EPA Oil & Gas NSPS Methane and VOC Proposed Rules

On November 15, 2021, the U.S. Environmental Protection Agency (EPA) published proposed rulemaking regarding methane and VOC emissions from oil and natural gas industries. A main thrust of the rule is to reduce the greenhouse gases (GHG) methane.

The proposed rules will affect existing and new Crude Oil and Gas industry operations. For crude oil production, the rules include the well to the point of custody transfer. It also includes natural gas production wells/boosting stations, gas processing, gas transmission, storage, and the local gas distribution company custody transfer station.

The proposed rules add new provisions for New Source Performance Standards (NSPS) for Crude Oil and Natural Gas Facilities and new Emission Guidelines for existing emission sources. The Clean Act Section 111 has different approaches for new and existing emission sources. Section 111(b) is used for Federal standards for new, modified and reconstruction sources. Section 111(d) is used to implement Emission Guidelines for State programs for existing sources.

The proposed rules are found in:

  • 40 CFR 60 Subpart OOOOa
  • 40 CFR 60 Subpart OOOOb – new sources
  • 40 CFR 60 Subpart OOOOc – Emissions Guidelines (EG) for existing sources

Link to proposed NSPS and Emission Guidelines for O&G.


Applicability Dates

Subpart Source Type Applicable Dates
40 CFR 60. Subpart OOOO New, modified, or reconstructed sources After 8-23-2011 and
on or before 9-18-2015
40 CFR 60, Subpart OOOOa New, modified, or reconstructed sources After 9-18-2015 and on or before 11-15-2021
40 CFR 60, Subpart OOOOb New, modified, or reconstructed sources After 11-15-2021
40 CFR 60, Subpart OOOOc Existing sources On or before 11-15-2021


Based on this information, once the OOOOc EGs are implemented, any source installed prior to 11-15-2021 would be required to comply NSPS OOOOc EG. NSPS OOOO and OOOOa would still apply while OOOOc EGs are being approved.

Comments Requested by EPA

The EPA specifically requested comments on the following:

  • Financial assurance and fugitive emissions monitoring at plugged and abandoned wells
  • Reducing the frequency of pigging events, eliminating or reducing gas vented during pigging blowdowns
  • Require emission controls during truck loadout operations
  • Ways to ensure control devices are operating properly and flare monitoring or testing

Public comments on all parts of the proposed rule can be submitted to the EPA. The comment period ends on January 14, 2022.

EPA prefers that you submit comments online through the Federal eRulemaking Portal. Visit https://www.regulations.gov/ and type EPA-HQ-OAR-2021-0317 in the search box. That will take you to a link to the docket for the proposed rule. Under the link, there will be a button that says “Comment.” Click on that button to submit your comments, or you can open the link, and use the blue button in the upper left to enter your comments.

For more detailed instructions for how to comment see: Comment Instruction Link

EPA Supplemental Proposal

The EPA intends to issue a supplemental proposal in 2022 to supply regulatory text for NSPS OOOOb and OOOOc EG.

Approval Timeline

These rules are on a fast track for approval.

NSPS OOOOb may be finalized by the end of 2022.

Since each State will have to add OOOOc EG requirements into their respective air quality programs, the full implementation across all States would likely extend to 2025 or later.

Legally and Practicably Enforceable Limits

Many operators limit storage tanks potential to emit (PTE) from storage tanks so that OOOOa emission standards, monitoring, recordkeeping and reporting requirements do not apply. Typically, limiting PTE is done using an enforceable State air permit. EPA has concerns regarding the validity of these PTE limits.

The proposal includes a definition for a “legally and practicably enforceable limit” as it relates to PTE limits for VOC emissions from storage vessels. This would include production limits, averaging time period for the production limit, performance tests for control devices, and ongoing monitoring, recordkeeping and reporting.


NSPS OOOOb would affect new sources constructed, reconstructed or modified after November 15, 2021. The proposal includes a table OOOOb listing best system of emission reduction (BSER) and presumptive standards for GHGs.

The November 15, 2021, Federal Register publication did not include regulatory text for OOOOb or OOOOc EG.

Optical Gas Imaging (OGI) EPA Test Method

The proposal included an EPA test method in 40 CFR 60, Appendix K, “Determination of Volatile Organic Compound and Greenhouse Gas Leaks Using Optical Gas Imaging.”

Leak Detection and Repair (LDAR) – Well Sites

One of EPA’s proposal is to require quarterly LDAR inspections and repairs at well sites with methane emissions equal to or greater than 3 tons per year (tpy).

As a co-proposal, well sites with methane emissions equal to or greater than 3 tpy and less than 8 tpy would be required to conduct semiannual leak monitoring and repairs. Also, well sites with methane emissions greater 8 tpy would be required to conduct quarterly leak monitoring and repairs.

The proposed LDAR requirements listed in OOOOc EG are the same as specified for OOOOb sources.

LDAR – Compressor Stations

All new and existing compressor stations would monitor and repair leaks on a quarterly basis. Sources on the Alaska North Slope would have different monitoring schedules to account for weather.

LDAR – Natural Gas Processing Plants

Natural gas processing plants would be required to conduct LDAR on a bimonthly basis. Sources on the Alaska North Slope would have different monitoring schedules to account for weather.

Storage Tanks

The proposed rule adds tank batteries (groups of tanks that are adjacent and receive fluids from the same source) to the definition of facilities that must reduce VOC and methane emissions.

The existing rules in NSPS OOOO and OOOOa have a 6 tons per year (tpy) of VOC per individual storage tank threshold for requiring emission controls (ECD, flare). The 6 tpy VOC limit would be applicable to the group of tanks at a tank battery.

Tank hatches or openings would have to be monitored for leaks as a part of LDAR program.

Natural Gas Driven Pumps

For the production segment (well sites, compressor stations) all new natural gas-driven diaphragm and piston pumps (piston pumps were previously exempt) with access to a control device already onsite must reduce emissions by 95%.

Diaphragm pumps in the transmission segment with access to a control device already onsite must reduce emissions by 95%.

EPA is seeking comment on whether it is technically feasible to require the use of zero emitting pneumatic pumps at new and existing facilities with access to electric power or solar power.

Natural Gas Pneumatic Controllers

Require all new and existing pneumatic controllers in production, processing, and transmission and storage facilities to have zero methane and VOC emissions, with the exception of sites in Alaska that do not have power.

This includes intermittent-bleed pneumatic controllers. Currently, only continuous bleed devices are regulated by OOOO/OOOOa.

Associated Gas from Oil Wells

Natural gas produced from some oil wells is not able to be sent to a natural gas pipeline and is often flared or vented to the atmosphere. This associated gas in the past has been regulated by a State’s oil and gas mineral agency (e.g., Texas Railroad Commission, Oklahoma Corporation Commission).

The proposed rule requires sending the gas to a sales pipeline and if a sales pipeline is not available, then the gas should be sent to a control device (e.g., ECD, flare). No venting will be allowed. Also, the proposal includes recordkeeping and reporting provisions to ensure the flares (and enclosed combustion devices) are operating properly.

Well Liquids Unloading – New Proposed Emission Source

The proposal adds well liquids unloading vent gas to the list of sources requiring controls.

The proposed rule requires performing liquids unloading with zero methane or VOC emissions. Best management practices may be used if this is not feasible for safety or technical reasons.

IMPORTANT: For NSPS OOOOb (as applicable to new, modified and/or reconstrued facilities), EPA states that any instance of an existing facility conducting a well unloading activity would be considered a modification. So, from the date of that unloading activity, an existing facility would be subject to these proposed requirements in OOOOb.

Wet Seal Centrifugal Compressors

For wet seal centrifugal compressors (not located at single well sites), capture and route emissions from

the wet seal fluid degassing system to a control device or to a process.

Reciprocating Compressors

For reciprocating compressors (not located at single well sites), replace the reciprocating compressor rod packing based on annual monitoring when the measured leak rate exceeds 2 standard cubic feet per minute (scfm) or route emissions to a process.

Potential New Emission Sources – Pigging Operations and Tank Truck Loading

The supplemental proposal in 2022 may address emissions from pipeline pigging operations and tank truck (or railcar) loading of crude oil.

NSPS OOOOc Environmental Guidelines

The NSPS OOOOc Environmental Guidelines (EG) will affect existing sources constructed prior to November 15, 2021.

The EPA proposal indicated that the OOOOb emission standards are used to develop the emissions guidelines used for OOOOc.

The emission guidelines included in OOOOc are standards that each State will be required to implement in their respective permitting/compliance regulations to regulate methane (as a GHG) and VOCs. The States regulations must be as strict as the OOOOc EG standards.

The proposal includes a table OOOOc EG listing best system of emission reduction (BSER) and presumptive standards for GHGs.

For OOOOc EG existing storage tanks or tank batteries with a potential to emit equal to or greater than 20 tons of methane per year would have to control emissions by 95 percent.

Summary and Conclusions

In November 2021, the U.S. Environmental Protection Agency (EPA) proposed regulations to control methane and VOC emissions from oil and natural gas industry operations. These rules add/replace existing rules in NSPS OOOO/OOOOa.

The proposed rules in OOOOb will affect new facilities after November 15, 2021. Facilities existing on or before November 15, 2021 are considered existing sources and would have to comply with NSPS OOOOc Emissions Guidelines (EG). OOOOc EG requirements would be implemented at the State level.

NSPS OOOO and OOOOa would still apply to facilities while the OOOOc EGs are being approved. There is no information regarding NSPS OOOO and OOOOa applicability while OOOOc EG rules are being approved for each State.

The affected emission sources include completions of hydraulically fractured wells, Compressors

Fugitive emissions, liquids unloading, pneumatic controllers, pneumatic pumps, storage vessels, sweetening units. Potential new emission sources not previously in OOOOa include pipeline pigging operations and tank truck loading operations.

The EPA will issue a supplemental proposal in 2022 to supply regulatory text for NSPS OOOOb and OOOOc EG. The supplemental proposal in 2022 may also address emissions from pipeline pigging operations and tank truck (or railcar) loading of crude oil.

The expected date for NSPS OOOOb approval is end of year 2022. Approval of OOOOc EG by each State would extend into 2025 or later.

Affected and interested parties are encouraged to submit comments to the EPA.


Cimarron – Who We Are

Cimarron’s vision is to work with our clients to create a cleaner environment by controlling their emissions.

The company engineers and manufactures environmental, production and process equipment for the upstream, midstream and downstream energy industries, as well as environmental control solutions for biogas at wastewater facilities, digester tanks and landfills.

Cimarron offers our customers the know-how and environmental expertise to meet the environmental standards of today and tomorrow. Cimarron is committed to bring value to the Energy industry and their shareholders based on our financial strength, experienced personnel, and engineering capabilities.

As a company, we thrive every day to make a difference through innovation (e.g. ESG), customer focus, and operational efficiency. In addition to being present in all major regions in the US, Cimarron serves more than 45 countries around the world, ranging from offshore to desert. From key operational centers in the United States, Italy and the United Arab Emirates, Cimarron offers ongoing service and support through its own field service personnel and strategic third-party partners, creating a cleaner environment for our customers and their shareholders.

Since its founding in the mid-1970’s in Oklahoma, the company’s product offering has expanded from production equipment to include the largest line of environmental solutions that capture or incinerate fugitive vapors. With the acquisitions of HY-BON/EDI in 2019 and AEREON (including Jordan Technologies) in 2020, Cimarron has added strong brands, products, and ervices to its portfolio.

Please contact us to learn more about our products and services and about all our emission control solutions at sales@cimarron.com or visit our website www.cimarron.com.

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