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1 . If any unanticipated surface disturbance (cracking, cratering or <br /> landsliding) manifests itself within the area potentially affected by <br /> subsidence (angle of draw equals 20.5°) , the operator will be required <br /> to immediately reinstitute the subsidence monitoring program. <br /> 2 . All existing monuments will be left in place and maintained . <br /> 3 . All existing monuments will be resurveyed at the conclusion of the <br /> current five year permit term, to determine whether additional <br /> subsidence manifests itself. <br /> 4. A subsidence monitoring program will be required above any double-pass <br /> long wall operations , in order to determine the ultimate subsidence <br /> factor above that relatively untested extraction technique. <br /> These conditions have all either been complied with or committed to by the <br /> operator in the permit renewal application. <br /> In a report dated October 25, 1988 , Dr. Bruce Collins of Mid-Continent <br /> Resources reported that two ground cracks were discovered on Huntsman Ridge <br /> while performing the subsidence resurvey required by Revision Stipulation 3. <br /> The larger of these two cracks "extends almost without interruption for <br /> approximately 3, 500 feet in length , along or closely on either side of the <br /> ridge line to the saddle between the south fork of Coal Creek and South Twin <br /> Creek. " Dr. Collins presents the opinion that these cracks are the result of <br /> reactivation of an ancient slip-plane related block landslide movement. He <br /> believes that this mass movement is the result of natural processes , <br /> "primarily the greater-than-normal precipitation experienced in the period <br /> from 1981 through 1986," and that it is "related to mining only indirectly if <br /> at all . " (Excerpts from Dr. Collins ' October 25 , 1988 letter. ) <br /> European and North American observations have documented that it is not <br /> uncommon fcr ground subsidence to contribute to the reactivation of landslide <br /> movement, which was one of the the reasons the Division imposed Stipulation 1 <br /> upon approval of the 1986 revision . The purpose of subsidence monitoring <br /> programs is to verify subsidence projections included in the permit <br /> application , in order to perfect projections so that material damage can be <br /> avoided. In the event that Mid-Continent Resources proposed an expansion of <br /> the permit area, the ability to accurately project areas of potential <br /> subsidence occurrence could be important, if structures or renewable resources <br /> were to exist within the potentially affected area. <br /> Dr. Collins requests in his October 25, 1988 report that "resumption of the <br /> monitoring program be limited to annual visual inspection and reporting. " He <br /> observes that no structures or renewable resource lands are in jeopardy from <br /> the ridge-line landslide. Because all of the potentially affected area lies <br /> within the existing Permit boundary and no structures or renewable resource <br /> lands are in jeopardy, the Division believes that a subsidence monitoring <br /> program limited to annual visual inspection of the potentially affected area <br /> and submission of in annual report is adequate . Mid-Continent has revised the <br /> subsidence section of the permit application to reflect the new data. <br /> In summary, the operator has now committed to conducting an annual visual <br /> inspection and reporting of any cracks , cratering, or lanosliding above the <br />