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<br />' D. Soil Loss and Sediment Deposition <br />' Goff Engineering acquired the RUSLE soil loss software for determining the <br />expected loss of the various sedimentation areas outlined on the attached map of <br />the fill area. The soil loss is based on the equation: A = R K LS C P, where A is the <br />' annual soil loss in Tons/ac.-yr., R is the factor for climatic erosivity, K is the soil <br />erodibility, LS is the slope factor, C is the cover management factor and P is the <br />factor for support practices. In all of the applications the sub-factors which most <br />' closely approximated construction or mining operations were used. The actual <br />printout generated by the software is attached, as is the extrapolation of the total <br />' soil loss across the entire area. It is felt that the soil loss values are representative in <br />that the stabilized areas measured much less than the 3 Tons/ac.-ft. recommended. <br />The brand new, "raw" fill pile measures considerably more than the 5 Tns/ac. yr. listed <br />' as a maximum. This, of course will be lessened later when the pile can be fully <br />stabilized and seeded. <br />t Goff Engineering topo.'d the Sediment Pond No. 2 and determined that the <br />pond bottom level has stayed essentially the same in the last 18 months (since the <br />' City of Durango aerial flight in April, 1994. From the results of the sediment <br />evaluation, it was determined that the sediment filling rate, For the first years, is <br />expected to be on the order of 0.5 feet per year. We will continue to monitor this <br />' filling rate over the next months and years. We will note any appreciable increases <br />over this rate and, as time goes by, the operator will remove the excess sediment <br />deposited. As directed by the Division of Minerals & Geology, a 10 and 25 storm <br />t event will be analyzed to determine if any diminution of the storage capacity can be <br />tolerated. That study will be performed in the first quarter of 1996. <br />' E. Conclusions <br />1 From the evaluations presented as a part of this report, it is determined that the <br />methods of placing and sloping within the fill pile are generally acceptable and in <br />' compliance with the terms of the permit. Certain additional sediment generation will <br />be realized as a result of these operations. That addition is of a tolerable rate and will <br />' be monitored closely in the future. <br /> <br /> <br /> <br />1 <br />