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Home My WebLink AboutNoise Report-Rev 5-8-15 May 8, 2015 Kimberly Spongberg Site Acquisition - NSB Velocitel, Inc. 4004 Kruse Way Pl, Suite 220 Lake Oswego, OR 97035 Re: Acoustical Report AT&T EG46 Fox Hollow Road & Amazon Road Site: 4060 W. Amazon Drive, Eugene, OR 97405 Dear Kimberly, This report presents a property line noise study for the proposed AT&T telecommunications facility at 4060 West Amazon Drive in Eugene, Oregon. This noise study extends from the proposed equipment to the nearest receiving 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 Larson-Davis 820 sound level meter on February 6, 2014. Measurements were conducted as close to the receiving property lines nearest the proposed location as possible in accordance with Oregon Administrative Rules (OAR) 340-35-035 subsection (3)(b). The average ambient noise level was 49 dB(A), primarily due to local traffic on Amazon Road. The weather during the measurements was cloudy and the roads were snowy. Code Requirements The site is located within the City of Eugene Zoning jurisdiction on property with an R-1 (Residential) zoning designation. All of the receiving properties are also zoned Residential. The proposed new equipment consists of equipment support cabinets and an emergency generator. The cabinets are expected to run intermittently 24 hours a day. The emergency generator would be in operation for less than 10 consecutive minutes during routine monthly testing (during daytime hours) and during a power outage. Eugene City Code Chapter 9.5750.7.f limits noise being received by an R-1 or other residential property to 45 dBA. Additionally, for this particular site the City has recommended that the equipment meet 35 dBA at the nearest receiving properties. 222 Etruria Street, Suite 100 Seattle, WA 98109 206.839.0819 P // 206.839.0824 F AT&T EG46 Fox Hollow Road & Amazon Road Page 2 Predicted Equipment Sound Levels 24-Hour Operation Equipment The equipment will be located in a shelter served by two Marviar air conditioning units. According to manufacturer data, the Marvair AVP48 air-conditioning which each produce 72 dB(A) at 5 feet. The equipment will operate on a lead/lag cycle such that one unit will be in operation at a time. To predict equipment noise levels at the receiving properties, this survey uses the methods established by ASHRAE and AHRI Standard 275-2010. Application factors such as location, height, and reflective surfaces, and noise reduction from intervening elements are accounted for in predicting the sound level at the receiving properties. The nearest receiving properties are approximately 90 feet to the west, 180 feet east across W. Amazon Road, and 200 feet south across Fox Hollow road. The building blocks the equipment noise to the property to the west, and the cedar fence surrounding the tower blocks the equipment to the east. The predicted sound levels are shown in the table below. Table 1 Application Factors and Predicted Noise Levels Proposed New Equipment Line Application Factor W E S Equipment Sound Pressure Level at 5 ft., L 72 72 1 72 PS Building / Wood Fence Reduction -6 2 -20 Distance Factor (DF) -25 -31 -32 3 DF = 20 log(D/D) (90 ft) (180 ft) (200 ft) 1012 4 New Equipment Sound Pressure Level at Receiver, L 27 35 40 PR According to the predicted noise levels, the equipment would be below the 45 dBA code limit, but would not meet the City's recommended 35 dBA level at the south property line. Mitigation measures to meet this recommended noise level are provided below. Noise Mitigation: The following noise mitigation must be implemented for the AC units: Install a Marvair External Low Noise Blower (ELNB) kit on each unit. The kit replaces the condenser prop fan and motor with a sound absorbing hood, blower and motor and controls to reduce external sound levels. The kit will reduce noise levels by 6 dBA. With the noise mitigation installed, noise levels from the AC units will be 34 dBA at the south property line and will meet the City AT&T EG46 Fox Hollow Road & Amazon Road Page 3 Emergency Equipment The proposed equipment includes one Kohler 50 kW Generator. According to the manufacturer, the generator will produce the following sound levels: Source Sound Level Engine unhoused 80 dBA @ 23 feet Exhaust open 102 dBA @ 3 feet The emergency generator would be in operation for less than 10 consecutive minutes during daytime hours on a monthly basis for routine testing, and for longer periods during emergencies. The generator will be located within a room on the south end of the existing church building. The nearest receiving properties are approximately 70 feet to the west and 200 feet south across Fox Hollow road. The building blocks the receiving property to the west. Because the proposed generator would run for less than 10 consecutive minutes at an agreed upon time during daytime hours (7 AM10 PM), it would not be considered a noise disturbance under the code even if the noise level briefly exceeds the 45 dBA limit. However, to minimize the noise levels from the generator, implement the following noise control measures for each source: Engine Discharge: Install a louver equivalent to Vibro-Acoustics ALV-MV-8 at the air discharge. Install a sheet metal hood on the outside of the air discharge opening. Hood to be lined Engine Intake: Install sound absorbing material with a minimum NRC rating of 0.90 on at least 96 square feet of the ceiling and 300 square feet of the walls of the generator room. Recommended products for this application are -Sorb or T-Max. Install a sheet metal hood on the outside of the air intake opening. Hood to be lined with Exhaust stack: Install a critical grade exhaust stack muffler on the engine exhaust stack that provides 30- 40 dBA noise reduction equivalent to GT Exhaust Muffler 201-5100. AT&T EG46 Fox Hollow Road & Amazon Road Page 4 PREDICTED NOISE LEVELS WITH MITIGATION The following are the predicted noise levels with the mitigation implemented: Receiving Property: West Source Sound Level Distance To Building Noise Distance dBA Level 123 Receiver Factor Control Factor Discharge 80 dBA @ 23 feet 70 -15 -27 -10 28 Intake 80 dBA @ 23 feet 70-22 -10 -10 38 Exhaust 102 dBA @ 3 feet 70 -35 -27 40 Total 42 Table Notes: 1. Building factor is plenum reduction / increase of building or interfering building element. 2. Noise Control is mufflers, silencers, or lined hoods. 3. Distance Factor = -10*LOG(Q)+20*LOG(R2/R1) for dBA or -10*LOG(Q)+20*LOG(R)+0.5 for LwA Receiving Property: South Source Sound Level Distance To Building Noise Distance dBA Level 123 Receiver Factor Control Factor Discharge 80 dBA @ 23 feet 200 -27 -19 34 Intake 80 dBA @ 23 feet 200 -7 -10 -19 44 Exhaust 102 dBA @ 3 feet 200 -35 -36 31 Total 45 Table Notes: 1. Building factor is plenum reduction / increase of building or interfering building element. 2. Noise Control is mufflers, silencers, or lined hoods. 3. Distance Factor = -10*LOG(Q)+20*LOG(R2/R1) for dBA or -10*LOG(Q)+20*LOG(R)+0.5 for LwA With the mitigation implemented, noise from proposed emergency generator will meet the 45 dBA code at the nearest residential properties when in operation. Please contact our office if you have questions or need further information. Sincerely, SSA Acoustics, LLP Alan Burt, P.E. AP SSOCIATE ARTNER AC COUSTICAL ONSULTANT