6560-50

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2012-0360; FRL-]

RIN 2060-AR47

National Emission Standards for Hazardous Air Pollutants: OffSite Waste and Recovery Operations

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

SUMMARY: The Environmental Protection Agency (EPA) is proposing 

amendments to the national emission standards for hazardous air 

pollutants (NESHAP) for off-site waste and recovery operations 

(OSWRO) to address the results of the residual risk and 

technology review (RTR) conducted under the Clean Air Act (CAA). 

In light of our residual risk and technology review, we are

proposing to amend the requirements for leak detection and 

repair and the requirements for certain tanks. In addition, the 

EPA is proposing amendments to revise regulatory provisions 

pertaining to emissions during periods of startup, shutdown and 

malfunction; add requirements for electronic reporting of 

performance test results; revise the routine maintenance 

provisions; clarify provisions pertaining to open-ended valves 

and lines; add monitoring requirements for pressure relief 
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devices; clarify provisions for some performance test methods 

and procedures; and make several minor clarifications and 

corrections. 

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

DATE 45 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. We do not plan to conduct a public hearing 

unless requested. If requested, we will hold a public hearing on 

[INSERT DATE 15 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL 

REGISTER]. To request a hearing, please contact the person 

listed in the following FOR FURTHER INFORMATION CONTACT section 

by [INSERT DATE 10 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL 

REGISTER]. 

ADDRESSES: Comments. Submit your comments, identified by Docket 

ID No. EPA-HQ-OAR-2012-0360, by one of the following methods:

 Federal eRulemaking Portal: http://www.regulations.gov. 

Follow the online instructions for submitting comments.

 Email: A-and-R-docket@epa.gov. Include Docket ID No. EPAHQ-OAR-2012-0360 in the subject line of the message.

 Fax: (202) 566-9744, Attention Docket ID No. EPA-HQ-OAR2012-0360.
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 Mail: Environmental Protection Agency, EPA Docket Center 

(EPA/DC), Mail Code 28221T, Attention Docket ID No. EPA-HQOAR-2012-0360, 1200 Pennsylvania Avenue, 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/Courier Delivery: EPA Docket Center, Room 3334, EPA 

WJC West Building, 1301 Constitution Avenue, NW., 

Washington, DC 20004, Attention Docket ID No. EPA-HQ-OAR2012-0360. 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 No. EPA-HQOAR-2012-0360. The EPA’s policy is that all comments received 

will be included in the public docket without change and may be 

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 
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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.

Docket. The EPA has established a docket for this proposed 

rule under Docket ID No. EPA-HQ-OAR-2012-0360. 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 
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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, WJC 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. If requested, we will hold a public hearing 

concerning this proposed rule on [INSERT DATE 15 DAYS AFTER DATE 

OF PUBLICATION IN THE FEDERAL REGISTER] in the Research Triangle 

Park, North Carolina area. The EPA will provide further 

information about the hearing at the following website, 

http://www.epa.gov/ttn/oarpg/t3main.html, if a hearing is 

requested. Persons interested in presenting oral testimony at 

the hearing should contact Ms. Virginia Hunt, Sector Policies 

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

and Standards, U.S. Environmental Protection Agency, Research 

Triangle Park, NC 27711, telephone number (919) 541-0832, by 

[INSERT DATE 15 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL 

REGISTER]. If no one requests to speak at the public hearing by 

[INSERT DATE 10 DAYS FROM DATE OF PUBLICATION OF THE PROPOSED 
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RULE IN THE FEDERAL REGISTER], then a public hearing will not be 

held, and a notification of such will be posted on 

http://www.epa.gov/ttn/oarpg/t3main.html.

FOR FURTHER INFORMATION: For questions about this proposed 

action, contact Ms. Paula Hirtz, Sector Policies and Programs 

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

Standards, U.S. Environmental Protection Agency, Research 

Triangle Park, NC 27711; telephone number: (919) 541–2618; fax 

number: (919) 541-0246; and email address: hirtz.paula@epa.gov.

For specific information regarding the risk modeling 

methodology, contact Ms. Darcie Smith, Health and Environmental 

Impacts Division (C504-06), Office of Air Quality Planning and 

Standards, U.S. Environmental Protection Agency, Research 

Triangle Park, NC 27711; telephone number (919) 541-2076; fax 

number: (919) 541-0840; and email address: smith.darcie@epa.gov

For information about the applicability of the National Emission 

Standards for Hazardous Air Pollutants (NESHAP) to a particular 

entity, contact Ms. Marcia Mia, EPA Office of Enforcement and 

Compliance Assurance, telephone number (202) 564-7042; email 

address: mia.marcia@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 
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preamble and for reference purposes, the EPA defines the 

following terms and acronyms here: 

AEGL acute exposure guideline levels 

AERMOD air dispersion model used by the HEM-3 model

CAA Clean Air Act

CalEPA California EPA

CBI Confidential Business Information

CDX Central Data Exchange 

CEDRI Compliance and Emissions Data Reporting Interface 

CFR Code of Federal Regulations

EPA Environmental Protection Agency

ERPG Emergency Response Planning Guidelines 

ERT Electronic Reporting Tool

FR Federal Register

HAP hazardous air pollutants

HCl hydrochloric acid

HEM-3 Human Exposure Model, Version 1.1.0

HF hydrogen fluoride

HI hazard index

HON Hazardous Organic NESHAP 

HQ hazard quotient

ICR Information Collection Request 

IRIS Integrated Risk Information System

km kilometer

kPa kilopascal

LDAR leak detection and repair 

LOAEL lowest-observed-adverse-effect level 

MACT maximum achievable control technology

m3 cubic meter

mg/kg-day milligrams per kilogram per day

mg/m3 milligrams per cubic meter

MIR maximum individual risk

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

NAS National Academy of Sciences

NATA National Air Toxics Assessment
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NESHAP National Emissions Standards for Hazardous Air 

Pollutants

NOAA National Oceanic and Atmospheric Organization

NOAEL no-observed-adverse-effect level 

NRC National Research Council

NTTAA National Technology Transfer and Advancement Act

OAQPS Office of Air Quality Planning and Standards

OMB Office of Management and Budget

OSWRO off-site waste and recovery operations

PB-HAP hazardous air pollutants known to be persistent and 

bio-accumulative in the environment 

PEL probable effect levels

POM polycyclic organic matter

ppm parts per million

PRD pressure relief device

PTE permanent total enclosure 

RCO recuperative thermal oxidizer 

RCRA Resource Conservation and Recovery Act

REL reference exposure level 

RFA Regulatory Flexibility Act

RfC reference concentration

RfD reference dose

RIA Regulatory Impact Analysis

RTR residual risk and technology review

SAB Science Advisory Board

SBA Small Business Administration

SCC source classification code

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

agencies 

SOP standard operating procedures

SSM startup, shutdown and malfunction

TEQ toxicity equivalence factor

TOC total organic compound

TOSHI target organ-specific hazard index

tpy tons per year

TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport 

and Ecological Exposure model

TSDF Solid Waste Treatment, Storage and Disposal Facility

TTN Technology Transfer Network
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UF uncertainty factor

UMRA Unfunded Mandates Reform Act

URE unit risk estimate

VCS voluntary consensus standards

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?

II. Background

A. What is the statutory authority for this action?

B. What is this source category and how does the current NESHAP

regulate its HAP emissions?

C. What data collection activities were conducted to support 

this action?

III. Analytical Procedures

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

category?

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 are the results of the risk assessment and analyses?

B. What are our proposed decisions regarding risk acceptability, 

ample margin of safety and adverse environmental effects?

C. What are the results of the technology review and our 

proposed decisions?

D. What other actions are we proposing?

E. What compliance dates are we proposing?

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

VI. Request for Comments

VII. Submitting Data Corrections
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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

A red-line 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-2012-0360).

I. General Information

A. Does this action apply to me?

Table 1 of this preamble lists the NESHAP and associated 

regulated industrial source category that is 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. The proposed standards, 

once promulgated, will be directly applicable to the affected 

sources. The Off-site Waste and Recovery Operations source 

category was initially titled the “Solid Waste Treatment, 

Storage, and Disposal Facilities (TSDF)” source category, which 
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included commercial facilities that treat, store or dispose of 

any solid waste received from off-site, as well as commercial 

facilities that recycle, recover and re-refine wastes received 

from off-site.1 On October 13, 1994 (59 FR 51913), the EPA 

explained that the source category was intended to represent 

those off-site waste and recovery operations that are not 

specifically listed as a separate distinct NESHAP source 

category such as hazardous waste incineration or municipal solid 

waste landfills and changed the title of the Solid Waste TSDF 

source category to “Off-Site Waste and Recovery Operations” to 

avoid confusion, to better distinguish this source category from 

other source categories, and to emphasize that this source

category addresses only activities that manage wastes received

from off-site.

Table 1. NESHAP and Industrial Source Categories Affected By 

This Proposed Action

Source 

Category NESHAP Examples of regulated entities

Off-Site 

Waste and 

Recovery 

Operations

Off-Site 

Waste and 

Recovery 

Operations

Businesses or government agencies 

that operate any of the following: 

Hazardous waste TSDF; Resource 

Conservation and Recovery Act 

(RCRA) exempt hazardous wastewater 

treatment facilities; nonhazardous 

wastewater treatment facilities 

other than publicly-owned treatment 

works; used solvent recovery 

 

1 See Initial List of Categories of Sources Under Section 112(c)(1) of the 

Clean Air Act Amendments of 1990 (57 FR 31576, July 16, 1992); U.S. EPA. 

Documentation for Developing the Initial Source Category List (EPA-450/3-91-

030; July 1992).
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plants; RCRA exempt hazardous waste 

recycling operations; used oil rerefineries.

This table is not intended to be exhaustive, but rather is 

meant to provide a guide for readers regarding entities likely 

to be affected by this action. If you have any questions 

regarding the applicability of this action to a particular 

entity, consult either the air permitting authority for the 

entity or your EPA regional representative, as listed in 40 CFR 

63.13 (General Provisions).

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 

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/offwaste/oswropg.html. Information on 
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the overall 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 

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 
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Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR2012-0360.

II. Background 

A. What is the statutory authority for this action? 

Section 112 of the CAA establishes a two-stage regulatory 

process to address emissions of hazardous air pollutants (HAPs) 

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 section 112(b), CAA section 112(d) requires us to 

promulgate technology-based 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 HAPs. For major sources, the technology-based 

NESHAP must reflect the maximum degree of emission reductions of 

HAPs 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 

pollutants through process changes, substitution of materials or 

other modifications; (2) enclose systems or processes to 
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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 

section 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 section 112(h)(1)-(2).

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

MACT standards promulgated under CAA section 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 

of existing sources in the category or subcategory (or the bestperforming five sources for categories or subcategories with 
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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 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 section

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

recalculate the MACT floor. Natural Resources Defense Council 

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

of Battery Recyclers, Inc. v. 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)(1) required EPA to 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 

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

that if Congress does not act on any recommendation in the 

Report, EPA must analyze and address residual risk for each 

category or subcategory of sources within 8 years after 

promulgation of such standards pursuant to 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 section 112(f) residual 

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 
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Circuit upheld as reasonable the EPA’s interpretation that 

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

the Benzene NESHAP. See NRDC v. 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.

1. Step 1-Determination of Acceptability

The agency in the Benzene NESHAP concluded that “the 

acceptability of risk under section 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 
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single factor.” Benzene NESHAP 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 v. 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 

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 
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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 

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.” 
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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 v. EPA, the court held that 

section 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.

2. Step 2-Determination of Ample Margin of Safety

CAA section 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 

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

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

According to CAA section 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 v. 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 

environmental effect,2 but must consider cost, energy, safety and 

other relevant factors in doing so.

 

2 “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 section 112(a)(7).
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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 section 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.

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 the EPA has determined is necessary to ensure risk is 
Page 24 of 231

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 section 112(f). 54 FR 38046, September 14, 

1989.

B. What is this source category and how does the current NESHAP

regulate its HAP emissions?

The NESHAP for OSWRO was proposed on October 13, 1994 (59 

FR 51913), promulgated on July 1, 1996 (61 FR 34140), and 

codified at 40 CFR part 63, subpart DD. The final rule was 

amended on July 20, 1999 (64 FR 38950). In general, the rule 

applies to waste management units and recovery operations that 

are: (1) located at major sources of HAP emissions; and (2) used 

to manage, convey or handle used oil, used solvent or waste 

received from other facilities and that contain at least one of 

97 organic HAP specified in the rule.3 The HAP emission sources 

at facilities subject to the OSWRO NESHAP are tanks, containers, 

surface impoundments, oil-water separators, organic-water 

separators, process vents and transfer systems used to manage 

 

3 The OSWRO MACT rule defines “waste,” “used oil” and “used solvent” in 40 CFR 

63.681 Definitions.
Page 25 of 231

off-site material and equipment leaks. The MACT standards 

regulate these emissions sources through emission limits, 

equipment standards and work practices. 

C. What data collection activities were conducted to support 

this action?

Under the authority of CAA section 114, we sent 

questionnaires to nine companies that own and operate OSWRO 

facilities. In the CAA section 114 questionnaires, we asked for 

information about process equipment, control devices, work 

practices, associated emission reductions, point and fugitive 

emissions, and other aspects of facility operations. We visited

three facilities, and reviewed permit data from 18 state and 

local agencies. In addition, we reviewed several EPA databases

to identify facilities that may be part of the source category. 

We also reviewed data in the EPA’s National Emissions Inventory 

(NEI) to identify emission sources and quantities of emissions

and the Toxics Release Inventory (TRI) to verify emissions 

estimates.

The data gathered through these activities are described 

further in the memorandum Development of the RTR Emissions 

Dataset for the Off-Site Waste and Recovery Operations Source 

Category, which is available in the docket for this proposed 

rule.
Page 26 of 231

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 

category?

The EPA conducted a risk assessment that provides estimates 

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

source category, 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 provides estimates of the distribution of cancer risks 

within the exposed populations, cancer incidence and an 

evaluation of the potential for adverse environmental effects 

for the source category. The eight sections that follow this 

paragraph describe how we estimated emissions and conducted the 

risk assessment. The docket for this proposed rule contains the 

following document which provides more information on the risk 

assessment inputs and models: Draft Residual Risk Assessment for 

the Off-Site Waste and Recovery Operations Source Category. The 

methods used to assess risks (as described in the eight primary 

steps below) are consistent with those peer-reviewed by a panel 

of the EPA’s Science Advisory Board (SAB) in 2009 and described 
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in their peer review report issued in 20104; 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?

Data for 38 OSWRO facilities were used to create an RTR 

emissions dataset (i.e., risk model input file). This RTR 

emissions dataset is based on a combination of data gathered 

through the CAA section 114 questionnaire and the 2005 NEI. The 

NEI is a database that contains information about sources that 

emit criteria air pollutants, their precursors and HAP. The 

database includes estimates of annual air pollutant emissions 

from point, nonpoint and mobile sources in the 50 states, the 

District of Columbia, Puerto Rico and the Virgin Islands. The 

EPA collects this information and releases an updated version of 

the NEI database every 3 years. The NEI includes information 

necessary for conducting risk modeling, including annual HAP 

emissions estimates from individual emission points at 

facilities and the related emissions release parameters. Other 

databases, including the TRI and Envirofacts, were consulted to 

verify emissions estimates and to identify facilities that are 

 

4 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.
Page 28 of 231

part of the OSWRO source category. As part of our quality 

assurance review, we reviewed the emissions data and release 

characteristics data in the RTR emissions dataset to ensure the 

data were accurate. We also checked the coordinates of each

emission source in the dataset using tools such as Google Earth 

and ArcView to ensure the emission point locations were correct.

While data for 38 OSWRO facilities were included in the RTR 

emissions dataset, available data indicate there are 52

currently operating major source facilities that are subject to 

the OSWRO MACT standards. The remaining 14 facilities were not 

included in the modeling file because the information available 

to the EPA, including the NEI, did not attribute any amount of 

HAP emissions to off-site waste and recovery operations at these 

facilities. It was also not possible to discern from the 

emission point identifiers or characteristics in the inventory 

which emissions could be attributed to the OSWRO source 

category. We note that available permit information indicates 

that five of these 14 facilities are only subject to off-site 

waste HAP content determination requirements and are not subject 

to the emissions standards and other requirements of the OSWRO 

NESHAP due to the low amount of HAP in the off-site waste 

accepted by these facilities. Also, available permit data 

indicates that two additional facilities are not subject to the 

emissions standards and other requirements of the OSWRO NESHAP 
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because they comply instead with 40 CFR 61 subpart FF, as 

allowed by the OSWRO NESHAP. For these seven facilities, we 

would not expect any emission points to be labeled as OSWRO 

emission points in the NEI because those emission points are not 

subject to any OSWRO MACT emissions standards. We also did not 

collect data from these facilities through our CAA section 114 

questionnaire. As noted in section VI of this preamble, we are 

requesting site-specific emissions data that would enable us to 

better characterize the maximum risks from the OSWRO source 

category. A list of the 52 facilities and additional information 

about the development of the RTR emissions dataset is provided 

in the technical document: Development of the RTR Emissions 

Dataset for the Off-Site Waste and Recovery Operations Source 

Category, which is available in the docket for this action.

2. How did we estimate MACT-allowable emissions?

The available emissions data in the RTR emissions dataset 

include estimates of the mass of HAP emitted during the 

specified annual time period. In some cases, 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 “MACTallowable” emissions level. We discussed the use of both MACTallowable and actual emissions in the final Coke Oven Batteries 

residual risk rule (70 FR 19998–19999, April 15, 2005) and in 
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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 used the emissions data gathered from the 2005 NEI and 

responses to the CAA section 114 questionnaire to estimate the 

MACT-allowable emissions levels. We estimate that the actual 

emissions level is representative of the MACT-allowable level 

for all emissions sources except tanks and process vents. Based 

on responses to the CAA section 114 questionnaire, we estimate

that MACT-allowable emissions from tanks and process vents could 

be up to five times the actual emissions. For some facilities, 

we cannot assign HAP emissions to a specific type of emission 

source (e.g., a process vent) due to a lack of specificity in 

the emission point identifiers in the NEI. For facilities where 

we could identify specific emission source types, we applied a 

factor of 5 to the actual emissions attributable to tanks and 

process vents. A factor of 1 was applied to the actual emissions 
Page 31 of 231

for other emissions sources (e.g., equipment leaks). For 

facilities where we could not identify specific emission source 

types, we developed and applied a factor of 2.5 to all the OSWRO 

emissions. The 2.5 factor is based on the factor of 5 for tanks 

and process vents and information from the responses to the CAA 

section 114 questionnaire indicating that tank and process vent

emissions comprise approximately half of the total OSWRO 

emissions.

For more detail about this estimate of the MACT-allowable 

emissions, see the memorandum, MACT-Allowable Emissions for the 

Off-Site Waste and Recovery Operations Source Category, which is 

available in the docket for this action.

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 category 

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 
Page 32 of 231

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 

calculations. This library includes 1 year (2011) of hourly 

surface and upper air observations for more than 800

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 

 

5 This metric comes from the Benzene NESHAP. See 54 FR 38046.

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).

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

are tabulated. 
Page 33 of 231

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 

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 
Page 34 of 231

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. 

The EPA estimated incremental individual lifetime cancer 

risks associated with emissions from the facilities in the 

source category 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 

evidence of carcinogenic potential8) 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 category as part of this 

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

consistent with both the analysis supporting the 1989 Benzene 

 

8 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 Science Advisory Board (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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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 

value, 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 

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 non-
Page 36 of 231

cancer 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 micrograms per cubic meter (μg/m3) for inhalation 

exposure and in a dose expressed in units of milligram per 

kilogram-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 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 
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exposure guideline levels (AEGL) and emergency response planning 

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

below, we used conservative assumptions for emissions rates, 

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.

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 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 
Page 38 of 231

Substances (http://www.epa.gov/oppt/aegl/pubs/sop.pdf),9 “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 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 non-regulatory 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 

 

9

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

Developing Acute Exposure Levels for Hazardous Chemicals, page 2.
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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 non-sensory effects. 

However, the effects 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 non-disabling odor, taste, and 

sensory irritation or certain asymptomatic, non-sensory 

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.
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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.”10 Id. at 1. The ERPG–1 value is defined 

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 

 

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

Industrial Hygiene Association.
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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. 

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. We choose the factor to 

use partially based on process knowledge and engineering 

judgment. The factor chosen also reflects a Texas study of 
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short-term emissions variability, which showed that most peak 

emission events in a heavily-industrialized four-county area 

(Harris, Galveston, Chambers and Brazoria Counties, Texas) were 

less than twice the annual average hourly emissions rate. The 

highest peak emissions event was 74 times the annual average 

hourly emissions rate, and the 99th percentile ratio of peak 

hourly emissions rate to the annual average hourly emissions 

rate was 9.11 Considering this analysis, to account for more than 

99 percent of the peak hourly emissions, we apply a conservative 

screening multiplication factor of 10 to the average annual 

hourly emissions rate in our acute exposure screening 

assessments as our default approach. However, we use a factor 

other than 10 if we have information that indicates that a 

different factor is appropriate for a particular source 

category. For this source category, there was no such 

information available and the default factor of 10 was used in 

the acute screening process. 

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 

 

11 See http://www.tceq.state.tx.us/compliance/field_ops/eer/index.html or 

docket to access the source of these data.
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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 this source 

category, there were no offsite acute values greater than 1, and 

no refined estimates were developed. 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 

the EPA’s RTR risk assessment methodologies,12 we generally 

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

RELs, AEGLs) than we do for our chronic risk assessments. This 

is in response to the SAB’s acknowledgement that there are 

 

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.
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generally more data gaps and inconsistencies in acute reference 

values than there are in chronic reference values. In some 

cases, 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). Initially, 

we determined whether any sources in the source category 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 EPA’s Air Toxics Risk Assessment Library (available at 

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

For the OSWRO source category, we identified emissions of 

polycyclic organic matter (POM) (analyzed as benzo(a)pyrene 

toxicity equivalence factor (TEQ)), polychlorinated biphenyls, 

hexachlorobenzene, chlordane, lindane (gamma hch), methoxyclor, 

 

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 online at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003.
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toxaphene, heptachlor, and trifluralin. Because one or more of 

these PB-HAP are emitted by at least one facility in the OSWRO 

source category, we proceeded to the next step of the 

evaluation. In this step, we determined whether the facilityspecific emissions rates 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 thresholds for 

several 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. The PB-HAP with emissions rate 

thresholds are: lead, cadmium, chlorinated dibenzodioxins and 

furans, mercury compounds, and polycyclic organic matter (POM). 

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 these PB–HAP were compared 

to the emission rate threshold values for these PB–HAP to assess 

the potential for significant human health risks via noninhalation pathways. We call this application of the TRIM.FaTE 

model the Tier I TRIM-screen or Tier I screen.
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For the purpose of developing emissions rates for our Tier 

I TRIM-screen, we derived emission levels for these PB-HAP 

(other than lead compounds) at which the maximum excess lifetime 

cancer risk would be 1-in-1 million (i.e., for polychlorinated 

dibenzodioxins and furans and POM) or, for HAP that cause noncancer health effects (i.e., cadmium compounds and mercury 

compounds), the maximum hazard quotient would be 1. If the 

emissions rate of any PB-HAP included in the Tier I screen 

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 PBHAP 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 multipathway impacts 

are significant, only that we cannot rule out that possibility 

based on the results of the screen. These facilities may be 
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further evaluated for multipathway risks using the TRIM.FaTE 

model. 

For further information on the multipathway analysis 

approach, see the Draft Residual Risk Assessment for the OffSite Waste and Recovery Operations Source Category, which is 

available in the docket for this action.

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. In these 

cases, the expected emission reductions were applied to the 

specific HAP and emission points in the RTR emissions dataset to 

develop corresponding estimates of risk and incremental risk 

reductions.

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 

section 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, 
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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 persistent 

bioaccumulative HAP (PB-HAP) and two acid gases. The five PB-HAP 

are cadmium, dioxins/furans, polycyclic organic matter (POM),

mercury (both inorganic mercury and methyl mercury) and lead

compounds. The two acid gases are hydrogen chloride (HCl) and 

hydrogen fluoride (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, 

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 
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percent of all PB-HAP emissions nationally from stationary 

sources (on a mass basis from the 2005 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 compounds, we compare 

the estimated HEM-modeled exposures from the source category 

emissions of lead with the level of the secondary National 

Ambient Air Quality Standard (NAAQS) for lead.14 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 

 

14 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.” 73 FR 66964, November 12, 

2008.
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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 

on the extent to which other HAP emitted by the source category 

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 category 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 
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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 (other than lead compounds), 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.

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

amphipods, isopods and crayfish) communities exposed to PBHAP 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 (other than lead compounds), we also evaluated 

the following population-level ecological assessment endpoint to 

screen for indirect HAP exposures of top consumers via the 

bioaccumulation of HAP in food chains:
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 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 ug 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 levels (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 

significant increases in frequency or severity of adverse 

effects.

No-observed-adverse-effect levels (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, 
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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., National Oceanic and Atmospheric Organization 

(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 

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 
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greater than the reference concentration for chronic inhalation 

exposure for human health. This means that where the 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, the 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.

e. Screening Methodology

For the environmental risk screening analysis, the EPA 

first determined whether any facilities in the OSWRO source 

category emitted any of the seven environmental HAP. For the 

OSWRO source category, we identified emissions of POM, HCl and 

HF. 

Because one or more of the seven environmental HAP 

evaluated are emitted by at least one facility in the source 

category, we proceeded to the second step of the evaluation. 

f. PB-HAP Methodology
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For cadmium, mercury, POM and dioxins/furans, the 

environmental screening analysis consists of two tiers, while 

lead compounds are analyzed differently as discussed earlier. In 

the first tier, we determined whether the maximum facilityspecific 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, 

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 
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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 5 modeled soil 

concentrations at various distances from the facility (5 soil 

concentrations x 8 octants = total of 40 soil concentrations per 

facility) and 1 lake with modeled concentrations for water, 

sediment and fish tissue. In the Tier II environmental risk 

screening analysis, the 40 soil concentration points are 

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 typically is 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.
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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-HAPs. 

For purposes of ecological risk screening, the EPA 

identifies a potential for adverse environmental effects to 

plant communities 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 the Draft Residual Risk Assessment for 

the Off-Site Waste and Recovery Operations Source Category, 

which is available in the docket for this action.
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7. How did we conduct facility-wide assessments?

To put the source category risks in context, we typically 

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 

data for estimating these “facility-wide” risks were obtained 

from the 2005 NEI (available at 

http://www.epa.gov/ttn/atw/nata2005). 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 facility-wide 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 the source category addressed in this proposal. We 

specifically examined the facility that was associated with the 

highest estimate of risk and determined the percentage of that 

risk attributable to the source category of interest. The Draft 

Residual Risk Assessment for the Off-Site Waste and Recovery 

Operations Source Category available through the docket for this 

action provides the methodology and results of the facility-wide 
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analyses, including all facility-wide 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 

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 RTR emissions dataset, 

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 Off-Site Waste and Recovery Operations Source 

Category, which is available in the docket for this action.

a. Uncertainties in the RTR Emissions Dataset

Although the development of the RTR emissions dataset 

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. 
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The emission estimates considered in this analysis generally are 

annual totals for certain years and they do not reflect shortterm fluctuations during the course of a year or variations from 

year to year. The estimates of peak hourly emission rates for 

the acute effects screening assessment were based on an emission 

adjustment factor applied to the average annual hourly emission 

rates, which are intended to account for emission fluctuations 

due to normal facility operations. 

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 estimated 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 
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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 

and long-term mobility between census blocks in the modeling 

domain were not considered.15 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 

 

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

who live farther 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 

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 
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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, 

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 

overestimate of 25 to 30 percent of exposures.16

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 

 

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

January 2001; page 85.)
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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 

exposures as it is unlikely that a person would be located at 

the point of maximum exposure when peak emissions and worst-case 

meteorological 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 
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relationships is given in the Draft Residual Risk Assessment for 

the Off-Site Waste and Recovery Operations Source Category, 

which is available in the docket for this action. 

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).17 In some 

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

in other circumstances the risk could be greater.18 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 

 

17 IRIS glossary (http://www.epa.gov/NCEA/iris/help_gloss.htm).

18 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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estimate (with uncertainty spanning perhaps an order of 

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,19 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 

 

19 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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further study might support development of reference values that 

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 
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vary appreciably between human individuals, hence a value of 3 

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 observed 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 this source category are lacking dose-response assessments. 
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Accordingly, these pollutants cannot be included in 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 not speciated (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 
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reference value from the other compounds in the group to 

estimate risk.

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.20

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 Science Advisory Board reviews and other reviews, 

 

20 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.
Page 71 of 231

we are confident that the models used in the screen are 

appropriate and state-of-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. 
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The assumptions and the associated uncertainties regarding the 

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 category. 

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.21

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 

through the soil? This type of uncertainty is difficult to 

 

21 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.
Page 74 of 231

quantify. However, based on feedback received from previous EPA 

Science Advisory Board 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 the PB-HAP (other than 

lead compounds, which were evaluated by comparison to the 

secondary lead NAAQS) that were included in the environmental 

screening assessment 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 
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account for meteorological patterns in the vicinity of 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 individual 

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 Program). 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 compounds, which were

evaluated through a comparison to the NAAQS), we searched for 

benchmarks at the following three effect levels, as described in 

section 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 Off-Site Waste and Recovery Operations Source Category, 

available in the docket for this action.

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

this proposal?

As discussed in section II.A of this preamble, in 

evaluating and developing standards under section 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)22 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, including the number of persons at risk 

levels higher than approximately 1-in-1 million, as well as 

 

22 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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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 MACTallowable emissions. See, e.g., 75 FR 65068, October 21, 2010; 

75 FR 80220, December 21, 2010; 76 FR 29032, May 19, 2011. 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 section 112(f). As 

explained in the Benzene NESHAP, “the first step judgment on 

acceptability cannot be reduced to any single factor” and thus 

“[t]he Administrator believes that the acceptability of risk 
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under [previous] section 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 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 section 112 regulations, and thereby 

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’.”
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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 section 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 

discussed earlier in this preamble, in our determinations of 

acceptability and ample margin of safety.
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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 

exposed may be sufficient to result in increased risk of adverse 

non-cancer health effects. In May 2010, the SAB advised the EPA 
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“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.”23

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 sources 

in the same category whose emissions result in exposures to the 

same individuals; and (3) for some persistent and bioaccumlative 

pollutants, analyzing the ingestion route of exposure. In 

addition, the RTR risk assessments have always considered 

aggregate cancer risk from all carcinogens and aggregate noncancer hazard indices from all non-carcinogens affecting the 

same target organ system.

Although we are interested in placing source category and 

facility-wide HAP risks in the context of total HAP risks from 

 

23 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 in this proposed 

rule docket from David Guinnup entitled, EPA’s Actions in Response to the Key 

Recommendations of the SAB Review of RTR Risk Assessment Methodologies.
Page 84 of 231

all sources combined in the vicinity of each source, we are 

concerned about the uncertainties of doing so. Because of the 

contribution to total HAP risk from emission sources other than 

those that we have studied in depth during this RTR review 

(i.e., those sources located at facilities within the source 

category), 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.

Based on our analyses of the available data and 

information, we identified potential developments in practices, 
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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).

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 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 in the 

OSWRO source category, as well as the costs, non-air impacts and 

energy implications associated with the use of these 

technologies. Additionally, we requested information from 
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facilities regarding developments in practices, processes or 

control technology. Finally, we reviewed information from other 

sources, such as state and/or local permitting agency databases 

and industry-supported databases.

IV. Analytical Results and Proposed Decisions

This section of the preamble provides the results of our 

RTR for the OSWRO source category and our proposed decisions 

concerning changes to the OSWRO NESHAP.

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

1. Inhalation Risk Assessment Results

Table 2 of this preamble provides a summary of the results 

of the inhalation risk assessment for the source category.

Table 2. Off-Site Waste and Recovery Operations 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 HQd

Actual 

Emissions 

Level

MACTallowable 

Emissions 

Levelc

Actual 

Emissions 

Level

MACTallowable 

Emissions 

Level

9 20

≥ 1-in-1 

million: 

210,000

≥ 10-in-1 

million: 0

0.02 0.6 1

HQREL = 1 

(glycol 

ethers) 

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 OSWRO source 

category for both actual and MACT-allowable emissions is the respiratory 

system. 

c The development of allowable emission estimates can be found in the memo 

entitled MACT-Allowable Emissions for the Off-Site Waste and Recovery 

Operations Source Category, which is available in the docket for this action.
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d The maximum off-site acute value of 1 for actuals is driven by emissions of 

glycol ethers. See Section III.A.E for an explanation of acute dose-response 

values. Acute assessments are not performed with MACT-allowable emissions.

The inhalation risk modeling performed to estimate risks 

based on actual and MACT-allowable emissions relied primarily on 

data from the CAA section 114 questionnaire responses and the 

NEI. The results of the chronic inhalation cancer risk 

assessment indicate that, based on estimates of current actual 

emissions, the maximum lifetime individual cancer risk posed by 

the OSWRO source category is 9-in-1 million, with emissions of 

benzidine and 2,4-toluene diamine accounting for the majority of 

the risk. The total estimated cancer incidence from the OSWRO 

source category based on the actual emissions levels is 0.02 

excess cancer cases per year, or one case every 50 years, with 

emissions of benzidine and 2,4-toluene diamine contributing to 

the majority of the incidence. In addition, we note that 

approximately 210,000 people are estimated to have cancer risks 

greater than or equal to 1-in-1 million as a result of actual 

emissions from this source category. When considering MACTallowable emissions, the maximum individual lifetime cancer risk 

is estimated to be up to 20-in-1 million, driven by emissions of 

benzidine and 2,4-toluene diamine. Due to the way MACT-allowable 

risks were calculated, estimates of population exposure and 

cancer incidence are not available, but would be greater than 

those estimates presented based on actual emissions. However, 
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since the MIR based on MACT-allowable emissions is 20-in-1 

million, there are no people exposed to cancer risks greater 

than 100-in-1 million.

The maximum modeled chronic non-cancer TOSHI value for the 

OSWRO source category based on actual emissions was estimated to 

be 0.6, with emissions of chlorine contributing to the majority 

of the TOSHI. There are no people estimated to have exposure to 

TOSHI levels greater than 1 as a result of actual emissions from 

this source category. When considering MACT-allowable emissions, 

the maximum chronic non-cancer TOSHI value was estimated to be

up to 1, driven by emissions of chlorine. There are no people 

estimated to have exposure to TOSHI levels greater than 1 as a 

result of emissions at the MACT-allowable levels from this 

source category. 

Our screening analysis for worst-case acute impacts based 

on actual emissions indicates that an HQ value of 1 is not 

exceeded for any pollutants at any facility, indicating that the 

HAP emissions are believed to be without appreciable risk of 

acute health effects. In characterizing the potential for acute 

non-cancer risks 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 
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peak hourly emissions as described earlier. Refer to Appendix 6 

of the Draft Residual Risk Assessment for the Off-Site Waste and 

Recovery Operations Source Category in the docket for this 

action for the detailed acute risk results.

2. Multipathway Risk Screening Results

Multiple facilities reported emissions of PB-HAP, including 

2-acetylaminofluorene (a POM compound), heptachlor, and 

trifluralin. Only one facility reported emissions of a PB-HAP 

that has an available RTR multipathway screening value: 2-

acetylaminofluorene, a polycylic organic matter (POM) compound 

that was analyzed as benzo(a)pyrene TEQ. Reported emissions of 

the POM 2-acetylaminofluorene are below the multipathway 

screening level for this compound, indicating low potential for 

multipathway risks as a result of emissions of this PB-HAP. The 

remaining PB-HAP do not currently have RTR multipathway 

screening values, and they were not evaluated for potential noninhalation risks. These HAP, however, are not emitted in 

appreciable quantities from OSWRO facilities. (For more 

information on PB-HAP emitted from this source category, please 

see the Draft Residual Risk Assessment for the Off-Site Waste 

and Recovery Operations Source Category document available in 

the docket for this action.)

3. Environmental Risk Screening Results
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As described in section III.A.5, we conducted an 

environmental risk screening assessment for the OSWRO source 

category. Emissions of three environmental HAP were reported by 

OSWRO facilities: POM, hydrogen chloride and hydrogen fluoride. 

For POM, 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 the acid gases HCl 

and HF, the average modeled concentration of these chemicals 

around each facility (i.e., the average concentration of all 

off-facility-site data points in the modeling domain) did not 

exceed any ecological benchmarks. In addition, each individual 

modeled concentration of hydrogen chloride and hydrogen fluoride 

(i.e., each off-facility-site data point in the modeling domain) 

was below the ecological benchmarks for all facilities. 

4. Facility-wide Inhalation Risk Assessment Results

Table 3 displays the results of the facility-wide risk 

assessment. This assessment is based on actual emission levels. 

For detailed facility-specific results, see Appendix 5 of the 

Draft Residual Risk Assessment for the Off-Site Waste and 

Recovery Operations Source Category in the docket for this 

proposed rule.

Table 3. Off-Site Waste and Recovery Operations Facility-Wide 

Risk Assessment Results

Number of facilities analyzed 38

Cancer Risk:
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Estimated maximum facility-wide 

individual cancer risk (in 1 

million)

200

Number of facilities with 

estimated facility-wide 

individual cancer risk of 100-

in-1 million or more

1

Number of facilities at which 

the OSWRO source category 

contributes 50 percent or more 

to the facility-wide individual 

cancer risks of 100-in-1 

million or more

0

Number of facilities with 

estimated facility-wide 

individual cancer risk of 1-in1 million or more

17

Number of facilities at which 

the OSWRO source category 

contributes 50 percent or more 

to the facility-wide individual 

cancer risk of 1-in-1 million 

or more

7

Chronic Non-cancer Risk:

Maximum facility-wide chronic 

non-cancer TOSHI 4

Number of facilities with 

facility-wide maximum noncancer TOSHI greater than 12

Number of facilities at which 

the OSWRO source category 

contributes 50 percent or more 

to the facility-wide maximum 

non-cancer TOSHI of 1 or more

0

The facility-wide MIR and TOSHI are based on actual 

emissions from all emissions sources at the identified OSWRO

facilities. The results indicate that 17 facilities have a 

facility-wide cancer MIR greater than or equal to 1-in-1 million

and one facility has a facility-wide cancer MIR greater than or 

equal to 100-in-1 million. The maximum facility-wide MIR is 200-
Page 92 of 231

in-1 million due to emissions of beryllium compounds from the

cement manufacturing processes at the facility site, with 

emission points from the OSWRO production source category 

contributing less than 1 percent of the maximum facility-wide 

risk. The results indicate that two facilities have a facilitywide non-cancer TOSHI greater than or equal to 1. The maximum 

facility-wide TOSHI is 4, and this TOSHI occurs at two

facilities. At one of these facilities, the TOSHI is driven 

mainly by emissions of beryllium compounds from the same cement 

manufacturing processes mentioned above. The TOSHI at the other 

facility is driven mainly by emissions of chlorine from 

industrial inorganic chemical manufacturing processes and 

synthetic organic chemical manufacturing processes at the 

facility site. In each instance, the OSWRO production source 

category contributes less than 1 percent to the facility-wide 

TOSHI. The focus of this analysis is the OSWRO source category 

and its low relative contribution to facility-wide risk. The 

maximum facility-wide MIR and TOSHI values presented here are

the result of a screening analysis for the other source 

categories located at common facility sites. The screening 

analysis requires further refinement and takes place during the 

RTR review for those source categories. We anticipate reductions 

of HAP from the cement manufacturing processes due to the 

implementation of the recently promulgated MACT standard, with a 
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compliance date of September 9, 2015, and the upcoming RTR 

review, with a consent decree deadline of June 15, 2017 for 

proposal and June 15, 2018 for promulgation. We may consider 

options for achieving further reduction of HAP from the 

inorganic chemical and synthetic organic chemical manufacturing 

processes in future reviews for those source categories. 

5. What demographic groups might benefit from this regulation?

To determine whether or not to conduct a demographics 

analysis, which is an assessment of risks to individual 

demographic groups, we look at a combination of factors 

including the MIR, non-cancer TOSHI, population around the 

facilities in the source category, and other relevant factors. 

Actual emissions from the OSWRO source category result in no 

individuals being exposed to cancer risk greater than 9-in-1 

million or a non-cancer TOSHI greater than 1. In addition, we 

estimate the cancer incidence for the source category to be 0.02 

cases per year. Therefore, we did not conduct an assessment of 

risks to individual demographic groups for this proposed rule. 

However, we did conduct a proximity analysis, which identifies 

any overrepresentation of minority, low income or indigenous 

populations near facilities in the source category. The results 

of this analysis are presented in the section of this preamble 

entitled “Executive Order 12898: Federal Actions to Address 
Page 94 of 231

Environmental Justice in Minority Populations and Low-Income 

Populations.”

B. What are our proposed decisions regarding risk acceptability, 

ample margin of safety and adverse environmental effects?

1. Risk Acceptability

As discussed in sections II.A and III.B of this preamble, 

we weigh all health risk factors in our risk acceptability 

determination, including the cancer MIR; the number of persons 

in various cancer and non-cancer risk ranges; cancer incidence; 

the maximum non-cancer TOSHI; the maximum acute non-cancer HQ; 

the extent of non-cancer risks; the potential for adverse 

environmental effects; the distribution of cancer and non-cancer 

risks in the exposed population; and risk estimation 

uncertainties (54 FR 38044, September 14, 1989).

For the OSWRO source category, the risk analysis we 

performed indicates that the cancer risks to the individual most 

exposed could be up to 9-in-1 million due to actual emissions 

and up to 20-in-1 million due to MACT-allowable emissions. These 

risks are considerably less than 100-in-1 million, which is the 

presumptive upper limit of acceptable risk. The risk analysis 

also shows relatively low cancer incidence (0.02 cases per 

year), as well as no appreciable risk of deleterious chronic or 

acute non-cancer health effects. In addition, the risk 
Page 95 of 231

assessment indicates no significant potential multipathway 

health effects. 

While our analysis of facility-wide risks shows one

facility with a maximum facility-wide cancer risk of 100-in-1 

million or greater and two facilities with a maximum chronic 

non-cancer TOSHI greater than 1, it also shows that OSWRO 

operations did not drive these risks. In fact, OSWRO operations 

contribute less than 1 percent to the cancer MIR and less than 1

percent to the non-cancer TOSHI).

Considering all of the health risk information and factors 

discussed above, including the uncertainties discussed in 

section III.A.8 of this preamble, we propose that the risks from 

the OSWRO source category are acceptable.

2. Ample Margin of Safety Analyses and Proposed Controls

Although we are proposing that the risks from the OSWRO 

source category are acceptable, risk estimates for 210,000 

individuals in the exposed population are above 1-in-1 million 

based on actual emissions. We recognize that our risk analysis 

indicates that the cancer risks to the individual most exposed

are well within EPA’s acceptable range(i.e., up to 9-in-1 

million due to actual emissions and up to 20-in-1 million due to 

MACT-allowable emissions). However, as stated in the Benzene 

NESHAP, in protecting public health with an ample margin of 

safety, “EPA strives to provide maximum feasible protection 
Page 96 of 231

against risks to health from HAP,” considering available health 

information, the incremental risk reduction associated with more

stringent standards, technological feasibility, and other 

factors, such as costs and economic impacts of controls. 54 FR 

at 38044-38045. Consequently, in this analysis, we investigated 

available emissions control options that might reduce the risk 

associated with emissions from the source category. We 

considered this information along with all of the health risks 

and other health information considered in determining risk 

acceptability. As explained below, we are proposing additional 

control requirements for equipment leaks and certain tanks 

because considering costs and other factors, we have determined 

that these additional controls are capable of further reducing 

risks to the individual most exposed, and thus, they provide an 

ample margin of safety.

For the OSWRO source category, we did not identify any 

options that would reduce HAP emissions from containers, surface 

impoundments, oil-water separators, organic-water separators or 

transfer systems beyond what is currently required in the rule. 

For process vents, tanks and equipment leaks, we identified 

additional control options, which are described below.

For 19 of the 38 facilities included in the OSWRO risk 

analysis, the available data (see discussion of emissions data 

in section III.A of this preamble) did not, in general, 
Page 97 of 231

attribute OSWRO emissions to specific emission sources. For 

example, the NEI data for many of these facilities grouped 

emissions under source classification codes (SCC) for nonspecific processes, such as 39999999 – Miscellaneous Industrial 

Processes. For these facilities, we lack information as to which 

processes and emission point types are contributing to the risk 

estimates developed in the risk assessment. In contrast, CAA 

section 114 response data for the other 19 facilities were 

available, and the emissions data for these facilities were 

attributed to specific emission point types. However, the 

maximum cancer MIR and noncancer TOSHI values for the OSWRO 

source category are attributed to a facility for which only NEI 

data are available and for which we lack information regarding 

the processes and emission point types that contribute to these 

maximum risk values. Because we were unable to precisely 

determine the magnitude of HAP emissions from specific process 

types and how those emissions relate to the risk estimates, we 

conservatively assumed that the type of equipment under 

investigation was responsible for the maximum risks. For 

example, in our assessment of process vents, we assumed the 

maximum risks for the OSWRO source category were due to process 

vents, and then we evaluated how further controls might reduce 

this risk. While these assumptions may introduce some 

uncertainty regarding the risk reductions that would be achieved 
Page 98 of 231

for each equipment type, we are presenting our analysis using 

the best information available. As noted in section VI of this 

preamble, we are requesting commenters to provide any sitespecific emissions or other data that would enable us to better 

characterize the maximum risks and the risk reductions from the 

proposed control options for the OSWRO source category.

In the ample margin of safety analysis, factors related to 

the appropriate level of control are considered, including the 

costs and economic impacts of the controls. For the OSWRO source 

category, the control options identified to reduce risks are the 

same as those identified in the technology review. As such, we 

relied on the control cost estimates and estimates of control 

cost effectiveness derived from the technology review analyses 

in our ample margin of safety determination. We believe that our 

ample margin of safety analysis is reasonable. However, we note 

that if we had data to more precisely assign HAP emissions to 

particular emission sources in the risk modeling file and if 

that data were to lead us to conclude that the MACT standards 

reflect an ample margin of safety, we are still proposing these 

same control options under the technology review because they 

are technologically applicable and cost effective for this 

source category based on our experience with similar emission 

sources emitting similar HAP at other chemical type facilities. 
Page 99 of 231

We request comments on the proposed controls discussed below to 

provide an ample margin of safety for this source category.

For process vents, as discussed in section IV.C of this 

preamble, we identified an emissions control option of requiring 

compliance with a 98 percent reduction rather than a 95 percent 

reduction in HAP emissions. To assess the maximum potential for 

risk reduction that could result from this process vent control 

option, we assumed that the maximum risks for the OSWRO source 

category are due to emissions from a process vent with emissions 

controlled at 95 percent. In this scenario, we estimate the HAP 

reduction resulting from compliance with a 98 percent reduction 

would be 10 tpy from the current emissions level, with a cost 

effectiveness of $350,000/ton HAP reduction. We estimate this 

option would reduce the MIR at the MACT-allowable emissions 

level for the source category from 20-in-1 million to 8-in-1 

million and reduce the maximum chronic non-cancer TOSHI from 1

to 0.4. Considering all of the health risks and other health 

information considered in our determination of risk 

acceptability, the potential for reductions in HAP emissions and 

risk, the uncertainty associated with the estimated potential 

risk reductions and the costs associated with this option, we 

are proposing that no additional HAP emissions controls for 

OSWRO process vents are necessary to provide an ample margin of 

safety to protect public health.
Page 100 of 231

For tanks, as discussed in section IV.C of this preamble, 

we identified two emissions control options. Option 1 requires

Level 2 control of emissions for additional tanks containing 

liquids with lower vapor pressures. Option 2 requires compliance 

with a 98 percent reduction rather than a 95 percent reduction 

in HAP emissions from tanks. As discussed above for process 

vents, to assess the maximum potential for risk reduction that 

could result from these two tank control options, we have 

assumed that the maximum risks for the OSWRO source category are 

due to emissions from tanks. For Option 1, we have assumed that 

the maximum risks are due to tanks that are not currently 

subject to Level 2 controls, which require a 95 percent 

reduction in emissions. In this scenario, we estimate the HAP 

reduction resulting from compliance with the control of 

additional tanks would be 73 tpy from the current emissions 

level, with a cost effectiveness of $300/ton HAP reduction. We 

estimate this option would reduce the MIR at the MACT-allowable 

emissions level for the source category from 20-in-1 million to 

1-in-1 million and reduce the maximum chronic non-cancer TOSHI 

from 1 to 0.05. Under Option 2, we estimate the HAP reduction 

incremental to Option 1 would be approximately 22 tpy, with a 

cost effectiveness of $13,000/ton HAP reduction and a cost 

effectiveness incremental to Option 1 of $56,000/ton HAP 

reduction. We estimate this option would reduce the MIR at the 
Page 101 of 231

MACT-allowable emissions level incremental to Option 1 for the 

source category from 1-in-1 million to 0.4-in-1 million and 

reduce the maximum chronic non-cancer TOSHI from 0.05 to 0.02. 

Considering all of the health risks and other health information 

considered in our determination of risk acceptability, the 

potential risk reductions and the costs associated with Option 

1, we are proposing to require this additional level of control 

to provide an ample margin of safety. Considering all of the 

health risks and other health information considered in our 

determination of risk acceptability, the potential for 

reductions in risk, the uncertainty associated with the 

estimated potential risk reductions and the costs associated 

with Option 2, we are proposing that the additional HAP 

emissions controls for OSWRO tanks under Option 2 are not 

necessary to provide an ample margin of safety to protect public 

health. In addition, as discussed further in preamble section 

IV.C, we are also proposing the Option 1 additional control 

level as a result of the technology review.

For equipment leaks, as discussed in section IV.C of this 

preamble, we identified two emission control options: Option 1 

requires compliance with 40 CFR part 63, subpart H, rather than 

40 CFR part 61, subpart V, without the connector leak detection 

and repair (LDAR) requirements of subpart H; Option 2 requires 

the same as Option 1 but includes the connector LDAR requirement 
Page 102 of 231

of subpart H. As discussed above for tanks, to assess the 

maximum potential for risk reduction that could result from 

these equipment leaks control options, we assumed that the 

maximum risks for the OSWRO source category are due to emissions 

from equipment leaks. We also assumed that since emissions from 

equipment leaks are estimated to be the same at actual and MACTallowable emission levels, the risks due to equipment leaks at 

the MACT-allowable level are the same as risks due to equipment 

leaks at actual emissions levels. We additionally assumed, based 

on our analysis of estimated baseline equipment leak emissions,24

that half of the equipment leak emissions causing the maximum 

risks are from non-connector components (i.e. pumps and valves), 

and the other half are from connectors. Given these assumptions, 

under Option 1, we estimate the HAP reduction resulting from 

compliance with subpart H without the subpart H connector 

monitoring requirements would be 69 tpy from the baseline actual 

emissions level, with a cost effectiveness of $1,000/ton HAP 

reduction. We estimate this option would reduce the MIR at the 

MACT-allowable emissions level for the equipment leaks at the 

source category from 9-in-1 million to 7-in-1 million and reduce 

the maximum chronic non-cancer TOSHI from 0.6 to 0.5. Under 

Option 2, we estimate the incremental HAP reduction resulting 

 

24 See Technology Review and Cost Impacts for the Proposed Amendments to the 

Off-Site Waste and Recovery Operations Source Category, which is available in 

the docket for this action.
Page 103 of 231

from compliance with subpart H including the subpart H connector 

monitoring requirements would be 70 tpy more than Option 1, with 

an overall cost effectiveness of $4,000/ton HAP reduction and a 

cost effectiveness incremental to Option 1 of $7,000/ton HAP 

reduction. We estimate this option would reduce the MIR at the 

MACT-allowable emissions level incremental to Option 1 for the 

equipment leaks at the source category from 7-in-1 million to 5-

in-1 million and reduce the maximum chronic non-cancer TOSHI 

from 0.5 to 0.3. We note, as discussed in preamble section IV.C, 

we are proposing the additional control level of Option 2 as a 

result of the technology review. Considering the health risks 

and other health information evaluated in our determination of 

risk acceptability, that some risk reduction occurs with Option 

2, and the costs associated with Option 2 are reasonable, we are 

proposing to require this additional level of control to provide

an ample margin of safety.

In accordance with the approach established in the Benzene 

NESHAP, the EPA weighed all health risk measures and information 

considered in the risk acceptability determination, along with 

the costs of emissions controls, technological feasibility, 

uncertainties and other relevant factors in making our ample 

margin of safety determination. Considering the health risk 

information, the potential risk reductions and the reasonable 

cost effectiveness of certain control options identified for 
Page 104 of 231

tanks and equipment leaks, we propose that the standards for the 

OSWRO source category be revised to include the proposed control 

Option 1 for tanks and the proposed control Option 2 for 

equipment leaks to provide an ample margin of safety to protect 

public health.

3. Adverse Environmental Effects

We conducted an environmental risk screening assessment for 

the OSWRO source category for POM, HCl and HF. For POM, none of 

the individual modeled Tier I concentrations for any facility in 

the source category exceeded any of the ecological benchmarks 

(either the LOAEL or NOAEL). 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, we are proposing that it is not necessary to set a more 

stringent standard to prevent such an adverse environmental 

effect, taking into consideration costs, energy, safety, and 

other relevant factors.

C. What are the results of the technology review and our 

proposed decisions?

As described in section III.C of this preamble, our 

technology review focused on identifying developments in 

practices, processes and control technologies for the emission 

sources in the OSWRO production source category. To identify 
Page 105 of 231

such developments since the MACT standards were developed, we 

consulted the EPA’s RACT/BACT/LAER Clearinghouse, reviewed 

subsequent regulatory development efforts and reviewed data from 

the 2013 CAA Section 114 survey of OSWRO facilities. For the 

OSWRO source category, we did not identify any developments in 

practices, processes or control technologies for containers, 

surface impoundments, oil-water separators, organic-water 

separators or transfer systems beyond what is currently required 

in the rule. For process vents, tanks and equipment leaks, we 

identified additional control options, and the following 

sections summarize the results of our technology review for 

these emissions sources.

To perform the technology review, we needed information 

that was not included in the RTR emissions dataset used for 

modeling OSWRO risks. Therefore, to evaluate the costs and 

cost-effectiveness of various control options, we used a model 

plant approach. The model plant approach we used resulted in 

different baseline emission estimates than those included in the 

risk modeling dataset. More information concerning our 

technology review and model plant approach can be found in the 

memorandum titled, Technology Review and Cost Impacts for the 

Proposed Amendments to the Off-Site Waste and Recovery 

Operations Source Category, which is available in the docket for 

this action.
Page 106 of 231

1. Tanks

For tanks at existing affected sources, we identified two 

potential developments in practices and control techniques. The 

current OSWRO MACT requirements at 40 CFR 63.685(b)(1) for tanks

at an existing affected source depend on the capacity of the 

tank and the vapor pressure of the material being stored. “Level 

2” control is required for: (1) tanks with capacities greater 

than or equal to 75 cubic meters (m3), but less than 151 m3 and a 

vapor pressure of 27.6 kilopascals (kPa) or greater and (2)

tanks with capacities greater than or equal to 151 m3 and a vapor 

pressure of 5.2 kPa or greater. “Level 2” control essentially 

requires one of five options: (1) a fixed roof tank equipped with 

an internal floating roof; (2) a fixed roof tank equipped with 

an external floating roof; (3) a tank with a vapor-tight cover 

and vented through a closed-vent system to a control device that 

has an efficiency of 95 percent or more; (4) a pressure tank; or 

(5) a tank inside a permanent total enclosure (PTE) that is 

vented through a closed-vent system to an enclosed combustion 

control device. Tanks of any capacity (effectively those less 

than 75 m3) with a vapor pressure of 76.6 kPa or greater are 

required to use one of the options listed above for Level 2 

control, except that fixed roof tanks with either an internal or 

an external floating roof cannot be used. For tanks with 

capacities and vapor pressures less than those stated above, 
Page 107 of 231

“Level 1” control is required. “Level 1” control generally 

requires a fixed roof with closure devices.

We evaluated two control options that would change the tank

requirements if adopted. Option 1 would lower the vapor pressure 

threshold above which Level 2 controls would be required for 

some tanks. Option 2 would revise the vapor pressure threshold 

as in Option 1 and increase the required control efficiency from 

the current 95 percent to a 98 percent emissions reduction for

all tanks required to use Level 2 controls. Through the review 

of air toxics MACT standards developed subsequent to the OSWRO 

MACT standards, we noted that several other MACT standards refer 

to the Hazardous Organic NESHAP (HON) for their storage tank 

requirements. We evaluated revising the applicability of the 

OSWRO existing source requirements to use the same thresholds 

for Level 2 control as the thresholds for control required by 

the HON. As shown in Table 4, Option 1 would require Level 2 

emissions control for tanks with capacities greater than or 

equal to 75 m3, but less than 151 m3, if the vapor pressure of 

the stored material is 13 kPa or greater, instead of 27.6 kPa or 

greater as required by the current MACT standard. No other tank 

size or vapor thresholds would be changed with Option 1. For 

tanks at new affected sources, the current OSWRO applicability 

thresholds are consistent with those required for the chemical 

industry under other NESHAP, including the HON, so no revised 
Page 108 of 231

applicability requirements were evaluated for tanks located at 

new sources.

Because available data for the source category indicate 

most OSWRO tanks currently have fixed-roofs with emissions 

routed through a closed vent system to a control device, under 

Option 2 we considered the impacts of requiring a higher control 

efficiency than currently required by the OSWRO MACT standard. 

While carbon adsorption and other control devices are assumed to 

have a control efficiency of 95 percent, other technologies are 

capable of achieving greater emissions control, such as thermal 

incinerators. Several of these devices have been demonstrated to 

achieve a control efficiency of 98 percent or greater. Under 

Option 2, we considered the impacts of requiring a 98 percent 

emissions reduction for tanks meeting the lowered vapor pressure 

threshold under Option 1, and all other tanks required to use 

Level 2 emission controls, assuming a recuperative thermal 

oxidizer (RCO) would be used to attain this increased level of 

control.

Table 5 presents the emission reductions and costs of the

two options considered for tanks at existing affected sources in 

the OSWRO source category under the technology review. For 

Option 1, data collected through our CAA section 114 

questionnaire indicate that only some facilities have tanks in 

the size and vapor pressure range considered for this option, 
Page 109 of 231

and based on these data we estimate that approximately three 

OSWRO facilities have tanks that would require additional 

control under Option 1. As seen in Table 5, for Option 1, we 

estimate the capital costs to be approximately $76,000, and the 

total annualized costs are estimated to be approximately 

$21,000. The estimated HAP emissions reduction is approximately 

73 tpy, and the cost effectiveness is approximately $300/ton. 

For Option 2, data collected through our CAA section 114 

questionnaire indicate that only some facilities have tanks that 

currently require Level 2 emissions controls or that would 

require Level 2 control with the revised vapor pressure 

threshold of Option 1, and based on this data we estimate that 

approximately 10 OSWRO facilities have tanks that would require 

additional control under Option 2. We estimate the capital costs 

to be approximately $2.8 million, and the total annualized costs 

are estimated to be approximately $1.3 million. The estimated 

HAP emissions reduction incremental to Option 1 is approximately 

22 tpy, and the incremental cost effectiveness between Option 1 

and Option 2 is approximately $56,000/ton.

Table 4. Requirements of Tank Options 1 and 2 for Existing 

OSWRO Affected Sources

Options 1 and 2

Applicability 

Thresholds

Then 

Control 

Level 

for 

Options 

1 and 2

Option 1 

Requirements

Option 2 

Requirements

If Size 

(m3)is

And 

Vapor 

Pressure 

(kPa)is
Page 110 of 231

< 75 <76.6 1 Fixed roof 

≥ 76.6 2a 95% controlb 98% controlb

75 ≤ 

capacity 

< 151

< 13.1 1 Fixed roof

≥ 13.1 2 95% controlc 98% controlc

151 ≤ 

capacity

< 5.2 1 Fixed roof

≥ 5.2 2 95% controlc 98% controlc

a Except that fixed roof tanks equipped with an internal floating roof and 

tanks equipped with an external floating roof shall not be used

b Control efficiency would apply to tanks vented through a closed vent system 

to a control device and tanks inside a PTE that are vented to a combustion 

control device; use of a pressure tank would still be an available control 

option.

c Control efficiency would apply to tanks vented through a closed vent system 

to a control device and tanks inside a PTE that are vented to a combustion 

control device; use of an internal or external floating roof or a pressure 

tank would still be available control options.

Table 5. Nationwide Emissions Reductions and Costs of Control 

Options for Tanks at OSWRO Facilities

Regulatory 

Options

HAP 

emissions 

reduction 

(tpy)

Capital 

cost ($)

Annual 

cost 

($/yr)

Cost 

effectivenes

s ($/ton HAP 

removed)

Incremental 

cost 

effectiveness 

($/ton HAP 

removed)

Option 1 72.8 76,000 21,000 300 -----

Option 2 95.0 2,800,000 1,300,000 13,000 56,000

Based on our analysis, the costs of Option 1 are 

reasonable, given the level of HAP emissions reduction that 

would be achieved with this control option. The costs of Option 

2 do not appear reasonable, given the level of HAP emissions 

reduction it would achieve. Therefore, as a result of the 

technology review, we are proposing to revise the OSWRO MACT 

standards in accordance with Option 1, i.e., to require Level 2 

controls for tanks at existing affected sources with capacities 
Page 111 of 231

greater than or equal to 75 m3, but less than 151 m3, and a vapor 

pressure of 13.1 kPa or greater. We solicit comment on our 

assessment and conclusions regarding all aspects of both 

options. As noted in section IV.B.2, we are concurrently 

proposing to revise the OSWRO MACT standards for existing 

affected sources to require Level 2 controls for these tanks 

under section 112(f)(2) of the CAA to provide an ample margin of 

safety to protect public health. 

2. Equipment Leaks

The OSWRO MACT standards at 40 CFR 63.691 currently require 

compliance with either 40 CFR part 61, subpart V, or 40 CFR part 

63, subpart H, to control emissions from equipment leaks at 

existing and new affected sources. While many provisions of 

these two rules are the same or similar, subpart H requires the 

use of a more stringent leak definition for valves in gas and 

vapor service and in light liquid service, pumps in light liquid 

service, and connectors. Specifically, subpart H lowers the leak 

definition for valves from 10,000 ppm (in subpart V) to 500 ppm, 

lowers the leak definition for pump seals from 10,000 ppm (in 

subpart V) to 1,000 ppm, and requires periodic instrument 

monitoring of connectors with a leak definition of 500 ppm, as 

opposed to instrument monitoring only being required if a 

potential leak is detected by visual, audible, olfactory, or 

other detection method (in subpart V). We identified the more 
Page 112 of 231

stringent leak definitions of subpart H as a development in 

practices, processes or control technologies. 

Assuming conservatively that each of the OSWRO facilities 

currently comply with subpart V and do not already comply with 

subpart H, we analyzed the costs and emission reductions of two 

options: Option 1 - switching from a subpart V LDAR program to a 

subpart H LDAR program, without the subpart H connector 

monitoring requirements; Option 2 - switching from a subpart V 

LDAR program to a subpart H LDAR program, with the subpart H 

connector monitoring requirements. The estimated costs and 

emissions reductions associated with these two options for the 

OSWRO source category are shown in Table 6. For Option 1 

(subpart H without connector monitoring), we estimated the 

capital costs to be approximately $320,000, and the total 

annualized costs are estimated to be approximately $67,000. The 

estimated HAP emissions reduction is approximately 69 tpy, and 

the cost effectiveness is approximately $1,000/ton. For Option 2 

(subpart H with connector monitoring), we estimated the capital 

costs to be approximately $1,900,000, and the total annualized 

costs are estimated to be approximately $530,000. The estimated 

HAP emissions reduction is approximately 138 tpy, and the cost 

effectiveness is approximately $4,000/ton. The incremental cost 

effectiveness between Option 1 and Option 2 is approximately 

$7,000.
Page 113 of 231

Table 6. OSWRO Equipment Leak Options

Emission Reductions and Costs

Regulatory 

alternatives

HAP 

emissions 

reduction 

(tpy)

Capital 

cost ($)

Annual 

cost 

($/yr)

Cost 

effectiveness 

($/ton HAP 

removed)

Incremental 

cost 

effectiveness 

($/ton HAP 

removed)

Option 1: 

Subpart H, 

no connector 

monitoring

68.5 320,000 67,000 1,000 --

Option 2: 

Subpart H

with 

connector 

monitoring

138.1 1,900,000 530,000 4,000 7,000

Based on our analysis, the costs of Option 2, which 

includes all of the requirements of Option 1, are reasonable, 

given the level of HAP emissions reduction that would be 

achieved with this control option. Therefore, as a result of the 

technology review, we are proposing to revise the OSWRO MACT 

standards, in accordance with Option 2, to require existing and 

new affected sources to comply with subpart H rather than 

subpart V, including the subpart H requirements for connectors 

in gas and vapor service and in light liquid service. As noted 

in section IV.B.2, we are concurrently proposing to revise the 

OSWRO MACT standards for existing and new affected sources to 

require compliance with subpart H rather than subpart V, 

including the subpart H requirements for connectors in gas and 

vapor service and in light liquid service under section 

112(f)(2) of the CAA to provide an ample margin of safety to 
Page 114 of 231

protect public health. We solicit comment on our assessment and 

conclusions regarding all aspects of both options.

3. Process Vents

The current OSWRO MACT standards at 40 CFR 63.690 require 

emissions from process vents at existing and new affected 

sources to be routed through a closed vent system to a control 

device achieving at least 95 percent control. As discussed above 

for tanks, while carbon adsorption and other control devices are 

assumed to have a control efficiency of 95 percent, other 

technologies are capable of achieving greater emissions control, 

such as thermal incinerators. Several of these devices have been 

demonstrated to achieve a control efficiency of 98 percent or 

greater. Based on the combination of reported control 

efficiencies for these devices and known application to low 

concentration organic vapor gas streams, we investigated the use 

of a regenerative thermal oxidizer with a control efficiency of 

98 percent as a potential control option.

Table 7 presents the emission reductions and costs of the 

98 percent control options considered for process vents at 

existing affected sources in the OSWRO source category under the 

technology review. Data collected through our CAA section 114 

questionnaire indicate that only some facilities have process 

vents, and based on these data we estimate that approximately 

eight OSWRO facilities have process vents that would require 
Page 115 of 231

additional control to reduce emissions by 98 percent. We

estimated the capital costs of complying with an increase from 

95 to 98 percent HAP control for process vents to be 

approximately $9.8 million, and the total annualized costs are 

estimated to be approximately $3.3 million. The estimated HAP 

emissions reduction is approximately 10 tpy, and the cost 

effectiveness is approximately $350,000/ton of HAP emission 

reduction.

Table 7. OSWRO Process Vent Option Impacts

Regulatory 

option

HAP 

emissions 

reduction 

(tpy)

Capital 

cost ($)

Annual 

cost 

($/yr)

Cost 

effectiveness 

($/ton HAP 

removed)

98 percent 

control 9.6 9,800,000 3,300,000 350,000

Based on our estimate of costs and HAP reduction, we do not 

consider increasing the emission reduction to 98 percent to be 

reasonable, and we are not proposing to revise the OSWRO MACT 

standards for process vents pursuant to CAA section 112(d)(6) to 

require this level of emissions control. We solicit comment on 

our analysis, and as noted in section IV.B.2, we also solicit 

comments regarding the emissions controls proposed as a result 

of this technology review, given the uncertainty in the 

emissions estimates and the potential impact on the estimates of 

cost effectiveness.

D. What other actions are we proposing? 
Page 116 of 231

We are also proposing revisions to the startup, shutdown 

and malfunction (SSM) provisions of the MACT rule to ensure that 

they are consistent with the court decision in Sierra Club v. 

EPA, 551 F. 3d 1019 (D.C. Cir. 2008), which vacated two 

provisions that exempted sources from the requirement to comply 

with otherwise applicable section 112(d) emission standards 

during periods of SSM. Second, we are proposing to require 

electronic reporting of emissions test results. Third, we are 

proposing to revise the routine maintenance provisions and limit 

those provisions only to tanks routing emissions to a control 

device. Fourth, we are proposing to clarify what “seal the open 

end at all times” means for open-ended lines and valves in the 

equipment leak provisions of the rule. Fifth, we are proposing

that emissions of HAP from safety devices and closure devices 

directly to the atmosphere are prohibited, and we are proposing 

to require monitoring of pressure releases from pressure relief 

devices (PRDs) that release directly to the atmosphere. Sixth, 

we are proposing minor clarifications to the sample run times

and sample site location required for some performance test 

methods, and we are proposing to allow the use of a different 

performance test method in two cases. Seventh, we are proposing 

various minor clarifications and corrections to the rule. In 

addition to these proposed revisions, we are seeking comments 

containing information regarding flares used by facilities in 
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this source category. We present details and the rationales for 

the proposed changes in the following sections.

1. Startup, Shutdown and Malfunctions

a. Background

In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 

(D.C. Cir. 2008), the United States Court of Appeals for the 

District of Columbia Circuit vacated portions of two provisions 

in the EPA’s CAA section 112 regulations governing the emissions 

of HAP during periods of SSM. Specifically, the Court vacated 

the SSM exemption contained in 40 CFR 63.6(f)(1) and 40 CFR 

63.6(h)(1) holding that under section 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 section 112 standards apply continuously.

We are proposing to eliminate the SSM exemption in the 

OSWRO NESHAP. Consistent with Sierra Club v. EPA, we are

proposing standards in this rule that apply at all times. We are 

also proposing several revisions to Table 2 (the General 

Provisions Applicability Table) as is 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. 
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The EPA has attempted to eliminate provisions that are 

inappropriate, unnecessary, or redundant in the absence of the 

SSM exemption in this proposal. 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, has not proposed alternate standards for those 

periods.

Information on periods of startup and shutdown received 

from OSWRO facilities through the CAA section 114 questionnaire 

responses indicate that emissions during these periods are the 

same as during normal operations. The facilities do not process 

waste unless and until their control devices are operating to 

fully control emissions. Therefore, separate standards for 

periods of startup and shutdown are not necessary and are not 

being proposed. We solicit comment on our findings and 

conclusions regarding periods of startup and shutdown at OSWRO 

facilities.

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 * * *” (40 CFR 
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63.2). The EPA has determined that CAA section 112 does not 

require that emissions that occur during periods of malfunction 

be factored into development of CAA section 112 standards. Under 

section 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 section 112 that directs the EPA to consider 

malfunctions in determining the level “achieved” by the best 

performing sources when setting emission standards. As 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, nothing in section 

112 requires the EPA to consider malfunctions as part of that 

analysis. A 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” and no 

statutory language compels the EPA to consider such events in 

setting standards based on “best performers.”
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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 v 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 v 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 

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 goal of a “best controlled or best performing source” is to 

operate in such a way as to avoid malfunctions of the source and 
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accounting for malfunctions 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 section 112 and is a 

reasonable interpretation of the statute.

In the event that a source fails to comply with the 

applicable CAA section 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 section 112(d) standard was, in fact, “sudden, 

infrequent, not reasonably preventable” and was not instead 

“caused in part by poor maintenance or careless operation.” 40 

CFR 63.2 (definition of malfunction). 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 
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any defense raised and determine whether administrative 

penalties are appropriate. 

In several prior rules, the EPA had included an affirmative 

defense to civil penalties for violations caused by malfunctions 

in an effort to create a system that incorporates some 

flexibility, recognizing that there is a tension, inherent in 

many types of air regulations, 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. 

Although the EPA recognized that its case-by-case enforcement 

discretion provides sufficient flexibility in these 

circumstances, it included the affirmative defense to provide a 

more formalized approach and more regulatory clarity. See 

Weyerhaeuser Co. v. 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. 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 
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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 a section 112(d) rule establishing emission 

standards for Portland cement kilns). The court found that the 

EPA lacked authority to establish an affirmative defense for 

private civil suits and held that under the CAA, the authority 

to determine civil penalty amounts lies exclusively with the 

courts, not the EPA. 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 proposed rule. 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 
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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.

b. Specific SSM-related proposed changes 

To address the United States Court of Appeals for the 

District of Columbia Circuit vacatur of portions of the EPA’s 

CAA section 112 regulations governing the emissions of HAP 

during periods of SSM, we are proposing revisions and additions 

to certain provisions of the OSWRO rule. As described in detail 

below, we are proposing to revise the General Provisions 

applicability table (Table 2 to Subpart DD) in several of the 

references related to requirements that apply during periods of 

SSM. We are also proposing revisions related to the following 

provisions of the OSWRO rule: (1) the general duty to minimize 

emissions at all times; (2) the requirement for sources to 

comply with the emission limits in the rule at all times, with 

clarifications for what constitutes a deviation; (3) performance 

testing conditions requirements; (4) excused monitoring 

excursions provisions; and (5) malfunction recordkeeping and 

reporting requirements.

i. General Duty 

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.6(e) by adding rows specifically 
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for 40 CFR 63.6(e)(1)(i), 63.6(e)(1)(ii), 63.6(e)(1)(iii), and 

63.6(e)(3) and to include a “no” in the second column for the 40 

CFR 63.6(e)(1)(i) entry. Section 63.6(e)(1)(i) describes the 

general duty to minimize emissions. Some of the language in that

section 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 63.683(e) that 

reflects the general duty to minimize emissions while 

eliminating the reference to periods covered by an SSM 

exemption. The current language in 40 CFR 63.6(e)(1)(i) 

characterizes what the general duty entails during periods of 

SSM. 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 for 40 CFR 63.683(e)

does not include that language from 40 CFR 63.6(e)(1). 

We are also proposing to include a “no” in the second 

column for the newly added entry for 40 CFR 63.6(e)(1)(ii). 

Section 63.6(e)(1)(ii) imposes requirements that are not 

necessary with the elimination of the SSM exemption or are 

redundant with the general duty requirement being added at

63.683(e). 

The provisions of 40 CFR 63.6(e)(1)(iii) still apply, and 

we are keeping the “yes” in the second column for that section. 
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For 40 CFR 63.6(e)(2), we are proposing to include a “no” in the 

second column for that section because it is a reserved section 

in the General Provisions.

We are also proposing to clarify in the applicability 

section of 40 CFR 63.680(g)(1) and (2) that the emission limits 

of subpart DD apply at all times except when the affected source 

is not operating and that the owner or operator must not shut 

down items of equipment required or used for compliance with the 

requirements of subpart DD. 

ii. SSM Plan

We are also proposing to include a “no” in the second 

column for the newly added 40 CFR 63.6(e)(3) entry. Generally, 

this paragraph requires development of an SSM plan and specifies 

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.

iii. Compliance with Standards

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.6(f)(1) by changing the “yes” in 

column 2 to a “no.” The current language of 40 CFR 63.6(f)(1) 
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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 section 112 standard apply continuously. 

Consistent with Sierra Club, the EPA is proposing to revise 

standards in this rule to apply at all times.

iv. Performance Testing

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.7(e)(1) by changing the “yes” in 

column 2 to a “no.” Section 63.7(e)(1) describes performance 

testing requirements. The EPA is instead proposing to add a 

performance testing requirement at 40 CFR 63.694(l). The 

performance testing requirements we are proposing to add 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. 

However, consistent with 40 CFR 63.7(e)(1), performance tests 

conducted under this subpart should be based on representative 

performance (i.e., performance based on normal operating 

conditions) of the affected source. 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 
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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” 

upon request, but does not specifically require the information 

to be recorded. The regulatory text the EPA is proposing to add 

to this provision builds on that requirement and makes explicit 

the requirement to record the information.

v. Monitoring

We are proposing to revise the General Provisions table 

(Table 2) entries for 40 CFR 63.8(c)(1)(i) and (iii) by changing 

the “yes” in column 2 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)) and that set out the requirements of a quality 

control program for monitoring equipment (40 CFR 63.8(d)).

vi. Recordkeeping

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.10(b)(2)(i) by changing the “yes” 

in column 2 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 
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special provisions applicable to startup and shutdown, such as a 

startup and shutdown plan, there is no reason to retain 

additional recordkeeping for startup and shutdown periods.

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.10(b)(2)(ii) by changing the “yes” 

in column 2 to a “no.” Section 63.10(b)(2)(ii) describes the 

recordkeeping requirements during a malfunction. The EPA is 

proposing to add such requirements to 40 CFR 63.696(h). The 

regulatory text we are proposing to add differs from the General 

Provisions it is replacing in that the General Provisions 

require the creation and retention of a record of the occurrence 

and duration of each malfunction of process, air pollution 

control, and monitoring equipment. The EPA is proposing that 

this requirement apply to any failure to meet an applicable 

standard and is requiring that the source record the date, time, 

and duration of the failure rather than the “occurrence.” The 

EPA is also proposing to add to 40 CFR 63.696(h) 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 volume of each regulated pollutant emitted over 

the standard for which the source failed to meet the 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 
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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 

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 General Provisions table 

(Table 2) entry for 40 CFR 63.10(b)(2)(iv) by changing the “yes” 

in column 2 to a “no.” When applicable, the provision 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 63.696(h).

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.10(b)(2)(v) by changing the “yes” 

in column 2 to a “no.” When applicable, the provision requires 

sources to record actions taken during SSM events to show that 

actions taken were consistent with their SSM plan. The 
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requirement is no longer appropriate because SSM plans will no 

longer be required.

vii. Reporting

We are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.10(d)(5)(i) by consolidating it 

with the entry for 63.10(d)(5)(ii) and changing the “yes” in 

column 2 to “no.” Section 63.10(d)(5)(i) describes the reporting 

requirements for startups, shutdowns, and malfunctions. To 

replace the General Provisions reporting requirements, the EPA 

is proposing to add reporting requirements to 40 CFR 

63.697(b)(3). The replacement language differs from the General 

Provisions requirement in that it eliminates periodic SSM 

reports as a stand-alone report. 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 

semi-annual summary report already required under this rule. 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 such methods would include product-loss 

calculations, mass balance calculations, measurements when 
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available, or engineering 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 plans would no longer be required. The 

proposed amendments therefore eliminate 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 are proposing to revise the General Provisions table 

(Table 2) entry for 40 CFR 63.10(d)(5)(ii) by consolidating it 

with the entry for 63.10(d)(5)(i) and changing the “yes” in 

column 2 to a “no.” Section 63.10(d)(5)(ii) describes an 

immediate report for startups, shutdown, and malfunctions when a 

source failed to meet an applicable standard but did not follow 

the SSM plan. We will no longer require owners and operators to 

report when actions taken during a startup, shutdown, or 
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malfunction were not consistent with an SSM plan, because 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 

EPA is proposing that owners and operators of OSWRO facilities 

submit electronic copies of required performance test reports by 

direct computer-to-computer electronic transfer using EPAprovided 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 Central Data Exchange is EPA’s portal for 

submittal of electronic data. The EPA-provided 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 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 
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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.

The proposal to submit performance test data electronically 

to the EPA applies only to those performance tests 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 
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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 have performance test data in hand, we 

expect that there may be fewer or less substantial data 

collection requests in conjunction with prospective required 

residual risk assessments or technology reviews. 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 
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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.

In addition the EPA must have performance test data to 

conduct effective reviews of CAA sections 111, 112 and 129 

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, though, 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, 
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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.

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, tribal agencies and the EPA significant time, money and 

effort, while also improving the quality of emission inventories 

and air quality regulations.

3. Routine Maintenance

40 CFR 63.693(b)(3)(i) of the OSWRO NESHAP allows for 

control devices to be bypassed to perform planned routine 

maintenance of the closed-vent system or control device in 

situations when the routine maintenance cannot be performed 

during periods that the emission point vented to the control 

device is shut down. The facility is allowed to bypass the 

control device for up to 240 hours per year. 

The routine maintenance provision was originally 

established in the Hazardous Organic NESHAP (HON) (see 40 CFR 

63.119(e)(3)-(4); 57 FR 62710, December 31, 1992 (proposed); 59 

FR 19402, April 22, 1994 (final)) for facilities that elected to 
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use a closed vent system and control device to comply with the 

emission limitation requirements for tanks. We included the 

routine maintenance provision in the HON for tanks routing 

emissions to control devices because the estimated HAP emissions 

to degas the tank would be greater than the emissions that would 

result if the tank emitted directly to the atmosphere for a 

short period of time during routine maintenance of the control

device.

We intended for the OSWRO NESHAP to track the HON 

maintenance provisions, and as such, those provisions should 

have been limited to tanks. We have not identified a basis for 

applying the routine maintenance provisions in the OSWRO NESHAP 

to emission points other than tanks. Therefore, we are proposing 

to limit the provision to tanks routing emissions to a control 

device, consistent with the rationale provided in the HON. We 

request comment on this proposed revision.

4. Open-Ended Valves and Lines

The OSWRO NESHAP at 40 CFR 63.691(b) requires an owner or 

operator to control emissions from equipment leaks according to 

the requirements of either 40 CFR part 61, subpart V or 40 CFR 

part 63, subpart H. For open-ended valves and lines, both 

subpart V in §61.242-6(a) and subpart H in §63.167(a) require 

that the open end be equipped with a cap, blind flange, plug, or 

second valve that shall “seal the open end.” However, “seal” is 
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not defined in either subpart, leading to uncertainty for the 

owner or operator as to whether compliance is being achieved. 

Inspections 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, these 

are not providing a “seal” as the EPA interprets the term.25

In response to this uncertainty, we are proposing to amend 

40 CFR 63.691(a) to clarify what “seal the open end” means for 

open-ended valves and lines. This proposed clarification 

explains that, for the purpose of complying with the 

requirements of 40 CFR 63.167 of subpart H, open-ended valves 

and lines are “sealed” by the cap, blind flange, plug, or second 

valve instrument monitoring of the open-ended valve or line 

conducted according to Method 21 of 40 CFR part 60, appendix A 

indicates no readings of 500 ppm or greater. 

In addition, 40 CFR 63.167(d) of subpart H and 40 CFR 

61.242-6(d) of subpart V exempt open-ended valves and lines that 

are in an emergency shutdown system, and which are designed to 

open automatically, from the requirements to be equipped with a 

cap, blind flange, plug, or second valve that seals the open 

end. We are proposing that these open-ended valves and lines 

follow the requirements of 40 CFR 63.693(c)(2) for bypass 

 

25 See “Region V OEL data for VV rulemaking” available in the docket for this 

action.
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devices that could be used to divert a vent stream from the 

closed-vent system to the atmosphere, which would require that 

each such open-ended line be equipped with either a flow 

indicator or a seal or locking device. We are also proposing 

recordkeeping and reporting requirements in 40 CFR 63.696(j)(2) 

and 40 CFR 63.697(b)(6) for these open-ended values and lines.

We solicit comments on our proposed approach to reducing 

the compliance uncertainty associated with “sealed” open-ended 

valves and lines and our proposed requirements for open-ended 

valves and lines that are in an emergency shutdown system and 

are designed to open automatically.

5. Safety Devices, Pressure Tanks, Bypasses and PRDs

The OSWRO MACT standards contain requirements for safety 

devices, closure devices on pressure tanks, PRDs and bypasses,

established with the recognition that emission releases to the 

atmosphere from these devices and from bypasses of control 

equipment occur only in the event of unplanned and unpredictable 

events. While emissions vented to the atmosphere in these events 

may contain HAP that would otherwise be subject to the OSWRO

MACT emission standards, the OSWRO MACT rule followed the EPA’s 

former practice prior to the Sierra Club decision of exempting 

malfunction events from otherwise applicable emissions 

standards. Consequently, as these events were assumed to occur 

during malfunctions, the OSWRO MACT standards did not restrict
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emissions of HAP from these equipment or events to the 

atmosphere.

In the Sierra Club decision, the Court determined that the 

SSM exemption violated the CAA and vacated the regulatory 

provisions in the General Provisions containing the exemption. 

See section IV.D.1 of this preamble for additional discussion. 

To ensure the OSWRO MACT standards are consistent with the 

Court’s action, we are proposing to remove the SSM exemption 

from the rule. In addition, in order for our treatment of 

malfunction-caused releases to the atmosphere to conform with 

the reasoning of the Court’s ruling, we are proposing to add a 

provision that releases of HAP listed in Table 1 of 40 CFR part 

63 subpart DD directly to the atmosphere from PRDs and closure 

devices on pressure tanks in off-site material service are 

prohibited. We are also proposing to prohibit bypasses that 

divert a process vent or closed vent system stream to the 

atmosphere such that it does not first pass through an emission 

control device, except to perform planned routine maintenance of 

the closed-vent system or emission control device for tanks, as 

discussed in section IV.D.3 of this preamble. We are further 

proposing to require owners or operators to keep records and 

report any bypass and the amount of HAP released to the 

atmosphere with the next periodic report. In addition, to add 

clarity to these proposed provisions, we are proposing to add 
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definitions for “bypass,” “pressure release,” “pressure relief 

device or valve,” “in gas/vapor service,” “in light liquid 

service” “in heavy liquid service” and “in liquid service” to 40 

CFR part 63, subpart DD. We are also proposing to remove the 

definition of “safety device” and the provisions related to 

safety devices from 40 CFR part 63, subpart DD, which would 

overlap with and be redundant of parts of the proposed 

definition of “pressure relief device or valve” and the 

provisions related to these devices. To our knowledge, pressure 

relief devices or valves are the only safety devices used in 

OSWRO processes. 

To address potential releases from PRDs, we are also 

proposing to require facility owners or operators subject to the 

OSWRO MACT standards to employ monitoring of PRDs in off-site 

material service using a device or monitoring system that is 

capable of: (1) identifying the pressure release; (2) recording 

the time and duration of each pressure release; and (3) 

notifying operators immediately that a pressure release is 

occurring. We are further proposing to require owners or 

operators to keep records and report any pressure release and 

the amount of HAP released to the atmosphere with the next 

periodic report.

Pressure releases to the atmosphere from PRDs in off-site 

material service have the potential to emit large quantities of 
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HAP. Where a release occurs, it is important to identify and 

mitigate it as quickly as possible. We recognize that releases 

from PRDs sometimes occur in order to protect systems from 

failures that could endanger worker safety and the systems that 

the PRDs are designed to protect. We have provided a balanced 

approach designed to minimize HAP emissions while recognizing 

that these events may be unavoidable even in a well-designed and 

maintained system. For purposes of estimating the costs of this 

requirement, we assumed that operators would install electronic 

indicators on each relief device that vents to the atmosphere to 

identify and record the time and duration of each pressure 

release. However, we are proposing that owners and operators 

could choose to use an existing system, such as a parameter 

monitoring system, as long as it is sufficient to identify a 

pressure release, notify operators immediately that a release is 

occurring and record the time and duration of the release. 

Based on our cost assumptions, the nationwide capital cost 

of installing these monitors for the OSWRO industry is 

approximately $1.75 million and the annualized cost of 

installing and operating these monitors is $250,000 per year. As 

noted above, the owner or operator may use parameter monitoring 

systems already in place. Therefore, our costs based on the 

installation of electronic indicators on each relief device that 
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vents to the atmosphere is conservative and likely overstates 

the costs.

6. Performance Test Method Clarifications and Alternative 

Methods 

The OSWRO NESHAP at 40 CFR 63.694 specifies test methods 

and procedures to be used in determining compliance with the 

requirements of subpart DD. We are proposing several minor 

changes to these provisions to correct errors and to provide 

consistency, clarification and flexibility. 

We are proposing several minor clarifications to align the 

testing requirements with standard testing practices. We are

proposing that test runs last “at least 1 hour”, rather than 

stating that tests last “1 hour” in §63.694(f)(1) and (i)(1). 

This is consistent with standard testing practice and other 

provisions of the rule that specify a minimum sampling time 

instead of an absolute sampling time. Requiring a minimum 

sampling time allows owners and operators to conduct longer 

sampling runs when necessary. For example, an owner or operator 

may conduct longer sampling runs to achieve a lower detection 

limit for a specific compound. We are proposing to specify that 

a minimum of three test runs are required in §63.694(l)(3)(i) 

and (l)(4)(i), consistent with the Part 63 General Provisions 

and standard testing practices. We are proposing to specify in 

§63.694(m)(2) that in the determination of process vent stream 
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flow rate and total HAP concentration, the sample site selected

must be at the center of the vent for vents smaller than 0.10 

meter in diameter. EPA Methods 1 and 1A do not apply to stack 

diameters smaller than 0.10 meter in diameter, and the 

regulation as currently written states that it is unnecessary to 

traverse vents less than 0.10 meter in diameter, but is unclear 

on how sampling point selection must be chosen. We are proposing 

to clarify that the sampling point must be at the center of the 

vent; this sample point is the point most likely to provide a 

representative sample of the gas stream. 

To provide consistency with other parts of the OSWRO MACT 

standards, we are proposing to clarify the requirements of 

§63.694(j)(3) for determining the maximum HAP vapor pressure for 

off-site material in a tank if the Administrator and the owner 

or operator disagree on a determination of the maximum HAP vapor 

pressure for an off-site material stream using knowledge. We are 

proposing that results from direct measurement of the HAP vapor 

pressure must be used in these instances. This is consistent 

with §63.694(b)(3)(iv), which uses the same language for VOHAP 

measurements. 

We also are proposing to correct a citation in 

§63.694(k)(3). The regulation currently references the wrong 

section of Method 21 for instrument response factors. The 

appropriate section in EPA Method 21 is 8.1.1, not 3.1.2(a). 
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We are proposing to allow the use of either EPA Method 25A 

or Method 18 in §63.694(l)(3) and (4). We are clarifying that 

Method 25A must be used for determining compliance with the 

enclosed combustion device total organic compound (TOC) limit, 

while Method 18 is used for determining compliance with the 

total HAP concentration limit. We are making this change because 

Method 25A is a flame ionization method that measures 

concentration as carbon equivalents. It is preferred over Method 

18 for the measurement of TOC. Method 18 is used to determine 

the concentration of individual compounds, making it appropriate 

for measuring individual HAPs that can be summed and compared 

with the total HAP limit, especially when a finite list of HAPs 

is specified (such as in Table 1 of the OSWRO NESHAP). Because 

TOC includes all organic compounds (minus methane and ethane) 

and Method 18 requires a set list of individual compounds to be 

measured. In order to use Method 18 for TOC measurements, one 

would have to know every organic compound in the gas stream and 

analyze each individually, which is a difficult and nearly

impossible task in most cases. Therefore, we are proposing that 

TOC is to be measured with Method 25A and total HAP is to be 

measured with Method 18. The changes in how the test methods are 

applied and how TOC is most appropriately measured result in

changes in some of the equations in §63.694 as well.
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We are proposing additional flexibility in some of the test 

methods that are allowed by the OSWRO NESHAP. We are including 

the use of EPA Method 3A as an alternative to EPA Method 3B in 

§63.694(l)(4)(iii)(A) for determining the oxygen concentration 

to use in oxygen correction equations. EPA Method 3A is just as 

effective as EPA Method 3B in determining oxygen concentration. 

We have also included the use of EPA Methods 2F and 2G as 

options for flow rate measurement in §63.694(l)(2) and (m)(3). 

These methods are newer velocity measurement methods that were 

published after the original OSWRO rule. By allowing these test 

method alternatives in the rule, we are providing greater 

flexibility to sources and easing the burden on sources and 

delegated agencies by reducing the number of potential 

alternative method requests.

7. Other Clarifications and Corrections

We are proposing several miscellaneous minor changes to 

improve the clarity of the rule requirements. These proposed 

changes include:

 Updating the list in §63.684(b)(5) of combustion devices 

that may be used to destroy the HAP contained in an offsite material stream, to include incinerators, boilers or 

industrial furnaces for which the owner or operator 

complies with the requirements of 40 CFR part 63 subpart 

EEE. Where the OSWRO MACT standards currently require 
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that combustion devices used for the purposes of 

compliance with the OSWRO MACT standards must be 

regulated under various subparts of RCRA, many of these 

units now comply with 40 CFR part 63 subpart EEE, which 

had not been promulgated when the OSWRO MACT standards 

were developed. We are also proposing conforming changes 

to the boiler and process heater control device 

requirements in §63.693(g)(1)(v). These changes clarify 

that combustion units complying with the requirements of 

subpart EEE may be used for the purposes of compliance 

with the OSWRO MACT standards. 

 Revising the tank control level tables and the text in 

§63.685(b) to clarify the control level required for 

tanks of any capacity (effectively those less than 75 m3) 

with a vapor pressure of 76.6 kPa or greater. Tanks 

meeting these capacity and vapor pressure thresholds are 

not included in the control level tables referred to in 

§63.685(b), currently Tables 3 and 4 of the OSWRO NESHAP, 

and instead text is included in §63.685(b)(4) for these 

tanks. To clarify the requirements for these tanks, we 

are proposing to specify the requirements for these tanks 

in the tank control level tables (proposed Tables 3, 4 

and 5) and remove the text in §63.685(b)(4).
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 Clarifying that where §63.691 requires the owner or 

operator to control the HAP emitted from equipment leaks 

in accordance with either 40 CFR part 61, subpart V or 40 

CFR part 63, subpart H, the definitions in 40 CFR 61.241 

and 40 CFR 63.161 apply, with the differences listed, 

for the purposes of the OSWRO NESHAP. 

 Clarifying the requirement of §63.683(c)(1)(ii) that the 

average VOHAP concentration of the off-site material must 

be less than 500 ppmw at the point-of-delivery and 

clarifying the requirements of §63.693(f)(1)(i)(B) and 

§63.693(f)(1)(ii)(B) are to achieve a total incinerator 

outlet concentration of less than or equal to 20 ppmv on 

a dry basis corrected to 3 percent oxygen. Due to 

clerical errors, the ppm values of these requirements are

not in the current OSWRO NESHAP, and we are proposing to 

insert them.

 Clarifying in §§63.684(h), 63.693(b)(8) and 

63.694(b)(3)(iv) that the Administrator may require a 

performance test, revisions to a control device design 

analysis, or that direct measurement be used in the 

determination of a VOHAP concentration, rather than that 

the Administrator may only request such actions. 

 Revising several references to the Part 63 General 

Provisions in Table 2 to correct errors, including errors 
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where the entries in Table 2 conflict with the regulatory 

text in subpart DD and where references to specific 

sections of the General Provisions do not exist or are 

reserved.

8. Flare Performance

In addition to our proposed actions discussed above, we are 

seeking comments on the performance of flares used to control 

HAP emissions in this source category, as governed by the EPA’s 

General Provisions at 40 CFR 63.11(b). In April 2012, the EPA 

conducted an external peer review of a draft technical report, 

“Parameters for Properly Designed and Operated Flares” 

(http://www.epa.gov/ttn/atw/flare/2012flaretechreport.pdf) 

(“draft flare technical report”). In this report, the EPA 

evaluated test data and identified a variety of parameters that 

may affect flare performance and that could be monitored to help 

ensure good combustion efficiency. Based on feedback received 

from the external ad-hoc peer review panel, the EPA has since 

undertaken an initiative to re-evaluate parameters that may 

affect overall flare performance at source categories known to 

use flares for controlling HAP emissions (e.g., petroleum 

refining).

Currently, OSWRO sources may choose from a variety of 

control techniques to control emissions from this source 

category. One option is to operate a flare to reduce HAP 
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emissions in accordance with the provision in 40 CFR 63.693(h). 

However, responses to the CAA section 114 questionnaire indicate 

that flares are not commonly used as control devices for this 

source category, and we know of only one facility that uses a 

flare as a primary control device in order to comply with the 

OSWRO NESHAP. In addition, none of the flare performance data 

used in the draft flare technical report comes from OSWRO 

sources nor does it provide any test data on non-assisted flare 

types, which based on available information, is the only flare 

type found in the OSWRO source category. As indicated in the EPA 

flare draft technical report, one of the primary factors that 

affects flare performance is over-assisting flares with too much 

steam or air and while this can potentially occur in steamassisted and air-assisted flare designs, non-assisted flare 

types do not have a potential to over-assist. Thus, we have no 

information to suggest that flares at OSWRO sources are 

achieving poor destruction efficiency. We solicit comments on 

our discussion and conclusions regarding flare performance, 

including additional information on flare performance related to

this source category. Examples of types of information we seek 

from commenters regarding flares for the OSWRO source category 

include: frequency of flaring; number and types of flares used; 

waste gas characteristics such as flow rate, composition and 

heat content; assist gas characteristics such as target assist 
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gas to waste gas ratios and minimum assist gas flow rates; use 

of flare gas recovery and other flare minimization practices; 

and existing flare monitoring systems.

E. What compliance dates are we proposing?

Under CAA section 112(d), the proposed compliance date for 

new and existing affected sources for the revised SSM 

requirements, electronic reporting requirements, the revised 

routine maintenance provisions, the operating and pressure 

release management requirements for PRDs, and the revised 

requirements regarding bypasses and closure devices on pressure 

tanks is the effective date of the final amendments. We are 

proposing this compliance date because available information 

indicates these new and revised requirements should be 

immediately implementable by the facilities. 

We are also proposing that for existing affected sources 

subject to the OSWRO MACT standards, the compliance date for the 

PRD monitoring requirements is 3 years from the effective date 

of the final amendments. This time is needed regardless of 

whether an owner or operator of a facility chooses to comply 

with the PRD monitoring provisions by installing PRD release 

indicator systems and alarms, employing parameter monitoring,

routing releases to a control device, or choosing another 

compliance option as permitted under the proposed provisions. 

This time period will allow OSWRO facility owners and operators
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to research equipment and vendors, and to purchase, install, 

test and properly operate any necessary equipment by the 

compliance date. For new affected sources, the proposed 

compliance date for PRD monitoring requirements is the effective 

date of the final amendments.

Finally, we are proposing revised requirements for 

equipment leaks and tanks under CAA sections 112(d)(6) and 

(f)(2). The compliance deadlines for standards developed under 

CAA section 112(f)(2) are addressed in CAA sections 112(f)(3) 

and (4). As provided in CAA Section 112(f)(4), risk standards 

shall not apply to existing affected 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. Here, the EPA is already aware of the 

steps needed for OSWRO facilities to comply with the proposed 

standards for equipment leaks and tanks and to reasonably 

estimate the amount of time it will take these facilities to do 

so. Therefore, consistent with CAA section 112(f)(4)(B), we are 

proposing that a two-year compliance period is necessary for the 

revised tank requirements to allow affected facilities to 

research equipment and vendors, purchase, install, test and 

properly operate any necessary equipment by the compliance date. 

We are also proposing, consistent with CAA section 112(f)(4)(B), 

that a one-year compliance period is necessary for the revised 
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equipment leak requirements to allow affected facilities that 

are currently complying with 40 CFR part 61, subpart V adequate 

time to purchase, install and test any necessary equipment and 

modify their existing LDAR programs. In addition, pursuant to 

CAA section 112(d)(6), we are proposing these same compliance 

dates for the revised tank and equipment leak standards. For new 

affected sources, the proposed compliance date for the revised 

tank and equipment leak standards is the effective date of the 

final amendments.

V. Summary of Cost, Environmental and Economic Impacts

A. What are the affected sources?

We estimate that there are approximately 52 major source 

OSWRO facilities. Based on available permit information, seven

facilities are known to be exempt from most of the rule 

requirements due to the low HAP content of the off-site waste 

they receive or because they comply instead with 40 CFR 61 

subpart FF, as allowed by the OSWRO NESHAP, and they are not 

expected to be affected by the proposed rule revisions. These 

facilities are only required to document that the total annual 

quantity of the HAP contained in the off-site material received 

at the plant site is less than 1 megagram per year, and they are 

not subject to any other emissions limits or monitoring, 

reporting or recordkeeping requirements. We are not aware of any 
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new OSWRO facilities that are expected to be constructed in the 

foreseeable future.

B. What are the air quality impacts?

For equipment leaks, we are proposing to eliminate the 

option of complying with 40 CFR part 61, subpart V, and

requiring facilities in the OSWRO source category to comply with 

40 CFR part 63, subpart H, including connector monitoring. We 

estimate the HAP emission reduction for this change to be 

approximately 138 tpy. For tanks, we are proposing to require 

tanks of certain sizes and containing materials above certain 

vapor pressures to use Level 2 controls. We estimate the HAP 

emission reduction for this change to be approximately 73 tpy. 

We do not anticipate any HAP emission reduction from our 

proposed clarification of the rule provision “seal the open end”

(in the context of open-ended valves and lines), clarification 

of the scope of the routine maintenance provisions, or

requirement to electronically report the results of emissions 

testing.

For the proposed revisions to the MACT standards regarding 

SSM, including monitoring of PRDs in off-site material service, 

we were not able to quantify the possible emission reductions so 

none are included in our assessment of air quality impacts.
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Therefore, the estimated total HAP emission reductions for 

the proposed rule revisions for the OSWRO source category are

estimated to be 211 tpy.

C. What are the cost impacts?

For equipment leaks, we are proposing to eliminate the 

option of complying with 40 CFR part 61, subpart V, and to 

require facilities in the OSWRO source category to comply with 

40 CFR part 63, subpart H (including connector monitoring). We 

estimate the nationwide capital costs to be $1.9 million and the 

annualized costs to be $530,000. For tanks, we are proposing to 

require tanks of certain sizes and containing materials above 

certain vapor pressures to use Level 2 controls. We estimate the 

nationwide capital costs to be $76,000 and the annualized costs 

to be $21,000. We do not anticipate any quantifiable capital or 

annualized costs for our proposed definition of “seal” (in the 

context of open-ended valves and lines), clarification of the 

scope of the routine maintenance provisions and requirement to 

electronically report the results of emissions testing.

For the proposed requirements to install and operate 

monitors on PRDs, we estimate the nationwide capital costs to be 

$1.75 million and the annualized costs to be $250,000.

Therefore, the total capital costs for the proposed 

standards for the OSWRO source category are approximately $3.7
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million and the total annualized costs are approximately 

$800,000.

D. What are the economic impacts?

Both the magnitude of control costs needed to comply with a 

regulation and the distribution of these costs among affected 

facilities can have a role in determining how the market will 

change in response to that regulation. Total annualized costs 

for the proposed amendments are estimated to be about $800,000. 

The average annualized cost per facility is estimated to be 

about $24,000.

Without detailed industry data, it is not possible to 

conduct a complete quantitative analysis of economic impacts. 

However, prior analyses suggest the impacts of these proposed 

amendments will be minimal. The Economic Impact Analysis for the 

Final OSWRO NESHAP26 found that demand for off-site waste 

services was highly inelastic. This means that suppliers are 

predominantly able to pass along cost increases to consumers 

through higher prices with little, if any, decrease in the 

quantity of service demanded. While we do not have specific 

information on prices charged or the quantity of service 

provided, company revenues are a function of both these factors. 

The cost-to-sales ratio is less than one quarter of one percent 

 

26 EPA. June 1996. 
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for all of the 27 firms included in this analysis, suggesting 

any increase in price would be minimal.

E. What are the benefits?

We have estimated that this action will achieve HAP 

emissions reduction of 211 tons per year. The proposed standards 

will result in significant reductions in the actual and MACTallowable emissions of HAP and will reduce the actual and 

potential cancer risks and non-cancer health effects due to 

emissions of HAP from this source category, as discussed in 

section IV.B.2. We have not quantified the monetary benefits 

associated with these reductions; however, these avoided 

emissions will result in improvements in air quality and reduced 

negative health effects associate with exposure to air pollution 

of these emissions.

VI. Request for Comments

We are soliciting comments on all aspects of this proposed 

action. In addition to general comments on this proposed action, 

we are also interested in any additional data that may help to 

improve the risk assessments and other analyses. We are 

specifically interested in receiving any improvements to the 

data used in the site-specific emissions profiles used for risk 

modeling. Such data should include supporting documentation in 

sufficient detail to allow characterization of the quality and 
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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 for download 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 included in the source category. 

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 No. EPA-HQ-OAR-2012-0360 (through one of the 

methods described in the ADDRESSES section 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

This action is not a "significant regulatory action" under 

the terms of Executive Order 12866 (58 FR 51735, October 4, 

1993) and is therefore not subject to review under Executive 

Orders 12866 and 13563 (76 FR 3821, January 21, 2011).

B. Paperwork Reduction Act
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The information collection requirements in this proposed

rule have been submitted for approval to OMB under the Paperwork 

Reduction Act, 44 U.S.C. 3501, et seq. The Information 

Collection Request (ICR) document prepared by the EPA has been 

assigned the EPA ICR number 1717.10. 

The information requirements are based on notification, 

recordkeeping and reporting requirements in the NESHAP General 

Provisions (40 CFR part 63, subpart A), which are mandatory for 

all operators subject to national emissions standards. These 

recordkeeping and reporting requirements are specifically 

authorized by CAA section 114 (42 U.S.C. 7414). All information 

submitted to the EPA pursuant to the recordkeeping and reporting 

requirements for which a claim of confidentiality is made is 

safeguarded according to agency policies set forth in 40 CFR 

part 2, subpart B.

We estimate approximately 52 regulated entities are 

currently subject to subpart DD; however, five facilities are 

only subject to off-site waste HAP content determination 

requirements and are not subject to the emissions standards and 

other requirements of the OSWRO NESHAP due to the low HAP 

content of the off-site waste they receive. Also, two facilities 

are not subject to the emissions standards and other 

requirements of the OSWRO NESHAP because they comply instead 

with 40 CFR 61 subpart FF, as allowed by the OSWRO NESHAP. 
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Therefore, we estimate that there is an annual average of 45

respondents that are subject to the annual monitoring, reporting 

and recordkeeping requirements of the regulation. This is a 

decrease of 191 regulated entities from our estimate for the 

previous ICR (EPA ICR Number 1717.09, OMB Control Number 2060-

0313) for the OSWRO source category. The annual monitoring, 

reporting and recordkeeping burden for this collection (averaged 

over the first 3 years after the effective date of the 

standards) for the proposed amended subpart DD, including 

existing rule provisions unchanged by this proposal, is 

estimated to be 45,147 labor hours at a cost of $2.5 million per 

year. This represents a decrease of approximately $15 million 

and 133,000 labor hours from the previous ICR, due primarily to 

the reduction in the estimated number of regulated entities. In 

order to more accurately assess the change in burden resulting 

from these proposed amendments, we estimate that the burden for 

each of the 45 facilities subject to the annual monitoring, 

reporting and recordkeeping requirements of the regulations has 

increased by $6,000 and 92 labor hours from the previous ICR 

estimate.

The total burden for the federal government (averaged over 

the first 3 years after the effective date of the standard) is 

estimated to be 449 labor hours per year at an annual cost of 

$20,200. Burden is defined at 5 CFR 1320.3(b).
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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 OMB control 

numbers for the EPA’s regulations in 40 CFR are listed in 40 CFR 

part 9. 

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 this 

ICR, under Docket ID No. EPA–HQ–OAR–2012–0360. Submit any 

comments related to the ICR to the EPA and OMB. See the 

ADDRESSES section at the beginning of this notice 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 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 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
Page 164 of 231

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. Small 

entities include small businesses, small organizations, and 

small governmental jurisdictions.

For purposes of assessing the impacts of this proposed rule 

on small entities, small entity is defined as: (1) A small 

business as defined by the Small Business Administration’s (SBA) 

regulations at 13 CFR 121.201; (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-forprofit enterprise that is independently owned and operated and 

is not dominant in its field. Facilities in this source category 

are not categorized as a single industry and, as a result, 

cannot be classified under a single NAICS code category. During 

the development of these proposed amendments, the EPA identified 

45 facilities affected by this proposal. These 45 facilities 

represent 27 firms in 20 industries. These industries and the 

SBA size standards are shown in Table 8. 

Table 8. Industries Included in OSWRO Source Category
Page 165 of 231

NAICS Description SBA Size Standard

211111 Crude Petroleum and Natural Gas 

Extraction 500 employees

221310 Water Supply and Irrigation 

Systems

$7.0 million annual 

receipts

237310 Highway, Street, and Bridge 

Construction

$33.5 million annual 

receipts

324110 Petroleum Refineries 1,500 employees

325180 Other Basic Inorganic Chemical 

Manufacturing 1,000 employees

325194

Cyclic Crude, Intermediate, and 

Gum and Wood 

Chemical Manufacturing

750 employees

325199 All Other Basic Organic Chemical 

Manufacturing 1,000 employees

325211 Plastics Material and Resin 

Manufacturing 750 employees

327310 Cement Manufacturing 750 employees

331313 Alumina Refining and Primary 

Aluminum Production 1,000 employees

333316 Photographic and Photocopying 

Equipment Manufacturing 1,000 employees

336411 Aircraft Manufacturing 1,500 employees

424690 Other Chemical and Allied 

Products Merchant Wholesalers 100 employees

561110 Office Administrative Services $7.0 million annual 

receipts

562111 Solid Waste Collection $35.5 million annual 

receipts

562211 Hazardous Waste Treatment and 

Disposal

$35.5 million annual 

receipts

562213 Solid Waste Combustion and 

Incinerators

$35.5 million annual 

receipts

562219 Other Nonhazardous Waste 

Treatment and Disposal

$35.5 million annual 

receipts
Page 166 of 231

562920 Materials Recovery Facilities $19.0 million annual 

receipts

928110 National Securitya n/a

a One facility is operated by the U.S. Department of 

Defense. Small business size standards are not established for 

this sector. 

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. For the small business screening analysis, the EPA 

identified the ultimate parent company (firm) for each facility 

and obtained firm-level employment and revenues using various 

sources, including the American Business Directory, Hoovers, 

corporate websites and publically available financial reports. 

The screening analysis shows that four of the 27 firms that own 

facilities in the OSWRO source category can be classified as 

small firms using the SBA size standards for their respective 

industries. Based on the sales test screening methodology, all 

four firms will experience minimal impact, or a cost-to-sales 

ratio of 1 percent or less. Details of this analysis can be 

found in the memo “Economic Impact Analysis for Risk and 

Technology Review: Off-site Waste and Recovery Operations Source 

Category” in the docket.
Page 167 of 231

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 rule does not contain a federal mandate that may

result in expenditures of $100 million or more for state, local 

and tribal governments, in aggregate, or the private sector in 

any one year. The total annualized cost of this rule is 

estimated to be no more than $800,000 in any one year. Thus, 

this proposed rule is not subject to the requirements of 

sections 202 or 205 of the UMRA.

This proposed rule is also not subject to the requirements 

of section 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 nor does it impose obligations upon them.

E. Executive Order 13132: Federalism

This action 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 

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 
Page 168 of 231

or operated by state governments. Thus, Executive Order 13132 

does not apply to this proposed 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). There 

are no Off-Site Waste Recovery Operation facilities that are 

owned or operated by tribal governments. Thus, Executive Order 

13175 does not apply to this action. The EPA specifically 

solicits 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 risks or safety 

risks addressed by this action present a disproportionate risk 

to children. Because the proposed rule amendments would result 

in reduced emissions of HAP and reduced risk to anyone exposed, 

the EPA believes that the proposed rule amendments would provide 
Page 169 of 231

additional protection to children. The EPA’s risk assessments

are included in the docket for this proposed rule.

The public is invited to submit comments or identify peerreviewed studies and data that assess effects of early life 

exposure to HAP emitted by OSWRO facilities.

H. Executive Order 13211: Actions Concerning Regulations That

Significantly Affect Energy Supply, Distribution, or Use

This action is not subject to Executive Order 13211 (66 FR 

28355, May 22, 2001), because it is not a significant regulatory 

action under Executive Order 12866.

I. National Technology Transfer and Advancement Act

Section 12(d) of the National Technology Transfer and 

Advancement Act of 1995 (NTTAA), Public Law 104–113 (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. NTTAA directs the EPA to 

provide Congress, through OMB, explanations when the agency 

decides not to use available and applicable VCS. 

This proposed rule involves technical standards. The EPA 

proposes to add EPA Methods 2F and 2G to the list of methods 

allowed to determine process vent stream gas volumetric flow 
Page 170 of 231

rate. No applicable VCS were identified for these methods. In 

addition, the EPA is proposing to allow EPA Method 3A as an 

alternative to EPA Method 3B for determining the oxygen 

concentration to use in oxygen correction equations. While 

several candidate VCS were identified (ANSI/ASME PTC 19-10-1981 

Part 10, ASME B133.9-1994 (2001), ISO 10396:1993 (2007), ISO 

12039:2001, ASTM D5835-95 (2013), ASTM D6522-00 (2011), and 

CAN/CSA Z223.2-M86 (1999)), we do not propose to use any of 

these standards in this proposed rule. The use of these VCS 

would not be practical due to lack of equivalency, 

documentation, validation data and other important technical and 

policy considerations. The EPA also proposes to require the use 

of EPA Method 25A to determine compliance with the control 

device percent reduction requirement, if the owner or operator 

chooses to measure total organic content. While the agency 

identified two candidate VCS (ISO 14965:2000(E), EN 12619 

(1999)) as being potentially applicable, we do not propose to 

use either standard in this proposed rule. The use of these VCS 

would not be practical due to the limited measurement ranges of 

these methods. (For more detail, see “Voluntary Consensus 

Standard Results for NESHAP: Off-Site Waste and Recovery 

Operations 40 CFR Part 63, Subpart DD” in the docket for this 

proposed rule.)
Page 171 of 231

The EPA welcomes comments on this aspect of the proposed 

rule 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 practical 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 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 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.
Page 172 of 231

To gain a better understanding of the source category and 

near source populations, the EPA conducted a proximity analysis 

for OSWRO facilities to identify any overrepresentation of 

minority, low income or indigenous populations. This analysis 

only gives some indication of the prevalence of sub-populations 

that may be exposed to air pollution from the sources; it does 

not identify the demographic characteristics of the most highly 

affected individuals or communities, nor does it quantify the 

level of risk faced by those individuals or communities. More 

information on the source category’s risk can be found in 

section IV of this preamble.

In determining the aggregate demographic makeup of the 

communities near affected sources, the EPA focused on those 

census blocks within 3 miles of affected sources, determined the 

demographic composition (e.g., race, income, etc.) of these 

census blocks, and compared them to the corresponding 

compositions nationally. The results of this proximity analysis

show that most demographic categories were below or within 20 

percent of their corresponding national averages except for the 

African American and minority populations. The African American 

segment of the population within 3 miles of any source affected 

by this proposed rule exceeds the national average by 166 

percent, or 21 percentage points (34 percent versus 13 percent). 

The minority population within 3 miles exceeds the national 
Page 173 of 231

average by 64 percent, or 24 percentage points, (61 percent 

versus 37 percent). However, as noted previously, risks from 

this source category were found to be acceptable for all 

populations. Additionally, the proposed changes to the standard 

increase the level of environmental protection for all affected 

populations by reducing emissions from equipment leaks and 

tanks. 

Further details concerning this analysis are presented in 

the December 3, 2013 memorandum titled, Environmental Justice 

Review: Off-Site Waste and Recovery Operations, RTR, a copy of 

which is available in the docket for this action (EPA-HQ-OAR2012-0360).
NATIONAL EMISSIONS STANDARDS for HAZARDOUS AIR POLLUTANTS: OFF-SITE WASTE and 

RECOVERY OPERATIONS Page 17 4 of 2 31 

List of Subjects in 40 CFR Part 63 

Environmental protection, Administrative practice and 

procedures, Air pollution control, Hazardous substances, 

Reporting and recordkeeping requirements, Volatile organic 

compounds. 

Dated: 1 
Page 175 of 231

For the reasons stated in the preamble, the Environmental 

Protection Agency (EPA) proposes to amend Title 40, chapter I, 

of the Code of Federal Regulations (CFR) as follows:

PART 63—[AMENDED]

1. The authority citation for part 63 continues to read as 

follows:

Authority: 42 U.S.C. 7401, et seq.

Subpart DD—[Amended]

2. Section 63.680 is amended by:

a. Revising paragraphs (e)(1)(i) and (ii);

b. Adding paragraph (e)(1)(iii);

c. Revising paragraph (e)(2); and

d. Adding paragraph (g) to read as follows:

§ 63.680 Applicability and designation of affected sources.

* * * * *

(e) * * *

(1) Existing sources. The owner or operator of an affected 

source that commenced construction or reconstruction before 

October 13, 1994, must achieve compliance with the provisions of 

this subpart on or before the date specified in paragraph 

(e)(1)(i),(ii) or (iii) of this section as applicable to the 

affected source.

(i) For an affected source that commenced construction or 

reconstruction before October 13, 1994 and receives off-site 
Page 176 of 231

material for the first time before February 1, 2000, the owner 

or operator of this affected source must achieve compliance with 

the provisions of the subpart (except §§ 63.685(b)(1)(ii), 

63.691(b), and 63.691(c)(3)(i) and (ii) of this subpart) on or 

before February 1, 2000 unless an extension has been granted by 

the Administrator as provided in 40 CFR 63.6(i). These existing 

affected sources shall be in compliance with the tank 

requirements of §63.685(b)(1)(ii) of this subpart two years 

after the publication date of the final amendments [INSERT DATE 

OF PUBLICATION OF THE FINAL RULE AMENDMENTS IN THE FEDERAL 

REGISTER], the equipment leak requirements of §63.691(b) of this 

subpart one year after the publication date of the final 

amendments [INSERT DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER], and the pressure relief 

device monitoring requirements of §63.691(c)(3)(i) and (ii) of 

this subpart three years after the publication date of the final 

amendments [INSERT DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER].

(ii) For an affected source that commenced construction or 

reconstruction before October 13, 1994, but receives off-site 

material for the first time on or after February 1, 2000, but 

before [INSERT DATE OF PUBLICATION OF THE FINAL RULE AMENDMENTS 

IN THE FEDERAL REGISTER], the owner or operator of the affected 

source must achieve compliance with the provisions of this 
Page 177 of 231

subpart (except §§ 63.685(b)(1)(ii), 63.691(b), and 

63.691(c)(3)(i) and (ii) of this subpart) upon the first date 

that the affected source begins to manage off-site material. 

These existing affected sources shall be in compliance with the 

tank requirements of §63.685(b)(1)(ii) of this subpart two years 

after the publication date of the final amendments [INSERT DATE 

OF PUBLICATION OF THE FINAL RULE AMENDMENTS IN THE FEDERAL 

REGISTER], the equipment leak requirements of §63.691(b) of this 

subpart one year after the publication date of the final 

amendments [INSERT DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER], and the pressure relief 

device monitoring requirements of §63.691(c)(3)(i) and (ii) of 

this subpart three years after the publication date of the final 

amendments [INSERT DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER].

(iii) For an affected source that commenced construction or 

reconstruction before October 13, 1994, but receives off-site 

material for the first time on or after [INSERT DATE OF 

PUBLICATION OF THE FINAL RULE AMENDMENTS IN THE FEDERAL 

REGISTER], the owner or operator of the affected source must 

achieve compliance with the provisions of this subpart (except 

§§ 63.685 (b)(1)(ii), 63.691(b), and 63.691(c)(3)(i) and (ii) of 

this subpart) upon the first date that the affected source 

begins to manage off-site material. These existing affected 
Page 178 of 231

sources shall be in compliance with the tank requirements of 

§63.685(b)(1)(ii) of this subpart two years after the 

publication date of the final amendments [INSERT DATE OF 

PUBLICATION OF THE FINAL RULE AMENDMENTS IN THE FEDERAL 

REGISTER], the equipment leak requirements of §63.691(b) of this 

subpart one year after the publication date of the final 

amendments [INSERT DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER], and the pressure relief 

device monitoring requirements of §63.691(c)(3)(i) and (ii) of 

this subpart three years after the publication date of the final 

amendments [INSERT DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER].

(2) New sources. The owner or operator of an affected 

source for which construction or reconstruction commences on or 

after October 13, 1994, must achieve compliance with the 

provisions of this subpart (except §§63.685(b)(2), 63.691(b), 

and 63.691(c)(i) and (ii) of this subpart) on or before July 1, 

1996, or upon initial startup of operations, whichever date is

later as provided in 40 CFR 63.6(b). New affected sources that 

commenced construction or reconstruction after October 13, 1994, 

but on or before [INSERT DATE OF PUBLICATION OF THE PROPOSED 

RULE AMENDMENTS IN THE FEDERAL REGISTER], shall be in compliance 

with the tank requirements of §63.685(b)(2) of this subpart two 

years after the publication date of the final amendments, the 
Page 179 of 231

equipment leak requirements of §63.691(b) of this subpart one 

after the publication date of the final amendments, and the 

pressure relief device monitoring requirements of §63.691(c)(i) 

and (ii) of this subpart three years after the effective date of 

the final amendments. New affected sources that commence 

construction or reconstruction after [INSERT DATE OF PUBLICATION 

OF THE PROPOSED RULE AMENDMENTS IN THE FEDERAL REGISTER], shall 

be in compliance with the tank requirements of §63.685(b)(2) of 

this subpart, the equipment leak requirements of §63.691(b) of 

this subpart, and the pressure relief device monitoring 

requirements of §63.691(c)(3)(i) and (ii) of this subpart upon 

initial startup or by the effective date of the final 

amendments, whichever is later.

* * * * *

(g) Applicability of this subpart. (1) The emission 

limitations set forth in this subpart and the emission 

limitations referred to in this subpart shall apply at all times 

except during periods of non-operation of the affected source 

(or specific portion thereof) resulting in cessation of the 

emissions to which this subpart applies.

(2) The owner or operator shall not shut down items of 

equipment that are required or utilized for compliance with this 

subpart during times when emissions are being routed to such 

items of equipment, if the shutdown would contravene 
Page 180 of 231

requirements of this subpart applicable to such items of 

equipment.

3. Section 63.681 is amended by:

a. Adding, in alphabetical order, definitions for “Bypass”, 

“In gas/vapor service”, “In heavy liquid service”, “In light 

liquid service”, “In liquid service”, “Pressure release”, and 

“Pressure relief device or valve”;

b. Revising the definitions of “Point-of-treatment” and 

“Process vent”; and

c. Removing the definition of “Safety device” to read as 

follows:

§ 63.681 Definitions.

* * * * *

Bypass means diverting a process vent or closed vent system 

stream to the atmosphere such that it does not first pass 

through an emission control device.

* * * * *

In gas/vapor service means that a piece of equipment in off-site 

material service contains a gas or vapor at operating 

conditions.

In heavy liquid service means that a piece of equipment in offsite material service is not in gas/vapor service or in light 

liquid service.
Page 181 of 231

In light liquid service means that a piece of equipment in offsite material service contains a liquid that meets the following 

conditions:

(1) The vapor pressure of one or more of the organic 

compounds is greater than 0.3 kilopascals at 20°C,

(2) The total concentration of the pure organic compounds 

constituents having a vapor pressure greater than 0.3 

kilopascals at 20°C is equal to or greater than 20 percent by 

weight of the total process stream, and

(3) The fluid is a liquid at operating conditions.

Note: Vapor pressures may be determined by the methods described 

in 40 CFR 60.485(e)(1).

In liquid service means that a piece of equipment in off-site

material service is not in gas/vapor service.

* * * * *

Point-of-treatment means a point after the treated material 

exits the treatment process but before the first point 

downstream of the treatment process exit where the organic 

constituents in the treated material have the potential to 

volatilize and be released to the atmosphere. For the purpose of 

applying this definition to this subpart, the first point 

downstream of the treatment process exit is not a fugitive 

emission point due to an equipment leak from any of the 
Page 182 of 231

following equipment components: pumps, compressors, valves, 

connectors, instrumentation systems, or pressure relief devices.

Pressure release means the emission of materials resulting from 

the system pressure being greater than the set pressure of the 

pressure relief device. This release can be one release or a 

series of releases over a short time period.

Pressure relief device or valve means a safety device used to 

prevent operating pressures from exceeding the maximum allowable 

working pressure of the process equipment. A common pressure 

relief device is a spring-loaded pressure relief valve. Devices 

that are actuated either by a pressure of less than or equal to 

2.5 pounds per square inch gauge or by a vacuum are not pressure 

relief devices.

* * * * *

Process vent means an open-ended pipe, stack, or duct through 

which a gas stream containing HAP is continuously or 

intermittently discharged to the atmosphere from any of the 

processes listed in §63.680(c)(2)(i) through (c)(2)(vi) of this 

section. For the purpose of this subpart, a process vent is none 

of the following: a pressure relief device; an open-ended line 

or other vent that is subject to the equipment leak control 

requirements under §63.691 of this subpart; or a stack or other 

vent that is used to exhaust combustion products from a boiler, 
Page 183 of 231

furnace, process heater, incinerator, or other combustion 

device.

* * * * *

4. Section 63.683 is revised by adding paragraphs (e) and 

(f) to read as follows:

§ 63.683 Standards: General.

* * * * *

(e) General Duty. At all times, the owner or operator must 

operate and maintain any affected source, including associated 

air pollution control equipment and monitoring equipment, in a 

manner consistent with safety and good air pollution control 

practices for minimizing emissions. The general duty to minimize 

emissions does not require the owner operator to make any 

further efforts to reduce emissions if levels required by the 

applicable standard have been achieved. Determination of whether 

a source is operating in compliance with operation and 

maintenance requirements will be based on information available 

to the Administrator, which may include, but is not limited to, 

monitoring results, review of operation and maintenance 

procedures, review of operation and maintenance records, and 

inspection of the source.

(f) In addition to the cases listed in §63.695(e)(4) of 

this subpart, deviation means any of the cases listed in 

paragraphs (f)(1) through (f)(6) of this section. 
Page 184 of 231

(1) Any instance in which an affected source subject to 

this subpart, or an owner or operator of such a source, fails to 

meet any requirement or obligation established by this subpart, 

including, but not limited to, any emission limit, operating 

limit or work practice standard.

(2) When a performance test indicates that emissions of a 

pollutant in Table 1 to this subpart are exceeding the emission 

standard for the pollutant specified in Table 1 to this subpart.

(3) When the average value of a monitored operating 

parameter, based on the data averaging period for compliance 

specified in §63.695 of this subpart, does not meet the 

operating limit specified in §63.693 of this subpart.

(4) When an affected source discharges directly into the 

atmosphere from any of the sources specified in paragraphs 

(f)(4)(i) and (ii) of this section.

(i) A pressure relief device, as defined in §63.681 of this 

subpart.

(ii) A bypass, as defined in §63.681 of this subpart.

(5) Any instance in which the affected source subject to

this subpart, or an owner or operator of such a source, fails to 

meet any term or condition specified in paragraph (f)(5)(i) or 

(ii) of this section.

(i) Any term or condition that is adopted to implement an 

applicable requirement in this subpart.
Page 185 of 231

(ii) Any term or condition relating to compliance with this 

subpart that is included in the operating permit for an affected 

source to obtain such a permit.

(6) Any failure to collect required data, except for 

periods of monitoring system malfunctions, repairs associated 

with monitoring system malfunctions, and required monitoring 

system quality assurance or quality control activities 

(including, as applicable, calibration checks and required zero 

and span adjustments).

5. Section 63.684 is amended by adding paragraph (b)(5)(v) 

and revising paragraph (h) to read as follows:

§ 63.684 Standards: Off-site Material Treatment.

* * * * *

(b) * * *

(5) * * *

(v) An incinerator, boiler, or industrial furnace for which 

the owner or operator has submitted a Notification of Compliance 

under 40 CFR 63.1207(j) and 63.1210(d) and complies with the 

requirements of 40 CFR part 63 subpart EEE at all times 

(including times when non-hazardous waste is being burned).

* * * * *

(h) The Administrator may at any time conduct or require 

that the owner or operator conduct testing necessary to 

demonstrate that a treatment process is achieving the applicable 
Page 186 of 231

performance requirements of this section. The testing shall be 

conducted in accordance with the applicable requirements of this 

section. The Administrator may elect to have an authorized 

representative observe testing conducted by the owner or 

operator. 

6. Section 63.685 is amended by:

a. Revising paragraphs (b), (b)(1) and (b)(2);

b. Removing paragraph (b)(4);

c. Revising paragraphs (c)(1), (c)(2)(i) and 

(c)(2)(iii)(B);

d. Revising paragraph (g)(2);

e. Revising paragraph (h)(3); 

f. Removing paragraphs (h)(3)(i) and (ii); and

g. Removing current paragraph (i)(3) and redesignating

current paragraph (i)(4) to (i)3) to read as follows:

§ 63.685 Standards: Tanks.

* * * * *

(b) According to the date an affected source commenced 

construction or reconstruction and the date an affected source 

receives off-site material for the first time as established in 

§63.680(e)(i)-(iii) of this subpart, the owner or operator shall 

control air emissions from each tank subject to this section in 

accordance with either paragraph (b)(1)(i) or (ii) of this 

section.
Page 187 of 231

(1)(i) For a tank that is part of an existing affected 

source but the tank is not used for a waste stabilization 

process as defined in §63.681 of this subpart, the owner or 

operator shall determine whether the tank is required to use 

either Tank Level 1 controls or Tank Level 2 controls as 

specified for the tank by Table 3 of this subpart based on the 

off-site material maximum HAP vapor pressure, the tank's design 

capacity. The owner or operator shall control air emissions from 

a tank required by Table 3 to use Tank Level 1 controls in 

accordance with the requirements of paragraph (c) of this 

section. The owner or operator shall control air emissions from 

a tank required by Table 3 to use Tank Level 2 controls in 

accordance with the requirements of paragraph (d) of this 

section.

(ii) For a tank that is part of an existing affected source 

but the tank is not used for a waste stabilization process as 

defined in §63.681 of this subpart, the owner or operator shall 

determine whether the tank is required to use either Tank Level 

1 controls or Tank Level 2 controls as specified for the tank by 

Table 4 of this subpart based on the off-site material maximum 

HAP vapor pressure and the tank's design capacity. The owner or 

operator shall control air emissions from a tank required by 

Table 4 to use Tank Level 1 controls in accordance with the 

requirements of paragraph (c) of this section. The owner or 
Page 188 of 231

operator shall control air emissions from a tank required by 

Table 4 to use Tank Level 2 controls in accordance with the 

requirements of paragraph (d) of this section.

(2) For a tank that is part of a new affected source but 

the tank is not used for a waste stabilization process as 

defined in §63.681 of this subpart, the owner or operator shall 

determine whether the tank is required to use either Tank Level 

1 controls or Tank Level 2 controls as specified for the tank by 

Table 5 of this subpart based on the off-site material maximum 

HAP vapor pressure and the tank's design capacity. The owner or 

operator shall control air emissions from a tank required by 

Table 5 to use Tank Level 1 controls in accordance with the 

requirements of paragraph (c) of this section. The owner or 

operator shall control air emissions from a tank required by 

Table 5 to use Tank Level 2 controls in accordance with the 

requirements of paragraph (d) of this section.

* * * * *

(c) * * *

(1) The owner or operator shall determine the maximum HAP 

vapor pressure for an off-site material to be managed in the 

tank using Tank Level 1 controls before the first time the offsite material is placed in the tank. The maximum HAP vapor 

pressure shall be determined using the procedures specified in 

§63.694(j) of this subpart. Thereafter, the owner or operator 
Page 189 of 231

shall perform a new determination whenever changes to the offsite material managed in the tank could potentially cause the 

maximum HAP vapor pressure to increase to a level that is equal 

to or greater than the maximum HAP vapor pressure limit for the 

tank design capacity category specified in Table 3, Table 4 or 

Table 5 of this subpart, as applicable to the tank. 

(2) * * *

(i) The owner or operator controls air emissions from the 

tank in accordance with the provisions specified in subpart OO 

of 40 CFR part 63—National Emission Standards for Tanks—Level 1, 

except that 40 CFR 63.902(c)(2) and (c)(3) shall not apply for 

the purposes of this subpart.

* * * * *

(iii) * * * 

(B) At all other times, air emissions from the tank must be 

controlled in accordance with the provisions specified in 40 CFR 

part 67, subpart OO—National Emission Standards for Tanks—Level

1, except that 40 CFR 63.902(c)(2) and (c)(3) shall not apply 

for the purposes of this subpart.

* * * * *

(g) * * *

(2) Whenever an off-site material is in the tank, the fixed 

roof shall be installed with each closure device secured in the 

closed position and the vapor headspace underneath the fixed 
Page 190 of 231

roof vented to the control device except that to the control 

device except that venting to the control device is not 

required, and opening of closure devices or removal of the fixed 

roof is allowed at the following times: 

(i) To provide access to the tank for performing routine 

inspection, maintenance, or other activities needed for normal 

operations. Examples of such activities include those times when 

a worker needs to open a port to sample liquid in the tank, or 

when a worker needs to open a hatch to maintain or repair 

equipment. Following completion of the activity, the owner or 

operator shall promptly secure the closure device in the closed 

position or reinstall the cover, as applicable, to the tank. 

(ii) To remove accumulated sludge or other residues from 

the bottom of the tank.

* * * * *

(h) * * *

(3) Whenever an off-site material is in the tank, the tank 

shall be operated as a closed system that does not vent to the 

atmosphere except at those times when purging of inerts from the 

tank is required and the purge stream is routed to a closed-vent 

system and control device designed and operated in accordance 

with the requirements of §63.693 of this subpart. 

(i) * * *
Page 191 of 231

(3) The owner or operator shall inspect and monitor the 

closed-vent system and control device as specified in §63.693.

7. Section 63.686 is amended by revising paragraphs (b)(1) 

through (b)(3) to read as follows:

§ 63.686 Standards: Oil-water and organic water separators.

* * * * *

(b) * * *

(1) A floating roof in accordance with all applicable 

provisions specified in 40 CFR 63 subpart VV—National Emission 

Standards for Oil-Water Separators and Organic-Water Separators, 

except that 63.1043(c)(2), 63.1044(c)(2) and 63.1045(b)(3)(i) 

shall not apply for the purposes of this subpart. For portions 

of the separator where it is infeasible to install and operate a 

floating roof, such as over a weir mechanism, the owner or 

operator shall comply with the requirements specified in 

paragraph (b)(2) of this section. 

(2) A fixed-roof that is vented through a closed-vent 

system to a control device in accordance with all applicable 

provisions specified in 40 CFR 63 subpart VV—National Emission 

Standards for Oil-Water Separators and Organic-Water Separators, 

except that 63.1043(c)(2), 63.1044(c)(2) and 63.1045(b)(3)(i) 

shall not apply for the purposes of this subpart. 

(3) A pressurized separator that operates as a closed 

system in accordance with all applicable provisions specified in 
Page 192 of 231

40 CFR part 63, subpart VV—National Emission Standards for OilWater Separators and Organic-Water Separators, except that 

63.1043(c)(2), 63.1044(c)(2) and 63.1045(b)(3)(i) shall not 

apply for the purposes of this subpart.

8. Section 63.687 is amended by revising paragraphs (b)(1) 

and (b)(2) to read as follows:

§ 63.687 Standards: Surface impoundments.

* * * * *

(b) * * *

(1) A floating membrane cover in accordance with the 

applicable provisions specified in 40 CFR 63 subpart QQ—National 

Emission Standards for Surface Impoundments, except that 

63.942(c)(2) and (c)(3) and 63.943(c)(2) shall not apply for the 

purposes of this subpart; or 

(2) A cover that is vented through a closed-vent system to 

a control device in accordance with all applicable provisions 

specified in 40 CFR 63 subpart QQ—National Emission Standards 

for Surface Impoundments, except that 63.942(c)(2) and (c)(3) 

and 63.943(c)(2) shall not apply for the purposes of this 

subpart. 

9. Section 63.688 is amended by revising paragraphs 

(b)(1)(i), (b)(1)(ii) and (b)(3)(i) to read as follows:

§63.688 Standards: Containers.

* * * * *
Page 193 of 231

(b) * * *

(1) * * *

(i) The owner or operator controls air emissions from the 

container in accordance with the standards for Container Level 1 

controls as specified in 40 CFR part 63, subpart PP—National 

Emission Standards for Containers, except that 63.922(d)(4) and 

(d)(5) and 63.923(d)(4) and (d)(5) shall not apply for the 

purposes of this subpart.

(ii) As an alternative to meeting the requirements in 

paragraph (b)(1)(i) of this section, an owner or operator may 

choose to control air emissions from the container in accordance 

with the standards for either Container Level 2 controls or 

Container Level 3 controls as specified in subpart PP of this 

part 63—National Emission Standards for Containers, except that 

63.922(d)(4) and (d)(5) and 63.923(d)(4) and (d)(5) shall not 

apply for the purposes of this subpart.

* * * * *

(3) * * *

(i) The owner or operator controls air emissions from the 

container in accordance with the standards for Container Level 2 

controls as specified in 40 CFR part 63, subpart PP—National 

Emission Standards for Containers, except that 63.922(d)(4) and 

(d)(5) and 63.923(d)(4) and (d)(5) shall not apply for the 

purposes of this subpart.
Page 194 of 231

* * * * *

10. Section 63.689 is amended by revising paragraph (d)(5) 

and removing paragraphs (d)(5)(i) and (ii) to read as follows:

§ 63.689 Standards: Transfer systems.

* * * * *

(d) * * *

(5) Whenever an off-site material is in the transfer 

system, the cover shall be installed with each closure device 

secured in the closed position, except the opening of closure 

devices or removal of the cover is allowed to provide access to 

the transfer system for performing routine inspection, 

maintenance, repair, or other activities needed for normal 

operations. Examples of such activities include those times when 

a worker needs to open a hatch or remove the cover to repair 

conveyance equipment mounted under the cover or to clear a 

blockage of material inside the system. Following completion of 

the activity, the owner or operator shall promptly secure the 

closure device in the closed position or reinstall the cover, as 

applicable. 

* * * * *

11. Section 63.691 is amended by:

a. Revising introductory paragraph (b);

b. Revising paragraphs (b)(1) and (b)(2); and

c. Adding paragraph (c) to read as follows:
Page 195 of 231

§ 63.691 Standards: Equipment leaks.

* * * * * 

(b) According to the date an affected source commenced 

construction or reconstruction and the date an affected source 

receives off-site material for the first time, as established in 

§63.680(e)(i)-(iii) of this subpart, the owner or operator shall 

control the HAP emitted from equipment leaks in accordance with

the applicable provisions specified in either paragraph (b)(1) 

or (b)(2) of this section.

(1)(i) The owner or operator controls the HAP emitted from 

equipment leaks in accordance with §61.241 through §61.247 in 40 

CFR part 61, subpart V—National Emission Standards for Equipment 

Leaks, with the difference noted in paragraphs (b)(1)(iii) and 

(iv) of this section for the purposes of this subpart; or 

(ii) The owner or operator controls the HAP emitted from 

equipment leaks in accordance with §63.161 through §63.182 in 40 

CFR part 63, subpart H—National Emission Standards for Organic 

Hazardous Air Pollutants from Equipment Leaks, with the 

differences noted in paragraphs (b)(2)(i) through (iv) of this 

section for the purposes of this subpart.

(iii) On or after [THE DATE OF PUBLICATION OF THE FINAL 

RULE AMENDMENTS IN THE FEDERAL REGISTER], for the purpose of 

complying with the requirements of 40 CFR 61.242-6(a)(2), the 

open end is sealed when instrument monitoring of the open-ended 
Page 196 of 231

valve or line conducted according to Method 21 of 40 CFR part 

60, appendix A indicates no readings of 500 ppm or greater.

(iv) On or after [THE DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER], for the purpose of 

complying with the requirements of 40 CFR 61.242-6(d), openended valves or lines in an emergency shutdown system which are 

designed to open automatically in the event of a process upset 

and that are exempt from the requirements in 40 CFR 61.242-6(a), 

(b), and (c) must comply with the requirements in §63.693(c)(2) 

of this subpart.

(2) The owner or operator controls the HAP emitted from 

equipment leaks in accordance with §63.161 through §63.183 in 40 

CFR part 63, subpart H – National Emission Standards for Organic 

Hazardous Air Pollutants for Equipment Leaks, with the 

differences noted in paragraphs (b)(2)(i) through (v) of this 

section for the purposes of this subpart. 

(i) For each valve in gas/vapor or in light liquid service, 

as defined in §63.681 of this subpart, that is part of an 

affected source under this subpart, an instrument reading that 

defines a leak is 500 ppm or greater as detected by Method 21 of 

40 CFR part 60, appendix A.

(ii) For each pump in light liquid service, as defined in 

§63.681 of this subpart, that is part of an affected source 

under this subpart, an instrument reading that defines a leak is 
Page 197 of 231

1,000 ppm or greater as detected by Method 21 of 40 CFR part 60, 

appendix A. Repair is not required unless an instrument reading 

of 2,000 ppm or greater is detected.

(iii) On or after [THE DATE OF PUBLICATION OF THE FINAL 

RULE AMENDMENTS IN THE FEDERAL REGISTER], for the purpose of 

complying with the requirements of 40 CFR 63.167(a)(2), the open 

end is sealed when instrument monitoring of the open-ended valve 

or line conducted according to Method 21 of 40 CFR part 60, 

appendix A indicates no readings of 500 ppm or greater.

(iv) On or after [THE DATE OF PUBLICATION OF THE FINAL RULE 

AMENDMENTS IN THE FEDERAL REGISTER], for the purpose of 

complying with the requirements of 40 CFR 63.167(d), open-ended 

valves or lines in an emergency shutdown system which are 

designed to open automatically in the event of a process upset 

and that are exempt from the requirements in 40 CFR 63.167(a), 

(b) and (c) must comply with the requirements in §63.693(c)(2) 

of this subpart.

(v) For the purposes of this subpart, the pressure relief 

device requirements of §63.691(c) of this subpart rather than 

those of 40 CFR 63.165 shall apply.

(c) Requirements for pressure relief devices. Except as 

provided in paragraph (c)(4) of this section, the owner or 

operator must comply with the requirements specified in 
Page 198 of 231

paragraphs (c)(1) through (3) of this section for pressure 

relief devices in off-site material service.

(1) Operating requirements. Except during a pressure 

release event, operate each pressure relief device in off-site 

material gas or vapor service with an instrument reading of less 

than 500 ppm above background as detected by Method 21 of 40 CFR 

part 60, appendix A.

(2) Pressure release requirements. For pressure relief 

devices in off-site material gas or vapor service, the owner or 

operator must comply with either paragraph (c)(2)(i) or (ii) of 

this section following a pressure release, as applicable.

(i) If the pressure relief device does not consist of or 

include a rupture disk, the pressure relief device shall be 

returned to a condition indicated by an instrument reading of 

less than 500 ppm above background, as detected by Method 21 of 

40 CFR part 60, appendix A, no later than 5 calendar days after 

the pressure release device returns to off-site material service 

following a pressure release, except as provided in 40 CFR 

63.171. 

(ii) If the pressure relief device consists of or includes 

a rupture disk, except as provided in 40 CFR 63.171, install a 

replacement disk as soon as practicable but no later than 5 

calendar days after the pressure release.
Page 199 of 231

(3) Pressure release management. Except as provided in 

paragraph (c)(4) of this section, emissions of HAP listed in 

Table 1 of this subpart may not be discharged directly to the 

atmosphere from pressure relief devices in off-site material 

service, and according to the date an affected source commenced 

construction or reconstruction and the date an affected source 

receives off-site material for the first time, as established in 

§63.680(e)(i)-(iii) of this subpart, the owner or operator must 

comply with the requirements specified in paragraphs (c)(3)(i) 

and (ii) of this section for all pressure relief devices in offsite material service.,

(i) The owner or operator must equip each pressure relief 

device in off-site material service with a device(s) or use a 

monitoring system that is capable of: 1) identifying the 

pressure release; 2) recording the time and duration of each 

pressure release; and 3) notifying operators immediately that a 

pressure release is occurring. The device or monitoring system 

may be either specific to the pressure release device itself or 

may be associated with the process system or piping, sufficient 

to indicate a pressure release to the atmosphere. Examples of 

these types of devices or monitoring systems include, but are 

not limited to, a rupture disk indicator, magnetic sensor, 

motion detector on the pressure relief valve stem, flow monitor, 

pressure monitor, or parametric monitoring system. 
Page 200 of 231

(ii) If any pressure relief device in off-site material 

service releases directly to the atmosphere as a result of a 

pressure release event, the owner or operator must calculate the 

quantity of HAP listed in Table 1 of this subpart released 

during each pressure release event and report this quantity as 

required in §63.697(b)(5) of this subpart. Calculations may be 

based on data from the pressure relief device monitoring alone 

or in combination with process parameter monitoring data and 

process knowledge. 

(4) Pressure relief devices routed to a drain system, 

process or control device. If a pressure relief device in offsite material service is designed and operated to route all 

pressure releases through a closed vent system to a drain 

system, process or control device, paragraphs (c)(1), (2), and 

(3) of this section do not apply. The closed vent system and the 

process or control device (if applicable) must meet the 

requirements of §63.693 of this subpart. The drain system (if 

applicable) must meet the requirements of §63.689 of this 

subpart.

12. Section 63.693 is amended by:

a. Revising paragraphs (b)(3) and (b)(8);

b. Revising paragraphs (c)(1)(ii) and (c)(2), and adding 

paragraph (c)(2)(iii); 

c. Revising paragraph (f)(1)(i)(B) and (ii)(B); and
Page 201 of 231

d. Revising paragraph (g)(1)(v) to read as follows:

§ 63.693 Standards: Closed-vent systems and control devices.

* * * * *

(b) * * *

(3) Whenever gases or vapors containing HAP are routed from 

a tank through a closed-vent system connected to a control 

device used to comply with the requirements of paragraph 

§63.685(b)(1), (2) or (3) of this subpart, the control device 

must be operating except as provided for in paragraphs (b)(3)(i) 

and (b)(3)(ii) of this section.

(i) The control device may only be bypassed for the purpose 

of performing planned routine maintenance of the closed-vent 

system or control device in situations when the routine 

maintenance cannot be performed during periods that tank 

emissions are vented to the control device.

(ii) On an annual basis, the total time that the closedvent system or control device is bypassed to perform routine 

maintenance shall not exceed 240 hours per each calendar year. 

* * * * *

(8) In the case when an owner or operator chooses to use a 

design analysis to demonstrate compliance of a control device 

with the applicable performance requirements specified in this 

section as provided for in paragraphs (d) through (g) of this 

section, the Administrator may require that the design analysis 
Page 202 of 231

be revised or amended by the owner or operator to correct any 

deficiencies identified by the Administrator. If the owner or 

operator and the Administrator do not agree on the acceptability 

of using the design analysis (including any changes required by 

the Administrator) to demonstrate that the control device 

achieves the applicable performance requirements, then the 

disagreement must be resolved using the results of a performance 

test conducted by the owner or operator in accordance with the 

requirements of §63.694(l) of this subpart. The Administrator 

may choose to have an authorized representative observe the 

performance test conducted by the owner or operator. Should the 

results of this performance test not agree with the 

determination of control device performance based on the design 

analysis, then the results of the performance test will be used 

to establish compliance with this subpart.

* * * * *

(c) * * *

(1) * * *

(i) * * *

(ii) A closed-vent system that is designed to operate at a 

pressure below atmospheric pressure. The system shall be 

equipped with at least one pressure gauge or other pressure 

measurement device that can be read from a readily accessible 
Page 203 of 231

location to verify that negative pressure is being maintained in 

the closed-vent system when the control device is operating.

(2) In situations when the closed-vent system includes 

bypass devices that could be used to divert a vent stream from 

the closed-vent system to the atmosphere at a point upstream of 

the control device inlet, each bypass device must be equipped 

with either a flow indicator as specified in paragraph (c)(2)(i) 

of this section or a seal or locking device as specified in 

paragraph (c)(2)(ii) of this section, except as provided for in 

paragraph (c)(2)(iii) of this section:

* * * * *

(iii) Equipment needed for safety reasons, including low 

leg drains, open-ended valves and lines not in emergency 

shutdown systems, and pressure relief devices subject to the 

requirements of §63.691(c) of this subpart are not subject to 

the requirements of paragraphs (c)(2)(i) and (ii) of this 

section.

* * * * *

(f) * * *

(1) * * *

(i) * * *

(B) To achieve a total incinerator outlet concentration for 

the TOC, less methane and ethane, of less than or equal to 20 

ppmv on a dry basis corrected to 3 percent oxygen.
Page 204 of 231

(ii) * * *

(B) To achieve a total incinerator outlet concentration for 

the HAP, listed in Table 1 of this subpart, of less than or 

equal to 20 ppmv on a dry basis corrected to 3 percent oxygen.

* * * * *

(g) * * *

(1) * * *

(v) Introduce the vent stream to a boiler or process heater 

for which the owner or operator either has been issued a final 

permit under 40 CFR part 270 and complies with the requirements 

of 40 CFR part 266, subpart H of this chapter; or has certified 

compliance with the interim status requirements of 40 CFR part 

266, subpart H of this chapter; or has submitted a Notification 

of Compliance under 40 CFR 63.1207(j) and 63.1210(d) and 

complies with the requirements of 40 CFR part 63, subpart EEE at 

all times (including times when non-hazardous waste is being 

burned).

* * * * *

13. Section 63.694 is amended by:

a. Revising paragraph (b)(3)(iv)

b. Revising paragraph (f)(1);

c. Revising paragraph (i)(1);

d. Revising paragraph (j)(3);

e. Revising paragraph (k)(3);
Page 205 of 231

f. Revising introductory paragraph (l), (l)(3), (l)(3)(i), 

(l)(3)(ii)(B), (l)(4), (l)(4)(i), (l)(4)(ii)(A), (l)(4)(ii)(B), 

(l)(4)(iii)(A); and

g. Revising paragraphs (m)(2) and (3) to read as follows:

63.694 Testing Methods and Procedures.

* * * * *

(b) * * *

(3) * * *

(iv) In the event that the Administrator and the owner or 

operator disagree on a determination of the average VOHAP 

concentration for an off-site material stream using knowledge, 

then the results from a determination of VOHAP concentration 

using direct measurement as specified in paragraph (b)(2) of 

this section shall be used to establish compliance with the 

applicable requirements of this subpart. The Administrator may 

perform or require that the owner or operator perform this 

determination using direct measurement. 

(f) * * *

(1) The actual HAP mass removal rate (MR) shall be 

determined based on results for a minimum of three consecutive 

runs. The sampling time for each run shall be at least 1 hour.

* * * * *

(i) * * *
Page 206 of 231

(1) The actual HAP mass removal rate (MRbio) shall be 

determined based on results for a minimum of three consecutive 

runs. The sampling time for each run shall be at least 1 hour.

* * * * *

(j) * * *

(3) Use of knowledge to determine the maximum HAP vapor 

pressure of the off-site material. Documentation shall be 

prepared and recorded that presents the information used as the 

basis for the owner's or operator's knowledge that the maximum 

HAP vapor pressure of the off-site material is less than the 

maximum vapor pressure limit listed in Table 3, Table 4, or 

Table 5 of this subpart for the applicable tank design capacity 

category. Examples of information that may be used include: the 

off-site material is generated by a process for which at other 

locations it previously has been determined by direct 

measurement that the off-site material maximum HAP vapor 

pressure is less than the maximum vapor pressure limit for the 

appropriate tank design capacity category. In the event that the 

Administrator and the owner or operator disagree on a 

determination of the maximum HAP vapor pressure for an off-site 

material stream using knowledge, then the results from a 

determination of HAP vapor pressure using direct measurement as 

specified in paragraph (j)(2) of this section shall be used to 

establish compliance with the applicable requirements of this 
Page 207 of 231

subpart. The Administrator may perform or require that the owner 

or operator perform this determination using direct measurement.

(k) * * *

(3) The detection instrument shall meet the performance 

criteria of Method 21 of 40 CFR part 60, appendix A, except the 

instrument response factor criteria in section 8.1.1 of Method 

21 shall be for the weighted average composition of the organic 

constituents in the material placed in the unit at the time of 

monitoring, not for each individual organic constituent.

* * * * *

(l) Control device performance test procedures. Performance 

tests shall be conducted under such conditions as the 

Administrator specifies to the owner or operator based on 

representative performance of the affected source for the period 

being tested. Representative conditions exclude periods of 

startup and shutdown. The owner or operator may not conduct 

performance tests during periods of malfunction. The owner or 

operator must 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. Upon request, the owner or operator 

shall make available to the Administrator such records as may be 

necessary to determine the conditions of performance tests.

* * * * *
Page 208 of 231

(3) To determine compliance with the control device 

percent reduction requirement, the owner or operator shall use 

Method 18 of 40 CFR part 60, appendix A of this chapter to 

measure the HAP in Table 1 of this subpart or Method 25A of 40 

CFR 60, appendix A of this chapter to measure TOC. Method 18 may 

be used to measure methane and ethane, and the measured 

concentration may be subtracted from the Method 25A measurement.

Alternatively, any other method or data that has been validated 

according to the applicable procedures in Method 301 in 40 CFR 

part 63, appendix A of this part may be used. The following 

procedures shall be used to calculate percent reduction 

efficiency: 

(i) A minimum of three sample runs must be performed. The 

minimum sampling time for each run shall be 1 hour. For Method 

18, either an integrated sample or a minimum of four grab 

samples shall be taken. If grab sampling is used, then the 

samples shall be taken at approximately equal intervals in time 

such as 15 minute intervals during the run. 

(ii) * * *

(B) When the TOC mass rate is calculated, the average 

concentration reading (minus methane and ethane) measured by 

Method 25A of 40 CFR part 60, appendix A shall be used in the 

equation in paragraph (l)(3)(ii)(A) of this section. 

* * * * *
Page 209 of 231

(4) To determine compliance with the enclosed combustion 

device total HAP concentration limit of this subpart, the owner 

or operator shall use Method 18 of 40 CFR part 60, appendix A to 

measure the total HAP in Table 1 of this subpart of Method 25A 

of 40 CFR part 60, appendix A to measure TOC. Method 18 may be 

used to measure methane and ethane and the measured 

concentration may be subtracted from the Method 25A measurement. 

Alternatively, any other method or data that has been validated 

according to Method 301 in appendix A of this part, may be used. 

The following procedures shall be used to calculate parts per 

million by volume concentration, corrected to 3 percent oxygen: 

(i) A minimum of three sample runs must be performed. The 

minimum sampling time for each run shall be 1 hour. For Method 

18, either an integrated sample or a minimum of four grab 

samples shall be taken. If grab sampling is used, then the 

samples shall be taken at approximately equal intervals in time, 

such as 15 minute intervals during the run. 

(ii) * * *

(A) The TOC concentration (CTOC) is the average 

concentration readings provided by Method 25 A of 40 CFR part 

60, appendix A, minus the concentration of methane and ethane.

(B) The total HAP concentration (CHAP) shall be computed 

according to the following equation:
Page 210 of 231

CHAP = ∑

∑ Cji

n

j=1

x

x

i=1

where:

CHAP = Total concentration of HAP compounds listed in Table 1 of 

this subpart, dry basis, parts per million by volume.

Cij = Concentration of sample components j of sample i, dry 

basis, parts per million by volume.

n = Number of components in the sample.

x = Number of samples in the sample run.

(iii) The measured TOC concentration or total HAP 

concentration shall be corrected to 3 percent oxygen as follows: 

(A) The emission rate correction factor or excess air, 

integrated sampling and analysis procedures of Method 3B of 40 

CFR part 60, appendix A shall be used to determine the oxygen 

concentration (%O2dry). Alternatively, the owner or operator may 

use Method 3A of 40 CFR part 60, appendix A to determine the 

oxygen concentration. The samples shall be collected during the 

same time that the samples are collected for determining TOC 

concentration or total HAP concentration. 

(B) The concentration corrected to 3 percent oxygen (Cc) 

shall be computed using the following equation: 
Page 211 of 231

where:

Cc=TOC concentration or total HAP concentration corrected to 3 

percent oxygen, dry basis, parts per million by volume. 

Cm=Measured TOC concentration or total HAP concentration, dry 

basis, parts per million by volume. 

%O2dry=Concentration of oxygen, dry basis, percent by volume.

(m) * * *

(2) No traverse site selection method is needed for vents 

smaller than 0.10 meter in diameter. For vents smaller than 0.10 

meter in diameter, sample at the center of the vent.

(3) Process vent stream gas volumetric flow rate must be 

determined using Method 2, 2A, 2C, 2D, 2F, or 2G of 40 CFR part 

60, appendix A, as appropriate.

* * * * *

14. Section 63.695 is amended by:

a. Revising paragraph (a);

b. Adding paragraph (a)(5);

c. Revising paragraphs (e)(4) and (5); and

d. Removing paragraphs (e)(6) and (7) to read as follows:

§ 63.695 Inspection and monitoring requirements.

(a) The owner or operator must install, calibrate, 

maintain, and operate all monitoring system components according 

to §63.8 of this part, §§63.684(e), 63.693(d)(3), (e)(3), 

(f)(3), (g)(3), (h)(3) of this subpart, and paragraph (5) of 
Page 212 of 231

this section and perform the inspection and monitoring 

procedures specified in paragraphs (a)(1) through (4) of this 

section.

* * * * *

(5)(i) Except for periods of monitoring system 

malfunctions, repairs associated with monitoring system 

malfunctions and required monitoring system quality assurance or 

quality control activities (including, as applicable, 

calibration checks and required zero and span adjustments), the 

owner or operator must operate the continuous monitoring system 

at all times the affected source is operating. A monitoring 

system malfunction is any sudden, infrequent, not reasonably 

preventable failure of the monitoring system to provide data. 

Monitoring system failures that are caused in part by poor 

maintenance or careless operation are not malfunctions. The 

owner or operator is required to complete monitoring system 

repairs in response to monitoring system malfunctions and to 

return them monitoring system to operation as expeditiously as 

practicable.

(ii) The owner or operator may not use data recorded during 

monitoring system malfunctions, repairs associated with 

monitoring system malfunctions, or required monitoring system 

quality assurance or control activities in calculations used to 

report emissions or operating levels. The owner or operator must 
Page 213 of 231

use all the data collected during all other required data 

collection periods in assessing the operation of the control 

device and associated control system. The owner or operator must 

report any periods for which the monitoring system failed to 

collect required data.

* * * * *

(e) * * *

(4) A deviation for a given control device is determined to 

have occurred when the monitoring data or lack of monitoring 

data result in any one of the criteria specified in paragraphs 

(e)(4)(i) through (e)(4)(iii) of this section being met. When 

multiple operating parameters are monitored for the same control 

device and during the same operating day more than one of these 

operating parameters meets a deviation criterion specified in 

paragraphs (e)(4)(i) through (e)(4)(iii) of this section, then a 

single deviation is determined to have occurred for the control 

device for that operating day.

(i) A deviation occurs when the daily average value of a 

monitored operating parameter is less than the minimum operating 

parameter limit (or, if applicable, greater than the maximum 

operating parameter limit) established for the operating 

parameter in accordance with the requirements of paragraph 

(e)(3) of this section.
Page 214 of 231

(ii) A deviation occurs when the period of control device 

operation is 4 hours or greater in an operating day and the 

monitoring data are insufficient to constitute a valid hour of 

data for at least 75 percent of the operating hours. Monitoring 

data are insufficient to constitute a valid hour of data if 

measured values are unavailable for any of the 15-minute periods 

within the hour.

(iii) A deviation occurs when the period of control device 

operation is less than 4 hours in an operating day and more than 

1 of the hours during the period does not constitute a valid 

hour of data due to insufficient monitoring data. Monitoring 

data are insufficient to constitute a valid hour of data if 

measured values are unavailable for any of the 15-minute periods 

within the hour.

(5) For each deviation, except when the deviation occurs 

during periods of non-operation of the unit or the process that 

is vented to the control device (resulting in cessation of HAP 

emissions to which the monitoring applies), the owner or 

operator shall be deemed to have failed to have applied control 

in a manner that achieves the required operating parameter 

limits. Failure to achieve the required operating parameter 

limits is a violation of this standard.

* * * * *
Page 215 of 231

15. Section 63.696 is amended by revising paragraph (h) and 

adding paragraphs (i) and (j) to read as follows:

63.696 Recordkeeping requirements.

* * * * *

(h) An owner or operator shall record the malfunction 

information specified in paragraphs (h)(1) through (h)(3) of 

this section.

(1) In the event that an affected unit fails to meet an 

applicable standard, record the number of failures. For each 

failure record the date, time and duration of the failure.

(2) For each failure to meet an applicable standard, record 

and retain a list of the affected sources or equipment, an 

estimate of the volume of each regulated pollutant emitted over 

any emission limit and a description of the method used to 

estimate the emissions. 

(3) Record actions taken to minimize emissions in 

accordance with §63.683(e) of this subpart and any corrective 

actions taken to return the affected unit to its normal or usual 

manner of operation.

(i) For pressure relief devices in off-site material 

service, keep records of the information specified in paragraphs 

(i)(1) through (5) of this section, as applicable.

(1) A list of identification numbers for pressure relief 

devices that the owner or operator elects to route emissions 
Page 216 of 231

through a closed-vent system to a control device, process or 

drain system under the provisions in §63.691(c)(4) of this 

subpart.

(2) A list of identification numbers for pressure relief 

devices that do not consist of or include a rupture disk, 

subject to the provisions in §63.691(c)(2)(i) of this subpart.

(3) A list of identification numbers for pressure relief 

devices equipped with rupture disks, subject to the provisions 

in §63.691(c)(2)(ii) of this subpart.

(4) The dates and results of the Method 21 of 40 CFR part 

60, appendix A, monitoring following a pressure release for each 

pressure relief device subject to the provisions in 

§63.691(c)(2)(i) of this subpart. The results of each monitoring 

event shall include:

(i) The measured background level.

(ii) The maximum instrument reading measured at each 

pressure relief device.

(5) For pressure relief devices in off-site material 

service subject to §63.691(c)(3) of this subpart, keep records 

of each pressure release to the atmosphere, including the 

following information:

(i) The source, nature, and cause of the pressure release.

(ii) The date, time, and duration of the pressure release.
Page 217 of 231

(iii) An estimate of the quantity of HAP listed in Table 1 

of this subpart emitted during the pressure release and the 

calculations used for determining this quantity.

(iv) The actions taken to prevent this pressure release.

(v) The measures adopted to prevent future such pressure 

releases.

(j) (1) For pressure tank closure devices, as specified in 

§63.685(h)(2) of this subpart, keep records of each release to 

the atmosphere, including the information specified in 

paragraphs (j)(3) though (7) of this section. 

(2) For each closed vent system that includes bypass 

devices that could divert a stream away from the control device 

and into the atmosphere, as specified in §63.693(c)(2) of this 

subpart, and each open-ended valve or line in an emergency 

shutdown system which is designed to open automatically in the 

event of a process upset, as specified in 40 CFR 63.167(d) or 40 

CFR 61.242-6(d), keep records of each release to the atmosphere, 

including the information specified in paragraphs (j)(3) though 

(9) of this section. 

(3) The source, nature, and cause of the release.

(4) The date, time, and duration of the release.

(5) An estimate of the quantity of HAP listed in Table 1 of 

this subpart emitted during the release and the calculations 

used for determining this quantity.
Page 218 of 231

(6) The actions taken to prevent this release.

(7) The measures adopted to prevent future such release.

(8) Hourly records of whether the bypass flow indicator 

specified under §63.693(c)(2) of this subpart was operating and 

whether a diversion was detected at any time during the hour, as 

well as records of the times of all periods when the vent stream 

is diverted from the control device or the flow indicator is not 

operating.

(9) Where a seal mechanism is used to comply with 

§63.693(c)(2) of this subpart, hourly records of flow are not 

required. In such cases, the owner or operator shall record that 

the monthly visual inspection of the seals or closure mechanism 

has been done, and shall record the duration of all periods when 

the seal mechanism is broken, the bypass line valve position has 

changed, or the key for a lock-and-key type lock has been 

checked out, and records of any car-seal that has broken.

16. Section 63.697 is amended by:

a. Revising paragraph (a) introductory text, adding 

paragraphs (a)(1)(i) and (ii) and (a)(3); 

b. Revising paragraph (b)(3) and (b)(4); and

c. Adding paragraphs (b)(5) and (b)(6) to read as follows:

§ 63.697 Reporting requirements.

(a) Each owner or operator of an affected source subject to 

this subpart must comply with the notification requirements 
Page 219 of 231

specified in paragraph (a)(1) of this section and the reporting 

requirements specified in paragraph (a)(2) and (a)(3) of this 

section.

(1) * * *

(i) For pressure relief devices in off-site material

service subject to the requirements of §63.691(c) of this 

subpart, the owner or operator must submit the information 

listed in paragraph (a)(1)(ii) of this section in the 

notification of compliance status required under §63.9(h) of 

this part within 150 days after the first applicable compliance 

date for pressure relief device monitoring.

(ii) For pressure relief devices in off-site material

service, a description of the device or monitoring system to be 

implemented, including the pressure relief devices and process 

parameters to be monitored (if applicable), a description of the 

alarms or other methods by which operators will be notified of a 

pressure release, and a description of how the owner or operator 

will determine the information to be recorded under § 

63.696(i)(5)(ii)-(iii) of this subpart (i.e., the duration of 

the pressure release and the methodology and calculations for 

determining the quantity of HAP listed in Table 1 of this 

subpart emitted during the pressure release).

* * * * *
Page 220 of 231

(3) Electronic reporting. Within 60 days after the date of 

completing each performance test (as defined in §63.2 of this 

part) required by this subpart, the owner or operator must 

submit the results of the performance test according to the 

manner specified by either paragraph (a)(3)(i) or (ii) of this 

section.

(i) For data collected using test methods supported by the 

EPA’s Electronic Reporting Tool (ERT) as listed on the EPA’s ERT 

website (http://www.epa.gov/ttn/chief/ert/index.html), the owner 

or operator must submit the results of the performance test to 

the EPA via the Compliance and Emissions Data Reporting 

Interface (CEDRI) accessed through the EPA’s Central Data 

Exchange (CDX) (http://cdx.epa.gov/epa_home.asp). Performance 

test data must be submitted in a file format generated through 

the use of the EPA’s ERT. Owners or operators who claim that 

some of the performance test information being submitted is 

confidential business information (CBI) must submit a complete 

file generated through the use of the EPA’s ERT, including 

information claimed to be CBI, on a compact disc, flash drive, 

or other commonly used electronic storage media to the EPA. The 

electronic media must be clearly marked as CBI and mailed to 

U.S. EPA/OAPQS/CORE CBI Office, Attention: WebFIRE 

Administrator, MD C404-02, 4930 Old Page Rd., Durham, NC 27703. 
Page 221 of 231

The same ERT file with the CBI omitted must be submitted to the 

EPA via the EPA’s CDX as described earlier in this paragraph.

(ii) For data collected using test methods that are not 

supported by the EPA’s ERT as listed on the EPA’s ERT website, 

the owner or operator must submit the results of the performance 

test to the Administrator at the appropriate address listed in 

40 CFR 60.4. 

(b) * * * 

(3) Reports of malfunctions. If a source fails to meet an 

applicable standard, report such events in the Periodic 

Report. Report the number of failures to meet an applicable 

standard. For each instance, report the date, time and duration 

of each failure. For each failure the report must include a list 

of the affected sources or equipment, an estimate of the volume 

of each regulated pollutant emitted over any emission limit, and 

a description of the method used to estimate the emissions. 

(4) A summary report specified in §63.10(e)(3) of this 

part shall be submitted on a semiannual basis (i.e., once every 

6-month period). The summary report must include a description 

of all deviations as defined in §63.695(e) of this subpart that 

have occurred during the 6-month reporting period. For each 

deviation caused when the daily average value of a monitored 

operating parameter is less than the minimum operating parameter 

limit (or, if applicable, greater than the maximum operating 
Page 222 of 231

parameter limit), the report must include the daily average 

values of the monitored parameter, the applicable operating 

parameter limit, and the date and duration of the period that 

the deviation occurred. For each deviation caused by lack of 

monitoring data, the report must include the date and duration 

of period when the monitoring data were not collected and the 

reason why the data were not collected.

(5) For pressure relief devices in off-site material 

service subject to §63.691(c) of this subpart, Periodic Reports 

must include the information specified in paragraphs (b)(5)(i) 

through (b)(5)(iii) of this section.

(i) For pressure relief devices in off-site material 

service subject to §63.691(c) of this subpart, report the 

results of all monitoring conducted within the reporting period.

(ii) For pressure relief devices in off-site material 

service subject to §63.691(c)(2)(i) of this subpart, report any 

instrument reading of 500 ppm above background or greater, if 

detected more than 5 days after the pressure release.

(iii) For pressure relief devices in off-site material 

service subject to §63.691(c)(3) of this subpart, report each 

pressure release to the atmosphere, including the following 

information:

(A) The source, nature, and cause of the pressure release.

(B) The date, time, and duration of the pressure release.
Page 223 of 231

(C) An estimate of the quantity of HAP listed in Table 1 of 

this subpart emitted during the pressure release and the method 

used for determining this quantity.

(D) The actions taken to prevent this pressure release.

(E) The measures adopted to prevent future such pressure 

releases.

(6) Pressure tank closure device or bypass deviation 

report. The owner or operator must submit to the Administrator 

the information specified in paragraph (b)(6)(iv) of this 

section when any of the conditions in paragraphs (b)(6)(i) 

through (iii) of this section are met. 

(i) Any pressure tank closure device, as specified in 

§63.685(h)(2) of this subpart, has released to the atmosphere.

(ii) Any closed vent system that includes bypass devices 

that could divert a vent a stream away from the control device 

and into the atmosphere, as specified in §63.693(c)(2) of this 

subpart, has released directly to the atmosphere.

(iii) Any open-ended valve or line in an emergency shutdown 

system which is designed to open automatically in the event of a 

process upset, as specified in 40 CFR 63.167(d) or 40 CFR 

61.242-6(d), has released directly to the atmosphere.
Page 224 of 231

(iv) The pressure tank closure device or bypass deviation 

report must include the information specified in paragraphs 

(b)(6)(iii)(A) through (E) of this section.

(A) The source, nature and cause of the release.

(B) The date, time and duration of the discharge.

(C) An estimate of the quantity of HAP listed in Table 1 of 

this subpart emitted during the release and the method used for 

determining this quantity.

(D) The actions taken to prevent this release.

(E) The measures adopted to prevent future such releases.

* * * * *

17. Section 63.698 is amended by:

a. Revising paragraph (c) and adding paragraph (c)(5) to 

read as follows: 

§ 63.698 Implementation and Enforcement.

* * * * *

(c) The authorities that cannot be delegated to State, 

local, or Tribal agencies are as specified in paragraphs (c)(1) 

through (5) of this section.

* * * * *

(5) Approval of alternatives to the electronic reporting 

requirements in §63.697(a)(3).

18. Table 2 to subpart DD of Part 63 is amended by:

a. Removing entries 63.1(a)(13) and 63.1(a)(14);
Page 225 of 231

b. Revising entries 63.1(b)(2), 63.1(c)(3), and 63.1(c)(4);

c. Removing entry 63.4(a)(1)–63.4(a)(3), and adding entries 

63.4(a)(1)–(2) and 63.4(a)(3);

d. Revising entries 63.4(a)(5) and 63.5(a)(1);

e. Revising entries 63.5(b)(5), 63.6(b)3), 63.6(b)(4);

f. Removing entry 63.6(e) and adding entries 63.6(e)(1)(i) 

through 63.6(e)(iii), 63.6(e)(2), and 63.6(e)(3);

g. Revising entry 63.6(f)(1);

h. Adding entry 63.7(a)(4);

i. Revising entries 63.7(e)(1) and 63.7(f);

j. Revising entry 63.8(c)(1)(iii);

k. Revising entry 63.9(g);

l. Revising entries 63.10(b)(2)(i)-(v);

m. Revising entries 63.10(c) and adding entries 

63.10(c)(1)-(6), (7)-(8), and (9)-(15);

n. Removing entries 63.10(d)(5)(i) and 63.10(d)(5)(ii), and 

adding entry 63.10(d)(5); 

o. Removing entry 63.10(e), and adding entries 63.10(e)(1)-

63.10(e)(2), 63.10(e)(3), and 63.10(e)(4); and

p. Adding entry 63.16 to read as follows:

Table 2 to Subpart DD of Part 63—Applicability of Paragraphs in 

Subpart A of This Part 63—General Provisions to Subpart DD

Subpart A 

reference

Applies 

to Explanation
Page 226 of 231

Subpart 

DD

* * * * * * *

63.1(b)(2) No Reserved.

* * * * * * *

63.1(c)(3) No Reserved.

63.1(c)(4) No Reserved.

* * * * * * *

63.4(a)(1)–

63.4(a)(2) Yes

63.4(a)(3) No Reserved.

* * * * * * *

63.4(a)(5) No. Reserved.

* * * * * * *

63.5(a)(1) Yes

* * * * * * *

63.5(b)(5) No Reserved.

* * * * * * *

63.6(b)(3) No

63.6(b)(4) No

* * * * * * *

63.6(e)(1)(i) No See §63.683(e) of this subpart for 

general duty requirement.

63.6(e)(1)(ii) No

63.6(e)(1)(iii) Yes

63.6(e)(2) No Reserved.

63.6(e)(3) No

63.6(f)(1) No

* * * * * * *

63.7(a)(4) Yes

* * * * * * *

63.7(e)(1) No See §63.694(l) of this subpart.

* * * * * * *

63.7(f) Yes

* * * * * * *

63.8(c)(1)(iii) No

* * * * * * *

63.9(g) Yes
Page 227 of 231

* * * * * * *

63.10(b)(2)(i) No

63.10(b)(2)(ii) No

See §63.696(h) of this subpart for 

recordkeeping of (1) date, time and 

duration; (2) listing of affected 

source or equipment, and an estimate 

of the volume of each regulated 

pollutant emitted over the standard; 

and (3) actions to minimize emissions 

and correct the failure.

63.10(b)(2)(iii) Yes

63.10(b)(2)(iv) No

63.10(b)(2)(v) No

* * * * * * *

63.10(c)(1)-(6) No

63.10(c)(7)-(8) Yes

63.10(9)-(15) No

* * * * * * *

63.10(d)(5) No See §63.697(b)(3) of this subpart for 

reporting of malfunctions.

63.10(e)(1) –

63.10(e)(2) No

63.10(e)(3) Yes

63.10(e)(4) No

* * * * * * *

63.16 No

* * * * *

19. Table 3 to subpart DD of Part 63 is amended by to read 

as follows:

Table 3 to Subpart DD of Part 63—Tank Control Levels for Tanks 

at Existing Affected Sources as Required by 40 CFR 

63.685(b)(1)(i)
Page 228 of 231

Tank design 

capacity 

(cubic 

meters)

Maximum HAP vapor 

pressure of offsite material 

managed in tank 

(kilopascals) 

Tank control level 

Design 

capacity less 

than 75 m3

Maximum HAP vapor 

pressure less than 

76.6 kPa

Level 1. 

Design 

capacity less 

than 75 m3

Maximum HAP vapor 

pressure equal to 

or greater than 

76.6 kPa

Level 2, except that fixed 

roof tanks equipped with an 

internal floating roof and 

tanks equipped with an 

external floating roof as 

provided for in §63.685(d)(1) 

and (2) of this subpart shall 

not be used.

Design 

capacity 

equal to or 

greater than 

75 m3 and 

less than 151 

m3

Maximum HAP vapor 

pressure less than 

27.6 kPa

Level 1. 

 

Maximum HAP vapor 

pressure equal to 

or greater than 

27.6 kPa

Level 2. 

Design 

capacity 

equal to or 

greater than 

151 m3

Maximum HAP vapor 

pressure less than 

5.2 kPa

Level 1. 

 

Maximum HAP vapor 

pressure equal to 

or greater than 5.2 

kPa

Level 2.

20. Table 4 to subpart DD of Part 63 is amended by to read 

as follows:
Page 229 of 231

Table 4 to Subpart DD of Part 63—Tank Control Levels for Tanks 

at Existing Affected Sources as Required by 40 CFR 

63.685(b)(1)(ii)

Tank design 

capacity 

(cubic 

meters)

Maximum HAP vapor 

pressure of offsite material 

managed in tank 

(kilopascals) 

Tank control level 

Design 

capacity less 

than 75 m3

Maximum HAP vapor 

pressure less than 

76.6 kPa

Level 1. 

Design 

capacity less 

than 75 m3

Maximum HAP vapor 

pressure equal to 

or greater than 

76.6 kPa

Level 2, except that fixed 

roof tanks equipped with an 

internal floating roof and 

tanks equipped with an 

external floating roof as 

provided for in §63.685(d)(1) 

and (2) of this subpart shall 

not be used.

Design 

capacity 

equal to or 

greater than 

75 m3 and 

less than 151 

m3

Maximum HAP vapor 

pressure less than 

13.1 kPa

Level 1. 

 

Maximum HAP vapor 

pressure equal to 

or greater than 

13.1 kPa

Level 2. 

Design 

capacity 

equal to or 

greater than 

151 m3

Maximum HAP vapor 

pressure less than 

5.2 kPa

Level 1. 

 

Maximum HAP vapor 

pressure equal to 

or greater than 5.2 

kPa

Level 2.
Page 230 of 231

21. Table 5 is added to subpart DD of Part 63 to read as 

follows:

Table 5 to Subpart DD of Part 63—Tank Control Levels for Tanks 

at New Affected Sources as Required by 40 CFR 63.685(b)(2)

Tank design 

capacity 

(cubic 

meters)

Maximum HAP vapor 

pressure of offsite material 

managed in tank 

(kilopascals) 

Tank control level 

Design 

capacity less 

than 38 m3

Maximum HAP vapor 

pressure less than 

76.6 kPa

Level 1. 

Design 

capacity less 

than 38 m3

Maximum HAP vapor 

pressure equal to

or greater than 

76.6 kPa

Level 2, except that fixed 

roof tanks equipped with an 

internal floating roof and 

tanks equipped with an 

external floating roof as 

provided for in §63.685(d)(1) 

and (2) of this subpart shall 

not be used.

Design 

capacity 

equal to or 

greater than 

38 m3 and 

less than 151 

m3

Maximum HAP vapor 

pressure less than 

13.1 kPa

Level 1.

 

Maximum HAP vapor 

pressure equal to 

or greater than 

13.1 kPa

Level 2.

Design 

capacity 

equal to or 

greater than 

151 m3

Maximum HAP vapor 

pressure less than 

0.7 kPa

Level 1.

 

Maximum HAP vapor 

pressure equal to Level 2.
Page 231 of 231

or greater than 0.7 

kPa