The state’s largest electric utility announced last week its wind farm on Lowell Mountain met noise standards during the latest reporting period.
Green Mountain Power told state regulators its 21-turbine Kingdom Community Wind project did not exceed legal limits, which are set at an hourly average of 45 decibels from May 22 to June 12. State regulars set the standards when the 63-megawatt wind project was approved in 2011.
Green Mountain Power violated the state’s noise standards in 2013. The company says this was caused by snow buildup on the turbine blades. The company said it later installed cameras and weather monitoring equipment to address snow buildup.
Dorothy Schnure, a spokeswoman for the utility, said Green Mountain Power has demonstrated definitively that it can meet noise standards set by state regulators in all weather conditions.
The utility hired the research firm Resource Systems Group (RSG) to conduct the report. The firm tested noise levels at four locations around the project site.
About 1,980 hours of data were collected and about 623 hours were discarded due to rain, high winds, and unusual non-turbine noise events, such as human activity, machinery, wind gusts, and animal sounds, the report states.
Information gathered during wind speeds above 5 meters per second – about 11 miles per hour – near data-gathering microphones at the base of the mountain is discarded, according to the report.
Robbin Clark is president of the Lowell Mountains Group, which formed in the early 2000s in opposition to the Kingdom Community Wind project proposal. She and other wind critics say the report is unscientific.
Clark said turbine noise is highest when it’s raining because of the low cloud cover. High winds also contribute to louder turbine noise. Clark said she lives about 1.6 miles from the wind project and turbine noise is “dramatically lower” when the sound is being monitored.
The Lowell Mountains Group is pushing Green Mountain Power to adopt a sound monitoring plan to measure noise continuously rather than in two- to three-week periods. Schnure said Green Mountain Power supports a continuous noise monitoring program for one year.
The Department of Public Service is working on the proposal. However, the Lowell Mountains Group and other wind critics say the current proposal is technically flawed and the department chose an acoustic consultant with ties to the wind industry.
The department proposes hiring the consulting firm Acentech. The department said it is willing to have experts selected by wind opponents to participate in the proposed sound monitoring program. A final proposal has not yet been submitted to state regulators for approval. The department was unavailable for comment on Monday.
Among the highest recorded sound levels in the report is location near the Nelson family’s property. Don and Shirley Nelson, who live below the Lowell Mountain ridgeline, have been vocal opponents of the wind project and have filed noise complaints with state regulators.
Green Mountain Power has since purchased the family’s property. As part of the settlement agreement, the Nelsons agreed to no longer publicly criticize the project.
Wind critics say turbine noise is a public health issue. They say turbines cause sleep disruption, headaches, nausea and other health issues. The state Department of Health says more information is needed on the health effects of turbine noise. Other studies indicate there are no health effects associated with the noise.
The Vermont Public Service Board set the project’s noise standards based on guidelines set by the World Health Organization and Environmental Protection Agency.
David Grass is environmental health surveillance chief for the Vermont Department of Health. He said the health department has received six reports from three health care providers related to symptoms associated with exposure to wind turbine noise.
“But I don’t think we have sufficient information or adequate numbers to be able to say definitively what’s causing the symptoms that they’re experiencing,” he said.
He said he does not know of any planned studies in Vermont underway to better understand the health impacts of turbine noise. He said the health department is waiting on a Health Canada study on turbine noise. Replicating a similar study in Vermont and across region would cost up to $2 million, he said.