EXHIBIT 4-2_55A_BRISTOL WIDENING TECHNICAL STUDIES

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addressed without that fence. In that case, this second line receptor would have future noise impacts and require noise walls as shown in the Appendix. The front yard noise impacts for the first line receptor (site 12) and for the second line receptor (site 13) when the first line house is removed, are typical impacts associated with a house facing a side street. Although a 6 -foot block wall would reduce noise impacts, a wall extending out to the corner would reduce the visibility of motorists on St. Gertrude Place and Bristol Street. Although the noise attenuation from a six -foot barrier placed at the right -of -way (60 feet from the centerline) in front of dwellings fronting on Bristol Street is evaluated in Table 4 -9, construction of a wall may prove infeasible. For most of these dwellings, noise barriers will conflict with existing driveways, pedestrian access, or reduce vehicular sight distances at cor- ners. Construction of a non - contiguous wall would lower noise levels behind the wail but reduce the effectiveness of the noise barrier such that the Caltrans minimum affectiveness criteria x would not be met. A map included as pages 19 through 24 of the Appendix indicates which residences appear to be noise impacted by future traffic volumes projected for Bristol Street with or without each of the proposed project alternatives. The map also indicates whether front yard or rear yard exterior impacts are anticipated, and where first and second line noise barriers may be constructed. The barriers proposed will mitigate noise below the federal criteria in all cases except where frontyard impacts occur on corner lots. City standards require a 25 -toot setback of noise walls from corners to allow for adequate sight distance. The resulting location of barriers along Bristol Street may not fully attenuate noise levels to meet the federal criteria. Second Line Receptors Second line receptors are buildings that are currently acous- tically shielded by a row of buildings located between them and the roadway. Since the proposed project could ultimately result in the removal of 200 existing buildings adjacent to Bristol Street, there is the potential for adverse noise impacts at approximately 200 second line receptors. Barriers should be constructed to shield the second line recep- tors that will exceed the 67 Leq standard (see the Appendix). In addition, barriers could be constructed per current Caltrans practices to shield those second Line recptors where exterior noise levels will approach the 67 Leq standard (i.e. 65 Leq to 67 Leq exposures as illustrated in the Appendix). After construc- tion of the noise walls for the second line receptors, the atten- uated noise levels will range from 59 to 63 Leq. It should be 4 -23