By now, you've heard how big Seattle's tunnel boring machine is.

It's the machine that will bore under the city to build the new Highway 99 tunnel.

It's currently laid out in 41 huge pieces just west of CenturyLink Field. By this summer, it will be assembled into a custom built, nearly 7,000-ton, tube-shaped, tunnel boring machine.

The machine is exerting a lot of pressure, and as they roll across a bolder, they'll crack the bolder, says WSDOT project manager Chris Dixon.

The cutter head, 57-and-a-half feet in diameter, the biggest drill of its kind in the world, will be the first thing to hit the rocks and boulders.

We should have a penetration rate, if you can imagine the whole machine going forward, of one, two or three inches per minute, according to Deputy Project Director Gregory Hauser.

After the cutter head - the widest ever built - spins and chews up the soil, the mud will be removed by conveyer belt and the huge tail-end of the machine will erect concrete rings to form the double decker highway.

We build rings. You push off that last ring and build the next ring so when you're done you have a tunnel, explained Dixon.

This summer, they'll put the cutter head up against the portal face, below King Street and start grinding.

Hauser says, It's not going to get stuck. It's going to cut all the way through.

In the launch pit, 80 feet deep, they've built a cradle for the machine to lay in.

Nearly 200 workers will be on the job six days a week, working to bring the machine to life.

This is the most awesome there is. says Hauser. This is the thrill of a lifetime. It's the highlight of my career.

Eventually, boring 200 feet below downtown Seattle, with soil and building sensors along the way, look for the Highway 99 Tunnel to open in 2015.

The machine is named Bertha, after Seattle's first female mayor, Bertha Landis.

There is a bathroom on the huge machine, but, so far, we are told, there are no living quarters for workers.

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