Lawmakers are preparing for one of the most ambitious transportation building seasons in state history this summer, majority Democrats in...

OLYMPIA — Lawmakers are preparing for one of the most ambitious transportation building seasons in state history this summer, majority Democrats in the House said Monday after unveiling their $4.9 billion transportation budget.

Using a combination of $300 million in federal stimulus money and revenue from the state’s gas tax, the proposed budget provides money for more than 400 statewide projects and could spur thousands of jobs, lawmakers said. Still, some 18 projects had to be shelved because state gas tax revenue is shrinking.

“We’re on track to see the largest transportation construction season ever this summer,” said Rep. Marko Liias, D-Mukilteo, vice chairman of the House Transportation Committee.

The Senate already released its proposed $4.3 billion transportation budget last Wednesday.

Many of the road projects are spread out across the state.

But some of the bigger-ticket items in the budget — the so-called “megaprojects” — are focused in the Puget Sound region, including $2.4 billion set aside for replacement of the Alaskan Way Viaduct in Seattle and another $2.6 billion for the State Highway 520 floating bridge across Lake Washington.

Also set aside in the budget was $309 million for new ferry construction and $1.5 billion for HOV lane projects in Tacoma.

Policy details on some of those megaprojects still aren’t settled. For instance, the earthquake-damaged viaduct may be replaced by a tunnel, but that decision still hasn’t been totally finalized. What exactly to do about the 520 bridge is still not fully resolved.

Republicans criticized the Democrats’ proposal, saying it fails to deliver what was promised when voters approved two separate gas tax hikes in recent years.

“There’s not enough revenue to cover all the projects promised. To promise one thing and not deliver is hurting us,” said Rep. Dan Roach, R-Bonney Lake, the ranking Republican on the House Transportation Committee.

Many of the projects slated to be started this summer were originally supposed to be undertaken later. But lawmakers moved the start dates up in an attempt to kickstart the state’s moribund economy.

However, while the next two years are shaping up to be a bumper year for statewide projects undertaken, lawmakers forecast hard times to come in the future.

Transportation projects rely on the state’s gas tax for a large slice of their financing — a revenue stream that is drying up. Add that to project cost increases, and Democratic lawmakers said the state is facing a grim prognosis.

“People are driving less,” said Rep. Judy Clibborn, D-Mercer Island, chairwoman of the House Transportation Committee. “It will not be possible for us to continue using the current revenue sources.”