Laserfiche WebLink
AG -1.0 and AG -1.5 indicate relatively stable and low concentrations for zinc. <br />Manganese and aluminum concentrations for AG -1.0 and AG -1.5 are elevated and show <br />seasonal fluctuations. Other trace metals are analyzed as part of the monitoring program. <br />Median values for arsenic, lead, mercury, and silver in the surface waters at AG -1.0 and <br />AG -1.5 were less than the analytical detection limits. Median concentrations of arsenic, <br />cadmium, chrome, copper, nickel, and selenium at AG -1.0 and cadmium, copper, and <br />nickel at AG -1.5 were above the analytical detection limits, but low. For metals above <br />the detection limit, the median concentrations decreased from AG -1.0 to AG -1.5. Trace <br />metal data also are provided in Tables 5 -12 and 5 -13. <br />The capture of precipitation by the impermeable liner of the AGVLF in the upper reaches <br />of Arequa Gulch (Phase II, III, and IV expansions in 2000 and later years) is decreasing <br />the infiltration and the saturation of the alluvium and the shallow bedrock. This has <br />decreased the surface water flows in the middle reaches of the Arequa Gulch drainage <br />(AG -1.0 and AG -1.5). The decreased infiltration also has lowered the water table in the <br />upper reaches of Arequa Gulch. As a result, the spent materials beneath the liner are <br />now being exposed to oxygen during low flow periods (late fall through winter), which is <br />increasing the sulfide oxidation in those exposed spent materials. The transport of these <br />oxidation products is likely the cause of the gradual increase in sulfate and the spikes of <br />sulfate and other metals at AG -1.0. Concentrations of sulfate and other parameters at <br />AG -1.0 may continue to spike seasonally and rise overall due to the sulfide oxidation <br />under the AGVLF in the upper reaches of Arequa Gulch. For most other parameters at <br />AG -1.0 and AG -1.5, water quality conditions are expected to be similar to or slight <br />elevated from the current conditions. <br />5.4.3.4 MLE2 Impacts to Surface Waters <br />Ongoing reductions in flow and variable water quality conditions are expected at AG -1.0 <br />and AG -1.5 due to the AGVLF. The implementation of MLE2 will have minimal impact <br />to surface water resources of Arequa Gulch drainage. <br />The flow and water quality conditions in the surface waters of Arequa Gulch will <br />continue to be monitored by AG -1.0, AG -1.5, and AG -2.0. <br />6 See footnote no. 2 for discussion of these spent materials. <br />'Cripple Creek & Victor Gold Mining Company <br />Cresson Project Hydrologic Evaluation for Mine Life Extension 2 <br />25 <br />