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Mr. Rick Siebel, Regional Director -3- May 16, 1995 <br />Office of Surface Mining <br />Western Region Coordinating Center <br />The No. 2 Portal highwall was previously approximately 50 feet in height and 1300 feet in <br />length. This area was also completely backfilled. Ten slope measurements were taken, with <br />the gradient also averaging 15.4°. This fell within the required 18.43° reclamation gradient <br />also. <br />One small twenty-foot section of the regraded substation area had a slope angle of 25°. <br />While this slope angle was less than the regulatory maximum of 26.57°, it was significantly <br />steeper than the approved angle of 18.43°. This area was thus proposed for denial from the <br />bond release request. <br />The coal mine waste bank comprises an area of approximately 6.5 acres. The outslopes <br />were designed by EFMC to be graded to an 18.43° slope (3H:1V gradient). This slope <br />angle is gentler than the State regulatory maximum of 26.57° (2H:1V gradient) for waste <br />bank terraces (Colorado's Regulations at Section 4.10.4(4)). Refuse material in the waste <br />bank was placed in one-foot lifts, which is thinner than the State regulatory maximum of two <br />feet (Colorado's Regulations at Section 4.101.4(3)(a)) and which would allow for a higher <br />degree of compaction. EFMC has compacted the refuse to 95.8% of the maximum dry <br />density value of the refuse of 96.4 lbs./ft 3 This exceeds the State regulatory minimum <br />compaction standard of 90% of the maximum dry density value (Section 4.10.4(3)(b)). <br />Finally, the refuse pile has attained a static safety factor of 2.5, 66.7% higher than the <br />minimum static safety factor of 1.5 required by the State (Section 4.10.4(2)). A copy of the <br />bond release application, and copies of the certified engineer's reports attesting to the <br />construction of the waste bank, were on file at the mine site at the time of the inspection. <br />The coal mine waste bank has two outslopes, one facing west and the other facing south. <br />During the March 8, 1995 Bond Release Inspection, Division personnel took three Abney <br />level measurements of the west-facing outslope. These angles were found to be 18.5°, <br />18.75° and 19.0°, producing an average slope angle for the west-facing outslope of 18.75°. <br />While each of the three measurements was slightly steeper than the 18.43 ° requirement, none <br />was more than 0.58° steeper than that requirement, and all were less than the regulatory <br />requirement of 26.57° (2H:1V gradient). The Division believes this 0.58° difference to be <br />within an acceptable margin of error (f 0.75°) for hand-held Abney level measurement. <br />Division personnel then took six slope measurements of the south-facing outslope of the <br />waste bank. These slope measurements were: 16.5°, 17.5°, 17.0°, 20.25°, 17.5°, and <br />16.0°, producing an average slope angle of 17.46°. Although the average slope angle for <br />the south-facing outslope was almost a degree gentler than that required by the permit, the <br />one slope that measured 20.25° exceeded both the permit requirement and an acceptable <br />margin of error for Abney level measurement. This section of the south-facing outslope was <br />thus proposed for denial from the bond release request. <br />Division personnel inspected the thickness of cover material placed over the coal waste. <br />Twelve measurements were made, using an EFMC-operated hydraulic excavator and a five- <br />