EO12866_Oil and Gas NSPS EG Climate Review 2060-AV15 and 2060-AV16 PROPOSAL 20210910
                                                                      6560-50-P
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 60
[EPA-HQ-OAR-2021-0317; FRL-XXXXX-XX-OAR]
RIN 2060-AV15 and 2060-AV16
Standards of Performance for New, Reconstructed, and Modified
Sources and Emissions Guidelines for Existing Sources: Oil and Natural Gas Sector Climate Review
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
SUMMARY: This proposed rule comprises three distinct actions under section 111 of the Clean Air Act (CAA) which are collectively intended to significantly reduce emissions of greenhouse gases (GHGs) and other harmful air pollutants from the Crude Oil and Natural Gas source category. First, the EPA proposes to revise the new source performance standards (NSPS) for GHGs and volatile organic compounds (VOCs) for the Crude Oil and Natural Gas source category under the CAA section 111(b) to reflect the Agency's most recent review of the feasibility and cost of reducing emissions from these sources. Second, this action proposes emissions guidelines (EG) under CAA section 111(d), for states to follow in developing, submitting, and implementing state plans to establish performance standards to limit GHGs from existing sources (designated facilities) in the Crude Oil and Natural Gas source category. Third, this action proposes to implement regulatory changes resulting from the June 30, 2021, joint resolution of disapproval of the final rule titled "Oil and Natural Gas Sector: Emission Standards for New, Reconstructed, and Modified Sources Review," 85 FR 57018 (September 14, 2020), enacted pursuant to the Congressional Review Act (CRA), and to address conflicting VOC standards and other modifications made in the final rule titled "Oil and Natural Gas Sector: Emission Standards for New, Reconstructed, and Modified Sources Reconsideration," 85 FR 57398 (September 15, 2020). This proposal responds to the President's Executive Order (EO) 13990, "Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis," which directed the EPA to consider taking the actions proposed here (January 20, 2021).
DATES: Comments. Comments must be received on or before [INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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 [INSERT DATE 30 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER].
	Public hearing: The EPA will hold a virtual public hearing on [INSERT DATE 15 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] and [INSERT DATE 16 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. See SUPPLEMENTARY INFORMATION for information on the hearing.
ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-OAR-2021-0317                  by any of the following methods:
 Federal eRulemaking Portal: https://www.regulations.gov/ (our preferred method). Follow the online instructions for submitting comments.
 Email<EMAIL_ADDRESS>Include Docket ID No. EPA-HQ-OAR-2021-0317                in the subject line of the message.
 Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-2021-0317.
 Mail: U.S. Environmental Protection Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2021-0317, 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 "Public Participation" heading of the SUPPLEMENTARY INFORMATION section of this document. Out of an abundance of caution for members of the public and our staff, the EPA Docket Center and Reading Room are closed to the public, with limited exceptions, to reduce the risk of transmitting COVID-19. Our Docket Center staff will continue to provide remote customer service via email, phone, and webform. We encourage the public to submit comments via https://www.regulations.gov/ or email, as there may be a delay in processing mail and faxes. Hand deliveries and couriers may be received by scheduled appointment only. For further information on EPA Docket Center services and the current status, please visit us online at https://www.epa.gov/dockets.
 FOR FURTHER INFORMATION CONTACT: For questions about this proposed action, contact Ms. Karen Marsh, Sector Policies and Programs Division (E143-05), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; and email address<EMAIL_ADDRESS>or Ms. Amy Hambrick, Sector Policies and Programs Division (E143 - 05), Office of Air Quality Planning and Standards, Environmental Protection Agency, Research Triangle Park, North Carolina 27711, telephone number: (919) 541 - 0964; facsimile number: (919) 541 - 3470; email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
Participation in virtual public hearing. Please note that the EPA is deviating from its typical approach for public hearings, because the President has declared a national emergency. Due to the current Centers for Disease Control and Prevention (CDC) recommendations, as well as state and local orders for social distancing to limit the spread of COVID-19, the EPA cannot hold in-person public meetings at this time.
The public hearing will be held via virtual platform on [INSERT DATE 15 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER], and [INSERT DATE 16 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER], and will convene at 11:00 a.m. Eastern Time (ET) and conclude at 9:00 p.m. ET each day. On each hearing day, the EPA may close a session 15 minutes after the last pre-registered speaker has testified if there are no additional speakers.The EPA will announce further details at https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-industry. If the EPA receives a high volume of registrations for the public hearing, we may continue the public hearing on [INSERT DATE 17 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. The EPA does not intend to publish a document in the Federal Register announcing the potential addition of a third day for the public hearing or any other updates to the information on the hearing described in this document. Please monitor https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-industry for any updates to the information described in this document, including information about the public hearing. For information or questions about the public hearing, please contact the public hearing team at<PHONE_NUMBER> or by email at<EMAIL_ADDRESS>
The EPA will begin pre-registering speakers for the hearing upon publication of this document in the Federal Register. The EPA will accept registrations on an individual basis. To register to speak at the virtual hearing, follow the directions at https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-industry or contact the public hearing team at<PHONE_NUMBER> or by email at<EMAIL_ADDRESS>The last day to pre-register to speak at the hearing will be [INSERT DATE 9 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. Prior to the hearing, the EPA will post a general agenda that will list pre-registered speakers in approximate order at: https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-industry.
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 5 minutes to provide oral testimony. The EPA encourages commenters to provide the EPA with a copy of their oral testimony electronically (via email) by emailing it to<EMAIL_ADDRESS>and<EMAIL_ADDRESS>The EPA also recommends submitting the text of your 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.
If you require the services of an interpreter or a special accommodation such as audio description, please pre-register for the hearing with the public hearing team and describe your needs by [INSERT DATE 7 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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-2021-0317. All 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-2021-0317. 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 information that you consider to be CBI or otherwise protected through https://www.regulations.gov/ or email. This type of information should be submitted by mail 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.
The EPA is temporarily suspending its Docket Center and Reading Room for public visitors, with limited exceptions, to reduce the risk of transmitting COVID-19. Our Docket Center staff will continue to provide remote customer service via email, phone, and webform. We encourage the public to submit comments via https://www.regulations.gov/ as there may be a delay in processing mail and faxes. Hand deliveries or couriers will be received by scheduled appointment only. For further information and updates on EPA Docket Center services, please visit us online at https://www.epa.gov/dockets.
The EPA continues to carefully and continuously monitor information from the CDC, local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19.
Submitting CBI. Do not submit information containing CBI to the EPA through https://www.regulations.gov/ or email. 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, mark the outside of the digital storage media as CBI and then 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. 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 CFR part 2. Send or deliver information identified as CBI only to the following address: OAQPS Document Control Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2021-0317. Note that written comments containing CBI  submitted by mail may be delayed and no hand deliveries will be accepted.
      Preamble acronyms and abbreviations. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:
ACE	Affordable Clean Energy rule
AEO	Annual Energy Outlook
AMEL	alternate means of emissions limitation
ANGA	American Natural Gas Alliance
ANSI	American National Standards Institute
APCD	air pollution control devices
API	American Petroleum Institute
ARPA-E	Advanced Research Projects Agency-Energy
ASME	American Society of Mechanical Engineers
ASTM	American Society for Testing and Materials
AVO	audio, visual, olfactory
BACT	best achievable control technology
BOEM	Bureau of Ocean Energy Management
BLM	Bureau of Land Management
BMP	best management practices
boe	barrels of oil equivalents
BSER	best system of emission reduction
BTEX	benzene, toluene, ethylbenzene and xylenes
CAA          	Clean Air Act
CBI	Confidential Business Information
CDC	Center for Disease Control
CDX	EPA's Central Data Exchange
CEDRI	Compliance and Emissions Data Reporting Interface
CFR          	Code of Federal Regulations
CH4	methane
cm	centimeter
CPI	consumer price index
CPI-U	consumer price index urban
CO	carbon monoxide
COPD	chronic obstructive pulmonary desease
CO2	carbon dioxide
CO2 Eq.	carbon dioxide equivalent
COA	condition of approval
COS	carbonyl sulfide
CRA	Congressional Review Act
CS2	carbon disulfide
CVS	closed vent systems
DC	direct current
DOE	Department of Energy
DOI	Department of the Interior
DOT	Department of Transportation
EAV	equivalent annualized value
EDF		      Environmental Defense Fund
EG                         emission guidelines
ECOS	                  Environmental Council of the States
EGU		      electricity generating units
EIA	U.S. Energy Information Administration
EJ	environmental justice
EO	Executive Order
EPA          	Environmental Protection Agency
ERT	Electronic Reporting Tool
FERC	The U.S. Federal Energy Regulatory Commission
fpm	feet per minute
GC	gas chromatograph
GHGs	greenhouse gases
GHGI	Inventory of U.S. Greenhouse Gas Emissions and Sinks
GHGRP	Greenhouse Gas Reporting Program
GRI	Gas Research Institute
GWP	global warning potential
HAP      	hazardous air pollutant(s)
HC	hydrocarbons
HFC	hydrofluorocarbons
H2S	hydrogen sulfide
ICR	Information Collection Request
IOGCC	Interstate Oil and Gas Compact Commission
IPCC	Intergovernmental Panel on Climate Change
IR	infrared
IRFA	initial regulatory flexibility analysis
kt	kilotons
kg	kilograms
low-e	low emission
LDAR 	leak detection and repair
Mcf 	thousand cubic feet
MMT	million metric tons
MRR	monitoring, recordkeeping, and reporting
MW	megawatt
NAAQS        	National Ambient Air Quality Standards
NAICS        	North American Industry Classification System
NCA4	2017-2018 Fourth National Climate Assessment
NEI	National Emissions Inventory
NEMS	National Energy Modeling System
NESHAP 	National Emissions Standards for Hazardous Air Pollutants
NGL	natural gas liquid
NGO	non-governmental organization
NOAA	National Oceanic and Atmospheric Administration
NOx	nitrogen oxides
NSPS	new source performance standards
NTTAA        	National Technology Transfer and Advancement Act
OCSLA 	The Outer Continental Shelf Lands Act
OAQPS 	Office of Air Quality Planning and Standards
OIG	Office of the Inspector General
OGI	optical gas imaging
OMB          	Office of Management and Budget
PE	professional engineer
PFCs	perfluorocarbons
PHMSA	hazardous materials safety administration
PM	particulate matter
PM2.5		         PM with a diameter of 2.5 micrometers or less
ppb	parts per billion
ppm	parts per million
PRA	Paperwork Reduction Act
PRD	pressure release device
PRV	pressure release valve
PSD	Prevention of Significant Deterioration
psig	pounds per square inch gauge
PTE 	potential to emit
PV	present value
REC 	reduced emissions completion
RFA	Regulatory Flexibility Act
RIA	Regulatory Impact Analysis
RTC	response to comments
SBAR	Small Business Advocacy Review
SC-CH4	social cost of methane
SCF	significant contribution finding
scf	standard cubic feet
scfh	standard cubic feet per hour
scfm 	standard cubic feet per minute
SF6	sulfur hexafluoride
SIP	state implementation plan
SO2	sulfur dioxide
SOx	sulfur oxides
tpy          	tons per year
D.C. Circuit	U.S. Court of Appeals for the District of Columbia Circuit
TAR	Tribal Authority Rule
TIP	Tribal Implementation Plan
TSD	technical support document
TTN 		      Technology Transfer Network
UAS	unmanned aircraft systems
UIC 		      underground injection control
UMRA	      Unfunded Mandates Reform Act
U.S.		      United States
USGCRP	U.S. Global Change Research Program
USGS	U.S. Geologic Survey
VCS 	Voluntary Consensus Standards
VOC	volatile organic compounds
VRD	vapor recovery device
VRU	vapor recovery unit

      Organization of this document. The information in this preamble is organized as follows:

I. Executive Summary
A. Purpose of the Regulatory Action
B. Summary of the Major Provisions of this Regulatory Action
C. Costs and Benefits
II. General Information
A. Does this action apply to me?
B. How do I obtain a copy of this document, background information, other related information?
III. Crude Oil and Natural Gas Emissions and Climate Change
A. Impacts of GHGs, VOC and SO2 Emissions on Public Health and Welfare
B. Oil and Natural Gas Industry and Its Emissions
IV. Statutory Background and Regulatory History
A. Statutory Background of CAA sections 111(b), 111(d) and General Implementing Regulations
B. What is the regulatory history and litigation background of NSPS and EG for the oil and natural gas industry?
C. Effect of the CRA.
V. Related Emissions Reduction Efforts
 A. Related State Actions and Other Federal Actions Regulating Oil and Natural Gas Sources
B. Industry and Voluntary Actions to Address Climate Change
VI. Environmental Justice Considerations, Implications, and Stakeholder Outreach
A. Environmental Justice and the Impacts of Climate Change
B. Impacted Stakeholders
C. Outreach and Engagement
D. Environmental Justice Considerations
VII. Other Stakeholder Outreach
A. Educating the Public, Listening Sessions, and Stakeholder Outreach
B. EPA Methane Detection Technology Workshop
C. How this information is being considered in this proposal?
 VIII. Legal Basis for Proposal
 A. Recent History of the EPA's Regulation of Oil and Gas Sources and Congress's Response
 B. Implications of Congress's Disapproval of the 2020 Policy Rule
 C. Alternative Conclusion Affirming the Legal Interpretations in the 2016 Rule
 D. Impacts on Regulation of Methane Emissions from Existing Sources
 IX. Overview of Control and Control Costs
 A. Control of Methane and VOC Emissions in the Crude Oil and Natural Gas Source Category - Overview
 B. How does EPA evaluate control costs in this action?
 X. Summary of Proposed Action for NSPS OOOO and NSPS OOOOa
 A. Amendments to Fugitive Emissions Monitoring Frequency
 B. Technical and Implementation Amendments
 XI. Summary of Proposed NSPS OOOOb and EG OOOOc
 A. Fugitive Emissions from Well Sites and Compressor Stations
 B. Storage Vessels
 C. Pneumatic Controllers
 D. Well Liquids Unloading Operations
 E. Reciprocating Compressors
 F. Centrifugal Compressors
 G. Pneumatic Pumps
 H. Equipment Leaks at Natural Gas Processing Plants
 I. Well Completions
 J. Sweetening Units
 K. Centralized Production Facilities
 L. Recordkeeping and Reporting
 M. Prevention of Significant Deterioration and Title V Permitting
 XII. Rationale for Proposed NSPS OOOOb and EG OOOOc
 A. Proposed Standards for Fugitive Emissions from Well Sites and Compressor Stations
 B. Proposed Standards for Storage Vessels
 C. Proposed Standards for Pneumatic Controllers
 D. Proposed Standards for Well Liquids Unloading Operations
 E. Proposed Standards for Reciprocating Compressors
 F. Proposed Standards for Centrifugal Compressors
 G. Proposed Standards for Pneumatic Pumps
 H. Proposed Standards for Equipment Leaks at Natural Gas Processing Plants
 I. Proposed Standards for Well Completions
 J. Proposed Standards for Sweetening Units
 K. Proposed Standards for Recordkeeping and Reporting
 XIII. Solicitations for Comment on Additional Emission Sources and Definitions
A. Associated Gas
B. Abandoned Wells
C. Pigging Operations and Related Blowdown Activities
D. Tank Truck Loading
E. Control Device Efficiency and Operation
F. Definition of Hydraulic Fracturing
 XIV. State, Tribal, and Federal Plan Development for Existing Sources
A. Overview
B.  Components of EG
C. Establishing Standards of Performance in State Plans
D. Components of State Plan Submission
E. Timing of State Plan Submissions and Compliance Times
F. EPA Action on State Plans and Promulgation of Federal Plans
G. Tribes and The Planning Process Under CAA Section 111(d)
XV. Prevention of Significant Deterioration and Title V Permitting                                                                 A. Overview
B. Applicability of Tailoring Rule Thresholds under the PSD Program                                                                   C. Implications for Title V Program
XVI. Impacts of This Proposed Rule
A. What are the air impacts?
B. What are the energy impacts?
C. What are the compliance costs?
D. What are the economic and employment impacts?
E. What are the benefits of the proposed standards?
XVII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review
B. Paperwork Reduction Act (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 Indian Tribal Governments
G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks
H. Executive Order 13211: Actions Concerning Regulations that Significantly Affect Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act (NTTAA)
J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations

I. Executive Summary
A. Purpose of the Regulatory Action
      This proposed rulemaking takes a significant step forward in mitigating climate change and improving human health by reducing GHG and VOC emissions from the Oil and Natural Gas Industry, specifically the Crude Oil and Natural Gas source category. The Oil and Natural Gas Industry is the United States' largest industrial emitter of methane. Human emissions of methane, a potent GHG, are responsible for about one third of the warming due to well-mixed GHGs, the second most important human warming agent after carbon dioxide. According to the Intergovernmental Panel on Climate Change (IPCC), strong, rapid, and sustained methane reductions are critical to reducing near-term disruption of the climate system and a vital complement to carbon dioxide (CO2) reductions critical in limiting the long-term extent of climate change and its destructive impacts. The Oil and Natural Gas Industry also emits other health-harming pollutants in varying concentrations and amounts, including CO2, VOC, sulfur dioxide (SO2), nitrogen oxide (NOx), hydrogen sulfide (H2S), carbon disulfide (CS2), and carbonyl sulfide (COS), as well as, benzene, toluene, ethylbenzene and xylenes (this group is commonly referred to as ``BTEX''), and n-hexane.
      Under the authority of CAA section 111, this rulemaking proposes comprehensive standards of performance for GHG emissions (in the form of methane limitations) and VOC emissions for new, modified, and reconstructed sources in the Crude Oil and Natural Gas source category, including the production, processing, transmission and storage segments. For designated facilities (existing sources), this rulemaking proposes EG containing presumptive standards for GHG in the form of methane limitations. When finalized, states shall utilize these EG to submit to the EPA plans that establish standards of performance for designated facilities and provide for implementation and enforcement of such standards. The EPA will provide support for states in developing their plans to reduce methane emissions from designated facilities within the Crude Oil and Natural Gas source category.
      The EPA is proposing these actions in accordance with its legal obligations and authorities following a review directed by EO 13990, "Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis," issued on January 20, 2021. The EPA intends for these proposed actions to address the far-reaching harmful consequences and real economic costs of climate change. According to the IPCC, "It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred." These changes have led to increases in heat waves and wildfire weather, reductions in air quality, more intense hurricanes and rainfall events, and rising sea level. These changes, along with future projected changes, endanger the physical survival, health, economic well-being, and quality of life of people living in America, especially those in the most vulnerable communities.
      Methane is both the main component of natural gas and a potent GHG. One ton of methane in the atmosphere has 80 times the warming impact of a ton of CO2, and also contributes to the creation of ground-level ozone which is another greenhouse gas. Methane has a global warming potential (GWP) of almost 30 which means that the emissions of one ton of methane has approximately as much climate impact over a 100-year period as the emissions of almost 30 tons of carbon dioxide. The IPCC AR6 assessment found that "Over time scales of 10 to 20 years, the global temperature response to a year's worth of current emissions of SLCFs (short lived climate forcer) is at least as large as that due to a year's worth of CO2 emissions", though they also cautioned that "The effects of the SLCFs decay rapidly over the first few decades after pulse emission. Consequently, on time scales longer than about 30 years, the net long-term temperature effects of sectors and regions are dominated by CO2." The IPCC estimated that, depending on the reference scenario, collective reductions in these SLCFs (methane, ozone precursors, and HFCs) could reduce warming by 0.2 degrees Celsius (°C) in 2040 and 0.8°C by the end of the century, which is important in the context of keeping warming to well below 2°C. As methane is the most important SLCF, this makes methane mitigation one of the best opportunities for reducing near term warming. Human emissions have already more than doubled atmospheric methane concentrations since 1750, and that concentration has been growing larger at record rates in recent years. In the absence of additional reduction policies, methane emissions are projected to continue rising through at least 2040.
      Methane's radiative efficiency means that reductions now in methane emissions can help reduce near-term warming. As natural gas is comprised primarily of methane, every natural gas leak or intentional release through venting or other process constitutes a release of methane. Reducing human-caused methane emissions, such as controlling natural gas leaks and releases as proposed in these actions, would contribute substantially to global efforts to limit temperature rise, aiding efforts to remain well below 2°C above pre-industrial levels. See preamble section III for further discussion on the Crude Oil and Natural Gas Emissions and Climate Change, including discussion of the GHGs, VOCs and SO2 Emissions on Public Health and Welfare.
      Methane and VOC emissions from the Crude Oil and Natural Gas source category are the result of industry operations, such as venting or under-performing flaring of associated gas from oil wells, oil storage vessels, and production-related equipment such as natural gas dehydrators, pig launchers and receivers, and pneumatic devices. As natural gas moves through the interconnected system, emissions primarily result from intentional venting, unintentional gas carry through, routine maintenance, unintentional fugitive emissions, flaring, malfunctions, abnormal process conditions, and system upsets. But technical innovations have produced a range of technologies and best practices to monitor, eliminate or minimize these emissions, which in many cases have the benefit of reducing multiple pollutants at once and recovering saleable product. These technologies and best practices have been deployed by individual oil and natural gas companies, required by state regulations, or reflected in regulations issued by the EPA and other federal agencies.
      In this action, the EPA has taken a comprehensive analysis of the most attainable data from emission sources in the Crude Oil and Natural Gas source category and the latest available information on control measures and techniques to identify achievable, cost-effective measures to significantly reduce emissions, consistent with the requirements of section 111 of the CAA. If finalized and implemented, the actions proposed in this rulemaking would lead to significant and cost-effective reductions in climate and health-harming pollution and encourage development and deployment of innovative technologies to further reduce this pollution in the Crude Oil and Natural Gas source category. The actions proposed in this rulemaking would:
 update, strengthen, and expand current requirements under CAA section 111(b) for methane and VOC emissions from new, modified, and reconstructed facilities,
 limit methane, and VOC emissions from new, modified, and reconstructed facilities that are not currently regulated under CAA section 111(b),
 establish the first nationwide EG for states to limit methane pollution from existing designated facilities in the source category under CAA section 111(d), and
 take comment on additional sources of pollution that, with understanding gained from more information, may offer opportunities for emission reductions in a potential supplemental rulemaking proposal under both CAA section 111(b) and (d).
      In developing this proposal, the EPA applied lessons learned from states' regulatory efforts; reviewed information about new and developing technologies, reviewed peer-reviewed research of emission measurement campaigns across the United States (U.S.); built upon emission reduction efforts of leading companies; considered communities' concerns, especially those with environmental justice implications; and used information and ideas collected through the EPA's extensive pre-proposal outreach. The EPA recognizes that several states and other federal agencies currently regulate the Oil and Natural Gas Industry. The EPA also recognizes that these state and other federal agency regulatory programs have matured since the EPA began implementing the current NSPS requirements in 2012 and 2016. The EPA further acknowledges the technical innovations that the Oil and Natural Gas Industry has made during the past decade; this industry operates at a fast pace and changes constantly as technology evolves. The EPA commends these efforts and recognizes states for their innovative standards, alternative compliance options, and implementation strategies, and intends these actions to build upon progress made by certain states and federal agencies in reducing GHG and VOC emissions. See preamble section V for fuller discussion of Related State Actions and Other Federal Actions Regulating Oil and Natural Gas Sources and Industry and Voluntary Actions to Address Climate Change.
      The EPA also considered community and environmental justice implications in the development of this proposal, and sought to ensure equitable treatment and meaningful involvement of all people regardless of race, color, national origin, or income in the process. The EPA engaged and consulted with the public, including representatives of frontline communities that are directly affected by and particularly vulnerable to the climate and health impacts of pollution from this source category, through interactions such as webinars, listening sessions and meetings. These opportunities allowed the EPA to hear directly from the public, especially overburdened and underserved communities, on the development of the proposed rule and to factor these concerns into this proposal. For example, in addition to establishing EG that extend fugitive emission requirements to existing oil and natural gas facilities, the EPA is proposing to expand leak detection programs already in effect for new sources to include known sources of large emission events and proposing to require more frequent monitoring at sites with more emissions. The EPA is also taking comment on ways to allow use of cutting-edge technologies for detecting methane and VOC emissions, including credible surveys undertaken by communities and other third parties. The sets of measures in this proposal, if finalized, would help reduce health impacts on communities adjacent to these emission sources. A full discussion of the Environmental Justice Considerations, Implications, and Stakeholder Outreach can be found in section VI of the preamble. A full discussion of Other Stakeholder Outreach is found in section VII of the preamble.
      The EPA believes that an "all-hands-on-deck" effort across all states and all federal agencies is essential to meaningfully address climate change. As the federal agency with primary responsibility to protect human health and the environment, the EPA has the unique responsibility and authority to regulate harmful air pollutants emitted by the Crude Oil and Natural Gas source category. The EPA recognizes that states and other federal agencies regulate in accordance with their respective legal authorities and within their respective jurisdictions, and collectively do not fully and consistently address the range of sources and emission reduction measures contained in this proposal. Direct Federal regulation of methane from new, reconstructed, and modified sources in this category, combined with approved state plans that are consistent with the EPA's presumptive standards for designated facilities (existing sources), will help level the regulatory playing field, help promote technological innovation, and reduce both climate- and other health-harming pollution from a large number of sources that either are unregulated or from which additional, cost-effective reductions are available. The EPA is committed to acting within its authority to provide opportunities for aligning its programs with other existing state and Federal programs in order to reduce unnecessary regulatory redundancy where appropriate, and the EPA will continue dialogue with its federal partners to minimize potential regulatory conflicts and regulatory burden on the part of owners and operators.
      Throughout this action, unless noted otherwise, the EPA is requesting comments on all aspects of the proposal to enable the EPA to develop a final rule that achieves the greatest possible reductions in methane and VOC emissions while being achievable and cost effective. In light of certain innovative elements of this proposed rulemaking and the potential of including additional sources as affected facilities for regulation, the EPA is considering issuing a supplemental proposed rule to allow the Agency to refine or expand this proposed rulemaking as appropriate in response to comments and information received in response.
B. Summary of the Major Provisions of this Regulatory Action
      This proposed rulemaking includes three distinct actions under the CAA that are each severable from the other. First, pursuant to CAA 111(b)(1)(B), has reviewed, and is proposing revisions of, the standards of performance for the Crude Oil and Natural Gas source category published in 2016 and amended in 2020, codified at 40 CFR part 60, subpart OOOOa - Standards of Performance for Crude Oil and Natural Gas Facilities for which Construction, Modification or Reconstruction Commenced After September 18, 2015 (2016 NSPS OOOOa). Specifically, the EPA is proposing to update, strengthen, and expand the current requirements under CAA section 111(b) for methane and VOC emissions from sources that commenced construction, modification, or reconstruction after [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER]. These proposed standards of performance will be in a new subpart, 40 CFR part 60, subpart OOOOb (NSPS OOOOb), and also include standards for emission sources previously not regulated under the 2016 NSPS OOOOa.
      Second, pursuant to CAA 111(d), the EPA is proposing the first nationwide EG for states to limit methane pollution from designated facilities in the Crude Oil and Natural Gas source category. The EG being proposed in this rulemaking will be in a new subpart, 40 CFR part 60, subpart OOOOc (EG OOOOc). The EG are designed to inform states in the development, submittal, and implementation of state plans that are required to establish standards of performance for GHGs from their designated facilities in the Crude Oil and Natural Gas source category.
      Third, this rulemaking proposes to implement regulatory changes resulting from the June 30, 2021, joint resolution of disapproval of the final rule titled "Oil and Natural Gas Sector: Emission Standards for New, Reconstructed, and Modified Sources Review," 85 FR 57018 (September 14, 2020) (2020 Policy Rule), enacted pursuant to the CRA, and to address (1) certain resulting inconsistencies between the VOC and methane standards resulting from the CRA, and (2) revisiting certain determinations made in the final rule titled "Oil and Natural Gas Sector: Emission Standards for New, Reconstructed, and Modified Sources Reconsideration," 85 FR 57398 (September 15, 2020) (2020 Technical Rule), particularly with respect to fugitive emissions monitoring at low production well sites and gathering and boosting stations. As described below, the EPA also proposed to rescind provisions of the 2020 Technical Rule that were not supported by the record for that rule, or by our subsequent information and analysis. For this third element of the proposal, the EPA is proposing amendments to its 2012 NSPS titled "Subpart OOOO-Standards of Performance For Crude Oil and Natural Gas Facilities for which Construction, Modification, or Reconstruction Commenced After August 23, 2011, and on or Before September 18, 2015" (2012 NSPS OOOO) and to its 2016 NSPS OOOOa (as amended by 2020 Technical Rule).
      As CAA section 111(a)(1) requires, the standards of performance being proposed in this action reflect "the degree of emission limitation achievable through the application of the best system of emission reduction [BSER] which (taking into account the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirement) the Administrator determines has been adequately demonstrated." This action further proposes EG for designated facilities, under which states must submit plans which establish standards of performance that reflect the degree of emission limitation achievable through application of the BSER, as identified in the final EG. In this proposed rulemaking, we evaluated potential control measures available for the affected facilities and the achievable emission reductions and employed multiple approaches to evaluate the reasonableness of control costs associated with the options under consideration. For example, in evaluating controls for reducing VOC and methane emissions from new sources, we considered a control measure's cost-effectiveness under both a "single pollutant cost-effectiveness" approach and a "multipollutant cost-effectiveness" approach, in order to appropriately take into account that the systems of emission reduction considered in this rule typically achieve reductions in multiple pollutants at once and secure a multiplicity of climate and public health benefits. For a detailed discussion of the EPA's consideration of this and other BSER statutory elements, please see sections IV and IX of this preamble.
TABLE 1: APPLICABILITY DATES FOR PROPOSED SUBPARTS ADDRESSED IN THIS PROPOSED ACTION
                                    Subpart
                                  Source Type
                               Applicable Dates
40 CFR part 60, subpart OOOOa
New, modified, or reconstructed sources
After September 18, 2015 and on or before [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER]
40 CFR part 60, subpart OOOOb
New, modified, or reconstructed sources
After [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER]
40 CFR part 60, subpart OOOOc
Existing sources
On or before [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER]

1. Proposed Standards for New, Modified and Reconstructed Sources after [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER] (Proposed NSPS OOOOb)
      As described in sections XI and XII of this preamble, under the authority of CAA section 111(b)(1)(B) the EPA has reviewed the VOC, GHG (in the form of limitations on methane), and SO2 standards in the 2016 NSPS OOOOa (as amended in 2020 by the Technical Rule). Based on its review, the EPA is proposing revisions to the standards for certain emissions sources to reflect the updated BSER for those affected sources. Where our analyses show that the BSER for an affected source remains the same, the EPA is proposing to retain the current standard for that affected source. In addition, the EPA is proposing methane and VOC standards for several new sources that are currently unregulated. The proposed NSPS described above would apply to new, modified, and reconstructed emission sources across the Crude Oil and Natural Gas source category, including the production, processing, transmission, and storage segments, for which construction, reconstruction, or modification commenced after [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER], which is the date of publication of the proposed revisions to the NSPS. In particular, this action proposes to retain the 2016 NSPS OOOOa SO2 performance standard for sweetening units and the 2016 OOOOa VOC and methane performance standard for well completions; proposes revisions to strengthen the 2016 NSPS OOOOa VOC and methane standards addressing fugitive emissions from well sites and compressor stations, storage vessels, pneumatic controllers, reciprocating compressors, centrifugal compressors, pneumatic pumps, and equipment leaks at natural gas processing plants; and proposes new VOC and methane standards for well liquids unloading operations and intermittent vent pneumatic controllers previously not regulated in the 2016 NSPS OOOOa. A summary of the proposed BSER determination and proposed NSPS for new, modified, and reconstructed sources (NSPS OOOOb) is presented in Table 2. See sections XI and XII of this preamble for a complete discussion of BSER determination and proposed NSPS requirements.
      This proposal also solicits certain information relevant to the potential identification of additional emissions sources as affected facilities. Specifically, the EPA is evaluating the potential for establishing standards for flaring and venting of associated gas, abandoned and unplugged wells, blowdown emissions associated with pipeline pig launchers and receivers, and tank truck loading operations. While the EPA has assessed these sources based on currently available information, we have determined that we need additional information to evaluate BSER and to propose NSPS for these emissions sources. A full discussion of the solicitation for comment regarding these additional emission sources is found in section XIII of the preamble.
2. Proposed EG for Sources Constructed Prior to ([INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER] (Proposed EG OOOOc)
      As described in sections XI and XII of this preamble, under the authority of CAA section 111(d), the EPA is proposing the first nationwide EG for GHG (in the form of methane limitations) for the Crude Oil and Natural Gas source category, including the production, processing, transmission, and storage segments (EG OOOOc). When the EPA establishes NSPS for a source category, the EPA is required to issue EG to reduce emissions of certain pollutants from existing sources in that same source category. In such circumstances, under CAA section 111(d), the EPA must issue regulations to establish procedures under which states submit plans to establish, implement, and enforce standards of performance for existing sources for certain air pollutants to which a federal NSPS would apply if such existing source were a new source. Thus, the issuance of CAA section 111(d) final EG does not impose binding requirements directly on sources but instead provides requirements for states in developing their plans. Although state plans bear the obligation to establish standards of performance, under CAA sections 111(a)(1) and 111(d), those standards of performance must reflect the degree of emission limitation achievable through the application of the BSER as determined by the Administrator, unless a state chooses to take into account remaining useful life and other factors in applying a standard of performance to a particular source, consistent with the CAA, the EPA's implementing regulations, and the final EG.
      In this action, the EPA is proposing BSER determinations and the degree of limitation achievable through application of the BSER for certain existing equipment, processes, and activities across the Crude Oil and Natural Gas source category. Section XIV of this preamble discusses the components of EG, including the steps, requirements, and considerations associated with the development, submittal, and implementation of state, tribal, and federal plans, as appropriate. For the EG, the EPA is proposing to translate the degree of emission limitation achievable through application of the BSER (i.e., level of stringency) into presumptive standards that states may use in the development of state plans for specific designated facilities. By doing this, the EPA has formatted the proposed EG such that if a state chooses to adopt these presumptive standards, once finalized, as the standards of performance in a state plan, the EPA could approve such a plan as meeting the requirements of CAA section 111(d) and the finalized EG, assuming that the plan meets all other applicable requirements. In this way, the presumptive standards included in the EG serve a function similar to that of a model rule, because they are intended to assist states in developing their plan submissions by providing states with a starting point for standards that are based on general industry parameters and assumptions. The EPA believes that providing these presumptive standards will create a streamlined approach for states in developing plans and the EPA in evaluating state plans. However, the EPA's action on each state plan submission is carried out via rulemaking, which includes public notice and comment. Inclusion of presumptive standards in the EG does not seek to pre-determine the outcomes of any future rulemaking.
      Designated facilities located in Indian country would not be encompassed within a state's CAA section 111(d) plan. Instead, an eligible tribe that has one or more designated facilities located in its area of Indian country would have the opportunity, but not the obligation, to seek authority and submit a plan that establishes standards of performance for those facilities on its tribal lands. If a tribe does not submit a plan, or if the EPA does not approve a tribe's plan, then the EPA has the authority to establish a federal plan for that tribe. A summary of the proposed EG for existing sources (EG OOOOc) for the oil and natural gas sector is presented in Table 3. See sections XI and XII of this preamble for a complete discussion of the proposed EG requirements.
      As discussed above for the proposed NSPS OOOOb, the EPA is considering including additional sources as affected facilities in a potential future supplemental rulemaking proposal under CAA section 111(b). The EPA is also considering including these additional sources as designated facilities under the EG in OOOOc in a potential future supplemental rulemaking proposal under CAA section 111(d). As with the proposed NSPS OOOOb, the EPA is evaluating the potential for establishing EG applicable to flaring and venting at wells producing associated gas, abandoned and unplugged wells, blowdown emissions associated with pipeline pig launchers and receivers, and tank truck loading operations (assuming the EPA establishes NSPS for these emissions points). As described in section XIII of this preamble, the EPA is soliciting information to assist in this effort.
3. Proposed Amendments to 2012 NSPS OOOO and 2016 NSPS OOOOa
      In this rulemaking, the EPA also is proposing amendments to its 2012 NSPS OOOO and 2016 NSPS OOOOa, in order to address the June 30, 2021, joint resolution under the CRA that disapproved the 2020 Policy Rule. By the terms of the CRA, the signing into law of the joint resolution of disapproval means that the 2020 Policy Rule is "treated as though [it] had never taken effect." 5 U.S.C. 801(f). Thus, the EPA is proposing to amend the regulatory text for the 2012 NSPS OOOO rule to reflect requirements for VOC emissions from sources in the transmission and storage segment that the 2020 Policy Rule had rescinded, and that the resolution of disapproval reinstated. See section VIII and section X of this preamble for further discussion on the Legal Basis for Proposal and the Summary of Proposed Action for NSPS OOOO and NSPS OOOOa.
      The EPA is further proposing to amend the regulatory text for the 2016 NSPS OOOOa to reflect requirements for methane emissions from sources in the production, processing, and transmission and storage segments that the 2020 Policy Rule had rescinded and that the resolution of disapproval reinstated. The EPA is also proposing certain additional modifications to the 2016 NSPS OOOOa to address certain amendments to the VOC standards for sources in the production and processing segments finalized in the 2020 Technical Rule. Because the methane standards for the production and processing segments and all standards for the transmission and storage segment were removed from the 2016 NSPS OOOOa via the 2020 Policy Rule prior to the finalization of the 2020 Technical Rule, the latter amendments apply only to the 2016 NSPS OOOOa VOC standards for the production and processing segments. In this proposed rulemaking, the EPA also is proposing to apply some of the 2020 Technical Rule amendments to the methane standards for all industry segments and to VOC standards for the transmission and storage segments in the 2016 NSPS OOOOa. These amendments are associated with the requirements for well completions, pneumatic pumps, closed vent systems, fugitive emissions, alternative means of emission limitation (AMELs), onshore natural gas processing plants, as well as other technical clarifications and corrections. The EPA also is proposing to repeal the amendments in the 2020 Technical Rule that (1) exempted low production well sites from monitoring fugitive emissions and (2) changed monitoring of VOC emissions at gathering and boosting compressor stations from quarterly to semiannual, which currently apply only to VOC standards (not methane standards) from the production and processing segments. A summary of the proposed amendments to the 2016 OOOOa NSPS is presented in section X of this preamble.
 TABLE 2: SUMMARY OF PROPOSED BSER AND PROPOSED STANDARDS OF PERFORMANCE FOR GHGS AND VOC (NSPS OOOOb)
 Affected Source
 Proposed BSER
 Proposed Standards of Performance for GHGs and VOCs
 Fugitive Emissions: Well Sites with Baseline Emissions >=15 tpy[1] Methane
 Monitoring and repair based on quarterly monitoring using OGI[2].

Quarterly OGI monitoring following Appendix K. (Optional quarterly EPA Method 21 monitoring with 500 ppm[3] defined as a leak).
 First attempt at repair within 30 days of finding fugitive emissions. Final repair within 30 days of first attempt.
 Fugitive Emissions: Well Sites with Baseline Emissions >=5 to <15 tpy Methane
 Monitoring and repair based on semiannual monitoring using OGI.

Semiannual OGI monitoring following Appendix K. (Optional semiannual EPA Method 21 monitoring with 500 ppm defined as a leak).

 First attempt at repair within 30 days of finding fugitive emissions. Final repair within 30 days of first attempt.
 Fugitive Emissions: Well Sites with Baseline Emissions >0 to <5 tpy Methane
 Calculate and maintain record of baseline methane emissions.
Calculate and maintain record of baseline methane emissions.
 Fugitive Emissions: Compressor Stations
 Monitoring and repair based on quarterly monitoring using OGI.

Quarterly OGI monitoring following Appendix K. (Optional quarterly EPA Method 21 monitoring with 500 ppm defined as a leak).

First attempt at repair within 30 days of finding fugitive emissions. Final repair within 30 days of first attempt.
 Storage Vessels: Tank Battery with PTE[4] of 6 tpy or More of VOC
 Capture and route to a control device.
95 percent reduction.
 Pneumatic Controllers: Subcategory 1 (at sites with onsite power available)
 Non-emitting pneumatic controllers.
VOC and methane emission bleed rate of zero.
 Pneumatic Controllers: Subcategory 2 (at sites where onsite power is not available -continuous bleed natural gas driven)
 Installation of low-bleed pneumatic controllers.
Natural gas bleed rate no greater than 6 scfh[5].
 Pneumatic Controllers: Subcategory 2 (at sites where onsite power is not available -intermittent natural gas driven)
 Monitor and repair through fugitive emissions program.
OGI monitoring and repair of emissions from controller malfunctions.
 Pneumatic Controllers: Natural Gas Processing Plants.
 Instrument air systems.
Zero natural gas bleed rate.
 Well Liquids Unloading
 Perform liquids unloading with zero methane or VOC emissions. If this is not feasible for safety or technical reasons, employ best management practices to minimize venting.
Each affected well that unloads liquids employ techniques or technology(ies) that eliminate or minimize venting of emissions during liquids unloading events to the maximum extent.

Co Proposal Options:

Option One- Affected facility would be defined as every well that undergoes liquids unloading.
-If the method is one that does not result in any venting to the atmosphere, maintain records specifying the technology or technique and record instances where an unloading event results in emissions.
-For unloading technologies or techniques that result in venting to the atmosphere, implement BMPs[6] to ensure that venting is minimized.
-Maintain BMPs as records, and record instances when they were not followed.

Option Two - Affected facility would be defined as every well that undergoes liquids unloading using a method that is not designed to totally eliminate venting.
 - -Wells that utilize non-venting methods would not be affected facilities that are subject to the NSPS OOOOb. Therefore, they would not have requirements other than to maintain records to demonstrate that they did not use non-venting methods and were not subject to NSPS OOOOb.
-The requirements for wells that use methods that vent would be the same as described above under Option 1.
 Wet Seal Centrifugal Compressors (except for those located at single well sites).
 Capture and route to a control device.
95 percent reduction.
 Reciprocating Compressors (except for those located at single well sites).
 Rod packing changeout based on annual monitoring (when measured leak rate exceeds 2 scfm[7]).
Replace the rod packing when measured leak rate exceeds 2 scfm based on the results of annual monitoring or route emissions from the rod packing to a process through a closed vent system under negative pressure.
 Pneumatic Pumps: Natural Gas Processing Plants.
 Instrument air systems in place of natural gas driven pumps.
Zero natural gas emissions.
 Pneumatic Pumps: Locations Other Than Natural Gas Processing Plants.
 Route to existing control device or process.
95 percent control if there is an existing control or process on site. 95 percent control not required if
(1) routed to an existing control that achieves less than 95 percent or (2) it is technically infeasible to route to the existing control device or process.
 Well Completions: Subcategory 1 (non-wildcat and non-delineation wells).
 Combination of REC[8] and the use of a completion combustion device.
REC in combination with a completion combustion device; venting in lieu of combustion where combustion would present safety hazards.

Initial flowback stage: Route to a storage vessel or completion vessel (frac tank, lined pit, or other vessel) and separator.

Separation flowback stage: Route all salable gas from the separator to a flow line or collection system, re-inject the gas into the well or another well, use the gas as an onsite fuel source or use for another useful purpose that a purchased fuel or raw material would serve. If technically infeasible to route recovered gas as specified above, recovered gas must be combusted. All liquids must be routed to a storage vessel or well completion vessel, collection system, or be re-injected into the well or another well.

The operator is required to have (and use) a separator onsite during the entire flowback period.
 Well Completions: Subcategory 2 (exploratory and delineation wells and low-pressure wells).
 Use of a completion combustion device.
The operator is not required to have a separator onsite. Either: (1) Route all flowback to a completion combustion device with a continuous pilot flame; or (2) Route all flowback into one or more well completion vessels and commence operation of a separator unless it is technically infeasible for a separator to function. Any gas present in
the flowback before the separator can function is not subject to control under this section. Capture and direct recovered gas to a completion combustion device with a continuous pilot flame.

For both options (1) and (2), combustion is not required in conditions that may result in a fire hazard or explosion, or where high heat emissions from a completion combustion device may negatively impact tundra, permafrost or waterways.
 Equipment Leaks at Natural Gas Processing Plants.
 LDAR[9] with bimonthly OGI.
 LDAR with OGI following procedures in Appendix K.
 Sweetening Units.
 Achieve SO2 emission reduction efficiency.
 Achieve required minimum SO2 emission reduction efficiency.
[1] tpy (tons per year)
[2] OGI (optical gas imaging)
[3] ppm (parts per million)
[4] PTE (potential to emit)
[5] scfh (standard cubic feet per hour)
[6] BMP (best management practices)
[7] scfm (standard cubic feet per minute)
[8] REC (reduced emissions completion)
9 LDAR (leak detection and repair)

 TABLE 3: SUMMARY OF PROPOSED BSER AND PROPOSED PRESUMPTIVE STANDARDS FOR GHGS FROM DESIGNATED FACILITIES (EG OOOOc)
 Designated Facility
 Proposed BSER
 Proposed Presumptive Standards for GHGs
 Fugitive Emissions: Well Sites >=15 tpy Methane
 Monitoring and repair based on quarterly monitoring using OGI.

Quarterly OGI monitoring following Appendix K. (Optional quarterly EPA Method 21 monitoring with 500 ppm defined as a leak).

 First attempt at repair within 30 days of finding fugitive emissions. Final repair within 30 days of first attempt.
 Fugitive Emissions: Well Sites >=5 to <15 tpy Methane
 Monitoring and repair based on semiannual monitoring using OGI.

Semiannual OGI monitoring following Appendix K. (Optional semiannual EPA Method 21 monitoring with 500 ppm defined as a leak).

 First attempt at repair within 30 days of finding fugitive emissions. Final repair within 30 days of first attempt.
 Fugitive Emissions: Well Sites >0 to <5 tpy Methane
 Calculate and maintain record of baseline methane emissions.
Calculate and maintain record of baseline methane emissions.
 Fugitive Emissions: Compressor Stations
 Monitoring and repair based on quarterly monitoring using OGI.

Quarterly OGI monitoring following Appendix K. (Optional quarterly EPA Method 21 monitoring with 500 ppm defined as a leak).

First attempt at repair within 30 days of finding fugitive emissions. Final repair within 30 days of first attempt.
 Storage Vessels: Tank Battery with PTE of 20 tpy or More of Methane
 Capture and route to a control device.
95 percent reduction.
 Pneumatic Controllers: Subcategory 1 (at sites with onsite power available)
 Non-emitting pneumatic controllers.
VOC and methane emission bleed rate of zero.
 Pneumatic Controllers: Subcategory 2 (at sites where onsite power is not available -continuous bleed natural gas driven)
 Installation of low-bleed pneumatic controllers.
Natural gas bleed rate no greater than 6 scfh.
 Pneumatic Controllers: Subcategory 2 (at sites where onsite power is not available -intermittent natural gas driven)
 Monitor and repair through fugitive emissions program.
OGI monitoring and repair of emissions from controller malfunctions.
 Pneumatic Controllers: Natural Gas Processing Plants.
 Instrument air systems.
Zero natural gas bleed rate.
 Wet Seal Centrifugal Compressors (except for those located at single well sites).
 Capture and route to a control device.
95 percent reduction.
 Reciprocating Compressors (except for those located at single well sites).
 Rod packing changeout based on annual monitoring (when measured leak rate exceeds 2 scfm).
Replace the rod packing when measured leak rate exceeds 2 scfm based on the results of annual monitoring or route emissions from the rod packing to a process through a closed vent system under negative pressure.
 Pneumatic Pumps: Natural Gas Processing Plants.
 Instrument air systems in place of natural gas driven pumps.
Zero natural gas emissions.
 Pneumatic Pumps: Locations Other Than Natural Gas Processing Plants.
 Route to existing control device or process.
95 percent control if there is an existing control or process on site. 95 percent control not required if
(1) routed to an existing control that achieves less than 95 percent or (2) it is technically infeasible to route to the existing control device or process.
 Equipment Leaks at Natural Gas Processing Plants.
 LDAR with bimonthly OGI.
 LDAR with OGI following procedures in Appendix K.

C. Costs and Benefits
	The EPA has projected the emissions reductions, benefits, and costs that may result from this proposed action. These results are presented in detail in the regulatory impact analysis (RIA) accompanying this proposal. The RIA focuses on the elements of the proposed rule that are likely to result in quantifiable cost or emissions changes compared to a baseline without the proposal. We estimated the cost, emissions, and benefit impacts for the 2023 to 2035 period. We present the present value (PV) and equivalent annual value (EAV) of costs, benefits, and net benefits of this action in 2019 dollars.
The projected national-level emissions reductions over the 2023 to 2035 period anticipated under the proposed requirements are presented in Table 4. Table 5 presents the PV and EAV of the projected benefits, costs, and net benefits over the 2023 to 2035 period under the proposed requirements using discount rates of 3 and 7 percent.
TABLE 4. PROJECTED EMISSIONS REDUCTIONS UNDER THE PROPOSED REQUIREMENTS, 2023-2035 TOTAL
                                   Pollutant
                    Emissions Reductions (2023-2035 Total)
Methane (million short tons)
                                     21.4
VOC (million short tons)
                                      6.8
Hazardous Air Pollutant (HAP) (million short tons)
                                      0.2
Methane (million metric tons CO2 Eq.)[a]
                                     484
a CO2 Eq. calculated using a global warming potential of 25.

TABLE 5. BENEFITS, COSTS, NET BENEFITS, AND EMISSIONS REDUCTIONS OF THE PROPOSED RULE, 2023 THROUGH 2035 (DOLLAR ESTIMATES IN BILLIONS OF 2019 DOLLARS)

                            3 Percent Discount Rate
                            7 Percent Discount Rate

                                      PV
                                      EAV
                                      PV
                                      EAV
Climate Benefits[b]
                                     $29
                                     $2.9
                                     $29
                                     $2.9
Net Compliance Costs
                                     $6.6
                                     $0.7
                                     $5.4
                                     $0.7
Compliance Costs
                                     $8.9
                                     $0.9
                                     $7.0
                                     $0.9
Value of Product Recovery
                                     $2.2
                                     $0.2
                                     $1.6
                                     $0.2
Net Benefits
                                      $22
                                     $2.3
                                     $24
                                     $2.2
                     Non-Monetized Benefits in this Table
Non-monetized climate benefits from 21.4 million short tons of methane reductions from 2023 to 2035

Health effects of PM2.5 and ozone exposure from 6.8 million short tons of VOC reductions from 2023 to 2035

Health effects of HAP exposure from 0.2 million short tons of HAP reductions from 2023 to 2035

Health effects of ozone exposure from 21.4 million short tons of methane reductions over the 2023 to 2035 period

                             Visibility impairment

                              Vegetation effects
[a] Rows may not appear to add correctly due to rounding.
[b] Climate benefits are based on reductions in methane emissions and are calculated using four different estimates of the social cost of methane (SC-CH4) (model average at 2.5 percent, 3 percent, and 5 percent discount rates; 95th percentile at 3 percent discount rate). For the presentational purposes of this table, we show the benefits associated with the average SC-CH4 at a 3 percent discount rate, but the Agency does not have a single central SC-CH4 point estimate. We emphasize the importance and value of considering the benefits calculated using all four SC-CH4 estimates; the present value (and equivalent annual value) of the additional benefit estimates range from $12 billion to $77 billion ($1.3 billion to $7.7 billion) over 2023 to 2035 for the proposed option. Please see Table 3-5 and Table 3-6 of the RIA for the full range of SC-CH4 estimates. As discussed in Chapter 3 of the RIA, a consideration of climate benefits calculated using discount rates below 3 percent, including 2 percent and lower, are also warranted when discounting intergenerational impacts. All net benefits are calculated using climate benefits discounted at 3 percent.

II. General Information
A. Does this action apply to me?
	Categories and entities potentially affected by this action include:
         TABLE 6. INDUSTRIAL SOURCE CATEGORIES AFFECTED BY THIS ACTION
Category
NAICS Code[1]
Examples of Regulated Entities
Industry
211120
Crude Petroleum Extraction.

211130
Natural Gas Extraction.

221210
Natural Gas Distribution.

486110
Pipeline Distribution of Crude Oil.

486210
Pipeline Transportation of Natural Gas.
Federal Government
. . . .
Not affected.
State/local/tribal government
. . . .
Not affected.
[1] North American Industry Classification System (NAICS).
      This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action. Other types of entities not listed in the table could also be affected by this action. To determine whether your entity is affected by this action, you should carefully examine the applicability criteria found in the final rule. If you have questions regarding the applicability of this action to a particular entity, consult the person listed in the FOR FURTHER INFORMATION CONTACT section, your air permitting authority, or your EPA Regional representative listed in 40 CFR 60.4 (General Provisions).
B. How do I obtain a copy of this document, background information, and other related information?
	In addition to being available in the docket, an electronic copy of the proposed action is available on the Internet. Following signature by the Administrator, the EPA will post a copy of this proposed action at https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-industry. Following publication in the Federal Register, the EPA will post the Federal Register version of the final rule and key technical documents at this same website. A redline version of the regulatory language that incorporates the proposed changes described in section X for NSPS OOOO and NSPS OOOOa is available in the docket for this action (Docket ID No. EPA-HQ-OAR-2021-0317). The EPA plans to propose the regulatory language for NSPS OOOOb and EG OOOOc through a supplemental action.
III. Crude Oil and Natural Gas Emissions and Climate Change
A. Impacts of GHGs, VOCs and SO2 Emissions on Public Health and Welfare
      As noted previously, the Oil and Natural Gas Industry emits a wide range of pollutants, including GHGs (such as methane and CO2), VOCs, SO2, NOX, H2S, CS2, and COS. See 49 FR 2636, 2637 (January 20, 1984). As noted below, to this point, the EPA has focused its regulatory efforts on GHGs, VOC, and SO2.
1. Climate Change Impacts from GHGs Emissions
      Elevated concentrations of GHGs are and have been warming the planet, leading to changes in the Earth's climate including changes in the frequency and intensity of heat waves, precipitation, and extreme weather events; rising seas; and retreating snow and ice. The changes taking place in the atmosphere as a result of the well-documented buildup of GHGs due to human activities are changing the climate at a pace and in a way that threatens human health, society, and the natural environment. Human induced GHGs, largely derived from our reliance on fossil fuels, are causing serious and life-threatening environmental and health impacts.
      Extensive additional information on climate change is available in the scientific assessments and the EPA documents that are briefly described in this section, as well as in the technical and scientific information supporting them. One of those documents is the EPA's 2009 Endangerment and Cause or Contribute Findings for GHGs Under Section 202(a) of the CAA (74 FR 66496, December 7, 2009). In the 2009 Endangerment Findings, the Administrator found under section 202(a) of the CAA that elevated atmospheric concentrations of six key well-mixed GHGs  -  CO2, CH4, N2O, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)  -  "may reasonably be anticipated to endanger the public health and welfare of current and future generations." (74 FR 66523), and the science and observed changes have confirmed and strengthened the understanding and concerns regarding the climate risks considered in the Finding. The 2009 Endangerment Findings, together with the extensive scientific and technical evidence in the supporting record, documented that climate change caused by human emissions of GHGs threatens the public health of the U.S. population. It explained that by raising average temperatures, climate change increases the likelihood of heat waves, which are associated with increased deaths and illnesses (74 FR 66497). While climate change also increases the likelihood of reductions in cold-related mortality, evidence indicates that the increases in heat mortality will be larger than the decreases in cold mortality in the U.S. (74 FR 66525). The 2009 Endangerment Findings further explained that compared to a future without climate change, climate change is expected to increase tropospheric ozone pollution over broad areas of the U.S., including in the largest metropolitan areas with the worst tropospheric ozone problems, and thereby increase the risk of adverse effects on public health (74 FR 66525). Climate change is also expected to cause more intense hurricanes and more frequent and intense storms of other types and heavy precipitation, with impacts on other areas of public health, such as the potential for increased deaths, injuries, infectious and waterborne diseases, and stress-related disorders (74 FR 66525). Children, the elderly, and the poor are among the most vulnerable to these climate-related health effects (74 FR 66498).
      The 2009 Endangerment Findings also documented, together with the extensive scientific and technical evidence in the supporting record, that climate change touches nearly every aspect of public welfare in the U.S. with resulting economic costs, including: changes in water supply and quality due to increased frequency of drought and extreme rainfall events; increased risk of storm surge and flooding in coastal areas and land loss due to inundation; increases in peak electricity demand and risks to electricity infrastructure; and the potential for significant agricultural disruptions and crop failures (though offset to some extent by carbon fertilization). These impacts are also global and may exacerbate problems outside the U.S. that raise humanitarian, trade, and national security issues for the U.S. (74 FR 66530).
      In 2016, the Administrator similarly issued Endangerment and Cause or Contribute Findings for GHG emissions from aircraft under section 231(a)(2)(A) of the CAA (81 FR 54422). In the 2016 Endangerment Findings, the Administrator found that the body of scientific evidence amassed in the record for the 2009 Endangerment Findings compellingly supported a similar endangerment finding under CAA section 231(a)(2)(A), and also found that the science assessments released between the 2009 and the 2016 Findings, "strengthen and further support the judgment that GHGs in the atmosphere may reasonably be anticipated to endanger the public health and welfare of current and future generations." (81 FR 54424).
      Since the 2016 Endangerment Findings, the climate has continued to change, with new records being set for several climate indicators such as global average surface temperatures, GHG concentrations, and sea level rise. Moreover, heavy precipitation events have increased in the eastern U.S. while agricultural and ecological drought has increased in the west along with more intense and larger wildfires. These and other trends are examples of the risks discussed the 2009 and 2016 Endangerment Findings that have already been experienced. Additionally, major scientific assessments continue to demonstrate advances in our understanding of the climate system and the impacts that GHGs have on public health and welfare both for current and future generations. These updated observations and projections document the rapid rate of current and future climate change both globally and in the U.S. These assessments include:
 U.S. Global Change Research Program's (USGCRP) 2016 Climate and Health Assessment and 2017-2018 Fourth National Climate Assessment (NCA4)[,]
 IPCC's 2018 Global Warming of 1.5°C, 2019 Climate Change and Land, and the 2019 Ocean and Cryosphere in a Changing Climate assessments, as well as the 2021 IPCC Sixth Assessment Report (AR6).
 The NAS 2016 Attribution of Extreme Weather Events in the Context of Climate Change, 2017 Valuing Climate Damages: Updating Estimation of the Social Cost of Carbon Dioxide, and 2019 Climate Change and Ecosystems assessments
 National Oceanic and Atmospheric Administration's (NOAA) annual State of the Climate reports published by the Bulletin of the American Meteorological Society, most recently in August of 2020.
 EPA Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts (2021).

      The most recent information demonstrates that the climate is continuing to change in response to the human-induced buildup of GHGs in our atmosphere. These recent assessments show that atmospheric concentrations of GHGs have risen to a level that has no precedent in recent geologic history and continue to climb, primarily as a result of both historic and current anthropogenic emissions, and that these elevated concentrations endanger our health by affecting our food and water sources, the air we breathe, the weather we experience, and our interactions with the natural and built environments. For example, atmospheric concentrations of one of these GHGs, CO2, measured at Mauna Loa in Hawaii and at other sites around the world reached 414 ppm in 2020, and has continued to rise. Global average temperature has increased by about 1.1 degrees Celsius (°C) (2.0 degrees Fahrenheit (°F)) in the 2011-2020 decade relative to 1850-1900. The years 2014  -  2020 were the warmest seven years in the 1880  -  2020 record, contributing to the warmest decade on record with a decadal temperature of 0.82°C (1.48°F) above the 20th century.[,] The IPCC determined (with medium confidence) that this past decade was warmer than any multi-century period in at least the past 100,000 years. Global average sea level has risen by about 8 inches (about 21 centimeters (cm)) from 1901 to 2018, with the rate from 2006 to 2018 (0.15 inches/year or 3.7 millimeters (mm)/year) almost twice the rate over the 1971 to 2006 period, and three times the rate of the 1901 to 2018 period.  The rate of sea level rise over the 20th century was higher than in any other century in at least the last 2,800 years. Higher CO2 concentrations have led to acidification of the surface ocean in recent decades to an extent unusual in the past 2 million years, with negative impacts on marine organisms that use calcium carbonate to build shells or skeletons. Arctic sea ice extent continues to decline in all months of the year; the most rapid reductions occur in September (very likely almost a 13 percent decrease per decade between 1979 and 2018) and are unprecedented in at least 1000 years. Human-induced climate change has led to heatwaves and heavy precipitation becoming more frequent and more intense, along with increases in agricultural and ecological droughts in many regions.
      The assessment literature demonstrates that modest additional amounts of warming may lead to a climate different from anything humans have ever experienced. The present-day CO2 concentration of 414 ppm is already higher than at any time in the last 2 million years. If concentrations exceed 450 ppm, they would likely be higher than any time in the past 23 million years: at the current rate of increase of more than 2 ppm a year, this would occur in about 15 years. While GHGs are not the only factor that controls climate, it is illustrative that 3 million years ago (the last time CO2 concentrations were this high) Greenland was not yet completely covered by ice and still supported forests, while 23 million years ago (the last time concentrations were above 450 ppm) the West Antarctic ice sheet was not yet developed, indicating the possibility that high GHGs concentrations could lead to a world that looks very different from today and from the conditions in which human civilization has developed. If the Greenland and Antarctic ice sheets were to melt substantially, sea levels would rise dramatically - the IPCC estimated that over the next 2000 years, sea level will rise by 7 to 10 feet even if warming is limited to 1.5°C (2.7°F), from 7 to 20 feet if limited to 2°C (3.6°F), and by 60 to 70 feet if warming is allowed to reach 5°C (9°F) above preindustrial levels. For context, almost all of the city of Miami is less than 25 feet above sea level, and the NCA4 stated that 13 million Americans would be at risk of migration due to 6 feet of sea level rise. Moreover, the CO2 being absorbed by the ocean has resulted in changes in ocean chemistry due to acidification of a magnitude not seen in 65 million years, putting many calcifying marine species at risk.
      The NCA4 found that it is very likely (greater than 90 percent likelihood) that by mid-century, the Arctic Ocean will be almost entirely free of sea ice by late summer for the first time in about 2 million years. Coral reefs will be at risk for almost complete (99 percent) losses with 1°C (1.8°F) of additional warming from today (2°C or 3.6°F since preindustrial). At this temperature, between 8 and 18 percent of animal, plant, and insect species could lose over half of their climatic ranges, and 7 to 10 percent of rangeland livestock would be projected to be lost.
      Every additional increment of temperature comes with consequences. For example, the half degree of warming from 1.5 to 2°C (0.9 °F of warming from 2.7°F to 3.6°F) above preindustrial temperatures is projected on a global scale to expose 420 million more people to frequent extreme heatwaves, and 62 million more people to frequent exceptional heatwaves (where an "extreme heatwave" is as warm or warmer than the 2003 Paris heatwave, and an "exceptional heatwave" is as warm or warmer than the 2010 Russian heatwave). It would increase the frequency of sea-ice-free Arctic summers from once in a hundred years to once in a decade. It could lead to 4 inches of additional sea level rise by the end of the century, exposing an additional 10 million people to risks of inundation, as well as increasing the probability of triggering instabilities in either the Greenland or Antarctic ice sheets. Between half a million and a million additional square miles of permafrost would be committed to thawing. Risks to food security would increase from medium to high for several lower income regions in the Sahel, southern Africa, the Mediterranean, central Europe, and the Amazon. In addition to food security issues, this temperature increase would have implications for human health in terms of increasing ozone concentrations, heatwaves, and vector-borne diseases. Moreover, every additional increment in warming leads to larger changes in extremes, including the potential for events unprecedented in the observational record. Every additional degree will intensify extreme precipitation events by about 7 percent. The peak winds of the most intense tropical cyclones (hurricanes) are projected to increase with warming. In addition to a higher intensity, the IPCC found that precipitation and frequency of rapid intensification of these storms has already increased, while the movement speed has decreased, and elevated sea levels have increased coastal flooding, all of which make these tropica cyclones more damaging.
      The NCA4 also evaluated a number of impacts specific to the U.S. Severe drought and outbreaks of insects like the mountain pine beetle have killed 100s of millions of trees in the western U.S. Wildfires have burned more than 3.7 million acres in 14 of the 17 years between 2000 and 2016, and Federal wildfire suppression costs were about a billion dollars annually. The National Interagency Fire Center has documented U.S. wildfires since 1983, and the ten years with the largest acreage burned have all occurred since 2004. Wildfire smoke degrades air quality increasing health risks, and more frequent and severe wildfires due to climate change would further diminish air quality, increase incidences of respiratory illness, impair visibility, and disrupt outdoor activities. Meanwhile, sea level rise has amplified coastal flooding and erosion impacts, requiring the installation of costly pump stations, flooding streets, and increasing storm surge damages. Tens of billions of dollars of U.S. real estate could be below sea level by 2050 under some scenarios. Increased frequency and duration of drought will reduce agricultural productivity in some regions, accelerate depletion of water supplies for irrigation, and expand the distribution and incidence of pests and diseases for crops and livestock. The NCA4 also recognized that climate change can increase risks to national security, both through direct impacts on military infrastructure, but also by affecting factors such as food and water availability that can exacerbate conflict outside U.S. borders. Droughts, floods, storm surges, wildfires, and other extreme events stress nations and people through loss of life, displacement of populations, and impacts on livelihoods. The Congressional Budget Office estimated that climate change impacts could reduce national GDP by 1% in 2050, though they cautioned that they had made an incomplete accounting of impacts.
      Some GHGs also have impacts beyond those mediated through climate change. For example, elevated concentrations of carbon dioxide stimulate plant growth (which can be positive in the case of beneficial species, but negative in terms of weeds and invasive species, and can also lead to a reduction in plant micronutrients) and cause ocean acidification. Nitrous oxide depletes the levels of protective stratospheric ozone.
      As methane is the primary GHG addressed in this proposal, it is relevant to highlight some specific trends and impacts specific to methane. Concentrations of methane reached 1879 parts per billion (ppb) in 2020, more than two and a half times the preindustrial concentration of 722 ppb. Moreover, the 2020 concentration was an increase of almost 13 ppb over 2019 - the largest annual increase in methane concentrations of the period since the early 1990s, continuing a trend of rapid rise since a temporary pause ended in 2007. Methane has a high radiative efficiency  -  almost 30 times that of carbon dioxide per ppb (and therefore, 80 times as much per unit mass). In addition, methane contributes to climate change through chemical reactions in the atmosphere that produce tropospheric ozone and stratospheric water vapor. Human emissions of methane are responsible for about one third of the warming due to well-mixed GHGs, the second most important human warming agent after carbon dioxide. Because of the substantial emissions of methane, and its radiative efficiency, methane mitigation is one of the best opportunities for reducing near term warming.
      The tropospheric ozone produced by the reaction of methane in the atmosphere has harmful effects for human health and plant growth in addition to its climate effects. In remote areas, methane is a dominant precursor to tropospheric ozone formation. Approximately 50 percent of the global annual mean ozone increase since preindustrial times is believed to be due to anthropogenic methane. Projections of future emissions also indicate that methane is likely to be a key contributor to ozone concentrations in the future. Unlike NOX and VOC, which affect ozone concentrations regionally and at hourly time scales, methane emissions affect ozone concentrations globally and on decadal time scales given methane's long atmospheric lifetime when compared to these other ozone precursors. Reducing methane emissions, therefore, will contribute to efforts to reduce global background ozone concentrations that contribute to the incidence of ozone-related health effects.[ ]The benefits of such reductions are global and occur in both urban and rural areas.
      These scientific assessments and documented observed changes in the climate of the planet and of the U.S. present clear support regarding the current and future dangers of climate change and the importance of GHG mitigation.
2. VOC
      Many VOC can be classified as HAP (e.g., benzene) which can lead to a variety of health concerns such as cancer and noncancer illnesses (e.g., respiratory, neurological). Further, VOC are one of the key precursors in the formation of ozone. Tropospheric, or ground-level, ozone is formed through reactions of VOC and NOX in the presence of sunlight. Ozone formation can be controlled to some extent through reductions in emissions of the ozone precursors VOC and NOX. A significantly expanded body of scientific evidence shows that ozone can cause a number of harmful effects on health and the environment. Exposure to ozone can cause respiratory system effects such as difficulty breathing and airway inflammation. For people with lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), these effects can lead to emergency room visits and hospital admissions. Studies have also found that ozone exposure is likely to cause premature death from lung or heart diseases. In addition, evidence indicates that long-term exposure to ozone is likely to result in harmful respiratory effects, including respiratory symptoms and the development of asthma. People most at risk from breathing air containing ozone include: children; people with asthma and other respiratory diseases; older adults; and people who are active outdoors, especially outdoor workers. An estimated 25.9 million people have asthma in the U.S., including almost 7.1 million children. Asthma disproportionately affects children, families with lower incomes, and minorities, including Puerto Ricans, Native Americans/Alaska Natives, and African-Americans.
      Scientific evidence also shows that repeated exposure to ozone can reduce growth and have other harmful effects on sensitive plants and trees. These types of effects have the potential to impact ecosystems and the benefits they provide.
3. SO2
      Current scientific evidence links short-term exposures to SO2, ranging from 5 minutes to 24 hours, with an array of adverse respiratory effects including bronchoconstriction and increased asthma symptoms. These effects are particularly important for asthmatics at elevated ventilation rates (e.g., while exercising or playing).
      Studies also show an association between short-term exposure and increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in at-risk populations including children, the elderly, and asthmatics.
      SO2 in the air can also damage the leaves of plants, decrease their ability to produce food  -  photosynthesis  -  and decrease their growth. In addition to directly affecting plants, SO2, when deposited on land and in estuaries, lakes, and streams, can acidify sensitive ecosystems resulting in a range of harmful indirect effects on plants, soils, water quality, and fish and wildlife (e.g., changes in biodiversity and loss of habitat, reduced tree growth, loss of fish species). Sulfur deposition to waterways also plays a causal role in the methylation of mercury.
B. Oil and Natural Gas Industry and Its Emissions
      This section generally describes the structure of the Oil and Natural Gas Industry, the interconnected production, processing, transmission and storage, and distribution segments that move product from well to market, and types of emissions sources in each segment and the industry's emissions.
1. Oil and Natural Gas Industry  -  Structure
      The EPA characterizes the Oil and Natural Gas Industry operations as being generally composed of four segments: (1) extraction and production of crude oil and natural gas ("oil and natural gas production"), (2) natural gas processing, (3) natural gas transmission and storage, and (4) natural gas distribution.[,]  The EPA regulates oil refineries as a separate source category; accordingly, as with the previous oil and gas NSPS rulemakings, for purposes of this proposed rulemaking, for crude oil, the EPA's focus is on operations from the well to the point of custody transfer at a petroleum refinery, while for natural gas, the focus is on all operations from the well to the local distribution company custody transfer station commonly referred to as the "city-gate."
a. Production Segment
      The oil and natural gas production segment includes the wells and all related processes used in the extraction, production, recovery, lifting, stabilization, and separation or treatment of oil and/or natural gas (including condensate). Although many wells produce a combination of oil and natural gas, wells can generally be grouped into two categories, oil wells and natural gas wells. Oil wells comprise two types, oil wells that produce crude oil only and oil wells that produce both crude oil and natural gas (commonly referred to as "associated" gas). Production equipment and components located on the well pad may include, but are not limited to, wells and related casing heads; tubing heads; "Christmas tree" piping, pumps, compressors; heater treaters; separators; storage vessels; pneumatic devices; and dehydrators. Production operations include well drilling, completion, and recompletion processes, including all the portable non-self-propelled apparatuses associated with those operations.
      Other sites that are part of the production segment include "centralized tank batteries," stand-alone sites where oil, condensate, produced water, and natural gas from several wells may be separated, stored, or treated. The production segment also includes gathering pipelines, gathering and boosting compressor stations, and related components that collect and transport the oil, natural gas, and other materials and wastes from the wells to the refineries or natural gas processing plants.
      Of these products, crude oil and natural gas undergo successive, separate processing. Crude oil is separated from water and other impurities and transported to a refinery via truck, railcar, or pipeline. As noted above, the EPA treats oil refineries as a separate source category, accordingly, for present purposes, the oil component of the production segment ends at the point of custody transfer at the refinery.
      The separated, unprocessed natural gas is commonly referred to as field gas and is composed of methane, natural gas liquids (NGL), and other impurities, such as water vapor, H2S, CO2, helium, and nitrogen. Ethane, propane, butane, isobutane, and pentane are all considered NGL and often are sold separately for a variety of different uses. Natural gas with high methane content is referred to as "dry gas," while natural gas with significant amounts of ethane, propane, or butane is referred to as "wet gas." Natural gas typically is sent to gas processing plants in order to separate NGLs for use as feedstock for petrochemical plants, burned for space heating and cooking, or blended into vehicle fuel.
b. Processing Segment
      The natural gas processing segment consists of separating certain hydrocarbons (HC) and fluids from the natural gas to produce "pipeline quality" dry natural gas. The degree and location of processing is dependent on factors such as the type of natural gas (e.g., wet or dry gas), market conditions, and company contract specifications. Typically, processing of natural gas begins in the field and continues as the gas is moved from the field through gathering and boosting compressor stations to natural gas processing plants, where the complete processing of natural gas takes place. Natural gas processing operations separate and recover NGL or other non-methane gases and liquids from field gas through one or more of the following processes: oil and condensate separation, water removal, separation of NGL, sulfur and CO2 removal, fractionation of NGL, and other processes, such as the capture of CO2 separated from natural gas streams for delivery outside the facility.
c. Transmission and Storage Segment
      Once natural gas processing is complete, the resulting natural gas exits the natural gas process plant and enters the transmission and storage segment where it is transmitted to storage and/or distribution to the end user.
      Pipelines in the natural gas transmission and storage segment can be interstate pipelines, which carry natural gas across state boundaries, or intrastate pipelines, which transport the gas within a single state. Basic components of the two types of pipelines are the same, though interstate pipelines may be of a larger diameter and operated at a higher pressure. To ensure that the natural gas continues to flow through the pipeline, the natural gas must periodically be compressed, thereby increasing its pressure. Compressor stations perform this function and are usually placed at 40- to 100-mile intervals along the pipeline. At a compressor station, the natural gas enters the station, where it is compressed by reciprocating or centrifugal compressors.
      Another part of the transmission and storage segment are aboveground and underground natural gas storage facilities. Storage facilities hold natural gas for use during peak seasons. The main difference between underground and aboveground storage sites is that storage takes place in storage vessels constructed of non-earthen materials in aboveground storage. Underground storage of natural gas typically occurs in depleted natural gas or oil reservoirs and salt dome caverns. One purpose of this storage is for load balancing (equalizing the receipt and delivery of natural gas). At an underground storage site, typically other processes occur, including compression, dehydration, and flow measurement.
d. Distribution Segment
      The distribution segment provides the final step in delivering natural gas to customers. The natural gas enters the distribution segment from delivery points located on interstate and intrastate transmission pipelines to business and household customers. The delivery point where the natural gas leaves the transmission and storage segment and enters the distribution segment is a local distribution company's custody transfer station, commonly referred to as the "citygate." Natural gas distribution systems consist of thousands of miles of piping, including mains and service pipelines to the customers. If the distribution network is large, compressor stations may be necessary to maintain flow; however, these stations are typically smaller than transmission compressor stations. Distribution systems include metering stations, which allow distribution companies to monitor the natural gas as it flows through the system.
2. Oil and Natural Gas Industry  -  Emissions
      The Oil and Natural Gas Industry sector is the largest source of industrial methane emissions in the U.S. Natural gas is comprised primarily of methane; every natural gas leak or intentional release through venting or other industrial processes constitutes a release of methane. Methane is a potent greenhouse gas; over a 100-year timeframe, it is nearly 30 times more powerful at trapping climate warming heat than CO2, and over a 20-year timeframe, it is 83 times more powerful. Because methane is a powerful greenhouse gas and is emitted in large quantities, reductions in methane emissions provide a significant benefit in reducing near-term warming. Indeed, on third of the warming due to GHGs that we are experiencing today is due to human emissions of methane. Additionally, the Crude Oil and Natural Gas sector emits, in varying concentrations and amounts, a wide range of other health-harming pollutants, including VOCs, SO2, NOX, H2S, CS2, and COS.
      Emissions of methane and these co-pollutants occur in every segment of the Crude Oil and Natural Gas source category. Many of the processes and equipment types that contribute to these emissions are found in every segment of the source category and are highly similar across segments. Emissions from the crude oil portion of the industry result primarily from field production operations, such as venting of associated gas from oil wells, oil storage vessels, and production-related equipment such as gas dehydrators, pig traps, and pneumatic devices. Emissions from the natural gas portion of the industry can occur in all segments. As natural gas moves through the system, emissions primarily result from intentional venting through normal operations, routine maintenance, unintentional fugitive emissions, flaring, malfunctions and system upsets. Venting can occur through equipment design or operational practices, such as the continuous and intermittent bleed of gas from pneumatic controllers (devices that control gas flows, levels, temperatures, and pressures in the equipment). In addition to vented emissions, emissions can occur from leaking equipment (also referred to as fugitive emissions) in all parts of the infrastructure, including major production and processing equipment (e.g., separators or storage vessels) and individual components (e.g., valves or connectors). Flares are commonly used throughout each segment in the Oil and Natural Gas Industry as a control device to provide pressure relief to prevent risk of explosions and to destroy methane, which has a high global warming potential, and convert it to CO2 which has a lower global warming potential, and to also control other air pollutants such as VOC.
      "Super-emitting" events, sites, or equipment, where a small proportion of sources account for a large proportion of overall emissions, can occur throughout the Oil and Natural Gas Industry. There are a number of definitions for the term "super-emitter." A 2018 National Academies of Sciences, Engineering, and Medicine report on methane discussed three categories of "high-emitting" sources:
 Routine or "chronic" high-emitting sources, which regularly emit at higher rates relative to "peers" in a sample. Examples include large facilities or large emissions caused by poor design or operational practices.
 Episodic high-emitting sources, which are typically large in nature and are generally intentional releases from known maintenance events at a facility. Examples include gas well liquids unloading, well workovers and maintenance activities, and compressor station or pipeline blowdowns.
 Malfunctioning high-emitting sources, which can occur in a sporadic and unpredictable manner due to malfunctions and poor work practices. Examples include malfunctioning intermittent pneumatic controllers and stuck open dump valves. Another example is well blowout events. For example, a 2018 well blowout in Ohio was estimated to have emitted over 60,000 tons of methane.
      Super-emitters have been observed at many different scales from site-level to component-level across many research studies. Studies will often develop a study-specific definition such as a top percentile of emissions in a study population (e.g., top 10 percent), emissions exceeding a certain threshold (e.g., 26 kg/day), emissions over a certain detection threshold (e.g., 1-3 g/s) or as facilities with the highest proportional emission rate. For many equipment types and activities, the EPA's GHG emission estimates include the full range of conditions, including "super-emitters." For other situations, where data are available, emissions estimates for abnormal events are calculated separately and included in the Inventory of U.S. Greenhouse Gas Emissions and Sinks ("GHGI") (e.g., Aliso Canyon leak event). Given the variability of practices and technologies across oil and gas systems and the occurrence of episodic events, it is possible that the EPA's estimates do not include all methane emissions from abnormal events. The EPA continues to work through its stakeholder process to review new data from the EPA's Greenhouse Gas Reporting Program ("GHGRP") petroleum and natural gas systems source category (40 CFR Part 98, subpart W, also referred to as "GHGRP subpart W") and research studies to assess how emissions estimates can be improved. Because lost gas, whether through fugitive emissions, unintentional gas carry through, or intentional releases, represents lost earning potential, the industry benefits from capturing and selling emissions of natural gas (and methane). Limiting super-emitting events and fugitive emissions, using lower emitting equipment where feasible, and employing best management practices will not only reduce emissions but reduce the loss of revenue from this valuable commodity.
      Below we provide estimated emissions of methane, VOC, and SO2 from Oil and Natural Gas Industry operation sources.
      Methane emissions in the U.S. and from the Oil and Natural Gas industry. Official U.S. estimates of national level GHG emissions and sinks are developed by the EPA for the GHGI in fulfillment of commitments under the United Nations Framework Convention on Climate Change. The GHGI, which includes recent trends, is organized by industrial sector. The oil and natural gas production, natural gas processing, and natural gas transmission and storage sectors emit 28 percent of U.S. anthropogenic methane. Table 7 below presents total U.S. anthropogenic methane emissions for the years 1990, 2010, and 2019.
      In accordance with the practice of the EPA GHGI, the EPA GHGRP, and international reporting standards under the UN Framework Convention on Climate Change, the 2007 IPCC Fourth Assessment Report value of the methane 100-year GWP is used for weighting emissions in the following tables. The 100-year GWP value of 25 for methane indicates that one ton of methane has approximately as much climate impact over a 100-year period as 25 tons of carbon dioxide. The most recent IPCC AR6 assessment has estimated a slightly larger 100-year GWP of methane of almost 30 (specifically, either 27.2 or 29.8 depending on whether the value includes the carbon dioxide produced by the oxidation of methane in the atmosphere). As mentioned earlier, because methane has a shorter lifetime than carbon dioxide, the emissions of a ton of methane will have more impact earlier in the 100-year timespan and less impact later in the 100-year timespan relative to the emissions of a 100-year GWP-equivalent quantity of carbon dioxide.
TABLE 7. U.S. METHANE EMISSIONS BY SECTOR (MILLION METRIC TONS CARBON DIOXIDE EQUIVALENT (MMT CO2 EQ.))
Sector
                                     1990
                                     2010
                                     2019
Oil and Natural Gas Production, and Natural Gas Processing and Transmission and Storage
                                      189
                                      176
                                      182
Landfills
                                     177
                                     124
                                     114
Enteric Fermentation
                                     165
                                     172
                                     179
Coal Mining
                                      96
                                      82
                                      47
Manure Management
                                      37
                                      55
                                      62
Other Oil and Gas Sources
                                      46
                                      17
                                      15
Wastewater Treatment
                                      20
                                      19
                                      18
Other Methane Sources
                                      46
                                      47
                                      42
Total Methane Emissions
                                     777
                                     692
                                     660
Emissions from the Inventory of United States Greenhouse Gas Emissions and Sinks: 1990-2019 (published April 14, 2021), calculated using GWP of 25. Note: Totals may not sum due to rounding.

      Table 8 below presents total methane emissions from natural gas production through transmission and storage and petroleum production, for years 1990, 2010, and 2019, in MMT CO2 Eq. (or million metric tons CO2 Eq.) of methane.
TABLE 8. U.S. METHANE EMISSIONS FROM NATURAL GAS AND PETROLEUM SYSTEMS (MMT CO2 EQ.)
Sector
                                     1990
                                     2010
                                     2019
Natural Gas Production
                                      63
                                      97
                                      94
Natural Gas Processing
                                      21
                                      10
                                      12
Natural Gas Transmission and Storage
                                      57
                                      30
                                      37
Petroleum Production
                                      48
                                      39
                                      38
Emissions from the Inventory of United States Greenhouse Gas Emissions and Sinks: 1990-2019 (published April 14, 2021), calculated using GWP of 25. Note: Totals may not sum due to rounding.

      Global GHG Emissions. For additional background information and context, we used 2018 World Resources Institute Climate Watch data to make comparisons between U.S. oil and natural gas production and natural gas processing and transmission and storage emissions and the emissions inventories of entire countries and regions. The U.S. methane emissions from oil and natural gas production and natural gas processing and transmission and storage constitute 0.4 percent of total global emissions of all GHGs (48,601 MMT CO2 Eq.) from all sources. Ranking U.S. emissions of methane from oil and natural gas production and natural gas processing and transmission and storage against total GHG emissions for entire countries (using 2018 Climate Watch data), shows that these emissions are comparatively large as they exceed the national-level emissions totals for all GHGs and all anthropogenic sources for Colombia, the Czech Republic, Chile, Belgium, and over 160 other countries. What that means is that the U.S. emits more of a single GHG -- methane -- from a single sector -- the oil and gas sector -- than the total combined GHGs emitted by 164 out of 194 total countries. Furthermore, U.S. emissions of methane from oil and natural gas production and natural gas processing and transmission and storage are greater than the sum of total emissions of 64 of the lowest-emitting countries and territories, using the 2018 Climate Watch data set.
      As illustrated by the domestic and global GHGs comparison data summarized above, the collective GHG emissions from the Crude Oil and Natural Gas source category are significant, whether the comparison is domestic (where this sector is the largest source of methane emissions, accounting for 28 percent of U.S. methane and 3 percent of total U.S. emissions of all GHGs), global (where this sector, accounting for 0.4 percent of all global GHG emissions, emits more than the total national emissions of over 160 countries, and combined emissions of over 60 countries), or when both the domestic and global GHG emissions comparisons are viewed in combination. Consideration of the global context is important. GHG emissions from U.S. Oil and Natural Gas production and natural gas processing and transmission and storage will become globally well-mixed in the atmosphere, and thus will have an effect on the U.S. regional climate, as well as the global climate as a whole for years and indeed many decades to come. No single GHG source category dominates on the global scale. While the Crude Oil and Natural Gas source category, like many (if not all) individual GHG source categories, could appear small in comparison to total emissions, in fact, it is a very important contributor in terms of both absolute emissions, and in comparison, to other source categories globally or within the U.S.
      The IPCC AR6 assessment determined that "From a physical science perspective, limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other GHG emissions." The report also singled out the importance of "strong and sustained CH4 emission reductions" in part due to the short lifetime of methane leading to the near-term cooling from reductions in methane emissions offsetting the unmasking of warming due to reductions in SO2 and other aerosols. Therefore, reducing methane emissions globally is an important facet in any strategy to limit warming. In the oil and gas sector, methane reductions are highly achievable and cost-effective using existing and well-known solutions and technologies that actually result in recovery of saleable product.
      VOC and SO2 emissions in the U.S. and from the oil and natural gas industry. Official U.S. estimates of national level VOC and SO2 emissions are developed by the EPA for the National Emissions Inventory (NEI), for which states are required to submit information under 40 CFR part 51, subpart A. Data in the NEI may be organized by various data points, including sector, NAICS code, and Source Classification Code. The oil and natural gas sources emit 5.8 and 2.4 percent of U.S. VOC and SO2, respectively. Tables 9 and 10 below present total U.S. VOC and SO2 emissions by sector, respectively, for the year 2017, in kilotons (kt) (or thousand metric tons).
                  TABLE 9. U.S. VOC EMISSIONS BY SECTOR (kt)
Sector
2017
Biogenics  -  Vegetation and Soil
25,823
Fires  -  Wildfires
4,578
Oil and Natural Gas Production, and Natural Gas Processing and Transmission
2,504
Fires  -  Prescribed Fires
2,042
Solvent  -  Consumer and Commercial Solvent Use
1,610
Mobile  -  On-Road non-Diesel Light Duty Vehicles
1,507
Mobile  -  Non-Road Equipment  -  Gasoline
1,009
Other VOC Sources
4,045
Total VOC Emissions
43,118
Emissions from the 2017 NEI (released April 2020). Note: Totals may not sum due to rounding.

                  TABLE 10. U.S. SO2 EMISSIONS BY SECTOR (kT)
Sector
2017
Fuel Combustion  -  Electric Generation  -  Coal
1,319
Fuel Combustion  -  Industrial Boilers, Internal Combustion Engines  -  Coal
212
Mobile  -  Commercial Marine Vessels
183
Industrial Processes  -  Not Elsewhere Classified
138
Fires  -  Wildfires
135
Industrial Processes  -  Chemical Manufacturing
123
Oil and Natural Gas Production and Natural Gas Processing and Transmission
65
Other SO2 Sources
551
Total SO2 Emissions
2,726
Emissions from the 2017 NEI (released April 2020). Note: Totals may not sum due to rounding.

      Table 11 below presents total VOC and SO2 emissions from oil and natural gas production through transmission and storage, for the year 2017, in kt. The contribution to the total anthropogenic VOC emissions budget from the oil and gas sector has been increasing in recent NEI cycles. In the 2017 NEI, the oil and gas sector makes up about 25 percent of the total VOC emissions from anthropogenic sources. The SO2 emissions have been declining in just about every anthropogenic sector, but the oil and gas sector is an exception where SO2 emissions have been slightly increasing or remaining steady in some cases in recent years.
TABLE 11. U.S. VOC AND SO2 EMISSIONS FROM NATURAL GAS AND PETROLEUM SYSTEMS (kt)
Sector
                                      VOC
                                      SO2
Oil and Natural Gas Production
                                     2,478
                                      41
Natural Gas Processing
                                      12
                                      23
Natural Gas Transmission and Storage
                                      14
                                       1
Emissions from the 2017 NEI, (published April 2020), in kt (or thousand metric tons). Note: Totals may not sum due to rounding.

IV. Statutory Background and Regulatory History
A. Statutory Background of CAA Sections 111(b), 111(d) and General Implementing Regulations
      The EPA's authority for this rule is CAA section 111, which governs the establishment of standards of performance for stationary sources. This section requires the EPA to list source categories to be regulated, establish standards of performance for air pollutants emitted by new sources in that source category, and establish EG for states to establish standards of performance for certain pollutants emitted by existing sources in that source category.
      Specifically, CAA section 111(b)(1)(A) requires that a source category be included on the list for regulation if, "in [the EPA Administrator's] judgment it causes, or contributes significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare." This determination is commonly referred to as an "endangerment finding" and that phrase encompasses both of the "causes or contributes significantly to" component and the "endanger public health or welfare" component of the determination. Once a source category is listed, CAA section 111(b)(1)(B) requires that the EPA propose and then promulgate "standards of performance" for new sources in such source category. CAA section 111(a)(1) defines a "standard of performance" as "a standard for emissions of air pollutants which reflects the degree of emission limitation achievable through the application of the best system of emission reduction which (taking into account the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated." As long recognized by the D.C. Circuit,"[b]ecause Congress did not assign the specific weight the Administrator should accord each of these factors, the Administrator is free to exercise his discretion in this area." New York v. Reilly, 969 F.2d 1147, 1150 (D.C.Cir.1992). See also, Lignite Energy Council v. EPA, 198 F.3d 930, 933 (D.C. Cir. 1999) ("Lignite Energy Council") ("Because section 111 does not set forth the weight that be [sic] should assigned to each of these factors, we have granted the agency a great degree of discretion in balancing them").
      In determining whether a given system of emission reduction qualifies as "the best system of emission reduction... adequately demonstrated," or "BSER," CAA section 111(a)(1) requires that the EPA take into account, among other factors, "the cost of achieving such reduction." As described in the proposal for the 2016 Rule, the U.S. Court of Appeals for the District of Columbia Circuit (the D.C. Circuit) has stated that in light of this provision, the EPA may not adopt a standard the cost of which would be "exorbitant," "greater than the industry could bear and survive," "excessive," or "unreasonable." These formulations appear to be synonymous, and for convenience, in this rulemaking, as in previous rulemakings, we will use reasonableness as the standard, so that a control technology may be considered the ``best system of emission reduction . . . adequately demonstrated'' if its costs are reasonable, but cannot be considered the BSER if its costs are unreasonable. See 80 FR 64662, 64720-21 (October 23, 2015).
      CAA section 111(a) does not provide specific direction regarding what metric or metrics to use in considering costs, affording the EPA considerable discretion in choosing a means of cost consideration. In this rulemaking, we evaluated whether a control cost is reasonable under a number of approaches that we find appropriate for assessing the types of controls at issue. For example, in evaluating controls for reducing VOC and methane emissions from new sources, we considered a control's cost effectiveness under both a "single pollutant cost-effectiveness" approach and a "multipollutant cost-effectiveness" approach, in order to appropriately take into account that the systems of emission reduction considered in this rule typically achieve reductions in multiple pollutants at once and secure a multiplicity of climate and public health benefits. We also evaluated costs at a sector level by assessing the projected new capital expenditures required under the proposal (compared to overall new capital expenditures by the sector) and the projected compliance costs (compared to overall annual revenue for the sector) if the rule were to require such controls. For a detailed discussion of these cost approaches, please see section IX of the proposal preamble.
      The standard that the EPA develops, based on the BSER, is commonly a numerical emissions limit, expressed as a performance level (typically, a rate-based standard). CAA section 111(b)(5) precludes the EPA from prescribing a particular technological system that must be used to comply with a standard of performance. Rather, sources can select any measure or combination of measures that will achieve the standard.
      CAA section 111(h)(1) authorizes the Administrator to promulgate "a design, equipment, work practice, or operational standard, or combination thereof" if in his or her judgment, "it is not feasible to prescribe or enforce a standard of performance." CAA section 111(h)(2) provides the circumstances under which prescribing or enforcing a standard of performance is "not feasible," such as, when the pollutant cannot be emitted through a conveyance designed to emit or capture the pollutant, or when there is no practicable measurement methodology for the particular class of sources. CAA section 111(b)(1)(B) requires the EPA to "at least every 8 years review and, if appropriate, revise" performance standards unless the "Administrator determines that such review is not appropriate in light of readily available information on the efficacy" of the standard.
      As mentioned above, once the EPA lists a source category under CAA section 111(b)(1)(A), CAA section 111(b)(1)(B) provides the EPA discretion to determine the pollutants and sources to be regulated. In addition, concurrent with the 8-year review (and though not a mandatory part of the 8-year review), the EPA may examine whether to add standards for pollutants or emission sources not currently regulated for that source category.
      Once the EPA establishes NSPS in a particular source category, the EPA is required in certain circumstances to issue EG to reduce emissions from existing sources in that same source category. Specifically, CAA section 111(d) requires that the EPA prescribe regulations to establish procedures under which states submit plans to establish, implement, and enforce standards of performance for existing sources for certain air pollutants to which a Federal NSPS would apply if such existing source were a new source. The EPA addresses this CAA requirement both through its promulgation of general implementing regulations for section 111(d) as well as specific EG. The EPA first published general implementing regulations in 1975, 40 FR 53340 (November 17, 1975) (codified at 40 CFR part 60, subpart B), and has revised its section 111(d) implementing regulations several times, most recently on July 8, 2019, 84 FR 32520 (codified at 40 CFR pt. 60, subpart Ba). In accordance with CAA section 111(d), states are required to submit plans pursuant to these regulations to establish standards of performance for existing sources for any air pollutant: (1) the emission of which is subject to a Federal NSPS; and (2) which is neither a pollutant regulated under CAA section 108(a) (i.e., criteria pollutants such as ground-level ozone and particulate matter, and their precursors, like VOC) or a HAP regulated under CAA section 112. See also definition of "designated pollutant" in 40 CFR 60.21a(a). The EPA's general implementing regulations use the term "designated facility" to identify those existing sources that may be subject to regulation under this provision of CAA section 111(d). See 40 CFR 60.21a(b).
 	While states are authorized to establish standards of performance for designated facilities, there is a fundamental obligation under CAA section 111(d) that such standards of performance reflect the degree of emission limitation achievable through the application of the BSER, as determined by the Administrator. This obligation derives from the definition of "standard of performance" under CAA section 111(a)(1), which makes no distinction between new-source and existing-source standards. The EPA identifies the degree of emission limitation achievable through application of the BSER as part of its EG. See 40 CFR 60.22a(b)(5). While standards of performance must generally reflect the degree of emission limitation achievable through application of the BSER, CAA section 111(d)(1) also requires that the EPA regulations permit the states, in applying a standard of performance to a particular source, to take into account the source's remaining useful life and other factors.