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n u n Li C i C F u 0 Forward Landfill LFG Acoustical Analysis May 18, 2011 Page 6 The facility was modeled as a four-sided industrial building with noise sources centered on each side with 1/3 -octave noise emission spectra based on the Keller Canyon measurements, adjusted for the revised selection of generator engine exhaust mufflers. Additional source terms were inserted to represent the roof -top ventilation fans and noise reduction canopies. 3. SoundPLAN 7.0 computed offsite noise levels using the ISO 9613-2 propagation model. In addition, five dB increment noise level contours for the project area were computed. Noise levels modeled at surrounding locations are shown in Table 3. Note that as the result of distance and substantial shielding, the predicted noise levels at residences are well below the San Joaquin County 45 dB nighttime criterion. Table 3. Summary of Project Noise Level at Off -Site Noise Sensitive Locations Name Side Floor X in Y in Z in Distance Direction Ld dB(A) Prison S 1. 1939283 654476 13.9 2940 NW 39.8 Nearest Floor Prison S 2. 1939283 654476 16.7 2940 NW 39.8 Nearest Floor Prison E 1. 1939288 654483 13.9 2940 NW 40.4 Nearest Floor Prison E 2. 1939288 654483 16.7 2940 NW 40.5 Nearest I Floor Landfill N 1. 1939919 653131 15.9 1940 S 44.3 Building Floor 1 Residence S 1. 1939880 654729 15.9 3320 N 39.5 2 Floor Residence S 1. 1939880 654912 16.4 4015 N 38.2 3 Floor South N 1. 1940702 651878 14.7 6900 SSE 29.3 Neighbor Floor 1 South W 1. 1940693 651873 14.7 6900 SSE 29.3 Neighbor Floor 1 South N 1. 1940027 651249 14.5 8100 S 27.5 Neighbor Floor 2 The modeled sound levels near existing residences southerly of the project are all in mid - to -high 20 dB range. The San Joaquin County standard for outdoor noise levels at residences is 45 dB at night. Typically a drop in sound level of 9-10 dB is judged subjectively as a halving of loudness, so in this case the outdoor sound level would be less than one quarter as loud as the County's allowable sound level. It may be noted that these predicted sound levels are consistent with ambient noise levels often measured at night in remote locations, so that there is little likelihood of resident disturbance.