1998-01-10_REVISION - M1988112 - Laserfiche WebLink

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t BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT CMLRD ADEQUACY LETTER RESPONSES Page 11 of 28 16. Section D. 6.1 states that, during Phase 1, 33% of the tailings will be placed in the upper disposal area. Section D. 6.5.3 states that, during Phase 1, the upper area will generate drainage at about 310 gpm, whi 1e the )ower area wi 11 generate about 230 gpm. Please explain ' why the Lesser volume of taiiings generates 120 gpm moue water. If these figures were used to evaluate the sizing and spatial placement of the aDS collector pipes, the design should be re-evaluated. It is essential that the drainage system be completely adequate to ' transmit flows from the tails to the catchment basin while minimizing the hydraulic head within the facility. ' RESPONSE: The quantity difference of 80 gpm is a result of the larger surface area of the upper area and thereby the drainage network under the upper area and is not related to the amount of tailings deposited. The quantities were conservatively calculated assuming that the entire surface area for drainage network for both the upper and lower areas was covered with tailings which exhibited permeabilities similar to permeabilities expected after one year of deposition. First year tailings permeabilities will decrease through consolidation over time. By assuming these high permeabilities over the entire drainage network area and not just the area of first year deposition, the maximum flows were conservatively estimated at 310 gpm for the upper area and 230 gpm for the lower area. In addition, the main collector pipes from the upper impoundment have 1 been designed to collect almost four times the conservatively calculated 310 gpm flow or 1200 gm. The main collector pipes from the lower impoundment have been designed to collect over three times 1 the 540 gpm total flow or 1800 gpm. Additional capacity is also available in the drainage blanket surrounding the pipe network. The figures presented represent a conservative design f'or the pipe ' network utilizing non-pressurized flow (zero head) and minimum grades. IT. The elevations contained on Figures D.6-3 through D.6-..5 should 6e ' corrected, and the figures resubmitted. RESPONSE: The elevations on Figures D.6-3 through D.6-5 have been corrected and the corrected figures are included with this submittal. 18. The pond cross-section shown on Figure C-8 indicates a six-inch PVC pipe will be used for the teak detection sump. The construction ' details provided in Appendix J state that an eight-incA pipe will be used. Please clarify. ' RESPONSE: The correct PVC pipe diameter shown on Figure C-8 should be 8" as stated in the construction details. The figure has been corrected.