Spanning 17. 6 miles across the mouth of the Chesapeake Bay, the Chesapeake Bay Bridge-Tunnel (CBBT) is a masterpiece of complex civil engineering. When constructed in the early 1960s, a standard long bridge was ruled out because traditional bridge piers would pose a catastrophic threat to major U.
S. Navy shipping channels leading into Norfolk and Hampton Roads. To solve this, engineers devised a hybrid solution: trestle bridges that dip into underwater tunnels precisely where naval and commercial vessels pass overhead.
To transition traffic from elevated bridge spans to subterranean tunnels, four 10-acre artificial islands were constructed in open waters up to 45 feet deep. Each island was engineered using millions of tons of granite armor stone and sand dredged from the bay floor. Heavy rock perimeter dikes were formed first to hold back waves, followed by hydraulic sand fill to raise the land surface well above high tide.
Cars descend down paved ramps into the island's core, entering sunken tube tunnels laid into pre-dredged trenches on the bay floor. The steel and concrete tunnel sections were pre-assembled on land, towed out to sea, sunk into position, and sealed together underwater. By placing the tunnels under Thimble Shoal and Chesapeake channels, the design guarantees that even if a ship were to crash or sink in the channel, it would not collide with bridge supports or trap the U.
S. Atlantic Fleet inside the bay. These artificial islands act as massive anchor points, balancing structural weight, wave absorption, and highway traffic seamless transition.