To: Neil Habig From: Isaac Old Kenneth Kaliski, P.E., INCE Bd. Cert. Subject: Sound Update for Deerfield Wind Project Modifications Date: 12 September, 2012 As part of the final civil design process, Iberdrola Renewables has revised the mix of Gamesa turbine models that were previously approved for the project in connection with the final design plans that will be submitted to the Forest Service. 1 As a result, Iberdrola has requested RSG to evaluate these changes to validate our prior conclusion that the Project does not create an undue adverse impact due to noise, that the modeled sound levels for the final design plan configuration would meet the noise limits set in the Certificate of Public Good (CPG) issued by the Public Service Board, and be consistent with the conclusions set out in the project EIS. MODELING Sound propagation modeling was done for the final design plan configuration using the same modeling software and parameters that were used in the EIS noise report. The as-approved configuration had Gamesa G87 turbines on the western ridge and a mixture of Gamesa G87 and G80 turbines on the eastern ridge. In the final design plan configuration, the western turbines are Gamesa G97s and the eastern turbines are Gamesa G87 CSs. 2 Table 1 provides the modeled sound power levels for all principle noise sources including the G87 CS turbine, the G97 turbine, the Zond turbine used at the existing Searsburg facility, and the Project s transformer. Figure 1 provides the results of the modeling for the final configuration. All residences would have outdoor sound levels below 45 dba, with the highest sound level at 40 dba. This is an increase of 1 db at the worst case receiver over what was forecast using the previouslyapproved layout. At non-residential receivers (e.g., USFS areas), the difference in sound level at modeled receivers between the previously-approved configuration and the final design plan configuration, range from no change to an increase of 1 db, depending on the location. Table 2 provides the results comparing sound levels at discrete receivers for the previouslyapproved and final design plan configurations. 1 The final design layout provided by Iberdrola has turbine shifts ranging between 60 and 62 feet. 2 The CPG applied noise limits are 45 dba (exterior)(leq)(1 hr) and 30 dba (interior)(leq)(1 hr). 55 Railroad Row White River Junction, Vermont 05001 TEL 802.295.4999 FAX 802.295.1006 www.rsginc.com
12 September, 2012 page 2 Figure 2 shows the modeling results for the final design plan configuration, with the addition of the existing Searsburg turbines. The highest combined sound level at any home would be 43 dba. This is the same as the as-approved configuration. Figure 3 shows the modeled difference in sound levels between the final design plan configuration and existing sources of noise the Searsburg project and highway traffic. That is, it subtracts the Deerfield project sound levels from the combination of Searsburg and the 24- hour equivalent sound level from VT 8 and VT 9. The existing sources of noise do not include any biogenic or other anthropogenic sources of sound, or any sound monitoring results. Additional detail showing the location of the Deerfield turbines, the Deerfield substation transformer, and the existing Searsburg turbines are shown in Table 3. CONCLUSIONS RSG modeled the sound levels that would be generated by final design plan configuration for the Deerfield Wind Project. The results are as follows: The highest modeled sound level caused by the project is 40 dba. When the existing Searsburg Turbines are included in modeling, the highest sound level at a receiver is 43 dba. The sound levels from the final design plan configuration are between 0 db and 7 db higher than the modeled no-action alternative. We make no changes to our prior recommendations or conclusions. The Project will have no undue adverse impact due to noise.
12 September, 2012 page 3 Table 1: Sound Power Levels (dba) Source ID 1/1 Octave Band Center Frequency (Hz) Sum 31.5 63 125 250 500 1000 2000 4000 8000 (dba) Existing Zond Turbines 120 112 109 107 104 103 100 95 88 108 121 Proposed Transformer 90 98 107 98 97 90 86 78 73 98 108 Gamesa G97 Turbine 1-111 108 107 105 102 96 88 79 106 115 Gamesa G87 CS Turbine 112 110 108 107 103 98 92 83 71 104 116 Sum (db) Table 2: Noise Modeling Results for Previously-Approved and Final Design s (Leq(exterior)(1 hour)) 2 Receiver ID Sound Level (dba) Coordinates (UTM NAD27 Previously Final Design Difference 3 Z18N) Approved Plan X (m) Y (m) Z (m) VT Route 8 South 43 43 0 665738 4748227 720 Shea 42 42 0 665710 4748465 738 Putnam Road 40 40 0 665237 4750137 763 Transmission Line 39 39 0 665717 4749432 737 Sleepy Hollow Road 37 37 0 666796 4749099 580 VT Route 8 North 38 38 0 665492 4750037 730 Lamb Brook 34 35 1 667436 4744588 711 VT Route 9 37 37 0 663419 4750764 685 Heartwellville 30 30 1 664481 4743654 547 Aiken 32 32 0 661738 4747893 666 Woodford Peak 27 27 0 660485 4749926 733 Woodford Contact Station 26 25 0 660222 4750212 706 Atherton Meadow 15 16 1 670069 4739037 510 Atherton NW 9 10 1 671021 4737980 566 1 The sound power shown for the G87CS and G97 are manufacturer reported means. The modeling adds 2 db to these to account for the manufacturer s stated uncertainty margin. 2 Includes Deerfield and Searsburg turbines. 3 Values in this table around rounded to the nearest whole number. Differences are calculated from the Previously Approved and Final Design Plan sound levels in tenths of decibels and then rounded.
12 September, 2012 page 4 Figure 1: Modeled Sound Levels of the Final Design Plan - Leq(exterior)(1 hour)
12 September, 2012 page 5 Figure 2: Modeled Sound Levels of the Final Design Plan combined with existing Searsburg Turbines - Leq(exterior)(1 hour)
12 September, 2012 page 6 Figure 3: Modeled Sound Levels of the Final Design Plan Minus Modeled Searsburg Turbines and Roadway Traffic (24-hour Leq)
12 September, 2012 page 7 Table 3: Sound Source Information Source ID Modeled Sound Power (dba) Included Uncertainty Factor (db) Relative Height (m) Coordinates (NAD27 UTM Z19N) X (m) Y (m) Z (m) Existing Turbine 108 0 40 666106 4746829 940 Existing Turbine 108 0 40 666125 4746885 940 Existing Turbine 108 0 40 666164 4746939 934 Existing Turbine 108 0 40 666193 4746980 925 Existing Turbine 108 0 40 666697 4747636 889 Existing Turbine 108 0 40 666526 4747496 888 Existing Turbine 108 0 40 666469 4747459 892 Existing Turbine 108 0 40 666416 4747398 898 Existing Turbine 108 0 40 666658 4747586 892 Existing Turbine 108 0 40 666398 4747340 898 Existing Turbine 108 0 40 666298 4747295 895 Transformer 98 0 3.66 664380 4749927 823 Turbine E1 106 2 78 665983 4746697 1000 Turbine E2 106 2 78 665865 4746472 967 Turbine E3 106 2 78 665738 4746261 983 Turbine E4 106 2 78 665651 4746034 996 Turbine E5 106 2 78 665899 4745841 1020 Turbine E6 106 2 78 666084 4745592 1020 Turbine E7 106 2 78 666230 4745383 1005 Turbine W1 108 2 78 664466 4749780 916 Turbine W2 108 2 78 664052 4749611 916 Turbine W3 108 2 78 664057 4749336 928 Turbine W4 108 2 78 664071 4749076 950 Turbine W5 108 2 78 664152 4748834 932 Turbine W6 108 2 78 664262 4748614 926 Turbine W7 108 2 78 664429 4748425 957 Turbine W8 108 2 78 664523 4748177 959