The latest twist in the ambitious plans to extend Caltrain and eventually the high-speed rail to the Salesforce Transit Center is a developer hoping to send the train tracks underground, and cover that land with new towers, one of which would be taller than the Transamerica Pyramid.If you’ve been following these elaborate plans to build a new downtown SF Caltrain stop at the Salesforce Transit Center, and all of the futuristic high-speed rail fantasies that come with it, be aware that another futuristic urbanist fantasy has entered the chat. The Chronicle reports today on an elaborate new development proposed on what is now just Caltrain tracks south of the SF’s main Fourth and King Street station, saying that (if it became reality) it would be “San Francisco’s second-densest transit-oriented development hub.”The project would extend Caltrain’s service from its current terminal at Fourth and King streets to the Salesforce Transit Center, which would allow it to accommodate high-speed rail service. https://t.co/1047V0weMZ— San Francisco Chronicle (@sfchronicle) January 8, 2025 In plain English, this scheme would put much of Caltrain’s SF tracks underground (which was already the plan for the downtown extension), but also adds an 850-foot tower to that land, one which would be even taller than the Transamerica Pyramid. There is no use or purpose described for this tower, just that the plans call for one.We wish we had some renderings of this proposal to get hot and bothered over, but alas, there are none in the new 23-page developer submission to the SF Planning Department. But this plan will be discussed at length at Thursday’s SF Planning Commission meeting, which starts at 12 noon, and will be broadcast on SFGovTV2. Image: SF Planning DepartmentStill, we have a handy map in those developer submission materials that explains the multiple prongs of this very complex endeavor. The red line is the new underground Caltrain tunnel to the Salesforce Transit Center, which is already approved and definitely going to happen, though likely at a years-long snail’s pace. The orange zone described as “4th and King Railyards” is the fugly and otherwise barren train track zone leading into and out of that Caltrain station.That orange zone gets covered with shiny office towers under this plan. Then Caltrain tracks go underground in what is being described as the “Pennsylvania Avenue Extension (PAX) Tunnel.” This effectively renders Caltrain an underground system from downtown to what we now call the 22nd Street station. And people who use that Caltrain 22nd Street station will likely notice that the map references an “Existing CalTrain 22nd Street Station” and a “Future CalTrain Station Location TBD.” Is Caltrain considering demolishing the 22nd Street station for something newer and more modern? I don’t see any other way to read this, and frankly, Potrero and Dogpatch commuters would probably welcome that with open arms.As a fun curiosity, Fifth and Sixth streets, which currently dead-end at the Caltrain station, could go all the way to Mission Creek under this proposal (maybe further with some nice little bridges). So that’s interesting.“It’s a complicated puzzle but the preliminary business case establishes what Caltrain’s needs are, the development needs are and how those could co-exist on the site,” said VP Genevieve Cadwalader of Prologis, the owner of the land on which the Caltrain tracks sit, told the Chronicle. “If you thread the needle there is something that can work for all parties involved.”Image: SF Planning DepartmentThe plans also include a timeline, seen above, and the many public agencies involved in this plan. Umm, even this best-case scenario describes 2028 as “Begin Phase 1 Building Permits.” So do not hold your breath. As the Chronicle puts it, "the project will likely take 20 years to build out."Any of this becoming reality is many years away, and maybe that’s a good thing. The SF office space market remains dismal, and even at projects for which there is demand, construction is stalled. Caltrain, for its part, is also included in those “doomsday scenario” and “death spiral” conversations affecting all Bay Area public transit. And while this plan initially appears largely paid for by the developer, you’ve got at least a half-dozen different SF city and county/regional transit authorities in this mix. So you figure there are inevitably going to be some taxpayer dollars involved.And very important, there is no mention of the potential cost of this whole thing in the 23-page packet that will be presented at Thursday’s SF Planning Commission meeting.Related: Feds Pony Up $3.4 Billion for Caltrain Extension to Salesforce Transit Center, Which Is Now Being Called ‘The Portal’ [SFist]Image: SF Planning Department