Laserfiche WebLink
July 30, 2010 10 of 24 <br />Table 1. Calculation of Rock Bulk Hydraulic Conductivity <br />Notes: Packer permeability tests indicate that the primary hydraulic conductivity of bedrock <=10 cm/sec <br />Assume inflow to the mine is analogous to a large well with a diameter of 500 feet and a depth of 2,200 feet. <br />Flow to the mine at maximum extent is approximated using the Theim equation for steady-state <br />radial flow: <br />21rLKH <br />Q_ ln(R/rh) <br />where: Q = <br />L= <br />K= <br />H= <br />R= <br />rh = <br />Volumetric inflow to the mine [071] <br />Length of the well screen [L] <br />Hydraulic conductivity [LT-1] <br />Drawdown [L] <br />Radius of influence [L] <br />Radius of the well bore or mine workings [L] <br />Now, one can rearrange the Theim steady-state equation to back-calculate the hydraulic <br />conductivity of all rock contributing flow to the mine: <br />K _ Q ln(R/rh) <br />27rLH <br />One can then solve for K using site-specific mine inflow data: <br />K _ Q 1n(R/rh) _ 190gpm ln(1000 ft / 500 ft) _ 43x10-6 gpm / ft 2 = 2.9x10-' cm /sec <br />21rLH 21r(2220ft)(2200ft) <br />Total Depth 2,220 ft <br />Saturated Thickness 2,220 ft <br />Drawdown 2200.0 ft <br />Yield 190.0 gpm <br />Yield 36,577.5 ft3/day <br />Hydraulic Conductivity 4.3E-06 gpm/ft2 <br />Hydraulic Conductivity 2.9E-07 cm/sec <br />For comparison, one can calculate inflow to the mine using 100,000 times the actual bulk <br />hydraulic conductivity as suggested by the Division: <br />Total Depth 2,200 ft <br />Saturated Thickness 2,220 ft <br />Hydraulic Conductivity 2.90E-02 cm/sec <br />Drawdown 2190.0 ft <br />Yield 3,622,832,660 ft3/day <br />Yield 18,818,603 gpm