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• • iii-iiiiiiiiiiiu iii <br />STATE OF COLORADO <br />Roy Romer, Govei <br />DEPARTMENT OF NATURAL RESOURCES <br />MINED LAND RECLAMATION DIVISION <br />FRED R. BANTA, Director <br />DATE: July 19, 1988 <br />T0: Cathy Begej <br />FROM: Jim Pendleton <br />RE: Colorado Westmoreland Inc.'s "1987 Annual Iydrology & Subsidence Report" <br />I have completed a review of the 1987 hydrology and subsidence monitoring <br />report for the Orchard Valley mine. Very briefly, the report concludes that <br />no hydrologic impact has resulted from mining at the Orchard Valley main and <br />west mines. The monitoring results appear to support this conclusion. <br />However, you should rely on your own expertise for the hydrologic evaluation. <br />The subsidence monitoring determined that some minimal additional subsidence <br />continued to occur over the 5 North, 11 North and 12 North panels of the old <br />Orchard Valley main workings. It appears to be more sporadic and less in <br />magnitude, as would be expected with time. CWI mentions states that they <br />believe that subsidence has practically reached its conclusion above 11 and 12 <br />North panels. Using the observed subsidence above these panels they calculate <br />an angle of draw of 16 degrees, which is smaller than the assumed angle used <br />in projecting areas of potential subsidence impact. Once subsidence has been <br />demonstrated to have ceased, CWI could propose to amend their projected areas <br />of potential impact. Candidly, I doubt that the implications are significant <br />to warrant the amendment effort. No subsidence has been detected above the <br />development workings of the west mine, <br />The subsidence monitoring aspects of the report are clear, concise and <br />supported by the accompanying data, I recommend that you accept the <br />subsidence portions of the report, as submitted, <br />cc: Susan Mowry <br />215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567 <br />