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

Home Browse Search

South Coast Technology Center Project CEQA Exemption 15183 The GPU PER determined that construction activity would generate varying degrees of ground vibration. GPU PER MM N-2, which requires preparation of a noise and vibration analysis for projects requiring pile driving during construction within 135 feet of fragile structures, such as historical resources, 100 feet of non -engineered timber and masonry buildings (e.g., most residential buildings), or within 75 feet of engineered concrete and masonry (no plaster), or use of a vibratory roller within 25 feet of any structure, and adherence to associated performance standards, would reduce impacts to a less -than -significant level. The GPU PER determined that implementation of GPU PER MM N-3, which applies to new residential projects located within 200 feet of existing railroad lines and GPU PER MM N-4, which applies to industrial developments, would reduce potential vibration impacts during operation to less than significant levels. The GPU PER determined that future development of noise -sensitive land uses could be located within areas where airport noise exceeds 60 dBA CNEL, but with implementation of the policies in the Noise Element, impacts would be less than significant. 4.13.2 Project Analysis The following section evaluates potential impacts related to noise and vibration that would result from the construction and operation of the proposed Project. The analysis is primarily based upon Attachment J, Noise and Vibration Assessment. The Noise and Vibration Assessment was prepared to fulfill the requirements of GPU PER MM N-4. EXISTING CONDITIONS The Project Site is surrounded by existing commercial and institutional uses to the north, south, and west. The primary sources of stationary noise in the Project vicinity are from urban -related activities (i.e., mechanical equipment and parking areas). Commercial and industrial operations in the Project vicinity can also generate varying degrees of ground vibration, depending on the operational procedures and equipment, which can range from no perceptible effects at the lowest vibration levels, to low rumbling sounds and perceptible vibrations at moderate levels, to slight structural damage at the highest levels. Such equipment -generated vibrations spread through the ground and diminish with distance from the source. The existing noise in the Project vicinity is generated predominately by traffic along surrounding roadways including MacArthur Boulevard, South Susan Street, and Lake Center Drive. These roadways also have the potential to generate vibrations. However, according to the Federal Transit Administration (FTA), it is unusual for vibration from sources, such as buses and trucks, to be perceptible, even in locations close to major roads.29 Existing Ambient Noise Levels Three short-term noise measurements were taken in the Project vicinity on March 12, 2024 to quantify existing ambient noise levels in the Project area. The noise measurement locations are described in Table 4.13-1, Noise Measurements and are representative of typical existing noise exposure at the nearest sensitive receptors. The 10-minute measurements were taken between 11:00 a.m. and 12:30 p.m. Short-term (Leq) measurements are considered representative of the noise levels throughout the day. The noise measurements were taken during "off-peak" (9:00 a.m. through 3:00 p.m.) traffic noise hours as this provides a more conservative baseline. During rush 29 Federal Transit Administration, Noise and Vibration Impact Assessment Manual, Section 5.2, Sources of Transit Ground -borne Vibration and Noise, September 2018. July 2024 Page 77