SEATTLE — A drop in sales tax revenue is forcing Sound Transit to consider putting the brakes on expanded rail and regional bus service, mostly in south and east King County.

But Snohomish County’s prospects for commuter and light rail look much better.

Projects planned for Snohomish County, including the Mountlake Terrace Freeway Station now under construction and a permanent commuter train station expected to open in Edmonds next spring, are expected to go forward, Sound Transit Chief Executive Joni Earl told the agency’s Board of Directors on Thursday.

Earl said a projected $3.9 billion drop in sales tax revenues over the next 15 years means some projects on the drawing board will be suspended or scrapped.

The only Snohomish County project likely to be suspended under the latest budget proposal is a longer-term plan to build a commuter rail station near the Edmonds waterfront south of the existing Edmonds Station. The project was part of Edmonds Crossing, a big proposal to place a new train station, bus depot and ferry dock together on another part of the Edmonds waterfront. That project is on hiatus because of the funding crunch.

Instead, Sound Transit is building the commuter train station that is expected to open next spring. It’s a much smaller version and will be a hub for train commuters only.

Snohomish County Executive Aaron Reardon, chairman of the board, lauded his associates for “having the foresight to look at this in an all-inclusive fashion.”

“The wisdom of the board is going to have to serve us as we go forward,” he said.

Voters in 2008 agreed to raise the sales taxes a half-cent on every dollar to pay for $18 billion in new rail and bus projects throughout the Puget Sound region by 2023.

That plan includes extending light rail from Seattle to Lynnwood by 2023.

“What we did not know and nobody knew at the time was how deep this recession was going to be,” Earl told the board.

In March, the agency predicted a $3.1 billion sales tax revenue shortfall from 2009 to 2023.

At the time, the agency had no plans to suspend any projects.

That’s different now, Earl said.

“This is a mixed-message story,” she said, noting the proposed suspensions. “We’re going to be able to carry millions of people around this region for years to come.”

The budget shortfall means a plan to extend light rail south of Sea-Tac International Airport could be suspended or dropped, Earl said.

Federal Way probably won’t get an extended Sounder Commuter train platform. And the agency will likely suspend an eastside passenger rail partnership, a planned carpool direct-access lane along I-405 in Renton and a Bothell Transit Center.

Oscar Halpert: 425-339-3429; ohalpert@heraldnet.com.