2018-06-01_REVISION - C1980007 (3)

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adding criteria pollutants to the environment. Moreover, there is a potential to reduce the amount that is vented by working to increase gob drainage and investigating other potential in -mine drainage schemes. West Elk ventilation air data is reported quarterly, with total volumes and methane concentration data reported separately. The reported data is acquired from four unique locations at mine: • flow from three sites within the mine, all of which exits the Deer Creek, or East South Mains (ESM) Shaft; • the remaining ventilation air volume exits the Sylvester Gulch Shaft. This analysis uses the data collected from the Deer Creek (ESM) shaft, as this shaft recorded the largest volume of VAM with the highest methane concentration. Concentration of methane ventilation air is key to safe effective operation of VAM destruction units. Methane concentration in ventilation air ranges from 0.059 percent to 0.321 percent in air, and the total volume ranges from 777,220 scfm to 1,030,234 scfm. The probabilistic analysis was carried out to determine: • p50 methane concentration in the ventilation stream for ESM shaft for years 2013-2016, as shown in Figure 2, and • p50 methane volumes in the ventilation stream for ESM shaft for years 2013-2016, shown in Figure 3. Figure 2: Probability Distribution for Methane Concentration in ESM Shaft Name: Methane Cancentration in Shaft 4 Venfllation for Four Years M .. Lognormal Distribution a a 0 a P10-0211% Mean -0.140% JL Median -0.131 % 50-0.131% sa-oosl% 0,100% 0.200% 0.300% 0.400% Location 0.000% ia! Mean 0.140% _! Std_ Dev_ O054%: N. P50 = Median, there is a 50 percent probability that the methane concentration in the shaft will be 0.131 percent. p1_o = There is a 10 percent probability that the methane concentration in the shaft will be 0.211 percent or greater. p90 = There is a 90 percent probability that the methane concentration in the shaft will be 0.081 percent or greater.