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The CTL report does not discuss any instrumentation or monitoring programs. It is not clear how long the 1993 landslide was monitored, what data was collected, or what that data revealed. Additionally, it is not clear whether any groundwater-level monitoring has been done at the site, and if so, what the data reveal. The analysis model is simplistic and does not fully represent all of the conditions present that may contribute to the slide. Bedding planes, rock-mass quality, extent of shear zones (CTL states the fault zone may be 1500-6000 feet wide), fault gauge, clay seams, and effects of the spoils were not taken into account in the model. For an adequate level of detail required to develop a mitigation strategy, a much more detailed analysis is required. The CTL report does not give detail as to how the strength parameters used in the analysis were derived, other than they were "estimated and back-calculated." It is not clear what assumed geologic conditions were used for these calculations. Some of the properties used do not reflect typical ranges for materials that CGS would expect to see, for example Wylie & Norrish (1996) show strength parameters for limestone with clay infillings to be in the 12-17° friction angle range, and cohesions between 1700-2400 psf. The CTL values may be representative, but without detail as to how they were derived, it is difficult to evaluate. Comments on CTL Conclusions and Recommendations: As stated above, a forensic stability evaluation was not done as part of the CTL report. The CTL report only evaluated the stability of the existing rubble zone of the rockslide. The analysis did not address future slope failures in the adjacent headwall blocks or rockfall that may impact future activities at the quarry. To fully understand the potential factors leading to the slide, the stability analysis should evaluate all the potential factors (slope geometry, buttressing effects, loading of spoils, rock-mass conditions, effects from blasting, groundwater, etc). CTL's conclusions are all qualified with rather nebulous terms and do not give a very confident or precise determination as to the cause of the slide, the ongoing hazards present at the quarry (particularly the headwall or upper block area), or mitigation strategies. CGS disagrees that the landslide was solely triggered by high groundwater levels (refer to the discussion above). As such, the material properties used by CTL are closer to, or lower than, those stated for the "Lower" groundwater level. Without detailed rock core information, the actual properties are merely a guess. It remains the conclusion of the CGS that the most likely factor that contributed to the slope failure was the continued excavation and lowering of Area H, which further daylighted the formation bedding dip slope along the base of the 1'/4:1 quarry wall slope. The CTL conclusion that the base of the slide may have moved along an unidentified clay seam is conjecture only as there has been no evidence of a clay seam provided. The mine permit indicates that the clay seam that was discussed as a possible slide surface for previous slides had been removed prior to 2000. CGS disagrees that the cliff portion of the southern scarp above the rockslide could be blasted with explosives set into the upper scarp features. While rubblizing the cliff portion of the scarp face to fall onto the existing rockslide rubble below would create a safer overall condition, we don't see a practical construction method that would allow the safe drilling of the pattern of blast 4