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extremely low hydraulic conductivities were expected in the unfractured volcanic <br />rocks (Freeze and Cherry, 1979, p.29). <br />The fractured core is thought to be the result of rock damage caused by blasting <br />during construction of the underground workings. Such blast damage is limited to the <br />immediate vicinity of the mine workings, typically extending no more than 5 feet <br />(Worsey, 1985; Worsey, 1986; and Siskind and Fumati, 19741. Hence, a damaged <br />rim a few feet thick around the tunnels is expected to have an artificially induced <br />permeability of 106 cm/sec. <br />Flow testing of boreholes in the American Tunnel resulted in an overall hydraulic <br />conductivity of 5x105 cm/sec when averaged from boreholes oriented perpendicular <br />to the general orientation of the fracture system (see Section 4.0). The hydraulic <br />conductivity of 5x10"5 cm/sec results from a relative few, widely-spaced fractures. <br />The proposed bulkhead sites were selected in areas where no major fractures were <br />observed. Hence, for the purpose of calculating leakage in the immediate vicinity of <br />the proposed bulkheads a value of 5x10-5 cm/sec is probably too high. <br />7.3 Leakage in the /mmediate Vicinity of the Bulkheads <br />Darcy's equation was used to estimate the rate of leakage through the fractured <br />volcanics in the immediate vicinity of the proposed bulkheads. Darcy's equation is: <br />sunnylwp\traci12251 \Mar1993.Rpt 43 <br />NCI SIR1011 HYDRO-SERRCH <br />