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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 <br /> Santa Ana General Plan Update <br /> CE 5T ac an Statement 32 — 57 2 <br /> Of ri ing onsiderations -34- 61 /Rer�0 2 1 <br />