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<br /> <br /> <br />1_~ <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />1 <br />t <br /> <br />1 <br /> <br /> <br /> <br />I~ <br />ngineering <br />Mr. Jim Barrett ~ <br />February 13, 1995 dynamics <br />Page 6 of 10 <br />7.1 Miniag Oparatioas <br />Calculated sound pressure levels for the residences closest to the <br />quarry are given in Table 7. Residence locations are shown on <br />Figure 1. These values were calculated with no abatement affects, <br />including those present due to topography, and include only the <br />highest values. Consequently, the values represent a worst case <br />scenario likely to occur only during the Bite preparation stage <br />and for a short period of time. The most invasive noise level, <br />that of a Front End Loader with Back-Up Beeper, was used, based on <br />the assumption that stationary equipment noise ie easier to abate. <br />Table 7: Projected Noise Levels at Closest Residences <br />Residence Distance Operation Phase SPL dB (A1 <br />A2 2500' Aggregate VII, north 48.4 <br />R3 2400' Cut Stone I 48.8 <br />R3 2000' Cut Stone Processing 50.4 <br />Area <br />R4 4500' Cut Stone I 43.4 <br />These numbers all fall within the limits given earlier in Section <br />4.2 of this report. <br />7.2 Haul Truck Operations <br />Projected haul truck volume is 20 to 24 vehicles per day, a low <br />volume compared to many quarry operations. The proposed route and <br />selected residences are shown in Figure 1. Haul trucks create a <br />moving noise contour which, from the view point of the stationary <br />observer, rises from ambient noise levels, briefly reaches a peak <br />value, and falls back to ambient noise levels. Calculations of <br />peak haul truck noise levels for a 25 ton truck, traveling at 30 <br />mph, are given in Table 6. The State Standard is based on 86 dB <br />at 50 feet and projected out to the receivers' locations. <br />Residences 3, 5, and 6 were selected due to proximity. <br />Table 6: Noise Level Comparison, EPA Standard and Projected <br />Residence State Standard dB(A1 Proiected SPL dB (A) <br />A3 55.9 49.3 <br />R5 70.1 63.2 <br />R6 66.0 59.1 <br />These values fall below the State standards without correcting for <br />topographical and atmospheric abatement. In addition, the <br />existing Ditmar Quarry requires a 15 mph speed limit on the access <br />road (as dictated by the State of Colorado Department of Health. <br />