B1 Emission scenarios Entech have evaluated the concentrations at the surface connections for the following ventilation scenarios: 1 Forced ventilation: in the event that the fans are not damaged in the explosion, the mine ventilation will exhaust all contaminants at Site 5 – Rise #2 vent. 2 Natural ventilation: in the event that the fan systems are damaged, the contaminants are expected to slowly disperse through the mine and may be emitted from Site 4 – Rise #1 or the two portal connections (Site 1 and Site 2) on OGNZL owned land. Volumetric flow in the natural ventilation scenario is 4.5% of that under mechanical ventilation and the contaminants take between 13 hours to three days to clear the underground mine. The parameters for each scenario are shown in Appendix B Table 1 below. This demonstrates that the scenario that will provide the most conservative assessment is the release of contaminants at high concentration over a short duration from Site 5 – Rise #2 under mechanical ventilation. Appendix B Table 1: Emission scenarios and parameters (Entech, 2022) Parameter Mechanical ventilation Natural ventilation - Summer Natural ventilation - Winter Fan on 1. Fan off 2. Fan off Fan off Site 5 – Rise #2 Site 4 – Rise #1 Site 1 – Plant Portal Site 2 – Willows Portal Site 4 – Rise #1 Temp (⁰C) 21.4 21.8 22.9 22.3 14.7 BP (hPa) 971 966 985 975 965 V (m/s) 16.4 0.9 0.4 0.4 0.5 Q (mᶟ/s) 387 17.4 9.5 10.6 10.6 Duration of release 15 minutes 40 seconds 13 hours 18 minutes 20 hours 7 minutes 20 hours 11 minutes 2 days 21 hours CO (g/s) 1,269.3 11.2 3.1 6.2 1.9 NO (g/s) 53.8 0.5 0.1 0.3 0.1 NO2 (g/s) 82.3 0.7 0.2 0.4 0.1 NOX (g/s) 164.6 1.4 0.4 0.8 0.2 NH3 (g/s) 20.3 0.2 0.05 0.1 0.03 The relative locations of the different surface connections are indicated onAppendix B Figure 1 below. Appendix B Figure 1: Surface connections Source: OGNZL Site 1 Site 2 Site 3 Site 4 Site 5 Site 6
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