Draft Ozone Procedures For a prevention ofsignificant deterioration (PSD) application, ifa project will emit 100 tons per year (tpy) or more ofVOC (volatile organic compounds) or NOx (nitrogen oxides) emissions, an ozone impact analysis to demonstrate predicted compliance with the eighthour ozone standard is required (1). Preconstruction ambient air monitoring is required as well, unless the applicant requests and receives a waiver. The Air Dispersion Modeling Team (ADM'!') will use the attached screening procedure for the ozone impact analysis. Determining Compliance with the Eight-Hour Ozone Standard Procedure: Step 1. Determine whethersite-specificmonitoringdata orrepresentative monitoring data willbe usedto obtain an ozone backgroundconcentration. A site-specific monitoring program must last a minimum ofat least 4-6 months up to 12 months during the ozone season before the application is submitted. Use the fourthhighest daily maximum 8-hour average ozone concentration monitored during a single ozone season (1, 2). Or, up to a 3-year average of the annual fourth-highest daily maximum 8-hour ozone concentration ifdata are available (3). "Representative" monitoring data may be available from the ozone network in Texas. Monitor in a different county: compare population and county-wide point, area, and mobile source emissions to find a similar county with monitored ozone data. Use the 3- year average ofthe annual fourth-highest daily maximum 8-hour ozone concentrations ifdata are available (3). Monitor in the same county: Use the 3-year average of the annual fourth-highest daily maximum 8-hour ozone concentrations ifdata are available (3). If the background concentration equals or exceeds 75 parts per billion (ppb), Step 2 cannot be used and approaches such as the applicant providing offsets or reducing VOC or NOx emissions for the project below 100 tpy would be considered. Step 2. Determine whetherthe site is VOC-limited orNOx-limited In VOC-fimitedareas (VOCto NOxratiosless than about4:1), minimizing orreducing VOCemissions is the most effective means o{/imitingorlowering ozone concentrations. In NOx-limitedareas (VOCto NOxratiosgreaterthan about 15:1) minimizingorreducingNOx emissions ismost effective. Identif'y the total allowable emissions of VOC and NOx in tpy from the site. Include requested increases from the project. Multiply the ratio by 2.875. This factor adjusts the ratio to relate the emissions to molar units consistent with ambient VOCjNOx ratios. It is derived by dividing moles of methane (CH4) by moles ofnitrogen dioxide (NOz).

### If the adjusted ratio is 2:1 or less, the site is 03-neutral and the demonstration is complete since there would not be a significant change to the current ozone levels in the local area. Ifthe adjusted ratio is greater than 2:1, go on to Step 3. 

### Step 3. 

### Contact the AkDispersion Modeling Team at512-239-1250forfurther guMance. The applicant should be prepared to present and discuss options. Some options may include thefollowing: Transportanalysis using windrose and pollution rose data Analysis ofsource type, for example low-level fugitive sources of VOC may not signillcantlyimpactozone concentrations References: (1) 40 

### CFR 52.21 (2) 40 

### CFR 58 

### Appendix D, 40 

### CFR 81 (3)40 

### CFR 50 

### Appendix I Resources for monitoring and emissions data: http:( (www.epa.gov(oar(data(repsst.html?st-TX

- Texas http://www.tceq.state.tx.us/nav/data/aq_data.html