7942 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 63 

[EPA–HQ–OAR–2024–0303; FRL–7623–01– 

OAR] 

RIN 2060–AU73 

National Emission Standards for 

Hazardous Air Pollutants: Chemical 

Manufacturing Area Sources 

Technology Review 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to establish 

a new area source category to address 

chemical manufacturing process units 

(CMPUs) using ethylene oxide (EtO). 

The EPA is proposing to list EtO in table 

1 to the National Emission Standards for 

Hazardous Air Pollutants (NESHAP) for 

Chemical Manufacturing Area Sources 

(referred to as the CMAS NESHAP in 

this document) and to add EtO-specific 

requirements to the CMAS NESHAP. 

The EPA is also proposing to add a 

fenceline monitoring program for EtO. 

In addition, the EPA is proposing new 

requirements for pressure vessels and 

pressure relief devices (PRDs). This 

proposal also presents the results of the 

EPA’s technology review of the CMAS 

NESHAP as required under the Clean 

Air Act (CAA). As part of this 

technology review, the EPA is proposing 

to add new leak detection and repair 

(LDAR) requirements to the CMAS 

NESHAP for equipment leaks in organic 

HAP service and heat exchange systems. 

The EPA is also proposing performance 

testing once every 5 years and to add 

provisions for electronic reporting. We 

estimate that the proposed amendments 

to the CMAS NESHAP, excluding the 

proposed EtO emission standards, 

would reduce hazardous air pollutant 

(HAP) emissions from emission sources 

by approximately 158 tons per year 

(tpy). Additionally, the proposed EtO 

emission standards are expected to 

reduce EtO emissions by approximately 

4.6 tpy. 

DATES: 

Comments. Comments must be 

received on or before March 24, 2025. 

Under the Paperwork Reduction Act 

(PRA), comments on the information 

collection provisions are best assured of 

consideration if the Office of 

Management and Budget (OMB) 

receives a copy of your comments on or 

before February 21, 2025. 

Public hearing: If anyone contacts us 

requesting a public hearing on or before 

January 27, 2025 we will hold a virtual 

public hearing. See SUPPLEMENTARY

INFORMATION for information on 

requesting and registering for a public 

hearing. 

ADDRESSES: You may send comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2024–0303, by any of the 

following methods: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Email: a-and-r-docket@epa.gov. 

Include Docket ID No. EPA–HQ–OAR– 

2024–0303 in the subject line of the 

message. 

• Fax: (202) 566–9744. Attention 

Docket ID No. EPA–HQ–OAR–2024– 

0303. 

• Mail: U.S. Environmental 

Protection Agency, EPA Docket Center, 

Docket ID No. EPA–HQ–OAR–2024– 

0303, Mail Code 28221T, 1200 

Pennsylvania Avenue NW, Washington, 

DC 20460. 

• Hand/Courier Delivery: EPA Docket 

Center, WJC West Building, Room 3334, 

1301 Constitution Avenue NW, 

Washington, DC 20004. The Docket 

Center’s hours of operation are 8:30 

a.m.–4:30 p.m., Monday–Friday (except 

Federal Holidays). 

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

SUPPLEMENTARY INFORMATION section of 

this document. 

FOR FURTHER INFORMATION CONTACT: For 

questions about this proposed action, 

contact U.S. EPA, Attn: Mr. William 

Gallagher, Mail Drop: E143–01, 109 

T.W. Alexander Drive, P.O. Box 12055, 

RTP, North Carolina 27711; telephone 

number: (919) 541–2336; and email 

address: gallagher.william@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Participation in virtual public hearing. 

To request a virtual public hearing, 

contact the public hearing team at (888) 

372–8699 or by email at 

SPPDpublichearing@epa.gov. If 

requested, the hearing will be held via 

virtual platform. The EPA will 

announce the date of the hearing and 

further details at https://www.epa.gov/ 

stationary-sources-air-pollution/ 

chemical-manufacturing-area-sourcesnational-emission-standards. The 

hearing will convene at 11:00 a.m. 

Eastern Time (ET) and will conclude at 

4:00 p.m. ET. The EPA may close a 

session 15 minutes after the last preregistered speaker has testified if there 

are no additional speakers. 

The EPA will begin pre-registering 

speakers for the hearing no later than 1 

business day after a request has been 

received. To register to speak at the 

virtual hearing, please use the online 

registration form available at https://

www.epa.gov/stationary-sources-airpollution/chemical-manufacturing-areasources-national-emission-standards or 

contact the public hearing team at (888) 

372–8699 or by email at 

SPPDpublichearing@epa.gov. The last 

day to pre-register to speak at the 

hearing will be February 3, 2025. Prior 

to the hearing, the EPA will post a 

general agenda that will list preregistered speakers at: https://

www.epa.gov/stationary-sources-airpollution/chemical-manufacturing-areasources-national-emission-standards. 

The EPA will make every effort to 

follow the schedule as closely as 

possible on the day of the hearing; 

however, please plan for the hearings to 

run either ahead of schedule or behind 

schedule. 

Each commenter will have 4 minutes 

to provide oral testimony. The EPA 

encourages commenters to submit a 

copy of their oral testimony as written 

comments to the rulemaking docket. 

The EPA may ask clarifying questions 

during the oral presentations, but will 

not respond to the presentations at that 

time. Written statements and supporting 

information submitted during the 

comment period will be considered 

with the same weight as oral testimony 

and supporting information presented at 

the public hearing. 

Please note that any updates made to 

any aspect of the hearing will be posted 

online at https://www.epa.gov/ 

stationary-sources-air-pollution/ 

chemical-manufacturing-area-sourcesnational-emission-standards. While the 

EPA expects the hearing to go forward 

as set forth above, please monitor these 

websites or contact the public hearing 

team at (888) 372–8699 or by email at 

SPPDpublichearing@epa.gov to 

determine if there are any updates. The 

EPA does not intend to publish a 

document in the Federal Register 

announcing updates. 

If you require the services of a 

translator or a special accommodation 

such as audio description, please preregister for the hearing with the public 

hearing team and describe your needs 

by January 29, 2025. The EPA may not 

be able to arrange accommodations 

without advanced notice. 

Docket. The EPA has established a 

docket for this rulemaking under Docket 

ID No. EPA–HQ–OAR–2024–0303. All 


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Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7943 

documents in the docket are listed in 

https://www.regulations.gov/. Although 

listed, some information is not publicly 

available, e.g., Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the internet and will be publicly 

available only in hard copy. With the 

exception of such material, publicly 

available docket materials are available 

electronically in https://

www.regulations.gov/. 

Instructions. Direct your comments to 

Docket ID No. EPA–HQ–OAR–2024– 

0303. The EPA’s policy is that all 

comments received will be included in 

the public docket without change and 

may be made available online at https:// 

www.regulations.gov/, including any 

personal information provided, unless 

the comment includes information 

claimed to be CBI or other information 

whose disclosure is restricted by statute. 

Do not submit electronically to https:// 

www.regulations.gov/ any information 

that you consider to be CBI or other 

information whose disclosure is 

restricted by statue. This type of 

information should be submitted as 

discussed below. 

The EPA may publish any comment 

received to its public docket. 

Multimedia submissions (audio, video, 

etc.) must be accompanied by a written 

comment. The written comment is 

considered the official comment and 

should include discussion of all points 

you wish to make. The EPA will 

generally not consider comments or 

comment contents located outside of the 

primary submission (i.e., on the Web, 

cloud, or other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. 

The https://www.regulations.gov/ 

website allows you to submit your 

comment anonymously, which means 

the EPA will not know your identity or 

contact information unless you provide 

it in the body of your comment. If you 

send an email comment directly to the 

EPA without going through https://

www.regulations.gov/, your email 

address will be automatically captured 

and included as part of the comment 

that is placed in the public docket and 

made available on the internet. If you 

submit an electronic comment, the EPA 

recommends that you include your 

name and other contact information in 

the body of your comment and with any 

digital storage media you submit. If the 

EPA cannot read your comment due to 

technical difficulties and cannot contact 

you for clarification, the EPA may not 

be able to consider your comment. 

Electronic files should not include 

special characters or any form of 

encryption and be free of any defects or 

viruses. For additional information 

about the EPA’s public docket, visit the 

EPA Docket Center homepage at https:// 

www.epa.gov/dockets. 

Submitting CBI. Do not submit 

information containing CBI to the EPA 

through https://www.regulations.gov/. 

Clearly mark the part or all of the 

information that you claim to be CBI. 

For CBI information on any digital 

storage media that you mail to the EPA, 

note the docket ID, mark the outside of 

the digital storage media as CBI, and 

identify electronically within the digital 

storage media the specific information 

that is claimed as CBI. In addition to 

one complete version of the comments 

that includes information claimed as 

CBI, you must submit a copy of the 

comments that does not contain the 

information claimed as CBI directly to 

the public docket through the 

procedures outlined in Instructions 

above. If you submit any digital storage 

media that does not contain CBI, mark 

the outside of the digital storage media 

clearly that it does not contain CBI and 

note the docket ID. Information not 

marked as CBI will be included in the 

public docket and the EPA’s electronic 

public docket without prior notice. 

Information marked as CBI will not be 

disclosed except in accordance with 

procedures set forth in 40 Code of 

Federal Regulations (CFR) part 2. 

Our preferred method to receive CBI 

is for it to be transmitted electronically 

using email attachments, File Transfer 

Protocol (FTP), or other online file 

sharing services (e.g., Dropbox, 

OneDrive, Google Drive). Electronic 

submissions must be transmitted 

directly to the Office of Air Quality 

Planning and Standards (OAQPS) CBI 

Office at the email address oaqpscbi@

epa.gov and, as described above, should 

include clear CBI markings and note the 

docket ID. If assistance is needed with 

submitting large electronic files that 

exceed the file size limit for email 

attachments, and if you do not have 

your own file sharing service, please 

email oaqpscbi@epa.gov to request a file 

transfer link. If sending CBI information 

through the postal service, please send 

it to the following address: U.S. EPA, 

Attn: OAQPS Document Control Officer, 

Mail Drop: C404–02, 109 T.W. 

Alexander Drive, P.O. Box 12055, RTP, 

North Carolina 27711, Attention Docket 

ID No. EPA–HQ–OAR–2024–0303. The 

mailed CBI material should be double 

wrapped and clearly marked. Any CBI 

markings should not show through the 

outer envelope. 

Preamble acronyms and 

abbreviations. Throughout this 

preamble the use of ‘‘we,’’ ‘‘us,’’ or 

‘‘our’’ is intended to refer to the EPA. 

We use multiple acronyms and terms in 

this preamble. While this list may not be 

exhaustive, to ease the reading of this 

preamble and for reference purposes, 

the EPA defines the following terms and 

acronyms here: 

ACC American Chemistry Council 

ACS American Community Survey 

ADAF age-dependent adjustment factor 

AFPM American Fuels and Petrochemical 

Manufacturers 

APCD air pollution control device 

API American Petroleum Institute 

AVO audio, visual, and olfactory 

BACT best available control technology 

CAA Clean Air Act 

CBI Confidential Business Information 

CEDRI Compliance and Emissions Data 

Reporting Interface 

CFR Code of Federal Regulations 

CMAS Chemical Manufacturing Area 

Source(s) 

CMPU chemical manufacturing process 

unit 

CO carbon monoxide 

CO2 carbon dioxide 

EAV equivalent annualized value 

EFR external floating roof 

EIS Emissions Inventory System 

EJ environmental justice 

EMACT Ethylene Production MACT 

EPA Environmental Protection Agency 

ERT Electronic Reporting Tool 

EtO ethylene oxide 

FID flame ionization detector 

FR Federal Register 

GACT generally available control 

technologies 

HAP hazardous air pollutant(s) 

HON Hazardous Organic NESHAP 

HQ hazard quotient 

HRVOC highly reactive volatile organic 

compound 

ICR information collection request 

IFR internal floating roof 

IRIS Integrated Risk Information System 

km kilometer(s) 

kPa kilopascal(s) 

LAER lowest achievable emission rate 

lb pound(s) 

lb/yr pound(s) per year 

LDAR leak detection and repair 

MACT maximum achievable control 

technology 

MIR maximum individual lifetime [cancer] 

risk 

MON Miscellaneous Organic Chemical 

Manufacturing NESHAP 

MTVP maximum true vapor pressure 

NAICS North American Industry 

Classification System 

NATA National Air Toxics Assessment 

NEI National Emissions Inventory 

NESHAP national emission standards for 

hazardous air pollutants 

NOX nitrogen oxides 

N2O nitrous oxide 


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7944 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

NPRA National Petrochemical and Refiners 

Association 

NSPS new source performance standards 

OAQPS Office of Air Quality Planning and 

Standards 

OAR Office of Air and Radiation 

OLD Organic Liquids Distribution 

OMB Office of Management and Budget 

P&R I Group I Polymers and Resins 

PDF portable document format 

PEPO Polyether Polyols Production 

PM2.5 particulate matter 2.5 

PMPU polyether polyol manufacturing 

process unit 

ppmv parts per million by volume 

ppmw parts per million by weight 

PRA Paperwork Reduction Act 

PRD pressure relief device 

PV present value 

RACT reasonably available control 

technology 

RDL representative detection limit 

RFA Regulatory Flexibility Act 

RTR risk and technology review 

SOCMI Synthetic Organic Chemical 

Manufacturing Industry 

SO2 sulfur dioxide 

TCEQ Texas Commission on Environmental 

Quality 

TOC total organic compounds 

TOSHI target organ-specific hazard index 

tpy tons per year 

TRE total resource effectiveness 

UMRA Unfunded Mandates Reform Act 

U.S.C. United States Code 

VCS voluntary consensus standards 

VOC volatile organic compound(s) 

mg/m3 micrograms per cubic meter 

Organization of this document. The 

information in this preamble is 

organized as follows: 

I. General Information 

A. Does this action apply to me? 

B. Where can I get a copy of this document 

and other related information? 

II. Background 

A. What is the statutory authority for this 

action? 

B. What are the source categories and how 

does the current NESHAP regulate HAP 

emissions? 

C. What data collection activities were 

conducted to support this action? 

D. What other relevant background 

information and data are available? 

E. What are the results of the EPA’s risk 

assessment? 

III. Analytical Procedures and DecisionMaking 

A. How do we determine GACT? 

B. How do we perform the technology 

review? 

IV. Analytical Results and Proposed 

Decisions 

A. What are our proposed decisions 

regarding standards representing GACT 

for EtO emissions from CMAS, and what 

is the rationale for those decisions? 

B. What are our other proposed decisions 

regarding GACT standards for CMAS, 

and what is the rationale for those 

decisions? 

C. What are the results and proposed 

decisions based on our technology 

review, and what is the rationale for 

those decisions? 

D. What other actions are we proposing, 

and what is the rationale for those 

actions? 

E. What compliance dates are we 

proposing, and what is the rationale for 

the proposed compliance dates? 

V. Summary of Cost, Environmental, and 

Economic Impacts 

A. What are the affected sources? 

B. What are the air quality impacts? 

C. What are the cost impacts? 

D. What are the economic impacts? 

E. What are the benefits? 

F. What analysis of environmental justice 

did we conduct? 

G. What analysis of children’s 

environmental health did we conduct? 

VI. Request for Comments 

VII. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

B. Paperwork Reduction Act (PRA) 

C. Regulatory Flexibility Act (RFA) 

D. Unfunded Mandates Reform Act 

(UMRA) 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer and 

Advancement Act (NTTAA) and 1 CFR 

Part 51 

J. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations and Executive Order 14096: 

Revitalizing Our Nation’s Commitment 

to Environmental Justice for All 

I. General Information 

A. Does this action apply to me? 

The source categories that are the 

subject of this proposal are Agricultural 

Chemicals and Pesticides 

Manufacturing, Chemical 

Manufacturing with Ethylene Oxide, 

Cyclic Crude and Intermediate 

Production, Industrial Inorganic 

Chemical Manufacturing, Industrial 

Organic Chemical Manufacturing, 

Inorganic Pigments Manufacturing, 

Miscellaneous Organic Chemical 

Manufacturing, Plastic Materials and 

Resins Manufacturing, Pharmaceutical 

Production, and Synthetic Rubber 

Manufacturing, regulated under 40 CFR 

part 63, subpart VVVVVV. The North 

American Industry Classification 

System (NAICS) code for the chemical 

manufacturing operations at any of the 

ten chemical manufacturing area source 

(CMAS) categories is 325. This list of 

categories and NAICS codes is not 

intended to be exhaustive, but rather 

provides a guide for readers regarding 

the entities that this proposed action is 

likely to affect. The proposed standards, 

once promulgated, will be directly 

applicable to the affected sources. 

Federal, state, local, and Tribal 

government entities would not be 

affected by this proposed action. We 

listed Cyclic Crude and Intermediate 

Production, Industrial Inorganic 

Chemical Manufacturing, Industrial 

Organic Chemical Manufacturing, 

Plastic Materials and Resins 

Manufacturing, and Synthetic Rubber 

Manufacturing as area source categories 

under CAA section 112(c)(3) as part of 

the 1999 Integrated Urban Air Toxics 

Strategy (64 FR 38721, July 19, 1999). 

On June 26, 2002, we amended the area 

source category list by adding source 

categories, including Agricultural 

Chemicals and Pesticides 

Manufacturing, Miscellaneous Organic 

Chemical Manufacturing, and 

Pharmaceutical Production (67 FR 

43112, 43113). On November 22, 2002, 

we added Inorganic Pigments 

Manufacturing to the area source 

category list (67 FR 70427, 70428). In 

this action, we are proposing to amend 

the area source category list by adding 

Chemical Manufacturing with Ethylene 

Oxide (see section II.A.1 of this 

preamble). The other nine CMAS 

categories are discussed further in 

section II.B of this preamble. 

B. Where can I get a copy of this 

document and other related 

information? 

In addition to being available in the 

docket, an electronic copy of this action 

is available on the internet. In 

accordance with 5 U.S.C. 553(b)(4), a 

summary of this rulemaking may be 

found at https://www.regulations.gov/, 

Docket ID No. EPA–HQ–OAR–2024– 

0303. Following signature by the EPA 

Administrator, the EPA will post a copy 

of this proposed action at https://

www.epa.gov/stationary-sources-airpollution/chemical-manufacturing-areasources-national-emission-standards. 

Following publication in the Federal 

Register, the EPA will post the Federal 

Register version of the proposal and key 

technical documents at this same 

website. 

A memorandum showing the edits 

that would be necessary to incorporate 

the changes to the CMAS NESHAP (40 

CFR part 63, subpart VVVVVV) 

proposed in this action is available in 

the docket (Docket ID No. EPA–HQ– 

OAR–2024–0303). Following signature 

by the EPA Administrator, the EPA also 

will post a copy of this document to 

https://www.epa.gov/stationary-sourcesair-pollution/chemical-manufacturingVerDate Sep<11>2014 20:27 Jan 21, 2025 Jkt 265001 PO 00000 Frm 00004 Fmt 4701 Sfmt 4702 E:\FR\FM\22JAP2.SGM 22JAP2

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1See 74 FR 56008, October 29, 2009. 

2The review is available at https://iris.epa.gov/ 

static/pdfs/1025tr.pdf. 3The report is available at https://

www.epaoig.gov/sites/default/files/2021-05/ 

documents/_epaoig_20210506-21-p-0129.pdf. 

4For additional details on these facilities, please 

see the document titled Risk Assessment for the 

Chemical Manufacturing Area Source (CMAS) 

Categories in Support of the 2025 Technology 

Review for the Proposed Rule in the docket for this 

action. 

area-sources-national-emissionstandards. 

II. Background 

A. What is the statutory authority for 

this action? 

The statutory authority for this action 

is provided by sections 112 and 301 of 

the CAA, as amended (42 U.S.C. 7401 et 

seq.). Several CAA sections are relevant 

to this action as they specifically 

address regulations of HAP emissions 

from area sources. Collectively, CAA 

sections 112(c)(3), (d)(5), and (k)(3) are 

the basis of the Area Source Program 

under the Urban Air Toxics Strategy, 

which provides the framework for 

regulation of area sources under CAA 

section 112. Section 112(k)(3)(B) of the 

CAA requires the EPA to identify at 

least 30 HAP that pose the greatest 

potential health threat in urban areas 

with a primary goal of achieving a 75 

percent reduction in cancer incidence 

attributable to HAP emitted from 

stationary sources. As discussed in the 

Integrated Urban Air Toxics Strategy (64 

FR 38706, 38715, July 19, 1999), the 

EPA identified 30 HAP emitted from 

area sources that pose the greatest 

potential health threat in urban areas, 

and these HAP are commonly referred 

to as the ‘‘30 urban HAP.’’ CAA section 

112(c)(3), in turn, requires the EPA to 

list sufficient categories or subcategories 

of area sources to ensure that area 

sources representing 90 percent of the 

emissions of the 30 urban HAP are 

subject to regulation. The EPA 

implemented these requirements 

through the Integrated Urban Air Toxics 

Strategy by identifying and setting 

standards for categories of area sources 

including the original nine CMAS 

categories that are addressed in this 

action. This proposed action presents 

the required CAA 112(d)(6) technology 

review of the generally available control 

technology (GACT) standards that the 

EPA established in 2009 1 for the nine 

CMAS categories. In this action, we are 

also proposing to set additional GACT 

standards for these categories. In 

addition to the source categories and 

subcategories listed pursuant to CAA 

section 112(c)(3), CAA section 112(c)(5) 

provides the EPA discretion to establish 

additional categories and subcategories 

of sources for regulation if a threat of 

adverse effects to human health or the 

environment is identified, per the 

criteria set forth in CAA section 

112(c)(1) and (3). Pursuant to CAA 

section 112(c)(5), and consistent with 

the requirements of CAA section 

112(c)(3), this action also proposes for 

regulation as part of the CMAS NESHAP 

a new area source category, Chemical 

Manufacturing with Ethylene Oxide, 

and proposes GACT standards for that 

new source category pursuant to CAA 

section 112(d)(5). Information about 

establishing a new area source category 

for regulation pursuant to CAA section 

112(c)(3) and (5), setting GACT 

standards under CAA section 112(d)(5), 

and reviewing standards under CAA 

section 112(d)(6) are provided in 

sections II.A.1, II.A.2, and II.A.3 of this 

preamble, respectively. 

1. Listing An Additional Category Under 

CAA Section 112(c)(5) 

CAA section 112(c)(5) provides that 

‘‘the Administrator may at any time list 

additional categories and subcategories 

of sources of hazardous air pollutants 

according to the same criteria for listing 

applicable under [CAA section 112(c)(1) 

and (3)].’’ CAA 112(c)(3), in turn, 

provides in part that ‘‘[t]he 

Administrator shall list . . . each 

category or subcategory of area sources 

which the Administrator finds presents 

a threat of adverse effects to human 

health or the environment (by such 

sources individually or in the aggregate) 

warranting regulation under this 

section.’’ 

In 2016, the EPA updated the 

integrated risk information system (IRIS) 

value for EtO to reflect new science 

related to the pollutant.2 The updated 

IRIS value indicates that EtO is far more 

carcinogenic than previously 

understood. In response to this update, 

the EPA Office of Inspector General 

(OIG) released a report in 2021 using 

data from the 2014 National Air Toxics 

Assessment (NATA) identifying 

facilities that could present lifetime 

cancer risks to the public greater than or 

equal to 100-in-1 million.3 Several of 

these facilities were area source 

chemical manufacturers. Based on the 

revised carcinogenicity of EtO, the EPA 

decided to assess whether EtO 

emissions from CMAS should be listed 

as an area source category pursuant to 

CAA section 112(c)(3) and (5). 

EtO is not one of the fifteen urban 

HAP currently regulated by the CMAS 

NESHAP. Therefore, to fully assess 

whether a source category including EtO 

emissions from area source chemical 

manufacturing operations presents an 

adverse effect to human health or the 

environment, facilities not currently 

part of the nine regulated source 

categories were considered. To that end, 

we conducted a risk assessment 

evaluating all reported HAP emissions 

from sources currently subject to the 

CMAS NESHAP as well as sources that 

we believe would become subject to the 

CMAS NESHAP if EtO were to be added 

to table 1 to 40 CFR part 63, subpart 

VVVVVV. The results of the risk 

assessment are summarized in section 

II.E of this preamble. Based on the 

assessment, seven area source chemical 

manufacturing facilities were estimated 

to have maximum cancer risks greater 

than 100-in-1 million, all of which were 

driven primarily (greater than 90 

percent) by EtO emissions.4 The 

maximum individual lifetime [cancer] 

risk (MIR) posed by the evaluated 

sources is 800-in-1 million, driven by 

EtO emissions from process vents (97 

percent). 

Given these estimates of risk, we 

propose that an area source category 

associated with EtO emissions from area 

source chemical manufacturers presents 

a threat of adverse effect on human 

health. Accordingly, consistent with 

CAA section 112(c)(3) and (5), we are 

proposing to list a new area source 

category. This area source category, 

Chemical Manufacturing with Ethylene 

Oxide, would encompass processes that 

produce a material or family of 

materials described by NAICS code 325 

where EtO is used as a feedstock, 

generated as a byproduct, or is the 

material produced. This proposed 

source category matches the scope of the 

nine source categories currently 

regulated by the CMAS NESHAP, as 

described in section II.B of this 

preamble. Since the existing CMAS 

NESHAP currently regulates these nine 

area source categories collectively, we 

are proposing to also regulate the new 

Chemical Manufacturing with Ethylene 

Oxide area source category under the 

CMAS NESHAP at 40 CFR part 63, 

subpart VVVVVV. Alongside the listing 

of this new area source category, the 

EPA is proposing to add EtO specific 

applicability requirements at 40 CFR 

63.11494(a)(2)(v) and to list EtO in table 

1 to 40 CFR part 63, subpart VVVVVV. 

In conjunction with proposing to 

establish a new area source category for 

Chemical Manufacturing with Ethylene 

Oxide, the EPA must establish the level 

of control for the source category. 

Section II.A.2 provides details on our 

authority to establish GACT standards 

pursuant to CAA section 112(d)(5) in 

lieu of maximum achievable control 


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5The EPA also considers the costs and economic 

impacts of available control technologies and 

management practices when determining whether 

to revise a standard pursuant to section 112(d)(6); 

and the EPA also considers costs, energy, and other 

relevant factors when determining whether to revise 

a standard in the second step of the ample margin 

of safety analysis pursuant to CAA section 

112(f)(2)(A). 

6On June 1, 2022, the EPA, in response to the 

OIG’s report stating that EPA should revise the 

CMAS NESHAP to regulate EtO and conduct a 

residual risk review, stated: ‘‘. . . technology-based 

standards for EtO have not yet been established for 

the CMAS source category. Therefore, we plan to 

first evaluate EtO emissions from the source 

category, and if EtO emissions present a public 

health concern (i.e., by considering risk 

information), we will regulate EtO in the CMAS 

rule . . . However, within four years of 

promulgation (enough time to understand the level 

of emissions remaining after implementation of new 

standards) of an any initial EtO standards for 

CMAS, EPA would assess the risks from EtO 

emissions from CMAS sources to inform us on 

whether an earlier review date is appropriate.’’ 

Refer to https://www.epaoig.gov/sites/default/files/ 

documents/2022-06/_epaoig_21-P-0129_Agency_

Response2.pdf for additional details. 

technology (MACT) standards pursuant 

to CAA section 112(d)(2) and (3). 

2. Alternative Standards for Area 

Sources Under CAA Section 112(d)(5) 

Under CAA section 112(d)(5), the EPA 

may elect to promulgate standards or 

requirements for area sources ‘‘which 

provide for the use of generally 

available control technologies or 

management practices by such sources 

to reduce emissions of hazardous air 

pollutants.’’ Additional information on 

GACT or management practices is found 

in the Senate report on the legislation 

(Senate report Number 101–228, 

December 20, 1989), which describes 

GACT as ‘‘. . . methods, practices and 

techniques which are commercially 

available and appropriate for 

application by the sources in the 

category considering economic impacts 

and the technical capabilities of the 

firms to operate and maintain the 

emissions control systems.’’ 

Consistent with the legislative history, 

we can consider costs and economic 

impacts in determining GACT. 

Determining what constitutes GACT 

involves considering the control 

technologies and management practices 

that are generally available to the area 

sources in the source category. As 

previously mentioned, GACT standards 

were set for the CMAS categories in 

2009. These GACT standards are 

discussed in section IV.C of this 

preamble. See section II.B of this 

preamble for details about each of the 

nine currently regulated CMAS 

categories. 

In this action, we are proposing to set 

additional GACT standards for the 

CMAS categories that would apply to 

certain emission sources (i.e., 

equipment leaks, heat exchange 

systems, process vents, storage tanks, 

wastewater, and transfer operations) 

associated with the proposed area 

source category, Chemical 

Manufacturing with Ethylene Oxide. In 

addition, we are proposing to set GACT 

standards for pressure vessels and PRDs. 

The proposed GACT standards are 

discussed in sections IV.A and IV.B of 

this preamble. In setting GACT, we 

always look to the standards applicable 

to major sources in the same industrial 

sector to determine if the control 

technologies and management practices 

are transferable and generally available 

to area sources. In appropriate 

circumstances, we may also consider 

technologies and practices at area and 

major sources in similar categories to 

determine whether such technologies 

and practices could be considered 

generally available for the area source 

category at issue. In this case, the 

control technologies and management 

practices for process units are 

transferable because process units at 

major source chemical manufacturing 

facilities are essentially no different 

than process units at area source 

chemical manufacturing facilities 

excepting that the former exceeds the 

major source HAP thresholds with 

respect to emissions and the latter does 

not. Finally, as we have already noted, 

in determining GACT for a particular 

area source category, we consider the 

costs and economic impacts of available 

control technologies and management 

practices on that category. 

GACT differs from MACT in that cost 

can be considered in the first instance 

when establishing a GACT standard. By 

contrast, when establishing MACT 

standards pursuant to CAA section 

112(d)(3), the EPA must determine the 

average emission limitation achieved by 

the best performing 12 percent of 

existing sources (or average emission 

limitation achieved by the best 

performing 5 sources for existing 

sources with fewer than 30 sources) and 

the emission limitation achieved by the 

best controlled similar source for new 

sources, without regard to cost. 

As explained in greater detail in 

sections IV.A and IV.B of this preamble, 

we determined that the GACT standards 

we are proposing for sources emitting 

EtO (i.e., GACT standards for equipment 

leaks, heat exchange systems, process 

vents, storage tanks, wastewater, and 

transfer operations) located at CMAS, 

and the GACT standards we are 

proposing for pressure vessels and PRDs 

at these same area sources, should be 

similar, if not the same, as the major 

source standards that were finalized in 

the Miscellaneous Organic Chemical 

Manufacturing NESHAP (MON) and 

Hazardous Organic NESHAP (HON) 

pursuant to CAA section 112(d)(6) and 

(f) (see 85 FR 49084, August 12, 2020 

and 89 FR 42932, May 16, 2024, 

respectively). Our rationale for this is 

based on the similarities between 

production processes, emission points, 

emissions, and control technologies that 

are characteristic of both major and area 

source chemical manufacturing facilities 

and considerations of cost.5

We note that if standards for EtO are 

finalized, the EPA has committed to the 

Office of the Inspector General (OIG) to 

assess the risk posed from EtO emission 

sources subject to the CMAS NESHAP. 

Specifically, the EPA committed to 

assess risk within four years of 

promulgation of standards. At that time, 

the EPA would determine if it is 

appropriate to review the standards 

prior to the date required by CAA 

section 112(d)(6) (i.e., 8 years).6

3. Technology Review Under CAA 

Section 112(d)(6) 

CAA section 112(d)(6) requires the 

EPA to review standards promulgated 

under CAA section 112(d) and revise 

them ‘‘as necessary (taking into account 

developments in practices, processes, 

and control technologies)’’ no less often 

than every 8 years following 

promulgation of those standards. This is 

referred to as a ‘‘technology review’’ and 

is required for all standards established 

under CAA section 112(d) including 

GACT standards that apply to area 

sources. 

As previously mentioned, GACT 

standards were set for the CMAS 

categories in 2009. Although in this 

action we are proposing additional 

GACT standards for these categories, 

this proposed action also presents the 

required CAA 112(d)(6) technology 

review of the 2009 GACT standards for 

these source categories. 

B. What are the source categories and 

how does the current NESHAP regulate 

HAP emissions? 

The EPA promulgated the CMAS 

NESHAP on October 29, 2009 (74 FR 

56008), and codified the NESHAP at 40 

CFR part 63, subpart VVVVVV. As 

promulgated in 2009, and further 

amended on December 21, 2012 (77 FR 

75740), the CMAS NESHAP regulates 

HAP emissions from chemical 

manufacturing process units at an area 

source of HAP emissions if HAP listed 

in table 1 to 40 CFR part 63, subpart 

VVVVVV are present in the CMPU. A 

CMPU includes all process vessels, 

equipment, and activities necessary to 


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7Except for: (1) processes classified in NAICS 

Code 325222, 325314, 325413, or 325998; (2) 

processes subject to standards for other listed area 

source categories in NAICS 325; (3) certain 

fabricating operations; (4) manufacture of 

photographic film, paper, and plate where material 

is coated or contains chemicals (but the 

manufacture of the photographic chemicals is 

regulated); and (5) manufacture of radioactive 

elements or isotopes, radium chloride, radium 

luminous compounds, strontium, and uranium. 

8Feedstocks are reactants, solvents, or any other 

additives to the process. 

9 ‘‘Table 1’’ refers to table 1 to 40 CFR part 63, 

subpart VVVVVV. 

operate a chemical manufacturing 

process that produces a material or a 

family of materials described by NAICS 

code 325.7 A CMPU consists of one or 

more unit operations and any associated 

recovery devices. A CMPU also includes 

each storage tank, transfer operation, 

surge control vessel, and bottoms 

receiver associated with the production 

of such NAICS code 325 materials. The 

affected source is the facility-wide 

collection of CMPUs and each heat 

exchange system and wastewater system 

associated with a CMPU. 

The CMAS NESHAP currently applies 

to chemical manufacturing operations at 

nine area source categories: (1) 

Agricultural Chemicals and Pesticides 

Manufacturing; (2) Cyclic Crude and 

Intermediate Production; (3) Industrial 

Inorganic Chemical Manufacturing; (4) 

Industrial Organic Chemical 

Manufacturing; (5) Inorganic Pigments 

Manufacturing; (6) Miscellaneous 

Organic Chemical Manufacturing; (7) 

Plastic Materials and Resins 

Manufacturing; (8) Pharmaceutical 

Production; and (9) Synthetic Rubber 

Manufacturing. These nine CMAS 

categories encompass facilities that use 

as feedstocks,8 generate as byproducts, 

or produce as products any of the 

following 15 HAP: 1,3-butadiene; 1,3- 

dichloropropene; acetaldehyde; 

chloroform; ethylene dichloride; 

hexachlorobenzene; methylene chloride; 

quinoline (these eight HAP are referred 

to as the ‘‘Table 1 9 organic HAP’’); 

compounds of arsenic, cadmium, 

chromium, lead, manganese, or nickel 

(these six HAP are referred to as the 

‘‘Table 1 metal HAP’’); or hydrazine. In 

this preamble we refer to the nine 

source categories collectively as CMAS 

categories (we are also proposing a tenth 

source category as discussed in section 

II.A.1 of this preamble). Descriptions of 

the nine source categories are as 

follows: 

Agricultural Chemicals and Pesticides 

Manufacturing. The agricultural 

chemicals and pesticides manufacturing 

source category is designated by NAICS 

codes 325311 (nitrogenous fertilizer 

manufacturing), 325312 (phosphatic 

fertilizer manufacturing), and 325320 

(pesticide and other agricultural 

chemical manufacturing). Products of 

this industry include nitrogenous and 

phosphatic fertilizer materials including 

anhydrous ammonia, nitric acid, 

ammonium nitrate, ammonium sulfate, 

urea, phosphoric acid, superphosphates, 

ammonium phosphates, and calcium 

metaphosphates. The source category 

also includes the formulation and 

preparation of ready-to-use agricultural 

and household pest control chemicals 

from technical chemicals or 

concentrates, the production of 

concentrates which require further 

processing before use as agricultural 

pesticides, and the manufacturing or 

formulating of other agricultural 

chemicals such as minor or trace 

elements and soil conditioners. 

Organic Chemical Production. The 

cyclic crude and intermediate 

production, industrial organic chemical 

manufacturing, and miscellaneous 

organic chemical manufacturing source 

categories are discussed collectively 

because there is considerable overlap in 

the NAICS codes that apply to these 

source categories. These source 

categories include cellulosic organic 

fiber manufacturing as well as other 

source categories that are designated by 

NAICS codes 32511 (petrochemical 

manufacturing), 325130 (synthetic dye 

and pigment manufacturing), 32519 

(other basic organic chemical 

manufacturing), and 3256 (soap, 

cleaning compound, and toilet 

preparation manufacturing). The source 

category also includes organic gases 

designated by NAICS code 325120 

(industrial gas manufacturing), and it 

includes production of chemicals such 

as explosives and photographic 

chemicals designated by NAICS code 

3259 (other chemical product and 

preparation manufacturing). Raw 

materials for this industry include, for 

example, refined petroleum chemicals, 

coal tars, and wood. The industry 

manufactures a wide variety of final 

products as well as numerous chemicals 

that are used as feedstocks to produce 

these final products and products in 

other chemical manufacturing source 

categories. Examples of types of 

products include solvents, organic dyes 

and pigments, plasticizers, alcohols, 

detergents, and flavorings. 

Industrial Inorganic Chemical 

Manufacturing. The industrial inorganic 

chemical manufacturing source category 

includes manufacturing of inorganic 

gases that are designated by NAICS code 

325120 (industrial gas manufacturing), 

manufacturing of inorganic dyes that are 

designated by NAICS code 325130 

(synthetic dye and pigment 

manufacturing), and most 

manufacturing designated by NAICS 

code 32518 (other basic inorganic 

chemical manufacturing). Exceptions to 

production designated by NAICS code 

32518 include carbon black and 

mercury cell chlor-alkali production, 

which are separate source categories. 

Inorganic Pigment Manufacturing. 

Inorganic pigments are part of NAICS 

code 325130 (synthetic dye and pigment 

manufacturing). The majority of 

inorganic pigments are oxides, sulfides, 

oxide hydroxides, silicates, sulfates, or 

carbonates that normally consist of 

single component particles. The 

inorganic pigment manufacturing 

processes can generally be divided 

between those that use partial 

combustion and those that use pure 

pyrolysis. Inorganic pigments generally 

are used to impart colors to a variety of 

compounds. They may also impart 

properties of rust inhibition, rigidity, 

and abrasion resistance. Inorganic 

pigments are generally insoluble and 

remain unchanged physically and 

chemically when mixed with a carrier. 

Pigment manufacturers supply 

inorganic colors in a variety of forms 

including powders, pastes, granules, 

slurries, and suspensions. Pigments are 

used in the manufacture of paints and 

stains, printing inks, plastics, synthetic 

textiles, paper, cosmetics, contact 

lenses, soaps, detergents, wax, modeling 

clay, chalks, crayons, artists’ colors, 

concrete, masonry products, and 

ceramics. 

Pharmaceutical Production. The 

pharmaceutical manufacturing source 

category consists of chemical 

production operations that produce 

drugs and medication. These operations 

include chemical synthesis (deriving a 

drug’s active ingredient) and chemical 

formulation (producing a drug in its 

final form). The source category is 

designated by NAICS codes 325411 

(medicinal and botanical 

manufacturing), 325412 (pharmaceutical 

preparation manufacturing), and 325414 

(biological product, except diagnostic, 

manufacturing). 

Plastic Materials and Resins 

Manufacturing. This source category is 

designated by NAICS code 325211 

(plastics material and resin 

manufacturing). Examples of products 

in this source category include epoxy 

resins, nylon resins, phenolic resins, 

polyesters, polyethylene resins, and 

styrene resins. The source category does 

not include polyvinyl chloride and 

copolymers production, which is a 

separate source category. 

Synthetic Rubber Manufacturing. The 

synthetic rubber manufacturing source 

category is designated by NAICS code 


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10While 29 facilities were identified to become 

subject to CMAS NESHAP if EtO were to be added 

to table 1 to 40 CFR part 63, subpart VVVVVV, four 

of the 251 facilities currently subject to the CMAS 

NESHAP also emit EtO. As such, in total, there are 

33 facilities emitting EtO that may be impacted by 

this action. 

11Refer to the 2017 NEI Technical Support 

Document for detailed discussion on the types of 

review and augmentation performed for 2017 NEI 

(https://www.epa.gov/sites/default/files/2021-02/ 

documents/nei2017_tsd_full_jan2021.pdf). 

12For facilities that would become subject (or are 

already subject) to the CMAS NESHAP if EtO were 

to be added to table 1 to 40 CFR part 63, subpart 

VVVVVV, as proposed. 

13HON CMPUs and polyether polyol 

manufacturing process units (PMPUs) associated 

with the PEPO NESHAP have similar processes as 

CMAS CMPUs in that regardless of size, each of 

these process units may include chemical 

manufacturing equipment, heat exchange systems, 

process vents, storage tanks, transfer operations, 

and/or wastewater. 

325212 (synthetic rubber 

manufacturing). Facilities in this source 

category manufacture synthetic rubber 

or vulcanizable elastomers by 

polymerization or copolymerization. For 

this source category, an elastomer is 

defined as a rubber-like material capable 

of vulcanization, such as copolymers of 

butadiene and styrene, copolymers of 

butadiene and acrylonitrile, 

polybutadienes, chloroprene rubbers, 

and isobutylene-isoprene copolymers. 

The HAP emission sources at facilities 

subject to the CMAS NESHAP include 

process vents, storage tanks, equipment 

leaks, transfer operations, and 

wastewater. Additionally, some 

facilities have cooling towers or other 

heat exchangers. The GACT standards 

for CMAS include emission standards in 

the form of management practices for 

each CMPU as well as emission limits 

for certain emission sources including 

process vents and storage tanks. The 

rule also establishes management 

practices and other emission reduction 

requirements for wastewater systems 

and heat exchange systems. 

As of May 1, 2024, the EPA identified 

251 facilities in operation that are 

subject to the CMAS NESHAP. In 

addition, we are aware of 29 more 

facilities that would become subject to 

the CMAS NESHAP if EtO were to be 

added to table 1 to the CMAS NESHAP, 

as proposed (see section II.A.1 of this 

preamble) 10. In this preamble, we 

referred to all 280 of these facilities 

collectively as ‘‘CMAS facilities.’’ The 

list of CMAS facilities located in the 

United States that are part of the CMAS 

categories with processes subject to the 

CMAS NESHAP is presented in the 

document titled List of Facilities Subject 

to the CMAS NESHAP, which is 

available in the docket for this 

rulemaking. 

C. What data collection activities were 

conducted to support this action? 

1. Facility List 

The EPA used several data sources to 

determine the facilities that are subject 

to the CMAS NESHAP discussed in 

section II.B of this preamble. We began 

with the facility list from the original 

rulemaking for the CMAS NESHAP (74 

FR 56008, October 29, 2009). This list 

was supplemented with information 

from the Office of Enforcement and 

Compliance Assurance’s Enforcement 

and Compliance History Online tool 

(https://echo.epa.gov) as well as other 

facility lists from the EPA’s recent 

chemical sector rulemakings (e.g., HON, 

MON, Organic Liquid Distribution 

NESHAP (OLD), Ethylene Production 

MACT standards (EMACT standards), 

and Polyether Polyols Production 

(PEPO) NESHAP). 

We also collected and considered 

facility specific information from the 

regions and/or states, if the information 

had not already been captured by the 

previous steps. For example, we 

obtained title V air permits from 

publicly available online state databases 

(where available). In cases where an 

online database was incomplete or did 

not exist, the EPA contacted the region 

and/or state for help in obtaining the air 

permits or determining whether a 

facility was subject to the CMAS 

NESHAP or may become subject to the 

CMAS NESHAP if EtO were to be added 

to table 1 to 40 CFR part 63, subpart 

VVVVVV. The EPA also conducted 

internet searches to determine the status 

of the facility (e.g., whether the facility 

was still open, permanently closed, and/ 

or sold). Additional details about how 

the facility list was developed are 

provided in the document titled List of 

Facilities Subject to the CMAS NESHAP, 

which is available in the docket for this 

rulemaking. 

The EPA solicits comment on the 

assumptions used to estimate the 

number of facilities anticipated to be 

impacted by this action. 

2. Emissions Inventory 

For each facility subject to the CMAS 

NESHAP, we gathered emissions data 

from the most recent version of the 2017 

National Emissions Inventory (NEI), 

published in January 2021. Apart from 

the 2020 NEI (which was the first year 

of the COVID–19 pandemic), the 2017 

NEI was the most vetted and recent 

publicly available data set at the time 

EPA began gathering information for 

this proposed rulemaking.11

We consulted with state agencies, 

EPA regions, air permits, and facilities 

to determine whether any EtO records 

in the CMAS emissions inventory 

needed to be updated (beyond the 2017 

NEI).12 This review revealed that several 

facilities have either voluntarily 

implemented EtO emission reduction 

measures since 2017 or implemented 

them due to state or other requirements; 

therefore, we made amendments to 

these EtO records to reflect the specific 

reduction measures. See appendix 1 of 

the document titled Risk Assessment for 

the Chemical Manufacturing Area 

Source (CMAS) Source Categories in 

Support of the 2025 Technology Review 

for the Proposed Rule, which is 

available in the docket for this 

rulemaking, for additional details on the 

analysis and methodology used to 

develop the CMAS emissions inventory. 

3. Other Data Collection Activities 

To inform our reviews of the Agency’s 

emission standards, we reviewed the 

EPA’s Reasonably Available Control 

Technology (RACT)/Best Available 

Control Technology (BACT)/Lowest 

Achievable Emission Rate (LAER) 

Clearinghouse and regulatory 

development efforts for similar sources 

published after the CMAS NESHAP was 

developed. 

In January 2022, the EPA issued 

requests, pursuant to CAA section 114, 

to collect information from HON 

facilities (nine being also subject to the 

PEPO NESHAP) owned and operated by 

eight entities (i.e., corporations). This 

effort focused on gathering 

comprehensive information about 

process equipment, control 

technologies, point and fugitive 

emissions, and other aspects of facility 

operations. Additionally, the EPA 

requested stack testing for certain 

emission sources (e.g., pollutants, 

including EtO, for vent streams). Also, 

the EPA required that facilities conduct 

fugitive emission testing (i.e., fenceline 

monitoring) for any of six specific HAP 

they emit: benzene; 1,3-butadiene; 

chloroprene; EtO; ethylene dichloride; 

and vinyl chloride. Companies 

submitted responses (and follow-up 

responses) and testing results to the EPA 

during the summer and fall of 2022. 

Given that CMPU sources subject to the 

CMAS NESHAP can be similar to HON 

CMPU sources and PEPO sources,13 the 

EPA used the collected information to 

estimate environmental and cost 

impacts associated with some of the 

regulatory options considered and 

reflected in this proposed action. The 

information not claimed as CBI by 

respondents is provided in the 

document titled Data Received from 

Information Collection Request for 


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14The report is available at https://

www.epaoig.gov/sites/default/files/2021-05/ 

documents/_epaoig_20210506-21-p-0129.pdf. 

15The MIR is defined as the cancer risk 

associated with a lifetime of exposure at the highest 

concentration of HAP where people are likely to 

live. The HQ is the ratio of the potential HAP 

exposure concentration to the noncancer doseresponse value; the HI is the sum of HQs for HAP. 

Chemical Manufacturers, which is 

available in the docket for this 

rulemaking. 

D. What other relevant background 

information and data are available? 

In proposing these amendments, we 

relied on certain technical reports and 

memoranda that the EPA developed for 

flares used as air pollution control 

devices (APCDs) in the Petroleum 

Refinery Sector risk and technology 

review (RTR) and new source 

performance standards (NSPS) 

rulemaking (80 FR 75178, December 1, 

2015). The Petroleum Refinery Sector 

rulemaking docket is at Docket ID No. 

EPA–HQ–OAR–2010–0682. For 

completeness of the rulemaking record 

for this action and for ease of reference 

in finding these items in the publicly 

available Petroleum Refinery Sector 

rulemaking docket, we are including the 

most relevant flare-related technical 

support documents in the docket for 

this proposed action (Docket ID No. 

EPA–HQ–OAR–2024–0303) and 

including a list of all documents used to 

inform the 2015 flare provisions in the 

Petroleum Refinery Sector RTR and 

NSPS rulemaking in the document titled 

Clean Air Act Section 112(d)(5) GACT 

Standard Analysis for Flares that Emit 

Ethylene Oxide and Section 112(d)(6) 

Technology Review for Flares 

Associated with Chemical 

Manufacturing Process Units at Area 

Sources Subject to the CMAS NESHAP, 

which is available in the docket for this 

rulemaking. 

We are also relying on data gathered 

to support the rulemakings for the 

EMACT standards, HON, and MON, as 

well as memoranda documenting the 

technology reviews for those processes. 

Many of the emission sources for 

ethylene production facilities, HON 

facilities, and MON facilities are similar 

to CMAS facilities, and the EPA 

analyzed several of the control options 

for the CMAS NESHAP that the Agency 

also analyzed for the rulemakings for 

the EMACT standards, HON, and MON. 

The memoranda and background 

technical information can be found in 

the Ethylene Production RTR 

rulemaking docket (Docket ID No. EPA– 

HQ–OAR–2017–0357), the HON 

rulemaking docket (Docket ID No. EPA– 

HQ–OAR–2022–0730), and the MON 

RTR rulemaking docket (Docket ID No. 

EPA–HQ–OAR–2018–0746). Additional 

information related to the promulgation 

and subsequent amendments of the 

CMAS NESHAP is available in Docket 

ID No. EPA–HQ–OAR–2008–0334. 

E. What are the results of the EPA’s risk 

assessment? 

As discussed in section II.A.1, the 

EPA conducted a human health risk 

assessment to determine if EtO 

emissions from CMAS present a threat 

of adverse effects to human health (e.g., 

a public health concern) and therefore 

warrant regulation via the creation of a 

new source category pursuant to CAA 

section 112(c)(3) and (5). Following the 

update to the IRIS value for EtO, it 

became apparent that emissions of EtO 

from CMAS could be posing a 

significant threat to public health. The 

OIG released a report in 2021 that 

identified potential elevated cancer 

risks due to EtO emissions from CMAS 

using data from the 2014 NATA.14

While the primary focus of the risk 

assessment was on EtO emissions, 

consistent with other risk assessments 

for HAPs, we estimated the MIR posed 

by emissions of HAP that are 

carcinogens from each evaluated CMAS, 

the hazard index (HI) for chronic 

exposures to HAP with the potential to 

cause noncancer health effects, and the 

hazard quotient (HQ) for acute 

exposures to HAP with the potential to 

cause noncancer health effects.15 This 

section summarizes the results of those 

analyses. 

The EPA often conducts risk 

assessments at both the facility and 

source category level when investigating 

human health concerns and uses 

standard methodology for all risk 

assessments. However, we note that this 

risk assessment was completed using 

the emissions inventory described in 

section II.C.2 of this preamble. As such, 

there are uncertainties with the results 

of the risk assessment engendered by 

the uncertainties associated with the 

emissions inventory. However, given 

the information available, we believe 

the risk assessment supports our 

conclusion that these sources present a 

threat of an adverse impact on human 

health. Additional details on the risk 

assessment and exact methodology are 

presented in the document titled, Risk 

Assessment for the Chemical 

Manufacturing Area Source (CMAS) 

Source Categories in Support of the 

2025 Technology Review for the 

Proposed Rule, which is available in the 

docket for this rulemaking. 

As discussed in section II.A.1 of this 

preamble, the MIR posed by the 

evaluated sources is 800-in-1 million, 

driven primarily (greater than 90 

percent) by EtO emissions from process 

vents (97 percent). Approximately 4.4 

million people within 50 kilometers 

(km) of the evaluated CMAS are 

estimated to have cancer risks above 1- 

in-1 million and 3,600 people are 

estimated to have cancer risks above 

100-in-1 million due to emissions from 

the sources. The people with risks above 

100-in-1 million all reside within 10 km 

of the sources. The sources are 

estimated to result in 0.4 additional 

cancer cases per year, or 1 cancer case 

every 2.5 years. Emissions from the 

evaluated CMAS drive cancer risk 

attributable to whole facility emissions, 

such that the risk posed by all HAP 

emissions from the facilities are 

generally the same as the risk posed by 

the evaluated sources, except that 

emissions from whole facility emissions 

increase the population with risk greater 

than 1-in-1 million living within 50 km 

by 200,000 people. 

The maximum chronic noncancer 

target organ-specific hazard index 

(TOSHI) for the evaluated CMAS is 

estimated to be 3 (for respiratory and 

immunological effects) at two facilities 

due to nickel compounds emissions 

from process vents at one facility and 

equipment leaks and fugitive emissions 

at the other facility. The same nickel 

emissions also drive the estimated 

maximum facility-wide TOSHI of 3. 

Approximately 1,500 people are 

estimated to have a TOSHI greater than 

1 due to emissions from the evaluated 

CMAS. 

The estimated reasonable worst-case 

off-site acute inhalation exposures to 

emissions from the CMAS categories 

results in an estimated maximum 

modeled acute noncancer HQ of 20 

based on CalEPA’s Chronic Reference 

Exposure Level for acrolein. It is 

important to note that when assessing 

acute inhalation exposures, the EPA 

makes conservative assumptions about 

emission rates, meteorology, and 

exposure location. We assume that an 

individual is present at the location of 

maximum exposure at the exact same 

hour that peak emissions occur (using a 

default factor of 10 from average actual 

annual emissions rates) and the exact 

same hour the reasonable worst-case air 

dispersion conditions (i.e., 99th 

percentile) occur. Together, these 

assumptions represent a reasonable 

worst-case actual exposure scenario. In 

most cases, it is unlikely that a person 

would be located at the point of 

maximum exposure during the time 

when peak emissions and reasonable 


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worst-case air dispersion conditions 

occur simultaneously. Furthermore, at 

the facility where the maximum HQ of 

20 is estimated, the maximum exposure 

is modeled to occur along the fenceline 

of the facility at a location immediately 

surrounded by farmland making it more 

unlikely a person would be located at 

that point at the exact hour the peak 

emissions and the reasonable worst-case 

air dispersion conditions occur. 

We also conducted a communitybased risk assessment for facilities 

currently subject to the CMAS NESHAP 

or who would become subject to the 

CMAS NESHAP with the proposal of 

the new area source category (see 

section II.C.1 of this preamble for details 

on how the facility list was developed). 

The goal of this assessment was to 

estimate cancer risk from HAP emitted 

from all local stationary point sources 

for which we have emissions data. We 

estimated the overall inhalation cancer 

risk due to emissions from all stationary 

point sources impacting census blocks 

within 10 km of the CMAS facilities. 

Specifically, we combined the modeled 

impacts from category and non-category 

HAP sources at CMAS facilities, as well 

as other stationary point source HAP 

emissions. The results indicate that the 

community-level maximum individual 

cancer risk is 5,000-in-1 million, with 

all risk attributable to chromium VI 

emissions from an area source iron 

foundry. The Agency will investigate 

these emissions to determine if followup action is necessary. We note that the 

2020 NEI data (the baseline for the 

community-level assessment) for the 

facility driving the community-level 

MIR present an anomalously high year 

of chromium VI emissions compared to 

other years. Also, the default speciation 

of chromium emissions to chromium III 

and chromium VI emissions done by the 

NEI is a conservative estimate of 

emissions and may not be representative 

of the actual emissions. In addition, we 

note that there is additional uncertainty 

in non-CMAS categories emissions 

because they were not reviewed to the 

same extent as emissions from CMAS 

facilities. Within 10 km, the population 

exposed to cancer risks greater than 100- 

in-1 million from all nearby emissions 

is approximately 5,600. For comparison, 

approximately 3,600 people have cancer 

risks greater than 100-in-1 million due 

to emissions from the evaluated CMAS 

NESHAP (see table 1 of this preamble). 

After the controls proposed in this 

action are implemented for the CMAS 

categories (see sections IV.A through 

IV.C of this preamble), including the 

contribution from all non-EtO HAP, the 

maximum individual cancer risk is 

estimated to be 100-in-1 million and no 

facilities are estimated to pose cancer 

risk greater than 100-in-1 million. The 

number of people living within 50 km 

of CMAS facilities with risk greater than 

1-in-1 million due to emissions from the 

CMAS categories will decrease from 4.4 

million to 2.3 million. Chronic and 

acute noncancer risk is not estimated to 

change, although our proposal to 

remove the 50 parts per million by 

volume (ppmv) criteria as part of the 

definition of ‘‘metal HAP process vent’’ 

(see section IV.C.3 of this preamble) is 

anticipated to reduce emissions of 

nickel that drive the chronic noncancer 

risk. After implementation of the 

proposed controls, the community-level 

maximum individual cancer risk will 

remain unchanged at 5,000-in-1 million. 

The population (within 10 km of CMAS 

facilities) exposed to cancer risks greater 

than 100-in-1 million from all nearby 

emissions will be reduced from 5,600 

people to 1,900 people; a 66 percent 

reduction from the baseline. The 

increased cancer risk for most of these 

1,900 people is driven largely by 

emissions of chromium VI from nonCMAS facilities within 10 km of CMAS 

facilities. 

See table 1 of this preamble for a 

summary of the CMAS NESHAP 

inhalation risk assessment results. We 

present the full results and methods of 

the risk assessment in more detail, in 

the document titled Risk Assessment for 

the Chemical Manufacturing Area 

Source (CMAS) Source Categories in 

Support of the 2025 Technology Review 

for the Proposed Rule, which is 

available in the docket for this 

rulemaking. 

TABLE 1—INHALATION CANCER RISK ASSESSMENT RESULTS FOR COMMUNITIES LIVING WITHIN 10 TO 50 KM OF CMAS 

FACILITIES

Risk assessment Number of 

facilities 1

Maximum 

individual 

cancer 

risk (-in-1 

million) 2

Estimated population at increased 

risk of cancer 

Estimated 

annual cancer 

incidence 

(cases per 

year) 

Maximum chronic noncancer 

TOSHI 

Refined 

maximum 

screening 

acute noncancer HQ >100-in-1 

million ≥1-in-1 million 

Baseline (Pre-Control) Actual Emissions 3

Source Category ........................ 248 800 3,600 (10 km)

3,600 (50 km)

2 million (10 

km).

4.4 million (50 

km).

0.2 (10 km) .....

0.4 (50 km) .....

3 (respiratory, immunological) .. 20 

Facility-wide ............................... 279 800 3,600 (10 km)

3,600 (50 km)

2.2 million (10 

km).

4.6 million (50 

km).

0.2 (10 km) .....

0.4 (50 km) .....

3 (respiratory, immunological) .. 4— 

Community-based ...................... 5 9,932 5,000 5,600 (10 km) 8.6 million (10 

km).

0.8 (10 km) ..... ................................................... ....................

Post-Control Emissions 

Source Category ........................ 248 100 0 ...................... 1.3 million (10 

km).

2.3 million (50 

km).

0.1 (10 km) .....

0.2 (50 km) .....

3 (respiratory, immunological) .. 20 

Facility-wide ............................... 279 100 0 ...................... 1.4 million (10 

km).

2.5 million (50 

km).

0.1 (10 km) .....

0.2 (50 km) .....

3 (respiratory, immunological) .. ....................

Community-based ...................... 3 9,932 5,000 1,900 (10 km) 8 million (10 

km).

0.6 (10 km) ..... ................................................... ....................

1Thirty-one (31) additional facilities were modeled for the CMAS whole-facility analysis compared to the CMAS categories analysis, because 279 facilities were 

originally identified as potentially subject to the CMAS NESHAP considering the current and proposed source categories based on permit review and/or the facility’s 

presence in the previous rulemaking’s facility list. However, upon further review, only 248 of these 279 facilities were identified as having emissions from the CMAS 

categories. 


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2 Maximum individual excess lifetime cancer risk due to HAP emissions. 

3Potential differences between actual emission levels and the maximum emissions allowable under EPA’s standards (i.e., ‘‘allowable emissions’’) were also evaluated for the CMAS categories. For the 248 CMAS facilities, there were 4 facilities with allowable emissions that differed from actual emissions. These emissions were 

evaluated and it was determined there would be no appreciable difference in the risk results; therefore, the risk results provided based on actual emissions also describe the risk assessment results based on allowable emissions. 4 ‘‘—’’ Indicates where an assessment was not conducted. 

5 9,653 nearby non-CMAS facilities in addition to the 279 facilities CMAS facilities evaluated. 

III. Analytical Procedures and 

Decision-Making 

A. How do we determine GACT? 

As provided in CAA section 112(d)(5), 

we are proposing standards representing 

GACT to regulate EtO emissions from 

equipment leaks, heat exchange 

systems, process vents, storage tanks, 

wastewater, and transfer operations 

located at CMAS. The statute does not 

set any condition precedent for issuing 

standards under CAA section 112(d)(5) 

other than that the area source category 

or subcategory at issue must be one that 

EPA listed pursuant to CAA section 

112(c), which is the case here. In 

determining what constitutes GACT for 

this proposed rule, we considered the 

control technologies and management 

practices that are generally available to 

EtO emission sources at CMAS by 

examining relevant data and 

information, including information 

collected from the Synthetic Organic 

Chemical Manufacturing Industry 

(SOCMI) and PEPO Production major 

source categories. We also considered 

the standards for major chemical 

manufacturing sources subject to the 

MON and HON (see 85 FR 49084, 

August 12, 2020, and 89 FR 42932, May 

16, 2024, respectively) to determine if 

the control technologies and work 

practice standards for the major sources 

are generally available to area sources as 

well. Finally, we considered the costs of 

available control technologies and 

management practices on area sources. 

From the information that we have 

collected to date in conjunction with 

this rulemaking, which includes 

information about process equipment, 

control technologies, point and fugitive 

emissions, and other aspects of facility 

operations at major chemical 

manufacturing sources, we know that 

area sources have the same types of 

emissions, emission sources, and 

controls as major sources. Equipment 

leaks, heat exchange systems, process 

vents, storage tanks, wastewater, and 

transfer operations at major and area 

sources are using the same control 

technologies. There are generally no 

discernible differences between the 

processes at area and major chemical 

manufacturing sources excepting size. 

In fact, major and area sources use 

similar, if not identical, control 

technologies and practices to manage 

process emissions. Therefore, the 

control technologies used by chemical 

manufacturing major sources are 

generally available for CMAS. 

B. How do we perform the technology 

review? 

For the NESHAP area source GACT 

standard, our technology review 

primarily focuses on the identification 

and evaluation of developments in 

practices, processes, and control 

technologies that have occurred since 

the standards were promulgated. Where 

we identify such developments, we 

analyze their technical feasibility, 

estimated costs, energy implications, 

and non-air environmental impacts. We 

also consider the emission reductions 

associated with applying each 

development. This analysis informs our 

decision of whether it is ‘‘necessary’’ to 

revise the emissions standards. In 

addition, we consider the 

appropriateness of applying controls to 

new sources versus retrofitting existing 

sources. For this exercise, we consider 

any of the following to be a 

‘‘development’’: 

• Any add-on control technology or 

other equipment that was not identified 

and considered during development of 

the original GACT standards; 

• Any improvements in add-on 

control technology or other equipment 

(that were identified and considered 

during development of the original 

GACT standards) that could result in 

additional emissions reduction; 

• Any work practice, management 

practice, or operational procedure that 

was not identified or considered during 

development of the original GACT 

standards; 

• Any process change or pollution 

prevention alternative that could be 

broadly applied to the industry and that 

was not identified or considered during 

development of the original GACT 

standards; and 

• Any significant changes in the cost 

(including cost effectiveness) of 

applying controls (including controls 

the EPA considered during the 

development of the original GACT 

standards). 

In addition to reviewing the practices, 

processes, and control technologies that 

were considered at the time we 

originally developed (or last updated) 

the CMAS NESHAP, we review a variety 

of data sources in our investigation of 

potential practices, processes, or 

controls to consider. See sections II.C 

and II.D of this preamble for information 

on the specific data sources that were 

reviewed as part of the technology 

review. 

IV. Analytical Results and Proposed 

Decisions 

A. What are our proposed decisions 

regarding standards representing GACT 

for EtO emissions from CMAS, and what 

is the rationale for those decisions? 

As discussed in section II.A.1 of this 

preamble, the EPA is proposing, 

pursuant to CAA section 112(c)(3) and 

(5), to create an area source category 

describing chemical manufacturing 

operations using EtO. Specifically, we 

are proposing at 40 CFR 

63.11494(a)(2)(v) that you are subject to 

the CMAS NESHAP if you own or 

operate a CMPU that is located at an 

area source of HAP and EtO is used as 

a feedstock at an individual 

concentration greater than 0.1 percent 

by weight; generated as a byproduct and 

is present in the CMPU in any liquid 

stream (process or waste) at a 

concentration of greater than or equal to 

1 part per million by weight (ppmw); 

generated as a byproduct and is present 

in the CMPU in any continuous process 

vent or batch process vent at a 

concentration greater than 1 ppmv; or is 

produced as a product of the CMPU. 

The EPA is also proposing amendments 

to the CMAS NESHAP pursuant to CAA 

section 112(d)(5) to include: 

• New monitoring requirements for 

leaks from equipment in EtO service; 

• New monitoring requirements for 

leaks from heat exchange systems in EtO 

service; 

• A new emissions standard for batch 

and continuous process vents in EtO 

service; 

• A new emissions standard for 

storage tanks in EtO service; 

• New control requirements for 

wastewater streams in EtO service; 

• Improved operational and 

monitoring requirements for flares that 

emit EtO; 

• A new fenceline monitoring 

standard related to EtO emissions; and 

• A requirement that any release 

event from a PRD in EtO service is a 

deviation. 

The data, analyses, results, and 

proposed decisions pursuant to CAA 

section 112(d)(5) are presented for each 


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16Natural Resources Defense Council v. EPA, 749 

F.3d 1055, 1060 (DC Circ. April 18, 2014) (‘‘Section 

112 does not command the EPA to use a particular 

form of cost analysis’’). 

emission source in sections IV.A.1 

through IV.A.8 of this preamble. 

The EPA considers multiple factors in 

assessing the costs of emission 

reductions.16 These factors include, but 

are not limited to, total capital costs, 

total annual costs, cost effectiveness, 

and annual costs compared to total 

annual revenues for ultimate owners of 

affected facilities (i.e., costs to sales 

ratios). EtO is a highly potent 

carcinogen and the cost-effectiveness 

numbers presented in sections IV.A.1 

through IV.A.8 of this preamble are 

within range of values that we have 

determined to be cost effective for 

highly toxic HAP. For small hard 

chromium electroplating, to provide an 

ample margin of safety to protect public 

health, costs of $15,000 per pound (lb) 

($30,000,000 per ton) were finalized due 

to the toxicity of hexavalent chromium 

(see 77 FR 58227–8 and 77 FR 58239, 

September 19, 2012). EtO is similarly 

highly toxic. The cost-effectiveness 

values presented in sections IV.A.1 

through IV.A.8 of this preamble are also 

within the range of cost-effectiveness for 

control of EtO emissions that the EPA 

found reasonable as part of the recent 

commercial sterilizers rulemaking (see 

89 FR 24090, April 5, 2024). In this 

rulemaking, the EPA accepted costs of 

up to $17,500,000/ton for existing 

sources in setting standards under CAA 

section 112(d)(5). In addition, our 

established methodology for assessing 

economic impacts of regulations 

indicates that the potential for adverse 

economic impacts begins when a costs 

to sales ratio exceeds three percent. 

According to our estimates, the 

anticipated annual costs of the proposed 

emission control options discussed 

below are well below three percent of 

annual sales for the majority of the 

owners of potentially impacted EtO 

sources. 

1. Equipment Leaks in EtO Service 

Emissions from equipment leaks 

occur in the form of gases or liquids that 

escape to the atmosphere through 

connection points (e.g., threaded 

connectors) or through the moving parts 

of components such as pumps and 

valves. EtO emissions are released from 

equipment leaks when the components 

are associated with equipment that 

contain EtO (referred to as equipment in 

EtO service). We provide details about 

equipment leaks, including how the 

CMAS NESHAP regulates them, in our 

technology review discussion (see 

section IV.C.1 of this preamble). For the 

GACT standard analysis, we evaluated a 

single control option for leaks from 

equipment in EtO service. The control 

option evaluated is identical to the HON 

standards for leaks from equipment in 

EtO service and similar (in terms of the 

technology, which is using EPA Method 

21 instrument monitoring) to the control 

options that we evaluated in the 

equipment leaks technology review (see 

section IV.C.1 of this preamble). The 

EPA recently added EtO-specific 

requirements into the HON for 

equipment in EtO service that requires 

a more stringent monitoring frequency 

(i.e., monthly monitoring) and lower 

leak definitions (i.e., 100 ppmv or 500 

ppmv) compared to monitoring for leaks 

from equipment not in EtO service. In 

the HON, equipment in EtO service is 

equipment that contains or contacts a 

fluid that is at least 0.1 percent by 

weight EtO. 

As such, given the transferability of 

major source work practice standards to 

CMAS management practices due to the 

minimal differences between 

performing instrument monitoring at a 

major source compared to an area 

source, we evaluated the following 

option to represent GACT for equipment 

‘‘in ethylene oxide service’’ that are 

located at CMAS: 

• Control Option 1 (if EtO was added 

to table 1 to 40 CFR part 63, subpart 

VVVVVV): conduct monthly EPA 

Method 21 monitoring at a leak 

definition of 100 ppmv for connectors 

and valves in EtO service and 500 ppmv 

for pumps in EtO service. 

We find this Control Option and the 

associated technologies to be ‘‘generally 

available’’ per the language of CAA 

section 112(d)(5). While it was not 

proposed in the original CMAS 

rulemaking, an instrument monitoring 

program similar to the MON was 

evaluated as part of the original CMAS 

rulemaking in 2008. In addition, 

conducting EPA Method 21 monitoring 

has been an option for the CMAS 

management practices since 

promulgation (i.e., owners and operators 

may perform EPA Method 21 

monitoring in lieu of conducting audio, 

visual, and olfactory (AVO) 

inspections). Also, the EPA is aware of 

facilities that have already implemented 

instrument monitoring in some capacity 

as part of complying with other 

regulatory requirements or as part of a 

company-wide initiative to address EtO 

emissions. Therefore, we conclude that 

instrument monitoring is generally 

available. 

We estimated the cost and emissions 

reductions of Control Option 1 for 33 

CMAS EtO facilities. Using background 

information available to the EPA 

(including air permits and information 

received from various EPA regional 

offices), it was determined that 10 

CMAS EtO facilities are already 

conducting instrument monitoring as 

part of an LDAR program for their 

equipment in EtO service. Based on this, 

there are two types of facilities for 

purposes of identifying their baseline 

LDAR program for equipment in EtO 

service: those that do not have an LDAR 

program of any kind; and those that 

already conduct EPA Method 21 

instrument monitoring. When 

evaluating the cost and emissions 

reductions for each facility, we 

calculated the incremental cost and 

reductions to meet Control Option 1 

compared to a facility’s baseline LDAR 

program. The memorandum Clean Air 

Act Section 112(d)(5) GACT Standard 

Analysis for Equipment Leaks that Emit 

Ethylene Oxide and Section 112(d)(6) 

Technology Review for Equipment Leaks 

from Chemical Manufacturing Process 

Units at Area Sources Subject to the 

CMAS NESHAP, which is available in 

the docket for this rulemaking, 

summarizes the baseline LDAR program 

for each of the 33 CMAS EtO facilities 

evaluated for this control option and 

presents details on the methodologies 

used in this analysis. 

Table 2 of this preamble presents the 

nationwide impacts for requiring 

owners and operators of equipment in 

EtO service to perform EPA Method 21 

monitoring in accordance with Control 

Option 1. Based on the costs and 

emission reductions, we are proposing 

to revise the CMAS NESHAP for 

equipment in EtO service to reflect 

Control Option 1 pursuant to CAA 

section 112(d)(5). 


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TABLE 2—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTION 1 FOR REQUIRING EPA 

METHOD 21 MONITORING FOR EQUIPMENT IN ETO SERVICE AT CERTAIN FACILITIES 1

Control option 

Total capital 

investment 

($) 

Total 

annualized 

costs w/o 

recovery 

credits 

($/yr) 

Total 

annualized 

costs with 

recovery 

credits 

($/yr) 

VOC emission 

reductions 

(tpy) 

EtO emission 

reductions 

(tpy) 2

EtO cost 

effectiveness 

w/o recovery 

credits 

($/ton) 

EtO cost 

effectiveness 

with recovery 

credits 

($/ton) 

1 ................................................................................ 511,000 1,261,000 1,129,400 146 83 15,100 13,500 

1Facilities that would either become subject to the CMAS NESHAP if EtO is added to table 1 to 40 CFR part 63, subpart VVVVVV, as proposed, or are already 

subject to the CMAS NESHAP and emit EtO. 2We note that EtO emission reductions from equipment leaks (and subsequent cost-effectiveness values for EtO from equipment leaks) differ from reductions expected to occur from reported emissions inventories due to use of model plants, engineering assumptions made to estimate baseline emissions, and uncertainties in 

how fugitive emissions may have been calculated for reported inventories compared to our model plants analysis (and are documented in the memorandum). 

The EPA is proposing to define 

equipment leaks ‘‘in ethylene oxide 

service’’ at 40 CFR 63.11502(b), by 

reference to the HON (40 CFR 63.101). 

We are proposing Control Option 1 for 

equipment leaks in EtO service at 40 

CFR 63.11495(a)(7). These proposed 

requirements would apply to all new 

and existing affected sources and 

specify that: 

• All connectors in EtO service be 

monitored monthly at a leak definition 

of 100 ppmv with no skip period, and 

delay of repair is not allowed unless the 

equipment can be isolated such that it 

is no longer in EtO service (see 40 CFR 

63.174(a)(3), (b)(3)(vi), and (g)(3), and 40 

CFR 63.171(f)). 

• All gas/vapor and light liquid 

valves in EtO service be monitored 

monthly at a leak definition of 100 

ppmv with no skip period, and delay of 

repair is not allowed unless the 

equipment can be isolated such that it 

is no longer in EtO service (see 40 CFR 

63.168(b)(2)(iv) and (d)(5), and 40 CFR 

63.171(f)). 

• All light liquid pumps in EtO 

service be monitored monthly at a leak 

definition of 500 ppmv, and delay of 

repair is not allowed unless the 

equipment can be isolated such that it 

is no longer in EtO service (see 40 CFR 

63.163(a)(1)(iii), (b)(2)(iv), (c)(4), and 

(e)(7), and 40 CFR 63.171(f)). 

2. Heat Exchange Systems in EtO 

Service 

Emissions of EtO from heat exchange 

systems occur when a heat exchanger’s 

internal tubing material corrodes or 

cracks, allowing some process fluids to 

mix or become entrained with the 

cooling water. Pollutants (e.g., EtO) in 

the process fluids may subsequently be 

released from the cooling water into the 

atmosphere when the water is exposed 

to air (e.g., in a cooling tower for closedloop systems or trenches/ponds in a 

once-through system). We provide more 

details about heat exchange systems, 

including how the CMAS NESHAP 

regulates them, in our technology 

review discussion (see section IV.C.2 of 

this preamble). Our CMAS heat 

exchange system technology review (see 

section IV.C.2 of this preamble) 

identified use of the Modified El Paso 

Method as a development in practice for 

heat exchange systems with a cooling 

water flow rate equal to or greater than 

8,000 gallons per minute (gpm). 

Specifically, we identified the following 

control option for heat exchange 

systems: quarterly monitoring with the 

Modified El Paso Method, using a leak 

action level defined as a total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas of 6.2 ppmv. This 

option would also require repairing a 

leak no later than 45 days after first 

identifying the leak, delay of repair 

within 120 days (except within no more 

than 30 days where a total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas of 62 ppmv or 

higher is found), and re-monitoring at 

the monitoring location where the leak 

was identified to ensure that any leaks 

found are fixed. 

To assess what GACT standards may 

be appropriate if EtO is added to table 

1 to 40 CFR part 63, subpart VVVVVV, 

we reviewed other rulemakings to 

identify the level of control required for 

heat exchange systems emitting EtO. As 

part of that review, we identified one 

rule requiring monitoring of heat 

exchange systems ‘‘in ethylene oxide 

service.’’ The EPA recently added EtOspecific requirements into the HON for 

heat exchange systems in EtO service 

that require more stringent monitoring 

frequency (weekly instead of quarterly) 

and repair of leaks within 15 days from 

the sampling date (in lieu of the current 

45-day repair requirement after 

receiving results of monitoring 

indicating a leak) (see 89 FR 42932, May 

16, 2024). Additionally, delay of repair 

is not allowed unless there is no longer 

an active EtO leak once the heat 

exchange system is isolated and not in 

EtO service. A heat exchange system in 

EtO service means any heat exchange 

system in a process that cools process 

fluids (liquid or gas) that are 0.1 percent 

or greater by weight of EtO. If 

knowledge exists that suggests EtO 

could be present in a heat exchange 

system, then the heat exchange system 

is considered to be ‘‘in ethylene oxide 

service’’ unless the procedures specified 

in the HON at 40 CFR 63.109 are 

performed to demonstrate that the heat 

exchange system does not meet the 

definition of being ‘‘in ethylene oxide 

service.’’ Examples of information that 

could suggest EtO could be present in a 

heat exchange system include 

calculations based on safety data sheets, 

material balances, process 

stoichiometry, or previous test results 

provided the results are still relevant to 

the current operating conditions. 

Given the EtO specific requirements 

in the HON for heat exchange systems 

in EtO service and minimal operational 

differences between heat exchange 

systems operating at SOCMI and CMAS 

facilities, we evaluated the following 

options in the selection of GACT for all 

heat exchange systems ‘‘in ethylene 

oxide service’’ that are located at CMAS: 

• Control Option 1: quarterly 

monitoring (after an initial six months 

of monthly monitoring) with the 

Modified El Paso Method, using a leak 

action level defined as a total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas of 6.2 ppmv; reduce 

the allowed amount of repair time from 

45 days after finding a leak to 15 days 

from the sampling date; and prohibit 

delay of repair. 

• Control Option 2: same as Control 

Option 1, except monthly monitoring 

with the Modified El Paso Method 

instead of quarterly monitoring. 

• Control Option 3: same as Control 

Option 1, except weekly monitoring 

with the Modified El Paso Method 

instead of quarterly monitoring. This 

option is required in the HON. 

The Modified El Paso Method is 

required and in use by sources regulated 

under other rulemakings including, but 

not limited to the MON, the HON, and 

the Petroleum Refineries NESHAP. The 

method works via air stripping and use 

of a flame ionization detector (FID), both 

of which are well understood 


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17EPA, 2008. Control Options and Impacts for 

Cooling Tower Control Measures Chemical 

Manufacturing Area Source Standards. September 

5, 2008. Docket ID No. EPA–HQ–OAR–2008–0334– 

0003; and EPA, 2009. Update to the Control Options 

and Impacts for Heat Exchange System Control 

Measures for Promulgation Chemical 

Manufacturing Area Source Standards. May 5, 

2009. Docket ID No. EPA–HQ–OAR–2008–0334– 

0081. 

technologies in the chemical 

manufacturing sector and have been in 

use for decades. Given the widespread 

use of the fundamental technologies and 

method in other, similar chemical 

manufacturing facilities, we consider 

use of the Modified El Paso Method to 

be ‘‘generally available.’’ 

We estimated the impacts of these 

Control Options using information from 

the original CMAS rulemaking.17 We 

estimated that 27 of the 33 facilities that 

either would become subject to the 

CMAS NESHAP if EtO is added to table 

1 to 40 CFR part 63, subpart VVVVVV 

or that are already subject to the CMAS 

NESHAP and emit EtO would be 

affected by Control Options 1 through 3; 

and we assumed each affected facility 

does not currently have an LDAR 

program for monitoring their cooling 

water. As part of our analysis, we also 

assumed all facilities monitoring 

quarterly for two or less heat exchange 

systems would elect to contract out the 

Modified El Paso monitoring (instead of 

purchasing a stripping column and FID 

analyzer and performing the monitoring 

in-house); however, facilities 

monitoring monthly or weekly would 

elect to purchase a stripping column 

and FID analyzer and perform in-house 

monitoring due to logistics. In addition, 

we assumed repairs could be performed 

by plugging a specific heat exchanger 

tube, and if a heat exchanger is leaking 

to the extent that it needs to be replaced, 

then it is effectively at the end of its 

useful life. Therefore, we determined 

that the cost of replacing a heat 

exchanger is an operational cost that 

would be incurred by the facility 

because of routine maintenance and 

equipment replacement, and it is not 

attributable to the Control Options. 

Table 3 of this preamble presents the 

nationwide impacts for requiring 

owners and operators of heat exchange 

systems in EtO service to use the 

Modified El Paso Method and repair 

leaks of total strippable hydrocarbon 

concentration (as methane) in 

accordance with Control Options 1 

through 3. See the document titled 

Clean Air Act Section 112(d)(5) GACT 

Standard Analysis for Heat Exchange 

Systems that Emit Ethylene Oxide and 

Section 112(d)(6) Technology Review for 

Heat Exchange Systems Associated with 

Chemical Manufacturing Process Units 

at Area Sources Subject to the CMAS 

NESHAP, which is available in the 

docket for this rulemaking, for details 

on the assumptions and methodologies 

used in this analysis. 

While all Control Options were 

identified as cost effective based on 

values accepted as part of other recent 

rulemakings regulating EtO emissions 

(see 89 FR 24090, April 5, 2024, for the 

commercial sterilizer rulemaking), the 

potency of EtO as a carcinogen, and 

historic cost-effectiveness values 

accepted for highly toxic HAP (such as 

hexavalent chromium), there are no 

records in the emissions inventory from 

heat exchangers in EtO service. We note 

that leaks from heat exchange systems 

handling EtO can still occur, even if 

there are no specific emissions records 

in the inventory. This absence of 

records is likely because most facilities 

emitting EtO have not been required to 

monitor leaks in their heat exchange 

systems. Consequently, the impacts 

associated with controlling these 

emissions are less certain due to the 

lack of records. In addition, there are 

concerns that monthly or weekly 

monitoring of heat exchangers in EtO 

service would be significantly more 

burdensome for area sources than major 

sources. Major sources may have 

additional capital and personnel 

bandwidth to accommodate installation 

and operation of a stripping column and 

lab equipment (such as a gas 

chromatograph/mass spectroscopy unit) 

necessary for in-house analysis 

compared to area sources who may not 

have previously been subject to any 

monitoring of heat exchange systems. 

As such, based on the costs, emissions 

reductions, and uncertainties, we are 

proposing that Control Option 1 

represents GACT for heat exchange 

systems in EtO service. However, we are 

soliciting comments and data on 

whether more frequent monitoring (i.e., 

Control Options 2 and 3) would be 

appropriate for CMAS considering the 

proposed addition of EtO to table 1 to 

40 CFR part 63, subpart VVVVVV. 

TABLE 3—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTIONS 1 THROUGH 3 FOR

REQUIRING THE MODIFIED EL PASO METHOD FOR HEAT EXCHANGE SYSTEMS IN ETO SERVICE AT CERTAIN FACILITIES 1

Control option 

Total capital 

investment 

($) 

Total 

annualized 

costs w/o 

recovery 

credits 

($/yr) 

Total 

annualized 

costs with 

recovery 

credits 

($/yr) 

VOC emission 

reductions 

(tpy) 

EtO emission 

reductions 

(tpy) 

EtO cost 

effectiveness 

w/o recovery 

credits 

($/ton) 

EtO cost 

effectiveness 

with recovery 

credits 

($/ton) 

EtO Incremental 

cost effectiveness 

with recovery 

credits 

(from option 1) 

($/ton) 

1 .................................... 122,000 157,000 117,900 43.4 24.8 6,300 4,700 ................................

2 .................................... 122,000 359,400 319,500 44.3 25.3 14,200 12,500 388,500 

3 .................................... 122,000 1,371,500 1,331,300 44.7 25.5 52,300 52,200 1,688,800 

1Facilities that would either become subject to the CMAS NESHAP if EtO is added to table 1 to 40 CFR part 63, subpart VVVVVV, as proposed, or are already 

subject to the CMAS NESHAP and emit EtO. 

The EPA is proposing to define a heat 

exchange system ‘‘in ethylene oxide 

service’’ at 40 CFR 63.11502(b), by 

reference to the HON (40 CFR 63.101). 

We are proposing Control Option 1 at 40 

CFR 63.11499(e) and item 2 of table 8 

to the CMAS NESHAP, by reference to 

the HON (40 CFR 63.104(a), (f) through 

(i), and (k)), to specify quarterly 

monitoring (after an initial six months 

of monthly monitoring) for leaks for all 

new and existing affected sources with 

heat exchange systems in EtO service 

using the Modified El Paso Method, and 

if a leak is found, we are proposing 

owners and operators must repair the 

leak to below the applicable leak action 

level as soon as practicable, but no later 

than 15 days after the sample was 

collected with no delay of repair 

allowed (see 40 CFR 63.104(h)(6)). 

3. Process Vents and Storage Tanks in 

EtO Service 

Emissions of EtO can occur from 

several types of gas streams associated 

with CMAS processes, such as 

distillation columns, evaporator vents, 

and vacuum operations, as well as 

during vapor displacements and heating 

losses. CMAS storage tanks are used to 

store liquid and gaseous feedstocks for 

use in a process, as well as to store 


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liquid and gaseous products from a 

process. EtO is typically stored under 

pressure as a liquified gas but may also 

be found in small amounts in 

atmospheric storage tanks storing liquid 

products that are formed with EtO as a 

reactant in their production. Typical 

emissions from atmospheric storage 

tanks occur from working and breathing 

losses while pressure vessels are 

considered closed systems and, if 

properly maintained and operated, 

should have virtually no emissions. In 

some instances, pressurized vessels also 

could use a blanket of inert gas, most 

often nitrogen, to maintain a nondecomposable vapor space, and 

continuous purge of vapor space from 

non-loading operations could also lead 

to emissions from storage tanks. We 

provide details about process vents and 

storage tanks, including how the CMAS 

NESHAP regulates them, in our 

technology review discussion (see 

sections IV.C.3 and IV.C.4 of this 

preamble, respectively). 

To assess what GACT standards may 

be appropriate, we reviewed other 

rulemakings to identify the level of 

control required for process vents and 

storage vessels emitting EtO. As part of 

that review, we identified two rules 

requiring stringent control of emissions 

from vents and process tanks ‘‘in 

ethylene oxide service.’’ The EPA 

recently added EtO-specific 

requirements into the MON and HON 

for process vents and storage vessels in 

EtO service (see 85 FR 49084, August 

12, 2020, and 89 FR 42932, May 16, 

2024, respectively). We note that the 

MON and HON use the term ‘‘storage 

vessel’’ in lieu of ‘‘storage tank’’ which 

is used in the CMAS NESHAP. 

According to the MON and HON, a 

process vent in EtO service is a process 

vent that contains a concentration of 

greater than or equal to 1 ppmv 

undiluted EtO when uncontrolled, and 

when all process vents within the 

process are combined, the sum of 

uncontrolled EtO emissions are greater 

than or equal to 5 pounds per year (lb/ 

yr) (2.27 kilogram per year, kg/yr). A 

storage vessel in EtO service means a 

storage vessel of any capacity and vapor 

pressure storing a liquid that is at least 

0.1 percent by weight of EtO. The EtOspecific standards established for the 

Miscellaneous Organic Chemical 

Manufacturing and SOCMI source 

categories are as follows: 

• Requirements that owners and 

operators must reduce emissions of EtO 

from process vents in EtO service by 

either: (1) venting emissions through a 

closed vent system to a control device 

that reduces EtO by greater than or 

equal to 99.9 percent by weight, to a 

concentration less than 1 ppmv for each 

process vent, or to less than 5 lb/yr for 

all combined process vents per CMPU; 

or (2) venting emissions through a 

closed vent system to a flare meeting 

certain new operating and monitoring 

requirements for flares; and 

• Requirements that owners and 

operators must reduce emissions of EtO 

from storage tanks in EtO service by 

either: (1) venting emissions through a 

closed vent system to a control device 

that reduces EtO by greater than or 

equal to 99.9 percent by weight or to a 

concentration less than 1 ppmv for each 

storage tank vent; or (2) venting 

emissions through a closed vent system 

to a flare meeting certain new operating 

and monitoring requirements for flares. 

Given the EtO specific requirements 

in the MON and HON for process vents 

and storage vessels in EtO service and 

minimal operational differences 

between an APCD controlling emissions 

from process vents or storage vessels/ 

tanks at MON, SOCMI, and CMAS 

facilities, we evaluated a Control Option 

to represent GACT for process vents and 

storage tanks that are ‘‘in ethylene oxide 

service’’ that would require owners and 

operators at certain CMAS (i.e., facilities 

that would either become subject to the 

CMAS NESHAP if EtO is added to table 

1 to 40 CFR part 63, subpart VVVVVV, 

as proposed, or are already subject to 

the CMAS NESHAP and emit EtO) to 

reduce emissions of EtO by 99.9 percent 

from process vents and storage tanks 

that are ‘‘in ethylene oxide service’’ as 

defined by the MON and HON (i.e., 

Control Option 1). Our evaluation 

considered the use of a thermal oxidizer 

achieving a 99.9 percent reduction of 

EtO emissions to control emissions from 

process vents and storage tanks in EtO 

service, as it is common for the same 

control device to control emissions from 

both emission sources at chemical 

plants. Control Option 1 reflects the 

EtO-specific requirements in the MON 

and HON for process vents and storage 

vessels in EtO service; therefore, it 

would apply to process vents in which 

the uncontrolled, undiluted EtO 

emissions from all process vents in a 

CMPU are greater than or equal to 5 lb/ 

yr and the concentration of the 

uncontrolled, undiluted stream is 

greater than or equal to 1 ppmv. This 

Control Option would also apply to 

storage tanks of any capacity and vapor 

pressure storing a liquid that is at least 

0.1 percent by weight of EtO. 

We find this Control Option to be 

‘‘generally available’’ per the language 

of CAA section 112(d)(5). Control 

devices include a wide array of 

potential technologies and so a facility 

may use whatever methods are available 

to achieve the 99.9 percent by weight 

reduction in EtO emissions. Thermal 

oxidizers, which we assumed will be 

installed by facilities needing to meet 

the proposed standards, are used to 

control emissions from process vents 

and storage tanks at sources regulated 

under other rulemakings including, but 

not limited to, the MON and the HON 

and have been in use in industry for 

decades. In addition, the CMAS 

NESHAP already allows for the venting 

of emissions through a closed vent 

system to a flare for both process vents 

and storage tanks. Given the widespread 

use of a readily available control 

technology such as a thermal oxidizer in 

other, similar chemical manufacturing 

facilities, we consider this Control 

Option of proposing a 99.9 percent by 

weight reduction of EtO emissions from 

process vents and storage tanks to be 

‘‘generally available.’’ 

To determine which emission points 

at facilities would need additional 

control of EtO emissions, we reviewed 

the CMAS emissions inventory data (see 

section II.C.2 of this preamble). For each 

process vent and storage tank emission 

point record with EtO emissions in the 

CMAS emissions inventory, we 

determined whether it was controlled 

by a non-flare combustion device, a 

non-combustion control device, a noncombustion control device able to 

achieve 99.9 percent emissions 

reduction, or was uncontrolled. There 

are no process vent or storage tank 

emission point records associated with 

a non-flare combustion device; however, 

for emission point records that are 

controlled by a non-combustion control 

device, our impacts analyses assumed 

that none of the facilities with existing 

non-combustion controls would be able 

to achieve 99.9 percent control of EtO, 

unless a stack test or data provided by 

a state agency confirmed otherwise. 

Therefore, we treated non-combustion 

control devices unable to achieve 99.9 

percent control and uncontrolled 

emission point records in the same 

manner and assumed that each would 

need to be controlled by a thermal 

oxidizer. Some facilities that would 

need to install a thermal oxidizer to 

control EtO have multiple process vent 

and/or storage tank emission points 

with EtO emissions. Rather than costing 

out multiple thermal oxidizers for these 

facilities, we assumed they would 

combine the streams together and install 

a single thermal oxidizer (to control all 

EtO emissions), as is commonly done at 

chemical plants. We also recognize that 

some emission points could possibly 

achieve a 99.9 percent reduction in EtO 

emissions by upgrading or installing a 


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18Refer to the file ‘‘Incinerators and Oxidizers 

Calculation Spreadsheet (note: updated on 1/16/ 

2018) (xlsm)’’ which follows the methodology from 

the sixth edition of the EPA Air Pollution Control 

Cost Manual and can be found at the following 

website: https://www.epa.gov/economic-and-costanalysis-air-pollution-regulations/cost-reports-andguidance-air-pollution. 

19The EPA finalized EtO emissions standards in 

the RTR for sterilization facilities with costs 

estimated to be as much as $17,500,000 per ton EtO. 

20For small hard chromium electroplating, to 

provide an ample margin of safety, the EPA 

finalized a requirement with a cost effectiveness of 

$15,000 per lb ($30,000,000 per ton) (see 77 FR 

58227–8 and FR 77 58239, September 19, 2012). 

new scrubber system instead of a new 

thermal oxidizer; and upgrading or 

installing a new scrubber system would 

likely cost less than installing a new 

thermal oxidizer. However, for 

simplicity, we only evaluated the use of 

a thermal oxidizer to meet the Control 

Option because using thermal oxidizers 

is common for controlling emissions 

from both process vents and storage 

tanks in EtO service at chemical plants. 

Ultimately, we determined that seven 

facilities would be impacted by Control 

Option 1 to reduce emissions of EtO by 

99.9 percent from process vents and 

storage tanks that are ‘‘in ethylene oxide 

service’’ as defined by the MON and 

HON (1 of these 7 facilities is already 

subject to the CMAS NESHAP and the 

remaining 6 facilities would become 

subject to the CMAS NESHAP if EtO is 

added to table 1 to 40 CFR part 63, 

subpart VVVVVV, as proposed). We 

estimated costs to install a thermal 

oxidizer using the EPA’s control cost 

template.18 Table 4 of this preamble 

presents the nationwide impacts of 

Control Option 1, requiring owners and 

operators to reduce emissions of EtO by 

99.9 percent from process vents and 

storage tanks that are ‘‘in ethylene oxide 

service’’ as defined by the MON and 

HON. See the document titled Clean Air 

Act Section 112(d)(5) GACT Standard 

Analysis for Process Vents and Storage 

Tanks that Emit Ethylene Oxide and 

Section 112(d)(6) Technology Review for 

Process Vents and Storage Tanks 

Associated with Chemical 

Manufacturing Process Units at Area 

Sources Subject to the CMAS NESHAP, 

which is available in the docket for this 

rulemaking, for details on the 

assumptions and methodologies used in 

this analysis. Based on the costs and 

emission reductions for Control Option 

1, we are proposing to revise the CMAS 

NESHAP for process vents and storage 

tanks in EtO service to reflect Control 

Option 1 pursuant to CAA section 

112(d)(5). The cost effectiveness of this 

Control Option is within the range of 

values that have been accepted in other 

recent rulemakings regulating EtO 

emissions such as the commercial 

sterilizer rulemaking (see 89 FR 24090, 

April 5, 2024) 19 and is within the range 

of historic cost-effectiveness values that 

have been accepted for highly toxic 

HAP (such as hexavalent chromium).20

EtO is similarly toxic due to its potency 

as a carcinogen. As such, we find that 

this Control Option is cost effective. 

TABLE 4—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTION 1 FOR REQUIRING 99.9 

PERCENT CONTROL OF PROCESS VENTS AND STORAGE TANKS IN ETO SERVICE AT CERTAIN FACILITIES 1

Control 

option 

Total capital 

investment 

($) 

Total 

annualized costs 

($/yr) 

EtO emission 

reductions 

(tpy) 

EtO cost 

effectiveness 

($/ton) 

1 ....................................................................................................... 1,395,000 2,126,000 1.1 1,933,000 

1Facilities that would either become subject to the CMAS NESHAP if EtO is added to table 1 to 40 CFR part 63, subpart VVVVVV, as proposed, or are already subject to the CMAS NESHAP and emit EtO. 

The EPA is proposing to define a 

process vent ‘‘in ethylene oxide service’’ 

at 40 CFR 63.11502(b), by reference to 

the HON (40 CFR 63.101). We are 

proposing Control Option 1 for all new 

and existing affected sources with 

process vents in EtO service at 40 CFR 

63.11496(j), item 4 of table 2 to the 

CMAS NESHAP (for batch process 

vents), and item 4 of table 3 to the 

CMAS NESHAP (for continuous process 

vents), by reference to the HON. These 

proposed requirements specify that 

owners and operators of process vents 

in EtO service must reduce emissions of 

EtO by venting emissions through a 

closed vent system to a flare in 

accordance with the requirements in 40 

CFR 63.108 and 40 CFR 63.124 (see 

section IV.A.6 of this preamble for 

additional details regarding our 

proposed requirements for flares that 

emit EtO), or to a control device that 

reduces EtO by greater than or equal to 

99.9 percent by weight, or to a 

concentration less than 1 ppmv for each 

process vent or to less than 5 lb/yr for 

all combined process vents within the 

process in accordance with the 

requirements in 40 CFR 63.124. 

The EPA is proposing to define a 

storage tank (vessel) ‘‘in ethylene oxide 

service’’ at 40 CFR 63.11502(b), by 

reference to the HON (40 CFR 63.101). 

We are also proposing that the 

exemption for ‘‘tanks storing organic 

liquids containing HAP only as 

impurities’’ listed in the definition of 

‘‘storage tank’’ at 40 CFR 63.11502(b) 

does not apply for storage tanks in EtO 

service. We are also proposing Control 

Option 1 for storage tanks in EtO service 

at 40 CFR 63.11497(e) and item 5 of 

table 5 to the CMAS NESHAP, by 

reference to the HON. These proposed 

requirements specify that owners and 

operators of storage tanks in EtO service 

must reduce emissions of EtO by 

venting emissions through a closed vent 

system to a flare in accordance with the 

requirements in 40 CFR 63.108 and 40 

CFR 63.124 (see section IV.A.6 of this 

preamble for additional details 

regarding our proposed requirements for 

flares that emit EtO), or to a control 

device that reduces EtO by greater than 

or equal to 99.9 percent by weight, or to 

a concentration less than 1 ppmv for 

each storage tank vent in accordance 

with the requirements in 40 CFR 63.124. 

In addition, given that 40 CFR 63.124 

requires owners and operators to 

comply with the HON leak inspection 

requirements in 40 CFR 63.148 and the 

delay of repair provisions associated 

with these inspection requirements (i.e., 

40 CFR 63.148(e)) rely on a definition 

for ‘‘shutdown’’ that does not include 

batch processes, we are also proposing 

to substitute the use of ‘‘shutdown’’ 

with language at 40 CFR 

63.11496(j)(5)(iv) and 40 CFR 

63.11497(e)(5)(iv) to accommodate both 

continuous and batch processes. We are 

proposing that for 40 CFR 63.148(e), the 

term ‘‘shutdown’’ for a continuous 

operation, means the cessation of the 

unit operation for any purpose. 

Shutdown begins with the initiation of 

steps as described in a written standard 

operating procedure or shutdown plan 

to cease normal/stable operation (e.g., 

reducing or immediately stopping feed). 

For batch operations, we are proposing 

that for 40 CFR 63.148(e), the term 

‘‘shutdown’’ means the cessation of a 


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21The Fr is the fraction of a HAP that is stripped 

from wastewater and is an indicator of the extent 

to which a HAP is effectively removed during the 

steam stripping process, which for EtO is 98 

percent. 

22EPA, 1992a. Hazardous Air Pollutant 

Emissions from Process Units in the Synthetic 

Organic Chemical Manufacturing Industry— 

Background Information for Proposed Standards, 

Volume 1B: Control Technologies. EPA–453/D–92– 

016b. November 1992; and EPA, 1992b. Hazardous 

Air Pollutant Emissions from Process Units in the 

Synthetic Organic Chemical Manufacturing 

Industry—Background Information for Proposed 

Standards, Volume 1C: Model Emission Sources. 

EPA–453/D–92–016c. November 1992. 

batch operation except shutdown does 

not apply to cessation of batch 

operations at the end of a campaign or 

between batches within a campaign 

when the steps taken to cease operation 

are normal operations. 

Finally, we are also proposing to 

remove the option to allow use of a 

design evaluation in lieu of performance 

testing to demonstrate compliance for 

controlling process vents and storage 

tanks that are in EtO service. In 

addition, owners or operators that 

choose to control emissions with a nonflare control device would be required 

to conduct an initial performance test 

on each control device in EtO service to 

verify performance at the required level 

of control, and would also be required 

to conduct periodic performance testing 

on non-flare control devices in EtO 

service every 5 years (see proposed 40 

CFR 63.11496(j) and 40 CFR 63.11497(e) 

by reference to 40 CFR 63.124). 

4. Wastewater in EtO Service 

EtO is emitted into the air from 

wastewater collection, storage, and 

treatment systems that are uncovered or 

open to the atmosphere through 

volatilization of the compound at the 

liquid surface. The rate of volatilization 

is related directly to the speed of the air 

flow over the water surface. We provide 

more details about wastewater streams, 

including how the CMAS NESHAP 

regulates them, in our technology 

review discussion (see section IV.C.5 of 

this preamble). 

To assess what GACT standards may 

be appropriate for wastewater in EtO 

service, we reviewed other rulemakings 

to identify the level of control required 

for wastewater emitting EtO. As part of 

that review, we identified one rule 

requiring control of emissions from 

wastewater ‘‘in ethylene oxide service.’’ 

In the HON rulemaking, the EPA 

recently added EtO-specific 

requirements for wastewater streams in 

EtO service (see 89 FR 42932, May 16, 

2024). These standards require owners 

and operators to manage and treat 

existing and new wastewater streams 

with total annual average concentration 

of EtO greater than or equal to 1 ppmw 

at any flow rate. As such, we evaluated 

a Control Option to represent GACT for 

wastewater streams that are ‘‘in ethylene 

oxide service’’ that would require 

owners and operators at certain CMAS 

(those that would either become subject 

to the CMAS NESHAP if EtO is added 

to table 1 to 40 CFR part 63, subpart 

VVVVVV, as proposed, or are already 

subject to the CMAS NESHAP and emit 

EtO) to comply with the HON Group 1 

wastewater requirements for wastewater 

streams that are ‘‘in ethylene oxide 

service’’ as defined by the HON (i.e., 

Control Option 1). 

The HON specifies performance 

standards for treatment processes 

managing Group 1 wastewater streams 

including performance standards for 

open or closed biological treatment 

systems or a design steam stripper with 

vent control. For APCDs (e.g., thermal 

oxidizers) used to control emissions 

from collection system components, 

steam strippers, or closed biological 

treatment, the HON provides owners or 

operators several compliance options, 

including a 95 percent destruction 

efficiency standard, a 20 ppmv outlet 

concentration standard, or design 

specifications for temperature and 

residence time. Given the EtO specific 

requirements in the HON at 40 CFR 

63.138(b)(3) and (c)(3) for wastewater 

streams in EtO service to reduce, by 

removal or destruction, the 

concentration of EtO to a level less than 

1 ppmw and minimal operational 

differences between controlling 

emissions from HON CMPUs and CMAS 

CMPUs, we evaluated the use of steam 

stripping to comply with Control Option 

1. While we acknowledge EtO can be 

biodegraded, the compound is not on 

table 37 to subpart G of the HON 

suggesting that it is not a readily 

biodegradable compound when using a 

biological treatment method, and EtO 

would need to be stripped out of the 

wastewater to meet the standard at 40 

CFR 63.138(b)(3) and (c)(3). Therefore, 

we evaluated Control Option 1 using a 

steam stripper achieving a 98 percent 

reduction of EtO emissions (based on 

the fraction removed (Fr) value of EtO 21

in table 9 to subpart G of the HON). 

We find Control Option 1 to be 

‘‘generally available’’ per the language 

of CAA section 112(d)(5). Steam 

strippers are used to control emissions 

from wastewater streams at sources 

regulated under other rulemakings 

including, but not limited to, the MON 

and the HON. In addition, steam 

stripping was evaluated as part of the 

original rulemaking and is currently a 

method of compliance for controlling 

certain CMPU wastewater streams. 

Given the widespread use of this control 

technology in other, similar chemical 

manufacturing facilities, and current 

applicability of the technology to certain 

CMAS wastewater streams, we consider 

this Control Option of proposing the use 

of steam strippers to control EtO 

emissions from wastewater to be 

‘‘generally available.’’ 

We reviewed the CMAS emissions 

inventory data (see section II.C.2 of this 

preamble) as well as air permits and 

determined that there are 4 CMAS 

facilities that have wastewater processes 

that use and emit EtO and therefore 

would be impacted by Control Option 1. 

To evaluate the impacts of requiring 

these facilities to meet Control Option 1, 

we used PEPO-specific wastewater data 

submitted in response to the EPA’s 2022 

CAA section 114 request (see section 

II.C.3 of this preamble). We used the 

PEPO-specific wastewater data rather 

than HON-specific data because for EtO 

processes, CMAS CMPUs are more like 

PEPO PMPUs given that both CMAS 

CMPUs and PEPO PMPUs use EtO as a 

reactant (often in batch reactions to 

make a product), whereas HON CMPUs 

produce EtO and are continuous. In 

addition, we removed all PEPO-specific 

wastewater data that could not be 

representative of an area source (based 

on the amount of HAP emissions that 

could potentially be emitted to the 

atmosphere from the wastewater 

streams); and therefore, not 

representative of a CMAS facility. We 

estimated costs to install a steam 

stripper using the cost algorithm for 

wastewater stripper steam requirements 

used for the development of the HON.22

Table 5 of this preamble presents the 

nationwide impacts of Control Option 1, 

requiring owners and operators to 

manage and treat existing and new 

wastewater streams with total annual 

average concentration of EtO greater 

than or equal to 1 ppmw at any flow rate 

in accordance with HON Group 1 

wastewater requirements. See the 

document titled Clean Air Act Section 

112(d)(5) GACT Standard Analysis for 

Wastewater Streams that Emit Ethylene 

Oxide and Clean Air Act Section 

112(d)(6) Technology Review for 

Wastewater Systems Associated with 

Chemical Manufacturing Process Units 

at Area Sources Subject to the CMAS 

NESHAP, which is available in the 

docket for this rulemaking, for details 

on the assumptions and methodologies 

used in this analysis. Based on the costs 

and emission reductions for Control 

Option 1, we are proposing to revise the 

CMAS NESHAP for wastewater in EtO 

service to reflect Control Option 1 

pursuant to CAA section 112(d)(5). The 


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23See footnote 19. 24See footnote 20. 

cost effectiveness of this Control Option 

is within the range of values that have 

been accepted in other recent 

rulemakings regulating EtO emissions, 

such as the commercial sterilizer 

rulemaking (see 89 FR 24090, April 5, 

2024) 23, and is within the range of 

historic cost-effectiveness values that 

have been accepted for highly toxic 

HAP (such as hexavalent chromium).24

EtO is similarly toxic due to its potency 

as a carcinogen. As such, we find that 

this Control Option is cost effective. 

TABLE 5—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTION 1 FOR REQUIRING CONTROL

OF WASTEWATER IN ETO SERVICE AT CERTAIN FACILITIES 1

Control option 

Total capital 

investment 

($) 

Total 

annualized costs 

($/yr) 

EtO emission 

reductions 

(tpy) 2

EtO cost 

effectiveness 

($/ton) 

1 ....................................................................................................... 12,899,400 5,471,300 8.3 659,200 

1Facilities that would either become subject to the CMAS NESHAP if EtO is added to table 1 to 40 CFR part 63, subpart VVVVVV, as proposed, or are already subject to the CMAS NESHAP and emit EtO. 2We note that EtO emission reductions from wastewater (and subsequent cost-effectiveness values for EtO from wastewater) differ from reductions expected to occur from reported emissions inventories due to use of model plants, engineering assumptions made to estimate baseline 

emissions, and uncertainties in how fugitive emissions may have been calculated for reported inventories compared to our model plants analysis 

(and are documented in the memorandum). 

The EPA is proposing to define a 

wastewater stream ‘‘in ethylene oxide 

service’’ at 40 CFR 63.11502(b), by 

reference to the HON (40 CFR 63.101). 

We are proposing Control Option 1 for 

all new and existing affected sources 

with wastewater streams in EtO service 

at 40 CFR 63.11498(c) and item 3 of 

table 6 to the CMAS NESHAP, by 

reference to the HON. These proposed 

requirements specify that owners and 

operators of wastewater in EtO service 

must reduce, by removal or destruction, 

the concentration of ethylene oxide in 

existing and new wastewater streams 

(i.e., wastewater streams with total 

annual average concentration of EtO 

greater than or equal to 1 ppmw at any 

flow rate) to a level less than 1 ppmw 

as determined by the procedures 

specified in § 63.145(b) and in 

accordance with the Group 1 

wastewater stream requirements of 

§§ 63.133 through 63.148 and the 

requirements referenced therein. 

Additionally, we are aware that some 

chemical manufacturing facilities 

dispose of certain wastewater streams 

that contain EtO by adding those 

wastewaters to the cooling water of their 

heat exchange systems, rather than 

considering those EtO-containing 

streams to be potential sources of 

wastewater. To eliminate these types of 

EtO emissions from wastewater being 

injected into heat exchange systems, we 

are also proposing to prohibit owners 

and operators from injecting water into 

or disposing of water through any heat 

exchange system in a CMPU meeting the 

conditions of 40 CFR 63.11494 if the 

water contains any amount of EtO, has 

been in contact with any process stream 

containing EtO, or the water is 

considered wastewater as defined in 40 

CFR 63.11502 (see proposed 40 CFR 

63.11495(b)(4) and items 1.c and 2 of 

table 8 to the CMAS NESHAP). 

5. Standards for Transfer Operations 

That Emit EtO 

The EPA includes transfer operations 

as part of the equipment collection that 

makes up a CMPU (see 40 CFR 

63.11494(b)). According to the CMAS 

NESHAP, transfer operations involve 

loading liquid containing organic HAP 

into tank trucks and rail cars from a 

transfer rack. This does not include 

loading into other containers like cans, 

drums, and totes. 

The CMAS NESHAP defines a transfer 

rack as the system used to load organic 

liquids into tank trucks and railcars at 

a single location. This system includes 

all necessary loading arms, pumps, 

meters, shutoff valves, relief valves, and 

other piping and equipment. Transfer 

equipment that do not share common 

piping, valves, and other equipment are 

considered separate transfer racks. 

The CMAS NESHAP regulates transfer 

operations through specific management 

practices. According to 40 CFR 

63.11495(a)(2), owners and operators 

must use one of the following methods 

to control total organic HAP emissions 

when transferring certain liquids (those 

containing any organic HAP listed in 

table 1 to 40 CFR part 63, subpart 

VVVVVV) to tank trucks or railcars: (1) 

submerged loading or bottom loading; 

(2) routing emissions to a fuel gas 

system or process; (3) vapor balancing 

back to the storage tank or another 

storage tank connected by a common 

header; or (4) venting through a closed 

vent system to a control device. 

Since we are proposing to add EtO to 

table 1 to 40 CFR part 63, subpart 

VVVVVV, owners and operators of new 

and existing affected sources with 

transferring liquids containing EtO to 

tank trucks or railcars would be subject 

to these same management practices. 

We are proposing that these 

management practices reflect GACT for 

these transfer operations. We anticipate 

that all facilities that may become 

subject to the CMAS NESHAP if EtO 

were to be added to table 1 to 40 CFR 

part 63, subpart VVVVVV already use at 

least one of these management practices 

when transferring liquids containing 

EtO to tank trucks or railcars. Therefore, 

we do not expect any additional costs 

from this proposed GACT standard. 

The EPA is soliciting comments and 

data on the proposed transfer operation 

practices. 

6. Standards for Flares That Emit EtO 

As previously discussed in section 

IV.A.3 of this preamble, the EPA is 

proposing to add specific requirements 

for EtO to the CMAS NESHAP for batch 

process vents, continuous process vents, 

and storage tanks in EtO service. Each 

of these requirements mandates 99.9 

percent control, reduction in 

concentration to less than 1 ppmw, or 

the use of a flare. These requirements 

are based on EtO-specific requirements 

in the MON and HON. If a flare is used 

to meet the MON and HON standards 

for process vents and storage tanks in 

EtO service, the owner or operator must 

comply with several operational and 

monitoring requirements that are 

reflective of requirements for petroleum 

refinery flares which address: (1) the 

presence of a pilot flame; (2) visible 

emissions; (3) flare tip velocity; (4) net 

heating value of flare combustion zone 

gas; and (5) net heating value dilution 

parameter (if the flare actively receives 

perimeter assist air). More details about 

these requirements are provided in our 


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25To estimate the baseline control efficiency of 

volatile organic compounds (VOC) and HAP 

anticipated by applying Control Option 1, we 

reviewed data submitted to the EPA in 2011 by the 

American Petroleum Institute (API), the American 

Chemistry Council (ACC), and the National 

Petrochemical and Refiners Association (NPRA), 

now known as the American Fuels and 

Petrochemical Manufacturers (AFPM). This dataset 

includes detailed hourly operational information 

for 38 steam-assisted flares, characterizing different 

operating conditions by waste gas flow rate, steam 

flow rate, waste gas composition, and duration of 

that operating condition. 

26See footnote 19. 

27See footnote 20. 

technology review discussion (see 

section IV.C.6 of this preamble). As 

such, we evaluated the option (i.e., 

Control Option 1) to require flares used 

to comply with the proposed GACT 

standards for process vents and storage 

tanks in EtO service to meet the same 

operational and monitoring 

requirements included in the MON and 

HON. 

Control Option 1 requires various 

monitoring equipment (i.e., hydrogen 

analyzers, calorimeters, and flow 

monitors) be installed on the flare vent 

gas stream header and/or steam- or airassist header. Flares are used to control 

emissions from sources such as process 

vents and storage tanks regulated under 

other rulemakings including, but not 

limited to, the HON and the MON. The 

HON and MON apply to chemical 

manufacturing facilities and already 

require these types of monitoring 

equipment. Given the widespread use of 

this monitoring equipment in other, 

similar chemical manufacturing 

facilities, we consider Control Option 1, 

which includes the use of hydrogen 

analyzers, calorimeters, and flow 

monitors, to be ‘‘generally available’’ per 

the language of CAA section 112(d)(5). 

Using information from the CMAS 

emissions inventory data (see section 

II.C.2 of this preamble), we estimated 

there are only two flares at two different 

facilities that would be impacted by 

Control Option 1 (one of the facilities is 

already subject to the CMAS NESHAP 

and the other facility would become 

subject to the CMAS NESHAP if EtO is 

added to table 1 to 40 CFR part 63, 

subpart VVVVVV, as proposed). We 

estimated costs for each flare for a given 

facility, considering current monitoring 

systems already installed on each 

individual flare. Given that the same 

type of equipment is used for flares in 

the CMAS categories and for the 

petroleum refinery sector, we estimated 

costs for any additional monitoring 

systems needed based on installed costs 

received from petroleum refineries. If 

those installed costs were unavailable, 

we estimated costs based on vendorpurchased equipment. The baseline 

emission estimate and the emission 

reductions achieved by Control Option 

1 were estimated based on the CMAS 

emissions inventory data (see section 

II.C.2 of this preamble) and current vent 

gas and steam flow data submitted by 

industry representatives.25 The results 

of the impact estimates are summarized 

in table 6 of this preamble for Control 

Option 1. See the document titled Clean 

Air Act Section 112(d)(5) GACT 

Standard Analysis for Flares that Emit 

Ethylene Oxide and Section 112(d)(6) 

Technology Review for Flares 

Associated with Chemical 

Manufacturing Process Units at Area 

Sources Subject to the CMAS NESHAP, 

which is available in the docket for this 

rulemaking, for details on the 

assumptions and methodologies used in 

this analysis. Based on the costs and 

emission reductions for Control Option 

1, we are proposing to revise the CMAS 

NESHAP for flares used to comply with 

the proposed GACT standards for 

process vents and storage tanks in EtO 

service to reflect Control Option 1 

pursuant to CAA section 112(d)(5). The 

cost-effectiveness of this Control Option 

is within the range of values that have 

been accepted in other recent 

rulemakings regulating EtO emissions 

such as the commercial sterilizer 

rulemaking (see 89 FR 24090, April 5, 

2024) 26 and is within range of historic 

cost-effectiveness values that have been 

accepted for highly toxic HAP (such as 

hexavalent chromium).27 EtO is 

similarly toxic due to its potency as a 

carcinogen. As such, we find that this 

Control Option is cost-effective. 

TABLE 6—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTION 1 FOR REQUIRING THE SUITE

OF OPERATIONAL AND MONITORING REQUIREMENTS FOR FLARES THAT EMIT ETO AT CMAS FACILITIES 1

Control option 

Total capital 

investment 

($) 

Total 

annualized costs 

($/yr) 

VOC emission 

reductions 

(tpy) 

EtO emission 

reductions 

(tpy) 

EtO cost 

effectiveness 

($/ton) 

1 ....................................................................... 3,770,000 960,000 12.8 1.56 606,700 

1Facilities that would either become subject to the CMAS NESHAP if EtO is added to table 1 to 40 CFR part 63, subpart VVVVVV, as proposed, or are already subject to the CMAS NESHAP and emit EtO. 

We are proposing Control Option 1 for 

flares at new and existing affected 

sources that are used to comply with the 

proposed GACT standards for process 

vents and storage tanks in EtO service 

at item 4.a of table 2 to the CMAS 

NESHAP, item 4.a of table 3 to the 

CMAS NESHAP, item 5.a of table 5 to 

the CMAS NESHAP, and 40 CFR 

63.11497(f)(5), all by reference to the 

HON (40 CFR 63.108 and 40 CFR 

63.124). These proposed requirements 

specify that owners and operators that 

choose to use a flare to comply with the 

proposed standards for process vents 

and storage tanks in EtO service as 

described in section IV.A.3 of this 

preamble must vent emissions through 

a closed vent system and meet the 

applicable requirements for flares as 

specified in 40 CFR 63.670 and 63.671, 

including the provisions in tables 12 

and 13 to 40 CFR part 63, subpart CC 

(i.e., the suite of operational and 

monitoring requirements for refinery 

flares). In addition, we are proposing 

amendments to 40 CFR 

63.11501(c)(2)(iii) and (c)(4)(vii) to align 

the recordkeeping requirements with 

this proposed Control Option. 

We also note that we are proposing an 

LDAR program for equipment leaks at 

40 CFR 63.11495(a)(6) and (7) (see 

sections IV.A.1 and IV.C.1 of this 

preamble). Part of this LDAR program 

requires owners and operators that vent 

equipment leak emissions through a 

closed vent system to a flare used to 

control equipment leaks in EtO service, 

to comply with the same suite of 

operational and monitoring 

requirements for flares as we are 

proposing for flares used to comply with 

the proposed GACT standards for 

process vents and storage tanks in EtO 

service (see proposed 40 CFR 

63.11495(a)(7)). Given that we only 

identified two flares in the CMAS 

emissions inventory data that emit EtO 

and we have already estimated impacts 

for these flares to comply with Control 


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28EPA, 2023. Clean Air Act Section 112(d)(6) 

Technology Review for Fenceline Monitoring 

located in the SOCMI Source Category that are 

Associated with Processes Subject to HON and for 

Fenceline Monitoring that are Associated with 

Processes Subject to Group I Polymers and Resins 

NESHAP. EPA Docket ID No. EPA–HQ–OAR–2022– 

0730–0091. 

Option 1, we do not expect any 

additional costs from this proposed 

GACT standard. 

7. Standards for Fenceline Monitoring 

EtO 

As discussed in section IV.C.7 of this 

preamble as well, fenceline monitoring 

is the practice by which monitors are 

placed around the perimeter of a facility 

to measure the concentration of certain 

pollutants. When required in 

conjunction with root cause analysis 

and corrective action, fenceline 

monitoring can reduce uncertainties 

associated with fugitive emissions 

estimation and characterization. This 

section of the preamble is limited to the 

discussion of fenceline monitoring for 

EtO. Section IV.C.7 of this preamble 

provides details on why we are not 

proposing fenceline monitoring for 

CMPUs using, producing, storing, or 

emitting other table 1 HAP. 

In the promulgated amendments to 

the HON, the EPA finalized a new EPA 

method (EPA Method 327 of 40 CFR 

part 63, appendix A) to monitor the 

concentration of EtO at facility fenceline 

locations. EPA Method 327 provides 

procedures for canister sampling and 

analysis for measuring trace levels of 

targeted VOC (including organic HAP) 

in air. EPA Method 327 collects ambient 

air samples using specially prepared 

and pre-cleaned evacuated stainlesssteel canisters. For analysis, the method 

specifies procedures for concentrating 

the target VOC (i.e., EtO) in a known 

volume of air drawn from the canister, 

desorbing the target VOC from the 

preconcentrator, and determining the 

concentration of the target VOC using a 

gas chromatograph–mass spectrometer. 

The EPA continues to investigate costeffective monitoring methods and 

technologies that could offer improved 

sensitivity, improved time resolution, or 

increased time integration. 

As part of the HON, fenceline 

monitoring in combination with root 

cause analysis and corrective action was 

required for affected sources using, 

producing, storing, or emitting EtO. The 

program requires a cannister sample to 

be collected in accordance with EPA 

Method 327 for one 24-hour period 

every five days. This monitoring 

frequency is necessary to ensure that all 

onsite processes are monitored regularly 

while maintaining the cost effectiveness 

of implementing a canister monitoring 

network. A sampling frequency of every 

5 days also ensures that the annual 

average concentration derived from the 

fenceline data are indicative of the 

actual average emissions from the site 

by reducing the possibility that 

sampling occurs only during emission 

spikes. Once samples are analyzed, the 

lowest sample value for EtO is 

subtracted from the highest sample 

value for EtO, generating a Dc. This 

approach subtracts the estimated 

contributions from background 

emissions that do not originate from the 

facility. The owner or operator would 

average the Dc for the most recent year 

of samples (73 sampling periods) to 

calculate an annual average Dc on a 

rolling basis (i.e., calculate a new annual 

average Dc every 5 days using data from 

the most recent 73 sampling periods). 

The owner or operator would compare 

this rolling annual average Dc against 

the concentration action level for EtO. 

The action level for EtO established as 

part of the HON is 0.2 micrograms per 

cubic meter (mg/m3) based on three 

times the representative detection limit 

(RDL) for EtO. 

If the annual average Dc for a facility 

exceeds the action level, then root cause 

analysis and corrective action must be 

performed. Root cause analysis is an 

assessment conducted through a process 

of investigation to determine the 

primary underlying cause and other 

contributing causes of an exceedance of 

the action level. If the underlying causes 

of the action level exceedance are 

deemed to be from sources under the 

control of the owner or operator, the 

owner or operator is required to take 

corrective action to address the 

underlying cause of the exceedance and 

to bring the annual average Dc back 

below the action level as expeditiously 

as possible. Completion of the root 

cause analysis and initial corrective 

action is required within 45 days of 

determining that the annual average Dc 

exceeded the action level. If the owner 

or operator requires longer than 45 days 

to implement the corrective actions 

identified by the root cause analysis, the 

owner or operator is required to submit 

a corrective action plan no later than 60 

days after completion of the root cause 

analysis. 

After completion of the initial 

corrective action, if the Dc for the next 

three sampling periods for samples 

collected by EPA Method 327 are below 

the action level, then the corrective 

action is assumed to have fixed the 

problem, and the owner and/or operator 

has no further obligation for additional 

corrective action. However, if the Dc for 

the subsequent sampling periods after 

initial corrective action is greater than 

the action level, then the owner or 

operator must submit a corrective action 

plan and schedule for implementing 

design, operation, and maintenance 

changes to eliminate as quickly as 

possible and prevent recurrence of the 

primary cause and other contributing 

causes to the exceedance of the action 

level, to reduce annual average 

concentrations below the action level. If 

the owner or operator cannot determine 

the root cause of the exceedance within 

30 days of determining that there was an 

exceedance of an action level, the 

proposed revisions require use of realtime sampling techniques (e.g., mobile 

gas chromatographs) to determine the 

root cause of the exceedance. While the 

action level(s) are based on annual 

average concentrations, once an action 

level is exceeded, each sampling period 

that exceeds the action level contributes 

to the Dc remaining above the action 

level. An investigation must be 

conducted to determine the root cause 

and, if appropriate, to correct the root 

cause expeditiously to bring the annual 

average Dc below the action level. 

Given the similarities between certain 

sources subject to the HON and CMAS 

CMPUs in EtO service, the threat of 

adverse effect on human health (as 

discussed in section II.A.1 of this 

preamble), and the observed 

inconsistency between modeling the 

fenceline concentrations of sources 

subject to the HON and actual fenceline 

concentration measurements,28 we 

assessed whether the same fenceline 

monitoring program was appropriate. 

We find fenceline monitoring via EPA 

Method 327 to be ‘‘generally available’’ 

per the language of CAA section 

112(d)(5). Canister measurements for 

EtO have been possible since 1999 via 

Method TO–15. While EPA Method 327 

was finalized in May 2024 as part of the 

revisions to the HON (see 89 FR 42932); 

many of the practices, media, and 

instrumentation necessary for the 

analysis have been available since 2019 

via an update to Method TO–15, 

Method TO–15A. EPA Method 327 

codifies the best practices of Method 

TO–15A and mandates enhanced QA/ 

QC approaches, such as a regular 

validation of the sampling media, site 

verification for the sampling, defined 

sample holding times, and ongoing field 

and spike blanks to evaluate 

performance. In addition, development 

of logistics and practices to support EPA 

Method 327 laboratory analysis will also 

be occurring alongside other, similar 

chemical manufacturing rulemakings. 

Lastly, as a practice, placing monitors 

around a facility to measure fugitive 

emissions has been required as part of 


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the Petroleum Refineries NESHAP (40 

CFR part 63, subpart CC) since 2018. 

Given the monitoring technology has 

been available for several decades and 

the methodology, while new, is an 

adjustment to a well understood 2019 

method to ensure the validity of 

samples, we find EPA Method 327 to be 

‘‘generally available’’ per the language 

of CAA section 112(d)(5). Both root 

cause analysis and corrective action 

already take place at facilities where 

large emission events occur. When an 

event occurs, the source will be 

determined and will be fixed. This is a 

regular part of operation and thus root 

cause analysis and corrective action are 

already available to every facility 

potentially impacted by the proposed 

fenceline monitoring management 

practice. 

For the 33 facilities within the 

proposed source category, Chemical 

Manufacturing with Ethylene Oxide, 

EtO is ubiquitous and should be present 

in most streams associated with CMPUs 

in EtO service. As such, for these 

facilities, EtO can act as a surrogate 

pollutant to track and limit overall 

fugitive emissions of HAP at the 

fenceline. Therefore, using information 

from the CMAS emissions inventory 

(see section II.C.2 of this preamble), we 

modeled what the fenceline 

concentrations for EtO would be for the 

33 facilities identified to use, produce, 

store, or emit EtO based on whole 

facility emissions when considering 

those options proposed in sections 

IV.A.1 through IV.A.6 and section 

IV.A.8. The modeling showed that 32 of 

the 33 facilities had EtO fenceline 

concentrations at or below 0.2 mg/m3, 

three times the RDL for EtO and the 

action level finalized as part of the 

HON. In addition, the one facility that 

was modeled to have a fenceline 

concentration greater than 0.2 mg/m3

was identified as having a high degree 

of uncertainty associated with their 

emissions inventory as the facility only 

reported a single EtO record. In addition 

to revisions made to the baseline data, 

post-control emission reductions were 

established using state permitting and 

approximate impacts (for additional 

details on facility specific adjustments 

to emissions, see appendix 1 of the 

document entitled Risk Assessment for 

the Chemical Manufacturing Area 

Source (CMAS) Category in Support of 

the 2025 Technology Review for the 

Proposed Rule, available in the docket 

for this rulemaking). While exact 

emission reductions cannot be 

calculated due to the nature of fugitive 

emissions and uniqueness of each root 

cause analysis and corrective action 

performed as part of the fenceline 

monitoring program, we anticipate there 

will be EtO emission reductions 

associated with fenceline monitoring. 

The cost of the fenceline monitoring 

program is shown in table 7 of this 

preamble. We estimated the cost 

required for each impacted facility to 

build the necessary housing for the 

cannisters, purchase and install the 

cannisters, and continually monitor the 

fenceline concentration of EtO. See the 

document titled Clean Air Act Section 

112(d)(5) GACT Standard Analysis and 

CAA Section 112(d)(6) Technology 

Review for Fenceline Monitoring for 

Chemical Manufacturing Process Units 

Associated with the Chemical 

Manufacturing Area Sources NESHAP, 

which is available in the docket for this 

rulemaking, for additional details on the 

analysis and methodology associated 

with these costs. 

Based on the costs and need to 

monitor for fugitive emissions of EtO, 

we are proposing to revise the CMAS 

NESHAP to require fenceline 

monitoring for EtO if a new or existing 

affected source uses, produces, stores, or 

emits EtO pursuant to CAA section 

112(d)(5). 

We are soliciting comment on the 

proposed fenceline monitoring program 

and the supporting analysis including 

the costs, benefits, and underlying 

assumptions. 

TABLE 7—NATIONWIDE COST IMPACTS

FOR REQUIRING FENCELINE MONITORING FOR CMAS THAT USE, 

PRODUCE, STORE, OR EMIT ETO AT

CMAS FACILITIES 1

Number of 

CMAS 

facilities 

impacted 

Total 

capital 

investment 

($) 

Total 

annualized 

costs 

($/yr) 

33 ........................ 488,000 20,990,000 

1Facilities that would either become subject to the 

CMAS NESHAP if EtO is added to table 1 to 40 CFR 

part 63, subpart VVVVVV, as proposed, or are already subject to the CMAS NESHAP and emits EtO. 

We are proposing to require fenceline 

monitoring for CMAS using, producing, 

storing, or emitting EtO at 40 CFR 

63.11495(a)(8) by reference to the HON 

(40 CFR 63.184). 

A primary requirement for a fenceline 

monitoring system is that it provides 

adequate spatial coverage for 

determination of representative 

pollutant concentrations at the 

boundary of the facility. In an ideal 

scenario, owners or operators would 

place fenceline monitors so that any 

fugitive plume originating within the 

facility would have a high probability of 

intersecting one or more monitors, 

regardless of wind direction. Therefore, 

by referencing 40 CFR 63.184(b)(3) via 

40 CFR 63.11495(a)(8) we propose that 

each facility would place eight canisters 

evenly spaced on the monitoring 

perimeter. The monitoring perimeter 

may be the facility fenceline or may be 

inside the facility fenceline, provided 

all sources of EtO are contained within 

the perimeter. The EPA is also 

proposing to require that facilities move 

the canister sampling locations with 

alternating sampling periods to ensure 

complete spatial coverage of the facility. 

For facilities with perimeters less than 

or equal to 5,000 meters, all eight 

sampling points would be monitored 

during each sampling period. For 

facilities with perimeters greater than 

5,000 meters but less than or equal to 

10,000 meters, 16 sampling points 

would be required; for facilities with 

perimeters greater than 10,000 meters, 

24 sampling points would be required. 

For facilities with EtO emission sources 

that are not contained within one 

contiguous area, the EPA is proposing 

monitoring of these secondary areas as 

well, with the size of the secondary area 

dictating the number of canisters. 

In addition, we are proposing to allow 

the subtraction of offsite interfering 

sources (as they are not within the 

control of the owner or operator) 

through site-specific monitoring plans, 

but we are not providing this option for 

onsite, non-source category emissions. 

We based the action level on facilitywide emissions; therefore, we 

considered these non-source category 

sources in its development. Applying 

the fenceline standard to the whole 

facility will also limit emissions of EtO 

from all sources and provide more 

certainty in decisions being made as to 

whether the entire facility emissions 

align with what is expected from the 

EPA’s analysis. It will also provide 

assurance to fenceline communities that 

emission reductions are achieved and 

maintained. 

The EPA is also proposing, by 

reference to the HON at 40 CFR 

63.182(e), that owners or operators 

report fenceline data on a quarterly 

basis. Each report would contain the 

results for each sample where the field 

portion of sampling is completed by the 

end of the quarter, as well as for 

associated field and method blanks (i.e., 

each report would contain data for 18 

canister sampling periods). Owners or 

operators would report these data 

electronically to the EPA within 45 days 

after the end of each quarterly period. 

See section IV.D.1 of this preamble for 

further discussion on electronic 

reporting and section IV.E.1 of this 

preamble for further discussion on the 

compliance dates being proposed. 


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29The study, Assessment of chemical facility 

ethylene oxide emissions using mobile and 

multipoint monitoring, focused on measuring the 

concentration of EtO at a chemical manufacturer’s 

fenceline. Elevated levels of EtO were measured 

nearest sources of ground level fugitive emissions 

such as wastewater outfall and during periods of 

irregular operation via PRD releases. The complete 

study can be found and read here: https://doi.org/ 

10.1016/j.aeaoa.2023.100214. 

30The current HON rule text does not define or 

use the term ‘‘deviation’’ and instead uses the term 

‘‘violation.’’ Given that both the CMAS NESHAP 

and the MON rule text define and uses the term 

‘‘deviation’’ to describe emissions events, we 

believe it is more appropriate to continue to use the 

term ‘‘deviation’’ (in lieu of ‘‘violation’’) in all of the 

CMAS rule text. 

31Randall, 2012. Memorandum from Randall, D., 

RTI International to Parsons, N., EPA/OAQPS. 

Survey of Control Technology for Storage Vessels 

and Analysis of Impacts for Storage Vessel Control 

Options. January 20, 2012. EPA Docket ID No. EPA– 

HQ–OAR–2010–0871. 

8. PRDs in EtO Service 

The CMAS NESHAP regulates PRDs 

through equipment leak management 

practices. These practices require 

owners and operators to conduct 

quarterly sensory-based inspections 

(using sight, sound, or smell) to ensure 

that equipment (including PRDs) is 

‘‘sound and free of leaks.’’ However, 

these provisions do not apply to an 

emissions release from a PRD (see 

section IV.B.2 of this preamble for more 

detail). 

The EPA is proposing an LDAR 

program (using EPA Method 21) for all 

equipment in organic HAP service (see 

section IV.C.1 of this preamble). 

Additionally, management practices for 

PRD releases are being proposed (see 

section IV.B.2 of the preamble). A 2023 

study at an area source chemical 

manufacturing facility indicated that 

EtO PRD releases because of railcar 

switchover contributed to elevated 

levels of EtO at the facility’s fenceline.29

If those emissions had not been released 

to the atmosphere, the emissions would 

be characterized as process vent 

emissions and potentially subject to the 

proposed provisions in section IV.A.3 of 

this preamble. Given that neither the 

equipment leaks nor the process vents 

analyses account for the episodic nature 

of PRD releases and the observed need 

via the 2023 study, it is reasonable to 

consider a management practice 

regulating PRDs in EtO service. 

To assess appropriate GACT 

standards for EtO releases from PRDs, 

we reviewed other rulemakings and 

identified two rules with requirements 

for PRDs ‘‘in ethylene oxide service.’’ 

The EPA recently added requirements to 

the MON and HON making any release 

event from a PRD in EtO service a 

deviation 30 from the work practice 

standards for PRD releases (see 85 FR 

49084, August 12, 2020, and 89 FR 

42932, May 16, 2024, respectively). 

Given these EtO specific requirements 

in the MON and HON for PRDs in EtO 

service, the minimal operational 

differences between PRDs at MON, 

SOCMI, and CMAS facilities, and to 

ensure that EtO is not released to 

atmosphere from a PRD, we are also 

proposing at 40 CFR 63.11495(a)(7), by 

reference to the HON (40 CFR 

63.165(e)(3)(v)(D)), that any release 

event from a PRD in EtO service at a 

new or existing affected source is a 

deviation of the standard. We do not 

expect any additional costs from this 

proposed GACT standard. 

B. What are our other proposed 

decisions regarding GACT standards for 

CMAS, and what is the rationale for 

those decisions? 

In addition to the GACT standards we 

are proposing for certain emission 

sources that emit EtO as discussed in 

section IV.A of this preamble, we are 

also proposing GACT standards for 

pressure vessels and PRDs as described 

in sections IV.B.1 and IV.B.2 of this 

preamble, respectively. In addition, we 

are proposing in section IV.B.3 of this 

preamble to clarify regulatory 

provisions for vent control bypasses for 

closed vent systems containing bypass 

lines. 

1. Pressure Vessels 

Pursuant to CAA section 112(d)(5), we 

are proposing new requirements for 

pressure vessels that are associated with 

processes subject to the CMAS 

NESHAP. The EPA is proposing to 

define pressure vessel at 40 CFR 

63.11502(a), by reference to the HON 

(40 CFR 63.101), to mean ‘‘a storage 

vessel that is used to store liquids or 

gases and is designed not to vent to the 

atmosphere as a result of compression of 

the vapor headspace in the pressure 

vessel during filling of the pressure 

vessel to its design capacity.’’ To 

eliminate any ambiguity in applicability 

or control requirements, the EPA is also 

proposing at 40 CFR 63.11502(b) to 

remove the exemption for ‘‘pressure 

vessels designed to operate in excess of 

204.9 kilopascals (kPa) and without 

emissions to the atmosphere’’ from the 

definition of storage tank. This longstanding exemption is ambiguous with 

respect to what ‘‘without emissions to 

the atmosphere’’ means. For example, 

most pressure vessels have relief 

devices that allow for venting when 

pressure exceeds setpoints. In many 

cases, these vents are routed to control 

devices; however, control devices are 

not completely effective (e.g., achieve 

95-percent control), and therefore there 

are emissions to the atmosphere from 

these pressure vessels, even if they are 

controlled. There are also instances 

where other components in pressure 

systems may allow for fugitive releases 

because of leaks from fittings or cooling 

systems. These events arguably are 

‘‘emissions to the atmosphere’’ and 

therefore it is likely that even if the 

CMAS NESHAP maintained this 

exemption, owners and operators of 

pressure vessels would still have 

uncertainty regarding whether they 

were subject to substantive 

requirements. Therefore, the proposed 

revisions remove the ambiguity 

associated with the exemption and set 

new GACT standards intended to limit 

emissions to the atmosphere from 

pressure vessels storing organic HAP 

with capacities greater than or equal to 

20,000 gallons at new and existing 

affected sources. We are proposing the 

same standards for pressure vessels of 

any capacity and vapor pressure storing 

EtO such that it can be considered to be 

a storage tank in EtO service. We are 

also clarifying in the definition of 

CMPU at 40 CFR 63.11494(b) that the 

collection of equipment that is part of a 

CMPU includes pressure vessels. 

We estimate a pressure vessel is 

located at 15 of the 247 CMAS facilities 

given that these 15 facilities reported 

1,3-butadiene emissions from processes 

subject to the CMAS NESHAP, and this 

chemical is stored in pressure vessels. 

We excluded CMAS facilities that may 

have pressure vessels storing EtO given 

that we are proposing more stringent 

standards for connectors in EtO service, 

gas/vapor and light liquid valves in EtO 

service, and light liquid pumps in EtO 

service (see section IV.A.1 of this 

preamble). Using information from a 

2012 analysis that identified 

developments for storage vessels at 

chemical manufacturing facilities and 

petroleum refineries,31 we estimate a 

total HAP emission reduction of 2.24 

tpy for all affected pressure vessels 

associated with processes subject to the 

CMAS NESHAP (assuming 10 percent of 

all CMAS pressure vessels storing 1,3- 

butadiene would have components that 

leak). The nationwide capital cost for 

the proposed pressure vessel LDAR 

requirements for the CMAS NESHAP is 

about $3,800 and the annualized capital 

cost is $3,330. 

Based on the costs and emission 

reductions, we are proposing LDAR 

requirements at 40 CFR 63.11497(f) and 

items 6 and 7 of table 5 to the CMAS 

NESHAP that are based on similar nodetectable emission requirements 

required for closed vent systems in most 

chemical sector NESHAP, including but 

not limited to the HON and MON. We 


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32Examples of prevention measures include the 

following: Flow indicators, level indicators, 

temperature indicators, pressure indicators, routine 

inspection and maintenance programs, operator 

training, inherently safer designs, safety 

instrumentation systems, deluge systems, and 

staged relief systems where the initial PRD 

discharges to a control system. 

33These facilities are already subject to, or may 

become subject to, the CMAS NESHAP if EtO were 

to be added to table 1 to 40 CFR part 63, subpart 

VVVVVV. 

34EPA, 2015. Coburn, Jeff, RTI International. 

Pressure Relief Device Control Option Impacts for 

Final Refinery Sector Rule. July 30, 2015. EPA 

Docket ID No. EPA–HQ–OAR–2010–0682. 

35EPA, 2017. Carey, Angela, EPA/OAQPS. 

Pressure Relief Device Control Options and Impacts 

for Off-Site Waste and Recovery Operations 

(OSWRO). June 26, 2017. EPA Docket ID No. EPA– 

HQ–OAR–2012–0360. 

are proposing that these LDAR 

requirements for pressure vessels reflect 

GACT at new and existing affected 

sources. We did not identify any 

additional options beyond this for 

controlling emissions from pressure 

vessels. The requirements would apply 

to all new and existing affected sources 

and impose a standard that requires no 

detectable emissions at all times (i.e., 

owners and operators would be required 

to meet a leak definition of 500 ppmv 

at each point on the pressure vessel 

where total organic HAP could 

potentially be emitted); require initial 

and annual leak monitoring using EPA 

Method 21 of 40 CFR part 60, appendix 

A–7; and require routing organic HAP 

through a closed vent system to a 

control device (i.e., no releases to the 

atmosphere through a pressure vessel’s 

PRD). These proposed LDAR 

requirements would also subject 

connectors in EtO service, gas/vapor or 

light liquid valves in EtO service, and 

light liquid pumps in EtO service to 

more stringent LDAR requirements 

under the proposed EtO equipment leak 

standards. 

See the document titled Clean Air Act 

Section 112(d)(5) GACT Standard 

Analysis for Pressure Vessels Associated 

with Processes Subject to the CMAS 

NESHAP, which is available in the 

docket for this rulemaking, for details 

on the assumptions and methodologies 

used in this analysis. 

2. PRDs 

The CMAS NESHAP regulates PRDs 

through equipment leak management 

practices. These practices require 

owners and operators to conduct 

quarterly sensory-based inspections 

(using sight, sound, or smell) to ensure 

that a PRD is ‘‘sound and free of leaks’’ 

(see 40 CFR 63.11495(a)(3)). These 

inspections typically occur when the 

PRD is seated, as PRDs are designed to 

open only during a pressure release (i.e., 

when the system pressure exceeds the 

PRD’s set pressure). 

The CMAS NESHAP does not 

explicitly regulate atmospheric pressure 

releases, regardless of whether they are 

single or multiple releases over time. 

Consequently, no CMAS facility is 

subject to numeric emission limits for 

PRDs that vent to the atmosphere. It is 

impractical to measure emissions from 

PRDs that release to the atmosphere, 

making numeric emission limits 

inappropriate. However, the EPA has 

included work practice standards that 

regulate atmospheric pressure releases 

from PRDs in other chemical sector 

NESHAP, such as the EMACT standards 

(85 FR 40386, July 6, 2020; see 40 CFR 

63.1107(h)(3)), the MON (85 FR 49084, 

August 20, 2020; see 40 CFR 

63.2480(e)(3)), and the HON and Group 

I Polymers and Resins Industry (P&R I) 

NESHAP (89 FR 42932, May 16, 2024; 

see 40 CFR 63.165(e)(3)). The EPA also 

added PRD work practice standards to 

the petroleum refinery NESHAP for 

similar reasons (81 FR 45241, December 

1, 2015; see 40 CFR 63.648(j)(3)). These 

PRD work practice standards (in all 

these listed NESHAP) require owners 

and operators to: (1) implement at least 

three prevention measures; 32 (2) 

perform root cause analysis and 

corrective action if a PRD releases 

emissions directly to the atmosphere; 

and (3) monitor PRDs using a system 

that can identify and record the time 

and duration of each pressure release 

and notify operators when a pressure 

release occurs. 

We assessed whether the same PRD 

work practice standards, already 

included in the previously mentioned 

NESHAPs, represent GACT (i.e., in the 

form of management practices) for 

CMAS. These standards would regulate 

emissions from CMAS PRDs during a 

pressure release. The PRD work practice 

standards require monitoring systems 

that can alert an owner or operator 

when a PRD release occurs. We find this 

equipment to be ‘‘generally available’’ 

according to CAA section 112(d)(5). As 

noted, this type of monitoring 

equipment is already mandated under 

other chemical sector regulations, 

including the HON and the MON. Given 

its widespread use in similar chemical 

manufacturing facilities, we consider 

the PRD work practice standards, which 

include the use of monitoring systems 

capable of alerting an owner or operator 

when a PRD release occurs, to be 

‘‘generally available.’’ 

The cost for CMAS facilities to 

implement a management practice 

identical to the work practice standard 

in the HON and MON and install 

monitors for PRDs that vent to the 

atmosphere is based on the number of 

PRDs at each facility. However, we do 

not have actual equipment counts for 

CMAS facilities. To estimate the number 

of PRDs at CMAS facilities nationwide, 

we used HON-specific PRD data that 

was submitted in response to the EPA’s 

2022 CAA section 114 request (see 

section II.C.3 of this preamble). We 

calculated an average of 14 atmospheric 

PRDs in organic HAP service per CMAS 

CMPU. Multiplying this average by the 

total CMAS processes nationwide (247, 

assuming one CMPU per CMAS 

facility), we estimated there are 3,458 

atmospheric PRDs in organic HAP 

service nationwide. We excluded 33 

facilities 33 from this analysis given that 

we anticipate that these facilities are 

likely to only operate PRDs in EtO 

service that already have PRD 

monitoring installed. We used work 

practice costs from a 2015 

memorandum 34 on PRD impacts for 

petroleum refineries to estimate costs 

for implementing at least three 

prevention measures and performing 

root cause analysis and corrective action 

at CMAS facilities. Similarly, based on 

the HON-specific PRD data from the 

EPA’s 2022 CAA section 114 request, 

we calculated an average of three 

atmospheric PRDs in organic HAP 

service per CMAS CMPU that have a 

monitoring system installed capable of 

identifying releases and recording the 

time and duration of each pressure 

release. Therefore, multiplying the 

average of 11 (14 atmospheric PRDs less 

the three that already have monitoring 

systems installed) atmospheric PRDs in 

organic HAP service per CMAS CMPU 

that do not have a monitoring system by 

the total CMAS processes nationwide 

(247, assuming one CMPU per CMAS 

facility), we estimated that of the 3,458 

PRDs in organic HAP service 

nationwide, 2,717 PRDs in organic HAP 

service nationwide vent to the 

atmosphere without a device or 

monitoring system capable of 

identifying releases and recording the 

time and duration of each pressure 

release. We then used PRD monitor 

costs from a 2017 memorandum 35 on 

PRD options for off-site waste and 

recovery operations to estimate the costs 

for installing PRD monitors at CMAS 

facilities. Based on our cost 

assumptions, the nationwide capital 

cost for complying with the PRD work 

practice requirements for the CMAS 

NESHAP (in the form of management 

practices) is $15.9 million, with 

annualized capital costs of $4.7 million. 

This translates to approximately 

$64,300 in total capital investment and 

$19,200 in total annual cost per CMAS 


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facility. We are unable to estimate HAP 

reductions from requiring owners and 

operators to comply with these 

management practices because PRD 

pressure releases can occur as single or 

multiple events over time. In other 

words, these releases can result from 

system overpressure caused by operator 

error, malfunctions such as power or 

equipment failures, or other unexpected 

causes that necessitate immediate 

venting of gas from process equipment 

to prevent safety hazards or equipment 

damage; all of which are too difficult to 

predict. Even so, we anticipate that 

implementing these additional PRD 

management practices, along with the 

proposed equipment leak LDAR 

program for PRDs (see section IV.C.1 of 

this preamble), will achieve 

significantly greater emission reductions 

than the equipment leak management 

practices currently required by the 

CMAS NESHAP. 

As such, pursuant to CAA section 

112(d)(5), we are proposing new 

requirements for PRDs that are 

associated with processes subject to the 

CMAS NESHAP. We are proposing PRD 

management practices for all new and 

existing affected sources at 40 CFR 

63.11495(a)(6), by reference to the HON 

(40 CFR 63.165(e)(1) through (8)), that 

require owners and operators to: (1) 

operate each PRD in organic HAP gas or 

vapor service with an instrument 

reading of less than 500 ppm above 

background as measured by the method 

specified in 40 CFR 63.180(c); (2) 

conduct instrument monitoring no later 

than 5 calendar days after the PRD 

returns to organic HAP gas or vapor 

service following a pressure release to 

verify that the PRD is operating with an 

instrument reading of less than 500 

ppm, or if applicable, install a 

replacement disk as soon as practicable 

after a pressure release, but no later than 

5 calendar days after the pressure 

release; (3) implement at least three 

prevention measures; (4) perform root 

cause analysis and corrective action if a 

PRD releases emissions directly to the 

atmosphere; and (5) monitor PRDs using 

a system that can identify and record 

the time and duration of each pressure 

release and notify operators when a 

pressure release occurs. The EPA is also 

proposing to define ‘‘pressure relief 

device or valve’’ at 40 CFR 63.11502(a), 

by reference to the HON (40 CFR 

63.101), to mean ‘‘a valve, rupture disk, 

or similar device used only to release an 

unplanned, nonroutine discharge of gas 

from process equipment in order to 

avoid safety hazards or equipment 

damage. A PRD discharge can result 

from an operator error, a malfunction 

such as a power failure or equipment 

failure, or other unexpected cause. Such 

devices include conventional, springactuated relief valves, balanced bellows 

relief valves, pilot-operated relief 

valves, rupture disks, and breaking, 

buckling, or shearing pin devices. 

Devices that are actuated either by a 

pressure of less than or equal to 2.5 

pounds per square inch gauge or by a 

vacuum are not pressure relief devices.’’ 

In addition, the EPA is proposing to 

define ‘‘pressure release’’ at 40 CFR 

63.11502(a), by reference to the HON 

(40 CFR 63.101), to mean ‘‘the emission 

of materials resulting from the system 

pressure being greater than the set 

pressure of the pressure relief device. 

This release can be one release or a 

series of releases over a short time 

period.’’ 

See the document titled Clean Air Act 

Section 112(d)(5) GACT Standard 

Analysis for Pressure Relief Devices 

Associated with Processes Subject to the 

CMAS NESHAP, which is available in 

the docket for this rulemaking, for 

details on the assumptions and 

methodologies used in this analysis. We 

solicit comments on the proposed 

management practice for PRDs and 

assumptions associated with the 

analysis. 

3. Closed Vent System Containing 

Bypass Lines 

For a closed vent system containing 

bypass lines that can divert the stream 

away from the APCD to the atmosphere, 

the CMAS NESHAP requires the owner 

or operator to either: (1) install, 

maintain, and operate a continuous 

parametric monitoring system for flow 

on the bypass line that is capable of 

detecting whether a vent stream flow is 

present at least once every hour, or (2) 

secure the bypass line valve in the nondiverting position with a car-seal or a 

lock-and-key type configuration. Under 

option 2, the CMAS NESHAP also 

requires owners or operators to inspect 

the seal or closure mechanism at least 

once per month to verify the valve is 

maintained in the non-diverting 

position (e.g., for more details see items 

1.a and 1.b of tables 2 and 3 to the 

CMAS NESHAP and items 1.b and 1.c 

of table 5 to the CMAS NESHAP, which 

all reference provisions in 40 CFR part 

63, subpart SS that ultimately point to 

bypass monitoring requirements in 40 

CFR 63.983(a)(3)). To expressly prohibit 

bypassing an APCD at affected sources, 

as implied by option 2, we are 

proposing that an owner or operator 

may not bypass the APCD at any time 

and that a bypass is a violation (see 

proposed 40 CFR 63.11495(e)), and 

owners and operators must estimate, 

maintain records, and report the 

quantity of organic HAP released (see 

proposed 40 CFR 63.11501(c)(10) and 

(d)(10)). We are proposing these 

revisions to ensure continuous 

compliance with the GACT standards 

because bypassing an APCD could result 

in a release of regulated organic HAP to 

the atmosphere that would be required 

to be controlled under the existing 

GACT standards in the CMAS NESHAP. 

We are also proposing that the use of a 

cap, blind flange, plug, or second valve 

on open-ended valves or lines 

(following the requirements specified in 

40 CFR 60.482–6(a)(2), (b), and (c) or 

following requirements codified in 

another regulation that are the same as 

40 CFR 60.482–6(a)(2), (b), and (c)) is 

sufficient to prevent a bypass. We solicit 

comments on these proposed revisions. 

In addition, we are proposing to 

remove the 40 CFR 63.107(h)(9) 

exemption for ‘‘a gas stream exiting an 

analyzer’’ from the definition of 

continuous process vent at 40 CFR 

63.11502(b) and we are proposing at 40 

CFR 63.11495(e) to not exempt analyzer 

vents from the bypass requirements. As 

such, we are proposing to require that 

these kinds of vents meet the standards 

applicable to process vents at all times. 

Analyzer vents, or ‘‘onstream 

analyzers,’’ generally refer to sampling 

systems that directly feed to an analyzer 

located at a process unit and venting is 

expected to be routine (continuous or 

daily intermittent venting). We also note 

that sampling connection systems for 

CMPUs will be required to be part of a 

closed loop, closed purge, or closed vent 

system under our proposed equipment 

leak standards (e.g., 40 CFR 63.166(a), 

see section IV.C.1 of this preamble for 

further details). In these applications, 

the analyzer vent would not be a bypass 

of emissions subject to the requirements 

in 40 CFR 63.11495 through 63.11498, 

rather the analyzer vent would be a 

process vent itself, thus engineering 

calculations would be used to determine 

if this vent is a process vent requiring 

control as specified in tables 2 through 

4 to the CMAS NESHAP. In rare 

instances, the owner or operator may 

classify a release point on a gaseous 

vent system associated with a CMPU as 

an ‘‘analyzer vent’’. In this case, the 

analyzer vent when open acts as a 

bypass line (allowing direct atmospheric 

release) of a process vent stream. These 

examples demonstrate that depending 

on the circumstance, an analyzer vent 

could be construed as a process vent or 

a bypass line. Thus, we see no reason to 

categorically allow use of analyzer vents 

to bypass controls required for 


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36Each equipment leak control option that we 

evaluated also includes the HON LDAR 

requirements specified in 40 CFR 63.164 for 

compressors, 40 CFR 63.166 for sampling 

connection systems, 40 CFR 63.167 for open-ended 

valves or lines, 40 CFR 63.169 for equipment in 

heavy liquid service, 40 CFR 63.173 for agitators in 

G/V or LL service. 

emissions subject to the requirements in 

40 CFR 63.11495 through 63.11498. 

C. What are the results and proposed 

decisions based on our technology 

review, and what is the rationale for 

those decisions? 

As described in section III.B of this 

preamble, the technology review for the 

CMAS NESHAP focused on the 

identification and evaluation of 

developments in practices, processes, 

and control technologies that have 

occurred since the NESHAP was 

promulgated in 2009. In conducting the 

technology review, we reviewed various 

sources of information related to the 

emissions from chemical manufacturing 

operations and other relevant 

information such as control 

technologies applied, management 

practices used, processes, and 

monitoring approaches. Through 

searches of these data sources, we 

identified, evaluated, and considered 

several developments in practices, 

processes, or control technologies. As 

discussed below, these include 

developments and improvements that 

could result in the addition of emission 

limits, management practices, and other 

emission reduction requirements, as 

well as revised compliance assurance 

measures. We analyzed costs and 

emissions reductions for each emission 

source and determined costeffectiveness (annualized cost per ton of 

emissions reduction) on a HAP basis. 

The data, analyses, results, and 

proposed decisions pursuant to CAA 

section 112(d)(6) are presented for each 

emission source in sections IV.C.1 

through IV.C.7 of this preamble. 

Based on this review, the EPA is 

proposing amendments to the CMAS 

NESHAP pursuant to CAA section 

112(d)(6) that improve monitoring of 

leaks from equipment and heat 

exchange systems and revises the 

definition of ‘‘metal HAP process vent.’’ 

We are not proposing any changes to the 

CMAS NESHAP for storage tanks and 

wastewater based on our technology 

review given that we did not identify 

any cost-effective developments in 

practices, processes, or control 

technologies for these emission sources 

that achieve a greater HAP emission 

reduction beyond the emission 

reduction already required by the CMAS 

NESHAP. 

1. Equipment Leaks 

Emissions from equipment leaks 

occur in the form of gases or liquids that 

escape to the atmosphere through 

connection points (e.g., threaded 

connectors) or through the moving parts 

of different components (e.g., agitators, 

compressors, PRDs, pumps, valves) and 

certain types of process equipment. 

Each component type has a unique 

manner in which emissions are released 

(e.g., connectors may leak if the threads 

become damaged or corroded or if not 

tightened sufficiently, pumps can leak 

at the point of contact between the 

moving shaft and stationary casing, 

valves can leak through the seal around 

the valve stem). 

The CMAS NESHAP requires that 

facilities conduct quarterly inspections 

of process vessels and equipment for 

each CMPU in organic HAP service or 

metal HAP service. Equipment is 

defined as ‘‘each pump, compressor, 

agitator, pressure relief device, sampling 

connection system, open-ended valve or 

line, valve, connector, and 

instrumentation system in or associated 

with a CMPU.’’ The inspections rely on 

AVO detection methods to determine 

whether process vessels and equipment 

are free of leaks. The CMAS NESHAP 

also allows instrument monitoring (i.e., 

use EPA Method 21 with a leak 

definition of 500 ppmv) in lieu of AVO 

methods; or, facilities may use EPA 

Method 21 to confirm the presence of 

HAP for leaks identified using AVO 

methods. 

To identify developments in 

practices, processes, and control 

technologies since the GACT standards 

were established, we reviewed 

subsequent regulatory efforts. After 

reviewing multiple regulations, we 

identified developments in LDAR 

program practices in the form of specific 

leak definitions and monitoring 

frequencies for LDAR programs that use 

EPA Method 21 monitoring that are 

different than those evaluated during 

the original CMAS rulemaking. We used 

the HON and MON as initial points of 

reference to identify developments, 

since these rules apply to major source 

chemical manufacturing facilities which 

are similar to CMAS facilities. The HON 

and MON require EPA Method 21 

monitoring for specific components at 

varying leak definitions (from 500 ppmv 

to 10,000 ppmv) and frequencies 

(monthly monitoring to monitoring 

every 4 years if few leaks are identified). 

We also reviewed the Gasoline 

Distribution area source rule, which 

recently undertook a similar technology 

review for equipment leaks where the 

EPA finalized an LDAR program that 

requires annual monitoring using EPA 

Method 21 at a leak definition of 10,000 

ppmv in lieu of only AVO methods. We 

used the Gasoline Distribution LDAR 

program, which requires annual 

monitoring at a leak definition of 10,000 

ppmv, as the starting option (i.e., 

Control Option 1). We then considered 

two additional options that would 

impose more stringent requirements that 

would allow us to assess the impacts of 

more frequent monitoring (i.e., Control 

Option 2 requiring semiannual 

monitoring) and a lower leak definition 

(i.e., Control Option 3 requiring a leak 

definition of 500 ppmv). We also 

evaluated the key component types for 

the LDAR programs (i.e., connectors, 

valves, pumps) and did not consider an 

option where connectors were not 

monitored. The following summarize 

the three equipment leak control 

options that we evaluated for this 

technology review: 36

• Control Option 1 (for connectors in 

gas and vapor (G/V) service or in light 

liquid (LL) service, valves in G/V or LL 

service, and pumps in LL service): 

monitor all components annually using 

EPA Method 21 and a leak definition of 

10,000 ppmv. 

• Control Option 2 (for connectors in 

G/V or LL service, valves in G/V or LL 

service, and pumps in LL service): 

monitor all components semiannually 

using EPA Method 21 and a leak 

definition of 10,000 ppmv. 

• Control Option 3 (for connectors in 

G/V or LL service, valves in G/V or LL 

service, and pumps in LL service): 

monitor all components annually using 

EPA Method 21 and a leak definition of 

500 ppmv. 

To estimate the costs and emission 

reductions, we assumed that 247 CMAS 

facilities currently follow the CMAS 

requirement of performing quarterly 

AVO inspections and are impacted by 

this technology review. For simplicity, 

we excluded 4 other CMAS facilities 

from our analysis that may have 

equipment leaks in EtO service; and 

instead, we included them in our GACT 

analysis discussed in section IV.A.1 of 

this preamble. To get the nationwide 

impacts of each Control Option, we 

estimated the cost and reductions for a 

model CMAS facility to implement each 

of the three control options and 

multiplied the model facility results by 

247. The memorandum Clean Air Act 

Section 112(d)(5) GACT Standard 

Analysis for Equipment Leaks that Emit 

Ethylene Oxide and Section 112(d)(6) 

Technology Review for Equipment Leaks 

from Chemical Manufacturing Process 

Units at Area Sources Subject to the 

CMAS NESHAP, which is available in 

the docket for this rulemaking, presents 


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details on the assumptions and 

methodologies used in this analysis. 

Table 8 of this preamble presents the 

nationwide impacts for requiring 

owners and operators to perform EPA 

Method 21 monitoring in accordance 

with Control Options 1–3. Based on the 

costs and emission reductions, we are 

proposing to revise the CMAS NESHAP 

for equipment in HAP service to reflect 

Control Option 1 pursuant to CAA 

section 112(d)(6). Control Options 2 and 

3 have incremental costs and emission 

reductions (i.e., incremental to Control 

Option 1) that are not cost effective and 

we are not proposing to revise the 

CMAS NESHAP to reflect either of these 

options. 

TABLE 8—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTIONS 1–3 FOR REQUIRING EPA 

METHOD 21 MONITORING FOR EQUIPMENT LEAKS AT CMAS FACILITIES

Control 

option 

Total 

capital 

investment 

($) 

Total 

annualized 

costs w/o 

recovery 

credits 

($/yr) 

Total 

annualized 

costs with 

recovery 

credits 

($/yr) 

VOC 

emission 

reductions 

(tpy) 

HAP 

emission 

reductions 

(tpy) 

HAP cost 

effectiveness 

w/o recovery 

credits 

($/ton) 

HAP cost 

effectiveness 

with recovery 

credits 

($/ton) 

HAP 

incremental 

cost 

effectiveness 

with recovery 

credits 

(from option 1) 

($/ton) 

1 ........................................ 2,499,600 2,220,500 862,000 1,510 151 14,700 5,700 

2 ........................................ 2,499,600 3,109,700 1,516,600 1,772 177 17,600 8,600 25,000 

3 ........................................ 2,499,600 3,465,400 1,968,600 1,662 166 20,900 11,800 72,700 

We are proposing Control Option 1 for 

equipment leaks at 40 CFR 

63.11495(a)(6). To effectively 

incorporate Control Option 1 into the 

CMAS NESHAP, we specify at proposed 

40 CFR 63.11495(a)(6) that owners and 

operators of new and existing affected 

sources with equipment in organic HAP 

service must conduct annual leak 

detection monitoring of all pumps in 

light liquid service, valves in gas/vapor 

service and in light liquid service, and 

connectors in gas/vapor service and in 

light liquid service by the method 

specified in 40 CFR 63.180(b)(1) through 

(3), with certain exceptions (e.g., 

pumps, valves, and connectors that are 

unsafe to monitor may be exempt). We 

also specify at proposed 40 CFR 

63.11495(a)(6) that a leak from any of 

these types of equipment is detected if 

the instrument reading equals or 

exceeds 10,000 ppmv and a first attempt 

at repair must be made no later than 5 

calendar days after a leak is detected. 

Also, we are proposing that equipment 

must be repaired as soon as practicable, 

but no later than 15 calendar days after 

the leak is detected, except as allowed 

in the HON for delay of repair at 40 CFR 

63.171. Additionally, we are proposing 

at 40 CFR 63.11495(a)(6) the HON LDAR 

requirements for compressors (i.e., 40 

CFR 63.164), sampling connection 

systems (i.e., 40 CFR 63.166), openended valves or lines (i.e., 40 CFR 

63.167), equipment in heavy liquid 

service (i.e., 40 CFR 63.169), and 

agitators in G/V or LL service (i.e., 40 

CFR 63.173). We note that we are also 

proposing the HON LDAR requirements 

for PRDs (i.e., 40 CFR 63.165) which are 

discussed in section IV.B.2 of this 

preamble, and the HON fenceline 

monitoring requirements (i.e., 40 CFR 

63.184) which are discussed in sections 

IV.A.7 and IV.C.7 of this preamble, 

respectively. 

2. Heat Exchange Systems 

Heat exchangers are devices or 

collections of devices used to transfer 

heat from process fluids to another 

process fluid (typically water) without 

intentional direct contact of the process 

fluid with the cooling fluid (i.e., noncontact heat exchanger). There are two 

types of heat exchange systems: closedloop recirculation systems and oncethrough systems. Closed-loop 

recirculation systems use a cooling 

tower to cool the heated water leaving 

the heat exchanger and then return the 

newly cooled water to the heat 

exchanger for reuse. Once-through 

systems typically use surface freshwater 

(e.g., from a nearby river) as the influent 

cooling fluid to the heat exchangers, and 

the heated water leaving the system is 

then discharged from the facility. At 

times, the internal tubing material of a 

heat exchanger can corrode or crack, 

allowing some process fluids to mix or 

become entrained with the cooling 

water. Pollutants in the process fluids 

may subsequently be released from the 

cooling water into the atmosphere when 

the water is exposed to air (e.g., in a 

cooling tower for closed-loop systems or 

trenches/ponds in a once-through 

system). 

The CMAS NESHAP at 40 CFR 

63.11502(a), by reference to the HON 

(40 CFR 63.101), defines a heat 

exchange system as ‘‘a device or 

collection of devices used to transfer 

heat from process fluids to water 

without intentional direct contact of the 

process fluid with the water (i.e., noncontact heat exchanger) and to transport 

and/or cool the water in a closed-loop 

recirculation system (cooling tower 

system) or a once-through system (e.g., 

river or pond water).’’ Pursuant to the 

recent technology review for the HON 

(see 79 FR 25080, May 16, 2024), the 

definition also clarifies that: (1) For 

closed-loop recirculation systems, the 

heat exchange system consists of a 

cooling tower, all CMPU heat 

exchangers that are in organic HAP 

service serviced by that cooling tower, 

and all water lines to and from these 

process unit heat exchangers; (2) for 

once-through systems, the heat 

exchange system consists of all heat 

exchangers that are in organic HAP 

service, servicing an individual CMPU 

and all water lines to and from these 

heat exchangers; (3) sample coolers or 

pump seal coolers are not considered 

heat exchangers and are not part of the 

heat exchange system; and (4) 

intentional direct contact with process 

fluids results in the formation of a 

wastewater. 

The current CMAS NESHAP 

requirements for heat exchange systems 

at 40 CFR 63.11499, by reference to the 

HON (40 CFR 63.104), includes an 

LDAR program for owners or operators 

of certain heat exchange systems (i.e., 

those not meeting one or more of the 

conditions in 40 CFR 63.104(a)) with a 

cooling water flow rate equal to or 

greater than 8,000 gpm. The LDAR 

program specifies that owners or 

operators must monitor heat exchange 

systems for leaks of process fluids into 

cooling water and take actions to repair 

detected leaks within 45 days; and 

owners or operators may delay the 

repair of leaks if they meet the 

applicable criteria in 40 CFR 63.104. 

The CMAS NESHAP allows owners or 

operators to use any method listed in 40 

CFR part 136 to sample cooling water 

for leaks for the HAP listed in table 4 

to 40 CFR part 63, subpart F (for 

recirculating systems) and table 9 to 40 

CFR part 63, subpart G (for oncethrough systems) (and other 


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Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7967 

37The Modified El Paso Method uses a dynamic 

or flow-through system for air stripping a sample of 

the water and analyzing the resultant off-gases for 

VOC using an FID analyzer. The method is 

described in detail in appendix P of the TCEQ’s 

Sampling Procedures Manual: The Air Stripping 

Method (Modified El Paso Method) for 

Determination of Volatile Organic Compound 

(VOC) Emissions from Water Sources. Appendix P 

is included in the docket for this rulemaking. 

representative substances such as total 

organic compounds (TOC) or VOC that 

can indicate the presence of a leak can 

also be used). A leak in the heat 

exchange system is detected if the exit 

mean concentration of HAP (or other 

representative substance) in the cooling 

water is at least 1 ppmw or 10 percent 

greater than (using a one-sided 

statistical procedure at the 0.05 level of 

significance) the entrance mean 

concentration of HAP (or other 

representative substance) in the cooling 

water. Furthermore, the CMAS NESHAP 

allows owners or operators to monitor 

for leaks using a surrogate indicator 

(e.g., ion-specific electrode monitoring, 

pH, conductivity), provided that certain 

criteria in 40 CFR 63.104(c) are met. The 

CMAS NESHAP requires quarterly 

monitoring for heat exchange systems. 

The leak monitoring frequencies are the 

same whether water sampling and 

analysis or surrogate monitoring is used 

to identify leaks. 

For heat exchange systems at CMAS 

CMPUs with a cooling water flow rate 

less than 8,000 gpm that are not meeting 

one or more of the conditions in 40 CFR 

63.104(a), owners and operators must 

develop and operate in accordance with 

a heat exchange system inspection plan 

that describes the inspections to be 

performed at least once per quarter. 

Inspections must provide evidence of 

hydrocarbons in the cooling water and 

may include checks for visible floating 

hydrocarbon on the water, hydrocarbon 

odor, discolored water, and/or chemical 

addition rates. Owners and operators of 

these heat exchange systems must also 

perform repairs to eliminate the leak 

within 45 calendar days after 

indications of the leak are identified but 

may delay the repair if a reason is 

documented in the next semiannual 

compliance report. As an alternative to 

the requirements described in this 

paragraph, owners and operators of heat 

exchange systems at CMAS CMPUs with 

a cooling water flow rate less than 8,000 

gpm can choose to comply with the 

LDAR monitoring options specified for 

heat exchange systems with a cooling 

water flow rate equal to or greater than 

8,000 gpm. 

As part of our technology review, we 

reviewed the criteria in 40 CFR 

63.11495(b) and 40 CFR 63.11499(a) 

(i.e., the reference to the exemptions 

listed in the HON at 40 CFR 63.104(a)), 

to see if these exemptions were still 

reasonable to maintain. We identified 

two criteria in 40 CFR 63.104 dealing 

with once-through heat exchange 

systems meeting certain NPDES permit 

conditions (i.e., 40 CFR 63.104(a)(3) and 

(4)) that warranted further assessment. 

Once-through heat exchange systems 

typically have systems open to the air 

(e.g., open sewer lines, trenches, and 

ponds) that are used to transport used 

cooling water to a discharge point (e.g., 

an outfall) of a facility. This cooling 

water can also be mixed with other 

sources of water (e.g., cooling water 

used in once-through heat exchange 

systems in non-CMAS processes, 

stormwater, treated wastewater, etc.) in 

sewers, trenches, and ponds prior to 

discharge from the plant. If this point of 

discharge from the plant is into a ‘‘water 

of the United States,’’ the facility is 

required to have a NPDES permit and to 

meet certain pollutant discharge limits. 

In reviewing the requirements of 40 CFR 

63.104(a)(3), we find that there is a clear 

disconnect between having a NPDES 

permit that meets certain allowable 

discharge limits (i.e., 1 ppmw or less 

above influent concentration, or 10 

percent or less above influent 

concentration, whichever is greater) at 

the discharge point of a facility (e.g., 

outfall) versus being able to adequately 

identify a leak from a once-through heat 

exchange system given that these 

systems are open to the atmosphere 

prior to this discharge point and, 

therefore, any volatile HAP leaking from 

a once-through heat exchange system 

would likely be emitted to the 

atmosphere prior to the NPDES outfall. 

Similarly, while the requirements of 40 

CFR 63.104(a)(4) allow facilities with 

once-through heat exchange systems 

that have certain requirements (i.e., the 

requirements of 40 CFR 63.104(a)(3) and 

(4)) incorporated into their NPDES 

permit to not comply with the 

requirements of 40 CFR 63.104(b) and 

(c), we find this exemption to be 

problematic. Specifically, the NPDES 

requirements at 40 CFR 63.104(a)(4) lack 

the specificity of where a sample must 

be taken to adequately find and quantify 

a leak from a once-through heat 

exchange system (e.g., just prior to the 

outfall from the plant versus from the 

exit of the once-through heat exchange 

system prior to being open to 

atmosphere), what concentration and/or 

mass emissions rate constitutes a leak 

that must be fixed, how quickly a leak 

must be fixed, what pollutants must be 

adequately accounted for, and what test 

method(s)/surrogates facilities are 

allowed. As such, we find 40 CFR 

63.104(a)(4) to be inadequate in terms of 

being able to detect and repair leaks that 

are at least as equivalent to those that 

would be identified if once-through heat 

exchange systems were complying with 

40 CFR 63.104(b) or (c) instead. 

Therefore, for purposes of 

demonstrating continuous compliance 

with the underlying GACT standard, we 

are proposing at 40 CFR 63.11495(b) and 

40 CFR 63.11499(d) and (e) to remove 

the exemptions for once-through heat 

exchange systems meeting certain 

NPDES permit conditions at 40 CFR 

63.104(a)(3) and (4) and to instead 

require facilities to monitor the cooling 

water for the presence of leaks. 

Our technology review also identified 

one development in LDAR practices and 

processes for heat exchange systems: the 

use of the Modified El Paso Method 37

to monitor for leaks. The EPA identified 

the Modified El Paso Method, which is 

included in the HON, MON, EMACT 

standards, the Petroleum Refinery 

Sector rule, and in our review of the 

RACT/BACT/LAER clearinghouse 

database. The Texas Commission on 

Environmental Quality (TCEQ) also 

requires the method for facilities 

complying with TCEQ’s highly reactive 

volatile organic compound (HRVOC) 

rule (i.e., 30 Texas Administrative Code 

Chapter 115, Subchapter H, Division 3). 

The Modified El Paso Method measures 

a larger number of compounds than the 

current methods required in the CMAS 

NESHAP and is more effective in 

identifying leaks. For LDAR programs 

applied to heat exchange systems, the 

compliance monitoring option, leak 

definition, and frequency of monitoring 

for leaks are all important 

considerations affecting emission 

reductions by identifying when there is 

a leak and when to take corrective 

actions to repair the leak. Therefore, we 

evaluated the Modified El Paso Method 

for use at CMAS facilities as described 

below, including an assessment of 

appropriate leak definitions and 

monitoring frequencies. 

To identify an appropriate Modified 

El Paso Method leak definition for 

facilities subject to the CMAS NESHAP, 

we identified five rules (i.e., TCEQ 

HRVOC rule, the HON, the MON, the 

EMACT standards, and the Petroleum 

Refinery Sector rule) all of which 

incorporate this monitoring method and 

have leak definitions corresponding to 

the use of this methodology. We also 

reviewed data submitted in response to 

a CAA section 114 request for the 

Ethylene Production RTR where 

facilities performed sampling using the 

Modified El Paso Method. 

The TCEQ HRVOC rule, the HON, the 

MON, EMACT standards, and the 


lotter on DSK11XQN23PROD with PROPOSALS2
7968 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

38EPA, 2008. Control Options and Impacts for 

Cooling Tower Control Measures Chemical 

Manufacturing Area Source Standards. September 

5, 2008. Docket ID No. EPA–HQ–OAR–2008–0334– 

0003; and EPA, 2009. Update to the Control Options 

and Impacts for Heat Exchange System Control 

Measures for Promulgation Chemical 

Manufacturing Area Source Standards. May 5, 

2009. Docket ID No. EPA–HQ–OAR–2008–0334– 

0081. 

Petroleum Refinery Sector rule have 

leak definitions of total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas ranging from 3.1 

ppmv to 6.2 ppmv. In addition, sources 

subject to the HON, the MON, EMACT 

standards, or the Petroleum Refinery 

Sector rule must repair a leak no later 

than 45 days after first identifying the 

leak, and also may not delay the repair 

of leaks for more than 30 days where, 

during subsequent monitoring, owners 

or operators find a total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas of 62 ppmv or 

higher. In reviewing the Ethylene 

Production RTR CAA section 114 data, 

we identified a clear delineation in the 

hydrocarbon mass emissions data at 6.1 

ppmv of total strippable hydrocarbon 

(as methane) in the stripping gas. Taking 

into account the range of actionable leak 

definitions in use by other rules that 

require use of the Modified El Paso 

Method currently (i.e., 3.1 ppmv to 6.2 

ppmv of total strippable hydrocarbon 

(as methane) in the stripping gas), and 

the magnitude of emissions for leaks as 

a result of total strippable hydrocarbon 

(as methane) in the stripping gas above 

6.1 ppmv, we chose to evaluate a leak 

definition at the upper end of identified 

actionable leak definitions in our 

analysis. Thus, we evaluated the 

Modified El Paso Method leak definition 

of 6.2 ppmv of total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas for both new and 

existing heat exchange systems, along 

with the requirement to repair a leak no 

later than 45 days after first identifying 

the leak, and not allowing delay of 

repair of leaks for more than 30 days 

where, during subsequent monitoring, a 

total strippable hydrocarbon 

concentration (as methane) in the 

stripping gas of 62 ppmv or higher is 

found. 

We also considered more stringent 

monitoring frequencies. Both the 

Petroleum Refinery Sector rule, which 

includes monthly monitoring for 

existing sources under certain 

circumstances, and the TCEQ HRVOC 

rule, which includes continuous 

monitoring provisions for existing and 

new sources, have more stringent 

monitoring frequencies. 

Based on this technology review, we 

identified the following two Control 

Options as developments in practices 

for heat exchanger systems at CMAS 

facilities: 

• Control Option 1 (for heat exchange 

systems with a cooling water flow rate 

equal to or greater than 8,000 gpm): 

quarterly monitoring with the Modified 

El Paso Method, using a leak action 

level defined as a total strippable 

hydrocarbon concentration (as methane) 

in the stripping gas of 6.2 ppmv (with 

the requirement to repair a leak no later 

than 45 days after first identifying the 

leak, and allow delay of repair up to 120 

days except no more than 30 days where 

a total strippable hydrocarbon 

concentration (as methane) in the 

stripping gas of 62 ppmv or higher is 

found). This option would also require 

re-monitoring at the monitoring location 

where the leak was identified to ensure 

that any leaks found are fixed. 

• Control Option 2: same as Control 

Option 1, except monthly monitoring 

with the Modified El Paso Method 

instead of quarterly monitoring. 

We then estimated the impacts of 

these Control Options. Using 

information from the original CMAS 

rulemaking,38 we estimated 51 of 247 

CMAS facilities would be affected by 

Control Options 1 and 2; and we 

assumed these facilities already conduct 

water sampling. For simplicity, we 

excluded 4 other CMAS facilities from 

our analysis that may have a heat 

exchange system in EtO service; and 

instead, we included them in our GACT 

analysis discussed in section IV.A.2 of 

this preamble. As part of our analysis, 

we also assumed all facilities 

monitoring quarterly for two or less heat 

exchange systems would elect to 

contract out the Modified El Paso 

monitoring (instead of purchasing a 

stripping column and FID analyzer and 

performing the monitoring in-house); 

however, facilities monitoring monthly 

would elect to purchase a stripping 

column and FID analyzer and perform 

in-house El Paso monitoring due to 

logistics. In addition, we assumed 

repairs could be performed by plugging 

a specific heat exchanger tube, and if a 

heat exchanger is leaking to the extent 

that it needs to be replaced, then it is 

effectively at the end of its useful life. 

Therefore, we determined that the cost 

of replacing a heat exchanger is an 

operational cost that would be incurred 

by the facility because of routine 

maintenance and equipment 

replacement, and it is not attributable to 

the Control Options. 

Table 9 of this preamble presents the 

nationwide impacts for requiring 

owners and operators to use the 

Modified El Paso Method and repair 

leaks of total strippable hydrocarbon 

concentration (as methane) in 

accordance to Control Options 1 and 2. 

See the document titled Clean Air Act 

Section 112(d)(5) GACT Standard 

Analysis for Heat Exchange Systems 

that Emit Ethylene Oxide and Section 

112(d)(6) Technology Review for Heat 

Exchange Systems Associated with 

Chemical Manufacturing Process Units 

at Area Sources Subject to the CMAS 

NESHAP, which is available in the 

docket for this rulemaking, for details 

on the assumptions and methodologies 

used in this analysis. Based on the costs 

and emission reductions for the 

identified Control Options, we are 

proposing to revise the CMAS NESHAP 

for heat exchange systems to reflect 

Control Option 1 pursuant to CAA 

section 112(d)(6). 

TABLE 9—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTIONS 1 AND 2 FOR REQUIRING THE

MODIFIED EL PASO METHOD FOR HEAT EXCHANGE SYSTEMS AT CMAS FACILITIES

Control option 

Total 

capital 

investment 

($) 

Total 

annualized 

costs w/o 

recovery 

credits 

($/yr) 

VOC 

emission 

reductions 

(tpy) 

HAP 

emission 

reductions 

(tpy) 

HAP cost 

effectiveness 

w/o recovery 

credits 

($/ton) 

Total 

annualized 

costs with 

recovery 

credits 

($/yr) 

HAP cost 

effectiveness 

with recovery 

credits 

($/ton) 

1 ........................... 0 57,100 44.6 4.46 12,800 16,900 3,800 

2 ........................... 1,046,400 214,200 46.1 4.61 46,500 172,700 37,500 


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Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7969 

39The TRE index value is a measure of the 

supplemental total resource requirement per unit 

VOC (or HAP) reduction. It takes into account all 

the resources which are expected to be used in VOC 

(or HAP) control by thermal oxidation and provides 

a dimensionless measure of resource burden based 

on cost effectiveness. Resources include 

supplemental natural gas, labor, and electricity. 

Additionally, if the off-gas contains halogenated 

compounds, resources will also include caustic and 

scrubbing and quench makeup water. For the 

CMAS NESHAP, the TRE index value is derived 

from the cost effectiveness associated with HAP 

control by a flare or thermal oxidation, and is a 

function of vent stream flowrate, vent stream net 

heating value, hourly emissions, and a set of 

coefficients. The TRE index value was first 

introduced in an EPA document titled: Guideline 

Series for Control of Volatile Organic Compound 

(VOC) Emissions from Air Oxidation Processes in 

Synthetic Organic Chemical Manufacturing 

Industry (SOCMI), which is available in the docket 

for this action (Docket ID No. EPA–HQ–OAR–2024– 

0303). 

We are proposing Control Option 1 at 

40 CFR 63.11499(d) and item 1.c of table 

8 to the CMAS NESHAP, by reference to 

the HON (40 CFR 63.104(a) and (f) 

through (l)), to specify quarterly 

monitoring for existing and new heat 

exchange systems (after an initial 6 

months of monthly monitoring) using 

the Modified El Paso Method and a leak 

definition of 6.2 ppmv of total 

strippable hydrocarbon concentration 

(as methane) in the stripping gas. 

Owners and operators of new and 

existing affected sources would be 

required to repair the leak to reduce the 

concentration or mass emissions rate to 

below the leak action level as soon as 

practicable, but no later than 45 days 

after identifying the leak. We are also 

proposing at 40 CFR 63.11499(d) and 

item 1.c of table 8 to the CMAS 

NESHAP, by reference to the HON, a 

delay of repair action level of total 

strippable hydrocarbon concentration 

(as methane) in the stripping gas of 62 

ppmv, that if exceeded during leak 

monitoring, would require immediate 

repair (i.e., the leak found cannot be put 

on delay of repair and would be 

required to be repaired within 30 days 

of the monitoring event). This would 

apply to both monitoring heat exchange 

systems and individual heat exchangers 

by replacing the use of any 40 CFR part 

136 water sampling method with the 

Modified El Paso Method and removing 

the option that allows for use of a 

surrogate indicator of leaks. We are also 

proposing at 40 CFR 63.11499(d) and 

item 1.c of table 8 to the CMAS 

NESHAP, by reference to the HON, that 

repair include re-monitoring at the 

monitoring location where a leak is 

identified to ensure that any leaks found 

are fixed. We are proposing that none of 

these proposed requirements would 

apply to heat exchange systems that 

have a maximum cooling water flow 

rate of less than 8,000 gallons per 

minute because owners and operators of 

smaller heat exchange systems would be 

disproportionally affected and forced to 

repair leaks with a much lower potential 

HAP emissions rate than owners and 

operators of heat exchange systems with 

larger recirculation rate systems. 

3. Process Vents 

A process vent is a gas stream that is 

discharged during the operation of a 

particular unit operation (e.g., 

separation processes, purification 

processes, mixing processes, reaction 

processes). The gas stream(s) may be 

routed to other unit operations for 

additional processing (e.g., a gas stream 

from a reactor that is routed to a 

distillation column for separation of 

products), sent to one or more recovery 

devices, sent to a process vent header 

collection system (e.g., blowdown 

system) and APCD (e.g., flare, thermal 

oxidizer, carbon adsorber), and/or 

vented to the atmosphere. Process vents 

may be generated from continuous and/ 

or batch operations, as well as from 

other intermittent types of operations 

(e.g., maintenance operations). If 

process vents are required to be 

controlled prior to discharge to the 

atmosphere to meet an applicable 

emissions standard, then they are 

typically collected and routed to an 

APCD through a closed vent system. 

The CMAS NESHAP defines batch 

process vents as a vent from a CMPU or 

vents from multiple CMPUs within a 

process that are manifolded together 

into a common header, through which 

a HAP-containing gas stream is, or has 

the potential to be, released to the 

atmosphere. Batch process vents 

include vents from batch operations and 

vents with intermittent flow from 

continuous operations that are not 

combined with any stream that 

originated as a continuous gas stream 

from the same continuous process. 

Batch process vents at existing affected 

sources are subject to controls if the 

total organic HAP emissions from all 

batch process vents combined are 

greater than or equal to 10,000 lb/yr. 

Owners and operators have three 

options for controlling batch process 

vents meeting the criteria: (1) reduce 

collective uncontrolled total organic 

HAP emissions from the sum of all 

batch process vents by greater than or 

equal to 85 percent by weight or to less 

than or equal to 20 ppmv by routing 

emissions through a closed vent system 

to any combination of control devices 

(except a flare); (2) route emissions from 

batch process vents containing greater 

than or equal to 85 percent of the 

uncontrolled total organic HAP through 

a closed vent system to a flare; or (3) 

comply with the alternative standard 

specified in 40 CFR 63.2505, which 

requires owners and operators to 

achieve specified outlet concentrations 

for TOC and total hydrogen halides and 

halogens on a continuous basis (both 

emission limits are 20 ppmv for 

combustion devices, and 50 ppmv for 

non-combustion devices). The 

requirements for batch process vents at 

new affected sources are the same, 

except instead of 85 percent control, the 

CMAS NESHAP requires 90 percent 

control. 

The CMAS NESHAP currently defines 

‘‘continuous process vents’’ using the 

definition of ‘‘process vent’’ in the HON 

(40 CFR part 63, subpart F), but includes 

a few caveats that address any 

references to the HON. In other words, 

a ‘‘continuous process vent’’ is the point 

of discharge to the atmosphere (or the 

point of entry into a control device, if 

any) of a gas stream if the gas stream has 

the characteristics specified in 40 CFR 

63.107(b) through (h), or meets the 

criteria specified in 40 CFR 63.107(i). 

Additionally, any references to ‘‘air 

oxidation reactors, distillation units, or 

reactors’’ in the HON process vent 

definition, instead mean ‘‘any 

continuous operation’’ within the 

context of the ‘‘continuous process 

vent’’ definition in the CMAS NESHAP. 

The definition of ‘‘continuous process 

vent’’ in the CMAS NESHAP also 

requires a separate determination for the 

emissions from each CMPU, even if 

emission streams from two or more 

CMPUs are combined prior to discharge 

to the atmosphere or to a control device. 

Continuous process vents at both 

existing and new affected sources with 

a total resource effectiveness (TRE) 

index value 39 less than or equal to 1.0 

are subject to controls and have three 

options to meet this requirement. 

Owners and operators can either: (1) 

reduce emissions of total organic HAP 

by greater than or equal to 95 percent by 

weight (85 percent by weight for periods 

of startup or shutdown) or to less than 

or equal to 20 ppmv by routing 

emissions through a closed vent system 

to any combination of control devices 

(except a flare); (2) reduce emissions of 

total organic HAP by routing all 

emissions through a closed vent system 

to a flare; or (3) comply with the 

alternative standard specified in 40 CFR 

63.2505. Continuous process vents at 

both existing and new affected sources 

with a TRE index value greater than 1.0 

but less than or equal to 4.0 may comply 

with the operating, monitoring, 

recordkeeping, and reporting 

requirements of 40 CFR 63.982(e) if a 

recovery device is used to maintain a 


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7970 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

40On January 30, 2012, the EPA proposed 

revisions to several provisions of the CMAS 

NESHAP (see 77 FR 4522). The proposed revisions 

were made, in part, in response to a petition for 

reconsideration received by the Administrator 

following the original promulgation of the October 

29, 2009, final rule. In the proposed rule revisions, 

the EPA solicited comment on whether the 

definition of ‘‘metal HAP process vent’’ was 

applicable to all types of equipment from which 

metal HAP are emitted. The original rule defined 

a metal HAP process vent as ‘‘the point of discharge 

to the atmosphere (or inlet to a control device, if 

any) of a metal HAP containing gas stream from any 

CMPU at an affected source,’’ regardless of the 

concentration of metal HAP in the stream. Based on 

two commenters’ requests, the EPA revised the 

definition of ‘‘metal HAP process vent’’ in the final 

rule revisions (77 FR 75740, December 21, 2012), 

to include only those streams which contain at least 

50 ppmv metal HAP. The EPA also revised the final 

rule to state that process vents from CMPUs that 

only contain metal HAP in a liquid solution or 

other form that will not result in particulate 

emissions of metal HAP (e.g., metal HAP that is in 

ingot, paste, slurry or moist pellet form or other 

form) are not required to comply with the metal 

HAP process vent requirements. 

TRE greater than 1.0 but less than or 

equal to 4.0. 

Additionally, both batch and 

continuous process vents have different 

requirements under the CMAS NESHAP 

if the process vent stream is 

halogenated. Halogenated batch and 

continuous process vent streams at new 

or existing sources that are controlled 

through combustion must also use 

halogen scrubbers to: (1) reduce overall 

emissions of hydrogen halide and 

halogen HAP after the combustion 

device by greater than or equal to 95- 

percent, to less than or equal to 0.45 

kilogram per hour (kg/hr), or to a 

concentration less than or equal to 20 

ppmv; or (2) reduce the halogen atom 

mass emission rate before the 

combustion device to less than or equal 

to 0.45 kg/hr or to a concentration less 

than or equal to 20 ppmv. 

The CMAS NESHAP also defines 

metal HAP process vents as the point of 

discharge to the atmosphere (or inlet to 

a control device, if any) of a metal HAPcontaining gas stream from any CMPU 

at an affected source containing at least 

50 ppmv metal HAP (see 40 CFR 

63.11502(b)). The metal HAP 

concentration may be determined using 

any of the following: process 

knowledge, an engineering assessment, 

or test data. For purposes of the CMAS 

NESHAP, metal HAP are the 

compounds containing metals listed as 

HAP in section 112(b) of the CAA. Metal 

HAP process vents at both existing and 

new affected sources with total metal 

HAP emissions greater than or equal to 

400 lb/yr are subject to controls. Owners 

and operators must reduce collective 

uncontrolled emissions of total metal 

HAP emissions by greater than or equal 

to 95 percent by weight by routing 

emissions from a sufficient number of 

the metal process vents through a closed 

vent system to any combination of 

control devices. 

We are proposing to make a change to 

the definition of ‘‘metal HAP process 

vent’’ at 40 CFR 63.11502(b). In 2012, as 

part of a response to a petition for 

reconsideration, the EPA added the 50 

ppmv threshold to the definition of 

‘‘metal HAP process vent’’ at 40 CFR 

63.11502(b).40 This threshold was 

included because two commenters 

argued it was necessary to better 

represent GACT, based on their sulfuric 

acid regeneration units already 

achieving over 95 percent reduction in 

metal HAP. However, the EPA did not 

conduct any analysis to justify this 

addition. We believe the threshold is 

inappropriate and has allowed process 

vents previously subject to control to 

freely emit metal HAP. We identified a 

facility through the emissions inventory 

(see section II.C of this preamble) that is 

currently subject to the CMAS NESHAP. 

This facility reported emitting 1.99 tpy 

of nickel compounds from process 

vents. Since the facility emits more than 

400 lb/year of metal HAP, the 

provisions in table 4 of 40 CFR part 63, 

subpart VVVVVV should apply. 

However, if these standards were 

applied, it would suggest that the 

facility was emitting nearly 40 tpy of 

nickel compounds uncontrolled. This 

amount of nickel seems 

unrepresentative of the source. It is 

more likely that, due to the 50 ppmv 

threshold, the facility determined it was 

not required to control the metal HAP 

process vents. Additionally, we note 

that this facility was included in the 

original rulemaking’s facility list, so the 

impacts of installing controls have 

already been considered. 

We are now proposing to remove the 

50 ppmv threshold from the definition 

of ‘‘metal HAP process vent’’ at 40 CFR 

63.11502(b). We believe this 

concentration-based threshold is 

unnecessary because the CMAS 

NESHAP already has a mass-based 

metal HAP threshold. Specifically, if the 

total uncontrolled metal HAP emissions 

from all metal HAP process vents from 

a CMPU are less than 400 lb/yr, then 

owners and operators are only subject to 

recordkeeping requirements, not the 

metal HAP process vent standards in 

table 4 of the CMAS NESHAP. 

In addition to being a necessary 

revision made as part of CAA section 

112(d)(6), the standards were originally 

promulgated as part of the Area Source 

Program under the Urban Air Toxics 

Strategy to ensure greater than 90 

percent of emissions of the 30 urban 

HAP were subject to regulation. In 

setting the 50 ppmv threshold, vents 

that were previously subject to 

regulation may have been improperly 

exempted from the standards that were 

established to address those emissions. 

By proposing to remove the 50 ppmv 

threshold and returning the definition to 

its originally promulgated state, the 

standards will once again apply to those 

metal HAP vents previously subject as 

part of the original rulemaking. 

As part of our technology review, we 

also examined subsequent regulatory 

development efforts and found that the 

EPA recently evaluated emission 

reduction options for continuous 

process vents subject to the HON, 

including the removal of the TRE 

concept in its entirety from the NESHAP 

or revising the TRE index value 

threshold from 1.0 to 5.0. The EPA 

determined that removing the TRE 

concept in its entirety from the HON 

was cost effective and finalized this in 

that rule (see 89 FR 42932, May 16, 

2024). It is reasonable to consider 

removing the TRE concept in its entirety 

from the CMAS NESHAP given that 

CMPU sources subject to the CMAS 

NESHAP are similar to CMPU sources 

that are subject to the HON; however, 

we do not have data representative of 

CMAS continuous process vents to 

evaluate this option. In other words, 

none of the continuous process vent 

data that the EPA used in the HON 

rulemaking are representative of an area 

source; and therefore, not representative 

of a CMAS facility. For further 

information, see the document titled 

Clean Air Act Section 112(d)(5) GACT 

Standard Analysis for Process Vents 

and Storage Tanks that Emit Ethylene 

Oxide and Section 112(d)(6) Technology 

Review for Process Vents and Storage 

Tanks Associated with Chemical 

Manufacturing Process Units at Area 

Sources Subject to the CMAS NESHAP, 

which is available in the docket for this 

rulemaking. We solicit comment and 

data on whether removing the TRE 

concept in its entirety is feasible for 

continuous process vents from CMAS 

CMPUs. 

Except for the proposed change to the 

definition of ‘metal HAP process vent’ 

and the TRE options we could not 

evaluate due to insufficient data on 

CMAS continuous process vents, we 

found no additional practices, 

processes, or control technologies 

beyond those already required by the 

CMAS NESHAP for process vents. Our 

review did not reveal any other 

developments in emissions reduction 

practices for CMAS process vents that 

are any more stringent than the GACT 

standards in the CMAS NESHAP. 


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Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7971 

41The HON uses the term ‘‘storage vessel’’ in lieu 

of ‘‘storage tank’’ like the CMAS NESHAP. 

42Process wastewater means wastewater which, 

during manufacturing or processing, comes into 

direct contact with or results from the production 

or use of any raw material, intermediate product, 

finished product, by-product, or waste product. 

Examples are product tank drawdown or feed tank 

drawdown; water formed during a chemical 

reaction or used as a reactant; water used to wash 

impurities from organic products or reactants; water 

used to cool or quench organic vapor streams 

through direct contact; and condensed steam from 

jet ejector systems pulling vacuum on vessels 

containing organics. 

43Maintenance wastewater means wastewater 

generated by the draining of process fluid from 

components in the CMPU into an individual drain 

system in preparation for or during maintenance 

activities. Maintenance wastewater can be 

generated during planned and unplanned 

shutdowns and during periods not associated with 

a shutdown. Examples of activities that can 

generate maintenance wastewater include descaling 

of heat exchanger tubing bundles, cleaning of 

distillation column traps, draining of pumps into an 

individual drain system, and draining of portions 

of the CMPU for repair. Wastewater from routine 

cleaning operations occurring as part of batch 

operations is not considered maintenance 

wastewater. 

Therefore, we are not proposing any 

other changes to the CMAS NESHAP for 

process vents pursuant to CAA section 

112(d)(6). 

4. Storage Tanks 

Storage tanks are used to store liquid 

and gaseous feedstocks for use in a 

process, as well as to store liquid and 

gaseous products from a process. Most 

CMAS storage tanks are designed for 

operation at atmospheric or near 

atmospheric pressures; pressure vessels 

are used to store compressed gases and 

liquefied gases. Atmospheric storage 

tanks are typically cylindrical with a 

vertical orientation, and they are 

constructed with either a fixed roof or 

a floating roof. Some, generally small, 

atmospheric storage tanks are oriented 

horizontally. Pressure vessels are either 

spherical or horizontal cylinders. As 

discussed in section IV.B.1 of this 

preamble, we are proposing new GACT 

standards for pressure vessels. 

The CMAS NESHAP requires owners 

and operators to control emissions from 

storage tanks with: (1) capacities greater 

than or equal to 40,000 gallons storing 

a liquid with a maximum true vapor 

pressure (MTVP) greater than or equal to 

5.2 kPa but less than 76.6 kPa; (2) 

capacities greater than or equal to 

20,000 gallons and less than 40,000 

gallons storing a liquid with a MTVP 

greater than or equal to 27.6 kPa and 

less than 76.6 kPa; and (3) capacities 

greater than or equal to 20,000 gallons 

storing a liquid with a MTVP greater 

than or equal to 76.6 kPa. Owners and 

operators of storage tanks meeting any 

of these criteria are required to reduce 

total organic HAP emissions by greater 

than or equal to 95 percent by weight by 

operating and maintaining a closed vent 

system and control device (other than a 

flare), reduce total HAP emissions by 

operating and maintaining a closed vent 

system and a flare, vapor balance, or 

route emissions to a fuel gas system or 

process. Owners and operators of 

storage tanks meeting the first two sets 

of capacity and MTVP criterion can also 

comply with the requirements of 40 CFR 

part 63, subpart WW which requires 

owners and operators to operate and 

maintain an external floating roof (EFR) 

or internal floating roof (IFR) according 

to specific monitoring, recordkeeping, 

and reporting standards. 

Additionally, storage tanks within the 

capacity and MTVP thresholds listed in 

the preceding paragraph have different 

requirements under the CMAS NESHAP 

if the storage tank emits a halogenated 

vent stream. Halogenated storage tank 

vent streams at new or existing sources 

that are controlled through a 

combustion device must also use a 

halogen reduction device to: (1) reduce 

emissions of hydrogen halide and 

halogen HAP after the combustion 

device by greater than or equal to 95- 

percent, to less than or equal to 0.45 kg/ 

hr, or to a concentration less than or 

equal to 20 ppmv; or (2) reduce the 

halogen atom mass emission rate before 

the combustion device to less than or 

equal to 0.45 kg/hr or to a concentration 

less than or equal to 20 ppmv. 

We did not identify any practices, 

processes, or control technologies 

beyond those already required by the 

CMAS NESHAP for storage tanks. Our 

review did not reveal any developments 

in emissions reduction practices for 

CMAS storage tanks that are any more 

stringent than the GACT standards in 

the CMAS NESHAP. Therefore, we are 

not proposing any changes to the CMAS 

NESHAP for storage tanks pursuant to 

CAA section 112(d)(6). As part of our 

technology review, we examined 

subsequent regulatory development 

efforts and found that the EPA recently 

evaluated emission reduction options 

for storage vessels 41 subject to the HON, 

including revising capacity and MTVP 

thresholds, requiring certain IFR 

controls pursuant to 40 CFR part 63, 

subpart WW, and requiring the 

conversion of EFRs to IFRs through use 

of geodesic domes. The EPA determined 

that revising capacity and MTVP 

thresholds and requiring certain IFR 

controls pursuant to 40 CFR part 63, 

subpart WW was cost effective for HON 

storage vessels and finalized this in the 

rule (see 89 FR 42932, May 16, 2024). 

It is reasonable to consider these Control 

Options for the CMAS NESHAP given 

that CMPU sources subject to the CMAS 

NESHAP are similar to CMPU sources 

that are subject to the HON; however, 

we do not have data representative of 

CMAS storage tanks to evaluate these 

options. In other words, none of the 

storage vessel data that the EPA used in 

the recent HON rulemaking are 

representative of an area source; and 

therefore, not representative of a CMAS 

facility. Even still, we note that the 

CMAS NESHAP already includes 

complying with 40 CFR part 63, subpart 

WW as an option. Additionally, the EPA 

found the option of converting EFRs to 

IFRs through the use of geodesic domes 

to not be cost effective for HON storage 

vessels; therefore, we anticipate this 

option would likewise not be cost 

effective for CMAS storage tanks. For 

further information, see the document 

titled Clean Air Act Section 112(d)(5) 

GACT Standard Analysis for Process 

Vents and Storage Tanks that Emit 

Ethylene Oxide and Section 112(d)(6) 

Technology Review for Process Vents 

and Storage Tanks Associated with 

Chemical Manufacturing Process Units 

at Area Sources Subject to the CMAS 

NESHAP, which is available in the 

docket for this rulemaking. 

5. Wastewater 

HAP are emitted into the air from 

wastewater collection, storage, and 

treatment systems that are uncovered or 

open to the atmosphere through 

volatilization of the compound at the 

liquid surface. Emissions occur by 

diffusive or convective means, or both. 

Diffusion occurs when organic pollutant 

concentrations at the water surface are 

much higher than ambient 

concentrations. The organic pollutants 

volatilize, or diffuse into the air, to 

reach equilibrium between the aqueous 

and vapor phases. Convection occurs 

when air flows over the water surface, 

sweeping organic vapors from the water 

surface into the air. The rate of 

volatilization is related directly to the 

speed of the air flow over the water 

surface. 

The CMAS NESHAP defines 

wastewater to mean water that is 

discarded from a CMPU or control 

device and that contains at least 5 

ppmw of any HAP listed in table 9 to 

40 CFR part 63, subpart G and has an 

annual average flow rate of 0.02 liters 

per minute (lpm). Wastewater means 

both process wastewater 42 and 

maintenance wastewater 43 that is 

discarded from a CMPU or control 

device. 

For each wastewater stream 

containing partially soluble HAP at a 

concentration greater than or equal to 


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7972 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

44See 73 FR 58352, October 6, 2008. ‘‘We are 

proposing that [wastewater] controls needed to 

meet more stringent emission limits like those 

required by the HON do not represent GACT for 

either subcategory because the costs are 

unreasonable.’’ 

45For a list of studies, refer to the technical report 

titled Parameters for Properly Designed and 

Operated Flares, in Docket ID Item No. EPA–HQ– 

OAR–2010–0682–0191. This document can also be 

found at https://www.epa.gov/stationary-sourcesair-pollution/review-peer-review-parametersproperly-designed-and-operated-flares. 

46To estimate the baseline control efficiency of 

VOC and HAP anticipated by applying Control 

Option 1, we reviewed data submitted to the EPA 

in 2011 by the API, the ACC, and the NPRA, now 

known as the AFPM. This dataset includes detailed 

hourly operational information for 38 steamassisted flares, characterizing different operating 

10,000 ppmw that also has separate 

organic and water phases, the CMAS 

NESHAP requires owners and operators 

to use a decanter, steam stripper, thin 

film evaporator, or distillation unit to 

separate the water phase from the 

organic phase(s); and the organic layer 

must be recycled to a process, used as 

a fuel, or disposed of as hazardous 

waste either onsite or offsite. The CMAS 

NESHAP also provides an alternative 

compliance option that allows owners 

and operators to hard-pipe the entire 

stream to onsite treatment as a 

hazardous waste or to a point of transfer 

to onsite or offsite hazardous waste 

treatment. For single phase wastewater 

streams and the aqueous phase for two 

phase streams, the CMAS NESHAP 

requires the wastewater streams be sent 

to a wastewater treatment process. 

As part of our technology review, we 

found that many of the NESHAP for 

different chemical manufacturing source 

categories (e.g., the HON, MON, and 

PEPO NESHAP) require treatment of 

wastewater streams that meet certain 

flow and HAP concentration levels. 

These standards require either the use of 

a treatment unit that meets specified 

design criteria or that achieves specified 

destruction efficiencies for the HAP in 

the wastewater. They also typically 

require the use of covers and other 

techniques to suppress emissions from 

the wastewater conveyance system and 

treatment units. During the original 

CMAS rulemaking (74 FR 56008, 

October 29, 2009), the EPA evaluated 

treating CMAS wastewater streams 

using controls that meet the HON 

requirements; however, the EPA found 

the option to not be cost effective.44 We 

find no reason for the HON 

requirements to be any more cost 

effective today compared to the cost 

effectiveness that was determined in 

2008. Therefore, we are not proposing 

any changes to the CMAS NESHAP for 

wastewater pursuant to CAA section 

112(d)(6). 

6. Flares 

The CMAS NESHAP allows for the 

use of a flare to control emissions 

(except halogenated emissions) from 

batch process vents, continuous process 

vents, and/or storage tanks. The CMAS 

NESHAP points to the flare 

requirements specified in 40 CFR part 

63, subpart SS which requires owners 

and operators to conduct a flare 

compliance assessment to demonstrate 

initial compliance, and continuously 

monitor applicable operating parameters 

in accordance with 40 CFR 63.11 to 

demonstrate continuous compliance. 

Although GACT for batch process vents 

is emission reductions of 85 percent by 

weight (for existing) and 90 percent by 

weight (for new); for continuous process 

vents is 95 percent by weight (except 85 

percent by weight for startup and 

shutdown); and for storage tanks is 95 

percent by weight, the available data at 

the time the CMAS NESHAP was 

promulgated suggested that flares 

meeting these design and operating 

requirements of 40 CFR 63.11 would 

achieve a minimum destruction 

efficiency of no less than 98 percent by 

weight emissions control. However, 

more recent studies on flare 

performance 45 indicate that the 

requirements in 40 CFR 63.11 are 

inadequate to ensure 98 percent by 

weight control. These studies compelled 

the EPA to finalize a suite of operational 

and monitoring requirements for 

refinery flares on December 1, 2015 (80 

FR 75178–75354; see 40 CFR 63.670 and 

40 CFR 63.671) including requirements 

addressing: (1) the presence of a pilot 

flame; (2) visible emissions; (3) flare tip 

velocity; (4) net heating value of flare 

combustion zone gas; and (5) net 

heating value dilution parameter (if the 

flare actively receives perimeter assist 

air). The EPA determined that this suite 

of operational and monitoring 

requirements for flares is necessary to 

ensure the level of destruction 

efficiency needed to conform with the 

petroleum refineries NESHAP. 

Importantly, given that the flare dataset 

that formed the underlying basis of the 

new standards for refinery flares also 

included flares at olefin and other 

petrochemical plants, the EPA also 

revised the suite of operational and 

monitoring requirements for flares in 

other chemical manufacturing source 

categories, including the EMACT 

standards (85 FR 40386, July 6, 2020; 

see 40 CFR 63.1103(e)(4)), the Organic 

Liquids Distribution (OLD) NESHAP (85 

FR 40740, July 7, 2020; see 40 CFR 

63.2380(a)), the MON (85 FR 49084, 

August 20, 2020; see 40 CFR 

63.2450(e)(5)), and the HON and P&R I 

NESHAP (89 FR 42932, May 16, 2024; 

see 40 CFR 63.108 and 63.508, 

respectively). The EPA did this for the 

same reason as was done for the 

petroleum refineries NESHAP, to ensure 

the level of destruction efficiency 

needed to conform with each NESHAP. 

We acknowledge that none of the 

performance standards in the CMAS 

NESHAP are as stringent as 98 percent 

by weight emissions control; however, 

under CAA section 112(d)(6), we still 

evaluated the option (i.e., Control 

Option 1) to require all flares at CMAS 

facilities to comply with the same suite 

of flare operational and monitoring 

requirements included in the petroleum 

refineries NESHAP, EMACT standards, 

OLD NESHAP, MON, HON, and P&R I 

and Group II Polymers and Resins 

NESHAP. The monitoring equipment 

needed to comply with the suite of flare 

operational and monitoring 

requirements (i.e., hydrogen analyzers, 

calorimeters, and flow monitors) were 

not identified or considered during 

development of the original GACT 

standards; therefore, we consider this a 

development under this technology 

review. Additionally, we believe the 

suite of flare operational and monitoring 

requirements could be relevant to the 

CMAS NESHAP due to the similarities 

between processes at chemical 

manufacturing plants, regardless of size. 

Using information from the CMAS 

emissions inventory data (see section 

II.C.2 of this preamble), we estimated 

there are 22 flares at 20 CMAS facilities 

that would be affected by Control 

Option 1 (we did not identify any other 

flares in the CMAS emissions 

inventory). To avoid double counting, 

we excluded two of the 22 flares from 

our analysis that emit EtO; and instead, 

we included them in our GACT analysis 

discussed in section IV.A.6 of this 

preamble. We estimated costs for each 

flare for a given facility, considering 

current monitoring systems already 

installed on each individual flare. Given 

that the same type of equipment is used 

for flares in the CMAS categories and for 

the petroleum refinery sector, we 

estimated costs for any additional 

monitoring systems needed based on 

installed costs received from petroleum 

refineries and, if installed costs were 

unavailable, we estimated costs based 

on vendor-purchased equipment. The 

baseline emission estimate and the 

emission reductions achieved by 

Control Option 1 were estimated based 

on the CMAS emissions inventory data 

(see section II.C.2 of this preamble) and 

current vent gas and steam flow data 

submitted by industry representatives.46


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Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7973 

conditions by waste gas flow rate, steam flow rate, 

waste gas composition, and duration of that 

operating condition. 

47 40 CFR 63.658(f)–(h). 

48Quarterly fenceline monitoring reports are 

available through the EPA’s WebFIRE database at 

https://cfpub.epa.gov/webfire/. The EPA has also 

developed a dashboard to improve public access to 

this data. The dashboard is available at https://

awsedap.epa.gov/public/extensions/Fenceline_

Monitoring/Fenceline_

Monitoring.html?sheet=MonitoringDashboard. 

49 In the same action (see 89 FR 42932, May 16, 

2024), the EPA also finalized EPA Method 327 of 

40 CFR part 63, appendix A, as a canister sampling 

and analysis method that provides procedures for 

measuring trace levels of targeted VOC (including 

organic HAP) in ambient air. 

The results of the impact estimates for 

Control Options 1 are summarized in 

table 10 of this preamble. See the 

document titled Clean Air Act Section 

112(d)(5) GACT Standard Analysis for 

Flares that Emit Ethylene Oxide and 

Section 112(d)(6) Technology Review for 

Flares Associated with Chemical 

Manufacturing Process Units at Area 

Sources Subject to the CMAS NESHAP, 

which is available in the docket for this 

rulemaking, for details on the 

assumptions and methodologies used in 

this analysis. We determined that 

Control Option 1 is not cost effective 

and are not proposing to revise the 

CMAS NESHAP to reflect the 

requirements of this option pursuant to 

CAA section 112(d)(6). 

TABLE 10—NATIONWIDE EMISSIONS REDUCTIONS AND COST IMPACTS OF CONTROL OPTION 1 FOR REQUIRING THE SUITE

OF OPERATIONAL AND MONITORING REQUIREMENTS FOR FLARES AT CMAS FACILITIES

Control option 

Total capital 

investment 

($) 

Total 

annualized 

costs 

($/yr) 

VOC emission 

reductions 

(tpy) 

HAP emission 

reductions 

(tpy) 

HAP cost 

effectiveness 

($/ton) 

1 ....................................................................................... 26,000,000 6,160,000 1,114 89.4 68,200 

7. Fenceline Monitoring 

Fenceline monitoring refers to the 

placement of monitors along the 

perimeter of a facility to measure 

pollutant concentrations. Coupled with 

requirements for root cause analysis and 

corrective action upon triggering an 

actionable level, this management 

practice is a development in practices 

considered under CAA section 112(d)(6) 

for the purposes of managing fugitive 

emissions. The measurement of 

pollutant concentrations and 

comparison to concentrations estimated 

from mass emissions via dispersion 

modeling is used to verify emission 

estimates from a facility’s emissions 

inventory. If concentrations at the 

fenceline are greater than expected, 

potential causes may include 

underreported or unknown emissions, 

leaking equipment, or other issues, 

usually related to ground-level fugitive 

emissions. Fenceline monitoring also 

provides information on the location of 

potential emissions sources because it 

provides complete spatial coverage of a 

facility. Further, when used with a 

mitigation strategy, such as root cause 

analysis and corrective action upon 

exceedance of an action level, fenceline 

monitoring can be effective in reducing 

emissions and reducing the uncertainty 

associated with emissions estimation 

and characterization. Finally, public 

reporting of fenceline monitoring data 

provides public transparency and 

greater visibility, leading to more focus 

and effort in reducing emissions. 

The EPA has successfully applied 

fenceline monitoring to the petroleum 

refineries source category as a technique 

to manage and reduce benzene 

emissions from fugitive emissions 

sources such as storage vessels, 

wastewater treatment systems, and 

leaking equipment. In 2015, the EPA 

promulgated the RTR for the petroleum 

refineries source category and required 

that refineries install and operate 

fenceline monitors following EPA 

Method 325 A/B to monitor benzene 

emissions. Additionally, the 2015 rule 

required that refineries conduct a root 

cause analysis to identify sources of 

high fenceline monitoring readings (i.e., 

above an annual action level) and then 

develop a corrective action plan to 

address the sources and reduce 

emissions to a level that will bring 

fenceline monitoring concentrations 

below the action level.47 To date, the 

EPA has received fenceline monitoring 

data from petroleum refineries for more 

than 5 years.48 These data show that 

petroleum refinery fenceline 

concentrations have dropped by an 

average of 30 percent since the 

inception of the monitoring program 

requirements and illustrate that 

fenceline monitoring is an effective tool 

in reducing emissions and preserving 

emission reductions on an ongoing basis 

for these sources. 

Additionally, in 2024, the EPA 

promulgated amendments to the HON 

(40 CFR part 63, subpart H) and the P&R 

I NESHAP (40 CFR part 63, subpart U) 

that included work practice standards 

requiring owners and operators to 

conduct fenceline monitoring for any of 

six specific HAP (i.e., benzene; 1,3- 

butadiene; ethylene dichloride; vinyl 

chloride; EtO; and chloroprene) if their 

affected source uses, produces, stores, or 

emits any of them, and conduct root 

cause analysis and corrective action 

upon exceeding the annual average 

concentration action level established 

for each HAP. The final HON and P&R 

I NESHAP amendments require owners 

and operators to conduct passive 

diffusive tube fenceline monitoring for 

benzene, 1,3-butadiene, chloroprene, 

and ethylene dichloride in accordance 

with EPA Methods 325A/B of 40 CFR 

part 63, appendix A, and to use canister 

sampling in accordance with EPA 

Method 327 of 40 CFR part 63, appendix 

A, for EtO and vinyl chloride.49

Given the similarities between CMAS 

CMPUs and sources subject to the HON 

or P&R I NESHAP, we evaluated the 

application of fenceline monitoring as a 

development in practices, processes, 

and control technologies pursuant to 

CAA section 112(d)(6). Non-EtO 

pollutants for which there are 

established EPA Methods to measure 

fenceline concentrations and which are 

one of the fifteen urban HAP regulated 

as part of the CMAS NESHAP include 

1,3-butadiene, 1,3-dichloropropene, 

ethylene dichloride, and chloroform. 

We reviewed the 2017 NEI to determine 

whether CMAS facilities reported 

emissions of 1,3-butadiene, chloroform 

1,3-dichloropropene, and ethylene 

dichloride. Based on this review, we 

determined that at most CMAS facilities 

that emit 1,3-butadiene, chloroform, 1,3- 

dichloropropene, and ethylene 

dichloride, small amounts of these HAP 

are emitted from fugitive sources. Most 

of the reported emissions are attributed 

to non-source category emission 

sources. Based on this information, the 

EPA is not proposing to implement a 

fenceline monitoring program for nonEtO pollutants under CAA section 

112(d)(6). However, we are proposing a 


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50https://www.epa.gov/electronic-reporting-airemissions/electronic-reporting-tool-ert. 

51See part_63_subpart_VVVVVV_63.11501(d)_

semiannual_compliance.xlsx available in the docket 

for this action. 

52We are proposing at 40 CFR 63.11503(b)(5) that 

the approval to an alternative to any electronic 

reporting to the EPA proposed for the CMAS 

NESHAP cannot be delegated to state, local, or 

Tribal agencies. 

53EPA’s Final Plan for Periodic Retrospective 

Reviews, August 2011. Available at: https://

www.regulations.gov/document?D=EPA-HQ-OA2011-0156-0154. 

54E-Reporting Policy Statement for EPA 

Regulations, September 2013. Available at: https:// 

www.epa.gov/sites/production/files/2016-03/ 

documents/epa-ereporting-policy-statement-2013- 

09-30.pdf. 

55 Digital Government: Building a 21st Century 

Platform to Better Serve the American People, May 

2012. Available at: https://

obamawhitehouse.archives.gov/sites/default/files/ 

omb/egov/digital-government/digitalgovernment.html. 

fenceline monitoring program to limit 

fugitive EtO emissions under CAA 

section 112(d)(5), as discussed in 

section IV.A.7 of this preamble and in 

further detail in the document titled 

Clean Air Act Section 112(d)(5) GACT 

Standard Analysis and CAA Section 

112(d)(6) Technology Review for 

Fenceline Monitoring for Chemical 

Manufacturing Process Units Associated 

with the Chemical Manufacturing Area 

Sources NESHAP available in the 

docket for this action. 

D. What other actions are we proposing, 

and what is the rationale for those 

actions? 

In addition to the proposed GACT 

standards pursuant to CAA 112(d)(5) 

(see sections IV.A and IV.B of this 

preamble) and our proposed actions on 

the CAA 112(d)(6) review (see section 

IV.C of this preamble), we are also 

proposing other changes to the CMAS 

NESHAP, including: revisions to the 

recordkeeping and reporting 

requirements to require the use of 

electronic reporting of certain reports; 

performance testing once every 5 years 

for batch and continuous process vents 

to demonstrate compliance with 

emission limits; and corrections to 

section reference errors and other minor 

editorial revisions. Our rationale and 

proposed changes related to these issues 

are discussed below. 

1. Electronic Reporting 

The EPA is proposing that owners and 

operators subject to the CMAS NESHAP 

submit electronic copies of required 

notification of compliance status 

reports, performance test reports, flare 

management plans, and periodic reports 

(including fenceline monitoring reports) 

through the EPA’s Central Data 

Exchange using the Compliance and 

Emissions Data Reporting Interface 

(CEDRI) (see proposed edits to 40 CFR 

63.11496(f)(3)(ii) for notification of 

compliance status reports associated 

with the HAP metals emissions limit, 

proposed 40 CFR 63.11501(b) for 

notification of compliance status 

reports, 40 CFR 63.11496(g)(1)(iv) for 

performance test reports, 40 CFR 

63.11501(d) for semiannual compliance 

reports, and references to flare 

requirements which include flare 

management plans in proposed entries 

4.a to tables 2 and 3 to subpart VVVVVV 

of part 63 and proposed entry 5.a to 

table 5 to subpart VVVVVV of part 63). 

A description of the electronic data 

submission process is provided in the 

document titled Electronic Reporting 

Requirements for New Source 

Performance Standards (NSPS) and 

National Emission Standards for 

Hazardous Air Pollutants (NESHAP) 

Rules, available in the docket for this 

action. 

The proposed rule requires that 

performance test results collected using 

test methods that are supported by the 

EPA’s Electronic Reporting Tool (ERT) 

as listed on the ERT website 50 at the 

time of the test be submitted in the 

format generated through the use of the 

ERT or an electronic file consistent with 

the xml schema on the ERT website, and 

other performance test results be 

submitted in portable document format 

(PDF) using the attachment module of 

the ERT. Flare management plans would 

be uploaded as a PDF file. 

For semiannual compliance reports 

(including fenceline monitoring 

reports), the proposed rules require that 

owners and operators use an 

appropriate spreadsheet template to 

submit information to CEDRI. A draft 

version of the proposed templates for 

these reports is included in the docket 

for this action.51 The EPA specifically 

requests comment on the content, 

layout, and overall design of the 

templates. We are proposing owners and 

operators begin using the templates for 

semiannual compliance reports other 

than fenceline reports within 3 years of 

the publication date of the final rule in 

the Federal Register, or after the 

reporting template for the subpart has 

been available on the CEDRI website for 

1 year, whichever date is later. Owners 

and operators would begin using the 

templates for fenceline monitoring 

reports starting when the first fenceline 

monitoring report is due. 

The electronic submittal of the reports 

addressed in these proposed 

rulemakings will increase the usefulness 

of the data contained in those reports, 

is in keeping with current trends in data 

availability and transparency, will 

further assist in the protection of public 

health and the environment, will 

improve compliance by facilitating the 

ability of regulated facilities to 

demonstrate compliance with 

requirements and by facilitating the 

ability of delegated state, local, Tribal, 

and territorial air agencies and the EPA 

to assess and determine compliance, 

and will ultimately reduce burden on 

regulated facilities, delegated air 

agencies, and the EPA.52 Electronic 

reporting also eliminates paper-based, 

manual processes, thereby saving time 

and resources, simplifying data entry, 

eliminating redundancies, minimizing 

data reporting errors, and providing data 

quickly and accurately to the affected 

facilities, air agencies, the EPA, and the 

public. Moreover, electronic reporting is 

consistent with the EPA’s plan 53 to 

implement Executive Order 13563 and 

is in keeping with the EPA’s Agencywide policy 54 developed in response to 

the White House’s Digital Government 

Strategy.55 For more information on the 

benefits of electronic reporting, see the 

document titled Electronic Reporting 

Requirements for New Source 

Performance Standards (NSPS) and 

National Emission Standards for 

Hazardous Air Pollutants (NESHAP) 

Rules, referenced earlier in this section. 

2. Affirmative Defense 

As part of the December 21, 2012, 

CMAS NESHAP final rule (see 77 FR 

75740), the EPA included the ability to 

assert an affirmative defense to civil 

penalties for violations caused by 

malfunctions (see 40 CFR 63.11501(e)) 

in an effort to create a system that 

incorporated some flexibility, 

recognizing that there is a tension, 

inherent in many types of air regulation, 

to ensure adequate compliance while 

simultaneously recognizing that despite 

the most diligent of efforts, emission 

standards may be violated under 

circumstances entirely beyond the 

control of the source. Although the EPA 

recognized that its case-by-case 

enforcement discretion provides 

sufficient flexibility in these 

circumstances, it included the 

affirmative defense provision to provide 

a more formalized approach and more 

regulatory clarity. See Weyerhaeuser Co. 

v. Costle, 590 F.2d 1011, 1057–58 (D.C. 

Cir. 1978) (holding that an informal 

case-by-case enforcement discretion 

approach is adequate); but see Marathon 

Oil Co. v. EPA, 564 F.2d 1253, 1272–73 

(9th Cir. 1977) (requiring a more 

formalized approach to consideration of 

‘‘upsets beyond the control of the permit 

holder.’’). Under the EPA’s regulatory 


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56The court’s reasoning in NRDC focuses on civil 

judicial actions. The court noted that ‘‘EPA’s ability 

to determine whether penalties should be assessed 

for CAA violations extends only to administrative 

penalties, not to civil penalties imposed by a 

court.’’ Id. 

57Although the NRDC case does not address the 

EPA’s authority to establish an affirmative defense 

to penalties that are available in administrative 

enforcement actions, we are not including such an 

affirmative defense in the proposed rule. As 

explained above, such an affirmative defense is not 

necessary. Moreover, assessment of penalties for 

violations caused by malfunctions in administrative 

proceedings and judicial proceedings should be 

consistent. Cf. CAA section 113(e) (requiring both 

the Administrator and the court to take specified 

criteria into account when assessing penalties). 

affirmative defense provisions, if a 

source could demonstrate in a judicial 

or administrative proceeding that it had 

met the requirements of the affirmative 

defense in the regulation, civil penalties 

would not be assessed. However, the 

court vacated the affirmative defense in 

one of the EPA’s CAA section 112 

regulations. NRDC v. EPA, 749 F.3d 

1055 (D.C. Cir., 2014) (vacating 

affirmative defense provisions in the 

CAA section 112 rule establishing 

emission standards for Portland cement 

kilns). The court found that the EPA 

lacked authority to establish an 

affirmative defense for private civil suits 

and held that under the CAA, the 

authority to determine civil penalty 

amounts 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, 749 F.3d at 

1063 (‘‘[U]nder this statute, deciding 

whether penalties are ‘appropriate’ in a 

given private civil suit is a job for the 

courts, not EPA.’’).56 In light of NRDC, 

the EPA is proposing to remove all of 

the regulatory affirmative defense 

provisions from the CMAS NESHAP at 

40 CFR 63.11501(e) in its entirety and 

the definition of ‘‘affirmative defense’’ 

at 40 CFR 63.11502(b). As explained 

above, if a source is unable to comply 

with emissions standards as a result of 

a malfunction, the EPA may use its caseby-case enforcement discretion to 

provide flexibility, as appropriate. 

Further, as the court 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, 749 

F.3d at 1064 (arguments that violation 

was 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.57

The EPA previously proposed to 

remove the affirmative defense 

provisions from the CMAS NESHAP as 

part of the Removal of Affirmative 

Defense Provisions from Specified New 

Source Performance Standards and 

National Emissions Standards for 

Hazardous Air Pollutants action (see 89 

FR 52425, June 24, 2024). We now 

propose the removal of these provisions 

as part of this action. We are soliciting 

comment on our proposal to remove the 

affirmative defense provisions from the 

CMAS NESHAP as part of this 

rulemaking. Comments previously 

submitted on the Removal of 

Affirmative Defense Provisions from 

Specified New Source Performance 

Standards and National Emissions 

Standards for Hazardous Air Pollutants 

proposal will not be considered as part 

of this action and must be submitted to 

the docket for this action (Docket ID No. 

EPA–HQ–OAR–2024–0303) in order to 

be considered. 

3. Technical and Editorial Changes 

We are proposing several technical 

amendments and definition revisions to 

improve the clarity and enforceability of 

certain provisions in the CMAS 

NESHAP. This section of the preamble 

described these additional proposed 

revisions and our rationale. 

a. Certain Definitions That Refer to the 

HON 

We note that to remove redundancy 

and improve consistency, the EPA 

recently finalized moving all of the 

definitions from NESHAP subpart G 

(i.e., 40 CFR 63.111) into the definition 

section of NESHAP subpart F (i.e., 40 

CFR 63.101) (see 89 FR 42932, May 16, 

2024). Given that the CMAS NESHAP 

directly references these subparts for 

certain definitions (see 40 CFR 

63.11502(a)), we are proposing to revise 

the phrasing used in 40 CFR 63.11502(a) 

to point to NESHAP subpart F in 

instances where a definition in the 

CMAS NESHAP points to NESHAP 

subpart G. We are also proposing 

editorial changes in 40 CFR 63.11502(b) 

that clarify references in the CMAS 

NESHAP definition of ‘‘point of 

determination’’ to properly cite the 

correct HON subpart. 

b. Performance Testing 

The EPA is proposing at 40 CFR 

63.11496(g)(1)(iii) and 40 CFR 

63.11497(g)(1)(iii) performance testing 

once every 5 years to demonstrate 

compliance with organic HAP emission 

limits for batch and continuous process 

vents and storage tanks (for owners and 

operators that route emissions to a 

control device other than a flare). 

Similarly, we are also proposing at 40 

CFR 63.11496(f)(3)(iv), (4), and (5) 

performance testing once every 5 years 

to demonstrate compliance with the 

metal HAP emission limit for batch and 

continuous process vents. We 

determined that periodic emission 

testing should be required to help 

ensure continuous compliance. 

Currently, facilities conduct a one-time 

performance test, engineering 

assessment, or design evaluation and 

then monitor operating parameters. A 

design evaluation (in lieu of 

performance testing) is currently 

allowed at 40 CFR 63.11496(g)(2) for 

determining initial compliance with a 

percent reduction or outlet 

concentration process vent organic HAP 

emission limit. A design evaluation (in 

lieu of performance testing) is also 

currently allowed at 40 CFR 

63.985(b)(1)(i) (via items 1.b, 2.a, and 

3.a of table 5 to the CMAS NESHAP) for 

determining initial compliance with a 

percent reduction or outlet 

concentration storage tank organic HAP 

emission limit. An engineering 

assessment (in lieu of performance 

testing) is currently allowed at 40 CFR 

63.11496(f)(3)(ii) for determining initial 

compliance with the percent reduction 

process vent metal HAP emission limit. 

However, we are proposing to remove 

the design evaluation option at 40 CFR 

63.11496(g)(2) and table 5 to the CMAS 

NESHAP, and the engineering 

assessment option at 40 CFR 

63.11496(f)(3)(ii), and instead, require 

on-going performance tests at proposed 

40 CFR 63.11496(f)(3)(iv), (4), and (5), 

and 40 CFR 63.11496(g)(1)(iii) (for 

owners and operators using a control 

device other than a flare to comply with 

the emission limits and other 

requirements for batch and continuous 

process vents) and 40 CFR 

63.11497(g)(1)(iii) (for owners and 

operators using a control device other 

than a flare to comply with the emission 

limits and other requirements for 

storage tanks). We are proposing that the 

on-going performance tests be 

conducted at a minimum frequency of 

once every 5 years to supplement the 

parameter monitoring and to ensure that 

emission controls continue to operate as 

demonstrated during the initial 

performance test. We are soliciting 

comment and data on whether design 

evaluations and engineering 

assessments are appropriate for 

demonstrating compliance for certain 

APCDs. 

We are also proposing to add a 

performance testing requirement at 40 

CFR 63.11496(g)(1)(iii) and 40 CFR 

63.11497(g)(1)(iii) intended to replace a 


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portion of the performance testing 

requirements of 40 CFR 63.997(e)(1)(i). 

The proposal does not include the 

language that precludes startup and 

shutdown periods from being 

considered ‘‘representative’’ for 

purposes of performance testing, and 

instead allows performance testing 

during periods of startup or shutdown if 

specified by the Administrator. In 

addition, as specified in 40 CFR 

63.997(e)(1)(i), performance tests should 

not be conducted during malfunctions 

because conditions during malfunctions 

are often not representative of normal 

operating conditions. The EPA is also 

proposing to add language at 40 CFR 

63.11496(g)(1)(iii) and 40 CFR 

63.11497(g)(1)(iii) that requires the 

owner or operator maintain records of 

process information that is necessary to 

document operating conditions during 

the test and include in such record an 

explanation to support that such 

conditions represent the entire range of 

normal operation, including operational 

conditions for maximum emissions if 

such emissions are not expected during 

maximum production. 

c. Other Editorial and Technical 

Corrections 

The EPA is proposing additional 

changes that address technical and 

editorial corrections for the CMAS 

NESHAP. The most significant of these 

corrections are summarized in table 11 

of this preamble. Please see the 

document Proposed Regulation Edits for 

40 CFR part 63 Subpart VVVVVV: 

National Emission Standards for 

Hazardous Air Pollutants for Chemical 

Manufacturing Area Sources, available 

in the docket for this rulemaking, to 

review all of the proposed technical and 

editorial corrections. 

TABLE 11—PROPOSED TECHNICAL AND EDITORIAL CORRECTIONS FOR THE CMAS NESHAP (NOT DISCUSSED

ELSEWHERE IN THIS PREAMBLE) 

Provision Issue summary Proposed revision 

40 CFR 63.11494(c)(2)(iv) ........ Provision refers to specific NAICS codes but does not specify 

which version (i.e., year) to use. 

The EPA is proposing to add language to specify the 2007 

version of the NAICS code. 

40 CFR 63.11495(d) .................. Provision does not include all language on the general duty to 

minimize emissions. 

The EPA is proposing to add the sentence ‘‘The general duty to 

minimize emissions does not require the owner or operator to 

make any further efforts to reduce emissions if levels required 

by the applicable standard have been achieved.’’ 

40 CFR 63.11496(g)(5) ............. Provision is redundant to the language at 40 CFR 63.11496(i). The EPA is proposing to remove the provision to eliminate redundancy and reduce confusion with how the standards are 

applied. 

40 CFR 63.11497(a) .................. Provision does not contain a heading; therefore, is inconsistent 

with other paragraphs within the section. 

The EPA is proposing to add the heading: ‘‘Organic HAP emissions from storage tanks’’ for consistency with the rest of the 

paragraphs included in the section. 

40 CFR 63.11497(c) .................. Provision does not contain a heading; therefore, is inconsistent 

with other paragraphs within the section. 

The EPA is proposing to add the heading: ‘‘SSM provisions’’ for 

consistency with the rest of the paragraphs included in the 

section. 

40 CFR 63.11498(b) .................. Provision provides an exemption for certain wastewater streams 

during periods of startup and shutdown. 

Given that in the October 29, 2009, final rule the EPA removed 

the exemption from emissions standards for periods of SSM 

in accordance with a decision of the United States Court of 

Appeals for the District of Columbia Circuit, Sierra Club v. 

EPA, 551 F.3d 1019 (D.C. Cir. 2008), cert. denied, 130 S. Ct. 

1735 (U.S. 2010), the EPA is proposing to remove the sentence ‘‘The requirements in Item 2 of table 6 to this subpart 

do not apply during periods of startup or shutdown.’’ 

40 CFR 63.11500(a)(2) ............. Provision contains a cross reference error to table 4 in 40 CFR 

part 63, subpart VVVVVV. 

The EPA is proposing to correct the reference to table 4 with a 

reference to table 5. 

40 CFR 63.11500(b) .................. Provision refers to certain NSPS but does not include the most 

recent promulgated versions of certain NSPS. 

The EPA is proposing to add NSPS subparts VVa, VVb, IIIa, 

NNNa, and RRRa to allow owners and operators to comply 

with any of the requirements in these rules that are at least as 

stringent as the corresponding requirements in the CMAS 

NESHAP to constitute compliance with the CMAS NESHAP. 

40 CFR 63.11501(c)(1)(vii) and 

(viii) and (d)(1) and (8).

Certain provisions are specific to malfunctions and are being 

clarified to include any deviation. Also, the deviation reporting 

provision does not specify all the information to be reported. 

The EPA is proposing to revise the malfunction and deviation 

recordkeeping and reporting requirements to clarify what must 

be maintained as records and reported. 

40 CFR 63.11501(d) .................. Provision does not specify how to report basic facility information. The EPA is proposing to clarify that all semiannual compliance 

reports must contain the company name and address (including county), as well as the beginning and ending dates of the 

reporting period. 

40 CFR 63.11501(d) .................. Provision allows facilities to skip semiannual reporting for periods where no events described by 40 CFR 63.11501(d)(1)– 

(8) occur. 

The EPA is proposing to remove this exemption as it contradicts 

the General Provisions at 40 CFR 63.10(e)(3)(v) and revise 

the paragraph to include a reference to 40 CFR 

63.10(e)(3)(v). 

40 CFR 63.11501(d)(1) ............. Provision does not specify what information to collect when a 

deviation occurs. 

The EPA is proposing to clarify that owners and operators must 

report the start date, start time, duration in hours, cause, a list 

of the affected sources or equipment, an estimate of the 

quantity of each regulated pollutant emitted over any emission 

limit, a description of the method used to estimate the emissions, actions taken to minimize emissions, and any corrective action taken to return the affected unit to its normal or 

usual manner of operation for each deviation from the standards. 

40 CFR 63.11502(b) .................. The definition of ‘‘batch process vent’’ does not consider the impacts of the proposed EtO standards. The EPA is proposing to update the definition to clarify that the 

exemption that ‘‘emission streams from emission episodes 

that are undiluted and uncontrolled containing less than 50 

ppmv HAP are not part of any batch process vent’’ does not 

apply to batch process vents in EtO service. 

40 CFR 63.11502(b) .................. The definition of ‘‘continuous process vent’’ does not consider 

the impacts of the proposed EtO standards. 

The EPA is proposing to clarify that the 0.005 weight percent 

total organic HAP criteria at 40 CFR 63.107(d) does not apply 

for continuous process vents in EtO service. 


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TABLE 11—PROPOSED TECHNICAL AND EDITORIAL CORRECTIONS FOR THE CMAS NESHAP (NOT DISCUSSED

ELSEWHERE IN THIS PREAMBLE)—Continued 

Provision Issue summary Proposed revision 

40 CFR 63.11502(b) .................. The definition of ‘‘continuous process vent’’ improperly relies on 

the control criteria of the HON as detailed at 40 CFR 

63.107(i). 

The EPA is proposing to replace the references to 40 CFR 

63.107(i) with a similar provision that relies on the requirements of table 3 in 40 CFR part 63, subpart VVVVVV. 

40 CFR 63.11502(b) .................. The definition of ‘‘in organic HAP service’’ does not consider the 

impact of the proposed EtO standards for equipment leaks 

and the proposed LDAR program for all equipment leaks, nor 

does it consider that the proposed term for ‘‘heat exchange 

system’’ uses the phrase ‘‘in organic HAP service’’. 

The EPA is proposing to revise the definition to specify that any 

piece of equipment in EtO service is also in organic HAP 

service and establish that, for the proposed LDAR programs 

associated with equipment and heat exchange systems, in organic HAP service means ‘‘that a piece of equipment or heat 

exchange system either contains or contacts a fluid (liquid or 

gas) that is at least 5 percent by weight of total organic HAP’s 

as determined according to the provisions of 40 CFR 

63.180(d).’’ The EPA is also proposing to clarify that for purposes of the definition of ‘‘heat exchange system’’, the term 

‘‘equipment’’ in § 63.180(d) includes heat exchange systems. 

40 CFR 63.11502(b) .................. The definition of ‘‘process vessel’’ is contradictory with the definition of ‘‘continuous process vent.’’ The EPA is proposing to revise the definition of ‘‘process vessel’’ to remove reactors and distillation units from the list of 

provided examples given that reactors and distillation units 

are a source of continuous process vents (i.e., some, or all, of 

a gas stream originates ‘‘as a continuous flow from an air oxidation reactor, distillation unit, or reactor during operation of 

the chemical manufacturing process unit’’). 

40 CFR 63.11502(b) .................. The definition of ‘‘wastewater’’ does not consider the impact of 

the proposed EtO standards. 

The EPA is proposing to specify that the phrase ‘‘and that contains at least 5 ppmw of any HAP listed in table 9 to subpart 

G of this part and has an annual average flow rate of 0.02 liters per minute’’ does not apply to wastewater in ethylene 

oxide service. 

Table 9 to subpart VVVVVV of 

Part 63.

Entries include language specific to malfunctions. The EPA is proposing to revise the entries for 63.10(b)(2)(ii), 

(c)(10), (c)(11), and (d)(5) to reflect the changes to the malfunction and deviation recordkeeping and reporting requirements. 

Table 9 to subpart VVVVVV of 

Part 63.

Entries do not consider EtO specific monitoring requirements. The EPA is proposing to update table 9 to the CMAS NESHAP 

to specify which General Provisions do not apply for EtO specific sources to be consistent with the proposed EtO standards. 

Various ....................................... Rule contains incorrect phrases, does not contain certain 

phrases, or incorrectly cross references other provisions. 

The EPA is proposing to make editorial corrections where necessary including, but not limited to, adding missing words, 

correcting errors, updating acronyms, and correcting cross 

references. 

E. What compliance dates are we 

proposing, and what is the rationale for 

the proposed compliance dates? 

The proposed amendments in this 

rulemaking for adoption under CAA 

section 112(d)(5) and (6) (see sections 

IV.A through IV.C of this preamble) are 

subject to the compliance deadlines 

outlined in the CAA under section 

112(i). For all the EtO requirements we 

are proposing under CAA section 

112(d)(5) (see section IV.A of this 

preamble), we are proposing at 40 CFR 

63.11494(l) that existing affected 

sources and affected sources that were 

new sources under the current CMAS 

NESHAP (i.e., they commenced 

construction or reconstruction after 

October 6, 2008 and on or before 

January 22, 2025) must comply with all 

of the amendments no later than 2 years 

after the effective date of the final rule 

or upon startup, whichever is later. For 

all the non-EtO requirements we are 

proposing under CAA section 112(d)(5) 

and all the requirements we are 

proposing under CAA section 112(d)(6) 

(see sections IV.B and IV.C of this 

preamble, respectively), we are 

proposing at 40 CFR 63.11494(k) that 

existing affected sources and affected 

sources that were new sources under the 

current CMAS NESHAP (i.e., they 

commenced construction or 

reconstruction after October 6, 2008 and 

on or before January 22, 2025) must 

comply with all of the amendments no 

later than 3 years after the effective date 

of the final rule or upon startup, 

whichever is later. 

For fenceline monitoring (see section 

IV.A.7 of this preamble), we are 

proposing at 40 CFR 63.11494(m) that 

owners and operators of all existing 

affected sources and all affected sources 

that were new under the current rule 

(i.e., sources that commenced 

construction or reconstruction after 

October 6, 2008, and on or before 

January 22, 2025) must begin fenceline 

monitoring 2 years after the effective 

date of the final rule and, starting 3 

years after the effective date of the final 

rule, perform root cause analysis and 

apply corrective action requirements 

upon exceedance of an annual average 

concentration action level. 

For existing sources, CAA section 

112(i) provides that the compliance date 

shall be as expeditious as practicable, 

but no later than 3 years after the 

effective date of the standard (‘‘Section 

112(i)(3)’s three-year maximum 

compliance period applies generally to 

any emission standard . . . promulgated 

under [section 112].’’ Association of 

Battery Recyclers v. EPA, 716 F.3d 667, 

672 (D.C. Cir. 2013)). In determining 

what compliance period is as 

expeditious as practicable, we consider 

the amount of time needed to plan and 

construct projects and change operating 

procedures. As provided in CAA section 

112(i) and 5 U.S.C. 801(3), all new 

affected sources that commenced 

construction or reconstruction after 

January 22, 2025 would be required to 

comply with these requirements upon 

the effective date of the final rule or 

upon startup, whichever is later (see 

proposed 40 CFR 63.11494(h) and (j)). 

1. Rationale for Proposed Compliance 

Dates of Proposed CAA Section112(d)(5) 

and (6) Amendments 

Many of the GACT requirements that 

we are proposing under CAA section 

112(d)(5) address emissions of EtO from 

equipment leaks, heat exchange 

systems, process vents, storage tanks, 

and wastewater at CMAS processes (see 

sections IV.A.1 through IV.A.4 of this 


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preamble). The proposed provisions 

will require time to plan, purchase, and 

install equipment for EtO control. For 

example, for CMAS process vents in EtO 

service (see section IV.A.3 of this 

preamble for additional details), if the 

affected source cannot demonstrate 99.9 

percent control of EtO emissions, or 

reduce EtO emissions to less than 1 

ppmv (from each process vent) or 5 lb/ 

yr (for all combined process vents), then 

the owner or operator would need to 

install a new control system, improve 

their existing control system, or 

otherwise reduce emissions. In addition, 

we are proposing a suite of operational 

and monitoring requirements for flares 

that emit EtO (see section IV.A.6 of this 

preamble). We anticipate that the 

proposed provisions for flares that emit 

EtO (used to control EtO emissions from 

process vents and storage tanks) would 

require the installation of new 

monitoring equipment, and we project 

owners and operators would need to 

install new control systems to monitor 

and adjust assist gas (air or steam) 

addition rates. Similar to the addition of 

new monitoring equipment and control 

systems, these new monitoring 

requirements for flares that emit EtO 

would require engineering evaluations, 

solicitation and review of vendor 

quotes, contracting and installation of 

the equipment, and operator training. 

Installation of new monitoring and 

control equipment on flares will require 

the flare to be taken out of service. 

Depending on the configuration of the 

flares and flare header system, taking 

the flare out of service may also require 

a significant portion of the CMPU to be 

shutdown. Therefore, we are proposing 

a compliance date of 2 years after the 

publication date of the final rule, or 

upon startup, whichever is later, to 

comply with the proposed EtO 

requirements for all existing affected 

sources and all new affected sources 

under the current rules that commenced 

construction or reconstruction after 

October 6, 2008, and on or before 

January 22, 2025. For all new affected 

sources that commence construction or 

reconstruction after January 22, 2025, 

we are proposing owners or operators 

comply with the EtO requirements upon 

the effective date of the final rule or 

upon startup, whichever is later. We are 

soliciting comment on whether an 

alternate compliance timeframe (i.e., 

shorter or longer than the proposed 2 

years) would be more appropriate for 

the EtO requirements established 

pursuant to CAA section 112(d)(5). 

Compliance dates for the fenceline 

monitoring provisions proposed under 

CAA section 112(d)(5) consider the 

amount of time that it will take owners 

and operators to develop their siting 

plans and secure the capabilities to 

conduct the monitoring and analyze the 

results. For fenceline monitoring, the 

compliance timeline also must consider 

time to allow commercial labs to 

conduct the needed method 

development, expand capacity, and 

develop the logistics needed to meet the 

requirements in the final rule. In 

addition, time is needed to read and 

assess the new fenceline monitoring 

requirements; prepare sampling and 

analysis plans; develop and submit sitespecific monitoring plans; identify 

representative, accessible, and secure 

monitoring locations for offsite monitors 

and obtain permission from the property 

owner to both place and routinely 

access the monitors; make any necessary 

physical improvements to fencelines to 

be able to site monitors, including 

construction of access roads, physical 

fencing, and potential drainage 

improvements; and obtain approval of 

any necessary capital expenditures. 

Therefore, we are proposing that owners 

and operators of all existing sources and 

all new affected sources under the 

current rules that commenced 

construction or reconstruction after 

October 6, 2008, and on or before 

January 22, 2025 must begin fenceline 

monitoring 2 years after the publication 

date of the final rule and must perform 

root cause analysis and apply corrective 

action requirements upon exceedance of 

an annual average concentration action 

level starting 3 years after the 

publication date of the final rule. For all 

new affected sources that commence 

construction or reconstruction after 

January 22, 2025, we are proposing that 

owners or operators begin fenceline 

monitoring upon the effective date of 

the final rule or upon startup, 

whichever is later. We are also 

proposing to require quarterly reporting 

of fenceline results beginning 1 year 

after monitoring begins for such sources. 

For PRDs, we are establishing 

management practices in the CMAS 

NESHAP under CAA section 112(d)(5) 

that require a process hazard analysis 

and implementation of a minimum of 

three redundant measures to prevent 

atmospheric releases (see section IV.B.2 

of this preamble). Alternately, owners or 

operators may elect to install closed 

vent systems to route these PRDs to a 

flare, drain (for liquid thermal relief 

valves), or other control system. We 

anticipate that sources will need to 

identify the most appropriate preventive 

measures or control approach; design, 

install, and test the system; install 

necessary process instrumentation and 

safety systems; and may need to time 

installations with equipment shutdown 

or maintenance outages. Therefore, for 

all existing affected sources, and all new 

affected sources under the current 

CMAS NESHAP that commenced 

construction or reconstruction after 

October 6, 2008, and on or before 

January 22, 2025, we are proposing a 

compliance date of 3 years from the 

publication date of the final rule (or 

upon startup, whichever is later) for 

owners or operators to comply with the 

management practices for atmospheric 

PRD releases. For all new affected 

sources that commence construction or 

reconstruction after January 22, 2025, 

we are proposing owners or operators 

comply with the management practices 

for atmospheric PRD releases upon the 

effective date of the final rule or upon 

startup, whichever is later. 

Other amendments we are proposing 

under CAA section 112(d)(5) include 

LDAR requirements for pressure vessels 

(see section IV.B.1 of this preamble). We 

are also proposing new LDAR 

requirements under CAA section 

112(d)(6) for equipment leaks in organic 

HAP service and heat exchange systems 

with cooling water flow rates greater 

than 8,000 gpm (see section IV.C.1 of 

this preamble). We project some owners 

and operators would require 

engineering evaluations, solicitation and 

review of vendor quotes, contracting 

and installation of monitoring 

equipment, and operator training. In 

addition, facilities will need time to 

read and understand the amended rule 

requirements and update standard 

operating procedures. Also, any of these 

proposed provisions may require 

additional time to plan, purchase, and 

install equipment for emissions control; 

and even if not, the EPA recognizes the 

confusion that multiple different 

compliance dates for individual 

requirements would create and the 

additional burden such an assortment of 

dates would impose. Lastly, other recent 

rulemakings are requiring updates to 

LDAR provisions for hundreds of 

sources not previously required to do 

EPA Method 21 monitoring (see the 

Gasoline Distribution NESHAP, 89 FR 

39304 May 8, 2024). As such, the 

demand on contractor support may be 

greater than can be immediately 

accommodated. Therefore, for all 

existing affected sources, and all new 

affected sources under the current rules 

that commenced construction or 

reconstruction after October 6, 2008, 

and on or before January 22, 2025, we 

are proposing a compliance date of 3 

years from the publication date of the 

final rule (or upon startup, whichever is 


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later) for owners or operators to comply 

with these other proposed amendments. 

For all new affected sources that 

commence construction or 

reconstruction after January 22, 2025, 

we are proposing owners or operators 

comply with these other proposed 

amendments upon the effective date of 

the final rule or upon startup, 

whichever is later. 

2. Rationale for Proposed Compliance 

Dates of Other Proposed Amendments 

We are proposing electronic reporting 

requirements (see section IV.D.1 of this 

preamble), and we anticipate that 

facilities would need some time to 

successfully accomplish these reporting 

revisions including time to read and 

understand the amended rule 

requirements, to make any necessary 

adjustments (including adjusting 

standard operating procedures), and to 

convert reporting mechanisms and 

install necessary hardware and software. 

From our assessment of the timeframe 

needed for compliance with the new 

proposed electronic reporting 

requirements for flare management 

plans and periodic reports, the EPA 

considers a period of 3 years after the 

publication date of the final rule to be 

the most expeditious compliance period 

practicable. Thus, we are proposing that 

all existing affected sources, and all new 

affected sources under the current rule 

that commenced construction or 

reconstruction after October 6, 2008, 

and on or before January 22, 2025 be in 

compliance with these revised 

requirements upon initial startup or 

within 3 years of the publication date of 

the final rule, whichever is later. For all 

new affected sources that commence 

construction or reconstruction after 

January 22, 2025, we are proposing 

owners or operators comply with these 

revised requirements upon the effective 

date of the final rule or upon startup, 

whichever is later. However, we are 

proposing at 40 CFR 63.11496(g)(1)(iv) 

to provide 60 days after the publication 

date of the final rule (or upon startup, 

whichever is later) for owners or 

operators of all affected sources to 

comply with the requirement to submit 

performance test reports electronically 

following the procedure specified in 40 

CFR 63.9(k). We are also proposing at 40 

CFR 63.11501(b) to provide 60 days 

after the publication date of the final 

rule (or upon startup, whichever is later) 

for owners or operators of all affected 

sources to submit all subsequent 

Notification of Compliance Status 

reports in PDF format electronically 

following the procedure specified in 40 

CFR 63.9(k). 

V. Summary of Cost, Environmental, 

and Economic Impacts 

A. What are the affected sources? 

We estimate that there are 251 

facilities subject to the CMAS NESHAP. 

There are another 29 facilities that 

would become subject to the rule if EtO 

were to be added to table 1 to 40 CFR 

part 63, subpart VVVVVV, as proposed. 

The list of facilities is available in the 

document titled List of Facilities Subject 

to the CMAS NESHAP, which is 

available in the docket for this 

rulemaking. 

B. What are the air quality impacts? 

This proposed action would reduce 

HAP and VOC emissions from CMAS 

emission sources. We estimate that the 

proposed amendments to the NESHAP 

would reduce overall HAP emissions, 

not including EtO emission reductions, 

from CMAS by approximately 158 tpy. 

In addition, the EPA estimates 

reductions of approximately 4.6 tpy of 

EtO emissions based on the emissions 

inventories. With respect to secondary 

impacts on non-HAP pollutants, the 

EPA estimates that the proposed 

amendments would reduce VOC 

emissions by 1,557 tpy and on net 

would reduce emissions of methane by 

251 tpy. 

The EPA also estimates that the 

proposed action would result in 

secondary impacts for greenhouse gas 

emissions and criteria air pollutant 

emissions. The increased electricity and 

natural gas use to power some of the 

proposed controls would increase 

emissions of several pollutants, 

including an estimated increase of 36 

tpy of carbon monoxide (CO), 57,000 

tpy of carbon dioxide (CO2), 43 tpy of 

nitrogen oxides (NOX) (including 0.97 

tpy of nitrous oxide (N2O)), 3 tpy of 

particulate matter (PM2.5), and 0.26 tpy 

of sulfur dioxide (SO2). On net, after 

accounting for the methane emission 

reductions and the increases in CO2 and 

N2O emissions, this proposed rule 

would increase GHG emissions on a 

CO2-equivalent basis (CO2e) by an 

estimated 50,000 tpy. More information 

about the estimated emission reductions 

and secondary impacts of this proposed 

action for the CMAS NESHAP can be 

found in the documents titled Economic 

Impact Analysis and Secondary Impacts 

for Flares, Thermal Oxidizers, and 

Wastewater Controls for the CMAS 

NESHAP, which are available in the 

docket for this action; and in documents 

referenced in sections IV.A through IV.C 

of this preamble. The EPA solicits 

comments on the quantitative aspects of 

the emissions reductions and secondary 

impacts of this proposed action. 

C. What are the cost impacts? 

The EPA estimates the cost of the 

requirements in this proposed action 

would be approximately $37.6 million 

(in 2022 dollars for the entire period of 

analysis) in total capital costs and $36.4 

million in total annual costs (including 

product recovery), based on our 

analyses of the proposed actions 

described in sections IV.A through IV.C 

of this preamble. The ‘total annual costs’ 

are the sum of the annualized capital 

costs and other annual costs (e.g., 

operating and maintenance costs, 

recordkeeping and reporting costs). To 

obtain annualized capital costs, a capital 

recovery factor is multiplied by the 

capital costs. The capital recovery factor 

is based on the lifetime of the capital 

equipment as well as the interest rate. 

The total annual cost of the proposed 

action without including the value of 

product recovery is estimated to be 

about $38 million. Thus, product 

recovery accounts for about $1.6 million 

in annual cost savings, or about four 

percent of the total annual costs without 

product recovery. 

D. What are the economic impacts? 

The economic impacts of this 

proposal, including the small entity 

impact analysis, are discussed in greater 

detail in the document titled Economic 

Impact Analysis, which is available in 

the docket for this action. 

As part of fulfilling the analytical 

requirements of Executive Orders 12866 

as amended by Executive Order 14094, 

the EPA presents estimates of the 

present value (PV) of the costs over the 

15-year analytical period from 2027 to 

2041. Costs are in 2022 dollars and 

discounted to 2027 at a two percent 

discount rate per the recommendation 

in OMB Circular A–4. The EPA also 

presents the equivalent annualized 

value (EAV) at a two percent discount 

rate. The EAV takes the non-uniform 

stream of costs (i.e., different costs in 

different years) and converts them into 

a single annual value that, if paid each 

year from 2027 to 2041, would equal the 

original stream of values in PV terms. 

The PV of the costs over the 15-year 

period from 2027 to 2041 without 

including the value of product recovery 

is estimated to be $495 million at a two 

percent discount rate and the EAV is 

$38.5 million. The PV of the costs 

including the value of product recovery 

is estimated to be $474 million at a two 

percent discount rate and the EAV is 

$37 million. 

This proposed action impacts 58 

small entities, which own a total of 64 

CMAS facilities. The EPA evaluates 

economic impacts of rulemakings on 


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58 ‘‘Technical Guidance for Assessing 

Environmental Justice in Regulatory Analysis’’, U.S. 

EPA, June 2016. Quote is from Section 3—Key 

Analytic Considerations, page 11. 

small entities by examining total annual 

cost estimates compared to the annual 

revenues of the companies (i.e., entities) 

that are the ultimate owners of the 

facilities affected by the rule. The EPA 

estimates cost-to-sales ratios, which are 

the total annual costs estimated for each 

entity divided by the entity’s annual 

revenues. This ratio provides a measure 

of the direct economic impact to 

ultimate owners of CMAS facilities. 

The EPA estimates the average costto-sales ratio for small entities impacted 

by the proposal will be 0.3 percent with 

a maximum cost-to-sales ratio estimated 

at 5.5 percent, not considering the value 

of product recovery due to compliance 

(i.e., the cost savings). With product 

recovery, the EPA estimates that the 

average cost-to-sales ratio for small 

entities impacted by the proposal will 

be 0.3 percent with a maximum cost-tosales ratio of 5.4 percent. We estimate 

that about nine percent of impacted 

small entities (five small entities out of 

a total of 58) will incur total annual 

costs greater than one percent of their 

annual revenue, and two percent of 

small entities (one small entity in total) 

will incur total annual costs greater than 

three percent of their annual revenue. 

The number of entities with a one 

percent or greater cost-to-sales ratio falls 

to three entities, or five percent of all 

small entities, when the total annual 

cost estimates include the value of 

product recovery, and one entity has a 

cost-to-sales ratio that remains above 

three percent. The EPA does not 

anticipate that this proposed action will 

have a substantial impact on a 

significant number of small entities. The 

EPA also does not expect this proposed 

action to have significant market 

impacts or employment impacts. 

It is important to note that the small 

entities that own facilities affected by 

the proposed EtO standards have 

relatively higher estimated cost-to-sales 

ratios, with an average cost-to-sales ratio 

of 3 percent for the three EtO facilities 

that are owned by small entities. The 

small entity with the maximum cost-tosales ratio of 5.5 percent owns a facility 

affected by the proposed EtO standards. 

These three small entities also have 

smaller average annual revenues 

compared to the whole population of 

small entities, averaging $47 million in 

annual revenues compared to $230 

million for all small entities. For 

additional details on the costs of this 

proposed rulemaking, please see the 

document titled Economic Impact 

Analysis, available in the docket for this 

action. 

E. What are the benefits? 

The EPA did not monetize the 

benefits from the estimated emission 

reductions of HAP associated with this 

proposed action. The EPA currently 

does not have sufficient methods to 

monetize benefits associated with HAP 

reductions and risk reductions for this 

rulemaking. However, we estimate that 

the final rule amendments would 

reduce EtO emissions by 4.6 tpy and 

expect that these reductions will lower 

the risk of adverse health effects, 

including cancer, for individuals in 

communities near CMAS facilities. For 

additional information on the 

nonmonetized benefits of this 

rulemaking and a qualitative discussion 

of the health risks associated with 

exposure to EtO and several other HAP, 

please see the document titled 

Economic Impact Analysis, available in 

the docket for this action. The EPA 

solicits comments on the benefits of 

HAP reductions discussed in this 

section. 

The secondary emissions impacts 

estimated for this proposed action 

include net reductions in VOC and 

methane emissions, and increases in 

emissions of PM2.5, SO2, NOX (including 

N2O), CO2, and CO. The EPA was not 

able to monetize the health and 

environmental impacts associated with 

the estimated changes in criteria air 

pollutant emissions for this proposed 

rule, which include increased PM2.5 and 

PM2.5 precursor emissions and changes 

in VOC and NOX emissions, which 

impact the formation of ground-level 

ozone. 

The EPA provided monetized 

estimates of the impacts associated with 

the methane emissions reductions and 

the net increases in CO2 and N2O 

emissions using the EPA’s social cost of 

greenhouse gas (SC–GHG) estimates. 

The estimated climate benefits are 

negative on net. The PV of the climate 

benefits for the 15-year period from 

2027 to 2041 is estimated to be negative 

$195 million in 2022 dollars discounted 

at a two percent rate, and the EAV is 

estimated to be negative $15 million. 

F. What analysis of environmental 

justice did we conduct? 

For purposes of analyzing regulatory 

impacts, the EPA relies upon its June 

2016 ‘‘Technical Guidance for Assessing 

Environmental Justice in Regulatory 

Analysis,’’ which provides 

recommendations that encourage 

analysts to conduct the highest quality 

analysis feasible, recognizing that data 

limitations, time, resource constraints, 

and analytical challenges will vary by 

media and circumstance. The Technical 

Guidance states that a regulatory action 

may involve potential environmental 

justice (EJ) concerns if it could: (1) 

create new disproportionate impacts on 

communities with EJ concerns; (2) 

exacerbate existing disproportionate 

impacts on communities with EJ 

concerns; or (3) present opportunities to 

address existing disproportionate 

impacts on communities with EJ 

concerns through this action under 

development. 

The EPA’s EJ technical guidance 

states that ‘‘[t]he analysis of potential EJ 

concerns for regulatory actions should 

address three questions: (1) Are there 

potential EJ concerns associated with 

environmental stressors affected by the 

regulatory action for population groups 

of concern in the baseline? (2) Are there 

potential EJ concerns associated with 

environmental stressors affected by the 

regulatory action for population groups 

of concern for the regulatory option(s) 

under consideration? (3) For the 

regulatory option(s) under 

consideration, are potential EJ concerns 

created or mitigated compared to the 

baseline?’’ 58

The EJ analysis is presented for the 

purpose of providing the public with as 

full as possible an understanding of the 

potential impacts of this proposed 

action. The EPA notes that analysis of 

such impacts is distinct from the 

determinations proposed in this action 

under CAA section 112, which are 

based solely on the statutory factors the 

EPA is required to consider under that 

section. 

To examine the potential for EJ 

concerns, the EPA conducted three 

different demographic analyses: a 

proximity analysis, a baseline cancer 

risk-based analysis (i.e., before 

implementation of any controls required 

by this proposed action), and a postcontrol cancer risk-based analysis (i.e., 

after implementation of the controls 

required by this proposed action). The 

proximity demographic analysis is an 

assessment of individual demographic 

groups in the total population living 

within 10 km (∼6.2 miles) and 50 km 

(∼31 miles) of the facilities. The baseline 

risk-based demographic analysis is an 

assessment of risks to individual 

demographic groups in the population 

living within 10 km and 50 km of the 

facilities prior to the implementation of 

any controls required by this proposed 

action (‘‘baseline’’). The post-control 

risk-based demographic analysis is an 

assessment of risks to individual 


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59There are 248 CMAS facilities with emissions 

data specific to the categories, however, one facility 

has no population living within 10 km and thus 

was not included in the EJ analysis. 

demographic groups in the population 

living within 10 km and 50 km of the 

facilities after implementation of the 

controls required by this proposed 

action (‘‘post-control’’). The risk-based 

demographic analyses were performed 

for the following three different HAP 

emissions scenarios (described in 

sections V.F.1 through V.F.3 of this 

preamble): CMAS categories HAP 

emissions (10 km and 50 km), CMAS 

whole-facility HAP emissions (10 km 

and 50 km), and CMAS community 

HAP emissions (10 km only). 

1. CMAS Categories Demographics 

For the CMAS categories, the EPA 

examined the potential for the 247 

CMAS facilities (for which the EPA had 

HAP emissions inventories for 

emissions from the CMAS categories) to 

pose concerns to communities living in 

proximity to facilities, both in the 

baseline and under the control option 

established in this proposed action. 

Specifically, to examine the potential 

for EJ concerns, the EPA conducted 

three different demographic analyses of 

the populations living within 10 km and 

50 km of the CMAS facilities: a 

proximity analysis, baseline cancer and 

noncancer risk-based analyses (i.e., 

before implementation of any controls 

required by this proposed action), and 

post-control cancer and noncancer riskbased analyses (i.e., after 

implementation of the controls required 

by this proposed action). In this 

preamble, we focus on the results from 

the demographic analyses using a 10 km 

radius because this area captures the 

majority of the population with higher 

cancer risks due to HAP emissions from 

CMAS facilities. Specifically, 100 

percent of the population with baseline 

cancer risks greater than or equal to 50- 

in-1 million and with noncancer hazard 

indices greater than 1 from emissions 

associated with the CMAS categories 

live within 10 km of the CMAS 

facilities. The methodology and detailed 

results of the demographic analysis, 

including the demographic analyses for 

populations living within 10 km and 50 

km of facilities, are presented in the 

document titled Analysis of 

Demographic Factors for Populations 

Living Near Chemical Manufacturing 

Area Source (CMAS) Facilities—Source 

Category Analysis of Proposed 

Amendments, which is available in the 

docket for this rulemaking. The 

following paragraphs briefly summarize 

the results of these demographic 

analyses. 

For all three demographic analyses, 

the affected populations (i.e., those 

living within 10 km of the facilities) are 

compared to the national population. 

The total population, population 

percentages, and population count for 

each demographic group for the entire 

U.S. population are shown in the 

column titled ‘‘Nationwide Average for 

Reference’’ in tables 11 through 13 of 

this preamble. These national data are 

provided as a frame of reference to 

compare the results of the proximity 

analysis, the baseline cancer and 

noncancer risk-based analyses, and the 

post-control cancer and noncancer riskbased analysis. The column titled 

‘‘Proximity Analysis for Population 

living within 10 km of CMAS Facilities’’ 

in tables 11 through 13 of this preamble 

shows the share and count of people for 

each of the demographic categories for 

the total population living within 10 km 

(∼6.2 miles) of CMAS facilities. These 

are the results of the proximity analysis 

and are repeated in tables 11 through 13 

of this preamble for ease of comparison 

to the risk-based analyses discussed 

later. 

The results of the proximity analysis 

indicate that a total of 33.7 million 

people live within 10 km of the 247 

CMAS facilities analyzed.59 The percent 

of the population living within 10 km of 

the CMAS facilities is above the 

corresponding national average for the 

following demographic groups: Black, 

Hispanic or Latino, Other/Multiracial, 

people living below the poverty level, 

people living below two times the 

poverty level, people over the age of 25 

without a high school diploma, and 

linguistic isolation. The results of the 

proximity analysis indicate that the 

proportion of other demographic groups 

living within 10 km of CMAS facilities 

is similar to or below the national 

average. 

The baseline cancer risk-based 

demographic analysis focuses on 

populations that have higher cancer 

risks. The baseline risk-based 

demographic analysis results are shown 

in the ‘‘baseline’’ column of tables 11 

through 13 of this preamble. This 

analysis focused on the populations 

living within 10 km (∼6.2 miles) of the 

CMAS facilities with estimated cancer 

risks greater than or equal to 1-in-1 

million resulting from emissions from 

CMAS categories (table 11 of this 

preamble), greater than or equal to 50- 

in-1 million (table 12 of this preamble), 

and greater than 100-in-1 million (table 

13 of this preamble). 

The results of the cancer risk-based 

demographic analysis indicate that a 

total of 2 million people living within 

10 km of 76 of the CMAS facilities 

analyzed have a cancer risk greater than 

or equal to 1-in-1 million from CMAS 

HAP emissions. The percent of the 

population living within 10 km of these 

CMAS facilities with cancer risks 

greater than or equal to 1-in-1 million is 

above the corresponding national 

average for the following demographic 

groups: Black, Hispanic or Latino, 

people living below the poverty level, 

people living below two times the 

poverty level, people over 25 without a 

high school diploma, and linguistic 

isolation. The percent of the population 

with cancer risks greater than or equal 

to 1-in-1 million that are Black (25 

percent) is higher than in the proximity 

analysis (19 percent) and is 

approximately two times higher than 

the national average (12 percent). The 

percent of the population with cancer 

risks greater than or equal to 1-in-1 

million that are Hispanic/Latino (25 

percent) is higher than in the proximity 

analysis (21 percent) and the national 

average (19 percent). 

The results of the cancer risk-based 

demographic analysis indicate that a 

total of 36,100 people living within 10 

km of 15 of the CMAS facilities 

analyzed have cancer risks greater than 

or equal to 50-in-1 million from CMAS 

HAP emissions. The percent of the 

population living within 10 km of these 

CMAS facilities with cancer risks 

greater than or equal to 50-in-1 million 

is above the corresponding national 

average for the following demographic 

groups: Hispanic or Latino, people 

living below the poverty level, people 

living below two times the poverty 

level, people over 25 without a high 

school diploma, and linguistic isolation. 

The percent of the population with 

cancer risks greater than or equal to 50- 

in-1 million that are Black is at the 

national average (12 percent), which is 

a lower percentage than for the 

proximity analysis (19 percent). The 

percent of the population with cancer 

risks greater than or equal to 50-in-1 

million that are Hispanic/Latino (40 

percent) is about two times that in the 

proximity analysis (21 percent) and the 

national average (19 percent). 

The results of the cancer risk-based 

demographic analysis indicate that a 

total of 3,600 people living within 10 

km of 4 of the CMAS facilities analyzed 

have a cancer risk greater than 100-in1 million from CMAS HAP emissions. 

The percent of the population living 

within 10 km of these CMAS facilities 

with cancer risks greater than 100-in-1 

million is above the corresponding 

national average for the following 

demographic groups: Hispanic or 

Latino, people living below the poverty 


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level, people living below two times the 

poverty level, and people over 25 

without a high school diploma. The 

percent of the population with cancer 

risks greater than 100-in-1 million that 

are Black (5 percent) is well below the 

national average (12 percent). The 

percent of the population with cancer 

risks greater than 100-in-1 million that 

are Hispanic/Latino (34 percent) is over 

1.5 times greater than in the proximity 

analysis (21 percent) and nearly double 

the national average (19 percent). 

The results of the noncancer riskbased demographic analysis indicate 

that a total of 1,500 people living within 

10 km of 2 CMAS facilities analyzed 

have a respiratory hazard index greater 

than 1 from CMAS HAP emissions. The 

percent of the population living within 

10 km of these CMAS facilities with 

respiratory hazard index greater than 1 

is above the corresponding national 

average for the following demographic 

groups: Hispanic or Latino (90 percent 

for the source categories compared to 19 

percent nationwide), people living in 

linguistic isolation (15 percent for the 

source categories compared to 5 percent 

nationwide), people 25 years old and 

older without a high school diploma (33 

percent for the source categories 

compared to 12 percent nationwide), 

people living below twice the poverty 

level (44 percent for the source 

categories compared to 29 percent 

nationwide), and people living below 

the poverty level (24 percent for the 

source categories compared to 13 

percent nationwide). 

The results of the noncancer riskbased demographic analysis indicate 

that a total of 1,300 people living within 

10 km of 2 CMAS facilities analyzed 

have an immunological hazard index 

greater than 1 from CMAS HAP 

emissions. The demographic results 

indicate that the percentage of the 

population potentially impacted by 

CMAS emissions is greater than its 

corresponding nationwide percentage 

for the following demographic groups: 

Hispanic or Latino (90 percent for the 

source category compared to 19 percent 

nationwide), people living in linguistic 

isolation (16 percent for the source 

category compared to 5 percent 

nationwide), people 25 years old and 

older without a high school diploma (33 

percent for the source category 

compared to 12 percent nationwide), 

people living below twice the poverty 

level (44 percent for the source category 

compared to 29 percent nationwide), 

and people living below the poverty 

level (24 percent for the source category 

compared to 13 percent nationwide). 

The post-control risk-based 

demographic analysis shows that the 

controls required by this proposed 

action will notably reduce the number 

of people who are exposed to cancer 

risks resulting from emissions from the 

CMAS categories at all risk levels. The 

results of the post-control risk-based 

demographics analysis are in the 

columns titled ‘‘Post-Control’’ of tables 

11 through 13 of this preamble. At 

greater than or equal to a cancer risk of 

1-in-1 million, the number of 

individuals exposed will decrease from 

2.1 million to 1.4 million. The 

demographic composition of those 

individuals exposed to cancer risk 

greater than or equal to 1-in-1 million 

post-control is similar to the 

demographic composition of the 

individuals exposed to a cancer risk of 

1-in-1 million at baseline. The number 

of individuals exposed to cancer risk 

greater than or equal to 50-in-1 million 

will decrease from 36,100 to 4,400. 

The percent of the population living 

within 10 km of these CMAS facilities 

with post-control cancer risks greater 

than or equal to 50-in-1 million is above 

the corresponding national average for 

the following demographic groups: 

Hispanic or Latino, Age 0–17, people 

living below poverty, people living 

below two times poverty, those over 25 

without a high school diploma, and 

linguistic isolation. The percent of the 

population with post-control cancer 

risks greater than or equal to 50-in-1 

million that are Hispanic or Latino (66 

percent) is over three times the national 

average (19 percent), with 98 percent of 

this Hispanic or Latino population 

living around two CMAS facilities (one 

in Illinois and one in Kansas). 

After control is implemented, the 

number of people who are exposed to 

cancer risks greater than 100-in-1 

million resulting from emissions from 

the CMAS categories will decrease from 

3,600 to zero. Therefore, there are no 

disparities among demographic groups 

at this risk level. The actions of this 

proposed rulemaking will improve 

human health of current and future 

populations that live near these 

facilities. 

The post-control noncancer risk 

demographic results are the same as 

those for the baseline scenario because 

the controls being proposed in this 

action do not directly reduce the nickel 

emissions that drive the noncancer risk. 

TABLE 11—SOURCE CATEGORIES: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS

WITH CANCER RISK GREATER THAN OR EQUAL TO 1-IN-1 MILLION LIVING WITHIN 10 KM OF CMAS FACILITIES TO

THE NATIONAL AVERAGE AND THE PROXIMITY DEMOGRAPHICS

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis 

for total population 

living within 10 km 

of CMAS facilities 

Cancer risk ≥1-in-1 million 

within 10 km 

of CMAS facilities 

Baseline Post-control 

Total Population ............................................................................................... 330M 33.7M 2.1M 1.4M 

Number of Facilities ......................................................................................... .................... 247 76 71 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

49% 

[16.7M] 

45% 

[925K] 

40% 

[564K] 

Black ................................................................................................................ 12% 

[40M] 

19% 

[6.5M] 

25% 

[513K] 

26% 

[377K] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[75K] 

0.2% 

[4.1K] 

0.2% 

[2.5K] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

21% 

[7.1M] 

25% 

[514K] 

28% 

[404K] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

10% 

[3.4M] 

6% 

[119K] 

5% 

[78K] 


lotter on DSK11XQN23PROD with PROPOSALS2
Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7983 

TABLE 11—SOURCE CATEGORIES: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS

WITH CANCER RISK GREATER THAN OR EQUAL TO 1-IN-1 MILLION LIVING WITHIN 10 KM OF CMAS FACILITIES TO

THE NATIONAL AVERAGE AND THE PROXIMITY DEMOGRAPHICS—Continued 

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis 

for total population 

living within 10 km 

of CMAS facilities 

Cancer risk ≥1-in-1 million 

within 10 km 

of CMAS facilities 

Baseline Post-control 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

22% 

[7.4M] 

24% 

[492K] 

24% 

[339K] 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

63% 

[21.3M] 

62% 

[1.3M] 

62% 

[881K] 

Age ≥65 years ................................................................................................. 16% 

[53M] 

15% 

[5M] 

14% 

[301K] 

14% 

[205K] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[4.7M] 

15% 

[318K] 

17% 

[240K] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

31% 

[10.4M] 

36% 

[750K] 

39% 

[554K] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

13% 

[4.3M] 

15% 

[306K] 

16% 

[232K] 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

6% 

[2.1M] 

6% 

[123K] 

7% 

[102K] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 American Community Survey (ACS) 5-year block 

group averages. Total population count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

TABLE 12—SOURCE CATEGORIES: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS

WITH CANCER RISK GREATER THAN OR EQUAL TO 50-IN-1 MILLION LIVING WITHIN 10 KM OF CMAS FACILITIES TO

THE NATIONAL AVERAGE AND THE PROXIMITY DEMOGRAPHICS

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis 

for total population 

living within 10 km 

of CMAS facilities 

Cancer risk 

≥50-in-1 million 

within 10 km 

of CMAS facilities 

Baseline Post-control 

Total Population ............................................................................................... 330M 33.7M 36K 4.4K 

Number of Facilities ......................................................................................... .................... 247 15 8 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

49% 

[16.7M] 

39% 

[14K] 

28% 

[1.2K] 

Black ................................................................................................................ 12% 

[40M] 

19% 

[6.5M] 

12% 

[4.5K] 

4% 

[200] 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[75K] 

0.1% 

[<100] 

0.0% 

[<100] 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

21% 

[7.1M] 

40% 

[14.4K] 

66% 

[2.9K] 

Other and Multiracial ....................................................................................... 9% 

[29M] 

10% 

[3.4M] 

8% 

[2.9K] 

2% 

[<100] 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

22% 

[7.4M] 

30% 

[11K] 

34% 

[1.5K] 


lotter on DSK11XQN23PROD with PROPOSALS2

I 
7984 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

TABLE 12—SOURCE CATEGORIES: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS

WITH CANCER RISK GREATER THAN OR EQUAL TO 50-IN-1 MILLION LIVING WITHIN 10 KM OF CMAS FACILITIES TO

THE NATIONAL AVERAGE AND THE PROXIMITY DEMOGRAPHICS—Continued 

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis 

for total population 

living within 10 km 

of CMAS facilities 

Cancer risk 

≥50-in-1 million 

within 10 km 

of CMAS facilities 

Baseline Post-control 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

63% 

[21.3M] 

60% 

[22K] 

59% 

[2.6K] 

Age ≥65 years ................................................................................................. 16% 

[53M] 

15% 

[5M] 

10% 

[3.7K] 

7% 

[300] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[4.7M] 

21% 

[7.5K] 

23% 

[1K] 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

31% 

[10.4M] 

49% 

[18K] 

47% 

[2.1K] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

13% 

[4.3M] 

27% 

[10K] 

30% 

[1.3K] 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

6% 

[2.1M] 

13% 

[4.5K] 

11% 

[500] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

TABLE 13—SOURCE CATEGORIES: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS

WITH CANCER RISK GREATER THAN 100-IN-1 MILLION LIVING WITHIN 10 KM OF CMAS FACILITIES TO THE NATIONAL

AVERAGE AND THE PROXIMITY DEMOGRAPHICS

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis 

for total population 

living within 10 km 

of CMAS facilities 

Cancer risk >100-in-1 

million within 10 km of 

CMAS facilities 

Baseline Post-control 

Total Population ............................................................................................... 330M 33.7M 3.6K 0 

Number of Facilities ......................................................................................... .................... 247 4 0 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................ 60% 

[196M] 

49% 

[16.7M] 

58% 

[2.1K] 

0% 

0 

Black ................................................................................................................ 12% 

[40M] 

19% 

[6.5M] 

5% 

[200] 

0% 

0 

American Indian and Alaskan Native .............................................................. 0.6% 

[2.1M] 

0.2% 

[75K] 

0.1% 

[<100] 

0.0% 

0 

Hispanic or Latino (white and nonwhite) ......................................................... 19% 

[63M] 

21% 

[7.1M] 

34% 

[1.2K] 

0% 

0 

Other and Multiracial ....................................................................................... 9% 

[29M] 

10% 

[3.4M] 

3% 

[100] 

0% 

0 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................ 22% 

[74M] 

22% 

[7.4M] 

34% 

[1.2K] 

0% 

0 

Age 18 to 64 years .......................................................................................... 62% 

[203M] 

63% 

[21.3M] 

55% 

[2K] 

0% 

0 

Age ≥65 years ................................................................................................. 16% 

[53M] 

15% 

[5M] 

11% 

[400] 

0% 

0 


lotter on DSK11XQN23PROD with PROPOSALS2
Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7985 

60See footnote 60. 

TABLE 13—SOURCE CATEGORIES: COMPARISON OF BASELINE AND POST-CONTROL DEMOGRAPHICS OF POPULATIONS

WITH CANCER RISK GREATER THAN 100-IN-1 MILLION LIVING WITHIN 10 KM OF CMAS FACILITIES TO THE NATIONAL

AVERAGE AND THE PROXIMITY DEMOGRAPHICS—Continued 

Demographic group 

Nationwide 

average for 

reference 

Proximity analysis 

for total population 

living within 10 km 

of CMAS facilities 

Cancer risk >100-in-1 

million within 10 km of 

CMAS facilities 

Baseline Post-control 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................ 13% 

[42M] 

14% 

[4.7M] 

15% 

[500] 

0% 

0 

Below 2x Poverty Level ................................................................................... 30% 

[100M] 

31% 

[10.4M] 

42% 

[1.5K] 

0% 

0 

Education by Percent [Number of People] 

*******

Over 25 and without a High School Diploma .................................................. 12% 

[38M] 

13% 

[4.3M] 

23% 

[800] 

0% 

0 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................... 5% 

[17M] 

6% 

[2.1M] 

5% 

[200] 

0% 

0 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

2. CMAS NESHAP Whole-Facility 

Demographics 

As described in section II.E of this 

preamble and the document titled Risk 

Assessment for the Chemical 

Manufacturing Area Source (CMAS) 

Source Categories in Support of the 

2025 Technology Review for the 

Proposed Rule, which is available in the 

docket for this rulemaking, we assessed 

the facility-wide (or ‘‘whole-facility’’) 

risks as part of a risk assessment for 278 

CMAS facilities, accounting for HAP 

emissions from the entire facility and 

not just those resulting from CMAS 

categories as discussed in the section 

V.F.1 of this preamble.60 The wholefacility risk analysis includes all sources 

of HAP emissions at each facility as 

reported in the emissions inventory 

developed using the NEI (described in 

section II.C.2 of this proposed rule). The 

following discussion of the wholefacility demographic analysis is focused 

on post-control risks. 

The whole-facility demographic 

analysis is an assessment of individual 

demographic groups in the total 

population living within 10 km (∼6.2 

miles) and 50 km (∼31 miles) of the 

facilities. In this preamble, we focus on 

the results from the demographic 

analyses using a 10 km radius because 

this area captures the majority of the 

population with higher cancer and 

noncancer risks due to HAP emissions 

from CMAS facilities. Specifically, 100 

percent of the population with baseline 

cancer risks greater than or equal to 50- 

in-1 million and with noncancer hazard 

indices greater than 1 from emissions 

from the CMAS categories live within 

10 km of the CMAS facilities. The 

results of the whole-facility 

demographic analysis for populations 

living within 10 km and 50 km of CMAS 

facilities are included in the document 

titled Analysis of Demographic Factors 

for Populations Living Near Chemical 

Manufacturing Area Source (CMAS) 

Facilities: Whole Facility Analysis of 

Proposed Amendments which is 

available in the docket for this 

rulemaking. 

The whole-facility demographic 

analysis post-control results are shown 

in table 14 of this preamble. This 

analysis focused on the populations 

living within 10 km of the CMAS 

facilities with estimated whole-facility 

post-control cancer risks greater than or 

equal to 1-in-1 million, greater than or 

equal to 50-in-1 million, and greater 

than 100-in-1 million, as well as with 

estimated whole-facility post-control 

noncancer hazard indices greater than 1. 

The risk analysis indicated that all 

emissions from the CMAS facilities, 

after the reductions imposed by the 

proposed rule, expose a total of about 

1.65 million people living around 80 

facilities to a cancer risk greater than or 

equal to 1-in-1 million, 5,600 people 

living around 10 facilities to a cancer 

risk greater than or equal to 50-in-1 

million, and zero people to a cancer risk 

greater than 100-in-1 million. The risk 

analysis indicated that all emissions 

from the CMAS facilities, after the 

reductions imposed by the proposed 

rule, expose a total of about 1,700 

people to a respiratory hazard index 

greater than 1 and about 1,700 people to 

an immunological hazard index greater 

than 1 (both values unchanged from 

baseline). 

When the CMAS whole-facility 

populations are compared to the CMAS 

categories populations in the postcontrol scenarios, we see 250,000 

additional people with risks greater than 

or equal to 1-in-1 million, 1,200 

additional people with risks greater than 

or equal to 50-in-1 million, zero 

additional people with risks greater than 

100-in-1 million, 200 additional people 

with respiratory hazard indices greater 

than 1, and 200 additional people with 

immunological hazard indices greater 

than 1. 


lotter on DSK11XQN23PROD with PROPOSALS2

I 
7986 Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 

The demographic distribution of the 

whole-facility population with postcontrol cancer risks greater than or 

equal to 1-in-1 million is almost 

identical to the distribution of the 

source category population with postcontrol cancer risks greater than or 

equal to 1-in-1 million. Therefore, the 

whole-facility population with postcontrol cancer risks greater than or 

equal to 1-in-1 million has 

disproportionately high representation 

from Blacks, Hispanics and Latinos, 

people living below the poverty level, 

people living below two times the 

poverty level, those over 25 without a 

high school diploma, and those that are 

linguistically isolated. 

The population with post-control 

cancer risks greater than or equal to 50- 

in-1 million in the whole-facility 

analysis is almost identical to the 

distribution of the source category 

population with post-control cancer 

risks greater than or equal to 50-in-1 

million. Therefore, the whole-facility 

population with post-control cancer 

risks greater than or equal to 50-in-1 

million has disproportionately high 

representation from Hispanics and 

Latinos, people living below the poverty 

level, people living below two times the 

poverty level, those over 25 without a 

high school diploma, and those that are 

linguistically isolated. As such, the 

Hispanic and Latino population is still 

disproportionately represented at 69 

percent, which is well above the 

national average of 19 percent. 

Based on results from the wholefacility emissions analysis, there are 

zero people with post-control risks 

greater than 100-in-1 million. 

The population with post-control 

respiratory hazard indices greater than 1 

in the whole-facility analysis is almost 

identical to the distribution of the 

source category population with 

baseline and post-control respiratory 

hazard indices greater than 1. Therefore, 

the whole-facility population with postcontrol respiratory hazard indices 

greater than 1 has disproportionately 

high representation from Hispanics or 

Latinos, people living below the poverty 

level, people living below two times the 

poverty level, those over 25 without a 

high school diploma, and those who are 

linguistically isolated. As such, the 

Hispanic and Latino population is 

disproportionately represented at 90 

percent, which is well above the 

national average of 19 percent, and 

people living below the poverty level 

are disproportionately represented at 24 

percent, which is nearly twice the 

national average of 13 percent. 

The population with post-control 

immunological hazard indices greater 

than 1 in the whole-facility analysis is 

almost identical to the distribution of 

the source category population with 

baseline and post-control 

immunological hazard indices greater 

than 1. Therefore, the whole-facility 

population with post-control 

immunological hazard indices greater 

than 1 has disproportionately high 

representation from Hispanics or 

Latinos, people living below the poverty 

level, people living below two times the 

poverty level, those over 25 without a 

high school diploma, and those who are 

linguistically isolated. As such, the 

Hispanic and Latino population is 

disproportionately represented at 90 

percent, which is well above the 

national average of 19 percent, and 

people living below the poverty level 

are disproportionately represented at 24 

percent, which is nearly twice the 

national average of 13 percent. 

TABLE 14—WHOLE-FACILITY: WHOLE-FACILITY POST-CONTROL DEMOGRAPHICS FOR CMAS FACILITIES BY RISK LEVEL

FOR POPULATIONS LIVING WITHIN 10 KM OF FACILITIES

Demographic group 

Nationwide 

average for 

reference 

Whole-facility post-control cancer risk for 

populations within 10 km of CMAS 

facilities 

≥1-in-1 

million 

≥50-in-1 

million 

>100-in-1 

million 

Total Population ............................................................................................................... 330M 1,651,083 5,625 0 

Number of Facilities ......................................................................................................... .................... 80 10 0 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................................ 60% 

[196M] 

41% 

[670K] 

24% 

[1.4K] 

0% 

0 

Black ................................................................................................................................ 12% 

[40M] 

26% 

[436K] 

5% 

[300] 

0% 

0 

American Indian and Alaskan Native .............................................................................. 0.6% 

[2.1M] 

0.2% 

[3K] 

0.0% 

[<100] 

0.0% 

0 

Hispanic or Latino (white and nonwhite) ......................................................................... 19% 

[63M] 

27% 

[450K] 

69% 

[4K] 

0% 

0 

Other and Multiracial ....................................................................................................... 9% 

[29M] 

6% 

[91K] 

1% 

[<100] 

0% 

0 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................................ 22% 

[74M] 

24% 

[393K] 

33% 

[2K] 

0% 

0 

Age 18 to 64 years .......................................................................................................... 62%

[203M] 

62% 

[1M] 

58% 

[3.3K] 

0% 

0 

Age ≥65 years ................................................................................................................. 16% 

[53M] 

14% 

[234K] 

8% 

[500] 

0% 

0 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................................ 13% 

[42M] 

17% 

[281K] 

24% 

[1.3K] 

0% 

0 


lotter on DSK11XQN23PROD with PROPOSALS2
Federal Register / Vol. 90, No. 13 / Wednesday, January 22, 2025 / Proposed Rules 7987 

61See footnote 60. 

TABLE 14—WHOLE-FACILITY: WHOLE-FACILITY POST-CONTROL DEMOGRAPHICS FOR CMAS FACILITIES BY RISK LEVEL

FOR POPULATIONS LIVING WITHIN 10 KM OF FACILITIES—Continued 

Demographic group 

Nationwide 

average for 

reference 

Whole-facility post-control cancer risk for 

populations within 10 km of CMAS 

facilities 

≥1-in-1 

million 

≥50-in-1 

million 

>100-in-1 

million 

Below 2x Poverty Level ................................................................................................... 30% 

[100M] 

39% 

[637K] 

45% 

[2.6K] 

0% 

0 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................................. 12% 

[38M] 

16% 

[262K] 

28% 

[1.6K] 

0% 

0 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................................... 5% 

[17M] 

7% 

[109K] 

11% 

[600] 

0% 

0 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 

3. CMAS NESHAP Community 

Demographics 

As described in section II.E of this 

preamble and the document titled Risk 

Assessment for the Chemical 

Manufacturing Area Source (CMAS) 

Source Categories in Support of the 

2025 Technology Review for the 

Proposed Rule, which is available in the 

docket for this rulemaking, we assessed 

the community risks as part of a 

discretionary risk assessment for 278 

CMAS facilities.61 The community risks 

include HAP emissions from all 

stationary point sources for which we 

have emissions data within 10 km of the 

CMAS facilities identified in section 

II.C.1 of this preamble. The following 

discussion of the community risk 

analysis is focused on post-control risks. 

This community demographic analysis 

characterizes the remaining risks 

communities face after implementation 

of the controls required in this proposal. 

The community demographic analysis 

is an assessment of individual 

demographic groups in the total 

population living within 10 km (∼6.2 

miles) of the CMAS facilities. The 

community risk assessment and 

demographics were only conducted at 

the 10 km radius because, based on 

emissions from the CMAS categories, 

this distance includes 100 percent of the 

population with cancer risks greater 

than or equal to 50-in-1 million. The full 

results of the community demographic 

analysis are in the document titled 

Analysis of Demographic Factors for 

Populations Living Near Chemical 

Manufacturing Area Source (CMAS) 

Facilities: Community-Based 

Assessment which is available in the 

docket for this rulemaking. 

The community demographic analysis 

post-control results are shown in table 

15 of this preamble. The following 

discussion of the community 

demographic analysis is focused on the 

populations living within 10 km of the 

CMAS facilities with estimated 

community post-control cancer risks 

greater than or equal to 1-in-1 million, 

greater than or equal to 50-in-1 million, 

and greater than 100-in-1 million. The 

risk analysis indicated that all emissions 

from all facilities within 10 km of the 

CMAS facilities, after the reductions 

imposed by the proposed rule, expose a 

total of about 8 million people living 

around 242 facilities to a cancer risk 

greater than or equal to 1-in-1 million, 

65,000 people living around 66 facilities 

to a cancer risk greater than or equal to 

50-in-1 million, and about 1,900 people 

living around nine facilities to a cancer 

risk greater than 100-in-1 million. 

When the CMAS community 

populations are compared to the CMAS 

categories populations in the postcontrol scenarios, we see 6.6 million 

additional people with cancer risks 

greater than or equal to 1-in-1 million, 

61,000 additional people with cancer 

risks greater than or equal to 50-in-1 

million, and 1,900 additional people 

with cancer risks greater than 100-in-1 

million. 

The demographic distribution of the 

community population with cancer 

risks greater than or equal to 1-in-1 

million is similar to the category 

population and the whole-facility 

population with cancer risks greater 

than or equal to 1-in-1 million in the 

post-control scenario. Therefore, the 

community population with postcontrol cancer risks greater than or 

equal to 1-in-1 million has 

disproportionately high representation 

from Blacks, Hispanics and Latinos, 

people living below the poverty level, 

people living below two times the 

poverty level, those over 25 without a 

high school diploma, and those living in 

linguistic isolation. 

The population with cancer risks 

greater than or equal to 50-in-1 million 

in the community analysis has a 

different demographic distribution than 

the source category population with 

cancer risks greater than or equal to 50- 

in-1 million in the post-control scenario. 

The percent of the population that is 

Black with risks greater than or equal to 

50-in-1 million is lower for the 

community post-control analysis (19 

percent) versus the category and wholefacility post-control analyses (26 

percent). For the community postcontrol assessment, the percentage of 

the population with cancer risks greater 

than or equal to 50-in-1 million that is 

below the poverty level (13 percent) and 

below two times the poverty level (27 

percent) is equal to or below their 

corresponding national averages (13 

percent and 30 percent, respectively). 


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The percentage of the population that is 

over 25 years old without a high school 

diploma (14 percent) is above the 

national average (12 percent) for 

community post-control population. 

Based on results from the community 

emissions analysis, there are about 

1,900 people with post-control cancer 

risks greater than 100-in-1 million. The 

CMAS categories emissions analysis 

indicated that there are no people with 

post-control cancer risks greater than 

100-in-1 million. The increased cancer 

risk for most of these 1,900 people is 

driven largely by emissions of 

chromium VI from non-CMAS facilities 

within 10 km of CMAS facilities. 

The percent of the population in the 

community analysis with post-control 

cancer risks greater than 100-in-1 

million that is Black (15 percent) and 

Hispanic or Latino (21 percent) are 

above their corresponding national 

averages (12 percent and 19 percent, 

respectively). The percent of the 

population in the community analysis 

with a post control cancer risk greater 

than 100-in-1 million that is below the 

poverty level (14 percent) and below 

two times the poverty level (36 percent) 

are above their corresponding national 

averages (13 percent and 30 percent, 

respectively). The percent of the 

population in the community analysis 

with a post control cancer risk greater 

than 100-in-1 million that is over 25 

years old without a high school diploma 

(21 percent) is above the national 

average (12 percent). 

TABLE 15—COMMUNITY: COMMUNITY POST-CONTROL DEMOGRAPHICS FOR CMAS FACILITIES BY RISK LEVEL FOR

POPULATIONS LIVING WITHIN 10 KM OF FACILITIES

Demographic group 

Nationwide 

average for 

reference 

Whole-facility post-control cancer risk for 

populations within 10 km of CMAS 

facilities 

≥1-in-1 

million 

≥50-in-1 

million 

>100-in-1 

million 

Total Population ............................................................................................................... 330M 8M 65K 2K 

Number of Facilities ......................................................................................................... .................... 242 66 9 

Race and Ethnicity by Percent [Number of People] 

White ................................................................................................................................ 60% 

[196M] 

40% 

[3.2M] 

49% 

[32K] 

64% 

[1.2K] 

Black ................................................................................................................................ 12% 

[40M] 

22% 

[1.8M] 

19% 

[12K] 

15% 

[300] 

American Indian and Alaskan Native .............................................................................. 0.6% 

[2.1M] 

0.2% 

[16K] 

0.3% 

[200] 

0.1% 

[<100] 

Hispanic or Latino (white and nonwhite) ......................................................................... 19% 

[63M] 

30% 

[2.4M] 

29% 

[19K] 

21% 

[400] 

Other and Multiracial ....................................................................................................... 9% 

[29M] 

8% 

[654K] 

4% 

[2.5K] 

1% 

[<100] 

Age By Percent [Number of People] 

Age 0 to 17 years ............................................................................................................ 22% 

[74M] 

23% 

[1.9M] 

25% 

[16K] 

25% 

[500] 

Age 18 to 64 years .......................................................................................................... 62%

[203M] 

63% 

[5M] 

64% 

[42K] 

62% 

[1.2K] 

Age ≥ 65 years ................................................................................................................ 16% 

[53M] 

14% 

[1.1M] 

11% 

[7.4K] 

13% 

[300] 

Income by Percent [Number of People] 

Below Poverty Level ........................................................................................................ 13% 

[42M] 

18% 

[1.4M] 

13% 

[8.6K] 

14% 

[300] 

Below 2x Poverty Level ................................................................................................... 30% 

[100M] 

38% 

[3.1M] 

27% 

[18K] 

36% 

[700] 

Education by Percent [Number of People] 

Over 25 and without a High School Diploma .................................................................. 12% 

[38M] 

18% 

[1.4M] 

14% 

[9.1K] 

21% 

[400] 

Linguistically Isolated by Percent [Number of People] 

Linguistically Isolated ....................................................................................................... 5% 

[17M] 

8% 

[598K] 

5% 

[3.3K] 

3% 

[<100] 

Notes: 

• Nationwide population and demographic percentages are based on Census’ 2016–2020 ACS 5-year block group averages. Total population 

count is based on 2020 Decennial Census block population. 

• To avoid double counting, the ‘‘Hispanic or Latino’’ category is treated as a distinct demographic category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race. 

• The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR was located at a user assigned receptor 

at an individual residence and not at a census block centroid, we were unable to estimate population and demographics for that facility. 

• The sum of individual populations with a demographic category may not add up to total due to rounding. K = Thousands, M = Millions. 


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62Children’s Health Policy available at: https://

www.epa.gov/children/childrens-health-policy-andplan. 

63U.S. EPA. 2005. Supplemental Guidance for 

Assessing Susceptibility from Early-Life Exposure to 

Carcinogens. U.S. EPA, Washington, DC, EPA/630/ 

R–03/003F. https://www.epa.gov/sites/default/files/ 

201309/documents/childrens_supplement_

final.pdf. 

G. What analysis of children’s 

environmental health did we conduct? 

This action proposes to reduce HAP 

emissions including those emissions 

from EtO. In addition, the EPA’s policy 

on Children’s Health 62 also applies to 

this action. Accordingly, we have 

evaluated the environmental health or 

safety effects of EtO emissions and 

exposures on children. 

Because EtO is mutagenic (i.e., it can 

act directly on deoxyribonucleic acid 

and cause chromosome damage), 

children are expected to be more 

susceptible to its harmful effects. To 

take this into account, as part of the risk 

assessment performed in supported of 

this rulemaking, the EPA followed its 

guidelines 63 and applied age-dependent 

adjustment factors (ADAFs) to the 

inhalation unit risk estimate for 

childhood exposures (from birth up to 

16 years of age). With the ADAF applied 

to account for greater susceptibility of 

children, the adjusted EtO inhalation 

unit risk estimate is 5 × 10¥3 per mg/m3. 

It should be noted that because EtO is 

mutagenic, the associated emission 

reductions proposed in this preamble 

will be particularly beneficial to 

children. The results of the risk 

assessment are contained in section II.E 

of this preamble and further 

documented in the risk report Risk 

Assessment for the Chemical 

Manufacturing Area Source (CMAS) 

Source Category in Support of the 2025 

Technology Review for the Proposed 

Rule which is available in the docket for 

this rulemaking. 

VI. Request for Comments 

We solicit comments on all aspects of 

this proposed action. In addition to 

general comments on this proposed 

action, we are also interested in 

additional data that may improve the 

risk assessments, economic impact 

analysis, and other analyses including 

our assumptions and estimates 

discussed in sections IV.A through IV.C 

of this preamble. We are specifically 

interested in receiving any information 

and data regarding developments, 

limitations, or related general 

considerations in practices, processes, 

and control technologies that reduce 

HAP emissions. We solicit comment on 

the effectiveness of these proposed 

requirements on reducing ethylene 

oxide emissions, any capital and annual 

costs that we did not account for, the 

time that is needed to come into 

compliance with the proposed 

requirements, or any other potential 

barriers to or impacts of imposing these 

requirements. We request comment on 

additional information on costs, 

emissions, product recovery, and 

potential broader impacts to markets 

including impacts small businesses and 

entities. We request comment on how to 

address the non-monetized costs and 

benefits of the proposed rule. We 

request estimates of any potential loss of 

production while bringing facilities into 

compliance and forgone returns due to 

displaced investment. 

We are requesting comments and data 

on risks and impacts (both direct and 

indirect) of these proposed requirements 

on specific critical industries such as 

production of active pharmaceutical 

ingredients. We are interested in 

comments and data around the extent of 

the costs of compliance with the 

proposed rule to manufacturers of 

pharmaceuticals or other critical 

medical products, including any 

potential impacts to the public health 

industrial base, drug shortages, or other 

supply chain issues. We are also 

interested in proposals for alternative 

mitigation strategies or technologies. 

We request comment on data, 

methods, and approaches to monetize 

non-fatal cancer, non-cancer health 

effects, and other benefits of reducing 

exposure to ethylene oxide and other 

table 1 HAP. 

In addition, we are requesting 

comment and data on if more frequent 

heat exchange system monitoring 

periods, namely continued monthly 

monitoring and/or weekly monitoring, 

are appropriate for CMAS (see section 

IV.A.2 of this preamble). As mentioned 

in section IV.C.3 of this preamble, we 

also request comment and data on 

whether the removal of the TRE concept 

is feasible for CMAS facilities. With 

respect to design evaluations and 

engineering assessments, we are 

soliciting comment and data on whether 

they are appropriate for demonstrating 

compliance for certain APCDs. Also, we 

are soliciting comment on whether an 

alternative compliance timeline for the 

EtO requirements, as discussed in 

section IV.E.1 of this preamble is 

appropriate. 

VII. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and Executive Orders can be 

found at https://www.epa.gov/lawsregulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

This action is a ‘‘significant regulatory 

action’’ as defined in Executive Order 

12866, as amended by Executive Order 

14094. Accordingly, the EPA submitted 

this action to the OMB for Executive 

Order 12866 review. Documentation of 

any changes made in response to the 

Executive Order 12866 review is 

available in the docket. The EPA 

conducted an economic impact analysis 

for this proposal in a document titled 

Economic Impact Analysis, which is 

available in the docket for this action. 

B. Paperwork Reduction Act (PRA) 

The information collection activities 

in this proposed rule have been 

submitted for approval to the OMB 

under the PRA. The Information 

Collection Request (ICR) document that 

the EPA prepared has been assigned 

EPA ICR number 2323.09. You can find 

a copy of the ICR in the docket for this 

rulemaking, and it is briefly 

summarized here. 

The EPA is proposing amendments to 

the CMAS NESHAP that revise 

provisions pertaining to emissions from 

PRDs, pressure vessels, heat exchange 

systems, and equipment leaks. The EPA 

is also proposing requirements 

pertaining to EtO emissions from 

process vents, storage vessels, heat 

exchange systems, equipment leaks, and 

wastewater. In addition, the EPA is 

proposing amendments to the NESHAP 

for CMAS that revise provisions 

pertaining to emissions during periods 

of SSM, add requirements for electronic 

reporting of periodic reports and 

performance test results, fenceline 

monitoring, and make other minor 

clarifications and corrections. This 

information will be collected to ensure 

compliance with the CMAS NESHAP. 

Respondents/affected entities: 

Owners or operators of CMAS facilities. 

Respondent’s obligation to respond: 

Mandatory (40 CFR part 63, subpart 

VVVVVV). 

Estimated number of respondents: 

280. 

Frequency of response: Initially, 

quarterly, and semiannually. 

Total estimated burden: Average 

annual recordkeeping and reporting 

burden is 25,300 hours (per year) to 

comply with the proposed amendments 

in the CMAS NESHAP. Burden is 

defined at 5 CFR 1320.3(b). 

Total estimated cost: Average annual 

cost is $25,500,000 (per year) which 

includes $23,000,000 annualized capital 

and operations and maintenance costs, 


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to comply with the proposed 

amendments in the CMAS NESHAP. 

An agency may not conduct or 

sponsor, and a person is not required to 

respond to, a collection of information 

unless it displays a currently valid OMB 

control number. The OMB control 

numbers for the EPA’s regulations in 40 

CFR are listed in 40 CFR part 9. 

Submit your comments on the 

Agency’s need for this information, the 

accuracy of the provided burden 

estimates, and any suggested methods 

for minimizing respondent burden to 

the EPA using the docket identified at 

the beginning of this rulemaking. The 

EPA will respond to any ICR-related 

comments in the final rule. You may 

also send your ICR-related comments to 

OMB’s Office of Information and 

Regulatory Affairs using the interface at 

https://www.reginfo.gov/public/do/ 

PRAMain. Find this particular 

information collection by selecting 

‘‘Currently under Review—Open for 

Public Comments’’ or by using the 

search function. OMB must receive 

comments no later than February 21, 

2025. 

C. Regulatory Flexibility Act (RFA) 

I certify that the proposed rule in this 

action will not have a significant 

economic impact on a substantial 

number of small entities under the RFA. 

The small entities subject to the 

requirements of this action are small 

businesses within the CMAS categories. 

The Agency has determined that the 58 

small entities affected by this action 

may experience an average impact of 

total annual costs being 0.32 percent of 

their annual revenues, not including 

product recovery, or 0.29 percent on 

average when product recovery from 

compliance is included. Five of these 58 

small entities are estimated to 

experience total annual costs above one 

percent of annual revenues when not 

including product recovery (three small 

entities when product recovery is 

included), and one small entity had 

estimated annual costs exceeding three 

percent of annual revenues regardless of 

whether product recovery is included. 

The percentage of impacted small 

entities estimated to experience total 

annual costs greater than one or three 

percent of their annual revenues is 

small and therefore this action will not 

have significant impacts on a substantial 

number of small entities. Details of the 

analysis for the proposed rule are 

presented in the document titled 

Economic Impact Analysis, which is 

available in the docket for this action. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain an 

unfunded mandate of $100 million or 

more as described in UMRA, 2 U.S.C. 

1531–1538, and does not significantly or 

uniquely affect small governments. The 

costs involved in this action are 

estimated not to exceed $183 million in 

2023$ ($100 million in 1995$ adjusted 

for inflation using the GDP implicit 

price deflator) or more in any one year. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the National 

Government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Consultation 

and Coordination With Tribal 

Governments 

This action has tribal implications. 

However, it will neither impose 

substantial direct compliance costs on 

federally recognized Tribal 

governments, nor preempt tribal law. 

We have identified two facilities located 

on Tribal lands that will potentially be 

impacted by this rulemaking, one of 

which emits EtO. Consistent with the 

EPA Policy on Coordination and 

Consultation with Indian Tribes, the 

EPA will provide tribal officials the 

opportunity to provide meaningful and 

timely input early in the development of 

this action through multiple outreach 

activities such as Tribal partnership 

calls, webinars, and offers for 

government-to-government consultation 

with potentially impacted Tribes and 

other Tribes as requested. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

Executive Order 13045 directs federal 

agencies to include an evaluation of the 

health and safety effects of the planned 

regulation on children in federal health 

and safety standards and explain why 

the regulation is preferable to 

potentially effective and reasonably 

feasible alternatives. This action is not 

subject to Executive Order 13045 

because it is not a significant regulatory 

action under section 3(f)(1) of Executive 

Order 12866, though the EPA believes 

the safety risks addressed by this action 

do present a disproportionate risk to 

children. This action’s assessments of 

potential impacts to human health are 

contained in section II.E of this 

preamble and in greater detail in the 

document titled Risk Assessment for the 

Chemical Manufacturing Area Source 

(CMAS) Source Categories in Support of 

the 2025 Technology Review for the 

Proposed Rule, which is available in the 

docket for this rulemaking. In addition, 

the EPA’s Policy on Children’s Health 

applies to this action. Information on 

how the Policy was applied is available 

in section V.G of this preamble. 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not a ‘‘significant 

energy action’’ because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

The overall economic impact of this 

proposed rule should be minimal for 

CMAS and their parent companies 

(which are engaged in the energy 

sector). 

I. National Technology Transfer and 

Advancement Act (NTTAA) and 1 CFR 

Part 51 

This proposed action involves 

technical standards. Therefore, the EPA 

conducted searches for the CMAS 

NESHAP through the Enhanced 

National Standards Systems Network 

Database managed by the American 

National Standards Institute. We also 

conducted a review of voluntary 

consensus standards (VCS) 

organizations and accessed and 

searched their databases. We conducted 

searches for EPA Methods 5, 5D, 21, and 

29 of 40 CFR part 60, appendix A. 

During the EPA’s VCS search, if the title 

or abstract (if provided) of the VCS 

described technical sampling and 

analytical procedures that are similar to 

the EPA’s reference method, the EPA 

ordered a copy of the standard and 

reviewed it as a potential equivalent 

method. We reviewed all potential 

standards to determine the practicality 

of the VCS for this rulemaking. This 

review requires significant method 

validation data that meet the 

requirements of EPA Method 301 for 

accepting alternative methods or 

scientific, engineering, and policy 

equivalence to procedures in the EPA 

reference methods. The EPA may 

reconsider determinations of 

impracticality when additional 

information is available for particular 

VCS. 

We did not identify any applicable 

voluntary consensus standards for EPA 

Methods 5D and 21. However, the EPA 

proposes to incorporate by reference 

VCS ASTM D6784–24, ‘‘Standard Test 

Method for Elemental, Oxidized, 

Particle-Bound and Total Mercury Gas 

Generated from Coal-Fired Stationary 


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Sources (Ontario Hydro Method)’’ as an 

acceptable alternative to EPA Method 29 

(referenced in the CMAS NESHAP at 40 

CFR 63.11496(f)(3)(iii)) with the 

following caveats. This ASTM 

procedure has been approved by the 

EPA as an alternative to EPA Method 29 

only when the target compound is 

mercury; and applies to concentrations 

approximately 0.5 to 100 mg/m3. This 

test method was developed initially for 

the measurement of mercury in coalfired power plants; however, it has also 

been extensively used on other 

stationary combustion sources including 

sources having a flue gas composition 

with high levels of hydrochloric acid 

and low levels of sulfur dioxide. The 

test method includes equipment and 

procedures for obtaining samples from 

effluent ducts and stacks, equipment 

and procedures for laboratory analysis, 

and procedures for calculating results of 

elemental, oxidized, particle-bound, and 

total mercury emissions. ASTM D6784– 

24 is available at ASTM International, 

1850 M Street NW, Suite 1030, 

Washington, DC 20036. See https://

www.astm.org/. The standard is 

available to everyone at a cost 

determined by the ASTM ($90). The 

ASTM also offers memberships or 

subscriptions that allow unlimited 

access to their methods. The cost of 

obtaining these methods is not a 

significant financial burden, making the 

methods reasonably available to 

stakeholders. 

While the EPA identified 7 other VCS 

as being potentially applicable, the 

Agency decided not to use them because 

these methods are impractical as 

alternatives because of the lack of 

equivalency, documentation, validation 

data and other important technical and 

policy considerations. The EPA 

documented the search and review 

results in the document titled Voluntary 

Consensus Standard Results for 

Technology Review of the National 

Emissions Standards for Hazardous Air 

Pollutants for Chemical Manufacturing 

Area Sources, which is available in the 

docket for this rulemaking. Additional 

information for the VCS search and 

determinations can be found in this 

document. The EPA welcomes 

comments on this aspect of the 

proposed rulemaking and, specifically, 

invites the public to identify potentially 

applicable VCS and to explain why such 

standards should be used in this 

regulation. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations and Executive 

Order 14096: Revitalizing Our Nation’s 

Commitment to Environmental Justice 

for All 

The EPA believes that the human 

health or environmental conditions that 

exist prior to this action result in or 

have the potential to result in 

disproportionate and adverse human 

health or environmental effects on 

communities with EJ concerns. For this 

rulemaking, we conducted a proximity 

demographic analysis as well as 

baseline and post-control demographic 

risk analyses for the source category and 

whole facility. The analysis identified 

that 33.7 million people live within 10 

km of the 247 CMAS facilities analyzed. 

The percent of the population living 

within 10 km of the CMAS facilities is 

above the corresponding national 

average for the following demographic 

groups: Black, Hispanic or Latino, 

Other/Multiracial, people living below 

the poverty level, people living below 

two times the poverty level, people over 

the age of 25 without a high school 

diploma, and linguistic isolation. More 

details on this analysis are provided in 

section V.F.1 of this preamble. 

For existing sources, the EPA believes 

that this action is likely to reduce 

existing disproportionate and adverse 

effects on communities with EJ 

concerns. Groups experiencing baseline 

disparities are expected to see reduced 

exposures due to the proposed level of 

control for those processes emitting EtO 

and proposed management practices to 

control fugitive emissions from sources 

of HAP. In addition, this action 

proposes fenceline monitoring for EtO 

to ensure proper function of those 

management practices. If the proposed 

changes are implemented, we expect no 

people would be exposed to cancer risk 

levels greater than 100-in-1 million due 

to emissions from the CMAS categories. 

However, for individuals exposed to 

cancer risk less than 100-in-1 million, 

disparities remain in the proportion of 

different groups facing elevated risk. 

The controls proposed for this action do 

not reduce the risk of noncancer health 

impacts and thus the disparities remain 

the same. For more information on the 

controls proposed in this action, please 

refer to sections IV.A through IV.D of 

this preamble. 

For new sources, the EPA believes 

that it is not practicable to assess 

whether this action is likely to result in 

new disproportionate and adverse 

effects on communities with EJ 

concerns, because it is not possible to 

know the location of any future new 

sources. 

The information supporting this 

Executive Order review is contained in 

section V.F of this preamble. 

List of Subjects in 40 CFR Part 63 

Environmental protection, Air 

pollution control, Hazardous 

substances, Incorporation by reference, 

Reporting and recordkeeping 

requirements. 

Jane Nishida, 

Acting Administrator. 

[FR Doc. 2025–00685 Filed 1–21–25; 8:45 am] 

BILLING CODE 6560–50–P 


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