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6.4.1 Monitoring Program <br />Ground water conditions in the Grassy Valley drainage are primarily assessed by 44 <br />monitor wells, 4 piezometers, and 16 boreholes. The monitor wells, piezometers, and <br />boreholes are grouped by their location in the upper (above GV -01), middle (between <br />GV -01 and GV -03), or lower (below GV -03) reaches of Grassy Valley. The monitor <br />well, piezometer, and borehole designations, the completion depth, the geology, the <br />monitored aquifer, the Grassy Valley reach, the presence of a pressure transducer, MLE2 <br />impact assessment, and whether water quality data are available are listed in Table 6 -4. <br />The monitor locations are shown on Figure 2 -2. Several monitor wells and boreholes are <br />co- located to allow assessment of vertical conditions of water level and water quality <br />between the alluvium, shallow bedrock and deeper bedrock in the Diatreme and the <br />adjacent granites. The co- located monitor wells and boreholes also are shown on Figure <br />2 -2. Numerous monitor locations have been plugged and abandoned due to <br />implementation of MLE and other factors. <br />Field parameters and water quality samples are periodically collected from the monitor <br />wells, piezometers, and boreholes. The sample programs are shown in Table 3 -2. <br />Pressure transducers were installed in several of the monitor wells, piezometers, and <br />boreholes to more frequently (up to 4x/day) monitor the water level. The data are <br />periodically downloaded and compiled. Table 6 -4 identifies the locations with pressure <br />transducers. <br />6.4.2 Data <br />The period of record and compiled field and water quality data (number of <br />measurements, less than detection events, maximum value, minimum value, average <br />value, standard deviation, and median value) for the monitor wells, piezometers, and <br />boreholes in Grassy Valley are provided in Tables 6 -5 to 6 -29. Figures 6 -3 to 6 -27 show <br />the hand level measurements and the pressure transducer data for the monitor wells, <br />piezometers, and boreholes and the time series plots of selected parameters (pH, nitrate, <br />and sulfate). Many monitor wells and boreholes have been dry since installation. The <br />locations of the dry monitor wells and boreholes are identified for the respective reaches <br />in Grassy Valley in Table 6 -4. <br />6.4.3 Discussion <br />6.4.3.1 Upper Grassy Valley <br />Table 6 -4 and Figure 2 -2 provide the details and locations of the monitor wells, <br />piezometers, and boreholes in the upper Grassy Valley. Ground water levels in the <br />'Cripple Creek & Victor Gold Mining Company <br />Cresson Project Hydrologic Evaluation for Mine Life Extension 2 <br />34 <br />