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Mr. Rod Attebery Neumiller& Beardslee - September 1, 2011 Page 7 Prior to BAC developing an optimized approach to heavy truck operations for the purposes of minimizing pass-by noise, single-event noise levels of Munn & Perkins aggregate trucks averaged 85 dB SEL at a reference distance of 50 feet from the roadway centerline. BAC's optimized approach of trucks travelling at slower speeds and utilizing specific combinations of gears, engine rpm, and truck speed, resulted in a 4 dB reduction in measured SEL values, or 81 dB SEL at a reference distance of 50 feet from the centerline. During the recently completed noise survey, the average SEL measured of all 1,928 single events was computed to be 83 dB, which is 2 dB lower than the non-optimized passby data. Keep in mind that the dataset includes non Munn & Perkins vehicles, which could have increased the average. In fact, BAC staff observed non-Munn & Perkins vehicles generating pass-by SEL's of 86 dB (Jeep with loud tires), 86 dB (pick-up with loud tires), 99 dB (highway patrol passby with siren), 82 dB (car driving very fast), 84 dB (non aggregate heavy truck), etc. - These observations indicate that loud vehicle pass-bys that are not related to Munn & Perkins operations occur regularly, and that many of the observed non-Munn & Perkins vehicles generated higher pass-by noise levels than those generated by Munn & Perkins aggregate trucks. During BAC observations (which were occurring without the knowledge of the truck drivers), in no case did a Munn & Perkins truck exceed 86 dB SEL. When the events which registered SEL values in excess of 86 dB were removed from the dataset, the mean SEL value decreased to 82 dB SEL, which is 3 dB lower than the non-optimized heavy truck passby noise level. The significance of this finding is that a 3 dB reduction in sound energy is equivalent to removal of half of the Munn & Perkins heavy trucks from the road. It can be concluded from the single-event noise measurement results, those both with and without BAC staff observations, that the use of the optimized heavy truck operating procedures is a viable noise mitigation option for this and any other project requiring nighttime deliveries of aggregate products. Although BAC observations noted that the majority of heavy truck pass- - by's appeared to be operating in accordance with the recommended optimized procedure, several of the returning (empty) trucks were observed to be travelling at speeds above those recommended in the optimized procedure. As a result, additional reductions in pass-by noise can be expected as operators become more familiar with the optimized procedures. The end result of the use of the optimized procedures as a noise mitigation measure is an indisputable numeric decrease in the percentages of persons potentially awakened by nighttime heavy aggregate truck pass-bys on East River Road. In summary, the results of the recent nighttime noise monitoring program fully support the conclusions of the BAC August 18, 2010 analysis of potential noise impacts associated with increased Munn & Perkins nighttime operations.