SU0004098 - Laserfiche WebLink

Home Browse Search

At the residences immediately north of Highway 132 however, ambient noise level data provided by Jones&Stokes(ADEIR Table 3.J-2& Buehler e-mail 6-6-06)indicate that ambient noise levels are much higher due to Highway132. Specifically, measured daytime ambient noise conditions were 57 dB Leq during the quietest daytime hour, and 54 dB Leq during the quietest nighttime _ hour. According to County Staff, (Chandler Martin), the County normally applies an ambient plus 3 dB — standard in cases where ambient noise levels already exceed County standards. As a result, the noise standards which would be more applicable to the residences on the north of Highway 132 would be 60 dB Leq during daytime periods, and 57 dB Ieq during nighttime periods. It should be noted that BAC concurs with the ADEIR conclusion that the County's Leq limits are _ more restrictive than the County's Lmax standards for this given noise source,and that the analysis should focus on compliance with the appropriate Leq standards. Processing Area Noise The processing area is located in the north-central portion of the project site, and consists of the Asphalt Plant, Concrete Plant, Main Crushing/Screening Plant, and Recycle Crushing/Screening Plant. This area would also utilize front-loaders for the load-out of aggregate products into heavy _ trucks for off-site delivery. The noise generation of each of these major noise sources and the duration of an hour these — sources are likely to operate is provided in Table 3.J-6 of the ADEIR. Noise from these sources was projected to the nearest residences using the Traffic Noise Model (TNM), with the results provided in Tables 3.J-7 through 3.J-9 of the ADEIR. BAC computed the noise from the processing area equipment at the nearest residences using the _ more industry-standard approach of assuming a 6 dB decrease in noise for each doubling of distance from the noise source (standard spherical spreading of sound from a point source), with an additional offset of-1.5 dB per thousand feet to account for atmospheric and excess ground attenuation. The results of the BAC computations for the Processing area are provided in Table 1, along with the applicable Leq noise standards. It should be noted that the Table 1 data includes a-5 dB offset at the receivers to the southeast and southwest to account for shielding by proposed earthen berms to the east (10 feet high), or the existing canal embankment to the west (15 feet high). _ Page -2-