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The Table 1 data indicate that processing area noise levels are anticipated to satisfy the project standards of significance at the nearest residences during daytime hours, except at N5, even with all processing area equipment operating concurrently. However, the Table 1 data also indicates that processing area equipment noise could exceed the nighttime standards at some locations with _ various combinations of processing equipment operating. Without mitigation,this would constitute a significant noise impact. Specific noise mitigation measures for processing area equipment are provided in a subsequent section of this report. — Mining Noise The mining areas are broken into three distinct regions of the site, as illustrated in Figure 2-7 of the ADEIR (Mining Activities Concept Plan). Equipment to be used in the mining operations will _ depend on whether the mining is conducted wet or dry. Regardless, the worst case noise generation associated with mining operations would occur during initial excavation prior to the equipment being depressed within the pits. Because wet pit mining would only occur once a — substantial depth has been reached in the pit,such equipment would be substantially shielded from view of existing residences by the pit walls. As a result, this analysis of noise impacts focuses on dry pit mining equipment operating at existing grades. The noise generation of the dry pit mining equipment and the duration of an hour these sources _ are likely to operate is provided in Table 3.J-6 of the ADEIR. It should be noted that the combined noise levels associated with the various types of mining equipment reported in Table 3.J-6 of the ADEIR equate to an average level of 89 dB Leq at a reference distance of 50 feet. BAC noise level data for similar sized mining activities (Teichert Vernalis BAC #2005-500, RMC Moosios Quarry BAC #2005-521, Teichert Marysville BAC #2005-600), indicate that mining activities typically generate noise levels ranging from 75-80 dB Leq at a reference distance of 50 feet. Given the comparatively small size of this proposed mining project, BAC believes that an average level of 80 dB Leq at 50 feet would more closely represent the noise generation of this portion of the project, _ rather than the ADEIR level of 89 dB Leq. BAC computed the noise from the mining equipment at the nearest residences using a combined — mining equipment reference level of 80 dB Leq at 50 feet with the industry-standard approach of assuming a 6 dB decrease in noise for each doubling of distance from the noise source, with an additional offset of -1.5 dB per thousand feet to account for atmospheric and excess ground — attenuation. In addition, a -5 dB offset was applied to the mining levels to account for shielding provided by the proposed berms (10 feet) and existing canal embankment (15 feet). Following _ removal of overburden, the shielding provided by these barriers will be even greater. The results of the BAC computations for the mining areas are provided in Table 2, along with the — applicable Leq noise standards. It should be noted that the Table 2 data are based on worst-case distances between mining sources and receivers, irrespective of whether the equipment is in the north or south pits, and of stage. — Page -4-