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<br />Mr. Jeff Gregg <br />October 23, 2000 <br />Page 4 <br />Inc <br />The nearest structure to the mine is the buried Sinclair gas line located 50 feet from the mine <br />excavation in an area with no stockpiles. Out stability analyses of the gas line scenario resulted in a <br />factor of safety of 1.5. <br />The nearest structure to the mine in an area with stockpiles is the buried AT&T cable located 60 <br />feet west of the mine excavation. For this scenario, we imposed a surcharge load of 1,200 psf in <br />the stockpile area. The resulting factor of safety was 1.6. Copies of the Spencer stability analysis <br />cross-sections and input files are attached to this letter. <br />Based on our analyses, the aggregate mining, mine related disturbances, and subsequent <br />reclamation activities should not compromise structures in the area. <br />LIMITATIONS <br />Our review is based on regional geologic mapping, present mining plans, bore hole data and slurry <br />wall construction details immediately south of the site, and stability analyses using typical soil <br />strength parameters. No exploratory borings have been drilled on the site itself. Should the mining <br />plans change or subsurface conditions vary from those portrayed in this letter, we should be <br />contacted in order to re-evaluate the potential affects on man-made structures. <br />Please call with questions or comments. <br />Sincerely, <br />R ~JCY MO NTAIN CONSULTANTS, INC. <br />i ,~ <br />-~ <br />Gary Linden, R.G. <br />Engineering Geologist <br />GL:sp <br />Hi0636 OSbllaPOUdre.hr.wpd <br />