Draft Environmental Impact Report - East Bay Municipal Utility District

Estates Reservoir Replacement Draft Environmental Impact ReportNoise and VibrationLimit the noisiest phases of construction to 10 working days at a time, wherefeasible.Notify neighbors/occupants within 300 feet of Project construction at leastthirty days in advance of extreme noise generating activities about theestimated duration of the activity.The effectiveness of noise attenuation measures shall be monitored by taking noisemeasurements during noise intensive activities of 90 dBA or greater over a nine weekperiod. However, it should be noted that although the goal is to limit construction noiseto the minimal feasible duration and to reduce noise levels to minimize disturbance tosensitive receptors (adjacent residents), mitigated construction noise could still causeoccasional, intermittent or periodic disturbance at the closest residential receptors. Inrecognition of this possibility and based on the significance criteria, construction noiseimpacts are therefore considered significant and unavoidable, even with mitigation.Significance after Mitigation: Significant and Unavoidable.Impact 3.9-2: Construction of the Estates Reservoir Replacement Project couldincrease noise levels along truck haul routes.Truck noise levels depend on vehicle speed, load, terrain, and other factors. The effects ofconstruction-related truck traffic would depend on the level of background noise alreadyoccurring at a particular receptor site. In quiet noise environments (Leq averaging 50 dBA),one truck per hour would be noticeable, even though such a low volume would notmeasurably increase noise levels. In slightly noisier environments (Leq averaging 60 dBA),the threshold level is higher, and it would take 10 trucks per hour to noticeably increase thenoise exposure. In moderately noisy environments (Leq averaging 70 dBA), a noiseincrease would be perceptible with the addition of 100 trucks per hour. In quietenvironments or during quieter times of the day, truck noise is mainly a single-eventdisturbance; although the hourly average associated with short, single events is not veryhigh, individual noise peaks of up to 91 dBA at 50 feet can occur during a single truckpassage. In noisy environments or during less noise-sensitive hours, truck noise isperceived as a part of the total noise environment rather than as an individual disturbance.Throughout the demolition and construction periods, there would be worker vehicle tripsand either haul trucks or materials trucks accessing the Estates Reservoir site. Haul routesinclude local residential streets (with quiet noise environments) to arterials with moderatelynoisy environments, and regional freeways. Truck volumes would vary from day to day,and the maximum number of daily truck trips would reach 120 to 150 materials trucksduring the reservoir construction period at Estates Reservoir (refer to Table 3.6-5, Trafficand Circulation section of the EIR).The combination of truck trips and/or vehicle trips is calculated to generate an hourlyaverage noise level of up to 62 dBA L eq along the access roadways. A review of theexisting ambient noise level data indicates ambient noise levels typically in the range of 45to 50 dBA L eq during the daytime periods when construction-related traffic would besb09_001.doc 3-9.18 7/22/2009