Agenda - 10-06-1981 - Laserfiche WebLink

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- � � ��684� w 7, � Page 4 ~ Structure Response (7t\ 3.0 psi Structures damaged 0.75 - 1.0 psi Most windows break 0.1 psi (1521/2 d8Y Some poorly unted windows break Fairly recent investigationt into the effects of airborne waves have cited or postulated instances of damage at levels slightly above 0-02 psi or 1401/2 dB. The writer knows of no reports of damage below this level. The regulations recently promulgated by the Office of Surface Mining governing surface coal mining operations specify that the airblast at buildings in the vicinity shall not exceed 0.0092 psi or 130 dB, as measured with the monitoring systems commercially available. This represents a restriction on atmospheric overpressures that is less than one-third of levels below which no damage has ever been reported. While considered too restrictive in some circles, the limit is federally sponsored and will gain credibility in lay circles as a result. Accordingly, we see no alternative but to offer the following recommendation: The peak atmospheric overpressure produced by blasting operations, as measured outside and adjacent to the nearest . residential , commercial, or industrial structure not on �� - quarry property, shall be limited to 0'0092 psi or 130 dB- \�� This measurement shall be obtained with a measuring system that has a flat response (±3 dB) at frequencies of 6 Hz, or lower. To lend perspective to the quantities ntities specffied above, we have measured over- pressures generated by nearby electr i cal storms o f more 135 dB or 0.016 psi. sf , This is a level approximately seventy percent (70%) higher than is permitted by the federal regulations. Stes4y-state vibrations will be generated by the production equipment and machinery at a quarry. The human body is very sensitive to steady-state motion; particle velocities as low as 0'04 or 0.05 inch per second are perceptible. Accordingly, the following limitation on steady-state ground motion is proposed: Steady-state vibrations (continuous earth-borne oscillations) caused at the nearest publicly or privately owned building not on quarry property bxproductjun equipment operatinQ at a quarry shall npt prodbce'� �� partiole velocity 1s'excess. of' -` ' 0.03 inch per second on any component of motion, longitudinal, transverse, or vertical, as measured with a three-component portable seismograph on the ground adjacent to said structure. From a practical standpoint, restrictions in this area are probably superfluous. The ground motion produced by the operation of quarry equipment or machinery cpzr,„ �I has never, in our experienze, bean percept1ble beyond plant prnperty 7imes^ ��* -.."