San Francisco Bay Southern Crossing

The Southern Crossing is a proposed highway bridge that would span San Francisco Bay in California, somewhere south of the San Francisco–Oakland Bay Bridge and north of the San Mateo–Hayward Bridge. Several proposals have been made for over the past half-century, varying in design and specific location, but none of them have ever been approved due to cost, environmental and other concerns.

The idea for the Southern Crossing dates back to the 1940s when several additional bridges across San Francisco Bay were studied. One early proposal called for the bridge to span between Third and Army Streets, with a direct connection to the Bayshore Freeway, in San Francisco to near Bay Farm Island in Alameda. Another idea was to connect the bridge directly to Alameda, enabling eastbound traffic to travel across that city and through the Posey and Webster Street Tubes to a point in Oakland near the present-day western terminus of Interstate 980.

Yet another alternative was to include both the Alameda and Bay Farm Island connections, and build a junction in the middle of the bay off the western shore of Alameda. In addition, architect Frank Lloyd Wright and engineer Jaroslav Joseph Polivka collaborated on designing a reinforced concrete "Butterfly Bridge", consisting of twin 2000-foot long arches providing 200 feet of clearance above the bay's main ship channel. However, such proposals never got beyond the drawing board because of cost concerns. A bond measure was put in the ballot in 1972 that would have funded a planned crossing from Hunters Point and Alameda, but voters rejected it. Then in the 1980s, State Senator Quentin L. Kopp attempted to pass legislation to help build the Southern Crossing, but that also died after facing opposition from environmental groups.

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