Commuters who go by way of the Caldecott Tunnel may have been wondering what the scoop is with the massive drill perched over the site of the fourth bore. It is actually a giant auger that grinds down, creates a hole, and excavates the dirt. Afterward a steel cage is inserted and concrete is poured into the hole. The process will be repeated until a subterranean wall has been built. Once the dirt in front of the wall is excavated, the retaining wall for the east portal will be revealed. A. Firth
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