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EPA has proposed some fundamental changes to its guidance for calculating emissions from storage tanks, namely, an emission calculations methodology for tank cleaning events and revised emission calculations for routine emissions. It has been no secret that EPA has ceased supporting the Tanks 4.09d software, but if the proposed changes to AP-42 become finalized, this will officially end the useful life of Tanks 4.09d.

Additional changes proposed to AP-42 Chapter 7.1 include several other methodology updates to:

  • Estimating flash emissions
  • Calculating net throughput for working loss from cumulative changes in the liquid level, rather than from pumping volume
  • Revising the default vapor pressure for No. 6 Oil upward significantly
  • Estimating emissions from tanks storing hot stocks, accounting for whether the tank is uninsulated, partially insulated, or fully insulated
  • Estimating emissions from low-pressure tanks

These changes would have varying degrees of impact on emissions estimated for most storage tanks. Changes to the guidance for estimating emissions from routine tank operations pertain primarily to refinements to the equations for estimating temperatures in a storage tank, which will result in higher estimated emissions in some cases, but lower in others. Although the estimated emissions will typically be within ten percent of the previously estimated values, the difference may be greater in certain scenarios. Guidance is also being considered for scenarios that had not previously been addressed in AP-42 Chapter 7.1, such as estimating emissions from the cleaning of storage tanks and adjustment to the equations for estimating emissions from routine operations in the case of partially or fully insulated tanks.

The comment period for these changes ended on November 26, 2018. A full analysis of the proposed changes, and the background for those changes, can be found here.

Trinity is offering a series of training courses related to storage tank regulations and emissions calculations with discounts available for booking partner courses. These include Tank Regulations Primer, Fundamentals of Tank Emission Calculations, and Tank Emission Calculation Workshop with TankESP Software.