San Francisco Bay Bridges - The Next Best Thing to Driving on Water
The San Francisco Bay is home to some of the most famous and magnificent bridges ever built, including the Golden Gate Bridge, San Francisco-Oakland Bay Bridge, Richmond-San Rafael Bridge, Hayward-San Mateo Bridge and the Dumbarton Bridge. Collectively, these five bridges represent a gamut of engineering structures and designs.
It’s no wonder, given the diverse geography they must span.
To the west of San Francisco sits the Pacific Ocean and due east through the strait of the Golden Gate lies the San Francisco Bay, extending 10 miles northeast to the San Pablo Bay entrance and 40 miles southeast into Palo Alto. At its greatest width the bay measures 13 miles with depths reaching over 200 feet, just inside the Golden Gate; yet, 70 percent of the bay is less than 12 feet deep.
At points along the 50-mile length of the bay, five structures of engineering excellence, some considered impossible to build, span gracefully over 23 miles of the bay waters and allow travelers to visit San Francisco, the peninsula and the East Bay easily, quickly and safely. Designed with a number of factors in mind, each bridge has its own navigational clearance, foundation conditions, total length of structure, cost and aesthetics, according to the California Department of Transportation, or Caltrans.
Crossing the strait of the Golden Gate from San Francisco to the Marin headlands for 1.7 miles is the world-renowned Golden Gate Bridge, easily identified by its International Orange color. Opened in 1937, the bridge was built at a cost of $33 million and 10 workers’ lives. The single-suspension span is anchored off the shores of the bay by twin towers that reach skyward 750 feet, and was once taller than any building in San Francisco. To support the suspended roadway, two cables more than 7,000 feet in length, containing 70,000 miles of wire stretch over the top of the towers and are rooted in concrete piers on shore. Ten years in planning due to formidable opposition, but only four years in actual construction, the Golden Gate Bridge brought the communities of San Francisco and Marin county closer together.
The Golden Gate’s eastern cousin, the San Francisco-Oakland Bay Bridge, was completed in 1936. In 1955 the Bay Bridge earned the honor of being declared the seventh wonder of the world in 1955 by the American Society of Civil Engineers. It is actually two different types of bridges--suspension on the San Francisco side and cantilever on the Oakland side--connected via tunnel through Yerba Buena Island. The eastern portion (a cantilever bridge) is currently being replaced with a self-anchored suspension bridge, which will be the longest of its type in the world.
Due to the extraordinary depth of the water, ranging from 50 to 105 feet, and a bay floor thick with several layers of mud, the building of the bridge brought about new engineering challenges. Special caissons, watertight chambers, were designed for digging through the Bay floor in order to embed the bridge’s foundation in bedrock.
As more people began making the East Bay their home, the Bay Bridge became the most heavily traveled bridge in the Bay Area, third busiest in the country, carrying more than 270,000 vehicles daily.
At the north end of the bay is the cantilever-truss Richmond-San Rafael Bridge that stretches 5.5 miles. This bridge has the dubious distinction of being struck on several occasions by passing ships, including a World War II vessel and a Navy radar ship that struck the bridge twice as the ship spun around. However, the bridge suffered no serious damage. Less elegant than its sister bridges, upon completion it was dubbed by bay area residents the "roller coaster bridge." But, even in its austerity, the bridge glides effortlessly across the bay, linking travelers to the hills of Marin and the wine-growing regions of Sonoma and Napa Valley.
Towards the south of the bay lies the San Mateo-Hayward Bridge, "6.8 miles of silver ribbon stretching gracefully in stunning relief across the bay," boasts Caltrans. The second to the youngest in the family of San Francisco Bay bridges, the bridge designers gave high priority to its aesthetics. Constructed of steel girders and trestles, the San Mateo-Hayward Bridge achieves its slim silhouette through the innovative technique of placing all bracings and hinge details on the inside of the box girders, making the structure the world’s longest, untraced girder span.
As a result, the bridge earned the American Society of Engineers’ "Outstanding Civil Engineering Achievement" honor and the American Institute of Steel Construction’s "Most Beautiful Bridge-Long Span" award in 1967.
Opened for use October 31, 1967, the San Mateo-Hayward Bridge provides closer proximity to the San Francisco International Airport for people in the south and east bay communities.
In 1927 a private corporation built the first of the bay bridges, the Dumbarton that crossed the narrowest portion at the south of the bay, a short 1.2 miles. The state purchased the bridge in 1951 and after several studies concluded that a replacement structure was needed.
In 1984 the state completed construction on the new bridge, made of steel box girders and prestressed concrete spans totaling 8,600 feet. The bridge’s graceful shape is heightened by the 15 twin trapezoidal girders that seem to float on the concrete piers extending just above the water. The original structure was completely demolished in 1985.
The bridge welcomes pedestrians and bicyclists on a separate path separated by a concrete safety barrier. Partially located within the San Francisco Bay National Wildlife Refuge, the toll plaza canopy serves as an overpass for visitors to the Wildlife Refuge and the Coyote Hills Park.
The Dumbarton Bridge connects the counties of San Mateo and Alameda and helps to lessen the congestion for commuters traversing to the East Bay and the lower San Francisco peninsula.
The five bridges of the San Francisco Bay provide not only an expedient means to residents’ daily commute, but also offer exceptional combinations of grace and strength that commuters and visitors alike can appreciate as they traverse the Bay Area.
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