The GC tapped other experienced partners for the effort, including electrical contractor Mass. Electric Construction Co. and water/wastewater facility builder Western Summit Constructors Inc. as well as AECOM.

Six months into the 18-month design, Kiewit started construction in spring 2013. "That's the benefit of design-build," says engineer Roger Ryburn, Kiewit's project manager. "You can be more fluid, more flexible, which has an impact on cost and scheduling. There's a cost-to-impact benefit."

By this summer, some 250 workers were laying track, installing piers and columns for bridges, drilling stabilization shafts, building barrier walls, installing light poles and fences and grading at different spots along the route. Contractors anticipate peak construction in mid-2015 for a 2016 opening, after testing.

The project has a 25% small-business enterprise requirement, divided into four categories based on contract price, to help grow small businesses. Contractors also are participating in RTD's federally funded Workforce Initiative Now (WIN) program, which helps to create and sustain well-paying jobs in the transportation and construction industries. Kiewit has an 8% WIN goal. "The idea is when the project is gone, the skills that people learned on it will still be here," says Kiewit public information manager Hunter Syndor.

The rail line hit a construction speed bump early last year, when a route component that would have gone directly through the Fitzsimons-Anschutz campus along Montview Boulevard had to be moved a half-mile north to Fitzsimons Parkway. Campus occupants such as the University of Colorado and other research centers worried that vibrations and electromagnetic interference from the light rail, which runs on electricity, would negatively affect sensitive equipment in their world-class laboratories. It would have cost an estimated $60 million to mitigate the trains' effect on labs—money that RTD, the city and CU said they didn't have—but ultimately all parties opted for the route change.

"The kind of interference that comes off light rail is the same kind you get with cell phones and elevators," says Culig. "We did a lot of testing to figure out how to minimize impact, but then we got a request from CU President Bruce Benson to change the alignment, to move it off campus."

One of the project's biggest safety issues has been dealing with the electrical demands of light rail. Two high-voltage electrical transmission towers near the Colfax Avenue Station, for example, were built extra tall—180 ft and 195 ft, respectively—to clear the rail cars' overhead contact wires. Other major power components include 11 traction power substations that will supply power to the rail cars' overhead contact wire; 37 relay houses containing equipment that controls signals; and crossing gates that allow trains to move safely and efficiently.

There will be eight communication houses with equipment such as supervisory control and data acquisition systems for providing information to light rail passengers. They also allow RTD dispatchers, supervisors and security people to monitor and control the system.

Contractors are using an automated grade control system that includes GPS to make sure rail grades are as level as possible and ensure the smoothest ride for train passengers. The rail itself is made of recycled steel produced in Pueblo, Colo.

"We're buying all our rail locally," Culig said. "That's for all the rail we're involved with—commuter rail, light rail."