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' CRAPTERFOUR Environmental conseyuences ' The screening level analysis indicates that significant impacts would not occur at distances further than 6 miles (10 km) (furthest distance modeled) for any pollutant. This established the boundary of the receptor grid. ' Meteorological Data The simulation of both short-term and annual average impacts was performed using the ISCST3 ' dispersion model. This model requires hourly values of temperature, wind speed, wind direction and atmospheric stability class. Monitoring stations in the general region were surveyed for the availability of data. For the Pazachute Site, one yeaz of data obtained by Unocal in 1989 at the Parachute Creek Oil Shale Upgrade Facility was selected. For the Piceance Site, one year of data from the Cathedral Bluffs Project Tract Cb collected during 1984, was selected. A wind rose portraying the wind speed and direction for the Piceance and Parachute Sites is provided in Figures D-3 and D-4, respectively (Appendix D). One year of site specific data generally represents the typical conditions that would be encountered. Although there may be some variation from yeaz to yeaz, these data have been determined by CDPHE to be representative of ' typical transport and dispersion conditions for the Project Area (Steigers 1998f). Further detail regarding the meteorological data is presented in the air quality construction permit ' (RTP 1998a,b). Modeling Results/,4alysis Piceance and Parachute Sites An air modeling analysis was performed for the Proposed Action as part of the air quality ' construction permit application. The modeling analysis included a National Ambient Air Quality Standazds (NAAQS) analysis, compazisons to the PSD Class I and II increments, visibility analyses, and Class I water analyses. The Piceance Creek Basin and Pazachute Creek valley aze Class II air quality areas, as aze most regions of the state of Colorado. Class II attainment areas under PSD regulations, have specified allowable increases (increments) of pollutants that should not be exceeded. Class II PSD increments are listed in Table 3.5-2. Class I azeas, which have more stringent air quality standards, aze located in the region (Figure 3.5-2). These include the Flat Tops and Mount Zirkel t Wildemess Areas at 41 miles (68 km) and 89 miles (148 km), respectively. Other Class I azeas neazby, include: the Mazoon Bells, West Elk, and Ragged Wildemess Areas which are each greater than 100 miles (167 km) from the Project Area. The estimated emissions resulting from the Proposed Action, and emissions resulting from other sources in the vicinity (cumulative impacts) were used to develop the PSD Class II increment ' analysis and the comparison to ambient air quality standards. The direct impacts from the project were demonstrated to be below significant impact levels at the neazest PSD Class I azea. ' NAAQS Analysis For the Piceance and Pazachute Sites, compliance was demonstrated with the NAAQS and Colorado Ambient Air Quality Standazds (CAAQS), by combining impacts from the Proposed Action with the predicted impacts from other existing major sources within and azound the Meteorology and Air Quality 4-23