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Lodestar Energy, Inc. <br />Munger Canyon Mine <br />Mine Portal Backfill Certification <br />Page 3-29 of the Munger Canyon Mine permit addresses slope stability at the portal bench. <br />The slopes analyzed at the mine site were at Station 49+25 and 51+00, shown on Figures 3.1-4 <br />and 3.1-7. Cross sections of these areas are shown on Figure 3.1-9. The slope at Station <br />51 +00 was chosen for analysis since it is the area where a slide developed when water draining <br />from the road which existed prior to mining above the slope saturated the slope and caused a <br />slide in the area. The slope has been stable since the water running down the road was <br />directed back into the natural drainage with a water bar. This will also be the tallest reclaimed <br />slope after the area has been re-contoured. Coal from the Loma Loadout was used to backfill <br />near the existing portals as is shown on Figures 3.1-4 and 3.1-7. Stability analyses indicated <br />the slope would be stable. Most of the above discussion is from page 3-29 of the permit. <br />Coal from the Loma Loadout was placed and compacted as shown on the drawings during <br />September and October 2001. Figure 3.1-7 shows the coal backfill placed in two separate <br />areas. The west area is about 100-feet long and 15-feet wide. The east area is approximately <br />80-feet long and 10-feet wide. Significantly more coal was placed in the fill than was <br />anticipated. The coal was placed in one (200-foot+) long pile in the east west direction. The <br />pile is approximately 75-feet wide and up to 15-feet deep. <br />The coal was placed and compacted with front end loaders. The loaders provided necessary <br />compactive effort. Compaction tests were taken on September 27 and November 13'". Two of <br />the tests taken on September 27 were noted as failing. One at the power pole (85%) and one <br />175-feet east of the power pole (91 %). Both areas were reworked and compacted but not <br />retested. The tests taken on the top of the coal fill on November 13'" all had a relative <br />compaction greater than 100%. <br />The stability analysis in the permit assumed coal strength parameters as a cohesion of 0, and <br />angle of friction of 15° and a density of 100 pounds per cubic foot. A representative sample of <br />the coal in the backfill was sent to Lambert and Associates for triaxial sh~ strength tests. The <br />coal material has a cohesiorff 3psi or 432 psf, a angle of friction of 33 and a density of 82~/ <br />pounds per cubic foot. The reclamation stability cross section at Station 51+00 was <br />reevaluated based on the additional coal placed in the backfill and the revised strength <br />parameters of the coal. The slope stability analysis was performed using SB-Slope by <br />Geosystem software. The slope stability analysis considered numerous possible failure surface <br />iterations to help identify the potential theoretical slope stability. The stability analysis indicates <br />a factor of safety of 1.78. <br />Based on my inspection of the coal backfill at the Munger Canyon Mine portal, compaction tests <br />performed by Western Colorado Testing and my stability analysis of the cross section at <br />Station 51+00, the proposed portal backfill will be stabl~,ai,it}e~inal proposed configurations <br />indicated on the site plans with the additional coali~f~i9C'~¢gn the portal bench. <br />.••- <br />104~••~ ~ j r •~ 9 <br />~ 1Y; JarrT~s F Stove[ <br />:A ~p.E. No. 192315 <br />p ~1 H'- ~ <br />~~~~J <br />