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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 19 <br />0.5% (infiltration increase in water level). This value is at the low end of specific yield values for <br />bedrock (Freeze and Cherry, 1979), and is consistent with low hydraulic conductivity. <br />4.1.2 Bedrock Permeability Tests <br />Permeability data for bedrock are available from 22 packer tests performed in seven underground <br />boreholes. The packer tests were performed by Cotter personnel during the spring of 1999 according to <br />methodology prepared by Adrian Brown Consultants (Appendix B). Data from the packer tests are <br />contained in Appendix B. Results are summarized in Table 10. <br />Hydraulic conductivity values calculated from the packer tests ranged from 3.3 x 10-5 cm/sec to 9.9 x 10.8 <br />cm/sec. The geometric mean hydraulic conductivity for all packer tests was calculated to be 4.7 x 10-' <br />cm/sec. The median hydraulic conductivity was calculated to be 2.7 x 10 -' cm/sec. Packer test results did <br />not indicate significant variation in hydraulic conductivity between the major lithologic units (LSHG, <br />GBG, and MS). In general, the permeability of unfractured bedrock was low (near 1 x 10"' cm/sec). FouS <br />of 22 tests returned values in the 10.6 cm/sec range and 2 of the tests indicated permeabilities in the low 10- <br />cm/sec range. Packer tests with hydraulic conductivities greater than 1 x 10"6 cm/sec are interpreted to <br />result from fracture flow, with permeabilities in the low 10.5 cm/sec range best representing the hydraulic <br />conductivity of transmissive fracture zones. <br />Packer tests completed in intrusive pegmatite rocks also indicated low permeability (<1x10"' cm/sec). In <br />contrast, the hydraulic conductivity of transmissive fracture zones is estimated to be on the order of 10"5 <br />cm/sec. This range is consistent with published values for fractured metamorphic rocks (Freeze and Cherry <br />1979) and professional experience at other underground mines in metamorphic terrains (Crandon Project, <br />Wisconsin; Monarch Mine, Venezuela; Midwest Project, Saskatchewan). These transmissive zones (faults, <br />fractures and pegmatites) are of limited distribution and extent but provided the bulk of the flow to the <br />underground workings during mine development and dewatering (Section 5.2.1). Most of the pegmatite <br />coreholes were pressure-grouted in 1994 (Section 5.2.1), and the average bulk permeability of remaining <br />fractured and unfractured bedrock was determined from mine inflow data to be 2.8x10-' cm/sec (Section 0). <br />The fact that the packer testing of pegmatite zones resulted in a very low permeability (<1x10-' cm/sec) <br />probably reflects the small number and limited aerial distribution of the packer tests rather than the actual <br />range of permeabilities associated with the pegmatites. <br />Whetstone Associates <br />4109B.071116 <br />