GOLDEN — A proposed high-speed rail system from Fort Collins to DIA and then south to Colorado Springs would cost about $9.8 billion and carry roughly 13 million passengers a year, according to planners Tuesday night.

That scenario is the most favored among those being considered as part of a overall push to connect the Front Range and Interstate 70 west to Eagle County with some form of high-speed rail.

Planners told those who attended an unveiling of the plans being considered by the Colorado Department of Transportation that no one plan has been formally selected.

In fact, the costs of such system might require it to be built in stages and would depend on funding from the federal government and local governments.

“This will cost of tens of millions of dollars just to complete the environmental studies,” said David Krutsinger, of CDOT’s division of transit and rail.

He said an alternative mode of travel will be needed in Colorado as the population is expected to increase from 5 million to 8 million by 2035.

Planners said any rail corridor would have to avoid cutting through the city of Denver to scale back costs. Still, a 340-mile system that would go from Fort Collins south to DIA and south to Pueblo and include I-70 to Eagle would cost over $30 billion.

Which is why CDOT planners say phasing the project makes sense. The preferred 132-mile route from Fort Collins to Colorado Springs omits, for the time being, the I-70 west portion.

Five other options — including one that includes the mountain corridor at a cost of $17 billion — were also presented Tuesday night.

The opinions of potential commuters may alter the planning, however, said Krutsinger. “Really, it’s down to how much do you want to speed,” he told the audience.

A draft report of CDOT’s recommendations will be released in December.