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1 Oakridge Energy -Carbon Junction Mine Division of Minerals 8~ Geology Permit No. C-92-080 Study of Stability and Sediments from the Fill Pile Area ' A. Background ' After a temporary cessation for approximately the last eight years, of all activities connected with the subject fill area, in October of 1994 Durango Construction, operator of the gravel operations within the overall permit limits, began ' once again to place material within the general fill area. Durango Construction's gravel crushing and asphalt mix operations require them to waste certain screenings which are not marketable. They are doing so by hauling the material to the fill area, ' dumping and spreading it and then wheel rolling in approximately one foot lifts. Lambert 8. Associates, geotechnical engineers, has been hired as a subcontractor to ' Goff Engineering to evaluate the slope stability of the placed embankment and to determine the results of the compactive effort being applied. At the same time Goff Engineering has acquired the RUSLE (Revised Universal Soil Loss Equation) sediment ' evaluation software from the Soil and Water Conservation Society and has run an initial evaluation on the drainage areas which effect Sediment Pond No. 2, including runoff through and over the fill area in question. The results of the above mentioned ' testing and evaluations are the subject of this report. ' B. Compaction Testing Results Lambert & Associates performed nuclear density tests on the site on November 16 and 21 and December 1, 1995. The results of those tests are attached. The results show that the compactive procedures are generally sufficient to produce 90% or above of the maximum dry density. Those tests which were under 90% were ' recompacted and retested with the indicated results. It is our intent to continue to work with the operator to consistently reach the required results. We had intended ' to have Lambert & Associates check the results again later in December but the operator shut down for two weeks over the holidays. ' C. Slope Stability Testing Results ' Lambert & Associates has performed a test on the material based on the Bishop method for slope analysis. The results of that test is attached. As stated, the results indicate that the material, when placed at 90% of M.D.D. can be expected to ' stand at a slope of 2:1 or flatter with a resulting safety factor of 1.57. Goff Engineering & Surveying has taken shots on the fill placement and determined that ' the existing and new slopes range from 2:1 to 3.5:1. We will continue to monitor the slopes as the fill deepens.