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III. Environmental Setting, P g Impacts,and Mitigations H. Noise vehicle traffic, noise decreases by about 3.0 to 4.5 dBA for every doubling of the distance from the roadway. For point or stationary noise sources,such as electric motors,a noise reduction of 6.0 to 9.0 dBA is experienced for each doubling of the distance from the source. The amount of noise attenuation(reduction)depends to a large extent on the sound absorptive characteristics of the intervening terrain. Soft earth with vegetative cover provides a 4.5 dBA attenuation with distance,while hard exposed surfaces provide a noise attenuation of only 3.0 dBA. Noise barriers or shielding devices that break the line of sight between the source and the receptor would generally provide a noise attenuation of about 5-10 dBA. Noise Regulations,Plans.and Policies The project site is under the jurisdiction of the City of Stockton and San Joaquin County, and the relevant planning documents are the Noise Elements of the City of Stockton and San Joaquin County. The land use/noise compatibility guidelines developed by the City of Stockton are shown in Figure III.H.2. According to the San Joaquin County Noise Element,the normally acceptable exterior noise level for residential developments is 65 dBA,Ldn,or less;and 60 dBA, Ldn,or less for schools and hospitals (San Joaquin County, 1992). The two Noise Elements provide general goals and policies designed to protect the public from excessive noise exposure and to prevent incompatible land uses near noisy environments. The City of Stockton has set performance standards for stationary noise sources(City of Stockton, 1990). For locally-regulated noise sources,the hourly exterior noise level standards are 55 dBA,Leq from 7:00 a.m.to 10:00 p.m., and 45 dBA,Leq,from 10:00 p.m. to 7:00 a.m, while the maximum noise level standards are 75 dBA,Lmax=from 7:00 a.m. to 10:00 p.m.,and 65 dBA,Lmax from 10:00 p.m. to 1:00 am (City of Stockton, 1990). Policy 4 of the San Joaquin County Noise Element states that"development shall be planned and designed to minimize noise impacts on neighboring noise sensitive areas and to minimize noise interference from outside noise sources." The City of Stockton does not have any noise ordinance(Heminger, 1993). San Joaquin County has a noise ordinance in place. Section 9-3800,Chapter 16 of the San Joaquin County Code specifies noise limits for industrial activities. According to the noise ordinance, no sound level shall exceed 65 dBA,Ldn,at the property line of properties that abut residential areas. III.H.3