Project phases

Construction began in 2009 and the extension is expected to open for service in 2016. Some of the highlights of the tunnel construction:

Preparing I-5 for the tunneling 

In order for the tunnel boring machine (TBM) to pass safely under Interstate-5, construction crews had to first modify the structures beneath the freeway. This work began in June 2009 and took about a year to complete. During that time the I-5 northbound Olive Way off-ramp was closed to traffic and the express lane Pike/Pine reversible ramp was restricted to southbound transit only. 

Demolition and utility relocation 

Before digging the tunnels, construction crews removed existing buildings from the construction site, had to dispose of any hazardous material in the ground and moved utilities out of the way.

Excavation and tunnel boring 

The first step in building tunnels is to dig a hole where the station will eventually go. The tunneling crews use this hole as a starting point to launch the tunnel boring machines. 

The tunnels for University Link were built by three tunnel boring machines. For detailed information about University Link tunneling:

Tunneling for University Link

Station construction

Each of the light rail stations is essentially a 10-story building built almost entirely underground. 

For more details on the construction and demolition:

Capitol Hill Station

University of Washington Station