Sound Transit completes tunnel for Northgate Link Extension

Sound Transit's tunnel boring machine has reached the University of Washington Station as it continues making way for northbound light-rail trains to Seattle's Northgate area.

The milestone marks the completion of one of two 3.5-mile tunnels for the Northgate Link Extension, agency officials said in a press release. One tunnel segment now remains before all mining work is complete.

Tunneling with the machines is expected to wrap up by the end of this year. Tunnel finishes and cross-passages, which connect the train tunnels and provide emergency exits, are slated for completion by first-quarter 2018.

The 4.3-mile, $1.9 billion Northgate Link Extension is expected to open for service in 2021. The route will run from Northgate Mall to downtown Seattle.