CORRESPONDENCE - 75A (COMMENT) - Laserfiche WebLink

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4.8 Nolse ■ Expose people residing or working in the project site to excessive noise levels from a project located within an airport land use plan or, where such a plan has not been adopted, within 2 miles of a public airport or public use airport ■ Expose people residing or working in the project site to excessive noise levels from a project located within the vicinity of a private airstrip The CEQA Guidelines do not define the levels at which temporary and permanent increases in ambient noise are considered "substantial." As discussed previously in this section, a noise level increase of 3 dBA is barely perceptible to most people, a 5 dBA increase is readily noticeable, and a difference of 10 dBA would be perceived as a doubling of loudness. Based on this information, the following thresholds would apply to the operational characteristics of the proposed project: ■ Less than 3 dBA: not discernable, not significant ■ Greater than 3 dBA but less than 5 dBA: noticeable, but not significant, if noise levels remain below 65 dBA CNEL noise level standard at sensitive land uses including residential uses ■ Five dBA or greater: potentially significant, if the noise increase would meet or exceed 65 dBA CNEL noise level standard at sensitive land uses including residential uses ■ Five dBA or greater: potentially significant - The CEQA Guidelines also do not define the levels at which groundbome vibration or groundborne noise is considered "excessive." For the purpose of this analysis, groundborne vibration impacts associated with human annoyance would be significant if the proposed project exceeds 85 VdB, which is the vibration level that is considered by FTA to be acceptable only if there are an infrequent number of events per day (as described in Table 4.8-2 [fIuman Response to Different Levels of Gooundbotne Vibration]). In terms of groundborne vibration impacts on structures, this analysis will use FTA's vibration damage threshold of approximately 100 VdB for fragile buildings and approximately 95 VdB for extremely fragile historic buildings (HMMH 2O06). Effects Found to Have No Impact Threshold If the project is located within an airport land use plan or, where such a plan has not been adopted, within 2 miles of a public airport or public use airstrip, would it expose people residing or working in the project site to excessive noise levels? As discussed in Section 4.6 (Hazards and Hazardous Materials), the proposed project is not located within an airport land use plan or within 2 miles of a public airport or public use airport. The nearest public airport to the project is the John Wayne Airport, which is located approximately 5.0 miles south of the proposed project. Further, the proposed project is located over 5,000 feet from the 60 CNEL noise contour for John Wayne Airport. Thus, no impact related to the exposure of people residing or working in the project area to excessive airport related noise levels is anticipated, and no further analysis is required in this FIR. City of Santa Ana Transit Zoning Code (SD 84A and SD 848) EIR 4.8-19