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4.4 NOISE ENVIRONMENTAL SETTING Existing Noise Environment The proposed project site and vicinity was visited on October 29, 1991. The lands around the project area are currently used for grazing and grape growing. The only noise sensitive uses in the area are two residences along Forest Lake Road. The residences have large setbacks from the road. Forest Lake Road is not a through road and traffic on Forest Lake Road was very sporadic during the site visit. Three 10-minute measurements were conducted to quantify existing noise levels on the site. The project area and its immediate vicinity are currently exposed to low noise levels due to lack of any significant noise sources. The only observed significant noise events were occasional aircraft overflights and sporadic vehicle passbys on Forest Lake Road. All of the measurements were conducted with Larson-Davis Laboratories Model LDL-700 integrating sound level meters equipped with Bruel&Kjaer type 4176 pre-polarized condenser microphones. These meters meet the electric frequency response criteria of the American National Institute Standard S 1.4 for Type I (precision)sound level meters. The meter was calibrated before and after each measurement. The measurement locations are shown in Figure 4.4-1. The first 10-minute measurement (Location 1 ) was conducted at a distance of 50 feet from Forest Lake Road. During the measurement, there was no traffic on Forest Lake Road. Two jet aircraft overflights at high altitude were the only significant noise events during this measurements. The Lw was 41 dB. The median noise level (L50) was 40 dB background noise level (L,) was 38 dB. The results are shown in Table 4.4-1. (Appendix C contains a discussion of acoustical terms and methodology.) The second 10-minute measurement (Location 2)was made on the site 200 feet from Forest Lake Road. Noise levels recorded at this location represent the exposure of the majority of the site. The L, was 40 dB, the median noise level was 40 dB and the background noise level was 39 dB. The sounds of birds and the motion of leaves in the wind were the significant noise generators. The last measurement (Location 3) was conducted at the southern end of the property, adjacent to the Mokelumne River. The Lu,was 32 dB, the median noise level was 30 dB and the background noise level was 28 dB. Noise levels were low due to the lack of activity within most of the project area and its immediate vicinity. 4.4-1