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• refuse pile advance progresses further to the west, the south refuse pile <br />collection ditch will be extended prior to disturbance of contributing <br />drainage areas in order to assure control of runoff from all disturbance <br />areas. <br />As previously noted, EFCI will to the extent possible, divert runoff from <br />those areas not disturbed by mining and related operations around effected <br />areas and will not mix disturbed and undisturbed area runoff. EFCI will <br />also control and monitor any discharge of disturbed area runoff to ensure <br />that the discharge complies with applicable effluent limitations under <br />the Southfield NPDES permits. Drainage from mine and loadout areas, after <br />retention in sedimentation ponds, is not anticipated to exceed applicable <br />effluent limitations or any other Federal or State water quality <br />limitations or standards. Historically, EFCI has experienced no pH <br />problems with water discharging from operating areas. As documented by <br />the NPDES reports submitted to the Colorado Department of Health, Water <br />Quality Control Division and U.S. EPA, pH values of water samples from the <br />existing mine and loadout areas have ranged between 6.1 and 8.6. Since <br />future operations will not vary significantly from current and historical <br />practices, no acid mine drainage is anticipated either from surface runoff <br />or from mine dewatering discharge. Any potential acid mine discharge from <br />mine dewatering flows is effectively controlled by routing these flows to <br />Freshwater Pond No. 3 and sampling water from this pond prior to any <br />controlled discharge. <br />Existing surface water quality in the mine area is effected by previous <br />mining activities and ongoing grazing activities. Surface water in the <br />mine area is generally a calcium carbonate type, is slightly alkaline and <br />has moderately high concentrations of suspended and dissolved solids with <br />elevated iron and manganese values. Post-mining water quality in the <br />Southfield mine area should generally be equivalent to pre-mining surface <br />water quality since no acid or toxic discharge will occur. There is a <br />potential for minor shifts in water chemistry from a strong calcium <br />carbonate type toward sodium sulfate, or more probably, a mixed chemical <br />. type. There may also be limited increases in TDS levels resulting from <br />increase concentrations of sodium, sulfate, iron, and manganese. However, <br />any changes in water chemistry or the concentration of specific chemical <br />4.05-6 <br />