Interstate 15 reconstruction through Utah County got a major boost on Thursday when Senate leadership announced they are endorsing a plan.

Under the proposal, I-15 would be rebuilt from 123000 South in Salt Lake County down to the S.R. 6 interchange in Spanish Fork.

"We who travel Highway 6 now find that 6 is the safest part to Salt Lake nowadays," said Sen. Mike Dimitrich, D-Price. He crossed the aisle to join with Republicans who are pushing the plan forward.

The compromise to include part of Salt Lake County and stop at Spanish Fork instead of Payson was for two reasons. The first is that it's now politically palatable to lawmakers from both counties, and the second is that it will leave additional funding for other road projects, including the Mountainview Corridor, during the six-year project.

Senate President John Valentine, R-Orem said the cost for bonding the smaller project will be about $3.8 billion, leaving $4.4 billion through 2030 for other roads.

Officials of the Utah Department of Transportation said earlier in the session they were only waiting for the go-ahead from lawmakers to get started. Because of rising construction costs and interest on bonds, the cost of the I-15 project is rising $400,000 every day.

It's also not as simple as adding new lanes. Most of Utah County's interchanges and bridges would have to be replaced, a difficult and expensive effort.

While the Senate is now backing the plan, the House majority caucus is still in discussions. But Utah County representatives say things are looking good for the proposal.

"I think that's got some real traction in our caucus," said Rep. Stephen Sandstrom, R-Orem.

Republicans in the House will take a position as early as next Tuesday, he said.

Though Utah County was viewed as secondary to the Salt Lake Valley as recently as a few years ago, the county is now the fastest growing in the state. I-15 through the area is also the most heavily traveled section of the freeway in the state, and what was once an outflow of traffic to work in Salt Lake City is now a 50/50 split of vehicles in and out.

Reconstruction could begin as early as 2009 and an environmental impact statement is currently being worked on.