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• 2.05.6 <br />(b)(iii) Probable Hydrologic Consequences <br />The underground mining operation could impact surface streams by vertical <br />settlement of the surface, local changes in the surface slope and subsidence <br />cracks. However, it is improbable the mining operation will have any effect <br />on the ephemeral drainages because most stream channels in the area are <br />very steep. Subsidence cracks would likely heal very quickly and settlement <br />of the surface would not reverse or significantly alter the grade in the steep <br />drainages. <br />The underground mining operation may impact the ground water in the <br />Mesaverde Formation. Potential fracturing of the formation and the local <br />increase of permeability above the extracted coal seam could drain all or a <br />portion of a perched water bearing zone. <br />• It is possible the indicated fault, shown on Map 9, could bisect the mine <br />workings and provide a means of communication with the Terror Creek <br />drainage. One drill hole, DH-48, penetrated the fault. The fault was <br />penetrated approximately 30-feet above the upper B-Seam. The water level <br />in DH-48 at the time it was logged was below the level of the fault which <br />would indicate the fault does not communicate any significant amount of <br />water. The impact to Terror Creek caused by mining through the fault trace <br />in the northwest portion of the mine, will be evaluated when more is known <br />of the characteristics of the fault, and before mining will be conducted in that <br />area. The First North Mains mined into the fault in late 1997 or early 1998. <br />The fault is characterized as a shear fault as opposed to a roll fault and little <br />or no gaff was encountered. The fault trace was virtually dry. <br />As stated above, the underground mining operation may impact the quantity <br />of water in the springs in the permit and adjacent areas. Potential fracturing <br />of the formation could intercept the source of water for a spring(s) and cause <br />the spring(s) to dry up. <br />The underground mining operation may impact the stockponds in the area. <br />• Potential fracturing of the formation could drain the ponds or intercept the <br />PR-06 2.05 - 71 - 08/0~ <br />fi PPRovEp <br />~~/ s~o z <br />