2012-02-28_REVISION - M1980244 (95)

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and deeper bedrock ground waters (when present) also are characterized as sodium - bicarbonate to calcium- sulfate waters. Data in Tables 6 -14 to 6 -24 show median field pH values in the shallow to deeper bedrock (monitor wells) to range from 6.18 SU to 7.67 SU. Median nitrate values range from <0.05 mg/L as N to 0.73 mg/L as N. Median sulfate values range from <10 mg/L to 583 mg/L. Two of the elevated sulfate values are from deeper bedrock at COB-1A and CAM -1A. These wells will be plugged and abandoned as part of the ECOSA development. Data in Tables 6 -25 to 6 -28 show field pH values in the alluvium (piezometers) to range from 4.04 SU to 6.79 SU. Nitrate values range from 0.59 mg/L as N to 5.92 mg/L as N. Sulfate values range from 57.9 mg/L to 712 mg/L. The lower pH values were collected from OSABH -1 collected in 2008 and 2011. This borehole will be plugged and abandoned as part of the ECOSA development. Time series plots are provided in Figures 6 -9 to 6 -11. Compiled data and statistics for aluminum, manganese, zinc, which are common geochemical indicators in the Diatreme, also are provided in Tables 6 -13 to 6 -23. The water quality data indicate that aluminum, manganese, and zinc concentrations have been low and or less than detection for the piezometers, boreholes, and shallow and deep bedrock monitor wells, except for COB-1A and COB -1B. These monitor wells have elevated aluminum concentrations. As noted above, these wells will be plugged and abandoned as part of the ECOSA development. Other trace metals are analyzed as part of the monitoring program. Median values for arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, and silver in the ground waters in the piezometers, boreholes, and shallow and deep bedrock monitor wells were less than or very close to the analytical detection limits. Trace metal data also are provided in Tables 6 -13 to 6 -23. 6.4.3.3 Lower Grassy Valley Table 6 -4 and Figure 2 -2 provide the details and locations of the monitor wells and boreholes in the lower reaches of Grassy Valley. Ground water levels in the alluvium (two boreholes) are dry at 28 and 39 feet bmp. Ground water levels in shallow bedrock monitor wells are deeper and vary from <1 to 100 feet bmp. Ground water levels in the one deeper bedrock monitor well are relatively stable at 128 feet bmp. GVMW -24B and the two OSABH locations have been dry or have very limited sample data since installation. Figure 6 -12 shows the hand measurements and the pressure transducer calculated depths to water in the lower reaches of Grassy Valley. A comprehensive 'Cripple Creek & Victor Gold Mining Company Cresson Project Hydrologic Evaluation for Mine Life Extension 2 37