The purpose of the San Francisco-Oakland Bay Bridge (SFOBB) East Span Seismic Safety Project (East Span Project) is to provide a lifeline vehicular connection that:

The SFOBB East Span Project will provide a seismically upgraded vehicular crossing for current and future users. SFOBB East Span Project replacement bridge alternatives will not preclude a bicycle/pedestrian path.


The existing East Span must be replaced or retrofitted because it is not expected to withstand an MCE on the San Andreas or Hayward faults, it does not meet lifeline criteria for providing emergency relief access following an MCE, and it does not meet current operational and safety design standards.

The project is proposed to address the following major transportation needs and deficiencies identified specifically on the bridge between YBI and the SFOBB Toll Plaza:

Each of these needs is described in the following sections.

1.2.1 Lifeline Connection - The existing SFOBB East Span does not provide a lifeline connection that is usable after an MCE.

Improvements to the existing East Span are needed to address seismic safety deficiencies and provide a bridge crossing that is usable soon after a major seismic event. It is likely that the existing SFOBB East Span would develop multi-span failures leading to collapse and loss of life in the event of an MCE, even with the recent completion of the interim retrofit project. The East Span does not provide for public safety during an MCE.

Maximum Credible Earthquake

On the basis of research conducted since the 1989 Loma Prieta earthquake, U.S. Geological Survey (USGS) and other scientists conclude that there is a 70 percent probability of at least one magnitude 6.7 or greater quake, capable of causing widespread damage, striking the San Francisco Bay region before 2030. Major quakes may occur in any part of this rapidly growing region. This emphasizes the urgency for all communities in the Bay region to continue preparing for earthquakes.

The seismic design criteria set for the East Span Project have been established as an 8 magnitude earthquake on the San Andreas fault or a 7-1/4 magnitude earthquake on the Hayward fault. The MCE on each of these faults is defined as the largest earthquake that appears to be reasonably capable of occurring based on current geological knowledge. While these values could be exceeded, the values represent the best estimates at this time. The probability of an MCE occurring on one of these faults is approximately one in four over the next two to three decades.

An MCE on either the San Andreas or Hayward fault would be expected to inflict far greater damage to the SFOBB than was experienced from the 1989 Loma Prieta earthquake, during which one section of the upper deck collapsed, killing one person. This is due to the potential for the epicenter of an event on either the San Andreas or Hayward fault to be nearer the bridge, as well as the expected greater magnitude of the MCE compared to that of the Loma Prieta earthquake (magnitude 7.1). It is estimated that an MCE with an 8 magnitude would generate in excess of 30 times more energy than the Loma Prieta earthquake. The feasibility of reopening the existing East Span to traffic following an MCE would be limited or precluded without the seismic safety improvements proposed in the East Span Project.

Lifeline Structure

The SFOBB provides a critical connection between San Francisco, the East Bay, and the I-80 corridor to the east. Designation by the California Department of Transportation (Caltrans) of the SFOBB corridor as a lifeline system connection represents the State’s intention to use the SFOBB to provide a high level of post-earthquake transportation service for emergency response and support for the safety and economic livelihood of the Bay Area. Combined with the West Span seismic retrofit (now under way), the retrofit of the west YBI viaduct and YBI tunnel, and the West Approach replacement, replacement of the East Span would complete the lifeline connection.

The criteria for state lifeline route designation and their applicability to the SFOBB East Span Project are listed below:

Cooperative earthquake response planning among Bay Area transportation providers focuses on the roles of agencies, including Caltrans, in post-earthquake response. Emphasis is placed on actions during the first 72 hours after an earthquake. Response scenarios do not call out procedures to be implemented at specified locations. Overall responsibilities for participating agencies are defined.

Caltrans preparedness planning consists of activities, including cooperation with the California Highway Patrol (CHP), in developing traffic control and evacuation procedures; activating emergency response resource centers; and establishing route recovery plans.

Although no detailed plan for a lifeline SFOBB post-earthquake use is defined, it can be anticipated that the structure would be used to transport heavy equipment, such as cranes and bulldozers, to work sites. The structure would also be used to distribute supplies from the San Francisco and Oakland ports to recovery centers. Automobile and bus transit traffic would likely be banned from the SFOBB so as not to interfere with emergency response, then would be restored on the SFOBB as feasible. As a lifeline vehicular bridge, the SFOBB would have the flexibility to move equipment and goods during post-earthquake recovery that cannot be accommodated by Bay Area Rapid Transit (BART) and ferry service.

1.2.2 People, Freight, and Goods Movement - The existing SFOBB East Span cannot maintain high levels of freight and goods movement following an MCE.

The SFOBB East Span, currently operating at capacity, is used by approximately 272,000 vehicles each day, making it a critical transportation link in the Bay Area. The volume of traffic on the SFOBB is approximately double that of the Golden Gate Bridge and almost equal to the combined traffic carried by the four other Bay Area bridges. For motor vehicle traffic, the Golden Gate Bridge and other Bay Area bridges are essentially non-redundant systems, with alternative routes to the other bridges being time consuming to a level that seriously impacts commercial and institutional productivity. Providing a seismically safe, lifeline vehicular bridge crossing is critical to retaining the ability to move high volumes of people between San Francisco, the San Francisco Peninsula, and the East Bay.

The SFOBB is a primary route for movement of freight and goods between the San Francisco Peninsula and the East Bay. It provides access for San Francisco to the intrastate and interstate trucking network in the East Bay and beyond. The SFOBB provides a link for seaport cargo and air freight delivery between the ports and airports in both San Francisco and Oakland. The bridge is also a link for local delivery of freight and goods. The SFOBB carries the greatest amount of total traffic and truck traffic of all the Bay Area toll bridges (see Table 1.2-1). Maintaining the capacity of the East Span to accommodate large volumes of truck traffic is important for distribution of freight and goods to facilitate economic recovery following an MCE. Disruption of this critical link in the transportation system by damage or failure due to an earthquake would require rerouting approximately 8,000 truck trips per day to other toll bridges, assuming these other bridges are not similarly damaged. Extended interruption of the capacity of the East Span to accommodate large numbers of trucks would have an adverse effect on the local and regional economy.

Table 1.2-1 Annual Average Daily Total (AADT) Traffic and Truck Traffic on Bay Area Toll Bridges







Percent Trucks

Percent Large Trucksa











San Mateo-Hayward





Golden Gate





Richmond-San Rafaelb















Source: 1998 Traffic Volumes on the California State Highway System, Caltrans, April 2000.

aPercentage of 4- and 5-axle trucks of total trucks.

bMeasurement location at junction of I-580/Route 101, Marin County.

1.2.3 Current Roadway Design Standards - The existing SFOBB East Span does not meet current roadway design standards for operations and safety.

Design standards are applied to bridge and roadway projects to provide a safe facility. The SFOBB East Span, constructed in the 1930s, does not meet all of the current mandatory and advisory design standards, including:


1.3.1 The San Francisco-Oakland Bay Bridge

The SFOBB is historically important in the Bay Area and worldwide. Construction of this structure began in 1933 and was completed and opened to traffic in 1936. At the time of its construction, the bridge was the world’s longest vehicular bridge, and the YBI tunnel, a double-decked structure, was the largest bore tunnel of its time at 23 meters (76 feet) long by 15 meters (50 feet) wide by 15 meters (50 feet) high (see Figure 1-1 in Appendix A).

The SFOBB currently serves 272,000 vehicles each day. The SFOBB provides regional access between the San Francisco Peninsula and the East Bay. As a component of Interstate 80 (I-80), it is a critical link in the interstate highway network. The Dwight D. Eisenhower System of Interstate and Defense Highways, established in 1954 during Eisenhower’s presidency, is a network of access-controlled and grade-separated highways designed to serve the national defense and to connect states and routes of continental importance in Canada and Mexico.

The SFOBB is a double-deck structure carrying five traffic lanes on each level. The West Span connects San Francisco to YBI. A concrete viaduct and approach ramps eastward from Fifth Street in San Francisco at the west end, 1,130 meters (3,707 feet) long, connect to the two suspension spans, each over 1,400 meters (4,593 feet) long. On the island, there are two concrete viaducts, 165 meters (541 feet) and 65 meters (213 feet) in length, at either end of the 164.4-meter (539-foot) long double-deck tunnel.

The East Span is the portion of the structure between YBI and Oakland. An 800-meter (2,625-foot) long viaduct extends from the YBI tunnel east portal eastward across the island. A series of steel truss spans carries the highway across the eastern portion of the Bay. The steel spans include a 737-meter (2,418-foot) cantilever truss adjacent to the island, followed by five high truss spans 155.1 meters (509 feet) each, and 14 shorter spans, which bring the roadways to the East Bay shoreline.

1.3.2 Overview of the Seismic Retrofit Program

Caltrans' design program to seismically retrofit State-owned, city, and county bridges has been highly influenced by recent earthquakes in California. In particular, the 1971 San Fernando earthquake, the 1987 Whittier Narrows earthquake, the 1989 Loma Prieta earthquake, and the 1994 Northridge earthquake greatly influenced the direction, design, scientific research, and priorities of Caltrans' seismic retrofit program. These earthquakes prompted new research and funding for the seismic retrofit of transportation structures, which has included pioneering research and design focusing on the seismic behavior of large bridges. This has led to increased understanding of how bridges behave in earthquakes, new techniques for retrofitting existing bridges, and improved design criteria for new construction. Over the past three decades, this work has placed Caltrans at the forefront of the evolving field of seismic retrofit design. For further information on how the program relates to the East Span Project, refer to Appendix K.

1.3.3 Effects of the Loma Prieta Earthquake and a Maximum Credible Earthquake

On October 17, 1989, the Loma Prieta earthquake struck the San Francisco Bay Area. Its epicenter was in a sparsely populated area of the Santa Cruz Mountains, 97 kilometers (60 miles) away from the SFOBB. The California Office of Emergency Services (OES) reports that the earthquake caused 62 deaths and $5.6 billion in property damage, and 8,000 people were left homeless. Over 1,300 buildings were destroyed and 20,000 buildings were damaged. On the SFOBB, the earthquake caused a portion of the upper deck of the East Span to collapse onto the lower deck, resulting in one death. The East Span was closed for four weeks while the damage was repaired. Caltrans estimated that the increased delay experienced by commuters rerouted to other Bay crossings, including other modes such as ferries or BART, cost as much as $12 million.

The Association of Bay Area Governments (ABAG) conducted an assessment of the regional macroeconomic impacts of the Loma Prieta earthquake. ABAG concluded that the maximum loss to the Gross Regional Product was in the range of $181 to $725 million. ABAG noted that San Francisco suffered a significant loss ($73 million) in taxable sales activity, and that "a major portion of the loss in economic activity in San Francisco may have been due to a loss in transportation access."

The Loma Prieta earthquake showed the vulnerability of the transportation system to a relatively distant earthquake. Future planning must recognize the likelihood and potential consequences of closer and more powerful events on the San Andreas and Hayward faults. An MCE on the San Andreas fault could generate over 30 times more energy than the Loma Prieta earthquake. An MCE on the Hayward fault could generate about the same energy as the Loma Prieta earthquake. Damage from an MCE on either of these faults could be heavier and much more widespread compared to damage from the Loma Prieta earthquake, including the collapse of thousands of buildings, extensive infrastructure damage, and major loss of life. The magnitude of such a natural disaster would necessitate the kind of emergency access provided by the bridge retrofitted to lifeline standards. On the existing SFOBB East Span, an MCE could cause catastrophic bridge failure, potentially resulting in numerous immediate casualties and requiring many months to reopen the bridge or years to build a replacement. Immediate emergency response and more long-term economic recovery would be delayed.

1.3.4 Analysis of Potential Retrofit of SFOBB East Span

Caltrans began action following the Loma Prieta earthquake to design seismic safety improvements for the SFOBB East Span. Seismic safety strategies initially investigated focused on retrofit of the existing East Span structure. A retrofit alternative was devised and initial environmental review conducted. Consultation with permitting and regulatory agencies was initiated.

An important consideration for the retrofit of bridges maintained by Caltrans is the cost of upgrading the existing structures to current seismic criteria measured against the remaining useful life of the bridges. Caltrans has developed a cost/benefit formula to assist in determining the need to retrofit a bridge compared to replacing it. First it must be determined that there is a viable retrofit alternative (i.e., the existing structure can be retrofitted to meet seismic safety criteria established for the structure). This decision is made by Caltrans with input from a Seismic Advisory Board, an industry and academic advisory panel which was established following the Loma Prieta earthquake to provide Caltrans assistance in determining effective seismic safety technologies.

The Caltrans formula takes into account both construction costs and life-cycle costs. Cost comparisons of retrofit and replacement alternatives indicated that seismic retrofit of the existing span could be accomplished at a lower cost than the cost to replace the structure. However, replacement bridge alternatives would have lower life-cycle costs; therefore, consideration of bridge replacement was recommended to Governor Pete Wilson by the Business, Transportation and Housing Agency.

1.3.5 Analysis of Potential Replacement of the SFOBB East Span

In February 1997, Governor Pete Wilson adopted the recommendations of the Business, Transportation and Housing Agency that replacement of the SFOBB East Span be considered. The Metropolitan Transportation Commission (MTC) organized the San Francisco-Oakland Bay Bridge Design Task Force (Task Force) to consider replacement bridge alternatives. Alternatives under consideration in this environmental document include replacement options defined through the Task Force proceedings. The Task Force mandate was to develop a consensus recommendation on a design option for a new eastern span of the SFOBB and to recommend any additional features that might be included in the design of the bridge that would not be borne by funding allocated from the State of California. A description of the MTC process is provided in the Preface and Appendix E — Consultation and Coordination of this Final EIS.

1.3.6 Other SFOBB Seismic Safety Projects

Caltrans is undertaking a number of independent actions to address the overall need of providing a lifeline bridge connection between the cities of San Francisco and Oakland. Design of one project does not determine or preclude design of the other projects. In combination, these actions will provide for a lifeline structure connecting San Francisco and the San Francisco Peninsula to the East Bay. The individual projects, in addition to contributing to the seismic safety improvement of the SFOBB, have been defined to contribute independently to seismic safety of bridge users in the event of an MCE and the associated economic benefits of keeping the bridge usable after an MCE. As each of the projects is completed, bridge users will benefit from seismic safety improvements and specific lifeline access issues will be resolved.

In addition to the East Span Project, Caltrans is undertaking other actions to seismically retrofit the SFOBB. The limits of these projects are shown in Figure 1-1 in Appendix A and consist of:

1.3.7 Legislative Framework

The California Legislature has in various legislative findings and declarations expressed its intent to complete the seismic retrofit of State-owned and State-operated highways. Following the 1971 San Fernando Valley earthquake, seismic design standards for transportation facilities were reassessed in light of the unanticipated damage to certain roadway structures, and a retrofit program was begun. The extensive roadway damage caused by the 1989 Loma Prieta earthquake in northern California and the 1994 Northridge earthquake in southern California prompted an acceleration of the retrofit program, including several efforts to increase program funding. In 1991, the legislature authorized financing seismic retrofit projects from motor vehicle fuel tax revenues and additional funding mechanisms, declaring that "it is in the best interests of the people of California to immediately finance retrofit projects to make state highways safe during seismic events, and to offset any possible delays caused by these projects on approved state highway projects contained in the state transportation improvement program for 1990..." (Government Code, Chapter 5, Article 1, Amended: Statutes of 1991, Chapter 195).

In 1995, recognizing the increasing financial drain of the ongoing seismic retrofit program on limited funding resources, the legislature placed the Seismic Retrofit Bond Act of 1996, or Proposition 192, on the March 1996 ballot, declaring that "the completion of seismic safety retrofit work is essential to the welfare and economy of the state" (Government Code, Title 2, Division 1, Chapter 12.48, Article 1). This act, approved by the voters in 1996, authorized the sale of over $2 billion in state revenue bonds for financing retrofit improvements and temporarily suspended state statutes that were deemed to potentially delay or unnecessarily encumber their implementation. The seismic retrofit and rehabilitation of the SFOBB East Span is a priority project under the state’s accelerated retrofit program.

Senate Bills 60 and 226 were passed by the State Legislature and signed into law by the Governor on August 20, 1997. Together, these bills provide a financing mechanism and identify funding sources for seismic improvements for Bay Area toll bridges, including the SFOBB East Span. Senate Bill 60 establishes a one dollar toll surcharge on the seven Bay Area State-owned bridges and identifies additional funds available for seismic upgrades. State fuel tax revenues earmarked for seismic upgrade projects will fund approximately 33.4 percent of the project costs. State Seismic Retrofit Revenue Bonds issued by the State after voter approval of Proposition 192 in March 1996 will fund an additional 30.2 percent. The one dollar toll surcharge on Bay Area toll bridges for eight years will fund the remaining 36.5 percent.

Senate Bill 226 transferred programming authority for Bay Area toll bridges from the California Transportation Commission to the Metropolitan Transportation Commission. As a result, the Bay Area Toll Authority (BATA) is permitted to extend the period of toll surcharges to cover the cost of amenities. These include a cable-supported or other bridge design, improvements to the Transbay Transit Terminal (including possible relocation and/or ramp reconfiguration), and the addition of bicycle/pedestrian access on the SFOBB. Assembly Bill 2038, which amended Senate Bill 60 in June 1998, allows BATA to fund the addition of bicycle/pedestrian access to either the new East Span or the retrofitted West Span or both, within the restrictions set forth by Senate Bill 60 or a future toll surcharge extension.

Seismic retrofit projects, including the East Span Project, are exempt from the requirements of the California Environmental Quality Act (CEQA) under California Streets and Highways Code Section 180.2 and CEQA Section 21080 (see Chapter 5). Although CEQA review has not been conducted for the project, detailed environmental and socioeconomic review is being undertaken to comply with the National Environmental Policy Act (NEPA) and other applicable state and federal laws. The East Span Project will also be subject to the permitting requirements of federal and state regulatory agencies. Consultation is under way with public agencies, including U.S. Coast Guard, U.S. Army Corps of Engineers, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, Advisory Council on Historic Preservation, National Marine Fisheries Service, San Francisco Bay Conservation and Development Commission, California Department of Fish and Game, State Historic Preservation Officer, State Lands Commission, and San Francisco Bay Regional Water Quality Control Board.

1.3.8 Concurrence in the Purpose and Need Statement

The project Purpose and Need Statement presented in this chapter was drafted following FHWA Technical Advisory T 6640.8, "Guidance Material for the Preparation of Environmental Documents." The advisory explains that the goals of the Purpose and Need Statement is to "Identify and describe the transportation problem(s) which the proposed action is designed to address." The format and topics described in the advisory were followed in the development of this Purpose and Need chapter.

Determination of the Purpose and Need was more fully developed with public input received at MTC Bay Bridge Design Task Force and Engineering Design Advisory Panel meetings on April 16, 22, 23, and May 8, 1997, which served as project scoping meetings.

The Purpose and Need Statement presented in this Chapter was refined through a collaborative process among federal agencies as outlined in the NEPA/404 Integration Memorandum of Understanding (MOU) (see Appendix F). The MOU sets out a consultation process among designated federal agencies resulting in written concurrence in the project Purpose and Need Statement. Signatories to the East Span Seismic Safety Project Purpose and Need Statement are FHWA, U.S. Fish and Wildlife Service, the U.S. Army Corps of Engineers, National Marine Fisheries Service, U.S. Environmental Protection Agency, and the Federal Transit Administration.

Non-signatory agencies participating in the development of the Purpose and Need Statement were the San Francisco Bay Regional Water Quality Control Board, the San Francisco Bay Conservation and Development Commission, U.S. Coast Guard, and the California Department of Fish and Game.

A summary of the consultation process resulting in obtaining concurrence in the Purpose and Need Statement is presented in Appendix F.