How did they build the Bart tunnel underwater?

In the case of the San Francisco-Oakland BART tunnel, it was constructed on shore in pieces and then floated out to their respective locations on the bay and “sunk” into place on top of a pre-dug trench. Each section is then connected together to form an airtight chamber.



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Built using the immersed tube technique, the Transbay tube was constructed on land in 57 sections, transported to the site, and then submerged and fastened to the bottom – primarily by packing its sides with sand and gravel. Opened in 1974, the tunnel was the final segment of the original BART system to open.

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Earthquake Safety Program The Transbay Tube is BART's most critical asset. Although the tube is structurally sound, in a very large and very rare earthquake, the outer shell and concrete liner are predicted to crack.

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Constructed in 57 sections, and reposing on the bay floor as deep as 135 feet beneath the surface, the remarkable $180 million structure took six years of toil and seismic studies to design, and less than three years to contract.

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The mountain material is solid and strong enough not to collapse the hole, or the hole is lined with reinforcement that transfers load from one side to the other. This is now iron/steel rings or reinforced concrete. Tunnel boring machines build the liners as they progress, and push forward using the last ring.

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Seats are scrubbed with hot water and disinfectant soap during a thorough clean. BART recently increased the frequency of thorough cleans from every 900 hours of train car service to every 450 hours, meaning we've doubled the number of times the cars in our system undergo a deep clean.

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Tunnel workers (affectionately known as 'sandhogs') dug through the mud by pneumatically pushing cylindrical shields through the river bottom. Those shields held back the earth, making way for construction of the thick tunnel walls, built of cast iron rings filled with concrete.

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“The first infrastructures of this type were built at the end of the 19th century, and at present there are nearly 200 underwater tunnels built worldwide. Although some are used for water and electricity supply, most are used to house road or rail connections.

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The size of BART's fleet will be dynamic while new trains are put into service and old trains are retired. BART has 8 DMU train cars which each have a seating capacity of 104. 70 mph maximum; 35 mph average, including 20-second station stops. For BART to Antioch DMU trains, the maximum speed is 75 mph; 60 mph average.

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