Opinion ID: 186132
Heading Depth: 3
Heading Rank: 1

Heading: Permit–Based MACT Floors

Text: for Existing Small Units First, Sierra Club challenges EPA’s decision to base existing small unit MACT floors on the emission limits contained in state permits. As in the 1995 Rule, in the 2000 Rule EPA based the MACT floor on the limits set for state-permitted MWC units in the particular subcategory. For each pollutant, EPA calculated the MACT floor by averaging the most stringent 12% of state permit limits in each class.15 For pollutants for which there were too few permitted units, EPA assigned a ‘‘default’’ emission level, namely, the estimated emission level of a totally uncontrolled unit. Sierra Club contends there is nothing in the record to demonstrate that state permit limits or the uncontrolled default levels reflect ‘‘the average emissions limitation achieved by the best performing 12 percent of units in the category,’’ the floor required by § 129(a)(2), 42 U.S.C. § 7429(a)(2). We agree with Sierra Club and conclude that the MACT floors for existing small units must therefore be remanded. 15EPA extracted the permit limits from its 1995 rulemaking database. EPA Permit Basis Mem. at 2 (J.A. 1757). 28 In Sierra Club v. EPA, 167 F.3d 658 (D.C. Cir. 1999), the court rejected EPA’s similar use of state permit limits to set the MACT floor for medical waste incinerators (MWIs). The court recognized that CAA § 129 may permissibly be construed ‘‘to permit the use of regulatory data’’ but only ‘‘if they allow EPA to make a reasonable estimate of the performance of the top 12 percent of units.’’ 167 F.3d at 662. The court rejected the use of such data in that case because ‘‘[a]lthough EPA said that it believed the combination of regulatory and uncontrolled data gave an accurate picture of the relevant MWIs’ performance, it never adequately said why it believed this.’’ Id. at 663. EPA fares no better here. It offered the following justification for deciding to use state permit limits: The EPA used a permit approach to determine the MACT floors in the 1995 emission guidelines (40 CFR part 60, subpart Cb) and believes that using the permit approach is appropriate for this rulemaking. Permit limits and regulatory limits provide a reasonable estimate of the actual performance of the best performing units under the worst reasonably foreseeable circumstances, making this approach consistent with the court opinion in the Sierra Club case. Permits include a margin for compliance and must be achievable. EPA Response to Comments at 75 (J.A. 2222). As in Sierra Club, EPA here stated only that it ‘‘believes’’ state permit limits reasonably reflect the actual performance of the best performing units without explaining why this is so. There is also evidence here that the MWCs, like the MWIs in Sierra Club, ‘‘might be substantially overachieving the permit limits,’’ that is, ‘‘the regulatory limits are in fact much higher than the emissions that units achieve in practice,’’ 167 F.3d at 663. See Sierra Club’s Br. at 22 (asserting, with record evidence, that EPA’s testing data show MWCs in general (and small MWCs in particular) ‘‘routinely overachieve their permit limits’’). Given the absence of evidence that the permit levels reflect the emission levels of the bestperforming 12 percent of existing MWCs and the affirmative 29 evidence that they do not, we cannot uphold the MACT floors for existing units under the CAA. In support of using state permit levels, EPA points to its determinations that emission levels are inherently variable, EPA Response to Comments (1995 Rule) (J.A. 1570), and that basing MACT floors on the Agency’s test data would not accurately reflect this variability, id. at J.A. 1633 (noting ‘‘it is not unusual for one or more of the annual tests to produce emissions that fall within the best 12–percent data, while the remaining annual test data fall outside this range’’). Even assuming actual testing data should not be used for setting MACT floors, EPA must still justify selecting state permit and uncontrolled default levels as alternative bases for the floors.