2008-10-07_GENERAL DOCUMENTS - M2005071 (2)

Home Browse Search

October 3, 2008 From: Greg Lazear 20508 Brimstone Rd. Cedaredge, Colorado 81413 (970) 856-6810 To: Mr. Steve Shuey Division of Minerals and Geology Grand Junction Field Office 101 S. 3`d Street, Room 301 Grand Junction, Colorado 81501 Mr. Tyson Powell Assistant Attorney General Business and Licensing Section Office of the Attorney General 1525 Sherman Street, 5th Floor Denver, Colorado 80203 Dear Mr. Shuey and Mr. Powell, OCT 0 7 2008 GRAND JL!N, ; I. F! L -D OFFICE DIVISION Gr RECLAMATION €b?IIli fi r- ? SAFETY 1!1, 7 LOOO .G;nation, S? ?v?1 /? l/1 'ts O ''t v r c4- o /7 Thank you for the copy of the most recent report by Revey Associates, Inc. From the brevity of the comments by Mr. Revey and the lack of any analysis by the Division of Minerals and Geology (DMG) it appears that this was just a token study to satisfy the stipulations on the permit for the Benson Brothers quarry. Unless someone looked past Mr. Revey's comments that implied the measured amplitudes at the quarry were even smaller than expected, the actual major change in vibration amplitudes probably went unnoticed by the DMG staff. As far as I can determine from the very minimal documentation, this data verifies several points I made at the Mined Land Reclamation Board (MLRB) hearing in May of 2006. The new study shows that vibration amplitudes at the actual quarry site are more than 10 to 34 times higher (0.1 to 0.34 in/s) than those measured in Mancos shale due to the much stronger sandstone bedrock. This data disproves Mr. Revey's claim that the amplitudes at the Austin site were representative of what would be measured at the quarry. It also verified my testimony to the MLRB that amplitudes at the actual quarry would likely be an order of magnitude greater than those Mr. Revey measured in Austin. The sensitivity of the instruments was cut in half for the latest study from a threshold trigger of 0.005 in/s in the first study to 0.01 in/s in the recent one. If this setting had been used in the first study no data would have been recorded at all since the maximum vibration level measured in the Mancos shale was less than 0.01 in/s. Mr. Revey's erroneous assumption resulted from failing to use a conversion factor to correct ground motions for the difference in material properties between the two sites. In spite of the much larger amplitudes in the recent study Mr. Revey seems to imply that they were in fact lower than what was predicted from measurements at the Austin site. In his one page