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HomeMy WebLinkAbout2011-07-05 Planning Board Supplemental Materials (7) October 13, 2010 The Town of North Andover, Massachusetts RE: Environmental Sound Assessment – AT&T Communication Equipment 300 Chestnut Street AT&T Mobility operates wireless communication equipment at the telecommunications facility at 300 Chestnut Street in North Andover, MA. Modeling Specialties, an environmental consulting firm located in Westford, Massachusetts, has conducted an assessment of environmental sound that results from the operation of wireless communication equipment by AT&T who commissioned this study. They provided the site details and access necessary to identify their equipment and evaluate its sound emissions. The purpose of this letter is to describe the equipment and the results of the survey. The wireless communication equipment includes antennae located on the 152 foot guyed tower, two wall mounted Bard HVAC units and a cable tray to connect the equipment. The Wireless compound includes the AT&T equipment as well as equipment under the control of other carriers that also produce sound from HVAC or ventilation fans. While the scope of this assessment is limited to the AT&T equipment, the field measurements also included sound energy from other site equipment. Figures 1 and 2 show the equipment in the context of the site boundaries and other carrier equipment. Figure 3 shows an orientation view of the AT&T wall mounted HVAC units (file photo of this site.) A site visit was conducted on Wednesday October 13, 2010 to evaluate the equipment sound. The survey was conducted at approximately 9:00 pm after daytime traffic had decreased in the area for the evening. The fluctuating ambient sound field (from offsite sources) ranged from the low 40's to over the 50 dBA standard. But AT&T equipment could be heard onsite when in operation. Other contributing sources include other HVAC systems, distant traffic, and commercial aircraft. During operation, the combined sound level of the AT&T equipment and ambient sources reached 47 dBA at the property line. The site evaluation was requested to evaluate whether the equipment meets the requirements of Town of North Andover bylaw. Section 8.9.4(e) addresses environmental standards for wireless service facilities, including sound generated by the facility equipment. Section 8.9.4(e)(iv) provides that, “Ground-mounted equipment for wireless service facilities shall not generate acoustic noise in excess of 50 dB at the security barrier.” The purpose of this report is to address the North Andover compliance requirements. The measurements at this site were made at stone walls that nearly surround the property. Because the equipment sound did not dominate the sound field at the property line locations, interim measurements were made and extrapolated to the property line. Only the property line to the south was measured directly. There is no sound associated with the antennas, cabling or the structural elements of the equipment shelters. Sound is only produced by supporting equipment like the two wall mounted HVAC units. Because of significant distance, the HVAC sound is well below the ambient at most property line locations. For that reason, interim measurements were made that will allow the measured WCF sound to be estimated at more distant property lines. Detailed measurements included various statistical metrics and 1/3 octave band frequency analysis. However, the results are presented in this statement as combined A-weighted levels consistent with the By Law requirements. The measured sound levels of are shown in the Table 1. Table 1: Measured Ground Level Sound Levels in the Site Area MeasurementGoal9:00 PM, 10/13/10 Dominant Location (dBA) (dBA, L)Sources Observed 90 Ambient (no Equip.) 40 Distant Roadway Traffic, aircraft Reference W @ 75 ft 46 Distant Roadway, HVAC Reference E @ 75 ft 45 Distant Roadway, HVAC Property Line S 50 47 Distant Traffic, Aircraft, HVAC Property Line W 50 42 Distant Traffic, Aircraft, Slight HVAC Property Line E 50 38 Distant Traffic, Aircraft, Slight HVAC Property Line N 50 38 Distant Traffic, Aircraft Conclusion: AT&T equipment meets By Law Standards and makes minor contribution to measured sound levels at offsite receptor locations These measurements were made using a Rion NA-28 sound level meter that meets the requirements of ANSI S1.4 Type 1 – Precision specification for sound level meters. The meter was held at arm's length, 5 feet above the ground. The microphone was fitted with the factory recommended 3-inch foam windscreen. The meter was programmed to take measurements and store the processed statistical data. Various statistical levels and 1/3 octave band spectra were documented for use in this analysis. But only the A-weighted L90 is presented here to represent the equipment sound level consistent with the North Andover Bylaw. The property line and interim measurements included sound from other carrier equipment and also sound from ambient sources. Nevertheless, the property line levels were consistently less than 50 dBA. This demonstrates that the AT&T equipment alone remains well below the North Andover By Law standard of 50 dBA. I certify that the analysis of sound levels is accurate and consistent with methods that are common to the acoustic analysis of such sources. I am qualified to make this statement based on training and experience in conducting analyses of environmental sounds. I am a Certified Consulting Meteorologist with more than 20 years experience conducting environmental analyses in the technical areas of air quality, noise, and visual aesthetics. I am a technical expert on the noise committee of Air & Waste Management Association headquartered in Pittsburgh, Pennsylvania. I have published many refereed papers on various aspects of environmental noise. I have analyzed the noise emissions of major industrial projects such as power plants, wastewater treatment plants and manufacturing facilities. Related to these analyses, I have testified as a technical expert before the Energy Facility Siting Boards of Massachusetts, Connecticut and Rhode Island. I have also testified before many regional and municipal approval boards in Massachusetts, Rhode Island, New Hampshire, Maine, New York, Michigan, Illinois, and California. Thank you for your attention. Respectfully, Modeling Specialties Douglas L. Sheadel, CCM Principal Figure 2: Detail of AT&T Ground Mounted Equipment in the Context of the WCF compound