A proposed rule on noise limits for wind turbines generated tense interactions Thursday between lawmakers.
The rule proposed by the Public Utility Commission sets a 42-decibel limit for wind turbines during the day, when measured 100 feet from the outside of neighboring homes, and a 39-decibel limit at night.
The Legislative Committee on Administrative Rules chose to extend the deadline for a vote on the rule.
Several lawmakers argued the nighttime noise limit seemed arbitrary or in conflict with the legislative intent of a new state statute.
Legislators called for the sound limits in a 2016 bill now known as Act 174, which instructed the PUC to write uniform sound rules for wind turbines. The commission can’t adopt the rules until they’ve been approved by the Legislative Committee on Administrative Rules.
Kevin Fink, a policy analyst with the Public Utility Commission, said the sound limits are the product of “judgment calls” made by the commission, but that doesn’t mean they’re arbitrary.
Commissioners sought to ensure that Vermonters living near wind turbines aren’t exposed to more than 30 decibels of noise at night, Fink said.
Fink cited a World Health Organization study from 1999 that said exterior noise should not exceed 30 decibels of continuous sound inside a home, in order to ensure residents can sleep.
An update of that study, published by the WHO in 2006, said countries should strive to ensure no more than 40 decibels of unwanted noise at night, when measured outside of residences.
Fink said that commissioners wanted to keep noise at or below 30 decibels at night, inside of homes near wind turbines. But they couldn’t find definitive guidance on how much sound diminishes as it travels to the inside of a home from its exterior, he said.
Commissioners, as they wrote the rule, heard testimony and read literature that said sound attenuates as little as one decibel, and as much as 26 decibels, by traveling through the exterior walls of a home.
Faced with such a “tremendous range of evidence,” Fink said, “I don’t think there’s any way for this decision to be anything but a judgment call.” Commissioners determined that turbine sound diminshes by 9 decibels as it travels through the exterior walls of neighboring homes.
Most legislators on the rules committee received the PUC’s claims with varying degrees of skepticism. Rep. Robin Chesnut-Tangerman, P-Middletown Springs, said he’s worried the rules as written could stifle development of wind turbines in the state.
Sen. Joe Benning, R-Caledonia, urged his colleagues to vote for the rule.
“We’ve really tried to hamstring a commission that’s bent over backwards to accommodate both sides,” Benning said.
The committee will re-examine the rule on Oct. 24.