New NSPS OOOO Storage Tank Definition & Methane Emissions Regulations
January 21, 2015

New NSPS OOOO Storage Tank Definition and Future Regulation of Methane Emissions from O&G Facilities

On December 31, 2014, the USEPA published in the Federal Register the latest changes to 40 CFR 60 Subpart OOOO (Quad O).   These changes are referred to as NSPS OOOO 1.5 since EPA is also working on more substantial changes referred to as NSPS OOOO 2.0. The next changes are expected to be proposed in 2015 and finalized in 2016.

In addition to this news, on January 14, 2015, the White House announced steps they are taking to further reduce methane and VOC emissions from the oil and gas industry. This is a part of the Administration’s Climate Action Plan. These steps will include regulation of methane emissions from new and modified oil and gas sources and facilities.

Below is a summary of the final changes that affect storage tanks and the Climate Action Plan.

NSPS OOOO Storage Tanks Rule Changes

Definition of a Storage Tank

The rule had a significant change in the definition of a storage vessel (i.e., storage tank). The rule added the following wording to the definition:

“Two or more storage vessels connected in parallel are considered equivalent to a single storage vessel with throughput equal to the total throughput of the storage vessels connected in parallel.”

Why is this storage tank definition change important?

This can impact how a facility determines the applicability of NSPS OOOO to their crude, condensate and produced water storage tanks. Based on this definition, if all storage tanks are connected in parallel and are considered one storage tank, then the facility cannot divide by the number of tanks to get the per tank VOC emissions (i.e., average VOC emissions across tanks). This may affect the regulatory status of affected storage tanks and could mean that the facilities storage tanks trigger NSPS OOOO requirements even with the use of a flare or vapor combustion device.

Qualification: The meaning and effect of this new storage tank definition is currently being discussed by industry, trade organizations and regulators. 

Compliance Heads-Up

Operators may want to review their air permits to determine how this new storage tank definition affects current and future operations. 




White House Climate Action Plan for Regulating Methane Emissions

Some elements of the Climate Action Plan announcement on January 14, 2015, include:

  1. The EPA will propose standards to reduce methane and ozone-forming emissions (e.g., VOCs) from new and modified oil and gas sources. The rule is scheduled to be proposed in the summer of 2015 and finalized in 2016. This may be a part of NSPS OOOO 2.0. Some potential emission sources to be targeted include: Oil well completions, Pneumatic pumps, Leaks from well sites, gathering, boosting and compressor stations
  2. Set new guidelines to reduce VOCs from existing oil and gas systems in areas that do not meet the ozone (smog) health standard and in states in the Ozone Transport Region. 
  3. Consider enhancing leak detection and GHG emissions reporting for oil and gas operations. 
  4. The Bureau of Land Management (BLM) will update standards to reduce venting, flaring, and leaks of natural gas from oil and gas wells on federal lands. 
  5. Reduce methane emissions while improving pipeline safety. Develop and demonstrate more cost-effective technologies to detect and reduce losses from natural gas transmission and distribution systems. Encourage steps to modernize natural gas transmission and distribution infrastructure.
  6. Enhance and expand the EPA Gas STAR Program. 
  7. Work with DOE, DOT, leading companies and initiatives such as the One Future Initiative to reduce methane emission voluntarily. One Future Initiative has a goal of achieving an eventual 1% leakage rate across the entire value chain (production through distribution). 


  1. NSPS OOOO updates and clarifications published on December 31, 2014 by EPA. Final Rule (PDF) and Fact Sheet (PDF)
  2. The White House, Office of the Press Secretary FACT SHEET: Administration Takes Steps Forward on Climate Action Plan by Announcing Actions to Cut Methane Emissions
  3. EPA Natural Gas STAR Program - The Natural Gas STAR Program is a flexible, voluntary partnership that fosters oil and natural gas companies to adopt cost-effective technologies and practices that improve operational efficiency and reduce methane emissions.



HY-BON help your company with compliance with NSPS OOOO.
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For more information on NSPS OOOO (Quad O) check out HY-BON’s Blog ( and the original rule’s summary at HY-BON NSPS OOOO Summary.