The public scrutiny of the Bonneville Power Administration’s proposal to build a transmission line through Clark and Cowlitz counties is well known, but as the BPA crafts detailed plans for the 500-kilovolt line, it’s also faced questions from one of the agencies responsible for permitting the project.

Last fall, the U.S. Army Corps of Engineers asked the federal power marketing agency for better justification in eliminating some alternative routes — including a citizen-proposed route some residents had rallied around for more than a year. The requests were detailed in an October memo made public this week by the citizen groups that have pushed for the so-called “Grey Line.”

The questions may not change the eventual outcome of the project. Both the BPA and the Army Corps described them as “routine” for planning something as large as a transmission line. But the document sheds light on the back-and-forth that goes into what will become the project’s draft environmental impact statement, due out this spring.

“They’ve been very responsive, and we’ll continue to work with them,” said Patricia Graesser, a spokeswoman with the Army Corps’ Seattle district. BPA has not submitted a permit application yet, she said.

BPA spokesman Doug Johnson said the Corps’ questions and suggestions will be reflected in the environmental impact statement.

Terry Constance chairs Another Way BPA, which has supported putting the line away from urban areas. He hopes the Corps’ involvement will lead to a different outcome than what BPA has proposed, he said.

“It just needs to be done right,” Constance said.

The project has run into stiff opposition from citizen groups with health and property concerns. Some have continued to advocate for the Grey Line, though the BPA announced in January that it had been dropped from consideration. Other residents have said they’d like to see the line routed into Vancouver, mostly along existing federal right of way.

BPA is expected to release its draft environmental impact statement this spring, which will offer a much more detailed look at the project plans. The agency has also indicated it’s working to identify a single preferred route as soon as possible.