Watch: biggest tunnel boring machine in the world (video)

“Big Bertha” was named after one of Seattle’s early mayors.

The $80 million drill is 326 feet long, five stories tall and weighs 6,700 tons.

It moves forward at 35 feet a day.

It cleans up after itself – carrying rock and dirt out on a conveyor belt.

Finally, it installs concrete panels – building the walls as it goes… leaving a finished tunnel behind.

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