BRUNSWICK, Maine — Six Democratic legislators are urging the organization that operates the Amtrak Downeaster to reconsider building a controversial, 60,000-square-foot layover facility in Brunswick and instead build it in South Portland.

In a June 18 letter to Patricia Quinn, executive director of the Northern New England Passenger Rail Authority, Sen. Edward Mazurek of Rockland and Reps. Michael Shaw of Standish, Ken Theriault of Madawaska, Wayne Werts of Auburn, Peggy Rotundo of Lewiston and Christine Powers of Naples asked that the authority cancel the Brunswick project and focus its efforts on upgrading its “‘core’ product: the Portland-to-Boston route.”

They suggest the facility be built instead at Rigby Yard in South Portland, which they labeled “a more logical hub.”

The layover facility as proposed would allow trains to idle during the day and power down overnight in Brunswick instead of returning to Portland late at night only to arrive early the next day to pick up more southbound passengers, Patricia Quinn, rail authority executive director, has said. The building also is designed to reduce noise and pollution by allowing trains to power down during the day.

The project has been mired in controversy since before Amtrak restored passenger rail service to Brunswick in November 2012, and neighbors of the proposed site continue to object to its scale and what they argue would be negative impacts on quality of life and property values.

In the letter, the legislators suggest, among other improvements, upgrading tracks in Saco, Wells and a 30-mile section of rail between Dover and Plaistow, New Hampshire, where trains cannot pass each other.

“We agree that the Brunswick expansion is valuable, but we question the concentration of resources on the current line above Portland,” the legislators said. “The current schedule provides passengers from Freeport, Brunswick and Boston morning departures and evening returns. The ridership numbers are much more robust south of Portland.”

They question whether Northern New England Passenger Rail Authority officials considered discussion of expanding passenger rail in Lewiston-Auburn and to Montreal when selecting Brunswick as the location for the proposed layover facility.

Werts, along with Mazurek, Powers and Theriault, are members of the Legislature’s Transportation Committee. He said Thursday that the site has been discussed by the committee, as well as other groups in the state, including an informal Androscoggin-Oxford-Coos County Rail Committee that meets monthly to talk about progress in extending rail lines in that direction.

“One of the concerns is the feeling that the layover facility being built in Brunswick would somehow circumvent rail moving up to Lewiston-Auburn, New Hampshire, Montreal and Vermont,” Werts said Thursday. “Every town on this corridor — Auburn, Lewiston, Bethel [and] Guilford, [New Hampshire] — has already signed on and said they want passenger rail through their territory. Bethel has already invested $4 million. They’re just waiting for the train.”

Shaw, who is a conductor on the Downeaster, said Thursday that after “a tough winter,” the tracks between Portland and Massachusetts could use attention.

“We’ve had problems down there pretty much ever since, because trains are running late a lot, but even before that,” he said Thursday.

“A lot of it is just one track,” he said, which makes running two trains in different directions problematic.

Shaw also noted that if passenger rail is extended to Lewiston-Auburn, a Brunswick facility would be 30 miles from those trains.

“I’ve been perplexed by the choice of Brunswick from the beginning,” he said. “Ninety-five percent of our riders are riding from Portland to Boston.”

Brunswick Rep. Matthea Daughtrey said she was not contacted about the letter, although she has spoken to the House members who signed the letter and does share their concerns — but she’s quick to add that the Portland-to-Brunswick line should be a focus of Northern New England Passenger Rail Authority’s.

Referring to a recent court decision to vacate a stormwater management permit for the Brunswick facility because abutters weren’t notified, Daughtry said she’s been troubled by the Northern New England Passenger Rail Authority process, adding, “[Northern New England Passenger Rail Authority] needs to be realistic. We all want to see the railroad succeed. We want it to be the best it can be, but we need to be in this as a team.”

In a release Thursday, members of a Brunswick neighbors’ group that opposes the Brunswick site, said the letter, following on the heels of a March request by Gov. Paul LePage for a review of the proposed location, “indicates growing bipartisan concern” about the location.

Bob Morrison, chairman of Brunswick West Neighborhood Coalition, said in the release that the legislators asked “common-sense questions” that members of the coalition have asked previously “but [that] have been ignored.”

“We have always said we’re not against passenger rail service in Maine,” Morrison said. “We just don’t understand the reasoning behind the location of the Brunswick facility, from safety, environmental, financial or operational standpoint.”

On Friday, Quinn told The Forecaster, “It appears there is not a good understanding” of what layover facility proposal, and said she planned to schedule a meeting with legislators to discuss the details.

Quinn said the Brunswick facility “in no way changes or minimizes or distracts from the work that needs to be done between Portland and Boston,” and said moving the facility out of Portland to the end of the line “really complements” long-term plans to expand service to Lewiston-Auburn and possibly Montreal.