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<br />• . 7 <br />lJyoming Fuels' Testing Results <br />Assumptions Produced by Other Operators <br />Waste Pile Spoils <br />Angle of Internal Friction 35 degrees 37 degrees <br />Cohesion 500 lbs./f t.2 100 lbs./ft.2 <br />Pit Wall Strength <br />Angle o£ Internal Friction 40 degrees 22 degrees <br />Cohesion 10,000 lbs./f t.2 4,000 lbs./f t.2 <br />Waste Pile Surcharge 10,000 lbs./f t.2 10,000 lbs./ft.2 <br />Based upon the obvious discrepancies between specific testing results developed <br />by other operators and the assumptions made by Wyoming Fuels, I would have to <br />disagree with the operator's contention that their assumed strength parameters <br />are conservative. Utilizing material input parameters similar to those developed <br />by other operators within the North Park coal province will probably result in <br />significantly reduced calculated factprs of safety for both the waste pile <br />slopes and the pit wall slope. <br />On page 54 of their application (April version), Wyoming Fuels states that the <br />nomograph (incorrectly referenced as Figure 7; in actuality appears to be <br />Figure 8) solution for the waste pile "stability number" was 41. Entering the <br />Figure 8 nomograph within input parameters for slope angle (i) equal 30 degrees <br />and ( ) equals 16.4, the correct nomograph solution for the stability number (N) <br />appears to be approximately 27. Utilizing this value results in a static slope <br />safety factor for the waste pile of 1.15, rather than the 1.8 reported within <br />the application A static slope safety factor of 1.15 will not satisfy the <br />requirements of Rule 4.09. <br />Utilizing nomographic solutions for stability analyses is only appropriate in <br />relatively small, hazard-free overburden spoil fills. Considering the close <br />proximity of Wyoming Fuels' waste pile to its Pit No. 1 at the Canadian Strip <br />Mine and the potentially sub-standard factor of safety, I do not believe that a <br />„ ,, nomographic technique is appropriate in this situation. I recommend that we <br />require the applicant to submit a thorough geotechnical and stability analysis <br />utilizing appropriate materials testing results and an "accurate" mathematical <br />technique such as the "modified Bishop's" method of analysis. <br />4.13 Contemporaneous Reclamation <br />As the present operations in Pit' lil will end soon, WF must explain why <br />reclamation cannot occur as soon as the initial cut in Pit lit 1s completed. The <br />schedule of mining and reclamation operations concerns the Division for several <br />reasons. First, the length of time the topsoil stockpiled for Pit 111 reclamation <br />may seriously reduce its value as a plant growing medium. Secondly, any problems <br />which may exist in establishing the desired plant community will not be known <br />until reclamation begins in Pit 112. Finally, the environmental problems caused <br />by the open pit and overburden stockpile will exist until 1987. <br />