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The previous Technical Revision (May 2010) was to permit the mine operator to 1) backfill material in <br />the north end of Area H, 2) lay back the southern end of the quarry to a more gradual slope, and 3) <br />do further blasting to remove unstable areas on both the north and south blocks. To our knowledge, <br />these actions have not yet taken place. <br />Of particular interest is the development of the graben area in the North Block, which is an area that <br />CGS has expressed concern for potential failure since the initial site visit in December 2008 when <br />fresh tension cracks were noted in our original January 7, 2009 report. These same tension cracks or <br />insipient scarpslshowed significant additional movements during and after the major September 2009 <br />reactivation that we, again, specifically addressed in our later November 2, 2009 memo. Monitoring <br />data from prism locations along the North Block or "Middle Bench" show progressive, ongoing <br />movement from! when the monitoring program initiated in September 2009. <br />Accessing the USFS land above the landslide for the purpose of laying back the slope has also been <br />discussed since the initial site visit in December 2008. <br />As with previous Technical Revisions reviewed by CGS, this TR does not include any analysis, <br />calculations, or design parameters. It is not clear whether the actions from the May 2010 TR are still <br />being considered, or if stabilization attempts will be developed pending the requested investigation <br />period. <br />Recommendations <br />Given the dangerous condition of the quarry and the ongoing rockslide movements, it will be very <br />difficult to conduct meaningful geological investigations, and to ultimately design solutions to mitigate <br />the quarry instability. However, additional detailed investigations, done by qualified geological and <br />geotechnical engineering consultants, must be done. This work is needed in order to develop a clear <br />understanding of the rockmass and rockslide behavior in order to meet the following goals: 1) a <br />mitigation strategy that provides the stability the owners want for continued mining, and 2) suitable <br />long-term safety, factors for a stable reclamation DRMS will require for the future. <br />As the investigation evolves, CGS can assist DRMS and the Quarry by reviewing the investigation <br />scope and mitigation plan to try to ensure that the best possible useful data is obtained and the <br />mitigation plan will achieve the two stated goals above. <br />Thank you for the opportunity to comment on this Technical Revision. If you have any questions <br />about the content of this review, please call TC Wait at 303-866-2611 ext. 8330 or Jon White at ext. <br />8332. <br />Cc: Vince Matthews, CGS <br />