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10-27-1997 11 :SdAM FROt~1~NG. WEST ELK t~1INE 970 9295050 p 3 • ~" Technical Revision No. 81 Page 1 October 24, /997 6. The access road will be graded to drain away from the pond, to minimize the amount of stormwater run-off wntributions to the mine water treatment pond. Drainage arrows have been added to Drawing 97009-02. MCC will install the fence so that it will not interfere with the function of the spillway by collecting debris. The spillway will also be inspected on a regular basis to clear debris, if accumulated. Map 54A has been revised to include a culvert designation and size specifications as requested by the Division. A revised map is included with this submittal. 9. The culvert sizings are provided on Drawing 970009-02. WESTEC has reviewed and refined the minimum designs for the culverts that will convey cleaz water to Lone Pine Gulch, and has determined that an ] 8-inch culvert would be ~. adequate (see the attached nomograph to be included in Exhibit 66). However, MCC plans to install 24-inch culverts in these locations. The culvert size has been included on Map 54B, which is enclosed. A 24-inch CMP will also be installed to convey the water through the spillway and under the light-use road to Lone Pine Gulch. 10. The emergency spillway was designed to convey 2,400 gpm with approximately 1.8 feet of freeboard. The approximate discharge from the 25-year, 24-hour storm event (2.3 inches) over the pond area is less than 300 gpm; therefore, the spillway has adequate capacity to route this stone event and design flows. I I . Any detention time will depend on the specific water quality of the mine water. MCC will hold the water for an adequate time to ensure that the water will meet effluent standards established by the Water Quality Control Division. MCC typically takes a sample at the existing sedimentation ponds prior to dischazge to ensure that the discharge will meet effluent limitations. MCC will continue this practice at the Lone Pine pond. If the pond is full and does not meet effluent standards, pumping from the Lone Pine portal will be stopped until the water quality is sufficient for discharge. Although MCC does not expect the quality of i. the mine water pumped from the Lone Pine portals to be problematic, MCC has conservatively designed the pond to hold and handle poor quality mine water. 12. MCC will install anti-seep collars as recommended by the Division. Drawing 97009-04 has been revised. 13. The reclamation estimate is acceptable to MCC.