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• Volumetric Flow Rate at Exhaust Shaft C1 - 47.2 m3/s (100,000 cfm) <br />• Mean Wind Speed - 2.0 m/s (default value for program) <br />• Air Temperature - 55 °F (default value for program) <br />• Exhaust Shaft C1 Vent Temperature - 55 °F (default value for program) <br />The resultant doses to the nearest residence for Phase IIA and Phase IIB were 2.3 and 1.5 <br />mrem/yr, respectively. <br />4.3.4 Phase III Emissions <br />The prorated exposed ore area of the Whirlwind Mine at the end of Phase III is <br />approximately 415,000 square feet giving a total radon-222 emission of 74.9 Ci per year. <br />These emissions were split equally between the Packrat portal and exhaust shaft Cl. This <br />value, along with the following inputs, were entered into the COMPLY-R program. <br />• PR Portal Release Height - 0 (ground level) <br />• Exhaust Shaft C1 Release Height - 2.0 meters <br />• Exhaust Shaft C1 Vent Diameter - 2.5 meters (8 feet) <br />• Distance from Packrat portal to Nearest Receptor - 805 meters <br />• Distance from Exhaust Shaft C1 to Nearest Receptor - 1,416 meters <br />• Volumetric Flow Rate at Exhaust Shaft C1 - 47.2 m3/s (100,000 cfm) <br />• Mean Wind Speed - 2.0 m/s (default value for program) <br />• Air Temperature - 55 °F (default value for program) <br />• Exhaust Shaft C1 Vent Temperature - 55 °F (default value for program) <br />The resultant dose to the nearest residence was 3.0 mrem/yr. <br />4.4 Abnormal Circumstances <br />Abnormal circumstances may occur in the mine such as placement of the mine on <br />standby or ceasing of ventilation due to planned maintenance or mechanical failure. As <br />evidenced by the radon-222 emission records in Table 1 for the Whirlwind Mine, <br />reducing the ventilation rate or ventilation time reduces the total radon-222 emitted. <br />The only anticipated abnormal circumstance that is expected to significantly increase <br />radon-222 emission from the mine is the initial ventilation of the Packrat drift. Because <br />the Packrat Mine is only naturally ventilated (low-flow rate), radon-222 has accumulated <br />in the mine's extensive drifts and stopes. The best available measurement of radon-222 <br />levels in the Packrat drift is 26.36 working levels, taken near the entrance of the mine. <br />16