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I' i <br />/C <br />Grand Mesa <br />Coal Company <br />October 23, 1986 <br />John T. Doerfer <br />Reclamation Specialist <br />Colorado Mined Land Reclamation <br />1313 Sherman Street, Room 423 <br />Denver, Colorado 80203-2273 <br />Re: Subsidence Monitoring, File C-034-81 <br />Dear John: <br /> <br />P. O. Box 1351 <br />Palisade, CO 81526 <br />(303) 464-7951 <br />The attached table is the result of a subsidence survey done September 19 <br />and 22, 1986 on the subsidence points within the projected area of influence <br />of subsidence as shown on Map 2.05.6(6)(f)(ii)(c)-1 in our permit application. <br />The original elevations were measured for baseline information in early 1982. <br />The "elevation change" is equal too the current elevation minus the original <br />elevation. The "relative elevation change" is equal too the "elevation change" <br />of the point minus the "elevation change" of the backsite. The backsite <br />is listed for each point. <br />As in the past, sub-points were monitored using vertical angle measurements <br />and houses were monitored using stadia. Sub-points 0 and Q show the greatest <br />relative change. Both points are outside the projected area of influence <br />of subsidence and have exhibited similar variation in the past. <br />As noted in our June 17, 1986 monitoring report and in compliance with our <br />October 17, 1986 mid term technical revision request, we intend to discontinue <br />monitoring of these points until subsidence is indicated visually. <br />The photos for the photo record of all structures monitored were taken in <br />correlation with the survey. The photo record will be kept at our Palisade <br />office. <br />If there are any further questions, let me know. <br />Sincerely, <br />,Larry Reeschke S Qj~ <br />Protect Engineer <br />LMR/c)t <br />attachments <br />cc: J. E. Stover <br />