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2.SH:1 V resulted in critical factors of safety of 1.36 and 1.40 for circular and block failures for an excavation slope of 2H:1 V. Based on these results, a maximum gob slope of 3H:1 V is recommended for maximum excavation slopes of 2H:1 V. This excavation and gob configuration will likely result in the greatest gob capacity. Critical factors of safety were greater than 1.50 for an excavation subgrade of 2.SH:1 V and gob slopes up to 2.SH:1 V. Based on these results, a maximum gob slope of 2.SH:1 V is recommended for maximtun excavation slopes of 2.SH:1 V. Table 6. Summary of Stability Evaluation Results subgrade Critical Factor of Safety' Excavation Gob Total Stress Effective Stress 2H:1V 3H:1V 1.53 (circlular) 1.55 1.55 (block) 2.5H:1V 1.36 (circular) 1.56 1.40 (block) 3H:1V 2.08 (circular) 1 52 2.SH:1V 2.02 (block) 2.SH:1V 1.91 (circular) 1.54 1.73 (block) Notes: Overall slope of excavation 2.5H:1V slope for lower 50 vertical feet. Slopes indicated for gob are above lower 50 feet. "No gob" indication is for evaluation of excavation only. 3. Factor of safety by Spencer's procedure i• 6.0 CONCLUSIONS AND 12ECOMbIENDATIONS Total and effective stress slope stability evaluations were conducted for Bowie Mine's Gob Pile No. 4 near Paonia, Colorado. The evaluations were based on information gathered from drilling investigations, laboratory testing of gob and native foundation soil, and our professional experience. Gob Pile No. 4 is located on the slopes of the north side of the North Fork of the Gunnison River Valley, between the existing Gob Pile No. 1 and Gob Pile No. 2. The Gob Pile No. 4 footprint is currently being used as a soil borrow area for cover material for Gob Pile No. 2. The excavation Bowie Gob Pile No. 4 stability report Project #OS-126-GEO Page 13 of I S 4H:1V 1.78 (circular) 1.54 1.85 (block)