Item 26 - EIR No. 2020-03 and GPA No.2020-06 Santa Ana General Plan Update

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