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downstream of the mine that may be used if necessary to replace a depleted water <br />source. <br />Construction of surface facilities in the permit azea will cause temporary <br />increases in the amount of suspended solids in the surface water system. <br />Furthermore, concentration of chemicals associated with increased sediment load, <br />such as iron and manganese, will also increase. At the Deserado Mine, <br />mitigation of sediment load will be accomplished primarily by sedimentation <br />ponds. Although sediment increases will occur in the early phases of <br />construction, the long-term sediment yield may actually decrease below the <br />already high natural occurrence of sediment concentrations due to the installation <br />of control measures. <br />Effects on the surface water system from the refuse disposal azea should be <br />minimal. Analysis of the waste material does not indicate that toxic or acid- <br />fonning characteristics aze present, so the disposal areas will not be lined to <br />prevent percolation into the ground water system unless further monitoring <br />results indicate that this is necessary. The waste will be covered with 30 inches <br />ofnon-toxic, non-combustible material (48 inches on RP-1), thereby reducing <br />infiltration of water into the pile and further reducing the potential for water <br />quality degradation. The size of the non-reclaimed disturbed area at the refuse <br />disposal azea will be a maximum of approximately 120 acres at any one time. All <br />runoff from the disturbed azea will be routed to properly sized sediment ponds; <br />therefore, any impacts of the disturbance on surface water quality will be <br />minimal. Darwin Reservoir, a lazge stock pond situated along the Red Wash <br />tributary, is approximately 800 feet from refuse subarea R-9, which will be <br />developed in future permit terms. Due to the distance of the stock pond from the <br />area of disturbance, no surface water impacts are anticipated. <br />Impacts to the surface water system for mine water discharges have been <br />experienced. High TDS (>5,000 mg/1) in the discharge water led to failure of <br />Whole Effluent Toxicity (WET) tests from 1989 through mid 1993. The WET <br />tests were performed in cooperation with the Colorado Water Quality Control <br />Division (WQCD). WFU has taken the following measures to reduce the toxicity <br />of the effluent: <br />On-site aeration structures were installed for HzS removal before discharging <br />the effluent. <br />A pilot test was conducted to identify a flocculent for removing high levels <br />of oil and grease from the effluent. <br />The main water source of the mine was changed from the high TDS (>5,000 <br />ppm) alluvial well water to a significantly lower TDS (500 ppm) surface <br />lagoon. <br />29 <br />