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4.8 Nolse threshold for people in the vicinity of the project site. Groundborne -vibration resulting from operation of the proposed project would primarily be generated by trucks making periodic deliveries to the proposed Transit Zoning Code (SD 84A and SD 84B) area. However, these types of deliveries would be consistent with deliveries that are currently made along roadways to commercial uses in the proposed Transit Zoning Code (SD 84A and SD 84B) area and in the proposed project vicinity and would not increase groundborne vibration above existing levels. Because no substantial sources of groundborne vibration would be built as part of the proposed project, no vibration impacts would occur during operation of the proposed project. Therefore, operation of the proposed project would not expose sensitive receptors on or off site to excessive groundborne vibration or groundborne noise levels, and this impact would be less than significant. Impact 4.8-4 Operation of the Southern California Regional Rail Authority's rail line would not generate and expose sensitive receptors located within the Transit Zoning Code (SD 84A and SD 8413) area to excessive groundborne vibration or groundborne noise levels. This is considered a less -than - significant impact. Implementation of the Transit Zoning Code (SD 84A and SD 84B) would locate new sensitive land uses within the vicinity of the existing railroad tracks. Problems for residential uses, such as disturbance due to groundborne vibration from these sources, are usually contained to areas with n about 200 feet of the vibration source (HMMII2006). Typically, the main effect of groundborne vibration is to cause annoyances for occupants of nearby buildings. The proposed residential uses in the Logan Neighborhood, Transit Village, and First Street Corridor could be located within 200 feet from the centerline of the railroad. As discussed earlier, trains typically produce a vibration level of 75 VdB at a distance of 50 feet from the tracks during operation and 65 dBA at a distance of 50 feet while stopped at a train station, both of which are below the human annoyance threshold of 85 VdB. Therefore, the occupants of the proposed residential units would not be exposed to potentially significant vibration levels, and th s impact would be less than significant. Threshold Would the project result in a substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without the project? Impact 4.8-5 Construction activities associated with the proposed project would result in a substantial temporary or periodic increase in ambient noise levels. However, the project's construction noise impacts would be temporary, would not occur during recognized sleep hours, and would be consistent with the exemption for construction noise that exists in the Municipal Code. Therefore, this impact would be considered less than significant. As discussed in Impact 4.8-1, construction activities associated with the proposed project could reach above 86 dBA Leg within 50 feet of the proposed project site. These construction activities would represent a substantial temporary or periodic increase in ambient noise levels. As discussed previously under "Thresholds of Significance," this analysis assumes that an increase of 5.0 dBA or greater over ambient noise levels is substantial and significant. As shown in Table 4.8-3, the highest existing daytime ambient noise level monitored in the project vicinity was 77.0 dBA Leg at the Rail Station Platform. As City of Santa Ana Transit Zoning Code (SD 84A and SD 848) EIR 4.8-25