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4.8 Noise ■ Noise sources associated with the maintenance of real property, provided said activities take place between 7:00 A.M. and 8:00 P.M. on any day except Sunday or a federal holiday, or between the hours of 9:00 A.M. and 8:00 P.M. on Sunday or a federal holiday ■ Any activity to the extent regulation thereof has been preempted by state or federal law Under Section 18-314(e) of the Municipal Code, construction activity noise sources are exempt from the Noise Ordinance standards so long that the activities do not take place between the hours of 8:00 P.m. and 7:00 A.M. on weekdays, including Saturday, or at any time on Sunday or a federal holiday. 4.8.3 Project Impacts and Mitigation Analytic Method Implementation of the proposed project could result in the introduction of noise levels that may exceed permitted City noise levels. The primary sources of noise associated with the proposed project would be construction activities within the Transit Zoning Code (SD 84A and SD 84B) area and project -related traffic volumes associated with operation of those projects. Secondary sources of noise would include new stationary sources (such as heating, ventilation, and air conditioning units) and increased human activity throughout the Transit Zoning Code (SD 84A and SD 84B) area. In addition, land use allowed under the Transit Zoning Code (SD 84A and SD 84B) could be affected by noise generated by existing rail operations along the AT&SF tracks, which run through the eastern portion of the Transit Zoning Code (SD 84A and SD 8413) area. The net increase in noise levels generated by these activities and other sources have been quantitatively estimated and compared to the applicable noise standards and thresholds of significance. Aside from noise levels, groundborne vibration would also be generated during the construction phase of the proposed projects within the Transit Zoning Code (SD 84A and SD 8413) area by various types of construction equipment. In addition, land uses allowed under the Transit Zoning Code (SD 84A and SD 8413) could be affected by groundborne vibration generated by existing rail operations along the AT&SF tracks. Thus, the groundborne vibration levels generated by construction equipment have also been quantitatively estimated and compared to applicable thresholds of significance. Construction Noise Levels Construction noise levels were estimated by data published by the U.S. Environmental Protection Agency (U.S. EPA). Potential noise levels are identified for on- and off -site locations that are sensitive to noise, including residences and schools. The EPA has compiled data regarding the noise -generating characteristics of typical construction activities. These noise levels would diminish rapidly with distance from the construction site, at a rate of approximately 6 dBA per doubling of distance. For example, a noise level of 86 dBA measured at 50 feet from the noise source to the receptor would reduce to 80 dBA at 100 feet from the source to the receptor, and reduce by another 6 dBA to 74 dBA at 200 feet from the source to the receptor. City of Santa Ana Transit Zoning Code (SD 84A and SD 848) EIR 4.8-17