EPA is proposing to disapprove a revision to Wisconsin’s State Implementation Plan (SIP) submitted by the Wisconsin Department of Natural Resources (WDNR) in a letter dated May 12, 2011. The revision concerns permitting requirements relating to particulate matter of less than 2.5 micrometers (PM2.5). EPA is proposing to disapprove the revisions because they do not meet the 2008 PM2.5 SIP requirements.

As background, in May 2008 EPA finalized regulations to implement the New Source Review (NSR) Implementation Rule for PM2.5 to include the major source threshold, significant emissions rate and offset ratios for PM2.5, interpollutant trading for offsets and applicability of NSR to PM2.5 precursors. On October 20, 2010, EPA amended the requirements for PM2.5 under the Prevention of Significant Deterioration (PSD) program by adding maximum allowable increase in ambient pollutant concentrations and screening tools known as the Significant Impact Levels and Significant Monitoring Concentration (SMC) for PM2.5.
On May 12, 2011, Wisconsin requested a revision to its SIP to include new permit requirements relating to PM2.5. The provisions were designed to match the requirements set forth in the May 2008 and October 2010 rules. The submittal included permanent rules to define major source thresholds and significant emission increase levels; establish the SMC for PM2.5; establish interpollutant trading ratios for PM2.5, sulfur dioxide (SO2) and nitrogen oxides (NOX); and clarify existing nonattainment area permitting rules.

On July 21, 2011, EPA announced a change in its policy concerning the development and adoption of interpollutant trading provisions for PM2.5. The new policy requires that any ratio involving PM2.5 precursors submitted to EPA for approval for use in a state’s interpollutant offset program for PM2.5 nonattainment areas must be accompanied by a technical demonstration that shows the net air quality benefits of such a ratio for the PM2.5 nonattainment area in which it will be applied. In a letter dated March 5, 2012, WDNR requested to withdraw its request to have NR 408.06(1)(cm), the provision pertaining to interpollutant trading ratios, included in its 2011 submittal.

EPA has evaluated WDNR’s proposed revisions to the Wisconsin SIP in accordance with the Federal requirements governing state permitting programs. EPA is proposing to disapprove these revisions because they do not meet all the requirements of the 2008 rules. According to EPA, Wisconsin’s current SIP does not contain the explicit language to account for PM2.5 and PM10 condensables in permitting decisions, as codified in 51.166(b)(49)(vi) and 40 CFR 52.21(b)(50)(vi), and to date, the State has not made a submission with such revisions.

EPA is proposing to disapprove the revisions to Wisconsin rules NR 400, 404, 405, 406, 407, 408 and 484, submitted by the State on May 12, 2011, for approval into the SIP. The full or partial disapproval of a SIP revision triggers the requirement under section 110(c) that EPA promulgate a Federal Implementation Plan (FIP) no later than two years from the date of the disapproval unless the state corrects the deficiency, and the Administrator approves the plan or plan revision before the Administrator promulgates such FIP.

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