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HomeMy WebLinkAboutCVL03312 Noise Study - 06-19-17Environmental Noise Assessment Report Site Number: CVL03312 Lower Forbestown Rd., Forbestown, CA 95941 June 19, 2017 Prepared for: 5001 Executive Parkway 4W550C San Ramon, CA 94583 Prepared by: Environmental Noise Assessment Report CVL03312 ____________________________________________________________________________________ Shore 2 Shore Wireless 1.0 EXECUTIVE SUMMARY AT&T proposes to locate an emergency back-up generator at an unstaffed wireless telecommunications facility at site number CVL03312. This site is located at Lower Forbestown Rd., Forbestown, CA 95941. This study evaluates potential noise impacts from the proposed emergency generators on the site vicinity. Acoustic modeling was performed to predict sound level impacts from the proposed equipment installation at the property line based on the Inverse Square Law of propagation. Based on the results of this study, S2S concludes that the emergency generator proposed for installation at CVL03312 will produce 45.10 dBA at the nearest property line when running at full capacity. 2.0 BACKGROUND All sounds originate from a source. The sound energy, produced by a source, creates variations in air pressure which travel in all directions much like a wave ripples across the water. The “loudness” or intensity of a sound is a function of the sound pressure level, defined as the ratio of two pressures: the measured sound pressure from the source divided by a reference pressure (i.e. threshold of human hearing). Should level measurements are most commonly expressed using the decibel (dB) scale. The decibel scale is logarithmic to accommodate the wide range of sound intensities the human ear is capable of responding to. On this scale, the threshold of human hearing is equal to 0 dB, while levels above 140 dB can cause immediate hearing damage. For reference, a quiet rural area has an average noise level of 30 dB, with bird calls registering around 44 dB, and the average ambient noise of a suburban neighborhood at around 50 dB. One property of the decibel scale is that the combined sound pressure level of separate sound sources is not simply the sum of the contributing sources. For example, if the sound of one source of 70 dB is added to another source of 70 dB, the total is only 73 dB, not a doubling to 140 dB. In terms of human perception of sound, a 3 dB difference is the minimum perceptible change for broadband sounds (i.e. sounds that include all frequencies). A difference of 10 dB represents a perceived halving or doubling of loudness. 3.0 Modeled Post Construction Noise Levels The nearest property line to the proposed noise source is measured at 227’ due West of the project location as referenced in Exhibit 1. The areas between the proposed location include existing trees and sporadic undergrowth. These obstructions are dB absorbent, which is to say, they offer additional reduction to noise levels year-round / day and night. The generator proposed is listed on the following page in Exhibit 2 and maintains an average 65 dB noise level under full load. The resultant Modeling Results are attached in Exhibit 3. Environmental Noise Assessment Report CVL03312 ____________________________________________________________________________________ Shore 2 Shore Wireless Exhibit 1 4.0 RESULTS AND CONCLUSIONS As shown in Exhibit 3, worst-case predictive modeling indicates that the proposed emergency back-up generator will produce 45.10 dBA at the nearest property line. Significant reduction in noise beyond the modeled level can be expected due to the surrounding absorbent materials. Worst-case modeling methodologies are based on the manufacturer-provided equipment specifications and distance to the property alone and do not include external absorbent materials. Manufacturer specifications include a decibel rating, which reflects the maximum decibel output the equipment will produce when running at full capacity. The Generac SG035 generator is assumed to run only during equipment testing (daytime only) or during a loss of power. 5.0 LIMITATIONS This report was prepared for the use of AT&T Mobility. The conclusions provided by Shore 2 Shore are based solely on the information provided by the client. The observations in this report are valid on the date and time of the investigation. Reported noise levels contained herein are a factor of meteorological and environmental conditions present at the time of the site survey, and represent “typical” site noise levels. Measurement and calculations contained in this report should be considered accurate to within one decibel. Any additional information that becomes available concerning the site should be provided to Shore 2 Shore so that our conclusions may be revised and modified, if necessary. This report has been prepared in accordance with Standard Conditions for Engagement and authorized proposal, both of which are integral parts of this report and has been designed to address the noise contributions of the proposed emergency back-up generator at the nearest property line. Environmental Noise Assessment Report CVL03312 ____________________________________________________________________________________ Shore 2 Shore Wireless 6.0 REVIEWER CERTIFICATION I, Chris Hatch, state that: I am a representative of Shore 2 Shore Wireless Inc. which provides acoustic survey and engineering management services to the wireless communications industry. I have reviewed the data collected during the site survey which is incorporated into this Site Compliance Report such that the information contained in this report is true and accurate to the best of my knowledge. Sincerely, By Shore 2 Shore Wireless Chris Hatch Engineering Manager Generac Power Systems, Inc. | P.O. Box 8 | Waukesha, WI 53187 P: (262) 544-4811 © 2017 Generac Power Systems, Inc. All rights reserved. All specifications are subject to change without notice. 1 OF 1 SU B M I T T A L D A T A Part No. 0193850SSD Rev C 03/07/17 SOUND EMISSION DATA 5.4L SG035 LEVEL 2 SOUND ATTENUATED ENCLOSURE 60Hz NO-LOAD DATA, dB(A)DISTANCE: 7 METERS MICROPHONE LOCATION OCTAVE BAND CENTER FREQUENCY (Hz) 31.5 63 125 250 500 1000 2000 4000 8000 dB(A) FRONT 36 50 59 60 64 60 55 52 46 65 RIGHT 35 49 57 58 59 57 53 50 44 62 REAR 29 47 56 57 58 55 49 49 41 60 LEFT 34 45 57 58 57 54 49 45 36 60 AVERAGE 34 48 57 58 60 56 52 49 42 62 60Hz FULL-LOAD DATA, dB(A)DISTANCE: 7 METERS MICROPHONE LOCATION OCTAVE BAND CENTER FREQUENCY (Hz) 31.5 63 125 250 500 1000 2000 4000 8000 dB(A) FRONT 36 53 67 59 61 59 53 50 40 67 RIGHT 35 50 66 58 59 57 52 49 40 65 REAR 33 50 63 58 59 56 50 48 38 63 LEFT 34 50 66 57 58 55 51 48 40 65 AVERAGE 35 51 65 58 59 57 52 49 40 65 1.All positions at 23 feet (7 meters) from side faces of generator set. 2.Test conducted on a 100 foot diameter asphalt surface. 3.Sound pressure levels are subject to instrumentation, installation and testing conditions. RIGHT LEFT FRONT REAR 56 58 60 62 64 66 68 FRONT RIGHT REAR LEFT dB ( a ) Full Load No Load Exhibit 2 Exhibit 3 Name M.ID Attenuation Freq.Direct Day Evening Night Type Value Norm.X Y Z (dBA)(dBA)(dBA)dB(A)(Hz)(Ft.)(Ft.)(Ft.)(Ft.) Generac DG035 35kW Generator S1 65.0 65.0 65.0 Lw/Li 108 20 500 1 3.00 g 0.00 0.00 0.00 Name M.ID Day Night Day Night Type Auto Noise Type X Y Z Nearest Property Line R1 45.10 45.10 0.00 0.00 X Total 5.00 r -227.00 0.00 -17.00 Height (Ft.) SOURCE Reciever Modeling Results CoordinatesResult. PWL Lw/Li Height Level Lr Limit. Value Land Use Coordinates