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TECN NOLOOIFS INC <br /> <br />January 31, 1997 <br />Mr. Jim Stover <br />3.E. Stover & Associates <br />2768 Compass Drive, Suite 101 <br />Grand Junction, Colorado 81506 <br />96 South Zuni Straet <br />Denver, Colorado 80223-1292 <br />Telephone: (3031 744-7706 <br />Fe ce im it e: 13031 744-0210 <br />Subject: Expansive Soil Evaluation, Reclaimed Fill Slopes, Bowie No. 2 Mine, Bowie, <br />Delta County, Colorado <br />Project No. 5002-60-2655.05 <br />Dear Mr. Stover: <br />At your request, we have performed additional laboratory analysis on typical material that will <br />comprise reclaimed fill slopes to evaluate the expansion potential of the material. We previously <br />provided recommendations for reclaimed slopes reported under our Project No. 5002-60- <br />• 2655.02, dated October 10, 1996. <br />In our October letter we recommended that the material in reclaimed fill slopes be placed at or <br />above optimum moisture content and compacted to a density of at least 85 % of the maximum <br />modified Proctor density. Disturbed bulk samples of the overburden soils (ancient landslide <br />mass) obtained during our preliminary geotechnical engineering study performed under Project <br />No. 5002-60-2655.01, dated July 10, 1996 were used for the labotatory analysis. Samples from <br />Borings B-17 at depths from 5 to 20 feet and B-18 at depths from 10 to 15 feet were selected <br />for testing. These materials were selected because they were representative of the material that <br />will comprise the majority of reclaimed fill slopes. In addition, material from Boring B-17 at <br />depths from 5 to 25 feet was previously evaluated in our July, 1996 preliminary study. Triaxial <br />shear testing was performed on this material in a remolded condition to depict fill strength. <br />These borings were also located in the areas of the highest cut slopes (adjacent to the portal and <br />stockpile bench areas) which will also be the highest reclaimed slopes. <br />The bulk samples selected for testing consisted of sandy lean clay with bedrock fragments, <br />considered typical of the ancient landslide mass. The material was remolded to approximately <br />85 % of the maximum modified Proctor density at optimum moisture content and 2 % above _ <br />optimum moisture. Swell-consolidation tests were performed on the remolded samples to <br />evaluate the expansion potential when the material is subjected to inundation, which is possible <br />for the reclaimed fill materials near the outer fill slope. Test results, presented on Figures 1 and <br />• 2, indicate no expansion and only slight consolidation when subjected to inundation. <br />Austin Research Engineers Chen-Northern Empire Soils Investigations <br />Kansas City Testing .Southwestern Laboratories .Twin City Testing <br />~s <br />yr M~ <br />