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Page 4 <br />Jim Herron <br />July 23, 1980 <br />input material parameters, as shown on figures 13.3.2 and 13.3.3, assume <br />the waste material density has 106pcf, and the existing colZuvial soil's <br />material density as Z20pcf. 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 correct <br />results. <br />Pseudo-Static Stability Analysis <br />Page 13-9 states that the pseudo-static stability analysis incorporated <br />a horizontal force of 0.025g 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 lower <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 zeguired <br />certification should include at least quarterly verifications of the <br />durability of the fill materials. The application should be amended to <br />reflect these inspections and certification requirements. <br />CC: Fred Banta <br />/k <br />