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III IIIIIIIIIIIIIIII ~~~~ <br />698 <br />blue <br />cb~bon <br />company <br />October 7, 1986 <br />Thomas A. Schreiner <br />Reclamation Specialist <br />Colorado Mined Land Reclamation <br />1313 Sherman Street, Room 423 <br />Denver, Colorado 80203-2273 <br />RE: Quarterly Bench Stability Monitoring, File #C-U4l-81 <br />Dear Tom: <br />blue ribbon coal company <br />p.o. box 1352 <br />palisade, Colorado 81526 <br />(303) 464-7951 <br /> <br />aCT D 996 <br />n, ~; n- <br />c11 .131'3.' .... ~f~,.,/•1 ::.t1.'/ .: <br />~.. <br />In accordance with your request in a letter dated September 3, 1986, the <br />bench stability monuments have been resurveyed. <br />As noted verbally during your September inspection, the auto-level being <br />used since December 23, 1985, was found to be in error. As a result of instrument <br />error, all survey results using this instrument are suspect of being in error. <br />The survey taken October 3, 1986, was done using vertical angles from the <br />subsidance monument used prior to December, 1985. As shown in the following <br />table, these results are more typical of what is expected of the points. <br /> 11/22/85 10/3/86 Change <br />S-1 6,400.90 6,400.80 -0.10 <br />S-2 6,396.06 6,395.95 -0.11 <br />S-3 6,385.77 6,385.62 -0.15 <br />S-4 6,383.30 ** <br />S-5 6,479.92 6,479.61 -0.31 <br />S-6 6,480.51 6,480.32 -0.19 <br />S-7 6,479.31 6,479.08 -0.23 <br />S-8 6,479.92 6,479.58 -0.34 <br />** Not surveyed because line of site was lost in the completion of <br />the bench cover project during the summer of 1986. <br />Monitoring will continue to be done with vertical angles. If there are any <br />further questions let me know. <br />Sincerel , <br />6~~~>~ ~ ~k~~ <br />Larry 1+~. Reschke <br />Project Engineer <br /> <br />LMR/clt <br />