Named after one of Seattle's early mayors, the $80 million drill Big Bertha is 326 feet long, weighs 6,700 tons, and does much more than drill. John Blackstone reports on what the high-tech machinery can do, as well as its latest challenge digging in the depths of Seattle.
- Күн бұрын
Big Bertha -- world's largest tunnel boring machine -- facing big Seattle challenge
- Рет қаралды 283,390
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