Neil Habig. To: From:

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1 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 TEL FAX

2 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.

3 12 September, 2012 page 3 Table 1: Sound Power Levels (dba) Source ID 1/1 Octave Band Center Frequency (Hz) Sum (dba) Existing Zond Turbines Proposed Transformer Gamesa G97 Turbine Gamesa G87 CS Turbine 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 Shea Putnam Road Transmission Line Sleepy Hollow Road VT Route 8 North Lamb Brook VT Route Heartwellville Aiken Woodford Peak Woodford Contact Station Atherton Meadow Atherton NW 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.

4 12 September, 2012 page 4 Figure 1: Modeled Sound Levels of the Final Design Plan - Leq(exterior)(1 hour)

5 12 September, 2012 page 5 Figure 2: Modeled Sound Levels of the Final Design Plan combined with existing Searsburg Turbines - Leq(exterior)(1 hour)

6 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)

7 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 Existing Turbine Existing Turbine Existing Turbine Existing Turbine Existing Turbine Existing Turbine Existing Turbine Existing Turbine Existing Turbine Existing Turbine Transformer Turbine E Turbine E Turbine E Turbine E Turbine E Turbine E Turbine E Turbine W Turbine W Turbine W Turbine W Turbine W Turbine W Turbine W Turbine W