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23. Vt~hicle-related air emissions. Provide an estimate of the effect of the project's traffic generation on air quality, including carbon monoxide levels. Discuss the effect of traffic improvements or other mitigation measures on air quality impacts. (If the project involves 500 or more parking spaces, consult "EA W Guidelines" about whether a detailed air quality analysis is needed.) Bused on the traffic analysis in Item No. 22, the increase in the number of average daily trips generated by the proposed project is 5,200. The traffic volumes projected in Item No. 22 have be,en used to estimate carbon monoxide (CO) emissions from the source and CO concentration levels near the most critical intersections in the year 2000, one year after construction of the project. Elnimating CO Emissions Using MOBILE 5a Model U.S. EPA's MOBILE 5a mobile source emission factor model was used to estimate CO emissions from the source. The input file was prepared using MPCA-approved default parameters. Emission factors were derived for a speed of 2.5 mph (for idling emissions) and speeds of 25, 30, 35 and 40 mph (corresponding to the typical free-flow traffic speeds observed at the most impacted intersections during the March 1997 traffic study). Einimating CO Concentrations Using CAL3QHC model The CAL3QHC highway air dispersion model was used to estimate downwind CO concentrations at receptor sites adjacent to the two most impacted intersections (County Road B2 at Long Lake Road and County Road B2 at Cleveland Avenue). Background CO Concentrations P]revious air quality studies in the study area include: · Centre Pointe Business Park, EAW 1/97 and ISP application 3/97 (revised) · Twin Lakes Business Park, EA W The background CO concentrations used here are based on those measured in a monitoring study performed by Interpoll Laboratories from December 31, 1996 through January 13, 1997 for the Centre Pointe Business Park EAW. This study reported maximum 1-hour and 8-hour average CO background concentrations of 2.2 and 1.6 ppm, respectively. In accordance with MPCA guidance, these 1997 background concentrations were adjusted to a<:count for both the decrease in fleet emissions due to advances in vehicle technology and the in.crease in emissions resulting from a growth in vehicular traffic. The former was determined by using the ratio of the idling emission factors for the years 2000 and 1997 (predicted by the MOBILE 5a model). The latter was calculated assuming a traffic growth factor of 3 percent per YE~ar between the years 1997 and 2000. 2000 Idling Emission Factor = 198.00 g/mile 1997 Idling Emission Factor = 238.80 g/mile Traffic Growth Factor, 1997 to 2000 = (1.03)3 = 1.093 i.la., the CO background concentrations for the year 2000 are as follows: 1-hour: 2.2 ppm x (198.00/238.80) x 1.093 = 2.0 ppm 8-hour: 1.6 ppm x (198.00/238.80) x 1.093 = 1.5 ppm 23624Ei8\48185-ltrMN 13