 4839, 5470) 

also state that a combined NOX and CO emissions limit could provide an advantage in terms of compliance 

flexibility. These commenters do not object to establishing an NOX + CO emission limit that EGU 

owners/operators could chose to comply with as an alternative to a NOX emissions limit. Other commenters 

(4715, 5715) support EPA establishing a mandatory NOX + CO NSPS emissions limit for EGUs. However, one 

commenter states that EPA failed to explain why the Agency believes that a NOX + 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 NOX-only emissions limit proposed alternative. The commenter concludes that the NSPS emissions limit for 

NOX + 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 that setting a sufficiently stringent CO standard that 

avoids poor combustion would be a better option than adopting a combined limit for NOX + CO. Allowing 

inappropriately high CO levels by establishing a combined standard will simply permit sources to use less 

effective SCR controls and emit higher levels of organic HAPs than would limits that are based on the level of 

NOX reduction and CO levels achievable by high efficiency SCRs controls. 

Response: While EPA believes that the limited data available supports the achievability of a combined NOx/CO 

standard in at least some circumstance, it does not support the imposition of such a standard across the board. As 

a result, the combined NOX/CO standard will be provided as an alternative to the amended NOX standard. The 

alternative standard will be 1.1 lb/MWh, as that is the lowest 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 NOX and CO limits in BACT permits. The majority of BACT-based CO standards are 0.10 

lb/MMBtu or greater. This translates to an approximate CO emissions rate of 1.0 lb/MWh. With corresponding 

BACT-based NOX 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 NOX 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 NOX standard. While supporting 

EPA’s suggested benefits of a combined NOX + CO standard, the commenter states concern over if and how the 

Agency weighed the different health and environmental impacts of NOX and CO in determining the proposed 

combined standard. It appears the Agency weighed them equally, which the commenter believes is not 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

18 

appropriate, given the greater health and environmental impacts of NOX and its contribution to ozone. While the 

commenter does not want CO emissions to significantly increase as a result of NOX controls, the commenter is 

concerned that the flexibilities of a combined NOX + CO standard will provide for an ultimately more lenient NOX

standard, resulting in fewer reductions. Therefore, the commenter recommends that EPA at the least set the most 

stringent standard feasible for NOX, in order to protect public health and the environment from the harmful 

impacts of ozone, PM, and other NOX related emissions. Another commenter (5208) states that a combined NOX

+ CO standard potentially would allow higher NOX emissions that would not protect the more stringent nitrogen 

dioxide (NO2) National Ambient Air Quality Standard (NAAQS). 

Response: The combined standard is based on the best performing facilities. New facilities would, at a minimum, 

have to reduce emissions to below the existing subpart Da NOx standard established in 2006 to comply with the 

standard. Therefore, it is a tightening and not a relaxation of the existing requirements and would not result in 

increased NOX emissions. 

Other federal and state permitting programs are designed to take into account the specific health and 

environmental issues. In regions where reductions in NOX emissions would result in more significant health and 

environmental benefits the permit could require the maximum reductions in NOX. However, as described in the 

preamble this could lead to significant increases in CO emissions such that the combined standard would not be 

achievable. 

2.5.3 NOX Emissions Limit 

Comment: Several commenters (4712, 4765, 4768, 4836, 5075) state that the proposed NOX emissions limit is 

not achievable on a nationwide basis, and the final rule should, therefore, be revised upwards to reflect the actual 

levels of performance achievable. In addition, a separate NOX 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 NOX emissions limit value does not sufficiently address variability in EGU fuel use, equipment design, 

and operation. One commenter (4768) includes their analysis of the data on which EPA based its determination 

that the proposed NOX emissions limit is achievable using BSER. Based on this analysis, the commenter asserts 

that an appropriate NOX 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 NOX 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-equipped cyclone boilers require NOX 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 recognition of the difficulties of retrofitting certain modified 

facilities with advanced combustion controls, the final NOX standard for modified facilities is 1.1 lb/MWh. Since 

the CEMS data used in establishing the standards included long term data, various operating conditions and 

variability are inherently accounted for. I The comment about 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 addition, the Dallman 4 EGU is a wet-bottom boiler with 

SCR operating below 0.70 lb/MWh. Cyclone boilers are the 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 NOX 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 Merrimack and Leland Olds facilities. These EGUs have 

demonstrated that cyclone EGUs can maintain NOX 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 NOX emissions to less than 

1.1 lb/MWh.

The differences in the calculated 30-day emission rates between 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 applicable pollutant divided by the sum of the gross output), 

while the commenter used the average of the hourly emission rates for the 30-day period. As stated in the 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

19 

proposal, the EPA procedure results in lower numerical emission 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 startup and shutdown periods have a particularly 

large impact on NOX 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 compliance with the standard. Further, 

EPA should set a higher NOX NSPS standard for modified units, since older 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 NOX NSPS of 0.70 lb/MWh appears to eliminate the 

further use of lignite coal for new EGUs. Section 111(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 have significant regional economic impacts. EPA has the 

discretionary authority to subcategorize EGUs such that lignite-fired EGUs could have different NOX standards 

based on BSER for lignite. Thus, EPA should subcategorize the lignite NOX 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 realistically achieved for non-lignite units, and no level lower 

than that should be considered for the NOX 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 using the same control configuration as Oak Grove 1 would 

theoretically reduce the NOX emissions rate to less than the 0.70 lb/MWh amended NOX standard. The permit for 

Oak Grove requires an NOX 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 NOX 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 NOX/CO standard. Furthermore, increasing the steam temperature and pressure to 

those used at the Weston 4 facility would reduce fuel use 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 newly designed EGU using the same control configuration 

as Sandow 5B would theoretically reduce the NOX emissions rate to below the 0.70 lb/MWh amended NOX

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 response to comments, the 0.70 lb NOX/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 bag 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 allowing affected EGUs using a PM CEMS, a fabric 

filter BLDS, or an electrostatic precipitator (ESP) predictive 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 requirements 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 visible emissions testing as long as the state testing is at 

least as frequent. 

Response: All the boiler rules have been amended to allow the permitting authority the discretion to establish 

site-specific monitoring plans for owners/operators of facilities 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 been reduced from every 6 months to every 12 months. The 

frequency of opacity monitoring for owners/operators of facilities with higher 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 eliminates 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 data 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

21 

availability requirements would have to obtain data using “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 amendatory 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 rolling 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 required reporting duration (i.e., 30 day rolling average). 

Response: We find the commenter's concern about a limited number of PM CEMS installations on utility units to 

be misplaced, as over 100 EGUs have installed and are operating PM CEMS. As we are unaware of situations that 

have caused or may cause data availability 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-of-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 burden 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 Electronic Reporting tool (ERT). The commenters state that 

this proposed requirement is unlawful, unsupported, and incomprehensible for the following reasons: 1) EPA has 

not articulated the purpose of the submission and reconciled 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 Management 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 the 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 other environmental data) to develop regulations. 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 rulemaking, 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 unsupported. 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 information 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 data 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 that the requirements are incomprehensible. The electronic 

reporting requirement is clear on its face and, for the reasons 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 response is that the ERT has been used by many source 

testing companies and is steadily improving. EPA has worked very closely with the source samplers and industry 

to identify and correct problems encountered with its use. In response to item 2, EPA is not sure what the 

commenters are asking. EPA developed the ERT using/in collaboration with former source 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. The 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 trouble in understanding what is 

required. The response to item 3 is that EPA will be accounting 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 Environmental 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 will have this process completed prior to the time when the ERT submittals are 

required.

Comment: One commenter (4674), a state air regulatory agency, intends to continue to request affected owner or 

operators to submit hard copies of stack test reports to the State, in addition to EPA’s collection of stack testing 

data via the Electronic Reporting Tool (ERT), and therefore supports EPA’s preservation of related requirements 

in 40 CFR 60.8 and 60.11. The commenter believes that the 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 believes 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 configuration and operation variables can be adequately 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 commenter supports EPA’s preservation of the submittal of 

written performance testing reports to state agencies, and requests 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 Control Agencies (S/Ls) should be able to continue 

to require stack test reports to be submitted in the format that best suits their needs. 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 ERT. EPA does believe that the S/Ls have the expertise and 

knowledge of their sources, such as operation variables and source configuration, and would generally be better 

able to evaluate stack test reports. Thus, we have designed the ERT, in conjunction with WebFIRE (the repository 

for ERT data), to allow for S/Ls to conduct a third-party review of the performance test reports. Regarding the 

comment to have the S/Ls submit the data, EPA is designing 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 with 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 owners and operators have adequate time to familiarize 

themselves with the requirements and procedures for using the CDX and ERT. Until then, affected facilities 

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

23 

should be changed to 90 days after completion of correlation and performance tests 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) needs to be extended for one year because the ERT is 

difficult to use. EPA believes that the source testing community, for the most part, has had plenty of experience in 

the past year using the ERT. EPA has 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 reports to be submitted 90 days after completion of correlation and performance 

tests. Among other things, this will provide time for owners/operators to familiarize 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 emissions 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 anticipate 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, the ESP predictive model would not apply and the 

owner/operator would be required to follow the specified 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 preamble, 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 proposed 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 output 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 materials such as engineered fuels that are produced from 

processing components of municipal solid waste. Because landfill gas and biogas are included under the proposed 
Response 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 relate to each other in implementing subpart Da. The 

commenter requests that EPA clarify the circumstances under 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 for 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 fossil fuels under subpart Da. The definition of gaseous fuel 

includes these fuels strictly to determine the appropriate 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 Utility 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 Administrator 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 associated with the construction and initial operations of an IGCC EGU. Adding 

shutdown would allow an operator to combust natural 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 Subpart 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 gaseous 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 commenters 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), and therefore is not coal at all; and as a result, the 

nature of the analysis required for setting NSPS would be different for petroleum coke as compared to coal; 2) 

EPA has failed to provide emissions data as to whether EPA’s proposed NSPS for PM, NOX or SO2 are 

achievable when petroleum coke is burned in a EGU, either during periods of normal operation or during periods 

of startup and shutdown. 

Response: When subpart Da was originally promulgated, petroleum coke was not as commonly used in utility 

boilers. Subsequently, when EPA finalized the industrial 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 amended 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 petroleum coke-fired EGUs are achieving the PM standard, 

the AES Deepwater petroleum coke-fired EGU is achieving the NOX standard, and the Northside 1A facility is 

achieving the combined NOX + CO standard. While none of the petroleum coke-fired EGUs are achieving the 

amended SO2 standard, the SO2 technology is directly transferrable and other facilities burning high sulfur fuels 

have demonstrated that 97% reduction in potential SO2 emissions is achievable. Furthermore, the recent permit 

for the proposed Las Brisas Energy Center indicates that the amended NOX and SO2 standards are achievable for a 

new petroleum coke-fired EGU. The proposed Las Brisas Energy Center would burn petroleum coke in a 

fluidized bed using subcritical steam conditions. The permit conditions for NOX and SO2 are 0.070 lb/MMBtu and 

0.114 lb/MMBtu respectively. The gross EGU efficiency would only have to be 34% (achievable using subcritical 

steam conditions) and 38% (achievable with supercritical steam conditions) to comply with the amended NOX and 

SO2 standards, respectively. In addition, based on the sulfur content of the petroleum coke, the SO2 control is 

designed to control over 97% of the potential SO2 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 necessary nor appropriate. Subpart 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 commenter 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 commenter 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 Congress's intent that citizen suit enforcement should avoid redelving into "technological or other considerations, "NRDC 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, there is simply no need for an affirmative defense to 

penalties to be written into the regulations. EPA has discretion 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) stated that the proposed “affirmative defense” provisions 

to be added to subpart Da need clarifications, 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 commenters provided specific recommended changes to the 

proposed rule language to address these issues. Another commenter (17975) states that EPA has not determined 

whether some emission control technologies are prone to malfunctions, 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 tension, inherent in many types of air regulation, to ensure adequate compliance 
Response to Comments on Proposed NSPS Amendments to Subparts D and Da

26 

while simultaneously recognizing that despite the most diligent 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 sections 113(e) and 304 and the EPA has 

concluded that courts are well equipped and often do evaluate and apply the type of criteria set forth in the 

affirmative defense. Many of the conditions were modeled after the conditions of the affirmative defense in 

EPA’s SIP SSM policy, which several states have adopted into their SIPs. (See, e.g., State Implementation Plans: 

Policy Regarding Excessive Emissions During Malfunctions, Startup, and Shutdown (Sept. 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 have had any significant difficulties 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 across various CAA programs will promote consistent implementation of those 

rules and policies. The affirmative defense does not require 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 proof remains with the plaintiff in an enforcement action. See, e.g., 40 C.F.R. 

22.24. If a violation has been established and a source wishes 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 eliminate duplicative or potentially even conflicting requirements 

for both state agencies and regulated entities. 

Response: As a general matter, state SIP provisions do not apply in the context of an EPA promulgated NSPS. 

States can, and in fact are encouraged to, take delegation 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 notification is required if an affected owner/operator 

wishes to claim an affirmative defense and the proposed rule allows notification by either telephone or facsimile. 

The commenter states that an electronic reporting mechanism should be allowed for this initial notification. 

However, telephone notifications should 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 defense 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 possible, 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 requests for an extension of the deadline for submitting these 

reports may also be submitted electronically. EPA has concluded that notification by telephone is appropriate 

since that notification must by followed by submission of a written report demonstrating that the affirmative 

defense provisions, including the notification 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 court ruling from the NSPS under 40 CFR 60 subpart Da). 

Response: The provisions have been removed. In addition, the 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 “are determined on a 30-day rolling average basis” does not 

appear to be intended to change the averaging time of any provision, but could cause confusion and should be 

better explained. 

Response: The revisions are only intended to make the rules easier to read and are not intended to change any of 

the existing provisions. 

2.7.6 Deletion of Obsolete Provision References in Rule 

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

SO2 standard exemption, references to percent reductions for NOX 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 “Osg” in Equation 2 should be defined 

as “Average hourly gross energy output from electric utility steam generating unit” to be consistent with the rule’s 

definitions. 

Response: A “steam generating unit” is a subset of an “electric 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 Proposed 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 units firing distillate fuel oil. One 

commenter (5749) requested that EPA explain why the definition for “distillate oil” in 40 CFR 60 subpart Db of 

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

the EGU NESHAP does not. 

Response: The definition of distillate oil has been amended as proposed. When the industrial boiler NSPS was 

originally promulgated, certain provisions in the NSPS assumed low fuel NOX 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 performance 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 for Kraft pulp mills) from the PM standards under subpart 

Db; and, iii) exempt owners/operators of fuel gas combustion devices subject to 40 CFR 60 subpart Ja (standards 

of performance for petroleum refineries) from the SO2 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 projects, are not stationary equipment and therefore do not fall 

under NSPS. In any event, even if such temporary sources could be considered “stationary,” 30 days is not 

enough time to implement the NSPS. 

Response: Section 111(a)(3) defines a "stationary source" as "any 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, therefore, 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 engines 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 temporal aspect to section 111(a)(3)'s definition of "stationary 

source.” In recognition of the special considerations associated with temporary boilers the final rule exempts 

temporary boilers that burn natural gas and/or low sulfur distillate oil from the NSPS. The requirement to limit 

temporary boilers fuels to inherently cleaner burning fuels minimizing emissions while providing flexibility to the 

regulated community. 

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

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

SO2 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 means 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 remains 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 calculating the consecutive time period. 

(3) The equipment is located at a seasonal facility and 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 another 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 agency could require affected owners and operators to 

conduct opacity testing only upon using a fuel for operational reasons rather than for compliance demonstrations. 

Further, a permitting agency could specify that each periodically 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 would 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). The permitting authority for the owner/operator of 

the affected steam generating unit determines appropriate procedures and criteria for establishing and monitoring 

specific parameters for the affected facility indicative of compliance with the opacity standard on a site-specific 

basis. The source specific requirements could be as described 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 subsequent Method 9 opacity performance tests after 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 discourage good air pollution control 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 emissions. 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 gas are often required to undergo a special startup using 

diesel fuel solely to satisfy the current compliance requirement to complete a Method 9 performance test every 12 

months. As proposed, those sources will now only be required to complete a Method 9 performance test within 45 

days of using diesel fuel, which will be dependent on the sources’ operational needs and not a compliance 

requirement. The State is in agreement with EPA’s proposed 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 for 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 during operation, which typically subsides quickly. At least 

one 6-minute opacity average is likely to exceed 0%. For many of the State’s sources, the primary fuel used is 

natural gas, and diesel fuel is used only as a backup. Because these sources are likely to have at least one 6-minute 

opacity average greater than 0% while using diesel fuel, they are required to repeat the Method 9 performance test 

even if they have ceased using diesel fuel in the interim. Repeating this performance test requires the affected 
Response to Comments on Proposed NSPS Amendments to Subparts Db and Dc 

30 

owner or operator to shut down the boiler and restart using 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 intending to limit unnecessary opacity monitoring for sources 

with no visible emissions, was not extended to sources which 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 State suggests that either EPA extend the 45-day allowance to 40 CFR 

60.47c(a)(1)(ii-iv), or that a permitting agency may authorize an alternative opacity monitoring schedule by 

means of the site-specific monitoring plan as discussed §60.47c(h). 

Response: Under subpart Dc §60.47c(h), state permitting authorities 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.