2020-10-27_PERMIT FILE - C1981035 (22)

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current and future activities occurring within the region such as agriculture, ranching/grazing, and vehicle traffic. To examine potential cumulative air quality impacts from activities that it authorizes, BLM initiated the CARMMS. The study version 2.0 was primarily concerned with assessing statewide impacts of projected oil and gas development (both federal and fee (i.e., private)) out to year 2025 for three development scenarios (low, medium, and high). Projections for development are based on either the most recent Reasonably Foreseeable Development (RFD) document (high), or a projection of the current 5-year average development pace forward to 2025 (low). The medium scenario includes the same well count projections as the high scenario, but assumes restricted emissions, whereas the high assumes current development practices and existing emissions controls required by regulations (Environ 2017). The CARMMS project leverages the work completed by the West-wide Jumpstart Air quality modeling study, and the base model platform configuration (CAMx), meteorology Weather Research Forecasting (WRF),and model performance metrics are based on those products.The complete report and associated data are available on our website at: https://www.blm.gov/documents/colorado/public-room/data. The CARMMS model domain has a minimum grid resolution of 2.5 miles (4 km). Because CAMx is a one-atmospheric dispersion model, it requires emissions inventories to be modeled accurately at both spatial and temporal scales.This fact allowed the BLM to leverage the study and apply the source apportionment technology to all the emissions from coal mines in Colorado that produce federal coal. Unfortunately,the BLM did not have the resources to track each mine independently as was done for each field office's oil and gas development (which was the primary purpose of the CARMMS model), but rather all the mines were tracked together as a single source group.The source group included the following existing and hypothetical mines: • Book Cliffs Area (Grand Junction) • Trapper(Little Snake) • McClane (Grand Junction) • Colowyo (Little Snake) • Bowie (Uncompahgre) • Sage Creek (Little Snake) • King II (Tres Rios) • West Elk(Uncompahgre) • Foidel (Kremmling) • Elk Creek(Uncompahgre) • Deserado (White River) • New Elk(Royal Gorge) The study provided for a single mining scenario based on each mine maximum allowable emissions rate, which were estimated based on the CDPHE APEN database and available EISs and EAs prepared for previous authorizations. We note that most mines in Colorado are not currently producing at their maximum (i.e., what CARMMS analyzed) authorized capacities. EPA default chemical speciation profiles were used in the SMOKE emissions modeling for mining except that the EPA mining PM2.5 speciation Dunn Ranch Area LBA and Mining Plan Modification 29 Technical Resources Report