EPA Releases Guidance on Compliance Demonstration for Ozone and Fine Particles in the PSD Program

Permitting authorities may develop their own SIL values if they are supported in the record for permitting actions or decisions. The discretion of EPA and permitting authorities is limited by the 2010 rulemaking. Since the rule established by regulation that a PM2.5 impact greater than a certain value will be considered to cause or contribute to a NAAQS violation, the permitting authorities may not use a value higher than the PM2.5 SIL values for NAAQS. Because ozone is not addressed in 40 CFR 51.165(b)(2), authorities may develop a higher ozone NAAQS SIL value than the recommended value. 40 CFR 51.165(b)(2) does not address PSD increments, so permitting authorities may develop a higher SIL value for PSD increment purposes. EPA intends to learn from permitting authorities voluntary use of the SIL values during the permitting process to determine whether the use of SILs are appropriate. The recommended SIL values for NAAQS are:

Table 1. Recommended SIL Values for Ozone and PM2.5 NAAQS
Criteria Pollutant (NAAQS level)	NAAQS SIL concentration
Ozone 8-hour (70 ppb)	1.0 ppb
PM2.5 24-hour (35 µg/m3 )	1.2 µg/m3 *
PM2.5 annual (12 µg/m3 or 15 µg/m3 )	0.2 µg/m3

* The table accounts for the significance level for the 24-hour PM2.5 NAAQS in 40 CFR 51.165(b)(2). Refer to the guidance discussion for details The recommended SIL values for ozone and PM2.5 NAAQS are the same regardless of the airshed class. The recommended SIL values for PSD Increments are:

Table 2. Recommended SIL Values for PM2.5 PSD Increments
Criteria Pollutant (averaging period)	PSD increment SIL concentration
	Class I	Class I	Class III
PM2.5 (24-hour)	0.27 µg/m3	1.2 µg/m3	1.2 µg/m3
PM2.5 (annual)	0.05 µg/m3	0.2 µg/m3	0.2 µg/m3

There are no PSD increments for ozone, so EPA has not calculated ozone SIL values for PSD increment compliance purposes.