Existing Dumbarton Rail Bridge

The existing Dumbarton Rail Bridge will see revived rail service within a few years. A new bridge for
high speed rail would replace it if the Altamont Alignment is chosen.


Bay Crossing



Building a new railway bridge at Dumbarton will be much easier than building the new East Span of the Bay Bridge. Let's look at the vital statistics of the two bridges:

East Span Bay Bridge

Elevation of the East Span of the Bay Bridge

Length    11,759’
Channel Clearance    1,200' x 184'
Deck Width    84’ x 2*

  • Must be built without interrupting existing traffic
  • Unique self-anchoring suspension design
  • Construction adjacent to busy Oakland Outer Harbor

* does not include bike/pedestrian path (15’)

New Dumbarton Rail Bridge

Elevation of the Dumbarton Bridge

Length    8,800’
Channel Clearance    340' x 85'
Deck Width    37’

  • Can be constructed from existing railway trestle
  • Minimal vessel traffic under span
  • Highway crossing built for $70m in 1984

Results of the comparison?

  • The East Span is 33% longer
  • The East Span is five times as wide
  • The East Span requires expensive temporary structures to connect the new bridge to Yerba Buena Island
  • The suspension portion of the East Span is an un-tested "self-anchoring" design
  • The East Span crosses much deeper water
  • The East Span crosses an extremely active channel
  • The East Span is next to the busy Port of Oakland
  • The Dumbarton rail bridge will be much less complicated - therefore much less expensive - to build
Remember, construction costs depend largely on unit costs, the mass of the structure that is being built. Some costs increase linearly, other exponentially.

The columns for the East Span of the Bay Bridge are over twice the girth of what would be needed for a Dumbarton HSR bridge. The Bay Bridge goes from sea level to over twice as high as the Dumbarton, but not back to sea level. The difference in volume of the columns is almost 1500%.

The difference in the width of the two bridges is almost 500%.

Considering its mass, structural components, and construction challenges, the Bay Bridge East Span project is eight to ten times greater than a Dumbarton HSR bridge.

Using the Caltrans Construction Cost Index and escalating the Caltrans’ 1984 construction cost for the Dumbarton highway bridge ($70m), the 2003 cost would be around $119m.

The recently completed trestle for the San Mateo Bridge is over three times longer than the Dumbarton, yet a much simpler structure. In 1999, the winning bid for the project was only $113m.


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