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III IIIIIIIIIIIII III <br />DEPARTMENT OF NATURAL RESOURCES <br />David H. Getches, E.ecutive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON, Director <br />Richard D. Lamm <br />Governor <br />DATE: December 7, 1984 <br />T0: Bob Liddle <br />FROM: Jim Pendleton ~ ~~~ <br />RE: Dorchester Co Comp 's Semi-Annual Subsidence Monitoring Report - <br />Dorchester N tne, Fremont County <br />Pursuant to your request, I have reviewed the November, 1984, Semi-Annual <br />Subsidence Monitoring Report submitted by Dorchester Coal Company for its <br />Dorchester No. 1 Underground Coal Kline (Permit C-014-81). This report was <br />prepared in accordance with the permits' requirements. To date, the <br />high-resolution subsidence grid installed above panel Two South has detected a <br />maximum vertical subsidence movement of 0.9 feet. Rocky Mountain <br />Geotechnical, consultant to the operator, had projected a maximum vertical <br />subsidence movement of 1.46 feet for this location. Further, the results <br />demonstrate an angle of draw between 17 and 22 degrees, versus the predicted <br />angle of draw 20 to 25 degrees. Results to date appear to verify the original <br />projections. Further monitoring should determine when cessation of subsidence <br />response occurs. <br />Observations of subsidence adjoining the Florence City Water Line have not <br />been conclusive, due to either error in surveying the benchmarks or subsidence <br />of the existing benchmarks. The operator indicates that the problem will be <br />resolved. We should notify the operator that we expect this problem to be <br />resolved as soon as possible, in order to allow the next semi-annual <br />subsidence monitoring report to determine the magnitude and character of <br />subsidence effecting the Florence Waterline. <br />ph/ <br />cc: Mike Long <br />Doc. No. 5871E <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel: (303) 866-3567 <br />