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u <br />Page 5 <br />7'om Gill is <br />Frarch 17, .1'?rll <br />0 <br />7. An appropriate. state-of-the-arC stability analysis of the propose) Coat <br />Nrocessiny I:i~:;te Ururk. 79ris nrathr•m•,l ical analysis ramnrld employ an approprirrt,: <br />".rccura[r,• ruo(borl of :;t.rtic ::.Iola' (,,~lor of ::.rfcl~l c,+lrul,r(.iun, :such as Lhc <br />Slx:ncer's Muthcnl, ur an equivalent t~•,:hniquc. '1'hr stability ana.ysis must <br />include hedroc!c, col)uvium and waste materials a:; pa~aiblr: critical failure <br />surfaces. '!'ho anaLJsis, in order to 1.•e representative, must accurately nrodel <br />the proposed waste LanY.. As such il: ahould include discrete materials <br />testing results detcrmtned forappropriate materials and degrees of ground water <br />saturation. In cases in which specific testing data is not available, seusitivity- <br />type analyses are recommender!. Sensil~.ivity analvsc; assume variation in <br />material properties and degree of saturation in order to determine the affect <br />inaccuracy in these assumptions wouL7 have upon the calculated slope factor <br />oC safety. Coal 1'rocessiny Waste !?:.uric are required to achieve a static slope <br />factor of safety of aC least 2.5 (Rulr 4.10.4/2]). <br />Colorado h'estmoreland's amended application for the Orchard Valley mine <br />includes a simplistic stability anaL~~:is utiliziny the "Culmann Method". 'lhe <br />"L'ulnrann Method" is an analytical procedure for determining the safety factor <br />of a uniform soil slope which assumo:: that the failure surface is planar in <br />steep slope cmbankrnents. Considerinu the extensive slope stability hazard <br />characteristic oC the site, Lhe potenCially low residual strengths of the <br />celluviu;n, the inhomogwrcous nature of the foundation and waste materials, and <br />the Icss th+rn lv:2h slope of the proposed pile, do analysis utilizing the <br />"Culmann Methnrl" is inappmpri.atc for the Orchard Val.lry pcrmi.t area and does <br />not satisfy the rerluirements of the C'~riorado Permanent Regulatory Program. <br />Furthermore, the stability analysis contained within the amended application <br />is based upon an assumption of shear atrength deri•~ed by correlation with one <br />penetration teat performed by Fox anJ nssociatr_s during an auyering project <br />near the truck loarlrnrt upslope from tiia proposed r.•aste site. This conversion <br />is extremely crude. 'Che materials tcr.ted mau not be representative of the <br />foundational soils Leneath the propn:;•d structure. The assumed property is <br />utilized for Lath bedrock, colluvium ,rod waste material, assruniny that a1I <br />materials are uniform. !'finally, th~~ analysis per.Cormed Ly CW.Z's personnel <br />determined that the "near slope" saf~~r~l factor only ach.icved 1.28, which does <br />not satisfy fhu requircurr_nLS of Ru1c •!.10.4(2). <br />ConClusinn <br />Colorado Wc::LlnoriJanrl, ]nc.'s wasl:c ,li::(r>sa] proposal .is inarlrquntcly supportc,l. <br />C h'I must comp]ctc ,gin appropriate uenlr,:lurical analysis of the proposed waste <br />rl.isposal si l.c. Thc. results of that ir,vesti gaCion must Lbcn Le used to produce <br />a detailrrl cnyincer'inq design which r:~:nCw'nu^ with Che requiremenCS of the <br />appropria tc sections of the Colorado I•~•r~ma neat I'ro yr am rcgu L~ti ons. A thorough <br />ma th~~matica/ .a taLility anal y:;i s, which proprrl~l n,ork: 1:: the propnsr:d Coal Crocceaing <br />IJastc~ Rank, ^nr;f 1,r: camp is tcd to der. i,~n :tra to cantor me u,cc with the required <br />;I nCie sl,~p~~ f,u:tor r~r ::., ru1y t'cquil, :~,. vlt of ].S ur I,i•lhc c. <br />CC: C. 1'ahlku <br />~• r„r ~, r,. ... tt <br />