Santa Clara Valley Transportation Authority (VTA) is working to extend Bay Area Rapid Transit (BART) into Silicon Valley. VTA’s BART Silicon Valley Phase II Extension (Phase II Project) is a six-mile (9.6km), four-station extension of BART from Berryessa/North San José Station (opened 2020) through downtown San José to the City of Santa Clara. The Phase II project is planned to include an approximately five-mile (8km) subway, three stations with underground platforms (28th Street/Little Portugal, Downtown San José, and Diridon), one ground-level station (Santa Clara), a train maintenance and storage facility, as well as other ancillary facilities.

TUNNEL OVERVIEW

VTA selected a single-bore tunnel over a twin-bore for the Phase II Project after extensive reviews, studies and industry feedback comparing cost, schedule, risks, and constructability of both alternatives. The singlebore tunnel significantly limits the amount of utility relocations and cut-and-cover construction in public right-of-way, thus reducing surface-level impacts (i.e. street closures and business disruptions) in Downtown San José while also providing operational flexibility. The single-bore tunnel was selected with public and city-input and was approved during the environmental clearance phase by BART and VTA.

One of the most unique elements of this project’s single-bore tunnel is that station platforms are inside with the twin-track guideway, and vertical circulation at stations is provided in shafts adjacent to the street and which connect to the tunnel and platforms via mined adits (Figure 2). With the platforms inside the tunnel, construction can largely take place off the street to buildout the station, reducing the need to close downtown San José’s streets. This configuration is the first of its kind for a transit project in the US. However, a similar project, albeit at a smaller scale is Barcelona’s Metro Line 9.

CONTRACTING OVERVIEW

VTA is delivering its Phase II Project in four contract packages (CPs). CP1 is Systems, and it focuses on system-wide train control and rail communication systems. CP3 will construct Newhall Yard and Santa Clara Station. CP4 includes fit out of the underground stations. These three contracts will be procured using the design-build method.

CP2 Tunnel and Trackwork – the largest valued contract – includes the procurement of an approximately 48ft external diameter tunnel boring machine (TBM), tunnel excavation, excavations for the three underground stations, trackwork within the tunnel, portal structures, and the two mid-tunnel facilities. This contract will be procured using an innovative procurement method called Progressive Design Build (PDB), which selects a designer-contractor team based primarily on their qualifications to perform the work. The design will be developed jointly with the VTA prior to agreeing on a final cost for constructing the project.

For the PDB contract, VTA initiated a prequalification process in early 2021 which resulted in a shortlist of three joint ventures with significant experience in large, complex underground construction projects and with alternative delivery methods like PDB. The three shortlisted teams will be submitting proposals including technical and management approaches, design schedule, and design stage pricing which will be used to select the preferred bidder.

Once the PDB contract is awarded in spring 2022, the project will go through a Programming Services phase where the contractor and VTA will jointly evaluate design concepts and alternatives and agree on the configuration to advance to final design. Following Programming Services, design work will advance to a more mature level to allow the contractor to develop a cost and construction schedule estimate. Both cost and schedule estimates will be ‘open-book’ and provide full visibility to VTA on how both the scope and risk are priced by the contractor. At the end of the design phase, the contractor will submit a formal cost proposal which will be used to negotiate a lump sum contract amendment to complete the remainder of the work.

To meet VTA’s desired overall program schedule, it is likely some construction activity will need to start prior to agreeing to the overall contract value and begin during the design phase. In these instances, VTA allows for the contractor to propose early works packages which will be negotiated as lump sum, standalone contract amendments and can be authorized prior to agreeing on the overall contract price. Some potential early works packages which will be considered by the contractor include TBM procurement, utility relocations, demolition and portal excavations.

CONTRACTING NEXT STEPS

CP1 and CP2 are set to begin in mid-2022 and extend until 2028 (CP2) and 2029 (CP1), while CP3 and CP4 are both set to start in late 2023 and extend until 2028. Revenue service is scheduled to begin in 2030.

More information on VTA’s BART Silicon Valley Phase II Project is available at
www.vta.org/bart