Sound Transit launches Emerald Mole to dig Beacon Hill tunnels

On Monday, I told you that our Executive Director, Andrew Villeneuve, was taking some time off from blogging to pursue other projects for NPI. His first few days off have certainly been busy ones.

On Wednesday, Andrew attended the launch ceremony for Sound Transit's Emerald Mole Tunnel Boring Machine. The machine, which is approixmately 21 feet in diameter and 30 feet long, will be used to dig the Beacon Hill tunnel system, a key part of Sound Transit's LINK Light Rail line.

Sound Transit's contractor for the project is Obayashi Corporation, which is responsible not only for digging and excavating the tunnels, but also the vertical shaft that will eventually house four high speed elevators that will bring riders down to the trains below in about 20 seconds.

The two tunnels - one for carrying southbound trains, the other for carrying northbound trains - will be dug seperately. The Emerald Mole is starting to bore the first tunnel from the west side, right under Interstate 5.

Here's a description of how the tunnel will be built from Sound Transit:

As it moves forward, the Emerald Mole will excavate dirt while a conveyer system moves spoils out of the back of the tunnel. A pre cast reinforced concrete liner will be assembled immediately behind the Emerald Mole to provide structual support and prevent settlement in the surrounding ground. The liner will also provide a firm footing for the Emerald Mole to push against and propel itself forward. The contractor [Obayashi] will build a temporary rail system to bring in pre-cast segments of tunnel liner. Excavated material from the tunnel will be stockpiled at the west portal and then trucked away.

Andrew reports that the launch ceremony was well attended:

There were a lot of people there...representing the blogging/activist community were myself and Ben Schiendelman, who writes Higher Frequency. Also with us was Richard Berkowski, of People for Modern Transit.

The media was out in force - all of the major television stations were there, as were reporters from 710 KIRO, the Times, and the P-I.

Several elected officials also showed up - Senator Patty Murray, Mayor Greg Nickels, and County Councilmembers Larry Phillips and Dow Constantine. Most of the people there, however, were either Sound Transit staff members or Obayashi personnel, because the event wasn't open to just anybody.

Hard hats and safety vests were required if you wanted to go up and see the Emerald Mole. Most people were even wearing them down below where the actual ceremony was being held.

I had an opportunity to go up and see the Emerald Mole for myself. It is indeed fairly massive. Everyone signed their name on the side of the machine, with some people scrawling messages of hope for the success of the light rail line.

In order to get to the the west portal, where the Emerald Mole was positioned to be begin digging, you had to walk around yard after yard of trailing machinery, which I'm told is about as long as a football field. That certainly seemed to be the case.

It was an exciting event. It certainly reinforced my feeling that the light rail project is indeed moving forward.

Of course, they say every picture is worth a thousand words.... so, here are some photos from the event. Thanks to Andrew for the pictures. Click on the thumbnails to see a bigger view.