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San Joaquin County Community Air Quality Technical Information <br /> Development Department <br /> s <br /> Vehicle Emission Rates <br /> Vehicle emission rates were determined using the California Air Resources <br /> Board's EMFAC2002 (version 2.2)emission rate program. The program <br /> assumed San Joaquin County regional traffic data operating during the winter <br /> months. A mean January temperature of 35 degrees Fahrenheit and humidity of <br /> *� 20%were assumed. <br /> Receptor Locations <br /> CO concentrations were estimated at 4 receptor locations located at the <br /> intersections of SR 132 EB &WB Ramps/Bird Road,Blewett Road/Bird Road, <br /> and Blewett Road/Koster Road. These receptors were placed 100 feet from the <br /> center of each intersection diagonal to represent a worst-case scenario, and <br /> IBM located 142 feet from each other. Receptors were also located along SR 132 <br /> between I-5 and Koster Road,Koster Ranch, and at the facility entrance along <br /> Koster Road to represent existing receptors in the vicinity of the proposed project <br /> area. All receptor heights were set at 5.9 feet. <br /> Meteorological Conditions <br /> Meteorological inputs to the CALINE4 model were determined using <br /> s. methodology recommended in Air Quality Technical Analysis Notes(California <br /> Department of Transportation 1988). The meteorological conditions used in the <br /> modeling represent a calm winter period. Worst-case wind angles were modeled <br /> to determine a worst-case concentration for each receptor. The meteorological <br /> inputs include: 0.5 meters per second wind speed, ground-level temperature <br /> inversion(atmospheric stability class G),wind direction standard deviation equal <br /> to 10 degrees,ambient temperature of 1.67 degrees centigrade, altitude above sea <br /> level of 0 feet,and a mixing height of 1,000 meters. <br /> Background Concentrations and Eight-Hour Values <br /> A background concentration of 4.53 ppm was added to the modeled cumulative <br /> 1-hour values, while a background concentration of 2.95 ppm was added to the <br /> modeled cumulative 8-hour values. Background concentration data for I- and 8- <br /> hour values were obtained from the EPA's Air Data webpage (U.S. <br /> Environmental Protection Agency 2005). Maximum I-and 8-hour values for the <br /> years 2002-2004 were averaged to obtain a background concentration. Eight- <br /> hour modeled values were calculated from the I-hour values using a persistence <br /> " factor of 0.6. Background concentrations for future 2007 and 2025 years were <br /> DeSilva Gates Quarry Project <br /> Draft Environmental Impact Report J-3 <br /> AS05105.05 <br /> • <br />