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Item 6D - Noise StudySAUNDERS & ASSOCIATES Acoustics and Technology Consulting To: John Rose — P.E. SAUNDERS & ASSOCIATES 1601 Elm Street, Floor 33 Dallas, TX 75201 Ph: 1-877-709-1400 Fax:1-877-309-7268 www.saundersassoc.com From: Melvin L. Saunders IV, MASA, INCE CC: Date: July 20, 2020 V V a Re: HEB - 1425 East Southlake Blvd Southlake Generator Noise Study At your request, we have conducted analysis of the property line noise levels for the proposed natural gas generators at the HEB Grocery Store Located at 1425 East Southlake Blvd in Southlake Texas. The following report highlights our findings and recommendations. City of Southlake Local Noise Ordinance It is our understanding that the generator noise levels at the property line must meet the current maximum permissible sound pressure levels as found in Chapter 11 - Offenses and Miscallaneous Provisions of the Ordinance. Section 11-60, subsection C, paragraph 12 states the following: (12) Conducting or permitting any activity that produces a dBA level beyond the immediate vicinity that exceeds the dBA levels specified in Table 1 hereinbelow. TABLE 1 PRIMA FACIE MAXIMUM ALLOWABLE NOISE LEVELS Property receiving sound Dayd me Nighttime Sundays Residential 60 dBA 55 dBA 55 dBA Commercial 70 dBA 65 dBA 65 dBA Product Information We understand that three natural gas generators are proposed to be installed on the south side of the HEB building. Each generator enclosure is rated to achieve an overall noise level of 68 dBA at a distance of 7 meters (23 feet) from the enclosure. The closest generator is understood to be approximately 148 feet away from the nearest residential property line. Our understanding of the site layout is shown below. RESIDENTIAL PROPERTY LINE 148 FEET BEYOND REST GENERATOR W -71 � I 2 O .I 0 O O O O GE ERATORS 0 0 KEYED NOTES 0 �EA O UTILITY SERVICE PAD MOUNT TRANSFORMER %XXKVA .1. /277-480V O U' O6 4 5 02 UTILITY MV SERVICE O O O3 UTILffY CONDUITS AND CABLING TO ATS O O4 CONDUITS AND CABLING TO STORE LOAD CENTER ng Ca O o tl _ OS STORE LOAD CENTER J NATURAL GAS GENERATORS (3) O7 EXTENDED PARALLEL OPERATION ATS WITH LSIG PROTECTION 8 PROPOSED GAS SERVICE MICROGRID, LLC ENCHANTED ROCK ELECTRIC ENCHANTED ROCK ELECTRIC CONFIDENTIALTEXAS ��INITIAL xE8 0055 SWN—E C. EEcx�naoTSEOe.R 111 T, SUITE 101 1113 VINE HOUSTONTX 77002 INFORMATION, DO NOT DISCLOSE WITHOUT RELEASE PROJECT LAYOUT AREA NONE , oa is WRITTEN AUTHO RIZATSN OB 7 19 JB 161012xEB xES 0055 I,EB 0055 nEB_SOV1xCM_0055 As currently designed, we estimate that the noise level at the property line with 3 generators operating simultaneously is 61-62 dBA and just above the allowable daytime noise limit. This assumes that there is a clear line of sight to the generator enclosures from the property line. If it is desired to operate the generators overnight or on Sundays, an acoustical screenwall will be required. Generally, the screenwall will need to be at least 3 ft taller than the tallest point on the generator enclosure and ideally no more that 6 ft from the generator enclosure. With this approach the resultant noise level will be approximately 50 dBA at the residential property line and will meet the City or Southlake noise ordinance. Barrier Height and Design To evaluate the effectiveness of the screen wall, we examined the distance of the generator from both the screen wall and the receiver location. The attenuation provided by a barrier is a function of the relationship between the source and receiver and the extra distance sound has to travel to the receiver due to the height of the barrier. The barrier provides a reduction of sound pressure level in its shadow zone. Figure 1.0 shows the relationships between typical source, receive, and barrier heights. For the HEB Southlake study, the receiver location was S A SAUNDERS & ASSOCIATES A—Mi.s and Technology C.—Illng SAUNDERS & ASSOCIATES 1601 Elm Street, Floor 33 Dallas, TX 75201 Ph:1-877-709-1400 Fax:1-877-309-7268 www.saundersassoc.com taken to be a standing person at the adjacent residential property line. In most instances, the grading height of the residential properties are higher than the loading dock and this was considered in the barrier calculation. For most barrier considerations, any sound transmitted through the barrier Figure 8. Barrier absorption, transmission, reflection, and diffraction. can be neglected because it will be at such low level relative to the sound that travels over the barrier. The sound that comes through the barrier will typically be at least 20 dB(A) below the sound that comes over the barrier. As a rule of thumb, any material that weighs approximately 2.5-4lbs/ sq. ft. has a transmission loss of at least 20 db(A) and will meet this requirement. For your use and consideration, the table below lists some common barrier material and the associated transmission loss values. It should be noted that the use of wood should consider treatments to minimize gaps due to warping or shrinking. Approximate sound transmission loss values for common materials. Thickness Weight Material Transmission mm kg/m2 (lbs/ft2) Loss (dB(A)) (inches) _ Concrete Block, 200mm x 200mm x 405 (8" x 8" x 16") 200mm (8") 151 (31) 34 light weight I _ Steel, 18 ga 1.27mm 10 (2.00) 25 _ (0.050") Steel, 20 ga 0.95mm 7.3 (1.50) 22 (0.0375") Steel, 22 ga 0.79mm 6.1 (1.25) 20 (0.0312") Wood, Fir 12mm (0.5") 8.3 (1.7) 18 Wood, Fir 25mm (1.0") 16.1(3.3) 21 Wood, Fir 50mm (2.0") 32.7 (6.7) 24 S I A SAUNDERS & ASSOCIATES A—Mi.. and T—h-1o9y C.—Ifiny SAUNDERS & ASSOCIATES 1601 Elm Street, Floor 33 Dallas, TX 75201 Ph:1-877-709-1400 Fax:1-877-309-7268 www.saundersassoc.com This concludes the review of the generator noise for the HEB Southlake project located in Southlake, TX. If there are any comments or questions, please don't hesitate to contact me. Melvin L. Saunders IV, MASA, INCE Principal Consultant Saunders & Associates S A SAUNDERS & ASSOCIATES A—Mi.s and T—h-1o9y C.—Ifiny SAUNDERS & ASSOCIATES 1601 Elm Street, Floor 33 Dallas, TX 75201 Ph:1-877-709-1400 Fax:1-877-309-7268 www.saundersassoc.com