Bancroft & Piedmont Cellular Facility

Transcription

1 Page 1 of 19 Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California BAC Job # Prepared For: Complete Wireless Consulting Attn: Ms. Kim Le 2009 V Street Sacramento, CA Prepared By: Bollard Acoustical Consultants, Inc. Paul Bollard, President January 28, Bankhead Road Loomis, CA Phone: (916) Fax: (916) BACNOISE.COM

2 Page 2 of 19 Bollard Acoustical Consultants, Inc. Introduction The Bancroft & Piedmont Verizon Wireless Unmanned Telecommunications Facility Project (project) proposes the installation of cellular equipment on the rooftop of a building located at 2700 Bancroft Way in Berkeley, California. The equipment cabinets and emergency diesel standby generator have been identified as primary noise sources associated with the project. Please see Figure 1 for the general site location. The studied site design is dated December 16, Bollard Acoustical Consultants, Inc. has been contracted by Complete Wireless Consulting, Inc. to complete an environmental noise assessment regarding the proposed project cellular equipment operations. Please refer to Appendix A for definitions of acoustical terminology used in this report. Appendix B illustrates common noise levels associated with various sources. Criteria for Acceptable Noise Exposure City of Berkeley Community Noise Ordinance The City of Berkeley Community Noise Ordinance provides exterior noise limits for stationary noise sources. The noise limits are determined by the zoning district of the property subject to the noise. For this project, the adjacent land uses are zoned residential. Exterior Noise Standards The exterior noise limits are applied at the property line of the receiving land use and are graduated depending on the duration of the intruding noise source. Section of the City of Berkeley Municipal Code, which contains the City s exterior noise level standards, is summarized below in Table 1: Table 1 Summary of City of Berkeley Community Noise Ordinance Exterior Noise Limits Applied at Residential Zoning Districts Duration Exceeded, Min. Statistical Noise Level, db Descriptor Daytime (7 a.m.-10 p.m.) Nighttime (10 p.m.-7 a.m.) 30 L L L L Any Lmax Source: City of Berkeley Community Noise Ordinance Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 1

3 Figure 1 Overall Project Site Plan Bancroft & Piedmont Cellular Facility City of Berkeley, California Page 3 of 19 Equipment Cabinets Generator Legend APN Property Lines Proposed Equipment Screen Wall Residential Building Scale (feet)

4 Page 4 of 19 Bollard Acoustical Consultants, Inc. Interior Noise Standards The City of Berkeley Community Noise Ordinance also provides interior noise limits for multifamily residential dwellings. The interior noise limits are graduated depending on the duration of the intruding noise source. Section of the City of Berkeley Municipal Code is summarized below in Table 2. Table 2 Summary of City of Berkeley Community Noise Ordinance Interior Noise Limits Applied Within Multi-Family Residential Dwellings Duration Exceeded, Min. Statistical Noise Level, db Descriptor Daytime (7 a.m.-10 p.m.) Nighttime (10 p.m.-7 a.m.) 5 L L Any L max Source: City of Berkeley Community Noise Ordinance Exemptions to the City of Berkeley Noise Ordinance Standards Section of the Community Noise Ordinance provides exemptions to the noise limits provided in Tables 1 and 2. Specifically, Section (A)(2) provides an exemption to the emission of sound in the performance of emergency work. Section (J) defines emergency work as, work or action made necessary to restore property to a safe condition after a public calamity, or work required to protect persons or property from imminent exposure to danger or damage, or work by public or private utilities to restore utility service. [Emphasis added]. Because the project cellular equipment would operate using City power, the specific purpose of the generator proposed as part of this project is to provide power to the system during an emergency power outage, thereby allowing the system to provide vital communications during the power outage. City of Berkeley Wireless Telecommunications Ordinance Chapter 23C.17 of the City s Municipal Code pertains specifically to Wireless Telecommunications Facilities. Section 23C B.6 states that an objective of the Telecommunications Ordinance is to Support the use of personal wireless services to enhance personal and public health and safety as well as the public welfare of the City of Berkeley. In cases of power outages, the function of the telecommunications facility s emergency generator is to continue to support this objective. Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 3

5 Page 5 of 19 Bollard Acoustical Consultants, Inc. Section 23C D Operation and Maintenance Standards, states the following: Each wireless telecommunications facility shall be operated in a manner that will minimize noise impacts to surrounding residents and persons using nearby parks, trails, and similar recreation areas. Except for emergency repairs, testing and maintenance activities that will be audible beyond the property line shall only occur between the hours of 8:00 a.m. and 7:00 p.m. on Monday through Friday, excluding holidays. All air conditioning units and any other equipment that may emit noise that would be audible from beyond the property line shall be enclosed or equipped with noise attenuation devices to the extent necessary to ensure compliance with applicable noise limitations under Chapter Backup generators shall only be operated during periods of power outages or for testing. At no time shall equipment noise from any source exceed the standards specified the Berkeley Community Noise Ordinance (BMC Chapter 13.40). Noise Standards Applied to this Project Equipment Cabinets Noise would be generated by this project in two ways. The first is the ongoing operation of the cellular equipment cabinets cooling systems. These systems utilize fans to circulate cooling air through the electric circuitry. During warmer periods, the cooling requirements will be greater and the fans will run continuously. During cooler periods, however, the heat transfer requirements are diminished and the fans will run intermittently as needed. Because the fan operation is a normal aspect of the project, and because the fans could run continuously during warm nighttime hours (i.e. more than 30 minutes per hour), the noise standards applied to the equipment cabinets are as follows: 55 db L50 at property line during daytime hours (Table 1) 45 db L50 at property line during nighttime hours (Table 1) 45 db L08 within residences during daytime hours (Table 2) 40 db L08 within residences during nighttime hours (Table 2) Satisfaction with the City s nighttime noise level standards at the project property lines, as well as within nearby residences, including residences located below proposed rooftop equipment, would ensure compliance with the City s less restrictive daytime noise level standards. As a result, this analysis of project-generated equipment cabinet noise levels focuses on achieving compliance with the City s nighttime noise standards of 45 db L50 at project property lines and 40 db L08 within residences. Emergency Generator The function of the emergency generator is to provide ongoing communications support during emergencies resulting in power outages. As a result, the emergency generator would operate only during routine testing and emergency power outages. With respect to testing, the emergency generator would be tested during daytime hours only, twice per month, for a duration not exceeding 15 minutes during each test. The purpose of this Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 4

6 Page 6 of 19 Bollard Acoustical Consultants, Inc. routine testing is to ensure that the generator will be properly lubricated and in good working order in the event of an emergency resulting in a power outage. This operation is consistent with the requirements of the City s Telecommunication Ordinance. Because this routine testing would occur for a period of 15 minutes per hour, and only during daytime hours, the Telecommunication Ordinance states that the noise generation of this aspect of the project should be evaluated relative to the City s Noise Ordinance standards. Specifically, the following City noise standards would be applicable to the routine daytime testing of the generator: 60 db L25 at property line during daytime hours (Table 1) 45 db L08 within residences during daytime hours (Table 2) Aside from routine daytime testing described above, the emergency generator would only operate during emergencies resulting in power outages. The City s Telecommunications Ordinance states that the noise standards of the Berkeley Noise Ordinance shall apply to project equipment. However, Section of the Community Noise Ordinance exempts the generator while it s performing emergency work. As a result, the analysis of generator noise levels focuses on achieving compliance with the standards identified above, as operation of the generator during emergency conditions resulting in power outages are identified as being exempt in the Noise Ordinance. Project Noise Generation As discussed previously, there are two project noise sources which are considered in this evaluation; the equipment cabinet cooling systems and the emergency generator. The evaluation of potential noise impacts associated with the operation of each noise source is evaluated separately below. Equipment Cabinet Noise Sources and Reference Noise Levels The project proposes the installation of two equipment cabinets on the rooftop of the project building, illustrated on Figure 1. Specifically, the cabinets assumed for the project are as follows: one Charles Industries 48V Power Plant and one miscellaneous cabinet cooled by a McLean Model T-20 air conditioner. The cabinets and their respective reference noise levels are provided below in Table 3. The manufacturer s noise level data specification sheets for the proposed equipment cabinets are provided as Appendix C. Table 3 Reference Noise Level Data of Proposed Equipment Cabinets Equipment Number of Cabinets Reference Noise Level, db Reference Distance, feet Charles Industries 48V Power Plant McLean T Notes: Manufacturer specification sheets provided as Appendix C. Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 5

7 Page 7 of 19 Bollard Acoustical Consultants, Inc. Generator Noise Sources and Reference Noise Levels The project also proposes the rooftop installation of a Polar 15 KW diesel generator. Noise exposure from the proposed generator is expected to be approximately 64 db at a distance of 23 feet from the equipment. The manufacturer s noise level data specification sheet for the proposed generator is provided as Appendix D. Predicted Equipment Cabinet & Generator Noise Levels at Nearest Residential Property Lines The project equipment maintain a separation of feet from the nearest residential property lines. Assuming standard spherical spreading loss (-6 db per doubling of distance), projectequipment noise exposure at the closest residential property lines was calculated and the results of those calculations are presented in Table 4. The predicted project equipment noise levels seen in Table 4 take into consideration the shielding provided by the proposed 8-foot tall screen wall, illustrated on Figure 1. The barrier insertion loss calculation worksheet is provided as Appendix E. Table 4 Project-Related Exterior Noise Exposure at Nearest Residential Property Lines Bancroft & Piedmont Verizon Wireless Telecommunications Facility Project Nearest Property Lines 1 Distance from Cellular Equipment (feet) 2 Predicted Exterior Noise Levels, (dba) 3,4 Cabinets Generator Cabinets, (L50) Generator, (L25) East South Notes: 1. Nearest property lines are shown on Figure Distances were scaled from the project equipment to the nearest residential property lines. 3. Predicted noise levels take into consideration the shielding provided by the proposed 8-foot tall screen wall, shown on Figure The noise-generating cooling fans of the equipment cabinets are proposed to face in the northerly direction, with a sideline exposure to the residential property line to the east, and away from the residential property line to the south. Noise level measurements conducted by BAC staff at a similarly configured facility, Livermore (5179 Preston Avenue), indicate that the proposed equipment cabinet cooling fans are approximately 5 and 8 db quieter when measured from the side and opposite side (rear) of the cooling fans, respectively. Predicted equipment cabinet noise levels were adjusted by -5 db at the eastern property line and -8 db at the southern property line to account for the directivity of the cooling fans. The two equipment cabinets were conservatively assumed to be in operation concurrently for the duration of an hour during nighttime hours. According to the City of Berkeley Community Noise Ordinance (Table 1), the corresponding noise level standard given an hour of nighttime operation would be 45 db L50. As shown in Table 4, the predicted equipment cabinet noise levels of db L50 at the nearest residential property lines would satisfy the City of Berkeley 45 db L50 nighttime noise level standard. As a result, no further consideration of noise mitigation measures would be warranted for this aspect of the project. Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 6

8 Page 8 of 19 Bollard Acoustical Consultants, Inc. As mentioned previously, project representatives have indicated that the proposed generator would be in operation for routine testing and maintenance twice a month during daytime hours for no more than 15 minutes. The corresponding noise level standard given less than 15 minutes of operation during daytime hours would be 60 db L25. As shown in Table 4, the predicted generator noise levels at the nearest residential property lines of db L25 would satisfy the City of Berkeley 60 db L25 daytime noise level standard. As a result, no further consideration of noise mitigation measures would be warranted for this aspect of the project. Predicted Equipment Cabinets & Generator Noise Levels within Residential Units Off-Site Residential Interiors Other than the building upon which the proposed telecommunications equipment will be located, the nearest residential building to the project equipment is located approximately 20 feet to the south. After consideration of shielding provided by the proposed screen wall, the predicted equipment cabinet and generator noise levels at that nearest building façade are 37 db and 56 db, respectively, while the equipment is operating. With windows in the open configuration, the exterior to interior building façade noise level reduction is estimated to be 15 db. The resulting interior noise level of 22 db for the equipment cabinets would satisfy the City s 40 db nighttime noise level standard. In addition, the resulting interior noise level of 41 db for routine daytime generator testing operations would satisfy the City s 45 db daytime noise level standard. As a result, no exceedance of the City s interior noise level standards are identified for routine operations of the equipment cabinets or generator equipment proposed as part of this project. On-Site Residential Interiors The proposed generator on the roof of the subject property would be located approximately 5 to 7 feet above a person standing in the unit directly below. Based on the reference generator noise level of 64 dba at a distance of 23 feet and the noise reduction provided by the existing roof deck assembly, the predicted interior noise level within the unit located below the generator was computed to be 41 db while the generator is running. The predicted level of 41 db within the residences below is based on the building roof/ceiling noise reduction analysis presented in Appendix F. The predicted value of 41 db would satisfy the City s interior noise level standard of 45 db within residences. As a result no additional noise mitigation measures would be warranted for the proposed rooftop generator provided it is adequately isolated from the rooftop by resilient mounts which prevent the transmission of perceptible vibration into the rooftop structure. The proposed outdoor equipment cabinets on the roof of the subject property would also be located approximately 5 to 7 feet above a person standing in the unit directly below. Based on the reference equipment cabinet noise level of 67 dba at a distance of 5 feet, and noise reduction provided by the existing roof deck assembly, the predicted interior noise level within the unit located below the equipment cabinets was computed to be 32 db while the equipment cabinet is running. This prediction, which assumes a 35 db reduction in equipment cabinet system noise from the existing roof construction, would satisfy the City s interior noise level Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 7

9 Page 9 of 19 Bollard Acoustical Consultants, Inc. standard of 40 db within residences located below the equipment cabinets. As a result no additional noise mitigation measures would be warranted for the proposed rooftop outdoor equipment cabinet system. Conclusions Based on the equipment noise level data and analyses presented above, project-related equipment noise exposure is expected to satisfy the applicable City of Berkeley noise exposure limits at the closest residential property lines and within the nearest residences. As a result, no additional noise mitigation measures would be warranted for the project. This concludes our environmental noise assessment for the proposed Bancroft & Piedmont Cellular Facility in Berkeley, California. Please contact BAC at (916) or paulb@bacnoise.com with any questions or requests for additional information. Environmental Noise Analysis Bancroft & Piedmont Cellular Facility Berkeley, California Page 8

10 Appendix A Acoustical Terminology Page 10 of 19 Acoustics Ambient Noise Attenuation A-Weighting The science of sound. The distinctive acoustical characteristics of a given space consisting of all noise sources audible at that location. In many cases, the term ambient is used to describe an existing or pre-project condition such as the setting in an environmental noise study. The reduction of an acoustic signal. A frequency-response adjustment of a sound level meter that conditions the output signal to approximate human response. Decibel or db Fundamental unit of sound, A Bell is defined as the logarithm of the ratio of the sound pressure squared over the reference pressure squared. A Decibel is one-tenth of a Bell. CNEL Frequency Ldn Leq Lmax Loudness Masking Noise Peak Noise Community Noise Equivalent Level. Defined as the 24-hour average noise level with noise occurring during evening hours (7-10 p.m.) weighted by a factor of three and nighttime hours weighted by a factor of 10 prior to averaging. The measure of the rapidity of alterations of a periodic signal, expressed in cycles per second or hertz. Day/Night Average Sound Level. Similar to CNEL but with no evening weighting. Equivalent or energy-averaged sound level. The highest root-mean-square (RMS) sound level measured over a given period of time. A subjective term for the sensation of the magnitude of sound. The amount (or the process) by which the threshold of audibility is for one sound is raised by the presence of another (masking) sound. Unwanted sound. The level corresponding to the highest (not RMS) sound pressure measured over a given period of time. This term is often confused with the Maximum level, which is the highest RMS level. RT60 The time it takes reverberant sound to decay by 60 db once the source has been removed. Sabin SEL Threshold of Hearing Threshold of Pain The unit of sound absorption. One square foot of material absorbing 100% of incident sound has an absorption of 1 sabin. A rating, in decibels, of a discrete event, such as an aircraft flyover or train passby, that compresses the total sound energy of the event into a 1-s time period. The lowest sound that can be perceived by the human auditory system, generally considered to be 0 db for persons with perfect hearing. Approximately 120 db above the threshold of hearing.

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15 Appendix E-1 Barrier Insertion Loss Calculation Page 15 of 19 Project Information: Job Number: Project Name: Bancroft & Piedmont Cellular Facility Location(s): Property Line Assessment Noise Level Data: Site Geometry: Source Description: Equipment Cabinets - Combined Source Noise Level, dba: 48 Source Frequency (Hz): 500 Source Height (ft): 5 Receiver Description: Property Line - East Source to Barrier Distance (C 1 ): 6 Barrier to Receiver Distance (C 2 ): 19 Pad/Ground Elevation at Receiver: 0 Receiver Elevation: 5 Base of Barrier Elevation: 0 Starting Barrier Height 8 Barrier Effectiveness: Top of Barrier Barrier Height Barrier Breaks Line of Site to Elevation (ft) (ft) Insertion Loss, db Noise Level, db Source? Notes:

16 Appendix E-2 Barrier Insertion Loss Calculation Page 16 of 19 Project Information: Job Number: Project Name: Bancroft & Piedmont Cellular Facility Location(s): Property Line Assessment Noise Level Data: Site Geometry: Source Description: Equipment Cabinets - Combined Source Noise Level, dba: 48 Source Frequency (Hz): 500 Source Height (ft): 5 Receiver Description: Property Line - South Source to Barrier Distance (C 1 ): 3 Barrier to Receiver Distance (C 2 ): 14 Pad/Ground Elevation at Receiver: 0 Receiver Elevation: 5 Base of Barrier Elevation: 0 Starting Barrier Height 8 Barrier Effectiveness: Top of Barrier Barrier Height Barrier Breaks Line of Site to Elevation (ft) (ft) Insertion Loss, db Noise Level, db Source? Notes:

17 Appendix E-3 Barrier Insertion Loss Calculation Page 17 of 19 Project Information: Job Number: Project Name: Bancroft & Piedmont Cellular Facility Location(s): Property Line Assessment Noise Level Data: Site Geometry: Source Description: Source Noise Level, dba: Source Frequency (Hz): Source Height (ft): Polar Power Diesel Generator Receiver Description: Property Line - East Source to Barrier Distance (C 1 ): 3 Barrier to Receiver Distance (C 2 ): 19 Pad/Ground Elevation at Receiver: 0 Receiver Elevation: 5 Base of Barrier Elevation: 0 Starting Barrier Height 8 Barrier Effectiveness: Top of Barrier Barrier Height Barrier Breaks Line of Site to Elevation (ft) (ft) Insertion Loss, db Noise Level, db Source? Notes:

18 Appendix E-4 Barrier Insertion Loss Calculation Page 18 of 19 Project Information: Job Number: Project Name: Bancroft & Piedmont Cellular Facility Location(s): Property Line Assessment Noise Level Data: Site Geometry: Source Description: Polar Power Diesel Generator Source Noise Level, dba: 67 Source Frequency (Hz): 500 Source Height (ft): 5 Receiver Description: Property Line - South Source to Barrier Distance (C 1 ): 2 Barrier to Receiver Distance (C 2 ): 14 Pad/Ground Elevation at Receiver: 0 Receiver Elevation: 5 Base of Barrier Elevation: 0 Starting Barrier Height 8 Barrier Effectiveness: Top of Barrier Barrier Height Barrier Breaks Line of Site to Elevation (ft) (ft) Insertion Loss, db Noise Level, db Source? Notes:

19 Appendix F Transmission Loss Calculations Bancroft & Piedmont Cellular Facility Page 19 of 19 Calculations: Frequency Spectrum Levels (dba) Overall Center Frequency (Hz) Source Noise Level (dba) Polar Generator at 5 feet* TL of Building Roof (see calculations below): Predicted Noise Level Within Residence * The sum of the indidual octave band sound pressure levels provided in Appendix C does not add up to the overall sound pressure levels reported in that same table. The manufacturer was contacted and cannot account for this descrepancy. As a result, BAC utilized frequency data for a Generac Generator and ajusted the frequency curve shape upward to match the reported overall level of 64.4 db at 23 feet for the Polar Generator. Roof Configuration: Transmission Loss (TL) by Frequency Band: Top: 1/2 inch waterproof decking over 2 layers of 3/4" plywood Gap: 11 inch airgap filled with fiberglass and I joists at 16" O.C. Bottom: 2 layers of 5/8" gypsum board over resilient channels Insul Representation: