2008-08-20_REPORT - M2005071

• Permit No: M2005071
• IBM Index Class Name: REPORT
• Doc Date: 8/20/2008
• Doc Name: Ground vibratons at Benson Brothers Red Shale Quarry
• From: REVEY Associates, Inc.
• To: DRMS
• Email Name: THM
• Media Type: D
• Archive: No

/91 - ?00?7_ 07 RECEIVED
1 a 12 AUG 2 0 2008 1--
GRAND JUNCTION FIELD OFFICE
DIVISION OF
FR EVEY Associates, ' nc¦ RECLAMATION MINING & SAFETY
Gordon F. Revey 8250 E. Morning Star Place
Principal SEP 17 200 Parker, CO 80134-5611
Phone: [phone]
Division of Reclamation, Fax: [phone]
August 8, 2008 Mining and Safety
Email: [e-mail]
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Attention: Messrs. Ed Benson, Benson Brothers and Michael Ripp, MVR Resources.
Gentlemen:
I have reviewed the baseline vibration measurements that Sara Nation of PreSeisTek, Inc.
made under my direction at the Red Shale Quarry.
As expected, the results indicate that the intensities of ground motions created by excavator,
dozers and operating crushers are not measureable at the rock bluff above the Croissant and
other area property.
At the measurement locations at the edge of the bluff (Locations 4 and 5), Levels of
recorded ground motion and air-overpressure (noise) were all below the trigger threshold
levels of the recording instruments; which are 0.01 in/s for ground motion and 106 dB (2-Hz
Linear Scale) for air-overpressure or noise.
In my report prepared in February 2006, PPV curves based on measurements of vibrations
from equipment operating at another Benson Brothers site indicated that the Dozers would
likely create the greatest ground vibrations. In the recent testing at the Red Shale Quarry
site, the peak ground motion caused by the D9 Dozer, at a distance of 20 feet was 0.08 in/s.
This value is less that the peak predicted value of 0.011 in/s (0.0187(20)-0178).
There are no surprises in these measurements and I am confident that ground vibrations
caused by future mining operations will have no impact of any kind on the stability of the
existing rock bluff.
Respectfully submitted,

Gordon Revey