SU0007300 - Laserfiche WebLink

Home Browse Search

Comment 6: The EIR provides mitigation for haul truck operations. Mitigation measure 3.4.1 provides what is described in Appendix B (BAC Report) as Optimization of Heavy Truck Operating Parameters to Minimize Passby Noise. This analysis provides good 1-27 insight into the variations in operating conditions and how they affect the noise generated by the trucks. However, requiring truck drivers to operate at speeds between 38 mph and 43 mph with engines in 8`' gear at 700 to 800 rpm for empty truck loads, and between 33 mph and 35 mph,with engines in 6t' or 7t' gear at 1,400 to 1,600 rpm seems difficult to enforce or even reasonably request from drivers. Comment 7: The analysis of the probability of awakening due to truck operations is nothing short of incorrect. The original BAC analysis indicated that the proposed nighttime truck traffic would result in only a 5%or less awakening of residents adjacent to the haul route, while assuming up to 182 trucks in a 7 hour period during the nighttime. This results in an average of 1 heavy truck passby every 2 minutes. We have previously made the point that intuitively this is not correct, and that the BAC analysis utilized a methodology which does not account for the number of noise events, or in this case, truck passbys. The American National Standards Institute (ANSI) has developed procedures for evaluating the potential for sleep disturbance. The Procedure ANTSI/ASA S12.9-2008 / Part 6 sets for the procedures for evaluating the potential for sleep disturbance. Based upon the ANSI procedures,the probability of awakening is 97%. The Draft EIR recognizes that that the ANSI procedure is the correct methodology for 1-2$ evaluating the potential awakening, states that nearly 100 percent of the people along the haul route will be awakened by the nighttime truck traffic. However, the EIR states that there are already approximately 250 automobiles during the 10:00 p.m. to 5:00 a.m. period, and that based upon the ANSI procedures, there is already a 92% probability of awakening. There are several reasons for arguing this comparison: ► The analysis assumes a Sound Exposure Level (SEL) of 75 dBA at the building; facades. When you compare this to the SEL assumed for heavy trucks of 79 dBA, it is difficult to believe that the noise level (SEL) for a haul truck is only 4 dBA higher than an automobile; • The Draft ETR does not provide information on where they got the 75 dBA SEL for automobiles. It does not appear to be based upon any research or noise measurements that they conducted. There needs to be some reference information for using this value; ► The calculation of existing sleep disturbance (92%)utilizes an interior SEL of 50 dBA. Based upon the ANSI specifications, any SEL below 50 dBA needs to be ignored. So, assuming that the interior SEL is 49 dBA, the ANSI procedure would assume that there would be little likelihood of sleep disturbance; 3