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<br />~~ <br />We do not anticipate any disturbance of existing structures <br />or other renewable resource lands under the crrently <br />Proposed Mine Plan. <br />Subsidence Monitoring <br />Subsidence monitoring stations have been established to <br />determine the effects of mining on renewable resource areas <br />and to evaluate the effects of controlled subsidence <br />resulting from longwall mining. Additional stations will be <br />established over the Northwest #2 longwall panel to better <br />define the angle of draw. The locations of existing and <br />proposed monitoring stations are shown on Map 17, Subsidence <br />Monitoring Stations. <br />Monitoring points will be established over renewable <br />resource areas, e. g. the Purgatorie River, Wet Canyon <br />alluvial valley floor, and other structures as shown on Map <br />16. These stations will be installed and surveyed at least <br />three months prior to mining. These stations will be <br />surveyed quarterly after mining. If no change in survey <br />coordinates (+/-0.25 ft. survey error) is detected after <br />four successive surveys, then these stations will be <br />surveyed annually. After five years with no change in <br />survey coordinates (+/-0.25 ft.) these surveys may be <br />discontinued with Division approval. <br />Monitoring points were established perpendicular to the <br />Third North panel prior to the panel advancing under the <br />Trinidad (formerly Colorado and Wyoming) Railroad trackage <br />and the Purgatorie River. These stations were established <br />in March 1988, and have been surveyed quarterly since mining <br />occurred under the area. They have shown no discernable <br />movement. <br />Subsidence resulting from Longwall Mining is considered a <br />form of controlled subsidence. Basin Resources established <br />monitoring stations on the first longwall panel north of the <br />Purgatorie River to help evaluated the effects of controlled <br />subsidence. Control points were established both parallel <br />and perpendicular to the panel. These points were located <br />such that at least one of the stations would be expected to <br />lie outside the anticipated maximum angle of draw typically <br />encountered at mines in the Western United States. These <br />points were surveyed prior to mining and weekly while <br />mining was proceeding under these stations. <br />2.05-50 <br />(Revised 03/02/90) <br />(Revised 1/17/94) <br />~~ ~~,~ <br />