_GENERAL DOCUMENTS - C1981017 (219)

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- 10 - In a report dated October 25, 1988, Dr. Bruce Collins of Mid-Continent Resources reported that two ground cracks were discovered on Huntsman Ridge while performing the subsidence resurvey required by revision stipulation (3 ). The larger of these two cracks "extends almost without interruption for approximately 3,500 feet in length , along or closely on either side of the ridge line to the saddle between the south fork of Coal Creek and South Twin Creek". Dr. Collins presents the opinion that these cracks are the result of reactivation of an ancient slip-plane related block landslide movement. He believes that this mass movement is the result of natural processes, "primarily the greater-than-normial precipitation experienced in the period from 1981 through 1986", and that it is "related to mining only indirectly if at all ". (Excerpts from Dr. Collins October 25, 1988 letter. ) European and North American observations have documented that it is not uncommon for ground subsidence to contribute to the reactivation of landslide movement, which was one of the the reasons the Division imposed Stipulation (1 ) upon approval of the 1986 revision. The purpose of subsidence monitoring programs is to verify subsidence projections included in the permit application, in order to perfect projections so that material damage can be avoided. In the event that Mid-Continent Resources proposed an expansion of the permit area, the ability to accurately project areas of potential subsidence occurrence could be important, if structures or renewable resources were to exist within the potentially affected area. Dr. Collins requests, in his October 25 , 1988 report, that "resumption of the monitoring program be limited to annual visual inspection and reporting". He observes that no structures or renewable resource lands are in jeopardy from the ridge-line landslide. Because all of the potentially affected area lies within the existing Permit boundary and no structures or renewable resource lands are in jeopardy, the Division believes that a subsidence monitoring program limited to annual visual inspection of the potentially affected area and submission of an annual report is adequate. Mid-Continent has revised the subsidence section of the permit application to reflect the new data. In summary, the operator has now committed to conducting an annual visual inspection and reporting of any cracks, cratering, or landsliding above the mine area and also to reinstitution of the subsidence survey prior to double-pass long wall extraction. These committments are detailed on pages 36 and 37 of Chapter IV in the permit application. XXIII. Special Categories of Mining - Rules 4.27 and 4.27 This section remains valid for the existing operation. XXIV . Miscellaneous Compliance - Rules 2.05.6(5 ) , 4.02 , 4.12 , 4.19, 4.21 , 4.28 and 4.30 This section remains valid for the existing operation.