The cubicles and desks were still rather tidy. Only a few large maps hung on the wall and just a scattering of workers appeared on-site.

But come January, things should look different. A last group of workers will move in with stacks of planning documents, maps and spreadsheets, the same flurry of paper that now occupies their work space on the second floor of the Utah Transit Authority's headquarters in southern Salt Lake City.

Since November, groups of UTA engineers, designers, consultants and contractors have been moving their desks to a new office in downtown Salt Lake. They're being gathered together to oversee a $2.5 billion project in Salt Lake and Utah counties to build 70 miles of rail in seven years.

Four new TRAX lines are planned to Draper, South Jordan, West Valley and the Salt Lake City International Airport. A commuter rail extension is planned from Salt Lake City to Provo.

The rail lines will be the largest transportation project ever done in the state, said Mike Allegra, UTA assistant general manager and chief capitol development officer.

And key to the project is getting hundreds of workers under one roof, he said.

"We are confident today that we will have all the right pieces and people ... to make it happen," Allegra said.

By January, as many as 240 people are expected to be in the new UTA office, located just west of the agency's intermodal transit hub, at 669 W. 200 South. During the peak of rail construction, as many as 400 workers could be in the office, with some on-site until at least 2015, Allegra said.

He describes the work as complicated, with coordination needed between teams working on the different lines, which are all in various stages of completion.

Of the four TRAX lines, the "Mid-Jordan" route to South Jordan appears furthest along. UTA has received one federal clearance to build and is waiting on a second. Some construction could begin next spring, although Allegra said any delays in getting the second approval could move the West Valley line to construction first.

The Draper and airport TRAX lines are being studied for environmental impacts. The Draper TRAX route is also subject to a case pending before the Supreme Court to decide whether residents can push a referendum to move the line away from their neighborhoods.

UTA declined to discuss any future impacts of the case, but said it was watching the issue closely.

As for commuter rail, all environmental work has been finished. UTA is now designing the line and seeking an agreement from Union Pacific to build adjacent to its rail line, Allegra said. He declined to give specific dates for construction to begin on all the rail lines, but said they would be finished by 2015.