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CNAPTERFIVE Di`ait EIS Recisions increment analyses for the Piceance and Pazachute Sites, respectively. I}ugac~ A:..eo..,.e .,..A D....,..6..m ..:~e~ ., a lo~~ ~6.,.. A.e rh~~ TT .. ..:A,..,..r :.., ~..r lo.,ol~ Page 4-28 Level 1 and 2 Visibility Analyses Piceance and Parachute Sites Selected National Pazks and wilderness azeas aze designated as Mandatory P'.~D Class I azeas and aze subject to additional protection from degradation of air quality, including potential visibility impacts at the Flat Tops Wilderness Area. ,~ ~~ ~~ A Level 1 regional haze visibility screenin analysis was performed based on pollutant emission rates, distances to the impact azea, and background visual range using procedures from the Interagency Workgroup on Air Quality Modeling (IWAQM) Phase I Report (EPA 1993). A Level 1 screening analysis is the most conservative, and is performed assuming very conservative (worst case) meteorological data. If compliance cannot be demonstrated with a Level 1 analysis, a Level 2 analysis may be required. The analysis used a reconstructed background visual range based on the "mean of the best 20 percentile" IMPROVE particulate matter data for the Mt. Zirkel Class I Area o_f 140 mile visual range (234 km), and relative humidity correction factor data (2.27) based on the annual average extinction information from the Interagency Monitoring of Protected Visual :Environments (IMPROVE) data (IMPROVE 1996). These factors were also used by Mr. J~~hn Vimont, NPS, for BLM's Glenwood Springs Resource Area Environmental Impact Statement (BLM 1998b). The IWAQM procedures assume a conversion rate ofNOx into ammonium nitrate based on the modeled concentrations. The calculation of extinction is based on the interference from ammonium nitrate and primary particulate (PMIO). The combined extinction from NOx and PMIo emissions from both the Piceance and Pazachute facilities is calculated and presented in Table D- 4 in Appendix D. The Level 1 screening analysis calculated visibility change is 0.5 deciview. A refined Leve12 analysis of the impacts from Yankee Gulch sources was also conducted using the CALMET/CALPLIFF modeling system and methodologies described in 'the "IWAQM Phase 2 Summary Report and Recommendations for Modeling Long-Range Transport Impacts" (EPA 1998). A similaz CALMET/CALPLTFF modeling analyses in the study azea had previously been reported in the BLM Glenwood Snrines Resource Area Oil & Gas Leasine bt Development Draft Supplemental EIS (BLM 1998a). CALMET was run for the yeaz 1990 using; surface and upper air data from Grand Junction, surface data from ] 0 Remote Automatic Weather Station sites, and azchived data. The wind field grid has a resolution of 5 km per grid cell and covered an azea of 400 km in the east-west direction and 300 km in the north-south direction, centered on Rifle, Colorado. The CALPLIFF model was run to evaluate the effects of NO emissions, as the emissions of SO_, and primary particulate matter from the proposed oil and gas development were insignificant. 5-22