Based on sound level testing done last year for the Scituate Wind turbine, results indicate the turbine is in compliance with the Massachusetts Department of Environmental Protection Noise Policy.
During a remote meeting of the Board of Selectmen on March 24, Al Bangert, special projects director, presented a summary of the final report on the wind turbine sound level compliance testing.
After ongoing complaints by neighbors to the turbine, in May 2018 the Board of Selectmen awarded a $50,000 contract to Epsilon Associates to conduct wind turbine noise compliance tests, Bangert said.
“Epsilon worked with the MassDEP over the course of five months to establish an agreed upon ‘Sound Level Compliance Monitoring Protocol’ involving four Scituate locations and specific wind conditions,” Bangert said. “Final agreement with the DEP was reached Nov. 27, 2018.”
Epsilon began monitoring wind conditions and completed the first test on April 19, 2019.
“Sound level testing consists of measuring the ‘Lmax’ or maximum sound emitted by the turbine when running versus the ‘L90’ or lowest sound level with the turbine shutdown,” Bangert explained. “Sound is quantified using the logarithmic decibel scale as dBA.”
Epsilon completed all four of the evening noise tests between 1 and 4 a.m., generating 16 data sets incorporating several hundred direct measurements of ambient and turbine sound levels. Scituate Wind LLC cooperated with Epsilon throughout the overnight testing periods.
“The results of the testing program show that sound levels due to the wind turbine operating during wind conditions producing maximum power and during wind conditions identified by resident noise complaints comply with the MassDEP Noise Policy with the exception of one night at one location,” Bangert said.
Compliance requires that the difference in decibels between maximum sound levels with the turbine running versus the lowest ambient noise level be less than 10 dBA.
“In order to further understand the apparent non-compliance that occurred at 151 Driftway on July 31, 2019, Epsilon analyzed the L90 sound level differences between turbine on and turbine off,” Bangert said. “The property is adjacent to the turbine and the sewage treatment plant, and the turbine is more audible at this location than at the other three locations although the L90 levels – the lack of sound between the turbine whoosh – are only 1 to 3 dBA different.”
On July 31, however, the L90 difference jumped to 11 dBA suggesting that something else may have influenced the recorded sound levels besides the wind turbine on this evening.
Selectmen plan to hold further discussions on this issue when the meeting can be more open for public participation, Bangert said.