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2004 Geologic Hazard Field Observations <br />South of Divide Mining Area <br />• based on the following observations made while conducting geologic mapping for the USGS <br />in the Somerset-Paonia azea: <br />1. In the Somerset Mine, coal pillars were extracted beneath Bear Creek in a 400 to 460 foot <br />wide panel at an average overburden depth to mined coal of 260 feet (overburden depth <br />range of 220 to 300 feet). No cracks were observed in the clay and silt alluvium <br />{estimated to be 10 to 15 feet thick) and the underlying colluvium (estimated at 30 to 50 <br />feet thick), even though cracks one to two inches wide were observed in the Beaz Creek <br />road, and cracks as much as 1 foot wide and 25 to 50 feet long were observed in the <br />weathered bedrock and thin colluvium (estimated to be 1 to 3 feet thick) on the side <br />slopes of Bear Creek. <br />2. No change in flow was observed downstream from the site and, to the author's <br />knowledge, no loss in stream flow was reported (Final Environmental Impact Statement, <br />Iron Point Coal Lease Tract & Elk Creek Coal Lease Tract, Delta and Gunnison Counties, <br />Colorado, February 2000, Appendix K, p. K-12 and K-19). <br />3. The more uniform longwall mining method (compared to room-and-pillar mining) will <br />make surface cracking and loss of water even less likely than the room-and-pillaz mining <br />method in Dry Fork and its tributaries. Furthermore, the minimum overburden depth is <br />greater (by about 15 to 35 percent) in the Dry Fork azea than it was in the Bear Creek <br />azea. <br />8.3 Aerial Photo Location 3 <br /> <br />This observation point is located at the upper part of a large landslide and rockfall area near the <br />head of Lion Gulch in the southwestem part of the South of Divide mining area (Figure 9 and <br />Map 1). <br />The northeastern, and active, part of the slide azea is located above the southwestern part of <br />projected longwall panel E8 in overburden ranging from 200 to 400 feet. <br />631-032.621 Wright Water Engineers, Inc. Page 29 <br />November 2004 <br />