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Santa Ana General Plan Update <br />CEQA Findings of Fact and Statement <br />Of Overriding Considerations -34- October 2021 <br />With implementation of Mitigation Measures N-2, N-3, and N-4, coupled with adherence to <br />associated performance standards, Impact 5.12-3 would be reduced to less-than-significant <br />levels. Specifically, Mitigation Measure N-2 would reduce potential vibration impacts during <br />construction below the pertinent thresholds, and Mitigation Measures N-3 and N-4 (operations- <br />related vibration) would reduce potential vibration impacts from commercial/industrial uses and <br />proposed uses near existing railroads and facilities to less-than-significant levels. No significant <br />and unavoidable vibration impacts would remain. <br />Operational Vibration Impacts. Commercial and industrial operations within the plan area would <br />generate varying degrees of ground vibration, depending on the operational procedures and <br />equipment. Such equipment-generated vibrations would spread through the ground and diminish <br />with distance from the source. The effect on buildings in the vicinity of the vibration source varies <br />depending on soil type, ground strata, and receptor-building construction. The results from <br />vibration can range from no perceptible effects at the lowest vibration levels, to low rumbling <br />sounds and perceptible vibrations at moderate levels, to slight structural damage at the highest <br />levels. In addition, future sensitive receptors could be placed within close proximity to existing <br />railroad lines through buildout in the plan area. <br />Because specific project-level information is not available at this time, it is not possible to quantify <br />future vibration levels at vibration-sensitive receptors that may be near existing and future <br />vibration sources. <br />With implementation of Mitigation Measures N-2, N-3, and N-4, coupled with adherence to <br />associated performance standards, Impact 5.12-3 would be reduced to less-than-significant <br />levels. Specifically, Mitigation Measure N-2 would reduce potential vibration impacts during <br />construction below the pertinent thresholds, and Mitigation Measures N-3 and N-4 (operations- <br />related vibration) would reduce potential vibration impacts from commercial/industrial uses and <br />proposed uses near existing railroads and facilities to less-than-significant levels. No significant <br />and unavoidable vibration impacts would remain. <br />Mitigation Measures <br />N-2 Prior to issuance of a building permit for a project requiring pile driving during <br />construction within 135 feet of fragile structures, such as historical resources, 100 feet <br />of non-engineered timber and masonry buildings (e.g., most residential buildings), or <br />within 75 feet of engineered concrete and masonry (no plaster); or a vibratory roller <br />within 25 feet of any structure, the project applicant shall prepare a noise and vibration <br />analysis to assess and mitigate potential noise and vibration impacts related to these <br />activities. This noise and vibration analysis shall be conducted by a qualified and <br />experienced acoustical consultant or engineer. The vibration levels shall not exceed <br />Federal Transit Administration (FTA) architectural damage thresholds (e.g., 0.12 <br />inches per second [in/sec] peak particle velocity [PPV] for fragile or historical <br />resources, 0.2 in/sec PPV for non-engineered timber and masonry buildings, and 0.3 <br />in/sec PPV for engineered concrete and masonry). If vibration levels would exceed