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• <br /> ( 1075-970) 105 feet . Therefore a buffer of ( 105/125 ( 200 ) = ) 168 feet <br /> should separate the edge of the landfill and the quarry wall . Mid way <br /> along the western wall of the quarry the cut will be ( 1055-970) 85 <br /> feet deep . Therefore a buffer of only ( 85/ 125 ( 200 ) = ) 136 feet would <br /> be needed . These buffer zone calculations could be modified with <br /> changes in the location of the quarry boundaries . The minimum buffer <br /> distance should be 136 feet . <br /> To protect against blast vibration induced cracking , the <br /> resultant particle velocity should be limited to 3 . 5 inches per second <br /> at the edge of the land fill nearest the blast . This ground motion <br /> should be monitored with a portable blasting seismograph . Even though <br /> the direct experimental measurements showed that there was no effect <br /> for the 3 . 34 ips blast , it could very well have been the 5 . 54 ips <br /> blast or the stress relief that was responsible for the observed <br /> change in hydraulic conductivity . Thus the 3 . 50 level is conservative . <br /> With the 3 . 5 ips velocity limit , the attached figure from <br /> Dowding ( 1985 ) may be employed to estimate the size of the charge that <br /> can be detonated per delay . Entering the figure at 3 . 5 ips on the <br /> vertical axis , and intersecting the 95% confidence line , the critical <br /> scaled distance (D/W ) is found to be 14 . Thus at 136 feet the maximum <br /> charge per delay that could be employed would be ( 136/ 14 ) squared or <br /> 94 lbs per delay . This charge size per delay would be greater for <br /> shots detonated further from the landfill . <br /> These recommendations should not be construed as supplanting <br /> other more restrictive constraints for safe blasting . <br />