page_title: Silicon Valley BART extension
section_title: Downtown San Jose/Santa Clara extension
hierarchical_section_title: Silicon Valley BART extension / Phases / Downtown San Jose/Santa Clara extension
caption_attribution_description: Santa Clara station
context_page_description: The Silicon Valley BART extension is an ongoing effort to expand service by Bay Area Rapid Transit into Santa Clara County from its former terminus at the Fremont station in Alameda County. Planned since at least 1981, the project has seven stations in three sequential phases. The first phase was the Warm Springs BART extension, built by BART at a cost of $790 million, terminating at the new Warm Springs/South Fremont station that opened in 2017. The Warm Springs extension broke ground in 2009, and was originally scheduled for completion in 2014.
  The $2.3-billion second phase, known as phase I of Silicon Valley BART extension or the Berryessa extension, includes two new stations, the Milpitas and Berryessa/North San Jose stations. The Berryessa extension broke ground in 2012, and was originally scheduled for completion in 2016. It opened on June 13, 2020.
  The Santa Clara Valley Transportation Authority built the Berryessa extension, and intends to build the final downtown San Jose extension, but BART operates and maintains the completed portion of the extension and will also do so for the final phase when completed.
context_section_description: The final Downtown San Jose/Santa Clara leg has been planned through downtown San Jose to Santa Clara at an estimated cost of $5.6 billion. This third phase, 6 miles (9.7 km) long, is largely underground, featuring a 5-mile-long (8.0 km) tunnel. It would continue south from Berryessa, entering a tunnel to cross the Bayshore Freeway before continuing to a 28th Street/Little Portugal station on the city's "east side". From there, the tunnel would continue west under Santa Clara Street to a Downtown San Jose subway station, which would be an interchange station to VTA light rail lines on the surface at Santa Clara. The original proposal had additional subway stations between Alum Rock and Downtown at Civic Plaza/SJSU and Plaza de César Chávez, but these were consolidated into a single station to cut costs. The line would continue underground to the San Jose Diridon station, a transfer point to Amtrak, Caltrain, Altamont Corridor Express, VTA light rail and bus, and the planned California High-Speed Rail system. The proposed BART subway station would be named "Diridon" to match. The extension would then surface and continue to the site of the current Santa Clara Caltrain Station. A 40-acre (16 ha) BART maintenance yard would also be created at Newhall as part of this phase, using land just south of Santa Clara station that was purchased by VTA from Union Pacific. Like the Berryessa Extension, it would be built by VTA, but operated by BART. 
  After funding was secured for Berryessa (the first phase of the Silicon Valley Extension) in March 2012, VTA began looking for additional funding to complete the $5.6 billion second phase. Completion is expected in 2029–2030.
  In late 2017, a disagreement arose between VTA and BART over whether the tunnel should have a single bore or dual bores. VTA favored a single 45-foot-wide (14 m) bore, configured as a double-deck stack, with one track on the upper level and one on the lower level. VTA preferred a single bore to shorten the construction schedule and avoid cut and cover construction in Santa Clara Street for station sites. City officials believed cut and cover construction would be disruptive to streets and businesses, citing the construction of the Market Street Subway as evidence.  The single-bore design is newer, but less tested in the United States. However, BART preferred dual bores, as used elsewhere in its system, to cut construction cost and standardize the procedure for emergency evacuations. The twin bores would each be 20 feet (6.1 m) wide, and separated horizontally. Local businesses, cities and VTA were lobbying for a single bore in 2018. The design decision was postponed for three months; in March, BART and VTA reached agreement on a single bore.  The $125 million contract for engineering the single bore tunnel was awarded to a joint venture bid placed by London-based Mott MacDonald and San Francisco-based PGH Wong Engineering.
  Initial construction and soil sampling began in January 2019. In September, it was announced that the project would be delayed three to four years, with revenue service to begin in 2029–2030.
caption: Site for planned Santa Clara BART station and Newhall Yard, taken in 2017 from the island platform of the Santa Clara Caltrain station. Avaya Stadium can be seen in the background.
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