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City of Santa Ana California Environmental Quality Act <br />Initial Study/Mitigated Negative Declaration <br />➢ Sonic Pile Driving - At the upper range reference vibration for the sonic/vibratory pile driver, the <br />risk for damage to nearby buildings begins when the equipment is 32 feet or closer to the <br />structure. The nearest piling is expected to be 20 feet from the closest structure, so vibration <br />limit exceedances would remain with use of a vibratory pile driver. <br />➢ Drilled Piles - Noise emission levels from bored/drilled pilling methods are approximately 15 dB <br />lower and peak particle velocity (PPV) levels may be more than 15 times lower than those due to <br />traditional impact piling. The use of these methods will eliminate the vibration impacts of all <br />receivers. These methods will also substantially reduce the noise impacts and in most cases they <br />will also be eliminated, with the use of a suitable noise barrier. <br />➢ Hammer Energy - A recommended way to reduce PPV is to lower the hammer energy since there <br />is a direct relationship between hammer energy and the resultant ground vibration. Ground PPV <br />generally follows a square root relationship with hammer energy (i.e. PPV — /Hammer Energy). <br />The degree of hammer energy reduction must be balanced against the likelihood/severity of <br />expected exceedances, increase in total driving time, and ability to drive to required friction <br />tolerances. <br />➢ Vibration Monitoring - It is recommended that vibration monitoring be conducted at any building <br />where equipment is operating closer than the limits noted in Table 3-4. <br />Table 3-4 Construction Equipment Vibration Reference Levels <br />Equipment Description <br />Minimum Separation Distance <br />Pile Driver (impact) <br />52 feet <br />Pile Driver (Vibratory) <br />32 feet <br />Vibratory Roller <br />14 feet <br />Compactor (Ground) <br />13 feet <br />Large Bulldozer <br />8 feet <br />-37CWE7 <br />- <br />