Opinion ID: 772539
Heading Depth: 3
Heading Rank: 1

Heading: EPA's Rationale

Text: 26 EPA designated as a de minimis source of PM-10 pollution in the Phoenix area any source that contributed less than one microgram per cubic meter of PM-10 to a location of expected annual exceedences, and less than five micrograms per cubic meter to a location of expected 24-hour standard exceedences. (To be considered de minimis, a source's PM-10 contribution had to contribute less than the amounts specified for both the annual and 24-hour standards.) 27 EPA eventually designated thirteen source categories as de minimis: industrial yards, surface mining, other industrial activities, fuel combustion, charbroiling, residential wood combustion, paved parking lots, locomotives, gasolinepowered on-road motor vehicles, diesel-powered on-road motor vehicles, airport ground support, major point sources, and other area sources (e.g. open burning, structural fires). Of these thirteen source categories, only four were unregulated in the FIP, either because the remaining nine were already controlled by existing control measures, or because no reasonably available control measures existed. The four sources of PM10 unregulated as de minimis were gas on-road motor vehicles, diesel on-road motor vehicles, locomotives, and airport ground support. 28 EPA adopted the de minimis thresholds from the federal new source review program for issuing permits to new stationary sources of pollution, including PM-10. See 40 C.F.R. 51.165(b). The new source review program applies to new sources of PM-10 pollution located in attainment areas. The de minimis levels in the program, however, were keyed to thenew sources' impact in nearby nonattainment areas. Ober challenges the use of the new source de minimis levels to establish de minimis thresholds in Phoenix's FIP. 29 In 1987, when EPA adopted the de minimis levels for the new source review program, the agency explained that the purpose of the thresholds was to enable the states to determine whether the modeled ambient impact of a new source or modification would significantly affect the air quality. 52 Fed. Reg. 24672, 24706 (1987). If the impact of a new source on PM-10 levels in a nonattainment area was below the specified thresholds, the impact was deemed insignificant, and no controls were required, because the source's impact would not be sufficient to cause or contribute to a NAAQS violation. Id. EPA would be required to make sure that the accumulated de minimis exemptions did not push the PM-10 levels in an area over the NAAQS. Id. at 24707. 30 EPA concluded that the de minimis levels for new sources of PM-10 would be applied to existing sources of PM-10 (such as those in this case) in 1994, relying on the inherent agency authority as described in Alabama Power : 31 [EPA] has the authority to exempt from regulation those source categories in the area which contribute only negligibly to ambient concentrations which exceed the NAAQS. The EPA believes the court's test for invoking the de minimis exemption authority would be satisfied in circumstances where a State demonstrates conclusively that, because of the small contribution of the source category's emissions to the nonattainment problem, the imposition of addi tional controls . . . on a particular source category in the area would not contribute significantly to the Act's purpose of achieving attainment of the NAAQS as expeditiously as practicable. 32 59 Fed. Reg. 41998, 42011 (1994). 33 EPA thus concluded that it will, in general, rely on the criteria applied under new source permitting programs (40 C.F.R. 51.165(b)) to determine when a source category contributes significantly to violations of the NAAQS in a PM-10 serious nonattainment area. Id. 3 The agency categorized PM10 pollution levels that were de minimis when generated by a new source of pollution as also de minimis when the pollution was generated by existing sources, such as the thirteen PM-10 sources considered de minimis in the Phoenix area. 34 EPA also concluded that it would be inappropriate to applythese de minimis standards automatically to every area that does not meet national air quality standards. Sources of de minimis amounts of PM-10 pollution would escape regulation only if the failure to regulate them would have little benefit on the affected area's air quality. EPA thus would decline to regulate de minimis sources of PM-10 only if the cumulative effect of controlling the pollution would not make the difference between attaining and not attaining clean air (the NAAQS) by the deadline set by the statute, December 31, 2000. See 42 U.S.C. S 7513(c)(2); 63 Fed. Reg. 15920, 15927 (de minimis categories cannot escape controls if such controls are needed for attainment).