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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 />