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Our computer analysis of the stability of the future tailings slope assumed the cycloned sands would form a slope of about 28 degrees (the minimum fraction angle or angle of repose) cited by Vick. This would result in a factor of safety of 1.0 if we used 28 degrees in stability calculations based on a infinite slope analysis (factor of safely = tangent of angle of friction divided by tangent of slope angle). Vick indicates that cycloned materials typically flow as a thick, ropy discharge and assume an angle of repose of 3:1 (18 degrees) to 4:1 (14 degrees). If we use the internal angle of friction of 28 degrees and a slope angle of 14 to 18 degrees, the infinite slope factor of safety for 3:1 and 4:1 slope is 1.6 and 2.1; respectively. The results of our slope stability analysis indicate that the overall design for the tailings pond will result in a stable configuration for both the embankment and initial tailings placed within it. The cycloned sands will stabilize in the mounded tailings at the angle of repose. This will likely be between about 14 to 18 degrees. This initial slope will increase in stability as the cycloned sands drain. EMBANKMENT FILL We understand that the natural, onsite soils below or near the planned tailings pond will be used to construct the embankment. Topsoil, organic soils, and other deleterious materials should not be used as embankment fill. Fill material should have a maximum particle size of 6 inches and contain at least 50 percent silt and clay sized particles (passing the No. 200 sieve). Natural soil samples obtained from beneath and adjacent to the embankment had natural in -situ moisture contents between about 5 and 18 percent. A Standard Proctor test performed on a sample from the stockpile indicated optimum moisture content of the soil will be 12.5 percent. This Proctor result is based upon 26 percent sand and 24 percent gravel with 50 percent silt and clay sized particles. Should gravel amounts in the material used as embankment fill vary significantly from this amount additional Proctor tests should be run. The near surface material (top five feet) was greater than 12.5 percent moisture content. Depending upon the time of year that construction takes place it should be anticipated that the top five feet of natural soils will need to be dried prior to placement as fill. Water will be required to raise the moisture content in the fill material taken from greater depths than about five feet and should be available during fill placement. Mixing with the wetter and shallower material may result in fill closer to the required moisture content. Water should be uniformly mixed into the fill during processing and prior to placement. Fill should be placed in 10 to 12 inch thick lifts. Compaction should be with a large, self - propelled sheepsfoot compactor. Smooth drum rollers should not be allowed. Fill should be moisture conditioned to within 2 percent of optimum moisture content and be compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698). Embankment fill should be placed in level lifts. Lifts should be scarified prior to placement of the next lift. A representative of THE UNION MILLING COMPANY TAILINGS POND EMBANKMENT AND FUTURE TAILINGS SLOPE UNION MILL CTL T PROJECT NO. DN45,584 -130 S:IPROJECTS4155001DN45584 .000113013. Letters11_11DN45584-130•L1.doc 9