Wisconsin utility's turbines have failed two noise-monitoring reports.
After two problematic noise-monitoring reports, Minnesota utilities regulators have taken the rare step of ordering a utility to justify why it should still have a permit to operate its wind farm.
The Minnesota Public Utilities Commission (PUC) on Thursday ordered owner Wisconsin Power and Light to "show cause" why its permit for the Bent Tree wind farm northwest of Albert Lea, Minn., shouldn't be suspended or revoked.
It's the first time the PUC has issued such a "show cause" order to an operating wind farm.
The PUC also required Wisconsin Power to continue curtailing power from three of the 122 wind turbines at Bent Tree. Since mid-February, the company has restricted operation of the three turbines from 7 p.m. to 7 a.m. and under certain weather conditions.
The recent study and another done last September by the Minnesota Department of Commerce — which represents the public before the PUC — were spurred by noise complaints, particularly from three landowners near the wind farm. They found potential violations of noise regulations.
Wisconsin Power, an arm of Madison-based Alliant Energy, said it has remained in compliance with state standards, and that the noise-monitoring studies have been flawed. "We have concerns about the study's methodology," Justin Foss, an Alliant spokesman, said particularly about the most recent report.
Still, he said the company is "looking forward to working with the landowners and the Department of Commerce to reach a resolution."
Bent Tree began producing electricity in 2011. Three residents who live in the wind farm's footprint have repeatedly complained about turbine noise. The Commerce Department found that the complaints were "unresolved and substantial," and potentially violated site permit conditions, according to an August 2016 PUC order.
Dave Langrud of Alden is one of Bent Tree's neighbors who complained about the noise, saying it has been loud enough to ruin his and family's sleep. The closest of several wind turbines near his house is 1,150 feet away. One of those turbines is now under restricted use.
"The PUC's order," Langrud said, "shows the wind company, 'Hey, we're taking this seriously.' "