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South Coast Technology Center Project <br />CEQA Exemption 15183 <br />Based on the above, the Project's operational mobile and stationary source impacts would be <br />less than significant and would be less than the impacts disclosed in the GPU PEIR, which <br />concluded that traffic noise impacts during operation would be significant and unavoidable, and <br />no feasible or practical mitigation are available to reduce traffic noise impacts. <br />Summary of Project -Generated Noise Impacts <br />Based on the above, the Project's construction and operational noise impacts would be less than <br />significant. The Project would not result in new or substantially more severe impacts compared <br />to the determinations of the GPU PEIR, which concluded that the Project's construction and <br />operational noise impacts would be significant and unavoidable. Therefore, no new project - <br />specific mitigation measures are required. <br />PROJECT -GENERATED VIBRATION IMPACTS <br />Short -Term Construction Vibration Impacts <br />Project construction activities have the potential to generate ground -borne vibration and result in <br />construction vibration impacts that include human annoyance and building damage. Human <br />annoyance occurs when construction vibration rises significantly above the threshold of human <br />perception for extended periods of time. The vibration level at which human annoyance is <br />perceived is 0.2 inch per second PPV. Building damage can be cosmetic or structural. Ordinary <br />buildings that are not particularly fragile would not experience any cosmetic damage (e.g., plaster <br />cracks) at distances beyond 25 feet from most construction vibration sources. This distance can <br />vary substantially depending on the soil composition and underground geological layer between <br />the vibration source and the receiver. In addition, not all buildings respond similarly to vibration <br />generated by construction equipment. The FTA architectural damage criterion for continuous <br />vibrations of 0.3 in/sec PPV for engineered concrete and masonry (refer to Table 4.13-2) is used <br />because the closest structures to the Project Site are institutional use buildings. The nearest <br />sensitive receptor building is located approximately 225 feet to the east of the Project construction <br />activities. As such, vibration impacts are analyzed at 225 feet to evaluate the architectural building <br />damage criterion. Groundborne vibration decreases rapidly with distance. As a result, vibration <br />velocities from the construction equipment would be barely perceptible at this distance. Typical <br />vibration produced by construction equipment is illustrated in Table 4.13-5, Typical Vibration <br />Levels for Construction Equipment. <br />Table 4.13-5 <br />Typical Vibration Levels for Construction Equipment <br />Approximate peak particle <br />Approximate peak particle <br />Equipment <br />velocity at 25 feet inch/sec <br />velocity at 225 feet inch/sec 1 <br />Large bulldozer <br />0.089 <br />0.0033 <br />Loaded trucks <br />0.076 <br />0.0028 <br />Small bulldozer <br />0.003 <br />0.0001 <br />Notes: <br />1. Calculated using the following formula: <br />PPV equip = PPV ref X (25/D)1' <br />where: PPV equip = the peak particle velocity in in/sec of the equipment adjusted for the distance <br />PPV er = the reference vibration level in in/sec from Table 7-4 of the FTA Transit Noise and Vibration Impact <br />Assessment Guidelines <br />D = the distance from the equipment to the receiver <br />Source: Federal Transit Administration, Transit Noise and Vibration Impact Assessment Guidelines, September 2018. <br />July 2024 Page 83 <br />