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CCP 01-21-2003
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CCP 01-21-2003
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<br />I <br />Ie <br />I <br /> <br />I <br />I <br /> <br />I <br /> <br />I <br />I <br /> <br />I <br />.. <br /> <br />I <br /> <br />I <br /> <br />I <br />I <br /> <br />I <br />I <br /> <br />.. <br />I <br /> <br />I <br /> <br />compliance with this contingency, air quality analyses of "worst-case" conditions were <br />performed for the study area to estimate the effect of the proposed campus expansion on <br />future CO concentrations at key intersections the study area. These analyses include <br />monitoring of existing background CO concentrations and modeling future CO <br />concentrations at worst-case intersections. <br /> <br />Carbon Monoxide Modeling Methodology and Assumptions <br /> <br />Carbon monoxide concentrations near the intersections were predicted using forecasted <br />traffic volumes, current and proposed intersection geometries, optimized signal timing, and <br />with computer models, including the U.S. EPA MOBILE5A' emission model and the U.S. <br />EP A CAL3QHC dispersion model. The scope of the air quality analyses was developed <br />based on input from MPCA staff. The modeling assumptions used in this analysis are <br />shown in Table 17. <br /> <br />TABLE 17 <br />CARBON MONOXIDE MODELING ASSUMPTIONS <br /> <br />Analysis Year: 2020 <br />Cold Start Percentage: 20.6 percent for all traffie <br />Hot Start Percentage: 27.3 percent for all traffic <br />Cruising Speed: Posted Speed Limits <br />Traffic Mix: National Default Values <br />Wind Speed: 1 meter/second (3.3 feet/second) <br />Temperature: -6.6 degrees Celsius (20 dcgrccs Fahrenheit) <br />Surface Roughness]: 108 centimeters (42.5 inches) <br />Stability Class': D <br />Inspcction Maintenance: No <br />Oxygenated Fuel: Yes <br />8-Hour Persistence Factor]: 0.7 <br />Wind Direction: 36 directions at 10 degree increments <br /> <br />Notes: <br />The Surface Roughness, Stability Class and 8-Hour Persistence Factor arc discussed in Guidelines for Air <br />Quality Maintenance Planning and Analysis Volume 9 (Revised): Evaluating Indirect Sources, U.S. EPA, <br />1978, and are summarized below. <br />1 Surface Roughness indicates the initial ground level turbulence into which the exhaust plume will be <br />released. Generally, the higher the rouglmess, the lower the concentration. The number used here is <br />conservatively low for the project area (results in a worst-case). <br />Stability Class characterizes the mixing potential of the atmosphere. Stability Class D is used as a worst- <br />case in suburban and urban areas. <br />The 8-Hour Persistence Factor is used to determine 8-hour localized CO contributions, and takes into <br />account fluctuating wind directions, temperature and traffic, which are morc likely to occur over eight <br />hours than during one hour. The factor is multiplied by the I-hour modeling result. <br /> <br />J The EP A has recently released the improved MOBILE6 emissions model. At the time of this analysis, the MPCA <br />bad not yet approved regional assumptions for MOBlLE6 inputs. The MOBlLE5A model is still approved for use <br />by the EP A. <br /> <br />Guidant Campus Master Plan <br />Final AUAR and Mitigation Plan <br /> <br />- 42- <br /> <br />January 2003 <br />
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