1

MEMORANDUM

Subject: Response to Public Comments on Proposed National Emission Standards for 

Hazardous Air Pollutants for Existing Stationary Reciprocating Internal 

Combustion Engines Located at Area Sources of Hazardous Air Pollutant 

Emissions or Have a Site Rating Less Than or Equal to 500 Brake HP Located at 

Major Sources of Hazardous Air Pollutant Emissions 

 

From: Melanie King, Energy Strategies Group 

To: EPA Docket EPA-HQ-OAR-2008-0708 

On March 5, 2009, the Environmental Protection Agency (EPA) proposed national emission 

standards for hazardous air pollutants (NESHAP) for stationary reciprocating internal 

combustion engines (RICE) that are either located at area sources of hazardous air pollutant 

(HAP) emissions or that have a site rating of less than or equal to 500 brake horsepower (HP) 

and are located at major sources of HAP emissions in 40 CFR part 63, subpart ZZZZ. EPA also 

proposed national emission standards for hazardous air pollutants for existing stationary 

compression ignition (CI) engines greater than 500 brake HP that are located at major sources of 

HAP emissions. It is important to note that the proposed rule covered both CI and spark ignition 

(SI) engines. The final rule will be promulgated in two parts. The first action will cover CI 

engines only. The purpose of this document is to present a summary of the public comments that 

EPA received on the proposed standards for CI engines and the responses developed. This 

summary of comments and responses serves as the basis for revisions made to the standards 

between proposal and promulgation. The comments on the proposed standards for SI engines 

and the responses to those comments will be summarized in a separate document that will be 

made available at the time that the final rule for SI engines is promulgated, which is expected to 

be in August 2010. 

EPA received 199 public comments on the proposed rule. A listing of all persons submitting 

comments, their affiliation, and the Document ID for their comments is presented in Table 1. 

The comments can be obtained online from the Federal Docket Management System at 

http://www.regulations.gov. The docket number for this rulemaking is EPA-HQ-OAR-2008-

0708. In this document, commenters are identified by the last three digits of the Document ID of 

their comments. Note that as stated above, this document includes the comments related to CI 

engines only, therefore the comments that pertain to SI engines will be summarized and 

responded to in a separate document.
2

Table 1. List of Commenters on the Proposed National Emission Standards for Hazardous 

Air Pollutants for Existing Stationary Reciprocating Internal Combustion Engines 

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0036 Bo Quick 

Southwire Company 

EPA-HQ-OAR-2008-0708-0038 

EPA-HQ-OAR-2008-0708-0062 

Jack Maley 

Director, Fleet Operations 

Exterran 

EPA-HQ-OAR-2008-0708-0039 

EPA-HQ-OAR-2008-0708-0180 

EPA-HQ-OAR-2008-0708-0242 

Stephanie R. Meadows 

Upstream Senior Policy Advisor 

American Petroleum Institute (API) 

EPA-HQ-OAR-2008-0708-0040 

EPA-HQ-OAR-2008-0708-0155 

Lisa Beal 

Director, Environment and Construction Policy 

Interstate Natural Gas Association of America (INGAA) 

EPA-HQ-OAR-2008-0708-0041 

Craig S. Harrison 

Hunton & Williams on behalf of the 

Utility Air Regulation Group (UARG) 

EPA-HQ-OAR-2008-0708-0042 R. L. Bedard 

EPA-HQ-OAR-2008-0708-0043 Anonymous 

EPA-HQ-OAR-2008-0708-0044 J. Hartz 

EPA-HQ-OAR-2008-0708-0045 

Mark Sutton 

Executive Director 

Gas Processors Association (GPA) 

EPA-HQ-OAR-2008-0708-0046 

Patrick J. Nugent 

Executive Director 

Texas Pipeline Association 

EPA-HQ-OAR-2008-0708-0047 Anonymous 

EPA-HQ-OAR-2008-0708-0048 Jorge Verde 

EPA-HQ-OAR-2008-0708-0050 Quinton Hancock 

Cree, Inc. 

EPA-HQ-OAR-2008-0708-0051 

Nancy C. Wrona 

Director, Air Quality Division 

Arizona Department of Environmental Quality (ADEQ) 

EPA-HQ-OAR-2008-0708-0052 K. W. Breeden Sr. 

EPA-HQ-OAR-2008-0708-0053 L. Jordan 

EPA-HQ-OAR-2008-0708-0054 Anonymous 

EPA-HQ-OAR-2008-0708-0055 Suneet K. Sikka 

Eastman Chemical Company 

EPA-HQ-OAR-2008-0708-0056 

Bruce Chrisman 

Manager of Engineering 

Cameron’s Compression Systems 

EPA-HQ-OAR-2008-0708-0057 

EPA-HQ-OAR-2008-0708-0059 

Gary L. Smith 

Consulting Engineer 

Cummings & Smith, Inc. 
3

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0058 

EPA-HQ-OAR-2008-0708-0060 

Gary L. Smith 

Consulting Engineer 

Cummings & Smith, Inc. 

EPA-HQ-OAR-2008-0708-0061 Dan Popp 

PM Technologies 

EPA-HQ-OAR-2008-0708-0063 

Robert L. (Bobby) Myers II 

Principal 

Cirrus Consulting, LLC 

EPA-HQ-OAR-2008-0708-0064 

EPA-HQ-OAR-2008-0708-0070 

Chris Mello 

Program Manager, Rural Energy 

Alaska Energy Authority (AEA) 

EPA-HQ-OAR-2008-0708-0065 

EPA-HQ-OAR-2008-0708-0073 

Alice Edwards 

Acting Director 

Alaska Department of Environmental Conservation 

Division of Air Quality 

EPA-HQ-OAR-2008-0708-0066 

Support the comments of 

EPA-HQ-OAR-2008-0708-0064 

Scott Newlun 

General Manger 

Yakutat Power 

EPA-HQ-OAR-2008-0708-0067 L. Stevens 

EPA-HQ-OAR-2008-0708-0068 

Support the comments of 

EPA-HQ-OAR-2008-0708-0064 

Keith Berggren 

Generation Supervisor 

Inside Passage Electric Cooperative (IPEC) 

EPA-HQ-OAR-2008-0708-0069 Ron Sober 

RFS Consulting, Inc. 

EPA-HQ-OAR-2008-0708-0071 

Joy Wiecks 

Air Quality Technician 

Fond du Lac Band of Lake Superior Chippewa (The 

Band) 

EPA-HQ-OAR-2008-0708-0074 

Ken Daubert 

Plant Superintendent 

Kapaia Generating Station, Kauai Island Utility 

Cooperative (KIUC) 

EPA-HQ-OAR-2008-0708-0075 

Support the comments of 

EPA-HQ-OAR-2008-0708-0064 

Jodi Mitchell 

Chief Executive Officer (CEO)/General Manager and 

Keith Berggren 

Generation Supervisor 

Inside Passage Electric Cooperative (IPEC) 

EPA-HQ-OAR-2008-0708-0076 

EPA-HQ-OAR-2008-0708-0114 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0096 

EPA-HQ-OAR-2008-0708-0123 

EPA-HQ-OAR-2008-0708-0242 

David F. Wesson 

EH&S (Environmental Health and Safety) Global 

Regulatory Affairs The Dow Chemical Company (Dow) 
4

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0077 

Robert E. Williams II 

Environmental Department 

FirstEnergy Corporation (FE) 

EPA-HQ-OAR-2008-0708-0078 

Russ D. Santiago 

Operations Superintendent, Port Allen Generating Station 

Kauai Island Utility Cooperative (KIUC) 

EPA-HQ-OAR-2008-0708-0079 

Bruce D. Alexander 

Environmental Regulatory Strategies Director 

Exelon Corporation 

EPA-HQ-OAR-2008-0708-0080 

Darryl Hoffman 

Utilities Program Manager 

Level 3 Communications, Inc. 

EPA-HQ-OAR-2008-0708-0081 

Kathleen Tobin 

Manager, Corporate Safety & Environmental Compliance 

Verizon Communications Inc. 

EPA-HQ-OAR-2008-0708-0082 

Don C. DiCristofaro 

CCM, President 

Blue Sky Environmental LLC 

EPA-HQ-OAR-2008-0708-0083 

Bruce J. Parker 

President and Chief Executive Officer (CEO), National 

Solid Wastes Management Association (NSWMA) and 

John H. Skinner 

Executive Director and Chief Executive Officer (CEO) 

Solid Waste Association of North America (SWANA) 

EPA-HQ-OAR-2008-0708-0084 

Incomplete Comment (No attachment) Innoventive Power, LLC & CPower, Inc. 

EPA-HQ-OAR-2008-0708-0085 

Support the comments of 

EPA-HQ-OAR-2008-0708-0084 

Demand Response Service Providers (DRSP Coalition) 

Innovative Power, LLC & CPower, Inc. 

EPA-HQ-OAR-2008-0708-0086 

Vincent St. Angelo 

Environmental Engineering 

Babcock & Wilcox Nuclear Operations Group 

(B&W NOG-L) 

EPA-HQ-OAR-2008-0708-0087 

Michael Garvin 

Assistant Vice President 

Scientific and Regulatory Affairs 

Pharmaceutical Research and Manufacturers of America 

(PhRMA) 

EPA-HQ-OAR-2008-0708-0088 

Michael Bradley 

 Director 

The Clean Energy Group (CEG) 
5

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0089 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

Kathleen M. Sgamma 

Director of Government Affairs 

Independent Petroleum Association of Mountain States 

(IPAMS) 

EPA-HQ-OAR-2008-0708-0090 

Steven A. Kent 

Manager -Standby Generation 

Industrial Energy Applications, Inc. (IEA) 

EPA-HQ-OAR-2008-0708-0091 

EPA-HQ-OAR-2008-0708-0096 

Joseph L. Suchecki 

Engine Manufacturers Association (EMA) 

EPA-HQ-OAR-2008-0708-0092 

Debbie Angotto 

Facilities Coordinator, on behalf of 

Thomas L. (surname illegible) 

Greenwich Hospital, Greenwich, CT 

EPA-HQ-OAR-2008-0708-0093 

EPA-HQ-OAR-2008-0708-0211 

Trina L. Vielhauer 

Chief, Bureau of Air Regulation 

Division of Air Resource Management 

Florida Department of Environmental Protection 

EPA-HQ-OAR-2008-0708-0094 

EPA-HQ-OAR-2008-0708-0165 

Laurel L. Kroack 

Chief, Bureau of Air 

Illinois Environmental Protection Agency (Illinois EPA) 

EPA-HQ-OAR-2008-0708-0095 

Reynaldo Tuazon 

Utilities Manager 

Adventist Hinsdale Hospital 

EPA-HQ-OAR-2008-0708-0097 

EPA-HQ-OAR-2008-0708-0163 

Kasey Gabbard 

Permits & Policy Group 

NiSource 

EPA-HQ-OAR-2008-0708-0098 

Brian W. Green 

Air Quality Specialist 

RRI Energy, Inc. 

EPA-HQ-OAR-2008-0708-0099 

Support the comments of 

EPA-HQ-OAR-2008-0708-0096 

Brady Winkleman 

Caterpillar Inc. 

EPA-HQ-OAR-2008-0708-0100 

EPA-HQ-OAR-2008-0708-0208 

Support the comments of 

EPA-HQ-OAR-2008-0708-0096 

Lynn Palmer 

Vice President, Engineering 

Dresser Waukesha 

EPA-HQ-OAR-2008-0708-0101 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0104 

EPA-HQ-OAR-2008-0708-0111 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0225 

EPA-HQ-OAR-2008-0708-0242 

Lee O. Fuller 

Independent Petroleum Association of America (IPAA) et 

al. 
6

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0102 

Scott W. Snedden 

HSE Manager 

Westlake Longview Corporation 

EPA-HQ-OAR-2008-0708-0103 

John Dutton 

HSE Committee Chairman 

Gas Compressor Association (GCA) 

EPA-HQ-OAR-2008-0708-0104 

Angie Burckhalter 

Vice President, Regulatory Affairs 

Oklahoma Independent Petroleum Association (OIPA) 

EPA-HQ-OAR-2008-0708-0105 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

Orland T. Pylant, 

Director, 

Compliance CenterPoint Energy-Mississippi River 

Transmission Corporation (MRT) 

EPA-HQ-OAR-2008-0708-0106 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

Laura L. Guthrie 

Manager, Air Program 

CenterPoint Energy Field Services, Inc. (CEFS)

EPA-HQ-OAR-2008-0708-0107 

Phil Kairis 

Vice President 

Energy Alternatives 

EPA-HQ-OAR-2008-0708-0108 

Bruce Chrisman 

Manager, Engineering 

Cameron Compression Systems 

EPA-HQ-OAR-2008-0708-0109 

Mark A. Young 

Executive Director 

Lowell Regional Wastewater Utility (LRWWU) 

EPA-HQ-OAR-2008-0708-0110 Union Pacific Railroad Company 

EPA-HQ-OAR-2008-0708-0111 

Frank Mortl 

President/Chief Executive Officer (CEO) 

Michigan Oil And Gas Association (MOGA) 

EPA-HQ-OAR-2008-0708-0112 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

Johnny Dreyer 

Director of Industry Affairs 

Gas Processors Association (GPA) 

EPA-HQ-OAR-2008-0708-0113 

EPA-HQ-OAR-2008-0708-0222 

John P. Duraes 

President 

New England Healthcare Engineers' Society (NEHES) 

EPA-HQ-OAR-2008-0708-0115 

Christopher Collins 

Source Water Manager 

Pawtucket Water Supply Board (PWSB) 

EPA-HQ-OAR-2008-0708-0116 

G. Vinson Hellwig 

Michigan and 

Robert H. Colby 

Chattanooga, Tennessee, Co-Chairs, Air Toxic 

Committee 

National Association of Clean Air Agencies (NACAA) 
7

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0117 Anonymous 

EPA-HQ-OAR-2008-0708-0118 

Robin Seguin 

CHMM, Environmental Manager, Qwest Risk 

Management 

Qwest 

EPA-HQ-OAR-2008-0708-0119 

EPA-HQ-OAR-2008-0708-0143 

Marie Robinson 

Chairperson, National Telecommunications Safety Panel 

(NTSP) AT&T Services, Inc. 

EPA-HQ-OAR-2008-0708-0120 

Matt Shields 

Milford Facilities Manager 

Milton Cat 

EPA-HQ-OAR-2008-0708-0121 

Valerie Ughetta 

Director, Stationary Sources 

Alliance of Automobile Manufacturers 

EPA-HQ-OAR-2008-0708-0122 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

John B. Kuhn 

Global Air Leader 

Celanese Corporation 

EPA-HQ-OAR-2008-0708-0123 

EPA-HQ-OAR-2008-0708-0134 

Jim Griffin 

Senior Director 

American Chemistry Council (ACC) 

EPA-HQ-OAR-2008-0708-0124 

EPA-HQ-OAR-2008-0708-0235 

Tim Knox 

Vice President, Engineering and Production 

Compressor Systems, Inc. (CSI) 

EPA-HQ-OAR-2008-0708-0125 

Martin E. Rock, P.E., J.D. 

President & Senior Principal 

OMNI Professional Environmental Associates, P.A. 

EPA-HQ-OAR-2008-0708-0126 

F. William Brownell and Craig S. Harrison 

Hunton & Williams LLP on behalf of the 

Utility Air Regulatory Group (UARG) 

EPA-HQ-OAR-2008-0708-0127 

Julie Frazier 

Senior Environmental Specialist 

Butler County Water and Sewer Department (BCWS) 

EPA-HQ-OAR-2008-0708-0128 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

Nicholas DeMarco 

Executive Director 

West Virginia Oil and Natural Gas Association 

EPA-HQ-OAR-2008-0708-0129 

Cathy Waxman 

Manager 

Air Quality Compliance, National Grid 

EPA-HQ-OAR-2008-0708-0130 

Steve Hensley 

Senior Director Regulatory Affairs 

USA Rice Federation 

EPA-HQ-OAR-2008-0708-0131 

John Dutton 

Manager, Operations 

J-W Power Company 
8

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0132 

Gerald Meinecke 

Vice President - Procurement & Compression 

Exterran 

EPA-HQ-OAR-2008-0708-0133 

Jim Griffin 

Senior Director 

American Chemistry Council (ACC) 

EPA-HQ-OAR-2008-0708-0135 

R. J. Riley 

Texas Agriculture Energy Users Association (TAEUA) 

and 

Texas Corn Growers Association 

EPA-HQ-OAR-2008-0708-0136 

EPA-HQ-OAR-2008-0708-0237 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0045 

EPA-HQ-OAR-2008-0708-0046 

EPA-HQ-OAR-2008-0708-0104 

EPA-HQ-OAR-2008-0708-0242 

Darren Smith 

Manager, Environmental Health and Safety (EHS) 

Devon Energy Corporation 

EPA-HQ-OAR-2008-0708-0137 

Tim Knox 

Vice President 

Engineering and Production 

Compressor Systems, Inc. (CSI) 

EPA-HQ-OAR-2008-0708-0138 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0101 

EPA-HQ-OAR-2008-0708-0104 

Gregory D. Russell 

Vorys, Sater, Seymour and Pease LLP on behalf of 

Ohio Oil and Gas Association (OOGA) 

EPA-HQ-OAR-2008-0708-0139 Craig Eckberg 

NRG Energy, Inc. 

EPA-HQ-OAR-2008-0708-0140 

Golder Associates Inc. on behalf of 

David A. Buff 

Principal Engineer 

Mosaic Fertilizer LLC (Mosaic) 

EPA-HQ-OAR-2008-0708-0141 

John Preczewski 

P.E., Assistant Director 

State of New Jersey Department of Environmental 

Protection (NJDEP) 

EPA-HQ-OAR-2008-0708-0142 

Michael S. Dae 

Wellfield and Environmental Compliance Manager 

Energy Developments, Inc. (EDI) 

EPA-HQ-OAR-2008-0708-0144 

Richard T. Wolbach 

CEM, Department of Physical Plant 

The University of Vermont (UVM) 

EPA-HQ-OAR-2008-0708-0145 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

Debra A. Ristig 

Vice President, Engineering and Compliance 

CenterPoint Energy Gas Transmission Company (CEGT) 
9

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0146 

Karl M. Bhatnagar, P.E., 

ESH&M, Air Quality 

Northrop Grumman, Aerospace Systems (NGAS) 

EPA-HQ-OAR-2008-0708-0147 

David A. Buff 

Principal Engineer, Golder Associates Inc. on behalf of 

The Florida Sugar Industry (FSI)

EPA-HQ-OAR-2008-0708-0148 

Ethan W. Hinkley 

Environmental Compliance Specialist, Air Quality 

Red Cedar Gathering Company 

EPA-HQ-OAR-2008-0708-0149 

Kathryn Garcia 

Commissioner 

New York City Department of Environmental Protection 

(NYCDEP) 

EPA-HQ-OAR-2008-0708-0150 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

Patrick J. Nugent 

Executive Director 

Texas Pipeline Association (TPA) 

EPA-HQ-OAR-2008-0708-0151 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

Bruce Thompson 

 President 

American Exploration and Production Council (AXPC) 

EPA-HQ-OAR-2008-0708-0152 Shannon S. Broome 

Air Permitting Forum 

EPA-HQ-OAR-2008-0708-0153 

Marilyn Leland 

Executive Director 

Alaska Power Association 

EPA-HQ-OAR-2008-0708-0154 

Robert D. Bessette 

President 

Council of Industrial Boiler Owners (CIBO) 

EPA-HQ-OAR-2008-0708-0156 

Kevin D. Bailey 

Air Compliance Supervisor 

ExxonMobil Production Company 

EPA-HQ-OAR-2008-0708-0157 

EPA-HQ-OAR-2008-0708-0096 

EPA-HQ-OAR-2008-0708-0123 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0221 

EPA-HQ-OAR-2008-0708-0242 

Debra J. Jezouit and 

 Megan Berge 

Baker Botts L.L.P. on behalf of 

Class of '85 Regulatory Response Group 

EPA-HQ-OAR-2008-0708-0158 

Terry L. Steinert 

Environmental Compliance Manager 

Koch Carbon, LLC (Koch Carbon) 
10

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0159 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0257 

Mary Uhl 

Chief, Air Quality Bureau (AQB) 

New Mexico Environment Department (NMED) 

EPA-HQ-OAR-2008-0708-0160 

EPA-HQ-OAR-2008-0708-0257 

Cynthia Finley 

Director, Regulatory Affairs 

National Association of Clean Water Agencies 

(NACWA) 

EPA-HQ-OAR-2008-0708-0161 

Dave Copeland 

Manager, Air Quality, Corporate Safety & Environmental 

Services Praxair, Inc. 

EPA-HQ-OAR-2008-0708-0162 

Kathryn R. Ross 

Senior Environmental Planner 

Consumers Energy Company 

EPA-HQ-OAR-2008-0708-0164 

Mary Uhl 

Air Quality Bureau 

New Mexico Environment Department (Incomplete) 

EPA-HQ-OAR-2008-0708-0166 

Aandy Ly, PE CEM 

Director, Facilities Management & Planning, Energy 

Administration & Operations 

Boston University (BU) 

EPA-HQ-OAR-2008-0708-0167 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0121 

EPA-HQ-OAR-2008-0708-0154 

Lawrence W. Kavanagh 

Vice President 

American Iron and Steel Institute (AISI) and 

Bruce A. Steiner 

President 

American Coke and Coal Chemicals Institute (ACCCI) 

EPA-HQ-OAR-2008-0708-0168 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0126 

William T. Horton 

Senior Environmental Specialist 

Environmental Health and Safety Air Management 

Duke Energy Corporation (Duke Energy) 

EPA-HQ-OAR-2008-0708-0169 

Rick N. Soucy 

Senior Project Manager 

GZA GeoEnvironmental, Inc. 

EPA-HQ-OAR-2008-0708-0170 

Mark Macarro 

Tribal Chairman 

Pechanga Band of Luiseno Indians (Tribe) 

EPA-HQ-OAR-2008-0708-0171 

Mark J. Sedlacek 

Director 

Environmental Services 

Los Angeles Department of Water and Power (LADWP) 

EPA-HQ-OAR-2008-0708-0172 

Kerwei Sew 

Senior Environmental Engineer, Environmental 

Operations 

3M Company 
11

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0173 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0206 

T. Moser 

Chairman, Strategic Team and Resource Sharing 

(STARS) 

Integrated Regulatory Affairs Group 

EPA-HQ-OAR-2008-0708-0174 

Mark Maslyn 

Executive Director, Public Policy 

American Farm Bureau Federation (AFBF) 

EPA-HQ-OAR-2008-0708-0175 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0241 

Pamela A. Lacey 

Senior Managing Counsel 

American Gas Association (AGA) 

EPA-HQ-OAR-2008-0708-0176 

Deirdre K. Hirner 

Executive Director 

Illinois Environmental Regulatory Group (IERG) et al. 

EPA-HQ-OAR-2008-0708-0177 

Shawne C. McGibbon 

Acting Chief Counsel for Advocacy and 

Keith Holman 

Assistant Chief Counsel for Environmental Policy, Office 

of Advocacy 

U.S. Small Business Administration (SBA) 

EPA-HQ-OAR-2008-0708-0178 

Lisa Goldberg 

Director, Environment, Safety and Health 

Aerospace Industries Association of America (AIA) 

EPA-HQ-OAR-2008-0708-0179 

Marilyn Crockett 

Executive Director 

Alaska Oil and Gas Association (AOGA) 

EPA-HQ-OAR-2008-0708-0181 

EPA-HQ-OAR-2008-0708-0243 

Scott Davis 

Director, Environmental, Health & Safety 

Arizona Public Service (APS) 

EPA-HQ-OAR-2008-0708-0182 

Shawn Wade 

Director, Communications 

Plains Cotton Growers, Inc. (PCG) 

EPA-HQ-OAR-2008-0708-0183 

Don Mark Anthony 

Air Quality Engineer 

Alyeska Pipeline Service Company (Alyeska) 

EPA-HQ-OAR-2008-0708-0184 

Jack F. Alvey 

Vice President, Generation 

Indiana Municipal Power Agency (IMPA) 

EPA-HQ-OAR-2008-0708-0185 

Earl C. Burke 

Facilities Engineering Manager 

Baltimore Washington Medical Center (BWMC) 
12

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0186 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

William W. (Bill) Grygar II 

Environmental and Regulatory Manager 

Anadarko Petroleum Corporation 

EPA-HQ-OAR-2008-0708-0187 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0096 

EPA-HQ-OAR-2008-0708-0155 

Karen St. John 

Director, Regulatory Affairs 

BP America Inc. (BP) 

EPA-HQ-OAR-2008-0708-0188 

Steve Donatiello, P.E. 

Senior Environmental Engineer 

Laclede Gas Company 

EPA-HQ-OAR-2008-0708-0189 

Ricke A. Kress 

President 

Southern Gardens Citrus Holding Corporation 

EPA-HQ-OAR-2008-0708-0190 

Stuart Latham 

Manager, Land and Environmental 

Southern Star Central Gas Pipeline, Inc. (Southern Star) 

EPA-HQ-OAR-2008-0708-0191 

EPA-HQ-OAR-2008-0708-0239 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0083 

EPA-HQ-OAR-2008-0708-0126 

EPA-HQ-OAR-2008-0708-0155 

Skiles Boyd 

Vice President, Environmental Management and 

Resources 

DTE Energy 

EPA-HQ-OAR-2008-0708-0192 Terry Steinert 

Koch Carbon LLC 

EPA-HQ-OAR-2008-0708-0193 

James D. Jones 

Senior Consultant, EHS Services North America 

Alcoa Inc. 

EPA-HQ-OAR-2008-0708-0194 

Larry LeJeune 

Director, Pesticide and Environmental Programs Division, 

Office of Agricultural and Environmental Sciences 

Louisiana Department of Agriculture and Forestry 

EPA-HQ-OAR-2008-0708-0195 

Michael L. R. Housley 

President 

Legacy Energy Group, LLC 

EPA-HQ-OAR-2008-0708-0196 

Sarah E. Amick 

Environmental Counsel 

Rubber Manufacturers Association (RMA) 

EPA-HQ-OAR-2008-0708-0197 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0126 

Nilaksh Kothari 

General Manager 

Manitowoc Public Utilities (MPU) 

EPA-HQ-OAR-2008-0708-0198 

Bernard Milam 

Energy Manager 

University of Maryland Medical Center (UMMC) 
13

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0199 

Joseph Kubsh 

Executive Director 

Manufacturers of Emission Controls Association (MECA) 

EPA-HQ-OAR-2008-0708-0200 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0242 

Michelle Koch 

HES (Health/Environment/Safety) Professional 

Marathon Oil Corporation 

EPA-HQ-OAR-2008-0708-0201 

Chad Gregory 

Senior Vice President 

United Egg Producers (UEP) 

EPA-HQ-OAR-2008-0708-0202 

Theresa Pfeifer 

Regulatory Compliance Officer 

Metro Wastewater Reclamation District 

EPA-HQ-OAR-2008-0708-0203 

Caroline Choi 

Director, Energy Policy & Strategy 

Progress Energy 

EPA-HQ-OAR-2008-0708-0204 

Jon E. Kallen 

Manager, Environmental Policy and Strategy 

MidAmerican Energy Holdings Company 

EPA-HQ-OAR-2008-0708-0205 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

Michael Tomko 

Counsel, Parsons Behle & Latimer on behalf of 

Utah Industry Environmental Coalition (UIENC) 

EPA-HQ-OAR-2008-0708-0206 

Amy Van Kolken Banister 

Senior Director, Air and Landfill Gas Programs and 

Kerry Kelly 

Director, Federal Public Affairs 

Waste Management (WM) 

EPA-HQ-OAR-2008-0708-0207 

EPA-HQ-OAR-2008-0708-0126 

John C. Butler 

Director, Operations Support 

Nuclear Energy Institute (NEI) 

EPA-HQ-OAR-2008-0708-0209 

Stephen R. Gossett, P.E. 

Senior Environmental Associate 

Eastman Chemical Company (ECC) 

EPA-HQ-OAR-2008-0708-0210 

Supports the comment of 

EPA-HQ-OAR-2008-0708-0155 

Vincent L. Brindley 

Principal Environmental Engineer 

El Paso Pipeline Group 

EPA-HQ-OAR-2008-0708-0212 

G. William Fowler 

Attorney, on behalf of the 

West Texas Gas Inc. (WTG) 

EPA-HQ-OAR-2008-0708-0213 

Ed Torres 

Director of Technical Services 

Orange County Sanitation District (OCSD) 

EPA-HQ-OAR-2008-0708-0214 

Brian Bonnell 

Senior Manager, Strategic Sourcing and Procurement 

Human Genome Sciences 
14

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0215 

Hilary Sinnamon 

Consultant 

Environmental Defense Fund (EDF) 

EPA-HQ-OAR-2008-0708-0216 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0088 

EPA-HQ-OAR-2008-0708-0157 

EPA-HQ-OAR-2008-0708-0207 

Rayburn L. Butts 

Director, Environmental Services 

Florida Power and Light Company (FPLC) 

EPA-HQ-OAR-2008-0708-0217 Michael Hutcheson 

Ameren Corporation 

EPA-HQ-OAR-2008-0708-0218 

EPA-HQ-OAR-2008-0708-0233 

Supports comments of 

EPA-HQ-OAR-2008-0708-0155 

Everette Johnson 

Director, Engineering 

Cameron Compression Systems 

EPA-HQ-OAR-2008-0708-0219 

Dan Pugliese 

Director, Engineering 

Hines 

EPA-HQ-OAR-2008-0708-0220 

Cathy S. Formigoni 

Legal Assistant, Hodge Dwyer & Driver on behalf of 

Illinois Municipal Electric Agency (IMEA) 

EPA-HQ-OAR-2008-0708-0221 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

Deb Hastings 

Vice President, Environmental Affairs 

Texas Oil and Gas Association (TXOGA) 

EPA-HQ-OAR-2008-0708-0223 

Elizabeth A. Rubino 

SVP Human Resources 

QVC 

EPA-HQ-OAR-2008-0708-0224 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0155 

Edward L. Kropp 

Chair, Air Subcommittee, Environmental Committee 

West Virginia Chamber of Commerce 

EPA-HQ-OAR-2008-0708-0225 

Deborah Seligman 

Vice President, Governmental Affairs 

New Mexico Oil & Gas Association (NMOGA) 

EPA-HQ-OAR-2008-0708-0226 

Shawne C. McGibbon 

Acting Chief Counsel and 

Kevin Bromberg 

Assistant Chief Counsel, Environmental Policy, Office of 

Advocacy Small Business Administration (SBA) 

EPA-HQ-OAR-2008-0708-0227 

Quinn V. Kilty 

Manager 

Air/Water, Xcel Energy, Inc. 

EPA-HQ-OAR-2008-0708-0228 

Eric L. Riser 

Jorden Bischoff & Hiser 

PLC Counsel for Nucor Corporation 
15

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0229 

Carl H. Batliner 

Director, Environmental Affairs 

AK Steel Corporation 

EPA-HQ-OAR-2008-0708-0230 

Andrew C. Lawrence 

Director, Office of Nuclear Safety, Quality Assurance and 

Environment, Office of Health, Safety and Security 

U.S. Department of Energy (DOE) 

EPA-HQ-OAR-2008-0708-0231 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0242 

John Robitaille 

Vice President 

Petroleum Association of Wyoming (PAW) 

EPA-HQ-OAR-2008-0708-0232 

David R. Bell 

Sustainability Engineer, Facilities Supervisor 

Becton Dickinson Diagnostic Systems 

Baltimore Campus 

EPA-HQ-OAR-2008-0708-0234 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

Ann W. McIver 

QEP, Director, Environmental Stewardship 

Citizens Gas 

EPA-HQ-OAR-2008-0708-0236 

John Quinn 

Director, Environmental Issues 

Constellation Energy 

EPA-HQ-OAR-2008-0708-0238 

EPA-HQ-OAR-2008-0708-0248 

EPA-HQ-OAR-2008-0708-0252 

Karl M. Kyriss 

President 

Aqua America, Inc. 

EPA-HQ-OAR-2008-0708-0240 

Bruce R. Byrd 

Vice President and General Counsel-Washington 

AT&T Services, Inc. 

EPA-HQ-OAR-2008-0708-0241 

Supports comments of 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0175 

William D. Schrand 

Administrator, Environmental Programs 

Southwest Gas Corporation 

EPA-HQ-OAR-2008-0708-0244 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0112 

EPA-HQ-OAR-2008-0708-0155 

Richard Bye 

Director, Environmental Services 

CenterPoint Energy, Inc. 

EPA-HQ-OAR-2008-0708-0245 

Ronald J. Schott Esq. 

Senior Corporate Counsel, Environment, Health and 

Safety 

Wyeth 

EPA-HQ-OAR-2008-0708-0246 Jim Valentine 

Combustion Components Associates, Inc. (CCA) 
16

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0247 

Supports the comments of 

EPA-HQ-OAR-2008-0708-0126 

EPA-HQ-OAR-2008-0708-0155 

EPA-HQ-OAR-2008-0708-0175 

Pamela F. Faggert 

Vice President and Chief Environmental Officer 

Dominion Resources Services, Inc. 

EPA-HQ-OAR-2008-0708-0249 

Kenneth D. Schisler 

Senior Director, Regulatory Affairs 

EnerNOC, Inc. (EnerNOC) 

EPA-HQ-OAR-2008-0708-0250 

Michael A. Caldarera 

Vice President, Regulatory and Technical Services 

National Propane Gas Association (NPGA) 

EPA-HQ-OAR-2008-0708-0251 

Marielle Daniels 

Manager, Patient Care Regulation 

Connecticut Hospital Association (CHA) 

EPA-HQ-OAR-2008-0708-0253 

EPA-HQ-OAR-2008-0708-0258 

EPA-HQ-OAR-2008-0708-0260 

Sean M. O’Keefe 

Director, Environmental Affairs 

Alexander & Baldwin, Inc. (A&B) 

EPA-HQ-OAR-2008-0708-0255 

John Otto 

Engineering Manager 

Brush Resources, Inc. 

EPA-HQ-OAR-2008-0708-0256 

Craig Wysong 

EHS Manager 

CARBO Ceramics, Inc. 

EPA-HQ-OAR-2008-0708-0259 

John Prescott 

Executive Vice President and General Manager 

Power Resources Cooperative (PRC) 

EPA-HQ-OAR-2008-0708-0261 

Michael H. Bernard 

President 

Mid-Continent Oil and Gas Association of Oklahoma 

(MCOGAO) 

EPA-HQ-OAR-2008-0708-0262 

Ed Hasely, Sr. 

Environmental Engineer 

Energen Resources 

EPA-HQ-OAR-2008-0708-0263 

Michael J. Kelly 

Director, Facilities Management 

University of Massachusetts Memorial Medical Center 

(UMassMMC) 

EPA-HQ-OAR-2008-0708-0264 

Chelly Reesman 

Environmental Engineer 

J.R. Simplot Company 

EPA-HQ-OAR-2008-0708-0265 

Scott Salisbury 

President 

Landfill Energy Systems 
17

Document ID Commenter/Affiliation

EPA-HQ-OAR-2008-0708-0267 

Jeffrey A. Smith 

Lead Environmental Scientist, Infrastructure Maintenance 

Division 

South Florida Water Management District 

EPA-HQ-OAR-2008-0708-0268 

Peter H. Zeliff 

President and CEO 

Innovative Energy Systems 

EPA-HQ-OAR-2008-0708-0269 

Ronnie Anderson 

President 

Louisiana Farm Bureau Federation (LFBF) 

EPA-HQ-OAR-2008-0708-0270 

Stephanie Cheng 

Chair, Air Issues and Regulations (AIR) Committee 

Bay Area Clean Water Agencies (BACWA) 
18

Summary of Public Comments and Responses 

The summary of public comments and responses is organized as follows:

1.0 General Approach 

2.0 Applicability 

2.1 Area Sources 

2.2 Small Engines 

2.3 Diesel Engines 

2.4 Other 

3.0 Startup, Shutdown, and Malfunction 

4.0 Emissions 

 4.1 RICE Emissions Database 

 4.2 Surrogates 

 4.3 Engine Test Data 

5.0 Emission Limits 

 5.1 Major Sources 

 5.1.1 MACT Floor 

 5.1.2 Subcategories 

 5.2 Area Sources 

 5.3 Emergency Stationary Engines 

 5.4 Small Engines 

 5.5 Diesel Engines 

 5.6 Format of Standards and Other Issues Related to Standards 

 5.7 Technology 

6.0 Exemptions/Special Allowances 

 6.1 Emergency Engines 

 6.2 Limited Use Engines 

 6.3 Nuclear Plants 

6.4 Other Engines 

7.0 Management Practices 

 7.1 General Comments 

 7.2 Specific Requirements 

8.0 Parameter Monitoring 

9.0 Compliance 

 9.1 Test Procedures 

 9.2 Test Methods 

 9.3 Frequency 
19

 9.4 Other 

10.0 Recordkeeping, Reporting and Notifications 

11.0 Fuel Requirements 

12.0 Docket Materials/Transparent Regulatory Process 

13.0 Rule Impacts 

 13.1 Economic Impacts 

 13.2 Environmental/Health Impacts 

 13.3 Cost of Controls 

 13.4 Implementation and Enforcement 

 13.5 Energy Impacts 

 13.6 Small Businesses 

14.0 Miscellaneous 

 14.1 Definitions 

 14.2 Clarifications 

 14.3 Errors 

 14.4 Discrepancies 

 14.5 Other 
20

1.0 General Approach 

1.1 Comment: A few commenters (61, 94, 116) support EPA’s proposed rulemaking. One 

commenter (94) supports EPA’s proposed actions to reduce exhaust pollutants from existing 

stationary RICE that are located at area sources of HAP emissions and certain existing stationary 

RICE and stationary compression ignition (CI) engines that are located at major sources of HAP 

emissions. One commenter (116) commended the EPA for proposing a regulation that will 

reduce HAP and diesel emissions from the RICE source category. 

Response: No response is needed.

1.2 Comment: A few commenters (155, 224 and 242) are concerned with how the proposed 

rulemaking is in some cases the first in addressing recent Court decisions. The commenters 

characterize some of the recent issues as including the following: 

• The Brick maximum achievable control technology (MACT) decision determined that 

EPA must set standards for HAP and cannot avoid standards in cases when the MACT 

floor is based on sources that have no added emission controls, 

• The Brick MACT decision indicated that EPA has to consider the range of emission level 

associated with the best performing sources; and 

• The rejection of the startup, shutdown and malfunction (SSM) exemption meaning that 

HAP emission standards must apply continuously. The Court expressed the need for 

some standard, but this does not mean an unchanging standard. 
21

The commenters state that the proposed rule is setting a precedent, but the commenters 

(155, 242) noted that there is no clear evidence of how EPA considered integrating these 

decisions into the rulemaking. Regarding the MACT floor decisions, the commenters (155, 242) 

believe the floor was based on flawed and deficient data. The commenters (155, 242) do not 

believe EPA has considered emissions variability. For SSM limits, the commenters (155, 242) 

said that EPA has set limits without any data from actual SSM events. The importance of 

integrating these Court decisions warrants considerable additional effort by EPA for this 

rulemaking, the commenters (155, 242) said. Commenters 155 and 242 specifically addressed 

each particular issue in separate comments, but noted that the issues reach beyond this 

rulemaking and will convey the Agency’s perspective that may be applied to future rulemakings. 

For these reasons, the commenters (155, 242) firmly believe that EPA should provide guidance 

material to communicate to the public the Agency’s interpretation of Court decisions and how 

those will be incorporated into future rules. 

Response: EPA understands the commenters’ concerns with respect to recent court decisions 

affecting how the regulations for existing stationary engines at area sources and existing 

stationary engines less than or equal to 500 HP were developed. The U.S. Court of Appeals for 

the District of Columbia Circuit on March 13, 2007 vacated EPA’s MACT standards for the 

Brick and Structural Manufacturing category (40 CFR part 63, subpart JJJJJ). This is referred to 

as the “Brick MACT decision” (Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007).) EPA 

recognizes that it had limited emissions data when it developed the MACT floor standards for 

the proposed rule. EPA has on several occasions requested emissions data from industry and 

solicited data in the preamble to the proposed rule. However, EPA had to propose emission 
22

standards based on what data was available at the time. During the public comment period and 

the months following the close of the public comment period, EPA has worked with various 

groups and been able to gather additional emissions test data for stationary engines. EPA has 

reviewed the original emissions test data used to develop the proposed standards to ensure that 

engines were properly identified and categorized, as well as to determine if there was any other 

information that may indicate that the data was used inappropriately at proposal. 

For the proposed MACT floor for existing engines at major sources, EPA selected the 

best performing 12 percent of sources it had emissions data for within each engine subcategory 

and averaged the emissions from those 12 percent. Commenters argued that EPA’s approach at 

proposal did not consider emissions variability. The approach at proposal counted each 

emissions test as a single data point. This meant that for cases where an engine was tested 

multiple times, the MACT floor may have included multiple data points from one engine, but 

only one data point from another engine. Commenters argued that this approach does not 

sufficiently take into account emissions variability or potentially inappropriately skews the 

MACT floor toward the one engine that was tested multiple times because with multiple data 

points emissions from that engine would have more weight in the top 12 percent. EPA believes 

that it is appropriate to use a different approach to incorporate emissions variability in the final 

standards. Subsequently, EPA has reanalyzed the available emissions data and considered 

different ways of taking into account the range of emissions that can occur. In the final rule, 

EPA has incorporated variability by considering the range of emissions that can be seen across 

different loads and during a single test. EPA believes that this approach more accurately 

considers variability in emissions. EPA discussed the final approach in setting the MACT floor 

limits more extensively in the memo entitled “MACT Floor and MACT Determination for 
23

Existing Stationary Non-Emergency CI RICE Greater Than or Equal to 100 HP Located at Major 

Sources.” 

 Regarding the proposed SSM limits, EPA received numerous concerns from affected 

stakeholders on a range of issues. These issues are discussed in Section 3.0. EPA is not 

finalizing particularized numerical emission limits specifically for periods of SSM, but is issuing 

work practice standards for periods of startup and including periods of shutdown and 

malfunction within the emission standards that generally apply to the various subcategories of 

stationary CI engines. The reasons for the approach we take in the final rule are discussed in the 

responses to comments in Section 3.0. 

EPA plans to make implementation and compliance material available to the regulated 

community following the promulgation of this rule. However, EPA cannot promise that such 

material will include the Agency’s interpretation of Court decisions and how those will be used 

in future rules. 

1.3 Comment: Several commenters (89, 93, 101, 104, 112, 129, 150, 151, 172, 186, 221, 231, 

242, 261, 264) noted concerns due to a complex proposed rulemaking and some commenters 

added that it is extra problematic to implement due to previous rulemakings issued that affect 

similar and sometimes the same engines. One commenter (242) noted that it has a number of 

outstanding and unresolved petitions submitted to EPA on the CI NSPS and spark ignited (SI) 

new source performance standards (NSPS)/NESHAP, where it has questions concerning 

implementation and enforcement of those rules. There is ongoing confusion among State and 

regional agencies in implementing these rules, something that is exacerbated by EPA’s lack of 

response and guidance on several implementation questions, the commenter (242) said. 
24

According to the commenter (242), the inclusion of natural gas engines with diesel engines in 

this rulemaking will lead to a further increase in unresolved, issues complicating rule 

requirements and implementation. For example, for the SI NSPS/NESHAP, the commenter 

(242) pointed out various issues, which included a discussion on the integration of risk-based 

criteria for area source engines under the NESHAP. For that rulemaking, compliance with the 

NESHAP was mostly shown by demonstrating compliance with the NSPS, therefore it seems the 

comment went largely unanswered by EPA, the commenter (242) said. The commenter (242) 

indicated that it was hoping EPA would address this issue in this rulemaking, but has not. In 

general, the commenter (242) recommended that EPA develop and publish substantive 

compliance tools and provide assistance in interpreting rule requirements from multiple 

overlapping engine rules. 

Commenters 89, 101, 151, 221, 231 stated that the rules are complex because of their 

overlap with and references to the mobile source engine rules (i.e., for automobiles, boats, 

construction equipment, etc.). The commenters (89, 101, 151, 221, 231) believe that the mobile 

source rules are not well understood by the agencies and industries involved with the stationary 

source rules, and added that EPA has done little to aid the agencies and industry in understanding 

these rules. Additionally, the commenters (89, 101, 151, 221, 231) believe that EPA should 

delay promulgation of these rules until compliance assistance material can be developed to aid 

the state agencies and regulated community in their compliance efforts. 

Two commenters (112, 150) contended that each of these engine regulations has brought 

significant changes to control requirements, training, monitoring, recordkeeping, and reporting. 

In addition, the commenter (112) pointed out that both the Consolidated Engine Rule and the CI 

NSPS are still under litigation by API. The commenter (112) believes that the proposed 
25

regulations add tremendously to the current requirements by bringing existing engines under the 

rules with more stringent requirements than new or reconstructed sources. The commenter (112) 

stated that its member companies have serious concerns with interpreting the complex current 

and proposed compliance requirements and asked that EPA attempt to simplify existing federal 

engine rule requirements before the SI rules are finalized. 

 The commenter (112) noted that determining applicability of the rule requires companies 

to define engines as existing, new, or reconstructed, which is difficult, and often impossible, 

primarily because records that are required to determine if the engine has been reconstructed may 

be on multiple authorizations for expenditures (AFEs) or may simply not exist. The commenter 

(112) said that most, if not all, states have preconstruction authorizations that require companies 

to begin the permitting process well in advance of commencement of construction. The 

permitting process is complicated because specific regulatory requirements cannot be determined 

until the unit is overhauled and the final invoices are received, according to commenter 112. 

Frequently, engines are leased and returned to distributors and later purchased or leased by other 

companies and records get lost or possibly never obtained or maintained, making it nearly 

impossible for the new owner to establish a complete life history of an engine, commenter 112 

added. Commenter 112 also pointed out that competing companies may be reluctant or 

unwilling to share their records with new owners. Also, in absence of sufficient documentation, 

some companies may make the conservative assumption that the rule applies, while others will 

assume by lack of documentation that the rule does not apply, the commenter (112) said. 

Two commenters (112 and 150) said that a modified engine could be “new” under NSPS 

and “existing” under NESHAP because NESHAP considers only reconstruction and not 

modification, whereas NSPS considers both reconstruction and modification. 
26

The commenter (112) additionally indicated that subpart ZZZZ is already very complex 

due to the numerous cross references to the mobile source regulations in 40 CFR parts 90 and 

1068, as well as the 2008 amendments that added requirements for new small lean burn engines 

at major sites. The commenter (112) believes that adding this proposed major amendment to 

cover existing sources would make subpart ZZZZ even more difficult for both regulatory 

agencies and industry to interpret and for those who are subject, to comply. To simplify the 

proposed regulation, several commenters (89, 101, 112, 151, 221, 231, 242) recommended a new 

separate section, subpart ZZZZa. Commenter 261 suggested a similar separation of subsections 

and that EPA should delay promulgation until compliance assistance material can be developed 

to aid the State agencies and regulated community in their compliance efforts. 

Commenter 150 said that the complexity has been exacerbated by the fact that the 

applicability of some requirements is uncertain due to ongoing litigation. The commenter (150) 

believes that the proposed rules will add to the complexity by bringing in existing engines. The 

commenter (150) gave the following examples of instances when it will be difficult to determine 

which rules apply to which engines: 

• Applicable requirements are different depending on whether an engine had or had not 

been reconstructed. Making that determination would be difficult or impossible in some 

cases because records may be hard to locate and hard to access or they may no longer 

exist. 

• Requirements may differ based on whether a source is a major source or minor source. 

As engines were added or subtracted, the facility’s status could vary, and so could the 

applicable rules. In this regard, the commenter (150) believes that EPA should allow a 

facility sufficient time to come into compliance when a facility’s status changes due to 
27

addition or removal of equipment. The commenter (150) proposed a 3-year compliance 

period, which the commenter said was done in the NESHAP for natural gas transmission 

and storage [40 CFR 63.1270(d)(1)]. 

One commenter (93) provided an 18-page applicability flow chart to illustrate the 

permitting and compliance applicability requirements for the subject engines. The commenter 

(93) reported that differing state agency flow charts and guidance materials reviewed by them 

(Texas and Nebraska) have reached different interpretations regarding the applicability of the 

proposed rule. The commenter (93) stated that this highlights concerns regarding the rule’s 

complexities, which the commenter believed could result in inconsistent implementation 

throughout the country. The commenter (93) further reported that it had received numerous 

telephone calls from consultants outside of Florida asking for the commenter’s interpretation of 

the proposed changes in an effort to gain a general consensus of the states on the rule’s 

applicability. For example, a new category was proposed for existing emergency SI engines with 

a site rating of less than or equal to 500 HP located at a major source of HAP. The commenter 

(93) reported that they were able to determine the emission and operating limitations, 

maintenance requirements and equipment needed. However, they stated that the compliance 

requirements (40 CFR 63.6630 Table 5 in the Appendix) are clearly identified for only a few 

specific engine categories and then appear to group the rest of the engine categories in one large 

category of engines with a site rating of less than or equal to 500 HP located at a major source of 

HAP. The commenter (93) expressed that it is unclear if this large category is meant to be 

inclusive or exclusive of the remaining specific engines categories, such as emergency engines 

and SI engines. 
28

The commenter (93) recommended that EPA revise the NESHAP to specify all the 

applicable requirements under a given engine category subheading. The commenter (93) opined 

that, this way, applicability would then only need to be determined once for each engine category 

as the applicable requirements (emissions and operating limitations, general compliance 

requirements, etc.) would be specified by regulated engine category. 

Response: The engines that are subject to the NSPS are new engines and are not the focus of this 

rulemaking. EPA, therefore, does not believe that those issues will affect this rulemaking. EPA 

notes that it is required to promulgate standards for new engines under section 111 NSPS 

provisions and for new and existing engines under section 112 NESHAP provisions. Much of 

the complication commenters discuss results from the straightforward implementation of the 

requirements of the Clean Air Act. In terms of having a combined rulemaking for natural gas 

and diesel engines, EPA does not think that this complicates the rule. Issuing a rulemaking that 

addresses all types of stationary engines regardless of fuel type is consistent with how the 

original 2004 RICE NESHAP was developed. 

 It is not true that there are multiple overlapping engine rules for existing engines. This 

rule addresses engines that have not been addressed before, i.e., existing stationary engines at 

area sources and existing stationary engines less than or equal to 500 HP at major sources. EPA 

has not issued regulations for these engines previously, but noted in earlier final rules that EPA 

would be addressing these engines in the future. Since the final CI NSPS and SI NSPS rules 

covered only new stationary engines and the original 2004 RICE NESHAP covered only 

stationary engines at major sources greater than 500 HP, there are no other requirements 

affecting existing stationary engines at area sources. There are also no other requirements 
29

affecting existing stationary engines less than or equal to 500 HP located at major sources since 

again, the CI NSPS and SI NSPS rules covered only new stationary engines and the original 

2004 RICE NESHAP covered only stationary engines at major sources greater than 500 HP. 

Commenters expressed concern regarding overlap and references to mobile sources rules. 

It is not clear what the commenters’ concerns are because there are minimal references to the 

mobile source regulations in the proposed rule. EPA recognizes that individual owners and 

operators may not be familiar with the mobile source requirements. That is one reason why this 

rulemaking is focused on source-specific requirements and is not a manufacturer-based program. 

In the NSPS rules for new CI and SI stationary engines it made sense to implement a program 

that addresses emissions from engines at the point of manufacturing rather than when these 

engines are installed in the field, and to coordinate the requirements for new stationary engines 

with requirements for similar new mobile engines. The coordination of mobile and stationary 

engine requirements has in fact reduced the complexity of meeting EPA regulations for these 

new engines, since manufacturers and users of such engines can comply by meeting the same 

standards whether they are mobile or stationary. 

In this regulation, since it affects existing stationary engines, the engines are already 

located at the affected source. EPA has made reference to the mobile source rules only when 

absolutely necessary in order to demonstrate that for example certain control technologies or 

fuels are currently available and technically feasible. Other references include citing parts of 40 

CFR part 80, which contain the specifics of the fuel requirements for existing non-emergency 

diesel engines. Therefore, it is unclear what references to the mobile source rules the 

commenters are referring that are problematic. 
30

EPA cannot delay promulgation of the final rule due to a court-ordered schedule 

requiring EPA to finalize the regulation by February 10, 2010. As discussed elsewhere in this 

document, EPA has already previously delayed the rulemaking affecting existing stationary 

engines at area sources and existing stationary engines less than or equal to 500 HP at major 

sources. 

In the final rule, EPA has made an effort to promulgate requirements that are as clear as 

possible and that minimize the burden of implementing these requirements. In conjunction with 

the promulgation of the final rule, EPA will publish this Response to Comments (RTC) 

Document, which summarizes the comments EPA received on the proposed rule and EPA’s 

responses to each comment. The RTC document will explain and provide supporting rationale 

for EPA’s regulatory decisions. The document will also be helpful as a compliance assistance 

tool in cases where commenters have asked for clarification on certain issues. Further, EPA also 

plans to provide other compliance assistance and implementation material to help sources in 

demonstrating compliance with the final rule. 

As far as the comment regarding the compliance period when a facility’s status changes 

from a minor to a major source, EPA already includes provisions in 63.6595(b) of the rule that 

allows an area source that becomes a major source, where construction or reconstruction is 

commenced before the date the area source becomes a major of HAP, up to 3 years to comply 

with the rule. EPA believes this addresses the commenter’s concern on this issue. 

1.4 Comment: Numerous commenters (38, 39, 41, 42, 45, 46, 130, 194, 205) believe that the 

comment period provided in the proposal was inadequate. Two commenters (45, 46) requested a 

90-day extension to the public comment period for the proposed rule, to August 3, 2009. The 
31

commenters (45, 46) believe that due to the breadth of coverage and implications for thousands 

of existing RICE, the proposed 60-day comment deadline is entirely inadequate to assess 

implications, review background documentation, and develop comments supported with 

complete technical data and facts. The commenters (45, 46) asserted that, in light of the pending 

EPA proposed rule that addresses Mandatory Reporting of Greenhouse Gases (GHGs) and 

affects the same stakeholders, failure to grant an extension will undermine the ability to provide 

necessary comments and respond effectively to either rule proposal. One commenter (39) 

requested an additional 90 days to comment in order to develop a more comprehensive analysis 

and subsequent comment submittal to EPA. Commenter 40 agreed with commenter 39, but said 

that if a 90-day extension was not provided that at least 60 days be provided. 

The commenter (45) added that it will take time to fully assess the implications of the 

proposed rule because it affects thousands of smaller engines at area source facilities that 

historically have been considered exempt or inconsequential emission sources. The commenter 

(45) asserted that his organization’s historical comments have been consistent with the 

administration goal of science-based decision making, and that a limited comment period will 

compromise scientific integrity in the decision making for the proposed rule. The commenter 

(45) understands that EPA’s schedule is constrained by a commitment to develop a final diesel 

engine rule, but believes that if a 90-day extension cannot be accommodated, at least an 

additional 60-days extension (i.e., 120 days total) is necessary. In the alternative, the commenter 

(45) suggested removing natural gas-fired engines from the proposal (see Section 1.2). 

Commenter 38 supported a 60-day extension. 

Due to the breadth of coverage and implications for thousands of existing engines, two 

commenters (41, 42) believe that the 60-day comment deadline is inadequate to assess 
32

implications, review background documentation, and develop comments substantiated with 

technical data and facts. Additionally, in order to prepare joint comment for its member 

companies, the commenter (41) must coordinate among its member companies, making location 

of relevant information and preparation of comments on the proposal in 60 days difficult. 

One commenter (194) requested on behalf of the agricultural industry in its state that 

EPA allow further consideration and review time to allow a more detailed comment to be 

submitted. 

Response: EPA provided a 30-day extension to the public comment period to allow additional 

time for commenters to prepare and submit their comments. EPA could not provide additional 

time beyond the 30 days due to the court-ordered deadline for the final rule of February 10, 

2010. In addition, EPA attempted to the best of its ability to review information that came to the 

Agency from the public after the end of the comment period. 

1.5 Comment: Two commenters (176, 220) expressed that it is inappropriate for EPA to use 

section 112 of the CAA to target non-HAP pollutants. The commenter (176) opined that EPA 

addresses criteria pollutants, both in terms of the degree to which such pollutants are emitted 

from these types of engines, and the benefits that the proposed compliance requirements would 

have on criteria pollutants to justify regulation of engines located at area sources that have 

minimal impact on urban areas from HAP emissions. 

Response: EPA is not using the CAA to target non-HAP pollutants from existing stationary 

RICE, but is applying the use of a surrogate for HAP emissions from certain engines. Measuring 
33

emissions of HAP is in many cases much more expensive than measuring surrogate emissions 

and setting a standard in terms of a single pollutant would mean simpler and cheaper emissions 

testing. Formaldehyde is the HAP emitted in the largest quantity from stationary RICE and is 

related to the level of other HAP emissions. Therefore, formaldehyde is an appropriate 

representation of HAP emissions. EPA studied emissions data to determine if CO would be 

representative of HAP emissions. Because EPA determined that there is a relationship between 

CO and formaldehyde for certain engine types, EPA is using CO as a surrogate for HAP 

emissions for these engines. Also, while EPA’s standards are based on HAP reductions, there is 

no reason to ignore the co-benefits of the rule in terms of reduction in non-HAP pollutants when 

calculating the benefits of the rule. 

1.6 Comment: One commenter (69) opposes the proposed rulemaking because it imposes a 

tremendous hardship on the regulated community; strains the resources needed to demonstrate 

and/or achieve compliance, and is of marginal benefit, particularly for the oil and gas industry. 

The commenter (69) suggests that the proposal rule should be stayed indefinitely, or at least 

phased until a more favorable economic time. 

Response: EPA is required by statute to develop regulations for all existing stationary engines to 

address HAP emissions under sections 112(d), 112(c)(3) and 112(k) of the CAA. To the extent 

possible, EPA has attempted to minimize the burden on the regulated community, but EPA does 

not believe that the requirements are significantly burdensome. EPA does not have the option to 

delay the rulemaking due to consent decrees requiring EPA to finalize and issue the regulation 

by February 2010. 
34

1.7 Comment: Four commenters (64, 66, 68, 75) requested that EPA provide additional time for 

Alaska to develop its arguments further if EPA did not agree that the proposed NESHAP 

requirements are not appropriate for rural Alaska. 

Response: EPA believes that the comment period provided for the proposed rule was sufficient 

and that additional time is not necessary. See comment 2.2.3 for EPA’s response to the 

comments related to the requirements for engines located in rural Alaska.

1.8 Comment: Several commenters (89, 101, 103, 130, 136, 151, 155, 167, 172, 187, 221, 224, 

226, 231, 241, 242) think that EPA should attempt to harmonize the proposed rule requirements 

with requirements in the other stationary engine rules (2004 RICE NESHAP, CI NSPS, SI 

NSPS, and 2008 RICE NESHAP revisions) in order to simplify the implementation process. 

According to commenter 155, owners/operators of the stationary engine rules have experienced 

issues with implementing these rules. 

The commenter (242) thinks that EPA should simplify and harmonize the various engine 

rules to simplify the implementation and enforcement process. As mentioned, the regulated 

community has been having issues and a hard time implementing the various engine rules that 

have been issued by EPA over the years since 2004 when the first engine rule was published. 

This proposed rulemaking will add to the confusion with competing requirements and other 

issues, the commenter (242) said. EPA should revisit rule requirements and think about options 

to harmonize requirements across rulemakings, the commenter (242) recommended. The 

commenter (242) referred to EPA simplifying the reporting and recordkeeping requirements for 
35

engines subject to the NESHAP (new and reconstructed) under the 2008 rulemaking. Those 

engines were allowed to demonstrate compliance by meeting the NSPS. However, the current 

proposal affecting existing engines will result in these existing engines having more onerous 

recordkeeping and reporting requirements than what is required for new engines, the commenter 

(242) said. In addition, existing engines will in some cases have more stringent emission limits 

than new engines, the commenter (242) noted. The commenter (242) suggested that EPA think 

about separating the requirements for existing area sources and existing small engines at major 

sources into a new subpart (e.g., subpart ZZZZa). In the new subpart, EPA could clearly indicate 

that only certain provisions of 40 CFR part 63, subpart A GP (GP) apply to these engines so that 

similar reporting, recordkeeping and maintenance requirements apply for the NSPS and subpart 

ZZZZa affected engines, the commenter (242) recommended. 

Commenter 136 noted that the 2004 RICE MACT and 2008 Consolidated NSPS and 

NESHAP engine rule and this proposed rule are inconsistent; for example, the proposed 

standards for some existing RICE are more stringent than the recent emission standards for 

new/reconstructed RICE. Commenters 130 and 136 believe that EPA should allow areas source 

RICE that require control to comply with the NSPS requirements in lieu of NESHAP 

requirements. Further, the commenter (136) urged that EPA simplify and harmonize the rules to 

avoid contradictions and minimize the potential for compliance and enforcement confusion. 

One commenter (103) stated that the requirements for all of the different rules (original 

40 CFR part 63, subpart ZZZZ; part 60, subpart JJJJ; and now revised part 63, subpart ZZZZ) are 

overly burdensome. The commenter (103) indicated that EPA should consider having standards 

for area sources that are consistent for all rules, and noted that new sources already have this 

standard, but existing sources are treated differently under this proposal. 
36

 The commenter (103) asserted that specific surrogates for HAP are not needed for area 

sources if an overall level of performance can be demonstrated by the engine. The commenter 

(103) asserted that if the costs for controls for rural area sources can be justified, then surrogates 

for the existing engines should be the same as for new sources. As an example, the commenter 

(103) indicated that if an existing rich burn engine is operating at NSPS standards (2.0 grams per 

horsepower-hour (g/HP-hr) NOx, 4 g/HP-hr carbon monoxide (CO), and 1.0 g/HP-hr volatile 

organic compounds (VOC)) then the NSCR can be considered to be functioning correctly and 

HAP will be reduced even though formaldehyde is not measured directly. 

One commenter (172) noted that there were inconsistent thresholds between these 

proposed rules and the related SI and CI NSPS, creating complications. For instance, engine size 

in the CI NSPS is defined in terms of cylinder displacement, while HP or kilowatt (KW) ratings 

are used in other rules. 

Another commenter (172) noted that while EPA based setting the 300 HP subcategory for 

CI RICE and the 250 HP subcategory for SI RICE on where the greatest emission reductions are 

achieved, the multiple levels resulted in more confusion. The commenter (172) suggested that 

500 HP be kept as the cutoff to identify a “large” engine for greater consistency and clarity. 

Response: To the extent possible, EPA has attempted to harmonize requirements and make 

provisions consistent across rulemakings affecting stationary engines. Existing stationary 

engines addressed in this rulemaking are not covered in the NSPS rules. In the CI and SI NSPS 

rules, EPA is primarily relying on engine manufacturer certifications. For engines likely to be 

covered under a certification program, EPA believes it is more appropriate to lessen the 

recordkeeping, reporting, and testing requirements on the individual owners and operators 
37

because of engine certificates. However, for existing stationary engines covered in this 

rulemaking, EPA is relying on each individual owner and operator to demonstrate compliance 

with the requirements. Records and testing are necessary to demonstrate that the engine is 

meeting the emission standards and that other requirements in the rule are followed 

appropriately. Also, NESHAP and NSPS rulemakings are developed under different sections of 

the statute and address different pollutants. In the NESHAP, EPA must address HAP emissions, 

but in the NSPS, EPA must address criteria pollutants like NOx, CO, and PM. 

 Regarding the comments that requirements applicable to existing stationary engines may 

be more stringent than the requirements for new stationary engines, EPA understands the 

concerns. However, due to the recent Brick MACT decision, which said that EPA could not set 

MACT floors of no emission reduction, EPA had to take a different approach in setting standards 

for existing stationary engines than was taken in earlier regulations. The outcome of the Brick 

MACT decision and the SSM decision occurred after the previous engine rulemakings and 

therefore EPA cannot help the fact that standards may become more stringent for older engines 

under a different analysis. 

In response to the comment regarding inconsistent threshold across rules, EPA again 

notes that the rules, in particular the NESHAP versus NSPS rules, rules for new versus existing 

engines, and rules for engines at major sources versus area sources, are developed to address 

different statutory requirements. Further, in the rules targeting new engines, EPA relied heavily 

on a manufacturer-based certification program. For both NSPS regulations, but more so in the 

CI NSPS, EPA modeled emission standards and requirements in the nonroad engine rules 

affecting similar engines. In those two rules, the emission standards were mostly targeted to 

engine manufacturers and since EPA followed nonroad requirements in many cases, it made 
38

sense to adopt engine size thresholds and emission standards similar to, and in the same units as 

was done in the nonroad engine rules. 

2.0 Applicability 

2.1 Area Sources 

2.1.1 Comment: Numerous commenters (64, 66, 68, 75, 104, 111, 112, 124, 131, 132, 136, 148, 

150, 155, 175, 183, 187, 225, 226, 241, 247, 253, 261, 262) expressed concern over EPA’s 

decision to not distinguish between rural and urban engines at area sources in the proposed rule. 

Several commenters (64, 66, 68, 75, 104, 112, 136, 183, 226) requested that EPA reevaluate its 

congressional authority to regulate area HAP sources in rural areas. The commenter (112) 

believes that the proposal is inconsistent with 42 U.S.C. 7412(n)(4)(B) [CAA section 

112(n)(4)(B)], which states that: 

“The Administrator shall not list oil and gas production wells (with its associated equipment) as 

an area source category under subsection (c) of this section, except that the Administrator may 

establish an area source category for oil and gas production wells located in any metropolitan 

statistical area or consolidated metropolitan statistical area with a population in excess of 

1 million, if the Administrator determines that emissions of hazardous air pollutants from such 

wells present more than a negligible risk of adverse effects to public health.” 

 Three commenters (104, 112, 136) requested clarification of EPA’s rationale to regulate 

low levels of emissions from engines at oil and gas production facilities outside metropolitan 

areas, contending that EPA has applied this rule more broadly than the Congressional intent of 
39

the CAA, and requested that EPA reevaluate this issue of whether EPA can regulate rural area 

sources in light of the 42 U.S.C. 7412(n)(4)(B) language. 

One commenter (220) stated most of its members are located at area sources in non-urban 

locales, where HAP emissions from the affected engines, some of which are emergency engines, 

are unlikely to impact urban areas. Thus, engines located at non-urban sources should be exempt 

from the requirements of the proposed rule. Commenter 220 added that EPA has not made a 

case for such stringent regulation of units in non-urban areas, particularly where operation of 

such units is minimal. EPA should only impose requirements for non-emergency units in urban 

areas. 

Four commenters (111, 150, 187, 225) stated that EPA has based this rulemaking for area 

sources on sections of the CAA and its Urban Air Toxics Strategy that are intended to remove 

threats to public health in urban areas. The commenters (111, 150, 225) do not believe that the 

remote RICE at area sources in the oil and gas industry threaten public health in urban areas. 

Three of the commenter (150, 187, 225) noted that the NESHAP for glycol gas dehydrators (40 

CFR part 63, subpart HH) takes into account the location of area sources and does not apply the 

specific requirements of the rule to rural area sources. The commenters (150, 225) believe that 

the same approach should be used for the RICE rule, i.e., engines that are not located in or near 

populated areas should be exempt or subject to an alternative set of requirements so as not to 

force expensive requirements on remote engines that have no impact on public health. In 

particular, one of these commenters (150) stated that rural sources should be excluded from 

requirements relating to catalytic controls. 

 One commenter (111) questioned the rationale for the statement in the proposal preamble 

the “it would not be practical or appropriate to limit the applicability to urban areas....” 
40

Regarding practicality, the commenter (111) stated that urban area and urban cluster boundaries 

have been well defined by the Census Bureau (2000 Census) and that it would be easy to 

determine whether a facility is inside or outside these boundaries. Regarding appropriateness, 

the commenter (111) stated that the rationale in the proposal preamble does not relate the density 

of RICE to population density nor other HAP sources, both stationary and mobile, while the 

1999 Integrated Urban Air Toxics Strategy document (which is the basis of this proposal) stated 

that “the vast majority of HAP emissions...are within counties with urban areas. Additionally, a 

greater number of different HAP may be emitted from the multiple sources present in urban 

areas than from the more limited number and variety of sources present in rural areas.” The 

commenter (111) indicated that significant impacts from small sources in non-urban areas are 

dependent on them being additive to another major emitter (i.e., at major sources) or dependent 

on multiple sources of the same or different types being located within additive impact areas. 

 The commenter (111) noted that the monetized benefits of the proposed rule (74 FR 

9712) do not distinguish between rural and urban benefits. The commenter (111) anticipates that 

the risk avoidance benefits would be skewed to urban populations and requested that the benefits 

be analyzed in this manner if rural sources are to be included in the rule. In addition, the 

commenter (111) requested that the rule be limited to urban areas as defined in the 1999 Urban 

Air Toxics Strategy document or, at a minimum, be limited to major sources (RICE less than or 

equal to 500 HP) in rural areas if a clear positive cost/benefit can be demonstrated. 

Several commenters (112, 124, 131, 132, 148, 155, 175, 187, 241, 242, 247, 253, 261, 

262) cited rules where EPA considered urban proximity by allowing owners/operators to 

determine whether their engines were located in an urban area by the distance to an urban cluster 

as defined by the U.S. Census Bureau. For those rules, requirements and implementation 
41

schedules are based on location, and units that are considered non-urban show compliance by 

meeting work practices. 

Several commenters recommended that EPA follow 40 CFR part 63, subpart HH for 

existing stationary engines and only require work practices for area sources engines in rural area. 

Commenter 241 concluded that following urban criteria ((defined as urban areas [UA] plus a 2 

mile buffer area and urban clusters [UC] greater than 10,000)) that parallel 40 CFR part 63, 

subpart HH, the final rule could provide an exemption for area source engines located in a rural 

area or require GACT work practices rather than MACT-equivalent emission limits. In addition, 

commenters 97 and 241 stated that with technology and cost limitations for emissions 

measurement and a lack of emissions data, EPA should consider section 112(h) of the CAA 

alternatives for promulgating design, equipment, work practice, or operational standards. 

Similarly, commenter 112 concluded that the proposed rules will be onerous and costly, and 

should not be imposed at area sources in rural areas unless the science supports the need for this 

type of regulation. The commenter (112) stated that engines in the oil and gas industry are 

installed in the same areas as glycol dehydrators and are typically installed away from residences 

when possible to reduce noise disturbances to nearby residences. 

The commenter (253) disagreed with EPA’s conclusion that “it would not be practical or 

appropriate to limit the applicability to urban areas.” The commenter (253) noted that large 

numbers of stationary RICE in rural areas do not necessarily correlate with high ambient 

concentrations of HAP, especially since many of the RICE in rural areas are likely to be 

emergency generators or engines with similarly low operating hours. The commenter (253) 

believed that irrigation systems associated with farming activities in particular will typically be 

located in isolated rural areas and are unlikely to contribute to ambient concentrations of HAP 
42

that remotely approach those which Congress intended to be addressed through the area source 

program. The commenter (262) recommended that engines that are not located in or near 

populated areas be exempted from the rule, because they have no impact on public health. The 

commenter (253) urged EPA to consider excluding all RICE that are located at area sources on 

farms, in particular, RICE associated with irrigation pumps that are used to provide water for 

farming activities from the rule. 

Some commenters (97, 226, 247) believed that EPA should conduct an analysis of urban 

versus rural emissions and rural engine impacts on urban areas. Commenter 97 believes that the 

results of the analysis will warrant different standards, or overall exemption, for rural engines, 

especially those in remote locations. The commenter (97) stated that section 112(h) of the CAA 

provides alternative approaches to emission limits if it is infeasible to prescribe or enforce 

emission standards based on the technical and economic practicality of applying measurement 

methodology. The commenter (97) believes that EPA should consider additional opportunities 

to rely on management or operating practices for compliance. The commenter stated that 

management practices are warranted for area sources under GACT provisions, and for both area 

and major sources engines under CAA section 112(h). 

Several commenters (65, 111, 170, 194, 242) provided methods they suggested could be 

used to identify rural area sources and some provided examples specific to their locations as 

reasons why rural area sources need not be regulated. The commenter (242) observed that EPA 

has not determined the prevalence of engines in certain areas and is therefore issuing nationwide 

standards. The commenter (242) does not understand why nationwide standards were concluded 

as being appropriate with the lack of analysis conducted. Sources such as State and Federal 

emission inventories, Title V permits, Bureau of Land Management maps, original engine 
43

manufacturer records, pipeline maps, agricultural bureaus, etc. are available references that 

might indicate how engines are distributed, the commenter (242) said. One commenter (224) 

suggested that EPA analyze the impacts of engine emissions in rural areas on public health risk 

in urban areas for consistency with the CAA section 112(k) intent for area sources. The 

commenter (224) asserted that exemptions or less stringent standards for engines located at area 

sources in rural areas would likely be justified by such an analysis. 

One commenter (170) provided that compliance with 40 CFR part 63, subpart ZZZZ 

would be onerous and costly for its tribe, especially if engine replacement is required. The 

commenter (170) requested that the scope of 40 CFR part 63, subpart ZZZZ be limited to RICE 

located at major sources of HAP and areas sources of HAP within urban areas. The commenter 

(170) suggested that the definition of “urban area” be based on either population density or 

standard metropolitan statistical area (SMSA). The commenter (170) opined that it was the 

original intent of section 112(k) of the CAA and the associated strategy to control HAP 

emissions from area sources in urban areas. 

The commenter (170) asserted that most of the economic impacts of the proposed rule 

will occur in more rural areas (such as tribal lands) where reliable power sources are less readily 

available and stationary RICE are required to provide power for essential functions. The 

commenter (170) stated that the significantly lower population density of rural areas reduces the 

potential health risks due to the greater distance between emission sources and urbanized areas 

with dense population centers. The commenter (170) opined that the determination that there are 

high concentrations of stationary RICE in rural areas does not mean that these area sources 

expose a large number of persons to HAP emitted by stationary RICE. The commenter (170) 
44

stated that any assessment of potential public health risks should take into account local 

meteorology, and risks to public health before imposing area source regulations in rural areas. 

The commenter (111) asserted that the distribution of oil and gas production RICE in 

Michigan (where the commenter’s organization is located) suggests that neither of these 

conditions is met. Using geographic information systems software, geocoded gas well locations, 

and urban areas defined by the Census Bureau (urbanized areas plus urban clusters, 2000 

Census), the commenter (111) found that 98 percent of the gas wells are located in rural areas. 

Because the compressor engines, located near the gas production wells, are used to transport the 

gas from the production facilities to the sales lines, commenter (111) asserted that it follows that 

Michigan oil and gas production RICE are overwhelmingly located in rural areas. 

One state commenter (194) on behalf of the agricultural industry in their state, expressed 

that the operational area of these engines has not been studied to evaluate the environmental 

benefit obtained in congested areas as compared to open agricultural locations. This commenter 

(194) opined that there should be some measure of variable compliance provided in relation to 

the area of operation of these engines. 

Commenter 76 indicated that in this context EPA should also consider the fact that a 

distinction has not been made between urban and rural areas. The commenter (76) has several 

engines in remotely located areas, which work on remote start and shutdown limiting staff 

access, particularly in those cases where remote locations have to be reached by boat. 

Response: EPA is finalizing its proposal to regulate existing stationary CI engines located at 

area sources on a nationwide basis. EPA has not made a final determination with regard to 
45

existing SI engines at area sources, and will do so in the later rule finalizing regulations for SI 

engines. EPA believes that the CAA provides the Agency with the authority to regulate area 

sources nationwide. Section 112(k)(1) of the CAA states that “It is the purpose of this 

subsection to achieve a substantial reduction in emissions of hazardous air pollutants from area 

sources and an equivalent reduction in the public health risks associated with such sources 

including a reduction of not less than 75 per centum in the incidence of cancer attributable to 

emissions from such sources.” Consistent with this expressed purpose of section 112(k) of the 

CAA to reduce both emissions and risks, CAA section 112(k)(3)(i) requires that EPA list not less 

than 30 HAP that, as a result of emissions from area sources, present the greatest threat to public 

health in the largest number of urban areas. Sections 112(c)(3) and (k)(3)(ii) of the CAA require 

that EPA list area source categories that represent not less than 90 percent of the area source 

emissions of each of the listed HAP. Section 112(c) of the CAA requires that EPA issue 

standards for listed categories under CAA section 112(d). These relevant statutory provisions 

authorize EPA to regulate listed area source engines and not just engines located in urban areas. 

EPA believes that sections 112(c) and 112(k) of the CAA do not prohibit issuing area source 

rules of national applicability. EPA also disagrees with the statement that the proposal was 

inconsistent with section 112(n)(4)(B) of the CAA. The term “associated equipment” was 

defined for the purposes of subpart ZZZZ in the first RICE MACT rule not to include stationary 

RICE. EPA has not revisited that issue in this rule and the commenter has not provided 

sufficient reason to revisit that issue. 

EPA does not believe that existing stationary CI engines are more prevalent in rural areas 

than in urban areas. Indeed, EPA estimates that only 17 percent of stationary CI area source 

engines subject to the rule are located in rural areas, using the definitions used in the Urban Air 
46

Toxics Strategy. Given the requirement to regulate all engines in the source category in urban 

areas, we do not believe requiring regulation on a national basis is inappropriate. 

The majority of stationary CI engines are used for emergency purposes. EPA has 

estimated that 80 percent of stationary CI engines are emergency engines and EPA has taken 

steps in the final rule to reduce the burden on owners and operators of these engines. All 

emergency CI engines located at area sources of HAP emissions are subject only to management 

practices under the final rule. EPA has also determined that existing emergency engines located 

at residential, institutional, and commercial facilities that are area sources of HAP emissions 

were not included in the original Urban Air Toxics Strategy inventory and therefore are not 

included in the source category listing. In the final rule, EPA has specified that those engines are 

not subject to subpart ZZZZ. In addition, existing non-emergency CI engines less than or equal 

to 300 HP that are located at area sources of HAP emissions are also only subject to management 

practices. EPA believes that requiring management practices instead of specific emission 

limitations and/or control efficiency requirements on the majority of existing stationary CI 

engines at area sources alleviates concerns regarding costly and burdensome requirements for 

rural sources. 

For existing stationary non-emergency CI engines greater than 300 HP, EPA determined 

that GACT was the use of oxidation catalyst control. The commenters did not provide a reason 

that GACT would be different for non-emergency stationary CI engines located in rural areas. In 

determining GACT, EPA can consider factors such as availability and feasibility of control 

technologies and management practices, as well as costs and economic impacts. These factors 

are not different for existing stationary non-emergency CI engines in urban versus rural areas. 

For example, the availability of oxidation catalysts would be the same for urban and rural 
47

engines, and if an engine was in a rural location, that would not preclude an owner from being 

able to install aftertreatment controls. For the final rule, EPA estimated the capital cost of 

retrofitting an existing stationary non-emergency CI engine to be around $7,000 for a 300 HP 

engine. Annual costs of operating and maintaining the control device are estimated to be 

approximately $2,000 per year for the same engine. These costs would not be prohibitive for any 

engines and either rural or urban areas and are expected to be the same no matter the location. 

Furthermore, the controls that are expected to be used on non-emergency engines above 300 HP 

will have the co-benefit of PM reductions. PM emissions can travel tens or hundreds of miles 

from their source, so emissions from diesel engines in rural areas can impact urban populations. 

EPA’s Diesel Health Assessment Document1

 (Diesel HAD) classified exposure to diesel exhaust 

as “likely to be carcinogenic to humans by inhalation” at environmental levels of exposure. 

Other agencies at the international, federal and state level have come to similar conclusions.2 The 

EPA Diesel HAD provided insight into the possible ranges of lung cancer risk that might be 

present in the population resulting from environmental exposure to diesel emissions. Lifetime 

cancer risk may exceed 10-5 and could be as high as 10-3. Because of uncertainties, the analysis 

acknowledged that the risks could be lower than 10-4 or 10-5, and a zero risk from diesel exhaust 

exposure was not ruled out. This range of values includes numerous uncertainties and, as 

discussed in the Diesel HAD, does not constitute an Agency cancer unit risk range suitable for 

estimating the number of cancer cases resulting from exposure to diesel exhaust. EPA’s 1999 

                                                           

1 Health Assessment Document for Diesel Engine Exhaust,’’ U.S. Environmental Protection 

Agency, 600/8–90/057F, http://www.epa.gov/ttn/atw/ dieselfinal.pdf, May 2002. 

2

 A number of other agencies (National Institute for Occupational Safety and Health, the 

International Agency for Research on Cancer, the World Health Organization, California EPA, 

and the U.S. Department of Health and Human Services) have made similar classifications 

regarding the diesel exhaust lung cancer hazard. 
48

National-Scale Air Toxics Assessment (NATA) does not include a quantitative estimate of 

cancer risk for diesel exhaust, but it concludes that diesel exhaust ranks with the other emissions 

that the national-scale assessment suggests pose the greatest relative risk.3 The purpose of this 

national-scale assessment is to provide a perspective on the magnitude of risks posed by outdoor 

sources of air toxics and to identify the pollutants and sources that are important contributors to 

these health risks. 

The Diesel HAD established an inhalation Reference Concentration (RfC) of 5 μg/m3 for 

diesel exhaust as measured by diesel PM.4 The Diesel HAD concludes “that acute exposure to 

DE [diesel exhaust] has been associated with irritation of the eye, nose, and throat, respiratory 

symptoms (cough and phlegm), and neurophysiological symptoms such as headache, 

lightheadedness, nausea, vomiting, and numbness or tingling of the extremities.”5 There is also 

evidence of immunologic effects such as the exacerbation of allergenic responses to known 

allergens and asthma-like symptoms. 

Diesel exhaust is a mixture that includes HAP that are known or suspected human 

carcinogens or have noncancer effects, including benzene, 1,3-butadiene, formaldehyde, 

acetaldehyde, polycyclic organic matter (POM), and naphthalene. Benzene6 and 1,3-butadiene7

are known human carcinogens. Noncancer health effects may include neurological, 

                                                           

3

 For more information on NATA, see http://www.epa.gov/ttn/atw/nata1999/risksum.html. 

4

 An RfC is defined by EPA as “an estimate of a continuous inhalation exposure to the human 

population, including sensitive subgroups, with uncertainty spanning perhaps an order of 

magnitude, which is likely to be without appreciable risks of deleterious noncancer effects during 

a lifetime.” 

5

 “Health Assessment Document for Diesel Engine Exhaust,” U.S. Environmental Protection 

Agency, 600/8–90/057F, http://www.epa.gov/ttn/ atw/dieselfinal.pdf, May 2002, p. 9–9.

6 Integrated Risk Information System File for Benzene, U.S. Environmental Protection Agency, 

http://www.epa.gov/ncea/iris/subst/0276.htm, 2000.

7 Integrated Risk Information System File for 1,3-Butadiene, U.S. Environmental Protection 

Agency, http://www.epa.gov/ncea/iris/subst/0139.htm, 2002.
49

cardiovascular, liver, kidney, and respiratory effects, as well as effects on the immune and 

reproductive systems. 

Several of the HAP emitted by diesel engines (e.g., acrolein, benzene, 1,3-butadiene, 

formaldehyde, naphthalene, and POM) were identified in EPA’s 1999 NATA as national or 

regional cancer and/or noncancer risk drivers.8 However, EPA does not have high confidence in 

the NATA data for all these compounds.9 It should be noted that the NATA modeling 

framework has a number of limitations which prevent its use as the sole basis for setting 

regulatory standards. These limitations and uncertainties are discussed on the 1999 NATA Web 

site. Even so, this modeling framework is very useful in identifying air toxic pollutants and 

sources of greatest concern, setting regulatory priorities, and informing the decision making 

process.10

Diesel emissions contain fine and ultra-fine PM and contribute significantly to ambient 

PM2.5 concentrations in many areas of the country.11 The nature of the effects that have been 

reported to be associated with fine particle exposures include premature mortality, aggravation of 

respiratory and cardiovascular disease (as indicated by increased hospital admissions and 

emergency department visits), changes in lung function and increased respiratory symptoms, as 

well as new evidence for more subtle indicators of cardiovascular health (71 FR 61152, October 

                                                           

8 More information on NATA risk drivers is available at: http://www.epa.gov/ttn/atw/nata1999/ 

risksum.html. 9 See ‘‘Control of Emissions From New Marine Compression-Ignition Engines at or Above 30 

Liters per Cylinder; Proposed Rule,’’ 72 FR 69521–69552, 

69534, http://www.epa.gov/fedrgstr/EPA-AIR/2007/December/Day-07/a23556.htm, December 

2007.

10 For more information on NATA, see http:// www.epa.gov/ttn/atw/nata1999/risksum.html. 11 ‘‘Health Assessment Document for Diesel Engine Exhaust,’’ U.S. Environmental Protection 

Agency, 600/8–90/057F, http://www.epa.gov/ttn/ atw/dieselfinal.pdf, May 2002, p. 2–97, Table 

2–23. 
50

17, 2006).12 The PM Air Quality Criteria Document also notes that the PM components of 

gasoline and diesel engine exhaust represent one class of hypothesized likely important 

contributors to the observed ambient PM-related increases in lung cancer incidence and 

mortality.13 The PM2.5 National Ambient Air Quality Standard is designed to provide protection 

from the noncancer and premature mortality effects of PM2.5 as a whole, of which diesel PM is a 

constituent.14

Diesel exhaust also includes NOx and volatile organic compounds, which react in the 

presence of sunlight to form ozone. Ozone contributes to serious public health problems, 

including aggravation of respiratory disease (as indicated by increased hospital admissions and 

emergency room visits, school absences, lost work days, and restricted activity days), changes in 

lung function and increased respiratory symptoms, altered respiratory defense mechanisms, and 

chronic bronchitis. In addition, there is suggestive evidence of a contribution of ozone to 

cardiovascular-related morbidity and highly suggestive evidence that short-term ozone exposure 

directly or indirectly contributes to non-accidental and cardiopulmonary-related mortality, but 

                                                           

12 Detailed information on the health effects of PM is provided in: ‘‘Air Quality Criteria for 

Particulate Matter,’’ U.S. Environmental Protection Agency, Volume I, EPA600/P–99/002aF 

and Volume II, EPA600/P–99/002bF, October 2004; ‘‘Review of the National Ambient Air 

Quality Standard for Particulate Matter: Policy Assessment of Scientific and Technical 

Information, OAQPS Staff Paper,’’ U.S. Environmental Protection Agency, EPA–452/R–05–

005, 2005; ‘‘National Ambient Air Quality Standards for Particulate Matter; Proposed Rule,’’ 71 

FR 2620–2708, 2626– 2637, http://www.epa.gov/air/particlepollution/ actions.html, January 17, 

2006 and ‘‘National Ambient Air Quality Standards for Particulate Matter; Final Rule,’’ 71 FR 

61144–61233, http:// www.epa.gov/air/particlepollution/actions.html, October 17, 2006.

13 ‘‘Air Quality Criteria for Particulate Matter,’’ U.S. Environmental Protection Agency, Volume 

I, EPA600/P–99/002aF and Volume II, EPA600/P–99/ 002bF, October 2004, p. 8–318.

14 Control of Emissions of Air Pollution From Locomotive Engines and Marine CompressionIgnition Engines Less Than 30 Liters per Cylinder; Proposed Rule,’’ 72 FR 15937–15986, 

15958, http://www.epa.gov/oms/locomotv.htm, April 3, 2007.
51

additional research is needed to more fully establish underlying mechanisms by which such 

effects occur.15 

There is also no reason to distinguish between the rural and urban area source engines 

that are subject to management practices. There is nothing limiting owners and operators of 

existing stationary CI engines located in rural areas from following the management practices 

specified in the final rule. 

In response to requests that agricultural stationary engines should be treated differently 

from other engines and should be allowed special provisions, EPA is of the understanding that 

the majority of stationary engines used for agricultural purposes are below 300 HP. Several 

commenters representing agricultural interests, including commenters 140, 147, and 174, have 

made the statement to EPA that most of their engines are below 300 HP. As previously 

discussed in this response, EPA is not issuing requirements that are based on the application of 

aftertreatment controls in the final rule, but is finalizing management practices for engines less 

than or equal to 300 HP. Therefore, it is not expected that many stationary agricultural engines 

will be required to put on controls. Agricultural engines less than or equal to 300 HP at rural and 

urban area sources would be required to follow the management practices specified in the final 

rule. Management practices will ensure that emissions are reduced and engines are properly 

operated. 

                                                           

15 Detailed information regarding the health effects of ozone[0] is provided in: ‘‘Air Quality 

Criteria for Ozone and Related Photochemical Oxidants (Final),’’ U.S. Environmental Protection 

Agency, EPA/600/R–05/004aF–cF, 2006, pp. 7–97 and 8–78; ‘‘Review of the National Ambient 

Air Quality Standards for Ozone: Policy Assessment of Scientific and Technical Information, 

OAQPS Staff Paper,’’ U.S. Environmental Protection Agency, EPA–452/R–07–003, January 

2007; and ‘‘National Ambient Air Quality Standards for Ozone: Proposed Rule,’’ 72 FR 37818–

37919, 37844 and 37836, http://www.epa.gov/air/ozonepollution/ actions.html, July 11, 2007.
52

Consistent with the proposal and for the reasons discussed, EPA is finalizing national 

requirements for existing stationary CI engines without a distinction between urban and nonurban areas. 

2.1.2 Comment: Five commenters (64, 65, 66, 68, 75) expressed that EPA’s proposal would 

have a significant impact to the State of Alaska, especially with respect to power generation in 

their rural communities. The commenter (65) explained that Alaska has unique regional 

circumstances whereby regulated diesel engine emissions in rural Alaska in the same manner as 

other engines nationwide could have unintended negative consequences. The commenter (65) is 

concerned about the extension of section 112(k) of the CAA requirements to rural sources, 

expressing that the purpose of CAA section 112(k) is to address urban issues. The commenter 

(65) opined that the scale of HAP emissions in rural areas of Alaska is different and should be 

addressed in a way that is appropriate to the rural conditions that exist there. The commenter 

(65) expressed that, historically, EPA has recognized the unique aspects of rural Alaska’s diesel 

distribution system and diesel engine use and has allowed Alaska some flexibility (e.g., under the 

CI NSPS). The commenter (65) requested that EPA assess and consider rural Alaska’s situation 

and allow for flexibility to address the challenges associated with the proposed rule. 

Four commenters (64, 66, 68, 75) disagreed with EPA that costs associated with 

implementing HAP reducing technology are reasonable and justified, and do not believe that 

MACT requirements are appropriate for rural area sources. The commenters (64, 66, 68, 75) 

stated that EPA lacks justification to implement MACT requirements for rural Alaska area 

source generators, when GACT is authorized under section 112(d)(5) of the CAA. The 

commenters (64, 66, 68, 75) stated a rural Alaska village using a pre-1996 diesel engine and 
53

approximately 100,000 gallons of fuel would emit less than 0.03 ton of HAP per year. The 

commenters (64, 66, 68, 75) estimated the cost effectiveness of adding HAP control would be 

$178,000 per ton of HAP reduction, which is twice the EPA estimate of $72,000 per ton of HAP 

reduction for a 200 HP engine. Therefore, the commenters (64, 66, 68, 75) believe that 

management practices should be GACT for area sources in rural Alaska. 

Response: The EPA agrees with the commenters that stationary CI engines located in remote 

areas of Alaska have special challenges that should be taken into consideration. As the 

commenters noted, over 180 rural communities in Alaska that are not accessible by the Federal 

Aid Highway System rely on stationary diesel engines and fuel for electricity. They are scattered 

over long distances in remote areas and are not connected to population centers by road or power 

grid. They are located in the most severe arctic environments in the United States. 

Transportation of diesel fuel to these areas is dependent on weather and communities typically 

pay some of the highest prices for fuel in the United States. Stationary engines located in rural 

areas of Alaska have different fuel storage and use logistics and higher operating and compliance 

costs. Many of these communities are accessible only by plane. In light of the comments, EPA 

believes it is appropriate to treat engines located at area sources in areas of Alaska that are not 

accessible by the Federal Aid Highway System (FAHS) as a separate subcategory. EPA reevaluated GACT for the subcategory of stationary engines located at area sources of HAP that 

are in an area of Alaska that is not accessible by the FAHS. For these engines, EPA determined 

that GACT is the same management practices as those required for non-emergency CI RICE less 

than or equal to 300 HP located at area sources. For more discussion of this issue, refer to the 

memo entitled “MACT Floor Determination for Existing Stationary Non-Emergency CI RICE 
54

Less Than 100 HP and Existing Stationary Emergency CI RICE Located at Major Sources and 

GACT for Existing Stationary CI RICE Located at Area Sources.” The management practices 

specify changing the oil and oil filter every 1,000 hours of operation (or 500 hours for 

emergency engines) or annually, whichever comes first, except that sources can extend the period for 

changing the oil if the oil is part of an oil analysis program as discussed below and none of the 

condemning limits are exceeded; inspecting the air cleaner every 1,000 hours of operation or 

annually, whichever comes first; and inspecting all hoses and belts and replacing as necessary 

every 500 hours of operation or annually, whichever comes first. Sources also have the option to 

use an oil change analysis program to extend the oil change frequencies. The analysis program 

must measure the total base number (TBN), viscosity, and water content. If the TBN is less than 

30 percent of the TBN of the oil when new, if the viscosity has changed by more than 20 percent 

from when the oil was new, or if the percent water content (by volume) is greater than 0.5, the oil 

must be changed. 

2.1.3 Comment: Two commenters (140, 148) suggested alternate ways to delineate major 

source RICE located in rural areas. Commenter 140 said its engines should not be regulated as 

major sources. Instead, EPA should clarify that RICE located in rural areas, used for mining or 

agricultural purposes, and operated for limited hours, will be subject to rules for area sources, 

even if such RICE are located at a major source. The commenter (140) concluded that there is 

no reason to impose new testing and emissions requirements on RICE units that, individually and 

collectively, are a very small source of HAP emissions. Alternatively, EPA could establish a 

separate subcategory of “rural” RICE under the major source category that would consider 

geographical location, emissions, and air quality impacts of these engines, the commenter (140) 
55

asserted. If established, this subcategory should have standards that are no more stringent than 

those promulgated for area sources, the commenter (140) said.

 

Response: EPA has to follow the definitions of a major source and an area source in CAA 

sections 112(a)(1) and (2). EPA is not at liberty to change those definitions, and EPA must 

regulate as major sources those stationary engines that are classified as being located at major 

sources under section 112(a). If a stationary engine is located at a source that has the potential to 

emit considering controls, in the aggregate, 10 tons per year or more of any HAP or 25 tons per 

year or more of any combination of HAP, it must be regulated as a major source. 

EPA is statutorily required to address HAP emissions from all existing major sources in 

listed source categories regardless of whether those sources are small or large or whether they 

are located in rural or urban areas. 

2.2 Small Engines 

2.2.1 Comment: Numerous commenters (51, 96, 116, 121, 132, 150, 154, 176, 225, 228, 230, 

262) said EPA must provide an appropriate applicability cut-off for smaller rated engines. 

Contrary to EPA’s statement that it does not expect to find engines of this size in the 

field, several members of the commenter’s (121) organization (automotive manufacturing) have 

engines at this level of HP supporting plant fire suppression or emergency systems. The 

formaldehyde limit is inappropriate for these CI engines, which cannot meet the limit. Some 

commenters (121, 154, 228) said that EPA should exercise de minimis authority to exclude 

smaller engines from the rule. At a minimum, smaller engines used in emergency applications 
56

should be excluded, commenter 121 said. The commenter (121) cited court cases supporting 

EPA’s use of such authority. The use of this authority is appropriate given the considerable cost 

per ton of HAP reduced with add-on controls for these smaller engines, according to commenter 

121. If EPA does not exclude such engines, it should at least subcategorize these engines and 

establish work practice standards, the commenter (121) said. 

The commenter (228) stated that the lack of a de minimis threshold sweeps in many 

facilities that operate a single small RICE, such as a remote repeater station that may rely upon a 

small RICE for backup power or even small motors used by hobbyists for various purposes. The 

commenter (228) stated that EPA has not explained how the emissions from these small units 

contribute significantly to the HAP exposure problem it seeks to redress, while inclusion of these 

sources creates substantial burdens on the agency, states, other air permitting authorities and 

enforcement offices. The commenter (228) added that under section 502(a) of the CAA, 

inclusion of these small sources potentially will require these small sources (e.g., the remote 

repeater backup power or a hobbyist) to obtain a Title V operating permit and may trigger 

permitting requirements under existing state and local permitting authority regulations. The 

commenter (228) stated that an operating permit requirement for such a small source imposes a 

considerable burden upon both the source and the permitting authority for little environmental 

gain. The commenter (228) noted that it is well within EPA’s discretion to exclude these small 

sources under its authority in section 112(c)(3) of the CAA. 

One commenter (176) reported that the state of Illinois exempts small engines from state 

permitting requirements when they are not covered from section 112 of the CAA. The 

commenter (176) asserted that the proposed rule would subject numerous owners and operators, 

who are not required to have a permit to operate their engines, to state permitting requirements. 
57

The commenter (176) expects that this would contribute to an increased delay in permitting and 

additional costs for owners and operators to obtain a permit. 

One commenter (51) believes that it is more important to regulate larger engines at all 

sources than to regulate small engines at area sources. One commenter (118) noted the 

questionable value of regulating small RICE (between 50 and 500 HP) at area sources. The 

commenter (118) noted that although the costs of the management practices would be minimal, 

some State rules are written such that they require any equipment subject to a MACT standard 

obtain a permit regardless how small the equipment may be. The commenter (118) felt that the 

air quality benefit of regulating these smaller sources is outweighed by the burden placed on area 

sources where a small engine may be their only equipment, and the administrative burden placed 

on the state agencies to administer permit programs for the large number of sources who would 

not otherwise be regulated. 

Response: EPA is required to regulate all engines in the stationary engine source category. The 

source category includes stationary engines of all sizes at major sources of HAP emissions. As 

discussed in the memorandum entitled “Analysis of the Types of Engines Used to Estimate the 

CAA Section 112(k) Area Source Inventory for Stationary Reciprocating Internal Combustion 

Engines” which is in the docket for this rule, EPA has found that existing stationary emergency 

engines located at residential, commercial, and institutional facilities were not included in the 

original Urban Air Toxics Strategy inventory and were not included in the listing of urban area 

sources and are therefore not included in the source category. In the final rule, EPA has 

specified that those engines are not subject to subpart ZZZZ. However, with regard to other 

stationary engines, EPA does not agree with the commenter who said that EPA should treat 
58

emissions from smaller engines as de minimis. It is unclear whether a de minimis exemption is 

even possible under section 112(d) of the Act in these circumstances, see National Lime Ass’n v. 

EPA, 233 F. 3d 625, 640 (D.C. Cir, 2000), but in any case the commenter did not provide 

enough specific information to justify EPA making such a de minimis finding in this instance. 

Given the narrow and specific circumstances delineated by the court in Alabama Power v. 

Costle, 636 F.2d 323 (D.C. Cir. 1979) for making such a finding, and the lack of specific 

information from the commenter that these circumstances exist in this instance, we do not make 

a de minimis finding. However, in the final rule, EPA has attempted to minimize the regulatory 

burden particularly on smaller sized stationary engines. For stationary engines located at area 

sources, EPA has flexibility to set non-numerical limits in the form of management practices. 

EPA is promulgating management practices for all emergency stationary engines located at area 

sources, and for stationary CI engines smaller than 300 HP located at area sources. These 

management practices are discussed in more detail in section 7.0. For existing stationary CI 

engines below 100 HP located at major sources, EPA has determined that it is not feasible within 

the context of this rulemaking to prescribe or enforce a numerical emission standard because the 

“application of measurement methodology to this class of engine is not practicable due to 

technological and economic limitations.” This determination is discussed in more detail in the 

memorandum entitled “MACT Floor Determination for Existing Stationary Non-Emergency CI 

RICE Less Than 100 HP and Existing Stationary Emergency CI RICE Located at Major Sources 

and GACT for Existing Stationary CI RICE Located at Area Sources.” As a result, existing 

engines below 100 HP located at major sources will be required to meet work practice standards 

to meet the maximum achievable control technology requirements for those engines. More 

information on the work practice standards can be found in the “MACT Floor Determination for 
59

Existing Stationary Non-Emergency CI RICE Less Than 100 HP and Existing Stationary 

Emergency CI RICE Located at Major Sources and GACT for Existing Stationary CI RICE 

Located at Area Sources” memorandum. 

Regarding the possibility of regulation under Title V, all stationary engines at area 

sources are exempted from Title V permit requirements under parts 70 and 71, as long as the 

sources do not otherwise have to meet such permit requirements. See 40 CFR § 63.6585(d). 

EPA understands the concerns of commenters regarding state permit requirements, but we 

believe that these concerns are best provided to the states in question. In addition, section 

112(c)(3) and 112(k) require that EPA regulate categories or subcategories of area sources 

representing 90 percent of the area source emissions of HAP presenting the greatest threat to 

public health in urban areas. Stationary engines located at area sources were included in that list 

of categories, and therefore must be regulated under section 112(c)(3). 

2.3 Diesel Engines 

2.3.1 Comment: Three commenters (179, 183, 242) asked that EPA consider management 

practices for diesel engines that are run for short periods or at variable loads due to the inability 

of add-on controls to reach effectiveness under these operating conditions. One example of 

variable load diesel engines are fixed crane units on offshore platforms and loading docks, where 

the exhaust may never achieve exhaust temperatures necessary for efficient catalyst operation, 

the commenter (242) said. In colder climates, such as areas of Alaska, Colorado, and Wyoming 

for example, there may also be issues with reaching temperatures necessary for maximum 

control efficiency. 
60

Response: EPA believes that the final emission standards are appropriate for all types of 

stationary diesel engines. The final standards are based on what is achievable using current 

control technologies that are available for existing stationary diesel engines. For variable load 

stationary diesel engines, vendors have developed active catalyst systems that include a heating 

element or fuel burner that heats the catalyst to the appropriate temperature for efficient HAP 

reduction. Both EPA and the California Air Resources Board (CARB) have verified HAP 

control retrofit technologies for existing stationary diesel engines and these technologies are 

presented on their respective websites. Not all existing diesel engines are subject to emission 

standards that require aftertreatment. In fact, several stationary diesel engines will be able to 

comply with the final rule by following management practices only. 

2.3.2 Comment: A number of commenters (74, 78, 85, 96, 97, 240, 242) expressed concerns 

over the proposed limits for stationary diesel engines. Commenter 96 said that the proposed 

limit is not reasonable for the majority of engines and noted that although EPA stated that it is 

cost prohibitive to require add-on controls for certain smaller sized stationary diesel engines, 

EPA has proposed an emission standard achievable only by the best controlled stationary engine 

without aftertreatment. Therefore, it is obvious that the remaining engines will have to install 

controls to be able to meet the emission level required, commenter 96 asserted. There is no 

control setting or engine modification that can be done to improve HAP emissions while at the 

same time meeting the requirements for NOx, hydrocarbons (HC) and particulate matter (PM) 

emissions and therefore the commenter (96) recommended that these engines be subject to only 

engine manufacturer’s maintenance practices. 
61

One commenter (242) said that existing diesel engines will not be able to meet the 40 

ppmvd proposed CO limit without applying add-on controls and the commenter is planning to 

submit test data supporting this claim. If the proposed limits stand, virtually all diesel engines 

subject to the 40 ppmvd limit for CO will need to apply post-combustion controls, which based 

on EPA’s discussion in the preamble was not the intent, commenter 242 said. According to 

commenter 242, available test data on four uncontrolled diesel crane engines show that 40 

ppmvd for CO is not attainable. The engines are 160 HP and 450 HP in size and had CO 

emissions of 130, 154, 224, and 480 ppmvd. 

One commenter (240) expressed that the CO emission limit of 40 ppmv at 15 percent 

oxygen (O2) for stationary CI engines greater than 500 HP is unsupported and legally flawed for 

the following reasons: 

(1) For area sources, EPA has the discretion to set standards at the “MACT” or “GACT” 

levels. EPA did not conduct a GACT analysis for stationary emergency CI engines less 

than 500 HP, but rather determined that those engines located in area sources should be 

subject to the same emission controls as the MACT standards for major sources. The 

commenter (240) believed that the better approach is to require management practices, as 

EPA requires for stationary emergency engines between 50 and 500 HP. The commenter 

(240) further stated that the data EPA relies on for determining the MACT floor was 

based on 10 tests that were conducted on one make and model of engine over a 3-day 

period in 1999. EPA reviewed emissions from all CO tests (10 tests) and selected the 

best performing 12 percent as MACT. The commenter (240) reported that in its 

evaluation of new engines [subject to the CI NSPS (40 CFR part 60, subpart IIII, which 

requires that new engines with a rated power greater than 560 KW meet the Tier 2 
62

emission standards in 40 CFR part 89 – Control of Emissions from New and In-use 

Nonroad CI Engines]) the commenter (240) only found one engine with emissions less 

than 40 ppmvd at 15 percent O2, and that the majority of the engines would exceed the 

CO emission standard. This commenter (240) stated that EPA should have evaluated the 

complete universe of existing engines to find the “top 12 percent,” and that if Tier 2 

certified engines cannot meet the numeric limit, it is unlikely that existing engines will be 

able to without addition of after-treatment controls. Additionally, the commenter (240) 

opined that it is not clear whether EPA’s limited evaluation would be consistent with 

applicable law as the U.S Court of Appeals for the D.C. Circuit has explained, “to 

comply with the statute, EPA’s method of setting emission floors must reasonably 

estimate the performance of the relevant best performing [sources].” See Nat’l Lime 

Asps’ v. EPA, 233 F.3d 625, 634 (D.C. Cir. 2000) (citing Sierra Club v. EPA, 167 F.3d 

658, 655 (D.C. Cir. 1999)). 

(2) The costs to meet the 40 ppmvd CO at 15 percent O2 standard for greater than 500 HP CI 

emergency engines are far above what EPA has determined to be acceptable in other 

GACT regulations. The commenter (240) expressed that, in the GACT standard for 

chemical manufacturing area sources, EPA rejected a number of control technologies as 

GACT for based on cost estimates lower than the projected costs of GACT in the RICE 

NESHAP proposal. See, e.g., 73 FR 58,352, 58,367 (Proposed NESHAP for Chemical 

Manufacturing Area Sources) (determining that $30,000 per ton of HAP removed is 

unreasonable for GACT for organic HAP continuous process vents); ($25,000 

unreasonable for organic HAP batch process vents, at 73 FR 58,368); ($0.5 million 

unreasonable for metal HAP process vents, at 73 FR 58,370); ($130,000 unreasonable for 
63

transfer operations, 72 FR 73611, 73618 [Final NESHAP for Hospital Ethylene Oxide 

Sterilizers]). This commenter (240) reported that EPA claims that the estimated cost of 

oxidation catalyst per ton for CI 50 < HP 500 HP to be “...from $1 million to $2.8 

million for emergency CI engines in this size range. For catalyzed diesel particulate 

filters (CDPF), the estimated cost per ton of HAP reduced for emergency CI engines 

between 50 and 500 HP ranges from $3.7 million to $8.7 million.” The commenter (240) 

asserted that any costs from $1 million to $8.7 million are too high to support a GACT 

determination and that add on controls would likely be required to meet the CO limit for 

CO engines which would lead to such costs. 

(3) If the final rule includes a numerical CO emission limit, the commenter (240) is 

concerned it will cause compliance issues with state and/or local air permitting agencies. 

The commenter (240) is concerned that permitting agencies may require that sources 

demonstrate compliance with the numerical limits proposed in the RICE NESHAP, 

including performance testing and potentially the addition of after-treatment control. 

This commenter (240) requested that EPA replace the numerical limit with management 

practices consistent with the proposed management practices for emergency CI engines 

less than 500 HP. 

 EPA should increase the CO emission limit, but should also analyze the production addon controls capacity and potential replacement engines because the commenter (242) questioned 

whether there will be a sufficient number of new engines and/or add-on control systems available 

in time necessary to comply with the rule. 

One commenter (97) stated that CI engines greater than 500 HP will probably not be able 

to achieve 40 ppmvd CO because two-stroke engines have emissions higher than 40 ppmvd of 
64

CO and the rule does not distinguish between two-stroke and four-stroke CI engines. In 

addition, the commenter stated that older engines with mechanical fuel injection or ignition 

retard technology emit higher levels of CO than newer electronic fuel injection engines. 

One commenter (85) asserted that the proposed limit for emergency CI engines greater 

than 500 HP of 40 ppmvd of CO is too stringent. The commenter (85) believes that most of the 

current installed emergency generators would need to install retrofit technology to make these 

units capable of reducing emissions by 90 percent in order to comply with the proposed 

requirement. The commenter (85) stated that the proposed requirement would impose significant 

costs for owners of facilities, who maintain these units for emergency purposes, and would have 

minimal impact upon the health concerns, which motivate the proposed rule. Additionally, the 

commenter (85) indicated that demand response participants would likely opt out of demand 

response programs should they be faced with costly installation of retrofit technology, given the 

current economic climate. The commenter (85) recommended that the emission limit for 

emergency CI engines greater than 500 HP be revised to 400 ppmvd. 

The commenter (85) believes that the proposed limit for emergency CI generators will 

result in extremely high costs for very little environmental benefit because these 

CI engines have limited operation, except for the few hours of testing annually and in operation 

hours only associated with Independent System Operators/Regional Transmission Operators 

(ISO/RTOs) electric power grid emergencies. The commenter (85) also believes that installation 

of retrofit technology on these engines is bound to have a negative impact upon the operation of 

these RICE units, which will diminish the value of the RICE units as a backup source. The 

commenter (85) added that it is important to consider that RICE units are installed in many 
65

locations where life-saving functions are critical. The commenter (85) believes it is not in the 

best interest of the public to compromise their ability to supply such a critical service. 

Two commenters (74, 78) addressed EPA’s proposed GACT standard for both 

emergency and non-emergency CI engines greater than 500 HP. The commenters (74, 78) said 

EPA needs to broaden its database of uncontrolled CO emissions for engines of this size to more 

realistically evaluate compliance feasibility, costs, and cost effectiveness. The data set is very 

limited, and it does not include emissions data from AP-42. The commenters (74, 78) said CO 

emissions data for existing stationary CI engines in Hawaii can be obtained from the State of 

Hawaii Department of Health, Clean Air Branch. This readily-available CO emissions data 

should be considered in developing GACT emissions limits for CI engines at area sources. 

Commenter 78 described an example where CO emissions are limited by permit to levels well 

above the 40 ppm CO emission rate that EPA is assuming for its uncontrolled emissions rate. A 

90 percent reduction from these engines would still be above the 4 ppmvd limit. The commenter 

(78) also described an example for untested units with no emission limits where annual 

emissions are based on AP-42 emission factors for large stationary diesel engines. This emission 

rate is equivalent to nearly 10 times higher than EPA’s assumed uncontrolled rate of 40 ppmvd. 

Response: The emission standard of 40 ppmvd for CO that EPA proposed for stationary nonemergency diesel engines less than or equal to 300 HP at major sources and certain stationary 

emergency diesel engines at major and area sources was based on the emissions data available at 

the time of the proposal. EPA used the RICE Population Database and the RICE Emissions 

Database to set the proposed MACT floors. Based on information from those two sources, EPA 

found it appropriate to propose a 40 ppmvd CO limit. The limit was not expected to require 
66

engine retrofits. As summarized in this comment, several commenters indicated that the diesel 

engines would not be able to meet the proposed CO limits without aftertreatment. During the 

post-proposal period, EPA received additional emissions test data for stationary CI engines, 

which has been incorporated into the MACT floor analysis. From this analysis, EPA determined 

that the MACT floor for existing non-emergency engines 100-300 HP is 230 ppmvd CO. EPA 

recognizes that not all existing engines are likely to meet this emission limitation without the use 

of add-on controls and has incorporated this into the cost analysis for the final rule. EPA is 

required to set an emission standard for these non-emergency engines at major sources that is 

equivalent to the MACT floor. In response to the concerns expressed by commenters regarding 

the emission limits for stationary emergency CI engines at area sources, EPA has reevaluated the 

GACT analysis for these engines and determined that management practices are more 

appropriate for these engines than numerical emission limitations. As discussed in much greater 

detail in comment 5.3.1, the final rule requires emergency engines at major sources to meet work 

practice standards. For non-emergency stationary CI engines above 300 HP, EPA does not agree 

with the commenters that the cost of emission control is too high compared to the reductions that 

can be achieved. While the emission standard in the final rule for these engines is based on the 

use of oxidation catalyst control, similar to proposal, EPA did incorporate the additional data 

received in the MACT floor and MACT analysis and determined that the emission standard is 49 

ppmvd CO or 70 percent reduction, which is not as stringent as the proposed emission limitation. 

This is discussed in more detail in the memorandum entitled “MACT Floor and MACT 

Determination for Existing Stationary Non-Emergency CI RICE Greater Than or Equal to 100 

HP Located at Major Sources.” 
67

2.3.3 Comment: Two commenters (183, 242) said that EPA should not promulgate standards for 

existing diesel engines at area sources that are more stringent than standards for new stationary 

diesel engines at area sources. The commenter (242) said that doing so does not appear to be 

warranted under CAA provisions for establishing GACT and in order to fix this issue, EPA 

should promulgate standards that are equal to those currently required under 40 CFR part 60, 

subpart IIII for new units. Otherwise, EPA should present a more thorough and improved 

analysis and justification for requiring more stringent limits for existing units, commenter 242 

said. Commenter 183 recommends that EPA establish CO limits greater than those required for 

new engines for any existing CI RICE subject to numerical CO limits. 

Response: EPA does not agree that the final standards that apply to existing stationary diesel 

engines at area sources must be less stringent than those that apply to new stationary diesel 

engines at area sources, which were promulgated at a different time. However, EPA points out 

that new stationary diesel engines at area sources must meet the final CI NSPS phase-in 

standards that in most cases will require CDPF controls in Tier 4 certified engines. EPA 

anticipates significant HAP reductions to be achieved through the use of CDPF under the 

stationary CI NSPS. In addition, the final standards for all stationary CI engines, and particularly 

for CI engines below 500 hp and emergency engines above 500 hp at area sources, are all less 

stringent than the proposed standards. For that reason, EPA does not agree with the commenter 

that the final standards for new diesel engines at area sources are necessarily less stringent than 

the ones EPA proposed for existing stationary diesel engines. The most stringent standards for 

existing stationary diesel engines are based on the use of oxidation catalyst, where, as discussed 

above, the standards for most new stationary diesel engines will require the application of CDPF. 
68

2.3.4 Comment: Two commenters (96, 215) agreed with the proposed cutoff of 300 HP as the 

above-the-floor threshold for non-emergency diesel engines, however, commenter 215 also 

encouraged EPA to reduce emissions from diesel engines smaller than 300 HP. In information 

submitted by the commenter (96) on the diesel engine ANPRM, the commenter stated that nearly 

60 percent of total PM emissions from the country’s diesel engines are from diesel engines above 

300 HP installed prior to 1996 and that 80 percent of all diesel engines are used for emergency 

purposes, which operate infrequently and consequently contribute little to the total HAP and PM 

inventory. Therefore, the commenter (96) agrees with EPA’s threshold of 300 HP for above-thefloor standards. Further, the commenter (96) added that non-emergency diesel engines above 

300 HP can be retrofitted with controls cost-effectively and can achieve significant reductions. 

The commenter (215) pointed out the ANPRM estimated 72 percent of the HAP 

emissions, 66 percent of the total PM emissions, and 62 percent of the total NOX emissions are 

from existing non-emergency engines greater than 300 HP. The commenter (215) agreed that 

diesel engines greater than 300 HP cover the majority of emissions from diesel engines, but the 

commenter also believes that EPA should set standards for the smaller categories of engines, 

possibly on an extended schedule. The commenter (215) noted that areas across the country that 

are marginal or nonattainment may need the additional reductions that can be achieved by 

regulating diesel engines less than 300 HP. A study produced by the commenter (215) showed 

that people in close proximity to emergency or back-up generators are exposed to more harmful 

diesel emissions than those living and working further away. In the study, the commenter (215) 

chose a threshold of one in a million excess cancer risk and found back-up generators operating 

less than 100 hrs/yr produced a risk zone of 63 to 118 acres. In addition, the commenter’s study 
69

found the population within the back-up generator risk zone is more likely to be low income, 

elderly, and of a racial minority. Based on these results, the commenter (215) recommends that 

EPA seriously consider establishing more stringent emission standards for diesel engines less 

than 300 HP, even if it is on a delayed schedule to reduce human exposures to diesel exhaust and 

to help states achieve clean air goals. 

Response: As EPA discussed in the January 24, 2008 ANPRM for stationary diesel engines and 

as commenter 215 indicated in its comments, the majority of stationary diesel toxic and PM 

emissions are emitted from larger and older non-emergency diesel engines. The cost and 

feasibility of applying retrofit controls are also more favorable the larger the stationary engine. 

EPA specifically solicited comment on the appropriate group of stationary diesel engines, 

including what the most reasonable size cutoff would be, in the January 2008 ANRPMN. 

Several commenters indicated that they agreed with EPA’s proposal to focus on non-emergency 

stationary diesel engines greater than 300 HP. In addition, during the development of the 

ANPRM, EPA worked with commenters 96 and 215 in order to determine the best approach for 

controlling emissions from existing stationary diesel engines. The proposed cutoff of 300 HP is 

consistent with the results of that effort. EPA notes that we do expect reductions in emissions as 

a result of this rule from stationary engines below 300 HP. Non-emergency engines between 

100-300 hp at major sources are subject to numerical emission standards equal to the average of 

the best controlled 12 percent of engines in that subcategory. Given that many engines are not 

expected to meet that standard without some emission control, and some engines may need to put 

on aftertreatment to meet that standard, some amount of quantifiable emission reduction is likely 

to occur for such engines. It is more difficult to quantify emission reductions for stationary 
70

engines that are meeting standards through work or management practices, but EPA believes that 

requiring engines to meet such requirements will also ensure reductions in emissions compared 

to engines that are not required to meet such practices. 

2.3.5 Comment: Three commenters (76, 96, 246) expressed that there may be issues with 

applying CDPF to older stationary diesel engines. One commenter (96) agrees with EPA’s 

decision to rely on oxidation catalyst and ultra low sulfur diesel (ULSD) to reduce emissions 

from non-emergency stationary diesel engines above 300 HP. The majority of diesel engines 

above 300 HP are pre-1996 model year engines that are pre-Tier 1 engines with few or no 

emissions controls, according to commenter 96. The emissions profile of these older engines do 

not allow for the use of CDPF and the only technically feasible option is to use lower sulfur fuel 

and oxidation catalyst, the commenter (96) said. Particulate filters can only be applied to certain 

older engines with specific emissions, e.g., a certain engine-out PM level, proper duty-cycle with 

an adequate exhaust temperature, and that can operate on ULSD, which typically means that 

filters cannot be applied to pre-1996 model year engines. In addition, the commenter (96) said 

that CDPF cost more to install and operate than oxidation catalyst and although application of 

CDPF could lead to a higher reduction, technical and cost limitations prevent implementing such 

controls. 

One commenter (76) believes that the operation of existing engines, 10 to 20 years old, 

may be impacted by the installation of CDPF. The commenter (76) stated that the there is not 

enough data to establish if CDPF can be retrofit on these older engines. Therefore, the 

commenter (76) asked that EPA allow a waiver that states that CDPF is not technically or 

economically feasible on older engines, and these engines should be exempt for control 
71

requirements, and owner or operators should only be allowed to submit a certification prior to the 

compliance date. The commenter (76) asked if older engines can be retrofit with control 

technology, and if owner or operators are required to purchase a new engine if an existing engine 

cannot be retrofit with control technology. 

One commenter (246) feels that the proposed regulation for the application of oxidation 

catalysts to lean burn engines is appropriate based on the expected high levels of CO and HAP 

reduction from an oxidation catalyst in addition to the moderate levels of particulate reduction 

achieved, and states that this can generally be accomplished with low capital cost, low 

backpressure and a relatively small footprint relative to the application of a CDPF to an existing 

engine. Further, this commenter (246) adds that most existing diesel engines face backpressure 

limitations which could be exceeded if the regulation were to call for the mandatory application 

of a CDPF to an older engine, and that even if the installation of a CDPF alone did not cause 

backpressure issues, it could preclude the future application of NOx control technology such as 

selective catalytic reduction (SCR) based on the backpressure resulting from the combination of 

the existing silencer and exhaust duct with a retrofitted CDPF and SCR. 

Citing expected backpressure increases of 1 to 3 inches water column from a oxidation 

catalyst plus 4 to 5 inches water column from an added SCR, versus 15 to 20 inches water 

column for a clean DPF, commenter 246 asserted that the combination of SCR and oxidation 

catalyst can address CO, HAP, PM and NOx emissions while generally remaining within 

backpressure limitations of existing older engines. Commenter 246 added that a study of 

backpressure limitations on existing engines would need to be undertaken prior to mandating a 

technology such as CDPF that potentially increased backpressure by 15 to 20 inches water 

column. 
72

Commenter 246 has evaluated a number of existing engines and found them unable to 

accept the backpressure increase from a CDPF. In contrast, the commenter (246) has applied the 

combination of SCR and oxidation catalyst to four 1965 vintage 2.2 megawatt (MW) diesel 

engines to achieve high levels of NOx and CO control. Commenter 246 adds that the 

combination of SCR followed by an oxidation catalyst has the benefit of reducing nitrogen 

dioxide (NO2) formation (by reducing NOx prior to the oxidation catalyst) and also reduces 

potential ammonia slip from the SCR. 

Commenter (246) claimed the mandatory application of CDPF technology to a broad 

base of existing engines could preclude the ability to apply retrofit NOx controls to existing 

engines based on cost, space and backpressure limitations. Further, given the need for NOx

reduction in many ozone non-attainment regions of the country and that NOx emissions far 

exceed the current level of PM emissions from existing lean burn engines, commenter 246 

asserts that a regulation that mandates a PM control strategy, which in turn prevents application 

of a NOx control strategy, may not be in the best interest of overall public health and welfare. 

Commenter 246 concluded that since the HAP reduction performance is suggested to be similar 

for a oxidation catalyst or a CDPF, the proposed rule should not mandate the further control of 

PM with a CDPF, especially given that neither PM or NOx is specifically covered as a HAP. 

Finally, commenter 246 added that performance and operating range of the oxidation 

catalyst and/or SCR will be enhanced through the proposed requirement for ULSD fuel 

Response: In the final rule, EPA is basing the emission standards on the use of oxidation catalyst 

controls for existing non-emergency diesel engines above 300 HP. EPA does not believe it is 

necessary to grant the request to allow a waiver for older engines that commenter 76 asked for 
73

because the emission limits are not based on CDPF. Further, EPA is not mandating a specific 

control technology to be used to meet the final emission limits either, so the affected source 

could apply any means of control in order to comply with the emission limits. Since the 

proposed regulation is an air toxics-based rule, EPA did not consider the use of SCR on existing 

stationary diesel engines. This rule addresses HAP emissions and SCR is typically used to 

control the emissions of NOx, a criteria pollutant that is not the focus of this rulemaking. 

2.3.6 Comment: One commenter (193) believed that EPA should refrain from promulgating a 

standard that requires the installation of CDPF on existing stationary diesel engines, to abate 

“black carbon emissions.” The commenter (193) cites CAA sections 112(c)(2) and 112(d)(1) 

which require the Administrator to “promulgate regulations establishing emission standards for 

each category or subcategory of major sources and area sources of hazardous air pollutants listed 

for regulation pursuant to subsection (c)...” CAA section 112(c)(1) instructs EPA to establish 

emission standards for source categories and subcategories with pollutants listed in section 

112(b) of the CAA. The EPA has listed both major and area source RICE as source categories 

for regulation pursuant to 112(c)(1) of the CAA. The commenter (193) notes that black carbon 

was not listed by Congress as a CAA section 112(b)(1) hazardous air pollutant and EPA has not 

added it to the 112(b)(1) listing of HAP, by rule, as required by CAA section 112(b)(2).  EPA’s 

stated purpose for this rulemaking is “to meet its statutory obligation to address HAP emissions 

from these sources under sections 112(d), 112(c)(3) and 112(k) of the CAA.” The commenter 

(193) believes the establishment of a control technology standard for black carbon using this 

rulemaking as EPA’s vehicle for obtaining reductions in black carbon emissions is inconsistent 

with the stated purpose of this rulemaking and its underlying statute. There is no indication that 
74

EPA has made the requisite findings that black carbon presents, or may present, “through 

inhalation or other routes of exposure, a threat of adverse human health ....,” nor has EPA 

amended the list of HAP in accordance with section 112(b)(2) to add black carbon to the list. 

Response: EPA is not establishing emission standards for black carbon in the final rule. EPA is 

not mandating a specific control technology in the final rule to be used to comply with the 

emission standards. EPA is finalizing national requirements to address HAP emissions from 

existing stationary engines in order to meet its statutory obligations under sections 112(d), 

112(c)(3), and 112(k) of the CAA. 

2.3.7 Comment: One commenter (215) noted that CDPF is more expensive than oxidation 

catalyst; however the fact that a control may cost more is not a sufficient basis for EPA to reject 

it. The commenter 215 also stated that the CAA does not authorize EPA to consider cost 

effectiveness in setting beyond-the-floor MACT standards. The commenter (215) asserted that 

cost is not cost effectiveness and said that nowhere does section 112 of the CAA mention cost 

effectiveness. Commenter 215 noted that EPA may allow engines that are unable to be retrofit 

with CDPF to use alternate standards, similar to what was adopted by California in the Air 

Toxics Control Measure for stationary diesel engines. 

Response: EPA has not rejected CDPF as a possible emission control strategy for this rule. If a 

source can feasibly use CDPF and can meet the standards using CDPF, the source may use it. 

EPA does not generally, and does not in this rule for its numerical emission standards, require 

sources to use any particular emission control strategy to meet the standards. Any strategy that 
75

can be used to meet the requirements of the rule may be used. However, EPA does determine 

beyond-the-floor standards based on the emissions expected from using the type of controls that 

it believes is MACT. Section 112(d)(2) of the CAA states that the Administrator may take into 

account the cost of achieving emission reductions in setting standards beyond the MACT floor. 

EPA also does not agree that EPA cannot consider the cost-effectiveness in setting beyond-thefloor standards. Cost-effectiveness is computed by merely dividing cost by the emission 

reductions expected. It would be strange indeed if section 112(d) of the CAA allowed us to use 

the cost of an emission control, but not the level of emissions reduced by the control, in 

determining a standard whose main purpose is the control of emissions. The EPA is justified in 

taking into account the emissions reductions that can be achieved in determining MACT, and 

therefore is justified in taking into account cost-effectiveness. Moreover, the commenter fails to 

show that CDPF technology is feasible for most existing stationary engines or actually achieves 

greater HAP emission reductions compared to diesel oxidation catalysts. 

2.4 Other 

2.4.1 Comment: One commenter (242) said that the rule will require all existing engines to 

obtain an NSR permit. Exemptions that have existed in NSR programs for minor sources will no 

longer be available for sources having NESHAP requirements and the commenter (242) said that 

EPA has not taken into account the burden associated with obtaining NSR permits for these 

sources. These costs should be included in EPA’s benefit analysis, the commenter (242) said. 
76

Response: The costs of compliance with NSR are not clear and result from operation of those 

regulations. They are outside the scope of this rulemaking. The decision to regulate stationary 

engines located at area sources came through operation of section 112(c)(3) and 112(k) of the 

CAA and was decided in the urban air toxics rule, not this rule. 

2.4.2 Comment: One commenter (136) noted that there is no limit on construction date for 

existing RICE in the proposed rule. The commenter (136) stated that older engines were never 

designed to comply with these stringent emissions and some are not easily retrofitted with 

catalysts, if it can be done at all. The commenter (136) added that the expectation for older 

RICE to meet the MACT Floor or Beyond the MACT Floor will not be possible in many cases, 

and there is no data in the docket to support that these emission limits are achievable. The 

commenter (136) believes that industry could be faced with replacing thousands of existing 

engines that will not be able to comply with the emission limits in this proposed rule. 

Response: EPA proposed emission standards for certain existing stationary engines based on the 

use of add-on controls. In those cases, EPA expects that owners/operators would be able to 

retrofit their existing engines with readily available control technologies such as oxidation 

catalyst. Based on available information at the time of proposal, there was no indication that the 

aftertreatment controls that the proposed emission standards were based on for a certain 

subcategory of stationary engines, would not be feasible to apply to older engines. Oxidation 

catalyst has been used for many years on existing and new stationary CI engines. 

 The commenter claims that the proposed emission standards that are based on retrofitting 

engines may not be achievable on older engines. The commenter does not define what is meant 
77

by older engines and further does not support the claim that the standards are not feasible. No 

details are provided as to why the proposed standards are not achievable, in the commenter’s 

opinion. 

2.4.3 Comment: One commenter (121) said EPA should exempt RICE used in product 

development, research, and testing operations at both major and area sources. For example, 

members of the commenter’s (121) organization employs engines to test transmissions, 

subsystems, and powertrain configuration using dynamometer facilities. EPA has traditionally 

excluded research activities from applicability of MACT standards, the commenter (121) said. 

Similarly, commenter 230 recommended modifying 63.6590(a) of the proposed rule to 

exclude stationary RICE used for research and testing because research engines operate for 

limited periods of time, and represent an insignificant source of emissions compared to the 

population of interest to EPA. 

Response: EPA does not agree that stationary CI engines used in product development, research, 

and testing operations should be exempted from subpart ZZZZ. The commenter did not provide 

any data to show that the emissions and operation from these engines are different and would 

justify exempting them from the rule. 

2.4.4 Comment: Two commenters (167, 213) thought that existing stationary engines should not 

be addressed in this rulemaking. One commenter (167) stated that existing stationary engines are 

already adequately regulated. The commenter (167) cited State and local permitting programs, 

other ordinances, and national standards such as those established by the National Fire Protection 
78

Association (NFPA) as evidence to support this statement. One commenter (213) said that it did 

not believe that EPA’s analysis on costs and benefits was detailed enough and the commenter 

asked that a more thorough analysis is necessary as it relates to the economic impacts of 

controlling HAP emissions. The commenter (213) thought that enhanced monitoring, 

recordkeeping and reporting to ensure improved compliance of engines already subject to 

rulemakings would be more instrumental and recommended that until further benefits of HAP 

reductions associated with existing engines can be proven, the proposed rule only be subject to 

new or reconstructed engines and existing engines remain subject to already promulgated 

requirements until they are no longer in service. 

Response: EPA is obligated by statutory requirements to develop regulations for all stationary 

engines. EPA has previously issued regulations for existing stationary engines greater than 500 

HP located at major sources of HAP emissions and is with this regulation finalizing regulations 

for the remainder of existing stationary engines not covered in the original RICE NESHAP 

regulation, i.e, existing stationary engines located at area sources of HAP emissions and existing 

stationary engines less than or equal to 500 HP located at major sources of HAP emissions. 

Therefore, EPA does not agree that existing stationary engines have already been adequately 

regulated since this is the first time EPA is addressing HAP emissions from these engines. What 

State programs and various other regulatory agencies across the country have done in the past to 

regulate existing stationary engines does not change EPA’s statutory requirements in this matter. 

2.4.5 Comment: One commenter (125) encouraged EPA to consider including an “off-ramp” 

from inappropriate requirements for facilities that can demonstrate that the additional controls 
79

will not provide any significant reduction in human health risk. The commenter (125) presented 

HEM-3 (AERMOD mode) modeling results for two diesel-fired peaking generator units located 

at the Outer Banks, NC that are used to provide power during peak times as well as for reliability 

and emergency conditions. The commenter’s (125) modeling results for the units (with 

conservative modeling inputs) show cancer risk of 1.1x10-7 and 1.5x10-7, total chronic hazard 

index values of 4.5x10-3 and 5.9x10 x10-3, and acute hazard index values less than 1.0, which 

commenter claims are below applicable EPA health criteria. The commenter (125) 

recommended that EPA provide alternative compliance options in certain cases where the risks 

posed by the emissions are very small, similar to health-based approaches in other MACT 

standards. The commenter (125) claimed that without such a health-risk approach, his example 

client would be required to pay $500,000 capital costs + about $66,000 in annual costs for 

emissions controls, plus additional costs related compliance such as recordkeeping and reporting 

requirements, performance tests, permit modifications, fuel-handling modifications, etc., all 

without any measurable reduction in human health-risk or accomplish any of the objectives 

stated in the proposed rule. 

Response: EPA does not agree that it would be appropriate to include a risk-based approach in 

the final rule. EPA has included several provisions in the final rule that it believes will alleviate 

the burden on owners and operators of existing stationary emergency engines that the commenter 

is concerned about. Existing stationary residential, institutional and commercial emergency 

engines located at area sources are not subject to the final rule. EPA has also specified in the 

final rule that emergency stationary CI engines and non-emergency stationary CI engines less 

than 300 HP located at area sources are not subject to emission limitations and will comply with 
80

management practices, which reduces the burden of the rule on those units. EPA notes that 

section 112(d) of the CAA provides few possible methods of allowing sources to avoid 

regulation based on risk and the commenter does not provide sufficient argument regarding how 

any such provision could be used for these engines. 

2.4.6 Comment: One commenter (228) recommended that the rule provide a method for a source 

to convert an engine from emergency to non-emergency classification and vice versa. The 

commenter (228) stated that sources will not know of the need to convert from emergency to 

some other use until the incident requiring the conversion occurs. The commenter (228) stated 

there needs to be a way to establish the time and requirements for conversion, and recommended 

that the source keep a log book of its RICE, their status, and submit a notice to the permitting 

authority administering the program within 30 days of any change in status. The commenter 

(228) stated that the new requirements would go into effect 30 days after mailing of the notice 

(e.g., new recordkeeping requirement start on the 30th day after mailing; an initial performance 

test would be due 210 days after mailing the notice). 

Response: EPA cannot provide guidelines in the final rule for what the commenter is requesting 

in terms of emergency to non-emergency engine conversions and vice versa. This question will 

be answered on a case-by-case basis. The commenter is advised to be familiar with the 

definition of emergency engine and to be in conformance either with that definition or with the 

requirements applicable to non-emergency engines when these regulations become applicable to 

the source. 
81

2.4.7 Comment: Two commenters (179 and 183) wanted clarification on whether the rule affects 

temporary replacement engines. One commenter (183) stated that EPA should clarify for 

temporary replacement engines that are considered stationary because that replace permanent 

engines at stationary sources may meet requirements of the NESHAP either by meeting the 

otherwise applicable requirements for stationary sources or by meeting the requirements for 

nonroad engines, including the use of certified engines. Two commenters (179, 183) stated that 

EPA should clarify in the preamble for temporary portable engines that do not trigger provisions 

in the definition of nonroad engine are not considered stationary engines and therefore would not 

be covered by the NESHAP. 

Response: This comment is similar to comment we received in the rule promulgating New 

Source Performance Standards for stationary SI engines and NESHAP for most new stationary 

engines. In the Response to Comments to that rule, we stated the following: “Portable electric 

generating engines that remain in one location for less than 12 consecutive months are 

considered nonroad engines and are subject to requirements for nonroad engines. Conversely, 

portable engines that are kept at one location for more than 1 year are considered stationary 

engines while they remain at the location, even if, as is possible for emergency engines, they are 

not used... There is an exception for replacement units that take the place of existing stationary 

units. Portable engines that replace existing stationary engines on a temporary basis would be 

considered stationary engines. This is an important provision in that it allows the permitting 

authority to count the emissions of the temporary unit in the emissions from the stationary 

source, as it would for the permanent unit. This prevents major sources from avoiding the 

counting of such units in its projected or actual emissions.” In the new engine rule, we allowed 
82

compliance by new temporary replacement engines with the nonroad engine standards to also be 

compliance with the standards for new stationary engines being promulgated in that rule. In that 

context, this allowance was sensible, since EPA had already determined that for the new engines 

being regulated, compliance with the nonroad engine standards also met the requirements for 

new stationary engines. However, in this context, we cannot make that determination, since 

many of the existing engines being regulated in this rule were never subject to regulation under 

the nonroad engine rule. Therefore, we have no assurance that compliance with nonroad engine 

regulations will also meet the requirements, in particular those requirements mandated by statute, 

that are applicable to existing stationary engines under section 112(d), and under the regulations 

promulgated in this action. We therefore cannot add the language requested by the commenters.

3.0 Startup, Shutdown, and Malfunction 

3.1 Comment: Several commenters (63, 74, 76, 78, 87, 89, 96, 97, 98, 99, 101, 103, 104, 112, 

121, 122, 124, 126, 129, 130, 131, 132, 134, 139, 146, 148, 150, 151, 152, 154, 155, 156, 157, 

160, 162, 167, 168, 175, 176, 177, 178, 183, 186, 187, 191, 197, 200, 202, 203, 204, 205, 207, 

209, 213, 216, 218, 221, 224, 225, 226, 227, 228, 229, 231, 236, 240, 242, 247, 253, 261, 262, 

264) expressed serious concern over the proposed emission standards for periods of SSM. The 

U.S. Court of Appeals for the District Columbia Circuit vacated the SSM exemption in 40 CFR 

part 63, subpart A on December 19, 2008. The decision requires the Agency to implement 

standards that apply at all times, including during SSM periods. Numerous commenters thought 

the quick response to the December 2008 Court decision on the SSM issue is premature and 

recommended that EPA wait for a final decision before incorporate elements from this case. 
83

Numerous commenters are of the opinion that EPA has not provided a technical basis for its 

establishment of SSM limits and that any SSM limits should be replaced with work practice 

standards and disagreed with the decision to include limits for SSM periods. In addition, several 

commenters said that emissions during SSM events cannot be measured and therefore cannot be 

confirmed and limits are not enforceable. One commenter (148) recommended that EPA require 

a SSM plan similar to the SSM plan currently required under 40 CFR part 63, subpart ZZZZ. 

The commenter (148) also pointed out that 40 CFR 63.6650(b) in the existing rule requires 

operators to operate and maintain their equipment in a manner consistent with good air pollution 

control practices at all times, including periods of SSM. The commenter (148) believes that this 

requirement in conjunction with a SSM plan will achieve the same goals as the proposed rules in 

a much more cost effective and logical manner. 

Based on CO baseline data presented by commenters (74, 78), EPA must consider a 

broader database of uncontrolled engines in determining what CO limits can be achieved during 

SSM periods. One commenter (78) asked how it can limit the concentration of CO to 40 ppmvd 

or less during startup and shutdown periods when catalytic control would not be effective, when 

CO emissions currently range for 160 to 382 ppmvd at 15 percent O2. Commenter 74 provided 

similar data and reached the same conclusion as commenter 78. 

Many commenters, including commenters 112, 155, 236, 242 and 247 recommended that 

EPA consider other alternatives to implement during SSM periods, such as possibly requiring 

work practice standards, which the commenters believe is the most reasonable approach and is 

justified under the CAA. Commenter 242 believes that work practices standards that minimize 

the emissions during of SSM periods is the most practical method of keeping HAP emissions 

from engines as low as possible. Commenter 242 offered to provide additional assistance and 
84

input in order to come up with reasonable work practices to include in the final rule. The 

commenter (155) also recommended that EPA describe the SSM requirements in the rule itself 

rather than in the GP. Alternatively, the commenter (155) recommended that the GP be revised 

due to confusing and conflicting requirements. 

 Several commenters, including commenters 96, 99, 156, and 242 said that there is no 

method to determine compliance during SSM periods. Commenter 242 said that it will be 

difficult or impossible to design a test program to describe emissions during SSM events, e.g., 

the commenter is not sure how a malfunction would be defined considering the unexpected and 

anomalous nature of the event. Therefore, emissions during these periods cannot be confirmed, 

commenter 242 said. Similarly, commenters 96 and 99 believe that it is not reasonable to set 

numerical limits during startup because there are no available or repeatable test methods or 

procedures for measuring emissions during startup or malfunction, plus there is no prescribed 

definition of what constitutes startup of an engine, which can vary significantly for a number of 

reasons such as engine and catalyst type, fuel, climatic conditions, application and load. 

Several commenters (63, 96, 104, 129, 139, 150, 162, 178, 191, 197, 242) expressed 

concern over the feasibility of measuring emissions during SSM events. One commenter (242) 

said that if EPA retains the SSM limits in the final rule that EPA must provide methodologies 

and details on how to determine compliance with the emission standards during these SSM 

events. The commenter (242) has previously stated its objection to SSM limits and favors work 

practice standards instead. However, if SSM limits are retained, two commenters (76, 242) said 

that EPA must specify how compliance is determined, e.g., the commenter (242) wondered how 

does a source determine compliance for SSM events that are short (which the majority of SSM 

events are) and less (e.g., 1 hour for warm startup) than the performance test length requirement 
85

of the average of three 1-hour tests. One commenter (96) said that this methodology (average of 

three 1-hour tests) is impossible to execute since startups usually take 30 minutes to complete. If 

EPA used Method 320 (FTIR) for short duration events, EPA should discuss any intent to 

modify the compliance method of taking the average of three 1-hour tests and state the length of 

a new tests, the commenter (242) said. The commenter (242) added that FTIR has the capability 

of taking short-term minute average concentration readings. 

One commenter (76) said that the rule should specify that concentration limit should be 

based on the time period of the startup or malfunction or a 1-hour period, whichever is longer. 

Another commenter (242) added that time is needed for catalyst elements to warm up and 

stabilize before CO and HAP are effectively reduced and uncontrolled or partially controlled 

emissions cannot comply with the proposed startup emission limits. Regarding malfunctions, the 

commenter (242) asserted that no assurance can ever be made in terms of emission limit 

compliance. The malfunction, by nature, is not predictable, unknown and undefined, of 

unknown frequency, and emissions cannot be predicted, implied or measured, the commenter 

(242) said and again urged EPA to adopt work practice standards that minimizes emissions 

during SSM events. 

 Finally, the commenter (242) noted that Title V operators would not be able to meet their 

obligation for compliance certification if the proposed SSM limits remain because affected 

sources would be required to show compliance with limits that have not been technically 

justified and will lead to implementation issues in the field. 

Since the rule offers no means of determining compliance during startup, one commenter 

(150) stated that clarification is needed on this issue. 
86

One commenter (129) stated that for a source that is not monitoring emissions with a 

CEMS, it is impossible to determine whether SSM limitations are being met. The commenter 

(129) added that the monitoring/testing requirements will not allow an operator to make a 

knowledgeable determination of compliance during SSM using available data. 

One commenter (99) said that there are no viable measurement methods available to 

measure CO, formaldehyde or VOC during transient operation and a review conducted by the 

commenter of Table 4 in the proposed rule shows the inconsistencies related to transient 

measurement acceptability with respect to stack gas moisture and flow rate, delays in the actual 

response of analyzers, issues in obtaining an accurate measurement during a transient test due to 

an axial diffusion function in long gaseous emissions sample lines, and field gaseous emission 

measurements require stack traverse as well for the emissions under measurement, per methods 

7, 10, 25, etc., which eliminates the possibility of getting an accurate measurement during 

transient events such as a startup. 

One commenter (152) claimed that issuance of numerical limits for SSM based on the 

emissions of the “best controlled sources prior to full warm up of the catalytic control” fails to 

consider emissions during malfunction of the engines themselves. The commenter (152) asserts 

that while EPA appropriately determined that during a control device malfunction, the floor and 

standard cannot be set assuming operation of the control device, EPA errs in limiting its analysis 

solely to operation of the controls since emissions can increase as a result of engine malfunctions 

as well. The commenter (152) noted that its experience is consistent with EPA’s statements that 

emissions during an engine malfunction may increase due to the effects on exhaust temperatures 

and composition. The commenter (152) concluded that emission limits would need to be based 

on the emissions level from the best performing sources without control while the engine is 
87

malfunctioning. Commenter 96 added that it does not make sense to set any numerical standards 

during a malfunction of an engine because inherent in the concept of a malfunction is that 

emissions will be malfunctioning as well. It is also not logical to apply the concept of “best 

performing” malfunctioning engine, the commenter (96) said. For these reasons, it is 

unreasonable for EPA to promulgate numerical emission limits for periods of malfunction, in the 

commenter’s (96) opinion. Emission testing for malfunctions would be near impossible to 

conduct given the sporadic and unpredictable nature of the events, the commenter (121) said. 

Commenter 154 said that the nature of malfunctions means it is not feasible to predict or 

simulate emissions that occur during periods of malfunctions. 

The commenter (152) asserted that with respect to engines, it is not technologically or 

economically feasible to apply measurement methodology for the emissions during SSM periods 

and further, that it is unreasonable for the Agency in the face of the lack of accurate emission 

measurements to simply set the standard at the level for normal operations (e.g., for sources not 

using a control device). The commenter (152) stated that this situation is precisely the 

circumstance in which Congress envisioned that a work practice standard would be established, 

and urged EPA to adopt a work practice standard applicable to malfunction and startup periods 

for engines consistent with section 112(h) of the CAA and not to apply the numerical limits for 

normal operations. 

 One commenter (157) believes that the startup and malfunction emission standards for 

RICE using catalytic controls should include maintenance checks and readiness testing, which 

are typically short in duration. Therefore, the commenter stated that the catalytic controls would 

not reach the required temperature for effective control. 
88

 One commenter (134) stated that EPA solicited comment on the level of specificity 

needed to define the periods of startup and malfunction. The commenter (134) believes the 

responses differ based on whether the event is a startup or malfunction. The commenter (134) 

noted that startup of an engine begins with the start of fuel flow to the engine and ends when the 

engine has achieved normal operating temperature and air to fuel flows as indicated by the 

manufacturers’ specifications, and while the initiation of a startup is predictable, its conclusion is 

not time-determined, but operationally-determined. The commenter (134) noted where a catalyst 

is used to control emissions; startup does not end until the required catalyst bed temperature has 

been achieved, however, this may happen before the engine air and fuel flows are normal and 

thus catalyst bed temperature is not the exclusive criterion that defines the end of the startup 

period. The commenter (134) noted that the start of the malfunction should be defined as when 

the normal operation emission limit is exceeded and the end of the malfunction should be set as 

when the normal operation emission limit is restored or the engine is shutdown. The commenter 

(134) noted that malfunctions often require shutdown to address, but such shutdowns can be 

delayed because immediate engine shutdown would cause other upsets. Therefore, the 

commenter (134) believes it would not be reasonable to set any specific time limits on either 

startup or malfunction periods, because their duration can be a function of operational need. 

Similarly, one commenter (96) disagreed that it would be appropriate to set a specific limit on 

the time allowed for startup because not all engines experience the same type of startup and 

malfunction. The length of startup will depend on many factors including engine type, size, fuel 

type and duty cycle, plus the frequency of required startups will also vary greatly among engines 

because some engines are only used for intermittent operation. 
89

Some commenters, including commenters 74, 78, 96 and 99 thought that limiting the 

engine startup time is a reasonable method to limit emissions. Commenter 99 added that the 

most effective way to control emissions during startup for engines with catalysts is to limit the 

amount of time it takes to warm up the exhaust to initialize the catalyzation process and startup 

time can be easily monitored. The commenter (99) added that the time to be monitored at startup 

be defined as from the initial engine in-cylinder combustion, corresponding with continuous 

operation, up to the point that a defined catalyst inlet temperature is reached. The commenter 

(99) also recommended that owners/operators be able to request additional startup time if 

necessary in special circumstances, e.g., in extremely cold climates or where sufficient load 

cannot be reached within 30 minutes. Commenters 74, 78 recommended a limit of 1 hour for 

startup and 30 minutes for shutdown. The rule should not include a time limit for malfunctions, 

as the length of time during which an engine will be out of compliance would depend on the type 

of malfunction, the commenters (74, 78) said. The commenters (74, 78) suggested that each 

affected source would be required to prepare a SSM plan, which would have to address 

appropriate actions and time limits for malfunctions. Commenter 112 suggested that for engine 

startups, the work practice should require loading the engine to normal operating load as soon as 

practicable so that the catalytic controls are within operating range as soon as practicable. 

Commenter 96 provided the following language to address the startup issue: 

“RICE startup operations, which constitute the time period from engine ignition to the time when 

the catalyst temperature is sufficient to enable effective catalyst operation, shall be minimized. 

Startup time shall not exceed 30 minutes or the manufacturer’s startup recommendations, unless 

the Administrator approves a longer time for certain engine classes or approves a longer startup 

time to address special conditions and requirements (e.g., cold weather installations) in response 
90

to a petition from the owner/operator. During initial commissioning of the engine/equipment 

installation, additional time may be required for the set-up procedures before normal catalyst 

operation can be expected. Malfunctioning RICE shall be shut down and repaired as soon as 

practicable based on the engine's application and use.” 

 Commenters (121, 154) do not support setting the same limits for SSM periods as for 

normal operations. Commenter (121) said that for engines with add-on controls, given that the 

catalysts have to reach a certain temperature to be effective, emissions during startup would be 

higher than during normal, steady state operation. The commenter (121) noted that EPA has a 

separate cold-start test with emission limits different from those required during the Federal Test 

Procedure. The commenter (121) attached a technical paper that illustrates the increased 

emissions during startup. Commenter (154) said there is no record support for this option and 

that any diesel engine could be expected to have different emissions as it starts up. Bag sampling 

by one industry member indicates CO emissions during startup are significantly higher (as much 

as double) than during steady state. 

 Commenters (121, 154) also objected to EPA’s proposed second option. Commenter 

(121) said the data are apparently derived from the best controlled engines not using catalytic 

controls. The commenter (121) said that emissions data from steady-state operation of 

uncontrolled engines does not account for the cooler engine and fuel temperature conditions 

during startup. Nor does the second option properly account for malfunctions. 

Two commenters (150, 154) said that EPA has not supported its assertion that emissions 

should not be different during periods of shutdown compared to normal operations. According 

the commenter (154), EPA has created no record to substantiate its assertion. The commenter 

(154) asserts that data would likely reveal variation among RICE shutdown emissions. For 
91

example, for RICE where there is a cool down period where the engine operates for a period of 

time (10 to 15 minutes) at reduced load and revolutions per minute, these conclusions could be 

wrong. All existing data has been acquired at 100 percent speed and load conditions, +/- 10 

percent. Normal operation can cover a wide range of speed and load conditions for which preand post-catalyst data do not exist. Without hard data at “off point” conditions, no defensible 

conclusion can be drawn, which makes EPA’s unsupported assertion arbitrary. The commenter 

(154) believes the best approach is for sources to follow appropriate operational procedures 

during shutdown periods. EPA should use section 112(h) of the CAA to allow facilities to 

establish source-appropriate procedures during shutdown, the commenter (154) said. 

One commenter (154) stressed that EPA needs to evaluate each source category 

independently regarding the time required for shutting down equipment in a controlled fashion 

and the emission control equipment effectiveness during the shutdown period. 

 After the conclusion of litigation, if EPA pursues SSM limits for this category, it should 

consider precedents in the mobile source counterparts and the NSPS, according to commenter 

121. These engines are already well-controlled through other standards set by EPA, and 

additional requirements or changes are unnecessary under the RICE MACT, in the commenter’s 

(121) opinion. Another difficulty is defining the exact time period for “startup,” the commenter 

(121) noted. For new engines, the commenter (121) recommends that EPA and engine 

manufacturers work together to determine whether startup emissions can be addressed in the 

certification process. 

 Commenter 154 proposed two options for EPA to address emissions during SSM events, 

both of which are fully supported by law and could be fully supported through data. Alternative 

1 would be to treat SSM emissions as de minimis, using the D.C. Circuit rationale in Alabama 
92

Power Co. v. Costle. The commenter (154) noted that catalyst systems do not perform at low 

temperatures, and the SSM periods vary in duration and intensity, which can significantly impact 

actual emissions profiles. The commenter (154) provided examples of why an assumption that 

SSM emissions are identical to normal stable operations emissions is erroneous and a gross oversimplification of unit operations. 

 Commenter 162 said EPA should explain the justification behind setting CO and 

formaldehyde emission limits during periods of SSM. The commenter (162) does not see how 

one can assure compliance with an emission limit during a malfunction and does not know of 

any test methods that can be conducted during the relatively short periods of startup or shutdown. 

The commenter (162) asserted the compliance with SSM plans will ensure emissions are 

minimized during these times. By imposing emission limits during periods of SSM, RICE 

owner/operators will have to report deviations for each instance, even if the owner/operators took 

actions in compliance with their SSM plan, because a reliable compliance demonstration is not 

available for existing equipment, according to commenter 162. 

Five commenters (89, 101, 151, 221, 231) stated that SSM emission limits are unproven 

and cause compliance uncertainty. The commenters (89, 101, 151, 221, 231) indicated that EPA 

set the SSM emission limits assuming that emissions during SSM periods are the same as steady 

state engine operation before the catalyst. According to the commenters (89, 101, 151, 221, 

231), HAP emissions during SSM activities have not been studied, but are definitely not stable 

over hourly averages like the proposed standard assumes. With today’s knowledge, the 

commenters (89, 101, 151, 221, 231) believe that SSM emissions standards are not feasible. 

 Two commenters (112, 225) stated that operators of facilities with Title V permits may 

have concerns about the annual compliance certifications since compliance with the standards is 
93

unknown during startup and malfunction since emissions are rapidly changing during startup. 

One of these commenters (112) asserted that the SSM standards are instantaneous standards, not 

hourly averages, but no one knows if the proposed instantaneous limits can be met without test 

data. This commenter (112) indicated that compliance certifications for Title V permits may 

necessitate testing, which is not included in EPA’s cost analysis. 

 The commenter (150) believes that a clarification is needed regarding the co-proposal 

associated with Table 3 of the preamble (74 FR 9703). The commenter (150) believes that EPA 

is suggesting an amendment to existing regulations for certain categories of engines in order to 

set limits during periods of startup and malfunction, but the commenter finds the scope and 

possible applicability of this co-proposal unclear. If EPA is proposing that standards be relaxed 

during SSM events, the commenter (150) would support such a concept. 

Commenter 240 said that in contrast to other subcategories that allow for higher emission 

limits during periods of startup and malfunction, EPA requires that emergency CI engines meet 

the same 40 ppmvd CO at 15 percent O2 standard at all times. This commenter (240) looked at 

manufacturer specifications for new engines that show higher CO emissions at lower loads, with 

decreasing emissions as the engine progresses to higher loads. In addition to lower loads that 

may occur during a startup or malfunction event, good engineering practice for these engines is 

not to operate at full loads during normal operations or startup and malfunction. 

One commenter (76) noted that the NFPA Code 24 requires emergency diesel fire pump 

engines to be operated for 30 minutes per week to readiness testing purposes. It will raise 

difficult questions for the owners/operators of these engines if EPA requires emission limits 

during startup times, e.g., what should the owner do if the engine is unable to reach the required 

limits within the 30 minutes startup, the commenter (76) asked. The commenter (76) asked if the 
94

owner would be required to run the engine for longer e.g., up to 1 hour in order to reach steady 

state conditions. Even if the owner does not meet the limits, the owner will still have to conduct 

the weekly test under NFPA code and replacing emergency diesel fire pumps in a short 

timeframe is not practical, the commenter (76) said. Therefore, the commenter (76) indicated 

that it may not be able to comply with both the EPA and NFPA requirements for emergency 

diesel engines. 

Two commenters (103, 154) responded to EPA’s request on how to define a startup and 

malfunction. One commenter (154) said that EPA’s request reveals the profound lack of 

foundation that EPA has to propose rulemaking options for regulation of RICE SSM emissions. 

The commenter (154) will be pleased to assist EPA in developing a record for a future 

rulemaking to address SSM and noted that such an effort should also address the health and 

safety implications of regulating SSM events. 

Response: EPA received extensive comments on the proposed requirements applicable to 

existing stationary engines during SSM. Consistent with the recent Court decision that vacated 

the exemption in 40 C.F.R. 63.6(f)(1) and (h)(1) for SSM (Sierra Club v. EPA, 551 F.3d 1019), 

EPA has established standards in this rule that apply at all times. EPA disagrees with those 

comments suggesting that EPA was premature in proposing standards during periods of startup, 

shutdown and malfunction. The United States Court of Appeals for the District of Columbia 

Circuit issued its opinion vacating the SSM exemption in December 2008, and we appropriately 

accounted for that decision in proposing the rule in February 2009. EPA does not believe it is 

appropriate to promulgate final rules that are inconsistent with the decision of the D.C. Circuit. 
95

EPA has determined that the emissions from stationary CI engines during startup are 

significantly different than the emissions during normal operation. During startup, incomplete 

combustion of the diesel fuel causes variations in the pollutant concentrations and fluctuations in 

the flow rate of the exhaust gas. Incomplete combustion is due to cold areas of the cylinder 

walls that cause the temperature to be too low for efficient combustion. As the engine continues 

to operate, these cold regions begin to heat up and allow for more complete combustion of the 

diesel fuel and stabilization of the exhaust flow rate and pollutant concentrations. In addition, 

the engine experiences extreme transient conditions during startup, including variations in speed 

and load, poor atomization of the fuel injection, which leads to variable engine and engine 

exhaust temperatures, variable exhaust gas flow rates, and variable diluent pollutant 

concentration. Note for example the brief time spent at different load conditions as shown in 

Figure 1 of the attachment to EMA’s letter dated February 17, 2009 (EPA-HQ-OAR-2008-0708-

0019), which illustrates the transient nature of the engine startup phase. Other factors that cause 

emissions to be higher during startup, including for engines that are not equipped with oxidation 

catalyst, are a higher propensity for engine misfire and poorer atomization of the fuel spray 

during startup. After-treatment technologies like oxidation catalysts and CDPFs must also reach 

a threshold temperature in order to reduce emissions effectively. In the February 17, 2009, EMA 

letter, EMA provided various graphs illustrating sample engine startup profiles and graphs 

demonstrating the effect of engine exhaust temperature on catalyst efficiency. Figure 6 of the 

attachment to EMA’s letter (EPA-HQ-OAR-2008-0708-0019.1) shows how the CO efficiency is 

a function of the catalyst inlet temperature. 

EPA has evaluated the criteria in section 112(h) and carefully considered and reviewed 

the comments on this issue. EPA has determined that it is not feasible to prescribe a numerical 
96

emission standard for stationary CI engines during periods of startup because the application of 

measurement methodology to these engines is not practicable due to the technological and 

economic limitations described below. 

EPA test methods (e.g., 40 CFR part 60, appendix A, Methods 2, 3A, 4, and 10) do not 

respond adequately to the relatively short term and highly variable exhaust gas characteristics 

occurring during these periods. The innate and substantial changes in the engine operations 

during startup operations create rapid variations in exhaust gas flow rate as well as changes in 

both pollutant and diluent gas concentrations. Correlating the exhaust gas flow rates and the gas 

components concentration data for each fraction of time over the entire period of a startup 

operation is necessary to apportion the values appropriately and to determine representative 

average emissions concentrations or total mass emissions rate. 

Measuring flow and concentration data in the types of rapidly changing exhaust gas 

conditions characteristic of stationary CI engines is unachievable with current technologies 

applicable to stack emissions testing. For example, application of Method 2 to measure stack 

flow rate requires collecting data for velocity pressure and stack temperature at each of 12 

traverse points and a corresponding stack moisture and oxygen concentration (for molecular 

weight determination). This traverse operation requires about 30 minutes to complete to produce 

a single value for the test period, which is approximately the same amount of time as the engine 

startup period. Clearly a single flow rate value would not sufficiently represent the variable flow 

conditions nor allow appropriate apportioning of the pollutant concentration measurements over 

that same period for calculating a representative average emissions value. Even if the start-up 

period is longer than 30 minutes, the stack flow rate test period could not be short enough to 

represent the short term (e.g., minute-by-minute) result necessary for representative emissions 
97

calculations. These findings lead us to conclude that correlating the flow and concentration data 

as necessary to determine appropriate proportional contributions to the emissions rates or 

concentrations in calculating representative emissions over these short highly variable conditions 

with currently available field testing procedures is problematic for stationary CI engines. In 

addition, even were it technically feasible to measure emissions during startups for stationary CI 

engines, the cost of doing so for every startup at every covered engine would impose a 

substantial economic burden. There are approximately 936,000 existing stationary CI engines 

that are subject to this rule; the cost for testing every one of these engines during engine startup 

could be more than $1 billion. 

EPA is therefore finalizing an operational standard in lieu of a numerical emission limit 

during periods of startup in accordance with section 112(h) of the CAA. EPA is limited to the 

information before it, which, of course, includes any information provided by the commenters. 

See 112(d)(3)(A). In this case, EPA carefully analyzed all of the information before it, including 

that provided by commenters, and determined that this standard complies with the requirements 

of sections 112(d) and 112(h). The final rule requires that owners and operators of stationary 

engines limit the startup time to 30 minutes or less. Engine startup is defined as the time from 

initial start until applied load and engine and associated equipment reaches steady state or normal 

operation. For stationary engine with catalytic controls, engine startup means the time from 

initial start until applied load and engine and associated equipment reaches steady state or normal 

operation, including the catalyst. Based on information received from engine producers and 

operators of stationary existing CI engines, EPA believes that limiting the engine startup time to 

30 minutes or less is representative of the best controlled engines’ operation during startup. EPA 

expects that this amount of time is consistent with the warm-up time needed and would be 
98

sufficient in most cases. EPA believes that 30 minutes is reflective of what the best controlled 

existing stationary CI engines are currently doing in order to reduce HAP emissions during 

periods of startup. Therefore, the final rule requires that owners and operators of stationary 

engines limit the startup time to 30 minutes or less. EPA is also including a requirement in the 

final rule to minimize the engine’s time spent at idle and minimize the engine’s startup time at 

startup to a period needed for appropriate and safe loading of the engine, not to exceed 30 

minutes, after which time the otherwise applicable emission standards apply. As with any work 

practice, CAA section 112(h)(3) and EPA’s implementing regulations at 40 CFR 63.6(g) provide 

that major sources can petition the Administrator for approval of an alternative work practice, 

which must be at least as stringent as what is required in the regulation. 

Regarding shutdown, EPA determined that it was not necessary to establish different 

standards that would be applicable during shutdown for stationary CI engines. The commenters 

did not provide any information that shows emissions would be higher during shutdown than 

during normal operation. In addition, commenters are incorrect that compliance with the 

standards must be instantaneous. Compliance with these emission standards has always been 

based on the results of testing that is conducted over a three-hour period; EPA has made this 

more explicit in this rule. Since the shutdown period for stationary CI engines is typically only a 

matter of minutes, it is believed that even if a shutdown occurred during the performance test, the 

engine would still be able to comply with the emission limitation. In a letter dated February 17, 

2009 (EPA-HQ-OAR-2008-0708-0019), EMA indicates that HAP emissions will be sufficiently 

controlled during periods of shutdown. EMA stated in its letter that according to manufacturers, 

emissions control equipment would most likely continue to reduce emissions as designed 

throughout the shutdown period. According to EMA, this is because engine emissions control 
99

systems and equipment are, during the start of an engine shutdown, at high enough temperatures 

to control HAP emissions and will continue to be sufficiently high until the engine shuts down. 

This trend is illustrated in the attachment to EMA’s February 17, 2009, letter to EPA, where 

EMA provided two graphs with sample engine shutdown profiles. Figure 2 of the attachment to 

EMA’s letter (EPA-HQ-OAR-2008-0708-0019.1) shows catalyst temperatures versus minutes 

during engine shutdown and illustrate stable catalyst temperatures. 

In establishing the standards in this rule, EPA has taken into account startup periods and, 

for the reasons explained above, has established different standards for those periods. With 

respect to malfunctions, EPA proposed two options for subcategories where the proposed 

emission standard was based on the use of catalytic controls. The first proposed option was to 

have the same standards apply during normal operation and malfunctions. The second proposed 

option was that standards during malfunctions be based on emissions expected from the best 

controlled sources prior to the full warm-up of the catalytic control. For subcategories where the 

proposed emission standard was not based on the use of catalytic controls, we proposed the same 

emission limitations apply during malfunctions and periods of normal operations. EPA is 

finalizing the first option described above, which is that the same standards apply during normal 

operation and malfunctions. In the proposed rule, EPA expressed the view that there are 

different modes of operation for any stationary source, and that these modes generally include 

startup, normal operations, shutdown, and malfunctions. However, after considering the issue of 

malfunctions more carefully, EPA believes that malfunctions are distinguishable from startup, 

shutdown and normal operations. Periods of startup, normal operations, and shutdown are all 

predictable and routine aspects of a source’s operations. However, by contrast, malfunction is 

defined as a “sudden, infrequent, and not reasonably preventable failure of air pollution control 
100

and monitoring equipment, process equipment or a process to operate in a normal or usual 

manner * * * ’’(40 CFR 63.2). EPA has determined that malfunctions should not be viewed as a 

distinct operating mode and, therefore, any emissions that occur at such times do not need to be 

factored into development of CAA section 112(d) standards, which, once promulgated, apply at 

all times. For example, we note that Section 112 uses the concept of “best performing” sources 

in defining MACT, the level of stringency that major source standards must meet. One 

commenter expressed the view that it is not logical to apply the concept of “best performing” to a 

source that is malfunctioning. Indeed, the goal of best performing sources is to operate in such a 

way as to avoid malfunctions of their units. Similarly, although standards for area sources are 

not required to be set based on “best performers,” we believe that what is "generally available" 

should not be based on periods in which there is a “failure to operate.” Moreover, even if 

malfunctions were considered a distinct operating mode, we believe it would be impracticable to 

take malfunctions into account in setting CAA section 112(d) standards for stationary CI 

engines. As noted above, by definition, malfunctions are sudden and unexpected events and it 

would be difficult to set a standard that takes into account the myriad different types of 

malfunctions that can occur across all sources. Moreover, malfunctions can vary in frequency, 

degree, and duration, further complicating standard setting. 

Finally, EPA believes that malfunctions will not cause stationary CI engines to violate the 

standard that applies during normal operations. Stationary CI engines would in most cases shut 

down immediately or with very little delay in the event of a malfunction. Because the standard is 

expressed as the average of three one-hour runs, or a work or management practice, any 

emissions that occur prior to engine shutdown should not affect a source’s ability to comply with 

the standard. Commenters' concerns regarding compliance certifications should not be a concern 
101

for this same reason. This approach will also encourage shutdowns as soon as practicable when 

a malfunction that affects emissions occurs. In the unlikely event that a source fails to comply 

with the applicable CAA section 112(d) standards as a result of a malfunction event, EPA would 

determine an appropriate response based on, among other things, the good faith efforts of the 

source to minimize emissions during malfunction periods, including preventative and corrective 

actions, as well as root cause analyses to ascertain and rectify excess emissions. EPA would also 

consider whether the source's failure to comply with the CAA section 112(d) standard was, in 

fact, “sudden, infrequent, not reasonably preventable” and was not instead “caused in part by 

poor maintenance or careless operation.” 40 C.F.R. § 63.2 (definition of malfunction). 

EPA does not agree with the commenter who said that EPA should treat SSM emissions 

as de minimis. It is doubtful whether a de minimis exemption is even possible under section 

112(d) of the Act in these circumstances, see National Lime Ass’n v. EPA, 233 F. 3d 625, 640 

(D.C. Cir, 2000), but in any case the commenter provides no specific information to justify EPA 

making such a de minimis finding in this instance. Given the very narrow and specific 

circumstances delineated by the court in Alabama Power v. Costle, 636 F.2d 323 (D.C. Cir. 

1979) for making such a finding, and the lack of specific information from the commenter that 

these circumstances exist in this instance, we do not make a de minimis finding. 

While commenters 74 and 78 do not provide emissions tests to verify the emissions they 

claim for their engines, EPA notes that, as discussed elsewhere in this document, it has revised 

its standards for existing stationary CI engines based on a broader database of engines, as 

suggested by the commenters, at various speed and load conditions, and this will affect the 

standards in place during periods of shutdown and malfunction. 
102

3.2 Comment: One commenter (99) said that it agrees with EPA that HAP emissions during 

shutdown are controlled by existing methods and technologies for engines that use catalysts 

because the exhaust will most likely be at a sufficient temperature for HAP control. 

Response: No response is needed. 

3.3 Comment: One commenter (134) believes the final rule must allow actions designed to 

prevent unsafe operations during SSM periods. The commenter (134) believes that by imposing 

numerical emission limits during startup and malfunction periods, this proposal could discourage 

sources from taking appropriate actions to respond to non-engine related emergencies since such 

actions could result in an emission noncompliance on the unit. The commenter (134) requested 

that the EPA include a provision in the final rule that allows sources to take actions necessary to 

protect life and property. The commenter (134) requested specific language be included in the 

final rule that allows an owner/operator of a RICE to take all appropriate actions when required 

to avoid unsafe conditions. The commenter (134) noted that this principle has been included in 

past rulemakings, e.g., 40 CFR §63.2450(p) of the Miscellaneous Organic NESHAP, as follows: 

“opening a safety device or taking other actions is allowed at any time conditions require it to 

avoid unsafe conditions.” 

Response: EPA shares the commenters’ concerns that engines must be operated safely. As EPA 

notes above, EPA believes the standard response to malfunction will usually be a fairly rapid 

shutdown of the engine, and given the fact that compliance is based on the average of three onehour tests, emissions during malfunction will not likely have a significant effect on compliance. 
103

In the highly unlikely event that a source fails to comply with the applicable CAA section 112(d) 

standards as a result of a malfunction event, EPA would determine an appropriate response based 

on, among other things, the good faith efforts of the source to minimize emissions during 

malfunction periods, including preventative and corrective actions, as well as root cause analyses 

to ascertain and rectify excess emissions. EPA does not think that any of the provisions in the 

final rule would preclude engine owners and operators from taking actions necessary to protect 

life and property. 

3.4 Comment: One commenter (228) believes that any numeric standards should have averaging 

times established consistent with the engine manufacturers’ averaging time for engine steady 

state operation. The commenter (228) noted that most engines are designed to operate under 

relatively steady-state conditions; however it may take some time for the engines to achieve that 

steady-state of operation. The commenter (228) stated that unless the SSM issues are resolved, 

EPA will need to ensure that there is an adequate averaging period to encompass both the startup 

period and the steady state period needed to stabilize engine emissions performance before 

expecting the engine to be able to demonstrate compliance with a standard based solely upon 

steady state conditions, which it appears that EPA’s emission database represents. 

Response: EPA is not finalizing numerical emission standards in the final rule for periods of 

startup. For the emission standards that are applicable during other operations, EPA has clarified 

that the standards are based on the average of three one-hour runs. This provides an adequate 

averaging period for compliance demonstrations during periods other than startup. 
104

3.5 Comment: One commenter (112) suggested that EPA make it clear that emission limitations 

do not apply during maintenance activities, such as tuning of the air-to-fuel ratio controller 

(AFRC) and engine timing adjustments. The commenter (112) believes that EPA can find under 

CAA section 112(h)(1) that it is infeasible to prescribe or enforce an emission standard for 

control of HAP during such periods. 

Response: The commenter has not provided any data to demonstrate the need for a different 

emission limitation during maintenance activities. Nonetheless, EPA believes that performance 

testing during maintenance would not be optimal since operation during maintenance activities 

may not be sufficiently continuous and lengthy enough for the time needed to conduct the 

performance testing. 

4.0 Emissions 

4.1 RICE Emissions Database 

4.1.1 Comment: Multiple commenters (57, 78, 90, 96, 97, 103, 118, 124, 126, 130, 131,132, 

150, 155, 174, 175, 176, 178, 187, 205, 226, 241, 242, 247) believe that the emissions data for 

engines is not adequate to conduct an appropriate MACT floor analysis. EPA should collect 

additional data and redo the MACT floor analysis, according to numerous commenters. The 

commenters (155, 241, 242, 247) believe that the data EPA used to develop the MACT floor is 

deficient and that certain data should be excluded from the analysis. The commenters (155, 187, 

241, 242, 247) also stated that EPA did not consider emissions variability in setting the MACT 
105

floor. Commenter (78) stressed than an accurate inventory of engines by size is needed to 

accurately evaluate the costs, benefits, and feasibility of a proposed regulation. This is 

particularly important in evaluating the feasibility of CDPF on larger engines. Several 

commenters offered to work with EPA to address the lack of data and determine where 

additional data can be supplemented. 

 Two commenters (155, 242) stated that the MACT floors should not be based on data 

using single measurements, when three measurements are a standard requirement for 

demonstrating compliance. In the absence of multiple measurements, outliers and erroneous 

errors cannot be caught, according to the commenters (155, 242). 

 The commenters (96, 155, 242) said that EPA should use data from units of similar size 

to set standards for sources of the same size, e.g., emissions from a large engine should not be 

used to set standards for a 100 HP engine unless EPA can demonstrate that such an assumption is 

justified. The commenters (96, 155, 242) are concerned that the data EPA has used for the 

MACT floor analysis is not representative of the current population of engines. 

Three commenters (90, 118, and 178) criticized the applicability and use of the RICE 

emissions database as representative of the engines being regulated. One commenter (118) noted 

that the 40 ppmvd numerical emissions limit for CO appears to be based on 10 tests of only one 

make and model of engine (Caterpiller, Model No. 3508) over a 3-day period in the Research 

and Development Laboratory of CSU in 1999 (Docket No. EPA-HQ-OAR-2008-0708-0006). 

The commenter (118) states that according to the engine population data presented in the impacts 

document in the docket (Docket No. EPA-HQ-OAR-2008-0798-0028) the promulgated rule 

would impose limits on more than 50,000 CI engines. The commenter (118) believed that basing 

the limit on such a small and unrepresentative sample jeopardizes the accuracy of any 
106

assumptions made about the operational conditions or performance of the regulated population as 

well as the accuracy of any cost of compliance estimates, and leads to an underestimation of the 

impact of the rule. 

Two other commenters (90 and 178) also noted that the data has no indication of whether 

the engines are used as emergency or non-emergency engines. One commenter (178) noted that 

that the pool of data included compliance tests conducted in the state of California, but that 

CARB does not subject emergency units to testing requirements. Both commenters (90, 178) 

concluded the data should not be used to set the MACT floor for emergency and/or limited use 

units. 

One commenter (90) noted that the data actually shows that the emergency units cannot 

be expected to meet the CO numerical limit of 40 ppmvd without control devices even though 

the impacts document (a memorandum dated February 25, 2009 “Impacts Associated with 

NESHAP for Existing Stationary RICE”) states that it is expected that owners and operators of 

emergency CI engines will be able to meet the emissions limitation without any aftertreatment 

controls and that no control costs were estimated for them. The commenter (90) cited a review 

of their file information and the EPA database as showing that there is no evidence that a 5-year 

old CI engine is likely to meet the CO limit without control. The commenter (90) noted that the 

rigorous NSPS standards and the replacement of units after their operating lifetime is adequate 

for emergency units that due to their few operating hours, emit a small fraction of HAP emitted 

from the source category. 

Response: Section 112(d)(3) of the CAA requires EPA to set MACT standards based on the test 

data that is available to the Agency and this is what EPA did at proposal. EPA recognizes that it 
107

had limited emissions test data at the time it developed the proposed rule. However, EPA notes 

that it used the data that was available at the time of proposal. EPA requested additional test data 

to supplement the emissions database during the development of previous rules for stationary 

engines and also in an advance notice of proposed rulemaking for this rule and did not receive 

any data. EPA again requested additional test data during the comment period for the current 

engine rulemaking and made an additional effort post-proposal to reach out to industry and other 

sources in order to supplement the existing emission data set. EPA did receive additional 

emissions data for stationary CI engines during the post-proposal period for this rulemaking. 

The additional data include tests for 13 stationary engines, ranging in size from 160 HP to 3,570 

HP. The inclusion of this additional data in the MACT floor analysis for the final rule addresses 

the commenters’ concerns about using data for one large engine to set the MACT floor for 

smaller engines. 

 EPA understands the concerns of commenters with regard to whether the MACT floor 

analysis for the proposed rule took emissions variability appropriately into account. EPA did 

take emissions variability into account when conducting the MACT floor analysis for the final 

rule. For engines where EPA had data for multiple tests on the same engine, EPA used the 

highest test run concentration as the representative emissions for that engine. EPA also used the 

lowest percent reduction observed in determining the percent reduction expected from applicable 

aftertreatment in determining beyond-the-floor MACT standards. Therefore, the variability in 

emissions from the engine was factored into the MACT floor analysis and beyond-the-floor 

MACT analysis. 

 The commenters are correct that EPA used data from single runs from the same engine in 

setting MACT floors. EPA appropriately used this data. The testing was conducted at steady 
108

state conditions in a controlled setting and it is believed that the data are representative of the 

emissions and that the results would not be different if a longer sampling time was used. 

 In response to comments about there being no indication whether diesel engines in EPA’s 

MACT Floor analysis were being used for emergency or non-emergency purposes, EPA 

explained in supporting documentation to the proposed rule that there is not expected to be a 

difference between emissions from a stationary emergency and non-emergency engine on a noncumulative basis. EPA determined that the emissions from stationary non-emergency engines 

are comparable to the emissions from emergency engines in terms of the per-engine 

concentration emissions. Therefore, EPA believes that it is appropriate to use non-emergency 

engine data to develop emission standards for emergency engines. Regarding the comment that 

emergency engines cannot meet the numerical limit for CO without control devices, as discussed 

in more detail in comment 5.3.1, the final rule contains work or management practice 

requirements for emergency engines and does not include numeric emission limitations for 

emergency engines. 

4.1.2 Comment: Two commenters (265, 268) referred to EPA’s Method 10 that went into effect 

in May of 2006 as being more stringent that previous requirements, and specifies that 

stratification measurements must be performed on the exhaust stack to ensure that emission 

sampling is not conducted in areas of the stack that have lower levels of CO. In addition, the 

commenters (265, 268) reported that the analyzer is used to measure CO must be certified to 

demonstrate it can pass an interference test to ensure that it is not biased by the presence of other 

components in the exhaust gas. This commenters (265, 268) stated that the use of source data 

that pre-dates the use of Method 10 testing requirements may not be as accurate (or reliable) for 
109

use in the developing of standards, especially since the proposed rule compliance demonstrations 

will be required to adhere to the revised 2006 CO testing procedures. 

Response: Method 10 has always required interference checks for NOx, CO2, and SO2. The 

addition to the method was a requirement for the tester to identify any additional compounds 

present in the gas stream that might be an interference and to demonstrate that these additional 

compounds did not bias the test results. It is unlikely that there are significant additional 

interferences present in the exhaust from RICE that would cause a negative bias in the measured 

CO using Method 10. While measuring emissions from a stratified stack at a single point could 

significantly affect the results of a particular test, it is equally likely to bias the results high as it 

is low so that the average result from many tests is unlikely to be biased. Therefore, the overall 

effect of failing to account for stratification when using Method 10 on the emissions from RICE 

would be unlikely to bias the results in either direction. 

4.1.3 Comment: One commenter (121) reviewed the supporting data and determined that EPA 

failed to specify the actual RICE units from the Emissions Database comprising the top 12 

percent for the various floors. While the database can be queried, in some cases the data entries 

do not directly correspond to the subcategory name. A query for CO will not produce any 

results. In other cases, it is impossible to know whether the query results are the correct list of 

engines relied on by EPA in developing the floor. The commenter (121) gave specific examples 

of these issues. 
110

Response: All of the data used to calculate the MACT floor could be queried from the 

Emissions Database; however, EPA agrees that it was difficult to determine the exact data that 

was used to calculate the MACT floor. EPA has provided more documentation to the final rule 

to clearly show the data that was used to determine the emission standards. This documentation 

includes the top 12 percent of facilities that are used to establish the floors for the various 

subcategories. This is shown in the memorandum, “MACT Floor and MACT Determination for 

Existing Stationary Non-Emergency CI RICE Greater Than or Equal to 100 HP Located at Major 

Sources.” This memorandum includes the steps that were taken to develop the MACT floor for 

all the subcategories. 

4.2 Surrogates 

4.2.1 Comment: One commenter (90) suggested that for emergency and limited use CI units, 

that operate only a small number of hrs/yr, the HAP surrogate of operating hours is more 

appropriate than CO. These engines are frequently limited to an operating hour level by permits 

in order to limit NOx. 

Response: EPA disagrees with the commenter. Operating hours cannot be used as a HAP 

surrogate for any emission source. While there obviously is a connection between the number of 

operating hours and total emissions from a particular source, operating hours do not correlate to 

emissions of HAP or maximum achievable control technology. Therefore, EPA believes that 

operating hours are not an appropriate surrogate for HAP emissions. 
111

4.2.2 Comment: One commenter (215) stated that the use of CO as a surrogate for HAP 

emissions from stationary diesel engines is flawed and does not meet the D.C. Courts three part 

test for reasonableness. According to the commenter, the D.C. Court surrogate three part test 

requires EPA to demonstrate each of the following: 1) HAP from the source must be “invariantly 

present” in the surrogate; 2) control technology that reduces the surrogate must “indiscriminately 

capture” HAP from the source; and 3) control of the surrogate is the only means to control HAP 

from the source. Commenter 215 pointed out that EPA admitted that CO may not be an adequate 

surrogate for metallic HAP emissions in the current proposal. Commenter 215 argued that 

oxidation catalyst is only capable of 30 percent reduction of PM, thus allowing 70 percent of the 

PM, including metallic and semi-volatile HAP to be emitted to the atmosphere. In addition, 

commenter 215 pointed out that technologies that control CO are not the only means by which a 

source can achieve reductions in HAP emitted from stationary diesel engines. The commenter 

(215) believes that based on the D.C. Court’s three tests, final standards are not appropriate, and 

recommended that EPA adopt standards based on PM rather than CO reductions. 

Response: EPA believes that CO emissions are an appropriate surrogate for HAP emissions for 

stationary CI engines. EPA has demonstrated the relationship between CO emissions and HAP 

emissions in previous rulemakings for stationary engines. EPA does not have any data to 

support a relationship between PM emissions and HAP emissions for stationary CI engines, nor 

did the commenter provide any data to support such a relationship for this source category. It is 

clear that there are methods for reducing PM emissions, like reducing sulfur from fuel, that may 

not lead to a reduction in HAP. In addition, it is not clear that reductions in PM would reduce 

emissions of all HAP emitted from stationary engines, particularly emissions of formaldehyde, 
112

acetaldehyde, etc., that represent the vast majority of the HAP emissions from this source 

category. Therefore, for this particular source category, use of PM as a surrogate for HAP is not 

appropriate. The commenter also did not provide any data from testing of stationary CI engines 

to show that CO is not a good surrogate for metallic HAP. CO is also a better surrogate for HAP 

emitted from stationary CI engines than PM because PM is more difficult and expensive to 

measure than CO for this source category. For semi-volatile HAP, the testing conducted by EPA 

at Colorado State University showed that an oxidation catalyst reduced PAH emissions by 

greater than 90 percent for most of the PAH that were tested, and that CO level reductions 

correlated with level reductions in such HAP. 

In addition, EPA is taking an additional action pursuant to its authority under section 

112(d)(2)(B) and (C) for further control of metallic HAP. EPA determined that the most 

effective and achievable method for controlling metallic HAP emissions from existing stationary 

CI engines is through the use of crankcase emission control systems. Combustion gases and oil 

mist that are vented from the engine crankcase are believed to be a substantial source of any 

metallic HAP emissions from stationary CI engines. Existing stationary CI engines are equipped 

with either an open crankcase or a closed crankcase. The open and closed crankcase on an 

existing stationary CI engine is used to relieve pressure from the crankcase due to blow-by gases 

from the pistons. These blow-by gases are a mixture of combustion gases, oil, and metals that 

escape around the pistons during the combustion process to the engine crankcase. Most existing 

stationary CI engines have open crankcases that vent the crankcase emissions directly to the 

atmosphere through a vent in the crankcase. For existing stationary CI engines with closed 

crankcases, the crankcase emissions are directed to a separator that removes oil mist before the 

crankcase gas is routed to the intake manifold to be used as combustion air. The metals in the 
113

blow-by gases are a result of the wear of the piston moving up and down in the combustion 

chamber and are considered the primary source of metallic HAP emissions from existing 

stationary engines. 

EPA notes that even if we accepted the commenter’s view that CO was not an 

appropriate surrogate for metallic HAP, EPA would promulgate the requirements discussed 

below as equipment or work practice requirements for control of such HAP for stationary CI 

engines at major sources. It would not be practicable to measure the metallic HAP emissions 

from an open crankcase for an existing stationary CI engine since the crankcase is open directly 

to the atmosphere rather than vented to the engine exhaust. Capturing these emissions using 

EPA Method 29 would be difficult due to the sporadic flowrate of the blow-by gases, making 

isokinetic sampling of the crankcase exhaust difficult. In addition, testing for metallic HAP is 

very costly and the emission levels from stationary CI engines are likely to be below method 

detection limits. Consequently, EPA believes that it would be infeasible to prescribe a numerical 

emission standard for metallic HAP. 

EPA is promulgating a further requirement pursuant to its authority under section 

112(d)(2)(B) and (C) that requires stationary non-emergency diesel engines greater than 300 HP 

to install either an open or closed crankcase filtration emission control system if the engine is not 

already equipped with one. The open or closed crankcase filtration emission control system 

reduces emissions from the crankcase by filtering the exhaust stream to remove oil mist, 

particulates, and metals. EPA expects the filter will remove nearly 98 percent of the metallic 

HAP and other particulates from the crankcase exhaust stream, based on comparable filtration 

systems for other processes (e.g., baghouses and cartridge filtration systems). Existing stationary 

engines with an open crankcase vent the filtered gas to the atmosphere, whereas the closed 
114

crankcase filtration system routes the filtered gas back to the intake manifold to be used as 

combustion gas. Oil collected by the filtration system for both open and closed crankcases is 

either collected and disposed of properly or routed back to the oil pan. The filter with the 

collected metallic HAP and other particulate in both the open and closed crankcase filtration 

system is replaced periodically and the used filter is disposed of properly. EPA believes this 

management practice will effectively reduce metallic HAP from the existing stationary CI engine 

emissions. As discussed in the memo “MACT Floor and MACT Determination for Existing 

Stationary Non-Emergency CI RICE Greater Than or Equal to 100 HP Located at Major 

Sources” EPA does not believe it is appropriate to require beyond-the-floor controls for engines 

below 300 HP. 

 

4.3 Engine Test Data 

4.3.1 Comment: One commenter (141) provided stack test results for uncontrolled diesel 

engines and diesel engines with SCR. The data showed CO levels ranging from 31 to 112 

ppmvd at 15 percent O2 for diesel engines. 

Response: EPA contacted the commenter and asked if they could provide EPA with the source 

test reports for the stack test data that were summarized in a table their comment, as EPA could 

not use the data without having the source test report. The commenter responded that they did 

not have the resources to provide copies of the documents to EPA. Since EPA did not have the 

test reports and could not review the data, EPA was unable to use the data submitted by the 

commenter in the MACT floor analysis. 
115

5.0 Emission Limits 

5.1 Major Sources 

5.1.1 MACT Floor 

5.1.1.1 Comment: Multiple commenters (89, 101, 103, 112, 122, 126, 150, 151, 155, 167, 187, 

205, 221, 225, 227, 228, 231, 242, 261) were concerned with how EPA set the MACT floor for 

the proposed rule. Several commenters, including 155, 205, 227, and 242 said that EPA has not 

considered variability in setting the MACT floor for the proposed rule. The commenter (155) 

cited the recent Brick MACT ruling which indicated that “floors may legitimately account for 

variability [in the best performing sources that are the MACT floor basis] because “each [source] 

must meet the [specified] standard every day and under all operating conditions.” The 

commenters (155, 242) stated EPA’s data set is not sufficient in covering variability. The 

commenters (155, 242) expressed that it is willing to work with EPA to resolve the issue, but 

efforts may be hindered by the limited timeframe for finalizing the rule. It is necessary to collect 

additional data and conduct a thoughtful and scientifically sound review and analysis process, 

several commenters said (including commenters 122, 155, and 242). 

 In terms of a variability analysis, the commenters (155, 242) specifically suggested as 

one alternative that EPA identify the top 12 percent of engines based on average emissions 

operating at high load. Then, EPA could use lower load of other non-optimum operating 

emissions data to assess variability in the best performers, i.e., the MACT floor must be set less 
116

stringent than the highest data point for the best performers and lead to a less stringent standard. 

Alternatively, EPA could use all data in the average calculation meaning that data from all loads 

would be included, however, this is complicated due to the lack of low load data or data from 

various operating conditions for most tests. Lack of data is also an issue with the first suggested 

approach, the commenters (155, 242) said. In any event, the scarcity of data may necessitate 

additional, focused testing. Both commenters (155 and 242) are willing to work with EPA to 

resolve this issue. 

One commenter (261) noted that the Courts have been critical of EPA’s process for 

setting minimum allowable emission limits. The commenter (261) stated that EPA set the 

emission limits by averaging the best 12 percent of all performance tests for each subcategory, 

but did not consider operational variations of the units. The commenter (261) recommended that 

EPA set emission limits at the emissions level that is actually achieved under the worst 

reasonably foreseeable circumstances for the best performing 12 percent as allowed by the 

Courts in the Cement Kiln MACT and Brick Kiln MACT decisions. 

The commenter (126) acknowledged the difficulties with obtaining test data for RICE, 

however EPA cannot rely on the absence of emissions data to justify its proposed limits. The 

commenter (126) stated that EPA should have issued information collection requests to obtain 

adequate emission data for promulgating standards. 

Multiple commenters (97, 124, 132, 155, 175, 191, 224) suggested that EPA should 

consider a scenario under which lower temperatures and reduced catalyst efficiencies may occur 

due to reduced engine speed or load, resulting in lower temperatures and consider an alternative 

work practice under section 112(h) of the CAA for the situation. 
117

Two commenters (155, 224) noted that the emission standards in the proposed rule apply 

at all times, but that there is no data or information in the rulemaking docket that supports the 

proposed limits at low loads or at operating conditions other than high load. The commenters 

(155, 224) expressed that EPA should provide data and analysis that supports requiring emission 

limits to be met at all times. The commenter (155) said that it is inaccurate to assume that 

emission levels observed at one operating condition can be met at a different operation condition, 

e.g., high load emissions are not the same as low load emissions. The commenter (155) 

recommended that EPA consider technical and economic feasibility of requiring and enforcing 

emission limits at operating conditions where measurements are not technologically and/or 

economically feasible. If emission limits are based on high load emissions data and compliance 

is validated at high load, operating, design or work practices should be considered as an 

alternative way to demonstrate compliance under other operating scenarios, the commenter (155) 

said. Otherwise, the commenter (155) said that EPA needs to undertake a significant effort to 

add emissions data to the docket to support a standard that applies at all times. 

Again, the commenter (155) stated that it could not locate any information in the docket 

that is supportive of requiring emission standards to apply at all times and that the lack of data 

and analysis is a serious oversight on EPA’s part. In terms of compliance, the commenter (155) 

indicated that EPA needs to explain how this would be determined. One question the commenter 

(155) had is what happens if an exceedance happens during a malfunction lasting only minutes. 

In such a case, the commenter (155) asked how that affects compliance. Also, for compliance at 

all times, the commenter (155) asked what averaging times apply. The commenter (155) noted 

that there are several other similar questions that need to be answered. In the commenter’s (155) 

opinion, these compliance issues challenge the enforceability of the emission standards and 
118

therefore section 112(h) of the CAA applies. The commenter (155) believes that emission 

standards would still apply at high load and the performance test is performed at high load, but 

that for other operating conditions, section 112(h) of the CAA would form the basis for 

alternative compliance demonstrations through work or management practices. 

Commenter (140) said there will be little or no environmental benefit to imposing an 

emission limit on CI engines with a power rating between 50 to 300 HP. If, as EPA notes, 

existing engines are expected to comply, there is no reason to impose additional regulatory 

burdens and costs. The requirement for a single initial performance test with no follow up 

testing renders the emission limit moot. The commenter (140) said that O&M requirements, 

similar to other engine types, should be set in lieu of emission limits.

Response: EPA agrees that emissions variability should be better incorporated and has provided 

for variability in the final MACT floor analysis. The final emission standards are based on test 

data collected from stationary engines produced by different engine manufacturers, operating at 

various loads and other conditions, and located in various types of service and locations. The 

engines range in size from 160 HP to 3,570 HP. The data includes engines operating at loads 

from 25-100 percent. To the extent commenters believed further data would have beneficial to 

EPA, EPA must make its determinations based on the information available to it. EPA asked for 

further data, and EPA did receive further data following the proposal, which led to changes in the 

final regulations. For engines operating at reduced speed or loads resulting in a reduced exhaust 

temperature, EPA believes that numerical emission requirements are still appropriate and there is 

no justification to only require work practice standards during these situations. We do not 

believe that the provisions of section 112(h) of the CAA are met (except as discussed elsewhere 
119

with regard to periods of start-up, emergency engines, and engines below 100 HP) because 

testing is not economically and technologically impractical and the emissions can be readily 

routed through a conveyance for purposes of emission testing. EPA believes that the final 

emission standards will be achievable at all times covered by the standards, and will reflect the 

numerous engine models and operating scenarios that can be expected from stationary engines. 

 Regarding the comment asking about the averaging times that apply, EPA has clarified in 

the final rule that the emission standards are based on the average of three one-hour runs. 

5.1.1.2 Comment: Two commenters (121, 154) were concerned with how the floor was 

determined for existing CI emergency engines. One commenter (121) said that the floor data for 

existing CI emergency engines of 300 to 500 HP located at major sources do not correspond to 

the subcategory, and work practices better address emissions from this subcategory. The MACT 

floor memo does not specify which individual data points comprise the best performing top 12 

percent from which the 40 ppmvd CO limit is derived. The commenter (121) described the 

difficulty of conducting a database query to independently verify the source units, but concluded 

that the limit appears to be the result of 10 data points from one test of a 1,000 HP Caterpillar 

engine run at 70 to 100 percent load. If this is the case, the HP of the engine in the database is 

significantly higher than those engines covered by the subcategory and the tests consist of a 

single run of one engine (which would not be a valid test for MACT purposes) at steady state. 

Furthermore, EPA looked only at the single lowest number, which is not the floor setting 

approach for existing sources. 

Commenter 154 said the test results show that the engine that was used to establish the 

emission limit would not be able to comply with the 40 ppm standard. Commenter 154 added 
120

that EPA does not sufficiently justify that the MACT floor determination, based on a 1000 HP 

unit, is applicable to emissions from smaller CI units and emergency units. The commenter 

concluded that additional data are needed to properly conduct a MACT floor analysis if numeric 

emission limits are to be established for smaller non-emergency CI engines under 500 HP. 

 

Response: The proposed MACT Floor for existing stationary CI emergency engines above 300 

HP was based on the data that EPA had available at the time of proposal. Unfortunately, EPA 

had limited emissions data at the time the rule was developed, as acknowledged several times, 

but EPA believes that it was justified in proposing the emission limits it did. 

The MACT floor for non-emergency stationary CI engines above 300 HP was 4 ppmvd 

of CO or 90 percent CO reduction at proposal. The commenter is correct that the proposed 

emission standard was based on emissions data from the study conducted at CSU on a 1,000 HP 

Caterpillar engine. It is true that the engine tested at CSU is larger than the engines included in 

the subcategory. Nevertheless and as previously stated, test data from this engine represented the 

only available data at the time of proposal and was therefore utilized to set the MACT Floor for 

this engine subcategory. EPA made an effort after the proposed rule was published to obtain 

additional test data for stationary CI engines to supplement the limited data set. The new data 

included emissions data from several stationary CI engines smaller than 500 HP, which has been 

incorporated into the MACT floor analysis. The MACT floor analysis for non-emergency 

engine greater than 300 HP but less than or equal to 500 HP was determined to be 137 ppmvd 

CO corrected to 15 percent O2, and is based on the test results from two 450 HP CI engines. For 

non-emergency engines between 100 and 300 HP, the MACT floor was determined to be 230 

ppmvd CO corrected to 15 percent O2, and is based on test results from engines in that size 
121

range. This addresses the concerns expressed by the commenter regarding using the emissions 

from one large engine to set standards for smaller size stationary engines. 

As discussed in greater detail in the response to comment 5.3.1 and 5.4.1, EPA 

reanalyzed MACT for stationary emergency engines at major sources and stationary engines 

smaller than 100 HP at major sources, and determined that it is not feasible to prescribe or 

enforce numerical emission standards for these subcategories of engines is and thus EPA is 

promulgating work practice standards for these subcategories. Thus, the commenters’ concerns 

regarding the data used to set the floor for these engines are no longer relevant. 

5.1.1.3 Comment: One commenter (155) said that EPA should allow alternatives under section 

112(h) of the CAA for demonstrating compliance at reduced load and other reduced temperature 

operating conditions where catalytic control is required. The commenter (155) believes that it is 

not possible to set a standard based on add-on catalyst control that is applicable at all times. The 

performance of the catalyst is dependent on the load, engine type, engine make or model, catalyst 

formulation, catalyst age, and so on, and so therefore, it is infeasible to define a standard as a 

function of load and temperature, according to the commenter (155). The commenter (155) 

recommended that EPA consider a work practice standard to be used at reduced load or other 

reduced temperature conditions where aftertreatment is required to meet the standard. 

Alternatively, if EPA finalizes a catalyst-based standard that applies at all times, such a standard 

must be well rationalized and supported with data and a clear presentation of how the analysis 

was conducted, the commenter (155) said. 
122

Response: EPA agrees that it is appropriate to consider variability in developing the final rule. 

The final emission standards account for operational variability of the stationary engine. This 

includes engines operating at low loads and other reduced operating temperatures. EPA has also 

specified in the final rule that performance tests can be conducted during normal operating 

conditions. The final standards and other requirements are well explained and detailed 

documentation of how the analysis was conducted is included in the docket material. EPA does 

not believe that it would be justified in using the provision in 112(h) to establish work practice 

standards in lieu of emission limits since it is not technically or economically infeasible to 

measure emissions during the operating conditions discussed by the commenter. 

5.1.1.4 Comment: One commenter (98) stated that emissions limits for new or reconstructed CI 

stationary RICE greater than 500 HP located at major sources should be developed using the 

“Tier” standard approach for CO emissions that is currently used by EPA. The commenter (98) 

indicated that new non-road CI engines greater than 500 HP are currently required to meet Tier 2 

/ Tier 3 CO emission standard of 3.5 g/KW-hr. In lieu of the proposed requirement to reduce CO 

emissions by a minimum of 70 percent for new or reconstructed CI engines, the commenter (98) 

believes that EPA should consult with CI engine manufacturers to determine a new Tier standard 

that can be obtained based on operation of RICE with manufacturer’s controls in place, which 

would allow emission limits to be based on demonstrated RICE emissions using procedures 

already employed by EPA. 

The commenter (98) stated that emission limits for existing stationary non-emergency CI 

RICE located at major sources are too stringent when compared with existing emission standards 

for these types of units. The commenter (98) asserted that comparing emission limits presented 
123

in Table 2c of the proposed RICE MACT (40 CFR part 63, subpart ZZZZ) with the Tier 2 / Tier 

3 CO standard for CI engines less than 500 HP (40 CFR 89.112) shows considerable difference 

and demonstrates that emission limits included in this proposed rule for nonemergency CI RICE 

50≤HP≤300 and > 300 HP located at major sources of HAP emissions are too stringent and 

should be revised. The commenter (98) explained that the referenced Tier 2 / Tier 3 CO standard 

(3.5 g/KW-hr) equates to a CO emission rate of 21.2 lb/hr for a nominal 2.75 MW (30 

MMBtu/hr) diesel-fired generator. According to the commenter (98), a 90 percent reduction 

from this value yields a CO emission rate of 2.1 lb/hr, or an equivalent CO concentration of 30 

ppmv at 15 percent O2 for a nominal 30 MMBtu/hr diesel-fired generator. Consequently, the 

commenter (98) believes that EPA should revise the maximum CO concentration required at all 

times except during periods of startup and malfunction from 4 to 30 ppmv at 15 percent O2. 

Response: EPA is not developing requirements for any new or reconstructed stationary engines 

with this rulemaking. New and reconstructed engines were the subject of prior regulations 

issued by EPA, namely the original 2004 RICE NESHAP, which addressed HAP emissions from 

existing, new and reconstructed stationary engines greater than 500 HP located at major sources, 

the CI NSPS, and the 2008 rule that promulgated the SI NSPS and the NESHAP for all new and 

reconstructed stationary engines not covered in the 2004 rule. It appears the commenter may be 

addressing requirements that have already been promulgated years ago and EPA is not taking 

comment on those pre-existing requirements at this time. EPA will be conducting the required 8-

year review in 2012 and will at that time review the emission standards applicable under the 

2004 RICE NESHAP. 
124

Regarding emission standards for existing stationary engines, the CAA requires that EPA 

develop an emission control floor based on the average emission limitation achieved by the top 

12 percent of existing sources. Therefore, basing a stationary engine standard directly on 

standards for nonroad engines is not an option that EPA has available for setting the final 

emission standards, if the nonroad standards are less stringent than the MACT floor. EPA must 

set an emission standard that is at least as stringent as the MACT floor, and this analysis must be 

based on emissions data for stationary engines and cannot take into consideration the emission 

standards for nonroad engines which are set under a different section of the CAA. EPA notes 

that its regulations for nonroad engines promulgate standards for new nonroad engines, and that 

EPA regulations do not cover many of the older nonroad engines that would be the basis of 

comparison to the existing engines regulated in this rule. 

However, based on further information that EPA received since the proposal, EPA did 

revise its standards for existing stationary CI engines. The final standard for non-emergency 

engines is 230 ppmvd CO corrected to 15 percent O2 for engines 100-300 HP; 49 ppmvd CO 

corrected to 15 percent O2 or 70 percent CO reduction for engines 300-500 HP; and 23 ppmvd 

CO corrected to 15 percent O2 or 70 percent CO reduction for engines above 500 HP. These 

standards are considerably closer, and in some cases less stringent than the standard suggested by 

the commenter. 

5.1.1.5 Comment: One commenter (215) stated that EPA determined the MACT floor based on 

the average CO emission from the best performing 12 percent of stationary diesel engines 

without add-on control. To properly meet the CAA requirement that 112 standards achieve the 

“maximum degree of reduction in emissions,” commenter 215 believes that EPA should have 
125

reviewed emissions of HAP in the particulate phase, or that condense on particles, as well as 

those in the gaseous form. 

Response: EPA believes that the final standards developed using test data from the top 12 

percent of emission sources meet the CAA requirements, and no additional review of HAP in the 

particulate phase or condensed on particulates needs to be evaluated. The commenter provides 

no data to show that average CO emissions could not also be used as a surrogate for HAP in 

particulate phase and EPA continues to believe that CO is an adequate surrogate for all HAP. 

However, EPA has reviewed metallic HAP separately from other HAP to determine if further 

reasonable controls are appropriate under section 112(d). As discussed more fully in the 

memorandum titled, “MACT Floor and MACT Determination for Existing Stationary NonEmergency CI RICE Greater Than or Equal to 100 HP Located at Major Sources,” EPA is 

promulgating separate requirements to reduce emissions from the crankcase because EPA 

believes that this will reduce metallic HAP in particular. EPA has discussed crankcase 

emissions and published crankcase emission factors (however, note that such data is based on 

limited information) in AP-42 section 3 for stationary diesel engines.16 There is also some 

information available on crankcase emissions from nonroad engines published by OTAQ in 

documentation published for the NONROAD model.17 Information from Donaldson provides 

                                                           

16 AP-42, Fifth Edition, Volume I Chapter 3: Stationary Internal Combustion Sources, section 

3.3 Gasoline and Diesel Industrial Engines, 

http://www.epa.gov/ttn/chief/ap42/ch03/final/c03s03.pdf and 

http://www.epa.gov/ttn/chief/ap42/ch03/bgdocs/b03s03.pdf. 

17 Exhaust and Crankcase Emission Factors for Nonroad Engine Modeling – Compression 

Ignition. EPA420-P-04-009. April 2004. NR-009c. 

http://www.epa.gov/oms/models/nonrdmdl/nonrdmdl2004/420p04009.pdf. 
126

some information on how much of total emissions the crankcase emissions account.18 

Information on crankcase emissions can also be found in a paper on emissions from heavy-duty 

diesel engines published by the Society of Automotive Engineers (SAE)19 and in a paper on 

locomotive PM crankcase emissions published by the American Society of Mechanical 

Engineers (ASME).20 

5.1.2 Subcategories 

5.1.2.1 Comment: One commenter (242) noted that a subcategory is justified for engines located 

on offshore platforms and in cold weather regions. According to commenter 242, due to space 

constraints on platforms, installation of add-on controls is expensive and/or impossible. In 

extreme cold weather it is difficult and sometimes impossible to maintain the exhaust hot enough 

for catalyst operation, particularly for emergency, limited use and intermittently used engines, 

the commenter (242) said. For these reasons, commenter 242 believes that it is reasonable that 

EPA create subcategories for non-continental areas/offshore platforms and for cold weather 

regions, i.e., less than 0°F as was done in 40 CFR part 60, subpart KKKK for stationary 

combustion turbines. The commenter (242) recommended that these special category engines 

only be subject to work practice standards. 

                                                           

18 Donaldson Filtration Solutions. Filtration System from Open and Closed Engine Crankcase 

Vents. Brochure No. F111118 (10/09). 

19 SAE International. A Study of the Emissions of Chemical Species from Heavy-Duty Diesel 

Engines and the Effects of Modern Aftertreatment Technology. 2009-01-1084. 

20 ASME 2009. Proceedings of the ASME Internal Combustion Engine Division 2009 Fall 

Technical Conference. ICEF 2009. September 20-24, 2009, Lucerne, Switzerland. Crankcase 

Emission Contributions to PM for Two Tier 2 Line-Haul Locomotives. ICEF2009-14021.
127

Response: The EPA does not agree that it would not be feasible to install add-on controls on 

offshore platforms. Catalyst manufacturers have had many experiences with installing controls 

in situations where space is a concern, for example in mobile source engines. Regarding engines 

located in cold weather regions, the commenter did not submit any data to show that the 

emission limitations could not be achieved by these engines. A subcategory for turbines located 

north of the Arctic Circle was created in subpart KKKK because the emission controls that are 

inherent to the turbines themselves did not operate as well in the cold weather, not because postcombustion controls such as oxidation catalyst were not feasible in these areas. 

5.1.2.2 Comment: Two commenters (78, 96) expressed concern over EPA not establishing 

additional subcategories for diesel engines beyond 300 HP. One commenter (96) said that EPA 

has not considered the very large diesel engines that exist and that having non-emergency diesel 

engines in the range of 300 to 500 HP as the largest category and representative of the entire 

range of large stationary engines is not appropriate nor consistent with the subcategorization 

scheme in the CI NSPS. A separate subcategory of engines with a displacement above 30 liters 

per cylinder (l/cyl) was created in the CI NSPS and the same subcategory should be established 

for this rulemaking, commenter 96 said. Very large CI engines are vastly different from smaller 

diesel engines that are often derived from mobile applications and the proposed rule 

inappropriately does not take this into account, the commenter (96) said. These very large 

engines utilize different fuels, are mostly derived from larger marine engines, can be several MW 

in size operating at low to medium speeds, and cannot rely on the same type of add-on controls 

as smaller diesel engines, according to commenter 96. The emission standards required in the 

proposed rule for diesel engines are not technically feasible for engines above 30 l/cyl, according 
128

to commenter 96. The commenter (96) said that not all very large engines can use ULSD, 

particularly those that are older engines, a key factor in potentially achieving lower emissions. 

Typical control devices applied to smaller engines like CDPF and oxidation catalyst are not 

applicable for very large engines because the control devices are either physically incompatible 

with large engines and exhaust flows, or, have not been demonstrated on very large engines, 

which is the case for oxidation catalysts and any technology that is required must be available, 

feasible and cost effective, the commenter (96) said. Closed crankcase ventilation typical on 

smaller engines is not recommended for large liquid-fueled engines because of risk associated 

with compressor fouling and negative impact on engine performance and reliability, the 

commenter (96) stated. 

One commenter (78) said EPA should divide the largest engine category into additional 

categories, as was done for the compression-ignition NSPS and for the locomotive and marine 

engine standards. The commenter (78) noted that a 300 HP engine is relatively small and that 

the smallest of the commenter’s (78) engines is six time this size, while the largest are over 25 

times this size. In order to fully evaluate the technical feasibility and cost-effectiveness of the 

proposed regulation, more size categories are needed. 

Response: In order to establish different requirements for large stationary CI engines, EPA 

would need information to show that these emissions and operation of these engines are 

sufficiently different to warrant subcategorization. The commenter has not provided any 

emissions or operating data to show that the emission limits are not achievable for these engines. 
129

5.1.2.3 Comment: One commenter (88) stated that EPA could establish an additional 

subcategory of engine types to address unique circumstances of nuclear emergency diesel 

generators as well as other power plant emergency diesel generators that operate for only a 

limited number of hrs/yr. For example, EPA could create a subcategory of engines that operate 

under 200 hrs/yr on the basis that these units rarely operate sufficiently long enough to reach the 

necessary temperature window to begin the control equipment’s optimal function. For these 

limited-use engines, EPA could require that they comply with good management practices.

Response: EPA agrees that emergency stationary engines should be a different subcategory than 

non-emergency engines. For emergency CI engines located at area sources, EPA has in the final 

rule established management practice standards, consistent with the commenters 

recommendation. For emergency CI engines at major sources, EPA has determined that work 

practice standards are appropriate for those engines. 

5.3 Emergency Stationary Engines 

5.3.1 Comment: Several commenters (36, 48, 74, 77, 79, 81, 86, 88, 90, 96, 97, 99, 112, 118, 

119, 121, 139, 140, 155, 157, 160, 161, 162, 167, 171, 173, 175, 176, 181, 196, 201, 209, 213, 

216, 220, 223, 224, 227, 229, 247, 249, 253, 256) expressed concern with the proposed limits for 

emergency engines at both area and major sources. Numerous commenters stated that EPA 

should adopt management practices for emergency engines at area sources and not require 

emission limits from these engines. Commenters stated that emergency engines need special 

consideration, due to minimal operation, and commenters 121 and 154 said that EPA should 
130

apply section 112(h) of the CAA for emergency engines at major sources because of this limited 

operation. Several commenters recommended that emergency engines be subject to only work 

practice standards that limit the number of hours allowed for operation during non-emergency 

events. 

For many existing engines in the field, add-on control technology is not feasible and not 

compatible with the engine and will cause potential performance problems as well as 

compromising functionality, commenter 121 said. Commenter 154 said that the numeric 

emission limits are not appropriate for emergency engines, because they cannot be met by most 

emergency engines as shown by available emissions test data on emergency engines. If EPA 

keeps emission limits for emergency engines, the commenter (155) thinks that EPA needs to 

provide justification as to the basis for such limits. Commenter 96 said that it is unreasonable to 

require existing emergency engines to meet numerical limits based on the best performing 12 

percent of sources, which consequentially leads to 88 percent of the engines not being able to 

meet the limits without installing some form of controls. EPA correctly concluded that add-on 

controls are inappropriate and too costly for emergency engines, some commenters said, 

including commenters 96 and 253, but the actual rule imposes limits not achievable in many 

cases without add-on controls, therefore forcing emergency engines to add emissions controls or 

be replaced, which was not the Agency’s intent. Commenter 96 provided in its comments 

various charts for different engine categories of where it has shaded several areas where it 

believes that EPA should replace limits with operational hour limits. 

 Commenter 99 said that if EPA decides to go final with emission standards for 

emergency engines, the standards must be such that all properly maintained emergency engines 

can comply. As discussed above, as proposed, emergency engines cannot comply with the 
131

standards by altering operating characteristics and the commenter 99 explained that there are no 

“knobs” available to “turn down” HAP emissions. The commenter (99) expressed that if EPA 

finalizes the proposed standard for emergency engines it would obsolete many engines in this 

group leading to loss of reliable emergency power, which would be unacceptable to the public, 

will jeopardize public safety, will directly interfere with existing building codes, and a lead to a 

high cost to industry in lost production during emergencies. 

One commenter (88) recommended that EPA require management practices rather than a 

numerical emission limit for emergency diesel generators greater than 500 HP at area sources. 

The commenter (88) suggested that such management practices could replace the existing 

proposed emission standard requirements for emergency CI engines greater than 500 HP that are 

identified in line 7 of Table 2d of the proposed rule. The commenter (88) stated that the 

proposed rule and related docket indicates that CI emergency diesel engines can achieve a 40 

ppmvd CO emission standard for both normal operations and startup or malfunction periods 

without add-on technology.21 The commenter (88) suggested that EPA may not have considered 

the following: 

• Two-stroke engines emit higher levels of CO than 40 ppmvd, but the proposed rule does 

not distinguish between two-stroke and four-stroke CI engines.

• Older engines with mechanical fuel injection or ignition retard technology emit higher 

levels of CO than newer electronic fuel injection engines.

                                                           

21 EPA Docket No. EPA-HQ-OAR-2008-0708-0028, Memorandum from Bradley Nelson, EC/R, 

Inc. and Tanya Parise, Alpha-Gamma Technologies, Inc. to Jaime Pagan, EPA 

OAQPS/SPPD/ESG, RE: Impacts Associated with NESHAP for Existing Stationary RICE 

(February 25, 2009).
132

• The rationale for 40 ppmvd CO during startup only acknowledged that controls, such as 

an oxidation catalyst, could not be used until the engine is up to temperature. In reality, 

CO levels are substantially higher during startup while the engine is cold and combustion 

of diesel fuel is more incomplete. 

One commenter (209) believes that the emission standards for emergency CI engines at 

area sources is flawed because it is based on the flawed MACT determination for CO, which has 

not been properly and lawfully established as MACT and likewise should not be used as GACT. 

One commenter (112) requested that EPA modify emission limits on emergency engines 

at major sources based on a redetermination of the MACT floor. The commenter (112) stated 

the opinion that EPA can account for the worst reasonably expected operating conditions of the 

best performing 12 percent of engines, and EPA should use that flexibility provided by Congress 

and the Courts. The commenter (112) believes that even with this adjustment, such a standard 

will effectively require many operators to replace or add catalytic control to emergency engines, 

contradicting industry standards for engines in emergency service. 

Two commenters (121, 162) said the proposed emission standards for existing emergency 

RICE are overly stringent. Commenter 121 added the proposed standards do not reflect what 

existing engines in this subcategory achieve in practice. The limits are significantly lower than 

the emission limits established for new engines in the 2008 NSPS and in some cases, they appear 

to be more stringent than standards established for comparable future nonroad engines, the 

commenter (121) said. The proposed standards also lack the flexibility of the nonroad programs, 

which typically provide for a selection of engine families and/or emission averaging and trading 

and engine certification, the commenter (121) added. 
133

Without seeing which engines are in the specific floors, one commenter (121) was unable 

to perform an effective assessment of whether the proposed MACT limits appropriately reflect 

the average of the top 12 percent. However, test data from several existing emergency engines in 

the commenters’ (121) industry (automotive manufacturing) indicated they are unlikely to meet 

the proposed limits because they either pre-date or were produced to meet the established nonroad engine standards or similar standards that are less stringent than those proposed. The 

commenter (121) said it is likely that these engines will have to be replaced. 

Commenter 74 raised concerns regarding the GACT standard for existing emergency CI 

engines greater than 500 HP. The commenter (74) said the proposed rulemaking does not 

provide any basis for the proposed standards for emergency engines of this size range, and the 

GACT determination has not been properly established for these engines. In particular, 

according to the commenters, subsection 1 of section IV.B. of the proposed rule, which is cited 

in subsection 2 as the basis for the area source standards for large CI engines, does not appear to 

include any discussion of emission controls for emergency CI engines greater than 500 HP. In 

the absence of such justification, the commenters state that the MACT floor for these large 

engines is no controls. The commenter acknowledged that such a no control argument may not 

be acceptable under the MACT because of the Brick MACT court case, but the commenters 

stated that there is no such limitation in making GACT determinations. Commenter (74) was 

concerned that establishing an emission standard for large emergency CI engines would establish 

requirements for the installation of add-on controls for some, if not most of the sources in that 

category. EPA needs to conduct a regulatory analysis and assessment of the costs of these 

controls. The commenter (74) gave an example of the impact of an emission limit and the 

impact of installing controls on one of his units. The commenter (74) concluded that because of 
134

the unit’s limited operation, an oxidation catalyst control will have limited, if any, control 

effectiveness in actual use. 

One commenter (171) requested that EPA include a general exemption from the 40 ppm 

CO limit for emergency engines, where emergency engines are defined as engines that operate 

up to 50 hrs/yr for maintenance and testing. The commenter (171) provided that current CO 

emission control devices must operate within specific temperature ranges to be effective and that 

they test the emergency engines for only 30 to 60 minutes every 2 weeks to ensure that they will 

operate reliably during emergencies. As a result, the commenter (171) asserted that startup 

emissions would remain largely uncontrolled and should be exempted from the 40 ppm CO limit. 

 Commenter (121) said that despite EPA’s claims that the agency is not requiring 

performance tests of emergency engines, major sources with existing emergency engines appear 

to have an implicit testing requirement to demonstrate that they comply with concentration 

limits. Such testing could significantly increase the time the typical emergency engine would be 

used in year and impose additional environmental impact and costs. The commenter (121) said 

EPA needs to resolve the conflict between the preamble and the regulatory language and replace 

the emission limits for emergency engines with work practices. Commenter (154) raised similar 

concerns about the apparent requirement for performance testing of emergency RICE due to 

ambiguous rule language and said it should be clarified to explicitly state that such testing is not 

required. Commenter (74) said the rule would require not only initial performance testing, but 

testing every 3 years. Because engine operation for performance testing would likely exceed 

typical operation for operational testing and maintenance, these testing requirements would result 

in increased operation of the engine with a corresponding significant increase in operating costs 

and emissions of other pollutants such as NOx. 
135

If EPA regulates emergency generators, the numerical limit for emergency engines rated 

greater than 500 HP must be eliminated, according to one commenter (81). It is not reasonable 

for EPA to propose emissions limits for equipment and then state it does not require or expect 

owners of regulated equipment to test equipment to assure that it meets the those limits. This 

puts the regulated community in a precarious position, and it may cause owners to test their 

engines rather than risk a regulatory inspection that discovers that their equipment is not meeting 

required emission limits. 

Commenter (119) said the proposed numerical emission limit on which emergency RICE 

greater than 500 HP relates to the use of emission data which is not representative of the engines 

being regulated to develop the numerical emissions limit for CI engines greater than 500 HP. 

The commenter (119) said it appears the 40 ppmvd emission limit was based on 10 tests, and that 

all tests were conducted on one make and model of engine over a 3-day period in 1999. The 

commenter (119) said these data are not representative of the existing engines of various makes, 

models and ages in operation throughout the U.S. Commenter (121) expressed similar concerns 

and added that the proposed limit is significantly more stringent than the NSPS for CI engines 

and the CO standards in Tier 1 through 3 for similar non-road engines. Two commenters (183, 

209) said that the MACT floor determination for emergency CI engines is flawed because it is 

based on limited testing of one engine. Also, this engine had been overhauled and was expected 

to operate like a new engine. Further, EPA is attempting to use Reference Method Testing, but 

the test in question only consisted of one run vs. three runs for each test. Thus, even this limited 

data is not valid Reference Method data on which to establish a standard. Since EPA only has 

data for one source, if it wants to use this source to establish the MACT floor, then it must use all 

of the 10 stack tests and determine the Upper Predicted Level (UPL). The commenter (209) 
136

contends that EPA could obtain a much more robust data set with reasonable effort, but the 

commenter (209) believes that work practice standards are more appropriate than numerical 

emission standards for emergency use engines. 

One commenter (183) stated that the CO emission concentration of 40 ppmv corrected to 

15 percent O2 listed in Table 2d for emergency engines greater than 500 HP appears to be based 

on data from a single engine test conducted in a laboratory. The commenter (183) noted that 

based on this analysis, EPA concluded that all emergency engines could meet this standard 

without add-on controls. The commenter (183) gathered data from CI engines in AP-42 

background document and from sources in Wyoming and Alaska and found that 80 percent of 

the engines would be unable to meet this limit even at full load. The commenter (183) further 

stated that controls would need to be retrofit to these engines, and using the EPA cost estimation 

procedures, the HAP cost per ton would be $519,730 per ton of HAP removed, which the 

commenter believes is excessive. In addition, the commenter (183) stated the proposed 4 ppmvd 

or 90 percent control for CI engines greater than 300 HP would be unable to be achieved in all 

cases, even with control technology. The commenter (183) pointed out that data in the docket 

showed only 70 percent control efficiency for CO for one engine. 

Commenter 209 said emergency engines are used only during emergencies, other than 

short (less than 1⁄2 hour) weekly tests to assure the engines will perform. According to the 

commenter, performance tests (initial or every 3 years) consisting of three 1-hour runs typically 

cost about $10,000 each and are not justified for limited use engines, the tests alone would add 

substantially to the fuel use of these engines are result in additional and unnecessary emissions 

and work practice standards under section 112(h) are more appropriate due to “technological and 

economic limitations.” 
137

One commenter (121) disputed EPA’s claim that add-on controls are reasonable and 

justified for existing emergency engines. The commenter (121) said a mandate for add-on 

controls would impose significant costs on engines that are run only an average of 26 hrs/yr. 

Commenter 48 pointed out that the proposed rule was too expensive and of limited benefit noting 

that emergency engines only run during emergencies. Instead, EPA should set management 

practices such as requirements to perform and record routine maintenance, retain copies of the 

engine manufacturer’s approved maintenance schedule or similar maintenance schedule, and 

mirror those requirements for engines located at major sources, according to commenter 121. 

One commenter (81) also disputed the rationale that established a numeric limit that EPA 

expects all emergency engines can meet without installing after treatment controls and, therefore, 

provides no additional environmental benefit. The commenter (81) concluded that EPA should 

exempt all emergency engines at area sources. Other commenters (119) pointed to the minimal 

environmental benefit of regulating emergency engines and the unreasonable administrative 

burden of regulating such sources. 

Based on EPA’s apparent intent that emergency CI engines greater than 500 HP located 

for area sources can meet the emission standard without add-on controls, commenter 79 said that 

EPA should instead establish management practices. These management practices should be 

consistent with manufacturer recommendations, nuclear industry guidance for maintaining high 

emergency diesel generator reliability and Nuclear Regulatory Commission (NRC) requirements, 

the commenter (79) said. Similar management practices have been proposed for other area 

source categories, the commenter (79) added. 

 One commenter (81) added that if add-on controls are required to meet the limit, the short 

operating periods of emergency units would not trigger the usefulness of add-on controls. 
138

 One commenter (121) said EPA should allow owners or operators the option to follow 

either the engine manufacturers’ recommended maintenance schedules or the specific 

maintenance requirements proposed by EPA and that this provision apply to engines at either 

area sources or major sources. 

 One commenter (201) stated that EPA’s reasoning used to apply the MACT for engines 

at major sources as GACT for larger engines at area sources was deeply inconsistent in the case 

of large emergency engines at area sources. The commenter (201) pointed out that EPA decided 

not to require after-treatment controls for emergency engines under 500 HP located at major 

sources because of the low average annual operating time (50 hrs/yr), but did not make the same 

decision for larger emergency engines at area sources despite the same low average annual 

operating times. The commenter stated that setting the GACT for large emergency engines at 

area sources the same as the MACT for non-emergency engines could not be justified given the 

high cost of the controls (estimated by the commenter (201) to be $4,000 to $20,000 per engine) 

and the low average annual operating time (estimated by the commenter (201) to be 25 to 50 

hrs/yr). The commenter (201) recommended that EPA eliminate numeric emission standards for 

emergency engines greater than 500 HP located at area sources and instead use the management 

practices and associated recordkeeping requirements proposed for small emergency engines 

located at area sources. 

One commenter (223) stated that EPA generators located at area sources should not be 

subject to emission standards under 40 CFR part 63, subpart ZZZZ. The commenter (223) stated 

that EPA is not required to promulgate emission standards for source categories located at area 

sources. The commenter (223) acknowledged the D.C. Court of Appeals ruling (Sierra Club v. 

EPA, 479 F.3d 875, 883 (2007)) on the NESHAP for Brick and Structural Clay Manufacturing 
139

and Clay Ceramics Manufacturing (which was vacated). The D.C. Court of Appeals ruling 

concluded that EPA’s use of work practice standards instead of emissions floors for certain 

subcategories of ceramic kilns located at major sources was not permitted under section 112(h) 

of the CAA and that EPA’s failure to set emissions reductions floors for certain major source 

brick kiln that do not use pollution control technology violated section 112(d)(3) of the CAA. 

This commenter (223) stated that for area sources under section 112(d)(5) of the CAA, EPA is 

allowed to promulgate alternative standards for “categories and subcategories of area 

sources....the Administrator may, in lieu of the authorities provided in [sections 112(d)(2) and 

(f) of the CAA, which provide, among other things, for the promulgation of emission standards 

for each category or subcategory of major sources and area sources,] elect to promulgate 

standards or requirements applicable to sources in such categories or subcategories which 

provide for the use of generally available control technologies [(“GACT”)] or management 

practices by such sources to reduce emissions of hazardous air pollutants” (emphasis added). 

The commenter (223) stated that consistent with the Court’s finding in Sierra Club v. EPA, 

which applied to major sources only, EPA is not required under section 112 of the CAA to 

promulgate standards for listed source categories located at area sources, and emergency 

generators located at area sources should not be subject to emissions standards. 

This commenter (223) further stated that it believes it is appropriate to subcategorize 

emergency generators located at area sources under 40 CFR part 63, subpart ZZZZ. The 

commenter (223) cited section 112(d) of the CAA as stating that “[t]he Administrator may 

distinguish among classes, types, and sizes of sources within a category or subcategory in 

establishing...standards” as support. This commenter (223) believes that significant operational 

and economic circumstances governing emergency generators warrant the promulgation of a 
140

standard for these generators based on management practices rather than emission limits. The 

commenter (223) listed the following circumstances as support for its position: 

• Unlike non-emergency engines, emergency generators are only used during emergency 

situations (provided examples). 

• Because emergency generators are only used during unforeseen and typically infrequent 

emergency situations, their annual emissions are meaningfully lower than those from 

non-emergency engines. Noted that the annual NOx emission from the four emergency 

generators at its West Chester facility, for example, are capped by permit, ensuring that 

such emissions remain below 7.63 tons NOx on an annual basis. 

• Emergency generators located at area sources are not subject to air quality permitting in 

many cases. The application of an emission standard under 40 CFR part 63, subpart 

ZZZZ could change a state’s current permitting approach toward emergency generators. 

State or interstate permitting authorities may establish more stringent Title V permitting 

requirements than mandated by the CAA, and therefore subject area sources to Title V 

permitting requirements. Furthermore, even in States that elect not to impose Title V 

permitting requirements on these sources, the mere fact that a source is subject to the 

NESHAP program could trigger State-level construction and operating permit 

requirements that otherwise would not apply. 

• It is economically infeasible for large emergency generators located at area sources to 

meet the applicable emission standards in the proposed rule. Table 2b of the proposed 

rule indicates that owners and operators of area source emergency generators greater than 

500 HP are required to limit the concentration of CO in the unit’s exhaust to 40 ppmvd or 

less at 15 percent O2 (including during periods of startup or malfunction). 74 FR 9723. 
141

Most of these generators would not be able to meet this standard without installing costly 

add-on control devices. The commenter’s (223) generators would need to add-on diesel 

oxidation catalyst technology that would be resistant to damage from mechanical or 

thermal shock and metallurgic erosion typically caused by engines. The cost of reducing 

CO emissions to 40 ppmvd using diesel oxidation catalyst technology for the 

commenter’s four emergency generators (whose combined emissions are limited to 7.63 

tons) would be approximately $33,000 per ton removed. Most facilities do not have the 

ability to account for the additional costs of installing and operating emissions control 

equipment as typical costs of doing business as they typically comprise of facilities that 

rely on emergency generators for critical systems during emergencies and are not 

involved in manufacturing-based operations (e.g., hospital, commercial office buildings, 

and data centers). 

Based on the aforementioned circumstances, the commenter (223) concluded that EPA failed to 

recognize that facilities that depend on emergency generators to provide power for critical 

systems during emergencies would be burdened by having to comply with the proposed emission 

standards applicable to emergency generators greater than 500 HP, unlike their counterparts in 

the manufacturing/industrial sector. This commenter (223) asserted that, as with other engines 

that EPA concluded GACT to be management practices, these engines should also be 

subcategorized and GACT should be management practices. 

 Finally, this commenter (223) expressed that EPA failed to evaluate existing emergency 

RICE located at area sources in determining the basis and level of the proposed emission 

standards. The commenter (223) opined that if EPA had evaluated emergency RICE as a 

subcategory of engines at area sources (rather than by engine size and selected industry-type, 
142

without considering the costs of compliance specific to emergency engines), EPA would not 

have been able to have identified an appropriate emission standard for emergency RICE at area 

sources. 

Commenter (121) asserted that emergency engines are required by local ordinances and 

national standards (e.g., NFPA) to keep these engines in good running condition. The 

commenter (121) argued that an emission limit is unnecessary and would necessitate 

performance testing. This is a redundant requirement and would result in additional operation, 

with no environmental benefit. The commenter (121) recommended that EPA only impose 

routine maintenance requirements on these older engines. 

For certain older emergency CI engines that may be capable of meeting the recent NSPS 

limits even though they were produced prior to the promulgation of the NSPS, the commenter 

(121) said that regular maintenance of these engines to ensure they operate during an emergency 

should be adequate for compliance with the RICE MACT. As an alternative, EPA should allow 

the owner or operator to retain records showing that the engine can meet emission levels 

comparable to the NSPS in lieu of a separate MACT emission limit for these engines. This is 

similar to the approach for new or reconstructed emergency engines less than or equal to 500 HP 

in the 2008 RICE MACT amendments. 

Commenter 88 stated that some engines serving electric sector facilities that play a role in 

maintaining reliable electric power supply and delivery, such as distribution company service 

buildings, customer call centers, and information technology data centers typically operate less 

than 200 hrs/yr and have low permitted capacity factors. The commenter (88) opined that 

emergency power at these facilities is critical to public safety and national security and should 

therefore not be subject to numerical emission limits, but to management practices instead. 
143

One commenter (181) stated that as the rule currently reads, the emergency diesel 

generators and smaller emergency generators would require installation of CDPF to meet 

emission requirements. The commenter (181) stated that installing control equipment is not cost 

effective and would impact the facility in the following ways: 

• Retrofit requirements will limit emergency diesel generator capacity potentially putting 

the facility out of compliance with NRC Reliability and Availability standards for the 

emergency diesel generators; 

• Retrofit requirements will limit the smaller emergency generators capacity potentially 

putting the facility out of compliance with NRC required Emergency and Security Plans 

for the smaller emergency generators; and 

• Retrofit costs far exceed the potential reduction in emissions. 

The commenter (181) stated that all emergency generators located at the facility run short 

periods (1-2 hours per month) for operational checks and preventative maintenance. The 

commenter (181) stated that the annual hours of operation for both the emergency diesel 

generators and the smaller emergency generators are so low that emission control retrofit costs 

associated with the compliance of this rule would be prohibitively large, and produce 

insignificant benefits to the environment. The commenter (181) attached to their comment an 

emission assessment of the emergency diesel generators that provide background information 

regarding the complexity of the issues surrounding emergency diesel generators at nuclear power 

plants. The commenter (181) believes that in reviewing the complex issues associated with the 

emergency diesel generators, it is clear that the EPA's cost estimates for complying with this 

proposed rule drastically underestimate the costs that could be incurred at nuclear power plants. 

The commenter (181) stated in addition to the evaluation of risk, other evaluations would be 
144

required thereby creating undue cost burdens not considered by the EPA, specifically, EPA has 

not considered the effect of backpressure created by a catalyzed particulate filter on the 

emergency generators. The commenter (181) stated that the emergency diesel generators are 

rated at 5500 KW, and the NRC site requirements for each emergency diesel generator during an 

emergency are 5432 KW. The commenter (181) pointed out that the difference between the 

rated output of the emergency diesel generators and the electrical output required by the NRC is 

less than one percent. The commenter (181) noted that increased backpressure would have a 

negative effect on electrical output, and prevent the facility from being able to meet electrical 

demand during an emergency. In addition, the commenter (181) stated that the impact of 

backpressure would decrease the reliability of the emergency diesel generators to a level not 

suitable for NRC regulations. The commenter (181) also added that control equipment would 

require further maintenance and repair downtime resulting in a decrease in availability of the 

emergency diesel generators, and the operational burden of control equipment has the potential 

to create a situation where the facility would not be able to meet current prerequisites for 

emergency electrical power. The commenter stated that the increase in electrical output that 

would be required to offset backpressure created by control equipment also impacts the smaller 

emergency generators, which would not be capable of meeting the added electrical demand and 

be out of compliance with NRC required Emergency and Security Plans. 

One commenter (79) said that emergency diesel generators CO emissions are inherently 

variable both during steady state and SSM operations based on a variety of factors, such as 

engine manufacturer, vintage of emergency diesel generators, and the operating practices and 

characteristics of existing emergency generators. Based on this variability, CO emissions may 

be higher or lower than the 40 ppmvd standard proposed for emergency CI greater than 500 HP 
145

located at area sources. The commenter (79) stated that one example where variable operating 

conditions occur is emergency diesel generators at nuclear power plants. 

Response: EPA reviewed the information submitted by the commenters and determined that it 

would be appropriate to require management practices for all emergency stationary CI engines at 

area sources. Because these engines are typically used only a few number of hours per year, the 

costs of emission control are not warranted when compared to the emission reductions that 

would be achieved. The proposed numeric emission levels are not GACT for emergency engines 

at area sources. Such engines rarely if ever use the type of emission controls that might have 

been necessary for many engines to meet the numeric standard, and such engines are rarely if 

ever subjected to emissions testing. Therefore, EPA determined that GACT for all stationary 

emergency engines at area sources is the use of management practices. 

EPA also analyzed the types of engines that were included in the area source category 

listing for stationary RICE. As a result of this analysis, EPA determined that emissions from 

existing stationary emergency engines located at residential, commercial, and institutional 

facilities that are area sources of HAP were not included in the 1990 baseline emissions 

inventory that was used as the basis for the listing of source categories needed to ensure that 90 

percent of area source emissions are regulated. Existing stationary emergency engines located at 

residential, commercial, and institutional facilities that are area sources are therefore not subject 

to this regulation. 

 For stationary emergency engines at major sources, EPA determined that it is not feasible 

to prescribe or enforce an emission standard because the application of measurement 

methodology to this class of engines is impracticable due to technological and economic 
146

limitations. A more detailed discussion of this determination can be found in the memorandum 

entitled “MACT Floor Determination for Existing Stationary Non-Emergency CI RICE Less 

Than 100 HP and Existing Stationary Emergency CI RICE Located at Major Sources and GACT 

for Existing Stationary CI RICE Located at Area Sources.” EPA determined that it is 

impracticable to test stationary CI emergency engines using the test procedures specified in 

subpart ZZZZ because using these procedures would increase the required number of hours of 

operation beyond the routinely scheduled reliability testing and maintenance operation, thereby 

increasing emissions. While emergency engines have periods of operation for scheduled 

maintenance and reliability testing, those periods are usually several hours shorter than the 

number of hours that would be required to run the necessary emissions tests under subpart ZZZZ. 

CARB conducted a survey of stationary emergency diesel engines in 200222 to determine the 

average number of hours that stationary emergency diesel engines operate. The average hours of 

operation for maintenance and testing were 22 hours per year, which is less than two hours per 

month. For the engines that CARB surveyed, 86 percent operated less than 30 hours/year for 

testing and maintenance. Thirty percent operated less than 10 hours/year. National Fire 

Protection Association (NFPA) codes require that stationary diesel engines that are used for 

emergency purposes are run 30 minutes per week (27 hours per year) for maintenance and 

testing purposes. It is impracticable to test emergency stationary engines as a result of 

emergency operation because emergencies are unplanned events and implementation of the 

procedures specified in subpart ZZZZ require advance planning before tests are conducted. In an 

emergency, the owner/operator does not have the advance planning time necessary to implement 

                                                           

22 California Air Resources Board Staff Report: Initial Statement of Reasons for Proposed Rulemaking. Airborne 

Toxic Control Measure for Stationary Compression Ignition Engines. Stationary Source Division, Emissions 

Assessment Branch. September 2003. 
147

subpart ZZZZ. It is also impracticable to test stationary CI emergency engines at major sources 

because of the large population of these engines. EPA estimates that there are over 200,000 

existing stationary CI engines from 100-500 HP at major sources that are subject to this 

rulemaking. There are only approximately 300-400 testing firms and these stationary engines are 

not the only sources that are required to be tested, so if testing were required for these engines, it 

would take many years to test all of these engines. The cost for testing all of these engines 

would also be approximately $200 million, which would be unreasonable. 

 EPA expects that these changes from the proposed rule address the concerns expressed 

by the commenters about the requirements for stationary emergency CI engines. Regarding the 

comments pertaining to performance testing for emergency engines, EPA did not intend for the 

rule to require performance testing for emergency engines. The final rule does not contain any 

performance testing requirements for emergency engines. 

 

5.3.2 Comment: One commenter (96) pointed out that there are no standards for emergency 

engines above 500 HP at major sources, but that emergency engines less than 500 HP and 

emergency engines above 500 HP at area sources have emissions requirements. The commenter 

(96) asserted that any standards or work practices applicable to emergency engines should be 

consistent across size classes and should not include emission standards during startup 

operations. 

Response: This rulemaking and the one developed in 2004 for stationary engines above 500 HP 

at major sources were developed at different times. While EPA has attempted, to the degree 

possible and justified, to maintain consistency across rulemakings affecting the same or similar 
148

engines, recent court decisions regarding the way that MACT floors are determined and the 

startup/shutdown/malfunction exemptions in NESHAP have affected the way EPA develops and 

sets standards since the standards for stationary emergency engines above 500 HP at major 

sources were promulgated in 2004. For stationary emergency engines at area sources and less 

than 500 HP at major sources, EPA is statutorily required to set requirements. As discussed in 

the response to comment 5.3.1, stationary emergency engines have to meet management or work 

practice requirements in the final rule. 

5.3.3 Comment: One commenter (121) argued that older, existing CI emergency engines should 

not be treated any differently than their mobile source counterparts. In the mobile source 

context, engines produced in a particular model year must be certified to an emission standard 

that corresponds to that model year, and there is no federal mandate to retrofit these older 

engines. According to the commenter (121), many older engines are incapable of being 

retrofitted, and even if they were, it is uncertain that the newly controlled engine would function 

properly or comply with the proposed standard. In some situations, existing engines are 

incorporated into generator sets, which cannot physically accommodate add-on controls. Also, 

many older engines are already regulated by state permitting programs through limits on fuel 

usage or limits based on emission factors in construction and operating permits. 

Response: EPA must regulate stationary source engines differently than mobile source 

engines because stationary engines are regulated under a different section of the CAA. Section 

112(d)(2) of the CAA specifies that NESHAP for existing stationary sources must reflect the 

maximum degree of reduction in HAP emissions that is achievable, taking into account the cost 
149

of achieving the emissions reductions, any non-air quality health and environmental benefits, and 

energy requirements. This level of control is commonly referred to as MACT. Section 

112(d)(3) of the CAA defines the minimum level of control or floor allowed for NESHAP. In 

essence, the MACT floor ensures that all affected sources achieve the level of control at least as 

stringent as that already achieved by the better-controlled and lower emitting sources in each 

source category or subcategory. The MACT standards for existing sources cannot be less 

stringent that the average emission limitation achieved by the best-performing 12 percent of 

existing sources in the category or subcategory. Mobile source engines are not subject to MACT 

standards and therefore it is not appropriate to compare the requirements for stationary engines to 

those for mobile source engines. Further, mobile source engines typically have different duty 

cycles than stationary engines. 

5.3.4 Comment: One commenter (76) supports the determination of emission limits without addon controls for emergency CI engines between 50 and 500 HP located at major sources. 

Response: No response is needed.

5.3.5 Comment: One commenter (226) stated that emergency engines only operate for short 

periods of time, and for many small businesses, it would be very expensive for a consulting firm 

to visit a remote site in order to perform emissions testing. Therefore, the commenter (226) 

believes replacing emissions testing with management practices is an appropriate way to reduce 

emissions for engines managed by small firms. 
150

Response: EPA did not propose to require performance testing for existing stationary emergency 

engines, see page 9711 of the proposed rule Federal Register notice. The final rule does not 

require performance testing of stationary emergency engines, which is consistent with what EPA 

proposed, and additionally does not require existing stationary emergency engines to meet 

numerical limits.

5.4 Small Engines 

5.4.1 Comment: Several commenters (96, 157, 216, 262) expressed opposition to EPA’s 

proposal to have emission standards apply to small engines at major sources. Three commenters 

(96, 157, 216) said that EPA should not finalize emission limits for engines less than 100 HP. 

One commenter (157) supported EPA’s proposed no compliance requirements beyond 

complying with the manufacturer’s instructions and no testing requirements for these engines. 

One commenter (96) argued that stationary engines that are less than 100 HP should be 

exempted from numerical HAP emission standards for some of the same reasons as those 

discussed by the commenter on the issue of emergency engine standards. In the commenter’s 

(96) opinion, it is not cost effective to install add-on controls on small engines or to purchase a 

new engine. According to the commenter, the majority of engines in this size range are operated 

for intermittent household or other infrequent use and emissions are naturally limited, the 

commenter (96) said, and low emissions do not justify the costs associated with requiring a 

numerical HAP limit. As stated, commenter 96 is opposed to numerical emission limits for 

engines less than 100 HP and provided in its comments charts for different engine categories of 

where it has shaded several areas where it believes that EPA should replace limits with 
151

manufacturer’s engine maintenance. Finally, commenter 96 added that a 2 ppmvd limit for 

formaldehyde is not achievable by diesel engines with a catalyst operating at 90 percent 

efficiency, catalysts are not cost effective for small engines, and 2 ppmvd is difficult to measure 

in lab conditions and impracticable in field measurements. 

One commenter (262) stated that because of how EPA conducted its MACT floor 

analysis, small engines may be forced to install add-on controls because the MACT floor was 

determined by the best 12 percent of engines. The commenter (228) is concerned that the 

proposed standards for RICE less than 50 HP will not meet the District of Columbia Circuit’s 

test for “work practice standards” set forth in the Sierra Club v. EPA (Brick Indus.), 479 F.3d 

875 (D.C. Cir. 2007), which allows work practice standards “only if measuring emission levels is 

technologically or economically impracticable.” The commenter (228) stated that emissions 

measurement likely meets these standards, but does not believe that measurement is 

economically practicable for a small unit as the cost of testing will likely exceed the value of the 

engine itself. The commenter (228) urged EPA to exclude small sources from the category. 

Response: EPA has reanalyzed its proposed standards based on the information and data 

presented and EPA concludes that it is not feasible within the context of this rulemaking to 

prescribe emission limitations for existing stationary CI engines smaller than 100 HP located at 

major sources, because the measurement of emissions from these engines is not practicable due 

to technological and economic limitations. In order to measure the emissions from these engines 

on a ppmvd at 15 percent O2 basis, the following test methods are required: EPA Method 1 or 

1A for selection of sampling ports; EPA Method 3, 3A, or 3B for determining the O2

concentration; EPA Method 4 for measuring the moisture content, and EPA Method 10 or 
152

ASTM D6522-00 (2005) for measuring the CO concentration. These test methods require the 

sample point to be a certain distance between the engine and the exhaust. Because engines 

below 100 HP often have exhaust pipes with very small diameters and lengths, stack testing 

using these methods could require a modification or extension of the exhaust pipe to accomplish 

the test. The cost to do the testing ranges from approximately $1,000-$5,000 depending on the 

method used. Generally, 100 HP engines cost around $5,000-$7,000 dollars and 50 HP engines 

cost approximately $4,000-$5,000, so the cost of performance testing could approach the cost of 

the engine itself. Given the cost of the testing itself, the physical adjustments necessary to 

accomplish the test, and the particular circumstances pertaining to stationary engines below 100 

HP, we believe that the application of measurement methodology to this class of engines is not 

practicable due to technological and economic limitations. Therefore, EPA is promulgating 

work practice standards for these engines. Additional detail regarding this analysis can be found 

in the memorandum entitled “MACT Floor Determination for Existing Stationary NonEmergency CI RICE Less Than 100 HP and Existing Stationary Emergency CI RICE Located at 

Major Sources and GACT for Existing Stationary CI RICE Located at Area Sources.” 

5.5 Diesel Engines 

5.5.1 Comment: One commenter (116) recommended that the standard require CDPF or a 

combination of oxidation catalysts and CDPF for new or existing non-emergency diesel RICE. 

The commenter (116) stated that EPA’s proposal calls for oxidation catalysts on non-emergency 

CI engines, which EPA reports will result in a 90 percent reduction in CO and 30 percent 
153

reduction in PM, whereas CDPF would result in greater reductions in PM (90 percent reductions 

or greater). 

Another commenter (141) reported that it had conducted risk assessment evaluations for 

diesel particulate emissions from non-emergency diesel engines and found that the diesel 

particulate emissions from non-emergency diesel engines and found that the diesel particulate 

emissions often create a significant cancer risk even when there is a 30 percent PM reduction. 

The commenter (141) recommended that EPA base standards on CDPF or a combination of 

oxidation catalyst and CDPF, for existing and new non-emergency diesel engines. 

Response: The standards that EPA proposed and that EPA is finalizing do not require a 

particular control technology. For the proposed rule, EPA’s beyond-the-floor analysis resulted in 

standards that were based on the use of oxidation catalyst control for stationary non-emergency 

diesel engines above 300 HP; EPA has made the same determination for the beyond-the-floor 

standards in the final rule. EPA determined that the MACT standards should be based on 

oxidation catalyst rather than CDPF because we do not have any data that shows that CDPF get 

greater reductions of HAP than oxidation catalysts on stationary engines, and CDPF are 

approximately four times as costly as oxidation catalyst.23 EPA also has concerns regarding the 

technical feasibility of CDPF for existing stationary diesel engines. Many existing diesel engines 

are not electronically controlled, and PM emissions from older engines are often too high for 

efficient operation of a CDPF. Further, engine exhaust temperatures are often not high enough 

for regeneration of the CDPF filter substrate. EPA notes that owners and operators are free to 

                                                           

23 California Air Resources Board Staff Report: Initial Statement of Reasons for Proposed Rulemaking. Airborne 

Toxic Control Measure for Stationary Compression Ignition Engines. Stationary Source Division, Emissions 

Assessment Branch. September 2003. 
154

choose whichever control technology, which could be oxidation catalyst or CDPF, as long as 

they meet the final standards. EPA is not addressing new diesel engines in this rulemaking. 

5.5.2 Comment: One commenter (264) provided that, when California implemented rules to 

control HAP emissions from diesel engines, the commenter contracted certified providers of addon controls to determine the feasibility of such measures in order to comply with California 

standards. This commenter (264) discovered the following three issues in trying to apply new 

emission control to old engines: (1) Manufacturers do not guarantee the device would fit an 

older unit; (2) Manufacturers do not guarantee there would be any emission reductions; and (3) 

Manufacturers do not guarantee that the engine would not be damaged from the control device. 

For these reasons, the commenter (264) recommended that the EPA limit the requirement for 

installation of CDPF to new engines. 

Response: The emission standards that EPA proposed for existing stationary diesel engines that 

require the installation of add-on controls were based on oxidation catalyst control and not 

CDPF. Furthermore, EPA is not mandating any particular type of control technology. Affected 

sources may use whichever controls they choose to be appropriate as long as they meet the 

applicable emission standards. For the final rule, EPA has not made any changes since proposal 

in terms of the control technology that is relied upon to meet the emission standards and for 

existing stationary non-emergency diesel engines above 300 HP the final emission standards are 

based on the use of oxidation catalyst control. 

5.6 Format of Standards and Other Issues Related to Standards 
155

5.6.1 Comment: Two commenters (96, 150) said that EPA should include the flexibility in the 

final rule of allowing all sources subject to emission standards the option of meeting either the 

concentration limit or the percent reduction standard. According to commenter 96, including 

such flexibility is necessary due to the large span in model year of the engines, emission 

characteristics and location conditions, and it may be more feasible to meet one compliance 

option over the other or even impossible to meet one of the options. 

 One commenter (99) asserted that where the percent reduction is available, it is generally 

attainable, but at a high cost. However, the numerical values proposed by EPA are not 

achievable, the commenter (99) said. 

Response: EPA provided the option of meeting either a concentration standard or a percent 

reduction for subcategories of engines that were expected to comply with the rule by applying 

add-on control technology, e.g., for stationary non-emergency CI engines above 300 HP. 

Including an option to meet a percent reduction does not make sense for sources that are not 

expected to apply add-on controls, and furthermore, EPA would not know what that percentage 

would be if the standard was based on levels achievable without aftertreatment. EPA does not 

agree with the commenters that the emission standards are not achievable. The standards are 

based on emissions data from existing stationary diesel engines.

5.7 Technology 
156

5.7.1 Comment: One commenter (199) commended the EPA for its continuing efforts to develop 

and implement effective emission control standards for major sources of air pollution such as this 

category of engines. The commenter (199) noted that diesel particulate filters (DPF), diesel 

oxidation catalysts, and flow-through filters (FTF) have been used to reduce diesel PM from 

stationary diesel engines. The commenter (199) stated that CDPF can reduce PM emissions by 

85 percent, CO emissions by 90 percent, and HC emissions by 95 percent. For oxidation 

catalyst, the commenter (199) stated that PM reductions range from 20 to 50 percent, reduction 

in HC of 60 to 90 percent, and significant reductions of CO, smoke and odor. The commenter 

(199) stated that FTF is capable of achieving PM reductions of about 30 to 75 percent. In 

addition to these technologies, the commenter (199) stated that PM emissions from the engine’s 

crankcase can be substantial (as much as 0.7 g/HP-hr PM during idle conditions) and closed 

crankcase ventilation (CCV) can reduce these emission by over 90 percent. The commenter 

(199) noted that the use of ULSD can result in modest PM reductions and enables the optimum 

use of catalyst-based emission control technologies. The commenter (199) stated these control 

technologies have been retrofitted on stationary diesel engines and verified by both CARB and 

EPA to be effective in reducing emissions of PM from diesel engines. The commenter (199) 

provided cost information from a September 2003 stationary CI engine Air Toxics Control 

Measure staff report for a typical prime stationary engine (rated at 590 HP operated for 1,040 

hrs/yr) retrofitted with a DPF. The report estimated the cost to be $22,400 for equipment and 

installation, $100 for reporting, and $550 per year for ash cleaning/maintenance. The total cost 

for the same engine retrofitted with a oxidation catalyst was about $6,250 with no annual 

maintenance. The commenter (199) noted that these technologies are also effective in reducing 

black carbon emissions. 
157

The commenter (199) recommended that EPA also consider the benefits of using 

selective catalytic reduction (SCR) to reduce both HAP and NOx emissions from both stationary 

CI and SI engines. The commenter (199) further stated that retrofit SCR systems can reduce 

NOx emissions from existing stationary diesel engines by 80 percent or more, and since retrofit 

SCR systems typically incorporate the use of a diesel oxidation catalyst, these SCR systems can 

also reduce HAP emissions as well. The commenter (199) noted that one member company has 

installed over 400 SCR systems worldwide for stationary engines with varying fuel 

combinations. 

The commenter (199) believes DPF should be installed on in-use stationary diesel 

engines wherever technically feasible and that these engines should be fueled with ULSD to 

provide the maximum flexibility in the design of effective retrofit DPF emission control 

solutions. The commenter (199) believes that the use of ULSD in combination with retrofit DPF 

on existing stationary diesel engines can be implemented in the 2010 timeframe on both prime 

and emergency stand-by engines with power ratings of 50 HP or greater. The commenter (199) 

noted that in situations where DPF are not technologically feasible, oxidation catalyst should be 

considered as an alternative option to help achieve at least a minimum level of PM control from 

applicable stationary diesel engines. 

Response: EPA acknowledges the information regarding applicable control technology that is 

currently available to apply to existing stationary engines that the commenter provided. EPA 

generally agrees with the commenter that the technologies identified can be used by at least some 

existing stationary engines. EPA for the most part also concurs with the commenter’s assertions 

regarding the capabilities of the control technologies discussed as far as which pollutants they 
158

reduce and the effectiveness. However, EPA notes that it has not seen any evidence that CDPF 

are more efficient in reducing HC emissions from stationary diesel engines than oxidation 

catalysts, which the commenter claims. EPA addressed the comment regarding the installation 

of DPF on in-use stationary engines in the response to comment 5.5.1 

 EPA did not specifically consider SCR because this rulemaking focuses on reducing HAP 

emissions and SCR alone does not reduce emissions of HAP. In order for an SCR to reduce 

HAP, an oxidation catalyst would have to be part of the aftertreatment package. With that said 

EPA notes that it does not mandate any specific control technology in the final rule. Owners are 

free to select whichever control technology they feel is appropriate as long as they demonstrate 

compliance with the emission standards. 

6.0 Exemptions/Special Allowances 

6.1 Emergency Engines 

6.1.1 Comment: Several commenters (67, 79, 80, 81, 82, 85, 87, 88, 90, 92, 95, 109, 113, 115, 

118, 119, 120, 126, 139, 144, 150, 162, 166, 168, 169, 172, 178, 185, 195, 198, 214, 219, 223, 

232, 238, 240, 241, 245, 249, 251, 263) voiced concerns regarding potential emission limits for 

emergency engines and numerous commenters expressed particular concern with their 

participation in demand response (DR) programs. 

Several commenters (82, 88, 92, 95, 185, 198) stated that EPA’s proposed definition of 

emergency is not clear as to whether it includes emergency engines that operate in emergency 

DR programs. The commenter (82) believed that the record on 40 CFR part 60, subpart IIII, 
159

from which the proposed rule definition was drawn, clearly indicates that the 40 CFR part 60, 

subpart IIII definition was meant to address peak shaving, not emergency engines participating in 

emergency DR programs. Several commenters (67, 81, 82, 90, 92, 118, 119, 126, 169) requested 

that EPA modify the proposed definition of emergency engines to enable engines to maintain 

their status as emergency engines, even though the engines that are used in DR programs are part 

of a financial agreement and based on the current definition would not be considered emergency 

engines. Two commenters (118, 119) stated that emergency DR programs should not be 

confused with economic DR programs (e.g., peak shaving). Emergency DR programs are 

initiated by the transmission system operators when the threat of power outages is imminent and 

are critical to maintaining available power during periods of extreme load on the electric power 

infrastructure, according to commenters 88 and 118. The events are rare and unplanned, out of 

the control of emergency engine owners/operators, and no power is supplied to the grid, but used 

at the individual facility, commenter 118 said. Commenter 88 said that emergency DR events 

during the year are typically limited to no longer than 2 to 6 hours per event, with the number of 

events per year capped by the regional power pool. The commenter (88) believed that, by 

establishing a subcategory for generators that serve facilities participating in a DR program and 

that only operate 200 hrs/yr, including any hours operated for maintenance purposes, EPA could 

require maintenance practices, and remove any disincentive that may be created over the 

increased administrative burden and potential post-combustion control retrofit costs if their 

emergency stationary RICE would be required to be re-characterized as “non-emergency” in 

order to participate in DR programs. Commenter 79 suggested that a 100 hour operating limit 

could also be considered as an alternative. Three commenters (95, 185, and 198) stated that they 

receive many benefits from their participation in the local DR program, and that they use 
160

emergency DR events and tests events to replace some of the Joint Commission on Accreditation 

of Healthcare Organizations’ mandated hospital generator tests. According to commenters 95, 

113, 85, 198, and 251 the costs that they would have to absorb to meet the proposed emission 

limits would be prohibitive and that to require facilities to meet rigid emission limits with very 

little reduction in emissions is not encouraged. Emergency engines are used throughout the U.S. 

and provide vital safety requirements at hospitals and healthcare institutions, the commenters 

(95, 185, and 198) said. Two commenters (113, 251) indicated that many healthcare institutions 

are operating in the red and requested that EPA consider the expense required to meet these new 

standards and take note that any additional financial burden would impact finances available to 

provide patient care. The definition recommended by several commenter should include the 

following statement: 

“Emergency generator does not include a load-shaving unit or peaking power production 

unit, but does include the operation of an emergency generator during periods in which the RTO 

or other local or regional entity responsible for maintaining reliability of electrical operations 

directs the implementation of emergency demand response procedures.” 

One commenter (67) provided two examples of situations where the commenter believed 

that the current definition of emergency engine would prohibit operation from being considered 

emergency use. The first scenario described by commenter 67 was follows: “Entity 1 owns and 

operates stationary engines that provide emergency power to critical components like elevators, 

emergency lighting, and fire pumps of Entity 2 via dedicated transmission lines that are not part 

of the electric grid. Entity 1 and 2 are separate in a financial sense and there is a Financial 

Agreement A for Entity 1 to provide emergency power to Entity 2 upon loss of power from the 

grid. Under Financial Agreement A, the engines are operating in an emergency capacity.” The 
161

second scenario described by commenter 67 was as follows: “In the case above, Entity 1 enters 

into a second and separate Financial Agreement B with an RTO. Under Financial Agreement B, 

Entity 1 agrees to provide electric power to Entity 2 when the RTO initiates their emergency load 

response program. At no time does Entity 1 send power to the electric grid, but instead provides 

power using dedicated transmission lines directly to Entity 2, for the purpose of reducing load 

from the electric grid. Entity 1 supplies power to critical and non-critical components of Entity 

2. In this case, the emergency is associated with reliability of the electric grid, as determined by 

the RTO. Under Financial Agreement B, the engines are operating in an emergency capacity.” 

The current emergency engine definition would exclude both examples, yet the engines are truly 

operating in an emergency capacity, according to commenter 67.” Commenter 67 asked that 

EPA adopt the following language in the final definition of emergency engine: “Stationary ICE 

used to supply power to an electric grid or which supply non-emergency power as part of a 

financial arrangement with another entity are not considered to be emergency engines.” 

On the recommendation of EPA staff, commenter (82) had submitted a formal 

Applicability Determination (included as attachment to comment) to EPA Region 1 regarding 

engines used for emergency DR, but has not received a response. Three commenters (82, 118, 

169) stated that emergency engines participating in emergency DR programs provide a critical 

service in stabilizing the electric grid on the rare occasions when the grid is about to fail. Many 

states endorse the use of emergency engines participating in emergency DR programs, according 

to commenter 82. Two commenters (82, 169) cited various DR programs in the New England 

area that existing engines participate in. A commenter (82) provided detailed discussion of 

several emergency DR programs across the country, including states in New England, the Mid 

Atlantic and Midwest, and the South, that are supportive of using emergency engines as part of 
162

their emergency DR programs, and that accommodate operation of these engines through various 

definitions of emergency, or through permitting. The commenter (82) concluded that it is very 

important that EPA not adopt rules that conflict with how much of the U.S. handles emergency 

DR. 

Response: EPA agrees that it would be appropriate to allow emergency engines to operate as 

part of emergency demand response programs for a limited number of hours of operation per 

year in situations where grid failure and a blackout are imminent. In the final rule, EPA has 

revised the requirements for emergency engines to reflect this. Regarding the first scenario of 

stationary engine operation that commenter 67 describes, EPA believes this type of operation as 

described would be considered emergency use and has revised the definition of emergency 

engine to make clear that financial arrangements limited solely to the provision of emergency 

power from one entity to other entities does not exclude engines from being emergency engines. 

As long as the engine operates only for emergency use and testing and maintenance as allowed, 

the engine would remain classified as an emergency engine and would not be subject to 

requirements that apply to non-emergency engines. 

6.1.2 Comment: One commenter (107) requested that the emergency use definition be expanded 

to peak shaving or interruptible power programs. Commenter 81 said the final rule should not 

discourage participation in peak shaving. Although there is a very small financial benefit to these 

arrangements, in many instances the benefit will not be as great as the cost associated with a loss 

of emergency generator status. Therefore, the operators of generators will likely forgo 

participation in such programs. The commenter (81) added that participation in these programs 
163

does not necessarily mean that an emergency engine would run for extensive periods of time. In 

the commenter’s (81) experience, these engines typically run less time of peak shaving than time 

required for annual testing and maintenance. Further, the time engines run for peak shaving 

serves as an opportunity to fully exercise the emergency power engines under load conditions. 

The commenter (81) asked EPA to consider allowing emergency engines to run up to 50 hours 

for peak shaving as long as those hours are counted together with the maintenance and readiness 

testing runtimes, and do not exceed 100 hour per year. 

Response: Peak shaving and normal interruptible power contracts are not limited to emergency 

situations and can be used to increase load during peak periods of power use. Engines used for 

peak shaving are part of general power management and do not qualify for treatment as 

emergency engines. EPA has made minor revisions to deal with demand management contracts 

that are limited to emergency situations (see response to 6.1.1), but peak shaving and 

interruptible contracts are not generally limited to emergencies, nor are they limited by the 

amount of time they can be used. EPA does not intend to prevent the use of peak shaving or 

interruptible power contracts, but engines using these contracts are not emergency engines and 

must meet the same requirements as other non-emergency stationary engines. EPA notes that 

that it does allow emergency engines some amount of time to operate outside of emergency 

conditions, but not as part of a specific contract designed to operate these engines at periods of 

peak load, when emissions are already high, and where they are not limited to emergency 

conditions. 
164

6.1.3 Comment: Another commenter (87) stated that the proposed rule inappropriately imposes 

an emission standard for certain emergency generators. Commenter 87 cited the exemption 

provided in the final RICE NESHAP (and retained in the current proposal) for RICE greater than 

500 HP located at major sources as the correct approach, and recommends that EPA exempt all 

emergency generators at major and area sources from the rule. Commenter 87 expressed 

concern that, unlike the exemption approach taken with larger engines, the EPA appears to have 

arbitrarily decided to define the emissions level achieved by these uncontrolled units and more 

specifically, (1) it is not known to what extent variation in emission levels of different brands 

and models was taken into account in defining this emission level; and (2) by setting an emission 

level rather than providing an exemption as for larger sources, the agency subjects those smaller 

units at major sources and equivalent units at area sources to performance testing. According to 

this commenter, for one site in their industry with more than 23 emergency generators, the cost 

of initial performance testing would exceed $200,000. Should the Agency not be able to exempt 

all emergency generators, the commenter (87) recommends that the Agency alternatively apply 

work practices (rather than emission limits) identified for identical small units at area sources to 

the small units at major sources, and identify a work practice standard for the RICE larger than 

500 HP at area sources. 

One commenter (150) believes that all emergency engines should be exempt from the 

proposed requirements. The commenter (150) stated that regulations on emergency engines 

would not meet a reasonable cost/benefit test, as the emissions reduction benefits would be 

minimal compared to the logistical burden and monetary costs associated with compliance. The 

commenter (150) added that the use of catalytic controls on emergency engines runs contrary to 

industry standards. Two commenters (150, 241) stated that if EPA places any restrictions on 
165

emergency engines, only management practice requirements should be imposed because the 

limited operating time of emergency units and the limitations in the ability to measure 

compliance make compliance with numerical limits infeasible. 

One commenter (169) stated that the proposed regulations do not clearly identify the 

compliance requirements that are applicable to emergency CI and emergency SI engines with a 

site rating of more than 500 HP that are located at area sources. This commenter added that (1) 

if it is indeed EPA’s intent to exempt these engines from performance testing, the rule language 

should be clarified; and (2) however, if no performance testing is to be required, then the 

imposition of any emission limits on these emergency engines must be seriously questioned. 

The second point is of special concern to this commenter (169) because it is believed that many 

existing emergency engines would not be able to comply with the proposed emission limits and, 

without performance test results, owners and operators will be unsure of their compliance status 

and will be unable to certify compliance with Title V permit conditions. Commenter (169) 

requests that EPA eliminate the emission standards for this source category and substitute 

management practice standards similar to those that are proposed for smaller emergency engines 

(rated at less than 500 HP) that are located at area sources. 

Commenter 119 said that the requirements in the existing RICE NESHAP, which state 

that an existing emergency stationary RICE does not have to meet the requirements of 40 CFR 

63 subparts ZZZZ and A and no initial notification is required, should be retained. The 

commenter (119) refers to the limited operating hours of these units and the fact that the existing 

maintenance procedures in the telecommunications industry are similar to those proposed in the 

RICE NESHAP. Imposing additional requirements would only add administrative burden and 

would not achieve any HAP emissions reduction. One commenter (77) supported the definition 
166

of stationary emergency RICE found in the present rule and the requirements for maintenance 

checks and readiness testing in the proposed rule. However, the commenter (77) suggested that 

the exemption for emergency RICE greater than 500 HP at major sources be extended to all 

emergency RICE at both major and area sources. The commenter (77) believes that it would 

simplify the rules and provide equitable treatment if all emergency RICE were treated the same. 

Commenter 162 said it is inconsistent and unjustified to exempt existing emergency and 

limited-use RICE greater than 500 HP from regulation while existing emergency RICE less than 

500 HP at both major and area sources will be burdened with meeting emission limits or have to 

perform the prescribed maintenance requirements. 

 Commenter 119 said that the numerical limit on RICE greater than 500 HP should be 

eliminated. The commenter (119) also requested that these engines be exempted from the rule 

based on the owners’ and operators’ ability to demonstrate they are following the engines 

manufacturer’s emission relate O&M requirements. If EPA is unwilling to provide a full 

exemption from the rule for these engines, the commenter (119) recommends that the numerical 

limit be replaced with management practices, consistent with those proposed for emergency CI 

less than 500 HP. 

Response: EPA is required to address HAP emissions from all existing stationary engines less 

than or equal to 500 HP at major sources and existing stationary engines at area sources. Due to 

the recent Brick MACT decision, EPA can no longer set floors of no emission reduction for 

limited use engines at major sources, or any other engines for that matter, as was done in the 

2004 RICE NESHAP that regulated existing and new stationary engines greater than 500 HP at 

major sources. EPA has determined that residential, commercial, and institutional stationary CI 
167

emergency engines located at area sources are not part of the stationary RICE source category 

and has not promulgated regulations for them in the final rule. In addition, EPA has required 

management practices for all emergency engines at area sources in the final rule, including 

emergency engines greater than 500 HP. For emergency engines at major sources, the final rule 

requires work practices. This is discussed in more detail in the response to comment number 

5.3.1. EPA believes these changes address the concerns expressed by the commenter regarding 

Title V compliance, as the emergency engines will not have to meet specific numerical emission 

limitations, and can certify compliance with the required work practices. 

6.1.4 Comment: One commenter (175) recommended that EPA establish a 100 hrs/yr threshold 

under which only recordkeeping would apply. One commenter (79) requested that, if EPA 

decides to promulgate numeric standards for non-nuclear emergency diesel generators, that EPA 

provide an exemption from regulation for emergency diesel generators that operate 200 hrs/yr or 

less. 

Response: EPA does not believe that the only requirements that should be applicable to 

stationary emergency engines that operate less than 100 hours per year are recordkeeping 

requirements. The commenter did not provide any justification for this claim and EPA believes 

that the requirements in the final rule for emergency engines are justified. EPA cannot exempt 

engines from regulation if they are in the source category and does not believe it is appropriate to 

increase to 200 hours the amount of time engines can operate for testing and maintenance and 

still be considered emergency engines. EPA has included a provision that would allow for more 

time if required by another regulatory entity. 
168

6.1.5 Comment: One commenter (81) said applying a NESHAP standard to emergency engines 

would force some states to require full air emission source permitting for such units or to modify 

their rules to exempt such engines. Many permitting authorities require permitting for all 

sources subject to NESHAP rules. This adds administrative burden, and these costs should be 

considered by EPA as it develops the final rule. The commenter (81) added that even if EPA 

decides to include only maintenance requirements for emergency engines, it should insert these 

requirements in a manner that would not automatically trigger state permitting requirements. 

One commenter (119) said the air quality benefit realized from regulating emergency 

engines is outweighed by the burden placed on area sources where a small engine may be their 

only equipment, and the administrative burden placed on state agencies to administer permit 

programs for the large number of sources that otherwise would not be regulated. 

Response: EPA has no control over what states require. EPA does not require permits for units 

at area sources and we agree that it would be an unnecessary administrative burden for states to 

require such permits; however, that is a determination that is made by the state, not EPA. 

6.1.6 Comment: Five commenters (90, 118, 139, 172, 178) requested that emergency and 

limited use RICE be exempted from the rule because of their low emissions due to infrequent 

usage. One commenter (90), who provides large emergency back-up electrical power supplies to 

clients in Iowa, South Dakota and Illinois, including grocery stores, schools, data centers, 

offices, and manufacturing facilities, provided statistics on peak usage and average years. In 

2008, which was a high use year due to extreme flooding in their service areas, their units were 
169

used an average of 58 hours across the fleet. Some units were used less than 5 hours for the year. 

In a more typical year, the average annual use may be 30 hours or less. The commenter (90) 

noted that even a large diesel engine used for emergency purposes in a typical year would emit 

well below 1 ton per year of CO and even much lower emissions of HAP. Another commenter 

(178) also cited the infrequent usage as a reason for exemption, stating that RICE units among 

their membership were used almost exclusively for emergency power and fire pump use and 

operated very little. The units are tested monthly, for 30 minutes or less per test. One member 

with multiple emergency engines noted that they are rarely, if ever, operated more than 50 hrs/yr 

and in most cases no more than 8 to 20 hrs/yr for routine maintenance. 

 The commenter (178) continued their justification for exempting emergency and limited 

use engines by referring to how the South Coast Air Quality Management District (SCAQMD) 

regulate the units. The commenter (178) noted that SCAQMD has one of the most stringent 

programs in the country for CI engines, yet exempts emergency generators, and limits CO to 250 

ppmvd for prime engines. They note that emissions rates specified by the manufacturers of new 

RICE will not meet EPA’s proposed Tier 2/Tier 3 requirements. 

One commenter (81) noted the vital role that emergency generation units play in the 

communications industry and that reliable communications is a critical component of the 

Emergency Support Function of the Department of Homeland Security’s National Response 

Framework. The commenter (81) said the proposed rule will require communication providers 

to spend a substantial amount of money to continue to operate these emergency engines, which 

will be borne by all consumers. However, the commenter (81) agrees with EPA statements in 

the preamble and docket that air quality benefits will be minimal or nonexistent. The commenter 

(81) referenced statements from supporting information to the proposal, which document that the 
170

operation and maintenance requirements proposed for emergency engines are, as a general rule, 

already being performed. If this is true, the regulations cannot be expected to result in any 

appreciable air quality improvements, the commenter (81) said. The commenter (81) added that 

the costs of complying with the proposed rule could be better spent on other environmental 

projects. The commenter (81) asked EPA to exempt all emergency engines located at area 

sources from the rulemaking. 

Commenter 81 also disputed the rationale that established a numeric limit that EPA 

expects all emergency engines can meet without installing after treatment controls and, therefore, 

provides no additional environmental benefit. The commenter (81) concluded that EPA should 

exempt all emergency engines at area sources. 

Commenter 119 also questioned the values of imposing a numerical standard on 

emergency CI engines, even if EPA does not require testing. The commenter (119) was 

concerned that state and/or local regulatory agencies would require testing, and if an engine were 

unable to demonstrate compliance with the numerical standard, aftertreatment controls would be 

required. As demonstrated by EPA’s analysis, such controls are not cost effective, and EPA’s 

costs are underestimated. The commenter (119) said that the catalyst aftertreatment technology 

requires elevated temperatures, and emergency generators often operate for short periods of time 

and may not reach the temperatures required for the oxidation of HAP.

One commenter (81) added that the rule could have the unintended effect of encouraging 

parties to reduce the size or availability of back-up power units, which are critical during power 

failures and other emergency situations. 

One commenter (139) stated that the proposed rule subjecting emergency RICE at major 

sources to emission limits is not warranted. The commenter (139) noted that the insignificance 
171

of these engines, which are operated infrequently, is illustrated by the compliance and testing 

requirements proposed by EPA: emergency RICE located at major sources would have no 

compliance requirements beyond complying with the manufacturer's instructions and no testing 

requirements whatsoever. Another commenter (118) requested that emergency engines be 

exempted from the rule based on the owner’s/operator’s ability to demonstrate they are following 

the engine manufacturer’s emission related O&M requirements. 

Response: As discussed in the response to comment 5.3.1, the final rule does not have any 

numeric emission limitations for emergency engines. Thus, the final rule should not reduce the 

availability of emergency engines or impose a substantial burden for these engines. Emergency 

engines are part of the listed source category and EPA cannot exempt them from regulation. We 

did, however, analyze the engines that were the basis of the source category listing for area 

sources and determined that residential, commercial, and institutional emergency engines at area 

sources were not part of the source category. These engines are therefore not subject to the final 

rule. 

6.1.7 Comment: One commenter (122) proposed that the allowance for non-emergency 

operations of emergency engines be expanded from the proposed 50 hours to 100 hours and that 

the limit for combined readiness testing and non-emergency operations be expanded from the 

proposed 100 hours to 200 hours. The commenter (122) operates some CI engines between 300 

and 500 HP that are primarily used for emergency purposes but are used between 50 and 100 

hrs/yr for non-emergency operations and not more than 200 hrs/yr for all operations. The 

commenter (122) recognized that those engines that operate above 50 hrs/yr for non-emergency 
172

purposes would be classified as non-emergency under the proposed rule and expected to use addon controls to meet the proposed limits which are based on an above-the-floor MACT 

determination for non-emergency CI engines between 300 and 500 HP. The commenter (122) 

noted that the cost analyses conducted to support this determination assumed 1,000 operating 

hrs/yr to justify the above-the-floor limits and asserted that, for engines operating not more than 

200 hrs/yr, the above-the-floor limits would likely not be justified on a cost basis. For this 

reason, the commenter (122) requested an expansion of the hours allowances for emergency 

engines so those operated by the commenter (122), and many similar ones operated by other 

sources, would be classified as emergency engines and not expected to apply costly add-on 

controls. 

Response: EPA does not agree that the allowance for non-emergency operations of stationary 

emergency engines should be expanded beyond 50 hours. If the owner/operator needs to operate 

the engine for additional hours beyond the 50 already allowed, and the 100 hours already 

allowed including testing and maintenance, then the engine should meet the requirements for 

non-emergency engines. 

6.1.8 Comment: One commenter (220) said that HAP emissions from their member’s engines 

are not likely to have any meaningful impact in the areas in which the engines are located. The 

AP-42 factors for engines show that HAP emissions from these units are miniscule, especially 

since they are only operated on an as-needed basis (peaking and/or emergency units). Short-term 

emissions are low, and EPA has offered no evidence that long-term HAP emissions from these 
173

types of units are worthy of significant regulation. The commenter (220) added that it is 

inappropriate for EPA to use a section 112 rulemaking to target non-HAP pollutants. 

Response: EPA does not agree with the commenter that these engines are not worthy of 

regulation. Section 112(d) requires regulation of stationary engines based on MACT or GACT 

and does not allow individual engines to be exempted. For emergency engines at area sources, 

EPA has included work practice standards instead of the emissions limitations that were in the 

proposed rule. This addresses the commenter’s concerns regarding the impacts on their 

emergency engines. Regarding peaking units, EPA does not agree with the commenter that they 

are not worthy of regulation. These types of units can typically operate for hundreds of hours per 

year and therefore are not insignificant sources of emissions. EPA is not using a section 112 

rulemaking to target non-HAP emissions, rather, it is using CO as a surrogate for HAP 

emissions. 

6.1.9 Comment: Commenter (226) recommended that all emergency generators less than 300 

HP be excluded from emission standards, because of the high costs and the small amount of 

emissions that they generate. The commenter (226) noted that EPA’s data shows that PM 

emissions from an average CI engine is below 10 pounds per year, even less for a smaller engine, 

would provide little emission reduction from the proposed rule. The commenter (226) noted that 

EPA has exempted all new emergency engines larger than 500 HP from emission standards, and 

does not see the merit in applying more stringent standards to smaller existing engines. The 

commenter (226) stated that EPA should exclude, at a minimum, all emergency RICE below 50 
174

HP to avoid the enforcement and permitting resources that this proposal would require. The 

commenter (226) also added that homeowners should not be subject to EPA enforcement. 

Response: As discussed in the response to comment 5.3.1, emergency generators at both area 

sources and major sources are not subject to numerical emission limitations in the final rule. In 

the final rule, EPA has excluded emergency engines that are located at residences that are area 

sources of HAP. EPA cannot exclude emergency engines at major sources from the rule because 

they are part of the listed source category. 

6.1.10 Comment: One commenter (228) noted that under the proposed rule, major source 

emergency RICE may operate an unlimited period of time for maintenance checks and readiness 

testing, while emergency RICE at area sources are limited to 100 hours for such maintenance 

checks and readiness with a right to petition for more. The commenter (228) stated that EPA has 

advanced no rationale for the discriminatory approach to area sources, which pose a lower risk to 

human health and the environment, than major sources. The commenter (228) also noted that 

major sources, which are presumably more familiar with the regulatory environment, are excused 

from the need to petition, while the much greater number of less sophisticated area sources are 

expected to petition. 

Response: The unlimited time period for maintenance checks and readiness testing for stationary 

emergency engines larger than 500 HP located at a major source of HAP was promulgated as 

part of the original RICE NESHAP action in 2004. In subsequent rulemakings, EPA determined 

that it would be appropriate to limit the hours for maintenance and testing for emergency 
175

engines. EPA has not yet revisited the section 112 requirements for the emergency engines that 

were subject to the 2004 RICE NESHAP but may do so in the future. 

6.2 Limited Use Engines 

6.2.1 Comment: Multiple commenters (78, 97, 107, 110, 126, 129, 130, 139, 150, 162, 168, 170, 

177, 178, 179, 183, 191, 197, 202, 207, 216, 227, 236, 247, 253) wanted EPA to expand the 

definition of limited use engines. Several commenters (162, 168, 236) said that a limited use 

category should be included in this rulemaking for area source engines and engines less than 500 

HP, as was included in the rule for engines greater than 500 HP located at major facilities. 

Commenters 97, 168 and 236 thought that limited use engines should be exempt from 

performance testing. According to commenters 97, 168 and 236, limited use engines should only 

be required to track and report hours of operation. 

Commenter 168 asked that limited use be defined as 250 hrs/yr. Commenters 126, 150, 

162, 197, 216, 236 and 247 asked EPA to provide 300 hrs/yr for limited use engines. If 300 

hrs/yr is not provided, commenter 162 requested clarification that readiness testing and 

maintenance are excluded from the annual hours of operation. This will allow companies to 

perform the necessary maintenance and testing requirements without worry of exceeding the 100 

hour limit, which could be easily exceeded if a malfunction or repair required diagnosis and/or 

engine tuning, the commenter (162) said. 

Two commenters (177, 253) asked that limited use be defined as 500 hrs/yr. The current 

rule defines limited use as “any stationary RICE that operates less than 100 hrs/yr.” The 

commenter believes that because of the low capacity factor (approximately 5.7 percent for an 
176

engine that operates 500 hrs/yr), the emissions are inherently low and would not pose a 

significant health hazard to the public. Similarly, commenter 168 said that its limited use 

engines, which are predominantly CI engines are inherently low-emitting and would not pose a 

significant health hazard to the public. Given the short periods of time the commenter’s units 

operate (startup engines for large combustion turbines), imposing emission limits is impractical. 

Therefore, startup engines should either be included in the definition of emergency stationary 

RICE, or limited-use RICE should continue to be exempt from emission limitations and 

additional requirements, according to commenter 162. 

Two commenters (126, 247) stated that if EPA declines to exempt the current limited use 

category to include all limited use engines, then EPA should establish a new subcategory of 

limited use RICE that are used in electric grid security. The commenters (126, 247) noted there 

are 500 such engines that operate less than 300 hrs/yr that are used to support the integrity and 

voltage of various electric utility transmission and distribution grids. The commenter (126) 

stated that these engines are similar to emergency engines, except they are used to respond to 

sags in voltage on remote portions of the utility’s grid. The commenters (126, 247) noted that 

the proposed rule would require retrofitting of these engines with catalytic converters, but 

believes these retrofits in many cases are impractical. 

One commenter (226) noted that it was incredulous to require significant regulation for 

small engines, but determine that larger limited use engines require no regulation. The 

commenter (226) stated that the Regulatory Flexibility Act requires EPA to consider less 

burdensome alternatives, and this should be done for the final rule. 

One commenter (110) recommended that EPA include a de minimis usage threshold of 

50 hours/year, below which, equipment will be exempt from the requirements of the proposed 
177

rule. The commenter (110) is concerned that the proposed rule will require a significant 

investment of resources for testing, personnel training, recordkeeping and reporting relative to 

the hours of usage for emergency standby generators or other limited use engines that are 

operated only for exercise or testing for 1 to 2 hours per month or less. The commenter (110) 

believes that the benefits are insignificant relative to the compliance cost, instead, could have the 

unintended consequence of generating more emissions as a result of the travel to conduct testing. 

One commenter (78) said the cost effectiveness of adding control devices to low-use 

engines should be evaluated regardless of the size of the engine. The costs associated with the 

installation and maintenance of a control device on a low use unit can be quite high per ton of 

pollutant abated. 

One commenter (202) recommended that an exemption for engines at an area source that 

is only used for backup purposes as long as the hours in any particular year do not exceed 500 

hours. The commenter (202) explained that it has four engines, each greater than 500 HP, that 

are maintained as backup units to ensure no digester gas build-up when the combustion turbines 

are off line. 

One commenter (107) proposed that EPA extend the exemption for limited use stationary 

engines that is currently available for engines above 500 HP at major sources to include existing 

engines at area sources that are above 300 HP. The commenter (107) noted that most of these 

engines are located at retail stores or office buildings where there are no other significant sources 

of HAP emissions and that the majority run less than 100 hrs/yr for backup power, peaking 

power, and maintenance combined. Additionally, the commenter (107) noted the proposed rule 

allows for an exemption for limited RICE rated greater than 500 HP at major sources, and the 

rule for area sources should not be more stringent than for units at major sources. 
178

One commenter (139) strongly supported the creation of a subcategory of limited use 

RICE, such as those with a 10 percent capacity factor or less. The commenter (139) believed 

that EPA’s rationale for proposing the installation of an oxidation catalyst on engines greater 

than 300 HP also supported the creation of a subcategory of limited use RICE, because in the 

proposed rule, EPA evaluates oxidation catalysts on a cost per ton HAP removal basis and 

concludes that the cost per ton increases as the size of the engine decreases. Similarly, the 

commenter (139) noted, there is a high cost per ton HAP removal associated with installing an 

oxidation catalyst on low capacity factor engines. The commenter (139) further noted that these 

limited use engines most closely resemble emergency RICE in their operation, but fall outside of 

that category because they do not meet the definition for emergency engines. Additionally, the 

infrequent use of limited use engines makes the application of pollution controls more difficult 

and costly. 

One commenter (78) said EPA should consider the distinction between baseload and 

peaking operation in developing the final regulation. Peaking engines typically operate far fewer 

hours each year than baseload engines (the commenter’s (78) peaking engines have capacity 

factors of 11 to 28 percent, which is typical). Retrofit requirements for engines in peaking 

operation will be far less cost effective because of the lower emissions benefits received. 

Another commenter (191) noted that many CI/diesel “peaker” units are not utilized 

simply in peak shaving, but more frequently act as “emergency” generation to stabilize the grid 

when requested by the regional electric Independent System Operator. The commenter (191) 

disagreed with EPA’s assumption of 1,000 hrs/yr operation times for peakers and provided data 

about their operating hours of peakers. Over the last 15 years, the commenter’s (191) 55 peaking 

units have averaged 40 operating hrs/yr. The maximum annual operating hours for any one site 
179

has been 269 hours in a year and the minimum 1 hour. The commenter (191) noted that in this 

circumstance the cost or emissions controls per ton of pollutant reduced becomes an order of 

magnitude greater and that EPA should lower the number of operating hours for which controls 

are not required to 300 per year. 

One commenter (130) requested that EPA expand the exemption for limited-use engines 

to include those used for rice irrigation. The commenter (130) specifically requested that the 

exemption be extended to area source engines that are less than or equal to 300 HP and that 

operate for 1,500 hours or less per year and provide that such engines only need to maintain 

records of annual operating hours to demonstrate that they comply with the limited-use 

exemption. To support the requested exemption, the commenter (130) noted that engines used 

for rice irrigation have a low capacity factor and are located in predominantly rural areas, thus 

presenting no significant health hazard to the public. Furthermore, the commenter (130) pointed 

out that EPA assumed the limited-use exemption would apply to engines used for electric power 

peak shaving that operate only during peak energy use periods, typically in the summer months. 

The commenter (130) asserted that, similarly, the use and operation of rice irrigation engines are 

different compared to typical engines because they are operated during limited periods of 

seasonal use and are mostly located in fields in rural areas. 

Response: EPA did not propose a category consisting of existing stationary limited use engines 

less than or equal to 500 HP located at major sources or existing limited use engines located at 

area sources. EPA did include a limited use category in the 2004 RICE NESHAP for existing 

and new stationary engines greater than 500 HP at major sources, defined as any stationary 

engine that operates less than 100 hours per year. However, that was a different rulemaking. It 
180

appears that some commenters might be commenting on that previous rule, which is not the 

subject of this action and EPA is not taking comment on requirements promulgated in 2004. 

EPA will revisit the 2004 regulation when the 8-year residual risk review must be conducted in 

2012. 

 EPA is required to address HAP emissions from all existing stationary engines less than 

or equal to 500 HP at major sources and existing stationary engines at area sources. Due to the 

recent Brick MACT decision, EPA can no longer set floors of no emission reduction for limited 

use engines at major sources, or any other engines for that matter, as was done in the 2004 RICE 

NESHAP that regulated existing and new stationary engines greater than 500 HP at major 

sources. 

 Various commenters requested that EPA establish a subcategory of limited use engines 

that would be allowed to operate up to 500 hrs/yr or a 10 percent capacity factor, which based on 

EPA’s estimates could account for the majority of an engine’s yearly operation. Commenters 

argue that based on an engine’s limited annual operation that the emissions from the unit are not 

significant. EPA does not agree with this claim. EPA considered the input and 

recommendations by commenters on establishing a subcategory of limited use engines, but EPA 

disagrees that such a subcategory is justified for existing stationary engines less than or equal to 

500 HP located at major sources and existing stationary engines located at area sources. Limited 

use engines are no different than other engines and EPA expects that engines even with low 

operation would be able to meet the same emission standards that apply to other stationary 

engines that may be operated more frequently. EPA does not see any reasons precluding limited 

use engines from applying aftertreatment controls, in those cases where addition control 

measures are needed to meet the final emission standards. EPA also points out that for stationary 
181

engines at major sources rated from 100-300 HP, the final standards are not based on the use of 

add-on controls and many engines are expected to be able to meet these standards without 

aftertreatment. Limited use engines are expected to exhibit the same or similar exhaust 

emissions profile as other stationary engines. In addition, commenters provided strong opinions 

on creating a limited use subcategory in the final rule, but did not give EPA adequate and 

persuasive information supporting their opinions. There are an estimated 71,000 stationary CI 

non-emergency engines less than 500 HP located at a major source of HAP. The total emissions 

from these engines if they operated 500 hours each are estimated to be 350 tons of HAP and 

2,300 tons of PM, so EPA does not agree that emissions from engines running 500 hours a year 

are insignificant. 

6.2.2 Comment: A few commenters (88, 126, 129, 184, 197, 247) were concerned about 

requirements that might apply to engines that startup turbines. Four commenters (126, 184, 197, 

247) suggested that RICE used to startup combustion turbines be exempt from the proposed rule, 

or deemed to fall under the “emergency” definition in 40 CFR §63.6675. The commenter (197) 

explained that turbine RICE only run for a few minutes to get the unit started and the total fuel 

consumption is not significant. The commenter (197) opined that the installation of expensive 

control equipment on RICE that has limited use does not make sense as the actual emissions for 

the RICE would be insignificant compared to the combustion turbine (burns more fuel oil in one 

minute of operation that the RICE would burn all year). Commenter 184 was concerned that the 

short run-time during each operation may not be long enough to get the filter up to its design 

temperature for achievement of its removal efficiency (and note that EPA discusses it in the 

preamble) or that a filter may require additional run time for regeneration. The commenter (184) 
182

further noted that the additional run-time required by the three year testing requirement could 

outstrip the run-time needed to support these combustion turbine peaking unit starting devices 

just for compliance with the RICE rule. The commenter noted that increased consumption of 

fuel for rule compliance would be wasting the natural resource and adding emissions for no 

measurable reduction being gained by the rule. 

Two commenters (88, 129) stated that EPA should not require post-combustion controls 

or emissions monitoring on CI engines serving gas turbine power facilities. The commenters 

(88, 129) supported this exemption because post-combustion controls will result in reduced 

dependability and significant cost increases, with little change in actual emissions since these 

engines rarely run long enough for such controls to reach minimum operating temperatures. 

Two commenters (88, 129) noted that every major power plant in the United States is required to 

have black start capability, which typically involves a small combustion turbine equipped with a 

diesel engine used for startup of the turbine. According to the commenter (129), the diesel 

starting engine, rated less than 500 HP, generally operates less than 10 minutes per combustion 

turbine start. The commenter (129) indicated that the majority of black start units only operate 

during emergencies or unusually high demand days, and that a review of the commenter’s 

company’s operating data determined that seven black start units in the system averaged 32 starts 

per year (which equates to less than 6 hours of operation per year, although some limited 

additional operation may occur as a result of routine maintenance and readiness testing). 

Response: In the final rule EPA has required that stationary engines used to startup combustion 

turbines meet work practice standards. EPA finds that the short time of operation for these 

engines (10-15 minutes per start) makes application of measurement methodology for these 
183

engines using the required procedures, which require continuous hours of operation, 

impracticable. Requiring numerical emission standards for these engines would actually require 

substantially longer operation than would occur normally in use, leading to greater emissions and 

greater costs. EPA also agrees with the commenters that it would not be appropriate to set 

emission limits that are based on the use of aftertreatment control for stationary CI engines that 

are used to startup combustion turbines. Oxidation catalyst control would not be effective for 

these engines due to their short time of operation (10-15 minutes per start). 

6.2.3 Comment: One commenter (127) expressed that it felt that it is unnecessary to limit the use 

of half of the 100 hours EPA has determined to be an acceptable cap for non-emergency 

generators under §63.6640 of the proposed rule. The commenter (127) requested that EPA 

remove the requirement limiting non-emergency operations to 50 hours for non-maintenance or 

testing purposes. The commenter (127) said that removing the requirement would make it easier 

for plant maintenance and recordkeeping purposes by allowing flexibility to use the hours (up to 

100) for non-emergency use without having to make the distinction of separately tracking and 

limiting the use of some of those hours. 

Response: EPA disagrees with the commenter. EPA has already included flexibility in that 

stationary emergency engines can maintain their classification as an emergency unit, but are 

allowed to operate for non-emergency purposes of up to 50 hours per year as long as such 

operation is not used to generate income for a facility to supply power to an electric grid or 

otherwise supply power as part of a financial arrangement with another entity. If an emergency 

engine is operated differently than described, it would be classified as a non-emergency engine 
184

and would be subject to different emission standards and compliance requirements. Therefore, 

EPA must require that operation by emergency engines is tracked and documented to ensure the 

requirements of the rule are being met. As EPA discussed in the preamble to the proposed rule 

(74 FR 9712), it is not expected that the recordkeeping requirements associated with emergency 

engine operation will be a significant burden, plus many stationary emergency engines may 

already be recording this information. Finally, these requirements are consistent with those 

finalized for new SI and CI stationary engines. 

6.2.4 Comment: One commenter (77) finds the limit of 100 hours in the definition of limited use 

RICE at 40 CFR 63.6675 to be unduly restrictive. The commenter (77) believes that 100 hours 

is very close to the amount of time that could be consumed by just the routine “maintenance 

checks and readiness testing” for similar emergency units. 

The commenter (77) noted that the electric utility industry has various blackstart, startup, 

peaking, and other units that are depended on for grid reliability, and a portion of these units are 

important for the reliable and safe operation of nuclear and other power plants. According to the 

commenter (77), some of the latter units provide the capability to restore power to an electric 

generating facility (of whatever type) that has lost all station power and must rely on itself to 

restore power and operation of the facility. The commenter (77) added that these units also 

provide for safety when other station power has failed, which is very important to the nuclear 

power industry. The commenter (77) stated that some of these RICE may also be able to provide 

power to the electrical grid, but all of them operate at historically very low capacity factors 

because of the high cost of operation. The commenter (77) believes that a 3-year average 

capacity factor of 5.7 percent is a more appropriate limit than 100 hrs/yr. The commenter (77) 
185

noted that the 5.7 percent value is more in line with the restriction of 500 hours placed on 

emergency generators by the State of Ohio. The commenter (77) added that additional controls 

on this category of units would be extremely cost ineffective due to the low capacity factors and 

actual tons of emissions that would be reduced. The commenter (77) conceded that the 

definition of limited use RICE was not a subject of this rulemaking, but believes that it is 

appropriate to modify the definition since it is used to exempt some facilities from the present 

proposed rule at 40 CFR 63.6590(b)(3). 

Response: The 100 hrs/yr the commenters are referring to with respect to limited use engines is 

a provision that EPA included in the original RICE NESHAP affecting stationary engines above 

500 HP located at major sources that was finalized in 2004. EPA is not taking comment on 

aspects of that rule at this time. The engines relevant to this proposed rulemaking are existing 

stationary engines less than or equal to 500 HP located at major sources and existing stationary 

engines located at area sources. A limited use category was not proposed for these engines, nor 

will one be included in the final rule. See EPA’s response to comment 6.2.1 on this issue. 

 Because EPA is revising 40 CFR part 63, subpart ZZZZ to add requirements for existing 

stationary engines less than or equal to 500 HP located at major sources and existing stationary 

engines located at area sources, it was necessary to modify section 63.6590(b)(3) of the proposed 

rule amendments in order to continue to exempt existing limited use stationary engines greater 

than 500 HP located at major sources. However, in terms of limited use engines, that section 

does not exempt any different or additional existing engines that were not already exempted from 

the original 40 CFR part 63, subpart ZZZZ promulgated in 2004. 

 
186

6.3 Nuclear Plants 

6.3.1 Comment: A few commenters (77, 79, 88, 139, 168, 203, 207, 216, 227, 236, 247) 

specifically recommend that EPA create a subcategory for RICE at nuclear generating plants. 

One commenter (173) believes that the proposal would impose significant additional costs on the 

industry and is potentially adverse to public safety from a nuclear safety perspective. 

Commenter 236 stated that RICE at nuclear facilities operate infrequently and are subject to 

mandatory startup standards that may not allow them to meet the limits in the proposed rule and 

recommends that the final rule address this subcategory separately with general exemptions for 

operation under NRC mandated operation. 

One commenter (79) said that for any requirements finalized by EPA that could require a 

physical change for nuclear emergency diesel generators must consider the normal outage 

schedules of nuclear power plants. The commenter (79) said any changes should be required 

within 6 years instead of 3 years. The commenter (79) described the nuclear-industry unique 

qualification requirements for safety-related equipment, and said that extended time is required 

to complete the design and certification process once a required physical change is identified at a 

commercial nuclear power plant. The commenter (79) also said that historically nuclear plant 

emergency generators have been exempted from EPA air emission regulations that might require 

post-combustion emissions controls in recognition of the need for rapid emergency diesel 

generators response at nuclear power plants to support critical safety functions. The commenter 

(79) cited an exemption provided in a 1979 NSPS regulation (44 FR 43156) affecting NOx from 

stationary engines, which stated the following: 
187

“Emergency standby engines also require special consideration. These engines operate less than 

200 hours per year under all but very unusual circumstances. Consequently, they add relatively 

little to regional or national total NOx emissions. The largest category of emergency standby 

units is for nuclear power plants, where these engines provide power for the pumps used for 

cooling the reactors. These engines must attain a set speed in ten seconds and must assume full 

rated load in 30 seconds. In some cases, application of the demonstrated NOx control technique 

limits the responsiveness of these engines in emergency situations. Therefore, all emergency 

standby engines are exempted from standards of performance.” 

The commenter (79) believes that this safety and performance rationale for exempting nuclear 

emergency diesel generators from post-combustion NOx controls, or numeric standards that 

would potentially drive such controls (even if not intended), is also relevant in the HAP context. 

Commenter 79 described additional emergency diesel generators operating requirements 

and regulations at nuclear power plants such as testing requirements, the prohibition for the use 

of nuclear emergency diesel generators to supply peaking power to the grid, and NRC 

regulations that add to the costs for making modifications to emergency diesel generators of two 

to three times greater than at non-NRC regulated emergency diesel generators. The commenter’s 

(79) preferred recommendation is that EPA should consider requiring good management 

practices consistent with engine manufacturer maintenance specifications, industry guidance for 

maintaining high emergency diesel generators reliability, and any relevant NRC requirements. 

Such practices could replace the existing proposed emission standard requirements. If needed, 

EPA could establish an additional subcategory of engine type to address the unique 

circumstances of nuclear emergency diesel generators. The commenter (79) suggested the 

following management practices for normal operations and SSM: 
188

• Change oil and filter after every 600 hours of operation (or use oil parameter analysis to 

monitor and trend the performance characteristics of the oil to verify that it remains 

within specification). 

• Inspect air cleaner after every 1,000 hours of operations and replace as necessary. 

• Inspect all hoses and belts after every 600 hours of operation and replace as necessary. 

Commenter (79) listed several reasons for the recommendation for management 

practices. Reasons include the fact that some engines might require controls and a management 

standard would prevent this inadvertent outcome. Installing post-combustion controls on nuclear 

emergency diesel generators could preclude successful rapid start and load acceptance, which are 

critical safety features of these engines. The proposal for 600 hour maintenance intervals is 

consistent with their existing 6-year maintenance program (100 hrs/yr of operation and correlated 

plant refueling outages). Nuclear emergency diesel generators are prohibited under NRC 

regulations from operating other than during periods of actual plant emergency or NRCmandated equipment testing, inherently limited their use. Also, nuclear emergency diesel 

generators operating hours are typically not more than 200 hrs/yr (75 to 100 hours is most 

typical). Post-combustion controls would not be cost-effective for HAP removal because annual 

HAP emissions range from less than 1 pound to 4 pounds per emergency diesel generator per 

year. These emissions generally occur in rural/remote areas of the country. Because of their 

critical nuclear safety-related function, the commercial nuclear power industry has invested 

substantial resources and oversight organizations to ensure emergency diesel generators are 

maintained to the highest standards of performance and reliability. 
189

If EPA does not agree with the preferred recommendation, the commenter (79) said that 

EPA should provide an exemption from the regulation for nuclear emergency diesel generators 

that operate 200 hrs/yr or less. 

Requiring nuclear utilities to concurrently comply with two different regulatory regimes 

for emergency back-up generators used to support safety systems could create substantial 

operational problems that would not serve the public health and safety, commenter 247 said. 

One commenter (203) added that nuclear power plants are required to provide back-up 

emergency power in case of loss of external electricity (i.e., off-site power) in order to assure the 

safe shutdown and cooldown of the nuclear reactor. Large emergency diesel generators are the 

preferred option for such back-up power systems. These emergency diesel generators are 

required by NRC regulations to be qualified for safety-related service and it is critical that the 

proposed emissions standards do not interfere with or jeopardize this critical safety function., 

commenters 203 and 207 said The commenter (203) noted that as required by the NRC-issued 

license, the emergency diesel generators must be maintained in operable condition during plant 

operation, and the period of time that the emergency diesel generator may be inoperable is 

limited. To assure operability of the emergency diesel generator, the license requires periodic 

testing and surveillance. For example, the diesel generators are started monthly and operate for 1 

to 2 hours, diesel fuel oil is tested regularly, during every refueling outage (either every 18 or 24 

months) the generators are typically run for 24 hours; however, the diesel generators typically 

operate less than 100 hrs/yr (1.1 percent of time available) and are not run for the purpose of 

producing electricity for retail sale. The commenter (203) advised that if the exhaust 

aftertreatment were to require maintenance during operation of the diesel generator in an 
190

emergency, it also could prevent the diesel generator from performing its safety-related function, 

thus placing the public at risk. 

One commenter (139) urged EPA to exclude RICE serving as emergency diesel 

generators at nuclear plants from NESHAP. Emergency diesel RICE at nuclear plants are 

essential to providing a safe shutdown, mitigating any potential malfunction, and providing spent 

fuel pool cooling. The commenter (139) believed the proposed rule would subject these engines 

to emissions limits that cannot be met without add-on controls; however, due to the configuration 

of nuclear plants, add-on controls could decrease the reliability of the emergency generators. 

The emergency engines at nuclear plants are required to start and be ready to accept load in 10 to 

15 seconds, with full load reached in 20 to 60 seconds, according to commenters 139 and 227. 

The short time periods are necessary to mitigate the consequences of a potential loss of reactor 

coolant, commenters 139 and 227 said. The commenters (139, 227) said that the imposition of 

aftertreatment controls could slow the time in which the emergency engine is prepared to supply 

backup power and any such decrease in reliability would violate nuclear safety standards. The 

commenter (139) also cited short operating periods, when the control equipment may never reach 

operating temperature before shut down, and costs in justifying the exemption. 

Commenter 207 noted that nuclear power plants have been exempted from many EPA 

regulations in recognition of unique safety and support equipment requirements and existing 

regulation by the NRC and recommends that the following exemption be added to the proposed 

rule: 

“Exemption for Emergency Engines at Nuclear Facilities. The requirements in 40 CFR part 63 

do not apply to any stationary RICE for which one or more of the following criteria are met: 

(1) the engine is regulated by the NRC; 
191

(2) the engine is used solely for the safe shutdown and maintenance of a nuclear facility 

when normal power service fails or is lost; or 

(3) the engine is an emergency standby engine. 

Further, commenters 207 and 247 said that RICE at nuclear power plants should not should not 

be subject to operating limits or have any annual restrictions for maintenance and testing that 

conflict with any current or future NRC requirements. As an example, commenter (207) asserts 

that emergency RICE at nuclear power plants should not be restricted to 100 hrs/yr or less 

whenever the required NRC maintenance and reliability testing necessitates longer operation. 

Nuclear generation facilities maintain records documenting the hours of operation for required 

maintenance and testing and should not be required to petition for approval to operate more than 

100 hours. 

Commenter 207 believes EPA should revise the limited use exclusion to include all sizes 

of engines, area sources in addition to major sources, and expand the definition of limited use to 

include operation up to 300 hrs/yr, and that such units should also be exempt from performance 

testing and only be obliged to maintain and report records of annual operating hours to show that 

they qualify as limited use RICE. Commenter 207 described the main categories of nonemergency “limited-use” engines operated at nuclear power stations: 

• RICE that provide black-start capability to the facility, 

• RICE that provide back-up power to critical information technology infrastructure, 

• RICE used during outages, 

• RICE that provide back-up power to emergency support facilities, and 

• RICE that provide back-up fire suppression water. 
192

Commenter 207 concluded that RICE installed at nuclear power station should be allowed a 

“limited use” exemption. 

Similar comments were submitted by commenter 88 who indicated that EPA should 

require management practices rather than a numerical emission limit for emergency diesel 

generators at nuclear facilities. Emergency engines at nuclear facilities operate less than 200 

hrs/yr, according to commenter 88, and under federal licensing requirements, nuclear emergency 

diesel generators must be tested on a monthly basis (generally for 1 or 2 hours) to ensure their 

availability. These engines are also subject to biennial endurance tests of up to 24 hours and may 

also be tested during periodic nuclear plant maintenance outages and after any major overhaul 

work, as required by the NRC. The commenter (88) argued that meeting the proposed numeric 

emission standard under such operating requirements mandated by the NRC could be difficult, if 

not impossible, for some older existing nuclear emergency diesel generators. Even assuming a 

facility installed post-combustion controls to meet the numeric standard, catalysts typically take 

time to reach the necessary temperature to begin their optimal function. This timeframe is 

inconsistent with the required safety performance response time of the emergency diesel 

generators at nuclear facilities. Additionally, post-combustion controls have the potential to 

introduce backpressure on the emergency diesel generator that may reduce response time and/or 

reduce the unit’s electric output versus its original technical specification. (Two-stroke CI 

engines have much less backpressure tolerance than four-stroke CI engines.) Finally, the 

commenter (88) reported that any modifications to existing emergency diesel generator 

configurations at nuclear power plants are heavily regulated by the NRC, and capital costs for 

modifications can run two to three times greater due to additional NRC testing and evaluation 

requirements than would be the case at a non-nuclear regulated emergency diesel engine. 
193

(Qualification testing required by NRC per Regulatory Guide 1.9 would be approximately $3-10 

million dollars per engine type. No engines with catalytic converters qualify under Regulatory 

Guide 1.9.) 

Another commenter (168) urged EPA to create and exempt a subcategory of RICE 

emergency engines that are required to meet NRC requirements. Commenter’s (168) three 

nuclear plants have CI RICE emergency back-up generators ranging in size from 5,500 to 7,500 

HP that are not connected to the grid for energy sales and are mandated by specific NRC 

requirements for the safe shutdown of the reactors. Further, commenter (168) states that the 

emergency back-up generators must be capable of full power and be able to accept station 

electrical loads within 11 seconds, and that the NRC considers these units to be part of the 

nuclear power plant. Commenter (168) maintains that these emergency back-up generators 

cannot be subject to any operating limits and it is also imperative that any initial testing under the 

final subpart ZZZZ rule be consistent with what is allowed under NRC rules. More specifically, 

commenter (168) states that applicable NRC rules in 10 CFR part 50 and Regulatory Guide 1.9 

insure that emergency back-up generators are regularly maintained and that owners conduct 

sufficient testing, and that any requirement under subpart ZZZZ to retrofit control devices would 

most likely negatively impact their ability to meet the NRC requirements and be costly and 

difficult due to space, temperature, and ventilation constraints. Commenter (168) also contends 

that emergency back-up RICE located at nuclear power plants should not have any annual 

restrictions for maintenance and testing that would conflict with current or future NRC 

requirements. 

In addition, commenter (168) claimed that the proposed exemption from petitioning EPA 

for approve to operate more than 100 hrs/yr does not apply on its face to back-up generators at 
194

nuclear power plants and stated that it would serve no good purpose to require owners and 

operators to petition EPA if NRC regulations require more than 100 hrs/yr for maintenance 

checks and readiness testing. 

Response: EPA agrees with the commenters that management practices are appropriate for 

stationary emergency generators at nuclear power plants that are area sources of HAP emissions. 

These engines are required to meet management practices in the final rule and have no emission 

limitation requirements. EPA believes that emergency engines located at nuclear plants that are 

major sources of HAP will be greater than 500 HP and therefore will not have to meet any 

requirements under subpart ZZZZ. Therefore, the concerns expressed by the commenters 

regarding the installation and operation of emission controls on these engines have been 

addressed. EPA does not agree that these engines should be excluded from the NESHAP. There 

are specific requirements for exemptions under section 112(d), but the commenters have not 

provided any information to indicate they would fall under any such exemption. EPA believes 

that it would be appropriate for operators of these engines to petition for additional operating 

hours if necessary, and in fact the final rule allows such engines to operate more than 100 hours 

per year if required by other regulatory authorities, without requesting such additional hours 

from EPA. EPA does not agree that a specific subcategory is necessary for emergency 

generators at nuclear power plants; there is no reason that those engines would be unable to meet 

the same management practice requirements as other types of stationary emergency engines. 

The final rule includes a provision that allows owners/operators to petition for alternative 

management practices if necessary. EPA has also included a provision in the final rule that if an 

emergency engine is operating during an emergency and it is not possible to shut down the 
195

engine in order to perform the work or management practice requirements on the schedule 

required in Table 2c of this subpart, the final rule, or if performing the work or management 

practice on the required schedule would otherwise pose an unacceptable risk under federal, state, 

or local law, the work or management practice can be delayed until the emergency is over or the 

unacceptable risk has abated. 

6.4 Other Engines 

6.4.1 Comment: One commenter (225) noted that there is no limit on construction date for 

existing RICE in the proposed rule. The commenter (225) stated that older engines were never 

designed to comply with these stringent emissions and some are not easily retrofitted with 

catalysts, if it can be done at all. The commenter (225) added that the expectation for old RICE 

to meet the MACT Floor or beyond-the-floor will be extremely challenging, and there is no data 

in the docket supporting whether the proposed emission limits are even possible. The 

commenter (225) believes that industry could be faced with replacing thousands of existing 

engines (most in rural areas) in order to meet the stringent standards in this proposed rule. 

Response: The commenter has not provided sufficient information to support the claim that 

existing engines cannot be retrofit with catalysts. EPA believes that older engines can use 

oxidation catalysts and is aware of installations of oxidation catalyst on older engines, both 

stationary and nonroad. Also, emission limits for many engines in the final rule do not rely on 

engines having to be retrofitted, but the expectation is that many engines can meet the final 

emission standards without installing aftertreatment. In fact, for several categories, particularly 
196

emergency engines and engines less than 100 HP, EPA is not finalizing numerical emission 

limits, but is instead adopting management practices, or use restrictions, instead. 

6.4.2 Comment: One commenter (200) noted that EPA provides an exemption for fire pump 

engines, but does not mention other sources that should be similarly exempted. Specifically, the 

commenter (200) recommended that EPA provide clarifying language to also exempt engines 

that are in similar service such as for mitigation systems. The commenter (200) said that these 

pumps are used for release events similar to fire events. 

Response: EPA does not provide a specific exemption for fire pump engines. It is possible that 

the commenter is referring to the fire pump provisions that were included in the final CI NSPS 

(40 CFR part 60, subpart IIII) finalized in 2006. Fire pump engines are not exempted from the 

CI NSPS, but have different requirements than other engines. Commenter 200 did not provide 

compelling evidence supporting why the sources it mentions should be exempted from the rule. 

EPA cannot exempt these engines from the rule, but if these engines meet the definition of 

emergency engines, which seems to be what the commenter is stating, the engines would be 

subject to the same requirements that apply to other existing stationary emergency engines under 

the final rule. 

6.4.3 Comment: One commenter (130) requested that generators used for residential purposes be 

exempted from the proposed rule. The commenter (130) stated that doing so would significantly 

lower the true economic impacts of the proposed rule. 
197

Response: In response to this comment, EPA analyzed the types of engines that were included in 

the area source category listing for stationary RICE. As a result of this analysis, EPA determined 

that emissions from existing stationary emergency engines located at residential, commercial, 

and institutional facilities that are area sources of HAP were not included in the 1990 baseline 

emissions inventory that was used as the basis for the listing of source categories needed to 

ensure that 90 percent of area source emissions are regulated. Therefore, EPA determined that 

these stationary engines will not be subject to this area source standard. 

6.4.4 Comment: Three commenters (129, 157, 216) urged EPA to exempt all CI RICE that use 

100 percent (commenter 157 said 99 percent) biofuels from the requirements of 40 CFR part 63, 

subparts A and ZZZZ, until further emissions data are available and it is conclusively determined 

that these engines warrant regulation. 

Response: EPA does not agree that stationary CI engines that use biofuels should be exempted 

from the requirements of subpart ZZZZ. The commenter did not provide any information or 

emissions data to show that these engines warrant subcategorization or that they are unable to 

meet the emission limitations for CI engines. 

6.4.5 Comment: One commenter (230) recommended that EPA allow state and local air 

agencies to determine appropriate exemptions from air permitting requirements, including Title 

V operating permit programs. The commenter cited several examples of state exemptions by 

engine type, size of engine and number of operating hours. The commenter noted that the 

proposed rule would require emergency engines to be incorporated into the Title V permit if 
198

located at a Title V source. The commenter also stated that states that allow Title V and minor 

source exemptions for area source RICE not regulated by EPA would no longer apply. The 

commenter believes the restrictions of hours and fuel types are adequate to limit HAP emissions. 

The commenter also noted that by EPA not proposing a permanent deferral for Title V area 

source permit applications, facilities subject to the proposed regulation will have to submit Title 

V area source applications, which the commenter believes will not enhance compliance and be 

unnecessarily burdensome.

Response: The provisions in 40 CFR 63.6585(d) indicate that area sources subject to 40 CFR 

part 63, subpart ZZZZ, would not be subject to permits under 40 CFR parts 70 or 71 solely 

because of this rule. That provision will apply to the existing stationary engines covered in this 

rulemaking, including existing stationary emergency engines that the commenter is concerned 

about. In addition, residential, institutional, and commercial existing stationary emergency 

engines at area sources are not subject to the final rule. 

6.4.6 Comment: One commenter (230) asked EPA to consider adding a provision to the rule that 

allows implementation of the relevant standards based on technological or economic feasibility 

similar to the 40 CFR 63 GP for reconstruction. 

Response: The requirements in the rule have already been determined to be technologically and 

economically feasible. Furthermore, affected sources have three years to comply with the rule. 

Therefore, EPA does not agree that the provision suggested by the commenter is necessary. 
199

7.0 Management Practices 

7.1 General Comments 

7.1.1 Comment: Several commenters (155, 176, 220, 226, 242, 253) supported EPA’s strategy 

with regards to proposing management practices for certain engines at area sources. Numerous 

commenters, including commenters 155, 226, and 242 stated that EPA can rely on management 

practices under GACT provisions for area sources and under section 112(h) of the CAA for 

major and area sources and several commenters said that EPA should consider applying 

management practices for additional categories of engines. Commenters claimed that EPA has 

concluded that where area sources are subject to an emission limit that the limit should be 

equivalent to MACT, but where the limit is a management practice that the limit can differ from 

MACT. The commenters (155, 242) said that EPA’s basis for this decision is not clear, nor does 

the docket provide evidence of this decision and what alternatives were considered. The 

commenters (155, 242) are of the opinion that EPA should consider additional opportunities to 

rely on management practices to demonstrate compliance for the following reasons: 

• Several engines at area sources are in rural locations and are often remotely located and 

EPA should apply GACT more broadly in those areas. If EPA retains MACT for these 

sources such a decision should be well-documented and justified; 

• Considering the limited and flawed data EPA used for this rulemaking questions the 

decision to rely on MACT for area sources. Cost effectiveness escalation should be 

considered for smaller engines when determining the appropriateness of GACT vs. 

MACT. In addition, EPA needs to take into account that extra costs may be associated 
200

with engines in rural areas due to the lack of electricity and often times unmanned 

facilities. 

One commenter (183) indicated that EPA did not contemplate the maintenance 

challenges for existing small (less than 50 HP) SI and CI RICE units located in remote 

unmanned locations. The commenter (183) stated that in Alaska remote locations, frequent visits 

for oil and filter changes every 200 hours and 500 hour belt inspections are impractical and 

unsafe. The commenter (183) noted that maintenance has been addressed by installation of large 

fuel tanks, winterization or expansion of the cooling systems, retrofit of oil reservoirs with 55 

gallon reservoirs, and the use of synthetic oils. The commenter (183) proposed that the rule be 

revised to exempt these types of remote unmanned sites from the maintenance interval 

requirements, or at least increase the maintenance intervals to an annual basis. 

Commenter 175 was also concerned about requiring specific maintenance activities for 

engines located in remote, unmanned area sources. The commenter (175) also pointed out that 

its members are developing and promoting new technologies to reduce CO2 emissions. Some of 

this new micro distributed energy covers engines less than 30 HP and it appears that these 

engines could be swept in under the proposed operations and maintenance standard for less than 

50 HP engines located at area sources. The commenter (175) said that it particularly worried that 

the proposed oil and filter replacement standards for such small engines would be overly 

burdensome, unnecessary and would persuade potential customers to instead install electric air 

conditioning and furnaces with a much larger carbon footprint and pollutant emissions measured 

from the source of the power generation (often coal-based) to the end use consumer. This will 

undermine efforts to reduce the carbon footprint of the commenter’s (175) members’ customers. 

The commenter (175) asked that EPA exempt area source engines less than 30 HP. 
201

One commenter (176) recommended that EPA consider allowing owners or operators of 

engines to utilize management or operating practices in accordance with section 112(h) of the 

CAA in lieu of requiring beyond GACT for stationary engines at area sources and having 

emission requirements for smaller engines at major sources. 

Similarly, commenter 220 said the proposed rule for area sources is over-inclusive as it 

regulates engines that have a minimal impact on urban areas and over-controls categories of 

engines. Instead of essentially requiring MACT, EPA should allow owners or operators of 

engines to utilize management or operating practices in accordance with sections 112(d)(5) and 

112(h) of the CAA. 

One commenter (253) agreed with EPA’s GACT assessment for smaller (500 HP or less) 

engines at area sources and believes that management practices to reduce HAP emissions from 

these engines are appropriate. One commenter (205) encouraged EPA to consider establishing 

maintenance and work practice standards for additional categories of engines within the 

proposed rule, particularly those that EPA expects to be able to meet the proposed numeric 

emission limits without the addition of controls. The commenter (205) stated that benefits of this 

approach include assuring that engines are being operated in a manner expected to minimize 

HAP emissions as well as eliminating the commenter’s (205) significant concerns regarding the 

adequacy of the data EPA used to establish the proposed numeric emission limits. While 

endorsing this approach, the commenter (205) did express some concerns regarding the 

stringency and frequency of the proposed maintenance and work practices, such as the lack of 

data supporting a relationship between frequent oil and filter changes (proposed at every 200 

hours) and HAP emissions. 
202

Several commenters (77, 118, 119, 129, 157, 205, 240) supported EPA’s use of 

maintenance and work practices standards and certain commenters said the management 

practices in Table 2d of the proposed rule (40 CFR 63 subpart ZZZZ) are consistent with the 

proper maintenance of engines, and that the management practices in the proposed RICE 

NESHAP are sufficient to ensure that the engines are properly maintained. 

Response: EPA does not agree with the commenters that management practices are GACT for 

stationary non-emergency CI engines above 300 HP located at area sources. EPA has evaluated 

the available control technologies for those engines and determined that GACT based on control 

of emissions using diesel oxidation catalysts is appropriate for these engines. On a per-engine 

basis, HAP reductions from a 400 HP non-emergency CI engine would be around 30 lb/yr and 

from a 600 HP engine the HAP reduced by oxidation catalyst would be approximately 45 lb/yr. 

Emissions of PM on a per-engine basis would be reduced by 84 and 126 lb/yr for a 400 HP and 

600 HP engine, respectively. On a nationwide basis, existing stationary non-emergency CI 

engines above 300 HP at area sources are estimated to emit on a yearly basis around 1,000 tons 

of HAP. Applying oxidation catalyst control to these engines would result in HAP reductions of 

70 percent or more, or 70 tons of HAP or more annually. Baseline emissions of PM from these 

engines are estimated at 6,500 tpy and would be reduced by 30 percent or nearly 2,000 tpy 

through the use of oxidation catalyst control. It is estimated that the benefits per ton are between 

$330,000 (Pope, 7%) and $790,000 (Laden, 7%) for PM for existing stationary CI engines at 

area sources. The benefits per ton outweigh the costs of oxidation catalyst control, which are 

estimated to be at most around $61,000 per ton of PM removed. (Additional information on the 

benefits associated with this final rule can be found in the Regulatory Impact Analysis. Further 
203

discussion of the GACT analysis can be found in the memorandum entitled “MACT Floor 

Determination for Existing Stationary Non-Emergency CI RICE Less Than 100 HP and Existing 

Stationary Emergency CI RICE Located at Major Sources and GACT for Existing Stationary CI 

RICE Located at Area Sources.” EPA does agree with the commenters that management 

practices are GACT for non-emergency CI engines 300 HP and below at area sources and 

emergency CI engines located at area sources of HAP. EPA also agrees that work practices are 

appropriate for stationary engines at major sources below 100 HP. Regarding the concerns 

expressed about the MACT floor data, see the response to comment section 5.1.1. 

 For the commenters that believed the proposed maintenance practices were not 

appropriate for their engines, EPA has made several changes to the management and work 

practice requirements based on such comments (see discussion below) and EPA has also 

included a provision in the final rule that allows sources to petition for alternative maintenance 

practices. 

7.2 Specific Requirements 

7.2.1 Comment: Several commenters (64, 66, 68, 75, 76, 89, 97, 101, 103, 104, 108, 111, 112, 

130, 131, 132, 136, 148, 150, 151, 154, 155, 159, 174, 176, 179, 183, 187, 204, 221, 224, 225, 

227, 228, 230, 231, 241, 242, 253, 261, 262, 264) did not agree with the specific management 

practices that EPA has proposed in the rule for area sources or recommended different 

maintenance practices. According to the commenters (103, 112, 131, 155, 179, 183, 224, 225, 

241, 242), the maintenance frequency in the proposed rule exceeds current practices or is not 

supported in the proposed rule. Several commenters agreed that management practices are 
204

appropriate for the proper operation of the engines and is a reasonable means to reduce HAP 

emissions, however, did not agree with the specific maintenance practices proposed by EPA. 

Numerous commenters recommended that EPA allow owners/operators to follow engine 

manufacturers’ recommended practices or the owners/operators own site-specific maintenance 

plan. 

One commenter (112) pointed out that operators have a direct interest in maintaining 

engine oil, hoses, and belts, so the engine runs reliably, but the appropriate frequency for these 

maintenance practices are specific to engine design and are not “one size fits all.” 

Ten commenters (89, 101, 103, 104, 150, 151, 155, 221, 231, 242, 264) recommended 

that EPA revise fixed maintenance (one-size-fits-all) requirements to maintenance plans. 

The commenters (89, 101, 151, 221, 231, 261) stated that, while fixed maintenance 

intervals work well for new mass produced engines similar to those in automobiles, they are 

inappropriate for the wide variety of existing engines used in the oil and gas, agriculture, and 

power generation industries across the nation. The commenters (89, 101, 151, 221, 231, 261) 

pointed out that EPA allows the use of operator-defined maintenance plans that are “consistent 

with good air pollution control practice for minimizing emissions” to be used in other portions of 

this same rule, and asserted that EPA should allow the use of operator-defined maintenance plans 

to greatly reduce cost and allow operators to optimize maintenance for each type of engine. 

 One of these commenters (221) added that current industry engine maintenance programs 

are driven by tried-and-true practices and since these practices effectively keep the engines 

running, they allow the products of the members of the commenter’s organization to go to 

market. The commenter (221) stated that additional, burdensome, frequent, and time-consuming 
205

maintenance requirements will cause the members of the commenter’s organization to morefrequently shut down engines and thus shut down production. 

Two commenters (155, 242) said that if EPA keeps the management practices as 

proposed, the frequencies associated with conducting engine maintenance should be revised to 

be commensurate with today’s practices. The commenter (155) believes the maintenance 

practices, as proposed, are significantly burdensome and lack basis. According to the 

commenters (155, 242), EPA should replace the maintenance hour intervals with company 

recommended performance-based maintenance practices to be documented in an operatordefined maintenance plan consistent with requirements in 40 CFR part 60, subpart JJJJ. 

Two commenters (155, 242) recommended that EPA allow owner and operator-defined 

management practices, in addition to the specific management practices required by the rule. 

EPA has previously adopted a similar approach, e.g., in 40 CFR part 60, subpart JJJJ. In the 

commenters’ (155, 242) opinion, owners and operators of engines are knowledgeable in the 

operation of their engines and are best-suited for determining what practices are appropriate for 

their specific engines. Commenter 242 believed that owner and operator-defined maintenance 

practices will be more cost effective, lead to more consistent and stable combustion efficiency, 

and lower emissions. 

The commenters (155, 242) requested that, if EPA does not allow operator-defined 

maintenance practices, and if EPA cannot define a more appropriate maintenance frequency, 

EPA should enlist the assistance and input of industry to determine appropriate management 

practices. The commenter (155) believes that soliciting the participation from stakeholders on 

this matter will ensure management practices that are consistent with reasonable engine 

practices. In general, it seems that the majority of comments received on this issue are in favor 
206

of adopting engine manufacturer’s maintenance recommendations and not the specific 

maintenance requirements and frequencies that would be applicable to all engines across the 

board. 

 One commenter (264) supported EPA’s proposal to require non-emergency RICE at 

major sources to properly operate and maintain their stationary RICE and aftertreatment control 

device. However, the commenter (264) has experienced situations where manufacturers’ 

emission-related instructions are inferior to operating experience and that, for old equipment, it 

may be impossible to obtain manufacturer recommendations. The commenter (264) 

recommended that the option of operating according to a maintenance plan developed by the 

owner/operator for the engine be allowed. 

Seven commenters (76, 96, 99, 111, 130, 154, 242) recommended that EPA specify that 

the engine manufacturer’s prescribed requirements can be used to demonstrate compliance. 

The commenters (96, 99) thought that there is a better way to make sure owners and 

operators maintain and run their engines appropriately and that would be to follow the 

recommendations of the engine manufacturer. Engine manufacturer’s instructions and 

recommendations are specifically designed to ensure the engine is properly maintained and 

operated. The commenter (96) listed specific areas where it believes EPA should replace the 

current proposed requirements with engine manufacturer’s maintenance practices. 

Commenter 76 asserted that there are so many engine designs installed that the engine 

manufacturer is best-suited to determine the appropriate maintenance practices and schedules. 

Commenter 154 said that the Table 2d instructions of the proposed rule may not be 

specifically-designed to ensure proper engine maintenance and operation and may void the 

warranties provided by manufacturers. The commenter (154) recommended that EPA specify 
207

that the engine manufacturer’s requirements be prescribed to demonstrate compliance. 

According to the commenter (154), in the absence of appropriate specifications, EPA should 

indicate that the current requirements listed in Table 2d of the proposed rule must be followed. 

This commenter (154) also said that EPA should clarify that the work practice requirements 

apply to periods of normal operation rather than SSM. 

Another commenter (111) in the oil and gas production industry noted that EPA proposed 

its maintenance intervals with the expressed purpose “to ensure that emission control systems are 

working properly.” In the commenter’s (111) opinion, the manufacturers’ O&M manuals are 

both appropriate and sufficient to address this goal. The commenter (111) stated that 

manufacturer O&M procedures are typically conservative and driven by the equipment-specific 

design. 

One commenter (130) stated that rice irrigation engines may need to be operated beyond 

the proposed maintenance schedules during periods of flooding of rice fields and that relying on 

manufacturer’s suggested maintenance schedules would be more practical and appropriate. In 

some cases, warranty violations may occur if engines are maintained according to the proposed 

stringent schedules, according to commenter 130. 

Four commenters (99, 112, 204, 225) provided specific input on the proposed rule oil 

change and air filter requirements (including frequency). 

Commenter 99 stated that there is not a one size fits all recommendation that suits oil 

change intervals for all engines and maintaining appropriate oil qualities is crucial, but replacing 

it too early is expensive and leads to unnecessary quantities of waste oil and filters. 

Commenter 112 noted that many operators use an oil testing program to determine oil life 

to reduce maintenance cost and used oil generated, while maintaining high engine reliability. 
208

The commenter (112) believes that EPA has failed to justify why recommended oil changes are 

included as a maintenance practice when oil changes have little to no effect on engine emissions. 

One commenter (204) noted that the vast majority of their applicable engines use a 

synthetic lubricant that does not need to be changed unless it is contaminated. This lubricant 

does not degrade over time and, in some instances, can be utilized in engines for over 30,000 

operating hours without requiring changing. The commenter’s (204) operating companies have 

in place sampling programs to ensure that the engine lubricant has not degraded and been 

contaminated. Air filters are regularly checked by determining the differential pressure across 

the filter to determine if a change is needed. The commenter (204) stated that by maximizing the 

useful life of oil and filters while maintaining a responsible maintenance schedule reduces costs 

and waste generation - a win-win proposition versus the proposed maintenance schedule that will 

increase the environmental impact from waste generation and the additional startup after 

maintenance of these engines as well as the costs of compliance for regulated entities. 

One commenter (225) stated that most of the engine manufacturers for the engines in the 

oil and gas industry recommend oil changes on a monthly schedule. The commenter (225) also 

indicated that it is common practice to periodically sample and test the engine oil to see if the oil 

properties are sufficient to extend this time period between oil changes. According to the 

commenter (225), this testing has shown in many cases that the oil change interval can be 

extended without any detrimental effects on the engine, which allows industry to maximize 

efficiencies, minimize oil usage, reduce waste, and streamline operations with no negative 

impacts to the engine or emissions. 

Two commenters (112, 51) provided specific comments on the engine hose and belt 

inspection requirements. 
209

One commenter (112) expressed that inspection of hoses and belts has no impact on HAP 

emissions. Commenter 51 expressed that, generally, it agreed that performing maintenance on 

engines will help to reduce HAP emissions, but that while inspecting belts and hoses is an 

important part of general engine maintenance (and most sources likely conduct regular 

inspections of their engines), such inspections have no effect on emissions and should be 

removed from the proposed rule. 

One commenter (183) also stated that O&M requirements should also be limited to 

emission related O&M, which does not include the inspection of belts and hoses. Commenter 

(179) recommended that EPA consider creating subcategories where GACT is management 

practices rather than post-combustion controls for units operating under adverse environmental 

conditions or in situations where space is not available to install enclosures sufficient to 

overcome environmental conditions. The commenter (179) stated that EPA could add minimum 

requirements to the maintenance plans such as the following: 

• Change oil and filter or verify satisfactory oil characteristics via testing every 4,000 hours 

of operation or less; and 

• Inspect air cleaner every 4,000 hours of operation or less and replace as necessary. 

Response: EPA proposed to require specific management practices for certain engines, primarily 

for smaller existing stationary engines at area sources where EPA thought that add-on controls 

were not GACT. EPA indicated at proposal that the management practices specified in the 

proposal reflected GACT and that such practices would provide a reasonable level of control, 

while at the same time ensuring that the burden on particularly small businesses and individual 
210

owners and operators would be minimized. EPA asked for comment on the proposed 

management practices and received comments on the proposal from industry. 

 EPA agrees with the commenters that it is difficult to adopt a set of management 

practices that are appropriate for all types of stationary engines. Regardless, EPA must 

promulgate emission standards pursuant to section 112(d) of the CAA for all engines at area 

sources covered by the final rule. EPA still believes that a management practice approach 

reflects GACT for emergency engines and smaller engines at area sources. These management 

practices represent what is generally available among such engines to reduce HAP, and the 

practices will ensure that emissions are minimized and engines are properly operated. EPA does 

not agree with the commenters that it would be appropriate to simply specify that owners and 

operators follow the manufacturers recommended maintenance practices for the engine. EPA 

cannot delegate to manufacturers the final decision regarding the proper management practices 

required by section 112(d); nor can EPA allow management practices to change from engine to 

engine based on the views of multiple manufacturers. To address the comments that there may 

be special and unique operating situations where the management practices in the rule may not 

be appropriate, for example engines using a synthetic lubricant, EPA notes that owners/operators 

may work with state permitting authorities pursuant to 40 CFR subpart E (‘‘Approval of State 

Programs and Delegation of Federal Authorities’’) for approval of alternative management 

practices for their engines. Subpart E implements section 112(l) of the CAA, which authorizes 

EPA to approve alternative state/local/tribal HAP standards or programs when such requirements 

are demonstrated to be no less stringent than EPA promulgated standards. 

 The management practices EPA proposed for stationary engines greater than 50 HP 

included changing the oil and filter every 500 hours, replacing the spark plugs every 1,000 hours, 
211

and inspecting all hoses and belts every 500 hours and replacing as necessary. For engines less 

than 50 HP, EPA proposed to require that these engines change the oil and filter every 200 hours, 

replace spark plugs every 500 hours, and inspect all hoses and belts every 500 hours and replace 

as necessary. 

 EPA received the most information on the proposed frequency of changing the oil and 

filter. Many commenters indicated that the oil quality is often monitored through an oil testing 

program. Other commenters stated that several engines use a synthetic lubricant, which does not 

degrade as compared to other oil and can be use for extended periods of time without having to 

be replaced. Additional commenters indicating varying appropriate periods of oil and filter 

changes, including every 250 hours to 4,000 hours. Mostly commenters indicated that there is 

not one set of maintenance procedures that can be applied to all engines across the board. 

According to the additional recommended maintenance procedures that EPA reviewed after the 

proposal for different engine makes and models, EPA agrees that there is a wide range of 

recommended maintenance procedures. Based on the different suggested maintenance 

recommendations EPA has reviewed, maintenance requirements appear to vary depending on 

whether the engine is used for standby, intermittent, or continuous operation. Maintenance is 

also dependent on the engine application, design, and model. Taking into consideration the 

information received from commenters on the proposed maintenance practices for oil and filter 

changes and carefully reviewing engine manufacturer recommended maintenance procedures, 

EPA has determined that for stationary non-emergency engines below 300 HP, GACT will 

require the oil and filter to be changed every 1,000 hours of operation or annually, whichever 

comes first, which reflects the management practices that are generally available. For stationary 

emergency engines, the final rule requires the oil and filter to be changed every 500 hours of 
212

operation or annually, whichever comes first. EPA notes that in the final rule it has clarified that 

spark plug changes are not required for stationary diesel engines since diesel engines do not use 

spark plugs. EPA also determined that it would be appropriate to include the option to use an oil 

analysis program in the final rule. Therefore, EPA is including an alternative in the final rule for 

monitoring the quality of the oil through an oil analysis program. Sources have the option to use 

an oil change analysis program to extend the oil change frequencies. The analysis program must 

measure the total base number (TBN), viscosity, and water content. If the TBN is less than 30 

percent of the TBN of the oil when new, if the viscosity has changed by more than 20 percent 

from when the oil was new, or if the percent water content (by volume) is greater than 0.5, the oil 

must be changed prior to further operation of the engine. 

 EPA does not agree with the comments that inspecting belts and hoses has no impact on 

emissions. Ensuring that the engine is properly operated and maintained will help minimize the 

HAP emissions from the engine. Properly maintained belts and hoses allow the engine to 

operate at maximum efficiency. Hoses are generally used to move coolant through the engine to 

prevent the engine from overheating. Overheating of the engine can cause a malfunction in the 

combustion process, and may also burn the engine oil in the combustion chamber. Both of these 

conditions may increase pollutant emissions from the engine. Belts are commonly used for 

electrical generation and engine timing, and if worn or broken can cause damage to the engine 

and increase emissions. Therefore, EPA has required management practices that reflect GACT 

and that, in EPA’s view, will ensure the proper operation and maintenance of the engine. 

7.2.2 Comment: Three commenters (129, 157, 227) asked that EPA clarify whether a 

maintenance plan would be required for each station containing affected RICE or whether a 
213

company can develop a single maintenance plan applicable to all stations owned by the 

company. The commenters (129, 157) believe that a company-wide maintenance plan should be 

sufficient. 

Response: As discussed in the response to comment 7.2.1, required maintenance practices 

should ensure the proper operation and maintenance of the engine. According to the additional 

recommended maintenance procedures that EPA reviewed after the proposal for different engine 

makes and models, EPA agrees that there is a wide range of recommended maintenance 

procedures. Based on the different suggested maintenance recommendations EPA has reviewed, 

maintenance requirements appear to vary depending on whether the engine is used for standby, 

intermittent, or continuous operation. Maintenance is also dependent on the engine application, 

design, and model. Therefore, a company should develop as many maintenance plans as it has 

types and kinds of engines and engine uses. Where the company uses same engine design, 

model and application, a single maintenance plan would generally suffice. A company should 

have as many maintenance plans as it has categories of engine design, model and application. 

7.2.3 Comment: One commenter (88) provided that, with regards to nuclear CI emergency 

diesel generators, good management practices should be coordinated with normal outage cycles 

(e.g., oil change frequency) so as to not interrupt normal plant operations or impose any plant 

safety risks. 

 

Response: EPA notes that engine owners/operators may work with state permitting authorities 

pursuant to 40 CFR subpart E (‘‘Approval of State Programs and Delegation of Federal 
214

Authorities’’) for approval of alternative management practices for their engines. EPA also 

added a provision stating that if an emergency engine is operating during an emergency and it is 

not possible to shut down the engine in order to perform the management practice requirements 

on the schedule required in the regulations, or if performing the management practice on the 

required schedule would otherwise pose an unacceptable risk under federal, state, or local law, 

the management practice can be delayed until the emergency is over or the unacceptable risk 

under federal, state, or local law has abated. The management practice should be performed as 

soon as practicable after the emergency has ended or the unacceptable risk under federal, state, 

or local law has abated. Sources must report any failure to perform the management practice on 

the schedule required and the federal, state or local law under which the risk was deemed 

unacceptable. The commenter did not provide any information to show that the proposed 

frequencies would interrupt normal plant operations or impose plant safety risks. 

 

7.2.4 Comment: One commenter (242) asked that EPA replace the proposed management 

practices with the following, which was recently agreed upon for 40 CFR part 60, subpart IIII: 

“Operate and maintain their engines according to engine manufacturer O&M practices or 

according to their own O&M practices, as long as the owner/operator, to the extent practicable, 

maintains and operates the engine in a manner consistent with good air pollution control practice 

for minimizing emissions. For owners and operators following their own O&M practices, keep a 

maintenance plan and records of conducted maintenance to demonstrate compliance.” The 

commenter (242) thinks that the specific work practice standards currently in the proposal are 

excessive and not commensurate with current industry practices. 
215

 The commenter (242) observed that Table 2d of the proposed rule requires engines less 

than 50 HP to replace spark plugs on a regular basis, however noted that diesel engines do not 

use spark plugs, but do necessitate the use of glow plugs or igniters for startup. The commenter 

(242) said that glow plugs are only necessary for brief startup periods and upon failure will cause 

a diesel engine to become inoperative and for this reason, replacing glow plugs on an hourly 

schedule is not appropriate. 

Response: EPA does not agree that the language proposed by the commenter is appropriate for 

management practices. Good operation and maintenance is not specific enough for a 

management practice for stationary CI engines. EPA does not agree that the types of 

management practices that were proposed were excessive; however, as discussed in the response 

to comment 7.2.1, EPA has reevaluated the appropriate frequency for some of the practices. 

 EPA agrees with the commenter that diesel engines do not use spark plugs and 

consequently owners/operators do not need to replace spark plugs on a regular basis. EPA has 

clarified in the final rule that the spark plug requirement is required for SI engines only. 

8.0 Parameter Monitoring 

8.1 Comment: Eight commenters (104, 126, 150, 155, 176, 220, 224, 242) had different remarks 

regarding parameter monitoring in the proposed rule. Three commenters (155, 220, 224) wanted 

EPA to clarify whether parameter monitoring is required for any existing engines under the 

proposal. According to the commenter (155), the preamble and regulatory language contain 

conflicting information and the commenter is uncertain if EPA intended to require parameter 
216

monitoring for area sources. The commenters (155, 242) said that Table 6 of the proposed rule 

does not required parameter monitoring for area sources, but that the preamble talks about such 

monitoring for larger area source engines. This should be clarified, commenters 155 and 242 

said. 

 Several commenters (97, 128, 155, 176 and 242) are strongly against parameter 

monitoring for area source engines and three commenters (155, 176, 242) are of the opinion that 

EPA should take into account limitations that exist for these engines that may be located at 

unmanned facilities. In addition, area sources may not have electricity, which will be 

problematic in terms of continuous temperature monitoring, the commenters (155, 242) said. 

Monthly pressure drop readings may also be an issue, the commenters (155, 242) said. 

Parameter monitoring will add significant technical challenges and cost burden, according to the 

commenters (155, 242). EPA has failed to consider all factors, but if EPA decides to require area 

source parameter monitoring, analysis supporting that decision must be presented and justified, 

two commenters (155, 242) asserted. 

Response: Parametric monitoring is required for existing non-emergency engines that are larger 

than 500 HP. EPA does not agree that parameter monitoring is not appropriate for area source 

engines. Parametric monitoring is appropriate for these engines because the parameters serve as 

surrogates of the catalyst performance. The pressure drop across the catalyst can indicate if the 

catalyst is damaged or fouled, in which case, catalyst performance would decrease. 

8.2 Comment: A few commenters (112, 126, 150, 155, 176, 224, 227) suggested that EPA 

clarify in the final rule that during months when the engine does not operate, engine operation is 
217

limited, or the engine operates at reduced load, pressure drop measurements are not required. 

For example, the commenters (112, 155) thought that an engine that has been idle should not be 

started up solely to conduct a monthly pressure drop measurement. According to a few 

commenters, including commenters 155 and 224, there has been implementation issues with 

regards to monthly pressure drop monitoring since the 2004 RICE NESHAP was issued. The 

commenters (112, 155) said that without clarifying this requirement, owners/operators may be 

required to start an engine only to conduct a pressure drop measurement or be forced to 

artificially load the engine to 90 percent of rated load, which may not be possible. In the 

alternative, an owner/operator has to submit an alternative monitoring request to EPA for 

approval. The commenter (155) believes this is an unnecessary burden. The commenter (155) 

noted that it has asked EPA for guidance on this issue, but that the guidance that EPA provided 

in the form of a question and answer document (available at: 

http://www.epa.gov/ttn/atw/rice/riceq_a_9-30-05.pdf), did not sufficiently address the issue of 

pressure drop monitoring. The commenter (155) had a number of specific recommendations that 

include the provision that if an engine does not operate during a specific month, does not reach 

100 percent load +/- 10 percent, or has limited operation and is shutdown prior to the 

owner/operator completing the pressure drop measurement, the owner/operator should not be 

required to startup the engine solely to record the pressure drop. The commenter (155) also 

recommended that the owner/operator should record the pressure drop as soon as practical after 

the engine is started again. 

Similarly, one commenter (112) also asked EPA to clarify that temperature and pressure 

readings are only required when the engine is operating after startup. The commenter (112) 

noted that Tables 1b & 2b, item 1.b of the proposed rule, require the operator to maintain the 
218

temperature above a set point. However, the commenter (112) pointed out that when an engine 

is first started, there will be an unavoidable but short period of time (approximately 15 minutes) 

when the exhaust temperature is less than 450 F. The commenter (112) requested clarification 

that this startup period will be allowed without resulting in a noncompliance situation. 

One commenter (150) stated that EPA should provide exceptions to the monitoring 

requirements for idle or broken engines inasmuch as a given engine may not always be 

operating. The commenter (150) believes that the rules should be clear that no reporting is 

required for a particular period if, during that period, the engine did not operate. 

One commenter (224) requested that EPA clarify the requirements for re-establishing the 

baseline pressure drop and for conducting catalyst replacement tests. 

Response: EPA reiterates its existing policy that a company is not required to increase the load 

for the sole purpose of measuring pressure drop across the compressor stations, nor is it required 

to start an engine that is idle or broken for the sole purpose of measuring pressure drop. 

However, a company is required to measure the pressure drop once the load is increased to the 

target window, or when operations exceed 30 days (regardless of load), and to document the time 

periods when the RICE is operated below the target window in its required reporting. 

8.3 Comment: One commenter (99) said that the operating limitations for temperature in Table 

2b of the proposed rule may not be consistently achieved by diesel engines at low loads and 

suggested that owners/operators be allowed to petition to be able to operate below the specific 

temperatures where it can be demonstrated as operationally necessary. 
219

Response: EPA has in the final rule added a provision that allows the owner/operator to petition 

for alternative operating limitations pursuant to the provisions in 40 CFR 63.8(f). 

8.4 Comment: Two commenters (112, 150) noted that when a catalyst must be cleaned or 

changed, the proposed rules require a 60-day notice prior to the retest. The commenters (112, 

150) requested clarification as to the operating values for the pressure drop across the catalyst 

that are to be used during this period, and added that it would appear impossible to operate the 

engine without generating a deviation during this period. The commenters (112, 150) 

recommended that EPA allow the use of an alternative test using a portable analyzer in this 

situation.

Response: The rule does require a 60-day notice prior to testing, however the owner/operator 

does not have to wait until after the catalyst is cleaned or changed to submit the notice. The test 

should be done as soon as possible after the catalyst is changed. Testing using a portable 

analyzer is already allowed by the rule. 

8.5 Comment: Several commenters (98, 126, 129, 157, 216, 220, 247) disagreed that 

owners/operators should conduct parameter monitoring continuously. Two commenters (98, 

129) stated that intervals for monitoring and recording temperature readings for catalysts should 

be reduced. The commenters (98, 129) asserted that measuring and recording catalyst 

temperature should only be required when the engine is operating. Commenter (98) believes that 

it is unnecessary to install continuous temperature monitoring equipment for recordkeeping 

purposes and that the requirements should be revised so that temperature is recorded each day 
220

that the unit is operated – it would then be at the operator’s discretion to decide to install 

continuous temperature monitoring equipment. The commenter (98) suggested that following 

revisions to the monitoring requirements, using as the basis of the revisions the language of the 

proposal preamble: 

“Owners and operators of existing stationary non-emergency 2SLB, 4SLB, 4SRB, and CI RICE 

that are greater than 500 HP and are located at a major/area source must continuously monitor 

and record catalyst inlet temperature at least once every 24-hour period the engine is operated if 

an oxidation catalyst or NSCR is being used on the engine. The pressure drop across the catalyst 

must also be measured monthly. If an oxidation catalyst is not being used on the engine, the 

owner or operator must continuously monitor and record the operating parameters (if any) 

approved by the Administrator.” 

Commenter (220) said EPA should not impose parameter monitoring requirements where 

there is minimal engine operation. 

Two commenters (126, 247) recommended that the inlet temperature testing be 

conducted during performance testing to verify that the inlet temperature is within the allowable 

range during normal operations. 

Response: EPA does not agree that the catalyst inlet temperature should not be monitored 

continuously. The temperature is an important determinate of catalytic activity and resulting 

emissions reduction. The continuous catalyst inlet temperature monitoring will help to 

demonstrate that the emission limitations are being achieved on a continuous basis. The rule 

already requires the catalyst inlet temperature to be testing during performance testing to verify 

that it is within the allowable range. 
221

9.0 Compliance 

9.1 Test Procedures 

9.1.1 Comment: Several commenters (97, 112, 155, 224, 227, 242) recommended that EPA 

allow sequential pre and post-catalyst testing instead of simultaneous testing for engines 

complying with the percent reduction option. FTIR testing is expensive and will be a significant 

burden, but if sequential pre and post-catalyst testing is allowed the cost can be minimized. 

According to commenters (155, 242), most owners/operators will choose to comply with the 

percent reduction standard and not the concentration standard. Commenter 242 noted that this is 

because the level of the ppmv standards is very stringent and is exacerbated by the high percent 

efficiency that EPA has assumed. The commenters (155, 242) suggested that EPA allow 

sequential pre and post-catalyst testing for formaldehyde and CO percent reduction, while also 

prescribing practical quality assurance measures (e.g., engine load monitoring) to make sure that 

the sequential measurements before and after the catalytic control device are conducted at similar 

engine operation. 

Response: EPA does not believe the use of sequential pre and post-catalyst testing is appropriate 

for measuring percent reduction for a compliance standard. There are too many variables in the 

operation of an engine and the generated emissions to ensure that the percent reduction was 

being achieved. Changes in load, temperature, or fuel type can change during the test, which 

also affects the emissions. 
222

9.1.2 Comment: Several commenters (112, 132, 148, 150, 155, 186, 242) noted concerns 

regarding the testing requirements with respect to load, specifically regarding the requirement to 

test at high load. However, 90 percent efficiency may not be achievable at reduced load, 

according to the commenter (242) and compliance at all load conditions and SSM periods cannot 

be certified by the responsible official if the performance during off-load conditions is unknown. 

The commenter (242) recommended that EPA consider the broader use of management 

practices, which will lead to less engines requiring performance testing. 

Commenters 132 and 242 is in favor of test requirements at the highest load that is 

achievable in practice +/- 10 percent and this test condition should also limit the emission 

standard applicability to an hourly average period and normal operating condition(s). One 

commenter (155) said that it is supportive of performance testing at full load or the highest load 

that is achievable in order to demonstrate compliance, but that it suggests that EPA specifically 

adds language to the NESHAP to be consistent with the NSPS requirements, which include 

allowing the performance test to be conducted at the maximum load achieved in practice, e.g., if 

greater than 90 percent load is unattainable. Three commenter (145, 155, 242) recommended 

that EPA add the language “or the maximum load achieved in practice” to §63.6610(d)(5) of the 

proposed rule. Commenters 97 and 224 had a similar suggestion. Commenter 230 

recommended the text: “The test must be conducted at any load condition within plus or minus 

10 percent; if the test cannot be conducted within this range, then the RICE cannot be operated at 

a load greater than 10 percent of the load during the most recent performance test that complies 

with the emission limitations specified within this subpart.” The commenter (230) indicated that 

it is not capable of achieving 100 percent load +/- 10 percent. 
223

Two commenters (150, 186) stated that engines should be allowed to be tested at 

maximum attainable load without need for an Alternative Testing Protocol obtained from the 

Administrator on a case-by-case basis. The commenters (150, 186) noted that the proposal 

requires testing at 100 percent load ± 10 percent, but does not specify whether it refers to full 

load for the engine rated at sea level or the site rating. The commenter (150) believes that 

because many engines physically cannot be operated at maximum rated HP for various reasons, 

the rule should contain some allowance to test at lower loads without requiring special approval 

on a case-by-case basis. The commenter (150) stated that the proposal retains high-load 

performance test requirements, but suggests that emission limits would apply at all loads 

including shutdown, while different limits for startup and malfunction. The commenter (150) 

believes that clarification is needed in this regard. Commenter (186) recommended that EPA 

include some allowance to test at lower loads without requiring operators to apply for and 

receive special approval from the administrator on a case-by-case basis. 

The commenter (155) also recommended that EPA indicate in the rule that the emission 

standards only apply at high load and that requirements for demonstrating compliance at other 

operating conditions should be shown with other alternatives. For demonstrating compliance 

and conditions other than high load, the commenter (155) believes that EPA should allow 

engines to use work practices. Requiring work practices would ensure that the engine is 

operating and performing as well as possible during periods other than high load and are 

appropriate since requiring emission standards is not technically and economically feasible, 

according to the commenter (155). The commenter (155) again mentioned that if EPA keeps 

emission standards that apply at all operating conditions, then data and a thorough analysis 

should be conducted and made evident and transparent in the rulemaking docket to support that 
224

decision. The commenter (155) reiterated how combustion chemistry does not support requiring 

the same emission standards at high and lower load, e.g., the commenter pointed to the testing 

conducted at CSU that was used to develop the 2004 RICE NESHAP. Finally, the commenter 

(155) added that the rule should address how cyclic operation and engines with a short run time 

should be addressed in terms of demonstrating compliance. Air compressors and other engines 

may need a separate subcategory that is allowed to demonstrate compliance using work practices 

and not emission standards, in the commenter’s (155) opinion. 

One commenter (112) asked that EPA allow engine testing at the maximum attainable 

load without requiring application for and receipt of special approval from the Administrator on 

a case-by-case basis. The commenter (112) noted that as proposed, engines tests must be 

conducted at load conditions of 100 +/- 10 percent, but the proposal does not specify whether 

that is 100 percent of full load for the engine rated at sea level or 100 percent of the site rating. 

The commenter (112) stated that many engines cannot physically be operated at the maximum 

rated HP due to gas field pressure, compressor restrictions, gathering system limitations, etc. 

One commenter (81) noted that the proposed limit is based on 100 percent load, which 

would seldom occur in the real world. This means the test limit would bear little relation to real 

operating conditions. In addition, testing may put the communication system at risk while the 

tests are being performed. Because few generators are likely installed to handle 100 percent 

loads, owners would likely have to use temporary load banks to meet test conditions. It may be 

necessary to disconnect the emergency engine from the network to test under load bank 

conditions, and the ability of the engine to respond effectively to an emergency situation will be 

reduced. 
225

Response: EPA revised the emission standards to include additional data collected at loads less 

than 90 percent to capture the variability in stationary engine operation that can affect the HAP 

emissions. Since the emission limitations are based on operation over a range of loads, EPA 

believes that it would be appropriate to allow performance testing to be conducted at normal 

operation rather than during high load. In the final rule, EPA has included language specifying 

that performance testing can be conducted at normal operating conditions to demonstrate 

compliance with the emission standards. In addition, EPA has lowered the percent reduction 

requirements, and revised the consequent specified emission levels, to take into account 

operation at varying levels of operation, consistent with the testing that was used to develop the 

2004 NESHAP. EPA believes this satisfies the commenters’ concerns on this issue. 

9.1.3 Comment: One commenter (96) asked that EPA include in-use measurement allowances in 

the final rule. The commenter (96) said that EPA will need to include adequate measurement 

allowances to account for the relative accuracy and variability of in-use measurement systems 

when compared with laboratory-based CVS emissions measurement systems, like is being done 

for in-use NTE testing for mobile sources, in order to make sure those in-use tests are fairly 

comparable to any certification tests related to the engines at issue.

Response: EPA does not believe the inclusion of in-use measurement allowances is necessary or 

appropriate for the final rule. EPA believes that the QA/QC requirements that have been 

developed for the approved test methods and procedures are sufficient measures to ensure that 

the engines are meeting the requirements.
226

9.1.4 Comment: One commenter (76) indicated that it had provided significant comments in 

February 2009 on EPA’s Continuous Parameter Monitoring Systems proposal and believes that 

extensive revisions are needed of Performance Specifications 17 and 4. The commenter (76) 

asked that EPA review these procedures to determine their appropriateness for even larger 

engines and suggested that EPA remove the reference to 40 CFR 63.8(a)(2) from Table 8 of the 

proposed rule, i.e., change “Yes” to “No” for this paragraph of the GP. 

Response: EPA does not agree with the commenter that that the reference to 40 CFR 63.8(a)(2) 

should be “no”. The commenter did not provide any information to support the claim that the 

Performance Specifications and section 63.8(a)(2) are not appropriate for stationary diesel 

engines. In response to this comment, EPA reviewed the proposed Performance Specification 

and determined that it is appropriate for stationary engines, including diesel engines. In order to 

clearly indicate the requirements from the Performance Specification that should be followed for 

the stationary engines subject to this rulemaking, EPA plans to include the Performance 

Specification requirements in subpart ZZZZ when the final requirements are promulgated for 

existing SI engines in August 2010.

9.1.5 Comment: Three commenters (76, 154, 188) supported the exemption of emergency 

and/or small engines from performance testing requirements. One commenter (188) noted that 

for smaller units at area sources, subject to numerical emission standards, it is unreasonable and 

not cost justified to require testing for such small emission units that in many cases only run a 

limited number of hrs/yr and produce negligible HAP emissions. The commenter (188) 

recommended that in the event EPA still believes testing is warranted for area sources, alternate, 
227

lower cost testing methodologies, i.e. grab samples of stack gas before and after the catalyst, 

should be allowed. 

Response: EPA agrees with the commenters that testing should not be required for emergency 

and small engines. The proposed rule specified that stationary emergency engines and stationary 

engines less than 100 HP were not subject to performance testing. EPA believed at proposal that 

it would not be reasonable to subject emergency engines at area sources to performance testing. 

In the final rule, stationary engines less than 100 HP and stationary emergency engines are 

subject to work practices or management practices, for which emissions performance testing are 

unnecessary and not required. EPA does believe that testing is warranted for stationary nonemergency CI engines at area sources that are larger than 300 HP. EPA does not believe that the 

costs for such testing are unreasonable and has specified that portable analyzers can be used for 

testing, which reduces the cost of testing. 

9.1.6 Comment: Two commenters (193, 267) recommended adding a provision in the emissions 

testing protocol to allow for initial and subsequent emission testing to be performed on a single 

engine when a facility has multiple equivalent engines. The commenter (267) stated that the 

district operates and maintains over 2,000 miles of canals, 60 pumping stations, and 2,200 water 

control structures. It (267) reported that the district pump stations have multiple engines 

consisting of the same manufacturer, model, manufactured date, approximate operating hours, 

HP rating and maintenance program. The commenter (267) opined that it is not cost effective to 

perform formal testing on multiple engines if it can be demonstrated through contemporaneous 
228

screening of each engine that the worst case engine was selected. The commenter recommended 

the following insert: 

“If a facility has multiple equivalent engines, the owner or operator can perform screening of 

each engine for the targeted pollutant using the applicable EPA Test Method. The formal testing 

must be performed on each engine until the readings are stable.” 

Response: For existing engines, EPA disagrees with the commenter that the performance of a 

compliance test on a single engine can be used to show compliance for the equivalent engines 

located at the same facility. EPA cannot be certain that the engines have been operated 

identically, have had the same operational, deterioration, and malfunction experiences, and have 

undergone the same maintenance, all of which could affect the emissions. Therefore, EPA does 

not believe that it is appropriate to allow the use of the test on a single existing engine to show 

compliance for other engines that are the same make and model. EPA has attempted to have as 

little testing as is necessary to ensure that engines are meeting the standard.

9.2 Test Methods 

9.2.1 Comment: A few commenters (97, 155, 224) support the CO test methods in the proposed 

rule, which include EPA Method 10, FTIR methods Method 320 and ASTM Method D6348-03, 

and ASTM Method D6522-00 (2005) using a portable analyzer. Two commenters (124, 132) 

also expressed that they support ASTM Method D6522. Commenter 242 also supports the use of 

EPA Method 10 and ASTM D6522 for CO testing. Commenters 124, 132, 155 and 242 said that 

EPA should also specify that alternative methods approved by the Administrator are allowed for 
229

portable analyzers and recommended the following specific language to be added to footnote a in 

Table 4 of the proposed rule: 

“Alternative portable analyzer methods approved by the Administrator or delegated 

authority are also acceptable.” 

Response: Table 8 of the rule allows for the use of alternative test provisions as specified in 

§63.7(f) of the GP. This provision allows the owner or operator to petition the Administrator of 

their intention to use an alternative test method at least 60 days before the performance test is 

scheduled to begin. Therefore, EPA does not believe that the suggested footnote is needed to be 

added to Table 4 of the final rule.

9.2.2 Comment: Two commenters (155, 224) were of the opinion that EPA should allow FTIR 

test methods in the final rule as acceptable methods for measuring CO percent reduction. The 

FTIR methods are already included for measuring concentration and the commenter (155) does 

not see why those methods should not also be included for percent reduction.

Response: EPA agrees that it is acceptable to measure the percent reduction of CO using the 

allowable FTIR methods and has specified that this is allowable in Table 4 of the final rule.

9.2.3 Comment: Three commenters (121, 149, 150) stated that EPA should allow alternatives to 

performance testing. One commenter (121) said EPA should allow sources the option to use test 

results from other non-EPA test methods to demonstrate compliance as long as the data was 

gathered using an approved procedure. The commenter (121) said that its members (automotive 
230

manufacturing) indicated that the cost per sample run using Methods 1, 3, 4, and 10 could easily 

exceed $10,000, excluding costs to prepare for the sampling (i.e., scaffolding, stack extensions, 

etc.). In addition to these cost considerations, as a practical matter, there would be significant 

difficulty in performing these EPA test methods on engine exhaust. To reduce the compliance 

burden, the commenter (121) suggested that EPA replace the emission limits with percent 

reduction and allow owners and operators to use portable analyzers for all performance testing, 

given the familiarity with this equipment and the significantly lower cost of this equipment. 

One commenter (150) stated that EPA should allow the use of portable analyzers (rather 

than EPA protocol testing) to assess CO emissions after catalyst replacement and 

overhaul/rebuild and for the 8,760-hour/3-year test. The commenter (150) indicated that this 

would be in keeping with state agency practice for sources that require periodic emission tests as 

part of their monitoring schedules. 

A similar comment was received from another commenter (149) who stated that 126 of 

the CI engines it uses under emergency conditions throughout the city (at pumping stations, 

combined sewer and overflow systems, water pollution control plants) located at both major and 

area sources would be subject to emission standards and requirements listed in Table 1 on page 

9702 and in Table 2 on page 9703 of the proposed rule. Although the commenter (149) 

supported this application of the rule, the commenter requested clarification on the method used 

to certify compliance and urged that EPA clarify in the rule that handheld instruments may be 

used to certify compliance. The commenter (149) expressed that traditional air sampling 

collection equipment, with laboratory analysis, would be more laborious with minor 

environmental benefit compared to the use of handheld instrumentation or portable meters.
231

Response: EPA has already addressed the commenters’ concerns. The NESHAP allows the use 

or portable analyzers to show compliance with the CO emission standards. The method ASTM 

D6522-00 is a portable analyzer method.

9.2.4 Comment: One commenter (98) stated that referenced ASTM D6522-00 (2005)a

 method is 

not approved for performance tests on RICE not fired with natural gas. The commenter (98) 

quoted the text of ASTM D6522-00 (2005)a

 page 1, §1 “Scope” as follows (with underlined text 

added for emphasis): 

“1.1 This test method covers the determination of nitrogen oxide and NO2, carbon 

monoxide (CO), and O2 concentrations in controlled and uncontrolled emissions from 

natural gas-fired reciprocating engines, combustion turbines, boilers, and process heaters. 

Due to the inherent cross sensitivities of the electrochemical cells, this test method should 

not be applied to other pollutants or emission sources without a complete investigation of 

possible analytical interferences and a comparative evaluation with EPA test methods.

The commenter (98) asserted that EPA must conduct the complete investigation and 

comparative analysis to approved EPA methods before this method can be listed as an acceptable 

test procedure; otherwise test results using this method may be challenged or invalidated. 

However, the commenter (98) believes that including a test method such as ASTM D6522-00 

(2005)a is necessary because many of the sources in question would not meet testing location 

requirements of approved EPA test methods. The commenter (98) added that ASTM D6522-00 

(2005)a

 also allows for shorter test durations which is preferable for RICE.. 
232

Response: EPA agrees with the commenter that allowing the use of ASTM D6522-00 for testing 

CO and O2 from engines other than those fired with natural gas is a desirable and useful 

alternative to EPA Methods 3A and 10. We note that there are laboratory and field studies of the 

electrochemical measurement technology for diesel-fired engines and other combustion sources 

of CO and other pollutant emissions that demonstrate the capabilities consistent with a method 

for determining compliance in the context of this rule. These studies include those managed 

through the EPA Environmental Technology Verification program and the German Technical 

Inspection Association (TUV) (e.g., http://www.epa.gov/etv/pubs/01_vr_testo_350.pdf, 

http://www.emersonprocess.com/raihome/documents/Gas_PDS_BINOS1002M_103-

170_200607.pdf). We have reviewed the reports of these studies and we believe that the 

technology as applied through ASTM D6522-00 is suitable for compliance testing for other than 

natural gas-fired engines under this rule. EPA has made it clear in the final rule that ASTM 

D6522-00 is an acceptable method for testing existing stationary CI engines by including a 

footnote to Table 4 in the final rule. 

9.3 Frequency 

9.3.1 Comment: A few commenters (104, 150, 155) were unclear on the requirements related to 

when a catalyst is replaced. One commenter (155) said that EPA should clarify in the final rule 

that after a catalyst has been changed when the owner/operator conducts a performance test that 

this test fulfills the periodic test requirement. In other words, the schedule to perform future tests 

should be reset when the catalyst change test is completed, the commenter (155) said. The 

commenter (155) additionally noted that the rule does not specify the timing to conduct a 
233

performance test after a catalyst has been replaced. It was recommended that 63.6640(b) of the 

proposed rule be revised to indicate that 180 days is allowed to conduct this test, by commenter 

(155). Alternatively, the commenter (155) suggested that EPA revise 63.6610(a) to indicate that 

180 days applies to both initial testing and after a catalyst change. 

The commenter (155) also wanted EPA to clarify that temporary catalysts used during 

washing or cleaning should not trigger a catalyst change test. According to the commenter 

(155), the original catalyst may be cleaned offsite by a catalyst vendor and in a the meantime a 

temporary catalyst is used. The commenter (155) said that an appropriate time period should be 

allowed to operate the temporary catalyst without having to conduct testing and recommended 

that sources be given 45 days to operate an engine with a temporary catalyst without conducting 

a test as long as the original catalyst is reinstalled following cleaning. 

One commenter (104) noted that proposed 40 CFR 63.6640 requires that when the 

catalyst is replaced, the operator must reestablish the values of the operating parameters 

measured during the initial performance test and then conduct a performance test to verify 

compliance and asked what the need for the initial test is as it may not be accurate. 

One commenter (150) stated that EPA should clarify the requirements regarding what 

testing is required after catalyst replacement. The commenter (150) believes that there is no need 

for a complete performance test after a catalyst is changed. 

Response: As the commenters noted, the rule does not specify a time for conducting a 

performance test after a catalyst change. However, the performance test after a catalyst change 

should be conducted as soon as possible to demonstrate that the engine is still in compliance with 

the applicable standards. It should be noted that the owner/operator must notify the EPA 
234

Regional office or the delegated authority 60 days prior to performing the test. The 

owner/operator may seek an adjustment to the 60 day notification requirement from the EPA 

Regional office or delegated authority if the owner wishes to conduct a performance test as soon 

as possible following the catalyst change. The performance test after a catalyst change can be 

used to satisfy the performance testing requirement. However, a request to waive the 

performance testing requirement must be submitted to the EPA Regional office or delegated 

authority indicating that the catalyst change performance test will be used to satisfy the 

requirements for the required testing requirement under the rule. 

 In regards to the issue of whether a performance test is required when a temporary or 

“loaner” catalyst is being used while the primary catalyst is being washed or cleaned, EPA 

believes that this should be addressed on a site-specific basis and is dependent on additional 

information such as the type of “loaner” catalyst, the length of time the “loaner” catalyst is used, 

and the compliance history of the engine. After the primary catalyst has been washed or cleaned, 

a performance test may be required if the delegated agency has decided that the initial 

performance test is no longer representative of the performance of the affected source. EPA 

believes that routine washing of the catalyst is unlikely to cause the initial test to no longer be 

representative. However, this determination of whether a retest is required should be made by 

the delegated agency on a case-by-case basis. 

9.3.2 Comment: Two commenters (112, 242) expressed similar concerns regarding the test 

requirements for engines that are rebuilt or overhauled. One commenter (242) said that EPA 

should clarify in the final rule that additional performance tests are not required for engines 

between 100 and 500 HP after a rebuild or overhaul or alternatively explain and justify the cost 
235

and benefits of requiring such testing. According to the commenter (242), the preamble and rule 

text contain conflicting information on this topic and EPA must clarify this in the final rule. 

One commenter (112) asked that EPA allow alternative test procedures under certain 

conditions. The commenter (112) noted that while EPA stated in the proposal preamble that 

engines 100 to 500 HP do not require subsequent tests, an additional test must be carried out if 

the engine is rebuilt or overhauled. The commenter (112) indicated that based on the applicable 

definition, compressor engines may undergo an overhaul as often as every 2 to 3 years. The 

commenter (112) believes that requiring a reference test method each time an engine is 

overhauled is excessive and unnecessary. 

 The commenter (112) indicated that State agencies accept portable analyzer data with 

short duration runs (i.e., 6 minutes) as an acceptable means to facilitate measuring emissions 

from sources that require periodic emission tests. The commenter (112) added that these State 

agencies typically require the use of an approved protocol to ensure consistency and to provide a 

minimum level of quality assurance during the testing process. The commenter (112) asserted 

that EPA should allow the use of portable analyzer tests, using a State approved protocol for the 

State in which the engine is operating rather than the EPA Reference Method Performance Tests 

in the following circumstances: 

• Engine rebuild or overhaul, 

• Replacement of O2 sensor (which occurs every 3 months), 

• Catalyst washing or replacement, 

• Re-establishment of benchmark pressure drop. 

 The commenter (112) believes that if EPA intends to require performance tests in these 

situations, the increased cost should be captured in EPA’s economic analysis. The commenter 
236

(112) added that EPA should reevaluate the frequency of testing that is required above that of 

annual performance testing. 

Response: EPA believes that it is appropriate to require testing for stationary engines that have 

been rebuilt or overhauled even though the engines may only normally be required to conduct an 

initial performance test and no subsequent testing. The rebuilding or overhaul of the engine may 

change the combustion characteristics of the engine. EPA does not believe that these 

performance tests after an engine is overhauled or rebuilt are excessive or unnecessary. The 

required testing will ensure that the rebuilt or overhauled engine still meet the applicable 

emission limits, therefore ensuring compliance with the applicable standards. 

 EPA has incorporated portable test methods that meet the QA/QC criteria of comparable 

EPA test methods. The rule does allow the petition of alternative test methods under 40 CFR 

§63.7(f) of the GP. This provision would allow the owner or operator to use an alternative test 

method from that specified in the standard provided that the owner notifies the Administrator of 

the intention to use an alternative test method at least 60 days before the performance test is 

scheduled to begin, uses Method 301 in appendix A of this part to validate the alternative test 

method, and submits the results of the Method 301 validation process along with the notification 

of intention and the justification for not using the specified test method. 

 In response to EPA including the costs of these tests for rebuilding or overhauling of 

engines, catalyst washing and replacement, or re-establishment of benchmark pressure drop, 

EPA does not believe that these additional testing costs need to be included because the analysis 

presented in the rule shows the costs in the year 2013, or the first full year after implementation 

of the rule, and it is unlikely these costs will be incurred in that year. For the replacement of the 
237

O2 sensor, EPA does not require testing and therefore the testing costs were not included in the 

economic analysis.

9.3.3 Comment: One commenter (76) asked that EPA modify 63.6612(b) of the proposed rule to 

allow past performance tests conducted in the last 5 years to be used instead of the 2 years that 

this paragraph currently requires. The commenter (76) believes that testing conducted in the last 

5 years is representative of current emissions in many cases and the commenter thinks that it is 

appropriate for EPA to allow such tests to be used to demonstrate compliance. 

 Another commenter (116) had a similar request that for areas sources that are subject to 

new testing requirements, this could be modified to allow tests that are not older than 3 years, 

since the promulgated rule will allow 3 years for compliance. The commenter (116) asserted that 

there are so many engines that will be required to be tested that it is reasonable to allow facilities 

more time to accomplish the testing before the compliance deadline. 

Response: EPA believes that the requirements in §63.6612(b) of the rule are appropriate. 

Performance tests older than 2 years may not be representative of the current emissions from the 

engine. Maintenance of the engine requires replacement of parts that may affect the combustion 

characteristics of the engine, which in turn will affect the emissions of the engine. In addition, 

EPA believes that the 2-year limit of performance test reports will also allow sufficient time for 

the sources to perform any applicable testing at their facility before the compliance deadline. 

9.3.4 Comment: Several commenters (87, 98, 112, 126, 139, 186, 197, 216, 227, 229, 236, 247) 

expressed that they disagreed with the testing requirements in the proposed rule. Multiple 
238

commenters (87, 112, 126, 139, 157, 186, 236) took issue with the testing requirements for nonemergency stationary RICE greater than 500 HP of every 8,760 hours of operation or 3 years. 

Two commenters (112, 186) indicated that strict adherence to a test schedule based on operating 

hours is difficult to manage in large fleets of engines due to availability of testing personnel, 

equipment breakdowns, weather conditions, safety considerations, etc. Consequently, the tests 

would necessarily be conducted more frequently than annually to ensure completion of tests for 

the entire fleet within the operating hour time limit. Two commenters (112, 186) suggested that 

reduced test frequency should be allowed when two consecutive tests demonstrate compliance 

with emissions limitations (such as is allowed in the footnote to Table 6 of the proposed rule). 

The commenters (112, 186) added that upon any non-compliance with emissions limitations, the 

test frequency could revert to the original schedule. The commenter (112) also suggested that 

EPA should consider a reduced testing frequency, 3 years, for any engine in compliance for two 

consecutive performance tests, regardless of operating hours. 

Two commenters (236, 247) stated that EPA’s proposed frequency of performance tests 

(every 3 years) is excessive and recommends that frequency of performance testing be based on 

hours of operation. The commenter (236) noted that some engines are run very infrequently over 

their entire service life. 

Two commenters (126, 197) suggested that the frequency of performance tests be based 

on hours of operation. The commenter (197) asserted that many RICE have low dispatching 

hours and the required performance testing would contribute to a significant amount of their 

operating time. The commenter (197) recommended that limited use RICE should not be 

required to demonstrate that the control equipment is functional more than once.
239

One commenter (87) stated that the requirement to test every 3 years for units that do not 

run very often is unreasonable. The commenter (87) added that based on actual run time 

(including peak shavers) for 14 stationary RICE that would be subject to this testing requirement, 

the average 3 year cumulative run time was 105 hours, and without peak shavers, 37 hours. 

Further, the commenter (87) stated that most generator engines are not equipped with easyaccess test ports and would have to be modified for testing, the cost of which have not been 

captured in this rule. The commenter (87) recommended that provisions for testing units that are 

not run frequently should be considered. 

One commenter (139) stated there is limited or no benefit for requiring owner and 

operators of non-emergency, limited use RICE greater than 500 HP to perform time-consuming 

and expensive tests every 3 years. The proposed rule would require owners and operators of all 

existing stationary non-emergency RICE greater than 500 HP to conduct an initial performance 

test and subsequent tests every 8,760 hours of operation or every three years, whichever comes 

first. For some RICE, operation would be required simply to conduct the testing, which is 

unreasonable. The commenter (139) urged EPA to revise the proposed rule so that subsequent 

testing of these engines is only required every 8,760 hours of operation. 

Commenter (227) said the proposed requirement for area sources to conduct an 

unnecessary and burdensome initial performance test should be replaced by an engine tune-up 

procedure, which would be adequate given the limited operation of the emergency engines. 

Commenter (216) said EPA should revise the proposed rule and limit performance testing 

requirements to non-emergency CI engines greater than 300 HP located at major sources 

Commenter (229) noted that while EPA is stipulating that performance testing of existing 

engines is not required for major source facilities in the proposed rule, because an emission 
240

limitation is being proposed, this does not preclude state agencies from specifying performance 

test requirements as a compliance demonstration condition in Title V Permits . Accordingly, 

commenter (229) reiterated that appropriate work practice standards are the practical requirement 

for all existing emergency engines at major and area source facilities in lieu of any emission 

limitation standards. 

One commenter (98) argued that performance test requirements for non-emergency RICE 

greater than 100 HP at major sources are too broad in scope and must be revised to exclude 

limited use units in order to avoid the need to operate these units for the sole purpose of 

generating emissions data. The commenter (98) stated that the proposed language imposes initial 

performance test requirements on CI engines 100≥HP≤300 even though these engines are not 

required to install aftertreatment controls and emission standards are based on emissions from 

uncontrolled units. 

One commenter (98) argued that performance test requirements for non-emergency RICE 

greater than 500 HP at major and area sources are required too frequently. The commenter (98) 

asserted that many RICE in this category operate infrequently (less than 20 percent annual 

utilization) and consequently requiring a performance test every 3 years is too frequent. The 

commenter (98) noted that RICE in this category are required to monitor catalyst pressure drop 

and catalyst temperature to assure proper operation of the control device, which approach is 

similar to the Compliance Assurance Monitoring (CAM) Plan established in 40 CFR part 64. 

The commenter (98) believes that the required monitoring indicates proper performance of the 

control device, so frequent performance tests for these units are unnecessary and redundant. The 

commenter recommended that the proposed rule language in 40 CFR 63.6615 be revised as 

follows: 
241

“Owners and operators of existing stationary non-emergency or non-limited use RICE that are 

greater than 500 HP and located at major/area sources must conduct an initial performance test 

and must test every 8,760 hours of operation or 3 5 years, whichever comes first, to demonstrate 

that they are achieving the required emission standards through required monitoring of aftertreatment control device(s). In the event that monitored parameters do not comply with specified 

after-treatment control equipment pressure drop and temperature criteria, corrective action or a 

performance test must be conducted to demonstrate that the emissions source is achieving the 

required emission standards. If corrective action involves modifications to the after-treatment 

control device which changes monitored parameters, a performance test must be conducted 

within 180 days of first operation of RICE after modification to the after-treatment control 

device occurred.” 

One commenter (157) believes these requirements are redundant and burdensome 

because many RICE in this category operate infrequently and are already subject to continuous 

monitoring of the catalyst pressure drop and catalyst temperature to assure proper operation of 

the control device. Therefore, the commenter (157) requested that the proposed rule only require 

subsequent testing of these units every 8,760 hours of operation. 

Response: EPA believes that the test frequency for stationary existing engines greater than 500 

HP located at area sources and non-emergency existing CI engines at major sources of HAP 

emissions is appropriate to ensure compliance with the applicable standards. As stated in the 

preamble to the proposed rule, additional testing on a regular basis is appropriate and not 

excessive for these engines because of their size and operating time. At most, these engines 

would be required to test yearly, which would actually be less than what is required for most of 
242

the engines subject to the 2004 RICE NESHAP. EPA believes that three years is an appropriate 

time between tests for larger engines to ensure that the emission standards are met on an ongoing 

basis. The option for reducing test frequency that the commenters cited in Table 6 allows for 

reducing from semiannual to annual testing; this proposal did not include any semiannual testing. 

The testing requirements are based on actual hours of operation. Regarding the comment that 

most generators are not equipped with easy access ports, the commenter did not submit any 

information to substantiate this claim. EPA does not agree that an engine tune-up would be an 

adequate replacement for an initial performance test as the tune-up would not provide any 

indication of what the emissions from the engine are. EPA has not required any performance 

testing for emergency engines at area sources. For stationary non-emergency CI engines at 

major sources larger than 100 HP, the final rule requires a performance test, which EPA has 

determined is necessary to adequately demonstrate that the engine is meeting the emission 

limitation. Emergency engines at major sources do not have emission limitations in the final 

rule, which addresses the concern expressed by the commenter regarding state agencies requiring 

testing to meet the emission limitations for these engines in the proposed rule. 

9.3.5 Comment: One commenter (264) supports EPA’s proposal to exclude existing nonemergency RICE located at major sources that are less than 100 HP and existing stationary 

emergency RICE located at major sources from the requirement to conduct performance testing. 

The commenter (264) expressed that it did not believe it was feasible to perform the testing base 

on size and potential configuration of equipment. This commenter (264) also supported EPA’s 

proposal to exclude existing stationary RICE located at area sources that are subject to 

management standards from the requirement to conduct performance testing. The commenter 
243

(264) expressed that, based on the fact that these RICE are area sources of HAP and are for 

smaller-sized equipment, the maintenance standards, in its opinion, are an adequate means of 

ensuring emissions are minimized. 

Response: No response is needed.

9.4 Other 

9.4.1 Comment: Several commenters (227, 229, 230, 253) expressed concern regarding potential 

performance testing for smaller engines. One commenter (227) said that while there is a 

proposed formaldehyde limit for existing stationary non-emergency RICE less than 100 HP at 

major sources and existing stationary emergency RICE at major sources, there are no testing 

requirements. These engines have maintenance and operating requirements to ensure 

compliance, based on manufacturer’s written emission-related instructions. Since testing is not 

required, the commenter (227) requested that EPA remove the emission standards for these 

RICE. 

One commenter (253) stated that there does not appear to be language in the proposed 

rule that would exempt emergency engines from this requirement. 

Commenter 229 noted that in Table 1, it appears that for all engines (emergency and nonemergency) less than 50 HP at a major source facility, EPA is proposing an emission limitation 

standard of 2 ppmvd formaldehyde. Commenter 229 questioned the purpose of this emission 

limit since EPA states that it does not expect any existing CI engines in this category to be 

operating at major source facilities, and if SI or CI engines less than 50 HP are operating at 
244

major source facilities, EPA is not stipulating a performance test for a compliance 

demonstration. Commenter 229 continued stating that this does not preclude state agencies from 

specifying performance test requirements or some other needless requirements as a compliance 

demonstration condition in Title V Permits. Commenter 229 therefore recommends that EPA 

exercise its de minimis authority under the CAA to exempt existing engines less than 50 HP 

from the RICE NESHAP regulations for major and area sources since HAP emissions from these 

sources will be negligible and any regulatory requirements will be unwarranted. 

One commenter (230) recommended that EPA modify Table 4 to exclude small RICE 

from performance testing requirements. The commenter (230) stated that the rationale used for 

excluding performance testing for small stationary and emergency engines because of cost 

should be applied to the same engines at major sources. The commenter (230) does not believe 

there is a useful benefit in performance testing of small (less than 50 HP) RICE located at major 

or area sources. 

Response: In the final rule, EPA has determined that engines below 100 HP and emergency 

engines will be subject to work standards or management practices, and are not subject to testing. 

These engines do not have any numerical emission limitation. Regarding the comments that 

these engines should be exempted under de minimis, EPA does not believe that there is sufficient 

justification for a de minimis finding for these engines. 

 

9.4.2 Comment: Two commenters (157, 216) said EPA should allow performance test to be 

done during periods of planned operation. The commenters (157, 216) said this change would 

avoid unnecessary emissions produced just for the purposes of testing. 
245

Response: EPA agrees that it is unreasonable to startup an engine solely for the purpose of 

conducting a performance test and believes it is appropriate to incorporate flexibility when an 

engine is non-operational. In the final rule, EPA has included language in the performance 

testing section that allows stationary engines that are non-operational to conduct performance 

testing when the engine is started up again. This is consistent with how EPA treats engines that 

must conduct monthly pressure drop readings (see EPA’s response to Question 22 in 

http://www.epa.gov/ttn/atw/rice/riceq_a_9-30-05.pdf) and does not require engines to be started 

up solely to record the pressure drop. 

9.4.3 Comment: One commenter (157) believes that EPA should revise the proposed initial 

performance test requirement for CI engines with a site rating between 100 HP and 300 HP 

because the proposed requirements conflict with EPA’s decision that such engines should not 

have to install controls. The commenter (157) states if one of these engines fails to meet the 

proposed emissions limit during the initial compliance test, then the owner is out of compliance 

unless the owner/operator reduces emissions from the engine, which will likely mandate the 

installation of controls. The commenter (157) noted that this is contrary to EPA’s determination 

that the cost of applying control to these engines is “too significant to outweigh the expected 

HAP reductions from these units.” Therefore, the commenter (157) believes that performance 

testing requirements should be limited to CI engines greater than 300 HP located at major 

sources. 
246

Response: Based on additional data received in the post-proposal period, EPA revised the 

MACT floor determination for these engines. The emission limitations for these engines in the 

final rule are higher than those at proposal. Therefore, EPA expects that the limits will be met 

without the use of add-on controls for many of these engines. For those engines that are required 

to use aftertreatment, this is the result of Congress’s mandate that standards be determined by 

reviewing the emissions of the best controlled sources. This means that some engines whose 

uncontrolled emissions are high will need aftertreatment to meet the standard. EPA does not 

agree that performance testing should not be required for non-emergency engines; the testing is 

necessary to show that the engine is complying with the emission limitation and these engines 

are not subject to the special provisions that EPA has provided for engines used solely in 

emergency circumstances. 

9.4.4 Comment: Two commenters (193, 230) said that EPA should allow owners to use engine 

manufacturer information to demonstrate compliance with the rule. One commenter (230) asked 

that EPA allow the use of manufacturers testing data on all models of RICE below 300 HP 

instead of requiring performance testing. Commenter 193 stated that EPA should provide 

owners and operators of existing stationary RICE with a streamlined compliance demonstration 

option whenever they are able to obtain documentation from the engine manufacturer that attest 

to an engine’s compliance with the emission limits of this proposed rule. The commenter (193) 

encouraged EPA to construct a compliance option in the final rule for existing source RICE less 

than 500 HP, much like the compliance option it created in its January 2008 final rule (73 FR 

3596) and afford owners and operators the compliance option of obtaining certification 

documentation from engine manufacturers that attest to an engine’s compliance with the 
247

emission limits of this proposed rule. The commenter (193) noted that this alternative 

compliance option could apply if entities operate and maintain the certified stationary engine and 

control device according to the manufacturer’s emission-related written instructions, and the 

owner or operator keeps records of conducted maintenance to demonstrate compliance. Under 

this compliance option, no performance testing would be required of the owners or operators. 

Response: EPA is not allowing owners of existing stationary engines to use manufacturer’s test 

data or any other information in lieu of conducting performance testing. EPA needs the 

assurance that each engine subject to performance testing is actually meeting the applicable 

emission standard. Manufacturer’s test data may be indicative of the engine performance when 

the engine is brand new, but may not be representative of the engine exhaust emissions after 

years in the field. Other factors that may affect the engine exhaust emissions include location, 

climate, fuel, controls, and how the engine has been operated and maintained over the years. The 

provisions the commenter is referring to in the January 2008 final rule on page 73 FR 3596 are 

for new stationary engines subject to the SI NSPS. For existing engines, EPA has no assurance 

that just because data from the manufacturer on the same model engine indicates that the engine 

is capable of meeting the emission standards when new, that the engine actually will after years 

of use in the field and EPA therefore believes that performance testing is justified and necessary. 

10.0 Recordkeeping, Reporting and Notifications 

10.1 Comment: Numerous commenters (97, 103, 104, 112, 126, 150, 155, 158, 224, 241, 230, 

242, 247) expressed concern over the proposed recordkeeping and reporting requirements. 
248

One commenter (155) indicated that for the 2008 RICE NESHAP EPA acknowledged 

that the 40 CFR part 63 General Provision requirements were burdensome in certain cases and 

limited these requirements for new area source and small major source engines. Three 

commenters (155, 224, 247) believe that EPA should make similar allowances for engines under 

this rulemaking and should not broadly apply the 40 CFR part 63 General Provision 

requirements to all existing engines. 

Commenters 112, 155, and 241 are of the opinion that fewer requirements from the 40 

CFR part 63 General Provisions should apply to area sources and smaller engines and said that 

EPA should exempt existing area source engines from 40 CFR part 63 General Provision 

requirements. Commenter 112 believes that at minimum, EPA should consider the cost and 

benefit of subjecting 40 CFR part 63 General Provision on area sources. Commenter 155 

suggested that EPA review the requirements from the 2008 RICE NESHAP and consider 

harmonizing the requirements in order to avoid implementation issues and adopt requirements 

that are similar for existing and new units. 

Commenter 241 stated under the proposed rule existing engines would have significantly 

more reporting and recordkeeping burden than new engines, and that requirements for new and 

existing engines should be complementary to avoid different implementation requirements. 

Commenter 242 suggested that EPA conduct additional analysis on costs and benefits 

associated with applying 40 CFR part 63 General Provision requirements and noted, like 

commenter 155, that the requirements for existing sources are more burdensome than those for 

new sources that comply with the NSPS. Two commenters (112, 242) specifically commented 

that it did not believe the hour estimate for emergency engines is accurate at 1 hr/yr and thought 

recordkeeping would take at least 15 minutes per occurrence, or at a minimum, at least once per 
249

month (3 hrs/yr). The commenters (112, 242) further expressed that they did not believe EPA 

has accounted for the costs associated with overhead and profit in its emergency engines 

analysis. 

Commenters 112 and 242 also stated that it is not evident that EPA has considered any 

recordkeeping for engines requiring maintenance and that, based on its experience, significant 

recordkeeping is necessary for maintenance and SSM requirements. The commenters (112, 242) 

estimated that it would take 2 hrs/month and 1 hr/month for maintenance and SSM 

recordkeeping, respectively. In terms of reporting costs, the commenter (242) expressed that it 

does not look like EPA considered the 167 percent overhead allowance, which would increase 

the reporting costs. 

The commenters (112, 242) added that EPA estimated 14 hours for reporting, but the 

commenter expressed that this is not sufficient time to become familiarized with the very 

complex rulemaking, which the commenters estimated would take about 40 hours. Commenter 

112 stated that EPA did not include the 167 percent overhead allowance in this calculation. 

Further, in terms of annual training, commenters 112 and 242 think this will take 8 hrs/yr. 

Considering the cumulative effect of notification, recordkeeping and reporting associated with 

the rule, the commenter (242) believes the rule will have an unprecedented impact on the 

regulated community and State agencies that will be implementing the rule. Commenters 155 

and 242 said that EPA has not recognized the extensive recordkeeping and reporting 

requirements in the 40 CFR part 63 GP and the commenters listed several requirements from the 

GP as examples of onerous and burdensome requirements (e.g., initial notification of 

applicability, various notifications including the notification of performance test, compliance 

reports, reporting related to SSM, various records required such as records of SSM, records of 
250

maintenance, records of monitoring). Based on the assumption that the average environmental 

professional will be responsible for 10 controlled engines, the commenter (112) estimated that 

19,800 environmental professionals will need to be trained at an initial cost of $58 million and 

annual cost of $12 million for refresher training, which does not include the cost for those 

professionals to educate field personnel about the requirements for which they are ultimately 

responsible. 

One commenter (126) believes the requirement for owners and operators to develop a 

maintenance plan that specifies how the management practices will be met provides little benefit 

to anyone. If the manufacturer’s maintenance plan requirements are met, then the commenter 

(126) suggested that there be no maintenance plan and that the owner operator keep appropriate 

records to demonstrate that it has met those requirements. 

 Commenter 242 reported that the 40 CFR part 63 GP requirements are currently being 

reviewed as a result of the litigation concerning SSM. The commenter (242) said that the 

applicability of 40 CFR 63.7(e)(1), shown in Table 8 of the rule, adds significant confusion and 

the commenter believes it is inconsistent with the requirements of the rule. It is unclear whether 

a source needs to be in compliance outside of normal operating conditions because the section 

with these requirements says “as applies” and the commenter (242) urged EPA to clearly spell 

out all rule requirements. 

One commenter (158) stated that the management practices and recordkeeping 

requirements are not practical for low-use equipment because logs could need to be retained for 

years, even decades. For example, if a facility uses a 60 HP diesel-powered welder ten times per 

year for one hour per use, the proposed regulation would require that operating hours be recorded 
251

for 50 years in order to conduct scheduled maintenance. The commenter (158) stated that this is 

impractical and creates an unjustified compliance risk. 

One commenter (104) noted that the proposed 40 CFR 63.6665 section includes 

additional 40 CFR part 63 GP that apply to this rulemaking. The commenter (104) believes that 

these requirements increase the complexity of the rule on small businesses that operate engines at 

oil and gas facilities, especially those entities that have never been regulated before. The 

commenter (104) asked how EPA plans to simplify the process for these entities. 

One commenter (230) stated that the additional recordkeeping and reporting requirements 

in Table 2d for uncontrolled RICE are unnecessary if a comprehensive planned maintenance 

program is utilized. The commenter believes that the oil and filter change management practices 

in Table 2d of the proposed rule may cause an inadvertent recordkeeping violation. The 

commenter recommends that the schedule should conform to an engine specific planned 

maintenance program, or the values in Table 2d of the proposed rule should provide an 

allowance for exceeding the recommended values during an emergency situation. 

Response: EPA believes the recordkeeping and reporting requirements are appropriate and 

justified in order to provide EPA with sufficient information to show that sources are in 

compliance with the rule. EPA does not believe that the requirements have to be the same for 

new and existing engines. In many cases, new engines are certified to achieve the emission 

limitations by the engine manufacturer and therefore EPA determined that these engines could 

have fewer recordkeeping and reporting requirements than what is in the part 63 General 

Provisions. EPA does not agree with the commenters that said that an estimate of one hour per 

year for recording emergency operation was not accurate. EPA did not include costs for 
252

recordkeeping for engine maintenance because EPA assumed that engine owners/operators 

would already be keeping these records even without this regulation. EPA believes that the costs 

estimated for recordkeeping and training are accurate. In terms of the cost of training and the 

impact of the rule on small businesses, EPA plans to provide implementation materials to assist 

affected facilities in complying with the final rule, which should decrease the amount of time 

needed to become familiar with the rule. 

In response to the comment regarding the 167 percent overhead allowance, EPA 

incorporated the 167 percent overhead and profit allowance in determining the labor rates, which 

means that the overhead allowance was included in the costs associated with emergency engines. 

EPA documented this in the proposed rule impacts memo. However, EPA believes the way that 

this was written up in the proposed rule impacts memo may have been confusing and makes it 

seem as if 167 percent was added to the $68/hr rate, which is not the case. EPA has clarified this 

in the final rule impacts memo and believes this resolves the concern on this issue. 

 EPA does not agree with the commenter that developing a maintenance plan will provide 

little benefit. It is important that sources have a written plan spelling out the maintenance to be 

conducted on their stationary CI engines. This plan can certainly be based on the manufacturer’s 

recommended maintenance. 

 Regarding the comment that the applicability of 40 CFR 63.7(e)(1) shown in Table 8 is 

confusing, EPA is currently conducting a review of the part 63 General Provisions as a result of 

the court decision on startup, shutdown, and malfunction. EPA will revise the General 

Provisions as appropriate. 

 Regarding the comment that the recordkeeping requirements are not practical for low-use 

equipment, 40 CFR 63.10(b) specifies that records only need to be kept for five years after the 
253

date of the maintenance. Therefore, it will not be necessary for the records to be kept for 50 

years. EPA has specified in the final rule that the maintenance should be conducted at yearly 

intervals at a minimum. EPA has also specified that sources may petition for different 

maintenance requirements. Any exceedances of the maintenance requirements that occur during 

emergencies will be handled on a case-by-case basis. 

10.2 Comment: Several commenters (76, 81, 103, 104, 118, 119, 129, 136, 148, 150, 157, 225, 

240) suggested alternatives to requiring owners and operators having to maintain records on-site. 

Several commenters (76, 81, 118, 136, 148, 240) suggested that EPA clarify that 

necessary records be kept in a central location and not on-site as currently required in 

63.6655(e). Commenter (76) recommended that §63.6660(c) be modified to allow records to be 

kept off-site at a central location for 5 years. According to the commenter (81), this is consistent 

with EPA and other Federal government efforts (e.g., electronic reporting). Commenter 119 

echoed these concerns and specifically requested that the final rule allow records to be 

maintained at an off-site location for engines located at area sources of HAP. 

One commenter (103) expressed that the proposed rule requires records to be kept on site 

unless a waiver is obtained. The commenter (103) believes that EPA and the states who will 

ultimately enforce the rule, do not have sufficient manpower to provide the thousands of waivers 

that will be requested and re-requested every time an engine is relocated. The commenter (103) 

asserted that a provision for keeping records at a field office should be written into the rule from 

the beginning because it is an unnecessary burden to require special waivers on items that are not 

only common place, but also the norm. 
254

Response: EPA agrees with the commenters that it would appropriate to allow records to be kept 

off-site at a central location. EPA has incorporated this requirement in the final rule. 

10.3 Comment: A few commenters (81, 129, 216) said the proposed recordkeeping requirements 

are unnecessarily rigid for emergency generators. The commenter (81) reported that it operates 

numerous remote, unoccupied, and often unmanned locations. Such areas are not easily accessed 

for the creation and maintenance of rigidly-defined documentation. The commenter requested 

that, should the recordkeeping requirements become too burdensome, it may become necessary 

to remove the use of emergency generators for use as needed backup power, potentially 

disrupting communications. 

Commenter (216) said EPA should reduce the proposed recordkeeping and reporting 

requirements for emergency engines. Most emergency RICE start automatically, and much of 

the equipment may be at remote locations. The requirement to record the purpose of all run 

events is a burden that will require additional manpower. 

Response: EPA does not agree that the recordkeeping requirements that were proposed for 

owners and operators of existing stationary emergency engines are too burdensome. EPA is 

finalizing requirements for emergency engines that do not require the application of 

aftertreatment controls. EPA developed distinct subcategories for emergency and nonemergency engines to account for different characteristics between these types of stationary 

engines. The analysis that was conducted leading to the final requirements for emergency and 

non-emergency engines is based on those differences. Therefore, in order to demonstrate that an 

engine is truly an emergency engine as defined in the final rule, there must be some 
255

recordkeeping and documentation associated with the operation of the engine to confirm that the 

engine is operating according to the definition of an emergency engine and subsequently entitled 

to meet the less stringent standards. In the case the emergency engine is operated in a nonemergency manner, the more stringent standards that apply to non-emergency engines would 

apply. EPA believes that keeping track of the hours of operation and the purpose of operation is 

necessary in order to ensure that the engines are meeting the applicable standards. 

10.4 Comment: One commenter (162) said that semiannual compliance status reporting is overly 

onerous for emergency and limited-use stationary RICE at area sources. The commenter (162) 

described the specific burden his company would face. The commenter (162) particularly 

objected to filing reports for RICE that do not even have emission limitations. The commenter 

(162) requested that semiannual compliance reports be waived for area sources, or at least, for 

area sources with RICE that do not have emissions limitations. 

Response: EPA agrees with the commenter that semiannual compliance reporting, and other 

types of reporting required under the General Provisions of 40 CFR part 63 are not appropriate 

for area sources that are not subject to numerical emission standards. EPA believes that 

recording information and maintaining records will provide EPA with assurance that facilities 

are meeting the work/management practices and other requirements applicable to their existing 

stationary engines. Further, EPA believes it is appropriate extend the same approach to any 

sources that are not subject to numerical emission standards, including existing stationary CI 

engines less than 100 HP and existing stationary emergency CI engines. Therefore, in the final 
256

rule, EPA has specified in 63.6645(a)(5) that these engines do not have to meet the notification 

requirements of the General Provisions that are specified in 63.6645(a). 

10.5 Comment: One commenter (103) stated that records of air filter change dates should only 

be required, if applicable, since not all engines contain air filters. 

Response: EPA agrees with the commenter and has made this clarification in the final rule. 

10.6 Comment: Several commenters (130, 150, 175, 227, 230, 255) provided comments on the 

requirement to maintain records of fuel consumption rates and/or the use of fuel and hour meters. 

One commenter (255) expressed that EPA should not apply the NESHAP meter 

requirement to existing emergency RICE which operate infrequently. The commenter (255) 

stated that the 100 hour per year limit (for which the meter requirement was established for) can 

be exceeded by petition or if state or local requirements mandate operation for more than 100 

hrs/yr, in which case no petition is necessary. The commenter (255) requested that the 

requirement to install a non-resettable hour meter not be imposed on existing RICE that are 

dedicated to emergency service. If it is necessary to record and report the annual operation of 

such engines, the commenter (255) suggested that the operator be permitted to use other 

methods. This commenter (255) opined that the cost of installing a meter on existing RICE 

dedicated to emergency service is unwarranted given the prospective limited operation of such 

engines. Commenter 230 suggested the use of an operating log book and tracking fuel usage. 

The fuel usage could be calculated from consumption rates at minimum load and tracked as a 

rolling 12-month period. 
257

One commenter (130) stated that not all engines used for agricultural purposes have hour 

meters. The commenter (130) noted that this could be problematic during a field inspection and 

suggested allowing owners/operators to use their estimates of operating time for the purposes of 

conducting scheduled maintenance. 

Response: EPA does not agree that existing emergency engines should not be required to install 

nonresettable hour meters. These meters will provide incontrovertible documentation of the total 

hours of operation for these engines, which would not be the case if fuel usage information is 

used. In response to commenter 130, the commenter did not explain why it would be 

problematic for agricultural engines to install hour meters or why this would be problematic 

during field inspections. 

10.7 Comment: One commenter (104) noted that proposed 40 CFR 63.6640 requires each 

instance in which an operator did not meet each emission or operating limitation to be reported. 

The commenter (104) questioned whether EPA really wants to know every instance an operator 

runs over an oil/filter or spark plug change or inspecting belts/hoses by 1 hour. The commenter 

(104) believes this reporting effort will be burdensome and costly and provide no environmental 

benefit. The commenter (104) requested that EPA remove this requirement when there is no 

specified emission limit for engines located at an area source. 

 Another commenter (150) also believes that the proposed reporting requirements are 

overbroad for operating requirements. The commenter (150) indicated that recordkeeping and 

reporting should be reserved for the most significant activities. 
258

Response: EPA believes that the reporting of failures to meet emission or operating limitations 

benefits the environment. This type of reporting provides information to the enforcing agency 

about the typical operation of the engine and therefore will help the enforcing agency better 

understand and identify problems and determine the compliance status of the affected source. 

The instances when the affected source does not meet the applicable emission or operating 

limitations are considered deviations and must be reported. These requirements are consistent 

with language in the General Provisions of 40 CFR part 63 and are appropriate for stationary 

engines subject to NESHAP.

10. 8 Comment: One commenter (104) noted that proposed 40 CFR 63.6645 requires existing 

stationary engines located at area sources to submit all notifications in accordance with 40 CFR 

63.9 (b) through (e), (g), and (h), which requires multiple notifications including a 120-day initial 

startup notification, a 60-day notification of an upcoming performance test, and notifications of 

compliance status. The commenter (104) stated that many states already have permitting or 

other processes in place whereby the state is “notified” that a facility is beginning operations, 

conducting performance tests, and showing compliance. The commenter (104) asserted that 

additional, duplicative notifications to EPA are burdensome and costly and provide no 

environmental benefit. The commenter (104) requested that the notification requirements be 

removed for engines less than 500 HP that are located at area sources. 

Response: In most instances the State or local agency will be the delegated authority for 

ensuring compliance with the NESHAP and will receive the rule notifications. Moreover, even 

in cases where it is not, the requirement of sending two notifications where two different entities 
259

are regulating the engine, is neither overly burdensome or unnecessary. Therefore, EPA 

disagrees that the reporting efforts are duplicative, burdensome and costly. EPA has retained the 

reporting requirements as proposed. 

10.9 Comment: One commenter (134) believes that the proposed reporting and recordkeeping 

requirements are confusing and contraindicated for RICE at area sources. The commenter (134) 

noted that the proposed §63.6665 identifies which RICE will be exempt from complying with 

any of the requirements of the 40 CFR part 63 GP and includes a new or reconstructed RICE 

located at an area source. The commenter (134) stated that all other RICE located at area 

sources, whether subject to numerical standards or work practices, must comply with numerous 

GP requirements, such as developing and maintaining an SSM plan, keeping records of SSM 

events and actions taken during periods of SSM, periodic reporting of any SSM events linked to 

exceedances and immediate reporting of any malfunction, records of any startup or shutdown 

that causes exceedances. The commenter (134) stated that these SSM requirements are just a 

few of the numerous requirements listed in Table 8 of the proposed rule. The commenter (134) 

stated while EPA has exempted existing RICE that are not subject to any numerical emission 

standards from complying with some notifications, we fail to understand, and EPA has not 

explained, why these RICE should be subjected to the onerous SSM recording and reporting 

requirements. The commenter (134) stated that it is unclear how RICE subject to work practice 

requirements will be able to record accurately the “duration” of a startup, shutdown or even a 

malfunction when there is no real technical ability to do so. The commenter (134) recommended 

that, for the “immediate reporting” requirements of §63.10(d)(5)(ii), these reports be 
260

incorporated into otherwise required periodic reports as provided for in other NESHAP for RICE 

subject to work practices at area sources. 

Response: New or reconstructed stationary RICE located at area sources do not have to comply 

with the part 63 General Provisions because they comply with subpart ZZZZ by complying with 

40 CFR part 60 subpart IIII or JJJJ as applicable, and therefore are subject to the 40 CFR part 60 

General Provisions. EPA does not agree with the commenter that the requirements in the part 63 

General Provisions are too burdensome. The recordkeeping and reporting requirements in the 

General Provisions allow EPA to determine whether sources are complying with subpart ZZZZ. 

The commenter did not provide any information to support the claim that it is not technically 

feasible to record the duration of startup, shutdowns, and malfunctions. 

10.10 Comment: One commenter (150) stated that the requirement to keep records of all 

maintenance activities would be onerous and unnecessary in practice. The commenter (150) 

recommended that the requirement be amended to require only records of key maintenance 

activities such as oil and filter changes, spark plug replacement, overhaul, and rebuild, or 

associated activities that require an engine to be brought off-line. 

Response: EPA disagrees and does not believe that keeping records of maintenance performed 

on the engine is an onerous activity. In many cases maintenance records are already being kept 

and it is in the best interest of the owner and operator to maintain such documentation to ensure 

that the engine is properly taken care of. 
261

10.11 Comment: One commenter (174) asked that, for engines used for agricultural purposes, 

recordkeeping only be required of affected engines located in non-attainment areas. The 

commenter (174) stated that the public health impacts from agricultural engines located in rural 

areas would be lower than the impacts from engines located in urban, and particularly nonattainment areas. 

Response: EPA must address emissions from existing stationary engines in all areas. The 

determination of whether an area is in attainment or non-attainment with the National Ambient 

Air Quality Standards (NAAQS) applies only to the few criteria pollutants for which these 

standards have been established. Section 112 of the CAA pertains to HAP and only one 

hazardous air pollutant listed in section 112 of the CAA (lead) is subject to NAAQS. Therefore, 

the NAAQS attainment status of the engine location is not an appropriate distinction for 

reporting requirements in this NESHAP. 

10.12 Comment: One commenter (87) stated that the determination of maintenance frequency 

for emergency generators must include input from the owner of the equipment who fully 

understands the risk to the business of the emergency generator failing to operate when needed. 

Commenter (87) recommends that the parties listed who can provide input for maintenance 

checks and readiness testing include the owner/operator of the equipment (in addition to Federal, 

State, or local government, the manufacturer, the vendor, or the insurance company associated 

with the engine). Related to recordkeeping requirements for emergency generators, this 

commenter (87) also questioned the value of recording the amounts of oil added to the RICE and 

its relationship to maintaining compliance with work practice standards, and characterized the 
262

proposed recordkeeping requirements as burdensome. Commenter (87) recommends the agency 

revise the recordkeeping requirements to focus on the dates of maintenance and a general 

description of the maintenance required. 

Response: In the final rule EPA has included a provision that allows owners/operators to 

petition the Administrator pursuant to 40 CFR 63.6(g) for alternative work practice requirements. 

EPA does not agree that the recordkeeping requirements are burdensome. The rule does not 

require records of the amounts of oil added. EPA is in agreement with the commenter that the 

records should include the dates of maintenance and the description of the maintenance that was 

performed. 

11.0 Fuel Requirements 

11.1 Comment: Two commenters (116, 141) expressed support for meeting the 15 parts per 

million (ppm) sulfur in diesel fuel for existing non-emergency CI engines. The commenters 

(116, 141) also recommended that ULSD fuel be used in existing CI emergency engines. The 

commenters (116, 141) provided that this would be consistent with 40 CFR part 60, subpart IIII, 

which requires all applicable engines (both emergency and non-emergency) to use ULSD fuel 

beginning on October 1, 2010. 

 One commenter (215) supported EPA’s proposal to require existing diesel engines 

greater than 300 HP to use ULSD, but requested EPA require the ULSD for all existing 

stationary diesel engines. The commenter (215) noted that EPA required ULSD for new 

stationary diesel engines in the NSPS, and believes the same standards are cost effective and 
263

achievable for all existing diesel engines. The commenter (215) pointed out that ULSD reduced 

emissions of SO2, and enables the use of aftertreatment control technologies. In addition, the 

commenter stated that existing diesel engines less than 300 HP should be required to use ULSD 

because of the direct emission reductions. 

Response: EPA is supportive of the use of ULSD in existing diesel engines but does not agree 

that it would be appropriate to mandate this for all existing diesel engines in this NESHAP. EPA 

does not have, and the commenters did not provide, any data on whether HAP reductions are 

achieved by using ULSD and therefore could not require the use of ULSD as a HAP reduction 

technique for emergency engines and for non-emergency engines smaller than 300 HP. The 

final rule requires non-emergency engines larger than 300 HP to use ULSD because the emission 

standards for those engines are based on the use of oxidation catalyst control; the use of ULSD 

will reduce the potential formation of sulfate compounds for engines equipped with oxidation 

catalyst control and will aid the operation of engines equipped with oxidation catalysts. 

EPA believes that as the supply of ULSD becomes widespread in the coming years, many 

emergency engines will utilize this fuel anyway, even though they are not required to do so by 

this regulation. 

11.2 Comment: One commenter (96) thought that EPA should only subject diesel engines with 

1996 or later model years to the ULSD requirements. Commenter 96 is in general support of the 

fuel requirements, but said that older engines are subject to fuel seals and other features that 

cannot tolerate ULSD without risking engine deterioration and for that reason should be exempt 
264

from ULSD requirements. Similarly, one commenter (76) noted that ULSD may not work well 

with older engines less than 300 HP. 

Response: EPA does not agree that diesel engines that are older than 1996 model year should 

not be required to use ULSD. The commenters did not provide any information in support of the 

claim that older existing engines would not be able to tolerate ULSD. 

11.3 Comment: One commenter (78) said the rulemaking assessment should include the effect 

of engine location when evaluating feasibility and cost of retrofit requirements. Fuel and 

infrastructure constraints must be considered. For example, the commenter (78) operates in 

Kauai, and electrical interties between the Hawaiian islands do not exist. There is no natural gas 

on Kauai, and all generating units use #2 diesel fuel, which must be brought by barge to the 

island. These factors affect the cost and feasibility of measures that require the use of ULSD. 

An additional cost relates to the fact that the commenter (78) does not own its own fuel storage 

facilities. A requirement to use lower sulfur fuels in one type of generating unit would mean that 

the commenter (78) would have to use the same fuel in all of his generating units, which would 

be an additional cost factor. 

Commenter (78) noted that Hawaii faces increased costs because everything used on the 

island (Kauai) must be shipped in. Any evaluation of cost effectiveness must account for the 

premiums that will be paid for materials, equipment, and labor on the island. 

Response: The commenter did not provide any information to indicate that it would be much 

more costly to fuel its engines with ULSD instead of #2 diesel fuel or that it would not be able to 
265

obtain ULSD. The use of ULSD is becoming widespread and will be even more widespread by 

the time existing engines must comply, because by that time ULSD will be required to be used in 

on-highway vehicles, nonroad engines, and new stationary engines, including those in Hawaii. 

The commenter did not provide any information to support the claim that the costs in Hawaii of 

changing from uncontrolled #2 diesel fuel to ULSD would be higher than for other areas of the 

U.S.

11.4 Comment: One commenter (261) believes that EPA should clarify in the rule that existing 

RICE should be allowed to complete use of existing fuel stocks even if they become subject to 

the ULSD requirements. The commenter (228) noted that many smaller sources have no 

effective way to drain and dispose of the fuel already placed in RICE tanks. The commenter 

(228) stated that EPA should clarify that no additional non-ULSD may be purchased for units 

after the effective date, but that existing in-tank stocks may be used until exhausted, at which 

time ULSD must be used. The commenter (228) believes this simplifies an otherwise complex 

problem in trying to drain tanks and manage the residual non-ULSD fuel. 

Response: Affected sources do not have to comply with the final rule until three years after the 

date the rule is promulgated. This time period would allow the existing fuel stocks to be used up.

11.5 Comment: Four commenters (108, 157, 216, 230) responded to EPA’s request for comment 

concerning an option to prohibit the burning of crankcase oil or mixing crankcase oil with fuel in 

engines equipped with exhaust after treatment technologies. The commenter (230) was 

concerned that EPA has not evaluated the potential net increase in used oil disposal costs which 
266

may result from this option. The commenter (230) noted that fuel oil blending costs 

approximately $50 per drum, whereas disposal by incineration is approximately $165 per drum. 

 One commenter (216) supports the utilization of on-specification used oil fuel as an 

important practice to support state and federal programs to reduce waste generation and as a 

good environmental practice. 

One commenter (157) believes that EPA should permit the use of crankcase oil for 

energy recovery, and to not further restrict the burning of specification used oil for energy 

recovery. The commenter noted that air permits for a power company that operates several 

diesel engines that supply electricity to remote locations are allowed to burn specification used 

oil, including crankcase oil when the following conditions are met: 

• The blend meets the used oil specification listed in 40 CFR §279.11;

• The blend is not classified as hazardous waste; and

• The blend is limited to equipment owned, operated, or maintained by the company.

The commenter (157) reviewed the companies fuel usage data for the past five years and found 

that specification oil accounted for less than 0.25 percent of the annual diesel fuel usage for these 

diesel engines. 

One commenter (108) believes contamination of catalyst elements has been an issue for 

many years, and the company has worked with oil suppliers and determined, by extended field 

testing over the past five years, that proper catalyst friendly oil will not foul the catalyst 

elements. The commenter (108) stated that oil provided by Mobil and labeled CF (catalyst 

friendly) is available as a standard item on the market. Therefore, according to the commenter 

(108), combusting crankcase oil will not have any effect on the catalysts and requested that no 

restrictions be imposed on burning of small amounts of oil with engine fuel. 
267

Response: The final rule does not specifically prohibit this practice but does contain fuel 

requirements for non-emergency engines greater than 300 HP that affected sources must meet in 

order to ensure proper operation of post-combustion controls. 

12.0 Docket Materials/Transparent Regulatory Process 

12.1 Comment: Several commenters (76, 112, 130, 150, 155, 224, 242) thought the docket for 

the proposed rulemaking is inadequate and relies on outdated information, and that information 

in the docket is not always appropriately cited in order to provide a transparent and clear picture 

of how EPA developed the proposed rule. EPA has not met its objective in providing 

rulemaking transparency, the commenters (155, 224, 242) said. For example, the PSR database, 

which is the basis for population estimates is not available in the docket because it is not a public 

product, commenters 155, 224, 242 said. Therefore, the commenters (155, 224, 242) were 

unable to review and verify the information regarding the number and types of engines. 

The commenters (155, 242) said that the use of proprietary data is in conflict with the idea of 

transparency outlined by the Administrator and the short comment period did not allow for a 

FOIA request to be submitted. EPA should document and fully disclose all relevant calculations, 

equations, and assumptions related to the PSR database and any spreadsheets used to support 

assumptions should also be provided in the docket, the commenters (155, 242) said. One 

commenter (76) noted that was no discussion in the preamble regarding the population database 

that discusses how and when the database was populated. Similarly, test reports used by EPA to 

set the standards were not in the docket either, the commenter (155) said. Commenters 155 and 
268

242 added that the docket relies in large parts upon old data from other rules. For example, such 

as the Emissions Database, which contains data primarily from the 1990’s and control cost 

information gathered in 2003, commenters 112, 150, and 155 said. The commenters (155, 242) 

could not find evidence of a more recent data gathering effort and information and assumptions 

were adopted from older rulemakings without revisions to current levels. 

One commenter (224) stated that documents from previous rulemakings that were used in 

the development of the proposed rule were not appropriately cited in the docket and that this 

oversight hinders commenters’ ability to review and comprehend EPA’s analysis. The 

commenter (224) was specifically concerned with documents related to the cost analysis. The 

commenter (224) noted that a robust docket should be developed in order to support regulatory 

transparency.

 The commenter (150) also believes that EPA has failed to give proper consideration to 

urban vs. rural area regulatory distinctions and that the docket lacks support for the conclusion 

that emissions from remote area sources cause adverse human health effects (which is used as 

the basis for the proposal to require catalysts on certain engines even in rural areas). The 

commenter (150) indicated that the docket reference for capital equipment and operating and 

maintenance costs for controls is flawed in that EPA has failed to address and consider 

guaranteed life, expected life, catalyst replacement cost, tuning or maintenance 

recommendations, and potential costs related to retrofit applications versus new equipment. The 

commenter (150) also stated that limitations related to fuel quality limitations have not been 

properly considered. 

One commenter (130) cited the following examples of EPA’s failure to comply with the 

new administration’s goals of science-based decision-making and transparent rulemaking: 
269

• Failure to conduct risk-based analyses for area sources; 

• Failure to consider the difference between urban and rural area sources; 

• Lack of transparency in cost-effectiveness determinations (e.g., based calculations on 

cost estimates from one vendor); 

• Failure to provide supporting data for proposed emission limits; and 

• Reversal of EPA’s previous assertion that the database developed for the 2004 RICE 

MACT contained insufficient data to regulate engines less than 500 HP by using the same 

database to develop the proposed rule, which includes emission standards for such 

engines. 

 The commenters (155, 242) expressed that it was in general difficult to understand EPA’s 

basis for regulatory decisions and in some cases information necessary to follow EPA’s analysis 

was not traceable. The commenter (155) stated that it was hindered in its review and indicated 

that it was not capable of providing complete input to EPA because of it. The commenter (155) 

believes EPA should obtain additional data, perform new analyses, and clearly present the 

analysis and supporting documentation in the docket for the regulated community to review. 

The commenters (155, 242) said that EPA has not met its goal of providing a transparent 

regulatory process. 

Response: The docket to the proposed rulemaking contained the information that was available 

to EPA at the time of the proposal development and that EPA used to support the proposed rule. 

While some of the information in the docket may be several years old, it was the best 

information EPA had on hand at that time. In response to comments related to the use of older 

stationary engine test reports, EPA has repeatedly asked industry to provide emissions test data 
270

for different rulemakings over the last several years; however, the response and submittal of 

actual test data for stationary engines has been minimal. EPA did an advance notice of proposed 

rulemaking for this rule to try to obtain additional new test data. However none was received. 

Since the publication of the proposal, EPA has received new test data for engines above and 

below 500 HP. EPA has incorporated the new test data into its final MACT floors for the 100-

300 HP, 300-500 HP, and 500 HP and above subcategories. 

EPA does not agree that information in the docket was not appropriately cited and EPA 

purposely tried to minimize duplication by referring to materials developed for previous 

rulemakings affecting the same and similar engines. EPA recognizes that commenters may not 

clearly have understood the analysis that was performed for the proposed rulemaking. EPA tried 

to answer any questions that were received post-proposal from industry and other affected 

stakeholders. For the final rulemaking, EPA has made an effort to be as clear as possible in 

support memoranda, preamble language, and other background materials, in order to provide at 

transparent rulemaking process. By clearly explaining rationale and assumptions, EPA believes 

the final rule is clear as far as the basis for regulatory decisions is concerned. 

Specifically, for the final rule, EPA has provided the original PSR figures that EPA used 

to develop population estimates. EPA has also clearly described in supporting documentation 

how the affected number of engines was estimated for the final rule. Both of these materials are 

available from the final rulemaking docket and commenters will be able to review and verify the 

information related to the stationary engine population. For more information on the population 

of engines affected by the final rule and the impacts associated with the final rule requirements, 

please refer to the memoranda entitled “Existing Population of Stationary RICE” and “Impacts 

Associated with NESHAP for Existing Stationary CI RICE.” EPA does not agree that it should 
271

have conducted risk-based analyses for area sources. Section 112(d) rulemaking is intended to 

be technology based, with only certain provisions, not applicable here, dealing with risk. EPA 

explains its rationale for regulating area source CI engines in rural areas in section 2.0 of this 

document. EPA did provide the data to support the emission limitations via the RICE Emissions 

Database that is publicly available on EPA’s website. 

EPA has in supporting documents to the final rule made a significant effort in clearly 

describing the basis and information used for the final rule. EPA believes that the docket to the 

final rule contains the information necessary, and the information is presented in such a manner 

that it clearly illustrates the process for arriving at final decisions and provides a transparent 

rulemaking process. 

13.0 Rule Impacts 

13.1 Economic Impacts 

13.1.1 Comment: Several commenters (81, 89, 93, 97, 101, 103, 104, 111, 112, 121, 126, 130, 

132, 136, 140, 150, 151, 155, 176, 186, 187, 203, 204, 205, 207, 216, 220, 221, 224, 231, 241, 

242, 249, 251, 261) expressed that the costs are not representative of actual costs of 

implementing the rule and numerous commenters said that the proposed rule will have a 

significant financial impact on their sources. According to the commenters (155, 242), EPA has 

underestimated the cost impacts of the rule by an order of magnitude or more. Numerous 

commenters indicated that EPA has used old, faulty, and inappropriate data on the cost of 

controls, testing, recordkeeping and reporting to estimate the economic impacts of the rule. 
272

Commenters 155 and 242 said that EPA should gather current information on the cost of 

controls and redo the cost calculations. The commenters (155, 242) provided specific examples 

of where they believe EPA has used inappropriate cost information in other comments in this 

RTC document, but the following also lists some main examples: (Commenter 241 noted some 

of the same concerns in its comments). 

• EPA should present all costs associated with the rule in 2013 dollars and not in 2007 

dollars. 

• The models used to estimate the capital and annual costs of add-on controls 

underestimate the costs and not all equipment components have been included. 

• Concerns regarding add-on controls for diesel engines being based on oxidation catalyst 

controls for gas engines rather than CDPF. The commenters (155, 242) believe that the 

oxidation catalyst cost model for natural gas engines should not be used for diesel 

engines and since based on EPA’s document (EPA-HQ-OAR-2008-0708-0017) the 

annual costs for oxidation catalyst are three to four times lower than CDPF, EPA has 

significantly underestimates the cost impact for diesel engines. 

• Efficient HAP, CO and NOx control is highly dependent on engine operation and exhaust 

gas temperature and 90 percent reduction cannot be assumed. Actual CO reductions and 

possible increases in greenhouse gas and ammonia emissions should be taken into 

account during a revised cost impact analysis. 

• Two commenters (104, 155) said that not all existing engines have hour meters. 

Similarly to the specific concerns listed above, commenters 112 and 186 believe that 

EPA has underestimated the total cost of this rule by underestimating the number of engines 

requiring the addition of catalyst; assuming that catalysts can simply be added to effectively 
273

control existing engines; overlooking the significant cost of field installation; and 

underestimating the complexity of and administrative/operational burdens added by this rule. 

The commenter (112) stated that the cost effectiveness of controls in $/ton are particularly 

concerning, because only the annual control cost of the catalyst and associated HAP reductions 

appear to have been considered and not all the additional costs after controls are added to an 

engine (i.e. performance testing, SSM and maintenance recordkeeping, reporting, lost 

production/revenue, etc.). The commenter (112) requested that EPA re-evaluate the economic 

analysis to include deficiencies in the cost estimates. 

Several commenters (90, 118, 146, 178, 184) provided comments about the economic 

impact of the rule on emergency units. One commenter (90) stated that overall the cost per ton 

of HAP or CO removal would be excessive for emergency CI engines since emissions were well 

below a ton/yr and the units use is very limited and intermittent. 

More specifically, one commenter (146) estimated only 2 of 14 emergency units at two of 

their major sources may be able to be retrofitted at a cost of $65,000 each. The others would 

need to be replaced at a cost of $1,350,000 plus an additional $110,000 each for source testing. 

The commenter’s (146) 9 area source RICE units that would be subject to a NESHAP emission 

standard would need to be replaced at $720,000 each. These costs would be for only 20 to 40 

hrs/yr of operation and thus resulting in minimal emissions reductions. Another commenter 

(178) noted that engine manufacturers do not recommend the use of after treatment devices for 

emergency engines, and that EPA appeared to support that position in the Regulatory Impact 

Analysis, which states that cost per ton removal of HAP ranged from $1 million to $2.8 million 

for engines larger than 500 HP and from $3.7 million to $8.7 million for engines between 50 and 

500 HP. 
274

One commenter (184) provided calculations of worst and nominal cases emissions and 

cost per ton removal of CO to justify exemption of combustion turbine peaking unit devices. 

The worst case estimate was 0.13 tons of CO removed at a cost of $107,692 per ton and 0.016 

tons CO removed for the nominal case at a cost of $875,000 per ton. 

One commenter (107) said that the proposed rule for existing CI engines greater than 300 

HP at area sources is cost prohibitive for facilities with peak shaving engines with low operating 

hours. The commenter (107) estimated that the cost per ton of HAP removed from these units 

would range from $200,000 to $1 million, similar to the cost for emergency generators. 

While reducing HAP is an important goal, one commenter (204) believed that the 

overbroad approach taken by EPA in subjecting all the RICE equipment in question to the 

requirements proposed, regardless of whether the equipment is located in urban or rural areas, 

particularly when considering the Congressional intent of reducing HAP in urban areas given the 

potential risks to public health, and the imposition of costs in excess of $528 million to reduce 

13,000 tons of HAP a year (i.e., a cost of $40,615 per ton) should be carefully scrutinized. 

 One commenter (203) noted an additional concern with the proposed rule is the potential 

impact of parasitic load resulting from the use of catalytic diesel particulate filters (CDPF) and 

oxidation catalysts. Some back pressure penalty is associated with the use of both CDPF and 

oxidation catalysts methods to control HAP, the back pressure can increase with time, which 

may require regeneration of the catalyst or changing filters. The commenter (203) believed that 

for those utilities that operate RICE with only marginal excess capacity, addition of either type of 

control could require installation of additional RICE capacity to maintain the needed reliability 

level. The commenter (203) noted that it will not be possible to design around the pressure drop 
275

for existing engines and that the penalty should have been addressed and included by EPA in the 

cost assessment of retrofit and operation for the control devices. 

Another commenter (136) indicated that EPA’s estimates are low for the capital and 

operating costs associated with the use of catalytic control, and are based on pricing data from 

one vendor and a limited number of data points. The commenter (136) asserted that EPA’s 

capital estimate and annual operating cost estimate for catalytic controls are each low by an order 

of magnitude of 2 to 3. The commenter (136) also stated that because beyond-the-floor 

standards (which require catalytic controls) are based on the cost per ton of HAP removed and 

EPA significantly underestimated capital and operating costs of catalytic controls, EPA must 

reanalyze the proposed rule with better cost data to determine when catalysts are economically 

practical. 

One commenter (81) said EPA’s cost estimates are based on a number of incorrect 

assumptions for emergency generators. The commenter (81) said EPA does not appear to 

consider any costs associated with testing emergency engines, even though owners may deem it 

prudent to test to confirm they are meeting the standard rather than risk an enforcement action if 

the unit does not meet the standard. Testing to comply with the 100 percent load requirement 

will require owners to purchase or rent load banks to meet the conditions contemplated in the 

standard, which can cost up to $10,000 per site. The load bank costs alone could add up to as 

much as $973 million. In addition, equipment modifications (sample ports) would be necessary 

to test emissions, and EPA has not included these costs in its calculations. 

 One commenter (121) said the cost information contained in the docket for test costs is 

not representative of the sampling costs required to comply with the standards as proposed. 

Members of the commenter’s (121) organization indicated that the cost per sample run using 
276

Methods 1, 3, 4, and 10 could easily exceed $10,000, excluding costs to prepare for the sampling 

(i.e., scaffolding, stack extensions, etc.). In addition to these cost considerations, as a practical 

matter, there would be significant difficulty in performing these EPA test methods on engine 

exhaust. 

 According to one commenter (81), if aftertreatment is required to meet the emergency 

engine numerical limitations, that cost must be considered. Because many emergency engines 

are likely located in older buildings where space is limited, installation of controls could 

necessitate some reconfiguration of the building, at substantial costs with minimal environmental 

benefit. 

One commenter (140) said the primary impact of the proposed rule on the company is the 

requirement to conduct an initial performance test on each engine with an emission limit. Using 

EPA cost numbers, the company would spend at least $47,600 to test its units. However, 

because the RICE are spread over such a large area (500 square miles), the testing costs would be 

as much as $200,000 due to logistics, travel costs, additional labor for travel, access to remote 

areas, etc. Additional costs would be incurred if add-on controls were needed to meet the 

emission limits and due to O&M requirements, recordkeeping, and reporting requirements 

imposed by the rule. 

One commenter (150) stated that if the General Provisions of 40 CFR part 63 are to be 

applied to engines that are the subject of this rulemaking, EPA should gather information on 

costs and complete a cost/benefit analysis for reporting and recordkeeping. 

One commenter (251) expressed that the proposed rule would put an incredible strain on 

not-for-profit entities, or hospitals, specifically. The commenter (251) reported that all of its 
277

hospitals are operating with negative margins and the cost of the proposed rule would pull 

resources from direct patient care. 

Commenter 249 contended that EPA’s proposed controls are cost prohibitive. This 

commenter (249) stated that the EPA should prepare a generic $/ton BACT analysis regarding 

the proposed controls that will be needed to meet proposed emission limits, and claimed that this 

analysis will clearly show that the $/ton costs are prohibitive. 

Commenter 249 noted that existing engines at area sources of HAP are required to meet 

emission limits ranging from 4 ppmvd or 90 percent CO reduction for non-emergency CI engines 

between 50 and 300 HP to 40 ppmvd CO for emergency CI engines greater than 500 HP. 

Commenter 249 claimed that costs to meet these rigid limits will be prohibitive and will impact 

emergency engines used throughout the United States at all kinds of facilities that provide vital 

safety requirements. 

Commenter 249 presented example cost quote and BACT analysis. Commenter’s (249) 

BACT analysis was prepared to reduce formaldehyde by 90 percent (from an emission rate of 

4.26 x 10-4 lb/hr to 4.26 x 10-5 lb/hr) using EPA recommended guidelines for a 0.5 MW (670 HP) 

engine. In commenter’s (249) analysis the cost effectiveness is calculated to be 

$109,639,280/ton (assuming 10 year amortization rate) for reducing formaldehyde base on 100 

hrs/yr of operation. By comparison, commenter 249 claimed that in most areas of the country, 

BACT is considered reasonable if the costs are approximately $5,000 to $10,000/ton depending 

on the pollutant. Commenter 249 noted that additional costs would be incurred for construction, 

maintenance and upkeep costs. 

Commenter 220 claimed that EPA has proposed compliance requirements that are more 

stringent than GACT requirements or management practices and that EPA has decided to 
278

institute MACT. However, even under MACT EPA can consider cost and energy impacts. The 

commenter (220) disagreed with EPA’s conclusion in the RIA that the rule will not likely have a 

significant impact on the supply, distribution, or use of energy. The commenter (220) said that 

the proposed standards could have a very detrimental impact on energy reliability, and many 

units may have to be shut down due to the cost of compliance. 

One commenter (261) believes that economic impact estimate by EPA is extremely low. 

The commenter (261) noted that EPA estimated the initial capital cost for control equipment to 

be $528 million and the annual cost to be $345 million. The commenter (261) stated that the 

industry believes that the capital cost is a factor of 10 higher and the annual cost to be a factor of 

4 higher. The commenter (261) gave the following reasons for EPA’s low estimate: 

• Not all existing engines requiring controls can simply add a catalyst, some engines must 

be replaced; 

• EPA estimated the performance test to cost $250-500 when the cost for many engines is 

approximately $8,000; 

• EPA falsely assumed the proposed maintenance requirements adds no cost to the 

industry; and 

• The administrative burdens of the rule were underestimated or left out entirely. 

One commenter (242) said, as also noted in earlier comments by this commenter and 

others, that EPA has not considered the high demand of catalysts that will be the result of this 

rulemaking. The impacts of a large demand of catalysts should be included in EPA’s cost 

analysis to determine the effect based on vendor and catalyst availability, precious metal 

markets, and potential replacement costs, commenter (242) said.
279

Two commenters (104, 112) stated that EPA estimates of the cost of performance testing 

(based on performing test using a portable analyzer and discounts for testing multiple engines at 

every site) at $500 for engines less than 500 HP and $250 for engines greater than 500 HP. 

While the commenter (112) conceded that performance testing using portable testing equipment 

is less expensive for CO testing for lean burn and CI engines, the commenter believes $500/$250 

per test is an extremely low estimate. 

Response: EPA used the information it had available at the time of proposal to estimate the cost 

impacts associated with the rule. This information included cost data obtained for the 

development of previous stationary engine rulemakings, which EPA believed would be 

appropriate to use for this rulemaking. Based on the significant number of comments received 

on the proposed rule costs, EPA revisited its cost analysis and assumptions underlying the 

proposed rule and revised that analysis in the final rule. 

 EPA has made several attempts to obtain more current cost information, including 

through an advance notice of proposed rulemaking for this rule. EPA agrees with the 

commenters that it is inappropriate to base the cost for a diesel oxidation catalyst on the costs for 

oxidation catalysts for spark ignition engines. Therefore, EPA has based the catalyst cost 

estimate in the final rule on cost data for diesel oxidation catalysts obtained from a CARB study. 

More information on the cost estimate can be found in the memorandum entitled “Control Costs 

for Existing Stationary CI RICE.” The cost estimates are based on the use of diesel oxidation 

catalyst rather than CDPF because CDPF is not required by this rule. All of the standards 

promulgated in this rule, to the extent they require aftertreatment, can be met using oxidation 

catalysts and we believe that sources will generally choose to use oxidation catalyst control 
280

because they are less costly that CDPF and achieve similar reduction in HAP. While some 

sources may choose to meet the standards using CDPF, that choice is not required by the 

standards promulgated in this rule. Based on a reanalysis of the MACT floor data and abovethe-floor options, taking variability into account, the final rule requires engines equipped with 

catalysts to achieve 70 percent reduction rather than the 90 percent that was proposed. The 

commenter did not provide any information to show that the aftertreatment controls likely to be 

used to meet this rule would lead to increases in greenhouse gas and ammonia emissions. 

Regarding the comment that catalysts cannot be added to existing engines, the 

commenter did not provide any information to show what engines would not be able to be 

retrofit. Regarding the concerns expressed about backpressure increases, the commenter did not 

provide any data to support the claim that the backpressure increases are so high that they would 

severely impact the engine output. 

EPA does not agree with the claim that the rule will put a strain on hospitals. The 

stationary diesel engines at hospitals are typically emergency engines and EPA has determined 

that emergency engines located at institutional facilities such as hospitals that are area sources 

are not part of the listed source category and are therefore not subject to the final rule. EPA does 

not agree with the commenters that it is not appropriate to require peaking units and stationary 

diesel engines that are located in rural areas to install controls. This is discussed in more detail 

in the response to comment 2.1.1. EPA has specified in the final rule that performance testing is 

not limited to 100 percent load, so it should not be necessary to include the cost of a load bank in 

the performance testing cost. EPA has incorporated the costs for testing, monitoring, 

recordkeeping, and reporting in the cost analysis and believes that its estimates for these costs are 

appropriate. The costs for testing are based on information from source testing companies. As a 
281

result of the comments on testing costs, EPA reevaluated the estimate of how many engines 

could be tested in a single day and determined that two engines could be tested at a facility in 

one day, rather than three as was estimated in the proposal. 

Regarding the concerns expressed by the commenters about the impact of the rule on 

emergency engines, the final rule requires existing stationary emergency engines to meet work 

practice or management practice standards, rather than numeric emission limitations; these work 

practices and management practices do not require that these engines be retrofit with 

aftertreatment controls or be tested to determine compliance. Information provided to EPA by 

engine manufacturers indicates that most engines are already equipped with an hour meter; 

therefore, EPA did not add this cost into the rule. EPA does not believe that the final rule will 

cause owners/operators to replace their emergency engines. The final rule imposes work or 

management practices on these engines, which EPA believes will not be overly burdensome to 

facilities and will not cause the retirement of existing stationary emergency engines. 

 

13.1.2 Comment: One commenter (242) said that EPA should develop an estimate of the costs 

for implementing NESHAP requirements for existing area sources within synthetic minor 

permits. Sources have in the past opted to install controls beyond what is required in order to 

avoid Title V thresholds and to become synthetic minors for HAP. This is a problem because the 

proposed rule would apply many onerous provisions that were previously avoided, including 

more stringent emission limits, and will become a disadvantage for those sources that chose to 

over-control their engines in the past. 
282

Response: EPA has made several revisions to the proposed requirements and is finalizing a rule 

that in many cases significantly reduces the burden on existing stationary engines located at area 

sources. Therefore, EPA does not believe the final rule places many onerous or inappropriate 

provisions on the existing stationary engines the commenter is referring to. Also, what the 

commenter is asking EPA to do in terms of synthetic minor sources is outside the scope of this 

rulemaking. 

13.1.3 Comment: Three commenters (101, 104, 177) were concerned how the proposed rule 

would impact small business. 

One commenter (177) believes that the SSM limits could significantly impact small 

businesses and force them into noncompliance during startup, shutdown, or malfunction 

conditions. The sources will become subject to noncompliance penalties and other enforcement 

risks even though the engines have been operating in the same way for more than a decade. The 

commenter recommended that EPA suspend the SSM rulemaking and convene a Small Business 

Advocacy Review (SBAR) Panel on SSM under section 609(b) of the Regulatory Flexibility Act 

(RFA). 

Response: The commenters did not provide any information to demonstrate why the proposed 

SSM requirements would have a more significant impact on small businesses than on other 

sources. Regardless, EPA in the final rule has specified work practices for startup that these 

sources can comply with that should not have a significant negative impact on these sources. As 

discussed in section 3.0, EPA has made changes in the final rule to the SSM requirements that 
283

were proposed, and EPA believes these changes will address the commenter’s concerns 

regarding the impacts of SSM on small entities. 

13.1.4 Comment: Two commenters (147, 194) expressed that the proposed rule would have a 

significant impact on agricultural sources. One commenter (194), on behalf of the agricultural 

industry in their state, stated that, because of the retroactive nature of the proposed rulemaking, it 

places a burden on agricultural operators without having viewed the costs of testing and other 

compliance measures for existing engines and lacks both economic and environmental 

justification. The commenter (194) stated that the operational use of engines used in the 

powering of irrigation and lift pump facilities has not been factored into EPA’s evaluation nor 

has data been submitted that supports a need beyond the normal replacement cycle of engines 

that is naturally occurring due to wear and tear of existing operating engines. The commenter 

(194) argued that the costs associated with requiring retroactive compliance does not recognize 

that the normal replacement process for such engines will produce the same reduction in 

emissions due to new engine performance standards being present when these existing engines 

are replaced without putting a burden on both the owners of the engines and on the regulatory 

agencies responsible for administering the programs. 

One commenter (147) stated that the economic impact of the proposed rule on the 

agriculture industry would be extremely high and would significantly outweigh any 

environmental benefit. The commenter (147) submitted data indicating total HAP emissions 

from all RICE operated by the Florida sugar industry to be less than 2 tpy. Based on EPA’s 

estimates for performance test costs, the commenter (147) calculated a cost effectiveness for this 

industry of $271,500 per ton of HAP reduced assuming all of the HAP emissions were 
284

eliminated due to the proposed rule. The commenter (147) therefore requested that rural, 

agricultural RICE be exempted from numeric emission limitations and performance test 

requirements. 

Response: For stationary non-emergency CI engines greater than 300 HP, EPA does not agree 

that it would be appropriate to wait until these engines are replaced to require emissions 

reductions. Stationary diesel engines can in some cases operate for decades before they are 

replaced. EPA determined that the costs of the rule are justified considering the emissions 

reductions that will be achieved. The commenter did not provide any information to support the 

contention that stationary agricultural engines are significantly different enough from other 

applications to warrant a separate subcategory, or that standards would be different even if there 

were such a subcategory. 

13.1.5 Comment: One commenter (207) stated that EPA has underestimated the cost of the 

proposed rule for nuclear power plants. According the commenter (207), components installed in 

nuclear applications are subject to a variety of quality assurance requirements, specifications, and 

code requirements, and none of the current catalytic converter manufacturers are qualified to 

nuclear safety related standards. Further, commenter (207) claims that the cost of producing 

catalytic converters to nuclear safety related standards, estimated at $0.85 million, is expected to 

be 5 to 10 times the cost of commercial applications, that installation costs associated with 

additional piping, supports, fire protection, heating/ventilation/air conditioning, etc., are 

estimated to be $2 to 4 million per RICE, and the cost of providing additional structures to 

protect this equipment is estimated at $3 to 5 million per RICE. Commenter (207) estimates that 
285

with approximately 250 emergency RICE currently installed at nuclear power plants, the total 

cost would exceed $2 billion. Commenter (207) believes that this large cost is not justified by 

the insignificant amount of emission reduction that would result from adoption of the proposed 

rule. Similarly, Commenter 216 estimated that the cost of making modifications to existing 

emergency diesel generators configurations at nuclear power plants to result in capital costs that 

are 5 to 10 times greater due to additional NRC testing and evaluation requirements than would 

be the case at a non-nuclear regulated emergency diesel generators. 

Commenter (216) found the proposed rule to be a monetarily significant rule for 

regulated entities, thus adding a burden to their customers while yielding a minimal impact on 

emissions reductions. The cost and NRC conflicts and duplications within the proposed rule 

create significant concerns for nuclear facilities. The commenter (216) is concerned about safety 

conflicts with the NRC and the financial burden that would be imposed on nuclear facilities. 

Response: The EPA does not agree that the rule will have an unreasonable burden on engines 

used at nuclear power plants. For stationary emergency engines at nuclear power plants that are 

area sources of HAP or are less than 500 HP and at major sources of HAP, the final rule requires 

the engines to meet management practices rather than the emission limitations that were 

proposed. Therefore, these engines will not incur the cost of aftertreatment controls for their 

emissions, so there will be no concerns with having to operate these engines with catalyst control 

and the engines will not have to be modified. Emergency engines at nuclear power plants that 

are major sources of HAP and are greater than 500 HP are not the subject of this rulemaking. 

13.2 Environmental/Health Impacts 
286

13.2.1 Comment: Two comments (140, 147) believe the proposed rule will have little 

environmental benefit. Specifically, one commenter (140) noted that the HAP and formaldehyde 

emissions associated with RICE owned and operated by the company are very low. Since, EPA 

anticipates that all of these units could meet the standard without installing additional controls, 

there would be no environmental benefit. If controls are required, they are still only applied to 

low level emission sources. The cost effectiveness of any modifications or add-on controls for 

these engines would be extremely high. 

 The commenter (140) said the RICE operated by the company are scattered throughout 

approximately 322,000 acres, resulting in an average engine density of approximately one engine 

per 4,000 acres (6 square miles). For the most part, these engines are very remote any residences 

or population areas, according to commenter 140. Therefore, there would minimal or no health 

related improvements associated with imposing emission limits or control equipment on these 

engines, according to commenters 140 and 147. The commenter (147) noted that the engines 

operated for agricultural purposes typically are spread over a large geographic area that is in a 

remote location with respect to residences or population areas and, in most cases, are below 300 

HP. The commenter (147) pointed out that EPA acknowledged in the preamble to the proposed 

rule that it expects all engines below 300 HP to meet the proposed emission standards without 

any additional control. Therefore, the proposed rule imposes new, costly regulatory burdens 

without providing any environmental benefit. For this reason, the commenter (147) requested 

that rural, agricultural RICE be exempted from numeric emission limitations and performance 

test requirements (see comment above in section 6.4).
287

Response: EPA disagrees with the comment that the rule will have little environmental benefit. 

The rule will reduce emissions of HAP as well as CO, VOC, and PM. EPA described the health 

effects of the HAP emitted from stationary diesel engines in the preamble to the original 

promulgation of subpart ZZZZ (69 FR 33474). These HAP emissions are known to cause or 

contribute significantly to air pollution which may reasonable be anticipated to endanger public 

health or welfare. The Regulatory Impact Analysis (RIA) for the proposal indicates that we 

expect $0.9 billion to $ 2 billion in benefits nationwide associated with implementation of the 

rule due to reductions in PM emissions that occur as a co-benefit of the HAP control 

requirements. 

EPA has determined that management practices are appropriate for small stationary 

engines at area sources as well as stationary emergency engines at area sources, which reduces 

the impact of the rule on those engines. 

13.2.2 Comment: One commenter (71) supports the proposed rule as issued by EPA in the 

Federal Register on March 5, 2009, in order to improve Reservation air quality and to help 

improve regional haze in nearby Class I areas. The commenter (71) also supports the EPA’s 

decision to help reduce greenhouse gas emissions through this rule. 

Response: EPA notes that this rulemaking is for HAP emissions and is not focused on reducing 

greenhouse gas emissions. 

13.2.3 Comment: Two commenters (146, 178) noted that from a life-cycle perspective, HAP 

emissions reductions attributable to replacement of emergency units (that are not recommended 
288

to have aftertreatment devices installed by their manufacturers) would be dwarfed by the carbon 

and HAP emissions that would result from manufacturing, transporting, and installing new 

replacement units that would be used for so few hrs/yr.

Response: EPA is not requiring the replacement of existing emergency engines in the rule. The 

commenter did not provide any information to explain why the emergency engines could not be 

retrofit with emission controls and would have to be replaced. Therefore, EPA is unable to fully 

respond to this comment. 

13.2.4 Comment: Four commenters (64, 66, 68, 75) stated that a rural Alaska village with a 

population of 500 people may spend thousands of dollars to comply with the proposed rule, but it 

is difficult to determine if there will be a corresponding savings of three to six times this amount 

in reduced lung ailments. The commenters (64, 66, 68, 75) stated that rural Alaska generators 

will be converting to cleaner units due to the NSPS over the next decade, and it is difficult to 

justify the increased costs due to the proposed NESHAP to rural Alaska. 

The commenters (64, 66, 68, 75) believe the proposed rule will create a significant 

economic impact on rural Alaska utilities, because power generators in rural Alaska will incur 

annualized costs greater than 1 percent of the operating costs, and are therefore not part of the 

“substantial number of small entities” without significant economic impact. The commenter 

believes that since rural Alaska power generators will eventually transition to clean burning 

engines through the NSPS, EPA should allow maximum flexibility for those rural utilities to 

continue operating in a way that minimizes some of the highest power costs in the nation. 
289

The commenters (64, 66, 68, 75) indicated that EPA determined that their estimates of 

future compliance costs by the proposed rule would not have any disproportionate budgetary 

effects on any particular areas of the country, state, or local government, or types of 

communities. The commenters (64, 66, 68, 75) could not find the citation for this estimate, or 

data that demonstrates this in either the federal register notice or Regulatory Impacts Analysis for 

the proposed rule. The commenters (64, 66, 68, 75) stated they have solid financial reasons to 

believe the proposed rule will have a disproportionate impact on rural Alaska communities. The 

commenters (64, 66, 68, 75) encouraged the EPA to study the cost impact of the proposed rule to 

rural Alaska, and offered an example of a study showing the cost impact to rural Alaska 

communities in transitioning to ULSD. The study can be found at 

Http://www.dec.state.ak.us/air/anpms/ulsd/ulsdecon.htm. 

The commenters (64, 66, 68, 75) believes that the proposed rule will unnecessarily raise 

power costs for rural Alaska populations that are predominately Alaska natives and have a higher 

percentage of incomes below the poverty level. The commenters (64, 66, 68, 75) believes that 

higher power costs may force the use of dirtier forms of fuel, such as wood or coal, which will 

increase air pollution and health impacts. The commenters (64, 66, 68, 75) believes that sources 

are already transitioning to ULSD, and moving rural power generation in Alaska to clean and 

renewable sources. The commenters (64, 66, 68, 75) believes that there is a potential for an 

environmental justice problem associated with the proposed rule due to the increased power 

costs. 

The commenters (64, 66, 68, 75) is concerned that the proposed rule will have potential 

to be a “significant energy action” in rural Alaska. The commenters (64, 66, 68, 75) stated that 

while annualized costs of this proposed rule are estimated to exceed 1 percent of the operating 
290

revenue in rural Alaska, compliance costs could easily exceed 50 percent of the net annual 

operating revenue. The commenters (64, 66, 68, 75) stated the cost of prematurely moving 

communities to ULSD, installation and maintenance of emission control devices, source testing, 

and continuous monitoring of emission controls has a large cost impact on the utilities providing 

power to rural Alaska. The commenters (64, 66, 68, 75) stated that diesel engines are the main 

source of power in rural Alaska outside the southeast. The commenters (64, 66, 68, 75) stated 

that the existing NSPS will shift the remaining diesel power production to cleaner engines and 

fuels over the next decade. 

Response: As discussed in the response to comment 2.1.2, EPA agrees with the commenters that 

the proposed rule could have a disproportionate impact on rural Alaska villages, due to the 

special challenges faced by operating stationary engines in these very remote areas of Alaska. 

For these engines, EPA has required compliance with management practices in the final rule for 

area sources in these areas, instead of the emission limitations that were proposed. EPA believes 

this addresses the commenters’ concerns regarding the impact of the rule on these engines. 

13.2.5 Comment: One commenter (140) provided a profile of the phosphate fertilizer company’s 

engine population, including emission estimates based on actual engine operating hours and AP42 emission factors. As shown, HAP emissions are estimated at less than 0.5 pounds per hour 

(lb/hr) (based on organic HAP emissions). The commenter (140) concluded that these emissions 

are not significant compared to the HAP threshold for major source facilities. 

Response: No response is necessary.
291

13.3 Cost of Controls 

13.3.1 Comment: Several commenters (78, 103, 104, 111, 112, 150, 156, 216, 220, 225, 227) 

indicated concerns with EPA’s estimate of the cost of controls, specifically that such costs have 

been underestimated. 

 One commenter (78) noted that the costs of retrofitting catalyst control systems to large 

diesel engines used for electric power generation can be significantly greater than just the cost of 

the catalysts themselves. The commenter (78) gave an example of a larger engine already 

equipped with SCR, where the retrofit of additional catalyst systems will likely require major 

ductwork changes, a complete rework of the continuous emissions monitoring systems, and 

potential relocation of the exhaust stacks. 

 The commenter (78) said the cost effectiveness of adding control devices to low-use 

engines should be evaluated regardless of the size of the engine. The costs associated with the 

installation and maintenance of a control device on a low use unit can be quite high per ton of 

pollutant abated. 

One commenter (225) made the general statement that EPA’s estimates are low for the 

capital and operating costs associated with the use of catalytic control, and are based on old 

pricing data from one vendor and a limited number of data points that were fit with a linear 

regression. The commenter (225) also stated that because above-the-floor standards (which 

require catalytic controls) are based on the cost per ton of HAP removed, EPA must reanalyze 

the proposed rule with better cost data to determine when catalysts are economically practical. 
292

 Commenter (220) said the cost data considered by EPA in developing the proposed rule 

is outdated and underestimates the costs to install, operate, and maintain the controls that will be 

necessary in order for owners and operators of RICE to comply with the proposed rule. The 

capital and annualized control cost formulas for oxidation catalysts only consider a small 

universe of engines. The commenter (220) collected vendor data on installation costs and 

concluded that EPA’s assumption that these costs are the same for existing and new engines is 

incorrect. The commenter (220) concluded that EPA’s costs are too low (e.g., at least 40 

percent). Even assuming a 40 percent correction factor, the average capital cost is likely still low 

for retrofitting older units. In addition, the commenter (220) said that the annual operating costs 

for the oxidation catalyst control of these units would average about $31,000 per year at each 

generating facility. The commenter said EPA should gather current data to update the cost 

equations and provide a specific basis for assuming the cost to install controls on existing and 

new sources would be the same. 

 Commenter (220) said that because of the drastic underestimation of the cost of control, 

EPA has also mischaracterized the cost per ton of emission reduction. As the commenter’s (220) 

engines do not operate for lengthy periods of time, the cost per ton of reduction is high. Based on 

total emissions from the commenter’s (220) facilities of 45 tons of CO, the commenter (220) 

calculated an estimated cost of $111,000 per ton using EPA’s cost assumptions, and said the real 

number would be much higher. This cost is too high to justify the rule’s stringent requirements. 

Operation of engines in urban areas in accordance with acceptable management practices is 

sufficient to protect public health and the environment. 

 Commenter (220) said that because of the high costs to comply with the proposed rule, 

many municipalities may have to shut down units, affecting the viability of backup power 
293

supplies. Members’ units provide a vital source of power in emergency situations. Because 

these same units may be used in peaking circumstances, they do not qualify for emergency unit 

status and are subject to stringent retrofit controls. In addition, members use engines in sewer 

systems and along sewer lines to continue sewer operations during power outages. Such units 

would likely be subject to the prescriptive maintenance requirements in the proposed rule. Other 

true emergency type units may be large enough to implicate emission reduction requirements for 

larger emergency units. 

Response: As a result of these comments, EPA reanalyzed the cost data used to estimate the cost 

of controls. EPA agrees that the equipment costs used for the cost estimate in the proposed rule 

were too low. As discussed in the memo “Control Costs for Existing Stationary CI RICE,” EPA 

has based the equipment cost of oxidation catalyst control in the final rule on costs from a cost 

study performed by CARB . The cost study included a retail cost range for oxidation catalyst for 

various sized engines, cost of retrofitting the control device to an existing engine, and the 

operating and maintenance costs for the control device. These costs are based on actual costs 

obtained by CARB during the development of their Risk Reduction Plan. The retrofit 

installation costs include the costs for ductwork, brackets and other miscellaneous parts. 

 Based on the results of the control costs, EPA believes that it is still appropriate to 

develop emission standards based on the use diesel oxidation catalyst for stationary nonemergency engines greater than 300 HP at major sources. We are also requiring the use of an 

open crankcase filtration system to reduce the blowby emissions from the combustion chamber 

for engines with open crankcases that are vented to the atmosphere. This reduces the oil mist 

emissions from the crankcase that may contain organic HAP or metallic HAP. Of further 
294

consideration are the co-benefits that would be achieved by requiring the use of the oxidation 

catalyst/crankcase ventilation option. The control technology will reduce other pollutants such 

as CO and PM, which are of significant health concern. In addition, the rule will also reduce the 

emissions of sulfur dioxide (SO2), because the rule requires the use of ULSD fuel for nonemergency engines above 300 HP. Taking into account the reductions in CO, SO2 and PM 

associated with applying oxidation catalyst/crankcase ventilation to non-emergency CI engines, 

the cost per ton of pollutants reduced is appropriate. Even for engines that have lower hours of 

usage, the cost per ton is reasonable when the benefits are considered. 

 For municipalities, the final rule requires management practices for emergency engines. 

Therefore, we do not believe that costs to comply with the final rule will cause the shut down of 

backup power for municipalities. If the engines are used for peak shaving, then they have to 

meet the requirements for non-emergency engines. 

13.3.2 Comment: Two commenters (103, 112) stated that the equipment life used by EPA to 

compute the capital recovery factor (20 years) is too high. Commenter (103) believes this 

equipment life would be reasonable for the engines alone, but is very high for the add-on 

controls. In the commenter’s (112) experience, control equipment life expectancy is 

approximately 10 years for engines greater than 500 HP and approximately 5 years for smaller 

engines. The commenter (103) believes that the recovery period should be a maximum of 10 

years due to the following factors: 

• The economic life of the control equipment is 10 years, during which the element will 

still need to be replaced every 2-3 years. 
295

• The electronic technology often becomes unsupportable in a time span significantly less 

than 10 years. 

• It is unlikely that the regulatory environment will enable these controls to be used for 

20 years. Ever increasing regulations will likely obsolete the technology before the 

20 year recovery period has elapsed. 

Response: EPA agrees with the commenter that the equipment life used to compute the capital 

recovery factor was too high. For the cost analysis in the final rule, EPA used an equipment life 

of 10 years, which is more accurate for these emission controls. 

13.3.3 Comment: Responding to EPA request for comments on CDPF, one commenter (87) 

stated that installation of CDPF are 8 to 10 times more expensive than oxidation catalysts and 

can cause back pressure which requires more maintenance in older engines. Commenter (87) 

recommends EPA abandon the possibility of requiring CDPF. 

Response: EPA agrees that CDPF are more costly than oxidation catalyst and discussed this in 

the preamble to the proposed rule. For the final rule, EPA is not mandating a particular control 

technology in order to comply with the emission standards. Affected sources are free to use any 

control option that will achieve the final emission standards. EPA has found that the standards 

can be achieved through the use of oxidation catalyst control. 

13.3.4 Comment: Two commenters (78, 170) said that the cost effectiveness of adding control 

devices to older engines should be addressed, because it may not be cost effective to install 
296

controls on engines that are nearing the end of their useful life. Control devices such as 

oxidation catalysts must be designed and sized to match the engines on which they are installed, 

and one cannot automatically assume that a catalyst system designed for one engine can be used 

on another. In addition, attempting to retain the catalyst system for use on a replacement engine 

may limit the source’s option for replacement engines. Consequently, if the useful life of the 

control device is considered in cost effectiveness calculations, if the control device will not be 

used for its predicted useful life, then the calculations will underestimate the cost effectiveness of 

the device. 

Response: EPA does not agree with the commenter that it should determine the cost 

effectiveness of adding control devices to engines that are nearing the end of their useful life. It 

is not feasible to determine the cost effectiveness of every type of operating scenario. Affected 

sources will have 3 years to comply with this regulation and therefore can decide whether to 

replace older equipment rather than retrofitting. 

13.3.5 Comment: One commenter (126) stated that large diesel engines greater than 3,000 HP 

would require a more expensive catalyst than the inline system that EPA has assumed in the 

support documents for the proposed rule. The commenter (126) stated that the more expensive 

“biscuit” system requires special steel supports to suspend the biscuit over the engine, and a preheater, which creates more emissions than the catalyst reduce. 

Response: The commenter makes the statement that catalysts are more expensive for larger size 

engines, specifically those above 3,000 HP, but the commenter did not provide any information 
297

to EPA supporting this claim. EPA understands that catalysts for larger size engines may not be 

available off-the-shelf and that costing is site-dependant. Even so, manufacturers of emission 

controls have indicated that oxidation catalysts that are fitted on larger engines are in general 

scaled-up versions of those applied on smaller engines. The commenter states that such catalysts 

are more costly than what EPA estimated for the proposed rule, but in the commenter’s letter, no 

specific costs were given. The commenter mentioned specific equipment that would be 

necessary with larger catalyst systems, but failed to provide alternative costs that the commenter 

believes would more accurately reflect the costs of such catalyst systems and associated 

equipment. The commenter (126) mentioned that a pre-heater is needed with larger systems, but 

again, did not provide EPA with any substantial information regarding why it is technically 

necessary to have a pre-heater. Nor did the commenter (126) elaborate on the emissions from a 

pre-heater. No background information was submitted by the commenter to support the claim 

that a pre-heater would create more emissions than what a catalyst might reduce. 

With that said, following the publication of the proposed rule, EPA reviewed a number of 

comments, in addition to this one, that asserted that different aspects of EPA’s assessment of 

control costs were not appropriate. Therefore, EPA obtained and reviewed additional cost 

information for oxidation catalyst control on stationary diesel engines. Based on this review, 

EPA believes that the cost estimate for oxidation catalyst developed for the proposal was low 

and likely not representative of current pricing. Subsequently, EPA has reassessed the cost to 

install and operate oxidation catalyst controls for the final rule and made updates to the cost 

methodology that was used for the proposal. This information is detailed in the memorandum 

titled “Control Costs for Existing Stationary CI RICE.” EPA looked at different sources of 

information, including capital and annual costs developed for the original RICE NESHAP rule, 
298

which was promulgated in 2004, cost information developed by CA ARB, miscellaneous quotes 

and information from catalyst vendors, engine manufacturers and trade associations. It was 

difficult to combine the different pieces of cost information and also to compare the various 

estimates received because of different assumptions and factors included making it nearly 

impossible to make an apples-to-apples comparison. EPA also found that there were some 

inconsistencies in the different pieces of information reviewed. EPA therefore had to make a 

determination which information it was most appropriate to use based on being complete and 

accurately reflective of costs. EPA determined that the most appropriate information that was 

available was information collected from a study performed by the CA ARB. The methodology 

for determining the costs are presented in the memorandum entitled “Control Costs for Existing 

Stationary CI RICE” in the rulemaking docket. EPA believes that information is the best 

available information on oxidation catalyst costs. Based on the capital cost equation developed 

by EPA for the final rule ($27.4 x HP - $939), the total capital cost of installing an oxidation 

catalyst on a 3,000 HP existing stationary CI engine would be around $81,000. This cost is 

nearly 2.5 times higher than the costs estimated at proposal and is consistent with actual costs of 

today’s oxidation catalyst. EPA believes the costs developed for oxidation catalyst control is 

applicable to the entire range of existing stationary diesel engines, including engines above 3,000 

HP. EPA believes this cost would cover the cost of the oxidation catalyst itself and any 

additional components that may be necessary. Certain installations may be more costly, but 

other installations may be less costly, however the final costs for oxidation catalyst are expected 

to be representative of average nationwide costs. This estimate is in the ballpark cost range of 

information commenter 183 submitted on the proposed rule who provided a cost breakdown for a 

2,250 kWe engine, which is around 3,000 HP. This engine is similar in size to the engine size 
299

commenter 126 is concerned with, but this engine incurs additional costs due to location. 

According to commenter 183’s cost breakdown, the total capital cost is around $94,000 

excluding the cost of a performance test. A member of EMA indicated that the total installed 

cost of DPF would be $90,000-$100,000 on a 3,000 HP engine and that the cost would not be 

more for a DOC installation. Again, this is in the ballpark range of the capital costs EPA has 

estimated for the final rule for oxidation catalyst. Thus, EPA believes the final costs for 

oxidation catalyst are appropriate for all engine sizes, including those above 3,000 HP. 

Therefore, EPA believes that it has appropriately accounted for and estimated impacts for 

oxidation catalyst control being retrofitted onto existing stationary diesel engines above 3,000 

HP. 

13.3.6 Comment: Two commenters (179, 183) stated that EPA’s cost methodology for 

retrofitting oxidation catalysts to existing CI engines is overly simplified and dramatically 

underestimates costs for operators in very cold climates, where housing is used to protect the 

engine. The commenter (179, 183) noted for these installations, the retrofit of control equipment 

would require extensive modification to the housing, and increase installation costs. In addition, 

the commenter (179, 183) noted that skilled labor would need to be transported to the remote 

location, and lodging and food would need to be provided. Commenter (179) added that the cost 

of complying with NSPS subpart GG and subpart KKKK NOx limits range from $75,000 to 

$125,000. The commenter (183) provided two BACT analyses for two different sized engines: 

the first was a limited duty cycle CI engine rated at 2,250 KWe operating less than 1,000 hrs/yr; 

and the second engine was a continuous duty engine rated at 410 KWe. The tables from the 

commenter (183) showed that the cost effectiveness of the larger limited use engine was 
300

approximately $167,000 per ton of HAP removed, and the cost effectiveness of the continuous 

duty engine was $134,000 per ton of HAP removed. The commenter (183) believes these values 

demonstrate that the cost impacts in remote locations in Alaska have not been adequately 

addressed in the proposed rule. The commenter (179) stated that it does not appear that EPA 

considered that control may not be feasible at facilities such as offshore platforms where space 

may not be available to install post-combustion control equipment. The commenter (179) noted 

that these platforms were constructed 20 to 40 years ago and were designed to minimize space 

utilization, and expansion of these platforms may not be physically or economically possible. 

The commenter (179) stated additional evaluation by EPA is necessary, because many of the 

RICE will not be able to achieve the proposed limits without post-combustion emission controls, 

and due to the infeasibility of retrofitting controls, many engines would need to be replaced. 

Commenter 179 said that EPA should conduct further study before requiring platform-mounted 

cranes, compressor drives, fire water pumps, and backup generator engines where the space may 

not be available, cannot be created, or the cost of creating additional space is exorbitant, to install 

controls. 

Response: As discussed in the response to comment 2.1.2, EPA acknowledges the special 

circumstances faced by owners/operators of stationary CI engines located at area sources in 

remote areas of Alaska. Therefore, EPA is requiring management practices for these engines. 

The final rule specifies that existing stationary non-emergency engines greater than 300 HP that 

are located at area sources in Alaska that are not accessible by the FAHS are not subject to 

numerical emission standards, but must meet specific management practices instead. All 

existing stationary emergency engines at area sources are subject to management practices. 
301

Existing stationary CI engines less than or equal to 300 HP that are located at area sources are 

subject to management practices only. 

For other existing stationary non-emergency CI engines greater than 300 HP, EPA 

believes that it is appropriate to require emission standards that require the use of oxidation 

catalyst control because the technology is available and feasible for all existing stationary nonemergency CI engines greater than 300 HP regardless of location. EPA discussed in response to 

comment 13.3.5 that a reassessment of costs was performed after the publication of the proposal. 

The outcome of the cost reassessment indicated that the costs developed for the proposal were 

low and likely not representative of actual costs of purchasing, installing, and operating 

oxidation catalyst systems. EPA believes that the final costs that are presented in the 

memorandum entitled “Control Costs for Existing Stationary CI RICE” are reflective of current 

costs and are commensurate with the costs provided by the commenter for catalyst controls for 

engines located in rural Alaska. EPA looked at the cost per ton of HAP (around $162,000 or 

less) reduced from these engines and determined that the cost is justified. EPA also considered 

the co-benefits that are associated with oxidation catalyst control on existing diesel engines. For 

example, the benefits per ton of PM and SO2 reduced are between $210,000 (Pope, 7%) and 

$500,000 (Laden, 7%) and between $27,000 (Pope, 7%) and $65,000 (Laden, 7%), for PM and 

SO2, respectively, for major sources. For area sources, the benefits per ton are between $330,000 

(Pope, 7%) and $790,000 (Laden, 7%) and between $18,000 (Pope, 7%) and $44,000 (Laden, 

7%), for PM and SO2, respectively. The benefits clearly outweigh the costs of requiring 

numerical emission standards based on oxidation catalyst control. Regarding the concern that 

extensive modification will be needed to the engine housing in order to accommodate an 

oxidation catalyst, information EPA received from a catalyst vendor indicated extensive 
302

modifications to the housing would not be needed because the catalyst could be installed on top 

of the engine housing. 

EPA adds, however, that the final cost estimates are an average estimate and EPA 

acknowledges and recognizes that not every scenario may be represented in the final costs. It 

would be impossible to account for every possible alternative condition that might necessitate 

higher or lower costs that what EPA has estimated. EPA also notes that the cost per ton estimate 

is conservatively based on 1,000 hours of operation per year. Assuming longer operation, the 

cost per ton estimate would decrease. EPA’s cost per ton analysis is presented in the 

memorandum titled “Cost per Ton of HAP Reduced for Existing Stationary CI RICE.” 

As stated above, EPA’s final cost estimates are consistent with the costs that commenter 

183 has estimated, at least for the 2,250 kWe engine operating 1,000 hours per year. However, 

EPA does not follow the commenter’s methodology for estimating the cost per ton for the 410 

kWe engine operating 8,760 hours per year. Upon inspecting the cost breakdown commenter 

183 provided, it appears that the total capital cost (TCC) used is inaccurate. The second page of 

Attachment 4 provides a breakdown of how the total annualized costs were estimated, which, for 

indirect costs, is primarily a function of the TCC. The total annualized cost shown is $34,387, 

however, looking closer at how items 7 through 11 of the indirect costs were estimated, it is clear 

that the TCC used is not correct. For example, the property tax totals $1,924, which means that 

TCC is $192,400 because the property tax is 0.01 TCC, according to the commenter. However, 

as shown on the first page of Attachment 4 of commenter 183’s letter, the TCC is $38,256. 

Therefore, the total annualized costs appear to be based on a TCC of $192,400 and not $38,256 

and seem to have been estimated incorrectly by the commenter. Certainly, the cost per ton of 

HAP removed would be significantly lower for an engine operating continuously. Therefore, 
303

EPA does not believe that the cost per ton of HAP removed for a 410 kWe continuously operated 

engine is representative. EPA estimates that the cost per ton of HAP removed for a 410 kWe 

engine, or around 550 HP engine operating 8,760 hours per year would be around $19,000. 

In regards to the comment concerning offshore platforms, EPA disagrees. If an engine is 

located on an offshore platform and is less than or equal to 300 HP and an area source, it is not 

subject to numerical emission standards. In this case, aftertreatment space concerns are a nonissue. Similarly, if the engine is an emergency engine or less than 100 HP, the engine is only 

subject to maintenance practices. In this scenario, there would be no space concerns either. 

Based on the list of engine applications the commenter (179) noted, EPA believes that many of 

those engines will fall into categories that do not require numerical emission standards under the 

final rule. Also, if the engine is less than or equal to 300 HP and a major source, it may not need 

aftertreatment in order to meet the numerical emission standards. 

If there are engines on platforms that are subject to numerical emission standards where 

aftertreatment is necessary in order to comply with the requirements, EPA believes that add-on 

controls are feasible. If add-on controls are needed to comply with the standards only minimum 

space requirements are expected. EPA contacted a catalyst vendor regarding this issue, and the 

vendor indicated that engines on offshore platforms are typically equipped with a silencer; the 

catalyst can be put in the silencer, so it would not take up any additional space on the platform. 

Commenter 179 did not provide any specific information regarding the size restrictions engines 

might have on offshore platforms. The commenter (179) did not provide any information related 

to the costs of applying add-on controls to engines on offshore platforms either and indicate what 

costs the commenter considers to be “exorbitant.” Aftertreatment controls have been installed 

and operated successfully on mobile sources engines, which also have limited space available. 
304

EPA believes that the emission standards based on the use of oxidation catalyst control are 

appropriate for existing stationary non-emergency engines greater than 300 HP. 

13.4 Implementation and Enforcement 

13.4.1 Comment: Four commenters (104, 150, 191, 207) believe that the proposed compliance 

date of 3 years is too short. 

One commenter (207) said that the compliance time would not be sufficient for 

installation of controls on back-up/emergency engines at nuclear power plants. According to the 

commenter (207) this is because components installed in nuclear applications are subject to a 

variety of quality assurance requirements, specifications, and code requirements, none of the 

current catalytic converter manufacturers are qualified to nuclear safety related standards, and 

the time frame for current vendors to meet the stringent quality assurance standards and produce 

an acceptable catalytic converter is estimated to be beyond the 3-year compliance period. 

Response: The compliance date provided in §63.6595(a)(1) of the proposed rule for stationary 

existing engines less than or equal to 500 HP located at major sources and stationary existing 

engines located at area sources is consistent with the typical date of compliance given for 

existing sources, i.e., 3 years from the effective date of the rule, and is the maximum amount of 

time that EPA can provide under Clean Air Act section 112(i)(3). EPA believes this is sufficient 

time for sources to comply with the requirements and does not agree that a 6 year compliance 

period should be provided. EPA has not included additional compliance time in the final rule. 
305

 As discussed in the response to comment 6.3.1, stationary emergency engines at nuclear 

facilities are not subject to numerical emission limitations. Therefore, there is no justification for 

a longer compliance time for these engines. 

 

13.4.2 Comment: One commenter (93) reiterated the February 25, 2008 request that EPA allow 

states to incorporate any new rules or revisions to rules at the next Title V revision or renewal as 

opposed to opening such permits for cause. The commenter (93) provided that the proposed rule 

will regulate thousands more engines than anticipated as it now includes: stationary engines of 

500 HP or less at major sources, stationary engines at area sources, and stationary CI engines of 

more than 500 HP at major sources. The commenter (93) stated that it heard from one existing 

Title V source that has over 300 engines that will be subject to the proposed rule. The 

commenter (93) requested that EPA consider the reasonableness and resources agencies would 

need to implement the 18 page flow chart for hundreds and possibly thousands of engines to 

determine permitting and compliance requirements. 

Response: EPA included provisions in the January 2008 final rule at 40 CFR 63.6585(d) that 

indicate that area sources subject to 40 CFR part 63, subpart ZZZZ, would not be subject to 

permits under 40 CFR parts 70 or 71 solely because of this rule. This provision will lessen the 

burden on numerous existing stationary engines located at area sources. EPA believes this 

should significantly reduce the commenter’s concern on this issue. In terms of the compliance 

burden and implementation process, EPA has made an effort to rely on management practices 

wherever possible, which will minimize the impact on particularly smaller sources and those 

individually owned and operated. Further, EPA has reserved regular performance testing for 
306

larger engines, though smaller engines subject to numerical emission limits will need to test at 

least once. Finally, EPA will be providing implementation material to assist affected sources in 

understanding the requirements of the final rule and implementing and demonstrating 

compliance with the specific provisions that apply to them. 

13.5 Energy Impacts 

13.5.1 Comment: One commenter (176) recommended that EPA re-evaluate its energy impact 

determination and consider the impact of the proposed rule’s energy requirements on a broader 

scale rather than limiting its analysis to only sectors of the regulated community. The 

commenter (176) stated that EPA’s evaluation of the energy impact of the proposed rule only 

considered the electric power sector and failed to account for the impact on the non-industry 

sector. 

One commenter (176) provided that, under section 112(d) of the CAA, EPA can consider 

cost and energy impacts. EPA concluded in the RIA for the proposed rule that it “is not likely to 

have a significant impact on the supply, distribution, or use of energy.” RIA at 5-9. The 

commenter (176) disagreed with EPA’s conclusion and stated that engines are placed because of 

concerns as to the reliability of power for the source, particularly in rural areas. The commenter 

(176) stated that the proposed standards could have a very detrimental impact on energy 

reliability and many units may have to be shut down due to the cost of compliance. 

Response: EPA focused its analysis of energy impacts on the electric power sector because this 

sector experiences the greatest impact on energy costs of any of the affected sectors. Close to 
307

half of the total annual costs of the proposed standard are incurred by the electric power sector 

(RIA at 4-39 and 5-2). We found that this industry would experience low annualized costs as a 

percent of industry revenue (less than 1 percent). This was also true for the other industries 

affected by the proposed standards. While we did not conduct an analysis for sectors not 

regulated by the proposed standards, we did provide some information on how demand for the 

agriculture and construction industries may respond to an increase in price based on impacts 

from the proposal (RIA at 5-6). This information, taken from the Department of Energy’s 

Energy Information Administration, shows that the demand for agricultural products may fall 0.2 

percent for a 1 percent increase in its product prices; for construction, the demand will fall 1 

percent for a 1 percent increase in product prices. 

13.5.2 Comment: One commenter (85) believes the proposed rule will have a significant 

negative impact upon the supply of energy. The commenter (85) indicated that through demand 

response program participation, non-emergency RICE units are valuable resources in minimizing 

and/or preventing power grid disruptions that lead to system-wide brown-outs and black-outs, 

which can and have occurred in the highly populated Northeast United States. The commenter 

(85) stated that RICE units have been installed to supply emergency backup service to support 

the reliability of facilities’ energy supply, within their locality, and a sub-set of these units also 

participates in regional capacity markets to support the reliability of the regional transmission 

system. The commenter (85) believes that engines that participate in DRP administered by the 

ISO/RTOs will be negatively affected by the proposed rule should the rule make it necessary to 

retrofit HAP control technology and, more importantly, the ISO/RTOs will be adversely affected 

by the proposed rule. The commenter (85) stated that ISO/RTO’s have modeled into their 
308

Reliability Studies, and built into the Resource Planning analysis, planned participation by these 

demand response resources. Should RICE units incur the additional costs associated with 

installation of HAP control technology, the commenter (85) believes that many of the RICE units 

will opt out of demand response programs, which will leave ISO/RTO’s with critical missing 

demand response resources. According to the commenter (85), without the inclusion of RICE 

resources for demand response, many ISO/RTO’s will have less available resources to tap during 

critical peak energy days, leaving ISO/RTO’s with inadequate reliability. 

 The commenter (85) recommended that the proposed rule be modified (using the 

language of the proposal preamble as the basis for the revision) to enable RICE units to 

participate in demand response programs. The commenter (85) recommended that the 

description of the rule in section III, “Summary of This Proposed Rule,” Subsection E, “What are 

the Reporting and Recordkeeping Requirements?” be modified as follows: 

“In addition, owners and operators are allowed to operate their stationary emergency RICE for 

non-emergency purposes for 50 hrs/yr, but those 50 hours are counted towards the total 100 

hours provided for operation other than for true emergencies and owners and operators may not 

engage in income-generating activities during those 50 hours. Notwithstanding the preceding 

text, hours of operation in response to activation calls from an ISO/RTO organization, electric 

power delivery company, and demand response programs, are not counted toward the total 100 

hours provided for operation other than for true emergencies. Tests called as part of participation 

in such demand response programs shall be counted towards the 100 hours provided for 

operation other than for true emergencies.” 

 The commenter (85) noted that many ISO/RTO markets, with the active encouragement 

of Federal Energy Regulatory Commission (FERC), have initiated demand response programs, 
309

including demand response programs administered by the NYISO, ISONE, PJM, and ERCOT 

which supply more than 100,000,000 people with reliable supply and delivery of electrical 

power. Based on an extensive example involving NYISO (the regional transmission 

organization serving New York), the commenter (85) sought to demonstrate that the loss of 

critical RICE units in the demand response program would not only jeopardize electric 

reliability, but would also increase electric rates for all New York State electric ratepayers. The 

commenter (85) also illustrated that the number of operating hours for which these engines 

actually run, to provide this safety net to the public, is quite small, averaging around 16 hrs/yr for 

the most active RTO demand response program. 

Response: As discussed in the response to comment 6.1.1, EPA believes that it would be 

appropriate to allow engines to retain their status as emergency engines under subpart ZZZZ if 

they operate as part of demand response programs for a 15 hours of operation per year or less in 

situations where grid failure and a blackout are imminent. The commenter’s information 

indicates that no engine has needed more than 15 hours per year to meet their requirements under 

their demand response programs. This alleviates the concerns expressed by the commenter. 

These engines will still be able to participate in demand response programs and the final rule will 

not impact the energy supply or grid reliability by providing a disincentive for facilities to 

participate in these programs. 

13.6 Small Businesses 
310

13.6.1 Comment: Two commenters (226, 242) expressed concern over how the proposed rule 

might impact small businesses. One commenter (242) said that EPA has not properly 

communicated to small businesses (e.g., Small Business Administration), government 

installations (e.g., fire and police stations), and homeowners on the proposed rulemaking. The 

commenter (242) stated that EPA needs to quantify the potential impacts associated with 

regulating these sources since these sources are not exempt. Also, the commenter (242) said, 

EPA should conduct an outreach program to communicate the requirements of the rule to the 

public. One commenter (226) stated that small businesses mostly use small engines and 

regulation of these engines yields the smallest emission benefits. 

Another commenter (226) had similar concerns stating that under the Regulatory 

Flexibility Act, EPA is required to analyze reasonable alternatives that minimize small business 

burdens while still achieving the statutory goals. The commenter (226) noted that in the 2002 

proposal that EPA acknowledged that small stationary RICE have generally not been regarded as 

significant sources of air pollution emissions, and solicited comment on ways to structure the 

proposed rule to focus on the facilities with significant risks and avoid the imposition of high 

costs on facilities that pose little risk to public health and the environment. However, the 

commenter (226) noted that the current proposal does not request any risk-based alternatives that 

would exclude small engines. 

Response: In response to the concerns expressed by commenters about the potential impact of 

this rule on small businesses and homeowners, EPA conducted a review of the types of engines 

that were included in the area source category listing for stationary RICE. As a result of this 

analysis, EPA determined that emissions from existing stationary emergency engines located at 
311

residential, commercial, and institutional facilities were not included in the 1990 baseline 

emissions inventory that was used as the basis for the listing of source categories needed to 

ensure that 90 percent of area source emissions are regulated. Therefore, EPA has determined 

that these engines are not part of this regulated source category, which will help address the 

commenters’ concerns about the impact of the rule on small businesses and homeowners. Both 

the proposed and final rule required small stationary engines at area sources to meet management 

practice requirements rather than emission limitations, which also lessens the burden of the rule 

on those engines. The final rule extends management practices to all emergency engines at area 

sources. In addition, the final rule requires only work practices for stationary engines 100 HP or 

smaller, also decreasing the burden of the rule on owner/operators of small engines. 

14.0 Miscellaneous 

14.1 Definitions 

14.1.1 Comment: One commenter (242) thinks that EPA should amend the definition of affected 

source to include area source engines and engines less than or equal to 500 HP at major sources 

to clarify rule applicability. 

Response: EPA does not agree that it should revise the definition of affected source in subpart 

ZZZZ because the definition already includes engines located at area sources and engines less 

than or equal to 500 HP located at major sources. 
312

14.1.2 Comment: Three commenters (126, 158, 168) urged EPA to clarify and improve its 

definition of “stationary” RICE, contending that as written, it is difficult to clearly understand 

what constitutes a stationary RICE subject to regulation under the proposed rule. A problem 

with the current definition, according to commenter 168 arises when a mobile RICE that has 

been rented and has been moved to a power plant is deemed to become a stationary RICE under 

the nonroad definition in 40 CFR 1068.30. Further, commenter 168 claims that many RICE that 

would be regulated by the proposed subpart ZZZZ are temporary, rental diesel engines that 

provide outage power and compressed air during refueling and maintenance outages at nuclear 

power plants or during construction and maintenance activities at coal-fired power plants. 

Commenters 126 and 168 requested that, in the final rule, EPA revise the definition of stationary 

RICE or nonroad engine or otherwise revise the proposal to insure that rental, non-self propelled, 

portable nonroad diesel engines that are located at a utility power plant or area facility for more 

than 12 months during construction or extended maintenance are exempt from 40 CFR part 63, 

subpart ZZZZ. If portable RICE were deemed to be “stationary,” commenters 126 and 168 

requested that the final rule clarify that the owner of the diesel engine, and not the entity that 

rents and uses it, is required to comply with the rule, including required maintenance and 

performance testing. 

One commenter (158) requested that EPA clarify the types of engines that are considered 

“non-road engines” versus “stationary RICE.” For example, the commenter’s (158) firm 

operates power washers which can be either propelled (moved by hand) while being used or 

transported to a location at a facility, kept stationary while being used, and then transported to 

another location within the facility. The commenter (158) requested clarification as to whether 

such equipment would fit under 40 CFR 1068.30 section (1)(ii) or (1)(iii), which contain parts of 
313

the definition of “non-road engine.” As another example, the commenter’s (158) firm operates 

portable water pumps, generators, and welders which remain at a facility year-round and are 

moved to different locations on-site as needed. The commenter (158) requested clarification as 

to whether the engines powering such equipment would be excluded from the definition of “nonroad engine” because they remain at a location for more than 12 consecutive months, which is an 

exclusion specified in 40 CFR 1068.30. 

Response: EPA does not agree that the definition of stationary RICE should be revised. EPA 

intends for portable engines that remain in one location at a facility for more than 12 months to 

be considered stationary engines. For the example provided by commenter 168 of temporary 

rental diesel engines that provide power and compressed air at a facility, if the engines remain at 

the same location within the facility for more than 12 months, then they would be considered 

stationary engines. If the engines are located at the same facility but are moved around within 

the facility, then they would not be considered stationary. 

 Regarding the clarifications requested by commenter 158, those engines would be 

considered stationary engines only if they remain in the same location within the facility for 

more than 12 months. Engines that are located at a facility but moved around the facility are not 

stationary engines unless they remain at the same location within the facility for more than 12 

months. 

 For engines that are rented, the final rule applies to both the owner and the operator, and 

the renter is the operator and is subject to the rule. Because both the owner and operator are 

liable under the rule, the rental agreement should address who will conduct emissions testing or 
314

employ management practices for the specific engine, and who will create records, who will hold 

them for the statutory period and who will report. 

14.1.3 Comment: One commenter (121) said EPA should include a definition for “commence 

construction” to clarify when new sources are covered by the RICE MACT because of the 

overlap between 40 CFR part 60, subparts JJJJ and IIII and the RICE MACT. Consistent with 

the NSPS, EPA should define “commence construction” as follows: 

“For purposes of this subpart, the date that construction commences is the date the engine is 

ordered by the owner or operator.” 

Engines at a closed facility may be relocated and installed at another facility. Clarifying the 

original order date will assist sources in understanding the applicability of the RICE MACT for 

engines in these situations, according to commenter 121. 

Response: EPA has already provided a definition of “commence construction” in the General 

Provisions for part 63. The definition can be found in 40 CFR 63.2. As the definitions and 

provisions for determining and regulating new engines have already been established, and this 

rule is concerned solely with existing stationary engines, EPA is not revisiting this issue in this 

rule. 

14.1.4 Comment: One commenter (103) believes that the phrase “Owners and Operators” needs 

to be better defined as it relates to the requirements. The commenter (103) believes that while it 

is convenient for the EPA to avoid distinguishing between the two, the reality is that there are 

tens of thousands of engines where the roles of owner and operator are often represented by two 
315

independent companies. In the case of a rental compressor, the engine is owned by the lessor 

and rented to the lessee. According to the commenter (103), the lessor typically (but not always) 

provides: 

• Maintenance including preventative maintenance, repairs, and overhauls. This would 

include maintenance plans and the documentation of the work performed. 

• Adjustment of the engine parameters that control combustion such as ignition timing, 

air/fuel ratios, etc. 

The commenter (103) added that the lessee is typically (but not always) responsible for: 

• The day to day operation of the engine including starting, stopping, loading and 

unloading. 

• Emissions testing 

• Environmental permitting with the RICE along with the rest of surface equipment 

including burners, tanks, fugitive emissions, etc. 

 The commenter (103) stated that EPA was asked to clarify the roles and responsibilities 

of Owner and Operator as it relates to the NSPS (40 CFR part 60, subpart JJJJ) but has yet to do 

so, and added that the same mistake should not be made on this proposed rule. The commenter 

believes that the effects of this ambiguity include doubling or tripling the manpower required for 

tracking compliance on engines and for recordkeeping because all data not only must be 

gathered, compiled, sorted, and stored, but in order to transfer to counter parties (from Owner to 

Operator, for example) the data must then be carved out according to rental relationships and 

then conveyed to the other party. The commenter (103) also believes that there is an increased 

chance of noncompliance from each entity believing the other entity has complied with certain 

provisions. 
316

 

Response: This rule applies to both the owner and the operator, regardless as to whether the 

operator is an agent of the owner or merely a lessee. Because both the owner and operator are 

liable under the rule, the rental agreement should address who will conduct emissions testing or 

employ management practices for the specific engine, and who will create records, who will hold 

them for the statutory period and who will report. The requirements under the rule are clear, 

divisible and openly subject to divided responsibility under a rental agreement. EPA is willing to 

work with rental agencies to develop a standard rental agreement clause to ease recordkeeping 

and reporting. 

14.1.5 Comment: Two commenters (90, 117) requested that the definition of emergency 

stationary RICE be modified to remove the clause that ICE that supply power “as part of a 

financial arrangement with another entity are not considered to be emergency engines.” One 

commenter (117) noted that when applied to major sources, as in existing rules, the language 

may appropriately differentiate between true emergency engines and engines used in a 

commercial capacity. However, for smaller operations, it is common for multiple entities to 

share the cost and responsibility for providing emergency power. An example the commenter 

(117) cited is landlord-tenant relationships where as a part of the lease the landlord provides 

emergency backup power to the tenant. This occurs at multi-tenant facilities, such as shopping 

centers, where one tenant’s emergency power may be shared by others. The commenter (117) 

believed that EPA did not intend for these small operations to be excluded from consideration as 

emergency units. Another commenter (90) noted that most of their units would be excluded 

from consideration as emergency units under the proposed definition because they provide 
317

emergency backup power for clients such as grocery stores, data management centers, and small 

industrial facilities as part of a financial arrangement. Additionally, they may participate in 

voluntary utility curtailment programs where they have entered in financial arrangements to self 

generate power during brief times of utility constraints. 

Response: EPA has revised the provisions applicable to emergency engines to clarify that 

engines that are operated as part of a financial arrangement but are used solely for emergency use 

(e.g. not for peak shaving) are still considered emergency engines. The examples provided by 

the commenters of a landlord that provides emergency backup power to a tenant or a company 

that provides emergency backup power to clients such as grocery stores, etc. are situations where 

the engines are still emergency engines (as long as they are operated per the requirements in 

§63.6640(f)). If the engine is used for a voluntary utility curtailment program to self generate 

power during times of utility constraints in return for financial considerations, the engine would 

have to meet the requirements for non-emergency engines except as discussed in the comments 

on emergency demand response engines in section 6 of this document. 

14.1.6 Comment: Two commenters (129, 157) believed that the definition of “diesel fuel” at 40 

CFR 63.6675 should be revised to include biodiesel and biodiesel-diesel blends. The 

commenters (129, 157) stated that such a revision would ensure consistency with the Agency’s 

regulatory programs and promote the use of environmentally beneficial renewable fuels. The 

commenter (129) also believes that such a revision would clarify for owners and operators that 

the fuel requirements in the proposed rule apply to biodiesel and biodiesel-diesel blends. 

According to the commenter (129), the number of companies using renewable fuels is increasing 
318

and this clarification will become more important in enabling regulatory compliance and 

avoiding costly litigation. 

Response: EPA agrees with the commenter that the definition of diesel fuel should be revised to 

include biodiesel and biodiesel blends and has made this change in the final rule.

14.1.7 Comment: One commenter (253) stated that under §63.6675, a major source is defined as 

a stationary source or group of stationary sources located in a contiguous area and under 

common control that emits or has the potential to emit, considering controls, 10 tpy or more of 

any HAP or 25 tpy or more of any combination of HAP, while an area source is any stationary 

source of HAP that is not a major source. Therefore, the commenter (253) noted a farm which 

operates several small stationary irrigation pumps or a commercial building with an installed 

emergency generator would be classified as an area source, while a food processing facility with 

an industrial boiler, an emergency generator, and a backup fire pump might be classified as a 

major source of HAP, due primarily to its boiler emissions. The commenter (253) pointed out 

that if the farm covers a large area such that it is contiguous with both the food processing 

facility and an adjacent commercial area, and if all three facilities are owned and operated by the 

same company, then it appears that the farm, the commercial building, and the food processing 

facility would all be considered part of the same major source of HAP even if the facilities’ 

operations had nothing to do with one another. The commenter (253) pointed out that as 

individual facilities operating existing diesel engines not currently regulated under subpart 

ZZZZ, neither the farm nor the commercial building requires a Title V operating permit because 

neither meets the definition of a major source under 40 CFR part 70. Further, the commenter 
319

(253) stated that although the food processing facility does require a Title V permit as a major 

source, the adjacent farming and commercial building facilities are not considered part of the 

Title V major source, despite being contiguous and under common ownership and control, 

because they belong to a different major industrial grouping than the food processing facility (see 

definition of major source under §70.2). The commenter (253) stated that as a result of being 

classified as a single major source of HAP under the proposed subpart ZZZZ, however, the 

combined farm/commercial building/food processing facility would also be considered a single 

major source under 40 CFR part 70; a Title V operating permit would therefore be required to 

cover all three operations. In addition, the commenter (253) stated that all existing stationary 

RICE at the farm and at the commercial building would be required to comply with standards of 

the proposed subpart ZZZZ applicable to RICE at major sources rather than those applicable to 

area sources. The commenter (253) believes that this situation is not an intended consequence of 

the proposed rule but is one that needs to be addressed. The commenter (253) strongly 

encouraged EPA to consider revising the definition of major source in §63.6675, or to otherwise 

modify the applicability provisions of the proposed subpart ZZZZ, to ensure that unnecessarily 

burdensome regulatory requirements are not imposed upon area sources with stationary RICE 

simply by virtue of their location adjacent to a major source of HAP. 

Response: EPA does not agree that the definition of major source needs to be revised. If the 

sources are located in a contiguous area and under common control, then they will be considered 

a major source. This is required by the statutory definition of major source in Clean Air Act 

section 112(a)(1), 42 USC § 7412. 
320

14.1.8 Comment: One commenter (126) requested that EPA provide guidance or clearly define 

the “source” with respect to RICE in the definition of reconstruction in 40 CFR §63.2. The 

commenter (126) asked if ancillary components such as control panels be considered a 

component or excluded. The commenter (126) requested clarity in terms of reconstruction in 

subpart ZZZZ, and a generic statement that all ancillary equipment that are necessary to make 

the unit operate are exempt. 

Response: EPA has defined the term “engine” as constituting all parts necessary to operate the 

engine during emissions testing, including fuel and air intake components, cooling components, 

exhaust and pollution control components, control computers and the crankshaft, as well as the 

basic engine block and associated reciprocating engine parts. Control panels consisting 

exclusively of monitors and gauges and a throttle are not considered parts of the engine and thus 

are not part of the source. Engine computers that manage the engine in response to a throttle are 

considered part of the engine and thus of the source. EPA finds the term “ancillary equipment 

necessary to make the unit operate” ambiguous. The Agency will determine the applicability of 

any argument that a specific piece of “ancillary” equipment is not part of the source on a case by 

case basis, as provided for in the CAA. 

14.1.9 Comment: One commenter (213) asked that EPA specifically define what constitutes an 

area source (i.e., by including the amount of HAP emitted) and not rely on the current definition 

that defines an area source as any source that is not a major source. 
321

Response: The description of an area source provided in the regulations at 40 CFR 63.6585(c), 

which is the same definition of area source found in the statute in section 112(a)(2), and in the 

general provisions at 40 CFR part 63, is appropriate and consistent with what has been used for 

previous rulemakings affecting stationary engines. EPA believes this definition is very clear and 

underscores that the universe of sources is made up of major sources or sources that are not 

major sources, which are called area sources. EPA is not finalizing a different definition. 

14.2 Clarifications 

14.2.1 Comment: Numerous commenters (112, 132, 154, 155, 162, 186, 227, 242) asked that 

EPA clarify in the rule where hours has been used to determine maintenance or testing frequency 

that it is operating hours and not calendar hours. Several commenters (112, 154, 155, 186, 242) 

said that EPA should clearly specify that the maintenance frequency in the rule are operating 

hours and not calendar hours. If the engine does not operate during a particular period, it is 

assumed that no wear, performance, or emissions degradation occur, the commenters (155, 242) 

said. Therefore, the commenters (155, 242) said, it is appropriate to specify that the maintenance 

interval is defined as operating hours. 

Similarly, commenter (162) said performance testing should be stipulated based on 

engine use and hours of operation instead of calendar years. Many of the commenter’s (162) 

engines are only operated seasonally. The number of hours operated varies greatly from year-to 

year, and testing every 3 years seems burdensome given the variable and infrequent operation for 

this types of uses. 
322

Response: EPA agrees with the commenters that the rule should clarify that the maintenance and 

testing frequency are based on operating hours and has made this clarification in the final rule. 

EPA does not agree that it is burdensome to require testing every three years; this frequency is 

necessary to show that the engines are continuing to comply with the emission limitations in the 

rule. 

14.2.2 Comment: One commenter (155) expressed that EPA should provide allowances for 

cases where the maintenance schedule elapses during engine operation, e.g., an emergency could 

occur requiring an engine to operate for more than 200 hours and with a 200 hour maintenance 

schedule the commenter assumes that EPA did not intend for the engine to be stopped to 

complete an oil change. The final rule should include a provision that does not require engine 

shutdown solely for the purpose of conducting maintenance. 

Response: EPA agrees that there may be situations where an emergency engine is operating 

during an emergency and it is not possible to shut down the engine in order to perform the 

work/maintenance practice requirements on the schedule required in the final rule. EPA has 

added a provision in the final rule to indicate that if the stationary engine is operating during an 

emergency situation, then the maintenance activity can be delayed until the emergency is over. 

The maintenance should be performed as soon as practicable after the emergency has ended. 

14.2.3 Comment: One commenter (96) indicated that it has found several issues with the 

proposed standards in terms of discrepancies, omissions, conflicts and other things that need 

correction. Specific comments by the commenter (96) are provided in other sections, but in 
323

general the commenter believes the rule is complex to follow. Especially since the proposed rule 

incorporates elements from previous engine rules, it is difficult to determine what requirements 

apply and commenters 96 and 132 urges EPA to provide guidance documents that will assist the 

regulated community in determining which requirements apply to the various types of engines. 

Response: EPA has made efforts in the final rule to be as clear as possible on the emission 

standards and other requirements that apply to existing stationary engines affected by the rule. 

EPA has also corrected discrepancies that were included in the proposed preamble and rule, 

which assists in making the final rule requirements as clear as possible. Finally, EPA will be 

developing guidance and implementation material for the final rule. This material will be 

available to affected stakeholders through EPA’s website and will help the regulated community 

in determining which requirements apply and demonstrating compliance. 

14.2.4 Comment: One commenter (96) noted that in 63.6603 of the proposed rule existing 

engines at area sources are required to meet operating limitations of Table 2b of the proposed 

rule, but that Table 2b indicates that it only applies to new and reconstructed sources. EPA 

should clarify what the intent is, the commenter (96) said. The commenter (96) provided various 

charts for different engine types where it believes that this clarification needs to be made. Two 

commenters (172, 178) said that §63.6603 of the proposed rule states that existing stationary 

RlCE located at an area source must comply with the operating limitations in Tables 1b and 2b 

of the rule. However, the operating limitations in Table 2b of the proposed rule appear to only 

apply to units at major sources. The EPA should remove the reference to Table 2b of the 

proposed rule in section 63.6603 of the proposal. 
324

Response: EPA agrees with the commenter that the title to Table 2b of the proposed rule on 

page 9721 of the Federal Register notice is confusing. EPA has clarified the title of Table 2b in 

the final rule to clearly indicate the applicability of operating limitations. EPA has also clarified 

and corrected various other inconsistencies that were included in the proposed rule and believes 

the final rule reads easily and clearly. 

14.2.5 Comment: Numerous commenters (50, 81, 90, 96, 98, 116, 119, 126, 127, 129, 139, 157, 

167, 178, 196, 201, 216, 220, 240) referred to apparently conflicting language in the proposed 

preamble that appears to require initial performance testing of emergency generators and many 

of these commenters were opposed to requiring performance testing on emergency engines. Two 

commenters (96, 126) noted that in the preamble of the proposed rule at page 9711, EPA makes 

the statement “Stationary non-emergency RICE located at major sources that are less than 100 

HP, stationary RICE located at area sources that are not subject to numerical emission standards, 

and all stationary emergency RICE are only subject to compliance requirements in the form of 

management practices to minimize emission levels.” The commenter (96) stated that this 

language contradicts later text requiring numerical emission standards for formaldehyde for 

engines below 50 HP, CO standards for diesel and 4SLB engines between 50 and 250 HP, and 

CO and formaldehyde standards for emergency engines at area sources greater than 500 HP. The 

commenter (96) thinks the preamble statement is the correct one and recommends that other 

language that conflicts with the preamble language be revised to clarify that only management 

practices, not numerical emission standards apply to these sources. One commenter (118) had 

similar concerns as those expressed by commenter 96. Commenters 188 and 203 also asked that 
325

EPA clarify whether performance testing is required for these units because it is not clear from 

the rule text and specifically wanted explicit language in the final rule that exempts these units 

from performance testing. 

Commenter 119 received clarification from EPA that this was not the intent of the rule, 

and commenters 119 and 201 requested that EPA clarify this intent in the final rule. 

One commenter (162) said that performance testing of emergency RICE seems onerous, 

may not provide an accurate emissions profile, and should not be required. Emergency RICE 

emissions during short periods of readiness testing vary from the emissions profile achieved 

during longer periods of operation when they are used in emergency situations, the commenter 

(162) said. Commenters 167 and 196 expressed similar comments as 162. 

One commenter (127) stated, for example, that page 9711 section C of the preamble to 

the proposed rule states that “all stationary emergency RICE are only subject to compliance 

requirements in the form of management practices to minimize emissions.” However, the 

commenter (127) pointed out that, in Table 2 of the proposal preamble and Table 2d of the 

proposed rule, stationary emergency RICE with greater than 500 HP is listed as having emissions 

limits. 

One commenter (116) stated that it was not clear from the proposal whether existing 

emergency RICE less than 500 HP at major sources are required to conduct a performance test to 

demonstrate compliance with the emission limit. The commenter (116) noted that, in Table 2c of 

the proposed rule, emergency SI RICE between 50 and 500 HP have an emission limit for 

formaldehyde of 2 ppmv on a dry basis (ppmvd) or less at 15 percent O2. The commenter (116) 

also stated that the preamble to the proposed rule, section D.1 states that “[o]wners and operators 

of existing stationary non-emergency RICE located at major sources that are less than 100 HP 
326

and existing stationary emergency RICE located at major sources do not have to conduct any 

performance testing,” but section 63.6612 of the proposed rule (requirements to conduct and 

initial performance test) states: “[i]f you own or operate an existing stationary RICE with a site 

rating of less than or equal to 500 brake HP located at major of HAP emissions...you are subject 

to the requirements of this section.” Section 63.6612 and Tables 4 and 5 do not distinguish 

between emergency RICE and non-emergency RICE. The proposed rule language suggests that 

if an engine has a numerical emission limit, a compliance test is required. The commenter (116) 

opined that the preamble language is incorrect, but if they are wrong, they suggested that EPA 

clarify that EPA does not intend to require emergency engines to be tested in Section 63.6612 

and in Tables 4 and 5 of the proposed rule. 

One commenter (90) noted there are conflicting statements in the preamble concerning if 

an initial compliance test is a requirement or not (e.g. on page 9704 of the proposed rule it states 

that area sources subject to an emission standard must do an initial compliance test while on 

Page 9705 of the proposed rule it states that operators of emergency RlCE are specifically 

excluded from the need to submit a notification of a compliance test). The commenter (90) 

stated that in EPA’s impacts memo, it is expressly stated that a compliance test for emergency 

use engines would not be required. The commenter (90) further stated that the most significant 

issue however is not that a compliance test is required for emergency use engines, but what the 

emission levels are for existing engines with no add-on controls. 

One commenter (176) recommended that EPA remove the testing requirements for 

emergency engines from the proposed rule. The commenter (176) stated that the preamble to the 

proposed rule provides that such engines are not subject to any performance testing 

requirements, but that the rule appears to include such testing requirements (i.e., in proposed 
327

Tables 3, 4 and 6 to 40 CFR part 63, subpart ZZZZ). The commenter (176) supported its 

recommendation by explaining that emergency engines only operate on a limited basis where 

periodic testing requirements are not necessary. 

One commenter (50) found the emissions testing and reporting requirements applicable to 

emergency generators to be contradictory. In Section III.E of the preamble (FR Page 9705), and 

again in part 63.6645, existing stationary emergency RICE are excluded from reporting 

requirements, including pre-emissions testing and post-emissions testing reporting requirements. 

However, emergency RICE greater than 500 HP are subject to emission limits and testing for CO 

per Table 2d, thereby making them subject to pre-testing and post-testing reporting requirements. 

The commenter requests that the rule be modified to clearly indicate that emergency generators 

are not subject to emissions testing and reporting requirements. 

Response: EPA understands the commenters’ points, but EPA disagrees that the statement on 

page 9711 of the proposed Federal Register notice that the commenters refer to conflicts with 

later text requiring numerical standards. The statement that the commenters refer to is in section 

IV.C. of the proposed preamble under the heading “How did EPA determine the compliance 

requirements.” That section of the preamble discusses the compliance requirements and how 

EPA determined appropriate compliance requirements, and is not a discussion of emission 

standards. Under the proposed rule, EPA did not require performance testing for stationary nonemergency engines at major sources that are less than 100 HP and stationary engines at area 

sources that are not subject to any numerical standards and stationary emergency engines. EPA 

explained why it believed it was appropriate to not require performance testing from these 
328

engines and this decision was not in conflict with the decision to require numerical emission 

standards from some of these engines at proposal. 

 The requirement that existing stationary engines at area sources subject to a numerical 

emission standard would be required to conduct an initial compliance test was intended for nonemergency engines at area sources and EPA does not believe that the requirement conflicts with 

the following statement that emergency engines are also not being subjected to performance 

testing. However, EPA sees that it may not have been absolutely clear in the proposed language 

and tables. Therefore, EPA has made clarifications in the final rule regarding which engines are 

subject to performance testing and believes this resolves the commenters’ concerns on this issue. 

EPA notes that several of the subcategories that were proposed to be subject to numerical limits 

have, in the final rule, been made subject to management practices or work practice standards, 

and thus would not be subject to performance testing. 

14.2.6 Comment: One commenter (96) indicated that it is not clear when new engines that are 

subject to SSM limits are supposed to comply and if these engines are supposed to comply as of 

the date of the proposed rulemaking, a date that has already passed, that is an impossible and 

unreasonable requirement the commenter (96) said. 

Response: New stationary engines should comply with the new requirements for SSM starting 

with the effective date of the final rule. 

14.2.7 Comment: One commenter (63) noted some inconsistencies or areas in need of 

clarification in the tables of the proposed rule and said that: 
329

• Table 2c, item 8 requires existing non-emergency CI greater than 300 HP at a major 

source to be retrofitted for more restrictive emissions limitations (90 percent reduction) 

than new units to be installed at the same major source (70 percent in the current Table 

2a, item 3). 

• In proposed Tables 2c and 2d, item 9 should be labeled “Non-Emergency CI <50 HP”. 

Response: Both of the citations that the commenter questioned were correct as written. The 

proposed limit in Table 2c, item 8 for existing non-emergency stationary CI engines greater than 

300 HP located at a major source was intended to be 90 percent reduction. This provision was 

revised in the final rule. In proposed Tables 2c and 2d, item 9 included all stationary engines 

smaller than 50 HP, so there is no reason it should be limited to “Non-Emergency CI.”

14.2.8 Comment: One commenter (119) said there is some inconsistency between 40 CFR 

63.6625(e) and the referenced Table 2d of the proposed rule. Table 2d of the proposed rule 

explicitly outlines maintenance requirements for engines, but it does not include the provisions in 

40 CFR 63.6625(e) relating to manufacturer or owner/operator maintenance plans. Two 

commenters (118, 119) said EPA should insert the following clause to 40 CFR 63.6625(e): . . 

.you must operate and maintain the stationary RICE and aftertreatment control device (if any) 

according to the maintenance schedule in Table 2d, or you must operate and maintain the 

stationary RICE. . . 

 The commenter (119) recommended that a clause be added to Table 2d of the proposed 

rule indicating that as an alternative to the proposed schedules, owners and operators can 
330

maintain the stationary RICE according to the manufacturer’s emission-related written 

instruction or develop their own maintenance plan. 

 One commenter (104) stated that the text in proposed 40 CFR 63.6625 and 63.6655 

appears to allow the owner/operator of the engine to develop a maintenance plan in lieu of the 

requirements provided in Table 2d (i.e., proposed replacement schedule for oil/filters and spark 

plugs and inspection of hoses/belts). The commenter (104) requested that EPA clarify this issue 

in the text. 

One commenter (77) supported proposed 40 CFR 63.6625(e), which the commenter 

interprets as allowing owners/operators that must demonstrate compliance with a written 

maintenance plan the flexibility to operate and maintain their units according to either a plan 

written by the manufacturers or themselves “consistent with good air pollution control practice 

for minimizing emissions.” 

In order to avoid confusion, commenter 240 also recommended the following clause be 

included in §63.6625(e) and to Table 2d of the final rule: 

“...you must operate and maintain the stationary RICE and aftertreatment control device (if any) 

according to the maintenance schedule in Table 2d, or you must operate and maintain the 

stationary RICE...” 

Response: EPA does not agree with the commenters that there is an inconsistency. The 

maintenance requirements in Table 2d are not the only emission-related operating and 

maintenance requirements that are recommended by the engine manufacturer, and the language 

in §63.6625(e) requires owners and operators to follow those requirements. The maintenance 
331

plan should include the maintenance practices from Table 2d as well as other maintenance 

necessary for the engine.

14.2.9 Comment: One commenter (111) indicated that the proposal states that the pressure drop 

across the catalyst must be monitored monthly for engines greater than 500 HP at area sources 

(74 FR 9704) and later states that the pressure drop must be monitored continuously (74 FR 

9711). 

Response: The commenter is correct that there is an inconsistency in the preamble for the 

proposed rule. The language on page 9711 should have said that the pressure drop must be 

measured monthly, rather than continuously. 

14.2.10 Comment: One commenter (188) noted that the heading on the middle column of Table 

2d to subpart ZZZZ of part 63 of the proposed rule, states, “You must meet the following 

emission or operating limitations at all times, except during periods of startup, or malfunction.” 

The commenter (188) believed that this language may possibly be interpreted by overly zealous 

regulators in the field to require a continuous emissions monitoring system (CEMS) on every 

engine and noted that installing, maintaining and calibrating CEMS would be another 

unjustifiable and costly burden; especially when applied to small engines and/or those that are 

redundant/standby. The commenter (188) continued that the same comment applies regarding 

the heading at the top of the far right column of Table 2d to subpart ZZZZ of part 63 of the 

proposed rule, which states “[y]ou must meet the following emission or operating limitations 

during periods of startup, or malfunction.” The commenter (188) recommended that the EPA 
332

clearly state that CEMS is not required, and that EPA consider more realistic standards that 

operators are able to comply with; specifically, that the wording “at all times” be deleted. 

Response: Subpart ZZZZ does not require CEMS. Sources may elect to install CEMS, but they 

are not required. EPA does not agree that the wording “at all times” should be deleted because 

those requirements apply at all times except as indicated.

14.2.11 Comment: One commenter (256) expressed that the proposed rule is ambiguous as to 

how an owner or operator of a stationary emergency RICE is to demonstrate initial and 

continuous compliance with the proposed numerical emissions limitations. The commenter 

(256) stated that, if the EPA does not believe it is reasonable to subject stationary emergency 

RICE to performance testing, then there is no purpose for setting a numerical emissions 

limitation for any stationary emergency RICE. 

Response: The final rule does not contain any numerical emission limitations for emergency CI 

engines. These engines have to meet work or management practices. This addresses the 

concerns expressed by the commenter. 

14.2.12 Comment: One commenter (76) asked if the requirements for less than 50 HP in Tables 

1 and 2 in the preamble apply to emergency or nonemergency engines. 
333

Response: The requirements in the preamble and rule tables for stationary engines less than 50 

HP apply to both emergency and non-emergency engines. The requirements were revised in the 

final rule.

14.2.13 Comment: One commenter (88) recommended that EPA clarify how sources 

demonstrate compliance with the applicable requirements. The proposed rule states that 

“stationary non-emergency RICE located at major sources that are less than 100 HP, stationary 

RICE located at area sources that are not subject to numerical standards, and all stationary 

emergency RICE are only subject to compliance requirements in the form of management 

practices to minimize emissions.” However, the language of the regulation conflicts with this 

statement. Section 63.6603 of the proposed rule requires that the owner or operator of existing 

stationary RICE located at an area source must comply with the requirements of Table 2d of the 

proposed rule. Additionally, Section 63.6640 of the proposed rule requires that the owner or 

operator demonstrate compliance with the provisions in Table 2d of the proposed rule by 

complying with the methods outlined in Table 6 of the proposed rule. For emergency CI 

included in line 6 of Table 2d of the proposed rule, continuous compliance is demonstrated 

through maintaining the RICE in accordance with the original equipment manufacturer 

recommendations or by the establishment of a maintenance plan (line 10 in Table 6 of the 

proposed rule). However, for CI greater than 500 HP, which has a proposed numeric standard 

(e.g., 40 ppmvd at 15 percent O2, as shown in line 7 in Table 2d of the proposed rule), line 11 in 

Table 6 indicates that performance tests must be conducted every 8,760 hours or three years. 

The commenter (88) suggested that EPA correct this contradiction by modifying Table 2d of the 

proposed rule so that emergency CI at area sources, no matter what HP rating, are required to 
334

meet specific management practices similar to those included in line 6 of Table 2d of the 

proposed rule. If EPA determines it must impose a numerical standard, line 10 of Table 6 of the 

proposed rule should, in the commenter’s (88) opinion, be modified to also include all RICE 

located at an area source, including those subject to numerical emission limitations. 

Response: EPA agrees with the commenter that the language in the preamble to the proposed 

rule and proposed regulatory text was unclear with regard to the compliance requirements for 

stationary emergency engines. EPA did not intend to require testing for emergency engines or 

for any engines less than 100 HP or engines at area sources. 

In the final rule, all CI engines that are less than 100 HP and located at major sources are 

subject to work practices only. Stationary CI engines that are less than or equal to 300 HP and 

located at area sources are subject to management practices only. Also, all existing stationary 

emergency CI engines are required to meet work or management practices in the final rule. 

14.2.14 Comment: One commenter (193) requested that EPA clarify that the category of small 

engines (i.e., less than 50 HP) at both major and area sources is not a universally applicable 

category of engines that is separate, distinct, all encompassing, and not otherwise associated with 

any of the other listed engine sub-categories. The commenter (193) noted that the information 

presented in the referenced tables that contain compliance related requirements should be 

clarified to express that all engine types less than 50 HP, are not required to fulfill the stated 

requirements, or EPA should modify the information in its tables to reflect its stated belief that 

there will be no CI, or lean burn engines of this size. The commenter (193) suggested EPA limit 
335

the applicability of the less than 50 HP classification to only those four cycle, rich burn SI 

engines it used to establish the MACT floor. 

Response: The commenter is not correct. The category of engines less than 50 HP as proposed 

did include all stationary engines below 50 HP, not just 4SRB SI engines. This final rule only 

includes CI engines; CI engines under 50 HP have been grouped as one subcategory with CI 

engines 51-99 HP for the final rule and are subject to work or management standards. 

14.2.15 Comment: One commenter (139) noted that the preamble of the proposed rule and 

Tables 2d of the proposed rule appear inconsistent in their treatment of emergency CI RICE 

greater than 500 HP. Table 2d of the proposed rule indicates that these engines are subject to a 

numeric limit of 40 ppmvd. The numeric limit is based on the best performing uncontrolled 

sources and, as such, many RICE cannot meet the standard without add-on controls. In contrast, 

the preamble states: "...all stationary emergency RICE are only subject to compliance 

requirements in the form of management practices to minimize emissions." 74 Fed. Reg. 791 1. 

Accordingly, the commenter (139) requested that EPA revise the requirements applicable to 

emergency CI RICE greater than 500 HP to ensure consistency between the proposed regulatory 

language and the Agency's intent. 

Response: The statement that the commenter cited in the preamble was only referring to the 

requirements for demonstrating compliance and not the actual emission or operating limitations 

for the engines. EPA recognizes that the language may have been confusing and has tried to 

make the requirements as clear as possible in the final rule. In any case, the final rule requires 
336

management practice standards for emergency engines above 500 HP at area sources. 

Emergency engines above 500 HP located at major sources were not subject to this rule.

14.2.16 Comment: Two commenters (98, 157) took issue with the proposal preamble discussion 

of oxidation catalysts, believing that the language presented in the preamble should be revised to 

clarify that oxidation catalysts are an appropriate device to reduce HAP emissions from CI 

engines. The commenter (98) noted that CDPF may be more effective at removing PM from CI 

engine exhaust, but are admittedly more expensive. The commenter (98) asserted that intention 

of this rule is to reduce HAP by reducing emissions of their surrogate, which for CI engines is 

CO not PM. Consequently, the commenter recommended that the language in the preamble be 

revised as follows: 

Oxidation catalysts are another type of aftertreatment that can be applied to diesel 

or natural gas fired stationary engines and are typically used with lean burn 

engines. The technology can be applied to either diesel or natural gas fired lean 

burn engines. 

Response: EPA believes the commenters are referring to the following statement in the proposed 

preamble language on page 9705 of the Federal Register notice: 

“Oxidation catalysts are another type of aftertreatment that can be applied to stationary engines 

and are typically used with lean burn engines. The technology can be applied to either diesel or 

natural gas fired lean burn engines.” The purpose of the first part of the statement is to indicate 

that oxidation catalyst is an appropriate technology for lean burn, and not rich burn engines. 

Lean burn engines as used in this context refers to diesel and natural gas engines as diesel 
337

engines are considered “lean.” EPA makes it clear in the second sentence of the above cited 

statement that oxidation catalyst can be used on either diesel engines or natural gas lean burn 

engines. EPA believes this is clear and does not think the commenters’ specific language 

revisions are necessary. 

14.2.17 Comment: One commenter (126) requested that the SI and CI subcategories be defined 

and clarified. The commenter (126) believes that EPA intended to provide the SI category as a 

“catch-all” for any spark ignition engines that do not fall into other categories.

Response: There are definitions for SI and CI in §63.6675. The commenter did not provide any 

information regarding what needs to be clarified for these subcategories, therefore EPA is unable 

to fully respond to the comment. 

14.2.18 Comment: One commenter (175) asked for clarification on whether the requirements in 

Table 2d of the proposed rule apply to engines manufactured prior to June 12, 2004. The 

commenter (175) indicated that it thought that under 40 CFR 63.6590(c), the standard for new 

area source engines manufactured after June 12, 2006, would be equivalent to NSPS, and that the 

NSPS requires a maintenance plan that is not as prescriptive as the oil, filter and spark plug 

replacement schedule in the proposed rule for existing engines less than 50 HP.

Response: The proposed Table 2d applies to existing stationary RICE located at an area source 

of HAP emissions. Section 63.6590 of subpart ZZZZ states that a stationary RICE located at an 
338

area source of HAP emissions is considered existing if construction of the engine commenced 

before June 12, 2006. 

14.3 Errors 

14.3.1 Comment: Several commenters (63, 96, 99, 116, 146, 155, 159, 193, 224, 227, 242) noted 

errors in the use of mathematical symbols in the proposed rule preamble and rule tables and 

provided corrections to the tables. The commenters (155, 242) indicated that the “≥” symbol 

should be changed to “≤” in several cases, e.g., “50≥HP≤249” should be changed to 

“50≤HP≤249.” Commenter 99 said that for example 50>HP<500 should be changed to 

50<HP<500. 

Response: The commenters are correct that some of the mathematical symbols in the proposed 

rule were incorrect. EPA has corrected the typos concerning the use of the ≤, ≥, <, and > signs in 

the final rule. 

14.3.2 Comment: One commenter (242) stated that in the EPA Fact Sheet and February 27 

News Release EPA said that the rule sets emission standards for engines that “have a site rating 

of greater than 500 HP, are located at major sources of air toxics emissions, and were constructed 

or reconstructed before December 19, 2002.” The commenter (242) said that the referenced 

engines are the engines covered by the 2004 RICE NESHAP, where existing rich burn engines 

where the only existing sources that required add-on controls. The proposed rule sets new 

requirements for existing diesel engines, but not existing natural gas engines greater than 500 HP 
339

at major sources. So it appears the EPA Fact Sheet and New Release contain errors, according to 

the commenter (242). It should be clarified in these publications that the proposed rule sets 

standards for existing diesel engines greater than 500 HP at major sources and SSM limits for 

natural gas rich burn engines greater than 500 HP at major sources. 

Response: EPA does not necessarily agree with the commenter that the February 25, 2009 Fact 

Sheet available at http://www.epa.gov/ttn/oarpg/t3/fact_sheets/rice_neshap_prop_fs_022509.pdf

was inaccurate. The applicability dates that distinguish stationary existing engines from 

stationary new engines are specified in 40 CFR 63.6590(a). Per 63.6590(a)(1)(i), stationary 

engines greater than 500 HP located at major sources of HAP emissions are considered existing 

if construction or reconstruction is commenced prior to December 19, 2002. This is consistent 

with bullet one, sub-bullet three, under the title “Action” in the February 25, 2009 Fact Sheet, 

which was intended for the existing stationary diesel engines greater than 500 HP located at 

major sources that EPA is addressing in this rulemaking. EPA could have been clearer in this 

bullet by stating that new emission standards only apply to existing diesel engines greater than 

500 HP at major sources, and not to natural gas engines, as well as specifying the applicability of 

the SSM limits that were being co-proposed. For the final rule, EPA has made sure that the Fact 

Sheet and other material are clear. 

14.3.3 Comment: One commenter (96) said that if EPA keeps standards for engines less than 50 

HP there needs to be a separate subcategory for emergency engines.
340

Response: The commenter did not provide any information to justify the need for a separate 

subcategory for emergency engines smaller than 50 HP. In any case, both emergency and nonemergency engines smaller than 50 HP are subject to either work or management practices under 

the final rule. The practices for emergency engines are slightly different from those for nonemergency engines. 

14.3.4 Comment: One commenter (186) noted that there is a typographical error on page 9711 

of the preamble where it says "of three years" instead of "or three years." 

Response: The commenter is correct. 

14.4 Discrepancies 

14.4.1 Comment: One commenter (193) noted that the §63.6640(f) requirement that precludes 

maintenance checks and readiness testing, unless it is recommended by governmental authorities, 

engine manufacturers, or insurance companies, conflicts with the proposed requirement in 

§63.6625. The problematic wording of §63.6640(f) establishes a prohibition to the operation of 

an emergency RICE for maintenance and readiness testing purposes unless the owner or operator 

possesses a recommendation from one of the listed entities. The commenter (0193) believes that 

if EPA is to require owners and operators to develop plans for the maintenance and operation of 

emergency engines, in the absence of recommended practices from “Federal, State or local 

government, the manufacturer, the vendor, or the insurance company,” it should not construct 

accompanying regulatory requirements that do not include the owner or operator developed 
341

maintenance and operation plans as valid criteria for authorizing maintenance and readiness 

testing activities. 

Response: EPA does not agree with the commenter that §63.6640(f) should include maintenance 

checks developed solely by the owner/operator and having no input whatsoever from one of the 

entities listed in §63.6640(f). 

14.4.2 Comment: One commenter (178) noted discrepancies in the applicability of the rule as 

presented in the text and tables. The commenter (178) states that in several places the tables do 

not support the text concerning applicability of the rule to specific RlCE unit types. There are 

numerous inconsistencies between the requirements for large stationary engines and smaller 

ones, and between those located at major sources and those at area sources. Although there are 

many more examples, the following are instances of inconsistency: 

• EPA should confirm that, in the descriptions to Table 2a and 2b of the proposed rule, the 

phrase “located at a Major Source . .” applies to all the categories of RlCE contained in 

those descriptions and not just the last category of RlCE in the titles. 

• Assuming that large engines have a larger potential impact, and that requirements 

proposed for small engines are not applicable to such larger engines, it is not reasonable 

to impose such requirements on small engines. For example, the requirements for an 

emergency stationary RlCE >500 HP does not have a 100 hr run-time restriction, yet 

smaller RlCE do. The commenter (178) suggested this requirement be removed for 

smaller engines. 
342

Response: The commenter is correct that the phrase “located at a Major Source . . .” applies to 

all of the RICE listed in the titles of Tables 2a and 2b. The run-time requirements for emergency 

stationary RICE greater than 500 HP at a major source were promulgated as part of the 2004 

RICE NESHAP and are not the subject of this rulemaking. EPA does not agree with the 

commenter that the 100 hour run-time restriction on maintenance and testing operation should be 

removed for stationary RICE smaller than 500 HP and stationary RICE located at area sources. 

Having a different requirement for large engines at major sources is not a sufficient justification 

for removing the 100 hour limit. 

14.5 Other

14.5.1 Comment: A few commenters (103, 111, 150, 155, 224, 225) noted other regulations 

allow a 200 hour burn-in period for engines with catalysts that are new, reconstructed, or rebuilt. 

The commenters (155, 224) believe this allowance should also be provided for commissioning of 

an engine after major maintenance. Major maintenance may not always be considered a rebuild; 

however, an engine burn-in period would still be necessary to ensure that catalyst damage does 

not occur, the commenter (155) said. In addition, the commenter (155) also believes that 

existing engines that are retrofitted should be given a burn-in period. Again, the retrofit may not 

constitute a modification, reconstruction or rebuild, but necessary upgrades that require burn-in 

time to prevent catalyst damage may be appropriate, according to the commenter (155). The 

commenter (155) recommended that EPA revise the current language in §63.6640(d) to read as 

follows (the commenter’s (155) additions are shown in bold): 
343

“For new, reconstructed, and rebuilt stationary RICE, and stationary RICE that have 

undergone maintenance that could result in catalyst damage upon startup or equipment 

changes to comply with the requirements of this subpart, deviations from the emission or 

operating limitations that occur during the first 200 hours of operation from engine startup 

(engine burn-in period) are not violations.” 

One commenter (103) stated that EPA should incorporate a provision for a 

commissioning period into the rule whereby the RICE is allowed to operate prior to installation 

of catalytic elements in order to prevent damage to the catalytic elements during engine break in. 

The commenter (103) attributed the following quotation to EPA but gave no citation: 

“EPA understands the “commissioning period” to be the final phase of the construction 

process. Activities conducted during the commissioning period include: checking all 

mechanical, electrical, and control systems for the RICE and all related equipment; and 

confirming the performance measures specified in the purchase agreement. EPA 

understands that the commissioning period may take up to two weeks to complete. EPA 

does not consider the “commissioning period” as the initial startup of the unit as long as 

the RICE is not being used for its intended purpose or any other beneficial use at the 

facility during this time. Site-specific determinations of initial startup may be required 

for facilities that operate in a commissioning mode for excessive periods of time.” 

 Two other commenters (111, 225) similarly noted that installation of the catalyst during 

the break-in period of a new or overhauled unit (typically 50-100 hours) is likely to result in 

catalyst malfunction due to fouling, masking, or poisoning of the catalyst element. 

 Another commenter (150) urged EPA to address the potential to generate a deviation 

during an SSM event consistent with the burn-in provisions set forth in 40 CFR 63.6640(d), 
344

which provides that “deviations from the emission or operating limits that occur during the first 

200 hours of operation from engine startup (engine burn-in period) are not violations.” This 

commenter (150) added that if the rules are promulgated not to allow burn-in time, costs would 

be increased due to the need to wash or replace catalyst which would be masked if left on during 

this period to meet emissions requirements. 

Response: EPA does not agree that it should provide a burn-in period in subpart ZZZZ for 

retrofitted engines or engines that have been subject to maintenance short of a rebuild. EPA does 

not have any information to indicate that retrofitted engines or engines subject to maintenance 

would not be able to meet the requirements of subpart ZZZZ immediately after the retrofit or 

maintenance, and therefore does not agree that such an exemption from the rule requirements 

should be provided. EPA notes that the pre-existing burn-in period for new, reconstructed and 

rebuilt engines has not been revised. Regarding the comments that stated that RICE should be 

allowed to operate prior to installation of catalyst elements, EPA does not agree that this is 

necessary because this rulemaking affects existing engines that have already been operated. In 

addition, sources have three years to comply with this rulemaking so they have sufficient time to 

operate their engines prior to catalyst installation and also have sufficient time to operate their 

engine following catalyst installation prior to the compliance date of the rule. 

14.5.2 Comment: One commenter (242) requested that EPA specify in the final rule that no 

more than one end of pipe control is required. According to the commenter (242), other air 

quality jurisdictions may require a CDPF or oxidation catalyst under separate regulations and the 

commenter believes that EPA should incorporate language stating that for diesel engines with 
345

CDPF or oxidation catalyst additional controls should not be required to ensure that engine and 

stack parameters are within the appropriate range that is required to satisfy engine performance 

(e.g., in-use output requirements) and control device performance, such as exhaust temperature 

or pressure drop. 

Response: EPA does not agree that it would be appropriate to specify that other air quality 

jurisdictions cannot require additional emission controls. 

14.5.3 Comment: One commenter (242) said that EPA’s failure to issue a proposed rule 

amendment with strikethrough and additions creates additional burden on the community and a 

rule with strikethrough and addition text would have eliminated the need to review and compare 

the previous rule text. The commenter (242) urged EPA to use this approach in future rule 

revisions to minimize rule interpretation issues and intent, inconsistencies, conflicts and 

unnecessary regulatory uncertainties. 

Response: EPA agrees with the commenter that a redline/strikeout copy of the rule would be 

useful in reviewing the amendments. However EPA does not agree that the failure to do so 

creates an undue burden on the community. 

14.5.4 Comment: A few commenters (127, 128) provided information regarding crankcase 

ventilation. One commenter (128) who indicated that it was in full support of commenter’s 155 

recommendations also responded to EPA’s request for comment on the use of CCV systems as a 

technology possibly able to reduce HAP emissions. The commenter (128) does not believe such 
346

systems would significantly reduce HAP emissions because emissions from such ventilation 

systems are minimal fugitive emissions and any reductions associated with such systems would 

be insignificant and does not justify the use of a closed system and the commenter recommends 

that this technology not be required in the final rule. 

Commenter 127 reported that estimates to retrofit its existing generators with these 

systems would cost between $5,000 and $10,000 per generator with some of the larger ones 

costing more. The commenter (127) also reported that the annual preventative maintenance costs 

would rise an additionally $200 to $500 per generator over the cost of its current maintenance 

program. This commenter (127) expressed that this increased cost when averaged over the few 

hours emergency generators operate in at area sources further supports its request that EPA limit 

the requirements for all emergency generators located at area sources to management practices 

only. 

Commenter 96 provided additional information on crankcase ventilation controls to EPA 

after the close of the comment period. The commenter suggested that metallic HAP emissions 

could potentially be reduced through the use of open crankcase filtration control systems. The 

commenter stated that open crankcase filtration control systems can remove upwards of 60-80% 

of the oil mist. 

Response: While emissions from the crankcase are only a small portion of total engine 

emissions, the crankcase emissions are expected to be one of the main sources of metallic HAP 

emissions from stationary diesel engines. The majority of existing stationary CI engines route 

blow-by emissions from the pistons to the crankcase which is open to the atmosphere to prevent 

pressure buildup (referred to as open crankcase ventilation). Blow-by emissions are the result of 
347

high pressure gases and oils escaping around piston rings and venting to the atmosphere. These 

blow-by gases contain small oil droplets and eroded metals from the pistons. EPA therefore does 

not agree with the commenter that the use of closed crankcase ventilation systems would not 

significantly reduce HAP emissions, at least for metallic HAP, and has included a requirement in 

the final rule that existing non-emergency CI engines larger than 300 HP be equipped with either 

open or closed crankcase ventilation systems to reduce the crankcase emissions from the engine. 

Open crankcase systems filter the crankcase cases to reduce oil mist before venting the crankcase 

gases to the atmosphere. Closed crankcase systems route the crankcase gases back to the 

combustion chamber, where the crankcase gases are combusted with the fuel mixture, or to the 

engine exhaust. EPA agrees with the comment that emergency engines should not be required to 

be retrofit with crankcase emission control systems. These engines are typically operated very 

infrequently and therefore the cost of the retrofit is not justified when compared to the emission 

reduction that would result.