The Charlotte Area Transit System is scheduled to announce Tuesday morning an official deal with the federal government to pay for half of the $1.16 billion light-rail extension from uptown to UNC Charlotte – the last hurdle before construction can begin.

The 9.2-mile Lynx extension will connect uptown to NoDa, then run along North Tryon Street before it terminates at UNC Charlotte. The line to the northeast has long been a dream of university leaders.

The signing of what’s known as a Full Funding Grant Agreement could be the last major transit construction announcement for years, as CATS struggles to raise enough money to build other projects pledged in 2007.

CATS has scheduled a 10 a.m. news conference at the old Ninth Street trolley stop, which would become the first station on the light-rail extension. Federal Transit Administration Director Peter Rogoff is scheduled to announce the deal, according to people familiar with the event.

CATS declined to comment Monday morning.

The FTA will spend $580 million for the extension. The N.C. Department of Transportation will spend $299 million, or 26 percent, of construction costs.

CATS – using revenue from a half-cent sales tax for transit – will spend $281 million, or 24 percent.

The transit system recently spent $87 million to buy 22 new light-rail cars from Siemens. That money is part of the overall $1.16 billion cost.

CATS hopes to begin construction next year. The extension could open in 2017.

Tuesday’s announcement comes three weeks before Election Day. President Barack Obama’s Democratic administration has been favorable to Charlotte, helping the city build a streetcar through a $25 million grant, as well as lobbying for federal grants for light-rail engineering studies.

North Carolina is considered a battleground state in the race between Obama and Republican challenger Mitt Romney.

Complex construction ups cost

When the original Lynx light-rail Blue Line opened in 2007, its cost seemed very high: $462 million for 9.6 miles. That was about $48 million a mile.

The extension will cost more than twice as much.

Five years ago, it was estimated to cost $750 million, which would have paid for an 11-mile line to Interstate 485. But worried that it would be unable to pay to operate and build the train line, CATS cut two stations from the design, including a large park-and-ride lot at the outerbelt. There are no plans to restore them.

Even with the reductions, the extension will cost about $125 million a mile.

Much of the cost increase is due to the complexity of construction. For instance, much of the rail line will run in the median on North Tryon Street, which will be complicated and costly to reconfigure.

The Lynx Blue Line, which runs between uptown and Interstate 485 in south Charlotte, averages about 15,000 passenger trips on a typical weekday. It is projected to handle 18,000 trips by 2025.

The extension is expected to handle even more passengers, with 24,500 trips by 2035.

The city hopes the Lynx extension can revitalize much of northeast Charlotte, just as the current light-rail line sparked new residential development in South End and near the New Bern station.

Recession shrunk tax revenues

Because of the light-rail extension’s higher costs – and the recession – CATS doesn’t have enough money to pay for previously planned projects.

In 2007, when Mecklenburg voters decided overwhelmingly to keep the local half-cent sales tax for transit, CATS planned several projects:

• A commuter train to Lake Norman. This $300 million project was supposed to be built around the same time as the light-rail extension.

But the Red Line, which would use heavy rail cars on existing Norfolk Southern tracks, has little chance of federal funding, and CATS may not have enough money to pay for even a portion of construction costs.

The N.C. DOT is working on creative ways to finance the project. But it appears to be years away.

• A streetcar to run from the Eastland Mall area through uptown, where it would branch to two destinations: Charlotte Douglas International Airport and Rosa Parks Transit Center on Beatties Ford Road in northwest Charlotte.

The city plans to start construction soon on a 1.5-mile starter line from Time Warner Cable Arena to Hawthorne Lane at Presbyterian Hospital. That $37 million project will be funded in part by a $25 million federal grant.

Earlier this year, Charlotte City Manager Curt Walton’s proposed capital improvement plan called for spending $119 million to extend that starter streetcar line to Johnson C. Smith University. But some council members balked at raising property taxes for the streetcar, and the proposal is still being debated.

• Some form of rapid transit along Independence Boulevard, either light rail or a busway. The Metropolitan Transit Commission has voted in favor of a busway on interior lanes of the highway. But there is no movement toward building a busway or stations that it would require.