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Caltrans Owns Land on Yerba Buena Island
Caltrans and the Federal Highway Administration have achieved a major milestone towards seismic safety by securing the right-of-way for the East Span Project. In October 2000 the Federal Highway Administration granted 20 acres of land on Yerba Buena Island to Caltrans for permanent right-of-way. Another 78 acres were granted to Caltrans for temporary access to land and water during the construction of the East Span. The transfer of the land previously held by the U.S. Navy was authorized under a federal law that gives precedence for the use of federal land for the U.S. Interstate Highway System. The permanent right-of-way and temporary construction easements are alternative-neutral.
There will be no physical changes to the land until the environmental compliance process is complete for the East Span Project. Any right-of-way not required for the East Span Project will revert to the U.S. Navy after the project is complete.
The transfer of real property from the U.S. Navy to another federal agency is categorically excluded from further documentation requirements under the National Environmental Policy Act. The deed for conveyance of property to the state was recorded on October 26, 2000 with the City and County of San Francisco recorders office.
Independent Studies Confirm Caltrans Should Proceed With Plans For East Span Project on Northern Alignment
In December 1998, after studying a range of alternatives in accordance with the National Environmental Policy Act, Caltrans identified a Preferred Alternative for the East Span of the San Francisco-Oakland Bay Bridge. The Preferred Alternative would construct a new bridge (two side-by-side bridge decks, both with five lanes and inside and outside shoulders) north of the existing bridge, which would be dismantled.
For the past several years Caltrans has been progressing with "risk design," which means design work is being conducted for the Preferred Alternative although it has not received final environmental approval. The risk is that the Preferred Alternative may not receive final environmental approval. Because of the public safety considerations of any seismic safety project, Caltrans believes that moving forward with risk design is prudent and would result in significant time savings in providing for public safety. If the Preferred Alternative is approved, it would save significant time to have the design complete upon approval.
While Caltrans has advanced the risk design, the project has been subject to several independent studies conducted by the U.S. Army Corps of Engineers (Corps). The Corps studies offered suggestions and requested responses from Caltrans on technical issues and concluded that Caltrans should proceed with its risk design for the East Span. The Corps reviews focused on three major issues, which are summarized below.
Should the alignment of a replacement bridge be located to the north or south of the existing bridge?
On January 6, 2000, the Corps released its findings on the alignments. Specifically the Corps examined a modified alignment south of the existing bridge that would cross an 8 diameter sewer line in the Bay. The sewer line was built in 1950 and is maintained by the East Bay Municipal Utility District.
In its review, the Corps examined several issues including costs, impacts to the project schedule, and construction complexities of building near the sewer line.
The Corps report concluded that building the new East Span over the sewer line would delay the schedule by a minimum of 8 to 15 months, increase construction risks, and increase project costs by tens of millions of dollars. The Corps study reaffirmed Caltrans decision to study the northern alignment as the Preferred Alternative.
Should the East Span of the bridge be retrofitted or replaced?
In response to the 1989 Loma Prieta earthquake, Caltrans began a program to seismically retrofit the damaged East Span of the San Francisco-Oakland Bay Bridge. As the plan to retrofit the East Span progressed, it became apparent to Caltrans that it would be more cost effective to replace the structure rather than to retrofit it.
The Corps was asked by the National Economic Council, an office in the Executive Branch of the Federal Government to independently review this decision by Caltrans. The Corps report, issued October 27, 2000, stated that "Based on safety considerations, it is the Corps teams opinion that, at this point in time, a replacement alternative is preferable to a retrofit alternative. A replacement alternative is the path that most quickly resolves the exposure of the public to the seismic vulnerabilities of the existing structure."
Is the design of the proposed new self-anchored suspension bridge seismically safe?
In the October 2000 report the Corps concluded that "Caltrans design team is highly qualified, using state-of-the-art design methods and is moving along a path to design a bridge that meets the seismic performance criteria." [See Seismic Safety Evaluations]
Now that these independent studies are complete, Caltrans is moving forward with completion of the environmental review process. [See environmental article, page 5].
Pile Installation Demonstration Project Completed
The Pile Installation Demonstration Project (PIDP) conducted from October 19, 2000 to December 13, 2000 is expected to provide information on construction techniques for the East Span Project. The piles used for the demonstration project are the same type that have been developed for the risk design's main span and skyway structure foundations. Similar foundations would be developed for the other build alternatives. The large, deeply driven piles repres ent innovative technology that will be used to construct the East Span. The support from the large steel piles is a critical seismic safety feature for the East Span.
Caltrans conducted the PIDP to test the procedures and effects of driving large steel piles through relatively soft soils into the dense sands of the Alameda Formation that exists below the Bays waters.
Caltrans installed massive battered piles (piles installed at an angle) through the Bay's waters. The piles measured 2.5 meters in diameter (8 feet) and 107 meters in length (350 feet). The pile size is unique, as is the method used to drive the piles into the soil. Two of the three piles were installed at an angle of one horizontal length to six vertical lengths or 9.5 degrees from vertical.
The test consisted of driving three piles at two sites near the existing East Span alignment. The test sites were located in open water and fell within the Caltrans maintenance area that extends both north and south from the centerline of the existing bridge. Caltrans identified the test sites based on soil conditions and their location within the East Span Project area. Caltrans also considered additional criteria including adequate water depth and minimal potential conflict with other marine vessels or future bridge construction operations.
The PIDP was conducted to determine the minimum hammer energy required to drive piles and to allow engineers to study the pile behavior during driving. The demonstration also allowed engineers to observe the process of welding large pile segments together at the open water sites. This information will allow project engineers to define appropriate construction procedures and equipment requirements for construction of the East Span.
Caltrans monitored and recorded aerial and underwater sound levels during the demonstration to identify possible effects on species such as harbor seals that have a rest area on Yerba Buena Island. Air bubble curtains were used for sound attenuation during pile driving. Caltrans and the National Marine Fisheries Service will use the data to establish mitigation measures that will help minimize potential impacts to marine mammals and to fish during construction of the East Span Project. The results of the PIDP are expected to reduce costs, reduce delays, and aid potential contractors in preparing accurate bids for the skyway and main span portion of the East Span Project.
Maritime Archaeology Research Complete
For thousands of years, Native American tule boats made their way back and forth across the San Francisco Bay. In 1775, the first non-native vessel, a Spanish ship of exploration, entered the Bay but for the next 75 years, only occasionally did a European clipper or whaling ship sail into Bay waters. Then, the Gold Rush of 1849 changed ship traffic in the area forever. Hundreds of vessels crisscrossed the Bay and sailed up the Sacramento River, ferrying people and supplies to and from the gold fields. The volume of shipping continued to grow from the mid-1800s through the early 1900s, as steamers, barges, and scow schooners carried freight and passengers to and from various ports around the Bay and into the Sacramento Delta. A few of these ships never made it to their destinations due to collisions or accidents often caused by fog or storms. Today, the remains of these unfortunate vessels rest at the bottom of the Bay.
In an effort to preserve and learn more about our history, the National Historic Preservation Act requires that historic and cultural resources located within a project area be identified and, if necessary, measures taken to reduce adverse effects from the project on these resources. Since a large portion of the project area is under water, the cold depths of the Bay had to be searched for potential historic resources. Caltrans maritime archaeologists investigated whether any shipwrecks might lie within the East Span Project area, and if so, whether they might be eligible for listing on the National Register of Historic Places (NRHP).
The archaeologists began by conducting archival research to identify potential shipwrecks in the area. This included examining early local newspapers and historic photo collections, ship records from the War and Commerce Departments at the National Archives, National Oceanographic and Atmospheric Administration sea floor maps, and other records at the Library of Congress, National Maritime Museum, and local libraries. The research was done to identify potential shipwrecks and their possible locations within the two-square mile project area. Several shipwrecks were identified near Yerba Buena Island one of them just west of Treasure Island. Following the archival work, the team shifted to on-site research using a combination of robotic cameras, human divers, and computer equipment to conduct an underwater exploration.
A remotely-operated camera intended to provide underwater video images could not function efficiently in the dark Bay waters. Instead, a powerful, side-scan sonar system provided high-resolution data of the Bay floor. Archaeologists then interpreted the sonar returns for images or "targets" that could indicate a cultural resource - such as the remains of a shipwreck. "Its a combination of skill and art to discern a ships remains from the computer print-outs," explains Janet Pape, Caltrans Archaeological Manager for the project.
Scuba divers went below the surface to get a clearer assessment of targets that could not be adequately defined by sonar. The Bays strong tidal currents and near-zero visibility water presented difficult and dangerous conditions for the divers. During dives, a buoy line was placed as close to the target location as possible and heavily weighted to overcome the currents. The diver was then tethered to a person acting as "dive tender" on board the support vessel. Two-way, diver-surface communication was conducted by both voice and tether signals. Guided to a target by voice instructions from the tender, the diver would carefully feel along the Bay floor, locating and examining a submerged item for indications of function and age. The age of an object was often judged by examining the fasteners that pinned the elements of the object together. For example, a determination of age can be deduced by examining how a ships hull is joined together. Galvanized steel bolts and wire nails are largely artifacts of the 20th century, while iron, brass, and bronze driftbolts, nails, and tacks are items from an earlier period.
After several weeks of research and a dozen dives, no significant historical resources were found in the project area and the maritime archaeologists concluded their operations. Although no historically significant resources were located, the Bay floor is far from empty, according to Pape. "We found plenty of cultural debris out there," she explains, "such as remains from the Key System Ferry Terminal." The Key System Ferry was the main transportation method between San Francisco and the East Bay before the Bay Bridge was built. "The remains we found from the Terminal include metal, railroad tracks, cable, and wood pilings, but since the remains lack historic integrity, they are not eligible for the National Register," Pape says. Eligibility for the National Register requires that a resource meet certain criteria such as possessing integrity of location, design, and workmanship.
As a result of the underwater exploration, Caltrans archaeologists have been able to confirm that constructing the East Span Project will not affect any significant historic resources at the bottom of the Bay. The exploration has generally contributed to knowledge about where historic resources in the Bay might be, and reminded us that precious remnants of our historic and cultural past could be lying just beyond our sight.
Seismic Safety Evaluations for the East Span
Earthquakes are commonly reported in terms of their magnitude. The larger the magnitude, the bigger the earthquake, and the greater the potential for damage. When engineers design structures to resist earthquakes, they use "rock motions" the vibrations that travel through the bedrock caused by the slipping of an earthquake fault.
Seismologists develop the rock motions based on the structures location in relation to the location of earthquake faults and historical and geotechnical project site data. Engineers use these rock motions to calculate the maximum seismic forces that the structure will experience and then design the structure to resist the forces.
Rock motions are at the bedrock level. They propagate up through the soil layers to the ground surface, where they become "ground motions" rock motions cause ground motions. Ground motions are not the same as rock motions. Ground motions caused by the same rock motions will vary due to the soil conditions. The rock motions can be uniform along a project site, but for a long bridge like the Bay Bridge, the ground motions change along the length of the bridge as the soil changes.
For example, during the Loma Prieta earthquake, the ground motions varied at different locations, and this was reflected in the differing amounts of damage. Rock motions were amplified by the soft Bay muds and the resulting ground motions caused substantial damage in particular areas (such as the I-880/Cypress Freeway and San Franciscos Marina District). Where the soil was more stable, the rock motions were not amplified as much, the ground motions were not as great, and there was little damage. Seismologists and geotechnical engineers use the rock motions and then translate them (by computer) into ground motions. However, rock motions are the basis of engineering calculations.
There are two methods of estimating the greatest rock motion that a particular structure will experience. In the past, Caltrans considered the motions from the Maximum Credible Earthquake, or MCE. The MCE is the largest reasonable earthquake at a fault without regard or consideration of how often the earthquake might occur (the return period). It also does not provide a consistent or rational assessment of the probability that a structure will experience the design earthquake. For the East Span Project, Caltrans estimated the greatest rock motions from the Safety Evaluation Earthquake, or SEE. This is defined as an earthquake that generates the largest motions expected to occur at the bridge site once every 1,500 years (a 1,500-year return period). The bridges expected life span is 150 years, so there is approximately a 10% chance that this earthquake would happen during its life span. Caltrans was aided in the development of the ground motions by the Ad Hoc Committee on Seismic Ground Motions. This ad hoc committee is comprised of four members:
The Seismic Safety Peer Review Panel and the Metropolitan Transportation Commissions Engineering and Design Advisory Panel both accepted and agreed that the bridge should be designed for these SEE ground motions.
The Ad Hoc Committee on Seismic Ground Motions evaluated the recently issued report by the Army Corps of Engineers (Corps) on retrofit versus replacement of the East Span. In particular, the Committee focused on one of the Corps conclusions: "The performance of the replacement bridge during a Maximum Credible Earthquake cannot be determined. The bridge has not been evaluated or designed for a MCE event, which is larger than the SEE event." The Committee pointed out that this conclusion is based on an error in plotting a graph included in the Corps report. In fact, the MCE motions fall well below the SEE motions in all relevant data ranges, particularly during the initial shaking. In addition, the Ad Hoc Committees evaluation of the Corps report explained that responses of structures (estimated for earthquakes of various magnitudes and for various source-to-site distances) depend crucially on the measurement of ground motions in actual large earthquakes. As additional recordings become available from such earthquakes, these new ground motion recordings are incorporated into the existing international database. Professor Bolt has stated that the SEE standard takes into account a wider range of possible ground motions, some of which are much higher in impact than MCEs predicted motions. The Ad Hoc Committee concluded that Caltrans studied both standards (MCE and SEE) and designed the bridge to the higher SEE standard.
Environmental Process Moving Towards Completion
The environmental process for the East Span Project continues to move forward. In accordance with the National Environmental Policy Act (NEPA), Caltrans has been conducting a comprehensive analysis of the projects potential environmental, social, and economic impacts. Since publishing the Draft Environmental Impact Statement (DEIS) in September 1998 and identifying the Preferred Alternative for the new span, Caltrans has progressed in its preparation of the Final Environmental Impact Statement (FEIS).
The FEIS will include all public comments made on the DEIS and Caltrans responses to them. During the DEIS public comment period, Caltrans received approximately 400 specific comments through letters, e-mail, and verbal comments from the projects four public hearings.
In addition to responses to comments, other environmental tasks are being completed, either for inclusion in the FEIS or to meet the requirements of state or federal agencies. Caltrans has made significant progress in the following areas:
The Dredged Material Management Plan has been published and distributed. This report was prepared in response to the U.S. Environmental Protection Agency and documents methods to dispose of materials dredged from the Bay for project construction. As part of the Dredged Material Management Plan, Caltrans has tested for potential contamination of dredged materials and found very little contamination. However, if any contaminated sediments are encountered during dredging, efforts would be made to minimize impacts. Caltrans hopes to beneficially reuse most of the dredged materials depending on cost factors and availability of reuse sites. The plan evaluates a number of local reuse/disposal options, recommends a combined reuse/disposal option, and lists other viable options. The volume of dredged materials for construction of a replacement bridge and dismantling of the existing bridge is anticipated to be a maximum of 540,000 cubic yards. The plan was distributed to federal, state, regional, and local agencies, and to interested organizations and individuals. Comments received on this plan are addressed in the FEIS.
The Supplemental Draft Section 4(f) Evaluation has been published and distributed. This document complies with the Department of Transportation Act of 1996 and evaluates the projects potential impacts on publicly owned parks and land from historic sites.
Caltrans submitted a Biological Assessment for the project to the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service. Required by the federal Endangered Species Act, this document identifies and evaluates potential impacts to species listed as threatened or endangered under the act.
Caltrans consulted with the NMFS regarding potential impacts to fish species. NMFS concluded this process by issuing a Biological Opinion in September 1999. NMFS determined that the measures Caltrans will implement during construction would avoid or minimize any impacts to endangered fish species. These measures will include the use of sound attenuation devices while pile driving during the peak migration period of juvenile salmon.
Consultation with U.S. Fish and Wildlife Service regarding the Peregrine Falcons nesting on the existing East Span was initiated, but further action by the agency is not required due to the falcons removal from the federal endangered species list in 1999. However, Caltrans will ensure protection of the falcon under the Migratory Bird Treaty Act and under the California Endangered Species Act.
Caltrans is identifying permanent and temporary construction period impacts to special aquatic sites, which include eelgrass beds, sand flats, and tidal and non-tidal wetlands. A conceptual mitigation plan has been prepared and identifies measures to avoid and minimize impacts to special aquatic sites and to offset unavoidable impacts. The conceptual mitigation plan includes on-site restoration of portions of the affected eelgrass beds and sand flats, and off-site creation of a tidal marsh ecosystem. Caltrans has worked closely with state and federal resource agencies to develop the conceptual mitigation plan and to solicit their concurrence.
Mitigation measures to reduce effects to historic properties have been developed and are included in a Memorandum of Agreement which has been signed by the Federal Highway Administration, the U.S. Coast Guard, the Federal Advisory Council on Historic Preservation, the State Office of Historic Preservation, and Caltrans.
Concurring parties including the U.S. Navy, the cities of Oakland and San Francisco, and Ohlone Indians were invited to sign the Memorandum of Agreement. Several Ohlone Indians have signed the agreement.
The properties addressed in the Memorandum of Agreement include such historic resources as the Nimitz House on Yerba Buena Island and the Bay Bridge itself.
Impacts to the Senior Officers Quarters Historic District are limited to construction period activities. Any vegetation removed as a result of construction will be replaced and the area will be returned to its pre-construction condition to the extent feasible. No historic buildings will be removed or demolished. Additionally, none of the bridge structures that are proposed under any of the alternatives will be built above the buildings of the Officers Quarters Historic District.
Caltrans is also consulting with the East Bay Regional Park District and other appropriate parties about incorporating interpretive exhibits about bridge history into the Districts proposed Oakland gateway park. These exhibits could display the Bay Bridge as originally constructed and include information about its history. Caltrans will also consult with the City and County of San Francisco regarding its interest in having similar interpretive exhibits installed on Yerba Buena Island.
Caltrans will consult with the Oakland Museum of California, the Academy of Sciences in San Francisco, and other Bay Area museums to determine interest in presenting an exhibit about the history and engineering of San Francisco Bay bridges. The exhibit could include elements such as salvaged bridge components, photographs, models, and oral histories.
The FEIS is targeted to be completed in winter 2001. The FEIS will be circulated for public review for 30 days. The Notice of Availability will be published in the Federal Register and the FEIS will be posted on Caltrans Website at www.dot.ca.gov/dist4.
The Metropolitan Transportation Commission (MTC) continues to provide key input to the East Span Project to ensure that region-wide interests are appropriately addressed.
MTCs Bay Bridge Design Task Force recommended modifying the design of the pedestrian/bicycle path to include several belvederes or rest stops along its length. The belvederes will provide space for pedestrian and cyclists to rest at various points along the span and enjoy sweeping views of the Bay and hills.
Additionally, the Task Force recommended using earth fill rather than structural elements at the Oakland touchdown. Earth fill will provide better seismic safety performance and will be easier to repair after a seismic event. This approach also eliminates some pilings, enhancing the appearance of the touchdown structure.
The Task Force has also supported Caltrans proposal to install motion detectors on the East Span. The detectors will measure the bridges response to future earthquakes and are a feature being added to many structures. The data provided by the detectors is necessary to confirm acceptable performance of the structures seismic safety features and will be useful in assessing the features value when designing future structures.
Other elements still desired by the Bay Bridge Design Task Force include specific lighting components for the bridge and concrete pigmentation. MTC continues to support a consistent color treatment for both the steel and concrete elements of the new bridge. It was determined that white pigment for the concrete is no longer an option. At MTCs Engineering and Design Advisory Panel meeting on December 7, 2000, the following suggestions were made: (a) the concrete on the exterior side girders of the viaduct should be as light and as consistent in color as possible; (b) the steel portions of the bridge should be painted to match the color of the concrete on the viaduct side girders.
The Engineering and Design Advisory Panel and MTC continue to support inclusion of the "light pipe" in the East Span design. The light pipe is not an eligible amenity for which MTC can extend the seismic retrofit toll surcharge. MTC will seek funding for this design enhancement in the context of the expected legislative deliberations in 2001 on providing additional funding for the overall toll bridge seismic retrofit program.
Pending specific recommendations and funding for these elements, Caltrans is continuing the detailed bridge design process using "baseline" design features, which are focused on safety and economy.
Upon completion of the public review period for the FEIS, the Federal Highway Administration can file a Record of Decision (ROD). The ROD will certify the findings and close the NEPA environmental process. Construction of the East Span Project is targeted to begin mid-2001.
If you have comments or questions about the East Span Seismic Safety Project, mail them to:
Public Information Office
Caltrans District 4
PO Box 23660
Oakland, CA 94623-0660
or send your