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DEPARTMENT OF NATURAL RESOURCES <br />David H. Getches, Executive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON, Director <br />Richard D. Lamm <br />Governor <br />MEMORANDUM <br />~8 August 1986 <br />T0: Tom Schreiner ~\) <br />FROM: Jim Pendleton ~" ~c`~ <br />RE: Second Quarter - Portal Bench Stability Monitoring Report - <br />bon Mine (Permit No: C-81-047) <br />I have reveiwed the report of the second quarter, 1986, portal bench stability <br />monitoring results submitted by Lary M. Reschke, P.E., of Blue Ribbon Coal <br />Company. For the past several years the monitoring reports have demonstrated <br />normal consolidation, with the settlement rate decreasing over time. This <br />report documents movement at five of the eight monuments. However, for the <br />first time, four of these stations appear to have undergone a rise of between <br />.02 feet and .09 feet in elevation. Two monuments which exhibit .09 feet of <br />rise are installed along the crest of the fill. Therefore, I doubt that these <br />monuments are exhibiting rise due to a rotational bench movement. The summer <br />season eliminates the possibility of a freeze/thaw problem. I suspect that an <br />• error entered the surveying due to an inaccuracy in setting up on the control <br />point, to some movement of the control point, or to the establishment of a new <br />control network, necessitated by the reclamation activities at the Blue Ribbon <br />mine. <br />Please direct the operator to investigate and remedy the apparent survey <br />inaccuracy. <br />cc: Bob Liddle <br /> <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />