MADISON, Wis. (AP) — Wisconsin utility regulators have authorized the construction of a $500 million power line, despite claims that they ignored complaints, concerns and alternative solutions.

The Public Service Commission approved the plan Thursday, rejecting the accusations of two conservation groups, the Driftless Area Land Conservancy and Wisconsin Wildlife Federation, of a conflict of interest, the Wisconsin State Journal reported. The groups said they’ll appeal.

The commission initially voted to approve the application for the project by electric transmission companies, American Transmission Co.; ITC Midwest and Dairyland Power Cooperative, in August.

The accusations targeted Chairwoman Rebecca Valcq and Commissioner Mike Huebsch, who both denied any bias regarding the power line proposal.

“I find these allegations to be opportunistic at best and at worst contemptible,” said Valcq, who spent 15 years as an attorney for the WEC Energy Group, which owns about 60% of ATC.

Huebsch serves on a Midcontinent Independent System Operator advisory committee, which worked with ATC to gain approval of the Cardinal-Hickory Creek line.

Most of the more than 50 groups and individuals that participated in the evaluation process opposed the line.

“The evidence that the interveners put forth, simply did not persuade me,” Valcq said. “Your arguments were not ignored. They were weighed and balanced and rejected on their merit.”

Transmission is necessary for renewable energy, Huebsch said.

“Either oppose it and oppose renewable energy,” he said, “or embrace it and the role it will play.”

Protestors even cited the commission for ignoring recommendations by their own staff.

The line would run between Dubuque, Iowa, and Middleton, west of Madison. Construction is expected to start in 2021, but it must first be approved by the U.S. Fish & Wildlife Service, U.S. Army Corps of Engineers and the Iowa Utilities Board.