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TABLEI <br />INDEX AND STRENGTH PROPERTIES OF SOILS FOR PONDS <br />SAh1PLE ATTERBERG , PARTICLE SIZE EFFECTIVE EFFE~'TIVE <br /> LIMITS DATA FRICTION ANGLE, COHESION, <br /> (Ll.-Pi) (°/passing No. 200) ~• c'(psn <br />Pond 1G Foundation ;9-20 9G 29.9 0 <br />Pond 10 Embankment Fill 38 - 22 86 27.5 _ <br />3:18 <br />The parameters described above were input into the SLOPE/W program to evaluate static ::[ability of the <br />Pond 016 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 static FOS of 1.502 for :t dounistream <br />slope of 3H:1V, which meets the required FOS under applicable provisions of Rule 4.OS.f~(11)(k). <br />The SLOPE/W compurer printouts, located in Appendix B, document all inputs and stability <br />analysis results. <br />3.0 RECOMMENDATIONS <br />In order to achieve the design paaameters, it is recommended that the following procedures be <br />utilized m the construction of the sedimentation pond embankments: <br />• <br />]) Given the location of the dam, the height of the dam (greater than 10 Eeet) and a <br />FOS of 1.5; prior to construction, soil samples should be collected from the borrow <br />areas and tested to verify the borrow material strength parameters used in • <br />association with this stability report. <br />2) Also, have Registered Engineer verify embankment fill properties prior to <br />COnS[rn CtlOn. <br />3) Construct embankment in maximum 1-foot horizontal lifts. <br />4) Compact each individual lift to 95% of standazd proctor using available equipment. <br />5) Maintain slopes no steeper than 3H:1V. <br />4.0 <br />Leidich, Tom (1999). Proposed Pond 016 Design. Exhibit 13-12.2. Seneca !! W Permit. Prepared for <br />Seneca Coal Company. <br />Lou L. and Peng S.S. (June 1999). Integrated Approach jot Predicting Mining Subsidence in Hi![y <br />Terrain. Mining Engineering. p. 101. <br />NCRS (1999 draft). Soi! Survey jot Routt County. NCRS. Craig, Colorado. <br />Northwest Colorado Consultants (July, 1994). "Geotechnica! Investigation, Haulroads Y-A & Y-B and <br />Sedimentation Pond 010, Seneca /f W Mine Area. Rout[ County, Colorado". Prepared for ,Seneca <br />Coal Company. <br />Northwest Colorado Consultants (August, 1996). "Geotechnical /nvestigation/Summary Report Pond 010 <br />Embankment -Permit C-94-082 Seneca /1 W Mine, Routt County, Colorado'. Prepared for Seneca <br />Coal Company. <br />Nyenhuis, Jim (1993-b). "Soil Types and Soil Salvage Map". Exhibit 9-!, Seneca /! W Permit. CSU Soil • <br />Testing Laboratory. PerFormed for Seneca Coal Company. <br />