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• <br />• <br />• <br />f <br />~~ <br />CTL/TnOiViPSON, INC. f <br />G"~~~IS'~'_TING CE~~TECH N!CAL AND MA`Er'-'.IA LS EN j!I~~C G~J <br />t4arch 24, 1980 <br />Director, Office of Surface i~!ining <br />Region H <br />Brooks Tetvers <br />i020 - i5th Street <br />Denver, Colorado 80202 <br />Attention: t•Ir. Keith Kirk <br />_; <br />f ~ `~ <br />~p UCi.S <br />Subject: Consultation <br />Slope Stability, Colotvyo Streeter Canyon Fill C O ' d O t~ <br />Bear.?•leeker, Colorado <br />Job tJo. 5358 <br />Gentlemen: <br />!•le have received a copy of the hiine Land P,eclamaiion Board letter of <br />Februar;~ 5, i980 co,;r-=_ntir.g on the slope stability anaiysis of the sub- <br />ject fill. "ha lette%, prepared by ?•lr. Jim Pendl e'ton, diSCUSSeS his Con- <br />cerns recardin^, the SUbjeCt report. !•te trould like to take this opportuni- <br />ty to discuss the co~~:.ents made by t•ir. Pendleton and present add-itional <br />infcrma~ion to aid in your evaluation of the t4LRB letter and the subjeet <br />report. To simplify t;:e re vie•;r we have organized our response in the same <br />general sequence as tr;e t•ILP.3 letter. <br />Before discussing f•1r. Pendleten's consents, it is appropriate to explain the <br />nature of she consultant's role in Llle report preparation. The consultant <br />was regained :,~~ The Office o Surface honing to re!liev; the data pro yid:~•~ 6y <br />OSi4 and to perform an anaiysis of the slope stability of the Colotvyo slope <br />and a similar configuration desiy^ned in accordance with the OSf•1 regulatory <br />program. The consultant was not given authority nor funds to conduct a field <br />or laborator•+ investic.atien. Ail analytical data tras to be obtained r"rpm <br />data submitted to OSt•1. Furthermore, the analysts was to be based upon a <br />parametric study of density, friction angle and water table conditions to <br />evaluate possible effects. <br />In paragraph 1, h1r. Pendleton e` h1LG3 ccmme:as :; •. the method of parameter <br />analysis and indicates up to a 135 percent chance in the factor of safety <br />for various analytical data combinations. As discussed in our original <br />report. dated August 15, 1979, o-re believe that the maximum change in the <br />factor or safety is a function of the water table and the angle of friction <br />of the colluvium. To verify this, the have conducted a parametric error <br />anaiysis usino the Colotvyo slope a+ith the following results: <br />1701 SOUTH FEDER A! OLVD. SUITED DENVER. COLORADO 80219 (303193.1-5-373 <br />