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LSA ASSOCIATES, INC. INITIAL STUDY/MITIGATED NEGATIVE DECLARATION JULY 2010 FIRST STREET BRIDGE REPLACEMENT PROJECT CITY OF SANTA ANA Would the project result in: A. Exposure of persons to or generation of noise levels in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies? Less than significant impact with mitigation. Implementation of the proposed project would not result in a noticeable increase in noise levels on site due to the fact that the proposed project does not introduce any new land use type. The project will replace the bridge and widen First Street, and therefore, would not introduce new noise sources. According to the Noise Analysis (LSA Associates, Inc., 2010) the noise levels under the proposed project conditions will be similar to the existing noise levels. A slight increase in noise level is some locations may be expected and therefore, the abatement measures like sound barrier walls will be implemented to reduce noise levels so it will not affect the nearby receptors. Sound barrier walls were necessary only on the north side because the centerline of the roadway would shift to the north and relocate travel lanes closer to residences on the north side of First Street (in the area where there are only two travel lanes in each direction today). Whereas, the curb on the south side remains very close to its existing location and therefore noise levels on the south side would not be substantially affected by the project. Two sound barrier walls are proposed, one in the northwest quadrant and one in the northeast quadrant of the project site, protecting apartment complex and mobile home park from elevated noise levels, accordingly. The locations of these sound barrier walls are shown in Figure 17 in Section 2. Sound barrier wall number 1 (north west quadrant) will be located in place of the existing 5 ft wall which separates the First Street from the apartment complex. The sound barrier wall will be approximately 9-12 ft height and extend 238 ft from the existing entrance on the First Street westerly to the N Susan Street. Sound barrier wall number 4 along the edge of shoulder on the north east side of the First Street will be 6-14 ft high and will extend 477 ft easterly from Santa Ana River to the existing entrance to the park at First Street. The sound barrier walls will be located approximately 12 ft from the nearest travel lane. These two sound barrier walls satisfy noise standards for the Federal Highway Administration Noise Abatement Criteria and the National Environmental Policy Act (NEPA), so they have been incorporated into the project. In addition, sound barrier wall number 2 would extend from the northwest edge of the bridge abutment and proceed west to the edge of the driveway access to the apartment complex would be required to meet the City's noise standards. This wall would be 10 feet high. This sound barrier wall is also shown in Figure 17 in Section 2.0. Table 4.1 shows the existing and after project noise conditions using a 24-hour noise standard called Community Noise Equivalent Level (CNEL).1 Table 4.1 shows the existing 2007 measured CNEL levels, future without the project modeled noise levels, and future with project modeled noise levels. The last two columns show the change from the with project and without project future conditions and whether the change triggers abatement under the City's policies. Where there is a 3 dB CNEL increase in the change, abatement is ' CNEL measurements are a weighted average of sound levels throughout a 24-hour period. Different weighting factors apply to day, evening, and nighttime periods. This recognizes that community members are most sensitive to noise in late night hours and are more sensitive during evening hours than in daytime hours. 07/25/10 «PADMJ070l\MND\4.0 Environmental Analysis.doco qll_llff;� 4-27