RTD is bringing in outside experts in construction and finance to evaluate its FasTracks cost and schedule estimates after indications that the original $4.7 billion program is over budget.

RTD is halfway through a four-month overhaul of every aspect of FasTracks. An estimate done as part of that study showed that it would now take $6.5 billion to finish the project.

RTD planners rejected that estimate, saying that it is too high because it counted some items twice and overestimated others. The new cost, due in two months, still may be over the original amount that voters were told.

"It's likely it'll be higher than $4.7 billion," said Cal Marsella, RTD general manager.

A report Friday in The Denver Post said that a draft cost analysis two weeks ago pegged the program at $6.5 billion.

FasTracks was presented to voters as $3.95 billion in 2002 dollars, which RTD inflated to just more than $4.7 billion in actual costs over 12 years of construction. The $6.5 billion estimate is an increase over the smaller figure, without an adjustment for inflation.

RTD hasn't yet hired the outside consultants who will look over the work, but expects them to be in town in April. A final report is due in mid-May.

Problems with the early spreadsheet prompted Liz Rao, RTD's FasTracks manager, to send it back to the staff and consultants for more detailed revisions.

Among the problems, Marsella said, is double-counting some items. For example, it attached the cost of building tracks from Union Station to 40th Avenue to two corridors at the same time, the line to the airport and the line to Thornton. Since those corridors share tracks to that point, the cost is incurred only once.

RTD planners also questioned some specific cost estimates. A light-rail maintenance facility was priced at $135 million, but RTD built one for T-REX that cost $50 million.