Federal grants totaling $2.1 million gave a boost to mass transit for Whidbey Island commuters this week.

The money, which goes to the state Department of Transportation, will start a planning effort designed to bring a new ferry dock, train and bus station to Mukilteo by 2008.

Now, with cash in hand, Washington State Ferries can take the first step to linking Whidbey Island with downtown Seattle.

Bill Green, spokesman with WSF corporate communications, said Thursday that WSF now has more than $3 million in federal money to start designing a new Mukilteo ferry dock. The three-slip dock, which is to be the counterpart of a new dock still under construction in Clinton, will be located north of the current one on land previously used by the Air Force as a fuel tank farm.

Eventually, the dock will also be the site of a Sound Transit light rail station and a transit bus stop, Green said. Combining these forms of transportation in one facility, he said, will make a trip from Whidbey Island to downtown Seattle — or anywhere in between — seamless.

Transportation like this, Green said, can only help the Puget Sound region.

“This is a project that is critical to the region,” he said.

Funding for the remainder of the project hinges on Referendum 51, a measure on the Nov. 5 election ballot that asks Washington citizens to pay a new, 9-cents-per-gallon gas tax. The project is one of several for which revenues from the tax are earmarked. The cost of the WSF portion of the project alone is expected to cost $108 million, Green said.

The federal grant money announced this week is only enough to go to the drawing board. Green said it will pay for design and engineering costs, as well as an environmental assessment of the project.

Even if the plans get drawn up quickly, the start of construction is some time off. Ed Paskovskis, the deputy director of the Port of Everett, said Wednesday the tank farm property will not be in the port’s hands for at least 12 months. The port will be the landlord for the multimodal terminal, once the federal government turns over the deed to the 22-acre tank farm.

East said initial planning for the multimodal terminal do not yet speak to how it might be linked to Highway 525. He said the highway, which serves the current Mukilteo dock, may be rerouted to the new terminal.