Environmental groups are appealing a federal judge’s decision to allow the U.S. Army Corps of Engineers and the U.S. Department of Energy to continue construction of the New England Clean Energy Connect corridor — a controversial 145-mile electricity transmission line through western Maine that is expected to be completed by the end of the year.

Chief U.S. District Judge Lance Walker ruled in favor of the federal agencies last month after the groups sued them for not thoroughly assessing the environmental impacts of the transmission line, which will span 53 miles of forest to bring power from hydroelectric dams in Quebec through Lewiston.

The project will bring 1,200 megawatts to the New England electrical grid.

The Army Corps previously determined that the $1.5 billion project had “no significant impact” on the environment. The Appalachian Mountain Club, Natural Resources Council of Maine and the Sierra Club-Maine Chapter asked the judge to revoke the permits because they say the agency failed to comprehensively analyze how the line could impact the aquatic ecosystem. But Walker ultimately decided the corps’ assessment was fair and thorough.

The groups filed a notice of appeal to the U.S. District Court on Wednesday.

The project is organized under Avangrid Inc., the parent company of Central Maine Power Co. and a subsidiary of Iberdrola, a Spanish multinational energy company.

Maine voters had opposed construction of the power line in a 2021 ballot referendum, but construction resumed a few years later after a Cumberland County jury found, in a separate lawsuit, that the developer had “vested rights” to continue the project.