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Only five structures exist in the area to be affected by the New <br />Elk Mine. Gentle trough subsidence of 3 to 4 inches will not disrupt or <br />materially damage these structures. Disruptions of aquifers and the <br />essential functions of the alluvial valley floor are not expected because <br />the area to be affected during the permit term is nearly all outside of the <br />renewable resource area. <br />As previously mentioned, no subsidence features were observed in <br />the Refuse Disposal Area. According to available mine maps and discussions <br />with long time mine personnel, this area was undermined as part of the <br />Allen Mine in the early 1960's by room and pillar mining methods and <br />recovery was less than 508. The refuse disposal area will be located over <br />the far northeast part of the mined out area which has been only partially <br />undermined. The refuse disposal area will be located 320 to 900 feet over <br />the old workings. <br />A comprehensive study of subsidence related to longwall mining was <br />~- initiated in the Allen Mine in 1981. The final report for this study is <br />dated September 19, 1982. This study obtained subsidence data (vertical and <br />horizontal) over longwall and roan and pillar mining areas. Data indicate <br />that subsidence in this area typically occurs as vertical displacement of <br />the total overburden unit (i.e., very little differential settlement) with <br />dampened horizontal status. Partial subsidence data indicate maximum <br />vertical displacement of about 3 feet over a 6 foot high longwall panel and <br />maximum horizontal displacement of less than 1 foot. This displacement <br />occurred within 6 months of undermining the movement by longwall. <br />Subsidence under roam and pillar areas was considerable less (maximum <br />vertical .3 and 1.4 feet) with most displacement occurring within 3 mont!is. <br />Based on the data, it can be inferred that subsidence over the New <br />Elk Mine occurs quickly and in mass, with very little visible surface <br />expression. Therefore, it is reasonable to conclude that any subsidence <br />that may have resulted from post undermining (more than 20 years ago) has <br />C <br />2.05-93 <br />