75A - PH 3321 SOUTH FAIRVIEW ST - Laserfiche WebLink

Home Browse Search

Environmental Checklist For CEQA Compliance A. No Impact. There are no areas designated in the Surface Mining and Reclamation Act of 1975 (SMARA) or existent oil fields within the City of Santa Ana (City of Santa Ana 1998:A- 44); therefore, no impacts would occur. XI. Noise Mestre Greve Associates (2007) prepared an acoustics analysis for the proposed project (Appendix E). The analysis contained within this section incorporates the results of the noise study and relies primarily upon the study by Mestre Greve Associates, unless otherwise noted. Sound is technically described in terms of the loudness (amplitude) of the sound and frequency (pitch) of the sound. The standard unit of measurement of the loudness of sound is the decibel (dB). Decibels are based on the logarithmic scale. Therefore, in terms of human response to noise, a sound of 10 dB higher than any other is judged to be twice as loud; and 20 dB higher four times as loud. Every day sounds normally range from 30 dB (very quiet) to 100 d6 (very loud). Since the human ear is not equally sensitive to sound at all frequencies, a special frequency- dependant rating scale is devised to relate noise to human sensitivity. The A-weighted decibel scale (dBA) discriminates against frequencies in a manner approximating the sensitivity of the human ear. Community noise levels are measured in terms of dBA. For example, 40 dBA is very quiet, such as bird calls, and 100 dBA is very loud, such as a jet fly over at 1,000 feet. There are a number of noise scales that have been developed to measure community noise, which account for the parameters of noise that have been shown to contribute to the effects of noise on people, the variety of noises found in the environment, the variations of noise levels that a person experiences moving through the environment, and the variations of noise associated with the time of day. Two of the predominant noise scales are the Equivalent Noise Level (LEQ) and the Community Noise Equivalent Level (CNEL). LEQ is the energy average noise level during the time period of the sample. It is typically measured for one hour and is the energy sum of all the events and background noise that occurred within that one hour. CNEL represents atime-weighted 24-hour average noise level based on the dBA. Time weighted means that noise that occurs during certain sensitive time periods are penalized for occurring at these times. The evening time period (7 p.m. to 10 p.m.) and the nighttime period (10 p.m. to 7 a.m.) are penalized should noise making activities occur at these times. This is because they seem louder during these quieter times of the day because there are few other competing noises. Many communities use the CNEL as their standard in California. Ldn is similar to CNEL, except that evening noises are not penalized, while nighttime noises are penalized. It is a measure of overall noise experienced during an entire day. L(%) is the method of describing noise that accounts for the variance in noise levels through a given measurement period. L(%) is a way of expressing the noise level exceeded for a percentage of time in a given measurement period. For example, since 5 minutes is 25% of 20 minutes, Alton Court August 2007 Initial Study/Mitigated Negative Declaration 3-30 J&S 00635.07 75A-96