The San Jose City Council and Valley Transportation Authority (VTA) staff agreed with San Jose Downtown Association on three key decisions for BART’s upcoming extension into San Jose. Now it’s up to the VTA Board, although BART staff have raised objections to digging a single-bore tunnel.
BART construction on the extension from Berryessa (North San Jose) to Santa Clara beneath downtown San Jose is expected to begin in 2019 and finish in 2026.
The City’s recommendations from Sept. 19:
Build the Downtown Station between Market and Third streets under Santa Clara Street. This was favored over a subway station closer to City Hall because of development potential; existing and projected densities; proximity to light-rail, Bus Rapid Transit and Transit Mall connections; and direct access to VTA’s property on Santa Clara and Market streets for construction staging.
Build the Diridon BART station near Santa Clara Street across from SAP Center rather than a couple blocks further south. Likewise, the preferred location offers construction, development and density advantages, plus synergies with future high-speed rail connections and avoidance of potential clashes with the Trammell Crow development project.
The key recommendation is to bore a single tunnel that is 85 feet under Santa Clara Street rather than two tunnels at 55-foot depth. This single-bore method, operational in Barcelona, Spain, would feature 14-foot platforms and trains traveling in opposite directions, one on top of the other, outside the stations.
By single-boring through downtown San Jose:
There would be no street-level “cut-and-cover” excavation, thus minimizing business, traffic and pedestrian impacts.
The amount of dirt and excavated materials to be removed would be drastically reduced. The number of trucks through downtown would decrease from 15,000 to about 1,250.
Construction schedule would be reduced by nine months.
The downtown station would be substantially shorter than a twin-bore station because a cross-over track would be eliminated.
Construction cost would be $70 million less.
Annual operating costs would increase about $1.6 million (2.8 percent).
BART staff, however, at a VTA Board meeting Sept. 22, disagreed with the single-bore approach, raising safety and operational concerns. The single-bore tunnel would be a first for a North American subway – all of BART’s current underground stations and tracks are in a twin-bore tunnel alignment.
The VTA Board was originally scheduled to make final alignment decisions Oct. 5, but given BART staff objections, will use that meeting to continue the discussion on the single-bore tunnel issues.
At the City Council meeting, all of San Jose’s five representatives on the VTA Board signed a memo recommending the single bore, including Mayor Sam Liccardo, and downtown Councilmember Raul Peralez.
“We must make every effort to protect businesses from the construction impacts,” said Vice Mayor Magdalena Carrasco, who emphasized the problems with Alum Rock Bus Rapid Transit — a much smaller project than BART — cannot be repeated as the subway is built under Santa Clara Street.
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