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<br />. <br /> <br />TABLE 17 <br />CARBON MONOXIDE MODELING ASSUMPTIONS <br /> <br />Analysis Year: 2020 <br />Cold Start Percentage: 20,6 percent for all traffic <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 degrees Fahrenheit) <br />Surface Roughness': 108 centimeters (42.5 inches) <br />Stability Class2: D <br />Inspection Maintenance: No <br />Oxygenated Fuel: Yes <br />8-Hour Persistence Factor3: 0.7 <br />Wind Direction: 36 directions at 10 degree increments <br /> <br />. <br /> <br />Notes: <br />The Surface Roughness, Stability Class and g.Hour Persistence Factor are discussed in Guidelines for Air <br />Quality Maintenance Planning and Analysis Volume 9 (Revised): Evaluating Indirect Sources, U.S. EP A, <br />1978, and are summarized below, <br />j Surface Roughness indicates the initial ground level turbulence into which the exhaust plume will be <br />released. Generally, the higher the roughness, the lower the concentration. The number used here is <br />conservatively low for the project area (results in a worst-case). <br />2 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 more likely to occur over eight <br />hours than during one hour. The factor is multiplied by the I-hour modeling result. <br /> <br />Background Carbon Monoxide Concentrations <br /> <br />Background CO concentrations are needed for air quality analysis purposes to represent <br />conditions without the influence of nearby vehicles. By definition, the background CO <br />concentration in any particular area is that concentration which exists independently of <br />direct contributions from nearby traffic. The background concentrations are added to <br />intersection-scale modeled results to yield predicted CO levels at modeled spot receptors <br />adjacent to intersections. <br /> <br />. <br /> <br />Previously monitored CO background concentrations were used for this project. The <br />Minnesota Department of Transportation monitored background CO concentrations for two <br />weeks (May 21, 1999 - June 12, 1999) at Little Canada Elementary School at 400 Eli Road <br />in Little Canada, (approximately four miles southeast of the Guidant development). <br />Maximum monitored concentrations of 1.23 ppm and 0.82 ppm for I-hour and 8-hours, <br />respectively, were found. <br /> <br />Guidant Campus Master Plan <br />Draft AUAR <br /> <br />- 42- <br /> <br />September 2002 <br />