Sound Transit is studying a new light-rail route in Bellevue that could include a shorter downtown tunnel. When combined with a route that runs along 112th Avenue Northeast, the new proposal could shave a possible $75 million or more in costs off of East Link.

The south portal, or tunnel entrance, has two potential locations: at Main Street or a couple blocks north at Northeast Second Street, said Don Billen, the agency's east-line project manager.

Engineering is still at a very early stage for these and several other variations entering downtown Bellevue and the hospital district just east of I-405, with a final alignment choice due next year.

If a shorter tunnel route did save $75 million, that could close a funding gap, Billen told transit-board members Thursday. A downtown tunnel is thought to cost $320 million more than going on the surface -- which city officials have resisted because the north-south trains would disrupt car traffic on downtown's limited east-west streets. Bellevue has offered to cover about half the tunnel costs, while Sound Transit is seeking cost cuts and federal grants to make the budget pencil out.

Billen said another reason to shift the tunnel north would be the chance to reduce noise in the nearby Surrey Downs neighborhood, where single family homes sit a few blocks from the bustling towers of downtown.

Meanwhile, transit officials also are considering routes on 112th Avenue, just to the south of downtown. Should trains go on the west, in the middle or on the east side of the street? Or should the trains run in a "retained cut" trench next to the Bellevue Club?

Surrey Downs residents have criticized a number of proposals, and fewer than half its voters favored the $18 billion ballot measure to extend light rail in three directions, including Bellevue and Overlake by around 2021. Severe noise problems near the Duwamish River rail bridge in Tukwila -- where tracks are elevated -- have prompted south-central Bellevue residents to worry about similar impacts on them.

Joni Earl, Sound Transit chief executive officer, said rail grinding this winter reduced noise in Seattle's Rainier Valley, but noise became worse in Tukwila. Contractors will try another grinding method and put temporary noise barriers on the elevated guideway, she said. The city of Tukwila is holding a noise meeting Thursday night, when transit officials will take questions.

Four of the six options for Bellevue shown Thursday would eliminate an elevated curve at 112th and Main Street in favor of a quieter, cheaper, at-grade approach to the downtown tunnel, a response to criticism in the city of the elevated option.

Seattle Mayor Mike McGinn, a transit board member, asked if the four lanes of 112th Street Southeast could be reduced to make rail construction cheaper and allow safer crossings for pedestrians. Bellevue Councilmember Claudia Balducci answered that 112th and Bellevue Way are the only big arterials in that area, and the city did not want to lose any of that capacity, especially as Bellevue's downtown continues to grow.

The full Sound Transit report detailing the options for South Bellevue and downtown is available here. Sound Transit also is holding a community meeting Tuesday in Bellevue to discuss the six 112th Avenue alternatives presented to the board. The workshop at City Hall, 450 110th Ave. N.E., runs from 6:30-8:30 p.m.