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• • <br />GOLD ffiLL MILL <br />SLOPE SrA1611.i'IY YVALUA7701V <br />OF E70'ANDED'fAILIIVGB EMBATIKM[JVT <br />Colito Oro Molina (COM, inc.) is ~tiY reviewing the teitirrgs embankment design after several <br />defiriertciea it the original design imposed by upaheam raise type of construction wero entail by the <br />Colorado Mined Land Reclamation Board. <br />The original design were based on a starter dike with upstreatn raises wnosting of Domes ink deposted <br />okxse to the inside embatJ¢nent of the starter dam. Just prior to corrstrtrctian, a impermeable synthetic liner <br />was tegneated by Colorado Mimed Lend Recamation Baatd (CMLRB) to prevent seepage of tares water <br />into the water table. The starter dgte downstremn firoe was designed a< 1.3:1-end was to bo tamed at this <br />slope wrth subsegtrerd dam raises. No dam raises have ban completed on ~ stmter drloe to date end an <br />tailings are conmined within the Brad eras of the tmlirtgs pond. <br />T]te new embanlmlad m designed To be raised ten feet above the origQtal starter dam erect elevation and elm <br />allow the liner to be continuous to the top of the new embmJuuent without compromising the embankment <br />idegIIty. m order to peas rrssornable fanLae standards analysis, the dorvrnstream elope was fiattmed to 2:l <br />with the upstream slope cattinumg from the irtside errst of the original starter drlx et s slope of 1.S:1. A <br />12.Sfoot road art the embmnl®erd cast was designed on the embenkuerrt <br />The cone of tine new embanl®att nett to the existing embenl®erd wtTl be constructed of mine dump <br />metrrial avmlable fiom the white Cloud and wyrwrte/Oacar mine dumps. The dump material win be <br />placed need to the existing embank®mt and wrTl not extend cheer than five feet tiomtha aufaoe ofihe rtew <br />embankment to preveru oxidation of the pyritic materd in the fin. The material whir fire fat of the <br />embmdanent surface wrIl be obtained from a borrow area behied the erdatirrg embankment The exiebtg <br />a~rter die anbankruent was canatiucted of the same materiel <br />Lt alder W meet static end eaamic n:quidnertb for an embattl®etd it mt area wish known active lirdfs <br />within a 23 male radius, the Golden and Derby ~ bring moat prodo[oinmd, a slope smbrlity analyse was <br />perSormed on the new embankment The active fauks it the area have a potential for moderato damage and <br />the area can be classed as a Zone 2 area with a potential for a edsmic event of up•to VQ an the Modified <br />Merafii Bale. <br />The computer program used to evahtate the stabtlily of the dam dmm~ng the most hloely fiultue mode it m< <br />earthfill dam involving a slip title failure is snail REAME (Rotatiornel F.gwLbrirmr Analysis of <br />MuhiLryered Embenkmertts) drat is based on a ~pliSed Bishop method of analysis. The progtmo was <br />developed by Ih. Y. H. Huang, Professor of CYvl Engiteemtg, Lhtiversity of [Certtuclty. <br />Origenany, aIl material for the new embanlunad was to come $om the borow area above the. existing <br />tailings pond, however, the depth of exavation to obtain the quantity of material rneceasery maeM that <br />bedrock would have to be excavated. It was felt that the grande bedrock would produce too moth Loge <br />rock end wouLi not Lave enough fines far a good ffi material The elteanate design deeded apart is fo build <br />ilne embmnlunerd with dump material with highs sad generNitg.material as s Dore and put the granite BQ <br />materiel an top to prevent addilionel oxidation of the are materiel <br />The existing stmter embmdunerd was sampled for Proctor and.tderual shear 6esfs to dete~ire the mdstirng <br />embarJ®en! stabrlity. Sins the material was taken gam the proposed borrow area, the Trsta also are <br />repreaertottiive of Tyne boaow for the new emberdunent The tarTmgs materiel co»Id not be eampked and <br />tested in tine for this report but the material in the dumps was takerr from the aerate deoarttpoeed grarrife ere <br />the barrow area above the ~ pond. Additional vain materiel that was deposited on the dumps has a <br />higher clay contertt that weer dete®ined by visual inspectiast of the sampka. The higher clay conterd is <br />nomrel for the veins in the area. The friction angle developed by the dump materiel should be simrler to the <br />samples. taken 6orrn the existing embartYJnent Tire cohesion wouLi be ~ Eor the dip material <br />because of the higher clay oonternt. The existing embarkment material a clesaified as a poorly graded Band <br />May 3I, 1993 <br />