City Staff Aligns Behind a Pennsylvania Ave. Tunnel for Downtown Connector

Mission Bay alignment receives poor marks as plans to bring trains into the Transbay Transit Center finally move forward

SF Planning staff's recommended alignment, now approved, follows the original DTX plan (green), but with an extended tunnel under Pennsylvania (orange) to help reconnect Mission Bay. Image: SF Planning
SF Planning staff's recommended alignment, now approved, follows the original DTX plan (green), but with an extended tunnel under Pennsylvania (orange) to help reconnect Mission Bay. Image: SF Planning

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San Francisco’s Downtown Extension (DTX) project, to get Caltrain and future High-speed Rail into the Transbay Transit Center, may finally be back in motion.

SF Planning, with the support of other city and county agencies, has completed a supplemental study of the DTX project alignments. Dubbed the “Rail Alignment and Benefits Study (RAB),” it helps narrow down the best way to get the trains from the current terminus at King Street Station to Transbay. City and county staff are recommending the project follow the original DTX alignment, approved 16 years ago, but with the tunnel extended under Pennsylvania Avenue. The city unveiled the recommendations during a presentation yesterday evening at the San Francisco War Memorial Performing Arts Center across from City Hall.

This supplemental plan should be cleared by the Feds this summer or Fall, explained Susan Gygi, an engineer who worked on the proposal.

This should finally put one of the alignments, the Mission Bay route, to rest. As reported previously, this supplemental study was done in part to look for ways to eliminate the remaining grade crossings on the Caltrain alignment through San Francisco (more on that below). The Mission Bay alignment would have run in a tunnel under Muni’s T-Third line, where utilities have already been cleared, making a tunnel simpler to build. But some felt it was only done with the hopes of adding a station in Mission Bay, to support and anchor real estate developments there.

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SF Planning Director John Rahaim at yesterday’s presentation of the Rail Alignment and Benefits Study. Photo: Streetsblog/Rudick

Whatever the reason, many remain perturbed that this supplement added so many years to the project. Editorials in this publication and others have criticized the delays and bemoaned the fact that the Transbay Transit Center will open as a very expensive bus stop or a “Grand Central Station of the West” without any trains. “It’s frustrating that it’s taken as long as it has to get where we are now,” said Peter Straus of the San Francisco Transit Riders, who came to hear the presentation. “But they’ve come up with a viable solution and we want the city to buy into it and move it ahead as fast as we can.”

The DTX “… is a 100-year decision,” said SF Planning Director John Rahaim. He likened it to when New Yorkers figured out the configuration for Grand Central Station’s approach tracks under Park Avenue. “They covered over the tracks on Park Avenue 90 years ago…. it’s important that we get this right.”

The rail components of the future Transbay Transit Centers train station. Image: SF Planning
The rail components of the future Transbay Transit Centers train station. Image: SF Planning

SF Planning studied two basic supplemental alignments, as seen in the lead image. The Mission Bay alignment was rejected by staff, said Rahaim, because it scored weakest on a cost-per-rider analysis. According to the study, the Mission Bay alignment (the blue line on the map in the lead image) would cost $9.3 billion and would not be completed until 2031. The “surface alignment” (the green line), would follow the original DTX proposals to build a tunnel from near the current King Street station and travel underground to the Transbay Terminal basement train box, but retained Caltrain’s current surface alignment south of King Street Station. It would cost $5.1 billion and get completed by 2026.

City and County planning staff united behind the so-called Pennsylvania Avenue alignment, which is similar to the “surface alignment” but has a much longer tunnel to eliminate grade crossings in San Francisco. If the plan is approved and the city moves forward, construction on this option would be completed in 2027 and would cost around $6 billion. The justification for the extra tunneling and cost? “It was decided that leaving grade crossings at 16th Street and Mission Bay Drive was unworkable, as far back as 2012 and even earlier,” explained Gygi in a follow-up call. Gygi said that given the additional train volumes, crossing gates would be lowered for roughly a third of every hour, a serious problem for ambulances headed to UCSF Medical Center.

The idea of trenching the street was also nicked, because, as shown in the graphic below, it would ruin the streetscape:

Staff is recommending a tunnel under Pennsylvania to avoid streetscapes such as this. Image: SF Planning
Staff is recommending a tunnel under Pennsylvania to avoid streetscapes such as this. Image: SF Planning

Gygi likened the undercrossing idea seen above to the environment around Geary and Masonic and Geary and Fillmore, although she added it would be double the depth. That’s why in the supplemental study they decided it would be worth the extra costs just to leave the streets at surface level, and instead extend the train tunnel.

The good news, she explained, is a train tunnel under Pennsylvania Avenue could be built in phases. They could build the tunnel envisioned in the “surface rail” plan by 2026 and start running trains into Transbay. The Pennsylvania Avenue tunnel would be completed a year later. It would take “a couple of weekends” to build the crossovers and start running trains all the way in a tunnel, explained Gygi. At that point the remaining surface tracks would be removed.

All the proposed alignments scored well for a future Transbay connection that would allow Caltrain and HSR to continue through a new tunnel from Transbay to Oakland and points farther east. When that would be built is still anybody’s guess. The study is also looking at ways to construct a turnback loop so trains can run through the Transbay Transit Center as fast as possible.

Whatever the individual reservations, most in the audience expressed enthusiasm for finally getting the DTX project moving again. “I’m really eager for San Francisco to solidify around a plan so the region can move this forward,” said Ratna Amin, Transportation Policy Director for SPUR.

Still, “The goal isn’t to finish the study,” quipped Straus, “it’s to get the damn trains running.”

For more information, the full study is available online.

  • Kieran

    I don’t mind the Pennsylvania st tunnel that’s proposed, partly because they’ll just move the existing 22nd st station and have it replaced except it’d be underground as depicted in the conceptual map in this article..

    Though as I’ve stated many times before, Caltrain and high speed rail should’ve already been connecting to Transbay Terminal in terms of having the infrastructure built at the very least…It’s a damn shame that it’s taken this long to get something built that’s only a couple miles long(counting the Pennsylvania st tunnel). Just get it built before the 2030s(and of course that’s being generous at this point).

  • Mike Jones

    Three right-angle curves on the way into the Transbay Terminal? Were talking about intercity trains, not bumper cars! Hardly a once in a lifetime decision.

  • ride_it_like_you_stole_it

    It could be straightened out for the low low price of an additional $4 billion and an extra 5 years of time. I have a hard time imagining how the first $5 billion will be found when there are multiple other billion dollar projects being proposed in the Bay Area simultaneously (second transbay tube, shoring up the seawall, and each mile of new subway)

  • p_chazz

    The sharp curves could pose a problem for train operation in future years. One likes to think that the sharp pencils calculated turning radii that could accommodate train operations, but considering the design problems the “Oakland Wye” has caused for BART, that is by no means a foregone conclusion.

  • Kieran

    You have a point about the Oakland wye, which could’ve definitely been done with less curves on both sides but that’s a whole nother thread..

    Obviously the Mission Bay alignment is much straighter than the Pennsylvania st tunnel but since it’ll cost many more billions to get the Mission Bay tunnel done and hence many more years before ground’s even broken on it, just so Caltrain/high speed rail MIGHT go to Transbay Terminal within our lifetimes I’ll settle for the Pennsylvania st tunnel.

    Ideally if the Mission Bay alignment were done, it could have a massive station underneath the Warriors Arena which would in turn also connect to UCSF and be a short walk from the Giants stadium. Not to mention also connecting to 16th st which would be served by another branch of the 22 Fillmore after the temporary 55 16th st line gets replaced when the overhead wire’s finally extended along the current 55 route.

  • Second tube is generations away from being built if it ever gets built.

    The Bay Area repeated the mistakes of LA…encouraged sprawl, ignored infrastructure, and never figured out how in the world all these additional folks would get around. The area keeps setting records, but not in a good way…5th worst congestion in the world, 4th straight year hitting record highs of congestion, etc.

  • I’d settle for HSR/Caltrain ending at 4th/Townsend. Build a big station, allow development of air rights, and call it a day.

  • ride_it_like_you_stole_it

    Even with that, you’d probably still want the tunnel up to 4th/Townsend.

  • keenplanner

    There is already an alignment. Why not just tunnel under it?
    It’s shameful that Caltrain still doesn’t go to the Transbay Terminal. How many years has MTC and SF been wanking on this one? And then-mayor Willie Brown derailing the project mid-stream. Epic fail for everyone in planning and transportation in SF.

  • DrunkEngineer

    Tear down I280 and there are any number of grade separation options that don’t require tunneling.

  • LazyReader

    All very lovely paintings and doodles, except assuming California high speed rail is ever finished. Finishing the high-speed rail line from San Francisco to Los Angeles is now expected to cost $77.3 billion in it’s latest cost estimates.
    10 billion more than 2016 assessments and a MASSIVE jump from 25 Billion when the project was under conception in 2000. It’s a decline from 100 billion, when governor Brown let the cat out of the bag and realized that this project was gonna cost over 98 Billion, he knew this project was losing steam so he converted the project to a blended system where shared moderate quality rail and new rail the trains would ride on. Governor Jerry Brown was hoping to finish the project with cap-and-trade money, but the state received less than $665 million in cap-and-trade funds in 2017, of which 25 percent was dedicated to the rail project. At this rate, unless the authority finds another pot of gold somewhere, it will take nearly 400 years to complete construction. Maybe back in 2008 it might have been easy to believe that $9 billion was a good start on a
    $25 billion project, since the federal government might pick up another
    $9 billion and the rest could come from a variety of sources including
    private operators But with the cost rising to $77 billion for a project that won’t
    keep its original promises, with little prospect for more federal
    funding and no prospect for private investors, it seems likely that this project is destined to fail, and the city is spending money for infrastructure for a train that wont arrive. HOW expensive does something have to get before even it’s enthusiasts admit it’s too expensive.

  • What gets me is that in SF, it will still take 45+ min to get to the HSR station from most areas of the city because our city mass transit is inadequate. Let’s focus the $$$ on upgrading and integrating local/regional transit first.

  • LazyReader

    I suppose. Intercity travel is only a small portion of the travel market. 90% of all miles traveled daily is less than 50 miles per day (commute) spending 80 Billion on something when buses are cheaper and planes faster.

  • Kieran

    Sad thing is I wouldn’t be surprised if that gets seriously proposed as a suggestion in the coming months..

  • Richard

    “The idea of trenching the street was also nicked, because, as shown in the graphic below, it would ruin the streetscape:”

    So deck it over and build a wonderful pedestrian space.

  • joechoj

    I’m sure this has been discussed at length, but bear with me: why do train tunnels have to follow street grid alignments? Why the 90-degree turns instead of shooting a tunnel straight to the TT? Do building foundations block the way?

  • LazyReader

    The typical route for SF to LA is Interstate 5 and Route 101, both of which handle about 300,000 riders per day. The question is how many of them are going the 383 mile distance to those two cities, the Answer is not very much. While Intercity travel is a portion of the travel market; but 90% of all miles traveled daily is less than 50 miles per day (commute) spending 80 Billion on something when buses are cheaper and planes faster. They keep saying by 2050 we’ll need 5 more airports and X amount of highway lanes, which is absurd because simple investments in technology will improve roadway and airway capacity.

    – driverless cars aren’t even necessary, Semi-autonomous cars and sensors will increase road capacity by as much as 20% or more

    – Megabus already offer trips from San Fran to LA, it does take longer but planned in advance….it costs a dollar….Greyhound can take you to any of the HSR’s routes for at least 25 bucks.
    – Airplanes will be 20% more fuel efficient in the foreseeable future. Do what Japan and Hong Kong did, and build artificial islands for new or expanded airports.
    The fact is there’s no reason to dump what will be over 100 Billion dollars plus on rail when planes are faster and buses vastly cheaper and can operate without subsidies (at least none on the scale of rail)

  • Urbanist Brian

    Short answer, YES! Building foundations do get in the way. The area has very bad artificial fill soil, so deep foundations are needed.

  • Roland Lebrun

    Here is how to get the job done in under 5 years for less than $2B:


A rendering of the Transbay terminal with Caltrain and HSR. Image: Transbay Authority

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