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SEP-O7-2006 05:15PM FROM-DIV RECLAMA*~nN MINING 8 SAFETY 3038328102 T-10g P.004/005 F-2B5 characteristics of the actual quarry site in the Cameo member of the Mesaverde Group. The illogical nature of this claim, and the lack of technical accuracy in the report cast serious doubt on the objectivity of Mr. Revey's study, and his qualifications with regazd to rockfall risk analysis. In his testimony under oath at the MLRB hearing, Mr. Revey stated that he had "trained under Dr. Houk" who is an acknowledged world expert in rockfall hazards, and a source I quoted in my testimony at the hearing. Follow-ug oa Mr. Revey's claim revealed that Ih. Houk has no knowledge of Mr. Revey (personal communication). Mr. Revey also claimed in his testimony to have consulted with the "principals" of SubTerra engineering, aworld-wide consulting firm, regarding the Benson Quany, and had been advised by them that rockfall risk analysis would be a "bloody waste of time". Follow-up failed to uncover anyone with that firm who knows Mr. Revey, let alone gave a professional opinion regazding rockfall risk analysis at the Benson site. T therefore have serious concerns regarding the professional integrity of Mr. Revey and his motives. I request that the MLRB require Mr. Revey to provide documentation of these claims made under oath, as they likely had significant weight in the decision of the Board. In my opinion, Mr. Revey is more concerned with getting the Henson permit approved for his client than with obtaining objective scientific evidence regarding the risk of rockfall on properties below Ure Rollins cliff. I do not feel an objective and professional analysis of rockfall hazard can be made under these circumstances, and do not consider Mr. Revey qualified to design or conduct a meaningful monitoring program. In my opinion, there are a number of critical questiontthat the monitoring program should be designed to evaluate. Mr. Sorensen ofthe DMG staff acknowledged at the MLRB hearing that natural resonances in rock layers can produce greatly amplified vibrations. These resonances ere site-specific, and in my opinion, can play an important role in triggering rockfalls. I therefore encourage the DMG staff to design monitoring at the site to look for potential resonance phenomena. Since vibration levels az the cliffface are of critical importance, monitoring of seismic energy transmitted to the sandstone by activity inclose proximity would be important. It is also important to evaluate the seismic energy produced by ripping of the hard sandstone stringers within the baked shale. Some of these are found on top of the south ridge overlooking the cliffs, and would provide the greatest potential for triggering rockfalls, since they can act as waveguides and support standing waves or mechanical flexure waves that attenuate slowly with distance from the source. White not directly related to vibrations, another critical question is the impact that water filled fractures could have on rockfall risk. Exposure of broken bedrock to precipitation doting excavation of the south ridgeline allows direct infiltration of water into joinu that dip toward the cliff face. Although this was downplayed by the DMG staff at the hearing, without any evidence to support their position, this hydraulic pressure is widely recognized as a significant factor in triggering rockfalls. Since removal of 50 feet of elevation from the south ridge during the mining operation will greatly enhance water infiltration, this must be accounted for in any rockfall hazard analysis. The current mining plan indicates that the south ridgeline will not be mined for years. It should be apparent that as the minim operation proceeds from north t0 south, the character of vibrations and water infiltration, and the proximity to the cliffs will change over time. If monitoring only takes place within the first 30 days of operarion, no meaningful estimate