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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 2 Tank Degassing and Cleaning Rules What are the current requirements? Why were the rules changed? What changed? When do changes take effect? Questions

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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.

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 8 Floating Roof Tank - Drain Dry Source: API, 2004

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 9 Floating Roof Tank with a Liquid Heel Source: API, 2004

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 10 What changed? Control degassing vapors until –VOC concentration of vapors ≤ 34,000 ppmv as methane, or –< 50% of lower explosive limit

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 11 What changed? Monitor VOC concentration of degassing vapors according to (11) –Allow flexibility in monitoring methods –Maintain records to demonstrate that method works for compounds present

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 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

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 15 When do changes take effect? Compliance date for new requirements is January 1, 2009

Air Quality Division Tank Degassing and Cleaning Rules; TSH :May 15, 2008 Page 16 For more information Teresa S. Hurley, P.E. TCEQ Air Quality Planning Section