In the case of the transition at the conclusion of the high ozone season from MTBE-based RFG to ethanol-based RFG, the prohibition at § 80.78(a)(8) would not apply because by its terms this prohibition is limited only to the period through September 15. As a result, beginning on September 16 each year ethanol-based RFG may be delivered to a retail station storage tank that contains MTBE-based RFG. In addition, the ethanol-based RFG that would be delivered subsequent to September 15 probably would not be VOC-controlled. Because the § 80.78(a)(8) prohibition only applies to mixtures of two VOC-controlled RFGs, the post-September 15 mixing would not violate the prohibition for this additional reason.
In the case of the transition in advance of the high ozone season, from ethanol-based RFG to MTBE-based RFG, the § 80.78(a)(8) prohibition would not be violated if MTBE-based RFG is added to a retail station storage tank through normal gasoline deliveries even if the tank contains ethanol-based RFG, provided that these deliveries occur in advance of June 1 of each year and the storage tank is completely transitioned to MTBE-based RFG (i.e., the tank contains no ethanol) beginning on June 1. This process for changing the service of a storage tank does not violate § 80.78(a)(8) because the ethanol-based RFG in the storage tank is not VOC-controlled, and this prohibition only applies to mixtures of two RFGs that are both VOC-controlled.
During the high ozone season for the retail station, June 1 through September 15 each year, the gasoline in the storage tank must be VOC-controlled, and as a result the prohibition at § 80.78(a)(8) would apply and the gasoline in the retail station's storage tank may not have a mixture of ethanol and any other oxygenate.
This answer does not alter the option available to parties for blending the gasoline in storage tanks to meet the RFG standard in advance of the onset of the RFG program, on January 1, 1995 at the retail level and December 1, 1994 at upstream facilities, that is discussed in question IX-A-1 of the July 1, 1994 Question and Answer Document.(9/26/94)
This question and answer was posted at Consolidated List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (PDF)(333 pp, 18.17 MB, EPA420-R-03-009, July 2003, About PDF)