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Chapter IV <br />b. Monitoring Net and Results. <br />The monitoring net was initiated in 1981 with the installation of control points TP -1 <br />through TP -5 and monitoring points MC -1 through MC -9. Control point TP -6 and <br />monitoring points MC -10 through MC -16 were installed during the fall of 1984. The <br />locations of these points are indicated on the map labeled IV -F -1 in a map jacket at the <br />rear of this report. A number of other points were installed over longwall panel 301, <br />L.S. Wood No. 3 Mine, in conjunction with the U.S. Department of Energy in 1982. <br />When the multi -lift demonstration project was moved to longwall panel 102, Dutch <br />Creek No. 1 mine, these points were removed, and as a result they are not included in <br />this discussion. <br />The subsidence monitoring program was initiated by MCR in 1981. Subsequent <br />surveys were carried out in 1982, 1983, 1984 and 1985 in accordance with a plan <br />agreed upon between Mid - Continent and MLRD. The results of this program are <br />covered in detail, starting on page 10 of Dr. Collins' study found in Appendix IV -F -4. <br />Mid - Continent contends that sufficient data have been collected to characterize <br />subsidence and subsidence - related phenomena in the Coal Basin area, i.e. that the <br />subsidence ratio of measured disturbance to coal thickness removed is approximatley <br />0.30, substantially less than the ratio of 0.55 as predicted in the initial permit; that the <br />angle of draw averages approximately 18 degrees as opposed to the CMLRD stipulated <br />value of 20.5 degrees; and that there are no visually observable effects of subsidence, <br />such as surface cracks, hummocked profiles (subsidence pits), or subsidence- induced <br />slumps or landslides. <br />There has been no observable damage to structures or other man -made facilities such <br />as roads or power lines over mined -out areas, in spite of nearly 30 years of mining <br />activites, including years of longwall mining, which results in essentially total extraction <br />of the full thickness of the coal bed involved over wide areas, or to renewable resource <br />lands or aquifer recharge areas. There are no significant variations in the general <br />geology of the area that would indicate that subsidence or subsidence - related <br />phenomena will differ in the future from what has been accumulated to date, that any <br />damage due to subsidence or subsidence - related phenomena will occur to structures, <br />renewable resource lands or aquifer recharge areas in the future. <br />c. Monitoring Schedule. <br />Because of the rugged terrain above the Coal Basin mines, deep snow pack, and the <br />extremely harsh winter weather, surveying of the subsidence monitoring net can only <br />be accomplished during the summer months from June through September. <br />In line with a plan approved by MLRD the monitoring points were surveyed in June and <br />September during the years 1981 through 1985. This was accomplished utilizing <br />helicopters, which proved to be very costly. <br />35 <br />