Laserfiche WebLink
bulkheads at each site. Each member of each pair of bulkheads would be constructed <br />to the specifications recommended by Abel (1993) for a single bulkhead. The twinned <br />bulkheads are proposed to be separated by a distance of more than 100 feet. The <br />purpose of twinning the bulkheads is to reduce the chances of a random permeable <br />fracture set in the rock bypassing a single bulkhead. <br />8.3 Transit Time for F/ow from Mine Workings to the Surface <br />The time required for ground water to move from the flooded mine workings to <br />Cement Creek can be roughly estimated with a form of Darcy's equation: <br />V = KI Where: <br />n <br />V = velocity, <br />K = hydraulic conductivity, <br />I = gradient, and <br />n = effective porosity. <br />Assuming flow is to the southwest (as in cases 1 and 2 in Section 8.2), possible <br />gradients range from 0.1 assuming a hydraulic head in the Sunnyside Basin to be just <br />below F-Level (the most likely case), to a maximum of 0.18 (assuming a head in the <br />Sunnyside Basin to be at land surface). Hydraulic conductivity in highly fractured <br />areas is on the order of 5x105 cm/sec (0.15 ft/day) based on flow testing in the <br />American Tunnel. However, this hydraulic conductivity is expected to be higher than <br />average considering that the degree of fracturing is somewhat greater than normal in <br />the vicinity of the flow testing. Average hydraulic conductivity is expected to be far <br />sunny~wp\traci12251 \Mer1893.Rpt 5 5 <br />HMI SI(11011 HYDRO-SEARCH <br />