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- Highway 10 and Sunfish Lake Boulevard. <br />CAL3OHC Model. In accordance with the EPA procedure for carbon monoxide <br />analysis, the CAL3QHC dispersion model was used to forecast the air quality along the <br />Highway 10 corridor. Required input for this model includes meteorological <br />characteristics, traffic characteristics, intersection geometries, and emission rates. <br />Meteorological Characteristics. The meteorological characteristics used in the model are <br />summarized in Table 22.2. The inputs listed are consistent with EPA and MPCA <br />recommendations. <br />Table 22.2 CAL3QHC Meteorological Characteristics <br />Characteristic <br />Analysis Year <br />Wind Speed <br />Wind Direction <br />Atmospheric Stability Class <br />Model Input <br />2002 (existing) 2008 (future) <br />Mixing Height <br />Surface Roughness <br />Averaging Time <br />Settling Velocity <br />Deposition Velocity <br />8-Hour Persistence Factor <br />l m/s <br />Tested 360 degrees at 10° increments <br />D <br />1000 cm <br />321 cm <br />60 min <br />0 cm/s <br />0 cm/s <br />0.7 <br />Traffic Characteristics. Traffic characteristics were based on the existing traffic <br />conditions in 2002 and the modeled levels of 2007 (including traffic generated by the <br />proposed project). Traffic volumes, saturation levels, lane configurations, signal type, <br />signal cycle length, red time length and clearance lost time were taken from the traffic <br />analysis conducted for the project. The heaviest traffic volumes were projected to occur <br />during the evening; therefore the CO concentrations using p.m. peak traffic data were <br />modeled as a worst -case scenario. <br />Intersection Geometries. Intersection geometries were based on existing roadway <br />dimensions from maps and aerial photographs. The proposed roadway improvements <br />discussed in Item 21 were not incorporated into the intersection geometries in order to <br />model a worst -case (most idling traffic) scenario. <br />Emission Rates. EPA model Mobile 5b was used to calculate carbon monoxide <br />emission rates. There are two types of emission rates needed for the CAL3QHC CO <br />dispersion model, and include a running emission rate and an idling emission rate. The <br />running emission rate was generated directly by the Mobile 5b model assuming an <br />average free flow speed of 35-mph on all roadways and links. The idling emission rate <br />was calculated by converting a 2.5-mph Mobile 5b running emission rate from grams per <br />22-3 <br />