BAY BRIDGE

MTC Bay Bridge Rail Feasibilty Study

CHAPTER 4. STRUCTURAL COSTS

Developing a cost estimate for adding rail to the Bay Bridge requires a separate analysis of the costs of structural changes to the bridge and the costs of rail infrastructure, including rails, rolling stock and signal systems.

Estimating the costs of the structural impacts of rail is further complicated by the fact that, on the West spans, rail would be added to a bridge that is already over 60 years old, and requires continuous traffic operations. Modifying the proposed East spans for rail operations is more straightforward because the design is not complete and construction will occur outside of current bridge operations.

Among the complexities of placing rail on the West spans which affect this cost estimate are:

• lead based paints
• custom-fit connections
• connections to, and modification of, fully loaded members
• working with traffic
• irregular foundations in deep water
• criticality of stage construction on a 60-year-old structure

These added costs are further inflamed by confined work areas on the San Francisco approaches due to occupied facilities and work over shipping channels that must remain clear. Because of these complexities, it is especially difficult to identify "peer projects" that might provide linear foot costs for a feasibility level cost estimate.

As a means of comparing these costs with other projects in the Bay Area, the proposed East spans are currently estimated to cost $1,000 per square foot for the suspension spans and $650 per square foot for the viaduct spans. Retrofit of the Golden Gate Bridge was in excess of $1,000 per square foot in 1991, and there was no planned foundation work on the suspended spans. In year 2000 dollars, the square foot cost could easily be $2,000. Internationally, the completion of the Oresund Link Cable-Stayed Bridge between Sweden and Denmark is $1,000 per square foot. The bridge has relatively shallow inexpensive foundations and seismic risk did not control the design. Considering complexities of working with an existing structure on the West spans, values of $2,000 per square foot are appropriate. Lower unit costs are, of course, assumed for other structures. These are relatively high-end estimates, which could be reduced through careful engineering at later study phases.

Figure 4-1 summarizes the structural costs of the rail alternatives, excluding all rail infrastructure costs. The West span costs dominate the calculation, requiring over $1 billion in investment on that span alone. Total costs vary between $3 billion and $3.3 billion, exclusive of rail infrastructure.

FIGURE 4-1: STRUCTURAL COST SUMMARY
(EXCLUDES INFRASTRUCTURE)

	Options
	Below	Side-By-Side
San Francisco Approaches	193	436
West Spans	1,334	1,447
Yerba Buena Island	317	198
East Spans*	546	546
Oakland Mole	60	40
Subtotal	2,450	2,667
25% Contingency	612	667
Total	$3,062	$3,333
Costs are in Millions *East span costs are based on revisions to the design prior to awarding the construction contract.

Figure 4-2 details this costs estimate.

FIGURE 4-2: STRUCTURAL COST ESTIMATE