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<br /> <br />~,ay., 4 <br />Jim N.erron <br />July 23, 190"0 <br />input material parameters, as shown on figures 13.3.2 and 13.3,3, assume - - <br />the waste material density has Z06pcf, and the existing colluvial soil's <br />material density as 120pcf. The applicant's consultant must verify the <br />appropriate nature of these material property assumptions in order to <br />utilize them within the stability analysis. Such a verification should _ <br />include field or laboratory testing to demonstrate that the assumed <br />density values appropriately model the proposed disposal fill. Without <br />this verification, the stability analysis cannot be considered representative <br />of the proposed disposal fill. If the applicant's consultant cannot . <br />verify and justify the use of the density values utilized in calculating <br />the factors of safety presented in the application, the stability analysis <br />will have to be repeated and the application amended to show the corx~ct <br />results. <br />Pseudo-Static~Stability Analysis <br />Page I3-4 states that the pseudo-static stability analysis incorporated <br />a horizontal force of 0.0258 to simulate the effect of an earthquake on <br />the stability of the proposed waste disposal pile. The applicant's <br />consultant should justify this assumption which is significantly Iower <br />than the acceleration factors assumed in several recently prepared <br />pseudo-static analyses for mines within the same region. <br />Certification and Inspection of the Disposal Fi11 <br />The application contains no reference to certification or inspection of <br />the proposed development waste fill. Northern Coal will have to. supply <br />the Division the inspection and certification by a registered professional <br />engineer, as specified in section 30 CFR 817.71(j). As mentioned above, <br />the company should also provide the Division with verification of the <br />durability of the waste material deposited within the fill. The required <br />certification should include at least quarterly verifications of the <br />durability of t::e fill materials. The application should be amended to <br />reflect these inspections and certification requirements- <br />CC: Fred Banta <br />/k <br />