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Mining and Reclamation Permit Amend.-M-1988-112 <br /> Groundwater Management Plan Battle Mountain Resources,Inc. <br /> saturated in this area. The hydraulic conductivity measured at PC-2 was much lower at <br /> 0.14 ft/d. The saturated thickness at PC-2 was reported as 25 ft (the length of the screen). <br /> The relatively high hydraulic conductivity value reported for DW-1 most likely <br /> represents that of a highly connected fracture system, whereas the hydraulic conductivity <br /> reported for PC-2 is more representative of the bulk conductivity value of the <br /> Precambrian aquifer system. <br /> Pumping test data for the Santa Fe Fm are limited. Slug test results from monitoring well <br /> G-1, completed in the Santa Fe Fm near the alluvial window, indicated a hydraulic <br /> conductivity value on the order of 0.0004 ft/d. Hydraulic conductivity reported for Santa <br /> Fe Fm monitoring well SF-2 was 0.0008 ft/d(Shepherd Miller, Inc., 1999). Constant rate <br /> pumping tests were conducted on three Santa Fe Fm monitoring wells installed near the <br /> tailings impoundment approximately one-mile southwest of the West Pit. The average <br /> hydraulic conductivity reported for those wells was 0.2 ft/d (John C. Halepaska and <br /> Associates, Inc. 1992). <br /> Additional investigation was recently conducted to further characterize hydrologic <br /> properties of the Santa Fe Fm aquifer along the southeast edge of the West Pit where <br /> groundwater flows into the Pit through an alluvial window (Engineering Analytics, Inc. <br /> 2023, included as Appendix A). The investigation included the drilling, installation, and <br /> development of one well (WP-6 shown on Figure G-3), conducting a pumping test of <br /> WP-6, and analysis of those test results. Results of the test analyses indicate that the <br /> consolidated sediments of the Santa Fe Fm aquifer have very low transmissivity (less <br /> than 0.12 ft2/d) and hydraulic conductivity of approximately 0.003 ft/d. These values are <br /> consistent with estimates from previous investigations and are more than three orders of <br /> magnitude lower than estimates for the alluvial aquifer. <br /> Water levels in Santa Fe Fm wells completed in 1999 were slow to stabilize and were <br /> notably lower than the surrounding alluvial and Precambrian monitoring wells (BMRI <br /> 1999a). This indicates that the Santa Fe hydrologic unit is in poor hydraulic <br /> communication with both the underlying and overlying hydrologic units. <br /> Hydrologic properties of the alluvial aquifer have been evaluated through numerous <br /> studies. Constant discharge pumping tests were conducted in thirteen alluvial wells in the <br /> 1999 study (BMRI, 1999b). Each of the wells was drilled to the top of the underlying <br /> unit, either Precambrian bedrock or Santa Fe Fm. Observation wells were utilized in three <br /> of the alluvial aquifer tests. BMRI reported an average hydraulic conductivity value of <br /> 9.1 ft/d, with a maximum of 22.5 ft/d and a minimum of 0.2 ft/d. The saturated thickness <br /> of the tested wells ranged from 22 to 43 ft with an average of 33 ft. The reported <br /> storativity ranged from 0.0003 to 0.0005, however, all of these tests were conducted on <br /> an unconfined aquifer and were of relatively short duration. The true storativity of an <br /> unconfined aquifer is dominated by the specific yield of that unit (the portion of porosity <br /> that will be gravity drained or dewatered during pumping), which is typically in the range <br /> of 0.1 to 0.3 (Lohman, 1972). <br /> April 2025 5 Engineering Analytics,Inc. <br />