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4. ENVIRONMENTAL ANALYSIS 4.5 NOISE • Expose people residing or working in the project area to excessive noise levels if the .• project is located within an area covered by an airport land use plan, or where such plan has not been adopted, within two miles of a public airport or public use airport. .. • Expose people residing or working in the project area to excessive noise levels if the project is located in the vicinity of a private airstrip. • Expose persons to or generation of excessive ground-borne vibration or ground-borne noise levels. ^ The significance of project-related noise impacts can be determined by comparing estimated project-related noise levels to existing no-project noise levels. An increase of at least 3 dBA is usually required before most people will perceive a change in noise levels, and an increase of 5 r dBA is required before the change will be clearly noticeable. A common practice has been to assume that minimally perceptible to clearly noticeable increases of 3-5 dB represent a significant increase in ambient noise levels. A sliding scale is commonly used to identify the .. significance of noise increases,allowing greater increases at lower absolute sound levels than at higher sound levels. This approach is based on research that relates changes in noise to the percentage of individuals that would be highly annoyed by the change(FICON, 1992). Thus,the ^ significance criteria for changes in noise from project operations are as follows: 1. A 3 dBA DNL increase in noise as a result of project operations if the resulting level exceeds the"normally acceptable range"for the land use(65 dBA DNL or less for residential development). 2. A 5 dBA DNL increase in noise as a result of project operations if the resulting level is within the"normally acceptable range"for the land use. 3. A 3 dBA increase in the hourly Les noise level as a result of stationary noise sources associated with the project if the resulting noise level exceeds the hourly standard of 50 dBA Leq during daytime hours (7:00 AM to 10:00 PM)or 45 dBA Leg during nighttime hours(10:00 PM to 7:00 AM) at an off-site outdoor activity area. 4. A 5 dBA increase in the hourly Les noise level as a result of stationary noise sources associated with the project if the resulting level is below the hourly standard of 50 dBA Leq during daytime hours(7:00 AM to 10:00 PM)or 45 dBA Leq during nighttime hours (10:00 ` PM to 7:00 AM)in an outdoor activity area. 5. The proposed project would introduce stationary noise sources that would result in tr maximum noise levels in excess of the San Joaquin County Development Title standard of 70 dBA L.during daytime hours(7:00 AM to 10:00 PM)or 65 dBA L.during nighttime hours(10:00 PM to 7:00 AM) at an off-site outdoor activity area. The MSHA 1999 noise standards would apply to the proposed project and are assumed to provide hearing protection for the miners. Occupational noise levels will not be further discussed in the impacts section of this chapter. ^ RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.5-11 ESA/203015 Admini,a at ve Dmft ERR Mamh 2004