2017-04-05_PERMIT FILE - C1982057 (7)

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005 Trib. DSC = O, 0000469 + 0.0000917 = 3450 mg/1 (494 TDS 0.0000298 x 0.00136 increase) 005 crib. L = 0.000015 x 3450 x 0.0027 = 0.000140 tons/day (494 tonnage increase) Dry Creek Alluvium DSC = 0,00014 + 0.000245 = 1038 mg/1 (164 TDS (0.0000298 + 0.000243) x 0 .00136 increase due to 005 spoil discharge) Dry Creek Alluvium L = 0.00014 x 7038 x 0.0027 = 0.000392 tons/day (754 tonnage increase due to 005 spoil discharge) Cumulative Dry Cree k Alluvial System Premining: Dry Creek Alluvium DSC = 0.000245 + 0.0000938 = 897 mg/1 (0.000248 + 0,00002975) x 0. 00136 Dry Creek Alluvium L = 0.00074 x 897 x 0.0027 = 0.00034 tons/day Cumulative Dry Cree k Alluvial System Postmining: Dry Creek Alluvium DSG = 0.000288 + 0,00014 = 1154 mg/1 (294 TDS (0.000243 + 0.0000298) x 0. 00136 increase) Dry Creek Alluvium L = 0.0001375 x 7154 x 0.0027 = 0.000428 tons/day (26$ • tonnage increase) Sage Creek Alluvial System Premining: 009 Trib. Dry Sage Creek Alluvium L = 0.0000398 x 955 x 0.0027 = 0.0001016 tons/day Sage Creek Alluvial System Postmining: 009 Trib. L = 0.000000463 x 4500 x 0.002 7 = 0.0000056 tons/day Sage Creek Alluvium DSC = 0.0001 + 0.0000056 = 972 mg/1 (1, 7+e TDS increase) (0.00000092 + 0.000079) x 0.0 0136 Sage Creek Alluvium L = 0.00004 x 972 x 0.0027 = 0.000105 tons/day (24 tonnage increase) The magnitude of the cumulative 705 increase in the Dry Creek alluvium below the 005 tributary confluence is approximately 30 percent. The range of the TDS increase extends from below the 006 pond outfall to probably one mile below the confluence of Dry Creek with the 005 tributary alluvium. The extent of the TDS increase is limited to this range because of the low hydraulic conductivity of the alluvium, additional downg radient geochemi cal changes and dilution from shallow aquifers which discharge to the alluvium, • The duration of the impact over the extent of the Dry Creek alluvial aquifer previously 46