1. Impact Area 1-hour standards

2. SILs used to determine when a proposed source’s ambient impacts warrant a comprehensive (cumulative) source impact analysis the size of the impact area within which the air quality analysis is completed whether the emissions increase from a proposed new major stationary source or major modification is considered to cause or contribute to a violation of any NAAQS

3. Misnomer? Is there a 1-hour standard or is it a three year standard whose metric is the 98 th or 99 th percentile of the distribution of 1-hour concentrations averaged over the 3- year period? Can there technically be more than one violation at a receptor over a given time period under the metric for the standard?

4. Distribution Sums The sum of n distributions of any type is approximately normal Its mean is equal to the sum of the means of the components The standard deviations add like the law of cosines.

5. Normal Distribution 99% of the data is below 2.3 standard deviations above the mean 98% of the data is below 2.06 standard deviations above the mean

7. EPA Proposed 1-hour SILS NO 2 1 st highest daily 1-hour value averaged over 5 years 7.52 ug/m 3 4 ppb 4% of the probabilistic standard SO 2 1 st highest daily 1-hour value averaged over 5 years 7.8 ug/m 3 3 ppb 4% of the probabilistic standard

8. SIL as Percentage Pollutant Averaging time (hours)/SIL as % of NAAQS Annual24831 SO 2 1.3%1.4% 1.9%4.0% PM 2.5 2.0%3.4% PM 10 N/A3.3% NO 2 1.0% 4.0% CO 4.9% 5.0% Pollutant Averaging time (hours)/SIL as % of Class 2 Increment Annual24831 SO 2 5.0%5.5% 4.9% PM 2.5 7.5%13.3% PM 10 5.9%16.7% NO 2 4.0% CO

9. Acute Exposure Guideline Levels AEGL-1 is the airborne concentration, expressed as parts per million or milligrams per cubic meter (ppm or mg/m 3 ) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure. NO 2 – 0.5 ppm (4% = 37.6 ug/m 3 ) SO 2 – 0.2 ppm (4% = 20.8 ug/m 3 )

10. Typical Impact Area 24-Hour <75 ug/m3 3-hour <8760 ug/m3 Annual

11. Possible Occurrence Outside Historical Impact Areas Concentration Averaging Period Annual24-hour3-hourAll 1100.00% 520.00%100.00% 20.00% 7.5213.30%66.49%100.00%8.84% 7.812.82%64.10%100.00%8.22% 1010.00%50.00%100.00%5.00% 156.67%33.33%100.00%2.22% 205.00%25.00%100.00%1.25% 254.00%20.00%100.00%0.80% 303.33%16.67%83.33%0.46% 352.86%14.29%71.43%0.29% 402.50%12.50%62.50%0.20% 452.22%11.11%55.56%0.14% 502.00%10.00%50.00%0.10% 551.82%9.09%45.45%0.08% 601.67%8.33%41.67%0.06% 651.54%7.69%38.46%0.05% 701.43%7.14%35.71%0.04% 751.33%6.67%33.33%0.03% 1001.00%5.00%25.00%0.01% 1100.91%4.55%22.73%0.01% 1200.83%4.17%20.83%0.01%

17. DesignDelta-DesignMAXDCONT 417.38057.01964 364.68265.83452 5.76713 430.97177.92233 387.21995.79543 378.97535.74531 298.8074.19981 311.26353.76977 348.11095.66055 305.83824.53899 308.07394.37661 340.55364.30596

18. Evaluate maximum 1-hour emissions against: Annual – 1 ug/m 3 24-hour – 5 ug/m 3 1-hour – 25 ug/m 3 If exceeded, culpability is determined by the difference in the design value with and without the project compared to EPA proposed SIL If not exceeded the project is considered insignificant.