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South Coast Technology Center Project <br />CEQA Exemption 15183 <br />recognized as a clearly discernable difference. Thus, the Project would result in a significant noise <br />impact if a permanent increase in ambient traffic noise levels of 3.0 dB occurs upon Project <br />implementation and the resulting noise level at the receiving sensitive receptor exceeds the <br />applicable exterior standard at a noise sensitive use. <br />PROJECT -GENERATED NOISE IMPACTS <br />Short -Term Construction Impacts <br />Construction activities generally are temporary and have a short duration, resulting in periodic <br />increases in the ambient noise environment. The Project involves construction activities <br />associated with demolition, grading, building construction, paving, and architectural coating <br />applications. The Project would be constructed over a duration of approximately 16 months. <br />Ground -borne noise and other types of construction -related noise impacts typically occur during <br />the initial grading phase, which has the potential to create the highest levels of noise. Construction <br />equipment produces maximum noise levels when equipment is operating under full power <br />conditions (i.e., the equipment engine at maximum speed). However, equipment used on <br />construction sites typically operates under less than full power conditions, at partial power. <br />Table 4.13-3, Noise Levels Generated Durinq Construction Phases displays the estimated <br />construction noise levels at the nearest sensitive receptors. To present a conservative impact <br />analysis, the estimated noise levels were calculated for a scenario in which all heavy construction <br />equipment were assumed to operate simultaneously. Results from RCNM also assumes a clear <br />line -of -sight and no other machinery or equipment noise that would mask project -related <br />construction noise. The shielding of buildings and other barriers that interrupt line -of -sight <br />conditions would help further reduce noise levels than what is shown in Table 4.13-3. According <br />to the General Noise Assessment methodology prescribed in the FTA Transit Noise and Vibration <br />Impact Assessment Manual, noise can be considered as concentrated at the center of the site. In <br />addition, construction activities would occur across the entire Project Site and therefore the <br />estimated noise levels were calculated from the center of the Project Site. The geographic center <br />of the Project Site is approximately 625 feet from the closest sensitive receptor (institutional use) <br />to the east and approximately 1,000 feet from the nearest residential uses to the south. <br />Table 4.13-3 <br />Noise Levels Generated During Construction Phases <br />Estimated Exterior Construction <br />Estimated Exterior Construction Noise <br />Noise Level at 625 feet <br />Level at 1,000 feet <br />Phase <br />(Center of Project Site) <br />(Center of Project Site) <br />dba LQ ' <br />dba LQ <br />Demolition <br />64.5 <br />60.4 <br />Grading <br />66.3 <br />62.2 <br />Building Construction <br />64.3 <br />60.3 <br />Paving <br />59.7 <br />55.6 <br />Architectural Coating <br />51.8 <br />47.7 <br />Notes: <br />1. These noise levels conservatively assume the simultaneous operation of all heavy construction equipment at the same precise <br />location. Modeled heavy construction equipment includes concrete saws, excavators, and dozers during demolition phase, <br />grader, dozers, and backhoes during the grading phase, forklifts, generator, crane, welders, and backhoes during the building <br />construction phase, pavers, paving equipment, rollers, and backhoes during the paving phase, and air compressor during the <br />architectural coating phase. <br />Source: Federal Highway Administration, Roadway Construction Noise Model (RCNM), 2006. <br />July 2024 Page 80 <br />