September 16, 2014

National Emission Standards for Hazardous Air 

Pollutant Emissions: Generic Maximum Achievable 

Control Technology Standards; and Manufacture of 

Amino/Phenolic Resins

Summary of Public Comments and Responses

on Proposed Rule (79 FR 1676, January 9, 2014)

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Sector Policies and Programs Division

Research Triangle Park, NC 27711
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FOREWORD

This document provides responses to public comments on the U.S. Environmental Protection 

Agency’s (EPA’s) proposed “National Emission Standards for Hazardous Air Pollutant 

Emissions: Generic Maximum Achievable Control Technology Standards; and Manufacture of 

Amino/Phenolic Resins.” The EPA Docket contains all comment letters submitted and are 

available for viewing at the EPA Docket Center Reading Room, or electronically through 

http://www.regulations.gov by searching Docket ID No. EPA-HQ-OAR-2012-0133 by docket 

number.

This document provides a summary of the public comments entered into the docket regarding 

specific issues and topics related to the development of the proposed amendments to the subject 

rules and the EPA’s responses to those comments. Within each comment summary, the EPA 

provides in parentheses one or more Docket ID numbers for commenters who raised particular 

issues. However, the list of commenter ID numbers is not meant to be exhaustive. The EPA does 

not individually identify each and every commenter who made a certain point in all instances, 

particularly in cases where multiple commenters express essentially identical arguments. 

Although portions of the preamble to the final rule are paraphrased in this document, to the

extent any ambiguity is introduced by paraphrasing, the preamble itself remains the definitive

statement of the rationale for the final rule.
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TABLE OF CONTENTS

1.0 Background..........................................................................................................................1

2.0 Risk-Related Assessment and Standards.............................................................................3

2.1 Risk Assessment Data and Methodology ......................................................................3

2.2 Consideration of Risks from Entire Facilities, Industrial Clusters, and Other Sources

in Risk Assessment ......................................................................................................12

2.3 Consideration of Demographics in Risk Assessment ..................................................14

2.4 Additional Standards to Address Risks........................................................................16

3.0 Startup, Shutdown, and Malfunction Exemption/Affirmative Defense Provisions...........19

3.1 Startup, Shutdown, and Malfunction Exemption.........................................................19

3.2 Affirmative Defense Provisions...................................................................................23

4.0 Electronic Reporting Requirements...................................................................................27

5.0 Open Ended Line Provisions .............................................................................................29

6.0 Pressure Relief Device Provisions.....................................................................................32

7.0 Source Category and Subpart-Specific Comments............................................................39

7.1 Source Category Specific Comments – Acrylic and Modacrylic Fibers Production...39

7.2 Source Category Specific Comments – Amino/Phenolic Resins Production..............40

7.3 Source Category Specific Comments – Polycarbonate Production.............................41

7.4 Subpart Specific Comments – Subpart YY (GMACT) ...............................................41

8.0 Other Comments................................................................................................................44
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ACRONYMS AND ABBREVIATIONS

Acronym/

Abbreviation Definition

Act or CAA Clean Air Act

ACA American Coatings Association

ACC American Chemistry Council

AEGL Acute Exposure Guideline Level

AMF Acrylic and Modacrylic Fibers Production

AMOS Ample Margin of Safety

APR Amino/Phenolic Resins Production

BBDR Biologically-Based Dose-Response

Cal OEHHA California Office of Environmental Health Hazard Assessment

CDX Central Data Exchange

CEDRI Compliance and Emissions Data Reporting Interface

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CFR Code of Federal Regulations

CHIEF Clearinghouse for Emission Inventories and Emissions Factors

CIIT Chemical Industry Institute of Toxicology

CRWI Coalition for Responsible Waste Incineration

EJ Environmental Justice

EO Executive Order

EPA U.S. Environmental Protection Agency

EPCRA Emergency Planning and Community Right-to-Know Act

ERPG Emergency Response Planning Guideline

ERT Electronic Reporting Tool

FR Federal Register

GMACT Generic MACT

HAP Hazardous Air Pollutants

HON National Emission Standards for Organic Hazardous Air Pollutants From the

Synthetic Organic Chemical Manufacturing Industry

HQ Hazard Quotient

ICR Information Collection Request

IRIS Integrated Risk Information System

LDAR Leak Detection and Repair

MACT Maximum Achievable Control Technology

NAAQS National Ambient Air Quality Standards

NACAA National Association of Clean Air Agencies

NAS National Academy of Sciences

NATA National Air Toxics Assessment

NEI National Emissions Inventory

NESHAP National Emission Standards for Hazardous Air Pollutants

NOCS Notice of Compliance Status
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NODA Notice of Data Availability

OECA Office of Enforcement and Compliance Assurance

PB Persistent and Bioaccumulative

PC Polycarbonate Production

POM Polycyclic Organic Matter

ppm Parts Per Million

PRA Paperwork Reduction Act

PRD Pressure Relief Device

REL Reference Exposure Level

RFA Regulatory Flexibility Act

RfC Reference Concentration

RfD Reference Dose

RO Responsible Official

RQ Reportable Quantity

RTR Risk and Technology Review

SAB Science Advisory Board

SARA Superfund Amendments and Reauthorization Act

SCAQMD South Coast Air Quality Management District

SOCMA Society of Chemical Manufacturers and Affiliates

SOCMI Synthetic Organic Chemical Manufacturing Industry

SSM Startup, Shutdown, and Malfunction

TOSHI Target Organ-Specific Hazard Index

VOC Volatile Organic Compound
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1.0 Background

On January 9, 2014 (79 FR 1676), the U.S. Environmental Protection Agency (EPA) 

proposed to revise two National Emission Standards for Hazardous Air Pollutants (NESHAP) 

applicable to three industrial source categories: Acrylic and Modacrylic Fibers Production 

(AMF), Polycarbonate Production (PC), and Amino/Phenolic Resins Production (APR), under 

the authority of section 112 of the Clean Air Act (CAA). This document presents summaries of 

the comments that were submitted in response to this action and our responses to those 

comments. The comments to which we are responding were submitted in 16 letters from industry 

representatives, governmental entities, and environmental advocacy groups during the public 

comment period. A list of the commenters, their affiliations, and the EPA docket number 

assigned to their correspondence is presented in Table 1-1.
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TABLE 1-1. LIST OF COMMENTERS ON PROPOSED NATIONAL EMISSION 

STANDARDS FOR HAZARDOUS AIR POLLUTANTS

Docket 

Numberab Commenter Affiliation

29 Russell A. Wozniak The Dow Chemical Company (Dow)

30 Jackson Morrill American Chemistry Council (ACC) 

Formaldehyde Panel

31 Lorraine Krupa Gershman American Chemistry Council (ACC)

32 Melvin E. Keener Coalition for Responsible Waste Incineration 

(CRWI)

33 Alphonse McMahon Sabic Innovative Plastics US LLC

34 David Darling and 

Javaneh Nekoomaram

American Coatings Association (ACA)

35 G. Vinson Hellwig and 

Robert H. Colby

National Association of Clean Air Agencies 

(NACAA) Air Toxics Committee

36 Emma Cheuse and Jim 

Pew

Sierra Club and California Communities Against 

Toxics

37 Barry H. Christensen Occidental Chemical Corporation (OxyChem)

38 Leslie Sue Ritts National Environmental Development 

Associations Clean Air Project (NEDA/CAP)

39 Russell Frye SSM Coalition

40 Matthew Todd Residual Risk Coalition (R2C)

41 Michael J. Manning Cytec Industries Inc.

42 Matthew Todd American Petroleum Institute (API)

45 Dana M. Schnobrich 3M

46 Traylor Champion Georgia Pacific, LLC (GP)

a Document ID identifies comments found in Docket No. EPA-HQ-OAR-2012-0133 by document number.

b

Individual comments from the public (and attachments submitted with comments) submitted to the docket 

are assigned a unique 4-digit docket number that follows the base docket number (i.e., EPA-HQ-OAR-2012-

0133-XXXX, where “XXXX” represents the unique 4-digit document docket number). The unique document 

docket numbers presented in this table and document represent that unique docket number without the 

preceding 0s. For example, docket number EPA-HQ-OAR-2012-0133-0030 is presented as 30 in this table and 

within the text of this document.

The following sections provide a summary of the comments received on the proposed 

standards for the AMF, APR, and PC source categories, as well as the EPA’s responses to these 

comments. For the purpose of orderly presentation, the comments have been categorized under 

the following topics:

Section 2: Risk-Related Assessment and Standards

Section 3: Startup, Shutdown, and Malfunction Exemption/Affirmative Defense

Provisions

Section 4: Electronic Reporting Requirements

Section 5: Open-Ended Line Provisions

Section 6: Pressure Relief Device Provisions

Section 7: Source Category and Subpart-Specific Comments

Section 8: Other Comments
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2.0 Risk-Related Assessment and Standards

2.1 Risk Assessment Data and Methodology

Comment 2.1.1: Commenter 35 is pleased to see the EPA placing increasing reliance on 

CalEPA Chronic Reference Exposure Level (REL) acute exposure threshold values and 

recommends continuing the use of RELs over Acute Exposure Guideline Level (AEGL) and 

Emergency Response Planning Guideline (ERPG) values, which the commenter does not feel are 

appropriate for assessing daily human exposure scenarios.

Response 2.1.1: As discussed in the preamble to the proposed rule (79 FR 1686), the

EPA considers various acute health effect reference values, including the California acute REL, 

and AEGL and ERPG values, in assessing the potential for risks from acute exposures.

Comment 2.1.2: Commenter 30 urges the EPA to use the Chemical Industry Institute of 

Toxicology (CIIT) cancer dose-response value for formaldehyde established in 1999 rather than 

the 1991 Integrated Risk Information System (IRIS) dose-response value, in keeping with the 

Information Quality Act and Executive Order 13563, which states that the regulatory system 

must “be based on the best available science.” 

Response 2.1.2: In 2004, the EPA determined that the CIIT cancer dose-response value 

for formaldehyde (5.5 x 10-9 per μg/m

3

) was based on better science than the IRIS cancer doseresponse value (1.3 x 10-5 per μg/m

3

), and we switched from using the IRIS value to the CIIT 

value in risk assessments supporting regulatory actions. Subsequent research published by the 

EPA suggested that the CIIT model was not appropriate and, in 2010, the EPA returned to using 

the 1991 IRIS value. The EPA has been working on revising the formaldehyde IRIS assessment 

and the National Academy of Science (NAS) completed its review of the EPA’s draft assessment 

in April of 2011.1 The EPA will follow the NAS Report recommendations and will present results 

obtained by implementing a biologically based dose-response (BBDR) model for formaldehyde. 

The EPA will compare these estimates with those currently presented in the External Review 

draft of the assessment and will discuss their strengths and weaknesses. As recommended by the 

NAS committee, appropriate sensitivity and uncertainty analyses will be an integral component 

of implementing the BBDR model. In the interim, we will present findings using the 1991 IRIS 

value as a primary estimate and the EPA may also consider other information as the science 

evolves.

We note that, except in the case of the APR source category, formaldehyde was not a 

primary driver of the risks for these source categories, and risks due to formaldehyde emissions 

did not change our decisions about acceptability and ample margin of safety of the risks 

associated with any of these source categories, or about our technology reviews for them. 

Therefore, in this rulemaking the choice between using the IRIS value or the CIIT value makes 

no difference in the regulatory outcome.

Comment 2.1.3: Commenter 36 states that the EPA cannot assume that hazardous air 

pollutants (HAP) with no peer-reviewed reference values for cancer or non-cancer effects have 

zero risk. The commenter states that the EPA must select health protective values based on the 

 

1

http://www.nap.edu/catalog.php?record_id=13142
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information it has or, at a minimum, add an uncertainty factor to the risk estimates. The 

commenter also requests that the EPA clearly state which HAP emitted by these source 

categories have no health reference values. 

Response 2.1.3: This issue was addressed by the EPA’s SAB in its May 10, 2010 (EPASAB-10-007) response to the EPA Administrator;

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

-SAB-10-007-unsigned.pdf. In that response, the SAB Panel recommended that, for HAP that do

not have dose-response values from the EPA’s hierarchy list, the EPA should consider and 

utilize, as appropriate, additional sources for such values that have undergone adequate and 

rigorous scientific peer review. The SAB panel further recommended that the inclusion of 

additional sources of dose-response values into the EPA’s hierarchy should be adequately 

documented in a transparent manner in any residual risk assessment case study. We agree with 

this approach and have considered other sources of dose-response data when conducting our 

risk determinations under RTR. However, in some instances no sources of information beyond 

the EPA’s hierarchy are available.

The EPA notes that we did state which HAP currently have no reference value. In the risk 

assessment document, there is a table for each source category that lists all the HAP emitted by 

the source category, and indicates whether there is an available cancer, chronic noncancer, 

and/or acute dose-response value. For those HAP currently with no reference value, we did not 

find any additional dose-response values from other sources.

Comment 2.1.4: Commenter 36 claims the EPA lags behind the best available science to 

address the real-world health risk for the individual most exposed to the current source categories 

and must apply this science in the rulemaking under CAA section 112(f)(2). In particular, the 

commenter believes the EPA should follow the recommendations of the NAS and SAB on the 

key issues that affect the most-exposed and most vulnerable populations, especially children and 

environmental justice (EJ) communities. The commenter states the EPA must consider the 

science and update its risk assessment in, at least, each of the following ways before finalizing 

the rule:

 Account for individual-level vulnerability in this risk assessment by better 

incorporating the vulnerability of children, early-life exposures, and the developing 

fetus into risk assessment methods:

 Account for increased susceptibility by using California Office of Environmental 

Health Hazard Assessment (Cal OEHHA) Cancer Guidelines (Age-Dependent 

Adjustment Factors) for all carcinogens, not just known mutagens and include prenatal susceptibility.

 For chronic non-cancer risk, consult and apply child-specific reference values (such 

as the Cal OEHHA values), where available.

 If child-specific reference values are unavailable, consult science on early exposure 

impacts, and use an additional default factor of at least 10X.

Response 2.1.4: We disagree with the general comment that the EPA should adopt the

Cal OEHHA child-protective scientific approach on cancer. The EPA has a hierarchy of 

appropriate health benchmark values and in general, this hierarchy places greater weight on the 

EPA derived health benchmarks than those from other agencies (see

http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf). Notably, this hierarchy 

favoring EPA benchmarks (when they exist) over all others has been endorsed by the SAB. 
5

Further, the EPA is currently evaluating whether it is appropriate to use the CalEPA childspecific reference doses, and we note that because there are currently no such values for HAP

inhalation, their current utility would be limited to persistent and bioaccumulative (PB)-HAP, 

which may be associated with non-negligible ingestion exposures. That is, before using these 

child-specific reference doses (RfDs), the EPA would need to evaluate whether they have been 

appropriately derived.

We also disagree with the comment that the risk assessment for these source categories 

does not consider the groups that may be most at-risk in its risk assessments (e.g., pregnant 

women). When the EPA derives exposure reference concentrations and unit risk estimates for 

metal HAP, it also considers the most sensitive populations identified in the available literature, 

and importantly, these are the values used in our risk assessments (see US EPA. (2002). A 

review of the reference dose and reference concentration processes. EPA/630/P-02/002F. Risk 

Assessment Forum, Washington, DC. Available online at 

http://www.epa.gov/raf/publications/pdfs/rfd-final.pdf). With respect to maternal exposure in

utero specifically, we are unaware of literature that would allow for a robust characterization of 

risk during this stage of development.

We acknowledge that population subgroups, including children, may have a potential for 

risk that is greater than the general population due to greater relative exposure and/or greater 

susceptibility to the toxicant. As explained in previous actions, including the final synthetic 

organic chemical manufacturing industry (SOCMI) hazardous organic NESHAP (HON) RTR (71

FR 76610-76611), the assessments we undertake to estimate risk account for this potential 

vulnerability. With respect to exposure, the risk assessments we perform implicitly account for 

this greater potential for exposure by assuming lifetime exposure, in which populations are 

conservatively presumed to be exposed to airborne concentrations at their residence 

continuously, 24 hours per day for a full lifetime, including childhood. With regard to children‘s 

potentially greater susceptibility to non-cancer toxicants, the assessments rely on EPA (or 

comparable) hazard identification and dose-response values which have been developed to be 

protective for all subgroups of the general population, including children.

For example, a review of the chronic reference value process concluded that the EPA’s 

reference concentration (RfC) derivation processes adequately considered potential 

susceptibility of different subgroups with specific consideration of children, such that the 

resultant RfC values pertain to the full human population including sensitive subgroups, “a

phrase which is inclusive of childhood.” With respect to cancer, the EPA uses the age-dependent 

adjustment factor approach referred to by the commenter, but limits the use of those factors only 

to carcinogenic pollutants that are known to act via mutagenic mode of action, in contrast to the 

OEHHA approach, which uses them across the board for all carcinogens regardless of mode of 

action (MOA). In lieu of chemical-specific data on which age or life-stage specific risk estimates 

or potencies can be determined, default age dependent adjustment factors can be applied when 

assessing cancer risk for early-life exposures to chemicals which cause cancer through a 

mutagenic MOA. At the present time, there have been no peer-reviewed assessments that 

explicitly make a determination that any of the chemicals emitted by the source categories 

considered in this action cause cancer through a mutagenic mode of action. However, the 

estimated risks must also be considered in the context of the full set of assumptions used for this 

risk assessment. For example, we used a health-protective assumption of a 70-year exposure 

duration in our risk estimates; however, using the national average residency time of 12 years

would reduce the estimate of risk by roughly a factor of 6. Our unit risk estimates for HAP are 
6

considered a plausible upper-bound estimate; actual potency is likely to be lower and some of 

which could be as low as zero. After considering these and other factors, we continue to consider

the risks from emissions after application of the revisions to the Maximum Achievable Control 

Technology (MACT) standards for these source categories to provide an ample margin of safety 

(consistent with the Benzene NESHAP framework).

The EPA disagrees with the commenter’s statement that the EPA should use California 

EPA’s child specific-reference doses2in order to address the potential for early-life 

susceptibility. The EPA methods for assessing hazard and dose-response relationships for HAPs 

and developing RfCs and cancer risk estimates, as noted above, specifically address the potential 

for early-life susceptibility. Whenever data indicate increased susceptibility of a developmental 

lifestage or of a population group, those data are factored into the analysis. When data are 

inadequate to understand the effects of a specific pollutant on sensitive subpopulations, which 

for some pollutants may include children, the EPA’s risk assessment methods take that into 

account to ensure that resulting assessments address the possibility that such subpopulations 

might be more or less sensitive. Further, in the RTR risk assessments performed using the 

agency’s preferred dose-response values, exposure is characterized as occurring all day and 

every day over a lifetime, rather than only during specific periods of time during childhood.

Comment 2.1.5: Commenter 35 recommends that the EPA consider risk based on 

potential or allowable emissions because emissions and associated impacts could increase over 

time, and analyses based on actual emissions may underestimate residual risk. The commenter 

notes that the thresholds for major source status were based on maximum potential-to-emit, and 

permits are issued based on potential emissions. Further, the commenter argues that limiting the 

scope of risk assessments to actual emissions would be inconsistent with the applicability 

sections of the MACT standards. While acknowledging that the EPA used allowable emissions 

in parts of the rulemaking, the commenter encourages the EPA to use allowable emissions also 

for acute health risks. 

In contrast, commenter 40 states that the EPA cannot lawfully use the MACT allowable

emissions in risk assessments and residual risk determinations because the EPA has allegedly 

failed to provide any reasoned explanation why risk assessments based on actual emissions are 

inadequate. The commenter states that the language of section 112 requires that the EPA report 

on the actual health effects for people living in the vicinity of affected sources, which the 

commenter claims clearly signals that Congress expected the EPA to focus on actual risk and not 

hypothetical risk in implementing the requirements of section 112(f). In addition, because the

risk methodology already reflects numerous conservative assumptions, the commenter asserts it 

makes no sense to add another layer of conservatism and the EPA has not provided any data to 

indicate analyses based on actual emissions result in negative bias.

Response 2.1.5: Consistent with previous risk assessments, the EPA considers both

allowable and actual emissions in assessing chronic exposure and risk under section 112(f)(2). 

(See, e.g., National Emission Standards for Coke Oven Batteries (70 FR 19998-19999, April 15,

 

2 We note that California EPA’s use of these numerical values, which do not exist for inhalation exposures, is 

limited to the context of risk assessment at proposed or existing California school sites and does not even extend to 

their Air Hot Spots Risk Assessment program. Further the guidance for the California EPA school site assessment 

program specifies the use of California OEHHA or U.S. EPA IRIS values in the absence of the school site risk 

assessment child-specific values (Cal OEHHA, 2004 -

http://www.oehha.ca.gov/public_info/public/kids/pdf/SchoolscreenFinal.pdf).
7

2005); proposed and final National Emission Standards for Organic Hazardous Air Pollutants 

from the Synthetic Organic Chemical Manufacturing Industry (71 FR 34428, June 14, 2006, and

71 FR 76603, December 21, 2006). This approach is both reasonable and consistent with the 

flexibility inherent in the Benzene NESHAP framework for assessing ample margin of safety. As

a general matter, modeling allowable emission levels is inherently reasonable since this reflects 

the maximum level sources could emit and still comply with national emission standards. But it is 

also reasonable to consider actual emissions, where such data are available, in both steps of the 

risk analysis. See National Emission Standards for Coke Oven Batteries, 70 FR 19992, 19998 

(April 15, 2005). We disagree with commenter 35’s claim that the additional consideration of 

actual emissions conflicts with either the statutory major source definition that is based on 

potential to emit, or with applicability thresholds in MACT standards that are tied to major 

source status. Those thresholds still have the same full effect for determining the applicability of 

section 112 standards that they had before we conducted our residual risk assessments.

Moreover, our risk assessments necessarily included information regarding sources with

potential – not necessarily actual – emissions at major source levels. We also note that our use 

of allowable emission levels in the risk assessments in this rulemaking did not result in revising 

the previously established standards due to risk concerns. Therefore, our consideration of 

allowable emissions in the risk assessments did not result in regulatory decisions that affect any 

facilities, and commenter 40’s objections to our use of allowable emissions are moot.

Comment 2.1.6: Commenter 35 states that the use of the census block centroid dilutes 

the effect of sources’ emissions, as the maximum point of impact can be far from the centroid 

and may be at or near a facility’s property line, and suggested that the risks for a source category 

be based on the risks to the maximally exposed individual. 

Response 2.1.6: As we have explained in previous RTRs, such as the SOCMI HON RTR

(71 FR 76603, December 21, 2006), the EPA believes that, in a national-scale assessment of 

lifetime inhalation exposures and health risks from facilities in a source category, it is 

appropriate to identify exposure locations where it may be reasonably expected that an 

individual will spend a majority of his or her lifetime. Further, in determining chronic risks, the 

EPA believes that it is appropriate to use census block information on where people actually 

reside, rather than points on a fence-line, to locate the estimation of exposures and risks to 

individuals living near such facilities. If a population did indeed live just outside of the fenceline 

of a facility, then it would result in a census block near the fenceline.

Census blocks are the finest resolution available as part of the nationwide population 

data (as developed by the US Census Bureau); each is typically comprised of approximately 40 

people or about 10 households. In EPA risk assessments, the geographic centroid of each census 

block containing at least one person is used to represent the location where all the people in that 

census block live. The census block centroid with the highest estimated exposure then becomes 

the location of maximum exposure, and the entire population of that census block experiences

the maximum individual risk. In some cases, because actual residence locations may be closer to 

or farther from facility emission points, this may result in an overestimate or underestimate of

the actual annual concentrations (although there is no systematic bias for average levels). Given 

the relatively small dimensions of census blocks in densely populated areas, there is little 

uncertainty introduced by using the census block centroids in lieu of actual residence locations. 

There is the potential for more uncertainty when census blocks are larger, although there is still
8

no bias on average.3 The EPA concludes that the most appropriate locations at which to estimate 

chronic exposures and risks are the census block centroids because: 1) census blocks are the 

finest resolution available in the national census data, 2) facility fencelines do not typically 

represent locations where chronic exposures are likely because people do not typically live near 

the fenceline, and 3) there is no bias introduced into the estimate of the MIR by using census 

block centroid locations.

Comment 2.1.7: Commenter 36 states that all emissions data the EPA currently has are 

primarily estimates subject to significant error in the estimation calculations. To improve the 

available data, the commenter states that the EPA needs to require remote sensing and 

continuous monitoring to track and measure emissions, with technologies such as differential 

absorption light detection and ranging, solar occultation flux, CEREX UV Hound, and 

Accusense. The commenter also states that in addition or as an alternative, the EPA should

require continuous emissions monitoring or performance tests every year, at a minimum, as it has

done for other source categories.

Response 2.1.7: The emissions data for the risk assessments in the proposed rules were 

derived from the National Emissions Inventory (NEI) as well as data provided by industry. The 

sources of the data are documented in the docket. As stated in the EPA’s documentation on the 

2005 NEI (http://www.epa.gov/ttn/chief/net/2005_nei_point.pdf), “[t]he 2005 NEI is a composite 

of emission estimates generated by state and local regulatory agencies, tribes, industry, and 

EPA. Because the estimates originated from a variety of sources and estimation methods, as well 

as for differing purposes, they will in turn vary in quality, pollutants included, level of detail, and 

geographic coverage. However, this compilation of emissions estimates represents the best 

available information to date.”

More generally, we note that the 2005 NEI for HAP is greatly improved since the first 

NEI compilation using 1996 data, and that it is sufficiently accurate and complete and 

constitutes the best information the EPA has to use in our analysis. We have worked diligently 

with state and local agencies and tribes to improve emission inventories over the years, and we 

have instituted a number of quality assurance (QA) measures to improve data received from 

state and local agencies since 1996. Documentation for the 2005 NEI point source emissions 

inventory is available on the EPA's Clearinghouse for Inventories and Emissions Factors 

(CHIEF) website, http://www.epa.gov/ttn/chief/net/2005inventory.html. Quality assurance and 

augmentation procedures used for the 2005 NEI point sources are contained in the report, EI 

Quality Assurance and Data Augmentation for Point Sources, posted at: 

http://www.epa.gov/ttn/chief/net/2002inventory.html. The 2005 NEI data have been reviewed 

extensively internally and externally during a 9-month effort as part of the development of the 

2005 National Air Toxics Assessment (NATA). As part of the 2005 NATA review, more than one 

million records for HAP were revised. Updated test data and emission point information were 

received during the public comment period that addressed inaccuracies in the data. For these 

source categories, the EPA‘s review included an evaluation of facilities contained in the source 

category, the emissions units expected to be included for the processes in the source categories, 

coordinates and stack parameters, and the HAP compounds and emission levels typically seen. 

The NEI data were also reviewed by industry trade groups, including ACC and the Society of 

Chemical Manufacturers and Affiliates (SOCMA), as well as several state air agencies, and the 

 

3 There is no bias because a residence has an equal likelihood of being farther from a source, compared to the block 

centroid’s distance, as it does being nearer to a source.
9

EPA revised the NEI data where we concluded comments from this review supported such 

adjustment. Section II.C of the January 9, 2014, proposal preamble (79 FR 1684) set forth a 

detailed explanation of the review that the EPA performed on the emissions data for the source 

categories subject to this final rule. As part of the proposal, we also made the data sets available 

for review using a RTR data review tool in the docket and solicited comments on the data sets. 

The RTR review of the proposal data sets act as another external third party review mechanism 

in addition to the external 2005 NATA review of the RTR data sets. Several opportunities have 

been provided to review the data used in the current proposal. Through enhanced NEI QA 

procedures, 2005 NATA review, industry, state, and NACAA review, public comment on 

proposal files, source category-specific engineering reviews, and modeling, improvements to the 

data files have been made. We believe the data sets used in this rulemaking are sufficiently 

accurate and complete and constitute the best information the EPA has concerning the emissions 

and risk from these source categories for conducting RTRs.

Comment 2.1.8: Commenter 36 states that the EPA should analyze risk including 

emissions that may occur above the existing MACT standards, considering malfunctions and 

violations. The commenter states that the EPA must assess public health risk based on the 

likelihood of such events and suggests that the EPA develop and apply a factor to the risk results 

based on available malfunction and violation data.

Response 2.1.8: We disagree with the commenter that emissions that exceed standards 

and are violations, whether or not they are caused by malfunction events, should be considered 

as part of the risk analysis for purposes of determining the sufficiency of pre-existing standards, 

particularly when we are revising the standards to eliminate any excused periods of noncompliance during upset periods. The purpose of the risk review under section 112(f)(2)(A) is to 

evaluate whether the emission limits -- the “standards promulgated pursuant to subsection (d),” 

not the non- compliance with those standards -- should be made more stringent to reduce the risk 

posed after compliance with the underlying MACT standard. To the extent that a source is 

violating the underlying MACT standard, no tightening of the emission standard under the 

residual risk rule will avoid or militate against such violations. In other words, a source that is 

violating the emission standard promulgated under section 112(d) would not be any more likely 

to be able to avoid such violations and comply with a different presumably more stringent 

standard promulgated under section 112(f). Such events are violations and subject to 

enforcement by the EPA, the states or citizens, and an action for injunctive relief is the most 

effective means to address violations whether or not they are caused by malfunctions if an 

emissions event poses a significant health or environmental risk.

Furthermore, the conservative estimates built into the acute risk assessment are sufficient 

to gauge worst-case potential acute health effects. The conservative estimates built in to the

assessment include worst-case meteorology, emissions at ten (or two) times the maximum peak 

emission rate from all point sources simultaneously, and the sum of the maximum impact of each 

emission source, regardless of receptor location. Thus, even if we were to consider emissions

that are in violation of the standard, we do not believe that they would result in any different

level of control than we are promulgating here.

Comment 2.1.9: Commenter 36 states that the EPA has not used a high enough 

emissions factor to account for acute risks. The EPA used an emissions factor of 2 for equipment 

leaks and 10 for all other emissions sources and has not demonstrated that these factors are high 
10

enough to assess true acute risks, considering that a facility could emit 100 times more than its 

usual emissions if it usually controls 99% of emissions. The commenter also states that 

equipment leaks can continue indefinitely and with no limit on emissions quantities.

Response 2.1.9: The acute risk assessment methodology uses a tiered, iterative approach 

that begins with an assessment of an approximation of a worst-case exposure. To this end, the 

assumption that peak 1-hour emissions are equal to 10 (or 2 for equipment leaks) times the 

average 1-hour emissions rate is only one of the worst-case assumptions that we made in our 

acute health risk screening analysis. Other worst-case assumptions included:

 For facilities with multiple emission points, peak 1-hour emissions were assumed to 

occur at all emission points at the same time.

 For facilities with multiple emission points, 1-hour concentrations at each receptor were 

assumed to be the sum of the maximum concentrations due to each emission point, 

regardless of whether those maximum concentrations occurred during the same hour.

 Worst-case meteorology (from one year of local meteorology) was assumed to occur at 

the same time the peak emission rates occur. The recommended EPA local-scale 

dispersion model, AERMOD, is used for simulating atmospheric dispersion.

 A person was assumed to be located downwind at the point of maximum impact during 

this same 1-hour period, but no nearer to the source than 100 meters.

 The maximum impact was compared to multiple short-term health benchmarks for the 

chemical being assessed to determine if a possible acute health risk might exist.

Based on industry-specific information, we determined that a refined emissions multiplier 

of 2, rather than a multiplier of 10, better represents the peak hourly emission rates for 

equipment leaks. Refer to a separate memorandum in the docket (Emissions Data and Acute Risk 

Factor Used in Residual Risk Modeling; Acrylic and Modacrylic Fibers, Amino/Phenolic Resins, 

and Polycarbonate Production) for a detailed description of how the refined emissions 

multipliers were developed for the source categories. Regarding the failure of a control device, 

this would constitute a violation of the emission standard. The acute risk emissions factor is 

designed to account for fluctuations in emissions for facilities complying with the standards, not 

for facilities in non-compliance. Therefore, it would be inappropriate to use the emissions factor 

suggested by the commenter for purposes of determining whether the MACT standards’ current 

requirements are in need of revision under section 112(f)(2).

Comment 2.1.10: Commenter 36 states that the EPA failed to perform an adequate 

multipathway risk assessment. One reason the commenter states the assessment is inadequate is 

that it does not account for all the PB pollutants. The commenter asserts that the EPA’s choice to 

restrict the multipathway screening assessment to only HAP that bioaccumulate is not supported 

by the 2003 Risk Assessment Guidance because it ignores other HAP that persist and accumulate 

in soils. In addition, the commenter states that the EPA should include all metals in the 

multipathway risk assessment, as recommended by California’s OEHHA and also recommends 

that naphthalene, a polycyclic aromatic hydrocarbon (PAH), be considered a polycyclic organic 

matter (POM), which is listed as a PB-HAP. In addition, the commenter notes that the EPA did 

not assess all exposure routes, did not use the information from the multipathway analysis in the 

overall risk analysis, and did not add the multipathway risk found to the inhalation risk. The 

commenter asserts that the EPA may not assume that risks under the multipathway threshold are 

not significant enough to require a full analysis. The commenter opines that the EPA should 

update the incidental soil ingestion factors it uses in its multipathway risk assessments to fully 
11

account for the greater multipathway exposure and risk for children.

Response 2.1.10: We disagree that the multipathway assessment is inadequate due to 

restrictions in the pollutants included in the screening assessment. In the Air Toxics Risk 

Assessment Reference Library, we developed the current PB-HAP list considering all of the 

available information on persistence and bioaccumulation (see http://www2.epa.gov/fera/airtoxics-risk-assessment-reference-library-volumes-1-3), specifically Volume 1 Appendix D). (The 

Air Toxics Risk Assessment Reference Library provides information on the fundamental 

principles of risk-based assessment for air toxics and how to apply those principles in different 

settings (e.g., facility-specific) as well as strategies for reducing risk at the local level.) This list

considered HAP identified as PB-HAP by other EPA Program Offices (e.g., the Great Waters 

Program), as well as information from the PBT profiler (see http://www.pbtprofiler.net/). This 

list was peer- reviewed by the SAB and found to be acceptable, and therefore we consider it to be 

reasonable for use in the RTR program. Based on these sources and the limited available 

information on the persistence and bioaccumulation of other HAP, we do not believe that the 

potential for multipathway risk from other HAP rises to the level of the PB-HAP currently on the 

list. Regarding naphthalene, it is listed separately from POM in the Act, and it is not included on 

the current list of PB-HAP. The properties of naphthalene do not indicate that it is persistent or 

bioaccumulative. Naphthalene evaporates easily. In the air, moisture and sunlight make it break 

down, often within a day. Naphthalene in water is destroyed by bacteria or evaporates into the 

air. Most naphthalene will be gone from water in rivers or lakes within two weeks. Naphthalene 

binds weakly to soils and sediments. In soil, some microorganisms break down naphthalene. 

When near the surface of the soil, naphthalene will evaporate into air. Microorganisms present 

in the soil will break down most of the naphthalene in one to three months. Naphthalene does not 

accumulate in the flesh of animals and fish.

4

We did not combine the inhalation and multipathway risk assessment results for each

pollutant because it is inappropriate to do so. The multipathway risk assessment conducted for 

proposal was a screening-level assessment (i.e., Tier 1). It used highly conservative assumptions 

designed to ensure that facilities with results below the screening threshold values did not have 

the potential for multipathway impacts of concern. The screening scenario is a hypothetical 

scenario. It is inappropriate to combine the results of a refined inhalation assessment, which 

produces a quantitative result, with a screening-level multipathway assessment, which produces 

a “yes/no” result. In situations where we have previously summed the inhalation and 

multipathway assessment results (e.g., secondary lead smelters), it was for two refined 

assessments, and still serves as an overestimate of potential risks given that it is highly unlikely 

that the same receptor has the maximum results in both assessments.

We further note that we generally draw no bright lines of acceptability regarding cancer

or noncancer risks from source category HAP emissions, and that it is always important to 

consider the specific uncertainties of the emissions and health effects information regarding the 

source category in question when deciding exactly what level of cancer and noncancer risk 

should be considered acceptable. In addition, the source category-specific decision of what 

constitutes an acceptable level of risk should be a holistic one; that is, it should simultaneously 

consider all potential health impacts -- chronic and acute, cancer and noncancer, and

multipathway, -- along with their uncertainties, when determining the acceptable level of source 

 

4 US Agency for Toxic Substances and Disease Registry. 2005. Toxicological Profile for Naphthalene, 1-

Methylnaphthalene, and 2-Methylnaphthalene. 

http://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=240&tid=43#bookmark08.
12

category risk. In other words, we look at the risk numbers within the context of uncertainty

associated with emissions, health benchmark values and, in the case of cancer and noncancer 

risks, the health effect associated with exposure. The Benzene NESHAP decision framework of

1989 acknowledged this; in today’s world, such flexibility is even more imperative, because new 

information relevant to the question of risk acceptability is being developed all the time, and the 

accuracy and uncertainty of each piece of information must be considered in a weight-ofevidence approach for each decision. This relevant body of information is growing fast (and it 

will continue to grow faster and faster), necessitating a flexible weight-of-evidence approach 

that acknowledges both complexity and uncertainty in the simplest and most transparent way 

possible. While this challenge is formidable, it is nonetheless the goal of the EPA’s RTR

decision-making, and it is the goal of the risk assessment to provide the information to support

the decision-making process.

Regarding incidental soil contamination, the EPA has estimated risks from both direct

and indirect pathways. Direct routes of exposure include direct ingestion of soil and exposure 

through dermal contact. However, because it has been demonstrated in past analyses that 

exposure levels associated with dermal contact are but a small fraction of exposure levels 

associated with ingestion and inhalation pathways, dermal exposures were not assessed for these 

source categories.

Comment 2.1.11: Commenter 36 states that the EPA must account for the health risk 

from underperforming flares in its assessment of risk. Where the EPA does not have enough 

information to assess the actual performance and emissions from flares, default values should be 

used.

Response 2.1.11: The EPA disagrees with the commenter that it has failed to adequately 

assess the risk from flares for these source categories. The commenter has failed to provide the 

EPA with evidence that the flares in these source categories (if any exist) are underperforming, 

nor do they provide data on how such a factor should be developed. Lacking that information, 

we do not believe it is appropriate to apply a default factor to flares. The EPA has already 

determined, based on risk assessments conducted for the subject source categories, that 

additional control to achieve an “ample margin of safety” for the AMF, PC, and APR source 

categories is not needed, as the previously promulgated MACT standards already achieve the 

level of protection required by section 112(f)(2). See Docket ID No. EPA-HQ-OAR-2012-0133 

for documentation of the risk assessments.

2.2 Consideration of Risks from Entire Facilities, Industrial Clusters, and

Other Sources in Risk Assessment

Comment 2.2.1: Commenter 36 states that the EPA should assess the cumulative burden 

of exposures to multiple pollutants and sources via multiple pathways. To do this, the commenter 

suggests that the EPA aggregate inhalation and non-inhalation-based cancer risks; include the 

interaction of multiple pollutants; and account for exposure to multiple emissions sources

including other emissions sources at the facilities and from other sources of toxic air pollutants in 

the area. The commenter states that until the EPA has a specific mechanism for estimating total 

exposures, use of a default factor of at least 10X should be incorporated in the risk assessments.

In contrast, commenter 40 states that the EPA does not have authority to consider risks 

from multiple emissions sources (referring to facility-wide risks) because the CAA section 

112(f)(2)(A) allegedly requires residual risk determinations to be conducted on a category-by-
13

category basis and risk assessments to be focused exclusively on emissions from sources in the 

category or subcategory.

Response 2.2.1: We have combined risk assessment results to the extent that it is 

appropriate to do so. We do consider the effect of mixtures of carcinogens. We do not use a 

target organ-specific hazard index (TOSHI) approach for acute noncancer like we do for 

chronic noncancer. We also do not combine the results of our inhalation and multipathway 

assessments.

As described in the risk assessment report (available in the docket for this action), we do 

not sum results of the acute noncancer inhalation assessment to create a combined acute risk 

number that would represent the total acute risk for all pollutants that act in a similar way on the 

same organ system or systems (similar to the chronic TOSHI). As noted in previous responses,

the worst-case acute screen is already a conservative scenario. That is, the acute screening

scenario assumes worst-case meteorology, peak emissions for all emission points occurring 

concurrently and an individual being located at the site of maximum concentration for an hour. 

Thus, as noted in section 2.7.2 of the Draft Residual Risk Assessment for the Acrylic and 

Modacrylic Fibers Production Source Category (Docket Item No. EPA-HQ-OAR-2012-0133-

0021), “because of the conservative nature of the acute inhalation screening and the variable 

nature of emissions and potential exposures, acute impacts were screened on an individual 

pollutant basis, not using the TOSHI approach.”

We did not combine the inhalation and multipathway risk assessment results for each 

pollutant because it is inappropriate to do so. The multipathway risk assessment conducted for 

proposal was a screening-level assessment (i.e., Tier 1). It used highly conservative assumptions 

designed to ensure that facilities with results below the screening threshold values did not have 

the potential for multipathway impacts of concern. The screening scenario is a hypothetical 

scenario, and due to the theoretical construct of the screening model, exceedances of the 

thresholds are not directly translatable into estimates of risk or hazard quotients for these 

facilities. In situations where we have previously summed the inhalation and multipathway 

assessment results (e.g., secondary lead smelters), it was for two refined assessments, and still 

serves as a conservative overestimate of potential risks given that it is highly unlikely that the 

same receptor has the maximum results in both assessments.

The EPA conducted an assessment of the cumulative cancer risks from emitted 

carcinogens and the cumulative noncancer hazard indices from all emitted non- carcinogens 

affecting the same target organ system for both the source category emissions and the facilitywide emissions. This assessment excludes background contributions because technical 

limitations in the data sets would be insufficient to conduct a meaningful analysis. While the 

incorporation of additional background concentrations from the environment in our risk 

assessments (including those from mobile sources and other industrial and area sources) could 

be technically challenging, they are neither mandated nor barred from our analysis. In 

developing the decision framework in the Benzene NESHAP currently used for making residual 

risk decisions, the EPA rejected approaches that would have mandated consideration of 

background levels of pollution in assessing the acceptability of risk, concluding that comparison 

of acceptable risk should not be associated with levels in polluted urban air (54 FR 38044,

38061, September 14, 1989). Background levels (including natural background) are not barred

from the EPA‘s ample margin of safety (AMOS) analysis, and the EPA may consider them, as

appropriate and as available, along with other factors, such as cost and technical feasibility, in 

the second step of its section 112(f) analysis.
14

We disagree with the comment that we failed to consider or account for cumulative risk. 

The EPA modeled whole-facility risks for both chronic cancer and non-cancer impacts to

understand the risk contribution of the sources within these MACT categories. The individual 

cancer risks for each source category were aggregated for all carcinogens. In assessing

noncancer hazard from chronic exposures for pollutants that have similar modes of action or

(where this information is absent) that affect the same target organ, we aggregated the hazard

quotients (HQ). This process creates, for each target organ, a TOSHI, defined as the sum of 

hazard quotients for individual HAP that affect the same organ or organ system. All TOSHI 

calculations presented here were based exclusively on effects occurring at the “critical dose” 

(i.e., the lowest dose that produces adverse health effects). Whole facility risks were estimated 

utilizing the 2005 NEI, with updated facility-wide and source category data files developed by 

the EPA through emission data updates from industry, states, and NACAA. We also disagree 

with the commenter’s assertion that additional quantitative assessment of risks from sources 

outside the source category is required under the statute. The statute requires the EPA to provide 

the quantitative risk information necessary to inform RTR regulatory decisions, and to this end, 

the EPA conducts a comprehensive assessment of the risks associated with exposure to the HAP 

emitted by the source category and supplements that with additional information that is 

available about other possible concurrent and relevant risks.

2.3 Consideration of Demographics in Risk Assessment

Comment 2.3.1: Commenter 35 commends the EPA for considering environmental 

justice (EJ) issues in the proposal issues in this proposal. However, the commenter suggests the 

EPA rule writers work with the EPA’s Office of Environmental Justice to develop specific 

criteria and guidance on how to interpret and apply the outcomes of EJ analyses in the 

rulemaking process. The commenter also specifically suggests that the EPA use a 5-kilometer 

radius rather than 3-mile radius in its demographic analyses; that the EPA conduct the 

demographic analysis for all people projected to experience risk greater than 1-in-1 million for 

cancer or an HQ above one, consistent with the approach used for the Hard and Decorative 

Chromium Electroplating and Chromium Anodizing Tanks source category; that the analysis be 

conducted using maximum allowable emissions; and that the EPA update the poverty statistics 

used in the analyses to include 2010 census data.

Response 2.3.1: The commenter is correct that we performed the demographic analyses 

for the AMF, PC, and APR source categories differently than we did for the October 2010 

proposed RTR for the chrome source categories. We performed the demographic analyses for the 

chrome source categories using two approaches as examples of how such analyses might be 

developed, and invited public comment on the approaches used and the interpretations made 

from the results. In the first approach, we focused the analysis on the total populations residing 

within 5 km of each facility, regardless of their estimated risks, and examined the distributions 

across various demographic groups within those 5 km circles. That analysis was a “proximity” 

analysis in that it considered only the distance from the emission sources to surrounding 

populations, and not the estimated risks to those populations

In the second approach, we focused the analysis on the populations within 5 km of any 

facility estimated to have exposures to HAP which result in cancer risks of 1-in-1 million or 

greater or non-cancer hazard indices of 1 or greater. We examined the distributions of those 

risks across various demographic groups. In each approach, we compared the percentages of 

particular demographic groups to the total number of people in those demographic groups 
15

nationwide. We stated in the proposed rule for the chrome source categories that in future rules 

we planned to extend the analyses to cover the entire modeled domain for a facility (50 km 

radius) to capture all individuals with risks above 1-in-1 million or greater or non-cancer 

hazard indices of 1 or greater. We also stated that generally we have found that using a 5 km 

radius in the analysis will capture more than 90 percent of the individuals with cancer risks 

above 1-in-1 million.

In the February 2012 supplemental proposal for the RTR for the chrome source 

categories, our demographic analyses included populations within 50 km of each source 

(including those very near the sources) with risks of 1-in-1 million or greater or non-cancer 

hazard indices of 1 or greater (77 FR 6628, Feb. 8, 2012). We did not include analyses using a 5 

km radius in that supplemental proposal nor in the RTR proposal for the AMF, PC, and APR 

source categories. We believe that, where a risk assessment has been performed, it is more 

informative to consider the demographics of all populations (including those beyond 5 km) with 

elevated risks than to limit the demographics analysis to populations located within 5 km of a 

facility. Where risk assessment has been performed, these populations are identified, and the 

source parameters (like the low release height mentioned by the commenter) are accounted for. 

As discussed above, we have found that most exposure locations with the highest estimated risks 

are within 5 km of a facility, so extending the radius to 50 km has little impact on an analysis 

based on risks, but makes more sense because 50 km corresponds to the risk modeling radius 

and includes all populations with elevated risk estimates.

We note that we are working with the Office of Environmental Justice in an ongoing 

effort to develop new tools for considering environmental justice in rulemakings. While we 

intend to use the 2010 census data in future analyses, we do not believe that a rerun of our 

analysis using the 2010 census data would yield results that would change our overall 

conclusions regarding EJ impacts. Therefore, we have decided not to rerun the EJ analysis using 

the 2010 Census data.

Comment 2.3.2: Commenter 40 states that CAA section 112(f)(2)(A) expressly instructs 

the EPA to impose additional emissions controls if needed to provide an ample margin of safety 

to protect public health. The commenter says that the term “public health” cannot reasonably be 

interpreted to include consideration of environmental justice in the context of section 112(f), and 

therefore the EPA’s proposal to consider demographic analyses in conducting risk reviews is not 

a proper exercise of the EPA’s authority. Although “public health” is not defined in section 112 

or in the EPA’s 40 CFR part 63 regulations, the commenter states that the Supreme Court 

observed in the context of the EPA’s National Ambient Air Quality Standards (NAAQS)

Program that the primary definition of the term should be applied, and that is public health 

means “the health of the public.” The commenter notes that in the NAAQS program, the EPA 

interprets the term “public health” to include consideration of impacts on the population as a 

whole but also considers sensitive subpopulations identified by their health-based sensitivities, 

recognizing that the objective is to protect the group rather than any particular individual in the 

group. These sensitive subpopulations are identified independent of their demographic 

classifications. The commenter says that the EPA’s proposal to introduce demographic analyses 

to the determination of acceptable risk suggests that risk to some individuals is deemed more 

acceptable than risk to other individuals, and the commenter asserts that this type of political 

judgment has no place in a scientific evaluation of risk to public health.
16

Response 2.3.2: In this rulemaking, the EPA developed comparative analyses of the

demographics of the populations within the vicinity of the facilities in these source categories as 

part of the risk assessment for each source category; the analyses did not change the results or 

conclusions in the assessments. As stated in the Benzene NESHAP, in determining the need for 

residual risk standards, we strive to limit to no higher than approximately 1-in-10 thousand

(100-in-1 million) the estimated cancer risk that a person living near a plant would have if he or 

she were exposed to the maximum pollutant concentrations for 70 years and, in the ample 

margin of safety decision, to protect the greatest number of persons possible to an individual 

lifetime risk level of no higher than approximately 1-in-1 million. These considerations are made 

for all people regardless of racial or socioeconomic status. However, in determining whether to 

require additional standards under section 112(f), these levels are not considered rigid lines, 

and we weigh the cancer risk values with a series of other health measures and factors in both 

the decision regarding risk acceptability and in the ample margin of safety determination. We 

also consider cost of controls in the ample margin of safety determination. While we analyzed 

the demographic makeup of the populations surrounding the facilities within source categories 

addressed by this rule making, we ultimately concluded that the risks from each source category 

were acceptable and protected public health with an ample margin of safety. Thus, the results of 

our demographic analyses only served to provide information about the demographic makeup of 

the populations near facilities in each of these source categories, but did not drive regulatory 

outcomes.

Comment 2.3.3: Commenter 36 states that the EPA should assess and account for 

increased vulnerability due to socioeconomic status and baseline overall health status in its risk 

assessment, which could be accomplished by adding a default factor to account for 

socioeconomic and other community-based stressors. 

Response 2.3.3: We are not able to determine the baseline health status of individuals or 

communities in a national rulemaking. Individual privacy issues as they relate to health records 

and the costs that would be associated with such an analysis make the analysis infeasible. 

Through the EPA’s interim guidance on EJ and the Action Development Process, the agency is 

encouraging rule writers and policy makers to look at the whole range of factors that impact 

communities and population groups when crafting rules. The EPA is continuing to discuss and

pilot approaches that are consistent with the agency’s responsibilities regarding EJ as outlined 

in EO 12898. In determining the need for tighter residual risk standards, the EPA strives to limit 

to no higher than 100-in-1 million the estimated cancer risk for persons living near a plant if 

exposed to the highest pollutant concentration for 70 years and to protect the greatest number of 

persons to an individual lifetime risk of no higher than 1-in-1 million. Considerations are made 

for all people regardless of racial or socioeconomic status, and the EPA does not believe it is 

necessary to establish a default factor to account for socioeconomic and other community-based 

stressors.

2.4 Additional Standards to Address Risks

Comment 2.4.1: Commenter 36 states that the EPA should revisit or update its presumed 

acceptable level of cancer risk considering information learned about children’s and 

overburdened community’s vulnerability and considering new information on ways to analyze 

and control the impacts of pollutants on human health. The commenter believes that 100-in-1 

million lifetime cancer risk cannot be considered safe or “acceptable.” The commenter also states 
17

that the EPA should factor in uncertainties and vulnerability factors to adjust the level of noncancer risk considered acceptable for both chronic and acute exposure.

Response 2.4.1: In 1990, Congress codified in section 112(f) of the CAA the approach we

use for our residual risk analyses (i.e., the Benzene NESHAP, 54 FR 38044). Under that 

approach, there is no single bright line (e.g., a 100-in-1 million cancer risk) that indicates that 

risk is “acceptable.” Rather, multiple health metrics, including the cancer risk, are considered 

to determine whether the risk is acceptable. Where we conclude that the risk is not acceptable, 

we cannot consider costs in requiring controls to bring risks down to an acceptable level. 

However, the analysis of whether risk is acceptable is not the endpoint. Once we determine that 

the existing MACT standards or identify what additional controls are sufficient to ensure risk is 

acceptable, we again review the health metrics in conjunction with considering the costs of

controls to determine whether further additional controls should be required to provide an 

ample margin of safety to protect public health. The commenter does not explain how science 

has evolved in a way that would undermine the codified framework for determining 

acceptability.

Comment 2.4.2: Commenter 36 states that the EPA refused to strengthen the existing 

standards for storage vessels and equipment leaks based purely on its cost-benefit analysis. The 

commenter states that the EPA’s approach considered only the cost per ton of HAP emission 

reduction, without assessing relevant factors such as: the individual HAPs emitted and the impact 

those HAPs can have at a level below 1 ton; how many people would be affected by the potential 

emission reductions; where they live and if they are in a community containing multiple HAP 

sources, or whether they face a longstanding environmental justice impact. The commenter 

further states that the EPA also did not consider or address whether the standards would provide 

any “margin of safety” to protect public health, much less whether the margin is “ample.” Thus, 

the commenter claims the EPA ignored and violated CAA section 112(f)(2).

Response 2.4.2: The EPA disagrees with the commenter’s assertion that the decision to 

not propose more stringent standards for storage vessels and equipment leaks was based entirely 

on a cost-benefit analysis. As noted in the preamble to the proposed rule, the EPA evaluated the 

estimated risk reduction that would occur as a result of more stringent standards for these 

emission points and determined that they were not reasonable, given the level of HAP emissions 

reduction these options would achieve. We also considered these options as part of our ample 

margin of safety analysis for each source category, and found that it was not necessary to 

propose more stringent standards to provide an ample margin of safety to protect public health.

Comment 2.4.3: One commenter 36 states that the EPA is legally required to remove all 

unlawful exemptions from the emission standards that have previously existed for startup, 

shutdown, and malfunction (SSM) periods, and not to set any new such exemptions. The 

commenter claims that equipment leaks are a kind of equipment malfunction and that EPA may 

not authorize any such leaks, because to do so would be in violation of CAA section 302(k) and 

D.C. Circuit precedent in the Sierra Club v. EPA decision. The commenter also stated that EPA’s 

proposal to not update the leak detection and repair (LDAR) requirements is an unlawful 

authorization of a malfunction exemption.

Response 2.4.3: We disagree with the commenter’s claim that the types of equipment 

leaks addressed in the AMF, APR, and PC MACT standards are “malfunctions.” Equipment 

leaks typically occur from equipment such as pumps, compressors, agitators, sampling collection 
18

systems, open-ended valves or lines, valves, and connectors in organic HAP service. 40 CFR 

63.1103 and 63.1410; See also 63 FR 55185-55186 (October 14, 1998) and 63 FR 68838 

(December 14, 1998). At the time we developed the MACT standards for these source categories, 

we recognized that these emission points regularly emit small quantities of HAP, and we 

promulgated standards regulating equipment leaks from these components at 40 CFR 63.1103 

and 63.1410. These provisions require AMF, APR, and PC production facilities to monitor for 

leaks and to repair any detected leaks. These requirements do not establish any exemption, and 

the commenter’s suggestion that leaks are “exempt” from regulation or that they are 

“authorized” is not supported. While any specific equipment leak is not predictable, the types of 

equipment leaks addressed by the regulations at 40 CFR 63.1103 and 63.1410 are fairly routine 

emissions from sources and are not the type of unpredictable or infrequent event for which we 

cannot anticipate when, where or how they may occur and that we generally consider to be 

malfunctions.
19

3.0 Startup, Shutdown, and Malfunction Exemption/Affirmative

Defense Provisions

3.1 Startup, Shutdown, and Malfunction Exemption

Comment 3.1.1: Commenter 31 states that the EPA has offered no basis for the 

statement that control devices will be operating normally in startup and shutdown periods. This

commenter and commenter 37 caution that thermal destruction control devices often need to 

achieve a certain temperature before optimal destruction occurs, and that provisions for startup 

for those equipment might need to be changed. Commenter 42 cautions that while different 

standards during startup and shutdown may not be needed for these source categories, alternative 

standards will be needed for some source categories, such as for ethylene manufacturing and the 

petroleum refinery sector.

Commenter 31 states that absorbers may need to be operated at different liquid/gas ratios 

during times of startup or shutdown where gas flow rates can vary and suggests that the rule 

allow for the use of engineering calculations to establish a different liquid/gas ratio during times 

of startup and shutdown if the calculations demonstrate that the emission reduction requirements 

can be met. Similarly, commenter 29 recommends that the EPA revise subpart YY to allow for 

the use of engineering calculations to establish separate operating limits or ranges for periods of 

startup and shutdown. The commenter states that since performance tests are required to be 

conducted during periods of normal operation, and not during a startup, shutdown or 

malfunction, engineering calculations are appropriate to establish ranges for periods of startup 

and shutdown. The commenter provides an example of a situation in which the established 

parameters can be exceeded while still attaining the emission limits during a period of shutdown.

Response 3.1.1: The EPA disagrees with commenters’ assertions that it is necessary to 

establish separate standards during periods of startup and shutdown for these source categories. 

We note that the commenters did not provide sufficient information or data to support the 

establishment of an alternative standard, so we continue to maintain that facilities in these 

source categories will be able to comply with the standards during periods of startup and 

shutdown. For the ethylene manufacturing and petroleum refinery sectors, any potential 

alternative standards for periods of startup and shutdown will be addressed as part of the

rulemakings for those specific source categories, and are not addressed in this final rule.

For the scenario described by commenters 29 and 31, the EPA does not believe it is 

necessary to amend the existing rules to explicitly allow the use of design evaluations to 

determine alternative operating parameters during periods of startup and shutdown. The 

standards being promulgated for periods of startup and shutdown for the AMF, APR, and PC 

MACT standards are all the same as those during periods of normal operation, and compliance 

with these standards is required at all times. If necessary, a facility may establish separate 

operating limits or ranges for a control device during periods of startup or shutdown in order to 

meet these standards.

Comment 3.1.2: Commenter 39 states that the EPA offers little support for the assertion 

that it is reasonable to interpret section 112 as not requiring the EPA to account for malfunctions 

in setting emission standards. The commenter states that it does not make sense for the EPA to 

assert that malfunctions are part of normal operations but then exclude emissions from these

parts of normal operations in the determination of the emission limits. The commenter states that

due to the unplanned nature and variety of potential malfunctions, it would be difficult if not 
20

impossible for the EPA to gather data and set an emission standard for periods of malfunction. 

Due to these difficulties, the commenter suggests that under the authority of CAA section 112(h), 

the EPA prescribe alternative design, equipment, work practice, or operational standards where it 

is not feasible to set or enforce a numerical emission limit. The commenter adds that there are 

work practices that can be identified as being the best to minimize emissions during a 

malfunction, and the EPA must acknowledge the fact that even the best-performing sources 

experience malfunction events.

Response 3.1.2: The EPA’s rationale for its approach to malfunctions is discussed in the

preambles to the proposed rule and this final action. 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. Accounting for malfunctions 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. Setting work practice 

standards under CAA section 112(h) for malfunctions – as opposed to startup or shutdown 

periods – presents the same issues as setting numerical emission limits given the varied nature of 

malfunctions. Please see Response 3.1.3 for further discussion.

Comment 3.1.3: Commenters 34 and 41 state that the EPA failed to provide adequate 

justification of why emission standards that apply during normal periods should also apply to 

malfunctions when emissions during malfunctions were not considered in developing the 

standards. The commenter states that CAA section 112 does not give the EPA the authority to 

replace MACT limits that consider the emission level achieved by the best performing sources, 

including periods where such sources experience malfunctions, with an affirmative defense to 

penalties. Commenter 41 adds that by establishing emission limits and standards without 

consideration of unforeseen upset conditions, the EPA is contradicting the CAA requirement that 

the standards by “achievable.” The commenter contends that since malfunctions were not 

considered in establishing the MACT floor, and given that standards must be “achievable,” the 

EPA should establish a separate work practice requirement for malfunctions.

Commenter 39 states that the affirmative defense provisions do not cure the EPA’s 

failure to set emission standards that are achievable during SSM events and are not a substitute 

for setting achievable emission standards for these periods.

Commenters 29, 31, and 34 believe the EPA should promulgate separate standards under 

CAA section 112(h)(1) for periods of malfunction. Commenter 29 suggests that the EPA 

establish a work practice for malfunctions that result in only small levels of excess HAP

emissions, such as 100 pounds of HAP, which requires the owner/operator to stop the emissions, 

stop the malfunction, and return to normal operations as soon as possible.

Response 3.1.3: The EPA first notes that, with regard to commenter 39, the affirmative 

defense provisions have been removed from the final rules. As we explained in the preamble to 

the proposed rule, 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 CAA section 112, emission 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 CAA section 112 that 

directs the agency to consider malfunctions in determining the level “achieved” by the best 
21

performing or best controlled sources when setting emission standards. Moreover, while the 

EPA accounts for variability in setting emission standards consistent with the CAA section 112 

case law, nothing in that case law requires the EPA to consider malfunctions as part of that 

analysis.

CAA section 112 uses the concept of “best controlled” and “best performing” unit in

defining the level of stringency that CAA section 112 performance standards must meet. 

Applying the concept of “best controlled” or “best performing” to a unit that is malfunctioning 

presents significant difficulties, as malfunctions are sudden and unexpected events. Accounting 

for malfunctions 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 accounting for malfunctions could lead to standards that are significantly less 

stringent than levels that are achieved by a well-performing non-malfunctioning source. The 

EPA’s approach to malfunctions is consistent with CAA section 112, and is a reasonable 

interpretation of the statute.

Comment 3.1.4: Commenter 42 notes that in 40 CFR 63.1107(c)(1) and (2), the sections 

for malfunction recordkeeping and reporting requirements, the word “failures” is used rather 

than “malfunctions.” The commenter states that since failures to meet emissions standards that 

are not due to malfunctions are addressed separately in 40 CFR 63.1109 and 63.1110, the 

requirements in these paragraphs should apply to malfunctions only, and the word “failures” 

should be replaced with “malfunctions.” The commenter also suggests that the requirement to 

record the “number of failures” in 40 CFR 63.1107(c)(1) be deleted because the failure to meet 

an applicable standard is by its nature a single occurrence, and the requirement to record the date, 

time and duration of each failure would already provide a count of such occurrences. The 

commenter also suggests that in 40 CFR 63.1107(c)(1)(ii), the requirements be reworded to 

clarify that the volume of only the pollutants regulated by the Generic MACT (GMACT) 

standards (i.e., total organic HAP) are required to be estimated and recorded. The commenter 

also notes that similar wording is used in the reporting requirements of 40 CFR 63.1107(c)(2)

and suggests the same changes at those for the recordkeeping requirements. Similarly, 

commenter 33 also suggests clarifications to the malfunction recordkeeping and reporting 

requirements in 40 CFR 63.1111(c)(1) and (2) to make the format consistent and content clearer.
22

Response 3.1.4: The EPA first notes that the malfunction recordkeeping and reporting 

requirements referenced by the commenter are contained in proposed 40 CFR 63.1111(c)(1) and 

(2), not 63.1107(c)(1) and (2). With regard to the commenter’s suggestions, we disagree that it is 

necessary to replace “failure” with “malfunction” because the malfunction recordkeeping and 

reporting language is clear that the provisions only apply to malfunction events, and therefore 

do not overlap with the requirements of 40 CFR 63.1109 and 63.1110. Additionally, we believe 

that the requirement to record the number of failures is necessary, as it shows whether there are 

multiple malfunctions on the same process unit. We also disagree that it is necessary to further 

clarify which pollutants are required to be included in the malfunction report. The final rule uses 

the term “regulated pollutant,” which for the GMACT is organic HAP. We also note that we 

have revised the final rule to require reporting of the “quantity” of regulated pollutants rather 

than the “volume,” as emissions are typically reported in terms of mass or weight.

Comment 3.1.5: Commenter 42 requests that one year be provided for implementing the 

SSM requirements for this and future rules. The commenter claims that time is needed to develop 

new procedures for handling malfunctions and provide staff training after the rule is finalized.

Response 3.1.5: The EPA disagrees with the commenter that one year is necessary for 

implementation of the revised SSM requirements. These requirements should be immediately

implementable by the facilities upon the next startup, shutdown, or malfunction event. The EPA 

has consistently been removing the SSM exemption from rules as part of the risk and technology 

review process for several years, so facilities should have already begun to educate their staff on 

how to handle SSM events and implemented procedures for avoiding such events.

Comment 3.1.6: Commenter 39 states that the EPA has not justified changing conditions 

that apply to performance testing. The commenter contends that where the proposed rule 

removed previously applicable references to the NESHAP General Provisions that required 

performance tests to be conducted based on normal operating conditions of the affected source 

and specified that “operations during periods of startup, shutdown, and malfunction shall not 

constitute representative conditions for the purpose of a performance test,” the proposal would 

allow the EPA to direct a source to conduct performance testing during abnormal operations, 

such as startups, shutdown, or malfunctions. The commenter states that the EPA cannot “amend” 

existing MACT standards in a way that can make the standards more stringent without first 

providing an adequate justification for departing from the EPA’s previous judgment about the 

appropriate conditions for performance testing.

Response 3.1.6: As noted by the commenter, we eliminated the SSM exemption as it 

applies to performance testing under 40 CFR 63.7(e)(1) and we specify that “[p]erformance 

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”

(at 40 CFR 63. 1108(b)(4)(ii) and 63.1413(a)(2)). One of the reasons for this is because the 

General Provisions selectively apply to part 63 standards and some part 63 standards establish 

alternative standards or compliance demonstration methods during startup and shutdown 

periods that may require performance testing during startup and shutdown periods. Sections 

63.1108(b)(4)(ii) and 63.1413(a)(2) specify the conditions that performance testing must be 

conducted for the AMF, PC, and APR MACT standards. The final requirements do not allow for 

performance tests to be conducted during periods of malfunction, and the conditions for 

conducting performance testing for the existing MACT standards have not changed.
23

3.2 Affirmative Defense Provisions

Comment 3.2.1: Commenter 36 urges the EPA not to adopt the affirmative defense 

provisions. The commenter states that the affirmative defense provisions are unlawful and 

harmful. The commenter argues that Congress plainly intended citizens to be able to enforce 

emission standards under the CAA using the full range of civil enforcement mechanisms 

available to the government, and, in the HAP context, subject only to the limitation that 

government not be “diligently prosecuting” its own civil enforcement action, according to CAA 

section 304(b)(1)(B).

The commenter further states that the EPA exceeded its authority by attempting to 

impose additional Agency-created limits on civil penalties and that the proposed affirmative 

defense goes directly against Congressional intent that judges should determine the size of civil 

penalties whenever they are sought, and that the proposal will impermissibly chill citizen 

participation and the ability to win an effective, deterrent remedy in CAA enforcement actions. 

The commenter adds that allowing only injunctive relief for violations that occur during 

malfunctions removes the primary deterrent to violations, which is paying a penalty. The 

commenter also states that the affirmative defense creates an unlawful after-the-fact exemption, 

since injunctive relief is still available to try to prevent further future violations, but provides no 

remedy for a past violation.

The commenter also states that the EPA seeks to rely on a Fifth Circuit case that upheld 

the EPA’s authority to partially approve an affirmative defense provision in a state 

implementation plan, but the D.C. Circuit will have jurisdiction over these final rules, and there 

is binding D.C. Circuit case law to suggest it may not follow the Fifth Circuit decision.

The commenter observes that the CAA gives the EPA minimal discretion that only 

applies to administrative penalties which may be imposed under subsection 113(d), but no 

authority to compromise, modify or limit civil penalties that a court may impose under section 

113(e) or section 304. The commenter states that it is improper for a court to fail to consider 

these factors, or to fail to make its own determination of what civil penalties are “appropriate” 

under CAA section 304(a). 

The commenter asserts that the burden the affirmative defense places on citizens makes it 

less likely that they will enforce the CAA, that citizen participation in CAA enforcement will be 

hindered, in violation of citizens‘ rights to protect themselves from pollution and in direct 

conflict with congressional intent. The commenter states that the affirmative defense imposes a 

technical burden on citizens, and the burden renders the defense impermissible. The commenter 

predicts that the affirmative defense will likely be used on a routine basis by polluters seeking to 

avoid penalties, just as the malfunction exemption was, and enforcement of the CAA could 

suffer.

The commenter also states that if the EPA had the authority to promulgate any 

affirmative defense to penalties for malfunction, it should also promulgate strong reporting, 

monitoring, and other compliance measures, require a specific monetary penalty for each 

malfunction, and require that the affirmative defense cannot be used by a specific facility or 

company more than once within a set period of time, such as 10 years. The commenter adds that 

notification of malfunctions or emissions standards exceedances submitted to the EPA by a 

facility should be made publicly available through the EPA’s website within 7 days. The 

commenter further adds that the EPA should also require the facility to provide same-day 

community notification through an appropriate public forum, such as the company website, 

written notice to the local municipality and local school district, or press release to the local 
24

newspaper, radio and TV news station. The commenter asserts that it is important for 

malfunction reports to be submitted electronically, be made publicly available as soon as 

possible, and that facilities should not be allowed to wait until the next semiannual report to 

report malfunctions.

Commenter 33 adds that the courts, and not the EPA determine whether any defense, 

affirmative or otherwise, is available for any type of claim, whether in law or in equity, and the 

EPA has no authority to restrict the power of the court in an enforcement action.

Commenters 29, 32, 33, 34, 39, and 46 state that the affirmative defense provisions are 

overly burdensome and are not realistically attainable due to the specific language of the required 

criteria. The commenters request that the EPA clarify and redefine the criteria considering 

attainability. Commenters 32 and 33 suggest several modifications to the affirmative defense 

provisions. One suggestion is to rely on the phrase “preponderance of evidence,” as is used in 

paragraph (a) of these provisions but is later contradicted by the use of “any” and “all.” Another 

suggestion is to make the definition of malfunction match that of the General Provisions, where 

the phrase “not reasonably preventable” is used rather than the phrase “sudden, infrequent, and 

unavoidable failure.” Commenters 29 and 33 suggest revising the affirmative defense provisions 

to remove the requirement for contemporaneous operating logs because their facilities use 

electronic media to document actions, and a printed and signed log is an outdated mode of 

documentation. Commenter 39 requested that the term “infrequent,” and subjective phrases, such 

as “if at all possible,” be removed from the regulatory text, as these terms could be subject to 

different interpretations by regulatory agencies. Commenter 33 states that some provisions are 

too vague and without defined limits, such as “better operation and maintenance practices” and 

“could not have foreseen and avoided.” 

Commenter 33 also states that many of the requirements are irrelevant to the facts or 

events of the underlying malfunction, including the requirement that repairs be made as 

expeditiously as possible. The commenter also states that the steps taken after the violation 

occurred to minimize the frequency, amount, duration and impact of the violation is not relevant 

to whether a violation that occurred was a malfunction. The commenter declares that whether 

emissions monitoring and control systems were kept in operation is also irrelevant to establishing 

whether the violation is excusable. The commenter adds that the requirement that “At all times, 

the affected source was operated in a manner consistent with good practices for minimizing 

emissions,” is a requirement redundant of the general duty provisions and is not relevant to 

whether a violation would have occurred. The commenter also asserts that the EPA may not 

condition the availability of an affirmative defense on whether a report regarding the violation 

was submitted, and the existence of such a report is not relevant to whether the violation was 

caused by a malfunction.

Commenter 29 suggests that as part of the affirmative defense, companies should only be 

required to report the amount of excess emissions that were the result of a malfunction and not 

be assessed penalties for any emissions caused by the malfunction. 

Commenter 39 is concerned that the affirmative defense provisions imply the facility is 

guilty until proven innocent and put the burden of proof on the facility rather than the EPA. This 

commenter states that the EPA must modify the provisions substantially so that they do not 

require sources to prove their innocence.

Commenters 29, 32, and 33 suggest revisions or removal of the formal root cause 

analyses required by the affirmative defense provisions. Commenter 32 suggests a formal root 

cause analysis should only be required when other reasonable methods fail to show the cause of a 
25

malfunction or when the serious nature of an event might make such an analysis necessary. 

Commenter 29 states that formal root cause analyses are not needed because malfunction events 

are already routinely investigated and formal root cause analyses will detract from candid 

inquiries into the events. Commenter 39 states that the root cause analysis requirement may 

make the affirmative defense unavailable if the source is not able to determine the primary cause 

of the malfunction. Commenter 33 adds that a defendant should be able to use any and all 

evidence to demonstrate the cause of a violation and not be limited to a root cause analysis. The 

commenter adds that whether the evidence is adequate will be determined by an independent 

judge, and it is not the EPA’s role to tell a judge what evidence is necessary or sufficient.

Commenter 39 states that the EPA estimate of $2,375 to assert an affirmative defense for 

a malfunction is not credible, appears entirely arbitrary, and is remarkably low given the number 

of different demonstrations and root cause analysis that are required of a source. 

Commenter 36 states that the EPA must promulgate specific public reporting and 

notification requirements for malfunctions and any exceedance that occurs. The commenter 

declares that the EPA must require telephone reporting by the facility 24 hours of a malfunction 

or exceedance and make a notice available publicly through the EPA’s website and through 

ECHO within 24 hours. The commenter also asserts that within 24 hours of receiving this 

notification, the EPA should provide this information to the appropriate EPA Regional Office 

and direct the Regional Office to notify the local community of the event on the Internet, direct 

communication, and through all available means. The commenter states that the EPA should 

further require the facility to provide notification to the community through an appropriate public 

forum, such as the company website, press release to the local newspaper, radio and TV news 

station, within 24 hours. The commenter further declares a written report should be required 

within 7 days and distributed to the public using the same distribution method as the earlier 

notification and that this report should include the nature of the event, the duration of the event, 

and estimate of emissions released during the event, and a description and time of correction 

actions taken and planned to be taken. 

Commenter 39 states that it is not clear what civil penalties the affirmative defense

covers. The commenter believes the affirmative defense should apply to civil penalties, civil 

administrative penalties, noncompliance penalties, enforcement actions by the EPA, states, or 

citizen-suit plaintiffs, and injunctive relief.

Commenter 39 believes the affirmative defense provisions should apply to the potential 

violation of emission limits during a startup or shutdown event as well as during malfunctions, if 

the EPA is to use such affirmative defense.

Commenter 29 requests that the EPA confirm in the final rule that an owner or operator 

may assert an affirmative defense against civil penalties for a malfunction causing a release from 

PRD in organic HAP service to the atmosphere.

Response 3.2.1: The EPA received numerous comments on the affirmative defense to civil 

penalties for violations caused by malfunctions that the EPA proposed to include in the rule. 

Several commenters supported the affirmative defense or supported the affirmative defense but 

made suggestions for revisions to its provisions. Other commenters opposed the affirmative 

defense or various components of the affirmative defense.

Recently, the United States Court of Appeals for the District of Columbia Circuit vacated 

an affirmative defense in one of the EPA’s Section 112(d) regulations. NRDC v. EPA, No. 10-

1371 (D.C. Cir. April 18, 2014) 2014 U.S. App. LEXIS 7281 (vacating affirmative defense 

provisions in Section 112(d) rule establishing emission standards for Portland cement kilns). The 
26

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 in such cases 

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.”). The EPA is not including a regulatory affirmative defense provision in the final rule. 

In the event that a source fails to comply with an applicable CAA section 112(d) standards as a 

result of a malfunction event, the EPA’s ability to exercise its case-by-case-enforcement 

discretion to determine an appropriate response provides sufficient flexibility in such 

circumstances as is explained in more detail in the preamble to the final rule. Further, as the 

D.C. Circuit recognized, in an EPA or citizen enforcement action, the court has the discretion to 

consider any defense raised and determine whether penalties are appropriate. Cf. NRDC, 2014 

U.S. App. LEXIS 7281 at *24 (arguments that violation were caused by unavoidable technology 

failure can be made to the courts in future civil cases when the issue arises). The same is true for 

the presiding officer in EPA administrative enforcement actions. In light of the EPA’s decision 

not to include the affirmative defense in the final rule, we are not responding to the comments 

opposing the affirmative defense. With respect to comments that supported the affirmative 

defense or supported the affirmative defense but made suggestions for revisions to some of its 

provisions, the preamble to the final rule explains in detail the EPA’s reasons for not including 

an affirmative defense provision in the final rule.
27

4.0 Electronic Reporting Requirements

Comment 4.1: Commenter 46 notes that stack test reports are commonly submitted to 

the ERT by stack testing companies. The commenter is concerned about the requirement for the 

Responsible Official (RO) to certify compliance with the testing requirement and/or the test 

result when it is being submitted by a third party. The commenter states that having a single 

electronic or paper copy available for technical review provides the RO with better assurance and 

ability to review and verify the information. 

Response 4.1: Originally, the Compliance and Emissions Data Reporting Interface 

(CEDRI) in the EPA’s Central Data Exchange (CDX) allowed testers and consultants to submit 

files of test reports generated through the use of the ERT on behalf of facility owners and 

operators. The CEDRI no longer allows testers and consultants to submit files on behalf of 

facility owners and operators. While testers and consultants may prepare files in CEDRI on 

behalf of facility owners and operators, only facility personnel may be registered as certifiers in 

CEDRI. Only a certifier may submit a report.

Comment 4.2: Commenter 31 comments that the proposal to require the use of the 

Electronic Reporting Tool (ERT) is not appropriate as the costs and burdens imposed cannot yet 

be determined. Also, the regulated community cannot fully comment on the cost of duplicating 

reports using the ERT for Method 18 and other methods not currently supported by the ERT.

Commenters 31 and 37 state that the EPA should ensure the ERT includes the ability to 

accommodate all of the required test data, including Method 18, which can be quite voluminous.

Response 4.2: The rule only requires that test methods supported by the ERT be reported

using the ERT. The EPA believes that the costs and burdens of using the ERT are not significant 

for several reasons. The electronic reporting requirement does not add any additional testing 

and it does not change the timing of when test reports are due: the requirement only states that 

reports be submitted electronically. The ERT is fully functional and has been used successfully

by industry for several years. It was designed to capture all of the information which is submitted

in a typical test report and was also designed with input from States and the stack testing 

industry.

Comment 4.3: Commenters 31 and 46 note that without a formal notice that changes are

being made to the ERT, facilities are at risk of noncompliance with the ERT requirements

because they have no way to know which test methods must be submitted to ERT unless they 

actively monitor the EPA’s web site. 

Response 4.3: The ERT website is kept up-to-date with the list of methods that are 

supported by the ERT. If the facilities wish, the EPA recommends joining the CHIEF listserv, 

which one can do by emailing join-chief@lists.epa.gov, to be notified of enhancements made to 

the ERT. Additionally, the test method dropdown box in the ERT contains a finite list of methods 

supported by the ERT. By using the latest version of the ERT, the facility will know from the 

dropdown box which methods are supported.

Comment 4.4: Commenters 29, 31, and 46 note that requiring electronic reporting to the 

EPA does not increase the ease and efficiency of data submittal for the regulated community 

because state agencies also want the reports submitted to them in their own standard format. 

Commenter 46 states this additional burden is in direct contradiction to the Paperwork Reduction 

Act (PRA). The commenters request that the EPA work with air agencies to provide a one-stop 
28

location for submittal of air emissions testing results. 

Response 4.4: The EPA worked with air agencies as well as stack testing companies 

(who typically prepare test reports) to develop the ERT. The ERT was designed to accept data 

and information that is typically collected during a performance test. Some air agencies have 

begun accepting the ERT as their reporting mechanism, and with experience, we believe 

acceptance by other air agencies will increase. In some instances air agencies may still want a 

hard copy of a test report. The ERT can generate a printed test report or export the report to a 

word processor for reformatting. This report can be submitted to the air agency. The EPA 

believes that electronic reporting is a more efficient way to collect test data and has set up a 

retrieval system such that air agencies can access files that have been submitted using the ERT. 

As more air agencies adopt electronic reporting, we believe that the need for paper reports will 

be diminished.

Comment 4.5: Commenter 31 comments that under the proposed rule 40 CFR 

63.1110(a)(9) and 63.1417(h)(8), all performance test reports must be submitted to the ERT 

within 60 days, but because the rule does not reference the general provisions 40 CFR 

63.10(d)(2), there is no allowance for obtaining additional time to complete this due to 

unforeseen circumstances or for the difficulties involved with completing particularly complex 

reports.

Response 4.5: The commenter is correct in that 40 CFR 63.10(d)(2) is not currently 

applicable to either Part 63 Subpart YY or Subpart OOO. The EPA does not believe that 

additional time needs to be provided for performance tests submitted using the ERT, as the ERT 

is fully functional and has been used successfully by industry for several years. Therefore, the 

EPA does not think that it is necessary at this time to add 40 CFR 63.10(d)(2) as applicable. If a 

facility requires additional time to submit the results of their performance test, they may submit a 

request under the existing provisions in 40 CFR 63.1112 and 63.1417.
29

5.0 Open Ended Line Provisions

Comment 5.1: Commenters 40 and 46 state that in the past, the EPA concluded that 

monitoring of caps, blind flanges, plugs, and second valves was not required since these did not 

meet the definition of “equipment.” Commenter 29 adds that these components are not usually in 

regulated material service if there is a closed valve upstream, and therefore regulated sources 

would not typically monitor these components. 

Response 5.1: Open-ended lines and valves are equipment which require the proper 

installation and use of caps, blind flanges, plugs and second valves to seal the OEL to prevent 

leaks. However, the EPA does agree with the commenters that monitoring of OELs is not 

currently required by the LDAR provisions for the AMF, PC, and APR MACT standards.

Comment 5.2: Commenter 42 states the EPA proposed to add a “no detectable 

emissions” limit and monitoring requirement for OELs to part 60 subpart VV in 2006, which 

contains the same OEL equipment standard as in subpart UU, and provided emission and cost 

estimates to support the proposed limit and monitoring in a 2007 Notice of Data Availability 

(NODA). This commenter and commenter 40 state that this action demonstrates that EPA 

believed as recently as 2007 that this change requires rulemaking. In addition, commenter 42

states that the fact that the EPA took action to propose a “no detectible emissions” limit and 

monitoring requirement for OELs to subpart VV confirms that these requirements did not 

already include such a limit or monitoring requirement.

Commenter 42 further states that the proposed definition of “seal” requires that a source 

demonstrate that the OEL is sealed by instrumental monitoring, but does not specify any details 

of that monitoring. The commenter states that in order to demonstrate an OEL is sealed at all 

times, it would appear that it must be monitored (on some undefined frequency) to ensure 

compliance with the proposed standard. Commenter 31 states that while there are no proposed 

monitoring requirements in the rule, facilities will have to establish their own monitoring 

programs and schedules for OELs without any assurance that their individual programs or

schedules would be considered to be in compliance by an EPA inspector. Commenters 37 and 46

also request clarification about whether routine monitoring is expected for OELs, given that the 

proposed definition references a Method 21 reading of less than 500 ppm. Commenter 29 adds 

that if the intent is to require routine monitoring of these components, rule changes are needed to 

add time periods for completion of repairs. Commenters 29 and 31 contend that if the EPA does 

intend to require periodic monitoring, such monitoring rules must be clearly proposed in a 

second rulemaking with a public comment period. Commenter 46 states that if the new term is 

established, the EPA should, at a minimum, subject the “seal” to the visual repair requirements 

of subpart UU, which would then also include leak repair requirements rather than an automatic 

violation of the OEL requirement. Commenter 33 adds that the essence of the LDAR work 

practice standards for leaking equipment is that the discovery of a leak triggers a repair 

requirement, and leaks are not automatic violations of the rule.

Commenter 31 states that the EPA did not develop any cost estimates or impacts on the 

regulated community resulting from the proposed definition of “seal.” However, the commenter 

states that facilities will need to develop monitoring plans and regularly monitor OEL seals to 

ensure they have instrument readings below 500 ppm, which will require capital costs including 

identifying, tagging and updating software systems for OEL seals. Commenter 42 also states that 

given the large number of OELs in refineries and chemical plants, the costs and burdens for 

monitoring OELs, even infrequently, are substantial and are not addressed in the rulemaking 
30

record or the Information Collection Request (ICR) for the three source categories specifically 

addressed in this proposal. The commenter also notes that the record does include any 

information on the likely emission reductions associated with this change, which the 2007 NSPS 

VV and GGG rulemaking record suggests would be minimal.

Response 5.2: The EPA is not imposing monitoring for OELs. There are no additional 

costs associated with the clarification that OELs be sealed. We also disagree with the 

commenters that the EPA is requiring facilities to regularly monitor their OELs, and thus incur 

capital and annual costs. The requirement that OELs be sealed is not a new standard and there 

is no requirement in any of the LDAR requirements for these source categories that requires 

facilities to monitor their OELs on a regular basis. Furthermore, since this is a not a new 

requirement, there are no new emission reduction estimates associated with this clarification of 

the “seal” definition.

Comment 5.3: Commenters 33 and 40 state that the term “seal” does not denote a certain 

numeric precision, and within the context of LDAR requirements in MACT standards, the EPA’s 

decision not to include a precise definition in the existing rules, which do include numeric leak 

definitions for other components, is a clear signal that the term “seal” does not implicitly 

incorporate a numeric leak definition. The commenters also state that the requirement to cap 

OELs was never “zero emissions” standard, but rather a work practice in the form of an 

equipment standard, and the proposed definition would transform this work practice into a 

numeric emissions limit. Commenter 29 states that the OEL provisions are “equipment 

standards” and compliance is determined by whether a cap, blind flange, plug, or second valve is 

physically installed, and the term “sealed” historically has meant one of these devices is present.

Response 5.3: The EPA disagrees with the commenter. The EPA’s intent has always been 

that caps, blind flanges, plugs or second valves that are installed on OELs provide a seal, i.e., no 

detectable emissions. This is further supported by examples of compliance audits conducted by 

OECA and Regional enforcement personnel in which companies were cited for OELs not being 

sealed. We have placed these audits in the docket for this action.

Comment 5.4: Commenter 42 notes that while until the mid-2000’s the EPA issued a 

multitude of OEL citations for failing to cap or plug an OEL, only since about 2005 have some 

of these citations identified a failure to meet a “no detectible emissions” limit as a parameter. 

The commenter notes that in most cases, the EPA continues to cite facilities for failing to have a 

cap or plug in place, without consideration of whether that OEL is leaking at more than 500 ppm, 

but each failure would apparently now be two violations - one for failing to meet the equipment 

standard and one for failing to meet the 500 ppm emission limit.

Response 5.4: The EPA disagrees with the commenter that the scenario in question 

would result in two separate violations for the facility. By defining “seal” to mean a reading of 

less than 500 ppm above background using instrument monitoring by Method 21, we are 

clarifying an existing requirement that the OEL be operated with no detectable emissions. This is 

consistent with how OECA has been enforcing this requirement during their inspections, and will 

not increase the number of violations issued for having a reading greater than 500 ppm from an 

OEL.

Comment 5.5: Commenters 29 and 31 state that there are cross-referencing issues with 

the proposed “seal” definition for OELs. Commenter 29 notes that for PC facilities complying 
31

with 40 CFR part 63 subpart H for equipment leaks, it is ambiguous what the term “seal” means 

relative to the open-ended valve or line requirements in subpart H at 40 CFR 63.167(a)(2). 

Commenter 31 notes that the AMF, PC, and APR subparts cross-reference subpart UU and states 

that if the EPA revises the definition of “seal” for these subparts, then it will also need to propose 

changes to subpart UU at 40 CFR 63.1033 to include the proposed emission limit of 500 ppm for 

OELs. The commenter adds that the EPA must update Method 21 to account for accurate OEL 

monitoring.

Response 5.5: It was the EPA’s intent that the term “seal” would apply to the LDAR 

requirements in subpart H as well, for those facilities that are complying with those provisions 

as part of the GMACT. As such, we have revised the definition of “seal” to clarify that subpart H 

is also included. With regard to commenter 31’s suggestion, the EPA is not imposing an 

emission limit for OELs, but rather we are clarifying the existing requirement that OELs be 

sealed. As such, it is not necessary for us to include a new emission limit in subpart UU.
32

6.0 Pressure Relief Device Provisions

Comment 6.1: Commenters 31, 33, 38, 39, 42, and 46 state that PRDs are safety devices, 

and these requirements will ask plant operators to choose between safety and committing a 

violation. Commenters 31, 38, 39, and 46 claim that this position is in direct contrast to the 

General Duty provisions, which state that, “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...” 

Response 6.1: The EPA disagrees with the commenters that we are forcing plant 

operators to choose between safety and committing a violation. We recognize that industry has 

stated that they believe 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 that is consistent with the General Duty 

provisions and is designed to minimize emissions while recognizing that these events may be

unavoidable even in a well-designed and maintained system.

Comment 6.2: Commenter 31 cites the EPA’s statements that PRD releases are caused 

by malfunctions and that the EPA is not required to establish separate standards for malfunctions 

because it is not required to do so, and it is too difficult to do so. The commenter asserts that a 

PRD release is unique in that the “release” is an inherent function of the device, and therefore a 

work practice standard or a numerical emissions limit could be established. The commenter 

believes the EPA could have considered data submitted by the commenter along with data from 

California’s South Coast Air Quality Management District to determine whether it may be 

feasible to group PRDs with process vents and propose a numerical emission standard under 

CAA section 112(d)(3). Alternatively, the commenter states the EPA could have established a 

work practice standard for PRD releases pursuant to its authority under CAA section 112(h). The 

commenter urges the EPA to consider either of these approaches.

Response 6.2: We disagree with the commenter. The releases are related to process 

upsets or other malfunctions that require the release of pressure to avoid damage to equipment 

and to prevent harm to personnel at the facility. Such releases are not routine, are unpredictable 

in nature, and are considered to be caused by malfunctions (e.g., poor design, improper 

maintenance, or operational error) that do not justify being allowed to continue. The commenter 

failed to establish that the criteria for setting a work practice had been met, and as we explained 

in the preamble, it is impracticable to establish work practices or other alternative standards to 

manage these events and CAA section 112 does not require that we do so. In addition, the 

commenter has not provided information that would support MACT floor and beyond-the-floor 

analyses to set numeric limits or work practice standards, in lieu of a prohibition of these 

malfunction emissions. Nor has the commenter provided cost or technological information on 

options to control such malfunction emissions to the atmosphere, even if the EPA were to 

consider it appropriate to set MACT limits for them.

Comment 6.3: Commenters 39, 40, and 42 assert that the EPA provided no evidence or 

justification of its assertion that PRD releases to the atmosphere are caused by malfunctions, and 

that, in fact, PRDs that release to the atmosphere due to excess pressure are functioning exactly 

as designed and are not malfunctioning. Commenter 42 states that while the MACT standards, 

including the GMACT, recognized that pressure releases can be due to malfunctions, typically in 
33

the definition of pressure release, this does not indicate that all pressure releases are due to 

malfunctions. The commenter further states that the EPA has been clear in all its discussion of 

malfunctions and in its enforcement that for an event to be a malfunction, it must generate excess 

emissions relative to the Federal rule being considered. The commenter also notes that the event 

must have been due to a sudden, infrequent, and not reasonably preventable failure and not due 

to poor maintenance or careless operation to meet the definition of malfunction. The commenter 

states that most pressure releases do not meet the definition of malfunction. The commenter also 

states that the treatment of malfunctions before or after Sierra Club v. EPA has no bearing on 

pressure releases not related to malfunctions.

Commenter 42 also states that the EPA cannot interpret the term malfunction narrowly 

for the purposes of affirmative defense and broadly with respect to PRDs. Commenter 33 states 

that the proposed definition of “pressure release” could be interpreted to be limited to only 

emission events that release to the atmosphere, and requests that the definition be revised clarify 

that the emission of materials from the PRD includes emissions to the atmosphere, to a closed 

vent system and control device, or to a process. Both commenters request that the definition of 

“pressure release” should be revised to reflect the fact that pressure releases do not only occur 

due to process malfunctions and suggest removing the last phrase of the definition “due to a 

malfunction in the process” to clarify this point.

Response 6.3: The EPA agrees with the commenters that not all pressure releases are 

caused by malfunctions and has revised the definition of “pressure release” to remove the 

phrase “due to a malfunction in the process.” Regarding commenter 33’s request for further 

clarification, we believe that this definition is already broad enough to include emissions to the 

atmosphere, control device, process, etc. A “pressure release” is defined as the release of 

materials from the system pressure exceeding the set pressure of the PRD, so it does not restrict 

where those materials are emitted to, nor what was the cause of the release. We also note that 

the prohibition and monitoring requirements do not apply to PRD release emissions that are 

captured and routed to a control device, process, fuel gas system or drain system, since such 

emissions are not released to the atmosphere.

As discussed in the Background Information Document (BID) for the HON, only those 

pressure releases that occurred as a result of a malfunction were able to use the SSM exemption 

(page 4-21). We also note that the definition of “pressure relief device” states that a PRD is “a 

safety device used to prevent operating pressure from exceeding the maximum allowable 

working pressure of the process equipment.” If, as the commenter asserts, most pressure 

releases do not meet the definition of “malfunction” (i.e., “sudden, infrequent, and not 

reasonably preventable”), then this implies that the PRD may be releasing often or at regular 

intervals and not necessarily due to process upsets. This further reinforces the EPA’s decision to 

prohibit HAP emissions from PRDs, as such unregulated emission points may result in a 

significant amount of uncontrolled HAP released to the atmosphere.

Comment 6.4: Commenters 45 and 46 state that they have effective programs in place to 

prevent pressure releases from PRDs, but that not all system components specifically have “time 

and duration” monitoring capability or flow monitoring equipment. However, the commenters 

believe sufficient information is almost always available to adequately determine the 

approximate time and amount of a HAP release. The commenters ask that the EPA limit the 

required monitoring to primary reaction vessels or to locations where pressure releases would 

likely occur during the normal course of processing and exclude systems or devices from the 
34

PRD requirements for insignificant releases of liquids, releases from small devices, and/or 

releases that will result in emissions below the relevant standard. Commenter 45 urges the EPA 

to consider allowing industry to establish a “standard of care” for PRDs in lieu of requiring 

specific monitoring or prohibitions.

Response 6.4: The EPA notes that the PRD monitoring provisions do not require a 

facility to equip each PRD with a specific device to monitor time, duration, or flow rate. Rather, 

the monitoring equipment or system must be capable of recording the time and duration of the 

leak, and facilities may use their best engineering judgment to calculate the emissions released 

during the pressure release event. The EPA also disagrees with the commenters’ suggestion to 

limit the applicability of the PRD monitoring requirements to only certain PRDs, as all 

emissions from PRDs in organic HAP service that release to the atmosphere should be 

regulated, regardless of where they are located within the process. We also do not believe that a 

“standard of care” approach for these emission points is appropriate, as this would not ensure a 

consistent level of monitoring for PRDs across the source category.

Comment 6.5: Commenter 46 notes that pressure releases due to over-pressurization are 

evaluated on a case-by-case basis and reported to the respective agencies via Title V permit 

conditions and/or MACT reporting requirements. The commenter believes the proposed PRD 

monitoring and reporting requirements are duplicative of the existing requirements.

Response 6.5: The EPA disagrees with the commenter that the proposed PRD monitoring 

and reporting requirements are duplicative of existing requirements. There were previously no 

requirements for these source categories that would require each facility to monitor their PRDs 

and report each release to the atmosphere. While certain states may have these requirements for 

certain PRDs or releases above a certain threshold, the EPA believes it is important to require 

all facilities subject to the AMF, PC, and APR MACT standards to monitor and report all PRD 

releases to the atmosphere, as this ensures that these releases will be reported nationally and not 

just in some states.

Comment 6.6: Commenters 38 and 42 state that controlling large atmospheric PRD 

releases is very costly, cost ineffective, and raises safety and environmental concerns. The 

commenters state that these PRDs are routed to the atmosphere because releases are very 

infrequent, routing them to flare systems can create backpressure and additional safety problems, 

the addition of flares increases emissions because of the additional pilot, purge and sweep gas 

combustion, flares are very expensive, space for new flares may not be available, and the 

community objects to the addition of flares. Commenter 42 also notes that additional flaring 

would have a negative impact on the EPA’s efforts to reduce flaring and flare emissions. 

Commenter 38 states that the EPA presumes it is technically feasible to vent all existing PRDs to 

existing control equipment but did not provide analyses of the feasibility or costs to support this 

conclusion. 

Response 6.6: The EPA is not requiring, nor do we claim it is necessarily feasible, for all 

PRDs to be routed to a flare or other control device. Rather, the EPA is not requiring that PRDs 

that route to a control device, process, or drain system be prohibited and monitored, since 

emissions from these PRDs will not be released uncontrolled to the atmosphere. 

Comment 6.7: Commenter 37 states that there are 5 PRDs at its facility, and there have 

been no known releases from these devices in the past 5 years, so it is difficult to identify the
35

benefit from monitoring these devices. However, the commenter supports the proposed 

flexibility to use parametric monitoring of the affected equipment or monitoring devices on the 

PRDs, if such monitoring is to be required. The commenter indicates that existing parametric 

monitoring will be sufficient for its facility to meet the PRD monitoring requirements. 

Commenter 46 states that the EPA’s estimate of 5 PRDs per facility is reasonable, but it failed to 

consider operating and maintenance costs for PRD monitors, such as a written operating 

program, data management, spare parts and reporting requirements, which the commenter 

estimates could be 10% of the installed cost.

Response 6.7: The EPA thanks the commenter for their support of the flexible PRD 

monitoring provisions. With regard to the comment on the EPA’s cost estimate for monitoring of 

PRDs, we believe that our costs represent the most expensive approach to satisfy this 

requirement (installation of electronic indicators on each PRD in organic HAP service), and that 

actual costs will be significantly less.

Comment 6.8: Commenter 46 states that the design of PRDs should be governed by 

good engineering practices and regulatory programs such as ASME standards, OSHA’s process 

safety management standard and the EPA’s risk management program exist to serve the hazards 

involved. The commenter states that additional PRD requirements in a MACT standard 

unnecessarily duplicates existing programs that already provide for adequate monitoring. The 

commenter also states that no single design monitoring standard for the several types and styles 

of PRDs can possibly work. 

Response 6.8: The EPA disagrees with the commenter that we are limiting the types of 

PRDs that can be used at a facility. Our requirements for PRDs only require that they be 

monitored for pressure releases using a device or parameter monitoring system capable of 

identifying and recording the time and duration of each pressure release and of notifying 

operators immediately that a pressure release is occurring. Nowhere do we restrict what type of 

PRD a facility may install on their equipment, and to assert so is incorrect. As stated previously, 

we disagree that the PRD monitoring requirements finalized in these rules are duplicative of 

existing programs.

Comment 6.9: Commenter 29 requests that the compliance dates for the PRD 

requirements dates in both subparts YY and OOO should not only reference the monitoring 

requirements but also the associated recordkeeping and reporting requirements. Commenter 38

requests three years to comply with the PRD requirements rather than the one year proposed. The 

commenter states that it would take more than one year to perform the assessment, design, 

engineering, procurement, and installation for PRD monitoring equipment and also more than 

one year, if it can be done at all, to implement a system to route PRDs to control devices.

Response 6.9: The EPA notes that the proposed PRD monitoring requirements did 

provide three years with which to comply with the requirements, and not the one year mentioned 

by commenter 38. Regarding commenter 29’s request for clarification, it was the EPA’s intent 

that the associated PRD monitoring recordkeeping and reporting requirements take effect upon 

promulgation of the final rule amendments. Since the prohibition of HAP emissions to the 

atmosphere from PRDs in organic HAP service takes effect immediately, it is important that 

information about these releases be included in a facility’s semi-annual report. While 

installation of a PRD monitoring system is not required until three years after promulgation of 

the final rule amendments, we expect facilities to be able to provide a reasonable estimate for 
36

this information in the interim, especially since they are already required to report most of this 

information after a pressure release event as part of compliance with the LDAR provisions of 

subpart UU.

Comment 6.10: Commenter 29 states that the PRD requirements for PRDs in upstream 

rupture disks in subparts YY and OOO should be changed to be consistent with the recently 

finalized rules for 40 CFR 63 subparts JJJ, MMM, and PPP, which include provisions to require 

replacement of the rupture disk within 5 days of a pressure release. This commenter and 

commenter 37 also request that the EPA clearly define when the 5-day Method 21 clock begins 

following a pressure release. The commenters suggest that a reference to the leak repair schedule 

of subpart UU in 40 CFR 63.1024(a) be inserted. Commenter 33 adds that monitoring after 

replacement of a rupture disk seems pointless since a rupture disk is impermeable. Commenter 

45 requests that pressure checks be allowed after the installment of a replacement rupture disc 

after a pressure release rather than monitoring to verify that the pressure relief device is properly 

operating. Commenters 29 and 33 state that the EPA should include delay of repair provisions 

for PRDs like those contained in 40 CFR 63.1030 of subpart UU. Commenter 46 requests that 

the EPA revise the definition of PRD to exclude those with rupture disks because rupture disks 

do not and cannot regulate the pressure within the process and are true safety devices. This 

commenter believes they should be treated differently than spring-loaded devices, which can be 

used to regulate pressure. Alternatively, the commenter requests that the EPA designate PRDs 

with rupture disks that have burst disk indicators as a parameter monitoring system. The 

commenter notes that if rupture disks are not excluded from the definition, the company will 

need to incur additional costs to install PRDs that are more suitable to the types of monitoring 

devices the EPA has described (i.e., acoustic sensors and pressure/differential pressure sensors).

Response 6.10: The EPA agrees with the commenters’ request for the addition of delay of 

repair provisions for leaking PRDs and has added these provisions to the final rules. The EPA 

also agrees with commenter 33’s request to remove the monitoring requirement after 

replacement of a rupture disk. Since we have removed this requirement, commenter 45’s request 

is moot. With regard to commenter 46’s question on burst disk indicators, the EPA believes that 

the PRD monitoring provisions are flexible enough to allow this type of monitoring system, 

provided that the system is capable of identifying and recording the time and duration of each 

pressure release and of notifying operators immediately that a pressure release is occurring.

Comment 6.11: Commenter 46 states that for the APR source category, subpart UU 

clarifies which equipment is subject to the provisions of the subpart, which excludes equipment 

in regulated material service less than 300 hours per year, equipment in vacuum service and lines 

and equipment not containing process fluids. The commenter states the EPA did not recognize or 

document these exclusions when proposing the new PRD requirements. 

Response 6.11: The EPA notes that the existing equipment applicability requirements in 

subpart OOO already define which equipment are subject to the existing MACT standards in 40 

CFR 63.1400(b), which includes equipment intended to operate less than 300 hours per year as 

part of the affected source for the rule. Given the specificity of the rule’s applicability 

requirements, we believe it would be inappropriate to apply the 300 hour per year exclusion 

suggested by the commenter. We also note that equipment not containing process fluids are 

already exempt from the definition of an amino/phenolic resin process unit.
37

Comment 6.12: Commenters 29, 31, 37, and 42 suggest certain types of PRDs should be 

excluded from PRD monitoring requirements because they have a low potential to emit large 

quantities of HAP. These commenters specifically state that PRDs in liquid service should be 

excluded. Commenter 29 adds that to be consistent with the recently finalized amendments to 40 

CFR 63 subparts JJJ, MMM, and PPP, PRDs in light liquid service that are routed into a drain 

system should be excluded. Commenter 37 further adds that tank conservation vents should be 

excluded because these devices are used to reduce the amount of vapor loss from the tank. For 

PRDs with little potential for loss to the atmosphere, this commenter and commenter 31 suggest 

that the EPA set a de minimis reporting value equal to the reportable quantity (RQ) values in 

EPCRA and/or CERCLA. Commenter 42 states that no explanation or CAA authorization, 

including the costs, burden or emissions reduction, was provided for amending the existing work 

practice requirements for PRDs in liquid service. The commenter states that the provisions of 40 

CFR 63.1029 are more adequate and appropriate for this class of PRDs

Commenters 29 and 42 suggest that, to be consistent with 40 CFR subparts UU and U,

gaseous streams from PRDs routed to fuel gas systems be excluded along with streams routed to 

controls and processes. Commenter 42 also requests that the provision be clarified to also treat 

piping that routes a vent stream to a process, fuel gas system or a recovery device as a closed 

vent system, since the GMACT closed vent system definition only includes such equipment that 

is routed to a control device. The commenter also requests that the language be clarified to 

exclude PRDs that are controlled, even if there are other PRDs on the same piece of equipment 

that could route to the atmosphere.

Response 6.12: We do not agree with the commenters’ suggestion that PRDs that emit 

smaller amounts of HAP to the atmosphere should be excluded from PRD monitoring and 

reporting requirements. The EPA agrees with commenters 29 and 42’s suggestion to exclude 

PRDs that release to a drain system or fuel gas system from the PRD monitoring provisions. 

With regard to monitoring of tank conservation vents, we do not believe that these vents meet the 

definition of a PRD and therefore are not subject to PRD monitoring requirements. We do agree 

with commenter 42’s suggestions that we clarify the provisions governing closed vent systems 

and which PRDs are subject to the monitoring requirements, and we have revised the final rule 

to reflect these changes.

Comment 6.13: Commenter 29 states that the EPA should clarify in 40 CFR 

63.1107(e)(3) and 63.1411(c)(1) that the trigger for reporting pressure releases are excess 

emissions and not malfunctions of pressure release indicators or process parameter monitoring 

systems. Commenter 42 also suggests the proposed language of 40 CFR 63.1107(e) be revised to 

clarify that the PRD release provisions only apply to PRDs that release to the atmosphere. 

Response 6.13: The EPA agrees with commenter 29 and has revised the final PRD 

monitoring requirements to no longer state that a malfunction of the release indicator or 

monitoring system is itself a violation. The EPA also agrees with commenter 42 that the PRD 

monitoring requirements only apply to PRDs that release to the atmosphere, and believe the 

final requirements reflect this.

Comment 6.14: Commenter 33 requests that the EPA clarify that it is an option to route 

pressure releases through a closed vent system to a control device or to a process and comply 

only with 40 CFR 63.1107(e)(4) or to comply with 40 CFR 63.1107(e)(1)-(3) if pressure releases 

are not routed in this manner. The commenter also requests that the EPA clarify the provisions of 
38

40 CFR 63.1107(e)(4), which state that the closed vent system and control device PRDs are 

routed to must comply with 40 CFR 63.1034 of subpart UU, which in turn references subpart SS. 

The commenter states that it is unclear whether the EPA intends for pressure releases sent to a 

closed vent system and control device to be treated as if they were equipment leaks. 

Response 6.14: The EPA agrees with the commenter that if a PRD is routed to a control 

device or process meeting the requirements of 40 CFR 63.1107(e)(4), then they retain the option

to comply either with the requirements in 40 CFR 63.1107(e)(1)-(3) or 63.1107(e)(4). Regarding 

the commenter’s question on whether pressure releases are to be considered equipment leaks, we 

have added language to the final rule stating that, when referencing the provisions of 40 CFR 

63.1034, the term “pressure relief device” shall apply instead of “equipment leaks,” in order to 

clarify this issue.

Comment 6.15: Commenter 29 states that some facilities in the PC source category were 

originally subject to 40 CFR part 63, subpart H, rather than either 40 CFR part 63, subpart TT or 

UU, and continue to comply through subpart H, as allowed by the rule overlap specifications of 

subpart YY in 40 CFR 63.1100(g)(4)(ii). The commenter requests that clarification be added to 

the equipment leaks portions of the PC requirements tables in subpart YY to include a reference 

to subpart H. The commenter also states that although it is clear in the tables to the rule, the EPA 

should clarify in 40 CFR 63.1107(e) that that owners or operators are obligated to comply with 

the requirements of that paragraph rather than PRD requirements in subpart UU or subpart H.

Response 6.15: The EPA agrees with the commenter and has incorporated references to 

the HON LDAR provisions and clarified which PRD provisions apply to affected sources.

Comment 6.16: Commenter 33 states that the concept of “in organic HAP service,” is 

not defined for the new PRD provisions. The commenter requests that the EPA clarify the rule 

text to accomplish this in the non-LDAR PRD context.

Response 6.16: The EPA has added the definition of “in organic HAP service” to the 

final rule, consistent with the definition used in both the HON and subpart UU.

Comment 6.17: Commenter 45 is concerned that the EPA may propose similar PRD 

requirements for 40 part 63 subpart FFFF, which the facility is also subject to. Some of the 

operations subject to subpart FFFF are very small and would have very small if any releases to 

the atmosphere from PRDs but would have the same costs as those associated with larger 

operations for installing and operating PRD monitoring systems. 

Response 6.17: The EPA cannot speculate as to whether or not the final requirements in 

this action are appropriate for the source category cited by the commenter. The EPA will 

consider this issue if and when it arises in a future rulemaking for that source category.

Comment 6.18: Commenter 36 supports the EPA’s recognition of the need to remove all 

SSM exemptions, including the need to prohibit releases to the atmosphere from PRDs and 

require monitoring of such devices. 

Response 6.18: We agree with the commenter that pressure release emissions to the 

atmosphere from PRDs should not continue to be permitted to occur. HAP emissions as a result 

of pressure releases from PRDs do occur, are considered to be the result of malfunctions, and 

are prohibited.
39

7.0 Source Category and Subpart-Specific Comments

7.1 Source Category Specific Comments – Acrylic and Modacrylic Fibers

Production

Comment 7.1.1: Commenter 41 concurs with the EPA’s conclusions that the residual 

risks associated with the AMF source category are less than the human health and ecological risk 

screening thresholds, that the multiplication factor of 10 for estimating acute risks is 

conservative, that beyond-the-floor controls for existing solution polymerization spinning lines 

are not reasonable based on cost and are not needed to support the EPA’s finding that the AMF 

MACT standards sufficiently protect public health, and that further control options are not 

needed for other emissions sources to protect human health. 

Response 7.1.1: We thank the commenter for this feedback.

Comment 7.1.2: Commenter 41 requests that the EPA formally designate weighted 

manway relief devices on affected HAP storage tanks as open‐ended lines or valves that are 

exempt from the requirement to be “sealed” per 40 CFR 63.1033(c) and (d). These relief devices 

currently do not fit any of the equipment definitions for LDAR components (e.g., valve, OEL, 

PRD). The commenter states that at its facility, this device is part of the safety design of a tank 

storing potentially polymerizing material and is there to prevent pressure build up if a runaway 

polymerization reaction occurs. This device is currently conservatively categorized as a valve in 

vapor service and monitored with a leak definition of 10,000 ppm under 40 CFR Subpart TT. 

The commenter states that if it is treated as a valve under Subpart UU, significant modifications 

to the current safety system and possibly tank design would be needed to meet the 500 ppm leak 

definition, and limited emissions reduction would result. The commenter believes a more 

appropriate designation would be to consider the weighted manway an open‐ended valve or line 

that is part of an emergency shutdown system and that if sealed would present an explosion, 

serious overpressure or other safety hazard. Cytec has historically not considered the weighted 

manway to be an “open‐ended line or valve” because the definition of this equipment in 40 CFR 

63 Subpart TT specifically excludes “relief valves.” Alternatively, the commenter proposes to 

allow compliance with either 40 CFR 63 subpart UU or subpart TT for these devices, in addition 

to the connectors that already have this option.

Response 7.1.2: The EPA believes that the commenter may have mischaracterized the 

weighted manway on their storage tanks as a valve in vapor service. Based on the commenter’s 

description and conferring with storage tank inspectors within OECA, we believe that the 

manway most likely fits the description of a deck fitting on the storage tank, and not a valve or 

connector. If this is the case, the LDAR requirements and 500 ppm leak definition in subpart UU 

would not apply. See 57 FR 62660 (December 31, 1992) for additional information on manways 

and how they are addressed under LDAR provisions.

Comment 7.1.3: Commenter 41 points out the limits for existing solution polymerization 

sources are based on total organic HAP, whereas limits for new, reconstructed or existing 

suspension polymerization lines are based only on acrylonitrile. In addition, the commenter notes 

that the LDAR compliance requirements are inconsistent in that some are based on organic 

HAPs and some have only acrylonitrile limits. The commenter requests that these requirements 

be made consistent to reflect either organic HAP or acrylonitrile limits for all existing and new 

processes in the AMF source category and for all equipment services. The commenter adds that 
40

if the EPA decides to word the requirements in terms of organic HAP, the definition of “in 

organic HAP service” should be added to subpart YY, and should include “equipment that 

contains or contacts greater than or equal to 10 weight percent organic HAP” rather than the 

definition provided in subpart UU, which specifies 5 weight percent organic HAP.

Response 7.1.3: The EPA agrees with the commenter and has revised the final rule to 

consistently refer to organic HAP instead of strictly acrylonitrile. The EPA has also added the 

definition of “in organic HAP service” to the final rule, consistent with the definition used in 

both the HON and subpart UU. However, to be consistent with the rest of the AMF provisions, 

this definition includes the 10 weight percent threshold suggested by the commenter.

Comment 7.1.4: Commenter 31 agrees with the EPA’s conclusion to set the MACT floor 

at the current emissions limit for the one identified source in this category. The commenter also 

agrees with the EPA’s proposal to require monitoring under subpart UU, with the exception of 

connectors, provided the EPA also finalizes the proposed compliance timeline of one year for 

existing sources in 40 CFR 63.1102(b).

Response 7.1.4: We thank the commenter for this feedback.

7.2 Source Category Specific Comments – Amino/Phenolic Resins Production

Comment 7.2.1: Commenter 31 agrees with the EPA’s conclusion that the costs for 

Option 1 for APR storage vessels are reasonable. Commenter 37 concurs with the EPA that the 

options to increase the tank control efficiency requirements in subpart OOO to 95% or 98% are 

above the floor options, that the incremental costs per tank are $2400 and $2,200,000, 

respectively, and that these options should not be considered in the final rule due to the high 

costs and minimal incremental emissions reduction. Commenters 31 and 37 also agree with the 

EPA’s conclusion that the costs of either beyond-the-floor option for APR continuous process 

vents are not reasonable given the anticipated level of HAP emissions reductions achieved with 

the control options. 

Response 7.2.1: We thank the commenters for this feedback.

Comment 7.2.2: Commenter 46 requests that the EPA change the compliance date for 

the storage tank requirements to 3 years from the effective date of the final amendments rather 

than the effective date of the final amendments to allow facilities the necessary time to evaluate 

the need for and type of controls required for storage vessels in the APR source category, 

anticipating that, contrary to the EPA’s assumptions, some storage vessels may need to install 

controls. The commenter also suggests that facilities subject to subpart OOO voluntarily update 

the data in the 2005 NEI for storage vessels. 

Response 7.2.2: The EPA agrees with the commenter that three years some storage 

vessels may need to install controls and that therefore should be provided to identify and install 

any new controls required to comply with the revised storage vessel requirements. We have 

revised the final rule to reflect this.

Comment 7.2.3: Commenter 46 states that in the EPA’s beyond-the-floor analysis for 

continuous process vents, it assumed that facilities have the ability to treat scrubber wastewater 

on-site. However, the commenter states that this is not the case, and most affected facilities 

would need to send this waste to a wastewater treatment facility. The commenter believes the 

EPA should include these costs in its analysis. The commenter also notes that the wastewater 
41

treatment costs the EPA did include were inaccurate, in that it used a price from the EPA Control 

Cost Manual per 100 gallons of wastewater, but attributed this cost to each 1,000 gallons. The 

commenter asks that the EPA update its analysis to include the correct wastewater treatment 

costs.

Response 7.2.3: The EPA has revised its beyond-the-floor calculations to incorporate the 

new data submitted by the commenter. We note, however, that the “per 100 gallons of 

wastewater” that the commenter refers to is a typo on page 1-40 of the EPA Control Cost 

Manual. The example calculation on this page does not work if 100 gallons is used, and a 

correct reference to 1000 gallons is listed in a footnote on page 1-42.

Comment 7.2.4: Commenter 37 states that it has a facility, which is regulated by subpart 

OOO, but was mistakenly not included in the EPA analyses for that source category. The 

commenter provided the pertinent NEI data for the facility for the year 2011 and also a summary 

of the capacity and vapor pressure of the storage tanks regulated by subpart OOO. 

Response 7.2.4: The EPA thanks the commenter for identifying themselves as being 

subject to the APR MACT standards and has revised the final risk modeling file to include the 

commenter’s facility.

7.3 Source Category Specific Comments – Polycarbonate Production

Comment 7.3.1: Regarding the proposed revision to the PC equipment leak standards, 

commenter 31 concurs with the EPA’s proposal to require instrument monitoring under subpart 

UU, with the exception of connectors, provided the EPA also finalizes the proposed compliance 

timeline of one year for existing sources in 40 CFR 63.1102(b).

Response 7.3.1: We thank the commenter for this feedback.

7.4 Subpart Specific Comments – Subpart YY (GMACT)

Comment 7.4.1: Commenter 29 notes that subpart YY references subpart SS for its 

closed vent system and control device requirement for the AMF and PC source categories and 

requests that the EPA clarify whether or not the various SSM provisions, including the excused 

excursion provisions, of subpart SS apply to the AMF and PC source categories. The commenter 

suggests that a paragraph could be added to subpart YY to provide for any exceptions or 

alternatives to 40 CFR part 63, subpart SS.

Response 7.4.1: The EPA agrees with the commenter that the language of subpart YY 

should be clarified to explicitly state that the excused excursion language of subpart SS does not 

apply to AMF and PC source, in keeping with the SSM exemption removal for these source 

categories. Accordingly, we have revised 40 CFR 63.1108(b)(1) to clarify that excused 

excursions are not allowed for the AMF and PC source categories.

Comment 7.4.2: Commenter 42 requests that the EPA clarify that while several sections 

of the GMACT would be modified under this proposal, comments will be requested and 

considered on these provisions as if they were proposed for the first time if the EPA proposes to 

make these provisions applicable to any other source categories. The commenter also suggests 

that to make this clear in 40 CFR 63.1108(b)(4)(ii), the proposed sentences added to this 

paragraph that apply to the AMF and PC source categories be put in a separate paragraph.
42

Response 7.4.2: The EPA agrees with the commenter that opportunity to comment on 

revisions to other source categories regulated by the GMACT will be provided. With regard to 

the commenter’s suggestion for 40 CFR 63.1108(b)(4)(ii), we have revised this paragraph to 

clarify which provisions only apply to the AMF and PC source categories.

Comment 7.4.3: Commenter 29 states that similar to the requirements for ethylene 

sources in subpart YY, subpart YY should contain exclusions from the rule for certain equipment 

for the other source categories regulated by that subpart.

Response 7.4.3: The EPA disagrees that the suggested equipment should be exempted 

from the requirements of the AMF and PC MACT standards. The commenter failed to provide 

rationale for why this equipment should no longer be subject to the rule, and so the EPA has no 

basis for which to comply with the commenter’s suggestion.

Comment 7.4.3: Commenter 29 requests that the EPA clarify in 40 CFR 63.1103 Tables 

5 and 6 that halogen reduction device requirements for process vents only apply to halogenated 

vent streams that are combusted. The commenter also requests that the EPA correct an incorrect 

reference in Table 5, Item 5 to 40 CFR 63.982(e) and 63.993(c) rather than 40 CFR 63.990(c). 

The commenter notes that the requirements for a process vent or combined vent stream with a 

TRE greater than 2.7 but less than 4.0 should point to the monitoring requirements for absorbers, 

condensers, and carbon adsorbers used as final recovery devices to maintain the TRE rather than 

those used to meet a weight-percent emission reduction. The commenter adds that the reference 

in this item to 40 CFR 63.995(c) is not needed because it was intended to apply to other control 

devices needed to meet a weight-percent emission reduction rather than to maintain a TRE value.

Response 7.4.3: The EPA agrees with the commenter and has corrected the errors.

Comment 7.4.4: Commenter 29 requests that the EPA add overlap provisions to subpart 

YY for all source categories with equipment leaks that may potentially be subject to 40 CFR part 

60, subpart VVa. The commenter notes that overlap with subpart VVa is not addressed in subpart 

YY nor is overlap with subpart UU (which is referenced in YY) addressed in subpart VVa. The 

commenter also requests that for equipment that is subject to 40 CFR part 60, subpart VV or 

VVa but is not subject to the equipment leak provisions of subpart YY, an owner or operator 

may choose to comply with subpart YY for all such equipment in the process unit so long as 

connector monitoring is still performed according to subpart VVa.

Response 7.4.4: The EPA disagrees with the commenter that the EPA should provide 

overlap provisions for subpart VVa. As certain provisions of subpart VVa are currently stayed, 

we do not believe it is appropriate at this time to make any determinations regarding the 

equivalency of subpart VVa and the equipment leak provisions of subpart TT and UU (as 

referenced by subpart YY).

Comment 7.4.5: Commenter 29 requests that the EPA change all references to “a range” 

or “operating range” in subpart YY to “operating limit” when in reference to subpart SS. The 

commenter states that the term “operating limit” is more technically correct. The commenter also 

requests that the EPA revise 40 CFR 63.1107(e)(2)(i) and (ii) to say “as described in Method 21” 

rather than “as detected by Method 21.” The commenter states the suggested revised language 

appears to be the intent of the EPA.
43

Response 7.4.5: The EPA agrees with the commenter on Method 21 and the final rule 

reflects the commenter’s suggested language. With regards to “range” vs “limit,” we believe 

that the existing language in subpart YY is clear and does not need to be revised.

Comment 7.4.6: Commenter 29 requests that the EPA correct several citation errors. 

These include: in 40 CFR 63.1106(a)(11), change reference from 40 CFR 63.1110(a)(3) to 40 

CFR 63.1110(a)(4) for the Notification of Compliance Status requirements; in 40 CFR 

63.1106(a)(12), change reference from 40 CFR 63.1110(a)(4) to 40 CFR 63.1110(a)(5) for the 

Periodic Report requirements; in 40 CFR 63.1106(a)(13), change reference from 40 CFR 

63.139(e)(1)(ii) to 40 CFR 63.139(c)(1)(ii); and in 40 CFR 63.1106(c)(6), correct the apparent 

incorrect reference to 40 CFR 63.119(e)(1) or (e)(2).

Response 7.4.6: The EPA has corrected the identified errors in the final rule.

Comment 7.4.7: Commenter 33 requests that the EPA revise 40 CFR 63.1107(f)(1) to 

also list PRDs that “vent to a process” and suggests a rephrasing of the requirement to be less 

clumsy. The commenter suggests the provision state “A list of identification numbers for 

pressure relief devices that vent to a closed vent system and control device or to a process, under 

the provisions in paragraph (e)(4) of this section.” 

The commenter also requests that the EPA revise 40 CFR 63.1110(a) to clarify that the 

reports required in paragraph 40 CFR 63.1110(a)(9) are required in addition to the other reports 

required under 40 CFR 63.1110(a). The commenter also requests that the EPA clarify that there 

is only one Notification of Compliance Status (NOCS) required by 40 CFR 63.1110(d)(1) and 

not a separate one for PRDs. The commenter suggests that the NOCS for PRDs be designated a 

supplement to the NOCS, which would alleviate potential confusion, and one NOCS would 

continue to be required.

Response 7.4.7: The EPA agrees with the commenter and the final rule has been revised 

to reflect the commenter’s suggestions.
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8.0 Other Comments

Comment 8.1: Commenter 35 supports the additional provisions added to the rule for a 

more stringent LDAR program for the AMF and PC source categories, more stringent control 

thresholds for storage vessels at new sources in the APR source category and the establishment 

of standards for previously unregulated emission points in the AMF and APR source categories.

Commenter 37 supports the proposed clarification in 40 CFR 63.1413(a)(2) stating that 

representative conditions for performance tests do not include periods of startup or shutdown.

Response 8.1: We acknowledge the commenters’ support for these additional standards

and clarification of the standards. 

Comment 8.2: Commenters 31, 37, 42, and 46 state that they adopt and incorporate the 

comments of the SSM Coalition by reference. Commenters 33 and 37 state that they endorse the 

comments submitted by the ACC. 

Response 8.2: We have addressed all of the comments from ACC and the SSM Coalition.

Comment 8.3: Commenter 36 states that the EPA should create a community complaint 

mechanism that ensures citizen complaints concerning air pollution receive an immediate 

response, in which the EPA commits to initiate an investigation and provide a publicly available 

report of the investigation results, including whether it leads to an enforcement action, within 7 

days.

Response 8.3: The EPA takes citizen pollution complaints seriously and is committed to 

responding to complaints. We invite you to help us protect our nation's environment by 

identifying and reporting environmental violations. The EPA's Report an Environmental 

Violation website provides a way for you to report suspected environmental violations. 

(http://www.epa.gov/compliance/complaints/moreinfor.html)

Assuring compliance with our nation's environmental laws is one of EPA's primary

commitments. In carrying out this responsibility, we use many different approaches. One 

approach is to seek help from you by asking you to provide EPA with information about 

potentially harmful environmental activities in your communities and workplaces. Reports from 

the public have led to state and federal enforcement cases and ultimately served environmental 

protection well.

Comment 8.4: Commenter 36 asserts the EPA must prohibit routine flaring, set a cap to 

limit special flaring, ensure its efficiency and monitor flaring. The commenter claims that since 

the original MACT standards were set, the EPA now has substantial new information on flaring 

and its impacts (for example, EPA’s 2012 peer-reviewed study Parameters for Properly Designed 

and Operated Flares) and must apply this new information in this rulemaking. The commenter 

claims that the changes in flaring use and knowledge about flaring are developments that must be 

considered under CAA section 112(d)(6) and that flares without proper limits violates National 

Lime Association. The commenter further states that the EPA has provided no valid basis to 

distinguish between flares at facilities like refineries and chemical plants and the sources under 

review here, and the EPA must take action to apply the new data on flaring in his rulemaking. 

Considering the new information the EPA now has that flares are less efficient than previously 

understood, the EPA should consider prohibiting the use of flaring, ensure less reliance on 

flaring, requiring flare gas recovery systems, requiring improved flare monitoring and ensuring 

the proper operating parameters are set. The commenter also notes that there is evidence that 
45

reduced flaring saves money by capturing and rerouting hydrocarbons for reprocessing and use. 

Commenter 31 notes that they are unaware of any member facilities that use flares to control 

HAP emissions in any of the source categories.

Response 8.4: The EPA is not at this time making changes to the flare provisions for the 

source categories addressed in this action. It is likely that, rather than to take commenter 36’s 

suggestion to simply adopt new flare requirements in the final rule, we would need to undertake 

another round of proposed rulemaking and solicit comment on any amendments to the flare 

provisions for these NESHAP, in order to meet our procedural obligations under CAA section 

307(d).

As noted in the preamble to the proposed rule, the EPA has recently begun studying the 

performance of flares to control HAP emissions, as governed by the EPA’s General Provisions 

at 40 CFR 63.11(b), in other contexts outside of this rulemaking. See 79 FR 1715. Additionally, 

in the preamble the EPA also requested information such as: “Prevalence 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 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.” We note that commenter 36 has not provided us with any of 

the information requested for these specific source categories, and the information provided by 

commenter 31 indicates that none of the facilities in these source categories may use flares to 

control emissions subject to the AMF, PC, or APR MACT standards.

Therefore, we are not at this time prepared to finalize any changes to the currently 

applicable regulations pertaining to the performance of flares in the AMF, PC, and APR source 

categories, but we may explore whether to revise flare requirements in the future, if we conclude 

that new requirements are warranted and would be applicable to subject source categories.