While there are technically three possible routes by which trains are slated to eventually reach San Francisco’s new Salesforce/Transbay Transit Center, in terms of the most probable path, there are really only two.

While a Citizens Working Group convened to study the potential paths continue to include a Mission Bay alignment, which would re-route the Caltrain tracks up Third Street, north of 23rd, and bypass the current terminus at 4th and King, we’re putting the probability of the Mission Bay Alignment coming to fruition at less than 5 percent.

Our odds are based on a presentation by the San Francisco County Transportation Authority to the Transbay Joint Power Authority’s Citizens Advisory Committee on Tuesday, a presentation which highlighted the need for three tracks “to provide reliable and dependable service at Salesforce Transit Center,” the “strategic and tactical significance” of the railyard at 4th and King, and the “significant residual operational value” of the railyard as well.

In addition, the TJPA is pushing forward with detailed plans and refinements for undergrounding the station at 4th and King and tunneling to the Transbay Center, with a focus on reducing the amount of “cut-and-cover” to “minimize surface disruption and socio-economic impacts,” albeit at a higher projected project cost.

In terms of timing, the projected budget for tunneling alone is currently running between 51 and 77 months, depending upon the approach. And that doesn’t include the budget for securing the necessary Environmental Clearances, which was preliminarily expected to take between 18 and 60 months.

In other words, we’re looking at a mid-point expectation of around 9 years to complete the Downtown Rail Extension (DTX) once the preferred approach has been approved, which would suggest rail service to the Salesforce/Transbay Transit Center isn’t likely to be operational until 2030, at the earliest.