The price tag for California's beleaguered high-speed rail project just went up again, and with inflation and construction costs rising we can expect it to just continue rising until the construction is actually all underway.

According to the latest environmental documents for the high-speed rail, released Friday, the Merced-to-San Jose segment of the rail line is now estimated to cost $19 billion, up 40% from the last estimate. And the biggest driver of the expenses for this segment is a planned 13.5-mile tunnel through a mountain at Pacheco Pass, which is part of the "preferred route" for the rail line as it stands.

Things could still change, and the Sierra Club still plans to sue to push for the high-speed rail to come to the Bay Area via Altamont Pass. But as the Mercury News reports, officials are forging ahead with the plan for the 119-mile segment as is, despite a total lack of funding thus far.

"Part of the reason we want to advance design [of the segment] further is to get a better grasp on exactly what the costs will be," says Boris Lipkin, the Northern California regional director for the rail service, who added that the $19 billion number is a current worst-case scenario.

That 13.5-mile tunnel, if it gets built, would become the longest rail tunnel in North America, surpassing the nine-mile Mount Macdonald Tunnel in British Columbia.

The unknowns, when it comes to putting boring machines to work through Pacheco Pass, are many. The mountain is comprised of a mix of shale and metamorphic rock, and while geologists will be studying the area to give the rail authority a better sense of potential costs, it won't all be easily predictable.

Map via California High Speed Rail/SFist

Darrel Cowan, a professor in the University of Washington’s Department of Earth and Space Sciences who studied the Diablo Range as a Stanford PhD student, told Bay Area News Group in 2020 that the drilling will be dicey.

"You’re drilling through soft shale, and then you run into a huge block," Cowan explained, saying that you can compare the metamorphic deposits to large nuts in a cake — which in reality could be the size of a house, and much larger than the drilling machines themselves. There's the potential to get stuck — and the project will have to plan for these contingencies.

The Pacheco Pass preferred route was selected both because it was believed to be the least costly and least disruptive option. The route will take the rail line south from San Jose's Diridon Station to downtown Gilroy, and the southeast through the pass to Los Banos, and another 55 miles east to Merced.

The 174-mile Central Valley section of the high-speed rail that's been under construction since 2015, involves 35 different work sites and will ultimately connected Merced with Bakersfield. Business plans in the last few years has had train service starting on some part of this leg by 2025 — though can we really believe that will come true?

The entire rail route connecting San Francisco to Los Angeles was estimated to be complete by 2031 at last count, but in reality service will probably start in smaller sections by that date, if it ever finds all its funding. Lipkin tells Bay Area News Group this week that a better estimate for full service on this Phase 1 segment will be "later into the 2030s." Phase 2, which adds track connecting Sacramento and Merced, and Los Angeles/Anaheim to San Diego, comes sometime after that.

As recently as October, legislators in Sacramento were debating whether to contract with a firm to design and construct the electrification system for the line — with some lawmakers starting to talk about diesel trains being a necessary interim solution if this whole project can't get funded.

Estimated costs for the whole project have ballooned from early (likely lowball) estimate of $33 billion, to $98 billion — and that was before this latest "worst-case" estimate for the San Jose-to-Merced link. But all U.S. rail projects are notorious for going way over budget.

Previously: Sacramento Legislators Are Holding Up the High-Speed Rail Project... Again