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Deambrr2001 Srarm Coal Carmpauy * Seurm II W Mine S<dimeatotion Poad 0077 Deign Slobrk'ryi4nalynr ~ 2 <br />1I 11 <br />lJ <br />-~~``~n` ~ ~~ <br />~~ '- ~~~TARLE''1~ ,r~~" <br />~ <br />,. ~ ~+ ~ ~r ., .., =.INDEX AND`STRENG Th :PROPERTIES O , SODS FOR;PONpS <br />SAMPLE ATTERBERG PARTICLE SIZE EFFECTIVE EFFECTIVE <br /> LIMITS DATA FRICTION ANGLE, COHESION, <br /> (LL-PI) (%passingNo. rp' c (psf) <br /> 200 <br />Pond 016 Foundation 49 - 20 96 29.9 0 <br />Pond 016 37 - 22 83 - - <br />Embankment Fill <br />Pond 010 38 - 22 86 27.5 338 <br />Embankment Fill <br />2.0 RESULTS <br />Using the described inputs, the stability analysis indicates a static FOS of 1.8 fox a downstream slope, <br />which meets the required FOS under applicable provisions of Rule 4.05.6(11)(k). The SLOPE/W <br />computer printouts, located in Appendix B, document all inputs and stability analysis results. This <br />stability analysis result is based on the assumption that construction practice employed for this <br />embankment resulted in embankment material compaction of at least 95% Standazd Proctor. <br />3.0 RECOMMENDATIONS <br />In order to achieve the design parameters, it is recommended that the following procedures 6e <br />utilized in the construction of the sedimentation pond embankments: <br />1) Upon denting topsoil and construction of the embankment keyway, have a <br />Registered Engineer (or qualified person under the supervision of a Registered <br />Engineer) verify the subgrade (foundation) material classification in association with <br />this stability analysis. <br />2) Given the location of the dam, the height of the dam (greater than IS feet) and a <br />FOS of 1.8; prior to construction, soil samples should be collected from the borrow <br />areas and tested to verify the borrow material/embankment fill strength parameters <br />used in assoaation with this stability report <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:1 V. <br />4.0 <br />Montgomery Watson Harza (December 2001). Pond 017 Design Revisor Attachment 13-SB, Seneca 17 W <br />Permit. Prepared for Seneca Coal Company. <br />Northwest Colorado Consultants (July, 1994). "Geotechnical Investigation, Haulroads Y-A & Y-B and <br />Sedimentation Pond 010, Seneca 11 W Mine Area, Routt County, Colorado". Prepared for Seneca <br />Coal Company. <br />Montgomery Wahou Har{a, 0165 Sautb Uuiou Boulruard, Suite 4010 * Lakrwoorl, Colorado 80218 * (303f 763-5140 <br />J:\1470108 Suura Coat~PR-03\Pond 17Rrv\POND 17 Dengn SIABILIIY.da <br />17/11/OI tyro <br />