VTA Confirms Preferred Tunnel Alignment and Configuration

Construction of the tunnel boring machine entrance is underway at the BART Silicon Valley Phase II West Portal site in Santa Clara.

Caption and Image courtesy of VTA

SAN JOSE, Calif. - Valley Transportation Authority (VTA) confirms the large single bore as the preferred tunnel configuration for the BART Silicon Valley Phase II project.

VTA says this decision follows a peer review that was conducted by “tunneling and transit experts from major transit agencies across the country.” In a meeting with the VTA Board of Directors on October 17, the Board voted in favor of a single bore as “the most viable option,” due to the cost, constructibility, and risk associated with the project. Using two boring machines would include a higher cost, a more complex approach, and disruption of downtown. It would have required a “cut-and-cover” excavation.

This now allows the project design to advance to 60% and meet the projected service date. During the meeting, the panel included suggestions to “ensure greater cost estimation, accuracy and budget alignment, reduce schedule delays, and manage tunnel risk.” The VTA owns the tunnel boring machine (TBM), and as such, it assumes responsibility for its performance. In managing this responsibility, the VTA says it will utilize a “top-tier tunneling team and embed Herrenknecht engineers” to offer support. Additionally, VTA will continue to engage with the industry to “secure experienced construction teams” and to develop its contract strategy. By using a peer review, this “reinforces the importance” of the partnership between VTA and BART with both committing to establishing “regular touchpoint and prioritizing communications between agencies.”