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,113M -D EXISTING SETTING. Noise sources contributing to the existing noise environment of the study area include motor vehicle traffic (cars and agricultural trucks) on Valpico Road, Linne Road, Chrisman Road, and MacArthur Drive. Gravel truck traffic entering and departing the gravel pits southwest of the site, and the Southern Pacific and Western Pacific Railroad lines also contribute to the noise environment. Light plane flights from Tracy Municipal Airport contribute only slightly to background sound levels. Noise emanating from gravel trucks and other large trucks on local roadways and the Western Pacific Railroad line would be considered the major noise sources in the project area. Land uses in the project area which contribute to the noise environment include agricultural uses, residences, gravel pit operations, Tracy Municipal Airport, Tracy Defense Depot, and Jefferson Elementary School. In relation to agricultural uses, orchards require periodic maintenance involving several machines which generate considerable noise. Mechanical pruners, mechanical sprayers, tractors, and trucks are among the commonly used and typically noisy machines in these orchard operations. The Western Pacific Railroad line runs through the study area. There are presently eight daily operations which consist of approximately 50 rail cars each. The existing projected 65 dBA CNEL (Community Noise Equivalent Level Scale) contour in relation to this railroad is located approximately 206 feet from the centerline of the railroad tracks (San Joaquin County Council of Governments, 1986). Sensitive Receptors. Sensitive receptors are defined as land uses where appropriate sound level conditions are needed for full enjoyment and use of the specified location. In the project area, sensitive receptors include residences and Jefferson Elementary School. Applicable Regulations and Guidelines. San Joaquin County Zoning Ordinance 9-3800 limits the sound level at residential property lines to 65 dBA on the Day and Night Average Noise Level (Ldn) scale for areas designated Residential on the General Plan Land Use/Circulation Element map (Baracco, 1987). The San Joaquin County Council of Government's Noise Element designates Linne and Chrisman Roads as critical noise routes and MacArthur Road as a problem noise route. In addition, the Western Pacific Railroad corridor is designated as a problem noise route. Existing Sound Levels. To quantify the existing sound environment, measure- ments where taken in February, 1987. The sound level measurements were performed at three locations on the project site (see Figure 3.7-1). Table 3.7-1 presents the results of the noise monitoring. The results are reported as Leq and Ldn (dBA). Leq is based on the average energy content of the sound during the sample period. The Day/Night Average Noise Level (Ldn) weights noise between 10:00 P.M. and 7:00 A.M. more heavily than other hours to account for the greater annoyance potential of nighttime noise. The Ldn is typically two dBA higher than the peak hour Leq. The instrument used for the noise measurements was a Bruel & Rjaer Precision Integrating Sound Level Meter Type 2230. The instrument continuously averages the varying sound pressure levels over the period of monitoring. Calibration was performed before every set of sampling utilizing a Bruel & Rjaer Calibrator Type 4230. 3.7-1