State regulators have proposed new sound limits for wind turbines that some renewable energy proponents say would effectively ban new utility-scale turbines from Vermont.
The rules say turbines could produce no more than 35 decibels at night when measured outside nearby homes. That is about half the perceived loudness of the current exterior sound limit of 45 decibels.
Some homeowners near wind energy projects say they welcome the scaled-back sound limits.
“It could be better, but given the history of the noise from turbines being ignored by the (Public Service Board), this is a huge step in the right direction,” said Melodie McLane, of Georgia, who lives less than a mile from a four-turbine project on top of Georgia Mountain.
But some advocates of wind power say the rules would keep Vermont from reaching its renewable energy goals.
The Public Service Board is writing the rules in response to Act 174, which the Legislature adopted last year. That law requires the board to study wind turbine sound and come up with a rule improving on what’s currently in effect.
The law does not instruct the Public Service Board to ban turbines, said Sen. Chris Bray, D-Addison, the chairman of the Senate Natural Resources and Energy Committee, where Act 174 originated.
“There’s no hint of a moratorium” in state statute, Bray said.
“Clearly we didn’t ask for a moratorium on wind,” he said. “We simply asked for their best thinking on what would make these acceptable on a working landscape.”
Bray said he’s unsure how the board arrived at a 35-decibel limit. As a legislator, he’s tried to “keep a respectful distance” as the rulemaking process moves along.
“But they took a lot of expert testimony,” he said. “I’m sure there’s a basis for their numbers.”
The board has conducted numerous workshops and hearings on wind turbine sound standards — which is as legislators hoped, Bray said.
“They really dug into this and took a lot of testimony,” he said. “That’s exactly why we engage in rule-making … (for) the in-depth, expert analysis that is literally beyond the expertise of the Legislature, and that’s why we engage the appropriate departments and agencies to do the work (of rule-making).”
The 35-decibel limit is also significantly lower than the 40 decibels proposed in a “discussion draft” of the rules that the board released in January.
Because decibels are measured on a logarithmic scale, the pressure of a sound wave doubles with an increase of 3 decibels. But because of imperfections in the human ear, the loudness is perceived to have doubled with an increase of about 10 decibels, said Les Blomberg, executive director of a national nonprofit based in Montpelier called the Noise Pollution Clearinghouse.
It’s unclear why the board so dramatically reduced the proposed sound limits since January, said Sarah Wolfe, a clean-energy advocate with the Vermont Public Interest Research Group.
Public Service Board representatives did not respond to requests for comment on the rules.
The proposed new sound limit would effectively ban any further wind energy development in the state, Wolfe said.
The rules do not explain how the board arrived at the 35-decibel limit. Wolfe said none of the sources in a list of citations provided with the rules contain a rationale for a 35-decibel limit either.
That’s troubling, said Olivia Campbell Anderson, executive director of the industry group Renewable Energy Vermont.
“It disregards the science provided by experts, and the published studies about the impacts of sound,” Campbell Anderson said of the 35-decibel limit.
“We’re confused as to why the science is being ignored,” she said. “We don’t ignore science in Vermont.”
Campbell Anderson said the proposed sound limits would spell trouble for some residential-size wind generators as well.
The smaller generators don’t need to meet the 35-decibel limit if their distance from the nearest home is at least 10 times the turbine’s height. “I’m not aware of any small turbine on the market that can meet that sound limit,” Campbell Anderson said.
Neighbors have not complained to the state about the 155 residential-size turbines already in Vermont, Campbell Anderson said.
Wolfe said the nighttime sound limit is especially problematic because that’s when wind energy is most needed and most abundant. Vermont is windier at night, and wind energy fills a supply gap when the sun goes down and solar panels stop generating power, she said.
“The sun shines in the day, and the wind blows at night,” Wolfe said.
The state’s comprehensive energy plan calls for 90 percent of the state’s energy to be supplied from renewable sources by 2050 — a goal legislators are working to establish in statute.
“We’ve looked at the numbers, we’ve looked at the facts, and we cannot get to that goal without wind power,” Wolfe said.
Blomberg, whose group advocates for greater silence, said the proposed rules aren’t the best way to achieve it.
The separate sound limits for daytime and nighttime will cause needless expense and confusion, because they regulate not the equipment but how it is operated, Blomberg said.
If wind turbine operators must dial back generators at night, they will need to invest in expensive monitoring. In addition, lawyers, hearings and acousticians will be required to evaluate nighttime operations.
These costs will be passed on to Vermonters, either through electricity rates or more oversight by state agencies.
“We have wasted so much money on noise,” Blomberg said. “You can regulate noise much more cheaply.”
A better approach would be to simply prescribe distances that are appropriate between wind turbines and residences, Blomberg said.
This approach is available for small turbines (150 kilowatts or smaller) under the proposed new rules, but not for larger turbines that typically sell power to utilities.
Vermont has already put itself in a tricky position. Extreme opposition to wind farms makes communities afraid of hosting them, Blomberg said.
“Because (regulators) haven’t done a good job of making sure that wind facilities fit, in the past, there isn’t a community that’s going to willingly take these,” Bloomberg said.
Wind developers have contributed to the problem, he said.
Individual developers who have tried to maximize revenue from their projects at the expense of neighbors, Blomberg said, “have kind of poisoned the acceptability of wind, and that’s bad for us, because we need them.”