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<br />• MINING AND RECLAMATION PLAN October, 1979 <br />MT. GUNNISON NO. t MINE Revised February, 1981 <br />Revised September 29, 1981 <br />The final design of this initial waste pile has been completed as stated in the <br />attached Letter 3.2.9.A on Page 3-43b from Geo-Hydro Consulting, Inc. Geo- <br />Hydro is recognized as an expert .certified professional engineering firm and is <br />qualified to design this waste pile. The dams and embankment (817.91-817.93) <br />requirement have been met in this design. The Geo-Hydro report also addresses <br />the method of stability analysis, and demonstrates that a factor of safety of 1.5 <br />shall be maintained. Compaction of the processing wastes shall be 90 percent of <br />the maximum dry density in order to prevent spontaneous combustion of any coal in <br />the waste, and to provide the required strength for the embankments. See Exhibits <br />3.2.9.A and 3.2.9.A.1, Phase I and Phase II respectively both entitled, "Report, <br />Preliminary Design Recommendations, Initial Waste Rock Pile, Mt. Gunnison Coal <br />Mine, Somerset, Colordo, for ARCO Coal Company. <br />The upper (future) waste pile shall not be designed in detail at this time since this <br />• pile will not be required during the first five-year permit. Additionally, the initial <br />waste pile shall be analyzed to see if our waste rock should be classified as <br />"durable rock fill" or not, and the upper waste pile designed accordingly. The <br />attached Exhibit 3.2.9.B Report Preliminary Stability Evaluation Upper Waste Rock <br />Pile Mt. Gunnison Coal Mine for ARCO Coal Company describes the stability <br />studies which have been made to satisfy regulatory concerns of the viability of <br />using the upper bench for a future rock storage area. <br />• <br />3-43a <br />