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6560-50-P 

EO-12866_Refinery RTR 2060- AQ-75 NPRM RTR_20140226514

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Parts 60 and 63 

[EPA-HQ-OAR-2010-0682; FRL- 9720-4] 

RIN 2060-AQ75 

Petroleum Refinery Sector Risk and Technology Review and New 

Source Performance Standards 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: This action proposes amendments to the national 

emission standards for hazardous air pollutants for petroleum 

refineries (40 CFR part 63, subparts CC and UUU) to address the 

risk remaining after application of the standards promulgated in 

1995 and 2002. This action also proposes amendments to the 

national emission standards for hazardous air pollutants for 

petroleum refineries based on the results of the Environmental 

Protection Agency (EPA) review of developments in practices, 

processes and control technologies and includes new monitoring, 

recordkeeping and reporting requirements. The EPA is also 

proposing new requirements related to emissions during periods 

of startup, shutdown and malfunction to ensure that the 

standards are consistent with court opinions issued since 

promulgation of the standards. This action also proposes 
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technical corrections and clarifications for new source 

performance standards for petroleum refineries (40 CFR part 60, 

subparts J and Ja) in an effort to improve consistency and 

clarity and address issues raised after the 2008 rule 

promulgation. Implementation of this proposed rule will result 

in projected reductions of 1,760 tons per year (tpy) of 

hazardous air pollutants (HAP), which will reduce cancer risk 

and chronic health effects. 

DATES: Comments. Comments must be received on or before [INSERT 

DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

A copy of comments on the information collection provisions 

should be submitted to the Office of Management and Budget (OMB) 

on or before [INSERT DATE 30 DAYS AFTER DATE OF PUBLICATION IN 

THE FEDERAL REGISTER]. 

Public Hearing. The EPA will be holding public hearings on this 

proposed rule on DATES at LOCATION and CITY. [Note: Coordinate 

w/Angela Hackel.]

ADDRESSES: Comments. Submit your comments, identified by Docket 

ID Number EPA-HQ-OAR-2010-0682, by one of the following methods: 

 http://www.regulations.gov: Follow the on-line instructions 

for submitting comments. 

 Email: a-and-r-docket@epa.gov. Attention Docket ID Number 

EPA-HQ-OAR-2010-0682. 

Formatted: Highlight
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 Fax: (202) 566-9744. Attention Docket ID Number EPA-HQ-OAR2010-0682. 

 Mail: U.S. Postal Service, send comments to: EPA Docket 

Center, EPA WestWilliam Jefferson Clinton (WJC) West 

Building (Air Docket), Attention Docket ID Number EPA-HQOAR-2010-0682, U.S. Environmental Protection Agency, 

Mailcode: 28221T, 1200 Pennsylvania Ave., NW, Washington, 

DC 20460. Please include a total of two copies. In 

addition, please mail a copy of your comments on the 

information collection provisions to the Office of 

Information and Regulatory Affairs, Office of Management 

and Budget (OMB), Attn: Desk Officer for EPA, 725 17th

Street, NW, Washington, DC 20503. 

 Hand Delivery: U.S. Environmental Protection Agency, EPAWJC

West Building (Air Docket), Room 3334, 1301 Constitution 

Ave., NW, Washington, DC 20004. Attention Docket ID Number 

EPA-HQ-OAR-2010-0682. Such deliveries are only accepted 

during the Docket’s normal hours of operation, and special 

arrangements should be made for deliveries of boxed 

information. 

Instructions. Direct your comments to Docket ID Number EPAHQ-OAR-2010-0682. The EPA’s policy is that all comments received 

will be included in the public docket without change and may be 
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made available online at http://www.regulations.gov, including 

any personal information provided, unless the comment includes 

information claimed to be confidential business information 

(CBI) or other information whose disclosure is restricted by 

statute. Do not submit information that you consider to be CBI 

or otherwise protected through http://www.regulations.gov or 

email. The http://www.regulations.gov website is an “anonymous 

access” system, which means the EPA will not know your identity 

or contact information unless you provide it in the body of your 

comment. If you send an email comment directly to the EPA 

without going through http://www.regulations.gov, your email 

address will be automatically captured and included as part of 

the comment that is placed in the public docket and made 

available on the Internet. If you submit an electronic comment, 

the EPA recommends that you include your name and other contact 

information in the body of your comment and with any disk or CDROM you submit. If the EPA cannot read your comment due to 

technical difficulties and cannot contact you for clarification, 

the EPA may not be able to consider your comment. Electronic 

files should not include special characters or any form of 

encryption and be free of any defects or viruses. For additional 

information about the EPA’s public docket, visit the EPA Docket 

Center homepage at: http://www.epa.gov/dockets. 
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Docket. The EPA has established a docket for this 

rulemaking under Docket ID Number EPA-HQ-OAR-2010-0682. All 

documents in the docket are listed in the regulations.gov index. 

Although listed in the index, some information is not publicly 

available, e.g., CBI or other information whose disclosure is 

restricted by statute. Certain other material, such as 

copyrighted material, is not placed on the Internet and will be 

publicly available only in hard copy. Publicly available docket 

materials are available either electronically in regulations.gov 

or in hard copy at the EPA Docket Center, EPAWJC West Building, 

Room 3334, 1301 Constitution Ave., NW, Washington, DC. The 

Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 

through Friday, excluding legal holidays. The telephone number 

for the Public Reading Room is (202) 566-1744, and the telephone 

number for the EPA Docket Center is (202) 566-1742. 

Public Hearing. The public hearing will be held on [INSERT 

DATE] at [INSERT LOCATION, ADDRESS, ROOM NUMBER IF AVAILABLE]. 

The hearing will convene at [INSERT TIME] XXX a.m. (Eastern 

Standard Time) and end at [INSERT TIME] XXX p.m. (Eastern 

Standard Time). A lunch break will be held from [INSERT TIME] 

XXX pm. (Eastern Standard Time) until [INSERT TIME] XXX pm 

(Eastern Standard Time). Please contact Ms. Virginia Hunt at 

(919) 541-0832 or at hunt.virginia@epa.gov to register to speak 

at the hearing. The last day to pre-register in advance to speak 
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at the hearing will be [INSERT DATE]. Additionally, requests to 

speak will be taken the day of the hearing at the hearing 

registration desk, although preferences on speaking times may 

not be able to be fulfilled. If you require the service of a 

translator or special accommodations such as audio description, 

please let us know at the time of registration. 

FOR FURTHER INFORMATION: For questions about this proposed 

action, contact Ms. Brenda Shine, Sector Policies and Programs 

Division (E143-01), Office of Air Quality Planning and Standards 

(OAQPS), U.S. Environmental Protection Agency, Research Triangle 

Park, North Carolina 27711; telephone number: (919) 541-3608; 

fax number: (919) 541-0246; and email address: 

shine.brenda@epa.gov. For specific information regarding the 

risk modeling methodology, contact Mr. Ted Palma, Health and 

Environmental Impacts Division (C539-02), Office of Air Quality 

Planning and Standards (OAQPS), U.S. Environmental Protection 

Agency, Research Triangle Park, North Carolina 27711; telephone 

number: (919) 541–5470; fax number: (919) 541–0840; and email 

address: palma.ted@epa.gov. For information about the 

applicability of the National Emissions Standards for Hazardous 

Air Pollutants (NESHAP) or the New Source Performance Standards 

(NSPS) to a particular entity, contact Maria Malave, Office of 

Enforcement and Compliance Assurance (OECA), telephone number: 
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(202) 564–7027; fax number: (202) 564–0050; and email address: 

malave.maria@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Preamble Acronyms and Abbreviations. 

We use multiple acronyms and terms in this preamble. While 

this list may not be exhaustive, to ease the reading of this 

preamble and for reference purposes, the EPA defines the 

following terms and acronyms here: 

10/25 tpy emissions equal to or greater than 10 tons per year 

of a single pollutant or 25 tons per year of 

cumulative pollutants 

ACGIH American Conference of Governmental Industrial 

Hygienists 

ADAF age-dependent adjustment factors 

AEGL acute exposure guideline levels 

AERMOD air dispersion model used by the HEM-3 model 

APCD air pollution control devices 

API American Petroleum Institute 

BDT best demonstrated technology 

BLD bag leak detectors 

BSER best system of emission reduction 

Btu/ft2

 British thermal units per square foot 

Btu/scf British thermal units per standard cubic foot 

CAA Clean Air Act 

CalEPA California EPA 

CBI confidential business information 

CCU catalytic cracking units 

Ccz combustion zone combustibles concentration 

CDDF chlorinated dibenzodioxins and furans 

CDX Central Data Exchange 

CEDRI Compliance and Emissions Data Reporting Interface 

CEMS continuous emissions monitoring system 

CFR Code of Federal Regulations 

CO carbon monoxide 

CO2 carbon dioxide 

CO2e carbon dioxide equivalents 

COMS continuous opacity monitoring system 

COS carbonyl sulfide 

CPMS continuous parameter monitoring system 
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CRU catalytic reforming units 

CS2 carbon disulfide 

DCU delayed coking units 

DIAL differential absorption light detection and ranging 

EBU enhanced biological unit 

EPA Environmental Protection Agency 

ERPG emergency response planning guidelines 

ERT Electronic Reporting Tool 

ESP electrostatic precipitator 

FCCU fluid catalytic cracking units 

FGCD fuel gas combustion devices 

FR Federal Register 

FTIR Fourier transform infrared spectroscopy 

g PM/kg grams particulate matter per kilogram 

GC gas chromatograph 

GHG greenhouse gases 

GPS global positioning system 

H2S hydrogen sulfide 

HAP hazardous air pollutants 

HCl hydrogen chloride 

HCN hydrogen cyanide 

HEM-3 Human Exposure Model, Version 1.1.0 

HF hydrogen fluoride 

HFC highest fenceline concentration 

HI hazard index 

HQ hazard quotient 

ICR Information Collection Request 

IRIS Integrated Risk Information System 

km kilometers 

lb/day pounds per day 

LDAR leak detection and repair 

LFL lower flammability limit 

LFLcz combustion zone lower flammability limit 

LMC lowest measured concentration 

LOAEL lowest-observed-adverse-effect level 

LTD long tons per day 

MACT maximum achievable control technology 

mg/kg-day milligrams per kilogram per day 

mg/L milligrams per liter 

mg/m3

 milligrams per cubic meter 

Mg/yr megagrams per year 

MFC measured fenceline concentration 

MFR momentum flux ratio 

MIR maximum individual risk 

mph miles per hour 

NAAQS National Ambient Air Quality Standards 

NAICS North American Industry Classification System 
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NAS National Academy of Sciences 

NATA National Air Toxics Assessment 

NEI National Emissions Inventory 

NESHAP National Emissions Standards for Hazardous Air 

Pollutants 

NFS near-field interfering source 

NHVcz combustion zone net heating value 

Ni nickel 

NIOSH National Institutes for Occupational Safety and 

Health 

NOAEL no-observed-adverse-effect level 

NOX nitrogen oxides 

NRC National Research Council 

NRDC Natural Resources Defense Council 

NSPS new source performance standards 

NTTAA National Technology Transfer and Advancement Act 

OAQPS Office of Air Quality Planning and Standards 

OECA Office of Enforcement and Compliance Assurance 

OMB Office of Management and Budget 

OSC off-site source contribution 

OTM other test method 

PAH polycyclic aromatic hydrocarbons 

PB-HAP hazardous air pollutants known to be persistent and 

bio-accumulative in the environment 

PBT persistent, bioaccumulative, and toxic 

PCB polychlorinated biphenyls 

PEL probable effect level 

PM particulate matter 

PM2.5 particulate matter 2.5 micrometers in diameter and 

smaller 

POM polycyclic organic matter 

ppm parts per million 

ppmv parts per million by volume 

ppmw parts per million by weight 

PEL Probable effect level 

psia pounds per square inch absolute 

psig pounds per square inch gauge 

REL reference exposure level 

REM Model Refinery Emissions Model 

RFA Regulatory Flexibility Act 

RfC reference concentration 

RfD reference dose 

RTR residual risk and technology review 

SAB Science Advisory Board 

SBA Small Business Administration 

SBAR Small Business Advocacy Review 

SCR selective catalytic reduction 
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SISNOSE significant economic impact on a substantial number 

of small entities 

S/L/Ts state, local and tribal air pollution control 

agencies 

SO2 sulfur dioxide 

SRU sulfur recovery unit 

SSM startup, shutdown and malfunction 

STEL short-term exposure limit 

TEQ toxicity equivalent 

TLV threshold limit value 

TOC total organic carbon 

TOSHI target organ-specific hazard index 

tpy tons per year 

TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, 

and Ecological Exposure model 

TTN Technology Transfer Network 

UB uniform background 

UF uncertainty factor 

UMRA Unfunded Mandates Reform Act 

URE unit risk estimate 

UV-DOAS ultraviolet differential optical absorption 

spectroscopy 

VCS voluntary consensus standards 

VOC volatile organic compounds 

WJC William Jefferson Clinton 

°F degrees Fahrenheit 

ΔC the concentration difference between the highest 

measured concentration and the lowest measured 

concentration 

μg/m3

 micrograms per cubic meter 

The EPA also defines the following abbreviations for 

regulations cited within this preamble: 

AWP Alternative Work Practice To Detect Leaks 

From Equipment (40 CFR 63.11(c), (d) and (e)) 

Benzene NESHAP National Emission Standards for Hazardous Air 

Pollutants: Benzene Emissions from Maleic 

Anhydride Plants, Ethylbenzene/Styrene 

Plants, Benzene Storage Vessels, Benzene 

Equipment Leaks, and Coke By-Product Recovery 

Plants (40 CFR part 61, subpart L as of 

publication in the Federal Register at 54 FR 

38044, September 14, 1989) 
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BWON National Emission Standard for Benzene Waste 

Operations (40 CFR part 61, subpart FF) 

Generic MACT National Emission Standards for Storage 

Vessels (40 CFR part 63, subpart WW) 

HON National Emission Standards for Organic 

Hazardous Air Pollutants (40 CFR part 63, 

subparts F, G and H) 

Marine Vessel MACT National Emission Standards for Marine Tank 

Vessel Loading Operations (40 CFR part 63, 

subpart Y) 

Refinery MACT 1 National Emission Standards for Hazardous Air 

Pollutants From Petroleum Refineries (40 CFR 

part 63, subpart CC) 

Refinery MACT 2 National Emission Standards for Hazardous Air 

Pollutants for Petroleum Refineries: 

Catalytic Cracking Units, Catalytic Reforming 

Units, and Sulfur Recovery Units (40 CFR part 

63, subpart UUU) 

Refinery NSPS J Standards of Performance for Petroleum 

Refineries (40 CFR part 60, subpart J) 

Refinery NSPS Ja Standards of Performance for Petroleum 

Refineries for which Construction, 

Reconstruction, or Modification Commenced 

After May 14, 2007 (40 CFR part 60, subpart 

Ja) 

Organization of This Document. The information in this 

preamble is organized as follows: 

I. General Information 

A. Does this action apply to me? 

B. Where can I get a copy of this document and other related 

information? 

C. What should I consider as I prepare my comments for the EPA? 

D. Public Hearing 

II. Background 

A. What is the statutory authority for this action? 

B. What are the source categories and how do the NESHAP and NSPS 

regulate emissions? 

C. What data collection activities were conducted to support 

this action? 

D. What other relevant background information and data are 

available? 

III. Analytical Procedures 
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A. How did we estimate post-MACT risks posed by the source 

categories? 

B. How did we consider the risk results in making decisions for 

this proposal? 

C. How did we perform the technology review? 

IV. Analytical Results and Proposed Decisions 

A. What actions are we taking pursuant to CAA Ssections 

112(d)(2) and 112(d)(3)? 

B. What are the results and proposed decisions based on our 

technology review? 

C. What are the results of the risk assessment and analyses? 

D. What are our proposed decisions regarding risk acceptability, 

ample margin of safety and adverse environmental effects? 

E. What other actions are we proposing? 

F. What compliance dates are we proposing? 

V. Summary of Cost, Environmental and Economic Impacts 

A. What are the affected sources, the air quality impacts and 

cost impacts? 

B. What are the economic impacts? 

C. What are the benefits? 

VI. Request for Comments 

VII. Submitting Data Corrections 

VIII. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review and 

Executive Order 13563: Improving Regulation and Regulatory 

Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation and Coordination with 

Indian Tribal Governments 

G. Executive Order 13045: Protection of Children from 

Environmental Health Risks and Safety Risks 

H. Executive Order 13211: Actions Concerning Regulations That 

Significantly Affect Energy Supply, Distribution, or Use 

I. National Technology Transfer and Advancement Act 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations 
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A redline version of the regulatory language that 

incorporates the proposed changes in this action is available in 

the docket for this action (Docket ID No. EPA-HQ-OAR-2010-0682). 

I. General Information 

A. Does this action apply to me? 

Table 1 of this preamble lists the industries that are the 

subject of this proposal. Table 1 is not intended to be 

exhaustive but rather to provide a guide for readers regarding 

the entities that this proposed action is likely to affect. 

These proposed standards, once promulgated, will be directly 

applicable to the affected sources. Thus, federal, state, local 

and tribal government entities would not be affected by this 

proposed action. As defined in the “Initial List of Categories 

of Sources Under Section 112(c)(1) of the Clean Air Act 

Amendments of 1990” (see 57 FR 31576, July 16, 1992), the 

“Petroleum Refineries - Catalytic Cracking (Fluid and other) 

Units, Catalytic Reforming Units, and Sulfur Plant Units” source 

category and the “Petroleum Refineries - Other Sources Not 

Distinctly Listed” both consist of any facility engaged in 

producing gasoline, naphthas, kerosene, jet fuels, distillate 

fuel oils, residual fuel oils, lubricants, or other products 

from crude oil or unfinished petroleum derivatives. The first of 

these source categories includes process vents associated with 

the following refinery process units: catalytic cracking (fluid 
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and other) units, catalytic reforming units and sulfur plant 

units. The second source category includes all emission sources 

associated with refinery process units except the process vents 

listed in the Petroleum Refineries – Catalytic Cracking (Fluid 

and Other) Units, Catalytic Reforming Units, and Sulfur Plant 

Units Source Category. The emission sources included in this 

source category include, but are not limited to, miscellaneous 

process vents (vents other than those listed in Petroleum 

Refineries – Catalytic Cracking (Fluid and Other) Units, 

Catalytic Reforming Units, and Sulfur Plant Units Source 

Category), equipment leaks, storage vessels, wastewater, 

gasoline loading, marine vessel loading, and heat exchange 

systems. 

Table 1. Industries Affected by this Proposed Action 

Industry 

NAICSa

Code Examples of Regulated Entities 

Petroleum Refining 

Industry 

324110 Petroleum refinery sources that 

are subject to 40 CFR part 60, 

subpart J and Ja and 40 CFR part 

63, subparts CC and UUU a

 North American Industry Classification System 

B. Where can I get a copy of this document and other related 

information? 

In addition to being available in the docket, an electronic 

copy of this action is available on the Internet through the 

EPA’s Technology Transfer Network (TTN) website, a forum for 
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information and technology exchange in various areas of air 

pollution control. Following signature by the EPA Administrator, 

the EPA will post a copy of this proposed action on the TTN’s 

policy and guidance page for newly proposed or promulgated rules 

at: http://www.epa.gov/ttn/oarpg/t3pfpr.html. Following 

publication in the Federal Register, the EPA will post the 

Federal Register version of the proposal and key technical 

documents on the project website: 

http://www.epa.gov/ttn/atw/petref.html. Information on the 

overall residual risk and technology review (RTR) program is 

available at the following website: 

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. 

C. What should I consider as I prepare my comments for the EPA? 

Submitting CBI. Do not submit information containing CBI to 

the EPA through http://www.regulations.gov or email. Clearly 

mark the part or all of the information that you claim to be 

CBI. For CBI information on a disk or CD-ROM that you mail to 

the EPA, mark the outside of the disk or CD-ROM as CBI and then 

identify electronically within the disk or CD-ROM the specific 

information that is claimed as CBI. In addition to one complete 

version of the comments that includes information claimed as 

CBI, you must submit a copy of the comments that does not 

contain the information claimed as CBI for inclusion in the 

public docket. If you submit a CD-ROM or disk that does not 
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contain CBI, mark the outside of the disk or CD-ROM clearly that 

it does not contain CBI. Information not marked as CBI will be 

included in the public docket and the EPA’s electronic public 

docket without prior notice. Information marked as CBI will not 

be disclosed except in accordance with procedures set forth in 

40 Code of Federal Regulations (CFR) part 2. Send or deliver 

information identified as CBI only to the following address: 

Roberto Morales, OAQPS Document Control Officer (C404-02), 

OAQPS, U.S. Environmental Protection Agency, Research Triangle 

Park, North Carolina 27711, Attention Docket ID Number EPA-HQOAR-2010-0682. 

D. Public Hearing 

The hearing will provide interested parties the opportunity 

to present data, views or arguments concerning the proposed 

action. The EPA will make every effort to accommodate all 

speakers who arrive and register. Because this hearing will be 

at a U.S. governmental facility, individuals planning to attend 

the hearing should be prepared to show valid picture 

identification to the security staff in order to gain access to 

the meeting room. In addition, you will need to obtain a 

property pass for any personal belongings you bring with you. 

Upon leaving the building, you will be required to return this 

property pass to the security desk. No large signs will be 

allowed in the building, cameras may only be used outside of the 
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building and demonstrations will not be allowed on federal 

property for security reasons. The EPA may ask clarifying 

questions during the oral presentations but will not respond to 

the presentations at that time. Written statements and 

supporting information submitted during the comment period will 

be considered with the same weight as oral comments and 

supporting information presented at the public hearing. Written 

comments on the proposed rule must be postmarked by [INSERT DATE 

60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

Commenters should notify Ms. Virginia Hunt if they will need 

specific equipment, or if there are other special needs related 

to providing comments at the hearing. The EPA will provide 

equipment for commenters to show overhead slides or make 

computerized slide presentations if we receive special requests 

in advance. Oral testimony will be limited to 5 minutes for each 

commenter. The EPA encourages commenters to provide the EPA with 

a copy of their oral testimony electronically (via email or CD) 

or in hard copy form. Verbatim transcripts of the hearings and 

written statements will be included in the docket for the 

rulemaking. The EPA will make every effort to follow the 

schedule as closely as possible on the day of the hearing; 

however, please plan for the hearing to run either ahead of 

schedule or behind schedule. Information regarding the hearing 
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will be available at: 

http://www.epa.gov/ttnatw01/petrefine/petrefpg.html. 

II. Background 

A. What is the statutory authority for this action? 

1. NESHAP 

Section 112 of the Clean Air Act (CAA) establishes a twostage regulatory process to address emissions of hazardous air 

pollutants (HAP) from stationary sources. In the first stage, 

after the EPA has identified categories of sources emitting one 

or more of the HAP listed in CAA Ssection 112(b), CAA Ssection 

112(d) requires us to promulgate technology-based national 

emissions standards for hazardous air pollutants (NESHAP) for 

those sources. “Major sources” are those that emit or have the 

potential to emit 10 tons per year (tpy) or more of a single HAP 

or 25 tpy or more of any combination of HAP. For major sources, 

the technology-based NESHAP must reflect the maximum degree of 

emissions reductions of HAP achievable (after considering cost, 

energy requirements and non-air quality health and environmental 

impacts) and are commonly referred to as maximum achievable 

control technology (MACT) standards. 

MACT standards must reflect the maximum degree of emissions 

reduction achievable through the application of measures, 

processes, methods, systems or techniques, including, but not 

limited to, measures that (1) reduce the volume of or eliminate 
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pollutants through process changes, substitution of materials or 

other modifications; (2) enclose systems or processes to 

eliminate emissions; (3) capture or treat pollutants when 

released from a process, stack, storage or fugitive emissions 

point; (4) are design, equipment, work practice or operational 

standards (including requirements for operator training or 

certification); or (5) are a combination of the above. CAA 

Ssection 112(d)(2)(A)-(E). The MACT standards may take the form 

of design, equipment, work practice or operational standards 

where the EPA first determines either that (1) a pollutant 

cannot be emitted through a conveyance designed and constructed 

to emit or capture the pollutant, or that any requirement for, 

or use of, such a conveyance would be inconsistent with law; or 

(2) the application of measurement methodology to a particular 

class of sources is not practicable due to technological and 

economic limitations. CAA Ssection 112(h)(1)-(2). 

The MACT “floor” is the minimum control level allowed for 

MACT standards promulgated under CAA Ssection 112(d)(3) and may 

not be based on cost considerations. For new sources, the MACT 

floor cannot be less stringent than the emissions control that 

is achieved in practice by the best-controlled similar source. 

The MACT floor for existing sources can be less stringent than 

floors for new sources but not less stringent than the average 

emissions limitation achieved by the best-performing 12 percent 
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of existing sources in the category or subcategory (or the bestperforming five sources for categories or subcategories with 

fewer than 30 sources). In developing MACT standards, the EPA 

must also consider control options that are more stringent than 

the floor. We may establish standards more stringent than the 

floor based on considerations of the cost of achieving the 

emission reductions, any non-air quality health and 

environmental impacts and energy requirements. 

The EPA is then required to review these technology-based 

standards and revise them “as necessary (taking into account 

developments in practices, processes, and control technologies)” 

no less frequently than every eight years. CAA Ssection 

112(d)(6). In conducting this review, the EPA is not required to 

recalculate the MACT floor. Natural Resources Defense Council 

(NRDC) Vv. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008). 

Association of Battery Recyclers, Inc. Vv. EPA, 716 F.3d 667 

(D.C. Cir. 2013). 

The second stage in standard-setting focuses on reducing 

any remaining (i.e., “residual”) risk according to CAA section 

112(f). Section 112(f). This provision requires, first,(1) 

required that the EPA by November 1996 prepare a report to 

Congress discussing (among other things) methods of calculating 

the risks posed (or potentially posed) by sources after 

implementation of the MACT standards, the public health 
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significance of those risks and the EPA’s recommendations as to 

legislation regarding such remaining risk. The EPA prepared and 

submitted the Residual Risk Report to Congress, EPA–453/R–99–001 

(Risk Report) in March 1999. CAA section 112(f)(2) then provides 

that if Congress diddoes not act on any recommendation in 

response, thereby triggering the EPA’s obligation under CAA 

Section 112(f)(2) toRisk Report, the EPA must analyze and 

address residual risk for each category or subcategory of 

sources 8 years after promulgation of such standards pursuant to 

CAA section 112(d). 

Section 112(f)(2) of the CAA requires the EPA to determine 

for source categories subject to MACT standards whether the 

emission standards provide an ample margin of safety to protect 

public health. Section 112(f)(2)(B) of the CAA expressly 

preserves the EPA’s use of the two-step process for developing 

standards to address any residual risk and the agency’s 

interpretation of “ample margin of safety” developed in the 

National Emissions Standards for Hazardous Air Pollutants: 

Benzene Emissions from Maleic Anhydride Plants, 

Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene 

Equipment Leaks, and Coke By-Product Recovery Plants (Benzene 

NESHAP) (54 FR 38044, September 14, 1989). The EPA notified 

Congress in the Risk Report that the agency intended to use the 

Benzene NESHAP approach in making CAA Ssection 112(f) residual 
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risk determinations (EPA–453/R–99–001, p. ES–11). The EPA 

subsequently adopted this approach in its residual risk 

determinations and in a challenge to the risk review for the 

Synthetic Organic Chemical Manufacturing source category, the 

United States Court of Appeals for the District of Columbia 

Circuit upheld as reasonable the EPA’s interpretation that 

subsection 112(f)(2) incorporates the standards established in 

the Benzene NESHAP. See NRDC Vv. EPA, 529 F.3d 1077, 1083 (D.C. 

Cir. 2008)(“[S]ubsection 112(f)(2)(B) expressly incorporates the 

EPA’s interpretation of the Clean Air Act from the Benzene 

standard, complete with a citation to the Federal Register.”); 

see also A Legislative History of the Clean Air Act Amendments 

of 1990, vol. 1, p. 877 (Senate debate on Conference Report). 

The first step in the process of evaluating residual risk 

is the determination of acceptable risk. If risks are 

unacceptable, the EPA cannot consider cost in identifying the 

emissions standards necessary to bring risks to an acceptable 

level. The second step is the determination of whether standards 

must be further revised in order to provide an ample margin of 

safety to protect public health. The ample margin of safety is 

the level at which the standards must be set, unless an even 

more stringent standard is necessary to prevent, taking into 

consideration costs, energy, safety and other relevant factors, 

an adverse environmental effect. 
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a. Step 1-Determining Acceptability 

The agency in the Benzene NESHAP concluded that “that the 

acceptability of risk under Ssection 112 is best judged on the 

basis of a broad set of health risk measures and information” 

and that the “judgment on acceptability cannot be reduced to any 

single factor.” Id. at 38046. The determination of what 

represents an “acceptable” risk is based on a judgment of “what 

risks are acceptable in the world in which we live” (Risk Report 

at 178, quoting NRDC Vv. EPA, 824 F. 2d 1146, 1165 (D.C. Cir. 

1987) (en banc) (“Vinyl Chloride”), recognizing that our world 

is not risk-free. 

In the Benzene NESHAP, we stated that “EPA will generally 

presume that if the risk to [the maximum exposed] individual is 

no higher than approximately one in 10 thousand, that risk level 

is considered acceptable.” 54 FR at 38045, September 14, 1989. 

We discussed the maximum individual lifetime cancer risk (or 

maximum individual risk (MIR)) as being “the estimated risk that 

a person living near a plant would have if he or she were 

exposed to the maximum pollutant concentrations for 70 years.” 

Id. We explained that this measure of risk “is an estimate of 

the upper bound of risk based on conservative assumptions, such 

as continuous exposure for 24 hours per day for 70 years.” Id. 

We acknowledged that maximum individual lifetime cancer risk 

“does not necessarily reflect the true risk, but displays a 
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conservative risk level which is an upper-bound that is unlikely 

to be exceeded.” Id. 

Understanding that there are both benefits and limitations 

to using the MIR as a metric for determining acceptability, we 

acknowledged in the Benzene NESHAP that “consideration of 

maximum individual risk * * * must take into account the 

strengths and weaknesses of this measure of risk.” Id. 

Consequently, the presumptive risk level of 100-in-1 million (1-

in-10 thousand) provides a benchmark for judging the 

acceptability of maximum individual lifetime cancer risk, but 

does not constitute a rigid line for making that determination. 

Further, in the Benzene NESHAP, we noted that: 

“[p]articular attention will also be accorded to the weight 

of evidence presented in the risk assessment of potential 

carcinogenicity or other health effects of a pollutant. 

While the same numerical risk may be estimated for an 

exposure to a pollutant judged to be a known human 

carcinogen, and to a pollutant considered a possible human 

carcinogen based on limited animal test data, the same 

weight cannot be accorded to both estimates. In considering 

the potential public health effects of the two pollutants, 

the Agency’s judgment on acceptability, including the MIR, 

will be influenced by the greater weight of evidence for 

the known human carcinogen.” 

Id. at 38046. The agency also explained in the Benzene NESHAP 

that: 

“[i]n establishing a presumption for MIR, rather than a 

rigid line for acceptability, the Agency intends to weigh 

it with a series of other health measures and factors. 

These include the overall incidence of cancer or other 

serious health effects within the exposed population, the 

numbers of persons exposed within each individual lifetime 
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risk range and associated incidence within, typically, a 50 

km exposure radius around facilities, the science policy 

assumptions and estimation uncertainties associated with 

the risk measures, weight of the scientific evidence for 

human health effects, other quantified or unquantified 

health effects, effects due to co-location of facilities, 

and co-emission of pollutants.” 

Id. at 38045. In some cases, these health measures and factors 

taken together may provide a more realistic description of the 

magnitude of risk in the exposed population than that provided 

by maximum individual lifetime cancer risk alone. 

As noted earlier, in NRDC Vv. EPA, the court held that 

Ssection 112(f)(2) “incorporates the EPA’s interpretation of the 

Clean Air Act from the Benzene Standard.” The court further held 

that Congress’ incorporation of the Benzene standard applies 

equally to carcinogens and non-carcinogens. 529 F.3d at 1081-82. 

Accordingly, we also consider non-cancer risk metrics in our 

determination of risk acceptability and ample margin of safety. 

b. Step 2-Determination of Ample Margin of Safety 

CAA Ssection 112(f)(2) requires the EPA to determine, for 

source categories subject to MACT standards, whether those 

standards provide an ample margin of safety to protect public 

health. As explained in the Benzene NESHAP, “the second step of 

the inquiry, determining an ‘ample margin of safety,’ again 

includes consideration of all of the health factors, and whether 

to reduce the risks even further.... Beyond that information, 

additional factors relating to the appropriate level of control 
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will also be considered, including costs and economic impacts of 

controls, technological feasibility, uncertainties and any other 

relevant factors. Considering all of these factors, the agency 

will establish the standard at a level that provides an ample 

margin of safety to protect the public health, as required by 

Ssection 112.” 54 FR at 38046, September 14, 1989. 

According to CAA Ssection 112(f)(2)(A), if the MACT 

standards for HAP “classified as a known, probable, or possible 

human carcinogen do not reduce lifetime excess cancer risks to 

the individual most exposed to emissions from a source in the 

category or subcategory to less than one in one million,” the 

EPA must promulgate residual risk standards for the source 

category (or subcategory), as necessary to provide an ample 

margin of safety to protect public health. In doing so, the EPA 

may adopt standards equal to existing MACT standards if the EPA 

determines that the existing standards (i.e., the MACT 

standards) are sufficiently protective. NRDC Vv. EPA, 529 F.3d 

1077, 1083 (D.C. Cir. 2008) (“If EPA determines that the 

existing technology-based standards provide an ‘ample margin of 

safety,’ then the Agency is free to readopt those standards 

during the residual risk rulemaking.”) The EPA must also adopt 

more stringent standards, if necessary, to prevent an adverse 
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environmental effect,1

 but must consider cost, energy, safety and 

other relevant factors in doing so. 

The CAA does not specifically define the terms “individual 

most exposed,” “acceptable level” and “ample margin of safety.” 

In the Benzene NESHAP, 54 FR at 38044-38045, September 14, 1989, 

we stated as an overall objective: 

In protecting public health with an ample margin of safety 

under Ssection 112, EPA strives to provide maximum feasible 

protection against risks to health from hazardous air 

pollutants by (1) protecting the greatest number of persons 

possible to an individual lifetime risk level no higher 

than approximately 1-in-1 million and (2) limiting to no 

higher than approximately 1-in-10 thousand [i.e., 100-in-1 

million] the estimated risk that a person living near a 

plant would have if he or she were exposed to the maximum 

pollutant concentrations for 70 years. 

The agency further stated that “[t]he EPA also considers 

incidence (the number of persons estimated to suffer cancer or 

other serious health effects as a result of exposure to a 

pollutant) to be an important measure of the health risk to the 

exposed population. Incidence measures the extent of health 

risks to the exposed population as a whole, by providing an 

estimate of the occurrence of cancer or other serious health 

effects in the exposed population.” Id. at 38045. 

 

1

 “Adverse environmental effect” is defined as any significant and widespread 

adverse effect, which may be reasonably anticipated to wildlife, aquatic life 

or natural resources, including adverse impacts on populations of endangered 

or threatened species or significant degradation of environmental qualities 

over broad areas. CAA Ssection 112(a)(7). 
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In the ample margin of safety decision process, the agency 

again considers all of the health risks and other health 

information considered in the first step, including the 

incremental risk reduction associated with standards more 

stringent than the MACT standard or a more stringent standard 

that EPA has determined is necessary to ensure risk is 

acceptable. In the ample margin of safety analysis, the agency 

considers additional factors, including costs and economic 

impacts of controls, technological feasibility, uncertainties 

and any other relevant factors. Considering all of these 

factors, the agency will establish the standard “at a level that 

provides an ample margin of safety to protect the public 

health,,” as required by CAA Ssection 112(f). 54 FR 38046, 

September 14, 1989. 

2. NSPS 

Section 111 of the CAA establishes mechanisms for 

controlling emissions of air pollutants from stationary sources. 

Section 111(b) of the CAA provides authority for the EPA to 

promulgate new source performance standards (NSPS) which apply 

only to newly constructed, reconstructed and modified sources. 

Once the EPA has elected to set NSPS for new and modified 

sources in a given source category, CAA Ssection 111(d) calls 

for regulation of existing sources, with certain exceptions 

explained below. 
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Specifically, Ssection 111(b) of the CAA requires the EPA 

to establish emission standards for any category of new and 

modified stationary sources that the Administrator, in his or 

her judgment, finds “causes, or contributes significantly to, 

air pollution which may reasonably be anticipated to endanger 

public health or welfare.” The EPA has previously made 

endangerment findings under this section of the CAA for more 

than 60 stationary source categories and subcategories that are 

now subject to NSPS. 

Section 111 of the CAA gives the EPA significant discretion 

to identify the affected facilities within a source category 

that should be regulated. To define the affected facilities, the 

EPA can use size thresholds for regulation and create 

subcategories based on source type, class or size. Emission 

limits also may be established either for equipment within a 

facility or for an entire facility. For listed source 

categories, the EPA must establish “standards of performance” 

that apply to sources that are constructed, modified or 

reconstructed after the EPA proposes the NSPS for the relevant 

source category.2

 

2

 Specific statutory and regulatory provisions define what constitutes a 

modification or reconstruction of a facility. 40 CFR 60.14 provides that an 

existing facility is modified and, therefore, subject to an NSPS, if it 

undergoes “any physical change in the method of operation . . . which 

increases the amount of any air pollutant emitted by such source or which 

results in the emission of any air pollutant not previously emitted.” 40 CFR 
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The EPA also has significant discretion to determine the 

appropriate level for the standards. Section 111(a)(1) of the 

CAA provides that NSPS are to “reflect the degree of emission 

limitation achievable through the application of the best system 

of emission reduction which (taking into account the cost of 

achieving such reduction and any non-air quality health and 

environmental impact and energy requirements) the Administrator 

determines has been adequately demonstrated.” This level of 

control is commonly referred to as best demonstrated technology 

(BDT) or the best system of emission reduction (BSER). The 

standard that the EPA develops, based on the BSER achievable at 

that source, is commonly a numerical emission limit, expressed 

as a performance level (i.e., a rate-based standard). Generally, 

the EPA does not prescribe a particular technological system 

that must be used to comply with a NSPS. Rather, sources remain 

free to elect whatever combination of measures will achieve 

equivalent or greater control of emissions. 

Costs are also considered in evaluating the appropriate 

standard of performance for each category or subcategory. The 

EPA generally compares control options and estimated costs and 

emission impacts of multiple, specific emission standard options 

 

60.15, in turn, provides that a facility is reconstructed if components are 

replaced at an existing facility to such an extent that the capital cost of 

the new equipment/components exceed 50 percent of what is believed to be the 

cost of a completely new facility. 
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under consideration. As part of this analysis, the EPA considers 

numerous factors relating to the potential cost of the 

regulation, including industry organization and market 

structure, control options available to reduce emissions of the 

regulated pollutant(s) and costs of these controls. 

B. What are the source categories and how do the NESHAP and NSPS 

regulate emissions? 

The source categories include petroleum refineries engaged 

in converting crude oil into refined products, including 

liquefied petroleum gas, gasoline, kerosene, aviation fuel, 

diesel fuel, fuel oils, lubricating oils and feedstocks for the 

petrochemical industry. Petroleum refinery activities start with 

the receipt of crude oil for storage at the refinery, include 

all petroleum handling and refining operations, and terminate 

with loading of refined products into pipelines, tank or rail 

cars, tank trucks, or ships or barges that take products from 

the refinery to distribution centers. Petroleum refineryspecific process units include fluid catalytic cracking units 

(FCCU) and catalytic reforming units (CRU), as well as units and 

processes found at many types of manufacturing facilities 

(including petroleum refineries), such as storage vessels and 

wastewater treatment plants. HAP emitted by this industry 

include organics (e.g., acetaldehyde, benzene, formaldehyde, 

hexane, phenol, naphthalene, 2-methylnaphthalene, dioxins, 
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furans, ethyl benzene, toluene and xylene); reduced sulfur 

compounds (i.e., carbonyl sulfide (COS), carbon disulfide (CS2)); 

inorganics (e.g., hydrogen chloride (HCl), hydrogen cyanide 

(HCN), chlorine, hydrogen fluoride (HF)); and metals (e.g., 

antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, 

mercury, manganese and nickel). Criteria pollutants and other 

non-hazardous air pollutants that are also emitted include 

nitrogen oxides (NOX), particulate matter (PM), sulfur dioxide 

(SO2), volatile organic compounds (VOC), carbon monoxide (CO), 

greenhouse gases (GHG), and total reduced sulfur. 

The federal emission standards that are the primary subject 

of this proposed rulemaking are: 

 National Emission Standards for Hazardous Air Pollutants 

from Petroleum Refineries (40 CFR part 63, subpart CC) 

(Refinery MACT 1); 

 National Emission Standards for Hazardous Air Pollutants 

for Petroleum Refineries: Catalytic Cracking Units, 

Catalytic Reforming Units, and Sulfur Recovery Units (40 

CFR part 63, subpart UUU) (Refinery MACT 2); 

 Standards of Performance for Petroleum Refineries (40 CFR 

part 60, subpart J) (Refinery NSPS J); and 

 Standards of Performance for Petroleum Refineries for 

which Construction, Reconstruction, or Modification 
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Commenced After May 14, 2007 (40 CFR part 60, subpart Ja) 

(Refinery NSPS Ja). 

1. Refinery MACT Standards 

The EPA promulgated MACT standards pursuant to CAA Ssection 

112(d)(2) and (3) for refineries located at major sources in 

three separate rules. On August 18, 1995, the first Petroleum 

Refinery MACT standard was promulgated in 40 CFR part 63, 

subpart CC (60 FR 43620). This rule is known as “Refinery MACT 

1” and covers the “Sources Not Distinctly Listed,” meaning it 

includes all emission sources from petroleum refinery process 

units, except those listed separately under the section 112(c) 

source category list expected to be regulated by other MACT 

standards. Some of the emission sources regulated in Refinery 

MACT 1 include miscellaneous process vents, storage vessels, 

wastewater, equipment leaks, gasoline loading racks, marine tank 

vessel loading and heat exchange systems. 

Certain process vents that were listed as a separate source 

category under CAA Ssection 112(c) and that were not addressed 

as part of the Refinery MACT 1 were subsequently regulated under 

a second MACT standard specific to these petroleum refinery 

process vents, codified as 40 CFR part 63, subpart UUU, which we 

promulgated on April 11, 2002 (67 FR 17762). This standard, 

which is referred to as “Refinery MACT 2,” covers process vents 
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on catalytic cracking units (CCU) (including FCCU), CRU and 

sulfur recovery units (SRU). 

Finally, on October 28, 2009, we promulgated MACT standards 

for heat exchange systems, which the EPA had not addressed in 

the original 1995 Refinery MACT 1 rule (74 FR 55686). In this 

same 2009 action, we updated cross-references to the General 

Provisions in 40 CFR part 63. On June 20, 2013 (78 FR 37133), we 

promulgated minor revisions to the heat exchange provisions of 

Refinery MACT 1. 

On September 27, 2012, Air Alliance Houston, California 

Communities Against Toxics and other environmental and public 

health groups filed a lawsuit alleging that the EPA missed 

statutory deadlines to review and revise Refinery MACT 1 and 2. 

The EPA has reached an agreement to settle that litigation. 

In a consent decree filed January 13, 2014 in the U.S. District 

Court for the District of Columbia, the EPA commits to perform 

the risk and technology review for Refinery MACT 1 and 2 and by 

May 15, 2014, either propose any regulations or propose that 

additional regulations are not necessary. Under the Consent 

Decree, the EPA commits to take final action by April 17, 2015, 

establishing regulations pursuant to the risk and technology 

review or to issue a final determination that revision to the 

existing rules is not necessary. 
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2. Refinery NSPS 

Refinery NSPS subparts J and Ja regulate criteria pollutant 

emissions, including PM, SO2, NOX and CO from FCCU catalyst 

regenerators, fuel gas combustion devices (FGCD) and sulfur 

recovery plants. Refinery NSPS Ja also regulates criteria 

pollutant emissions from fluid coking units and delayed coking 

units (DCU). 

The NSPS for petroleum refineries (40 CFR part 60, subpart 

J; Refinery NSPS J) were promulgated in 1974, amended in 1976 

and amended again in 2008, following a review of the standards. 

As part of the review that led to the 2008 amendments to 

Refinery NSPS J, the EPA developed separate standards of 

performance for new process units (40 CFR part 60, subpart Ja; 

Refinery NSPS Ja). However, the EPA received petitions for 

reconsideration and granted reconsideration on issues related to 

those standards. On December 22, 2008, the EPA addressed 

petition issues related to process heaters and flares by 

proposing amendments to certain provisions. Final amendments to 

Refinery NSPS Ja were promulgated on September 12, 2012 (77 FR 

56422). 

In this action, we are proposing amendments to address 

technical corrections and clarifications raised in a 2008 

industry petition for reconsideration applicable to Refinery 

NSPS Ja. We are addressing these issues in this proposal because 
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they also affect sources included within these proposed 

amendments to Refinery MACT 1 and 2. 

C. What data collection activities were conducted to support 

this action? 

In 2010, the EPA began a significant effort to gather 

additional information and perform analyses to determine how to 

address statutory obligations for the Refinery MACT standards 

and the NSPS. This effort focused on gathering comprehensive 

information through an industry-wide Information Collection 

Request (ICR) on petroleum refineries, conducted under CAA 

Ssection 114 authority. The information not claimed as CBI by 

respondents is available in the docket (see Docket Item Nos. 

EPA-HQ-OAR-2010-0682-0064 through 0069). The EPA issued a single 

ICR (OMB Control Number 2060-0657) for sources covered under 

Refinery MACT 1 and 2 and Refinery NSPS J and Ja. 

On April 1, 2011, the ICR was sent out to the petroleum 

refining industry. In a comprehensive manner, the ICR collected 

information on processing characteristics, crude slate 

characteristics, emissions inventories and source testing to 

fill known data gaps. The ICR had four components: (1) a 

questionnaire on processes and controls to be completed by all 

petroleum refineries (Component 1); (2) an emissions inventory 

to be developed by all petroleum refineries using the emissions 

estimation protocol developed for this effort (Component 2); (3) 
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distillation feed sampling and analysis to be conducted by all 

petroleum refineries (Component 3); and (4) emissions source 

testing to be completed in accordance with an EPA-approved 

protocol for specific sources at specific petroleum refineries 

(Component 4). We received responses from 149 refineries. We 

have since learned that seven refineries are synthetic minor 

sources, bringing the total number of major source refineries 

operating in 2010 to 142. 

Information collected through the ICR was used to establish 

the baseline emissions and control levels for purposes of the 

regulatory reviews, to identify the most effective control 

measures, and to estimate the environmental and cost impacts 

associated with the regulatory options considered. As part of 

the information collection process, we provided a protocol for 

survey respondents to follow in developing the emissions 

inventories under Component 2 (Emission Estimation Protocol for 

Petroleum Refineries, available as Docket Item Number EPA-HQOAR-2010-0682-0060). The protocol contained detailed guidance 

for estimating emissions from typical refinery emission sources 

and was intended to provide a measure of consistency and 

replicability for emission estimates across the refining 

industry. Prior to issuance of the ICR, the protocol was 

publicly disseminated and underwent several revisions after 

public comments were received. Draft and final versions of the 
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emission estimation protocol are provided in the docket to this 

rule (Docket ID Number EPA-HQ-OAR-2010-0682). The protocol 

provided a hierarchy of methodologies available for estimating 

emissions that corresponded to the level of information 

available at refineries. For each emission source, the various 

emission measurement or estimation methods specific to that 

source were ranked in order of preference, with “Methodology 

Rank 1” being the preferred method, followed by “Methodology 

Rank 2,” and so on. Refinery owners and operators were requested 

through the ICR to use the highest ranked method (with 

Methodology Rank 1 being the highest) for which data were 

available. Methodology Ranks 1 or 2 generally relied on 

continuous emission measurements. When continuous measurement 

data were not available, engineering calculations or sitespecific emission factors (Methodology Ranks 3 and 4) were 

specified in the protocol by EPA; these methods generally needed 

periodic, site-specific measurements. When site-specific 

measurement or test data were not available, default emission 

factors (Methodology Rank 5) were provided in the protocol by 

EPA. 

As we reviewed the ICR-submitted emissions inventories, we 

determined that, in some cases, refiners either did not follow 

the protocol methodology or made an error in their calculations. 

This was evident because pollutants that we expected to be 
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reported from certain emission sources were either not reported 

or were reported in amounts that were not consistent with the 

protocol methodology. In these cases, we contacted the 

refineries and, based on their replies, made corrections to 

emission estimates. The original Component 2 submittals, 

documentation of the changes as a result of our review, and the 

final emissions inventories we relied on for our analyses are 

available in the technical memorandum entitled Emissions Data 

Quality Memorandum and Development of the Risk Model Input File, 

in Docket ID Number EPA-HQ-OAR-2010-0682. 

Collected emissions test data (test reports, continuous 

emissions monitoring system (CEMS) data and other continuous 

monitoring system data) were used to assess the effectiveness of 

existing control measures, to fill data gaps and to examine 

variability in emissions. The ICR requested source testing for a 

total of 90 specific process units at 75 particular refineries 

across the industry. We received a total of 72 source tests; in 

some cases, refinery sources claimed that units we requested to 

be tested were no longer in operation, did not exist or did not 

have an emission point to the atmosphere (this was the case for 

hydrocrackers). In other cases, refiners claimed they were not 

able to conduct testing because of process characteristics. For 

example, source testing of DCU proved to be difficult because 

the moisture content of the steam vent required a significant 
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amount of gas to be sampled to account for dilution. Venting 

periods of less than 20 minutes did not accommodate this 

strategy and, therefore, if refiners vented for less than 20 

minutes, they did not sample their steam vent. As a result, only 

two DCU tests out of eight requested were received as part of 

Component 4. Results of the stack test data are compiled and 

available in Docket ID Number EPA-HQ-OAR-2010-0682. 

D. What other relevant background information and data are 

available? 

Over the past several years, the EPA has worked with the 

Texas Commission on Environmental Quality and industry 

representatives to better characterize proper flare performance. 

Flares are used to control emissions from various vents at 

refineries as well as at other types of facilities not in the 

petroleum refinery source categories, such as chemical and 

petrochemical manufacturing facilities. In April 2012, we 

released a technical report for peer review that discussed our 

observations regarding the operation and performance of flares. 

The report was a result of the analysis of several flare 

efficiency studies and flare performance test reports. To 

provide an objective evaluation of our analysis, we asked a 

third party to facilitate an ad hoc peer review process of the 

technical report. This third party established a balanced peer 

review panel of reviewers from outside the EPA. These reviewers 
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consisted of individuals that could be considered “technical 

combustion experts” within four interest groups: the refinery 

industry, industrial flare consultants, academia, and 

environmental stakeholders. 

The EPA developed a charge statement with ten charge 

questions for the review panel. The peer reviewers were asked to 

perform a thorough review of the technical report and answer the 

charge questions to the extent possible, based on their 

technical expertise. The details of the peer review process and 

the charge questions, as well as comments received from the peer 

review process, were posted online to the Consolidated Petroleum 

Refinery Rulemaking Repository at the EPA's Technology Transfer 

Network Air Toxics Web Site (see 

http://www.epa.gov/ttn/atw/petref.html). These items are also 

provided in a memorandum entitled Peer Review of “Parameters for 

Properly Designed and Operated Flares” (see Docket ID Number 

EPA-HQ-OAR-2010-0682). After considering the comments received 

from the peer review process, we developed a final technical 

memorandum (see technical memorandum, Flare Performance Data: 

Summary of Peer Review Comments and Additional Data Analysis for 

Steam-Assisted Flares, in Docket ID Number EPA-HQ-OAR-2010-

0682). 
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III. Analytical Procedures 

In this section, we describe the analyses performed to 

support the proposed decisions for the RTR and other issues 

addressed in this proposal. 

A. How did we estimate post-MACT risks posed by the source 

categories? 

The EPA conducted a risk assessment that provided estimates 

of the MIR posed by the HAP emissions from each source in the 

source categories, the hazard index (HI) for chronic exposures 

to HAP with the potential to cause non-cancer health effects, 

and the hazard quotient (HQ) for acute exposures to HAP with the 

potential to cause non-cancer health effects. The assessment 

also provided estimates of the distribution of cancer risks 

within the exposed populations, cancer incidence and an 

evaluation of the potential for adverse environmental effects 

for each source category. The eight sections that follow this 

paragraph describe how we estimated emissions and conducted the 

risk assessment consisted of eight primary steps, as discussed 

below. The docket for this rulemaking (Docket ID Number EPA-HQOAR-2010-0682) contains the following document which provides 

more information on the risk assessment inputs and models: Draft 

Residual Risk Assessment for the Petroleum Refining Source 

Sector. The methods used to assess risks (as described in the 

eight primary steps below) are consistent with those peer-
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Page 43 of 396 

reviewed by a panel of the EPA’s Science Advisory Board (SAB) in 

2009 and described in their peer review report issued in 20103

; 

they are also consistent with the key recommendations contained 

in that report. 

1. How did we estimate actual emissions and identify the 

emissions release characteristics? 

We compiled data sets using the ICR emission inventory 

submittals as a starting point. The data sets were refined 

following an extensive quality assurance check of source 

locations, emission release characteristics, annual emission 

estimates and FCCU release parameters. They were then updated 

based on additional information received from refineries. In 

addition, we supplemented these data with results from stack 

testing, which were required later than the inventories under 

the ICR. As the stack test information was received, we compared 

these data against the refined emission inventories and the 

default emission factors provided in the Emission Estimation 

Protocol for Petroleum Refineries (Docket Item Number EPA-HQOAR-2010-0682-0060). 

Based on the stack test data for FCCU, we calculated that, 

on average, HCN emissions were a factor of 10 greater than the 

 

3

 U.S. EPA SAB. Risk and Technology Review (RTR) Risk Assessment 

Methodologies: For Review by the EPA’s Science Advisory board with Case 

Studies – MACT I Petroleum Refining Sources and Portland Cement 

Manufacturing, May 2010. 
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average emission factor of 770 pounds per barrel FCCU feed 

provided in the protocol. Therefore, we revised the HCN 

emissions for FCCU in the emissions inventory used for the risk 

modeling runs (the results are presented in this preamble). For 

the 10 facilities that performed a stack test to determine HCN 

emissions from their FCCU, we used the actual emissions measured 

during the stack tests in place of the inventories originally 

supplied in response to the ICR. For those facilities that did 

not perform a stack test, but reported HCN emissions in the 

emissions inventory portion of the ICR, we increased the 

emissions of HCN by a factor of 10, assuming the original 

emission inventory estimates for FCCU HCN emissions were based 

on the default emission factor in the protocol. The emissions 

inventory from the ICR and documentation of the changes made to 

the file as a result of our review are contained in the 

technical memorandum entitled Emissions Data Quality Memorandum 

and Development of the Risk Model Input File, in Docket ID 

Number EPA-HQ-OAR-2010-0682 and available on our website.4

2. How did we estimate MACT-allowable emissions? 

The available emissions data in the RTR dataset (i.e., the 

emissions inventory) include estimates of the mass of HAP 

emitted during the specified annual time period. In some cases, 

 

4

 The emissions inventory and the revised emissions modeling file can also be 

found at http://www.epa.gov/ttn/atw/petref.htm. 
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these “actual” emission levels are lower than the emission 

levels required to comply with the MACT standards. The emissions 

level allowed to be emitted by the MACT standards is referred to 

as the “MACT-allowable” emissions level. We discussed the use of 

both MACT-allowable and actual emissions in the final Coke Oven 

Batteries residual risk rule (70 FR 19998–19999, April 15, 2005) 

and in the proposed and final Hazardous Organic NESHAP residual 

risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609, 

December 21, 2006, respectively). In those previous actions, we 

noted that assessing the risks at the MACT-allowable level is 

inherently reasonable since these risks reflect the maximum 

level facilities could emit and still comply with national 

emission standards. We also explained that it is reasonable to 

consider actual emissions, where such data are available, in 

both steps of the risk analysis, in accordance with the Benzene 

NESHAP approach. (54 FR 38044, September 14, 1989.) 

We requested allowable emissions data in the ICR. However, 

unlike for actual emissions, where the ICR specified the use of 

the Emission Estimation Protocol for Petroleum Refineries 

(available as Docket Item Number EPA-HQ-OAR-2010-0682-0060), we 

did not specify a method to calculate allowable emissions. As a 

result, in our review of these data and when comparing estimates 

between facilities, we found that facilities did not estimate 

allowable emissions consistently across the industry. In 
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addition, facilities failed to report allowable emissions for 

many emission points, likely because they did not know how to 

translate a work practice or performance standard into an 

allowable emission estimate and they did not know how to 

speciate individual HAP where the MACT standard is based on a 

surrogate, such as PM or VOC. Therefore, the ICR-submitted 

information for allowable emissions did not include emission 

estimates for all HAP and sources of interest. Consequently, we 

used our Refinery Emissions Model (REM Model) to estimate 

allowable emissions. The REM model relies on model plants that 

vary based on throughput capacity. Each model plant contains 

process-specific default emission factors, adjusted for 

compliance with the Refinery MACT 1 and 2 emission standards. 

The risks associated with the allowable emissions were 

evaluated using the same dispersion modeling practices, exposure 

assumptions and health benchmarks as the actual risks. However, 

because each refinery’s allowable emissions were calculated by 

using model plants, selected based on each refinery’s actual 

capacities and throughputs, emission estimates for point sources 

are not specific to a particular latitude/longitude location. 

Therefore, for risk modeling purposes, all allowable emissions 

were assumed to be released from the centroid of the facility. 

(Note: for fugitive (area) sources, the surface area was 

selected by the size of the model plant and the release point 
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was shifted to the southwest so the center of the fugitive area 

was near the centroid of the facility). The emission and risk 

estimates for the actual emission inventory were compared to the 

allowable emissions and risk estimates. For most work practices, 

where allowable emission estimates are difficult to predict, the 

actual risk estimates were higher than those projected using the 

REM Model estimates. Consequently, we post-processed the two 

risk files, taking the higher risk estimates from the actual 

emissions inventory for sources subject to work practice 

standards, such as process equipment leaks, and sources that 

were not covered in the REM Model and, combining them with the 

risk estimates from sources with more readily determined 

allowable emissions. The combined post-processed allowable risk 

estimates provide a conservatively high estimate of the risk 

allowed under Refinery MACT 1 and 2. The REM Model assumptions 

and emission estimates, along with the post-processing of risk 

estimate results that produced the final risk estimates for the 

allowable emissions, are provided in the docket (see Refinery 

Emissions and Risk Estimates for Modeled “Allowable” Emissions 

in Docket ID Number EPA-HQ-OAR-2010-0682). 
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3. How did we conduct dispersion modeling, determine inhalation 

exposures and estimate individual and population inhalation 

risks? 

Both long-term and short-term inhalation exposure 

concentrations and health risks from the source categories 

addressed in this proposal were estimated using the Human 

Exposure Model (Community and Sector HEM-3 version 1.1.0). The 

HEM–3 performs three primary risk assessment activities: (1) 

conducting dispersion modeling to estimate the concentrations of 

HAP in ambient air, (2) estimating long-term and short-term 

inhalation exposures to individuals residing within 50 

kilometers (km) of the modeled sources5

, and (3) estimating 

individual and population-level inhalation risks using the 

exposure estimates and quantitative dose-response information. 

The air dispersion model used by the HEM–3 model (AERMOD) 

is one of the EPA’s preferred models for assessing pollutant 

concentrations from industrial facilities.6

 To perform the 

dispersion modeling and to develop the preliminary risk 

estimates, HEM-3 draws on three data libraries. The first is a 

library of meteorological data, which is used for dispersion 

 

5

 This metric comes from the Benzene NESHAP. See 54 FR 38046, September 14, 

1989. 

6

 U.S. EPA. Revision to the Guideline on Air Quality Models: Adoption of a 

Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and 

Other Revisions (70 FR 68218, November 9, 2005). 
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calculations. This library includes 1 year (2011) of hourly 

surface and upper air observations for 824 meteorological 

stations, selected to provide coverage of the United States and 

Puerto Rico. A second library of United States Census Bureau 

census block7

 internal point locations and populations provides 

the basis of human exposure calculations (U.S. Census, 2010). In 

addition, for each census block, the census library includes the 

elevation and controlling hill height, which are also used in 

dispersion calculations. A third library of pollutant unit risk 

factors and other health benchmarks is used to estimate health 

risks. These risk factors and health benchmarks are the latest 

values recommended by the EPA for HAP and other toxic air 

pollutants. These values are available at: 

http://www.epa.gov/ttn/atw/toxsource/summary.html and are 

discussed in more detail later in this section. 

In developing the risk assessment for chronic exposures, we 

used the estimated annual average ambient air concentrations of 

each HAP emitted by each source for which we have emissions data 

in the source category. The air concentrations at each nearby 

census block centroid were used as a surrogate for the chronic 

inhalation exposure concentration for all the people who reside 

in that census block. We calculated the MIR for each facility as 

 

7

 A census block is the smallest geographic area for which census statistics 

are tabulated. 
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the cancer risk associated with a continuous lifetime (24 hours 

per day, 7 days per week, and 52 weeks per year for a 70-year 

period) exposure to the maximum concentration at the centroid of 

inhabited census blocks. Individual cancer risks were calculated 

by multiplying the estimated lifetime exposure to the ambient 

concentration of each of the HAP (in micrograms per cubic meter 

(μg/m3

)) by its unit risk estimate (URE). The URE is an upper 

bound estimate of an individual’s probability of contracting 

cancer over a lifetime of exposure to a concentration of 1 

microgram of the pollutant per cubic meter of air. For residual 

risk assessments, we generally use URE values from the EPA’s 

Integrated Risk Information System (IRIS). For carcinogenic 

pollutants without EPA IRIS values, we look to other reputable 

sources of cancer dose-response values, often using California 

EPA (CalEPA) URE values, where available. In cases where new, 

scientifically credible dose-response values have been developed 

in a manner consistent with the EPA guidelines and have 

undergone a peer review process similar to that used by the EPA, 

we may use such dose-response values in place of, or in addition 

to, other values, if appropriate. 

We note here that several carcinogens emitted by facilities 

in these source categories have a mutagenic mode of action. For 

these compounds, we applied the age-dependent adjustment factors 

(ADAF) described in the EPA’s Supplemental Guidance for 
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Assessing Susceptibility from Early-Life Exposure to 

Carcinogens. (“Supplemental Guidance”)8 This adjustment has the 

effect of increasing the estimated lifetime risks for these 

pollutants by a factor of 1.6. Although only a small fraction of 

the total polycyclic organic matter (POM) emissions were 

reported as individual compounds, the EPA expresses carcinogenic 

potency of POM relative to the carcinogenic potency of 

benzo[a]pyrene, based on evidence that carcinogenic POM have the 

same mutagenic mode of action as does benzo[a]pyrene. The EPA’s 

Science Policy Council recommends applying the ADAF to all 

carcinogenic polycyclic aromatic hydrocarbons (PAH) for which 

risk estimates are based on potency relative to benzo[a]pyrene. 

Accordingly, we have applied the ADAF to the benzo[a]pyreneequivalent mass portion of all POM mixtures. 

The EPA estimated incremental individual lifetime cancer 

risks associated with emissions from the facilities in the 

source categories as the sum of the risks for each of the 

carcinogenic HAP (including those classified as carcinogenic to 

humans, likely to be carcinogenic to humans, and suggestive 

 

8

 Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure 

to Carcinogens. Risk Assessment Forum, U.S. Environmental Protection Agency, 

Washington, DC. EPA/630/R-03/003F. March 2005. Available at 

http://www.epa.gov/ttn/atw/childrens_supplement_final.pdf. 
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evidence of carcinogenic potential9

) emitted by the modeled 

sources. Cancer incidence and the distribution of individual 

cancer risks for the population within 50 km of the sources were 

also estimated for the source categories as part of this 

assessment by summing individual risks. A distance of 50 km is 

consistent with both the analysis supporting the 1989 Benzene 

NESHAP (54 FR 38044, September 14, 1989) and the limitations of 

Gaussian dispersion models, including AERMOD. 

To assess the risk of non-cancer health effects from 

chronic exposures, we summed the HQ for each of the HAP that 

affects a common target organ system to obtain the HI for that 

target organ system (or target organ-specific HI, TOSHI). The HQ 

is the estimated exposure divided by the chronic reference 

level, which is a value selected from one of several sources. 

First, the chronic reference level can be the EPA Reference 

Concentration (RfC) 

(http://www.epa.gov/riskassessment/glossary.htm), defined as “an 

estimate (with uncertainty spanning perhaps an order of 

 

9

 These classifications also coincide with the terms "known carcinogen, 

probable carcinogen, and possible carcinogen," respectively, which are the 

terms advocated in the EPA's previous Guidelines for Carcinogen Risk 

Assessment, published in 1986 (51 FR 33992, September 24, 1986). Summing the 

risks of these individual compounds to obtain the cumulative cancer risks is 

an approach that was recommended by the EPA's SAB in their 2002 peer review 

of EPA's National Air Toxics Assessment (NATA) entitled, NATA - Evaluating 

the National-scale Air Toxics Assessment 1996 Data -- an SAB Advisory, 

available at: 

http://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/$

File/ecadv02001.pdf. 
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Page 53 of 396 

magnitude) of a continuous inhalation exposure to the human 

population (including sensitive subgroups) that is likely to be 

without an appreciable risk of deleterious effects during a 

lifetime.” Alternatively, in cases where an RfC from the EPA’s 

IRIS database is not available or where the EPA determines that 

using a value other than the RfC is appropriate, the chronic 

reference level can be a value from the following prioritized 

sources: (1) The Agency for Toxic Substances and Disease 

Registry Minimum Risk Level 

(http://www.atsdr.cdc.gov/mrls/index.asp), which is defined as 

“an estimate of daily human exposure to a hazardous substance 

that is likely to be without an appreciable risk of adverse noncancer health effects (other than cancer) over a specified 

duration of exposure”; (2) the CalEPA Chronic Reference Exposure 

Level (REL) 

(http://www.oehha.ca.gov/air/hot_spots/pdf/HRAguidefinal.pdf), 

which is defined as “the concentration level (that is expressed 

in units of μg/m3

 for inhalation exposure and in a dose expressed 

in units of milligram per kilogram per day (mg/kg-day) for oral 

exposures), at or below which no adverse health effects are 

anticipated for a specified exposure duration”; or (3), as noted 

above, a scientifically credible dose-response value that has 

been developed in a manner consistent with the EPA guidelines 
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and has undergone a peer review process similar to that used by 

the EPA, in place of or in concert with other values. 

The EPA also evaluated screening estimates of acute 

exposures and risks for each of the HAP at the point of highest 

off-site exposure for each facility (i.e., not just the census 

block centroids), assuming that a person is located at this spot 

at a time when both the peak (hourly) emissions rate and worstcase dispersion conditions occur. The acute HQ is the estimated 

acute exposure divided by the acute dose-response value. In each 

case, the EPA calculated acute HQ values using best available, 

short-term dose-response values. These acute dose-response 

values, which are described below, include the acute REL, acute 

exposure guideline levels (AEGL) and emergency response planning 

guidelines (ERPG) for 1-hour exposure durations. As discussed 

below, we used realistic assumptions based on knowledge of the 

emission point release characteristics for emission rates, and 

conservative assumptions for meteorology and exposure location 

for our acute analysis. 

As described in the CalEPA’s Air Toxics Hot Spots Program 

Risk Assessment Guidelines, Part I, The Determination of Acute 

Reference Exposure Levels for Airborne Toxicants, an acute REL 

value (http://www.oehha.ca.gov/air/pdf/acuterel.pdf) is defined 

as “the concentration level at or below which no adverse health 

effects are anticipated for a specified exposure duration.” Id. 
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at page 2. Acute REL values are based on the most sensitive, 

relevant, adverse health effect reported in the peer-reviewed 

medical and toxicological literature. Acute REL values are 

designed to protect the most sensitive individuals in the 

population through the inclusion of margins of safety. Because 

margins of safety are incorporated to address data gaps and 

uncertainties, exceeding the REL value does not automatically 

indicate an adverse health impact. 

AEGL values were derived in response to recommendations 

from the National Research Council (NRC). As described in 

Standing Operating Procedures (SOP) of the National Advisory 

Committee on Acute Exposure Guideline Levels for Hazardous 

Substances (http://www.epa.gov/oppt/aegl/pubs/sop.pdf),10 “the 

NRC’s previous name for acute exposure levels—community 

emergency exposure levels—was replaced by the term AEGL to 

reflect the broad application of these values to planning, 

response, and prevention in the community, the workplace, 

transportation, the military, and the remediation of Superfund 

sites.” Id. at 2. 

This document also states that AEGL values “represent 

threshold exposure limits for the general public and are 

 

10 National Academy of Sciences (NAS), 2001. Standing Operating Procedures for 

Developing Acute Exposure Levels for Hazardous Chemicals, page 2.
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applicable to emergency exposures ranging from 10 minutes to 

eight hours.” Id. at 2. The document lays out the purpose and 

objectives of AEGL by stating that “the primary purpose of the 

AEGL program and the National Advisory Committee for Acute 

Exposure Guideline Levels for Hazardous Substances is to develop 

guideline levels for once-in-a-lifetime, short-term exposures to 

airborne concentrations of acutely toxic, high-priority 

chemicals.” Id. at 21. In detailing the intended application of 

AEGL values, the document states that “[i]t is anticipated that 

the AEGL values will be used for regulatory and nonregulatory 

purposes by U.S. Federal and state agencies and possibly the 

international community in conjunction with chemical emergency 

response, planning and prevention programs. More specifically, 

the AEGL values will be used for conducting various risk 

assessments to aid in the development of emergency preparedness 

and prevention plans, as well as real-time emergency response 

actions, for accidental chemical releases at fixed facilities 

and from transport carriers.” Id. at 31. 

The AEGL–1 value is then specifically defined as “the 

airborne concentration (expressed as ppm (parts per million) or 

mg/m3

 (milligrams per cubic meter)) of a substance above which it 

is predicted that the general population, including susceptible 

individuals, could experience notable discomfort, irritation, or 

certain asymptomatic nonsensory effects. However, the effects 
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are not disabling and are transient and reversible upon 

cessation of exposure.” Id. at 3. The document also notes that, 

“Airborne concentrations below AEGL–1 represent exposure levels 

that can produce mild and progressively increasing but transient 

and nondisabling odor, taste, and sensory irritation or certain 

asymptomatic, nonsensory effects.” Id. Similarly, the document 

defines AEGL–2 values as “the airborne concentration (expressed 

as parts per million or milligrams per cubic meter) of a 

substance above which it is predicted that the general 

population, including susceptible individuals, could experience 

irreversible or other serious, long-lasting adverse health 

effects or an impaired ability to escape.” Id. 

ERPG values are derived for use in emergency response, as 

described in the American Industrial Hygiene Association’s ERP 

Committee document entitled, ERPGS Procedures and 

Responsibilities

(http://sp4m.aiha.org/insideaiha/GuidelineDevelopment/ERPG/Docum

ents/ERP-SOPs2006.pdf), which states that, “Emergency Response 

Planning Guidelines were developed for emergency planning and 

are intended as health-based guideline concentrations for single 

exposures to chemicals.”11 Id. at 1. The ERPG–1 value is defined 

 

11 ERP Committee Procedures and Responsibilities. November 1, 2006. American 

Industrial Hygiene Association. Available at https://www.aiha.org/getinvolved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Document

s/ERP-SOPs2006.pdf.
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as “the maximum airborne concentration below which it is 

believed that nearly all individuals could be exposed for up to 

1 hour without experiencing other than mild transient adverse 

health effects or without perceiving a clearly defined, 

objectionable odor.” Id. at 2. Similarly, the ERPG–2 value is 

defined as “the maximum airborne concentration below which it is 

believed that nearly all individuals could be exposed for up to 

one hour without experiencing or developing irreversible or 

other serious health effects or symptoms which could impair an 

individual’s ability to take protective action.” Id. at 1. 

As can be seen from the definitions above, the AEGL and 

ERPG values include the similarly-defined severity levels 1 and 

2. For many chemicals, a severity level 1 value AEGL or ERPG has 

not been developed because the types of effects for these 

chemicals are not consistent with the AEGL-1/ERPG-1 definitions; 

in these instances, we compare higher severity level AEGL–2 or 

ERPG–2 values to our modeled exposure levels to screen for 

potential acute concerns. When AEGL-1/ERPG-1 values are 

available, they are used in our acute risk assessments. 

Acute REL values for 1-hour exposure durations are 

typically lower than their corresponding AEGL–1 and ERPG–1 

values. Even though their definitions are slightly different, 

AEGL–1 values are often the same as the corresponding ERPG–1 

values, and AEGL–2 values are often equal to ERPG–2 values. 
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Maximum HQ values from our acute screening risk assessments 

typically result when basing them on the acute REL value for a 

particular pollutant. In cases where our maximum acute HQ value 

exceeds 1, we also report the HQ value based on the next highest 

acute dose-response value (usually the AEGL–1 and/or the ERPG–1 

value). 

To develop screening estimates of acute exposures in the 

absence of hourly emissions data, generally we first develop 

estimates of maximum hourly emissions rates by multiplying the 

average actual annual hourly emissions rates by a default factor 

to cover routinely variable emissions. However, for the 

petroleum refineries category, we incorporated additional 

information and process knowledge in order to better 

characterize acute emissions, as described below. The ICR 

included input fields for both annual emissions and maximum 

hourly emissions. The maximum hourly emission values were often 

left blank or appeared to be reported in units other than those 

required for this emissions field (pounds per hour). 

Consequently, instead of relying on the inadequate data provided 

in response to the ICR, we elected to estimate the hourly 

emissions based on the reported annual emissions (converted to 

average hourly emissions in terms of pounds per hour) and then 

to apply an escalation factor, considering the different types 

of emission sources and their inherent variability, in order to 
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calculate maximum hourly rates. For sources with relatively 

continuous operations and steady state emissions, such as FCCU, 

sulfur recovery plants, and continuous catalytic reformers, a 

factor of 2 was used to estimate the maximum hourly rates from 

the average hourly emission rates. For sources with relatively 

continuous emissions, but with more variability, like storage 

tanks and wastewater systems, a factor of 4 was used to estimate 

the maximum hourly rates from the average hourly emission rates. 

For non-continuous emission sources with more variability, such 

as DCU, cyclic CRU, semi-regenerative CRU, and transfer and 

loading operations, the number of hours in the venting cycle and 

the variability of emissions expected in that cycle were used to 

determine the escalation factor for each emissions source. The 

escalation factors for these processes range from 10 to 60. For 

more detail regarding escalation factors and the rationale for 

their selection, see Derivation of Hourly Emission Rates for 

Petroleum Refinery Emission Sources Used in the Acute Risk 

Analysis, available in the docket for this rulemaking (Docket ID 

Number EPA-HQ-OAR-2010-0682). 

As part of our acute risk assessment process, for cases 

where acute HQ values from the screening step were less than or 

equal to 1 (even under the conservative assumptions of the 

screening analysis), acute impacts were deemed negligible and no 

further analysis was performed. In cases where an acute HQ from 
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the screening step was greater than 1, additional site-specific 

data were considered to develop a more refined estimate of the 

potential for acute impacts of concern. For these source 

categories, the data refinements employed consisted of using the 

site-specific facility layout to distinguish facility property 

from an area where the public could be exposed. These 

refinements are discussed more fully in the Draft Residual Risk 

Assessment for the Petroleum Refining Source Sector, which is 

available in the docket for this rulemaking (Docket ID Number 

EPA-HQ-OAR-2010-0682). Ideally, we would prefer to have 

continuous measurements over time to see how the emissions vary 

by each hour over an entire year. Having a frequency 

distribution of hourly emissions rates over a year would allow 

us to perform a probabilistic analysis to estimate potential 

threshold exceedances and their frequency of occurrence. Such an 

evaluation could include a more complete statistical treatment 

of the key parameters and elements adopted in this screening 

analysis. Recognizing that this level of data is rarely 

available, we instead rely on the multiplier approach. 

To better characterize the potential health risks 

associated with estimated acute exposures to HAP, and in 

response to a key recommendation from the SAB’s peer review of 
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the EPA’s RTR risk assessment methodologies,12 we generally 

examine a wider range of available acute health metrics (e.g., 

REL, AEGL) than we do for our chronic risk assessments. This is 

in response to the SAB’s acknowledgement that there are 

generally more data gaps and inconsistencies in acute reference 

values than there are in chronic reference values. In some 

cases, e.g., when Reference Value Arrays13 for HAP have been 

developed, we consider additional acute values (i.e., 

occupational and international values) to provide a more 

complete risk characterization. 

4. How did we conduct the multipathway exposure and risk 

screening? 

The EPA conducted a screening analysis examining the 

potential for significant human health risks due to exposures 

via routes other than inhalation (i.e., ingestion). We first 

determined whether any sources in the source categories emitted 

any hazardous air pollutants known to be persistent and bioaccumulative in the environment (PB-HAP). The PB-HAP compounds 

or compound classes are identified for the screening from the 

 

12 The SAB peer review of RTR Risk Assessment Methodologies is available at: 

http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$

File/EPA-SAB-10-007-unsigned.pdf. 

13 U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference Values for 

Formaldehyde in Graphical Arrays of Chemical-Specific Health Effect Reference 

Values for Inhalation Exposures (Final Report). U.S. Environmental Protection 

Agency, Washington, DC, EPA/600/R-09/061, and available on-line at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003. 
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EPA’s Air Toxics Risk Assessment Library (available at 

http://www.epa.gov/ttn/fera/risk_atra_vol1.html). 

For the petroleum refinery source categories, we identified 

emissions of cadmium compounds, chlorinated dibenzodioxins and 

furans (CDDF), lead compounds, mercury compounds, 

polychlorinated biphenyls (PCB), and polycylic organic matter 

(POM). Because PB-HAP are emitted by at least one facility, we 

proceeded to the second step of the evaluation. In this step, we 

determined whether the facility-specific emission rates of each 

of the emitted PB–HAP were large enough to create the potential 

for significant non-inhalation human health risks under 

reasonable worst-case conditions. To facilitate this step, we 

developed emissions rate thresholdsscreening levels for each PB–

HAP using a hypothetical upper-end screening exposure scenario 

developed for use in conjunction with the EPA’s “Total Risk 

Integrated Methodology. Fate, Transport, and Ecological 

Exposure” (TRIM.FaTE) model. We conducted a sensitivity analysis 

on the screening scenario to ensure that its key design 

parameters would represent the upper end of the range of 

possible values, such that it would represent a conservative but 

not impossible scenario. The facility-specific emissions rates 

of each of the PB–HAP were compared to thetheir corresponding

emission rate thresholdscreening values for each of the PB–HAP 

identified to assess the potential for significant human health 
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risks via non-inhalation pathways. We call this application of 

the TRIM.FaTE model the Tier I TRIM- Screen or Tier I screen. 

For the purpose of developing emissions rates for our Tier 

I TRIM-Screen, we derived emission levels for each PB-HAP (other 

than lead) at which the maximum excess lifetime cancer risk 

would be 1-in-1 million or, for HAP that cause non-cancer health 

effects, the maximum HQ would be 1. If the emissions rate of any 

PB-HAP exceeds the Tier I screening emissions rate for any 

facility, we conduct a second screen, which we call the Tier II 

TRIM-screen or Tier II screen. In the Tier II screen, the 

location of each facility that exceeded the Tier I emission rate 

is used to refine the assumptions associated with the 

environmental scenario while maintaining the exposure scenario 

assumptions. We then adjust the risk-based Tier I screening 

level for each PB-HAP for each facility based on an 

understanding of how exposure concentrations estimated for the 

screening scenario change with meteorology and environmental 

assumptions. PB-HAP emissions that do not exceed these new Tier 

II screening levels are considered to pose no unacceptable 

risks. When facilities exceed the Tier II screening levels, it 

does not mean that multi-pathway impacts are significant, only 

that we cannot rule out that possibility based on the results of 

the screen. These facilities may be further evaluated for multipathway risks using the TRIM.FaTE model. 
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In evaluating the potential for multi-pathway risk from 

emissions of lead compounds, rather than developing a screening 

emissions rate for them, we compared modeled maximum estimated 

chronic inhalation exposures with the level of the current 

National Ambient Air Quality Standards (NAAQS) for lead.14 Values 

below the level of the primary (health-based) lead NAAQS were 

considered to have a low potential for multi-pathway risk. 

For further information on the multi-pathway analysis 

approach, see the Draft Residual Risk Assessment for the

Petroleum Refining Source Sector, which is available in the 

docket for this action (Docket ID Number EPA-HQ-OAR-2010-0682). 

5. How did we assess risks considering emissions control 

options? 

In addition to assessing baseline inhalation risks and 

screening for potential multipathway risks, we also estimated 

risks considering the potential emission reductions that would 

be achieved by the control options under consideration. We used 

 

14 In doing so, EPA notes that the legal standard for a primary NAAQS – that a 

standard is requisite to protect public health and provide an adequate margin 

of safety (CAA Section 109(b)) – differs from the Section 112(f) standard 

(requiring among other things that the standard provide an “ample margin of 

safety”). However, the lead NAAQS is a reasonable measure of determining risk 

acceptability (i.e., the first step of the Benzene NESHAP analysis) since it 

is designed to protect the most susceptible group in the human population – 

children, including children living near major lead emitting sources. 73 FR 

67002/3; 73 FR 67000/3; 73 FR 67005/1, November 12, 2008. In addition, 

applying the level of the primary lead NAAQS at the risk acceptability step 

is conservative, since that primary lead NAAQS reflects an adequate margin of 

safety. 
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the same emissions inventory that we used for the risk modeling 

and applied emission reduction estimates for the control options 

we are proposing to calculate the post-control risk. We note 

that for storage vessels, in response to the ICR some facilities 

reported emissions for their tank farm or a group of storage 

vessels rather than for each individual storage vessel. In order 

to calculate emissions for each storage vessel, we used unitspecific data from the ICR to estimate the pre- and post-control 

emissions based on the operating characteristics and controls 

reported for each unit. For example, HAP emissions from each 

storage vessel were estimated based on the size, contents, and 

controls reported for that storage vessel. If additional 

controls would be necessary to comply with proposed requirements 

for storage vessels, the HAP emissions were again estimated 

based on the upgraded controls. The pre- and post-control 

emissions were summed across all storage vessels at the facility 

to determine a facility-specific emission reduction factor. The 

facility-specific emission reduction factor was then used to 

adjust the emissions for each of the pollutants reported for 

storage vessels at that facility to account for the post-control 

emissions. In this manner, the expected emission reductions were 

applied to the specific HAP and emission points in the source 

category dataset to develop corresponding estimates of risk and 

incremental risk reductions. The resulting emission file used 
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for post-control risk analysis is available in the docket for 

this action (Docket ID Number EPA-HQ-OAR-2010-0682). 

6. How did we conduct the environmental risk screening 

assessment? 

a. Adverse Environmental Effect 

The EPA has developed a screening approach to examine the 

potential for adverse environmental effects as required under 

Ssection 112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA 

defines “adverse environmental effect” as “any significant and 

widespread adverse effect, which may reasonably be anticipated, 

to wildlife, aquatic life, or other natural resources, including 

adverse impacts on populations of endangered or threatened 

species or significant degradation of environmental quality over 

broad areas.” 

b. Environmental HAP 

The EPA focuses on seven HAP, which we refer to as 

“environmental HAP,” in its screening analysis: five PB-HAP and 

two acid gases. The five PB-HAP are cadmium, dioxins/furans, 

POM, mercury (both inorganic mercury and methyl mercury) and 

lead compounds. The two acid gases are HCl and HF. The rationale 

for including these seven HAP in the environmental risk 

screening analysis is presented below. 

HAP that persist and bioaccumulate are of particular 

environmental concern because they accumulate in the soil, 
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sediment and water. The PB-HAP are taken up, through sediment, 

soil, water, and/or ingestion of other organisms, by plants or 

animals (e.g., small fish) at the bottom of the food chain. As 

larger and larger predators consume these organisms, 

concentrations of the PB-HAP in the animal tissues increases as 

does the potential for adverse effects. The five PB-HAP we 

evaluate as part of our screening analysis account for 99.8 

percent of all PB-HAP emissions nationally from stationary 

sources (on a mass basis from the 2005 National Emissions 

Inventory (NEI)). 

In addition to accounting for almost all of the mass of PBHAP emitted, we note that the TRIM.Fate model that we use to 

evaluate multipathway risk allows us to estimate concentrations 

of cadmium compounds, dioxins/furans, POM and mercury in soil, 

sediment and water. For lead compounds, we currently do not have 

the ability to calculate these concentrations using the 

TRIM.Fate model. Therefore, to evaluate the potential for 

adverse environmental effects from lead, we compare the 

estimated HEM-modeled exposures from the source category 

emissions of lead with the level of the secondary NAAQS for 
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lead.15 We consider values below the level of the secondary lead 

NAAQS to be unlikely to cause adverse environmental effects. 

Due to their well-documented potential to cause direct 

damage to terrestrial plants, we include two acid gases, HCl and 

HF, in the environmental screening analysis. According to the 

2005 NEI, HCl and HF account for about 99 percent (on a mass 

basis) of the total acid gas HAP emitted by stationary sources 

in the U.S. In addition to the potential to cause direct damage 

to plants, high concentrations of HF in the air have been linked 

to fluorosis in livestock. Air concentrations of these HAP are 

already calculated as part of the human multipathway exposure 

and risk screening analysis using the HEM3-AERMOD air dispersion 

model, and we are able to use the air dispersion modeling 

results to estimate the potential for an adverse environmental 

effect. 

The EPA acknowledges that other HAP beyond the seven HAP 

discussed above may have the potential to cause adverse 

environmental effects. Therefore, the EPA may include other 

relevant HAP in its environmental risk screening in the future, 

as modeling science and resources allow. The EPA invites comment 

 

15 The secondary lead NAAQS is a reasonable measure of determining whether 

there is an adverse environmental effect since it was established considering 

“effects on soils, water, crops, vegetation, man-made materials, animals, 

wildlife, weather, visibility and climate, damage to and deterioration of 

property, and hazards to transportation, as well as effects on economic 

values and on personal comfort and well-being.”
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on the extent to which other HAP emitted by the source 

categories may cause adverse environmental effects. Such 

information should include references to peer-reviewed 

ecological effects benchmarks that are of sufficient quality for 

making regulatory decisions, as well as information on the 

presence of organisms located near facilities within the source 

categories that such benchmarks indicate could be adversely 

affected. 

c. Ecological Assessment Endpoints and Benchmarks for PB-HAP 

An important consideration in the development of the EPA’s 

screening methodology is the selection of ecological assessment 

endpoints and benchmarks. Ecological assessment endpoints are 

defined by the ecological entity (e.g., aquatic communities 

including fish and plankton) and its attributes (e.g., frequency 

of mortality). Ecological assessment endpoints can be 

established for organisms, populations, communities or 

assemblages, and ecosystems. 

For PB-HAP, we evaluated the following community-level 

ecological assessment endpoints to screen for organisms directly 

exposed to HAP in soils, sediment and water: 

 Local terrestrial communities (i.e., soil invertebrates, 

plants) and populations of small birds and mammals that 

consume soil invertebrates exposed to PB-HAP in the 

surface soil. 
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 Local benthic (i.e., bottom sediment dwelling insects, 

amphipods, isopods and crayfish) communities exposed to 

PB-HAP in sediment in nearby water bodies. 

 Local aquatic (water-column) communities (including fish 

and plankton) exposed to PB-HAP in nearby surface waters. 

For PB-HAP, we also evaluated the following populationlevel ecological assessment endpoint to screen for indirect HAP 

exposures of top consumers via the bioaccumulation of HAP in 

food chains. 

 Piscivorous (i.e., fish-eating) wildlife consuming PBHAP-contaminated fish from nearby water bodies. 

For cadmium compounds, dioxins/furans, POM and mercury, we 

identified the available ecological benchmarks for each 

assessment endpoint. An ecological benchmark represents a 

concentration of HAP (e.g., 0.77 micrograms of HAP per liter of 

water) that has been linked to a particular environmental effect 

level (e.g., a no-observed-adverse-effect level (NOAEL)) through 

scientific study. For PB-HAP we identified, where possible, 

ecological benchmarks at the following effect levels: 

 Probable effect level (PEL): Level above which adverse 

effects are expected to occur frequently. 

 Lowest-observed-adverse-effect level (LOAEL): The lowest 

exposure level tested at which there are biologically 
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significant increases in frequency or severity of adverse 

effects. 

 No-observed-adverse-effect level (NOAEL): The highest 

exposure level tested at which there are no biologically 

significant increases in the frequency or severity of 

adverse effect. 

We established a hierarchy of preferred benchmark sources 

to allow selection of benchmarks for each environmental HAP at 

each ecological assessment endpoint. In general, the EPA sources 

that are used at a programmatic level (e.g., Office of Water, 

Superfund Program) were used, if available. If not, the EPA 

benchmarks used in regional programs (e.g., Superfund) were 

used. If benchmarks were not available at a programmatic or 

regional level, we used benchmarks developed by other federal 

agencies (e.g., NOAA) or state agencies. 

Benchmarks for all effect levels are not available for all 

PB-HAP and assessment endpoints. In cases where multiple effect 

levels were available for a particular PB-HAP and assessment 

endpoint, we use all of the available effect levels to help us 

to determine whether ecological risks exist and, if so, whether 

the risks could be considered significant and widespread. 

d. Ecological Assessment Endpoints and Benchmarks for Acid Gases 

The environmental screening analysis also evaluated 

potential damage and reduced productivity of plants due to 
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direct exposure to acid gases in the air. For acid gases, we 

evaluated the following ecological assessment endpoint: 

 Local terrestrial plant communities with foliage exposed 

to acidic gaseous HAP in the air. 

The selection of ecological benchmarks for the effects of 

acid gases on plants followed the same approach as for PB-HAP 

(i.e., we examine all of the available chronic benchmarks). For 

HCl, the EPA identified chronic benchmark concentrations. We 

note that the benchmark for chronic HCl exposure to plants is 

greater than the reference concentration for chronic inhalation 

exposure for human health. This means that where EPA includes 

regulatory requirements to prevent an exceedance of the 

reference concentration for human health, additional analyses 

for adverse environmental effects of HCl would not be necessary. 

For HF, EPA identified chronic benchmark concentrations for 

plants and evaluated chronic exposures to plants in the 

screening analysis. High concentrations of HF in the air have 

also been linked to fluorosis in livestock. However, the HF 

concentrations at which fluorosis in livestock occur are higher 

than those at which plant damage begins. Therefore, the 

benchmarks for plants are protective of both plants and 

livestock. 
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e. Screening Methodology 

For the environmental risk screening analysis, the EPA 

first determined whether any petroleum refineries emitted any of 

the seven environmental HAP. For the petroleum refinery source 

categories, we identified emissions of cadmium, dioxins/furans, 

POM, mercury (both inorganic mercury and methyl mercury), lead, 

HCl and HF. 

Because one or more of the seven environmental HAP 

evaluated are emitted by at least one petroleum refinery, we 

proceeded to the second step of the evaluation. 

f. PB-HAP Methodology 

For cadmium, mercury, POM and dioxins/furans, the 

environmental screening analysis consists of two tiers, while 

lead is analyzed differently as discussed earlier. In the first 

tier, we determined whether the maximum facility-specific 

emission rates of each of the emitted environmental HAP were 

large enough to create the potential for adverse environmental 

effects under reasonable worst-case environmental conditions. 

These are the same environmental conditions used in the human 

multipathway exposure and risk screening analysis. 

To facilitate this step, TRIM.FaTE was run for each PB-HAP 

under hypothetical environmental conditions designed to provide 

conservatively high HAP concentrations. The model was set to 

maximize runoff from terrestrial parcels into the modeled lake, 
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which in turn, maximized the chemical concentrations in the 

water, the sediments, and the fish. The resulting media 

concentrations were then used to back-calculate a screening 

threshold emission rate that corresponded to the relevant 

exposure benchmark concentration value for each assessment 

endpoint. To assess emissions from a facility, the reported 

emission rate for each PB-HAP was compared to the screening 

threshold emission rate for that PB-HAP for each assessment 

endpoint. If emissions from a facility do not exceed the Tier I 

threshold, the facility “passes” the screen, and therefore, is 

not evaluated further under the screening approach. If emissions 

from a facility exceed the Tier I threshold, we evaluate the 

facility further in Tier II. 

In Tier II of the environmental screening analysis, the 

screening emission thresholds are adjusted to account for local 

meteorology and the actual location of lakes in the vicinity of 

facilities that did not pass the Tier I screen. The modeling 

domain for each facility in the Tier II analysis consists of 

eight octants. Each octant contains five modeled soil 

concentrations at various distances from the facility (5 soil 

concentrations x 8 octants = total of 40 soil concentrations per 

facility) and one lake with modeled concentrations for water, 

sediment and fish tissue. In the Tier II environmental risk 

screening analysis, the 40 soil concentration points are 
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averaged to obtain an average soil concentration for each 

facility for each PB-HAP. For the water, sediment and fish 

tissue concentrations, the highest value for each facility for 

each pollutant is used. If emission concentrations from a 

facility do not exceed the Tier II threshold, the facility 

passes the screen, and is typically not evaluated further. If 

emissions from a facility exceed the Tier II threshold, the 

facility does not pass the screen and, therefore, may have the 

potential to cause adverse environmental effects. Such 

facilities are evaluated further to investigate factors such as 

the magnitude and characteristics of the area of exceedance. 

g. Acid Gas Methodology 

The environmental screening analysis evaluates the 

potential phytotoxicity and reduced productivity of plants due 

to chronic exposure to acid gases. The environmental risk 

screening methodology for acid gases is a single-tier screen 

that compares the average off-site ambient air concentration 

over the modeling domain to ecological benchmarks for each of 

the acid gases. Because air concentrations are compared directly 

to the ecological benchmarks, emission-based thresholds are not 

calculated for acid gases as they are in the ecological risk 

screening methodology for PB-HAP. 

For purposes of ecological risk screening, EPA identifies a 

potential for adverse environmental effects to plant communities 
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from exposure to acid gases when the average concentration of 

the HAP around a facility exceeds the LOAEL ecological 

benchmark. In such cases, we further investigate factors such as 

the magnitude and characteristics of the area of exceedance 

(e.g., land use of exceedance area, size of exceedance area) to 

determine if there is an adverse environmental effect. 

For further information on the environmental screening 

analysis approach, see Ssection IV.C.5 of this preamble and the 

Draft Residual Risk Assessment for the Petroleum Refining Source 

Sector, which is available in the docket for this action (Docket 

ID Number EPA-HQ-OAR-2010-0682). 

7. How did we conduct facility-wide assessments? 

To put the source category risks in context, we 

typicallyfollowing the assessment approach outlined in the SAB 

(2010) review, we examine the risks from the entire “facility,” 

where the facility includes all HAP-emitting operations within a 

contiguous area and under common control. In other words, we 

examine the HAP emissions not only from the source category 

emission points of interest, but also emissions of HAP from all 

other emission sources at the facility for which we have data. 

The emissions inventories provided in response to the ICR 

included emissions information for all emission sources at the 

facilities that are part of the refineries source categories. 

Generally, only a few emission sources located at refineries are 
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not subject to either Refinery MACT 1 or 2; the most notable are 

boilers, process heaters and internal combustion engines, which 

are addressed by other MACT standards. 

We analyzed risks due to the inhalation of HAP that are 

emitted “facility-wide” for the populations residing within 50 

km of each facility, consistent with the methods used for the 

source category analysis described above. For these facilitywide risk analyses, the modeled source category risks were 

compared to the facility-wide risks to determine the portion of 

facility-wide risks that could be attributed to each of the 

source categories addressed in this proposal. We specifically 

examined the facility that was associated with the highest 

estimates of risk and determined the percentage of that risk 

attributable to the source category of interest. The Draft 

Residual Risk Assessment for the Petroleum Refining Source 

Sector available through the docket for this action (Docket ID 

Number EPA-HQ-OAR-2010-0682) provides the methodology and 

results of the facility-wide analyses, including all facilitywide risks and the percentage of source category contribution to 

facility-wide risks. 

8. How did we consider uncertainties in risk assessment? 

In the Benzene NESHAP we concluded that risk estimation 

uncertainty should be considered in our decision-making under 

the ample margin of safety framework. Uncertainty and the 
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potential for bias are inherent in all risk assessments, 

including those performed for this proposal. Although 

uncertainty exists, we believe that our approach, which used 

conservative tools and assumptions, ensures that our decisions 

are health protective and environmentally protective. A brief 

discussion of the uncertainties in the emissions datasets, 

dispersion modeling, inhalation exposure estimates and doseresponse relationships follows below. A more thorough discussion 

of these uncertainties is included in the Draft Residual Risk 

Assessment for the Petroleum Refining Source Sector, which is 

available in the docket for this action (Docket ID Number EPAHQ-OAR-2010-0682). 

a. Uncertainties in the Emission Datasets 

Although the development of the RTR datasets involved 

quality assurance/quality control processes, the accuracy of 

emissions values will vary depending on the source of the data, 

the degree to which data are incomplete or missing, the degree 

to which assumptions made to complete the datasets are accurate, 

errors in emission estimates and other factors. The emission 

estimates considered in this analysis are annual totals for 

2010, and they do not reflect short-term fluctuations during the 

course of a year or variations from year to year. The estimates 

of peak hourly emissions rates for the acute effects screening 

assessment were based on emission adjustment factors applied to 
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the average annual hourly emission rates, which are intended to 

account for emission fluctuations due to normal facility 

operations. 

As discussed previously, we attempted to provide a 

consistent framework for reporting of emissions information by 

developing the refinery emissions estimation protocol and 

requesting that refineries follow the protocol when reporting 

emissions inventory data in response to the ICR. This protocol, 

called Emission Estimation Protocol for Petroleum Refineries, is 

available in the docket for this rulemaking (Docket Item Number 

EPA-HQ-OAR-2010-0682-0060). Additionally, we developed our own 

estimates of emissions that are based on the factors provided in 

the protocol and the REM Model. We developed emission estimates 

based on refinery unit capacities, which also provided an 

estimate of allowable emissions. We then conducted risk modeling 

using REM Model estimates and by locating emissions at the 

centroid of each refinery in an attempt to understand the risk 

associated with emissions from each refinery. Therefore, even if 

there were errors in the emission inventories reported in the 

ICR, as was the case in many instances, emissions for those 

facilities were also modeled using the protocol emission 

factors. The risk modeling of allowable emissions based on 

emission factors and unit capacities did not result in 

significantly different risk results than the actual emissions 
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modeling runs. Results of the allowable emissions risk estimates 

are provided in the Draft Residual Risk Assessment for the 

Petroleum Refining Source Sector, which is available in Docket 

ID Number EPA-HQ-OAR-2010-0682. 

b. Uncertainties in Dispersion Modeling 

We recognize there is uncertainty in ambient concentration 

estimates associated with any model, including the EPA’s 

recommended regulatory dispersion model, AERMOD. In using a 

model to estimate ambient pollutant concentrations, the user 

chooses certain options to apply. For RTR assessments, we select 

some model options that have the potential to overestimate 

ambient air concentrations (e.g., not including plume depletion 

or pollutant transformation). We select other model options that 

have the potential to underestimate ambient impacts (e.g., not 

including building downwash). Other options that we select have 

the potential to either under- or overestimate ambient levels 

(e.g., meteorology and receptor locations). On balance, 

considering the directional nature of the uncertainties commonly 

present in ambient concentrations estimated by dispersion 

models, the approach we apply in the RTR assessments should 

yield unbiased estimates of ambient HAP concentrations. 

c. Uncertainties in Inhalation Exposure 

The EPA did not include the effects of human mobility on 

exposures in the assessment. Specifically, short-term mobility 
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and long-term mobility between census blocks in the modeling 

domain were not considered.16 The approach of not considering 

short- or long-term population mobility does not bias the 

estimate of the theoretical MIR (by definition), nor does it 

affect the estimate of cancer incidence because the total 

population number remains the same. It does, however, affect the 

shape of the distribution of individual risks across the 

affected population, shifting it toward higher estimated 

individual risks at the upper end and reducing the number of 

people estimated to be at lower risks, thereby increasing the 

estimated number of people at specific high-risk levels (e.g., 

1-in-10 thousand or 1-in-1 million). 

In addition, the assessment predicted the chronic exposures 

at the centroid of each populated census block as surrogates for 

the exposure concentrations for all people living in that block. 

Using the census block centroid to predict chronic exposures 

tends to over-predict exposures for people in the census block 

who live further from the facility and under-predict exposures 

for people in the census block who live closer to the facility. 

Thus, using the census block centroid to predict chronic 

exposures may lead to a potential understatement or 

 

16 Short-term mobility is movement from one micro-environment to another over 

the course of hours or days. Long-term mobility is movement from one 

residence to another over the course of a lifetime. 
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overstatement of the true maximum impact, but is an unbiased 

estimate of average risk and incidence. We reduce this 

uncertainty by analyzing large census blocks near facilities 

using aerial imagery and adjusting the location of the block 

centroid to better represent the population in the block, as 

well as adding additional receptor locations where the block 

population is not well represented by a single location. 

The assessment evaluates the cancer inhalation risks 

associated with pollutant exposures over a 70-year period, which 

is the assumed lifetime of an individual. In reality, both the 

length of time that modeled emission sources at facilities 

actually operate (i.e., more or less than 70 years) and the 

domestic growth or decline of the modeled industry (i.e., the 

increase or decrease in the number or size of domestic 

facilities) will influence the future risks posed by a given 

source or source category. Depending on the characteristics of 

the industry, these factors will, in most cases, result in an 

overestimate both in individual risk levels and in the total 

estimated number of cancer cases. However, in the unlikely 

scenario where a facility maintains, or even increases, its 

emissions levels over a period of more than 70 years, residents 

live beyond 70 years at the same location, and the residents 

spend most of their days at that location, then the cancer 

inhalation risks could potentially be underestimated. However, 
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annual cancer incidence estimates from exposures to emissions 

from these sources would not be affected by the length of time 

an emissions source operates. 

The exposure estimates used in these analyses assume 

chronic exposures to ambient (outdoor) levels of pollutants. 

Because most people spend the majority of their time indoors, 

actual exposures may not be as high, depending on the 

characteristics of the pollutants modeled. For many of the HAP, 

indoor levels are roughly equivalent to ambient levels, but for 

very reactive pollutants or larger particles, indoor levels are 

typically lower. This factor has the potential to result in an 

overestimatement of 25 to 30 percent of exposures.17

In addition to the uncertainties highlighted above, there 

are several factors specific to the acute exposure assessment 

that should be highlighted. The accuracy of an acute inhalation 

exposure assessment depends on the simultaneous occurrence of 

independent factors that may vary greatly, such as hourly 

emissions rates, meteorology and human activity patterns. In 

this assessment, we assume that individuals remain for 1 hour at 

the point of maximum ambient concentration as determined by the 

co-occurrence of peak emissions and worst-case meteorological 

conditions. These assumptions would tend to be worst-case actual 

 

17 U.S. EPA. National-Scale Air Toxics Assessment for 1996. (EPA 453/R–01–003; 

January 2001; page 85.) 
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exposures as it is unlikely that a person would be located at 

the point of maximum exposure during the time ofwhen peak 

emissions and worst-case impactmeteorological conditions occur 

simultaneously. 

d. Uncertainties in Dose-Response Relationships 

There are uncertainties inherent in the development of the 

dose-response values used in our risk assessments for cancer 

effects from chronic exposures and non-cancer effects from both 

chronic and acute exposures. Some uncertainties may be 

considered quantitatively, and others generally are expressed in 

qualitative terms. We note as a preface to this discussion a 

point on dose-response uncertainty that is brought out in the 

EPA’s 2005 Cancer Guidelines; namely, that “the primary goal of 

EPA actions is protection of human health; accordingly, as an 

Agency policy, risk assessment procedures, including default 

options that are used in the absence of scientific data to the 

contrary, should be health protective” (EPA 2005 Cancer 

Guidelines, pages 1–7). This is the approach followed here as 

summarized in the next several paragraphs. A complete detailed 

discussion of uncertainties and variability in dose-response 

relationships is given in the Draft Residual Risk Assessment for 

the Petroleum Refining Source Sector, which is available in the 

docket for this action (Docket ID Number EPA-HQ-OAR-2010-0682). 
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Cancer URE values used in our risk assessments are those 

that have been developed to generally provide an upper bound 

estimate of risk. That is, they represent a “plausible upper 

limit to the true value of a quantity” (although this is usually 

not a true statistical confidence limit).18 In some 

circumstances, the true risk could be as low as zero; however, 

in other circumstances, the risk could also be greater.19 When 

developing an upper-bound estimate of risk and to provide risk 

values that do not underestimate risk, health-protective default 

approaches are generally used. To err on the side of ensuring 

adequate health-protection, the EPA typically uses the upper 

bound estimates rather than lower bound or central tendency 

estimates in our risk assessments, an approach that may have 

limitations for other uses (e.g., priority-setting or expected 

benefits analysis). 

Chronic non-cancer RfC and reference dose (RfD) values 

represent chronic exposure levels that are intended to be 

health-protective levels. Specifically, these values provide an 

estimate (with uncertainty spanning perhaps an order of 

 

18 IRIS glossary 

(http://wwwofmpub.epa.gov/NCEA/iris/help_gloss.htmsor_internet/registry/termr

eg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryNam

e=IRIS%20Glossary). 

19 An exception to this is the URE for benzene, which is considered to cover a 

range of values, each end of which is considered to be equally plausible, and 

which is based on maximum likelihood estimates. 
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magnitude) of a continuous inhalation exposure (RfC) or a daily 

oral exposure (RfD) to the human population (including sensitive 

subgroups) that is likely to be without an appreciable risk of 

deleterious effects during a lifetime. To derive values that are 

intended to be “without appreciable risk,” the methodology 

relies upon an uncertainty factor (UF) approach (U.S. EPA, 1993, 

1994) which considers uncertainty, variability and gaps in the 

available data. The UF are applied to derive reference values 

that are intended to protect against appreciable risk of 

deleterious effects. The UF are commonly default values,20 e.g., 

factors of 10 or 3, used in the absence of compound-specific 

data; where data are available, UF may also be developed using 

compound-specific information. When data are limited, more 

assumptions are needed and more UF are used. Thus, there may be 

a greater tendency to overestimate risk in the sense that 

further study might support development of reference values that 

 

20 According to the NRC report, Science and Judgment in Risk Assessment (NRC, 

1994) “[Default] options are generic approaches, based on general scientific 

knowledge and policy judgment, that are applied to various elements of the 

risk assessment process when the correct scientific model is unknown or 

uncertain.” The 1983 NRC report, Risk Assessment in the Federal Government: 

Managing the Process, defined default option as “the option chosen on the 

basis of risk assessment policy that appears to be the best choice in the 

absence of data to the contrary” (NRC, 1983a, p. 63). Therefore, default 

options are not rules that bind the Agency; rather, the Agency may depart 

from them in evaluating the risks posed by a specific substance when it 

believes this to be appropriate. In keeping with EPA’s goal of protecting 

public health and the environment, default assumptions are used to ensure 

that risk to chemicals is not underestimated (although defaults are not 

intended to overtly overestimate risk). See EPA, 2004, An Examination of EPA 

Risk Assessment Principles and Practices, EPA/100/B–04/001 available at: 

http://www.epa.gov/osa/pdfs/ratf-final.pdf. 
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are higher (i.e., less potent) because fewer default assumptions 

are needed. However, for some pollutants, it is possible that 

risks may be underestimated. 

While collectively termed “UF,” these factors account for a 

number of different quantitative considerations when using 

observed animal (usually rodent) or human toxicity data in the 

development of the RfC. The UF are intended to account for: (1) 

variation in susceptibility among the members of the human 

population (i.e., inter-individual variability); (2) uncertainty 

in extrapolating from experimental animal data to humans (i.e., 

interspecies differences); (3) uncertainty in extrapolating from 

data obtained in a study with less-than-lifetime exposure (i.e., 

extrapolating from sub-chronic to chronic exposure); (4) 

uncertainty in extrapolating the observed data to obtain an 

estimate of the exposure associated with no adverse effects; and 

(5) uncertainty when the database is incomplete or there are 

problems with the applicability of available studies. 

Many of the UF used to account for variability and 

uncertainty in the development of acute reference values are 

quite similar to those developed for chronic durations, but they 

more often use individual UF values that may be less than 10. 

The UF are applied based on chemical-specific or health effectspecific information (e.g., simple irritation effects do not 

vary appreciably between human individuals, hence a value of 3 
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is typically used), or based on the purpose for the reference 

value (see the following paragraph). The UF applied in acute 

reference value derivation include: (1) heterogeneity among 

humans; (2) uncertainty in extrapolating from animals to humans; 

(3) uncertainty in lowest observable adverse effect (exposure) 

level to no observed adverse effect (exposure) level 

adjustments; and (4) uncertainty in accounting for an incomplete 

database on toxic effects of potential concern. Additional 

adjustments are often applied to account for uncertainty in 

extrapolation from observations at one exposure duration (e.g., 

4 hours) to derive an acute reference value at another exposure 

duration (e.g., 1 hour). 

Not all acute reference values are developed for the same 

purpose and care must be taken when interpreting the results of 

an acute assessment of human health effects relative to the 

reference value or values being exceeded. Where relevant to the 

estimated exposures, the lack of short-term dose-response values 

at different levels of severity should be factored into the risk 

characterization as potential uncertainties. 

Although every effort is made to identify appropriate human 

health effect dose-response assessment values for all pollutants 

emitted by the sources in this risk assessment, some HAP emitted 

by these source categories are lacking dose-response 

assessments. Accordingly, these pollutants cannot be included in 
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the quantitative risk assessment, which could result in 

quantitative estimates understating HAP risk. To help to 

alleviate this potential underestimate, where we conclude 

similarity with a HAP for which a dose-response assessment value 

is available, we use that value as a surrogate for the 

assessment of the HAP for which no value is available. To the 

extent use of surrogates indicates appreciable risk, we may 

identify a need to increase priority for new IRIS assessment of 

that substance. We additionally note that, generally speaking, 

HAP of greatest concern due to environmental exposures and 

hazard are those for which dose-response assessments have been 

performed, reducing the likelihood of understating risk. 

Further, HAP not included in the quantitative assessment are 

assessed qualitatively and considered in the risk 

characterization that informs the risk management decisions, 

including with regard to consideration of HAP reductions 

achieved by various control options. 

For a group of compounds that are unspeciated (e.g., glycol 

ethers), we conservatively use the most protective reference 

value of an individual compound in that group to estimate risk. 

Similarly, for an individual compound in a group (e.g., ethylene 

glycol diethyl ether) that does not have a specified reference 

value, we also apply the most protective reference value from 

the other compounds in the group to estimate risk. 
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e. Uncertainties in the Multipathway Assessment 

For each source category, we generally rely on sitespecific levels of PB-HAP emissions to determine whether a 

refined assessment of the impacts from multipathway exposures is 

necessary. This determination is based on the results of a twotiered screening analysis that relies on the outputs from models 

that estimate environmental pollutant concentrations and human 

exposures for four PB-HAP. Two important types of uncertainty 

associated with the use of these models in RTR risk assessments 

and inherent to any assessment that relies on environmental 

modeling are model uncertainty and input uncertainty.21

Model uncertainty concerns whether the selected models are 

appropriate for the assessment being conducted and whether they 

adequately represent the actual processes that might occur for 

that situation. An example of model uncertainty is the question 

of whether the model adequately describes the movement of a 

pollutant through the soil. This type of uncertainty is 

difficult to quantify. However, based on feedback received from 

previous EPA SAB reviews and other reviews, we are confident 

that the models used in the screen are appropriate and state-of-

 

21 In the context of this discussion, the term “uncertainty” as it pertains to 

exposure and risk encompasses both variability in the range of expected 

inputs and screening results due to existing spatial, temporal, and other 

factors, as well as uncertainty in being able to accurately estimate the true 

result. 
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the-art for the multipathway risk assessments conducted in 

support of RTR. 

Input uncertainty is concerned with how accurately the 

models have been configured and parameterized for the assessment 

at hand. For Tier I of the multipathway screen, we configured 

the models to avoid underestimating exposure and risk. This was 

accomplished by selecting upper-end values from nationallyrepresentative data sets for the more influential parameters in 

the environmental model, including selection and spatial 

configuration of the area of interest, lake location and size, 

meteorology, surface water and soil characteristics and 

structure of the aquatic food web. We also assume an ingestion 

exposure scenario and values for human exposure factors that 

represent reasonable maximum exposures. 

In Tier II of the multipathway assessment, we refine the 

model inputs to account for meteorological patterns in the 

vicinity of the facility versus using upper-end national values 

and we identify the actual location of lakes near the facility 

rather than the default lake location that we apply in Tier I. 

By refining the screening approach in Tier II to account for 

local geographical and meteorological data, we decrease the 

likelihood that concentrations in environmental media are 

overestimated, thereby increasing the usefulness of the screen. 

The assumptions and the associated uncertainties regarding the 
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selected ingestion exposure scenario are the same for Tier I and 

Tier II. 

For both Tiers I and II of the multipathway assessment, our 

approach to addressing model input uncertainty is generally 

cautious. We choose model inputs from the upper end of the range 

of possible values for the influential parameters used in the 

models, and we assume that the exposed individual exhibits 

ingestion behavior that would lead to a high total exposure. 

This approach reduces the likelihood of not identifying high 

risks for adverse impacts. 

Despite the uncertainties, when individual pollutants or 

facilities do screen out, we are confident that the potential 

for adverse multipathway impacts on human health is very low. On 

the other hand, when individual pollutants or facilities do not 

screen out, it does not mean that multipathway impacts are 

significant, only that we cannot rule out that possibility and 

that a refined multipathway analysis for the site might be 

necessary to obtain a more accurate risk characterization for 

the source categories. 

For further information on uncertainties and the Tier I and 

II screening methods, refer to the risk document Appendix 4, 

Technical Support Document for TRIM-Based Multipathway Tiered 

Screening Methodology for RTR. 
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f. Uncertainties in the Environmental Risk Screening Assessment 

For each source category, we generally rely on sitespecific levels of environmental HAP emissions to perform an 

environmental screening assessment. The environmental screening 

assessment is based on the outputs from models that estimate 

environmental HAP concentrations. The same models, specifically 

the TRIM.FaTE multipathway model and the AERMOD air dispersion 

model, are used to estimate environmental HAP concentrations for 

both the human multipathway screening analysis and for the 

environmental screening analysis. Therefore, both screening 

assessments have similar modeling uncertainties. 

Two important types of uncertainty associated with the use 

of these models in RTR environmental screening assessments—and 

inherent to any assessment that relies on environmental 

modeling—are model uncertainty and input uncertainty.22

Model uncertainty concerns whether the selected models are 

appropriate for the assessment being conducted and whether they 

adequately represent the movement and accumulation of 

environmental HAP emissions in the environment. For example, 

does the model adequately describe the movement of a pollutant 

 

22 In the context of this discussion, the term “uncertainty,” as it pertains 

to exposure and risk assessment, encompasses both variability in the range of 

expected inputs and screening results due to existing spatial, temporal, and 

other factors, as well as uncertainty in being able to accurately estimate 

the true result.
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through the soil? This type of uncertainty is difficult to 

quantify. However, based on feedback received from previous EPA 

SAB reviews and other reviews, we are confident that the models 

used in the screen are appropriate and state-of-the-art for the 

environmental risk assessments conducted in support of our RTR 

analyses. 

Input uncertainty is concerned with how accurately the 

models have been configured and parameterized for the assessment 

at hand. For Tier I of the environmental screen for PB-HAP, we 

configured the models to avoid underestimating exposure and risk 

to reduce the likelihood that the results indicate the risks are 

lower than they actually are. This was accomplished by selecting 

upper-end values from nationally-representative data sets for 

the more influential parameters in the environmental model, 

including selection and spatial configuration of the area of 

interest, the location and size of any bodies of water, 

meteorology, surface water and soil characteristics and 

structure of the aquatic food web. In Tier I, we used the 

maximum facility-specific emissions for cadmium compounds, 

dioxins/furans, POM, and mercury and each of the media when 

comparing to ecological benchmarks. This is consistent with the 

conservative design of Tier I of the screen. In Tier II of the 

environmental screening analysis for PB-HAP, we refine the model 

inputs to account for meteorological patterns in the vicinity of 
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the facility versus using upper-end national values, and we 

identify the locations of water bodies near the facility 

location. By refining the screening approach in Tier II to 

account for local geographical and meteorological data, we 

decrease the likelihood that concentrations in environmental 

media are overestimated, thereby increasing the usefulness of 

the screen. To better represent widespread impacts, the modeled 

soil concentrations are averaged in Tier II to obtain one 

average soil concentration value for each facility and for each 

PB-HAP. For PB-HAP concentrations in water, sediment and fish 

tissue, the highest value for each facility for each pollutant 

is used. 

For the environmental screening assessment for acid gases, 

we employ a single-tiered approach. We use the modeled air 

concentrations and compare those with ecological benchmarks. 

For both Tiers I and II of the environmental screening 

assessment, our approach to addressing model input uncertainty 

is generally cautious. We choose model inputs from the upper end 

of the range of possible values for the influential parameters 

used in the models, and we assume that the exposed 

individualorganism (e.g., invertebrate, fish) exhibits ingestion 

behavior that would lead to a high total exposure. This approach 

reduces the likelihood of not identifying potential risks for 

adverse environmental impacts. 
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Uncertainty also exists in the ecological benchmarks for 

the environmental risk screening analysis. We established a 

hierarchy of preferred benchmark sources to allow selection of 

benchmarks for each environmental HAP at each ecological 

assessment endpoint. In general, EPA benchmarks used at a 

programmatic level (e.g., Office of Water, Superfund Program) 

were used if available. If not, we used EPA benchmarks used in 

regional programs (e.g., Superfund). If benchmarks were not 

available at a programmatic or regional level, we used 

benchmarks developed by other agencies (e.g., NOAA) or by state 

agencies. 

In all cases (except for lead, which was evaluated through 

a comparison to the NAAQS), we searched for benchmarks at the 

following three effect levels, as described in Ssection III.A.6 

of this preamble: 

1. A no-effect level (i.e., NOAEL). 

2. Threshold-effect level (i.e., LOAEL). 

3. Probable effect level (i.e., PEL). 

For some ecological assessment endpoint/environmental HAP 

combinations, we could identify benchmarks for all three effect 

levels, but for most, we could not. In one case, where different 

agencies derived significantly different numbers to represent a 

threshold for effect, we included both. In several cases, only a 

single benchmark was available. In cases where multiple effect 
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levels were available for a particular PB-HAP and assessment 

endpoint, we used all of the available effect levels to help us 

to determine whether risk exists and if the risks could be 

considered significant and widespread. 

The EPA evaluated the following seven HAP in the 

environmental risk screening assessment: cadmium, 

dioxins/furans, POM, mercury (both inorganic mercury and methyl 

mercury), lead compounds, HCl and HF. These seven HAP represent 

pollutants that can cause adverse impacts for plants and animals 

either through direct exposure to HAP in the air or through 

exposure to HAP that is deposited from the air onto soils and 

surface waters. These seven HAP also represent those HAP for 

which we can conduct a meaningful environmental risk screening 

assessment. For other HAP not included in our screening 

assessment, the model has not been parameterized such that it 

can be used for that purpose. In some cases, depending on the 

HAP, we may not have appropriate multipathway models that allow 

us to predict the concentration of that pollutant. The EPA 

acknowledges that other HAP beyond the seven HAP that we are 

evaluating may have the potential to cause adverse environmental 

effects and, therefore, the EPA may evaluate other relevant HAP 

in the future, as modeling science and resources allow. 

Further information on uncertainties and the Tier I and II 

environmental screening methods is provided in Appendix 5 of the 
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document Technical Support Document for TRIM-Based Multipathway 

Tiered Screening Methodology for RTR: Summary of Approach and 

Evaluation. Also, see the Draft Residual Risk Assessment for the

Petroleum Refining Source Sector, available in the docket for 

this action (Docket ID Number EPA-HQ-OAR-2010-0682). 

B. How did we consider the risk results in making decisions for 

this proposal? 

As discussed in Ssection II.A.1 of this preamble, in 

evaluating and developing standards under CAA Ssection 

112(f)(2), we apply a two-step process to address residual risk. 

In the first step, the EPA determines whether risks are 

acceptable. This determination “considers all health 

information, including risk estimation uncertainty, and includes 

a presumptive limit on maximum individual lifetime [cancer] risk 

(MIR)23 of approximately [1-in-10 thousand] [i.e., 100-in-1 

million].” 54 FR 38045, September 14, 1989. If risks are 

unacceptable, the EPA must determine the emissions standards 

necessary to bring risks to an acceptable level without 

considering costs. In the second step of the process, the EPA 

considers whether the emissions standards provide an ample 

margin of safety “in consideration of all health information, 

 

23 Although defined as “maximum individual risk,” MIR refers only to cancer 

risk. MIR, one metric for assessing cancer risk, is the estimated risk were 

an individual exposed to the maximum level of a pollutant for a lifetime. 
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including the number of persons at risk levels higher than 

approximately 1-in-1 million, as well as other relevant factors, 

including costs and economic impacts, technological feasibility, 

and other factors relevant to each particular decision.” Id. The 

EPA must promulgate tighter emission standards if necessary to 

provide an ample margin of safety. 

In past residual risk actions, the EPA considered a number 

of human health risk metrics associated with emissions from the 

categories under review, including the MIR, the number of 

persons in various risk ranges, cancer incidence, the maximum 

non-cancer HI and the maximum acute non-cancer hazard. See, 

e.g., 72 FR 25138, May 3, 2007; 71 FR 42724, July 27, 2006. The 

EPA considered this health information for both actual and 

allowable emissions. See, e.g., 75 FR 65068, October 21, 2010, 

and 75 FR 80220, December 21, 2010). The EPA also discussed risk 

estimation uncertainties and considered the uncertainties in the 

determination of acceptable risk and ample margin of safety in 

these past actions. The EPA considered this same type of 

information in support of this action. 

The agency is considering these various measures of health 

information to inform our determinations of risk acceptability 

and ample margin of safety under CAA Ssection 112(f). As 

explained in the Benzene NESHAP, “the first step of judgment on 

acceptability cannot be reduced to any single factor,” and thus 
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“[t]he Administrator believes that the acceptability of risk 

under [previous] Ssection 112 is best judged on the basis of a 

broad set of health risk measures and information.” 54 FR 38046, 

September 14, 1989. Similarly, with regard to making the ample 

margin of safety determination, “the Agency again considers all 

of the health risk and other health information considered in 

the first step. Beyond that information, additional factors 

relating to the appropriate level of control will also be 

considered, including cost and economic impacts of controls, 

technological feasibility, uncertainties, and any other relevant 

factors.” Id. 

The Benzene NESHAP approach provides flexibility regarding 

factors the EPA may consider in making determinations and how 

the EPA may weigh those factors for each source category. In 

responding to comment on our policy under the Benzene NESHAP, 

the EPA explained that: 

“[t]he policy chosen by the Administrator permits 

consideration of multiple measures of health risk. Not only 

can the MIR figure be considered, but also incidence, the 

presence of non-cancer health effects, and the 

uncertainties of the risk estimates. In this way, the 

effect on the most exposed individuals can be reviewed as 

well as the impact on the general public. These factors can 

then be weighed in each individual case. This approach 

complies with the Vinyl Chloride mandate that the 

Administrator ascertain an acceptable level of risk to the 

public by employing [her] expertise to assess available 

data. It also complies with the Congressional intent behind 

the CAA, which did not exclude the use of any particular 

measure of public health risk from the EPA’s consideration 

with respect to CAA Ssection 112 regulations, and thereby 
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implicitly permits consideration of any and all measures of 

health risk which the Administrator, in [her] judgment, 

believes are appropriate to determining what will ‘protect 

the public health.’” 

See 54 FR at 38057, September 14, 1989. Thus, the level of the 

MIR is only one factor to be weighed in determining 

acceptability of risks. The Benzene NESHAP explained that “an 

MIR of approximately one in 10 thousand should ordinarily be the 

upper end of the range of acceptability. As risks increase above 

this benchmark, they become presumptively less acceptable under 

CAA Ssection 112, and would be weighed with the other health 

risk measures and information in making an overall judgment on 

acceptability. Or, the Agency may find, in a particular case, 

that a risk that includes MIR less than the presumptively 

acceptable level is unacceptable in the light of other health 

risk factors.” Id. at 38045. Similarly, with regard to the ample 

margin of safety analysis, the EPA stated in the Benzene NESHAP 

that: “EPA believes the relative weight of the many factors that 

can be considered in selecting an ample margin of safety can 

only be determined for each specific source category. This 

occurs mainly because technological and economic factors (along 

with the health-related factors) vary from source category to 

source category.” Id. at 38061. We also consider the 

uncertainties associated with the various risk analyses, as 
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discussed earlier in this preamble, in our determinations of 

acceptability and ample margin of safety. 

The EPA notes that it has not considered certain health 

information to date in making residual risk determinations. At 

this time, we do not attempt to quantify those HAP risks that 

may be associated with emissions from other facilities that do 

not include the source categories in question, mobile source 

emissions, natural source emissions, persistent environmental 

pollution or atmospheric transformation in the vicinity of the 

sources in these categories. 

The agency understands the potential importance of 

considering an individual’s total exposure to HAP in addition to 

considering exposure to HAP emissions from the source category 

and facility. We recognize that such consideration may be 

particularly important when assessing non-cancer risks, where 

pollutant-specific exposure health reference levels (e.g., RfCs) 

are based on the assumption that thresholds exist for adverse 

health effects. For example, the agency recognizes that, 

although exposures attributable to emissions from a source 

category or facility alone may not indicate the potential for 

increased risk of adverse non-cancer health effects in a 

population, the exposures resulting from emissions from the 

facility in combination with emissions from all of the other 

sources (e.g., other facilities) to which an individual is 
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exposed may be sufficient to result in increased risk of adverse 

non-cancer health effects. In May 2010, the SAB advised the EPA 

“that RTR assessments will be most useful to decision makers and 

communities if results are presented in the broader context of 

aggregate and cumulative risks, including background 

concentrations and contributions from other sources in the 

area.”24

In response to the SAB recommendations, the EPA is 

incorporating cumulative risk analyses into its RTR risk 

assessments, including those reflected in this proposal. The 

agency is: (1) conducting facility-wide assessments, which 

include source category emission points as well as other 

emission points within the facilities; (2) considering 

overlapping sources in the same category whose emissions result 

in exposures to the same individuals; and (3) for some 

persistent and bioaccumulative pollutants, analyzing the 

ingestion route of exposure. In addition, the RTR risk 

assessments have always considered aggregate cancer risk from 

all carcinogens and aggregate non-cancer hazard indices from all 

non-carcinogens affecting the same target organ system. 

 

24 EPA’s responses to this and all other key recommendations of the SAB’s 

advisory on RTR risk assessment methodologies (which is available at: 

http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$

File/EPA-SAB-10-007-unsigned.pdf) are outlined in a memo to this rulemaking 

docket from David Guinnup entitled, EPA’s Actions in Response to the Key 

Recommendations of the SAB Review of RTR Risk Assessment Methodologies. 
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Although we are interested in placing source category and 

facility-wide HAP risks in the context of total HAP risks from 

all sources combined in the vicinity of each source, we are 

concerned about the uncertainties of doing so. Because we have 

not conducted in-depth studies of the contributionrisks due to 

total HAP riskemissions from emission sources other than those 

that we have studied in depth duringat refineries subject to

this RTR review, such estimates of total HAP risks would have 

significantly greater associated uncertainties than the source 

category or facility-wide estimates. Such aggregate or 

cumulative assessments would compound those uncertainties, 

making the assessments too unreliable. 

C. How did we perform the technology review? 

Our technology review focused on the identification and 

evaluation of developments in practices, processes and control 

technologies that have occurred since the MACT standards were 

promulgated. Where we identified such developments, in order to 

inform our decision of whether it is “necessary” to revise the 

emissions standards, we analyzed the technical feasibility of 

applying these developments, and the estimated costs, energy 

implications, non-air environmental impacts, as well as 

considering the emission reductions. We also considered the 

appropriateness of applying controls to new sources versus 

retrofitting existing sources. 
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Based on our analyses of the available data and 

information, we identified potential developments in practices, 

processes and control technologies. For this exercise, we 

considered any of the following to be a “development”: 

 Any add-on control technology or other equipment that was 

not identified and considered during development of the 

original MACT standards. 

 Any improvements in add-on control technology or other 

equipment (that were identified and considered during 

development of the original MACT standards) that could 

result in additional emissions reduction. 

 Any work practice or operational procedure that was not 

identified or considered during development of the original 

MACT standards. 

 Any process change or pollution prevention alternative that 

could be broadly applied to the industry and that was not 

identified or considered during development of the original 

MACT standards. 

 Any significant changes in the cost (including cost 

effectiveness) of applying controls (including controls the 

EPA considered during the development of the original MACT 

standards). 
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We reviewed a variety of data sources in our investigation 

of potential practices, processes or controls to consider. Among 

the sources we reviewed were the NESHAP for various industries 

that were promulgated since the MACT standards being reviewed in 

this action. We reviewed the regulatory requirements and/or 

technical analyses associated with these regulatory actions to 

identify any practices, processes and control technologies 

considered in these efforts that could be applied to emission 

sources subject to Refinery MACT 1 or 2, as well as the costs, 

non-air impacts and energy implications associated with the use 

of these technologies. Additionally, we requested information 

from facilities as described in Ssection II.C of this preamble. 

Finally, we reviewed information from other sources, such as 

state and/or local permitting agency databases and industrysupported databases. 

IV. Analytical Results and Proposed Decisions 

A. What actions are we taking pursuant to CAA Ssections 

112(d)(2) and 112(d)(3)? 

In this action, we are proposing the following revisions to 

the Refinery MACT 1 and 2 standards pursuant to CAA Ssection 

112(d)(2) and (3)25: (1) adding MACT standards for DCU decoking 

 

25 The EPA has authority under CAA section 112(d)(2) and (d)(3) to set MACT 

standards for previously unregulated emission points. EPA also retains the 

discretion to revise a MACT standard under the authority of sSection 

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operations; (2) revising the CRU purge vent pressure exemption; 

(3) adding operational requirements for flares used as air 

pollution control devices (APCD) in Refinery MACT 1 and 2; and 

(4) adding requirements and clarifications for vent control 

bypasses in Refinery MACT 1. The results and proposed decisions 

based on the analyses performed pursuant to CAA Ssection 

112(d)(2) and (3) are presented below. 

1. Delayed Coking Units 

a. Description of Delayed Coker Process Operations and Emissions 

We are proposing to establish MACT standards specific to 

the DCU pursuant to CAA Ssection 112(d)(2) and (3). The DCU uses 

thermal cracking to upgrade heavy feedstocks and to produce 

petroleum coke. Unlike most other refinery operations that are 

continuous, the DCU operates in a semi-batch system. Most DCU 

consist of a large process heater, two or more coking drums, and 

a single product distillation column. The DCU feed is actually 

fed to the unit’s distillation column. Bottoms from the 

distillation column are heated to near cracking temperatures and 

the resulting heavy oil is fed to one of the coking drums. As 

the cracking reactions occur, coke is produced in the drum and 

 

112(d)(2) and (3), see Portland Cement Ass’n v. EPA, 665 F.3d 177, 189 (D.C. 

Cir. 2011), such as when it identifies an error in the original standard. 

See also Medical Waste Institute v. EPA, 645 F. 3d at 426 (upholding EPA 

action establishing MACT floors, based on post-compliance data, when 

originally-established floors were improperly established). 

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begins to fill the drum with sponge-like solid coke material. 

During this process, the DCU is a closed system, with the 

produced gas streams piped to the unit’s distillation column for 

product recovery. 

When the first coke drum becomes filled with coke, the feed 

is diverted to the second coke drum and processing continues via 

the second coke drum. The full coke drum, which is no longer 

receiving oil feed, is taken through a number of steps, 

collectively referred to as decoking operations, to remove the 

coke from the drum and prepare the drum for subsequent oil feed 

processing. The decoking steps include: purging, 

cooling/quenching, venting, draining, deheading, and coke 

cutting. A description of these steps and the potential 

emissions from these activities are provided in the next several 

paragraphs. Once the coke is removed, the vessel is re-sealed 

(i.e., the drain valve is closed and the “head” is re-attached), 

pressure tested (typically using steam), purged to remove 

oxygen, then slowly heated to processing temperatures so it can 

go back on-line. When the second coke drum becomes filled with 

coke, feed is diverted back to the first coke drum and the 

second drum is then decoked. In this manner, the DCU allows for 

continuous processing of oil even though the individual coke 

drums operate in cyclical batch fashion. 
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The first step in decoking operations is to purge the coke 

drum with steam. This serves to cool the coke bed and to flush 

oil or reaction products from the coke bed. The steam purge is 

initially sent to the product distillation column and then 

diverted to the unit’s blowdown system. The blowdown system 

serves to condense the steam and other liquids entrained in the 

steam. Nearly all DCU operate a ”closed blowdown” system, such 

that uncondensed gases from the blowdown system are sent to the 

product distillation column or the facility’s light gas plant, 

recovered as fuel gas, or combusted in a flare. In an open 

blowdown system, these uncondensed gases would be vented 

directly to atmosphere. The DCU vent discharge to the blowdown 

system is specifically defined in Refinery MACT 1 as the 

“delayed coker vent.” 

The next step in the decoking process is cooling/quenching 

the coke drum and its contents via the addition of water, 

commonly referred to as quench water, at the bottom of the coke 

drum. The water added to the vessel quickly turns to steam due 

to the high temperature of the coke bed. The water/steam helps 

to further cool the coke bed and “quench” any residual coking 

reactions that may still occur within the hot coke bed. As with 

the steam purge, steam off-gas from the cooling/quenching cycle 

is recovered in the unit’s blowdown system and this vent 
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discharge is specifically defined in Refinery MACT 1 as the 

“delayed coker vent.” 

After several hours, the coke drum is sufficiently cooled 

so that the water level in the drum can be raised to entirely 

cover the coke bed. Although water covers the coke bed, the 

upper portion of the coke bed may still be well above 212 

degrees Fahrenheit (°F) and will continue to generate steam. In 

fact, since the coke drum vessel pressure is greater than 

atmospheric pressure, the equilibrium boiling point of water in 

the vessel is greater than 212 °F. Therefore, the water at the 

top of the coke drum is typically well above 212 °F (superheated 

water). As the coke drum and its contents continue to cool from 

the evaporative cooling effect of the steam generation, the 

steam generation rate and the pressure within the vessel will 

decrease. 

Owners or operators of DCU may use different indicators or 

set points to determine when the system has cooled sufficiently 

to move to the venting step; however, one of the most common 

indicators monitored is the pressure of the coke drum vessel (or 

steam vent line just above the coke drum, where steam exits the 

coke drum en route to the blowdown system). When the vessel has 

cooled sufficiently (e.g., when the coke drum vessel pressure 

reaches the desired set point), valves are opened to allow the 

steam generated in the coke drum to vent directly to the 
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atmosphere rather than the closed blowdown system. This vent is 

commonly referred to as the “coker steam vent” and is typically 

the first direct atmospheric emission release during the 

decoking operations when an enclosed blowdown system is used. 

While this vent gas contains predominately steam, methane and 

ethane, a variety of HAP are also emitted with this steam. These 

HAP include light aromatics (e.g., benzene, toluene, and xylene) 

and light POM (predominately naphthalene and 2-methyl 

naphthalene). The level of HAP emitted from the DCU has been 

found to be a function of the quantity of steam generated (see 

the technical memorandum entitled Impacts Estimates for Delayed 

Coking Units in Docket ID Number EPA-HQ-OAR-2010-0682). 

In general, the next step in the decoking process is 

draining the water from the coke drum by opening a large valve 

at the bottom of the coke drum. The drain water typically falls 

from the coke drum onto a slanted concrete pad that directs the 

water to the coke pit area (where water and coke are collected 

and separated). Some DCU owners or operators initiate draining 

at the same time they initiate venting; other owners or 

operators may allow the vessel to vent for 20 or more minutes 

prior to initiating draining. While draining immediately may 

reduce the amount of steam exiting the unit via the stack, as 

explained below, it is not expected to alter the overall 

emissions from the unit. During the venting and draining 
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process, the pressure of the system falls to atmospheric. Steam 

will be generated until the evaporative cooling effect of that 

steam generation cools the coker quench water to 212 °F. If 

draining is initiated immediately, some of the superheated water 

may drain from the DCU before being cooled. A portion of that 

drained water will then flashconvert to steam during the 

draining process as that superheated water contacts the open 

atmosphere. Therefore, draining quickly is not expected to alter 

the total amount of steam generated from the unit nor alter the 

overall emissions from the unit. It will, however, alter the 

relative proportion of the emissions that are released via the 

vent versus the quench water drain area. 

The next step in the decoking process is “deheading” the 

coke drum. At the top of the coke drum is a large 3- to 5-foot 

diameter opening, which is sealed with a gasketed lid during 

normal operations. When the steam generation rate from the coke 

drum has sufficiently subsided, this gasketed lid is removed to 

allow access for a water drill that will be used to remove coke 

from the drum. The process of removing this lid is referred to 

as “deheading” the coke drum. Different DCU owners or operators 

may use different criteria for when to dehead the coke drum. If 

the coke drum is deheaded soon after venting is initiated, some 

steam and associated HAP emissions may be released from this 

opening. As with draining, it is anticipated that the total 
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volume of steam generated will be a function of the 

temperature/pressure of the coke drum. Deheading the coke drum 

prior to the coke drum contents reaching 212 °F will generally 

mean that some of the steam will be released from the coke drum 

head opening. However, this will not alter the total amount of 

steam generated; it merely alters the location of the release 

(coke drum head opening versus steam vent). The HAP emissions 

from the deheading process are expected to be proportional to 

the amount of steam released in the same manner as the emissions 

from the steam vent. 

The final step of the decoking process is coke cutting. A 

high-pressure water jet is used to drill or cut the coke out of 

the vessel. The drilling water and coke slurry exits the coke 

drum via the drain opening and collects in the coke pit. 

Generally, the coke drum and its contents are sufficiently 

cooled so that this process is not expected to yield significant 

HAP emissions. However, if the other decoking steps are 

performed too quickly, hot spots may exist within the coke bed 

and HAP emissions may occur as water contacts these hot spots 

and additional steam and emissions are released. 

Once the coke is cut out of the drum, the drum is closed 

and prepared to go back on-line. This process includes 

pressurizing with steam to ensure there are no leaks (i.e., that 

the head is properly attached and sealed and the drain valve is 
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fully closed). The vessel is then purged to remove any oxygen 

and heated by diverting the produced gas from the processing 

coke drum through the empty drum prior to sending it to the 

unit’s distillation column. A coke drum cycle is typically 28 to 

36 hours from start of feed to start of the next feed. 

b. How Delayed Coker Vents are Addressed in Refinery MACT 1 

Delayed coker vents are specifically mentioned as an 

example within the first paragraph of the definition of 

“miscellaneous process vent” in 40 CFR 63.641 of Refinery MACT 

1. However, the definition of “miscellaneous process vent later” 

also excludes: “Ccoking unit vents associated with coke drum 

depressuring (at or below a coke drum outlet pressure of 15 

pounds per square inch gauge [psig]), deheading, draining, or 

decoking (coke cutting) or pressure testing after decoking” (see 

40 CFR 63.641). According to. Refinery MACT 1, “[d]elayed also 

includes a definition of “delayed coker vent means a ” in 40 CFR 

63.641. This vent that is typically intermittent in nature, and 

usually occurs only during the initiation of the depressuring 

cycle of the decoking operation when vapor from the coke drums 

cannot be sent to the fractionator column for product recovery, 

but instead is routed to the atmosphere through a closed 

blowdown system or directly to the atmosphere in an open 

blowdown system. The emissions from the decoking phases of DCU 

operations, which include coke drum deheading, draining, or 
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decoking (coke cutting), are not considered to be delayed coker 

vents” (see 40 CFR 63.641). 

The first paragraph of the definition of “miscellaneous 

process vent” also includes blowdown condensers/accumulators as 

an example of a miscellaneous process vent. Therefore, the DCU 

blowdown system is a miscellaneous process vent regardless of 

whether or not the blowdown system is associated with a DCU or 

another process unit. Further, the inclusion of the “delayed 

coker vent” as an example of a miscellaneous process vent makes 

it clear that the DCU’s blowdown system vent (if an open 

blowdown system is used) is considered a miscellaneous process 

vent. It is less clear from the regulatory text whether the 

direct venting of the coke drum to the atmosphere via the steam 

vent during the final depressurization is considered to be a 

“delayed coker vent” (i.e., whether direct venting to the 

atmosphere is equivalent to venting “directly to the atmosphere 

in an open blowdown system”). 

The regulatory text is clear that this steam vent is exempt 

from the definition of “miscellaneous process vent” when the 

pressure of the vessel is less than 15 psig. It is also clear 

that the subsequent release points from the decoking operations 

(i.e., deheading, draining, and coke cutting) are excluded from 

both the definition of “delayed coker vent” and the definition 

of “miscellaneous process vent.” Further, based on the 
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statements in the background information document for the August 

1995 final Refinery MACT 1 rule,26 the 15 psig pressure limit for 

the direct venting of the DCU to the atmosphere was not 

established as a MACT floor control level; it was established to 

accommodate all DCU at whatever pressure they typically switched 

from venting to the closed blowdown system to venting directly 

to the atmosphere. Based on this information, as well as the 

data from the 2011 Refinery ICR, refinery enforcement 

settlements and other information available, which indicate that 

all refineries depressurize the coke drum below 15 psig, we have 

determined that the direct atmospheric releases from the DCU 

decoking operations are currently unregulated emissions. These 

unregulated releases include emissions during atmospheric 

depressuring (i.e., the steam vent), deheading, draining, and 

coke cutting. 

c. Evaluation of MACT Emission Limitations for Delayed Coking 

Units 

We evaluated emissions and controls during DCU decoking 

operations in order to identify appropriate MACT emission 

limitations pursuant to CAA Ssection 112(d)(2) and (3). 

Establishing a lower pressure set point at which a DCU owner or 

operator can switch from venting to an enclosed blowdown system 

 

26 National Emission Standards for Hazardous Air Pollutants Petroleum 

Refineries - Background Information for Final Standards; EPA-453/R-95-015b. 
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to venting to the atmosphere is the control technique identified 

for reducing emissions from delayed coking operations. 

Essentially, there is a fixed quantity of steam that will be 

generated as the coke drum and its contents cool. The lower 

pressure set point will require the DCU to vent to the closed 

blowdown system longer, where the organic HAP can be recovered 

or controlled. This will result in fewer emissions released 

during the venting, draining and deheading process. 

We consider this control technique, which is a work 

practice standard, appropriate for the DCU for the reasons 

discussed below for each of the four possible emission points at 

the DCU: draining, deheading, coke cutting and the steam vent. 

For the first three steps, the emissions cannot be emitted 

through a conveyance designed and constructed to emit or capture 

such pollutant. For example, during draining, the drain water 

typically falls from the coke drum onto a slanted concrete pad 

that directs the water to an open coke pit area (where water and 

coke are collected and separated). When the coke drum is 

deheaded, the coke drum head must be removed to provide an 

accessible opening in the drum so the coke cutting equipment can 

be lowered into the drum. This opening cannot be sealed during 

coke cutting because the drilling shaft will occupy the opening 

and the shaft must be free to be lowered or raised during the 

coke cutting process. 
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While the emissions from the fourth point, the DCU steam 

vent, are released via a conveyance designed and constructed to 

emit or capture such pollutant, as provided in CAA Ssection 

112(h)(2)(B), it is not feasible to prescribe or enforce an 

emission standard for the DCU steam vent because the application 

of a measurement methodology for this source is not practicable 

due to technological and economic limitations. 

First, it is not practicable to use a measurement 

methodology for the DCU steam vent. The emissions from the vent 

typically contain 99- percent water, which interferes with 

common sample collection and analysis techniques. Also, the flow 

rate from this vent is not constant; rather, it decreases during 

the venting process as the pressure in the DCU coke drum 

approaches atmospheric pressure. Additionally, the venting time 

can be very short. As part of the ICR, we requested stack 

testing of eight DCU. After discussions with stack testing 

experts within the agency and with outside contractors used by 

industry to perform the tests, we concluded that sources with 

venting times less than 20 minutes would not be able to perform 

an emissions test that would yield valid results. Therefore, 

only two of the eight facilities actually performed the tests. 

We anticipate all units complying with the proposed standards 

for DCU steam vents would vent for less than 20 minutes. 
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Second, it is not feasible to enforce an emission standard 

only on the steam vent because the timing of drainage and 

deheading can alter the portion of the decoking emissions that 

are released from the actual steam vent. If draining and 

deheading are initiated quickly after venting, this will reduce 

the emissions discharged from the vent (although as explained 

above, it does not reduce the emissions from the collective set 

of decoking operations release points). 

Consequently, due to the unique nature of DCU emissions, 

the difficulties associated with monitoring the DCU steam vent, 

and the inability to construct a conveyance to capture emissions 

from all decoking release points, we are proposing that it is 

appropriate to develop work practice standards in place of 

emission limits for the DCU. 

WeTo establish the MACT floor, we then reviewed 

regulations, permits and consent decrees that require coke 

controls to establish the MACT floor. Refinery NSPS Ja 

establishes a pressure limit of 5 psig prior to allowing the 

coke drum to be vented to the atmosphere. Based on a review of 

permit limits and consent decrees, we found that coke drum 

vessel pressure limits have been established (and achieved) as 

low as 2 psig. There are 75 operating DCU according to the 

Refinery ICR responses, so the sixth percentile is represented 

by the fifth-best performing DCU. We identified eight DCU with 
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permit requirements or consent decrees specifying a coke drum 

venting pressure limit of 2 psig; we did not identify any permit 

or consent decree requirements more stringent than 2 psig. 

Refinery owners and operators were asked to provide the “typical 

coke drum pressure just prior to venting” for each DCU in their 

responses to the Refinery ICR, and the responses indicate that 

four DCU operate such that the typical venting pressure is 1 

psig or less. However, this “typical coke drum pressure” does 

not represent a not-to-be-exceeded pressure limit; it is 

expected that these units are operated this way to meet a 

pressure limit of 2 psig. We do not have information to indicate 

whether these facilities are always depressurized at 1 psig or 

less. Moreover, there were only four units for which a typical 

venting pressure of 1 psig was identified and the MACT floor for 

existing sources is represented by the fifth-best operating DCU, 

not the best-performing unit. Therefore, we are proposing that 

the MACT floor for DCU decoking operations is to depressure at 2 

psig or less prior to venting to the atmosphere for existing 

sources. We are also proposing that the MACT floor for new 

sources is 2 psig, since the best-performing source is permitted 

to depressure at 2 psig or less. For additional details on the 

MACT floor analysis, see memorandum entitled MACT Analysis for 

Delayed Coking Unit Decoking Operations in Docket ID Number EPAHQ-OAR-2010-0682. 
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We then considered control options beyond the floor level 

of 2 psig to determine if additional emission reductions could 

be cost-effectively achieved. We considered establishing a 

venting pressure limit of 1 psig or less, since four facilities 

reported in the ICR that the typical coke drum pressure prior to 

depressurizing was 1 psig. There are several technical 

difficulties associated with establishing a pressure limit at 

this lower level. First, the lowest pressure at any point in a 

closed blowdown system is generally designed to be no lower than 

0.5 psig. Consequently, the DCU compressor system would operate 

with an inlet pressure of no less than 0.5 psig. Second, there 

are several valves and significant piping (for cooling and 

condensing steam) between the DCU drum and the recovery 

compressor. There is an inherent pressure drop when a fluid 

flows through a pipe or valve. Two valves are used for all DCU 

lines to make sure that the unit is either blocked off from the 

processing fluids or blocked in so there are no product losses 

out the steam line during processing. Considering the need for 

two valves and piping needed in the cooling system, DCU designed 

for a minimal pressure loss will generally still have a 0.5 to 1 

psig pressure drop between the DCU drum and the recovery 

compressor inlet, even for a new DCU designed to minimize this 

pressure drop. Finally, in order to meet a 1 psig pressure limit 

at all times, the DCU closed vent system would need to be 
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designed to achieve a vessel pressure of approximately 0.5 psig. 

Given the above considerations, it is not technically feasible 

for new or existing DCU to routinely achieve a vessel pressure 

of 0.5 psig in order to comply with a never-to-be-exceeded drum 

vessel pressure of 1 psig. As noted previously, facilities that 

“typically” achieve vessel pressures of about 1 psig or less are 

expected to do so in order to meet a never-to-be-exceeded drum 

vessel pressure limit of 2 psig and they are not expected to be 

able to comply with a never-to-be-exceeded drum vessel pressure 

limit of 1 psig. 

We considered setting additional work practice standards 

regarding draining, deheading, and coke cutting. The decoking 

emissions can be released from a variety of locations, and the 

2-psig-or-less limit for depressurizing the coke drum will 

effectively reduce the emissions from all of these emission 

points, provided that atmospheric venting via the DCU steam vent 

is the first step in the decoking process. However, it is 

possible to start draining water prior to opening the steam 

vent. We are concerned that owners or operators may adopt this 

practice as a means to reduce pressure in the coke drum prior to 

venting the drum to the atmosphere. Initiating water draining 

prior to reaching 2 psig would result in draining water that is 

hotter than it would be had the drum been sufficiently cooled 

(i.e., the pressure limit achieved) prior to draining the 
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vessel, effectively diverting HAP emissions to the water drain 

area rather than capturing these HAP in the enclosed blowdown 

system, where they can be either recovered or controlled. 

Therefore, we are proposing that the coke drum must reach 2 psig 

or less prior to any decoking operations, which includes 

atmospheric venting, draining, deheading, and coke cutting. 

We could not identify any other emission reduction options 

that could lower the emissions from the DCU decoking operations. 

Since we could not identify a technically feasible control 

option beyond the MACT floor, we determined that the MACT floor 

pressure limit of 2 psig is MACT for existing sources. We also 

determined that the same technical limitations of going beyond 

the 2 psig pressure limit for existing sources exist for new 

sources; therefore we determined that the MACT floor pressure 

limit of 2 psig is MACT for new sources. We request comment on 

whether depressurizing to 2 psig prior to venting to the 

atmosphere is the appropriate MACT floor and whether it is 

appropriate to include restrictions for the other three decoking 

operations draining, deheading and coke cutting, in the MACT 

requirements. We request comments on whether we have adequately 

interpreted the information that indicates that there is 

currently no applicable MACT floor for delayed coking. Under a 

different interpretationIf Refinery MACT 1 currently provided 

standards for DCU based on the MACT floor, we would evaluate the 
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needwhether it is necessary to proposerevise such delayed coking 

standards only under the risk and technology review requirements 

of the Act (i.e., CAA Ssection 112(f) and 112(d)(6)) as 

discussed later in this preamble. 

Finally, we request comment and supporting information on 

any other practices that may be used to limit emissions during 

the decoking operations. 

d. Evaluation of Cost and Environmental Impacts of MACT Emission 

Limitations for Delayed Coking Units 

DCU that cannot currently meet the 2 psig pressure limit 

would be expected to install a device (compressor or steam 

ejector system) to lower the DCU vessel pressure. In the 

Refinery NSPS Ja impact analysis, facilities not able to meet 

the pressure threshold were assumed to purchase and install a 

larger compressor to lower the blowdown system pressure. Other 

approaches to lowering blowdown system (and coke drum) pressure 

exist. Specifically, steam ejectors have been identified as a 

method to help existing units depressurize more fully in order 

to achieve a set vessel pressure or drum bed temperature. 

Upgrading the closed vent system to reduce pressure losses or to 

increase steam condensing capacity may also allow the DCU to 

depressurize more quickly while the emissions are still vented 

to the closed blowdown system. This is important because delays 

in the decoking operations may impact process feed rates. That 
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is, if the decoking and drum preparation steps take too long, 

the feed rate to the other coke unit must be reduced to prevent 

overfilling one coke drum prior to being able to switch to the 

other coke drum. This issue is less critical for DCU that 

operate with 3 or 4 drums per distillation column, but a 

consistent increase in the decoking times across all drums may 

still limit the capacity of the DCU at some petroleum 

refineries. 

For existing sources, we assumed all DCU that reported a 

“typical drum pressure prior to venting” of more than 2 psig 

would install and operate a steam ejector system to reduce the 

coke drum pressure to 2 psig prior to venting to atmosphere or 

draining. 

The operating costs of the steam ejector system are offset, 

to some extent, by the additional recovered vapors. Vapors from 

the additional gases routed to the blowdown system contain high 

levels of methane (approximately 70 percent by volume on a dry 

basis) based on DCU steam vent test data. If these vapors are 

directed to the closed blowdown system rather than to the 

atmosphere, generally the dry gas can be recovered in the 

refinery fuel gas system or light-ends gas plant. This recovered 

methane is expected to off-set natural gas purchases for the 

fuel gas system. 
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For new sources, it is anticipated that the DCU’s closed 

vent system could be designed to achieve a 2 psig vessel 

pressure with no significant increase in capital or operating 

costs. Designing the system to vent at a lower pressure would 

also result in additional vapor recovery, which is expected to 

off-set any additional capital costs associated with the low 

pressure design closed vent system. 

The costs of complying with the 2 psig coke drum threshold 

prior to venting or draining are summarized in Table 2 of this 

preamble. The costs are approximately $1,000 per ton of VOC 

reduced and approximately $5,000 per ton of organic HAP reduced 

when considering VOC and methane recovery credits. In addition 

to VOC and HAP reductions, the proposed control option will 

result in a reduction in methane emissions of 18,000 tpy or 

343,000 metric tonnes per year of carbon dioxide equivalents 

(CO2e), assuming a global warming potential of 21 for methane.

Table 2. Nationwide Emissions Reduction and Cost Impacts of 

Control Option for Delayed Coking Units at Petroleum Refineries 

Control 

Option 

Capital 

Cost 

(million 

$) 

Annualized 

Costs 

Without 

Recovery 

Credits 

(million 

$/yr) 

Emissions 

Reduction, VOC 

(tpy) 

Emissions 

Reduction, HAP 

(tpy) 

Cost 

Effectiveness 

($/ton 

HAP) 

Total 

Annualized 

Costs 

with VOC 

Recovery 

Credit 

(million 

$/yr) 

Overall 

Cost 

Effectiveness with 

VOC 

Recovery 

Credit 

($/ton 

HAP) 

2 psig 52 10.2 4,250 850 12,000 3.98 4,700 
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2. CRU Vents 

A CRU is designed to reform (i.e., change the chemical 

structure of) naphtha into higher-octane aromatics. Over time, 

coke deposits form on the reforming catalyst, which reduces the 

catalyst activity. When catalyst activity is reduced to a 

certain point, the catalyst is regenerated by burning the coke 

off of the catalyst. Prior to this coke burn-off process, the 

catalyst (or reactor vessel containing the catalyst) must be 

removed from active service and organics remaining on the 

catalyst (or in the reactor) must be purged from the system. 

This is generally accomplished by depressurizing the vessel to a 

certain vessel pressure, then re-pressurizing the vessel with 

nitrogen and depressurizing the vessel again. The repressurization and depressurization process is repeated several 

times until all organics have been purged from the system. The 

organic HAP emissions from this depressurization/purge cycle 

vent are typically controlled by directing the purge gas 

directly to the CRU process heater or venting the gas to a 

flare. 

Refinery MACT 2 requires a 98-percent reduction of organic 

HAP measured as total organic carbon (TOC) or non-methane TOC or 

an outlet concentration of 20 ppmv or less (dry basis, as 

hexane, corrected to 3-percent oxygen), whichever is less 

stringent, for this CRU depressurization/purge cycle vent 
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(purging prior to coke-burn-off). The emission limits for 

organic HAP for the CRU do not apply to emissions from process 

vents during depressuring and purging operations when the 

reactor vent pressure is 5 psig or less. The Refinery MACT 2 

requirements were based on the typical operation of CRU 

utilizing sequential pressurization and passive 

depressurization. The 5 psig pressure limit exclusion was 

provided based on state permit conditions, which recognized that 

depressurization to an APCD (without other active motive of 

flow) is limited by the back pressure of the control system, 

which is often a flare or process heater. Source testing 

information collected from the 2011 Refinery ICR indicates that 

facilities could interprethave interpreted the rule to allow the 

5 psig pressure limit exclusion to be used by units using active 

purging techniques (such as continuous nitrogen purge or vacuum 

pump on the CRU reactor at low pressures) to discharge to the 

atmosphere without emission controls. The information collected 

indicates that HAP emissions from a continuous, active purging 

technique could result in emissions of HAP from CRU 

depressurization vents much higher than expected to be allowed 

under the Refinery MACT 2 requirements, which presumed 

sequential re-pressurization and purging cycles. The testing 

information received indicated that at one facility, the active 

purge vent had non-methane TOC concentrations of 700 to 10,000 
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ppmv (dry basis, as hexane, corrected to 3-percent oxygen) 

compared to less than 10 ppmv for the typical passive purge vent 

tested. The annual HAP emissions for the CRU with the active 

purge vent were estimated to exceed 10 tpy, while a comparable 

unit using the cyclic re-pressurization and passive 

depressurization purge technique is projected to have HAP 

emissions of less than 0.1 tpy. 

Therefore, we are proposing to amend the exclusion in 40 

CFR 63.1566(a)(4) to clarify the application of the 5 psig 

exclusion, consistent with the MACT floor under CAA Ssection 

112(d)(2) and (3). Specifically, we are limiting the vessel 

pressure limit exclusion to apply only to passive vessel 

depressurization. Units utilizing active purging techniques have 

a motive of flow that can be used to direct the purge gas to a 

control system, regardless of the CRU vessel pressure. If a CRU 

owner or operator uses active purging techniques (e.g., a 

continual nitrogen purge) or active vessel depressurization 

(e.g., vacuum pump), then the 98-percent reduction or 20 ppmv 

TOC emission limits would apply to these discharges regardless 

of the vessel pressure. 

3. Refinery Flares 

The EPA is proposing under CAA Ssection 112(d)(2) and (3) 

to amend the operating and monitoring requirements for petroleum 

refinery flares. We have determined that the current 
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requirements for flares are not adequate to ensure compliance 

with the Refinery MACT standards. In the development of Refinery 

MACT 1, the EPA determined that the average emission limitation 

achieved by the best-performing 12 percent of existing sources 

was established as the use of combustion controls for 

miscellaneous process vents. Further, the EPA stated that “data 

analyses conducted in developing previous NSPS and the [National 

Emission Standards for Organic Hazardous Air Pollutants (40 CFR 

part 63, subparts F, G, and H)] HON determined that combustion 

controls can achieve 98-percent organic HAP reduction or an 

outlet organic HAP concentration of 20 ppmv for all vent 

streams” (59 FR 36139, July 15, 1994). The requirements 

applicable to flares at refineries are set forth in the General 

Provisions to 40 CFR part 63 and are cross-referenced in 

Refinery MACT 1 and 2. In general, flares used as APCD were 

expected to achieve 98-percent HAP destruction efficiencies when 

designed and operated according to the requirements in the 

General Provisions. Recent studies on flare performance, 

however, indicate that these General Provisions requirements are 

inadequate to ensure proper performance of refinery flares, 

particularly when assist steam or assist air is used. Over the 

last decade, flare minimization efforts at petroleum refineries 

have led to an increasing number of flares operating at well 

below their design capacity, and while this effort has resulted 
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in reduced flaring of gases at refineries, situations of overassisting with steam or air have become exacerbated, leading to 

the degradation of flare combustion efficiency. Therefore, these 

amendments are necessary to ensure that refineries that use 

flares as APCD meet the MACT standards at all times when 

controlling HAP emissions. 

Refinery MACT 1 and 2 require flares used as an APCD to 

meet the operational requirements set forth in the General 

Provisions at 40 CFR 63.11(b). These General Provisions 

requirements specify that flares shall be: (1) steam-assisted, 

air-assisted, or non-assisted; (2) operated at all times when 

emissions may be vented to them; (3) designed for and operated 

with no visible emissions (except for periods not to exceed a 

total of 5 minutes during any 2 consecutive hours); and (4) 

operated with the presence of a pilot flame at all times. The 

General Provisions also specify requirements for both the 

minimum heat content of gas combusted in the flare and maximum 

exit velocity at the flare tip. The General Provisions only 

specify monitoring requirements for the presence of the pilot 

flame and the operation of a flare with no visible emissions. 

For all other operating limits, Refinery MACT 1 and 2 require an 

initial performance evaluation to demonstrate compliance but 

there are no specific monitoring requirements to ensure 

continuous compliance. As noted previously, flare performance 
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tests conducted over the past few years suggest that the current 

regulatory requirements are insufficient to ensure that refinery 

flares are operating consistently with the 98-percent HAP 

destruction efficiencies that we determined were the MACT floor. 

In 2012, the EPA compiled information and test data 

collected on flares and summarized its preliminary findings on 

operating parameters that affect flare combustion efficiency 

(see technical report, Parameters for Properly Designed and 

Operated Flares, in Docket ID Number EPA-HQ-OAR-2010-0682). The 

EPA submitted the report, along with a charge statement and a 

set of charge questions to an external peer review panel.27 The 

panel concurred with the EPA’s assessment that three primary 

factors affect flare performance: (1) the flow of the vent gas 

to the flare; (2) the amount of assist media (e.g., steam or 

air) added to the flare; and (3) the combustibility of the vent 

gas/assist media mixture in the combustion zone (i.e., the net 

heating value, lower flammability, and/or combustibles 

concentration) at the flare tip. 

Following is a discussion of requirements we are proposing 

for refinery flares, along with impacts and costs associated 

with these new requirements. Specifically, this action proposes 

that refinery flares operate pilot flame systems continuously 

 

27 These documents can also be found at 

http://www.epa.gov/ttn/atw/petref.html. 
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and with automatic re-ignition systems and that refinery flares 

operate with no visible emissions. In addition, this action also 

consolidates requirements related to flare tip velocity and 

proposes new operational and monitoring requirements related to 

the combustion zone gas. Prior to these proposed amendments, 

Refinery MACT 1 and 2 cross-reference the General Provisions 

requirements at 40 CFR 63.11(b) for the operational requirements 

for flares used as APCD. Rather than revising the General 

Provisions requirements for flares, which would impact dozens of 

different source categories, this proposal will specify all 

refinery flare operational and monitoring requirements 

specifically in Refinery MACT 1 and cross-reference these same 

requirements in Refinery MACT 2. All of the requirements for 

flares operating at petroleum refineries in this proposed 

rulemaking are intended to ensure compliance with the Refinery 

MACT 1 and 2 standards when using a flare as an APCD. Also, 

since we are proposing to amend Refinery MACT 1 and 2 so that 

these standards include all of the regulatory provisions 

applicable to flares, these subparts would no longer crossreference the flare requirements in the General Provisions.

a. Pilot Flames 

Refinery MACT 1 and 2 reference the flare requirements in 

the General Provisions, which require a flare used as an APCD 

device to operate with a pilot flame present at all times. Pilot 
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flames are proven to improve flare flame stability; even short 

durations of an extinguished pilot could cause a significant 

reduction in flare destruction efficiency. In this action, we 

are proposing to remove the cross-reference to the General 

Provisions and instead include the requirement that flares 

operate with a pilot flame at all times and be continuously 

monitored for using a thermocouple or any other equivalent 

device in Refinery MACT 1 and 2. We are also proposing to amend 

Refinery MACT 1 and 2 to add a new operational requirement to 

use automatic relight systems for all flare pilot flames. An 

automatic relight system provides a quicker response time to 

relighting a snuffed-out flare compared to manual methods and 

thereby results in improved flare flame stability. In 

comparison, manual relighting is much more likely to result in a 

longer period where the pilot remains unlit. Because of safety 

issues with manual relighting, we anticipate that nearly all 

refinery flares are already equipped with an automated device to 

relight the pilot flame in the event it is extinguished. Also, 

due to the possibility that a delay in relighting the pilot 

could result in a flare not meeting the 98-percent destruction 

efficiency for the period when the pilot flame is out, we are 

proposing to amend Refinery MACT 1 and 2 to add this requirement 

to ensure that the pilot operates at all times. 
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b. Visible Emissions 

Refinery MACT 1 and 2 reference the flare requirements in 

the General Provisions, which require a flare used as an APCD to 

operate with visible emissions for no more than 5 minutes in a 

2-hour period. Owners or operators of these flares are required 

to conduct an initial performance demonstration for visible 

emissions using EPA Method 22 of 40 CFR part 60, Appendix A-7. 

We are proposing to remove the cross-reference to the General 

Provisions and include the limitation on visible emissions in 

Refinery MACT 1 and 2. In addition, we are proposing to amend 

Refinery MACT 1 and 2 to add a requirement that a visible 

emissions test be conducted each day and whenever visible 

emissions are observed from the flare. We are proposing that 

owners or operators of flares monitor visible emissions at a 

minimum of once per day using an observation period of 5 minutes 

and EPA Method 22 of 40 CFR part 60, Appendix A-7. Additionally, 

any time there are visual emissions from the flare, we are 

proposing that another 5-minute visible emissions observation 

period be performed using EPA Method 22 of 40 CFR part 60, 

Appendix A-7, even if the minimum required daily visible 

emission monitoring has already been performed. For example, if 

an employee observes visual emissions or receives notification 

of such by the community, the owner or operator of the flare 

would be required to perform a 5-minute EPA Method 22 
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observation in order to check for compliance upon initial 

observation or notification of such event. We are also proposing 

that if visible emissions are observed for greater than one 

continuous minute during any of the required 5-minute 

observation periods, the monitoring period shall be extended to 

2 hours. 

Industry representatives have suggested to the EPA that 

flare combustion efficiency is highest at the incipient smoke 

point (the point at which black smoke begins to form within the 

flame). They stated that the existing limit for visible 

emissions could be increased from 5 minutes to 10 minutes in a 

2-hour period to encourage operation near the incipient smoke 

point (see memorandum, Meeting Minutes for February 19, 2013;,

Meeting Between the U.S. EPA and Representatives from the 

Petroleum Refining Industry, in Docket ID Number EPA-HQ-OAR2010-0682). While we agree that operating near the incipient 

smoke point results in good combustion at the flare tip, we 

disagree that the allowable period for visible emissions be 

increased from 5 to 10 minutes for a 2-hour period. Smoking 

flares can contribute significantly to emissions of particulate 

matter 2.5 micrometers in diameter and smaller (PM2.5)emissions, 

and we are concerned that increasing the allowable period of 

visible emissions from 5 minutes to 10 minutes for every 2-hour 
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period could result in an increase in the PM2.5 emissions from 

flares. 

As discussed later in this section, we are proposing 

additional operational and monitoring requirements for refinery 

flares which we expect will result in refineries installing 

equipment that can be used to fine-tune and control the amount 

of assist steam or air introduced at the flare tip such that 

combustion efficiency of the flare will be maximized. These 

monitoring and control systems will assist refinery flare owners 

or operators operating near the incipient smoke point without 

exceeding the visible emissions limit. While combustion 

efficiency may be highest at the incipient smoke point, it is 

not significantly higher than the combustion efficiency achieved 

by these proposed operating limits, discussed below in Ssection 

IV.A.3.d of this preamble. As seen in the performance curves for 

flares (see technical memorandum, Petroleum Refinery Sector 

Rule: Operating Limits for Flares, in Docket ID Number EPA-HQOAR-2010-0682), there is very limited improvement in flare 

performance beyond the performance achieved at these proposed 

operating limits. We solicit comments and data on appropriate 

periods of visible emissions that would encourage operation at 

the incipient smoke point while not significantly increasing 

PM2.5 emissions. 
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c. Flare Tip Velocity 

The General Provisions at 40 CFR 63.11(b) specify maximum 

flare tip velocities based on flare type (non-assisted, steamassisted, or air-assisted) and the net heating value of the 

flare vent gas. These maximum flare tip velocities are required 

to ensure that the flame does not “lift off” the flare, which 

could cause flame instability and/or potentially result in a 

portion of the flare gas being released without proper 

combustion. We are proposing to remove the cross-reference to 

the General Provisions and consolidate the requirements for 

maximum flare tip velocity into Refinery MACT 1 and 2 as a 

single equation, irrespective of flare type (i.e., steamassisted, air-assisted or non-assisted). Based on our analysis 

of the various studies for air-assisted flares, we identified 

air-assisted test runs with high flare tip velocities that had 

high combustion efficiencies (see technical memorandum, 

Petroleum Refinery Sector Rule: Evaluation of Flare Tip Velocity 

Requirements, in Docket ID Number EPA-HQ-OAR-2010-0682). These 

test runs exceeded the maximum flare tip velocity limits for 

air-assisted flares using the linear equation in 40 CFR 

63.11(b)(8). When these test runs were compared with the test 

runs for non-assisted and steam-assisted flares, the airassisted flares appeared to have the same operating envelope as 

the non-assisted and steam-assisted flares. Therefore, we are 
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proposing that air-assisted flares at refineries use the same 

equation that non-assisted and steam-assisted flares currently 

use to establish the flare tip velocity operating limit. 

In developing these proposed flare tip velocity 

requirements, we considered whether any adjustments to these 

velocity equations were necessary. The flare tip velocity 

equations require the input of the net heating value of the vent 

gas going to the flare, as opposed to the net heating value of 

the gas mixture at the flare tip (i.e., the combustion zone 

gas). As discussed later in this section, we found that the 

performance of the flare was much more dependent on the net 

heating value of the gas mixture in the combustion zone than on 

the net heating value of only the vent gas going into the flare 

(excluding all assist media). We considered replacing the term 

in the velocity equation for the net heating value of the vent 

gas going into the flare with the net heating value of the gas 

mixture in the combustion zone. However, the steam addition 

rates were not reported for the tests conducted to evaluate 

flame stability as a function of flare tip velocity, so direct 

calculation of all the terms needed for calculating the net 

heating value in the combustion zone could not be made. At 

higher flare tip velocities, we expect that the steam assist 

rates would be small in comparison to the total vent gas flow 

rate, so there would not be a significant difference between the 
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net heating value of the vent gas going into the flare and the 

combustion zone gas net heating value for the higher velocity 

flame stability tests. We request comment on the need and/or 

scientific reasons to use the flare vent gas net heating value 

versus the combustion zone net heating value when determining 

the maximum allowable flare tip velocity. 

In the 2012 flare peer review, we also discussed the effect 

of flame lift off and velocity on flare flame stability (see 

technical report, Parameters for Properly Designed and Operated 

Flares, in Docket ID Number EPA-HQ-OAR-2010-0682). In looking at 

ways of trying to prohibit flame instability, we examined the 

use of the Shore equation as a means to limit flare tip 

velocity. However, after receiving many comments on use of this 

equation from the peer reviewers, the uncertainty with how well 

the Shore equation models the large range of flare operation, 

and the limited dataset with which recent testing used high 

velocities (all recent test runs were performed at 10 feet per 

second or less), we determined that use of the existing velocity 

equation discussed above was still warranted. 

We are also proposing for Refinery MACT 1 and 2 to not 

include the special flare tip velocity equation in the General 

Provisions at 40 CFR 63.11(b)(6)(i)(A) for non-assisted flares 

with hydrogen content greater than 8 percent. This equation, 

which was developed based on limited data from a chemicals 
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manufacturer, has very limited applicability for petroleum 

refinery flares in that it only provides an alternative for nonassisted flares with large quantities of hydrogen. Approximately 

90 percent of all refinery flares are either steam- or airassisted. Furthermore, we are proposing compliance alternatives 

in this section that we believe provide a better way for flares 

at petroleum refineries with high hydrogen content to comply 

with the rule while ensuring proper destruction performance of 

the flare (see Ssection IV.A.3.d of this preamble for additional 

details). Therefore, we are proposing to not include this 

special flare tip velocity equation as a compliance alternative 

for refinery flares. We request comment on the need to include 

this equation. If a commenter supports inclusion of this 

equation, we request that the commenter submit supporting 

documentation regarding the vent gas composition and flows and, 

if available, combustion efficiency determinations that indicate 

that this additional equation is needed and is appropriate for 

refinery flares. We also request documentation that the maximum 

allowable flare tip velocity predicted by this equation 

adequately ensures proper combustion efficiency. 

The General Provisions require an initial demonstration 

that a flare used as an APCD meets the applicable flare tip 

velocity requirement in 40 CFR 63.11(b). However, most refinery 

flares can have highly variable vent gas flows and a single 
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initial demonstration is insufficient to demonstrate continuous 

compliance with the flare tip velocity requirement. 

Consequently, we are proposing to amend Refinery MACT 1 and 2 to 

require continuous monitoring to determine flare tip velocity, 

calculated by monitoring the flare vent gas volumetric flow rate 

and dividing by the cross-sectional area of the flare tip. As an 

alternative to installing continuous volumetric flow rate 

monitors, we are proposing that the owner or operator may elect 

to install a pressure- and temperature-monitoring system and use 

engineering calculations to determine the flare tip velocity. 

d. Refinery Flare Operating and Monitoring Requirements 

The current requirements for flares in the General 

Provisions specify that the flare vent gas must meet a minimum 

net heating value of 200 British thermal units per standard 

cubic foot (Btu/scf) for non-assisted flares and 300 Btu/scf for 

air- and steam-assisted flares. Refinery MACT 1 and 2 reference 

these requirements, but neither the General Provisions nor 

Refinery MACT 1 and 2 include specific monitoring requirements 

to monitor the net heating value of the vent gas. Moreover, 

recent flare testing results indicate that this parameter alone 

does not adequately address instances when the flare may be 

over-assisted since it only considers the gas being combusted in 

the flare and nothing else (e.g., no assist media). However, 

many industrial flares use steam or air as an assist medium to 
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protect the design of the flare tip, promote turbulence for the 

mixing, induce air into the flame and operate with no visible 

emissions. Using excessive steam or air results in dilution and 

cooling of flared gases and can lead to operating a flare 

outside its stable flame envelope, reducing the destruction 

efficiency of the flare. In extreme cases, over-steaming or 

excess aeration can actually snuff out a flame and allow 

regulated material to be released into the atmosphere completely 

uncombusted. Since approximately 90 percent of all flares at 

refineries are either steam- or air-assisted, it is critical 

that we ensure the assist media be accounted for in some form or 

fashion. Recent flare test data have shown that the best way to 

account for situations of over-assisting is to consider the 

properties of the mixture of all gases at the flare tip in the 

combustion zone when evaluating the ability to combust 

efficiently. As discussed in the introduction to this section, 

the external peer review panel concurred with our assessment 

that the combustion zone properties at the flare tip are 

critical parameters to know in determining whether a flare will 

achieve good combustion. The General Provisions, however, solely 

rely on the net heating value of the flare vent gas. 

We are proposing to add definitions of two key terms 

relevant to refinery flare performance. First, we are proposing 

to define “flare vent gas” to include all waste gas, sweep gas, 
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purge gas and supplemental gas, but not include pilot gas or 

assist media. We are proposing this definition because 

information about “flare vent gas” (e.g., flow rate and 

composition) is one of the necessary inputs needed to evaluate 

the make-up of the combustion zone gas. To that end, we are also 

proposing to define the “combustion zone gas” as flare vent gas 

plus the total steam-assist media and premix assist air that is 

supplied to the flare. 

Based on our review of the recent flare test data, we have 

determined that the following combustion zone operational limits 

can be used to determine good combustion: net heating value 

(Btu/scf), lower flammability limit (LFL) or a total 

combustibles fraction (e.g., a simple carbon count). In this 

action, we are proposing these new operational limits, along 

with methods for determining these limits in the combustion zone 

at the flare tip for steam-assisted, air-assisted and nonassisted flares to ensure that there is enough combustible 

material readily available to achieve good combustion. 

For air-assisted flares, use of too much perimeter assist 

air can lead to poor flare performance. Based on our analysis, 

we found that including the flow rate of perimeter assist air in 

the calculation of combustion zone operational limits in itself 

does not identify all instances of excess aeration. The data 

suggest that the diameter of the flare tip, in concert with the 
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amount of perimeter assist air, provides the inputs necessary to 

calculate whether or not this type of flare is over-assisted. 

Therefore, we are proposing that in addition to complying with 

combustion zone operational limits to ensure that there is 

enough combustible material available to adequately combust the 

gas and pass through the flammability region, air-assisted 

flares would also comply with an additional dilution parameter 

that factors in the flow rate of the flare vent gas, flow rates 

of all assist media (including perimeter assist air), and 

diameter of flare tip to ensure that degradation of flare 

performance from excess aeration does not occur. This dilution 

parameter is consistent with the combustion theory that the more 

“time” the gas spends in the flammability region above the flare 

tip, the better it will combust. Also, since both the volume of 

the combustion zone (represented by the diameter here) and how 

quickly this gas is diluted to a point below the flammability 

region (represented by perimeter assist air flow rate) 

characterize this “time,” it makes sense that we propose such a 

term (see technical memorandum, Petroleum Refinery Sector Rule: 

Operating Limits for Flares, in Docket ID Number EPA-HQ-OAR2010-0682). 

It should be noted that in the 2012 flare peer review 

report, we considered a limit for perimeter assist air via the 

stoichiometric air ratio. This stoichiometric air ratio is the 
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ratio of the actual mass flow rate of assist air to the 

theoretical stoichiometric mass flow rate of air (based on 

complete chemical combustion of fuel to carbon dioxide (CO2) and 

water) needed to combust the flare vent gas. However, we are not 

proposing to include this term as part of the calculation 

methodology, as we have determined that the dilution parameter 

discussed in this section better assures that air-assisted flare 

performance is not degraded due to excess aeration. 

The proposed rule allows the owner or operator flexibility 

to select the form of the combustion zone operational limit 

(i.e., net heating value, LFL, or total combustibles fraction) 

with which to comply in order to provide facilities the option 

of using monitors they may already have in place. The monitoring 

methods we are proposing take into account the combustible 

properties of all gas going to the flare (i.e., flare vent gas, 

assist gas, and premix air) that affects combustion efficiency, 

and they can be used to determine whether a flare has enough 

combustible material to achieve the desired level of control 

(and whether it is being over-assisted). These methods require 

the owner or operator to input the flow of the vent gas to the 

flare, the characteristics of the vent gas going to the flare 

(i.e., either a heat content (Btu/scf), LFL, or total 

combustible fuel content, depending on how the operational limit 

is expressed), and the flow of assist media added to the flare. 
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To estimate the LFL, we are proposing to use a calculation 

method based on the Le Chatelier equation. The Le Chatelier 

calculation uses the reciprocal of the volume-weighted average 

over the LFL of the individual compounds in the gas mixture to 

estimate the LFL of the gas mixture. Although Le Chatelier’s 

equation was originally limited to binary mixtures of 

combustible gases, we are proposing a method that was developed 

by Karim, et al. (1985) and assumes a LFL of infinity for inert 

gases. We are also aware of other methods and/or adjustments 

that can be made to the Le Chatelier equation in order to 

calculate a more accurate estimate of the LFL of a gas mixture 

(see technical memorandum, Parameters for Properly Designed and 

Operated Flares, in Docket ID Number EPA-HQ-OAR-2010-0682). We 

are soliciting comment on the use of this proposed method. 

Recent data indicate that one set of operational limits may 

not be sufficient for all refinery flares. Flares that receive 

vent gas containing significant levels of both hydrogen and 

olefins often exhibit lower combustion efficiencies than flares 

that receive vent gas with only one (or none) of these 

compounds. Therefore, we are proposing more stringent 

operational limits for flares that simultaneously receive vent 

gas containing significant levels of both hydrogen and olefins 

(see technical memorandum, Petroleum Refinery Sector Rule: 

Operating Limits for Flares, in Docket ID Number EPA-HQ-OAR-
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2010-0682). Although the minimum net heating value in the 

combustion zone (i.e., Btu/scf) is a good indicator of 

combustion efficiency, as noted in the flare peer review report, 

the LFL and combustibles concentration (or total combustibles) 

in the combustion zone are also good indicators of flare 

combustion efficiency. For some gas mixtures, such as gases with 

high hydrogen content, the LFL or combustibles concentration in 

the combustion zone may be better indicators of performance than 

net heating value. Consequently, we are proposing operational 

limits expressed all three ways, along with associated 

monitoring requirements discussed later in this section. 

The three operating limits were established in such a way 

that each limit is protective on its own. As such, the owner or 

operator may elect to comply with any of the three alternative 

operating limits at any time, provided they use a monitoring 

system capable of determining compliance with each of the 

proposed alternative operating limits on which they rely (see 

technical memorandum, Petroleum Refinery Sector Rule: Operating 

Limits for Flares, in Docket ID Number EPA-HQ-OAR-2010-0682). 

For example, the owner or operator may elect to install 

monitoring for only one of the three alternative operating 

limits, in which case the owner or operator must comply with 

that selected operating limit at all times. If the owner or 

operator installs a system capable of monitoring for all three 
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of the alternative operating limits, the owner or operator can 

choose which of the three operating limits the source will rely 

on to demonstrate compliance. 

A summary of the operating limits specified in this 

proposed rule is provided in Table 3 of this preamble. We are 

proposing that owners or operators of flares used as APCD would 

conduct an initial performance test to determine the values of 

the parameters to be monitored (e.g., the flow rate and heat 

content of the incoming flare vent gas, the assist media flow 

rate, and pre-mix air flow rate, if applicable) in order to 

demonstrate continuous compliance with the operational limits in 

Table 3. We are proposing to require owners or operators to 

record and calculate 15-minute block average values for these 

parameters. Our rationale for selecting a 15-minute block 

averaging period is provided below in Ssection IV.A.3.e of this 

preamble. 

Table 3. Operating Limits for Flares in this Proposed Action 

Operating 

Parametera

Operating Limits: Flares 

without Hydrogen-Olefin 

Interactionb

Operating Limits: Flares 

with Hydrogen-Olefin 

Interactionb

Combustion zone parameters for all flares 

NHVcz ≥270 Btu/scf ≥380 Btu/scf 

LFLcz ≤0.15 volume fraction ≤0.11 volume fraction 

Ccz ≥0.18 volume fraction ≥0.23 volume fraction 

Dilution parameters for flares using perimeter assist air 

NHVdil ≥22 Btu/ft2 ≥32 Btu/ft2

LFLdil ≤2.2 volume fraction/ft ≤1.6 volume fraction/ft 

Cdil ≥0.012 volume fraction-ft ≥0.015 volume fraction-ft a

 The operating parameters are: 
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NHVcz = combustion zone net heating value 

LFLcz = combustion zone lower flammability limit 

Ccz = combustion zone combustibles concentration 

NHVdil = net heating value dilution parameter 

LFLdil = lower flammability limit dilution parameter 

Cdil = combustibles concentration dilution parameter b

 Hydrogen-Olefin interactions are assumed to be present when the 

concentration of hydrogen and olefins in the combustion zone exceed all three 

of the following criteria: 

(1) The concentration of hydrogen in the combustion zone is greater than 1.2 

percent by volume. 

(2) The cumulative concentration of olefins in the combustion zone is 

greater than 2.5 percent by volume. 

(3) The cumulative concentration of olefins in the combustion zone plus the 

concentration of hydrogen in the combustion zone is greater than 7.4 percent 

by volume. 

Btu/ft2

 = British thermal units per square foot. 

We are soliciting comment on the appropriateness of the 

operating limits and dilution parameters in Table 3 of this 

preamble and whether they ensure that refinery flares operate in 

a manner that that will ensure compliance with the MACT 

requirements for vents to achieve a 98-percent organic HAP 

reduction. 

Combustion zone gas monitoring alternatives. As discussed 

previously in this section, we are proposing to define the 

combustion zone gas as the mixture of gas at the flare tip 

consisting of the flare vent gas, the total steam-assist media 

and premix assist air. In order to demonstrate compliance with 

the three combustion zone parameter operating limits of net 

heating value, LFL and total combustibles fraction, the owner or 

operator would need to monitor four things: (1) flow rate of the 

flare vent gas; (2) flow rate of total steam assist media; (3) 

flow rate of premix assist air and (4) specific characteristics 
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associated with the flare vent gas (e.g., heat content, 

composition). In order to monitor the flow rates of the flare 

vent gas, total steam assist media, and premix assist air, we 

are proposing that refinery owners or operators use a continuous 

volumetric flow rate monitoring system or a pressure- and 

temperature-monitoring system with use of engineering 

calculations. We are also proposing use of either of these 

monitoring methods for purposes of determining the flow rate of 

perimeter assist air (for compliance with the dilution 

parameter). However, the one component that will determine how 

many combustion zone parameter operating limits an owner or 

operator can comply with is the specific type of monitor used to 

characterize the flare vent gas. 

Monitoring the individual component concentrations of the 

flare vent gas using an on-line gas chromatograph (GC) along 

with monitoring vent gas and assist gas flow rates will allow 

the owner or operator to determine compliance with any of the 

three proposed combustion zone operating limits and any of the 

three proposed dilution operating limits (if using air-assisted 

flares). We considered requiring all refinery owners or 

operators of flares to only use a GC to monitor the flare vent 

gas composition but since facilities may have other non-GC 

monitors already in place (e.g., calorimeters), we are not 

proposing such a requirement at this time. However, use of a GC 
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can improve refinery flare operation and management of 

resources. For example, use of a GC to characterize the flare 

vent gas can lead to product/cost savings for refiners because 

they could more readily identify and correct instances of 

product being unintentionally sent to a flare, either through a 

leaking pressure relief valve or other conveyance that is 

ultimately routed to the flare header system. In addition, an 

owner or operator that chooses to use a GC (in lieu of one of 

the other proposed monitoring alternatives) will be more likely 

to benefit from the ability to continuously fine-tune their 

operations (by reducing assist gas addition and/or supplemental 

gas to the flare) in order to meet any one of the three 

operating limits. Furthermore, some facilities are already 

required to use a GC to demonstrate compliance with state flare 

requirements. We are soliciting comment on the additional 

benefits that using a GC offers and whether it would be 

reasonable to require a GC on all refinery flares. 

As an alternative to a continuous compositional monitoring 

system, we are proposing to allow the use of grab samples along 

with engineering calculations to determine the individual 

component concentration. Like the on-line GC, the grab sampling 

option relies on compound speciation and is therefore flexible 

to use with any form of the operational limits we are proposing. 

The disadvantage of this option is that if a grab sample 
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indicates non-compliance with the operational limits, the 

permitting authority could presume non-compliance from the time 

of the previous grab sample indicating compliance, which would 

include all 15-minute periods in that time period. However, 

there are a number of situations where the refinery owner or 

operator may find this option advantageous. For example, some 

flares receive flows only from a specific process with a 

consistent composition and high heat content. In this case, the 

owner or operator may elect to actively adjust the assist gas 

flow rates using the expected vent gas composition and rely on 

the analysis of the grab sample to confirm the expected vent gas 

composition. This alternative may also be preferred for flares 

that are used infrequently (non-routine flow flares) or that 

have flare gas recovery systems designed and operated to recover 

100 percent of the flare gas under typical conditions. For these 

flares, flaring events may be so seldom that the refinery owner 

or operator may prefer the uncertainty in proactive control to 

the higher cost of continuous monitors that would seldom be 

used. 

As an alternative to performing a compositional analysis 

with use of a GC (through either on-line monitoring or analysis 

of the grab sample), we are proposing that owners or operators 

of flares may elect to install a device that directly monitors 

vent gas net heating value (i.e., a calorimeter). If the owner 
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or operator elects this monitoring method, we are proposing that 

they must comply with the operating limits that are based on the 

net heating value operating limit. Similarly, we are also 

proposing that owners or operators of flares may elect to 

install a device that directly monitors the total hydrocarbon 

content of the flare vent gas (as a measure of the combustibles 

concentration). If the owner or operator elects this monitoring 

method, they must comply with the operating limits that are 

based on the combustibles concentration. 

e. Data Averaging Periods for Flare Gas Operating Limits 

We are proposing to use a 15-minute block averaging period 

for each proposed flare operating parameter (including flare tip 

velocity) to ensure that the flare is operated within the 

appropriate operating conditions. As flare vent gas flow rates 

and composition can change significantly over short periods of 

time, a short averaging time was considered to be the most 

appropriate for assessing proper flare performance. Furthermore, 

since flare destruction efficiencies can fall precipitously fast 

below the proposed operating limits, short time periods where 

the operating limits are not met could seriously impact the 

overall performance of the flare. With longer averaging times, 

there may be too much opportunity to mask these short periods of 

poor performance (i.e., to achieve the longer-term average 

operating limit while not achieving a high destruction 
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efficiency over that time period because of short periods of 

poor performance). 

Moreover, a 15-minute averaging period is in line with the 

test data and the analysis used to establish the operating 

limits in this proposed rule. Ninety-three percent of the flare 

test runs used as a basis for establishing the proposed 

operating limits ranged in duration from 5 to 30 minutes, and 77 

percent of the runs ranged in duration from 5 to 20 minutes. The 

failure analysis (discussed below in Ssection IV.A.3.f of this 

preamble) considered minute-by-minute test run data, but as 

there are limitations on how quickly compositional analyses can 

be conducted, many of the compositional data still reflect set 

values over 10- to 15-minute time intervals. Because the GC 

compositional analyses generally require 10 to 15 minutes to 

conduct, shorter averaging times are not practical. To be 

consistent with the available test data and to ensure there are 

no short periods of significantly poor performance, we are 

proposing 15-minute block averaging times. 

Given the short averaging times for the operating limits, 

we are proposing special calculation methodologies to enable 

refinery owners or operators to use “feed forward” calculations 

to ensure compliance with the operating limits on a 15-minute 

block average. Specifically, the results of the compositional 

analysis determined just prior to a 15-minute block period are 
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to be used for the next 15-minute block average. Owners or 

operators of flares will then know the vent gas properties for 

the upcoming 15-minute block period and can adjust assist gas 

flow rates relative to vent gas flow rates to comply with the 

proposed operating limits. 

Owners or operators of flares that elect to use grab 

sampling and engineering calculations to determine compliance 

must still assess compliance on a 15-minute block average. The 

composition of each grab sample is to be used for the duration 

of the episode or until the next grab sample is taken. We are 

soliciting comment on whether this approach is appropriate, and 

whether grab samples are needed on a more frequent basis to 

ensure compliance with the operating limits. 

f. Other Peer Review Considerations 

In an effort to better inform the proposed new requirements 

for refinery flares, in the spring of 2012 the EPA summarized 

its preliminary findings on operating parameters that affect 

flare combustion efficiency in a technical report and put this 

report out for ad-hoc peera letter review. Based on the feedback 

received from the ad-hoc peer review panel, the EPA considered 

many of the concerns peer reviewers expressed in their comments 

in the development of this proposal for refinery flares (see 

memorandum, Peer Review of “Parameters for Properly Designed and 

Operated Flares”, in Docket ID Number EPA-HQ-OAR-2010-0682). 
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While the more substantive issues have been previously discussed 

in Ssections IV.A.3.a through e of this preamble, the following 

discussion addresses other peer review considerations that the 

EPA either discussed in the peer review technical document or 

considered from comments received by the peer review panel that 

played a role in the development of this proposal. 

Test data quality and analysis. For steam-assisted flares, 

we asked peer reviewers to comment on our criteria for excluding 

available flare test data from our analyses. In general, peer 

reviewers considered the EPA’s reasons for removing certain test 

data (prior to performing any final analysis) to be appropriate; 

however, one reviewer suggested the EPA complete an analysis of 

quality on the data before applying any criteria, and several 

reviewers commented on the level of scrutiny of the 10 data 

points specifically discussed in the technical report for not 

meeting the combustion zone LFL trend. These reviewers stated it 

appeared the EPA had scrutinized test data more if it were 

inconsistent with the LFL threshold conclusions made in the 

report. Although we felt it was appropriate to discuss specific 

test data not fitting the trend, we do agree with the reviewers 

that a more general and standard set of criteria should be 

applied to all test data prior to making any conclusion. In 

addition, other peer reviewers saw no reason why the EPA should 

exclude 0-percent combustion efficiency data points, or data 
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points where smoking occurs, or single test runs when there was 

also a comparable average test run. Therefore, in response to 

these peer review comments, the EPA performed a validation and 

usability analysis on all available test data. This resulted in 

a change to the population of test data used in our final 

analysis (see technical memorandum, Flare Performance Data: 

Summary of Peer Review Comments and Additional Data Analysis for 

Steam-Assisted Flares, in Docket ID Number EPA-HQ-OAR-2010-0682 

for a more detailed discussion of the data quality and 

analysis). 

To help determine appropriate operating limits, several 

peer reviewers suggested the EPA perform a false-positive-tofalse-negative comparison (or failure type) analysis between the 

potential parameters discussed in the technical report as 

indicators of flare performance. The reviewers suggested that 

the EPA attempt to minimize the standard error of all false 

positives (i.e., poor observed combustion efficiency when the 

correlation would predict good combustion) and false negatives 

(i.e., good observed combustion efficiency when the correlation 

would predict poor combustion). In response to these comments, 

the EPA has conducted a failure analyses of these parameters 

which helped form the basis for the operating limits we are 

proposing for flares (see technical memorandum, Petroleum 
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Refinery Sector Rule: Operating Limits for Flares, in Docket ID 

Number EPA-HQ-OAR-2010-0682). 

Some peer reviewers contended that it is appropriate for 

the EPA to round each established operating limit to the nearest 

whole number, because using a decimal implies far more accuracy 

and reliability than can be determined from the test data. Based 

on these comments, we have given more consideration to the 

number of significant figures used in the operating limits, and 

we are proposing to use two significant figures for the flare 

operating limits in these proposed amendments. 

Multiple peer reviewers performed additional analyses to 

try and determine the appropriateness of the limits raised in 

the technical report. Some peer reviewers tried to fit the data 

to a curve, others performed various failure analyses, while 

others looked at different metrics not discussed in the 

technical report (see memorandum, Peer Review of “Parameters for 

Properly Designed and Operated Flares”, in Docket ID Number EPAHQ-OAR-2010-0682). Based on the conclusions drawn from these 

various analyses, a range of combustion zone net heating value 

targets from 200 Btu/scf to 450 Btu/scf were identified as 

metrics that would provide a high level of certainty regarding 

good combustion in flares (Note: 450 Btu/scf was the assumed to 

be approximately equivalent to a combustion zone LFL of 10 

percent). We solicit comment on this range and the 
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appropriateness for which the operating limits selected in this 

proposal will ensure compliance with the MACT requirements for 

vents at petroleum refineries. 

Effect of supplemental gas use. Most flares normally 

operate at a high turndown ratio, which means the actual flare 

gas flow rate is much lower than what the flare is designed to 

handle. In addition, steam-assisted flares have a manufacturers’ 

minimum steam requirement in order to protect the flare tip. A 

combination of high turndown ratio and minimum steam requirement 

will likely require some owners or operators to add supplemental 

gas to achieve one of the combustion zone gas operating limits 

we are proposing here (e.g., combustion zone combustibles 

concentration (Ccz) ≥ 18 volume percent; combustion zone lower 

flammability limit (LFLcz) ≤ 15 volume percent; or combustion 

zone net heating value (NHVcz) ≥ 270 Btu/scf). However, finetuning the actual steam flow to the flare should significantly 

reduce the need for supplemental gas. We considered proposing a 

steam-to-vent gas ratio limitation on steam-assisted flares. 

however, a steam-to-vent gas ratio alone cannot fully address 

over-steaming because it would not account for the variability 

of chemical properties within the flare gas. We request that 

commenters on this issue provide supporting documentation on 

their potential to reduce steam as well as their use of 

supplemental gas to achieve the proposed operating limit(s), and 
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how it could affect cost and potential emissions. We emphasize 

that the amount and cost of supplemental gas should be 

reflective of conditions after any excess steam use has been 

rectified. It would not be valuable to consider situations where 

large amounts of supplemental gas are added, while steam is 

simultaneously added far in excess of the amount recommended by 

the flare manufacturer or other guidance documents. 

In assessing the combustion zone gas and looking at all the 

gas at the flare tip, another potential source of added heat 

content comes from the gas being used as fuel to maintain a 

continuously lit pilot flame. However, since pilot gas is being 

used as fuel for a continuous ignition source and is burned to 

create a flame prior to (or at the periphery of) the combustion 

zone, this gas does not directly contribute to the heat content 

or flammability of the gas being sent to the flare to be 

controlled under Refinery MACT 1 or 2. In addition, in looking 

at available test data, the pilot gas flow rate is generally so 

small that it does not significantly impact the combustion zone 

properties at all. Furthermore, by leaving pilot gas out of the 

combustion zone operating limit calculations, the equations 

become simplified and a requirement to continuously monitor 

pilot gas flow rate can be avoided. Therefore, we are proposing 

that the owner or operator not factor in the pilot gas 

combustible component (or net heating value) contribution when 
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determining any of the three proposed combustion zone gas 

operating limits (Ccz, LFLcz, or NHVcz). 

Effects of wind on flame performance. Several published 

studies have investigated the significance of wind on the fluid 

mechanics of a flare flame (see technical memorandum, Parameters 

for Properly Designed and Operated Flares, in Docket ID Number 

EPA-HQ-OAR-2010-0682). These studies were conducted in wind 

tunnels at crosswind velocities up to about 60 miles per hour 

(mph) and have illustrated that increased crosswind velocity can 

have a strong effect on flare flame dimensions and shape, 

causing the flame to become segmented or discontinuous, and 

wake-dominated (i.e., where the flame is bent over on the 

downwind side of a flare pipe and is imbedded in the wake of the 

flare tip), which may lead to poor flare performance due to fuel 

stripping. However, the majority of this research is confined to 

laboratory studies on flares with effective diameters less than 

3 inches, which have been shown not to be representative of 

industrial-sized flares. Research that does include performance 

tests conducted on flares scalable to refinery flares (i.e., 3-

inch, 4-inch, and 6-inch pipe flares) was conducted with flare 

tip velocities as low as 0.49 feet per second and crosswind 

velocities of about 26 mph and less; all tests resulted in good 

flare performance. Furthermore, there is no indication that 

crosswind velocities negatively impact flare performance in the 
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recent flare performance tests. These tests were conducted on 

various sizes of industrial flares (i.e., effective diameters 

ranging between 12 and 54 inches) in winds of about 22 mph and 

less, and at relatively low flare tip velocities (i.e., 10 feet 

per second or less). (See Parameters for Properly Designed and 

Operated Flares, in Docket ID Number EPA-HQ-OAR-2010-0682.) 

We are aware of flare operating parameters that consider 

crosswind velocity; however, using the available flare 

performance test data, we were unable to determine a clear 

correlation that would be appropriate for all refinery flares. 

For example, the momentum flux ratio (MFR) is a measure of 

momentum strength of the flare exit gas relative to the 

crosswind (i.e., the product of flare exit gas density and 

velocity squared divided by the product of air density and 

crosswind velocity squared). The plume buoyancy factor is the 

ratio of crosswind velocity to the flare exit gas velocity, and 

considers the area of the flare pipe. The power factor is the 

ratio of the power of the crosswind to the power of combustion 

of the flare gas. Because the available flare performance test 

data have relatively low flare tip velocities, and crosswind 

velocities were relatively constant during each test run, we are 

unable to examine these parameters to the fullest extent. 

In light of the data available from performance tests 

(Gogolek et al., 2010), we asked peer reviewers whether the MFR 
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could be used in crosswind velocities greater than 22 mph at the 

flare tip to indicate wake-dominated flame situations. We also 

asked for comment on observations that in the absence of 

crosswind greater than 22 mph, a low MFR does not necessarily 

indicate poor flare performance. Peer reviewers suggested that 

there are no data available from real industrial flares in winds 

greater than 22 mph to support that MFR could be used to 

identify wake-dominated flame situations. In addition, we 

received no further peer review comments that have caused us to 

reconsider the observation we made in the April 2012 technical 

report that in the absence of crosswind greater than 22 mph, a 

low MFR does not necessarily indicate poor flare performance. We 

request comment with supporting data and rationale on any of 

these, or other parameters, as a measure of wind effects on 

flare combustion efficiency. 

We considered including observation requirements for 

detecting segmented or discontinuous wake-dominated flames, 

especially for winds greater than 22 mph (where limited test 

data is available). However, owners or operators of flares 

cannot control the wind speed, and it would be detrimental to 

increase the quantity of flared gases in high crosswind 

conditions in efforts to improve the MFR and reduce wakedominated flow conditions. Furthermore, there is no indication 

that crosswind velocities negatively impact flare performance in 
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the recent flare performance tests. For these reasons, we are 

not proposing any flare operating parameter(s) to minimize wind 

effects on flare combustion efficiency. 

g. Impacts of the Flare Operating and Monitoring Requirements 

The EPA expects that the newly proposed requirements for 

refinery flares discussed in this section will affect all flares 

at petroleum refineries. Based on data received as a result of 

the Refinery ICR, we estimate that there are 510 flares 

operating at petroleum refineries and that 285 of these receive 

flare vent gas flow on a regular basis (i.e., other than during 

periods of startup, shutdown, and malfunction). Costs were 

estimated for each flare for a given refinery, considering 

operational type (e.g., receive flare vent gas flow on a regular 

basis, use flare gas recovery systems to recover 100 percent of 

routine flare flow, handle events during startup, shutdown, or 

malfunction only, etc.) and current monitoring systems already 

installed on each individual flare. Costs for any additional 

monitoring systems needed were estimated based on installed 

costs received from petroleum refineries and, if installed costs 

were unavailable, costs were estimated based on vendor-purchased 

equipment. The baseline emission estimate and the emission 

reductions achieved by the proposed rule were estimated based on 

current vent gas and steam flow data submitted by industry 

representatives. The results of the impact estimates are 
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summarized in Table 4 of this preamble. We note that the 

requirements for refinery flares we are proposing in this action 

will ensure compliance with the Refinery MACT standards when 

flares are used as an APCD. As such, these proposed operational 

and monitoring requirements for flares at refineries have the 

potential to reduce excess emissions from flares by 

approximately 3,800 tpy of HAP, 33,000 tpy of VOC, and 327,000 

metric tonnes per year of carbon dioxide equivalents (CO2e). The 

VOC compounds are non-methane, non-ethane total hydrocarbons. 

According to the Component 2 database from the Refinery ICR, 

there are approximately 50 individual HAP compounds included in 

the emission inventory for flares, but many of these are emitted 

in trace quantities. A little more than half of the HAP 

emissions from flares are attributable to hexane, followed next 

by benzene, toluene, xylenes, and 1,3-butadiene. For more detail 

on the impact estimates, see the technical memorandum Petroleum 

Refinery Sector Rule: Flare Impact Estimates in Docket ID Number 

EPA-HQ-OAR-2010-0682. 

Table 4. Nationwide Cost Impacts of Proposed Amendments to 

Ensure Proper Flare Performance 

Affected source 

Total capital investment 

(million $) 

Total annualized costs 

(million $/ yr) 

Flare Monitoring 147 36.3 
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4. Vent Control Bypasses 

a. Relief Valve Discharges 

Refinery MACT 1 recognized relief valve discharges to be 

the result of malfunctions. Relief valves are designed to remain 

closed during normal operation and only release as the result of 

unplanned and/or unpredictable events. A release from a relief 

valve usually occurs during an over pressurization of the 

system. However, emissions vented directly to the atmosphere by 

relief valves in organic HAP service contain HAP that are 

otherwise regulated under Refinery MACT 1. 

Refinery MACT 1 regulated relief valves through equipment 

leak provisions that applied only after the pressure relief 

occurred. In addition the rule followed the EPA’s then-practice 

of exempting startup, shutdown and malfunction (SSM) events from 

otherwise applicable emission standards. Consequently, with 

relief valve releases defined as unplanned and nonroutine and 

the result of malfunctions, Refinery MACT 1 did not restrict 

relief valve releases to the atmosphere but instead treated them 

the same as all malfunctions through the SSM exemption 

provision. 

In Sierra Club Vv. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the 

Court determined that the SSM exemption violates the CAA. See 

section IV.E. of this preamble for additional discussion. To 

ensure this standard is consistent with that decision, these 
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proposed amendments remove the malfunction exemption in Refinery 

MACT 1 and 2 and provide that emissions of HAP may not be 

discharged to the atmosphere from relief valves in organic HAP 

service. To ensure compliance with this amendment, we are also 

proposing to require that sources monitor relief valves using a 

system that is capable of identifying and recording the time and 

duration of each pressure release and of notifying operators 

that a pressure release has occurred. Pressure release events 

from relief valves to the atmosphere have the potential to emit 

large quantities of HAP. Where a pressure release occurs, it is 

important to identify and mitigate it as quickly as possible. 

For purposes of estimating the costs of this requirement, we 

assumed that operators would install electronic monitors on each 

relief valve that vents to the atmosphere to identify and record 

the time and duration of each pressure release. However, we are 

proposing to allow owners and operators to use a range of 

methods to satisfy these requirements, including the use of a 

parameter monitoring system (that may already be in place) on 

the process operating pressure that is sufficient to indicate 

that a pressure release has occurred as well as record the time 

and duration of that pressure release. Based on our cost 

assumptions, the nationwide capital cost of installing these 

electronic monitors is $9.54 million and the annualized capital 

cost is $1.36 million per year. 
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As defined in the Refinery MACT standards, relief valves 

are valves used only to release unplanned, nonroutine 

discharges. A relief valve discharge results from an operator 

error, a malfunction such as a power failure or equipment 

failure, or other unexpected cause that requires immediate 

venting of gas from process equipment in order to avoid safety 

hazards or equipment damage. Even so, to the extent that there 

are atmospheric HAP emissions from relief valves, we are 

required to follow the Sierra Club ruling to address those 

emissions in our rule, and we can no longer exempt them as 

permitted malfunction emissions as we did under Refinery MACT 1. 

Our information indicates that there are approximately 12,000 

pressure relief valves that vent to the atmosphere (based on the 

ICR responses) and that the majority of relief valves in the 

refining industry are not atmospheric, but instead are routed to 

flares (see letter from API, Docket Item Number EPA-HQ-OAR-2010-

0682-0012). We request comment on our approach and on 

alternatives to our approach to regulating releases from 

pressure relief valves and also request commenters to provide 

information supporting any such comments. 

b. Bypass Lines 

For a closed vent system containing bypass lines that can 

divert the stream away from the APCD to the atmosphere, Refinery 

MACT 1 requires the owner or operator to either: (1) install, 
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maintain and operate a continuous parametric monitoring system 

(CPMS) for flow on the bypass line that is capable of detecting 

whether a vent stream flow is present at least once every hour, 

or (2) secure the bypass line valve in the non-diverting 

position with a car-seal or a lock-and-key type configuration. 

Under option 2, the owner or operator is also required to 

inspect the seal or closure mechanism at least once per month to 

verify the valve is maintained in the non-diverting position 

(see 40 CFR 63.644(c) for more details). We are proposing under 

CAA Ssection 112(d)(2) and (3) that the use of a bypass at any 

time to divert a Group 1 miscellaneous process vent is a 

violation of the emission standard, and to specify that if 

option 1 is chosen, the owner or operator would be required to 

install, maintain and operate a CPMS for flow that is capable of 

recording the volume of gas that bypasses the APCD. The CMPS 

must be equipped with an automatic alarm system that will alert 

an operator immediately when flow is detected in the bypass 

line. We are proposing this revision because, as noted above, 

APCD are not to be bypassed because doing so could result in a 

release of regulated organic HAP to the atmosphere. In Sierra 

Club Vv. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the Court 

determined that standards under CAA Ssection 112(d) must provide 

for compliance at all times and a release of uncontrolled HAP to 

the atmosphere is inconsistent with that requirement. 
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c. In Situ Sampling Systems (Onstream Analyzers) 

The current Refinery MACT 1 definition of “miscellaneous 

process vent” states that “in situ sampling systems (onstream 

analyzers)” are not miscellaneous process vents. 40 CFR 63.641. 

For several reasons, we are proposing to remove “in situ 

sampling systems (onstream analyzers)” from the list of vents 

not considered miscellaneous process vents. First, the language 

used in this exclusion is inconsistent. We generally consider 

“in situ sampling systems” to be non-extractive samplers or inline samplers. There are certain in situ sampling systems where 

the measurement is determined directly via a probe placed in the 

process stream line. Such sampling systems do not have an 

atmospheric vent, so excluding these from the definition of 

“miscellaneous process vent” is not meaningful. The 

parenthetical term “onstream analyzers” generally refers to 

sampling systems that feed directly to an analyzer located at 

the process unit, and has been interpreted to exclude the 

“onstream” analyzer’s vent from the definition of miscellaneous 

process vents. As these two terms do not consistently refer to 

the same type of analyzer, the provision is not clear. 

Second, we find that there is no technical reason to 

include analyzer vents in a list of vents not considered 

miscellaneous process vents. For extractive sampling systems and 

systems with purges, the equipment leak standards in Refinery 
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MACT 1 require that the material be returned to the process or 

controlled. Thus, the only potential emissions from any sampling 

system compliant with the Refinery MACT 1 equipment leak 

provisions would be from the analyzer’s “exhaust gas” vent. The 

parenthetical term “onstream analyzers” indicates that the focus 

of the exemption is primarily on the analyzer (or analyzer vent) 

rather than the sampling system. This phrase has been 

interpreted to exclude the “onstream” analyzer’s vent from the 

definition of miscellaneous process vents. Analyzer venting is 

expected to be routine (continuous or daily intermittent 

venting). 

We are proposing to delete this exclusion from the 

definition of “miscellaneous process vent” and to require these 

vents to meet the standards applicable to miscellaneous process 

vents at all times. We expect most analyzer vents to be Group 2 

miscellaneous process vents because analyzer vents are not 

expected to exceed the 72 pounds per day (lb/day) emissions 

threshold for Group 1 miscellaneous process vents. However, if 

there are larger analyzer vents that exceed the 72 lb/day 

emissions threshold for Group 1 miscellaneous process vents, 

these emission sources would need to be controlled as a Group 1 

miscellaneous process vent under this proposal. We solicit 

comment on the existence of any onstream analyzers that have VOC 
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emissions greater than 72 lb/day and why such vents are not 

amenable to control. 

d. Refinery Flares and Fuel Gas Systems 

The current definition of “miscellaneous process vent” in 

Refinery MACT 1 states that “gaseous streams routed to a fuel 

gas system” are not miscellaneous process vents. Furthermore, 

the affected source subject to Refinery MACT 1 does not 

specifically include “emission points routed to a fuel gas 

system, as defined in §63.641 of this subpart.” The EPA allowed 

these exemptions for streams routed to fuel gas systems because 

according to the 1994 preamble for Refinery MACT 1, “these vents 

are already controlled to the most stringent levels achievable” 

(59 FR 36141, July 15, 1994). Since gaseous streams routed to a 

fuel gas system are eventually burned as fuel, typically in a 

boiler or process heater, these combustion controls burning the 

gaseous streams as fuel effectively achieve this most stringent 

level of control (i.e., 98-percent organic HAP reduction or an 

outlet organic HAP concentration of 20 ppmv for all vent 

streams). However, there can be instances when gaseous streams 

from the fuel gas system that would otherwise be combusted in a 

boiler or process heater are instead routed to a flare (e.g., 

overpressure in the fuel gas system, used as flare sweep gas, 

used as flare purge gas). In cases where an emission source is 

required to be controlled in Refinery MACT 1 and 2 but is routed 
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to a fuel gas system, we are proposing that any flare receiving 

gases from that fuel gas system must comply with the flare 

operating and monitoring requirements discussed in Ssection 

IV.A.3 of this preamble. 

B. What are the results and proposed decisions based on our 

technology review? 

1. Refinery MACT 1 – 40 CFR Part 63, Subpart CC 

Refinery MACT 1 sources include miscellaneous process 

vents, storage vessels, equipment leaks, gasoline loading racks, 

marine vessel loading operations, cooling towers/heat exchange 

systems, and wastewater. 

a. Miscellaneous Process Vents 

Many unit operations at petroleum refineries generate 

gaseous streams containing HAP. These streams may be routed to 

other unit operations for additional processing (e.g., a gas 

stream from a reactor that is routed to a distillation unit for 

separation) or they may be sent to a blowdown system or vented 

to the atmosphere. Miscellaneous process vents emit gases to the 

atmosphere, either directly or after passing through recovery 

and/or APCD. Under 40 CFR 63.643, the owner or operator must 

reduce organic HAP emissions from miscellaneous process vents 

using a flare that meets the equipment specifications in 40 CFR 

63.11 of the General Provisions (subpart A) or use APCD (e.g., 

thermal oxidizers, carbon adsorbers) to reduce organic HAP 
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emissions by 98 weight-percent or to a concentration of 20 parts 

per million by volume (ppmv) dry basis, corrected to 3-percent 

oxygen. 

In the technology review, we did not identify any 

practices, processes or control technologies beyond those 

already required by Refinery MACT 1. Therefore, we are proposing 

that it is not necessary to revise Refinery MACT 1 requirements 

for miscellaneous process vents pursuant to CAA Ssection 

112(d)(6). 

b. Storage Vessels 

Storage vessels (also known as storage tanks) are used to 

store liquid and gaseous feedstocks for use in a process, as 

well as liquid and gaseous products coming from a process. Most 

storage vessels are designed for operation at atmospheric or 

near atmospheric pressures; high-pressure vessels are used to 

store compressed gases and liquefied gases. Atmospheric storage 

vessels are typically cylindrical with a vertical orientation, 

and they are constructed with either a fixed roof or a floating 

roof. Some, generally small, atmospheric storage vessels are 

oriented horizontally. High pressure vessels are either 

spherical or horizontal cylinders. 

Section 63.646(a) requires certain existing and new storage 

vessels to comply with 40 CFR 63.119 through 40 CFR 63.121 of 

the HON. Under 40 CFR 63.119 through 63.121, storage vessels 
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must be equipped with an internal floating roof with proper 

seals, an external floating roof with proper seals, an external 

floating roof converted to an internal floating roof with proper 

seals or a closed vent system routed to an APCD that reduces HAP 

emissions by 95 percent. Storage vessels at existing sources 

that use floating roofs are not required under Refinery MACT 1 

to install certain fitting controls included in 40 CFR 63.1119 

of the HON (e.g., gaskets for automatic bleeder vents, slit 

fabric covers for sample wells, flexible fabric seals or 

gasketed sliding covers for guidepoles and gasketed covers for 

other roof openings). See 40 CFR 63.646(c). 

In 2012, we conducted a general analysis to identify the 

latest developments in practices, processes and control 

technologies for storage vessels at chemical manufacturing 

facilities and petroleum refineries, and we estimated the 

impacts of applying those practices, processes and technologies 

to model storage vessels. (See Survey of Control Technology for 

Storage Vessels and Analysis of Impacts for Storage Vessel 

Control Options, December 29, 2011, inJanuary 20, 2012, Docket 

IDItem Number EPA-HQ-OAR-2010-0871-0027.) We used this analysis 

as a starting point for conducting the technology review for 

storage vessels at refineries. In this analysis, we identified 

fitting controls, particularly controls for floating roof 

guidepoles, and monitoring equipment (liquid level monitors and 
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leak monitors) as developments in practices, processes and 

control technologies for storage vessels. In our refineryspecific review, we also noted that the Group 1 storage vessel 

size and vapor pressure thresholds in Refinery MACT 1 were 

higher than those for storage vessels in MACT standards for 

other similar industries. Therefore, we also evaluated revising 

the Group 1 storage vessel thresholds as a development in 

practices for storage vessels in the refining industry. 

We used data from our 2011 ICR to evaluate the impacts of 

requiring the additional controls identified in the technology 

review for the petroleum refinery source category. The emission 

reduction options identified during the technology review are: 

(1) requiring guidepole controls and other fitting controls for 

existing external or internal floating roof tanks as required in 

the Generic MACT for storage vessels (40 CFR part 63, subpart 

WW) in 40 CFR 63.1063; (2) option 1 plus revising the definition 

of Group 1 storage vessel to include smaller capacity storage 

vessels and/or storage vessels containing materials with lower 

vapor pressures and (3) option 2 plus requiring additional 

monitoring to prevent roof landings, liquid level overfills and 

to identify leaking vents and fittings from tanks. We identified 

options 1 and 2 as developments in practices, processes and 

control technologies because these options are required for 

similar tanks in some chemical manufacturing MACT standards and 
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we believe they are technologically feasible for storage vessels 

at refineries (e.g., Generic MACT, the HON). Option 3 is also an 

improvement in practices because these monitoring methods have 

been required for refineries by other regulatory agencies. 

Under option 1, we considered the impacts of requiring 

improved deck fittings and controls for guidepoles as is 

required for other chemical manufacturing sources in the Generic 

MACT. Specifically, we considered these controls for storage 

vessels with existing internal or external floating roof tanks. 

This option also includes the inspection, recordkeeping, and 

reporting requirements set forth in the Generic MACT to account 

for the additional requirements for fitting controls. We are 

aware of recent waiver requests to EPA to allow in-service, topside inspections instead of the out-of-service inspections 

required on a 10-year basis for internal floating roof tanks for 

facilities that are currently subject to 40 CFR part 60, subpart 

Kb and Refinery MACT 1. The requirements of Generic MACT allow 

for this option if there is visual access to all the deck 

components. Under option 1, we considered the Generic MACT 

provisions for in-service, top-side inspection. We are 

requesting comment on whether or not these in-service 

inspections are adequate for identifying conditions that are 

indicative of deck, fitting, and rim seal failures; we are also 
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requesting comment on methods to effectively accomplish top-side 

inspections. 

For option 2, we evaluated revising the definition of Group 

1 storage vessels to include smaller capacity storage vessels 

and/or storage vessels with lower vapor pressure, such that 

these additional storage vessels would be subject to the Group 1 

control requirements. For storage vessels at existing sources, 

Refinery MACT 1 currently defines Group 1 storage vessels to be 

those with a capacity of 177 cubic meters (46,760 gallons) or 

greater, and a true vapor pressure of 10.4 kilopascals (1.5 

pounds per square inch absolute (psia)) or greater. Under 

option 2, we evaluated the impacts of changing the definition of 

Group 1 storage vessels to include storage vessels with a 

capacity of 151 cubic meters (40,000 gallons) or greater and a 

true vapor pressure of 5.2 kilopascals (0.75 psia) or greater, 

and also evaluated including storage vessels with a capacity of 

76 cubic meters (20,000 gallons) or greater (but less than 151 

cubic meters), provided the true vapor pressure of the stored 

liquid is 13.1 kilopascals (1.9 psia) or greater. These 

thresholds are consistent with storage vessel standards already 

required for the chemical industry (e.g., the HON). We believe 

the predominant effect of changing these thresholds will be 

fixed roof tanks at existing petroleum refineries shifting from 

Group 2 storage vessels to Group 1 storage vessels. These fixed 
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roof tanks would thus need to be retrofitted with floating roofs 

or vented to an APCD in order to comply with the provisions for 

Group 1 storage vessels. We estimated the impacts of option 2 by 

assuming all uncontrolled fixed roof storage vessels that meet 

or exceed the proposed new applicability requirements for Group 

1 storage vessels (based on the information collected in the 

Refinery ICR) would install an internal floating roof with a 

single rim seal and deck fittings to the existing fixed roof 

tank. The costs of these fixed roof retrofits were added to the 

costs determined for option 1 to determine the cost of option 2. 

Under option 3, we considered the impacts of including 

additional monitoring requirements for Group 1 storage vessels 

(in addition to fitting controls and fixed roof retrofits 

considered under options 1 and 2). The monitoring requirements 

evaluated include monitoring of internal or external floating 

roof tanks with EPA Method 21 (of 40 CFR part 60, Appendix A-7) 

or optical gas imaging for fittings, and requiring the use of 

liquid level overfill warning monitors and roof landing warning 

monitors. These costs were estimated based on the total number 

of Group 1 storage vessels considering the change in the 

applicability thresholds included in option 2. For further 

details on the assumptions and methodologies used in this 

analysis, see the technical memorandum titled Impacts for 
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Control Options for Storage Vessels at Petroleum Refineries, 

June 27, 2012, in Docket ID Number EPA-HQ-OAR-2010-0682. 

Table 5 of this preamble presents the impacts for the three 

options considered. Although the options were considered 

cumulatively, the calculation of the incremental cost 

effectiveness allows us to assess the impacts of the incremental 

change between the options. As seen by the incremental cost 

effectiveness column in Table 5, both options 1 and 2 result in 

a net cost savings considering the VOC recovery credit for 

product not lost to the atmosphere from the storage vessel.28 We 

seek comment on the appropriateness of the VOC recovery credit 

we used. The incremental cost effectiveness for option 3 exceeds 

$60,000 per ton of HAP removed. We consider option 3 not to be 

cost effective and are not proposing to require this additional 

monitoring. 

Based on this analysis, we consider option 2 to be cost 

effective. We are, therefore, proposing to revise Refinery MACT 

1 to cross-reference the corresponding storage vessel 

requirements in the Generic MACT (including requirements for 

guidepole controls and other fittings as well as inspection 

 

28 The VOC recovery credit is $560 per ton, based on $1.75/gal price for 

generic refinery product (gasoline/diesel fuel). (See the technical 

memorandum titled Impacts for Control Options for Storage Vessels at 

Petroleum Refineries, in Docket ID Number EPA-HQ-OAR-2010-0682 for more 

details). 
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requirements), and to revise the definition of Group 1 storage 

vessels to include storage vessels with capacities greater than 

or equal to 20,000 gallons but less than 40,000 gallons if the 

maximum true vapor pressure is 1.9 psia or greater and to 

include storage tanks greater than 40,000 gallons if the maximum 

true vapor pressure is 0.75 psia or greater. 

Table 5. Nationwide Emissions Reduction and Cost Impacts of 

Control Options for Storage Vessels at Petroleum Refineries 

Control 

Option 

Capital 

Cost 

(million 

$) 

Annualized 

Costs 

Without 

Recovery 

Credits 

(million 

$/yr) 

Emissions 

Reduction, 

VOC 

(tpy) 

Emissions 

Reduction, 

HAP 

(tpy) 

Cost 

Effectiveness 

($/ton 

HAP) 

Total 

Annualized 

Costs 

with VOC 

Recovery 

Credit 

(million 

$/yr) 

Overall 

Cost 

Effectiveness 

with VOC 

Recovery 

Credit 

($/ton 

HAP) 

Incremental 

Cost 

Effectiveness 

with VOC 

Recovery 

Credit 

($/ton 

HAP) 

1 11.9 1.8 11,800 720 2,470 (4.8) (6,6900) (6,690)--

2 18.5 3.1 14,600 910 3,430 (5.0) (5,530) (1,140) 

3 36.4 9.6 16,000 1,000 9,580 0.56 560 61,500 

c. Equipment Leaks 

Equipment leaks are releases of process fluid or vapor from 

processing equipment, including pump and compressor seals, 

process valves, relief devices, open-ended valves and lines, 

flanges and other connectors, agitators and instrumentation 

systems. These releases occur primarily at the interface between 

connected components of equipment or in sealing mechanisms. 

Refinery MACT 1 requires the owner or operator of an 

existing source to comply with the equipment leak provisions in 
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40 CFR part 60, subpart VV (Standards of Performance for 

Equipment Leaks of VOC in the Synthetic Organic Chemicals 

Manufacturing Industry) for all equipment in organic HAP 

service. The term “in organic HAP service” means that a piece of 

equipment either contains or contacts a fluid (liquid or gas) 

that is at least 5 percent by weight of total organic HAP. 

Refinery MACT 1 specifies that the owner or operator of a new 

source must comply with the HON, as modified by Refinery MACT 1. 

The provisions for both new and existing sources require 

inspection (either through instrument monitoring using EPA 

Method 21 of 40 CFR part 60, Appendix A-7, or other method such 

as visible inspection) and repair of leaking equipment. For 

existing sources, the leak definition under 40 CFR part 60, 

subpart VV triggers repair at an instrument reading of 10,000 

parts per million (ppm) for all equipment monitored using EPA 

Method 21 of 40 CFR part 60, Appendix A-7 (i.e., pumps and 

valves; instrument monitoring of equipment in heavy liquid 

service and connectors is optional). For new sources, the 

Refinery MACT 1-modified version of the HON triggers repair of 

leaks for pumps at 2,000 ppm and for valves at 1,000 ppm. 

Refinery MACT 1 requires new and existing sources to install a 

cap, plug or blind flange, as appropriate, on open-ended valves 

or lines. Refinery MACT 1 does not require instrument monitoring 

of connectors for either new or existing sources. 
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We conducted a general analysis to identify the latest 

developments in practices, processes and control technologies 

applicable to equipment leaks at chemical manufacturing 

facilities and petroleum refineries, and we estimated the 

impacts of applying the identified practices, processes and 

technologies to several model plants. (See Analysis of Emissions 

Reduction Techniques for Equipment Leaks, December 21, 2011, in 

Docket IDItem Number EPA-HQ-OAR-2010-0869-0029.) We used this 

general analysis as a starting point for conducting the 

technology review for equipment leaks at refineries, but did not 

identify any developments beyond those in the general analysis. 

We estimated the impacts of applying the practices, processes 

and technologies identified in the general analysis to equipment 

leaks in petroleum refinery processes using the information we 

collected through the 2011 Refinery ICR. In general, leak 

detection and repair (LDAR) programs have been used by many 

industries for years to control emissions from equipment leaks. 

Over the years, repair methods have improved and owners and 

operators have become more proficient at implementing these 

programs. The specific developments identified include: (1) 

requiring repair of leaks at a concentration of 500 ppm for 

valves and 2,000 ppm for pumps for new and existing sources 

(rather than 10,000 ppm for valves and pumps at existing sources 

and 1,000 for valves at new sources); (2) requiring monitoring 
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of connectors using EPA Method 21 (of 40 CFR part 60, Appendix 

A-7) and repair of leaks for valves and pumps at a concentration 

of 500 ppm; and (3) allowing the use of optical gas imaging 

devices as an alternative method of monitoring. 

The first option we evaluated was to require repair based 

on a leak definition of 500 ppm for valves and a leak definition 

of 2,000 ppm for pumps at both new and existing sources. The 

nationwide costs and emission reduction impacts of applying 

those lower leak definitions to equipment leaks at petroleum 

refineries are shown in Table 6 of this preamble. For further 

details on the assumptions and methodologies used in this 

analysis, see the technical memorandum titled Impacts for 

Equipment Leaks at Petroleum Refineries, in Docket ID Number 

EPA-HQ-OAR-2010-0682. The emissions reduction results in product 

not being lost by a leak; this additional product can be sold to 

generate revenue, referred to as a VOC recovery credit. Table 6 

shows costs and cost effectiveness both with and without the VOC 

recovery credit. Based on the estimated organic HAP emission 

reductions of 24 tpy and the cost effectiveness of $14,100 per 

ton of organic HAP (including VOC recovery credit), we consider 

lowering the leak definition not to be a cost-effective option 

for reducing HAP emissions. We are, therefore, proposing that it 

is not necessary to revise Refinery MACT 1 pursuant to CAA 

Ssection 112(d)(6) to require repair of leaking valves at 500 
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ppm or greater and repair of leaking pumps at 2,000 ppm or 

greater. 

Table 6. Nationwide Emissions Reduction and Cost Impacts of 

Monitoring and Repair Requirements at Lower Leak Definitions 

(500 ppm for Valves; 2,000 ppm for Pumps) 

Capital 

Cost 

(million 

$) 

Annualized 

Costs 

Without 

Recovery 

Credits 

(million 

$/yr) 

Emissions 

Reduction, 

VOC 

(tpy) 

Emissions 

Reduction, 

HAP 

(tpy) 

Cost 

Effectiveness 

($/ton 

VOC) 

Cost 

Effectiveness 

($/ton 

HAP) 

Total 

Annualized 

Costs 

with VOC 

Recovery 

Credit 

(million 

$/yr) 

Overall 

Cost 

Effectiveness with 

VOC 

Recovery 

Credit 

($/ton 

VOC) 

Overall 

Cost 

Effectiveness 

with VOC 

Recovery 

Credit 

($/ton 

HAP) 

1.22 0.53 342 24 1,550 22,100 0.34 987 14,100 

We note that we are aware that some owners and operators 

are required to repair leaking valves as low as 100 ppm and 

pumps as low as 500 ppm. However, given that we consider 

requiring repair of leaking valves at 500 ppm or greater and 

repair of leaking pumps at 2,000 ppm or greater not to be cost 

effective. As documented in Analysis of Emissions Reduction 

Techniques for Equipment Leaks (December 21, 2011, in Docket ID 

Number EPA-HQ-OAR-2010-0869), the cost effectiveness for this 

option would be even higher than the values shown in Table 6 of 

this preamble. 

The second option we considered was connector monitoring 

and repair. Several standards applying to chemical manufacturing 

facilities, including the HON, include requirements for 
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connector monitoring using EPA Method 21 (of 40 CFR part 60, 

Appendix A-7) and requirements for repair of any connector leaks 

above 500 ppm VOC. Neither the Refinery MACT 1 nor the NSPS for 

equipment leaks from refineries (40 CFR part 60, subpart GGG and 

40 CFR part 60, subpart GGGa) currently require connector 

monitoring and repair (provisions are provided for connector 

monitoring in Refinery MACT 1, but they are optional). We 

evaluated the costs and emissions reduction of requiring 

connector monitoring and repair requirements for equipment leaks 

at refineries. The nationwide costs and emission reduction 

impacts, both with and without VOC recovery credit, are shown in 

Table 7 of this preamble. For further details on the assumptions 

and methodologies used in this analysis, see the technical 

memorandum titled Impacts for Equipment Leaks at Petroleum 

Refineries, in Docket ID Number EPA-HQ-OAR-2010-0682. Based on 

the high annualized cost ($13.9 million per year) and high cost 

effectiveness ($153,000 per ton of HAP) of connector monitoring 

and repair for equipment leaks at refineries, we are proposing 

that it is not necessary to revise Refinery MACT 1 pursuant to 

CAA Ssection 112(d)(6) to require connector monitoring using EPA 

Method 21 (of 40 CFR part 60, Appendix A-7) and repair. 
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Table 7. Nationwide Emissions Reduction and Cost Impacts of 

Applying Monitoring and Repair Requirements to Connectors at 

Petroleum Refineries (500 ppm) 

Capital 

Cost 

(million 

$) 

Annualized 

Costs 

Without 

Recovery 

Credits 

(million 

$/yr) 

Emissions 

Reduction, 

VOC 

(tpy) 

Emissions 

Reduction, 

HAP 

(tpy) 

Cost 

Effectiveness 

($/ton 

VOC) 

 Cost 

Effectiveness 

($/ton 

HAP) 

Total 

Annualized 

Costs 

with VOC 

Recovery 

Credit 

(million 

$/yr) 

Overall 

Cost 

Effectiveness

with VOC 

Recovery 

Credit 

($/ton 

VOC) 

Overall 

Cost 

Effectiveness 

with VOC 

Recovery 

Credit 

($/ton 

HAP) 

52.1 13.9 1,230 86 11,300 161,000 13.2 10,700 153,000 

Another development identified was to provide optical gas 

imaging provisions (including the required instrument 

specifications, monitoring frequency, and repair threshold) as 

an alternative monitoring option where instrument monitoring 

using EPA Method 21 of 40 CFR part 60, Appendix A-7, is required 

in Refinery MACT 1. Since Refinery MACT 1 was issued, there have 

been developments in LDAR work practices using remote sensing 

technology for detecting leaking equipment. In this method of 

detecting leaks, an operator scans equipment using a device or 

system specially designed to use one of several types of remote 

sensing techniques, including optical gas imaging of infrared 

wavelengths, differential absorption light detection and ranging 

(DIAL), and solar occultation flux. 

The most common remote sensing instrument is a passive 

system that creates an image based on the absorption of infrared 

wavelengths (also referred to as a “camera”). A gas cloud 

containing certain hydrocarbons (i.e., leaks) will show up as 
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black or white plumes (depending on the instrument settings and 

characteristics of the leak) on the optical gas imaging 

instrument screen. This type of instrument is the device on 

which our evaluation of optical gas imaging instruments is 

based, and the instrument to which we are referring when we use 

the term “optical gas imaging instrument.” These optical gas 

imaging instruments can be used to identify specific pieces of 

equipment that are leaking. Other optical methods, such as DIAL 

and solar occultation flux, are used primarily to assess 

emissions downwind of a source. These methods cannot be used to 

identify specific leaking equipment; they would only measure the 

aggregate emissions from all equipment and any other source upwind of the measurement location. While we did review these 

technologies as discussed further (see the discussion under 

fenceline monitoring, Ssection IV.B.1.h of this preamble), we do 

not consider DIAL and solar occultation flux methods to be 

suitable alternatives to EPA Method 21 for monitoring equipment 

leaks and are not considering them further in our technology 

review for equipment leaks. 

We expect that all refinery streams “in organic HAP 

service” will include at least one of the compounds visible with 

an optical gas imaging instrument, such as benzene, methane, 

propane or butane. Therefore, it is technically feasible to use 

an optical gas imaging instrument to detect leaks at petroleum 
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refineries. The optical gas imaging device can monitor many more 

pieces of equipment than can be monitored using instrument 

monitoring over the same period of time, and we expect that 

specific requirements for using an optical gas imaging device to 

detect leaks without accompanying instrument monitoring could be 

an appropriate alternative to traditional leak detection methods 

(EPA Method 21, as specified in 40 CFR part 60, Appendix A-7). 

Owners and operators currently have the option to use the 

Alternative Work Practice To Detect Leaks From Equipment (AWP) 

at 40 CFR 63.11(c), (d) and (e). This AWP includes provisions 

for using optical gas imaging in combination with annual 

monitoring using EPA Method 21 of 40 CFR part 60, Appendix A-7. 

In this proposal, we are considering the use of optical gas 

imaging without an accompanying requirement to conduct annual 

monitoring using EPA Method 21, and developing a protocol for 

using optical gas imaging techniques. We anticipate proposing 

the protocol as Appendix K to 40 CFR part 60. Rather than 

specifying the exact instrument that must be used, this protocol 

would outline equipment specifications, calibration techniques, 

required performance criteria, procedures for conducting surveys 

and training requirements for optical gas imaging instrument 

operators. This protocol would also contain techniques to verify 

that the instrument selected can image the most prevalent 

chemical in the monitored process unit. Because field conditions 
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greatly impact detection of the regulated material using optical 

gas imaging, the protocol would describe the impact these field 

conditions may have on readings, how to address them and 

instances when monitoring with this technique is inappropriate. 

Finally, the protocol would also address difficulties with 

identifying equipment and leaks in dense industrial areas. 

Pursuant to CAA Ssection 112(d)(6), we are proposing to 

allow refineries to meet the LDAR requirements in Refinery MACT 

1 by monitoring for leaks via optical gas imaging in place of 

EPA Method 21 (of 40 CFR part 60, Appendix A-7), using the 

monitoring requirements to be specified in Appendix K to 40 CFR 

part 60. When Appendix K is proposed, we will request comments 

on that appendix and how those requirements would apply for 

purposes of this proposed action. We will not take final action 

adopting use of Appendix K to 40 CFR part 60 for optical gas 

imaging for refineries subject to Refinery MACT 1 until such 

time as we have considered any comments on that protocol as it 

would apply to refineries. We do not yet know the exact 

requirements of Appendix K to 40 CFR part 60, and this cannot 

provide a reliable estimate of potential costs at this time. 

However, we have calculated an initial estimate of the potential 

costs and emission reduction impacts, assuming that Appendix K 

to 40 CFR part 60 is similar to the AWP without the annual 

monitoring using EPA Method 21 of 40 CFR part 60, Appendix A-7. 
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For more information on these potential impacts, see the 

technical memorandum titled Impacts for Equipment Leaks at 

Petroleum Refineries, in Docket ID Number EPA-HQ-OAR-2010-0682. 

d. Gasoline Loading Racks 

Loading racks are the equipment used to fill gasoline cargo 

tanks, including loading arms, pumps, meters, shutoff valves, 

relief valves and other piping and valves. Emissions from 

loading racks may be released when gasoline loaded into cargo 

tanks displaces vapors inside these containers. Refinery MACT 1 

specifies that Group 1 gasoline loading racks at refineries must 

comply with the requirements of the National Emission Standards 

for Gasoline Distribution Facilities (Bulk Gasoline Terminals 

and Pipeline Breakout Stations) in 40 CFR part 63, subpart R. 

The standard specified in 40 CFR part 63, subpart R is an 

emission limit of 10 milligrams of total organic compounds per 

liter of gasoline loaded (mg/L). Additionally, 40 CFR part 63, 

subpart R requires all tank trucks and railcars that are loaded 

with gasoline to undergo annual vapor tightness testing in 

accordance with EPA Method 27 of 40 CFR part 60, Appendix A-8. 

For our technology review of Group 1 gasoline loading racks 

subject to Refinery MACT 1, we relied on two separate analyses. 

First, we previously conducted a technology review for gasoline 

distribution facilities (71 FR 17353, April 6, 2006), in which 

no new control systems were identified. Second, more recently, 
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we conducted a general analysis to identify any developments in 

practices, processes and control technologies for transfer 

operations at chemical manufacturing facilities and petroleum 

refineries. (See Survey of Control Technology for Transfer 

Operations and Analysis of Impacts for Transfer Operation 

Control Options, January 20, 2012, in Docket IDItem Number EPAHQ-OAR-2010-0871-0021.) We identified several developments as 

part of this analysis and evaluated the impacts of applying the 

developments to gasoline loading racks subject to Refinery MACT 

1. We have not identified any developments beyond those in the 

second analysis. The identified developments include controlling 

loading racks above specific throughput thresholds by submerged 

loading and by venting displaced emissions from the transport 

vehicles through a closed vent system to an APCD that reduces 

organic regulated material emissions by at least 95 percent. 

We evaluated the emissions projected using this control 

technique for a range of different gasoline vapor pressures (to 

consider the different seasonal formulations of gasoline). We 

determined that submerged loading in combination with 95-percent 

control of displaced vapors would allow emissions of 12 to 42 

mg/L of gasoline loaded, depending on the vapor pressure of the 

gasoline (see Evaluation of the Stringency of Potential 

Standards for Gasoline Loading Racks at Petroleum Refineries in 

Docket ID Number EPA-HQ-OAR-2010-068712.) The current Refinery 
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MACT 1 emission limit for gasoline loading is 10 mg/L of 

gasoline loaded. We did not identify any developments in 

practices, process and control technologies for gasoline loading 

racks that would reduce emissions beyond the levels already in 

Refinery MACT 1. Therefore, we are proposing that it is not 

necessary to revise Refinery MACT 1 requirements for gasoline 

loading racks pursuant to CAA Ssection 112(d)(6). 

e. Marine Vessel Loading Operations 

Marine vessel loading operations load and unload liquid 

commodities in bulk, such as crude oil, gasoline and other 

fuels, and naphtha. The cargo is pumped from the terminal’s 

large, above-ground storage tanks through a network of pipes and 

into a storage compartment (tank) on the vessel. The HAP 

emissions are the vapors that are displaced during the filling 

operation. Refinery MACT 1 specifies that marine tank vessel 

loading operations at refineries must comply with the 

requirements in 40 CFR part 63, subpart Y (National Emission 

Standards for Marine Tank Vessel Loading Operations, “Marine 

Vessel MACT”). 

We previously completed a technology review of the Marine 

Vessel MACT (40 CFR part 63, subpart Y) and issued amendments to 

subpart Y in 2011 (76 FR 22595, Apr. 21, 2011). The analysis 

conducted for the marine vessel loading source category 

specifically considered loading of petroleum products such as 
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conventional and reformulated gasoline. As such, the conclusions 

drawn from this analysis are directly applicable to marine 

vessel loading operations at petroleum refineries. We have not 

identified any developments beyond those addressed in that 

analysis. 

The Marine Vessel MACT required add-on APCD for loading 

operations with HAP emissions equal to or greater than 10 tpy of 

a single pollutant or 25 tpy of cumulative pollutants (referred 

to as “10/25 tpy”). In our technology review of the Marine 

Vessel MACT standards, we considered the use of add-on APCD for 

marine vessel loading operations with HAP emissions less than 

10/25 tpy. We also evaluated the costs for lean oil absorption 

systems as add-on APCD under the Marine Vessel MACT technology 

review. Depending on the throughput of the vessel, costs ranged 

from $77,000 per ton HAP removed for barges to $510,000 per ton 

HAP removed for ships ($3,900 per ton VOC removed to $25,000 per 

ton VOC removed) (see Cost Effectiveness and Impacts of Lean Oil 

Absorption for Control of Hazardous Air Pollutants from Gasoline 

Loading - Promulgation in Docket Item Number EPA-HQ-OAR-2010-

0600-0401). We consider requiring add-on APCD for these smaller 

marine vessel loading operations not to be cost effective. 

As part of the technology review of 40 CFR part 63, subpart 

Y, we also considered requiring marine vessel loading operations 

with emissions less than 10/25 tpy and offshore operations to 
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use submerged loading (also referred to as submerged filling). 

We did include this requirement in the Marine Vessel MACT. 

However, when we amended the Marine Vessel MACT, we specifically 

excluded marine vessel loading operations at petroleum 

refineries from these provisions, deferring the decisions to 

include this requirement until we performed the technology 

review for Refinery MACT 1. The submerged filling requirement in 

40 CFR part 63, subpart Y cites the cargo filling line 

requirements developed by the Coast Guard in 46 CFR 153.282. We 

project that applying the submerged filling requirements to 

marine vessel loading operations at petroleum refineries will 

have no costs or actual emission reductions because marine 

vessels carrying bulk liquids, liquefied gases or compressed gas 

hazardous materials are already required by 46 CFR 153.282 to 

have compliant “submerged fill” cargo lines that also meet the 

requirements of the Marine Vessel MACT. While we do not 

anticipate that this requirement will affect actual emissions, 

it will lower the allowable emissions for these sources under 

Refinery MACT 1. Therefore, we are proposing, pursuant to CAA 

Ssection 112(d)(6), to amend 40 CFR part 63, subpart Y to delete 

the exclusion for marine vessel loading operations at petroleum 

refineries, which would require small marine vessel loading 

operations (i.e., operations with HAP emissions less than 10/25 

tpy) and offshore marine vessel loading operations to use 
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submerged filling based on the cargo filling line requirements 

in 46 CFR 153.282. 

f. Cooling Towers/Heat Exchange Systems 

Heat exchange systems include equipment necessary to cool 

heated non-contact cooling water prior to returning the cooling 

water to a heat exchanger or discharging the water to another 

process unit, waste management unit or to a receiving water 

body. Heat exchange systems are designed as closed-loop 

recirculation systems with cooling towers or once-through 

systems that do not recirculate the cooling water through a 

cooling tower. Heat exchangers in heat exchange systems are 

constructed with tubes designed to prevent contact between hot 

process fluids and cooling water. Heat exchangers occasionally 

develop leaks that allow process fluids to enter the cooling 

water. The volatile HAP and other volatile compounds in these 

process fluids are then emitted to the atmosphere due to 

stripping in a cooling tower or volatilization from a cooling 

water pond or receiving water body. 

We established MACT standards for heat exchange systems at 

refineries in 2009 (see 74 FR 55686, October 28, 2009, as 

amended at 75 FR 37731, June 30, 2010). The EPA received a 

petition for reconsideration from the American Petroleum 

Institute (API) and granted reconsideration on certain issues. 

On June 20, 2013, we issued a final rule addressing the 
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petition, clarifying rule provisions, and revising the 

monitoring provisions to provide additional flexibility (78 FR 

37133). We are not aware of any developments in processes, 

practices or control technologies beyond those we recently 

considered in our analysis of emission reduction techniques for 

heat exchange systems, which can be found in the docket (Docket 

Item Number EPA-HQ-OAR-2003-0146-0229). Therefore, we are 

proposing that it is not necessary to revise Refinery MACT 1 

requirements for heat exchange systems pursuant to CAA Ssection 

112(d)(6). 

g. Wastewater Treatment 

Wastewater collection includes components such as drains, 

manholes, trenches, junction boxes, sumps, lift stations and 

sewer lines. Wastewater treatment systems are divided into three 

categories: primary treatment operations, which include oilwater separators and equalization basins; secondary treatment 

systems, such as biological treatment units or steam strippers; 

and tertiary treatment systems, which further treat or filter 

wastewater prior to discharge to a receiving body of water or 

reuse in a process. 

Refinery MACT 1 requires wastewater streams at a new or 

existing refinery to comply with 40 CFR 61.340 through 61.355 of 

the NESHAP for Benzene Waste Operations (BWON) in 40 CFR part 

61, subpart FF. The BWON requires control of wastewater 
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collection and treatment units for facilities with a total 

annual benzene quantity of greater than or equal to 10 megagrams 

per year (Mg/yr). Individual waste streams at refineries with a 

total annual benzene quantity greater than or equal to 10 Mg/yr 

are not required to adopt controls if the flow-weighted annual 

average benzene concentration is less than 10 parts per million 

by weight (ppmw) or the flow rate is less than 0.02 liters per 

minute at the point of generation. The BWON requires affected 

waste streams to comply with one of several options for 

controlling benzene emissions from waste management units and 

for treating the wastes containing benzene (55 FR 8346, March 7, 

1990; 58 FR 3095, January 7, 1993). 

Although the BWON specifically regulates benzene only, 

benzene is considered a surrogate for organic HAP from 

wastewater treatment systems at petroleum refineries. Benzene is 

present in nearly all refinery process streams. It is an 

excellent surrogate for wastewater pollutants because its unique 

chemical properties cause it to partition into the wastewater 

more readily than most other organic chemicals present at 

petroleum refineries. We stated our rationale regarding the use 

of benzene as a surrogate for refinery HAP emissions from 

wastewater in the original preamble to Refinery MACT 1 (59 FR 

36133, July 15, 1994). 
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We performed a technology review for wastewater treatment 

systems to identify different control technologies for reducing 

emissions from wastewater treatment systems. We also reviewed 

the current standards for wastewater treatment systems in 

different rules including the HON, the proposed NSPS for 

wastewater systems at petroleum refineries, and the BWON (See 

Technology Review for Industrial Wastewater Collection and 

Treatment Operations at Petroleum Refineries, in Docket ID 

Number EPA-HQ-OAR-2010-0682.) We identified several developments 

in processes, practices and control technologies for wastewater 

treatment, and evaluated the cost and cost effectiveness of each 

of those developments: (1) requiring wastewater drain and tank 

controls at refineries with a total annualized benzene (TAB)

quantity of less than 10 Mg/yr; (2) requiring specific 

performance parameters for an enhanced biological unit (EBU) 

beyond those required in the BWON; and (3) requiring wastewater 

streams with a VOC content of 750 ppmv or higher to be treated 

by steam-stripping prior to any other treatment process for 

facilities with high organic loading rates (i.e., facilities 

with total annualized benzene quantity of 10 Mg/yr or more). 

These options are, for the most part, independent of each other, 

so the costs and cost effectiveness of each option are 

considered separately. 
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Option 1 was evaluated because refineries with a total 

annual benzene quantity of less than 10 Mg/yr are not required 

to install additional controls on their wastewater treatment 

system. Thus, these refineries are limiting the amount of 

benzene produced in wastewater streams to less than 10 Mg/yr, 

which effectively limits their benzene emissions from wastewater 

to less than 10 Mg/yr. 

Option 2 is intended to improve the performance of 

wastewater treatment systems that use an EBU, and thereby 

achieve additional emission reductions. The BWON, as it applies 

under Refinery MACT 1, has limited operational requirements for 

an EBU. Available data suggest that these systems are generally 

effective for degrading benzene and other organic HAP; however, 

without specific performance or operational requirements, the 

effectiveness of the EBU to reduce emissions can be highly 

variable. Under option 2, more stringent operating requirements 

are considered for the EBU at refineries. 

Option 3 considers segregated treatment of wastewater 

streams with a volatile organic content of greater than 750 

ppmw, or high-strength wastewater streams, directly in a steam 

stripper (i.e., not allowing these streams to be mixed and 

treated in the EBU). Preliminary investigations revealed direct 

treatment of wastewater by steam-stripping is only cost 

effective for high-strength wastewater streams of sufficient 
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quantities. For more detail regarding the impact analysis for 

these control options, see Technology Review for Industrial 

Wastewater Collection and Treatment Operations at Petroleum 

Refineries, in Docket ID Number EPA-HQ-OAR-2010-0682. 

Table 8 provides the nationwide impacts for the control 

options. Based on the costs and emission reductions for each of 

the options, we consider none of the options identified to be 

cost effective for reducing emissions from petroleum refinery 

wastewater treatment systems. We are proposing that it is not 

necessary to revise Refinery MACT 1 to require additional 

controls for wastewater treatment systems pursuant to CAA 

Ssection 112(d)(6). 

Table 8. Nationwide Emissions Reduction and Cost Impacts of 

Control Options Considered for Wastewater Treatment Systems at 

Petroleum Refineries 

Control 

Option 

Capital 

Cost 

(million $) 

Annualized 

Costs 

(million 

$/yr) 

Emissions 

Reduction, 

VOC (tpy) 

Emissions 

Reduction, 

HAP (tpy) 

Cost 

Effectiveness 

($/ton 

VOC) 

Cost 

Effectiveness 

($/ton 

HAP) 

1 19.7 4.2 592 158 7,100 26,600 

2 223 28.6 2,060 549 13,900 52,100 

3 142 50.7 3,480 929 14,500 54,500 

h. Fugitive Emissions 

The EPA recognizes that, in many cases, it is impractical 

to directly measure emissions from fugitive emission sources at 

refineries. Direct measurement of fugitive emissions from 

sources such as wastewater collection and treatment operations, 
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equipment leaks and storage vessels can be costly and difficult, 

especially if required to be deployed on all sources of 

fugitives within a refinery and certainly on a national scale. 

This is a major reason why fugitive emissions associated with 

refinery processes are generally estimated using factors and 

correlations rather than by direct measurement. For example, 

equipment leak emissions are estimated using factors and 

correlations between leak rates and concentrations from EPA 

Method 21 instrument monitoring. Fugitive emissions from 

wastewater collection and treatment are estimated based on 

process data, material balances and empirical correlations. 

Relying on these kinds of approaches introduces uncertainty into 

the emissions inventory for fugitive emission sources. 

For each of the individual fugitive emission points, we 

evaluated developments in processes, practices and control 

technologies for measuring and controlling fugitive emissions 

from these sources. For storage vessels, as discussed in section 

IV.B.1.b of this preamble, we are proposing to lower the size 

and vapor pressure threshold and to require additional fittings 

on tanks, similar to requirements for tanks in the chemical 

industry because we project a cost savings due to recovered 

product. However, we considered but are not proposing to require 

EPA Method 21 of 40 CFR part 60, Appendix A-7 or optical gas 

imaging monitoring to identify fugitive emissions from each 
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individual storage vessel. For equipment leaks, as discussed in 

section IV.B.1.c of this preamble, we considered and arelowering 

the leak definition for equipment at petroleum refineries from 

the current Refinery MACT 1 level of 10,000 ppm for pumps and 

valves down to the 500 ppm definition that is used in all the 

other MACT standards applying to the chemical industry, as well 

as adding a requirement for connectors to be included in the 

LDAR program because we consider these more stringent LDAR 

requirements to be technically feasible for the petroleum 

refining industry. Nevertheless, we rejected these options under 

the technology review as not being cost effective, based on 

costs projected by using the industry-reported emissions 

inventories. We are, however, proposing to adopt the use of 

optical gas imaging devices following 40 CFR part 60, Appendix K 

in lieu of as an alternative to using EPA Method 21, which will 

be an alternative available to petroleum refiners that could 

offer cost savings, once the monitoring protocol set forth in 

Appendix K is promulgated. For wastewater treatment systems, as 

discussed in section IV.B.1.g of this preamble, we considered 

but are not proposing to require both lowering the threshold for 

refinery wastewater streams requiring control, as well as 

requiring refineries to comply with enhanced monitoring and 

operating limits for the EBU, such as the requirements contained 

in most of the chemical sector MACT standards, because we 
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consider these requirements to be technically feasible for the 

refining industry. The monitoring techniques evaluated in the 

subsections above have been very specific to the emission points 

being evaluated andHowever, like equipment leaks, we are 

generally labor intensive. Given the number of potential 

fugitive emission points at refineries, coupled with the 

difficulty of accessing some release points because of safety 

concerns makes more frequent or additional direct or pointspecific monitoring beyond what is being proposed above 

impracticalrejecting further controls for wastewater because 

using the industry-reported emissions inventory, we determined 

that further wastewater requirements are not cost effective. 

Although we are not proposing to require several sourcespecific monitoring approaches thata number of additional 

control options for fugitive emission sources because we 

evaluateddetermined them not cost effective, we remain concerned 

regarding the potential for high emissions from these 

regulatedfugitive sources due to the difficulties in monitoring 

actual emission levels. For example, the regulations require 

infrequent monitoring of storage tank floating roof seals 

(visual inspections are required annually and direct inspections 

of primary seals are required only when the vessel is emptied 

and degassed, or no less frequently than once every 5 years for 

internal floating roofs or 10 years for external floating roofs 
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with secondary seals). Given these inspection frequencies, tears 

or failures in floating roof seals may exist for years prior to 

being noticed, resulting in much higher emissions than expected 

or estimated for these sources in the emissions inventory. 

Similarly, water seals, which are commonly used to control 

emissions from wastewater collection drain systems, may be 

difficult to monitor (e.g., some are underground so visible 

emissions tests cannot be performed) and are subject only to 

infrequent inspections. During hot, dry months, these water 

seals may dry out, leaving an open pathway of vapors to escape 

from the collection system to the atmosphere. Significant 

emission releases may occur from these “dry” drains, which could 

persist for long periods of time prior to the next required 

inspection. 

Because the requirements and decisions that we are 

proposing in this action are based upon the emissions inventory 

reported by facilities in response to the 2011 Refinery ICR, and 

considering the uncertainty with estimating emissions from 

fugitive emission sources, we believe that it is appropriate 

under CAA section 112(d)(6) to require refiners to monitor, and 

if necessary, take corrective action to minimize fugitive 

emissions, to ensure that facilities appropriately manage 

emissions of HAP from fugitive sources. In other words, in this 

action, we are proposing a HAP concentration to be monitored in 
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the ambient air around a refinery, that if exceeded, would 

trigger corrective action to minimize fugitive emissions. The 

fenceline concentration action level would be set at a level 

such that no facility in the category would need to undertake 

additional corrective measures if the facility’s estimate of 

emissions from fugitive emissions is consistent with the level 

of fugitive emissions actually emitted. On the other hand, if a 

facility’s estimate of fugitive HAP emissions was not accurate, 

the owner or operator may need to take some corrective action to 

minimize fugitive emissions. This approach would provide the 

owner or operator with the flexibility to determine how best to 

reduce HAP emissions to ensure levels remain below the fenceline 

concentration action level. The details of this proposed 

approach are set forth in more detail in the following 

discussions in this preamble section. 

In light of the impracticality of directly monitoring many 

of these fugitive emission sources on a regular basis, which 

would help ensure these fugitive sources are properly 

functioning to the extent practical, we evaluated a fenceline 

monitoring program under CAA Ssection 112(d)(6). In this 

section, we evaluate the developments in processes, practices 

and control technologies for measuring and controlling fugitive 

emissions from the petroleum refinery as a whole through 

fenceline monitoring techniques. Fenceline monitoring will 
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identify a significant increase in emissions in a timely manner 

(e.g., a large equipment leak or a significant tear in a storage 

vessel seal), which would allow corrective action measures to 

occur more rapidly than it would if a source relied solely on 

the traditional infrequent monitoring and inspection methods. 

Small increases in emissions are not likely to impact the 

fenceline concentration, so a fenceline monitoring approach will 

generally target larger emission sources that have the most 

impact on the ambient pollutant concentration near the refinery. 

Historically, improved information through measurement data 

has often led to emission reductions. However, without a 

specific emission limitation, there may be no incentive for 

owners or operators to act on the additional information. 

Therefore, as part of the fenceline monitoring approach, we seek 

to develop a not-to-be exceeded annual fenceline concentration, 

above which refinery owners or operators would be required to 

implement corrective action to reduce their fenceline 

concentration. We sought to develop a maximum fenceline 

concentration action level that is consistent with the emissions 

projected from fugitive sources compliant with the provisions of 

Refinery MACT 1the refinery MACT standards as modified by the 

additional controls proposed in this action (e.g., additional 

fittings on storage vessels). 
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Thus, thisThis section details our technology review to 

identify developments in processes, practices and technologies 

for measuring air toxics at the fenceline of a facility. Upon 

selection of a specific fenceline monitoring method, we provide 

our rationale for the specific details regarding the fenceline 

monitoring approach, including requirements for siting the 

monitors, procedures for adjusting for background interferences, 

selection of the fenceline action level, and requirements for 

corrective action. 

Developments in monitoring technology and practices. The 

EPA reviewed the available literature and identified several 

different methods for measuring fugitive emissions around a 

petroleum refinery. These methods include: (1) passive diffusive 

tube monitoring networks; (2) active monitoring station 

networks; (3) ultraviolet differential optical absorption 

spectroscopy (UV-DOAS) fenceline monitoring; (4) open-path 

Fourier transform infrared spectroscopy (FTIR); (5) DIAL 

monitoring; and (6) solar occultation flux monitoring. We 

considered these monitoring methods as developments in practices 

under CAA Ssection 112(d)(6) for purposes of all fugitive 

emission sources at petroleum refineries. Each of these methods 

has its own strengths and weaknesses, which are discussed in the 

following paragraphs. 
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Fenceline passive diffusive tube monitoring networks employ 

a series of diffusive tube samplers at set intervals along the 

fenceline to measure a time-integrated ambient air concentration 

at each sampling location. A diffusive tube sampler consists of 

a small tube filled with an adsorbent, selected based on the 

pollutant(s) of interest, and capped with a specially designed 

cover with small holes that allow ambient air to diffuse into 

the tube at a small, fixed rate. Diffusive tube samplers have 

been demonstrated to be a cost-effective, accurate technique for 

measuring ambient concentrations of pollutants resulting from 

fugitive emissions in a number of studies.29,30 In addition, 

diffusive samplers are used in the European Union to monitor and 

maintain air quality, as described in European Union directives 

2008/50/EC and Measurement Standard EN 14662-4:2005 for benzene. 

The International Organization for Standardization developed a 

standard method for diffusive sampling (ISO/FDIS 16017-2). 

In 2009, the EPA conducted a year-long fenceline monitoring 

pilot project at Flint Hills West Refinery in Corpus Christi, 

Texas, to evaluate the viability and performance of passive 

 

29 McKay, J., M. Molyneux, G. Pizzella, V. Radojcic. Environmental Levels of 

Benzene at the Boundaries of Three European Refineries, prepared by the 

CONCAWE Air Quality Management Group’s Special Task Force on Benzene 

Monitoring at Refinery Fenceline (AQ/STF-45), Brussels, June 1999. 

30 Thoma, E.D., M.C. Miller, K.C. Chung, N.L. Parsons, B.C. Shine. 2011. 

Facility Fenceline Monitoring using Passive Sampling, J. Air & Waste Manage 

Assoc. 61: 834-842. 
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diffusive sampling technology. Overall, we found the technology 

to be capable of providing cost effective, high spatial-density 

long-term monitoring. This approach was found to be relatively 

robust and implementable by modestly trained personnel and 

provided useful information on overall concentration levels and 

source identification using simple upwind and downwind 

comparisons.31 Combined with on-site meteorological measurements, 

2-week time-integrated passive monitoring has been shown to 

provide useful facility emission diagnostics. 

There are several drawbacks of time-integrated sampling, 

including the lack of immediate feedback on the acquired data 

and the loss of short-term temporal information. Additionally, 

time-integrated monitoring usually requires the collected sample 

to be transported to another location for analysis, leading to 

possible sample integrity problems (e.g., sample deterioration, 

loss of analytes, and contamination from the surrounding 

environment). However, time-integrated monitoring systems are 

generally lower-cost and require less labor than time-resolved 

monitoring systems. Furthermore, while passive diffusive tube 

monitoring employs time-integrated sampling, these timeintegrated samples still represent much shorter time intervals 

(2 weeks) than many of the current source-specific monitoring 

 

31 Thoma, et al, 2011. 
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and inspection requirements (annually or less frequently). 

Consequently, passive diffusive tube monitoring still allows 

earlier detection of significant fugitive emissions than 

conventional source-specific monitoring. 

Active monitoring station networks are similar to passive 

diffusive tube monitoring networks in that a series of discrete 

sampling sites are established; however, each sampling location 

uses a pump to actively draw ambient air at a known rate through 

an adsorption tube. Because of the higher sampling rate, 

adsorption tubes can be analyzed on a daily basis, providing 

additional time resolution compared to diffusive tube sampling 

systems. Alternatively, the active sampling system can directly 

feed an analyzer for even more time resolution. However, this 

direct analysis of ambient air generally has higher detection 

limits than when the organic vapors are collected and 

concentrated on an adsorption matrix prior to analysis. Active 

monitoring stations have been used for a variety of pollutants 

in a variety of settings and the methods are well-established. 

However, compared to the passive diffusive tube monitoring 

stations, the sampling system is more expensive, more laborintensive, and generally requires highly-trained staff to 

operate. 

UV-DOAS fenceline monitoring is an “open-path” technology. 

An electromagnetic energy source is used to emit a beam of 
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electromagnetic energy (ultraviolet radiation) into the air 

towards a detection system some distance from the energy source 

(typically 100 to 500 meters). The electromagnetic energy beam 

interacts with components in the air in the open path between 

the energy source and the detector. The detector measures the 

disruptions in the energy beam to determine an average pollutant 

concentration across the open path length. Because the UV-DOAS 

system can monitor integrated concentrations over a fairly long 

path-length, fewer monitoring “stations” (energy source/detector 

systems) would be needed to measure the ambient concentration 

around an entire refinery. However, each UV-DOAS monitoring 

system is more expensive than an active or passive monitoring 

station and generally requires significant instrumentation 

shelter to protect the energy source and analyzer when used for 

long-term (ongoing) measurements. Advantages of UV-DOAS systems 

include providing real-time measurement data with detection 

limits in the low parts per billion range for certain compounds. 

Fog or other visibility issues (e.g., dust storm, high pollen, 

wildfire smoke) will interfere with the measurements. UV-DOAS 

systems have been used for fenceline monitoring at several U.S. 

petroleum refineries and petrochemical plants. UV-DOAS 

monitoring systems are specifically included as one of the 
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measurement techniques suitable under EPA’s Other Test Method 10 

(OTM-10).32

Open-path FTIR is similar to UV-DOAS monitoring except that 

an infrared light source and detector system are used. Like the 

UV-DOAS monitoring approach, the open-path FTIR monitoring 

system will measure the average pollutant concentration across 

the open path length between the infrared source and detector. 

Path lengths and equipment costs for an open-path FTIR system 

are similar to those for a UV-DOAS system, and the open-path 

FTIR system provides real-time measurement data. The open-path 

FTIR system has spectral interferences with water vapor, CO and 

CO2, which can impact the lower detection limit for organic 

vapors. Open-path FTIR fenceline monitoring has also been used 

to measure ambient air concentrations around several petroleum 

refineries and petrochemical plants. Open-path FTIR is 

specifically included as a measurement technique in EPA’s OTM10. Although open-path FTIR can be used to measure a larger 

number of compounds than UV-DOAS, the detection limit of openpath FTIR for benzene is higher than for UV-DOAS, as noted in 

OTM-10. In other words, open-path FTIR is not as sensitive to 

benzene levels as is UV-DOAS. As benzene is an important 

 

32 “Optical Remote Sensing for Emission Characterization from Non-Point 

Sources.” Final ORS Protocol, June 14, 2006. Available at: 

http://www.epa.gov/ttn/emc/prelim/otm10.pdf. 
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pollutant from fugitive sources at petroleum refineries and can 

often be used as a surrogate for other organic HAP emissions, 

this high detection limit for benzene is a significant 

disadvantage. Thus, for the purposes of measuring organic HAP 

from fugitive sources at the fenceline of a petroleum refinery, 

a UV-DOAS monitoring system is expected to be more sensitive 

than an open-path FTIR system. As the cost and operation of 

open-path FTIR and UV-DOAS systems are very comparable, the 

benzene detection limit issue is a significant differentiator 

between these two methods when considering fenceline monitoring 

to measure fugitives around a petroleum refinery. 

DIAL monitoring systems employ a pulsed laser beam across 

the measurement path. Small portions of the light are 

backscattered due to particles and aerosols in the measurement 

path. This backscattered light is collected through a telescope 

system adjacent to the laser and measured via a sensitive light 

detector. The timing of the received light provides a measure of 

the distance of the emission plume. Two different wavelengths of 

light are pulsed in quick succession: one wavelength that is 

absorbed strongly by the pollutant of interest and one that is 

not absorbed. The difference in the returned signal strength 

between these two light pulses provides a measure of the 

concentration of the pollutant. Thus, a unique advantage of the 

DIAL monitoring system is that it can provide spatially resolved 
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pollutant concentrations in two dimensions. Measurements can be 

made in a relatively short period of time, so the method also 

provides good time resolution. 

The DIAL monitoring system has been used in a variety of 

studies to measure emissions from petroleum refinery and 

petrochemical sources. It is typically used for specific, 

shorter-term studies (one to several weeks in duration). The 

equipment is expensive, has limited availability in the U.S., 

and requires highly trained professionals to operate. Although 

DIAL monitoring is included as an appropriate method for EPA’s 

OTM-10, there are no known long-term applications of this 

technology for the purpose of fenceline monitoring. Given the 

limited availability of the equipment and qualified personnel to 

operate the equipment, we do not consider DIAL monitoring to be 

technically feasible for the purposes of ongoing, long-term 

fenceline monitoring. 

The last fenceline monitoring method evaluated was solar 

occultation flux. Solar occultation flux uses the sun as the 

light source and uses an FTIR or UV detector to measure the 

average pollutant concentration across the measurement path. In 

this case, the measurement path is vertical. In order to measure 

the concentrations around an industrial source, the measurement 

device is installed in a specially equipped van, which is slowly 

driven along the perimeter of the facility. Measurement signal 
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strength and a global positioning system (GPS) enables 

determination of pollutant concentrations along the perimeter of 

the site. This method provides more spatial resolution of the 

emissions than the UV-DOAS or open-path FTIR methods and is less 

expensive than a DIAL system. It has the advantage that only one 

monitoring system is needed per facility, assuming a mobile 

device is used. Disadvantages of this method include the need of 

full-time personnel to drive the equipment around the perimeter 

of the facility (or the need to buy a detector for each 

measurement location around the perimeter of the facility, if 

set locations are used), potential accessibility issues for some 

fenceline locations (e.g., no road near the fenceline), and the 

measurement method cannot be used at night or during cloudy 

periods. It would be possible to purchase numerous detection 

devices and establish fixed monitoring stations similar to the 

passive or active monitoring approaches described earlier, but 

this would be very expensive. Furthermore, any application of 

solar occultation flux is dependent on the sun, so this approach 

would mean significant periods each calendar day when the 

monitoring system would not be able to provide data. Based on 

our evaluation of this technology, we determined that this 

method is not a reasonable approach for monitoring fenceline 

concentrations of pollutants around a petroleum refinery on a 

long-term, ongoing basis. We are soliciting comment on the 
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application of alternative monitoring techniques previously 

discussed for purposes of fenceline monitoring at refineries. 

Costs associated with fenceline monitoring alternatives. 

Based on our review of available monitoring methods, we 

determined that the following monitoring methods were 

technically feasible and appropriate for monitoring organic HAP 

from fugitive emission sources at the fenceline of a petroleum 

refinery on a long-term basis: (1) passive diffusive tube 

monitoring networks; (2) active monitoring station networks; (3) 

UV-DOAS fenceline monitoring; and (4) open-path FTIR. While DIAL 

monitoring and solar occultation flux monitoring can be used for 

short-term studies, we determined that these methods were not 

appropriate for continuous monitoring at petroleum refineries. 

This section evaluates the costs of these technically feasible 

monitoring methods. As noted previously, the cost identified for 

the open-path monitoring methods (UV-DOAS and FTIR) are very 

similar. Therefore, we developed costs for only the UV-DOAS 

system because this method provides lower detection limits for 

pollutants of interest (specifically, benzene). 

Costs for the fenceline monitoring methods are dependent on 

the sampling frequency (for passive and active monitoring 

locations) and the number of monitoring locations needed based 

on the size and geometry of the facility. For the open-path 

methods, we estimated that four monitoring systems (along the 
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east, west, north and south fencelines) would be needed, 

regardless of the size of the refinery. Some fencelines at 

larger refineries may be too long for a single open path length, 

but we did not vary the number of detectors needed for the openpath systems based on refinery size in order to provide a 

reasonable lower-cost estimate for the open-path monitoring 

option. For small petroleum refineries (less than 750 acres), we 

estimated 12 passive or active monitoring stations would be 

sufficient. For medium-sized refineries (750 to 1,500 acres), we 

estimated 18 monitoring stations would be required; for large 

refineries (greater than 1,500 acres), we estimated that 24 

monitoring stations would be needed. For the passive diffusive 

tube monitoring we assumed a 2-week sampling interval; for 

active monitoring stations, we assumed a daily sampling 

frequency. 

We estimated the first year installation and equipment 

costs for the passive tube monitoring system could cost up to 

$100,000 for larger refineries (i.e., 24 sampling locations). 

Annualized costs for ongoing monitoring are projected to be 

approximately $40,000 per year, assuming the ongoing sample 

analyses are performed in-house. Capital costs for active 

sampling systems were estimated to be approximately twice that 

of the passive system for the larger refinery. Ongoing costs 

were more than 10 times higher, however, due to the daily 
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sampling frequency. Equipment costs for a single UV-DOAS system 

were estimated to be about $100,000, so a complete fenceline 

monitoring system (four systems plus shelters) was estimated to 

cost more than $500,000. A refinery using this technology for 

two fenceline locations estimated the annualized cost of 

calibrating and maintaining these systems approaches $1-million 

per year. (See Fenceline Monitoring Technical Support Document, 

in Docket ID Number EPA-HQ-OAR-2010-0682). 

Table 9 provides the nationwide costs of the monitoring 

approaches as applied to all U.S. petroleum refineries. 

Table 9. Nationwide Cost Impacts of Fenceline Monitoring Options 

at Petroleum Refineries 

Monitoring 

Option Monitoring Option Description 

Capital 

Cost 

(million 

$) 

Annual 

Operating 

Costs 

(million 

$/yr)

Total 

Annualized 

Costs 

(million 

$/yr) 

1 Passive diffusive tube monitoring 

network 

12.2 3.83 5.58 

2 Active sampling monitoring network 20.6 30.2 33.1 

3 Open-path monitoring (UV-DOAS, 

FTIR) 

71.0 35.5 45.6 

The primary goal of a fenceline monitoring network is to 

ensure that the emission reductions projectedowners and 

operators properly monitor and manage fugitive HAP emissions. As 

explained further in this preamble section, we are proposing a 

concentration action level that was derived by the Refinery 

modeling fenceline benzene concentrations (as a surrogate for 

HAP) at each facility after full compliance with the refinery 

Inserted Cells
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MACT 1 standards for fugitive sources are achieved in practice. 

The cumulative nationwide emissions from storage vessels, 

equipment leaks, and wastewater treatment systems projected 

after the implementation of these, as amended by this proposed 

standards is approximately 37,000 tpy VOC and 5,300 tpy HAP. It 

is difficult to estimate the emission reductionsaction. As such, 

we are proposing a fenceline benzene concentration that all 

facilities in the category can meet, according to the emissions 

inventories reported in response to the 2011 Refinery ICR. 

Therefore, we do not project a HAP emission reduction that the 

fenceline monitoring network will achieve. If a facility is 

experiencing no significant leaks from the required control 

equipment, then we anticipate that emission reductions resulting 

from the fenceline monitoring would be minimal. However, where 

if an owner or operator has underestimated the fugitive 

emissions from one or more significant leaks are occurring at a 

facilitysources, or if a leak develops or a tank seal or fitting 

fails, a fenceline monitoring system would provide for 

identification of such leaks much earlier than current 

monitoring requirements and would also help ensure that , where 

emissions are beyond those projected from implementation of the 

MACT standards, would help ensure that such emissions are 

quickly addressed. We note that any costs for a fugitive 

monitoring system would be offset, to some extent, by product 
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recovery since addressing these leaks more quickly than would 

otherwise occur based on the more infrequent monitoring required 

would reduce product losses. 

Based on the low cost and relative benefits of passive 

monitoring, which include the ability to generate timeintegrated concentration measurements at low detection limits, 

coupled with relative ease of deployment and analysis, the EPA 

is proposing to require refineries to deploy passive timeintegrated samplers at the fenceline. These samplers would 

monitor the level of fugitive emissions that reach the fenceline 

from all fugitive emission sources at the facility. The EPA is 

proposing to require fugitive emission reductions if fenceline 

concentrations exceed a specified concentration action level, as 

described further below. These proposed fenceline monitoring 

requirements complement the EPA’s proposal to allow the use of 

the optical gas imaging camera as described in Appendix K of 40 

CFR part 60 as an alternative work practice for measuring 

emissions from equipment leaks, in lieu of monitoring with EPA 

Method 21 of 40 CFR part 60, Appendix A-7 (see Ssection IV.B.1.c 

of this preamble for further discussion). Both approaches 

utilize low-cost methods to help ensure that total fugitives 

from a facility are adequately controlled. 

Because there is no current EPA test method for passive 

diffusive tube monitoring, as part of this action we are 
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proposing specific monitor citing and sample collection 

requirements as EPA Method 325A of 40 CFR part 63, Appendix A, 

and specific methods for analyzing the sorbent tube samples as 

EPA Method 325B of 40 CFR part 63, Appendix A. We are proposing 

to establish an ambient concentration of benzene at the 

fenceline that would trigger required corrective action. A brief 

summary of the proposed fenceline sampling requirements and our 

rationale for selecting the corrective action concentration 

levels are provided below. 

Siting, design and sampling requirements for fenceline 

monitors. The EPA is proposing that passive fenceline monitors 

collecting 2-week time-integrated samples be deployed to measure 

fenceline concentrations at refineries. We are proposing that 

refineries deploy passive samplers at 12 to 24 points circling 

the refinery perimeter. A primary requirement for a fenceline 

monitoring system is that it provides adequate spatial coverage 

for determination of representative pollutant concentrations at 

the boundary of the facility or operation. In an ideal scenario, 

fenceline monitors would be placed so that any fugitive plume 

originating within the facility would have a high probability of 

intersecting one or more monitors, regardless of wind direction. 

This proposed monitoring program would require that monitors be 

placed at 15 to 30 degree intervals along the perimeter of the 

refinery, depending on the size of the facility. For small 
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refineries (less than 750 acres), monitors should be placed at 

30 degree intervals, for a total of 12 locations; for facilities 

that are larger than 750 acres and less than 1,500 acres, 

monitors should be placed at 20 degree intervals, at 18 

locations; and for facilities greater than 1,500 acres, monitors 

should be placed at 15 degree intervals, accounting for 24 

locations. We have also established an alternative siting 

procedure where monitors can be placed every 2,000 feet along 

the fenceline of the refinery, which may be easier to implement, 

especially for irregularly-shaped facilities. In proposing these 

requirements for the number and location of required monitors, 

the EPA assumes that all portions of the facility are contiguous 

such that it is possible to define a single facility boundary or 

perimeter, although this perimeter may be irregular in shape. We 

request comment on how these monitoring requirements should be 

adapted for instances where one or more portions of the facility 

are not contiguous, and on the number and location of facilities 

for which special fenceline monitoring requirements to 

accommodate non-contiguous operations might apply. 

We are proposing that the highest concentration of benzene, 

as an annual rolling average measured at any individual monitor 

and adjusted for background (see below), would be compared 

against the concentration action level in order to determine if 

there are significant excess emissions of fugitive emissions 
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that need to be addressed. Existing sources would be required to 

deploy samplers no later than 3 years after the effective date 

of the final rule; new sources would be required to deploy 

samplers by the effective date of the final rule or startup, 

whichever is later. Because the proposed concentration action 

level is composed of 1 year’s worth of data, we are proposing 

that refinery owners and operators would be required to 

demonstrate compliance with the concentration action level for 

the first time 1 year following the compliance date, and 

thereafter on a 1-year rolling annual average basis (i.e., 

considering results from the most recent 26 consecutive 2-week 

sampling intervals and recalculating the average every 2 weeks). 

Benzene as an appropriate target analyte. Passive diffusive 

tube monitors can be used to determine the ambient concentration 

of a large number of compounds. However, different sorbent 

materials are typically needed to collect compounds with 

significantly different properties. Rather than require multiple 

tubes per monitoring location and require a full analytical 

array of compounds to be determined, which would significantly 

increase the cost of the proposed fenceline monitoring program, 

we are proposing that the fenceline monitors be analyzed 

specifically for benzene. Refinery owners or operators may elect 

to do more detailed speciation of the emissions, which could 

help identify the process unit that may be contributing to a 
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high fenceline concentration, but we are only establishing 

monitoring requirements and action level requirements for 

benzene. We consider benzene to be an excellent surrogate for 

organic HAP from fugitive sources for multiple reasons. First, 

benzene is ubiquitous at refineries, and is present in nearly 

all refinery process streams such that leaking components 

generally will leak benzene at some level (in addition to other 

compounds). Benzene is also present in crude oil and gasoline, 

so most storage tank emissions include benzene. As described 

previously in our discussion of wastewater treatment systems, 

benzene is also a very good surrogate for organic HAP emissions 

from wastewater and is already considered a surrogate for 

organic HAP emissions in the wastewater treatment system control 

requirements in Refinery MACT 1. Second, the primary releases of 

benzene occur at ground level as fugitive emissions from process 

equipment, storage vessels and wastewater collection and 

treatment systems, and the highest ambient benzene 

concentrations outside the facility will likely occur near the 

property boundary near ground level, so fugitive releases of 

benzene will be effectively detected at the ground-level 

monitoring sites. According to the emissions inventory we have 

relied on for this proposed action, 85 percent of benzene 

emissions from refineries result from ground-level fugitive 

emissions from equipment and wastewater collection and treatment 
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(see the Component 2 database contained in Docket ID Number EPAHQ-OAR-2010-0682). Finally, benzene is present in nearly all 

process streams. Therefore, the presence of benzene at the 

fenceline is also an indicator of other air toxics emitted from 

fugitive sources at refineries. 

For the reasons discussed above, we believe that benzene is 

the most appropriate pollutant to monitor. We believe that other 

compounds, such as PAH or naphthalene, would be less suitable 

indicators of total fugitive HAP for a couple of reasons. First, 

they are prevalent in stack emissions as well as fugitive 

emissions, so there is more potential for fenceline monitors to 

pick up contributions from non-fugitive sources. In contrast, 

almost all benzene comes from fugitive sources, so monitoring 

for benzene increases our confidence that the concentration 

detected at the fenceline is from fugitives. Second, as compared 

to benzene, these other compounds are expected to be present at 

lower concentrations and, therefore, would be more difficult to 

measure accurately using fenceline monitoring. We request 

comments on the suitability of selecting benzene or other HAP, 

including PAH or naphthalene, as the indicator to be monitored 

by fenceline samplers. We also request comment on whether it 

would be appropriate to require multiple HAP to be monitored at 

the fenceline considering the capital and annual cost for 
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additional monitors, and if so, which pollutants should be 

monitored. 

Adjusting for background benzene concentrations. Under this 

proposed approach, absolute measurements along a facility 

fenceline cannot completely characterize which emissions are 

associated with the refinery and which are associated with other 

background sources. The EPA recognizes that sources outside the 

refinery boundaries may influence benzene levels monitored at 

the fenceline. Furthermore, background levels driven by local 

upwind sources are spatially variable. Both of these factors 

could result in inaccurate estimates of the actual contribution 

of fugitive emissions from the facility itself to the 

concentration measured at the fenceline. Many refineries and 

petrochemical industries are found side-by-side along waterways 

or transport corridors. With this spatial positioning, there is 

a possibility that the local upwind neighbors of a facility 

could cause different background levels on different sides of 

the facility. To account for background concentrations (i.e., to 

remove the influence of benzene emissions from sources outside 

the refinery on monitored fenceline values), we are proposing to 

adjust monitored fenceline values to account for background 

concentrations as described below. We solicit comments on 

alternative approaches for making these adjustments for 

background benzene. 
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Fenceline-deployed passive samplers measure concentrations 

that originate from both the observed facility and from off-site 

sources. The relative contribution of the facility versus offsite source(s) to the measured concentration depends on the 

emission levels of the observed facility and off-site sources 

(including both near-field and remote sources), transporting 

wind direction and atmospheric dispersion. The ability to 

identify facility and off-site source contributions is reliant 

on the measurement scheme selected. The most basic (and lowest 

cost) approach involves different calculations using 2-week 

deployed samplers located only at the facility fenceline. 

Greater discrimination capability is found by adding passive 

samplers to specific areas of the facility, reducing the time 

duration of the passive samplers, and coupling measured 

meteorology information to the passive sampler analysis. 

Selective use of time-resolved monitoring or wind sector 

sampling approaches provides the highest source and background 

discrimination capability. The approach we are proposing seeks 

to remove off-site source contributions to the measured 

fenceline concentrations to the greatest extent possible using 

the most cost-effective measurement solutions. 

The highest fenceline concentration (HFC) for each 2-week 

sampling period can be expressed as: 
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  HFC  Maximum MFCi OSCi   HFC  Maximum MFCi OSCi

where: 

HFC = highest fenceline concentration, corrected for 

background. 

MFCi = measured fenceline concentration for the sampling 

period at monitoring location i. 

OSCi = estimated off-site source contribution for the 

sampling period at monitoring location i. 

The off-site source contribution (OSC) consists of two 

primary components: (1) a slowly varying, spatially uniform 

background (UB) concentration and, in some cases, (2) potential 

near-field interfering sources. 

OSCi  UB  NFSi

where: 

UB = uniform background concentration. 

NFSi = near-field interfering source concentration 

contribution at monitoring location i. 

In some deployment scenarios (such as spatially isolated 

facilities), the major off-site source component can be 

identified as background concentrations that are uniform across 

the facility fenceline and neighboring area. In this scenario, a 

UB concentration level can be determined and subtracted from the 

measured fenceline concentrations for each sampling period. This 
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can be accomplished through use of facility-measured or 

otherwise available, quality assured time-resolved (or wind 

sector-resolved) background monitoring data, or from placement 

of additional passive samplers at upwind locations away from the 

facility fenceline and other sources. 

In other scenarios, such as where other industrial sources 

or a highway are located nearby, background concentrations are 

likely not uniform. These outside sources would influence some, 

but not perhaps not all, fenceline monitors and, therefore, the 

true “background” concentration would vary, depending where on 

the fenceline the measurement was taken. In this case, 

background is not uniform, and monitoring location-specific 

near-field interfering source (NFS) values would need to be 

determined. 

Due to the difficulties associated with determining 

location-specific NFS values, we are proposing to approximate 

OSC by using the lowest measured concentration (LMC) at the 

facility fenceline for that period. In this case, the HFC for 

the monitoring period, corrected for background, would be 

calculated as: 

HFC  C  HMC  LMC

where: 

ΔC = concentration difference between the highest and 

lowest measured concentrations for the sampling period. 
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HMC = highest measured fenceline concentration for the 

sampling period. 

LMC = lowest measured fenceline concentration for the 

sampling period. 

This alternative is directly applicable for all refinery 

locations and requires no additional, off-site, upwind monitors, 

the placement of which is impossible to prescribe a priori. Use 

of LMC provides a reasonable proxy for OSC in most cases, but 

can over- or underestimate OSC in some cases. In locations where 

there are few upwind source contributions and where wind 

direction is relatively consistent, upwind passive samples on 

the fenceline can provide a realistic approximation of the 

actual off-site background levels. As the meteorology becomes 

more complicated (e.g., mixed wind directions, higher percentage 

of calm winds), the LMC will reflect a progressively larger 

amount of emissions from the facility itself, so differential 

calculations may underestimate the true HFC for some monitoring 

periods (by inadvertently allowing some facility emissions to be 

subtracted as part of “background”). On the other hand, if a 

near-field source impacts the highest measured concentration 

monitoring location significantly, but contributes little to the 

monitoring location with the LMC, the LMC differential 

calculation (i.e., ΔC) could lead to an artificially elevated 
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assessment of the highest fenceline concentration, corrected for 

background. 

Based on our examination of previous fenceline monitoring 

results, we expect that the use of the LMC differential will 

provide an accurate method by which to determine HFC. Therefore, 

we are not proposing to limit the use of the LMC differential 

calculation in cases where there are no near-field sources and 

where mixed wind direction (or calm wind) is common. In these 

special cases, use of the UB concentration alone (no NFS term) 

may be more accurate than using LMC. We are seeking comment on 

how to identify conditions under which the LMC differential may 

underestimate the highest fenceline concentration, corrected for 

background, and the need to require facilities to determine and 

use UB rather than LMC in these cases. 

We also recognize that under different site-specific 

conditions, the NFS contribution may affect certain fenceline 

monitoring stations more than others, causing the LMC 

differential calculation to overestimate the facility’s 

contribution to the highest fenceline concentration. Therefore, 

we are also proposing to allow owners or operators of petroleum 

refineries to develop site-specific monitoring plans to 

determine UB and NFSi. 

If standard 2-week passive fenceline data and site analysis 

indicate potential near-field off-site source interferences at a 
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section of the refinery, the proposal allows the owner or 

operator to conduct additional sampling strategies to determine 

a local background (OSC term) for use in the HFC calculation. 

The owner or operator would be required to report the basis for 

this correction, including analyses used to identify the sources 

and contribution of benzene concentration to the passive sampler 

concentration, within 45 days of the date the owner or operator 

first measures an exceedance of the concentration action level. 

We envision that facilities would implement these 

additional strategies to refine fenceline concentration 

estimates only if appropriate given site-specific 

characteristics and only if HFC determined by the LMC approach 

is likely to exceed the concentration action level (see 

discussion below regarding this action level). Facilities with 

HFC below the concentration action level based on the simple LMC 

differential calculation would not be required to make any 

further demonstration of the influence of background sources on 

concentrations measured at the fenceline. For facilities where 

additional background adjustment is appropriate, optional 

strategies could include deployment of additional passive 

samplers at distances from the fenceline (toward and away from 

suspected NFS) and reducing the time intervals of passive 

deployments to increase time resolution and wind directioncomparison capability. In complex cases, such as two refineries 
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sharing a common fenceline, wind-sector sampling or various 

forms of time-resolved monitoring may be required to ascertain 

the fenceline concentrations. 

We are proposing that owners or operators of petroleum 

refineries electing to determine monitoring location-specific 

NFS concentrations must prepare and submit a site-specific 

monitoring plan. The monitoring plan is required to identify 

specific near-field sources, identify the location and type of 

monitors used to determine UB and NFS concentrations, identify 

the monitoring location(s) for which the NFS concentrations 

would apply, and delineate the calculations to be used to 

determine monitoring location specific NFS concentrations (for 

those monitoring locations impacted by the near-field source). 

We are proposing that the site-specific monitoring plan must be 

submitted to the Administrator for approval and receive approval 

prior to its use for determining HFC values. 

The EPA requests comment on the most appropriate 

approach(es) for adjusting measured fenceline concentrations for 

background contributions, including (in complex cases) where 

meteorology is highly variable or where one or more near-field 

off-site sources affect the measured fenceline concentration 

(MFC) at a refinery. We are also seeking comment on the adequacy 

of the proposed requirements for developing and approving sitespecific monitoring plans. 
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Concentration action level. As mentioned above, the EPA is 

proposing to require refineries to take corrective action to 

reduce fugitive emissions if monitored fenceline concentrations 

exceed a specific concentration action level on a rolling annual 

average basis (recalculated every two weeks). We selected this 

proposed fenceline action level to be consistentby modeling 

fenceline benzene concentrations using the emissions inventories 

reported in response to the 2011 Refinery ICR, assuming that 

those reported emissions represented full compliance with the 

maximum projectedall refinery MACT requirements, adjusted for 

additional control requirements we are proposing in today’s 

action. Thus, if the reported inventories are accurate, all 

facilities should be able to meet the fenceline concentration 

for petroleum refineries when all fugitive sources are 

controlled to the levels projected after the implementation of 

these proposed standardsaction level. We estimated the long-term 

ambient post-control benzene concentrations at each petroleum 

refinery using the post-control emission inventory and EPA’s 

American Meteorological Society/EPA Regulatory Model dispersion 

modeling system (AERMOD). Concentrations were estimated by the 

model at a set of polar grid receptors centered on each 

facility, as well as surrounding census block centroid receptors 

extending from the facility outward to 50 km. For purposes of 

this modeling analysis, we assumed that the nearest off-site 
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polar grid receptor was the best representation of each 

facility’s fenceline concentration in the post-control case, 

unless there was a census block centroid nearer to the fenceline 

than the nearest off-site polar grid receptor or an actual 

receptor was identified from review of the site map. In those 

instances, we estimated the fenceline concentration as the 

concentration at the census block centroid. Only receptors 

(either the polar or census block) that were estimated to be 

outside the facility fenceline were considered in determining 

the maximum benzene level for each facility. We note that this 

analysis does not correlate to any particular metric related to 

risk. The maximum post-control benzene concentration modeled at 

the fenceline for any facility is 9 micrograms per cubic meter 

(μg/m3

) (annual average). (For further details of the analysis, 

see memo entitled Fenceline Ambient Benzene Concentrations 

Surrounding Petroleum Refineries in Docket ID Number EPA-HQ-OAR2010-0682.) 

The facility inventories generally project emissions with 

the required fugitive controls working as designed (e.g., no 

tears in seals for storage vessel floating roofs and water in 

all water drain seals). If facility inventories are correct, 

annual average benzene concentrations would not exceed 9 μg/m3

 at 

the fenceline of any facility. Because the modeling approach 

considers only the emissions from the refinery, with no 
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contribution from background or near-field sources, this 

concentration is comparable to the highest modeled fenceline 

concentration after correcting for background concentrations, as 

described previously. The EPA is proposing to set the standard 

at this concentration action level. We also note that this 

modeling effort evaluated the annual average benzene 

concentration at the fenceline, so that this action level 

applies to the annual average fenceline concentration measured 

at the facility. 

The EPA recognizes that, because it is difficult to 

directly measure emissions from fugitive sources, there is 

significant uncertainty in current emissions inventories for 

fugitives. Thus, there is the potential for benzene 

concentrations monitored at the fenceline to exceed modeled 

concentrations. However, given the absence of fenceline monitors 

at most facilities, there is very limited information available 

at present about fenceline concentrations and the extent to 

which they may exceed concentrations modeled from inventories. 

In the absence of additional data regarding the concentration of 

fugitive emissions of benzene at the fenceline, the EPA believes 

it is reasonable to rely on the maximum modeled fenceline value 

as the concentration action level. We are soliciting comment on 

alternative concentration action levels and other approaches for 

establishing the concentration action level. 
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Due to differences in short-term meteorological conditions, 

short-term (i.e., two-week average) concentrations at the 

fenceline can vary greatly. Given the high variability in shortterm fenceline concentrations and the difficulties and 

uncertainties associated with estimating a maximum 2-week 

fenceline concentration given a limited number of years of 

meteorological data used in the modeling exercise, we determined 

that it would be inappropriate and ineffective to propose a 

short-term concentration action level that would trigger 

corrective action based on a single 2-week sampling event. 

One objective for this monitoring program is to identify 

significant fugitive emission releases earlymore quickly, so 

that corrective action can be implemented in a more timely 

fashion, and thereby achieve additional emission reductions that 

would not be achieved than might otherwise occur without the 

fenceline monitoring requirement. We believe the proposed 

fenceline monitoring approach and a rolling annual average 

concentration action limit (i.e., using results from the most 

recent 26 consecutive 2-week samples and recalculating the 

average every 2 weeks) will achieve this objective. The proposed 

fenceline monitoring will provide the refinery owner or operator 

with fenceline concentration information once every 2 weeks. 

Therefore, the refinery owner or operator will be able to timely 

identify occurrences of unusually high emissions leading to 
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elevated fenceline concentrations. We anticipate that the 

refinery owners or operators will elect to identify and correct 

these sources early, in efforts to avoid exceeding the annual 

benzene concentration action level. 

An “exceedance” of the benzene concentration action level 

would occur when the rolling annual average highest fenceline 

concentration, corrected for background (determined as described 

previously), exceeds 9 μg/m3

. Upon exceeding the concentration 

action level, we propose that refinery owners or operators would 

be required to conduct analyses to identify sources contributing 

to fenceline concentrations and take corrective action to reduce 

fugitive emissions to ensure fenceline benzene concentrations 

remain at or below 9 μg/m3

 (rolling annual average). 

Corrective action requirements. As described previously, 

the EPA is proposing that the owner or operator analyze the 

samples and compare the rolling annual average fenceline 

concentration, corrected for background, to the concentration 

action level. This section summarizes the corrective action 

requirements in this proposed rule. First, we are proposing that 

the calculation of the rolling annual average fenceline 

concentration must be completed within 30 days after the 

completion of each sampling episode. If the rolling annual 

average fenceline benzene concentration, corrected for 

background, exceeds the proposed concentration action level 
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(i.e., 9 μg/m3

), the facility must, within 5 days of comparing 

the rolling annual average concentration to the concentration 

action level, initiate a root cause analysis to determine the 

primary cause, and any other contributing cause(s), of the 

exceedance. The facility must complete the root cause analysis 

and implement corrective action within 45 days of initiating the 

root cause analysis. We are not proposing specific controls or 

corrections that would be required when the concentration action 

level is exceeded because the cause of an exceedance could vary 

greatly from facility to facility and episode to episode, since 

many different sources emit fugitive emissions. Rather, we are 

proposing to allow facilities to determine, based on their own 

analysis of their operations, the action that must be taken to 

reduce air concentrations at the fenceline to levels at or below 

the concentration action level, representing full compliance 

with all refinery MACT requirements, adjusted for additional 

control requirements we are proposing in today’s action. 

If, upon completion of the corrective action described 

above, the owner or operator exceeds the action level for the 

next two-week sampling episode following the completion of a 

first set of corrective actions, the owner or operator would be 

required to develop and submit to EPA a corrective action plan 

that would describe the corrective actions completed to date. 

This plan would include a schedule for implementation of 
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additionalemission reduction measures to achieve compliance 

within a timeframe that the owner or operator can demonstrate is 

as soon as practical. This plan would be submitted to the 

Administrator for approval within 30 days of an exceedance 

occurring during the next two-week sampling episode following 

the completion of the initial round of corrective action. The 

EPA would evaluate this plan based on the ambient concentrations 

measured, the sources identified as contributing to the high 

fenceline concentration, the potential emission reduction 

measures identified, and the emission reduction measures 

proposed to be implemented in light of the costs of the options 

considered and the reductions needed to reduce the ambient 

concentration below the action level threshold. To minimize 

burden on the state implementing agencies and provide additional 

resources for identifying potential emission sources, we are 

proposing not to delegate approval of this plan. The refinery 

owner or operator is not deemed out of compliance with the 

proposed concentration action level, provided that the 

appropriate corrective action measures are taken according to 

the time-frame detailed in an approved corrective action plan. 

The EPA requests comment on whether it is appropriate to 

establish a standard time frame for compliance with actions 

listed in a corrective action plan. We also request comment on 
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whether the approval of the corrective action plan should be 

delegated to state, local and tribal governments. 

The EPA’s post-control dispersion modeling (described in 

Ssection III.A of this preamble), which relies on reported 

emissions inventories from the 2011 Refinery ICR, adjusted to 

reflect compliance with the existing refinery MACT standards as 

modified by the additional controls on equipment leaks and 

storage vessels proposed in this rulemaking, indicates that 

fugitive emissions at all refineries are low enough to ensure 

that fenceline concentrations of benzene do not exceed the 

proposed concentration action level. Assuming the reported 

inventories and associated modeling are accurate, we expect that 

few, if any, facilities will need to engage in required 

corrective action. We do, however, expect that facilities may 

identify “poor-performing” sources (e.g., unusual leaks) from 

the fenceline monitoring data and will implement voluntary 

corrective action measures to avoid exceeding the annual average 

concentration action level. As mentioned previously, we envision 

most of these “voluntary actions” would be similar to actions to 

correct issues that would be required to be corrected once 

identified by the traditional periodic inspections or 

monitoring. To the extent a source needs to take a corrective 

action measure, such measure is necessary to ensure compliance 

with MACT, and those projected costs are already included in the 
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projected costs of the Refinery MACT 1 rule requirements, as 

modified by the proposed amendments. While the emission 

reductions are also included in the projected benefits of the 

initial MACT standards and those standards as modified by the 

risk and technology review, earlier detection and correction of 

these issues would lead to emission reductions from actual 

emission levels. It is difficult to quantify these emission 

reductions. Therefore, we have not estimated any emission 

reductions specific to the fenceline monitoring requirements, 

based on this additional information, will take action to reduce 

HAP emissions before they would have otherwise been aware of the 

issue through existing inspection and enforcement measures. 

By selecting a ground-level fenceline monitoring approach 

and by selecting benzene as the surrogate for organic HAP 

emissions, we believe that the proposed monitoring approach will 

effectively target Rrefinery MACT 1 -regulated fugitive emission 

sources. However, there may be instances where the fenceline 

concentration is impacted by a low-level miscellaneous process 

vent, heat exchange system or other similar source. As these 

sources are regulated under Refinery MACT 1 and the emissions 

from these sources were included in our post-control modeling 

file (from which the 9 μg/m3

 fenceline concentration action level 

was developed), sources would not be able to avoid taking 

corrective action by claiming the exceedance of the fenceline 
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concentration was from one of these emission points rather than 

from fugitive emission sources. 

There may be instances in which the high fenceline 

concentration is impacted by a non-Refinery MACT 1refinery

emission source. The most likely instance of this would be leaks 

from HON equipment or HON storage vessels co-located at the 

refinery. Because these sources have similar control 

requirements and corrective action requirements as the Refinery 

MACT 1 emission sources, we believe that petroleum refineries 

with these additional sources should still be able to meet the 

9 μg/m3 fenceline concentration action level. However, we 

consider the fenceline monitoring requirement to be specific to 

Refinery MACT 1refinery emission sources. Therefore, we are 

proposing to allow refinery owners or operators to develop sitespecific monitoring plans to determine the impact of these nonRefinery MACT 1 emission sources on the ambient benzene 

concentration measured at the fenceline. This monitoring plan 

would be identical to those used by refinery owners or operators 

that elect to determine monitoring location-specific NFS values 

for nearby off-site sources. In this case, however, the NFS is 

actually within the refinery fenceline. Upon approval and 

implementation of the monitoring plan, the refinery owner or 

operator would determine the highest fenceline concentration 

corrected for background; the background correction in this case 
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includes a correction for the co-located non-Refinery MACT 1 

emission source(s). 

The EPA requests comment on whether the corrective action 

requirements should be limited to exceedances of the fenceline 

concentration solely from Refinery MACT 1refinery emission 

sources and whether a refinery owner or operator should be 

allowed to exceed the annual average fenceline concentration 

action level if they can provedemonstrate the exceedance of the 

action level is due to a non-Refinery MACT 1refinery emissions 

source. We also request comment on the requirements proposed for 

refinery owners or operators to demonstrate that the exceedance 

is caused by a non-Refinery MACT 1refinery emissions source. 

Specifically, we request comment on whether the “near-field 

source” correction is appropriate for on-site sources and 

whether there are other methods by which refinery owners or 

operators with co-located, non-Refinery MACT 1refinery emission 

sources can demonstrate compliance withthat their benzene 

concentrations do not exceed the proposed fenceline 

concentration action level for Refinery MACT 1 emission sources. 

Additional requirements of the fenceline monitoring 

program. We are proposing that fenceline data at each monitor 

location be reported electronically for each semiannual period’s 

worth of sampling periods (i.e., six13 to seven14 2-week 

sampling periods per semiannual period). These data would be 
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reported within 45 days of the end of each quartersemiannual 

period, and will be made available to the public through the 

EPA’s electronic reporting and data retrieval portal, in keeping 

with the EPA’s efforts to streamline and reduce reporting burden 

and to move away from hard copy submittals of data where 

feasible. 

We are proposing to require the reporting of raw fenceline 

monitoring data, and not just the HFC, on a semiannual basis; 

considering the fact that the fenceline monitoring standard is a 

new approach for fugitive emissions control, and it involves the 

use of new methods, both analytical and siting methods, this 

information is necessary for the EPA to evaluate whether this 

standard has been implemented correctly. Further, the 

information provided by the raw data, such as the need for 

additional or less monitoring sites, the range of measured 

concentrations, the influence of background sources, and the 

ability to collect and compare data from all refineries, will 

inform us of further improvements we can make to the fenceline 

standard, monitoring and analytical methods, approaches for 

estimating refinery fugitive emissions, and guidance that may be 

helpful to improve implementation of the fenceline monitoring 

approach. We seek comment on suggestions for other ways we can 

monitor and improve the fenceline monitoring requirement. 
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We are proposing that facilities be required to conduct 

fenceline monitoring on a continuous basis, in accordance with 

the specific methods described above, even if benzene 

concentrations, as measured at the fenceline, routinely are 

substantially lower than the concentration action level. In 

light of the low annual monitoring and reporting costs 

associated with the fenceline monitors (as described in the next 

section), and the importance of the fenceline monitors as a 

means of ensuring the control of fugitives achieves the expected 

emission levels, we believe it is appropriate to require 

collection of fenceline monitoring data on a continuous basis. 

However, the EPA recognizes that fugitive benzene emissions from 

some facilities may be so low as to make it improbable that 

exceedances of the concentration action level would ever occur. 

In the interest of reducing the cost burden on facilities 

to comply with this rule, the EPA solicits comment on approaches 

for reducing or eliminating fenceline monitoring requirements 

for facilities that consistently measure fenceline 

concentrations below the concentration action level, and the 

measurement level that should be used to provide such relief. 

Such an approach would be consistent with graduated requirements 

for valve leak monitoring in Refinery MACT 1 and other equipment 

leak standards, where the frequency of required monitoring 

varies depending on the percent of leaking valves identified 
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during the previous monitoring period (see, for example, 40 CFR 

63.648(c) and 40 CFR 63.168(d)). The EPA requests comment on the 

minimum time period facilities should be required to conduct 

fenceline monitoring; the level of performance, in terms of 

monitored fenceline concentrations, that would enable a facility 

to discontinue use of fenceline monitors or reduce the frequency 

of data collection and reporting; and any adjustments to the 

optical gas imaging camera requirements that would be necessary 

in conjunction with such changes to the fenceline monitoring 

requirements. 

i. Delayed Coking Units 

As noted in Ssection IV.A of this preamble, we are 

soliciting comments on the need to establish MACT standards for 

DCU under CAA Ssection 112(d)(2) and (3). Even if we were to 

assume that there is already an applicable MACT standard for 

DCU, a technology review of this emission source, as prescribed 

under CAA Ssection 112(d)(6), would lead us to propose a 

depressurization limit of 2 psig because of technology 

advancements since the MACT standards were originally issued and 

because it is cost effective. Industry representatives have 

pointed out that Refinery NSPS Ja requires DCU at new and 

modified sources to depressure to 5 psig, and they have 

indicated that EPA should not require a lower depressurization 

limit under a CAA Ssection 112(d)(6) technology review. Further, 
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industry representatives also provided summary-level information 

(available in Docket ID Number EPA-HQ-OAR-2010-0682 as 

correspondence from API entitled Coker Vent Potential Release 

Limit Preliminary Emission, Cost and Cost Effectiveness 

Estimates) on costs to depressure to 5 psig versus 2 psig. While 

the cost information does not show large differences for any 

particular facility to depressure at 5 psig versus 2 psig, the 

information does show a large range in potential costs between 

refineries. At this time, we do not have the detailed, refineryspecific cost breakdowns to compare against our cost 

assumptions, which were derived from data obtained for a 

facility that did install the necessary equipment to meet a 2 

psig limit. We also do not have detailed information on the 

design and operation of the DCU in industry’s cost study to 

evaluate whether there are any differences that would warrant 

subcategories. We solicit information on designs, operational 

factors, detailed costs and emissions data for DCU, and we 

specifically solicit comments on what should be the appropriate 

DCU depressurization limit if we were to adopt such a 

requirement pursuant to CAA Ssection 112(d)(6) rather than 

pursuant to CAA Ssection 112(d)(2) and (3). 

2. Refinery MACT 2 – 40 CFR Part 63, Subpart UUU 

The Refinery MACT 2 source category regulates HAP emissions 

from FCCU, CRU and SRU process vents. Criteria pollutant 
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emissions from FCCU and SRU are regulated under 40 CFR part 60, 

subparts J and Ja (Refinery NSPS J and Refinery NSPS Ja, 

respectively). We conducted a technology review of Refinery NSPS 

J emission limits from 2005 to 2008 and promulgated new 

standards for FCCU and SRU (among other sources) in Refinery 

NSPS Ja on June 24, 2008 (73 FR 35838). Our current technology 

review of Refinery MACT 2 relies upon, but is not limited to, 

consideration of this recent technology review of Refinery NSPS 

J for FCCU and SRU. 

a. FCCU Process Vent 

The FCCU has one large atmospheric vent, the coke burn-off 

exhaust stream for the unit’s catalyst regenerator. HAP 

emissions from this FCCU process vent include metal HAP 

associated with entrained catalyst particles and organic HAP, 

mostly by-products of incomplete combustion from the coke burnoff process. As the control technologies associated with each of 

these classes of pollutants are very different, the controls 

associated with each of these classes of pollutants are 

considered separately. 

Metal HAP emission controls. The current Refinery MACT 2 

includes several different compliance options, some based on PM 

as a surrogate for total metal HAP and some based on nickel (Ni) 

as a surrogate for total metal HAP. Refinery NSPS J was the 

basis of the PM emission limits and the metal HAP MACT floor in 
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Refinery MACT 2. Refinery NSPS J limits PM from FCCU catalyst 

regeneration vents to 1.0 gram particulate matter per kilogram 

(g PM/kg) of coke burn-off, with an additional incremental PM 

allowance for liquid or solid fuel burned in an incinerator, 

waste heat boiler, or similar device. Refinery MACT 2 states 

that FCCU subject to Refinery NSPS J PM emission limits are 

required to demonstrate compliance with Refinery NSPS J PM 

emission limits as specified in Refinery NSPS J. As provided in 

Refinery NSPS J, ongoing compliance with the PM emission limits 

is determined by compliance with a 30-percent opacity limit, 

except for one 6-minute average per hour not to exceed 60-

percent opacity. FCCU not subject to Refinery NSPS J may elect 

to comply with the FCCU PM provisions in Refinery NSPS J. 

Alternatively, they may comply with a 1.0 g PM/kg of coke burnoff emission limit in Refinery MACT 2 (with no provision for an 

additional incremental PM allowance for liquid or solid fuel 

burned in an incinerator, waste heat boiler, or similar device). 

Compliance with this limit in Refinery MACT 2 is demonstrated by 

either a 1-hour average site-specific opacity limit using a 

continuous opacity monitoring system (COMS) or APCD-specific 

daily average operating limits using CPMS. 

Refinery MACT 2 also includes two emission limit 

alternatives that use Ni, rather than PM, as the surrogate for 

metal HAP. The first of these Ni alternatives is a mass emission 
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limit of 13 grams Ni per hour; the second nickel alternative is 

an emission limit of 1.0 milligrams Ni per kilogram of coke 

burn-off. Compliance with the Ni emission limits in Refinery 

MACT 2 is demonstrated by either a daily average site-specific 

Ni operating limit (using a COMS and weekly determination of Ni 

concentration on equilibrium FCCU catalyst), or APCD-specific 

daily average operating limits using CPMS and monthly average Ni 

concentration operating limit for the equilibrium FCCU catalyst. 

Under Refinery MACT 2, an initial performance demonstration 

(source test) is required to show that FCCU is compliant with 

the emission limits selected by the refinery owner or operator. 

No additional performance test is required for facilities 

already complying with Refinery NSPS J. The performance test is 

a one-time requirement; additional performance tests are only 

required if the owner or operator elects to establish new 

operating limits, or to modify the FCCU or control system in 

such a manner that could affect the control system’s 

performance. 

Under the review for Refinery NSPS J, we conducted a 

literature review as well as a review of the EPA’s refinery 

settlements and state and local regulations affecting refineries 

to identify developments in practices, processes and control 

technologies to reduce PM emissions from refinery sources (see 

Summary of Data Gathering Efforts: Emission Control and Emission 
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Reduction Activities, August 19, 2005, and Review of PM Emission 

Sources at Refineries, December 20, 2005, Docket Item Number 

EPA-HQ-OAR-2007-0011-0042). At that time, we identified 

regulations for PM from FCCU that were more stringent than the 

Refinery NSPS J requirements for PM, and we promulgated more 

stringent PM limits in Refinery NSPS Ja. Refinery NSPS Ja limits 

PM from FCCU catalyst regeneration vents to 1.0 g PM/kg of coke 

burn-off for modified or reconstructed FCCU, with no incremental 

allowance for PM-associated liquid or solid fuels burned in a 

post-combustion device. Furthermore, an emission limit of 0.5 g 

PM/kg of coke burn-off was established for FCCU constructed 

after May 14, 2007. 

In addition, the Refinery NSPS J review identified 

improvements in APCD monitoring practices, which were included 

in the Refinery NSPS Ja standards. Refinery NSPS J includes a 

30-percent opacity limit as the only ongoing monitoring 

requirements for PM from the FCCU. This 30-percent opacity limit 

has shown to be lenient and high in comparison to recent federal 

rules that have included more stringent opacity limits (e.g., 40 

CFR part 60, subpart Db with 20-percent opacity), and recent 

state and local agency rules that omit opacity limits altogether 

in favor of operating limits for the emission control systems. 

Based on the Refinery NSPS J review, Refinery NSPS Ja does not 

include an opacity limit, but includes updated and more 
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appropriate monitoring approaches, such as requiring bag leak 

detectors (BLD) for fabric filter control systems, and requiring 

CPMS for electrostatic precipitators (ESP) and wet scrubbers. 

Additionally, Refinery NSPS Ja includes an option to measure PM 

emissions directly using a PM CEMS. For this monitoring 

alternative, a direct PM concentration limit (equivalent to the 

conventional FCCU PM emission limit in terms of g PM/kg of coke 

burn-off) is included in the rule. Finally, in our review for 

Refinery NSPS J, we noted that, even with improved monitoring 

methods, periodic source testing is needed to verify the 

performance of the control system as it ages. In Refinery NSPS 

Ja, annual performance demonstrations are required for affected 

FCCU. The Refinery NSPS Ja standards for PM from FCCU reflect 

the latest developments in practices, processes and control 

technologies. In our current review of Refinery MACT 2, we did 

not identify any other developments in practices, processes or 

control technologies since we promulgated Refinery NSPS Ja in 

2008. 

The conclusions of the technology review conducted for the 

Refinery NSPS J PM emission limits are directly applicable to 

Refinery MACT 2; the initial Refinery MACT 2 rule recognized 

this by providing that compliance with Refinery NSPS J would 

also be compliance with Refinery MACT 2. We considered the 

impacts of proposing to revise Refinery MACT 2 to incorporate 
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the developments in monitoring practices and control 

technologies reflected in the Refinery NSPS Ja limits and 

monitoring provisions. 

As noted above, Refinery NSPS Ja includes a limit of 0.5 g 

PM/kg of coke burn-off for newly constructed sources. There 

would be no costs associated with requiring the lower emission 

limit of 0.5 g PM/kg of coke burn-off for Refinery MACT 2 new 

sources under CAA Ssection 112(d)(6) because these sources would 

already be required to comply with that limit under Refinery 

NSPS Ja. Therefore, we are proposing that it is necessary 

pursuant to CAA Ssection 112(d)(6) to revise Refinery MACT 2 to 

incorporate the Refinery NSPS Ja PM limit for new sources. 

We are also proposing to establish emission limits and 

monitoring requirements in Refinery MACT 2 that are consistent 

with those in Refinery NSPS Ja. This option would not impose any 

additional cost on sources already subject to Refinery NSPS Ja. 

We note that for facilities subject to Refinery NSPS J, this 

would not lead to duplicative or conflicting monitoring 

requirements because Refinery NSPS J already includes a 

provision that allows affected facilities subject to Refinery 

NSPS J to instead comply with the provisions in Refinery NSPS Ja 

(see 40 CFR 60.100(e)). 

In addition, in conjunction with our proposal to revise 

Refinery MACT 2 to include the more stringent requirements in 
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Refinery NSPS Ja, we are proposing to remove the less stringent 

compliance option of meeting the requirements of Refinery NSPS 

J. As described previously, Refinery NSPS J includes an 

incremental PM emissions allowance for post-combustion devices 

and relies on a 30-percent opacity limit that is outdated and 

has been demonstrated to be ineffective at identifying 

exceedances of the 1.0 g PM/kg coke burn-off emissions limit. 

We also reviewed the compliance monitoring requirements for 

the Refinery MACT 2 PM and Ni-based emission limits. As 

described previously, Refinery MACT 2 includes operating limits 

based on APCD operating parameters or site-specific opacity 

limits. There are differences between the monitoring approaches 

in Refinery MACT 2 for these limits and Refinery NSPS Ja 

monitoring approaches for the NSPS PM limit, so we evaluated 

whether it is necessary, pursuant to CAA Ssection 112(d)(6), to 

revise the monitoring provisions in Refinery MACT 2 consistent 

with the requirements in Refinery NSPS Ja. 

The first significant difference is in the averaging times 

used for the different operating limits. Refinery NSPS Ja 

requires a 3-hour rolling average for the operating limits for 

parametric monitoring systems; Refinery MACT 2 includes daily 

averaging of the operating limits. Typically, the averaging time 

for operating limits is based on the duration of the performance 

test used to establish those operating limits. As the 
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performance test duration is 3 hours (three 1-hour test runs) 

and compliance with the PM (or Ni) emission limit is based on 

the average emissions during this 3-hour period, the most 

appropriate averaging period for these operating limits is 3 

hours. Using a daily average could allow poor performance (i.e., 

control equipment for shorter periods (e.g., 3-hour averages 

that are higher than the PM emissions limit in Refinery NSPS 

Ja). For example, assume an operating limit developed from a 

performance test has a value of 1 and that values exceeding this 

level would suggest that the control system is not operating as 

well as during the performance test (i.e., potentially exceeding 

the PM emission limit). If the control system is run for 18 

hours operating at a level of 0.9 and 6 hours at a level of 1.2, 

the unit would be in compliance with the daily operating limit 

even though the unit may have 6 consecutive hours during which 

the operating limit was exceeded. Reducing the averaging time 

does not impact the types of monitors required; it merely 

requires the owner or operator of the unit to pay more careful 

attention to the APCD operating parameters. We are proposing 

that it is necessary, pursuant to CAA Ssection 112(d)(6), to 

incorporate the use of 3-hour averages rather than daily 

averages for parameter operating limits in Refinery MACT 2 for 

both the PM and Ni limits, because this is a cost-effective 

development in monitoring practice. 
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The site-specific opacity operating limit for PM in 

Refinery MACT 2 (for units not electing to comply with Refinery 

NSPS J) has a 1-hour averaging period, but the Ni operating 

limits (which use opacity monitoring) have a 24-hour averaging 

period. These averaging periods are inconsistent with the 

duration of the performance test, which is over a 3-hour period. 

We are proposing, pursuant to CAA Ssection 112(d)(6), to 

incorporate the use of 3-hour averages for the site-specific 

opacity operating limit and the Ni operating limits rather than 

daily averages because this is a cost-effective development in 

monitoring practice. 

We also compared the APCD-specific operating parameters 

used in Refinery MACT 2 to those that we promulgated for 

Refinery NSPS Ja. The Refinery NSPS Ja rule includes monitoring 

approaches that are not included in Refinery MACT 2. These 

include the option of using PM CEMS and requiring BLD for fabric 

filter control systems. Adding a PM CEMS as an option for 

demonstrating compliance with the Refinery MACT 2 PM limit 

(similar to what is provided in Refinery NSPS Ja) would not 

impact the costs of complying with Refinery MACT 2 because 

sources can choose whether or not to adopt this monitoring 

method. With respect to BLD, there is only one refinery that 

currently uses a baghouse (fabric filter) to control emissions 

from its FCCU (although one additional unit has indicated that 
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it has plans to install a fabric filter control within the next 

few years). Under the existing requirements in Refinery MACT 2 

(assuming that the FCCU currently operating with a fabric filter 

has not elected to comply with the Refinery NSPS J PM emission 

limit option), it is required to comply with a site-specific 

opacity operating limit. For new, reconstructed, or modified 

FCCU, Refinery NSPS Ja requires use of BLD. While we generally 

consider the BLD to be superior to opacity monitors for ensuring 

fabric filter control systems are operating efficiently, it is 

difficult to determine what, if any, increment in assurance that 

the unit is properly controlled would be achieved by requiring 

the one facility currently operating a fabric filter control 

system and complying with a site-specific opacity operating 

limit to switch from a COMS to BLD. Therefore, we are proposing 

that it is not necessary to require the one existing FCCU with a 

fabric filter control system to switch from COMS to a BLD system 

because this would require additional monitoring equipment (with 

additional costs) and little to no associated increase in 

assurance that the unit is properly controlled. Although we are 

not proposing to require existing sources using a fabric filter 

to use BLD, we are proposing to include BLD as an option to 

COMS; owners or operators of FCCU using fabric filter-type 

control systems at existing sources can elect (but are not 
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required) to use BLD in lieu of COMS and the site-specific 

opacity operating limit. 

The Refinery NSPS Ja monitoring requirements for ESP 

include CPMS for monitoring and recording the total power and 

the secondary current to the entire system. The current MACT 

requires monitoring voltage and secondary current or monitoring 

only the total power to the APCD. While these monitoring 

requirements are similar, we consider that the Refinery NSPS Ja 

requirements will provide improved operation of the ESP. As the 

monitors required to measure these parameters are a routine part 

of ESP installations, we project no additional costs for 

monitoring equipment. We expect that a new performance test 

would be needed to ensure that both total power and secondary 

current are recorded during the source test. As discussed later 

in this section, we are proposing to require ongoing performance 

tests regardless of the monitoring option, so we are not 

projecting any additional costs specific to revising the 

monitoring requirements for ESP. Because the Refinery NSPS Ja 

monitoring and operating requirements for ESP are expected to 

provide improved performance of the APCD with no incremental 

costs, we propose that it is necessary, pursuant to CAA Ssection 

112(d)(6), to incorporate the total power and the secondary 

current operating limits into Refinery MACT 2. 
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Refinery NSPS Ja provides a specific monitoring alternative 

to pressure drop for jet ejector-type wet scrubbers or any other 

type of wet scrubbers equipped with atomizing spray nozzles. 

Owners or operators of FCCU controlled by these types of wet 

scrubbers can elect to perform daily checks of the air or water 

pressure to the spray nozzle rather than monitor pressure. 

Refinery MACT 2 currently excludes these types of control 

systems from monitoring pressure drop but includes no specific 

monitoring to ensure the jet ejectors or atomizing spray nozzle 

systems are properly operating. Since proper functioning of the 

jet ejectors or atomizing spray nozzles is critical to ensuring 

these control systems operate at the level contemplated by the 

MACT, some monitoring/inspection requirement of these components 

is necessary to ensure compliance with the FCCU PM or Ni 

emission limit. The owner or operator of a jet ejector-type wet 

scrubber or other type of wet scrubber equipped with atomizing 

spray nozzles should be performing routine checks of these 

systems, such as the daily checks of the air or water pressure 

to the spray nozzles, as required in Refinery NSPS Ja. These 

daily checks are consistent with good operational practices for 

wet scrubbers and should not add significant burden to the FCCU 

wet scrubber owner or operator. For these reasons, we propose it 

is necessary to require owners or operators of a jet ejectortype wet scrubber or other type of wet scrubber equipped with 
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atomizing spray nozzles to perform daily checks of the air or 

water pressure to the spray nozzles pursuant to CAA Ssection 

112(d)(6). 

Finally, in our action promulgating Refinery NSPS Ja, we 

noted that, even with improved monitoring methods, periodic 

source testing is needed to verify the performance of the 

control system as it ages. In Refinery NSPS Ja, annual 

performance demonstrations are required for new sources. FCCU 

subject to Refinery MACT 2 as new sources would also be subject 

to Refinery NSPS Ja and would have to comply with the annual 

testing requirements in Refinery NSPS Ja. However, Refinery MACT 

2 does not include periodic performance tests for any FCCU. We 

considered adding an annual testing requirement for FCCU subject 

to Refinery MACT 2. The annual nationwide cost burden exceeds $1 

million per year and we project only modest improvement in 

control performance resulting from the performance 

demonstrations. We considered requiring FCCU performance tests 

once every 5 years (i.e., once per title V permit period). The 

nationwide annual cost of this additional testing requirement 

for FCCU is projected to be, on average, $213,000 per year. We 

consider this to be a reasonable minimum frequency for which 

affected sources should demonstrate direct compliance with the 

FCCU emission limits and that this cost is reasonable. 

Therefore, we propose that it is necessary, pursuant to CAA 
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Ssection 112(d)(6), to require a performance test once every 5 

years for all FCCU under to Refinery MACT 2. 

Organic HAP. Refinery MACT 2 uses CO as a surrogate for 

organic HAP and establishes an emission limit of 500 ppmv CO 

(dry basis). Some FCCU, referred to as complete-combustion FCCU, 

employ excess oxygen in the FCCU regenerator and are able to 

meet this emission limit without the need for a post-combustion 

device. Other FCCU, referred to as partial-combustion FCCU, do 

not supply enough air/oxygen for complete combustion of the coke 

to CO2 and, therefore, produce a significant quantity of CO in 

the regenerator exhaust. Partial-combustion FCCU are typically 

followed by a post-combustion unit, commonly referred to as a CO 

boiler, to burn the CO in the regenerator exhaust in order to 

meet the 500 ppmv CO limit (and to recover useful heat from the 

exhaust stream). 

In our review of Refinery NSPS J, we conducted a review of 

state and local regulations affecting refineries to identify 

control strategies to reduce CO emissions or VOC emissions from 

refinery sources (see Review of VOC Emission Sources at 

Refineries, December 14, 2005, Docket Item Number EPA-HQ-OAR2007-0011-0043). We also conducted a review of federal, state 

and local regulations affecting refineries to identify control 

strategies to reduce CO emissions from refinery sources (see 

Review of CO Emission Sources at Refineries, December 22, 2005, 
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Docket Item Number EPA-HQ-OAR-2007-0011-0044). We did not 

identify any developments in practices, processes and control 

technologies to reduce CO or VOC emissions from FCCU as part of 

the review of Refinery NSPS J, and we have not identified any 

developments in practices, processes and control technologies 

for FCCU that would reduce organic HAP since promulgation of 

Refinery MACT 2. We are proposing that it is not necessary to 

revise the regulatory provisions for organic HAP in the current 

MACT standards for FCCU, pursuant to CAA Ssection 112(d)(6). 

Inorganic HAP. As mentioned previously, Refinery MACT 2 

includes a CO emission limit of 500 ppmv. Although this limit is 

expressly provided as a limit addressing organic HAP emissions, 

this emission limit is also expected to limit the emissions of 

oxidizable inorganic HAP, such as HCN. That is, the CO 

concentration limit was developed as an indicator of complete 

combustion for all oxidizable pollutants typically found in 

exhaust gas from the FCCU regenerator operated in partial burn 

mode. We note that HCN concentrations in FCCU regenerator 

exhaust with high CO levels also have high HCN concentrations 

and that HCN concentrations in the regenerator exhaust from 

complete-combustion FCCU (those meeting the 500 ppmv CO limit 

without the need for a post-combustion device) are much lower 

than those from partial burn FCCU prior to a post-combustion 

device. Thus, we consider that the CO emission limit also acts 
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as a surrogate for the control of oxidizable inorganic HAP, such 

as HCN. 

The source test data from the ICR effort revealed that HCN 

emissions from FCCU are greater than previous tests indicated, 

particularly for complete-combustion FCCU. The increase in HCN 

emissions was observed at units meeting lower NOX emission 

limits, which have recently been required by consent decrees, 

state and local requirements and Refinery NSPS Ja. The higher 

HCN emissions from complete-combustion FCCU appear to be 

directly related to operational changes made in efforts to meet 

these lower NOX emission limits (e.g., reduced excess oxygen 

levels in the regenerator and reduced regenerator bed 

temperatures). These higher HCN emissions were only observed in 

complete-combustion FCCU; FCCU that operated in partial burn 

mode followed by a CO boiler or similar post-combustion device 

had significantly lower HCN emissions subsequent to the postcombustion device. 

Based on our review of the available ICR data and the 

technologies used in practice, we considered establishing 

specific emission limits for HCN. In order to comply with 

emission limits for HCN, owners or operators of completecombustion FCCU would either have to operate their FCCU 

regenerator at slightly higher temperatures and excess oxygen 

concentrations (to limit the formation of HCN in the 
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regenerator) or employ a post-combustion device or thermal 

oxidizer to destroy HCN exhausted from the FCCU regenerator. 

However, each of these options comes with significant secondary 

energy and environmental impacts. First, both of these control 

strategies would yield a significant increase in NOX emissions. 

We anticipate that most FCCU owners or operators would have to 

install a selective catalytic reduction (SCR) system to meet 

their NOX emission limits, if applicable. Operation of the SCR 

would have energy impacts and may have additional secondary PM2.5

impacts (associated with ammonia slip from the SCR). We expect 

that modifying the regenerator operating characteristics is the 

most cost-effective option, although installing and using a 

thermal oxidizer may be necessary, depending on the operational 

characteristics of the regenerator and the HCN control 

requirement. Using a thermal oxidizer to treat FCCU regenerator 

exhaust, a gas stream that has limited heating value (due to the 

already low CO concentrations) would be much more expensive and 

would have additional energy and secondary impacts associated 

with the auxiliary fuel needed for the device, as compared to 

modifying regenerator operating conditions. 

We first performed a screening analysis of the impacts of 

making only operational changes to the FCCU with the highest HCN 

concentrations. If this control option is not cost effective for 

these FCCU, it would not be cost effective for units that have 
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lower HCN concentrations and lower HCN emissions. Similarly, if 

operating changes in the FCCU regenerator alone are not cost 

effective, then we can assume that installing a thermal oxidizer 

to achieve this same level of HCN emission reductions would also 

not be cost effective. We calculated the cost of changing the 

regenerator parameters and adding an SCR for the FCCU with the 

highest HCN emissions rate reported in the ICR, which is an 

annual emissions rate of 460 tpy. This is also the largest FCCU 

in operation in the United States and its territories. Based on 

the size of this unit, we project that an SCR would be expected 

to cost approximately $13-million and have annualized costs of 

approximately $4.0-million/yr. Thus, if the HCN emissions can be 

reduced by 95 percent, the cost effectiveness would be 

approximately $9,000 per ton of HCN. A smaller FCCU had similar 

HCN concentrations and annual HCN emissions of 141 tpy. Based on 

the size of this unit, we project an SCR would be expected to 

cost approximately $7-million and have annualized costs of 

approximately $1.5-million/yr. Assuming a 95-percent reduction 

in HCN emissions, the cost effectiveness would be approximately 

$11,000 per ton of HCN. The second-highest emitting FCCU was 

larger than this unit, but had lower HCN concentrations. This 

third unit had emissions of 184 tpy. Based on the size of this 

unit, we expect that an SCR would cost approximately $9-million 

and have annualized costs of approximately $2.2-million/yr. 
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Assuming a 95-percent reduction in HCN emissions, the cost 

effectiveness would be approximately $12,600 per ton of HCN. 

These costs are for the FCCU with the largest HCN emissions 

and the lowest control cost (assuming operational changes alone 

are insufficient to significantly reduce HCN emissions), and the 

average cost effectiveness for these units exceeds $10,000 per 

ton HCN emissions reduced. Based on the economies of scale and 

considering lower HCN concentrations for all other units, the 

costs per ton of HCN removed for a nationwide standard would be 

higher. If a post-combustion device is needed to achieve a 

specific HCN emissions limit, the costs would be even higher. 

Based on the cost, secondary energy and secondary 

environmental impacts of an HCN emission limit beyond that 

achieved by the CO emission limit as a surrogate for HCN, we are 

proposing, at this time, that it is not necessary, pursuant to 

CAA Ssection 112(d)(6), to revise the MACT standard to establish 

a separate HCN standard. As our understanding of the mechanisms 

of HCN and NOX formation improves and as catalyst additives 

evolve, it may be possible to achieve both low NOX and low HCN 

emissions without the use of an SCR and/or post-combustion 

controls. However, at this time our test data indicate an 

inverse correlation between these two pollutants. The three 

facilities with the highest HCN concentrations were the 

facilities with the lowest NOX concentrations, all of which were 
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below 20 ppmv (dry basis, 0-percent excess air) during the 

performance tests. While a 20 ppmv NOX limit may be achievable, 

we anticipate that further reducing the NOX new source 

performance limits for FCCU would either increase PM2.5 secondary 

emissions (via the use of an SCR and its associated ammonia 

slip) or further increase HCN emissions (if combustion controls 

are used). 

b. CRU Process Vents 

A CRU is designed to reform (i.e., change the chemical 

structure of) naphtha into higher-octane aromatics. The 

reforming process uses a platinum or bimetal (e.g., platinum and 

rhenium) catalyst material. Small amounts of coke deposit on the 

catalyst during the catalytic reaction and this coke is burned 

off the catalyst to regenerate catalyst activity. There are 

three types of CRU classified by differences in how the units 

are designed and operated to effect reforming catalyst 

regeneration. Semi-regenerative reforming is characterized by 

shutting down the reforming unit at specified intervals, or at 

the operator’s convenience, for in situ catalyst regeneration. 

Semi-regenerative CRU typically regenerate catalyst once every 8 

to 18 months, with the regeneration cycle lasting approximately 

2 weeks. Cyclic-regeneration reforming is characterized by 

continuous or continual reforming operation with periodic (but 

frequent) regeneration of catalyst in situ by isolating one of 
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the reactors in the series, regenerating the catalyst, then 

returning the reactor to the reforming operation. The 

regeneration of the catalyst in a single reactor may occur 

numerous times per year (e.g., once a month), and the 

regeneration of each reactor may take 3 to 5 days to complete. 

Continuous-regeneration reforming units use moving catalyst bed 

reactors situated vertically (which is why they are often 

referred to as platforming units). Catalyst flows down the 

series of reactors. At the bottom of the last reactor, catalyst 

is continually isolated and sent to a special regenerator. After 

regeneration, the regenerated catalyst is continually fed to the 

first (top) reactor. Thus, continuous-regeneration reforming 

units are characterized by continuous-reforming operation along 

with continuous-regeneration operation. 

The catalytic reforming reaction is performed in a closed 

reactor system; there are no emissions associated with the 

processing portion of the CRU. There is a series of emission 

points associated with the CRU catalyst regenerator. Regardless 

of the type of CRU used, there is a series of steps conducted to 

effect catalyst regeneration. These steps are: (1) initial 

depressurization/purge; (2) coke burn-off; (3) catalyst 

rejuvenation; and (4) reduction/final purge. The primary 

emissions during the depressurization/purge cycle are organic 

HAP. Inorganic HAP, predominately HCl and chlorine, are emitted 
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during the coke burn-off and rejuvenation cycles. The reduction 

purge is mostly inert materials (nitrogen and/or hydrogen). 

Refinery MACT 2 contains organic HAP emission limits for the 

depressurization/purge cycle (purging prior to coke-burn-off) 

and inorganic HAP emission limits for the coke burn-off and 

catalyst rejuvenation cycles. Our technology review, summarized 

below, considers each of these emission limits separately. For 

additional details on the technology review for CRU, see 

Technology Review Memorandum for Catalytic Reforming Units at 

Petroleum Refineries in Docket ID Number EPA-HQ-OAR-2010-0682. 

Organic HAP. Refinery MACT 2 requires the owner or operator 

to comply with either a 98-percent reduction of TOC or nonmethane TOC, or an outlet concentration of 20 ppmv or less (dry 

basis, as hexane, corrected to 3-percent oxygen). The emission 

limits for organic HAP for the CRU do not apply to emissions 

from process vents during depressuring and purging operations 

when the reactor vent pressure is 5 psig or less. Control 

technologies used include directing the purge gas directly to 

the CRU process heater to be burned, recovering the gas to the 

facility’s fuel gas system, or venting to a flare or other APCD. 

The pressure limit exclusion was provided to allow atmospheric 

venting of the emissions when the pressure of the vessel fell 

below that needed to passively direct the purge gas to the APCD 

(most commonly the CRU process heater or flare). 
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We did not identify any developments in practices, 

processes and control technologies for reducing organic HAP 

emissions from CRU. However, as noted in Ssection IV.A.2 of this 

preamble, we are proposing to amend the pressure limit exclusion 

pursuant to CAA Ssections 112(d)(2) and (3) to clarify that this 

limit only applies during passive vessel depressuring. Also, as 

described in Ssection IV.A.3 of this preamble, we are proposing 

revisions to Refinery MACT 1 and 2, pursuant to CAA Ssections 

112(d)(2) and (3), to ensure flares used as APCD meet the 

required destruction efficiency, which includes flares used to 

control the organic HAP emissions from the CRU 

depressurization/purge vent streams. 

Inorganic HAP. Refinery MACT 2 uses HCl as a surrogate for 

inorganic HAP during the coke burn-off and rejuvenation cycles. 

Refinery MACT 2 requires owners or operators of existing semiregenerative CRU to reduce uncontrolled emissions of HCl by 92-

percent by weight or to a concentration of 30 ppmv (dry basis, 

corrected to 3-percent oxygen) during the coke burn-off and 

rejuvenation cycles. Owners or operators of new semiregenerative CRU, new or existing cyclic CRU, or new or existing 

continuous CRU are required to reduce uncontrolled emissions of 

HCl by 97-percent by weight or to a concentration of 10 ppmv 

(dry basis, corrected to 3-percent oxygen) during the coke burnoff and rejuvenation cycles. Technologies used to achieve these 
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limits include caustic spray injection, wet scrubbers, and solid 

adsorption systems. We conducted a technology review for CRU by 

reviewing the ICR responses and scientific literature. We did 

not identify any developments in practices, processes and 

control technologies for reducing inorganic HAP emissions from 

CRU. We are proposing that it is not necessary to revise the 

current inorganic HAP MACT standards for CRU, pursuant to CAA 

Ssection 112(d)(6). 

c. SRU Process Vents 

Most sulfur recovery plants at petroleum refineries use the 

Claus reaction to produce elemental sulfur. In the Claus 

reaction, two moles of hydrogen sulfide (H2S) react with one mole 

of SO2 in a catalytic reactor to form elemental sulfur and water 

vapor. Prior to the Claus reactors, one-third of the H2S in the 

sour gas feed to the sulfur plant must be oxidized to SO2 to have 

the correct proportion of H2S and SO2 for the Claus reaction. 

This oxidation step is performed in the “Claus burner.” The 

remaining gas stream, after the elemental sulfur is condensed, 

is referred to as “tail gas.” HAP emissions in tail gas from 

sulfur recovery plants are predominately COS and CS2, which are 

primarily formed as side reactions of the Claus process. 

Refinery MACT 2 contains HAP standards for SRU that were 

based on the Refinery NSPS J SO2 and reduced sulfur compounds 

emission limits. Refinery NSPS J includes an emission limit of 
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300 ppmv reduced sulfur compounds for a reduction control system 

not followed by an incinerator, and an emission limit of 250 

ppmv SO2 (dry basis, 0-percent excess air) for oxidative control 

systems or reductive control systems followed by incineration. 

These Refinery NSPS J limits apply only to Claus sulfur recovery 

plants with a sulfur recovery capacity greater than 20 long tons 

per day (LTD). These emission limits effectively required sulfur 

recovery plants to achieve 99.9-percent sulfur recovery. 

Refinery MACT 2 defines SRU as “a process unit that 

recovers elemental sulfur from gases that contain reduced sulfur 

compounds and other pollutants, usually by a vapor-phase 

catalytic reaction of sulfur dioxide and hydrogen sulfide (see 

40 CFR 63.1579).” This definition specifically excludes sulfur 

recovery processes that do not recover elemental sulfur, such as 

the LO-CAT II process, but does not necessarily limit 

applicability to Claus SRU. Refinery MACT 2 requires owners or 

operators of an SRU that is subject to Refinery NSPS J to meet 

the Refinery NSPS J limits. Owners or operators of an SRU that 

is not subject to Refinery NSPS J can elect to meet the emission 

limits in Refinery NSPS J or meet a reduced sulfur compound 

limit of 300 ppmv (dry basis, 0-percent excess air) regardless 

of the type of control system or the presence of an incinerator. 

Unlike Refinery NSPS J, Refinery MACT 2 does not have a capacity 

applicability limit, so this 300 ppmv reduced sulfur compound 
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limit is applicable to all SRU (as that term is defined), 

regardless of size. 

Upon completion of our technology review for Refinery NSPS 

J, we promulgated Refinery NSPS Ja, which includes new 

provisions for the sulfur recovery plant. First, Refinery NSPS 

Ja limits are now applicable to all sulfur recovery plants, not 

just Claus sulfur recovery plants. Second, emission limits were 

added for sulfur recovery plants with a capacity of 20 LTD or 

less, to require new, small sulfur recovery plants to achieve a 

target sulfur recovery efficiency of 99-percent. These limits 

are a factor of 10 higher than the emission limits for larger 

sulfur recovery plants (i.e., 3,000 ppmv reduced sulfur 

compounds for a reduction control system not followed by an 

incinerator and 2,500 ppmv SO2 for oxidative control systems or 

reductive control systems followed by incineration). Refinery 

NSPS J did not include emission limits for these smaller sulfur 

recovery plants. Third, new correlations were introduced to 

provide equivalent emission limits for systems that use oxygenenriched air in their Claus burner. 

The technology review conducted for Refinery NSPS J focused 

on SO2 emissions. Under our current technology review for 

Refinery MACT 2, we considered the developments in practices, 

processes or control technologies identified in the Refinery 
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NSPS J technology review as they pertain to HAP emissions and 

the existing Refinery MACT 2 requirements. 

We considered the new Refinery NSPS Ja limits for small 

sulfur recovery plants. While Refinery NSPS Ja establishes 

criteria pollutant emission limits for these smaller sulfur 

recovery plants that were previously unregulated for such 

emissions, these sources are already covered under Refinery MACT 

2. Refinery MACT 2 requires these SRU to meet a 300 ppmv reduced 

sulfur compound limit, which is more stringent than the 3,000 

ppmv limit established in Refinery NSPS Ja. 

We also considered the new correlations in Refinery NSPS Ja 

for SRU that use oxygen-enriched air in their Claus burner. In 

the technology review under Refinery NSPS J, we identified a 

change in practice in the operation of certain Claus SRU. At the 

time we promulgated Refinery MACT 2, we assumed that all units 

were using ambient air in the Claus burner, and we established 

the same emission limits as in Refinery NSPS J. Now, however, we 

understand that some facilities are using oxygen-enriched air. 

This practice lowers the amount of inert gases introduced into 

the SRU and improves operational performance and reliability of 

the sulfur recovery plant. Air is approximately 20.9 percent by 

volume oxygen and 79.1-percent inert gases (predominately 

nitrogen with 1-percent argon and other inert gases). The inert 

gases introduced in the Claus burner become a significant 
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portion of the overall tail gas flow. When oxygen enrichment is 

used in the Claus burner, there are fewer inert gases in the 

tail gas and a lower overall tail gas flow rate. The same molar 

flow rate of reduced sulfur compounds will be present in the 

tail gas, but without the additional flow of inerts from the 

ambient air, the concentration of the reduced sulfur compounds 

(or SO2) in the tail gas is higher. 

In developing Refinery NSPS Ja, we included a correlation 

equation that facilities can use to adjust the concentration 

limit based on the enriched-oxygen concentration used in the 

Claus burner. This equation is designed to allow the same mass 

of emissions for these units as is allowed for units using only 

ambient air. That is, the emission equation establishes a 

concentration limit for units using oxygen enrichment so that 

the mass emissions from the unit do not exceed the mass 

emissions allowed under the 250 ppmv SO2 (or 300 ppmv reduced 

sulfur compounds) emissions limits in Refinery NSPS J and in 

Refinery MACT 2. The new equation in Refinery NSPS Ja for large 

sulfur recovery plants (those with sulfur recovery greater than 

20 LTD) provides an equivalent mass emissions rate of reduced 

sulfur HAP from the SRU as is currently required in Refinery 

MACT 2 while allowing a practice that improves the operational 

reliability of the unit. There are no costs to providing this 

option for units using oxygen-enriched air because: (1) it is an 
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option that the owner or operator can elect to meet instead of 

the existing 250 ppmv SO2 emissions limit and (2) owners or 

operators of SRU that use oxygen-enriched air are expected to 

already routinely monitor the inlet air oxygen concentration for 

operational purposes. Therefore, we are proposing that it is 

necessary, pursuant to CAA Ssection 112(d)(6), to amend Refinery 

MACT 2 sulfur recovery requirements to include this equation 

that addresses the use of oxygen-enriched air as a development 

in practice in SRU process operations. 

The emission limits for large sulfur recovery plants (those 

with sulfur recovery greater than 20 LTD) in Refinery NSPS Ja 

are equivalent to those in Refinery MACT 2. We are proposing to 

allow owners or operators subject to Refinery NSPS Ja limits for 

sulfur recovery plants with a capacity greater than 20 LTD to 

comply with Refinery NSPS Ja as a means of complying with 

Refinery MACT 2. 

We have not identified any additional developments in 

practices, processes or control technologies for HAP from SRU 

since development of Refinery NSPS Ja. 

C. What are the results of the risk assessment and analyses? 

1. Inhalation Risk Assessment Results 

Table 10 of this preamble provides an overall summary of 

the results of the inhalation risk assessment. 
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Table 10. Petroleum Refining Source Sector Inhalation Risk 

Assessment Results 

Maximum 

Individual 

Cancer Risk 

(-in-1 million)a

Estimated 

Population at 

Increased Risk 

Levels of 

Cancer 

Estimated 

Annual Cancer 

Incidence 

(cases per 

year) 

Maximum 

Chronic 

Non-cancer 

TOSHIb

Maximum 

Screening 

Acute Noncancer HQc

Actual Emissions 

60 

≥ 1-in-1 

million: 

5,000,000 

≥ 10-in-1 

million: 

100,000 

≥ 100-in-1 

million: 0 

0.3 0.9 

HQREL = 5 

(Nickel 

Compounds) 

Allowable Emissionsd

100 

≥ 1-in-1 

million: 

7,000,000e

≥ 10-in-1 

million: 

Greater than 

90,000e

≥ 100-in-1 

million: 0 

0.6 <1 - 

a

 Estimated maximum individual excess lifetime cancer risk due to HAP 

emissions from the source category. 

b

 Maximum TOSHI. The target organ with the highest TOSHI for the Petroleum 

Refining source sector is the thyroid system for actual emissions and the 

neurological system for allowable emissions. 

c

 The maximum off-site HQ acute value of 5 is driven by emissions of nickel 

from CCU. See Ssection III.A.3 of this preamble for explanation of acute 

dose-response values. Acute assessments are not performed on allowable 

emissions because of a lack of detailed hourly emissions data. However, 

because of the conservative nature of the actual annual to actual hourly 

emissions rate multiplier, allowable acute risk estimates will be comparable 

to actual acute estimates. 

d

 The development of allowable emission estimates can be found in the memo 

entitled Refinery Risk Estimates for Modeled “Allowable” Emissions, which can 

be found in Docket ID Number EPA-HQ-OAR-2010-0682. 

e

 Population risks from allowable emissions were only calculated for the model 

plant emissions (REM) approach. For the 138 facilities modeled using the 

modeled plant approach the population risks greater than 10-in-1 million was 

estimated to be 90,000. If we consider the second approach to determining 

allowable emissions (combined the results of the actual and REM emissions 

estimates) we estimate that the allowable population risks greater than 10-

in-1 million would be greater than 90,000 people. Further, the number of 
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people above 1-in-1 million would also be higher than the 7,000,000 estimated 

using the REM model. 

The inhalation risk modeling performed to estimate risks 

based on actual emissions relied primarily on emissions data 

from the ICR, updated based on our quality assurance review as 

described in Ssection III.A.1 of this preamble. 

The results of the chronic baseline inhalation cancer risk 

assessment indicate that, based on estimates of current actual 

emissions, the maximum individual lifetime cancer risk (MIR) 

posed by the refinery source category is 60-in-1 million, with 

benzene and naphthalene emissions from equipment leaks and 

storage tanks accounting for 98 percent of the MIR risk. The 

total estimated cancer incidence from refinery emission sources 

based on actual emission levels is 0.3 excess cancer cases per 

year or one case in every 3.3 years, with emissions of 

naphthalene, benzene, and 2-methylnaphthalene contributing 22 

percent, 21 percent and 13 percent, respectively, to this cancer 

incidence. In addition, we note that approximately 100,000 

people are estimated to have cancer risks greater than 10-in-1 

million, and approximately 5,000,000 people are estimated to 

have risks greater than 1-in-1 million as a result of actual 

emissions from these source categories. When considering the 

MACT-allowable emissions, the maximum individual lifetime cancer 
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risk is estimated to be up to 100-in-1 million, driven by 

emissions of benzene and naphthalene from refinery fugitives 

(e.g., storage tanks, equipment leaks and wastewater) and the 

estimated cancer incidence is estimated to be 0.6 excess cancer 

cases per year or one excess case in every 1.5 years. Greater 

than 90,000 people were estimated to have cancer risks above 10-

in-1 million and approximately 7,000,000 people were estimated 

to have cancer risks above 1-in-1 million considering allowable 

emissions from all petroleum refineries. 

The maximum modeled chronic non-cancer HI (TOSHI) value for 

the source sector based on actual emissions was estimated to be 

less than 1. When considering MACT-allowable emissions, the 

maximum chronic non-cancer TOSHI value was also estimated to be 

less thanabout 1. 

2. Acute Risk Results 

Our screening analysis for worst-case acute impacts based 

on actual emissions indicates the potential for five pollutants 

– acetaldehyde, acrolein, arsenic, benzene and nickel - to 

exceed an HQ value of 1, with an estimated worst-case maximum HQ 

of 5 for nickel based on the REL values. This REL occurred at a 

facility reporting nickel emissions from the FCCU vent. One 

hundred thirty -six (136) of the 142 petroleum refineries had an 

estimated worst-case HQ less than or equal to 1 for all HAP; 

except for the one facility that had an estimated REL of 5, the 
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remaining five5 refineries with an REL above 1 had an estimated 

worst-case HQ less than or equal to 3. 

To better characterize the potential health risks 

associated with estimated worst-case acute exposures to HAP, and 

in response to a key recommendation from the SAB’s peer review 

of EPA’s RTR risk assessment methodologies, we examine a wider 

range of available acute health metrics than we do for our 

chronic risk assessments. This is in acknowledgement that there 

are generally more data gaps and inconsistencies in acute 

reference values than there are in chronic reference values. By 

definition, the acute CalEPA REL represents a health-protective 

level of exposure, with no risk anticipated below those levels, 

even for repeated exposures; however, the health risk from 

higher-level exposures is unknown. Therefore, when a CalEPA REL 

is exceeded and an AEGL-1 or ERPG-1 level is available (i.e., 

levels at which mild effects are anticipated in the general 

public for a single exposure), we have used them as a second 

comparative measure. Historically, comparisons of the estimated 

maximum off-site 1-hour exposure levels have not been typically 

made to occupational levels for the purpose of characterizing 

public health risks in RTR assessments. This is because 

occupational ceiling values are not generally considered 

protective for the general public since they are designed to 

protect the worker population (presumed healthy adults) for 
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short-duration (less than 15-minute) increases in exposure (less 

than 15 minutes). As a result, for most chemicals, the 15-minute 

occupational ceiling values are set at levels higher than a 1-

hour AEGL-1, making comparisons to them irrelevant unless the 

AEGL-1 or ERPG-1 levels are also exceeded. Such is not the case 

when comparing the available acute inhalation health effect 

reference values for some of the pollutants considered in this 

analysis. 

The worst-case maximum estimated 1-hour exposure to 

acetaldehyde outside the facility fence line for the source 

categories is 1 mg/m3

. This estimated worst-case exposure exceeds 

the 1-hour REL by a factor of 2 (HQREL=2) and is well below the 

1-hour AEGL-1 (HQAEGL-1=0.01) and the ERPG-1 (HQERPG-1=0.05). 

The worst-case maximum estimated 1-hour exposure to 

acrolein outside the facility fence line for the source 

categories is 0.005 mg/m3

. This estimated worst-case exposure 

exceeds the 1-hour REL by a factor of 2 (HQREL=2) and is below 

the 1-hour AEGL-1 (HQAEGL-1=0.1) and the ERPG-1 (HQERPG-1=0.04). 

The worst-case maximum estimated 1-hour exposure to nickel 

compounds outside the facility fence line for the source 

categories is 0.001 mg/m3

. This estimated worst-case exposure 

exceeds the 1-hour REL by a factor of 5 (HQREL=5). There are no 

AEGL, ERPG or short-term occupational values for nickel to use 

as comparison to the acute 1-hour REL value. 
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The worst-case maximum estimated 1-hour exposure to arsenic 

compounds outside the facility fence line for the source 

categories is 0.0004 mg/m3

. This estimated worst-case exposure 

exceeds the 1-hour REL by a factor of 2 (HQREL=2). There are no 

AEGL, ERPG or short-term occupational values for arsenic to use 

as comparison to the acute 1-hour REL value. 

The maximum estimated 1-hour exposure to benzene outside 

the facility fence line is 2.7 mg/m3

. This estimated exposure 

exceeds the REL by a factor of 2 (HQREL=2), but is significantly 

below both the 1-hour ERPG-1 and AEGL-1 value (HQ ERPG-1 (or 

AEGL-1) = 0.02). This exposure estimate neither exceeds the 

AEGL-1/ERPG-1 values, nor does it exceed workplace ceiling level 

guidelines designed to protect the worker population for short -

duration (<15 minute) exposure (less than 15 minutes) to 

benzene, as discussed below. The occupational short-term 

exposure limit (STEL) standard for benzene developed by the 

Occupational Safety and Health Administration is 16 mg/m3

, “as 

averaged over any 15-minute period.”33 Occupational guideline 

STEL for exposures to benzene have also been developed by the 

American Conference of Governmental Industrial Hygienists 

 

33 29 CFR 1910.1028, Benzene. Available online at 

http://www.osha.gov/pla/oshaweb/owadisp.show_document?p_table=STANDARD&p_id=1

0042.
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(ACGIH)34 for less than 15 minutes35 (ACGIH threshold limit value 

(TLV) – STEL value of 8.0 mg/m3

), and by the National Institute 

for Occupational Safety and Health (NIOSH)36 “for any 15 minute 

period in a work day” (NIOSH REL – STEL of 3.2 mg/m3

). These 

shorter duration occupational values indicate potential concerns 

regarding health effects at exposure levels below the 1-hour 

AEGL-1 value. 

All other HAP and facilities modeled had worst-case acute 

HQ values less than 1, indicating that they carry no 

potentialthe HAP emissions are believed to posebe without 

appreciable risk of acute concernshealth effects. In 

characterizing the potential for acute non-cancer impactsrisks

of concern, it is important to remember the upward bias of these 

exposure estimates (e.g., worst-case meteorology coinciding with 

a person located at the point of maximum concentration during 

the hour) and to consider the results along with the 

conservative estimates used to develop hourly emissions as 

described earlier, as well as the screening methodology. Refer 

 

34 ACGIH (2001) Benzene. In Documentation of the TLVs® and BEIs® with Other 

Worldwide Occupational Exposure Values. ACGIH, 1300 Kemper Meadow Drive, 

Cincinnati, OH 45240 (ISBN: 978-1-882417-74-1) and available online at 

http://www.acgih.org. 

35 The ACGIH definition of a TLV-STEL states that “Exposures above the TLV-TWA 

up to the TLV-STEL should be less than 15 minutes, should occur no more than 

four times per day, and there should be at least 60 minutes between 

successive exposures in this range.” 

36 NIOSH. Occupational Safety and Health Guideline for Benzene; 

http://www.cdc.gov/niosh/74-137.htmldocs/81-123/pdfs/0049.pdf.
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to the memo in the docket for this rulemaking (Docket ID Number 

EPA-HQ-OAR-2010-0682, Derivation of hourly emission rates for 

petroleum refinery emission sources used in the acute risk 

analysis) for a detailed description of how the hourly emissions 

were developed for this source sector. 

3. Multipathway Risk Screening Results 

Results of the worst-case Tier I screening analysis 

indicate that PB-HAP emissions (based on estimates of actual 

emissions) from several facilities in this source sector exceed 

the screening emission rates for POM (PAH), CDDF, mercury 

compounds, and cadmium compounds. For the compounds and 

facilities that did not screen out at Tier I, we conducted a 

Tier II screen. The Tier II screen replaces some of the 

assumptions used in Tier I with site-specific data, including 

the land use around the facilities, the location of fishable 

lakes, and local wind direction and speed. The Tier II screen 

continues to rely on high-end assumptions about consumption of 

local fish and locally grown or raised foods (adult female 

angler at 99th consumption for fish37 and 90th percentile for 

consumption of locally grown or raised foods38) and uses an 

 

37 Burger, J. 2002. Daily consumption of wild fish and game: Exposures of high 

end recreationists. International Journal of Environmental Health Research 

12:343-354 

38 U.S. EPA. Exposure Factors Handbook 2011 Edition (Final). U.S. 

Environmental Protection Agency, Washington, DC, EPA/600/R-09/052F, 2011. 
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assumption that the same individual consumes each of these foods 

in high end quantities (i.e., that an individual has high end 

ingestion rates for each food). The result of this analysis was 

the development of site-specific emission screening 

thresholdslevels for POM, CDDF, mercury compounds, and cadmium 

compounds. It is important to note that, even with the inclusion 

of some site-specific information in the Tier II analysis, the 

multi-pathway screening analysis is a still a very conservative, 

health-protective assessment (e.g., upper-bound consumption of 

local fish, locally grown, and/or raised foods) and in all 

likelihood will yield results that serve as an upper-bound 

multi-pathway risk associated with a facility. 

While the screening analysis is not designed to produce a 

quantitative risk result, the factor by which the emissions 

exceed the thresholdscreening value serves as a rough gauge of 

the “upper-limit” risks we would expect from a facility. Thus, 

for example, if a facility emitted a PB-HAP carcinogen at a 

level 2 times the screening thresholdvalue, we can say with a 

high degree of confidence that the actual maximum cancer risks 

will be less than 2-in-1 million. Likewise, if a facility 

emitted a noncancer PB-HAP at a level 2 times the screening 

level, the maximum noncancer risks would represent a HQ less 

than 2. The high degree of confidence comes from the fact that 
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the screens are developed using the very conservative (healthprotective) assumptions that we describe above. 

Based on the Tier II screening analysis, one facility emits 

cadmium compounds above the Tier II screening level and exceeds 

that level by about a factor of 2. Twenty-three facilities emit 

CDDF as 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalent 

(TEQ) above the Tier II screening level, and the facility with 

the highest emissions of dioxins exceeds the Tier II screening 

level by about a factor of 40. No facilities emit mercury 

compounds above the Tier II screening levels. Forty-four 

facilities emit POM as benzo(a)pyrene TEQ above the Tier II 

screening level, and the facility with the highest emissions of 

POM as benzo(a)pyrene TEQ exceeds its screening level by a 

factor of 30. 

Polychlorinated biphenyls (PCB) are PB-HAP that do not 

currently have multi-pathway screening values and so are not 

evaluated for potential non-inhalation risks. These HAP, 

however, are not emitted in appreciable quantities (0.001 tpy) 

from refinery operations, and we do not believe they contribute 

to multi-pathway risks for this source category. 

Results of the analysis for lead indicate that the maximum 

annual off-site ambient lead concentration was only 2 percent of 

the NAAQS for lead, and even if the total annual emissions 

occurred during a 3-month period, the maximum 3-month rolling 
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average concentrations would still be less than 8 percent of the 

NAAQS, indicating that there is no concern for multi-pathway 

risks due to lead emissions. 

4. Refined Multipathway Case Study 

To gain a better understanding of the uncertainty 

associated with the multipathway Tier I and II screening 

analysis, a refined multipathway case study using the TRIM.Fate 

model was conducted for a single petroleum refinery. The site, a 

refinery in St. John the Baptist Parish, Louisiana, was selected 

based upon its close proximity to nearby lakes and farms as well 

as having one of the highest potential multipathway risks for 

PAH based on the Tier II analysis. The refined analysis for this 

facility showed that the Tier II screen for each pollutant overpredicted the potential risk when compared to the refined 

analysis results. For this site, the Tier II screen for mercury 

indicated that mercury emissions were 3 times lower than the 

screening thresholdvalue, indicating a potential maximum HQ for 

mercury of 0.3. In the refined analysis, the potential HQ was 

0.04 or about 7 times lower than that predicted by the Tier II 

screen. For cadmium emissions, the Tier II screen for this 

facility indicated that cadmium emissions were about 20 times 

lower than the screening thresholdvalue, indicating a potential 

maximum HQ for mercury of 0.05. The results of the refined 

analysis for the selected site in Louisiana show a maximum 
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cadmium HQ of 0.02 or about 3 times lower than that predicted by 

the Tier II screen. For PAH emissions, the site selected for the 

refined analysis had PAH emissions 20 times the PAH Tier II 

screening thresholdvalue, indicating a potential cancer risk of 

20-in-1 million. When the more refined analysis was conducted 

for this site, the potential cancer risks were estimated to be 

2-in-1 million or about 14 times lower than predicted by the 

Tier II analysis. Finally, for the facility selected for the 

refined assessment, the emissions of CDDF as 2,3,7,8-

tetrachlorodibenzo-p-dioxin TEQ are 5 times higher than the 

dioxin Tier II screening thresholdvalue, indicating a potential 

maximum cancer risk of 5–in-1 million. In the refined 

assessment, the cancer risk from dioxins was estimated to be 2-

in-1 million, about one-third of the estimate from the Tier II 

screen. 

Overall, the refined analysis predicts a potential lifetime 

cancer risk of 4-in-1 million to the maximum most exposed 

individual (MIR). The non-cancer HQ is predicted to be well 

below 1 for all target organs. The chronic inhalation cancer 

risk assessment estimated inhalation cancer risk around this 

same facility to be approximately 10-in-1 million, due in large 

part to emissions of naphthalene and 2-methylnaphthalene (both 

non-persistent, bioaccumulative, and toxic (PBT) HAP). Thus, 

although highly unlikely, if around this facility the person 
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with the highest chronic inhalation cancer risk is also the same 

person with the highest individual multipathway cancer risk, 

then the combined, worst-case MIR for that facility could 

theoretically be 10-in-1 million (risk estimates are expressed 

as 1 significant figure). 

While this refined assessment was performed on only a 

single facility, the results of this single refined analysis 

indicate that if refined analyses were performed for other 

sites, the risk estimates would consistently be lower than those 

estimated by the Tier II analysis. In addition, the risks 

predicted by the multipathway analyses at most facilities are 

considerably lower than the risk estimates predicted by the 

inhalation assessment, indicating that the inhalation risk 

results are in all likelihood the primary factor in our residual 

risk determination for this source category. 

Further details on the site-specific case study can be 

found in Appendix 10 of the Draft Residual Risk Assessment for 

the Petroleum Refining Source Sector, which is available in 

Docket ID Number EPA-HQ-OAR-2010-0682. 

5. Environmental Risk Screening Results 

As described in the Draft Residual Risk Assessment for the 

Petroleum Refining Source Sector, which is available in Docket 

ID Number EPA-HQ-OAR-2010-0682, we conducted an environmental 

risk screening assessment for the petroleum refineries source 
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category. In the Tier I screening analysis for PB-HAP (other 

than lead, which was evaluated differently, as noted in Ssection 

III.A.6 of this preamble), the individual modeled Tier I 

concentrations for one facility in the source category exceeded 

some of the ecological benchmarks for mercury. In addition, Tier 

I modeled concentrations for four facilities exceeded sediment 

and soil ecological benchmarks for PAH. Therefore, we conducted 

a Tier II assessment. 

In the Tier II screening analysis for PB-HAP, none of the 

individual modeled concentrations for any facility in the source 

category exceeded any of the ecological benchmarks (either the 

LOAEL or NOAEL). 

For lead compounds, we did not estimate any exceedances of 

the secondary lead NAAQS. Therefore, we did not conduct further 

assessment for lead compounds. 

For acid gases, the average modeled concentration around 

each facility (i.e., the average concentration of all off-site 

data points in the modeling domain) did not exceed any 

ecological benchmark. In addition, for both HCL and HF, each 

individual concentration (i.e., each off-site data point in the 

modeling domain) was below the ecological benchmarks for all 

facilities. 
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6. Facility-Wide Risk Results 

Table 11 of this preamble displays the results of the 

facility-wide risk assessment. 

Table 11. Petroleum Refining Facility-Wide Risk Assessment 

Results 

Number of facilities analyzed 142 

Cancer Risk: 

Estimated maximum facility-wide individual cancer risk 

(-in-1 million) 

70 

Number of facilities with estimated facility-wide 

individual cancer risk of 10-in-1 million or more 

54 

Number of petroleum refining operations contributing 50 

percent or more to facility-wide individual cancer risk of 

10-in-1 million or more 

50 

Number of facilities with facility-wide individual cancer 

risk of 1-in-1 million or more 

115 

Number of petroleum refining operations contributing 50 

percent or more to facility-wide individual cancer risk of 

1-in-1 million or more 

107 

Chronic Non-cancer Risk: 

Maximum facility-wide chronic non-cancer TOSHI 4 

Number of facilities with facility-wide maximum non-cancer 

TOSHI greater than 1 

5 

Number of petroleum refining operations contributing 50 

percent or more to facility-wide maximum non-cancer TOSHI 

of 1 or more 

0 

The maximum individual cancer whole-facility risk from all 

HAP emissions at any petroleum refinery is estimated to be 70-

in-1 million, based on actual emissions. Of the 142 facilities 

included in this analysis, 54 have facility-wide maximum 

individual cancer risks of 10-in-1 million or greater. At the 

majority of these facilities (50 of 54), the petroleum refinery 

operations account for over 50 percent of the risk. 
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There are 115 facilities with facility-wide maximum 

individual cancer risks of 1-in-1 million or greater. At the 

majority of these facilities (107 of 115), the petroleum 

refinery operations account for over 50 percent of the risk. The 

facility-wide maximum individual chronic non-cancer TOSHI is 

estimated to be 4, based on actual emissions. Of the 142 

refineries included in this analysis, five have a TOSHI value 

greater than 1. The highest non-cancer TOSHI results from 

emissions of chlorine from cooling towers. In each case, the 

petroleum refinery operations account for less than 20 percent 

of the TOSHI values greater than 1. 

Additional detail regarding the methodology and the results 

of the facility-wide analyses are included in the risk 

assessment documentation (Draft Residual Risk Assessment for the 

Petroleum Refining Source Sector), which is available in the 

docket for this rulemaking (Docket ID Number EPA-HQ-OAR-2010-

0682). 

7. What demographic groups might benefit from this regulation? 

To examine the potential for any environmental justice 

issues that might be associated with the source categories, we 

performed a demographic analysis of the population close to the 

facilities. In this analysis, we evaluated the distribution of 

HAP-related cancer and non-cancer risks from petroleum 

refineries across different social, demographic, and economic 
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groups within the populations living near facilities identified 

as having the highest risks. The methodology and the results of 

the demographic analyses are included in a technical report, 

Draft Risk and Technology Review – Analysis of Socio-Economic 

Factors for Populations Living Near Petroleum Refineries, 

available in the docket for this action (Docket ID Number EPAHQ-OAR-2010-0682). 

The results of the demographic analysis are summarized in 

Table 12 of this preamble. These results, for various 

demographic groups, are based on the estimated risks from actual 

emissions levels for the population living within 50 km of the 

facilities. 

Table 12. Petroleum Refining Demographic Risk Analysis Results 

 Nationwide 

Population with 

Cancer Risk at or 

Above 1-in-1 

Million 

Population with 

Chronic Hazard 

Index Above 1 

Total Population 312,861,265 5,204,234 0 

Race by Percent 

White 72 50 0 

All Other Races 28 50 0 

Race by Percent 

White 72 50 0 

African American 13 28 0 

Native American 1 1 0 

Other and 

Multiracial 14 21 0 

Ethnicity by Percent 

Hispanic 17 29 0 

Non-Hispanic 83 71 0 

Income by Percent 

Below Poverty 

Level 14 21 0 
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Above Poverty 

Level 86 79 0 

Education by Percent 

Over 25 and 

without High 

School Diploma 

15 23 0 

Over 25 and with 

a High School 

Diploma 

85 77 0 

The results of the demographic analysis indicate that 

emissions from petroleum refineries expose approximately 

5,000,000 people to a cancer risk at or above 1-in-1 million. 

The percentages of the at-risk population in each demographic 

group (except for White and non-Hispanic) are similar to or 

lower than their respective nationwide percentages. 

Implementation of the provisions included in this proposal is 

expected to reduce the number of people estimated to have a 

cancer risk greater than 1-in-1 million due to HAP emissions 

from these sources from 5,000,000 people to about 4,000,000. Our 

analysis of the demographics of the population within 50 km of 

the facilities indicates potential disparities in certain 

demographic groups, including the African American, Other and 

Multiracial, Hispanic, Below the Poverty Level, and Over 25 

without a High School Diploma. The population living within 50 

km of the 142 petroleum refineries has a higher percentage of 

minority, lower income and lower education persons when compared 

to the nationwide percentages of those groups. For example, 50 
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percent are in one or more minority demographic group, compared 

to 28 percent nationwide. As noted above, approximately 

5,000,000 people currently living within 50 km of a petroleum 

refinery have a cancer risk greater than 1-in-1 million. Thus, 

weWe would expect that half of those people are in one or more 

minority demographic groups. 

Because minority groups make up a large portion of the 

population living near refineries, as compared with their 

representation nationwide, those groups would similarly see a 

greater benefit from the implementation of the controls proposed 

in this rule, if finalized. For example, we estimate that after 

implementation of the controls proposed in this action (i.e., 

post-controls), about 1,000,000 fewer people will be exposed to 

cancer risks greater than 1-in-1 million (i.e., 4,000,000 

people). Further, we estimate that approximately 500,000 people 

no longer exposed to a cancer risk greater than 1-in-1 million 

would be in a minority demographic group. The post-control risk 

estimates are discussed further in Ssection III.A.5 of this 

preamble. 

Although the EPA’s proposed fenceline monitoring 

requirement is intended to ensure that owners and operators 

monitor, manage and, if necessary, reduce fugitive emissions are 

controlled as expected by the MACT standards, it isof HAP, we

also expected the collected fenceline data to help the EPA 
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understand and identify emissions of benzene and other fugitives 

emissions that are impacting communities in close proximity to 

the facility. While currently-available emissions and monitoring 

data do not indicate that risks to nearby populations are 

unacceptable (see Ssection IV.D.1 of this preamble), we 

recognize that the collection of additional data through routine 

fenceline monitoring can provide important information to 

communities concerned with potential risks associated with 

emissions from fugitive sources. We note that the data we are 

proposing to collect on a semiannual basis may include 

exceedances of the fenceline action level that a facility could 

have addressed or could still be actively addressing at the time 

of the report. As noted in sSection IV.B.1.h of this preamble, 

directly monitoring fugitive emissions from each potential 

emissions source at the facility is impractical. Fenceline 

monitoring offers a cost-effective alternative for monitoring 

fugitive emissions from the entire facility. The EPA’s proposal 

to require the electronic reporting of fenceline monitoring data 

on a regularsemiannual basis (i.e., every 2 weeks) will ensure 

that communities have access to data on benzene levels near the 

facility, which is directly relevant to the potential health 

risks posed by the facility. In light of the disproportionate 

number of some minority and low-income groups exposed to 

refinery emissions, the fenceline monitoring information is 
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particularly relevant to these communities. The proposed 

requirements for fenceline monitoring and corrective action when 

fugitive emissions from a facility exceed the specified 

corrective action level will serve as an important backstop to 

protect the health of the populations surrounding the facility, 

including minority and low-income populations. 

D. What are our proposed decisions regarding risk acceptability, 

ample margin of safety and adverse environmental effects? 

1. Risk Acceptability 

As noted in Ssection II.A.1 of this preamble, the EPA sets 

standards under CAA Ssection 112(f)(2) using “a two-step 

standard-setting approach, with an analytical first step to 

determine an ‘acceptable risk’ that considers all health 

information, including risk estimation uncertainty, and includes 

a presumptive limit on maximum individual lifetime risk (MIR) of 

approximately 1 in 10 thousand[39].” (54 FR 38045, September 14, 

1989). 

In this proposal, we estimate risks based on actual 

emissions from petroleum refineries. We also estimate risks from 

allowable emissions; as discussed earlier, we consider our 

analysis of risk from allowable emissions to be conservative and 

as such to represent an upper bound estimate on risk from 

 

39 1-in-10 thousand is equivalent to 100-in-1 million. The EPA currently 

describes cancer risks as ‘n-in-1 million’. 
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emissions allowed under the current MACT standards for the 

source categories. 

a. Estimated Risks from Actual Emissions 

The baseline inhalation cancer risk to the individual most 

exposed to emissions from sources regulated by Refinery MACT 1 

and 2 is 60-in-1 million based on actual emissions. The 

estimated incidence of cancer due to inhalation exposures is 0.3 

excess cancer cases per year, or 1 case every 3.3 years. 

Approximately 5,000,000 people face an increased cancer risk 

greater than 1-in-1 million due to inhalation exposure to actual 

HAP emissions from these source categories, and approximately 

100,000 people face an increased risk greater than 10-in-1 

million and up to 60-in-1 million. The agency estimates that the 

maximum chronic non-cancer TOSHI from inhalation exposure is 0.9 

due to actual emissions of HCN from FCCU. 

The screening assessment of worst-case acute inhalation 

impacts from actual emissions indicates the potential for five 

pollutants – nickel, arsenic, acrolein, benzene and acetaldehyde 

- to exceed an HQ value of 1, with an estimated worst-case 

maximum HQ of 5 for nickel based on the REL values. One hundred 

thirty-six of the 142 petroleum refineries had an estimated 

worst-case HQ less than or equal to 1 for all HAP. One facility 

had an estimated worst-case maximum HQ of 5 and the remaining 

five refineries with an HQ above 1 had an estimated worst-case 
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HQ less than or equal to 3. Considering the conservative, 

health-protective nature of the approach that is used to develop 

these acute estimates, it is highly unlikely that an individual 

would have an acute exposure above the REL. Specifically, the 

analysis is based on the assumption that worst-case emissions 

and meteorology would coincide with a person being at this exact 

location for a period of time long enough to have an exposure 

level above the conservative REL value. 

The Tier II multipathway screening analysis of actual 

emissions indicated the potential for PAH emissions that are 

about 30 times the screening level for cancer, dioxin and furans 

emissions that are about 40 times the cancer thresholdscreening 

level and cadmium emissions that are about 2 times the 

thresholdscreening level for non-cancer health effects. No 

facility’s emissions were above the thresholdscreening level for 

mercury. As we note above, the Tier II multipathway screen is 

conservative in that it incorporates many health-protective 

assumptions. For example, we choose inputs from the upper end of 

the range of possible values for the influential parameters used 

in the Tier II screen and we assume that the exposed individual 

exhibits ingestion behavior that would lead to a high total 

exposure. A Tier II exceedance cannot be equated with a risk 

value or a HQ or HI. Rather, it represents a high-end estimate 

of what the risk or hazard may be. For example, an exceedance of 
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2 for a non-carcinogen can be interpreted to mean that we have 

high confidence that the HI would be lower than 2. Similarly, an 

exceedance of 30 for a carcinogen means that we have high 

confidence that the risk is lower than 30-in-1-million. Our 

confidence comes from the conservative, or health-protective, 

assumptions that are used in the Tier II screen. 

The refined analysis that we conducted for a specific 

facility showed that the Tier II screen for each pollutant overpredicted the potential risk when compared to the refined 

analysis results. That refined multipathway assessment showed 

that the Tier II screen resulted in estimated risks that are 

higher than the risks estimated by the refined analysis by 14 

times for PAH, 3 times for dioxins and furans, and 3 times for 

cadmium. The refined assessment results indicate that the 

multipathway risks are considerably lower than the estimated 

inhalation risks, and our refined multipathway analysis 

indicates that multipathway risks are low enough that, while 

they are considered in our proposed decisions, they do not weigh 

heavily into those decisions because risks for the source 

category are driven by inhalation. 

b. Estimated Risks from Allowable Emissions 

We estimate that the baseline inhalation cancer risk to the 

individual most exposed to emissions from sources regulated by 

Refinery MACT 1 and 2 is up toas high as 100-in-1 million based 
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on allowable emissions. The EPA estimates that the incidence of 

cancer due to inhalation exposures could be up toas high as 0.6 

excess cancer cases per year, or 1 case approximately every 1.5 

years. About 7,000,000 people face an increased cancer risk 

greater than 1-in-1 million due to inhalation exposure to 

allowable HAP emissions from these source categories, and 

greater than 90,000 people face an increased risk greater than 

10-in-1 million, and up toas high as 100-in-1 million. Further, 

we estimate that the maximum chronic non-cancer TOSHI from 

inhalation exposure values at all refineries is less than 1 

based on allowable emissions. 

The baseline risks summarized above do not account for 

additional risk reductions that we anticipate due to the MACT 

standards or the technology review requirements we are proposing 

in this action. 

c. Acceptability Determination 

In determining whether risk is acceptable, the EPA 

considered all available health information and risk estimation 

uncertainty as described above. As noted above, the agency 

estimated risk from actual and allowable emissions. While there 

are uncertainties associated with both the actual and allowable 

emissions, we consider the allowable emissions to be an upper 

bound, based on the conservative methods we used to calculate 

allowable emissions. 
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The results indicate that both the actual and allowable 

inhalation cancer risks to the individual most exposed are no 

greater than approximately 100–in-1 million, which is the 

presumptive limit of acceptability. The MIR based on actual 

emissions is 60-in-1 million, a little more than 50approximately 

60 percent of the presumptive limit. Based on the results of the 

refined site-specific multipathway analysis summarized above and 

described in Ssection IV.C.3 of this preamble, we also conclude 

that the ingestion cancer risk to the individual most exposed is 

significantly less than 100-in-1 million. In addition, the 

maximum chronic non-cancer TOSHI due to inhalation exposures is 

less than 1, and our refined multipathway analysis indicates 

that non-cancer ingestion risk isrisks are estimated to be less 

significant than non-cancer risk from inhalation. Finally, the 

evaluation of acute non-cancer risks was very conservative, and 

showed acute risks below a level of concern. 

In determining risk acceptability, we also evaluated 

population impacts because of the large number of people living 

near facilities in the source category. The analysis indicates 

that there are approximately 5 million people exposed to actual 

emissions resulting in a cancer risk greater than 1-in-1 

million, and a substantially smaller number of people (100,000) 

are exposed to a cancer risk of greater than 10-in-1 million but 

less than 100-in-1 million (with a maximum risk of 60-in-1 
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million). The inhalation cancer incidence is approximately one 

case in every 3 years based on actual emissions. More detail on 

this risk analysis is presented in Ssection IV.C and summarized 

in Tables 10 and 11 of this preamble. The results of the 

demographic analysis for petroleum refineries indicate that a 

greater proportion of certain minority groups and low-income 

populations live near refineries than the national demographic 

profile. More detail on these population impacts areis presented 

in Ssection IV.C.7 of this preamble. We did not identify any 

sensitivity to riskspollutants emitted from these source 

categories particular to minority and low income populations

from pollutants emitted from these source categories. 

Considering the above information, we propose that the risks 

remaining after implementation of the existing NESHAP for the 

Refinery MACT 1 and 2 source categories is acceptable for all 

proximate populations. 

We also note that the estimated baseline risks for the 

refineries source categories include risks from emissions from 

DCUs, which are a previously unregulated emission source. As 

discussed in section IV.A. of this preamble, we are proposing 

new MACT standards for these sources that would reduce emissions 

of HAP by 850 TPYtpy. We estimate that these new standards would 

not affect the MIR, but would reduce the source category cancer 

incidence by 15 percent. 
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We solicit comment on all aspects of our proposed 

acceptability determination. We note that while we are proposing 

that the risks estimated from actual and allowable emissions are 

acceptable, the risks based on allowable emissions are at the 

high endpresumptive limit of the rangeacceptable risk. 

Furthermore, a significant number of people live in relative 

proximity to refineries across the country, and therefore a 

large population is exposed to the risks we estimate heregreater 

than 1-in-1 million. In particular, we solicit comment on the 

methodology used to estimate allowable emissions. As noted 

above, we consider the allowable emissions to be an upper bound 

estimate based on the conservative methods used to calculate 

such emissions. We recognize, however, that some of the health 

information concerning allowable emissions arguably borders on 

the edge of acceptability. Specifically, the analysis of 

allowable analysisemissions resulted in a MIR of 100-in-1 

million, which is the presumptive limit of acceptability, a 

large number of people (7,000,000) estimated to be exposed at a 

cancer risk above 1-in-1 million, and an estimated high cancer 

incidence (one case approximately every 1.5 years). Although we 

believe that our allowable emissions represent an upper end 

estimate, we nonetheless solicit comment on whether the health 

information currently before the Agency should be deemed 

unacceptable. We also solicit comment on whether our allowable 
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emissions analysis reflects a reasonable estimate of emissions 

allowed under the current MACT standards. Lastly, we solicit 

comment on the acceptability of risk considering individuals’ 

potential cumulative inhalation and ingestion pathway exposure. 

Please provide comments and data supporting your position. Such 

information will aid the Agency to make an informed decision on 

risk acceptability as it moves forward with this rulemaking. 

2. Ample Margin of Safety 

We next considered whether the existing MACT standards 

provide an ample margin of safety to protect public health. In 

addition to considering all of the health risks and other health 

information considered in the risk acceptability determination, 

in the ample margin of safety analysis we evaluated the cost and 

feasibility of available control technologies and other measures 

that could be applied in these source categories to further 

reduce the risks due to emissions of HAP. For purposes of the 

ample margin of safety analysis, we evaluated the changes in 

risk that would occur through adoption of a specific technology 

by looking at the changes to the risk due to actual emissions. 

Due to the nature of the allowable risk analysis, which is based 

on model plants and post processing to combine risk results40, we 

 

40 As described in the memorandum entitled “Refinery Emissions and Risk 

Estimates for Modeled “Allowable” Emissions, available in Docket EPA-HQ-OAR2010-0682, the use of model plants and post-processing was for the purpose of 

Formatted: Underline
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did not evaluate the risk reductions resulting from applying 

controls toreducing allowable emissions at individual emission 

sources. Such an approach would require an unnecessarily 

complex analysis that would not provide any more useful 

information. Therefore, for purposes of the ample margin of 

safety, we evaluated the changes in risk that would occur 

through adoption of a specific technology by looking at the 

changes to the risk due to actual emissions. than the analysis 

we undertook using actual emissions. We note that while we did 

not conduct a specific analysis for allowable emissions, it is 

reasonable to expect reductions in risk similar to those for 

actual emissions. 

As noted in our discussion of the technology review in 

Ssection IV.B of this preamble, we identified a number of 

developments in practices, processes or control technologies for 

reducing HAP emissions from petroleum refinery processes. As 

part of the risk review, we evaluated these developments to 

determine if any of them could reduce risks and whether it is 

necessary to require any of these developments to provide an 

ample margin of safety to protect public health. 

We evaluated the health information and control options for 

all of the emission sources located at refineries, including: 

 

ensuring that our analysis would provide a conservative estimate of actual 

emissions and thus a conservative estimate of risk. 
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storage vessels, equipment leaks, gasoline loading racks, marine 

vessel loading operations, cooling towers/heat exchange systems, 

wastewater collection and treatment, FCCU, flares, miscellaneous 

process vents, CRU and SRU. For each of these sources, we 

considered chronic cancer and non-cancer risk metrics as well as 

acute risk. Regarding our ample margin of safety analyses for 

chronic non-cancer risk for the various emission sources, we 

note that the baseline HI isTOSHIs are less than 1 for the 

entire source category and significantlyconsiderably less than 1 

for all of the emission sources except for the FCCU (which had 

an TOSHI slightly less than 1of 0.9). Therefore, we did not 

quantitatively evaluate reductions in the chronic non-cancer 

TOSHI for sources other than FCCU in the ample margin of safety 

analysis. Regarding our ample margin of safety analyses for 

acute risk for all of the various emission sources, we note that 

our analyses did not identify acute risks at a level of concern 

and, therefore, we did not quantitatively evaluate reductions in 

the acute HQ values for each individual emission source in the 

ample margin of safety analysis. Accordingly, the following 

paragraphs focus on cancer risk in the determination of whether 

the standards provide an ample margin of safety to protect 

public health. 

For storage vessels, as discussed in Ssection IV.B of this 

preamble, we identified and evaluated three control options. 
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Under the technology review, we determined that two of the 

options, which we call options 1 and 2, are cost effective. We 

are proposing option 2, which includes all of the requirements 

of option 1, as part of the technology review. The option 2 

controls that we are proposing under the technology review would 

result in approximately 910 tpy reduction in HAP (a 40-percent 

reduction from this emission source). As described in Ssection 

IV.B of this preamble, not only are these controls cost 

effective, but we estimate a net cost savings because the 

emission reductions translate into reduced product loss. These 

controls would reduce the cancer risk to the individual most 

exposed from 60-in-1 million to 50-in-1 million based on actual 

emissions at the facility where storage tank emissions were 

driving the risk. However, the MIR remains unchanged for the 

refinery source categories, at 60-in 1-million, because the 

facility with the next highest cancer risk is 60-in-1 million 

and this risk is driven by another emission source. The option 

2 controls also would reduce cancer incidence by approximately 2 

percent. Finally, we estimate that the option 2 controls reduce 

the number of people with a cancer risk greater than 10-in-1 

million storage tanks from 3,000 to 60 and reduce the number of 

people with a cancer risk greater than 1-in-1 million from 

storage tanks from 140,000 to 72,000. Since these controls 

reduce cancer incidence, and reduce the number of people exposed 
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to cancer risks greater than 1-in-10 million and 1-in-1 million 

from storage tank emissions, and are cost effective, we propose 

that these controls are necessary to provide an ample margin of 

safety to protect public health. We also evaluated one 

additional control option for storage vessels, option 3, which 

incorporated both options 1 and 2 along with additional 

monitoring requirements. We estimate incremental HAP emission 

reductions (beyond those provided by option 2) of 90 tpy. The 

incremental cost effectiveness for option 3 exceeds $60,000 per 

ton, which we do not consider cost effective. In addition, the 

option 3 controls do not result in quantifiable reductions in 

the cancer risk to the individual most exposed or the cancer 

incidence beyond the reductions estimated for the option 2 

controls. For these reasons, we propose that it is not necessary 

to require the option 3 controls in order to provide an ample 

margin of safety to protect public health. 

For equipment leaks, we identified and evaluated three 

control options discussed previously in the technology review 

section of this preamble (Ssection IV.B). These options are: o 

 Option 1 - monitoring and repair at lower leak 

definitions; o 

 Option 2 - applying monitoring and repair requirements to 

connectors; and o 
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 Option 3 - optical gas imaging and repair. 

We estimate that these three independent control options 

reduce industry-wide emissions of organic HAP by 24 tpy, 86 tpy, 

and 24 tpy, respectively. We estimate that none of the control 

options would reduce the risk to the individual most exposed. We 

also estimate that the cancer incidence would not change 

perceptively if these controls were required. Finally, we 

estimate that the control options do not reduce the number of 

people with a cancer risk greater than 10-in-1 million or the 

number of people with a cancer risk greater than 1-in-1 million. 

As discussed above, the available control options for equipment 

leaks do not provide quantifiable risk reductions and, 

therefore, we propose that these controls are not necessary to 

provide an ample margin of safety. 

For gasoline loading racks, we identified and evaluated one 

control option discussed previously in the technology review 

section of this preamble (Ssection IV.B). As discussed earlier, 

this option is a new development that results in emissions that 

are higher than the current level required under Refinery MACT 

1. Since we estimate that no emission reductions would result 

from this new technology and thus no reduction in risk, we 

propose that this control option is not necessary to provide an 

ample margin of safety. 
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For marine vessel loading operations, we identified and 

evaluated two control options discussed previously in the 

technology review section of this preamble (Ssection IV.B). The 

first option would be to require submerged fill for small and 

offshore marine vessel loading operations. Based on actual 

emissions, we project no HAP emission reductions for this 

option, as all marine vessels that are used to transport bulk 

refinery liquids are expected to already have the required 

submerged fill pipes. Accordingly, we do not project any changes 

in risk. While we are proposing this option under the technology 

review, because the option is not projected to reduce emissions 

or risk, we propose that a submerged loading requirement is not 

necessary to provide an ample margin of safety. We also 

identified and evaluated the use of add-on controls for gasoline 

loading at small marine vessel loading operations. In the 

technology review, we rejected this control option because the 

cost effectiveness exceeded $70,000 ton of HAP reduced. We 

estimate that this option would not result in quantifiable 

changes to any of the risk metrics. Because add-on controls 

would not result in quantifiable risk reductions and we do not 

consider the controls to be cost effective, we are proposing 

that add-on controls for gasoline loading at small marine vessel 

loading operations are not necessary to provide an ample margin 

of safety. 
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For cooling towers and heat exchangers, we did not identify 

as part of our technology review any developments in processes, 

practices or controls beyond those that we considered in our 

beyond-the-floor analysis at the time we set the MACT standards. 

We note that we issued MACT standards for heat exchange systems 

in a final rule on October 28, 2009 (74 FR 55686), but existing 

sources were not required to comply until October 29, 2012. As a 

result, the reductions were not reflected in the inventories 

submitted in response to the ICR for refineries and therefore 

were not included in our risk analysis based on actual 

emissions. We estimate that these MACT standards will result in 

an industry-wide reduction of over 600 tons HAP per year (or 85 

percent). The projected contribution to risk associated with 

cooling tower emissions after implementation of these MACT 

standards for heat exchange systems is approximately 1 percent. 

Because we did not identify any control options beyond those 

required by the current standards for cooling towers and heat 

exchange systems, we are proposing that additional controls for 

these systems are not necessary to provide an ample margin of 

safety. 

For wastewater collection and treatment systems, we 

identified and evaluated three options for reducing emissions. 

We estimate implementing these independent control options would 

result in emission reductions of 158 tpy (4 percent), 549 tpy 
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(15 percent), and 929 tpy (25 percent), respectively. None of 

the control options would reduce the cancer risk to the 

individual most exposed from 60-in-1 million. Option 1 would 

reduce the cancer incidence by less than 1 percent, and we 

expect any reduction in cancer incidence that would result from 

options 2 or 3 to be small because this source accounts for 

about 10 percent of the cancer incidence from refineries as a 

whole and the most stringent control option would reduce 

emissions from these source by only 25 percent. Finally, we 

estimate that control option 1 would not reduce the number of 

people with a cancer risk greater than 10-in-1 million or the 

number of people with a cancer risk greater than 1-in-1 million. 

We expect any changes to the number of people with a cancer risk 

greater than 1-in-1 million from implementation of options 2 or 

3 to be small for the same reasons mentioned above for cancer 

incidence. We estimate the cost effectiveness of these options 

to be $26,600 per ton, $52,100 per ton, and $54,500 per ton of 

organic HAP reduced, and we do not consider any of these options 

to be cost effective. Because of the very small reductions in 

risk and the lack of cost-effective control options, we propose 

that these controls are not necessary to provide an ample margin 

of safety. 

For FCCU, we did not identify any developments in 

processes, practices or control technologies for organic HAP. 
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For inorganic HAP from FCCU, in the technology review, we 

identified and evaluated one control option for an HCN emissions 

limit and one control option for a PM emissions limit. The PM 

limit was adopted for new sources in Refinery NSPS Ja as part of 

our review of Refinery NSPS J. We considered the costs and 

emission reductions associated with requiring existing sources 

to meet the new source level for PM under Refinery NSPS Ja 

(i.e., 0.5 g PM/kg of coke burn-off rather than 1.0 g PM/kg). As 

indicated in our promulgation of Refinery NSPS Ja, the cost 

effectiveness of lowering the PM limit for existing sources to 

the level we are requiring for new sources was projected to be 

$21,000 per ton of PM reduced (see 73 FR 35845, June 24, 2008). 

Based on the typical metal HAP concentration in PM from FCCU, 

the cost effectiveness of this option for HAP metals is 

approximately $1 million per ton of HAP reduced. We estimate 

that this control option would not reduce the cancer risk to the 

individual most exposed, would not change the cancer incidence, 

and would not change the number of people with estimated cancer 

risk greater than 1-in-1 million or 10-in-1 million. For the HCN 

emissions limit, we evaluated the costs of controlling HCN using 

combustion controls in combination with SCR. The cost 

effectiveness of this option was approximately $9,000 per ton of 

HCN. This control option would reduce the non-cancer HI from 0.9 

to 0.8 and would not change any of the cancer risk metrics. 
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Based on the cost effectiveness of these options and the limited 

reduction in cancer and non-cancer risk (the non-cancer risk is 

below a level of concern based on the existing standards), we 

propose that additional controls for FCCU are not necessary to 

provide an ample margin of safety. 

Flares are used as APCD to control emissions from several 

emission sources covered by Refinery MACT 1 and 2. In this 

proposed rule, under CAA Ssections 112(d)(2) and (3), we are 

proposing operating and monitoring requirements to ensure flares 

achieve the 98-percent HAP destruction efficiency identified as 

the MACT Floor in the initial MACT rulemaking in 1995. Flares 

are critical safety devices that effectively reduce emissions 

during startup, shutdown, and process upsets or malfunctions. In 

most cases, flares are the only means by which emissions from 

pressure relief devices can be controlled. Thus, we find that 

properly-functioning flares act to reduce HAP emissions, and 

thereby risk, from petroleum refinery operations. The changes to 

the flare requirements that we are proposing under the 

technology reviewCAA sections 112(d)(2) and (3) will result in 

sources meeting the level required by the original standards, 

and we did not identify any control options that would further 

reduce the HAP emissions from flares. Therefore, we are 

proposing that additional controls for flares are not necessary 

to provide an ample margin of safety. 
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For the remaining emission sources within the Refinery MACT 

1 and Refinery MACT 2 source categories, including miscellaneous 

process vents, CRU, and SRU, we did not identify any 

developments in processes practices and control technologies. 

Therefore, we are proposing that additional controls for these 

three Refinery MACT 1 and 2 emission sources are not necessary 

to provide an ample margin of safety. 

In summary, we propose that the original Refinery MACT 1 

and 2 MACT standards, along with the proposed requirements for 

storage vessels described above, provide an ample margin of 

safety to protect public health. We are specifically requesting 

comment on whether there are additional control measures for 

emission sources subject to Refinery MACT 1 and Refinery MACT 2 

that are necessary to provide an ample margin of safety to 

protect public health. In particular, we are requesting that 

states identify any controls they have already required for 

these facilities, controls they are currently considering, or 

other controls of which they may be aware. 

While not part of our decisions regarding residual risk, we 

note that DCU are an important emission source with respect to 

risk from refineries. As described in Ssection IV.A of this 

preamble, we are proposing new MACT standards under CAA 

Ssections 112(d)(2) and (3) for DCU. For informational purposes, 

we also looked at the risk reductions that would result from 
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implementation of those standards. We estimate no reduction in 

the cancer risk to the individual most exposed and a decrease in 

cancer incidence of 0.05 cases per year, or approximately 15 

percent. While our decisions on risk acceptability and ample 

margin of safety are supported even in the absence of these 

reductions, if we finalize the proposed requirements for DCU, 

they would further strengthen our conclusions that risk is 

acceptable withthe standards provide an ample margin of safety 

to protect public health. 

3. Adverse Environmental Effects 

We conducted an environmental risk screening assessment for 

the petroleum refineries source category for lead, mercury, 

cadmium, PAH, dioxins and furans, HF, and HCl. For mercury, 

cadmium, PAH, and dioxins and furans, none of the individual 

modeled concentrations for any facility in the source category 

exceeded any of the Tier II ecological benchmarks (either the 

LOAEL or NOAEL). For lead, we did not estimate any exceedances 

of the secondary lead NAAQS. For HF and HCl, the average modeled 

concentration around each facility (i.e., the average 

concentration of all off-site data points in the modeling 

domain) did not exceed any ecological benchmark. Based on these 

results, EPA proposes that it is not necessary to set a more 

stringent standard to prevent, taking into consideration costs, 
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energy, safety, and other relevant factors, an adverse 

environmental effect.

E. What other actions are we proposing? 

We are proposing the following changes to Refinery MACT 1 

and 2 as described below: (1) revising the startup, shutdown, 

and malfunction (SSM) provisions in order to ensure that the 

subparts are consistent with the court decision in Sierra Club 

Vv. EPA, 551 F. 3d 1019 (D.C. Cir. 2008), which vacated two 

provisions that exempted sources from the requirement to comply 

with otherwise applicable Ssection 112(d) emission standards 

during periods of SSM; (2) adding a definitionproposing to 

clarify leak detection requirements related to open-ended valves 

or lines; (3) adding electronic reporting requirements in 

Refinery MACT 1 and 2; and (4) updating the General Provisions 

cross-reference tables. 

1. SSM and Affirmative Defense

In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 

(D.C. Cir. The2008), the United States Court of Appeals for the 

District of Columbia Circuit vacated portions of two provisions 

in the EPA’s CAA Ssection 112 regulations governing the 

emissions of HAP during periods of SSM. Sierra Club V. EPA, 551 

F.3d 1019 (D.C. Cir. 2008), cert. denied, 130 S. Ct. 1735 (U.S. 

2010). Specifically, the Court vacated the SSM exemption 

contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), holding 
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that under Ssection 302(k) of the CAA, emissions standards or 

limitations must be continuous in nature and that the SSM 

exemption violates the CAA's requirement that some Ssection 112 

standards apply continuously. 

We are proposing the elimination of the SSM exemption in 40 

CFR part 63, subparts CC and UUU. Consistent with Sierra Club 

Vv. EPA, the EPA iswe are proposing standards in these rules 

that apply at all times. We are also proposing several revisions 

to Table 6 of subpart CC of 40 CFR part 63 and to Table 44 to 

subpart UUU of 40 CFR part 63 (the General Provisions 

Applicability tables for each subpart) as explained in more 

detail below. For example, we are proposing to eliminate the 

incorporation of the General Provisions’ requirement that the 

source develop an SSM plan. We also are proposing to eliminate 

and revise certain recordkeeping and reporting requirements 

related to the SSM exemption as further described below. 

The EPA has attempted to ensure that the provisions we are 

proposing to eliminate are inappropriate, unnecessary, or 

redundant in the absence of the SSM exemption. We are 

specifically seeking comment on whether we have successfully 

done so. 

In proposing the standards in this rule, the EPA has taken 

into account startup and shutdown periods and, for the reasons 

explained below, we are proposing alternate standards for those 
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periods for a few select emission sources. We expect facilities 

can meet nearly all of the emission standards in Refinery MACT 1 

and 2 during startup and shutdown, including the amendments we 

are proposing in this action. For most of the emission sources, 

APCD are operating prior to process startup and continue to 

operate through process shutdown. 

For Refinery MACT 1 and 2, we identified three emission 

sources for which specific startup and shutdown provisions may 

be needed. First, as noted above, most APCD used to control 

metal HAP emissions from FCCU under Refinery MACT 2 (e.g., wet 

scrubber, fabric filter, cyclone) would be operating before 

emissions are routed to them and would be operating during 

startup and shutdown events in a manner consistent with normal 

operating periods, such that the monitoring parameter operating 

limits set during the performance test are maintained and met. 

However, we recognize that there are safety concerns associated 

with operating an ESP during startup of the FCCU, as described 

in the following paragraphs. Therefore, we are proposing 

specific PM standards for startup of FCCU controlled with an ESP 

under Refinery MACT 2. 

During startup of the FCCU, “torch oil” (heavy oil 

typically used as feed to the unit via the riser) is injected 

directly into the regenerator and burned to raise the 

temperature of the regenerator and catalyst to levels needed for 
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normal operation. Given the poor mixing of fuel and air in the 

regenerator during this initial startup, it is difficult to 

maintain optimal combustion characteristics, and high CO 

concentrations are common. Elevated CO levels pose an explosion 

threat due to the high electric current and potential for sparks 

within the ESP. Consequently, it is common practice to bypass 

the ESP during startup of the FCCU. Once torch oil is shut off 

and the regenerator is fueled by catalyst coke burn-off, the CO 

levels in the FCCU regenerator off-gas will stabilize and the 

gas can be sent to the ESP safely. 

When the ESP is offline, the operating limits for the ESP 

are meaningless. During much of the startup process, either 

catalyst is not circulating between the FCCU regenerator and 

reactor or the catalyst circulation rate is much lower than 

during normal operations. While the catalyst is not circulating 

or is circulating at reduced rates, the PM and metal HAP 

emissions are expected to be much lower than during normal 

operations. Therefore, the cyclone separators that are internal 

to the FCCU regenerator should provide reasonable PM control 

during this initial startup. To ensure the internal cyclones are 

operating efficiently, we are proposing that FCCU using an ESP 

as the APCD meet a 30-percent opacity limit (on a 6-minute 

rolling average basis) during the period that torch oil is used 

during FCCU startup. This opacity limit was selected because it 
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has been used historically to assess compliance with the PM 

emission limit for FCCU in Refinery NSPS J and because the 

emission limit can be assessed using manual opacity readings, 

eliminating the need to install a COMS. We note that Refinery 

NSPS J includes the exception for one 6-minute average of up to 

60-percent opacity in a 1-hour period primarily to accommodate 

soot blowing events. As no soot blowing should be performed 

prior to the ESP coming on-line, we are not including this 

exception to the proposed 30-percent opacity limit during 

startup for FCCU that are controlled by an ESP. 

Second, for emissions of organic HAP from FCCU under 

Refinery MACT 2, we also expect that APCD would be operating 

before emissions are routed to them, and would be operating 

during startup and shutdown events in a manner consistent with 

normal operating periods, such that the monitoring parameter 

operating limits set during the performance test are maintained 

and met. However, many FCCU operate in “complete combustion” 

mode without a post-combustion device. In other words, for FCCU 

without a post-combustion device, organic HAP are controlled by 

the FCCU itself, so there is no separate APCD that could be 

operating during startup and demonstrating continuous compliance 

with the monitoring parameter operating limits. Therefore, we 

are proposing specific CO standards for startup of FCCU without 

a post-combustion device under Refinery MACT 2. 
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As mentioned previously, “torch oil” is injected directly 

into the regenerator and burned during FCCU startup to raise the 

temperature of the regenerator and catalyst to levels needed for 

normal operation. During this period, CO concentrations often 

will exceed the 500 ppm emissions limit due to the poor mixing 

of fuel and air in the regenerator. The emissions limit is based 

on CO emissions, as a surrogate for organic HAP emissions, and 

the emission limit is evaluated using a 1-hour averaging period. 

This 1-hour averaging period does not provide adequate time for 

short-term excursions that occur during startup to be offset by 

lower emissions during normal operational periods. 

Based on available data during normal operations, ensuring 

adequate combustion (indicated by CO concentration levels below 

500 ppmv) minimizes organic HAP emissions. Low levels of CO in 

the exhaust gas are consistently achieved during normal 

operations when oxygen concentrations in the exhaust gas exceed 

1-percent by volume (dry basis). Thus, maintaining an adequate 

level of excess oxygen for the combustion of fuel in the FCCU is 

expected to minimize organic HAP emissions. Emissions of CO 

during startup result from a series of reactions with the fuel 

source and are dependent on mixing, local oxygen concentrations, 

and temperature. While the refinery owner or operator has direct 

control over air blast rates, CO emissions may not always 

directly correlate with the air blast rate. Exhaust oxygen 
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concentrations are expected to be more directly linked with air 

blast rates and are, therefore, more directly under control of 

the refinery owner or operator. We are proposing an excess 

oxygen concentration of 1 volume percent (dry basis) based on a 

1-hour average during startup. We consider the 1-hour averaging 

period for the oxygen concentration in the exhaust gas from the 

FCCU to be appropriate during periods of FCCU startup because 

air blast rates can be directly controlled to ensure adequate 

oxygen supply on a short-term basis. 

Third, we note that the SRU is unique in that it 

essentially is the APCD for the fuel gas system at the facility. 

The SRU would be operating if the refinery is operating, 

including during startup and shutdown events. There are 

typically multiple SRU trains at a facility. Different trains 

can be taken off-line as sour gas production decreases to 

maintain optimal operating characteristics of the operating SRU 

during startup or shutdown of a set of process units. Thus, the 

sulfur recovery plant is expected to run continuously and would 

only shut down its operation during a complete turnaround or 

shutdown of the facility. For these limited situations, the 12-

hour averaging time provided for the SRU emissions limitation 

under Refinery MACT 2 may not be adequate time in which to shut 

down the unit without exceeding the emissions limitation. 
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Therefore, we are proposing specific standards for SRU during 

periods of shutdown. 

We note also that, for SRU subject to Refinery NSPS J or 

electing to comply with Refinery NSPS J as provided in Refinery 

MACT 2, the emissions limit is in terms of SO2 concentration for 

SRU with oxidative control systems or reductive control systems 

followed by an incinerator. While the SO2 concentration limit 

provides a reasonable proxy of the reduced sulfur HAP emissions 

during normal operations, it does not necessarily provide a good 

indication of reduced sulfur HAP emissions during periods of 

shutdown. During periods of shutdown, the sulfur remaining in 

the unit is purged and combusted generally in a thermal oxidizer 

or a flare. Although the sulfur loading to the thermal oxidizer 

during shutdown may be higher than during normal operations 

(thereby causing an increase in the SO2 concentration and 

exceedance of the SO2 emissions limitation), appropriate 

operation of the thermal oxidizer will adequately control 

emissions of reduced sulfur HAP. Thus, during periods of 

shutdown, the 300 ppmv reduced sulfur compound emission limit 

alternative (provided for SRU not subject to Refinery NSPS J) is 

a better indicator of reduced sulfur HAP emissions. In Refinery 

MACT 2, SRU that elect to comply with the 300 ppmv reduced 

sulfur compound emission limit (i.e., those not subject to 

Refinery NSPS J or electing to comply with Refinery NSPS J) and 
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that use a thermal incinerator for sulfur HAP control are 

required to maintain a minimum temperature and excess oxygen 

level (as determined through a source test of the unit) to 

demonstrate compliance with the reduced sulfur compound emission 

limitation. 

In Refinery MACT 2, SRU subject to Refinery NSPS J (or that 

elect to comply with Refinery NSPS J) that use an incinerator to 

control sulfur HAP emissions are required to install an SO2 CEMS 

to demonstrate compliance with the SO2 emission limitation. For 

these units, it is impractical to require installation of a 

reduced sulfur compound monitor or to require a source test to 

establish operating parameters during shutdown of the SRU 

because of the few hours per year that the entire series of SRU 

trains are shutdown. Although the autoignition temperature of 

COS is unknown, based on the autoignition temperature of CS2

(between 200 and 250 °F) and the typical operating 

characteristics of thermal oxidizers used to control emissions 

from SRU, we are proposing that, for periods of SRU shutdown, 

diverting the purge gases to a flare meeting the design and 

operating requirements in 40 CFR 63.670 (or, for a limited 

transitional time period, 40 CFR 63.11) or to a thermal oxidizer 

operated at a minimum temperature of 1200 °F and a minimum 

outlet oxygen concentration of 2 volume percent (dry basis). We 

believe that this provides adequate assurance of compliance with 
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the 300 ppmv reduced sulfur compound emission limitation for SRU 

because incineration at these temperatures was determined to be 

the MACT floor in cases where no tail gas treatment units were 

used (i.e., units not subject to Refinery NSPS J). 

For all other emission sources, we believe that the 

requirements that apply during normal operations should apply 

during startup and shutdown. For Refinery MACT 1, these emission 

sources include process vents, transfer operations, storage 

tanks, equipment leaks, heat exchange systems, and wastewater. 

Emission reductions for process vents and transfer operations, 

such as gasoline loading racks and marine tank vessel loading, 

are typically achieved by routing vapors to thermal oxidizers, 

carbon adsorbers, absorbers and flares. It is common practice to 

start an APCD prior to startup of the emissions source it is 

controlling, so the APCD would be operating before emissions are 

routed to it. We expect APCD would be operating during startup 

and shutdown events in a manner consistent with normal operating 

periods, and that these APCD will be operated to maintain and 

meet the monitoring parameter operating limits set during the 

performance test. We do not expect startup and shutdown events 

to affect emissions from equipment leaks, heat exchange systems, 

wastewater, or storage tanks. Leak detection programs associated 

with equipment leaks and heat exchange systems are in place to 

detect leaks, and, therefore, it is inconsequential whether the 
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process is operating under normal operating conditions or is in 

startup or shutdown. Wastewater emissions are also not expected 

to be significantly affected by startup or shutdown events 

because the control systems used can operate while the 

wastewater treatment system is in startup or shutdown. Working 

and breathing losses from storage tanks are the same regardless 

of whether the process is operating under normal operating 

conditions or if it is in a startup or shutdown event. Degassing 

of a storage tank is common for shutdown of a process; the 

residual emissions in a storage tank are vented as part of the 

cleaning of the storage tank. We evaluated degassing controls as 

a control alternative for storage vessels and do not consider 

these controls to be cost effective (see memorandum Survey of 

Control Technology for Storage Vessels and Analysis of Impacts 

for Storage Vessel Control Options, Docket Item Number EPA-HQOAR-2010-0871-0027). Based on this review, we are not proposing 

specific standards for storage vessels during startup or 

shutdown. 

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 and monitoring equipment, process equipment or 

a process to operate in a normal or usual manner * * *” ((see 40 
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CFR 63.2). The EPA has determined that CAA Ssection 112 does not 

require that emissions that occur during periods of malfunction 

be factored into development of Ssection 112 standards. Under 

Ssection 112, emissions standards for new sources must be no 

less stringent than the level “achieved” by the best-controlled 

similar source and for existing sources generally must be no 

less stringent than the average emission limitation “achieved” 

by the best-performing 12 percent of sources in the category. 

There is nothing in Ssection 112 that directs the EPA to 

consider malfunctions in determining the level “achieved” by the 

best-performing or best-controlled sources when setting emission 

standards. Moreover, whileAs the D.C. Circuit has recognized, 

the phrase “average emissions limitation achieved by the best 

performing 12 percent of” sources “says nothing about how the 

performance of the best units is to be calculated.” Nat'l Ass'n 

of Clean Water Agencies v. EPA, 734 F.3d 1115, 1141 (D.C. Cir. 

2013). While the EPA accounts for variability in setting 

emissions standards consistent with the Section 112 case law, 

nothing in that case lawsection 112 requires the EPA to consider 

malfunctions as part of that analysis. Section 112 uses the 

concept of “best controlledA malfunction should not be treated 

in the same manner as the type of variation in performance that 

occurs during routine operations of a source. A malfunction is a 

failure of the source to perform in a “normal or usual manner” 
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and “best performing” unit in defining the level of stringency 

that Section 112 performance no statutory language compels EPA 

to consider such events in setting standards must meet. Applying 

the concept of “best controlled” or “best performing” to a unit 

that is malfunctioning presents significant difficulties, as 

malfunctions are sudden and unexpected events.based on “best 

performers.”

Further, accounting for malfunctions in setting emissions 

standards would be difficult, if not impossible, given the 

myriad different types of malfunctions that can occur across all 

sources in the category, and given the difficulties associated 

with predicting or accounting for the frequency, degree, and 

duration of various malfunctions that might occur. As such, the 

performance of units that are malfunctioning is not “reasonably” 

foreseeable. See, e.g., Sierra Club Vv. EPA, 167 F. 3d 658, 662 

(D.C. Cir. 1999) (the EPA typically has wide latitude in 

determining the extent of data-gathering necessary to solve a 

problem. We generally defer to an agency’s decision to proceed 

on the basis of imperfect scientific information, rather than to 

“invest the resources to conduct the perfect study.”). See also, 

Weyerhaeuser Vv. Costle, 590 F.2d 1011, 1058 (D.C. Cir. 1978) 

(“In the nature of things, no general limit, individual permit, 

or even any upset provision can anticipate all upset situations. 

After a certain point, the transgression of regulatory limits 
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caused by ‘uncontrollable acts of third parties,’ such as 

strikes, sabotage, operator intoxication or insanity, and a 

variety of other eventualities, must be a matter for the 

administrative exercise of case-by-case enforcement discretion, 

not for specification in advance by regulation.”). In addition, 

the goalemissions during a malfunction event can be 

significantly higher than emissions at any other time of a bestcontrolled or best-performing source is to operate in such a way 

as to avoid malfunctions of the sourceoperation, and thus, 

accounting for malfunctions in setting standards could lead to 

standards that are significantly less stringent than levels that 

are achieved by a well-performing non-malfunctioning source. It 

is reasonable to interpret section 112 to avoid such a result. 

The EPA’s approach to malfunctions is consistent with CAA 

Ssection 112 and is a reasonable interpretation of the statute. 

In the event that a source fails to comply with the 

applicable CAA Ssection 112(d) standards as a result of a 

malfunction event, the 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. The 

EPA would also consider whether the source’s failure to comply 

with the CAA Ssection 112(d) standard was, in fact, “sudden, 
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infrequent, not reasonably preventable” and was not instead 

“caused in part by poor maintenance or careless operation.” 40 

CFR 63.2 (, as described in the definition of malfunction (see 

40 CFR 63.2). Further, to the extent the EPA files an 

enforcement action against a source for violation of an emission 

standard, the source can raise any and all defenses in that 

enforcement action and the federal district court will determine 

what, if any, relief is appropriate. The same is true for 

citizen enforcement actions. Similarly, the presiding officer in 

an administrative proceeding can consider any defense raised and 

determine whether administrative penalties are appropriate.

FinallyIn several prior rules, the EPA recognizes that even 

equipment that is properly designed and maintained can sometimes 

fail and that such failure can sometimes cause a violation of 

the relevant emission standard. See, e.g., State Implementation 

Plans: Response to Petition for Rulemaking; Findings of Excess 

Emissions During Periods of Startup, Shutdown, and Malfunction; 

Proposed rule, 78 FR 12460 (Feb. 22, 2013); State Implementation 

Plans: Policy Regarding Excessive Emissions During Malfunctions, 

Startup, and Shutdown (Sept. 20, 1999); Policy on Excess 

Emissions During Startup, Shutdown, Maintenance, and 

Malfunctions (Feb. 15, 1983). The EPA is therefore proposing to 

add an affirmative defense had included an affirmative defense 

to civil penalties for violations of emission standards that are 
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caused by malfunctions. (See 40 CFR 63.641 and 40 CFR 63.1579 

defining “affirmative defense” to mean, in the context of an 

enforcement proceeding, a response or defense put forward by a 

defendant, regarding which the defendant has the burden of 

proof, and the merits of which are independently and objectively 

evaluated in a judicial or administrative proceeding). We also 

are proposing other regulatory provisions to specify the 

elements that are necessary to establish this affirmative 

defense; the source must prove by a preponderance of the 

evidence that it has met all of the elements set forth in 40 CFR 

63.642 or 40 CFR 63.1570. (See 40 CFR 22.24.) The criteria are 

designed in part to ensure that the affirmative defense is 

available only where the event that causes a violation of the 

emission standard meets the narrow definition of malfunction in 

40 CFR 63.2 (sudden, infrequent, not reasonably preventable, and 

not caused by poor maintenance and/or careless operation). For 

example, to successfully assert the affirmative defense, the 

source must prove by a preponderance of the evidence that the 

violation “[w]as caused by a sudden, infrequent, and unavoidable 

failure of air pollution control, process equipment, or a 

process to operate in a normal or usual manner....” The criteria 

also are designed to ensure that steps are taken to correct the 

malfunction, to minimize emissions in accordance with 40 CFR 

63.642 or 40 CFR 63.1570 and to prevent future malfunctions. For 
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example, the source must prove by a preponderance of the 

evidence that “[r]epairs were made as expeditiously as possible 

when a violation occurred...” and that “[a]ll possible steps were 

taken to minimize the impact of the violation on ambient air 

quality, the environment and human health....” In any judicial or 

administrative proceeding, the Administrator may challenge the 

assertion of the affirmative defense and, if the respondent has 

not met its burden of proving all of the requirements in the 

affirmative defense, appropriate penalties may be assessed in 

accordance with Section 113 of the Clean Air Act (see also 40 

CFR 22.27). 

The EPA included an affirmative defense in the proposed 

rule in an attempt to balanceeffort to create a system that 

incorporates some flexibility, recognizing that there is a 

tension, inherent in many types of air regulation, to ensure 

adequate compliance while simultaneously recognizing that 

despite the most diligent of efforts, emission standards may be 

violated under circumstances entirely beyond the control of the 

source. The EPA must establish emission standards that “limit 

the quantity, rate, or concentration of emissions of air 

pollutants on a continuous basis.” 42 U.S.C. § 7602(k) (defining 

“emission limitation” and “emission standard”). See generally 

Sierra Club V. EPA, 551 F.3d 1019, 1021 (D.C. Cir. 2008). Thus, 

the EPA is required to ensure that emissions standards are 
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continuous. The affirmative defense for malfunction events meets 

this requirement by ensuring that even where there is a 

malfunction, the emission standard is still enforceable through 

injunctive relief. The United States Court of Appeals for the 

Fifth Circuit recently upheld the EPA’s view that an affirmative 

defense provision is consistent with Section 113(e) of the Clean 

Air Act. Luminant Generation Co. LLC V. United States EPA, 714 

F.3d 841 (5th Cir. Mar. 25, 2013) (upholding the EPA’s approval 

of affirmative defense provisions in a CAA State Implementation 

Plan). While “continuous” standards, on the one hand, are 

required, there is also Although the EPA recognized that its 

case law indicating that in many situations it is appropriate 

for the EPA to account for the practical realities of 

technology. For example, in Essex Chemical V. Ruckelshaus, 486 

F.2d 427, 433-by- (D.C. Cir. 1973), the D.C. Circuit 

acknowledged that in setting standards under CAA Section 111 

“variant provisions” such as provisions allowing for upsets 

during startup, shutdown and equipment malfunction “appear 

necessary to preserve the reasonableness of the standards as a 

whole and that the record does not support the ‘never to be 

exceeded’ standard currently in force.” See also, Portland 

Cement Association V. Ruckelshaus, 486 F.2d 375 (D.C. Cir. 

1973). Though intervening case law such as Sierra Club V. EPA 

and the CAA 1977 amendments call into question the relevance of 
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these cases today, they support the EPA’s view that a system 

that incorporates some level of flexibility is reasonable. The 

affirmative defense simplyenforcement discretion provides for a 

defense to civil penalties for violations that are proven to be 

beyond the control of the source. By incorporating an 

affirmative defense, the EPA has formalized its approach to 

malfunctions. In a Clean Water Act setting, the Ninth Circuit 

required this type of formalized approach when regulating 

“upsets beyond the control of the permit holder.” Marathon Oil 

Co. Vsufficient flexibility in these circumstances, it included 

the affirmative defense to provide a more formalized approach 

and more regulatory clarity. See. EPA, 564 F.2d 1253, 1272-73 

(9th Cir. 1977). See also, Mont. Sulphur & Chem. Co. V. EPA, 666 

F.3d. 1174 (9th Cir. 2012) (rejecting industry argument that 

reliance on the affirmative defense was not adequate). But see,

Weyerhaeuser Co. Vv. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 

1978) (holding that an informal case-by-case enforcement 

discretion approach is adequate); but see Marathon Oil Co. v. 

EPA, 564 F.2d 1253, 1272-73 (9th Cir. approach is adequate). The 

affirmative defense provisions give the EPA the flexibility to 

both ensure that its emission standards are “continuous” as 

required by 42 U.S.C. § 7602(k), and account for unplanned 

upsets, and thus support the reasonableness of the standard as a 

whole. The EPA is proposing the affirmative defense applicable 
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to malfunctions under the delegation of general 1977) (requiring 

a more formalized approach to consideration of “upsets beyond 

the control of the permit holder.”). Under the EPA’s regulatory 

affirmative defense provisions, if a source could demonstrate in 

a judicial or administrative proceeding that it had met the 

requirements of the affirmative defense in the regulation, civil 

penalties would not be assessed. Recently, the United States 

Court of Appeals for the District of Columbia Circuit vacated 

such an affirmative defense in one of the EPA’s section 112(d) 

regulations. NRDC v. EPA, No. 10-1371 (D.C. Cir. April 18, 2014) 

2014 U.S. App. LEXIS 7281 (vacating affirmative defense 

provisions in section 112(d) rule establishing emission 

standards for Portland cement kilns). The court found that the 

EPA lacked authority set out in Section 301(a)(1) of the Act, 42 

U.S.C. § 7601(a)(1), in order to balance this tension between 

provisions of the Act and the practical reality, as caselaw 

recognizes, that technology sometimes fails. See generally 

Citizens to Save Spencer County V. U.S. Environmental Protection 

Agency, 600 F.2d 844, 873 (D.C. Cir. 1979) (using Section 301(a) 

to establish an affirmative defense for private civil suits and 

held that under the CAA, the authority to harmonize inconsistent 

guidelines related to the implementation of federal 

preconstruction review requirements).determine civil penalty 

amounts lies exclusively with the courts, not the EPA. 
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Specifically, the Court found: “As the language of the statute 

makes clear, the courts determine, on a case-by-case basis, 

whether civil penalties are ‘appropriate.’” See NRDC, 2014 U.S. 

App. LEXIS 7281 at *21 (“[U]nder this statute, deciding whether 

penalties are ‘appropriate’ in a given private civil suit is a 

job for the courts, not EPA.”).41 In light of NRDC, the EPA is 

not including a regulatory affirmative defense provision in this 

rulemaking. As explained above, if a source is unable to comply 

with emissions standards as a result of a malfunction, the EPA 

may use its case-by-case enforcement discretion to provide 

flexibility, as appropriate. Further, as the D.C. Circuit 

recognized, in an EPA or citizen enforcement action, the court 

has the discretion to consider any defense raised and determine 

whether penalties are appropriate. Cf. NRDC, 2014 U.S. App. 

LEXIS 7281 at *24. (arguments that violation were caused by 

unavoidable technology failure can be made to the courts in 

future civil cases when the issue arises). The same logic 

applies to EPA administrative enforcement actions.

a. General Duty 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.6(e)(1)(i) by 

 

41 The court’s reasoning in NRDC focuses on civil judicial actions. The Court 

noted that “EPA's ability to determine whether penalties should be assessed 

for Clean Air Act violations extends only to administrative penalties, not to 

civil penalties imposed by a court.” Id.
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changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.6(e)(1)(i) by changing 

the “Yes” in the third column to a “No.” We are making this 

change because Ssection 63.6(e)(1)(i) describes the general duty 

to minimize emissions and the current characterizes what the 

general duty entails during periods of SSM and that language is 

no longer necessary or appropriate in light of the elimination 

of the SSM exemption. We are proposing instead to add general 

duty regulatory text at 40 CFR 63.642(n) and 40 CFR 63.1570(c) 

that reflects the general duty to minimize emissions while 

eliminating the reference to periods covered by an SSM 

exemption. With the elimination of the SSM exemption, there is 

no need to differentiate between normal operations, startup and 

shutdown, and malfunction events in describing the general duty. 

Therefore the language the EPA is proposing does not include 

that language from 40 CFR 63.6(e)(1). 

We are also proposing to revise the 40 CFR part 63, subpart 

CC General Provisions table (Table 6) entry for 63.6(e)(1)(ii) 

by changing the “Yes” in the second column to a “No.” Similarly, 

we are also proposing to revise the 40 CFR part 63, subpart UUU 

General Provisions table (Table 44) entry for §63.6(e)(1)(ii) by 

changing the “Yes” in the third column to a “No.” Section 

63.6(e)(1)(ii) imposes requirements that are not necessary with 
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the elimination of the SSM exemption or are redundant of the 

general duty requirement being added at 40 CFR 63.642(n) and 40 

CFR 63.1570(c). 

b. SSM Plan 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entries for 63.6(e)(3)(i) and 

63.6(e)(3)(iii)–63.6(e)(3)(ix) by changing the “Yes” in the 

second column to a “No.” Similarly, we are proposing to revise 

the 40 CFR part 63, subpart UUU General Provisions table (Table 

44) entries for §63.6(e)(3)(i)-(iii), §63.6(e)(3)(iv), 

§63.6(e)(3)(v)-(viii), §63.6(e)(3)(ix) to be entries for 

63.6(e)(3)(i) and 63.6(e)(3)(iii)–63.6(e)(3)(ix) with “No” in 

the third column and §63.6(e)(3)(ii) with “Not Applicable” in 

the third column (that section is reserved). Generally, these 

paragraphs require development of an SSM plan and specify SSM 

recordkeeping and reporting requirements related to the SSM 

plan. As noted, the EPA is proposing to remove the SSM 

exemptions. Therefore, affected units will be subject to an 

emission standard during such events. The applicability of a 

standard during such events will ensure that sources have ample 

incentive to plan for and achieve compliance and thus the SSM 

plan requirements are no longer necessary. 
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c. Compliance with Standards 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.6(f)(1) by 

changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.6(f)(1) by changing 

the “Yes” in the third column to a “No.” The current language of 

40 CFR 63.6(f)(1) exempts sources from non-opacity standards 

during periods of SSM. As discussed above, the court in Sierra 

Club vacated the exemptions contained in this provision and held 

that the CAA requires that some Ssection 112 standard apply 

continuously. Consistent with Sierra Club, the EPA is proposing 

to revise standards in this rule to apply at all times. 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.6(h)(1) by 

changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.6(h)(1) by changing 

the “Yes” in the third column to a “No.” The current language of 

40 CFR 63.6(h)(1) exempts sources from opacity standards during 

periods of SSM. As discussed above, the court in Sierra Club 

vacated the exemptions contained in this provision and held that 

the CAA requires that some Ssection 112 standard apply 
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continuously. Consistent with Sierra Club, the EPA is proposing 

to revise standards in this rule to apply at all times. 

d. Performance Testing 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.7(e)(1) by 

changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.7(e)(1) by changing 

the “Yes” in the third column to a “No.” Section 63.7(e)(1) 

describes performance testing requirements. The EPA is instead 

proposing to add performance testing requirements at 40 CFR 

63.642(d)(3) and 40 CFR 63.1571(b)(1). The performance testing 

requirements we are proposing differ from the General Provisions 

performance testing provisions in several respects. The 

regulatory text does not include the language in 40 CFR 

63.7(e)(1) that restated the SSM exemption. The regulatory text 

also does not preclude startup and shutdown periods from being 

considered “representative” for purposes of performance testing, 

however, the testing. However, the specific testing provisions 

proposed at 40 CFR 63.642(d)(3) and 40 CFR 63.1571(b)(1) do not 

allow performance testing during startup or shutdown. As in 40 

CFR 63.7(e)(1), performance tests conducted under this subpart 

may not be conducted during malfunctions because conditions 

during malfunctions are often not representative of normal 
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operating conditions. The EPA is proposing to add language that 

requires the owner or operator to record the process information 

that is necessary to document operating conditions during the 

test and include in such record an explanation to support that 

such conditions represent normal operation. Section 63.7(e) 

requires that the owner or operator make available to the 

Administrator such records “as may be necessary to determine the 

condition of the performance test” available to the 

Administrator upon request, but does not specifically require 

the information to be recorded. The regulatory text EPA is 

proposing to add to Refinery MACT 1 and 2 builds on that 

requirement and makes explicit the requirement to record the 

information. 

e. Monitoring 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entries for 63.8(c)(1)(i) and 

63.8(c)(1)(iii) by changing the “Yes” in the second column to a 

“No.” Similarly, we are proposing to revise the 40 CFR part 63, 

subpart UUU General Provisions table (Table 44) entry for 

§63.8(c)(1)(i) and §63.8(c)(1)(iii) by changing the “Yes” in the 

third column to a “No.” The cross-references to the general duty 

and SSM plan requirements in those subparagraphs are not 

necessary in light of other requirements of 40 CFR 63.8 that 

require good air pollution control practices (40 CFR 63.8(c)(1)) 
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and that set out the requirements of a quality control program 

for monitoring equipment (40 CFR 63.8(d)). 

We are proposing to revise the 40 CFR part 63, subpart UUU 

General Provisions table (Table 44) entry for §63.8(d) to 

include separate entries for specific paragraphs of 40 CFR 

63.8(d), including an entry for §63.10(d)(3) with “No” in the 

third column. The final sentence in 40 CFR 63.8(d)(3) refers to 

the General Provisions’ SSM plan requirement which is no longer 

applicable. The EPA is proposing to add to the rule at 40 CFR 

63.1576(b)(3) text that is identical to 40 CFR 63.8(d)(3) except 

that the final sentence is replaced with the following sentence: 

“The program of corrective action should be included in the plan 

required under §63.8(d)(2).” 

f. Recordkeeping 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.10(b)(2)(i) by 

changing the “Yes” in the second column to a “No.” Section 

63.10(b)(2)(i) describes the recordkeeping requirements during 

startup and shutdown. These recording provisions are no longer 

necessary because the EPA is proposing that recordkeeping and 

reporting applicable to normal operations will apply to startup 

and shutdown. In the absence of special provisions applicable to 

startup and shutdown, such as a startup and shutdown plan, there 
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is no reason to retain additional recordkeeping for startup and 

shutdown periods. 

We are proposing to revise the 40 CFR part 63, subpart UUU 

General Provisions table (Table 44) entry for §63.10(b) to 

include separate entries for specific paragraphs of 40 CFR 

63.10(b), including an entry for §63.10(b)(2)(i) with “No” in 

the third column. Section 63.10(b)(2)(i) describes the 

recordkeeping requirements during startup and shutdown. We are 

instead proposing to add recordkeeping requirements to 40 CFR 

63.1576(a)(2). When a source is subject to a different standard 

during startup and shutdown, it will be important to know when 

such startup and shutdown periods begin and end in order to 

determine compliance with the appropriate standard. Thus, the 

EPA is proposing to add language to 40 CFR 63.1576(a)(2) 

requiring that sources subject to an emission standard during 

startup or shutdown that differs from the emission standard that 

applies at all other times must record the date, time, and 

duration of such periods. 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.10(b)(2)(ii) by 

changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.10(b) to include 

separate entries for specific paragraphs of 40 CFR 63.10(b), 
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including an entry for §63.10(b)(2)(ii) with “No” in the third 

column. Section 63.10(b)(2)(ii) describes the recordkeeping 

requirements during a malfunction. The EPA is proposing to add 

such requirements to 40 CFR 63.655(i)(11) and 40 CFR 

63.1576(a)(2). The regulatory text we are proposing to add 

differs from the General Provisions language that was crossreferenced, which provides the creation and retention of a 

record of the occurrence and duration of each malfunction of 

process, air pollution control, and monitoring equipment. The 

proposed text would apply to any failure to meet an applicable 

standard and would require the source to record the date, time, 

and duration of the failure. The EPA is also proposing to add to 

40 CFR 63.655(i)(11) and 40 CFR 63.1576(a)(2) a requirement that 

sources keep records that include a list of the affected source 

or equipment and actions taken to minimize emissions, an 

estimate of the quantity of each regulated pollutant emitted 

over the standard for which the source failed to meet a 

standard, and a description of the method used to estimate the 

emissions. Examples of such methods would include product-loss 

calculations, mass balance calculations, measurements when 

available, or engineering judgment based on known process 

parameters. The EPA is proposing to require that sources keep 

records of this information to ensure that there is adequate 

information to allow the EPA to determine the severity of any 
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failure to meet a standard, and to provide data that may 

document how the source met the general duty to minimize 

emissions when the source has failed to meet an applicable 

standard. 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.10(b)(2)(iv) by 

changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.10(b) to include 

separate entries for specific paragraphs of 40 CFR 63.10(b), 

including an entry for §63.10(b)(2)(iv)-(v) with “No” in the 

third column. When applicable, 40 CFR 63.10(b)(2)(iv) requires 

sources to record actions taken during SSM events when actions 

were inconsistent with their SSM plan. The requirement is no 

longer appropriate because SSM plans will no longer be required. 

The requirement previously applicable under 40 CFR 

63.10(b)(2)(iv)(B) to record actions to minimize emissions and 

record corrective actions is now applicable by reference to 40 

CFR 63.655(i)(11)(iii) and 40 CFR 63.1576(a)(2)(iii). 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entry for 63.10(b)(2)(v) by 

changing the “Yes” in the second column to a “No.” Similarly, we 

are proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entry for §63.10(b) to include 
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separate entries for specific paragraphs of 40 CFR 63.10(b), 

including an entry for §63.10(b)(2)(iv)-(v) with “No” in the 

third column. When applicable, 40 CFR 63.10(b)(2)(v) requires 

sources to record actions taken during SSM events to show that 

actions taken were consistent with their SSM plan. The 

requirement is no longer appropriate because SSM plans would no 

longer be required. 

We are proposing to revise the 40 CFR part 63, subpart UUU 

General Provisions table (Table 44) entry for §63.10(c)(9)-(15) 

to include separate entries for specific paragraphs of 40 CFR 

63.10(c), including an entry for §63.10(c)(15) with “No” in the 

third column. The EPA is proposing that 40 CFR 63.10(c)(15) no 

longer apply. When applicable, the provision allows an owner or 

operator to use the affected source's SSM plan or records kept 

to satisfy the recordkeeping requirements of the SSM plan, 

specified in 40 CFR 63.6(e), to also satisfy the requirements of 

40 CFR 63.10(c)(10) through (12). The EPA is proposing to 

eliminate this requirement because SSM plans would no longer be 

required, and therefore 40 CFR 63.10(c)(15) no longer serves any 

useful purpose for affected units. 

g. Reporting 

We are proposing to revise the 40 CFR part 63, subpart CC 

General Provisions table (Table 6) entries for 63.10(d)(5)(i) 

and 63.10(d)(5)(ii) by combining them into one entry for 
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63.10(d)(5) with a “No” in the second column. Similarly, we are 

proposing to revise the 40 CFR part 63, subpart UUU General 

Provisions table (Table 44) entries for 63.10(d)(5)(i) and 

63.10(d)(5)(ii) by combining them into one entry for 63.10(d)(5) 

with a “No” in the third column. Section 63.10(d)(5) describes 

the reporting requirements for startups, shutdowns, and 

malfunctions. To replace the General Provisions reporting 

requirement, the EPA is proposing to add reporting requirements 

to 40 CFR 63.655(g)(12), 40 CFR 63.1575(c)(4), 40 CFR 

63.1575(d), and 40 CFR 63.1575(e). The General Provisions 

requirement that was cross-referenced requires periodic SSM 

reports as a stand-alone report. In its place, we are proposing 

language that requires sources that fail to meet an applicable 

standard at any time to report the information concerning such 

events in the periodic report already required under each of 

these rules. We are proposing that the report must contain the 

number, date, time, duration, and the cause of such events 

(including unknown cause, if applicable), a list of the affected 

source or equipment, an estimate of the quantity of each 

regulated pollutant emitted over any emission limit, and a 

description of the method used to estimate the emissions. 

Examples of methods that can be used to estimate emissions 

would include product-loss calculations, mass balance 

calculations, measurements when available, or engineering 
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judgment based on known process parameters. The EPA is proposing 

this requirement to ensure that there is adequate information to 

determine compliance, to allow the EPA to determine the severity 

of the failure to meet an applicable standard, and to provide 

data that may document how the source met the general duty to 

minimize emissions during a failure to meet an applicable 

standard. 

We will no longer require owners or operators to determine 

whether actions taken to correct a malfunction are consistent 

with an SSM plan, because SSM plans would no longer be required. 

The proposed rule eliminates the cross-reference to 40 CFR 

63.10(d)(5)(i) that contains the description of the previously 

required SSM report format and submittal schedule from this 

section. These specifications are no longer necessary because 

the events will be reported in otherwise required reports with 

similar format and submittal requirements. 

We note that reporting a failure to meet an applicable 

standard could include malfunction events for which a source may 

choose to submit documentation to support an assertion of 

affirmative defense. If a source provides all the material 

required in 40 CFR 63.642(p) or 40 CFR 63.1570(g), as 

applicable, to support an affirmative defense, the source need 

not submit the same information two times in the same report. 

While assertion of an affirmative defense is not mandatory and 
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occurs only if a source chooses to take advantage of the 

affirmative defense, the affirmative defense also requires 

additional reporting that goes beyond these routine requirements 

related to a failure to meet an applicable standard for a reason 

other than a malfunction. 

As noted above, we are proposing to revise the 40 CFR part 

63, subpart CC General Provisions table (Table 6) entries for 

63.10(d)(5)(i) and 63.10(d)(5)(ii) by combining them into one 

entry for 63.10(d)(5) with a “No” in the second column. 

Similarly, we are proposing to revise the 40 CFR part 63, 

subpart UUU General Provisions table (Table 44) entries for 

63.10(d)(5)(i) and 63.10(d)(5)(ii) by combining them into one 

entry for 63.10(d)(5) with a “No” in the third column. Section 

63.10(d)(5)(ii) describes an immediate report for startups, 

shutdown, and malfunctions when a source fails to meet an 

applicable standard but does not follow the SSM plan. We are 

proposing to no longer require owners and operators to report 

when actions taken during a startup, shutdown, or malfunction 

were not consistent with an SSM plan, because such plans would 

no longer be required. 

2. Electronic Reporting 

In this proposal, the EPA is describing a process to 

increase the ease and efficiency of performance test data 

submittal while improving data accessibility. Specifically, the 
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EPA is proposing that owners and operators of petroleum 

refineries submit electronic copies of required performance test 

and performance evaluation reports by direct computer-tocomputer electronic transfer using EPA-provided software. The 

direct computer-to-computer electronic transfer is accomplished 

through the EPA’s Central Data Exchange (CDX) using the 

Compliance and Emissions Data Reporting Interface (CEDRI). The 

CDX is EPA’s portal for submittal of electronic data. The EPAprovided software is called the Electronic Reporting Tool (ERT) 

which is used to generate electronic reports of performance 

tests and evaluations. The ERT generates an electronic report 

package which will be submitted using the CEDRI. The submitted 

report package will be stored in the CDX archive (the official 

copy of record) and the EPA’s public database called WebFIRE. 

All stakeholders will have access to all reports and data in 

WebFIRE and accessing these reports and data will be very 

straightforward and easy (see the WebFIRE Report Search and 

Retrieval link at 

http://cfpub.epa.gov/webfire/index.cfm?action=fire.searchERTSubm

ission). A description and instructions for use of the ERT can 

be found at http://www.epa.gov/ttn/chief/ert/index.html and 

CEDRI can be accessed through the CDX website (www.epa.gov/cdx). 

A description of the WebFIRE database is available at: 

http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main. 
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The proposal to submit performance test data electronically 

to the EPA applies only to those performance tests (and/or 

performance evaluations) conducted using test methods that are 

supported by the ERT. The ERT supports most of the commonly used 

EPA reference methods. A listing of the pollutants and test 

methods supported by the ERT is available at: 

http://www.epa.gov/ttn/chief/ert/index.html. 

We believe that industry would benefit from this proposed 

approach to electronic data submittal. Specifically, by using 

this approach, industry will save time in the performance test 

submittal process. Additionally, the standardized format that 

the ERT uses allows sources to create a more complete test 

report resulting in less time spent on data backfilling if a 

source failed to include all data elements required to be 

submitted. Also through this proposal industry may only need to 

submit a report once to meet the requirements of the applicable 

subpart because stakeholders can readily access these reports 

from the WebFIRE database. This also benefits industry by 

cutting back on recordkeeping costs as the performance test 

reports that are submitted to the EPA using CEDRI are no longer 

required to be retained in hard copy, thereby reducing staff 

time needed to coordinate these records. 

Since the EPA will already have performance test data in 

hand, another benefit to industry is that fewer or less 
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substantial data collection requests in conjunction with 

prospective required residual risk assessments or technology 

reviews will be needed. This would result in a decrease in staff 

time needed to respond to data collection requests. 

State, local and tribal air pollution control agencies 

(S/L/Ts) may also benefit from having electronic versions of the 

reports they are now receiving. For example, S/L/Ts may be able 

to conduct a more streamlined and accurate review of electronic 

data submitted to them. For example, the ERT would allow for an 

electronic review process, rather than a manual data assessment, 

therefore, making review and evaluation of the source provided 

data and calculations easier and more efficient. In addition, 

the public stands to benefit from electronic reporting of 

emissions data because the electronic data will be easier for 

the public to access. How the air emissions data are collected, 

accessed and reviewed will be more transparent for all 

stakeholders. 

One major advantage of the proposed submittal of 

performance test data through the ERT is a standardized method 

to compile and store much of the documentation required to be 

reported by this rule. The ERT clearly states what testing 

information would be required by the test method and has the 

ability to house additional data elements that might be required 

by a delegated authority. 
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In addition the EPA must have performance test data to 

conduct effective reviews of CAA Ssections 111 and 112 

standards, as well as for many other purposes including 

compliance determinations, emission factor development and 

annual emission rate determinations. In conducting these 

required reviews, the EPA has found it ineffective and time 

consuming, not only for us, but also for regulatory agencies and 

source owners and operators, to locate, collect and submit 

performance test data. In recent years, stack testing firms have 

typically collected performance test data in electronic format, 

making it possible to move to an electronic data submittal 

system that would increase the ease and efficiency of data 

submittal and improve data accessibility. 

A common complaint heard from industry and regulators is 

that emission factors are outdated or not representative of a 

particular source category. With timely receipt and 

incorporation of data from most performance tests, the EPA would 

be able to ensure that emission factors, when updated, represent 

the most current range of operational practices. Finally, 

another benefit of the proposed data submittal to WebFIRE 

electronically is that these data would greatly improve the 

overall quality of existing and new emissions factors by 

supplementing the pool of emissions test data for establishing 

emissions factors. 
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In summary, in addition to supporting regulation 

development, control strategy development and other air 

pollution control activities, having an electronic database 

populated with performance test data would save industry, state, 

local and tribal agencies and the EPA significant time, money 

and effort while also improving the quality of emission 

inventories and air quality regulations. 

In addition, we are proposing that the fenceline data at 

each monitor location (as proposed above) would be reported 

electronically on a quarterlysemiannual basis. All data reported 

electronically would be submitted to CDX through CEDRI and made 

available to the public. 

3. Technical Amendments to Refinery MACT 1 and 2 

a. Open-Ended Valves and Lines 

Refinery MACT 1 requires an owner or operator to control 

emissions from equipment leaks according to the requirements of 

either 40 CFR part 60, subpart VV or 40 CFR part 63, subpart H. 

For open-ended valves and lines, both subparts require that the 

open end be equipped with a cap, blind flange, plug or second 

valve that “shall seal the open end at all times.” However, 

neither subpart defines “seal” or explains in practical and 

enforceable terms what constitutes a sealed open-ended valve or 

line. This has led to uncertainty on the part of the owner or 

operator as to whether compliance is being achieved. Inspections 
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under the EPA’s Air Toxics LDAR initiative have provided 

evidence that while certain open-ended lines may be equipped 

with a cap, blind flange, plug or second valve, they are not 

operating in a “sealed” manner as the EPA interprets that term. 

In response to this uncertainty, we are proposing to amend 

40 CFR 63.6418 to add a definition ofclarify what is meant by

“seal.” This proposed definitionamendment clarifies that, for 

the purpose of complying with the requirements of 40 CFR 63.648, 

open-ended valves and lines are “sealed” by the cap, blind 

flange, plug, or second valve when there are no detectable 

emissions from the open-ended valve or line at or above an 

instrument reading of 500 ppm. We solicit comment on this 

approach to reducing the compliance uncertainty associated with 

open-ended valves and lines and our proposed definition of 

“seal.”amendment.

b. General Provisions Cross-Referencing 

We have reviewed the application of 40 CFR part 63, subpart 

A (General Provisions) to Refinery MACT 2. The applicable 

requirements of 40 CFR part 63, subpart A are contained in Table 

44 of 40 CFR part 63, subpart UUU. As a result of our review, we 

are proposing several amendments to Table 44 of 40 CFR part 63, 

subpart UUU (in addition to those discussed in Ssection IV.E.1 

of this preamble that address SSM) to bring the table up-to-date 

with requirements of the General Provisions that have been 
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amended since this table was created, to correct crossreferences, and to incorporate additional sections of the 

General Provisions that are necessary to implement other 

subparts that are cross-referenced by this rule. 

Although we reviewed the application of the General 

Provisions to Refinery MACT 1 and amended Table 6 of 40 CFR part 

63, subpart CC in 2009, we are proposing a few additional 

technical corrections to this table (in addition to those 

discussed in Ssection IV.E.1 of this preamble that address SSM). 

We are not discussing the details of these proposed technical 

corrections in this preamble but the rationale for each change 

to Table 6 of 40 CFR part 63, subpart CC and Table 44 of 40 CFR 

part 63, subpart UUU (including the proposed amendments to 

address SSM discussed above), is included in Docket ID Number 

EPA-HQ-OAR-2010-0682. 

4. Amendments to Refinery NSPS J and Ja 

As discussed in Ssection II.B.2 of this preamble, we are 

addressing a number of technical corrections and clarifications 

for Refinery NSPS J and Ja to address some of the issues raised 

in the petition for reconsideration and to improve consistency 

and clarity of the rule requirements. These issues are addressed 

in detail in API’s amended petition, dated August 21, 2008 (see 

Docket Item Number EPA-HQ-OAR-2007-0011-0246) and the meeting 
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minutes for a September 11, 2008 meeting between EPA and API 

(see Docket Item Number EPA-HQ-OAR-2007-0011-0266). 

a. The Depressurization Work Practice Standard for Delayed 

Coking Units 

HOVENSA and the Industry Petitioners raised several issues 

with the analysis conducted to support the DCU work practice 

standard in Refinery NSPS Ja. With the promulgation and 

implementation of the standards we are proposing for the DCU 

under Refinery MACT 1, the DCU work practice standards in 

Refinery NSPS Ja are not expected to result in any further 

decreases in emissions from the DCU. Any DCU that becomes 

subject to Refinery NSPS Ja would already be in compliance with 

Refinery MACT 1, which is a more stringent standard than the DCU 

work practice standards in Refinery NSPS Ja. As such, we are 

contemplating various ideas for harmonizing the requirements for 

the DCU in these two regulations. One option is to amend 

Refinery NSPS Ja to incorporate the same requirements being 

proposed for Refinery MACT 1 (the DCU work practice standard in 

Refinery NSPS Ja is less stringent than the proposed 

requirements for Refinery MACT 1). Another option we are 

contemplating is deleting the DCU work practice standard within 

Refinery NSPS Ja once the DCU standards in Refinery MACT 1 are 

promulgated and fully implemented. We believe deletion of this 

work practice standard is consistent with the objectives of 
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Executive Order 13563, “Improving Regulation and Regulatory 

Review.” We solicit comment on these options as well as any 

other comments regarding the interaction between the DCU 

requirements in these two rules (i.e., the need to keep the DCU 

work practice standard in Refinery NSPS Ja after promulgation of 

these revisions to Refinery MACT 1.) 

b. Technical Corrections and Clarifications 

In addition to their primary issues, the Industry 

Petitioners enumerated several points of clarification and 

recommended amendments to Refinery NSPS J and Ja. These issues 

are addressed in detail in API’s amended petition for 

reconsideration, dated August 21, 2008 (see Docket Item Number 

EPA-HQ-OAR-2007-0011-0246) and the meeting minutes for a 

September 11, 2008 meeting between EPA and API (see Docket Item 

Number EPA-HQ-OAR-2007-0011-0266). We are including several 

proposed amendments in this rulemaking to specifically address 

these issues. These amendments are discussed in the remainder of 

this section. We are addressing these issues now while we are 

proposing amendments for Refinery MACT 2 in an effort to improve 

consistency and clarity for sources regulated under both the 

NSPS and Refinery MACT 2. 

We are proposing a series of amendments to the requirements 

for sulfur recovery plants in 40 CFR 60.102a, to clarify the 

applicable emission limits for different types of sulfur 
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recovery plants based on whether oxygen enrichment is used. 

These amendments also clarify that emissions averaging across a 

group of emission points within a given sulfur recovery plant is 

allowed from each of the different types of sulfur recovery 

plants, and that emissions averaging is specific to the SO2 or 

reduced sulfur standards (and not to the H2S limit). The 10 ppmv 

H2S limit for reduction control systems not followed by 

incineration must be met on a release point-specific basis. 

These amendments are being made to clarify the original intent 

of the Refinery NSPS Ja requirements for sulfur recovery plants. 

We are proposing a series of corresponding amendments in 40 

CFR 60.106a to clarify the monitoring requirements, particularly 

when oxygen enrichment or emissions averaging is used. The 

monitoring requirements in Refinery NSPS Ja were incomplete for 

these provisions and did not specify all of the types of 

monitoring devices needed for implementation. We are also 

proposing in 40 CFR 60.106a to use the term “reduced sulfur 

compounds” when referring to the emission limits and monitoring 

devices needed to comply with the reduced sulfur compound 

emission limits for sulfur recovery plants with reduction 

control systems not followed by incineration. The term “reduced 

sulfur compounds” is a defined term in Refinery NSPS Ja, and the 

emissions limit for sulfur recovery plants with reduction 

control systems not followed by incineration is specific to 
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“reduced sulfur compounds.” Therefore, the proposed amendments 

to the monitoring provisions provide clarification of the 

requirements by using a consistent, defined term. 

We are proposing amendments to 40 CFR 60.102a(g)(1) to 

clarify that CO boilers, while part of the FCCU affected 

facility, can also be fuel gas combustion devices (FGCD). 

Industry Petitioners suggested that the CO boiler should only be 

subject to the FCCU NOX and SO2 limits and should not be 

considered a FGCD. While Refinery NSPS Ja clearly states that 

the coke burn-off exhaust from the FCCU catalyst regenerator is 

not considered to be fuel gas, other fuels combusted in the CO 

boiler must meet the H2S concentration requirements for fuel gas 

like any other FGCD. This amendment is provided to clarify our 

original intent with respect to fuel gas. Industry Petitioners 

also noted that some CO boiler “furnaces” may be used as process 

heaters rather than steam-generating boilers. While we did not 

originally contemplate that CO furnaces would be used as process 

heaters, available data from the detailed ICR suggests that 

there are a few CO furnaces used as process heaters. These CO 

furnaces are all forced-draft process heaters, and the newly 

amended NOX emissions limit in Refinery NSPS Ja for forced-draft 

process heaters is 60 ppmv, averaged over a 30-day period. Given 

the longer averaging time of the process heater NOX limits, these 

two emission limits (for FCCU NOX and for process heater NOX) are 
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reasonably comparable and are not expected to result in a 

significant difference in the control systems selected for 

compliance. As such, we are not amending or clarifying the NOX

standards for the FCCU or process heaters at this time. We are, 

however, clarifying (through this response) that if an emission 

source meets the definition of more than one affected facility, 

that source would need to comply with all requirements 

applicable to the emissions source. 

We are proposing to revise the annual testing requirement 

from “conductin 40 CFR 60.104a(b) to clarify our original 

intent. Instead of requiring a PM performance test at least once 

every 12 months” to “conduct, the rule would require a PM 

performance test annually (i.e.,and specify that annually means

once per calendar year, with an interval of at least 8 months 

but no more than 16 months between annual tests)” in 40 CFR 

60.104a(b) to clarify our original intent. This provision will 

ensure that testing is conducted at a reasonable interval while 

giving owners and operators flexibility in scheduling the 

testing. We are also proposing to amend 40 CFR 60.104a(f) to 

clarify that the provisions of that paragraph are specific to 

owners or operators of an FCCU or FCU that use a cyclone to 

comply with “the PM per coke burn-off emissions limit” (rather 

than just the “PM limit”) in 40 CFR 60.102a(b)(1), to clarify 

that facilities electing to comply with the concentration limit 
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using a PM CEMS would not also be required to install a COMS. We 

are also proposing to amend 40 CFR 60.104a(j) to delete the 

requirements to measure flow for the H2S concentration limit for 

fuel gas, as these are not needed in the performance evaluation. 

We are proposing amendments to 40 CFR 60.105a(b)(1)(ii)(A) 

to require corrective action be completed to repair faulty 

(leaking or plugged) air or water lines within 12 hours of 

identification of an abnormal pressure reading during the daily 

checks. We are also proposing amendments to 40 CFR 60.105a(i) to 

include periods when abnormal pressure readings for a jet 

ejector-type wet scrubber (or other type of wet scrubber 

equipped with atomizing spray nozzles) are not corrected within 

12 hours of identification, and periods when a bag leak 

detection system alarm (for a fabric filter) is not alleviated 

within the time period specified in the rule. These proposed 

amendments are necessary so that periods when the APCD operation 

is compromised are properly managed and/or reported. 

We are proposing amendments to 40 CFR 60.105(b)(1)(iv) and 

60.107a(b)(1)(iv) to allow “using tubes with a maximum span 

between 10 and 40 ppmv, inclusive, when 1≤N≤10, where N = number 

of pump strokes” rather than “requiring use of tubes with ranges 

0–10/0–100 ppm (N = 10/1”) because different length-of-stain 

tube manufacturers have different span ranges, and none of the 

commercially-available tubes have a specific span of 0–10/0–100 
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ppm (N = 10/1). We are also proposing to amend 40 CFR 

60.105(b)(3)(iii) and 40 CFR 60.107a(b)(3)(iii) to specify that 

the temporary daily stain sampling must be made “using length-of 

stain tubes with a maximum span between 200 and 400 ppmv, 

inclusive, when 1≤N≤5, where N = number of pump strokes”. This 

proposed amendment clarifies this monitoring requirement, 

ensures the proper tube range is used, and provides some 

flexibility in span range to accommodate different manufacturers 

of the length-of-stain tubes. We also propose to delete the last 

sentence in 40 CFR 60.105(b)(3)(iii), as there is no long-term 

H2S concentration limit in Refinery NSPS J. 

We are proposing to clarify that flares are subject to the 

performance test requirements. We are also proposing to clarify 

those performance test requirements in 40 CFR 60.107a(e)(1)(ii) 

and 40 CFR 60.107a(e)(2)(ii) to remove the distinction between 

flares with or without routine flow. The term “routine flow” is 

not defined and it is difficult to make this distinction in 

practice. 

F. What compliance dates are we proposing? 

Amendments to Refinery MACT 1 and 2 proposed in this 

rulemaking for adoption under CAA Ssection 112(d)(2) and (3) and 

CAA Ssection 112(d)(6) are subject to the compliance deadlines 

outlined in the CAA under Ssection 112(i). For all of the 

requirements we are proposing under CAA Ssection 112(d)(2) and 
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(3) or CAA Ssection 112(d)(6) except for storage vessels, which 

we are also requiring under 112 (f)(2), we are proposing the 

following compliance dates. As provided in CAA Ssection 112(i), 

new sources would be required to comply with these requirements 

by the effective date of the final amendments to Refinery MACT 1 

and 2 or startup, whichever is later. 

For existing sources, CAA Ssection 112(i) provides that the 

compliance date shall be as expeditiously as practicable, but no 

later than 3 years after the effective date of the standard. In 

determining what compliance period is as expeditious as 

practicable, we consider the amount of time needed to plan and 

construct projects and change operating procedures. Under CAA 

Ssection 112(d)(2) and (3), we are proposing new operating 

requirements for DCU. In order to comply with these new 

requirements, we project that most DCU owners or operators would 

need to install additional controls (e.g., steam ejector 

systems). Similarly, the proposed revision in the CRU pressure 

limit exclusions would require operational changes and, in some 

cases, additional controls. The addition of new control 

equipment would require engineering design, solicitation and 

review of vendor quotes, contracting and installation of the 

equipment, which would need to be timed with process unit outage 

and operator training. Therefore, we are proposing that it is 

necessary to provide 3 years after the effective date of the 
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final rule for these sources to comply with the DCU and CRU 

requirements. 

We are proposing new operating and monitoring requirements 

for flares under CAA Ssection 112(d)(2) and (3). We anticipate 

that these requirements would require the installation of new 

flare monitoring equipment and we project most refineries would 

install new control systems to monitor and adjust assist gas 

(air or steam) addition rates. Similar to the addition of new 

control equipment, these new monitoring requirements for flares 

would require engineering evaluations, solicitation and review 

of vendor quotes, contracting and installation of the equipment, 

and operator training. Installation of new monitoring and 

control equipment on flares will require the flare to be taken 

out of service. Depending on the configuration of the flares and 

flare header system, taking the flare out of service may also 

require a significant portion of the refinery operations to be 

shut down. Therefore, we are proposing that it is necessary to 

provide 3 years after the effective date of the final rule for 

owners or operators to comply with the new operating and 

monitoring requirements for flares. 

Under CAA Ssection 112(d)(2) and (3), we are proposing new 

vent control requirements for bypasses. These requirements would 

typically require the addition of piping and potentially new 

control requirements. As these vent controls would most likely 
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be routed to the flare, we are proposing to provide 3 years 

after the effective date of the final rule for owners or 

operators to afford coordination of these bypass modifications 

with the installation of the new monitoring equipment for the 

flares. 

Under our technology review, we are proposing to require 

fenceline monitoring pursuant to CAA Ssection 112(d)(6). These 

proposed provisions would require refinery owners or operators 

to install a number of monitoring stations around the facility 

fenceline. While the diffusive tube sampling system is 

relatively low-tech and is easy to install, site-specific 

factors must be considered in the placement of the monitoring 

systems. We also assume all refinery owners or operators would 

invest in the analytical equipment needed to perform automated 

sample analysis on-site and time is needed to select an 

appropriate vendor for this equipment. Furthermore, additional 

monitoring systems may be needed to account for near-field 

contributing sources, for which the development and approval of 

a site-specific monitoring plan. Considering all of the 

requirements needed to implement the fenceline monitoring 

system, we are proposing to provide 3 years from the effective 

date of the final rule for refinery owners or operators to 

install and begin collecting ambient air samples around the 
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fenceline of their facility following an approved (if necessary) 

site-specific monitoring plan. 

As a result of our technology review for equipment leaks, 

we are proposing to allow the use of optical gas imaging devices 

in lieu of using EPA Method 21 of 40 CFR part 60, Appendix A-7 

without the annual compliance demonstration with EPA Method 21 

as required in the AWP (see 73 FR 73202, December 22, 2008), 

provided that the owner and operator follows the provisions of 

Appendix K to 40 CFR part 60. The provision to allow the use of 

optical gas imaging devices without the annual compliance 

demonstration using EPA Method 21 is predicated on the use of 

fenceline monitoring to ensure that leaking equipment are 

effectively identified. Facilities could begin to comply with 

the optical gas imaging alternative as soon as Appendix K to 40 

CFR part 60 is promulgated. Alternatively, as is currently 

provided in the AWP, the refinery owner or operator can elect to 

use the optical gas imaging monitoring option prior to 

installation and use of the fenceline monitoring system, 

provided they conduct an annual compliance demonstration using 

EPA Method 21 as required in the AWP. 

Under our technology review for marine vessel loading 

operations, we are proposing to add a requirement for submerged 

filling for small and for offshore marine vessel loading 

operations. We anticipate that the submerged fill pipes are 
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already in place on all marine vessels used to transport 

petroleum refinery liquids, so we are proposing that existing 

sources comply with this requirement on the effective date of 

the final rule. We request comment regarding the need to provide 

additional time to comply with the submerged filling 

requirement; please provide in your comment a description of the 

vessels loaded that do not already have a submerged fill pipe, 

how these vessels comply with (or are exempt from) the Coast 

Guard requirements at 46 CFR 153.282, and an estimate of the 

time needed to add the required submerged fill pipes to these 

vessels. 

We are also proposing to require FCCU owners and operators 

currently subject to Refinery NSPS J (or electing that 

compliance option in Refinery MACT 2) to transition from the 

Refinery NSPS J option to one of the alternatives included in 

the proposed rule. We are also proposing altering the averaging 

times for some of the operating limits. A PM performance test is 

needed in order to establish these new operating limits prior to 

transitioning to the proposed requirements. Additionally, we are 

proposing that a PM performance test be conducted for each FCCU 

once every 5 years. We do not project any new control or 

monitoring equipment will be needed in order to comply with the 

proposed provisions; however, compliance with the proposed 

provisions is dependent on conducting a performance test. 
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Establishing an early compliance date for the first performance 

test can cause scheduling issues as refinery owners or operators 

compete for limited number of testing contractors. Considering 

these scheduling issues, we propose to require the first 

performance test for PM and compliance with the new operating 

limits be completed no later than 18 months after the effective 

date of the final rule. 

In this action, we are proposing revisions to the SSM 

provisions of Refinery MACT 1 and 2, including specific startup 

or shutdown standards for certain emission sources, and we are 

proposing electronic reporting requirements in Refinery MACT 1 

and 2. The proposed monitoring requirements associated with the 

new startup and shutdown standards are expected to be present on 

the affected source, so we do not expect that owners or 

operators will need additional time to transition to these 

requirements. Similarly, the electronic reporting requirements 

are not expected to require a significant change in operation or 

equipment, so these requirements should be able to be 

implemented more quickly than those that require installation of 

new control or monitoring equipment. Based on our review of 

these requirements, we propose that these requirements become 

effective upon the effective date of the final rule. 

Finally, we are proposing additional requirements for 

storage vessels under CAA Ssections 112(d)(6) and (f)(2). The 
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compliance deadlines for standards developed under CAA Ssection 

112(f)(2) are delineated in CAA Ssections 112(f)(3) and (4). As 

provided in CAA Ssection 112(f)(4), risk standards shall not 

apply to existing sources until 90 days after the effective date 

of the rule, but the Administrator may grant a waiver for a 

particular source for a period of up to 2 years after the 

effective date. While additional controls will be necessary to 

comply with the proposed new control and fitting requirements 

for storage vessels, the timing for installation of these 

controls areis specified within the Generic MACT (40 CFR part 

63, subpart WW). Therefore, we propose that these new 

requirements for storage vessels become effective 90 days 

following the effective date of the final rule. 

V. Summary of Cost, Environmental and Economic Impacts 

A. What are the affected sources, the air quality impacts and 

cost impacts? 

The sources affected by significant amendments to the 

petroleum refinery standards include storage vessels, equipment 

leaks, fugitive emissions and DCU subject to Refinery MACT 1. 

The proposed amendments for other sources subject to one or more 

of the petroleum refinery standards are expected to have minimal 

air quality and cost impacts. 

The total capital investment cost of the proposed 

amendments and standards is estimated at $239 million, $82.8 
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million from proposed amendments and $156 million from standards 

to ensure compliance. We estimate annualized costs to be 

approximately $4.53 million, which includes an estimated $14.4 

million credit for recovery of lost product and the annualized 

cost of capital. We also estimate annualized costs of the 

proposed standards to ensure compliance to be approximately 

$37.9 million. The proposed amendments would achieve a 

nationwide HAP emission reduction of 1,760 tpy, with a 

concurrent reduction in VOC emissions of 18,800 tpy. Table 13 of 

this preamble summarizes the cost and emission reduction impacts 

of the proposed amendments, and Table 14 of this preamble 

summarizes the costs of the proposed standards to ensure 

compliance. 

Table 13. Nationwide Impacts of Proposed Amendments 

Affected 

source 

Total 

capital 

investment 

(million 

$) 

Total 

annualized 

cost 

without 

credit 

(million 

$/yr) 

Product 

recovery 

credit 

(million 

$/yr) 

Total 

annualized 

costs 

(million 

$/ yr) 

VOC 

emission 

reductions 

(tpy) 

Cost 

effectiveness 

($/ton 

VOC) 

HAP 

emission 

reductions 

(tpy) 

Cost 

effectiveness 

($/ton 

HAP) 

Storage 

Vessels 18.5 3.13 (8.16) (5.03) 14,600 (345) 910 (5,530) 

Delayed 

Coking 

Units 52.0 10.2 (6.20) 3.98 4,250 937 850 4,680 

Fugitive 

Emissions 

(Fenceline 

Monitoring) 12.2 5.58 -- 5.58 

Total 82.8 18.9 (14.4) 4.53 18,800 241 1,760 2,570 
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Table 14. Nationwide Costs of Proposed Amendments to Ensure 

Compliance 

Affected source 

Total capital 

investment 

(million $) 

Total 

annualized 

cost without 

credit 

(million $/yr)

Product 

recovery 

credit 

(million 

$/yr) 

Total 

annualized 

costs 

(million $/ 

yr) 

Relief Valve 

Monitoring 9.54 1.36 -- 1.36 

Flare Monitoring 147 36.3 -- 36.3 

FCCU Testing -- 0.21 -- 0.21 

Total 156 37.9 -- 37.9 

Note that any corrective actions taken in response to the 

fenceline monitoring program are not included in the impacts 

shown in Table 13. Any corrective actions associated with 

fenceline monitoring will result in additional emission 

reductions and additional costs. 

The impacts shown in Table 14 do not consider emission 

reductions associated with relief valve or flare monitoring 

provisions or emission reductions that may occur as a result of 

the additional FCCU testing requirements. The proposed 

operational and monitoring requirements for flares at refineries 

have the potential to reduce excess emissions from flares by 

approximately 3,800 tpy of HAP, 33,000 tpy of VOC, and 327,000 

metric tonnes per year of carbon dioxide equivalents (CO2e). When 

added to the reductions in CO2e achieved from proposed controls 

on DCU, these proposed amendments are projected to result in 
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reductions of 670,000 metric tonnes of CO2e due to reductions of 

methane emissions.42

B. What are the economic impacts? 

We performed a national economic impact analysis for 

petroleum product producers. All petroleum product refiners will 

incur annual compliance costs of much less than 1 percent of 

their sales. For all firms, the minimum cost-to-sales ratio is 

<0.01 percent; the maximum cost-to-sales ratio is 0.87 percent; 

and the mean cost-to-sales ratio is 0.03 percent. Therefore, the 

overall economic impact of this proposed rule should be minimal 

for the refining industry and its consumers. 

In addition, the EPA performed a screening analysis for 

impacts on small businesses by comparing estimated annualized 

engineering compliance costs at the firm-level to firm sales. 

The screening analysis found that the ratio of compliance cost 

to firm revenue falls below 1 percent for the 28 small companies 

likely to be affected by the proposal. For small firms, the 

minimum cost-to-sales ratio is <0.01 percent; the maximum costto-sales ratio is 0.62 percent; and the mean cost-to-sales ratio 

is 0.07 percent. 

 

42 The flare operational and monitoring requirements are projected to reduce 

methane emissions by 29,500 tpy while increasing CO2 emissions by 260,000 tpy, 

resulting in a net GHG reduction of 327,000 metric tonnes per year of CO2e, 

assuming a global warming potential of 21 for methane. Combined with methane 

emissions reduction of 18,000 tpy from the proposed controls on DCU, the 

overall GHG reductions of the proposed amendments is 670,000 metric tonnes 

per year of CO2e assuming a global warming potential of 21 for methane. 
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More information and details of this analysis are provided 

in the technical document Economic Impact Analysis for Petroleum 

Refineries Proposed Amendments to the National Emissions 

Standards for Hazardous Air Pollutants, which is available in 

the docket for this proposed rule (Docket ID Number EPA-HQ-OAR2010-0682). 

C. What are the benefits? 

The proposed rule is anticipated to result in a reduction 

of 1,760 tons of HAP (based on allowable emissions under the 

MACT standards) and 18,800 tons of VOC emissions per year, not 

including potential emission reductions that may occur as a 

result of the proposed provisions for flares or fenceline 

monitoring. These avoided emissions will result in improvements 

in air quality and reduced negative health effects associated 

with exposure to air pollution of these emissions; however, we 

have not quantified or monetized the benefits of reducing these 

emissions for this rulemaking. 

VI. Request for Comments 

We solicit comments on all aspects of this proposed action. 

In addition to general comments on this proposed action, we are 

also interested in additional data that may improve the risk 

assessments and other analyses. We are specifically interested 

in receiving any improvements to the data used in the sitespecific emissions profiles used for risk modeling. Such data 
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should include supporting documentation in sufficient detail to 

allow characterization of the quality and representativeness of 

the data or information. Section VII of this preamble provides 

more information on submitting data. 

VII. Submitting Data Corrections 

The site-specific emissions profiles used in the source 

category risk and demographic analyses and instructions are 

available on the RTR web page at: 

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The data files 

include detailed information for each HAP emissions release 

point for the facilities in the source categories. 

If you believe that the data are not representative or are 

inaccurate, please identify the data in question, provide your 

reason for concern and provide any “improved” data that you 

have, if available. When you submit data, we request that you 

provide documentation of the basis for the revised values to 

support your suggested changes. To submit comments on the data 

downloaded from the RTR page, complete the following steps: 

1. Within this downloaded file, enter suggested revisions 

to the data fields appropriate for that information. 

2. Fill in the commenter information fields for each 

suggested revision (i.e., commenter name, commenter 

organization, commenter email address, commenter phone number 

and revision comments). 
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3. Gather documentation for any suggested emissions 

revisions (e.g., performance test reports, material balance 

calculations). 

4. Send the entire downloaded file with suggested 

revisions in Microsoft® Access format and all accompanying 

documentation to Docket ID Number EPA-HQ-OAR-2010-0682 (through 

one of the methods described in the ADDRESSES Ssection of this 

preamble). 

5. If you are providing comments on a single facility or 

multiple facilities, you need only submit one file for all 

facilities. The file should contain all suggested changes for 

all sources at that facility. We request that all data revision 

comments be submitted in the form of updated Microsoft® Excel 

files that are generated by the Microsoft® Access file. These 

files are provided on the RTR web Page at: 

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. 

VIII. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review and 

Executive Order 13563: Improving Regulation and Regulatory 

Review 

Under Executive Order 12866 (58 FR 51735, October 4, 1993), 

this action is a “significant regulatory action” because it 

raises novel legal and policy issues. Accordingly, the EPA 

submitted this action to the Office of Management and Budget 
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(OMB) for review under Executive Orders 12866 and 13563 (76 FR 

3821, January 21, 2011) and any changes made in response to OMB 

recommendations have been documented in the docket for this 

action (Docket ID Number EPA-HQ-OAR-2010-0682). 

B. Paperwork Reduction Act 

The information collection requirements in this rule have 

been submitted for approval to OMB under the Paperwork Reduction 

Act, 44 U.S.C. 3501, et seq. 

Revisions and burden associated with amendments to 40 CFR 

part 63, subparts CC and UUU are discussed in the following 

paragraphs. OMB has previously approved the information 

collection requirements contained in the existing regulations in 

40 CFR part 63, subparts CC and UUU under the provisions of the 

Paperwork Reduction Act, 44 U.S.C. 3501, et seq., OMB control 

numbers for the EPA’s regulations in 40 CFR are listed in 40 CFR 

part 9. Burden is defined at 5 CFR 1320.3(b). 

The ICR document prepared by the EPA for the amendments to 

the Petroleum Refinery MACT standards for 40 CFR part 63, 

subpart CC has been assigned the EPA ICR number 1692.08. Burden 

changes associated with these amendments would result from new 

monitoring, recordkeeping and reporting requirements. The 

estimated average annual increase in recordkeeping and reporting 

burden per response is 1.3 hours (this is the total 

reporting53,619 hours in the second year, technical, managerial, 
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and clerical divided by the total responses in the second year); 

the frequency of response is semiannual for all reports for all 

respondents that must comply with the rule’s reporting 

requirements; and the estimated average number of likely 

respondents per year is 95 (this is the average in the second 

year). The cost burden to respondents resulting from the 

collection of information includes the total capital cost 

annualized over the equipment’s expected useful life (about $17 

million, which includes monitoring equipment for bypass valves, 

fenceline monitoring, relief valves, and flares), a total 

operation and maintenance component (about $16 million per year 

– this is the average in the second yearfor fenceline and flare 

monitoring), and a labor cost component (about $4.5 million per 

year – this is, the average incost of the second yearadditional 

53,619 labor hours). An agency may not conduct or sponsor (and a 

person is not required to respond to) a collection of 

information unless it displays a currently-valid OMB control 

number. 

The ICR document prepared by the EPA for the amendments to 

the Petroleum Refinery MACT standards for 40 CFR part 63, 

subpart UUU has been assigned the EPA ICR number 1844.05. Burden 

changes associated with these amendments would result from new 

testing, recordkeeping and reporting requirements being proposed 

with this action. The estimated average burden per response is 
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26 hours; the frequency of response is both once and every 5 

years for respondents that have FCCU, and the estimated average 

number of likely respondents per year is 67. The cost burden to 

respondents resulting from the collection of information 

includes the performance testing costs (approximately $356,000 

per year over the first 3 years for the initial performance test 

and $213,000 per year starting in the fourth year), and a labor 

cost component (approximately $238,000 per year for 2,860 

additional labor hours). An agency may not conduct or sponsor 

(and a person is not required to respond to) a collection of 

information unless it displays a currently-valid OMB control 

number. 

To comment on the agency’s need for this information, the 

accuracy of the provided burden estimates, and any suggested 

methods for minimizing respondent burden, the EPA has 

established a public docket for this rule, which includes the 

ICR, under Docket ID Number EPA-HQ-OAR-2010-0682. Submit any 

comments related to the ICR to the EPA and OMB. See the 

ADDRESSES Ssection at the beginning of this preamble for where 

to submit comments to the EPA. Send comments to OMB at the 

Office of Information and Regulatory Affairs, Office of 

Management and Budget, 725 17th Street, NW, Washington, DC 

20503, Attention: Desk Office for the EPA. Since OMB is required 

to make a decision concerning the ICR between 30 and 60 days 
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after [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER], a 

comment to OMB is best assured of having its full effect if OMB 

receives it by [INSERT DATE 30 DAYS AFTER DATE OF PUBLICATION IN 

THE FEDERAL REGISTER]. The final rule will respond to any OMB or 

public comments on the information collection requirements 

contained in this proposal. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) generally requires an 

agency to prepare a regulatory flexibility analysis of any rule 

subject to notice and comment rulemaking requirements under the 

Administrative Procedure Act or any other statute, unless the 

agency certifies that the rule will not have a significant 

economic impact on a substantial number of small entities 

(SISNOSE). Small entities include small businesses, small 

organizations and small governmental jurisdictions. For purposes 

of assessing the impacts of this proposed rule on small 

entities, a small entity is defined as: (1) a small business in 

the petroleum refining industry having 1,500 or fewer employees 

(Small Business Administration (SBA), 2011); (2) a small 

governmental jurisdiction that is a government of a city, 

county, town, school district or special district with a 

population of less than 50,000; and (3) a small organization 

that is any not-for-profit enterprise which is independently 

owned and operated and is not dominant in its field. 
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After considering the economic impacts of this proposed 

rule on small entities, I certify that this action will not have 

a significant economic impact on a substantial number of small 

entities. The small entities subject to the requirements of this 

proposed rule are small refiners. We have determined that 36 

companies (59 percent of the 61 total) employ fewer than 1,500 

workers and are considered to be small businesses. For small 

businesses, the average cost-to-sales ratio is about 0.05 

percent, the median cost-to-sales ratio is 0.02 percent and the 

maximum cost-to-sales ratio is 0.55 percent. The potential costs 

do not have a more significant impact on small refiners and 

because no small firms are expected to have cost-to-sales ratios 

greater than 1 percent, we determined that the cost impacts for 

this rulemaking will not have a SISNOSE. 

Although not required by the RFA to convene a Small 

Business Advocacy Review (SBAR) Panel; because the EPA has 

determined that this proposal would not have a significant 

economic impact on a substantial number of small entities, the 

EPA originally convened a panel to obtain advice and 

recommendations from small entity representatives potentially 

subject to this rule’s requirements. The panel was not formally 

concluded; however, a summary of the outreach conducted and the 

written comments submitted by the small entity representatives 
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can be found in the docket for this proposed rule (Docket ID 

Number EPA-HQ-OAR-2010-0682). 

We continue to be interested in the potential impacts of 

the proposed rule on small entities and welcome comments on 

issues related to such impacts. 

D. Unfunded Mandates Reform Act 

This proposed rule does not contain a federal mandate under 

the provisions of Title II of the Unfunded Mandates Reform Act 

of 1995 (UMRA), 2 U.S.C. 1531-1538 that may result in 

expenditures of $100 million or more for state, local and tribal 

governments, in the aggregate, or the private sector in any one 

year. As discussed earlier in this preamble, these amendments 

result in nationwide costs of $42.4 million per year for the 

private sector. Thus, this proposed rule is not subject to the 

requirements of Ssections 202 or 205 of the UMRA. 

This proposed rule is also not subject to the requirements 

of Ssection 203 of UMRA because it contains no regulatory 

requirements that might significantly or uniquely affect small 

governments because it contains no requirements that apply to 

such governments and does not impose obligations upon them. 

E. Executive Order 13132: Federalism 

This rule does not have federalism implications. It will 

not have substantial direct effects on the states, on the 

relationship between the national government and the states, or 
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on the distribution of power and responsibilities among the 

various levels of government, as specified in Executive Order 

13132. None of the facilities subject to this action are owned 

or operated by state governments, and, because no new 

requirements are being promulgated, nothing in this proposal 

will supersede state regulations. Thus, Executive Order 13132 

does not apply to this rule. 

In the spirit of Executive Order 13132, and consistent with 

the EPA policy to promote communications between the EPA and 

state and local governments, the EPA specifically solicits 

comment on this proposed rule from state and local officials. 

F. Executive Order 13175: Consultation and Coordination with 

Indian Tribal Governments 

This action does not have tribal implications, as specified 

in Executive Order 13175 (65 FR 67249, November 9, 2000). It 

will not have substantial direct effects on tribal governments, 

on the relationship between the federal government and Indian 

tribes, or on the distribution of power and responsibilities 

between the federal government and Indian tribes as specified in 

Executive Order 13175. Thus, Executive Order 13175 does not 

apply to this action. 

Although Executive Order 13175 does not apply to this 

action, the EPA consulted with tribal officials in developing 

this action. The EPA sent out letters to tribes nationwide to 
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invite them to participate in a tribal consultation meeting and 

solicit their input on this rulemaking. The EPA conducted the 

tribal consultation meeting on December 14, 2011. Participants 

from eight tribes attended the meeting, but they were interested 

only in outreach, and none of the tribes had delegation for 

consultation. The EPA presented all the information prepared for 

the consultation and conducted a question and answer session 

where participants asked clarifying questions about the 

information that was presented and generally expressed their 

support of the rulemaking requirements. 

The EPA specifically solicits additional comment on this 

proposed action from tribal officials. 

G. Executive Order 13045: Protection of Children from 

Environmental Health Risks and Safety Risks 

This action is not subject to Executive Order 13045 (62 FR 

19885, April 23, 1997) because it is not economically 

significant as defined in Executive Order 12866, and because the 

agency does not believe the environmental health or safety risks 

addressed by this action present a disproportionate risk to 

children. This action’s health and risk assessments are 

contained in Ssections III.A and B and Ssections IV.C and D of 

this preamble. 
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The public is invited to submit comments or identify peerreviewed studies and data that assess effects of early life 

exposure to emissions from petroleum refineries. 

H. Executive Order 13211: Actions Concerning Regulations That 

Significantly Affect Energy Supply, Distribution, or Use 

This action is not a “significant energy action” as defined 

under Executive Order 13211 (66 FR 28355, May 22, 2001), because 

it is not likely to have significant adverse effect on the 

supply, distribution or use of energy. The overall economic 

impact of this proposed rule should be minimal for the refining 

industry and its consumers. 

I. National Technology Transfer and Advancement Act 

Section 12(d) of the National Technology Transfer and 

Advancement Act of 1995 (NTTAA), Public Law No. 104-113, 12(d) 

(15 U.S.C. 272 note) directs the EPA to use voluntary consensus 

standards (VCS) in its regulatory activities unless to do so 

would be inconsistent with applicable law or otherwise 

impractical. VCS are technical standards (e.g., materials 

specifications, test methods, sampling procedures, and business 

practices) that are developed or adopted by VCS bodies. The 

NTTAA directs the EPA to provide Congress, through OMB, 

explanations when the agency decides not to use available and 

applicable VCS. 
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This proposed rulemaking involves technical standards. The 

EPA proposes to use ISO 16017-2, “Air quality Sampling and 

analysis of volatile organic compounds in ambient air, indoor 

air and workplace air by sorbent tube/thermal 

desorption/capillary gas chromatography Part 2: Diffusive 

sampling” as an acceptable alternative to EPA Method 325A. This 

method is available at http://www.iso.org. This method was 

chosen because it meets the requirements of EPA Method 301 for 

equivalency, documentation and validation data for diffusive 

tube sampling. 

The EPA welcomes comments on this aspect of the proposed 

rulemaking and, specifically, invites the public to identify 

potentially-applicable VCS and to explain why such standards 

should be used in this regulation. 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations 

Executive Order 12898 (59 FR 7629, February 16, 1994) 

establishes federal executive policy on environmental justice. 

Its main provision directs federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental 

justice part of their mission by identifying and addressing, as 

appropriate, disproportionately high and adverse human health or 

environmental effects of their programs, policies and activities 
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on minority populations and low-income populations in the United 

States. 

The EPA has determined that this proposed rule will not 

have disproportionately high and adverse human health or 

environmental effects on minority, low-income or indigenous 

populations because it maintains or increases the level of 

environmental protection for all affected populations without 

having any disproportionately high and adverse human health or 

environmental effects on any population, including any minority, 

low-income or indigenous populations. Further, the EPA believes 

that implementation of the provisions of this rule will provide 

an ample margin of safety to protect the public health of all 

demographic groups. 

To examine the potential for any environmental justice 

issues that might be associated with the refinery source 

categories associated with today’s proposed rule, we evaluated 

the percentages of various social, demographic and economic 

groups within the at-risk populations living near the facilities 

where these source categories are located and compared them to 

national averages. Our analysis of the demographics of the 

population with estimated risks greater than 1-in-1 million 

indicates potential disparities in risks between demographic 

groups, including the African American, Other and Multiracial, 

Hispanic, Below the Poverty Level, and Over 25 without a High 
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School Diploma groups. In addition, the population living within 

50 km of the 142 petroleum refineries has a higher percentage of 

minority, lower income and lower education persons when compared 

to the nationwide percentages of those groups. These groups 

stand to benefit the most from the emission reductions achieved 

by this proposed rulemaking, and this proposed rulemaking is 

projected to result in 1 million fewer people exposed to risks 

greater than 1-in-1 million. 

The EPA defines “Environmental Justice” to include 

meaningful involvement of all people regardless of race, color, 

national origin or income with respect to the development, 

implementation and enforcement of environmental laws, 

regulations and policies. To promote meaningful involvement, the 

EPA conducted numerous outreach activities and discussions, 

including targeted outreach (such as conference calls and 

webinars) to communities and environmental justice 

organizations. In addition, after the rule is proposed, the EPA 

will be conducting a webinar to inform the public about the 

proposed rule and to outline how to submit written comments to 

the docket. Further stakeholder and public input is expected 

through public comment and follow-up meetings with interested 

stakeholders. 
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Petroleum Refinery Sector Risk and Technology Review and New 

Source Performance Standards 

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List of Subjects in 40 CFR Part 60 

Environmental protection, Administrative practice and 

procedure, Air pollution control, Incorporation by reference, 

Intergovernmental relations, Reporting and recordkeeping 

requirements. 

List of Subjects in 40 CFR Part 63 

Environmental protection, Air pollution control, Hazardous 

substances, Incorporation by reference, Reporting and 

recordkeeping requirements, Volatile organic compounds. 

____________________________ 

Dated: 

____________________________ 

Gina McCarthy, 

Administrator.
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