Rare photos from the BART Transbay Tube construction project Archival photos show the building of the wondrous SF Transbay tube

San Francisco Bay Area Rapid Transit (BART) construction progress as of July 23, 1970. From the San Francisco Chronicle: "They rolled out the Municipal Railway's 'Old Iron Monster' yesterday to publicize the public's first chance to visit the cavernous world of steel and concrete the Bay Area Rapid Transit is building below Market Street. BART officials, PUC commissioners, Market Street business leaders, newsmen, photographers and TV cameramen hauled aboard the Muni's first streetcar, put in service in 1912, for a rumbling, bone-shaking ride down Market Street to BART's new Montgomery Station. The ride was memorable for the historic touch, but mercifully short. At the end of the one day line was an advance peek at what San Franciscans will see if they take advantage of BART's open house on Sunday for the station at Montgomery and Market Streets." July 23, 1970 less San Francisco Bay Area Rapid Transit (BART) construction progress as of July 23, 1970. From the San Francisco Chronicle: "They rolled out the Municipal Railway's 'Old Iron Monster' yesterday to publicize the ... more Photo: Barney Peterson, San Francisco Chronicle Photo: Barney Peterson, San Francisco Chronicle Image 1 of / 57 Caption Close Rare photos from the BART Transbay Tube construction project 1 / 57 Back to Gallery

Human beings are capable of accomplishing great feats, even with the most daunting of challenges. Creating the Transbay tube connecting BART from San Francisco to the East Bay was one of them.

If you've looked out of the back window in the last car during a ride below the San Francisco Bay, you've seen the walls of the tube with an almost mesmerizing affect. The archival photos in the gallery show many facets of just how this wondrous structure was accomplished. Some of the images haven't been seen for decades.

"The structure is made of 57 individual sections that were built on land at the Bethlehem Steel shipyard on Pier 70, and towed out into the bay by a large catamaran barge," according to BART's historical information. "After the steel shell was completed, water-tight bulkheads were fitted and concrete was poured to form the 2.3-foot thick interior walls and track bed. They were then floated into place (positioned above where they were to sit), and the barge was tethered to the Bay floor, acting as a temporary tension leg platform.

The section was ballasted with 500 short tons of gravel before being lowered into a trench packed with soft soil, mud, and gravel for leveling along the Bay's bottom. Once the section was in place, divers connected the section with the sections that had already been placed underwater, the bulkheads between placed sections were removed and a protective layer of sand and gravel was packed against the sides."

Construction of the tube began in 1964. The first test trains passed under the Bay in August of 1973. According to BART's history of the construction, "The cost of the Transbay tube rose to $180 million from an original estimate of $133 million."

Below is a video from December 22, 1966, showing Construction on San Francisco's BART System.

The BART website has a handy timeline of the BART system evolution for those who are interested.

Bob Bragman is a producer for SFGATE. His writing reflects his love of the Bay Area, in addition to his passion for vintage pop culture, ephemera and vernacular photographs. To see more of his content, please click here.