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iii iiiiiiiiiiiiiiii STATE OF COLORrtuv Roy Romer, Governor DEPARTMENT OF NATURAL RESOURCES MINED LAND RECLAMATION DIVISION FRED R. BANTA, Director DATE: November 14, 1988 T0: Matt Hayes FROM: Jim Pendleton RE: Mt. Gunni No. 1 ower (Permit Waste Pile Semi-Annual Monitoring Report No: C-80-007) I have completed a review of the semi-annual monitoring report submitted by West Elk Coal, Inc., regarding their lower waste pile. The brief letter report includes the compaction test results and survey monitoring of the surface stability monuments. The compaction test results submitted included relative compaction results from nine separate determinations performed on August 25, 1988. These results vary from a relative compaction of 107.29% to 123.13%, with an average of 115.62%. Frankly, based upon my field experience, these results appear suspiciously high. Its not impossible to achieve occasional relative compactions in this range, but is uncommon for an entire set of results to group this high. An occasional high result can be attributed to an undetected large clast of rock in the embankment material near the probe location. Normally these errant results are anomalously high, even exceeding 130%, because of the high density of rock. The Mt. Gunnison No. 1 lower waste pile results which are uniformly high suggest that the Proctor density being used as the optimum dry density standard may be too low. In order to resolve this question, I revisited the last two semi-annual reports submitted by West Elk Coal Co. The compaction results reported from tests performed on November 20, 1987, range from relative compactions of 87.9% to 113.5%, with an average of 97.2%. The results from tests performed on June 15, 1988 range from 92.5% to 120.0%, with an average of 103.2% (obviously erroneous 155,0% ignored). All three of these testing episodes have used the same standard Proctor Test results to determine relative compaction, maximum dry density of 83.0 pcf at an optimum moisture content of 13.5%. The average measured relative compactions have risen from 97.2% to 103.2% to 115.6%. I suspect that the materials arriving at the waste pile have changed in their properties. This can be the result of a number of variations; such as lithologic changes in the seam being mined and wasted, methods of extraction resulting in different waste material, or different separation methodology and equipment, etc. 215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567