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<br /> <br />The general plan for development entries consists of a <br />maximum of seven 18 ft, wide entries driven on 100 ft. <br />centers, leaving a pillar which has an average size of <br />approximately 82 feet on each side. Obviously, during this <br />phase of mining, considerably less than 50~ of the coal will <br />be removed. (The actual extraction ratio for First North <br />and Third North was 330. The safety factor for these <br />pillars will be significantly greater than 1.9) As mining <br />continues in the Purgatorie River alluvial valley, a maximum <br />of 50`•k of the coal will be extracted. Variances in pillar <br />size will be dependent on the configuration of the <br />development entries, rooms, and geologic factors associated <br />with the Maxwell Seam. <br />The probable hydrologic consequences of subsidence are <br />discussed in Section 2.04.7 of the permit. No significant <br />deep aquifers are found above the Maxwell seam. The <br />alluvial aquifer was evaluated in the AVF study of <br />Santistevan canyon. It was determined to not be of <br />significance in this area. <br />No known beneficial aquifers exist within the area. However, <br />Monitoring wells will be established adjacent to the <br />Northwest Longwall panels to document the potential affects <br />of subsidence on the hydrologic regime. Monitoring wells <br />will be completed within each water bearing zone. These <br />wells will be established during 1994 and prior to longwall <br />mining in the Northwest #3 Longwall panel. <br />2.05-53 <br />(Revised 1-17-94) <br />