Noise and Vibration Assessment

Table 6 Vibration Source Levels for Construction Equipment 2EquipmentPPV at 25 ft. (in/sec)Clam shovel drop 0.202Hydromill (slurry wall) in soil 0.008in rock 0.017Vibratory Roller 0.210Hoe Ram 0.089Large bulldozer 0.089Caisson drilling 0.089Loaded trucks 0.076Jackhammer 0.035Small bulldozer 0.003Impact c)Impact d)Not applicable. The operation of the project would not result in measurable noiselevels above ground. Therefore, this significance criterion is not applicable to theproposed project.Less than Significant Impact. The project would not result in a substantialtemporary or periodic increase in ambient noise levels in the project vicinity abovelevels existing without the project.Noise levels at sensitive receivers adjacent to the pipeline alignment would increase during theconstruction period when activities are located in close proximity. Pipeline installation would occurat a rate of approximately 60 to 80 linear feet per day, therefore, construction noise levels would onlybe substantially increased over a short period of time. Construction activities would only occurduring the daytime hours only; no evening or nighttime work is proposed.Noise impacts from project construction activities are a function of the level of noise generated byindividual pieces of construction equipment, the amount of equipment operating at any given time,the distance and sensitivities of nearby land uses, the presence of noise barriers or other structuresthat provide acoustical shielding, and the timing and duration of the noise-generating activities.Where noise from construction activities exceeds 60 dBA L eq and exceeds the ambient noiseenvironment by at least 5 dBA L eq at noise-sensitive residential uses in the project vicinity for aperiod of more than one construction season, the impact would be considered significant.Construction noise would primarily consist of the operation of vehicles and equipment duringpavement removal, excavation, pipeline installation, backfill operations, and the repaving of theportion of the street disturbed by the project. The highest construction noise levels would begenerated during trenching operations. Table 7 presents the typical range of hourly average noiselevels generated by different phases of construction measured at a distance of 50 feet. Hourlyaverage noise levels generated by public works-type projects at a distance of 50 feet from the centerof a busy construction site typically range from 79 dBA to 88 dBA L eq .2 Transit Noise and Vibration Impact Assessment, United States Department of Transportation, Office of Planning andEnvironment, Federal Transit Administration, May 2006.13