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HomeMy WebLinkAboutSEA Logan Avenue Noise Study 222 Etruria Street, Ste 100, Seattle, Washington 98109 t. 206.839.0819 f. 206.839.0824 December 28, 2017 Richard Cardoza LDC, Inc. 20210 142nd Ave NE Woodinville, WA 98072 Re: Acoustical Report – Verizon SEA Logan Ave – Carpenter’s Union Site: 231 Burnett Avenue N, Renton, WA 98057 Dear Richard, The following report presents a noise study for the proposed Verizon telecommunications facility at 231 Burnett Avenue N in Renton, Washington. This noise study extends from the proposed equipment to the nearest properties. The purpose of this report is to document the existing conditions and the impacts of the acoustical changes due to the proposed equipment. This report contains data on the existing and predicted noise environments, impact criteria and an evaluation of the predicted sound levels as they relate to the criteria. Ambient Conditions Existing ambient noise levels were measured on site with a Svantek 971 sound level meter on December 28, 2017. Measurements were conducted as close to the proposed location as possible and the property lines in accordance with the State of Washington code for Maximum Environmental Noise Levels WAC 173-60-020. The average ambient noise level was 61.2 dBA, due primarily to traffic noise on Logan Avenue. Code Requirements The site is located within the City of Renton Zoning jurisdiction on property designated with a UC zoning. The nearest receiving properties, to the west and south, are zoned R-10. Renton Municipal Code 8-7-4 designates UC as Class B EDNA and R-10 as Class A EDNA. The proposed new equipment includes equipment support cabinets and an emergency generator. The equipment support cabinets are expected to run 24 hours a day. The generator will run once a week during daytime hours for maintenance and testing purposes only. Renton Municipal Code Chapter 8-7-2 adopts Washington Administrative Code Sections 173-60- 020, 173-60-040, 173-60-050 and 173-60-090. Under WAC 173-60-040, noise from equipment on a Class B EDNA property is limited as follows: Class A EDNA Receiver: Noise is limited to 57 dBA during daytime hours. During nighttime, defined as the hours between 10 p.m. and 7 a.m., maximum sound levels are reduced by 10 dBA Verizon SEA Logan Ave – Carpenter’s Union Page 2 for receiving properties within Class A EDNA's. Since the support cabinets are expected to operate 24 hours a day, they must meet the 47 dBA nighttime limit. Additionally, WAC 173-60-040 allows that during any one-hour period, the maximum permissible noise level may be exceeded by 5 dBA for a 15 minute period. Therefore, the generator must not exceed 62 dBA when running during daytime hours for maintenance testing. The generator is exempt during emergency operation. Predicted Equipment Sound Levels: 24-Hour Operation Equipment The following table presents a summary of the equipment and their associated noise levels: Table 1: Equipment Noise Levels Equipment dBA (each) Quantity Combined dBA @ 5 ft Charles CUBE-SS4D207XNZ which is equipped with (3) total Delta HET200PB Thermoelectric Cooling units. 61 dBA @ 3ft 3 61 Charles CUBE-PM63912UNZ which is equipped with a Dantherm 707893 10,000 BTU Air Conditioner 74 dBA @ 5ft 1 74 Total dBA (All cabinets combined) 74 Methods established by ARI Standard 275-2010 and ASHRAE were used in predicting equipment noise levels to the receiving properties. Application factors such as location, height, and reflective surfaces are accounted for in the calculations. The equipment will be located at grade surrounded by an 8’ tall chain link fence. The nearest receiving properties are approximately 45 feet south, and 6 feet west of the equipment cabinets. The following table presents the predicted sound levels: Table 2: Predicted Noise Levels for the Proposed Equipment Cabinets Line Application Factor S W 1 Sound Pressure Level at 5 ft (dBA), Lp1 74 74 2 Location Factor (Unit Shielded by Cabinet) -0 -10 3 Distance Factor (DF) Inverse-Square Law (Free Field): DF = 20*log (d1/d2) -19 (45 ft) -2 (6 ft) 4 New Equipment Sound Pressure Level at Receiver, Lpr (Add lines 1 - 3) 55 62 As shown in Table 2, the sound pressure level from the proposed equipment is predicted to be 55 dBA to the south and 62 dBA to the west, which does not comply with the 47 dBA nighttime code limit at a residential receiving property. It will be necessary to incorporate a barrier into the fence in order to reduce noise. Noise levels are expected to comply at all other receiving property lines. Verizon SEA Logan Ave – Carpenter’s Union Page 3 Predicted Equipment Sound Levels: Emergency Equipment The proposed equipment includes one Generac SDC20 20 KW generator with a Level 1 sound enclosure and has a sound level of 65 dBA at 23 feet. The generator will be lo located at grade surrounded by a chain link fence. The nearest receiving properties are approximately 40 feet south, and 2 feet west of the generator. The following table shows the predicted sound levels: Table 3: Predicted Noise Levels: Proposed Emergency Generator Line Application Factor S W 1 Equipment Sound Pressure Level at 23 ft. (dBA), Lp1 65 65 2 Distance Factor (DF) Inverse-Square Law (Free Field): DF = 20log (d1/d2) -5 (40 ft) +21 (2 ft) 3 New Equipment Sound Pressure Level at Receiver, Lpr (Add lines 1-2) 60 86 As shown in Table 3, the sound pressure level from the generator is predicted to be 60 dBA at the to the south, which complies with the 62 dBA code limit to a residential property during test cycle operation. The sound pressure level is predicted to be 86 dBA to the west, which does not comply. It will be necessary to mitigate noise by 24 dBA to the west. Generator Noise Mitigation: It will be necessary to move the generator 4 feet to the east so that it is no more than 6 feet from the west property line. The current location is within 2 feet of the property line and will not meet the noise limits even with a barrier. A barrier will be required as well. Barrier Design: The barrier shall be constructed on the west and south sides of the concrete equipment pad per the following: The new predicted noise levels are shown in Table 4. 1. Construct a noise barrier around the equipment that is at least 8 feet tall, as indicated by the bold red line in Figure 1. A general detail of the barrier is provided in Figure 2. 2. Construct the noise barrier of a solid material that has a surface mass of 2 lbs/sq ft. (1) layer of 3/4” exterior grade plywood or (1) layer of 16-gauge sheet metal is approximately 2 lbs/sq ft. It is permitted to add additional material to the outside of the barrier, such as fence board or siding for aesthetic purposes. However, these added materials cannot substitute for the required continuous plywood or metal. 3. Line the inside of the noise barrier (side facing cabinets) with a sound absorbing material that has a minimum NRC rating of 0.50. Weather-resistant materials that meet this requirement include 2-inch thick exterior grade F-Sorb, available from Forrest Sound Products (425) 881-1111. 4. Leave no air gaps between joints in the barrier material. All air gaps must be sealed with a non-hardening acoustical sealant. The most efficient barrier for reducing noise has materials that are air-tight to create a continuous envelope. Verizon SEA Logan Ave – Carpenter’s Union Page 4 Figure 1: Required Barrier Location Verizon SEA Logan Ave – Carpenter’s Union Page 5 Figure 2: General Barrier Detail Table 4: Predicted Noise Levels for the Proposed Equipment Cabinets with the Required Mitigation Line Application Factor S W 1 Sound Pressure Level at 5 ft (dBA), Lp1 74 74 2 Location Factor (Unit Shielded by Cabinet) -0 -10 3 Barrier Attenuation Factor -10 -15 4 Distance Factor (DF) Inverse-Square Law (Free Field): DF = 20*log (d1/d2) -19 (45 ft) -2 (6 ft) 5 New Equipment Sound Pressure Level at Receiver, Lpr (Add lines 1 - 4) 45 47 As shown in Table 4, the sound pressure level from the proposed equipment cabinets will meet the 47 dBA code limit with the required barrier. Verizon SEA Logan Ave – Carpenter’s Union Page 6 Table 5: Predicted Noise Levels for the Proposed Emergency Generator with the Required Mitigation Line Application Factor S W 1 Equipment Sound Pressure Level at 23 ft. (dBA), Lp1 65 65 2 Barrier Attenuation Factor -10 -15 3 Distance Factor (DF) Inverse-Square Law (Free Field): DF = 20log (d1/d2) -5 (40 ft) +12 (6 ft) 4 New Equipment Sound Pressure Level at Receiver, Lpr 50 62 As shown in Table 5, the sound pressure level from the proposed generator will meet the 62 dBA day-time code limit during test cycle operation with the required relocation and noise barrier. Please contact us if you have any questions or require further information. Sincerely, SSA Acoustics, LLP Joel Esselstrom Acoustical Consultant 222 Etruria St., Seattle, WA 98109 (206)839-0819 joel@ssaacoustics.com This report has been prepared for the titled project or named part thereof and should not be used in whole or part and relied upon for any other project without the written authorization of SSA Acoustics, LLP. SSA Acoustics, LLP accepts no responsibility or liability for the consequences of this document if it is used for a purpose other than that for which it was commissioned. Persons wishing to use or rely upon this report for other purposes must seek written authority to do so from the owner of this report and/or SSA Acoustics, LLP and agree to indemnify SSA Acoustics, LLP for any and all resulting loss or damage. SSA Acoustics, LLP accepts no responsibility or liability for this document to any other party other than the person by whom it was commissioned . The findings and opinions expressed are relevant to the dates of the works and should not be relied upon to represent conditions at substantially later dates. Opinions included therein are based on information gathered during the study and from our experience. If additional information becomes available which may affect our comments, conclusions or recommendations SSA Acoustics, LLP reserves the right to review the information, reassess any new potential concerns and modify our opinions accordingly.