Sound Transit is wading through a myriad of possibilities for the 18-mile East Link light rail extension, which will eventually run through Bellevue.

The agency announced a series of open houses aimed at limiting its choices, which include five alternatives for south Bellevue, six for the the city’s downtown core, and four that lead northeast toward Redmond’s Overlake transit center.

Also up for discussion are plans for a segment along I-90 and a possible extension into downtown Redmond that would come with a later mass-transit package.

Sound Transit must decide where to lay tracks and whether they should run along the surface, below ground, or on elevated structures.

Public meetings to discuss the alternatives will take place Jan. 28, 5:30-8:30 p.m. at Bellevue High and Jan. 29, 3:30-6:30 p.m. at Bellevue City Hall.

City officials were expected to meet Dec. 8 to develop a game plan for getting additional input and eventually making a recommendation to Sound Transit.

“We need to be thinking long-term, because this is a huge investment and probably a 100-year project,” said Bellevue Mayor Grant Degginger. “We need to think about the alternatives that will serve the city for decades to come.”

What’s already known about East Link is that the south Bellevue segment will include up to two light-rail stations, additional bus transfers, and either a new Park-and-Ride along 118th Avenue Southeast or a garage at the existing facility on Bellevue Way Southeast.

The downtown portion is due for two to three stations, one of which will be located in Bellevue’s hospital district.

The section that runs northeast to Overlake will include two to four stations, new Park-and-Ride lots, and a reconfiguration of the Overlake transit center to accommodate 320 vehicles.

Costs for elevated and surface tracks to the Overlake area are estimated at $2.3-$2.8 billion, while the calculations for tunneling are pricier at $2.9-$3.7 billion.

Among the five south Bellevue alternatives, one runs entirely along Bellevue Way Southeast, three go from Bellevue Way Southeast to 112th Avenue Southeast, and one travels along the BNSF rail corridor.

The downtown segment presents a tangle of alternatives – three that run through tunnels, two on elevated structures, and one at ground level.

The Overlake portion includes two options that travel through the Bel-Red neighborhood and another that operates almost entirely along Highway 520. Those routes would be either elevated or surface lines.

Among the issues Sound Transit will consider when deciding among potential routes are impacts on homes, businesses, parks, traffic, and sensitive habitats.

Up to 106 homes and 137 business could be affected by the East Link line depending on which options the agency chooses.

Another consideration is the BNSF freight corridor, a 42-mile tract of land that the Port of Seattle plans to buy for $107 million.

The Cascadia Center for Regional Development is pressuring Sound Transit to use that property for a commuter-train line, similar to the one running between Tacoma and Everett.

“It could be done for millions of dollars in just a few years rather than waiting decades for light rail,” said Cascadia Center representative Tom Jones. “This puts rail on the Eastside immediately.”

Voters approved the East Link extension in November by passing Proposition 1, an $18 billion mass-transit plan that includes light-rail expansion and additional bus service.

Local transit agencies have already started paving the way for the line with an initiative to create new HOV lanes along I-90 and open up the interstate’s center roadway for light rail.

The Washington State Department of Transportation constructed a second westbound HOV lane between Bellevue and Mercer Island, along with new access ramps to serve those lanes from the two cities.

Future plans for expanding capacity along the I-90 include adding an eastbound HOV lane between Bellevue and Mercer Island, and later constructing HOV lanes in both directions between Mercer Island and Seattle’s Rainier Avenue.

Joshua Adam Hicks can be reached at jhicks@bellevuereporter.com or 425-453-4290.