2007-06-29_PERMIT FILE - C1981022A (2)

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SErtiaz - 2.05.3 and modification of Sedimentation Pond B and [he Substation No. 3 Sedimentation Pond and associated ditches were prepared or modified by Thomas E. Leidich, P.E. No. 31459. Detailed design plans for Sedimentation Pond C and the associated ditches and culverts for both the West Valley Fill and associated haul road were prepared by or under the direction of Greg Eddy, P.E. No. 31270. These plans were reviewed and modified to address specific DMG concerns by William P. Balaz, P.E. No. 17129. Detailed design plans for culverting the middle portion of Elk Creek, the collection and diversion ditches and alternative sediment control measures implemented for the Elk Creek Mme surface facilities, and Sedimentation Pond D were prepared by or trader the direction of Thomas E. Leidich, P.E. No. 31459, and Daniel J. Keuscher, P.E. No. 33307. Mine Water Storage and Discharge -Mine workings in the Elk Creek D Seam Mine produce excess water from spillage, dust control over spray, cooling of motors, etc. There are only very minor natural seeps into the mine workings. Mine dewatering flows are transferred to a large underground sump (up to 7.8 million gallons capaci[}~ for temporary storage and to allow suspended solids in the water to settle out. Accumulated water is then recovered and pumped back into the mine water system for reuse. Any excess mine water will be pumped from the sump to the Elk Creek Mine head tank for temporary storage and reuse in the mine water system, or discharged to the surface as NPDES Ou[fall 015 or transferred to the underlying Somerset Mme B seam workings via a stung water injection borehole. The B seam borehole will be monitored for water level at the frequency of the OMLLC groundwa[er monitoring program and the results reported in the AHR The annual volume of water transferred from [he D seam workings to the B/C seam workings will also be reported in the AHIL A representative sample of the transferred water will be sampled for pH and TSS and reported in the AHR TSS levels could be elevated due to the presence of fine-grained mine rock dust. For the closed Sanborn Creek Mine, excess mine dewatering flow was pumped from underground sumps fhst to a mine water settling pond then later directly to the surface as NPDES outfall 011. The mine dewatexing pond is a totally incised pond with a bottom elevation of 6,056 fee[ and a two- foot deep collection ditch around the perimeter of the pond. The up- stream, interior sideslopes of the pond are 2H1V. On completion of active mining operations in the Sanborn Creek Mine, pumping ceased, and the mine workings were allowed to collect any future drainage. Pond removal will involve removal of discharge structures, backfilling the pond basin, grading the pond area, replacing available soil material, and revegetating [he regraded area. Design information for the Sanborn Creek Mine Dewatering Pond is provided in Exhibi[ 2.05-E3, Drainage and Sediment Control Plan, and pond design configuration is illustrated by the Sanborn Creek Mine Dewatering Pond Map, (Map 2.05-M-SI~. Sedimentation Ponds -Given that surface disturbance is limited by the underground mining operations, OMLLC utilizes alternative sedimen[ control measures where reasonably feasible to both intercept and control drainage and sediment as close to it's source as possible and to minimise further surface disturbance. For larger disturbance areas, however, this approach is not effective in TR-50 2.05-33 Revised Februarv 2005