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Chapter 4 Environmental Setting, Impacts, and Mitigation Measures Roadway Noise Levels Roadway noise levels have been calculated for various locations in and around the Transit Zoning Code (SD 84A and SD 84B) area. The noise levels were calculated using the FHWA-RD-77-108 model and traffic volumes from the project traffic study. The average vehicle noise rates (energy rates) utilized in the FHWA Model have been modified to reflect average vehicle noise rates identified for California by Caltrans. Traffic volumes used in the FHWA model are derived from the project traffic study, which is provided in its entirety Appendix G and summarized in Section 4.11 (Transportation/Traffic) of this document. Railway Noise Levels Railway noise levels resulting from railway operations occurring within the Transit Zoning Code (SD 84A and SD 84B) area were estimated using data published by Harris Miller Miller & Hanson Inc. (HMMH 2O06) for the Federal Transit Administration (FTA). Vibration Levels Associated with Construction Equipment Groundborne vibration levels resulting from construction activities occurring within the Transit Zoning Code (SD 84A and SD 84B) area were estimated using data published by Harris Miller Miller & Hanson Inc. (HMMH 2O06) for the FTA. Potential vibration levels are identified for on- and off -site locations that are sensitive to vibration, including residences and schools. Vibration Levels Associated with Railway Operations Groundborne vibration levels resulting from railway operations occurring within the Transit Zoning Code (SD 84A and SD 8413) area and were estimated using data published by Harris Miller M ller & Hanson Inc. (HMMH 2O06) for the FTA. Potential vibration levels are identified for on -site locations that are sensitive to vibration, including residences and schools. FA Thresholds of Significance The following thresholds are based on Appendix G of the CEQA Guidelines, as amended. For purposes of this EIR, implementation of the proposed project may have a significant adverse impact on noise if it would result in any of the following: ■ Expose persons to or generate noise levels in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies ■ Expose persons to or generate excessive groundborne vibration or groundborne noise levels ■ Cause a substantial permanent increase in ambient noise levels in the project vicinity above levels existing without the project ■ Cause a substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without the project 4.8-18 City of Santa Ana Transit Zoning Code (SD 84A and SD 848) EIR