A $14.5 billion roads plan for King, Snohomish and Pierce counties is finally ready for the November ballot — after elected officials and environmentalists compromised Friday over the controversial Cross-Base Highway near Fort Lewis.

The Regional Transportation Investment District, a delegation of County Council members, voted 19-2 to endorse the measure.

The proposal would mainly pay for highway lanes that can't be funded through gas taxes alone. Among other projects, it would widen Highway 9 from Bothell to Lake Stevens; extend Highway 509 from SeaTac to Interstate 5; add lanes to Highway 167 in the Green River Valley; provide partial funding for a new Highway 520 floating bridge; and add two lanes in each direction to Interstate 405 from Renton to Bellevue.

The I-405 project, especially, will improve traffic for people who must "drive until you qualify" for affordable suburban homes, said King County Councilmember Reagan Dunn. "The benefits are real. It will help young people; it will help our future," he said.

But the plan nearly came unhinged over the Cross-Base Highway, an east-west route that would link fast-growing Spanaway and the Frederickson industrial area to Interstate 5. Tahoma Audubon has fought the project, saying it threatens rare oak prairie.

Officials dropped Cross-Base under pressure last week, but Pierce County Executive John Ladenburg threatened to veto his county's piece of the highway plan unless Cross-Base was restored.

After all-night negotiations, officials agreed Friday morning to spend $427 million on interchange and road projects nearby, including at least $10 million for environmental work. However, the main highway can't be started until after talks with a mediator in 2009, and until another $200 million is found to complete the full project, said RTID spokesperson Charla Neuman.

Politically, the situation resembles Seattle's aging Alaskan Way Viaduct, where the state has decided to rebuild the south portion while leaders continue arguing about whether to build a new highway along the central waterfront or seek a "surface-transit" alternative.

The roads portion would be funded by a sales-tax increase of 1 cent per $10 purchase and an annual car-tab tax of $80 per $10,000 of vehicle value. The road projects are worth $6.9 billion in 2006 dollars, or $14.5 billion if inflation, cash reserves, finance costs and overhead are included throughout the 20-year construction period.

It will be combined with Sound Transit's 50-mile light-rail-expansion plan in a single ballot question.

Snohomish County Council members Gary Nelson and John Koster, both Republicans, voted "no."

Nelson said the proposed taxing boundaries create three classes of people: urban residents who pay a "double-whammy" of both Sound Transit and highway tax; residents on the fringe who would pay just highway tax; and people farther out who would pay neither.

"It makes a tough sell in Snohomish County to try and explain that," Nelson said.

Mike Lindblom: 206-515-5631

or mlindblom@seattletimes.com