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2004 Geologic Hazard Field Observations <br />South of Divide Mining Area <br />r1 <br />LJ <br />• <br />~J <br />9.0 EFFECTS OF SUBSIDENCE AND MINE-INDUCED SEISMIC <br />ACTIVITY ON MAN-MADE STRUCTURES AND RENEWABLE <br />RESOURCES <br />Man-made structures and renewable resources in the South of Divide mining area basically <br />consist of 1) a reservoir (Minnesota Reservoir), 2) stock watering ponds, 3) streams-primarily <br />Dry Fork (and the Deep Creek Ditch diversion to Dry Fork and the upper part of Lick Creek), 4) <br />roads, and 5) local cabins. Minnesota Reservoir, the ponds, and the Deep Creek Ditch diversion <br />to Dry Fork serve the dual purpose of being both man-made structures and containment <br />structures for the renewable water resources in the azea. Based on annual subsidence <br />observations in the Jumbo Mountain, Apache Rocks, and Box Canyon mining areas during the <br />last nine years, the following findings are considered appropriate for the South of Divide mining <br />area. <br />9.1 Minnesota Reservoir <br />This reservoir, which provides storage water primarily for irrigation, is located between two <br />landslides--one beginning at the north shore and the other beginning at the south shore. As <br />explained in Section 8.0, landslide movement on Jumbo Mountain occurred during unusually wet <br />periods before mining began, during mining, and after mining and subsidence was complete. <br />The conclusion was that landslide movement occurs in response to ground saturation and is not <br />noticeably affected by subsidence and seismic activity produced by longwall mining beneath, or <br />near, landslide areas. <br />The landslides on Jumbo Mountain and those north and south of Minnesota Reservoir occur in <br />surficial material (loose rock, gravel, sand, silt, clay, and soil) and local bedrock outcrops. <br />Therefore, it is expected that mining of longwall panel E9 will not noticeably affect the large <br />landslide south of Minnesota Reservoir. <br />831-032.621 Wright Water Engineers, Inc. Page 32 <br />November 2004 <br />