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Subsidence Evaluation For ExMbit 608 South of Divide Mining Area Page 23 • occumng rockfalls-such as remnant boulders at the base of steep slopes, or in the nm-out zones of these areas with a rockfall potential should be documented prior to mining- 11.0 EFFECTS OF SUBSIDENCE AND MINE-INDUCED SEISMIC ACTMTY ON MAN-MADE STRUCTURES AND RENEWABLE RESOURCES Man-made structures and renewable resources in the South of Divide mining area basically consist of 1) a reservoir (Minnesota Reservoir), 2) stock watering ponds, 3) streams (primarily Dry Fork and the upper part of Lick Creek), 4) roads, and 5) local cabins. Minnesota Reservoir, the ponds, and the Deep Creek Ditch diversion to Dry Fork serve the dual purpose of being both man-made structures and containment structures for the valuable water resources in the area. Based on annual subsidence observations in the Jumbo Mountain, Apache Rocks, and Box Canyon mining areas during the last ten years, the following information is considered appropriate for the South of Divide mining area. 11.1 Minnesota Reservoir Minnesota Reservoir, which provides storage water primarily for irrigation, is located between two landslides~ne beginning at the north shore and the other beginning at the south shore. As explained in Section 10,1.1 (above), landslide movement on Jumbo Mountain occurred during unusually wet periods before mining began, during mining, and after mining and subsidence was complete. The conclusions were that landslide movement occurs in response to ground saturation and is not noticeably affected by subsidence and seismic activity produced by longwall mining beneath, or near, landslide areas. Both the landslides on Jumbo Mountain and those north and south of Minnesota Reservoir occur in surficial material (loose rock, gravel, sand, silt, clay, and soil) and local bedrock outcrops. The author therefore expects drat the mining of longwall panel E9 will not noticeably affect the large landslide south of Minnesota Reservoir. Mining of the nine longwall mining panels in the Soutlt of Divide mining area, as currently planned (Map 1) will not affect Minnesota Reservoir. The reservoir is located outside the area of mining influence, using the most conservative 45-degree angle of draw. In order to verify and demonstrate the accuracy of predictions, based on the results of past subsidence observations in the Apache Rocks and Box Canyon mining areas, it is recommended that three procedures be implemented to monitor this stntcnue prior to mining. The following procedures will be implemented in order to account for seasonal precipitation changes. Conduct periodic aerial photo surveys of the landslides located north and south of dre reservoir, using the July 2004 photos as a baseline reference. • 831-032.690 WnghtWaferEngineers, Inc.