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~~ s.o ~~- <br />This report will sm„arizn the results of an irnestigation conducted at the site <br />of the ex1-ttitxJ coal refuse Pile at the Southfield Mine Site of F~esgy Ftiels <br />coal, InC. near Florence, Colorado. Regulations of the Colorado Mine Land <br />Reclamation division require crnq~action of the coal waste n+iterial to 9oi of the <br />maxitttam drY density based o» A7LCtiDp specification T99-74 (refererxoed density <br />,a,tai++gn usi.nq a 5.5 pound ham++P-r and a 12 irk dtnp). it appears that the last <br />record of density tests being performed in the pile were in May o! 1982. The <br />papoea of the density testing reported in this doamient is to update information <br />u1 densities achieved usilg aurer~t oautnxtian practices in the pile. <br />J The coal waste consists of a mixture of 2 separate materials. <br />1) Fine waste (-28 mevhh) <br />7 Z) Cioarse waste (evezythirq lazr}er than 28 a,rsh) <br />The original repose pile design was based on a mixt~u~e ratio of s parts coarse to <br />1 part fine. Earlier work oo~leted by Ror3cy Mountain Ceotechaical, mac. in <br />lSe,:t#- of 1982, detezmined maxinman dry densities from various blends Lrcin ooartire <br />7 and fine material ranging frun loos fine/oi coarse to Ot fine,/100t ma*~ with <br />irltexmEdiate blends o! 25R, 50~ and 753 fines, respectively. Densities were <br />abrerved to vary iron a low of 71.5 pc! to 90 pcf with the maxinwn value of 90 <br />pct repxesentltxJ the 75; ooasse/25~ tine blend. <br />~e original design a1BO asstaoed that the onarae and fine materials would be <br />blerxied prlar to disposal in the refuse pile. It is our understanding that at <br />this time, coarse end line materials are being dispceed of in disc-rate, <br />segregated layers (i.e., they ar+e not blerdsd or mixed prior to dispo6e-1). <br />i Therelaze, refereitoe densities pertaining to the variau blends of materials no <br />J longer apply. All samples will bs c~arncterized oithar as liras (maximnn dzy <br />density of 71.3 pcf) ar coarse (maximan dzy density of 86.1 pcf). <br />Also of ornoarn is the effect o! the density and the layering on the shear <br />strength and stability of the refuse pile. Bulk samples oP the weaker of the two <br />materials (i.e., the fines), have been obtained and tented in direct shear in <br />ozder to dntnrmine the adequacy o! arigirsal design asstaoptions in licit of <br />agent od~Rsvction practices. <br />7 <br />