Item 28 - Public Hearing - ZOA No. 20204-01 South Coast Technology Center

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South Coast Technology Center Project CEQA Exemption 15183 proposed on -site stationary sources. Operational noise levels are analyzed at the surrounding nearest sensitive receptors to the east and south. The Project would install 14 rooftop HVAC units on each warehouse building. Typically, mechanical equipment, such as HVAC units, generate noise levels of 60 dBA (or 84 dBA in sound power level (L,,))34 at 20 feet from the source.35 Typical noise associated with loading dock activities would include noise from lift gate operation, backup alarms, load drops, forklifts/pallet jacks, and personnel. Loading dock activity would occur at the western side of Building 1 and the southern side of Building 2 and Building 3. Loading dock activities can typically generate a maximum noise level of approximately 80 dBA in L,N per meter. Another major noise source from a warehousing facility is from slow -moving trucks. According to the proposed truck routes, slow - moving truck activities would occur at the western side of Building 1 and the southern side of Building 2 and Building 3. Slow -moving trucks can typically generate a maximum noise level of approximately 62 dBA in LW per square meter. Table 4.13-4, Operational Noise Levels, shows the combined long-term operational noise levels from all noise sources occurring simultaneously at the surrounding sensitive receptors. Table 4.13-4 Operational Noise Levels Estimated Project Generated Noise Level Criteria Noise Levels Receptor Land Use Operational Noise Level (dba Leq)2 Exceeds dba Leg)' (Daytime/Nighttime) Standards? Residential Uses to the East 35.2 55/50 No Residential Uses to the South 38.8 55/50 No Institutional Building to the East 40.7 55/50 No School Playground to the Southeast 39.5 55/50 No Notes: 1. Operational noise levels conservatively assume the simultaneous operation of all operational activities at the same time. 2. Noise level criteria are based on the SAMC Section 18.312. For informational purposes, noise level criteria for residential uses in the Costa Mesa Municipal Code Chapter 8 are also 55 dBA for daytime (7 am — 11 pm) and 50 dBA for nighttime (11 am — 7 pm). Source: SoundPLAN Version 5.1. As shown in Table 4.13-4, the nearest sensitive receptors surrounding the Project Site would experience noise levels ranging from 35.2 to 40.7 dBA Leq from the Project's operational activities. The Project's operational noise levels would not exceed noise level standards in the SAMC. Furthermore, the existing ambient noise level at the institutional and residential uses to the east is approximately 72.6 dBA Leq and the existing ambient noise level at the residential use to the south is approximately 68.2 dBA Leq, which are higher than the projected operational noise levels at these sensitive receptors. As such, the Project's operational noise levels would not be audible above existing ambient noise levels and would not increase the ambient noise levels experienced by these sensitive uses. Therefore, the nearest sensitive receptors would not be directly exposed to substantial noise from on -site operational activities, and impacts would be less than significant. 34 Sound power level is used in SoundPlan modeling. The SoundPlan noise model was utilized to predict the anticipated operational noise levels and impacts associated with a worst -case scenario, where all operational activities are assumed to occur simultaneously. SoundPLAN is a three-dimensional noise model that allows computer simulations of noise situations, and creates noise contour maps using reference noise levels, topography, point and area noise sources, mobile noise sources, and intervening structures. 35 Elliot H. Berger, Rick Neitzel, and Cynthia A. Kladden, Noise Navigator Sound Level Database with Over 1700 Measurement Values, July 26, 2015. July 2024 Page 82