CHAPTER 2

This chapter describes the alternatives that were analyzed in the Draft Environmental Impact Statement (DEIS), project alternatives that were initially considered but withdrawn from consideration prior to preparation of the DEIS, the reasons for their withdrawal, and identification of the Preferred Alternative.

The Metropolitan Transportation Commission (MTC) is the transportation planning, coordinating, and financing agency for the nine-county San Francisco Bay Area. It functions both as the region’s transportation planning agency (RTPA) and as the region’s metropolitan planning organization (MPO)—state and federal designations, respectively. The Regional Transportation Plan (RTP), which MTC prepares, is a comprehensive guide for the development of mass transit, highway, airport, seaport, railroad, bicycle, and pedestrian facilities within the Bay Area. The MTC also allocates state and federal funds for transportation projects based on compatibility with this plan.

The MTC-recommended alternative included in this FEIS is Replacement Alternative N-6, self-anchored suspension design variation with a bicycle/pedestrian path. The California Department of Transportation (Caltrans) and Federal Highway Administration (FHWA) identified Replacement Alternative N-6 as the Preferred Alternative. The Preferred Alternative has been identified as the Least Environmentally Damaging Practicable Alternative (LEDPA) in consultation with the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (ACOE). See Section 2.2.6 ­ Preferred and Least Environmentally Damaging Practicable Alternative for more details.

Pursuant to the National Environmental Policy Act (NEPA), the EIS identifies environmental impacts and values of all reasonable alternatives in sufficient detail to enable decision-makers to evaluate their comparative merits. The East Span Project is a seismic safety project and does not change bridge capacity. As such, a Major Investment Study (MIS) for the SFOBB corridor was not prepared. Identification of the Preferred Alternative occurred following circulation of the DEIS for a 60-day public review period and consideration of all public comments received. Responses to all substantive comments have been prepared and can be found in Volume II, Section I ­ DEIS Comments and Responses.

The No-Build Alternative does not satisfy the project purpose and need. It is presented and evaluated as a basis of comparison with the reasonable alternatives. As noted in Chapter 1, Caltrans added selected minimal seismic strengthening and stiffening elements to the existing East Span structure as an interim measure. That project, completed in summer 2000, received environmental approval pursuant to NEPA and is not evaluated as an alternative in this Final EIS. The No-Build Alternative assumes completion of this interim work.

2.1 INTRODUCTION

2.1.1 Development of Alternatives

Caltrans has performed preliminary engineering and impact analysis on a range of possible project alternatives in the EIS. The retrofit and replacement alternatives, along with the No-Build Alternative, are described in Section 2.2. Replacement bridge design variations considered in the DEIS are described in Section 2.3, including design variations incorporated into the Preferred Alternative. Section 2.4 provides a comparison of the alternatives, including costs, constructibility, and potential to meet the purpose and need. Section 2.5 discusses multi-modal options for alternatives, and Section 2.6 describes construction scenarios for each of the build alternatives. Section 2.7 describes the alternatives, design variations, and detour options that were considered and subsequently withdrawn from further consideration and the reasons for their withdrawal.

The range of alternatives considered in the EIS was established by Caltrans and FHWA in accordance with NEPA requirements and in consultation with permitting and regulatory agencies under guidance of the NEPA/404 Integration Memorandum of Understanding (NEPA/404 MOU). The NEPA/404 integration process is implemented when a project has the potential to affect waters of the U.S. under the jurisdictional authority of the U.S. Army Corps of Engineers (ACOE), and it is anticipated that an individual Section 404 permit will be required. Participants considered options and provided written concurrence on the range of alternatives and the criteria established for selection of alternatives. The following criteria were agreed upon by the NEPA/404 signatories:

• Meets Caltrans criteria for designation as a lifeline route;
• Meets current standards for operations and safety to the greatest extent possible;
• Maintains the existing number of traffic lanes during peak hours and after construction;
• Does not preclude a bicycle/pedestrian path;
• Does not preclude future improvements to YBI access ramps;
• Minimizes impacts to environmental resources;
• Provides a high level of visual quality; and
• Is a cost-effective solution.

Consistent with the NEPA/404 MOU, NEPA/404 integration process signatories (ACOE and EPA) also concurred on the identification of the Least Environmentally Damaging Practicable Alternative (LEDPA). (See Appendix F for the concurrence letters from the NEPA/404 signatories.)

2.1.2 Project Limits/Location

The SFOBB crosses San Francisco Bay in an east-west direction in the central portion of the San Francisco Bay Area and provides a travel route between San Francisco and Alameda counties (see Figure 2-1 in Appendix A). The bridge touches down near Pier 26 in San Francisco and in northwest Oakland between the East Bay Municipal Utility District (EBMUD) wastewater treatment facility and the Emeryville Crescent. The West and East Spans of the bridge are connected on YBI by viaduct sections on either side of the YBI tunnel. A main navigation opening channel is located between Columns E2 and E3 of the SFOBB East Span. The channel, shown on Figure 2-2 (Appendix A), is 405 meters (1,328 feet) wide, with vertical clearance of 60 meters (197 feet) above Mean Sea Level (MSL).

The East Span Project will retrofit and/or replace the portion of the SFOBB between the eastern portal of the YBI tunnel and the SFOBB Toll Plaza in Oakland. The western project limit is the eastern portal of the YBI tunnel; however, project-related traffic controls may extend to the western portal of the YBI tunnel and project signage may extend to the west approach in San Francisco. The eastern project limit is located approximately 400 meters (1,312 feet) west of the toll plaza on a spit of land referred to as the Oakland Touchdown area. The project area limits are shown on Figure 2-2 (Appendix A). The project area is defined as the area within the project limits in which temporary and permanent structures would be placed by any of the alternatives and defines the area within which construction activities, including temporary detours, would be expected to occur. The project area widens over water to allow for marine construction activities. In addition, Bay waters on the north side of YBI are included within the project area to allow staging for the delivery of bulk materials and construction equipment by barge or vessel to staging areas on YBI.

2.2 ALTERNATIVES CONSIDERED

Five alternatives, No-Build, Retrofit Existing Structure, Replacement Alternatives N-2, N-6, and S-4, were considered for the East Span Project. Replacement Alternatives N-2 and N-6 are aligned to the north of the existing bridge and Replacement Alternative S-4 aligns south of the existing bridge (see Figure 2-3 in Appendix A). Alignment drawings for the build alternatives are presented in Appendix A (see Figure Series 2-4, 2-7, 2-10, and 2-11). In order to reroute traffic around the construction area while portions of the existing East Span are dismantled and a new transition structure is completed where the existing bridge now stands on YBI, temporary detours would be required on YBI for the three replacement alternatives (N-2, N-6, and S-4).

Caltrans completed a separate Pile Installation Demonstration Project (PIDP) in December 2000 to provide empirical data to contractors and resource agencies about pile driving in the Central Bay. Three test piles were installed as part of the PIDP. The three installed piles would not be used as structural components of any build alternative, though they would be left in place during construction of the East Span Project and could be used for barge mooring. Prior to completion of the East Span Project, all build alternatives would include removal of these three test piles to an elevation of at least 0.46 meter (1.5 feet) below the mudline, to be measured at the time of removal.

In order to connect the new bridge with the existing retrofitted viaduct on YBI and the SFOBB Toll Plaza at the Oakland Touchdown area, all three replacement alternatives would require dismantling the existing East Span structure. Dismantling would also be required by USCG regulations. A description of the dismantling process is provided in Section 2.6.3.

2.2.1 No-Build Alternative

The No-Build Alternative would retain the existing SFOBB East Span and only assumes the seismic improvements that were completed under the Interim Retrofit Project. The Interim Retrofit Project strengthened bents and columns on the viaduct section on YBI and strengthened or stiffened columns, bents, and trusses at selected locations on the structure, so that the existing East Span would be able to withstand a smaller and more probable earthquake. This work was completed during summer 2000. The No-Build Alternative is evaluated primarily as a basis for comparison with the build alternatives.

2.2.2 Replacement Alternative N-6 (Preferred Alternative)

Replacement Alternative N-6 would construct a 3,514-meter long (11,526-foot long) new bridge north of the existing East Span and dismantle the existing structure. (See Figures 2-10.1a through 2-10.5b in Appendix A).

The western limit of construction for Replacement Alternative N-6 is the eastern portal of the YBI tunnel; however, the limits of work may extend to the western approach of the West Span in San Francisco due to project-related traffic controls and signage. Part of the existing YBI East Viaduct would be retrofitted, modified, partially demolished, and reconstructed. At Bent 48 (see Figures 2-10.1a through 2-10.1c in Appendix A), the new bridge begins with transition structures separating the double-decked lanes into two parallel structures. Outrigger supports would be used to support the upper deck as the lower deck transitions to a structure parallel with the upper deck. The parallel structures curve, enter a tangent or straight section over the existing main navigation opening, curve, then align on tangent toward the Oakland Touchdown area. The parallel structures reach the Oakland shore along the northern edge of the existing Oakland Touchdown area and conform to the existing traffic lanes west of the SFOBB Toll Plaza.

Replacement Alternative N-6 consists of two parallel structures supported by 25 piers over water and 19 bents, set on YBI, and the Oakland Touchdown area. The structures would each be 25.07 meters (82 feet) wide and typically separated by 15 meters (50 feet). The typical roadway section for each bridge deck consists of five lanes, each 3.6 meters (12 feet) wide, left and right shoulders, each 3 meters (10 feet) wide, and traffic barriers (see Figure 2-8 in Appendix A). A 4.7-meter (15.5-foot) bicycle/pedestrian path would be located on the south side of the eastbound deck, 0.3 meter (1 foot) above the roadway elevation and includes viewing areas or belvederes. The five belvederes on the skyway would be 12 meters (39 feet) long by 1.2 meters (4 feet) deep. Caltrans is still investigating whether to include one or two belvederes on the main span that would be 20 meters (66 feet) long by 1.2 meters (4 feet) deep. A simulation of a belvedere design is shown on Figure 2-24 in Appendix A.

The height of the bridge, including the transition structure and the parallel structures, would vary in elevation from 50-55 meters (164-180 feet) above Mean Sea Level (MSL) at the YBI East Viaduct to 5 meters (16 feet) above MSL at the Oakland Touchdown. A typical profile for replacement alternatives is presented in Figure 2-9 in Appendix A.

2.2.3 Replacement Alternative N-2

Replacement Alternative N-2 would construct a new 3,479-meter long (11,411-foot long) new bridge north of the existing East Span and dismantle the existing structure. (See Figures 2-7.1a through 2-7.5 in Appendix A). The alignment parallels the existing bridge and maintains minimal clearance between the old and new structures to accommodate construction of the new bridge and dismantling of the existing structure.

The western limit of construction for Replacement Alternative N-2 is the eastern portal of the YBI tunnel; however, the limits of work may extend to the western approach of the West Span in San Francisco due to project-related traffic controls and signage. The existing YBI East Viaduct would be retrofitted, modified, partially demolished, and reconstructed. At Bent 48 (sees Figure 2-7.1a and 2-7.1b in Appendix A), the new bridge would begin with new transition structures separating the double-decked lanes to two parallel structures. Outrigger supports would be used to support the upper deck as the new lower deck transitions to a structure parallel with the new upper deck. The parallel structures would curve, enter a tangent (or straight section) over the existing main navigation opening, curve, and align on tangent toward the Oakland Touchdown area. The parallel structures would reach the Oakland shore along the northern edge of the existing Oakland Touchdown area and conform to the existing traffic lanes to the west of the SFOBB Toll Plaza.

Replacement Alternative N-2 would consist of two parallel structures supported by 22 piers over water and 19 bents set on YBI and the Oakland Touchdown area. The structures would each be 25 meters (82 feet) wide and separated by 15 meters (50 feet). The typical roadway section for each bridge deck would consist of five lanes, each 3.6 meters (12 feet) wide, left and right shoulders, each 3 meters (10 feet) wide, and traffic barriers. A 4.7-meter (15.5-foot) bicycle/pedestrian path would be located on the south side of the eastbound deck, 0.3 meter (1 foot) above the roadway elevation and includes viewing areas or belvederes. The five belvederes on the skyway would be 12 meters (39 feet) long by 1.2 meters (4 feet) deep. Caltrans is still investigating whether to include one or two belvederes on the main span that would be 20 meters (66 feet) long by 1.2 meters (4 feet) deep. A simulation of a belvedere design is shown on Figure 2-24 in Appendix A.

The height of the bridge, including the transition structure and the parallel structures, would vary in elevation from 50 to 55 meters (164 to 180 feet) above MSL at the East Viaduct on YBI to 5 meters (16 feet) above MSL at the Oakland Touchdown. A typical profile for replacement alternatives is presented in Figure 2-9 in Appendix A.

2.2.4 Replacement Alternative S-4

Replacement Alternative S-4 would construct a 3,550-meter (11,644-foot) long bridge south of the existing East Span and dismantle the existing structure. (See Figures 2-11.1a through 2-11.5 in Appendix A.) Replacement Alternative S-4 was developed to minimize bridge length, avoid use of flat land to the north of the existing East Span on YBI and avoid an in-Bay crossing with the EBMUD sewer outfall located to the south of the existing East Span (see Figure 2-3 in Appendix A).

The western limit of construction for Replacement Alternative S-4 is the eastern portal of the YBI tunnel; however, the limits of work may extend to the western approach of the West Span in San Francisco due to project-related traffic controls and signage. The existing YBI East Viaduct would be retrofitted, modified, partially demolished, and reconstructed. At Bent 48 (see Figures 2-11.1a and 2-11.1b in Appendix A), the new structure would begin with new transition structures separating the double-decked lanes to two parallel structures. Outrigger supports would be used to support the upper deck as the lower deck transitions to a structure parallel with the upper deck. The parallel structures would curve, enter a tangent or straight section over the existing main navigation opening, curve gradually, and align toward the Oakland Touchdown area. The parallel structures would reach the Oakland shore to the south of the existing East Span and transition to the existing roadway west of the SFOBB Toll Plaza.

Replacement Alternative S-4 would consist of two parallel structures supported by 23 piers over water and 19 bents set on YBI, and the Oakland Touchdown area. The structures would each be 25.07 meters (82 feet) wide and separated by 15 meters (50 feet). The typical section for each bridge deck would consist of five lanes, each 3.6 meters (12 feet) wide, left and right shoulders, each 3 meters (10 feet) wide and traffic barriers. A 4.7-meter (15.5-foot) bicycle/pedestrian path would be located on the south side of the eastbound deck, 0.3 meter (1 foot) above the roadway elevation and includes viewing areas or belvederes. The five belvederes on the skyway would be 12 meters (39 feet) long by 1.2 meters (4 feet) deep. Caltrans is still investigating whether to include one or two belvederes on the main span that would be 20 meters (66 feet) long by 1.2 meters (4 feet) deep. A simulation of a belvedere design is shown on Figure 2-24 in Appendix A.

The height of the bridge, including the transition structure and the parallel structures, would vary in elevation from 50-55 meters (164-180 feet) above MSL at the East Viaduct to 5 meters (16 feet) above MSL at the Oakland Touchdown. A typical profile for the replacement alternatives is presented in Figure 2-9 in Appendix A.

2.2.5 Retrofit Existing Structure Alternative

Interim seismic retrofit work on the existing East Span was completed at the Oakland Touchdown area in 1998 and in the summer of 2000 on the truss spans and cantilever main span sections, but these are not components of the Retrofit Existing Structure Alternative. This alternative would retrofit the existing SFOBB East Span to withstand a maximum credible earthquake (MCE) on the San Andreas or Hayward faults. The seismic retrofit strategy of this alternative is based on isolating the superstructure from the substructure (towers and foundations). This work would include constructing additional large diameter piles and new pile caps around the existing foundations, strengthening and stiffening the towers, installing isolation bearings at the top of the towers, and strengthening and/or stiffening the superstructure truss members. Two new large deepwater columns would be added to the cantilever span in the main navigation opening.

However, constrained by a 1930s level of material and construction technology and the complexity of the structure, it is impossible to retrofit the existing East Span to lifeline standards with any reasonable degree of confidence. The seismic capacity of many of the existing materials, the interaction of major structural elements during a seismic event, and the condition of existing foundations are all uncertain. Although substantial modifications to the East Span are proposed as a part of the Retrofit Existing Structure Alternative, it is nevertheless anticipated that substantial damage would occur as a result of an MCE and require extensive reconstruction or replacement. Potential modes of failure are the superstructure unseating from the towers, a failure of column support due to a lack of sufficient reinforcement, the concrete foundations snapping from the tops of the timber piles, structure members bending in the cantilever section, and mangled deck joints that could impede traffic. Replacement would be necessary if structural safety criteria could not be met through repairs to the damaged bridge.

If damage is such that repair of the cantilever section is feasible, this may require complete closure of the East Span from six months to one year. If, however, damage is sufficiently severe that replacement becomes necessary, the East Span would be completely closed for a substantially longer period of time.

The Retrofit Existing Structure Alternative would retrofit both the existing East Span and the East Viaduct section on YBI. The alignment of the bridge would remain unchanged and the bridge would remain a double-deck structure. (See Figures 2-4.1 through 2-4.4 in Appendix A.) Each deck roadway cross section would also remain the same, five 3.5-meter (11.5-foot) wide lanes with no roadway shoulders.

Portion of East Span in Bay

The seismic retrofit strategy for the Retrofit Existing Structure Alternative is based on strengthening and stiffening the substructure (below deck towers and foundations) and isolating the superstructure. Large-diameter piles would be added around the perimeter or on both sides of all existing foundations. New, larger pile caps would be constructed to join the expanded foundations with the existing foundations. Figures 2-5 and 2-6 (Appendix A) show the "before" condition and the "after" simulation of the retrofitted bridge.

The tower legs in the main navigation opening would be encased in concrete. Isolation bearings would be installed on the tops of towers to isolate the superstructure from the substructure and allow differential horizontal movements of approximately 1.2 meters (4 feet) between the two to minimize force transfer during earthquake events.

Two new columns (E2A and E2B) would be added to the cantilever main span just east of YBI (see Figures 2-4.1 and 2-4.2 in Appendix A for locations of new columns).

The seismic retrofit strategy would also add a new edge truss to restrict deformations in the cantilever section. An edge truss is a spanning horizontal truss beam that is extended from the bottom of the lower deck to the bottom of the upper deck (see Figure 2-6 in Appendix A). Retrofitting truss members would include wind bracing and strengthening floor grid and vertical members.

Portion of East Span on Yerba Buena Island

The Retrofit Existing Structure Alternative would strengthen the East Viaduct and columns. The substructure of the East Viaduct would be retrofitted by enlarging and encasing selected columns and footings in concrete, adding cast-in-drilled-hole piles/tie-downs under the footings, enlarging the footings and the pile caps, and installing isolation bearings at the top of columns, and strengthening the deck by replacing expansion joints. Columns YB2, YB3, and YB4 would be encased in concrete and the foundations would be expanded.

2.2.6 Preferred and Least Environmentally Damaging Practicable Alternative (LEDPA)

In December 1998, after a thorough evaluation of project alternatives and consideration of comments from the public and agencies on the DEIS, Caltrans identified Replacement Alternative N-6, self-anchored suspension design variation, including a bicycle/pedestrian path, as its Preferred Alternative. In October 2000, FHWA also identified Replacement Alternative N-6 as the Preferred Alternative.

The Preferred Alternative has been identified as the Least Environmentally Damaging Practicable Alternative (LEDPA) by ACOE (on February 12, 2001) and EPA (on March 15, 2001). Documentation letters can be found in Appendix F. Identification of Replacement Alternative N-6 as the Preferred Alternative and the LEDPA in this FEIS has been coordinated through the NEPA/404 Integration MOU. The LEDPA is identified under the Federal Clean Water Act Section 404 (b)(1) alternatives evaluation process. The Section 404 (b)(1) process requires the ACOE, with input from the EPA, to make a determination of the LEDPA for any action involving discharge of dredge or fill material into waters of the U.S.

As a result of the alternatives analysis process undertaken for the East Span Project, it was determined that Replacement Alternative S-4 would have fewer permanent impacts to special aquatic sites protected by Section 404. Based on the 1999 eelgrass survey, Replacement Alternatives N-2 and N-6 would permanently affect 1.36 hectares (3.36 acres) of sand flats and 0.22 hectare (0.55 acre) of eelgrass, whereas Replacement Alternative S-4 would permanently affect 0.01 hectare (0.02 acre) of sand flats, 0.05 hectare (0.12 acre) of wetland and 0.15 hectare (0.37 acre) of eelgrass.

The "Guidelines for Specification of Disposal Sites for Dredged or Fill Material" (40 CFR 230) state that a Section 404 permit shall not be issued for discharge of dredged or fill materials into waters of the U.S. if there is a practicable alternative which would have less adverse impacts on the aquatic ecosystem, so long as the alternative does not have other significant adverse environmental consequences (40 CFR 230.10(a). An alternative is practicable if it is available and capable of being done after taking into consideration cost, existing technology, and logistics in light of overall purpose (40 CFR 230.10(a)(2)). Although Replacement Alternative S-4 would have fewer impacts on eelgrass and sand flats, it would pose several logistical problems that render it not practicable. Replacement Alternative S-4 would take land from an operating USCG facility, thereby constraining the mission of that facility; it uses land from a Section 4(f) resource (Gateway Park) for which there are prudent and feasible alternatives that avoid that use; it compromises the operation of an important sewer outfall that serves over 610,000 people along the east side of the Bay; it results in more complex construction to protect that outfall; and it results in more extensive and more difficult in-Bay construction because of considerably greater depth to bedrock to construct the main span tower. As a result of these logistical impediments, Replacement Alternative S-4 does not meet the standards for practicability as defined in the Section 404 guidelines.

Replacement Alternatives N-2 and N-6 meet the Section 404 standards of practicability. The following are the key logistical benefits of these alternatives:

• Replacement Alternatives N-2 and N-6 avoid conflicts with the USCG base that is responsible for search and rescue operations, marine safety, vessel traffic management, and aid to navigation and communication in the Bay. The base operates 24 hours a day, 7 days a week. The USCG coordinates over 2,000 local emergency response requests each year. In 1999 alone, its YBI facility saved 180 lives and over $34 million in property. Its Vessel Traffic Service is essential for the safe passage of large ocean-going ships (such as those moving daily to and from the Ports of Oakland and San Francisco) and is important in protecting the Bay environment by averting maritime accidents. In a letter to Caltrans dated October 18, 2000, the USCG stated that a southern alignment for the East Span Project (such as Replacement Alternative S-4) would severely restrict USCG's flexibility to utilize that part of its already limited footprint. It further stated that a southern alignment would constrain USCG's ability to effectively conduct emergency service operations from YBI.

• Replacement Alternatives N-2 and N-6 avoid land on the Oakland Touchdown designated by the Oakland Base Reuse Authority (OBRA) for a proposed park. The proposed park was determined by FHWA to be protected by the provisions of Section 4(f) of the Department of Transportation Act. Under Section 4(f), the Secretary of Transportation may approve a transportation project requiring the use of publicly owned land of a public park only if there is no prudent and feasible alternative to using that land, and the project includes all possible planning to minimize harm to the park. FHWA's implementing regulations (771.135(a)(2)) state that alternatives that avoid Section 4(f) properties are not prudent and feasible if they have unique problems or unusual factors, or if the cost, social, economic, and environmental impacts, or community disruption resulting from such alternatives reach extraordinary magnitudes. Replacement Alternatives N-2 and N-6 were not found to involve unique problems, unusual factors, or environmental impacts that reach extraordinary magnitudes; they are both prudent and feasible alternatives that avoid the use of the public park by Replacement Alternative S-4. In addition, because all build alternatives result in Section 4(f) uses (please see Section 6.3 — Description of Section 4(f) Resources Used by Project Alternatives), Caltrans and FHWA evaluated the Section 4(f) uses to establish which alternative results in the least net harm to Section 4(f) resources. Replacement Alternatives N-2 and N-6 were determined to be the feasible and prudent alternatives with the least net harm to Section 4(f) resources. For a detailed evaluation of Section 4(f) resources, see Chapter 6 — Section 4(f) Evaluation of this FEIS.

• The alignments of Replacement Alternatives N-2 and N-6 provide easier access to bedrock to construct the main span tower than Replacement Alternative S-4. With Replacement Alternative N-2, depth to bedrock would be approximately 11-14 meters (36-46 feet) below the mudline, and with Replacement Alternative N-6, the depth to bedrock would be approximately 6-9 meters (20-30 feet) below the mudline. In contrast, the depth to bedrock for Replacement Alternative S-4 would be approximately 67-71 meters (220-233 feet) below the mudline. Easier access to bedrock for Replacement Alternatives N-2 and N-6 (easiest for N-6) would allow for shorter piles, which would reduce the overall seismic load demands on the main span tower. For construction of Replacement Alternative S-4, the tower would need to be longer to reach bedrock, thereby subjecting it to greater stresses in an earthquake. Its design would need to be more massive to provide the same seismic resistance provided by a shorter tower for Replacement Alternative N-2 or N-6. As a result, the foundation would also need to be more massive to support the longer and more massive tower. The greater depth to bedrock and the larger foundation together would increase the area of excavation and the quantity of excavated material requiring disposal. Placing a key structural element of the bridge in over 60 meters (200 feet) of soft sediments would present substantial logistical challenges during construction.

• Replacement Alternatives N-2 and N-6 avoid conflicts with East Bay Municipal Utility District’s (EBMUD’s) facilities and operations. They would not conflict with the sewer outfall or its dechlorination facility. The outfall is a concrete pipeline 2.8 meters (9 feet) in diameter, and the onshore portion of the pipeline is buried 0.5 to 1.5 meters (2 to 5 feet) below ground surface. This shallow layer of cover does not provide adequate protection for the pipe; it is a zero-load facility, meaning that the pipeline cannot support any weight and must be protected or spanned to prevent damage. The alignment of Replacement Alternative S-4 would obliquely cross an onshore portion of the outfall pipeline. The skew angle between the roadway alignment and the outfall pipeline, buried under minimal cover from 0.5 to 1.5 meters (2 to 5 feet) deep, would result in a conflict area on land that is approximately 400 meters (1,300 feet) long. Protecting and avoiding this 2.8-meter (9-foot) diameter, zero-load pipeline would substantially increase construction complexity in this area, in terms of both bridge design and constraints on the contractor. It would also hamper any future inspections and repairs of either the outfall or the bridge. Damage to the onshore outfall during construction of Replacement Alternative S-4 could cause release of secondarily treated effluent containing elevated levels of chlorine into the Bay.

Replacement Alternatives N-2 and N-6 are the practicable alternatives pursuant to Section 404 of the Clean Water Act, and they are also feasible and prudent alternatives with the least net harm to Section 4(f) resources. Replacement Alternative N-6 has been chosen as the Preferred Alternative over Replacement Alternative N-2 on the basis of greater ease of construction of the main tower based on geologic conditions, aesthetic benefits such as enhanced drivers’ views, and consistency with the regionally preferred alignment and design features as expressed by the MTC.

2.3 REPLACEMENT ALTERNATIVES DESIGN VARIATIONS

Replacement alternatives are proposed as two parallel skyway structures, each having five traffic lanes, inside and outside shoulders, and a bicycle/pedestrian path on the south side of the eastbound deck. Design variations identified for the replacement alternatives are limited to the type of bridge to be constructed over the main navigation opening. For the portion of the span between the east side of the navigational channel and the Oakland Touchdown, a skyway design (a span supported from under the bridge deck) is the most practical structure type because of the alignment, the geology, the seismic characteristics, shallow water, and deep Young Bay Muds in that area. Other structure types could be built in this area; however, because of the site conditions, they would substantially increase design and construction costs and the time needed to construct. Designing these other structure types to a lifeline standard would also be much more difficult.

It has been determined that for the main span, steel would be used to construct the main tower and superstructure and a steel/concrete composite would be used to construct the substructure. For the skyway, concrete would be used for the superstructure and concrete or a steel/concrete composite would be used for the substructure. For the Oakland Touchdown portion of the bridge, concrete would be used to construct the superstructure and the substructure.

Selection of the superstructure type to be used for the bridge was based on seismic engineering and cost analyses, material availability, maintenance requirements, and impacts to construction schedule. To minimize costs, the span lengths were maximized, which increased load demands. While a 5-meter (16.4-foot) deep structure depth is sufficient for most of the span, it is insufficient to resist the bending and shear demands at the piers, so the superstructure had to be deepened at those points. As a result, a "haunched", or slightly arched, design was selected for the superstructure. This type of superstructure is thick at either end where it sits on a column. (See Figure 2-23 in Appendix A).

2.3.1 Main Span Types

For the replacement alternatives, design variations were considered for the main span section that crosses the main navigation opening. A number of bridge types, as discussed below, were evaluated by MTC’s Bay Bridge Design Task Force Engineering and Design Advisory Panel (EDAP) based on seismic performance, aesthetic considerations, costs, ability to construct the bridge as soon as possible due to seismic vulnerability, and the possible location of a bicycle/pedestrian path. The public had an opportunity to participate during this process at 34 Task Force and EDAP meetings and through letters, phone calls, and e-mails received by MTC. In June 1998, based on the recommendations of the EDAP, MTC voted for a self-anchored suspension design that includes a single tower of 160 meters (525 feet) in height above MSL and maintains the main navigation opening east of YBI.

EDAP’s recommendation was based on seismic safety and the aesthetic value of the bridge. The seismic safety of the self-anchored suspension design was judged to be equal to that of the single-tower, cable-stayed span; however, its aesthetic value was judged to be greater and more visually consistent with the tradition of suspension bridges in the central Bay. In addition, this design involves fewer long-term maintenance costs than the cable-stayed design variation evaluated by the EDAP and allows for the optimum location of the tower foundation while providing a wider shipping channel. (See Appendix E for further detail on the MTC recommendation process).

Replacement Alternatives N-2, N-6, and S-4 could accommodate any of the three variations discussed below, although the optimum locations for the main span foundations could not be provided by all replacement alternatives due to limited access to bedrock.

Cable-stayed Design

The cable-stayed design includes the use of steel cables to connect the bridge deck directly to towers. Most cable-stayed bridges have a single tower which supports both decks or separate "H" towers that support each individual deck. A single concrete vertical tower was considered for the East Span Project (see Figure 2-12 in Appendix A). Cable-stayed bridges have been used in several different countries since the 1940s. Recent examples constructed in the United States include the Sunshine Skyway Bridge in Tampa, Florida, and the Thomas Bridge in Georgia.

The cable-stayed system allows for longer spans crossing the navigational channel than could be provided with a skyway variation which requires additional piers in the channel. However, any cable-supported structure imposes additional alignment constraints. To support the two decks from a single tower, the decks of each of the parallel bridge structures must be almost parallel and at the same approximate elevation for the entire length of the main span. The main span cannot begin until each deck alignment meets these constraints. The replacement alternatives under consideration have been set to accommodate the geometric requirements for a cable-stayed main span.

The cable-stayed design variation would exceed the USCG’s minimum requirements for horizontal and vertical clearances of the main navigation opening.

The cable-stayed main span was estimated to cost approximately $100-$250 million more than the total estimated cost of an island-to-shore skyway replacement bridge.

Suspension Bridge Design (Preferred Design Variation)

The suspension design is a commonly used design for long channel crossings and has been used previously in the Bay Area on the Golden Gate Bridge and the SFOBB West Span. A classic suspension bridge has cables that are draped from towers and connected to anchorages founded on the ground at both ends of the main span. Vertical cables ("suspenders") support the bridge by connecting the draped cable to the bridge deck. While bedrock on YBI could be used for a west anchorage, bedrock is approximately 135 meters (443 feet) below the mudline for an east anchorage at the Oakland Touchdown. The use of ground-founded traditional anchorage structures at this bridge site is therefore considered less feasible and less cost-effective relative to other options.

A self-anchored suspension design variation has been identified as the preferred design variation. In a self-anchored suspension bridge, the main cables are anchored to the ends of the main span deck, eliminating the need for ground-founded anchorage structures (see Figure 2-13 in Appendix A). The self-anchored suspension design variation suspends the bridge from a steel tower. Alignment constraints for the self-anchored suspension design variation are similar to those described for the cable-stayed design variation. Decks of the bridge structures must be almost parallel and at the same approximate elevation for the entire length of the main span. The main span cannot begin until each deck alignment meets these constraints. Although a self-anchored suspension bridge looks similar to more conventional suspension bridges, it is structurally different in that it uses the bridge deck as the integral structural component that balances the force usually taken by anchorages founded on the ground. The replacement alternatives under consideration have been set to accommodate the geometric requirements for a self-anchored suspension design variation.

The self-anchored suspension design variation exceeds the USCG’s minimum requirements for horizontal and vertical clearances of the main navigation opening.

The self-anchored suspension main span was estimated to cost about $150-$300 million more than the total estimated cost of an island-to-shore skyway replacement bridge.

Skyway Design

The skyway design variation is a structure constructed of precast concrete supported by columns. With this structure type, eastbound and westbound bridges would be constructed as separate, independent structures. Under the skyway design variation, spans over the main navigation opening area could be a maximum of 150-170 meters (490-550 feet) in length. The skyway design variation would require three spans in the main span area, compared to two spans for both the cable-stayed and self-anchored suspension design variations. The skyway design does not require a complete tangent or straight section over the main span, which is needed to construct the cable-supported design variations. As a result, there could be a slight curve in the main span. An example of a skyway structure is depicted in Figure 2-14 in Appendix A.

The skyway design variation would meet but not exceed the USCG’s minimum requirements for horizontal and vertical clearances of the main navigation opening.

A skyway design variation is considered as the baseline for cost comparison purposes. A skyway span was estimated to cost approximately $90 million.

2.4 COMPARISON OF ALTERNATIVE CHARACTERISTICS

2.4.1 Funding

The base budget for the East Span Project, established in Section 188 of the California Streets and Highways Code (CSHC), is about $1.285 billion. Project funding comes from a combination of state taxes, bond revenues, and moneys collected through a one-dollar bridge toll surcharge effective January 1, 1998, on all state-owned bridges in the Bay Area. Some federal funding is also being sought for the project. State taxes, in the form of state fuel tax revenues, are 33.3 percent of the project budget, state Seismic Retrofit Bond revenues will fund 30.2 percent of the budget, and the toll surcharges from state-owned Bay Area toll bridges will fund the remaining 36.5 percent.

The legislation creating the funding mechanism for the East Span Project established the Bay Area Toll Authority (BATA) (with the same board as the Metropolitan Transportation Commission) and authorized the Authority to collect the one-dollar toll surcharge for eight years, issue revenue bonds, and allocate revenues to toll bridge projects, including the East Span Project. On June 24, 1998, through BATA Resolution No. 10, the Authority chose to extend the one-dollar toll surcharge for an additional two years beyond the eight years to fund the inclusion of specified amenities. Extension of the toll surcharge for 15 months is anticipated to generate $230 million; amenities specified in Resolution No. 10 total $141 million: $50 million for a bicycle/pedestrian path and $91 million toward the self-anchored steel suspension main span. On September 22, 1999, through BATA Resolution No. 19, the one-dollar toll surcharge was extended for an additional 0.4 months to pay for rest areas, a planning and feasibility study of a West Span bike lane, and a concept study of improvements to the Transbay Transit Terminal. The incorporation of the two resolutions results in a $1.427 billion budget for the SFOBB East Span Project.

On June 28, 2000, the Authority approved a revision to BATA Resolution No. 19 to extend the surcharge for the remaining 8.9 months permitted by statute to fund the additional costs of the Bay Bridge West Span bicycle and pedestrian study ($1,020,000) and for the remainder ($84,430,000) to be placed in a reserve account.

The total base budget of $1.285 billion includes an allocation of $80 million for a cable-supported structure. The type of cable-supported structure is not specified in the CSHC. The design options presented in Section 2.3 include cable-supported structures. Funding of a cable-supported system costing more than $80 million would require the Authority to extend the one-dollar toll surcharge beyond the initial eight-year period.

Cable-supported design variations are included in the East Span Project description of replacement alternatives. The potential visual impacts of these design options are addressed in this document.

2.4.2 Costs

Estimated total costs for each of the alternatives identified above are listed in Table 2.4-1. These costs are based on 1998 estimates and are presented in 2002 dollars. Comparative life-cycle costs are presented in Table 2.4-2. These cost estimates are conceptual and are based on available information that was available in 1998 about the existing East Span, new proposed alignments, existing utilities, historic construction costs, and quotations from various local suppliers and contractors. These estimated costs range from zero for the No-Build Alternative to $1.65 billion for Replacement Alternative N-6, suspension design option. No-Build Alternative costs do not include the $19 million interim retrofit improvements that were completed during summer 2000.

In April 2001, Caltrans published updated cost information for the Preferred Alternative (Replacement Alternative N-6, suspension bridge design option). It reflects cost increases due to such factors as increasing construction costs in a robust and competitive local economy; significant increases in the costs of steel; schedule delays which magnified the inflationary effect; and additional design amenities such as the belvederes and a wider bicycle path than is standard. Caltrans estimates that the current cost of Replacement Alternative N-6, suspension bridge option, would be $2.6 billion.

Caltrans did not prepare updated cost estimates for the other project alternatives in April 2001. However, the most significant factors contributing to increased costs would apply to all of the build alternatives.

The enabling legislation for the project, Senate Bill 60, signed by then-Governor Pete Wilson in 1997, anticipated the possible need for additional funding beyond original estimates and required Caltrans to return to the Legislature if necessary. In accordance with Senate Bill 60, Caltrans has submitted its cost estimates to the Legislature and anticipates that it will address the need for additional funding within the next few months.

Based on a comparative cost study prepared by Caltrans in 1996, it is estimated that the bridge maintenance costs for the retrofit alternative over the projected 50-year life span of the existing structure would be $44 million. A replacement structure is expected to have a service life of 150 years. Life-cycle costs of replacement alternatives have not been developed for the projected 150-year life spans of the structures. A comparison of selected maintenance operations and repairs of the first 50 years of service indicated that differences among replacement alternatives are small (see Table 2.4-2). Comparing the life-cycle costs of the replacement structure in Table 2.4-2 to the maintenance costs of the retrofit structure

Table 2.4-1 Cost Estimate Summary

Source: SFOBB East Span Seismic Safety Project 30% Type Selection Report, Caltrans, May 1998.

Notes: ^a Cost estimates reflect the potential range in construction costs depending on skyway structure type rounded to the nearest 50 million. A haunched-concrete skyway structure is estimated to have the least cost, a uniform depth concrete skyway a mid-range cost, and a uniform depth steel structure the greatest cost.

^b The cost information in this table represents the estimated cost of the various alternatives in 1998. The costs are relative to each other at the time that they were estimated. They do not represent the current costs of the alternatives, which would be greater, but still have the same relative relationship.

Source: SFOBB East Span Seismic Safety Project 30% Type Selection Report, Caltrans, May 1998.

Notes:

^a Comparative life-cycle cost analysis estimates costs of maintenance and repair of the bridge over a projected life span (150 years) to better determine the overall bridge structure "value." A comparative analysis requires calculation of life-cycle costs of only those maintenance operations and repairs that are appreciably different for bridge design variations that are being evaluated. The table only reports costs for the first 50 years of the life span because beyond that period, it becomes increasingly difficult to make reliable estimates.

^b For purposes of comparative life-cycle costs, differences between replacement alternatives were minimal.

($54 million in 2002 dollars) means that a new bridge, which would last 100 years longer, would be less expensive to maintain over the long term.

2.4.3 Constructibility

In addition to cost, "constructibility" provides a valuable comparison between the alternatives and options previously described. Constructibility encompasses the anticipated duration of construction, as well as any unusual delays, environmental issues, or risks associated with the construction process. The environmental impact issues are discussed in Section 4.14 — Temporary Impacts During Construction.

The No-Build Alternative would have no construction activity. Tasks would be limited to regular maintenance.

The Retrofit Existing Structure Alternative would include constructing two new columns in Bay waters to support the main span over the navigational channel. A total bridge closure would be necessary to connect the new columns to the cantilever section. This could be accomplished at night. During other activities, such as superstructure construction, numerous lane closures would be necessary but would be timed to minimize the impact on bridge users. Construction on the superstructure would be expected to last for the majority of the retrofit schedule, approximately six years.

The Retrofit Existing Structure Alternative is less safe for the traveling public and for Caltrans staff who will maintain the bridge during and after construction. Because there are no shoulders on the existing East Span, the construction zone for the retrofit would be highly constrained. Motorists would pass within close distances of the construction activities through the entire 4-kilometer (2.5-mile) long project, and construction equipment and workers would have to maneuver adjacent to passing traffic for the installation and removal of lane closures and other work on or above the five lanes.

Multi-staged construction and temporary detours would be required on YBI and the Oakland Touchdown area for all three replacement alternatives. Most of the construction in the Bay can be performed without affecting the existing roadways and bridge structure. The vast majority of the construction would be separated from the existing East Span. This separation would minimize traffic delays and safety hazards for construction crews, maintenance crews, and the traveling public. Caltrans is continuing to investigate lane and bridge closures to transition traffic from the existing bridge to the temporary detours and to a replacement bridge. Caltrans would plan the closures in an effort to simultaneously minimize public inconvenience, facilitate construction, and maximize public safety. The closures would be scheduled to occur during off-peak hours to the maximum extent feasible. Caltrans would implement a Traffic Management Plan to manage impacts to traffic.

A replacement alternative would also provide two standard shoulders to accommodate disabled vehicles and routine bridge maintenance activities. The replacement alternatives are expected to take five years to complete plus approximately two years to dismantle the existing structure, for a seven-year construction schedule.

2.4.4 Ability to Address the Project Purpose and Need

The No-Build Alternative would not meet the project purpose and need as described in Chapter 1 because it would not provide a lifeline vehicular connection between Oakland and YBI; would not maintain high levels of people, freight, and goods movement following an MCE; and would not correct deficiencies in design standards. The retrofit and replacement alternatives would meet the project purpose and need to varying degrees as summarized below.

The Retrofit Existing Structure Alternative would retain the vehicular connection between YBI and Oakland and would maintain the current vehicular capacity of the East Span. It would improve the seismic performance of the existing structure, enabling the bridge to withstand a seismic event, and potentially an MCE; however, it would not meet lifeline criteria. In the event of an MCE, it is anticipated that major damage to the bridge could occur. Post-earthquake repair of the bridge could require closure of the SFOBB for several months, removing the SFOBB as a transportation link and, if damage is excessive, impeding the bridge’s ability to provide emergency relief access. Replacement or repair of the bridge following an earthquake could require closure of the SFOBB for years, depending on the degree of damage.

Opportunities to improve operational safety elements of the East Span would not be possible under the Retrofit Existing Structure Alternative. The retrofit alternative would not permit changes to the existing roadway design; therefore, current roadway design standards could not be attained (see Section 1.2.3 — Current Roadway Design Standards).

Each of the replacement alternatives would continue to provide a connection between YBI and Oakland and would provide a lifeline connection between West and East Bay communities. The replacement alternatives would be constructed to withstand an MCE, providing for safety of bridge users during an earthquake. As a lifeline structure, the span would continue to provide a critical connection between San Francisco, the East Bay, and the I-80 corridor to the east. The span would provide post-earthquake transportation service for emergency response and support for the economic livelihood of the Bay Area.

The replacement alternatives would meet current roadway design standards to the maximum extent feasible. Replacement alternatives would maintain existing vehicular capacity on the East Span by providing five travel lanes in each direction, including provision of standard 3.6-meter (12-foot) wide traffic lanes and inside and outside (3-meter [10-foot]) shoulders. The replacement alternatives would also conform to current horizontal and vertical alignment, superelevation, clearance, and stopping-sight distance standards as defined in Section 1.2.3 — Current Roadway Design Standards of this report.

2.5 ACCOMMODATION OF MULTI-MODAL STRATEGIES

The SFOBB is within an important corridor of transbay travel between San Francisco and the East Bay. The bridge is currently a multi-modal highway facility that is used by public and private vehicles, trucks, buses, carpools, and vanpools. The corridor is also served by Bay Area Rapid Transit (BART), which provides rapid rail service via the submerged BART "tube," and a network of ferries.

Based on available data, approximately 36,000 people travel through the Transbay Corridor during the weekday morning peak hour in the peak direction (westbound). The following table summarizes existing person trips in the Transbay Corridor by mode:

Source: Caltrans, September 1997, June 1998, and May 2000.

Because the SFOBB is a critical regional facility whose approaches are severely congested during peak periods, the feasibility of incorporating an additional high-occupancy transportation facility within the corridor (either road- or rail-based) was evaluated. The purpose of such a facility would be to increase mobility within the corridor.

Due to the scale of the project, some members of the regional community urged that congestion relief be included as part of the project purpose in addition to providing a vehicular lifeline connection. The scope of the project was not expanded to include congestion relief, because this would have resulted in lengthy public and agency debate about how best to implement a congestion relief solution. This would have caused the seismic safety component of the project to be substantially delayed. Caltrans anticipates beginning construction of this critical safety project in fall 2001. This would not have been possible if the scope of the project had included congestion relief.

2.5.1 Historical Background

Rail service was provided on the SFOBB from 1939 to 1958 by the Key System. The Key System was an electrified interurban light-rail system that utilized the south side of the lower deck of the East and West Spans of the SFOBB. It shared the lower deck with trucks and buses while automobile traffic only traveled in six lanes on the upper deck. The Key System commenced operation in 1939 and continued service until 1958. From 1939 to 1941, two other rail lines, the Interurban Electric and the Sacramento Northern, also operated on the SFOBB.

The Key System connected Oakland and Berkeley with San Francisco. The system terminated in San Francisco at the Transbay Transit Terminal where passengers could transfer to the San Francisco Municipal Railway system (Muni). In total, the Key System trains operated on 106 kilometers (66 miles) of track on the SFOBB and in the East Bay. It served the East Bay cities of Richmond, El Cerrito, Albany, Berkeley, and Oakland. The Key System also operated transbay buses.

Patronage on the Key System peaked in 1945 with 26.5 million annual passengers, with an average daily ridership of about 102,000 (including both trains and Key System buses). By 1957, ridership had declined to about 5.2 million annually (about 17,000 average daily riders). As a result of the decrease, the Key System rail lines were abandoned, and the routes were converted to Alameda-Contra Costa Transit District (AC Transit) bus service in 1958.

When Key System rail service ended, the lower deck of the SFOBB was converted to automobile use. To accommodate these changes, substantial modifications were made in San Francisco, on the SFOBB, and in the Oakland Touchdown area. New vehicle access to and from the SFOBB was constructed in San Francisco; tracks at the Transbay Transit Terminal were converted to bus lanes, and buses were rerouted onto the former rail access in the Terminal; track, ties, and other railroad facilities were removed from the lower deck of the SFOBB; and new roadways to and from the SFOBB were constructed in Oakland. Load capacity from the rail system was used to allow modern traffic loadings on the bridge, including truck traffic in any of the lanes on the top deck.

2.5.2 MTC SFOBB Rail Feasibility Study

Background

In November 1998, voters in the cities of San Francisco, Berkeley, Oakland and Emeryville passed an advisory ballot measure requesting that the feasibility of passenger rail on the SFOBB be studied by MTC. In response to this measure and general public interest, MTC studied transit service options in the Transbay Corridor, especially the possibility of rail (see MTC letter dated December 16, 1998, that was sent to the Mayors of Berkeley, Emeryville, Oakland, and San Francisco in Appendix G). Concurrently, MTC prepared two studies: a long-term capital and operating cost analysis for various transit options for the Transbay Transit Terminal, as well as a feasibility analysis of rail on the SFOBB. Because the SFOBB and the Transbay Transit Terminal are linked by function, the technical analyses conducted in each study have been coordinated and are based on shared assumptions and data.

There are two phases in the Bay Bridge Rail Alternatives Study. Phase I explored the technology options for placing rail on the SFOBB and assessed the structural feasibility and modifications that would be required for the retrofitted West Span, YBI and the new East Span of the SFOBB as currently proposed. Phase I also identified potential SFOBB rail alignments in the East Bay and in San Francisco. A final report was completed in July 2000.

The work scope for Phase II of the study will be incorporated into the Bay Crossing Study to be completed by MTC by fall 2002. MTC will study non-SFOBB transbay rail crossings, including new tubes for rail or BART, additional or expanded auto bridges with or without rail, and enhancements to existing transbay transit services, including BART, transbay buses, and ferries.

The following working papers and final report were prepared for MTC’s SFOBB Rail Alternatives Study:

• Working Paper 2A.2: "Initial Definition and Description for Bay Bridge Rail Options," July 28, 1999;
• "Structural Assessment of Rail on the Bay Bridge: Summary Report," October 22, 1999;
• Working Paper 2A.3: "Structural Assessment of Rail on the Bay Bridge," October 22, 1999;
• Working Paper 3A.1: "Operational Description of Bay Bridge Rail Alignment Options," Draft, November 29, 1999; and
• Final Report, "Bridge Rail Feasibility Study," July 2000.

These documents are available from the MTC Library, 101 8^th Street, Oakland, California.

MTC Findings

Structural Feasibility and Costs. The structural feasibility of rail on the SFOBB was analyzed in the MTC study. This study analyzed four types of rail vehicles: light rail (LRT), BART, commuter rail, and high-speed rail. These vehicles vary by their loaded car weight and the rail envelope size.

The East Span replacement alternatives, as currently being designed by Caltrans, would have the structural capacity to accommodate one railroad track for LRT on the inside of each deck (north side of eastbound deck, and south side of westbound deck), four travel lanes with no shoulders, and live loads representing BART and LRT vehicle types. The MTC study found that additional strengthening beyond the established design criteria would be required if five travel lanes or vehicle types with higher live loads were desired. The placement of rail on the inside of each of the side-by-side decks limits the options for crossing YBI and connecting to the West Span. The MTC study notes that "…moving rail to the outside of the decks would provide the needed flexibility, allowing for new tunnel bores to be constructed without impacting current traffic operations."

The MTC study also observes that the feasibility of an SFOBB rail system would also be constrained by the structural requirements for rail on the West Span. The MTC structural assessment study identified two rail configurations that would accommodate rail on the West Span. Both configurations would require extensive modifications, in addition to the West Span retrofit that is currently under way. The cost for the modifications would range from $3.06 billion (Rail Suspended Below the West Span Lower Deck option) to $3.33 billion (Rail Cantilevered from the West Span Lower or Upper Decks option). These estimates include the cost of strengthening and modifying the West and East Spans to accommodate rail and four travel lanes, new tunnels through YBI, and a new tunnel or structures to Harrison Street in San Francisco. The costs do not include a structure to carry rail beyond the SFOBB Toll Plaza, structure or tunnel to the Transbay Transit Terminal in San Francisco, or costs of the rail tracks or other infrastructure to operate a rail system.

Rail Service Options. The MTC study identified four rail service options for operating rail on the SFOBB. The study notes that these options would serve different, potentially large markets but were not based on detailed analyses of demand or potential patronage.

Alternative A ­ Transbay Light Rail Service. This option, considered a modern version of the Key System, would connect the Transbay Transit Terminal with several trunk lines in the East Bay with LRT. Frequent all-day service would be provided.

Alternative B ­ BART Transbay Bridge Service. This option would take one of the existing transbay BART lines and move it to the SFOBB, expanding the capacity of BART’s peak hour transbay service. For purposes of the MTC analysis, it was assumed that the SFOBB BART would connect to the bridge via a direct connection with BART’s MacArthur station.

Alternative C ­ Basic Bridge Railroad Passenger Service. This option identifies rail service that would link the Peninsula and the East Bay via the Transbay Transit Terminal and the SFOBB. Both electrified commuter rail and high speed trains would operate on this alignment on a skip-stop "A-train/B-train" operating plan, as described in MTC’s "Blueprint" concepts for Caltrain. "A" and "B" trains would operate on 30-minute headways, resulting in 15-minute headways between major stations. In the East Bay, commuter rail trains would merge with the existing Union Pacific corridors both north and south of the SFOBB. To the north, some of the trains would extend to Sacramento as part of Capitol Corridor service. High speed rail would terminate at a new station in West Oakland.

Alternative D ­ Aggressive Bridge Railroad Passenger Service. This option is basically identical to Alternative C. However, for Alternative D, the northern "A" and southern "B" branches would extend beyond central East Bay core cities. Frequency of service would also be improved. Northbound trains would continue to Martinez with half of the trains continuing to Suisun-Fairfield. Some trains would be extended to Sacramento. High speed trains would operate over the SFOBB every 30 minutes, with every train continuing to Sacramento. The southbound commuter rail line would extend to San Jose.

Rail Infrastructure and Rolling Stock Costs. The MTC study estimated the capital costs of implementing each of the rail options, including infrastructure and rolling stock. Operational costs were not included in these estimates but they would be substantial. Total infrastructure and rolling stock cost estimates are summarized below:

• Alternative A - $1.6 to 1.8 billion
• Alternative B - $1.94 billion
• Alternative C - $918 million
• Alternative D - $4.77 billion

Therefore, the MTC study estimated that the total cost of rail implementation, including bridge structural modifications, rail infrastructure, and rolling stock would be between $4 billion and $9 billion.

Structurally, rail is feasible on the SFOBB; however, there are numerous non-structural issues that have not been examined, such as system-wide operations, routing, costs, attaining ridership, acquiring right-of-way, and resolving environmental issues.

2.5.3 Operational Issues

This section evaluates the potential operational impacts of implementing an HOV lane or rail on the East Span.

In general, the existing East Span or a replacement span could physically accommodate an HOV lane without additional right-of-way. A replacement East Span, as currently designed, could also accommodate rail service. Rail service would require the use of one travel lane in each direction, reducing the capacity of the East Span to four travel lanes. Significant modifications to the current design would be necessary to accommodate rail service and five travel lanes.

The operational impacts on vehicular flows due to the loss of one travel lane with either multi-modal strategy are described below.

HOV Lane

An HOV lane on the SFOBB is evaluated as an extension of the existing HOV facilities at the San Francisco and East Bay approaches. Under this scenario, one of five mixed-flow lanes on the SFOBB (in both the eastbound and westbound directions) would be converted to an HOV lane. The HOV lane would be a dedicated facility for use only by vehicles with three or more people. Because right-of-way constraints on the existing or replacement East Span would preclude the use of barriers or buffers, the facility would be separated from mixed-flow traffic by striping and signing only.

An HOV lane on the SFOBB would adversely affect mobility in the Transbay Corridor, compared to the SFOBB facility without an HOV lane. During the morning peak period, the existing HOV lanes and metering signals at the SFOBB Toll Plaza operate together as a system to ensure that the capacity of the five westbound lanes on the SFOBB is maximized. As the HOV lane volume varies during the peak period, the mixed-flow metering rates are adjusted accordingly to maintain capacity flow for five lanes on the bridge. During the peak hour when the HOV volume exceeds the capacity of a single HOV lane, total vehicular capacity could be maintained if one of the five lanes on the bridge is operated as an HOV lane. The metering signals would release fewer mixed-flow vehicles as the excess HOV demand shifts into the mixed-flow lanes. However, the HOV volume before and after the peak hour would be less than the capacity of an HOV lane. Since mixed-flow vehicles would be restricted from using the HOV lane, total vehicular capacity would be less than the existing capacity as the excess HOV lane capacity would go unused. This would result in additional congestion on the approaches to the SFOBB. It is likely that the additional congestion would increase to the point of restricting access to the HOV lanes, particularly for the I-580 and I-880 approaches.

Other constraints associated with implementing the HOV lane on the SFOBB would be the result of the physical integration of the lane with existing HOV lanes, ramps, and SFOBB approaches. Substantial physical modifications, such as an HOV flyover (to connect the existing westbound HOV lanes, including the HOV flyover constructed as part of the I-880/Cypress Freeway Replacement Project, with a new HOV lane) and/or new ramps at YBI, would be necessary to minimize impacts to traffic flow operations. Therefore, costs associated with implementation of the HOV lane could be substantial and there would be no net change in person trip throughput on the bridge.

Rail

If rail on the SFOBB were implemented, one travel lane and one shoulder in each direction on the East Span would need to be converted to rail use. The loss of a traffic lane on either span would substantially impact SFOBB traffic operations. The vehicular capacity of the proposed East Span would be reduced by 20 percent. However, to accommodate rail on the existing West Span deck, it would need to occupy two travel lanes, reducing the vehicular capacity by 40 percent. This is because the West Span does not have shoulders. Consequently, the vehicular capacity of the East Span would also be reduced by 40 percent because traffic flow on the East Span would be constrained by the lowest capacity available in the corridor. As a result, about 7,300 morning peak-hour westbound person trips (4,000 vehicle trips per hour) would be displaced. (These figures are based on counts taken by Caltrans in May 2000 at the SFOBB Toll Plaza.) If this significant loss in vehicle capacity was not made up through rail ridership, it would increase the existing congestion levels on the approaches to the SFOBB for mixed-flow vehicles, as well as create delays for vehicles accessing the existing HOV facilities.

To maintain or increase the person throughput capacity of the SFOBB due to the loss of vehicle capacity as a result of rail on the bridge, the rail system must attract all of the displaced person trips (about 7,300 morning peak-hour, westbound person trips). The ability of the rail system to attract new transit trips is not solely dependent on the SFOBB segment; instead, the rail system must provide a superior mode choice in terms of travel time, convenience, cost, and reliability compared to driving. It must also not duplicate service already provided by either AC Transit, BART, or ferries. These factors would limit the number of displaced person trips to be attracted to the rail system. Further, to be successful, any new rail system would need a supporting feeder infrastructure. Rail lines, terminals, parking areas, and new bus lines would need to be developed to deliver riders to the system. Future improvements on the other existing modes would also affect new rail system ridership by providing capacity increases in the corridor. The implementation of BART’s Advanced Automatic Train Control (AATC) will allow BART to increase its capacity to 21,000 passengers during the peak hour. The AC Transit Transbay Comprehensive Service Plan calls for 140 westbound, morning peak-hour buses in the future, about an 80 percent increase over existing levels.

2.5.4 Institutional and Funding Issues

Institutional and funding issues related to implementation of either a road-based or a rail-based multi-modal strategy are summarized below.

• Multi-modal strategies have not been identified as necessary in any regional planning process or document. MTC is the regional agency responsible for programming, transportation planning, and financing within the nine-county San Francisco Bay Area. It functions both as the regional transportation planning agency and as the region’s MPO. These designations are mandated through state and federal legislation, respectively.

• MTC’s Bay Crossing Study (1991);
• HOV Lane Master Plan (1997);
• Interstate 80 Corridor Study (1987);
• Phase I ACR 132 Intercity Rail Corridor Upgrade Study (1989);
• Greater East Bay Rail Opportunities Coalition’s Commute Rail Operating Plan (1994);
• AC Transit’s Alternative Modes Analysis (1993);
• Transbay Comprehensive Service Plan (1998);
• Caltrans’ Rail Passenger Program Report 1993/94 - 2002/03 (1993);
• California High Speed Rail Commission studies;
• MTC’s Blueprint for the 21^st Century (1999); and
• MTC SFOBB Rail Alternatives Study (2000).

• No funding has been programmed or identified for either strategy. MTC recently estimated the cost to implement rail on the SFOBB to be between $4 and $9 billion, depending on the technology used, and the infrastructure and bridge structural modifications required. The structural modifications to both the proposed East Span and West Span to accommodate rail would cost between $3.06 and $3.3 billion. The MTC study noted that heavy rail could be accommodated on the East Span with significant and costly modifications to its current design.

• Both strategies would require new institutional arrangements to implement and operate the facilities. Neither the HOV lane nor a rail system is currently identified as a regional transportation priority. Before either can be included in the RTP, new institutional arrangements would be required, such as the identification of a governing body to operate the rail system. This body would not be created until there is regional consensus and agency interest in the strategies. This consensus does not currently exist.

The East Span Project’s purpose is to provide a seismically upgraded vehicular crossing between YBI and Oakland. Although multi-modal strategies were evaluated as part of the alternative definition process, no multi-modal strategies are within the purpose and scope of the SFOBB East Span Project.

The East Span Project would maintain the current vehicular capacity of the existing East Span. The implementation of any multi-modal strategy on the SFOBB would be subject to independent evaluation and funding as a separate project in the future. Not all rail systems could be accommodated by the East Span Project without significant modifications to the currently proposed design; however, the East Span Project does not create any additional obstacles to implementing a rail project, or other technologies, in the Transbay Corridor in the future.

The near-term implementation of either a road- or rail-based high-occupancy transportation multi-modal strategy would be constrained by several factors. Planning, funding, and implementing new transit services, which would be integrated with the existing transportation system in the Bay Area, would take substantially longer than the East Span Project would take to build. Implementing an HOV lane or rail-based transit facility on the East Span without additional infrastructure improvements, such as grade-separating structures or barriers, would adversely impact traffic operations on the approaches at either end of the bridge.

2.6 CONSTRUCTION ACTIVITIES

The retrofit and replacement alternatives have similar construction issues with respect to scale of work, in-water construction, and extent of laydown areas on YBI and the Oakland Touchdown area.

Scale of Work

Construction of the retrofit and replacement alternatives would require use of large-scale construction equipment and would involve labor-intensive construction activities. Noise emitted from driving large piles would be similar for the retrofit and replacement alternatives. The construction period for all build alternatives is anticipated to be approximately 6-7 years, including dismantling of the existing bridge under the replacement alternatives.

In-Water Construction

For all build alternatives, barges would be used for material delivery, dredging, drilling, pile driving, lifting, pile extraction, constructing cofferdams, and dismantling. Special barges and lifting equipment would be used to accommodate heavy equipment needed to support large-scale pile drivers. In areas of shallow water, some construction would take place from trestles and barges, and in deeper water, construction would take place from barges.

In-water construction activities would have similar impacts on the movement of commercial vessels and recreational boats, which would be diverted from construction areas. The main navigation opening near YBI would remain open during construction. The width would be reduced during construction, but not less than the minimum width required by the USCG.

Dredging would be required for portions of both the retrofit and the replacement alternatives for excavation, for cofferdams, and to accommodate barge access because some locations have water depths that are shallower than the draft of a barge. The anticipated maximum draft for the barges is 3 meters (10 feet). To ensure adequate clearance over potential irregularities in channel depth, to allow for some potential resettlement of materials in the channel after dredging and ""listing of barges during heavy lifts, the channel would be dredged to a depth of 3.6 meters (12 feet) adjacent to the Oakland Touchdown and 4.3 meters (14 feet) for the rest of the access channel. Dredging to a depth of 4.3 meters (14 feet) would also be required northeast of the USCG facility on YBI for Replacement Alternative S-4.

Construction Staging Areas on Yerba Buena Island and Oakland Touchdown

Construction laydown and access areas would be needed on YBI and at the Oakland Touchdown area for construction storage and staging. The entire eastern end of YBI would be required, except for Building 262 and the structures and some landscaped areas in the Senior Officers’ Quarters Historic District. A dock and vessel mooring facility would be constructed near the Parade Grounds and/or offshore from the eastern end of the island to facilitate the delivery of material and equipment from barges. Access to the Oakland Touchdown construction area would most likely be from surface streets located south of I-80, such as Burma Road.

2.6.1 Retrofit Existing Structure

Retrofit construction would require large-scale construction equipment and labor-intensive construction activities. Equipment used for construction of the retrofit would include delivery trucks, cranes, barges, dredges, pile drivers, concrete mixers, batch plants, cofferdams and forms, excavators, backhoes, and manual equipment to remove rivets and add bolts. The sequencing of work would depend largely on the contractor, but it is anticipated that construction activity would not be in progress concurrently along the entire length of the existing bridge. Construction is estimated to require six years to complete.

A possible construction scenario for the retrofit alternative is summarized below. Activities are described for three distinct construction areas: YBI, the Oakland Touchdown area, and in the Bay. Additional information on construction activities, impacts, and avoidance and minimization measures can be found in Section 4.14 — Temporary Impacts During Construction Activities.

Yerba Buena Island

Equipment, materials, and work crews would be transported to YBI by motor vehicles and/or barges. Contractors would require construction laydown and access areas on YBI to retrofit the YBI East Viaduct and retrofit Columns YB2 through YB4 and E1 (Figure 2-4.1 in Appendix A) and for construction storage and staging for the entire retrofit. The contractor would be responsible for arranging additional space requirements. It is anticipated that, except for Building 262 and the structures and some landscaped areas in the Senior Officers’ Quarters Historic District, all open spaces on the eastern end of YBI would be required for construction staging. Construction activities on YBI are expected to include soil and rock removal to expand and supplement footings for columns on the island and to install concrete enclosures for the towers at Columns YB2, YB3, and YB4.

Oakland Touchdown Area

No retrofit activities are anticipated in this area because retrofit work was completed for bents east of Bent 22 in March 1998. However, portions of the Oakland Touchdown area may be used for construction staging, equipment storage, and parking for work crews.

In the Bay

Construction in the Bay would take place from barges and/or trestles. Substructure (below bridge deck) activities would consist primarily of expansion of existing footings, pile caps, and columns, which may require removal of some existing material such as concrete. In areas of shallow water at the Oakland Touchdown, cofferdams would need to be constructed to provide work access at each column where foundations are being expanded. Dredging would be required to provide an access channel in shallow water for barges. Dredge quantities for the retrofit alternative are shown on Table 4.14-4. In areas of deeper water, prefabricated pile caps would be used to retrofit the columns.

Tower strengthening would be required to minimize the damage or instability that would occur during a large earthquake and to reduce displacements at the top of the tower to manageable levels. This would be achieved by encasing either whole towers or tower members in concrete. The steel towers at Columns YB2, YB3, and YB4 would be completely encased in concrete; the steel members of the towers at Columns E6 to E8 and E10 to E22 would be encased in concrete.

All foundations, except for that of Column E9, would also be strengthened to reduce and manage the displacement of the foundations.

At Columns YB2 to YB4, cast-in-drilled-hole concrete piles would be used to surround the existing spread footing foundations. The new pile caps would enclose the modified footings.

The existing timber pile foundations from Columns E6 to E16 would be strengthened and stiffened by installing a total of 44 large capacity 1.5-meter (5-foot) diameter cast-in-steel shell pipe piles around each existing column footing. A reinforced and prestressed concrete pile cap would fix the top of the new piles and surround the existing column to strengthen it and connect it to the new piles.

The existing timber pile foundations from Columns E17 to E23 would be strengthened and stiffened by installing a total of 36 large capacity 1.5-meter (5-foot) diameter steel pipe piles at the north and south ends of each existing column footing. A reinforced and prestressed concrete pile cap would fix the top of the new piles and surround the existing column to strengthen it and connect it to the new piles.

In addition, two new columns, E2A and E2B, would be constructed to support the existing cantilever structure (see Figures 2-4.1 and 2-4.2 in Appendix A). The towers for the new columns would be constructed of concrete and would be approximately 30 meters (98 feet) tall. The large diameter steel pipe piles for the new columns would need to be driven deep into the Bay mud to be founded on stable bearing materials. For Column E2B, the distance to bedrock would be nearly 91 meters (300 feet) below Mean Low Water (MLW). Construction of the new columns would require large-scale construction equipment to drive large-diameter piles, approximately 3 meters (10 feet) in diameter, into stable Bay bottom sediments or rock. Pile drivers would be mounted on deep-draft barges.

It is anticipated that retrofit activities in shallow-water areas near the Oakland Touchdown would be conducted from barges and temporary trestles constructed adjacent to the existing East Span. Dredging would be required to provide barge access in locations where the water depth is shallower than the draft of a barge.

Superstructure

Retrofit of the superstructure would include any construction on or above the lower roadway deck. Isolation bearings would be installed on top of the towers at the connections to the steel truss superstructure. Many of the truss elements adjacent to and above traffic would be strengthened and stiffened. Cross members of the truss would be strengthened or stiffened by adding steel plates, replacing rivets with high-strength steel bolts, and replacing lattice members with solid members or plating them.

A steel space frame (external edge truss) may also be used to strengthen portions of the cantilever section. These frames would extend from the top roadway deck to the lower roadway deck. In addition to the space frame, elements of the cantilever truss at the top would be removed to help isolate each of the cantilever segments from each other.

2.6.2 Bridge Replacement Alternatives

Construction of any of the replacement alternatives would require use of large-scale construction equipment, but because numerous pre-cast materials would be used with a replacement alternative, construction activities would not be as labor-intensive as with the Retrofit Existing Structure Alternative. The replacement alternatives are expected to take five years to complete plus approximately two years to dismantle the existing structure, for a seven-year construction schedule. Traffic would be diverted onto the new structure before the existing bridge is removed. As a result, seismic safety and lifeline criteria would be achieved for westbound traffic four years after the start of construction and, for eastbound travelers, five years after the start of construction.

Possible construction scenarios for a replacement alternative are summarized below. Activities are described for three distinct construction areas: YBI, the Oakland Touchdown area, and in the Bay. Additional information on construction activities, impacts, and avoidance and minimization measures can be found in Section 4.14 — Temporary Impacts During Construction Activities.

Yerba Buena Island

Temporary Construction Easements. The land within the existing easement held by Caltrans on YBI would be insufficient for all of the project’s staging and construction area requirements. While the contractor would be responsible for arranging additional construction space requirements, it is anticipated that all open spaces on the eastern end of YBI would be required for construction staging, except for Building 262 and the structures and some landscaped areas in the Senior Officers’ Quarters Historic District. A portion of the northern temporary detour would be built in landscaped areas of the Historic District. The Parade Grounds would be used for temporary administrative offices (trailers), parking, maintenance, equipment and material storage, and related activities.

Arrival of Material and Work Crews. Equipment, materials, and work crews would be transported to YBI either by motor vehicles or by barges. Trucks would use Macalla Road to deliver materials. Materials delivered by truck, during non-peak traffic hours, if feasible, may include cement, reinforcing steel, prestressing steel, structural steel for the temporary detours, falsework material and form lumber. Barges would be used to deliver larger structural segments of the bridge (piles for the tower and structural steel for the tower and main span deck). Cranes situated at locations within the temporary construction easement and/or contractor-leased work areas on the island would be used to lift materials into place. Also, some material trucked to YBI would be loaded onto barges and barged to construction sites along the bridge.

Mobilization/Grading. Grading would occur in the area surrounding the temporary detours and new structures, the Parade Grounds, and hillside areas to provide access for cranes, delivery vehicles, and other construction. Some of the most extensive grading would probably occur where the contractor is creating access to build footings for the temporary detours and the permanent structures. The graded area around the new span would need to be a minimum distance horizontally from the structure to provide adequate vertical clearance for cranes and other equipment.

Soil and rock removal would be required up slope on the island near the tunnel portal in preparation for temporary detour and transition structures, a maintenance garage, a power substation, and construction of footings for columns on the island. Graders, backhoes, loaders, excavators, dump trucks, hoe rams, compactors, survey equipment, sieves, water trucks, concrete trucks, and cranes would be used to complete this task. For the temporary detour footings positioned on hillside areas, sheet pile and/or other temporary shoring may be used to stabilize excavated areas of slope; and cement-modified soil backfill may be used to stabilize the foundations of the transition structure.

Roadway Modifications. Several roadways on YBI would require modifications as a result of construction of the new East Span. Figure 2-20 in Appendix A depicts the existing configurations of the roadways and also shows the modifications to existing roadways (represented by shading). The modifications shown are for Replacement Alternative N-6. The other replacement alternatives would require similar roadway modifications, but the vertical and horizontal changes to the roadways would be slightly different, depending on the bridge alignment.

Macalla Road would be lowered about 1 meter (3 feet) at the intersection of Southgate Road and Macalla Road. The lowered Macalla Road would conform back to the existing grade 75 meters (246 feet) up slope and about 60 meters (197 feet) down slope. The Macalla Road hairpin at the Southgate Road intersection would be shifted about 5 meters (16 feet) towards the inside of the curve.

Once the eastbound temporary detour is constructed, Southgate Road would be closed to public access for approximately 20 months. As a result, direct access from one side of the bridge to the other, east of the tunnel, would be eliminated during this period. Access from one side of the island to the other side would be via Hillcrest Road and Treasure Island Road. Vehicles traveling to or from San Francisco on the south side of the island would make a U-turn at the Hillcrest Road/Macalla Road intersection.

Before Southgate Road is re-opened, it would be realigned both horizontally and vertically and the lanes would be upgraded to standard width. It is expected that Southgate Road would be shifted approximately 13 meters (43 feet) east at its greatest divergence from the existing alignment, and the roadway would be lowered up to 3 meters (10 feet) from the existing roadway profile for all replacement alternatives. The modification would be made because the existing roadway is located where new columns and abutments would be placed.

In addition, construction of the eastbound temporary detour would require closure of the eastbound off-ramp and the westbound on-ramp on the east side of the YBI tunnel for approximately three years. Access to the SFOBB would continue through the use of the ramps at Hillcrest Road on the west side of the island. The intersection of Treasure Island Road and Southgate Road serves traffic exiting the bridge onto Yerba Buena Island on the east side of the tunnel. A temporary intersection would be constructed south of the existing intersection to serve this traffic and would require a temporary road through an existing slope approximately 35 meters (115 feet) south of Building 206 and Quarters 8.

In consultation with the USCG, the USCG road would be permanently realigned to avoid the columns of the new bridge. For each replacement alternative, the realigned road would be configured differently to avoid different column locations. The section of the USCG road that is roughly parallel to the existing bridge would be shifted south. A new gate and guard shack would be constructed for the realigned road. The access road from the USCG road to the parking lot would be moved from its present location northeast toward the access gate. This temporary access road would be in place for most of the construction period.

A portion of the access road to Building 262 would be modified in two phases (once to avoid the footings of the eastbound temporary detour and, ultimately, to avoid columns of the new bridge). The road would be modified for each replacement alternative but would be configured differently to avoid different column locations. While the eastbound temporary detour is in place, the road would be temporarily realigned approximately 50 meters (164 feet) south of the existing road (see Figure 2-20 in Appendix A). A portion of the access road leading to Building 262 would be permanently realigned approximately 15 meters (49 feet) to the south and would become a two-lane roadway that would conform to the existing single-lane dirt road approximately 115 meters (377 feet) from the eastern end of YBI.

Support Construction. A dock may be constructed on the north side of YBI near the Parade Grounds to facilitate the loading and offloading of material from barges and/or one other temporary barge dock would be constructed under the main span and adjoined to the eastern end of YBI near Building 262. Support facilities such as a maintenance garage and power substation would be constructed.

Construction of Temporary Detours and New Span. A summary of the staging sequence on YBI follows.

• Construction of the new bridge leading up to the eastern end of YBI;
• Construction of eastbound and westbound temporary detours;
• Redirecting westbound traffic onto the new bridge and temporary detour and eastbound traffic from the existing structure onto the temporary detour;
• Removal of the existing bridge from Bent 48 to YBI;
• Construction of the remaining section of the transition structure and eastbound on-ramp;
• Redirecting westbound and eastbound traffic from temporary detours onto new bridge;
• Dismantling the temporary detours and the remainder of the existing bridge; and
• Regrading and replanting vegetation.

The temporary detours would be operational for approximately two years. The period from the beginning of construction to the end of dismantling would be approximately four years. The detours may be removed as soon as they are no longer needed to carry traffic or they may be removed as one of the last steps of bridge construction on YBI, because the contractor may use them as platforms from which to construct other portions of the bridge.

New footings, new columns, and retrofitting and widening the East Viaduct would require drilling, forming, excavation, backfilling, driving piles or tie-downs, erecting steel, placing reinforcing steel, placing concrete, and constructing concrete forms. The majority of excavation would be conducted to provide access to construct the footings. Falsework would be constructed underneath the cast-in-place-concrete structures until those structures are self-supporting. Concrete might be mixed at a batch plant located either on the island or remotely. Trucks would deliver concrete to the site, and it would be poured or pumped into place. Cranes would be used for steel erection, lifting forms, placing reinforcing steel, and raising materials and equipment to locations on top of the structure.

For construction of Column W2 with a northern alternative, substantial excavation and bedrock removal would be necessary to reach the elevation of the footing. The exterior of the column would be concrete, and the interior of the column would consist of four pre-cast shell tubular units that would be filled with concrete. The tubular units would arrive on a barge via Clipper Cove and be lifted into place by crane. The bent cap atop this tubular unit would be a cast-in-place concrete box girder.

The columns for the transition structures would be cast-in-place concrete, and the deck would be a cast-in-place post-tensioned box girder. Pile drivers would be used to drive the steel H-piles that would be used for most of the footings.

Oakland Touchdown

Temporary Construction Easements. As is the case on YBI, the right-of-way available for staging operations would not be sufficient for constructi