King County has entered into exclusive negotiations with BNSF Railway to buy a 47-mile rail corridor stretching from Renton to Snohomish County for use as a trail.

If the county succeeds in acquiring the right of way, the new trail would cut through the heart of the Eastside's major cities and could tie into an existing urban-trail network to create a seamless, countywide recreational path.

"This is the pinnacle, the granddaddy of trails," King County Executive Ron Sims, who is leading the effort to acquire the route, said in an interview Friday. "This would become the spine of our system, and we think the public should own it."

Discussions about purchasing the line, which now carries the Spirit of Washington Dinner Train, began quietly about six months ago, said Sims, who planned to announce the talks today. He would not say how much the corridor would cost, except to say it could be purchased without raising taxes.

If the route became a trail, all rail traffic, including the dinner train, would cease on that line.

The negotiations come on the heels of the county's long-awaited success last week with the East Lake Sammamish Trail. After nearly a decade, and more than 20 lawsuits between the county and property owners, that controversial, 11-mile trail was finally approved.

The new trail, besides being a potential boon for recreationists, would almost certainly attract tourists, county planners say. The corridor would connect with the Sammamish River Trail, which in turn links to the Burke-Gilman. It would also tie into the Centennial Trail, which now runs from Snohomish to Arlington.When the trails are complete, an uninterrupted route could be possible from Renton to Skagit County.

County planners say it's too early to say what the trail would look like or when it would open.

The route could have major implications for the region's transportation infrastructure.

If a deal were struck, King County would acquire the corridor through "railbanking," in which railroads sell, lease or donate rights of way on routes they no longer operate to private organizations or local governments for use as trails. The corridors are often sold at reduced rates, sometimes at below market value, in exchange for a tax deduction for the railroad.

While the routes are then converted to trails, they can be returned to mass-transportation use in the future.

Without railbanking, it would be nearly impossible for the public to buy a similar stretch of right of way through the heart of the Eastside, because the county would have to negotiate costly purchases one lot at a time, said Rod Brandon, King County's director of environmental sustainability.

Instead, the rail route would instantly provide the county with an unbroken stretch of open land just minutes from often-congested Interstate 405.

RON WURZER / THE SEATTLE TIMES, 1998 A photographer snaps a shot of the Spirit of Washington Dinner Train as it travels down the rail corridor King County is negotiating to buy. If the route becomes a trail, all rail traffic, including the dinner train, would cease on that line.

The corridor averages 100 feet wide or more, so it one day could fit both a trail and public transportation, Sims acknowledged. But the immediate focus, he said, is to create a trail.

"In the past, this route has been recommended for bus rapid transit, light rail, single-engine uses," Sims said. "But I'm buying it to have as a trail. If future leaders want to add a use ... it will be added to the trail, it would not be instead of that."

Larry Phillips, chairman of the Metropolitan King County Council, said, "It's got great potential as a trail and would certainly connect the Eastside in that respect. And it could be something more.

"Those decisions will happen in the next decade or two."

BNSF Railway first publicly expressed interest in selling the line in 2003. The company Friday confirmed the negotiations with King County.

"They seem to be sincere," said Jerry Johnson, assistant vice president of the railroad.

The scenic corridor is lightly used now, but it was once a major freight route.

It runs mostly parallel to I-405, winding through Renton, up the eastern shore of Lake Washington, through Bellevue and Kirkland, into Redmond via a small spur, along the sleepy Sammamish River and past the wineries of Woodinville, then into rural Snohomish County and to the city of Snohomish.

If the line became a trail, the landmark 102-foot-high wooden Wilburton Trestle in Bellevue would likely remain part of the route, with safety upgrades, Sims said.

Because serious negotiations with the railroad have just begun, the county would not publicly estimate how much it might pay for the route. But Sims said that sources of money have already been identified, and they don't include new taxes.

To secure the right to exclusive negotiations, preventing the railroad from talking with other parties until August, the county will have to put down a $3.5 million deposit, similar to earnest money on a home purchase. If the deal is made, the money goes to the purchase price. If not, the railroad can keep some of the interest earned on the money during the talks, but the county gets the $3.5 million back.

"We wanted to show them that we are really serious," Sims said, especially since the railroad had been approached by other potential buyers — including commercial developers — about the property.

The County Council still has to approve the deposit. The issue will go to the council's budget and natural-resources committees within the next few weeks.

The deal has the potential for controversy. In other rail-to-trail cases, including the battle over the East Lake Sammamish Trail, nearby homeowners have opposed railbanked trails, worried about crime and property-rights violations and loss of privacy.

But King County Councilwoman Carolyn Edmonds, who chairs the natural-resources committee, predicted that most people along the route will be excited about the idea.

"Railroad lines are not pretty, and they're noisy. We're going to turn this into an asset for communities," she said.

While the route cuts through some residential neighborhoods, it's generally more separated from homes than the East Lake Sammamish route, which in some cases divides million-dollar properties in half, said Matt Cohen, a lawyer the county hired to help with the negotiations.

Sims promised to work with cities along the route on trail construction and design, and he predicted cooperation from nearby mayors.

"I can't believe any public official would have heartburn over this," Sims said. "I don't think we'll have the issues with this that we had with the East Lake Sammamish Trail."

The county has sought help from several groups, including the nonprofit Cascade Land Conservancy, in exploring what would be a complex purchase.

The conservancy has experience negotiating with railroads and working with rail-side property owners, said Gene Duvernoy, conservancy president. He said he didn't want to pre-judge how controversial a sale might be.

"Some of the concerns might be access across the trail, access to existing business," he said.

But, Duvernoy said, "this is an incredibly important resource that the public could benefit from for generations."

Natalie Singer: 206-464-2704 or nsinger@seattletimes.com