• Specialty:

    Noise / Vibration
  • Location:

    Energy / Power
  • Type:

    Permitting / Compliance
  • Timespan:

  • Location:

    Bridgewater, ME

Project Number:


Number Nine Wind Project


Independent Peer Review of Sound Assessment


Tech completed an independent peer review of the Sound Assessment of the Number Nine Wind Project in Aroostook County for Maine DEP. The purpose of this peer review was to determine if the acoustic studies submitted with the permit application are reasonable and technically correct according to standard engineering practices and t­o determine if the proposed project will comply with the Department Regulations on Control of Noise.

The review was performed by analyzing each variable of the Sound Assessment; these variables included: assumed sound power levels, applied uncertainty factor, and acoustic model assumptions and results. This information allowed Tech to conclude that the assessment was done properly and the modeling results represent 'worst-case' conditions.

The applicant has designed the nighttime NRO operations plan so that the maximum sound level at a Protected Location is exactly at the nighttime decibel limit. Consequently, Tech suggested regular compliance sound testing at more than one Protected Location along Number Nine Lake. In addition, Short Duration Repetitive Sound (SDRS) occurrences may increase the measured nighttime sound levels above the nighttime limit at one or more Protected Locations. Compliance testing will have to carefully document SDRS events.

A separate analysis of the Generator Lead Line sound impacts was presented and it was found that the report failed to analyze the Generator Lead Lines for Tonal Sound. Tech suggested that the authors of the report be contacted to provide additional information regarding these deficiencies.

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Key Points

  • An independent peer review of a sound assessment for a large wind far was conducted by Tech, by thoroughly analyzing each variable of the Sound Assessment.
  • Tech made suggestions to Maine DEP regarding routine compliance testing and noted deficiencies within the report that required additional information.

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