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~~ <br />EVALUATION OF STABILITY MONITORING <br />ORCHARD VALLEY MINE CUTS AND FILLS <br />FOR COLORADO WESTMORELAND INC. <br />1.0 INTRODUCTION <br /> <br /> <br />During the later part of 1982 and early 1983, Geo-Hydro <br />Consulting, Inc. (Geo-Hydro) was contracted by Colorado <br />Westmoreland Inc. (CWI) to perform certain geotechnical studies <br />related to surface facilities of the Orchard Valley coal mine <br />at Paonia, Colorado. These studies included stability analyses <br />of important cuts and fills that were constructed at the mine <br />site. The results of .these analyses (see "Report, Phase II <br />Geotechnical Studies, Orchard Valley Coal Mine, Paonia, <br />Colorado, for Colorado Westmoreland Inc.") indicated that the <br />factors of safety of important fills may be lower than 1.3. A <br />factor of safety 1.3 is required by Regulations of the Colorado <br />Mined Land Reclamation Board (4.14.2 (1) (b)). Monitoring of im- <br />portant fills and cuts was recommended. <br />CWI instructed Geo-Hydro to install five inclinometers and <br />piezometers at selected locations and to perform long-term <br />monitoring of the fills' and cuts' behavior. Five inclinometers <br />and five vibrating-wire piezometers were installed in October, <br />1982 and a systematic monitoring program was initiated. For a <br />period of one year, reading of the installed instruments was <br />performed on a monthly basis; at present (winter 1983 - 64), <br />readings are taken at three-month intervals: ' <br />In 1983, CWI contracted Geo-Hydro to prepare a detailed <br />reclamation plan of surface facilities of the Orchard Valley <br />mine with an emphasis on cuts and fills. A set of design <br />drawings titled "Orchard Valley Mine, Paonia, Colorado, Surface <br />Facilities Reclamation Plan" was prepared for CWI; CWI later <br />presented the reclamation plan for the approval of the Mined <br />Land Reclamation Division. <br />As the results of more than a year of monitoring are <br />available at present, MLRD requires an evaluation of the <br />results and the evaluation of impacts on the reclamation plans. <br />Such evaluations are presented in this report. <br />Five inclinometers and five piezometers were installed at <br />the mine to monitor the stability of cuts and fills. Two are <br />located in the Crushing and Screening Level Fill, and one each <br />in the Warehouse Level Fill, the Fan Level Fill, and the <br />Diversion Ditch Cut. These locations correspond to the <br />following Reclamation Zones defined on Sheet 3 of the <br />Reclamation Plan: <br />eeo~roQO cor~.w~nN6, u+e. <br />Y <br />