Regional Transportation District officials on Wednesday threatened to file a formal notice of default to the contractor building the N-Line commuter rail from downtown Denver to Thornton, the opening of which has been delayed for more than a year.

In a press release, RTD said it is contemplating the action against Regional Rail Partners “due to the contractor’s continued delays in meeting project milestones and inability to fulfill its contractual obligations.”

RTD said the delays already experienced mean the N-Line won’t open before August. The 13-mile line will also serve Northglenn and Commerce City with six stations.

“I commend the RTD board for finally standing up to the contractor,” Commerce City Mayor Benjamin Huseman told The Denver Post. “It’s been too long that the contractors are allowed to run around and not meet deadline.”

RTD said Regional Rail Partners, which is a joint venture of Balfour Beatty Rail Infrastructure and Graham Contracting, “has failed to meet several target dates for project turnover, the latest being Feb. 3, and the project schedule continues to be affected.”

The “contractor has yet to reach substantial completion on the project and turn the corridor over to RTD,” the release stated. Work began on the N-Line, which is an electrified commuter rail line akin to the University of Colorado A-Line, nearly six years ago and was supposed to open to passengers in 2018.

Angie Rivera-Malpiede, chair of RTD’s board of directors, said “the fact that this project is still not complete is completely unacceptable and frustrating to not only us at RTD, but to our stakeholders and the public we serve.”

Regional Rail Partners issued a statement on the situation, saying the N-Line project “has experienced delays due to circumstances outside of the control of Regional Rail Partners.”

“We remain committed to cooperating with our customer, the Regional Transportation District, and to the completion of the North Metro Rail Line project to bring enhanced services to the greater Denver community,” the company said.

The threatened legal action follows a similar move by RTD against the contractor building the G-Line to Arvada and Westminster. In 2018, the agency threatened to terminate its contract with Denver Transit Partners, saying at the time that the long-delayed opening of the G-Line “is unacceptable to RTD.”

That action followed a lawsuit that Denver Transit Partners filed against RTD, in which the contractor claimed that RTD owed it tens of millions of dollars for costs incurred over the timing of crossing gates that failed for years to get regulatory approvals from federal and state officials.

The G-Line finally opened last April.

Northglenn Mayor Meredith Leighty said residents of her city are “frustrated” at the slow progress of the N-Line’s debut, which is made worse by the fact that test trains are running the tracks on a regular basis.

“That’s just a tease,” she said.

She said RTD’s threat of default is what’s needed to get things moving more quickly.

“I’m hopeful this action will move them forward,” Leighty said.

Dammit, it’s been too long already! I’m sure this will push back the August opening. We’ve been paying this tax for nearly 2 decades, c’mon! https://t.co/2g9eYmGdrF — Dan Brown (@hydrorium) February 12, 2020

RTD said Regional Rail Partners met with agency officials in recent days and said it will be dedicating what resources it can to the project, which is part of the 2004 voter-approved FasTracks initiative.

“If they do not, RTD is prepared to file the notice,” the agency said.

Another 5.5-mile segment of the N-Line, which would take tracks further north into Thornton, is planned but no funding has been identified for it thus far.