Changes to Tank Degassing and Cleaning Rules Texas Association of Environmental Professionals

1. Changes to Tank Degassing and Cleaning Rules Texas Association of Environmental Professionals Air Quality Division • Teresa Hurley, P.E. • May 15, 2008

2. Tank Degassing and Cleaning Rules • What are the current requirements? • Why were the rules changed? • What changed? • When do changes take effect? • Questions

3. What are the current requirements? • 30 TAC Chapter 115 Subchapter F Division 3: Degassing or Cleaning of Stationary, Marine, or Transport Vessels • Applicability: • Stationary tanks with capacity ≥ one million gallons • Transport vessels with capacity ≥ 8,000 gallons • Marine vessels with capacity ≥ 420,000 gallons • Vapor space partial pressure ≥ 0.5 psia

4. What are the current requirements? • Control Requirements: • 90% control of vapors • No avoidable leaks • Must use vapor-tight connections • No intentional bypass of vapor control device

5. What are the current requirements? • Vapors must be routed to control device until: • Partial vapor pressure < 0.5 psia; 19,000 ppm by weight; 34,000 ppm by volume as methane; OR • Turnover of at least four vapor space volumes has occurred • Vapors can be vented to the atmosphere after any of the above conditions is satisfied

6. Why were the rules changed? • Studies have indicated that VOC emissions in HGB area are under-reported in emissions inventories. • Remote sensing study results have indicated that degassing emissions are under-reported. • Rule changes were made to reduce the previously under-reported emissions.

7. What changed? • Eliminated “four turnover” condition for allowing vent to atmosphere • Confusion over measurement: must be volume passing through tank vapor space; not measured after combustion control • Does not account for presence of residual liquid in the tank

8. Floating Roof Tank - Drain Dry Source: API, 2004

9. Floating Roof Tank with a Liquid Heel Source: API, 2004

10. What changed? • Control degassing vapors until • VOC concentration of vapors ≤ 34,000 ppmv as methane, or • < 50% of lower explosive limit

11. What changed? • Monitor VOC concentration of degassing vapors according to 115.545(11) • Allow flexibility in monitoring methods • Maintain records to demonstrate that method works for compounds present

12. What changed? • Specified monitoring methods: • Test Method 21 (40 CFR Part 60, Appendix A) • Test Method 18 (40 CFR Part 60, Appendix A) • Bag samples • Test Method 25A (40 CFR Part 60, Appendix A) • Portable hydrocarbon gas analyzer using appropriate detector • Lower explosive limit detector calibrated and maintained according to manufacturer's specifications

13. What changed? • Monitoring must continue while vapors are vented to atmosphere: • At least once every 12 hours if ventilation is continuous • If ventilation ceases for more than 4 hours, concentration must be rechecked before venting to atmosphere • Monitoring can be discontinued after five consecutive readings less than 34,000 ppmv or 50% of LEL

14. What changed? • Require control of vapors for smaller tanks: • Capacity ≥ 250,000 with vapor pressure ≥ 0.5 psia • Capacity ≥ 75,000 with vapor pressure > 2.6 psia

15. When do changes take effect? • Compliance date for new requirements is January 1, 2009

16. For more information Teresa S. Hurley, P.E. TCEQ Air Quality Planning Section 512-239-5316 thurley@tceq.state.tx.us