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4.5 Noise V The effect of mining noise on nearby sensitive receptors would depend on multiple variables, including the distance to nearby sensitive receptors, whether a direct line of site exists between the noise source and receptors, mining depth,the rate of noise attenuation, and the existing ambient sound levels at sensitive receptors. Mining activities would reach an average depth of ` 100 feet below the existing ground surface. When mining activities take place close to the surface, noise levels would have a greater potential to impact nearby residences; as the mined pit becomes deeper, noise levels would drop off since there would be no clear line of sight between the source and the receptor. Similarly, mining noise would be less noticeable at sensitive receptors if a wall or berm impedes its line of sight to the noise source. Mining noise would be ` more noticeable during nighttime hours when ambient noise levels are typically quieter. Mining noise could result in increased noise levels at the locations of three separate nearby ` residences.The two residences located adjacent to the northeast side of the site(residences R4 and R5 along the south side of Blewett Road) would he most affected by mining noise generated at the northeast corner of Phase IV(see Figure 4.5-3). A berm has not been proposed by the V applicant along the eastern boundary of Phase IV. Assuming mining activity would generate noise levels as high as 91 dBA L,q at a distance of 50 feet and a worst-case noise attenuation rate of 6 dBA for every doubling of distance, noise levels from mining operations located only 200 feet from the residence would attenuate to 79 dBA L,q As shown in Table 4.5-2,existing daytime noise levels at this residence are 58 dBA L.on weekdays and 46 dBA L,q on Saturdays, and existing nighttime noise levels are 48 dBA L.,or or less on both weekdays and weekends. 6— Because the resultant noise level from excavation activity is considerably higher than existing ambient daytime and nighttime levels,the increase would be a significant impact. Three other residences on the north side of Blewett Road to the northeast(residences R6, R7, and R8) could ` also be affected. These residences, which are located about 1,200 to 1,500 feet from the mining equipment, would experience noise levels with the project of approximately 61 to 63 dBA L At r each of the residences R4-R8,the increases in noise levels with the project mining activities would be significant because the increases would exceed existing noise levels by more than 3 dBA and the noise levels from the stationary sources would exceed the daytime L,noise daytime standard(50 dBA)and the L q nighttime standard(45 dBA) in the San Joaquin County Development Title. Figure 4.5-3 shows the projected future noise contours at these residences during operation of the portable plant site and mining in the northeast comer of the site. The most northerly residence located west of the project site(residence R3)and across the Delta- Mendota Canal (see Figure 4.5-4) would be most affected by the noise of mining activity on the r west side of Phases III and V. Existing noise levels at this residence are 52 to 54 dBA L,q during the daytime and 51-52 dBA L,q at night,as shown by Measurement B in Table 4.5-2, and a berm has not been proposed by the applicant along the west sides of Phases III and V. Mining noise, generated as close as 500 feet away, would attenuate to 71 dBA L.at the property line of the residence(see Figure 4.5-4). At this residence, project noise would be a significant impact because mining activities would increase noise levels by more than 3 dBA and the resulting noise ` levels from project stationary sources would exceed the daytime L,q noise daytime standard (50 dBA)and the L.nighttime standard(45 dBA) in the San Joaquin County Development Title. RMQ Pacific Vernalis Quarry Mining and Reclamation Project 4.5-15 ESA/203015 Draft Environmental Impact Report May 2006