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<br />RECEIVED <br />PIINING UNDER CURTIS CREEK <br />ti~AY 2 7 1981 <br />Subsidence Monitor <br />AIINTD LAND RECLAL1ATi0!+ ~ COAL <br />COLO. DEPT. OF Nh1UflAl R:SG::xCES <br />Differences in the surveyed elevations of subsidence points have occurred <br />between January 16, 1981 and May 1, 1981. The largest resultant elevation <br />change t9 date was a lowering of monument 1115 by 0.31 feet (3.7 inches). <br />The average elevation change over the same time period was 0.1.2 feet or <br />1.4 inches. Maximum horizontal movement surveyed between Janccary 16, 1981 <br />and April 2, 1981 was 0.29 feet (3.5 inches) at monument 1118. The average <br />horizontal change over the same time period was 0.23 feet (2.8 inches). <br />The area of monitoring did show slight movement. However, as documented <br />on the monitoring reports and mine maps, the four entries beiTTg driven <br />(advance mining only) were 220 feet (horizontal) distant from the <br />monitoring stations at the time the movement was initially recorded. <br />This distance would place the monuments outside of the area of expected <br />influence. The movement reported in the enclosed data set is, therefore, <br />probably attributable to frost heave. <br />