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III 1111111-~~i~~~i~ <br />sss <br />STATE OF COLORADO <br />P. C. <br />r~ <br />LJ <br />Roy Romer, Governor <br />DEPARTMENT OF NATURAL RESOURCES <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SNELTON, Dlreetor <br />MEMORANDUM <br />1987 <br />C~ <br />r1 <br />lJ <br />T0: Jeff Deckler ~\ ./ <br />FROM: Jim Pendleton 1. <br />RE: 1986 Annual R - lowyo Coal Company (Permit C-81-019) <br />I have reviewed the 1986 annual report submitted by Colowyo Coal Company for <br />the Colowyo Mine. I specifically concentrated on the survey monitoring of the <br />Streeter Fill and the overburden swell analysis contained within the annual <br />report. <br />The survey monitoring of the fill monuments shows continued consolidation of <br />the fill. As in the past years' observations, the fill continues to settle. <br />This consolidation has resulted in vertical lowering and migration of all <br />monuments towards the west, into the body of the fill. This is consistent <br />with past observations and with normal expectations. Visual monitoring of the <br />extension cracks on the facial terraces confirmed that no additional cracking <br />has occurred and that the existing cracks are stable. <br />The overburden swell analysis determined that the overburden swell has <br />increased slightly from 16.9% in 1985 to 18.5% in 1986. This increase is the <br />result of an increase in the proportion of the fill excavated by dragline from <br />43% in 1985 to 44% in 1986. <br />In my opinion, the geotechnical aspects of the 1986 annual report are <br />acceptable as submitted. The report demonstrates the continued stability of <br />the Streeter fill and the accuracy of the projected overburden swell factor. <br />The operator expresses a desire to decrease the frequency of their overburden <br />swell verifications to twice during the 5-year permit period, as a portion of <br />their 1988 and 1991 annual reports. I recommend approval of this request. <br />cc: Mike Long <br />~' <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567 <br />