Chapter 7
1989: San Francisco–Oakland
Bay Bridge Earthquake
Collapse
89
THE REPORTED STORY
The New York Times Abstract:
A devastating earthquake rocked the San Francisco Bay area at rush hour
last night, killing at least 200 people, collapsing a mile-long span of an Interstate
highway and wrecking part the Bay Bridge to Oakland. (Barron, 1989)
THE BACK STORY
TRANSPORTATION IN THE BAY AREA IN THE 1920S
During the 1920s, the San Francisco Bay area was the most densely settled
region of California. As San Francisco and Oakland grew during this time,
transportation between these two major cities became more important.
Passenger and vehicular ferries carried citizens between both ports across the
San Francisco Bay. In 1929, passenger ferries carried 36 million passengers
and vehicular ferries carried 10 million passengers with their automobiles.
During these years, the number of annual passengers was decreasing while
the number of annual autos was increasing. This was not surprising, because
Californians owned one car for every 2.7 people in 1929. East Bay residents
89
Ch07-P088531.qxd 2/22/06 11:46 AM Page 89
90 Engineering Ethics: An Industrial Perspective
used the East Bay Highway to travel from suburbs to the Oakland area.
Vehicles were ferried from Berkeley to Hyde Pier in San Francisco. Once in
San Francisco, vehicles used the Bay Shore Highway to travel between San
Francisco and San Mateo.
The Southern Pacific railroad also had indirect routes between the two
cities. One railroad crossing across the bay spanned Dumbarton Port in
Alameda County and Redwood City in San Mateo County; the second
crossing spanned Benicia and Martinez.
With this transportation system in place, the San Francisco–Oakland Bay
bridge began its construction in 1933. Designed only to improve highway
and mass transit services between the East Bay and San Francisco, this
bridge was congested on the day of its dedication in 1936 and has remained
congested almost without interruption (HAER, 1999).
BRIDGE DESIGN AND CONSTRUCTION
The Bay Bridge design was based on the following requirements:
Capacity of six lanes for highway traffic and at least two operative
and one passing or emergency track for interurban trains;
One or two bridge spans between San Francisco and Yerba Buena
island (the west channel), and one span between the island and
Oakland;
Vertical and horizontal clearances of 220 feet and 1650 feet,
respectively, mandated by the War Department.
Unlike other prominent bridges built at the time, such as the Golden Gate
Bridge, the Bay Bridge was designed by committee, rather than under the
vision of one designer/architect. It was efficiently designed during a 24-month
period, from early 1931 to early 1933. In 1931 the California legislature
authorized the California Toll Bridge Authority (CTBA), which it had
created in 1929, to build the bridge and provided $650,000 for its design.
C. H. Purcell, who studied civil engineering at Stanford University, was
appointed chief engineer for the bridge; Charles Andrew, who studied civil
engineering at the University of Illinois, was named as his assistant, or bridge
engineer.When Purcell and Andrew’s requested exemption from civil service
was approved, they hired a talented team of more than 50 engineers along
with allied specialists, including surveyors, draftsmen, and a clerical staff. Two
prominent team members were Ralph Modjeski, one of the best known
bridge engineers of the early 20th century, and Daniel Moran, one of the best
known foundation engineers.
Due to the horizontal clearances requested by the War Department, a
suspension design, rather than a cantilever design, was selected for the
Ch07-P088531.qxd 2/22/06 11:46 AM Page 90

Get Engineering Ethics now with the O’Reilly learning platform.

O’Reilly members experience live online training, plus books, videos, and digital content from nearly 200 publishers.