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^.r. James ?endieton <br />`liay 5, 198 <br />Pace 4 <br />• <br />5. A thorough technical discussion of tine hypo- <br />thetical fracturing mechanism forwarded by ARCO <br />to explain the observed fracturing; <br />Initially, the fractures were thought to be the <br />result of differential compaction along channel <br />margins. The detailed documentation of frequency <br />orientation, and character of the fractures has <br />neither supported nor refuted this origin. The <br />most appropriate terms which describe the <br />fractures would be to call them extensions or <br />strike joints. It must be noted that their <br />orientation does not correspond to surface joints <br />in the five year permit area, and every occurrence <br />exhibits evidence that they existed before the <br />development of the mine. As a result, it seems <br />reasonable to assume the fractures are the result <br />of geologic activity which preceeded the develop- <br />ment of the surface jointing in the five year <br />permit area. <br />• <br />6. A thorough discussion of the hypothesized fractur- <br />ing mechanism for the stability of the underground <br />operations approved within the five year permit <br />plan: <br />We have experienced problems with the instal- <br />lation of some roof bolts due to the geometry <br />of the fractured areas; however, they have not <br />posed any problems after the face has advanced <br />beyond the narrow affected zones. <br />The fractured zones have been confined to areas <br />of sandstone roof. Enclosure No. 3 is a map <br />showing areas where the immediate roof is likely <br />to consist of sandstone. If we assume that the <br />fractures will continue to occur only in areas <br />of sandstone immediate roof, it is obvious that <br />the overall impact on the five year permit .area <br />is likely to be insignificant. <br />In conclusion, after conducting an extensive in-mine <br />and surface geologic review of the fractures in the Mt. <br />Gunnison No. 1 Mine, we concur with the finding of the <br />partial geotechnical inspection of August 31, 1982. <br />That is ... the observed fracturing does not constitute <br />a hazard for the stability of the mine workings, permit <br />area, or adjacent areas. <br />• <br />