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M <br />iii i iui <br />blue <br />ribbon blue ribbon coal company <br />coal <br />company <br />P. O. Box 1352 <br />{I~~~~ v ~® (303) 464-78 1 81526 <br />January 13, 1986 JAN 15 <br />f~ii~fED LAND Ri:CLAMAT9aiV <br />Susan Mowry 0610. DUpt. 0} ~3!i!?~1 Resruress <br />Reclamation Specialist <br />Colorado Mined Land Reclamation <br />1313 Sherman Street, Room 423 <br />Denver, CO 80203-2273 <br />Re: Quarterly bench stability monitoring, File # C-047-81 <br />Dear Susan: <br />The following is the initial monitoring information and the monitoring results <br />for the last quarter of 1985, on the stability monuments placed in the restabil- <br />ized mine ben ch: <br /> 7/1/85* 10/16/85* 11/22/85* 12/23/85** <br />S-1 6401.38 6401.26 6400.90 6400.46 <br />S-2 6396.23 6396.13 6396.06 6395.55 <br />S-3 6385.83 6385.76 6385.77 6385.45 <br />S-4 6483.45 6383.33 6383.30 6363.03 <br />S-5 Installed 11 /7/85 6479.92 6479.73 <br />S-6 6480.51 6480.07 <br />S-7 6479.31 6479.80 <br />S-8 6479.92 6479.92 <br />"These elevations were taken using stadia and a vertical angle. Part of <br />the elevation difference on the first 4 may have to do with their displace- <br />ment during the backfilling with cover material. <br />**These elevations were taken using level loops. S-1 thru -4 were <br />calculated relative to the U. S. Steel subsidance monument used for the <br />previous stadia measurements. S-5 thru -8 were calculated relative to <br />the elevation of S-8 which hit solid rock, presumably bedrock. <br />The majority of the difference seen between 11/22 and 12/23/85 can be <br />attributed to the stadia used to calculate the vertical and horizontal distances. <br />Level loops will continue to be used for monitoring these points. The elevation <br />of S-5 thru -8 will now be taken relative to a point marked on a concrete pad <br />near the fan portal. <br />