GREEN RIVER - Wyoming officials are warily watching an ambitious plan to build a 400-mile-long pipeline through the state to pump water from Flaming Gorge Reservoir for up to 900,000 families across Colorado's Front Range.

Businessman Aaron Million has been quietly shopping the idea around for two years and plans to file for permits by year's end to start the approval process. He envisions building a $4 billion pipeline from the reservoir on the Wyoming-Utah border to the Front Range, following Interstate 80 to Laramie then heading south along U.S. Highway 287 into Colorado.

He said it would deliver 250,000 to 450,000 acre feet of water to points as far south as Pueblo. An acre foot of water is enough for one or two urban families for a year.

Wyoming Gov. Dave Freudenthal doesn't know a lot about the proposal at this stage, spokeswoman Lara Azar said Friday. "But he's incredibly skeptical … He's not inclined to say much until he knows whether it's just another pipe dream or whether it really goes forward," Azar said in an e-mail.

Wyoming Water Development Commission Director Mike Besson said Million spoke with state water officials about the proposal. "We're watching this, but I think they've got a mighty tall mountain to climb and a lot of hurdles ahead of them," Besson said in a telephone interview.

"First of all, this is all in the private sector, and I think even getting an easement for a pipeline that long would be problematic," he said. "I think the only way this will fly is if the state of Colorado really gets involved in this at a state level."

Million has hired former Wyoming State Engineer Jeff Fassett to help make the project go.

"You would have been run out of town as a crazy man 25 years ago for reaching that far," Fassett said.

Drawing water from Flaming Gorge, which can hold up to 3.8 million acre feet of water, and the Green River impacts few irrigators or other water users, Fassett said.

"You don't decimate the Green by taking out what Aaron's taking out," Fassett said.

The tug-of-war for scarce water between farmers and cities came to a head in May when Colorado's engineer told farmers along the South Platte River to turn off 440 wells after forecasting lower-than-average flows in the river and well owners failed to come up with plans to replace the water they were using.

Millions of dollars worth of crops in northern Colorado were left to die after three cities and farmers dependent on the water rejected an emergency plan that would have allowed well owners to continue pumping.

"The irrigated ag base is getting decimated on the Front Range," Million said.

Besson said the real key to the possible success of the proposal is whether the amount of water being taken from Flaming Gorge would be within Colorado's share of water allocated under the Upper Colorado River Compact.

"It's the volume of water that I think is the real problem," Besson said.

"I worry that 450,000 acre feet of water or even 250,000 acre feet of water might exceed (Colorado's) allocation, because that allocation is basically a percentage of whatever Mother Nature says the hydrology is," he said.

"I doubt very many people have considered this last seven years of drought on all the hydrology … Those studies and analysis sure needs to be done first," Besson said.

"If it is in within (Colorado's) allocation, then Wyoming needs to watch this," Besson said. "It will be tough project for them with a lot of hurdles, but I'm not losing any sleep (over it) yet. We'll be watching it, though."

If all goes well, the pipeline would be built and delivering water in five to seven years, Million says.

"If he can do it in five years, he'll set a record," said Eric Wilkinson, general manager of the Berthoud, Colo.-based Northern Colorado Water Conservancy District. The district manages the Colorado-Big Thompson Project, which pipes water from Colorado's Western Slope to the state's Front Range, including Fort Collins.

Million said he has done much of the heavy lifting, including lining up financing.

"This is a forever type project, but the old adage is that water flows to money … and this might be affordable from their perspective," Besson said.