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EPA issues final rule to repeal PM10 Surrogate Policy

08.01.2011

As reported in the first quarter 2010 Greenebaum Air Quality Letter, on February 11, 2010, EPA proposed to end its policy that allowed permittees to rely on analyses of coarse particulate emissions (PM10) as a surrogate for analyses of fine particulate emissions (PM2.5) in PSD permit reviews. A basis for the PM10 surrogate policy was that technical issues relating to evaluation of PM2.5 emissions for PSD review purposes had not been resolved. In its proposal, EPA requested comment on whether technical difficulties with respect to conducting PM2.5 ambient air impact analyses had in fact been resolved. DAQ submitted comments on EPA’s proposal on March 22, 2010 and disagreed with EPA’s findings noting that technical issues that gave rise to the PM10 surrogate policy still remained with respect to modeling protocols as well as finalization of PSD increments, significant monitoring concentrations (SMCs), and significant impact levels (SILs). On October 20, 2010, EPA published a final rule establishing increments, SILs, and SMCs for PM2.5 emissions.

In its May 10, 2011 final rule repealing the “grandfather” provision in the Federal Register, EPA found that the technical issues “have largely been resolved” and that it was no longer appropriate to rely on PM10 as a surrogate for PM2.5 analyses. However, EPA acknowledged that current modeling techniques do not adequately account for the secondarily-formed ambient impacts of PM2.5 caused by PM2.5 precursors. Nevertheless, EPA noted it was reasonable to carry out the required air quality impact analyses with models that evaluate the ambient impact of direct PM2.5 emissions.

EPA also identified several additional developments as important progress for addressing technical issues that previously impeded PM2.5 analyses: deployment and operation of expanded monitoring networks for PM2.5; promulgation of significant emission rates, SILs, and SMCs; and issuance of revised test methods for sampling PM2.5 and its condensable fraction. Finally, EPA noted it has issued modeling guidance entitled “Modeling Procedures for Demonstrating Compliance with the PM2.5 NAAQS” that can be utilized to reasonably predict PM2.5 impacts from sources. With respect to concerns expressed by states regarding the adequacy of PM2.5 emission inventories and emission factors, EPA noted that while such inventories are evolving, their quality is sufficient for modeling emissions sources other than the source being permitted.

As a result of EPA’s final rule, the PM10 surrogate policy is repealed for purposes of the PSD program administered by EPA in states without SIP-approved PSD programs. For states with SIP-approved PSD programs such as Kentucky, use of the 1997 PM10 surrogate policy ended on May 16, 2011 in accordance with EPA’s discussion in the May 16, 2008 preamble.


To view a complete PDF of the Second Quarter 2011 issue of the Air Quality Letter, click HERE.

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