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Mr. Rod Attebery Neunller & Beardslee September 1, 2011 Page 4 Figure B indicates that ambient noise levels measured at Site 3 varied over the course of the approximately 11 hours of monitoring during the three nights. BAC staff set up and removed the meter at this location on all three nights, and noted that the asphalt plant was in full operation for the entire duration of the monitoring period on these nights. The first column of data in each interval (blue column) represents the measured average noise level for the interval (Leq). This value is important because the San Joaquin County nighttime noise level standard applicable to non-transportation noise sources is 45 dB Leq, The Figure 3 data indicate that the measured ambient levels were at or below 45 dB Ldn during 5 of the intervals (41-45 dB Leq) and slightly above 45 dB Leq during 7 of the intervals (46-47 dB Leq). It is important to note that, in addition to noise generated by the asphalt plant equipment, the measured ambient noise levels recorded at Site 3 also included noise from natural sounds (insects); distant traffic, and distant railroad events. In fact, nighttime noise measurements conducted at this same location in September of 2008 when the asphalt plant was not in operation were measured to exceed 45 dB Leq on several occasions. Therefore, it should not . be concluded that the exceedances of the 45 dB Leq values in Figure B were caused by Munn & Perkins nighttime operations. In addition to Leq, Figure B also includes the median (1-50), background (1-90) and minimum (Linin) values measured during each interval. While the median values were close to the measured average values, the background and minimum values were considerably lower. Specifically, the L90 values, which represent the quietest 10% of the hour, did not exceed 45 during any of the intervals. Because the plant operated 100% of the hour, the plant noise emissions would be included within the L90 value, whereas extraneous sources of noise not attributable to plant operations would not. The conclusion that is reached from the all of the nighttime noise measurement data (both with and without the plant operating), is that the Munn & Perkins asphalt plant generated noise levels were at or below the County's 45 dB Leq noise level standard applicable to non-transportation noise sources, and that the asphalt plant operation was not responsible for the exceedances of the 45 dB Leq standard noted during the most recent (September 2011) BAC noise monitoring % program. Prediction of an-Site Equipment Noise Levels at Nearest Receivers In addition to the monitoring of nighttime ambient noise levels at monitoring Site 3, BAC also modeled asphalt plant noise levels for the entire project area using a state-of-the-art, three- dimensional noise prediction model called SoundPlan Version 7.1. Inputs to the SoundPlan model included the noise source characteristics of the asphalt plant and related plant equipment, including frequency content, intensity, and directionality, as well as the locations of �. the five (5) nearest residences in the immediate plant vicinity, the topographic relief between those residences and the asphalt plant, and intervening ground type. The SoundPlan model results are plotted in the form of noise contours on Figure C. The Figure C contours indicate that the location of the theoretical 45 dB Leq contour (outermost yellow contour) does not extend to any of the existing residences in the project area. The residence represented by R4 on Figure C corresponds to BAC's noise measurement Site 3. At that location, the SoundPlan model results indicate that asphalt plant noise emissions would be