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Table 22.1: National and State Ambient Air Quality Standards <br />Pollutant <br />Averaging <br />Period <br />National Standards <br />Primary Secondary <br />MN State Standards <br />Primary Secondary <br />Carbon <br />Monoxide <br />(CO) <br />8-hour <br />1-hour <br />9 ppm 9 ppm 9 ppm 9 ppm <br />(10 mg/m3) (10 mg/m3) (10 mg/m3) (10 mg/m3) <br />35 ppm 35 ppm 30 ppm 30 ppm <br />(40 mg/m3) (40 mg/m3) (35 mg/m3) (35 mg/m3) <br />Carbon Monoxide Modeling Methodology <br />The methodology for identifying potential local air quality impacts follows the EPA - <br />recommended procedure for carbon monoxide micro -scale impact analysis. The general <br />evaluation procedure, outlined in the Guideline for Modeling Carbon Monoxide for <br />Roadway Intersections (EPA 1992), includes a multiple intersection screening process <br />followed by micro -scale CO analysis with the CAL3QHC line -source dispersion model. <br />Screening Process. The intersection screening process includes the following steps: <br />1. Identify the signalized intersections in the project vicinity that will be <br />impacted by the project alternatives. <br />2. Determine the average delay and Level of Service (LOS) for those <br />intersections. <br />3. Determine total intersection delay as the product of average delay and total <br />intersection approach volume. <br />4. Rank the intersections according to total delay and select the intersections <br />with the highest total vehicle delay for analysis. <br />Carbon monoxide concentrations are generally highest at intersections with poor levels of <br />service and consequently, more idling vehicles. Typically intersections with levels of <br />service of D, E, and F (worst levels) are analyzed. As described in Item 21, all of the <br />major intersections within the project area were analyzed to determine both present and <br />forecasted levels of service. Peak hour traffic volumes used for this analysis assumed <br />that the Ramsey Town Center would reach full built -out potential by 2007. <br />Based on consultation with the Minnesota Pollution Control Agency (MPCA), it was <br />agreed that carbon monoxide analysis would be performed at intersections that were <br />projected to operate at level of service D or worse for year 2008 (one year after the <br />anticipated Ramsey Town Center completion). The traffic study identified that the three <br />intersections of prime concern are all located along the Highway 10 corridor. The <br />locations of these intersections in relationship to the project site are shown on Figure 22.1 <br />and include the following: <br />- Highway 10 and Armstrong Boulevard <br />- Highway 10 and Ramsey Boulevard <br />22-2 <br />