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APPCOR10501
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APPCOR10501
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Last modified
8/24/2016 6:26:53 PM
Creation date
11/19/2007 2:11:08 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1984065
IBM Index Class Name
Application Correspondence
Doc Date
8/29/1984
Doc Name
MEMO GEOTECHNICAL ADEQUACY
From
JIM PENDLETON
To
JIM HERRON
Media Type
D
Archive
No
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<br />-4- <br /> <br />(2) In response to our original adequacy comments, the consultant amended <br />pages 39.3 through 39.7 of Appendix 4.5-1 to present a more <br />comprehensive discussion of slope stability and subsidence <br />relationships on Coal Ridge. The amended application observes that <br />moderate slumping and landsliding is limited to areas "outside and <br />below the anticipated areas of surface subsidence effects." (page <br />39.5) With the exception of one questionable portion of the <br />northeastern face of Horse Mountain, the Division concurs with that <br />opinion. There appears, however, to be extensive geomorphic evidence <br />of ancient slope movements throughout large portions of the slopes on <br />the northeast face of Coal Ridge. <br />On pages 41.1 and 41.2 of the amended Appendix 4.5-1, the consultant <br />describes a proposed visual monitoring program which will specifically <br />observe slope characteristics considered indicative of slope movement, <br />such as ". surface cracking, movement of large rock blocks and the <br />development of bulging ground near the base of the slope." The amended <br />application's Appendix 4.5-1 also presents a detailed proposed program <br />for mitigation of slope stability problems. Simplistically, in areas <br />where no danger is presented to structures, mine personnel or the <br />public, the applicant proposes to restrict access and visually observe <br />manifested slope instability phenomena. In any areas where a hazard <br />exists to structures, mine personnel or the public, the operator will <br />also, "... as necessary and appropriate, provide slope stabilization <br />techniques". As amended, however, vagueness exists concerning the role <br />of the Division in the decision of whether or not a hazard to <br />structures, mine personnel or the public exists. To avoid possible <br />future disagreement, our eventual findings should impose a stipulation <br />which clearly states that the Division shall review and concur with any <br />decision of whether a hazard is represented by any specific slope <br />movement event and whether a slope stabilization program should be <br />developed and implemented. <br />(3) As mentioned above, in response to earlier Division adequacy comments, <br />the consultant significantly amended the discussion of the proposed <br />visual monitoring program contained in the original version of <br />Appendix 4.5-1. The amended visual monitoring program's description <br />has been expanded to include observations designed to determine <br />development of sinkhole collapse and slope instability. The consultant <br />also amended the application to state that monitoring, both visual and <br />survey, would continue until cessation is approved by the Division, in <br />writing. <br />The application's proposed survey subsidence monitoring program has not <br />been amended in response to our earlier adequacy comments. The <br />application proposes the installation of one linear set of <br />widely-spaced subsidence monitoring monuments, oriented perpendicular <br />to the spine of Coal Ridge. Considering the importance of verifying <br />subsidence projections contained within the application <br />(Appendix 4.5-1), reliance upon only one limited set of monuments is <br />considered imprudent. Our eventual findings should impose a <br />stipulation specifically requiring the installation of a second <br />analogous set of subsidence monitoring monuments at another agreed <br />location on Coal Ridge. <br />
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