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HomeMy WebLinkAboutAttachment 13-Environmental Sound Assessment Environmental Sound Assessment Wireless Communications Facility Site MA-875052 1060 Falmouth Street Barnstable, Massachusetts 02632 January 21, 2022 Prepared For: Advanced Engineering Group 500 North Broadway, East Providence, RI 02914 Prepared By: Modeling Specialties 30 Maple Road Westford, MA 01886 Advanced Engineering Group, Centerville MA 1 Sound Assessment ENVIRONMENTAL SOUND ASSESSMENT Advanced Engineering Group is supporting Crown Castle in the relocation of a Wireless Telecommunications Facility in Barnstable, Massachusetts to support wireless communications in the area. The proposed installation will include antennas on a new 110-foot monopole at 1060 Falmouth Road replacing an existing monopole across the street at 1047 Falmouth Road. Supporting electronic equipment will be in a fenced compound at the foot of the pole. Up to four carriers will be supported by the facility. Each carrier is expected to have electronics cabinets. Three of the carriers are expected to have generators. The fence to be installed is an 8 foot wood panel fence ‘dog eared design’ with an acoustic liner on the inside of the fence in the direction of the residences within 500 feet. This report addresses the existing sound levels in the area, sources of sound expected at this installation and an evaluation of its potential to affect the neighboring land uses. The equipment configuration and siting were designed specifically to minimize environmental effects. Overview of Project and Site Vicinity The project is located on a site that is zoned residential and commercial along Falmouth Road (Route 28) in Centerville/Hyannis, Barnstable, MA. The existing building is commercial and surrounded by a large parking area. The facility is planned within the residentially zoned area of the site adjacent to the rear of the commercial parking lot. The terrain is reasonably flat. Some residences in the area will have shielding benefits of the forest and vegetation but the nearest residences will have essentially line-of-sight in some seasons so the conservative model has no shielding benefit from terrain or forest. Daytime and nighttime field measurements were made to survey existing conditions. The equipment sound was estimated using vendor data and measurements made at similar installations. The corresponding levels expected at the nearby sensitive locations were estimated using standard noise modeling techniques prescribed in acoustical literature. This study is based on the plans issued by the Advanced Engineering Group dated January 10, 2022. This conservative study is based on the highest sound levels that the equipment is expected to make even though it makes that sound only a small fraction of the time. Figure 1 has a backdrop of a Google aerial image and is annotated to show the proposed site, surrounding area and nearby receptor locations with their orientations and distances to the monopole. Advanced Engineering Group, Centerville MA 2 Sound Assessment Figure 1: Project Area Showing the Proposed Equipment Compound, Property Lines and Nearest Receptors Advanced Engineering Group, Centerville MA 3 Sound Assessment Discussion of General Noise Analysis Methods There are a number of ways in which sound (noise) levels are measured and quantified. All of them use the logarithmic decibel (dB) scale. Following is a brief introduction to the noise measurement terminology used in this assessment. Noise Metrics The Sound Level Meter used to measure noise is a standardized instrument.1 It contains “weighting networks” to adjust the frequency response of the instrument to approximate that of the human ear under various circumstances. One of these is the A-weighting network. A-weighted sound levels emphasize the middle frequency sounds and de- emphasize lower and higher frequency sounds; they are reported in decibels designated as “dBA.” All broadband levels represented in this study are weighted using the A - weighting scale. Figure 2 illustrates typical sound levels produced by sources that are familiar to most people. The sounds in our environment usually vary with time, so they cannot always be described with a single number. Two methods are used for describing variable sounds. These are exceedance levels and equivalent level. Both are derived from a large number of moment-to-moment A-weighted sound level measurements. Exceedance levels are designated Ln, where “n” can have any value from 0 to 100 percent. For example:  L90 is the sound level in dBA exceeded 90 percent of the time during the measurement period. The L90 is close to the lowest sound level observed. It is essentially the same as the residual sound level, which is the sound level observed when there are no loud, transient noises.  L50 is the median sound level: the sound level in dBA exceeded 50 percent of the time during the measurement period.  L10 is the sound level in dBA exceeded only 10 percent of the time. It is close to the maximum level observed during the measurement period. The L10 is sometimes called the intrusive sound level because it is caused by occasional louder noises like those from passing motor vehicles. By using exceedance levels, it is possible to separate prevailing, steady sounds (L90) from occasional, louder sounds (L10) in the environment. 1 American National Standard Specification for Sound Level Meters, ANSI S1.4-1983, published by the Standards Secretariat of the Acoustical Society of America, NY. Advanced Engineering Group, Centerville MA 4 Sound Assessment Figure 2: Typical Sound Levels from Everyday Experience Advanced Engineering Group, Centerville MA 5 Sound Assessment The equivalent level is the level of a hypothetical steady sound that has the same energy as the actual fluctuating sound observed. The equivalent level is designated Leq, and is also A-weighted. The equivalent level is strongly influenced by occasional loud, intrusive noises. When a steady sound is observed, all of the Ln and Leq are equal. In the design of noise control treatments, it is essential to know something about the frequency spectrum of the sound of interest. Noise control treatments do not function like the human ear, so simple A-weighted levels are not useful for noise-control design or the identification of tones. The spectra of sounds are usually stated in terms of octave band sound pressure levels in dB, with the octave frequency bands being those established by standard.2 The sounds at the proposed site were evaluated with respect to the octave band sound pressure levels, as well as the A-weighted equivalent sound level. Only the A-weighted values are presented here since they represent the more easily recognized sound scale that is relevant to the Town and regional standards. Noise Regulations and Criteria Sound compliance is judged on two bases: the extent to which governmental regulations or guidelines are met, and the extent to which it is estimated that the community is protected from the excessive sound levels. The governmental regulations that may be applicable to sound produced by activities at the project site are summarized below. Federal • Occupational noise exposure standards: 29 CFR 1910.95. This regulation restricts the noise exposure of employees at the workplace as referred to in OSHA requirements. Workers will not routinely attend this facility. Furthermore, the facility will emit only occasional sounds of modest levels, as demonstrated by this study. State • In Massachusetts, noise is regulated as an air pollutant. 310 CMR §7.10 U qualitatively prohibits “unnecessary emissions from [a] source of sound that may cause noise”. This is interpreted quantitatively by MDEP’s Form BWP AQ SFP3 and their DAQC Policy 90-001. The MDEP’s Noise Policy states that a new noise intrusion may not increase the broadband sound level by more than 10 dBA over the pre-existing L90 ambient level. Tonal sounds, defined as any octave band level that exceeds the levels in adjacent octave bands by 3 dB or more, are also prohibited. The MDEP usually defers to applicable quantitative local ordinances when available. 2 American National Standard Specification for Octave, Half-octave and Third-octave Band Filter Sets, ANSI S1.11-1966(R1975). Advanced Engineering Group, Centerville MA 6 Sound Assessment Regional • The Cape Cod Commission provides a Technical Bulletin 97-001 entitled: Guidelines for DRI Review of Wireless Communication Towers adopted 10/9/97; Revised 3/4/99; Revised 9/30/2010. It provides quantitative sound requirements of the equipment at this facility shown in the excerpt: VI B. Noise: Ground mounted personal wireless service facilities should not generator noise from equipment and/or wind in excess of 50 db at the property line. It is noted that in Section III the definition R. Personal Wireless Service Facility: Facility for the provision of personal wireless services, including the mount, antenna(s), equipment shelter(s) and security barrier. While a common feature at the facilities, the standby generator is not included in the definition. The facility sound (without generator) will be evaluated against this standard. Local • The Town of Barnstable has ordinances that control noise and control Wireless Facilities at Sections 133 and 240, but a review did not identify any quantitative requirements that would apply to the sound from the equipment in the compound. For that reason, the criteria provided by the Cape Cod Commission and the MDEP will be used to evaluate the sound at this project. Existing Community Sound Levels A site survey and noise measurement study were conducted on January 4, 2022 to measure the existing sound levels at and around the site. The measured levels included occasional intrusive sound from traffic, commercial activities, birds and small aircraft. The area around the existing building is paved for access and parking for the commercial use. The daytime survey was conducted in business hours. The nighttime survey was conducted during the quietest hours of the night (typically midnight to 5:00 am). The routine operation of the generator is never expected at night, but the nighttime sound levels were used as a reference for the character of the existing sound field and for the routine facility operation. Measurement Methodology Since sound impacts are greatest when existing sound levels are lowest, this study was designed to measure community sound levels under conditions typical of “quiet periods” for the area. This study uses methodology to support a MDEP type study (increase in ambient) and also supports the property line analysis. The MDEP uses the background metric (L90), which statistically excludes all non-steady sources. The L90 metric gives the lowest 10 percent of the many samples gathered during a 20-minute measurement taken in the project area. Meteorological conditions during the surveys were all within the ANSI required conditions to conduct sound measurements. This includes representative seasonal temperatures, calm or light winds and no precipitation (or water standing on roadways). All meteorological conditions were noted from field Advanced Engineering Group, Centerville MA 7 Sound Assessment observations, but were also compared to the reports at Barnstable Municipal Airport, MA (KHYA). It is typical for airport winds to be higher than measured in the community because they are measured at elevated locations in widely open areas. The site area is largely forested, so the sound level meter was shielded from much of the prevailing wind. Measurements were attended and made with a Rion NA-28 sound level meter. The meter meets the requirements of ANSI S1.4 Type 1 – Precision specification for sound level meters. The meter was mounted at approximately 5 feet above the ground. The microphone was fitted with factory recommended foam windscreen. The meter was used to sample the environmental sound and to process the sound into various statistical metrics for use in this analysis. The meter is equipped with real time octave band filter set, which allowed it to process sound levels into 1/3 octave bands. While frequency specific data were collected, the survey results are reported only in combined A- weighted levels for simplicity and consistency with the applicable criteria. The filters comply with the requirements of the ANSI S1-11 for octave band filter sets. The meter was calibrated in the field using a Larsen Davis Cal-200 sound level calibrator before and after the measurement sessions. The results of the field calibration indicated that the meter did not drift during the study. The results of the surveys allow both quantitative and qualitative analyses of the acoustical environment surrounding the proposed equipment. The characterization of ambient sound levels reflects the variations caused by volume of traffic on local roadways, occasional aircraft passes and community sounds. The measurements were made at near freezing temperatures in the off season for the Cape. Therefore, the traffic levels and human outdoor activity are low. It is anticipated that the ambient baseline would be higher than observed under higher traffic conditions. Measurement Results The measured background levels in the project area ranged from 42 dBA during the daytime to 36 dBA in the quietest hours of the night. The corresponding Leq values were 47 dBA to 42 dBA. These levels were measured on the east side of the rear parking lot. An additional spot measurement was taken on the east side of the wooded parcel along Wequaquet Lane with observed levels within 1 dB of the parking area. The project baseline results are summarized in Table 1. Table 1: Measured Background Sound Levels in the Project Area Period Time Leq dBA L90 dBA Daytime 1:53 PM 47 42 Nighttime 4:21 AM 42 36 Advanced Engineering Group, Centerville MA 8 Sound Assessment Sounds from the Proposed Installation The project plans include space for four carriers. Most of the infrastructure produces no sound. Cabling and piping for utilities will be underground. The monopole and antenna assemblies are acoustically inert and are designed for minimal risk of wind noise. Only two types of sources are planned for this facility as quantified in this study. The antennas will be supported by cabinet mounted radio electronics and generators at the foot of the tower. Each carrier can be expected to have electronic equipment cabinets. Three of the planned carriers have indicated that they will have a generator. The facility layout is shown in Figure 3. The corresponding elevation sketch is shown in Figure 4. Routine Sound Emissions The only routine sound emissions from typical T-Mobile equipment is from the electronics cabinet fans. The small fans in the BTS cabinet draws outside air through the unit. It has a smooth broadband character that produces about 50 dBA at 15 feet from the unit. The field image to the right has an inset showing that the rear or sides have no louvered openings. All of the sound is emitted from the front of the cabinet. The modeling is based on a single cabinet emitting to the South. AT&T commonly uses Walk-In-Cabinet (WIC) for their equipment, which is usually cooled by ambient air. The WIC cooling fans increase in speed as the need for cooling increases. Their sound at full speed exceeds the modest sound from the supplemental door mounted cooler. The cooler engages before the full speed fans are needed, usually about 90°F. The highest sound is expected from the WIC plus cooler is about 50 dBA at 23 feet. The fans on the WIC will operate continuously, so there will be no variation from moment to moment or cycling from equipment startup. Fans are mounted on the inside of the cabinet (which will always remain closed). In this way, the cabinet configuration is designed for minimal effect on the surrounding area. The sketch to the right shows the cooler on the front of the AT&T WIC. There are two Verizon cabinets in their typical equipment configuration. One cabinet has only batteries and is not cooled. Their electronics cabinet is usually cooled by small fans that draw air in through vents and distribute it to cool the cabinet. It has a smooth broadband character that produces about 50 dBA at 3 feet from the unit. When the cabinet exceeds a save temperature, usually about 90°F, the door mounted cooler supplements the cooling fans to protect the electronics. The cooler emits sound only from the front of the cabinet at about 50 dBA at a distance of 23 feet. The modeling is based on the unit’s sound being emitted to the South. Advanced Engineering Group, Centerville MA 9 Sound Assessment Figure 3: Plan Showing the Equipment Compound behind the Existing Parking Lot All Carrier Equipment is Expected to be within their Lease Areas (1-4) in an order TBD Advanced Engineering Group, Centerville MA 10 Sound Assessment Figure 4: Elevation Plan Showing the Vertical Character of the Monopole and Compound Also Shows the Acoustic Barrier Liner on the Fence Nearest to Residences Advanced Engineering Group, Centerville MA 11 Sound Assessment 7.5 kW Delta Electronics 30 kW MTU GC6NLT1 35 kW Generac SG035 Non-Routine Sound Emissions The installation will include three generators installed inside sound reducing enclosures. The three generators will be different models, but all are designed for quiet operation and are fueled by natural gas. One is a Delta Electronics generator rated for 7.5 kW of Direct Current (DC) and is sound rated at less than 60 dBA at a standardized 23 feet. Another is an MTU Onside Energy 30-GC6NLT1 unit with a power rating of 30 kW and a sound rating of 60 dBA. The third is a Generac SG035 with a power rating of 35 kW and a sound rating of 65 dBA at 23 feet. The proposed generators will be monitored remotely by the respective carriers and tested regularly. The test schedule varies by the carrier, but is commonly for about a half hour during a daytime hour every week or two. The testing is a maintenance function and assures the safe and effective operation of the respective carrier’s wireless equipment even in the event of an extended power outage. Project Sound Level Mitigation Features Various design features were implemented at this facility to reduce the potential sound. While the cabinets produce some sound, their modest sound is primarily directed to the south and won’t affect the neighbors. Nevertheless, the cabinet sound is included in the numerical model. The primary source of facility sound is the infrequent operation of the generators. Carriers tend to select generator models that are highly mitigated for sound. As a comparison, a typical residential mobile gasoline generator in the 4,000 to 6000-Watt range, common in most residential communities, operates at about 70 dBA at 23 feet. All of the planned units are far higher capacity, yet each is expected to operate at a lower sound level at the same reference distance. A supplementary 6-foot sound barrier is planned to further shield the receivers from the generator sound. Worst-case modeling of the facility assumes simultaneous operation of the generator and cooler (which may never happen). If they were operated separately, the resulting level would be significantly less. The Cape Cod Commission recommendation that gaseous fuel be used further quiets the operating sound. Gaseous fuel like natural gas and propane is quieter, but also lowers the equipment profile by eliminating the generator’s fuel tank (which would be installed underneath the unit in a liquid fuel configuration). The lower height increases the benefit of the proposed sound barrier lining of the fence. Modeling Details Noise prediction modeling was performed using CADNA software under downwind weather conditions as assumed in the standard ISO 9613-2. Table 2 summarizes the modeling input parameters. Advanced Engineering Group, Centerville MA 12 Sound Assessment Table 2: Modeling Input Parameters Item Modeling Input and Description Terrain Flat Terrain assumed Temperature 10oC Relative Humidity 70% Weather Condition 6.5 mph, directly from facility to receptor* Ground Attenuation 0.2, hard surface (0.5 = soft ground, 0.0 = pure reflection) Atmospheric Inversion CONCAWE – Category F** # of Sound Reflections 2 Receptor Height 1.5 meter above ground level * Propagation calculations incorporate the adverse effects of certain atmospheric and meteorological conditions on sound propagation, such as gentle breeze of 1 to 5 m/s (ISO 1996-2: 1987) from source to receiver. ** Category F represents a stable atmosphere that promotes noise propagation. Sound Level Modeling Results Since all the equipment with the potential to emit sound will be at ground level, the sound will be shielded in some directions by other equipment. Only the shielding by the sound barriers are included in the modeling. The combined sound from the routine equipment operation will be 50 dBA or less at the property lines as shown in Table 3. The occasional daytime generator tests are expected to meet the MDEP criteria at all residences as shown in Table 4. Graphical summaries of the results are also provided in Figure 5 and 6. Table 3: Summary of Property Line Sound Levels for Routine Wireless Equipment Receptor Location Dist (Ft) Ambient Level Day/Night (dBA) Routine Ops (dBA) Comply? CCC P/L SW 42 42 / 36 50 Yes P/L NW 249 42 / 36 32 Yes P/L NE 110 42 / 36 41 Yes P/L East 200 42 / 36 39 Yes P/L South 319 42 / 36 37 Yes Table 4: Summary of Sound Levels at the Residences (all equipment plus generators) Receptor Location Dist (Ft) Ambient Level Day (dBA) Combined Sound (dBA) Increase (dB) Comply MDEP Res West1 372 42 41 +3 Yes Res NW2 368 42 39 +2 Yes Res NW3 349 42 39 +2 Yes Res North4 206 42 44 +4 Yes Res North5 125 42 47 +6 Yes Res North6 323 42 40 +2 Yes Res NE7 585 42 39 +2 Yes Res NE8 570 42 42 +3 Yes Advanced Engineering Group, Centerville MA 13 Sound Assessment Conclusions The potential sound of the proposed Wireless Telecommunications Facility was evaluated using measured field data, manufacturers data and numerical modeling methods. Ambient sound levels were established by field measurements using equipment that is standardized to the current ANSI standards. Equipment operating sound levels were quantified using vendor estimates confirmed by representative field measurement at other installations. Much of the infrastructure and equipment produces no significant sound. The cabinet fans will operate as needed to protect the cabinet electronics from over-heating. The carrier fans typically operate continuously at a very low level of sound that will be well below the ambient level s at the residences, so are not expected to be noticed in the community. They may be noticeable at the nearest commercial property line. Under high ambient temperatures, usually above 90° F, the walk-in cabinet will trigger elevated fan power or the supplementary cooling system on its door. This represents worst-case nighttime sound and could occur during nighttime conditions during only the few hottest days a year). Under the worst-case emissions, the facility is expected to meet the 50 dBA standard at the property lines. Infrequently, for one half-hour per week, the proposed facility sounds will include the daytime testing of the emergency generators. The combined sound from the carrier cabinets and generators is expected to be the worst-case daytime sound level. During a simultaneous test, the facility sound is expected to be 47 dBA or less at the nearest residences. This study is based on the facility’s worst-case daytime and nighttime sounds, which represent very infrequent conditions. The combined sound from the three generators is used to represent the worst-case daytime sound level but it is very unlikely to ever happen. The generators are operated independently by various carriers in support of their own networks by their own operating guidelines. While the tests are expected to only occur during the daytime hours, they are likely to be tested at varied times. For this reason, the highest sound from generator testing will be lower than modeled here. The modeling shows that the facility will meet the MDEP criteria at all residences in the area. The Cape Cod Commission guidelines were also evaluated in this study. The modeling of equipment and wind from the facility indicates that the CCC criterion will also be met. Advanced Engineering Group, Centerville MA 14 Sound Addendum Figure 5: Graphical Summary of the Routine Facility Sound (Combined all Wireless Equipment) Advanced Engineering Group, Centerville MA 15 Sound Addendum Figure 6: Graphical Summary of the Modeled Community Sound Levels (Combined Wireless Equipment plus 3 Generators)