Opinion ID: 621128
Heading Depth: 3
Heading Rank: 4

Heading: Variable versus Fixed Emission Limits

Text: Montana Sulphur contends that the EPA acted arbitrarily and capriciously when it granted variable emission limits to a nearby power plant and the ExxonMobil refinery, but imposed fixed emission limits on it instead. In Montana's SIP, the state used a variable emissions limit for all three sources, which involved a computer dispersion model that required Montana to run 1,320 modeling scenarios. 73 Fed.Reg. at 21,444. However, as discussed above, in that modeling, Montana had improperly calculated the stack height credit for Montana Sulphur's primary 100-meter stack ( see section II.A., supra ). Because the EPA disapproved the SIP's use of the stack height credit in the modeling calculation, it was left with no fixed or variable emissions limit for Montana Sulphur; thus, it needed to fill this gap with the FIP. 67 Fed.Reg. at 22,170, 22,206. The EPA explained that it considered fixed emissions limits to be easier to model, monitor and enforce, 71 Fed.Reg. at 39,268, and that this was the type of limit used at virtually every other source in the country (with the exception of the other two Montana sources). 73 Fed.Reg. at 21,444-21,445. The EPA also notes that based on past reporting data, it appeared Montana Sulphur would be able to attain the fixed limit without the need for any additional pollution controls. 71 Fed.Reg. at 39,268. Because the EPA would have primary enforcement responsibility regarding the FIP and the Montana Sulphur emissions, it chose what it perceived as a simpler method. Although the EPA approved Montana's use of the variable limits with respect to the other two sources, the emission limits at play there did not involve improper stack calculations, and, in addition, the State was primarily responsible for ensuring the other sources' compliance with the variable limits. Montana Sulphur does not point to any other source in which the EPA itself imposed variable limits in a FIP. Moreover, the EPA expressed reservations about the State's use of the variable limits as to the other sources; it indicated it would be monitoring the situation closely and might reconsider its approval of those conditions if doubts arose about the accuracy of the monitoring and/or reporting under that system. 67 Fed.Reg. at 22,207. Thus, contrary to Montana Sulphur's argument, this is not a case where the EPA depart[ed], sub silentio, from its usual rules of decision to reach a different, unexplained result in a single case. See Western States Petroleum Ass'n v. EPA, 87 F.3d 280, 284 (9th Cir.1996) (quotation marks omitted). Rather, it offered a reasonable explanation for why it selected a different type of emissions limit than the State had chosen, and, in fact, explained that fixed emissions limits are the norm and the preferred method. 73 Fed.Reg. at 21,444-21,445.