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iiiiiiiuiiiiiuiii 999 Mountain Coal Company West Elk Mine Post Oflke Box 591 ` ' Somerset, Cokxado 81434 Telephone 970.92&5015 \ 1 ~ n RGr~FI I / July 29, 1997 JUi_ 3 0 1991 Mr. Michael Boulay Ivision of r,imelals ts<Geology Colorado Division of Minerals and Geolo~y 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Minor Revision No. 223 (ROM Pad Expansion); West Elk Mine; Permit No. C-80-007 Dear Mike: Mountain Coal Company (MCC) submits the enclosed minor revision application to expand the existing run-of--mine (ROM) coal stockpile pad. The expansion area will increase the coal storage azea by approximately 5.1 acres as shown on Drawing 97010-02. WESTEC, Inc. designed the expansion. WESTEC's design of the pad expansion is based on their field reconnaissance of the site in January 1997, a geotechnical field investigation conducted in March 1997, and the review of geotechnical data collected by MCC. Pertinent components of the design include foundation preparation, geogrid reinforcement system, sub-pad drain system, subdrains, and diversion systems and are discussed below. The expansion azea will be cleared of vegetation prior to removal of the topsoil. Approximately 8,200 CY of topsoil will be stripped. The topsoil will be placed in a topsoil stockpile that will be proposed in a future revision. As the cut-and-fill will balance, there will be no need for a subsoil stockpile or for material to be imported. A minimum three-foot high berm will be constructed around the perimeter of the pad. A light-use road will be constructed on the north and west side of the ROM pad. The road will be approximately 14-feet wide and surfaced with road base. The northern side of the expanded pad will be reinforced using a geogrid system to increase stability. The geogrid will have a minimum 2,000 Ib/ft tensile strength similar to Strata grid S00 or other appropriate material as approved by the Construction Engineer. Detail of the geogrid is provided on Drawing 97010-05. Precipitation falling onto the pad expansion will be collected using drains located beneath the pad surface. The sub-pad drains will convey the surface water off the pad expansion to a main collector pipe and will be routed to the existing sedimentation pond, MB-5. The pond was checked for its ability to process flows from the new coal storage area, in addition to the design flows. An excerpt from WESTEC's design report is provided which details their method for evaluating the pond. In