Laserfiche WebLink
~,. <br />~II ~I~~I~II~~~~~~I~ <br />STATE Gr ~~iLVtc~DO <br /> <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1373 Sherman St.. Room 275 <br />Denver, CO 60203 <br />303 866 3567 <br />FA X: 303 832-6106 <br />OF Cp(~ <br />~F' •P9 <br />he / ~ O <br />i a,o Q ~ <br />. . <br />~ r876 ~ <br />Roy Romer, <br />Governor <br />April 28, 1992 <br />Michael e. Long. <br />Division Director <br />TO; Janet Binns_ ~i <br />FM: Shawn Smit~ <br />Re: Slope analysis for reclamation of Fruita #1 Mine rock fill and <br />embankment <br />Dear Janet: <br />I have reviewed both the laboratory sample test results and the <br />pre-mining reclamation plan proposed by Mr. Greg Lewicki and find <br />them both to be satisfactory and comprehensive with one concern <br />noted below. <br />Initially, I studied the facts of the analysis by Fox Consultants <br />and then reviewed their analysis for assumptions made during the <br />research phase. Both the facts and assumptions, along with my <br />comments are presented below. <br />The facts of the analysis include: <br />o Pile stability since 1980, 12 years with no problems of <br />sliding or slump~ing_1•__~~ ~H~ ,~ i:sCN): i(v) ~! <br />o A low slope Y.3 aveT age; 9 ~~J ~z9 <br />• The pile is well-drained due to the peripheral drainage <br />ditch that effectively prohibits water saturation or <br />surface contact with the fill material; <br />• Finally, with the reconstruction proposed and now already <br />in place, the rock fill has reached a minimum factor of <br />safety of 1.773, well within desirable parameters of 1.5 <br />according to Rule 4.10.4 (2). <br />The factor of safety analysis was conducted using the Bishop's <br />slice methodology, which justified that should a slide occur, that <br />the slope angle would be such that it would produce only low angle <br />surficial slide occurring at a maximum depth of five feet. Since <br />the analysis also considered a depth of 10, 25 and 50 feet <br />respectively and produced a factor of safety that only increased as <br />the depth increased, we can gather that the relationship is <br />proportional between depth and factor of safety. <br />