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-IZ- <br /> <br /> <br />Characteristics of Materials <br />The characteristics of the spoil fill material were estimated -from <br />observation of performance of existing spoil piles, review of various reports <br />performed for the Coiowyo Coat Company, our experience with spoil <br />generated from similar overburden materials in other areas of Routt and <br />Moffat Counties, and published data regarding strength characteristics of <br />rock fills. In our opinion, the fill will function essentially as a granular <br />material. We used an angle of internal friction in the range of 35 to 39 <br />degrees. No cohesion was assumed to occur in the spoil. <br />The stiff to very stiff clays found in our borings at the valley bottom <br />were tested using triaxial strength tests and unconfined compressive strength <br />tests. The unconfined compressive strength tests indicated cohesion of about <br />3,000 psf; this represents undrained shear strength. A triaxial strength test <br />performed using aconsolidated-undrained test procedure with pore pressure <br />measurements indicated drained shear strength of 500 psf and a friction angle <br />of 15° for the clay. <br />We assumed the underlying bedrock found below the valley bottom and <br />near the surface on the slopes of the spoil area to have a cohesion intercept <br />of 5,000 psf and no friction. This is likely a conservative estimate of the <br />actual shear strength of the bedrock. <br />Drainage Conditions <br />Performance of any fill, or natural slope, is highly influenced by The <br />location of the free water surface which develops in the slope. Diversion of <br />surface drainage around the spoil will limit the amount of water entering the <br />• <br />