One of many world’s largest deliberate subway tunnels — bringing BART trains by downtown San Jose — might get 20% larger.
On Friday, Santa Clara Valley Transportation Authority officers unveiled a plan to develop the controversial tunnel’s diameter from 43 to 48 toes, in regards to the width of a four-lane freeway, in an effort to fulfill issues over passenger entry and station security. The brand new tunnel proposal, nonetheless being finalized, would require constructing a fair bigger boring machine to excavate mammoth sums of earth because it crawls almost 5 miles below San Jose.
For critics already involved about ballooning building prices on the biggest building venture in Santa Clara County historical past, the VTA now says a wider tunnel might really make the venture cheaper. And a presentation on Friday gained uncommon approval from downtown San Jose’s main enterprise pursuits, who would bear the brunt of building, transit advocates and a few BART board members.
The primary change for Bay Space riders — who're anticipated to lastly see a downtown San Jose BART extension within the early or mid 2030s — is that trains would run side-by-side with one platform separating east and westbound BART vehicles.
The prior smaller tunnel plan had the trains stacked on high of each other, requiring passengers to navigate between platforms.
“Aspect-by-side tracks is an actual recreation changer for the one bore venture,” mentioned Scott Knies, San Jose Downtown Affiliation govt director. Knies acknowledged that a bigger tunnel bringing cheaper prices was a “bit counterintuitive.”
“There’s no concern of, ‘Am I on the proper platform degree?’ ” BART’s Assistant Common Supervisor Carl Holmes mentioned throughout a joint BART and VTA assembly on Friday.
BART, which is able to take over operations of the rail line after VTA builds it, additionally mentioned the brand new design alleviates evacuation security and air flow issues posed by the stacked platforms.
This isn't the primary time the VTA proposed a bigger tunnel. Santa Clara County residents watching the long-delayed venture would possibly do not forget that earlier than April 2020 venture planners proposed a record-breaking 55-foot-wide subway tunnel. However the VTA then backtracked to a 43-foot diameter amid spiraling price and threat estimates.
Now, VTA and BART planners mentioned just lately employed contractor Kiewit Shea Traylor advised them that an enlarged 48-foot tunnel diameter will result in a less expensive general venture as a result of side-by-side platforms are simpler to construct. Takis Salpeas, VTA’s lead for the venture, mentioned they're additionally limiting prices by lowering the scale and depth of the twenty eighth Avenue Little Portugal Station from 88 to 77 toes underground.
“Whenever you add all of that up, the financial savings overcome the price of the diameter and the muck elimination,” Matt Scott, the managing accomplice at Kiewit Shea Traylor, mentioned Friday, including that the development staff can “stand behind” their cost-saving guarantees.
The huge tunnel design, often called single-bore, has lengthy been controversial amid booming prices which might be estimated to hit $9.1 billion, in response to a federal estimate, a $2.25 billion enhance over the present price range. Whereas the VTA initially downplayed the federal estimate’s price overrun issues, the company now acknowledges needing to safe the entire funding to make sure federal dollars for the venture.
In 2018, the VTA and BART boards agreed to dig one of many world’s largest subway tunnels with a single bore as a substitute of a extra typical twin bore, which might construct smaller parallel tunnels however would require tearing up massive sections of Santa Clara Avenue. Critics argued that the single-bore design compromises the expertise of riders by requiring passengers to descend almost 90 toes to get from the road to their trains and failing to offer a number of station entrances.
Issues over the single-bore tunnel design pressured the VTA board to fee an impartial panel of specialists to evaluate the fee and design impacts of the single- versus twin-bore design. Whereas that ongoing evaluate will present suggestions on tunnel designs, VTA officers haven't indicated any plans to change their tunneling plans.
Because the widened tunnel alleviates some passenger entry issues, transit advocates have shifted their worries to the variety of station entrances. The VTA is contemplating including new entrances, however the present plan for the downtown San Jose station solely contains entrances on the north aspect of Santa Clara Avenue. BART’s Carl Holmes mentioned his company is reluctant so as to add further entrances that might make working the stations harder as soon as VTA palms over the keys.
However transit advocates say a venture of this scale calls for a number of entrances.
“It's doable to ship entrances on either side of the road from day one,” Adina Levin of Seamless Bay Space, a transit advocacy group, mentioned on the board assembly.