OLYMPIA — I-5, the West Coast freeway linking Portland, Ore., to Seattle, has been submerged in pastoral Lewis County three times in the past 17 years by supposedly 100-year floods.

But local leaders and officials in Olympia and Washington, D.C., are still debating what the expensive fix should look like — and who should pay.

One conservative state lawmaker is even suggesting a new commercial corridor that could cost $50 billion.

Democratic Gov. Chris Gregoire said Wednesday she’s convinced the latest closure will finally result in a solution to the chronic flood-control problems. The freeway was still under more than 5 feet of water Wednesday at Centralia, and in its third day of closure, requiring some interstate truckers to detour all the way through Eastern Washington to get to Seattle.

State Transportation director Paula Hammond said 10,000 trucks and 44,000 passenger vehicles use I-5 through the region every day, and that the state economy loses $4 million each day that vital link is out of commission.

A solution has been debated for years. A segment of the freeway at the same spot also was submerged in 1990 and 1996.

Locals, as well as the heavy interstate traffic, are “sick and tired” of the threat of flood closure on such an important artery, said the local state senator, Dan Swecker, R-Rochester, his party’s transportation leader.

Over the past decade, state, federal and local governments haven’t agreed on a fix or how to finance it. The Legislature allocated $30 million in 2003 for a plan to build levees along the corridor and expand the Skookumchuck River dam so it could better protect the region.

But the project stalled when key players, including Lewis County, withdrew support and the cities of Centralia and Chehalis resisted the potential obligation to cover maintenance costs.

Swecker and the governor both said the region has two basic choices:

A flood-control plan for I-5 between Napavine and Centralia, 10 miles to the north.

A new “commerce corridor” running north and south between I-5 and the Cascade Range between Lewis County and the Canadian border. The corridor, long advocated by Swecker, would accommodate a new bypass highway for freight and general motorists, a rail line and an energy pipeline. A state study has said it would cost between $42 billion and $50 billion.