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Proposed Changes to Standards of Performance for Volatile Organic Liquid Storage Vessels Could Save Money, Cut Emissions

Posted: December 7th, 2020

Authors: Paul S. 

U.S. Environmental Protection Agency (U.S. EPA) has proposed a revision to 40 CFR Part 60, Subpart Kb [Standards of Performance for Volatile Organic Liquid (VOL) Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which Construction, Reconstruction, or Modification Commenced After July 23, 1984], that will make inspection procedures less expensive and decrease volatile organic compound (VOC) emissions that result from the current methodology.  The proposed changes to Subpart Kb will apply to external floating roof tanks (EFR) and internal floating roof tanks (IFR) either with a design capacity greater than or equal to 151 m3 containing a VOL with a maximum true vapor pressure equal to or greater than 5.2 kilopascals (kPa) and less than 76.6 kPa, or with a design capacity equal to or greater than 75 m3 and less than 151 m3 containing a VOL that has a true vapor pressure equal to or greater than 27.6 kPa and less than 76.6 kPa.  If finalized, these changes will allow owners of certain storage vessels the choice to comply with the inspection requirements of 40 CFR Part 63, Subpart WW [National Emission Standards for Storage Vessels (Tanks) – Control Level 2] to satisfy the requirements of §§60.112b-60.117b in 40 CFR Part 60, Subpart Kb.  U.S. EPA took comments on the proposed revision until November 30.

Currently, under the requirements of 40 CFR Part 60, Subpart Kb, there are inspection procedures for IFR and EFR tanks to check for defects in the floating roof, seal, and deck fittings.  The required inspection involves the draining and degassing of the tank, followed by visual inspection of the primary seal, floating roof, and secondary seal (if one is in service).  For IFR tanks, this inspection must be conducted at least once every ten years.  For EFR tanks, an inspection must be conducted each time the tank is emptied and degassed.  Draining and degassing costs both time and money and causes VOC emissions.  However, the option to comply using procedures in 40 CFR Part 63, Subpart WW would eliminate the need to drain and degas the tank prior to a visual inspection.

40 CFR Part 63, Subpart WW was written to be referenced by other regulations to control air emissions from storage vessels and is considered by U.S. EPA as the flagship standard for EFR and IFR requirements under the National Emission Standards for Hazardous Air Pollutants (NESHAP).  Other regulations that rely on the provisions in Subpart WW include 40 CFR Part 63, Subparts YY, EEEE, and FFFF.  Under the inspection requirements for floating roof tanks codified in Subpart WW, visual inspections are performed to determine that the floating roof is sealed, all components are intact, no stored liquid is above the floating roof, all components that are required to be closed are closed and the floating roof is floating.  This inspection only requires “visual access” to all deck components in order to be performed, meaning there is no requirement to drain the tank.

To summarize, if the proposed changes are finalized, owners and operators of facilities with specific EFR and IFR that are subject to Subpart Kb will be given the choice to comply with the testing requirements of 40 CFR Part 63, Subpart WW to satisfy the requirements of §§60.112b-60.117b in Subpart Kb.  A notification would be required prior to conducting the first Subpart WW inspection.  Owners of applicable facilities can save money and reduce VOC emissions if they choose to comply with Subpart WW.  U.S. EPA estimates these provisions will save about $1 million per year across the country and prevent up to 83 tons per year of VOC emissions associated with emptying and degassing tanks at an estimated 385 facilities.

If you have any questions concerning the proposed changes to Subpart Kb, please email me at psarles@all4inc.com.

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