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underlying sediments may have high sensitivity, construction activity shall be <br /> monitored by a qualified paleontologist. The paleontologist shall have the authority to <br /> halt construction during construction activity as outlined in Mitigation Measure GEO-3. <br /> GEO-3 All Projects. In the event of any fossil discovery, regardless of depth or geologic <br /> formation, construction work shall halt within a 50-foot radius of the find until its <br /> significance can be determined by a qualified paleontologist. Significant fossils shall <br /> be recovered, prepared to the point of curation, identified by qualified experts, listed in <br /> a database to facilitate analysis, and deposited in a designated paleontological <br /> curation facility in accordance with the standards of the Society of Vertebrate <br /> Paleontology (2010). The most likely repository is the Natural History Museum of Los <br /> Angeles County. The repository shall be identified and a curatorial arrangement shall <br /> be signed prior to collection of the fossils. <br /> Finding <br /> Finding 1. The City hereby makes Finding 1. Changes or alterations have been required in, or <br /> incorporated into, the project that avoid or substantially lessen the significant environmental <br /> effect as identified in the PER. These changes are identified in the form of the mitigation <br /> measures above. The City of Santa Ana hereby finds that implementation of the mitigation <br /> measures is feasible, and the measures are therefore adopted. <br /> 5. Noise <br /> Impact 5.12-3: Buildout of the individual land uses and projects for implementation of the <br /> GPU may expose sensitive uses to excessive levels of groundborne <br /> vibration. <br /> Construction Vibration Impacts. Construction activity at projects within the plan area would <br /> generate varying degrees of ground vibration, depending on the construction procedures and <br /> equipment. Operation of construction equipment generates vibrations that spread through the <br /> ground and diminish with distance from the source. The effect on buildings in the vicinity of the <br /> construction site varies depending on soil type, ground strata, and receptor-building construction. <br /> The results from vibration can range from no perceptible effects at the lowest vibration levels, to <br /> low rumbling sounds and perceptible vibrations at moderate levels, to slight structural damage at <br /> the highest levels. Vibration from construction activities rarely reaches the levels that can damage <br /> structures but can achieve the audible and perceptible ranges in buildings close to the <br /> construction site. <br /> Vibration generated by construction equipment has the potential to be substantial, since it has the <br /> potential to exceed the FTA criteria for architectural damage (e.g., 0.12 inches per second [in/sec] <br /> PPV for fragile or historical resources, 0.2 in/sec PPV for non-engineered timber and masonry <br /> buildings, and 0.3 in/sec PPV for engineered concrete and masonry). Construction details and <br /> equipment for future project-level developments under the GPU are not known at this time but <br /> may cause vibration impacts. <br /> Santa Ana General Plan Update <br /> CE 5T ac an Statement 32 — 56 2 <br /> Of ri ing onsiderations -33- 61 /Rer�0 2 1 <br />