Sound Transit is nearing 50 percent completion of its light rail expansion to the Eastside, but will the agency need to shut-down I-90 to complete the link to Mercer Island?

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KIRO Radio morning host Dave Ross brought this question to me a few weeks ago. There is a giant gap in the flyover connection where the light rail tracks move from the center of I-90 to Bellevue Way, just across the East Channel Bridge. He was concerned about a potential closure of the freeway to connect the two sides.

I met with Rachelle Cunningham of Sound Transit at the site to discuss the upcoming schedule.

“The main span is going to be completed in two segments, and they are going to meet in the middle, right over the freeway,” she said. “We’re very close to finishing the first span.”

That should happen in March. Sound Transit is using what it calls a “traveler” to build the elevated track. The machine sits at the end of the span and pushes forward as it lays the concrete.

“It moves about 12 feet at a time,” Cunningham said. “It pours the concrete, and it cures and then it will move out again.”

When it reaches the end — just over westbound lanes of I-90 — the contractor will need just one night to remove the traveler so it can be moved to the other side to start work on the connection.

“They’ll move out to the middle and then join, but to do that we will need to close the lanes of traffic once, overnight, in March, and then this will all be completed in November,” Cunningham said.

She also said it will take one more night closure in November to finish the job. Only two night-time closures to complete the span, under the current schedule, sounds more than manageable for putting a train track over the freeway.

This project is going to make big strides in 2019. Track is already being laid along the route, and it will start going on the floating bridge this summer. Station construction is also underway in a few locations, and Cunningham said the timing looks good.

“Things are on schedule,” she said. “Things are going really well. It’s on budget, it’s on schedule, and we’re just plugging ahead.”