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<br /> <br /> <br /> <br />on <br /> <br /> <br /> <br />to <br /> <br />9:41 <br />9:48 AM <br />9:56 AM <br />10:03 <br /> <br />50 <br /> <br />0.045 <br />049 <br />0.033 <br /> <br />14 <br />16 <br />14 <br /> <br /> <br />200 <br /> <br />DISCUSSION <br /> <br />Studies of construction related earthborne vibrations have been performed by numerous <br />organizations worldwide. The most commonly accepted study was performed by the United States <br />Bureau of Mines (USBM). This study related earthborne vibration levels and frequencies to the <br />probability of damage to existing structures. A copy of the USBM Alternative Blasting Level <br />Criteria table which was developed from their research is attached. <br /> <br />Based upon the Bureau of Mines study, the vibration levels recorded in the Shafer pit as a result <br />of the rock crushing activities are below the safe limits of motion for buildings and residential <br />structures, at <br />within the Shafer pit. Vibration levels can be affected by several factors. including primary <br />factors such as the media (soil types or bedrock) through which the waves [ravel. and <br />(2) the rock crushing machinery settings. Therefore, the vibration levels should be expected to <br />vary on a site to site basis. <br />