Bridge on suspension The San Francisco-Oakland Bay Bridge consists of two bridge segments: a skyway structure/single-anchored suspension bridge between Oakland and Yerba Buena Island, and a suspension span connecting the island and San Francisco. The world's biggest diameter bore tunnel connects the two. When it opens in 2017, it will be the first tunnel crossing of the bay since the 1939 Golden Gate Bridge.
The $6.5 billion project was designed to meet all state and federal requirements for clearance under water, while minimizing environmental impacts. It is the largest construction project in California history, with over 7,000 workers participating in its construction.
It replaces an aging bridge that has been listed for replacement since 1976. The previous bridge was built in 1937 by John C. Montgomery using a novel design that combined vertical lift beams with horizontal trusses to create one of the first cable-stayed bridges. The original bridge was named after its architect, Joseph Strauss, who went on to become known for his work on the Atomic Energy Labovratory near Detroit.
The new bridge is also designed by John C. Montgomery and uses similar components as its predecessor. However, instead of vertical lift beams, it uses horizontal trusses to support the deck from underneath while cables attached to anchor points high above the water allow traffic to pass through the center of the bridge without blocking the view.
With the central support in place, the western span of the Bay Bridge, which connects San Francisco with Yerba Buena Island, was built as a suspension bridge. The bridge between Yerba Buena and Oakland was built with a cantilever truss design with a bridge pier 242 feet below the water line. The eastern span, which connects East Bay counties with the rest of San Francisco, is a four-lane divided highway bridge that crosses over the Carquinez Strait. It has three large towers with heights of 456 feet, 408 feet, and 335 feet.
The first section of the new Bay Bridge, which carries its namesake vehicular traffic, opened to much fanfare on January 9, 1936. At the time, it was the longest suspension bridge in the world. The central portion of the new bridge began construction in 2009 and was completed in 2013. It features two 12-lane roadways that cross above busy U.S. 101 with no vertical barriers between traffic streams.
In order to construct such a long bridge over deep waters, the government acquired some of the land under the bridge from Chevron and Shell. Environmental groups have criticized this practice as premature development. They claim that the soil is still toxic after 70 years due to chemical dumping for decades by the oil companies who owned the land before the government took it over.
As part of their maintenance budget, bridge owners charge drivers to use the toll lanes.
Golden Gate Bridge The Golden Gate Bridge is a suspension bridge that spans the Golden Gate, a one-mile-wide (1.6-kilometer) strait that connects San Francisco Bay with the Pacific Ocean. It is the only major road bridge across the channel. The Golden Gate Bridge is one of the most recognized symbols of San Francisco and the West Coast of America.
The Golden Gate Bridge is also known as the "World's Most Famous Bridge". It is the longest suspension bridge in the world and was the first large scale project built using a prefabricated section system. The main cable suspension span is 1,080 feet (335 m) long while the total length of the bridge including approaches is 2,400 feet (737 m). It is estimated that when it was completed in 1937, the Golden Gate Bridge was the largest single-span steel structure in the world.
The bridge has been criticized for its environmental impact because it uses up much of the water that flows into the bay each day. The amount of water that runs off its surfaces into the bay has increased over time because there are more vehicles crossing it, so more water flows off the sides than did back then when there were far fewer cars.
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