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A Bridge for a New Century
On Thursday afternoon, November 12, 1936, the San Francisco- Oakland Bay Bridge opened for business. People cheered as the first direct bridge crossing between San Francisco and the East Bay was opened. Built during the Depression, the structure was an engineering marvel of its day - the longest high level bridge in the world.
More than 60 years after it opened, the Bay Bridge is now the busiest toll bridge in the country, carrying 274,000 vehicles each day. As part of the interstate highway network and as a primary route for transporting goods and people between San Francisco, the Peninsula, and the East Bay, the bridge plays a vital part in the Bay Area's economic vitality.
When the Loma Prieta earthquake struck at 5:04 p.m. on October 17, 1989, this critical transportation link was seriously damaged. Part of the upper deck of the bridge's eastern cantilever span collapsed onto the lower deck. The bridge was closed for repairs for four weeks.
Following the San Fernando quake in 1971, state officials began a thorough reassessment of bridge seismic design standards. Using research developed since that time, the California Department of Transportation (Caltrans) has been leading a statewide, multi-billion dollar Seismic Retrofit Program to modify the structural design of many bridges in the state to make them less susceptible to damage in an earthquake. Caltrans significantly increased the program after the Loma Prieta quake, in order to identify and strengthen bridges that needed to be brought up to current seismic safety standards. Upgrading the Bay Bridge is a critical part of the Seismic Retrofit Program.
The East Span Project
The Bay Bridge seismic upgrade consists of six separate projects (see page 7 for descriptions of the other five projects in development). The full seismic upgrade for the east span between Yerba Buena Island and the Oakland shore is known formally as the San Francisco- Oakland Bay Bridge East Span Seismic Safety Project. The East Span Project is the focus of this and future issues of East Span News.
Caltrans District 4 is responsible for maintenance and operation of the seven state-owned toll bridges on San Francisco Bay. District 4 is managing environmental review, design, development, and construction of the East Span Project. The Metropolitan Transportation Commission (MTC) is responsible for allocating the toll revenue collected on the seven state-owned bridges in the Bay Area. MTC is also the region's transportation planning agency and is working closely with Caltrans to provide its input on the project at all stages of review. In addition, government agencies, elected officials and the public have been and will remain involved throughout the process.
Some have coined the East Span Project as the "bridge of a lifetime." A replacement bridge for the eastern span combined with seismic work on the western span will make the Bay Bridge last well into the 21st century. The project provides a rare opportunity to make a lasting, contemporary mark on the Bay and will be a proud continuation of the vision of those who designed the original bridge many years ago.
Few can forget the image of the collapsed section of the Bay Bridge following the Loma Prieta earthquake. Yet the east span is vulnerable to much greater damage. The 1989 earthquake was centered 60 miles from the bridge. Scientists have determined that a Maximum Credible Earthquake (MCE) occurring on faults closer to the bridge could subject the structure to forces up to 31 times greater than those of the Loma Prieta temblor.
The East Span Project and other Bay Bridge seismic upgrades will allow the bridge to withstand a Maximum Credible Earthquake (defined as a quake of magnitude 8 on the Richter scale along the San Andreas Fault, or a magnitude 7 1/4 quake along the Hayward Fault) with minimum risk of collapse.
Protecting the Lifeline
Caltrans has designated the Bay Bridge as an emergency "lifeline" route to be used in disaster response activities. Under Caltrans criteria, a lifeline transportation route
As a lifeline route, the state would use the bridge to provide a high level of post-earthquake transportation service for emergency response and support for the region's economy. It is critical that the bridge remain open and functional following an earthquake. Without seismic upgrades, the bridge could experience structural failure in a Maximum Credible Earthquake, eliminating a lifeline route at its time of greatest need.
Meeting Modern Traffic Safety Standards
While seismic safety is the primary consideration for the east span, other safety issues are also important. Built in the 1930s, the structure does not conform to current operational safety standards. The East Span Project will improve conformity with operational and safety standards to the greatest extent possible. Proposed designs for a replacement bridge will meet current standards for roadway shoulders, lane widths, stopping sight distances and other factors.
Regardless of bridge design, seismic and operational safety and protecting the lifeline route are the key factors in upgrading the east span. The project will significantly enhance public safety in the coming years and for future generations.
A Partnership Effort
The decision-making process for the East Span Project will involve many different parties. Government agencies are involved with environmental impacts or project permits; elected officials provide a major leadership role, while interest groups and the public have identified key issues. Caltrans will lead this effort and work with all interests to determine the best option for the East Span Project.
In addition to the Metropolitan Transportation Commission (MTC), the Federal Highway Administration (FHWA) and the San Francisco Bay Conservation and Development Commission (BCDC) play key roles in the project. FHWA is the lead federal agency in the environmental process. Any work within BCDC's jurisdiction requires a BCDC permit. BCDC's jurisdiction includes the San Francisco Bay. Caltrans will work closely with these agencies and consider all recommendations in its decision-making process. Caltrans is also coordinating with agencies responsible for managing the Bay's resources and who are responsible for environmental permitting, review and approvals.
Federal Highway Administration
Opportunities for Local and Public Involvement
The East Span Project's relation to local and regional planning efforts - and public concerns - is a project priority. Caltrans is forming a Project Development Team with representatives from the City of Oakland, Alameda County and the City and County of San Francisco, congestion management agencies, East Bay Regional Parks District, Department of the Navy, Department of the Army, transit providers and others. This group will meet throughout the study process to provide input to Caltrans on key project issues. In addition, there will be many opportunities for the public to comment on the project. These include informational open houses and public meetings, MTC Task Force meetings, EIS public comment period and the Caltrans East Span Project Web site at www.dot.ca.gov/dist4/sfobbrto.htm.
The Metropolitan Transportation Commission (MTC) is providing significant leadership for the East Span Project. The Commission became involved at the request of Governor Wilson and Bay Area legislative leaders to ensure that region-wide interests are appropriately addressed in the project development process. MTC provides regional transportation planning, financing and coordination of transportation activities for the nine-county Bay Area and is also responsible for administering revenue collected from the state-owned toll bridges.
To foster public involvement and consensus in the selection of the design for a possible replacement bridge, MTC formed the Bay Bridge Design Task Force in February 1997. The group's primary objective early this year was to review preliminary bridge design concepts submitted by Caltrans, as well as other considerations. The Task Force assembled an Engineering and Design Advisory Panel (EDAP) to conduct expert technical analysis of the design options and possible alignments.
In April and May, the Task Force held public scoping meetings to discuss bridge design options and other project-related issues. In addition to comments received at the meetings, the Task Force received hundreds of phone calls, letters and e-mails from the public. The key issues raised focused on technical and design concepts, bicycle/pedestrian access, the scope of environmental studies and the relationship of the project to the Transbay Transit Terminal.
In July, EDAP and the Design Task Force made 17 recommendations to the MTC Commissioners on considerations for a new bridge design. MTC presented the recommendations to the state legislature, Governor Wilson and Caltrans.
In summary, MTC recommends that two cable-supported design alternatives (a single-tower cable-stayed bridge and a single-tower, self-anchored suspension bridge) be taken to a level of 30% design completion before a final selection is made. The design teams must produce designs to a sufficient level of detail to support reliable judgments concerning cost, seismic performance and visual appearance.
Additional recommendations include the following
MTC also ranked its priorities for additional project funding authorized by the legislature (see story on page 7), with a "signature" bridge first priority, relocation/reconstruction of the Transbay Transit Terminal second, and adding bicycle/pedestrian access on the east span as the third priority. The 30% bridge designs will provide options both with and without a bike path and are expected to be completed in the spring of 1998.
During the formal environmental review process, MTC's recommendations will be considered, as well as other technical data, permitting requirements and public response.
Both the Design Task Force and EDAP will remain active and involved throughout the design process to provide review of detailed design and engineering activities and to make a final recommendation on bridge design. MTC will continue to provide opportunities for public involvement during their design review process. Further information about MTC's Bay Bridge Design Task Force - including a complete listing of its recommendations for the new bridge - can be found at MTC's web site at www.mtc.dst.ca.us.
Designing a bridge for San Francisco Bay is a complex and challenging task. The structure must meet standards for safety and traffic flow, be pleasing to the eye and integrate with its surroundings. To assist in developing a new bridge and provide a framework for future design discussions, the Bay Bridge Design Task Force's Engineering Design and Advisory Panel drafted a set of guidelines for a new east span. These guidelines will be considered in the project's design phase.
East Span Design Guidelines
Bridge Design Overview
The primary goal of the East Span Project is seismic safety. Yet designing a new span provides an opportunity to create a distinctive "signature" bridge on the Bay, one that reflects engineering and aesthetic design knowledge at the beginning of the 21st century.
A new East Span has sparked the imagination of people in the area. Early this year, many design concepts were submitted to Caltrans and MTC by engineers and architects - even school children - painting their visions for a new bridge. Many imaginative ideas were explored.
Three concepts for a replacement bridge are currently undergoing detailed review by Caltrans and MTC. Caltrans has developed a full-length skyway concept. MTC has recommended two combination skyway/ cable-supported concepts, each of which includes a skyway structure for 86% of the entire bridge length.
Caltrans will select two design teams in late 1997 to further develop the skyway/cable supported concepts. The teams will develop their concepts to a 30% level of design, which will help Caltrans and MTC in effectively assessing and selecting a final design for a replacement bridge. MTC will make a recommendation on a final design concept in the spring of 1998. Caltrans will select the preferred alternative for a bridge in the fall of 1998.
In addition to the type of replacement bridge built, three "profiles" for a new bridge are being reviewed. (See sidebar, this page). These will be evaluated for operational, visual and cost considerations. Finally, the East Span Project may include a pedestrian/bike path. The 30% replacement bridge design concepts will be developed both with and without this feature, allowing for further study.
Caltrans and MTC recognize the public's interest in the visual appearance of a new East Span. They welcome public input on the bridge design and will work to achieve consensus for the final design. Meetings will be held in the coming months to receive public feedback and to report on the design process.
A design for a new East Span must factor in several considerations. The first and most important is safety. Visual considerations include what the bridge would look like from various points around the Bay and what the views from the bridge would be.
Three design concepts are being considered for a possible new East Span structure. At least 86% of the length of any bridge design would be a skyway structure. All concepts propose to replace the double-deck configuration of the existing bridge with two parallel, five-lane (plus shoulders) roadways, one for each direction. Beyond these factors, there is opportunity for design variation within each concept.
Self-Anchored Suspension Bridge
This is one of the two cable-supported concepts recommended by MTC for further study. Both the west span of the Bay Bridge and the Golden Gate Bridge are suspension bridges, but neither are self-anchored. The defining visual element of this design is the curving suspender cable that is stretched between towers and anchored in foundations. The roadway "hangs" on vertical cables attached to the suspender cable.
Because the geologic conditions for the East Span corridor cannot adequately support cable anchor foundations, the proposed suspension design options are "self-anchoring," with the suspender cables anchored in the roadbed itself. The use of single or twin towers and various tower shapes provide additional options for this design.
Like the cable-stayed concept, the suspension portion would be high enough to allow for ship travel. After crossing the shipping channel, the bridge would connect to a skyway structure leading to Oakland.
This concept is more costly than the skyway-for-the-entire-length concept. Additional funds for this design would be required (see related article on project funding sources, page 7).
This is the other cable-supported concept recommended by MTC for further study. It is a very contemporary design that is popular for new bridge construction. Although they exist in other American cities, cable-stayed bridges are new to the Bay Area and California. The defining visual element is taut cables that fan out from a supporting tower or pylon. The appearance is similar to the strings of a harp.
There are many visual design variations for this concept. One option would include a single tower and cables between the two roadways. Another would include twin tower/cable assemblies, one for each roadway. Tower shape provides additional options. The shape of the supporting tower or towers can range from a simple mast to an "A" shape or a squared-off arch.
Under this design concept, the cable-stayed portion would be high enough to allow ships to pass under. Beyond the shipping channel, the bridge would descend in a series of shorter, skyway spans to Oakland.
This concept is more costly than the skyway-for-the-entire-length concept. Additional funds for this design would be required.
Skyway for the Entire Length
This is Caltrans' original design for the new span. MTC has not recommended this design for the replacement bridge, but it will continue to be studied in the environmental review process. The appearance is similar to other elevated roadways in the Bay Area. This design consists of two steel-reinforced, concrete roadways rising gradually from the Oakland shore to Yerba Buena Island to allow ships to pass under. The roadway sits on piers driven into the ground beneath the Bay. A preliminary skyway de sign is being developed by Caltrans and is open to revision based on public input during further design reviews.
The skyway-for-the-entire-length is the lowest cost option. Design and construction would be funded by a combination of state funds and toll bridge surcharges.
The profile of a bridge is essentially the line that the structure draws across the horizon. Some bridges maintain the same elevation, following a flat, horizontal profile. Because the East Span must rise in elevation from the Oakland shore to the tunnel at Yerba Buena Island and provide a wide elevated section to accommodate ships, a replacement bridge would have a sloping profile. The three profiles under review for a new east span are illustrated below.
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Identifying Impacts of the East Span Project
State and federal laws require a formal review of projects that may affect the environment. Seismic safety projects, including the East Span Project, are exempt from the California Environmental Quality Act (CEQA) under California law. The state legislature concluded that the critical need for public safety in seismic events superseded environmental considerations. This exemption will continue through 2005. Caltrans is preparing an Environmental Impact Statement (EIS) for the East Span Project to comply with the National Environmental Policy Act (NEPA). The results of this detailed review will guide officials in determining the best way to carry out the project.
Caltrans began the environmental review for the East Span Project by filing a Notice of Intent to prepare an EIS in the Federal Register on April 21, 1997. A scoping process is used to gather public input and help develop project alternatives to be studied in the EIS. Scoping meetings were held jointly by the Bay Bridge Design Task Force and Caltrans during the spring and were attended by members of various interest groups and the general public.
Under NEPA, two meetings have been held with resource agencies to review purpose and need for the project and discuss the range of alternatives. Caltrans will continue to work closely with these agencies as part of the environmental permitting, review and approval process. Caltrans is also available to meet with other interested parties as requested throughout the environmental review process.
East Span Project Alternatives
Based on preliminary studies, scoping and recommendations from MTC, Caltrans will study six alternatives for implementing the East Span Project: no-build, retrofitting the existing span, and four alignments for a new span.
No-build is a standard EIS alternative. It studies the impacts of taking no action on the project and serves as a point of comparison for the impacts of the other alternatives. The Retrofit Alternative would seismically strengthen the bridge to withstand a Maximum Credible Earthquake (MCE). It would not, however, fully meet Caltrans lifeline standards, nor would it meet current design and operational standards or increase the useful life of the bridge to the extent of the replacement alternatives. Study of the retrofit alternative completes the full range of alternatives for meeting the seismic safety purpose of the project, as required by the National Environmental Policy Act. Finally, two of the Replacement Alternatives for a new span are north of the existing bridge, and two are south.
Alternatives for the East Span Project - EIS
N1 - Far North Replacement Alternative
The EIS for the East Span Project will study six project alternatives for their potential impact on the following issue areas:
Like other seismic upgrades on state toll bridges, the East Span Project will be funded by a combination of state taxes, bond revenues, and monies collected through a $1 bridge toll surcharge on all state-owned toll bridges in the Bay Area.
State taxpayers will fund 64% of the cost of a basic, full-length skyway bridge design. These funds will come from state fuel tax revenues earmarked for seismic upgrade projects and seismic retrofit bonds issued by the state after voter approval of Proposition 192 in March 1996.
Bay Area toll bridge users will fund 36% of the basic bridge costs through a $1 bridge toll surcharge signed into law by Governor Wilson this summer under Senate Bill 226 and Senate Bill 60. The surcharge on the San Mateo-Hayward, Benicia-Martinez, Richmond-San Rafael, Carquinez, Antioch, Dumbarton and Bay bridges will take effect January 1, 1998. The $1 toll increase will remain in effect for eight years until the Bay Area share of funds for seismic upgrades to local toll bridges has been collected.
Any additional options to a basic bridge project will be fully funded by Bay Area bridge tolls. MTC is allowed to extend the toll surcharge for up to two additional years to fund these or other bridge amenities. These include a cable-supported or other "signature" bridge design, the Transbay Transit Terminal, and the addition of bicycle/pedestrian access on the new span.
Bounded by 5th Street and the San Francisco cable anchorage structure. Reconstructs the main line of Interstate 80 and on- and off-ramps in San Francisco, including modifications to the ramps at the Transbay Transit Terminal. Work expected to begin Fall 1999.
Encompasses suspension bridge between the San Francisco and Yerba Buena Island anchorage structures. Strengthens various support structures including the anchorages, towers, and piers. Work expected to begin Spring 1998.
Connects the west span suspension bridge to the Yerba Buena Island tunnel. Strengthens various support structures. Work expected to begin Spring 1998.
Yerba Buena Island Tunnel
Specific actions have not been finalized. Work expected to begin Summer 1999.
East Span Interim Retrofit
Encompasses the full east span bridge from Yerba Buena Island to Oakland, including the viaduct connecting the bridge to the tunnel. The east span interim retrofit will strengthen the bridge to withstand a likely earthquake, but not a Maximum Credible Earthquake. The interim retrofit will provide increased safety until final seismic upgrade actions for the east span are completed. Construction expected to begin Winter or Spring 1998.
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