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<br />MECRMD <br />.?v D MAR 1 1 2010 <br />1 Division of Reclamation, <br />Associates ' nc¦ Mining and Safety <br />R EV EY <br />Gordon F. Revey 8250 E. Morning Star Place <br />Trincipal Parker, CO 80134-5611 <br />Phone: (303) 470-0416 <br />/ Fax: (303) 791-0140 <br />December 2, 2008 ? / Email: grevey@earthlink.net <br />Permit <br />Attention: Mr. Ed Benson, <br />Benson Brothers <br />21240 Austin Rd. <br />Austin, CO 80410 <br />Dear Mr. Benson: <br />,/t4 - 2.OO5- 0-7 ( ?' <br />I have received the letter from the State of Colorado Division of Reclamation, Mining and <br />Safety, dated October 24, 2008, regarding additional information required for full <br />compliance with the terms of your Mining Permit. My responses to the three specific <br />requests follow. <br />1) Instrument conformance to ISEE Standards and Calibration: <br />The instrument used to record vibrations during the site study at the Benson Brothers Red <br />Shale quarry was a Mini-Seis instrument manufactured by White Seismology, Inc. The <br />serial number of this instrument is 932 and a copy of the Calibration certificate for this <br />instrument confirming it was calibrated on June 6, 2008 accompanies this letter. This <br />calibration certificate confirms the instrument was calibrated about one month before the <br />study was performed. Specifications for the Mini-Seis instrument, showing that it is in full <br />conformance with all standards recommended by ISEE are also attached. Randy Wheeler, <br />the president of White Seismology, serves on the Vibration committee of the ISEE - the <br />group that authored the ISEE standards. A copy of the ISEE vibration monitoring standards <br />is also attached. <br />2) Trigger Level: <br />For the measurements made at the Red Shale quarry, the instrument was set up in histogram <br />mode so there was no minimum trigger threshold. Instead, the unit took vibration samples <br />every six seconds and reported the highest value recorded for each minute. The recording <br />range of the unit in this mode is from 0.005 to 2.5 in/s. The frequency measurement range of <br />the Mini-Seis unit is from 2.0 to 500 Hz. <br />3) Clarification of Measurement: <br />In my letter discussing the measurements made by Sara Nation, I mistakenly said the peak <br />o 171 <br />0.08-in/s measurement was less than the 0.011-in/s (0.0187(20) ) value based on the