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C-1. Since the mining operations and all associated activity will operate out of the South Platte <br /> River floodplain area and will not discharge into it, it is not expected that the activity presented in <br /> this application will increase any sediment,trace elements, dissolved solids or other water quality <br /> parameter in any way for the South Platte River. Most runoff on the active site will either be <br /> captured by berms and stormwater ponds. The final plan incorporates the reclamation of the site <br /> and will have established revegetation on all disturbed areas. <br /> 2. Surface Water <br /> As described in the mine plan,the combination of earth or gravel berms along the east side of <br /> Highway 9 combined with an elaborate system of sediment collection ditches and ponds will <br /> contain the runoff from the 100 year 24 hour event on-site. A system of four ponds is located in <br /> the permit area to provide pit water capacity to withhold the 100 year runoff. Similarly,the mining <br /> cuts will contain stormwater in them during activity.No non-cut areas will be developed to the <br /> southeast as the operation progresses,therefore no additional sediment ponds will be necessary. <br /> The calculated 100 year runoff for the site is 21.2 ac-ft, (areas that do not drain into the active pits) <br /> and the ponds/berms have a storage capacity of over 30 ac-ft.All downstream users are fully <br /> protected. A National Pollution Discharge Elimination Permit(NPDES) is not required because <br /> there will be no discharge from the site. If water pumping from the pit is greater than the <br /> evaporative capacity of the pond system,the gold operation will stop pumping until either the <br /> pond system can be expanded or a NPDES permit is obtained. <br /> Both gold and gravel processing plants will have a series of detention ponds to trap sediment <br /> from fine slurry discharges. These ponds will be cleaned as needed and all silt will be stockpiled <br /> as substitute soil. Sufficient silt will be left in the ponds to maintain a slit lining to prevent <br /> infiltration. As mentioned above,water will be withdrawn from the Columbia Ditch in existing <br /> takeoff ditches that lead to the Alma Placer property. <br /> Due to the coarse soil textures found at the sight,permeability is very high and most <br /> precipitation and runoff percolates quickly into the ground. Surface water flows, in general, that <br /> do not immediately infiltrate will be gathered in silted sediment ponds for evaporation. No <br /> Alma Placer Mine G"1<w.k'and%Smw ft-,Vi IC <br /> December 2017 G-2 <br />