Giant tunneling machine ready to dig Alaskan Way Viaduct

SEATTLE - Bertha's green cutting head is seeing its last rays of sunlight.

Beginning Tuesday afternoon it will start digging, as workers are just finishing its steel starting blocks.

"It has to push off of something in order to force its way into the dirt," says Matt Preedy, WSDOT Alaskan Way Viaduct Replacement Program deputy administrator.

Along its route are 36 laser-equipped automatic measure systems targeting thousands of structural monitoring points bolted to buildings sitting above.

Gallery owner Richard Smith wonders what it's going to feel like.

"I'm glad they are monitoring vibrations," Smith says. "It would be kind of a concern if I was sitting there during the day and things started shaking off the walls."

The system is already collecting data.

"We need about 6-months of base line that way we can justify when movement is," Tyler Husby says.

The system needs line of sight to operate, so crews are doing major tree trimming.

"We are pruning back the trees where the AMTS can automatically find them over the next couple of years," says Husby.

The Alexis Hotel has two of the laser stations.

"It doesn't intimidate me, honestly it gives me a sense of security," Jenne Neptune, general manager says.

While they look like surveillance cameras, Washington DOT says they are strictly measuring the movement of the buildings - especially when Bertha gets up to speed.

"We'll get about 6.5-feet a day at the very start, and about 20-feet a day by the time we get up to Yesler Way," Preedy says.

Bertha will be boring for over one year until late 2014. The tunnel is set to open for drivers at the beginning of 2016.