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' Schmi~Surveys ~ <br />National R3ng.Coa1 <br />1016 1/2 Pain Ave. <br />Durango, CO 81302 <br />RE. Subsidence monitoring on surface property above the <br />pillared portion of the underground mine <br />lis. Helmin; <br />During the winter and spring we have established 9 <br />additional points. Two points were placed !n the NE 1/4 of <br />section 32. One (the moat northerly) was placed over the <br />pillared-out, abandoned section. These points were placed so <br />we could more closely observe ground movement along the <br />Huntington Ditch. As o! flay, 1991 there has been no movement <br />in ttrls area'. - <br />In Nov 1990 I established two points (ci do c2) in the NE 1/4 , <br />SE 1/4 section 31 and In Apr11 1991 I established ilve (c3, <br />c4, c6, c9, & c7) more points in this area. Points ci, c4, ' <br />and c6 are located over portions of the mine that have NOT <br />been pillared, points c2, c3, c6, & c7 are over pillared <br />sections. '. <br />There is a large subsidence crack (approx. 1000 feet °long),. <br />running northeasterly through the NE 1/4 SE 1/4. Pointa'c2, . <br />and c3 are located on the north side of the crack and have <br />moved downward 0.08 Lt. more or less. Point c2 has not moved <br />laterally however point c3 has moved northerly 0:04,ft. more <br />or less. - <br />Two additional polnta <c9 and c7) have been established • <br />however a comparison check has not been made. <br />We now have a total of 16 polnta which are being monitored 4 <br />times a year: <br />..,uuuu,~.._ ~. <br />P.O. Box 2017 • Durango, Colorado 81302 • (303) 259-3248 <br /> <br />