E~stern 

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Air Pollution Control District Dae~C?.fo!YsE 0 

Air Pollution Con)WG~et012 

August 21,2012 

Gerardo Rios 

Chief, Air Permits Office (Air-3) 

EPA Region 9 

75 Hawthorne Street 

San Francisco, CA 94105 

SUBJECT: Additional Clarifications for Rule 210.4 and 40 CFR 51.166 

Dear Mr. Rios: 

Pennits Oftice Alr-3 

U.S. EPA. Region 9 

This letter is in response to your request for additional information regarding Eastern Kern Air 

Pollution Control District (District) Rule 210.4 PSD. In a letter dated July 19, 2012, we 

responded to your initial request for clarifications regarding Rule 210.4 and the requirements for 

a Prevention of Significant Deterioration (PSD) permitting program. Below we provide an 

additional clarification regarding Rule 21 0.4. 

To implement the PSD permitting program under the Clean Air Act (CAA), the District 

incorporated section 40 CFR 52.21(k)(2) ofEPA's regulations by reference into Rule 210.4 and 

included this provision as part of a SIP revision submitted to EPA for approval. The District 

understands that EPA has recently stated, in response to litigation, that EPA intends to revise its 

PSD permitting regulations at 40 CFR 51.166(k)(2) and 40 CFR 52.21 (k)(2) to ensure that these 

provisions are consistent with EPA statements in the supporting rulemaking record and the CAA. 

In light of EPA's response to the litigation and in order to ensure that permitting actions by the 

District are consistent with the CAA, I am writing to clarify that the District interprets and 

intends to apply the PSD program provisions in the District's portion of the California SIP in a 

manner that is consistent with certain EPA statements included in the preamble of the 2010 final 

rule that added section 52.2l(k)(2) to the federal regulations. 

Section 52.21(k)(2) establishes Significant Impact Levels (SILs) for PM2.s and reads as follows: 

(k)(2) Significant impact levels. For purposes ofPM25, the demonstration required in 

paragraph (k)(l) ofthis section is deemed to have been made if the emissions increase from 

the new stationary source alone or from the modification alone would cause, in all areas, air 

quality impacts less than the following amounts: 

Administrative Office: 2700 "M" Street, Suite 302, Bakersfield, CA 93301-2370 

Phone (661) 862-5250- Fax (66/) 862-5251 

www. kernair. org- ekapcd@co.kern.ca. us 
EKAPCD Rule 210.4 

August 21, 2012 

Page2 

Pollutant 

PM2.s ................. 

Averaging time 

Annual ............ 

24-hour ........... 

Class I area Class II area Class III area 

0.06j.!g/mj 0.3 jlg/mj 0.3 11g/mj 

0.07 jlg/mj 1.2 jlg/mj 1.2jlg/mJ 

Paragraph (k)(l) requires that sources applying for a new PSD permit demonstrate that any 

allowable emission increases from the proposed source or modification, in conjunction with all 

other applicable emissions increases or reductions, will not cause or contribute to a violation of 

any NAAQS or any applicable increment. In the preamble to the 2010 final rule adding the 

(k)(2) provision, EPA advised that, "notwithstanding the existence of a SIL, permitting 

authorities should determine when it may be appropriate to conclude that even a de minimis 

impact will 'cause or contribute' to an air quality problem and to seek remedial action from the 

proposed new source or modification." PSD for Particulate Matter Less than 2.5 Micrometers 

(PM2.5)-Increments, SILs and Significant Monitoring Concentration (SMC), 75 Fed. Reg. 

64,864,64,892 (Oct. 20, 2010). In another passage ofthe preamble, EPA also observed that "the 

use of a SIL may not be appropriate when a substantial portion of any NAAQS or increment is 

known to be consumed." Id. at 64,894. 

Consistent with these statements by EPA in the preamble to the 2010 final rule, the District does 

not interpret section 52.21 (k)(2) to preclude the District from exercising the discretion to 

determine when it may be appropriate to conclude that even a de minimis impact on air quality 

(an impact below the PM2.s SIL values) will cause or contribute to an air quality problem and to 

seek remedial action from the proposed new source or modification. Based on this 

interpretation, the District will not read section 52.21(k)(2) as an absolute "safe harbor," but will 

exercise discretion to determine whether a particular application of the PM2.s SILs is appropriate 

when a substantial portion of the PM2.s NAAQS or increment is known to be consumed. The 

District retains the discretion to require additional information from a permit applicant as needed 

to assure that the source will not cause or contribute to a violation of any NAAQS or applicable 

increment pursuant to paragraph 52.21 (k )(1 ). 

Our expectation is that the need for the District to exercise this discretion will only arise in 

limited circumstances. The District looks forward to receiving additional guidance from EPA on 

how to identify when a permitting authority should exercise this type of discretion before 

applying the PM2.5 SILs in section 52.21(k)(2) to support a demonstration that a source will not 

cause or contribute to a violation of the PM2.s NAAQS and increments. 

Sincerely, 

Air Pollution Control Officer 

DLJ: JC: dm