LOWELL -- Wet snow on turbine blades during windy conditions caused the roaring sound that drew complaints about the Lowell wind turbines on Nov. 3 and 4.
The noise, which at least 21 neighbors described as unbearable, began early in the morning of Saturday, Nov. 3, and continued into the next evening.
The neighbors wrote a letter of complaint to the Vermont Department of Public Service, which acts as the electricity consumer advocate for the state.
This week, Green Mountain Power spokesman Robert Dostis said that the noise was caused by the weather conditions, which caused wet snow to build up on the blades during windy conditions. It created noise because of the angle and speed of the blades, he said.
Mike Nelson of Albany described the sound, at three and a half miles away, as a cross between a helicopter and high winds blowing through the trees. Others called it "unbearable," loud enough to be heard inside of homes up to two miles away.
GMP has a protocol to follow when the turbines make too much noise, Dostis said.
The neighbors are asked to contact GMP about unusual noise so that GMP's operational team can adjust the turbines or shut them down.
If neighbors had called immediately when they began hearing the unusually load noise from the operating turbines, GMP would have shut them down immediately, Dostis said.
The turbines are all operating now, although not all at the same time as GMP contractors do final testing on each turbine before beginning the complete commercial operation before the end of the year, Dostis said.
Anyone who hears unusual noise from the turbines is asked to contact Lucy Leriche, who is working for GMP through the end of the year until the commercial operation begins fully. Her number is 802-793-0130.
Or neighbors can also call Dostis at 802-655-8412.
Dostis said he and Leriche can be contacted at any time about noise.
After the New Year, GMP will announce the permanent contact number for noise or other problems, he said.
All 21 turbines are completely up and operational. The last of the 21 was commissioned Tuesday, meaning that the turbine generated electricity that was transported into the electricity grid.
And that was good news for GMP, which qualified as of Tuesday for more than $40 million in federal production tax credits, more than a month ahead of when those tax credits are scheduled to end.
The tax credits will go directly to reduce the rates for GMP ratepayers and for the members of Vermont Electric Cooperative, which is buying electricity from the wind project at cost.
GMP said the cost of the electricity from the Lowell wind project, at 9-10 cents per kilowatt hour, is the cheapest new renewable energy available in Vermont.