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2004 Geologic Hazard Field Observations <br />South of Divide Mining Area <br />LJ <br />11.0 CONCLUSIONS <br />One of the more important conclusions derived from observations in the West Elk Mining area is <br />that all subsidence parameters (in terms of the ratio of maximum vertical displacement to mine <br />overburden depth compared to the ratio of longwall mining panel width to overburden depth) fall <br />within the range of those observed during the annual subsidence observations. The subsidence <br />parameters also plot favorably on appropriate graphs published by the National Coal Boazd of the <br />United Kingdom. <br />Results of analyses of field subsidence measurements in the West Elk Mine monitoring network <br />agree favorably with computer modeling programs developed in the Eastern United States. <br />These favorable comparative results, when calibrated to the West Elk subsidence data, provide <br />added assurance that the subsidence parameters projected for the South of Divide mining area are <br />conect. Based on annual observations of subsidence effects in the Apache Rocks Mining Area, <br />• the pazameter values maybe less than those predicted in Table 1. <br />Based on nine yeazs of annual subsidence observations in areas of the West Elk mining area <br />(Jumbo Mountain, Apache Rocks, and Box Canyon), predictions can be accurately made on <br />subsidence and seismic effects on 1) Minnesota Reservoir, 2) the alluvium in the Dry Fork <br />drainage, 3) landslides, and 4) rockfalls. However, it is recommended that subsidence <br />measurements be made in Dry Fork above the western part of longwall panels E2 and E3, in <br />order to compaze predicted results (Table 1) with field measurements. Specific conclusions aze <br />as follows: <br />1. Mining of the nine planned longwall mining panels in the South of Divide Mining area <br />will not impact Minnesota Reservoir The reservoir is completely out of the azea of <br />mining influence. All mine workings, including longwall panels E2, E3, and E9 aze 500 <br />to 600 feet farther away from the reservoir footprint, using even using the most <br />conservative 4S-degree angle of draw. <br /> <br />831-032.621 Wright Water Engineers, Inc. Page 47 <br />November 2064 <br />