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*:/ :11-1 Ill WA <br />The nearest residences to the proposed skate area at the Raitt Street Site ace approximately 25 feet to the north. <br />Additionally, there is an existing wall on the northern and eastern property lines, therefore reducing noise levels <br />by approximately 5 dBA by bfeakmg line -of -sight. The residences to the west and south are over 100 feet from <br />skate area. Although no site -specific noise monitoring was conducted, it is assumed that the ambient noise level <br />would be similar to that of the 6u Street Site at 46 dBA Lso. Because the nearest residences to the north me <br />one-story buildings, and the existing wallbreaks the line -of -sight from the skate area, the ambient noise increase <br />would eb reduced by at least 5 dBA, and the noise increase is projected to be about 3 dBA Lso, therefore, <br />impacts would be considered less than significant without mitigation for the Raitt Street Site. <br />Project -Related Roadway Noise <br />The proposed parks are both intended to be walk-up parks that would primarily serve the local neighborhood. <br />As such, no vehicle parking will be constructed, and the projectrelatedtrips would be limited to maintenance <br />workers and some park visitors. The 6th Street Site is anticipated to generate 0.33 daily trips and the Raitt Street <br />Site is anticipated to generate 0.85 daily trips. <br />In general, to create a 3 dBA CNEL increase in trafficgeneratednoise levels (i.e., barely detectable), a doubling <br />of traffic flows (i.e., 10,000 vehicles per day to 20,000 per day) would be needed. Therefore, such a minor <br />increase in traffic volumes on the streets in the vicinity of the replacement park sites (less than 1 trip per day <br />on average) would not result in significant traffic noise increase and this would be a less -than -significant impact. <br />Mitigation Measure <br />N0I-1 The City of Santa Ana shall turn off park lights and festrict operating hours of the skate area <br />at the 6th Street Site to no later than 8:00 PM to reduce evening noise levels at adjacent <br />residential uses; <br />Of <br />The City of Santa Ana shall construct a noise barrier along the western and southern property <br />lines adjacent to the skate area of the 6th Street Site. The barrier shall be continuous from <br />glade to top, with no cracks or gaps, and have a minimum surface density of four pounds per <br />square foot. A minimum barrier height of 10 feet at the 6th Street Site, as measured from the <br />base elevation, shall be provided. <br />b) Generation of excessive groundbome vibration or groundbome noise levels? <br />Less Than Significant Impact. The proposed park facilities do not include any vibration-genefating sources <br />of activities; therefore, no persons would be exposed to excessive groundbofne vibration during operation. <br />Construction activities can generate varying degrees of ground vibration, depending on the construction <br />procedures, construction equipment used, and proximity to vibration -sensitive uses. Operation of construction <br />equipment generates vibrations that spread through the ground and diminish in amplitude with distance from <br />the source. Ground vibrations from construction activities can but rarely reach levels that can damage <br />structures. The term `architectural damage' is defined as minor surface cracks (in plaster, drywall, tile, of stucco) <br />75C-116 <br />