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0� OCTA I Santa Ana/Garden Grove Fixed Guideway Project <br />Noise and Vibration Technical Analysis Re-evaluation in Support of Minor Design Modifications <br />8 <br />R13 <br />2 <br />55 <br />58 <br />69 <br />44 <br />N/A <br />69 <br />Severe Impact <br />10 <br />R14 <br />2 <br />58 <br />55 <br />N/A <br />N/A <br />63 <br />64 <br />Severe Impart <br />Source: URS (February 2012) and HDR (June 2016). <br />The February 2012 Noise and Vibration Technical Report and the adopted EA/FONSI <br />recommended the following mitigation measures to reduce the severe impacts: <br />• N1 Horn sounding exemption at grade crossings; <br />• N2 Location and design of special trackwork elements; and <br />• N3 Wayside noise barriers. <br />As discussed above, the project plans call for the use of flange bearing frogs at all crossovers. <br />This design feature of special trackwork is a typical mitigation for noise. Therefore, no new <br />measures are required for the special trackwork (N2). <br />N3 WAYSIDE NOISE BARRIERS <br />The FTA Manual indicates that the shielding attenuation provided by a wayside noise barrier for <br />the first row receptors would be 4.5 dBA. The 2012 noise analysis evaluation identified the need <br />for noise barriers for receptor locations R10, R12, R13, and R14. Due to the change in train <br />speed, elevation, and the shift in centerline an additional wayside noise barrier would be <br />required to reduce the noise level in the vicinity of receptor R7 (located in NSA 3). Table G lists <br />the train noise levels after the wayside noise barrier has been implemented. As shown, <br />receivers R7 and R14 are reduced to moderate after the implementation of the proposed design <br />feature. Attachment D shows the locations and heights for the proposed barriers. <br />Table G: Modified Project — After Wayside Noise Barrier Design Features <br />NSA <br />Rec. <br />Land <br />Use <br />Cat. <br />Existing <br />Noise <br />Level <br />(d BA) <br />Predicted Project Only Noise Level <br />Ldn or Lday jdBA) <br />Impact <br />Overall <br />Streetcar Warning Project <br />Ops Horn Crossing O&M Noise <br />3 <br />R7 <br />2 <br />50 <br />59 <br />N/A N/A <br />N/A <br />59 <br />Moderate Impact <br />6 <br />R10 <br />2 <br />53 <br />53 <br />64 51 <br />N/A <br />65 <br />Severe Impact <br />7 <br />R12 <br />2 <br />50 <br />54 <br />68 49 <br />N/A <br />68 <br />Severe Impact <br />8 <br />R13 <br />2 <br />55 <br />53 <br />64 44 <br />N/A <br />64 <br />Severe Impact <br />10 <br />R14 <br />2 <br />58 <br />53 <br />N/A N/A <br />59 <br />60 <br />Moderate Impact <br />Source: URS (February 2012) and HDR (June 2016). <br />N1 HORN SOUNDING EXEMPTION AT GRADE CROSSINGS <br />The California Public Utilities Commission (CPUC) requires that vehicle warning horns be <br />sounded at public road crossings for all light rail transit vehicles and streetcar vehicles operating <br />on a dedicated ROW (CPUC General Order 143-B). However, the CPUC may also allow a horn <br />sounding exemption in cases for which supplemental safety measures are used in place of the <br />warning horn to provide an equivalent level of safety at the grade crossing. <br />If a horn sounding exemption is established and approved at each crossing, the required use of <br />warning horns would be exempted and horns would not be sounded except in an emergency <br />V1 <br />