For purposes of § 80.69, computer controlled sequential blending is considered to be a form of computer controlled in line blending, and qualifies for the sampling and testing rates applicable to computer controlled oxygenate blending under §§ 80.69(a)(7)(i)(B)(2) and (e)(2)(ii)(A). The fact that the blend is carried out with the help of computer technology provides an additional level of oversight over non-computer controlled splash blending. This extra margin of confidence is the reason for the reduced sampling frequency where computer controlled in line blending is used.
The only concern with sequential blending is whether or not the resulting splash blend will be homogeneous. This can also be a concern for in line blending if the pumping rates of the blendstocks are not consistent throughout the entire blend. For example, if oxygenate is added last in a sequential blend, or if the oxygenate addition of an in line blend finishes at a rate greater than the target ratio, then portions of the tank compartment will most likely be non-homogeneous.
In either case, sampling can be compromised by the possibility of an unmixed blend. To avoid this problem it is recommended that oxygenate be added to the truck before RBOB during sequential blending in order to facilitate complete blending of the oxygenate.(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)