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OCTA I Santa Ana/Garden Grove Fixed Guideway Project <br />FNNoise and Vibration Technical Addendum <br />5 <br />R11 <br />3 <br />134 <br />115 <br />63 <br />63 <br />0 <br />6 <br />R10 <br />2 <br />55 <br />66 <br />71 <br />70 <br />-1 <br />7 <br />R12 <br />2 <br />49 <br />58 <br />71 <br />71 <br />0 <br />8 <br />R13 <br />2 <br />60 <br />78 <br />70 <br />69 <br />-1 <br />9 <br />R15 <br />2 <br />N/A <br />N/A <br />66 <br />66 <br />0 <br />10 <br />R14 <br />2 <br />110 <br />97 <br />65 <br />65 <br />0 <br />Source: HDR (June 2016 and February 2017). <br />The impact threshold for Land Use Category 2 is 72 VdB and for Land Use Category 3 is <br />75 VdB. As shown in Table L, the vibration levels are below the impact threshold at all receptor <br />locations. Therefore, no minimization design features are required. <br />Traction Power Substation Noise Analysis <br />The noise sources on traction power substation (TPSS) units are the transformer hum and noise <br />from cooling systems. The wall mounted HVAC units are the primary noise source on the <br />proposed TPSS units. The noise level at a distance of 40 ft from the cooling fan of a Gold Line <br />TPSS unit in South Pasadena was measured to be 51 dBA, which is equivalent to 49 dBA at a <br />distance of 50 ft. This measured noise level is consistent with the maximum sound level limit of <br />50 dBA at a distance of 50 feet from any surface included in the purchase agreement of TPSS <br />units used in several recently completed light rail projects. The audible noise from the TPSS unit <br />in South Pasadena was caused by a ventilation fan. The hourly TPSS noise levels are <br />converted to daily Ldn noise levels using the following formula: <br />// Leq Leq+10\ <br />Ldn= 10*Log I15*1010 +910 10 I-13.8 <br />Using an hourly noise level of 50 dBA, the Ldn noise level for the TPSS units is 56 dBA at a <br />distance of 50 feet. <br />The 60% design plans move TPSS unit 4 to the Santa Ana Regional Transportation Center <br />(SARTC) on the north side of the parking structure adjacent to Santiago Street. At this location <br />the TPSS unit would be located within 100 feet of the main SARTC structure and 350 feet frorr <br />the nearest residences. <br />Table M shows the predicted noise level at the TPSS sites assuming the units are specified to <br />have a maximum sound level of 50 dBA at a distance of 50 feet from any surface. As shown, by <br />orienting the TPSS units so that the noise from the HVAC units is directed away from the <br />sensitive uses, the noise levels at all receptors closest to the TPSS units would result in no <br />impacts. <br />13 <br />