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-87- <br />XXII. Subsidence - Rules 2.05.6(6) and 4.20 <br />Mining within the Bear No. 1 and No. 2 mines will be curtailed no Later than the early <br />summer of 1982. Therefore, the approval of a subsidence control plan is considered <br />unnecessary at this stage in time, because little additional disturbance is projected <br />to occur outside the areas which have already been previously undermined by the Bear <br />Coal Company. In the case of proposed mining within the Bear No. 3 mine, the applicant <br />must conform with the requirements of the permanent program regulations regarding <br />subsidence control. No structures overlie the underground workings of the Bear No. 3 <br />mine. In addition, potentially affected renewable resource lands are limited to <br />the aquifers of the Barren Member of the Mesa Verde and the coal seams overlying the <br />seam to be extracted within the Bear No. 3 mine. However, the limited area of these <br />potentially affected aquifers which occur within the permit area, and the fact that <br />potential effects to these aquifers are limited to the down-dip, near-ourcrop portions <br />of those aquifers and coal seams, will extremely Limit the possible hydrologic effects <br />of subsidence upon this aquifer and the coal seams. Therefore, the proposed mining <br />within the Bear No. 3 mine is considered, by the Division, to represent no potential <br />threat to either structures or renewable resource lands. <br />However, mapping of the Somerset quadrangle, performed by Rahe Junge of the Colorado <br />Geological Survey, has determined that the majority of the surface area above the <br />Bear No. 3 mine permit area is veneered by ancient and modern landslide deposits. <br />In addition, a geotechnical investigation performed by Rocky Mountain Geotechnical, <br />Inc., for Bear Coal Company has confirmed the existence of ancient and modern landslide <br />deposits adjoining the areas of the proposed portalaccess road and portal facilities <br />for the Bear No. 3 mine. The stability of these ancient and modern landslide deposits <br />could be affected by differential surface subsidence, if it were to occur, above the <br />Bear No. 3 mine workings. Although the Bear Coal Company projects no surface indications <br />of subsidence will occur within these areas, the Division considers the following <br />stipulation necessary to find compliance with the subsidence requirements of the <br />permanent program regulations. <br />STIPULATION NO. 15: <br />THE DIVISION DIRECTS BEAR COAL COMPANY TO SUBMIT A SUBSIDENCE MONITORING PROGRAM <br />FOR REVIEW AND APPROVAL BY THE DIVISION. THIS PROGRAM SHALL INCLUDE THE <br />INSTALLATION OF APPROPRIATE PROFILE LINES OF PERMANENT MONUMENTS, CAPABLE OF <br />RESISTING NORMAL TRAFFIC AND METEOROLOGICAL PHENOMENA. MONUMENTS SHALL BE <br />LOCATED TO MONITOR POSSIBLE SUBSIDENCE OF RRERS DESIGNATED FOR THE INITIATION <br />OF RETREAT OR SECONDARY EXTRACTION. THESE PLANS SHALL INCLUDE R TYPICAL <br />MONUMENT DETAIL DRAWING. THIS SUBSIDENCE MONITORING PROGRAM SHALL BE SUBMITTED, <br />FOR REVIEW BY THE DIVISION, WITHIN 30 DAYS FOLLOWING PERMIT APPROVAL. <br />FURTHER, TXE APPROVED SUBSIDENCE MONITORING MONUMENTS SHALL BE INSTALLED RND <br />INITIALLY MONITORED PRIOR TO THE COMMENCEMENT OF RETREAT OR SECONDARY EXTRACTION <br />WITHIN THE BEAR NO. 3 MINE. FOLLOWING THE INITIAL MONITORING, THE SUBSIDENCE <br />MONUMENTS SHALL BE MONITORED ON R SEMI-ANNUAL BASIS, AND THE RESULTS OF THAT <br />MONITORING SHALL BE SUBMITTED TO THE DIVISION WITHIN 30 DAYS FOLLOWING COMPLETION <br />OF EACH MONITORING SURVEY. <br />