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5.1 E:CONSTRUCTION EMISSIONS AND IMPACT ANALYSIS <br /> The 1-hour and annual average concentrations of NO2 were computed following the revised <br /> EPA guidance for computing these concentrations (August 9,1995 Federal Register, <br /> 60 FR 40465). The OLM method was used for the 1-hour average NO2 impacts;uncorrected <br /> 1-hour impacts are also reported for comparison. The annual average was calculated using <br /> the ambient ratio method (ARM) with the national default value of 0.75 for the annual <br /> average NO2/NOx ratio. <br /> The modeling analysis results are shown in Table 5.1E-4. Also included in the table are the <br /> maximum background levels that have occurred in the last 3 years and the resulting total <br /> ambient impacts. Construction impacts alone for all modeled pollutants are expected to be <br /> below the most stringent state and national standards. With the exception of the 24-hour <br /> and annual average PMlo standards,construction activities are not expected to cause an <br /> exceedance of state or federal ambient air quality standards. However, the state 24-hour and <br /> annual PM10 standards are exceeded in the absence of the construction emissions for the <br /> project. <br /> The dust mitigation measures already proposed by the applicant are expected to be effective <br /> in minimizing fugitive dust emissions. The attached isopleth diagrams show the extent of <br /> the modeled impacts from construction PMlo for the 24-hour and annual averaging periods. <br /> TABLE 5.1 E-4 <br /> Modeled Maximum Onsite Construction Impacts <br /> Maximum Onsite Total State Federal <br /> Averaging Construction Background Impact Standard Standard <br /> Pollutant Time Impact(Ng/m3) (fag/m3) (pg/m3) (fag/m3) (fag/m3) <br /> NO2 1-hour 91.6 163.6 255 338 — <br /> Annual — 100 <br /> 3.6 34.0 38 <br /> SO2 1-hour 0.4 46.8 47 650 — <br /> 3-hour — 1300 <br /> 24-hour 0.3 28.6 29 109 365 <br /> Annual 0.1 10.8 11 80 <br /> 0.01 2.7 2.7 <br /> CO 1-hour 210 5,500 5,710 23,000 40,000 <br /> 8-hour 10,000 10,000 <br /> 94 3,178 3,272 <br /> PM10b 24-hour 35.6 85 121 50 150 <br /> Annual 20 -- <br /> 4.2 33.4 37.6 <br /> PM2.5b 24-Hour 10.2 48 58 — 35 <br /> Annual 12 15 <br /> 1.1 13.1 14.2 <br /> 5.1 E 6 SAC/371322/082330017(LEC-5.1 E_APPENDIX.DOC) <br />