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Deambrr 2001 Srner° Coal C°mpauy * Srnrrn II W Mine Sedimentation Pond 0017 Drngn St°bidty Analyrir ~ 2 <br />`'^ R W r~re <br />,.~~ ,:. ~ INp ~~,,, rr <br />EX AND'STAENG m~~-TARE .. <br />7~l PEIOPEI)TIES Ot' <br />SC}. ~,. FOFitPONDS n <br />SAMPLE ATTERBERG PARTICLE SIZE EFFECTIVE EFFECTIVE <br /> LIMITS DATA FAIC710N ANGLE, COHESION, <br /> (LL-PI) (%passingNo. ~ c {psi) <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 for a downstream slope, <br />which meets the required FOS under applicable provisions of Rule 4.05.G(]1)(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 be <br />utilized in the constmction of the sedimentation pond embankments: <br />1) Upon clearing 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 15 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 standard proctor using available equipment. <br />5) Maintain slopes no steeper than 3H:1V. <br />4.0 <br />Montgomery Watson Hazza (December 2001). Pond 017 Design Revison Attachment 13-SB, Seneca 11 W <br />Permit. Prepazed for Seneca Coal Company. <br />Northwest Colorado Consultants (July, 1994). "Geotechnical lnvestigation, Haulroads Y-A & Y-B and <br />Sedimentation Pond 010, Seneca 11 W Mine Area, Roust County, Colorado". Prepazed for Seneca <br />Coal Company. <br />Momtgomrry W°trou Hor{a, 0165 S°utb Union Bou/rnar~f Suite 4010 * Ivkraoo~ Colorado 80218 * (303J 763-5140 <br />J:\2J70f08 Srnsm Cmt~PR-03\Pand 17Reu\POND 17 Design SfABIL7lY.dor <br />12/72/07 djm <br />