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<br />For purposes of the 2020 analyses, the background concentrations were adjusted for <br />region-wide increases in traffic volumes and vehicle emissions. The adjustment factor for <br />traffic growth was based on the regional travel forecast model. The adjustment factor for <br />vehicle emission was based on the MOBILE5A emissions model, which incorporates <br />anticipated decreases in CO emissions from motor vehicles due to emission controls. The <br />Holzworth (temperature) correction factor was required to adjust for worst-case winter <br />conditions. The results are summarized in Table 18. <br /> <br />. <br /> <br />TABLE 18 <br />CALCULATION OF CO BACKGROUND CONCENTRATIONS <br /> <br /> 2020 <br />Factor I-Hour 8-Hour <br />Maximum 1999 Monitored Concentration (ppm) 1.23 0.82 <br />Background Traffic Volume Adjustment Factor 2.28 2.28 <br />Emission Adjustment Factor 0.89 0.89 <br />Holzworth (temperature) Correction 2.00 2.00 <br />Worst-Case Background Concentration (ppm) 5.0 3.3 <br />State Standard (ppm) 30 9 <br />Federal Standard (ppm) 35 9 <br /> <br />. <br /> <br />Intersection Carbon Monoxide Modeling <br /> <br />Carbon monoxide analyses were performed for the Build alternative in the year 2020 at the <br />following key intersections: Lexington AvenuelTH 96, Hamline Avenue/TH 96, <br />Lexington Avenue/County Road F, Hamline Avenue/County Road F, and Lexington <br />A venue/I-694, These intersections, both signalized and unsignalized, were chosen after <br />consultation with the MPCA because of their low levels of service and their impact on the <br />surrounding area. The No-Build Alternative was not modeled because the 2020 Build <br />Alternative represents a worst-case situation. <br /> <br />Forecast traffic volumes and optimized signal tlmmg was obtained from the Guidant <br />Corporation Traffic Impact Study, prepared by Parsons Transportation Group in July 2002. <br /> <br />Locations of likely outdoor human activity adjacent to the analyzed interchanges were <br />selected for air quality modeling receptors; Figure 15 depicts the receptor locations. <br />Carbon monoxide concentrations modeled for peak traffic volumes for the year 2020 are <br />shown in Tables 19 and 20. The CO concentrations shown for each receptor are the <br />predicted maximum CO concentrations taken from the results of all modeled wind angles . <br />(0 - 360 degrees). <br /> <br />Guidant Campus Master Plan <br />Draft AUAR <br /> <br />- 43- <br /> <br />September 2002 <br />