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APPCOR10323
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Entry Properties
Last modified
8/24/2016 6:26:43 PM
Creation date
11/19/2007 2:09:47 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981023
IBM Index Class Name
Application Correspondence
Doc Date
5/15/1981
Doc Name
REVIEW OF THE GEOTECHNICAL INVESTIGATION FOR THE EXISTING SPOIL AREA 1 CHIMNEY ROCK COAL MINE
From
MLR
To
MIKE LONG
Media Type
D
Archive
No
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,~ <br />brn1~ ;~i ,. or or.nr)p ~~~~~~:. ~~~,u ".a++ ~.,.. ~.~„~~~ IIIIIIIIIIIIIIII III <br />O EPARTMENT OF NATURAL RESOURCES <br />D. Monte Pasroe, Executive Dveemr 999 <br />All~'t~;l) LA\'U fiE(:LAAI:~TION <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 839-3567 <br />David C. Shelton <br />Director <br />April 15, 1981 <br />TO: Mike :.ony <br />FROM: Jim Pendleton ~ ~ ', -__ ~-c .-a~~ ~-~~~~- -' <br />r <br />RE: Review of thE~~Geotechnical Investigation for the Ex.~sting <br />Spoil Rrea q1, Chimney Rock Cosl Mine <br />Pursuant to your request, I have reviewed the 9eotechnical investigation <br />for the existing spoil pile, prepared by CTL Thompson, Inc., for <br />Perms Resources, Inc. This geotechnical investigation represents the <br />redrafting of an earlier geotechnical investigation prepared in ~~ <br />response to the interim program regulations. It is now included within <br />the permanent program permit application for the Chimney Rock Coal Mine. <br />I fozward the following comments for your consideration. <br />The original analysis o.f the Chimney Rock spoil pile was completed in <br />August 1979 by CTL Thompson, Inc. An initial review by the Division <br />indicated several concerns, Site inspections had determined that the <br />fill had not been built as originally analyzed in the August, I9'9 <br />report. As a result, the applicant was instructed to revise the <br />analyses to reflect the actual fill situation. The earlier analysis <br />and design were based upon the installation of a drain beneath the <br />spoil pile. Field inspections by Fred Banta had discerned that the <br />drain had not been installed by the previous operator. <br />The revised analysis, completed in July of 1980 by CTL Thompson, Inc., <br />assumes slightly different groundwater configurations to reflect the <br />lack of the drain. The original analysis ascertained tiTat a static <br />Factor of safety of 1.5 or greater could be obtained usiny a 1 vertical <br />to 2 horizontal slope without benching. The revised analysis determined, <br />based upon the revised groundwater assumption, that an overall slope <br />angle of 2.25 horizontal to 1 vertical would have to be constructed in <br />order to assure a factor of safety above 1.5, as required by Rule 4.09.1(7). <br />CTL Thompson recommends that the outslope of the fill be designed with <br />an overall slope no steeper than 2.25:1. T;tey r_.bserve that this overall <br />slope could be obtained by designing the slope for a uniform 2.25:1 ratio, <br />or by utilizing a 2;1 slope with intermediate benches to prc,vide an overall <br />2.25:1 from the head to the toe of the slope. They further caution that <br />the slope be properly constructed with adequate diversion ditches and <br />yoo,: drainage to insure that in:'iltration is kept to a minimrun. <br />(con t' d) <br />
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