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Appendix G <br />Air Quality Analysis Modeling Report <br />Ground-level ozone data for 2006 was obtained from the Clean Air Status and Trends <br />Network (CASTNET), and monthly ozone averages were calculated for the Gothic <br />(GTH161), Canyonlands National Park (CAN407) and Rocky Mountain National Park <br />(ROM206) monitors. Each Class I and sensitive Class II area was assigned the <br />calculated monthly ozone averages from the monitor located closest to that area, as <br />noted below: <br />~ Arches National Park and Canyonlands National Park (Class IAreas) - <br />Canyonlands National Park monitor monthly average ozone value; <br />~ Black Canyon of the Gunnison Wilderness and Maroon Bells - Snowmass <br />Wilderness (Class Iareas) -Gothic monitor monthly average ozone <br />concentrations; <br />~ Colorado National Monument (sensitive Class II area) Gothic monitor monthly <br />average ozone concentrations; <br />~ Flat Tops Wilderness (Class I area) and Dinosaur National Monument (sensitive <br />Class II area) - a Gothic /Rocky Mountain National Park average of the monthly <br />average ozone concentrations. <br />Maximum mixing height is established at 5,000 meters rather than the CALPUFF-Cite <br />default value of 3,000 meters, due to the fact that the mixing height in Colorado is <br />much higher during the summer. Typical summertime overland mixing heights in the <br />Denver, Colorado Front Range area are often well in excess of 3,000 meters, at 3,600 to <br />6,000 meters above sea level (As an example, a sounding for the evening of July 1, <br />2002 suggests a mixing height of almost 6,000 meters.) <br />Monthly ammonia concentrations input to CALPUFF-Cite were based on the <br />surrounding land use for each area (Class I or sensitive Class II) analyzed. The <br />IWAQM recommendations suggest that typical values are 10 ppb for grasslands, 0.5 <br />ppb for forested lands, and 1 ppb for arid lands at 20 degrees Celsius. Weighted <br />ammonia concentrations were calculated for each sector that contained certain Class I <br />or sensitive Class II Areas. <br />Only PMio was modeled in CALPUFF-Cite; PMz.s and coarse particulate matter (with diameters <br />between 2.5 and 10 micron) were not modeled. However, impacts are assessed in the model <br />using different light extinction coefficients for the different PM sizes. In order to assess impacts <br />based on contribution from the different PM sizes, a weighted light extinction coefficient was <br />calculated based on the assumption that fugitive PM2.5 emissions equal 30 percent of the <br />expected PMIO emissions. This weighted coefficient was applied in CALPOSTpnst-processing <br />for all PM concentrations. <br />G-19 <br />DBMS 531 <br />