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Monitoring of the slide initiated in September 2009 shows continued and consistent movement in the southern <br />hanging block, northern block, and rubble zone (Figure 2). The earlier January 2010 Technical Revision was to <br />attempt to remove a portion of the unstable south block with explosives. The blast was done in February 2010 but <br />did not result in triggering any additional failures of the South Block. <br />Based on a 1986 MSHA recommendation, the mine operator feels the only way to stabilize the slide would be to <br />remove the remaining limestone blocks from the underlying granite, In particular, this revision is focusing on <br />removing the north, then the south blocks and would allow for processing of the removed limestone. Backfill is being <br />proposed along the northern portion of Area H (The Hole) to match the elevation of the production floor east of Area <br />H. Remote controlled equipment will be used during drilling, blasting, and removal of limestone. <br />Please consider the following observations and recommendations. <br />Neither of the Technical Revisions reviewed by CGS includes any sort of analysis or calculations to estimate <br />parameters of the slide mass that would be useful or necessary for design of mitigation methods. The second <br />Technical Revision continually refers to the ongoing stabilization efforts as an "investigation" which would indicate <br />that the proposed work (fill buttress, removal of hanging blocks, etc) is not intended to be a final stabilization method. <br />It should be noted that the proposed work, even if it is able to be completed, may not stabilize the slope. Even if the <br />monitoring following the Technical Revision work shows the slope has stopped moving, this should not be considered <br />a "final" remediation solution. <br />The discussion on the blasting methods is brief. We are assuming the remote controlled equipment mentioned will <br />be used to drill blast holes and the method used last February (inserting explosives into the open fissures of the <br />rockmass, including the headwall scarp) will not be considered at this time. We don't consider this Technical <br />Revision to be a blast plan since the proposed locations of the drill holes, explosive quantities, and delays are not <br />given. The brief discussion in the revision document seems to emphasize the removal of the northern and southern <br />blocks where prisms 21, 22, 24, and 13, 15, and 18 are located. <br />Figure 2. Prism map provided by mine operator. Photo shows both the December 2008 and September <br />2009 rockslides. Prisms numbers with red circles presently show landslide movement. Those with black <br />circles have been lost due to ground movements. Those within black boxes were recently installed <br />above the rockslide head scarp as per the recommendation of DRMS and CGS.