When a subway project runs late, the boring machine usually takes the blame. Seattle’s Bertha stalled under downtown for two years and became the cautionary tale anyone brings up when a transit agency signs off on a giant custom borer.<\/p>\n
The BART extension into San Jose has the opposite problem. The machine is the part that’s finished.<\/p>\n
Herrenknecht built it at Schwanau in southwest Germany, put it through factory acceptance testing, and handed it over at a ceremony where founder Martin Herrenknecht pressed a buzzer alongside the client to start the cutting wheel turning. It measures nearly 54 feet across. By Herrenknecht’s own account<\/a>, the main drive alone weighs more than 300 metric tons, which is about 330 US tons before you bolt a single other component to it.<\/p>\n What the machine doesn’t have is a hole to go into. The five-mile tunnel it was built for is still in design, the contract to dig it was pulled apart last summer and restructured again this month, and on June 17 a Santa Clara County civil grand jury put out 40 pages arguing that the agency in charge has no credible plan for the money.<\/p>\n That figure covers the main drive on its own. It’s the assembly that spins the cutting wheel, and Herrenknecht’s photo report on the build shows it going in first, lifted by gantry crane onto the shield before crews secured the stud bolts and hung the motors.<\/p>\n The blue-painted center of the cutting wheel came next at roughly 150 metric tons, and the four wheel segments were bolted on around it. Behind all that sits the conveyor screw, because this is an earth pressure balance shield, the type built for wet, loose ground rather than rock.<\/p>\n That choice is deliberate. The ground under San Jose is sand, gravel, silt and clay with a high water table, a very different job from the diabase the Gateway machines are cutting in New Jersey<\/a>.<\/p>\n Herrenknecht turned 50 last year and builds most of the machines you read about. The 700-ton borer heading for New York’s Second Avenue subway<\/a> is one of theirs, and so are the four assigned to the new Hudson River rail tunnel<\/a>. The San Jose machine is bigger than any of them.<\/p>\n Most subways get two tubes, one per direction, with the stations dug separately as their own construction projects. San Jose is doing the reverse.<\/p>\n The single bore is wide enough to carry both tracks side by side plus the passenger platforms for the Downtown San Jose and Diridon stations inside the tube itself, connected to street level by passageways. VTA says it would be the first single-bore subway tunnel in the United States.<\/p>\n The argument for it is what happens above ground. A twin-bore approach through downtown would have meant cut-and-cover work along Santa Clara Street, which is exactly what businesses on that street spent years objecting to. VTA’s board reaffirmed the single bore in October 2025 after an independent peer review, and the bore alone carries an estimated price of about $3 billion<\/a>. Los Angeles Metro has been weighing the same one-tube approach for its Sepulveda corridor<\/a>, which is still in procurement.<\/p>\n The grand jury makes a sharper point about when the decision actually became final. It notes that VTA approved fabrication and purchase of the $76 million machine in December 2022, and that buying a borer of that diameter effectively locked in the single-bore design before the wider argument was settled. San Jose Mayor Matt Mahan said as much in late 2023, telling the Mountain View Voice there was no turning back.<\/p>\n The joint venture standing next to Martin Herrenknecht at that handover was Kiewit Shea Traylor, made up of Kiewit Infrastructure West, JF Shea Construction and Traylor Brothers. KST won the tunnel and trackwork package in 2022 under a progressive design-build deal worth $235 million for the initial stage.<\/p>\n By June 2025 that arrangement had come apart. VTA said it had received “repeated proposals exceeding twice the project budget”<\/a>, triggered an offramp clause and told its board it would go find someone else to dig. The grand jury reports that VTA believed KST’s proposed design could add as much as $1 billion to the project.<\/p>\n The machine stayed. VTA owns it outright, which the agency’s own peer review flagged as a transfer of risk rather than a saving, since an agency that owns a one-off borer also owns its performance. VTA’s answer was to plan on embedding Herrenknecht engineers with the tunneling crew.<\/p>\n Then it changed course again. VTA reported on July 9 that its board had approved moving KST’s tunnel and trackwork contract onto a target price, incentive-based model with “open-book accounting”<\/a>, and authorized $400 million for early works, with further funding requiring separate board approval.<\/p>\n That matters because of what the previous plan looked like. In November 2025, VTA said it expected to issue a fresh tunneling solicitation in the first quarter of 2026, award it in the second quarter of 2027 and begin tunneling in 2029. The agency now says the project is being re-baselined to produce updated cost and schedule figures.<\/p>\n The civil grand jury report<\/a> landed on June 17 and its conclusion is not subtle. The panel found that the VTA board had “failed in its responsibility to provide effective management, oversight, and financial control” of the project.<\/p>\n The cost history is most of the case. The extension was estimated at $4.7 billion in 2014, $6.9 billion in 2020, $9.1 billion in 2022 and $12.2 billion in October 2023. It now sits at $12.7 billion, with revenue service targeted for 2037. The federally appointed oversight consultant models 2039.<\/p>\n The funding side is thinner than the headline number suggests. VTA asked the Federal Transit Administration for $6.3 billion and was capped at $5.1 billion in August 2024. The grand jury puts the remaining hole at roughly $1.075 billion, part of it resting on a sales tax measure that has not gone to voters yet.<\/p>\n Ridership is the number that should worry anyone in Santa Clara County, because VTA is contractually on the hook for the net operating cost of running BART inside its county. Phase I forecast 20,110 daily riders at Milpitas and Berryessa. January 2026 actuals came in at 2,789. Phase I has lost an average of $69 million a year across its first five years of service.<\/p>\n For Phase II, VTA’s own records put average annual operating, maintenance and capital costs at $274 million for the first three years against $60 million in fare revenue. That is a $214 million annual gap before anything goes wrong.<\/p>\nThe 300-ton number is just the motor<\/h2>\n
San Jose is putting the stations inside the tunnel<\/h2>\n
VTA owns the machine, so VTA owns the risk<\/h2>\n
The grand jury put numbers on the argument<\/h2>\n