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JmIP 1999 Srnrrn Cae! Carr~ur0~ ~ Snixa Il U~ d (trig J «Lma~latrun Pond 017 SlaLrlitr Ana~ait ~ 2 <br />sand clay mixture (SC) the cohesion c:tn vary from 0 to 100 psf and the angle of internal friction can vary <br />from 27.9 to 33.8 degrees. The following conservative strength parameters were used for the natural soils. <br />Cohesion 0 psf <br />Angle of internal Friction 28 degrees <br />The following soil parameters for the embankment material were obtained from similar fill materials used <br />at Pond 010: <br />Cohesion 48~ psf <br />Angle of Internal Friction 14.2 degrees <br />The parameters described above were input into the XSTABL program to evaluate static stability of the <br />Pond 017 structure and are shown in the attached program printouts with associated results. <br />2.0 RESULTS <br />Using the described inputs, the stability analysis indicates a staoc SF of 2.1, which meets the required <br />FOS under apphcable pcoaisions of Rule 4.OS.G(11)(k). The _l'ST,'.BL computer printouts, located in <br />Appendix B, document all inputs and stability analtsis results. <br />3.0 RECOMMENDATIONS <br />In order to achieve the des+gn parameters, it is recommended that the following procedures be utilized in <br />the construction of the sedimentation pond embankments: <br />1) Upon clearing topsoil and non-engineered fill materials, and construction of embankment <br />key-way, have Registered Engineer verify subgrade material classification in assoc+ation <br />with this stability report. <br />2) Also, have Registered Engineer verify embankment fill properties prior to construction. <br />3) Construct embankment in maximum 1-foot horizontal lifts. <br />4) Compact each individual lift to 959e of standard proctor using available equipment. <br />5) Maintain upstream and downstream slopes no steeper than 3H:1 V. <br />4.0 REFERENCES <br />Huang, Yane H. (1983). Stobi[in~ Analysis of Eartlt Slopes. University of Kentucky. Van Nostrand <br />Reinhold Company, New York, NY. <br />Leidich, Tom (1999). Proposed Pond 017 Design. Exhibit l3-12.2, Senecn 1I W Permit. Prepared for <br />Seneca Coal Company. <br />Luo L. and Peng S.S. (June 1999). Integrated Approach for Predicting Mining Subsidence in Hilli~ <br />Terrnit+. Mining Engineering. p. 101. <br />NCRS (1999 draft). Soi/ Suney for Rmut County. NCRS. Craig, Colorado. <br />Northwest Colorado Consultants (Jul}'. 1994). "Geotechnica! lttvestigation, Haulroads Y-A & Y-B a+d <br />Sedimentation Pond 0/0. Seneca 11 W Mine Area, Routr Cmu+n•, Colorado". Prepared for Seneca <br />Coal Company. <br />Northwest Colorado Consultants (.4ugus[, 1996). "Geotechnica! /nvestigatiott/Summan' Report Pnted 0/0 <br />• Etnbmeknrent -Permit C-94-082 Seneca 11 W Mine, Routt Counn', Colorado". Prepared for Seneca <br />Coal Company. <br />:tlomtgome~~ IF%lran ~tmrn:ar, Int. 165 Sowth Uniw~ Bou/etard, Suitt -!t0 ~Ir.Eewwd Co/amdo 80??8 `(303J iG3a 140 <br />J:\8i 1 \rrpor+\/~ondt7ttu(n'G0 <br />07/11 /99 ab <br />