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evaluation of the overall traffic noise,this analysis is misleading. A typical noise analysis for traffic noise impacts would first evaluate the existing traffic noise levels and compare them to the standard, and then evaluate the existing+ project noise levels to show the comparison. The BAC report estimated the project-related truck trips to result in an interior Ldn of 38 dB at a distance of 60 feet. j.c. brennan & associates, Inc. utilized the Federal Highway Administration (FHWA RD77-108) traffic noise prediction model to evaluate the project-related truck traffic noise levels along E. River Road. The inputs assumed 248 total truck trips, with 66 of those trips occurring during the daytime hours. It assumed a speed of 40 mph (This is probably underestimating the actual travel speeds). The FHWA traffic noise prediction model resulted in an interior Ldn of 41 dBA. 17.Page 34 of the BAC report provides a discussion entitled"Traffic Noise Impacts Relative to Existing Nighttime Hourly Noise Levels Without the Project'. This analysis seems to indicate that there is no significant noise impact due to truck traffic as it is compared to the ambient noise environment. Based upon the BAC report, the project could typically result in 26 hourly truck trips per hour during the nighttime hours. Based upon Table 6 of the BAC report, the average measured hourly background noise levels during the nighttime periods ranged between 59 dBA Leq and 62 dBA Leq at a distance of 60 feet from the centerline (Site 4). This corresponds with the closest building fagade to the roadway, as stated in the BAC report. If you use the lowest SEL value shown in the BAC report for truck passbys (79 dBA) at 60 feet, the Leq associated with the 26 trucks would be 62 dBA. Therefore, the nighttime noise levels would increase between 3 dBA and 4 dBA Leq. Based upon the FICON criteria shown in Table 3 of the report, this would result in a significant increase in noise levels. What the analysis does not mention, is that the increase in noise levels which trigger a significant impact is based upon an increase in noise levels of the same character. So, if the ambient noise during the nighttime period is not a function of truck traffic, the increase in noise levels due to truck traffic could be more annoying than indicated. 18. Page 29 of the BAC report provides an Analysis of Potential Project Noise Impacts. • Asphalt Plant impacts are considered less than significant. Based upon our review, as described earlier in this review, the BAC report states that they utilize the noise measurement data collected at Sites A and B to isolate the asphalt plant noise levels. This process was used to determine the potential noise levels during nighttime operations. Once again, the noise measurement locations do not accurately represent potential noise levels at the elevated residences. This is due to the fact that the noise measurement location used for evaluating the asphalt plant operations was 8