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low and variable in the mid to late 1990s, but low and relatively stable since 1999. Other <br />trace metals are analyzed as part of the monitoring program. Median values for arsenic, <br />cadmium, chromium, copper, lead, mercury, nickel, selenium, and silver in the ground <br />waters at WCMW -2, WCMW -3, and WCMW -6 were less than the analytical detection <br />limits. Trace metal data also are provided in Tables 4 -7, 4 -8, and 4 -9. <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 of precipitation to, and the saturation of the alluvium and the shallow <br />bedrock in both Arequa Gulch and in the upper reaches of the adjacent Bateman Creek <br />drainage. The decreased infiltration also has lowered the water table in the upper reaches <br />of Arequa Gulch. The sulfide oxidation in the exposed spent materials beneath the liner <br />are now being exposed to oxygen during low flow periods (late fall through winter), <br />which is increasing the sulfide oxidation in those exposed spent materials. The transport <br />of the oxidation products likely is causing the gradual increase in sulfate and other metals <br />(since 2000) in the shallow bedrock ground water (WCMW -2) similar to that observed in <br />the Arequa Gulch monitor wells (see Section 5 for discussion). Concentrations of sulfate <br />and other parameters at WCMW -2 may continue to rise due to the sulfide oxidation under <br />the AGVLF in the upper reaches of Arequa Gulch and the close proximity of WCMW -2 <br />to the Arequa Gulch drainage. For most other parameters at WCMW -2, water quality <br />conditions in the alluvium and shallow bedrock are expected to be similar to or slight <br />elevated from the current conditions. <br />4.1.4.4 MLE2 Impacts to Ground Waters <br />No impacts are anticipated to the ground water resources in the Bateman Creek drainage <br />due to MLE2. Water level and water quality conditions at WCMW -3 and WCMW -6 are <br />expected to remain consistent with historic measurements. The concentration of sulfate <br />in the ground water at WCMW -2 may increase with the continued reduction of <br />infiltration and recharge by precipitation to the alluvium and shallow bedrock in the <br />upper Bateman Creek drainage due to the impermeable liner system of the AGVLF in the <br />adjacent and upgradient Arequa Gulch drainage. <br />4 The spent materials pre -date CC &V operations (before early 1990's) and are composed of tailings that were produced by a milling and cyanide <br />leach operation and contained trace levels of cyanide, as well as sulfide minerals associated with the ore body Also present are overburden <br />deposits that were generally run -of -mine material produced from early surface mining and underground mine development, and which contained <br />low levels of sulfide minerals, in particular pyrite. <br />'Cripple Creek & Victor Gold Mining Company <br />Cresson Project Hydrologic Evaluation for Mine Life Extension 2 <br />10 <br />