Bay Bridge

Retrofit vs. Replacement

The Bay Bridge is actually two separate bridges. The west span consists of two suspension bridges joined at a common center anchorage in the deep, rocky floor of the Bay and anchored at their outer ends on Yerba Buena Island and in San Francisco. The east span, between Yerba Buena Island and Oakland, is a cantilever-truss structure, supported by a number of piers placed in layers of mud on the shallow eastern side of the Bay.

While Caltrans engineers and panels of seismic experts determined that the sturdy west-side suspension spans could be strengthened to meet current seismic safety standards, they concluded in late 1996 that the east span is far more vulnerable to a major earthquake, and, in the long run, it would be safer, less disruptive to traffic and more cost effective to build a new structure rather than retrofit the existing one.

Below is a chart that summarizes the issues involved in determining the decision to replace -- instead of retrofit -- the eastern span.

Retrofitting of the east span would substantially alter its appearance, requiring bulky concrete jackets on steel piers, and the addition of a number of new piers, particularly across the shipping channel.

 

Bay Bridge East Span
Retrofit vs. Replacement Issues
(as of 1997)

ISSUES	RETROFIT	REPLACEMENT
Seismic Performance and Damage After Major Seismic Event	Moderate to major damage. Weeks to months of repair. Performance not as reliable as new bridge. Normal traffic may never be allowed back on bridge. Replacement may be necessary, at a time when entire region will need emergency funding. Post-earthquake recovery to region impaired.	Minor to moderate damage. Slow speeds/operational within hours. Normal service restored within months. Post-earthquake recovery to region enhanced. Seismic Advisory Board (a panel of outside experts from academia and the private sector) and two independent Value Analysis studies concluded that bridge should be replaced and not retrofit.
Lifeline Connection	No. Would NOT provide safe route for emergency equipment and supplies.	Yes. Would provide safe route for emergency equipment and supplies.
Life Expectancy	50 years	150 years
Design/ Construction Cost	$1.085 billion (escalated to 2002 at 3%/yr)	$1.5 billion (escalated to 2002 at 3%/yr)
Life Cycle Maintenance	Bridge will need to be redecked in about 20 years. Continuous painting of entire structure.	Modern structure mostly concrete; steel portion will have a modern paint system requiring minimal maintenance and painting.
Rail	Any rail accommodation would require significant modification and the removal of lanes plus significant cost.	Can accommodate average weight light rail.
Financing	May need to go back to the Legislature for an amendment to the existing legislatively defined financing package (SB 60), which assumes replacement.	Has a financing package. SB 60 (1997) authorized up to 10 years of toll surcharge to pay for a new bridge plus amenities.
Bicycle/Pedestrian Path	None.	15.5-foot wide pedestrian/bike path elevated 1 foot above the roadway.
Traffic During Construction	Many lane closures, but not during commute hours; scheduled during the rest of the day and evening. Some lane closures almost every day for various construction activities.	Minimal impact. New bridge constructed adjacent to existing bridge, then traffic switch. Traffic switch will involve nighttime traffic control.
Traffic After Construction	Bridge will continue to operate as it does today.	East spans will operate significantly better due to existence of standard size (12-foot) lanes, 2 shoulders (providing a refuge area for stalled vehicles, emergency vehicle access, etc.). Overall bridge operation will be enhanced.
Aesthetics	Substantial alteration of appearance of existing bridge by addition of new piers and new support structures, encasing steel piers in concrete, and enclosure of cantilever span with external space-frame. Bridge will appear heavy, clunky, and unattractive. Limited views from existing bridge traveling eastbound toward Oakland will be reduced further.	Unique single tower suspension bridge and skyway. Open views from bridge in all directions of travel since the new bridge will have side-by-side decks rather than the existing double deck configuration. Viaducts from Oakland shore will lead to dramatic suspension span across deep-water channel.
Bay Fill	Net increase of solid fill in the Bay.	Significant net reduction of solid fill in the Bay.
Noise	Remains the same.	Will decrease.
Historic Properties	Adverse effect on existing historic bridge due to substantial modifications. Addition of concrete in-fill (shear) walls between existing bridge columns will block views from some historic buildings on Yerba Buena Island.	Adverse effect on existing historic bridge through its removal. Adverse effect on Torpedo House on YBI (northern alignment only). Will change views from historic buildings on YBI.
Land Use	Effect on redevelopment of YBI unknown as existing plans are not consistent and final plans are unknown. Will significantly reduce contiguous area available to planned regional park on Oakland shore.	Effect on redvelopment of YBI unknown as existing plans are not consistent and final plans are unknown. Northern alignment will maximize contiguous area available to planned regional park on Oakland shore. Southern alignment will bisect planned park.

Source: Caltrans