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-~- <br /> <br />• "Some collapse Of the old mine to the :vest due to the dump <br />surcharge is possible. However, the chances of sini: holes <br />appearing at ti:e surrace of the dump must b•~ regarded as <br />low due Lo the bridging nature of the dump material itself. <br />Silauld these features develop they should occur concurrently <br />or shortly after the aiace~ient of the waste dump." <br />Tile primary factor to be considered in assessing the effect of the under- <br />ground o-ror::ings on the stability is the current condition of the spoil <br />p112. ~b5e r!'3 t10nS ana available Cd La do nOt lnOlCaLe dny eY,Ce5SlV2 3BLLie- <br />ment or othe~• features vrhich :•rould indicate settlement or collapse of the <br />underground wor'r,inas. 41e understand that portions of the fill 'nave been <br />in place for i.. excess of 3 years. The fill was originally constructed at <br />d toe elevation of ~pD rc l mate :y 6600 dnG dt the tlm2 Of Ollr 1nSCeCt10n On <br />June 13, 1979 construction :•ras continuing at the 7000-foot level. Thus, <br />approximately u00 =eel of fill has been placed with no sign of excessive <br />settlement or any ir.dicaLion of file underground ~:rorl:ings creating problems <br />erith the fill. These factors are strong indications that future problem; <br />with the fill, as a result of underground •:rorkings, are exiremeiy unlii:ely . <br />A review of our report, yob Rn. 5363, dated August 15, 1979 and the avail- <br />ale referer•ces indicate file analyses presented are valid for the condi- <br />tions studied. In sere cases the analysis may,_in fact, be some:•rhat con- <br />servative sine Effects due to plane strain, the reverse "V" canyon effect, <br />• and the unrealistic aSSL'iT,Dt10n5 regarding 473 ter table were included in the <br />anal}'sis. In our opinion, the Colot•ryo slope as presented in the.'report is <br />stable under dry conditions. <br />If you have any questions concerning this information or need additional <br />data, please contact our office. <br />Very truly yours, ~y~''"~~13 c~~~\~ <br />CTLITi'Dh1P5DN, 1NC.,, ~,z`m" gt~~aG'' <br />a <br />_ d <br />Dar.~~~ lJ. Holm^yuist -~ E. \sry\~.;,ep~l~~~`,a i <br />~toi;ert ll. ir.ompson, r. E <br />DUH:°SR:dm <br />(3 copies sent) <br />• <br />