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The general plan of the main development entries consists of <br />seven 18 ft wide entries which are driven in 100 ft centers, <br />leaving a pillar which has an average size of approximately 82 ft <br />on each side. During this phase of mining, considerably less than <br />50$ of the coal will be removed. As mining continues in this <br />renewable resource area, a maximum of 50~ of the coal may be <br />extracted. Variances in pillar size will be dependent on the <br />configuration of the development entries, rooms, and geologic <br />factors associated with the Maxwell Seam. <br />Surface subsidence over room and pillar areas having less than <br />50$ overall extraction should be minimal to negligible for the <br />following reasons: <br />1. Sufficient pillar capability to resist overburden loading <br />with a safety factor greater than 1.9. <br />2. Reconsolidation of overfurden and creation of an arch <br />• should occur well below the surface should the <br />pillars fail. <br />3. Most development openings beneath the renewable resource <br />area will be long-life mains and submains, <br />requiring large protection barrier pillars <br />during the term of this permit. <br />4. Prior experience at the New Elk Mine (previously Allen <br />Mine) has indicated that extraction less than <br />50~ results in negligible surface impacts. <br />WFC's monitoring program consists of eight equally-spaced, <br />permanent monuments located on the surface and in a line <br />perpendicular to the Third North entries as shown on the Mine Plan <br />Map (Map 3) . WFC first surveyed these monuments in March 1988 <br />prior to mining, and will re-servey them and on a quarterly basis <br />to determine the amount of subsidence which occurs with the mining <br />of the Third North entries. Surveying will be completed by <br />• standard transit and level survey methods common to the industry. <br />As the monitoring program continues, the relationship of any <br />