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pD~~ 2~s~-~ r ~! f D I <br />UedKoR Dro~r2~S~~ S~`~~2.P11~/ <br />t~~~: REVEY Associates, Inc ~ <br />~~. - <br />Gordon F. Revey R• 8250 E. Morning Star Place <br />Principal ~~@~@O Parker, CO 80134-5611 <br />APR 1 9 2006 ~ Fa°n~so3j X91-0i 0416 <br />April 19, 2006 Gfend Junction Field Office Email: grevey@earthlinknet <br />Division of Miaerels & Geology <br />RE: Response to Concerns Re ag rding the Sesimic Stability of the Rollins Sandstone Bluffs <br />Adjacent to Proposed Red Shale Quarry in Delta County, CO <br />Tai Attention: Messrs. Ed Benson~Benson Brothers and Michael Ripp, MVR ResourcesJ~ <br />Gentlemen: <br />I have reviewed the comments and calculations provided in letters by Mr. Gregory D. <br />Lazear dated April 11, 2006 and April 13, 2006, and a letter from Mr. Robert Flinn, dated <br />April 10, 2006. <br />My specific responses to concerns and calculations expressed in the subject letters follow. <br />Robert Flinn Letter -April 10, 2006: <br />Rangeland Description: Description of the immediate quarry site as rangeland is accurate <br />because it is currently undeveloped land with no improvements. Adjacent property with <br />residential buildings is not par[ of the proposed acreage defined in the mining permit <br />application. <br />In-Situ Rock Properties: All of the vibration measurements made at the Austin Quarry were <br />done on hard-packed ground. The author is very confident that vibration testing done <br />through overburden covering rock at the proposed quarry site would generate more <br />favorable curves due to increased attenuation of vibration energy passing through <br />unconsolidated soils. Since the testing was done on compacted ground resembling how the <br />ground surface would be at the proposed quarry site during active mining, analyses made <br />from the data from the Austin Quarry site are appropriate and cautious. While elastic rock <br />properties, density and other physical rock characteristics do influence the transmission of <br />vibration waves and resulting particle motions, densities are rarely measured when <br />developing vibration attenuation curves. For this case, the significance of increased vibration <br />intensity predictions from curves derived from testing done on compacted ground would far <br />outweigh any potential site differences caused by variations in rock densities and other <br />physical characteristics. <br />ISEE Monitoring Standards Page <br />