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<br />#24397 <br /> <br />Background CO concentrations were derived from air quality monitoring conducted by Interpoll <br />Laboratories at a nearby site. The monitoring was conducted at 2983 Centre Pointe Road, between the <br />dates of December 21, 1996 and January 13, 1997. The Minnesota Pollution Control Agency (MPCA) <br />conducted a performance audit at the monitoring site on January 7, 1997. The results of the MPCA <br />audit indicate that the monitoring results are acceptable. <br /> <br />The maximum measured CO levels at the monitoring site were as follows: <br /> <br />· I-Hour Averaging Period: 2.2 ppm <br />· 8-Hour Averaging Period: 1.6 ppm <br /> <br />The maximum monitored CO concentrations were used to estimate background CO concentrations for <br />Year 2011. The monitoring results were adjusted from Year 1997 to Year 2011 based on projected <br />decreases in average CO emission rates from the MOBILE5a model, and on expected increases in <br />background vehicle-miles of travel (VMT) from the City of Roseville Travel Demand Model. The <br />adjustments are shown in Table 2. <br /> <br />Table 2. Year 2011 Background CO Concentration <br /> I-Hour 8-Hour <br /> Averaging Averaging <br /> Period Period <br />1997 CO Monitoring Results 2.2 ppm 1.6 ppm <br />MOBILE5a Idle Emission Rate Adjustment 0.6804 0.6804 <br />Year 1997: 597.0 glhr <br />Year 2011: 406.2 glhr <br />City of Roseville VMT Adjustment 1.1808 1.1808 <br />Year 1997: 1,574,557 vehicle-miles <br />Year 2011: 1,859,237 vehicle-miles <br />2011 Background CO Concentration 1.77 ppm 1.29 ppm <br /> <br />Using the CAL3QHC model line-source dispersion model, Year 2011 CO concentrations were <br />predicted at nine different receptor locations in the vicinity of the three selected intersections. The <br />receptor locations are illustrated in Figure A. <br /> <br />The results of the air quality analysis are summarized in Table 3. The maximum predicted CO <br />concentrations occurred at Receptor Rl, which was located in the northwest quadrant of the <br />Snelling/County Road C intersection. All of the predicted CO concentrations are below the applicable <br />state air quality standards, as shown in Table I. <br /> <br />Based upon these results and the highly conservative nature of the analys'is methodology and <br />assumptions, it can be concluded that the proposed Twin Lakes redevelopment project will not have <br />air quality impacts significant enough to cause a violation of state CO standards. <br /> <br />19 <br />