PM10 Concentration (μg/m3) Comparison of PM10-2.5 Design Values and PM10 Concentrations for the Same Day for Exceedances of the Proposed PM10-2.5 NAAQS Monitor Year PM10-2.5 Design Value (μg/m3) PM10 Concentration (μg/m3) Percent Equivalent PM10 NAAQS Tucson Orange Grove 2002 72 76 94.7% 74 Nogales 2000 77 92 83.7% 84 98 104 94.2% Douglas 2001 101 125 80.8% 87 2003 114 151 75.5% 93 Phoenix Super Site 134 167 80.2% 1999 150 164 91.5% 153 160 95.6% 73

Phoenix Area Visibility Index Excellent < 15 dv Good 15 – 20 dv Fair 21 – 24 dv Poor 25 – 28 dv Very Poor > 28 dv All Poor visibility days < 30 μg/m3 2/3rd Very Poor visibility days < 30 μg/m3

November 21, 2005 11am 14.3 ug/m3 26dv/19mi – Poor

December 21, 2005 noon 30.3 ug/m3 31dv/11mi – Very Poor