BRUNSWICK, Maine — The Northern New England Passenger Rail Authority is eager to move forward on a proposed train layover facility, after receiving tentative approval last week for a stormwater license from the Maine Department of Environmental Protection.

But opponents of the project are not backing down.

A DEP-issued storm-water license is the final hurdle NNEPRA must clear to begin construction on the $12.7 million layover facility between Stanwood Street and Church Road.

“We are pleased with (DEP’s) draft decision,” NNEPRA Executive Director Patricia Quinn said Tuesday.

In a June 3 memorandum, DEP found NNEPRA had met all of the department’s rules concerning stormwater management, and outlined the draft license.

“Based on the proposed project design and the department’s review … (DEP) finds that the proposed project will not adversely affect groundwater quantity or quality,” DEP said in its memo. “Therefore, the Department approves the application of (NNEPRA) to build a stormwater management system.”

The draft contains several conditions of approval, including a revised spill contingency plan, a dewatering plan, and retaining a third-party inspector.

Quinn said that NNEPRA’s technical team will review the draft in the upcoming weeks, but the initial response is that the permit and its conditions will be “easy to comply with.”

“Through the entire process, DEP has done a very, very thorough review, and the draft decision was also very thorough,” she said.

NNEPRA wants to build the layover facility so it can keep Amtrak Downeaster trains overnight in Brunswick. Currently, trains return to Portland for overnight maintenance and come back up to Brunswick in the morning for the first run of the day.

Quinn has said that eliminating those two “dead-head” runs would allow the Downeaster to offer a third trip between Brunswick and Boston.

The proposed facility would house up to three passenger trains, according to NNEPRA’s website.

But the plan has been consistently opposed by nearby residents, led by the Brunswick West Neighborhood Coalition, who claim the facility will increase air and groundwater pollution.

“We are certainly disappointed because we think we had presented a very strong case,” BWNC Chairman Robert Morrison said. “… We thought that there were many instances where we presented materials that indicated that (NNEPRA) had not addressed the requirements … that govern the stormwater application process.”

John Shumadine, the attorney representing the coalition, said the group will submit comments on the draft to the DEP.

“We think this has never been a completed application,” he said. “The draft order is basically indicating that by asking for whole host of documents that should have been provided beforehand,” he added, referring to 15 conditions of approval outlined in the draft.

He argued that the “appropriate” response would be to deny the permit and have the applicant supply the documents in a new application.

“The order is not final yet,” Shumadine noted.

NNEPRA was previously granted a storm-water permit for the site, but it was voided in July 2014 by a Superior Court judge who found the rail authority had failed to notify property abutters of its permit application.

NNEPRA then reapplied for the necessary permit, but DEP returned it in August, saying it was incomplete.

The current application was submitted last October, and received a day-long public hearing in March at the Brunswick Golf Club. It was the first public hearing the DEP ever held for a storm-water permit application.

Comments on the draft approval were due Wednesday, and the final license decision will be issued by June 17, the DEP said.

If the permit is approved, the decision can be appealed to the Board of Environmental Protection. The board consists of seven members, appointed by the governor and confirmed by the Legislature.

With final approval, NNEPRA can finally break ground on the layover facility.

Even if the decision is appealed, “my understanding is that construction does not have to wait,” Quinn said.

“The intent is to move forward,” she added.

But opponents promise to be there, too.

“We have every intention of pushing on through the different steps, the comments, and if necessary, the appeal to the board,” Morrison said. “We are taking action to make sure (the facility) moves somewhere else and is not placed in a suburban development.”