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BAY BRIDGE

MTC Bay Bridge Rail Feasibilty Study

CHAPTER 6. CONCLUSIONS AND NEXT STEPS

This feasibility level analysis was designed to identify possible transbay rail options and to determine whether any of these options is feasible from a structural engineering perspective, based on their impact on the Bay Bridge. The study was limited to the retrofitted west spans and the proposed replacement East spans of the Bay Bridge. The four rail technologies included in the study were light rail, BART, commuter rail and high speed rail.

The study concluded that it is feasible to incorporate any of the rail technologies on the Bay Bridge, but at very high cost. The high cost of putting rail on the Bay Bridge is primarily the result of adding live and dead weight to the West spans, which are being retrofitted, but not replaced under the current plan. Adding a significant amount of weight to that structure would almost certainly require seismic and structural strengthening work on the foundations and the main cable, even if a lighter decking material were to be implemented. The cost for structural improvements to the configuration studied in this analysis could be as high as $3 Billion, with significant additional investment required for rail infrastructure, rolling stock and operations.

This feasibility level study was not intended as a substitute for a full corridor study. As the demand for transbay travel increases, additional capacity and additional alternatives to the private auto will be needed. BART's Transbay tube will soon reach capacity, and transbay buses, mixing with vehicular traffic for at least a portion of their route, may not be able to compete for the market share that could otherwise be gained by transit. While the cost of adding rail to the bridge is high, the cost of doing nothing may be higher, in terms of hours of delay, impact on the region's economic vitality and quality of life.

To determine the true costs and benefits of this potential rail crossing, other opportunities for transbay transit services must be considered. The next step would be a full multi-modal corridor study that could compare the benefits of putting rail on the Bay Bridge to other potential transbay transit projects. These could include a busway, a second bridge (either a rail bridge or auto bridge, relieving the need to retain full roadway capacity on the Bay Bridge itself), or a new submerged tube for rail service. Any of these alternatives appear to be feasible and workable with the underground rail terminal in the basement of the Transbay Terminal.

MTC has committed to completing a Bay Crossing Study that would further the analysis done in this feasibility study and would provide the information necessary to compare this potential investment against investments in other modes or rail options. MTC will be studying a number of new Transbay crossing options including:

  • Additional or expanded auto bridges, with or without rail service
  • An rail tube under the Bay
  • A second BART tube
  • A rail tube connecting Oakland and San Francisco airports
  • Expanded ferry service
  • Expanded bus service and busway options
If after a feasibility level study of the other options, rail on the Bay Bridge remains competitive, a more detailed study of the bridge structures is required. This more detailed study would not complete significant engineering, but would help to better understand the improvements needed and the costs of construction.

A sample workplan would include:

  • Adopt an optimal location for vehicles and rail on the bridge to develop a more detailed structural assessment and cost assessment.
  • Assess the feasibility highway operations impacts of placing rail on the deck of the existing structure and placing additional vehicle lanes on either side or below the structure. While this option appears to be structurally feasible, no highway operations assessment has been completed.
  • Develop a more detailed understanding of the life cycle implications of alternative decking materials, including newer light weight technologies that are not currently used by Caltrans.
  • Finalize selection of the train system and set operational speeds over the bridge given the alignment geometry and the service and seismic movements of the bridge.
  • Develop three-dimensional computer models of the East and West spans and the Yerba Buena Tunnel. Include the proposed structural modifications for adding rail to determine the structural integrity and the need for additional seismic improvements if this work is completed.
  • Complete both service and seismic analysis and design for the selected rail and deck scenario.
  • Define required realignments of roadway ramps and alignment of rail into San Francisco and through the Oakland Mole, and include costs of ramp changes in the overall cost estimate.
  • Prepare a refined cost estimate.

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