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~` ~' DIVlS10N OF MINERALS AND GEOLOGY Department of Natural Resources 1313 Sherman St., Room 215 Denver, CO 80203 Phone: (3031 866-3567 FAX: (303) 832.8106 January 7, 1993 Ms. Kathleen Welt Environmental Supervisor Mountain Coal Company West Elk Mine P.O. Box 591 Somerset, CO 81434 Ill 1111111111111111 STATE OF COLORADO pF' ~O~ w° ~~~9 ~6 , Fny Romer Governor Michael 0. Lonq Divismn Direcbr RE: Preliminary Adequacy Review; Technical Revision No. 63; West Elk Mine; File No. C-80-007 Dear Ms. Welt; The Division has reviewed the above referenced technical revision which is a reconfiguration of the Lower Refuse Pile. The following items are the Division's adequacy concerns which need to be addressed before the technical revision can be approved. From review of Figure 2.0, it appears from the contour lines that the south side of the pile drains down to the road and does not enter the drainage system. Positive drainage should be maintained in this area. If positive drainage does not exist, the amount of moisture infiltrating into the head of the pile will increase and subsequently affect the stability of the pile. How does MCC intend to maintain positive drainage along the access road in this area above the head of the pile? Figure 2.0 should more clearly show the location of the sediment and clear water ditches. In reference to question 1, provide verification that the ditches can handle the revised drainage pattern due to the reconfiguration of the pile. 3. In Exhibit 51, in response to the Division's adequacy review letter concerning sediment control, MCC has stated that riprap in the ditches will not be necessary until Phase V. Since Phase V is being omitted, will the final revised configuration of the pile require riprapped