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Ms. Paige Beville -4- December 17, 1984 <br /> <br />2. According to the bond estimates ten acres of topsoil will need to be <br />redistributed. WECC should recognize that bond needs to be calculated for the <br />~h worst case distrubance situation and that actual on the ground disturbance <br />~ ~ ~~- cannot exceed this worst case scenario. The bond estimate is acceptable so <br />~"~ long as WECC is aware that we cannot allow more than 10 acres of disturbance <br />~~ ~~~~t any one time that will need to be retopsoiled. <br />3. The bond should include a regrading cost estimate to cover costs of <br />~;~ ~ shaping the waste. The reason is that in a worst case situation if the pile <br />~ ~~ is abandoned it will not be completed. Some hauling, regrading, shaping, and <br />j~""` compacting of the pile will be needed. The amount of bond submitted should be <br />~~ c ~.a. based on the worst case situation expected, keeping in mind that this scenario <br />~w.l~ cannot be exceeded on the ground. <br />4. From the discussion in the application it is not clear on what is the <br />timing and maximum extent of stirpping, placing waste, and retopsoiling. The <br />p"Ian should show estimated extent of disturbance (subdivided into stripped, <br />~d waste, and retopsoiled areas) on a yearly basis and indicate how much lag time <br />there will be between stripping, placing waste, and retopsoiling the pile <br />face. At present it is difficult to envision the progression of the pile and <br />assess whether the bond is adequate. <br />GEOTECHNICAL CONCERNS • <br />The app ication includes extensive material testing data regarding the <br />current underground development waste produced at the mine. The applicant <br />commits, on page 13 of the application, to performance of additional materials <br />~°~ testing on. eventual coal processing plant waste when it is produced, in order <br />to verify the design values used in the engineered design and stability <br />analyses. However, the application fails to state that these results will be <br />submitted to the Division. It will be necessary for the Division to require <br />submittal of all testing results, in order for the Division to complete a <br />determination of whether or not redesign or reanalysis is necessary. <br />2. The permit revision application presents the results of extensive and <br />prudent sensitivity-type analyses of the slope stability of the proposed ~~ <br />pile's configuration. The Division finds these analyses to be acceptable for " ~,J <br />~~ the purpose of demonstrating the structure's internal integrity, assuming <br />foundation on a stable base. The Division is concerned, however, regarding <br />the potential effect of placing a 9 million ton surcharge load above the <br />partially extracted F-seam. The waste pile location overlies the area of the <br />main entries of the Mt. Gunnison No. 1 mine. The application states that the <br />pile foundation is separated vertically from the F-seam mine workings by <br />between 110' to 550' of overburden. In relation to this overburden thickness, <br />the Division suspects that the average 160' thickness of coal processing waste <br />may represent a significant additional load. The immediate bedrock <br />orientation represents an approximately 5o dip downslope into the adjoining <br />valley of the North Fork of the Gunnison River. As the application observes, • <br />the. area of the surface facilities has experienced recent surficial landslide <br />movement. <br />Observations within the existing mine workings, beneath the proposed <br />location of the upper waste pile, have determined that a problematic floor <br />