The Historical Importance of the Carquinez Bridge
Written by J.R. Manning
The Carquinez Straits Bridge was an important link that connected the Bay area to Sacramento and northern California. The waters around San Francisco presented a significant obstacle to transportation in the area, and the Carquinez Straits required either ferry service or long detours to avoid the area completely. A bridge across the straits was an absolute necessity to the economy of the area. It had been discussed in the late 19th Century, finally coming to fruition in the 1920's.
At the time the Carquinez Straits Bridge opened, it was longest bridge west of the Mississippi River. (It predated the San Francisco Bay Bridge and Golden Gate Bridge by eleven years.) It was also the first bridge to be designed to resist seismic forces. The two main spans were 1100 feet in length, making it, at the time, the fourth longest cantilever bridge in the world. Construction began in 1923 and the bridge opened in 1927, replacing ferry service across the straits.
The original route of The Lincoln Highway avoided the ferry crossing by coming from Stockton through Altamont Pass, then through Hayward to Oakland. Ferry service then carried the highway across the San Francisco Bay until 1938. When the Lincoln Highway was rerouted to cross the Carquinez Straits Bridge, the route was shortened by thirty miles.
With the development of the Interstate Highway System, I-80 also needed to cross the Straits of Carquinez. It was an incredibly important crossing, as evidenced by the fact the bridge carried 10 Million vehicles in 1955, compared to the one million it carried the year it opened. Using the extant bridge was an obvious choice, but the 1927 bridge only carried two lanes of traffic. A parallel bridge was built, 200 feet upstream, that opened in 1958. The new cantilever truss bridge resembled the 1927 structure in many ways, but was wider to carry four lanes of eastbound traffic. The deck of the 1927 bridge was widened by eliminating the pedestrian walkways, allowing the bridge to carry three very tight lanes for westbound traffic.
By the turn of the 21st Century, the old bridges were inadequate to meet modern traffic standards. The 1927 bridge did not meet current seismic standards and the deck was too narrow to carry three lanes of Interstate level traffic. Rebuilding of the 1927 bridge was determined too impractical and expensive. Access to the truss members was difficult, at best, and the traffic load too heavy to rebuild the bridge while open to traffic. The traffic snarl that would be created by simply closing the bridge for rebuilding would be controversial as well as impractical. The Carquinez Bridges were carrying an average of over 105,000 vehicles per day, closing one of the spans was just out of the question.
The 1927 bridge and the westbound Crockett exit ramp are listed on the National Register of Historic places, requiring special effort to replace the historic, but sadly obsolete, structure. A 54 page report that documents the 1927 Carquinez Straits Bridge can be viewed on the HAER website.
The new bridge now carries eastbound traffic. The 1958 bridge, after retrofitting, now carries the westbound lanes of I-80. After the opening the new bridge, the 1927 Carquinez Straits Bridge was dismantled. Photos of the dismantling, taken by Nicolas Janberg, can be found on the Structurae website at http://en.structurae.de/structures/data/index.cfm?id=s0000482.
