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The following table presents some subsidence measurements from the Bowie No. 2 <br />Mine. The location of the subsidence monitoring stations are shown on Map 27 and Map <br />27 -B. The basis for the calculation are a D -Seam thickness of 9.5 feet and a B -Seam <br />thickness of 11.0 feet. The virgin ground correct factor is applied to the D -Seam thickness <br />as well as the correction factor shown in the table. The subsidence monitoring stations <br />were selected where they were near the center of the D -Seam panels. Most of the <br />monitoring stations do not coincide with the center of the B -Seam panels so the actual <br />subsidence measured is much less than the predicted subsidence. <br />Subsidence timing graphs are presented at the end of this section for each of the <br />subsidence monitoring stations shown in the following table. The graphs show the ground <br />surface elevation each time the monitoring station was surveyed. The initial subsidence <br />occurs fairly soon after a longwall passes under a subsidence monitoring station. A <br />precise determination of the initial subsidence cannot be determined because of the <br />infrequent surveys. However, the data clearly shows initial subsidence occurs within a few <br />months. As an example, the D -Seam mined under subsidence monitoring station 2 -A in <br />March 2000. The November 2000 subsidence survey of station 2 -A detected 5.75 feet of <br />subsidence. The graphs show there is little residual subsidence after the initial <br />subsidence. <br />PR -14 - 7 - 03/14 <br />