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<br />- 14 - <br />The report, and the application text, both candidly state that, because <br />of snow conditions during the preparation of the application, specific <br />geotechnical site investigations of the excess spoil fill sites have <br />not been completed. The applicant commits to the completion of <br />appropriate investigations, material sampling, and laboratory testing, <br />in order to verify the projections included within the permit revision <br />application, Based upon the considerable geotechnical information <br />contained in previous geotechnical reports concerning adjoining areas <br />of Eckman Park, this commitment is acceptable. We will need to <br />carefully stipulate the completion of the appropriate geotechnical <br />investigation, materials sampling, laboratory testing, stability <br />analysis and redesign, if appropriate, prior to any disturbance of the <br />site. Contrary to several statements containe in t e app ication, a 1 <br />results of the stipulated investigations, testing and analyses will <br />new be submitted to the Division for review and approval, rip 'or to <br />any disturbance of the site. <br />We are concerned with two specific components of the Golder report. <br />The consultant observes that the spoil is expected to be relatively dry <br />during and following mining and reclamation of the site. Experience <br />within the adjacent Eckman Park mine areas suggests that a significant <br />spoil acquifer develops within the mined spoil of similar dip slopes <br />and that considerable phreatic surface elevation may occur. Located as <br />the excess spoil piles are, at the toe of the mined spoils, Exhibit 19 <br />will require amendment to thoroughly discuss the hydrologic <br />consequences of spoil acquifer development for phreatic considerations <br />within the proposed excess spoil disposal fills. The stability <br />analyses will need to be amended, incorporating more appropriate <br />phreatic surface assumptions. The consultant will also need to <br />demonstrate that the carrying capacity of the proposed subdrains is <br />appropriate for the projected effluent quantities. <br />Secondly, a portion of the proposed eastern area excess spoil disposal <br />fill is founded on top of previously mined and backfilled Wadge coal <br />seam spoil. Wadge seam spoil has been subject to land sliding at the <br />nearby Edna mine. Large landslides have occurred recently in which the <br />plane of failure parallels the pit floor, occurring in fire clays <br />beneath the pit bottom. <br />The Area 41 spoils at the Eckman Park mine have evidenced extensional <br />cracking, which the operator has hypothesized to be caused by <br />consolidation settlement of those spoils. On page 32 and 33 of Exhibit <br />19, the consultant discounts the likelihood of failure occurring within <br />the Wadge seam spoils due to the superposition of the Little Middle <br />Creek excess spoils. The consultant should amend the report to <br />consider the constituency of the Area 41 spoils and the immediate <br />underlying pit floor stratigraphy. Specifically, if the Area 41 pit <br />floor is underlain by a fire clay, the analysis should be repeated, <br />including an appropriately low shear strength value for that strata. <br />Further, the development of a spoil acquifer within the Area 41 and <br />Little Middle Creek spoils might also exascerbate the potential for <br />failure below the Wadqe pit floor of Area 41, and this possibility <br />should be considered by the consultant in amending Exhibit 19, <br />