Opinion ID: 815697
Heading Depth: 3
Heading Rank: 2

Heading: Significant Monitoring Concentration

Text: In 1980, the EPA “adopted regulations that exempt sources from preconstruction monitoring requirements [i.e., § 165(e)(2) of the Act] for a pollutant if the source can demonstrate that its ambient air impact is less than a value known as the [SMC].” Id. at 54,141. When the EPA first adopted SMCs for other pollutants in 1980, 1 it described the SMCs as “air quality concentration de minimis levels for each 1 When the EPA established the preconstruction monitoring exemption in 1980, it did not label the emissions values below which the exemption applied as “SMCs,” instead terming them “de minimis emissions levels.” See 45 Fed. Reg. 52,676, 52,709 (Aug. 7, 1980). But because the de minimis emissions levels promulgated in 1980 serve the same function as the PM2.5 SMC, we will refer to the 1980 de minimis levels as SMCs throughout this opinion. 8 pollutant for the purpose of providing a possible exemption from monitoring requirements.” Id. (internal alterations and citations omitted). In its proposed rule establishing an SMC for PM2.5, the EPA explained that “[i]f a source can show through modeling of its emissions alone that its impacts are less than the corresponding SMC, there is little to be gained by requiring that source to collect additional monitoring data on PM2.5 emissions to establish background concentrations for further analysis.” Id. The EPA proposed different methodologies for establishing a value for the SMC and, as with the SILs, relied on the de minimis discussion from Alabama Power as the legal basis for establishing an SMC for PM2.5. 72 Fed. Reg. at 54,141. C. Final Rule In its final rule, the EPA adopted and set values for both the SILs and SMC for PM2.5. See 75 Fed. Reg. at 64,864. The EPA gave three purposes for the SILs in the final rule, which were to determine:
warrant a comprehensive (cumulative) source impact analysis; (2) the size of the impact area within which the air quality analysis is completed, and (3) whether the emissions increase from a proposed new major stationary source or major modification is considered to cause or contribute to a violation of any NAAQS. Id. at 64,890. In adopting the SMC, the EPA emphasized that it retained discretion “to determine when it may be appropriate to exempt a proposed new major stationary source or major modification from the ambient monitoring data requirements 9 under the PSD rules.” Id. at 64,895. The rule codified the SILs at 40 C.F.R. § 51.166(k)(2) and 40 C.F.R. § 52.21(k)(2), and the SMC at 40 C.F.R. § 51.166(i)(5)(i)(c) and 40 C.F.R. § 52.21(i)(5)(i)(c). 75 Fed. Reg. at 64,902–07. The rule also codified the PM2.5 SILs in the EPA’s regulations on new source review and permitting requirements at 40 C.F.R. § 51.165(b)(2). Unlike the PSD regulations (40 C.F.R. §§ 51.166, 52.21), § 51.165(b)(2) does not use the SILs to exempt a source from conducting a cumulative air quality analysis. Instead, § 51.165(b)(2) states that a proposed source or modification will be considered to cause a violation of a NAAQS when that source or modification would, at a minimum, exceed the SIL in any area that does not or would not meet the applicable NAAQS.