The Dallas Area Rapid Transit board on Tuesday approved $872 million to build its first east-west commuter rail line — the Cotton Belt — even though it doesn't have the actual cash quite yet.

DART leaders met with the Build America Bureau in Washington, D.C., last week to confirm that the federal loan that will finance a 26-mile route connecting Plano, Richardson, Addison, North Dallas and DFW International Airport is expected to close Dec. 20.

Within the next few weeks, DART expects to be issued a notice to move forward on the project with its design-build partner, Archer Western Herzog 4.0, which was unanimously awarded an $815 million contract Tuesday night, contingent on the federal loan. The contract will run through Dec. 28, 2022, the anticipated completion date.

In a separate vote, the board unanimously approved $49.2 million for a company to represent its interest as an extension of DART staff during the process.

It also kept the door open for the board to decide next month whether to spend an additional $90 million to $120 million to add a second track along the line, something the board listed as a preference.

"We've discussed the double-track subject for a couple of years," board member Paul Wageman said. "We're going to have significant savings over what we thought the finance costs were on this."

Cotton Belt was budgeted as a $1.1 billion project.

About half of the project, including the nine rail stations, is double-tracked as currently bid. Though plans are for Cotton Belt to debut as an every-30-minute service, the contract also calls for 3 more miles to be double-tracked. That would enable enough two-way passing opportunities to allow runs every 20 minutes.

If it doesn't fully double-track the line, the board also has the option to spend $27 million to add a second track to a 3-mile area of Far North Dallas, where grade levels and four bridge crossings pose a challenge.

The contract already includes $32 million in "betterments" for neighborhoods lining the route, providing for sound walls, rubber chips to minimize track vibration and other amenities.

The first six to eight months, according to staff presentations, will focus on design of the project. The first signs of progress on the ground will be utility relocation and foundation work for bridges.

Archer Western Herzog 4.0 is a joint venture between Atlanta-based Archer Western — one of the nation's largest transit, bridge and rail builders — and Missouri-based rail and highway specialist Herzog Contracting Group. They will use Jacobs Engineering Group as designer.

Archer Western Herzog 4.0 was among five outfits that showed interest when DART in March 2017 posted plans to convert the former freight line. Three proposals were received in May, and negotiations with AWH began in September.

The two runners-up will receive stipends of about $4 million each from DART, an incentive that Texas allows and that DART staff opted to pursue last year.

Avenue K near the 12th street in Plano is the planned site of the 12th Street DART Station. The east-west Cotton Belt commuter line will also cross through the location. (Vernon Bryant / Staff Photographer)

"It is not uncommon for these companies to spend $10 to $12 million on a pursuit like this," said Timothy McKay, DART vice president. He said that in the months since the bids, DART met several times with each company and that the stipend not only helps to offset their costs but secures for DART and the winning contractor the right to incorporate ideas from the other plans.

The Cotton Belt will also connect to DART's existing light rail system at stops in Carrollton, Plano and Richardson. But it will be a commuter rail line, similar to the Trinity River Express, which DART co-owns with Fort Worth's Trinity Metro and connects downtown Dallas and Fort Worth.

Update on TRE safety technology

The TRE, as also announced at Tuesday's board meeting, is off the Federal Railroad Administration's "at risk" list for installation and demonstration of safety technology known as Positive Train Control.

DART has met requirements to submit a request for a two-year extension of the Dec. 31 deadline for Positive Train Control. It is field testing the equipment and expects the railroad administration to approve implementation in early 2019.

"We anticipate toward the end of January, we will be in actual revenue service demonstration, [the stage] where we will have all the actual functionality turned on," McKay said.